Role of the ROS-JNK Signaling Pathway in Hypoxia-Induced Atrial Fibrotic Responses in HL-1 Cardiomyocytes

Abstract

By promoting atrial structural remodeling, atrial hypoxia contributes to the development of the atrial fibrillation substrate. Our study aimed to investigate the modulatory effect of hypoxia on profibrotic activity in cultured HL-1 cardiomyocytes and explore the possible signaling transduction mechanisms of profibrotic activity in vitro. Hypoxia (1% O2) significantly and time-dependently increased the expression of hypoxia-inducible factor (HIF)-1α and fibrotic marker proteins collagen I and III (COL1A and COL3A), transforming growth factor (TGF)-β1 and α-smooth muscle actin (SMA). Western blot or immunohistochemistry analysis showed that hypoxia-induced increase in COL1A and COL3A was significantly attenuated by the addition of SP600125 (a specific c-Jun N-terminal kinase [JNK] inhibitor) or expression of dominant-negative JNK before hypoxia treatment. The inhibition of hypoxia-activated phosphorylation of JNK signal components (JNK, MKK4, nuclear c-Jun and ATF-2) by pre-treatment with SP600125 could suppress hypoxia-stimulated HIF-1α upregulation and fibrotic marker proteins expression. Hypoxia significantly increased reactive oxygen species (ROS) production in cultured HL-1 atrial cells. Pre-treatment with N-acetylcysteine significantly abrogated the expression of nuclear HIF-1α, JNK transduction components and fibrotic marker proteins. Taken together, these findings indicated that the hypoxia-induced atrial profibrotic response occurs mainly via the ROS/JNK pathway, its downstream upregulation of HIF-1α and c-Jun/ATF2 phosphorylation and nuclear translocation to up-regulate the expression of fibrosis-related proteins (COL1A, COL3A, TGF-β1 and α-SMA). Our result suggests that suppression of ROS/JNK signaling pathway is a critical mechanism for developing a novel therapeutic strategy against atrial fibrillation.

MicroRNA Let-7a, -7e and -133a Attenuate Hypoxia-Induced Atrial Fibrosis via Targeting Collagen Expression and the JNK Pathway in HL1 Cardiomyocytes

“…A previous study demonstrated that stress-response kinase JNK in the atria was involved in arrhythmic remodeling by activating calcium/calmodulin-dependent protein kinase (CaMK) II and, in turn, up-regulating diastolic sarcoplasmic reticulum calcium leak, leading to aberrant intracellular waves and enhanced AF propensity [ 41 ]. Recently, we discovered the role of the JNK pathway in hypoxia-induced fibrosis and already confirmed that fibrotic protein under hypoxia can be expressed via the JNK pathway [ 6 ]. This research concluded that MAPK signaling could modulate fibrosis marker expression.…”

“…Abundant deposition of the ECM has been shown in the maturation of fibrosis and the ratio of collagen type I has been shown to be increased in fibrosis [ 5 ]. In our previous research, we concluded that aldosterone significantly increased the protein expressions of collagen I, III (COL1A, COL3A), transforming growth factor (TGF)-β1 and α-smooth muscle actin (SMA), which demonstrated the critical role of mineralocorticoid receptor activity in aldosterone-mediated activation of the mitogen-activated protein kinase (MAPK) signaling pathway and subsequent atrial profibrotic effects [ 6 ]. Furthermore, it was shown that hypoxia resulted in cardiac fibrosis by inducing the up-regulation of COL1A and COL3A in atrial cardiac muscle (HL-1) cells.…”

MKK4 Knockdown Plays a Protective Role in Hemorrhagic Shock-Induced Liver Injury through the JNK Pathway

“…The expression of HIF-1 α seemed to be positively correlated with that of MKK4 in HS rats. Suppression of hypoxia-induced activation of JNK signaling including MKK4 inhibited HIF-1 α expression [ 37 ]. MKK4/7-JNK signaling involved in upregulation of HIF-1 α via activating transcription factor NF- κ B [ 38 ].…”

MiRNA-Regulated Pathways for Hypertrophic Cardiomyopathy: Network-Based Approach to Insight into Pathogenesis

“…SMAD-dependent signaling is one of main mechanisms to transduce signals of TGF-β cytokine to the cell nucleus, where SMAD2/SMAD3:SMAD4 heterotrimer complex plays a considerable role in regulating the expression of TGF-β-dependent genes [ 29 ]. Increase of TGF-β level promotes the pathological remodeling of different tissues [ 30 , 31 , 32 ]. In human and mice myocardium TGF-β level correlates with fibrosis [ 33 , 34 , 35 ].…”