Irisin deficiency exacerbates diet-induced insulin resistance and cardiac dysfunction in type II diabetes in mice.

Irisin is involved in the regulation of a variety of physiological conditions, metabolism, and survival. We and others have demonstrated that irisin contributes critically to modulation of insulin resistance and the improvement of cardiac function. However, whether the deletion of irisin will regulate cardiac function and insulin sensitivity in type II diabetes remains unclear. We utilized the CRISPR/Cas-9 genome-editing system to delete irisin globally in mice and high-fat diet (HFD)-induced type II diabetes model. We found that irisin deficiency did not result in developmental abnormality during the adult stage, which illustrates normal cardiac function and insulin sensitivity assessed by glucose tolerance test in the absence of stress. The ultrastructural analysis of the transmission electronic microscope (TEM) indicated that deletion of irisin did not change the morphology of mitochondria in myocardium. Gene expression profiling showed that several key signaling pathways related to integrin signaling, extracellular matrix, and insulin-like growth factors signaling were coordinately downregulated by deletion of irisin. However, when mice were fed a high-fat diet and chow food for 16 wk, ablation of irisin in mice exposed to HFD resulted in much more severe insulin resistance, metabolic derangements, profound cardiac dysfunction, and hypertrophic response and remodeling as compared with wild-type control mice. Taken together, our results indicate that the loss of irisin exacerbates insulin resistance, metabolic disorders, and cardiac dysfunction in response to HFD and promotes myocardial remodeling and hypertrophic response. This evidence reveals the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.NEW & NOTEWORTHY By utilizing the CRISPR/Cas-9 genome-editing system and high-fat diet (HFD)-induced type II diabetes model, our results provide direct evidence showing that the loss of irisin exacerbates cardiac dysfunction and insulin resistance while promoting myocardial remodeling and a hypertrophic response in HFD-induced diabetes. This study provides new insight into understanding the molecular evidence and the critical role of irisin in modulating insulin resistance and cardiac function in type II diabetes.

Transcriptomics of acute myeloid leukaemia core bone marrow biopsies reveals distinct therapy response-specific osteo-mesenchymal profiles.

While the bone marrow (BM) microenvironment is significantly remodelled in acute myeloid leukaemia (AML), molecular insight into AML-specific alterations in the microenvironment has been historically limited by the analysis of liquid marrow aspirates rather than core biopsies that contain solid-phase BM stroma. We assessed the effect of anthracycline- and cytarabine-based induction chemotherapy on both haematopoietic and non-haematopoietic cells directly in core BM biopsies using RNA-seq and histological analysis. We compared matched human core BM biopsies at diagnosis and 2 weeks after cytarabine- and anthracycline-based induction therapy in responders (<5% blasts present after treatment) and non-responders (≥5% blasts present after treatment). Our data indicated enrichment in vimentin (VIM), platelet-derived growth factor receptor beta (PDGFRB) and Snail family transcriptional repressor 2 (SNAI2) transcripts in responders, consistent with the reactivation of the mesenchymal population in the BM stroma. Enrichment of osteoblast maturation-related transcripts of biglycan (BGN), osteopontin (SPP1) and osteonectin (SPARC) was observed in non-responders. To the best of our knowledge, this is the first report demonstrating distinct osteogenic and mesenchymal transcriptome profiles specific to AML response to induction chemotherapy assessed directly in core BM biopsies. Detailing treatment response-specific alterations in the BM stroma may inform optimised therapeutic strategies for AML.

NF-κB signaling in neoplastic transition from epithelial to mesenchymal phenotype.

NF-κB transcription factors are critical regulators of innate and adaptive immunity and major mediators of inflammatory signaling. The NF-κB signaling is dysregulated in a significant number of cancers and drives malignant transformation through maintenance of constitutive pro-survival signaling and downregulation of apoptosis. Overactive NF-κB signaling results in overexpression of pro-inflammatory cytokines, chemokines and/or growth factors leading to accumulation of proliferative signals together with activation of innate and select adaptive immune cells. This state of chronic inflammation is now thought to be linked to induction of malignant transformation, angiogenesis, metastasis, subversion of adaptive immunity, and therapy resistance. Moreover, accumulating evidence indicates the involvement of NF-κB signaling in induction and maintenance of invasive phenotypes linked to epithelial to mesenchymal transition (EMT) and metastasis. In this review we summarize reported links of NF-κB signaling to sequential steps of transition from epithelial to mesenchymal phenotypes. Understanding the involvement of NF-κB in EMT regulation may contribute to formulating optimized therapeutic strategies in cancer. Video Abstract.

Inhibition of integrin alpha v/beta 5 mitigates the protective effect induced by irisin in hemorrhage.

INTRODUCTION: Irisin plays an important role in regulating tissue stress, cardiac function, and inflammation. Integrin αvß5 was recently identified as a receptor for irisin to elicit its physiologic function. It remains unknown whether integrin αvß5 is required for irisin's function in modulating the physiologic response to hemorrhage. The objective of this study is to examine if integrin αvß5 contributes to the effects of irisin during the hemorrhagic response. METHODS: Hemorrhage was induced in mice by achieving a mean arterial blood pressure of 35-45 mmHg for one hour, followed by two hours of resuscitation. Irisin (0.5  µg/kg) was administrated to assess its pharmacologic effects in hemorrhage. Cilengitide, a cyclic Arg-Gly-Asp peptide (cRGDyK) which is an inhibitor of integrin αvß5, or control RGDS (1 mg/kg) was administered with irisin. In another cohort of mice, the irisin-induced protective effect was examined after knocking down integrin ß5 with nanoparticle delivery of integrin ß5 sgRNA using CRSIPR/Cas-9 gene editing. Cardiac function and hemodynamics were measured using echocardiography and femoral artery catheterization, respectively. Systemic cytokine releases were measured using Enzyme-linked immunosorbent assay (ELISA). Histological analyses were used to determine tissue damage in myocardium, skeletal muscles, and lung tissues. Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) was carried out to assess apoptosis in tissues. RESULTS: Hemorrhage induced reduction of integrin αvß5 in skeletal muscles and repressed recovery of cardiac performance and hemodynamics. Irisin treatment led to significantly improved cardiac function, which was abrogated by treatment with Cilengitide or knockdown of integrin ß5. Furthermore, irisin resulted in a marked suppression of tumor necrosis factor-α (TNF-α) and interleukin-1 (IL-1), muscle edema, and inflammatory cells infiltration in myocardium and skeletal muscles, which was attenuated by Cilengitide or knockdown of integrin ß5. Irisin-induced reduction of apoptosis in the myocardium, skeletal muscles, and lung, which were attenuated by either the inhibition of integrin αvß5, or knockdown of integrin ß5. CONCLUSION: Integrin αvß5 plays an important role for irisin in modulating the protective effect during hemorrhage.

Inhibition of lipid phosphatase SHIP1 expands myeloid-derived suppressor cells and attenuates rheumatoid arthritis in mice.

Rheumatoid arthritis (RA) is a debilitating autoimmune disease of unknown cause, characterized by infiltration and accumulation of activated immune cells in the synovial joints where cartilage and bone destructions occur. Myeloid-derived suppressor cells (MDSCs) are of myeloid origin and are able to suppress T cell responses. Src homology 2 domain-containing inositol polyphosphate 5-phosphatase 1 (SHIP1) was shown to be involved in the regulation of MDSC differentiation. The purpose of the present study was to investigate the effect of inhibition of SHIP1 on the expansion of MDSCs in RA using a collagen-induced inflammatory arthritis (CIA) mouse model. In DBA/1 mice, treatment with a small molecule-specific SHIP1 inhibitor 3α-aminocholestane (3AC) induced a marked expansion of MDSCs in vivo. Both pretreatment with 3AC of DBA/1 mice prior to CIA induction and intervention with 3AC during CIA progression significantly reduced disease incidence and severity. Adoptive transfer of MDSCs isolated from 3AC-treated mice, but not naïve MDSCs from normal mice, into CIA mice significantly reduced disease incidence and severity, indicating that the 3AC-induced MDSCs were the cellular mediators of the observed amelioration of the disease. In conclusion, inhibition of SHIP1 expands MDSCs in vivo and attenuates development of CIA in mice. Small molecule-specific inhibition of SHIP1 may therefore offer therapeutic benefit to patients with RA and other autoimmune diseases.

Irisin counteracts high glucose and fatty acid-induced cytotoxicity by preserving the AMPK-insulin receptor signaling axis in C2C12 myoblasts.

Irisin, a newly identified myokine, is critical to modulating body metabolism and biological homeostasis. However, whether irisin protects the skeletal muscles against metabolic stresses remains unknown. In this study, we determine the effect of irisin on high glucose and fatty acid-induced damages using irisin-overexpressed mouse C2C12 (irisin-C2C12) myoblasts and skeletal muscle from irisin-injected mice. Compared with empty vector-transfected control C2C12 cells, irisin overexpression resulted in a marked increase in cell viability and decrease in apoptosis under high-glucose stress. Progression of the cell cycle into the G2/M phase in the proliferative condition was also observed with irisin overexpression. Furthermore, glucose uptake, glycogen accumulation, and phosphorylation of AMPKα/insulin receptor (IR) ß-subunit/Erk1/2 in response to insulin stimulation were enhanced by irisin overexpression. In irisin-C2C12 myoblasts, these responses of phosphorylation were preserved under palmitate treatment, which induced insulin resistance in the control cells. These effects of irisin were reversed by inhibiting AMPK with compound C. In addition, high glucose-induced suppression of the mitochondrial membrane potential was also prevented by irisin. Moreover, suppression of IR in irisin-C2C12 myoblasts by cotransfection of shRNA against IR also mitigated the effects of irisin while not affecting AMPKα phosphorylation. As an in vivo study, soleus muscles from irisin-injected mice showed elevated phosphorylation of AMPKα and Erk1/2 and glycogen contents. Our results indicate that irisin counteracts the stresses generated by high glucose and fatty acid levels and irisin overexpression serves as a novel approach to elicit cellular protection. Furthermore, AMPK activation is a crucial factor that regulates insulin action as a downstream target.

Bone marrow-specific loss of ABI1 induces myeloproliferative neoplasm with features resembling human myelofibrosis.

Although the pathogenesis of primary myelofibrosis (PMF) and other myeloproliferative neoplasms (MPNs) is linked to constitutive activation of the JAK-STAT pathway, JAK inhibitors have neither curative nor MPN-stem cell-eradicating potential, indicating that other targetable mechanisms are contributing to the pathophysiology of MPNs. We previously demonstrated that Abelson interactor 1 (Abi-1), a negative regulator of Abelson kinase 1, functions as a tumor suppressor. Here we present data showing that bone marrow-specific deletion of Abi1 in a novel mouse model leads to development of an MPN-like phenotype resembling human PMF. Abi1 loss resulted in a significant increase in the activity of the Src family kinases (SFKs), STAT3, and NF-κB signaling. We also observed impairment of hematopoietic stem cell self-renewal and fitness, as evidenced in noncompetitive and competitive bone marrow transplant experiments. CD34+ hematopoietic progenitors and granulocytes from patients with PMF showed decreased levels of ABI1 transcript as well as increased activity of SFKs, STAT3, and NF-κB. In aggregate, our data link the loss of Abi-1 function to hyperactive SFKs/STAT3/NF-κB signaling and suggest that this signaling axis may represent a regulatory module involved in the molecular pathophysiology of PMF.

p38-Regulated/activated protein kinase plays a pivotal role in protecting heart against ischemia-reperfusion injury and preserving cardiac performance.

p38-Regulated/activated protein kinase (PRAK) plays a critical role in modulating cellular survival and biological function. However, the function of PRAK in the regulation of myocardial ischemic injury remains unknown. This study is aimed at determining the function of PRAK in modulating myocardial ischemia-reperfusion injury and myocardial remodeling following myocardial infarction. Hearts were isolated from adult male homozygous PRAK-/- and wild-type mice and subjected to global ischemia-reperfusion injury in Langendorff isolated heart perfusion. PRAK-/- mice mitigated postischemic ventricular functional recovery and decreased coronary effluent. Moreover, the infarct size in the perfused heart was significantly increased by deletion of PRAK. Western blot showed that deletion of PRAK decreased the phosphorylation of ERK1/2. Furthermore, the effect of deletion of PRAK on myocardial function and remodeling was also examined on infarcted mice in which the left anterior descending artery was ligated. Echocardiography indicated that PRAK-/- mice had accelerated left ventricular systolic dysfunction, which was associated with increased hypertrophy in the infarcted area. Deletion of PRAK augmented interstitial fibrosis and terminal deoxynucleotidyl transferase nick-end labeling (TUNEL)-positive myocytes. Furthermore, immunostaining analysis shows that CD31-postive vascular density and α-smooth muscle actin capillary staining decreased significantly in PRAK-/- mice. These results indicate that deletion of PRAK enhances susceptibility to myocardial ischemia-reperfusion injury, attenuates cardiac performance and angiogenesis, and increases interstitial fibrosis and apoptosis in the infarcted hearts.

Irisin promotes cardiac progenitor cell-induced myocardial repair and functional improvement in infarcted heart.

Irisin, a newly identified hormone and cardiokine, is critical for modulating body metabolism. New evidence indicates that irisin protects the heart against myocardial ischemic injury. However, whether irisin enhances cardiac progenitor cell (CPC)-induced cardiac repair remains unknown. This study examines the effect of irisin on CPC-induced cardiac repair when these cells are introduced into the infarcted myocardium. Nkx2.5+ CPC stable cells were isolated from mouse embryonic stem cells. Nkx2.5 + CPCs (0.5 × 10 6 ) were reintroduced into the infarcted myocardium using PEGlylated fibrin delivery. The mouse myocardial infarction model was created by permanent ligation of the left anterior descending (LAD) artery. Nkx2.5 + CPCs were pretreated with irisin at a concentration of 5 ng/ml in vitro for 24 hr before transplantation. Myocardial functions were evaluated by echocardiographic measurement. Eight weeks after engraftment, Nkx2.5 + CPCs improved ventricular function as evident by an increase in ejection fraction and fractional shortening. These findings are concomitant with the suppression of cardiac hypertrophy and attenuation of myocardial interstitial fibrosis. Transplantation of Nkx2.5 + CPCs promoted cardiac regeneration and neovascularization, which were increased with the pretreatment of Nkx2.5 + CPCs with irisin. Furthermore, irisin treatment promoted myocyte proliferation as indicated by proliferative markers Ki67 and phosphorylated histone 3 and decreased apoptosis. Additionally, irisin resulted in a marked reduction of histone deacetylase 4 and increased p38 acetylation in cultured CPCs. These results indicate that irisin promoted Nkx2.5 + CPC-induced cardiac regeneration and functional improvement and that irisin serves as a novel therapeutic approach for stem cells in cardiac repair.

Myocyte-specific overexpressing HDAC4 promotes myocardial ischemia/reperfusion injury.

BACKGROUND: Histone deacetylases (HDACs) play a critical role in modulating myocardial protection and cardiomyocyte survivals. However, Specific HDAC isoforms in mediating myocardial ischemia/reperfusion injury remain currently unknown. We used cardiomyocyte-specific overexpression of active HDAC4 to determine the functional role of activated HDAC4 in regulating myocardial ischemia and reperfusion in isovolumetric perfused hearts. METHODS: In this study, we created myocyte-specific active HDAC4 transgenic mice to examine the functional role of active HDAC4 in mediating myocardial I/R injury. Ventricular function was determined in the isovolumetric heart, and infarct size was determined using tetrazolium chloride staining. RESULTS: Myocyte-specific overexpressing activated HDAC4 in mice promoted myocardial I/R injury, as indicated by the increases in infarct size and reduction of ventricular functional recovery following I/R injury. Notably, active HDAC4 overexpression led to an increase in LC-3 and active caspase 3 and decrease in SOD-1 in myocardium. Delivery of chemical HDAC inhibitor attenuated the detrimental effects of active HDAC4 on I/R injury, revealing the pivotal role of active HDAC4 in response to myocardial I/R injury. CONCLUSIONS: Taken together, these findings are the first to define that activated HDAC4 as a crucial regulator for myocardial ischemia and reperfusion injury.

M1 Macrophage-Induced Endothelial-to-Mesenchymal Transition Promotes Infantile Hemangioma Regression.

Infantile hemangiomas are benign tumors of vascular endothelial cells (ECs), characterized by three distinct stages: proliferating phase, involuting phase, and involuted phase. The mechanisms that trigger involution of hemangioma into fibro-fatty tissue remain unknown. We report a novel mechanism by which M1-polarized macrophages induce endothelial-to-mesenchymal transition (EndMT) and promote hemangioma regression. M1- but not M2-polarized macrophages induced EndMT in ECs. Tumor necrosis factor-α and, to a lesser extent, IL-1ß and interferon-γ were the most potent cytokines produced by the M1 macrophages that induce in vitro EndMT. Western blot analysis and gene expression profiling showed that ECs treated with M1 macrophages, tumor necrosis factor-α, or IL-1ß decreased the expression of endothelial markers, whereas mesenchymal markers increased concomitantly. Immunohistochemical staining of patient samples revealed that a significant perivascular infiltration of M1, but not M2, macrophages coincides with endothelial expression of the critical EndMT transcription factors Snail/Slug in involuting hemangiomas. Most strikingly, M1 macrophage-treated ECs isolated from patient hemangiomas (HemECs) but not untreated HemECs readily differentiated into adipocytes on adipogenic induction. Thus, in vitro EndMT and adipogenesis of HemECs have, in part, recapitulated the natural history of hemangioma regression. In conclusion, our findings indicate that EndMT induced by M1 macrophages promotes infantile hemangioma regression and may lead to novel therapeutic treatments for this vascular tumor.

Irisin plays a pivotal role to protect the heart against ischemia and reperfusion injury.

Irisin, a newly identified hormone, is critical to modulating body metabolism, thermogenesis and reducing oxidative stresses. However, whether irisin protects the heart against myocardial ischemia and reperfusion (I/R) injury remains unknown. In this study, we determine the effect of irisin on myocardial I/R injury in the Langendorff perfused heart and cultured myocytes. Adult C57/BL6 mice were treated with irisin (100 mg/kg) or vehicle for 30 min to elicit preconditioning. The isolated hearts were subjected to 30 min ischemia followed by 30 min reperfusion. Left ventricular function was measured and infarction size were determined using by tetrazolium staining. Western blot was employed to determine myocardial SOD-1, active-caspase 3, annexin V, p38, and phospho-p38. H9c2 cardiomyoblasts were exposed to hypoxia and reoxygenation for assessment of the effects of irisin on mitochondrial respiration and mitochondrial permeability transition pore (mPTP). Irisin treatment produced remarkable improvements in ventricular functional recovery, as evident by the increase in RPP and attenuation in LVEDP. As compared to the vehicle treatment, irisin resulted in a marked reduction of myocardial infarct size. Notably, irisin treatment increased SOD-1 and p38 phosphorylation, but suppressed levels of active-caspase 3, cleaved PARP, and annexin V. In cardiomyoblasts exposed to hypoxia/reoxygenation, irisin treatment significantly attenuated hypoxia/reoxygenation (H/R), as indicated by the reduction of lactate dehydrogenase (LDH) leakage and apoptotic cardiomyocytes. Furthermore, irisin treatments suppressed the opening of mPTP, mitochondrial swelling, and protected mitochondria function. Our results indicate that irisin serves as a novel approach to eliciting cardioprotection, which is associated with the improvement of mitochondrial function.

Sodium Butyrate Protects -Against High Fat Diet-Induced Cardiac Dysfunction and Metabolic Disorders in Type II Diabetic Mice.

Histone deacetylases are recently identified to act as key regulators for cardiac pathophysiology and metabolic disorders. However, the function of histone deacetylase (HDAC) in controlling cardiac performance in Type II diabetes and obesity remains unknown. Here, we determine whether HDAC inhibition attenuates high fat diet (HFD)-induced cardiac dysfunction and improves metabolic features. Adult mice were fed with either HFD or standard chow food for 24 weeks. Starting at 12 weeks, mice were divided into four groups randomly, in which sodium butyrate (1%), a potent HDAC inhibitor, was provided to chow and HFD-fed mice in drinking water, respectively. Glucose intolerance, metabolic parameters, cardiac function, and remodeling were assessed. Histological analysis and cellular signaling were examined at 24 weeks following euthanization of mice. HFD-fed mice demonstrated myocardial dysfunction and profound interstitial fibrosis, which were attenuated by HDAC inhibition. HFD-induced metabolic syndrome features insulin resistance, obesity, hyperinsulinemia, hyperglycemia, lipid accumulations, and cardiac hypertrophy, these effects were prevented by HDAC inhibition. Furthermore, HDAC inhibition attenuated myocyte apoptosis, reduced production of reactive oxygen species, and increased angiogenesis in the HFD-fed myocardium. Notably, HFD induced decreases in MKK3, p38, p38 regulated/activated protein kinase (PRAK), and Akt-1, but not p44/42 phosphorylation, which were prevented by HDAC inhibition. These results suggest that HDAC inhibition plays a critical role to preserve cardiac performance and mitigate metabolic disorders in obesity and diabetes, which is associated with MKK3/p38/PRAK pathway. The study holds promise in developing a new therapeutic strategy in the treatment of Type II diabetic-induced heart failure and metabolic disorders. J. Cell. Biochem. 118: 2395-2408, 2017. © 2017 Wiley Periodicals, Inc.

Molecular targeting in acute myeloid leukemia.

Acute myeloid leukemia (AML) is a heterogenous disease associated with distinct genetic and molecular abnormalities. Somatic mutations result in dysregulation of intracellular signaling pathways, epigenetics, and apoptosis of the leukemia cells. Understanding the basis for the dysregulated processes provides the platform for the design of novel targeted therapy for AML patients. The effort to devise new targeted therapy has been helped by recent advances in methods for high-throughput genomic screening and the availability of computer-assisted techniques for the design of novel agents that are predicted to specifically inhibit the mutant molecules involved in these intracellular events. In this review, we will provide the scientific basis for targeting the dysregulated molecular mechanisms and discuss the agents currently being investigated, alone or in combination with chemotherapy, for treating patients with AML. Successes in molecular targeting will ultimately change the treatment paradigm for the disease.

Essential role for Abi1 in embryonic survival and WAVE2 complex integrity.

Abl interactor 1 (Abi1) plays a critical function in actin cytoskeleton dynamics through participation in the WAVE2 complex. To gain a better understanding of the specific role of Abi1, we generated a conditional Abi1-KO mouse model and MEFs lacking Abi1 expression. Abi1-KO cells displayed defective regulation of the actin cytoskeleton, and this dysregulation was ascribed to altered activity of the WAVE2 complex. Changes in motility of Abi1-KO cells were manifested by a decreased migration rate and distance but increased directional persistence. Although these phenotypes did not correlate with peripheral ruffling, which was unaffected, Abi1-KO cells exhibited decreased dorsal ruffling. Western blotting analysis of Abi1-KO cell lysates indicated reduced levels of the WAVE complex components WAVE1 and WAVE2, Nap1, and Sra-1/PIR121. Although relative Abi2 levels were more than doubled in Abi1-KO cells, the absolute Abi2 expression in these cells amounted only to a fifth of Abi1 levels in the control cell line. This finding suggests that the presence of Abi1 is critical for the integrity and stability of WAVE complex and that Abi2 levels are not sufficiently increased to compensate fully for the loss of Abi1 in KO cells and to restore the integrity and function of the WAVE complex. The essential function of Abi1 in WAVE complexes and their regulation might explain the observed embryonic lethality of Abi1-deficient embryos, which survived until approximately embryonic day 11.5 and displayed malformations in the developing heart and brain. Cells lacking Abi1 and the conditional Abi1-KO mouse will serve as critical models for defining Abi1 function.

Complement or Insult: the emerging link between complement cascade deficiencies and pathology of myeloid malignancies.

The complement cascade is an ancient and highly conserved arm of the immune system. The accumulating evidence highlights elevated activity of the complement cascade in cancer microenvironment and emphasizes its effects on the immune, cancer and cancer stroma cells, pointing to a role in inflammation-mediated etiology of neoplasms. The role the cascade plays in development, progression and relapse of solid tumors is increasingly recognized, however its role in hematological malignancies, especially those of myeloid origin, has not been thoroughly assessed and remains obscure. As the role of inflammation and autoimmunity in development of myeloid malignancies is becoming recognized, in this review we focus on summarizing the links that have been identified so far for complement cascade involvement in the pathobiology of myeloid malignancies. Complement deficiencies are primary immunodeficiencies that cause an array of clinical outcomes including an increased risk of a range of infectious as well as local or systemic inflammatory and thrombotic conditions. Here, we discuss the impact that deficiencies in complement cascade initiators, mid- and terminal- components and inhibitors have on the biology of myeloid neoplasms. The emergent conclusions indicate that the links between complement cascade, inflammatory signaling and the homeostasis of hematopoietic system exist, and efforts should continue to detail the mechanistic involvement of complement cascade in the development and progression of myeloid cancers.

Inhibition of histone deacetylase-induced myocardial repair is mediated by c-kit in infarcted hearts.

Histone deacetylases (HDACs) play a critical role in the regulation of gene transcription, cardiac development, and diseases. The aim of this study was to test whether inhibition of HDACs induces myocardial repair and cardiac function restoration through c-kit signaling in mouse myocardial infarction models. Myocardial infarction in wild type Kit(+/+) and Kit(W)/Kit(W-v) mice was created following thoracotomy by applying permanent ligation to the left anterior descending artery. The HDAC inhibitor, trichostatin A (TSA, 0.1 mg/kg), was intraperitoneally injected daily for a consecutive 8 weeks after myocardial infarction. 5-Bromo-2-deoxyuridine (BrdU, 50 mg/kg) was intraperitoneally delivered every other day to pulse-chase label in vivo endogenous cardiac replication. Eight weeks later, inhibition of HDACs in vivo resulted in an improvement in ventricular functional recovery and the prevention of myocardial remodeling in Kit(+/+) mice, which was eliminated in Kit(W)/Kit(W-v) mice. HDAC inhibition promoted cardiac repairs and neovascularization in the infarcted myocardium, which were absent in Kit(W)/Kit(W-v) mice. Re-introduction of TSA-treated wild type c-kit(+) CSCs into Kit(W)/Kit(W-v) myocardial infarction heart restored myocardial functional improvement and cardiac repair. To further validate that HDAC inhibition stimulates c-kit(+) cardiac stem cells (CSCs) to facilitate myocardial repair, GFP(+) c-kit(+) CSCs were preconditioned with TSA (50 nmol/liter) for 24 h and re-introduced into infarcted hearts for 2 weeks. Preconditioning of c-kit(+) CSCs via HDAC inhibition with trichostatin A significantly increased c-kit(+) CSC-derived myocytes and microvessels and enhanced functional recovery in myocardial infarction hearts in vivo. Our results provide evidence that HDAC inhibition promotes myocardial repair and prevents cardiac remodeling, which is dependent upon c-kit signaling.

Release of an ~55kDa fragment containing the actin-binding domain of ß-spectrin by caspase-8 during FND-induced apoptosis depends on the presence of protein 4.1.

Analyses of the status of the membrane spectrin-based skeleton during fludarabine/mitoxantrone/dexamethasone-induced (FND-induced) apoptosis revealed proteolytic degradation of ß-spectrin, with the prevalent appearance of a specific fragment with a molecular weight of ~55kDa, containing the actin-binding domain (ABD). Appearance of this fragment was dependent on induction of apoptosis. In silico proteolysis of spectrin identified caspase-8 as a candidate protease responsible for the generation of this ~55kDa ABD-containing fragment. Analyses of spectrin and procaspase-8 localization during early apoptosis indicated temporary (<30-120min) submembranous colocalization of both proteins. Proteolytic release of the N-terminal ~55kDa fragment of purified spectrin by recombinant caspase-8 does not occur in normal cells, but does occur in isolated membrane, such as red blood cell ghosts, or in vitro in the presence of apoptotic cell extracts. Surprisingly, proteolysis of purified spectrin by recombinant caspase-8 resulted in the generation of the ~55kDa fragment only in the presence of purified protein 4.1. This suggests that only the appropriate spatial arrangement of the spectrin-based membrane skeleton or the appropriate conformational state of spectrin, which are both known to be induced by 4.1, can sensitize ß-spectrin to cleavage by caspase-8 at the N-terminal ABD-containing region.