Accumulation of 4-hydroxynonenal-modified proteins in hippocampal CA1 pyramidal neurons precedes delayed neuronal damage in the gerbil brain

Upregulation of the TFEB-mediated lysosome function relieves 4-Hydroxynonenal-Induced apoptosis

4-Hydroxynonenal (4-HNE), the most toxic end-product of lipid peroxidation formed during oxidative stress, has been implicated in many diseases including neurodegenerative diseases, metabolic diseases, myocardial diseases, cancer and age-related diseases. 4-HNE can actively react with DNA, proteins and lipids, causing rapid cell death. The accumulation of 4-HNE leads to induction of autophagy, which clears damaged proteins and organelles. However, the underlying mechanism of 4-HNE-regulated autophagy is still not known. Transcriptional factor EB (TFEB) is a master regulator of lysosomal and autophagic functions, which we show here that TFEB is activated by 4-HNE. 4-HNE induces TFEB nuclear translocation and activated TFEB then upregulates the expression of genes required for autophagic and lysosomal biogenesis and function. Reactive oxygen species and Ca²⁺ are required in this process and TFEB activity is required for 4-HNE-mediated lysosomal function. Most importantly, genetic inhibition of TFEB (TFEB-KO) exacerbates 4-HNE-induced cell death, suggesting that TFEB is essential for cellular adaptive response to 4-HNE-induced cell damage. Hence, targeting TFEB to promote autophagic and lysosomal function may represent a promising approach to treat neurodegenerative and metabolic diseases in which 4-HNE accumulation has been implicated.

Differential Effects of 2-Deoxyglucose and Glucose Deprivation on 4-Hydroxynonenal Dependent Mitochondrial Dysfunction in Primary Neurons

Mitochondrial dysfunction and metabolic decline are prevalent features of aging and age-related disorders, including neurodegeneration. Neurodegenerative diseases are associated with a progressive loss of metabolic homeostasis. This pathogenic decline in metabolism is the result of several factors, including decreased mitochondrial function, increased oxidative stress, inhibited autophagic flux, and altered metabolic substrate availability. One critical metabolite for maintaining neuronal function is glucose, which is utilized by the brain more than any other organ to meet its substantial metabolic demand. Enzymatic conversion of glucose into its downstream metabolites is critical for maintaining neuronal cell growth and overall metabolic homeostasis. Perturbation of glycolysis could significantly hinder neuronal metabolism by affecting key metabolic pathways. Here, we demonstrate that the glucose analogue 2-deoxyglucose (2DG) decreases cell viability, as well as both basal and maximal mitochondrial oxygen consumption in response to the neurotoxic lipid 4-hydroxynonenal (HNE), whereas glucose deprivation has a minimal effect. Furthermore, using a cell permeabilization assay we found that 2DG has a more pronounced effect on HNE-dependent inhibition of mitochondrial complex I and II than glucose deprivation. Importantly, these findings indicate that altered glucose utilization plays a critical role in dictating neuronal survival by regulating the mitochondrial response to electrophilic stress.

Anti-inflammatory effects of N-cyclooctyl-5-methylthiazol-2-amine hydrobromide on lipopolysaccharide-induced inflammatory response through attenuation of NLRP3 activation in microglial cells

Microglial activation is closely associated with neuroinflammatory pathologies. The nucleotide-binding and oligomerization domain-like receptor containing a pyrin domain 3 (NLRP3) inflammasomes are highly organized intracellular sensors of neuronal alarm signaling. NLRP3 inflammasomes activate nuclear factor kappa-B (NF-κB) and reactive oxygen species (ROS), which induce inflammatory responses. Moreover, NLRP3 dysfunction is a common feature of chronic inflammatory diseases. The present study investigated the effect of a novel thiazol derivative, N-cyclooctyl-5-methylthiazol-2-amine hydrobromide (KHG26700), on inflammatory responses in lipopolysaccharide (LPS)-treated BV-2 microglial cells. KHG26700 significantly attenuated the expression of several pro-inflammatory cytokines, including tumor necrosis factor-α, interleukin-1β, and interleukin-6, in these cells, as well as the LPS-induced increases in NLRP3, NF-κB, and phospho-IkBα levels. KHG26700 also suppressed the LPS-induced increases in protein levels of autophagy protein 5 (ATG5), microtubule-associated protein 1 light chain 3 (LC3), and beclin-1, as well as downregulating the LPS-enhanced levels of ROS, lipid peroxidation, and nitric oxide. These results suggest that the anti-inflammatory effects of KHG26700 may be due, at least in part, to the regulation of the NLRP3-mediated signaling pathway during microglial activation.

Protective effects of N,4,5-trimethylthiazol-2-amine hydrochloride on hypoxia-induced β-amyloid production in SH-SY5Y cells

Although hypoxic/ischemic injury is thought to contribute to the incidence of Alzheimer’s disease (AD), the molecular mechanism that determines the relationship between hypoxia-induced β-amyloid (Aβ) generation and development of AD is not yet known. We have now investigated the protective effects of N,4,5-trimethylthiazol-2-amine hydrochloride (KHG26702), a novel thiazole derivative, on oxygen-glucose deprivation (OGD)-reoxygenation (OGD-R)-induced Aβ production in SH-SY5Y human neuroblastoma cells. Pretreatment of these cells with KHG26702 significantly attenuated OGD-R-induced production of reactive oxygen species and elevation of levels of malondialdehyde, prostaglandin E₂, interleukin 6 and glutathione, as well as superoxide dismutase activity. KHG26702 also reduced OGD-R-induced expression of the apoptotic protein caspase-3, the apoptosis regulator Bcl-2, and the autophagy protein becn-1. Finally, KHG26702 reduced OGD-R-induced Aβ production and cleavage of amyloid precursor protein, by inhibiting secretase activity and suppressing the autophagic pathway. Although supporting data from in vivo studies are required, our results indicate that KHG26702 may prevent neuronal cell damage from OGD-R-induced toxicity.

The effects of epothilone D on microtubule degradation and delayed neuronal death in the hippocampus following transient global ischemia

Disruption of microtubule cytoskeleton plays an important role during the evolution of brain damage after transient cerebral ischemia. However, it is still unclear whether microtubule-stabilizing drugs such as epothilone D (EpoD) have a neuroprotective action against the ischemia-induced brain injury. This study examined the effects of pre- and postischemic treatment with different doses of EpoD on the microtubule damage and the delayed neuronal death in the hippocampal CA1 subfield on day 2 following reperfusion after 13-min global cerebral ischemia. Our results showed that systemic treatment with 0.5 mg/kg EpoD only slightly alleviated the microtubule disruption and the CA1 neuronal death, while treatment with 3.0 mg/kg EpoD was not only ineffective against the CA1 neuronal death, but also produced additional damage in the dentate gyrus in some ischemic rats. Since the pyramidal cells in the CA1 subfield and the granule neurons in the dentate gyrus are known to be equipped with dynamically different microtubule systems, this finding indicates that the effects of microtubule-disrupting drugs may be unpredictably complicated in the central nervous system.

Neuroprotective effects of a novel carnosine-hydrazide derivative on hippocampal CA1 damage after transient cerebral ischemia

Ischemia-reperfusion injuries produce reactive oxygen species that promote the peroxide lipid oxidation process resulting in the production of an endogenic lipid peroxide, 4-hydroxy-trans-2-nonenal (4-HNE), a highly cytotoxic aldehyde that induces cell death. We synthesized a novel 4-HNE scavenger - a carnosine-hydrazide derivative, l-carnosine hydrazide (CNN) - and examined its neuroprotective effect in a model of transient ischemia. PC-12 cells were pre-incubated with various doses (0-50 mmol/L) of CNN for 30 min, followed by incubation with 4-HNE (250 μM). An MTT assay was performed 24 h later to examine cell survival. Transient ischemia was induced by bilateral common carotid artery occlusion (BCCO) in the Mongolian gerbil. Animals were assigned to sham-operated (n = 6), placebo-treated (n = 12), CNN pre-treated (20 mg/kg; n = 12), CNN post-treated (100 mg/kg; n = 11), and histidyl hydrazide (a previously known 4-HNE scavenger) post-treated (100 mg/kg; n = 7) groups. Heat shock protein 70 immunoreactivity in the hippocampal CA1 region was evaluated 24 h later, while delayed neuronal death using 4-HNE staining was evaluated 7 days later. Pre-incubation with 30 mmol/L CNN completely inhibited 4-HNE-induced cell toxicity. CNN prevented delayed neuronal death by >60% in the pre-treated group (p < 0.001) and by >40% in the post-treated group (p < 0.01). Histidyl hydrazide post-treatment elicited no protective effect. CNN pre-treatment resulted in high heat shock protein 70 and low 4-HNE immunoreactivity in CA1 pyramidal neurons. Higher 4-HNE immunoreactivity was also found in the placebo-treated animals than in the CNN pre-treated animals. Our novel compound, CNN, elicited highly effective 4-HNE scavenging activity in vitro. Furthermore, CNN administration both pre- and post-BCCO remarkably reduced delayed neuronal death in the hippocampal CA1 region via its induction of heat shock protein 70 and scavenging of 4-HNE.

Rat hippocampal CA3 neuronal injury induced by limb ischemia/reperfusion: A possible restorative effect of alpha lipoic acid

Limb ischemia reperfusion (I/R) injury is associated with serious local and systemic effects. Reperfusion may augment tissue injury in excess of that produced by ischemia alone. The hippocampus has been reported to be vulnerable to I/R injury. Alpha lipoic acid (ALA) is an endogenous antioxidant with a powerful antioxidative, anti-inflammatory, and antiapoptotic properties. We studied the probable restorative effect of ALA on limb I/R-induced structural damage of rat hippocampus. Forty adult male albino rats were divided equally into four groups: group I (sham); group II (I/R-1 day) has undergone bilateral femoral arteries occlusion (3 h), then reperfusion for 1 day; group III (I/R-7 days) has undergone reperfusion for seven days; group IV (I/R-ALA) has undergone I/R as group III and received an intraperitoneal injection of ALA (100 mg/kg) for 7 days. I/R groups revealed degenerative changes in the pyramidal neuronal perikarya of CA3 field in the form of dark-stained cytoplasm, dilated RER cisternae, mitochondrial alterations, and dense bodies' accumulation. Their dendrites showed disorganized microtubules. Astrogliosis is featured by an increased number and increased immunoreactivity of astrocytes for glial fibrillary acid protein. Morphometric data revealed significant reduction of light neurons, surface area of neurons, and thickness of the CA3 layer. Most blood capillaries exhibited narrow lumen and irregular basal lamina. ALA ameliorated the neuronal damage. Pyramidal neurons revealed preservation of normal structure. Significant increase in the thickness of pyramidal layer in CA3 field and surface area and number of light neurons was observed but astrogliosis persisted. Limb I/R had a deleterious remote effect on the hippocampus aggravated with longer period of reperfusion. This work may encourage the use of ALA in the critical clinical settings with I/R injury.

Resveratrol supplementation confers neuroprotection in cortical brain tissue of nonhuman primates fed a high-fat/sucrose diet

Previous studies have shown positive effects of long-term resveratrol (RSV) supplementation in preventing pancreatic beta cell dysfunction, arterial stiffening and metabolic decline induced by high-fat/high-sugar (HFS) diet in nonhuman primates. Here, the analysis was extended to examine whether RSV may reduce dietary stress toxicity in the cerebral cortex of the same cohort of treated animals. Middle-aged male rhesus monkeys were fed for 2 years with HFS alone or combined with RSV, after which whole-genome microarray analysis of cerebral cortex tissue was carried out along with ELISA, immunofluorescence, and biochemical analyses to examine markers of vascular health and inflammation in the cerebral cortices. A number of genes and pathways that were differentially modulated in these dietary interventions indicated an exacerbation of neuroinflammation (e.g., oxidative stress markers, apoptosis, NF-κB activation) in HFS-fed animals and protection by RSV treatment. The decreased expression of mitochondrial aldehyde dehydrogenase 2, dysregulation in endothelial nitric oxide synthase, and reduced capillary density induced by HFS stress were rescued by RSV supplementation. Our results suggest that long-term RSV treatment confers neuroprotection against cerebral vascular dysfunction during nutrient stress.

Regulation of autophagy, mitochondrial dynamics, and cellular bioenergetics by 4-hydroxynonenal in primary neurons

The production of reactive species contributes to the age-dependent accumulation of dysfunctional mitochondria and protein aggregates, all of which are associated with neurodegeneration. A putative mediator of these effects is the lipid peroxidation product 4-hydroxynonenal (4-HNE), which has been shown to inhibit mitochondrial function, and accumulate in the postmortem brains of patients with neurodegenerative diseases. This deterioration in mitochondrial quality could be due to direct effects on mitochondrial proteins, or through perturbation of the macroautophagy/autophagy pathway, which plays an essential role in removing damaged mitochondria. Here, we use a click chemistry-based approach to demonstrate that alkyne-4-HNE can adduct to specific mitochondrial and autophagy-related proteins. Furthermore, we found that at lower concentrations (5-10 μM), 4-HNE activates autophagy, whereas at higher concentrations (15 μM), autophagic flux is inhibited, correlating with the modification of key autophagy proteins at higher concentrations of alkyne-4-HNE. Increasing concentrations of 4-HNE also cause mitochondrial dysfunction by targeting complex V (the ATP synthase) in the electron transport chain, and induce significant changes in mitochondrial fission and fusion protein levels, which results in alterations to mitochondrial network length. Finally, inhibition of autophagy initiation using 3-methyladenine (3MA) also results in a significant decrease in mitochondrial function and network length. These data show that both the mitochondria and autophagy are critical targets of 4-HNE, and that the proteins targeted by 4-HNE may change based on its concentration, persistently driving cellular dysfunction.

Look into brain energy crisis and membrane pathophysiology in ischemia and reperfusion

In an ischemic environment, brain tissue responds to oxygen deprivation with the initiation of rapid changes in bioenergetic metabolism to ensure ion and metabolic homeostasis. At the same time, the accelerated cleavage of membrane phospholipids changes membrane composition and increases free fatty acid concentration. Phospholipid breakdown also generates specific messengers that participate in signaling cascades that can either promote neuronal protection or cause injury. The net impact of signaling events affects the final outcome of the stroke. While reoxygenation is a life-saving intervention, it can exacerbate brain damage. Although compromised energy metabolism is restored shortly after reperfusion, alterations in membrane phospholipid composition with subsequent accumulation of lipid oxoderivates are neurotoxic, causing oxidative stress and ischemia-reperfusion (IR) injury. Thus, plasma and mitochondrial membranes are the first responders as well as mediators of IR-induced stress signals. In this review, we focus on ischemia-induced changes in brain energy metabolism and membrane functions as the causal agents of cell stress responses upon reoxygenation. The first part of the review deals with the specificities of neuronal bioenergetics during IR and their impact on metabolic processes. The second part is concentrated on involvement of both plasma and mitochondrial membranes in the production of messengers which can modulate neuroprotective pathways or participate in oxidative/electrophilic stress responses. Although the etiology of IR injury is multifactorial, deciphering the role of membrane and membrane-associated processes in brain damage will uncover new therapeutic agents with the ability to stabilize neuronal membranes and modulate their responses in favor of prosurvival pathways.

Radon inhalation protects against transient global cerebral ischemic injury in gerbils

Although brain disorders are not the main indication for radon therapy, our previous study suggested that radon inhalation therapy might mitigate brain disorders. In this study, we assessed whether radon inhalation protects against transient global cerebral ischemic injury in gerbils. Gerbils were treated with inhaled radon at a concentration of 2,000 Bq/m(3) for 24 h. After radon inhalation, transient global cerebral ischemia was induced by bilateral occlusion of the common carotid artery. Results showed that transient global cerebral ischemia induced neuronal damage in hippocampal CA1, and the number of damaged neurons was significantly increased compared with control. However, radon treatment inhibited ischemic damage. Superoxide dismutase (SOD) activity in the radon-treated gerbil brain was significantly higher than that in sham-operated gerbils. These findings suggested that radon inhalation activates antioxidative function, especially SOD, thereby inhibiting transient global cerebral ischemic injury in gerbils.

Inhibition of glycolysis attenuates 4-hydroxynonenal-dependent autophagy and exacerbates apoptosis in differentiated SH-SY5Y neuroblastoma cells

How cellular metabolic activities regulate autophagy and determine the susceptibility to oxidative stress and ultimately cell death in neuronal cells is not well understood. An important example of oxidative stress is 4-hydroxynonenal (HNE), which is a lipid peroxidation product that is formed during oxidative stress, and accumulates in neurodegenerative diseases causing damage. The accumulation of toxic oxidation products such as HNE, is a prevalent feature of neurodegenerative diseases, and can promote organelle and protein damage leading to induction of autophagy. In this study, we used differentiated SH-SY5Y neuroblastoma cells to investigate the mechanisms and regulation of cellular susceptibility to HNE toxicity and the relationship to cellular metabolism. We found that autophagy is immediately stimulated by HNE at a sublethal concentration. Within the same time frame, HNE induces concentration dependent CASP3/caspase 3 activation and cell death. Interestingly, both basal and HNE-activated autophagy, were regulated by glucose metabolism. Inhibition of glucose metabolism by 2-deoxyglucose (2DG), at a concentration that inhibited autophagic flux, further exacerbated CASP3 activation and cell death in response to HNE. Cell death was attenuated by the pan-caspase inhibitor Z-VAD-FMK. Specific inhibition of glycolysis using koningic acid, a GAPDH inhibitor, inhibited autophagic flux and exacerbated HNE-induced cell death similarly to 2DG. The effects of 2DG on autophagy and HNE-induced cell death could not be reversed by addition of mannose, suggesting an ER stress-independent mechanism. 2DG decreased LAMP1 and increased BCL2 levels suggesting that its effects on autophagy may be mediated by more than one mechanism. Furthermore, 2DG decreased cellular ATP, and 2DG and HNE combined treatment decreased mitochondrial membrane potential. We conclude that glucose-dependent autophagy serves as a protective mechanism in response to HNE.

Pre- and post-treatments with escitalopram protect against experimental ischemic neuronal damage via regulation of BDNF expression and oxidative stress

Selective serotonin re-uptake inhibitors (SSRI) have been widely used in treatment of major depression because of their efficacy, safety, and tolerability. Escitalopram, an SSRI, is known to decrease oxidative stress in chronic stress animal models. In the present study, we examined the neuroprotective effects of pre- and post-treatments with 20 mg/kg and 30 mg/kg escitalopram in the gerbil hippocampal CA1 region (CA1) after transient cerebral ischemia. Pre-treatment with escitalopram protected against ischemia-induced neuronal death in the CA1 after ischemia/reperfusion (I/R). Post-treatment with 30 mg/kg, not 20 mg/kg, escitalopram had a neuroprotective effect against ischemic damage. In addition, 20 mg/kg pre- and 30 mg/kg post-treatments with escitalopram increased brain-derived neurotrophic factor (BDNF) protein levels in the ischemic CA1 compared to vehicle-treated ischemia animals. In addition, 20 mg/kg pre- and 30 mg/kg post-treatments with escitalopram reduced microglia activation and decreased 4-hydroxy-2-nonenal and Cu,Zn-superoxide dismutase immunoreactivity and their levels in the ischemic CA1 compared to vehicle-treated ischemia animals after transient cerebral ischemia. In conclusion, these results indicated that pre- and post-treatments with escitalopram can protect against ischemia-induced neuronal death in the CA1 induced by transient cerebral ischemic damage by increase of BDNF as well as decrease of microglia activation and oxidative stress.

Hypothyroid state does not protect but delays neuronal death in the hippocampal CA1 region following transient cerebral ischemia: focus on oxidative stress and gliosis

We investigated protective effects of hypothyroidism on delayed neuronal death, gliosis, lipid peroxidation and Cu,Zn-superoxide dismutase (SOD1) in the gerbil hippocampal CA1 region (CA1) after 5 min of transient cerebral ischemia. The hypothyroidism was induced by 0.025% methimazole treatment. Free triiodothyronine and thyroxine levels were markedly decreased in the hypothyroid group. Four days after ischemia/reperfusion, only a few NeuN-immunoreactive (+) neurons were detected in the CA1 of euthyroid-ischemia (eu-ischemia) group; however, at this time point, the number of NeuN(+) neurons was significantly higher in the hypothyroid-ischemia (hypo-ischemia) group than in the eu-ischemia group. At 5 days postischemia, NeuN(+) neurons were significantly decreased in the hypo-ischemia group: The number of NeuN(+) neurons in this group was similar to that in the eu-ischemia group. Activations of GFAP(+) astrocytes and Iba-1(+) microglia in the CA1 were higher in the eu-ischemia group 3 and 4 days after ischemia/reperfusion. At 5 days postischemia, the activations of both the glial cells in the CA1 were similar between the two groups. 4-Hydroxy-2-nonenal (HNE), a marker for lipid peroxidation, immunoreactivity in the eu-ischemia group was higher than in the hypo-ischemia group; at 5 days postischemia, the immunoreactivity was similar between the two groups. In contrast, SOD1 level was lower in the CA1 of the eu-ischemia group. These results suggest that hypothyroid state does not protect against delayed neuronal death but only delays the neuronal death in the hippocampal CA1 region after transient cerebral ischemia by reducing lipid peroxidation and increasing SOD1.

Postischemic administration of liposome-encapsulated luteolin prevents against ischemia-reperfusion injury in a rat middle cerebral artery occlusion model

Oxidative stress-induced neuronal cell death has been implicated in neurodegenerative diseases; one such disease is ischemic stroke. Using reactive oxygen species (ROS)-insulted primary neurons, we screened neuroprotectants with clinical potential and then, using ischemia/reperfusion (I/R) model, investigated the anti-ischemic potential of candidate neuroprotectants. Here, we showed that luteolin, isolated from the ripe fruit of Perilla frutescens (L.) Britt, exhibited a neuroprotective action upon the in vitro platform, thus serving as candidate for in vivo pharmacological evaluation. Liposome-encapsulated luteolin produced dramatic preventing effects on I/R-induced behavioral and histological injuries after a 13-day post-ischemic treatment. Furthermore, this phytochemical not only lowered the increased level of mitochondrial ROS but also substantially up-regulated the decreased activity of catalase and glutathione in I/R rat brains. Collectively, luteolin as a neuroprotectant acts by anti-ischemic activity likely through a rebalancing of pro-oxidant/antioxidant status. Its multitarget mechanisms implicate potential effectiveness for clinically treating ischemia stroke.

Advances in methods for the determination of biologically relevant lipid peroxidation products

Lipid peroxidation is recognized to be an important contributor to many chronic diseases, especially those of an inflammatory pathology. In addition to their value as markers of oxidative damage, lipid peroxidation products have also been shown to have a wide variety of biological and cell signalling effects. In view of this, accurate and sensitive methods for the measurement of lipid peroxidation products are essential. Although some assays have been described for many years, improvements in protocols are continually being reported and, with recent advances in instrumentation and technology, highly specialized and informative techniques are increasingly used. This article gives an overview of the most currently used methods and then addresses the recent advances in some specific approaches. The focus is on analysis of oxysterols, F(2)-isoprostanes and oxidized phospholipids by gas chromatography or liquid chromatography mass spectrometry techniques and immunoassays for the detection of 4-hydroxynonenal.

Cerebralcare Granule, a Chinese herb compound preparation, improves cerebral microcirculatory disorder and hippocampal CA1 neuron injury in gerbils after ischemia-reperfusion

AIM OF THE STUDY

Cerebralcare Granule (CG) is a Chinese herb compound preparation that has been used for treatment of cerebrovascular related diseases. However, the effect of post-treatment with CG on ischemia and reperfusion (I/R) induced cerebral injury is so far unclear.

MATERIALS AND METHODS

In present study, cerebral global I/R was induced in Mongolian gerbils by clamping bilateral carotid arteries for 30 min followed by reperfusion for 5 days, and CG (0.4 g/kg or 0.8 g/kg) was administrated 3h after the initiation of reperfusion.

RESULTS

Post-treatment with CG for 5 days attenuated the I/R-induced production of hydrogen peroxide in, leukocyte adhesion to, and albumin leakage from cerebral microvessels, and, meanwhile, protected neuron from death, reduced the number of caspase-3- and Bax-positive cells, and increased Bcl-2-positive cells in hippocampal CA1 region.

CONCLUSION

The results suggest that CG given after initiation of reperfusion is able to ameliorate cerebral microvascular dysfunction and hippocampal CA1 neuron damage caused by I/R.

Roles of the lipid peroxidation product 4-hydroxynonenal in obesity, the metabolic syndrome, and associated vascular and neurodegenerative disorders

A rising tide of obesity and type 2 diabetes has resulted from the development of technologies that have made inexpensive high calorie foods readily available and exercise unnecessary for many people. Obesity and the metabolic syndrome (insulin resistance, visceral adiposity and dyslipidemia) wreak havoc on cells throughout the body thereby promoting cardiovascular and kidney disease, and degenerative diseases of the brain and body. Obesity and insulin resistance promote disease by increasing oxidative damage to proteins, lipids and DNA as the result of a combination of increased free radical production and an impaired ability of cells to detoxify the radicals and repair damaged molecules. By covalently modifying membrane-associated proteins, the membrane lipid peroxidation product 4-hydroxynonenal (HNE) may play particularly sinister roles in the metabolic syndrome and associated disease processes. HNE can damage pancreatic beta cells and can impair the ability of muscle and liver cells to respond to insulin. HNE may promote atherosclerosis by modifying lipoproteins and can cause cardiac cell damage by impairing metabolic enzymes. An adverse role for HNE in the brain in obesity and the metabolic syndrome is suggested by studies showing that HNE levels are increased in brain cells with aging and Alzheimer's disease. HNE can cause the dysfunction and degeneration of neurons by modifying membrane-associated glucose and glutamate transporters, ion-motive ATPases, enzymes involved in amyloid metabolism, and cytoskeletal proteins. Exercise and dietary energy restriction reduce HNE production and may also increase cellular systems for HNE detoxification including glutathione and oxidoreductases. The recent development of low molecular weight molecules that scavenge HNE suggests that HNE can be targeted in the design of drugs for the treatment of obesity, the metabolic syndrome, and associated disorders.

Oral administration of grape polyphenol extract ameliorates cerebral ischemia/reperfusion-induced neuronal damage and behavioral deficits in gerbils: comparison of pre- and post-ischemic administration

Oxidative stress has been regarded as an important underlying cause for the delayed neuronal death (DND) after cerebral ischemia. In this study, the effects of short-term oral administration of grape polyphenol extract (GPE) on ischemia/reperfusion (I/R) injury in a gerbil global ischemia model were determined. Ischemia was induced by occlusion of the common carotid arteries for 5 min. GPE (30 mg/ml)-containing formula or formula without GPE was administered daily via gavage for 4 days prior to and/or for 4 days after I/R. I/R resulted in hyperlocomotion, extensive DND, oxidative and fragmented DNA damage, and an increase in reactive astrocytes and microglial cells in the hippocampal CA1 region. GPE administration for 4 days prior to I/R and for 4 days after I/R attenuated DND, DNA damage and glial cell activation. However, neuroprotection was more pronounced when GPE was administered for 4 days after I/R than when administered for 4 days prior to I/R. GPE administration after I/R attenuated I/R-induced hyperlocomotion. These findings indicate that oral GPE intake may confer protection against I/R injury and emphasize that early intervention may be an effective therapeutic measure for ameliorating brain injury in stroke.

Immunohistochemical study on distribution of NF-kappaB and p53 in gerbil hippocampus after transient cerebral ischemia: effect of pitavastatin

We investigated the immunohistochemical alterations of the transcription nuclear factor kappa-B (NF-kappaB) and transcription factor p53 in the hippocampus after transient cerebral ischemia in gerbils. We also examined the effect of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitor pitavastatin against the alterations of NF-kappaB, p53 and neuronal nuclei in the hippocampus after ischemia. Severe neuronal damage was observed in the hippocampal CA1 neurons 5 and 14 days after ischemia. In the present study, the increase of NF-kappaB immunoreactivity in glial cells and p53 immunoreactivity in neurons preceded neuronal damage in the hippocampal CA1 sector after ischemia. Thereafter, NF-kappaB immunoreactivity was induced highly in reactive astrocytes and microglia of the hippocampal CA1 sector where severe neuronal damage was observed. Our immunohistochemical study showed that pitavastatin prevented the alterations of NF-kappaB and p53 in the hippocampal CA1 sector 5 days after transient ischemia. Furthermore, our results with neuronal nuclei immunostaining indicate that pitavastatin dose-dependently prevented the neuronal cell death in the hippocampal CA1 sector 5 days after transient cerebral ischemia. These results suggest that the up-regulations of NF-kappaB in glia and p53 in neurons can cause neuronal cell death after ischemia. Our findings also support the hypothesis that NF-kappaB- and/or p53-mediated neuronal cell death is prevented through decreasing oxidative stress by pitavastatin. Thus, NF-kappaB and p53 may provide an attractive target for the development of novel therapeutic approaches for brain stroke.

Development of the New Group of Indole-Derived Neuroprotective Drugs Affecting Oxidative Stress

1. The role of oxidative stress, and accordingly uncontrolled reactive oxygen species generation/action, have been widely documented in a number of different neuronal pathologies. However, the concept of pharmacological interventions in prevention and therapy of oxidative stress-related diseases has not found adequate application in clinical practice. This may be due to the insufficient efficacy of drugs available, their unsuitable pharmacokinetics, side effects, toxicity, etc. 2. Based on stobadine, (--)-cis-2,8-dimethyl-2,3,4,4a,5,9b-hexahydro-1H-pyrido[4,3-b]indole, a well-known antioxidant, free radical scavenger, and neuroprotectant, it was attempted to develop new stobadine derivatives with improved pharmacodynamic and toxicity profiles, on applying molecular design, synthesis and adequate tests. Stobadine molecule was modified mostly by electron donating substitution on the benzene ring and by alkoxycarbonyl substitution at N-2 position. A total of >70 derivatives were prepared. 3. In a mice model of head trauma, some of the new stobadine derivatives administered i.v. immediately after the trauma, significantly improved sensomotoric outcome in the animals assessed 1 h later. Accordingly, decrease in brain edema was proved histologically as well as by brain wet weight assessment. 4. Putative neuroprotective action of the compounds was confirmed on rat hippocampal slices exposed to reversible 6 min hypoxia/low glucose by analysis of synaptic transmission in CA1 region neurons. Irreversible impairment of neurotransmission resulting from the hypoxia was significantly reduced by the presence of SMe1EC2, one of the new compounds, in concentration range 0.03-10.0x10(-6) mol l(-1). Both the neuroprotective and antioxidant effect of the compound closely resembled those of stobadine, melatonin, 21-aminosteroids, alpha-phenyl-tert-butylnitrone and others, all well-established antioxidants, except the range of effective concentrations was by 1-2 orders lower in SMe1EC2. 5. A remarkable antioxidant efficacy was observed in the new compounds in rat brain homogenates exposed to iron/ascorbate system by protection of lipids and creatine kinase against the oxidative impairment. A link between the neuroprotective and antioxidant/ scavenger properties in the compounds can be assumed. 6. Acute toxicity of some of the new pyridoindoles was diminished compared to stobadine. That might be due to the virtually full elimination of stobadine's undesired alpha (1)-adrenolytic activity attained by appropriate modifications of its molecule. 7. The new pyridoindoles extend the range of available neuroprotectants interfering with oxidative stress in neuronal tissue.

Lipids and lipidomics in brain injury and diseases

Lipidomics is systems-level analysis and characterization of lipids and their interacting moieties. The amount of information in the genomic and proteomic fields is greater than that in the lipidomics field, because of the complex nature of lipids and the limitations of tools for analysis. The main innovation during recent years that has spurred advances in lipid analysis has been the development of new mass spectroscopic techniques, particularly the "soft ionization" techniques electrospray ionization and matrix-assisted laser desorption/ionization. Lipid metabolism may be of particular importance for the central nervous system, as it has a high concentration of lipids. The crucial role of lipids in cell signaling and tissue physiology is demonstrated by the many neurological disorders, including bipolar disorders and schizophrenia, and neurodegenerative diseases such as Alzheimer's, Parkinson's, and Niemann-Pick diseases, that involve deregulated lipid metabolism. Altered lipid metabolism is also believed to contribute to cerebral ischemic (stroke) injury. Lipidomics will provide a molecular signature to a certain pathway or a disease condition. Lipidomic analyses (characterizing complex mixtures of lipids and identifying previously unknown changes in lipid metabolism) together with RNA silencing, using small interfering RNA (siRNA), may provide powerful tools to elucidate the specific roles of lipid intermediates in cell signaling and open new opportunities for drug development.

Apocynin protects against global cerebral ischemia-reperfusion-induced oxidative stress and injury in the gerbil hippocampus

Increased production of reactive oxygen species (ROS) following cerebral ischemia-reperfusion (I/R) is an important underlying cause for neuronal injury leading to delayed neuronal death (DND). In this study, apocynin, a specific inhibitor for NADPH oxidase, was used to test whether suppression of ROS by the NADPH oxidase inhibitor can protect against ischemia-induced ROS generation and decrease DND. Global cerebral ischemia was induced in gerbils by a 5-min occlusion of bilateral common carotid arteries (CCA). Using measurement of 4-hydroxy-2-nonenal (HNE) as a marker for lipid peroxidation, apocynin (5 mg/kg body weight) injected i.p. 30 min prior to ischemia significantly attenuated the early increase in HNE in hippocampus measured at 3 h after I/R. Apocynin also protected against I/R-induced neuronal degeneration and DND, oxidative DNA damage, and glial cell activation. Taken together, the neuroprotective effects of apocynin against ROS production during early phase of I/R and subsequent I/R-induced neuronal damage provide strong evidence that inhibition of NADPH oxidase could be a promising therapeutic mechanism to protect against stroke damage in the brain.

Toward a Multimodal Neuroprotective Treatment of Stroke

Background and Purpose— Stroke remains a common medical problem with importance attributable to the demographic changes in industrialized societies.

Summary of Review— After years of setbacks, acute stroke therapy has finally emerged, including thrombolysis with tissue plasminogen activator (t-PA). However, t-PA treatment is limited by a narrow time window and side effects, so that only 3% of all stroke patients receive thrombolysis. Unimodal targeting of key events in stroke pathophysiology was not effective in providing long-term benefits, leading to negative results in previous clinical neuroprotective stroke trials. A successful future stroke therapy should approach multiple pathophysiological mechanisms besides revascularization at once, including reduction of t-PA–related side effects, prevention of cell death, stimulation of neuroregeneration, and plasticity.

Conclusions— Strategies targeting these processes include multiple combination therapies as well as treatment with multimodal drugs that interact with these mechanisms. Here, we review such combination approaches, and outline how this concept could be developed into future stroke treatment.

Neuroprotective mechanisms of curcumin against cerebral ischemia-induced neuronal apoptosis and behavioral deficits

Increased oxidative stress has been regarded as an important underlying cause for neuronal damage induced by cerebral ischemia/reperfusion (I/R) injury. In recent years, there has been increasing interest in investigating polyphenols from botanical source for possible neuroprotective effects against neurodegenerative diseases. In this study, we investigated the mechanisms underlying the neuroprotective effects of curcumin, a potent polyphenol antioxidant enriched in tumeric. Global cerebral ischemia was induced in Mongolian gerbils by transient occlusion of the common carotid arteries. Histochemical analysis indicated extensive neuronal death together with increased reactive astrocytes and microglial cells in the hippocampal CA1 area at 4 days after I/R. These ischemic changes were preceded by a rapid increase in lipid peroxidation and followed by decrease in mitochondrial membrane potential, increased cytochrome c release, and subsequently caspase-3 activation and apoptosis. Administration of curcumin by i.p. injections (30 mg/kg body wt) or by supplementation to the AIN76 diet (2.0 g/kg diet) for 2 months significantly attenuated ischemia-induced neuronal death as well as glial activation. Curcumin administration also decreased lipid peroxidation, mitochondrial dysfunction, and the apoptotic indices. The biochemical changes resulting from curcumin also correlated well with its ability to ameliorate the changes in locomotor activity induced by I/R. Bioavailability study indicated a rapid increase in curcumin in plasma and brain within 1 hr after treatment. Together, these findings attribute the neuroprotective effect of curcumin against I/R-induced neuronal damage to its antioxidant capacity in reducing oxidative stress and the signaling cascade leading to apoptotic cell death.

Phospholipase A2, reactive oxygen species, and lipid peroxidation in cerebral ischemia

Ischemic stroke is caused by obstruction of blood flow to the brain, resulting in energy failure that initiates a complex series of metabolic events, ultimately causing neuronal death. One such critical metabolic event is the activation of phospholipase A2 (PLA2), resulting in hydrolysis of membrane phospholipids and release of free fatty acids including arachidonic acid, a metabolic precursor for important cell-signaling eicosanoids. PLA2 enzymes have been classified as calcium-dependent cytosolic (cPLA2) and secretory (sPLA2) and calcium-independent (iPLA2) forms. Cardiolipin hydrolysis by mitochondrial sPLA2 disrupts the mitochondrial respiratory chain and increases production of reactive oxygen species (ROS). Oxidative metabolism of arachidonic acid also generates ROS. These two processes contribute to formation of lipid peroxides, which degrade to reactive aldehyde products (malondialdehyde, 4-hydroxynonenal, and acrolein) that covalently bind to proteins/nucleic acids, altering their function and causing cellular damage. Activation of PLA2 in cerebral ischemia has been shown while other studies have separately demonstrated increased lipid peroxidation. To the best of our knowledge no study has directly shown the role of PLA2 in lipid peroxidation in cerebral ischemia. To date, there are very limited data on PLA2 protein by Western blotting after cerebral ischemia, though some immunohistochemical studies (for cPLA2 and sPLA2) have been reported. Dissecting the contribution of PLA2 to lipid peroxidation in cerebral ischemia is challenging due to multiple forms of PLA2, cardiolipin hydrolysis, diverse sources of ROS arising from arachidonic acid metabolism, catecholamine autoxidation, xanthine oxidase activity, mitochondrial dysfunction, activated neutrophils coupled with NADPH oxidase activity, and lack of specific inhibitors. Although increased activity and expression of various PLA2 isoforms have been demonstrated in stroke, more studies are needed to clarify the cellular origin and localization of these isoforms in the brain, their responses in cerebral ischemic injury, and their role in oxidative stress.

Modulation of voltage-gated Ca2+ current by 4-hydroxynonenal in dentate granule cells

Although recent studies have suggested that dentate granule cells play a key role in hippocampal functions, electrophysiological properties in these cells have not been sufficiently explored. In the present study, modification of voltage-gated Ca2+ channels by 4-hydroxynonenal (4HN), a major aldehydic product of membrane lipid peroxidation, in cultured dentate granule cells was examined using the whole-cell patch clamp technique. When whole-cell voltage clamp was applied, the cells exhibited a high-voltage-activated Ca2+ current, which was totally sensitive to 30 microM Cd2+ and partially sensitive to 2 microM nifedipine. 4HN enhanced the Ca2+ current in these cells. When L-type Ca2+ channels were blocked by application of nifedipine, the enhancement was completely canceled, whereas application of omega-conotoxin-GVIA or omega-agatoxin-IVA, blockers of N- and P/Q-type Ca2+ channels, respectively, had no effect. These results suggest that 4HN modulates L-type Ca2+ channels in the dentate granule cells, and thereby plays a role in the physiological and pathophysiological responses of these cells to oxidative stress.

Lipid peroxidation, caspase-3 immunoreactivity, and pyknosis in late-gestation fetal sheep brain after umbilical cord occlusion

Umbilical cord occlusion (UCO), a known risk factor for perinatal brain damage, causes severe fetal asphyxia leading to oxidative stress, lipid peroxidation, and cell death. We have determined the effects of two 10-min UCO on the distribution of the lipid peroxidation marker 4-hydroxynonenal (4-HNE) and the activated form of the apoptosis marker caspase-3 in the brains of late-gestation fetal sheep. UCO caused asphyxia, hypertension, and bradycardia, but these parameters normalized 2 h after the occlusion. At postmortem, 48 h after the second UCO there were significantly higher numbers of 4-HNE-positive cells in all layers of the hippocampus and cerebellum, the parietal cortex, substantia nigra, caudate nucleus, putamen, and thalamus compared with control brains. 4-HNE immunoreactivity was also found in white matter tracts of the subcallosal bundle, external medullary lamina, reticular thalamic nucleus, and cerebellar fiber tracts only in UCO brains. Double-labeling identified these cells as predominantly neurons and astrocytes, with oligodendrocytes showing lower levels of 4-HNE immunoreactivity. After UCO, the number of caspase-3-immunopositive cells was increased significantly in the hippocampal CA1, molecular layer and dentate gyrus, ventrolateral thalamic nucleus, substantia nigra, putamen, and cerebellar granular and molecular layers compared with controls. Double-labeling revealed caspase-3 immunoreactivity was mainly in neurons, and to lesser extent in astrocytes and oligodendrocytes. Pyknotic cell numbers were significantly increased in hippocampal CA1 and CA3, parietal cortex, caudate nucleus, putamen, and cerebellar Purkinje cells after UCO. These data indicate that brief asphyxia induces widespread lipid peroxidation involving all cell types of the fetal brain and apoptosis in both neurons and glia.

S-allyl-L-cysteine selectively protects cultured rat hippocampal neurons from amyloid beta-protein- and tunicamycin-induced neuronal death

S-allyl-L-cysteine (SAC), one of the organosulfur compounds found in aged garlic extract, has been shown to possess various biological effects including neurotrophic activity. In our previous experiments, we found that SAC could protect against amyloid beta-protein (Abeta)- and tunicamycin-induced cell death in differentiated PC12 cells. In the study described here, we characterized the neuronal death induced by Abeta, 4-hydroxynonenal (HNE), tunicamycin, and trophic factor deprivation, and investigated whether and how SAC could prevent this in cultured rat hippocampal neurons. Treatment with SAC protected these cells against Abeta- and tunicamycin-induced neuronal death, which is mediated predominantly through caspase-12-dependent pathway in a concentration-dependent manner. In contrast, it afforded no protection against HNE- and trophic factor-deprivation-induced cell death, which has been shown to be mediated by caspase-3-dependent pathway. SAC also attenuated the Abeta-induced increase of intracellular reactive oxygen species in hippocampal neurons. SAC had no effect on Abeta-induced cell death in cultured cerebellar granule neurons, which was prevented by a caspase-3 inhibitor. These results suggest that SAC could protect against the neuronal cell death that is triggered by ER dysfunction in the hippocampus, and that it has no effect on neuronal cell death that is dependent upon the caspase-3 mediated pathway.

Delayed treatment with nimesulide reduces measures of oxidative stress following global ischemic brain injury in gerbils

Metabolism of arachidonic acid by cyclooxygenase is one of the primary sources of reactive oxygen species in the ischemic brain. Neuronal overexpression of cyclooxygenase-2 has recently been shown to contribute to neurodegeneration following ischemic injury. In the present study, we examined the possibility that the neuroprotective effects of the cyclooxygenase-2 inhibitor nimesulide would depend upon reduction of oxidative stress following cerebral ischemia. Gerbils were subjected to 5 min of transient global cerebral ischemia followed by 48 h of reperfusion and markers of oxidative stress were measured in hippocampus of gerbils receiving vehicle or nimesulide treatment at three different clinically relevant doses (3, 6 or 12 mg/kg). Compared with vehicle, nimesulide significantly (P<0.05) reduced hippocampal glutathione depletion and lipid peroxidation, as assessed by the levels of malondialdehyde (MDA), 4-hydroxy-alkenals (4-HDA) and lipid hydroperoxides levels, even when the treatment was delayed until 6 h after ischemia. Biochemical evidences of nimesulide neuroprotection were supported by histofluorescence findings using the novel marker of neuronal degeneration Fluoro-Jade B. Few Fluoro-Jade B positive cells were seen in CA1 region of hippocampus in ischemic animals treated with nimesulide compared with vehicle. These results suggest that nimesulide may protect neurons by attenuating oxidative stress and reperfusion injury following the ischemic insult with a wide therapeutic window of protection.

Assessment of the relative contribution of COX-1 and COX-2 isoforms to ischemia-induced oxidative damage and neurodegeneration following transient global cerebral ischemia

We investigated the relative contribution of COX-1 and/or COX-2 to oxidative damage, prostaglandin E2 (PGE2) production and hippocampal CA1 neuronal loss in a model of 5 min transient global cerebral ischemia in gerbils. Our results revealed a biphasic and significant increase in PGE2 levels after 2 and 24-48 h of reperfusion. The late increase in PGE2 levels (24 h) was more potently reduced by the highly selective COX-2 inhibitor rofecoxib (20 mg/kg) relative to the COX-1 inhibitor valeryl salicylate (20 mg/kg). The delayed rise in COX catalytic activity preceded the onset of histopathological changes in the CA1 subfield of the hippocampus. Post-ischemia treatment with rofecoxib (starting 6 h after restoration of blood flow) significantly reduced measures of oxidative damage (glutathione depletion and lipid peroxidation) seen at 48 h after the initial ischemic episode, indicating that the late increase in COX-2 activity is involved in the delayed occurrence of oxidative damage in the hippocampus after global ischemia. Interestingly, either selective inhibition of COX-2 with rofecoxib or inhibition of COX-1 with valeryl salicylate significantly increased the number of healthy neurons in the hippocampal CA1 sector even when the treatment began 6 h after ischemia. These results provide the first evidence that both COX isoforms are involved in the progression of neuronal damage following global cerebral ischemia, and have important implications for the potential therapeutic use of COX inhibitors in cerebral ischemia.

4-Hydroxy-2-nonenal: a product and mediator of oxidative stress

The onset of lipid peroxidation within cellular membranes is associated with changes in their physiochemical properties and with the impairment of enzymatic functions located in the membrane environment. There is increasing evidence that aldehydic molecules generated endogenously during the process of lipid peroidation are causally involved in most of the pathophysiological effects associated with oxidative stress in cells and tissues. 4-Hydroxy-2-nonenal (HNE), among them, is believed to be largely responsible for cytopathological effects observed during oxidative stree in vivo and has achieved the status of one of the best recognized and most studied of the cytotoxic products of lipid peroxidation. In the present review, I provide a comprehensive summary of HNE, as the product and mediator or oxidative stress.

Protective effect of S-allyl-L-cysteine, a garlic compound, on amyloid beta-protein-induced cell death in nerve growth factor-differentiated PC12 cells

Aged garlic extract (AGE) contains several neuroactive compounds, including S-allyl-L-cysteine (SAC) and allixin. We characterized cell death induced by amyloid beta-protein (Abeta), 4-hydroxynonenal (HNE), tunicamycin, an endoplasmic reticulum (ER) stressor, or trophic factor deprivation, and investigated whether and how SAC could prevent this in nerve growth factor (NGF)-differentiated PC12 cells, a model of neuronal cells. Exposure of the cells to amyloid beta-protein(1-40) (Abeta(1-40)) decreased the extent of [3-(4,5)-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium (MTT) reduction activity and loss of neuronal integrity, but these effects were not prevented by Ac-DEVD-CHO, a caspase-3 inhibitor. Simultaneously applied SAC protected the cells against Abeta-induced cell death in a concentration-dependent manner. It also protected them against tunicamycin-induced neuronal death. In contrast, it afforded no protection against cell death induced by HNE and trophic factor deprivation, which is mediated by a caspase-3-dependent pathway. These results suggest that SAC may selectively protect cell death induced by Abeta and tunicamycin, which may be triggered by ER dysfunction in NGF-differentiated PC12 cells.

Apoptosis and brain ischaemia

There is increasing evidence that some neuronal death after brain ischaemia is mediated by the action of cysteine-requiring aspartate-directed proteases (caspases), the proteases responsible for apoptosis in mammals, although this form of neuronal death is not always accompanied by the morphological changes that are typical of apoptosis in other tissues. Caspase-mediated neuronal death is more extensive after transient than permanent focal brain ischaemia and may contribute to delayed loss of neurons from the penumbral region of infarcts. The activation of caspases after brain ischaemia is largely consequent on the translocation of Bax, Bak, and other BH3-only members of the Bcl-2 family to the mitochondrial outer membrane and the release of cytochrome c, procaspase-9, and apoptosis activating factor-1 (Apaf-1) from the mitochondrial intermembrane space. How exactly ischaemia induces this translocation is still poorly understood. NF-kappaB, the c-jun N-terminal kinase-c-Jun pathway, p53, E2F1, and other transcription factors are probably all involved in regulating the expression of BH3-only proteins after brain ischaemia, and mitochondrial translocation of Bad from sequestering cytosolic proteins is promoted by inactivation of the serine-threonine kinase, Akt. Other processes that are probably involved in the activation of caspases after brain ischaemia include the mitochondrial release of the second mitochondrial activator of caspases (Smac) or direct inhibitor-of-apoptosis-binding protein with low pI (DIABLO), the accumulation of products of lipid peroxidation, a marked reduction in protein synthesis, and the aberrant reentry of neurons into the cell cycle. Non-caspase-mediated neuronal apoptosis may also occur, but there is little evidence to date that this makes a significant contribution to brain damage after ischaemia. The intracellular processes that contribute to caspase-mediated neuronal death after ischaemia are all potential targets for therapy. However, anti-apoptotic interventions in stroke patients will require detailed evaluation using a range of outcome measures, as some such interventions seem simply to delay neuronal death and others to preserve neurons but not neuronal function.

Oxidative stress causes ERK phosphorylation and cell death in cultured retinal pigment epithelium: prevention of cell death by AG126 and 15-deoxy-delta 12, 14-PGJ2

BACKGROUND

The retina, which is exposed to both sunlight and very high levels of oxygen, is exceptionally rich in polyunsaturated fatty acids, which makes it a favorable environment for the generation of reactive oxygen species. The cytotoxic effects of hydrogen peroxide (H2O2) induced oxidative stress on retinal pigment epithelium were characterized in this study.

METHODS

The MTT cell viability assay, Texas-Red phalloidin staining, immunohistochemistry and Western blot analysis were used to assess the effects of oxidative stress on primary human retinal pigment epithelial cell cultures and the ARPE-19 cell line.

RESULTS

The treatment of retinal pigment epithelial cells with H2O2 caused a dose-dependent decrease of cellular viability, which was preceded by a significant cytoskeletal rearrangement, activation of the Extracellular signal-Regulated Kinase, lipid peroxidation and nuclear condensation. This cell death was prevented partially by the prostaglandin derivative, 15d-PGJ2 and by the protein kinase inhibitor, AG126.

CONCLUSION

15d-PGJ2 and AG126 may be useful pharmacological tools in the future capable of preventing oxidative stress induced RPE cell death in human ocular diseases.

Cerebral vasculature is the major target of oxidative protein alterations in bacterial meningitis

We have previously shown that antioxidants such as a-phenyl-tert-butyl nitrone or N-acetylcysteine attenuate cortical neuronal injury in infant rats with bacterial meningitis, suggesting that oxidative alterations play an important role in this disease. However, the precise mechanism(s) by which antioxidants inhibit this injury remain(s) unclear. We therefore studied the extent and location of protein oxidation in the brain using various biochemical and immunochemical methods. In cortical parenchyma, a trend for increased protein carbonyls was not evident until 21 hours after infection and the activity of glutamine synthetase (another index of protein oxidation) remained unchanged. Consistent with these results, there was no evidence for oxidative alterations in the cortex by various immunohistochemical methods even in cortical lesions. In contrast, there was a marked increase in carbonyls, 4-hydroxynonenal protein adducts and manganese superoxide dismutase in the cerebral vasculature. Elevated lipid peroxidation was also observed in cerebrospinal fluid and occasionally in the hippocampus. All of these oxidative alterations were inhibited by treatment of infected animals with N-acetylcysteine or alpha-phenyl-tert-butyl nitrone. Because N-acetylcysteine does not readily cross the blood-brain barrier and has no effect on the loss of endogenous brain antioxidants, its neuroprotective effect is likely based on extraparenchymal action such as inhibition of vascular oxidative alterations.

Time course of oxidative damage in different brain regions following transient cerebral ischemia in gerbils

The time course of oxidative damage in different brain regions was investigated in the gerbil model of transient cerebral ischemia. Animals were subjected to both common carotid arteries occlusion for 5 min. After the end of ischemia and at different reperfusion times (2, 6, 12, 24, 48, 72, 96 h and 7 days), markers of lipid peroxidation, reduced and oxidized glutathione levels, glutathione peroxidase, glutathione reductase, manganese-dependent superoxide dismutase (MnSOD) and copper/zinc containing SOD (Cu/ZnSOD) activities were measured in hippocampus, cortex and striatum. Oxidative damage in hippocampus was maximal at late stages after ischemia (48-96 h) coincident with a significant impairment in glutathione homeostasis. MnSOD increased in hippocampus at 24, 48 and 72 h after ischemia, coincident with the marked reduction in the activity of glutathione-related enzymes. The late disturbance in oxidant-antioxidant balance corresponds with the time course of delayed neuronal loss in the hippocampal CA1 sector. Cerebral cortex showed early changes in oxidative damage with no significant impairment in antioxidant capacity. Striatal lipid peroxidation significantly increased as early as 2 h after ischemia and persisted until 48 h with respect to the sham-operated group. These results contribute significant information on the timing and factors that influence free radical formation following ischemic brain injury, an essential step in determining effective antioxidant intervention.

Effects of citicoline on phospholipid and glutathione levels in transient cerebral ischemia

BACKGROUND AND PURPOSE

Cytidine-5'-diphosphocholine (citicoline or CDP-choline) is an essential intermediate in the biosynthesis of phosphatidylcholine, an important component of the neural cell membrane. Citicoline provided significant neuroprotection after transient forebrain ischemia in gerbils. This study was undertaken to examine changes and effects of citicoline on phospholipids and glutathione synthesis after transient cerebral ischemia and reperfusion.

METHODS

Ten-minute transient forebrain ischemia was induced by bilateral carotid artery occlusion in male Mongolian gerbils with reperfusion up to 6 days. Citicoline (500 mg/kg IP in saline) was given to gerbils just after the end of ischemia, at 3-hour reperfusion, and daily thereafter until 1 day before euthanasia. Hippocampal lipids were extracted and analyzed by thin-layer and gas chromatography. Glutathione was measured by using an enzymatic recycling assay. Glutathione reductase activity was determined by measuring NADPH oxidation.

RESULTS

Significant decreases in phospholipids occurred at 1-day reperfusion. Citicoline significantly restored the phosphatidylcholine, sphingomyelin, and cardiolipin levels but did not affect phosphatidylinositol and phosphatidylserine at 1 day. The phospholipids returned to sham levels over days 2 to 6 and were unaffected by citicoline. Ceramide levels significantly increased by 3 and 6 days of reperfusion and were unaltered by citicoline. Ischemia resulted in significant decreases in glutathione and glutathione reductase activity over 3 days of reperfusion. Citicoline significantly increased total glutathione and glutathione reductase activity and decreased the glutathione oxidation ratio, an indicator of glutathione redox status.

CONCLUSIONS

Our data indicated that the effects of citicoline on phospholipids occurred primarily during the first day of reperfusion, with effects on glutathione being important over the 3-day reperfusion period.

Does CDP-choline modulate phospholipase activities after transient forebrain ischemia?

Ten min forebrain ischemia/1-day reperfusion resulted in significant decreases in total phosphatidylcholine (PtdCho), phosphatidylinositol (PtdIns), and cardiolipin in gerbil hippocampus. CDP-choline restored cardiolipin levels, arachidonic acid content of PtdCho, partially but significantly restored total PtdCho, and had no effect on PtdIns. These data suggest that CDP-choline prevented the activation of phospholipase A(2) (rather than inhibiting phospholipase A(2) activity) but did not affect activities of PtdCho-phospholipases C and/or D, or phosphoinositide-phospholipase C. CDP-choline also provided significant protection for hippocampal CA(1) neurons.