title: Proximal tubular cholesterol loading after mitochondrial, but not glycolytic, blockade.
abstract: Diverse forms of injury cause proximal tubular cholesterol accumulation. However, underlying mechanisms in general, and those involved with ATP depletion injury in particular, remain poorly defined. To help elucidate this issue, cholesterol homeostasis and its determinants were assessed after partial ATP depletion states. Serum-exposed HK-2 cells were subjected to mild ATP depletion, induced by mitochondrial inhibition (antimycin A; AA) or glycolytic blockade (2-deoxyglucose; DG). Four or 18 h later, cell cholesterol levels, hydroxymethylglutaryl (HMG)-CoA reductase (HMGCR), the LDL receptor (LDL-R), and ABCA1/SR-B1 cholesterol transporters were assessed. AA and DG each induced mild, largely sublethal ATP depletion injury. Each also caused significant HMGCR increments and SR-B1 decrements and left ABCA1 intact. In contrast, only AA increased the LDL-R, and only AA evoked a cholesterol-loading state (approximately 25% up). One-half of this increase was statin inhibitable, and one-half could be blocked by serum deletion, implying that both synthetic and nonsynthetic (e.g., LDL-R transport) pathways were involved. The AA-induced HMGCR and LDL-R protein changes were paralleled by their mRNAs, suggesting the presence of altered transcriptional events. We conclude that 1) sublethal ATP depletion, whether induced by mitochondrial or glycolytic blockade, can upregulate HMGCR and decrease SR-B1, and these changes represent a previously unrecognized ATP depletion "phenotype"; 2) mitochondrial blockade can also upregulate the LDL-R and evoke a cholesterol-loading state; 3) the latter likely occurs via synthetic and transport pathways; and 4) the mitochondrion may be a critical, and previously unrecognized, determinant of postinjury cell cholesterol homeostasis, potentially by impacting the LDL-R.
authors.affiliation: Fred Hutchinson Cancer Research Center, University of Washington, Rm. D2-190, 1100 Fairview Avenue N, Seattle, WA 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
authors.forename: Sherry Y
authors.initials: SY
authors.lastname: Hanson
mesh_terms: D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D000924:Anticholesteremic Agents / Q000494:pharmacology; D000963:Antimetabolites / Q000494:pharmacology; D000968:Antimycin A / Q000494:pharmacology; D018955:CD36 Antigens / Q000378:metabolism; D002461:Cell Line, Transformed; D002784:Cholesterol / Q000378:metabolism*; D003847:Deoxyglucose / Q000494:pharmacology; D006019:Glycolysis / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D006903:Hydroxymethylglutaryl CoA Reductases / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000166:cytology / Q000378:metabolism*; D008148:Lovastatin / Q000031:analogs & derivatives* / Q000494:pharmacology; D008565:Membrane Proteins; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D017368:Protein Prenylation; D011971:Receptors, Immunologic; D011973:Receptors, LDL / Q000378:metabolism; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D012402:Rotenone / Q000494:pharmacology; D051122:Scavenger Receptors, Class B; D014475:Uncoupling Agents / Q000494:pharmacology; D018631:ras Proteins / Q000378:metabolism; D020741:rho GTP-Binding Proteins / Q000378:metabolism
chemical_list: C577836:ABCA1 protein, human; D064286:ATP Binding Cassette Transporter 1; D018528:ATP-Binding Cassette Transporters; D000900:Anti-Bacterial Agents; D000924:Anticholesteremic Agents; D000963:Antimetabolites; D018955:CD36 Antigens; D008565:Membrane Proteins; D011971:Receptors, Immunologic; D011973:Receptors, LDL; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C495124:SCARB1 protein, human; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D014475:Uncoupling Agents; D012402:Rotenone; C012258:mevastatin; D000968:Antimycin A; D000255:Adenosine Triphosphate; D002784:Cholesterol; D003847:Deoxyglucose; D008148:Lovastatin; D006903:Hydroxymethylglutaryl CoA Reductases; D018631:ras Proteins; D020741:rho GTP-Binding Proteins