Modulation of Bovine Wnt Signaling Pathway Genes by Cowpea Phenolic Extract

The Wingless (Wnt) signaling pathway is a conserved pathway with essential roles in cellular and biological processes in mammals. Wnt signal transduction has been implicated in inflammation, innate immunity and homeostasis via Toll-like receptor and NF-kB pathways. Plant bioactive compounds are capable of modulating the Wnt signalling pathway, which can be either a canonical (B-Catenin dependent) or non-canonical (B-Catenin independent) mechanism. This study evaluated the effect of cowpea phenolic extract (CPE) on the expression and modulation of genes of the Wnt signaling pathway in cow blood. Whole blood collected from six Holstein-Friesian cows was treated with 10 ug/ml of the extract, and evaluated for packed cell volume (PCV), total count and viability of cells, and white blood cell differential count before and after treatment. Cowpea phenolic extract agonist activity in blood was measured using a Bovine toll-like receptor (TLR) 2, and TLR 4 ELISA kit. Total RNA was isolated from the blood cell pellet, reverse transcribed and used for real-time PCR to detect expression of 84 genes on the Cow Wnt signaling pathway array. The total cell-associated B-Catenin level was measured using a commercial ELISA kit. There was no treatment effect on PCV, total cell and viability (P > 0.05). The percentage of mononuclear cells were influenced by treatment, % monocytes (P = 0.0136) decreased and % lymphocytes (P = 0.0114) increased. Treatment with CPE activated cow blood cells, increased TLR2 release and total B-Catenin levels (6 ng/ml, P < 0.05), but TLR4 was not detected. Polyphenols from cowpea modulated the expression of Wnt signalling genes, especially canonical B-Catenin mediated pathway genes. Modulation of Wingless gene expression may be an important mechanism by which polyphenols in cowpea feed impact cellular immune response and homeostasis. Thus, further studies are needed to determine the association of CPE-mediated Wnt gene modulation on blood leucocytes subpopulations and animal health.