Effect of nitric oxide in protective effect of melatonin against chronic constriction sciatic nerve injury induced neuropathic pain in rats

Developing a successful treatment strategy for neuropathic pain has remained a challenge among researcher and clinicians. Various animal models have been employed to understand the pathogenic mechanism of neuropathic pain in experimental animals. The present study was designed to explore the possible nitric oxide mechanism in the protective effect of melatonin against chronic constriction injury (CCI) of sciatic nerve in rats. Following chronic constriction injury, various behavioral tests (thermal hyperalgesia, cold allodynia) and biochemical parameters (lipid peroxidation, reduced glutathione, catalase, and nitrite) were assessed in sciatic nerves. Drugs were administered for 21 consecutive days from the day of surgery. CCI significantly caused thermal hyperalgesia, cold allodynia and oxidative damage. Chronic administration of melatonin (2.5 or 5 mg/kg, ip) significantly attenuated hyperalgesia, cold allodynia and oxidative damage in sciatic nerves as compared to CCI group. Further, L-NAME (5 mg/kg) pretreatment with sub-effective dose of melatonin (2.5 mg/kg, ip) significantly potentiated melatonin's protective effect which was significant as compared to their individual effect per se. However, L-arginine (100 mg/kg) pretreatment with melatonin (2.5 mg/kg, ip) significantly reversed its protective effects. Results of the present study suggest the involvement of nitric oxide pathway in the protective effect of melatonin against CCI-induced behavioral and biochemical alterations in rats.     

Possible nitric oxide modulation in protective effect of (Curcuma longa, Zingiberaceae) against sleep deprivation-induced behavioral alterations and oxidative damage in mice

Sleep is essential for the physical and mental health of a human being. Problems of sleep deprivation are increasing in modern society nowadays. Recently, various antioxidants have been implicated as neuroprotectants in the treatment of stress and stress related problems. The present study was designed to explore the possible role of nitric oxide in the protective effect of Curcumin (Curcuma longa, Zingiberaceae) against 72-h sleep deprivation-induced behavioral alterations and oxidative damage in mice. 72-h sleep deprivation significantly caused weight loss, anxiety like behavior, impaired locomotor activity and oxidative damage (increased lipid peroxidation, nitrite level and deplete glutathione and catalase activity) in animals. Treatment with Curcumin extract (10 and 20 mg/kg, ip) for 5 days significantly prevented weight loss, impairment in locomotor activity, anxiety like effects in all behavioral paradigms tasks (mirror chamber, plus maze, zero maze) as compared to control (72-h sleep-deprived) (P<0.05). Biochemically, Curcumin extract treatment significantly restored depleted reduced glutathione, catalase activity, attenuated raised lipid peroxidation and nitrite level as compared to control (72-h sleep-deprived) animals. Further, pretreatment of l-arginine (50 mg/kg, ip), nitric oxide precursor reversed the protective effect of Curcumin (10 mg/kg, ip) (P<0.05). However, pretreatment of l-NAME (5 mg/kg, ip), nitric oxide synthase inhibitor caused a potentiation in the protective effect of Curcumin (P<0.05). The present study suggests that nitric oxide modulation is involved in the protective effect of Curcumin in ameliorating sleep deprivation-induced behavioral alterations and oxidative damage.     

Possible nitric oxide mechanism in the protective effect of hesperidin against ischemic reperfusion cerebral injury in rats

Stroke is the third leading cause of death and disability around the globe. The aim of the present investigation was to evaluate the protective effect of hesperidin and its nitric oxide mechanism against cerebral ischemia reperfusion injury. Bilateral common carotid artery occlusion for 30 min followed by 24 h reperfusion was given to induce ischemia in rats. Animals were pretreated with hesperidin (50 and 100 mg/kg, po) for 7 days. Various behavioural tests, oxidative stress parameters, endogenous antioxidant system, antioxidant enzyme activity and mitochondrial enzyme complex (I, II, III and IV) dysfunctions in cortex and striatum were assessed subsequently. Hesperidin (50 and 100 mg/kg) significantly improved neurobehavioral alterations (neurological score, locomotor activity, resistance to lateral push and hanging wire latency), attenuated oxidative damage, restored antioxidant and mitochondrial complex enzyme activities in cortex and in striatum regions of the brain as compared to their respective controls. L-arginine (100 mg/kg) or L-NAME (10 mg/kg) pretreatment with lower dose of hesperidin (50 mg/kg) significantly reversed or potentiated its protective effect, respectively which was significant as compared to hesperidin (50 mg/kg). The results highlight the involvement of nitric oxide mechanism in the protective effect of hesperidin against ischemia reperfusion injury induced alterations.     

Endothelium-derived relaxing factor (nitric oxide) has protective actions in the stomach

The role that nitric oxide, an endothelium-derived relaxing factor, may play in the regulation of gastric mucosal defence was investigated by assessing the potential protective actions of this factor against the damage caused by ethanol in an ex vivo chamber preparation of the rat stomach. Topical application of glyceryl trinitrate and sodium nitroprusside, which have been shown to release nitric oxide, markedly reduced the area of 70% ethanol-induced hemorrhagic damage. Topical application of a 0.01% solution of authentic nitric oxide also significantly reduced the severity of mucosal damage. Pretreatment with indomethacin precluded the involvement of endogenous prostaglandins in the protective effects of these agents. The protective effects of NO were transient, since a delay of 5 minutes between NO administration and ethanol administration resulted in a complete loss of the protective activity. The protection against ethanol afforded by 10 micrograms/ml nitroprusside could be completely reversed by intravenous infusion of either 1% methylene blue or 1 mM hemoglobin, both of which inhibit vasodilation induced by nitric oxide. Intravenous infusion of 1% methylene blue significantly increased the susceptibility of the mucosa to damage induced by topical 20% ethanol. These results indicate that ethanol-induced gastric damage can be significantly reduced by nitric oxide. The mechanisms underlying the protective actions of nitric oxide are unclear, but may be related to its vasodilator or anti-aggregatory properties.     

Protective effect of tetrahydroxystilbene glucoside on 6-OHDA-induced apoptosis in PC12 cells through the ROS-NO pathway

Oxidative stress plays an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson's disease. The molecule, 2,3,5,4'-tetrahydr- oxystilbene-2-O-β-D-glucoside (TSG), is a potent antioxidant derived from the Chinese herb, Polygonum multiflorum Thunb. In this study, we investigated the protective effect of TSG against 6-hydroxydopamine-induced apoptosis in rat adrenal pheochromocytoma PC12 cells and the possible mechanisms. Our data demonstrated that TSG significantly reversed the 6-hydroxydopamine-induced decrease in cell viability, prevented 6-hydroxydopamine-induced changes in condensed nuclei and decreased the percentage of apoptotic cells in a dose-dependent manner. In addition, TSG slowed the accumulation of intracellular reactive oxygen species and nitric oxide, counteracted the overexpression of inducible nitric oxide syntheses as well as neuronal nitric oxide syntheses, and also reduced the level of protein-bound 3-nitrotyrosine. These results demonstrate that the protective effects of TSG on rat adrenal pheochromocytoma PC12 cells are mediated, at least in part, by the ROS-NO pathway. Our results indicate that TSG may be effective in providing protection against neurodegenerative diseases associated with oxidative stress.     

Prenatal bupropion exposure enhances the cocaine reward and stress susceptibility in adult mice

Although a growing body of evidence supports the notion that certain antidepressant treatments in pregnancy produce earlier delivery and minor behavioral teratogenesis in infants, the long-term effects of such treatments in adulthood remain ill-defined. Recently, postnatal exposure to psychotropic drugs was found to affect the emotional development and susceptibility to abused drugs. Thus, this study aimed to examine whether prenatal exposure of four frequently-used antidepressants, bupropion, fluvoxamine, citalopram, and trazodone, altered the responsiveness to stress and cocaine in the adulthood. Dams received daily injection of bupropion (25 or 12.5 mg/kg), citalopram (5 mg/kg), fluvoxamine (10 mg/kg), trazodone (20 mg/kg) or saline throughout their third trimester of gestation, and several birth outcome indices were then examined. Locomotor activity, naive anxiety levels, and the sensitivity to the cocaine reinforcing effects were observed in pups at their day 56-60 post partum. We found that trazodone treatment produced a high mortality rate in pups after weaning. Mice, prenatally treated with bupropion at 25 mg/kg, exhibited lower rearing numbers and ambulatory activity as compared to the saline-treated mice. More importantly, such treatment enhanced the mouse sensitivity to the reinforcing effects of cocaine. Taken together, these results suggest that use of bupropion in the late pregnancy may run a risk of enhancing the offspring's susceptibility to stress and cocaine reward in adulthood.     

Salicylic acid and nitric oxide alleviate osmotic stress in wheat (Triticum aestivum L.) seedlings

Salicylic acid (SA) and nitric oxide (NO) are reported to alleviate the damaging effects of stress in plants rather similarly when applied at appropriate low concentrations. An experiment was therefore conducted to study the impact of SA, sodium nitroprusside (SNP; as NO donor), and methylene blue (MB; as a guanylate cyclase inhibitor) on wheat seedling performance under osmotic stress. Osmotic stress significantly reduced shoot fresh weight (SFW), chlorophyll contents (Chla, Chlb, total Chl), and membrane stability index (MSI) and also increased malondialdehyde (MDA) level, lipoxygenase (LOX) activity, and hydrogen peroxide production. Moreover, enzymatic antioxidant activities including superoxide dismutase, guaiacol peroxidase, and glutathione reductase activity were enhanced under osmotic stress. On the contrary, SA or SNP pretreatment reduced the damaging effects of osmotic stress by further enhancing the antioxidant activities that led to increased SFW, Chl, and MSI and reduced MDA level and LOX activity. However, pretreatment of plants with MB reversed or reduced the protective effects of SA and SNP suggesting that the protective effects were likely attributed to NO signaling. Therefore, NO may act as downstream of SA signaling in reduction of induced oxidative damage in wheat seedlings.     

Protective effect of endothelial nitric oxide synthase against induction of chemically-induced diabetes in mice.

Since activation of endothelial nitric oxide synthase has been shown to exert protective effects against the metabolic syndrome, while endothelial nitric oxide synthase knockout mice develop hyperinsulinemia and glucose intolerance, we hypothesised that endothelial nitric oxide might play a protective role against induction of diabetes. The role of endothelial nitric oxide in the development of chemically-induced diabetes has been determined using mice in which the bioavailability of endothelial nitric oxide was either increased, through upregulation of endothelial nitric oxide synthase, or absent, through deletion of endothelial nitric oxide synthase gene. Diabetes was induced intraperitoneally with either a single dose of alloxan, streptozotocin, or multiple low doses of streptozotocin and blood glucose monitored twice a week. The role of cyclic guanosine monophosphate was investigated in wildtype mice by treatment with the phosphodiesterase inhibitor, tadalafil, during diabetes induction. Results showed that the incidence of diabetes was markedly decreased in mice overexpressing endothelial nitric oxide synthase, compared to wildtype or endothelial nitric oxide synthase knockout mice, regardless of the method of diabetes induction. Under normal physiological conditions, or during diabetes induction with alloxan or multiple low doses of streptozotocin, blood glucose was significantly lower in mice overexpressing endothelial nitric oxide synthase compared to wildtype or knockout mice. Treatment with tadalafil had no effect on the incidence or severity of diabetes in wildtype mice. We conclude that upregulation of endothelial nitric oxide synthase exerts a protective action against diabetes induction through a direct effect of nitric oxide, independently of cyclic guanosine monophosphate.     

Inhibition of endogenous CO by ZnPP protects against stress-induced gastric lesion in adult male albino rats

Carbon monoxide (CO) has been found to be produced in every living cell in a biochemical reaction catalyzed by heme-oxygenase (HO) enzyme which degrades heme into biliverdin, CO, and iron. Endogenous CO is not a waste product, but acts as a chemical messenger mediating and modulating many intracellular biochemical reactions that regulate physiological functions. This study was designed to investigate the effect of inhibition of endogenous CO production by zinc protoporphyrin (ZnPP), an HO inhibitor, on the gastric secretion and ulceration induced by cold-restraint stress (CRS) in adult male albino rats. Rats were pylorically ligated and divided randomly into the following groups (six rats each): control, ZnPP treated (50 μmol/kg/day, s.c. for 10 days), CRS, and stressed ZnPP treated groups. Blood samples were collected from the retro-orbital sinus of anesthetized rats for determination of CO concentration. We found that ZnPP pretreatment significantly decreased HO-1 level, CO level, and volume of gastric juice as compared to the control non-stressed rats. In the present study, ZnPP pretreatment proved to be protective against development of ulcerative lesions in CRS model as evidenced by reduction of the ulcer index, and this could be mediated through reduction of free and total acidity of gastric secretion and decreased lipid peroxidation but with significantly decreased gastric protective nitric oxide and prostaglandin E(2) levels. In conclusion and according to our results, the protective effect of ZnPP on CRS-induced gastric ulcers despite of inhibition of endogenous CO could be attributed to the presence of zinc which is known to have a protective anti-ulcer effect.     

The effect of alpha-melanocyte stimulating hormone on colonic inflammation in the rat

The effect of alpha-melanocyte stimulating hormone (alpha-MSH) on colonic inflammation in the rat. In this study, we investigated the effects of alpha-MSH administration on trinitrobenzene sulfonic acid-induced colitis and the role of nitric oxide and prostaglandins in this response. alpha-MSH treatment (25 microg/rat, intraperitoneally; twice daily for 3 days) reduced the colonic macroscopic lesions compared to untreated ones in both acute and chronic colitis groups. This effect was reversed by pretreatment with the nitric oxide donor, sodium NP (4 mg/kg, intravenously) or cyclooxygenase-1 selective antagonist indomethacin (5 mg/kg, subcutaneously) in the acute group and with the cyclooxygenase-2 selective antagonist nimesulide (3 mg/kg, subcutaneously) in the chronic group. alpha-MSH had no effect on colonic wet weight and myeloperoxidase activity compared to the untreated colitis group. However, protein oxidation was markedly elevated in the alpha-MSH-treated group compared to untreated ones. Nitroprusside and indomethacin reversed the effect of alpha-MSH on macroscopic lesions in the acute groups, whereas nimesulide showed a similar effect in the chronic group. In conclusion, the results of our study show a protective role of alpha-MSH on colonic lesions which partially involves nitric oxide and prostaglandins.     

Protection of Human Keratinocyte mtDNA by Low-Level Nitric Oxide

This study was designed to evaluate the DNA damaging effects of nitric oxide and to determine whether the endogenous generation of nitric oxide at low levels in the cell exerts a protective effect against this damage. Damage to mitochondrial and nuclear DNA in normal human epidermal keratinocytes (NHEK) was assessed after treatment of these cells with varying concentrations of S-nitroso-N-acetylpenicillamine, which decomposes to release nitric oxide. The results showed that mitochondrial DNA was more vulnerable to nitric oxide-induced damage than was a similarly sized fragment of the beta-globin gene. To evaluate the effects on DNA damage by pretreatment of cells with low-levels of nitric oxide, NHEK cells were treated with the prodrug V-PYRRO/NO. This agent is metabolized inside these cells and releases small quantities of nitric oxide. The cells then were exposed to damaging amounts of nitric oxide produced by S-nitroso-N-acetylpenicillamine. The results of these studies showed that pretreatment of NHEK cells with V-PYRRO/NO attenuated the mtDNA damage and loss of cell viability produced by exposure to S-nitroso-N-acetylpenicillamine.     

The effect of alpha-melanocyte stimulating hormone on endotoxin-induced intestinal injury.

We investigated the effect of alpha-melanocyte stimulating hormone (alpha-MSH) on endotoxin-induced intestinal inflammation and the role of nitric oxide and prostaglandins in this response. alpha-MSH treatment (25 microg/rat, intraperitoneally (i.p.); twice daily) reduced the severity of the lesions macroscopically and microscopically. This protective effect was found to be confined mainly to the distal ileum. These lesions were reversed by pretreatment with the non-selective COX inhibitor indomethacin (10 mg/kg, subcutaneously (s.c.)) but not by the selective COX-2 inhibitor nimesulide (3 mg/kg, s.c.), the NO donor sodium nitroprusside (4 mg/kg, i.v.) or the iNOS inhibitor dexamethasone (3 mg./kg, i.p.) at macroscopic level and reversed by Indo or Dex at microscopic level. Increased peroxidase activity -index of tissue neutrophil infiltration- in the distal ileum of LPS-treated rats was decreased by alpha-MSH and this effect was reversed by pretreatment with Indo. In conclusion, the neuropeptide alpha-MSH has a beneficial effect on endotoxin-induced distal intestinal lesions by a mechanism which probably involves nitric oxide and COX-1 derived prostaglandins.     

Neuroprotective effects of non-steroidal anti-inflammatory drugs by direct scavenging of nitric oxide radicals

Recently, it has been reported that inflammatory processes are associated with the pathophysiology of Alzheimer's disease and that treatment of non-steroidal anti-inflammatory drugs reduce the risk for Alzheimer's disease. In the present study, we examined nitric oxide radical quenching activity of non-steroidal anti-inflammatory drugs and steroidal drugs using our established direct in vitro nitric oxide radical detecting system by electron spin resonance spectrometry. The non-steroidal anti-inflammatory drugs, aspirin, mefenamic acid, indomethacin and ketoprofen directly and dose-dependently scavenged generated nitric oxide radicals. In experiments of nitric oxide radical donor, NOC18-induced neuronal damage, these four non-steroidal drugs significantly prevented the NOC18-induced reduction of cell viability and apoptotic nuclear changes in neuronal cells without affecting the induction of inducible nitric oxide synthase-like immunoreactivity. However, ibuprofen, naproxen or steroidal drugs, which had less or no scavenging effects in vitro, showed almost no protective effects against NOC18-induced cell toxicity. These results suggest that the protective effects of the former four non-steroidal anti-inflammatory drugs against apoptosis might be mainly due to their direct nitric oxide radical scavenging activities in neuronal cells. These direct NO. quenching activities represent novel effects of non-steroidal anti-inflammatory drugs. Our findings identified novel pharmacological mechanisms of these drugs to exert not only their anti-inflammatory, analgesic, antipyretic activities but also neuroprotective activities against neurodegeneration.     

Isoliquiritigenin isolated from licorice Glycyrrhiza uralensis prevents 6-hydroxydopamine-induced apoptosis in dopaminergic neurons

Licorice (Glycyrrhiza uralensis) is a medicinal herb containing various bioactive components implicated in antioxidative, anti-inflammatory, antiviral, and neuroprotective effects, but the effects of licorice against Parkinson's disease (PD)-related dopaminergic cell death have not been studied. In this study, we investigated the protective effects of isoliquiritigenin (ISL) isolated from Glycyrrhiza uralensis on 6-hydroxydopamine (6-OHDA)-induced neurotoxicity in a dopaminergic cell line, SN4741. ISL (1 μM) significantly attenuated 6-OHDA (50 μM)-induced reactive oxygen species (ROS) and nitric oxide (NO) generation and apoptotic cell death. ISL pretreatment effectively suppressed 6-OHDA-mediated upregulation of Bax, p-c-Jun N-terminal kinase (JNK), p-p38 mitogen-activated protein (MAP) kinase, cytochrome c release, and caspase 3 activation. In addition, ISL significantly attenuated 6-OHDA-induced Bcl-2, brain-derived neurotrophic factor (BDNF), and mitochondrial membrane potential (MMP) reduction. Pharmacological inhibitors of the phosphatidylinositol 3-kinase (PI3K)-Akt/protein kinase B (PKB) pathway reversed ISL-mediated neuroprotection against 6-OHDA toxicity in SN4741 cells. These results provide the first evidence that ISL can protect dopaminergic cells under oxidative stress conditions by regulating the apoptotic process.     

Nitric oxide acts as a signal molecule in microwave pretreatment induced cadmium tolerance in wheat seedlings

The microwave has been widely used in the field of biology with the development of microwave technology. Previous studies suggest that suitable doses of microwave irradiation improved plant metabolism and enzymatic activities under cadmium stress and enhanced cadmium tolerance in wheat seedlings. The objective of this study was to test whether nitric oxide is involved in microwave pretreatment induced cadmium tolerance in wheat seedlings due to its nature as a second messenger in stress responses. Plant were treated with 10 s microwave pretreatment, microwave pretreatment in combination with NO scavenger, 2-(4-carboxyphenyl)-4, 4,5,5-tetramethylimidazoline-1-oxyl-3-oxide (cPTIO) and their effects on the lipid peroxidation, the activities of antioxidant enzymes, the concentration of antioxidant compounds and wheat seedlings growth and development were compared. The results showed that 10 s microwave pretreatment dramatically alleviated growth suppression induced by cadmium stress, reflected by decreased malondialdehyde, hydrogen peroxide and superoxide radical production. Furthermore, the activities of antioxidant enzymes (superoxide dismutase, peroxidase, catalase, ascorbate peroxidase and glutathione reductase) and the concentration of antioxidant metabolites (ascorbate, reduced glutathione, carotenoids and nitric oxide) were increased in wheat seedlings pretreated with microwave under cadmium stress. Nevertheless, the promotive effect of microwave pretreatment induced cadmium tolerance in wheat seedlings was effectively reversed by the addition of 0.5 % (w/v) cPTIO (NO scavenger), suggesting that NO was involved in microwave pretreatment induced cadmium tolerance in wheat seedlings.     

Protective effect of l-ascorbic acid on nickel induced pulmonary nitrosative stress in male albino rats

Nickel sulfate stimulates inducible nitric oxide synthase (i-NOS) and increases serum nitric oxide concentration by overproduction of reactive nitrogen species due to nitrosative stress. The present study was undertaken to assess possible protective role of l-ascorbic acid as an antioxidant against nickel induced pulmonary nitrosative stress in male albino rats. We studied the effect of the simultaneous treatment with l-ascorbic acid (50 mg/100 g b. wt.; orally) and nickel sulfate (2.0 mg/100 g b. wt.; i.p.) on nitric oxide synthesis by quantitative evaluation of serum i-NOS activities, serum and lung nitric oxide, l-ascorbic acid and protein concentrations of Wister strain male albino rats. We have further studied histopathological changes in lung tissue after nickel sulfate treatment along with simultaneous exposure of l-ascorbic acid. Nickel sulfate treatment significantly increased the serum i-NOS activity, serum and pulmonary nitric oxide concentration and decreased body weight, pulmonary somatic index, serum and lung l-ascorbic acid and protein concentration as compared to their respective controls. Histopathological changes induced by nickel sulfate showed loss of normal alveolar architecture, inflammation of bronchioles, infiltration of inflammatory cells and patchy congestion of alveolar blood vessels. The simultaneous administration of l-ascorbic acid and nickel sulfate significantly improved all the above biochemical parameters along with histopathology of lung tissues of rats receiving nickel sulfate alone. The study clearly showed a protective role of l-ascorbic acid against nickel induced nitrosative stress in lung tissues.     

Effect of plantain banana on gastric ulceration in NIDDM rats: role of gastric mucosal glycoproteins, cell proliferation, antioxidants and free radicals

Methanolic extract of Musa sapientum var. Paradisiaca (MSE, 100 mg/kg) was studied for its antiulcer and mucosal defensive factors in normal and non-insulin dependent diabetes mellitus (NIDDM) rats. NIDDM was induced by administering streptozotocin (STZ, 70 mg/kg, ip) to 5 days old rat pups. The animals showing blood glucose level >140mg/dL after 12 weeks of STZ administration were considered as NIDDM positive. Effects of MSE were compared with known ulcer protective drug, sucralfate (SFT, 500 mg/kg) and anti-diabetic drug glibenclamide (GLC, 0.6 mg/kg) when administered orally, once daily for 6 days against gastric ulcers (GU) induced by cold-restraint stress (CRS) and ethanol and subsequent changes in gastric mucosal glycoproteins, cell proliferation, free radicals (lipid peroxidation and nitric oxide) and anti-oxidants enzymes (super oxide dismutase and catalase) and glutathione (GSH) levels. MSE showed better ulcer protective effect in NIDDM rats compared with SFT and GLC in CRS-induced GU. NIDDM caused a significant decrease in gastric mucosal glycoprotein level without having any effect on cell proliferation. However, all the test drugs reversed the decrease in glycoprotein level in NIDDM rats, but cell proliferation was enhanced in case of MSE alone. Both CRS or NIDDM as such enhanced gastric mucosal LPO, NO and SOD, but decreased CAT levels while CRS plus NIDDM rats caused further increase in LPO and NO level without causing any further changes in SOD and CAT level. MSE pretreatment showed reversal in the levels of all the above parameters better than GLC. Ethanol caused a decrease in glutathione level which was further reduced in NIDDM-ethanol rats. MSE reversed the above changes significantly in both normal as well as in NIDDM rats, while GLC reversed it only in NIDDM rats. However, SFT was ineffective in reversing the changes induced by CRS or ethanol or when given in NIDDM-CRS or NIDDM-ethanol rats. The results indicated that the ulcer protective effect of MSE could be due to its predominant effect on mucosal glycoprotein, cell proliferation, free radicals and antioxidant systems.     

The counteracting effects of (-)-Epigallocatechin-3-Gallate on the immobilization stress-induced adverse reactions in rat pancreas

Many studies suggest that Epigallocatechin-3-Gallate (EGCG) has many protective effects. But little is known about its protective effects against chronic restraint stress-induced damage in rats. The aim was to demonstrate the potential protective effects of EGCG against harmful pancreatic damage to the immobilization stress in the rat model. Forty rats, 2 months old, were divided into four groups (n = 10): control group; EGCG group, rats received EGCG by gavage (100 mg/kg /day) for 30 days; stressed group, rats exposed to immobilization stress; and stressed with EGCG group, rats exposed to immobilization stress and received EGCG for 30 days. Glycemic status parameters, corticosterone, and inflammatory markers were investigated on the first day, 15th day, and the 30th day of the experiment. Pancreatic oxidative stress markers and cytokines were evaluated. Histological, immunohistological, and statistical studies were performed. On the 15th day, fasting blood glucose (FBG), fasting plasma insulin (FPI), homeostatic model assessment for insulin resistance (HOMA-IR), and fasting plasma corticosterone were significantly higher in the stressed group when compared with first and 30th day in the same group as well as when compared with control and stressed with EGCG groups. The stressed group revealed significantly higher pancreatic IL-1β, IL-6, TNF-α, MDA, and NO, serum amylase and serum lipase, and significantly lower GSH, SOD, and CAT when compared to control and stressed with EGCG groups. EGCG treatment attenuated the pancreatic stress-induced cellular degeneration, leucocytic infiltration, and cytoplasmic vacuolations; significantly decreased area percentage of collagen fibers; and significantly increased mean area percentage of insulin immunopositive cell as compared with stressed group. EGCG is a protective agent against immobilization stress because of its anti-diabetic, anti-inflammatory, and and anti-oxidative stress properties, as confirmed by biochemical and histological alterations.     

Gastroprotective and vasodilatory effects of epidermal growth factor: the role of sensory afferent neurons

Epidermal growth factor (EGF) has been shown to exert gastric hyperemic and gastroprotective effects via capsaicin-sensitive afferent neurons, including the release of calcitonin gene-related peptide (CGRP). We examined the protective and vasodilatory effects of EGF on the gastric mucosa and its interaction with sensory nerves, CGRP, and nitric oxide (NO) in anesthetized rats. Intragastric EGF (10 or 30 microg) significantly reduced gastric mucosal lesions induced by intragastric 60% ethanol (50.6% by 10 microg EGF and 70.0% by 30 microg EGF). The protective effect of EGF was significantly inhibited by pretreatment with capsaicin desensitization, human CGRP1 antagonist hCGRP-(8-37), or N(omega)-nitro-L-arginine methyl ester (L-NAME). Intravital microscopy showed that topically applied EGF (10-1,000 microg/ml) dilated the gastric mucosal arterioles dose dependently and that this vasodilatory effect was significantly inhibited by equivalent pretreatments. These findings suggest that EGF plays a protective role against ethanol-induced gastric mucosal injury, possibly by dilating the gastric mucosal arterioles via capsaicin-sensitive afferent neurons involving CGRP and NO mechanisms.     

应激状态下NO的胃粘膜保护作用及其与壁细胞泌酸的关系

目的:探讨应激状态下一氧化氮(NO)的胃粘膜保护作用及其与壁细胞泌酸的关系.方法:采用水浸-束缚应激(WRS)方法制备应激性溃疡(SU)动物模型,检测胃粘膜溃疡指数(UI)、胃粘膜NO含量和壁细胞H ,K -ATPase活性,观察L-硝基精氨酸甲酯(L-NAME)和L-精氨酸(L-Arg)对应激后大鼠壁细胞H ,K -ATPase活性及胃粘膜损伤的影响.结果:L-NAME(20 mg·kg-1)可使胃粘膜NO含量减少(P＜0.01),壁细胞H ,K -AT-Pase活性增加(P＜0.05),并加重应激所致的胃粘膜损伤;L-Arg(300 mg·kg-1)则使胃粘膜NO含量增加(P＜0.01),壁细胞H ,K -ATPase活性下降(P＜0.05),减轻应激所致胃粘膜损伤.结论:NO对应激状态下大鼠胃粘膜具有保护作用,其机制与抑制壁细胞H ,K -ATPase活性有关.