The immune-enhancing activity of egg white ovalbumin hydrolysate prepared with papain via MAPK signaling pathway in RAW 264.7 macrophages

Ovalbumin (OA) is a major protein in egg white, and enzymatic hydrolysis of OA is well-known to improve its functional properties. In this study, the immune-enhancing effects of OA hydrolysates (OAH), prepared using proteolytic enzymes (Alcalase®, α-chymotrypsin, Flavourzyme®, Neutrase®, and papain) in RAW 264.7 macrophages, were investigated. All the OAH enhanced NO production, with the maximum level found in the OAH prepared with papain (OAPP) by increasing the expression of iNOS mRNA and protein. RAW 264.7 macrophages treated with the OAPP showed higher mRNA expression levels and the production of pro-inflammatory cytokines (TNF-α and IL-6). The evaluation results with specific inhibitors showed that the mitogen-activated protein kinase (MAPK) signaling pathway involved the macrophage activation induced by the OAPP. Moreover, the immunomodulatory activity of OAPP was improved under the in vitro gastrointestinal digestion model, indicating that the OAPP could be used as an effective immune-enhancing agent in the functional food industry.