Novel Hybrid Peptide DEFB126 (1-39)-TP5 Inhibits LPS-Induced Inflammatory Responses and Oxidative Stress by Neutralizing LPS and Blocking the TLR4/MD2-NFκB Signaling Axis

Lipopolysaccharide (LPS), an essential structural molecule in the outer membrane of Gram-negative bacteria, is recognized as a principal trigger of inflammatory responses and oxidative stress. Thus, the control and clearance of LPS is essential to inhibit LPS-induced excessive inflammation, oxidative stress, and liver injury. In recent years, some native bioactive peptides, such as human β-defensin 126 (DEFB126) and thymopentin (TP5), have been reported to have inhibitory effects against LPS-induced inflammation and oxidative stress. However, the cytotoxicity, weak stability, and poor biological activity have hindered their practical application and clinical development. The development of novel hybrid peptides is a promising approach for overcoming these problems. In this study, we designed a novel hybrid peptide [DTP, DEFB126 (1-39)-TP5] that combines the active center of DEFB126 and full-length thymopentin (TP5). Compared to the parental peptides, DTP has a longer half-life, lower cytotoxicity, and greater anti-inflammatory and antioxidant activity. The anti-inflammatory and antioxidant effects of DTP were demonstrated in a murine LPS-induced sepsis model, which showed that DTP successfully inhibited the indicators associated with LPS-induced liver injury; decreased the contents of TNF-α, IL-6, and IL-1β; increased the level of glutathione (GSH); and improved the activities of catalase (CAT) and superoxide dismutase (SOD). Furthermore, our study revealed that the anti-inflammatory and antioxidant activities of DTP were associated with LPS neutralization, blockade of LPS binding to the Toll-like receptor 4/myeloid differentiation factor 2 (TLR4/MD-2) complex, reduction in reactive oxygen species content, and inhibition of the activation of the nuclear factor kappa-B (NF-кB) signaling pathway. These results elucidate the structural and functional properties of the peptide DTP, reveal its underlying molecular mechanisms, and shed light on its potential as a multifunctional agent for applications in agriculture, food technology, and clinical therapeutics.