Ischemic proximal tubular injury primes mice to endotoxin-induced TNF-alpha generation and systemic release.
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.
Zager
R A
RA
Department of Medicine, University of Washington, Seattle, 98109, USA. dzager@fhcrc.org
Johnson
Ali C M
AC
Hanson
Sherry Y
SY
Lund
Steve
S
D000818:Animals; D002478:Cells, Cultured; D016207:Cytokines / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology*; D066298:In Vitro Techniques; D007501:Iron / Q000494:pharmacology; D007511:Ischemia / Q000378:metabolism* / Q000473:pathology; D007668:Kidney / Q000473:pathology; D007672:Kidney Cortex / Q000187:drug effects / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000098:blood supply / Q000378:metabolism* / Q000473:pathology; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008070:Lipopolysaccharides / Q000494:pharmacology; D008297:Male; D051379:Mice; D009392:Nephrectomy; D018384:Oxidative Stress / Q000187:drug effects; D012333:RNA, Messenger / Q000096:biosynthesis; D012079:Renal Circulation / Q000187:drug effects / Q000502:physiology; D015427:Reperfusion Injury / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000096:biosynthesis* / Q000378:metabolism* / Q000494:pharmacology
D016207:Cytokines; D004731:Endotoxins; D008070:Lipopolysaccharides; D012333:RNA, Messenger; D014409:Tumor Necrosis Factor-alpha; D007501:Iron; D007770:L-Lactate Dehydrogenase