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

Insects have been proposed as new sources of bioactive peptides and functional materials. Mantidis Oötheca (Sang piao xiao in Chinese, SPX) is an insect medicine for the treatment of kidney disease. In this study, SPX improved kidney function in Adriamycin (ADR)-induced nephropathy mice model. Transcriptomics revealed that SPX inhibited complement activation by targeting the MASP1-C3/C3aR pathway. Then 304 peptides were identified from SPX via peptidomic analysis, and 49 peptides were selected to be evaluated using prediction tools and molecular docking with complement core protein C3. Three peptides (PMGFPFDR, FNDPK, AAQFFNR) with lower docking scores less than -8.0 were synthesized to verify complement inhibition and the anti-fibrotic activities. The results showed that the synthetic peptide AAQFFNR significantly inhibited complement activation with CH50 of 24.54 μM, and displayed the strongest protective effects on ADR-induced HK-2 cells. SPR results showed that AAQFFNR could interact with complement C3 directly with Kd value of 16.8 μM. Furthermore, the reno-protective effect of AAQFFNR was verified in ADR-induced mice. This study provided preliminary evidence that the complement C3-inhibiting peptides from insect had the potential in preventing nephropathy in mice using in silico and in vivo validation approaches.