Hepatic redox regulation of transcription factors activator protein-1 and nuclear factor-kappaB after hemorrhagic shock in vivo.

Abstract

Ischemia and reperfusion result in a hepatocellular stress gene response, characterized by a zonal heterogeneity with pericentral hepatocytes being the primary target. In the present study, we assessed cell type-specific and zonal pattern of activation of redox-sensitive transcription factors nuclear factor-kappaB (NFkappaB) and activator protein-1 (AP-1) in a graded model of hemorrhage and their modulation by the antioxidants trolox and tempol. Hemorrhagic hypotension (35-40 mm Hg) up to 3 h without subsequent resuscitation led to an only moderate activation of NFkappaB and AP-1. In contrast, fluid resuscitation after 1 or 2 h of hemorrhage induced a profound activation of AP-1 within the first hour of reperfusion. Consistent with a regulation by oxygen free radicals, activation of AP-1 was substantially attenuated by antioxidants. The faint activation of NFkappaB with various intervals of hemorrhage was unaffected by antioxidants and did not exceed activation with sham operation. Immunohistochemistry for the AP-1 subunit c-Jun revealed a predominant expression in nuclei of pericentral and midzonal hepatocytes. These data suggest activation of AP-1 in hepatocytes most susceptible to injury and reprogramming of gene expression in low-flow ischemia. Whereas activation of NFkappaB is weak in this model and is not modulated by either reperfusion or antioxidants, regulation of AP-1 after hemorrhage and subsequent resuscitation seems to depend on oxygen free radical formation because it requires reperfusion and is inhibitable by antioxidants.