Thrombin induces interleukin-6 expression through the cAMP response element in vascular smooth muscle cells

An Emerging Role for Type I Interferons as Critical Regulators of Blood Coagulation

Type I interferons (IFNs) are central mediators of anti-viral and anti-bacterial host defence. Detection of microbes by innate immune cells via pattern recognition receptors (PRRs), including Toll-like receptors (TLRs) and cGAS-STING, induces the expression of type I IFN-stimulated genes. Primarily comprising the cytokines IFN-α and IFN-β, type I IFNs act via the type I IFN receptor in an autocrine or exocrine manner to orchestrate rapid and diverse innate immune responses. Growing evidence pinpoints type I IFN signalling as a fulcrum that not only induces blood coagulation as a core feature of the inflammatory response but is also activated by components of the coagulation cascade. In this review, we describe in detail recent studies identifying the type I IFN pathway as a modulator of vascular function and thrombosis. In addition, we profile discoveries showing that thrombin signalling via protease-activated receptors (PARs), which can synergize with TLRs, regulates the host response to infection via induction of type I IFN signalling. Thus, type I IFNs can have both protective (via maintenance of haemostasis) and pathological (facilitating thrombosis) effects on inflammation and coagulation signalling. These can manifest as an increased risk of thrombotic complications in infection and in type I interferonopathies such as systemic lupus erythematosus (SLE) and STING-associated vasculopathy with onset in infancy (SAVI). We also consider the effects on coagulation of recombinant type I IFN therapies in the clinic and discuss pharmacological regulation of type I IFN signalling as a potential mechanism by which aberrant coagulation and thrombosis may be treated therapeutically.

Erlotinib overcomes paclitaxel-resistant cancer stem cells by blocking the EGFR-CREB/GRβ-IL-6 axis in MUC1-positive cervical cancer

Cancer stem cells (CSCs) are often enriched after chemotherapy and contribute to tumor relapse. While epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are widely used for the treatment of diverse types of cancer, whether EGFR-TKIs are effective against chemoresistant CSCs in cervical cancer is largely unknown. Here, we reveal that EGFR correlates with reduced disease-free survival in cervical cancer patients with chemotherapy. Erlotinib, an EGFR-TKI, effectively impedes CSCs enrichment in paclitaxel-resistant cells through inhibiting IL-6. In this context, MUC1 induces CSCs enrichment in paclitaxel-resistant cells via activation of EGFR, which directly enhances IL-6 transcription through cAMP response element-binding protein (CREB) and glucocorticoid receptor β (GRβ). Treatment with erlotinib sensitizes CSCs to paclitaxel therapy both in vitro and in vivo. More importantly, positive correlations between the expressions of MUC1, EGFR, and IL-6 were found in 20 cervical cancer patients after chemotherapy. Mining TCGA data sets also uncovered the expressions of MUC1-EGFR-IL-6 correlates with poor disease-free survival in chemo-treated cervical cancer patients. Collectively, our work has demonstrated that the MUC1-EGFR-CREB/GRβ axis stimulates IL-6 expression to induce CSCs enrichment and importantly, this effect can be abrogated by erlotinib, uncovering a novel strategy to treat paclitaxel-resistant cervical cancer.

Benzo[a]pyrene activates interleukin-6 induction and suppresses nitric oxide-induced apoptosis in rat vascular smooth muscle cells

Benzo[a]pyrene, a ubiquitous environmental pollutant, has been suggested to be capable of initiating and/or accelerating atherosclerosis. Accumulation of vascular smooth muscle cells (VSMCs) in vessel intima is a hallmark of atherosclerosis. Nitric oxide (NO) can suppress VSMCs proliferation and induce VSMCs apoptosis. NO plays a compensatory role in the vascular lesions to reduce proliferation and/or accelerate apoptosis of VSMCs. The aim of this study was to investigate whether benzo[a]pyrene can affect VSMCs growth and apoptosis induced by NO. Benzo[a]pyrene (1–30 μmol/L) did not affect the cell number and cell cycle distribution in VSMCs under serum deprivation condition. Sodium nitroprusside (SNP), a NO donor, decreased cell viability and induced apoptosis in VSMCs. Benzo[a]pyrene significantly suppressed SNP-induced cell viability reduction and apoptosis. VSMCs cultured in conditioned medium from cells treated with benzo[a]pyrene could also prevent SNP-induced apoptosis. Benzo[a]pyrene was capable of inducing the activation of nuclear factor (NF)-κB and phosphorylation of p38 mitogen-activated protein kinase (MAPK) in VSMCs. Both NF-κB inhibitor and p38 MAPK inhibitor significantly reversed the anti-apoptotic effect of benzo[a]pyrene on SNP-treated VSMCs. Incubation of VSMCs with benzo[a]pyrene significantly and dose-dependently increased interleukin (IL)-6 production. A neutralizing antibody to IL-6 effectively reversed the anti-apoptotic effect of benzo[a]pyrene on SNP-treated VSMCs. Taken together, these results demonstrate for the first time that benzo[a]pyrene activates IL-6 induction and protects VSMCs from NO-induced apoptosis. These findings propose a new mechanism for the atherogenic effect of benzo[a]pyrene.

Transcription factor cAMP response element modulator (Crem) restrains Pdgf-dependent proliferation of vascular smooth muscle cells in mice

Transcription factors of the cAMP response element-binding protein (Creb)/cAMP response element modulator (Crem) family were linked to the switch from a contractile to a proliferating phenotype in vascular smooth muscle cells (VSMCs). Here, we analyzed the vascular function of Crem in mice with a global inactivation of Crem (Crem(-/-)). CRE-mediated transcriptional activity was enhanced in primary Crem(-/-) VSMCs under nonstimulated conditions and under stimulation with Forskolin and platelet-derived growth factor (Pdgf) whereas stimulation with nitric oxide or cGMP showed no effect. This elevated CRE-mediated transcriptional activity as a result of Crem inactivation did not alter aortic contractility or fractions of proliferating or apoptotic aortic VSMCs in situ, and no impact of Crem inactivation on the development of atherosclerotic plaques was observed. Crem(-/-) mice exhibited an increased neointima formation after carotid ligation associated with an increased proliferation of VSMCs in the carotid media. Pdgf-stimulated proliferation of primary aortic Crem(-/-) VSMCs was increased along with an upregulation of messenger RNA (mRNA) levels of Pdgf receptor, alpha polypeptide (Pdgfra), cyclophilin A (Ppia), the regulator of G-protein signaling 5 (Rgs5), and Rho GTPase-activating protein 12 (Arhgap12). Taken together, our data reveal the inhibition of Pdgf-stimulated proliferation of VSMCs by repressing the Pdgf-stimulated CRE-mediated transcriptional activation as the predominant function of Crem in mouse vasculature suggesting an important role of Crem in vasculoproliferative diseases.

Gα(h)/transglutaminase-2 activity is required for maximal activation of adenylylcyclase 8 in human and rat glioma cells

Gα(h) (or transglutaminase-2 (TG2)) is an atypical guanine nucleotide binding-protein that associates with G protein-coupled receptors. TG2 also exerts transglutaminase activity that catalyzes posttranslational protein cross-linking with the formation of ε-(γ-glutamyl) lysine or (γ-glutamyl) polyamine bonds. Here, the role of Gα(h)/TG2 in signal transduction in glial cells was examined in detail. In 1321N1 human astrocytoma cells that lack Gα(h)/TG2, overexpression of Gα(h)/TG2 caused an enhancement of cAMP accumulation stimulated with the β-adrenergic receptor agonist, isoproterenol, or the adenylylcyclase activator, forskolin. This cAMP-enhancement was reversed by the TG2 inhibitor, ERW1069. In rat C6 glioma cells that express endogenous Gα(h)/TG2, cAMP accumulation induced by isoproterenol or forskolin was significantly inhibited by overexpression of Gα(h)/TG2-C277V, a dominant-negative mutant that lacks transglutaminase activity, but was not inhibited by the Gα(h)/TG2-S171E mutant that cannot bind GTP/GDP. These results suggest Gα(h)/TG2 potentiates adenylylcyclase activity by its transglutaminase activity and not by its G-protein activity. Gα(h)/TG2 also increased the activities of the cAMP response element and interleukin-6 promoter, accompanied by an of cAMP in both glioma cells. Since adenylylcyclase 8 plays a major role in cAMP production, we focused on post-translational modification of adenylylcyclase 8 by Gα(h)/TG2. Adenylylcyclase 8 is expressed in both 1321N1 and C6 cells; however, Gα(h)/TG2 affected neither adenylylcyclase 8 expression levels, glycosylation, nor dimerization status. In contrast, pentylamine, a substrate of Gα(h)/TG2, was incorporated into adenylylcyclase 8 in a transglutaminase activity-dependent manner. Taking these results together, Gα(h)/TG2 promotes cAMP production accompanied by a modification of adenylylcyclase 8 in glioma cells.

Lack of bcr and abr promotes hypoxia-induced pulmonary hypertension in mice

BACKGROUND

Bcr and Abr are GTPase activating proteins that specifically downregulate activity of the small GTPase Rac in restricted cell types in vivo. Rac1 is expressed in smooth muscle cells, a critical cell type involved in the pathogenesis of pulmonary hypertension. The molecular mechanisms that underlie hypoxia-associated pulmonary hypertension are not well-defined.

METHODOLOGY/PRINCIPAL FINDINGS

Bcr and abr null mutant mice were compared to wild type controls for the development of pulmonary hypertension after exposure to hypoxia. Also, pulmonary arterial smooth muscle cells from those mice were cultured in hypoxia and examined for proliferation, p38 activation and IL-6 production. Mice lacking Bcr or Abr exposed to hypoxia developed increased right ventricular pressure, hypertrophy and pulmonary vascular remodeling. Perivascular leukocyte infiltration in the lungs was increased, and under hypoxia bcr-/- and abr-/- macrophages generated more reactive oxygen species. Consistent with a contribution of inflammation and oxidative stress in pulmonary hypertension-associated vascular damage, Bcr and Abr-deficient animals showed elevated endothelial leakage after hypoxia exposure. Hypoxia-treated pulmonary arterial smooth muscle cells from Bcr- or Abr-deficient mice also proliferated faster than those of wild type mice. Moreover, activated Rac1, phosphorylated p38 and interleukin 6 were increased in these cells in the absence of Bcr or Abr. Inhibition of Rac1 activation with Z62954982, a novel Rac inhibitor, decreased proliferation, p38 phosphorylation and IL-6 levels in pulmonary arterial smooth muscle cells exposed to hypoxia.

CONCLUSIONS

Bcr and Abr play a critical role in down-regulating hypoxia-induced pulmonary hypertension by deactivating Rac1 and, through this, reducing both oxidative stress generated by leukocytes as well as p38 phosphorylation, IL-6 production and proliferation of pulmonary arterial smooth muscle cells.

Thrombin and vascular inflammation

Vascular endothelium is a key regulator of homeostasis. In physiological conditions it mediates vascular dilatation, prevents platelet adhesion, and inhibits thrombin generation. However, endothelial dysfunction caused by physical injury of the vascular wall, for example during balloon angioplasty, acute or chronic inflammation, such as in atherothrombosis, creates a proinflammatory environment which supports leukocyte transmigration toward inflammatory sites. At the same time, the dysfunction promotes thrombin generation, fibrin deposition, and coagulation. The serine protease thrombin plays a pivotal role in the coagulation cascade. However, thrombin is not only the key effector of coagulation cascade; it also plays a significant role in inflammatory diseases. It shows an array of effects on endothelial cells, vascular smooth muscle cells, monocytes, and platelets, all of which participate in the vascular pathophysiology such as atherothrombosis. Therefore, thrombin can be considered as an important modulatory molecule of vascular homeostasis. This review summarizes the existing evidence on the role of thrombin in vascular inflammation.

LPA induces IL-6 secretion from aortic smooth muscle cells via an LPA1-regulated, PKC-dependent, and p38alpha-mediated pathway

Lysophosphatidic acid (LPA) is a potent bioactive lysophospholipid. Accumulated evidence supports a role for LPA in inflammation. To profile LPA-induced cytokine production in vascular smooth muscle cells (SMCs), we used a cytokine antibody array system and found that LPA prominently induces the secretion of IL-6 and monocyte chemoattractant protein (MCP)-1 from human aortic SMCs (HASMCs). The mechanism by which LPA induces MCP-1 expression in SMCs has been previously reported. However, LPA induction of IL-6 secretion from vascular SMCs and its regulatory mechanism are unknown. The present study reveals that LPA induces the expression of IL-6 mRNA and protein in HASMCs as well as the secretion of IL-6 protein in a time-dependent manner. Our results demonstrate that LPA-specific receptor 1 (LPA(1)) mediates LPA-induced IL-6 secretion and that LPA induction of IL-6 is independent of the EGF receptor pathway. Our data further show that PKC-mediated p38 MAPK is responsible for the IL-6 secretion. Finally, small interfering RNA depletion experiments revealed that p38alpha is specifically responsible for the LPA-induced IL-6 secretion. The present study profiles the regulatory relationship between LPA and multiple cytokines in vascular SMCs for the first time, provides the first evidence that LPA upregulates IL-6 in vascular SMCs, and reveals the regulatory mechanism of LPA-induced IL-6 production in HASMCs. In light of the emerging roles of LPA and IL-6 in vascular inflammation, the understanding of the regulatory mechanism may contribute to the treatment and prevention of cardiovascular disorders.

Cyclic AMP response element-binding protein is implicated in IL-6 production from arthritic synovial cells

Overproduction of interleukin (IL)-6 from synovial cells is critically involved in the pathogenesis of rheumatoid arthritis (RA). Cyclic adenosine monophosphate (AMP) response element-binding protein (CREB), a leucine zipper transcription factor, is expressed at a high level in synovial cells of patients with RA. Although CREB transactivates IL-6 expression in vascular smooth muscle cells, the relation between CREB expression and IL-6 production from arthritic synovial cells remains unclear. In this study, to determine whether CREB is implicated in IL-6 production from arthritic synovial cells, a dominant negative molecule of activation transcription factor 1 (ATF-1) was transfected into synovial cells obtained from arthritic joints of env-pX rats. These transgenic rats carrying the env-pX gene of human T-cell leukemia virus type-1 develop destructive arthritis with high titers of serum rheumatoid factor and are thus regarded as a suitable model of RA. The dominant negative ATF-1 (ATF-1DN) constitutes a heterodimer with CREB and inhibits CREB function, as CREB/ATF-1DN heterodimers no longer bind to the target sequence of CREB. We showed that transfection of ATF-1DN significantly reduced IL-6 production from arthritic synovial cells. These findings suggest that CREB is implicated in IL-6 production from synovial cells and plays an important role in RA pathogenesis.

Regulation of protease-activated receptor-1 by vasodilatory prostaglandins via NFAT

AIMS

We recently reported that prostacyclin suppresses protease-activated receptor-1 (PAR-1) in human vascular smooth muscle cells (VSMC) via cyclic AMP and protein kinase A. This study examines the downstream mechanisms, particularly the role of nuclear factor of activated T-cells (NFAT).

METHODS AND RESULTS

Human saphenous vein VSMC were exposed to phorbol 12-myristate 13-acetate (PMA) to induce endogenous cyclooxygenase-2-dependent prostaglandin generation. This was found to attenuate PAR-1 expression; similar suppression was seen with the EP2-prostaglandin receptor agonist butaprost. Stimulation of the 'exchange protein directly activated by cyclic AMP' (EPAC) was without effect. The NFAT inhibitor cyclosporin A (CsA) or NFAT2 siRNA both reduced PAR-1 mRNA and protein expression and prevented the stimulatory effects of thrombin or PAR-1 activating peptide (TFLLRN) on ERK1/2 phosphorylation and interleukin-6 expression. CsA or mutation of the NFAT binding motif in the PAR-1 promoter also blunted PAR-1 promoter activity (luciferase reporter assay). These inhibitory actions of CsA were comparable to those of the prostacyclin-mimetic iloprost, and both CsA and iloprost similarly attenuated nuclear NFAT2 localization and binding to the PAR-1 promoter (chromatin immunoprecipitation assay).

CONCLUSIONS

This study provides the first evidence that NFAT2 contributes to the transcriptional control of PAR-1 in human VSMC and that PKA-dependent NFAT2 inhibition represents a mechanism by which vasodilatory prostaglandins regulate the vascular actions of thrombin.

Influence of epinastine hydrochloride, an H1-receptor antagonist, on the function of mite allergen-pulsed murine bone marrow-derived dendritic cells in vitro and in vivo

There is established concept that dendritic cells (DCs) play essential roles in the development of allergic immune responses. However, the influence of H(1) receptor antagonists on DC functions is not well defined. The aim of the present study was to examine the effect of epinastine hydrochloride (EP), the most notable histamine H(1) receptor antagonists in Japan, on Dermatophagoides farinae (Der f)-pulsed mouse bone marrow-derived DCs in vitro and in vivo. EP at more than 25 ng/mL could significantly inhibit the production of IL-6, TNF-alpha and IL-10 from Der f-pulsed DCs, which was increased by Der f challenge in vitro. On the other hand, EP increased the ability of Der f-pulsed DCs to produce IL-12. Intranasal instillation of Der f-pulsed DCs resulted in nasal eosinophilia associated with a significant increase in IL-5 levels in nasal lavage fluids. Der f-pulsed and EP-treated DCs significantly inhibited nasal eosinophila and reduced IL-5. These results indicate that EP inhibits the development of Th2 immune responses through the modulation of DC functions and results in favorable modification of clinical status of allergic diseases.

Is thrombin a key player in the 'coagulation-atherogenesis' maze?

In addition to its established roles in the haemostatic system, thrombin is an intriguing coagulation protease demonstrating an array of effects on endothelial cells, vascular smooth muscle cells (VSMC), monocytes, and platelets, all of which are involved in the pathophysiology of atherosclerosis. There is mounting evidence that thrombin acts as a powerful modulator of many processes like regulation of vascular tone, permeability, migration and proliferation of VSMC, recruitment of monocytes into the atherosclerotic lesions, induction of diverse pro-inflammatory markers, and all of these are related to the progression of cardiovascular disease. Recent studies in transgenic mice models indicate that the deletion of the natural thrombin inhibitor heparin cofactor II promotes an accelerated atherogenic state. Moreover, the reduction of thrombin activity levels in apolipoprotein E-deficient mice, because of the administration of the direct thrombin inhibitor melagatran, attenuates plaque progression and promotes stability in advanced atherosclerotic lesions. The combined evidence points to thrombin as a pivotal contributor to vascular pathophysiology. Considering the clinical development of selective anticoagulants including direct thrombin inhibitors, it is a relevant moment to review the different thrombin-induced mechanisms that contribute to the initiation, formation, progression, and destabilization of atherosclerotic plaques.

Involvement of Mst1 in tumor necrosis factor-alpha-induced apoptosis of endothelial cells

Mammalian sterile 20-kinase 1 (Mst1), a member of the sterile-20 family protein kinase, plays an important role in the induction of apoptosis. However, little is know about the physiological activator of Mst1 and the role of Mst1 in endothelial cells (ECs). We examined whether Mst1 is involved in the tumor necrosis factor (TNF)-alpha-induced apoptosis of ECs. Western blot analysis revealed that TNF-alpha induced activation of caspase 3 and Mst1 in a time- and dose-dependent manner. TNF-alpha-induced Mst1 activation is almost completely prevented by pretreatment with Z-DEVD-FMK, a caspase 3 inhibitor. Nuclear staining with Hoechst 33258 and fluorescence-activated cell sorting of propidium iodide-stained cells showed that TNF-alpha induced apoptosis of EC. Diphenyleneiodonium, an inhibitor of NADPH oxidase, and N-acetylcysteine, a potent antioxidant, also inhibited TNF-alpha-induced activation of Mst1 and caspase 3, as well as apoptosis. Knockdown of Mst1 expression by short interfering RNA attenuated TNF-alpha-induced apoptosis but not cleavage of caspase 3. These results suggest that Mst1 plays an important role in the induction of TNF-alpha-induced apoptosis of EC. However, positive feedback mechanism between Mst1 and caspase 3, which was shown in the previous studies, was not observed. Inhibition of Mst1 function may be beneficial for maintaining the endothelial integrity and inhibition of atherogenesis.

Neuron-derived orphan receptor-1 (NOR-1) is induced by thrombin and mediates vascular endothelial cell growth

BACKGROUND AND AIM

Neuron-derived orphan receptor-1 (NOR-1) is a transcription factor overexpressed in human atherosclerotic plaques that is involved in vascular smooth muscle cell (VSMC) proliferation. The aim of this study was to analyze the role of NOR-1 in thrombin-induced endothelial cell growth.

RESULTS

Thrombin induced an early and transient up-regulation of NOR-1 in human umbilical vein endothelial cells (HUVEC). NOR-1 up-regulation by thrombin is dependent on multiple pathways, including cytosolic Ca(2+), activation of protein kinase C (PKC), mitogen-activated protein kinase (MAPK) pathways [both extracellular-regulated kinase (ERK) and p38 MAPK], and downstream activation of cAMP response element binding protein (CREB). The critical role of CREB in the induction of NOR-1 by thrombin was demonstrated using a dominant-negative of CREB. By site-direct mutagenesis we identified two CRE sites present at -79 and -53 bp in the NOR-1 promoter involved in the up-regulation of NOR-1 by thrombin. Inhibition of thrombin receptor PAR-1 abolished CREB activation, NOR-1 up-regulation and DNA synthesis (used as an index of cell proliferation). TRAP-6 mimicked both NOR-1 up-regulation and CREB activation induced by thrombin, while PPACK (an irreversible thrombin inhibitor) prevented such an effect. Direct inhibition of thrombin-induced NOR-1 up-regulation, using antisense oligonucleotides or siRNA against NOR-1, reduced DNA synthesis and endothelial cell re-growth after injury in an in vitro model of wound repair.

CONCLUSIONS

These results indicate that NOR-1 up-regulation plays a key role in thrombin-induced endothelial cell growth. Strategies aimed to block NOR-1 could be useful to prevent vascular effects triggered by thrombin.

The Interleukin-6 inflammation pathway from cholesterol to aging--role of statins, bisphosphonates and plant polyphenols in aging and age-related diseases

We describe the inflammation pathway from Cholesterol to Aging. Interleukin 6 mediated inflammation is implicated in age-related disorders including Atherosclerosis, Peripheral Vascular Disease, Coronary Artery Disease, Osteoporosis, Type 2 Diabetes, Dementia and Alzheimer's disease and some forms of Arthritis and Cancer. Statins and Bisphosphonates inhibit Interleukin 6 mediated inflammation indirectly through regulation of endogenous cholesterol synthesis and isoprenoid depletion. Polyphenolic compounds found in plants, fruits and vegetables inhibit Interleukin 6 mediated inflammation by direct inhibition of the signal transduction pathway. Therapeutic targets for the control of all the above diseases should include inhibition of Interleukin-6 mediated inflammation.

A new RXR agonist, HX630, suppresses intimal hyperplasia in a mouse blood flow cessation model

The nuclear receptor retinoid X receptor (RXR) forms heterodimers with other nuclear receptors and exerts anti-inflammatory effects. RXR is implicated in the progression of arteriosclerosis; however, the effects of selective RXR activation on smooth muscle cell (SMC) proliferation are unknown. We synthesized a novel RXR agonist, HX630, and examined its effect on vascular SMC (VSMC) proliferation. Male C57BL/6 mice (n=15) were subjected to ligation of the left carotid artery and fed 5 or 10 mg/kg/day HX630 for 4 weeks. HX630-fed mice showed significantly suppressed intimal hyperplasia progression compared to that in control mice (0.286+/-0.093 vs. 1.022+/-0.134 intima/media ratio, P<0.05). Immunohistochemistry of the carotid artery showed that HX630 suppressed cytokine and adhesion molecule staining in lesions undergoing intimal thickening. Interleukin (IL)-1beta-induced VSMC proliferation was inhibited by HX630 and the expression of IL-6 mRNA and protein in VSMCs was suppressed. The RXR agonist HX630 exerts antiproliferative effects in VSMCs in vivo and in vitro. Thus, the RXR may serve as a therapeutic target for vascular injury and intimal thickening.

CAMP-response element-binding protein mediates tumor necrosis factor-alpha-induced vascular cell adhesion molecule-1 expression in endothelial cells

Hypertension causes endothelial dysfunction, which plays an important role in atherogenesis. The vascular cell adhesion molecule-1 (VCAM-1) contributes to atherosclerotic lesion formation by recruiting leukocytes from blood into tissues. Tumor necrosis factor-alpha (TNFalpha) induces endothelial dysfunction and VCAM-1 expression in endothelial cells (ECs). We examined whether the cAMP-response element binding protein (CREB), a transcription factor that mediates cytokine expression and vascular remodeling, is involved in TNFalpha-induced VCAM-1 expression. TNFalpha induced phosphorylation of CREB with a peak at 15 min of stimulation in a dose-dependent manner in bovine aortic ECs. Pharmacological inhibition of p38 mitogen-activated protein kinase (p38-MAPK) inhibited TNFalpha-induced CREB phosphorylation. Adenovirus-mediated overexpression of a dominant-negative form of CREB suppressed TNFalpha-induced VCAM-1 and c-fos expression. Although activating protein 1 DNA binding activity was attenuated by overexpression of dominant negative CREB, nuclear factor-kappaB activity was not affected. Our results suggest that the p38-MAPK/CREB pathway plays a critical role in TNFalpha-induced VCAM-1 expression in vascular endothelial cells. The p38MAPK/CREB pathway may be a novel therapeutic target for the treatment of atherosclerosis.

Depolarization-induced slow Ca2+ transients stimulate transcription of IL-6 gene in skeletal muscle cells

Contracting skeletal muscle produces and releases interleukin-6 (IL-6) in high amounts. Nevertheless, the mechanisms underlying IL-6 expression are not understood. Because inositol-1,4,5-trisphosphate (IP(3))-mediated slow Ca(2+) signals evoked by depolarization of skeletal myotubes appears to play a role in the regulation of gene expression, we examined its involvement on IL-6 transcription. With the use of semiquantitative RT-PCR, we have shown that K(+) depolarization of myotubes induces a transient increase in IL-6 mRNA level, which peaks at 3-4 h and is independent of extracellular Ca(2+). Inhibitors of IP(3)-dependent Ca(2+) signals, like 2-aminoethoxydiphenyl borate (2-APB) and U-73122, decreased activation of IL-6 gene expression as did Ca(2+) signals inhibitor BAPTA-AM, whereas ryanodine, a fast Ca(2+) transient inhibitor, had no effect on IL-6 induction. Depolarization of myotubes transiently transfected with a reporter gene construct, containing 651 bp of IL-6 promoter, induced a twofold increase in promoter activity, which was abolished by either 2-APB or U-73122 and remained unaffected after ryanodine treatment. Site-directed mutagenesis of parental construct allowed us to identify activator protein-1 and NF-kappaB sequences as regulatory elements involved in IL-6 upregulation. Our results provide evidence for involvement of IP(3)-mediated Ca(2+) signals on IL-6 transcription in skeletal muscle cells.

cAMP-response element-binding protein mediates prostaglandin F2alpha-induced hypertrophy of vascular smooth muscle cells

Prostaglandin F(2alpha) (PGF(2alpha)) is a vasoactive factor that causes constriction and hypertrophy of vascular smooth muscle cells (VSMCs). However, the mechanism of PGF(2alpha)-induced hypertrophy is largely unknown. Cyclic AMP-response element (CRE)-binding protein (CREB), the best characterized stimulus-induced transcription factor, activates transcription of target genes with CRE and promotes cell growth. We examined the role of CREB in PGF(2alpha)-induced hypertrophy of VSMCs. PGF(2alpha) induced phosphorylation of CREB at serine 133, which is a critical marker of activation, after 5-10min of stimulation in a dose-dependent manner. Pharmacological inhibition of extracellular signal-regulated protein kinase and p38 mitogen-activated protein kinase (p38-MAPK) suppressed PGF(2alpha)-induced CREB phosphorylation. Inhibition of epidermal growth factor receptor (EGFR) and mitogen- and stress-activated protein kinase-1 also suppressed PGF(2alpha)-induced CREB phosphorylation. Overexpression of dominant-negative form of CREB (AdCREB M1), of which serine 133 was replaced with alanine, inhibited PGF(2alpha)-induced c-fos mRNA expression as well as hypertrophy of VSMCs [hypertrophy index (microg/10(4)cell); control 8.13, PGF(2alpha) 9.85, AdCREB M1 7.91, and AdCREB M1+PGF(2alpha) 8.43]. These results suggest that PGF(2alpha) activated CRE-dependent gene transcription through EGFR transactivation, and the CREB pathway plays a critical role in PGF(2alpha)-induced hypertrophy of VSMCs.

Adenylyl cyclase-cAMP system inhibits thrombin-induced HSP27 in vascular smooth muscle cells

We previously reported that thrombin stimulates the induction of heat shock protein (HSP) 27 via p38 mitogen-activated protein (MAP) kinase activation in aortic smooth muscle A10 cells. In the present study, we investigated the effect of the adenylyl cyclase-cAMP system on the thrombin-stimulated induction of HSP27 in A10 cells. Forskolin, a direct activator of adenylyl cyclase, reduced the thrombin-induced p38 MAP kinase phosphorylation, and significantly suppressed the thrombin-stimulated accumulation of HSP27. However, dideoxyforskolin, a forskolin derivative that does not activate cAMP, failed to suppress the HSP27 accumulation. Furthermore, dibutyryl-cAMP (DBcAMP), a permeable analog of cAMP, significantly suppressed the accumulation of HSP27. On the other hand, calphostin C, an inhibitor of protein kinase C (PKC), reduced the thrombin-induced p38 MAP kinase phosphorylation, and significantly suppressed the thrombin-stimulated accumulation of HSP27. Moreover, forskolin reduced the p38 MAP kinase phosphorylation induced by the 12-O-tetradecanoylphorbol-13-acetate (TPA), a PKC-activating phorbol ester, and significantly suppressed the TPA-stimulated accumulation of HSP27. These results indicate that adenylyl cyclase-cAMP system has an inhibitory role in thrombin-stimulated HSP27 induction in aortic smooth muscle cells, and the effect seems to be exerted on the thrombin-induced PKC- p38 MAP kinase signaling pathway.

Thromboxane A2 promotes interleukin-6 biosynthesis mediated by an activation of cyclic AMP-response element-binding protein in 1321N1 human astrocytoma cells

1321N1 human astrocytoma cells express thromboxane A2 (TXA2) receptors (TP). However, physiological consequences of TXA2 signaling in glial cells remain unclear. Herein, we show that TXA2 promotes interleukin-6 (IL-6) biosynthesis in glial cells. A TP agonist, 9,11-dideoxy-9alpha,11alpha-methanoepoxy-prosta-5Z,13E-dien-1-oic acid (U46619), enhanced IL-6 production in both 1321N1 cells and cultured mouse astrocytes. It has been shown that IL-6 gene expression is regulated by various transcription factors. Among them, we found a significant increase in cyclic AMP-response element-binding protein (CREB) activity with its phosphorylation at Ser133 by U46619 in 1321N1 cells. Although U46619 increased IL-6 promoter activity, a mutation at cyclic AMP-response element (CRE) on the promoter clearly suppressed the effect, suggesting that CRE is involved in U46619-induced IL-6 expression. Furthermore, both CREB and IL-6 promoter activities were suppressed by SB203580 [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)-1H-imidazole], a p38 mitogen-activated protein kinase (MAPK) inhibitor, and H89 [N-[2-(4-bromocinnamylamino)-ethyl]-5-isoquinoline], a protein kinase A (PKA) inhibitor, indicating involvements of p38 MAPK and PKA in CREB activation and IL-6 expression. To determine which G-proteins are implicated in the U46619-induced IL-6 synthesis, the interfering mutants of Galpha(q), Galpha12, or Galpha13 by were overexpressed in 1321N1 cells adenoviral approach. It is noteworthy that the Galpha(q) or Galpha13 mutant blocked the IL-6 production by U46619. The constitutively active mutant of Galpha(q), Galpha12, or Galpha13 enhanced IL-6 production, indicating that Galpha(q) and Galpha13 were involved in U46619-induced IL-6 production. In conclusion, TXA2 enhances the IL-6 biosynthesis via the PKA p38 MAPK/CREB pathway in 1321N1 cells. IL-6 induction depends on Galpha(q) and Galpha13 as well. This is the first report showing TP-mediated IL-6 production in glial cells.

Akt regulates thrombin-induced HSP27 phosphorylation in aortic smooth muscle cells: function at a point downstream from p38 MAP kinase

We previously reported that p38 MAP kinase takes part in thrombin-induced HSP27 phosphorylation in aortic smooth muscle A10 cells. In the present study, we investigated whether Akt is involved in the phosphorylation of HSP27 and the role of adenylyl cyclase-cAMP system. Thrombin time-dependently induced the phosphorylation of heat shock protein 27 (HSP27) and Akt in aortic smooth muscle A10 cells. SB203580, a p38 MAP kinase inhibitor, significantly suppressed the thrombin-induced phosphorylation of Akt and the Akt inhibitor suppressed the phosphorylation of HSP27. Furthermore, the thrombin-induced phosphorylation of HSP27, p38 MAP kinase and Akt were decreased by dibutyryl-cAMP (DBcAMP). These results strongly suggest that Akt functions the thrombin-induced phosphorylation of HSP27 at a point downstream from p38 MAP kinase in aortic smooth muscle cells and the adenylyl cyclase-cAMP system is upstream regulator of the HSP27 phosphorylation in these cells.

Low-insulin-response diets may decrease plasma C-reactive protein by influencing adipocyte function

Hepatic production of many acute phase reactants, including C-reactive protein (CRP), is induced primarily by interleukin-6 (IL-6). A significant fraction of the plasma pool of IL-6 derives from adipocytes. Physiological concentrations of insulin as well as of catecholamines have been shown to boost adipocyte production of IL-6 dose-dependently. High fasting and postprandial insulin levels can increase adipocyte exposure to catcholamines by activating the sympathetic nervous system, as well as by provoking postabsorptive hypoglycemia that triggers adrenal secretion of epinephrine. It follows that diets which promote low diurnal insulin levels - by minimizing the stimulus to postprandial insulin release, and by aiding muscle insulin sensitivity - should be associated with lower CRP levels. In fact, recent epidemiology demonstrates a correlation between dietary glycemic load and serum CRP in women, and a recent clinical study reports a 28% reduction in serum CRP following adoption of a whole-food vegan diet rich in soluble fiber. Whether very-low-fat diets which promote insulin sensitivity - and thus down-regulate insulin secretion - can influence CRP, remains to be seen. These considerations suggest that it may be possible to achieve worthwhile reductions in CRP by avoiding high-insulin-response starchy foods and by ingesting more soluble fiber, in foods or as a meal-time supplement.

Oxidative stress mediates sodium arsenite-induced expression of heme oxygenase-1, monocyte chemoattractant protein-1, and interleukin-6 in vascular smooth muscle cells

Arsenic exposure is associated with an increased risk of vascular disorders, and results in increased oxidative stress in endothelial cells and vascular smooth muscle cells (VSMCs). Since oxidative stress is involved in regulating the expression of genes related to atherogenesis, we investigated its involvement in the enhanced expression of three atherosclerosis-related genes coding for heme oxygenase-1 (HO-1), monocyte chemoattractant protein-1 (MCP-1), and interleukin-6 (IL-6) in VSMCs treated with inorganic sodium arsenite (iAs). In human VSMCs (hVSMCs) and rat VSMCs (rVSMCs), HO-1, MCP-1, and IL-6 mRNA levels were significantly increased by iAs treatment. An increase in HO-1 protein levels in hVSMCs was confirmed by Western blotting technique, while increased MCP-1 and IL-6 secretion by hVSMCs was demonstrated by enzyme-linked immunosorbent assay. Although modulators of oxidative stress inhibited this iAs-induced increase in the expression of these three genes, different modulators had differential effects. In iAs-treated rVSMCs, catalase, dimethylsulfoxide, and L-omega-nitro-L-arginine significantly inhibited the increase in expression of all three genes, allopurinol inhibited the increase in MCP-1 and IL-6 expression, but had no effect on HO-1 expression, while superoxide dismutase had no significant effect on HO-1 expression, but had an inhibitory effect on IL-6 expression and a stimulatory effect on MCP-1 expression. Therefore, iAs may enhance the expression of HO-1, MCP-1, and IL-6 in VSMCs via different reactive oxygen molecules. Furthermore, using tin protoporphyrin IX (SnPP) and anti-MCP-1 antibody to abolish iAs-induced HO-1 and MCP-1 activity, respectively, shows that HO-1 has protective effect against iAs-induced injury in VSMCs and MCP-1 is chemoattractive to human monocytes, THP-1.

Adenovirus-mediated expression of heparin cofactor II inhibits thrombin-induced cellular responses in fibroblasts and vascular smooth muscle cells

Heparin cofactor II functions as a physiological inhibitor of thrombin activity. The rate of inactivation of thrombin by heparin cofactor II is increased in the presence of dermatan sulfate, which is produced by fibroblasts or smooth muscle cells. To elucidate the role of heparin cofactor II in the extravascular cells, we induced expression of heparin cofactor II in cultured human fibroblasts or vascular smooth muscle cells using adenovirus-mediated gene transfer. After infection of adenovirus vector, these cells secreted heparin cofactor II protein into culture medium. The expressed heparin cofactor II formed the complex with exogenous thrombin and inhibited the proteolytic activity of thrombin. Expression of heparin cofactor II by infection of adenovirus vector inhibited thrombin-induced tissue-type plasminogen activator and interleukin-6 releases from fibroblasts and thrombin-induced interleukin-6 release from vascular smooth muscle cells. These findings show that fibroblasts and vascular smooth muscle cells expressing heparin cofactor II are resistant to thrombin-induced cellular responses.

What turns CREB on?

The transactivation domain of the cAMP response element-binding protein (CREB) consists of two major domains. The glutamine-rich Q2 domain, which interacts with the general transcription factor TAFII130/135, is sufficient for the recruitment of a functional RNA polymerase II complex and allows basal transcriptional activity. The kinase-inducible domain, however, mediates signal-induced activation of CREB-mediated transcription. It is generally believed that recruitment of the coactivators CREB-binding protein (CBP) and p300 after signal-induced phosphorylation of this domain at serine-133 strongly enhances CREB-dependent transcription. Transcriptional activity of CREB can also be potentiated by phosphoserine-133-independent mechanisms, and not all stimuli that provoke phosphorylation of serine-133 stimulate CREB-dependent transcription. This review presents an overview of the diversity of stimuli that induce CREB phosphorylation at Ser-133, focuses on phosphoserine-133-dependent and -independent mechanisms that affect CREB-mediated transcription, and discusses different models that may explain the discrepancy between CREB Ser-133 phosphorylation and activation of CREB-mediated transcription.

C-reactive protein and interleukin-6 in vascular disease: culprits or passive bystanders?

Recent advances in basic science have shown that atherosclerosis should be considered as a chronic inflammatory process, and that a pivotal role of inflammation is evident from initiation through progression and complication of atherosclerosis. In the past few years many studies have examined the potential for biochemical markers of inflammation to act as predictors of coronary heart disease (CHD) risk in a variety of clinical settings. Several large, prospective epidemiological studies have shown consistently that C-reactive protein (CRP) and interleukin-6 (IL-6) plasma levels are strong independent predictors of risk of future cardiovascular events, both in patients with a history of CHD and in apparently healthy subjects. These molecules could be useful to complement traditional risk factors, as well as to identify new categories of subjects prone to atherosclerosis development. An intriguing question is whether these inflammatory molecules simply represent sensitive markers of systemic inflammation or if they actively contribute to atherosclerotic lesion formation and instability. In this paper we will review the evidence concerning the cardiovascular prognostic value and the potential direct involvement of CRP and IL-6 in atherogenesis.

Proliferation of dental pulp fibroblasts in response to thrombin involves mitogen-activated protein kinase signalling

AIM

To examine the involvement of mitogen-activated protein kinases (MAPK) signalling on thrombin-stimulated human dental pulp fibroblasts (DPF).

METHODOLOGY

Dental pulp fibroblasts were isolated from dental pulp connective tissue of third molars and expanded in vitro. Expression of thrombin receptors was analysed by RT-PCR, and cell proliferation was measured by 3[H]-thymidine incorporation assay. Phosphorylation levels of MAPK were determined by Western blot analysis, and alkaline phosphatase activity was measured to serve as a marker for odontogenic differentiation. Statistical analysis was performed by Student's t-test.

RESULTS

Dental pulp fibroblasts express the thrombin receptors protease-activated receptor-1 (PAR-1), PAR-3 and PAR-4. Measurement of 3[H]-thymidine incorporation revealed a dose-dependent increase of DNA synthesis in response to thrombin treatment. The thrombin-induced mitogenic activity was decreased by the extracellular signal-regulated protein kinase (ERK) signalling inhibitor PD98059 (P < 0.05), and by SB203580 (P < 0.05), a p38 MAPK inhibitor. Western blot analysis demonstrated increased phosphorylation of ERK in DPF following stimulation with thrombin, while p38 MAPK and c-Jun NH2-terminal kinase (JNK) were not activated. Alkaline phosphatase activity of DPF remained unchanged upon incubation with thrombin.

CONCLUSIONS

These results suggest that signalling via MAPK mediates the mitogenic activity of thrombin on DPF and may thus play a role during the early stages of pulp repair.

Thrombin, inflammation, and cardiovascular disease: an epidemiologic perspective

The exploration of coagulation led to identifying inflammation as a major factor in arterial disease throughout life. "Integrative molecular physiology" reflects our emerging understanding of how coagulation and inflammation integrate with one another, in both normal physiology and in pathophysiology. Our own responses to environmental challenge provide much of the damage that cumulatively results in chronic cardiovascular disease. Only by intervening in exquisitely precise ways can we hope to effectively and safely modify the course of lifelong chronic diseases, such as atherosclerosis.

Rho family GTPases are required for activation of Jak/STAT signaling by G protein-coupled receptors

As do cytokine receptors and receptor tyrosine kinases, G protein-coupled receptors (GPCRs) signal to Janus kinases (Jaks) and signal transducers and activators of transcription (STATs). However, the early biochemical events linking GPCRs to this signaling pathway have been unclear. Here we show that GPCR-stimulated Rac activity and the subsequent generation of reactive oxygen species are necessary for activating tyrosine phosphorylation of Jaks and STAT-dependent transcription. The requirement for Rac activity can be overcome by addition of hydrogen peroxide. Expression of activated mutants of Rac1 is sufficient to activate Jak2 and STAT-dependent transcription, and the activation of Jak2 correlates with the ability of Rac1 to bind to NADPH oxidase subunit p67(phox). We further show that GPCR agonists stimulate tyrosine phosphorylation of STAT1 and STAT3 proteins in a Rac-dependent manner. The tyrosine phosphorylation of STAT3 is biphasic; the first peak of phosphorylation is weak and correlates with rapid activation of Jaks by GPCRs, whereas the second peak is stronger and requires the synthesis of an autocrine factor. Rho also plays an essential role in the induction of STAT transcriptional activity. Our results highlight a novel role for Rho GTPases in mediating the regulatory effects of GPCRs on STAT-dependent gene expression.