The bioactivity of colostrum and milk exosomes of high, average, and low immune responder cows on human intestinal epithelial cells

摘要

Bovine milk contains bioactive components that arenutritionally and immunologically important to calvesand humans. Dairy cows classified as high (H) immuneresponders using the patented high immune responsetechnology have higher concentrations of immunoglobulinand specific antibodies in sera and milk comparedwith average (A) and low (L) responders. MicroRNApost-transcriptionally regulate expression of milk bioactivecomponents and are enriched in extracellularvesicles known as exosomes, which protect them fromdegradation. The bioactivity of colostrum and milkexosomes at the human intestinal epithelial barrierremains to be explored, particularly in the context ofthe high immune response technology. Therefore, thepurpose of this study was to evaluate the functionalrole of bovine milk exosomes compared with colostrumexosomes from H, A, and L responders at the intestinalinterface using human colorectal adenocarcinoma epithelial(Caco-2) cells. Exosomes were isolated by successiveultracentrifugation and confirmed by western blotanalysis for the presence of common exosomal proteins(CD9, CD63, and heat shock protein 70). Fluorescentlabeling of exosomes using PKH67 dye confirmed theiruptake by Caco-2 cells, demonstrating their potentialbioavailability. The MTT assays showed that colostrumand milk exosomes maintain Caco-2 metabolic activityand are not cytotoxic to these cells. Specifically, metabolicactivity after co-incubation with colostrum andmilk exosomes from H responder cows was significantlygreater than after co-incubation with exosomes from Lresponders. Caspase 3 activity, an indicator of apoptosis,was significantly lower after co-incubation of Caco-2 cells with milk exosomes compared with colostrumexosomes, suggesting that unlike colostrum exosomes,particularly those from L responders, milk exosomesdo not activate the caspase 3 pathway in Caco-2 cells.This study helps us better understand the functionalimportance of colostrum and milk exosomes from dairycows and emphasizes differences in functionality amongexosomes from H, A, and L immune responders.