Augmenting hematoma-scavenging capacity of innate immune cells by CDNF reduces brain injury and promotes functional recovery after intracerebral hemorrhage.

During intracerebral hemorrhage (ICH), hematoma formation at the site of blood vessel damage results in local mechanical injury. Subsequently, erythrocytes lyse to release hemoglobin and heme, which act as neurotoxins and induce inflammation and secondary brain injury, resulting in severe neurological deficits. Accelerating hematoma resorption and mitigating hematoma-induced brain edema by modulating immune cells has potential as a novel therapeutic strategy for functional recovery after ICH. Here, we show that intracerebroventricular administration of recombinant human cerebral dopamine neurotrophic factor (rhCDNF) accelerates hemorrhagic lesion resolution, reduces peri-focal edema, and improves neurological outcomes in an animal model of collagenase-induced ICH. We demonstrate that CDNF acts on microglia/macrophages in the hemorrhagic striatum by promoting scavenger receptor expression, enhancing erythrophagocytosis and increasing anti-inflammatory mediators while suppressing the production of pro-inflammatory cytokines. Administration of rhCDNF results in upregulation of the Nrf2-HO-1 pathway, but alleviation of oxidative stress and unfolded protein responses in the perihematomal area. Finally, we demonstrate that intravenous delivery of rhCDNF has beneficial effects in an animal model of ICH and that systemic application promotes scavenging by the brain's myeloid cells for the treatment of ICH.

Modulating Microglia/Macrophage Activation by CDNF Promotes Transplantation of Fetal Ventral Mesencephalic Graft Survival and Function in a Hemiparkinsonian Rat Model.

Parkinson's disease (PD) is characterized by the loss of dopaminergic neurons in substantia nigra pars compacta, which leads to the motor control deficits. Recently, cell transplantation is a cutting-edge technique for the therapy of PD. Nevertheless, one key bottleneck to realizing such potential is allogenic immune reaction of tissue grafts by recipients. Cerebral dopamine neurotrophic factor (CDNF) was shown to possess immune-modulatory properties that benefit neurodegenerative diseases. We hypothesized that co-administration of CDNF with fetal ventral mesencephalic (VM) tissue can improve the success of VM replacement therapies by attenuating immune responses. Hemiparkinsonian rats were generated by injecting 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle of Sprague Dawley (SD) rats. The rats were then intrastriatally transplanted with VM tissue from rats, with/without CDNF administration. Recovery of dopaminergic function and survival of the grafts were evaluated using the apomorphine-induced rotation test and small-animal positron emission tomography (PET) coupled with [18F] DOPA or [18F] FE-PE2I, respectively. In addition, transplantation-related inflammatory response was determined by uptake of [18F] FEPPA in the grafted side of striatum. Immunohistochemistry (IHC) examination was used to determine the survival of the grated dopaminergic neurons in the striatum and to investigate immune-modulatory effects of CDNF. The modulation of inflammatory responses caused by CDNF might involve enhancing M2 subset polarization and increasing fractal dimensions of 6-OHDA-treated BV2 microglial cell line. Analysis of CDNF-induced changes to gene expressions of 6-OHDA-stimulated BV2 cells implies that these alternations of the biomarkers and microglial morphology are implicated in the upregulation of protein kinase B signaling as well as regulation of catalytic, transferase, and protein serine/threonine kinase activity. The effects of CDNF on 6-OHDA-induced alternation of the canonical pathway in BV2 microglial cells is highly associated with PI3K-mediated phagosome formation. Our results are the first to show that CDNF administration enhances the survival of the grafted dopaminergic neurons and improves functional recovery in PD animal model. Modulation of the polarization, morphological characteristics, and transcriptional profiles of 6-OHDA-stimualted microglia by CDNF may possess these properties in transplantation-based regenerative therapies.

Post-stroke Delivery of Valproic Acid Promotes Functional Recovery and Differentially Modifies Responses of Peri-Infarct Microglia.

The specific role of peri-infarct microglia and the timing of its morphological changes following ischemic stroke are not well understood. Valproic acid (VPA) can protect against ischemic damage and promote recovery. In this study, we first determined whether a single dose of VPA after stroke could decrease infarction area or improve functional recovery. Next, we investigated the number and morphological characteristic of peri-infarct microglia at different time points and elucidated the mechanism of microglial response by VPA treatment. Male Sprague-Dawley rats were subjected to distal middle cerebral artery occlusion (dMCAo) for 90 min, followed by reperfusion. Some received a single injection of VPA (200 mg/kg) 90 min after the induction of ischemia, while vehicle-treated animals underwent the same procedure with physiological saline. Infarction volume was calculated at 48 h after reperfusion, and neurological symptoms were evaluated. VPA didn't significantly reduce infarct volume but did ameliorate neurological deficit at least partially compared with vehicle. Meanwhile, VPA reduced dMCAo-induced elevation of IL-6 at 24 h post-stroke and significantly decreased the number of CD11b-positive microglia within peri-infarct cortex at 7 days. Morphological analysis revealed that VPA therapy leads to higher fractal dimensions, smaller soma size and lower circularity index of CD11b-positive cells within peri-infarct cortex at both 2 and 7 days, suggesting that VPA has core effects on microglial morphology. The modulation of microglia morphology caused by VPA might involve HDAC inhibition-mediated suppression of galectin-3 production. Furthermore, qPCR analysis of CD11b-positive cells at 3 days post-stroke suggested that VPA could partially enhance M2 subset polarization of microglia in peri-infarct cortex. Analysis of VPA-induced changes to gene expressions at 3 days post-stroke implies that these alternations of the biomarkers and microglial responses are implicated in the upregulation of wound healing, collagen trimmer, and extracellular matrix genes within peri-infarct cortex. Our results are the first to show that a low dose of VPA promotes short-term functional recovery but does not alter infarct volume. The decreases in the expression of both IL-6 and galectin-3 might influence the morphological characteristics and transcriptional profiles of microglia and extracellular matrix remodeling, which could contribute to the improved recovery.

Clinacanthus nutans Mitigates Neuronal Death and Reduces Ischemic Brain Injury: Role of NF-κB-driven IL-1ß Transcription.

Neuroinflammation has been shown to exacerbate ischemic brain injury, and is considered as a prime target for the development of stroke therapies. Clinacanthus nutans Lindau (C. nutans) is widely used in traditional medicine for treating insect bites, viral infection and cancer, due largely to its anti-oxidative and anti-inflammatory properties. Recently, we reported that an ethanol extract from the leaf of C. nutans could protect the brain against ischemia-triggered neuronal death and infarction. In order to further understand the molecular mechanism(s) for its beneficial effects, two experimental paradigms, namely, in vitro primary cortical neurons subjected to oxygen-glucose deprivation (OGD) and in vivo rat middle cerebral artery (MCA) occlusion, were used to dissect the anti-inflammatory effects of C. nutans extract. Using promoter assays, immunofluorescence staining, and loss-of-function (siRNA) approaches, we demonstrated that transient OGD led to marked induction of IL-1ß, IL-6 and TNFα, while pretreatment with C. nutans suppressed production of inflammatory cytokines in primary neurons. C. nutans inhibited IL-1ß transcription via preventing NF-κB/p65 nuclear translocation, and siRNA knockdown of either p65 or IL-1ß mitigated OGD-mediated neuronal death. Correspondingly, post-ischemic treatment of C. nutans attenuated IκBα degradation and decreased IL-1ß, IL-6 and TNFα production in the ischemic brain. Furthermore, IL-1ß siRNA post-ischemic treatment reduced cerebral infarct, thus mimicking the beneficial effects of C. nutans. In summary, our findings demonstrated the ability for C. nutans to suppress NF-κB nuclear translocation and inhibit IL-1ß transcription in ischemic models. Results further suggest the possibility for using C. nutans to prevent and treat stroke patients.

Expression of DHA-Metabolizing Enzyme Alox15 is Regulated by Selective Histone Acetylation in Neuroblastoma Cells.

The omega-3 polyunsaturated fatty acid, docosahexaenoic acid (DHA) is enriched in neural membranes of the CNS, and recent studies have shown a role of DHA metabolism by 15-lipoxygenase-1 (Alox15) in prefrontal cortex resolvin D1 formation, hippocampo-prefrontal cortical long-term-potentiation, spatial working memory, and anti-nociception/anxiety. In this study, we elucidated epigenetic regulation of Alox15 via histone modifications in neuron-like cells. Treatment of undifferentiated SH-SY5Y human neuroblastoma cells with the histone deacetylase (HDAC) inhibitors trichostatin A (TSA) and sodium butyrate significantly increased Alox15 mRNA expression. Moreover, Alox15 expression was markedly upregulated by Class I HDAC inhibitors, MS-275 and depsipeptide. Co-treatment of undifferentiated SH-SY5Y cells with the p300 histone acetyltransferase (HAT) inhibitor C646 and TSA or sodium butyrate showed that p300 HAT inhibition modulated TSA or sodium butyrate-induced Alox15 upregulation. Differentiation of SH-SY5Y cells with retinoic acid resulted in increased neurite outgrowth and Alox15 mRNA expression, while co-treatment with the p300 HAT inhibitor C646 and retinoic acid modulated the increases, indicating a role of p300 HAT in differentiation-associated Alox15 upregulation. Increasing Alox15 expression was found in primary murine cortical neurons during development from 3 to 10 days-in-vitro, reaching high levels of expression by 10 days-in-vitro-when Alox15 was not further upregulated by HDAC inhibition. Together, results indicate regulation of Alox15 mRNA expression in neuroblastoma cells by histone modifications, and increasing Alox15 expression in differentiating neurons. It is possible that one of the environmental influences on the immature brain that can affect cognition and memory, may take the form of epigenetic effects on Alox15 and metabolites of DHA.

Clinacanthus nutans Mitigates Neuronal Apoptosis and Ischemic Brain Damage Through Augmenting the C/EBPß-Driven PPAR-γ Transcription.

Clinacanthus nutans Lindau (C. nutans) is a traditional herbal medicine widely used in Asian countries for treating a number of remedies including snake and insect bites, skin rashes, viral infections, and cancer. However, the underlying molecular mechanisms for its action and whether C. nutans can offer protection on stroke damage in brain remain largely unknown. In the present study, we demonstrated protective effects of C. nutans extract to ameliorate neuronal apoptotic death in the oxygen-glucose deprivation model and to reduce infarction and mitigate functional deficits in the middle cerebral artery occlusion model, either administered before or after hypoxic/ischemic insult. Using pharmacological antagonist and siRNA knockdown approaches, we demonstrated ability for C. nutans extract to protect neurons and ameliorate ischemic injury through promoting the anti-apoptotic activity of peroxisome proliferator-activated receptor-gamma (PPAR-γ), a stress-induced transcription factor. Reporter and chromatin immunoprecipitation promoter analysis further revealed C. nutans extract to selectively increase CCAAT/enhancer binding protein (C/EBP)ß binding to specific C/EBP binding site (-332~-325) on the PPAR-γ promoter to augment its transcription. In summary, we report a novel transcriptional activation involving C/EBPß upregulation of PPAR-γ expression to suppress ischemic neuronal apoptosis and brain infarct. Recognition of C. nutans to enhance the C/EBPߠ→ PPAR-γ neuroprotective signaling pathway paves a new way for future drug development for prevention and treatment of ischemic stroke and other neurodegenerative diseases.

Clinacanthus nutans Extracts Modulate Epigenetic Link to Cytosolic Phospholipase A2 Expression in SH-SY5Y Cells and Primary Cortical Neurons.

Clinacanthus nutans Lindau (C. nutans), commonly known as Sabah Snake Grass in southeast Asia, is widely used in folk medicine due to its analgesic, antiviral, and anti-inflammatory properties. Our recent study provided evidence for the regulation of cytosolic phospholipase A2 (cPLA2) mRNA expression by epigenetic factors (Tan et al. in Mol Neurobiol. doi: 10.1007/s12035-015-9314-z , 2015). This enzyme catalyzes the release of arachidonic acid from glycerophospholipids, and formation of pro-inflammatory eicosanoids or toxic lipid peroxidation products such as 4-hydroxynonenal. In this study, we examined the effects of C. nutans ethanol leaf extracts on epigenetic regulation of cPLA2 mRNA expression in SH-SY5Y human neuroblastoma cells and mouse primary cortical neurons. C. nutans modulated induction of cPLA2 expression in SH-SY5Y cells by histone deacetylase (HDAC) inhibitors, MS-275, MC-1568, and TSA. C. nutans extracts also inhibited histone acetylase (HAT) activity. Levels of cPLA2 mRNA expression were increased in primary cortical neurons subjected to 0.5-h oxygen-glucose deprivation injury (OGD). This increase was significantly inhibited by C. nutans treatment. Treatment of primary neurons with the HDAC inhibitor MS-275 augmented OGD-induced cPLA2 mRNA expression, and this increase was modulated by C. nutans extracts. OGD-stimulated increase in cPLA2 mRNA expression was also reduced by a Tip60 HAT inhibitor, NU9056. In view of a key role of cPLA2 in the production of pro-inflammatory eicosanoids and free radical damage, and the fact that epigenetic effects on genes are often long-lasting, results suggest a role for C. nutans and phytochemicals to inhibit the production of arachidonic acid-derived pro-inflammatory eicosanoids and chronic inflammation, through epigenetic regulation of cPLA2 expression.

Clinacanthus nutans Protects Cortical Neurons Against Hypoxia-Induced Toxicity by Downregulating HDAC1/6.

Many population-based epidemiological studies have unveiled an inverse correlation between intake of herbal plants and incidence of stroke. C. nutans is a traditional herbal medicine widely used for snake bite, viral infection and cancer in Asian countries. However, its role in protecting stroke damage remains to be studied. Despite of growing evidence to support epigenetic regulation in the pathogenesis and recovery of stroke, a clear understanding of the underlying molecular mechanisms is still lacking. In the present study, primary cortical neurons were subjected to in vitro oxygen-glucose deprivation (OGD)-reoxygenation and hypoxic neuronal death was used to investigate the interaction between C. nutans and histone deacetylases (HDACs). Using pharmacological agents (HDAC inhibitor/activator), loss-of-function (HDAC siRNA) and gain-of-function (HDAC plasmid) approaches, we demonstrated an early induction of HDAC1/2/3/8 and HDAC6 in neurons after OGD insult. C. nutans extract selectively inhibited HDAC1 and HDAC6 expression and attenuated neuronal death. Results of reporter analysis further revealed that C. nutans suppressed HDAC1 and HDAC6 transcription. Besides ameliorating neuronal death, C. nutans also protected astrocytes and endothelial cells from hypoxic-induced cell death. In summary, results support ability for C. nutans to suppress post-hypoxic HDACs activation and mitigate against OGD-induced neuronal death. This study further opens a new avenue for the use of herbal medicines to regulate epigenetic control of brain injury.

PPAR-γ Ameliorates Neuronal Apoptosis and Ischemic Brain Injury via Suppressing NF-κB-Driven p22phox Transcription.

Peroxisome proliferator-activated receptor-gamma (PPAR-γ), a stress-induced transcription factor, protects neurons against ischemic stroke insult by reducing oxidative stress. NADPH oxidase (NOX) activation, a major driving force in ROS generation in the setting of reoxygenation/reperfusion, constitutes an important pathogenetic mechanism of ischemic brain damage. In the present study, both transient in vitro oxygen-glucose deprivation and in vivo middle cerebral artery (MCA) occlusion-reperfusion experimental paradigms of ischemic neuronal death were used to investigate the interaction between PPAR-γ and NOX. With pharmacological (PPAR-γ antagonist GW9662), loss-of-function (PPAR-γ siRNA), and gain-of-function (Ad-PPAR-γ) approaches, we first demonstrated that 15-deoxy-∆(12,14)-PGJ2 (15d-PGJ2), via selectively attenuating p22phox expression, inhibited NOX activation and the subsequent ROS generation and neuronal death in a PPAR-γ-dependent manner. Secondly, results of promoter analyses and subcellular localization studies further revealed that PPAR-γ, via inhibiting hypoxia-induced NF-κB nuclear translocation, indirectly suppressed NF-κB-driven p22phox transcription. Noteworthily, postischemic p22phox siRNA treatment not only reduced infarct volumes but also improved functional outcome. In summary, we report a novel transrepression mechanism involving PPAR-γ downregulation of p22phox expression to suppress the subsequent NOX activation, ischemic neuronal death, and brain infarct. Identification of a PPAR-γ → NF-κB → p22phox neuroprotective signaling cascade opens a new avenue for protecting the brain against ischemic insult.

Novel link of anti-apoptotic ATF3 with pro-apoptotic CTMP in the ischemic brain.

Activating transcription factor 3 (ATF3) is a stress-induced transcription factor with diverse functions under disease states in multiple cell types. ATF3 has neuroprotective action against cerebral ischemia, which may involve caspase 3. However, the molecular mechanisms underlying ATF3 regulation of apoptosis are largely unknown. Here, we used gain- and loss-of-function and rescue approaches to demonstrate ATF3 attenuating hypoxic neuronal apoptosis. As well, the protective effect of ATF3 was mediated by downregulation of carboxyl-terminal modulator protein (CTMP), a pro-apoptotic factor that inhibits the anti-apoptotic Akt/PKB cascade. ATF3 (1) downregulated the mRNA and protein levels of CTMP; (2) its temporal expression pattern was reciprocal to that of CTMP; and (3) nuclear localization suggested that ATF3 may regulate CTMP transcription following hypoxic insult. Reporter assays demonstrated that ATF3 suppressed CTMP transcription, whereas ATF3 fusion with VP16, converting ATF3 to transcriptional activator, boosted CTMP transcription. By contrast, NF-κB increased CTMP transcription, and degradation-resistant IκBα decreased CTMP transcription. ChIP assays further confirmed that binding of ATF3 to the ATF/CREB site hindered NF-κB binding to the CTMP promoter, which repressed CTMP expression. Furthermore, CTMP siRNA treatment reduced hypoxic neuronal apoptosis by increasing p-Akt (Ser473) levels and leaving the upstream ATF3 level unchanged. We have identified an endogenous neuroprotective ATF3→CTMP signal cascade that may be a therapeutic target for reducing ischemic brain injury.

15-Deoxy-∆12,14-PGJ 2, by activating peroxisome proliferator-activated receptor-gamma, suppresses p22phox transcription to protect brain endothelial cells against hypoxia-induced apoptosis.

15-Deoxy-∆(12,14)-PGJ(2) (15d-PGJ(2)) and thiazolidinedione attenuate reactive oxygen species (ROS) production via a peroxisome proliferator-activated receptor-gamma (PPAR-γ)-dependent pathway. Nonetheless, how PPAR-γ mediates ROS production to ameliorate ischemic brain injury is not clear. Recent studies indicated that nicotinamide adenine dinucleotide phosphate (NADPH) oxidase is the major source of ROS in the vascular system. In the present study, we used an in vitro oxygen-glucose deprivation and reoxygenation (hypoxia reoxygenation [HR]) paradigm to study whether PPAR-γ interacts with NADPH oxidase, thereby regulating ROS formation in cerebral endothelial cells (CECs). With pharmacological (PPAR-γ antagonist GW9662), loss-of-function (PPAR-γ siRNA), and gain-of-function (Ad-PPAR-γ) approaches, we first demonstrated that 15d-PGJ(2) protected HR-treated CECs against ROS-induced apoptosis in a PPAR-γ-dependent manner. Results of promoter and subcellular localization analyses further revealed that 15d-PGJ(2), by activating PPAR-γ, blocked HR-induced NF-κB nuclear translocation, which led to inhibited transcription of the NADPH oxidase subunit p22phox. In summary, we report a novel transrepression mechanism whereby PPAR-γ downregulates hypoxia-activated p22phox transcription and the subsequent NADPH oxidase activation, ROS formation, and CEC apoptosis.

Peroxisome proliferator-activated receptor gamma (PPAR-γ) and neurodegenerative disorders.

As the growth of the aging population continues to accelerate globally, increased prevalence of neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and stroke, has generated substantial public concern. Unfortunately, despite of discoveries of common factors underlying these diseases, few drugs are available to effectively treat these diseases. Peroxisome proliferator-activated receptor gamma (PPAR-γ) is a ligand-activated transcriptional factor that belongs to the nuclear hormone receptor superfamily. PPAR-γ has been shown to influence the expression or activity of a large number of genes in a variety of signaling networks, including regulation of insulin sensitivity, glucose homeostasis, fatty acid oxidation, immune responses, redox balance, cardiovascular integrity, and cell fates. Recent epidemiological, preclinical animal, and clinical studies also show that PPAR-γ agonists can lower the incidence of a number of neurological disorders, despite of multiple etiological factors involved in the development of these disorders. In this manuscript, we review current knowledge on mechanisms underlying the beneficial effect of PPAR-γ in different neurodegenerative diseases, in particular, AD, PD, and stroke, and attempt to analyze common and overlapping features among these diseases. Our investigation unveiled information suggesting the ability for PPAR-γ to inhibit NF-κB-mediated inflammatory signaling at multiple sites, and conclude that PPAR-γ agonists represent a novel class of drugs for treating neuroinflammatory diseases.

Stroke, angiogenesis and phytochemicals.

Stroke, or brain attack, is the third leading cause of death and the leading cause of adult disability worldwide. There is a great demand for intervention therapy. Unfortunately, although more than 700 drugs that target neuroprotection showed beneficial effects in preclinical animal studies, none of them proved efficacious in treating stroke patients. There is recent interest in understanding mechanism for post-ischemic angiogenesis in the penumbra area, and correlation of the extent of angiogenesis with survival in stroke patients. It is postulated that besides replenishing oxygen and nutrients to ischemic tissue, angiogenesis may play a crucial role in neural protection and tissue recovery. Consequently, therapeutic agents to promote angiogenesis and formation of new vessels after stroke can offer promising approach. Several large population epidemiological and clinical studies have revealed a reciprocal relationship between intake of phytochemicals and incidence of stroke. However, the detailed cellular and molecular mechanisms leading to these beneficial effects remain to be elucidated. In this article, we review the current knowledge on phytochemicals and post-ischemic angiogenesis, and discuss the possibility of a combinatorial treatment, including neuroprotection, angiogenesis, neurogenesis, and phytochemicals regimen for stroke.

Anti-apoptotic actions of PPAR-gamma against ischemic stroke.

Stroke is a leading cause of adult disability and mortality. Diabetes is a major risk factor for stroke. Patients with diabetes have a higher incidence of stroke and a poorer prognosis after stroke. Peroxisome proliferator-activated receptor gamma (PPAR-gamma) is a ligand-modulated transcriptional factor and a therapeutic target for treating type II diabetes. It is well-documented that activation of PPAR-gamma can also attenuate postischemic inflammation and damage. In this review, we focus on the newly revealed anti-apoptotic actions of PPAR-gamma against cerebral ischemia. PPAR-gamma, by increasing superoxide dismutase/catalase and decreasing nicotinamide adenine dinucleotide phosphate oxidase levels, attenuated ischemia-induced reactive oxygen species and subsequently alleviated the postischemic degradation of Bcl-2, Bcl-xl, and Akt. The preserved Akt phosphorylated Bad. Meanwhile, PPAR-gamma also promotes the transcription of 14-3-3epsilon. Elevated 14-3-3epsilon binds and sequesters p-Bad and prevents Bad translocation to neutralize the anti-apoptotic function of Bcl-2. This review further supports the notion that PPAR-gamma may serve as a potential therapeutic target for treating ischemic stroke.

Rosiglitazone and PPAR-gamma overexpression protect mitochondrial membrane potential and prevent apoptosis by upregulating anti-apoptotic Bcl-2 family proteins.

To determine the involvement of peroxisome proliferator-activated receptor-gamma (PPAR-gamma) in cytoprotection, we subjected N2-A cells to oxygen-glucose deprivation followed by reoxygenation (H-R). Following H-R insults, H(2)O(2) production was increased while cell viability declined, which was accompanied by loss of mitochondrial membrane potential (MMP), cytochrome c release, caspases 9 and 3 activation, poly(ADP-ribose)polymerase (PARP) cleavage and apoptosis. Rosiglitazone up to 5 microM protected cell viability, normalized MMP, and prevented apoptotic signals. The protective effect of rosiglitazone was abrogated by GW9662, a PPAR-gamma antagonist, or a specific PPAR-gamma small interference RNA (siRNA) but not a control scRNA. PPAR-gamma overexpression alone was effective in maintaining MMP and preventing apoptosis and its protective effect was also abrogated by PPAR-gamma siRNA or GW9662. To elucidate the mechanism by which PPAR-gamma protects MMP and prevents apoptosis, we analyzed Bcl-2, Bcl-xl, and phosphorylated Bad (p-Bad). H-R suppressed them. Rosiglitazone or PPAR-gamma overexpression restored them via PPAR-gamma. Rosiglitazone or PPAR-gamma overexpression preserved phosphorylated Akt and 3-phosphoinositide-dependent kinase-1 (PDK-1) in a PPAR-gamma dependent manner. These results indicate that ligand-activated PPAR-gamma protects N2-A cells against H-R damage by enhancing Bcl-2/Bcl-xl and maintaining p-Bad via preservation of p-Akt.

Ligand-activated peroxisome proliferator-activated receptor-gamma protects against ischemic cerebral infarction and neuronal apoptosis by 14-3-3 epsilon upregulation.

BACKGROUND: Thiazolidinediones have been reported to protect against ischemia-reperfusion injury. Their protective actions are considered to be peroxisome proliferator-activated receptor-gamma (PPAR-gamma)-dependent; however, it is unclear how PPAR-gamma activation confers resistance to ischemia-reperfusion injury. METHODS AND RESULTS: We evaluated the effects of rosiglitazone or PPAR-gamma overexpression on cerebral infarction in a rat model and investigated the antiapoptotic actions in the N2-A neuroblastoma cell model. Rosiglitazone or PPAR-gamma overexpression significantly reduced infarct volume. The protective effect was abrogated by PPAR-gamma small interfering RNA. In mice with knock-in of a PPAR-gamma dominant-negative mutant, infarct volume was enhanced. Proteomic analysis revealed that brain 14-3-3epsilon was highly upregulated in rats treated with rosiglitazone. Upregulation of 14-3-3epsilon was abrogated by PPAR-gamma small interfering RNA or antagonist. Promoter analysis and chromatin immunoprecipitation revealed that rosiglitazone induced PPAR-gamma binding to specific regulatory elements on the 14-3-3epsilon promoter and thereby increased 14-3-3epsilon transcription. 14-3-3epsilon Small interfering RNA abrogated the antiapoptotic actions of rosiglitazone or PPAR-gamma overexpression, whereas 14-3-3epsilon recombinant proteins rescued brain tissues and N2-A cells from ischemia-induced damage and apoptosis. Elevated 14-3-3epsilon enhanced binding of phosphorylated Bad and protected mitochondrial membrane potential. CONCLUSIONS: Ligand-activated PPAR-gamma confers resistance to neuronal apoptosis and cerebral infarction by driving 14-3-3epsilon transcription. 14-3-3epsilon Upregulation enhances sequestration of phosphorylated Bad and thereby suppresses apoptosis.

Induction of prostacyclin/PGI2 synthase expression after cerebral ischemia-reperfusion.

Prostacyclin (PGI2), a potent vasodilator and inhibitor of platelet aggregation and leukocyte activation, is crucial in vascular diseases such as stroke. Prostacyclin synthase (PGIS) is the key enzyme for PGI2 synthesis. Although expression of PGIS was noted in the brain, its role in ischemic insult remains unclear. Here we reported the temporal and spatial expression of PGIS mRNA and protein after 60-min transient ischemia. Northern blot and in situ hybridization revealed a delayed increase of PGIS mRNA in the ischemic cortex at 24- to 72-h after ischemia; PGIS was detected mainly in the ipsilateral penumbra area, pyriform cortex, hippocampus, and leptomeninges. Western blot and immunohistochemical analysis revealed that PGIS proteins were expressed temporally and spatially similar to PGIS mRNA. PGIS was heavily colocalized with PECAM-1 to endothelial cells at the leptomeninges, large and small vessels, and localized to neuronal cells, largely at the penumbra area. A substantial amount of PGIS was also detected in the macrophage and glial cells. To evaluate its role against ischemic infarct, we overexpressed PGIS by adenoviral gene transfer. When infused 72 h before ischemia (- 72 h), Adv-PGIS reduced infarct volume by approximately 50%. However, it had no effect on infarct volume when infused immediately after ischemia (0 h). Eicosanoid analysis revealed selective elevation of PGI2 at - 72 h while PGI2 and TXB2 were both elevated at 0 h, altering the PGI2/thromboxane A2 (TXA2) ratio from 10 to 4. These findings indicate that PGIS protects the brain by enhancing PGI2 synthesis and creating a favorable PGI2/TXA2 ratio.

15d-prostaglandin J2 protects brain from ischemia-reperfusion injury.

OBJECTIVE: Brain expresses abundant lipocalin-type prostaglandin (PG) D2 (PGD2) synthase but the role of PGD2 and its metabolite, 15-deoxy-Delta(12,14) PGJ2 (15d-PGJ2) in brain protection is unclear. The aim of this study is to assess the effect of 15d-PGJ2 on neuroprotection. METHODS AND RESULTS: Adenoviral transfer of cyclooxygenase-1 (Adv-COX-1) was used to amplify the production of 15d-PGJ2 in ischemic cortex in a rat focal infarction model. Cortical 15d-PGJ2 in Adv-COX-1-treated rats was increased by 3-fold over control, which was correlated with reduced infarct volume and activated caspase 3, and increased peroxisome proliferator activated receptor-gamma (PPARgamma) and heme oxygenase-1 (HO-1). Intraventricular infusion of 15d-PGJ2 resulted in reduction of infarct volume, which was abrogated by a PPARgamma inhibitor. Rosiglitazone infusion had a similar effect. 15d-PGJ2 and rosiglitazone at low concentrations suppressed H2O2-induced rat or human neuronal apoptosis and necrosis and induced PPARgamma and HO-1 expression. The anti-apoptotic effect was abrogated by PPARgamma inhibition. CONCLUSIONS: 15d-PGJ2 suppressed ischemic brain infarction and neuronal apoptosis and necrosis in a PPARgamma dependent manner. 15d-PGJ2 may play a role in controlling acute brain damage induced by ischemia-reperfusion.

Detection of apoptosis and necrosis in normal human lung cells using 1H NMR spectroscopy.

This study aimed to detect apoptosis and necrosis in MRC-5, a normal human lung cell line, by using noninvasive proton nuclear magnetic resonance (1H NMR). Live MRC-5 cells were processed first for 1H NMR spectroscopy; subsequently their types and the percentage of cell death were assessed on a flow cytometer. Cadmium (Cd) and mercury (Hg) induced apoptosis and necrosis in MRC-5 cells, respectively, as revealed by phosphatidylserine externalization on a flow cytometer. The spectral intensity ratio of methylene (CH2) resonance (at 1.3 ppm) to methyl (CH3) resonance (at 0.9 ppm) was directly proportional to the percentage of apoptosis and strongly and positively correlated with PI staining after Cd treatment (r2 = 0.9868, P < 0.01). In contrast, this ratio only increased slightly within 2-h Hg treatment, and longer Hg exposure failed to produce further increase. Following 2-h Hg exposure, the spectral intensity of choline resonance (at 3.2 ppm) was abolished, but this phenomenon was absent in Cd-induced apoptosis. These findings together demonstrate that 1H NMR is a novel tool with a quantitative potential to distinguish apoptosis from necrosis as early as the onset of cell death in normal human lung cells.

Mediating of caspase-independent apoptosis by cadmium through the mitochondria-ROS pathway in MRC-5 fibroblasts.

Cadmium (Cd) is an environmental pollutant of global concern with a 10-30-year biological half-life in humans. Accumulating evidence suggests that the lung is one of the major target organs of inhaled Cd compounds. Our previous report demonstrated that 100 microM Cd induces MRC-5 cells, normal human lung fibroblasts, to undergo caspase-independent apoptosis mediated by mitochondrial membrane depolarization and translocation of apoptosis-inducing factor (AIF) from mitochondria into the nucleus. Here, using benzyloxycarbonyl-Val-Ala-Asp-(ome) fluoromethyl ketone (Z-VAD.fmk) as a tool, we further demonstrated that Cd could induce caspase-independent apoptosis at concentrations varied from 25 to 150 microM, which was modulated by reactive oxygen species (ROS) scavengers, such as N-acetylcysteine (NAC), mannitol, and tiron, indicating that ROS play a crucial role in the apoptogenic activity of Cd. Consistent with this notion, the intracellular hydrogen peroxide (H2O2) was 2.9-fold elevated after 3 h of Cd treatment and diminished rapidly within 1 h as detected by flow cytometry with 2',7'-dichlorodihydrofluorescein diacetate (DCFH-DA) staining. Using inhibitors of the mitochondrial electron transport chain (ETC) (oligomycin A and rotenone for complex I and V, respectively) and mitochondrial permeability transition pore (MPTP) (cyclosporin A and aristolochic acid), we coincidently found the ROS production, mitochondrial membrane depolarization, and apoptotic content were almost completely or partially abolished. As revealed by confocal microscopy staining with chloromethyl-X-rosamine (CMXRos) and an anti-AIF antibody, the collapse of mitochondrial membrane potential induced by Cd (3 h-treatment) was a prelude to the translocation of caspase-independent pro-apoptotic factor, AIF, into the nucleus (after 4 h of Cd treatment). In summary, this study demonstrated that, in MRC-5 fibroblasts, Cd induced caspase-independent apoptosis through a mitochondria-ROS pathway. More importantly, we provide several lines of evidence supporting a role of mitochondrial ETC and MPTP in the regulation of caspase-independent cell death triggered by Cd.