Abstract P262: Repression of Genes Involved in Fatty Acid Metabolism during Acute Renal Failure

Abstract

Peroxisome proliferator-activated receptors (PPARs) are highly expressed in the kidney, but their role in acute renal failure (ARF) remains elusive. Previously, we have shown PPARγ-ligand attenuated renal injury and improved renal function in ARF. In this study, we explored specific downstream targets of PPARγ that may be involved in reno-protection. Male Sprague-Dawley rats (250-300 gm) were randomly divided into two groups, control, and ARF: where they received GW1929 (PPARγ ligand), apocynin (NADPH oxidase inhibitor), or vehicle. After 7 days of pretreatment, ARF was induced by injecting glycerol (50% v/v, 8 ml/kg; i.m.). After 24 hours, blood and kidneys were collected and processed for mRNA extraction. The expression of PPARγ-responsive genes was determined by a PCR array using qRT-PCR. Markers for renal injury and oxidative stress and NADPH oxidase activity were determined by ELISA. The data revealed that fatty acid (FA) transporter genes ( Slc27a2, ApoE , FABP2, FABP3, and CD36 ) , were strikingly suppressed (>100-folds, p<0.001) in ARF compared to control. Genes involved in FA metabolism such as FABP , PGC1α, Cpt1b, Creb1 were also markedly inhibited (>20-folds, p<0.001). In addition, expressions of key survival genes PCK2, Pten , Crebbp , and SRC , were concurrently diminished (>25-folds, p<0.001). However, this attenuation was restored to normal levels with GW1929 treatment. Pretreatment with GW1929 reduced the activity of KIM1 (14.8±1.5 vs. 18.7±0.3 ng/μg; p<0.05) and NGAL (129±6 vs. 233±5 ng/μg; p<0.01), isoprostane levels (73.3±3.7 vs. 110±8 pmol/mg), and NADPH oxidase activity (0.96±0.04 vs. 1.7±0.04 nmol/mg protein), indicating reversal of renal injury and oxidative stress. Interestingly, apocynin treatment also inhibited ARF-induced downregulation of genes involved in FA metabolism and growth signals, demonstrating the ROS-dependency of ARF-induced repression of PPARγ-responsive genes. As expected, apocynin reduced isoprostane levels but did not impact KIM1 expression in ARF, suggesting no improvement in glomerular injury with this treatment. Collectively, the data suggest that renal damage in ARF is preceded by impairment in FA metabolism and growth signals via a ROS-dependent manner.