High serum levels of silica nanoparticles in systemic sclerosis patients with occupational exposure: Possible pathogenetic role in disease phenotypes

• Published in: Seminars in arthritis and rheumatism Vol. 48; no. 3; pp. 475 - 481
• Main Authors: Ferri, Clodoveo, Artoni, Erica, Sighinolfi, Gian Luca, Luppi, Fabrizio, Zelent, Gabriele, Colaci, Michele, Giuggioli, Dilia
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2018
• Subjects: Adult; Aged; Case-Control Studies; Etiopathogenesis; Female; Humans; Interstitial lung fibrosis; Lung Diseases, Interstitial - blood; Lung Diseases, Interstitial - etiology; Male; Microparticles; Middle Aged; Nanoparticles; Occupational Exposure; Risk Factors; Scleroderma; Scleroderma, Systemic - blood; Scleroderma, Systemic - etiology; Silica; Silicon Dioxide - blood; Systemic sclerosis; Nanoparticles; Systemic sclerosis; Etiopathogenesis; Interstitial lung fibrosis; Scleroderma; Occupational exposure; Silica; Microparticles
• ISSN: 0049-0172; 1532-866X
• DOI: 10.1016/j.semarthrit.2018.06.009

Systemic sclerosis (SSc) is an autoimmune systemic disease characterized by diffuse fibrosis of skin and visceral organs due to different genetic, infectious, and/or environmental/occupational causative factors, including the inhalation of silica dust. To investigate serum trace elements including silicon (s-Si) levels in SSc patients living in a restricted geographical area with high density of worksites with silica exposure hazard. This case-control study included 80 SSc patients (M:F 10:70; aged 58.4 ± 11.9SD years, mean disease duration 10.1 ± 7.8SD) and 50 age-/sex-matched healthy control subjects consecutively investigated at our University-based Rheumatology Unit. Patients and controls were evaluated for environmental/occupational exposure categories (structured questionnaire), morphological characterization of serum micro-/nanoparticles (Environmental Scanning Electron Microscopy and Energy Dispersive X-ray Spectroscopy microanalysis), and quantitative assessment of trace elements (inductively coupled plasma atomic emission spectroscopy). Among various categories, only occupational exposure to silica dust was recorded in a significant proportion of SSc patients compared to controls (55% vs. 11%; p < .0001). Qualitative analysis showed serum silica micro- and nanoparticles in all exposed patients. Quantitative evaluation evidenced significantly higher s-Si levels in SSc patients versus controls (p < .0001); in addition, higher s-Si levels were detected in patients with occupational exposure (p < .0001), diffuse cutaneous SSc (p = .0047), myositis (p = .0304), and/or lung fibrosis (p = .0004) compared to those without; notably, the severity of lung fibrosis scoring positively correlated with s-Si levels (p < .0001). The study first demonstrated high s-Si levels in exposed SSc patients; this element might represent a pathogenetic co-factor of more severe clinical phenotypes, mainly diffuse scleroderma with lung fibrosis.