Nitric oxide plays a key role in the platelet-activating factor-induced enhancement of resistance against systemic candidiasis.

Platelet-activating factor (PAF) has been demonstrated to augment resistance against Candida albicans infection. In this study, the role of nitric oxide (NO) in PAF-induced resistance in the kidneys was investigated. Pretreatment of the C. albicans-infected mice with PAF resulted in strong expression of messenger RNA (mRNA) and the protein synthesis of inducible nitric oxide synthase (iNOS). These PAF effects were inhibited to a significant degree by pretreatment with the nuclear factor-kappaB inhibitor, pyrrolidinedithiocarbamate. Pretreatment with PAF protected the mice from death caused by C. albicans infection and reduced the growth of fungus in the kidneys. The protective activity of PAF was abrogated by pretreatment with the iNOS inhibitor, aminoguanidine, and in the iNOS(-/-) mice. The PAF markedly increased the infiltration of neutrophils, but not macrophages, and also enhanced the mRNA expression levels of the CXC chemokine, keratinocyte-derived chemokine, in C. albicans-infected kidneys. These effects of PAF were attenuated in the aminoguanidine-treated mice and the iNOS(-/-) mice. These data show that NO plays an important role in PAF-induced protection against C. albicans.