Background and Aims: COX-2 enzyme inhibition is responsible for the anti-inflammatory effects of NSAIDs, COX-1 for their effects upon the gastrointestinal system (GIS), along with other side effects. We investigated the relationship between COX levels and those adrenergic receptors known to play a role in gastroprotection and anti-inflammatory activity. Method: The effects of adrenaline and prednisolone on gastric COX-1 and COX-2 levels in both intact and adrenalectomized rats treated with doxazosin, yohimbine, propranolol, and metoprolol were determined. Results: We found that adrenaline increases COX-1 levels in the gastric tissue of both intact and adrenalectomized rats by stimulating -2 receptors. Adrenaline decreases COX-2 levels by stimulating ß-2 adrenergic receptors. Prednisolone inhibits both COX-1 and COX-2 in the gastric tissue of intact rats. In adrenalectomized rats, prednisolone increases gastric COX-1 by stimulating -2 receptors, and decreases COX-2 levels by stimulating ß-2 receptors. Conclusion: Prednisolone cannot bind to a adrenergic receptors in the presence of adrenaline (intact rats) but, in its absence (adrenalectomy), binds to -2 receptors, and stimulates them more effectively than adrenaline, suggesting a direct relationship between -2 adrenergic receptors and COX-1 levels, whereas ß-2 receptors are directly related to COX-2 levels.
The purpose of this paper is to overview the relations between plant-originated substances and their bioactivity measured in terms of antioxidant, cytoprotective and antiulcer activities. In addition, we assessed whether these compounds are capable of affecting the gastric mucosal lesions induced by absolute ethanol applied intragastrically (i.g.). The following plant-originated flavonoid substances were considered; Solon (Sophoradin extract), Amaranth seed extract, grapefruit-seed extract (GSE) and capsaicin (extract of chilly pepper). The area of gastric mucosa lesions and gastric blood flow were measured in rats with ethanol-induced lesions without (control) and with one of the tested substances without and with capsaicin denervation of afferent nerves or administration of L-nitro-arginine (L-NNA), an inhibitor of nitric oxide synthase (NOS). Male Wistar rats, weighing 180-220 g fasted for 24 h before the study where used 100% ethanol was applied i.g. to induce gastric lesions, whose area was determined by planimetry. Gastric blood flow was assessed using electrolytic regional blood flowmeter. All tested plant-originated substances afforded gastroprotection against ethanol-induced damage and this was accompanied by increase in gastric microcirculation, both changes being reversed by pretreatment with neurotoxic dose of capsaicin or by pretreatment with L-NNA. We conclude that plant-originated flavonoid substances are highly gastroprotective probably due to enhancement of the expression of constitutive NOS and release of NO and neuropeptides such as calcitonin gene related peptide (CGRP) released from sensory afferent nerves increasing gastric microcirculation.
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Previous studies have shown that stimulation of cannabinoid 1 (CB1) receptor protects the gastric mucosa against stress-induced lesion. Aim of the present study was to examine the influence of anandamide on lipid peroxidation and antioxidant defense system in gastric mucosa and the role of sensory nerves in gastroprotective effects of cannabinoids. Studies were performed on rats with intact or ablated sensory nerves (by neurotoxic doses of capsaicin). Gastric lesions were induced by water immersion and restrain stress (WRS). Anandamide was administered at the dose of 0.3, 1.5 or 3.0 µmol/kg, 30 min before exposure to WRS. CB1 receptor antagonist, AM251 (4.0 µmol/kg) was administered 40 min before WRS. WRS induced gastric lesions associated with the decrease in gastric blood flow, mucosal DNA synthesis and mucosal activity of superoxide dismutase (SOD). Serum level of interleukin-1ß (IL-1ß) and mucosal level of malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) were increased. Administration of anandamide reduced the ulcers area, generation of MDA+4-HNE and serum level of IL-1ß, and this effect was associated with the reduction in the WRS-induced decrease in gastric mucosal blood flow, mucosal DNA synthesis and SOD activity. Ablation of sensory nerves increased the area of ulcers, serum level of IL-1ß and mucosal content of MDA+4-HNE, whereas mucosal DNA synthesis, SOD activity and blood flow were additionally decreased. In rats with ablation of sensory nerves, administration of anandamide at the high doses (1.5 and 3.0 µmol/kg) partly reduced deleterious effect of WRS on gastric mucosa, but this effect was weaker than in animals with intact sensory nerves. Low dose of anandamide (0.3 µmol/kg) was ineffective in the protection of gastric mucosa against the WRS-induced lesions in rats with ablation of sensory nerves. In rats with intact sensory nerves and exposed to WRS, administration of AM251 exhibited deleterious effect. In rats with ablation of sensory nerves and exposed to WRS, AM251 failed to affect mucosal injury in the stomach. We conclude that anandamide reduces the mucosal oxidative stress and exhibits gastroprotective effect against WRS-induced ulcers. These effects are partly mediated by sensory nerves.
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