Aggregation-induced emission of 1-methyl-1,2,3,4,5-pentaphenylsilole

Aggregation greatly boosts emission efficiency of the silole, turning it from a weak luminophor into a strong emitter.

DAMBE: software package for data analysis in molecular biology and evolution

DAMBE (data analysis in molecular biology and evolution) is an integrated software package for converting, manipulating, statistically and graphically describing, and analyzing molecular sequence data with a user-friendly Windows 95/98/2000/NT interface. DAMBE is free and can be downloaded from http://web.hku.hk/~xxia/software/software.htm. The current version is 4.0.36.

Bax directly induces release of cytochrome c from isolated mitochondria

Bax is a pro-apoptotic member of the Bcl-2 protein family that resides in the outer mitochondrial membrane. It is controversial whether Bax promotes cell death directly through its putative function as a channel protein versus indirectly by inhibiting cellular regulators of the cell death proteases (caspases). We show here that addition of submicromolar amounts of recombinant Bax protein to isolated mitochondria can induce cytochrome c (Cyt c) release, whereas a peptide representing the Bax BH3 domain was inactive. When placed into purified cytosol, neither mitochondria nor Bax individually induced proteolytic processing and activation of caspases. In contrast, the combination of Bax and mitochondria triggered release of Cyt c from mitochondria and induced caspase activation in cytosols. Supernatants from Bax-treated mitochondria also induced caspase processing and activation. Recombinant Bcl-XL protein abrogated Bax-induced release of Cyt c from isolated mitochondria and prevented caspase activation. In contrast, the broad-specificity caspase inhibitor benzyloxycarbonyl-valinyl-alaninyl-aspartyl-(0-methyl)- fluoromethylketone (zVAD-fmk) and the caspase-inhibiting protein X-IAP had no effect on Bax-induced release of Cyt c from mitochondria in vitro but prevented the subsequent activation of caspases in cytosolic extracts. Unlike Ca2+, a classical inducer of mitochondrial permeability transition, Bax did not induce swelling of mitochondria in vitro. Because the organellar swelling caused by permeability transition causes outer membrane rupture, the findings, therefore, dissociate these two events, implying that Bax uses an alternative mechanism for triggering release of Cyt c from mitochondria.

Bax and adenine nucleotide translocator cooperate in the mitochondrial control of apoptosis

The proapoptotic Bax protein induces cell death by acting on mitochondria. Bax binds to the permeability transition pore complex (PTPC), a composite proteaceous channel that is involved in the regulation of mitochondrial membrane permeability. Immunodepletion of Bax from PTPC or purification of PTPC from Bax-deficient mice yielded a PTPC that could not permeabilize membranes in response to atractyloside, a proapoptotic ligand of the adenine nucleotide translocator (ANT). Bax and ANT coimmunoprecipitated and interacted in the yeast two-hybrid system. Ectopic expression of Bax induced cell death in wild-type but not in ANT-deficient yeast. Recombinant Bax and purified ANT, but neither of them alone, efficiently formed atractyloside-responsive channels in artificial membranes. Hence, the proapoptotic molecule Bax and the constitutive mitochondrial protein ANT cooperate within the PTPC to increase mitochondrial membrane permeability and to trigger cell death.

Control of RNA polymerase II elongation potential by a novel carboxyl-terminal domain kinase

The entry of RNA polymerase II into a productive mode of elongation is controlled, in part, by the postinitiation activity of positive transcription elongation factor b (P-TEFb) (Marshall, N. F., and Price, D. H. (1995) J. Biol. Chem. 270, 12335-12338). We report here that removal of the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II abolishes productive elongation. Correspondingly, we found that P-TEFb can phosphorylate the CTD of pure RNA polymerase II. Furthermore, P-TEFb can phosphorylate the CTD of RNA polymerase II when the polymerase is in an early elongation complex. Both the function and kinase activity of P-TEFb are blocked by the drugs 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and H-8. P-TEFb is distinct from transcription factor IIH (TFIIH) because the two factors have no subunits in common, P-TEFb is more sensitive to DRB than is TFIIH, and most importantly, TFIIH cannot substitute functionally for P-TEFb. We propose that phosphorylation of the CTD by P-TEFb controls the transition from abortive into productive elongation mode.

Cytochrome c release and apoptosis induced by mitochondrial targeting of nuclear orphan receptor TR3

TR3, an immediate-early response gene and an orphan member of the steroid-thyroid hormone-retinoid receptor superfamily of transcription factors, regulates apoptosis through an unknown mechanism. In response to apoptotic stimuli, TR3 translocates from the nucleus to mitochondria to induce cytochrome c release and apoptosis. Mitochondrial targeting of TR3, but not its DNA binding and transactivation, is essential for its proapoptotic effect. Our results reveal a mechanism by which a nuclear transcription factor translocates to mitochondria to initiate apoptosis.

Fracture-related infection: A consensus on definition from an international expert group

Fracture-related infection (FRI) is a common and serious complication in trauma surgery. Accurately estimating the impact of this complication has been hampered by the lack of a clear definition. The absence of a working definition of FRI renders existing studies difficult to evaluate or compare. In order to address this issue, an expert group comprised of a number of scientific and medical organizations has been convened, with the support of the AO Foundation, in order to develop a consensus definition. The process that led to this proposed definition started with a systematic literature review, which revealed that the majority of randomized controlled trials in fracture care do not use a standardized definition of FRI. In response to this conclusion, an international survey on the need for and key components of a definition of FRI was distributed amongst all registered AOTrauma users. Approximately 90% of the more than 2000 surgeons who responded suggested that a definition of FRI is required. As a final step, a consensus meeting was held with an expert panel. The outcome of this process led to a consensus definition of FRI. Two levels of certainty around diagnostic features were defined. Criteria could be confirmatory (infection definitely present) or suggestive. Four confirmatory criteria were defined: Fistula, sinus or wound breakdown; Purulent drainage from the wound or presence of pus during surgery; Phenotypically indistinguishable pathogens identified by culture from at least two separate deep tissue/implant specimens; Presence of microorganisms in deep tissue taken during an operative intervention, as confirmed by histopathological examination. Furthermore, a list of suggestive criteria was defined. These require further investigations in order to look for confirmatory criteria. In the current paper, an overview is provided of the proposed definition and a rationale for each component and decision. The intention of establishing this definition of FRI was to offer clinicians the opportunity to standardize clinical reports and improve the quality of published literature. It is important to note that the proposed definition was not designed to guide treatment of FRI and should be validated by prospective data collection in the future.

Widespread white matter microstructural differences in schizophrenia across 4322 individuals: results from the ENIGMA Schizophrenia DTI Working Group

The regional distribution of white matter (WM) abnormalities in schizophrenia remains poorly understood, and reported disease effects on the brain vary widely between studies. In an effort to identify commonalities across studies, we perform what we believe is the first ever large-scale coordinated study of WM microstructural differences in schizophrenia. Our analysis consisted of 2359 healthy controls and 1963 schizophrenia patients from 29 independent international studies; we harmonized the processing and statistical analyses of diffusion tensor imaging (DTI) data across sites and meta-analyzed effects across studies. Significant reductions in fractional anisotropy (FA) in schizophrenia patients were widespread, and detected in 20 of 25 regions of interest within a WM skeleton representing all major WM fasciculi. Effect sizes varied by region, peaking at (d=0.42) for the entire WM skeleton, driven more by peripheral areas as opposed to the core WM where regions of interest were defined. The anterior corona radiata (d=0.40) and corpus callosum (d=0.39), specifically its body (d=0.39) and genu (d=0.37), showed greatest effects. Significant decreases, to lesser degrees, were observed in almost all regions analyzed. Larger effect sizes were observed for FA than diffusivity measures; significantly higher mean and radial diffusivity was observed for schizophrenia patients compared with controls. No significant effects of age at onset of schizophrenia or medication dosage were detected. As the largest coordinated analysis of WM differences in a psychiatric disorder to date, the present study provides a robust profile of widespread WM abnormalities in schizophrenia patients worldwide. Interactive three-dimensional visualization of the results is available at www.enigma-viewer.org.

Channel formation by antiapoptotic protein Bcl-2

Bcl-2 is the prototypical member of a large family of apoptosis-regulating proteins, consisting of blockers and promoters of cell death. The three-dimensional structure of a Bcl-2 homologue, Bcl-XL, suggests striking similarity to the pore-forming domains of diphtheria toxin and the bacterial colicins, prompting exploration of whether Bcl-2 is capable of forming pores in lipid membranes. Using chloride efflux from KCl-loaded unilamellar lipid vesicles as an assay, purified recombinant Bcl-2 protein exhibited pore-forming activity with properties similar to those of the bacterial toxins, diphtheria toxin, and colicins, i.e., dependence on low pH and acidic lipid membranes. In contrast, a mutant of Bcl-2 lacking the two core hydrophobic alpha-helices (helices 5 and 6), predicted to be required for membrane insertion and channel formation, produced only nonspecific effects. In planar lipid bilayers, where detection of single channels is possible, Bcl-2 formed discrete ion-conducting, cation-selective channels, whereas the Bcl-2 (Deltah5, 6) mutant did not. The most frequent conductance observed (18 +/- 2 pS in 0.5 M KCl at pH 7.4) is consistent with a four-helix bundle structure arising from Bcl-2 dimers. However, larger channel conductances (41 +/- 2 pS and 90 +/- 10 pS) also were detected with progressively lower occurrence, implying the step-wise formation of larger oligomers of Bcl-2 in membranes. These findings thus provide biophysical evidence that Bcl-2 forms channels in lipid membranes, suggesting a novel function for this antiapoptotic protein.

Release of caspase-9 from mitochondria during neuronal apoptosis and cerebral ischemia

Caspase-9 is critical for cytochrome c (cyto-c)-dependent apoptosis and normal brain development. We determined that this apical protease in the cyto-c pathway for apoptosis resides inside mitochondria in several types of cells, including cardiomyocytes and many neurons. Caspase-9 is released from isolated mitochondria on treatment with Ca2+ or Bax, stimuli implicated in ischemic neuronal cell death that are known to induce cyto-c release from mitochondria. In neuronal cell culture models, apoptosis-inducing agents trigger translocation of caspase-9 from mitochondria to the nucleus, which is inhibitable by Bcl-2. Similarly, in an animal model of transient global cerebral ischemia, caspase-9 release from mitochondria and accumulation in nuclei was observed in hippocampal and other vulnerable neurons exhibiting early postischemic changes preceding apoptosis. Loss of mitochondrial barrier function during neuronal damage from ischemia or other insults therefore may play an important role in making certain caspases available to participate in apoptosis.

Oocyte apoptosis is suppressed by disruption of the acid sphingomyelinase gene or by sphingosine-1-phosphate therapy

The time at which ovarian failure (menopause) occurs in females is determined by the size of the oocyte reserve provided at birth, as well as by the rate at which this endowment is depleted throughout post-natal life. Here we show that disruption of the gene for acid sphingomyelinase in female mice suppressed the normal apoptotic deletion of fetal oocytes, leading to neonatal ovarian hyperplasia. Ex vivo, oocytes lacking the gene for acid sphingomyelinase or wild-type oocytes treated with sphingosine-1-phosphate resisted developmental apoptosis and apoptosis induced by anti-cancer therapy, confirming cell autonomy of the death defect. Moreover, radiation-induced oocyte loss in adult wild-type female mice, the event that drives premature ovarian failure and infertility in female cancer patients, was completely prevented by in vivo therapy with sphingosine-1-phosphate. Thus, the sphingomyelin pathway regulates developmental death of oocytes, and sphingosine-1-phosphate provides a new approach to preserve ovarian function in vivo.

Oligomerization of mu- and delta-opioid receptors. Generation of novel functional properties

The existence of dimers and oligomers for many G protein-coupled receptors has been described by us and others. Since many G protein-coupled receptor subtypes are highly homologous to each other, we examined whether closely related receptors may interact with each other directly and thus have the potential to create novel signaling units. Using mu- and delta-opioid receptors, we show that each receptor expressed individually was pharmacologically distinct and could be visualized following electrophoresis as monomers, homodimers, homotetramers, and higher molecular mass oligomers. When mu- and delta-opioid receptors were coexpressed, the highly selective synthetic agonists for each had reduced potency and altered rank order, whereas endomorphin-1 and Leu-enkephalin had enhanced affinity, suggesting the formation of a novel binding pocket. No heterodimers were visualized in the membranes coexpressing mu- and delta-receptors by the methods available. However, hetero-oligomers were identified by the ability to co-immunoprecipitate mu-receptors with delta-receptors and vice versa using differentially epitope-tagged receptors. In contrast to the individually expressed mu- and delta-receptors, the coexpressed receptors showed insensitivity to pertussis toxin and continued signal transduction, likely due to interaction with a different subtype of G protein. In this study, we provide, for the first time, evidence for the direct interaction of mu- and delta-opioid receptors to form oligomers, with the generation of novel pharmacology and G protein coupling properties.

An evolutionarily conserved family of Hsp70/Hsc70 molecular chaperone regulators

Heat Shock Protein 70 kDa (Hsp70) family molecular chaperones play critical roles in protein folding and trafficking in all eukaryotic cells. The mechanisms by which Hsp70 family chaperones are regulated, however, are only partly understood. BAG-1 binds the ATPase domains of Hsp70 and Hsc70, modulating their chaperone activity and functioning as a competitive antagonist of the co-chaperone Hip. We describe the identification of a family of BAG-1-related proteins from humans (BAG-2, BAG-3, BAG-4, BAG-5), the invertebrate Caenorhabditis elegans (BAG-1, BAG-2), and the fission yeast Schizosaccharomyces pombe (BAG-1A, BAG-1B). These proteins all contain a conserved approximately 45-amino acid region near their C termini (the BAG domain) that binds Hsc70/Hsp70, but they differ widely in their N-terminal domains. The human BAG-1, BAG-2, and BAG-3 proteins bind with high affinity (KD congruent with 1-10 nM) to the ATPase domain of Hsc70 and inhibit its chaperone activity in a Hip-repressible manner. The findings suggest opportunities for specification and diversification of Hsp70/Hsc70 chaperone functions through interactions with various BAG-family proteins.

Holocene—Late Pleistocene Climatic Ice Core Records from Qinghai-Tibetan Plateau

Three ice cores to bedrock from the Dunde ice cap on the north-central Qinghai-Tibetan Plateau of China provide a detailed record of Holocene and Wisconsin-Würm late glacial stage (LGS) climate changes in the subtropics. The records reveal that LGS conditions were apparently colder, wetter, and dustier than Holocene conditions. The LGS part of the cores is characterized by more negative delta(18)O ratios, increased dust content, decreased soluble aerosol concentrations, and reduced ice crystal sizes than the Holocene part. These changes occurred rapidly approximately 10,000 years ago. In addition, the last 60 years were apparently one of the warmest periods in the entire record, equalling levels of the Holocene maximum between 6000 and 8000 years ago.

BAG-1 modulates the chaperone activity of Hsp70/Hsc70

The 70 kDa heat shock family of molecular chaperones is essential to a variety of cellular processes, yet it is unclear how these proteins are regulated in vivo. We present evidence that the protein BAG-1 is a potential modulator of the molecular chaperones, Hsp70 and Hsc70. BAG-1 binds to the ATPase domain of Hsp70 and Hsc70, without requirement for their carboxy-terminal peptide-binding domain, and can be co-immunoprecipitated with Hsp/Hsc70 from cell lysates. Purified BAG-1 and Hsp/Hsc70 efficiently form heteromeric complexes in vitro. BAG-1 inhibits Hsp/Hsc70-mediated in vitro refolding of an unfolded protein substrate, whereas BAG-1 mutants that fail to bind Hsp/Hsc70 do not affect chaperone activity. The binding of BAG-1 to one of its known cellular targets, Bcl-2, in cell lysates was found to be dependent on ATP, consistent with the possible involvement of Hsp/Hsc70 in complex formation. Overexpression of BAG-1 also protected certain cell lines from heat shock-induced cell death. The identification of Hsp/Hsc70 as a partner protein for BAG-1 may explain the diverse interactions observed between BAG-1 and several other proteins, including Raf-1, steroid hormone receptors and certain tyrosine kinase growth factor receptors. The inhibitory effects of BAG-1 on Hsp/Hsc70 chaperone activity suggest that BAG-1 represents a novel type of chaperone regulatory proteins and thus suggest a link between cell signaling, cell death and the stress response.

Ouabain interaction with cardiac Na+/K+-ATPase initiates signal cascades independent of changes in intracellular Na+ and Ca2+ concentrations

We have shown previously that partial inhibition of the cardiac myocyte Na(+)/K(+)-ATPase activates signal pathways that regulate myocyte growth and growth-related genes and that increases in intracellular Ca(2+) concentration ([Ca(2+)](i)) and reactive oxygen species (ROS) are two essential second messengers within these pathways. The aim of this work was to explore the relation between [Ca(2+)](i) and ROS. When myocytes were in a Ca(2+)-free medium, ouabain caused no change in [Ca(2+)](i), but it increased ROS as it did when the cells were in a Ca(2+)-containing medium. Ouabain-induced increase in ROS also occurred under conditions where there was little or no change in [Na(+)](i). Exposure of myocytes in Ca(2+)-free medium to monensin did not increase ROS. Increase in protein tyrosine phosphorylation, an early event induced by ouabain, was also independent of changes in [Ca(2+)](i) and [Na(+)](i). Ouabain-induced generation of ROS in myocytes was antagonized by genistein, a dominant negative Ras, and myxothiazol/diphenyleneiodonium, indicating a mitochondrial origin for the Ras-dependent ROS generation. These findings, along with our previous data, indicate that increases in [Ca(2+)](i) and ROS in cardiac myocytes are induced by two parallel pathways initiated at the plasma membrane: One being the ouabain-altered transient interactions of a fraction of the Na(+)/K(+)-ATPase with neighboring proteins (Src, growth factor receptors, adaptor proteins, and Ras) leading to ROS generation, and the other, inhibition of the transport function of another fraction of the Na(+)/K(+)-ATPase leading to rise in [Ca(2+)](i). Evidently, the gene regulatory effects of ouabain in cardiac myocytes require the downstream collaborations of ROS and [Ca(2+)](i).

Involvement of Src and epidermal growth factor receptor in the signal-transducing function of Na+/K+-ATPase

Nontoxic concentrations of ouabain, causing partial inhibition of the cardiac myocyte Na(+)/K(+)-ATPase, induce hypertrophy and several growth-related genes through signal pathways that include the activation of Ras and p42/44 mitogen-activated protein kinase (MAPK). The aim of this work was to examine the ouabain-induced events upstream of the Ras/MAPK cascade. Treatment of myocytes with genistein antagonized ouabain-induced activation of the MAPK, suggesting that protein tyrosine phosphorylation has a role. Tyrosine phosphorylation of several myocyte proteins was increased rapidly upon cell exposure to ouabain. Lowering of extracellular K(+) had a similar ouabain-like effect. Ouabain also increased protein tyrosine phosphorylation in A7r5, HeLa, and L929 cells. In cardiac myocytes and A7r5 cells, herbimycin A antagonized the ouabain-induced increase in protein tyrosine phosphorylation and MAPK activation. In both cell types, ouabain stimulated Src kinase activity, Src translocation to the Triton-insoluble fraction, Src association with the epidermal growth factor receptor, and the tyrosine phosphorylation of this receptor on site(s) other than its major autophosphorylation site, Tyr(1173). The findings suggest that (a) the ouabain-induced activation of Src and the Src-induced phosphorylation of the growth factor receptor provide the scaffolding for the recruitment of adaptor proteins and Ras and the activation of Ras/MAPK cascade; and (b) the activation of such pathways may be a common feature of the signal-transducing function of Na(+)/K(+)-ATPase in most cells.

Intracellular reactive oxygen species mediate the linkage of Na+/K+-ATPase to hypertrophy and its marker genes in cardiac myocytes

We showed before that in cardiac myocytes partial inhibition of Na+/K+-ATPase by nontoxic concentrations of ouabain causes hypertrophy and transcriptional regulations of growth-related marker genes through multiple Ca2+-dependent signal pathways many of which involve Ras and p42/44 mitogen-activated protein kinases. The aim of this work was to explore the roles of intracellular reactive oxygen species (ROS) in these ouabain-initiated pathways. Ouabain caused a rapid generation of ROS within the myocytes that was prevented by preexposure of cells to N-acetylcysteine (NAC) or vitamin E. These antioxidants also blocked or attenuated the following actions of ouabain: inductions of the genes of skeletal alpha-actin and atrial natriuretic factor, repression of the gene of the alpha3-subunit of Na+/K+-ATPase, activation of mitogen-activated protein kinases, activation of Ras-dependent protein synthesis, and activation of transcription factor NF-kappaB. Induction of c-fos and activation of AP-1 by ouabain were not sensitive to NAC. Ouabain-induced inhibition of active Rb+ uptake through Na+/K+-ATPase and the resulting rise in intracellular Ca2+ were also not prevented by NAC. A phorbol ester that also causes myocyte hypertrophy did not increase ROS generation, and its effects on marker genes and protein synthesis were not affected by NAC. We conclude the following: (a) ROS are essential second messengers within some but not all signal pathways that are activated by the effect of ouabain on Na+/K+-ATPase; (b) the ROS-dependent pathways are involved in ouabain-induced hypertrophy; (c) increased ROS generation is not a common response of the myocyte to all hypertrophic stimuli; and (d) it may be possible to dissociate the positive inotropic effect of ouabain from its growth-related effects by alteration of the redox state of the cardiac myocyte.

Bcl-2 and Bax regulate the channel activity of the mitochondrial adenine nucleotide translocator

Bcl-2 family protein including anti-apoptotic (Bcl-2) or pro-apoptotic (Bax) members can form ion channels when incorporated into synthetic lipid bilayers. This contrasts with the observation that Bcl-2 stabilizes the mitochondrial membrane barrier function and inhibits the permeability transition pore complex (PTPC). Here we provide experimental data which may explain this apparent paradox. Bax and adenine nucleotide translocator (ANT), the most abundant inner mitochondrial membrane protein, can interact in artificial lipid bilayers to yield an efficient composite channel whose electrophysiological properties differ quantitatively and qualitatively from the channels formed by Bax or ANT alone. The formation of this composite channel can be observed in conditions in which Bax protein alone has no detectable channel activity. Cooperative channel formation by Bax and ANT is stimulated by the ANT ligand atractyloside (Atr) but inhibited by ATP, indicating that it depends on the conformation of ANT. In contrast to the combination of Bax and ANT, ANT does not form active channels when incorporated into membranes with Bcl-2. Rather, ANT and Bcl-2 exhibit mutual inhibition of channel formation. Bcl-2 prevents channel formation by Atr-treated ANT and neutralizes the cooperation between Bax and ANT. Our data are compatible with a ménage à trois model of mitochondrial apoptosis regulation in which ANT, the likely pore forming protein within the PTPC, interacts with Bax or Bcl-2 which influence its pore forming potential in opposing manners.

Multiple signal transduction pathways link Na+/K+-ATPase to growth-related genes in cardiac myocytes. The roles of Ras and mitogen-activated protein kinases

We showed before that in neonatal rat cardiac myocytes partial inhibition of Na+/K+-ATPase by nontoxic concentrations of ouabain causes hypertrophic growth and transcriptional regulations of genes that are markers of cardiac hypertrophy. In view of the suggested roles of Ras and p42/44 mitogen-activated protein kinases (MAPKs) as key mediators of cardiac hypertrophy, the aim of this work was to explore their roles in ouabain-initiated signal pathways regulating four growth-related genes of these myocytes, i.e. those for c-Fos, skeletal alpha-actin, atrial natriuretic factor, and the alpha3-subunit of Na+/K+-ATPase. Ouabain caused rapid activations of Ras and p42/44 MAPKs; the latter was sustained longer than 90 min. Using high efficiency adenoviral-mediated expression of a dominant-negative Ras mutant, and a specific inhibitor of MAPK kinase (MEK), activation of Ras-Raf-MEK-p42/44 MAPK cascade by ouabain was shown. The effects of the mutant Ras, an inhibitor of Ras farnesylation, and the MEK inhibitor on ouabain-induced changes in mRNAs of the four genes indicated that (a) skeletal alpha-actin induction was dependent on Ras but not on p42/44 MAPKs, (b) alpha3 repression was dependent on the Ras-p42/44 MAPK cascade, and (c) induction of c-fos or atrial natriuretic factor gene occurred partly through the Ras-p42/44 MAPK cascade, and partly through pathways independent of Ras and p42/44 MAPKs. All ouabain effects required extracellular Ca2+, and were attenuated by a Ca2+/calmodulin antagonist or a protein kinase C inhibitor. The findings show that (a) signal pathways linked to sarcolemmal Na+/K+-ATPase share early segments involving Ca2+ and protein kinase C, but diverge into multiple branches only some of which involve Ras, or p42/44 MAPKs, or both; and (b) there are significant differences between this network and the related gene regulatory pathways activated by other hypertrophic stimuli, including those whose responses involve increases in intracellular free Ca2+ through different mechanisms.

Association of clinical factors and recent anticancer therapy with COVID-19 severity among patients with cancer: a report from the COVID-19 and Cancer Consortium

BACKGROUND

Patients with cancer may be at high risk of adverse outcomes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We analyzed a cohort of patients with cancer and coronavirus 2019 (COVID-19) reported to the COVID-19 and Cancer Consortium (CCC19) to identify prognostic clinical factors, including laboratory measurements and anticancer therapies.

PATIENTS AND METHODS

Patients with active or historical cancer and a laboratory-confirmed SARS-CoV-2 diagnosis recorded between 17 March and 18 November 2020 were included. The primary outcome was COVID-19 severity measured on an ordinal scale (uncomplicated, hospitalized, admitted to intensive care unit, mechanically ventilated, died within 30 days). Multivariable regression models included demographics, cancer status, anticancer therapy and timing, COVID-19-directed therapies, and laboratory measurements (among hospitalized patients).

RESULTS

A total of 4966 patients were included (median age 66 years, 51% female, 50% non-Hispanic white); 2872 (58%) were hospitalized and 695 (14%) died; 61% had cancer that was present, diagnosed, or treated within the year prior to COVID-19 diagnosis. Older age, male sex, obesity, cardiovascular and pulmonary comorbidities, renal disease, diabetes mellitus, non-Hispanic black race, Hispanic ethnicity, worse Eastern Cooperative Oncology Group performance status, recent cytotoxic chemotherapy, and hematologic malignancy were associated with higher COVID-19 severity. Among hospitalized patients, low or high absolute lymphocyte count; high absolute neutrophil count; low platelet count; abnormal creatinine; troponin; lactate dehydrogenase; and C-reactive protein were associated with higher COVID-19 severity. Patients diagnosed early in the COVID-19 pandemic (January-April 2020) had worse outcomes than those diagnosed later. Specific anticancer therapies (e.g. R-CHOP, platinum combined with etoposide, and DNA methyltransferase inhibitors) were associated with high 30-day all-cause mortality.

CONCLUSIONS

Clinical factors (e.g. older age, hematological malignancy, recent chemotherapy) and laboratory measurements were associated with poor outcomes among patients with cancer and COVID-19. Although further studies are needed, caution may be required in utilizing particular anticancer therapies.

CLINICAL TRIAL IDENTIFIER

NCT04354701.

Arsenite induces apoptosis via a direct effect on the mitochondrial permeability transition pore

The molecular mode of action of arsenic, a therapeutic agent employed in the treatment of acute promyelocytic leukemia, has been elusive. Here we provide evidence that arsenic compounds may act on mitochondria to induce apoptosis. Arsenite induces apoptosis accompanied by a loss of the mitochondrial transmembrane potential (Delta Psim). Inhibition of caspases prevents the arsenite-induced nuclear DNA loss, but has no effect on the Delta Psim dissipation and cytolysis induced by arsenite. In contrast, Bcl-2 expression induced by gene transfer prevents all hallmarks of arsenite-induced cell death, including the Delta Psim collapse. PK11195, a ligand of the mitochondrial benzodiazepine receptor, neutralizes this Bcl-2 effect. Mitochondria are required in a cell-free system to mediate arsenite-induced nuclear apoptosis. Arsenite causes the release of an apoptosis-inducing factor (AIF) from the mitochondrial intermembrane space. This effect is prevented by the permeability transition (PT) pore inhibitor cyclosporin A, as well as by Bcl-2, which is known to function as an endogenous PT pore antagonist. Arsenite also opens the purified, reconstituted PT pore in vitro in a cyclosporin A- and Bcl-2-inhibitible fashion. Altogether these data suggest that arsenite can induce apoptosis via a direct effect on the mitochondrial PT pore.

Exaggerated left ventricular dilation and reduced collagen deposition after myocardial infarction in mice lacking osteopontin

Osteopontin (OPN), an extracellular matrix protein, is expressed in the myocardium with hypertrophy and failure. We tested the hypothesis that OPN plays a role in left ventricular (LV) remodeling after myocardial infarction (MI). Accordingly, OPN expression and LV structural and functional remodeling were determined in wild-type (WT) and OPN knockout (KO) mice 4 weeks after MI. Northern analysis showed increased OPN expression in the infarcted region, peaking 3 days after MI and gradually decreasing over the next 28 days. In the remote LV, OPN expression was biphasic, with peaks at 3 and 28 days. In situ hybridization and immunohistochemical analyses showed increased OPN mRNA and protein primarily in the interstitium. Infarct size, heart weight, and survival were similar in KO and WT mice after MI (P=NS), whereas the lung wet weight/dry weight ratio was increased in the KO mice (P<0.005 versus sham-operated mice). Peak LV developed pressure was reduced to a similar degree after MI in the KO and WT mice. The number of terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL)-positive myocytes was similar in KO and WT mice after MI. In contrast, post-MI LV chamber dilation was approximately twice as great in KO versus WT mice (P<0.001). Myocyte length increased after MI in WT mice (P<0.001) but not in KO mice. Electron microscopy showed increased collagen content in WT mice after MI but not in KO mice after MI. Type I collagen content was increased approximately 3-fold and approximately 7-fold in remote and infarcted regions, respectively, of WT hearts after MI but not in KO hearts (P<0.01 versus WT hearts). Likewise, Northern analyses showed increased collagen I(alpha(1)) mRNA after MI in remote regions of WT hearts but not in KO hearts. Thus, increased OPN expression plays an important role in regulating post-MI LV remodeling, at least in part, by promoting collagen synthesis and accumulation.