Involvement of heme oxygenase-1 induction in the cytoprotective and immunomodulatory activities of 6,4'-dihydroxy-7-methoxyflavanone in murine hippocampal and microglia cells

6,4'-Dihydroxy-7-methoxyflavanone (DMF), a biologically active compound, was isolated from the heartwood of Dalbergia odorifera T. Chen (Leguminosae). The present study proposed to examine the role of DMF as an anti-oxidative and anti-inflammatory heme oxygenase-1 (HO-1) inducer in mouse hippocampal HT22 cells and BV2 microglia cells. The effect of DMF on cell viability was determined by MTT assay and the effects of DMF on pro-inflammatory enzymes and cytokines were analyzed by western blot and ELISA. Parameters such as DMF induced HO-1 protein immunocontents, HO activity and mitogen-activated protein kinases (MAPK) activation were also measured. DMF increased cellular resistance to oxidative injury caused by glutamate-induced cytotoxicity in HT22 cells, via JUN N-terminal kinase (JNK) pathway dependent HO-1 expression. Furthermore, DMF suppressed the lipopolysaccharide (LPS)-induced expression of pro-inflammatory enzymes and inflammatory mediators in BV2 microglia. DMF suppressed production of nitric oxide (NO), prostaglandin E2 (PGE(2)), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), through extracellular signal-regulated kinase (ERK) pathway dependent HO-1 expression. This study indicates that DMF effectively modulates the regulation of anti-oxidative and anti-inflammatory action, via up-regulation of HO-1 in HT22 cells and BV2 microglia. These results suggest that DMF possesses therapeutic potentials against neurodegenerative diseases that are induced by oxidative stress and neuroinflammation.     

Cytoprotective and anti-inflammatory effects of spinasterol via the induction of heme oxygenase-1 in murine hippocampal and microglial cell lines

Spinasterol, which is isolated from the aerial parts of Aster scaber Thunb. (Asteraceae), is involved in various biological activities. In this study, we report the efficacy of spinasterol in effectively modulating the regulation of antioxidative and anti-inflammatory activity through the upregulation of heme oxygenase (HO)-1 in murine hippocampal HT22 cells and BV2 microglia. We showed that spinasterol increased the cellular resistance of HT22 cells to oxidative injury caused by the glutamate-induced cytotoxicity by extracellular signal-regulated kinase (ERK) pathway-dependent expression of HO-1. Furthermore, spinasterol suppressed the lipopolysaccharide (LPS)-induced expression of pro-inflammatory enzymes and inflammatory mediators in BV2 microglia. Spinasterol also suppressed the production of nitric oxide (NO), prostaglandin E2 (PGE?), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) through extracellular signal-regulated kinase (ERK) pathway-dependent expression of HO-1. These results suggest that spinasterol has a therapeutic potential against neurodegenerative diseases that are caused by oxidative stress and neuroinflammation.     

Lavandulyl flavanones from Sophora flavescens protect mouse hippocampal cells against glutamate-induced neurotoxicity via the induction of heme oxygenase-1

Lavandulyl flavanones of Sophora flavescens roots are anti-malarial, anti-inflammatory, and cytotoxic. Here, we examined whether four lavandulyl flavanones, (2S)-2'-methoxykurarinone (1), sophoraflavanone G (2), leachianone A (3), and (-)-kurarinone (4), isolated from S. flavescens could protect HT22 immortalized hippocampal cells against glutamate-induced oxidative stress. Compounds 1 and 2 induced the expression of heme oxygenase (HO)-1 and increased HO activity dose- and time-dependently. These two compounds also suppressed glutamate-induced reactive oxygen species generation in HT22 cells, whereas compounds 3 and 4 were not protective. These two lavandulyl flavanones (compounds 1, 2) may protect against glutamate-induced neurotoxicity via HO-1 induction.     

Cudratricusxanthone A protects mouse hippocampal cells against glutamate-induced neurotoxicity via the induction of heme oxygenase-1

Cudratricusxantone A (CTXA), isolated from the roots of Cudrania tricuspidata Bureau (Moraceae), has potent hepatoprotective, antiproliferative, and monoamine oxidase inhibitory effects. In this study, we examined whether CTXA could protect HT22-immortalized hippocampal cells against glutamate-induced oxidative stress through the induction of heme oxygenase (HO)-1 expression. CTXA induced the expression of HO-1 and increased HO activity dose- and time-dependently. CTXA also suppressed glutamate-induced ROS generation in HT22 cells. Interestingly, treatment of neuronal cells with CTXA enhanced cellular resistance to glutamate oxidative stress. The protective effect of CTXA was abrogated by tin protoporphyrin IX, an HO inhibitor. In addition, treatment with the HO-1 inducer, cobalt protoporphyrin IX, and bilirubin, one of the enzymatic products of HO-1, produced comparable protection. These results demonstrate that CTXA protects neuronal cells from glutamate-induced oxidative stress via the induction of HO-1.     

Neuroprotective effects of constituents of the root bark of <Emphasis Type="Italic">Dictamnus dasycarpus</Emphasis> in mouse hippocampal cells

Glutamate-induced oxidative injury causes neuronal degeneration related to many central nervous system diseases, such as Parkinson’s disease, Alzheimer’s disease, epilepsy and ischemia. The bioassay-guided fractionation of the EtOH extract of the root bark of Dictamnus dasycarpus Trucz. provided one neuroprotective limonoid, obacunone, together with a degraded limonoid, fraxinellone and two alkaloids, dictamine and haplopine. At concentrations of 100–150 μM, obacunone showed the potent neuroprotective effects on glutamateinduced neurotoxicity and induced the expression of heme oxygenase (HO)-1 in the mouse hippocampal HT22 cells. In addition, we found that obacunone increased p38 MAPK phosphorylation and induced HO-1 expression via p38 MAPK pathway. These results suggest that obacunone isolated from the root bark of D. dasycarpus increases cellular resistance to glutamate-induced oxidative injury in mouse hippocampal HT22 cells, presumably through the p38 MAPK pathway-dependent HO-1 expression. These results suggest that obacunone could be the effective candidates for the treatment of ROS-related neurological diseases.     

Neuroprotective and free radical scavenging activities of phenolic compounds fromHovenia dulcis

The EtOAc-soluble fraction from a methanolic extract of Hovenia dulcis Thunb. exhibited neuroprotective activity against glutamate-induced neurotoxicity in mouse hippocampal HT22 cells. The neuroprotective activity-guided isolation resulted in 8 phenolic compounds (1-8), such as vanillic acid (1), ferulic acid (2), 3,5-dihydroxystilbene (3), (+)-aromadendrin (4), methyl vanillate (5), (-)-catechin (6), 2,3,4-trihydrobenzoic acid (7), and (+)-afzelechin (8). Among these, compounds 6 and 8 had a neuroprotective effect on the glutamate-induced neurotoxicity in HT22 cells. Furthermore, compound 6 had a DPPH free radical scavenging effect with an IC50 value of 57.7 microM, and a superoxide anion radical scavenging effect with an IC50 value of 8.0 microM. Both compounds 6 and 8 had ABTS cation radical scavenging effects with IC50 values of 7.8 microM and 23.7 microM, respectively. These results suggest that compounds 6 and 8 could be neuroprotectants owing to their free radical scavenging activities.     

Antioxidant and anti-inflammatory activities of the methanolic extract of Neorhodomela aculeate in hippocampal and microglial cells

The antioxidant and anti-inflammatory properties of the marine red alga Neorhodomela aculeate (N. aculeata) MASUDA were investigated with neuronal and microglial cells. Extracts of N. aculeata had potent neuroprotective effects on glutamate-induced neurotoxicity and inhibited reactive oxygen species (ROS) generation in the murine hippocampal HT22 cell line. Also, extracts of N. aculeata inhibited H(2)O(2)-induced lipid peroxidation in rat brain homogenates. The properties of the extract as an anti-inflammatory agent were investigated in microglial activation by interferon-gamma (IFN-gamma): it reduced the inducible nitric oxide synthase that consequently resulted in the reduction of nitric oxide. These results suggest that the marine red alga N. aculeata could be considered as a potential source for reducing reactive oxygen species and inflammation related to neurological diseases.     

Involvement of heme oxygenase-1 in neuroprotection by sanguinarine against glutamate-triggered apoptosis in HT22 neuronal cells

Sanguinarine is a natural compound isolated from the roots of Macleaya cordata and M. microcarpa, has been reported to possess several biological activities such as anti-inflammatory and anti-oxidant effects. In the present study, we demonstrated that sanguinarine markedly induces the expression of HO-1 which leads to a neuroprotective response in mouse hippocampus-derived neuronal HT22 cells from apoptotic cell death induced by glutamate. Sanguinarine significantly attenuated the loss of mitochondrial function and membrane integrity associated with glutamate-induced neurotoxicity. Sanguinarine protected against glutamate-induced neurotoxicity through inhibition of HT22 cell apoptosis. JC-1 staining, which is a well-established measure of mitochondrial damage, was decreased after treatment with sanguinarine in glutamate-challenged HT22cells. In addition, sanguinarine diminished the intracellular accumulation of ROS and Ca²⁺. Sanguinarine also induced HO-1, NQO-1 expression via activation of Nrf2. Additionally, we found that si RNA mediated knock-down of Nrf2 or HO-1 significantly inhibited sanguinarine-induced neuroprotective response. These findings revealed the therapeutic potential of sanguinarine in preventing the neurodegenerative diseases.     

Effects of Resveratrol and trans-3,5,4’-Trimethoxystilbene on Glutamate-Induced Cytotoxicity,Heme Oxygenase-1, and Sirtuin 1 in HT22 Neuronal Cells

Resveratrol (trans-3,5,4’-trihydroxystilbene) has received considerable attention recently for the potential neuroprotective effects in neurodegenerative disorders where heme oxygenase-1 (HO-1) and sirtuin 1 (SIRT1) represent promising therapeutic targets. Resveratrol has been known to increase HO-1 expression and SIRT1 activity. In this study, the effects of resveratrol and trans-3,5,4’-trimethoxystilbene (TMS), a resveratrol derivative, on cytotoxicity caused by glutamate-induced oxidative stress, HO-1 expression, and SIRT1 activation have been investigated by using murine hippocampal HT22 cells, which have been widely used as an in vitro model for investigating glutamate-induced neurotoxicity. Resveratrol protected HT22 neuronal cells from glutamateinduced cytotoxicity and increased HO-1 expression as well as SIRT1 activity in a concentration-dependent manner. Cytoprotec-tion afforded by resveratrol was partially reversed by the specific inhibition of HO-1 expression by HO-1 small interfering RNA and the nonspecific blockage of HO-1 activity by tin protoporphyrin IX, but not by SIRT1 inhibitors. Surprisingly, TMS, a resveratrol derivative with methoxyl groups in lieu of the hydroxyl groups, and trans-stilbene, a non-hydroxylated analog, failed to protect HT22 cells from glutamate-induced cytotoxicity and to increase HO-1 expression and SIRT1 activity. Taken together, our findings suggest that the cytoprotective effect of resveratrol was at least in part associated with HO-1 expression but not with SIRT1 activation and, importantly, that the presence of hydroxyl groups on the benzene rings of resveratrol appears to be necessary for cytoprotection against glutamate-induced oxidative stress, HO-1 expression, and SIRT1 activation in HT22 neuronal cells.     

Neuroprotective and anti-inflammatory effects of flavonoids isolated from Rhus verniciflua in neuronal HT22 and microglial BV2 cell lines

The neuroprotective and anti-inflammatory activities of the methanolic extract of Rhus verniciflua Stokes (Anacardiaceae) were investigated with mouse hippocampal and microglial cells. Bioactivity-guided isolation yielded 10 flavonoids including fustin (1), fisetin (2), sulfuretin (3), butein (4), butin (5), eriodictyol (6), morin hydrate (7), quercetin (8), kaempferol (9) and isoliquiritigenin (10). Among the isolated flavonoids, compounds 2–5 significantly protected the murine hippocampal HT22 cells against glutamate-induced neurotoxicity and attenuated reactive oxygen species (ROS) generations. In addition, these flavonoids significantly maintained antioxidative defense systems preserving the activities of superoxide dismutase (SOD), glutathione reductase (GR), glutathione peroxidase (GSH-Px) and the content of glutathione (GSH) decreased by glutamate insult. These compounds also showed significant inhibitory effects on LPS-induced nitric oxide (NO) production in BV2 cells. Especially, compound 4 dose-dependently suppressed the expression of both inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). These results suggest that these flavonoids possess therapeutic potentials as a multipotent agent against neurodegenerative diseases related to oxidative stress and pathological inflammatory responses.     

Neuroprotective diarylheptanoids from the leaves and twigs of juglans sinensis against glutamate-induced toxicity in HT22 cells

A new diarylheptanoid, juglanin C(1), was isolated from the 80 % methanolic extract of the leaves and twigs of JUGLANS SINENSIS with three known diarylheptanoids, juglanin A(2), juglanin B (3), and (5R)-5-hydroxy-7-(4-hydroxy-3-methoxyphenyl)-1(4-hydroxyphenyl)-3-heptanone (4), using bioactivity-guided fractionation and chromatographic techniques. Among the isolated diarylheptanoids, compounds 1 and 2 significantly showed neuroprotective activities against glutamate-induced toxicity in HT22 cells. These two diarylheptanoids significantly reduced the overproduction of cellular peroxide in glutamate-injured HT22 cells. Moreover, these two diarylheptanoids significantly maintained antioxidative defense systems, including glutathione, glutathione reductase, and glutathione peroxidase, under glutamate-induced oxidative stress in HT22 cells.     

Neuroprotective Effect of Steamed and Fermented Codonopsis lanceolata

Codonopsis lanceolata has been used as an herbal medicine for several lung inflammatory diseases, such as asthma, tonsillitis, and pharyngitis. Previously, we showed the neuroprotective effect of steamed and fermented C. lanceolata (SFC) in vitro and in vivo. In the current study, the treatment of HT22 cells with SFC decreased glutamate-induced cell death, suggesting that SFC protected HT22 cells from glutamate-induced cytotoxicity. Based on these, we sought to elucidate the mechanisms of the neuro-protective effect of SFC by measuring the oxidative stress parameters and the expression of Bax and caspase-3 in HT22 cells. SFC reduced contents of ROS, Ca²⁺ and NO. Moreover, SFC restored contents of glutathione and glutathione reductase as well as inhibited Bax and caspase-3 activity in HT22 cells. These results indicate that steamed and fermented C. lanceolata (SFC) extract protected HT22 cells by anti-oxidative effect and inhibition of the expression of Bax and caspase-3.     

Chroman/catechol hybrids: synthesis and evaluation of their activity against oxidative stress induced cellular damage

Three series of chromans substituted at positions 2 or 5 by catechol derivatives were synthesized, and their activity against oxidative stress induced cellular damage was studied. Specifically, the ability of the new molecules to protect cultured cells from H(2)O(2)-induced DNA damage was evaluated using single cell gel electrophoresis (comet assay), while the neuroprotective activity of the new compounds against oxidative stress induced programmed cell death was studied using glutamate-challanged hippocampal HT22 cells. The majority of the new compounds are stronger neuroprotectants than quercetin. 5-Substituted chroman analogues such as the caffeic acid amides 12 and 16 and the dihydrostilbene analogue 24 were the most potent against both H(2)O(2)- and glutamate-induced damage in Jurkat T cells and HT22 cells, respectively.     

Crambescidin 800, a pentacyclic guanidine alkaloid,protects a mouse hippocampal cell line against glutamate-induced oxidative stress

Oxidative stress is implicated in the pathogenesis of neuronal degenerative diseases. In our search for protective substances against glutamate-induced oxidative stress using mouse hippocampal cell line HT22, we have isolated crambescidin 800, a pentacyclic guanidine alkaloid, from the Indonesian marine sponge, Monanchora ungiculata. Crambescidin 800 (1) protected HT22 cells against glutamate-induced oxidative toxicity at 0.06 μM (EC₅₀) concentration. Crambescidin 800 (1) also protected HT22 and neuroblastoma cells from the oxidative stress induced by a hypoxic condition or nitric oxide (NO). Crambescidin 800 (1) showed no effect on the depletion of intracellular glutathione (GSH) of HT22 cells induced by glutamate, and production of reactive oxygen species (ROS) and activation of mitogen-activated protein kinase (MAPK) were inhibited only by the high concentration (1 μM) of 1.     

Anti-neuroinflammatory effects of tannic acid against lipopolysaccharide-induced BV2 microglial cells via inhibition of NF-κB activation

Microglia mediated neuroinflammation is known to cause various neurodegenerative and neurological ailments. Tannic acid is a natural polyphenol which has been reported to possess antioxidant, anti-inflammatory, anticarcinogenic, antimutagenic, antitumor, and antimicrobial activities. As there are no reports till date on the anti-neuroinflammatory effects of tannic acid, this study was conducted to analyze the possible mechanism and pathway involved in the prevention of neuroinflammation by tannic acid in BV2 microglial cells. BV2 microglial cells were pretreated with tannic acid (10, 25, and 50 μM/mL) and induced with lipopolysaccharide (LPS; 1 μM/mL) to assess the production of reactive oxygen species (ROS), nitric oxide (NO), prostaglandin E2 (PGE2), pro-inflammatory cytokines (IL-6, IL-1β, and TNF-α), and nuclear factor-kappa B (NF-κB) protein expressions through western blotting. The results showed that LPS significantly activated the BV2 cells via toll-like receptor 4 to induce elevated productions of ROS, NO, PGE2, IL-6, and IL-1β. However, tannic acid was able to reverse all the neuroinflammatory effects of LPS-induced BV2 cells in a dose-dependent manner. Collectively, the anti-inflammatory effects of tannic acid on LPS-induced BV2 microglial cells are attributed to the inhibition of ROS formation and the suppression of NF-κB pathway activation. Tannic acid could be a potential therapeutic agent for the treatment of neurological related disorders.     

Novel diosgenin derivative attenuates hippocampal neurogenesis and cognition impairment through blocking microglial activation underlying NF-κB and JNK MAPK signaling in LPS induced-adult mice

OBJECTIVE Diosgenin(DG), a naturally occurring steroidal saponin, has been reported to offer a variety ofpharmacological activities including anti-diabetic and anti-tumor activity, anti-inflammatory and anti-AD. However, the clinical application of DG is limited by its extremely low solubility and poor pharmacokinetic profile. In the present report,a novel diosgenin derivative with improved water-solubility was synthesized and its effect on the LPS-impaired hippocampal neurogenesis, cognition function and underlying mechanism was investigated. METHODS The effects of DG derivative on the adult hippocampal neurogenesis and cognition decline were investigated in a central LPS-induced inflammatory mice model, along with the fundamental mechanisms in vivo and in vitro using LPS-stimulated microglial BV2 cells. RESULTS DG derivative attenuates LPS-impaired neurogenesis by ameliorating the proliferation and differentiation of neural stem cells(NSCs), and prolonging their survival. The impaired neurogenesis in the hippocampal DG triggered the cognitive function, and that treatment of Arg-DG led to the recovery of cognitive decline. Arg-DG also suppressed the production of LPS-induced pro-inflammatory cytokines in hippocampal DG by blocking microglial activation. In in vitro study, Arg-DG inhibited the production of nitric oxide(NO), nitric oxide synthase(i NOS), cyclooxygenase-2(COX-2) expression, and prostaglandin D2 production(PGD2), as well as the pro-inflammatory cytokines, such as interleukin(IL)-6, IL-1β, and tumor necrosis factor alpha(TNF-α). The anti-inflammatory effect of Arg-DG was regulated by NF-κB and MAPK JNK signaling both in vivo, and in LPS-stimulated microglial BV2 cells. CONCLUSION These results suggest that Arg-DG might have the potential to treat the neurodegenerative disorders resulting from microgliamediated neuroinflammation.     

Exopolysaccharide of Laetiporus sulphureus var. miniatus downregulates LPS-induced production of NO, PGE2, and TNF-α in BV2 microglia cells via suppression of the NF-κB pathway

Our previous study showed that the exopolysaccharide (EPS) of Laetiporus sulphureus var. miniatus was well characterized and prevented cell damage in streptozotocin-induced apoptosis. However, little is known about the molecular mechanisms underlying its anti-inflammatory effects. Therefore, we attempted in this study to determine whether EPS induces a significant inhibition of pro-inflammatory mediators in lipopolysaccharide (LPS)-stimulated murine BV2 microglia cells. Our results showed that EPS significantly inhibited LPS-induced pro-inflammatory mediators, such as nitric oxide (NO), prostaglandin E₂ (PGE₂), and tumor necrosis factor-α (TNF-α), without any significant cytotoxicity. EPS also downregulated mRNA and protein expression of inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and TNF-α in LPS-induced BV2 microglia cells. Our data also revealed that EPS treatment significantly reduced translocation of nuclear factor-κB (NF-κB) subunit p65 and its DNA-binding activity in LPS-stimulated BV2 microglia cells. Furthermore, we confirmed by using proteasome inhibitor N-acetyl-l-cysteine (NAC), that the inhibition of NF-κB activity influenced the expression of pro-inflammatory genes in LPS-induced BV2 microglia cells. As expected, NAC suppressed the expression of iNOS, COX-2, and TNF-α by blocking proteasome-mediated degradation. Taken together, our data indicate that EPS inhibits the expression of pro-inflammatory mediators by suppressing NF-κB activity.     

Gastrodin protects against glutamate-induced ferroptosis in HT-22 cells through Nrf2/HO-1 signaling pathway

Gastrodin (GAS) is a component of Gastrodia elata Blume, with strong antioxidant activity in neurodegenerative diseases. Ferroptosis is similar to glutamate-induced cell death. This study was designed to explore the protective effects of GAS against glutamate-induced neurotoxicity in mice hippocampal neurons (HT-22) cells. HT-22 cells were cultured with glutamate in the presence or absence of GAS (1, 5, 25 μM). Results showed that GAS inhibited glutamate-induced ferroptosis via Nrf2/HO-1 signaling pathway. Pretreatment of HT-22 cells with GAS significantly decreased glutamate-induced cell death and release of LDH. Ferrostatin-1, liproxstatin-1, and DFO treatments canceled these effect. GAS decreased glutamate-treatment ROS production in HT-22 cells. The concentration of iron ion was analyzed using ICP-MS. Metal analysis showed that GAS pretreatment normalized iron ion concentration in HT-22 cells. We found that GAS increased the nuclear translocation of Nrf2, up-regulated the downstream HO-1 protein expression in HT-22 cells following treatment with glutamate. Nrf2 knockdown greatly decreased glutamate-induced ferroptosis through HO-1. In conclusion, these results show that GAS protects HT-22 cells from the ferroptosis induced by glutamate through a new mechanism of Nrf2/HO-1 signaling pathway.