Evaluation of the effect of LA9498, a novel highly potent and selective HDAC3 inhibitor, on adipocyte and macrophage phenotype compared to vehicle and MS275, a class I HDAC inhibitor, as reference compound

INTRODUCTION and AIM: Epigenetics and metabolism play a role in physiological and pathological conditions such as obesity and inflammatory diseases. Histone deacetylases (HDACs) are epigenome modifiers regulating adipocyte and macrophage phenotype and metabolism. We previously demonstrated that HDAC3 genetic inactivation causes the metabolic rewiring in white adipose tissue towards browning. Moreover, HCDA3 silencing or inhibition are proved to be effective in reducing cytokine secretion in monocytes and M1 macrophages. The aim of this project is to evaluate the effect of LA9498, a novel highly potent and selective HDAC3 inhibitor, on adipocyte and macrophage phenotype compared to vehicle and MS275, a class I HDAC inhibitor, as reference compound. METHODS: C3H/10T1/2 adipocytes were treated with vehicle, MS275 or LA9498 throughout the differentiation. RAW264.7 macrophages were treated with vehicle, MS275 or LA9498 and/or 10 ng/mL interferon gamma (IFNγ) for 4 hours. At the end of the treatment, gene expression, protein expression, lipid accumulation, and mitochondrial functionality and mass were analyzed. RESULTS: LA9498 was more potent than MS275 in increasing the expression of genes involved in adipocyte differentiation, lipid mobilization, fatty acid β-oxidation, browning, and mitochondrial functionality. Indeed, the selected concentration for LA9498 treatment was 300 nM, lower than 1 µM of MS275. Additionally, i) higher accumulation of lipids, ii) increased mitochondrial functionality (i.e., basal respiration, ATP production, proton leak, coupling efficacy, maximal respiration, spare respiratory capacity, non-mitochondrial oxygen consumption), and iii) greater expression of protein belonging to complexes II, III, and IV of the electron transport chain are observed in cells treated with LA9498. LA9498 treatment of macrophages activated with IFNγ reduced the expression of pro-inflammatory genes (i.e., Il1b, Tnf, Nos2) and increased the expression of Arg2, a potentially anti-inflammatory gene. This effect was not observed with MS275 treatment. CONCLUSIONS: LA9498 is a promising compound for inducing browning of adipocytes and promoting anti-inflammatory effects in macrophages. Further studies are warranted to characterize the effect of this novel compound on cytokine and adipokine secretion and to evaluate the in vivo dose and effects of the compound.