OXIDATION OF THE MESANGIAL MATRIX METALLOPROTEINASE-2 IMPAIRS GELATINOLYTIC ACTIVITY

Glomerulosclerosis is characterized by an accumulation of mesangial ex tracellular matrix. Oxygen radicals are strongly implicated in glomeru lar injury but it is unclear by what mechanism they could modulate mat rix turnover dynamics. We evaluated whether oxidation of the 72 kD mes angial matrix metalloproteinase-2 (MMP-2), the major mesangial matrix- degrading enzyme, could alter its gelatinolytic activity. Oxidation of the MMP-2 using a FeCl3/ascorbate system resulted in impaired ability to degrade [H-3]gelatin compared to control. Samples were also subjec ted to SDS-PAGE gelatin substrate zymography. At the 72 kD position a significant impairment of gelatinolytic activity of oxidized samples w as observed, a decrease attenuated by coincubation of samples with the FeCl3/ascorbate system plus the radical spin trap N-tert-butyl-alpha- phenylnitrone suggesting specificity of oxidative changes in the decre ase in enzymatic activity. These data represent the first report demon strating that oxidation of the MMP-2 diminishes its activity and sugge st a previously undescribed mechanism by which oxygen radicals may con tribute to altered turnover of extracellular matrix.