Individual regulation of different hepatocellular functions during sepsis

The liver as a central regulator of hydrogen sulfide

The liver is likely exposed to high levels of hydrogen sulfide (H2S) from endogenous hepatic synthesis and exogenous sources from the gastrointestinal tract. Little is known about the consequence of H2S exposure on the liver or hepatic regulation of H2S levels. We hypothesized that the liver has a high capacity to metabolize H2S and that H2S oxidation is decreased during sepsis, a condition in which hepatic O2 is limited and H2S synthesis is increased. Using a nonrecirculating isolated and perfused liver system, we demonstrated rapid hepatic H2S metabolism up to an infusion concentration of 200' μM H2S. Hydrogen sulfide metabolism was associated with an increase in O2 consumption from a baseline 96.7 ± 7.6 μmol O2/min/kg to 109 ± 7.4 μmol O2/min/kg at an infusion concentration of 150 μM H2S (P < 0.001). Removal of O2 from the perfusate decreased H2S clearance from a maximal 97% to only 23%. Livers isolated from rats subjected to cecal ligation and puncture (CLP) did not differ significantly from control livers in their capacity to metabolize H2S, suggesting that H2S oxidation remains a priority during sepsis. To test whether H2S induces O2 consumption in vivo, intravital microscopy was utilized to monitor the oxygen content in the hepatic microenvironment. Infusion of H2S increased the NADH/NAD+ ratio (645 gray-scale-unit increase, P = 0.035) and decreased hepatic O2 availability visualized with Ru(Phen)3(2+) (439 gray-scale-unit increase, P = 0.040). We conclude that the liver has a high hepatic capacity for H2S metabolism. Moreover, H2S oxidation consumes available oxygen and may exacerbate the tissue hypoxia associated with sepsis.

Liver dysfunction and sepsis determine operative mortality after liver resection

BACKGROUND

Liver failure is the principal cause of death after hepatectomy. Its progression towards death and its relationship with sepsis are unclear. This study analysed predictors of mortality in patients with liver dysfunction and the role of sepsis in the death of these patients.

METHODS

The study focused on patients with liver dysfunction, excluding those with vascular thrombosis, after liver resection at one of two centres between 1998 and 2006.

RESULTS

Liver dysfunction occurred after 57 (4.5 per cent) of 1271 hepatectomies. Fifty-three patients without vascular thrombosis were included in the analysis, with a mortality rate of 23 per cent. Independent predictors of death were age (odds ratio (OR) 1.18 per year increase; P = 0.017), cirrhosis (OR 54.09; P = 0.004) and postoperative sepsis (OR 37.58; P = 0.005). Sepsis occurred in 15 patients (28 per cent), seven of whom died. Intestinal pathogens were isolated in 12 patients with sepsis. The risk of sepsis was significantly increased in those with surgical complications (11 of 16 versus four of 37; P < 0.001).

CONCLUSION

Sepsis plays a key role in the death of patients with liver dysfunction after hepatectomy. Early recognition and aggressive treatment of sepsis may reduce mortality.

Nuclear receptors: mediators and modifiers of inflammation-induced cholestasis

Inflammation-induced cholestasis (IIC) is a frequently occurring phenomenon. A central role in its pathogenesis is played by nuclear receptors (NRs). These ligand-activated transcription factors not only regulate basal expression of hepatobiliary transport systems, but also mediate adaptive responses to inflammation and possess anti-inflammatory characteristics. The latter two functions may be exploited in the search for new treatments for IIC as well as for cholestasis in general. Current knowledge of the pathogenesis of IIC and the dual role NRs in this process are reviewed. Special interest is given to the use of NRs as potential targets for intervention.

Sensitive chemiluminescence immunoassay for the determination of rat serum alpha1-acid glycoprotein

We present the establishment of a sensitive immunoassay for the determination of alpha1-acid glycoprotein (orosomucoid, AGP) in rat serum. The assay is based upon antigen capture by surface-immobilized specific polyclonal rabbit anti-AGP antibodies with biotinylated rat AGP (rAGP) as the tracer, and formatted as competitive enzyme immunoassay. Signaling is performed by streptavidin-conjugated horseradish peroxidase. Enzyme activity is quantified by an enhanced chemiluminometric method, allowing the sensitive detection of rAGP serum levels in small sample volumes.