HDAC6-specific inhibitor suppresses Th17 cell function via the HIF-1α pathway in acute lung allograft rejection in mice

Background: Previous animal experiments and clinical studies indicated the critical role of Th17 cells in lung transplant rejection. Therefore, the downregulation of Th17 cell function in lung transplant recipients is of great interest. Methods: We established an orthotopic mouse lung transplantation model to investigate the role of histone deacetylase 6-specific inhibitor (HDAC6i), Tubastatin A, in the suppression of Th17 cells and attenuation of pathologic lesions in lung allografts. Moreover, mechanism studies were conducted in vitro. Results: Tubastatin A downregulated Th17 cell function in acute lung allograft rejection, prolonged the survival of lung allografts, and attenuated acute rejection by suppressing Th17 cell accumulation. Consistently, exogenous IL-17A supplementation eliminated the protective effect of Tubastatin A. Also, hypoxia-inducible factor-1 alpha (HIF-1 alpha) was overexpressed in a lung transplantation mouse model. HIF-1 alpha deficiency suppressed Th17 cell function and attenuated lung allograft rejection by downregulating retinoic acid-related orphan receptor yt (ROR yt) expression. We showed that HDAC6i downregulated HIF-1 alpha transcriptional activity under Th17-skewing conditions in vitro and promoted HIF-1 alpha protein degradation in lung allografts. HDAC6i did not affect the suppression of HIF-1 alpha-/- naive CD4+ T cell differentiation into Th17 cell and attenuation of acute lung allograft rejection in HIF-1 alpha-deficient recipient mice. Conclusion: These findings suggest that Tubastatin A downregulates Th17 cell function and suppresses acute lung allograft rejection, at least partially, via the HIF-1 alpha/ RORyt pathway.