Occupational exposure to solvents and gender-related risk of systemic sclerosis: a metaanalysis of case-control studies.

OBJECTIVE: In 2001 a metaanalysis reported an excess risk of systemic sclerosis (SSc) related to solvents exposure. The magnitude of risk varied among studies and sources of heterogeneity have not been investigated due to a lack of statistical power. We conducted a new metaanalysis to identify features associated with the magnitude of SSc risk in patients exposed to solvents. METHODS: We searched 4 databases (Medline, Pascal, Pascal Biomed, Francis). Inclusion criteria were: case-control study, occupational exposure to solvents (OES) assessed by questionnaire and summarized to "any solvent" or "any organic solvent," SSc defined by the American College of Rheumatology or the consultant's criteria. The quality of studies within this metaanalysis was scored according to the Newcastle-Ottawa scale. Odds ratios (OR) were adjusted for the "publication bias" and validated by a sensitivity analysis. Subgroup analyses investigated the effect of gender, quality of studies, and the type of controls. RESULTS: Among 11 studies (1291 patients and 3435 controls), 9 involved a majority of women (76.2 to 100%), while 2 involved men only. The risk of SSc associated with OES was variable among studies (p for heterogeneity = 0.01) and overrepresentation of higher OR values in smaller studies (p = 0.003) suggested "publication bias." SSc was associated with OES (OR 2.4; 95% CI 1.7-3.4; p < 0.0001), including after adjusting for bias (OR 1.8; 95% CI 1.2-2.5; p = 0.002). The relative risk was higher (p = 0.03) in men (OR 3.0; 95% CI 1.9-4.6; p < 0.0001) than in women (OR 1.8; 95% CI 1.5-2.1; p < 0.0001). CONCLUSION: Whereas SSc affects women predominantly, among subjects with occupational exposure to solvents, men are at higher risk than women for the disease.

Ribonuclease L proteolysis in peripheral blood mononuclear cells of chronic fatigue syndrome patients.

A 37-kDa binding polypeptide accumulates in peripheral blood mononuclear cell (PBMC) extracts from chronic fatigue syndrome (CFS) patients and is being considered as a potential diagnostic marker (De Meirleir, K., Bisbal, C., Campine, I., De Becker, P., Salehzada, T., Demettre, E., and Lebleu, B. (2000) Am. J. Med. 108, 99-105). We establish here that this low molecular weight 2-5A-binding polypeptide is a truncated form of the native 2-5A-dependent ribonuclease L (RNase L), generated by an increased proteolytic activity in CFS PBMC extracts. RNase L proteolysis in CFS PBMC extracts can be mimicked in a model system in which recombinant RNase L is treated with human leukocyte elastase. RNase L proteolysis leads to the accumulation of two major fragments with molecular masses of 37 and 30 kDa. The 37-kDa fragment includes the 2-5A binding site and the N-terminal end of native RNase L. The 30-kDa fragment includes the catalytic site in the C-terminal part of RNase L. Interestingly, RNase L remains active and 2-5A-dependent when degraded into its 30- and 37-kDa fragments by proteases of CFS PBMC extract or by purified human leukocyte elastase. The 2-5A-dependent nuclease activity of the truncated RNase L could result from the association of these digestion products, as suggested in pull down experiments.