Functional characterization of HR-CATH2, a novel cathelicidin from Hoplobatrachus rugulosus with anti-sepsis activity.

Cathelicidins are central effectors of innate host immunity against invading microorganisms and represent a promising source of next-generation anti-infective agents. However, current understanding of both antimicrobial activity and immunomodulatory function within this peptide family remains incomplete. In the present study, a novel cathelicidin peptide, designated HR-CATH2, was identified from the skin of the Chinese tiger frog ( Hoplobatrachus rugulosus). The peptide consisted of 30 amino acid residues (GRCNLLCKAKKKLRAVGNKIKEIKNVVFNR) and adopted a highly amphipathic α-helical structure. Functional analyses indicated that HR-CATH2 exerted potent antimicrobial activity through induction of intracellular reactive oxygen species (ROS) accumulation and direct disruption of bacterial membrane integrity. Moreover, HR-CATH2 inhibited overproduction of proinflammatory cytokines (interleukin-6, interleukin-1β, and tumor necrosis factor-α) and nitric oxide (NO) in RAW264.7 cells through lipopolysaccharide (LPS) binding and consequent inactivation of MAPK signaling. In vivo, HR-CATH2 markedly attenuated the acute inflammatory response and reduced mortality in mice subjected to cecal ligation and puncture (CLP)-induced sepsis. Together, these findings identify HR-CATH2 as a multifunctional cathelicidin with antibacterial, LPS-neutralizing, and anti-inflammatory activities, and support its potential as a therapeutic candidate for bacterial infectious diseases, including sepsis.