Ji Ha Choi

Therapeutic effects of resveratrol during acute periods following experimental ischemic stroke.

We defined whether resveratrol administration during the acute phase of ischemic stroke reduces brain injury in mice. Infarct volumes were decreased significantly in both sexes with different doses of resveratrol (5mg/kg for males and 1mg/kg for females) administered 3h after ischemic stroke. Administration of resveratrol 6h after insult was also effective to decrease infarct volumes. Resveratrol suppressed expressions of IL-1β and TNF-α, microglial activation, and ROS production in the ischemic cortex. The findings suggest that the suppression of inflammation is partly associated with the neuroprotective effects of resveratrol, and resveratrol can be developed as a therapeutic drug for acute ischemic stroke.

Conserved aquaporin 4 levels associated with reduction of brain edema are mediated by estrogen in the ischemic brain after experimental stroke

Aquaporin 4 (AQP4), the most abundant water channel protein in the brain, is involved in brain edema induced by ischemic insults. To evaluate whether the neuroprotective effects of estrogen are associated with AQP4 expression and edema formation, changes in AQP levels and ischemic edema were examined in the brains of male and female mice subjected to transient middle cerebral artery occlusion. Infarct volume and edema formation were markedly less in females than in males. AQP4 expression in the ischemic cortex of females was relatively well preserved, whereas it was significantly decreased in males. These effects disappeared in ovariectomized females but were reversed by estrogen replacement. Furthermore, AQP4 expression was decreased with increased brain edema in females treated with ICI182,780, an estrogen receptor antagonist. These findings suggest that the estrogen effect on the reduction of ischemic brain edema is associated with the preserved level of AQP4 that is partly mediated by estrogen receptors.

ULK1 prevents cardiac dysfunction in obesity through autophagy-meditated regulation of lipid metabolism

AimsnAutophagy is essential to maintain tissue homeostasis, particularly in long-lived cells such as cardiomyocytes. Whereas many studies support the importance of autophagy in the mechanisms underlying obesity-related cardiac dysfunction, the role of autophagy in cardiac lipid metabolism remains unclear. In the heart, lipotoxicity is exacerbated by cardiac lipoprotein lipase (LPL), which mediates accumulation of fatty acids to the heart through intravascular triglyceride (TG) hydrolysis.nnnMethods and resultsnIn both genetic and dietary models of obesity, we observed a substantial increase in cardiac LPL protein levels without any change in messenger ribonucleic acid (mRNA). This was accompanied by a dramatic down-regulation of autophagy in the heart, as revealed by reduced levels of unc-51 like kinase-1 (ULK1) protein. To further explore the relationship between cardiac LPL and autophagy, we generated cardiomyocyte-specific knockout mice for ulk1 (Myh6-cre/ulk1fl/fl), Lpl (Myh6-cre/Lplfl/fl), and mice with a combined deficiency (Myh6-cre/ulk1fl/flLplfl/fl). Similar to genetic and dietary models of obesity, Myh6-cre/ulk1fl/fl mice had a substantial increase in cardiac LPL levels. When these mice were fed a high-fat diet (HFD), they showed elevated cardiac TG levels and deterioration in heart function. However, with combined deletion of LPL and ULK1 in Myh6-cre/ulk1fl/flLplfl/fl mice, HFD feeding did not lead to alterations in levels of TG or diacylglycerol, or in cardiac function. To further elucidate the role of autophagy in cardiac lipid metabolism, we infused a peptide that enhanced autophagy (D-Tat-beclin1). This effectively lowered LPL levels at the coronary lumen by restoring autophagy in the genetic model of obesity. This decrease in cardiac luminal LPL was associated with a reduction in TG levels and recovery of cardiac function.nnnConclusionnThese results provide clear evidence of the critical role of modulating cardiac LPL activity through autophagy-mediated proteolytic clearance as a potential novel strategy to overcome obesity-related cardiomyopathy.

Functional characterization of MATE2-K genetic variants and their effects on metformin pharmacokinetics.

Objective Human multidrug and toxin extrusion member 2 (MATE2-K, SLC47A2) plays an important role in the renal elimination of various clinical drugs including the antidiabetic drug metformin. The goal of this study was to characterize genetic variants of MATE2-K and determine their association with the pharmacokinetics of metformin. Methods We screened DNA samples from 48 healthy Koreans for variants in the promoter and coding regions of MATE2-K and examined the function of common haplotypes in the promoter region using in-vitro luciferase assays. Then, the metformin pharmacokinetic study was carried out to determine the association between MATE2-K promoter haplotypes and metformin pharmacokinetics. Results Nine variants in the promoter region of MATE2-K and one nonsynonymous variant, p.G211V, were identified. The MATE2-K promoter haplotype 1 containing a known functional polymorphism, g.−130G>A and haplotype 2 containing two polymorphisms, g.−609G>A and g.−396G>A showed a significant increase in reporter activity. Among the 45 individuals who participated in the metformin pharmacokinetic study, 12 healthy Koreans who were homozygous for haplotype 1 or 2 showed a significant increase in renal clearance [539±76 (reference group) vs. 633±102 (variant group) ml/min; P=0.006] and secretion clearance [439±81 (reference group) vs. 531±102 (variant group) ml/min; P=0.007] of metformin compared with that shown by the reference group. Conclusion Our study suggests that common promoter haplotypes of MATE2-K are associated with the pharmacokinetics of metformin.

Transcriptional regulation of adrenomedullin by oncostatin M in human astroglioma cells: Implications for tumor invasion and migration

Adrenomedullin (ADM), a secretory peptide with multiple functions in physiological to pathological conditions, is upregulated in several human cancers, including brain, breast, colon, prostate, and lung cancer. However, the molecular mechanisms underlying the regulation of ADM expression in cancerous cells are not fully understood. Here, we report that oncostatin M (OSM), a cytokine belonging to the interleukin-6 family, induces ADM expression in astroglioma cells through induction of signal transducer and activator of transcription-3 (STAT-3) phosphorylation, nuclear translocation, and subsequent DNA binding to the ADM promoter. STAT-3 knockdown decreased OSM-mediated expression of ADM, indicating that ADM expression is regulated by STAT-3 in astroglioma cells. Lastly, scratch wound healing assay showed that astroglioma cell migration was significantly enhanced by ADM peptides. These data suggest that aberrant activation of STAT-3, which is observed in malignant brain tumors, may function as one of the key regulators for ADM expression and glioma invasion.

Benzylideneacetophenone derivatives attenuate IFN-γ-induced IP-10/CXCL10 production in orbital fibroblasts of patients with thyroid-associated ophthalmopathy through STAT-1 inhibition

The aim of the present study was to identify a new candidate anti-inflammatory compound for use in the active stage of thyroid-associated ophthalmopathy (TAO). Benzylideneacetophenone compound JC3 [(2E)-3-(4-hydroxy-3-methoxyphenyl)phenylpro-2-en-l-one] was synthesized based on a structural modification of yakuchinone B, a constituent of the seeds of Alpinia oxyphylla, which belongs to the ginger family (Zingiberaceae), has been widely used in folk medicine as an anti-inflammatory phytochemical. Orbital fibroblasts were primarily cultured from patients with TAO, and the potential of JC3 to suppress the interferon (IFN)-γ-induced protein (IP)-10/CXCL10 production in these cells was determined. IFN-γ strongly increased the level of IP-10/CXCL10 in orbital fibroblasts from patients with TAO. JC3 exerted a significant inhibitory effect on the IFN-γ-induced increase in IP-10/CXCL10 in a dose-dependent manner; its potency was greater than that of an identical concentration of yakuchinone B with no toxicity to cells at the concentration range used. Moreover, the constructed dimer and trimer polystructures of JC3, showed greater potency than JC3 in suppressing the IFN-γ-induced production of IP-10/CXCL10. JC3 significantly attenuated the IP-10/CXCL10 mRNA expression induced by IFN-γ, and a gel-shift assay showed that JC3 suppressed IFN-γ-induced DNA binding of signal transducer and activator of transcription-1 (STAT-1) in TAO orbital fibroblasts. Our results provide initial evidence that the JC3 compound reduces the levels of IP-10/CXCL10 protein and mRNA induced by IFN-γ in orbital fibroblasts of TAO patients. Therefore, JC3 might be considered as a future candidate for therapeutic application in TAO that exerts its effects by modulating the pathogenic mechanisms in orbital fibroblasts.

Extracellular matrix-derived extracellular vesicles promote cardiomyocyte growth and electrical activity in engineered cardiac atria

Extracellular matrix (ECM) plays a critical role in the provision of the necessary microenvironment for the proper regeneration of the cardiac tissue. However, specific mechanisms that lead to ECM-mediated cardiac regeneration are not well understood. To elucidate the potential mechanisms, we investigated ultra-structures of the cardiac ECM using electron microscopy. Intriguingly, we observed large quantities of micro-vesicles from decellularized right atria. RNA and protein analyses revealed that these contained exosomal proteins and microRNAs (miRNAs), which we referred to herein as ECM-derived extracellular vesicles (ECM-EVs). One particular miRNA from ECM-EVs, miR-199a-3p, promoted cell growth of isolated neonatal cardiomyocytes and sinus nodal cells by repressing homeodomain-only protein (HOPX) expression and increasing GATA-binding 4 (Gata4) acetylation. To determine the mechanisms, we knocked down Gata4 and showed that miR-199a-3p actions required Gata4 for cell proliferation in isolated neonatal cardiomyocytes and sinus nodal cells. To further explore the role of this miRNA, we isolated neonatal cardiac cells and recellularized into atrial ECM, referred here has engineered atria. Remarkably, miR-199a-3p mediated the enrichment of cardiomyocyte and sinus nodal cell population, and enhanced electrocardiographic signal activity of sinus nodal cells in the engineered atria. Importantly, antisense of miRNA (antagomir) against miR-199a-3p was capable of abolishing these actions of miR-199a-3p in the engineered atria. We further showed in Ang II-infused animal model of sinus nodal dysfunction that miR-199-3p-treated cardiac cells remarkably ameliorated and restored the electrical activity as shown by normalization of the ECG, in contrast to untreated cells, which did not show electrical recovery. In conclusion, these results provide clear evidence of the critical role of ECM, in not only providing a scaffold for cardiac tissue growth, but also in promoting atrial electrical function through ECM-derived miR-199a-3p.

Functional characterization of ABCB4 mutations found in progressive familial intrahepatic cholestasis type 3

Multidrug resistance 3 (MDR3), encoded by the ATP-binding cassette, subfamily B, member 4 gene (ABCB4), localizes to the canalicular membrane of hepatocytes and translocates phosphatidylcholine from the inner leaflet to the outer leaflet of the canalicular membrane. Progressive familial intrahepatic cholestasis type 3 (PFIC3) is a rare hepatic disease caused by genetic mutations of ABCB4. In this study, we characterized 8 ABCB4 mutations found in PFIC3 patients, using in vitro molecular assays. First, we examined the transport activity of each mutant by measuring its ATPase activity using paclitaxel or phosphatidylcholine. Then, the pathogenic mechanisms by which these mutations affect MDR3 were examined through immunoblotting, cell surface biotinylation, and immunofluorescence. As a result, three ABCB4 mutants showed significantly reduced transport activity. Among these mutants, one mutation A364V, located in intracellular domains, markedly decreased MDR3 expression on the plasma membrane, while the others did not affect the expression. The expression of MDR3 on the plasma membrane and transport activity of A364V was rescued by a pharmacological chaperone, cyclosporin A. Our study provides the molecular mechanisms of ABCB4 mutations and may contribute to the understanding of PFIC3 pathogenesis and the development of a mutation-specific targeted treatment for PFIC3.

Identification of OCTN2 variants and their association with phenotypes of Crohn's disease in a Korean population.

Crohn’s disease (CD) is a chronic inflammatory bowel disease and a genetic variant in the OCTN2, g.-207Gu2009>u2009C is significantly associated with CD susceptibility. This study was aimed to identify novel OCTN2 functional promoter variants and their roles in transcriptional regulation using various in vitro assays. In addition, we investigated the association between OCTN2 genotypes and CD through genetic analysis using DNA samples from 193 patients with CD and 281 healthy controls. Among the three major promoter haplotypes of OCTN2 identified, one haplotype, H3, showed a significant decrease in promoter activity: two polymorphisms in H3 were associated with a significant reduction in promoter activity. In particular, we found that the reduced transcriptional activity of those two polymorphisms results from a reduction in the binding affinity of the activators, NF-E2 and YY1, to the OCTN2 promoter. The functional haplotype of the OCTN2 promoter was associated with clinical course of CD such as the disease behavior and need for surgery. However, genetic variants or haplotypes of OCTN2 did not affect the susceptibility to CD. Our results suggest that a common promoter haplotype of OCTN2 regulates the transcriptional rate of OCTN2 and influences the clinical course of CD.

Repression of adenosine triphosphate–binding cassette transporter ABCG2 by estrogen increases intracellular glutathione in brain endothelial cells following ischemic reperfusion injury

The adenosine triphosphate-binding cassette efflux transporter ABCG2, which is located in the blood-brain barrier limits the entry of endogenous compounds and xenobiotics into the brain, and its expression and activity are regulated by estrogen. This study was aimed to define the role of ABCG2 in estrogen-mediated neuroprotection against ischemic injury. ABCG2 protein levels before and after ischemic stroke were increased in the brain of female mice by ovariectomy, which were reversed by estrogen replacement. In brain endothelial cell line bEnd.3, estrogen reduced the basal ABCG2 protein level and efflux activity and protected cells from ischemic injury without inducing ABCG2 expression. When bEnd.3xa0cells were transfected with ABCG2 small interfering RNA, ischemia-induced cell death was reduced, and the intracellular concentration of glutathione, an antioxidant that is transported by ABCG2, was increased. In addition, after ischemic stroke in ovariectomized mice, estrogen prevented the reduction of intracellular glutathione level in brain microvessels. These data suggested that the suppression of ABCG2 by estrogen is involved in neuroprotection against ischemic injury by increasing intracellular glutathione, and that the modulation of ABCG2 activity offers a therapeutic target for brain diseases in estrogen-deficient aged women.