Lung Cancer Survivorship: Physical, Social, Emotional, and Medical Needs of NSCLC Survivors.

BACKGROUND: Newer therapies prolong survival for patients with lung cancer. Beyond extending survival, the needs of lung cancer (LC) survivors are poorly described. METHODS: We conducted a single-institution needs assessment survey of LC survivors alive ≥1 year from diagnosis. Needs were rated on a 5-point Likert scale for 4 domains (physical, social, emotional, and medical). Multiple regression models identified demographic or treatment characteristics associated with more needs in each category. A subset analysis of survivors with metastatic LC was performed. RESULTS: Of 360 patients approached, 235 surveys were completed. Among completed survey respondents, the median age was 69 years; most were female (62%), married (71%), and White (74%); and 41% had stage IV cancer. Finding support resources (34%) was the most common medical need. Fatigue (70%), sleep disturbance (60%), memory and concentration (57.5%), weakness (54%), and trouble breathing (51%) were physical needs affecting more than half of respondents. The most common social need was managing daily activities (42%). Emotional needs were highly prevalent, with 79% of respondents reporting a fear of recurrence and 74.5% reporting living with uncertainty. Multiple regression analysis identified that receipt of multiple lines of systemic therapy and lower household income were associated with higher physical and social needs. Younger age was associated with having a greater number of social and emotional needs. Similar results were found in the subset of survivors with metastatic disease at diagnosis. CONCLUSIONS: The needs of LC survivors are diverse across multiple domains. Several clinical and demographic factors are independently associated with higher numbers of patient-reported needs. Our study identifies critical gaps in survivorship care for LC survivors with all stages of disease and highlights areas of future intervention.

Effect of Fatty Acid Composition in Polysorbate 80 on the Stability of Therapeutic Protein Formulations.

PURPOSE: Polysorbate excipients are commonly used as surfactants to stabilize therapeutic proteins in formulations. Degradation of polysorbates could lead to particle formation and instability of the drug formulation. We investigated how the fatty acid composition of polysorbate 80 impacts the degradation profile, particle formation, and product stability under stress conditions. METHODS: Two polysorbate 80-containing therapeutic protein formulations were reformulated with either Polysorbate 80 NF synthesized from a fatty acid mixture that contains mainly oleic acid (≥58%) or a version of polysorbate 80 synthesized with high oleic acid (>98%). Stress conditions, including high temperature and esterase spiking, were applied and changes to both the polysorbate and the therapeutic protein product were investigated for stability, purity, innate immune response and biological activity. RESULTS: The addition of esterase and storage at 37°C led to significant hydrolysis of the polysorbate and increases in sub-visible particle formation for both polysorbates tested. The fatty acid composition of polysorbate 80 did not directly alter the stability profile of either therapeutic protein as measured by size exclusion chromatography, or significantly impact innate immune response or biological activity. However, formulations with Polysorbate 80 NF showed greater propensity for sub-visible particle formation under stress conditions. CONCLUSIONS: These results suggest that composition of fatty acids in polysorbate 80 may be a promoter for sub-visible particulate formation under the stress conditions tested but may not impact protein aggregation or biological activity.

Metastasis-Specific Gene Expression in Autochthonous and Allograft Mouse Mammary Tumor Models: Stratification and Identification of Targetable Signatures.

Breast cancer metastasis is a leading cause of cancer-related death of women in the United States. A hurdle in advancing metastasis-targeted intervention is the phenotypic heterogeneity between primary and secondary lesions. To identify metastasis-specific gene expression profiles we performed RNA-sequencing of breast cancer mouse models; analyzing metastases from models of various drivers and routes. We contrasted the models and identified common, targetable signatures. Allograft models exhibited more mesenchymal-like gene expression than genetically engineered mouse models (GEMM), and primary culturing of GEMM-derived metastatic tissue induced mesenchymal-like gene expression. In addition, metastasis-specific transcriptomes differed between tail vein and orthotopic injection of the same cell line. Gene expression common to models of spontaneous metastasis included sildenafil response and nicotine degradation pathways. Strikingly, in vivo sildenafil treatment significantly reduced metastasis by 54%, while nicotine significantly increased metastasis by 46%. These data suggest that (i) actionable metastasis-specific pathways can be readily identified, (ii) already available drugs may have great potential to alleviate metastatic incidence, and (iii) metastasis may be influenced greatly by lifestyle choices such as the choice to consume nicotine products. In summary, while mouse models of breast cancer metastasis vary in ways that must not be ignored, there are shared features that can be identified and potentially targeted therapeutically. IMPLICATIONS: The data we present here exposes critical variances between preclinical models of metastatic breast cancer and identifies targetable pathways integral to metastatic spread. VISUAL OVERVIEW: http://mcr.aacrjournals.org/content/molcanres/18/9/1278/F1.large.jpg.

The genomic landscape of metastasis in treatment-naïve breast cancer models.

Metastasis remains the principle cause of mortality for breast cancer and presents a critical challenge because secondary lesions are often refractory to conventional treatments. While specific genetic alterations are tightly linked to primary tumor development and progression, the role of genetic alteration in the metastatic process is not well-understood. The theory of tumor evolution postulated by Peter Nowell in 1976 has yet to be proven in the context of metastasis. Therefore, in order to investigate how somatic evolution contributes to breast cancer metastasis, we performed exome, whole genome, and RNA sequencing of matched metastatic and primary tumors from pre-clinical mouse models of breast cancer. Here we show that in a treatment-naïve setting, recurrent single nucleotide variants and copy number variation, but not gene fusion events, play key metastasis-driving roles in breast cancer. For instance, we identified recurrent mutations in Kras, a known driver of colorectal and lung tumorigenesis that has not been previously implicated in breast cancer metastasis. However, in a set of in vivo proof-of-concept experiments we show that the Kras G12D mutation is sufficient to significantly promote metastasis using three syngeneic allograft models. The work herein confirms the existence of metastasis-driving mutations and presents a novel framework to identify actionable metastasis-targeted therapies.

Integrated analyses of murine breast cancer models reveal critical parallels with human disease.

Mouse models have an essential role in cancer research, yet little is known about how various models resemble human cancer at a genomic level. Here, we complete whole genome sequencing and transcriptome profiling of two widely used mouse models of breast cancer, MMTV-Neu and MMTV-PyMT. Through integrative in vitro and in vivo studies, we identify copy number alterations in key extracellular matrix proteins including collagen 1 type 1 alpha 1 (COL1A1) and chondroadherin (CHAD) that drive metastasis in these mouse models. In addition to copy number alterations, we observe a propensity of the tumors to modulate tyrosine kinase-mediated signaling through mutation of phosphatases such as PTPRH in the MMTV-PyMT mouse model. Mutation in PTPRH leads to increased phospho-EGFR levels and decreased latency. These findings underscore the importance of understanding the complete genomic landscape of a mouse model and illustrate the utility this has in understanding human cancers.

Kinase Inactive Tyrosine Kinase (Tyk2) Supports Differentiation of Brown Fat Cells.

It has been known for decades that brown adipose tissue (BAT) plays a central role in maintaining body temperature in hibernating animals and human infants. Recently, it has become evident that there are also depots of brown fat in adult humans, and the mass of brown fat is inversely correlated with body weight. There are a variety of transcription factors implicated in the differentiation of classical Myf5+ brown preadipocytes, one of the most important of which is PRDM16. We have recently identified that in addition to PRDM16, the tyrosine kinase Tyk2 and the STAT3 transcription factor are required for the differentiation of Myf5 positive brown preadipocytes both in cell culture and in mice. Tyk2 is a member of the Jak family of tyrosine kinases, which are activated by exposure of cells to different cytokines and growth factors. In this study we report the surprising observation that a mutated form of Tyk2, which lacks tyrosine kinase activity (Tyk2KD) restores differentiation of brown preadipocytes in vitro as well as in Tyk2-/- mice. Furthermore, expression of the Tyk2KD transgene in brown fat reverses the obese phenotype of Tyk2-/- animals. Treatment of cells with Jak-selective inhibitors suggests that the mechanism by which Tyk2KD functions to restore BAT differentiation is by dimerizing with kinase active Jak1 or Jak2. These results indicate that there are redundant mechanisms by which members of the Jak family can contribute to differentiation of BAT.

Endothelial precursor cell-based therapy to target the pathologic angiogenesis and compensate tumor hypoxia.

Hypoxia-inducing pathologies as cancer develop pathologic and inefficient angiogenesis which rules tumor facilitating microenvironment, a key target for therapy. As such, the putative ability of endothelial precursor cells (EPCs) to specifically home to hypoxic sites of neovascularization prompted to design optimized, site-specific, cell-mediated, drug-/gene-targeting approach. Thus, EPC lines were established from aorta-gonad-mesonephros (AGM) of murine 10.5 dpc and 11.5 dpc embryo when endothelial repertoire is completed. Lines representing early endothelial differentiation steps were selected: MAgEC10.5 and MagEC11.5. Distinct in maturation, they differently express VEGF receptors, VE-cadherin and chemokine/receptors. MAgEC11.5, more differentiated than MAgEC 10.5, displayed faster angiogenesis in vitro, different response to hypoxia and chemokines. Both MAgEC lines cooperated to tube-like formation with mature endothelial cells and invaded tumor spheroids through a vasculogenesis-like process. In vivo, both MAgEC-formed vessels established blood flow. Intravenously injected, both MAgECs invaded Matrigel(TM)-plugs and targeted tumors. Here we show that EPCs (MAgEC11.5) target tumor angiogenesis and allow local overexpression of hypoxia-driven soluble VEGF-receptor2 enabling drastic tumor growth reduction. We propose that such EPCs, able to target tumor angiogenesis, could act as therapeutic gene vehicles to inhibit tumor growth by vessel normalization resulting from tumor hypoxia alleviation.

Acquired deficiency of tafazzin in the adult heart: Impact on mitochondrial function and response to cardiac injury.

The content and composition of cardiolipin (CL) is critical for preservation of mitochondrial oxidative phosphorylation (OXPHOS) and inner membrane integrity. Tafazzin (Taz) is an enzyme responsible for remodeling of immature CL containing mixed acyl groups into the mature tetralinoleyl form (C18:2)4-CL. We hypothesized that acquired defects in Taz in the mature heart would impact remodeling of CL and augment cardiac injury. The role of acquired Taz deficiency was studied using the inducible Taz knockdown (TazKD) mouse. Taz-specific shRNA is induced by doxycycline (DOX). One day of DOX intake decreased Taz mRNA in the heart to 20% vs. DOX-treated WT. Knockdown was initiated at an adult age and was stable during long term feeding. CL phenotype was assessed by (C18:2)4-CL content and was reduced 40% vs. WT at two months of DOX. TazKD showed increased production of reactive oxygen species and increased susceptibility to permeability transition pore opening at baseline. However, OXPHOS measured using the rate of oxygen consumption was unchanged in the setting of acquired Taz deficiency. Infarct size, measured in isolated buffer-perfused Langendorff hearts following 25min. Stop flow ischemia and 60min. Reperfusion was not altered in TazKD hearts. Thus, impaired Taz-function with onset at adult age does not enhance susceptibility to ischemia-reperfusion injury.

The Signal Transducer and Activator of Transcription 1 (STAT1) Inhibits Mitochondrial Biogenesis in Liver and Fatty Acid Oxidation in Adipocytes.

The transcription factor STAT1 plays a central role in orchestrating responses to various pathogens by activating the transcription of nuclear-encoded genes that mediate the antiviral, the antigrowth, and immune surveillance effects of interferons and other cytokines. In addition to regulating gene expression, we report that STAT1-/- mice display increased energy expenditure and paradoxically decreased release of triglycerides from white adipose tissue (WAT). Liver mitochondria from STAT1-/- mice show both defects in coupling of the electron transport chain (ETC) and increased numbers of mitochondria. Consistent with elevated numbers of mitochondria, STAT1-/- mice expressed increased amounts of PGC1α, a master regulator of mitochondrial biogenesis. STAT1 binds to the PGC1α promoter in fed mice but not in fasted animals, suggesting that STAT1 inhibited transcription of PGC1α. Since STAT1-/- mice utilized more lipids we examined white adipose tissue (WAT) stores. Contrary to expectations, fasted STAT1-/- mice did not lose lipid from WAT. ß-adrenergic stimulation of glycerol release from isolated STAT1-/- WAT was decreased, while activation of hormone sensitive lipase was not changed. These findings suggest that STAT1-/- adipose tissue does not release glycerol and that free fatty acids (FFA) re-esterify back to triglycerides, thus maintaining fat mass in fasted STAT1-/- mice.

Cardioprotective function of mitochondrial-targeted and transcriptionally inactive STAT3 against ischemia and reperfusion injury.

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor that contributes a crucial role in protection against ischemia (ISC)-reperfusion (REP) injury by driving expression of anti-apoptotic and anti-oxidant genes. STAT3 is also present in the mitochondria, where it modulates the activity of the electron transport chain (ETC) and the permeability transition pore. Transgenic mice that overexpress a mitochondrial-targeted, transcriptionally inactive STAT3 in cardiomyocytes (MLS-STAT3E mice) exhibit a persistent, partial blockade of electron transfer through complex I that uniquely did not lead to tissue dysfunction at baseline, yet increased mitochondrial ischemic tolerance. The direct contribution of non-transcriptional, mitochondria-localized STAT3 to protection during ISC-REP remains to be established. We hypothesized that the enhanced mitochondrial tolerance to ischemia present in MLS-STAT3E mice would decrease cardiac injury during ISC-REP. In the isolated buffer-perfused heart model, MLS-STAT3E hearts exhibit a decreased infarct size compared to non-transgenic littermate hearts. Contractile recovery, expressed as a percent of LV developed pressure before ISC, is improved in MLS-STAT3E mice. Mitochondria isolated at the end of 60 min. of REP from MLS-STAT3E hearts show attenuated ROS release. The partial and persistent blockade of complex I present in MLS-STAT3E mice decreases cardiac injury during REP, in part via a persistent decrease in ROS production and attenuation of mitochondrial permeability transition pore opening at the onset of REP. In vivo, MLS-STAT3E hearts exhibit substantially higher postoperative survival rate and a substantial decrease in myocardial infarct size. STAT3 mediates cardioprotection not only via canonical action as a transcription factor, but also as a modulator of ETC activity directly in the mitochondria.

Targeting metastatic breast cancer: problems and potential.

Breast cancer is one of the leading causes of cancer-related mortality of women in the United States. Since the majority of cancer deaths are due to metastases rather than the primary tumor, a better understanding of the biological mechanisms that lead to metastatic disease is critical to reduce breast cancer associated mortality. Current adjuvant therapies use the same broadly cytotoxic and targeted strategies against metastases as are used against the primary tumor. However, resistance to chemotherapy due to the cellular dormancy, high genotypic and phenotypic heterogeneity between primary tumor and metastases as well as among individual metastases, and the limitations in detection of disseminated tumor cells and micrometastases significantly hinder the efficiency of currently available therapies. While it is crucial to directly address the issue of metastatic dormancy and evaluate for anti-metastatic therapy the relevance of molecular targets chosen based on primary tumor profiling, it is also imperative to address metastasis-specific mechanisms of growth and survival that are likely to be distinct from those of the primary tumor. We believe that a three-pronged approach to therapy will be necessary to deal with progressive disease: blocking of further dissemination after diagnosis; eradication of disseminated tumor cells and prevention of the dormant-to-proliferative switch of those remaining; and elimination of established metastatic tumors. The implementation of this strategy requires a greater depth of knowledge of metastasis driver and maintenance genes and suggests the need for a "Metastasis Genome Atlas" project to complement the current investigations into cancer genomic landscapes.

A deficiency of apoptosis inducing factor (AIF) in Harlequin mouse heart mitochondria paradoxically reduces ROS generation during ischemia-reperfusion.

BACKGROUND AND AIMS: AIF (apoptosis inducing factor) is a flavin and NADH containing protein located within mitochondria required for optimal function of the respiratory chain. AIF may function as an antioxidant within mitochondria, yet when released from mitochondria it activates caspase-independent cell death. The Harlequin (Hq) mouse has a markedly reduced content of AIF, providing an experimental model to query if the main role of AIF in the exacerbation of cell death is enhanced mitochondrial generation of reactive oxygen species (ROS) or the activation of cell death programs. We asked if the ROS generation is altered in Hq heart mitochondria at baseline or following ischemia-reperfusion (IR). METHODS: Buffer perfused mouse hearts underwent 30 min ischemia and 30 min reperfusion. Mitochondrial function including oxidative phosphorylation and H2O2 generation was measured. Immunoblotting was used to determine the contents of AIF and PAR [poly(ADP-ribose)] in cell fractions. RESULTS: There were no differences in the release of H2O2 between wild type (WT) and Hq heart mitochondria at baseline. IR increased H2O2 generation from WT but not from Hq mitochondria compared to corresponding time controls. The complex I activity was decreased in WT but not in Hq mice following IR. The relocation of AIF from mitochondria to nucleus was increased in WT but not in Hq mice. IR activated PARP-1 only in WT mice. Cell injury was decreased in the Hq mouse heart following in vitro IR. CONCLUSION: A deficiency of AIF within mitochondria does not increase ROS production during IR, indicating that AIF functions less as an antioxidant within mitochondria. The decreased cardiac injury in Hq mouse heart accompanied by less AIF translocation to the nucleus suggests that AIF relocation, rather than the AIF content within mitochondria, contributes to cardiac injury during IR.

Electron flow into cytochrome c coupled with reactive oxygen species from the electron transport chain converts cytochrome c to a cardiolipin peroxidase: role during ischemia-reperfusion.

BACKGROUND: Cytochrome c (Cyt c) is a mobile component of the electron transport chain (ETC.) which contains a tightly coordinated heme iron. In pathologic settings, a key ligand of the cyt c's heme iron, methionine (Met80), is oxidized allowing cyt c to participate in reactions as a peroxidase with cardiolipin as a target. Myocardial ischemia (ISC) results in ETC. blockade and increased production of reactive oxygen species (ROS). We hypothesized that during ischemia-reperfusion (ISC-REP); ROS generation coupled with electron flow into cyt c would oxidize Met80 and contribute to mitochondrial-mediated ETC. damage. METHODS: Mitochondria were incubated with specific substrates and inhibitors to test the contributions of ROS and electron flow into cyt c. Subsequently, cyt c and cardiolipin were analyzed. To test the pathophysiologic relevance, mouse hearts that underwent ISC-REP were tested for methionine oxidation in cyt c. RESULTS: The combination of substrate/inhibitor showed that ROS production and electron flux through cyt c are essential for the oxidation of methionine residues that lead to cardiolipin depletion. The content of cyt c methionine oxidation increases following ISC-REP in the intact heart. CONCLUSIONS: Increase in intra-mitochondrial ROS coupled with electron flow into cyt c, oxidizes cyt c followed by depletion of cardiolipin. ISC-REP increases methionine oxidation, supporting that cyt c peroxidase activity can form in the intact heart. GENERAL SIGNIFICANCE: This study identifies a new site in the ETC. that is damaged during cardiac ISC-REP. Generation of a neoperoxidase activity of cyt c favors the formation of a defective ETC. that activates signaling for cell death.

Transient complex I inhibition at the onset of reperfusion by extracellular acidification decreases cardiac injury.

A reversible inhibition of mitochondrial respiration by complex I inhibition at the onset of reperfusion decreases injury in buffer-perfused hearts. Administration of acidic reperfusate for a brief period at reperfusion decreases cardiac injury. We asked if acidification treatment decreased cardiac injury during reperfusion by inhibiting complex I. Exposure of isolated mouse heart mitochondria to acidic buffer decreased the complex I substrate-stimulated respiration, whereas respiration with complex II substrates was unaltered. Evidence of the rapid and reversible inhibition of complex I by an acidic environment was obtained at the level of isolated complex, intact mitochondria and in situ mitochondria in digitonin-permeabilized cardiac myocytes. Moreover, ischemia-damaged complex I was also reversibly inhibited by an acidic environment. In the buffer-perfused mouse heart, reperfusion with pH 6.6 buffer for the initial 5 min decreased infarction. Compared with untreated hearts, acidification treatment markedly decreased the mitochondrial generation of reactive oxygen species and improved mitochondrial calcium retention capacity and inner mitochondrial membrane integrity. The decrease in infarct size achieved by acidic reperfusion approximates the reduction obtained by a reversible, partial blockade of complex I at reperfusion. Extracellular acidification decreases cardiac injury during reperfusion in part via the transient and reversible inhibition of complex I, leading to a reduction of oxyradical generation accompanied by a decreased susceptibility to mitochondrial permeability transition during early reperfusion.

Mitochondrial localized Stat3 promotes breast cancer growth via phosphorylation of serine 727.

Signal transducer and activator of transcription 3 (Stat3) is a key mediator in the development of many cancers. For 20 years, it has been assumed that Stat3 mediates its biological activities as a nuclear localized transcription factor activated by many cytokines. However, recent studies from this laboratory and others indicate that Stat3 has an independent function in the mitochondria (mitoStat3) where it controls the activity of the electron transport chain (ETC) and mediates Ras-induced transformation of mouse embryo fibroblasts. The actions of mitoStat3 in controlling respiration and Ras transformation are mediated by the phosphorylation state of serine 727. To address the role of mitoStat3 in the pathogenesis of cells that are transformed, we used 4T1 breast cancer cells, which form tumors that metastasize in immunocompetent mice. Substitution of Ser-727 for an alanine or aspartate in Stat3 that has a mitochondrial localization sequence, MLS-Stat3, has profound effects on tumor growth, complex I activity of the ETC, and accumulation of reactive oxygen species (ROS). Cells expressing MLS-Stat3(S727A) display slower tumor growth, decreased complex I activity of the ETC, and increased ROS accumulation under hypoxia compared with cells expressing MLS-Stat3. In contrast, cells expressing MLS-Stat3(S727D) show enhanced tumor growth and complex I activity and decreased production of ROS. These results highlight the importance of serine 727 of mitoStat3 in breast cancer and suggest a novel role for mitoStat3 in regulation of ROS concentrations through its action on the ETC.

Reverse electron flow-mediated ROS generation in ischemia-damaged mitochondria: role of complex I inhibition vs. depolarization of inner mitochondrial membrane.

BACKGROUND: The reverse electron flow-induced ROS generation (RFIR) is decreased in ischemia-damaged mitochondria. Cardiac ischemia leads to decreased complex I activity and depolarized inner mitochondrial membrane potential (ΔΨ) that are two key factors to affect the RFIR in isolated mitochondria. We asked if a partial inhibition of complex I activity without alteration of the ΔΨ is able to decrease the RFIR. METHODS: Cardiac mitochondria were isolated from mouse heart (C57BL/6) with and without ischemia. The rate of H2O2 production from mitochondria was determined using amplex red coupled with horseradish peroxidase. Mitochondria were isolated from the mitochondrial-targeted STAT3 overexpressing mouse (MLS-STAT3E) to clarify the role of partial complex I inhibition in RFIR production. RESULTS: The RFIR was decreased in ischemia-damaged mouse heart mitochondria with decreased complex I activity and depolarized ΔΨ. However, the RFIR was not altered in the MLS-STAT3E heart mitochondria with complex I defect but without depolarization of the ΔΨ. A slight depolarization of the ΔΨ in wild type mitochondria completely eliminated the RFIR. CONCLUSIONS: The mild uncoupling but not the partially decreased complex I activity contributes to the observed decrease in RFIR in ischemia-damaged mitochondria. GENERAL SIGNIFICANCE: The RFIR is less likely to be a key source of cardiac injury during reperfusion.

Cardioprotection by modulation of mitochondrial respiration during ischemia-reperfusion: role of apoptosis-inducing factor.

The transient, reversible blockade of electron transport (BET) during ischemia or at the onset of reperfusion protects mitochondria and decreases cardiac injury. Apoptosis inducing factor (AIF) is located within the mitochondrial intermembrane space. A release of AIF from mitochondria into cytosol and nucleus triggers caspase-independent cell death. We asked if BET prevents the loss of AIF from mitochondria as a mechanism of protection in the buffer perfused heart. BET during ischemia with amobarbital, a rapidly reversible inhibitor of mitochondrial complex I, attenuated a release of AIF from mitochondria into cytosol, in turn decreasing the formation of cleaved and activated PARP-1. These results suggest that BET-mediated protection may occur through prevention of the loss of AIF from mitochondria during ischemia-reperfusion. In order to further clarify the role of mitochondrial AIF in BET-mediated protection, Harlequin (Hq) mice, a genetic model with mitochondrial AIF deficiency, were used to test whether BET could still decrease cell injury in Hq mouse hearts during reperfusion. BET during ischemia protected Hq mouse hearts against ischemia-reperfusion injury and improved mitochondrial function in these hearts during reperfusion. Thus, cardiac injury can still be decreased in the presence of down-regulated mitochondrial AIF content. Taken together, BET during ischemia protects both hearts with normal mitochondrial AIF content and hearts with mitochondrial AIF deficiency. Although preservation of mitochondrial AIF content plays a key role in reducing cell injury during reperfusion, the protection derived from the BET is not fully dependent on AIF-driven mechanisms.

Metabolic gene remodeling and mitochondrial dysfunction in failing right ventricular hypertrophy secondary to pulmonary arterial hypertension.

BACKGROUND: Right ventricular (RV) dysfunction (RVD) is the most frequent cause of death in patients with pulmonary arterial hypertension. Although abnormal energy substrate use has been implicated in the development of chronic left heart failure, data describing such metabolic remodeling in RVD remain incomplete. Thus, we sought to characterize metabolic gene expression changes and mitochondrial dysfunction in functional and dysfunctional RV hypertrophy. METHODS AND RESULTS: Two different rat models of RV hypertrophy were studied. The model of RVD (SU5416/hypoxia) exhibited a significantly decreased gene expression of peroxisome proliferator-activated receptor-γ coactivator-1α, peroxisome proliferator-activated receptor-α and estrogen-related receptor-α. The expression of multiple peroxisome proliferator-activated receptor-γ coactivator-1α target genes required for fatty acid oxidation was similarly decreased. Decreased peroxisome proliferator-activated receptor-γ coactivator-1α expression was also associated with a net loss of mitochondrial protein and oxidative capacity. Reduced mitochondrial number was associated with a downregulation of transcription factor A, mitochondrial, and other genes required for mitochondrial biogenesis. Electron microscopy demonstrated that, in RVD tissue, mitochondria had abnormal shape and size. Lastly, respirometric analysis demonstrated that mitochondria isolated from RVD tissue had a significantly reduced ADP-stimulated (state 3) rate for complex I. Conversely, functional RV hypertrophy in the pulmonary artery banding model showed normal expression of peroxisome proliferator-activated receptor-γ coactivator-1α, whereas the expression of fatty acid oxidation genes was either preserved or unregulated. Moreover, pulmonary artery banding-RV tissue exhibited preserved transcription factor A mitochondrial expression and mitochondrial respiration despite elevated RV pressure-overload. CONCLUSIONS: Right ventricular dysfunction, but not functional RV hypertrophy in rats, demonstrates a gene expression profile compatible with a multilevel impairment of fatty acid metabolism and significant mitochondrial dysfunction, partially independent of chronic pressure-overload.

Tyk2 and Stat3 regulate brown adipose tissue differentiation and obesity.

Mice lacking the Jak tyrosine kinase member Tyk2 become progressively obese due to aberrant development of Myf5+ brown adipose tissue (BAT). Tyk2 RNA levels in BAT and skeletal muscle, which shares a common progenitor with BAT, are dramatically decreased in mice placed on a high-fat diet and in obese humans. Expression of Tyk2 or the constitutively active form of the transcription factor Stat3 (CAStat3) restores differentiation in Tyk2(-/-) brown preadipocytes. Furthermore, Tyk2(-/-) mice expressing CAStat3 transgene in BAT also show improved BAT development, normal levels of insulin, and significantly lower body weights. Stat3 binds to PRDM16, a master regulator of BAT differentiation, and enhances the stability of PRDM16 protein. These results define Tyk2 and Stat3 as critical determinants of brown fat lineage and suggest that altered levels of Tyk2 are associated with obesity in both rodents and humans.

Multi-tasking: nuclear transcription factors with novel roles in the mitochondria.

Coordinated responses between the nucleus and mitochondria are essential for the maintenance of homeostasis. For over 15 years, pools of nuclear transcription factors (TFs), such as p53 and nuclear hormone receptors, have been observed in the mitochondria. The contribution of the mitochondrial pool of these TFs to their well-defined biological actions is in some cases clear and in others not well understood. Recently, a small mitochondrial pool of the TF signal transducer and activator of transcription factor 3 (STAT3) was shown to modulate the activity of the electron transport chain (ETC). The mitochondrial function of STAT3 encompasses both its biological actions in the heart as well as its oncogenic effects. This review highlights advances in our understanding of how mitochondrial pools of nuclear TFs may influence the function of this organelle.