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The bovine uterus is susceptible to bacterial infections after calving, particularly from Escherichia coli (E. coli), which often results in endometritis. Additionally, postpartum stress in cows can elevate cortisol levels in the body, inhibiting endometrial regeneration and reducing immune function, thereby further increasing the risk of infection. Selenium (Se) is a common feed additive in dairy farming, known for its anti-inflammatory and antioxidant effects. The aim of this study was to investigate the regulatory role of Se in the growth of bovine endometrial stromal cells (BESCs) under the conditions of LPS-induced inflammatory damage at high cortisol levels. BESCs were treated with 1, 2, 4 μM Se in combination with co-treatment of LPS and cortisol. The results indicated that LPS inhibited the cell viability and reduced the mRNA expression of CTGF, TGF-β1, and TGF-β3. Additionally, LPS increased apoptosis, hindered the cell cycle progression by blocking it in the G0/G1 phase, and suppressed the PI3K/AKT/GSK-3β and Wnt/β-catenin signaling pathways. Furthermore, increased concentrations of cortisol can exacerbate the impacts of LPS on cell proliferation and apoptosis. Conversely, the supplementation of Se promoted cell viability, increased the mRNA expression of TGF-β1 and TGF-β3, and enhanced cell cycle progression, while simultaneously repressing cell apoptosis as well as activating the PI3K/AKT/GSK-3β and Wnt/β-catenin signaling pathways. The above findings demonstrated that Se can promote cell proliferation, reduce cell apoptosis, and aid in the growth of BESCs damaged by LPS under high levels of cortisol. The potential mechanisms may be associated with the regulation of the PI3K/AKT/GSK-3β and Wnt/β-catenin signaling pathways.

Klebsiella pneumoniae (K. pneumoniae) is a significant pathogen associated with clinical mastitis in cattle. Anti-inflammatory drugs are necessary to alleviate pain and inflammation during clinical mastitis. Among many drugs, meloxicam (MEL) has been widely used in clinical mastitis because of its excellent inhibitory effect on the cyclooxygenase-2 (COX-2) enzyme. However, the effectiveness of MEL on the inflammatory response and oxidative stress induced by K. pneumoniae are unclear. In the present study, primary BMECs were infected with K. pneumoniae in the presence or absence of plasma maintenance concentration of MEL (0.5 and 5 μM). Following 1 or 3 h of combined treatment with K. pneumoniae and MEL, BMECs were gathered to assess the related indicators. The results showed that MEL at plasma maintenance concentrations exerted no influence on the viability of uninfected BMECs and also had no impact on bacterial load in BMECs. At these concentrations, MEL was able to inhibit the mRNA expression of COX-2, Interleukin (IL)-1β, Tumor necrosis factor α (TNF-α), and IL-6 while simultaneously elevating the mRNA levels of IL-8 in K. pneumoniae-infected BMECs. MEL had clear effects on relieving oxidative stress by increasing the activity of superoxide dismutase (SOD) and catalase (CAT) and the level of total antioxidant capacity (T-AOC). The mechanisms by which MEL mitigated the inflammatory response and oxidative stress were partially attributed to inhibition of the nuclear transcription factor-kappa B (NF-κB) signaling pathway and improvement of the activation of the nuclear factor erythroid 2-related factors (Nrf2) signaling pathway. To conclude, the results manifested that MEL at plasma maintenance concentrations protected BMECs from inflammatory and oxidative damage induced by K. pneumoniae.

Endometritis represents a prevalent condition in perinatal dairy cows. Bovine endometrial epithelial cells (BEECs), as the primary interface between cavity and the external environment, are particularly vulnerable to infection by pathogenic bacteria following parturition. A20 is essential for regulating inflammation and modulating immune responses. Nevertheless, the exact role of A20 in the BEECs in response to inflammatory response is not fully understood. An endometritis model infected by Escherichia coli (E. coli) in vivo and a BEECs inflammation model induced with lipopolysaccharide (LPS) in vitro were built to investigate the function and governing mechanisms of A20 in endometritis. The results showed that infection with E. coli resulted in endometrial damage, inflammatory cell infiltration, and upregulation of inflammatory factors in dairy cows. Furthermore, A20 expression was upregulated in the endometrium of cows with endometritis and in BEECs following LPS stimulation. A20 overexpression attenuated the level of proinflammatory cytokines in LPS-stimulated BEECs; conversely, A20 knockdown lead to an exacerbated response to LPS stimulation. The overexpression of A20 was shown to activate autophagy and suppress the NF-κB signaling pathway in LPS-stimulated BEECs. However, blocking autophagy with chloroquine notably attenuated the anti-inflammatory effect of A20, leading to the activation of the NF-κB signaling pathway. In summary, the study demonstrated that A20’s suppression of inflammation in LPS-stimulated BEECs is associated with the activation of autophagy. Therefore, the A20 protein showed potential as a novel treatment focus for managing endometritis in dairy cows.

Colibactin is a complex secondary metabolite that leads to genotoxicity that interferes with the eukaryotic cell cycle. It plays an important role in many diseases, including neonatal mouse sepsis and meningitis. Avian pathogenic Escherichia coli (APEC) is responsible for several diseases in the poultry industry and may threaten human health due to its potential zoonosis. In this study, we confirmed that clbG was necessary for the APEC XM strain to produce colibactin. The deletion of clbG on APEC XM contributed to lowered γH2AX expression, no megalocytosis, and no cell cycle arrest in vitro. None of the 4-week Institute of Cancer Research mice infected with the APEC XM ΔclbG contracted meningitis or displayed weakened clinical symptoms. Fewer histopathological lesions were observed in the APEC XM ΔclbG group. The bacterial colonization of tissues and the relative expression of cytokines (IL-1β, IL-6, and TNF-α) in the brains decreased significantly in the APEC XM ΔclbG group compared to those in the APEC XM group. The tight junction proteins (claudin-5, occludin, and ZO-1) were not significantly destroyed in APEC XM ΔclbG group in vivo and in vitro. In conclusion, clbG is necessary for the synthesis of the genotoxin colibactin and affects the development of APEC meningitis in mice.