Low-dose cadmium potentiates lung inflammatory response to 2009 pandemic H1N1 influenza virus in mice

BACKGROUND Cadmium (Cd) is a toxic, pro-inflammatory metal ubiquitous in the diet that accumulates in body organs due to inefficient elimination. Many individuals exposed to dietary Cd are also infected by seasonal influenza virus. The H1N1 strain causes mild to severe pneumonia which can be fatal. OBJECTIVES To determine the influence of low-dose Cd exposure on inflammatory responses to H1N1 influenza A virus. METHODS We exposed mice to low-dose (1 mg CdCl2/l) Cd or vehicle (water) for 16 weeks prior to infection with a sub-lethal dose of H1N1. Lung inflammation was assessed by histopathology and flow cytometry. We used a combination of transcriptomics, metabolomics and bioinformatics to determine the molecular associations of inflammatory cells important in Cd-exacerbated responses. RESULTS Cd-treated mice had increased lung tissue inflammatory cells, including neutrophils, monocytes, T lymphocytes and dendritic cells, following H1N1 infection. Lung genetic responses to infection (increasing TNF-a, interferon and complement, and decreasing myogenesis) were also exacerbated. Global correlations with immune cell counts, leading edge gene transcripts and metabolites revealed that Cd increased correlation of myeloid immune cells with pro-inflammatory genes, particularly interferon-γ, and metabolites in amino acid, nucleobase, glycerophospholipid and vitamin B3 pathways. DISCUSSION Cd burden in mice increased inflammation in response to sub-lethal H1N1 challenge, which was coordinated by genetic and metabolic responses, and could provide new targets for intervention against lethal inflammatory pathology of clinical H1N1 infection. Dr. Young-Mi Go and Dr. Dean P. Jones share equal senior authorship in this collaborative research. We thank the Emory Integrated Genomics Core, Dana B. Barr PhD and Priya E. D’Souza MPH for technical assistance. This study was supported by NIEHS Grant R01 ES023485 (DPJ and YMG), R21 ES025632 (DPJ and YMG), NIH S10 OD018006 (DPJ), NIH/NIAID grants R01 AI105170 (SMK), R01 AI093772 (SMK), and R21 AI119366 (SMK), and NHLBI F32 1F32HL132493 (JDC) and Cystic Fibrosis Foundation CHANDL16F0 (JDC). ### Author Contributions Abbreviations : Cd : Cadmium; Ctl : control; Cys : cysteine; CySS : cystine; FACS : fluorescence-activated cell sorting; FDR : False discovery rate; GSEA : Gene set enrichment analysis; H1N1 : pandemic 2009 influenza A (H1N1) virus; HRM : High resolution metabolomics; ICP-MS : Inductively coupled plasma mass spectrometer; IFNγ : interferon gamma IL-1β : interleukin-1beta; LC : liquid chromatograph; MS : mass spectrometer; m/z : mass to charge; RT : retention time; sPLS : sparse partial least squares; Trx : thioredoxin