Abstract 18791: Sex Differences in the Phosphorylation of Argonaute 2 Result in Reduced Translocation of Micro RNA-181c Into the Mitochondria and Cardioprotection in Pre-Menopausal Females

Abstract

Introduction: MicroRNAs (miRNAs) play a crucial role in regulating gene expression and have been implicated in various aspects of cardiovascular health and disease. miR-181c is known to be upregulated in obesity, and its translocation into cardiomyocyte mitochondria leads to excessive production of Reactive Oxygen Species(ROS). ROS-mediated degradation of Sp1, a transcription factor for MICU1, results indecreased MICU1 expression and subsequent mitochondrial [Ca2+] accumulation, leading to heart failure. We hypothesized that phosphorylation of Argonaute 2 (pAGO2) at Ser 387could inhibit the translocation of miR-181c into mitochondria by enhancing the stability of the RNA-induced silencing complex in the cytoplasm. Estrogen (E2) could provide cardioprotection in pre-menopausal women against the consequences of mitochondrial miR-181c upregulation by phosphorylating AGO2. Hypothesis: We hypothesize that sex differences in pAGO2 levels lead to reduced translocation of miR-181c into mitochondria, thereby influencing the cardiac response observed in pre-menopausal females compared to males. Methods: This study utilized male, female, and ovariectomized (OVX) mice as in vivo model. AC16 cardiomyocyte cell line was treated with E2 and transfected with miR-181c to mimic conditions of miR-181c upregulation. qRT-PCR was performed to assess miR-181c, SP1, and MICU1 expression levels. Western blot analysis was employed to detect protein levels. Results: Our results revealed significantly higher levels of pAGO2 in pre-menopausal female mice compared to males. This increased pAGO2 phosphorylation was associated with decreased translocation of miR-181c into mitochondria in pre-menopausal females, and this condition was reversed in OVX mice. In AC16 cells, E2 treatment normalized the aberrant degradation of Sp1 and the dysregulation of MICU1 induced by miR-181c overexpression. Conclusion: This study provides evidence of sex differences in pAGO2 levels, suggesting that reduced translocation of miR-181c into mitochondria contributes to the observed cardiac effects in pre-menopausal females.