Dysregulation of cytokine expression in tubulointerstitial nephritis associated with murine malaria

Abstract

We examined the circulating levels of the proinflammatory cytokines tumor necrosis factor-alpha (TNF-α), interleukin (IL)-1α, IL-6, granulocyte macrophage-colony stimulating factor (GM-CSF), and the anti-inflammatory cytokine IL-10, and their expression in kidneys acutely infected with murine malaria parasite P. berghei ANKA in C57BL/6J mice. Groups of six mice sacrified on days 5, 10, 15, and 20, and normal controls were used for cytokine analysis. High concentrations of TNF-α and IL-10 were detected in plasma as shown by ELISA, and elevated levels of mRNA specific for TNF-α and IL-10 in infected kidneys were demonstrated by reverse transcription- polymerase chain reaction (RT-PCR) analysis. Kidney sections stained with antibodies against TNF-α, IL-1α, IL-6, GM-CSF and IL-10 for immunohistochemistry showed markedly enhanced staining for TNF-α, and progressively increased staining for IL-1α and IL-6 both in the tubules and the walls of arteries during the course of infection. The endothelia of blood vessels and inflammatory cells located around small arteries showed positive staining for GM-CSF from day 10 onwards. Unlike the staining for proinflammatory cytokines, the anti-inflammatory cytokine IL-10 showed strongly positive staining in normal tubules and walls of arteries, especially in the brush border of proximal tubules, but the staining intensity decreased dramatically after day 15 post-infection. A strongly positive correlation was found between the antibody staining for TNF-α/IL- 1α in tubules, and the severity of proteinuria. In contrast, there was an inverse correlation between the staining for IL-10 with TNF-α/IL-1α, and the degree of proteinuria. Plenty of pigmented macrophages showed positive staining both for proinflammatory and anti-inflammatory cytokines in the tubulointerstitium. Our findings imply that the up-regulation of proinflammatory cytokines and the dysregulation of anti-inflammatory cytokines are involved in the pathogenesis of tubulointerstitial nephritis associated with malaria.