Gastroprotective effects of Corchorus olitorius leaf extract against ethanol-induced gastric mucosal hemorrhagic lesions in rats.

BACKGROUND AND AIM: Corchorus olitorius is a medicinal plant traditionally utilized as an antifertility, anti-convulsive, and purgative agent. This study aimed to evaluate the gastroprotective effect of an ethanolic extract of C. olitorius against ethanol-induced gastric ulcers in adult Sprague Dawley rats.
METHODS: The rats were divided into seven groups according to their pretreatment: an untreated control group, an ulcer control group, a reference control group (20 mg/kg omeprazole), and four experimental groups (50, 100, 200, or 400 mg/kg of extract). Carboxymethyl cellulose was the vehicle for the agents. Prior to the induction of gastric ulcers with absolute ethanol, the rats in each group were pretreated orally. An hour later, the rats were sacrificed, and gastric tissues were collected to evaluate the ulcers and to measure enzymatic activity. The tissues were subjected to histological and immunohistochemical evaluations.
RESULTS: Compared with the extensive mucosal damage in the ulcer control group, gross evaluation revealed a marked protection of the gastric mucosa in the experimental groups, with significantly preserved gastric wall mucus. In these groups, superoxide dismutase and malondialdehyde levels were significantly increased (P < 0.05) and reduced (P < 0.05), respectively. In addition to the histologic analyses (HE and periodic acid-Schiff staining), immunohistochemistry confirmed the protection through the upregulation of Hsp70 and the downregulation of Bax proteins. The gastroprotection of the experimental groups was comparable to that of the reference control medicine omeprazole.
CONCLUSIONS: Our study reports the gastroprotective property of an ethanolic extract of C. olitorius against ethanol-induced gastric mucosal hemorrhagic lesions in rats.

Introduction

Alcohol is associated with various types of gastric mucosal damage, including gastritis and peptic ulcer diseases. Other etiologies of these pathologies include stress, smoking, dietary inadequacies, and diseases, as well as haphazard administration of non-steroidal anti-inflammatory drugs.1 Different models have been proposed to induce lesions in the gastric trunk.2–3 Ethanol exerts its dangerous effects either by directly producing reactive metabolites, which, together with free radical species, alter the structure and function of a number of cellular proteins, or by supporting other pathways that maintain high levels of oxidative damage.4 Ethanol-aggravated gastric mucosal wounds are linked to widespread damage to mucosal capillaries and increased vascular permeability.5 Mucosal capillary necrosis, vascular congestion, and thrombosis in the subepithelial microvasculature are other pathologies that may develop from a gastric mucosal obstruction. In addition to the direct negative consequences of ethanol on the gastric mucosa, other elements are considered to contribute to the pathogenesis of the wound.6

Several plants, such as Polygonum chinense, Carica papaya, Polygonum minus, and Corchorus olitorius, have been reported to have antiulcer properties.7–10 C. olitorius, generally known as “Jute,” is a member of Tiliaceae family and is a widespread vegetable found in Egypt, Sudan, Malaysia, Philippines, tropical Africa, South America, and the Caribbean.8 Jute is also referred to as long-fruited jute, tossa jute, jute mallow, and jew’s mallow.11 Jute contains large amounts of all of the amino acids except methionine, which is present in low concentrations.12 The plant has a high protein content in its supplementary leafy species, which serve as the main source for dietary protein in several tropical countries.12 The young leaves of C. olitorius L. are edible and are used as an ingredient for an ethnic soup in Egypt. This plant is also rich in potassium, calcium, phosphorous, iron, ascorbic acid, and carotene. A phenolic extract of C. olitorius exhibited antioxidant activity through the radical generator-initiated peroxidation of linoleic acid. Furthermore, the role of phenolic antioxidants in the activities of this vegetable was suggested from their activity patterns.13 C. olitorius has demulcent, diuretic, purgative, and tonic properties, and it is served as a lactagogue.14 The leaves showed therapeutic effects against cystitis, dysuria, fever, and gonorrhea. Ingestion of this plant mixture helps to stimulate appetite and vitality. It is an ingredient in facial creams, lotions, hair tonic, and hand creams15 and has been reported to have diuretic, antipyretic, analgesic, and antimicrobial activity.13–17 Jute leaves contain antitumor agents, such as phytol, monogalactosyldiacylglycerol,18 and antioxidants, including carotenoids, flavonoids, and vitamin C.13,16 This study was performed to assess the gastroprotective properties of C. olitorius against absolute ethanol-induced acute hemorrhagic lesions in rats.

Methods

Chemicals

All of the chemicals used in this study were obtained from Sigma-Aldrich (USA). Omeprazole was acquired from the University Malaya Medical Centre Pharmacy and was used as the reference drug. It was dissolved in carboxymethyl cellulose (CMC) and administered orally to the rats at a dose of 20 mg/kg body weight (5 mL/kg) as previously described.20

Plant specimens and extract preparation

C. olitorius leaves were obtained from Ethno Resources Sdn Bhd (Selangor, Malaysia) and were confirmed by comparing them to the voucher sample at the Herbarium of Rimba Ilmu, Institute of Science Biology, University of Malaya, Kuala Lumpur. The desiccated leaves were ground into powder and soaked in 95% ethanol. The ethanol mixture was then evaporated using an Eyela rotary evaporator (Sigma-Aldrich, St. Louis, MO, USA). The dry extract was dissolved in CMC (0.25% w/v) and then administered orally to rats at doses of 50, 100, 200, and 400 mg/kg body weight (5 mL/kg body weight) according to a previously published study.7

Acute toxicity

Mature male and female Sprague Dawley rats (6–8 weeks old, weight 150–180 g) were acquired from the animal house at the Faculty of Medicine, University of Malaya, Kuala Lumpur [Ethics No. RM 07/05/2008/MMA (a) (R)]. They received normal rat pellets with pipe-borne water ad libitum. A severe toxicity experiment was performed to determine the maximum prescribed dose of leaf extract that did not kill the animals according to a previous study with some modifications.21

Gastroprotective experimental design

Experimental animals

Healthy, mature Sprague Dawley male rats were provided by the Experimental Animal House, Faculty of Medicine, University of Malaya [Ethic No. RM28/09/2006/MAA (R)]. The animals were randomly separated into seven groups containing six rats per group. The rats (200–225 g) were kept individually in wide mesh wire bottom cages to prevent coprophagia during the test.21

Gastric ulcer induction by ethanol

The animals were fasted for 24 h prior to the test but were allowed to drink water until 2 h prior to the test. Gastric ulcers were aggravated through the gastric intubation of absolute ethanol (5 mL/kg) as previously described.7–22

Measurement of gastric juice acidity

The gastric content was collected and centrifuged at 4000 rpm for 10 min. The supernatant was used to determine the hydrogen ion concentration by titration with NaOH solution (0.1 N), and it was measured with a digital pH meter (Hanna instruments, Ann Arbor, MI, USA).

Macroscopic appearance of gastric mucosa

Ulcers associated with the gastric mucosa presented as stretched bands of hemorrhagic lesions similar to the extended axis of the stomach. The total area of the lesions of each stomach was used to calculate the ulcer region (UA) as follows:

This equation was used as previously described23 with minor changes. The restraining percentage (I %) was calculated using the formula described by Njar et al.24 with minor adjustments.

Content measurement of gastric wall mucus

The glandular regions of the stomach were removed from the rats, measured, and evaluated to measure the content of the gastric wall mucus. The gastric wall mucus was evaluated in accordance with the method of Corne et al.25

Antioxidant activity

Preparation of stomach homogenate

Glandular gastric tissue was carefully rinsed with ice-cold saline. Using a homogenizer (Polytron, Heidolph RZR 1, Schwabach, Germany), the homogenate was prepared on ice in potassium phosphate buffer (10% [w/v], 50 mmol, pH 7.8) containing mammalian protease inhibitors. The homogenate was centrifuged at 4500 rpm for 30 min at 4°C.

Measurement of superoxide dismutase (SOD)

SOD activity was measured as previously described.26

Measurement of membrane lipid peroxidation

The rate of lipoperoxidation in the gastric mucous membrane was determined through the measurement of membrane lipid peroxidation (malondialdehyde [MDA]) using the Bradford assay.27

Histology of gastric lesions

HE staining

Samples of gastric tissue were fixed in 10% buffered formalin and processed in a paraffin tissue-processing machine (Leica TP1020; Leica Biosystems, Solms, Germany). The stomach was sectioned at 5 μm and stained with HE for histological assessment.28

Study of mucosal glycoproteins

Stomach sections from each group were stained with periodic acid-Schiff (PAS) to observe mucus production and to evaluate modifications of acidic and essential glycoproteins.29

Immunohistochemistry

The tissue sections were heated at 60°C for 25 min in a hot air oven (Venticell, MMM, Einrichtungen, Germany). The tissue sections were deparaffinized in xylene and dried with ethanol. The antigens were recovered in 10 mmol sodium citrate buffer after boiling in a microwave. Immunohistochemical staining was performed in accordance with the manufacturer’s guidelines (Dako Cytomation, Carpinteria, CA, USA). Endogenous peroxidase activity was blocked with peroxidase (0.03% hydrogen peroxide supplemented with sodium azide). The tissue sections were gently cleaned with wash buffer and were then incubated with either Hsp70 (1:500) or Bax (1:200) biotinylated primary antibodies for 15 min. The sections were gently washed with wash buffer and placed in a buffer bath. The sections were then positioned in a wet room. A sufficient amount of streptavidin–HRP (streptavidin conjugated to horseradish peroxidase in phosphate-buffered saline supplemented with an antimicrobial agent) was incubated with the sections for 15 min, gently washed in the wash buffer, and incubated in the buffer bath. Diaminobenzidine substrate-chromogen was incubated with the sections for 5 min followed by washing and counterstaining with hematoxylin for 5 s. The tissue sections were then immersed in a low concentration of ammonia (37 mmol) 10 times and washed with purified water prior to mounting on cover slips. Positive immunohistochemical staining was observed as a brown color under a light microscope.

Statistical analysis

All the values were reported as the mean ± standard error of mean. The differences between groups were evaluated using a one-way anova followed by Tukey’s post hoc test for multiple comparisons using SPSS 20 software (SPSS Inc, Chicago, IL, USA). A value of P < 0.05 was considered to be statistically significant.

Results

Acute toxicity study

No hepatic or renal toxicity was observed in the biochemical and histological analyses. The rats were alive and never manifested signs of toxicity at the administered dosages. There was no detectable sign of either hepatic or renal toxicity in the treated groups compared with the control group.

Gastroprotective evaluation

Evaluation of gastric gross lesions and gastric wall mucosa

The antiulcer activity of C. olitorius in the ethanol-induced gastric lesion model is shown in Table 1. The results showed that the rats pretreated with C. olitorius extract prior to the administration of absolute alcohol had considerably fewer regions of gastric ulcer development compared with the rats pretreated with only CMC (ulcer control group) (Fig. 1). Furthermore, this plant extract considerably inhibited ulcer development. Interestingly, we observed a flattening of the gastric mucosal folds in the rats pretreated with C. olitorius. The level of gastric wall mucus was significantly reduced in the ulcer control group, whereas the rats pretreated with C. olitorius showed a significant inhibition of gastric wall mucus depletion. In the ulcer control group, the gastric wall mucus layer was thinner after ethanol administration. However, pretreatment with C. olitorius significantly inhibited this reduction (Table 1, Fig. 1).

Table 1

Effects of Corchorus olitorius ethanolic extract on gastric ulcer area, pH of gastric content and Alcian blue binding capacity in the gastric mucosa of rats

Animal group	pH	Ulcer area (sq mm)	Inhibition (%)	GWM (μg Alcian blue/g)
CMC (Normal control)	6.28 ± 0.14	—	—	483.98 ± 1.77
CMC (Ulcer control)	4.42 ± 0.25	962.25 ± 4.14	—	169.01 ± 2.71
Omeprazole (20 mg/kg)	5.92 ± 0.23*	189.12 ± 3.64**	80.3	396.20 ± 2.08**
C. olitorius (50 mg/kg)	4.71 ± 0.32	215.38 ± 5.81**	77.6	315.43 ± 1.88**
C. olitorius (100 mg/kg)	5.16 ± 0.30	105.25 ± 6.35**	89.1	326.92 ± 1.97**
C. olitorius (200 mg/kg)	5.64 ± 0.31*	15.27 ± 2.72**	98.4	337.32 ± 2.68**
C. olitorius (400 mg/kg)	6.01 ± 0.29*	0.00 ± 0.00**	100	456.99 ± 1.93**

P < 0.05;

P < 0.001.

All the values are expressed as the mean ± standard error of the mean. The mean difference is significant when compared with the ulcer control group. The data were analyzed using one-way anova with SPSS 20 software.

CMC, carboxymethyl cellulose; GWM, gastric wall mucus.

Figure 1

Gross appearance of the gastric mucosa in rats. (a) Normal control group. (b) Group pretreated with carboxymethyl cellulose (CMC) (ulcer control). Severe injuries of the gastric mucosa are apparent with extensive hemorrhagic necrosis. (c) Rats pretreated with omeprazole (20 mg/kg). The gastric mucosa injuries are mild compared with the ulcer control rats. (d) Rats pretreated with 50 mg/kg Corchorus olitorius show moderate injuries to the gastric mucosa. (e) Rats pretreated with 100 mg/kg C. olitorius have moderate injuries of gastric mucosa. (f) Pretreatment with 200 mg/kg C. olitorius lessens the gastric mucosa injuries. (g) Pretreatment with 400 mg/kg C. olitorius completely protects the gastric mucosa.

Antioxidant activity of SOD and MDA levels in stomach homogenates

The rats in the ulcer control group showed a significant reduction in SOD activity compared with the pretreated groups, whereas the administration of absolute alcohol significantly increased the gastric homogenate MDA levels in the ulcer control group compared to the pretreated groups (Table 2).

Table 2

Effects of Corchorus olitorius on the antioxidant activity of SOD and the MDA levels in the stomach homogenate of rats

Animals	MDA (μM/g Tissue)	SOD (U/g)
CMC (Normal control)	12.37 ± 0.64	8.49 ± 0.34
CMC (Ulcer control)	25.35 ± 1.66	3.53 ± 0.58
Omeprazole (20 mg/kg)	13.40 ± 1.35*	7.56 ± 1.12
C. olitorius (50 mg/kg)	15.13 ± 1.72*	5.14 ± 0.70
C. olitorius (100 mg/kg)	11.79 ± 1.02*	7.22 ± 1.40
C. olitorius (200 mg/kg)	7.27 ± 0.93*	15.17 ± 1.48*
C. olitorius (400 mg/kg)	4.33 ± 0.81*	20 ± 1.28*

P < 0.001.

All the values are expressed as the mean ± standard error of the mean. The mean difference is significant when compared with the ulcer control group. The data were analyzed using one-way anova with SPSS 20 software.

CMC, carboxymethyl cellulose; SOD, superoxide dismutase; MDA, malondialdehyde.

Histological evaluation of gastric lesions

HE

Histological analysis of ethanol-induced gastric mucosal lesions in the ulcer control group revealed substantial injuries to the gastric mucosa as well as edema and leukocyte infiltration into the submucosal layer. The rats pretreated with C. olitorius demonstrated significantly improved protection of the gastric mucosa with decreased total ulcer area, edema, and leukocyte infiltration into the submucosal layer (Fig. 2).

Figure 2

HE staining of the gastric tissue in rats (20×). (a) Normal control group. (b) Rats pretreated with carboxymethyl cellulose (CMC) (ulcer control). Disruption to the gastric epithelium, necrotic lesions penetrated deeply into the mucosa, extensive edema in the submucosal layer and leukocyte infiltration are apparent. (c) Rats pretreated with omeprazole (20 mg/kg). Mild disruption of the surface epithelium mucosa was present, but deep mucosal damage was absent. (d, e, f and g) The rats pretreated with 50, 100, 200, and 400 mg/kg Corchorus olitorius, respectively. There was no disruption to the surface epithelium and no edema or leukocyte infiltration into the submucosal layer.

PAS of mucosal glycoproteins

There was increased PAS staining of the gastric mucosa in the pretreated groups compared with the ulcer control group, which indicated an increase in the glycoprotein content of the gastric mucosa. However, the pretreated group showed increased PAS staining induced by ethanol, as shown in Figure 3.

Figure 3

Glycoprotein secretion (periodic acid-Schiff [PAS] staining) of the gastric tissue in rats (20×). (a) Normal control group. (b) Ulcer control group. (c) Omeprazole-treated group. (d, e, f and g) Groups pretreated with 50, 100, 200 and 400 mg/kg Corchorus olitorius extract, respectively.

Immunohistochemical evaluation

The immunohistochemical results showed that the groups pretreated with C. olitorius extract had increased Hsp70 protein expression levels. Hsp70 protein expression in the ulcer control group was lower compared with the pretreated groups (Fig. 4).

Figure 4

Immunohistochemical analysis of Hsp70 expression in the gastric mucosa of rats (20×). (a) Normal control group. (b) The ulcer control group. (c) Omeprazole-treated group. (d, e, f and g) Groups pretreated with 50, 100, 200, and 400 mg/kg plant extract, respectively.

The immunohistochemical staining of Bax demonstrated that the rats in the pretreated groups had decreased Bax protein expression. As shown in the ulcer control group, ethanol resulted in increased Bax expression, whereas the pretreatment with the plant extract decreased the expression of this protein in the pretreated groups (Fig. 5).

Figure 5

Immunohistochemical analysis of Bax expression in the gastric mucosa of rats (20×). (a) Normal control group. (b) Ulcer control group. (c) Omeprazole-treated group. (d, e, f and g) Groups pretreated with 50, 100, 200, and 400 mg/kg plant extract, respectively.

Discussion

Neither hepatic nor renal toxicity was observed upon high doses of C. olitorius. Peptic ulcers occur upon the disruption of the normal equilibrium between aggressive factors, such as acid and pepsin, and defensive mechanisms, such as mucus production, bicarbonate, mucosal turnover, and blood supply (mucosal barrier).30 Gastric lesions generated by ethanol treatment appear as multiple hemorrhagic red bands of various sizes along the glandular stomach. Ethanol is generally used for inducing ulcer formation in rats because it results in severe gastric mucosal injury. Ethanol generates necrotic lesions in the gastric mucosa by exerting irreversible toxic effects and by decreasing bicarbonates and mucus production.10–31 Omeprazole is a proton pump inhibitor that is generally used to treat gastric acid discharge32 by inhibiting acid secretion into the gastric mucosa.33 Oxidative stress plays a vital role in the pathogenesis of various ailments, including gastric ulcers, as antioxidants help to protect the gastric mucosa against necrotic agents. In this study, C. olitorius was shown to be an antioxidant. It has been suggested that the gastroprotective effect exerted by this plant could be due to its antioxidant properties, which might neutralize the oxidative injury induced by absolute ethanol toxicity. Previous studies have shown that antioxidants may be connected to antiulcer activity34 through gastroprotection.35 The results of this study also showed that the plant extract could protect the gastric mucosa as well as reduce leukocyte infiltration into the gastric wall in rats. Teprenone treatment had a protective effect against mucosal lesions36 by slowing the rate of neutrophil infiltration into ulcerated gastric tissue.37 The reduction of neutrophil infiltration into ulcerated gastric tissue prevented the development of gastric ulcers in rats. The administration of absolute alcohol may significantly harm the gastric mucosa, resulting in increased neutrophils in the gastric mucosa. Wasman et al.7 showed that oral treatment with a P. minus aqueous leaf extract prior to ethanol administration reduced neutrophil infiltration into the gastric mucosa. Moreover, the Centella asiatica leaf extract reduced neutrophil infiltration into ulcerated gastric tissue and blocked the development of gastric ulcers in rats.10,20

In the present study, we noted a flattening of the mucosal folds, which suggests that this plant could reduce gastric motility. It has been reported that modifications in gastric motility can affect the growth of experimental gastric lesions.38 A Jasminum sambac leaf extract shielded the gastric mucosa by flattening the folds.39 This flattening was suggested to increase the mucosal region exposed to necrotizing agents and decrease the quantity of gastric irritants on the rugal crest.40 This result was consistent with the gastroprotective effect of a cupper complex.31 The PAS histochemistry showed distinctive carmine staining of the stomach areas that release mucopolysaccharides. The group pretreated with 400 mg/kg C. olitorius showed high levels of mucus in the gastric glands. Mucus production is one of the major mechanisms of local gastric mucosal defense.41 Several factors are known to control ulcer prevention. Mucus and bicarbonate production may be vital for ulcer prevention because the mucus/bicarbonate layer serves to shield recently produced cells from acidic and peptic injury.42 Hsp70 is a 70-kDa protein from the heat shock protein family that is found in mammalian cells. It is the most preserved and most abundantly manufactured protein that responds to various types of stress,43 such as heat, toxic agents, infection, and proliferation.44 Bax (a pro-apoptotic protein) promotes cell death,45 whereas Bcl-2 (an anti-apoptotic protein) inhibits this process. In stress-induced ulcers, apoptosis occurs as a result of the disparity between the Bcl-2 family of anti-apoptotic proteins and the apoptotic Bax protein.46 The susceptibility of a cell to apoptosis depends on the balance between apoptosis-promoting and apoptosis-suppressing factors.47 These proteins protect cellular homeostatic processes from ecological and physiological damage by promoting the formation of standard proteins as well as either restoring or eliminating aberrantly formed proteins.48 Hsp70 proteins protect cells from oxidative stress and heat shock. Ethanol-produced reactive oxygen species usually function by reducing the expression of Hsp70 and enhancing the expression of Bax. Hsp70 prevents these partially denatured proteins from aggregating and activates pathways that allow them to refold.49 The increased expression of Hsp70 observed in this study suggests that the plant extract preserved the gastric tissues via upregulating Hsp70. Our results showed significant Hsp70 expression in the groups pretreated with C. olitorius. Hsp70 exerts its cytoprotective effects by protecting mitochondria and interfering with the stress-induced apoptotic program.50 Immunohistochemical staining of Bax in the gastric mucosa of rats pretreated with the C. olitorius extract and omeprazole showed a reduction in Bax protein levels, whereas Bax expression in the ulcer control group was increased. The immunohistochemistry results of our study were consistent with the previous study on an aqueous leaf extract of P. chinense.10 In conclusion, C. olitorius was shown to protect the gastric mucosa against ethanol-induced damage. This defense was characterized by a reduction of the area of ulcerated regions in the gastric wall and a decrease in edema and leukocyte infiltration into the submucosal layers. The rats pretreated with the plant extract showed increased Hsp70 expression and downregulated Bax expression. The increase in PAS staining of the gastric mucosa of the pretreated rats suggests an increase in glycoprotein content. C. olitorius reversed the reduction in PAS staining induced by ethanol treatment. The measurement of SOD activity and MDA levels in the gastric tissue homogenates revealed that pretreatment with this plant markedly increased SOD activity and reduced the levels of lipid peroxidation (MDA). The data corroborate the long-established anecdotes reported about this herb and provide a new therapeutic option for the treatment of gastric ailments.