Gastric lipid peroxidation, glutathione and calcium channel blockers in the stress-induced ulcer model in rats

Effect of Rumex dentatus on Gastrointestinal Protection and Toxicology in Rodents via Investigating H+/K+-ATPase, Calcium Channels, and PDE Mediated Signaling

This present study aims to delineate Rumex dentatus crude extract (Rd.Cr), n-Hexane, ethyl acetate, aqueous fractions (Rd.n-Hex, Rd.ETAC, and Rd.Aq), and emodin for antidiarrheal, antisecretory effects, anti-spasmodic, gastrointestinal transient time, anti-H. pylori, antiulcer effects, and toxicology. Plant extracts attributed dose-dependent protection against castor oil-induced diarrhea and dose-dependently inhibited intestinal fluid secretions in mice. They decreased the distance transverse by charcoal in the gastrointestinal transit model in rats. In rabbit jejunum preparations, it causes a concentration-dependent relaxation of both spontaneous and K⁺ (80 mM)-induced contraction, Rd.n-Hex and verapamil were relatively potent against K⁺-induced contractions and shifted the Ca²⁺ concentration-response curves (CRCs) to the right, Rd.Cr and Rd.ETAC shifted the isoprenaline-induced inhibitory CRCs to the left, showing potentiating effect similar to papaverine. Rd.n-Hex showed anti-H. pylori effect. Extracts and emodin also show an inhibitory effect against H⁺/K⁺-ATPase. Rumex dentatus showed a gastroprotective and antioxidant effect. Histopathological evaluation showed improvement in cellular architecture and decrease in the expression of inflammatory markers such as cyclooxygenase (COX2), tumor necrosis factor (TNF-α), and phosphorylated nuclear factor kappa B (p-NFƙB), validated through immunohistochemistry, ELISA, and western blot techniques. In RT-PCR, it decreases H⁺/K⁺-ATPase mRNA levels. Rumex dentatus was analyzed for certain safety aspects and exhibited a relative safety profile as no impairment was observed in kidneys, heart, liver, and brain further assisted by biochemical and hematological analysis. Docking studies revealed that emodin against H⁺/K⁺-ATPase pump and voltage gated L-type calcium channel showed E-value of −7.9 and −7.4 kcal/mol, respectively. MD simulations and molecular mechanics Poisson Boltzmann surface area and molecular mechanics Generalized Born surface area MMPBSA/GBSA findings are consistent with the in-vitro, in-vivo, and docking results. In conclusion, Rumex dentatus extracts and its phytoconstituent could be considered a potent antioxidant and anti-inflammatory drug candidates that possess anti-diarrheal, anti-secretary, antispasmodic, anti-H. pylori, and anti-ulcer potential. Toxicity studies were done according to OECD standards 425. It belongs to group 5 (LD50 > 2000 mg/kg), which suggests that it is in the lower toxicity class.

Anti-ulcerogenic effect of methanolic extract of Elaeagnus conferta Roxb. seeds in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Elaeagnus conferta Roxb. (Elaeagnaceae) is a subtropical shrub mainly native to India, Vietnam, Malaysia and South China, whose various parts are used for treatment of diabetes, gastric ulcers, pain, oxidative stress and pulmonary disorders. Though the other parts of the plant have been reported for their ethnic use i.e. fruits as astringent locally and for cancer systemically, leaves for body pain and flowers for pain in chest and the seeds are mentioned as edible, there is no report per se on the medicinal use of seeds. Based on the fact that seeds of closely resembling species i.e. Elaeagnus rhamnoides has demonstrated significant anti-gastroulcerative property, the probability of the seeds of E. conferta possessing similar activity seemed quite significant.

AIM OF THE STUDY

Phytochemical investigation and assessment of pharmacological mechanism(s) involved in anti-ulcer effect of methanolic extract of the seeds of E. conferta.

MATERIALS AND METHODS

Bioactive phytoconstituents were isolated by column chromatography. These were identified by spectroscopic techniques including infrared (IR) spectroscopy, nuclear magnetic resonance (NMR) and mass spectrometry. Methanolic extract (MEC) of the seeds was prepared by cold maceration and its anti-ulcerogenic potential was evaluated using indomethacin (50 mg/kg) and water immersion stress models in male rats. The animals were pre-treated with different doses of MEC (400 and 800 mg/kg) and the therapeutic effect was compared with standard drug i.e. ranitidine (RANT; 50 mg/kg). The ameliorative effects of MEC were investigated on gastric juice pH, total acidity, free acidity and ulcer index. The assays of malionaldehyde (MDA), catalase (CAT), superoxide dismutase (SOD), glutathione (GSH) and pro-inflammatory cytokines i.e. interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α) were carried out to find out the possible mechanism(s) of protection. Further, histopathological changes were also studied.

RESULTS

Chromatography studies and further confirmation by spectroscopic techniques revealed the presence of four different compounds in MEC i.e oleic acid (1), stearic acid (2), ascorbic acid (3) and quercetin (4). MEC exhibited anti-ulcerogenic effect in dose dependent manner which may be attributed to suppression of pro-inflammatory cytokines (IL-6, TNF-α) and MDA (112.7%), and up-regulation of protective factors such as CAT (90.48%), SOD (92.77%) and GSH (90.01%). Ulcer inhibition, reduction in total and free acidity and increase in gastric juice pH were observed in MEC treated rats as compared to disease control animals. Histopathological findings confirmed decreased cell infiltration, less epithelial cell damage and regeneration of gastric mucosa in dose dependent manner.

CONCLUSIONS

The anti-ulcer effect of MEC may be attributed to its ability to scavenge free radicals and anti-inflammatory property via suppression of TNF-α and IL-6, thus offers a complete and holistic approach for management of peptic ulcer.

Antisecretory, antioxidative and antiapoptotic effects of montelukast on pyloric ligation and water immersion stress induced peptic ulcer in rat

In the present study, we tried to explore the mechanism of montelukast as an antiulcerogenic agent in pyloric ligation (PL) and water immersion stress (WIS) induced peptic ulcer. The ameliorative effects of montelukast (5, 10, and 20 mg/kg, p.o.) on gastric volume and total acidity were studied in PL model. We have investigated the alteration in the ulcerative index, thiobarbituric acid reactive substances, reduced glutathione, activity of myeloperoxidase, and total calcium level in both models. Estimation of DNA fragmentation by gel electrophoresis was also performed. Medium and higher doses of montelukast showed significant (p<0.05) ameliorative potential on all the above parameters as compared with omeprazole treated group. DNA fragmentation pattern clearly indicated the antiapoptotic effect of montelukast in preventing mucosal erosion in both models. Hence, the gastroprotective effect of montelukast may be attributed to its antisecretory, antioxidative along with its antiapoptotic effect.

Effects of Bidens pilosa L. var. radiata Scherff on experimental gastric lesion

Bidens pilosa L. var. radiata Scherff: (BP) is a plant used as a traditional folk medicine. BP, cultivated with only green manure on Miyako Island, Okinawa prefecture, was processed to powder and is referred to as MMBP. We have reported that MMBP has antioxidant, anti-inflammatory, and anti-allergy properties. In this study, we investigated the effects of MMBP on several experimental gastric lesions induced by HCl/EtOH, a non-steroidal anti-inflammatory drug, or cold-restraint stress, comparing these results with those of rutin or anti-ulcerogenic drugs (cimetidine or sucralfate) based on the lesion index and hemorrhage from the gastric lesions. Orally administered MMBP prevented the progression of the gastric lesions. Moreover, treatment with MMBP, rutin, or sucralfate, which had potent antioxidative activity, inhibited increases in the levels of thiobarbituric acid reactive substances (TBARS) in the gastric mucosal lesions. The inhibition of the gastric mucosal TBARS content by MMBP may have been due to the antioxidant effects of MMBP. These results indicate that MMBP prevents the progression of acute gastric mucosal lesions, possibly by suppressing oxidative stress in the gastric mucosa.

Mechanism of the beneficial effects of dantrolene sodium on ethanol-induced acute gastric mucosal injury in rats

In our study, we examined anti-ulcerogen and antioxidant effects of dantrolene sodium on ethanol-induced gastric lesions in rats. Dantrolene sodium was administered intraperitoneally (i.p.) in several doses, and famotidine was used at a dose of 20 mg kg (-1). It was found that pretreatment with dantrolene sodium at doses of 1, 5 and 10 mg kg(-1) significantly reduced ethanol-induced gastric damage and malondialdehyde levels, and significantly increased antioxidant enzymes superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities. We conclude that dantrolene sodium clearly has antioxidant properties and that the protective effect of dantrolene sodium against ethanol-induced gastric mucosal lesion, at least in part, depends upon the reduction in the lipid peroxidation and an increase in the activity of antioxidant enzymes SOD and GSH-Px.

Chloroacetonitrile (CAN) induces glutathione depletion and 8-hydroxylation of guanine bases in rat gastric mucosa

Chloroacetonitrile (CAN) is detected in drinking-water supplies as a by-product of the chlorination process. Gastroesophageal tissues are potential target sites of acute and chronic toxicity by haloacetonitriles (HAN). To examine the mechanism of CAN toxicity, we studied its effect on glutathione (GSH) homeostasis and its impact on oxidative DNA damage in gastric mucosal cells of rats. Following a single oral dose (38 or 76 mg/Kg) of CAN, animals were sacrificed at various times (0-24 h), and mucosa from pyloric stomach were collected. The effects of CAN treatment on gastric GSH contents and the integrity of genomic gastric DNA were assessed. Oxidative damage to gastric DNA was evaluated by measuring the levels of 8-Hydroxydeoxyguanosine (8-OHdG) in hydrolyzed DNA by HPLC-EC. The results indicate that CAN induced a significant, dose- and time-dependent, decrease in GSH levels in pyloric stomach mucosa at 2 and 4 hours after treatment (56 and 39% of control, respectively). DNA damage was observed electrophoretically at 6 and 12 hours following CAN administration. CAN (38 mg/Kg) induced significant elevation in levels of 8-OHdG in gastric DNA. Maximum levels of 8-OHdG in gastric DNA were observed at 6 hours after CAN treatment [9.59+/-0.60 (8-OHdG/10(5)dG) 146% of control]. When a high dose of CAN (76 mg/Kg) was used, a peak level of 8-OHdG [11.59+/-1.30 (8-OHdG/10(5)dG) 177% of control] was observed at earlier times (2 h) following treatment. When CAN was incubated with gastric mucosal cells, a concentration-dependent cyanide liberation and significant decrease in cellular ATP levels were detected. These data indicate that a mechanism for CAN-induced toxicity may be partially mediated by depletion of glutathione, release of cyanide, interruption of the energy metabolism, and induction of oxidative stress that leads to oxidative damage to gastric DNA.

Induction of oxidative stress and TNF-alpha secretion by dichloroacetonitrile, a water disinfectant by-product, as possible mediators of apoptosis or necrosis in a murine macrophage cell line (RAW)

The water disinfectant by-product dichloroacetonitrile (DCAN) is a direct-acting mutagen and induces DNA strand breaks in cultured human lymphoblastic cells. Cellular activation by environmental agents may exert detrimental effects to the cells. Activated macrophages produce reactive oxygen intermediates such as H(2)O(2), (-)OH and O(2). Therefore, the effect of various concentrations of DCAN (100-400 microM) on the activity macrophage cells (RAW 264.7) was studied. In these cells, DCAN-induced oxidative stress was characterized by the production of reactive oxygen intermediates (ROI). Also, the ratios of intracellular GSH/GSSG was assessed and used as a biomarker for oxidative stress. The secretion of TNF-alpha was assessed since macrophages are known to secrete TNF-alpha as a result of cellular oxidative stress. Electrophoretic detection of DNA degradation and light microscopy was utilized for the characterization of DCAN-induced apoptosis. Lactate dehydrogenase (LDH) leakage and trypan blue exclusion were used as markers of cellular necrosis. Following exposure to DCAN (200 microM and 400 microM), intracellular GSSG was increased (2.5-fold of control, P<0. 05). DCAN activation of RAW cells was detected by elevated levels of intracellular ROI (1.9-2.5-fold than control, P<0.05) and increased secretion of TNF-alpha (4.5 fold-than control, P <0.05). Elecrophoresis of genomic DNA of treated cells indicated a dose-dependent increase in degradation of genomic DNA. Morphological studies also indicated that exposure of RAW cells to 100 microM or 200 microM DCAN incites apoptotic cell death. At higher concentrations (400 microM), however, significant (P<0.05) increase in LDH leakage and decrease in cell viability (55% of control) indicative of cellular necrosis, were observed. These studies indicate that DCAN induces dose-dependent apoptosis or necrosis in RAW cells that could be due to the disturbance in intracellular redox status and initiation of ROI-mediated oxidative mechanisms of cellular damage.