Title

 

Authors

A. Tiengo¹, P. Brun², S. Mazzorana¹, C. Zoppellaro¹, M. Qesari¹, R.M. Gaion¹, I. Castagliuolo², M.C. Giron^1
 
1Department of Pharmacology and Anesthesiology, University of Padova
²Department of Histology, Microbiology & Medical Biotechnologies, University of Padova

 

Abstract

Background. Gastrointestinal motor disorders (GIMDs) are a clinically heterogeneous group of diseases in which symptoms appears to arise as a result of neuromuscular dysfunction (Wingate et al., 2002). Among common pathogens the herpes simplex virus type 1 (HSV-1) is a potential candidate involved in GIMDs. Recently, we have shown that HSV-1 infects the enteric nervous system (ENS) leading to altered gut contractility, intestinal transit and cytokines release in rat ileum longitudinal smooth muscle-myenteric plexus preparations (Brun et al, 2010). The aim of the study was to characterize the altered neural pathways involved in HSV-1-induced gut dysmotility during the acute and chronic phases of the viral infection, at 1 and 8 weeks post intragastric inoculum, respectively. Methods. Male C57Bl/6 mice (age=3 months) were inoculated with HSV-1 intranasally (IN; 10³ p.f.u.) and after 4 weeks intragastrically (IG; 10⁸ p.f.u.).Infected or mock infected mice were sacrificed 1 and 8 weeks after IG inoculation. The presence of HSV-1 infection was determined by PCR amplification of HSV-1-tk gene, RT-PCR for HSV-1 latency associated transcripts (LATs) and early gene ICP-4 in the brain and in freshly isolated myenteric ganglia. In isolated ileum segments, mounted vertically in organ baths, changes in muscle tension were recorded using isometric transducersfollowing treatments with: charbacol (0.001-100 mM), serotonin (5-HT; 1 µM), substance P (SP; 3 μM), KCl (60 mM), electric field stimulation (EFS, 1-40 Hz) in the presence or absence of 1μM TTX or atropine. Non-adrenergic, non-cholinergic neurotransmission (NANC; EFS=20 Hz in the presence of 1 µM atropine and 3 µM guanethidine) was also evaluated with and without 0.1 mM L-NAME. Results. No signs of histological abnormalities were observed in the gut of IG infected rodents. In the brain and ENS HSV-1 established a latent infection demonstrated by the presence of viral tk-DNA and LATs mRNA. Emax values for carbachol-induced contractions were significantly increased at 1 and 8 weeks post-infection (48% and 75%, respectively) without any changes of pD2 values. Response to KCl was significantly augmented at 1 and 8 weeks post inoculum (41% and 69%, respectively) whereas neurally-mediated contractions induced by EFS (20 Hz) were significantly reduced at 1 week (-47%) and increased at 8 weeks (+32%) in HSV-1 infected mice. 5-HT and SP responses were also reduced at 1 week (-64% and -44%, respectively) and increased at 8 weeks (+214% and +167%, respectively) post-infection. Furthermore, nonadrenergic, noncholinergic relaxations of ileum segments induced by EFS (10 Hz) in the presence of 1 mM atropine and 3 mM guanethidine were significantly increased at 1 and 8 weeks after HSV-1 inoculum. These changes at 1 week were not reverted by pretreatment with L-NAME. Conclusions. HSV-1 latent infection in the ENS affects significantly enteric neurochemical pathways leading to altered gut motor function and appears to be an innovative animal model to uncover the basic mechanisms of enteric neuropathies.
 
Wingate et al. (2002). J Gastroenterol Hepatol. 17:S1-14.
Brunet al. (2010). Gastroenterology. 138:1790-801.