Simvastatin attenuates oleic acid-induced oxidative stress through CREB-dependent induction of heme oxygenase-1 in renal proximal tubule cells.
BACKGROUND
Statins elicit antioxidant effects independently of their lipid-lowering properties. Heme oxygenase-1 (HO-1) induction may be a part of these pleiotropic effects, which are insufficiently described in the kidney. We hypothesize that simvastatin (SIM) transcriptionally activates HO-1 that protects renal proximal tubule cells from lipotoxic injury.


METHODS
Impact of SIM on 100 μmol/l oleic acid (OA)-mediated reactive oxygen species (ROS) production and consequent oxidative stress (4-hydroxynonenal (HNE) content) as well as cell injury/apoptosis (lactate dehydrogenase (LDH) release, caspase-3 activation) were determined in cultured renal proximal tubule (NRK52E) cells. Effect of SIM on the HO-1 promoter and its enhancer elements (antioxidant response element (ARE), CCAAT, AP1, and cAMP response element (CRE)) was also determined in reporter luciferase assays. Dominant-negative (dnMEK, M1CREB) and pharmacologic (H89) approaches were used to inhibit activation of extracellular signal regulated kinase (ERK), CREB, and protein kinase A (PKA), respectively.


RESULTS
SIM dose-dependently activated the HO-1 promoter that was essential for protection against OA-dependent ROS production/oxidative stress and LDH release/caspase-3 activation. We found that the HO-1 promoter was induced through ERK and PKA-dependent activation of the CRE by SIM.


CONCLUSIONS
SIM may protect the kidney from adverse effects of circulating fatty acids by upregulating the antioxidant HO-1, aside from its well-described lipid-lowering effects.
Department of Pediatrics, Division of Critical Care, University of Mississippi Medical Center, Jackson, Mississippi.
Meaghan
M
Barnett
Department of Pediatrics, Division of Pediatric Nephrology, University of Mississippi Medical Center, Jackson, Mississippi.
Samuel
S
Hall
Department of Pediatrics, Division of Pediatric Nephrology, University of Mississippi Medical Center, Jackson, Mississippi.
Mehul
M
Dixit
Department of Pediatrics, Division of Pediatric Nephrology, University of Mississippi Medical Center, Jackson, Mississippi.
Istvan
http://orcid.org/0000-0001-5744-8373
I
Arany
D000818:Animals; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D002460:Cell Line; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D019610:Cytoprotection; D004305:Dose-Response Relationship, Drug; D004790:Enzyme Induction; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000096:biosynthesis* / Q000235:genetics; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000201:enzymology / Q000473:pathology; D019301:Oleic Acid / Q000633:toxicity*; D018384:Oxidative Stress / Q000187:drug effects*; D011401:Promoter Regions, Genetic; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D019821:Simvastatin / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D014162:Transfection
D000975:Antioxidants; C508137:Creb1 protein, rat; D017362:Cyclic AMP Response Element-Binding Protein; D017382:Reactive Oxygen Species; D019301:Oleic Acid; D019821:Simvastatin; D006419:Heme Oxygenase (Decyclizing); C491523:Hmox1 protein, rat; D017868:Cyclic AMP-Dependent Protein Kinases; D048049:Extracellular Signal-Regulated MAP Kinases