Heat Tolerance-Associated\ncircRNA3685 Regulates Apoptosis\nand Autophagy in Bovine Mammary Epithelial Cells via Sponging bta-miR-138

Heat stress negatively affects dairy cow production,\nand health,\nleading to significant losses. Identifying mechanisms associated with\nheat tolerance is crucial for developing breeding strategies. Circular\nRNAs (circRNAs), a type of noncoding RNA, regulate cell functions\nlike autophagy, apoptosis and proliferation. In this study, dairy\ncows were classified into heat stress tolerant (HST, <i>n</i> = 15) and heat stress sensitive (HSS, <i>n</i> = 15) groups\nbased on respiratory and drooling score during the heat stress. A\nsignificant difference in milk production decline was observed, with\nthe HST group showing less decline, indicating better heat tolerance.\nBlood transcriptomics analysis identified 166 differentially expressed\ncircRNAs with circRNA3685 being highlighted as a key candidate linked\nto heat tolerance. Overexpression of circRNA3685 in bovine mammary\n(MAC-T) cells inhibited autophagy and apoptosis. The circRNA3685 was\nfound to interact with bta-miR-138, targeting HIF1A. These findings\nprovide insights into circRNAs’ role in heat stress adaptation\nin dairy cows.