Glucocorticoids-driven mitochondrial GR translocation promotes heat stress-induced mastitis via the mtDNA-cGAS-STING-NF-κB/NLRP3 pathway.

Heat stress (HS) significantly affects dairy production and animal welfare. However, the precise mechanisms by which HS leads to mastitis remain unclear. To elucidate this, we established a mouse model of HS. Our results show that HS induces systemic inflammation, gut microbiota dysbiosis, and oxidative stress, culminating in mitochondrial dysfunction in both mammary and colon tissues. This dysfunction was evidenced by elevated mitochondrial ROS production, loss of mitochondrial membrane potential (MMP), and suppression of respiratory chain complex activity. Pharmacological inhibition assays identified glucocorticoids (GCs), but not norepinephrine (NA), as the principal mediators of the HS-triggered inflammatory response. Mechanistically, GCs facilitates the translocation of the glucocorticoid receptor (GR) to mitochondria, and inhibiting this translocation mitigates HS-induced mastitis. Furthermore, mitochondrial GR translocation triggers the release of mitochondrial DNA (mtDNA), which activates the cGAS-STING-NF-κB/NLRP3 axis and amplifies inflammation. In summary, our research reveals a novel pathway whereby GCs-mediated mitochondrial GR translocation drives HS-induced mastitis and blood-milk barrier (BMB) disruption through mtDNA-cGAS-STING-NF-κB/NLRP3 activation. These findings provide critical insights into the pathophysiology of HS-related diseases and highlight potential therapeutic targets.