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.

Keywords:

• Crystalline silica
• lung
• omega fatty acid
• autoantibody
• ectopic lymphoid tissue
• systemic lupus erythematosus
• glomerulonephritis

Acknowledgments

The authors thank Amy Porter of the Michigan State University Laboratory for Investigative Histopathology for their assistance with histotechnology. The authors also thank Dr. Kevin Childs and the Research Technology Support Genomics Core Facility for processing samples using the NanoString nCounter Analysis System.

Author contributions

LH: study design, coordination, feeding study, necropsy, data curation, data analysis/interpretation, figure preparation, manuscript preparation, and submission; TS: morphometric analysis, data acquisition and interpretation; JW: study design, necropsy, lab analysis; RL: instillations, necropsy, lab analysis; AB: data procurement and statistical analysis; AS: morphometric analysis; AT: animal handling, urinalysis; JH: study design, oversight, lung/kidney histopathology, morphometry, data analysis, manuscript preparation; JP: study design, oversight, funding acquisition, data analysis, manuscript preparation.

Disclosure statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Data availability statement

Original NanoString normalized linear counts and statistical analyses from the NanoString autoimmune profiling panel, and a summary of statistical analyses are available at Dryad. https://doi.org/10.5061/dryad.2280gb5vx.

Additional information

Funding

This research was funded by NIH T32ES007255 (LH), NIH ES027353 (JP), Lupus Foundation of America (JP), and Dr. Robert and Carol Deibel Family Endowment (JP).