Impaired clearance of influenza A virus in obese, leptin receptor deficient mice is independent of leptin signaling in the lung epithelium and macrophages - PubMed (original) (raw)

. 2014 Sep 18;9(9):e108138.

doi: 10.1371/journal.pone.0108138. eCollection 2014.

Luisa Morales-Nebreda 1, Saul Soberanes 1, Trevor Nicholson 1, Recep Nigdelioglu 1, Takugo Cho 1, Monica Chi 1, Robert B Hamanaka 1, Alexander V Misharin 2, Harris Perlman 2, G R Scott Budinger 1, Gökhan M Mutlu 1

Affiliations

Impaired clearance of influenza A virus in obese, leptin receptor deficient mice is independent of leptin signaling in the lung epithelium and macrophages

Kathryn A Radigan et al. PLoS One. 2014.

Abstract

Rationale: During the recent H1N1 outbreak, obese patients had worsened lung injury and increased mortality. We used a murine model of influenza A pneumonia to test the hypothesis that leptin receptor deficiency might explain the enhanced mortality in obese patients.

Methods: We infected wild-type, obese mice globally deficient in the leptin receptor (db/db) and non-obese mice with tissue specific deletion of the leptin receptor in the lung epithelium (SPC-Cre/LepR fl/fl) or macrophages and alveolar type II cells (LysM-Cre/Lepr fl/fl) with influenza A virus (A/WSN/33 [H1N1]) (500 and 1500 pfu/mouse) and measured mortality, viral clearance and several markers of lung injury severity.

Results: The clearance of influenza A virus from the lungs of mice was impaired in obese mice globally deficient in the leptin receptor (db/db) compared to normal weight wild-type mice. In contrast, non-obese, SP-C-Cre+/+/LepR fl/fl and LysM-Cre+/+/LepR fl/fl had improved viral clearance after influenza A infection. In obese mice, mortality was increased compared with wild-type mice, while the SP-C-Cre+/+/LepR fl/fl and LysM-Cre+/+/LepR fl/fl mice exhibited improved survival.

Conclusions: Global loss of the leptin receptor results in reduced viral clearance and worse outcomes following influenza A infection. These findings are not the result of the loss of leptin signaling in lung epithelial cells or macrophages. Our results suggest that factors associated with obesity or with leptin signaling in non-myeloid populations such as natural killer and T cells may be associated with worsened outcomes following influenza A infection.

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Conflict of interest statement

Competing Interests: Co-author Gökhan Mutlu is a PLOS ONE Editorial Board member. This does not alter the authors' adherence to PLOS ONE Editorial policies and criteria.

Figures

Figure 1

Figure 1. Effect of leptin receptor function on the survival, the degree of lung injury and inflammation during influenza A infection.

db/db and C57BL/6 mice were inoculated with influenza A virus (A/WSN/33 [H1N1]) (a) 1500 pfu/mouse or (b) 500 pfu/mouse and mortality was subsequently assessed on a daily basis. Percentage of weight loss was also followed daily for the mice infected with (c) 1500 pfu/mouse or (d) 500 pfu/mouse. Four days after infection with influenza A virus 1500 pfu/mouse, db/db and C57BL/6 mice underwent a bronchoalveolar lavage for (e) assessment of cell count, (f) total protein, (g,h) inflammatory cytokines, (i) flow cytometry, and (j) the assessment of lung pathology (Hematoxylin and Eosin staining). * p<0.05 compared to PBS control. ** p<0.05 db/db compared to wild-type mice.

Figure 2

Figure 2. Effect of leptin receptor function on viral replication.

Plaque forming units (pfu) were counted in MDCK cells treated with lung homogenates from db/db and C57BL/6 mice infected with influenza A virus (a) 1500 pfu/mouse on Day 4 and (b) 500 pfu/mouse on Day 2 and Day 4. We also measured (c) interferon-α (IFN- α) levels in BALF in wild-type and db/db mice 2 days after infection with influenza A virus (1500 pfu/mouse).

Figure 3

Figure 3. Effect of the leptin receptor function specifically within lung epithelium and within macrophages and neutrophils on survival, lung injury, and inflammation during influenza A infection.

(a) Representative images and (b) weights of db/db, LepRfl/fl, SP-C-Cre+/+/LepRfl/fl, and LysM-Cre+/+/LepRfl /fl mice are shown. Quantitative real-time PCR reveals appropriate knockout of the leptin receptor (c) within the macrophages in LysM-Cre+/+/LepRfl /fl mice and (d) within the lung epithelium in SP-C-Cre+/+/LepRfl/fl mice. LepRfl/fl, SP-C-Cre+/+/LepRfl/fl, and LysM-Cre+/+/LepRfl /fl mice were inoculated with influenza A virus (500 pfu/mouse) with assessment of (e) mortality and (f) daily weight. Four days after infection with influenza A virus (500 pfu/mouse), LepRfl/fl, SP-C-Cre+/+/LepRfl/fl, and LysM-Cre+/+/LepRfl /fl mice underwent bronchoalveolar lavage for levels of (g) cell count, (h) total protein, (i–k) inflammatory cytokines and (l) lung pathology (Hematoxylin and Eosin staining).

Figure 4

Figure 4. Effect of leptin receptor function specifically within lung epithelium and within macrophages and neutrophils on viral replication.

Plaque forming units (pfu) were counted in MDCK cells treated with lung homogenates from LepRfl/fl, SP-C-Cre+/+/LepRfl/fl, and LysM-Cre+/+/LepRfl /fl mice infected with Influenza A virus 500 pfu/mouse on Day 2 and Day 4. * p<0.05 LysM-Cre+/+/LepRfl /fl and SP-C-Cre+/+/LepRfl/fl mice compared to LepRfl/fl mice.

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