Regarding the mechanisms of renal
scarring in
pyelonephritis, several hypotheses have been put forward, among which oxidative stress is prominent. The present study investigated the possible protective effect of
melatonin treatment against Escherichia coli-induced oxidative injury and
scarring in renal tissue. For this purpose, 0.1 mL E. coli (ATCC 25922; 10(10) colony-forming units/mL) or saline was injected directly into the renal parenchyma of Wistar rats. Pyelonephritic rats were treated with either saline or
melatonin (10 mg/kg) intraperitoneally. Twenty-four hours or 1 wk after E. Coli injection, rats were decapitated and trunk blood samples were collected for BUN,
creatinine,
tumor necrosis factor-alpha (
TNF-alpha) and
lactate dehydrogenase (LDH) determination. In kidney samples, histological analysis was performed, and
malondialdehyde (MDA),
glutathione (GSH) levels,
myeloperoxidase (MPO) activity and
collagen contents were measured. Formation of
reactive oxygen species was monitored using a chemiluminescence (CL) technique. Escherichia Coli inoculation caused a significant reduction in renal GSH levels, which was accompanied by significant increases in MDA levels, MPO activity, CL levels and
collagen content of the renal tissues (P < 0.05-0.001). Similarly, serum
TNF-alpha and, LDH, BUN and
creatinine levels were elevated in the pyelonephritic rats when compared with control animals.
Melatonin treatment reversed all these biochemical indices, as well as histopathological alterations induced by acute
pyelonephritis. The protective effects of
melatonin can be ascribed to its ability to inhibit neutrophil infiltration, to balance the
oxidant-
antioxidant status, and to regulate the generation of inflammatory mediators, suggesting a future role for
melatonin in the treatment of acute
pyelonephritis.