Wollastonite Fibers in Vitro Generate Reactive Oxygen Species Able to Lyse Erythrocytes and Activate the Complement Alternate Pathway

Wollastonite Fibers in Vitro Generate Reactive Oxygen Species Able to Lyse Erythrocytes and Activate the Complement Alternate Pathway

Mario Governa*, Lamberto Camilucci, Monica Amati*, Isabella Visonà*, Matteo Valentino*, Gian Carlo Botta, Antonella Campopiano and Carla Fanizza
*Institute of Occupational Medicine, University of Ancorn Ospedale di Torrette. I-60020 Torrette di Ancona. Italy Department of Industrial Hygiene ISPELS, I-00040 Monte Porzio Catone, Italy Institute of Occupational Medicine, University of Turin Ospedale CTO, via Zuretti 29, I-10126 Torino, Italy

Received May 27, 1997; accepted February 3, 1998

Wollastonite fibers were tested in vitro for their ability to produce reactive oxygen species (ROS) with two different systems: a cell-free reactive mixture containing deoxyribose and a polymorphonuclear leukocyte suspension. After adding the fibers, we measured the thiobarbituric acid-reactive substances pduced by deoxyribose degradation and luminol-enhanced chemiluminescence, respectively. Compared with asbestos, wollastonite fibers produced higher ROS levels both in the PMN suspensions and in the cell-free reactive mixtures. A large amount of these ROS were not hydroxyl radicals. Indeed we obtained remarkable differences in ROS generation between unground and ground wollastonite fibers and negative results with fibers modified with ferric chloride and dithionite. In addition, ROS generation was partially inhibited (by 46–54%) in the reactions performed in the presence of 1,3-dimethyl-2-thiourea (DMTU), a strong hydroxyl radical scavenger. Wollastonite fibers were also analyzed for their ability to lyse erythrocytes and activate complement. Hemolytic potency was about twice that of chrysotile and half that of crocidolite. The levels of complement activation (via the alternate pathway) were about four-fifths of those measured in zyrnosan-activated plasma (a typical stimulus used to activate the alternate pathway), equal to those obtained with crocidolite, and two-thirds of those found with chrysotile. The addition of DMTU markedly reduced both these activities. Since asbestos fiber toxicity is mainly due to hydroxyl radical generation, our results indicate that wollastonite fibers are probably less toxic than asbestos fibers.

Key Words: wollastonite fibers; asbestos substitutes; reactive oxygen species; complement activation via alternate pathway; hemolysis in vitro.

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