Effect of size of man-made and natural mineral fibers on chemiluminescent response in human monocyte-derived macrophages

Our plain-English summary of Effect of size of man-made and natural mineral fibers on chemiluminescent response in human monocyte-derived macrophages, by M. Ohyama, T. Otake, K. Morinaga (Environmental Health Perspectives, 2001).

The study

• Authors: M. Ohyama, T. Otake, K. Morinaga
• Journal: Environmental Health Perspectives
• Published: 2001;109(10):1033-8
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Fiber size is an important factor in the tumorigenicity of various mineral fibers and asbestos fibers in animal experiments. We examined the time course of the ability to induce lucigenin-dependent chemiluminescence (CL) from human monocyte-derived macrophages exposed to Japan Fibrous Material standard reference samples (glass wool, rock wool, micro glass fiber, two types of refractory ceramic fiber, refractory mullite fiber, potassium titanium whisker, silicon carbide whisker, titanium oxide whisker, and wollastonite). We determined how fiber length or width might modify the response of cells. We found that the patterns of time-dependent increase of CL (sigmoid type) were similar for each sample except wollastonite. We observed a strong correlation between geometric-mean length and ability to induce CL in seven samples > 6 microm in length over the time course (largest r(2) = 0.9760). Although we also observed a close positive correlation between geometric-mean width and the ability to induce CL in eight samples < 1.8 microm in width at 15 min (r(2) = 0.8760), a sample of 2.4 microm in width had a low ability to induce CL. Moreover, the relationship between width and the rate of increase in ability to induce CL had a negative correlation at 30-60 min (largest r(2) = 0.7473). Our findings suggest that the release of superoxide from macrophages occurs nonspecifically for various types of mineral fibers depending on fiber length.

In plain English

This was a laboratory experiment on human cells. It did not study people, and it did not test asbestos. The authors grew macrophages, a type of immune cell, from healthy donors' blood. They exposed the cells to ten Japanese standard reference samples of man-made and natural mineral fibers, including glass wool, rock wool, refractory ceramic fibers and wollastonite. Every 15 minutes for two hours they measured light given off by the cells (chemiluminescence), which they used as a sign of superoxide release. All samples except wollastonite caused a dose-dependent response, and the response rose over time in a similar S-shaped pattern. Wollastonite was dropped from later analyses. In samples described as longer than 6 µm, response per fiber rose with average length; the peak correlation (r2 = 0.9760, at 45 minutes) used the six such samples with usable data. In eight thinner samples, the response tracked fiber width at 15 minutes (r2 = 0.8766), but this weakened by 45 minutes. The widest fiber (2.4 µm) gave a low response. The authors concluded that macrophages release superoxide nonspecifically for various fiber types, depending on fiber length.

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 cultured human monocyte-derived macrophages
• Who was studied: Macrophages grown from monocytes in blood from healthy donors. The article does not state the number of donors or where and when the blood was collected.
• Exposure: Ten Japan Fibrous Material standard reference samples, described by geometric-mean length, geometric-mean width and fibers per microgram: glass wool (GW1, 20.0 µm; 0.88 µm), rock wool (RW1, 16.5; 1.8), micro glass fiber (MG1, 3.0; 0.24), refractory ceramic fiber (RF1, 12.0; 0.77 and RF2, 11.0; 1.1), refractory mullite fiber (RF3, 11.0; 2.4), potassium titanium whisker (PT1, 6.0; 0.35), silicon carbide whisker (SC1, 6.4; 0.30), titanium oxide whisker (TO1, 2.1; 1.00) and wollastonite (WO1, 10.5; 1.00). Each sample was given at several concentrations. No asbestos was tested in this study.
• Main results:
  • All fiber samples except wollastonite (WO1) caused a dose-dependent chemiluminescence response. Adding superoxide dismutase, a superoxide scavenger, almost completely blocked each response (data not shown).
  • For each sample analysed, the per-fiber response rose over time in an S-shaped (sigmoid) pattern. The pattern was similar across samples, although the values differed.
  • In the samples described as longer than 6 µm (GW1, RW1, RF1, RF2, RF3, SC1 and PT1), the per-fiber response correlated closely with average fiber length. Samples shorter than about 6 µm had a low per-fiber response. According to Table 4, the r2 was 0.8191 at 15 minutes (lowest; seven samples with usable data). It was 0.9760 at 45 minutes (highest; six samples with usable data, because data with r2 below 0.9 in Table 1 were excluded).
  • In eight samples less than 1.8 µm wide, the per-fiber response correlated with average fiber width at 15 minutes (r2 = 0.8766). This relationship did not continue: r2 was 0.5138 at 45 minutes.
  • The response correlated more with width than with length at 15 minutes, and more with length than with width after 30 minutes.
  • The widest fiber (2.4 µm, refractory mullite fiber RF3) had a low ability to induce chemiluminescence.
  • The rate at which the response increased was related to fiber width over 30 to 45 minutes (r2 = 0.5309) and over 45 to 60 minutes (r2 = 0.7473), with negative slopes in Table 6. There was no correlation over 60 to 75 minutes. The rate of increase showed no correlation with fiber length at any time point (data not shown).
• The authors' conclusion: The authors concluded that macrophages release superoxide nonspecifically for various fiber types, depending on fiber length. They also stated that their findings do not support the hypothesis that oxidant release occurs during 'frustrated' phagocytosis, which is when cells cannot fully engulf long fibers.
• Limitations the authors state:
  • Wollastonite was excluded from the analyses because its response did not follow a linear dose-response. The authors said their data were not sufficient to define it as an exception.
  • When responses were compared by sample weight, the linear dose-response did not continue for some samples. By 120 minutes some curves had leveled off, with short fibers leveling off at low doses.

Topics

Medical terms in this study, explained in our Lexicon: Mineral Fiber, Macrophage, Wollastonite, Fiber Length, Superoxide.

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• The chemiluminescent response of human phagocytic cells to mineral dusts — I.P. Gormley, M.J. Kowolik, et al. (1985)
• Polyvinylpyridine-N-oxide and carboxymethyl cellulose inhibit mineral dust-induced production of reactive oxygen species by human macrophages — P. Nyberg (1991)

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