Lectin-induced renal local complement activation is involved in tubular interstitial injury in diabetic nephropathy

Background: Complement has been suggested to be involved in diabetic nephropathy (DN), but the exact significance and underlying mechanisms remain unclear. Data about renal local complement activation in DN patients is scarce. The purpose of the study was to clarify the significance and mechanism of renal local complement activation in DN. Methods: Sixty-two biopsy-proven DN patients were recruited. Renal expression of Cl Q, factor B, C5b-9, MBL and MBL-associated serine protease 1 (MASP1) were detected and associated with the kidney damage. Results: C5b-9, MBL and MASP1 was found to increase with the progression of DN. Especially, the level of C5b-9, MBL and MASP1 in tubular interstitium was closely associated with the damage degree of tubular interstitium. In addition, MBL and MASH co-localized and their levels in tubular interstitium correlated with the levels of C5b-9 in tubules and tubular interstitium. Conclusion; Increased renal local complement activation was present in DN patients and might contribute to the kidney damage, especially tubular interstitial damage. MBL pathway might play an important role in renal tubular interstitial complement activation. Methods against complement activation or MBL pathway might be effective in reducing renal tubular interstitial damage in DN patients.