The inhibition of FTO attenuates the antifibrotic effect of leonurine in rat cardiac fibroblasts.

BACKGROUND: Myocardial fibrosis (MF) is a common pathological condition in cardiovascular diseases that often causes severe cardiac dysfunction. MF is characterized by changes in cardiomyocytes, cardiac fibroblasts (CFs), levels of collagen (Col) -1, -3, and overdeposition of the extracellular matrix. Our previous research showed that leonurine (LE) effectively inhibits collagen synthesis and differentiation of CFs, but the mechanism is not fully elucidated. Recent evidence indicates that fat mass and obesity-associated proteins (FTO) regulates the occurrence and development of MF. This study aimed to explore the role of FTO in the antifibrotic effects of LE. METHODS: Neonatal rat CFs were isolated, and induced using angiotensin II (Ang II) to establish a cell model of MF. Cell viability, wound healing and transwell assays were used to detect cell activity and migration ability. The protein and mRNA levels of MF-related factors were measured following stimulation with Ang II and LE under normal conditions or after FTO knockdown. The RNA methylation level was measured by dot blot assay. RESULTS: The results showed that LE (20, 40 µM) was not toxic to normal CFs. LE reduced the proliferation, migration and collagen synthesis of Ang II-induced CFs. Further investigation showed that FTO was downregulated by Ang II stimulation, whereas LE reversed this effect. FTO knockdown facilitated the migration of CFs, upregulated the protein levels of Col-3, α-SMA and Col-1 in Ang II and LE-stimulated CFs, and enhanced the fluorescence intensity of α-SMA. Furthermore, LE reduced N6-methyladenosine (m6A) RNA methylation, which was partially blocked by FTO knockdown. FTO knockdown also reduced the expression levels of p53 protein in Ang II and LE-stimulated CFs. CONCLUSIONS: Our findings suggest that the inhibition of FTO may attenuate the antifibrotic effect of LE in CFs, suggesting that FTO may serve as a key protein for anti-MF of LE.

The p53/miR-29a-3p axis mediates the antifibrotic effect of leonurine on angiotensin II-stimulated rat cardiac fibroblasts.

Overactivation of cardiac fibroblasts (CFs) is one of the main causes of myocardial fibrosis (MF), and inhibition of CF activation is a crucial strategy for MF therapy. A previous study by our group demonstrated that leonurine (LE) effectively inhibits collagen synthesis and myofibroblast generation originated from CFs, and eventually mitigates the progression of MF (where miR-29a-3p is likely to be a vital mediator). However, the underlying mechanisms involved in this process remain unknown. Thus, the present study aimed to investigate the precise role of miR-29a-3p in LE-treated CFs, and to elucidate the pharmacological effects of LE on MF. Neonatal rat CFs were isolated and stimulated by angiotensin II (Ang II) to mimic the pathological process of MF in vitro. The results show that LE distinctly inhibits collagen synthesis, as well as the proliferation, differentiation and migration of CFs, all of which could be induced by Ang II. In addition, LE promotes apoptosis in CFs under Ang II stimulation. During this process, the down-regulated expressions of miR-29a-3p and p53 are partly restored by LE. Either knockdown of miR-29a-3p or inhibition of p53 by PFT-α (a p53 inhibitor) blocks the antifibrotic effect of LE. Notably, PFT-α suppresses miR-29a-3p levels in CFs under both normal and Ang II-treated conditions. Furthermore, ChIP analysis confirmed that p53 is bound to the promoter region of miR-29a-3p, and directly regulates its expression. Overall, our study demonstrates that LE upregulates p53 and miR-29a-3p expression, and subsequently inhibits CF overactivation, suggesting that the p53/miR-29a-3p axis may play a crucial role in mediating the antifibrotic effect of LE against MF.