Role of neuronal and inducible nitric oxide synthases in the guinea pig ileum myenteric plexus during in vitro ischemia and reperfusion

Abstract

Our data demonstrate that both iNOS and nNOS represent sources for NO overproduction in ileal myenteric plexus during I/R, although iNOS undergoes more consistent changes suggesting a more relevant role for this isoform in the alterations occurring in myenteric neurons following I/R.

Interaction between NMDA glutamatergic and nitrergic enteric pathways during in vitro ischemia and reperfusion

“…High extracellular concentrations of the amino acid can be neurotoxic and kill neurons mainly via activation of NMDA receptors, which is responsible for increased NO production (Lau and Tymianski, 2010). In agreement with previous reports, in this study both glutamate and NO overflow from guinea pig ileum increase after I/R injury (Giaroni et al, 2011(Giaroni et al, , 2013. In these conditions, NO may influence changes in glutamate release as indicated by the ability of NPLA and 1400W to decrease I/R-induced amino acid overflow.…”

“…Participation of Ca þ þ -independent NOS, such as iNOS, is also possible (Starkey et al, 2001). Spontaneous NO release from the guinea pig ileum, human colon and mouse ileum involves both nNOS and iNOS (LePard, 2005;Bagyánski et al, 2011;Giaroni et al, 2013). It is, thus, possible that, in guinea pig ileum, NMDA receptors modulate NO production from myenteric neurons by activating both nNOS and iNOS.…”

“…The effect of reperfusion was evaluated by substituting the hypoxic/hypoglycaemic medium with a normal oxygenated glucose-containing Tyrode's solution. Ileal segments were exposed to in vitro ischemic conditions for 60 min and subsequently reperfused for another 60 min period, since, in previous studies we documented major changes of neurotransmitter overflow from the guinea pig ileum within these time periods (Giuliani et al, 2006;Giaroni et al, 2013), albeit enteric neurons are not yet irreversibly damaged (Lindeström and Ekblad, 2004). Concentrations of NMDA antagonists, nNOS and iNOS inhibitors were chosen on the basis of previous data showing their efficacy in reducing in vitro I/R-stimulated glutamate and NO overflow from the guinea pig ileum (Giuliani et al, 2006;Giaroni et al, 2011Giaroni et al, , 2013.…”

“…The effect of test drugs on protein levels was expressed as the percent change vs. control preparations. Specificity of GluN1, iNOS and nNOS primary antibodies was evaluated as described by Giaroni et al (2011Giaroni et al ( , 2013.…”

“…In the rat ileum after a severe I/R injury, up-regulation of iNOS was associated with a decrease of the gastrointestinal transit (Hassoun et al, 2001). Accordingly, both iNOS and nNOS represent the major sources for NO overproduction in the guinea pig ileum myenteric plexus during I/R, albeit iNOS undergoes more consistent changes (Giaroni et al, 2013). Glutamate represents another well known player in the scenario of neuronal damage following I/R (Lau and Tymianski, 2010).…”