Protective effect of edible bird’s nest peptides against oxidative stress and inflammation in TNF-α stimulated endothelial cells

Bioactive peptides from edible bird’s nest (EBN) represent a unique natural source that exhibits various attractive bioactivities. Four EBN peptides (P1: LFWSPSVYLK, P2: GWPHLEDNYLDW, P3: NPPADLHK and P4: GDLAYLDQGHR) were previously identified with potential antioxidant and anti-inflammatory activities. However, their bioactivities at cellular levels and underlying mechanisms are poorly understood. This study aimed to investigate the antioxidant and anti-inflammatory activities of these four EBN peptides in human vascular endothelial cells (EA. hy926) and identify the mechanisms involved. Four EBN peptides were screened for their antioxidant effects (superoxide scavenging) and anti-inflammatory effects (reducing cyclooxygenase-2 (COX-2) and vascular cell adhesion molecule 1 (VCAM-1) level) in tumour necrosis factor (TNF-α) induced EA. hy926 cells. Stability in a gastrointestinal (GI) digestion model was assessed. The expression levels of phospho-Nrf2 (p-Nrf2), mitogen-activated protein kinase (MAPK) family proteins (p38, ERK, and JNK) and sirtuin 1 (SIRT1) were studied. Results indicated that P1, among four peptides tested, potently lowered the superoxide (38%), COX-2 (26.63%), and VCAM-1 (58.88%) levels, thus exhibiting antioxidant and anti-inflammatory activities. Importantly, P1 maintained these activities after the simulated GI digestion. Additionally, P1 significantly improved p-Nrf2 (44.30%) and SIRT1 (40.26%) levels, while inhibiting MAPK proteins [p38 (72.29%), ERK (27.22%) and JNK (50%)], indicating its potential to modulate the Nrf2 and MAPK signalling pathways. This study is the first to report the potential role of EBN peptides in protecting vascular endothelial cells from oxidative and inflammation damage.