Involvement of protein kinase Cδ and extracellular signal-regulated kinase-2 in the suppression of microglial inducible nitric oxide synthase expression by N-[3,4-dimethoxycinnamoyl]-anthranilic acid (tranilast)

TPPB modulates PKC activity to attenuate neuroinflammation and ameliorate experimental multiple sclerosis

Protein kinase C (PKC) plays a key role in modulating the activities of the innate immune cells of the central nervous system (CNS). A delicate balance between pro-inflammatory and regenerative activities by microglia and CNS-associated macrophages is necessary for the proper functioning of the CNS. Thus, a maladaptive activation of these CNS innate immune cells results in neurodegeneration and demyelination associated with various neurologic disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Prior studies have demonstrated that modulation of PKC activity by bryostatin-1 (bryo-1) and its analogs (bryologs) attenuates the pro-inflammatory processes by microglia/CNS macrophages and alleviates the neurologic symptoms in experimental autoimmune encephalomyelitis (EAE), an MS animal model. Here, we demonstrate that (2S,5S)-(E,E)-8-(5-(4-(trifluoromethyl)phenyl)-2,4-pentadienoylamino)benzolactam (TPPB), a structurally distinct PKC modulator, has a similar effect to bryo-1 on CNS innate immune cells both in vitro and in vivo, attenuating neuroinflammation and resulting in CNS regeneration and repair. This study identifies a new structural class of PKC modulators, which can therapeutically target CNS innate immunity as a strategy to treat neuroinflammatory and neurodegenerative disorders.

TPPB modulates PKC activity to attenuate neuroinflammation and ameliorate experimental multiple sclerosis

Protein kinase C (PKC) plays a key role in modulating the activities of the innate immune cells of the central nervous system (CNS). A delicate balance between pro-inflammatory and regenerative activities by microglia and CNS-associated macrophages is necessary for the proper functioning of the CNS. Thus, a maladaptive activation of these CNS innate immune cells results in neurodegeneration and demyelination associated with various neurologic disorders, such as multiple sclerosis (MS) and Alzheimer's disease. Prior studies have demonstrated that modulation of PKC activity by bryostatin-1 (bryo-1) and its analogs (bryologs) attenuates the pro-inflammatory processes by microglia/CNS macrophages and alleviates the neurologic symptoms in experimental autoimmune encephalomyelitis (EAE), an MS animal model. Here, we demonstrate that (2S,5S)-(E,E)-8-(5-(4(trifluoromethyl)phenyl)-2,4-pentadienoylamino)benzolactam (TPPB), a structurally distinct PKC modulator, has a similar effect to bryo-1 on CNS innate immune cells both in vitro and in vivo, attenuating neuroinflammation and resulting in CNS regeneration and repair. This study identifies a new structural class of PKC modulators, which can therapeutically target CNS innate immunity as a strategy to treat neuroinflammatory and neurodegenerative disorders.

The key role of organic anion transporter 3 in the drug-drug interaction between tranilast and methotrexate

Tranilast, N-(3',4'-dimethoxycinnamoyl)-anthranilic acid, is an anti-allergic drug and is considered for use in the treatment of rheumatoid arthritis. Methotrexate, an antimetabolite and folate antagonist to treat some cancers, is also a first-line drug for RA. The aim of this study was to understand whether tranilast could inhibit renal uptake transporters (Oat1, Oat3, and Oct2) and whether MTX combined with TL would have drug-drug interactions. The results of kidney slices and HEK293T-OAT3 cell uptake experiments showed that TL (10 μM) could inhibit the uptake of penicillin G and MTX, which are substrates of OAT3. When TL (10 mg/kg) was combined with MTX (5 mg/kg), the area under the curve and peak concentration of MTX increased by 46.46% and 113.51%, respectively, while the pharmacokinetic process of tranilast (10 mg/kg) was not changed by methotrexate (5 mg/kg). TL could increase plasma exposure of MTX by inhibiting Oat3 in vitro and in vivo.

Enhanced nose-to-brain delivery of tranilast using liquid crystal formulations

Intranasal administration is poised as a competent method in delivering drugs to the brain, because the nasal route has a direct link with the central nervous system bypassing the formidable blood-brain barrier. C₁₇-monoglycerol ester (MGE) and glyceryl monooleate (GMO) as liquid crystal (LC)-forming lipids possess desirable formulation characteristics as drug carriers for intranasally administered drugs. This study investigated the effect of LC formulations on the pharmacokinetics of tranilast (TL), a lipophilic model drug, and its distribution in the therapeutic target regions of the brain in rats. The anatomical biodistribution of LC formulations was monitored using micro-computed tomography tandem in vivo imaging systems. MGE and GMO effectively formed LC with suitable particle size, zeta potential, and viscosity supporting the delivery of TL to the brain. MGE and GMO LC formulations enhanced brain uptake by 10- to 12-fold and 2- to 2.4- fold, respectively, compared with TL solution. The olfactory bulb had the highest TL concentration and fluorescent signals among all the brain regions, indicating a direct nose-to-brain delivery pathway of LC formulations. LC-forming lipids, MGE and GMO, are potential biomaterials in formulations intended for intranasal administration.

Determination of the Role and Active Sites of PKC-Delta-Like from Lamprey in Innate Immunity

Protein kinase C-δ (PKC-δ) is an important protein in the immune system of higher vertebrates. Lampreys, as the most primitive vertebrates, have a uniquevariable lymphocyte receptor (VLR) immune system. PKC-δ-like is a crucial functional gene in lampreys and is highly expressed in their immune organs. In this study, lampreys were stimulated with different immunogens, and lipopolysaccharide (LPS) was found to increase the expression of PKC-δ-like. Overexpression of PKC-δ-like could also effectively activate the innate immune response. We further demonstrated that PKC-δ-like-CF, a catalytic fragment of PKC-δ-like, is responsible for activating the innate immune response, and Thr-211, which is Thr-419 of PKC-δ-like, was confirmed to be the key site affecting PKC-δ-like-CF activity. These results indicated that PKC-δ-like from lamprey may have an important role in the innate immune response.

Teucrium polium Extract Enhances the Anti-Angiogenesis Effect of Tranilast on Human Umbilical Vein Endothelial Cells

Purpose: Angiogenesis plays an important role in numerous pathophysiological events like cancer. As a result of this, tranilast as an anti-fibrotic drug induces the promising antitumor activities through the inhibition of angiogenesis. Further, Teucrium polium (TP) is a herbal medicine (family Lamaceae) with antitumor properties. This study was conducted to investigate the combination effects of tranilast and T. polium on human umbilical vein endothelial cells (HUVECs) viability and apoptotic genes expression. Methods: The HUVECs line was treated using different doses of tranilast and T. polium alone or their combination. The cell cytotoxicity was evaluated using MTT and LDH assays; apoptosis was examined using acridine orange/ethidium bromide staining, nitric oxide (NO) production was evaluated using Griess reaction and the expression of BAX and BCL-2 genes were detected using real-time RT-PCR. One-way analysis of variance (ANOVA) test was used to compare the data in different groups. Results: The survival rate of HUVECs was significantly reduced (p<0.05) in a dose dependent manner by tranilast and T. polium. However, T. polium and tranilast combination significantly (p<0.001) reduced cell viability and increased apoptotic cells as compared to each drug alone. Also, HUVECs treated with Tranilast / T. polium combination showed a reduced level of NO as regards to cells exposed only to Tranilast or T. polium (p<0.05). Furthermore, a significant increase in BAX and a decrease in BCL-2 mRNA expression were observed in combination group (p<0.001). Conclusion: T. polium synergistically increased the antiangiogenic effect of tranilast on in vitro angiogenic model of HUVECs.

Determination of tranilast in bio-samples by LC-MS/MS: Application to a pharmacokinetic and brain tissue distribution study in rats

As a potent drug used to improve the neurodegenerative conditions, there is few information about the brain tissue distribution of tranilast by now. In this study, a novel sensitive LC-MS/MS method has been developed and validated to determine tranilast in rat brain tissue samples. The calibration curve showed good linearity ranged from 2.140 to 428.0ng·mL^-1. The method was fully validated and successfully applied in the brain tissue distribution study of tranilast in rats, which had never been reported in detail by now. Furthermore, a rapid LC-MS/MS method with a short run time of 3min was developed and validated for the determination of tranilast in rat plasma and the application to a pharmacokinetic study of tranilast in rats. After oral dosage of 10.5mg·kg^-1 tranilast, the maximum plasma concentration (C_max¹) of tranilast was (18.59±5.40) μg·mL^-1 at (0.667±0.408) h while the area under the curve (AUC_0-24) was (54.87±14.13) μg·h·mL^-1 with the elimination half-life of (2.93±0.41) h. The ratio calculated by dividing the concentration of tranilast in brain with the concentration of tranilast in the plasma, was (0.6042%±0.0572%), (0.7484%±0.0883%), (0.5914%±0.0416%) and (0.3830%±0.1632%) at 0.167, 0.5, 2 and 8h, respectively. The results showed that tranilast with fast absorption could penetrate the rat brain blood barrier after oral gavage. The obtained data also showed that tranilast could be quickly distributed and eliminated in brain tissue.

The tryptophan derivative, tranilast, and conditioned medium with indoleamine 2,3-dioxygenase-expressing cells inhibit the proliferation of lymphoid malignancies

Indoleamine 2,3-dioxygenase (IDO) is an enzyme that catalyzes tryptophan degradation and induces immunosuppression. Although IDO is an important factor that allows tumors to escape from immunological attack, its effect on lymphoid malignancies has not been fully revealed. We evaluated the expression of IDO in samples from patients with B-cell malignancies. The IDO expression in the tumor samples was comparable to those in peripheral blood mononuclear cells from healthy donors and had mainly originated from non-B cell populations. We introduced IDO gene into Chinese hamster ovary (CHO) cells. We then cultured various cell lines using CHO- or CHO-IDO-conditioned medium. Compared with the CHO medium (CHO-CM), the CHO-IDO medium (IDO-CM) decreased the viability of lymphoid cell lines but not those of the non-lymphoid lines. Next, we examined the effects of tryptophan metabolites on lymphoid tumors, and revealed that the drug N-[3',4'-dimethoxycinnamoyl] anthranilic acid (tranilast), a synthetic derivative of the tryptophan metabolite, was able to repress proliferation and dose-dependently induce cell death of lymphoid cell lines. Tranilast induced the activation of the c-Jun N-terminal kinase, which is activated by cellular stress, in lymphoid cells. The effect of tranilast on lymphoid cells was independent of the aryl hydrocarbon receptor (AhR) although tranilast has been reported to be an AhR agonist. Finally, the administration of tranilast decreased murine lymphoid tumor progression in vivo. These results indicated that IDO and tryptophan derivatives, particularly tranilast, can be tools for the therapy for lymphoid malignancies.

Tranilast: a review of its therapeutic applications

Tranilast (N-[3',4'-dimethoxycinnamoyl]-anthranilic acid) is an analog of a tryptophan metabolite. Initially, tranilast was identified as an anti-allergic agent, and used in the treatment of inflammatory diseases, such as bronchial asthma, atypical dermatitis, allergic conjunctivitis, keloids and hypertrophic scars. Subsequently, the results showed that it could be also effective in the management of a wide range of conditions. The beneficial effects of tranilast have also been seen in a variety of disease states, such as fibrosis, proliferative disorders, cancer, cardiovascular problems, autoimmune disorders, ocular diseases, diabetes and renal diseases. Moreover, several trials have shown that it has very low adverse effects and it is generally well tolerated by patients. In this review, we have attempted to accurately summarize previously published studies relating to the use of tranilast for a range of disorders and discuss the drug's possible mode of action. The major mode of the drug's efficacy appears to be the suppression of the expression and/or action of the TGF-β pathway, but the drug affects other factors as well. The findings presented in this review demonstrate the potential of tranilast for the control of a vast array of pathological situations, furthermore, it is a prescribed drug without severe side effects.

Tranilast increases vasodilator response to acetylcholine in rat mesenteric resistance arteries through increased EDHF participation

Background and Purpose

Tranilast, in addition to its capacity to inhibit mast cell degranulation, has other biological effects, including inhibition of reactive oxygen species, cytokines, leukotrienes and prostaglandin release. In the current study, we analyzed whether tranilast could alter endothelial function in rat mesenteric resistance arteries (MRA).

Experimental Approach

Acetylcholine-induced relaxation was analyzed in MRA (untreated and 1-hour tranilast treatment) from 6 month-old Wistar rats. To assess the possible participation of endothelial nitric oxide or prostanoids, acetylcholine-induced relaxation was analyzed in the presence of L-NAME or indomethacin. The participation of endothelium-derived hyperpolarizing factor (EDHF) in acetylcholine-induced response was analyzed by preincubation with TRAM-34 plus apamin or by precontraction with a high K⁺ solution. Nitric oxide (NO) and superoxide anion levels were measured, as well as vasomotor responses to NO donor DEA-NO and to large conductance calcium-activated potassium channel opener NS1619.

Key Results

Acetylcholine-induced relaxation was greater in tranilast-incubated MRA. Acetylcholine-induced vasodilation was decreased by L-NAME in a similar manner in both experimental groups. Indomethacin did not modify vasodilation. Preincubation with a high K⁺ solution or TRAM-34 plus apamin reduced the vasodilation to ACh more markedly in tranilast-incubated segments. NO and superoxide anion production, and vasodilator responses to DEA-NO or NS1619 remained unmodified in the presence of tranilast.

Conclusions and Implications

Tranilast increased the endothelium-dependent relaxation to acetylcholine in rat MRA. This effect is independent of the nitric oxide and cyclooxygenase pathways but involves EDHF, and is mediated by an increased role of small conductance calcium-activated K+ channels.

PKCδ-IRAK1 axis regulates oxidized LDL-induced IL-1β production in monocytes

This study examined the role of interleukin (IL)-1 receptor-associated kinase (IRAK) and protein kinase C (PKC) in oxidized LDL (Ox-LDL)-induced monocyte IL-1β production. In THP1 cells, Ox-LDL induced time-dependent secretory IL-1β and IRAK1 activity; IRAK4, IRAK3, and CD36 protein expression; PKCδ-JNK1 phosphorylation; and AP-1 activation. IRAK1/4 siRNA and inhibitor (INH)-attenuated Ox-LDL induced secreted IL-1β and pro-IL-1β mRNA and pro-IL-1β and mature IL-1β protein expression, respectively. Diphenyleneiodonium chloride (NADPH oxidase INH) and N-acetylcysteine (free radical scavenger) attenuated Ox-LDL-induced reactive oxygen species generation, caspase-1 activity, and pro-IL-1β and mature IL-1β expression. Ox-LDL-induced secretory IL-1β production was abrogated in the presence of JNK INH II, Tanshinone IIa, Ro-31-8220, Go6976, Rottlerin, and PKCδ siRNA. PKCδ siRNA attenuated the Ox-LDL-induced increase in IRAK1 kinase activity, JNK1 phosphorylation, and AP-1 activation. In THP1 macrophages, CD36, toll-like receptor (TLR)2, TLR4, TLR6, and PKCδ siRNA prevented Ox-LDL-induced PKCδ and IRAK1 activation and IL-1β production. Enhanced Ox-LDL and IL-1β in systemic inflammatory response syndrome (SIRS) patient plasma demonstrated positive correlation with each other and with disease severity scores. Ox-LDL-containing plasma induced PKCδ and IRAK1 phosphorylation and IL-1β production in a CD36-, TLR2-, TLR4-, and TLR6-dependent manner in primary human monocytes. Results suggest involvement of CD36, TLR2, TLR4, TLR6, and the PKCδ-IRAK1-JNK1-AP-1 axis in Ox-LDL-induced IL-1β production.

Protein kinase C and toll-like receptor signaling

Protein kinase C (PKC) is a family of kinases that are implicated in a plethora of diseases, including cancer and cardiovascular disease. PKC isoforms can have different, and sometimes opposing, effects in these disease states. Toll-like receptors (TLRs) are a family of pattern recognition receptors that bind pathogens and stimulate the secretion of cytokines. It has long been known that PKC inhibitors reduce LPS-stimulated cytokine secretion by macrophages, linking PKC activation to TLR signaling. Recent studies have shown that PKC-α, -δ, -ε, and -ζ are directly involved in multiple steps in TLR pathways. They associate with the TLR or proximal components of the receptor complex. These isoforms are also involved in the downstream activation of MAPK, RhoA, TAK1, and NF-κB. Thus, PKC activation is intimately involved in TLR signaling and the innate immune response.

The anti-inflammatory activity of Phellinus linteus (Berk. & M.A. Curt.) is mediated through the PKCdelta/Nrf2/ARE signaling to up-regulation of heme oxygenase-1

It has been reported that heme oxygenase-1 (HO-1) mediates the anti-inflammatory activity of the n-BuOH subfraction (PL) prepared from fruiting bodies of Phellinus linteus. This continuing work aimed to elucidate the signaling pathway to the up-regulation of HO-1 by PL. In RAW264.7 macrophage cells, PL was able to enhance phosphorylation of protein kinase Cdelta (PKCdelta), but not PKCalpha/betaII, in a time-dependent manner. PL-induced HO-1 expression was dramatically released by GF109203X, a general inhibitor of PKC, and rottlerin, a specific PKCdelta inhibitor but not by Gö6976, a selective inhibitor for PKCalpha/beta. Additionally, PL treatment resulted in a marked increase in antioxidant response element (ARE)-driven transcriptional activity, which was dependent on PKCdelta but not PKCalpha. An increase by PL treatment in the ARE-driven transcriptional activity was further enhanced by Nrf2, whereas it was diminished by Keap1. Furthermore, pretreatment of rottlerin and overexpression of PKCdelta (K376R), a kinase-inactive form of PKCdelta, partly blocked the suppression by PL of nitric oxide (NO) production and inducible nitric oxide synthase (iNOS) expression, and iNOS promoter activity, which were elevated in the lypopolysaccharide (LPS)-activated macrophages. Similarly, expression of matrix metalloproteinase-9 (MMP-9) and its promoter activity were suppressed by PL, which were dependent upon PKCdelta. The present findings indicate that Phellinus linteus gives rise to an anti-inflammatory activity though the PKCdelta/Nrf2/ARE signaling to the up-regulation of HO-1 in an in vitro inflammation model.

Protein kinase Cdelta binds TIRAP/Mal to participate in TLR signaling

Toll-like receptor (TLR) family members recognize specific molecular patterns within pathogens. Signaling through TLRs results in a proximal event that involves direct binding of adaptor proteins to the receptors. We observed that TIRAP/Mal, an adaptor protein for TLR2 and TLR4, binds protein kinase Cdelta (PKCdelta). TIRAP/Mal GST-fusion protein and a TIRAP/Mal antibody were able to precipitate PKCdelta from rat peritoneal macrophage and THP1 cell lysates. Truncation mutants of TIRAP/Mal showed that the TIR domain of TIRAP/Mal is responsible for binding. TLR2- and TLR4-mediated phosphorylation of p38 MAPK, IKK, and IkappaB in RAW264.7 cells were abolished by depletion of PKCdelta. These results suggest that PKCdelta binding to TIRAP/Mal promotes TLR signaling events.

Mechanisms of endotoxin-induced NO, IL-6, and TNF-alpha production in activated rat hepatic stellate cells: role of p38 MAPK

Compelling experimental evidence indicates that the interactions between endotoxin and hepatic stellate cells (HSCs) can play a significant role in the pathogenesis of liver disease. Endotoxin-induced release of a multifunctional mediator NO (via inducible NO synthase) and the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-6 by HSCs could be an important mechanism of pathological changes in the liver. However, the signaling mechanisms of these effects are poorly understood. In this study, we found that endotoxin causes activation of mitogen-activated protein kinases (MAPKs) (extracellular signal-regulated protein kinase [ERK] 1 and 2, p38, and c-Jun NH2-terminal kinase [JNK]) and nuclear factor kappaB (NF-kappaB) and production of H(2)O(2) in culture-activated HSCs. However, only p38 and NF-kappaB were found to be responsible for the synthesis of NO, IL-6, and TNF-alpha. Exogenous H(2)O(2) caused modest stimulation of TNF-alpha synthesis, did not affect the synthesis of NO or IL-6, and did not activate NF-kappaB or MAPKs. Inhibition of p38 and NF-kappaB activation by SB203580 and pyrrolidine dithiocarbamate, respectively, blocked endotoxin-induced H(2)O(2), NO, TNF-alpha, and IL-6 synthesis. Inhibition of ERK1/2 and JNK phosphorylation did not alter these effects of endotoxin. Whereas SB203580 inhibited endotoxin-induced NF-kappaB activation, pyrrolidine dithiocarbamate did not affect p38 phosphorylation in endotoxin-stimulated cells. In conclusion, endotoxin-induced synthesis of NO, TNF-alpha, and IL-6 in HSCs is mediated by p38 and NF-kappaB, with involvement of H(2)O(2) in TNF-alpha production.

Inhibitory effects of glucosamine on lipopolysaccharide‐induced activation in microglial cells

The aim of the present study was to investigate the effects of glucosamine on lipopolysaccharide (LPS)-induced cellular activation in microglia and to evaluate the inhibitory mechanisms involved. Lipopolysaccharide (100 ng/mL) was used for the activation of primary cultured rat microglial or BV2 microglial cells. Changes in intracellular Ca2+ levels and outward K+ currents were measured using fura-2/AM and whole-cell patch-clamp methods, respectively. Lipopolysaccharide-induced expression of tumour necrosis factor (TNF)-alpha mRNA was analysed by reverse transcription-polymerase chain reaction. Lipopolysaccharide transformed cell morphology into an amoeboid shape in vitro and induced microglial activation in vivo, as measured by immunohistochemical staining, but glucosamine inhibited this activation. Glucosamine also inhibited LPS-induced Ca2+ influx, outward K+ currents and TNF-alpha mRNA expression, which are typically representative of microglial activation. 4. The results suggest that the inhibitory mechanisms of glucosamine on LPS-induced microglial activation include inhibition of Ca2+ influx and outward K+ currents, as well as downregulation of the microglial activator gene TNF-alpha.

HIV-1 Tat and opiate-induced changes in astrocytes promote chemotaxis of microglia through the expression of MCP-1 and alternative chemokines

Opiates exacerbate human immunodeficiency virus type 1 (HIV-1) Tat(1-72)-induced release of key proinflammatory cytokines by astrocytes, which may accelerate HIV neuropathogenesis in opiate abusers. The release of monocyte chemoattractant protein-1 (MCP-1, also known as CCL2), in particular, is potentiated by opiate-HIV Tat interactions in vitro. Although MCP-1 draws monocytes/macrophages to sites of CNS infection, and activated monocytes/microglia release factors that can damage bystander neurons, the role of MCP-1 in neuro-acquired immunodeficiency syndrome (neuroAIDS) progression in opiate abusers, or nonabusers, is uncertain. Using a chemotaxis assay, N9 microglial cell migration was found to be significantly greater in conditioned medium from mouse striatal astrocytes exposed to morphine and/or Tat(1-72) than in vehicle-, mu-opioid receptor (MOR) antagonist-, or inactive, mutant Tat(delta31-61)-treated controls. Conditioned medium from astrocytes treated with morphine and Tat caused the greatest increase in motility. The response was attenuated using conditioned medium immunoneutralized with MCP-1 antibodies, or medium from MCP-1(-/-) astrocytes. In the presence of morphine (time-release, subcutaneous implant), intrastriatal Tat increased the proportion of neural cells that were astroglia and F4/80+ macrophages at 7 days post-injection. This was not seen after treatment with Tat alone, or with morphine plus inactive Tat(delta31-61) or naltrexone. Glia displayed increased MOR and MCP-1 immunoreactivity after morphine and/or Tat exposure. The findings indicate that MCP-1 underlies most of the response of microglia, suggesting that one way in which opiates exacerbate neuroAIDS is by increasing astroglial-derived proinflammatory chemokines at focal sites of CNS infection and promoting macrophage entry and local microglial activation. Importantly, increased glial expression of MOR can trigger an opiate-driven amplification/positive feedback of MCP-1 production and inflammation.

Distinct signaling pathways for induction of type II NOS by IFNγ and LPS in BV-2 microglial cells

Nitric oxide (NO) release upon microglial cell activation has been implicated in the tissue injury and cell death in many neurodegenerative diseases. Recent studies have indicated the ability of interferon-gamma (IFNgamma) and lipopolysaccharides (LPS) to independently induce type II nitric oxide synthase (iNOS) expression and NO production in BV-2 microglial cells. However, a detailed comparison between the signaling pathways activating iNOS by these two agents has not been accomplished. Analysis of PKC isoforms revealed mainly the presence of PKCdelta, iota and lambda in BV-2 cells. Although both IFNgamma and LPS could specifically enhance the tyrosine phosphorylation of PKCdelta, treatment with IFNgamma induced a steady increase of phospho-PKCdelta for up to 1h, whereas treatment with LPS elevated phospho-PKCdelta levels only transiently, with peak activity at 5 min. Rottlerin, a specific inhibitor for PKCdelta, dose-dependently inhibited IFNgamma- and LPS-induced NO production. Despite the common involvement of PKCdelta, IFNgamma- but not LPS-induced NO production involved extracellular signal-regulated kinases (ERK1/2) cascade and IFNgamma-induced phosphorylation of ERK1/2 was mediated through PKC. On the other hand, LPS- but not IFNgamma-induced NO production was through stimulation of NF-kappaB activation and nuclear translocation to interact with DNA. These results demonstrated distinct signaling pathways for induction of iNOS by IFNgamma and LPS in BV-2 microglial cells.

Estrogen and brain inflammation: effects on microglial expression of MHC, costimulatory molecules and cytokines

To model the effects of estrogen on adaptive immunity in the brain, we examined the effects of 17beta-estradiol on microglial parameters related to antigen presentation and T cell activation. Specifically, the effects of 17beta-estradiol on basal and LPS-induced surface staining of Class I and II MHC, as well as CD40, CD80, CD86, CD152, CD28, CD8, CD11b, Fas, FasL, and also ERalpha and ERbeta, were examined in N9 microglial cells. Additionally, the effects of 17beta-estradiol on basal and LPS-induced release of cytokines (TNF-alpha, IFN-gamma, IL-2, IL-4, and IL-10) were determined. Data indicate that estrogen increases IL-10 while decreasing TNFalpha and IFNgamma release from resting and LPS-stimulated N9 cells. Additionally, LPS-induced surface staining of MHC Class I, CD40, and CD86 was significantly attenuated by estrogen pretreatment. The basal percentage of cells positive for MHC Class I and II, CD40, and CD152, Fas, and FasL was significantly decreased by estrogen exposure. However, CD8, CD86, CD11b, and CD28 were unaffected by estrogen, and CD80 cell surface staining significantly increased following estrogen exposure. Taken together, these data indicate that estrogen can significantly decrease components of adaptive immunity in microglial cells, and highlight the multi-faceted regulatory effects of estrogen on microglial parameters related to antigen presentation and T cell interaction.

Cancer, inflammation and the AT1 and AT2 receptors

The critical role of inappropriate inflammation is becoming accepted in many diseases that affect man, including cardiovascular diseases, inflammatory and autoimmune disorders, neurodegenerative conditions, infection and cancer.

This review proposes that cancer up-regulates the angiotensin II type 1 (AT1) receptor through systemic oxidative stress and hypoxia mechanisms, thereby triggering chronic inflammatory processes to remodel surrounding tissue and subdue the immune system. Based on current literature and clinical studies on angiotensin receptor inhibitors, the paper concludes that blockade of the AT1 receptor in synergy with cancer vaccines and anti-inflammatory agents should offer a therapy to regress most, if not all, solid tumours.

With regard to cancer being a systemic disease, an examination of supporting evidence for a systemic role of AT1 in relationship to inflammation in disease and injury is presented as a logical progression. The evidence suggests that regulation of the mutually antagonistic angiotensin II receptors (AT1 and AT2) is an essential process in the management of inflammation and wound recovery, and that it is an imbalance in the expression of these receptors that leads to disease.

In consideration of cancer induced immune suppression, it is further postulated that the inflammation associated with bacterial and viral infections, is also an evolved means of immune suppression by these pathogens and that the damage caused, although incidental, leads to the symptoms of disease and, in some cases, death.

It is anticipated that manipulation of the angiotensin system with existing anti-hypertensive drugs could provide a new approach to the treatment of many of the diseases that afflict mankind.