The effect of inflammation on the expression and distribution of the MAS-related gene receptors MrgE and MrgF in the murine ileum

Abstract

The MAS-related gene (Mrg) receptor MrgE has been suggested to be expressed at all tissue levels involved in pain sensation and to influence the expression of another Mrg receptor, MrgF. Given the knowledge on the role of the enteric nervous system (ENS) in sensation, and the plasticity of enteric neurons during intestinal inflammation, it can be hypothesized that MrgE is expressed in enteric neurons, and that MrgE and MrgF change expression in intestinal inflammatory conditions. Therefore, we aimed to reveal the expression details of MrgE and MrgF in the murine ileum in normal and inflamed conditions. Using reverse transcriptase-PCR, quantitative-PCR and immunohistochemistry, we compared the ileum of non-inflamed control mice with that of two models of intestinal inflammation, i.e. intestinal schistosomiasis and chemically induced ileitis. MrgE and MrgF mRNAs were detected in control and inflamed conditions. MrgE and MrgF mRNAs showed a trend towards downregulation during intestinal schistosomiasis and a significant reduction during ileitis. MrgE and MrgF receptors were expressed in distinct enteric neuronal subpopulations, such as the sensory, secretomotor and vasodilator neurons, and in nerve fibres in the tunica muscularis and lamina propria of control and inflamed ileum. Only a minor proportion of enteric neurons co-expressed MrgE and MrgF. The number of enteric neurons expressing MrgE and MrgF receptors was significantly reduced during intestinal schistosomiasis and ileitis. This is the first report on the expression of MrgE and MrgF in the ENS in (patho)physiological conditions. The expression of MrgE and MrgF in enteric neurons was negatively affected by inflammation.

Pharmacology and Signaling of MAS-Related G Protein–Coupled Receptors

“…In accordance with these findings, transcripts of MRGPRF, formally known as rat thoracic aorta receptor, were detected in small and large intestine (Ross et al, 1990). More precisely, MRGPRE and MRGPRF proteins were detected in both myenteric and submucosal neurons, the latter showing coexpression of both receptors in 30-50% of neurons analyzed (Avula et al, 2011). The same study reported that intestinal schistosomiasis and trinitrobenzene sulfonic acidinduced ileitis resulted in decreased expression of both receptors, whereas other neuronal marker proteins, e.g., calretinin or neuronal nitric oxide synthetase (nNOS), were not affected by either inflammatory insult.…”

“…MRGPRE transcripts were also monitored in medium-and large-diameter neurons of human DRG sections (Zhang et al, 2005) and in other areas of the central nervous system, including cerebral cortex, hippocampus, spinal cord, and cerebellum, as well as in human, mouse, and rat placenta (Zhang et al, 2005;Milasta et al, 2006). MRGPRE and MRGPRF are also expressed in enteric neurons (Avula et al, 2011), belonging to one of the main divisions of the autonomic nervous system that regulates gastrointestinal functions. In accordance with these findings, transcripts of MRGPRF, formally known as rat thoracic aorta receptor, were detected in small and large intestine (Ross et al, 1990).…”

Mas and Its Related G Protein–Coupled Receptors, Mrgprs

“…However, the localization of rMrgprA expression in the vasculature and in the collecting duct of the kidney was recently reported in detail, and an inhibition of vasopressin signaling by rMrgprA was postulated (Kishore et al, 2013). One group has systematically analyzed the expression of all Mrgprs in mouse intestine (Avula et al, 2011(Avula et al, , 2013. With a few exceptions, they are all expressed on different types of enteric neurons in varying levels; however, the function of Mrgprs in these cells is elusive.…”

Proof‐of‐concept: neonatal intravenous injection of adeno‐associated virus vectors results in successful transduction of myenteric and submucosal neurons in the mouse small and large intestine

“…Whole-mounts and cryosections were prepared as described before. 8,9 Tissue samples were preincubated in 0.1 M phosphatebuffered saline (PBS; pH 7.4) with 0.05% thimerosal, 10% normal horse serum, and 1% triton X-100. In case of anti-HuC/D staining this was supplemented with Mouse-On-Mouse blocking reagent (Vector Labs, Burlingame, CA, USA).…”