Wollastonite fibers in vitro generate reactive oxygen species able to lyse erythrocytes and activate the complement alternate pathway

Our plain-English summary of Wollastonite fibers in vitro generate reactive oxygen species able to lyse erythrocytes and activate the complement alternate pathway, by M. Governa, L. Camilucci, M. Amati, et al (Toxicological Sciences, 1998).

The study

• Authors: M. Governa, L. Camilucci, M. Amati, I. Visonà, M. Valentino, G.C. Botta, A. Campopiano, C. Fanizza
• Journal: Toxicological Sciences
• Published: 1998;44(1):32-8
• Cited by: 16 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

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 produced 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 zymosan-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.

In plain English

This laboratory study compared commercial wollastonite fibers, an asbestos substitute, with reference samples of chrysotile and crocidolite asbestos, at doses matched by fiber surface area. In a cell-free chemical test and in suspensions of human white blood cells, wollastonite produced significantly more reactive oxygen species than either asbestos type. Chrysotile gave no detectable reading in the cell-free test. Adding DMTU, a substance that removes hydroxyl radicals, lowered wollastonite's cell-free reading by about 47 percent for unground fibers and 63 percent for ground fibers. To break apart half of a sample of human red blood cells, wollastonite needed about twice the surface area of chrysotile and half that of crocidolite. Its activation of complement, part of the immune system, was about four-fifths of that from a standard stimulus and equal to crocidolite's. DMTU markedly reduced both effects. The authors concluded that much of the reactive oxygen produced by wollastonite was not hydroxyl radicals. They also concluded that, because asbestos toxicity is mainly due to hydroxyl radicals, wollastonite fibers are probably less toxic than asbestos fibers.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: In vitro laboratory experiment comparing wollastonite fibers with asbestos fibers (cell-free chemical assay, human white blood cell suspensions, red blood cell lysis assay, complement activation assay)
• Who was studied: Fiber samples, not people: a high-purity NYAD wollastonite sample (Interpace Corp., Willsboro, NY), obtained from an Italian company producing fiber-reinforced cement, and UICC Canadian chrysotile type B and crocidolite. Test cells were polymorphonuclear leukocytes and red blood cells from apparently healthy human volunteers aged 25 to 45, plus normal human serum.
• Exposure: Wollastonite, chrysotile and crocidolite fibers, unground and ground. Some wollastonite was surface-modified with ferric chloride or dithionite. Doses were set by specific surface area: 10 cm2 in the reactive oxygen species assays, and 50 to 400 cm2 per ml in the hemolysis and complement assays.
• Main results:
  • In the cell-free deoxyribose test, unground and ground wollastonite gave significantly higher readings (mean absorbance 1.15 and 2.05) than unground and ground crocidolite (0.34 and 0.42) and chrysotile. Chrysotile gave no detectable absorbance.
  • In the cell-free test, adding DMTU lowered absorbance with unground and ground wollastonite by about 47% and 63%. Adding desferoxamine lowered it by about 88% and 91%.
  • Pretreating wollastonite with ferric chloride or dithionite did not significantly change production of thiobarbituric acid-reactive substances.
  • In human white blood cell suspensions, chemiluminescence (a measure of reactive oxygen species) was significantly higher with unground and ground wollastonite (378.6% and 1431.1% of control) than with chrysotile (256.9% and 615.1%) and crocidolite (277.5% and 351.9%).
  • For each mineral, ground fibers produced significantly more chemiluminescence in white blood cell suspensions than unground fibers.
  • Surface area needed to lyse half of the red blood cells (HC 50%) was 217.47 cm2/ml for wollastonite, 100.19 for chrysotile and 424.58 for crocidolite. Wollastonite was therefore less hemolytic than chrysotile and more hemolytic than crocidolite.
  • Wollastonite's hemolysis was nearly abolished by 5 mM DMTU, with no significant change at 0.5 mM.
  • Complement activation by wollastonite was about four-fifths of that with zymosan-activated plasma, equal to crocidolite and, per the authors, two-thirds of chrysotile.
  • Wollastonite's complement-derived chemotactic activity fell by about 35% with 0.5 mM DMTU.
  • Activity with wollastonite was significantly lower in EDTA-chelated serum than in EGTA-chelated serum or normal serum. The authors interpreted this as involvement of the alternate complement pathway. Similar results were seen with chrysotile and crocidolite.
• The authors' conclusion: The authors concluded that the surface of wollastonite fibers generates reactive oxygen species, a large amount of which are not hydroxyl radicals. Because asbestos toxicity is mainly due to hydroxyl radical generation, they share the view that wollastonite fibers are probably less toxic than asbestos fibers.
• Limitations the authors state:
  • The authors stated that further studies are needed to explain how wollastonite causes hemolysis and complement activation despite relatively low hydroxyl radical generation.
  • The authors suggested the 10 cm2 dose of chrysotile probably did not supply enough iron to produce a reading in the cell-free test.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite.

Medical terms in this study, explained in our Lexicon: Wollastonite, Reactive Oxygen Species (ROS), Hydroxyl Radical, Chrysotile, Crocidolite.

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