RETRACTED: Mitochondrial Fission and Mitophagy Reciprocally Orchestrate Cardiac Fibroblasts Activation

Abstract

Although mitochondrial fission has been reported to increase proliferative capacity and collagen production, it can also contribute to mitochondrial impairment, which is detrimental to cell survival. The aim of the present study was to investigate the role of mitochondrial fission in cardiac fibroblasts (CF) activation and explore the mechanisms involved in the maintenance of mitochondrial health under this condition. For this, changes in the levels of mitochondrial fission/fusion-related proteins were assessed in transforming growth factor beta 1 (TGF-β1)-activated CF, whereas the role of mitochondrial fission during this process was also elucidated, as were the underlying mechanisms. The interaction between mitochondrial fission and mitophagy, the main defense mechanism against mitochondrial impairment, was also explored. The results showed that the mitochondria in TGF-β1-treated CF were noticeably more fragmented than those of controls. The expression of several mitochondrial fission-related proteins was markedly upregulated, and the levels of fusion-related proteins were also altered, but to a lesser extent. Inhibiting mitochondrial fission resulted in a marked attenuation of TGF-β1-induced CF activation. The TGF-β1-induced increase in glycolysis was greatly suppressed in the presence of a mitochondrial inhibitor, whereas a glycolysis-specific antagonist exerted little additional antifibrotic effects. TGF-β1 treatment increased cellular levels of reactive oxygen species (ROS) and triggered mitophagy, but this effect was reversed following the application of ROS scavengers. For the signals mediating mitophagy, the expression of Pink1, but not Bnip3l/Nix or Fundc1, exhibited the most significant changes, which could be counteracted by treatment with a mitochondrial fission inhibitor. Pink1 knockdown suppressed CF activation and mitochondrial fission, which was accompanied by increased CF apoptosis. In conclusion, mitochondrial fission resulted in increased glycolysis and played a crucial role in CF activation. Moreover, mitochondrial fission promoted reactive oxygen species (ROS) production, leading to mitophagy and the consequent degradation of the impaired mitochondria, thus promoting CF survival and maintaining their activation.

RETRACTED: High Glucose Activated Cardiac Fibroblasts by a Disruption of Mitochondria-Associated Membranes

“…The effects of MFN2 and the alterations of MAMs in this process are certainly notwithstanding; the precise role of MAMs should be interpreted in caution, which could be confounded by mitochondrial dynamics. The enhanced MFN2 expression increased the mitochondrial fusion while reducing fission, and this has been reported to decrease glycolysis during the cardiac fibroblast activation (Gao et al, 2020). Previous studies found that HG-induced mitochondrial fission in various cell types, (Kobayashi et al, 2020;Wu Q. R. et al, 2021) and these may further support the MAM-independent effects in the study.…”

“…Human ventricular CFs were purchased from the ScienCell Research Laboratories (ScienCell, CA, United States) and maintained according to the instructions and previous reports of the manufacturer (Gao et al, 2020;Tao et al, 2021). Briefly, cells were cultured in the complete medium containing basic medium (fibroblast medium, FM-2; ScienCell) and supplements (10% fetal bovine serum, Gibco, CA, United States; fibroblast growth supplement-2, diluted to ×1 according to the instruction of the manufacturer, ScienCell; and 1% penicillin/streptomycin, Gibco) in the incubator at 37 • C and 5% CO 2 .…”

“…The seahorse assays assessing the capacity of mitochondrial respiration indicated by the oxygen consumption rate (OCR) and assessing the glycolytic levels indicated by the extracellular acidification rate (ECAR) were performed according to previous report (Chen et al, 2020;Gao et al, 2020). The Seahorse XF Cell Mito Stress Test Kit (Agilent, DE, United States) was used to measure OCR, and the Seahorse XF glycolytic rate assay kit (Agilent) was used to determine ECAR.…”

Epigenetic Repression of Chloride Channel Accessory 2 Transcription in Cardiac Fibroblast: Implication in Cardiac Fibrosis

“…Cell Culture, Plasmids, Transient Transfection, and Reporter Assay Primary cardiac fibroblasts were isolated and maintained in DMEM supplemented with 10% FBS as previously described (Gao et al, 2020;Liu et al, 2020;He et al, 2021;Zhao et al, 2021). Mouse embryonic fibroblasts (MEFs) were isolated and maintained in DMEM supplemented with 10% FBS as previously described (Angrisani et al, 2021).…”

Hyperphosphorylated Human Tau Accumulates at the Synapse, Localizing on Synaptic Mitochondrial Outer Membranes and Disrupting Respiration in a Mouse Model of Tauopathy

“…Importantly, the interaction of tau with Drp1 is enhanced by tau phosphorylation and further reduces mitochondrial fission, promoting elongation of mitochondrial networks and consequently disrupting mitochondrial membrane potential ( Manczak and Reddy, 2012 ). Although loss of mitochondrial membrane potential is a trigger of mitophagy, tau-Drp1 interactions may blunt this process due to reduced mitochondrial fragmentation ( Shutt et al, 2011 ; Shirihai et al, 2015 ; Gao et al, 2021 ). Further exacerbating this, tau can sequester Parkin in the cytosol, preventing mitochondrial recruitment ( Hu et al, 2016 ; Cummins et al, 2019 ).…”