Effects of selective class IIa HDAC inhibition with TMP195 on pro-atherogenic mechanisms in endothelial cells and macrophages

Background: Targeting inflammation for CVD prevention remains a challenge. Genome-wide association studies have associated HDAC9 with both major artery stroke and coronary artery disease, highlighting it as a target for therapeutic development. TMP195 functions as a selective, competitive inhibitor of class IIa HDACs. Previous data from our laboratory revealed an anti-atherogenic role of TMP195 in ApoE-deficient mice. Nevertheless, the mechanisms underlying the atheroprotective effect of selectively inhibiting class IIa HDACs are poorly understood. Methods: The anti-inflammatory effects of TMP195 were investigated in vivo using ApoE-deficient mice with induced peritonitis, and in vitro using endothelial cells and macrophages, where cytokine and adhesion molecule expression and secretion were assessed by immunohistochemistry and qPCR. The impact of TMP195 on NFκB signaling was studied using immunoprecipitation and subsequent Western blotting. HDAC9-specific effects were investigated in vitro by using ApoE-/- HDAC9-/- macrophages and in vivo through double-knockout mice. Results: Our findings show that selective inhibition of class IIa HDACs with TMP195 impairs the NFB signaling pathway. Specifically, TMP195 treatment resulted in a significant reduction of p65 phosphorylation in HAoECs and MAoECs at the serine sites 536 and 276 owing to an increased acetylation of IKKβ. Additionally, TMP195 treatment could significantly decrease the expression and secretion of the pro-inflammatory cytokines IL-1β and IL-6 and the adhesion molecule VCAM1 in endothelial cells and macrophages. In HDAC9-deficient mice, treatment with TMP195 did not result in a significant decrease in atherosclerotic lesion size. Conclusions: The generated data demonstrate that there is an anti-inflammatory effect of TMP195 on human and mouse aortic endothelial cells and bone marrow-derived macrophages that underlies the atheroprotective effect of selectively inhibiting class IIa HDACs. In conclusion, targeting HDAC9 with TMP195 could offer an effective new treatment for atherosclerosis.