Rapid screening of possible cytotoxic effects of particulate air pollutants by measurement of changes in cytoplasmic free calcium, cytosolic pH, and plasma membrane potential in alveolar macrophages by flow cytometry

Our plain-English summary of Rapid screening of possible cytotoxic effects of particulate air pollutants by measurement of changes in cytoplasmic free calcium, cytosolic pH, and plasma membrane potential in alveolar macrophages by flow cytometry, by A. Tárnok, M. Dörger, I. Berg, et al (Cytometry, 2001).

The study

• Authors: A. Tárnok, M. Dörger, I. Berg, G. Gercken, T. Schlüter
• Journal: Cytometry
• Published: 2001;43(3):204-10
• Cited by: 11 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Background: Inhalable particulate dusts are involved in the genesis of several lung diseases. Besides the well-known toxic dusts, i.e., asbestos and quartz, heavy metal-containing pollutants are considered as possible harmful substances. In the present study, we compared the effect of silica chemically coated with certain metal oxides and dusts from industrial productions on cell physiological parameters of bovine alveolar macrophages (BAM).

Methods: The cytosolic free calcium concentration, [Ca2+](i), the intracellular pH (pH(i)), and the plasma membrane potential (MP) of BAM were measured by flow cytometry. The dust-induced secretion of reactive oxygen species (ROS) was measured enzymatically.

Results: Compared with control incubations with pure silica, the dust-induced secretion of ROS by BAM was not affected when the particles were coated with Cr(2)O(3), NiO, and Fe(3)O(4), whereas VO(2)-coated dust induced a marked increase in ROS release. This effect was not correlated to changes in [Ca2+](i), pH(i), or MP. On the other hand, Cr(2)O(3)-coated silica caused alterations in all of the three latter parameters. The same pattern of changes has been reported previously for quartz dusts (Tárnok et al.: Anal Cell Pathol 15:61-72, 1997).

Conclusions: We conclude that cell physiological measurements by flow cytometry could extend the palette of tools to evaluate possible toxic effects of environmental dust samples.

Copyright 2001 Wiley-Liss, Inc.

In plain English

This was a laboratory study testing a flow cytometry method for quickly screening dusts for possible harm to lung cells. Asbestos was not tested; it appears only in the background. The authors exposed alveolar macrophages (lung scavenger cells) taken from cattle to several dusts: pure silica particles, silica coated with one metal oxide each (chromium, nickel, iron or vanadium oxide), a quartz dust (Quso G32), titanium dioxide (anatas), and dusts from industry. They measured the cells' release of reactive oxygen species, plus changes in cell calcium, internal pH and membrane potential. Compared with pure silica, vanadium oxide-coated silica raised superoxide release nearly 10-fold and hydrogen peroxide release 1.4-fold, without changing calcium, pH or membrane potential. Chromium oxide-coated silica changed all three. Calcium showed a slight but significant rise, to 10% of the maximum rise produced by a reference chemical, the calcium ionophore 4-bromo-A23187. pH fell to 7.25, against a control mean of 7.39. Membrane potential went from minus 74 mV to minus 40 mV. This pattern resembled quartz but was weaker. Industrial dusts caused no calcium change. The authors concluded that these measurements could extend the tools for evaluating possible toxicity of dust samples.

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 on isolated animal cells (methods study)
• Who was studied: Bovine (cattle) alveolar macrophages collected by bronchoalveolar lavage. Experiments used cells from at least three different animals, and the reactive oxygen experiments used cells from four animals. No location or dates are given for collection.
• Exposure: Pure LiChrospher silica particles; silica coated with Cr2O3, NiO, Fe3O4/Fe2O3 or VO2; the quartz dust Quso G32; titanium dioxide (anatas modification); and industrial dusts (grinding machine filter sediment from CrV steel, city waste incinerator fly ash, power station fly ash). No asbestos was tested.
• Main results:
  • In macrophages exposed to VO2-coated silica, superoxide release was increased nearly 10-fold (p less than 0.001) and hydrogen peroxide release 1.4-fold (p less than 0.05), compared with pure LiChrospher silica.
  • Hydrogen peroxide release did not differ significantly between titanium dioxide, Quso G32, the industrial dusts, pure silica, and Fe3O4-, NiO- or Cr2O3-coated silica.
  • Cr2O3-coated silica induced a slight but significant rise in cell calcium, to 10% of the maximum rise achieved with the calcium ionophore 4-bromo-A23187. Calcium returned to baseline after 5 to 7 minutes. Titanium dioxide, untreated particles, the other coated silicas and the industrial dusts showed no calcium effect.
  • Mean internal pH of untreated control cells was 7.39. Cr2O3-coated silica lowered it to 7.25 after 6 minutes. Control experiments indicated a specific acidification by the iron oxide- and Cr2O3-coated dusts. The authors used these control experiments to detect interference from dust particle signals, and the apparent pH drop with NiO-coated silica remained in them.
  • Baseline membrane potential was minus 74 mV. Cr2O3-coated silica and the quartz dust Quso G32 depolarized the cells to minus 40 mV and minus 30 mV respectively. Titanium dioxide and the iron-, NiO- and VO2-coated silicas caused no change.
  • Quartz dust did not cause significantly higher reactive oxygen secretion than titanium dioxide (anatas). However, quartz changed calcium, pH and membrane potential, while anatas changed none of them.
• The authors' conclusion: The authors concluded that flow cytometry measurements of calcium, pH and membrane potential could extend the tools for evaluating possible toxic effects of environmental dusts. They suggested that particulate Cr2O3 could possibly have a harmful respiratory effect resembling that of cytotoxic dusts. They also suggested the industrial dusts might be of relatively low toxicity.
• Limitations the authors state:
  • The authors stated that it is still unclear which functional aspects of the cells are ultimately influenced by the observed changes.
  • The authors stated that the real toxicity of the industrial dusts should be further characterized by other methods. They had no information on what percentage of the dusts' metal compounds were in oxidized form or on the dusts' surface composition.
  • For the grinding machine metal dust, pH and membrane potential could not be measured because the dust caused cell clumping that clogged the cytometer.

Topics

Medical terms in this study, explained in our Lexicon: Alveolar Macrophage, Reactive Oxygen Species (ROS).

Related studies

• Changes in free intracellular calcium and production of reactive oxygen metabolites in human leukocytes by soluble and particulate stimuli — M. Tuomala, M.R. Hirvonen, et al. (1993)
• A comparison of asbestos and urban particulate matter in the in vitro modification of human alveolar macrophage antigen-presenting cell function — R.F. Hamilton, A. Holian, et al. (2004)
• Asbestos-induced disruption of calcium homeostasis induces endoplasmic reticulum stress in macrophages — A.J. Ryan, J.L. Larson-Casey, et al. (2014)
• Role of extracellular calcium in chrysotile asbestos stimulation of alveolar macrophages — B. Kalla, R.F. Hamilton, et al. (1990)
• Activation of alveolar macrophages and peripheral red blood cells in rats exposed to fibers/particles — F. Afaq, P. Abidi, et al. (1998)
• Asbestos and silica-induced changes in human alveolar macrophage phenotype — A. Holian, M.O. Uthman, et al. (1997)

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