Variability of biological effects of silicas: different degrees of activation of the fifth component of complement by amorphous silicas.

A biogenic and a pyrogenic amorphous silica were incubated in normal human plasma and compared on a per unit surface basis for their ability to split C5 molecules and yield small C5a peptides. Since C5a peptides induce selective chemotactic attraction of polymorphonuclear leukocytes (PMN), measurement of PMN-induced chemotaxis was used as an index of C5 activation. Though to a lesser extent than the crystalline forms, amorphous silicas can promote the cleavage of C5 protein and generation of C5a-like fragment.

[The in vitro release of hydroxyl radicals from dust containing fluoro-edenite fibers identified in the volcanic rocks of Biancavilla (eastern Sicily)].

Background: Epidemiological studies revealed an unusually high incidence of malignant pleural mesothelioma in Biancavilla, a town in eastern Sicily located in a volcanic area. In the absence of occupational risk factors connected with asbestos inhalation, a nearby stone quarry, which has long been providing most of the local building materials (e.g.

Cleavage of the fifth component of human complement and release of a split product with C5a-like activity by crystalline silica through free radical generation and kallikrein activation.

The effects of the same form of crystalline silica variously modified were compared to investigate the mechanisms by which silica activates C5 molecules. After incubation in human plasma, silica generated C5a-type fragments that stimulated polymorphonuclear leukocyte chemotaxis. This activity was totally abolished when plasma, adsorbed with antiserum against C5a or thermally inactivated, was used.