title: Nrf2 promotes alveolar mitochondrial biogenesis and resolution of lung injury in Staphylococcus aureus pneumonia in mice.
abstract: Acute lung injury (ALI) initiates protective responses involving genes downstream of the Nrf2 (Nfe2l2) transcription factor, including heme oxygenase-1 (HO-1), which stimulates mitochondrial biogenesis and related anti-inflammatory processes. We examined mitochondrial biogenesis during Staphylococcus aureus pneumonia in mice and the effect of Nrf2 deficiency on lung mitochondrial biogenesis and resolution of lung inflammation. S. aureus pneumonia established by nasal insufflation of live bacteria was studied in mitochondrial reporter (mt-COX8-GFP) mice, wild-type (WT) mice, and Nrf2⁻/⁻ mice. Bronchoalveolar lavage, wet/dry ratios, real-time RT-PCR and Western analysis, immunohistochemistry, and fluorescence microscopy were performed on the lung at 0, 6, 24, and 48 h. The mice survived S. aureus inoculations at 5×10⁸ CFU despite diffuse lung inflammation and edema, but the Nrf2⁻/⁻ lung showed increased ALI. In mt-COX8-GFP mice, mitochondrial fluorescence was enhanced in bronchial and alveolar type II (AT2) epithelial cells. WT mice displayed rapid HO-1 upregulation and lower proinflammatory TNF-α, IL-1β, and CCL2 and, especially in AT2 cells, higher anti-inflammatory IL-10 and suppressor of cytokine signaling-3 than Nrf2⁻/⁻ mice. In the alveolar region, WT but not Nrf2⁻/⁻ mice showed strongly induced nuclear respiratory factor-1, PGC-1α, mitochondrial transcription factor-A, SOD2, Bnip3, mtDNA copy number, and citrate synthase. These findings indicate that S. aureus pneumonia induces Nrf2-dependent mitochondrial biogenesis in the alveolar region, mainly in AT2 cells. Absence of Nrf2 suppresses the alveolar transcriptional network for mitochondrial biogenesis and anti-inflammation, which worsens ALI. The findings link redox activation of mitochondrial biogenesis to ALI resolution.
authors.affiliation: Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA.
authors.forename: Janhavi
authors.initials: J
authors.lastname: Athale
authors.forename: Allison
authors.initials: A
authors.lastname: Ulrich
authors.forename: Nancy Chou
authors.initials: NC
authors.lastname: MacGarvey
authors.forename: Raquel R
authors.initials: RR
authors.lastname: Bartz
authors.forename: Karen E
authors.initials: KE
authors.lastname: Welty-Wolf
authors.forename: Hagir B
authors.initials: HB
authors.lastname: Suliman
authors.forename: Claude A
authors.initials: CA
authors.lastname: Piantadosi
mesh_terms: D055371:Acute Lung Injury / Q000209:etiology* / Q000378:metabolism / Q000473:pathology; D000818:Animals; D015153:Blotting, Western; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism; D005260:Female; D006801:Humans; D007124:Immunoenzyme Techniques; D018836:Inflammation Mediators / Q000378:metabolism; D016753:Interleukin-10 / Q000235:genetics / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D063269:Mitochondrial Turnover; D051267:NF-E2-Related Factor 2 / Q000502:physiology*; D010084:Oxidation-Reduction; D011014:Pneumonia / Q000209:etiology* / Q000473:pathology; D011023:Pneumonia, Staphylococcal / Q000150:complications* / Q000382:microbiology / Q000473:pathology; D011650:Pulmonary Alveoli / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D011654:Pulmonary Edema / Q000378:metabolism / Q000382:microbiology / Q000473:pathology; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013211:Staphylococcus aureus / Q000472:pathogenicity; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000235:genetics / Q000378:metabolism
chemical_list: D004272:DNA, Mitochondrial; D018836:Inflammation Mediators; D051267:NF-E2-Related Factor 2; C495636:Nfe2l2 protein, mouse; D012333:RNA, Messenger; C491411:Socs3 protein, mouse; D000071223:Suppressor of Cytokine Signaling 3 Protein; D050826:Suppressor of Cytokine Signaling Proteins; D014409:Tumor Necrosis Factor-alpha; D016753:Interleukin-10