Diphenyleneiodonium chloride synergizes with diazoxide to enhance protection against amyloid ß induced neurotoxicity.

We examined synergistic effects of inhibiting reactive oxygen species generated from the mitochondria and from nicotinamide adenine dinucleotide phosphate oxidase on neurotoxicity. Primary hippocampal neurons were exposed to amyloid ß, and the cells were treated with diazoxide or/and diphenyleneiodonium chloride. We found that the cell viability was decreased significantly after exposure to amyloid ß for 72 h with higer reactive oxygen species and malondialdehyde levels, higher caspase-3 and cleaved caspase-3 levels and lower B-cell lymphoma 2 (Bcl-2) level. Both diazoxide and diphenyleneiodonium increased cell viability by inhibiting the increase in reactive oxygen species and caspase-3 activity as well as the decrease in Bcl-2 induced by amyloid ß. The combination of diazoxide and diphenyleneiodonium exhibited better protective effects compared to a single treatment. In conclusion, the activation of a mitochondrial potassium channel in combination with the inhibitor of nicotinamide adenine dinucleotide phosphate oxidase exhibit synergistic protective effects against amyloid ß neurotoxicity.

Association of the p22phox polymorphism C242T with the risk of late-onset Alzheimer's disease in a northern Han Chinese population.

The C242T polymorphism of the CYBA gene that encodes p22phox, a component of nicotinamide adenine dinucleotide phosphate oxidase, has been found to modulate reactive oxygen species (ROS) production. Oxidative stress is thought to play a pivotal role in the pathophysiology of Alzheimer's disease (AD), which is manifested as increased availability of ROS because of an imbalanced redox state. Therefore, the aim of this study was to investigate potential associations of the p22phox C242T polymorphism with the risk of late-onset AD (LOAD) in a northern Han Chinese population. Patients with LOAD (n = 276) and 320 control subjects were recruited for the study. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the genotypes. No significant differences were found between LOAD and p22phox C242T polymorphism, but a significant association was obtained in the genotype and allele distributions of p22phox C242T between LOAD patients and controls in apolipoprotein E (ApoE) ϵ4 carriers. These results suggested that p22phox C242T polymorphism has a possible role in changing the genetic susceptibility to LOAD in ApoE ϵ4 carriers of this northern Han Chinese population.

Association of insulin receptor H1085H C>T, insulin receptor substrate 1 G972R and insulin receptor substrate 2 1057G/A polymorphisms with refractory temporal lobe epilepsy in Han Chinese.

PURPOSE: Insulin/insulin receptor (INSR) signaling plays diverse roles in the central nervous system, including regulation of blood glucose, synaptic plasticity, dendritic growth, modulation of electrophysiological activity, proliferation of astrocytes and neuronal apoptosis. Interestingly, many of these and/or related processes represent biological mechanisms associated with temporal lobe epilepsy (TLE). Thus, insulin signaling may play a role in the development of TLE and its therapeutic responses. We hypothesized that functional polymorphisms in the insulin pathway genes INSR, insulin receptor substrate 1 (IRS1), and IRS2 may be associated with the therapeutic responses of TLE. Therefore, in this study we analyzed the association of three single nucleotide polymorphisms (SNPs) showing a risk for TLE drug resistance using a hospital-based case-control design. METHOD: Two hundred and one patients with refractory TLE and one hundred and seventy-five drug-responsive TLE patients were recruited for the study. Polymerase chain reaction-restriction fragment length polymorphism was used to detect the genotypes of INSR His1085His, IRS1 G972R and IRS2 1057G/A. RESULTS: No significant differences between refractory and drug-responsive TLE patients were observed for the IRS1 G972R and IRS2 1057G/A polymorphisms (P>0.05), but a significant association was found for the INSR His1085His polymorphism for both genotypes (P=0.035) and alleles (P=0.011). IRS2 1057G/A combined with the INSR His 1085 His polymorphism increased the odds ratio of drug resistance in TLE (P=0.011, OR=2.263, 95% CI: 1.208-4.239). CONCLUSION: These results suggest that a genetic variation in the insulin signaling pathway genes may affect the therapeutic response of TLE.

Diazoxide pretreatment prevents Aß1-42 induced oxidative stress in cholinergic neurons via alleviating NOX2 expression.

The aggregation and accumulation of amyloid-ß (Aß) plays a significant role in the pathogenesis of Alzheimer's disease. Aß is known to increase free radical production in neuronal cells, leading to oxidative stress and cell death. Diazoxide (DZ), a highly selective drug capable of opening mitochondrial ATP-sensitive potassium channels, has neuroprotective effects against neuronal cell death. However, the mechanism through which DZ protects cholinergic neurons against Aß-induced oxidative injury is still unclear. The present study was designed to investigate the effects of DZ pretreatment against Aß1-42 induced oxidative damage and cytotoxicity. Through measures of DZ effects on Aß1-42 induced cellular damage, reactive oxygen species (ROS) and MDA generation and expressions of gp91phox and p47phox in cholinergic neurons, new insights into the neuroprotective mechanisms can be derived. Aß1-42 significantly decreased 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide levels and increased ROS and MDA production; all effects were attenuated by pretreatment with DZ or diphenyleneiodonium chloride (a NOX2 inhibitor). Pretreatment with DZ also attenuated the upregulation of NOX2 subunits (gp91phox and p47phox) induced by Aß1-42. Since NOX2 is one of the main sources of free radicals, these results suggest that DZ can counteract Aß1-42 induced oxidative stress and associated cell death by reducing the level of ROS and MDA, in part, by alleviating NOX2 expression.

Diazoxide preconditioning antagonizes cytotoxicity induced by epileptic seizures.

Diazoxide, an activator of mitochondrial ATP-sensitive potassium channels, can protect neurons and astrocytes against oxidative stress and apoptosis. In this study, we established a cellular model of epilepsy by culturing hippocampal neurons in magnesium-free medium, and used this to investigate effects of diazoxide preconditioning on the expression of inwardly rectifying potassium channel (Kir) subunits of the ATP-sensitive potassium. We found that neuronal viability was significantly reduced in the epileptic cells, whereas it was enhanced by diazoxide preconditioning. Double immunofluorescence and western blot showed a significant increase in the expression of Kir6.1 and Kir6.2 in epileptic cells, especially at 72 hours after seizures. Diazoxide pretreatment completely reversed this effect at 24 hours after seizures. In addition, Kir6.1 expression was significantly upregulated compared with Kir6.2 in hippocampal neurons after seizures. These findings indicate that diazoxide pretreatment may counteract epileptiform discharge-induced cytotoxicity by suppressing the expression of Kir subunits.