HDAC3 inhibition improves urinary-concentrating defect in hypokalaemia by promoting AQP2 transcription

TGR5 attenuates DOCA-salt hypertension through regulating histone H3K4 methylation of ENaC in the kidney

Epithelial sodium channel (ENaC), located in the collecting duct principal cells of the kidney, is responsible for the reabsorption of sodium and plays a critical role in the regulation of extracellular fluid volume and consequently blood pressure. The G protein-coupled bile acid receptor (TGR5) is a membrane receptor mediating effects of bile acid and is implicated in kidney diseases. The current study aims to investigate whether TGR5 activation in the kidney regulated ENaC expression and potential mechanism. Lithocholic acid (LCA), a TGR5 agonist, markedly decreased systolic blood pressure induced by DOCA-salt in mice, which was associated with decreased ENaC expression in the kidney. DOCA-salt treatment increased renal expression of histone H3 lysine 4 trimethylation (H3K4me3) and decreased expression of lysine-specific demethylase 5A (KDM5A), a lysine demethylase, which was markedly reversed by LCA. TGR5 knockout caused further increased systolic blood pressure and ENaC expression in mice with DOCA-salt in association with increased H3K4me3 and decreased KDM5A. In immortalized mouse cortical collecting duct (mpkCCD) cells LCA markedly inhibited aldosterone-induced ENaC-mediated current. LCA treatment or TGR5 overexpression markedly inhibited ENaC and H3K4me3 protein expression in association with decreased KDM5A in mpkCCD cells treated with either aldosterone or angiotensin II. Inhibition or knockdown of KDM5A in mpkCCD cells prevented LCA-induced downregulation of ENaC expression by promoting H3K4me3 on the ENaC transcription start site. LCA upregulated KDM5A expression was likely through JNK/c-Jun signal pathway. In conclusion, LCA decreased blood pressure and ENaC protein expression in the kidney of mice with DOCA-salt, likely through activating TGR5 and upregulating KDM5A-induced H3K4me3 demethylation in ENaC promoter region.

Mechanism by which HDAC3 regulates manganese induced H3K27ac in SH-SY5Y cells and intervention by curcumin

Long-term excessive exposure to manganese can impair neuronal function in the brain, but the underlying pathological mechanism remains unclear. Oxidative stress plays a central role in manganese-induced neurotoxicity. Numerous studies have established a strong link between abnormal histone acetylation levels and the onset of various diseases. Histone deacetylase inhibitors and activators, such as TSA and ITSA-1, are often used to investigate the intricate mechanisms of histone acetylation in disease. In addition, recent experiments have provided substantial evidence demonstrating that curcumin (Cur) can act as an epigenetic regulator. Given these findings, this study aims to investigate the mechanisms underlying oxidative damage in SH-SY5Y cells exposed to MnCl2·4H2O, with a particular focus on histone acetylation, and to assess the potential therapeutic efficacy of Cur. In this study, SH-SY5Y cells were exposed to manganese for 24 h, were treated with TSA or ITSA-1, and were treated with or without Cur. The results suggested that manganese exposure, which leads to increased expression of HDAC3, induced H3K27 hypoacetylation, inhibited the transcription of antioxidant genes, decreased antioxidant enzyme activities, and induced oxidative damage in cells. Pretreatment with an HDAC3 inhibitor (TSA) increased the acetylation of H3K27 and the transcription of antioxidant genes and thus slowed manganese exposure-induced cellular oxidative damage. In contrast, an HDAC3 activator (ITSA-1) partially increased manganese-induced cellular oxidative damage, while Cur prevented manganese-induced oxidative damage. In summary, these findings suggest that inhibiting H3K27ac is a possible mechanism for ameliorating manganese-induced damage to dopaminergic neurons and that Cur exerts a certain protective effect against manganese-induced damage to dopaminergic neurons.

The lysine methyltransferase SMYD2 facilitates neointimal hyperplasia by regulating the HDAC3-SRF axis

Coronary restenosis is an important cause of poor long-term prognosis in patients with coronary heart disease. Here, we show that lysine methyltransferase SMYD2 expression in the nucleus is significantly elevated in serum- and PDGF-BB-induced vascular smooth muscle cells (VSMCs), and in tissues of carotid artery injury-induced neointimal hyperplasia. Smyd2 overexpression in VSMCs (Smyd2-vTg) facilitates, but treatment with its specific inhibitor LLY-507 or SMYD2 knockdown significantly inhibits VSMC phenotypic switching and carotid artery injury-induced neointima formation in mice. Transcriptome sequencing revealed that SMYD2 knockdown represses the expression of serum response factor (SRF) target genes and that SRF overexpression largely reverses the inhibitory effect of SMYD2 knockdown on VSMC proliferation. HDAC3 directly interacts with and deacetylates SRF, which enhances SRF transcriptional activity in VSMCs. Moreover, SMYD2 promotes HDAC3 expression via tri-methylation of H3K36 at its promoter. RGFP966, a specific inhibitor of HDAC3, not only counteracts the pro-proliferation effect of SMYD2 overexpression on VSMCs, but also inhibits carotid artery injury-induced neointima formation in mice. HDAC3 partially abolishes the inhibitory effect of SMYD2 knockdown on VSMC proliferation in a deacetylase activity-dependent manner. Our results reveal that the SMYD2-HDAC3-SRF axis constitutes a novel and critical epigenetic mechanism that regulates VSMC phenotypic switching and neointimal hyperplasia.