vasoactive-intestinal-peptide and Muscular-Dystrophy--Duchenne

Alterations of gastric mechanical activity have been reported in mdx mouse, animal model for Duchenne muscular dystrophy. This study examined if alterations in the vasoactive intestinal polypeptide (VIP) system are present in mdx stomach. Gastric mechanical activity was recorded in vitro as changes of endoluminal pressure and neurally or pharmacologically evoked relaxations were analysed in mdxvs normal stomach. Reverse-transcription polymerase chain reaction was used to detect inducible nitric oxide synthase (iNOS) expression. Relaxations to sodium nitroprusside in mdx stomach showed no difference in comparison with normal preparations. In normal stomach, VIP produced relaxation, which was reduced by VIP6-28, antagonist of VIP receptors, but was not modified by Nomega-nitro-L-arginine methyl ester (L-NAME), 1-H-oxodiazol-[1,2,4]-[4,3-a]quinoxaline-1-one (ODQ) or by N-(3-(aminomethyl)-benzyl)acetamidine (1400W) and aminoguanidine, inhibitors of iNOS. In contrast, in mdx stomach VIP responses were antagonized not only by VIP6-28, but also by L-NAME, ODQ, 1400W or aminoguanidine. In normal stomach, the slow relaxation evoked by stimulation at high frequency was reduced by VIP6-28, but it was unaffected by 1400W or aminoguanidine. In mdx stomach, it was reduced by VIP6-28 or 1400W, which did not show additive effects. iNOS mRNA was expressed only in mdx stomach. The results suggest that in mdx gastric preparations, iNOS is functionally expressed, being involved in the slow relaxation induced by VIP.

Topics: Animals; Disease Models, Animal; Enzyme Inhibitors; Imines; Male; Mice; Mice, Inbred mdx; Muscle Relaxation; Muscle, Smooth; Muscular Dystrophy, Duchenne; NG-Nitroarginine Methyl Ester; Nitric Oxide Synthase Type II; Organ Culture Techniques; Oxadiazoles; Quinoxalines; Receptors, Vasoactive Intestinal Peptide; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stomach; Vasoactive Intestinal Peptide

Using a combination of molecular and immunohistochemical methods, we have obtained evidence for a distinctive change in the expression patterns of ATP-gated (P2X) receptor subunits in dystrophic muscle from both Duchenne muscular dystrophy (DMD) patients and the mdx mouse model. In control myofibres there was no staining for any P2X subtype studied here, although P2X1 stained the smooth muscle of the blood vessels and P2X6 nerves and the tunica intima in small arteries. In contrast, P2X1 and P2X6 were co-expressed strongly in small regenerating muscle fibres in the dystrophic muscles, whereas this expression decreased in fully regenerated fibres. Moreover, immunoreactivity for the P2X2 receptor re-appeared in dystrophic muscle, where it co-localised with the Type 1 fibres. There is, thus, a burst of production of several P2X receptor subtypes in regenerating dystrophic muscle, which may have implications for drug targets for this muscle pathology.

Topics: Animals; Blotting, Northern; Blotting, Western; Dystrophin; Embryo, Mammalian; Gene Expression Regulation; Humans; Immunohistochemistry; Male; Methyl Green; Mice; Mice, Inbred C57BL; Mice, Inbred mdx; Muscle, Skeletal; Muscular Dystrophy, Animal; Muscular Dystrophy, Duchenne; Rats; Receptors, Purinergic P2; Receptors, Purinergic P2X2; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Sequence Alignment; Sequence Analysis, Protein; Succinate Dehydrogenase; Vasoactive Intestinal Peptide