Overexpression of Toll-like receptor 4 contributes to the internalization and elimination of Escherichia coli in sheep by enhancing caveolae-dependent endocytosis

Background:Gram-negative bacterial infections have a major economic impact on both the livestock industry and public health.Toll-like receptor 4(TLR4)plays a crucial role in host defence against Gram-negative bacteria.Exploring the defence mechanism regulated by TLR4 may provide new targets for treatment of inflammation and control of bacterial infections.In a previous study,we generated transgenic sheep overexpressing TLR4 by microinjection to improve disease resistance.The defence mechanism through which TLR4 overexpression protected these sheep against pathogens is still not fully understood.Results:In the present study,we used Escherichia coli to infect monocytes isolated from peripheral blood of the animal model.The overexpression of TLR4 strongly enhanced the percentage of endocytosis and capacity of elimination in monocytes during the early stages of infection.This phenomenon was mainly due to overexpression of TLR4 promoting caveolae-mediated endocytosis.Pretreatment of the transgenic sheep monocytes with inhibitors of TLR4,Src signalling,or the caveolae-mediated endocytosis pathway reduced the internalization of bacteria,weakened the ability of the monocytes to eliminate the bacteria,and increased the pH of the endosomes.Conclusion:Together,our results reveal the effects of TLR4 on the control of E.coli infection in the innate immunity of sheep and provide crucial evidence of the caveolae-mediated endocytosis pathway required for host resistance to invading bacteria in a large animal model,providing theoretical support for breeding disease resistance in the future.Furthermore,Src and caveolin 1(CAV1)could be potentially valuable targets for the control of infectious diseases.

Gut microbiota,inflammation,and molecular signatures of host response to infection

Gut microbial dysbiosis has been linked to many noncommunicable diseases.However,little is known about specific gut microbiota composition and its correlated metabolites associated with molecular signatures underlying host response to infection.Here,we describe the construction of a proteomic risk score based on 20 blood proteomic biomarkers,which have recently been identified as molecular signatures predicting the progression of the COVID-19.We demonstrate that in our cohort of 990 healthy individuals without infection,this proteomic risk score is positively associated with proinflammatory cytokines mainly among older,but not younger,individuals.We further discover that a core set of gut microbiota can accurately predict the above proteomic biomarkers among 301 individuals using a machine learning model and that these gut microbiota features are highly correlated with proinflammatory cytokines in another independent set of 366 individuals.Fecal metabolomics analysis suggests potential amino acid-related pathways linking gut microbiota to host metabolism and inflammation.Overall,our multi-omics analyses suggest that gut microbiota composition and function are closely related to inflammation and molecular signatures of host response to infection among healthy individuals.These results may provide novel insights into the cross-talk between gut microbiota and host immune system.