Effect of lipopolysaccharide and cytokines on oxidative metabolism in neonatal rat hepatocytes

Background/Purpose: Lipopolysaccharide (LPS) and cytokines produced during neonatal sepsis trigger free radical production, which eventually results i n inhibition of liver metabolism. Studies in adults have indicated a hyperm etabolic belie response to sepsis; however, evidence for a hypermetabolic r esponse in neonates is equivocal. This study was carried out to determine w hether LPS and cytokines can cause liver hypermetabolism in neonates. Methods: The initial bacterial insult and cytokine cascade were mimicked by the addition of lipopolysaccharide (Escherichia coli 055:B5), tumour necro sis factor (TNF-alpha), and interleukin-g (IL6) during the isolation of hep atocytes by collagenase digestion from 11- to 13-day-old Wistar rats. Hepat ocyte oxygen consumption was measured polarographically with cells respirin g on palmitate (0.5 mmol/L). Myxothiazol, a specific inhibitor of mitochond rial respiration, was used to distinguish extra- and intramitochondrial oxy gen consumption. Morphologic changes were assessed by electron microscopy. Results: The addition of LPS, TNF-alpha and IL6 during hepatocyte isolation resulted in a 10% decrease in cell yield (P < .05) compared with untreated controls; however, cell viability was unchanged (n = 31). Both total and e xtramitochondrial oxygen consumption were significantly greater in treated cells compared with untreated controls (P < .05, Student's t test). Electro n microscopy indicated that LPS, TNF-alpha, and IL6 did not cause ultrastru ctural changes to hepatocytes. Conclusions: The increase in oxygen consumption was predominantly extramito chondrial and likely to be caused by increased oxygen requirement for cytos olic detoxification and repair purposes. This study shows that liver hyperm etabolism metabolism can occur in response to LPS and cytokines. However, d uring in vivo neonatal sepsis, additional free radical damage may blunt thi s hypermetabolic response. Copyright (C) 2001 by W.B. Saunders Company.