p38 mitogen-activated protein kinase down-regulates nitric oxide and up-regulates prostaglandin E2 biosynthesis stimulated by interleukin-1beta

Impact of Myeloid p38α/MAPK on Orthodontic Tooth Movement

Objectives: Myeloid p38α/MAPK regulate and coordinate osteoclastogenesis. The present study was conducted to investigate the role of myeloid p38α/MAPK during orthodontic tooth movement. Methods: Orthodontic tooth movement was performed in wildtype and p38α^Δmyel mice lacking p38α/MAPK expression in myeloid cells. First, bone parameter as well as osteoblast and osteoclast number were determined in tibiae. RNA was isolated from the untreated and orthodontically treated maxillary jaw side and expression of genes involved in inflammation and bone remodelling were analysed. Finally, periodontal bone loss, alveolar bone density and extent of orthodontic tooth movement were assessed. Results: Bone density was increased in p38α^Δmyel mice compared to wildtype mice in tibiae (p = 0.043) and alveolar bone (p = 0.003). This was accompanied by a reduced osteoclast number in tibiae (p = 0.005) and TRAP5b in serum (p = 0.015). Accordingly, expression of osteoclast-specific genes was reduced in p38α^Δmyel mice. Extent of tooth movement was reduced in p38α^Δmyel mice (p = 0.024). This may be due to the higher bone density of the p38αΔmyel mice. Conclusions: Myeloid p38α/MAPK thus appears to play a regulatory role during orthodontic tooth movement by regulating osteoclastogenesis.

PKCδ/MAPKs and NF-κB Pathways are Involved in the Regulation of Ingenane-Type Diterpenoids from Euphorbia neriifolia on Macrophage Function

PURPOSE

Euphorbia neriifolia Linn. has important medicinal value in the treatment of ulcers, tumors, inflammation, chronic respiratory troubles, and so on. Although many ingredients with anti-inflammatory activity have been discovered and isolated from the Euphorbia neriifolia, the current research still cannot explain its multivariate effects on the immune response. This article aims to introduce two Ingenane-type diterpenoids from Euphorbia neriifolia with macrophage regulatory effects and to investigate the mechanism of their action.

METHODS

The stem bark of E. neriifolia was extracted with various separation methods to obtain ingenane-type diterpenoids. The RAW264.7 cells were treated with lipopolysaccharide (LPS, 1 μg/mL) to establish an inflammatory cell model. The cell viability was detected by MTT assay. The secretion of PGE2, TNF-α, IL-1β, and IL-6 was tested with ELISA. The levels of iNOS, COX-2, IκBα, JNK, ERK, p38, p-IκBα, p-JNK, p-ERK, and p-p38 in cells were detected by Western blotting. The translocation of nuclear factor-kappa B (NF-κB)/p65 subunit were evaluated by Immunofluorescence staining.

RESULTS

Ingenane-type diterpenoids, eurifoloid A (Euri A) and a new compound euphorneroid E (Euph E), were isolated from the EtOAc fraction of E. neriifolia stem bark extracts. Euph E and Euri A exhibited significant inhibition on the levels of pro-inflammatory mediators NO, IL-1β, IL-6, and iNOS on LPS-induced macrophage RAW264.7. Cellular signaling pathway studies showed that they prevented the degradation of IκBα and the translocation of NF-κB/p65 subunit. Furthermore, the production of PGE2, TNFα, and COX-2 was dramatically increased under the influence of the compounds, which were closely related to the phosphorylation of protein kinase C δ (PKCδ) and activation of mitogen-activated protein kinase (MAPKs) signaling pathway.

CONCLUSION

These results demonstrated that Euph E and Euri A exhibited multidirectional regulation on cytokines and immune function of macrophages, in addition to a good anti-inflammatory activity, and which was closely related to the regulation of PKCδ/MAPKs and NF-κB signal pathways.

Bradykinin stimulates prostaglandin E2 release in human skeletal muscular fibroblasts

Local mediator prostaglandins and bradykinin are involved in inflammation and pain. We explored bradykinin effects on prostaglandin E2 (PGE2) release from fibroblasts derived from human skeletal muscular biopsies. Bradykinin induced PGE₂ release through bradykinin B2 receptors, since PGE₂ release was blocked by the bradykinin B2 receptor selective antagonist FR173657 and B2 receptor agonist (Hyp³)-bradykinin showed effects comparable to bradykinin. Consistently, bradykinin induced both mRNA cyclooxygenase 2 (COX-2) and protein. Bradykinin also induced ERK1/2 and p38 phosphorylation and provoked the translocation from the cytosol to the nucleus of p65/NF-kB. The release of PGE₂ by bradykinin could be blocked inhibiting COX-2 and p65/NF-kB, ERK1/2 or p38 activation. Both ERK1/2 and p38 were upstream to NF-kB inasmuch siRNAs significantly blocked the p65/NF-kB activation induced by bradykinin. Thus, bradykinin, acting via B2 receptors, induced PGE₂ release through ERK1/2 and p38-dependent pathways and consequent p65/NF-kB translocation to nucleus. p65/NF-kB induced COX-2 transcription. The release of PGE₂ provide a possible explanation for the role of bradykinin in inflammatory diseases.

The Role of Nitric Oxide in Regulating Intestinal Redox Status and Intestinal Epithelial Cell Functionality

Important functions of intestinal epithelial cells (IECs) include enabling nutrient absorption to occur passively and acting as a defense barrier against potential xenobiotic components and pathogens. A compromise to IEC function can result in the translocation of bacteria, toxins, and allergens that lead to the onset of disease. Thus, the maintenance and optimal function of IECs are critically important to ensure health. Endogenous biosynthesis of nitric oxide (NO) regulates IEC functionality both directly, through free radical activity, and indirectly through cell signaling mechanisms that impact tight junction protein expression. In this paper, we review the current knowledge on factors that regulate inducible nitric oxide synthase (iNOS) and the subsequent roles that NO has on maintaining IECs' intestinal epithelial barrier structure, functions, and associated mechanisms of action. We also summarize important findings on the effects of bioactive dietary food components that interact with NO production and affect downstream intestinal epithelium integrity.

Molecular Mechanisms of Nitric Oxide in Cancer Progression, Signal Transduction, and Metabolism

SIGNIFICANCE

Cancer is a complex disease, which not only involves the tumor but its microenvironment comprising different immune cells as well. Nitric oxide (NO) plays specific roles within tumor cells and the microenvironment and determines the rate of cancer progression, therapy efficacy, and patient prognosis. Recent Advances: Key understanding of the processes leading to dysregulated NO flux within the tumor microenvironment over the past decade has provided better understanding of the dichotomous role of NO in cancer and its importance in shaping the immune landscape. It is becoming increasingly evident that nitric oxide synthase 2 (NOS2)-mediated NO/reactive nitrogen oxide species (RNS) are heavily involved in cancer progression and metastasis in different types of tumor. More recent studies have found that NO from NOS2+ macrophages is required for cancer immunotherapy to be effective.

CRITICAL ISSUES

NO/RNS, unlike other molecules, are unique in their ability to target a plethora of oncogenic pathways during cancer progression. In this review, we subcategorize the different levels of NO produced by cells and shed light on the context-dependent temporal effects on cancer signaling and metabolic shift in the tumor microenvironment.

FUTURE DIRECTIONS

Understanding the source of NO and its spaciotemporal profile within the tumor microenvironment could help improve efficacy of cancer immunotherapies by improving tumor infiltration of immune cells for better tumor clearance.

Regulatory role of IKKɑ in myocardial ischemia/reperfusion injury by the determination of M1 versus M2 polarization of macrophages

The IκB kinase (IKK) complex plays a well-documented role in cancer and immune system. This function has been widely attributed to its role as the master regulator of the NF-κB family. Particularly, IKKɑ, a member of IKK complex, is reported to have various regulating effects in inflammatory and malignant diseases. However, its role as well as its mechanism of function in macrophages following myocardial ischemia and reperfusion (I/R) injury remains unexplored. In vivo, sham or I/R operations were performed on macrophage-specific IKKɑ knockout (mIKKɑ^-/-) mice and their IKKɑ^flox/flox littermates. We ligated the left anterior descending (LAD) coronary artery of I/R groups simulating ischemia for 30 min, followed by a reperfusion period of 3 days and 7 days, respectively. The hearts of mIKKɑ^-/- mice exhibited significantly increased inflammation and macrophage aggregation as compared to their IKKɑ^flox/flox littermates. Moreover, in the mIKKɑ^-/- group subjected to I/R macrophages had a tendency to polarize to M1 phenotype. In vitro, we stimulated RAW264.7 cells with Lipopolysaccharides (LPS) after infection by the lentivirus, either knocking-down or overexpressing IKKɑ. We discovered that a deficiency of IKKɑ in RAW264.7 caused increased expression of pro-inflammatory markers compared to normal RAW264.7 after LPS stimulation. Inversely, pro-inflammatory factors were inhibited with IKKɑ overexpression. Mechanistically, IKKɑ directly combined with RelB to regulate macrophage polarization. Furthermore, IKKɑ regulated MEK1/2-ERK1/2 and downstream p65 signaling cascades after LPS stimulation. Overall, our data reveals that IKKɑ is a novel mediator protecting against the development of myocardial I/R injury via negative regulation of macrophage polarization to M1 phenotype. Thus, IKKɑ may serve as a valuable therapeutic target for the treatment of myocardial I/R injury.

RNF25 promotes gefitinib resistance in EGFR-mutant NSCLC cells by inducing NF-κB-mediated ERK reactivation

Non-small cell lung cancer (NSCLC) patients with EGFR mutations initially respond well to EGFR tyrosine kinase inhibitors (TKIs) but eventually exhibit acquired or innate resistance to the therapies typically due to gene mutations, such as EGFR T790M mutation or a second mutation in the downstream pathways of EGFR. Importantly, a significant portion of NSCLC patients shows TKI resistance without any known mechanisms, calling more comprehensive studies to reveal the underlying mechanisms. Here, we investigated a synthetic lethality with gefitinib using a genome-wide RNAi screen in TKI-resistant EGFR-mutant NSCLC cells, and identified RNF25 as a novel factor related to gefitinib resistance. Depletion of RNF25 expression substantially sensitized NSCLC cells to gefitinib treatment, while forced expression of RNF25 augmented gefitinib resistance in sensitive cells. We demonstrated that RNF25 mediates NF-κB activation in gefitinib-treated cells, which, in turn, induces reactivation of ERK signal to cause the drug resistance. We identified that the ERK reactivation occurs via the function of cytokines, such as IL-6, whose expression is transcriptionally induced in a gefitinib-dependent manner by RNF25-mediated NF-κB signals. These results suggest that RNF25 plays an essential role in gefitinib resistance of NSCLC by mediating cross-talk between NF-κB and ERK pathways, and provide a novel target for the combination therapy to overcome TKI resistance of NSCLC.

Neuron-Glia Crosstalk in the Autonomic Nervous System and Its Possible Role in the Progression of Metabolic Syndrome: A New Hypothesis

Metabolic syndrome (MS) is characterized by the following physiological alterations: increase in abdominal fat, insulin resistance, high concentration of triglycerides, low levels of HDL, high blood pressure, and a generalized inflammatory state. One of the pathophysiological hallmarks of this syndrome is the presence of neurohumoral activation, which involve autonomic imbalance associated to hyperactivation of the sympathetic nervous system. Indeed, enhanced sympathetic drive has been linked to the development of endothelial dysfunction, hypertension, stroke, myocardial infarct, and obstructive sleep apnea. Glial cells, the most abundant cells in the central nervous system, control synaptic transmission, and regulate neuronal function by releasing bioactive molecules called gliotransmitters. Recently, a new family of plasma membrane channels called hemichannels has been described to allow the release of gliotransmitters and modulate neuronal firing rate. Moreover, a growing amount of evidence indicates that uncontrolled hemichannel opening could impair glial cell functions, affecting synaptic transmission and neuronal survival. Given that glial cell functions are disturbed in various metabolic diseases, we hypothesize that progression of MS may relies on hemichannel-dependent impairment of glial-to-neuron communication by a mechanism related to dysfunction of inflammatory response and mitochondrial metabolism of glial cells. In this manuscript, we discuss how glial cells may contribute to the enhanced sympathetic drive observed in MS, and shed light about the possible role of hemichannels in this process.

Prolonged Cre expression driven by the α-myosin heavy chain promoter can be cardiotoxic

Studying the importance of genetic factors in a desired cell type or tissue necessitates the use of precise genetic tools. With the introduction of bacteriophage Cre recombinase/loxP mediated DNA editing and promoter-specific Cre expression, it is feasible to generate conditional knockout mice in which particular genes are disrupted in a cell type-specific manner in vivo. In cardiac myocytes, this is often achieved through α-myosin heavy chain promoter (αMyHC)-driven Cre expression in conjunction with a loxP-site flanked gene of interest. Recent studies in other cell types demonstrate toxicity of Cre expression through induction of DNA damage. However, it is unclear to what extent the traditionally used αMyHC-Cre line [1] may exhibit cardiotoxicity. Further, the genotype of αMyHC-Cre(+/-) is not often included as a control group in cardiac myocyte-specific knockout studies. Here we present evidence that these αMyHC-Cre(+/-) mice show molecular signs of cardiac toxicity by 3months of age and exhibit decreased cardiac function by 6months of age compared to wild-type littermates. Hearts from αMyHC-Cre(+/-) mice also display evidence of fibrosis, inflammation, and DNA damage. Interestingly, some of the early functional changes observed in αMyHC-Cre(+/-) mice are sexually dimorphic. Given the high level of Cre recombinase expression resulting from expression from the αMyHC promoter, we asked if degenerate loxP-like sites naturally exist in the mouse genome and if so, whether they are affected by Cre in the absence of canonical loxP-sites. Using a novel bioinformatics search tool, we identified 619 loxP-like sites with 4 or less mismatches to the canonical loxP-site. 227 sites overlapped with annotated genes and 55 of these genes were expressed in cardiac muscle. Expression of ~26% of the 27 genes tested was disrupted in αMyHC-Cre(+/-) mice indicating potential targeting by Cre. Taken together, these results highlight both the importance of using αMyHC-Cre mice as controls in conditional knockout studies as well as the need for a less cardiotoxic Cre driver for the field.

Delta-tocotrienol induces apoptotic cell death via depletion of intracellular squalene in ED40515 cells

Here, we examined the effect of tocotrienols (T3) on the growth of adult T-cell leukemia (ATL) cells. All three forms (β-, γ-, and δ-T3) inhibited cell proliferation in a dose-dependent manner; δ-T3 showed the strongest growth-inhibitory effect. δ-T3 increased the G1, G2/M, and subG1 populations and induced internucleosomal DNA fragmentation. δ-T3 treatment also increased the levels of cleaved caspase-3, -6, -7, -9, and poly-ADP ribose polymerase (PARP), and this was accompanied by downregulation of Bcl-2, Bcl-xL, and XIAP. Moreover, δ-T3 decreased nuclear p65 NF-κB levels, indicating downregulation of NF-κB activity. This cytotoxic effect of δ-T3 was abrogated by squalene (SQL) but not mevalonate (MVL), farnesyl diphosphate (FPP), geranylgeranyl diphosphate (GGPP), or cholesterol (CL). δ-T3 decreased intracellular SQL levels, and inhibition of de novo cholesterol synthesis did not affect the action of SQL. Furthermore, δ-T3 significantly decreased farnesyl-diphosphate farnesyltransferase 1 (FDFT1) expression. Taken together, it is evident that δ-T3, due to its ability to potently induce apoptosis via the depletion of intracellular SQL, shows the potential to be considered a therapeutic agent in patients with ATL.

Functional analysis of the uropathogenic Escherichia coli R049 gene

The objective of this study was to determine the function of the novel uropathogenic Escherichia coli (UPEC) gene R049 during host infection. We infected the urinary tracts of mice with E. coli UPEC132 or the R049 deletion mutant UPEC132ΔR049.The mouse kidneys were harvested at 4 and 8h post-infection and screened for differentially expressed genes by microarray analysis. We identified 379 and 515 differentially expressed genes at 4 and 8 h post-infection, respectively. Thirty-four of these genes were associated with inflammatory and immune signaling pathways, including those related to mitogen-activated protein kinase signaling, leukocyte transendothelial migration, cytokine-cytokine receptor interaction, Toll-like receptor signaling, and apoptosis. Protein binding (GO 0005515) was the most prevalent molecular function in the Gene Ontology terms related to differentially expressed genes. In conclusion, R049 expression in UPEC132 is related to the early innate immune and inflammatory responses in UPEC-infected hosts. This work lays the foundation for further research on anti-infective immunity against UPEC.

Identification of nitric oxide-releasing derivatives of oleanolic acid as potential anti-colon cancer agents

NO-releasing hybrid 6 regulates colon cancer-related signaling pathways, exhibiting potent anti-colon cancer activity in vitro and in vivo.

Ethyl acetate fraction from Angelica sinensis inhibits IL-1β-induced rheumatoid synovial fibroblast proliferation and COX-2, PGE2, and MMPs production

Background

The root of Angelica sinensis (AS), also known as “Dang-gui,” was a popular herbal medicine widely used in the treatment of gynecological diseases in China, Korea, and Japan for a long time. This study aimed to determine the effects of ethyl acetate fraction from Angelica sinensis (EAAS) on the interleukin-1β (IL-1β)-induced proliferation of rheumatoid arthritis synovial fibroblasts (RASFs), and production of matrix metalloproteinases (MMPs), cyclooxygenase (COX) 2, and prostaglandin E2 (PGE2), involved in articular bone and cartilage destruction, by RASFs.

Results

RASF proliferation was evaluated with cholecystokinin octapeptide (CCK-8) reagent in the presence of IL-1β with/without EAAS. Expression of MMPs, tissue inhibitor of metalloproteinases-1 (TIMP-1), COXs, PGE2, and intracellular mitogen-activated protein kinase (MAPK) signaling molecules, including p-ERK, p-p38, p-JNK, and NF-κB, were examined using immunoblotting or semi-quantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay. EAAS inhibited IL-1β-induced RASF proliferation; MMP-1, MMP-3, and COX-2 mRNA and protein expressions; and PGE2 production. EAAS also inhibits the phosphorylation of ERK-1/2, p38, and JNK, and activation of NF-κB by IL-1β.

Conclusion

EAAS might be a new therapeutic modality for rheumatoid arthritis management.

IL-1β-stimulated urokinase plasminogen activator expression through NF-κB in gastric cancer after HGF treatment

The potential of hepatocyte growth factor (HGF) to regulate the expression of urokinase plasminogen activator (uPA) in a gastric cancer cell is not widely acknowledged. To identify the genes associated with the plasminogen activator proteolytic axis by HGF, we used cDNA microarray technology and selected genes upregulated or downregulated in two gastric cell lines (NUGC-3 and MKN-28). First, IL-1β RNA and protein were confirmed to be upregulated. Then, we investigated the effect of IL-1β induced by HGF on the uPA system, facilitating the migration and invasion of cancer cells in the metastatic process. The role for IL-1β in HGF-induced upregulation of uPA was determined by knockdown of IL-1β with IL-1β shRNA and a chromatin immune precipitation assay. The levels of IL-1β and uPA were upregulated in cells treated with HGF in a dose-dependent manner. HGF-induced upregulation of uPA was suppressed by IL-1β knockdown. HGF enhanced the binding activity of NF-κB to the uPA promoter in control cells, but not in the IL-1β shRNA cells. We confirmed the functional role of HGF inactivation of the uPA promoter by a reporter gene assay. Downregulation of IL-1β using IL-1β shRNA also decreased cell proliferation and in vitro cell invasion. IL-1β stimulated uPA expression through ERK and NF-κB in gastric cancer, which may therefore be promising targets for gastric cancer therapy.

In vitro and in vivo anti-inflammatory effects of a novel 4,6-bis ((E)-4-hydroxy-3-methoxystyryl)-1-phenethylpyrimidine-2(1H)-thione

Inflammation plays a critical defensive role in the human body. However, uncontrolled or aberrant inflammatory responses contribute to various acute and chronic diseases. The Nrf2-ARE pathway plays a pivotal role in the regulation of inflammatory markers, such as inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). On the basis of this concept, we synthesized a novel anti-inflammatory 4,6-bis ((E)-4-hydroxy-3-methoxystyryl)-1-phenethylpyrimidine-2(1H)-thione (HPT), and in vitro experiments using HepG2-C8 ARE-luciferase-transfected cells demonstrated the induction of Nrf2-ARE activity. In lipopolysaccharide (LPS)-induced RAW 264.7 cells, HPT treatment reduced the production of nitric oxide (NO) as well as the protein and mRNA expression levels of COX-2 and iNOS, in a dose-dependent manner. In addition, HPT suppressed the mRNA expression of inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6. In LPS-induced macrophages, HPT inhibited COX-2 and iNOS by blocking the activation of p38 and c-Jun NH2-terminal kinase (JNK) but not extracellular signal-regulated kinase (ERK1/2). Furthermore, an in vivo anti-inflammatory study was performed using a TPA-induced skin inflammation mouse model, and the results showed that HPT reduced TPA-induced inflammation and attenuated the expression of COX-2 and iNOS in TPA-induced mouse skin tissue. Thus, HPT demonstrated anti-inflammatory activity both in LPS-induced RAW 264.7 cells and TPA-stimulated mouse skin and may therefore serve as a potential anti-inflammatory agent.

The prostaglandin E2 receptor EP4 is integral to a positive feedback loop for prostaglandin E2 production in human macrophages infected with Mycobacterium tuberculosis

Prostaglandin E2 (PGE2) is an important biological mediator involved in the defense against Mycobacterium tuberculosis (Mtb) infection. Previously, we reported that in macrophages (Mϕs), infection with avirulent Mtb H37Ra resulted in inhibition of necrosis by an inhibitory effect on mitochondrial permeability transition via the PGE2 receptor EP2. However, human Mϕs also express EP4, a PGE2 receptor functionally closely related to EP2 that also couples to stimulatory guanine nucleotide binding protein, but the functional differences between EP2 and EP4 in Mtb-infected Mϕs have been unclear. EP4 antagonist addition to H37Ra-infected Mϕs inhibited the expression of cyclooxygenase 2 (COX2) and microsomal prostaglandin E synthase-1 (mPGES-1), which are involved in PGE2 production. Moreover, H37Ra infection induced PGE2 production through the Toll-like receptor (TLR) 2/p38 mitogen-activated protein kinase (MAPK) signaling pathway. Induction of COX2 and mPGES-1 expression by TLR2 stimulation or Mtb infection was increased after additional stimulation with EP4 agonist. Hence, in Mtb-infected Mϕs, PGE2 production induced by pathogen recognition receptors/p38 MAPK signaling is up-regulated by EP4-triggered signaling to maintain an effective PGE2 concentration.

Dual functions of Insig proteins in cholesterol homeostasis

The molecular mechanism of how cells maintain cholesterol homeostasis has become clearer for the understanding of complicated association between sterol regulatory element-binding proteins (SREBPs), SREBP cleavage-activating protein (SCAP), 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) and Insuin induced-genes (Insigs). The pioneering researches suggested that SREBP activated the transcription of genes encoding HMG-CoA reductase and all of the other enzymes involved in the synthesis of cholesterol and lipids. However, SREBPs can not exert their activities alone, they must form a complex with another protein, SCAP in the endoplasmic reticulum (ER) and translocate to Golgi. Insigs are sensors and mediators that regulate cholesterol homeostasis through binding to SCAP and HMG-CoA reductase in diverse tissues such as adipose tissue and liver, as well as the cultured cells. In this article, we aim to review on the dual functions of Insig protein family in cholesterol homeostasis.

IFN-α and lipopolysaccharide upregulate APOBEC3 mRNA through different signaling pathways

APOBEC3 (A3) proteins are virus-restriction factors that provide intrinsic immunity against infections by viruses like HIV-1 and mouse mammary tumor virus. A3 proteins are inducible by inflammatory stimuli, such as LPS and IFN-α, via mechanisms that are not fully defined. Using genetic and pharmacological studies on C57BL/6 mice and cells, we show that IFN-α and LPS induce A3 via different pathways, independently of each other. IFN-α positively regulates mouse APOBEC3 (mA3) mRNA expression through IFN-αR/PKC/STAT1 and negatively regulates mA3 mRNA expression via IFN-αR/MAPKs-signaling pathways. Interestingly, LPS shows some variation in its regulatory behavior. Although LPS-mediated positive regulation of mA3 mRNA occurs through TLR4/TRIF/IRF3/PKC, it negatively modulates mA3 mRNA via TLR4/MyD88/MAPK-signaling pathways. Additional studies on human peripheral blood mononuclear cells reveal that PKC differentially regulates IFN-α and LPS induction of human A3A, A3F, and A3G mRNA expression. In summary, we identified important signaling targets downstream of IFN-αR and TLR4 that mediate A3 mRNA induction by both LPS and IFN-α. Our results provide new insights into the signaling targets that could be manipulated to enhance the intracellular store of A3 and potentially enhance A3 antiviral function in the host.

Involvement of P2Y6 receptor in p38 MAPK-mediated COX-2 expression in response to UVB irradiation of human keratinocytes

Ultraviolet B (UVB) radiation induces inflammation in human skin. Extracellular nucleotides are released from cells in response to various stimuli and act as intercellular signaling molecules through activation of P2 receptors. In this study, we investigated the involvement of extracellular nucleotides and P2 receptors in UVB-radiation-induced inflammation using human keratinocyte-derived HaCaT cells. UVB radiation induced rapid ATP release from HaCaT cells; this was inhibited by pretreatment with anion transporter blockers or maxi-anion channel blockers. In addition, the radiation-induced activation of p38 MAPK was significantly blocked by pretreatment with ecto-nucleotidase (apyrase) or P2Y6 receptor antagonist (MRS2578). Expression of COX-2, mediated by activation of p38 MAPK, was also induced by UVB radiation. Both pretreatment with MRS2578 and knockdown of the P2Y6 receptor by siRNA transfection attenuated the induction of COX-2 in HaCaT cells exposed to UVB radiation. Our results indicate that UVB radiation evokes ATP release from human keratinocytes and also that activation of P2Y6 receptor mediates the UVB-radiation-induced activation of p38 MAPK and expression of COX-2. Thus P2Y6 receptor is a mediator of UVB-radiation-induced inflammatory responses in keratinocytes.

Tim3 binding to galectin-9 stimulates antimicrobial immunity

The interaction between Tim3 on Th1 cells and galectin-9 on Mycobacterium tuberculosis–infected macrophages restricts the bacterial growth by stimulating caspase-1–dependent IL-1β secretion.

T cell immunoglobulin and mucin domain 3 (Tim3) is a negative regulatory molecule that inhibits effector T_H1-type responses. Such inhibitory signals prevent unintended tissue inflammation, but can be detrimental if they lead to premature T cell exhaustion. Although the role of Tim3 in autoimmunity has been extensively studied, whether Tim3 regulates antimicrobial immunity has not been explored. Here, we show that Tim3 expressed on T_H1 cells interacts with its ligand, galectin-9 (Gal9), which is expressed by Mycobacterium tuberculosis–infected macrophages to restrict intracellular bacterial growth. Tim3–Gal9 interaction leads to macrophage activation and stimulates bactericidal activity by inducing caspase-1–dependent IL-1β secretion. We propose that the T_H1 cell surface molecule Tim3 has evolved to inhibit growth of intracellular pathogens via its ligand Gal9, which in turn inhibits expansion of effector T_H1 cells to prevent further tissue inflammation.

Signaling mechanisms involved in altered function of macrophages from diet-induced obese mice affect immune responses

Recent research links diet-induced obesity (DIO) with impaired immunity, although the underlying mechanisms remain unclear. We find that the induction of inducible NO synthase (iNOS) and cytokines is suppressed in mice with DIO and in bone marrow macrophages (BMMPhi) from mice with DIO exposed to an oral pathogen, Porphyromonas gingivalis. BMMPhi from lean mice pre-treated with free fatty acids (FFAs) and exposed to P. gingivalis also exhibit a diminished induction of iNOS and cytokines. BMMPhi from lean and obese mice exposed to P. gingivalis and analyzed by a phosphorylation protein array show a reduction of Akt only in BMMPhi from mice with DIO. This reduction is responsible for diminished NF-kappaB activation and diminished induction of iNOS and cytokines. We next observed that Toll-like receptor 2 (TLR2) is suppressed in BMMPhi from DIO mice whereas carboxy-terminal modulator protein (CTMP), a known suppressor of Akt phosphorylation, is elevated. This elevation stems from defective TLR2 signaling. In BMMPhi from lean mice, both FFAs and TNF-alpha--via separate pathways--induce an increase in CMTP. However, in BMMPhi from DIO mice, TLR2 can no longer inhibit the TNF-alpha-induced increase in CTMP caused by P. gingivalis challenge. This defect can then be restored by transfecting WT TLR2 into BMMPhi from DIO mice. Thus, feeding mice a high-fat diet over time elevates the CTMP intracellular pool, initially via FFAs activating TLR2 and later when the defective TLR2 is unable to inhibit TNF-alpha-induced CTMP. These findings unveil a link between obesity and innate immunity.

Immune and behavioral consequences of microglial reactivity in the aged brain

Bidirectional communication between the immune system and the brain is essential for mounting the appropriate immunological, physiological, and behavioral responses to immune activation. Aging, however, may impair this important bi-directional interaction. In support of this notion, peripheral infection in the elderly is associated with an increased frequency of behavioral and cognitive complications. Recent findings in animal models of aging and neurodegenerative disease indicate that microglia, innate immune cells of the brain, become primed or reactive. Understanding age- and disease-associated alterations in microglia is important because glia (microglia and astrocytes) play an integral role in propagating inflammatory signals that are initiated in the periphery. In this capacity, brain glia produce inflammatory cytokines that target neuronal substrates and elicit a sickness-behavior syndrome that is normally beneficial to the host organism. Increased reactivity of microglia sets the stage for an exaggerated neuroinflammatory cytokine response following activation of the peripheral innate immune system, which may underlie subsequent long-lasting behavioral and cognitive deficits. In support of this premise, recent findings indicate that stimulation of the peripheral immune system in aged rodents causes exaggerated neuroinflammation that is paralleled by cognitive impairment, prolonged sickness, and depressive-like complications. Therefore, the purpose of this review is to discuss the new evidence that age-associated priming of microglia could play a pathophysiological role in exaggerated behavioral and cognitive sequelae to peripheral infection.

Stimulatory and suppressive signal transduction regulates vasoactive intestinal peptide receptor-1 (VPAC-1) in primary mouse CD4 T cells

Vasoactive intestinal peptide receptor-1 (VPAC-1) is an anti-proliferative, G-protein coupled receptor that is highly expressed on naïve T cells, and has been reported to be downregulated upon T cell activation. The T cell signaling molecules involved in mediating low VPAC-1 levels have not been identified. Therefore, to gain a greater understanding into this regulation, this study investigated the signaling pathways that regulate (VPAC-1) in murine, primary CD4 T cells. To this end, murine, splenic CD4 T cells were pretreated separately with 10 different pharmacological inhibitors and incubated +/- anti-CD3 for 24h. Total RNA was isolated, and VPAC-1 mRNA levels were measured by qPCR. Our results support that JNK kinases, downstream from the protein kinase, Zap70, are involved in suppressive regulation of VPAC-1 steady-state mRNA levels after anti-CD3 treatment. In contrast, inhibitors against PKC, ERK, p38, Zap70 and Rac1 supported a stimulatory influence in VPAC-1 regulation in the absence of T cell signaling. By studying the signaling pathways that regulate VPAC-1 in T cells, we can gain greater insight into the role of this anti-inflammatory receptor in autoimmunity and infectious diseases.

Evidence that age-related changes in p38 MAP kinase contribute to the decreased steroid production by the adrenocortical cells from old rats

The current studies were initiated to investigate whether excessive oxidative stress exerts its antisteroidogenic action through modulation of oxidant-sensitive mitogen-activated protein kinase (MAPK) signaling pathways. Western blot analysis indicated that aging caused increased phosphorylation and activation of rat adrenal p38 MAPK, but not the ERK1/2 or JNK1/2. Lipid peroxidation measurements (an index of cellular oxidative stress) indicated that adrenal membranes from young animals contained only minimal levels of endogenous thiobarbituric acid-reactive substances (TBARS), and exposure of membranes to enzymatic and non-enzymatic pro-oxidants enhanced TBARS formation approximately 12- and 20-fold, respectively. The adrenal membranes from old animals showed much more susceptibility to lipid peroxidation and exhibited roughly 4- to 6-fold higher TBARS formation than young controls both under basal conditions and in response to pro-oxidants. Qualitatively similar results were obtained when lipid peroxide formation was measured using a sensitive FOXRS (ferrous oxidation-xylenol orange-reactive substances) technique. We next tested whether aging-induced excessive oxidative insult alters steroidogenesis through modulation of MAPK signaling pathway. Treatment of adrenocortical cells from old rats with specific p38 MAPK inhibitors restored Bt(2)cAMP-stimulated steroidogenesis approximately 60-70% of the value seen in cells of young animals. Likewise, pretreatment of cells with reactive oxygen species (ROS) scavengers MnTMPyP and N-acetyl cysteine also partially rescued age-induced loss of steroid production. In contrast, simultaneous treatment of cells with ROS scavengers and p38 MAPK inhibitor did not produce any additional effect suggesting that both types of inhibitors exert their stimulatory action through inhibition of p38 MAPK activation. Collectively, these results indicate that p38 MAPK functions as a signaling effector in oxidative stress-induced inhibition of steroidogenesis during aging.

Cx43 hemichannels and gap junction channels in astrocytes are regulated oppositely by proinflammatory cytokines released from activated microglia

Astrocytes have a role in maintaining normal neuronal functions, some of which depend on connexins, protein subunits of gap junction channels and hemichannels. Under inflammatory conditions, microglia release cytokines, including interleukin-1beta and tumor necrosis factor-alpha, that reduce intercellular communication via gap junctions. Now, we demonstrate that either conditioned medium harvested from activated microglia or a mixture of these two cytokines enhances the cellular exchange with the extracellular milieu via Cx43 hemichannels. These changes in membrane permeability were not detected in astrocytes cultured from Cx43 knock-out mice and were abrogated by connexin hemichannel blockers, including La3+, mimetic peptides, and niflumic acid. Both the reduction in gap junctional communication and the increase in membrane permeability were mediated by a p38 mitogen-activated protein kinase-dependent pathway. However, the increase in membrane permeability, but not the gap junction inhibition, was rapidly reversed by the sulfhydryl reducing agent dithiothreitol, indicating that final regulatory mechanisms are different. Treatment with proinflammatory cytokines reduced the total and cell surface Cx43 levels, suggesting that the increase in membrane permeability was attributable to an increase in hemichannels activity. Indeed, unitary events of approximately 220 pS corresponding to Cx43 hemichannels were much more frequent in astrocytes treated with microglia conditioned medium than under control conditions. Finally, the effect of cytokines enhanced the uptake and reduced the intercellular diffusion of glucose, which might explain changes in the metabolic status of astrocytes under inflammatory conditions. Accordingly, this opposite regulation may affect glucose trafficking and certainly will modify the metabolic status of astrocytes involved in brain inflammation.

Lipopolysaccharide-stimulated RAW 264.7 macrophage inducible nitric oxide synthase and nitric oxide production is decreased by an omega-3 fatty acid lipid emulsion

BACKGROUND

Omega-3 fatty acids (omega-3 FA) have been demonstrated to have anti-inflammatory properties, postulated to occur through several principal mechanisms, including (1) displacement of arachidonic acid from the cellular membrane; (2) shifting of prostaglandin E(2) and leukotriene B(4) production; and (3) molecular level alterations including decreased activation of nuclear factor kappa B and activator protein-1. An additional regulator that is likely associated is the production of nitric oxide (NO) by nitric oxide synthetase. NO is a short-lived free radical involved in many biological functions. However, excessive NO production can lead to complications, suggesting that decreased NO production is a potential target for some inflammatory diseases. We hypothesized that pretreating with an omega-3 FA lipid emulsion would decrease the production of NO in macrophages and that this effect would occur through alterations in inducible nitric oxide synthetase (iNOS).

MATERIALS AND METHODS

Greiss reagent was used to assess NO production in RAW 264.7 macrophages following omega-3 or omega-6 FA treatment alone or in combination with lipopolysaccharide (LPS) stimulation for 12 h/24 h. iNOS levels were determined by Western blot. Tumor necrosis factor-alpha levels were determined by enzyme-linked immunosorbent assay.

RESULTS

Following LPS-stimulation, omega-3 FA pretreatment at 12 and 24 h produced significantly less NO (P < 0.05) compared to omega-6 FA or media-only conditions. omega-3 FA pretreatment at 12 and 24 h also had less iNOS protein expression compared to omega-6 FA or media-only conditions. Tumor necrosis factor-alpha production was significantly decreased with omega-3 FA treatment compared to omega-6 FA treatment (P < 0.05) after 24 h LPS stimulation.

CONCLUSION

These experiments demonstrate that, in addition to other anti-inflammatory effects, omega-3 FA lipid emulsions also significantly lower NO production in LPS-stimulated macrophages through altered iNOS protein expression.

Jak2 dampens the induction by IL-1beta of prostaglandin endoperoxide H synthase 2 expression in human orbital fibroblasts: evidence for divergent influence on the prostaglandin E2 biosynthetic pathway

Prostaglandin endoperoxide H synthase 2 (PGHS-2) catalyzes the rate-limiting steps in the synthesis of PGE(2). It is substantially but transiently induced in human orbital fibroblasts treated with IL-1beta. In this study, we report that the induction of PGHS-2 by IL-1beta is dramatically enhanced and prolonged when Jak2 signaling is abrogated, either with the specific inhibitor AG490 or by transiently transfecting fibroblasts with a dominant negative mutant Jak2. Attenuating Jak2 increases PGHS-2 steady-state mRNA levels, a consequence of increased gene transcription and mRNA survival in IL-1beta-treated cultures. Surprisingly, interrupting Jak2 function also blocked the expected increase in PGE(2) synthesis usually provoked by IL-1beta. This resulted from the rapid loss of IL-1beta-dependent arachidonate release and by attenuation of group IIA secreted PLA(2) (sPLA(2)) gene induction. Supplying Jak2-compromised cultures with exogenous arachidonate failed to increase PGE(2) production in response to IL-1beta until cells were mechanically disrupted. However, transiently transfecting them with wild-type sPLA(2) fully restored prostanoid production to anticipated levels. sPLA(2) expression following transfection resulted in increased IL-1beta-dependent PGHS-2 and microsomal PGE(2) synthase levels. Thus, sPLA(2) plays important roles in PGE(2) synthesis in addition to its release of arachidonate. Our findings suggest that Jak2 ordinarily dampens and limits the duration of the PGHS-2 induction by IL-1beta. Moreover, it is required for IL-1beta-dependent signaling to sPLA(2), the expression and activity of which are necessary for up-regulating PGE(2) synthesis in orbital fibroblasts.

Differential effects of anti-IL-1R accessory protein antibodies on IL-1alpha or IL-1beta-induced production of PGE(2) and IL-6 from 3T3-L1 cells

Soluble or cell-bound IL-1 receptor accessory protein (IL-1RAcP) does not bind IL-1 but rather forms a complex with IL-1 and IL-1 receptor type I (IL-1RI) resulting in signal transduction. Synthetic peptides to various regions in the Ig-like domains of IL-1RAcP were used to produce antibodies and these antibodies were affinity-purified using the respective antigens. An anti-peptide-4 antibody which targets domain III inhibited 70% of IL-1beta-induced productions of IL-6 and PGE(2) from 3T3-L1 cells. Anti-peptide-2 or 3 also inhibited IL-1-induced IL-6 production by 30%. However, anti-peptide-1 which is directed against domain I had no effect. The antibody was more effective against IL-1beta compared to IL-1alpha. IL-1-induced IL-6 production was augmented by coincubation with PGE(2). The COX inhibitor ibuprofen blocked IL-1-induced IL-6 and PGE(2) production. These results confirm that IL-1RAcP is essential for IL-1 signaling and that increased production of IL-6 by IL-1 needs the co-induction of PGE(2). However, the effect of PGE(2) is independent of expressions of IL-1RI and IL-1RAcP. Our data suggest that domain III of IL-1RAcP may be involved in the formation or stabilization of the IL-1RI/IL-1 complex by binding to epitopes on domain III of the IL-1RI created following IL-1 binding to the IL-1RI.

Attenuation of iNOS in an LPS-stimulated macrophage model by omega-3 fatty acids is independent of COX-2 derived PGE2

BACKGROUND

Omega-3 fatty acids (n-3 FA) demonstrate significant anti-inflammatory properties thought to occur through three principal mechanisms; (1) displacement of arachidonic acid from the cellular membrane, (2) differential prostaglandin E2 (PGE2) and LTB4 production, and (3) molecular level alterations such as diminished nuclear factor kappa B and AP-1 activation. Recently, n-3 FA have been demonstrated to significantly decrease nitric oxide (NO) production in a lipopolysaccharide (LPS)-stimulated M Phi model. We hypothesized that decreased NO production by n-3 FA occurs through inhibition of cyclooxygenase-2 (COX-2) derived PGE2 and that repletion of the system with PGE2 would obliterate these effects. Selective COX-2 inhibitor (L-748,731) experiments and separate PGE2 repletion studies were used to test this hypothesis.

METHODS

NO production was assessed following 24 h with or without LPS/PGE2 in the presence of n-3 FA, L-748,731 (a selective COX-2 inhibitor), or combination (n-3 FA + L-748,731) treatment. Western blots were used to assess inducible NO synthase protein expression.

RESULTS

Independently or in the presence of LPS, treatment with a COX-2 inhibitor significantly increased NO production compared with control, n-3 FA, and combination treatment. NO production in combination treatment is slightly increased compared to n-3 FA treatment. In control cells treated with LPS, PGE2 repletion resulted in a significant decrease in NO. All other treatment groups repleted with PGE2 demonstrated no significant alterations in NO production. Inducible NO synthase protein expression levels were similar to NO production across all treatments.

CONCLUSION

These experiments disproved our original hypothesis that the decrease in NO production associated with n-3 FA treatment occurs through a COX-2 derived PGE2 dependent mechanism. Eliminating COX-2 derived PGE2 by a selective inhibitor actually increased NO production. Exogenous PGE2 repletion did not restore the system. Therefore, mechanisms other than n-3 FA associated alterations in COX-2 derived PGE2 are likely involved in decreasing NO production in LPS stimulated M Phi.

Inhibition of p38 mitogen-activated protein kinase enhances c-Jun N-terminal kinase activity: implication in inducible nitric oxide synthase expression

Background

Nitric oxide (NO) is an inflammatory mediator, which acts as a cytotoxic agent and modulates immune responses and inflammation. p38 mitogen-activated protein kinase (MAPK) signal transduction pathway is activated by chemical and physical stress and regulates immune responses. Previous studies have shown that p38 MAPK pathway regulates NO production induced by inflammatory stimuli. The aim of the present study was to investigate the mechanisms involved in the regulation of inducible NO synthesis by p38 MAPK pathway.

Results

p38 MAPK inhibitors SB203580 and SB220025 stimulated lipopolysaccharide (LPS)-induced inducible nitric oxide synthase (iNOS) expression and NO production in J774.2 murine macrophages. Increased iNOS mRNA expression was associated with reduced degradation of iNOS mRNA. Treatment with SB220025 increased also LPS-induced c-Jun N-terminal kinase (JNK) activity. Interestingly, JNK inhibitor SP600125 reversed the effect of SB220025 on LPS-induced iNOS mRNA expression and NO production.

Conclusion

The results suggest that inhibition of p38 MAPK by SB220025 results in increased JNK activity, which leads to stabilisation of iNOS mRNA, to enhanced iNOS expression and to increased NO production.

Up-regulation of glomerular COX-2 by angiotensin II: role of reactive oxygen species

BACKGROUND

Prostaglandins such as prostaglandin E(2) (PGE(2)) and prostaglandin I(2) (PGI(2)) counteract the angiotensin II (Ang II)-induced vasoconstriction in the glomerular microcirculation. We have shown that Ang II promotes mesangial cell hypertrophy via reactive oxygen species (ROS), which originate from nicotinamide adenine dinucleotide phosphate and its reduced form (NADH/NADPH) oxidase. It has been reported that conditions associated with activation of the renin-angiotensin system result in increased glomerular cyclooxygenase-2 (COX-2) expression and activity.

METHODS

We designed studies to determine (1) whether Ang II induces COX-2 in the glomerulus in vivo in the glomerulus as well as in vitro in mesangial cells, (2) whether ROS originated from Ang II are involved, and (3) whether COX-2-derived prostaglandins modulate the growth promoting effects of Ang II in mesangial cells. Rats were infused with Ang II (0.7 mg/kg/day) for 5 days and glomerular COX-2 expression and activity assessed in isolated glomeruli.

RESULTS

Ang II increased glomerular PGE(2) production (100%) accompanied by a concomitant increase in glomerular COX-2 expression at the mRNA (1.7-fold) and protein level (sixfold). In mesangial cells, Ang II significantly increased mesangial cell PGE(2) (200%) and PGI(2) (100%) production as well as COX-2 mRNA that was prevented by the angiotensin type 1 (AT1) receptor blocker irbesartan and the COX-2 inhibitor NS-398. The NADPH oxidase inhibitor diphenyleneiodonium (DPI), the ROS scavenger tiron as well as catalase, inhibited Ang II-induced PGE(2) production suggesting that Ang II-induced ROS mediate COX-2 up-regulation. Strikingly, COX-2 inhibition as well as blockade of the type 1 PGE(2) receptor (EP1) prevented Ang II-induced mesangial cell hypertrophy suggesting that COX-2-derived prostaglandins, and specifically PGE(2), importantly contribute to the growth promoting effects of Ang II.

CONCLUSION

These studies suggest that blockade of specific PGE(2) receptors may be a novel strategy to modulate the pathologic effects of COX-2-derived prostaglandins without simultaneously affecting protective vasodilatory mechanisms.

Src activation of NF-kappaB augments IL-1beta-induced nitric oxide production in mesangial cells

NF-kappaB is a critical transcription factor that is involved in glomerulonephritis and inflammatory host responses and a critical transactivator of the inducible nitric oxide (NO) synthase gene in mesangial cells. The Src protein tyrosine kinases (SFK) are involved in several signaling pathways and have been proposed to mediate cytokine activation of NF-kappaB in a few cell types. However, the specific involvement of SFK in IL-1beta induction of NO production has not been clearly established. Accordingly, pharmacologic and molecular tools were used to clarify this issue in cultured murine mesangial cells. The SFK antagonist 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo(3,4-d)pyrimidine (PP2) dramatically inhibited IL-1beta-mediated induction of endogenous NO production as measured by the Griess reaction, as well as the induction of NF-kappaB p50/p65 DNA-binding activity in gel shift assays and the activity of an NF-kappaB-responsive promoter-reporter construct transiently transfected into the cells. Immunoprecipitation and immunoblotting with anti-IkappaBalpha and anti-phosphotyrosine antibodies revealed that PP2 also inhibited IL-1beta-stimulated tyrosine phosphorylation of IkappaBalpha, a requisite step in NF-kappaB activation in this signaling cascade. In agreement with the pharmacologic inhibition studies, siRNA directed against c-Src specifically limited c-Src protein expression and inhibited IL-1beta-mediated induction of NF-kappaB DNA-binding activity, whereas control siRNA had no effect. Conversely, overexpression of constitutively active c-Src augmented basal and IL-1beta-mediated induction of NF-kappaB DNA-binding activity and NO production. Thus, SFK play a key role in IL-1beta-induced NO production in mesangial cells and do so via tyrosine phosphorylation of IkappaBalpha and consequent NF-kappaB activation.

Inhibition of p38 mitogen-activated protein kinase attenuates interleukin-1beta-induced thermal hyperalgesia and inducible nitric oxide synthase expression in the spinal cord

We have reported recently that intrathecal (i.t.) injection of interleukin-1beta (IL-1beta), at a dose of 100 ng, induces inducible nitric oxide synthase (iNOS) expression and nitric oxide (NO) production in the spinal cord and results in thermal hyperalgesia in rats. This study further examines the role of mitogen-activated protein kinase (MAPK) in i.t. IL-1beta-mediated iNOS-NO cascade in spinal nociceptive signal transduction. All rats were implanted with an i.t. catheter either with or without an additional microdialysis probe. Paw withdrawal latency to radiant heat is used to assess thermal hyperalgesia. The iNOS and MAPK protein expression in the spinal cord dorsal horn were examined by western blot. The [NO] in CSF dialysates were also measured. Intrathecal IL-1beta leads to a time-dependent up-regulation of phosphorylated p38 (p-p38) MAPK protein expression in the spinal cord 30-240 min following IL-1beta injection (i.t.). However, neither the phosphorylated extracellular signal-regulated kinase (p-ERK) nor phosphorylated c-Jun NH2-terminal kinase (p-JNK) was affected. The total amount of p38, ERK, and JNK MAPK proteins were not affected following IL-1beta injection. Intrathecal administration of either selective p38 MAPK, or JNK, or ERK inhibitor alone did not affect the thermal nociceptive threshold or iNOS protein expression in the spinal cord. However, pretreatment with a p38 MAPK inhibitor significantly reduced the IL-1beta-induced p-p38 MAPK expression by 38-49%, and nearly completely blocked the subsequent iNOS expression (reduction by 86.6%), NO production, and thermal hyperalgesia. In contrast, both ERK and JNK inhibitor pretreatments only partially (approximately 50%) inhibited the IL-1beta-induced iNOS expression in the spinal cord. Our results suggest that p38 MAPK plays a pivotal role in i.t. IL-1beta-induced spinal sensitization and nociceptive signal transduction.

Prostacyclin signaling in the kidney: implications for health and disease

The balance between vasodilator and vasoconstrictor pathways is key to the maintenance of homeostasis and the outcome of disease. In the kidney, prostaglandins (PGs) uphold this balance and regulate renal function: hemodynamics, renin secretion, growth responses, tubular transport processes, and cell fate. With the advent of cyclooxygenase (COX)-2-selective inhibitors, targeted deletions in mice (COX knockouts, PG receptor knockouts), and the discovery of intracrine signaling options for PGs (peroxisome proliferator-activated receptors and perinuclear PGE2receptors: EP1,3,4), many advances have been made in the study of arachidonic acid metabolites. Although prostacyclin (PGI2) is a major product of the COX pathway, there is very little emphasis on its importance to the kidney. This review will discuss PGI2biology and its relevance to different aspects of renal disease (growth, fibrosis, apoptosis), highlighting the most significant research from the past decade of PGI2literature, what we have learned from other organ systems, while stressing the significance of cross talk between various PGI2signaling pathways and its implications for renal health and disease.

Inflammation-associated gene expression is altered between normal human ovarian surface epithelial cells and cell lines derived from ovarian adenocarcinomas

Ovulation is believed to contribute to the development of ovarian cancers that derive from the ovarian surface epithelium (OSE). The process of ovulation is synonymous with inflammation and inflammatory cytokines such as interleukin-1α (IL-1α) have recently been shown to induce both inflammatory and anti-inflammatory responses in human OSE (HOSE) cells. In this study we directly compared levels of IL-1α-induced gene expression by analysing the levels of 11β-hydroxysteroid dehydrogenase (11βHSD) types 1 (11βHSD-1) and 2 (11βHSD-2), cyclooxygenase-2 (COX-2), IL-1 receptor (IL-1R) and glucocorticoid receptor α (GRα) mRNA between normal HOSE cells and cell lines derived from poorly differentiated (SKOV-3, BG-1, PEO-4) and well-differentiated (PEO-14) ovarian adenocarcinoma. In HOSE cell cultures, and to a lesser extent PEO-14 cells, the basal mRNA levels of COX-2 and 11βHSD-1 were relatively high and further shown to be induced in response to IL-1α (for HOSE cells; >20-fold, P<0.05 and PEO-14 cells; >3fold, P<0.05). However, whereas HOSE cells expressed a low level of 11βHSD-2 mRNA that was only mildly responsive to IL-1α (1.3-fold, P<0.001), all cell lines exhibited a higher basal level of 11βHSD-2 mRNA that was in some cases further stimulated in PEO-4 cells (five-fold; P<0.05) or suppressed in SKOV-3 cells (two-fold; P<0.01) in response to IL-1α. All cells tested expressed IL-1R and, with the exception of BG-1, GRα. These results indicate that cell lines derived from ovarian cancers have lost the ability to respond normally to inflammatory cytokines such as IL-1α. The finding that normal OSE cells, in contrast to cell lines derived from patients with ovarian adenocarcinoma, abundantly express 11βHSD-1 mRNA but are essentially devoid of 11βHSD-2 mRNA supports the concept that the pattern of 11βHSD isoform gene expression is a defining feature of neoplastic cellular transformation, which might have particular relevance to the ovary.

Effects of naltrexone on lipopolysaccharide-induced sepsis in rats

Naltrexone, an opioid antagonist, has been reported to possess an anti-inflammatory effect via blockade of opioid receptor. The aim of this study is to evaluate the protective effect of naltrexone on LPS-induced septic shock in rats. Sepsis was induced by administration of LPS (10 mg/kg, i.v.) in anesthetized rats. Results demonstrated that pretreatment with naltrexone (10 mg/kg, i.v.) significantly ameliorated hypotension and bradycardia of rats 6 h after LPS administration. In isolated blood vessel, study showed that pretreatment with naltrexone significantly improved norepinephrine-induced vasoconstriction and ACh-induced vasorelaxation in aorta of endotoxemic animals. Naltrexone significantly reduced the elevation of serum glutamate-oxalacetate transaminase and glutamate-pyruvate transaminase (as index of hepatic function) induced by LPS. The infiltration of polymorphonuclear neutrophils into liver 48 h after LPS treatment in mice was also reduced by naltrexone. On the other hand, naltrexone significantly decreased the levels of plasma TNF-alpha and inhibited overproduction of superoxide anions in aortic rings. However, naltrexone did not suppress the overproduction of NO (measured by its metabolites nitrite/nitrate in plasma) and iNOS expression in lungs induced by LPS. In in vitro study, naltrexone did not attenuate non-enzymatic iron-induced lipid peroxidation in rat brain homogenates. In conclusion, pretreatment with naltrexone significantly improved circulatory failure and hepatic dysfunction in sepsis. These effects were associated with reduction of TNF-alpha levels and superoxide anion formation, which may be attributed to antagonism of opioid receptors.

Effects of RWJ 67657, a p38 mitogen activated protein kinase (MAPK) inhibitor, on the production of inflammatory mediators by rheumatoid synovial fibroblasts

OBJECTIVE

To investigate the effect of the p38 mitogen activated protein kinase (MAPK) inhibitor RWJ 67657 on inflammatory mediator production by rheumatoid synovial fibroblasts (RSF).

METHODS

RSF were pretreated with RWJ 67657 and stimulated with TNF alpha and/or IL-1 beta. Protein levels and mRNA expression of MMP-1, MMP-3, TIMP-1, IL-6, and IL-8 were determined, as was mRNA expression of COX-2 and ADAMTS-4.

RESULTS

MMP-3 production was significantly inhibited at 1 microM RWJ 67657 and MMP-1 production at 10 microM, while TIMP-1 production was not inhibited. Inhibition of IL-6 and IL-8 protein production was seen at 0.1 microM RWJ 67657. Expression profiles of mRNA were in accordance with protein production. Inhibition of COX-2 mRNA expression occurred at 0.01 microM RWJ 67657.

CONCLUSIONS

RWJ 67657 inhibits major proinflammatory mediator production in stimulated RSF at pharmacologically relevant concentrations. These findings could have important relevance for the treatment of rheumatoid arthritis.

Hypermethylation of the inducible nitric-oxide synthase gene promoter inhibits its transcription

Exuberant generation of nitric oxide (NO) by inducible nitric-oxide synthase (iNOS) can cause unintended injury to host cells during glomerulonephritis and other inflammatory diseases. Although much is known about the mechanisms of iNOS induction, few transcriptional repression mechanisms have been found. We explored the role of cytosine methylation in the regulation of iNOS transcription. Treatment of mesangial cells with DNA methylation inhibitors augmented cytokine induction of endogenous NO production and iNOS protein levels, as well as iNOS promoter activity. In a corresponding manner, in vitro methylation of the murine iNOS promoter was sufficient to silence its activity in mesangial cells. In contrast, antisense knockdown of DNA methyltransferase-3b expression and activity increased iNOS promoter activity and nitrite production. Bisulfite treatment and sequencing analysis of the iNOS promoter identified methylation of cytosines framing an enhancer element at -879/-871. In vitro methylation inhibited binding of NFkappaB p50 to this element, and deletion of the element resulted in relief of transcriptional repression. These results provide evidence for a unique molecular mechanism involved in transcriptional regulation of iNOS gene expression.

Differential effects of TGF-β1 and BMP-4 on the hypoxic induction of cyclooxygenase-2 in human pulmonary artery smooth muscle cells

Chronic hypoxia-induced pulmonary hypertension results partly from proliferation of smooth muscle cells in small peripheral pulmonary arteries. Previously, we demonstrated that hypoxia modulates the proliferation of human peripheral pulmonary artery smooth muscle cells (PASMCs) by induction of cyclooxygenase-2 (COX-2) and production of antiproliferative prostaglandins ( 55 ). The transforming growth factor (TGF)-β superfamily plays a critical role in the regulation of pulmonary vascular remodeling, although to date an interaction with hypoxia has not been examined. We therefore investigated the pathways involved in the hypoxic induction of COX-2 in peripheral PASMCs and the contribution of TGF-β1 and bone morphogenetic protein (BMP)-4 in this response. In the present study, we demonstrate that hypoxia induces activation of p38MAPK, ERK1/2, and Akt in PASMCs and that these pathways are involved in the hypoxic regulation of COX-2. Whereas inhibition of p38MAPKor ERK1/2 activity suppressed hypoxic induction of COX-2, inhibition of the phosphoinositide 3-kinase pathway enhanced hypoxic induction of COX-2. Furthermore, exogenous TGF-β1 induced COX-2 mRNA and protein expression, and our findings demonstrate that release of TGF-β1 by PASMCs during hypoxia contributes to the hypoxic induction of COX-2 via the p38MAPKpathway. In contrast, BMP-4 inhibited the hypoxic induction of COX-2 by an MAPK-independent pathway. Together, these findings suggest that the TGF-β superfamily is part of an autocrine/paracrine system involved in the regulation of COX-2 expression in the distal pulmonary circulation, and this modulates hypoxia-induced pulmonary vascular cell proliferation.

Altered processing of the amyloid precursor protein and decreased expression of ADAM 10 by chronic hypoxia in SH-SY5Y: no role for the stress-activated JNK and p38 signalling pathways

Clinical studies suggest that the incidence of Alzheimer's disease (AD) is increased following an ischaemic or hypoxic episode, such as stroke. Furthermore, levels of the AD-associated amyloid beta-peptides (Abeta) and the amyloid precursor protein (APP) are enhanced in experimental ischaemia. In our previous study [Webster, N.J., Green, K.N., Peers, C., Vaughan, P.F., Altered processing of amyloid precursor protein in the human neuroblastoma SH-SY5Y by chronic hypoxia, J. Neurochem., 83 (2002) 1262-1271] we reported that exposing cells of neuronal origin to a period of chronic hypoxia (CH; 2.5% O(2), 24 h) led to a decrease in processing of the amyloid precursor protein (APP) by the alternative and neuroprotective alpha-secretase pathway. In SH-SY5Y cells, the most likely mechanism was that CH inhibits the protein level of ADAM 10, a disintegrin metalloprotease widely believed to be the alpha-secretase. One effect of CH is to alter the activity of the stress-activated protein kinases (SAPKs) c-Jun amino terminal kinase (JNK) and p38. Thus, the main aims of this study were to investigate the effect of CH on (1) the activity of these SAPKs in SH-SY5Y and (2) whether changes in the activity of these kinases may account for the CH-induced decreases in ADAM 10 expression and sAPPalpha secretion. We demonstrated that the phosphorylation (activity) of JNK was decreased approximately 50% following a period of CH. An inhibitor of JNK did not mimic the effects of CH on either ADAM 10 expression or sAPPalpha secretion under conditions in which the phosphorylation of c-Jun was inhibited by approximately 80%. Thus the loss of JNK activity does not appear to be linked to the decrease in expression of ADAM 10 and secretion of sAPPalpha. In contrast, phosphorylation (activity) of p38 was enhanced approximately 300% following a period of CH. However, inhibitors of p38 were unable to reverse the loss of sAPPalpha in CH cells, indicating that this increase in activity was not linked to the altered processing of APP.

Bacterial DNA induced iNOS expression through MyD88-p38 MAP kinase in mouse primary cultured glial cells

To study the role of bacterial DNA in the immune function of the brain, we examined the effect of CpG-DNA on the inducible nitric oxide synthase (iNOS) expression in mouse primary cultured glial cells. The expression of Toll-like receptor 9 (TLR9), the receptor of bacterial DNA, was detected by RT-PCR. We observed an increase in iNOS mRNA 6 h after CpG-DNA application. The expression of iNOS protein peaked at 12 h and declined thereafter. CpG-DNA increased p38 mitogen-activated protein kinase (MAPK) activation in primary cultured glial cells. SB203580, a specific inhibitor of p38 MAP kinase, inhibited the CpG-DNA-induced iNOS expression. Moreover, CpG-DNA failed to activate p38 MAP kinase and iNOS induction in the primary cultured glial cells prepared from myeloid differentiation factor 88 (MyD88) deficient mice. Therefore, it is suggested that functional receptor for bacterial DNA exists in primary cultured glial cells and CpG-DNA induces iNOS expression via the MyD88-p38 MAP kinase-dependent mechanisms. Thus, the present results point to the important role of bacterial DNA by acting on glial cells to operate brain immune function.

Regulation of inducible nitric oxide synthase expression in advanced glycation end product-stimulated raw 264.7 cells: the role of heme oxygenase-1 and endogenous nitric oxide

Advanced glycation end products (AGEs) are closely linked to the development of diabetic atherosclerosis. The current study examines the induction of inducible nitric oxide (NO) synthase (iNOS) and heme oxygenase (HO)-1 expression by AGEs, as well as the signaling pathways involved and the interplay between these two enzymes. The stimulation of RAW 264.7 cells with 6.64 or 33.2 microg/ml AGEs leads to HO-1 protein expression, iNOS protein expression, and nitrite accumulation. AGEs lead to the phosphorylation of p42/44 and p38 mitogen-activated protein kinase (MAPK). The inhibition of p42/44 MAPK and protein kinase C prevented, whereas inhibition of p38 MAPK augmented, AGE-induced nitrite release and iNOS expression. In contrast, HO-1 expression was downregulated by inhibition of p38 MAPK. Furthermore, the expression of both proteins was prevented by coincubation with acetovanillone (NADPH oxidase inhibitor). AGE-induced iNOS expression was negatively regulated by stimulation of HO-1 expression with cadmium chloride or endogenous NO. Tin-protoporphyrin IX (HO-1 inhibitor) partially reversed the cadmium chloride-mediated downregulation of iNOS expression. The current study demonstrates that multiple signaling molecules are involved in AGE-stimulated iNOS and HO-1 expression. There also exists a downregulation of iNOS by its own product as well as the products of HO-1.

Interleukin-1β stimulates IL-8 expression through MAP kinase and ROS signaling in human gastric carcinoma cells

Recent studies have suggested that the expression of interleukin-8 (IL-8) directly correlates with the vascularity of human gastric carcinomas. In this study, the effect of IL-1beta on IL-8 expression in human gastric cancer TMK-1 cells and the underlying signal transduction pathways were investigated. IL-1beta induced the IL-8 expression in a time- and concentration-dependent manner. IL-1beta induced the activation of extracellular signal-regulated kinases-1/2 and P38 mitogen-activated protein kinase (MAPK), but not the activation of c-jun amino-terminal kinse and Akt. Specific inhibitors of MEK-1 (PD980590) and P38 MAPK (SB203580) were found to suppress the IL-8 expression and the IL-8 promoter activity. Expression of vectors encoding a mutated-type MEK-1 and P38 MAPK resulted in decrease in the IL-8 promoter activity. IL-1beta also induced the production of reactive oxygen species (ROS). N-acetyl cysteine (NAC) prevented the IL-1beta-induced ROS production and IL-8 expression. In addition, exogenous H2O2 could induce the IL-8 expression. Deletional and site-directed mutagenesis studies on the IL-8 promoter revealed that activator protein-1 (AP-1) and nuclear factor (NF)-kappaB sites were required for the IL-1beta-induced IL-8 transcription. Electrophoretic mobility shift assay confirmed that IL-1beta increased the DNA-binding activity of AP-1 and NF-kappaB. Inhibitor (PD980590, SB203580) and ROS scavenger (NAC) studies revealed that the upstream signalings for the transcription factors AP-1 and NF-kappaB were MAPK and ROS, respectively. Conditioned media from the TMK-1 cells pretreated with IL-1beta could remarkably stimulate the in vitro growth of HUVEC and this effect was partially abrogated by IL-8-neutralizing antibodies. The above results suggest that MAPK-AP-1 and ROS-NF-kappaB signaling pathways are involved in the IL-1beta-induced IL-8 expression and that these paracrine signaling pathways induce endothelial cell proliferation.