Protective effect of N-acetylcysteine against lipopolysaccharide injury in hepatocytes of neonatal mice

Abstract

N-Acetylcysteine (NAC) is a sulfhydryl donor molecule with antioxidant and antiinflammatory effects. A major role has been described for inducible nitric oxide (NO) synthase in several inflammatory liver diseases. NAC attenuates NO generation following lipopolysaccharide injection in rats. The purpose of this study was to investigate the effect of NAC against lipopolysaccharide injury in hepatocytes of neonatal mice and the molecular mechanisms by which NAC influences inflammatory responses of the hepatocytes. The liver of neonatal mouse was digested by collagenase to dissociate the hepatocytes. The hepatocytes were cultured and isolated. After 7 days of culture the normal hepatocytes were divided into two groups: LPS group and NAC group. In LPS group, 10 microg/ml LPS was added into the culture medium. In NAC group, 5 mmol/L NAC was added into the culture medium firstly, 10 microg/ml LPS was added after 1 h of culture. There were 12 mice in each group. The cell supernatants and the hepatocytes were collected at 0, 6 and 12 hours after adding LPS. The cell supernatants were taken to measure the alanine aminotransferase (ALT) level and nitric oxide (NO) production by the biochemical methods. The cells were taken to analyze the gene expression of induced nitric oxide synthase (iNOS) by the RT-PCR. In LPS group, the levels of ALT, NO and iNOS mRNA increased significantly at the time points 6 h and 12 h compared with the time point 0, (P < 0.01). Compared with the LPS group, the levels of ALT, NO and iNOS mRNA of NAC group were lower at the time points 6 h and 12 h (P < 0.01). NAC may play a protective role in the hepatocytes injury caused by LPS in the neonatal mice. The protective mechanism works partially through the inhibition of iNOS activation by LPS.