The clinical utility of anthracycline anticancer agents, especially doxorubicin, is limited by a progressive toxic cardiomyopathy linked to mitochondrial damage and cardiomyocyte apoptosis. Here we demonstrate that the post-doxorubicin mouse heart fails to upregulate the nuclear program for mitochondrial biogenesis and its associated intrinsic antiapoptosis proteins, leading to severe mitochondrial DNA (mtDNA) depletion, sarcomere destruction, apoptosis, necrosis, and excessive wall stress and fibrosis. Furthermore, we exploited recent evidence that mitochondrial biogenesis is regulated by the CO/heme oxygenase (CO/HO) system to ameliorate doxorubicin cardiomyopathy in mice. We found that the myocardial pathology was averted by periodic CO inhalation, which restored mitochondrial biogenesis and circumvented intrinsic apoptosis through caspase-3 and apoptosis-inducing factor. Moreover, CO simultaneously reversed doxorubicin-induced loss of DNA binding by GATA-4 and restored critical sarcomeric proteins. In isolated rat cardiac cells, HO-1 enzyme overexpression prevented doxorubicin-induced mtDNA depletion and apoptosis via activation of Akt1/PKB and guanylate cyclase, while HO-1 gene silencing exacerbated doxorubicin-induced mtDNA depletion and apoptosis. Thus doxorubicin disrupts cardiac mitochondrial biogenesis, which promotes intrinsic apoptosis, while CO/HO promotes mitochondrial biogenesis and opposes apoptosis, forestalling fibrosis and cardiomyopathy. These findings imply that the therapeutic index of anthracycline cancer chemotherapeutics can be improved by the protection of cardiac mitochondrial biogenesis.

The induction of heme oxygenase-1 (HO-1; Hmox1) by inflammation, for instance in sepsis, is associated both with an anti-inflammatory response and with mitochondrial biogenesis. Here, we tested the idea that HO-1, acting through the Nfe2l2 (Nrf2) transcription factor, links anti-inflammatory cytokine expression to activation of mitochondrial biogenesis. HO-1 induction after LPS stimulated anti-inflammatory IL-10 and IL-1 receptor antagonist (IL-1Ra) expression in mouse liver, human HepG2 cells, and mouse J774.1 macrophages but blunted tumor necrosis factor-␣ expression. This was accompanied by nuclear Nfe2l2 accumulation and led us to identify abundant Nfe2l2 and other mitochondrial biogenesis transcription factor binding sites in the promoter regions of IL10 and IL1Ra compared with pro-inflammatory genes regulated by NF-〉. Mechanistically, HO-1, through its CO product, enabled these transcription factors to bind the core IL10 and IL1Ra promoters, which for IL10 included Nfe2l2, nuclear respiratory factor (NRF)-2 (Gabpa), and MEF2, and for IL1Ra, included NRF-1 and MEF2. In cells, Hmox1 or Nfe2l2 RNA silencing prevented IL-10 and IL-1Ra up-regulation, and HO-1 induction failed post-LPS in Nfe2l2-silenced cells and post-sepsis in Nfe2l2 ؊/؊ mice. Nfe2l2 ؊/؊ mice compared with WT mice, showed more liver damage, higher mortality, and ineffective CO rescue in sepsis. Nfe2l2 ؊/؊ mice in sepsis also generated higher hepatic TNF-␣ mRNA levels, lower NRF-1 and PGC-1␣ mRNA levels, and no enhancement of anti-inflammatory Il10, Socs3, or bcl-x L gene expression. These findings disclose a highly structured transcriptional network that couples mitochondrial biogenesis to counter-inflammation with major implications for immune suppression in sepsis.Early survivors of severe sepsis often develop immune suppression (1, 2) and may later die with the multiple organ dysfunction syndrome (3). A key effector of multiple organ dysfunction syndrome is the liver, which is integral to the host response, especially in infections that activate Toll-like receptor 4 and NF-〉-dependent cytokine synthesis (4). The persistence of inflammatory cytokines such as TNF-␣ and IL-1␤ perpetuates immune activation, causing tissue damage and remodeling (5) and leads to sustained production of anti-inflammatory modulators and suppressors of adaptive immunity (6, 7).These anti-inflammatory modulators include the type II cytokine IL-10, the soluble IL-1 receptor antagonist (sIL-1Ra) 2 (5), and SOCS (suppressor of cytokine signaling) proteins (8). IL-10 is widely expressed in the liver (9, 10) by Kupffer cells (11), stellate cells (12), and hepatocytes (13), where it contributes to LPS tolerance (14). The IL-10 receptor activates JAK/STAT (Janus kinase/signal transducer and activator of transcription) to block the production of TNF-␣ and other NF-〉-dependent mediators (15), the basis for its anti-inflammatory effects (16). IL-10 also suppresses mononuclear cell function (17), and IL-10 secretion by macrophages and neutrophils negatively regulates the respon...

Rationale: The extent, timing, and significance of mitochondrial injury and recovery in bacterial sepsis are poorly characterized, although oxidative and nitrosative mitochondrial damage have been implicated in the development of organ failure. Objectives: To define the relationships between mitochondrial biogenesis, oxidative metabolism, and recovery from Staphylococcus aureus sepsis. Methods: We developed a murine model of fibrin clot peritonitis, using S. aureus. The model yielded dose-dependent decreases in survival and resting energy expenditure, allowing us to study recovery from sublethal sepsis. Measurements and Main Results: Peritonitis caused by 10 6 colonyforming units of S. aureus induced a low tumor necrosis factor-a state and minimal hepatic cell death, but activated prosurvival protein kinase A, B, and C sequentially over 3 days. Basal metabolism by indirect calorimetry was depressed because of selective mitochondrial oxidative stress and subsequent loss of mitochondrial DNA copy number. During recovery, mitochondrial biogenesis was strongly activated by regulated expression of the requisite nuclear respiratory factors 1 and 2 and the coactivator peroxisome proliferatoractivated receptor g coactivator-1a, as well as by repression of the biogenesis suppressor nuclear receptor interacting protein-140. Biogenesis reconstituted mitochondrial DNA copy number and transcription, and restored basal metabolism without significant hepatocellular proliferation. These events dramatically increased hepatic mitochondrial density in transgenic mice expressing mitochondrially targeted green fluorescent protein.Conclusions: This is the first demonstration that mitochondrial biogenesis restores oxidative metabolism in bacterial sepsis and is therefore an early and important prosurvival factor.

Sepsis-induced tissue factor (TF) expression activates coagulation in the lung and leads to a procoagulant environment, which results in fibrin deposition and potentiates inflammation. We hypothesized that preventing initiation of coagulation at TF-Factor VIIa (FVIIa) complex would block fibrin deposition and control inflammation in sepsis, thereby limiting acute lung injury (ALI) and other organ damage in baboons. A model of ALI was used in which adult baboons were primed with killed Escherichia coli (1 x 10(9) CFU/kg), and bacteremic sepsis was induced 12 h later by infusion of live E. coli at 1 x 10(10) CFU/kg. Animals in the treatment group were given a competitive inhibitor of TF, site-inactivated FVIIa (FVIIai), intravenously at the time of the infusion of live bacteria and monitored physiologically for another 36 h. FVIIai dramatically protected gas exchange and lung compliance, prevented lung edema and pulmonary hypertension, and preserved renal function relative to vehicle (all p < 0.05). Treatment attenuated sepsis-induced fibrinogen depletion (p < 0.01) and decreased systemic proinflammatory cytokine responses, for example, interleukin 6 (p < 0.01). The protective effects of TF blockade in sepsis-induced ALI were confirmed by using tissue factor pathway inhibitor. The results show that TF-FVIIa complex contributes to organ injury in septic primates in part through selective stimulation of proinflammatory cytokine release and fibrin deposition.