OXIDATIVE STRESS MEDIATES MONOCROTALINE-INDUCED ALTERATIONS IN TENASCIN EXPRESSION IN PULMONARY-ARTERY ENDOTHELIAL-CELLS

Oxidative stress may be involved in monocrotaline (MCT)-induced endoth elial cell injury and upregulation of extracellular matrix proteins in the pulmonary vasculature. To test this hypothesis, cytotoxicity, exp ression and distribution of tenascin (TN) as well as cellular oxidatio n were determined in porcine pulmonary artery endothelial cells (PAECs ) exposed to MCT and/or to an oxygen radical scavenger, dimethylthiour ea (DMTU). Relative to controls, treatment with 2.5 mM MCT for 24 hr p roduced cytotoxicity as evidenced by changes in cellular morphology, c ell detachment, hypertrophy, reduction in cellular proliferation and s evere cytoplasmic vacuolization. Parallel studies showed that MCT mark edly altered the expression and distribution of TN in PAEC as determin ed by immunocytochemistry. Western analysis showed that MCT increased cellular TN content and promoted the appearance of an additional, smal ler TN isoform, Northern analysis demonstrated an increase in the stea dy-state level of TN-specific mRNA in response to MCT treatment, Expos ure to MCT also increased the synthesis of cell-associated and media-a ssociated TN as determined by immunoprecipitation. In addition, MCT in creased the intensity of cellular oxidative stress as measured by 2,7- dichlorofluorescein fluorescence. Go-treatment with DMTU prevented MCT -induced cytotoxicity, alterations in TN distribution and content, and reduced the increase in DCF fluorescence, These results suggest that MCT-induced cytotoxicity and upregulation of TN are mediated, at least in part, by induction of cellular oxidative stress. (C) 1997 Elsevier Science Ltd.