Aberrant regulation of autophagy disturbs fibrotic liver regeneration after partial hepatectomy

Verapamil inhibits TXNIP-dependent NLRP3 Inflammasome activation in an ulcerative colitis rat model: A new evolving role of the calcium channel blocker

Ulcerative colitis (UC) is a long-term inflammatory bowel disease (IBD) associated with significant morbidity. It is marked by inflammation and damage to the colon's mucosal lining. Studies have shown that NLRP3 inflammasome activation, apoptosis, and impaired autophagy are critical in its pathogenesis. Verapamil, a calcium channel blocker, has been found to inhibit NLRP3 inflammasome activation in various preclinical models. However, the potential influence of verapamil on the TXNIP in UC remains unexplored. This study investigates the effects of verapamil on an UC rat model induced chemically by acetic acid. Verapamil effectively inhibited the TXNIP-NLRP3-caspase-1 axis, reducing inflammasome activation and the release of IL-1β and IL-18. Additionally, verapamil suppressed NFκB, the priming step of NLRP3 activation. The drug enhanced autophagic activity, as indicated by increased expression of LC3-II and Beclin-1, along with reduced LC3-I and mTOR expression. Moreover, it demonstrated anti-apoptotic effects mediated by regulating Bax and cleaved caspase-3. These molecular changes contributed to mucosal healing and improved microscopic and macroscopic outcomes in the colitis model. Furthermore, verapamil improved the colon weight-to-length ratio and disease activity scores and mitigated oxidative stress. As verapamil has been safely used in clinics to treat hypertension, our findings suggest it may be a safe therapeutic option for ameliorating inflammation and apoptosis and activating autophagy in UC pathology. Since hypertension demonstrates a strong association with UC, the use of verapamil merits particular attention in hypertensive patients fighting against IBD.

N6-Methyladenosine Modification in the Metabolic Dysfunction-Associated Steatotic Liver Disease

Epigenetics of N6-methyladenine (m6A) modification may play a key role during the regulation of various diseases, including metabolic dysfunction-associated steatotic liver disease (MASLD). The m6A modification has been shown to be accomplished via the exploitation of several players such as methyltransferases, demethylases, and/or methylation-binding molecules. Significantly, the m6A methylation can regulate the key eukaryotic transcriptome by affecting the subcellular localization, splicing, export, stability, translation, and decay of those RNAs. An increasing amount of data has designated that the m6A modification of RNAs can also modulate the expression of autophagy-related genes, which could also control the autophagy in hepatocytes. Oxidative stress with reactive oxygen species (ROS) can induce m6A RNA methylation, which might be associated with the regulation of mitochondrial autophagy (mitophagy) and/or the development of MASLD. Therefore, both autophagy and the m6A modification could play important roles in regulating the pathogenesis of MASLD. Comprehending the relationship between m6A and mitophagy may be helpful for the development of future therapeutic strategies against MASLD. This review would advance the understanding of the regulatory mechanisms of m6A RNA modification, focusing on the impact of mitochondrial dysregulation and mitophagy in the liver with MASLD.

Adipose tissue macrophage infiltration and hepatocyte stress increase GDF-15 throughout development of obesity to MASH

Plasma growth differentiation factor-15 (GDF-15) levels increase with obesity and metabolic dysfunction-associated steatotic liver disease (MASLD) but the underlying mechanism remains poorly defined. Using male mouse models of obesity and MASLD, and biopsies from carefully-characterized patients regarding obesity, type 2 diabetes (T2D) and MASLD status, we identify adipose tissue (AT) as the key source of GDF-15 at onset of obesity and T2D, followed by liver during the progression towards metabolic dysfunction-associated steatohepatitis (MASH). Obesity and T2D increase GDF15 expression in AT through the accumulation of macrophages, which are the main immune cells expressing GDF15. Inactivation of Gdf15 in macrophages reduces plasma GDF-15 concentrations and exacerbates obesity in mice. During MASH development, Gdf15 expression additionally increases in hepatocytes through stress-induced TFEB and DDIT3 signaling. Together, these results demonstrate a dual contribution of AT and liver to GDF-15 production in metabolic diseases and identify potential therapeutic targets to raise endogenous GDF-15 levels.

TAZ deficiency impairs the autophagy-lysosomal pathway through NRF2 dysregulation and lysosomal dysfunction

Transcriptional coactivator with a PDZ-binding motif (TAZ) plays a key role in normal tissue homeostasis and tumorigenesis through interaction with several transcription factors. In particular, TAZ deficiency causes abnormal alveolarization and emphysema, and persistent TAZ overexpression contributes to lung cancer and pulmonary fibrosis, suggesting the possibility of a complex mechanism of TAZ function. Recent studies suggest that nuclear factor erythroid 2-related factor 2 (NRF2), an antioxidant defense system, induces TAZ expression during tumorigenesis and that TAZ also activates the NRF2-mediated antioxidant pathway. We thus thought to elucidate the cross-regulation of TAZ and NRF2 and the underlying molecular mechanisms and functions. TAZ directly interacted with NRF2 through the N-terminal domain and suppressed the transcriptional activity of NRF2 by preventing NRF2 from binding to DNA. In addition, the return of NRF2 to basal levels after signaling was inhibited in TAZ deficiency, resulting in sustained nuclear NRF2 levels and aberrantly increased expression of NRF2 targets. TAZ deficiency failed to modulate optimal NRF2 signaling and concomitantly impaired lysosomal acidification and lysosomal enzyme function, accumulating the abnormal autophagy vesicles and reactive oxygen species and causing protein oxidation and cellular damage in the lungs. TAZ restoration to TAZ deficiency normalized dysregulated NRF2 signaling and aberrant lysosomal function and triggered the normal autophagy-lysosomal pathway. Therefore, TAZ is indispensable for the optimal regulation of NRF2-mediated autophagy-lysosomal pathways and for preventing pulmonary damage caused by oxidative stress and oxidized proteins.

Autophagy modulates physiologic and adaptive response in the liver

Autophagy is a physiological process that is ubiquitous and essential to the disposal or recycling of damaged cellular organelles and misfolded proteins to maintain organ homeostasis and survival. Its importance in the regulation of liver function in normal and pathological conditions is increasingly recognized. This review summarizes how autophagy regulates epithelial cell- and non-epithelial cell-specific function in the liver and how it differentially participates in hepatic homeostasis, hepatic injury response to stress-induced liver damage such as cholestasis, sepsis, non-alcoholic and alcohol-associated liver disease, viral hepatitis, hepatic fibrosis, hepatocellular and cholangiocellular carcinoma, and aging. Autophagy-based interventional studies for liver diseases that are currently registered in clinicatrials.gov are summarized. Given the broad and multidirectional autophagy response in the liver, a more refined understanding of the liver cell-specific autophagy activities in a context-dependent manner is necessary.