Opposing roles of STAT1 and STAT3 in T cell-mediated hepatitis: regulation by SOCS.
T cell-mediated fulminant hepatitis is a life-threatening event for which the underlying mechanism is not fully understood. Injection of concanavalin A (Con A) into mice recapitulates the histological and pathological sequelae of T cell-mediated hepatitis. In this model, both signal transducer and activator of transcription factor 1 (STAT1) and STAT3 are activated in the liver. Disruption of the STAT1 gene by way of genetic knockout attenuates liver injury, suppresses CD4(+) and NK T cell activation, and downregulates expression of proapoptotic interferon regulatory factor-1 protein and suppressor of cytokine signaling-1 ( SOCS1), but enhances STAT3 activation and STAT3-controlled antiapoptotic signals. Studies from IFN-gamma-deficient mice indicate that IFN-gamma not only is the major cytokine responsible for STAT1 activation but also partially accounts for STAT3 activation. Moreover, downregulation of STAT3 activation in IL-6-deficient mice is associated with decreased STAT3-controlled antiapoptotic signals and expression of SOCS3, but upregulation of STAT1 activation and STAT1-induced proapoptotic signals and exacerbation of liver injury. Taken together, these findings suggest that STAT1 plays a harmful role in Con A-mediated hepatitis by activation of CD4(+) and NK T cells and directly inducing hepatocyte death, whereas STAT3 protects against liver injury by suppression of IFN-gamma signaling and induction of antiapoptotic protein Bcl-X(L). STAT1 and STAT3 in hepatocytes also negatively regulate one another through the induction of SOCS.[1]References
- Opposing roles of STAT1 and STAT3 in T cell-mediated hepatitis: regulation by SOCS. Hong, F., Jaruga, B., Kim, W.H., Radaeva, S., El-Assal, O.N., Tian, Z., Nguyen, V.A., Gao, B. J. Clin. Invest. (2002) [Pubmed]
Annotations and hyperlinks in this abstract are from individual authors of WikiGenes or automatically generated by the WikiGenes Data Mining Engine. The abstract is from MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.About WikiGenesOpen Access LicencePrivacy PolicyTerms of Useapsburg
