Experimental Analysis of Bacterial and Host Factors Involved in Renal Scarring

The effects on renal scarring of bacterial pili and superoxide released by polymorphonuclear leukocytes (PMN) were examined using a rat experimental pyelonephritis model. Bacteria which possessed mannose-sensitive (MS) pili were found to promote renal scarring following their direct inoculation into the renal parenchyma. Treatment with cyclophosphamide to induce leukopenia, colchicine to modulate PMN migration, and superoxide dismutase or an experimental antioxidant to reduce PMN superoxide release suppressed renal scarring following infection with MS-piliated bacteria. In contrast, treatment with phorbol myristate acetate significantly enhanced renal scarring. In addition, the production of superoxide by PMN was significantly greater following stimulation by MS-piliated bacteria than after stimulation with either non-piliated or MR-piliated strains. These findings suggest that MS-piliated bacteria stimulate renal scarring more markedly than do non-piliated or MR-piliated bacteria, and that superoxide released from PMNs plays an important role in the development of renal scarring following infection by MS-piliated strains