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Angiotensin II‐mediated Proliferation of Neonatal Cardiac Fibroblasts and Role of Mitochondrial Ca 2+ Uptake and Superoxide Generation
Author(s) -
Mishra Jyotsna,
Fu Deming,
Jhun Bong Sook,
Sheu SheyShing,
OUchi Jin
Publication year - 2017
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.31.1_supplement.lb690
Subject(s) - angiotensin ii , mitochondrial ros , mitochondrion , microbiology and biotechnology , reactive oxygen species , cardiac fibrosis , stimulation , endoplasmic reticulum , uniporter , chemistry , superoxide , cytosol , signal transduction , myocyte , medicine , endocrinology , biology , fibrosis , receptor , biochemistry , enzyme
Cardiac fibroblasts (CFs) are the major cell type in addition to cardiomyocytes in the mammalian heart, and they play a vital role in regulating normal cardiac function and adaptive cardiac remodeling during adverse clinical conditions, including fibrosis. Recent studies have revealed Angiotensin II (AngII) as a one of the principal effectors for promoting fibroblast differentiation and cardiac remodeling in the failing heart. In addition, evidences have shown that the downstream effects of AngII are mediated by elevated levels of reactive oxygen species (ROS) which have also been implicated in CF proliferation. However, the detailed signaling mechanism of ROS generation by AngII signaling in the CFs still remains unclear. We previously demonstrated in cardiac myoblast H9C2 cells that the main Ca 2+ uptake mechanism, the mitochondrial Ca 2+ uniporter (MCU)‐mediated mitochondrial Ca 2+ overload, induces mitochondrial superoxide (mtSO) generation. Therefore, we hypothesize that Ang‐II mediated stimulation may increase mitochondrial Ca 2+ ‐induced mtSO generation, which may further activate ROS‐dependent proliferation signaling in CFs. Using mitochondria‐targeted Ca 2+ biosensor in neonatal rat CFs (NCF), we first established that AngII (≥1 μM) stimulation significantly increases the mitochondrial Ca 2+ uptake in response to cytosolic Ca 2+ elevation induced by the Ca 2+ release from the endoplasmic reticulum (ER). Further, we also found that AngII stimulation leads to increase in the mtSO levels. We next confirmed that proliferative pathways, including ERK1/2 and p38 AT‐II were also activated in a time‐dependent manner on AngII stimulation in CFs, while the effect was abolished by pretreatment with mitochondria‐targeted antioxidant, Mito‐tempo without affecting the profiles of AngII ‐induced ER Ca 2+ release and mitochondrial Ca 2+ uptake. Finally, genetic inhibition of MCU function by overexpressing dominant‐negative MCU also blocked AngII‐mediated activation of proliferative pathways in CFs. In conclusion, these data suggest that MCU‐mediated mitochondrial Ca 2+ accumulation induces mtSO generation and this ROS generation serves as an important regulator for the proliferative pathway in CFs under Ang II stimulation. Support or Funding Information • 14BGIA18830032 and 16SDG27260248 from AHA to J.O‐U. • Medical Research Grant (#H1403) from W.W. Smith Foundation to J.O.‐U. • NIH grant (R01 HL093671) to S.‐S.S