tretinoin and Mastitis

Mastitis is a serious disease for humans and animals, which causes huge economic losses in the dairy industry and is hard to prevent due to the complex and unclear pathogenesis. Subacute ruminal acidosis (SARA) has contributed to the development of mastitis by inducing ruminal dysbiosis and subsequent low-grade endotoxemia (LGE), however, how ruminal metabolic changes regulate this progress is still unclear. Our previous study revealed that cows with SARA had increased ruminal retinoic acid (RA) levels, a metabolic intermediate of vitamin A that plays an essential role in mucosal immune responses. Hence, the aim of this study was to investigate the protective effect of RA on LGE-induced mastitis and the underlying mechanisms in mice. The results showed that RA alleviated LGE-induced mastitis, as evidenced by RA significantly reduced the increase in mammary proinflammatory cytokines and improved blood-milk barrier injury caused by LGE. In addition, RA increased the expression of tight junction proteins, including ZO-1, occludin and claudin-3. Furthermore, we found that RA limited the mammary inflammatory responses by inhibiting the activation of NF-κB and NLRP3 signaling pathways. These findings suggest that RA effectively alleviates LGE-induced mastitis and implies a potential strategy for the treatment and prevention of mastitis and other diseases.

Topics: Animals; Cattle; Endotoxemia; Female; Humans; Lipopolysaccharides; Mastitis; Mice; NF-kappa B; Signal Transduction; Tretinoin

The retinoids, a group of natural or synthetic derivatives of vitamin A, exert various anti-neoplastic and immunomodulatory actions. Recent studies have demonstrated that retinoic acid protects rats against lipopolysaccharide (LPS)-induced mastitis, but the mechanism of action is unclear. In the present study, an LPS-induced rat mastitis model and primary cultures of rat mammary epithelial cells were used to investigate the effect of retinoic acid on the TLR4/NF-kappaB signaling pathway. The data indicated that toll-like receptor 4 (TLR4) gene expression reached its peak value earlier in retinoic acid-treated rats than in the control group, and that retinoic acid significantly decreased NF-kappaB DNA binding activity and the level of IL-1beta in the mammary gland. The animal study result was confirmed by an in vitro cell culture system trial. TLR4 protein expression and NF-kappaB DNA binding activity were significantly decreased in primary rat mammary epithelial cells pretreated with 1mumol/l retinoic acid at 1h post-LPS stimulation. IL-1beta gene expression was also significantly decreased at 2, 4 and 8h post-LPS stimulation. These findings demonstrate that direct action by retinoic acid leads to attenuation of the LPS-induced inflammatory response by suppression of the TLR4/NF-kappaB signalling system, thereby providing a novel explanation for the underlying effect proposed for retinoic acid in the protection of mammary tissue during LPS-induced acute mastitis.

Topics: Animals; Cell Culture Techniques; Cells, Cultured; Epithelial Cells; Immunosuppression Therapy; Interleukin-1beta; Lipopolysaccharides; Mammary Glands, Animal; Mastitis; NF-kappa B; Rats; Signal Transduction; Toll-Like Receptor 4; Transcriptional Activation; Tretinoin