V. Nimet İzgüt-Uysal

Effect of carnitine on stress-induced lipid peroxidation in rat gastric mucosa.

Purpose. Carnitine is an essential cofactor in the mitochondrial transfer of fatty acids, but is also a scavenger of oxygen free radicals in mammalian tissues. It has been shown that cold-restraint stress (CRS) produces gastric mucosal injury due to oxygen free radicals. The aim of this study was to determine the effect of l-carnitine on lipid peroxidation induced by CRS in rat stomachs. Methods. Rats pretreated with l-carnitine (50 mg/kg per day for 10 days) were restrained in a wire cage for 4 h at 4°C. At the end of the experimental period, the lesion index in gastric mucosa was determined. In blood and gastric mucosa samples, the content of mucin, prostaglandin (PG)E2, the products of lipid peroxidation, and catalase activity were measured. Results. CRS caused a significant decrease in gastric mucin and PGE2 content, while in the gastric mucosa of rats pretreated with l-carnitine, the changes in gastric mucin and PGE2 content, as well as gastric lesion development and enhanced lipid peroxide formation due to stress, were prevented. On the other hand, catalase activity in blood increased in the CRS group, while its value in gastric mucosa was not different from that in the control rats. l-Carnitine treatment increased catalase activity in both blood and gastric mucosa in control animals. Following stress, increased catalase activity of blood was associated with decreased mucosal catalase activity in rats that received l-carnitine. Conclusions.l-Carnitine prevents the occurrence of mucosal lesions by strengthening the gastric mucosal barrier and by reducing the products of lipid peroxidation against noxious factors that cause elevation of lipid peroxidation, such as CRS.

Effect of L-Carnitine on carrageenan-induced inflammation in aged rats

Background: It is known that L-carnitine is a cofactor in the transport of fatty acids across the inner mitochondrial membrane for β-oxidation. However, L-carnitine is an antioxidant compound widely used for the treatment of deficits in functions due to the aging process. Objective: The purpose of the study was to investigate the effect of L-carnitine on carrageenan-induced inflammation in aged rats. Methods:L-Carnitine (50 mg/kg/day) or control vehicle was given by gavage for 30 consecutive days to young (2-month-old) and aged (24-month old) rats. 6 ml of air was injected subcutaneously into the dorsum of each rat, followed 2 days later by 4 ml of 2% carrageenan. After 2 days, the exudate was collected from the inflamed site of each rat. The quantity of collected exudate and the number of cells which have migrated to the inflamed site were determined. Results: No differences were observed in quantity of exudate in all groups; a decrease in the number of exudate cells was established in aged rats. However, L-carnitine treatment significantly increased the number of exudate cells in both young and aged rats. The exudate cells from the aged rats exhibited a decline of both phagocytic and chemotactic activities as compared with those from the young rats, and the decreased functions were significantly enhanced by L-carnitine treatment. However, superoxide anion release was seen to be unchanged in exudate cells due to aging, and L-carnitine intake decreased the production of superoxide anion by these cells in young and aged rats. Conclusions: These findings demonstrate that L-carnitine is capable of restoring the age-related changes in the functions of inflammatory cells. Moreover, L-carnitine may play a protective role in the tissue destruction in inflammation by decreasing the superoxide anion production.

Effect of orexin-a on ischemia-reperfusion-induced gastric damage in rats.

BackgroundOrexins are involved in the regulation of sleeping behavior and energy homeostasis, and they are also implicated in the regulation of gastrointestinal functions. Previous reports have demonstrated the expression of orexin receptors in the gastrointestinal system. The aim of this study was to investigate the gastroprotective effect of orexin-A in ischemia-reperfusion-induced gastric mucosal injury.MethodsThe gastric ischemia-reperfusion model was established by clamping the celiac artery for 30 min and reperfusing for 60 min. Orexin-A was administered in doses of 500 pmol·kg−1·min−1 by infusion throughout the ischemia-reperfusion period. The mean lesion area, gastric prostaglandin E2 and mucus content, myeloperoxidase activity, and production of thiobarbituric acid reactive substances were measured.ResultsOrexin-A significantly attenuated the ischemia-reperfusion-induced gastric lesions and also decreased myeloperoxidase activity and the thiobarbituric acid reactive substances content in gastric mucosa of rats exposed to ischemia-reperfusion. However, the decline in gastric prostaglandin E2 and mucus content was not restored by orexin-A treatment.ConclusionsOrexin-A exhibited a gastroprotective effect against ischemia-reperfusion-induced lesions by decreasing neutrophil activation and lipid peroxidation.

Immunohistochemical and ultrastructural changes in the renal cortex of cadmium-treated rats

The aim of this study was to determine the cadmium-induced immunohistochemical and morphological changes in the renal cortex of adult male rats exposed to high doses of cadmium for 30 d. Animals used as controls received a standard diet and water ad libitum. The animals used for this study received 15 ppm CdCl2 in their drinking water for 1 mo. The mean arterial pressure (MAP), the mean blood Cd level, and the mean tissue Cd content were significantly higher when compared to controls (p < 0.01). Immunohistochemical studies demonstrated a weak labeling to type IV collagen and laminin, but a strong labeling to fibronectin in the renal cortex of the Cd-treated animals when compared to controls. The ultrastructural alterations found in Cd-treated rats were a diminution in the amount of filtration slits, increased fusion of foot processes in epithelial cells of the glomeruli, increase of lysosomal structures and pinocytic vesicles as well as large mitochondria in proximal tubule cells, and degenerated cells in distal tubules. Additionally, the glomerular basement membrane was slightly thickened. In conclusion, cadmium toxicity results in alterations in the renal extracellular matrix and tubular or glomerular cells, which could play an important role in renal dysfunction.

Peritoneal macrophages function modulation by L-carnitine in aging rats

Background and aims: The aging process is associated with a progressive decline in physiological functions involving immune response in most species. The aim of the present study was to determine the effect of L-carnitine on impaired macrophages function in aged rats. Methods: Superoxide anion production, chemotaxis and phagocytic activity were studied in peritoneal macrophages obtained from young (2 months old) and aged (24 months old) rats. L-carnitine (50 mg/kg bw) or control vehicle was orally gavaged into young and aged rats for 30 consecutive days. Results: The peritoneal macrophages of the aged rats exhibited an increase in superoxide anion generation and a decline in chemotaxis and phagocytic index by comparison with the young rats. Superoxide anion production in aged rats was significantly reduced by L-carnitine treatment, as accompanied by a significant enhancement of chemotactic activity, which was restored to control levels observed in young rats. The age-related reduction in phagocytic index was only slightly, but not significantly, restored by L-carnitine administration, however. Conclusion: The findings suggest that L-carnitine administration may be useful in reversing some age-related changes.

Effects of l-carnitine on neutrophil functions in aged rats

Several age-related alterations occur at the cellular level in the immune system leading to a decrease in the immune response. The present study was designed to determine the effect of L-carnitine on impaired neutrophil functions of aged rats. For this reason, superoxide anion radical production, chemotaxis and phagocytic activity were studied in the neutrophils obtained from the peripheral blood of young and old rats. We orally gavaged L-carnitine (50 mg/kg b.w. per day) or control vehicle into young (2 months) and aged (24 months) rats for 30 consecutive days. The neutrophils of aged rats exhibited an increase in superoxide anion production and decline in phagocytosis and chemotaxis when compared with that in young rat neutrophils. Superoxide anion production in aged rats was significantly decreased by L-carnitine treatment which was accompanied with a significant enhancement of chemotactic and phagocytic activity being restored to control levels. These findings demonstrated that L-carnitine is capable of restoring the age-related changes of neutrophil functions.

Expressions of Inducible Nitric Oxide Synthase and Cyclooxygenase-2 in Gastric Ischemia-Reperfusion: Role of Angiotensin II

BACKGROUND Angiotensin II contributes to the pathogenesis of inflammation induced by ischemia-reperfusion (I/R) in various organs. Angiotensin II increases vascular permeability that initiates the inflammatory process and leads to the migration of inflammatory cells into the tissue. The aim of the present study was to investigate the effect of angiotensin II on ischemia-reperfusion induced expressions of inducible NO synthase (iNOS) and cyclooxygenase-2 (COX-2) in rat stomachs exposed to ischemia-reperfusion. METHODS Wistar rats were randomly separated into five groups: sham operated, I/R, I/R plus candesartan (an AT1 receptor antagonist), I/R plus PD123319 (an AT2 receptor antagonist), and I/R plus captopril (an angiotensin-converting enzyme inhibitor). Candesartan (1mg/kg/d), PD123319 (3mg/kg/d), and captopril (20mg/kg/d) were given subcutaneously twice a day for 5 d before I/R. The rats were submitted to gastric ischemia by clamping the celiac artery for 30min followed by 24h reperfusion. RESULTS Candesartan decreased the neutrophil accumulation, iNOS expression, and increased NOx level, COX-2 expression in the gastric tissue exposed to I/R compared with I/R group. PD123319 did not change the neutrophil accumulation, iNOS expression, PGE(2), or NOx levels, but increased the expression of COX-2 in the gastric tissue exposed to I/R. However, captopril did not play any role in I/R induced change in gastric mucosa. CONCLUSIONS The results suggest that Angiotensin II via angiotensin II type 1 receptor increases the accumulation of neutrophils and iNOS expression and plays a significant role in mediating inflammation in gastric mucosa exposed to I/R.

Endogenous orexin-A modulates gastric motility by peripheral mechanisms in rats

Orexin-A (OXA) and orexin receptor type 1 (OX1R) are found in enteric nervous system and smooth muscle cells in the digestive tract. Fasting is a stimulant for OXA synthesis. The aim of the present study was to investigate central and peripheral effects of endogenous OXA on gastric motility. Endogenous OXA synthesis was induced by 36h fasting. Vagotomy was used to evaluate N.vagus-mediated effects of OXA. Gastric emptying and interdigestive gastric motility were measured by spectrophotometric and manometric methods, respectively. Rats were pretreated with OX1R antagonist SB-334867 prior to measurements. Plasma OXA concentration was assayed with radioimmunoassay while preproorexin (PPO) expression was determined with Western blotting in gastric and hypothalamic tissues. OXA immunoreactivity in antrum was determined with immunohistochemistry. Plasma OXA level, PPO protein expression and OXA immunoreactivity were significantly increased in response to 36h fasting. Endogenous OXA facilitated gastric emptying and inhibited gastric interdigestive motility. As these effects were abolished with SB-334867, it is likely that gastrokinetic effects of OXA are mediated via OX1R. Vagotomy did not alter OXA-mediated effects. According to current data, OXA is up-regulated both centrally and peripherally upon fasting. Endogenous OXA accelerates gastric emptying while it inhibits interdigestive motility.

Effect of L-arginine on age-related changes in macrophage phagocytic activity.

Aging is associated with decline in the functioning of immune cells and reductions in serum L‐arginine and excretion of nitric oxide metabolites. Studies have shown that L‐arginine plays an important role in many physiological, biological and immunological processes. The present study was performed to determine if treatment with L‐arginine could prevent age‐related changes in phagocytic function of peritoneal macrophages. The effects of L‐arginine on phagocytic activity of peritoneal macrophages were compared between young and middle‐aged rats. Studies were performed in four groups of rats for 8 weeks: group 1 (3 month‐old) received physiological saline; group 2 (3 month‐old) received L‐arginine (160 mg/kg/day); group 3 (12 month‐old) received physiological saline; group 4 (12 month‐old) received L‐arginine (160 mg/kg/day). There were no significant differences in percentage of cells which were phagocytized. However, the phagocytosis of activated charcoal by peritoneal macrophages reduced with age. Thus, the phagocytic index was lower in macrophages of middle‐aged rats. L‐arginine treatment increased phagocytosis by peritoneal macrophages of both young and middle‐aged rats. L‐arginine‐induced augmentation in phagocytosis by macrophages were much higher in the middle‐aged rats compared with young rats. In summary, we found that L‐arginine prevented the age‐related reduction in phagocytic capability of peritoneal macrophages.

PROSTAGLANDINS, CAPSAICIN-SENSITIVE SENSORY NERVES AND NEUTROPHIL INFILTRATION, BUT NOT NITRIC OXIDE, CONTRIBUTE TO COLD RESTRAINT STRESS-INDUCED GASTRIC ADAPTATION IN RATS

1 The aim of the present study was to determine the role of prostaglandins (PG), nitric oxide (NO) and capsaicin‐sensitive sensory nerves in neutrophil infiltration in gastric adaptation to cold restraint stress in rats. 2 Wistar rats were exposed to single or repeated cold restraint stress for 3.5 h every other day for up to 4 days. Prior to repeated stress, rats were pretreated with NG‐nitro‐l‐arginine methyl ester (l‐NAME; 10 mg/kg, s.c.), indomethacin (10 mg/kg, s.c.) or capsaicin (125 mg/kg, s.c.). The extent of gastric mucosal lesions was evaluated histologically and myeloproxidase (MPO) activity, PGE2, NO and calcitonin gene‐related peptide (CGRP) levels were measured in gastric tissue. 3 Cold restraint stress produced haemorrhagic lesions and reduced PGE2 and CGRP levels in the stomach, with an increase in MPO activity and NO levels. Repeated stress insults reduced stress‐induced gastric damage, NO production and MPO activity, with an increase in PGE2 and CGRP levels compared with rats exposed to single cold restraint stress. Adaptation to cold restraint stress was prevented by indomethacin and capsaicin pretreatment, but not by l‐NAME. 4 We conclude that the stomach has the ability to adapt to repeated exposure to cold restraint stress and that the adaptation, via inhibition of neutrophil infiltration, is mediated, at least in part, by endogenous PG and CGRP.