Guanosine prevents nuclear factor-κB nuclear translocation ameliorating experimental colitis in rats

Abstract

Background inflammatory bowel diseases (IBDs), including Crohn’s disease (CD) and ulcerative colitis (UC), are prevalent and debilitating health problems worldwide. Due to the adverse effects of classical treatment for IBD, therapeutic options and approaches for these diseases continue to evolve. Guanosine, a guanine-based purine, is an extracellular signalling molecule that seems to exert anti-inflammatory and antioxidative effects in several in vivo and in vitro injury models. The aim of the present study was to investigate whether exogenous guanosine may have protective effects on 2,4-dinitrobenzene sulfonic acid (DNBS)-induced Colitis in rat. Methods Experimental Colitis was induced by intrarectal administration of 0.25 ml of DNBS in 50% EtOH solution. After the induction of colitis animal received daily for 6 consecutive days i.p injection of guanosine (8 mg/kg). The effects of guanosine on DNBS-induced colitis were assessed by determination of body weight loss, stool consistency, colon weight/length, histological analysis, Furthermore the myeloperoxidase activity was biochemically evaluated and the mRNA expression of pro-inflammatory cytokines was detected by real-time quantitative reverse transcription PCR (qRT-PCR). In addition, nuclear factor-κB (NF-κB) p65 protein expression levels in colon tissues was investigated using Western blotting and markers of oxidative and nitrosative stress were detected. Results Inflammation in DNBS-rat is characterised by symptoms of losing body weight, loose feces/watery diarrhoea, leukocyte infiltration upregulation of proinflammatory cytokines, oxidative and nitrosative stress. Treatment with guanosine (8 mg/kg) significantly ameliorated the severity of DNBS-induced colitis as evidenced by the reduction in body weight loss and in diarrhoea. Guanosine also prevented the macroscopic and microscopic damage to the colonic mucosa, and the increase in myeloperoxidase activity induced by DNBS. Furthermore, the guanosine treated colitis rats also exhibited a lower mRNA level of pro-inflammatory cytokines, namely interleukin-1β , interleukin-6 and tumour necrosis factor-α. Importantly, the ameliorative effect of guanosine was related to an inhibition of the NF-κB signalling pathway by downregulating the expression levels of NF-κB p-65, and to a reduction of DNBS increased levels of reactive oxygen species and nitrite. Conclusion Overall these results indicate that guanosine is able to alleviate colonic inflammation in DNBS- rats mainly by down-regulation of the NF-κB signalling pathway and of the production of anti-inflammatory cytokines, reactive oxygen species and nitrite. Further studies are encouraging for disclosure guanosine as a novel drug candidate for the treatment of colonic inflammation.