Manipulation of nitric oxide in an animal model of acute liver injury. The impact on liver and intestinal function

Abstract

Background: Nitric oxide may have a protective effect on the liver during endotoxemia and chronic inflammation. There is evidence that it maintains liver and intestinal tissue integrity during inflammatory processes. We evaluated the impact of altering nitric oxide release on acute liver injury, the associated gut injury and bacterial translocation, at different time intervals.

Methods: An acute rat liver injury model induced by D-galactosamine was used. Sprague Dawley rats were divided into four main groups: normal control, acute liver injury control, acute liver injury + N-nitro-L-arginine methyl ester (L-NAME), acute liver injury + L-NAME + L-arginine. Each group was divided into three subgroups according to the different time intervals (6, 12, 24 hours) after the induction of the liver injury. Liver enzymes and bilirubin were evaluated, as well as bacterial translocation, cecal and colonic microflora, and histological study of liver, ileum and cecum.

Results: Liver enzymes increased significantly at all time intervals in acute liver injury + L-NAME compared to liver injury control groups. Bacterial translocation increased significantly in liver injury + L-NAME groups; at 6 hours to the liver, at 12 hours to the liver and mesenteric lymph nodes (MLNs), and at 24 hours to arterial and portal blood, liver and MLNS. Inhibition of nitric oxide increased significantly the Enterobacteriaceae count in cecum compared to normal and liver injury control groups. The G-negative anaerobes increased significantly in the colon compared to the liver injury control group.

Conclusion: Inhibition of nitric oxide in an acute liver injury model potentiates the liver injury as evidenced by increased appearance of hepatocellular necrosis and elevated liver enzymes and bilirubin. It increases the Enterobacteriaceae in both cecum and colon and Gnegative anaerobes in the colon. It also increases bacterial translocation to extra-intestinal sites. The increased bacterial translocation could be one of the mechanisms potentiating liver injury and nitric oxide may be pathophysiologically involved. Further studies are required to confirm this hypothesis.

Keywords: Acute liver injury; Arginine; Bacterial translocation; Intestinal microflora; L-NAME; Nitric oxide.

Figure 1

Histological appearance of the liver 6 hours after the injury (Hematoxylin-Eosin, ×100). The liver injury control group (Fig. 1A) showing hepatocellular necrosis and inflammatory cell infiltration. The liver injury + L-NAME group (Fig. 1B) showing more hepatocellular necrosis and inflammatory cell infiltration compared to the liver injury control group.

Figure 2

Histological appearance of the liver 12 hours after the injury (Hematoxylin-Eosin, ×100). The liver injury control group (Fig. 2A) showing hepatocellular necrosis and inflammatory cell infiltration. The liver injury + L-NAME group (Fig. 2B) showing more hepatocellular necrosis and inflammatory cell infiltration compared to the liver injury control group.

Figure 3

Histological appearance of the liver 24 hours after the injury (Hematoxylin-Eosin, ×100). The liver injury control group ( Fig. 3 A) showing hepatocellular necrosis and inflammatory cell infiltration. The liver injury + L-NAME group ( Fig. 3 B) showing more hepatocellular necrosis and inflammatory cell infiltration.