The antioxidant, pyrrolidine dithiocarbamate, induces stromelysin expression in mesangial cells via a tyrosine kinase - ap-1 pathway. Yokoo, Takashi, and Masanori Kitamura. Department of Medicine, University College London Medical School, The Rayne Institute, 5 University Street, London WC1E 6JJ, U.K.
APStracts 2:0210F, 1995.
Takashi Yokoo and Masanori Kitamura. The antioxidant, pyrrolidine dithiocarbamate, induces stromelysin expression in mesangial cells via a tyrosine kinase - AP-1 pathway. We found that an antioxidant, pyrrolidine dithiocarbamate (PDTC), induces the matrix metalloproteinase stromelysin in cultured glomerular mesangial cells. Although PDTC is a well-known inhibitor of nuclear factor-kappa B (NF-kB), this effect was independent of the NF-kB activity since overexpression of a dominant negative mutant of p50 NF-kB subunit repressed activity of the kB site whereas failed to induce stromelysin. To elucidate the intracellular mechanisms involved, we focused on the role of activator protein-1 (AP-1) since its binding site, the 12-o-tetradecanoylphorbol-13-acetate (TPA) response element (TRE), is located in the 5'-flanking region of the stromelysin gene. Northern blot analysis revealed that PDTC up-regulated expression of c-jun and c-fos prior to the expression of stromelysin. Transient transfection studies using a TRE-LacZ reporter plasmid elucidated that activity of AP-1 was significantly increased by PDTC. Stable transfection with a c-jun antisense cDNA or pretreatment with curcumin, a pharmacological inhibitor of c-Jun/AP-1, revealed that inactivation of AP-1 diminished the induction of stromelysin by PDTC. To identify the machinery involved upstream of AP-1 activation, the role of tyrosine kinases was investigated. Western blot analysis of phosphotyrosine showed that PDTC induced phosphorylation of tyrosine kinases. Treatment of mesangial cells with tyrosine kinase inhibitors suppressed activation of AP-1 as well as induction of stromelysin by PDTC. These findings demonstrate that the antioxidant PDTC induces stromelysin expression via stimulation of the tyrosine kinase - AP-1 pathway independent of its suppressive action on NF-kB. 

Received 1 August 1995; accepted in final form 27 November 1995.
APS Manuscript Number F252-5.
Article publication pending Am. J. Physiol. (Renal Fluid Electrolyte
Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95