Crystalline silica-induced pulmonary inflammation and autoimmunity in mature adult NZBW/f1 mice: age-related sensitivity and impact of omega-3 fatty acid intervention.

Abstract

Objective: Occupational exposure to respirable crystalline silica (cSiO₂) has been linked to lupus development. Previous studies in young lupus-prone mice revealed that intranasal cSiO₂ exposure triggered autoimmunity, preventable with docosahexaenoic acid (DHA). This study explores cSiO₂ and DHA effects in mature lupus-prone adult mice, more representative of cSiO₂-exposed worker age.

Methods: Female NZBWF1 mice (14-week old) were fed control (CON) or DHA-supplemented diets. After two weeks, mice were intranasally instilled saline (VEH) or 1 mg cSiO₂ weekly for four weeks. Cohorts were then analyzed 1- and 5-weeks postinstillation for lung inflammation, cell counts, chemokines, histopathology, B- and T-cell infiltration, autoantibodies, and gene signatures, with results correlated to autoimmune glomerulonephritis onset.

Results: VEH/CON mice showed no pathology. cSiO₂/CON mice displayed significant ectopic lymphoid tissue formation in lungs at 1 week, increasing by 5 weeks. cSiO₂/CON lungs exhibited elevated cellularity, chemokines, CD3⁺ T-cells, CD45R ⁺ B-cells, IgG ⁺ plasma cells, gene expression, IgG autoantibodies, and glomerular hypertrophy. DHA supplementation mitigated all these effects.

Discussion: The mature adult NZBWF1 mouse used here represents a life-stage coincident with immunological tolerance breach and one that more appropriately represents the age (20-30 yr) of cSiO2-exposed workers. cSiO₂-induced robust pulmonary inflammation, autoantibody responses, and glomerulonephritis in mature adult mice, surpassing effects observed previously in young adults. DHA at a human-equivalent dosage effectively countered cSiO₂-induced inflammation/autoimmunity in mature mice, mirroring protective effects in young mice.

Conclusion: These results highlight life-stage significance in this preclinical lupus model and underscore omega-3 fatty acids' therapeutic potential against toxicant-triggered autoimmune responses.