Subacute ruminal acidosis induces inflammation, autophagy, and apoptosis by disrupting Cahomeostasis via STIM1/ORAI1 upregulation in mammary gland tissues.

Abstract

Subacute ruminal acidosis (SARA) is a prevalent metabolic disorder in ruminants that induces mastitis, while Ca&#xb2;&#x207a; homeostasis disruption is closely linked to mammary gland diseases. This study aimed to uncover the role of Ca&#xb2;&#x207a; signaling in SARA-induced mammary gland injury by investigating its regulation of inflammation, autophagy, and apoptosis. In this study, we induced SARA by feeding a high-concentrate (HC, 70% concentrate) diet to Hu sheep (pH<5.6 for more than 3 h). The diets were administered over a period of 56 d. We collected samples of blood and mammary gland tissues from the animals at the end of the experiment. Compared with the low-concentrate (LC, 30% concentrate) diet, HC diet increased the mRNA and protein expression of STIM1 and ORAI1, and Cacontent in mammary gland tissues. Elevated Caactivated the CaMKK&#x3b2;-NF-&#x3ba;B pathway, as evidenced by increased p-I&#x3ba;B, p-p65, upregulation of pro-inflammatory cytokines (IL-6, IL-8, IL-1&#x3b2;, TNF-&#x3b1;) in mammary gland tissues, and enhanced interaction between ORAI1 and p65. Concurrently, HC diet activated the CaMKK&#x3b2;-AMPK pathway, which in turn upregulates the expression of autophagy-related proteins and induces autophagy. Finally, the HC diet promoted apoptosis by upregulating the expression of pro-apoptotic proteins (Cytochrome C, Cleaved-Caspase3 and BAX) and downregulating anti-apoptotic proteins (Bcl-2). In summary, SARA disrupts Ca&#xb2;&#x207a; homeostasis via STIM1/ORAI1 upregulation, triggering a cascade of inflammation, autophagy, and apoptosis in Hu sheep mammary glands through the CaMKK&#x3b2;-mediated NF-&#x3ba;B and AMPK-mTOR pathways.