Ischemic proximal tubular injury primes mice to endotoxin-induced TNF-alpha generation and systemic release

Am J Physiol Renal Physiol. 2005 Aug;289(2):F289-97. doi: 10.1152/ajprenal.00023.2005. Epub 2005 Mar 29.

Abstract

Endotoxemia (LPS) can exacerbate ischemic tubular injury and acute renal failure (ARF). The present study tested the following hypothesis: that acute ischemic damage sensitizes the kidney to LPS-mediated TNF-alpha generation, a process that can worsen inflammation and cytotoxicity. CD-1 mice underwent 15 min of unilateral renal ischemia. LPS (10 mg/kg iv), or its vehicle, was injected either 45 min before, or 18 h after, the ischemic event. TNF-alpha responses were gauged 2 h post-LPS injection by measuring plasma/renal cortical TNF-alpha and renal cortical TNF-alpha mRNA. Values were contrasted to those obtained in sham-operated mice or in contralateral, nonischemic kidneys. TNF-alpha generation by isolated mouse proximal tubules (PTs), and by cultured proximal tubule (HK-2) cells, in response to hypoxia-reoxygenation (H/R), oxidant stress, antimycin A (AA), or LPS was also assessed. Ischemia-reperfusion (I/R), by itself, did not raise plasma or renal cortical TNF-alpha or its mRNA. However, this same ischemic insult dramatically sensitized mice to LPS-mediated TNF-alpha increases in both plasma and kidney (approximately 2-fold). During late reperfusion, increased TNF-alpha mRNA levels also resulted. PTs generated TNF-alpha in response to injury. Neither AA nor LPS alone induced an HK-2 cell TNF-alpha response. However, when present together, AA+LPS induced approximately two- to fivefold increases in TNF-alpha/TNF-alpha mRNA. We conclude that modest I/R injury, and in vitro HK-2 cell mitochondrial inhibition (AA), can dramatically sensitize the kidney/PTs to LPS-mediated TNF-alpha generation and increases in TNF-alpha mRNA. That ischemia can "prime" tubules to LPS response(s) could have potentially important implications for sepsis syndrome, concomitant renal ischemia, and for the induction of ARF.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Cells, Cultured
  • Cytokines / metabolism
  • Endotoxins / pharmacology*
  • In Vitro Techniques
  • Iron / pharmacology
  • Ischemia / metabolism*
  • Ischemia / pathology
  • Kidney / pathology
  • Kidney Cortex / drug effects
  • Kidney Cortex / metabolism
  • Kidney Tubules, Proximal / blood supply
  • Kidney Tubules, Proximal / metabolism*
  • Kidney Tubules, Proximal / pathology
  • L-Lactate Dehydrogenase / metabolism
  • Lipopolysaccharides / pharmacology
  • Male
  • Mice
  • Nephrectomy
  • Oxidative Stress / drug effects
  • RNA, Messenger / biosynthesis
  • Renal Circulation / drug effects
  • Renal Circulation / physiology
  • Reperfusion Injury / pathology
  • Tumor Necrosis Factor-alpha / biosynthesis*
  • Tumor Necrosis Factor-alpha / metabolism*
  • Tumor Necrosis Factor-alpha / pharmacology

Substances

  • Cytokines
  • Endotoxins
  • Lipopolysaccharides
  • RNA, Messenger
  • Tumor Necrosis Factor-alpha
  • Iron
  • L-Lactate Dehydrogenase