A toll-like receptor 2 pathway regulates the Ppargc1a/b metabolic co-activators in mice with Staphylococcal aureus sepsis

Activation of the host antibacterial defenses by the toll-like receptors (TLR) also selectively activates energy-sensing and metabolic pathways, but the mechanisms are poorly understood. This includes the metabolic and mitochondrial biogenesis master co-activators, Ppargc1a (PGC-1α) and Ppargc1b (PGC-1β) in Staphylococcus aureus (S. aureus) sepsis. The expression of these genes in the liver is markedly attenuated inTLR2(-/-) mice and markedly accentuated in TLR4(-/-) mice compared with wild type (WT) mice. We sought to explain this difference by using specific TLR-pathway knockout mice to test the hypothesis that these co-activator genes are directly regulated through TLR2 signaling. By comparing their responses to S. aureus with WT mice, we found that MyD88-deficient and MAL-deficient mice expressed hepatic Ppargc1a and Ppargc1b normally, but that neither gene was activated in TRAM-deficient mice. Ppargc1a/b activation did not require NF-kβ, but did require an interferon response factor (IRF), because neither gene was activated in IRF-3/7 double-knockout mice in sepsis, but both were activated normally in Unc93b1-deficient (3d) mice. Nuclear IRF-7 levels in TLR2(-/-) and TLR4(-/-) mice decreased and increased respectively post-inoculation and IRF-7 DNA-binding at the Ppargc1a promoter was demonstrated by chromatin immunoprecipitation. Also, a TLR2-TLR4-TRAM native hepatic protein complex was detected by immunoprecipitation within 6 h of S. aureus inoculation that could support MyD88-independent signaling to Ppargc1a/b. Overall, these findings disclose a novel MyD88-independent pathway in S. aureus sepsis that links TLR2 and TLR4 signaling in innate immunity to Ppargc1a/b gene regulation in a critical metabolic organ, the liver, by means of TRAM, TRIF, and IRF-7.     

Blockade of tissue factor-factor X binding attenuates sepsis-induced respiratory and renal failure

Tissue factor expression in sepsis activates coagulation in the lung, which potentiates inflammation and leads to fibrin deposition. We hypothesized that blockade of factor X binding to the tissue factor-factor VIIa complex would prevent sepsis-induced damage to the lungs and other organs. Acute lung injury was produced in 15 adult baboons primed with killed Escherichia coli [1 x 10(9) colony-forming units (CFU)/kg], and then 12 h later, they were given 1 x 10(10) CFU/kg live E. coli by infusion. Two hours after live E. coli, animals received antibiotics with or without monoclonal antibody to tissue factor intravenously to block tissue factor-factor X binding. The animals were monitored physiologically for 34 h before being killed and their tissue harvested. The antibody treatment attenuated abnormalities in gas exchange and lung compliance, preserved renal function, and prevented tissue neutrophil influx and bowel edema relative to antibiotics alone (all P < 0.05). It also attenuated fibrinogen depletion (P < 0.01) and decreased proinflammatory cytokines, e.g., IL-6 and -8 (P < 0.01), in systemic and alveolar compartments. Similar protective effects of the antibody on IL-6 and -8 expression and permeability were found in lipopolysaccharide-stimulated endothelial cells. Blockade of factor X binding to the tissue factor-factor VIIa complex attenuates lung and organ injuries in established E. coli sepsis by attenuating the neutrophilic response and inflammatory pathways.     

Aerosolized manganese SOD decreases hyperoxic pulmonary injury in primates. II. Morphometric analysis

Welty-Wolf, Karen E., Steven G. Simonson, Yuh-Chin T. Huang,Stephen P. Kantrow, Martha S. Carraway, Ling-Yi Chang, James D. Crapo, and Claude A. Piantadosi. Aerosolizedmanganese SOD decreases hyperoxic pulmonary injury in primates. II.Morphometric analysis. J. Appl.Physiol. 83(2): 559-568, 1997.Hyperoxia damages lung parenchyma via increased cellular production of reactive oxygenspecies that exceeds antioxidant defenses. We hypothesized thataerosolized human recombinant manganese superoxide dismutase (rhMnSOD)would augment extracellular antioxidant defenses and attenuateepithelial injury in the lung during hyperoxia in primates. Twenty-fouradult male baboons were anesthetized and mechanically ventilated with100% oxygen for 96 h. The baboons were divided equally into fourgroups. Oxygen alone and oxygen plus rhMnSOD given at 3 mg · kg¹ · day¹were compared to assess efficacy of the drug. Subsequently, aerosolized rhMnSOD was given at 1 or 10 mg · kg¹ · day¹to study dose effects and toxicity. Quantitative morphometry showedprotection of alveolar epithelium from hyperoxia by 3 mg · kg¹ · day¹rhMnSOD (P < 0.05). In addition,interstitial fibroblast volumes were increased in the treatment group(P = 0.06). This effect appearedgreater at the two higher doses of the rhMnSOD. The aerosolized drugwas localized to the surface of airways and air spaces and macrophagesby immunolabeling studies, suggesting efficacy via physicochemicalproperties that localize it to cell surfaces or by effects on alveolarmacrophage function.

     

Aerosolized manganese SOD decreases hyperoxic pulmonary injury in primates. I.Physiology and biochemistry

Simonson, Steven G., Karen E. Welty-Wolf, Yuh-Chin T. Huang,David E. Taylor, Stephen P. Kantrow, Martha S. Carraway, James D. Crapo, and Claude A. Piantadosi. Aerosolizedmanganese SOD decreases hyperoxic pulmonary injury in primates. I. Physiology and biochemistry. J. Appl.Physiol. 83(2): 550-558, 1997.Prolonged hyperoxia causes lung injury andrespiratory failure secondary to oxidative tissue damage mediated, inpart, by the superoxide anion. We hypothesized that aerosol treatmentwith recombinant human manganese superoxide dismutase (rhMnSOD) wouldattenuate hyperoxic lung damage in primates. Adult baboons wereanesthetized and ventilated with 100% oxygen for 96 h or until death.Six animals were treated with aerosolized rhMnSOD (3 mg · kg¹ · day¹in divided doses), and six control animals did not receive enzyme therapy. Physiological variables were recorded every 12 h, and ventilation-perfusion ratio relationships were evaluated by using themultiple inert-gas elimination technique. After the experiments, surfactant composition and lung edema were measured. We found thatrhMnSOD significantly decreased pulmonary shunt fraction (P < 0.01) and preserved arterialoxygenation (P < 0.01) during hyperoxia. The rhMnSOD increased lung phospholipids,phosphatidylcholine and disaturated phosphatidylcholine, and decreasedlung edema in this model. Testing of higher and lower doses of MnSOD (1 and 10 mg · kg¹ · day¹)in two other groups of baboons produced variable physiological protection, suggesting a "window" of effective dosage. Weconclude that aerosolized MnSOD (3 mg · kg¹ · day¹)affords significant preservation of pulmonary gas exchange during hyperoxic lung injury.

     

Staphylococcus aureus Sepsis Induces Early Renal Mitochondrial DNA Repair and Mitochondrial Biogenesis in Mice

Acute kidney injury (AKI) contributes to the high morbidity and mortality of multi-system organ failure in sepsis. However, recovery of renal function after sepsis-induced AKI suggests active repair of energy-producing pathways. Here, we tested the hypothesis in mice that Staphyloccocus aureus sepsis damages mitochondrial DNA (mtDNA) in the kidney and activates mtDNA repair and mitochondrial biogenesis. Sepsis was induced in wild-type C57Bl/6J and Cox-8 Gfp-tagged mitochondrial-reporter mice via intraperitoneal fibrin clots embedded with S. aureus. Kidneys from surviving mice were harvested at time zero (control), 24, or 48 hours after infection and evaluated for renal inflammation, oxidative stress markers, mtDNA content, and mitochondrial biogenesis markers, and OGG1 and UDG mitochondrial DNA repair enzymes. We examined the kidneys of the mitochondrial reporter mice for changes in staining density and distribution. S. aureus sepsis induced sharp amplification of renal Tnf, Il-10, and Ngal mRNAs with decreased renal mtDNA content and increased tubular and glomerular cell death and accumulation of protein carbonyls and 8-OHdG. Subsequently, mtDNA repair and mitochondrial biogenesis was evidenced by elevated OGG1 levels and significant increases in NRF-1, NRF-2, and mtTFA expression. Overall, renal mitochondrial mass, tracked by citrate synthase mRNA and protein, increased in parallel with changes in mitochondrial GFP-fluorescence especially in proximal tubules in the renal cortex and medulla. Sub-lethal S. aureus sepsis thus induces widespread renal mitochondrial damage that triggers the induction of the renal mtDNA repair protein, OGG1, and mitochondrial biogenesis as a conspicuous resolution mechanism after systemic bacterial infection.     

Similar but not the same: normobaric and hyperbaric pulmonary oxygen toxicity, the role of nitric oxide

Pulmonary manifestations of oxygen toxicity were studied and quantified in rats breathing >98% O(2) at 1, 1.5, 2, 2.5, and 3 ATA to test our hypothesis that different patterns of pulmonary injury would emerge, reflecting a role for central nervous system (CNS) excitation by hyperbaric oxygen. At 1.5 atmosphere absolute (ATA) and below, the well-recognized pattern of diffuse pulmonary damage developed slowly with an extensive inflammatory response and destruction of the alveolar-capillary barrier leading to edema, impaired gas exchange, respiratory failure, and death; the severity of these effects increased with time over the 56-h period of observation. At higher inspired O(2) pressures, 2-3 ATA, pulmonary injury was greatly accelerated but less inflammatory in character, and events in the brain were a prelude to a distinct lung pathology. The CNS-mediated component of this lung injury could be attenuated by selective inhibition of neuronal nitric oxide synthase (nNOS) or by unilateral transection of the vagus nerve. We propose that extrapulmonary, neurogenic events predominate in the pathogenesis of acute pulmonary oxygen toxicity in hyperbaric oxygenation, as nNOS activity drives lung injury by modulating the output of central autonomic pathways.