Diabetes, Vol 44, Issue 7 753-758, Copyright © 1995 by American Diabetes Association
Cloning and expression of cytokine-inducible nitric oxide synthase cDNA from rat islets of Langerhans
AE Karlsen, HU Andersen, H Vissing, PM Larsen, SJ Fey, BG Cuartero, OD Madsen, JS Petersen, SB Mortensen, T Mandrup-Poulsen and al. et
Steno Diabetes Center, Gentofte, Denmark.
An inducible nitric oxide (NO) synthase isoform (iNOS) is specifically
induced in the beta-cells of interleukin (IL)-1 beta-exposed rat islets,
suggesting a role for NO in the pathogenesis of type I diabetes. The aim of
this study was to clone and characterize iNOS cDNA from cytokine-exposed
islets. Neither NO production nor iNOS transcription could be detected in
rat islets or in rat insulinoma RIN-5AH beta-cells cultured in the absence
of cytokines. Addition of IL-1 beta alone or in combination with tumor
necrosis factor-alpha induced a concentration- and time-dependent
expression of the iNOS gene and associated NO production (measured as
nitrite) from both islets and RIN cells. iNOS transcripts were cloned by
reverse transcriptase-polymerase chain reaction from the cytokine-exposed
rat islets and RIN cells, and DNA sequence analysis revealed a near 100%
identity to the recently published iNOS cDNA cloned from cytokine-exposed
rat hepatocytes and smooth muscle cells. Recombinant rat islet iNOS was
transiently and stably expressed in human kidney 293 fibroblasts, and the
high enzymatic activity was inhibited by addition of the L-arginine
analogs, N omega-nitro-L-arginine methyl ester and aminoguanidine.
Two-dimensional gel electrophoresis revealed the recombinant iNOS as a
series of spots with the expected molecular mass of 131 kDa and pI values
in the range of 6.8 to 7.0. In conclusion, the IL-1 beta-induced iNOS
cloned and expressed from rat islets and RIN cells is encoded by the same
transcript as the iNOS induced in other cell types.