Complement is activated in kidney by endotoxin but does not cause the ensuing acute renal failure

Kidney Int. 2000 Oct;58(4):1580-7. doi: 10.1046/j.1523-1755.2000.00319.x.

Abstract

Background: Acute renal failure (ARF) in sepsis occurs when the release of multiple inflammatory mediators is induced by bacterial endotoxins. C3 mRNA is markedly up-regulated in mouse kidney after exposure to lipopolysaccharide (LPS). We hypothesized that LPS could induce tubular synthesis and secretion of C3, leading to activation of the complement cascade and direct renal tubular injury.

Methods: ARF was induced in mice by intravenous injection of LPS and was confirmed by an acute rise in blood urea nitrogen (BUN) and histologically by acute tubular necrosis. Three separate strategies were used to investigate the role of the complement system in this model of ARF: (1) Crry-Ig, a recombinant protein containing the potent murine complement C3 activation inhibitor Crry was injected at the same time as LPS (N = 8). (2) LPS was injected into transgenic mice overexpressing Crry in glomeruli and tubules (N = 8), and (3) LPS was injected into C3-deficient mice (N = 5).

Results: Compared with unmanipulated mice, C3 staining by immunofluorescence (IF) microscopy in mice injected with LPS was greater in renal cortical tubular cells (IF score of 2. 1 +/- 0.1 vs. 1.4 +/- 0.2 in controls, P = 0.013), most prominently at the basolateral surface. LPS injection led to a 16- to 42-fold increase in urinary C3 excretion. Despite reduction or complete elimination of renal C3 with maneuvers suppressing complement activation, BUN values were not statistically different across all groups. In no experiment did BUN values correlate with the extent of C3 staining.

Conclusion: Although LPS up-regulates renal C3 synthesis, resulting in basolateral tubular C3 deposition, this is not responsible for LPS-induced ARF in mice.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Acute Kidney Injury / chemically induced*
  • Acute Kidney Injury / etiology
  • Acute Kidney Injury / immunology*
  • Albuminuria
  • Animals
  • Complement Activation / drug effects
  • Complement Activation / immunology*
  • Complement C3 / genetics
  • Complement C3 / urine*
  • Gene Expression / drug effects
  • Gene Expression / immunology
  • Kidney Glomerulus / immunology
  • Kidney Glomerulus / metabolism
  • Lipopolysaccharide Receptors / pharmacology*
  • Mice
  • Mice, Knockout
  • Receptors, Complement / genetics
  • Recombinant Fusion Proteins / genetics
  • Sepsis / complications

Substances

  • Complement C3
  • Cr1l protein, mouse
  • Lipopolysaccharide Receptors
  • Receptors, Complement
  • Recombinant Fusion Proteins