Identification and screening of bioactive peptides against nephropathy derived from Mantidis Oötheca based on complement C3 inhibition

Insects represent emerging sources of bioactive peptides and functional materials. Mantidis Oötheca (Sang-Piao-Xiao in Chinese, SPX) serves as an insect-derived medicine for treating kidney disease. This study demonstrated that supernatant (SPX) improved kidney function in adriamycin (ADR)-induced nephropathy mice model. Transcriptomic analysis revealed that SPX inhibited complement activation by targeting the MASP1-C3/C3a receptor (C3aR) pathway. Peptidomic analysis identified 304 peptides from SPX, with 49 peptides selected for evaluation using prediction tools and molecular docking with complement core protein C3. Three peptides (PMGFPFDR, FNDPK, AAQFFNR) exhibiting docking scores below −8.0 were synthesized to verify complement inhibition and anti-fibrotic activities. The synthetic peptide AAQFFNR demonstrated complement inhibitory activity, with an inhibitory complement hemolytic 50% (ICH₅₀) value of 24.54 μmol·L⁻¹, and exhibited superior protective effects in ADR-induced HK-2 cells. Surface plasmon resonance (SPR) assay revealed direct interaction between AAQFFNR and complement C3 with K_d value of 16.8 μmol·L⁻¹. The reno-protective effect of AAQFFNR was subsequently verified in ADR-induced mice. This research provides initial evidence that complement C3-inhibiting peptides from insects demonstrate potential in preventing nephropathy through in silico and in vivo validation approaches.