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.

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.

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.

Background: In dairy cows, the stress-related cortisol level increases the susceptibility to postpartum uterine diseases. Oxidative stress is an important component of the disease process and causes morphological and functional alterations in the bovine endometrium. Selenium (Se) has an antioxidant property, and an appropriate Se supplementation is recommended to enhance bovine disease resistance. Methods and results: Here, we aimed to answer two questions: (1) how does cortisol affect the oxidative status of bovine endometrial cells; and (2) does Se supplementation protect cells from oxidative injury with a high cortisol condition? The oxidative stress of primary bovine endometrial epithelial cells (BEECs) was established by Escherichia coli lipopolysaccharide (LPS) stimulation, as marked by the increased oxidative markers and the suppressions of antioxidant indicators and Nrf2 signaling. In the absence of LPS, cortisol levels of 15 ng/mL showed a more significant antioxidative effect than cortisol levels of 5 and 30 ng/mL. In the presence of LPS, cortisol levels of 15 and 30 ng/mL elicited antioxidation, whereas 5 ng/mL of cortisol did not. Regardless of LPS stimulation, Se pretreatment of 1, 2, and 4 μM protected BEEC from oxidative stress, as evidenced by the decreased oxidative markers, increased antioxidant indices, and the activated Nrf2 signaling. With the presence of 30 ng/mL of cortisol, there was an enhanced Se antioxidant effect, which can be abolished by the block of cortisol receptor. Conclusions: Both cortisol and Se elicited antioxidant properties in BEEC through the Nrf2 pathway. In addition, the Se antioxidation was enhanced by cortisol.

Meloxicam has been identified as an adjuvant therapeutic component in the management of bovine uterine diseases, exhibiting anti-inflammatory and antioxidant effects. However, the mechanisms underlying its antioxidant actions in the context of bovine uterine diseases remain incompletely understood. The objective of this research was to determine whether meloxicam exerts its antioxidant effects through the Nrf2/HO-1 signaling pathway. By employing N-acetylcysteine (NAC), a scavenger of reactive oxygen species (ROS), along with inhibitors directed against heme oxygenase-1 (HO-1) or nuclear factor erythroid 2-related factor 2 (Nrf2), we investigated the dynamic changes in oxidative stress markers (ROS and malondialdehyde) and antioxidant indices (comprising catalase, superoxide dismutase, and glutathione), as well as the expression profiles of Nrf2 and inflammation-associated genes and proteins in bovine endometrial epithelial cells (BEECs) subjected to lipopolysaccharide (LPS) stimulation. As a result, meloxicam alleviated the LPS-induced elevation of oxidative stress marker levels and the reduction in antioxidant enzyme activities and antioxidant substance contents in BEECs. Compared to NAC, meloxicam demonstrated superior efficacy in activating the Nrf2 pathway, with the promotion of NRF2 expression (~1.6-fold) and nuclear translocation. The pretreatment of cells with HO-1 or Nrf2 inhibitors markedly attenuated the antioxidant activity of meloxicam. In summary, meloxicam primarily alleviates LPS-induced oxidative stress through the activation of the Nrf2/HO-1 pathway in BEECs.