Inhibition of Histone Deacetylase 6 activity provides protection against atherogenesis: A role for HDAC6 NEDDylation

[Speaker] Deepesh Pandey:1
[Co-author] Yohei Nomura:1, Max C Rossberg:1, Anil Bhatta:1, Lew Romer:1, Dan Berkowitz:1
1:School of Medicine, Johns Hopkins University, USA

We have recently demonstrated that Histone Deacetylase 6 (HDAC6) has a critical role in endothelial function through the regulation of the H2S-producing enzyme-Cystathionine Gamma Lyase (CSE). However, uncertainty persists regarding a role for HDAC6 in atherogenesis. We investigated whether pharmacological inhibition of HDAC6 by the small molecule inhibitor tubacin would attenuate atherogenesis. We further determined some of the specific molecular mechanism(s) that regulate endothelial HDAC6 activity. We have previously shown that HDAC6 regulates CSE expression. Moreover, preliminary data suggest that overexpression of HDAC6 dramatically reduces endothelial nitric oxide synthase expression. Given that eNOS and CSE are two of the genes that regulate endothelial function, we tested the hypothesis that HDAC6 is critical regulator of endothelial function via modulation of CSE and eNOS. To test this hypothesis, we adopted a novel strategy to induce endothelial dysfunction and atherosclerosis in mice. This involved a single i.p injection of PCSK9 AAV followed by a high fat diet (HFD) for 12 weeks. We evaluated whether administration of tubacin attenuated or reversed the endothelial dysfunction and atherosclerosis induced in these mice. Tubacin significantly blunted PCSK9-induced increases in pulse wave velocity (index of vascular stiffness and overall vascular health) that are also seen in atherogenic mice. Furthermore, tubacin significantly protected vessels from defective vasorelaxation, as evaluated by acetycholine-mediated relaxation using wire myograph. Plaque burden defined by Oil Red O staining was also found to be significantly less in mice that received tubacin than in those that received PCSK9 alone. inhibition of the NEDD8 -activating enzyme 1 (NAE1) by MLN4924 significantly increased HDAC6 activity in Human Aortic Endothelial Cells (HAEC). Interestingly, levels of HDAC6 remain unchanged in these animals. This finding consistent with the etiology of the change in function being the post-translational modification of HDAC6, and not due to its overall abundance. Human aortic endothelial cells exposed to the atherogenic stimulus OxLDL exhibited enhanced HDAC6 activity. This increase in HDAC6 activity was attenuated in a dose response manner by pre-treatment with MLN4924. Taken together, HDAC6 Neddylation provides a novel molecular pathway that could regulate genes that impact endothelial control of vasomotor tone and reactivity, and atherosclerosis.

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