Primary Rat Astrocytes Research Articles

Regulation of hemeoxygenase-1 gene expression by Nrf2 and c-Jun in tertiary butylhydroquinone-stimulated rat primary astrocytes

Hemeoxygenase-1 (HO-1) is a phase II antioxidant enzyme that is primarily involved in detoxification and cytoprotection in a variety of tissues. However, the mechanism underlying HO-1 gene expression remains unclear. In the present study, we investigated the regulation of HO-1 expression in primary cultured astrocytes by using the natural antioxidant compound tertiary butylhydroquinone (tBHQ). We found that tBHQ increased HO-1 mRNA and protein levels. Promoter analysis revealed that tBHQ enhanced HO-1 gene transcription in an antioxidant response element (ARE)-dependent manner. In addition, tBHQ increased the nuclear translocation and DNA binding of Nrf2 and c-Jun to ARE. Small interfering RNA (siRNA) experiments demonstrated that Nrf2 and c-Jun are involved in the differential modulation of HO-1 expression. Thus, Nrf2 knockdown reduced the basal level of HO-1 expression but did not affect the fold induction by tBHQ. On the other hand, knockdown of c-Jun diminished tBHQ-mediated induction of HO-1 without affecting basal expression. The data suggest that Nrf2 generally modulates the basal expression of HO-1, while c-Jun mediates HO-1 induction in response to tBHQ. The results of co-immunoprecipitation assays demonstrated a physical interaction between Nrf2 and c-Jun in tBHQ-treated astrocytes. The results suggest that Nrf2 and c-Jun regulate HO-1 expression via their coordinated interaction in tBHQ-treated rat primary astrocytes.

Manganese accumulation in membrane fractions of primary astrocytes is associated with decreased γ-aminobutyric acid (GABA) uptake, and is exacerbated by oleic acid and palmitate

Manganese (Mn) exposure interferes with GABA uptake; however, the effects of Mn on GABA transport proteins (GATs) have not been identified. We sought to characterize how Mn impairs GAT function in primary rat astrocytes. Astrocytes exposed to Mn (500μM) had significantly reduced 3H-GABA uptake despite no change in membrane or cytosolic GAT3 protein levels. Co-treatment with 100μM oleic or palmitic acids (both known to be elevated in Mn neurotoxicity), exacerbated the Mn-induced decline in 3H-GABA uptake. Mn accumulation in the membrane fraction of astrocytes was enhanced with fatty acid administration, and was negatively correlated with 3H-GABA uptake. Furthermore, control cells exposed to Mn only during the experimental uptake had significantly reduced 3H-GABA uptake, and the addition of GABA (50μM) blunted cytosolic Mn accumulation. These data indicate that reduced GAT function in astrocytes is influenced by Mn and fatty acids accumulating at or interacting with the plasma membrane.

Cell survival during complete nutrient deprivation depends on lipid droplet‐fueled β‐oxidation of fatty acids (577.3)

Cells exposed to stress of different origins synthesize triacylglycerols and generate lipid droplets (LD), but the physiological relevance of this response is uncertain. Using complete nutrient deprivation of cells in culture as a simple model of stress, we have addressed whether LD biogenesis has a protective role in cells committed to die. Complete nutrient deprivation induced the biogenesis of LD in human LN18 glioblastoma and HeLa cells and also in CHO and rat primary astrocytes. In all cell types, death was associated with LD depletion and was accelerated by blocking LD biogenesis after pharmacological inhibition of Group IVA phospholipase A2 (cPLA2α) or down‐regulation of ceramide kinase. Nutrient deprivation also induced β‐oxidation of fatty acids that was sensitive to cPLA2α inhibition, and cell survival in these conditions became strictly dependent on fatty acid catabolism. These results show that, during nutrient deprivation, cell viability is sustained by β‐oxidation of fatty acids that requires biogenesis and mobilization of LD.

Differential inflammatory response to acrylonitrile in rat primary astrocytes and microglia

Acrylonitrile (ACN) is extensively used in the production of plastics, resins, nitriles and other commercial products. Chronic low dose exposures to ACN cause glial cell tumors in rats, primarily microglial in origin. Recently it has been determined that astrocytes and microglia respond to ACN-induced oxidative stress differently, which may influence cell-specific activation of inflammatory and carcinogenic pathways. This study was conducted to compare the inflammatory responses of astrocytes and microglia following ACN treatment in vitro to further characterize differential sensitivities and adaptive responses in these cell types. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and p53 levels were measured along with levels of 12 different cytokines and chemokines in primary rat microglia and astrocytes. Additionally levels of cytochrome P450 2E1 (CYP2E1) were measured to evaluate the cells’ ability to metabolize ACN. Results indicate that while both cells upregulate p53 and NF-κB, the cytokines and chemokines produced differ between the cell types. Astrocytes, but not microglia, upregulated CYP2E1 in response to ACN, which may be due to the astrocytes accumulating more ACN than the microglia. Altogether our data implicate the inflammatory response as an important event in ACN-induced neurotoxicity.

Anthocyanin-Rich Açaí (Euterpe oleracea Mart.) Extract Attenuates Manganese-Induced Oxidative Stress in Rat Primary Astrocyte Cultures

Manganese (Mn) is an essential element for human health. However, at high concentrations Mn may be neurotoxic. Mn accumulates in astrocytes, affecting their redox status. In view of the high antioxidant and anti-inflammatory properties of the exotic Brazilian fruit açaí (Euterpe oleracea Mart.), its methanolic extract was obtained by solid-phase extraction (SPE). This açaí extract showed considerable anthocyanins content and direct antioxidant capacity. The açaí extract scavenged 2,2-diphenyl-1-picrylhydrazyl radicals (DPPH•) with an EC50 of 19.1 ppm, showing higher antioxidant activity compared to butylated hydroxytoluene (BHT), but lower than ascorbic acid and quercetin. This obtained açaí extract also attenuated Mn-induced oxidative stress in primary cultured astrocytes. Specifically, the açaí extract at an optimal and nutritionally relevant concentration of 0.1 μg/ml prevented Mn-induced oxidative stress by (1) restoring GSH/GSSG ratio and net glutamate uptake, (2) protecting astrocytic membranes from lipid peroxidation, and (3) decreasing Mn-induced expression of erythroid 2-related factor (Nrf2) protein. A larger quantity of açaí extract exacerbated the effects of Mn on these parameters except with respect to lipid peroxidation assessed by means of F2-isoprostanes. These studies indicate that at nutritionally relevant concentration, anthocyanins obtained from açaí protect astrocytes against Mn neurotoxicity, but at high concentrations, the “pro-oxidant” effects of its constituents likely prevail. Future studies may be profitably directed at potential protective effects of açaí anthocyanins in nutraceutical formulations.

Interplay between Endothelin and Erythropoietin in Astroglia: The Role in Protection against Hypoxia

We show that, under in vitro conditions, the vulnerability of astroglia to hypoxia is reflected by alterations in endothelin (ET)-1 release and capacity of erythropoietin (EPO) to regulate ET-1 levels. Exposure of cells to 24 h hypoxia did not induce changes in ET-1 release, while 48–72 h hypoxia resulted in increase of ET-1 release from astrocytes that could be abolished by EPO. The endothelin receptor type A (ETA) antagonist BQ123 increased extracellular levels of ET-1 in human fetal astroglial cell line (SV-FHAS). The survival and proliferation of rat primary astrocytes, neural precursors, and neurons upon hypoxic conditions were increased upon administration of BQ123. Hypoxic injury and aging affected the interaction between the EPO and ET systems. Under hypoxia EPO decreased ET-1 release from astrocytes, while ETA receptor blockade enhanced the expression of EPO mRNA and EPO receptor in culture-aged rat astroglia. The blockade of ETA receptor can increase the availability of ET-1 to the ETB receptor and can potentiate the neuroprotective effects of EPO. Thus, the new therapeutic use of combined administration of EPO and ETA receptor antagonists during hypoxia-associated neurodegenerative disorders of the central nervous system (CNS) can be suggested.

The relationship between glial cell mechanosensitivity and foreign body reactions in the central nervous system

Devices implanted into the body become encapsulated due to a foreign body reaction. In the central nervous system (CNS), this can lead to loss of functionality in electrodes used to treat disorders. Around CNS implants, glial cells are activated, undergo gliosis and ultimately encapsulate the electrodes. The primary cause of this reaction is unknown. Here we show that the mechanical mismatch between nervous tissue and electrodes activates glial cells. Both primary rat microglial cells and astrocytes responded to increasing the contact stiffness from physiological values (G′ ∼ 100 Pa) to shear moduli G′ ≥ 10 kPa by changes in morphology and upregulation of inflammatory genes and proteins. Upon implantation of composite foreign bodies into rat brains, foreign body reactions were significantly enhanced around their stiff portions in vivo. Our results indicate that CNS glial cells respond to mechanical cues, and suggest that adapting the surface stiffness of neural implants to that of nervous tissue could minimize adverse reactions and improve biocompatibility.

Dynamics of β‐adrenergic/cAMP signaling and morphological changes in cultured astrocytes

The morphology of astrocytes, likely regulated by cAMP, determines the structural association between astrocytes and the synapse, consequently modulating synaptic function. β-Adrenergic receptors (β-AR), which increase cytosolic cAMP concentration ([cAMP]i ), may affect cell morphology. However, the real-time dynamics of β-AR-mediated cAMP signaling in single live astrocytes and its effect on cell morphology have not been studied. We used the fluorescence resonance energy transfer (FRET)-based cAMP biosensor Epac1-camps to study time-dependent changes in [cAMP]i ; morphological changes in primary rat astrocytes were monitored by real-time confocal microscopy. Stimulation of β-AR by adrenaline, noradrenaline, and isoprenaline, a specific agonist of β-AR, rapidly increased [cAMP]i (∼15 s). The FRET signal response, mediated via β-AR, was faster than in the presence of forskolin (twofold) and dibutyryl-cAMP (>35-fold), which directly activate adenylyl cyclase and Epac1-camps, respectively, likely due to slow entry of these agents into the cytosol. Oscillations in [cAMP]i have not been recorded, indicating that cAMP-dependent processes operate in a slow time domain. Most Epac1-camps expressing astrocytes revealed a morphological change upon β-AR activation and attained a stellate morphology within 1 h. The morphological changes exhibited a bell-shaped dependency on [cAMP]i . The 5-10% decrease in cell cross-sectional area and the 30-50% increase in cell perimeter are likely due to withdrawal of the cytoplasm to the perinuclear region and the appearance of protrusions on the surface of astrocytes. Because astrocyte processes ensheath neurons, β-AR/cAMP-mediated morphological changes can modify the geometry of the extracellular space, affecting synaptic, neuronal, and astrocyte functions in health and disease.

Acrylamide-induced apoptosis in rat primary astrocytes and human astrocytoma cell lines

This study aimed to evaluate the acrylamide (ACR)-induced apoptotic effects on rat primary astrocytes and three human astrocytoma-derived cell lines (U-1240 MG, U-87 MG, and U-251 MG). As determined through the MTT assay, treatment with 1 and 2mM ACR for 24–72h resulted in decreased cell viability in all cells. Decreases in cell viability could be blocked in all cells with the exception of U-251 MG cells by Z-DEVD FMK. ACR-induced dose-dependent apoptotic effects were also demonstrated by increases in the sub-G1 phase cell population in all cells. The decreased expressions of pro-caspase 3, 8, and 9 and the interruption of the mitochondrial membrane potential were observed in all cells. Exposure to 2mM ACR for 48h resulted in increased Bax/Bcl-2 ratios in primary astrocytes and U-87 MG cells, whereas the overexpression of Bcl-2 was observed in U-1240 MG and U-251 MG cells. The ACR-induced increases in the levels of p53 and pp53 in primary astrocytes could be attenuated by caffeine. These results suggest the existence of a common apoptotic pathway among all cell types and that U-87 MG cells may be a suitable substitute in vitro model for primary astrocytes in future studies on ACR-induced neurotoxicity.

β₂-adrenergic agonists modulate TNF-α induced astrocytic inflammatory gene expression and brain inflammatory cell populations.

BackgroundThe NF-κB signaling pathway orchestrates many of the intricate aspects of neuroinflammation. Astrocytic β2-adrenergic receptors have emerged as potential regulators in central nervous system inflammation and are potential targets for pharmacological modulation. The aim of this study was to elucidate the crosstalk between astrocytic β2-adrenergic receptors and the TNF-α induced inflammatory gene program.MethodsProinflammatory conditions were generated by the administration of TNF-α. Genes that are susceptible to astrocytic crosstalk between β2-adrenergic receptors (stimulated by clenbuterol) and TNF-α were identified by qPCR-macroarray-based gene expression analysis in a human 1321 N1 astrocytoma cell line. Transcriptional patterns of the identified genes in vitro were validated by RT-PCR on the 1321 N1 cell line as well as on primary rat astrocytes. In vivo expression patterns were examined by intracerebroventricular administration of clenbuterol and/or TNF-α in rats. To examine the impact on the inflammatory cell content of the brain we performed extensive FACS analysis of rat brain immune cells after intracerebroventricular clenbuterol and/or TNF-α administration.ResultsParallel transcriptional patterns in vivo and in vitro confirmed the relevance of astrocytic β2-adrenergic receptors as modulators of brain inflammatory responses. Importantly, we observed pronounced effects of β2-adrenergic receptor agonists and TNF-α on IL-6, CXCL2, CXCL3, VCAM1, and ICAM1 expression, suggesting a role in inflammatory brain cell homeostasis. Extensive FACS-analysis of inflammatory cell content in the brain demonstrated that clenbuterol/TNF-α co-administration skewed the T cell population towards a double negative phenotype and induced a shift in the myeloid brain cell population towards a neutrophilic predominance.ConclusionsOur results show that astrocytic β2-adrenergic receptors are potent regulators of astrocytic TNF-α-activated genes in vitro and in vivo, and ultimately modulate the molecular network involved in the homeostasis of inflammatory cells in the central nervous system. Astrocytic β2-adrenergic receptors and their downstream signaling pathway may serve as potential targets to modulate neuroinflammatory responses.

Leukemia inhibitory factor inhibits the proliferation of primary rat astrocytes induced by oxygen-glucose deprivation.

Leukemia inhibitory factor (LIF) is a neuroprotective cytokine that is necessary for the normal development of astrocytes. Oxygen-glucose deprivation (OGD) can induce astrocyte proliferation by increasing hypoxia-inducible factor alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF). Here, we studied whether LIF affects the proliferation of cultured primary rat astrocytes under OGD conditions by measuring EdU incorporation into astrocyte DNA and the expression of proliferating cell nuclear antigen (PCNA) mRNA and protein. Our findings show that low concentrations of LIF (5 and 10 ng/mL) significantly decreased EdU incorporation and downregulated the expression of PCNA mRNA and PCNA protein in astrocytes subjected to OGD. A low concentration of LIF (10 ng/mL) clearly inhibited astrocyte proliferation induced by OGD, while a higher concentration (50 ng/mL) had no effect. To investigate the mechanism of this inhibition by LIF (10 ng/mL), the expression of 3 related genes (LIF receptor, HIF-1alpha, and VEGF) was assessed using real-time PCR; VEGF protein expression was measured by Western blot. Our results indicate that LIFR mRNA was downregulated in astrocytes subjected to OGD. Interestingly, treatment with LIF further reduced LIFR mRNA expression in these cells. LIF treatment also decreased the expression of HIF-1alpha mRNA, VEGF mRNA, and VEGF protein induced by OGD. Low concentrations of LIF were observed to inhibit astrocyte proliferation induced by OGD.

Quantification of a Thermal Damage Threshold for Astrocytes Using Infrared Laser Generated Heat Gradients

The response of cells and tissues to elevated temperatures is highly important in several research areas, especially in the area of infrared neural stimulation. So far, only the heat response of neurons has been considered. In this study, primary rat astrocytes were exposed to infrared laser pulses of various pulse lengths and the resulting cell morphology changes and cell migration was studied using light microscopy. By using a finite element model of the experimental setup the temperature distribution was simulated and the temperatures and times to induce morphological changes and migration were extracted. These threshold temperatures were used in the commonly used first-order reaction model according to Arrhenius to extract the kinetic parameters, i.e., the activation energy, E a, and the frequency factor, A c, for the system. A damage signal ratio threshold was defined and calculated to be 6% for the astrocytes to change morphology and start migrating.

Enhanced GLT-1 mediated glutamate uptake and migration of primary astrocytes directed by fibronectin-coated electrospun poly-l-lactic acid fibers

Bioengineered fiber substrates are increasingly studied as a means to promote regeneration and remodeling in the injured central nervous system (CNS). Previous reports largely focused on the ability of oriented scaffolds to bridge injured regions and direct outgrowth of axonal projections. In the present work, we explored the effects of electrospun microfibers on the migration and physiological properties of brain astroglial cells. Primary rat astrocytes were cultured on either fibronectin-coated poly-l-lactic acid (PLLA) films, fibronectin-coated randomly oriented PLLA electrospun fibers, or fibronectin-coated aligned PLLA electrospun fibers. Aligned PLLA fibers strongly altered astrocytic morphology, orienting cell processes, actin microfilaments, and microtubules along the length of the fibers. On aligned fibers, astrocytes also significantly increased their migration rates in the direction of fiber orientation. We further investigated if fiber topography modifies astrocytic neuroprotective properties, namely glutamate and glutamine transport and metabolism. This was done by quantifying changes in mRNA expression (qRT-PCR) and protein levels (Western blotting) for a battery of relevant biomolecules. Interestingly, we found that cells grown on random and/or aligned fibers increased the expression levels of two glutamate transporters, GLAST and GLT-1, and an important metabolic enzyme, glutamine synthetase, as compared to the fibronectin-coated films. Functional assays revealed increases in glutamate transport rates due to GLT-1 mediated uptake, which was largely determined by the dihydrokainate-sensitive GLT-1. Overall, this study suggests that aligned PLLA fibers can promote directed astrocytic migration, and, of most importance, our in vitro results indicate for the first time that electrospun PLLA fibers can positively modify neuroprotective properties of glial cells by increasing rates of glutamate uptake.

Comparison of Primary and Secondary Rat Astrocyte Cultures Regarding Glucose and Glutathione Metabolism and the Accumulation of Iron Oxide Nanoparticles

Astrocyte-rich primary cultures (APCs) are frequently used as a model system for the investigation of properties of brain astrocytes. However, as APCs contain a substantial number of microglial and oligodendroglial cells, biochemical parameters determined for such cultures may at least in part reflect also the presence of the contaminating cell types. To lower the potential contributions of microglial and oligodendroglial cells on properties of the astrocytes in APCs we prepared rat astrocyte-rich secondary cultures (ASCs) by subculturing of APCs and compared these ASCs with APCs regarding basal metabolic parameters, specific enzyme activities and the accumulation of iron oxide nanoparticles. Immunocytochemical characterization revealed that ASCs contained only minute amounts of microglial and oligodendroglial cells. ASCs and APCs did not significantly differ in their specific glucose consumption and lactate production rates, in their specific iron and glutathione contents, in their specific activities of various enzymes involved in glucose and glutathione metabolism nor in their accumulation of iron oxide nanoparticles. Thus, the absence or presence of some contaminating microglial and oligodendroglial cells appears not to substantially modulate the investigated metabolic parameters of astrocyte cultures.

Nanoparticle-emitted light attenuates amyloid-β-induced superoxide and inflammation in astrocytes

Alzheimer’s disease (AD) is the sixth leading cause of age-related death with no effective intervention yet available. Our previous studies have demonstrated the potential efficacy of Low Level Laser Therapy (LLLT) in AD cell models by mitigating amyloid-β peptide (Aβ)-induced oxidative stress and inflammation. However, the penetration depth of light is still the major challenge for implementing LLLT in animal models and in the clinical settings. In this study, we present the potential of applying Bioluminescence Resonance Energy Transfer to Quantum Dots (BRET-Qdots) as an alternative near infrared (NIR) light source for LLLT. Our results show that BRET-Qdot-emitted NIR suppresses Aβ-induced oxidative stress and inflammatory responses in primary rat astrocytes. These data provide a proof of concept for a nanomedicine platform for LLLT. From the Clinical EditorLow Level Laser Therapy has already been demonstrated to mitigate amyloid-β peptide induced oxidative stress and inflammation, a key driver of Alzheimer's disease. The major issue in moving this forward from cell cultures to live animals and potentially to human subjects is light penetration depth. In this novel study, BRET-Qdots were used as an alternative near infrared light source with good efficacy, paving the way to the development of a nanomedicine platform.

Effects of Korean Red Ginseng extract on tissue plasminogen activator and plasminogen activator inhibitor-1 expression in cultured rat primary astrocytes

Korean Red Ginseng (KRG) is an oriental herbal preparation obtained from Panax ginseng Meyer (Araliaceae). To expand our understanding of the action of KRG on central nervous system (CNS) function, we examined the effects of KRG on tissue plasminogen activator (tPA)/plasminogen activator inhibitor-1 (PAI-1) expression in rat primary astrocytes. KRG extract was treated in cultured rat primary astrocytes and neuron in a concentration range of 0.1 to 1.0 mg/mL and the expression of functional tPA/PAI-1 was examined by casein zymography, Western blot and reverse transcription-polymerase chain reaction. KRG extracts increased PAI-1 expression in rat primary astrocytes in a concentration dependent manner (0.1 to 1.0 mg/mL) without affecting the expression of tPA itself. Treatment of 1.0 mg/mL KRG increased PAI-1 protein expression in rat primary astrocytes to 319.3±65.9% as compared with control. The increased PAI-1 expression mediated the overall decrease in tPA activity in rat primary astrocytes. Due to the lack of PAI-1 expression in neuron, KRG did not affect tPA activity in neuron. KRG treatment induced a concentration dependent activation of PI3K, p38, ERK1/2, and JNK in rat primary astrocytes and treatment of PI3K or MAPK inhibitors such as LY294002, U0126, SB203580, and SP600125 (10 μM each), significantly inhibited 1.0 mg/mL KRG-induced expression of PAI- 1 and down-regulation of tPA activity in rat primary astrocytes. Furthermore, compound K but not other ginsenosides such as Rb1 and Rg1 induced PAI-1 expression. KRG-induced up-regulation of PAI-1 in astrocytes may play important role in the regulation of overall tPA activity in brain, which might underlie some of the beneficial effects of KRG on CNS such as neuroprotection in ischemia and brain damaging condition as well as prevention or recovery from addiction.

Induction of multiple sclerosis and response to tyrosine kinase inhibitors.

The goal of this work is to determine the role of the autoimmune cells in multiple sclerosis (MS) induction and the immunomodulatory mechanism of therapy with tyrosine kinase inhibitors (TKIs) in MS attenuation. Samples (5×10(5) cells per well) of C6 and primary rat astrocytes were stimulated with 10ng/mL of platelet-derived growth factor (PDGFbb) as a positive control forming a mouse model of MS. PDGFbb was added to the astrocytes in the absence or presence of 0.1 and 1μM of imatinib. Proliferation of C6 and primary rat astrocytes samples were assessed for samples staging by the addition of 1μCi of (3)H-thymidine per well. Samples of RAW 264.7 cells were stimulated for 48h with 10ng/mL of PDGFbb in the absence or presence of 0.1 and 1μM of sorafenib. Tumour necrotic factor (TNF) levels in culture supernatants from RAW 264.7 cells were measured by ELISA. The histologic grade (HG) and the level of TNF of the mouse model of MS was 1/5 and 5 times respectively of those in the control one to clarify that MS induction is due to a major decrease in HG inversely proportional to the accompanied increase in TNF level perpetuating local inflammation and demyelination in MS lesion. The addition of 0.1 and 1μM doses of imatinib increased HG of the mouse model of MS by 6 and 11 times respectively while 0.1 and 1μM doses of sorafenib decreased TNF level to be 1/2 and 1/5 of that in the mouse model of MS respectively restoring normal rate of TNF level of normal lesion to show that HGand TNF level would be strongly inversely correlated (r=-0.99) in attenuating MS effectively by TKIs therapy but not in an inverse proportion as in MS induction.

Anti-inflammatory Effect of Acetylpuerarin on Eicosanoid Signaling Pathway in Primary Rat Astrocytes

Astrocytes activation has been implicated in the inflammatory responses underlying brain injury and neurodegenerative diseases including bacterial infections, cerebral ischemia, and Parkinson's diseases. Acetylpuerarin is a newly modified isoflavone based on puerarin that has neuroprotective and antioxidant effects. In this study, we investigated the anti-inflammatory action of acetylpuerarin in regulating the eicosanoids generation and its underlying molecular mechanisms in lipopolysaccharide (LPS)-induced production of arachidonic acid (AA) metabolites in primary rat astrocytes. The results showed that acetylpuerarin concentration dependently inhibited the LPS-induced production of AA metabolites such as prostaglandin E2 (PGE2) and leukotriene C4 (LTC4), and acetylpuerarin significantly attenuated the expression and immunoreactivity of group V secretory phospholipase A2 (sPLA2) protein induced by LPS in astrocytes. Furthermore, in astrocytes pretreated with acetylpuerarin, the time course of phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and of cytosolic PLA2 alpha (cPLA2α) and expression of transcription factors, nuclear factor kappa B (NF-κB), was markedly truncated. Acetylpuerarin concentration dependently abolished the LPS-induced expressions of AA-metabolizing enzymes including cyclooxygenase-2 (COX-2) and lipooxygenase-5 (LOX-5). This study indicates that acetylpuerarin inhibited LPS-induced AA-metabolizing enzymes and AA metabolites in astrocytes via downregulation expression of group V sPLA2 and phosphorylation of ERK1/2, cPLA2α, and NF-κB. These findings reveal, in part, the molecular basis underlying the anti-inflammatory properties of acetylpuerarin.

NAD+-Carrying Mesoporous Silica Nanoparticles Can Prevent Oxidative Stress-Induced Energy Failures of Both Rodent Astrocytes and PC12 Cells

AimTo test the hypothesis that NAD+-carrying mesoporous silica nanoparticles (M-MSNs@NAD+) can effectively deliver NAD+ into cells to produce cytoprotective effects.Methods & MaterialsNAD+ was incorporated into M-MSNs. Primary rat astrocyte cultures and PC12 cells were treated with H2O2, followed by post-treatment with M-MSNs@NAD+. After various durations of the post-treatment, intracellular NAD+ levels, intracellular ATP levels and lactate dehydrogenase (LDH) release were determined.Results & DiscussionM-MSNs can be effectively loaded with NAD+. The M-MSNs@NAD+ can significantly attenuate H2O2-induced NAD+ and ATP decreases in both astrocyte cultures and PC12 cells. M-MSNs@NAD+ can also partially prevent the H2O2-induced LDH release from both astrocyte cultures and PC12 cells. In contrast, the NAD+ that is spontaneously released from the M-MSNs@NAD+ is insufficient to prevent the H2O2-induced damage.ConclusionsOur study has suggested the first approach that can effectively deliver NAD+ into cells, which provides an important basis both for elucidating the roles of intracellular NAD+ in biological functions and for therapeutic applications of NAD+. Our study has also provided the first direct evidence demonstrating a key role of NAD+ depletion in oxidative stress-induced ATP decreases.

Protective properties of tanshinone I against oxidative DNA damage and cytotoxicity

Tanshinone I, a naturally occurring diterpene from Danshen, has been shown to possess hepatocyte protective, anticancer, and memory enhancing properties. However, there are few stringent pharmacological tests for neuroprotection of tanshinone I thus far. Since peroxynitrite is involved in the pathogenesis of neurodegenerative disorders, this study was undertaken to investigate whether the neuroprotective effect of tanshinone I is associated with inhibition of peroxynitrite-caused DNA damage, a critical event leading to peroxynitrite-induced cytotoxicity. Our results show that tanshinone I can significantly inhibit peroxynitrite-induced DNA damage both in φX-174 plasmid DNA and rat primary astrocytes. EPR spectroscopy indicates that tanshinone I potently diminished the DMPO-hydroxyl radical adduct signal from peroxynitrite. Taken together, these results demonstrate for the first time that tanshinone I can protect against peroxynitrite-induced DNA damage, hydroxyl radical formation and cytotoxicity, which might have implications for tanshinone I-mediated neuroprotection.