STAT3 S-glutathionylation regulates Th17 differentiation in experimental immune thrombocytopenia.

BACKGROUND: Immune thrombocytopenia (ITP) is an autoimmune condition marked by an abnormal response of T cells, particularly driven by splenic T helper cells under the regulation of STAT3. Protein S-glutathionylation (PSSG), a vital post-translational modification, significantly impacts the function of numerous proteins. However, the role of S-glutathionylation in modulating STAT3 activation and T helper cells in ITP has not been previously investigated. This study reveals that S-glutathionylation, regulated by the deglutathionylation enzyme glutaredoxin 1 (Grx1), is essential in the pathogenesis of ITP.

METHODS: Levels of S-glutathionylation in ITP patients were evaluated using Western blotting and GSSG/GSH assay kits. To explore the role of S-glutathionylation in ITP, we employed wild-type (WT) and glutaredoxin 1 knockout (Grx1 KO) mice to create a passive ITP mouse model. The differentiation of Th17 cells was assessed both in vitro and in vivo via flow cytometry. Additionally, STAT3 activation was examined using Western blotting, GSSG assays, and immunofluorescence.

RESULTS: An elevation in protein S-glutathionylation (PSSG) was observed in ITP patients. In our mouse model, Grx1 KO mice displayed higher PSSG levels, which were associated with a reduction in ITP symptoms. Mechanistically, Grx1 KO enhanced STAT3 S-glutathionylation, thereby inhibiting its activation and decreasing the production of inflammatory cytokines. Moreover, STAT3 S-glutathionylation significantly suppressed Th17 cell differentiation, underscoring its role in modulating immune responses in ITP.

CONCLUSIONS: Elevated PSSG levels due to Grx1 KO enhance STAT3 S-glutathionylation, which subsequently inhibits STAT3 activation and Th17 cell differentiation, thereby alleviating ITP symptoms.