Hypoxia promotes fibrogenesis in human renal fibroblasts

Kidney Int. 2000 Dec;58(6):2351-66. doi: 10.1046/j.1523-1755.2000.00419.x.

Abstract

Background: The mechanisms underlying progressive renal fibrosis are unknown, but the common association of fibrosis and microvascular loss suggests that hypoxia per se may be a fibrogenic stimulus.

Methods: To determine whether human renal fibroblasts (HRFs), the primary matrix-producing cells in the tubulointerstitium, possess oxygen-sensitive responses relevant to fibrogenesis, cells were exposed to 1% O2 in vitro.

Results: Hypoxia simultaneously stimulated extracellular matrix synthesis and suppressed turnover with increased production of collagen alpha1(I) (Coll-I), decreased expression of collagenase, and increased tissue inhibitor of metalloproteinase (TIMP)-1. These effects are time dependent, require new RNA and protein synthesis, and are specific to hypoxia. The changes in Coll-I and TIMP-1 gene expression involve a heme-protein O2 sensor and protein kinase- and tyrosine kinase-mediated signaling. Although hypoxia induced transforming growth factor-beta1 (TGF-beta1), neutralizing anti-TGF-beta1-antibody did not block hypoxia-induced Coll-I and TIMP-1 mRNA expression. Furthermore, hypoxic-cell conditioned-medium had no effect on the expression of these mRNAs in naive fibroblasts, suggesting direct effects on gene transcription. Transient transfections identified a hypoxia response element (HRE) in the TIMP-1 promoter and demonstrated HIF-1-dependent promoter activation by decreased ambient pO2.

Conclusions: These data suggest that hypoxia co-ordinately up-regulates matrix production and decreases turnover in renal fibroblasts. The results support a role for hypoxia in the pathogenesis of fibrosis and provide evidence for novel, direct hypoxic effects on the expression of genes involved in fibrogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actins / genetics
  • Antimutagenic Agents / pharmacology
  • Cell Division / drug effects
  • Cell Division / physiology
  • Cell Hypoxia / physiology
  • Cell Size / drug effects
  • Cell Size / physiology
  • Cell Survival / drug effects
  • Cell Survival / physiology
  • Cells, Cultured
  • Chelating Agents / pharmacology
  • Cobalt / pharmacology
  • Collagen / genetics
  • Collagen / metabolism
  • Collagenases / genetics
  • Collagenases / metabolism
  • Culture Media, Conditioned / pharmacology
  • Deferoxamine / pharmacology
  • Extracellular Matrix / metabolism
  • Fibroblasts / cytology
  • Fibroblasts / drug effects
  • Fibroblasts / enzymology
  • Gene Expression Regulation, Enzymologic / drug effects
  • Humans
  • Hypoxia / metabolism*
  • Hypoxia / pathology*
  • Kidney Cortex / pathology*
  • Kidney Failure, Chronic / metabolism
  • Kidney Failure, Chronic / pathology
  • Oxygen / pharmacology
  • Promoter Regions, Genetic / physiology
  • Protein Kinase C / antagonists & inhibitors
  • Protein-Tyrosine Kinases / antagonists & inhibitors
  • RNA, Messenger / analysis
  • Tissue Inhibitor of Metalloproteinase-1 / genetics
  • Tissue Inhibitor of Metalloproteinase-1 / metabolism
  • Transcription, Genetic / physiology
  • Transfection
  • Transforming Growth Factor beta / genetics
  • Transforming Growth Factor beta / metabolism
  • Transforming Growth Factor beta1

Substances

  • Actins
  • Antimutagenic Agents
  • Chelating Agents
  • Culture Media, Conditioned
  • RNA, Messenger
  • TGFB1 protein, human
  • Tissue Inhibitor of Metalloproteinase-1
  • Transforming Growth Factor beta
  • Transforming Growth Factor beta1
  • Cobalt
  • Collagen
  • Protein-Tyrosine Kinases
  • Protein Kinase C
  • Collagenases
  • cobaltous chloride
  • Deferoxamine
  • Oxygen