Initiation of remote hepatic injury in the rat: Interactions between Kupffer cells, tumor necrosis factor-alpha, and microvascular perfusion

Severe trauma may initiate a systemic inflammatory response, which in turn may result in remote organ injury. After limb ischemia/reperfusion (I/R), i ntravital fluorescence microscopy was applied to the livers of normotensive rats to investigate the initiation of remote injury to the liver. Addition ally, we determined whether Kupffer cell activation and tumor necrosis fact or-alpha (TNF-alpha) were involved, via perfusion deficits, in such injury. TNF-alpha, measured by immunoassay, peaked at 30 minutes of reperfusion, b ut returned to baseline within 60 minutes. Limb I/R resulted in significant increases to global hepatocellular injury measured by alanine transaminase (ALT) and lethal hepatocyte injury as seen with intravital fluorescence mi croscopy. Although the number of perfused sinusoids went unchanged, a signi ficantly augmented perfusion heterogeneity was measured. After 1.5 hours of reperfusion, both TNF-alpha and Kupffer cells were shown to contribute to global hepatocellular injury (e.g., ALT). After 3 hours, TNF-alpha was no l onger essential for this injury, suggesting that some other mechanism(s) ac tivated Kupffer cells and initiated hepatocellular injury. Using propidium iodide and fluorescence microscopy, we found that both TNF-alpha and Kupffe r cell activation were necessary to drive hepatocytes toward lethal injury. No additional benefits were observed with a combination of TNF-alpha inhib ition and Kupffer cell suppression. These results not only implicate both K upffer cells and TNF-alpha in the initiation of remote hepatic injury, but suggest that sinusoidal perfusion deficits are not essential for the initia tion of such injury. Other mechanism(s) are likely involved in the pathogen esis of remote hepatic parenchymal injury.