Effect of tubastatin A on NLRP3 inflammasome activation in macrophages under hypoxia/reoxygenation conditions.

Background: There are currently no effective drugs to mitigate the ischemia/reperfusion injury caused by fluid resuscitation after hemorrhagic shock (HS). The aim of this study was to explore the potential of the histone deacetylase 6 (HDAC6)-specific inhibitor tubastatin A (TubA) to suppress nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) inflammasome activation in macrophages under hypoxia/reoxygenation (H/R) conditions.

Methods: The viability of RAW264.7 cells subjected to H/R after treatment with different concentrations of TubA was assessed using a cell-counting kit-8 (CCK8) assay. Briefly, 2.5 μmol/L TubA was used with RAW264.7 cells under H/R condition. RAW264.7 cells were divided into three groups, namely the control, H/R, and TubA groups. The levels of reactive oxygen species (ROS) in the cells were detected using fluorescence microscopy. The protein expression of HDAC6, heat shock protein 90 (Hsp90), inducible nitric oxide synthase (iNOS), NLRP3, gasdermin-D (GSDMD), Caspase-1, GSDMD-N, and Caspase-1 p20 was detected by western blotting. The levels of interleukin-1β (IL-1β) and IL-18 in the supernatants were detected using enzyme-linked immunosorbent assay (ELISA).

Results: HDAC6, Hsp90, and iNOS expression levels were significantly higher (P<0.01) in the H/R group than in the control group, but lower in the TubA group than in the H/R group (P<0.05). When comparing the H/R group to the control group, ROS levels were significantly higher (P<0.01), but significantly reduced in the TubA group (P<0.05). The H/R group had higher NLRP3, GSDMD, Caspase-1, GSDMD-N, and Caspase-1 p20 expression levels than the control group (P<0.05), however, the TubA group had significantly lower expression levels than the H/R group (P<0.05). IL-1β and IL-18 levels in the supernatants were significantly higher in the H/R group compared to the control group (P<0.01), but significantly lower in the TubA group compared to the H/R group (P<0.01).

Conclusion: TubA inhibited the expression of HDAC6, Hsp90, and iNOS in macrophages subjected to H/R. This inhibition led to a decrease in the content of ROS in cells, which subsequently inhibited the activation of the NLRP3 inflammasome and the secretion of IL-1β and IL-18.