Escherichia coli infection mediates pyroptosis via activating p53-p21 pathway-regulated apoptosis and cell cycle arrest in bovine mammary epithelial cells

Escherichia coli (E. coli) is a major environmental pathogen that causes mammary tissue damage and cell death, which results in substantial economic losses. Pyroptosis, a novel form of programmed cell death characterized by DNA fragmentation, chromatin condensation, cell swelling and leakage of cell contents, often occurs after inflammatory apoptotic pathways activation. Our objective was to investigate the intraction between E. coli infection and bovine mammary epithelial cells (bMECs) with pyroptosis and to explore the underlying regulatory mechanism. bMECs were infected with E. coli for 6 h. Lactic dehydrogenase activities, interleukin (IL)-10, IL-1β, IL-18 and tumor necrosis factor-α concentrations, total apoptosis indexes, and protein expressions of P-cdc25c, P-CDK1, cleaved caspase 9, cleaved caspase 3, cleaved PARP, P-NF-κB, NLRP3, ASC, caspase 1, gasdermin D N-terminal, IL-1β and IL-18 were significantly increased in E. coli infected bMECs. Whereas, cell membrane potential, protein levels of cdc25c, CDK1, cyclin B1, and Bcl-2/Bax level were markedly reduced. Furthermore, Ac-DEVD-CHO (specific inhibitor of apoptosis) dramatically suppressed pyroptosis in bMECs. Moreover, expressions of p53 and p21 promptly improved after E. coli infection, however, Pifithrin-α (specific inhibitor of p53) inhibited p53-p21 pathway, apoptosis, cell cycle arrest and pyroptosis. These results elaborated that E. coli infection of bMECs induced pyroptosis through activating the p53-p21 pathway-mediated apoptosis and cell cycle arrest. Taken together, inhibition of pyroptosis via suppressing of p53-p21 pathway may be an effective therapeutic approach for treating E. coli-induced mastitis, offering efficient theoretical support for the protection and treatment of bovine mastitis.

Lactiplantibacillus plantarum Strain FLPL05 Promotes Longevity in Mice by Improving Intestinal Barrier

This study aimed to evaluate the effect of oral administration of probiotic Lactiplantibacillus plantarum FLPL05 on the lifespan and intestinal barrier of aged mice. L. plantarum FLPL05 significantly prolonged the lifespan of naturally aged mice, maintained the integrity of intestinal mucosal barrier, and reduced the inflammation level. The analysis of intestinal microbiota revealed that L. plantarum FLPL05 increased the relative abundance of Firmicutes and decreased the abundance of Bacteroides, accompanied by the increased proportions of Lactobacillus and Desulfovibrio in intestinal microbiota as well as the reduced proportions of Roseburia and Parabacteroides. The intestinal proteomics revealed that the oral administration of L. plantarum FLPL05 significantly upregulated the tight junction and simultaneously inhibited the expression of apoptotic-related proteins. The immunohistochemistry results also indicated that L. plantarum FLPL05 promoted the expression of tight junction proteins (ZO-1 and occludin) and reduced the apoptosis of intestinal cells. In addition, L. plantarum FLPL05 and the fermented supernatant increased the activity of HT-29. L. plantarum FLPL05 prolonged the lifespan by improving the health of the intestinal tract after aging and may be a potential probiotic and nutritional supplement for the elderly people.

Molecular mechanism of Enteroaggregative Escherichia coli induced apoptosis in cultured human intestinal epithelial cells

Background. Enteroaggregative Escherichia coli (EAEC) is an evolving etiological agent of acute and persistent diarrhoea worldwide. The previous study from our laboratory has reported the apoptosis-inducing activity of EAEC in human small intestinal and colonic epithelial cell lines. In the present investigation, we have explored the underlying mechanism of EAEC-induced apoptosis in human intestinal epithelial cell lines.Methods. INT-407 and HCT-15 cells were infected with EAEC-T8 and EAEC-pT8 (plasmid cured strain of EAEC-T8) separately. Cells cultured in the absence of bacteria served as a negative control in all the experiments. For the subsequent experiments, the molecular mechanism(s) of epithelial cell aposptosis was measured in EAEC infecting both the cell lines by flow cytometry, real-time PCR and Western blotting.Results and conclusions. EAEC was found to activate the intrinsic/mitochondrial apoptotic pathway in both the cell lines through upregulation of pro-apoptotic Bax and Bak, un-alteration/reduction in the level of anti-apoptotic Bcl-2 and Bcl-XL, decrease in mitochondrial transmembrane potential, accumulation of cytosolic cytochrome c leading to activation of procaspase-9 and procaspase-3, which ultimately resulted in DNA fragmentation and apoptosis. Further, an increased expression of Fas, activation of procaspase-8 and upregulation of pro-apoptotic Bid in the EAEC-infected cells indicated the involvement of extrinsic apoptotic pathway too in this process. Our finding has undoubtedly led to an increased understanding of EAEC pathogenesis, which may be helpful to develop an improved strategy to combat the infection.

A Novel Probiotic Bacillus subtilis Strain Confers Cytoprotection to Host Pig Intestinal Epithelial Cells during Enterotoxic Escherichia coli Infection

Enteric infections caused by enterotoxic Escherichia coli (ETEC) negatively impact the growth performance of piglets during weaning, resulting in significant economic losses for the producers. With the ban on antibiotic usage in livestock production, probiotics have gained a lot of attention as a potential alternative. However, strain specificity and limited knowledge on the host-specific targets limit their efficacy in preventing ETEC-related postweaning enteric infections. We recently isolated and characterized a novel probiotic Bacillus subtilis bacterium (CP9) that demonstrated antimicrobial activity. Here, we report anti-ETEC properties of CP9 and its impact on metabolic activity of swine intestinal epithelial (IPEC-J2) cells. Our results showed that pre- or coincubation with CP9 protected IPEC-J2 cells from ETEC-induced cytotoxicity. CP9 significantly attenuated ETEC-induced inflammatory response by reducing ETEC-induced nitric oxide production and relative mRNA expression of the Toll-like receptors (TLRs; TLR2, TLR4, and TLR9), proinflammatory tumor necrosis factor alpha, interleukins (ILs; IL-6 and IL-8), augmenting anti-inflammatory granulocyte-macrophage colony-stimulating factor and host defense peptide mucin 1 (MUC1) mRNA levels. We also show that CP9 significantly (P < 0.05) reduced caspase-3 activity, reinstated cell proliferation and increased relative expression of tight junction genes, claudin-1, occludin, and zona occludens-1 in ETEC-infected cells. Finally, metabolomic analysis revealed that CP9 exposure induced metabolic modulation in IPEC J2 cells with the greatest impact seen in alanine, aspartate, and glutamate metabolism; pyrimidine metabolism; nicotinate and nicotinamide metabolism; glutathione metabolism; the citrate cycle (TCA cycle); and arginine and proline metabolism. Our study shows that CP9 incubation attenuated ETEC-induced cytotoxicity in IPEC-J2 cells and offers insight into potential application of this probiotic for ETEC infection control. IMPORTANCE ETEC remains one of the leading causes of postweaning diarrhea and mortality in swine production. Due to the rising concerns with the antibiotic use in livestock, alternative interventions need to be developed. In this study, we analyzed the cytoprotective effect of a novel probiotic strain in combating ETEC infection in swine intestinal cells, along with assessing its mechanism of action. To our knowledge, this is also the first study to analyze the metabolic impact of a probiotic on intestinal cells. Results from this study should provide effective cues in developing a probiotic intervention for ameliorating ETEC infection and improving overall gut health in swine production.

Retinoids delay cell cycle progression and promote differentiation of intestinal epithelial cells exposed to nutrient deprivation

OBJECTIVE

Vitamin A is commonly recommended as a treatment for diarrhea and undernutrition; however, little is known about the underlying cellular mechanisms. The aim of this study was to investigate the modulation of cell cycle by vitamin A derivatives (retinyl palmitate or retinol) in undernourished intestinal epithelial crypts (IEC-6).

METHODS

IEC-6 cells were exposed to nutrient deprivation (no serum and no glutamine) and supplemented with retinyl palmitate or retinol at a range of 2 to 20 μM. Proliferation, apoptosis/necrosis, cell cycle process, and gene transcription were assessed.

RESULTS

Nutrient deprivation for 6, 12, 24, or 48 h decreased cell proliferation, and retinyl palmitate further decreased it after 24 and 48 h. Apoptosis rates were reduced by undernourishment and further reduced by retinyl palmitate after 48 h; whereas necrosis rates were unaltered. Undernourishment induced overall cell quiescence, increased percentage of cells in G0/G1 phase and decreased percentage of cells in S phase after 12 h and in G2/M phases at 6, 12, and 24 h after treatment. Both retinoids also showed cell quiescence induction with less cells in G2/M phases after 48 h, whereas only retinol showed significant modulation of G0/G1 and S phases. Both retinoids also increased markers of cell differentiation Fabp and Iap gene transcriptions in about fivefold rates after 42 h. Furthermore, specific gene transcriptions related to MAP kinase signaling pathway regulation of cell differentiation and cell cycle regulation were triggered by retinoids in undernourished IEC-6, with higher levels of expression for Atf2 and C-jun genes.

CONCLUSIONS

These findings indicated that both vitamin A derivatives induce further survival mechanisms in undernourished intestinal epithelial crypt cells. These mechanisms include increased cell quiescence, decreased apoptosis, increased cell differentiation, and transcription of genes related to MAP kinase signaling pathway.

Anti-inflammatory Effect of Astragalin and Chlorogenic Acid on Escherichia coli-Induced Inflammation of Sheep Endometrial Epithelium Cells

Endometritis is one of the main diseases which harm sheep husbandry. Astragalin and chlorogenic acid (CGA) are common active ingredients of traditional Chinese medicine (TCM) with immunoprotective, antioxidant, and anti-inflammatory properties. In the present study, sheep endometrial epithelium cells (SEECs) were successfully purified and identified, and the in vitro inflammation model of SEECs induced by Escherichia coli (E. coli) was successfully established. To explore the effect of astragalin and CGA on the inflammation induced by E. coli and its potential mechanism, six groups were set up, namely, group C, M, astragalin, CGA, BAY, and STR. Cells in group C were incubated with DMEM/F12 for 6 h, while cells in group M, astragalin, CGA, BAY, and STR were incubated with DMEM/F12, astragalin, CGA, BAY, and STR for 3 h, respectively, followed by E. coli infection at a multiplicity of infection (MOI) of 1 E. coli per cell for 3 h. Subsequently, the cells and the supernatant were collected to detect the expression of genes in the toll-like receptor 4 (TLR4)/nuclear factor-kappa B (NF-κB) pathway by ELISA, qPCR, and western blot. The results showed that E. coli could induce inflammation of SEECs in vitro, while astragalin and CGA could alleviate the inflammatory response induced by E. coli via inhibiting the activation of the TLR4/NF-κB signaling pathway, which provides a theoretical and experimental foundation for preventing sheep endometritis clinically.

Baicalin modulates apoptosis via RAGE, MAPK, and AP-1 in vascular endothelial cells during Haemophilus parasuis invasion

Glässer’s disease, caused by Haemophilus parasuis, is a chronic disease related to an inflammatory immune response. Baicalin exerts important biological functions. In this study, we explored the protective efficacy of treatment with baicalin and the potential mechanism of activation of the MAPK signaling pathway in porcine aortic vascular endothelial cells (PAVECs) induced by H. parasuis. H. parasuis stimulated expression of receptor for advanced glycation end products, induced a significant increase in the level of protein kinase-α and protein kinase-δ phosphorylation, and significantly up-regulated ERK, c-Jun N-terminal kinase, and p38 phosphorylation in PAVECs. H. parasuis also up-regulated the levels of apoptotic genes (Bax, C-myc, and Fasl) and the expression levels of c-Jun and c-Fos, and induced S-phase arrest in PAVECs. However, treatment with baicalin inhibited expression of RAGE, suppressed H. parasuis-induced protein kinase-α and protein kinase-δ phosphorylation, reduced ERK, c-Jun N-terminal kinase, and p38 phosphorylation, down-regulated apoptotic genes (Bax, C-myc, and Fasl), attenuated phospho-c-Jun production from the extracellular to the nuclei, and reversed S-phase arrest in PAVECs. In conclusion, baicalin treatment inhibited the MAPK signaling pathway, thereby achieving its anti-inflammatory responses, which provides a new strategy to control H. parasuis infection.

Alanyl-glutamine Protects Against Damage Induced by Enteroaggregative Escherichia coli Strains in Intestinal Cells

BACKGROUND

Enteroaggregative Escherichia coli (EAEC) is an important pathogen causing enteric infections worldwide. This pathotype is linked to malnutrition in children from developing countries. Alanyl-glutamine (Ala-Gln) is an immune modulator nutrient that acts during intestinal damage and/or inflammation. This study investigated the effect of EAEC infection and Ala-Gln on cell viability, cell death, and inflammation of intestinal epithelium cells (IEC-6).

METHODS

Cells were infected with an EAEC prototype 042 strain, an EAEC wild-type strain isolated from a Brazilian malnourished child, and a commensal E coli HS. Gene transcription and protein levels of caspases-3, -8, and -9 and cytokine-induced neutrophil chemoattractant 1 (CINC-1/CXCL1) were evaluated using RT-qPCR, western blot analysis, and ELISA.

RESULTS

Infections with both EAEC strains decreased cell viability and induced apoptosis and necrosis after 24 hours. Ala-Gln supplementation increased cell proliferation and reduced cell death in infected cells. Likewise, EAEC strain 042 significantly increased the transcript levels of caspases-3, -8, and -9 when compared to the control group, and Ala-Gln treatment reversed this effect. Furthermore, EAEC induced CXCL1 protein levels, which were also reduced by Ala-Gln supplementation.

CONCLUSION

These findings suggest that EAEC infection promotes apoptosis, necrosis, and intestinal inflammation with involvement of caspases. Supplementation of Ala-Gln inhibits cell death, increases cell proliferation, attenuates mediators associated with cell death, and inflammatory pathways in infected cells.