[The relationship between LPS-induced apoptosis in hepatocyte, Kupffer cell and hepatocytic damage]

To study the role of tumor necrosis factor (TNF alpha) in the mechanisms of liver injury and the relationship between LPS-induced apoptosis in hepatocyte (HC), kupffer cell (KC), and hepatic damage.

In vitro, kupffer cells (1 x 10/ml) were stimulated with different concentrations of endotoxin (1-10 micrograms/ml) for 1-24 hr; the kupffer cells, which had been cultured with endotoxin for 24 hr, were isolated to coculture with hepatocytes (1:1) for 1-24 hr. Two kinds of cells of apoptosis and the block effect of TNF alpha antibody were detected by cell death ELISA, and the supernatant was performed to determine the levels of alanine aminotransferase (ALT), lactate dehydrogenase (LDH) at different time points.

Following stimulation with LPS, the number of positive apoptotic KC increased in a concentration and time (3 h-24 h) dependent manner. In contrast, coincubation of HC with LPS-stimulated KC resulted in a marked increase in positive apoptotic hepatocyte when LPS concentration was greater than 1 microgram/ml. TNF alpha antibody blocked apoptosis in both KC and HC. Only when the LPS concentration was higher than 1 microgram/ml and cultured for 6 hr, the release of liver enzymes (ALT, LDH), responsible for hepacyte damage, rose significantly, but the process was behind of apoptosis, and TNF alpha antibody couldn't block it.

TNF alpha mediates LPS-induced apoptosis in KC and HC, and the apoptosis precedes cellular damage. Massive apoptosis of KC may lead to the decrease of clearance of LPS, thereby exacerbating septic shock, hepatocyte damage and apoptosis.