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Glutamate-induced oxidative injury contributes to neuronal degeneration such as Alzheimer's disease, Parkinson's disease and Huntington's disease in the central nervous system (CNS). Siegesbeckia pubescens is used in oriental medicine to treat arthritis, stroke, rash, edema, and skin itching eczema in South-East Asia. This study provides evidence that 5,3'-dihydroxy-3,7,4'-trimethoxyflavone (DTMF), a compound isolated from 90% MeOH extract of Siegesbeckia pubescens, effectively has neuroprotective and anti-neuroinflammatory activities. DTMF has cytoprotective and reactive oxygen species (ROS) reductive effects in HT22 cells. DTMF also decreased LPS-induced inducible nitric oxide synthase (iNOS), cyclooxygenase (COX-2) expression but attenuated LPS-induced nitrite (NO) and prostaglandin E2 (PGE2), as well as TNF-α and IL-1β production. In addition, DTMF induced Heme oxygenase (HO)-1 expression, HO activity, nuclear transcription factor erythroid-2 related factor 2 (Nrf2) nuclear translocation, and antioxidant response element (ARE)-luciferase activity. DTMF increased p38 phosphorylation in HT22 cells and JNK phosphorylation in BV2 microglia cells. Thus, p38 inhibitor (SB203580) in HT22 cells and JNK inhibitor (SP600125) in BV2 microglia cells significantly suppressed HO-1 expression by DTMF. Furthermore, treatment with SnPP (an inhibitor of HO activity) significantly blocked the cytoprotective effects and the anti-neuroinflammatory action of DTMF. In addition, activated microglia-mediated cell death of mouse hippocampal HT22 cells was significantly repressed by DTMF. We also investigated the protective effect of DTMF on the death of glutamate-induced primary mouse hippocampal neurons. These results demonstrated that DTMF may be a good therapeutic agent against neurodegenerative diseases induced by oxidative stress.

We previously reported that Nardostachys jatamansi (NJ) exhibits anti-inflammatory activity against lipopolysaccharide (LPS). However, the active compound in NJ is unknown. Therefore, here, we examined the effects of desoxo-narchinol-A (DN) isolated from NJ against LPS-induced inflammation. To demonstrate the anti-inflammatory effect of DN against LPS, we used two models; murine endotoxin shock model for in vivo model, and peritoneal macrophage responses for in vitro. In endotoxin shock model, DN was administrated intraperitoneally 1h before LPS challenge, then we evaluated mice survival rates and organ damages. Pretreatment with DN (0.05mg/kg, 0.1mg/kg, or 0.5mg/kg) dramatically reduced mortality in a murine LPS-induced endotoxin shock model. Furthermore, DN inhibited tissue injury and production of pro-inflammatory cytokines, such as interleukin (IL)-1β, IL-6, and tumor necrosis factor alpha (TNF-α), in the liver and lung. In in vitro macrophage model, we examined the inflammatory mediators and regulatory mechanisms such as mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-κB). DN inhibited the production of inflammatory mediators, such as inducible nitric oxide synthase (iNOS) and its derivative nitric oxide (NO), cyclooxygenase-2 (COX-2), prostaglandin E2 (PGE2), IL-1β, IL-6 and TNF-α and H3 protein acetylation in murine peritoneal macrophages. DN also inhibited p38 activation, but not extracellular signal-regulated kinase (ERK), c-jun NH2-terminal kinase (JNK), and NF-κB. These results suggest that DN from NJ exhibits protective effects against LPS-induced endotoxin shock and inflammation through p38 deactivation.

Cudratricusxanthone A (CTXA), isolated from the roots of Cudrania tricuspidata Bureau (Moraceae) has an isoprenylated xanthone skeleton that is known to exert a variety of biological activities. In the present study, we demonstrated that CTXA inhibited cyclooxygenase-2 (COX-2) and inducible nitric oxide (NO) synthase (iNOS) expression, and thereby reduced COX-2-derived prostaglandin E2 (PGE(2)) and iNOS-derived NO production in lipopolysaccharide (LPS)-stimulated macrophages. Similarly, CTXA suppressed tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) production. Moreover, CTXA inhibited the induced phosphorylation and degradation of IkappaB-alpha as well as the LPS-induced increase in p65 in the nuclear fraction of macrophages. CTXA also induced heme oxygenase-1 (HO-1) expression and increased heme oxygenase (HO) activity in RAW264.7 macrophages. We also demonstrated that the effects of CTXA on LPS-induced PGE(2), NO, TNF-alpha, and IL-1beta production were partially reversed by the HO-1 inhibitor tin protoporphyrin, suggesting that CTXA-induced HO-1 expression was partly responsible for the resulting anti-inflammatory effects of the drug. Thus CTXA was shown to be an effective HO-1 inducer, capable of inhibiting macrophage-derived pro-inflammatory mediators.

In the course of a search for anti-neuroinflammatory metabolites from marine fungi, aurantiamide acetate (1) was isolated from marine-derived Aspergillus sp. as an anti-neuroinflammatory component. Compound 1 dose-dependently inhibited the production of nitric oxide (NO) and prostaglandin E2 (PGE2) in BV2 microglial cells. It also attenuated inducible NO synthase (iNOS), cyclooxygenase-2 (COX-2), and other pro-inflammatory cytokines, such as interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). In a further study designed to elucidate the mechanism of its anti-neuroinflammatory effect, compound 1 was shown to block the activation of nuclear factor-kappa B (NF-κB) in lipopolysaccharide (LPS)-induced BV2 microglial cells by inhibiting the phosphorylation of the inhibitor kappa B-α (IκB)-α. In addition, compound 1 decreased the phosphorylation levels of c-Jun N-terminal kinase (JNK) and p38 mitogen-activated protein kinases (MAPKs). These results suggest that compound 1 has an anti-neuroinflammatory effect on LPS stimulation through its inhibition of the NF-κB, JNK and p38 pathways.

The heartwood of Dalbergia odorifera T. Chen (Leguminosae) is an important source of traditional Korean and Chinese medicines. 9-Hydroxy-6,7-dimethoxydalbergiquinol (HDDQ), a compound isolated from D. odorifera, has various biological activities. The aim of this study was to determine the efficacy of HDDQ in modulating the regulation of anti-inflammatory activity through the upregulation of heme oxygenase (HO)-1 in BV2 microglia. HDDQ inhibited the protein expression of inducible nitric oxide synthase (iNOS), iNOS-derived nitric oxide (NO), and the production of cyclooxygenase (COX)-2 and COX-2-derived prostaglandin E2 (PGE2) in lipopolysaccharide (LPS)-stimulated mouse BV2 microglia. HDDQ also reduced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production, and suppressed the phosphorylation and degradation of IκB-α and the nuclear translocation of p65 in mouse BV2 microglia in response to LPS. Furthermore, HDDQ upregulated HO-1 expression via nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) in mouse BV2 microglia. Using tin protoporphyrin (SnPP), an HO activity inhibitor, we verified that the inhibitory effects of HDDQ on the proinflammatory mediators NO, PGE2, TNF-α, and IL-1β, and nuclear factor kappa B (NF-κB) DNA-binding activity are associated with the induction of HO-1 expression. Our data suggest that HDDQ has therapeutic potential against neurodegenerative diseases caused by neuroinflammation.

Dalbergia odorifera T. Chen (Leguminosae) has traditionally been used as an ingredient in East Asian medicines to treat various diseases. In the present study, 4,2′,5′-trihydroxy-4′-methoxychalcone (TMC), a biologically active chalcone isolated from the heartwood of D. odorifera, inhibited cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) expression, leading to a reduction in COX-2-induced prostaglandin E2 (PGE2) and iNOS-induced nitric oxide (NO) production in lipopolysaccharide (LPS)-stimulated murine peritoneal macrophages. Furthermore, TMC suppressed tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production, and the phosphorylation and degradation of IκB-α as well as the LPS-stimulated nuclear translocation of p65 in macrophages. The present study also demonstrated that TMC induced heme oxygenase-1 (HO-1) expression through the nuclear translocation of nuclear factor E2-related factor 2 (Nrf2) in macrophages. The effects of TMC on LPS-induced NO, PGE2, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β production were partially reversed by the HO inhibitor tin protoporphyrin (SnPP). These results suggest that TMC inhibits pro-inflammatory mediators by inducing the expression of anti-inflammatory HO-1 via the Nrf2 pathway.

Several sesquiterpene lactones are the active components of several medicinal plants and have been demonstrated to perform various pharmacological functions. In this study, we investigated the anti-inflammatory effects of alantolactone, a sesquiterpene lactone isolated from the root of Aucklandia lappa, in lipopolysaccharide (LPS)-stimulated RAW 264.7 cells and peritoneal macrophages. Alantolactone inhibited inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2) protein and mRNA transcription, as well as the downstream products, nitric oxide (NO), prostaglandin E(2) (PGE(2)) and tumor necrosis factor-α (TNF-α). Investigation of the effects on nuclear factor κB (NF-κB) signaling showed that alantolactone inhibits the phosphorylation of inhibitory κB (IκB)-α and IκB kinase (IKK) and the subsequent translocation of the p65 and p50 NF-κB subunits to the nucleus. Moreover, inhibition of mitogen-activated protein kinases (MAPKs), including c-Jun N-terminal kinase (JNK), extracellular signal-regulated kinase (ERK) and p38 MAPK, and activator protein-1 (AP-1) was also observed. A further study indicated that alantolactone attenuated the phosphorylation of Akt and inhibited the expression of MyD88 and Toll-interleukin 1 receptor domain-containing adaptor protein (TIRAP), an upstream signaling molecule required for IKK and MAPKs activation. Taken together, these results suggest that alantolactone exerts its anti-inflammatory effect in LPS-stimulated RAW 264.7 cells by suppressing NF-κB activation and MAPKs phophorylation via downregulation of the MyD88 signaling pathway. Thus, alantolactone may provide a useful therapeutic approach for inflammation-associated diseases.

Saussurea lappa C.B. Clarke (Compositae) is indigenous to India and Pakistan. The dried root of S. lappa has been traditionally used for alleviating pain in abdominal distention and tenesmus, indigestion with anorexia, dysentery, nausea, and vomiting. Santamarin is a sesquiterpene lactone isolated from S. lappa. In the present study, santamarin inhibited inducible nitric oxide synthase (iNOS) protein, reduced iNOS-derived nitric oxide (NO), suppressed COX-2 protein and reduced COX-derived PGE(2) production in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and murine peritoneal macrophages. Similarly, santamarin reduced tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) production. In addition, santamarin suppressed the phosphorylation and degradation of IκB-α as well as the nuclear translocation of p65 in response to LPS in RAW264.7 cells. Furthermore, santamarin induced heme oxygenase (HO)-1 expression mRNA and protein level that plays a cytoprotective role against inflammation. The induction of HO-1 is primarily regulated at the transcriptional level, and its induction by various agents is mediated by the nuclear transcription factor E2-related factor 2 (Nrf2), master regulator of antioxidant responses. Unbound Nrf2 translocates into the nucleus and binds to the antioxidant response element (ARE) in the upstream promoter region of many antioxidative genes, where it initiates their transcription. The effects of santamarin on LPS-induced NO, PGE(2), TNF-α, and IL-1β production were partially reversed by the HO-1 inhibitor, tin protoporphyrin (SnPP). Therefore, our data suggest that the anti-inflammatory effect of santamarin in macrophages may be exerted through a novel mechanism that involves HO-1 expression.

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 (PGE₂), 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.

Rhus verniciflua Stokes (Anacardiaceae) has traditionally been used as an ingredient in East Asian medicines used to treat oxidative damage and cancer. Sulfuretin is one of the major flavonoid components isolated from R. verniciflua. In the present study, we isolated sulfuretin from R. verniciflua and demonstrated that sulfuretin inhibited inducible nitric oxide synthase (iNOS) protein and mRNA expression, reduced iNOS-derived NO, suppressed COX-2 protein and mRNA expression, and reduced COX-derived PGE(2) production in lipopolysaccharide (LPS)-stimulated RAW264.7 and murine peritoneal macrophages. Similarly, sulfuretin reduced tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) production. In addition, sulfuretin suppressed the phosphorylation and degradation of I kappaB-alpha as well as the nuclear translocation of p65 by the stimulation of LPS in RAW264.7 macrophages. Furthermore sulfuretin induced heme oxygenase (HO)-1 expression through nuclear translocation of nuclear factor E2-related factor 2 (Nrf)2 and increased heme oxygenase (HO) activity in RAW264.7 macrophages. The effects of sulfuretin on LPS-induced NO, PGE(2), TNF-alpha, and IL-1 beta production were partially reversed by the HO-1 inhibitor, tin protoporphyrin (SnPP). Therefore, it is suggested that sulfuretin-induced HO-1 expression plays a role of the resulting anti-inflammatory effects in macrophages. This indicated that the anti-inflammatory effects of sulfuretin in macrophages might be exerted through a novel mechanism that involves HO-1 expression.