Peroxisome Proliferator–Activated Receptor α Protects against Glomerulonephritis Induced by Long-Term Exposure to the Plasticizer Di-(2-Ethylhexyl)Phthalate

Abstract

Safety concerns about di-(2-ethylhexyl)phthalate (DEHP), a plasticizer and a probable endocrine disruptor, have attracted considerable public attention, but there are few studies about long-term exposure to DEHP. DEHP toxicity is thought to involve peroxisome proliferator-activated receptor ␣ (PPAR␣), but this contention remains controversial. For investigation of the long-term toxicity of DEHP and determination of whether PPAR␣ mediates toxicity, wild-type and PPAR␣-null mice were fed a diet that contained 0.05 or 0.01% DEHP for 22 mo. PPAR␣-null mice that were exposed to DEHP exhibited prominent immune complex glomerulonephritis, most likely related to elevated glomerular oxidative stress. Elevated NADPH oxidase, low antioxidant enzymes, and absence of the PPAR␣-dependent anti-inflammatory effects that normally antagonize the NFB signaling pathway accompanied the glomerulonephritis in PPAR␣-null mice. The results reported here indicate that PPAR␣ protects against the nephrotoxic effects of long-term exposure to DEHP. , a probable endocrine disruptor, is used widely as a plasticizer for production of many types of polyvinyl chloride (PVC) consumer products. DEHP provides PVC items with the desired mechanical properties, including flexibility and strength. The presence of DEHP in the environment has been confirmed, as has product-related human exposure to DEHP; recent safety assessments of DEHP thereby have attracted much public interest (1). DEHP continually enters the human body via food, water, and the atmosphere. Moreover, substantial human exposure to DEHP occurs via PVC-containing medical devices that are used in intravenous therapy, enteral and parenteral nutrition support, blood transfusion, hemodialysis, cardiopulmonary bypass, and extracorporeal membrane oxygenation (2). Maximal medical exposure has been estimated to be near the US no-observed-adverse-effect level (3.7 to 14 mg/kg body wt per d). Many previous experimental animal studies yielded no obvious evidence of DEHP toxicities at these low exposure levels, but periods of exposure in the studies generally were brief. Long-term exposure to DEHP is important for safety assessment of real-world toxicity.Past experimental animal studies using short-term exposure to high-dosage DEHP have demonstrated hepatotoxicity, testicular toxicity, renal toxicity, developmental disturbance, reproductive toxicity, and teratogenicity (3-5). The peroxisome proliferator-activated receptor ␣ (PPAR␣), a member of the steroid/nuclear receptor superfamily of ligand-dependent transcription factors, has been implicated as a causative factor in these toxicities (6). PPAR␣ is expressed abundantly in the rodent liver, testis, kidney, heart, digestive tract, and retina (7) and participates in diverse physiologic functions, including maintenance of lipid and glucose homeostasis (8 -11), regulation of cell proliferation (12), and modulation of inflammatory responses (13). In humans, some ligands for this receptor, termed peroxisome proliferators, are used clinically as hypolipid...

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