Depletion of activating transcription factor 3 (ATF3) expression has previously been reported to promote hypertrophy, dysfunction and fibrosis in stress overload‑induced hearts; however, the mechanism involved remains poorly understood. In the present study, the mechanism underlying the activation of cysteine‑rich angiogenic protein 61 (Cyr61) by ATF3 in hyperproliferative and fibrotic human cardiac fibroblasts (HCFs), induced by angiotensin II (Ang II), was evaluated. The mRNA and protein expression levels of ATF3 and Cyr61 were assessed using reverse transcription‑quantitative PCR and western blotting, respectively. The Cell Counting Kit‑8 assay was used to assess cell viability. Cell migration was assessed using the wound healing assay and western blotting, whereas the extent of cell fibrosis was evaluated using immunofluorescence staining and western blotting. The binding site of ATF3 to the Cyr61 promoter was predicted using the JASPAR database, and verified using luciferase reporter and chromatin immunoprecipitation assays. The results demonstrated that the mRNA and protein expression levels of ATF3 were significantly upregulated in Ang II‑induced HCFs. Overexpression of ATF3 significantly inhibited the Ang II‑induced viability, migration and fibrosis of HCFs, whereas ATF3 knockdown mediated significant opposing effects. Mechanistically, ATF3 was demonstrated to transcriptionally activate Cyr61. Cyr61 silencing was subsequently revealed to reverse the effects of ATF3 overexpression on HCFs potentially via regulation of the TGF‑β/Smad signaling pathway. The results of the present study suggested that ATF3 could suppress HCF viability and fibrosis via the TGF‑β/Smad signaling pathway by activating the transcription of Cyr61.
Keywords: activating transcription factor 3; angiotensin II; cardiac hypertrophy; cysteine‑rich angiogenic protein 61; fibrosis; proliferation.