Jung-Won Choi

hnRNP Q regulates translation of p53 in normal and stress conditions

The responses to numerous stress signals are important for cellular growth and survival. The p53 tumor-suppressor protein is stabilized under stress conditions and induces transcription of several genes to regulate cell cycle and apoptosis. Regarding p53 protein accumulation, inhibition of proteasomal degradation of p53 protein, which is mainly mediated by Mdm2, has received much attention. Here, we demonstrate that regulation of translation initiation is also crucial for p53 protein accumulation. Furthermore, we report that heterogeneous nuclear ribonucleoprotein (hnRNP) Q binds to the 5′-untranslated region (UTR) of mouse p53 mRNA and regulates translation efficiency of p53 and apoptosis progression. We also suggest that changes in cytosolic hnRNP Q levels contribute to cell cycle-dependent translational differences in p53 mRNA.

Regulatory Effect of Common Promoter Polymorphisms on the Expression of the 11β-Hydroxysteroid Dehydrogenase Type 1 Gene

Background/Aims: Glucocorticoids play an important role in the pathogenesis of obesity and insulin resistance. 11β-hydroxysteroid dehydrogenase type 1 (HSD11B1), which converts inactive cortisone to active cortisol, has become an emerging therapeutic target for type 2 diabetes mellitus and obesity. In this study, we examined the association between HSD11B1 polymorphisms and type 2 diabetes and metabolic phenotypes in Koreans. Methods: We sequenced all exons including exon-intron boundaries and the promoter region of the HSD11B1 gene. Of 8 polymorphisms identified, we selected 4 common single-nucleotide polymorphisms (g.–19835G>A, g.–19609A>G, g.+27447G>C and g.+27810C>T) based on location, linkage disequilibrium and frequency and which were genotyped in 757 subjects with type 2 diabetes and 644 nondiabetic subjects. Results: There was no association between the 4 common polymorphisms of HSD11B1 and type 2 diabetes. g.–19835G>A and g.–19609A>G showed modest associations with fasting plasma glucose and body mass index but the significance of these associations was lost after adjustment for multiple comparison. With regard to promoter polymorphisms in the HSD11B1 gene, a haplotype construct carrying both g.–19835A and g.–19609G showed significantly decreased promoter activity compared to other common haplotype constructs. Conclusion: The variations in HSD11B1 were not associated with susceptibility to type 2 diabetes or metabolic phenotypes in Koreans. However, the common promoter variants of the gene might exert a polymorphic regulatory effect on HSD11B1 expression.

Genome-Wide Profiling of Antigen-Induced Time Course Expression Using Murine Models for Acute and Chronic Asthma

Background: Asthma is a complex-trait disease caused by complicated interactions among multiple genetic and environmental risk factors. The clinical symptoms of asthma, such as periodic airway obstruction, hyperresponsiveness and mucus hypersecretion, are mediated by acute and chronic bronchial inflammation. Methods: To better understand the mechanisms by which allergen-induced acute inflammation leads to chronic asthma accompanied by irreversible airway remodeling, we analyzed time course transcriptional responses in the lungs of model mice that were exposed to aerosolized ovalbumin for up to 9 weeks after an initial sensitization. Results: We observed increased levels of total plasma IgE and histological changes in lung tissues from the ovalbumin-treated mice, which is consistent with the typical inflammatory phenotypes of asthma pathogenesis. Our oligonucleotide microarray analyses revealed a total of 776 differentially expressed genes induced by antigenic challenge (≧1.5-fold change, p < 0.05). Of these genes, most of the immune-responsive genes were transiently up-regulated in the early phase of the allergen treatment (within a week) with a concomitant up-regulation of genes involved in mucus production. These genes were not differentially regulated in the mice challenged for a longer period of time (up to 6 weeks). We also identified some of the genes implicated in extracellular matrix remodeling, for which the time course expression did not necessarily coincide with the expression patterns of immune-responsive genes. Conclusion: Our data suggest that there is a complex interregulatory genetic network associated with the structural changes that accompany the progression of the allergic inflammatory reaction in chronic asthma.

CD137 induces adhesion and cytokine production in human monocytic THP-1 cells

CD137, which is expressed on activated T cells, plays a critical role in inflammatory responses. However, the exact role that CD137 plays in monocytes is not fully known. Here we studied the expression and function of CD137 in human monocytic THP-1 cells, which we found constitutively expresses CD137 at the mRNA and protein level. Cross-linking of CD137 increased the secretion of IL-8 and TNF-α, promoted the expression of CD54 and CD11b, and increased adhesion to extracellular matrix (ECM) proteins. In particular CD137-induced adhesion of THP-1 cells was inhibited by an inhibitor of mitogen-activated protein kinase kinase (MEK), but not by a p38 kinase inhibitor. Taken together, these results show that the adhesion and cytokine production of THP-1 cells induced by CD137 occur via activation of MEK, which results in the activation of ERK-1/2 signaling pathways. Therefore, this study suggests that CD137 induces an activating and migrating signal during inflammatory processes.

Interaction of small G protein signaling modulator 3 with connexin 43 contributes to myocardial infarction in rat hearts

Connexin 43 (Cx43), a ubiquitous connexin expressed in the heart and skin, is associated with a variety of hereditary conditions. Therefore, the characterization of Cx43-interacting proteins and their dynamics is important to understand not only the molecular mechanisms underlying pathological malfunction of gap junction-mediated intercellular communication but also to identify novel and unanticipated biological functions of Cx43. In the present study, we observed potential targets of Cx43 to determine new molecular functions in cardio-protection. MALDI-TOF mass spectrometry analysis of Cx43 co-immunoprecipitated proteins showed that Cx43 interacts with several proteins related to metabolism. In GeneMANIA network analysis, SGSM3, which has not been previously associated with Cx43, was highly correlated with Cx43 in heart functions, and high levels of SGSM3 appeared to induce the turnover of Cx43 through lysosomal degradation in myocardial infarcted rat hearts. Moreover, we confirmed that lysosomal degradation of Cx43 is dependent upon the interaction between SGSM3 and Cx43 in H9c2 cardiomyocytes. The functional importance of the interaction between SGSM3 and Cx43 was confirmed by results showing that Cx43 expression was enhanced by SGSM3 siRNA knockdown in H9c2 cells. In summary, the results of this study elucidate the molecular mechanisms in which Cx43 with SGSM3 is degraded in myocardial infarcted rat hearts, which may contribute to the establishment of new therapeutic targets to modulate cardiac function in physiological and pathological conditions.

Effects of donor age on human adipose-derived adherent stromal cells under oxidative stress conditions

Objective Adipose-derived stromal vascular fractions (SVFs) are heterogeneous complex populations of cells with therapeutic efficacy for tissue generation and vascular stabilization. SVFs have cardiomyogenic potential, and many researchers have examined the possibility of SVF transplantation for heart disease. In cell-based therapies, donor age affects the regenerative capability, cell yield, and differentiation potential of adult tissues; however, opposing or controversial results have been found in humans. We examined whether SVF transplantation into impaired heart tissue shows differential effects according to donor age. Methods We investigated differences in protein expression in human umbilical vein endothelial cells (HUVECs) co-cultured with adipose-derived adherent stromal cells (ADASs) from donors of different ages [>40-year-olds (40s group) and >60-year-olds (60s group)] under oxidative stress conditions. Results Although co-culturing HUVECs with ADASs ameliorated inflammation due to increased oxidative stress conditions, few differences were observed between the ADASs from the 40s and 60s groups. Moreover, the Database for Annotation, Visualization, and Integrated Discovery classification tool revealed differentially expressed genes in the Kyoto Encyclopedia of Genes and Genomes pathway associated with cytokine–cytokine receptor interaction in response to ADASs. Conclusion Protein expression profiles were unchanged in HUVECs induced by isolated ADASs from donors of different ages under oxidative stress conditions.

TAK-733 inhibits inflammatory neointimal formation by suppressing proliferation, migration, and inflammation in vitro and in vivo

As a potent and selective allosteric inhibitor of MEK, TAK-733 has been shown to exert anti-cancer effects for a wide range of cancers both in vitro and in vivo. However, its effects on inhibiting growth have never been investigated in the cardiovascular system, where regulation of abnormal vascular smooth muscle cell growth in neointimal hyperplasia is an important area of focus. Angiotensin II was used to mimic inflammatory neointimal hyperplasia in an in vitro environment, and balloon catheter-induced injury with an infusion of angiotensin II was used to generate an in vivo rat restenosis model under inflammatory conditions. TAK-733 exerted anti-proliferative and anti-migratory effects on human vascular smooth muscle cells. These multiple effects of TAK-733 were evaluated using various assays, such as cell cycle analysis and wound healing. Interestingly, TAK-733 did not induce apoptosis in smooth muscle cells but only reduced the proliferation rate; additionally, it did not affect EC viability. TAK-733 also exhibited anti-inflammatory activity, as observed by attenuated monocyte adhesion to smooth muscle cells via inhibition of ICAM1 and VCAM1 overexpression. The in vivo study demonstrated that neointimal hyperplasia after balloon injury and angiotensin II stimulation was suppressed by TAK-733, and downregulation of the inflammatory signal and enhanced re-endothelialization were observed. TAK-733 may have therapeutic potential for treating neointimal hyperplasia by attenuating smooth muscle cell proliferation, migration, and inflammation. Thus, TAK-733 could be a promising drug candidate for treating patients with restenosis.Atherosclerosis: Potential therapy based on prospective cancer drugDrug undergoing trials as a cancer treatment shows promise in tackling the narrowing of blood vessels in other diseases. The thickening of arterial walls and consequent restriction of blood flow, typical of conditions like atherosclerosis, increases the risk of heart attacks and strokes. Soyeon Lim and Ki-Chul Hwang at the Catholic Kwandong University, South Korea, and co-workers have investigated the efficacy of a prospective cancer drug called TAK-733 against atherosclerosis both in cell culture and in trials on rat models of the disease. The team hypothesized that TAK-733’s anti-cancer effects could prove useful in treating other conditions. They demonstrated that TAK-733 successfully blocked the proliferation and migration of vascular smooth muscle cells, the overexpression of which is a dominant factor in the development of atherosclerosis.

Multipoint targeting of TGF-β/Wnt transactivation circuit with microRNA 384-5p for cardiac fibrosis

Cardiac fibrosis is a common precursor to ventricular dysfunction and eventual heart failure, and cardiac fibrosis begins with cardiac fibroblast activation. Here we have demonstrated that the TGF-β signaling pathway and Wnt signaling pathway formed a transactivation circuit during cardiac fibroblast activation and that miR-384-5p is a key regulator of the transactivation circuit. The results of in vitro study indicated that TGF-β activated an auto-positive feedback loop by increasing Wnt production in cardiac fibroblasts, and Wnt neutralizing antibodies disrupted the feedback loop. Also, we demonstrated that miR-384-5p simultaneously targeted the key receptors of the TGF-β/Wnt transactivation circuit and significantly attenuated both TGF-β-induced cardiac fibroblast activation and ischemia-reperfusion-induced cardiac fibrosis. In addition, small molecule that prevented pro-fibrogenic stimulus-induced downregulation of endogenous miR-384-5p significantly suppressed cardiac fibroblast activation and cardiac fibrosis. In conclusion, modulating a key endogenous miRNA targeting multiple components of the TGF-β/Wnt transactivation circuit can be an effective means to control cardiac fibrosis and has great therapeutic potential.

Protective effects of kenpaullone on cardiomyocytes following H2O2-induced oxidative stress are attributed to inhibition of connexin 43 degradation by SGSM3

A previous study showed that small G protein signaling modulator 3 (SGSM3) was highly correlated with Cx43 in heart functions and that high levels of SGSM3 may induce Cx43 turnover through lysosomal degradation in infarcted rat hearts. Here, we investigated the protective effects of kenpaullone on cardiomyocytes following H2O2-induced oxidative stress mediated by the interaction of SGSM3 with Cx43. We found that the gap junction protein Cx43 was significantly down-regulated in an H2O2 concentration-dependent manner, whereas expression of SGSM3 was up-regulated upon H2O2 exposure in H9c2 cells. The effect of kenpaullone pretreatment on H2O2-induced cytotoxicity was evaluated in H9c2 cells. H2O2 markedly increased the release of lactate dehydrogenase (LDH), while kenpaullone pretreatment suppressed LDH release in H9c2 cells. Moreover, kenpaullone pretreatment significantly reduced ROS fluorescence intensity and significantly down-regulated the level of apoptosis-activating genes (cleaved caspase-3, cleaved caspase-9 and cytochrome C), autophagy markers (LC3A/B), and the Cx43-interacting partner SGSM3. These results suggest that kenpaullone plays a role in protecting cardiomyocytes from oxidative stress and that the turnover of Cx43 through SGSM3-induced lysosomal degradation underlies the anti-apoptotic effect of kenpaullone.