Transforming growth factor alpha-mediated gastroprotection against stress ulceration in the rat: involvement of capsaicin-sensitive sensory neurons

Capsaicin-sensitive afferent fibers mediate the protective effect of electrical stimulation of paraventricular nucleus against gastric ischemia-reperfusion injury in rats

AIM: To elucidate the role of capsaicin-sensitive afferent fibers in mediating the effect of electrical stimulation (ES) of paraventricular nucleus (PVN) against rat gastric ischemia-reperfusion (GI-R) injury.

METHODS: GI-R injury was induced in rats by clamping the celiac artery for 30 min and then reperfusing for 1 h. The methods of nuclear electric stimulation to excite the PVN and pretreatment with a high dose of capsaicin to ablate the capsaicin-sensitive afferent fibers were used to explore the role of capsaicin-sensitive afferent fibers in the regulation of PVN on GI-R injury.

RESULTS: Pretreament with a high dose of capsaicin to ablate afferent fibers partly abolished the protective effect of PVN against GI-R injury and the injury was increased by 54.85% as compared with that in the PVN stimulation group (P < 0.01); Pretreament with L-nitro-L-arginine methyl ester (L-NAME) significantly abolished the protective effect of PVN against GI-R injury and the injury was increased by 72.98% as compared with that in the PVN stimulation group (P < 0.01).

CONCLUSION: Capsaicin-sensitive afferent fibers and endogenous NO are involved in the protective effect of PVN stimulation against GI-R injury.

Dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress in rats

AIM: To investigate the dynamic functional and ultrastructural changes of gastric parietal cells induced by water immersion-restraint stress (WRS) in rats.

METHODS: WRS model of Sprague-Dawley (SD) rats was established. Fifty-six male SD rats were randomly divided into control group, stress group and post-stress group. The stress group was divided into 1, 2 and 4 h stress subgroups. The post-stress group was divided into 24, 48 and 72 h subgroups. The pH value of gastric juice, ulcer index (UI) of gastric mucosa and H⁺, K⁺-ATPase activity of gastric parietal cells were measured. Ultrastructural change of parietal cells was observed under transmission electron microscope (TEM).

RESULTS: The pH value of gastric juice decreased time-dependently in stress group and increased in post-stress group. The H⁺, K⁺-ATPase activity of gastric parietal cells and the UI of gastric mucosa increased time-dependently in stress group and decreased in post-stress group. Compared to control group, the pH value decreased remarkably (P = 0.0001), the UI and H⁺, K⁺-ATPase activity increased significantly (P = 0.0001, P = 0.0174) in 4 h stress subgroup. UI was positively related with stress time (r = 0.9876, P < 0.01) but negatively with pH value (r = -0.8724, P < 0.05). The parietal cells became active in stress group, especially in 4 h stress subgroup, in which plenty of intracellular canalicular and mitochondria were observed under TEM. In post-stress group, the parietal cells recovered to resting state.

CONCOUSION: The acid secretion of parietal cells is consistent with their ultrastructural changes during the development and healing of stress ulcer induced by WRS and the degree of gastric mucosal lesions, suggesting gastric acid play an important role in the development of stress ulcer and is closely related with the recovery of gastric mucosal lesions induced by WRS.

Expression of vanilloid receptor-1 in epithelial cells of human antral gastric mucosa

OBJECTIVE

Capsaicin, which acts by binding to the vanilloid receptor-1 (VR1), has been shown to give protection against gastric mucosal injury and to enhance healing of gastric ulcers. Although VR1 has recently been reported to be present in non-neural tissues, it is primarily considered to be expressed in nociceptor sensory neurons of small diameter. The aim of the present study was to evaluate the distribution of VR1 immunoreactivity in the normal human gastric mucosa.

MATERIALS AND METHODS

Ten volunteers underwent gastroscopy and biopsies were obtained from the corpus and the antrum. The specimens were labelled immunohistochemically using polyclonal goat anti-VR1 and evaluated at the light- and electronmicroscopic level. Moreover, post-embedding immunogold labelling was performed and subsequently analysed at the electronmicroscopic level.

RESULTS

In the antrum, VR1 immunoreactivity was located in epithelial cells that fulfilled the criteria of endocrine cells of the "open type". These cells were located primarily in the neck region of the antral glands and the labelling was concentrated on the microvilli of these cells. At the ultrastructural level, round granulae with differences in electron density were identified in the basal compartment of the labelled cells. VR1 immunoreactivity was also identified in axon-like structures that were located in the lamina propria, often in close vicinity of vessels, in the corpus as well as in the antrum.

CONCLUSIONS

VR1-immunoreactivity was evident in antral epithelial cells exhibiting characteristics of endocrine-like cells. This may indicate that the gastroprotective effects of capsaicin, which hitherto have been attributed to primary afferent neurons, at least partly may be explained by an action on specific epithelial cells in the antrum.