Characterization of the Regulatory Mechanisms of Activating Transcription Factor 3 by Hypertrophic Stimuli in Rat Cardiomyocytes

Abstract

AimsActivating transcription factor 3 (ATF3) is a stress-activated immediate early gene suggested to have both detrimental and cardioprotective role in the heart. Here we studied the mechanisms of ATF3 activation by hypertrophic stimuli and ATF3 downstream targets in rat cardiomyocytes.Methods and ResultsWhen neonatal rat cardiomyocytes were exposed to endothelin-1 (ET-1, 100 nM) and mechanical stretching in vitro, maximal increase in ATF3 expression occurred at 1 hour. Inhibition of extracellular signal-regulated kinase (ERK) by PD98059 decreased ET-1– and stretch–induced increase of ATF3 protein but not ATF3 mRNA levels, whereas protein kinase A (PKA) inhibitor H89 attenuated both ATF3 mRNA transcription and protein expression in response to ET-1 and stretch. To characterize further the regulatory mechanisms upstream of ATF3, p38 mitogen-activated protein kinase (MAPK) signaling was investigated using a gain-of-function approach. Adenoviral overexpression of p38α, but not p38β, increased ATF3 mRNA and protein levels as well as DNA binding activity. To investigate the role of ATF3 in hypertrophic process, we overexpressed ATF3 by adenovirus-mediated gene transfer. In vitro, ATF3 gene delivery attenuated the mRNA transcription of interleukin-6 (IL-6) and plasminogen activator inhibitor-1 (PAI-1), and enhanced nuclear factor-κB (NF-κB) and Nkx-2.5 DNA binding activities. Reduced PAI-1 expression was also detected in vivo in adult rat heart by direct intramyocardial adenovirus-mediated ATF3 gene delivery.ConclusionsThese data demonstrate that ATF3 activation by ET-1 and mechanical stretch is partly mediated through ERK and cAMP-PKA pathways, whereas p38 MAPK pathway is involved in ATF3 activation exclusively through p38α isoform. ATF3 activation caused induction of modulators of the inflammatory response NF-κB and Nkx-2.5, as well as attenuation of pro-fibrotic and pro-inflammatory proteins IL-6 and PAI-1, suggesting cardioprotective role for ATF3 in the heart.

Urinary exosomal activating transcriptional factor 3 as the early diagnostic biomarker for sepsis-induced acute kidney injury

“…Moreover, activated caspase-3 was also detectable from renal tissue at 6 h of CLP by Western blot analysis support the association of apoptosis and ATF3 or NGAL as previously described [33]. Despite ATF3 is not specific to kidney as it was also demonstrated in other organs as previously known [34–36], it seems to be activated only in condition with organs injury as there was no ATF3 expression in sham mice. Then ATF3 in urine should be a better representative renal biomarker than serum ATF3.…”

Mitogen‐activated protein kinase p38 target regenerating islet‐derived 3γ expression is upregulated in cardiac inflammatory response in the rat heart

“…) as well as transcription factors involved in cardiac inflammatory response (Koivisto et al. ), but whether mechanical stress functions directly as a proinflammatory stimulus remains to be established. It is noteworthy that although the primary cultures derived from the adult rat heart would reflect better the situation in the adult heart, the limitation is that these cultured cells either lose their morphology or they lose their ability to undergo spontaneous contractions, if cultured under conditions where the rod‐shaped morphology is retained (Jacobson and Piper ; Mitcheson et al.…”

“…In addition, mechanical stretch coupled cellular release of Ang II could mediate the increase in Reg3c mRNA levels (Sadoshima et al 1993;Liang and Gardner 1998). Mechanical stretch is also known to induce gene expression of other inflammatory mediators such as IL-18, tumor necrosis factor-like weak inducer of apoptosis (TWEAK) and its receptor Fn14 (Mustonen et al 2010;Yoshida et al 2014) as well as transcription factors involved in cardiac inflammatory response (Koivisto et al 2014), but whether mechanical stress functions directly as a proinflammatory stimulus remains to be established. It is noteworthy that although the primary cultures derived from the adult rat heart would reflect better the situation in the adult heart, the limitation is that these cultured cells either lose their morphology or they lose their ability to undergo spontaneous contractions, if cultured under conditions where the rod-shaped morphology is retained (Jacobson and Piper 1986;Mitcheson et al 1998).…”

Time-resolved profiling reveals ATF3 as a novel mediator of endocrine resistance in breast cancer

“…ATF3 upregulation under stress was proven to be mediated exclusively by the p38 476 signaling pathway in HeLa cells, while through ERK, SAPK and p38 in colorectal cancer 18,56 . 477 Other reports showed that its activation is mediated through ERK and p38α in myocytes or by 478 ERK/JNK but not by p38 in rat brains 57,58 . Again, these findings demonstrate that the regulation 479 of ATF3 is highly cell and context specific.…”