Seong Ho Koh

Glycogen synthase kinase-3β activity plays very important roles in determining the fate of oxidative stress-inflicted neuronal cells

Glycogen synthase kinase-3, especially the beta form (GSK-3beta), plays key roles in oxidative stress-induced neuronal cell death, an important pathogenic mechanism of various neurodegenerative diseases. Although the neuroprotective effects of GSK-3beta inhibitors have been described, the optimal level of GSK-3beta inhibition for neuronal cell survival has not yet been determined. We investigated the effect of varying GSK-3beta activity on the viability of oxidative stress-injured neuronally differentiated PC12 (nPC12) cells and intracellular signals related with the GSK-3beta and caspase-3 pathways. Compared to the nPC12 control cells treated with only 100 microM H(2)O(2), treatment of 50-200 nM GSK-3beta inhibitor II or 25-500 nM GSK-3beta inhibitor VIII reduced the increased enzyme activity by about 50% and protected the cells against H(2)O(2)-induced oxidative stress. The optimal concentration of GSK-3beta inhibitor II enhanced heat shock transcription factor-1 levels, decreased levels of phosphorylated tau (Ser202) and cytosolic cytochrome c, activated caspase-3, and cleaved poly (ADP-ribose) polymerase. In contrast, higher concentrations of GSK-3beta inhibitor II (more than 500 nM) induced neuronal cell death and showed opposite effects relative to the above described intracellular signals. These results suggest that optimized inhibitor levels for modulating GSK-3beta activity may prevent apoptosis induced by oxidative stress associated with neurodegenerative diseases.

Neuroprotective effects of donepezil against Aβ42-induced neuronal toxicity are mediated through not only enhancing PP2A activity but also regulating GSK-3β and nAChRs activity

The main purpose of this study was to evaluate whether donepezil, acetylcholinesterase inhibitor, shown to play a protective role through inhibiting glycogen synthesis kinase‐3β (GSK‐3β) activity, could also exert neuroprotective effects by stimulating protein phosphatase 2A (PP2A) activity in the amyloid‐beta (Aβ)42‐induced neuronal toxicity model of Alzheimers disease. In Aβ42‐induced toxic conditions, each PP2A and GSK‐3β activity measured at different times showed time‐dependent reverse pattern toward the direction of accelerating neuronal deaths with the passage of time. In addition, donepezil pre‐treatment showed dose‐dependent stepwise increase of neuronal viability and stimulation of PP2A activity. However, such effects on them were significantly reduced through the depletion of PP2A activity with either okadaic acid or PP2Ac siRNA. In spite of blocked PP2A activity in this Aβ42 insult, however, donepezil pretreatment showed additional significant recovering effect on neuronal viability when compared to the value without donepezil. Moreover, donepezil partially recovered its dephosphorylating effect on hyperphosphorylated tau induced by Aβ42. This observation led us to assume that additional mechanisms of donepezil, including its inhibitory effect on GSK‐3β activity and/or the activation role of nicotinic acetylcholine receptors (nAChRs), might be involved. Taken together, our results suggest that the neuroprotective effects of donepezil against Aβ42‐induced neurotoxicity are mediated through activation of PP2A, but its additional mechanisms including regulation of GSK‐3β and nAChRs activity would partially contribute to its effects.

β-PIX Is Critical for Transplanted Mesenchymal Stromal Cell Migration

Bone marrow-derived mesenchymal stromal cells (MSCs) have been used successfully as a source of stem cells for treating neurodegenerative diseases. However, for reasons that are not clear, autologous MSC transplants have not yielded successful results in human trials. To test one possible reason, we compared the migratory ability of MSCs from amyotrophic lateral sclerosis (ALS) patients with those of healthy controls. We found that MSCs derived from ALS patients (ALS-MSCs) had a reduced ability to migrate, which may explain why autologous transplantation is not successful. We also found that expression of one of the intracellular factors implicated in migration, β-PIX, was significantly reduced in ALS-MSCs compared with healthy stem cells. Restoration of β-PIX expression by genetic manipulation restored the migratory ability of ALS-MSCs, and inhibition of β-PIX expression with shRNA reduced the migration of healthy MSCs. We suggest that transplantation of allogeneic or genetically modified autologous stem cells might be a more promising strategy for ALS patients than transplantation of autologous stem cells.

Preoperative Coronary Stenosis Is a Determinant of Early Vascular Outcome after Carotid Endarterectomy

Background and Purpose The benefit of carotid endarterectomy (CEA) is directly influenced by the risk of perioperative adverse outcomes. However, patient-level risks and predictors including coronary stenosis are rarely evaluated, especially in Asian patients. The aim of this study was to determine the relationship between the vascular risk factors underlying CEA, including coronary stenosis, and postoperative outcome. Methods One hundred and fifty-three consecutive CEAs from our hospital records were included in this analysis. All patients underwent coronary computed tomography angiography before CEA. Data were analyzed to determine the vascular outcomes in patients with mild-to-moderate vs. severe coronary stenosis and high vs. standard operative risk, based on the criteria for high operative risk defined in the Stenting and Angioplasty with Protection in Patients at High Risk for Endarterectomy (SAPPHIRE) trial. The vascular outcome was defined as the occurrence of postoperative (≤30 days) stroke, myocardial infarction (MI), or death. Results An adverse vascular outcome occurred in 8 of the 153 CEAs, with 6 strokes, 2 MIs, and 3 deaths. The vascular outcome differed significantly between the groups with mild-to-moderate and severe coronary stenosis (p=0.024), but not between the high- and standard-operative-risk groups (stratified according to operative risk as defined in the SAPPHIRE trial). Multivariable analysis adjusting for potent predictors revealed that severe coronary stenosis (odds ratio, 6.87; 95% confidence interval, 1.20-39.22) was a significant predictor of the early vascular outcome. Conclusions Severe coronary stenosis was identified herein as an independent predictor of an adverse early vascular outcome.

Reduction of MMP-9 and MIF Levels is Associated with the Beneficial Effects of Cilostazol in the Patients with Silent Brain Infarcts

Silent brain infarcts (SBIs) are cerebral infarcts seen on brain computed tomography (CT) or magnetic resonance imaging (MRI) in the absence of any clinical symptoms of stroke. In a previous study, cilostazol was shown to prevent the appearance or progression of SBIs. The present study aimed to evaluate the possible mechanisms of cilostazol in its beneficial effects on patients with SBIs by serially measuring inflammation- and angiogenesisassociated biomarkers such as matrix metalloproteinase-9 (MMP-9), macrophage migration inhibitory factor(MIF), visceral fat–derived adipokine (visfatin), C-X-C motif ligand 12 (CXCL12), and vascular endothelial growth factor (VEGF). We consecutively enrolled 26 patients with SBIs. SBIs were interpreted by two neuroradiologists and two neurologists. MMP-9, MIF, visfatin, CXCL12, and VEGF were measured in fasting blood samples from these 26 patients and 10 healthy volunteers at baseline and after taking cilostazol (200 mg/day) for one week and for 3 months. Serum MMP-9 was higher in patients with SBIs than in healthy controls at baseline (p<0.05), and levels of MMP-9 and MIF decreased after taking cilostazol for 3 months (p<0.01). MMP-9 levels were also lower at 1 week in the cilostazol group (p<0.05). Cilostazol had no significant effect on the other inflammatory biomarkers such as visfatin, CXCL12 and VEGF. Cilostazol decreases the inflammatory biomarkers MMP-9 and MIF in patients with SBIs and it may contribute to its beneficial effects in these patients.