Epigallocatechin gallate targets the hexokinase 2-voltage-dependent anion channel 1 axis in myofibroblasts to attenuate pulmonary fibrosis. - GreenMedInfo Summary

BACKGROUND: Pulmonary fibrosis (PF) is sustained by apoptosis-resistant myofibroblasts that undergo a metabolic shift toward aerobic glycolysis. Hexokinase 2 (HK2) couples these two features: it catalyzes the first committed step of glycolysis and, by occupying voltage-dependent anion channel 1 (VDAC1) on the outer mitochondrial membrane, physically excludes the pro-apoptotic effector Bcl-2 Associated X protein (BAX) from VDAC1, thereby raising the apoptotic threshold. Epigallocatechin gallate (EGCG), a principal green tea catechin, exhibits anti-fibrotic activity in preclinical models, yet its direct molecular target and mechanism of action in myofibroblasts remain undefined.

PURPOSE: To identify the direct molecular target of EGCG in myofibroblasts and to delineate how target engagement restores apoptotic competence and metabolic homeostasis in PF.

METHODS: Target engagement was assessed using drug affinity responsive target stability (DARTS), cellular thermal shift assay (CETSA), and surface plasmon resonance (SPR). HK2 stability, ubiquitination, and proteasome dependence were examined alongside mitochondrial complex formation, Bcl-2 Associated X protein (BAX) recruitment, and apoptosis readouts. Anti-fibrotic efficacy and metabolic remodeling were evaluated in a bleomycin (BLM)-induced murine PF model and in HK2-deficient settings.

RESULTS: EGCG bound HK2 with high affinity and promoted its ubiquitination-dependent proteasomal degradation rather than functioning solely as an enzymatic inhibitor. Loss of HK2 disrupted the mitochondrial HK2-VDAC1 complex, liberated VDAC1 for BAX engagement, and restored mitochondrial outer membrane permeabilization and apoptosis in transforming growth factor-beta 1 (TGF-β1)-activated myofibroblasts. In BLM-injured lungs, EGCG administration attenuated fibrotic remodeling, suppressed glycolysis-biased metabolic reprogramming, and improved mitochondrial oxidative phosphorylation. Genetic depletion of HK2-both in vivo and in vitro-phenocopied the pro-apoptotic, anti-glycolytic, and anti-fibrotic effects of EGCG, and largely abolished the additional benefit conferred by EGCG treatment, establishing HK2 as an obligatory mediator of EGCG action.

CONCLUSION: These findings identify HK2 as a bona fide molecular target of EGCG and establish a mechanistic framework in which EGCG-induced HK2 degradation disrupts the HK2-VDAC1 complex, re-enables BAX-dependent apoptosis, and concurrently corrects pathological glycolytic reprogramming in myofibroblasts. This HK2-VDAC1-BAX axis represents a druggable vulnerability that may inform the development of targeted anti-fibrotic therapies.