title: Progressive histone alterations and proinflammatory gene activation: consequences of heme protein/iron-mediated proximal tubule injury.
abstract: Rhabdomyolysis (Fe)-induced acute renal failure (ARF) causes renal inflammation, and, with repetitive insults, progressive renal failure can result. To gain insights into these phenomena, we assessed the impact of a single episode of glycerol-induced rhabdomyolysis on proinflammatory/profibrotic [TNF-alpha, monocyte chemoattractant protein-1 (MCP-1), and transforming growth factor-beta1 (TGF-beta1)] gene expression and the time course of these changes. CD-1 mice were studied 1-7 days after glycerol injection. Normal mice served as controls. RNA polymerase II (Pol II) binding to the TNF-alpha, MCP-1, and TGF-beta1 genes, "gene-activating" histone modifications [histone 3 lysine 4 (H3K4) trimethylation (H3K4m3) and histone 2 variant H2A.Z], and cognate mRNA levels were assessed. Results were contrasted to changes in anti-inflammatory heme oxygenase-1 (HO-1). Glycerol produced severe ARF (blood urea nitrogen approximately 150-180 mg/dl) followed by marked improvement by day 7 (blood urea nitrogen approximately 40 mg/dl). Early increases in TNF-alpha, MCP-1, and TGF-beta1 mRNAs, Pol II gene binding, and H3K4m3/H2A.Z levels were observed. These progressed with time, despite resolution of azotemia. Comparable early HO-1 changes were observed. However, HO-1 mRNA normalized by day 7, and progressive Pol II binding/histone alterations did not occur. Fe-mediated injury to cultured proximal tubule (HK-2) cells recapitulated these in vivo results. Hence, this in vitro model was used for mechanistic assessments. On the basis of these studies, it was determined that 1) the H3K4m3/H2A.Z increases are early events (i.e., they precede mRNA increases), 2) subsequent mRNA elevations reflect transcription, not mRNA stabilization (actinomycin D assessments), and 3) increased transcription, per se, helps sustain elevated H2A.Z levels. We conclude that 1) Fe/glycerol-induced tubular injury causes sustained proinflammatory gene activation, 2) decreasing HO-1 expression, as reflected by mRNA levels, may facilitate this proinflammatory state, and 3) gene-activating histone modifications are early injury events and progressively increase at selected proinflammatory genes. Thus they may help sustain a proinflammatory state, despite resolving ARF.
authors.affiliation: Fred Hutchinson Cancer Research Center and Department of Medicine, University of Washington, Seattle, Washington 98109, USA. dzager@fhcrc.org
authors.forename: Richard A
authors.initials: RA
authors.lastname: Zager
authors.forename: Ali C M
authors.initials: AC
authors.lastname: Johnson
mesh_terms: D058186:Acute Kidney Injury / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D001806:Blood Urea Nitrogen; D002470:Cell Survival; D002478:Cells, Cultured; D018932:Chemokine CCL2 / Q000235:genetics; D004195:Disease Models, Animal; D018450:Disease Progression; D005355:Fibrosis; D005786:Gene Expression Regulation; D005990:Glycerol; D051547:Heme Oxygenase-1 / Q000378:metabolism; D006420:Hemeproteins / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D018836:Inflammation Mediators / Q000378:metabolism*; D007501:Iron / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D012319:RNA Polymerase II / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis; D012206:Rhabdomyolysis / Q000139:chemically induced / Q000150:complications / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D013997:Time Factors; D015533:Transcriptional Activation; D053773:Transforming Growth Factor beta1 / Q000235:genetics; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics
chemical_list: C491768:Ccl2 protein, mouse; D018932:Chemokine CCL2; D006420:Hemeproteins; D006657:Histones; D018836:Inflammation Mediators; D008565:Membrane Proteins; D012333:RNA, Messenger; D053773:Transforming Growth Factor beta1; D014409:Tumor Necrosis Factor-alpha; D007501:Iron; C496541:HMOX1 protein, human; D051547:Heme Oxygenase-1; C496542:Hmox1 protein, mouse; D012319:RNA Polymerase II; D005990:Glycerol