Cytokines contribute to early hepatic parenchymal injury and microvascular dysfunction after bilateral hindlimb ischemia.

PURPOSE: Hepatic dysfunction may contribute to death from multiple organ dysfunction after abdominal aortic surgery. Several factors are likely responsible, and the purpose of this study was to determine whether the cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin 1 (IL-1) are involved in initiating this remote hepatic injury.
METHODS: In a normotensive rat model of 4-hour bilateral hindlimb ischemia/reperfusion (I/R), we measured systemic TNF-alpha and IL-1 levels throughout the I/R period. Rats were randomly assigned to either the 3-hour control group, the 3-hour I/R group, or the I/R group with administration of a polyclonal antibody (PAb) to TNF-alpha (I/R + TNF-alpha PAb). Direct evidence of lethal hepatocyte injury through the labeling of nuclei by propidium iodide (per 10(-1)mm(3)) and altered microvascular perfusion were assessed by using intravital microscopy.
RESULTS: Systemic TNF-alpha peaked at 83.97 pg/mL (P <.05, n = 5) at 30 minutes of reperfusion and returned to baseline in 60 to 90 minutes. No significant change in systemic IL-1 was detected (P <.05, n = 4). Alanine aminotransferase increased 2.5-fold in the I/R group through 3 hours of reperfusion (P <.05, n = 4), and TNF-alpha PAb did not attenuate this alanine aminotransferase increase (P <.05, n = 6). Lethal hepatocyte injury increased by 8-fold in the I/R group compared with the control group (P <.05, n = 5), whereas TNF-alpha PAb significantly reduced this injury (P <.05, n = 4). No regional differences in injury were noted within the acinus. Total perfusion within the microvascular unit did not drop; however, significant flow heterogeneity was observed. The proportion of continuously perfused sinusoids declined in the I/R group after 3 hours of reperfusion in both periportal (62.0 +/- 2.2, P <.05) and, to a lesser, although significant, degree, in the pericentral regions (73. 2 +/- 1.73, P <.05).
CONCLUSION: By scavenging extracellular TNF-alpha with a PAb, we provide direct evidence that TNF-alpha contributes to, but is not solely responsible for, early remote hepatocellular injury and microvascular dysfunction. The administration of TNF-alpha PAb reduced lethal hepatocyte injury in both regions of the acinus and also improved perfusion in the periportal region (76.8 +/- 5.41, P <.05), but not in the pericentral region. This suggests that TNF-alpha released during reperfusion mediates early remote hepatocellular injury and microvascular dysfunction after a remote ischemic insult.