Caveolin-1 influences mitochondrial plasticity and function in hepatic stellate cell activation.

Caveolin-1 (Cav-1) is an integral membrane protein present in all organelles, responsible for regulating and integrating multiple signals as a platform. Mitochondria are extremely adaptable to external cues in chronic liver diseases, and expression of Cav-1 may affect mitochondrial flexibility in hepatic stellate cells (HSCs) activation. We previously demonstrated that exogenous expression of Cav-1 was sufficient to increase some classical markers of activation in HSCs. Here, we aimed to evaluate the influence of exogenous expression and knockdown of Cav-1 on regulating the mitochondrial plasticity, metabolism, endoplasmic reticulum (ER)-mitochondria distance, and lysosomal activity in HSCs. To characterize the mitochondrial, lysosomal morphology, and ER-mitochondria distance, we perform transmission electron microscope analysis. We accessed mitochondria and lysosomal networks and functions through a confocal microscope and flow cytometry. The expression of mitochondrial machinery fusion/fission genes was examined by real-time polymerase chain reaction. Total and mitochondrial cholesterol content was measured using Amplex Red. To define energy metabolism, we used the Oroboros system in the cells. We report that GRX cells with exogenous expression or knockdown of Cav-1 changed mitochondrial morphometric parameters, OXPHOS metabolism, ER-mitochondria distance, lysosomal activity, and may change the activation state of HSC. This study highlights that Cav-1 may modulate mitochondrial function and structural reorganization in HSC activation, being a potential candidate marker for chronic liver diseases and a molecular target for therapeutic intervention.

The interplay between apoptosis, mitophagy and mitochondrial biogenesis induced by resveratrol can determine activated hepatic stellate cells death or survival.

Resveratrol has been the focus of numerous studies reporting opposite effects that depend on its concentration. The GRX is an activated hepatic stellate cells model used to study liver fibrosis development and resolution. We recently showed that GRX treatment with RSV (0.1-50 µM) for 24 h triggered dose-dependent pro-oxidant effects, resulting in cytotoxicity and cell damage only at the highest concentration. Here, we evaluated whether the pro-oxidant effect of resveratrol treatment is accompanied by alterations on the GRX mitochondrial metabolism, and whether the concomitantly autophagy/mitophagy induction can influence on cell death or survival. We demonstrated that all concentrations of resveratrol promoted an increase of GRX cell death signals, altering the mitochondrial dynamics and function. Cells treated with all resveratrol concentrations presented higher autophagy/mitophagy features, but only treatments with 1 and 10 µM of resveratrol-induced mitochondrial biogenesis. Since cell damage was higher and there was no mitochondrial biogenesis in GRX treated with 50 µM of resveratrol, we suggest that these cells failed to remove and replace all damaged mitochondria. In conclusion, the cytotoxic effect of resveratrol that effectively promotes cell death could be related to the interrelation between the concomitant induction of apoptosis, autophagy/mitophagy and mitochondrial biogenesis in GRX.