[Relationship of tumor necrosis factor alpha expression with activation of sphingomyelinase and lipid peroxidation after removal of cholestatic factor].

The goal of this work was to study the expression of tumor necrosis factor alpha (TNFalpha), sphingomyelin cycle activation, and lipid peroxidation (LPO) processes after the removal of a cholestatic factor in the liver subjected to different durations of cholestasis. Restored bile flow after a 9-day hepatic cholestasis normalized sphingomyelinase (SMase) activity and levels of TNFalpha and LPO products. The removal of a cholestatic factor after a 12-day cholestasis did not normalize the studied parameters: SMase activity and the levels of TNFalpha and LPO products remained much higher compared to control. A significant positive correlation between TNFalpha expression, SMase activity, and LPO rate has been revealed. The obtained data indicate that hepatocyte apoptosis after bile outflow restoration in late cholestasis can be due to the activation of the sphingomyelin cycle, LPO, and TNFalpha expression. The synergistic interaction can sharply increase the proapoptotic capacity of each of these factors since TNFalpha activates SMase and LPO, SMase activity depends on the LPO rate, while ceramide, an SMase-produced secondary messenger of apoptosis, can induce oxidative stress.

[Changes in sphingomyelinase activity, tumor necrosis factor alpha level, and lipid peroxidation rate in the course of development of cholestatic liver injury].

Changes in sphingomyelinase activity, tumor necrosis factor alpha expression, and lipid peroxidation rate in the course of development of cholestatic liver injury have been studied. The same type phase shifts in the parameters analyzed were observed, which included a marked decrease at the early stages of cholestasis (days 3-6) and a pronounced increase at the later stages (days 12-16), i.e., under the conditions of developed pathology. There is a significant positive linear correlation between tumor necrosis factor alpha expression, sphingomyelinase activity, and lipid peroxidation rate during cholestatic injury. The changes detected may reflect balance between the effects of the two major bile components--bilirubin, which is accumulated in the liver at the early stages of cholestasis, and bile acids, whose influence dominates at the later stages of pathologic process. Our results indicate that tumor necrosis factor alpha overexpression, the sphingomyelin cycle activation, and lipid peroxidation intensification may cause apoptosis of hepatocytes at the late stages of cholestasis.