Attenuation of Benign Prostatic Hyperplasia by Optimized Tadalafil Loaded Pumpkin Seed Oil-Based Self Nanoemulsion: In Vitro and In Vivo Evaluation.

The FDA has approved tadalafil (TDL) for the treatment of benign prostatic hyperplasia (BPH)-associated symptoms. Pumpkin seed oil (PSO) has shown promise for the relief of prostatitis-related lower urinary tract symptoms. The aim was to improve TDL delivery to the prostate and assess the combined effect of TDL with a PSO-based formula in the management of BPH. PSO, Tween 80, and polyethylene glycol 200 were selected for the optimization of self nano-emulsified drug delivery system (SNEDDS). The formed vesicles were assessed for their globule size and zeta potential. A rat in vivo study was carried out to investigate prostate weight and index, histopathology, and pharmacokinetics. The average globule size for the optimized TDL-PSO SNEDDS was 204.8 ± 18.76 nm, with a zeta-potential value of 7.86 ± 1.21 mV. TDL-PSO SNEDDS produced a marked drop in prostate weight by 35.51% and prostate index by 36.71% compared to the testosterone-only group. Pharmacokinetic data revealed a 2.3-fold increase of TDL concentration, from optimized TDL-PSO SNEDDS, in the prostate compared with the raw TDL group. This study indicated that the combination of TDL and PSO in an optimized TDL PSO SNEDDS formula improved the efficacy of TDL in the management of BPH.

1. Introduction

Benign prostatic hyperplasia (BPH) is characterized by the non-cancerous enlargement of the prostate. The benign and enlarged prostate places a pushing pressure on the urethra and leads to the thickening of the bladder wall. This may lead to the weakening of the bladder and a loss of complete emptying of the bladder, ultimately resulting in urine retention. No definite etiology has so far been defined, but several theories exist. BPH develops as a result of the estrogen/testosterone imbalance that manifests in older males [1,2]. Another study attributes BPH to the male hormone dihydrotestosterone (DHT), which contributes to the development and growth of the prostate [3]. BPH develops from several pathophysiological changes. These changes include overactivity of the autonomic nervous system, pelvic ischemia, a decrease in pelvic nitric oxide (NO)/cyclic guanosine monophosphate (cGMP) signaling, atherosclerosis, and elevated Rho-kinase activity (which results in control of myosin phosphatase activity and, therefore, facilitates smooth prostatic muscle contractions) [3]. Several research studies suggest an elevated expression of phosphodiesterase type 5 (PDE5) to be present in the lower part of the urinary tract and the supporting vasculature [4,5,6,7,8]. Furthermore, inhibition of PDE5 has been observed to decrease the proliferation of prostate cells, while also decreasing the number of smooth muscle cells (SMCs) in the prostate, bladder, neck, and supporting vasculature. PDE5 also elevates the amount of blood reaching the lower urinary tract, while influencing the afferent nerve activity of the bladder [5,9,10]. Moreover, bladder performance can be impacted by functional and structural variations in the prostate, bladder, and the vasculature supporting such structures [11]. This elevation in cGMP concentration results in an efflux of calcium and relaxation of the SMCs. Several processes may aid in the alleviation of lower urinary tract symptoms (LUTS) and can be facilitated by PDE5 isoenzyme inhibition in the lower part of the urinary tract [4]. Altogether, the administration of 5 mg of tadalafil (TDL) in a daily manner led to significantly better results compared to the placebo. The safety profile of TDL was promising, and TDL was found to be well-tolerated [1,12]. Thus, the findings of these studies supported administering TDL 5 mg once a day as a treatment for benign LUTS suggestive of BPH [1,12,13]. TDL (5 mg) was approved by the FDA to be taken once a day for the treatment of LUTS symptoms linked to BPH. A randomized, double-blind, placebo-controlled, parallel design study using 2.5 mg of TDL over 12 weeks indicated improvements in the international prostate symptom score (IPSS) [14]. TDL increased pelvic perfusion by up-regulating NO and cGMP, which reduced the prostatic ischemia and improved the blood circulation.

Pumpkin seed oil (PSO) is a part of the Cucurbitaceae family that has demonstrated excellent potential for the treatment of nocturia, urinary incontinence, and the frequency of urination in clinical trials [9]. PSO’s chemical composition includes fatty acids, tocopherols, and phytosterols, in addition to squalene (triterpene). The main fatty acids that constitute about 90% of PSOs are palmitic acid, oleic acid, and linoleic acid [15,16,17,18]. The few studies available on PSOs involved in vivo research and indicated a positive effect on the prostate through the prevention of testosterone-induced hyperplasia [2,19,20,21]. This endogenous effect could be attributed to the physiological effect of PSO on the inhibition of 5-α-reductase, which converts testosterone into DHT (dihydrotestosterone), the active form of testosterone. Pumpkins tend to be mainly eaten, but other members of the Cucurbitaceae family are also utilized in various nations, such as in China, North India, Mexico, and the Caribbean. However, in North America and Europe, the use of nutraceuticals, especially pumpkin seeds, as therapy for the prostate and bladder is gaining interest [22,23,24]. Nutraceuticals tend to be marketed as a range of dietary supplements for this reason. Like the other members of the Cucurbitaceae family, pumpkins are also utilized in the Caribbean and have been cultivated for tens of years in Austria, where they are used as a supplement in food [19]. Pumpkin bioactive characteristics are an under-investigated research area. Moreover, in cases where pumpkin seeds have been examined, the seeds were usually part of a mixture consisting of other ingredients and plants. Abnormal regulation of steroid hormone receptors has been linked to prostate hyperplasia, so this link was investigated. However, the findings did not clearly indicate any mechanisms involving sex steroid receptors. The growth of both hyperplastic and cancerous cells is prevented by hydroalcoholic pumpkin seed extract, although the impact on hyperplastic cells is more pronounced [23]. This is a statistically significant finding, as it indicates a compound with greater efficacy against hyperplastic cells, including cancer cells and other rapidly growing cells that are present in hyperplastic tissue and only slightly impact non-hyperplastic cells [24]. Therefore, this extract is a possible treatment option [2,19,20,21]. Similar results obtained in vivo would indicate the significance of this compound as a supportive treatment for conditions, such as BPH, which frequently occurs in males aged 50 and over [25,26,27].

Self nano-emulsified drug delivery systems (SNEDDSs) are increasingly being utilized in the pharmaceutical field as a vehicle or drug delivery system in various formulations, such as creams, foams, liquids, and sprays. This is because of their high degree of drug permeation through tissues, stability, and fewer side effects compared to other modern drug delivery systems [28,29,30,31,32]. SNEDDSs are superior to microemulsion because of their smaller size, larger surface area, and absence of any inherent creaming, flocculation, coalescence, or sedimentation. SNEDDSs consist of isotopic mixtures of oil, surfactants, and co-surfactant components, forming emulsions spontaneously in situ upon contact with gastrointestinal tract (GIT) fluids [28]. They favor fast dispersion processes and are less affected by other factors, such as food effects and inter-subject variability, during their formulation process. Following dilution, the creation of nanoemulsion droplets, of sizes of less than 20 nm (with 200 nm being the upper limit), takes place. Besides enhancing stability, these lipid-based nano-entities employed as novel drug delivery systems (DDSs) are indicated to improve drug solubility, dissolution behavior in the GIT, and thus are known to increase the absorption of the poorly water-soluble drugs [28,29,30,31,32].

One of the aims of nanomedicine is to improve the efficacy of active pharmaceutical agents for application in chronic ailments. Consequently, TDL was loaded on a PSO-based nanocarrier. This study aimed to optimize the tadalafil-pumpkin seed oil-self nano-emulsified drug delivery system (TDL-PSO SNEDDS) formulation with a minimum globule size and maximum zeta potential to enhance TDL delivery to the prostate and to evaluate the joint impact of TDL and PSO when used in BPH-management.

2. Materials and Methods

TDL was supplied as a gift by Spimaco pharmaceuticals (Al Qassim, Saudi Arabia). PSO, polyethylene glycol (PEG) 200, and Tween 80 were all bought from Sigma Aldrich (St. Louis, MO, USA). Testosterone enanthate (250 mg/mL) ampoules were provided by the Chemical Industries Development Company (Giza, Egypt).

2.1. Experimental Design TDL-PSO SNEDDS

A mixture of experimental design was utilized in this study. Optimization of the effects for the three formula components (PSO% (X1, 10–30%), tween 80% (X2, 30–60%), and PEG 200 (X3, 20–40%)) was carried out [33]. The responses were the mean globule size (Y1) and zeta potential (Y2). The selected factors for the optimization of the TDL-PSO SNEDDS formulations using a mixture design within the stated ranges are shown in Table 1.

Table 1

Formula factors and responses tadalafil-pumpkin seed oil-self nano-emulsified drug delivery system.

Factors	Levels
	Low	High
PSO (%)	10	30
Tween 80 (%)	30	60
PEG 200 (%)	20	40
Responses	Low	High	Goal
Globule size (nm)	55	324	Minimize
Zeta potential (mV)	1.45	13.75	Maximize

Abbreviations: PSO, pumpkin seed oil; PEG, polyethylene glycol.

2.1.1. TDL-PSO SNEDDS Formulation

Based on the preliminary solubility studies, Tween 80 and PEG 200 were chosen together with PSO for the formation of SNEDDS [34]. The percentage of each formula component (total weight 1 g), according to the experimental design, and 5 mg TDL, were mixed and then vortexed for five minutes. The formulation was then sonicated for 50 s in a Sonics probe sonicator (20 kHz, 1500 W, Sonics, Newtown, CT, USA).

2.1.2. TDL-PSO SNEDDS Evaluation

TDL-PSO SNEDDS aqueous dispersions were visually assessed for their tendency to emulsify spontaneously and for clarity [31]. The thermodynamic stability study objective was to assess the phase separation of the formulation, together with an assessment of the impact of temperature differences on the SNEDDS formulation. Stability was evaluated through three steps. The first, centrifugation, involved the dilution of the formulation with an aqueous medium before centrifugation of the mixture at 15,000 rpm for 15 min and then visual observation of the mixture for phase separation. The second and third steps involved freeze-thaw and heating-cooling cycles. First, the formulation was diluted using deionized water at a ratio of 1:50. It was then frozen to −20 °C for two days before being allowed to thaw and was then visualized for phase separation. Next, the mixture was heated to 40 °C for two days, left to cool, and observed for phase separation.

2.1.3. Vesicular Size and Zeta Potential

Ten milliliters of distilled water were added to 50 μL of the formulation. This mixture was vortexed for two minutes, and then the size and zeta potential of the vesicles were measured using Malvern ZSP (Malvern Inst. Ltd., Malvern, UK).

2.1.4. TDL-PSO SNEDDS Mixture Design Analysis

The effects of TDL-PSO SNEDDS factors (X1–X3) on globule size and zeta potential were investigated using the Statgraphics Centurion XV version 15.2.05 software (StatPoint Technologies Inc, Warrenton, VA, USA). The optimum desirability was identified, and an optimized formula with the minimum globule size and maximum zeta potential was proposed. This optimized formula was prepared and characterized for globule size and zeta potential, as previously described. The predicted values deduced by the software were then compared with the observed values the residual was calculated.

2.1.5. TDL-PSO SNEDDS Examination by Transmission Electron Microscopy

Once the vesicle size was determined, the vesicles were prepared for imaging by negatively staining them with 1% w/v phosphotungstic acid and air drying. The vesicles were then examined under a transmission electron microscope (TEM) (JEOL JEM-HR-2100, JEOL, Ltd., Tokyo, Japan).

2.2. TDL-PSO SNEDDS Formulation In Vivo Studies

King Abdulaziz University’s Research Ethics Committee for the Faculty of Pharmacy ethically approved all procedures conducted on animals (reference number (PH-122-40, approval date: 15 May 2019). Moreover, guidelines set by the US government for the use and care of vertebrate animals in testing, research, and training were also followed in all procedures conducted. Wistar rats that were ten weeks old weighing between 220 to 250 g were supplied by the King Fahd Medical Research Center, King Abdulaziz University. Rats were maintained in a half-day light/dark cycle in an air-conditioned environment at a room temperature of 23 °C with 60% relative humidity where they were fed with a standard food pellet diet ad libitum. This food and water were made freely accessible to the animals. The acclimatization of the animals was conducted for one week prior to the start of the experiments.

2.2.1. Design of In Vivo Study Protocol for the Evaluation of TDL-PSO SNEDDS Effects

There were six experimental animal groups, each containing eight rats. The normal group (group 1) was not administered any treatment or testosterone. The remaining five groups were treated with 3 mg/kg testosterone enanthate subcutaneously (SC) five days a week for two weeks for BPH induction [35]. One control group (group 2) only received 3 mg/kg testosterone enanthate subcutaneously (SC) five days a week for two weeks. Another control group (group 3) was orally administered 2.5 mL/kg plain formula without TDL or PSO, together with 3 mg/kg testosterone enanthate SC five days a week for two weeks. Group 4 was administered optimized TDL-PSO SNEDDS formulation (PSO 100 mg/kg and TDL 2 mg/kg) orally following its dilution with water. This was administered 1 h prior to the administration of 3 mg/kg testosterone enanthate (testosterone SC) five days a week for two weeks. Group 5 was administered 2 mg/kg of TDL orally 1 h prior to administration of 3 mg/kg testosterone enanthate (testosterone SC) five days a week for two weeks. Group 6 was administered 100 mg/kg of PSO orally, 1 h prior to the administration of 3 mg/kg testosterone enanthate (testosterone SC) five days a week for two weeks. The rats were euthanized 72 h after the final testosterone dose, and their prostatic tissue was obtained by dissection. For the pharmacokinetics study, 36 rats were divided into two groups and treated the same as groups 4 and 5. Samples of the prostate were withdrawn on days 1, 3, 6, 8, 12, 14, and 18. These samples were homogenized prior to analysis in a liquid chromatography-mass spectrometer (LC-MS). Prostatic ventral lobe samples were maintained in 10% neutral buffered formalin before their use in histological imaging.

2.2.2. Chromatographic Analysis of TDL Quantitation in Rat Prostates

For analysis of the samples, liquid chromatography with tandem mass spectrometry was used [36]. This method was also validated for TDL quantitation in the rat prostates. The initial sample preparation involved extraction using methyl tertbutyl ether in an alkaline environment. This was followed by TDL separation by HPLC employing a C18 column for the separation of an isocratic mobile phase. This phase was composed of methanol and 2 mM ammonium acetate containing formic acid (0.05%) in water (52:48, v/v). Separation occurred with a flow rate of 0.2 mL/min over 5 min. A triple-quadruple tandem mass spectrometer was employed for the detection step. This step used domperidone as the internal standard and detected masses following electrospray ionization (ESI) using multiple reaction monitoring (MRM). Linear calibration curves were generated for concentrations of TDL ranging from 2 ng/mL to 1000 ng/mL in the prostate sample homogenate and from 2 ng/mL to 100 ng/mL in the seminal plasma. Consequently, the lower limit of quantitation (LLOQ) for both samples was 2 ng/mL. Precision relative standard deviation (RSD) values were lower than 15%, and accuracy fell between 3.12% and 7.71% for the prostate. Therefore, for both matrices, the inter- and intra-day precision and accuracy readings for all Quality Control (QC) samples were recorded within the criteria specified as acceptable for bio-analytical techniques.

2.2.3. Prostate Weight and Prostate Index

The rat prostates were promptly dissected and weighed, followed by a calculation of the prostate index for each rat. This index was obtained by dividing the weight of the prostate by the bodyweight (g/g).

2.2.4. Histopathology

Four micrometers of paraffin-embedded fixed prostatic tissue sections were prepared. This was followed by deparaffinization, rehydration, and hematoxylin and eosin (H&E) staining. A minimum of three sections was photographed after staining. These photographs were examined to establish the height of the prostate glandular epithelium using image analysis software (Image J, 1.46a, NIH, Bethesda, Maryland, USA).

2.2.5. Pharmacokinetic Analysis

The Kinetica™ software (Version 4; Thermo Fisher Scientific, Waltham, MA, USA, 2005) was used to estimate the pharmacokinetic parameters. The following values were calculated: Cmax, which is the maximum prostate concentration attained by the drug, and AUC0–t, which is the area under the curve.

2.3. Statistical Analysis

Data are presented as the Mean ± SD. Statistical analyses were performed with the GraphPad Prism 6 software (GraphPad Software, Inc., San Diego, CA, USA, 2012). A comparison of means was performed using a one-way analysis of variance (ANOVA) followed by Tukey as a post hoc test. Differences at p-values below 0.05 (p < 0.05) were deemed statistically significant.

3. Results and Discussion

3.1. Formulation and Characterization of TDL-PSO SNEDDS

The primary purpose of the combinational delivery of TDL with PSO was enhancing the biological activity of TDL against BPH. This was based on using PSO, with its established activity in prostate tissues, as the oil component for TDL SNEDDS instead of using an inactive oil formula component. According to the preliminary studies performed, the selected factors for the optimization of TDL-PSO SNEDDS formulations using mixture design within the stated ranges are shown in Table 1. The detailed composition and characterization of the TDL-PSO SNEDDS formulations, according to the experimental design, are shown in Table 2. A TDL load of 5 mg/1 g PSO SNEDDS was fixed in the prepared formulations to avoid TDL precipitation and for the in vivo investigation dose calculation. The optimization of TDL-PSO SNEDDS formulation using the experimental design was carried out to improve stability and absorption (i.e., efficacy) characteristics by controlling the size and charge of the SNEDDS globules. Size and load can also be modulated for intracellular delivery [37,38]. Previous reports indicated that drug delivery at a higher drug concentration (improved bioavailability) was achieved by loading the drug into SNEDDS formulations [28,39].

Table 2

TDL-PSO SNEDDS components for the mixture design-suggested formulations and the observed and fitted mean globule size and zeta potential values.

TDL-PSO SNEDDS Formula	Factors (X1–X3)			Responses (Y1–Y2)
	PSO (%)	Tween 80 (%)	PEG 200 (%)	Globule Size (nm)		Zeta Potential (mV)
				Observed	Fitted	Observed	Fitted
1	30	50	20	287.0	269.65	13.75	10.36
2	30	30	40	324.0	313.99	10.70	10.03
3	20	60	20	160.0	155.00	5.98	6.35
4	10	60	30	55.0	62.53	1.45	2.17
5	10	50	40	89.0	84.70	0.76	2.01
6	25	50	25	197.0	223.41	6.22	8.27
7	25	40	35	209.0	245.58	4.70	8.11
8	20	55	25	183.0	166.09	7.6	6.26
9	15	55	30	135.0	119.85	6.89	4.18
10	15	50	35	145.0	130.94	6.10	4.09
11	30	40	30	324.0	291.82	9.50	10.20
12	25	55	20	189.0	212.32	7.10	8.35
13	20	50	30	167.0	177.17	6.29	6.18
14	20	40	40	189.0	199.34	8.30	6.02
15	15	60	25	110.0	108.76	3.45	4.26
16	10	55	35	78.0	73.61	2.10	2.09
17	20	50	30	171.0	177.17	4.30	6.18

The evaluation of the prepared formulations for visual assessment showed the spontaneous formation of clear to slightly clear emulsions with globule sizes in the nano-range [40]. To assess the thermodynamic stability of the prepared TDL-PSO SNEDDS formulations, various stress tests were conducted, as previously described. The SNEDDS formulation was found to be stable under all three stress conditions (data not shown), thereby eliminating the risk of metastable formation and not necessitating regular testing throughout storage.

3.1.1. Evaluation of TDL-PSO SNEDDS Formulation Globule Size

TDL-PSO SNEDDS formulations prepared according to the mixture design were investigated for their globule sizes. The data were fitted to a linear model that showed the lowest p-value of 0.00001. The determination coefficient (R2) indicated that the fitted linear model explained 94.75% of the variability in globule size. The triangular dimensional contour plot (Figure 1A) showed the effect of the TDL-PSO SNEDDS components on globule size. The blank (white) areas shown in the triangular plot represent areas not applied in the regression because of the constraints of the components. The equation for the TDL-PSO SNEDDS, according to the linear model, is shown below (Equation (1)).

Figure 1

Triangular dimensional contour plots for the effect of TDL-PSO SNEDDS components (pumpkin seed oil, surfactant (Tween 80), and co-surfactant (PEG 200)) on globule size (A) and zeta potential (B). TDL-PSO SNEDDS, tadalafil-pumpkin seed oil-self nano-emulsified drug delivery system.

In order to optimize the TDL-PSO SNEDDS formula components for the minimum globule size, the optimum components deduced by design showed the optimum levels of PSO, tween 80, and PEG to be 10%, 60%, and 30%, respectively. These levels revealed the optimum value for the globule size to be 62.53 nm, as indicated by the mixture design.

3.1.2. Evaluation of the TDL-PSO SNEDDS Formulation Zeta Potential

The triangular dimensional contour plot (Figure 1B) showed the effect of the TDL-PSO SNEDDS components on zeta potential. The yellow area (top part of the contour plot in the triangle) represents the maximum zeta potential value of the TDL-PSO SNEDDS formulations. These data were fitted to the linear model, showing the lowest p-value to be 0.0003 with an R2 value, indicating that the fitted linear model explained 69.37% of the variability in globule zeta potential. The equation for TDL-PSO SNEDDS, according to the linear model, is shown below (Equation (2)).

To maximize the zeta potential in order to optimize TDL-PSO SNEDDS formula components, based on this response, the optimum components deduced by design showed the optimum PSO, tween 80, and PEG levels to be 30%, 50%, and 20%, respectively. These levels revealed the optimum value for the zeta potential to be 10.365 mV. SNEDDS short- and long-term stability was related to globule zeta potential value. A high value of zeta potential (either –ve or +ve value) was an indication of stable SNEDDS. On the other hand, a low zeta potential value (close to zero) was an indication of SNEDDS’ poor physical stability.

3.1.3. TDL-PSO SNEDDS Mixture Design Analysis for an Optimized Formula

The effect of TDL-PSO SNEDDS factors (X1–X3) on globule size and zeta potential was investigated utilizing the experimental design software. An optimized formula with the minimum globule size and maximum zeta potential was utilized. The results showed that the optimized formula revealed optimum PSO, tween 80, and PEG levels to be 25%, 55%, and 20%, respectively. Those combinations predicted a globule size of 212.33 nm and a zeta potential value of 8.36 mV for the optimized TDL-PSO SNEDDS formula. The optimized formula components were prepared according to the deduced percent estimated by design, and the observed values for the globule size and zeta potential of the optimized formula were 204.8 ± 18.76 nm and 7.86 ± 1.21 mV, respectively.

3.1.4. Vesicles Examination by TEM

To visualize the oily droplets under TEM, distilled water was used to dilute the TDL-PSO SNEDDS to form a nanoemulsion. A characteristic TEM image is illustrated in Figure 2. This figure showed that the formed vesicles were spherical in appearance.

Figure 2

The TEM image of the TDL-PSO SNEDDS vesicles.

3.2. TDL-PSO SNEDDS Formulation In Vivo Studies

3.2.1. Prostate Weight and Prostate Index

Animals in the treatment groups did not show any symptoms of toxicity, and all survived. From Table 3, it is clear that the testosterone challenge significantly (p < 0.05) increased prostate weight by 57.3% and the prostate index by 58.6% when compared to the control group. A significant decrease in prostate weight and index by 35.51% and 36.71%, respectively, was noted in the co-treatment groups using doses of optimized TDL-loaded PSO SNEDDS when compared to the testosterone-only group. PDE5 inhibitors, as TDL, have been reported to decrease the proliferation of prostate cells, while also decreasing the number of smooth muscle cells (SMCs) in the prostate, bladder, neck, and supporting vasculature [5,9,10]. In addition, a previous study has revealed improvement in symptoms of BPH for patients receiving PSO and/or saw palmetto oil [20,21,24]. The efficacy of PSO for improved BPH symptoms is attributed to its reported 5-α-reductase inhibition activity [19].

Table 3

Effect of TDL-PSO SNEDDS on prostate weight and prostate index (prostate weight/body weight ratio) in testosterone-induced BPH in rats.

Group	Rat Weight	Prostate Weight	Prostate Index (× 103)
Group 1 (Normal)	267.4 ± 4.72	0.68 ± 0.04	2.54 ± 0.15
Group 2 (Testosterone only)	265.2 ± 21.99	1.07 ± 0.13	4.03 ± 0.39
Group 3 (Plain formula)	270.0 ± 16.60	1.09 ± 0.15	4.04 ± 0.49
Group 4 optimized (TDL-PSO SNEDDS)	270.6 ± 15.77	0.69 ± 0.04 *$#&	2.55 ± 0.20 *$#&
Group 5 (TDL)	257.4 ± 21.97	0.85 ± 0.04	3.30 ± 0.39
Group 6 (PSO)	280.2 ± 13.81	0.86 ± 0.08	3.07 ± 0.35

* Significantly different (p < 0.05) from group 2. $ Significantly different (p < 0.05) from group 3. # Significantly different (p < 0.05) from group 5. & Significantly different (p < 0.05) from group 6.

3.2.2. Histopathological Examination

The H&E-stained prostatic tissue sections of the control rats appeared normal when examined under the microscope. Their structures included distinctively sized and shaped acini that were available in abundance. A homogenous acidophilic substance was identified within them. The acini lining the epithelium consisted of both acinar (principle) cells and basal cells. The former was columnar and stretched from the basal lamina to the duct lumen and contained characteristic spherical or oval nuclei that were situated in the lower half of the cytoplasm, which was eosinophilic and granular in appearance (Figure 3A). In contrast, for prostate tissue, derived from rat groups, treated with testosterone and testosterone with the plain formula, there was a disturbance in the histological architecture. This was indicated by hyperplasia, acinar folding in an irregular manner with intraluminal projections, and evidence of congestion (Figure 3B,C). Hypertrophy, hyperplasia, and intraluminal projections that were present in the testosterone group were efficaciously improved when the optimized TDL-PSO SNEDDS formula was administered, leading to cells with nearly normal histological architecture (Figure 3D). However, the images in Figure 3E,F show decreased levels of irregular acinar folding, together with less intraluminal projections compared to cells from groups treated with testosterone and testosterone with the plain formula. In the normal (group 1) and optimized TDL-PSO SNEDDS (group 4) rat groups, the prostate glands were surrounded by fibrous connective tissue that was loosely attached and consisted of both blood vessels and smooth muscle fibers.

Figure 3

Histology of (A) (group 1) ventral lobe of intact rats, H&E, ×40; (B) (group 2) testosterone-induced BPH (benign prostatic hyperplasia) (irregular acinar shape with villous projections of different sizes into the lumen), ×40; (C) (group 3) 14 days of co-administration of testosterone and the plain formula (irregular acinar shape with villous projections of different sizes into the lumen), ×40; (D) (group 4) 14 days of co-administration of testosterone and optimized TDL-PSO SNEDDS (normalized ventral lobe structure), H&E, ×60; (E) (group 5) 14 days of co-administration of testosterone with TDL 2 mg/kg (glands are partially atrophic, with dilated, angular, profiles and adenomatous hyperplasia), H&E, ×60; and (F) (group 6) 14 days of co-administration of testosterone and PSO 100 mg/kg (glands are partially atrophic, with dilated, angular, profiles and adenomatous hyperplasia), H&E, ×60.

3.2.3. TDL Prostate Levels

Figure 4 illustrates the concentrations of TDL in the prostate within three to 18 days after the administration of raw TDL and optimized TDL-PSO SNEDDS after daily dosing. The findings indicated significant improvements in the levels of TDL in the prostate when the optimized TDL-loaded SNEDDS formula was administered compared to the raw TDL.

Figure 4

Mean ± SD of TDL prostate concentration within 3–18 days after daily subcutaneous (SC) administration of raw TDL and TDL PSO SNEDDS. * Significantly different (p < 0.05) compared to raw TDL.

3.2.4. In Vivo Pharmacokinetics in Prostate Tissue

The results for the TDL pharmacokinetic analyses indicated significant differences (p < 0.05) for the optimized TDL-PSO SNEDDS formula compared to TDL with respect to the Cmax and AUC0–inf values, as depicted in Table 4. This, therefore, demonstrated that the bioavailability of TDL from the optimized TDL-PSO SNEDDS formula was greatly improved compared to TDL.

Table 4

The mean ± SD for the pharmacokinetic parameters of the TDL and TDL-PSO SNEDDS in prostate tissues.

Parameter	Unit	TDL	TDL-PSO SNEDDS
Cmax	ng/mL	38.69 ± 6.5	88.10 ± 7.6 *
AUC 0–t	ng/mL *d	494.96 ± 34.2	1187.81 ± 89.2 *
Ke	1/d	0.43 ± 0.06	0.36 ± 0.06
t1/2	d	1.63 ± 0.20	1.96 ± 0.30
Tmax	d	11.3 ± 3.05	12.7 ± 1.15
MRT 0–inf_obs	d	10.45 ± 0.41	10.12 ± 0.21

* Significant difference (p < 0.05) between the TDL and TDL-PSO SNEDDS groups (unpaired t-test with Welch’s correction).

The improvement in the Cmax and AUC after loading TDL into the optimized PSO SNEDDS formula when compared with raw TDL indicated that TDL-PSO SNEDDS showed enhanced concentrations of TDL in prostatic tissues. In addition, the reported anti-BPH activities of PSO cannot be excluded [21,23]. Thus, the observed decrease in the prostate weight and index than those in the oral TDL treated group could be attributed to both enhanced TDL distribution to prostatic tissues and additive and/or synergistic effects of the SNEDDS component formula PSO.

In relation to toxicity concerns for the long-term use of the PSO SNEDDS formula, previous toxicity reports showed that TDL studies on humans did not provide further evidence for testicular toxicity. Concerns about testicular toxicity have been raised based on TDL related testicular data alterations in dogs that proved to be unlikely in humans [41]. No toxicity reports, however, on liver or kidney patients with either liver or kidney impairment recommended a lower TDL starting dose [41,42]. On the other hand, there are no reports on the kidney or liver toxicity of PSO. It has been reported that an extract from pumpkin seeds, at a dose of 5000 mg/kg, provides a considerable safety margin and is devoid of acute toxicity [43]. On the other hand, reports revealed PSO to exert protective effects against liver and kidney toxicities when co-administered with emamectin and azathioprine [44,45]. The data acquired from this study showed the possible utilization of TDL-PSO SNEDDS as a promising formula for the management of BPH.

4. Conclusions

This study suggested that the optimization of TDL-loaded PSO SNEDDS formulation could be an efficient way to manage BPH, rather than using each component alone. TDL-PSO SNEDDS optimized the prostatic index to be within the normal range after BPH induction by testosterone. Furthermore, the optimized SNEDDS formula enhanced TDL delivery to the prostate by more than 2-fold. Histopathological images confirmed the reduced papillary projections and hyperplasia in testosterone-induced BPH via the optimized TDL-PSO SNEDDS formula.