Degradation of human glomerular basement membrane by stimulated neutrophils. Activation of a metalloproteinase(s) by reactive oxygen metabolites.

Abstract

We examined the role of reactive oxygen metabolites in the degradation of human glomerular basement membrane (GBM) by stimulated human neutrophils. Neutrophils stimulated with phorbol myristate acetate (PMA) caused a significant degradation of GBM over 3 h resulting in 11.4±0.9% (SEM), n = 11 release of hydroxyproline compared with 03±0.09%, n = 11 release by unstimulated neutrophils. Superoxide dismutase, a scavenger of superoxide, did not inhibit the GBM degradation, whereas catalase, a scavenger of hydrogen peroxide, caused a marked inhibition (-60±7%, n = 4, P < 0.001) of hydroxyproline release. Neither alpha-i proteinase inhibitor, an inhibitor of elastase, nor soya bean trypsin inhibitor, an inhibitor of cathepsin G, caused any significant inhibition of GBM degradation. GBM degradation by cell-free supernatants obtained from stimulated neutrophils was markedly impaired in the presence of metal chelators EDTA (-72±7, n = 6, P < 0.001) and 1,10,phenanthroline (-85±5%, n = 3, P < 0.001). Considering these results, we postulated that reactive oxygen metabolites generated by the stimulated neutrophils activate a latent GBM degrading metalloproteinase(s). GBM degradation by supernatants obtained from incubations with catlase azide, an inhibitor of myeloperoxidase, and methionine and taurine, scavengers of hypochlorous acid, was markedly reduced. Our data thus indicate that degradation of the GBM by PMA-stimulated neutrophils is due to activation of a latent metalloproteinase by hypochlorous acid or a similar oxidant generated by the myeloperoxidase-hydrogen peroxidehalide system.

New mechanism for glomerular injury. Myeloperoxidase-hydrogen peroxide-halide system.

“…Other indirect effects of this system may also be operative. For example, hypohalous acid generated by the MPO-H202-halide system has been shown to potentiate protease action by activating a latent neutrophil collagenase (37) and a latent metalloenzyme protease (38) and by inactivating alpha 1 proteinase inhibitor (36 sipated. Similarly, it is difficult to relate the concentration of infused H202 (10-3 M) to that which may be produced locally by granulocytes at the site of degranulation.…”

Oxidants in Chronic Kidney Disease

“…Several immune reactants, such as serumtreated zymosan (a C 3 b receptor stimulus), heat-aggregated IgG (an Fc receptor stimulus), immune complexes, complement components, and antinuclear antibody (15) all have been shown to trigger the oxidative burst. This suggests that oxidants may anti-GBM-induced GN (12) • enhanced superoxide and hydroxyl radical are generated by macrophages that are isolated from glomeruli of rabbits with anti-GBM antibody disease (14) • enhanced superoxide generation by macrophages that are isolated from nephritic glomeruli (anti-thymocyte serum) (125) Effects of oxidants that are relevant to occurrence of proteinuria in glomerular injury • oxidants participate in GBM degradation (16) • infusion of phorbol myristate acetate, an activator of neutrophils, results in proteinuria and a fall in GFR. These effects are prevented by a catalase.…”

“…The degradation of the GBM by stimulated neutrophils is caused by the activation of a latent metalloenzyme (most likely gelatinase) by HOCl or a similar oxidant that is generated by the MPO-H 2 O 2 -halide system (16). In addition to this in vitro observation, infusion of phorbol myristate acetate (a potent activator of leukocytes) or of cobra venom factor in the renal artery caused significant proteinuria that was prevented by catalase (which destroys H 2 O 2 ) and neutrophil depletion (17)(18)(19)).…”

Isoform switching of type IV collagen is developmentally arrested in X-linked Alport syndrome leading to increased susceptibility of renal basement membranes to endoproteolysis.

“…These analyses used hydroxyproline release as an assessment of triple helical collagen degradation (19,46). Detergent-extracted XAS kidney basement membrane was more readily degradable by bacterial collagenase, P. elastase, cathepsin B, and cathepsin G (Fig.…”