Objective: Examine the presence of functional inducible nitric oxide synthase (iNOS) in lupus nephritis lesions.
Methods: Seventeen kidney biopsies from patients with lupus nephritis and an equal number of normal control kidney biopsies were examined for the presence of iNOS and endothelial nitric oxide synthase (eNOS) and citrulline by using immunohistochemical methods. Additionally, iNOS and eNOS mRNAs were examined by reverse transcription -PCR amplification of total renal RNA.
Results: All biopsies expressed constitutive eNOS, but in contrast to normal kidney biopsies, 70% of the lupus biopsies also expressed iNOS mRNA and the cognate protein. Eight positive biopsies corresponded to class IV lupus nephritis, which also had a high degree of citrullination.
Conclusions: The data indicate that functional iNOS activity is present in glomeruli as part of the inflammatory process in the kidney; therefore the products of iNOS could play a role in the pathogenesis of lupus nephritis.