HDACs x TFEB

Targeting metabolic disorders has emerged as a promising therapeutic strategy in the treatment of chronic kidney disease (CKD). 18β-glycyrrhetinic acid (18β-GA) is known for its metabolic regulatory and antioxidant effects in various diseases. However, the precise effects and underlying mechanisms of 18β-GA on CKD remain unclear.

This study aims to evaluate the therapeutic efficacy of 18β-GA on CKD and to identify the molecular targets of 18β-GA with a particular emphasis on its role in metabolic regulation.

A high-fat diet-induced CKD model was established to investigate the influence of 18β-GA on lipid metabolic disorders, cellular senescence and fibrosis in the kidneys. Co-immunoprecipitation was performed to investigate the impact of 18β-GA on the interaction between transcription factor EB (TFEB) and sirtuin 1 (SIRT1). Additionally, network pharmacology and molecular docking analyses were conducted to identify the specific target proteins of 18β-GA.

18β-GA alleviated renal lipid accumulation, tubular cell senescence and renal interstitial fibrosis in CKD mice. Treatment with 18β-GA largely restored mitochondrial function and attenuated intracellular lipotoxicity and associated cellular senescence by promoting lipophagy in renal tubular cells. Mechanistically, 18β-GA acting as a partial antagonist of peroxisome proliferator-activated receptor gamma (PPARγ) enhanced lipophagy through SIRT1-mediated nuclear translocation of TFEB which induced the expression of microtubule-associated protein light chain 3 (LC3).

Our findings demonstrate that 18β-GA, functioning as a partial antagonist of PPARγ, counteracts CKD progression by activating the SIRT1-TFEB-LC3 signaling axis-mediated lipophagy and thus uncover a novel mechanism by which 18β-GA improves renal lipid metabolism disorders and exerts renoprotective effects. These results highlight the potential of 18β-GA as a promising therapeutic agent for the treatment and prevention of CKD.

The microphthalmia/transcription factor E (MiT/TFE) family activates macroautophagy/autophagy and lysosomal genes during acute nutrient deficiency. However, the mechanisms that suppress transcription of these genes under steady-state, nutrient-rich conditions to prevent unnecessary expression remain unclear. In this study, we identified a previously unrecognized mechanism of transcriptional repression for autophagy and lysosomal genes. Under nutrient-rich conditions, USF2 (upstream transcription factor 2) binds to the coordinated lysosomal expression and regulation (CLEAR) motif, recruiting a repressive complex containing HDAC (histone deacetylase). In contrast, during nutrient deficiency, TFEB (transcription factor EB) displaces USF2 at the same motif, activating transcription. This switch is regulated by USF2 phosphorylation at serine 155 by GSK3B (glycogen synthase kinase 3 beta). Reduced phosphorylation under nutrient-deprived conditions weakens USF2's DNA binding affinity, allowing TFEB to competitively bind and activate target genes. Knockdown or knockout of Usf2 upregulates specific autophagy and lysosomal genes, leading to enhanced lysosomal functionality and increased autophagic flux. In USF2-deficient cells, the SERPINA1 Z variant/antitrypsin Z - an aggregation-prone mutant protein used as a model - is rapidly cleared via the autophagy-lysosome pathway. Therefore, modulation of USF2 activity may be a therapeutic strategy for managing diseases associated with autophagy and lysosomal dysfunction.Abbreviation: CLEAR: coordinated lysosomal expression and regulation; GSK3B: glycogen synthase kinase 3 beta; HDAC: histone deacetylase; MiT/TFE: microphthalmia/transcription factor E; NuRD: nucleosome remodeling and deacetylation; SERPINA1 Z variant/ATZ/antitrypsin Z; TFE3: transcription factor E3; TFEB: transcription factor EB; USF2: upstream transcription factor 2.

Multiple environmental factors contribute to digestive system damage caused by food contamination in both humans and animals. Mycotoxins, such as deoxynivalenol (DON) and T-2 toxin, have emerged as the most significant factors due to their extensive contamination and difficulty in removal. Transcription factor EB (TFEB) serves as a crucial transcriptional regulator governing lysosomal biogenesis and autophagy, a lysosomal-driven degradation system that safeguards cells against harmful stressors. However, little is known about whether the post-translational modification of TFEB affects autophagy activity, which could explain the toxicity disparity between DON and T-2 toxin. Here, we discovered that T-2 toxin induces excessive autophagy by significantly reducing TFEB acetylation, whereas DON surprisingly inhibits autophagy activity via maintaining high TFEB acetylation, which impairs lysosomal biogenesis, thereby boosting their respective toxicity. Mechanically, the T-2 toxin decreases TFEB acetylation via enhanced SIRT1-TFEB interaction and SIRT1 deacetylase activity, while DON maintains high TFEB acetylation by reversing the process. Together, our study revealed that the acetylation state of TFEB mediated by SIRT1 alters autophagy phenotypes in intestinal cells, shedding light on the various toxicological mechanisms and an important target of DON and T-2 toxin.