Extracellular catalase activity protects cysteine cathepsins from inactivation by hydrogen peroxide

Abstract 

The resistance of secreted cysteine cathepsins to peroxide inactivation was evaluated using as model THP-1 cells. Differentiated cells released mostly cathepsin B, but also cathepsins H, K, and L, with a maximum of endopeptidase activity at day 6. Addition of non-cytotoxic concentrations of H₂O₂ did not affect mRNA expression levels and activity of cathepsins, while the catalase activity remained also unchanged, consistently with RT-PCR analysis. Conversely inhibition of extracellular catalase led to a striking inactivation of secreted cysteine cathepsins by H₂O₂. This report suggests that catalase may participate in the protection of extracellular cysteine proteases against peroxidation.

Abbreviations: AMC, 7-amino-4-methyl coumarin, 3-AT, 3-amino-l, 2, 4-triazole, BALF, bronchoalveolar lavage fluid, BCA, bicinchoninic acid, CA-074, N-(l-3-trans-propylcarbamoyl oxirane-2-carbonyl)-l-isoleucyl-l-proline, CP, cysteine protease, DTT, dl-dithiothreitol, E-64, l-3-carboxy-trans-2.3-epoxypropionyl-leucylamido-(4-guanidino) butane, ECM, extra cellular matrix, FBS, fetal bovine serum, GM-CSF, granulocyte–macrophage colony-stimulating factor, MDM, monocyte-derived macrophage, MMTS, methylmethanethiosulfonate, PMA, phorbol myristate acetate, PMSF, phenylmethylsulfonyl fluoride, ROS, reactive oxygen species, Z, benzyloxycarbonyl

Keywords: Cathepsin, Cysteine protease, Inflammation, Oxidation, Proteolysis, THP-1 cell