Abstract
Mastitis is a complex inflammatory disease caused by pathogenic infection of mammary tissue in dairy cows. The molecular mechanism behind its occurrence, development, and regulation consists of a multi-gene network including microRNA (miRNA). Until now, there is no report on the role of miR-125b in regulating mastitis in dairy cows. This study found that miR-125b expression is significantly decreased in lipopolysaccharide (LPS)-induced MAC-T bovine mammary epithelial cells. Also, its expression is negatively correlated with the expression of NF-κB inhibitor interacting Ras-like 2 (NKIRAS2) gene. MiR-125b target genes were identified using a double luciferase reporter gene assay, which showed that miR-125b can bind to the 3′ untranslated region (3′ UTR) of the NKIRAS2, but not the 3′UTR of the TNF-α induced protein 3 (TNFAIP3). In addition, miR-125b overexpression and silencing were used to investigate the role of miR-125b on inflammation in LPS-induced MAC-T. The results demonstrate that a reduction in miR-125b expression in LPS-induced MAC-T cells increases NKIRAS2 expression, which then reduces NF-κB activity, leading to low expression of the inflammatory factors IL-6 and TNF-α. Ultimately, this reduces the inflammatory response in MAC-T cells. These results indicate that miR-125b is a pro-inflammatory regulator and that its silencing can alleviate bovine mastitis. These findings lay a foundation for elucidating the molecular regulation mechanism of cow mastitis.
Highlights
Bovine mastitis is an inflammatory disease caused by pathogenic infection of mammary tissue and is one of the most common diseases found on dairy farms [1]
MiR-125b is significantly downregulated in mammary tissue obtained from dairy cows clinically diagnosed with mastitis [16] or in Staphylococcal enterotoxin B (SEB) treated bovine mammary epithelial cells (bMECs) [17], suggesting that bovine miR-125b may play a critical role in mastitis
Differential expression of miR‐125b and nuclear factor kappa-B (NF-κB) inhibitor interacting Ras-like 2 (NKIRAS2) in LPS‐induced MAC‐T cells Aiming at evaluating the variation in expression of miR-125b and of NKIRAS2 upon LPS induction, LPSinduced MAC-T cells were collected and total RNA was extracted to detect the expression of miR-125b and NKIRAS2 by quantitative real-time PCR (qPCR)
Summary
Bovine mastitis is an inflammatory disease caused by pathogenic infection of mammary tissue and is one of the most common diseases found on dairy farms [1]. Infection of the mammary tissue by pathogenic microorganisms increases the secretion of inflammatory cytokines by bovine mammary epithelial cells (bMECs). This induces cellular immune and inflammatory responses, leading to the recruitment of white blood cells to the infection site [2–4]. As an Luoreng et al Vet Res (2021) 52:122 important member of the miRNA family, miR-125b regulates the expression of TNF-α [11, 12], TNFAIP3 [13, 14], and NKIRAS2 [15] in humans. These three genes are related to the cellular inflammatory response. This study lays a foundation for future studies on the molecular network behind bovine mastitis
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