Inhibition of hepatocyte H-2Kb by triptolide leads to
natural-killer-cell-mediated cytotoxicity against self-hepatocytes under
LPS stimulation
Abstract
Background and Purpose: Triptolide (TP) is the major active and toxic
component of Tripterygium wilfordii Hook. F. Previous studies reported
that a toxic pretreatment dose of triptolide leads to hepatic
intolerance to exogenous lipopolysaccharide stimulation in mice and
liver failure rather than damaging the liver directly. However, the
immune mechanisms involved have not been elucidated. Experimental
Approach: Flow cytometry analysis, LDH release measurement, blood
biochemical analysis, ELISA, qPCR, magnetic beads sorting, plasmid
transfection and AAV-DNA transduction were performed to investigate the
immune mechanism in TP- and LPS-induced fulminant hepatitis. Key
Results: The results show that IFN-γ-mediated necroptosis occurred in
C57BL/6N mice treated with 500 μg/kg TP and 0.1 mg/kg LPS to induce
fulminant hepatitis. Intracellular IFN-γ levels of natural killer cells
increased significantly in mice administered TP and LPS, indicating
primary source of IFN-γ in innate lymphocytes in the liver.
Flow-cytometry analysis and in vivo depletion of NK cells showed that NK
cells in the liver were activated and exhibited potent cytotoxicity. In
vivo and in vitro TP administration significantly inhibited hepatocyte
major histocompatibility complex class I molecules, H-2Kb, in mice.
Further in vitro analysis confirmed that TP-pretreated hepatocytes were
susceptible to NK-cell-mediated cytotoxicity, and the induction of
hepatocyte H-2Kb significantly decreased NK-cell-mediated cytotoxicity.
In vivo induction or of overexpression of hepatocyte H-2Kb also
protected against TP- and LPS-induced liver injury. Conclusion and
Implications: In conclusion, inhibiting hepatocyte H-2Kb accounted for
TP-induced hepatic intolerance to exogenous LPS stimulation and was
directly related to NK-cell-mediated cytotoxicity against
self-hepatocytes.