Chemical indexes and in-vitro solubility

Different chemical indexes have been proposed in the literature, in order to predict the influence of the chemical composition of mineral fibers on their properties. One of these properties is the acellular in-vitro dissoludon behavior (noted thereafter: solubility) in synthetic lung fluids at pH 7.4, which has been shown to be a reliable predictor of the results of expensive chronic long-term in-vivo tests conducted up to now with fibers [1 and 2]. This in-vitro solubility has been reported as being a function of the chemical composition [3 and 4]. The aim of this investigation was to assess if the in-vitro solubility could easily be predicted through conventional chemical indexes already reported in the literature; such as the following: - nonbridging oxygen (NBO) as calculated by Moore and Brown [5]; - optical basicity (OB) as defined by Baucke and Duffy [6]; - free enthalpy (ΔG°) of hydration as evaluated from tables in Paul [7]; - "Kanzerogenitätsindex" (KI) as defined in [8]. The relationship between the acellular in-vitro solubility expressed as KDISSiO2 or KDISCaO and these four different indexes has been analyzed. Nene of these indexes could be reliably used to prediet the in-vitro solubility at pH 7.4 for a broad range of composidons. KI is an acceptable indicator of in-vivo biopersistence [9], in a narrow range (15 to 40). It is the best of all the analyzed indexes giving a general trend for the solubility. The calculated correlation coefficient between KI and KDISSiO2 is then 0.78. This work shows that calculated indexes derived from the literature are not sufficient to prediet the results of in-vitro dissolution tests; and thus the need for a reliable standardized in-vitro test method is emphasized

Gene expression profile in monocyte during in vitro mineral fiber degradation

A human monocytes cell line, U-937, incubated in the presence of filtered medium from Escherichia coli culture (FS) has been previously reported to degrade man made mineral fiber and it has been indicated as a good paradigm of in vivo fiber biopersistence evaluation (manuscript accepted for publication). In the present paper, a study is reported aimed to define the molecular modification occurring in the U-937 monocytes during in vitro fiber degradation. The induction of gene expression was investigated in U-937 exposed to rock wool fibers (HDN) in the presence of FS by transcriptome analysis using 20 K DNA microarrays and quantitative RT-PCR. The over-expression of genes related to mobility and cellular adhesion, oxidative stress, immune system stimulation, enzymes, and ions transport protein systems were identified. Among them NCF1 gene, the gene encoding a subunit of NADPH oxidase, over-expression was detected. As the product of this gene allows the formation of superoxide anion that could lead to oxidative stress, HDN fibers were exposed to hydrogen peroxide. Fiber degradation similar to those observed upon incubation with U-937 in the presence of FS was obtained thus suggesting that reactive oxygen species production may be responsible for fiber degradation by U-937 monocytes

EURIMA test guideline: In-vitro acellular dissolution of man-made vitreous silicate fibres

[no abstract available

Gene expression profile in monocyte during in vitro mineral fiber degradation

A human monocytes cell line, U-937, incubated in the presence of filtered medium from Escherichia coli culture (FS) has been previously reported to degrade man made mineral fiber and it has been indicated as a good paradigm of in vivo fiber biopersistence evaluation (manuscript accepted for publication). In the present paper, a study is reported aimed to define the molecular modification occurring in the U-937 monocytes during in vitro fiber degradation. The induction of gene expression was investigated in U-937 exposed to rock wool fibers (HDN) in the presence of FS by transcriptome analysis using 20 K DNA microarrays and quantitative RT-PCR. The over-expression of genes related to mobility and cellular adhesion, oxidative stress, immune system stimulation, enzymes, and ions transport protein systems were identified. Among them NCF1 gene, the gene encoding a subunit of NADPH oxidase, over-expression was detected. As the product of this gene allows the formation of superoxide anion that could lead to oxidative stress, HDN fibers were exposed to hydrogen peroxide. Fiber degradation similar to those observed upon incubation with U-937 in the presence of FS was obtained thus suggesting that reactive oxygen species production may be responsible for fiber degradation by U-937 monocytes