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Park D.-W.,Aging Associated Vascular Disease Research Center | Lee H.-K.,Aging Associated Vascular Disease Research Center | Lyu J.H.,Aging Associated Vascular Disease Research Center | Chin H.,Aging Associated Vascular Disease Research Center | And 4 more authors.
Biochemical and Biophysical Research Communications | Year: 2013

ATP-binding cassette transporter A1 (ABCA1) is a membrane-bound protein that regulates cardiovascular disease including atherosclerosis by the efflux of excess cholesterol from cells and by suppression of inflammation. Using a mouse macrophage cell line Raw264.7, we studied the importance of toll-like receptor 2 (TLR2) on ABCA1 expression and the signaling pathway responsible for TLR2-mediated ABCA1 expression. Interestingly, our data demonstrated that treatment of macrophages with TLR2 agonist Pam3CSK4 significantly increased ABCA1 mRNA and protein levels. We found that ABCA1 induction is myeloid differentiation primary response gene 88 (MyD88)-dependent as well as TLR2-dependent. ABCA1 induction upon Pam3CSK4 is controlled by protein kinase C-η (PKC-η) and phospholipase D2 (PLD2). Furthermore, direct treatment of dioctanoyl phosphatidic acid (diC8PA) into cells also induced ABCA1 mRNA and protein indicating that PLD2-mediated PA involve in the TLR2-stimulated ABCA1 expression. Cumulatively, these results demonstrate for the first time that activation of PKC-η and PLD2 signaling pathway is an important mechanism for regulation of TLR2-induced ABCA1 expression. © 2012 Elsevier Inc. Source

Lyu J.H.,Aging Associated Vascular Disease Research Center | Park D.-W.,Aging Associated Vascular Disease Research Center | Huang B.,Aging Associated Vascular Disease Research Center | Kang S.H.,Yeungnam University | And 5 more authors.
Journal of Cellular Biochemistry | Year: 2015

Regulator of G protein signaling 2 (RGS2) is a member of a family of proteins that functions as a GTPase-activating protein (GAP) for Gα subunits. RGS2 mRNA expression is lower in breast cancerous tissues than in normal tissues. In addition, expression of RGS2 is also lower in MCF7 (cancerous breast cells) than in MCF10A (normal breast cells). Here we investigated whether RGS2 inhibits growth of breast cancer cells. RGS2 overexpression in MCF7 cells inhibited epidermal growth factor- or serum-induced proliferation. In HEK293T cells expressing RGS2, cell growth was also significantly suppressed (In addition, exogenous expression of RGS2 in HEK293T cells resulted in the significant suppression of cell growth). These results suggest that RGS2 may have a tumor suppressor function. MG-132 treatment of MCF7 cells increased endogenous or exogenous RGS2 levels, suggesting a post-transcriptional regulatory mechanism that controls RGS2 protein levels. RGS2 protein was degraded polyubiquitinated the K71 residue, but stabilized by deubiquitinase monocyte chemotactic protein-induced protein 1 (MCPIP1), and not affected by dominant negative mutant (C157A) of MCPIP1. Gene expression profiling study showed that overexpression of RGS2 decreased levels of testis specific Y encoded like protein 5 (TSPYL5), which plays a causal role in breast oncogenesis. TSPYL5 protein expression was low in MCF10A and high in MCF7 cells, showing the opposite aspect to RGS2 expression. Additionally, RGS2 or MCPIP1 overexpression in MCF7 cells decreased TSPYL5 protein level, indicating that RGS2 stabilized by MCPIP1 have diminished TSPYL5 protein levels, thereby exerting an inhibitory effect of breast cancer cell growth. © 2014 Wiley Periodicals, Inc. Source

Jung B.-C.,Fatima General Hospital | Lee S.-H.,Aging Associated Vascular Disease Research Center | Cho Y.-K.,Kyungpook National University | Park H.-S.,Daegu University | And 3 more authors.
Journal of Korean Medical Science | Year: 2011

Under conditions of Na + channel hyperactivation with aconitine, the changes in action potential duration (APD) and the restitution characteristics have not been well defined in the context of aconitine-induced arrhythmogenesis. Optical mapping of voltage using RH237 was performed with eight extracted rabbit hearts that were perfused using the Langendorff system. The characteristics of APD restitution were assessed using the steadystate pacing protocol at baseline and 0.1 μM aconitine concentration. In addition, pseudo-ECG was analyzed at baseline, and with 0.1 and 1.0 μM of aconitine infusion respectively. Triggered activity was not shown in dose of 0.1 μM aconitine but overtly presented in 1.0 μM of aconitine. The slopes of the dynamic APD restitution curves were significantly steeper with 0.1 μM of aconitine than at baseline. With aconitine administration, the cycle length of initiation of APD alternans was significantly longer than at baseline (287.5 ± 9.6 vs 247.5 ± 15.0 msec, P = 0.016). The functional reentry following regional conduction block appears with the progression of APD alternans. Ventricular fibrillation is induced reproducibly at pacing cycle length showing a 2:1 conduction block. Low-dose aconitine produces arrhythmogenesis at an increasing restitution slope with APD alternans as well as regional conduction block that proceeds to functional reentry. © 2011 The Korean Academy of Medical Sciences. Source

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