Vagus-mediated activation of mucosal mast cells in the stomach: effect of ketotifen on gastric mucosal lesion formation and acid secretion induced by a high dose of intracisternal TRH analogue

Nervous mechanisms of restraint water-immersion stress-induced gastric mucosal lesion

Stress-induced gastric mucosal lesion (SGML) is one of the most common visceral complications after trauma. Exploring the nervous mechanisms of SGML has become a research hotspot. Restraint water-immersion stress (RWIS) can induce GML and has been widely used to elucidate the nervous mechanisms of SGML. It is believed that RWIS-induced GML is mainly caused by the enhanced activity of vagal parasympathetic nerves. Many central nuclei, such as the dorsal motor nucleus of the vagus, nucleus of the solitary tract, supraoptic nucleus and paraventricular nucleus of the hypothalamus, mediodorsal nucleus of the thalamus, central nucleus of the amygdala and medial prefrontal cortex, are involved in the formation of SGML in varying degrees. Neurotransmitters/neuromodulators, such as nitric oxide, hydrogen sulfide, vasoactive intestinal peptide, calcitonin gene-related peptide, substance P, enkephalin, 5-hydroxytryptamine, acetylcholine, catecholamine, glutamate, γ-aminobutyric acid, oxytocin and arginine vasopressin, can participate in the regulation of stress. However, inconsistent and even contradictory results have been obtained regarding the actual roles of each nucleus in the nervous mechanism of RWIS-induced GML, such as the involvement of different nuclei with the time of RWIS, the different levels of involvement of the sub-regions of the same nucleus, and the diverse signalling molecules, remain to be further elucidated.

Mechanisms of Probiotic VSL#3 in a Rat Model of Visceral Hypersensitivity Involves the Mast Cell-PAR2-TRPV1 Pathway

BACKGROUND

Mast cells (MCs), PAR2 and TRPV1, play a key role in the regulation of visceral pain. Several studies have found that probiotics regulate visceral sensitivity.

AIMS

The purpose of the current study was to explore the role of MC-PAR2-TRPV1 in VH and the mechanism of VSL#3 in a rat model of VH.

METHODS

A total of 64 rats were randomly divided into eight groups: Control VH, VH + ketotifen, VH + FSLLRY-NH2, VH + SB366791, VH + VSL#3, VH + VSL#3 + capsaicin, and VH + VSL#3 + SLIGRL-NH2. The rat model of VH was induced by acetic acid enema and the partial limb restraint method. VH was assessed by the abdominal withdrawal reflex score. MCs in colonic tissue were detected by the toluidine blue staining assay. The expression of PAR2 and TRPV1 in DRGs (L6-S1) was measured by immunohistochemistry and Western blotting.

RESULTS

The established VH was abolished by treatment with ketotifen, a mast cell stabilizer FSLLRY-NH2, a PAR2 antagonist SB366791 a TRPV1 antagonist, and probiotic VSL#3 in rats. The administration of ketotifen or probiotic VSL#3 caused a decrease in mast cell number in the colon and decreased PAR2 and TRPV1 expression in DRGs. Intrathecal injection of FSLLRY-NH2 or SB366791 caused decreased expression of PAR2 and/or TRPV1 in DRGs in VH rats. SLIGRL-NH2, a PAR2 agonist, and capsaicin, a TRPV1 agonist, blocked the effects of probiotic VSL#3.

CONCLUSIONS

The probiotic VSL#3 decreases VH in rat model of VH. The mechanism may be related with the mast cell-PAR2-TRPV1 signaling pathway.

Regional Differences in Chronic Stress-induced Alterations in Mast Cell and Protease-activated Receptor-2-positive Cell Numbers in the Colon of Ws/Ws Rats

Background/Aims

There have been no reports on the effect of chronic psychological stress on colonic immune cells or the regional differences. We aimed to investigate the effect of chronic psychological stress on the number of mast cells and protease-activated receptor (PAR)-2-positive cells in the rat colonic mucosa.

Methods

Six-week-old and 14-week-old Ws/Ws rats, which lack mast cells after 10 weeks, were used as control and mast cell-deficient groups, respectively. The rats were divided into stress and sham-treated groups. Rats in the stressed group were exposed to water avoidance stress (WAS, 1 hour/day) for 13 days. Fecal pellet output and the number of mast cells and PAR-2-positive cells in colonic mucosa were compared between the WAS and sham groups.

Results

In 6-week-old rats, the WAS group showed a significantly higher number of mast cells compared to the sham group. In 14-week-old rats, mast cells were nearly absent in the colonic mucosa. WAS significantly increased PAR-2-positive cells in 14-week-old rats, but not in 6-week-old rats. Indirect estimation of PAR-2-positive mast cells in 6-week-old rats suggested that the majority of increased mast cells following WAS did not express PAR-2. WAS increased mast cells and PAR-2-positive cells mainly in the proximal colon. Fecal pellet output was continuously higher in the WAS group than in the sham group, and the difference was significant for both 6-week-old and 14-week-old rats.

Conclusions

Chronic psychological stress increased the number of mast cells and PAR-2-positive cells in rat colonic mucosa, and these increases were more prominent in the proximal colon.

Central nervous system effects of thyrotropin-releasing hormone and its analogues: opportunities and perspectives for drug discovery and development

Besides its well-known endocrine role in the thyroid system, thyrotropin-releasing hormone (L-pyroglutamyl-L-histidyl-L-prolinamide) has been long recognized as a modulatory neuropeptide. After a brief overview of the extrahypothalamic and receptor distribution, and of the neurophysiological, neuropharmacological and neurochemical effects of this tripeptide, this review discusses efforts devoted to enhance therapeutically beneficial central nervous system effects via structural modifications of the endogenous peptide. An enormous array of maladies affecting the brain and the spinal cord has been a potential target for therapeutic interventions involving agents derived from thyrotropin-releasing hormone as a molecular lead. Successful development of several centrally active analogues and recent accounts of efforts aimed at improving metabolic stability, selectivity and bioavailability are highlighted.