MiR-20a-5p Targeting the TGFBR2 Gene Regulates Inflammatory Response of Chicken Macrophages Infected with Avian Pathogenic E. coli.

Avian pathogenic E. coli (APEC) causes localized and systemic infections and are a threat to human health. microRNAs (miRNAs) play critical roles in inflammation and immune regulation following pathogen invasion. However, the related regulatory mechanism remains unclear. This study aimed to elucidate the involvement of chicken microRNA-20a-5p (gga-miR-20a-5p) in host defense against APEC in chickens and the underlying mechanisms. We evaluated the expression levels of gga-miR-20a-5p in chicken tissues and cells and observed a significant decrease in expression following APEC infection. Dual luciferase reporter assays showed that gga-miR-20a-5p directly targeted transforming growth factor-beta receptor 2 (TGFBR2), specifically by binding to the 3'-untranslated region (3'UTR) of TGFBR2. Overexpression of gga-miR-20a-5p markedly reduced both the mRNA and protein levels of TGFBR2, whereas inhibition of gga-miR-20a-5p significantly increased expression. Mechanistic investigations revealed that overexpression of gga-miR-20a-5p also attenuated the expression levels of the pro-inflammatory cytokines IL8, TNFα, IL6, and IL1ß, whereas inhibition of gga-miR-20a-5p had the opposite effects. Collectively, our findings suggest that gga-miR-20a-5p regulates the immune response during APEC infection by targeting TGFBR2, thereby suppressing inflammatory cytokine production. This study provides valuable insights into the role of gga-miR-20a-5p in the host defense against APEC.

PTEN regulated by gga-miR-20a-5p is involved in chicken macrophages inflammatory response to APEC infection via autophagy.

Colibacillosis, a bacterial disease caused by avian pathogenic E. coli (APEC), is a prevalent condition in the poultry industry, resulting in substantial economic losses annually. Previously, we identified PTEN as a crucial candidate gene that may play a significant role in chicken's immune response to APEC infection. Bioinformatics analysis indicated that the PTEN protein was unstable, hydrophilic and nuclear localization, with multiple putative phosphorylation sites and a high degree of similarity to duck and goose PTEN. Moreover, PTEN exhibited high expression levels in various tissues such as the stomach, cecum, small intestine, spleen, thymus, harderian gland, muscle, cerebrum, cerebellum, lung, and liver in comparison to heart tissue. Overexpression of PTEN resulted in a significant promotion of the expression level of pro-apoptosis genes and inflammatory mediators, as well as the production of NO, with or without APEC infection, which led to cellular injury. Furthermore, overexpression of PTEN was found to regulate the expression levels of autophagy related genes, regardless of APEC infection. Additionally, PTEN was a target gene of gga-miR-20a-5p and regulated by gga-miR-20a-5p upon APEC infection. Taken together, these findings establish a foundation for investigating the biological function of chicken PTEN, providing a potential target for future treatments against APEC infection as well as the breeding of genetically resistant poultry.