Abstract
Hypercapnia, elevated partial pressure of CO2 in blood and tissue, develops in many patients with chronic severe obstructive pulmonary disease and other advanced lung disorders. Patients with advanced disease frequently develop bacterial lung infections, and hypercapnia is a risk factor for mortality in such individuals. We previously demonstrated that hypercapnia suppresses induction of NF-κB-regulated innate immune response genes required for host defense in human, mouse, and Drosophila cells, and it increases mortality from bacterial infections in both mice and Drosophila. However, the molecular mediators of hypercapnic immune suppression are undefined. In this study, we report a genome-wide RNA interference screen in Drosophila S2∗ cells stimulated with bacterial peptidoglycan. The screen identified 16 genes with human orthologs whose knockdown reduced hypercapnic suppression of the gene encoding the antimicrobial peptide Diptericin (Dipt), but did not increase Dipt mRNA levels in air. In vivo tests of one of the strongest screen hits, zinc finger homeodomain 2 (Zfh2; mammalian orthologs ZFHX3/ATBF1 and ZFHX4), demonstrate that reducing zfh2 function using a mutation or RNA interference improves survival of flies exposed to elevated CO2 and infected with Staphylococcus aureus. Tissue-specific knockdown of zfh2 in the fat body, the major immune and metabolic organ of the fly, mitigates hypercapnia-induced reductions in Dipt and other antimicrobial peptides and improves resistance of CO2-exposed flies to infection. Zfh2 mutations also partially rescue hypercapnia-induced delays in egg hatching, suggesting that Zfh2's role in mediating responses to hypercapnia extends beyond the immune system. Taken together, to our knowledge, these results identify Zfh2 as the first in vivo mediator of hypercapnic immune suppression.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 655-667 |
| Number of pages | 13 |
| Journal | Journal of Immunology |
| Volume | 196 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 15 2016 |
Funding
This work was supported by National Institutes of Health/National Heart, Lung, and Blood Institute Grants R01 HL107629 (to G.J.B. and P.H.S.S.) and R01 HL085534 and R01 HL071643 (to J.I.S.), as well as by grants from the Drosophila RNAi Screening Center (National Institute of General Medical Sciences Grant R01 GM067761), the RNAi Project at Harvard Medical School (National Institutes Health/National Institute of General Medical Sciences Grant R01 GM084947), and the Bloomington Drosophila Stock Center (National Institutes of Health Grant P40 OD018537), the Northwestern University Robert H. Lurie Comprehensive Cancer Center to the Northwestern University High Throughput Analysis Laboratory, and by American Heart Association Grant-in-Aid Award 0855686G (to G.J.B.) and Predoctoral Fellowship 0715562Z (to I.T.H.) We thank the staff of the Northwestern High Throughput Analysis Laboratory and Harvard DRSC, in particular Sara Fernandez Dunne and Chi-Hao Luan (Northwestern University High Throughput Analysis Laboratory) and Stephanie Mohr and Quentin Gilly (Harvard DRSC), for technical assistance. We also thank Emilia Lecuona and Neal Silverman for advice; Chris Doe for anti-Zfh2 antisera; and the Bloomington Drosophila Stock Center, the Transgenic RNAi Project at Harvard Medical School, and Sarah Elgin for fly stocks.
ASJC Scopus subject areas
- Immunology and Allergy
- Immunology
