Effects of subchronic exposure of silver nanoparticles on intestinal microbiota and gut-associated immune responses in the ileum of Sprague-Dawley rats

Abstract

Silver nanoparticles (AgNP) are widely used for their antibacterial properties. Incorporation of AgNP into food-related products and health supplements represents a potential route for oral exposure to AgNP; however, the effects of such exposure on the gastrointestinal system are mostly unknown. This study evaluated changes in the populations of intestinal-microbiota and intestinal-mucosal gene expression in Sprague-Dawley rats (both male and female) that were gavaged orally with discrete sizes of AgNP (10, 75 and 110 nm) and silver acetate. Doses of AgNP (9, 18 and 36 mg/kg body weight/day) and silver acetate (100, 200 and 400 mg/kg body weight/day) were divided and administered to rats twice daily (∼10 h apart) for 13 weeks. The results indicate that AgNP prompted size- and dose-dependent changes to ileal-mucosal microbial populations, as well as, intestinal gene expression and induced an apparent shift in the gut microbiota toward greater proportions of Gram-negative bacteria. DNA-based analyses revealed that exposure to 10 nm AgNP and low-dose silver acetate caused a decrease in populations of Firmicutes phyla, along with a decrease in the Lactobacillus genus. Analysis of host gene expression demonstrated that smaller sizes and lower doses of AgNP exposure prompted the decreased expression of important immunomodulatory genes, including MUC3, TLR2, TLR4, GPR43 and FOXP3. Gender-specific effects to AgNP exposure were more prominent for the gut-associated immune responses. These results indicate that the oral exposure to AgNP alter mucosa-associated microbiota and modulate the gut-associated immune response and the overall homeostasis of the intestinal tract.

• Bacteria
• microbiome
• mucosal immunity

Acknowledgements

The authors would like to thank Drs. Syed Ali and Jyotshanabala Kanungo for their critical reviewing of the manuscript. Authors would like to extend their thanks to Dr. Paul Howard for help provided by the FDA NanoCore facility for the characterization of AgNP.

Declaration of interest

This study was supported, in part, by an Interagency Agreement between the US Food and Drug Administration and the National Institute of Environmental Health Sciences (FDA IAG #224-12-003/NIEHS IAG #AES12013) and by the NCTR-US Food and Drug Administration (E07506). Ms. Katherine Williams, Ms. Jessica Milner and Dr. Kuppan Gokulan are supported through the Oak Ridge Institute for Science and Education.

The findings/opinions presented here represent the views of the authors. They do not reflect the views of the U.S. Food and Drug Administration.