Youngchul Kim

Neuroprotective effects of donepezil through inhibition of GSK‐3 activity in amyloid‐β‐induced neuronal cell death

Acetylcholinesterase inhibitors (AChE‐inhibitors) are used for the treatment of Alzheimer’s disease. Recently, the AChE‐inhibitor donepezil was found to have neuroprotective effects. However, the protective mechanisms of donepezil have not yet been clearly identified. We investigated the neuroprotective effects of donepezil and other AChE‐inhibitors against amyloid‐β1–42 (Aβ42)‐induced neurotoxicity in rat cortical neurons. To evaluate the neuroprotective effects of AChE‐inhibitors, primary cultured cortical neurons were pre‐treated with several concentrations of AChE‐inhibitors for 24 h and then treated with 20 μM Aβ42 for 6 h. In addition to donepezil, other AChE‐inhibitors (galantamine and huperizine A) also showed increased neuronal cell viability against Aβ42 toxicity in a concentration‐dependent manner. However, we demonstrated that donepezil has a more potent effect in inhibiting glycogen synthase kinase‐3 (GSK‐3) activity compared with other AChE‐inhibitors. The neuroprotective effects of donepezil were blocked by LY294002 (10 μM), a phosphoinositide 3 kinase inhibitor, but only partially by mecamylamine (10 μM), a blocker of nicotinic acetylcholine receptors. Additionally, donepezil’s neuroprotective mechanism was related to the enhanced phosphorylation of Akt and GSK‐3β and reduced phosphorylation of tau and glycogen synthase. These results suggest that donepezil prevents Aβ42‐induced neurotoxicity through the activation of phosphoinositide 3 kinase/Akt and inhibition of GSK‐3, as well as through the activation of nicotinic acetylcholine receptors.

Inhibition of glycogen synthase kinase-3 suppresses the onset of symptoms and disease progression of G93A-SOD1 mouse model of ALS.

Glycogen synthase kinase (GSK)-3 has recently been implicated in the pathogenesis of neurodegenerative diseases. Although the neuroprotective effects of GSK-3 inhibitors in Alzheimers disease have been established, their effects on amyotrophic lateral sclerosis (ALS) have not been well defined. This study was undertaken to evaluate the effects of GSK-3 inhibition in the G93A-SOD1 mouse model of ALS. Groups of G93A-SOD1 mice were treated with varying concentrations of GSK-3 inhibitor VIII, a specific GSK-3 inhibitor that crosses the BBB, intraperitoneally 5 days a week after 60 days of age. The GSK-3 inhibitor VIII treatment significantly delayed the onset of symptoms and prolonged the life span of the animals, and inhibited the activity of GSK-3 in a concentration-dependent manner. Furthermore, this treatment preserved survival signals and attenuated death and inflammatory signals. These data suggest that GSK-3 plays an important role in the pathogenic mechanisms of ALS and that inhibition of GSK-3 could be a potential therapeutic candidate for ALS.

Recombinant human erythropoietin suppresses symptom onset and progression of G93A-SOD1 mouse model of ALS by preventing motor neuron death and inflammation.

Multifactorial pathogenic mechanisms, including inflammation, attenuated survival signals and enhanced death signals, are involved in amyotrophic lateral sclerosis (ALS). Erythropoietin (EPO) has recently been highlighted as a cytokine with various potent neuroprotective effects, including reduction of inflammation, enhancement of survival signals and prevention of neuronal cell death. This study was undertaken to evaluate the effect of recombinant human EPO (rhEPO) on ALS model mice. We treated 96 ALS model mice with vehicle only, or 1, 2.5 or 5 iµ of rhEPO/g of mouse once every other week after they were 60 days old. The treatment significantly prolonged symptom onset and life span, preserved more motor neurons, enhanced survival signals, and attenuated inflammatory signals in a dose‐dependent manner. These data suggest that treatment with rhEPO represents a potential therapeutic strategy for ALS.

Neuroprotective effects of a novel poly (ADP-ribose) polymerase-1 inhibitor, JPI-289, in hypoxic rat cortical neurons

Excessive activation of poly (ADP‐ribose) polymerase‐1 (PARP‐1) is known to develop neuronal apoptosis, necrosis and inflammation after ischaemic brain injury. Therefore, PARP‐1 inhibition after ischaemic stroke has been attempted in successful animal studies. The purpose of present work was to develop a novel water soluble PARP‐1 inhibitor (JPI‐289) and explore its neuroprotective effect on ischaemic injury in an in vitro model. The half‐life of JPI‐289 after intravenous or oral administration in rats was relatively long (1.4‐1.5 hours) with 65.6% bioavailability. The inhibitor strongly inhibited PARP‐1 activity (IC50=18.5 nmol/L) and cellular PAR formation (IC50=10.7 nmol/L) in the nanomolar range. In rat cortical neuronal cells, JPI‐289 did not affect cell viability up to 1 mmol/L as assayed by Trypan blue staining (TBS) and lactate dehydrogenase (LDH) assay. Treatment of JPI‐289 for 2 hours after 2 hours of oxygen glucose deprived (OGD) rat cortical neuron attenuated PARP activity and restored ATP and NAD+ levels. Apoptosis‐associated molecules such as apoptosis inducing factor (AIF), cytochrome C and cleaved caspase‐3 were reduced after JPI‐289 treatment in the OGD model. The present findings suggest that the novel PARP‐1 inhibitor, JPI‐289, is a potential neuroprotective agent which could be useful as a treatment for acute ischaemic stroke.

Note: Interpolation for evaluation of a two-dimensional spatial profile of plasma densities at low gas pressures

An interpolation algorithm for the evaluation of the spatial profile of plasma densities in a cylindrical reactor was developed for low gas pressures. The algorithm is based on a collisionless two-dimensional fluid model. Contrary to the collisional case, i.e., diffusion fluid model, the fitting algorithm depends on the aspect ratio of the cylindrical reactor. The spatial density profile of the collisionless fitting algorithm is presented in two-dimensional images and compared with the results of the diffusion fluid model.