Neshat S, deVries M, Barajas-Espinosa AR, Skeith L, Chisholm SP, Lomax AE. Loss of purinergic vascular regulation in the colon during colitis is associated with upregulation of CD39. Am J Physiol Gastrointest Liver Physiol 296: G399 -G405, 2009. First published December 12, 2008 doi:10.1152/ajpgi.90450.2008.-Evidence from patients with inflammatory bowel disease (IBD) and animal models suggests that inflammation alters blood flow to the mucosa, which precipitates mucosal barrier dysfunction. Impaired purinergic sympathetic regulation of submucosal arterioles, the resistance vessels of the splanchnic vasculature, is one of the defects identified during IBD and in mouse models of IBD. We hypothesized that this may be a consequence of upregulated catabolism of ATP during colitis. In vivo and in vitro video microscopy techniques were employed to measure the effects of purinergic agonists and inhibitors of CD39, an enzyme responsible for extracellular ATP catabolism, on the diameter of colonic submucosal arterioles from control mice and mice with dextran sodium sulfate [DSS, 5% (wt/vol)] colitis. Using a luciferase-based ATP assay, we examined the degradation of ATP and utilized real-time PCR, Western blotting, and immunohistochemistry to examine the expression and localization of CD39 during colitis. Arterioles from mice with DSS colitis did not constrict in response to ATP (10 M) but did constrict in the presence of its nonhydrolyzable analog ␣,␤-methylene ATP (1 M). ␣,␤-Methylene ADP (100 M), an inhibitor of CD39, restored ATP-induced vasoconstriction in arterioles from mice with DSS-induced colitis. CD39 protein and mRNA expression was markedly increased during colitis. Immunohistochemical analysis demonstrated that, in addition to vascular CD39, F4/80-immunoreactive macrophages accounted for a large proportion of submucosal CD39 staining during colitis. These data implicate upregulation of CD39 in impaired sympathetic regulation of gastrointestinal blood flow during colitis. purinergic neurotransmission; ectonucleotidase; inflammation; sympathetic; vasoconstriction STUDIES OF PATIENTS WITH INFLAMMATORY bowel disease (IBD) and animal models of IBD have revealed alterations in gastrointestinal (GI) blood flow (2,15,22,26) and angiogenesis (4 -6). These changes may contribute to disease pathogenesis, inasmuch as defects in mucosal perfusion render the mucosal barrier susceptible to breakdown. One potential mechanism of altered mucosal blood flow is defective neural regulation of GI blood vessels during inflammation.Submucosal arterioles are the resistance vessels of the splanchnic vasculature and thus regulate mucosal perfusion (13,23,31). We previously identified a defect in sympathetic vasoconstrictor regulation of colonic submucosal arterioles in the 2,4,6-trinitrobenzene sulfonic acid (TNBS) mouse model of IBD (22). Neurally evoked vasoconstrictions in control mice were sensitive to ␣ 1 -adrenoceptor and purinergic receptor antagonism, and superfusion of ATP and phenylephrine caused robust vasoconstrictions. I...

1. Inflammatory bowel diseases (IBD) alter the function of the enteric nervous system and the sensory innervation of the gastrointestinal (GI) tract. Less is known about whether IBD also affects the sympathetic nervous system (SNS). Given the importance of the SNS in regulating GI function and possibly immune system activation, the present review examines the evidence of sympathetic dysfunction during IBD and its possible consequences. 2. Sympathetic axons within the GI tract innervate several cell types, including vascular myocytes, enteric neurons and immune cells. The major neurotransmitters released from sympathetic varicosities are noradrenaline, neuropeptide Y and ATP or a related purine. 3. Clinical studies of IBD patients have provided evidence of an association between IBD and axonal or demyelinating neuropathy. Assays of autonomic function suggest that ulcerative colitis and Crohn's disease, the two major forms of IBD, have contrasting effects on sympathetic neural activity. 4. Animal models of IBD have been used to examine the effects of these diseases on sympathetic neurophysiology. A decrease in the release of noradrenaline from sympathetic varicosities in inflamed and uninflamed regions of the GI tract has consistently been reported. Recent findings suggest that the decrease in neurotransmitter release may be due to inhibition of N-type voltage-gated Ca(2+) current in post-ganglionic sympathetic neurons. 5. Interest in the role of the SNS in IBD is rapidly increasing. However, much work needs to be done to enhance understanding of how SNS function is altered during IBD and what contribution, if any, these changes make to pathogenesis.

Inflammation has profound effects on the innervation of affected tissues, including altered neuronal excitability and neurotransmitter release. As Ca 2+ influx through voltage-gated Ca 2+ channels (VGCCs) is a critical determinant of excitation-secretion coupling in nerve terminals, the aim of this study was to characterize the effect of overnight incubation in the inflammatory mediator tumour necrosis factor α (TNFα; 1 nm) on VGCCs in dissociated neurons from mouse superior mesenteric ganglia (SMG). Voltage-gated Ca 2+ currents (I Ca ) were measured using the perforated patch clamp technique and the VGCC subtypes present in SMG neurons were estimated based on inhibition by selective VGCC blockers: ω-conotoxin GVIA (300 nm; N-type), nifedipine (10 μm; L-type), and ω-conotoxin MVIIC (300 nm; N-, P/Q-type). We used intracellular Ca 2+ imaging with Fura-2 AM to compare Ca 2+ influx during depolarizations in control and TNFα-treated neurons. TNF receptor and VGCC mRNA expression were measured using PCR, and channel α subunit (CaV2.2) was localized with immunohistochemistry. Incubation in TNFα significantly decreased I Ca amplitude and depolarization-induced Ca

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These findings identify IL-17A as a potential mediator of neuroanatomical remodeling of the gut innervation during IBD.