Theranostics 2018; 8(22):6149-6162. doi:10.7150/thno.29303

Research Paper

Iron oxide nanozyme suppresses intracellular Salmonella Enteritidis growth and alleviates infection in vivo

Shourong Shi1,5,6✉, Shu Wu1,2, Yiru Shen1, Shan Zhang1, Yunqi Xiao1, Xi He2, Jiansen Gong1, Yuhua Farnell4, Yan Tang3, Yixin Huang3, Lizeng Gao3✉

1. Department of Feed and Nutrition, Poultry Institute, Chinese Academy of Agricultural Sciences, Yangzhou, Jiangsu 225125, China
2. College of Animal Science and Technology, Hunan Agricultural University, Changsha, Hunan 410128, China
3. Jiangsu Key Laboratory of Experimental & Translational Non-coding RNA Research, Institute of Translational Medicine , School of Medicine, Yangzhou University, Yangzhou, Jiangsu 225000, China
4. Department of Poultry Science, Texas A&M AgriLife Research, Texas A&M University, College Station, TX 77843, USA
5. Institute of Effective Evaluation of Feed and Feed Additive (Poultry institute), Ministry of Agriculture, Yangzhou, Jiangsu 225125, China
6. Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu 225000, China

Abstract

Rational: Salmonella Enteritidis (S. Enteritidis) is a globally significant zoonotic foodborne pathogen which has led to large numbers of deaths in humans and caused economic losses in animal husbandry. S. Enteritidis invades host cells and survives within the cells, causing resistance to antibiotic treatment. Effective methods of elimination and eradication of intracellular S. Enteritidis are still very limited. Here we evaluated whether a new intracellular antibacterial strategy using iron oxide nanozymes (IONzymes) exerted highly antibacterial efficacy via its intrinsic peroxidase-like activity in vitro and in vivo.

Methods: The antibacterial activities of IONzymes against planktonic S. Enteritidis, intracellular S. Enteritidis in Leghorn Male Hepatoma-derived cells (LMH), and liver from specific pathogen free (SPF) chicks were investigated by spread-plate colony count method and cell viability assay. Changes in levels of microtubule-associated protein light chain 3 (LC3), a widely used marker for autophagosomes, were analyzed by immunoblotting, immunofluorescence, and electron microscopy. Reactive oxygen species (ROS) production was also assessed in vitro. High-throughput RNA sequencing was used to investigate the effects of IONzymes on liver transcriptome of S. Enteritidis-infected chicks.

Results: We demonstrated that IONzymes had high biocompatibility with cultured LMH cells and chickens, which significantly inhibited intracellular S. Enteritidis survival in vitro and in vivo. In addition, co-localization of IONzymes with S. Enteritidis were observed in autophagic vacuoles of LMH cells and liver of chickens infected by S. Enteritidis, indicating that IONzymes mediated antibacterial reaction of S. Enteritidis with autophagic pathway. We found ROS level was significantly increased in infected LMH cells treated with IONzymes, which might enhance the autophagic elimination of intracellular S. Enteritidis. Moreover, orally administered IONzymes decreased S. Enteritidis organ invasion of the liver and prevented pathological lesions in a chicken-infection model. Non-target transcriptomic profiling also discovered IONzymes could change hepatic oxidation-reduction and autophagy related gene expressions in the S. Enteritidis infected chickens.

Conclusion: These data suggest that IONzymes can increase ROS levels to promote the antibacterial effects of acid autophagic vacuoles, and thus suppress the establishment and survival of invading intracellular S. Enteritidis. As a result, IONzymes may be a novel alternative to current antibiotics for the control of intractable S. Enteritidis infections.

Keywords: Salmonella Enteritidis, iron oxide nanozyme, autophagy, reactive oxygen species, intracellular bacteria

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How to cite this article:
Shi S, Wu S, Shen Y, Zhang S, Xiao Y, He X, Gong J, Farnell Y, Tang Y, Huang Y, Gao L. Iron oxide nanozyme suppresses intracellular Salmonella Enteritidis growth and alleviates infection in vivo. Theranostics 2018; 8(22):6149-6162. doi:10.7150/thno.29303. Available from http://www.thno.org/v08p6149.htm