Disruption of cyclooxygenase type 2 exacerbates apoptosis and renal damage during obstructive nephropathy

Area of Science:

• Nephrology
• Molecular Biology
• Pathology

Background:

• Ureteral obstruction elevates renal oxidative stress.
• Cyclooxygenase-2 (COX-2) activity shows in vitro protective effects against oxidants.

Purpose of the Study:

• To investigate the in vivo role of COX-2 in counteracting oxidative stress and apoptosis in obstructive nephropathy.
• To determine if COX-2 activity is necessary for protection against tubular injury and oxidative damage following ureteral obstruction.

Main Methods:

• Utilized COX-2 knockout (COX-2(-/-)) and wild-type (WT) mice subjected to unilateral ureteral obstruction (UUO) for 3 or 7 days.
• Assessed renal oxidative stress markers (4-hydroxynonenal, nitrotyrosine), antioxidant enzymes (heme oxygenase-1, SOD2), and markers of tubular injury and apoptosis (kidney injury molecule-1, caspase-3).
• Administered a selective COX-2 inhibitor, parecoxib, to WT mice undergoing sham operation or UUO.

Main Results:

• COX-2 expression increased following UUO.
• Oxidative stress markers were elevated in UUO kidneys without genotype differences.
• COX-2 deletion aggravated tubular injury, evidenced by increased tubular dilatation, kidney injury molecule-1, caspase-3, and apoptosis.
• Antioxidant enzymes heme oxygenase-1 and SOD2 showed higher levels in COX-2(-/-) mice, suggesting COX-2 does not directly regulate these enzymes.

Conclusions:

• COX-2 is crucial for protecting renal tubules against injury and apoptosis in the context of ureteral obstruction.
• COX-2 activity is not essential for mitigating the overall oxidative stress induced by ureteral obstruction.
• The protective mechanism of COX-2 in obstructive nephropathy appears independent of direct regulation of heme oxygenase-1 and SOD.