Insufficiency of pro-heparin-binding epidermal growth factor-like growth factor shedding enhances hypoxic cell death in H9c2 cardiomyoblasts via the activation of caspase-3 and c-Jun N-terminal kinase

Dendritic cell functions in vivo: a user's guide to current and next generation mutant mouse models

Dendritic cells (DCs) do not just excel in antigen presentation. They orchestrate information transfer from innate to adaptive immunity, by sensing and integrating a variety of danger signals, and translating them to naïve T cells, to mount specifically tailored immune responses. This is accomplished by distinct DC types specialized in different functions and because each DC is functionally plastic, assuming different activation states depending on the input signals received. Mouse models hold the key to untangle this complexity and determine which DC types and activation states contribute to which functions. Here, we aim to provide comprehensive information for selecting the most appropriate mutant mouse strains to address specific research questions on DCs, considering three in vivo experimental approaches: (i) interrogating the roles of DC types through their depletion; (ii) determining the underlying mechanisms by specific genetic manipulations; (iii) deciphering the spatiotemporal dynamics of DC responses. We summarize the advantages, caveats, suggested use and perspectives for a variety of mutant mouse strains, discussing in more detail the most widely used or accurate models. Finally, we discuss innovative strategies to improve targeting specificity, for the next generation mutant mouse models, and briefly address how humanized mouse models can accelerate translation into the clinic. This article is protected by copyright. All rights reserved.

Notoginsenoside R1 protects hypoxia-reoxygenation deprivation-induced injury by upregulation of miR-132 in H9c2 cells

BACKGROUND

Myocardial ischemia/reperfusion injury (IRI) is a common perioperative complication of heart and great vessels surgery, aggravating the original myocardial damage and seriously affecting the postoperative recovery of cardiac function. The aim of this study was to reveal the functional effects and potential mechanisms of notoginsenoside R1 (NG-R1) in myocardial cells injured by hypoxia-reoxygenation (H/R).

METHODS

The rat cardiomyocyte line H9c2 was subjected to H/R with or without NG-R1 treatment. The levels of miR-132 and HBEGF in the cell were altered by microRNA or short-hairpin RNA transfection. Cell viability, apoptosis, lactate dehydrogenase (LDH) and malondialdehyde (MDA) were monitored. Dual luciferin was used to detect the relationship between miR-132 and HBEGF.

RESULTS

NG-R1 (20 μM) had no impact on H9c2 cells, but cell viability was significantly reduced at 80 μM. NG-R1 (20 μM) protected H9c2 cells against H/R-induced cell damage, accompanied by increased cell viability, reduced cell apoptosis, and downregulation of LDH and MDA. Furthermore, the level of miR-132 was decreased in response to H/R exposure but then increased after NG-R1 treatment. When miR-132 was overexpressed, H/R-induced cell damage could be recovered. Downregulation of miR-132 limited the protective effect of NG-R1 on H/R damage. We also found that HBEGF was a direct target of miR-132. The expression of HBEGF was increased upon H/R damage, and this increase was reversed after NG-R1 treatment.

CONCLUSIONS

This study demonstrated that NG-R1 markedly protected H9c2 cells against H/R-induced damage via upregulation of miR-132 and downregulation of its target protein HBEGF.

Protective Effect of Ferulic Acid against Hydrogen Peroxide Induced Apoptosis in PC12 Cells

Ferulic Acid (FA) is a highly abundant phenolic phytochemical which is present in plant tissues. FA has biological effects on physiological and pathological processes due to its anti-apoptotic and anti-oxidative properties, however, the detailed mechanism(s) of function is poorly understood. We have identified FA as a molecule that inhibits apoptosis induced by hydrogen peroxide (H₂O₂) or actinomycin D (ActD) in rat pheochromocytoma, PC12 cell. We also found that FA reduces H₂O₂-induced reactive oxygen species (ROS) production in PC12 cell, thereby acting as an anti-oxidant. Then, we analyzed FA-mediated signaling responses in rat pheochromocytoma, PC12 cells using antibody arrays for phosphokinase and apoptosis related proteins. This FA signaling pathway in PC12 cells includes inactivation of pro-apoptotic proteins, SMAC/Diablo and Bad. In addition, FA attenuates the cell injury by H₂O₂ through the inhibition of phosphorylation of the extracellular signal-regulated kinase (ERK). Importantly, we find that FA restores expression levels of brain-derived neurotrophic factor (BDNF), a key neuroprotective effector, in H₂O₂-treated PC12 cells. As a possible mechanism, FA increases BDNF by regulating microRNA-10b expression following H₂O₂ stimulation. Taken together, FA has broad biological effects as a neuroprotective modulator to regulate the expression of phosphokinases, apoptosis-related proteins and microRNAs against oxidative stress in PC12 cells.

Selection in Australian Thoroughbred horses acts on a locus associated with early two-year old speed

Thoroughbred horse racing is a global sport with major hubs in Europe, North America, Australasia and Japan. Regional preferences for certain traits have resulted in phenotypic variation that may result from adaptation to the local racing ecosystem. Here, we test the hypothesis that genes selected for regional phenotypic variation may be identified by analysis of selection signatures in pan-genomic SNP genotype data. Comparing Australian to non-Australian Thoroughbred horses (n = 99), the most highly differentiated loci in a composite selection signals (CSS) analysis were on ECA6 (34.75–34.85 Mb), ECA14 (33.2–33.52 Mb and 35.52–36.94 Mb) and ECA16 (24.28–26.52 Mb) in regions containing candidate genes for exercise adaptations including cardiac function (ARHGAP26, HBEGF, SRA1), synapse development and locomotion (APBB3, ATXN7, CLSTN3), stress response (NR3C1) and the skeletal muscle response to exercise (ARHGAP26, NDUFA2). In a genome-wide association study for field-measured speed in two-year-olds (n = 179) SNPs contained within the single association peak (33.2–35.6 Mb) overlapped with the ECA14 CSS signals and spanned a protocadherin gene cluster. Association tests using higher density SNP genotypes across the ECA14 locus identified a SNP within the PCDHGC5 gene associated with elite racing performance (n = 922). These results indicate that there may be differential selection for racing performance under racing and management conditions that are specific to certain geographic racing regions. In Australia breeders have principally selected horses for favourable genetic variants at loci containing genes that modulate behaviour, locomotion and skeletal muscle physiology that together appear to be contributing to early two-year-old speed.

DTR-mediated conditional cell ablation-Progress and challenges

Cell ablation is a valuable complement to mutagenesis for experimentally defining specific cell functions in physiology and pathophysiology in small animal models. One of the most popular ablation strategies involves transgenic expression of a primate diphtheria toxin receptor (DTR) on murine cells that are otherwise resistant to the bacterial exotoxin. The efforts of many laboratories using the DTR approach over the years have yielded numerous valuable insights into specific cell functions. Here, we will discuss the technical aspects of the DTR approach, including the strengths, pitfalls, and future strategies to overcome the shortcomings, highlighting a recent paper published in the European Journal of Immunology [El Hachem et al. Eur. J. Immunol. 2018 https://doi.org/10.1002/eji.201747351]. A particular focus will be given to the application of DTR approach to decipher in vivo functions of the murine myeloid cell compartment.

Spatiotemporal visualization of proHB-EGF ectodomain shedding in living cells

Heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF) is a member of the EGF family, each of which is produced as a type I transmembrane precursor. The juxtamembrane domain of proHB-EGF, a precursor of HB-EGF, is cleaved by a disintegrin and metalloproteases. HB-EGF is released into the extracellular space and strongly activates EGF receptor. The relevance of better understanding proHB-EGF shedding relates to the importance of the process in the proliferation, differentiation and survival of various types of cells. Shedding of proHB-EGF is normally evaluated using an alkaline phosphatase-tagged proHB-EGF assay or a western blotting assay that involves multiple cells, which makes it difficult to observe spatiotemporal differences in the activities of the individual cells. In this study, we developed a fluorescent proHB-EGF-based metalloprotease biosensor, named Fluhemb, to visualize spatiotemporal regulation of proHB-EGF shedding in individual cells using a simple method that measures changes in fluorescence ratios. Fluhemb might be very useful for detecting the activity of proHB-EGF shedding in various types of cells under different conditions in vitro and in vivo.

Hypoxia inhibits cardiomyocyte proliferation in fetal rat hearts via upregulating TIMP-4

Maternal hypoxia inhibits cardiomyocyte proliferation in the heart of fetal and neonatal rats. The present study tested the hypothesis that hypoxia has a direct effect inhibiting cardiomyocyte proliferation via upregulating tissue inhibitors of metalloproteinases (TIMP) in fetal rat hearts. Isolated fetal rat hearts and rat embryonic ventricular myocyte H9c2 cells were treated ex vivo with 20% or 1% O(2) for 48 or 24 h, respectively. Hypoxia caused a significant reduction in cardiomyocyte Ki-67 expression and bromodeoxyuridine incorporation in fetal hearts and H9c2 cells. In both fetal hearts and H9c2 cells, hypoxia resulted in a significant decrease in a cell division marker cyclin D2 but an increase in a cell division inhibitor p27. Additionally, hypoxia caused an upregulation of TIMP-3 and TIMP-4 in fetal hearts and H9c2 cells. Knockdown of TIMP-3 in H9c2 cells significantly increased cyclin D2 and Ki-67 and partially blocked the hypoxia-induced inhibition of cyclin D2 and Ki-67 in H9c2 cells. Unlike TIMP-3, TIMP-4 knockdown had no significant effects on the basal levels of cell proliferation but completely abrogated the hypoxia-mediated effects. These findings provide evidence of a novel causal role of TIMP-4 and TIMP-3 in the direct inhibitory effect of hypoxia on cardiomyocyte proliferation in the developing heart.

Human antigen R-mediated mRNA stabilization is required for ultraviolet B-induced autoinduction of amphiregulin in keratinocytes

All members of the EGF family are produced as transmembrane precursors that are proteolytically processed into soluble forms by disintegrin and metalloproteinases (ADAMs) for autocrine/paracrine pathways. In turn, the ligand-activated EGF receptor (EGFR) induces the expression of EGF family members, so-called "autoinduction." However, it is not well understood how this autoinduction occurs. In this study, we investigated the molecular mechanism of the autoinduction of amphiregulin (AREG), a member of the EGF family. We found that ultraviolet B (UVB) exposure increased the AREG mRNA level by stabilization of its mRNA in a human immortalized keratinocyte cell line, HaCaT. The 3' UTR of AREG mRNA was responsible for binding to an mRNA-binding protein, human antigen R (HuR), and the interaction between AREG mRNA and HuR was enhanced by UVB. Inducible knockdown of HuR expression significantly decreased AREG mRNA stability. Interestingly, treatment of HaCaT cells with an EGFR inhibitor, an EGFR neutralizing antibody, or an ADAM inhibitor destabilized AREG mRNA. In the case of ADAM inhibition, administration of soluble AREG restored the mRNA level, indicating that the stabilization occurs in a shedding-dependent manner of EGFR ligands. The HuR dependence of AREG mRNA and protein expression was also confirmed in human primary keratinocytes. Taken together, we propose a novel mechanism by which HuR regulates the stability of AREG mRNA in keratinocytes after UVB exposure and suggest that targeting of HuR functions might be crucial for understanding skin cancers caused by aberrant EGF family member-EGFR signaling.

Positive regulation of osteoclastic differentiation by growth differentiation factor 15 upregulated in osteocytic cells under hypoxia

Osteocytes are thought to play a role as a mechanical sensor through their communication network in bone. Although osteocytes are the most abundant cells in bone, little attention has been paid to their physiological and pathological functions in skeletogenesis. Here, we have attempted to delineate the pivotal functional role of osteocytes in regulation of bone remodeling under pathological conditions. We first found markedly increased osteoclastic differentiation by conditioned media (CM) from osteocytic MLO-Y4 cells previously exposed to hypoxia in vitro. Using microarray and real-time PCR analyses, we identified growth differentiation factor 15 (GDF15) as a key candidate factor secreted from osteocytes under hypoxia. Recombinant GDF15 significantly promoted osteoclastic differentiation in a concentration-dependent manner, with concomitant facilitation of phosphorylation of both p65 and inhibitory-κB in the presence of receptor activator of nuclear factor-κB ligand. To examine the possible functional significance of GDF15 in vivo, mice were subjected to ligation of the right femoral artery as a hypoxic model. A significant increase in GDF15 expression was specifically observed in tibias of the ligated limb but not in tibias of the normally perfused limb. Under these experimental conditions, in cancellous bone of proximal tibias in the ligated limb, a significant reduction was observed in bone volume, whereas a significant increase was seen in the extent of osteoclast surface/bone surface when determined by bone histomorphometric analysis. Finally, the anti-GDF15 antibody prevented bone loss through inhibiting osteoclastic activation in tibias from mice with femoral artery ligation in vivo, in addition to suppressing osteoclastic activity enhanced by CM from osteocytes exposed to hypoxia in vitro. These findings suggest that GDF15 could play a pivotal role in the pathogenesis of bone loss relevant to hypoxia through promotion of osteoclastogenesis after secretion from adjacent osteocytes during disuse and/or ischemia in bone.

Cell surface annexins regulate ADAM-mediated ectodomain shedding of proamphiregulin

Ectodomain shedding of EGFR ligands by ADAM17 is a key step of transactivation of epidermal growth factor receptor (EGFR) and the downstream signaling network. In this study, we identified cell surface annexins as regulators of ectodomain shedding of amphiregulin precursor. We propose that cell surface annexins act as a shedding platform to determine the substrate selectivity of ADAM17.

A disintegrin and metalloproteinase (ADAM) is a family of enzymes involved in ectodomain shedding of various membrane proteins. However, the molecular mechanism underlying substrate recognition by ADAMs remains unknown. In this study, we successfully captured and analyzed cell surface transient assemblies between the transmembrane amphiregulin precursor (proAREG) and ADAM17 during an early shedding phase, which enabled the identification of cell surface annexins as components of their shedding complex. Annexin family members annexin A2 (ANXA2), A8, and A9 interacted with proAREG and ADAM17 on the cell surface. Shedding of proAREG was increased when ANXA2 was knocked down but decreased with ANXA8 and A9 knockdown, because of enhanced and impaired association with ADAM17, respectively. Knockdown of ANXA2 and A8 in primary keratinocytes altered wound-induced cell migration and ultraviolet B–induced phosphorylation of epidermal growth factor receptor (EGFR), suggesting that annexins play an essential role in the ADAM-mediated ectodomain shedding of EGFR ligands. On the basis of these data, we propose that annexins on the cell surface function as “shedding platform” proteins to determine the substrate selectivity of ADAM17, with possible therapeutic potential in ADAM-related diseases.

Hypoxia-derived oxidative stress mediates epigenetic repression of PKCε gene in foetal rat hearts

AIMS

Hypoxia causes protein kinase C epsilon (PKCε) gene repression in foetal hearts, resulting in heightened cardiac susceptibility to ischaemic injury in offspring. We tested the hypothesis that hypoxia inducible factor 1 (HIF-1) and/or reactive oxygen species (ROS) mediate hypoxia-induced PKCε gene repression.

METHODS AND RESULTS

Hypoxia induced in vivo to pregnant rats, ex vivo to isolated foetal rat hearts, and in vitro in the rat embryonic ventricular myocyte cell line H9c2 resulted in a comparable decrease in PKCε protein and mRNA abundance in foetal hearts and H9c2 cells, which was associated with a significant increase in CpG methylation of the SP1-binding sites at the PKCε promoter. In H9c2 cells and foetal hearts, hypoxia caused nuclear accumulation of HIF-1α, which was inhibited by 3-(5'-hydroxymethyl-2'-furyl)-1-benzylindazole and 2-methoxy estradiol. The HIF-1α inhibitors had no significant effect on hypoxia-induced PKCε mRNA repression. Hypoxia produced a time-dependent increase in ROS production in H9c2 cells and foetal hearts that was blocked by ROS scavengers N-acetyl-cysteine or tempol. In accordance, N-acetyl-cysteine and tempol, but not apocynin, inhibited the hypoxic effect and restored PKCε protein and mRNA expression to the control values in foetal hearts and H9c2 cells. The ROS scavengers blocked hypoxia-induced CpG methylation of the SP1-binding sites, restored SP1 binding to the PKCε promoter, and abrogated the hypoxia-induced increase in the susceptibility of the heart to ischaemic injury in offspring.

CONCLUSIONS

The results demonstrate that hypoxia induces epigenetic repression of the PKCε gene through a NADPH oxidase-independent ROS-mediated pathway in the foetal heart, leading to heightened heart vulnerability to ischaemic injury in offspring.

Ectodomain shedding and remnant peptide signalling of EGFRs and their ligands

Both receptor tyrosine kinases epidermal growth factor receptors (EGFRs) and their ligands are transmembrane proteins. It has been known that ligand binding activates cytoplasmic tyrosine kinase domains of EGFRs, resulting in the transduction of signals for cell proliferation, migration, differentiation or survival. In an EGFRs-ligands system, however, signal transduction occurs not only unidirectionally but also bidirectionally, which is regulated by cell-cell contact and proteolytic cleavage. Recent studies of proteolytic cleavage 'ectodomain shedding' of EGFRs and their ligands mediated by membrane-type metalloproteinases, a disintegrin and metalloproteinases have been unveiling novel functions and molecular mechanism of their remnant peptides. In addition, the study of the remnant peptide signalling would be essential for understanding the physiological and pathological relevance of anti-shedding therapeutic strategies for diseases such as cancer.

Mitogen-activated protein kinase signaling in the heart: angels versus demons in a heart-breaking tale

Among the myriad of intracellular signaling networks that govern the cardiac development and pathogenesis, mitogen-activated protein kinases (MAPKs) are prominent players that have been the focus of extensive investigations in the past decades. The four best characterized MAPK subfamilies, ERK1/2, JNK, p38, and ERK5, are the targets of pharmacological and genetic manipulations to uncover their roles in cardiac development, function, and diseases. However, information reported in the literature from these efforts has not yet resulted in a clear view about the roles of specific MAPK pathways in heart. Rather, controversies from contradictive results have led to a perception that MAPKs are ambiguous characters in heart with both protective and detrimental effects. The primary object of this review is to provide a comprehensive overview of the current progress, in an effort to highlight the areas where consensus is established verses the ones where controversy remains. MAPKs in cardiac development, cardiac hypertrophy, ischemia/reperfusion injury, and pathological remodeling are the main focuses of this review as these represent the most critical issues for evaluating MAPKs as viable targets of therapeutic development. The studies presented in this review will help to reveal the major challenges in the field and the limitations of current approaches and point to a critical need in future studies to gain better understanding of the fundamental mechanisms of MAPK function and regulation in the heart.

Chronic prenatal hypoxia induces epigenetic programming of PKC{epsilon} gene repression in rat hearts

RATIONALE

Epidemiological studies demonstrate a clear association of adverse intrauterine environment with an increased risk of ischemic heart disease in adulthood. Hypoxia is a common stress to the fetus and results in decreased protein kinase C epsilon (PKCepsilon) expression in the heart and increased cardiac vulnerability to ischemia and reperfusion injury in adult offspring in rats.

OBJECTIVES

The present study tested the hypothesis that fetal hypoxia-induced methylation of cytosine-phosphate-guanine dinucleotides at the PKCepsilon promoter is repressive and contributes to PKCepsilon gene repression in the heart of adult offspring.

METHODS AND RESULTS

Hypoxic treatment of pregnant rats from days 15 to 21 of gestation resulted in significant decreases in PKCepsilon protein and mRNA in fetal hearts. Similar results were obtained in ex vivo hypoxic treatment of isolated fetal hearts and rat embryonic ventricular myocyte cell line H9c2. Increased methylation of PKCepsilon promoter at SP1 binding sites, -346 and -268, were demonstrated in both fetal hearts of maternal hypoxia and H9c2 cells treated with 1% O(2) for 24 hours. Whereas hypoxia had no significant effect on the binding affinity of SP1 to the unmethylated sites in H9c2 cells, hearts of fetuses and adult offspring, methylation of both SP1 sites reduced SP1 binding. The addition of 5-aza-2'-deoxycytidine blocked the hypoxia-induced increase in methylation of both SP1 binding sites and restored PKCepsilon mRNA and protein to the control levels. In hearts of both fetuses and adult offspring, hypoxia-induced methylation of SP1 sites was significantly greater in males than in females, and decreased PKCepsilon mRNA was seen only in males. In fetal hearts, there was significantly higher abundance of estrogen receptor alpha and beta isoforms in females than in males. Both estrogen receptor alpha and beta interacted with the SP1 binding sites in the fetal heart, which may explain the sex differences in SP1 methylation in the fetal heart. Additionally, selective activation of PKCepsilon restored the hypoxia-induced cardiac vulnerability to ischemic injury in offspring.

CONCLUSIONS

The findings demonstrate a direct effect of hypoxia on epigenetic modification of DNA methylation and programming of cardiac PKCepsilon gene repression in a sex-dependent manner, linking fetal hypoxia and pathophysiological consequences in the hearts of adult offspring.

Resolvin E1 protects the rat heart against reperfusion injury

The purpose of the present study was to assess whether resolvin E1 (RvE1), an anti-inflammatory mediator derived from eicosapentaenoic acid, would limit myocardial infarct size in the rat. The H9c2 cell line was used to assess whether RvE1 has direct protective effects on cardiomyocytes. In in vivo experiments, Male Sprague-Dawley rats underwent 30 min of ischemia/4 h of reperfusion. Before reperfusion, rats received intravenous RvE1 (0, 0.03, 0.1, or 0.3mg/kg). In in vitro experiments, H9c2 cells were incubated with RvE1 (0, 1, 10, 100, or 1000 nM). Cells were subjected to 18 h of incubation under normoxic conditions, 16 h of hypoxia, or 16 h of hypoxia and 2 h of reoxygenation. In vivo, RvE1 dose dependently reduced infarct size (30.7 +/- 1.7% of the area at risk in the control group and 29.1 +/- 1.6%, 14.7 +/- 1.3%, and 9.0 +/- 0.6% in the 0.03, 0.1, and 0.3 mg/kg groups, respectively, P < 0.001). In vitro, RvE1 increased viability and decreased apoptosis in a dose-dependent fashion in cells exposed to hypoxia or hypoxia/reoxygenation. A maximal effect was achieved at a concentration of 100 nM. RvE1 augmented phosphoinositide 3-kinase activity, attenuated caspase-3 activity, and augmented calcium-dependent nitric oxide synthase activity in cells exposed to hypoxia or hypoxia/reoxygenation. RvE1 increased Akt, ERK1/2, and endothelial nitric oxide synthase phosphorylation and attenuated the levels of activated caspase-3 and phosphorylated p38 levels. AG-1478, an EGF receptor tyrosine kinase inhibitor, blocked the protective effect of RvE1 both in vivo and in vitro and attenuated the RvE1-induced increase in Akt and ERK1/2 phosphorylation. In conclusion, RvE1, an anti-inflammatory mediator derived from eicosapentaenoic acid, has a direct protective effect on cardiomyocytes against ischemia-reperfusion injury and limits infarct size when administered intravenously before reperfusion.

Intestinal phenotype in mice overexpressing a heparin-binding EGF-like growth factor transgene in enterocytes

PRIMARY OBJECTIVE

Heparin-binding EGF-like growth factor (HB-EGF) protects the intestine from damage in animals. Future clinical trials of HB-EGF may involve administration of repeated doses of HB-EGF. Since HB-EGF activates EGF receptors which have been implicated in tumor development, we examined the effects of HB-EGF overexpression in the intestine.

RESEARCH DESIGN

We generated transgenic (TG) mice in which the human HB-EGF gene is driven by the villin promoter to overexpress HB-EGF along the crypt-villous axis from the duodenum to the colon.

RESULTS

HB-EGF TG mice have increased enterocyte proliferation balanced by increased enterocyte apoptosis. Despite prolonged overexpression of HB-EGF, no evidence of intestinal hyperplasia or tumor formation occurs. Although HB-EGF TG mice have no significant phenotypic alterations under basal conditions, they have increased resistance to intestinal injury.

CONCLUSIONS

Prolonged intestinal HB-EGF overexpression results in no significant phenotypic alterations under basal conditions, but confers protection against intestinal injury.