Pro-inflammatory cytokines stimulate mitogen-activated protein kinase subfamilies, increase phosphorylation of c-Jun and ATF2 and upregulate c-Jun protein in neonatal rat ventricular myocytes

Regulation of mRNA stability contributes to the function of innate lymphoid cells in various diseases

Innate lymphoid cells (ILCs) are important subsets of innate immune cells that regulate mucosal immunity. ILCs include natural killer cells, innate lymphoid cells-1 (ILC1s), ILC2s, and ILC3s, which have extremely important roles in the immune system. In this review, we summarize the regulation of mRNA stability mediated through various factors in ILCs (e.g., cytokines, RNA-binding proteins, non-coding RNAs) and their roles in mediating functions in different ILC subsets. In addition, we discuss potential therapeutic targets for diseases such as chronic obstructive pulmonary disease, cancer, and pulmonary fibrosis by regulation of mRNA stability in ILCs, which may provide novel directions for future clinical research.

A Comprehensive Review of Calcineurin Inhibitors Used for Immunosuppression in Cardiac Transplantation

Calcineurin inhibitors (CNIs) have been the foundation of immunosuppression in solid organ transplantation since the 1980s. Cyclosporine A (CSA), the first in class, was identified as the metabolite of the soil fungus Tolypocladium inflatum Gams as part of a larger program of screening for naturally occurring fungal metabolites with biologic activity in the 1970s. Significant immunosuppressive effects were discovered and consequently CSA was trialed as an immunosuppressant in renal transplantation. This initial success led to its widespread study and adoption in solid organ transplantation. This novel agent yielded significant improvements in both 1 year and longer-term allograft and patient survival. Subsequently, a similar and more potent CNI, tacrolimus was developed. Today, it is the principal CNI used for prevention of allograft rejection. Like all other immunosuppressives, the benefits of CNIs are counterbalanced by side effects and complications resulting from drug toxicity. This chapter comprehensively reviews the clinical use of CNIs in cardiac transplantation.

Peroxiredoxin-6 regulates p38-mediated epithelial-mesenchymal transition in HCT116 colon cancer cells

Background

Peroxiredoxins (Prxs) are antioxidant enzymes that protect cells from oxidative stress induced by several factors. They regulate several signaling pathways, such as metabolism, immune response, and intracellular reactive oxygen species (ROS) homeostasis. Epithelial–mesenchymal transition (EMT) is a transforming process that induces the loss of epithelial features of cancer cells and the gain of the mesenchymal phenotype. The EMT promotes metastasis and cancer cell progression mediated by several pathways, such as mitogen-activated protein kinases (MAPKs) and epigenetic regulators.

Methods

We used Prx6 overexpressed and downregulated HCT116 cells to study the mechanism between Prx6 and colon cancer. The expression of Prx6, GAPDH, Snail, Twist1, E-cadherin, Vimentin, N-cadherin, ERK, p-ERK, p38, p-p38, JNK, and p-JNK were detected by Western blotting. Additionally, an animal study for xenograft assay was conducted to explore the function of Prx6 on tumorigenesis. Cell proliferation and migration were determined by IncuCyte Cell Proliferation and colony formation assays.

Results

We confirmed that the expression of Prx6 and EMT signaling highly occurs in HCT116 compared with that in other colon cancer cell lines. Prx6 regulates the EMT signaling pathway by modulating EMT-related transcriptional repressors and mesenchymal genes in HCT116 colon cancer cells. Under the Prx6-overexpressed condition, HCT116 cells proliferation increased significantly. Moreover, the HCT116 cells proliferation decreased in the siPrx6-treated cells. Eleven days after HCT116 cell injection, Prx6 was overexpressed in the HCT116-injected mice, and the tumor volume increased significantly compared with that of the control mice. Furthermore, Prx6 regulates EMT signaling through p38 phosphorylation in colon cancer cells.

Conclusion

We suggested that Prx6 regulates EMT signaling pathway through p38 phosphorylation modulation in HCT116 colon cancer cells.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40709-021-00153-6.

An in vivo study of the effect of c-Jun on intervertebral disc degeneration in rats

Intervertebral disc degeneration (IDD) has been well-recognized as one of the causes of vast lower back pain. The objective of the current study intends to elucidate the influence and regulatory molecular mechanisms of c-Jun on IDD. This study established an IDD model of Sprague-Dawley (SD) rats by needle puncture. An LV5-c-Jun lentiviral vector was constructed and injected into rats’ intervertebral disc (IVD) tissue to increase the c-Jun expression following the establishment of modeling. The pathological changes of IVD tissue structure and collagen fibers were visualized following the processes of hematoxylin-eosin (HE) staining method and transmission electron microscopy. Real-time PCR, western blot, immunohistochemistry, and ELISA assays were performed to detect the expression levels of TGF-β, TIMP-3, COL2A1, and inflammatory cytokines. The collagen fibers were arranged in parallel and the surface was smooth after c-Jun overexpression, whereas the collagen fibers in the control group were disorderly arranged with a rough surface. The findings indicated that c-Jun was responsible for upregulating expression levels of TGF-β, TIMP-3, and COL2A1 in the mRNA and proteins, but simultaneously downregulating expression levels of inflammatory factors IL-1β, IL-17, IL-6, and TNF-α. c-Jun overexpression produced a positive effect on IDD, inhibited inflammatory response in vivo, and might delay the degeneration of IVD. Thus, c-Jun may act as a novel potential agent in treating IDD.

IL-33 promotes type 1 cytokine expression via p38 MAPK in human NK cells

This study tests the hypothesis that activation of MAPK by physiologically relevant concentrations of IL-33 contributes to enhanced cytokine expression by IL-12 stimulated human NK cells. While IL-33 canonically triggers type 2 cytokine responses, this cytokine can also synergize with type 1 cytokines like IL-12 to provoke IFN-γ. We show that picogram concentrations of IL-12 and IL-33 are sufficient to promote robust secretion of IFN-γ by human NK cells that greatly exceeds resposes to either cytokine alone. Nanogram doses of IL-33, potentially consistent with levels in tissue microenvironments, synergize with IL-12 to induce secretion of additional cytokines, including TNF and GM-CSF. IL-33-induced activation of the p38 MAPK pathway in human NK cells is crucial for enhanced release of IFN-γ and TNF in response to IL-12. Mechanistically, IL-33-induced p38 MAPK signaling enhances stability of IFNG transcripts and triggers A disintegrin and metalloproteinase domain 17 (ADAM17) mediated cleavage of TNF from the cell surface. These data support our hypothesis and suggest that altered sensitivity of NK cells to IL-12 in the presence of IL-33 may have important consequences in diseases associated with mixed cytokine milieus, like asthma and chronic obstructive pulmonary disease.

Heavy Alcohol Exposure Activates Astroglial Hemichannels and Pannexons in the Hippocampus of Adolescent Rats: Effects on Neuroinflammation and Astrocyte Arborization

A mounting body of evidence indicates that adolescents are specially more susceptible to alcohol influence than adults. However, the mechanisms underlying this phenomenon remain poorly understood. Astrocyte-mediated gliotransmission is crucial for hippocampal plasticity and recently, the opening of hemichannels and pannexons has been found to participate in both processes. Here, we evaluated whether adolescent rats exposed to ethanol exhibit changes in the activity of astrocyte hemichannels and pannexons in the hippocampus, as well as alterations in astrocyte arborization and cytokine levels. Adolescent rats were subjected to ethanol (3.0 g/kg) for two successive days at 48-h periods over 14 days. The opening of hemichannels and pannexons was examined in hippocampal slices by dye uptake, whereas hippocampal cytokine levels and astroglial arborization were determined by ELISA and Sholl analysis, respectively. We found that adolescent ethanol exposure increased the opening of connexin 43 (Cx43) hemichannels and pannexin-1 (Panx1) channels in astrocytes. Blockade of p38 mitogen-activated protein kinase (MAPK), inducible nitric oxide synthase (iNOS) and cyclooxygenases (COXs), as well as chelation of intracellular Ca²⁺, drastically reduced the ethanol-induced channel opening in astrocytes. Importantly, ethanol-induced Cx43 hemichannel and Panx1 channel activity was correlated with increased levels of interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), IL-6 in the hippocampus, as well as with profound alterations in astrocyte arbor complexity. Thus, we propose that uncontrolled opening of astrocyte hemichannels and pannexons may contribute not only to the glial dysfunction and neurotoxicity caused by adolescent alcohol consumption, but also to the pathogenesis of alcohol use disorders in the adulthood.

The Hypothalamic Inflammatory/Gliosis Response to Neonatal Overnutrition Is Sex and Age Dependent

Astrocytes participate in both physiological and pathophysiological responses to metabolic and nutrient signals. Although most studies have focused on the astrocytic response to weight gain due to high-fat/high-carbohydrate intake, surplus intake of a balanced diet also induces excess weight gain. We have accessed the effects of neonatal overnutrition, which has both age- and sex-dependent effects on weight gain, on hypothalamic inflammation/gliosis. Although both male and female Wistar rats accumulate excessive fat mass as early as postnatal day (PND) 10 with neonatal overnutrition, no increase in hypothalamic cytokine levels, markers of astrocytes or microglia, or inflammatory signaling pathways were observed. At PND 50, no effect of neonatal overnutriton was found in either sex, whereas at PND 150, males again weighed significantly more than their controls, and this was coincident with an increase in markers of inflammation and astrogliosis in the hypothalamus. Circulating triglycerides and free fatty acids were also elevated in these males, but not in females or in either sex at PND 10. Thus, the effects of fatty acids and estrogens on astrocytes in vitro were analyzed. Our results indicate that changes in circulating fatty acid levels may be involved in the induction of hypothalamic inflammation/gliosis in excess weight gain, even on a normal diet, and that estrogens could participate in the protection of females from these processes. In conclusion, the interaction of developmental influences, dietary composition, age, and sex determines the central inflammatory response and the associated long-term outcomes of excess weight gain.

ATF2 partly mediated the expressions of proliferative factors and inhibited pro-inflammatory factors' secretion in arsenite-treated human uroepithelial cells

Inorganic arsenic (iAs) could induce the expression of activating transcription factor-2 (ATF2) in the human urinary bladder epithelial cell line (SV-HUC-1 cells). ATF2, as a member of the bZIP transcription factor family, has been implicated in a transcriptional response leading to cell growth, migration and malignant tumor progression. However, little is known about the effects of ATF2 on proliferative factors in iAs treated human urothelial cells. In this study, ATF2 siRNA was employed to investigate the relationship between ATF2 activation and the expressions of proliferative factors, such as BCL2, cyclin D1, COX-2, MMP1 and PCNA, and pro-inflammatory factors (TNFα, TGFα and IL-8) in SV-HUC-1 cells. The results showed that low concentration arsenite increased the expressions of proliferative factors BCL2, cyclin D1, COX-2, MMP1 and PCNA in SV-HUC-1 cells, and ATF2 siRNA partly decreased the expressions of BCL2, cyclin D1, and COX-2. A neutralizing antibody of IL-8 was used for attenuating the levels of IL-8 and neutralizing antibody of IL-8 did not relieve the expressions of ATF2 and proliferative factors induced by arsenite in SV-HUC-1 cells. In addition, ATF2 knockdown did not decrease the expressions of pro-inflammatory cytokines induced by arsenite in SV-HUC-1 cells, but dramatically increased mRNA expressions of TNFα, TGFα and IL-8 under arsenite and non-arsenite conditions. In conclusion, our present study indicated that ATF2, but not IL-8, played a partial role in the expressions of proliferative factors induced by arsenite in human uroepithelial cells.

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.

Spiranthes sinensis Suppresses Production of Pro-Inflammatory Mediators by Down-Regulating the NF-κB Signaling Pathway and Up-Regulating HO-1/Nrf2 Anti-Oxidant Protein

Spiranthes sinensis is an east Asian wild orchid used in Chinese folk medicine. In this study, an ethyl acetate fraction from S. sinensis(SSE) was found to suppress the production of LPS-stimulated inflammatory mediators in RAW264.7 cells and BALB/c mice. SSE inhibited the production of pro-inflammatory mediators such as nitric oxide (NO), prostaglandin E2 (PGE2), tumo necrosis factor-α (TNF-α), IL-1β, and IL-6 in LPS-stimulated RAW264.7 cells. SSE also significantly suppressed LPS-stimulated protein levels of iNOS and mPGES-1 by blocking IκB phosphorylation, NF-κB nuclear translocation, and MAPKs phosphorylation. In addition, SSE treatment also enhanced protein levels of HO-1 and anti-oxidant enzymes (SOD-1, CAT, and GPx-1) through the nuclear translocation of Nrf2 in LPS-stimulated RAW264.7 cells. In vivo, we demonstrated that SSE attenuated the levels of pro-inflammatory mediators (NO, TNF-α, IL-1β, and IL-6), ALT, and AST in the serum of LPS-stimulated BALB/c mice. Western blotting revealed that SSE enhanced HO-1 expression in lung and liver tissue after LPS injection in mice. These results suggest that the anti-inflammatory properties of SSE involve the suppression of iNOS, mPGES-1, and inflammatory mediators by inducing the HO-1 pathway in LPS-stimulated RAW264.7 cells and BALB/c mice.

Progesterone and the Repression of Myometrial Inflammation: The Roles of MKP-1 and the AP-1 System

Progesterone (P4) maintains uterine quiescence during pregnancy and its functional withdrawal is associated with increased prostaglandin synthesis and the onset of labor. In primary human myometrial cells, the glucocorticoid receptor (GR) rather than the P4 receptor mediates P4 antagonism of IL-1β-induced cyclooxygenase-2 (COX-2) expression, the rate-limiting enzyme in prostaglandin synthesis. We now report that P4 also acts via GR to induce MAPK phosphatase (MKP)-1 and knockdown of MKP-1 impairs the ability of P4 to repress IL-1β-dependent COX-2 induction. Microarray analysis revealed that P4 repressed preferentially activator protein-1-responsive genes in response to IL-1β. Consistent with these observations, we found that the ability of P4 to reduce c-Jun activation was lost upon GR as well as MKP-1 knockdown. Interestingly, c-Jun levels in human myometrial cells declined upon GR and MKP-1 knockdown, which suggests the presence of an activator protein-1 feedback loop. This is supported by our observation that c-Jun levels declined after an initial rise in primary myometrial cells treated with phorbol 12-myrisatate 13-acetate, a potent activator of c-Jun N-terminal kinase. Finally, we show that MKP-1 is an intermediate in P4-mediated repression of some but not all IL-1β-responsive genes. For example, P4 repression of IL11 and IRAK3 was maintained upon MKP-1 knockdown. Taken together, the data show that P4 acts via GR to drive MKP-1 expression, which in turn inhibits IL-1β-dependent c-Jun activation and COX-2 expression.

Moxonidine modulates cytokine signalling and effects on cardiac cell viability

Regression of left ventricular hypertrophy and improved cardiac function in SHR by the centrally acting imidazoline I1-receptor agonist, moxonidine, are associated with differential actions on circulating and cardiac cytokines. Herein, we investigated cell-type specific I1-receptor (also known as nischarin) signalling and the mechanisms through which moxonidine may interfere with cytokines to affect cardiac cell viability. Studies were performed on neonatal rat cardiomyocytes and fibroblasts incubated with interleukin (IL)-1β (5 ng/ml), tumor necrosis factor (TNF)-α (10 ng/ml), and moxonidine (10(-7) and 10(-5) M), separately and in combination, for 15 min, and 24 and 48 h for the measurement of MAPKs (ERK1/2, JNK, and p38) and Akt activation and inducible NOS (iNOS) expression, by Western blotting, and cardiac cell viability/proliferation and apoptosis by flow cytometry, MTT assay, and Live/Dead assay. Participation of imidazoline I1-receptors and the signalling proteins in the detected effects was identified using imidazoline I1-receptor antagonist and signalling protein inhibitors. The results show that IL-1β, and to a lower extent, TNF-α, causes cell death and that moxonidine protects against starvation- as well as IL-1β -induced mortality, mainly by maintaining membrane integrity, and in part, by improving mitochondrial activity. The protection involves activation of Akt, ERK1/2, p38, JNK, and iNOS. In contrast, moxonidine stimulates basal and IL-1β-induced fibroblast mortality by mechanisms that include inhibition of JNK and iNOS. Thus, apart from their actions on the central nervous system, imidazoline I1-receptors are directly involved in cardiac cell growth and death, and may play an important role in cardiovascular diseases associated with inflammation.

Nerve injury-induced c-Jun activation in Schwann cells is JNK independent

We investigated (a) if activation of the mitogen activated protein kinase (MAPK) pathway was linked to the stress activated protein kinase (SAPK) pathway and (b) if JNK was required for activation of c-Jun in Schwann cells of rat sciatic nerve following injury. To this aim, ERK1/2 and the transcription factors c-Jun and ATF-3 were studied by immunohistochemistry in segments of transected nerves. We utilized pharmacological inhibitors of both signal transduction pathways in vitro to determine the effects on downstream signalling events, such as c-Jun activation, and on Schwann cell survival and proliferation. A transection induces c-Jun and ATF-3 transcription in Schwann cells. These events are followed by Schwann cell activation of c-Jun in the injured nerve. The MAPK inhibitor U0126 blocked ERK1/2 activation and reduced Schwann cell proliferation as well as induction of c-Jun transcription. The JNK inhibitor SP600125 reduced Schwann cell proliferation, but did not affect the expression of ERK1/2 or injury-induced increases in c-Jun or ATF-3 levels. Importantly, nerve injury induces Schwann cell activation of c-Jun by phosphorylation, which, in contrast to in sensory neurons, is JNK independent. MAP kinases, other than JNK, can potentially activate c-Jun in Schwann cells following injury; information that is crucial to create new nerve reconstruction strategies.

The early transcriptomic response to interleukin 1β and interleukin 33 in rat neonatal cardiomyocytes

In the heart, inflammatory cytokines including interleukin (IL) 1β are implicated in regulating adaptive and maladaptive changes, whereas IL33 negatively regulates cardiomyocyte hypertrophy and promotes cardioprotection. These agonists signal through a common co-receptor but, in cardiomyocytes, IL1β more potently activates mitogen-activated protein kinases and NFκB, pathways that regulate gene expression. We compared the effects of external application of IL1β and IL33 on the cardiomyocyte transcriptome. Neonatal rat cardiomyocytes were exposed to IL1β or IL33 (0.5, 1 or 2h). Transcriptomic profiles were determined using Affymetrix rat genome 230 2.0 microarrays and data were validated by quantitative PCR. IL1β induced significant changes in more RNAs than IL33 and, generally, to a greater degree. It also had a significantly greater effect in downregulating mRNAs and in regulating mRNAs associated with selected pathways. IL33 had a greater effect on a small, select group of specific transcripts. Thus, differences in intensity of intracellular signals can deliver qualitatively different responses. Quantitatively different responses in production of receptor agonists and transcription factors may contribute to qualitative differences at later times resulting in different phenotypic cellular responses.

Monophosphothreonyl extracellular signal-regulated kinases 1 and 2 (ERK1/2) are formed endogenously in intact cardiac myocytes and are enzymically active

ERK1 and ERK2 (ERK1/2) are central to the regulation of cell division, growth and survival. They are activated by phosphorylation of the Thr- and the Tyr- residues in their Thr-Glu-Tyr activation loops. The dogma is that dually-phosphorylated ERK1/2 constitute the principal activities in intact cells. We previously showed that, in neonatal rat cardiac myocytes, endothelin-1 and phorbol 12-myristate 13-acetate (PMA) powerfully and rapidly (maximal at ~ 5 min) activate ERK1/2. Here, we show that dually-phosphorylated ERK1/2 rapidly (< 2 min) appear in the nucleus following stimulation with endothelin-1. We characterized the active ERK1/2 species in myocytes exposed to endothelin-1 or PMA using MonoQ FPLC. Unexpectedly, two peaks of ERK1 and two peaks of ERK2 activity were resolved using in vitro kinase assays. One of each of these represented the dually-phosphorylated species. The other two represented activities for ERK1 or ERK2 which were phosphorylated solely on the Thr- residue. Monophosphothreonyl ERK1/2 represented maximally ~ 30% of total ERK1/2 activity after stimulation with endothelin-1 or PMA, and their k_cat values were estimated to be minimally ~ 30% of the dually-phosphorylated species. Appearance of monophosphothreonyl ERK1/2 was rapid but delayed in comparison with dually-phosphorylated ERK1/2. Of 10 agonists studied, endothelin-1 and PMA were most effective in terms of ERK1/2 activation and in stimulating the appearance of monophosphothreonyl and dually-phosphorylated ERK1/2. Thus, enzymically active monophosphothreonyl ERK1/2 are formed endogenously following activation of the ERK1/2 cascade and we suggest that monophosphothreonyl ERK1/2 arise by protein tyrosine phosphatase-mediated dephosphorylation of dually-phosphorylated ERK1/2.

Effect of pressure overload-induced hypertrophy on the expression and localization of p38 MAP kinase isoforms in the mouse heart

p38 mitogen-activated protein kinases (MAPKs) are serine/threonine specific protein kinases that respond to cellular stress and regulate a broad range of cellular activities. There are four major isoforms of p38 MAPK: alpha, beta, gamma, and delta. To date, the prominent isoform in heart has been thought to be p38alpha. We examined the expression of each p38 isoform at both the mRNA and protein level in murine heart. mRNA for all four p38 isoforms was detected. p38gamma and p38delta were expressed at protein levels comparable to p38alpha and 38beta, respectively. In the early phase of pressure-overload hypertrophy (1-7 days after constriction of the transverse aorta), the abundance of p38beta, p38gamma and p38delta mRNA increased; however, no corresponding changes were detected at the protein level. Confocal immunofluorescence studies revealed p38alpha and p38gamma in both the cytoplasm and nucleus. In the established phase of hypertrophy induced by chronic pressure overload (7-28 days after constriction of the transverse aorta), p38gamma immunoreactivity accumulated in the nucleus whereas the distribution of p38alpha remained unaffected. Hence, both p38alpha and p38gamma are prominent p38 isoforms in heart and p38gamma may play a role in mediating the changes in gene expression associated with cardiac remodeling during pressure-overload hypertrophy.

Modulation of interleukin signalling and gene expression in cardiac myocytes by endothelin-1

The related inflammatory cytokines, interleukin- (IL-) 1beta and IL-33, are both implicated in the response of the heart to injury. They also activate mitogen-activated protein kinases (MAPKs) in cardiac myocytes. The hypertrophic Gq protein-coupled receptor agonist endothelin-1 is a potentially cardioprotective peptide and may modulate the inflammatory response. Endothelin-1 also stimulates (MAPKs) in cardiac myocytes and promotes rapid changes in expression of mRNAs encoding intercellular and intracellular signalling components including receptors for IL-33 (ST2) and phosphoprotein phosphatases. Prior exposure to endothelin-1 may specifically modulate the response to IL-33 and, more globally, influence MAPK activation by different stimuli. Neonatal rat ventricular myocytes were exposed to IL-1beta or IL-33 with or without pre-exposure to endothelin-1 (5h) and MAPK activation assessed. IL-33 activated ERK1/2, JNKs and p38-MAPK, but to a lesser degree than IL-1beta. Endothelin-1 increased expression of soluble IL-33 receptors (sST2 receptors) which may prevent binding of IL-33 to the cell-surface receptors. However, pretreatment with endothelin-1 only inhibited activation of p38-MAPK by IL-33 with no significant influence on ERK1/2 and a small increase in activation of JNKs. Inhibition of p38-MAPK signalling following pretreatment with endothelin-1 was also detected with IL-1beta, H(2)O(2) or tumour necrosis factor alpha (TNFalpha) indicating an effect intrinsic to the signalling pathway. Endothelin-1 pretreatment suppressed the increase in expression of IL-6 mRNA induced by IL-1beta and decreased the duration of expression of TNFalpha mRNA. Coupled with the general decrease in p38-MAPK signalling, we conclude that endothelin-1 attenuates the cardiac myocyte inflammatory response, potentially to confer cardioprotection.

WISP1, a pro-mitogenic, pro-survival factor, mediates tumor necrosis factor-alpha (TNF-alpha)-stimulated cardiac fibroblast proliferation but inhibits TNF-alpha-induced cardiomyocyte death

WNT1-inducible signaling pathway protein-1 (WISP1), a member of the CYR61/CTGF/Nov family of growth factors, can mediate cell growth, transformation, and survival. Previously we demonstrated that WISP1 is up-regulated in post-infarct heart, stimulates cardiac fibroblast proliferation, and is induced by the proinflammatory cytokine tumor necrosis factor-alpha (TNF-alpha). Here we investigated (i) the localization of TNF-alpha and WISP1 in post-infarct heart, (ii) the mechanism of TNF-alpha-mediated WISP1 induction in primary human cardiac fibroblasts (CF), (iii) the role of WISP1 in TNF-alpha-mediated CF proliferation and collagen production, and (iv) the effects of WISP1 on TNF-alpha-mediated cardiomyocyte death. TNF-alpha and WISP1 expressions were increased in the border zones and non-ischemic remote regions of the post-ischemic heart. In CF, TNF-alpha potently induced WISP1 expression in cyclic AMP response element-binding protein (CREB)-dependent manner. TNF-alpha induced CREB phosphorylation in vitro and DNA binding and reporter gene activities in vivo. TNF-alpha induced CREB activation via ERK1/2, and inhibition of ERK1/2 and CREB blunted TNF-alpha-mediated WISP1 induction. Most importantly, WISP1 knockdown attenuated TNF-alpha stimulated collagen production and CF proliferation. Furthermore, WISP1 attenuated TNF-alpha-mediated cardiomyocyte death, thus demonstrating pro-mitogenic and pro-survival effects for WISP1 in myocardial constituent cells. Our results suggest that a TNF-alpha/WISP1 signaling pathway may contribute to post-infarct cardiac remodeling, a condition characterized by fibrosis and progressive cardiomyocyte loss.

Increased PrPC expression correlates with endoglin (CD105) positive microvessels in advanced carotid lesions

Normal cellular prion protein (PrP(C)) has multiple functions but its role in the development of atherosclerosis has not been studied. Our pilot microarray data showed increased expression of PrP(C) in tissue samples of complicated carotid lesions. Therefore in this study, we aimed to investigate its localisation within atherosclerotic arteries and its concentration in patient plasma. PrP(C) expression was examined using an enzyme immunometric assay (EIA) in plasma from patients undergoing endarterectomy. Carotid specimens and control vascular transplants were studied for PrP(C) and CD105 (endoglin, a marker of active vessels) expression by immunohistochemistry and real-time PCR. Patients with carotid disease had higher levels of plasma PrP(C) than the control group [4.35 ng/ml (n = 22; 3.1-5.3) vs. 1.95 ng/ml (n = 21; 1.1-2.5), P < 0.001]. Furthermore, CD105-positive plaques had higher PrP(C) expression which colocalized with CD105 in neovessels. There was a significant correlation between mRNA expression of PrP(C) and CD105 in tested plaques (P < 0.001; r = 0.7) supporting our immunohistochemical findings. We conclude that PrP(C) is expressed in carotid specimens and may be associated with neovessel growth or survival in these plaques. Our results suggest a role for PrP(C) in modulating neovessel formation in complicated plaques.

Inflammatory pathways are activated during cardiomyocyte hypertrophy and attenuated by peroxisome proliferator-activated receptors PPARalpha and PPARdelta

Accumulating evidence indicates an important role for inflammation in cardiac hypertrophy and failure. Peroxisome proliferator-activated receptors (PPARs) have been reported to attenuate inflammatory signaling pathways and, as such, may interfere with cardiac remodeling. Accordingly, the objectives of the present study were to explore the relationship between cardiomyocyte hypertrophy and inflammation and to investigate whether PPARalpha and PPARdelta are able to inhibit NF-kappaB activation and, consequently, the hypertrophic growth response of neonatal rat cardiomyocytes (NCM). mRNA levels of markers of both hypertrophy and inflammation were increased following treatment with the pro-hypertrophic factor phenylephrine (PE) or the chemokine TNF-alpha. Induction of inflammatory genes was found to be fast (within 2 h after stimulation) and transient, while induction of hypertrophic marker genes was more gradual (peaking at 24-48 h). Inflammatory and hypertrophic pathways appeared to converge on NF-kappaB as both PE and TNF-alpha increased NF-kappaB binding activity as measured by electrophoretic mobility shift assay. Following transient transfection, the p65-induced transcriptional activation of a NF-kappaB reporter construct was significantly blunted after co-transfection of PPARalpha or PPARdelta in the presence of their respective ligands. Finally, adenoviral overexpression of PPARalpha and PPARdelta markedly attenuated cell enlargement and the expression of hypertrophic marker genes in PE-stimulated NCM. The collective findings reveal a close relationship between hypertrophic and inflammatory signaling pathways in the cardiomyocyte. It was shown that both PPARalpha and PPARdelta are able to mitigate cardiomyocyte hypertrophy in vitro by inhibiting NF-kappaB activation.

Differential regulation of Krüppel-like factor family transcription factor expression in neonatal rat cardiac myocytes: effects of endothelin-1, oxidative stress and cytokines

Krüppel-like transcription factors (Klfs) modulate fundamental cell processes. Cardiac myocytes are terminally-differentiated, but hypertrophy in response to stimuli such as endothelin-1. H₂O₂ or cytokines promote myocyte apoptosis. Microarray studies of neonatal rat myocytes identified several Klfs as endothelin-1-responsive genes. We used quantitative PCR for further analysis of Klf expression in neonatal rat myocytes. In response to endothelin-1, Klf2 mRNA expression was rapidly increased (∼ 9-fold; 15–30 min) with later increases in expression of Klf4 and Klf6 (∼ 5-fold; 30–60 min). All were regulated as immediate early genes (cycloheximide did not inhibit the increases in expression). Klf5 expression was increased at 1–2 h (∼ 13-fold) as a second phase response (cycloheximide inhibited the increase). These increases were transient and attenuated by U0126. H₂O₂ increased expression of Klf2, Klf4 and Klf6, but interleukin-1β or tumor necrosis factor α downregulated Klf2 expression with no effect on Klf4 or Klf6. Of the Klfs which repress transcription, endothelin-1 rapidly downregulated expression of Klf3, Klf11 and Klf15. The dynamic regulation of expression of multiple Klf family members in cardiac myocytes suggests that, as a family, they are actively involved in regulating phenotypic responses (hypertrophy and apoptosis) to extracellular stimuli.

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.

Tumor necrosis factor-alpha antagonism protects from myocardial inflammation and fibrosis in experimental diabetic cardiomyopathy

To investigate the effect of anti-cytokine-based therapy in the course of diabetic cardiomyopathy, we performed a study using an anti-TNF-alpha monoclonal antibody treatment (mab) in Sprague male Dawley (SD) rats with streptozotocin-induced diabetic cardiomyopathy. Five days after streptozotocin injection, rats were treated with the anti-TNF-alpha mAb C432A for 6 weeks.At the end of the study, left ventricular (LV) function was determined by a pressure-catheter. Intercellular adhesion molecule (ICAM)-1, vascular adhesion molecule (VCAM)-1, beta2-lymphocyte-integrins(+) (CD18(+), CD11a(+), CD11b(+)), ED1/CD68(+) and cytokine (TNF-alpha, interleukin (IL)-1beta)- expressing infiltrates, total collagen content and stainings of collagen I and III were quantified by digital image analysis. LV phosphorylated and total ERK protein levels were determined by Western Blot. TNFalpha-antagonism reduced ICAM-1- and VCAM-1 expression and leukocyte infiltration to levels of non-diabetics and decreased macrophage residence by 3.3-fold compared with untreated diabetics. In addition, anti-TNF-alpha mAb-treatment decreased diabetes-induced cardiac TNF-alpha and IL-1beta expression by 2.0-fold and 1.8- fold, respectively, and reduced the ratio of phosphorylated to total ERK by 2.7-fold. The reduction in intramyocardial inflammation was associated with a 5.4-fold and 3.6-fold reduction in cardiac collagen I and III content, respectively. This was reflected by a normalization of cardiac total collagen content to levels of non-diabetics and associated with an improved LV function. TNFalpha-antagonism attenuates the development of experimental diabetic cardiomyopathy associated with a reduction of intramyocardial inflammation and cardiac fibrosis.

Involvement of JNKs and p38-MAPK/MSK1 pathways in H2O2-induced upregulation of heme oxygenase-1 mRNA in H9c2 cells

One of the most important challenges that cardiomyocytes experience is an increase in the levels of reactive oxygen species (ROS), i.e., during ischemia, reperfusion as well as in the failing myocardium. HOX-1 has been found to protect cells and tissues against oxidative damage; therefore, we decided to study the signalling cascades involved in its transcriptional regulation. HOX-1 mRNA levels were found to be maximally induced after 6h of treatment with 200 microM H2O2 and remained elevated for at least 24h. Inhibition of JNKs, p38-MAPK and MSK1 pathways, by pharmacological inhibitors, reduced HOX-1 mRNA levels in H2O2-treated H9c2 cells. In parallel, we observed that all three subfamilies of the mitogen-activated protein kinases (MAPKs) attained their maximal phosphorylation levels at 5-15 min of H2O2 treatment, with mitogen- and stress-activated-protein kinase 1 (MSK1) also being maximally phosphorylated at 15 min. H2O2-induced MSK1 phosphorylation was completely abrogated in the presence of the selective p38-MAPK inhibitor SB203580. In an effort to define possible substrates of MSK1, we found that ATF2 as well as cJun phosphorylation were equally induced after 30 min and 60 min, respectively, a response inhibited by SP600125 (JNKs inhibitor) and H89 (MSK1 inhibitor), indicating the involvement of these kinases in the observed response. This finding was further substantiated with the detection of a potential signalling complex composed of either p-MSK1 and p-cJun or p-MSK1 and p-ATF2 (co-immunoprecipitation). ATF2 and cJun are known AP1 components. Given the presence of an AP-1 site in HOX-1 promoter region, the activity of AP1 transcription factor was examined. Electrophoretic mobility shift assays performed showed a maximal upregulation of AP1 binding activity after 60 min of H2O2 treatment, which was significantly inhibited by SP600125 and H89. Our results show for the first time the potential role of JNKs, p38-MAPK and MSK1 in the mechanism of transducing the oxidative stress-signal to HOX-1, possibly promoting cell survival and preserving homeostasis.

The proinflammatory cytokines interleukin-1beta and tumor necrosis factor-alpha activate serotonin transporters

Proinflammatory cytokines and serotonergic homeostasis have both been implicated in the pathophysiology of major psychiatric disorders. We have demonstrated that activation of p38 mitogen-activated protein kinase (MAPK) induces a catalytic activation of the serotonin transporter (SERT) arising from a reduction in the SERT Km for 5-hydroxytryptamine (5-HT). As inflammatory cytokines can activate p38 MAPK, we hypothesized that they might also activate neuronal SERT. Indeed, Interleukin-1beta (IL-1beta) and tumor necrosis factor alpha (TNF-alpha) stimulated serotonin uptake in both the rat embryonic raphe cell line, RN46A, and in mouse midbrain and striatal synaptosomes. In RN46A cells, IL-1beta stimulated 5-HT uptake in a dose- and time-dependent manner, peaking in 20 min at 100 ng/ml. This was abolished by IL-1ra (20 ng/ml), an antagonist of the IL-1 receptor, and by SB203580 (5 microM), a p38 MAPK inhibitor. TNF-alpha also dose- and time-dependently stimulated 5-HT uptake that was only partially blocked by SB203580. Western blots showed that IL-1beta and TNF-alpha activated p38 MAPK, in an SB203580-sensitive manner. IL-1beta induced an SB203580-sensitive decrease in 5-HT Km with no significant change in Vmax. In contrast, TNF-alpha stimulation decreased 5-HT Km and increased SERT Vmax. SB203580 selectively blocked the TNF-alpha-induced change in SERT Km. In mouse midbrain and striatal synaptosomes, maximal stimulatory effects on 5-HT uptake occurred at lower concentrations (IL-1beta, 10 ng/ml; TNF-alpha, 20 ng/ml), and over shorter incubation times (10 min). As with RN46A cells, the effects of IL-1beta and TNF-alpha were completely (IL-1beta) or partially (TNF-alpha) blocked by SB203580. These results provide the first evidence that proinflammatory cytokines can acutely regulate neuronal SERT activity via p38 MAPK-linked pathways.

Helicobacter pylori upregulates prion protein expression in gastric mucosa: a possible link to prion disease

AIM

Pathological prion protein (PrP(sc)) is responsible for the development of transmissible spongiform encephalopathies (TSE). While PrPc enters the organism via the oral route, less data is available to know about its uptake and the role of gastrointestinal inflammation on the expression of prion precursor PrPc, which is constitutively expressed in the gastric mucosa.

METHODS

We studied PrPc expression in the gastric mucosa of 10 Helicobacter pylori-positive patients before and after successful H pylori eradication compared to non-infected controls using RT-PCR and Western blotting. The effect of central mediators of gastric inflammation, i.e., gastrin, prostaglandin E(2) (PGE(2)), tumor necrosis factor alpha (TNF-alpha) and interleukin 1 beta (IL-1beta) on PrPc expression was analyzed in gastric cell lines.

RESULTS

PrPc expression was increased in H pylori-infection compared with non-infected controls and decreased to normal after successful eradication. Gastrin, PGE(2), and IL-1beta dose-dependently upregulated PrPc in gastric cells, while TNF-alpha had no effect.

CONCLUSION

H pylori infection leads to the upregulation of gastric PrPc expression. This can be linked to H pylori induced hypergastrinemia and increased mucosal PGE(2) and IL-1beta synthesis. H pylori creates a milieu for enhanced propagation of prions in the gastrointestinal tract.

p38 MAPK regulates IL-1beta induced IL-6 expression through mRNA stability in osteoblasts

Osteoblast-derived IL-6 functions in coupled bone turnover by supporting osteoclastogenesis favoring bone resorption instead of bone deposition. Gene regulation of IL-6 is complex occurring both at transcription and post-transcription levels. The focus of this paper is at the level of mRNA stability, which is important in IL-6 gene regulation. Using the MC3T3-E1 as an osteoblastic model, IL-6 secretion was dose dependently decreased by SB203580, a p38 MAPK inhibitor. Steady state IL-6 mRNA was decreased with SB203580 (2 microM) ca. 85% when stimulated by IL-1beta (1-5 ng/ml). These effects require de novo protein synthesis as they were inhibited by cycloheximide. p38 MAPK had minor effects on proximal IL-6 promoter activity in reporter gene assays. A more significant effect on IL-6 mRNA stability was observed in the presence of SB203580. Western blot analysis confirmed that SB203580 inhibited p38 MAP kinase, in response to IL-1beta in a dose dependent manner in MC3T3-E1 cells. Stably transfected MC3T3-E1 reporter cell lines (MC6) containing green fluorescent protein (GFP) with the 3'untranslated region of IL-6 were constructed. Results indicated that IL-1beta, TNFalpha, LPS but not parathyroid hormone (PTH) could increase GFP expression of these reporter cell lines. Endogenous IL-6 and reporter gene eGFP-IL-6 3'UTR mRNA was regulated by p38 in MC6 cells. In addition, transient transfection of IL-6 3'UTR reporter cells with immediate upstream MAP kinase kinase-3 and -6 increased GFP expression compared to mock transfected controls. These results indicate that p38 MAPK regulates IL-1beta-stimulated IL-6 at a post transcriptional mechanism and one of the primary targets of IL-6 gene regulation is the 3'UTR of IL-6.

Thyroid hormone induces cardiac myocyte hypertrophy in a thyroid hormone receptor alpha1-specific manner that requires TAK1 and p38 mitogen-activated protein kinase

Alterations in TR [thyroid hormone (TH) receptor]1 isoform expression have been reported in models of both physiologic and pathologic cardiac hypertrophy as well as in patients with heart failure. In this report, we demonstrate that TH induces hypertrophy as a direct result of binding to the TRalpha1 isoform and, moreover, that overexpression of TRalpha1 alone is also associated with a hypertrophic phenotype, even in the absence of ligand. The mechanism of TH and TRalpha1-specific hypertrophy is novel for a nuclear hormone receptor and involves the transforming growth factor beta-activated kinase (TAK1) and p38. Mitigating TRalpha1 effects, both TRalpha2 and TRbeta1 attenuate TRalpha1-induced myocardial growth and gene expression by diminishing TAK1 and p38 activities, respectively. These findings refine our previous observations on TR expression in the hypertrophied and failing heart and suggest that manipulation of thyroid hormone signaling in an isoform-specific manner may be a relevant therapeutic target for altering the pathologic myocardial program.

Regulation of matrix metalloproteinases by cytokines and reactive oxygen/nitrogen species in the myocardium

Dysregulation of the myocardial extracellular matrix contributes to abnormal cardiac muscle function. Changes in the balance between matrix deposition and matrix degradation by matrix metalloproteinases (MMPs) can lead to cardiac fibrosis and dilation. In this review, we discuss the regulation of MMPs, their endogenous inhibitors (TIMPs) and collagen synthesis by inflammatory cytokines and reactive oxygen/nitrogen species (ROS/RNS). Inflammatory cytokines, such as interleukin-1beta and tumor necrosis factor-alpha, and ROS activate mitogen-activated protein kinases and stress-responsive protein kinases in cardiac cells. In non-cardiac tissues, inflammatory cytokine activation of these kinases is redox sensitive, suggesting ROS may also be involved in cytokine signaling in the heart. Subsequent activation of transcription factors including AP-1, Ets, and nuclear factor kappa-B leads to increased transcription of MMPs. ROS also directly activate MMPs post-translationally. In addition, inflammatory cytokines and ROS lead to decreased TIMP levels and collagen synthesis. Work in animal models suggests that inhibition of inflammatory cytokine or ROS signaling leads to less myocardial remodeling. Further study of the signaling of regulation of the cardiac extracellular matrix may lead to new approaches for the treatment of myocardial remodeling and failure.

Human vaccinia-related kinase 1 (VRK1) activates the ATF2 transcriptional activity by novel phosphorylation on Thr-73 and Ser-62 and cooperates with JNK

In the human kinome, vaccinia-related kinase-1 (VRK1) is a new Ser-Thr kinase associated with proliferating tissues. VRK1 colocalizes with ATF2 in the nucleus and can form a stable complex. We have studied the phosphorylation of the transcription factor ATF2, which regulates gene expression by forming dimers with proteins with basic region-leucine zipper domains and recognizing cAMP-response element or AP1 sequences implicated in cellular responses to stress. VRK1 phosphorylates ATF2 mainly on Thr-73, stabilizing the ATF2 protein and increasing its intracellular level. Mutagenesis studies showed that Thr-73 and Ser-62 are implicated in ATF2 transcriptional activation by VRK1 detected in a functional assay based on ATF2 dimerization. VRK1 can activate the collagenase gene promoter that is regulated by ATF2 in a dose-dependent manner. Loss of kinase activity (K179E mutant) or the T73A substitution in ATF2 prevents both its accumulation and activation of transcription. VRK1 and JNK, which phosphorylates ATF2 in Thr-69 and Thr-71, have an additive effect on ATF2-dependent transcription at suboptimal doses. Therefore, two groups of amino acids in the ATF2 amino-terminal region can integrate different cellular signals mediated by at least five different kinases. VRK1 is an element of a novel signaling pathway that regulates gene transcription.

ATF2, a member of the CREB/ATF family of transcription factors, in chronic stress and consequent to antidepressant treatment: animal models and human post-mortem brains

The regulation of gene expression has been implicated in the etiology and treatment of depression. Transcription factors serve as the intermediates between intracellular cascades and gene expression, and may therefore be involved in the pathophysiology and pharmacotherapy of depression. We and others have previously reported an increase in the phosphorylation of the transcription factor cAMP response element binding protein (CREB) by antidepressants, alongside brain region-specific alterations in pCREB by stress. In the present study, we examined the expression of another member of the CREB/ATF family of transcription factors, ATF2, in the brains of rats chronically treated with two different antidepressants, and in rats 4 months after their exposure to prolonged stress. ATF2 phosphorylation was decreased by antidepressants and increased at the aftermath of prolonged stress, specifically in the frontal cortex. We also examined ATF2 expression in the ventral parieto-occipital region of post-mortem human brains of normal controls, depressed, bipolar, and schizophrenic patients, obtained from the Stanley Foundation Brain Consortium. No alterations were observed in the levels of ATF2. However, in the depressed group, the pATF2 levels were higher in unmedicated compared to medicated patients, suggesting an antidepressant-induced reduction in pATF2. We discuss the possible role of ATF2 in depression, and propose that an interplay between ATF2 and CREB, and possibly other transcription factors, determines the final gene expression pattern in the etiology and treatment of depression.

Tumor necrosis factor alpha (TNF) increases granulosa cell proliferation: dependence on c-Jun and TNF receptor type 1

TNF alpha has significant in vitro effects on steroidogenesis and folliculogenesis and reproductive alterations occur in TNF receptor type 1 (TNFR1) knockout mice. The present study investigated the effect of in vitro TNF on granulosa cell proliferation from immature mice at 28 d of age, with emphasis on intracellular signaling that regulates granulosa cell proliferation. TNF dose dependently increased granulosa cell proliferation and the proto-oncogene c-Jun protein. However, other Jun family members such as JunD was expressed constitutively and JunB was not expressed. In vitro TNF did not increase c-Jun and proliferation in granulosa cells from TNFR1 knockout mice. The time course of TNF-induced c-Jun revealed biphasic patterns of short-term (3 h) and long-term (24 h) induction. The time courses of Ser63- and Ser73-phospho c-Jun coincided with changes in total c-Jun. Among MAPK cascades, stress-activated protein kinase/c-Jun-NH(2)-teminal kinase signaling was increased transiently in TNF-treated cells, whereas p38MAPK and ERK1 and 2 were not changed. In addition, overexpression of nuclear factor-kappa B and addition of ceramide and 8-bromo-cAMP did not increase c-Jun or proliferation. Antisense oligonucleotides for c-Jun blocked cell proliferation induced by TNF. In conclusion, the above results demonstrate that TNF increased c-Jun by activating stress-activated protein kinase/c-Jun-NH(2)-teminal kinase signaling via TNFR1 in mouse granulosa cells, and the induced c-Jun resulted in increased cell proliferation.

Regulation of Toll-like receptor-2 expression by the Gal-lectin of Entamoeba histolytica

The Gal/GalNAc lectin (Gal-lectin) of Entamoeba histolytica is a surface molecule involved in parasite adherence to host cells and is the most promising subunit vaccine candidate against amoebiasis. As macrophages are the major effector cells in host defense against amoebas, we studied the molecular mechanisms by which Gal-lectin activates macrophage. Microarray analysis showed that Gal-lectin up-regulated mRNAs of several cytokines and receptor genes involved in proinflammatory responses. The mechanism whereby the Gal-lectin regulates Toll-like receptor 2 (TLR-2) expression in macrophages was studied. Native Gal-lectin increased TLR-2 mRNA expression in a dose- and time-dependent fashion; peak response occurred with 1 microg/ml after 2 h stimulation. By immunoflourescence, enhanced surface expression of TLR-2 was observed after 12 h. With the use of nonoverlapping anti-Gal-lectin monoclonal antibodies that map to the carbohydrate recognition domain, amino acid 596-1082 was identified as the TLR-2 stimulating region. The Gal-lectin increased TLR-2 gene transcription, and the half-life of the mRNA transcripts was 1.4 h. Inhibition of nuclear factor (NF)-kappaB suppressed TLR-2 mRNA induction by the Gal-lectin. Moreover, cells pretreated with an inhibitor of p38 kinase (SB 208530) inhibited Gal-lectin induced TLR-2 mRNA expression by 40%. We conclude that the Gal-lectin activates NF-kappaB and MAP kinase-signaling pathways in macrophages culminating in the induction of several genes including TLR-2 and hypothesize that this could have a significant impact on macrophage activation and contribute to amoebic pathogenesis.

How nerve growth factor drives physiological and inflammatory expressions of acid-sensing ion channel 3 in sensory neurons

Nerve growth factor (NGF) is a key element of inflammatory pain. It induces hyperalgesia by up-regulating the transcription of genes encoding receptors, ion channels, and neuropeptides. Acid-sensing ion channel 3 (ASIC3), a depolarizing sodium channel gated by protons during tissue acidosis, is specifically expressed in sensory neurons. It has been associated to cardiac ischemic and inflammatory pains. We previously showed that low endogenous NGF was responsible for ASIC3 basal expression and high NGF during inflammation increased ASIC3 expression parallely to the development of neuron hyperexcitability associated with hyperalgesia. NGF is known to activate numerous signaling pathways through trkA and p75 receptors. We now show that (i). NGF controls ASIC3 basal expression through constitutive activation of a trkA/phospholipase C/protein kinase C pathway, (ii). high inflammatory-like NGF induces ASIC3 overexpression through a trkA/JNK/p38MAPK pathway and a p75-dependent mechanism as a transcriptional switch, and (iii). NGF acts through AP1 response elements in ASIC3 encoding gene promoter. These new data indicate potential targets that could be used to develop new treatments against inflammatory pain.

Opening of mitochondrial ATP-sensitive potassium channels is a trigger of 3-nitropropionic acid-induced tolerance to transient focal cerebral ischemia in rats

BACKGROUND AND PURPOSE

The role of mitochondrial ATP-sensitive potassium channels (mitoK(ATP)) in ischemic tolerance has been well documented in heart, but little work has been done in brain. To investigate the involvement of mitoK(ATP) activation in chemical preconditioning in brain, we examined the effect of 5-hydroxydecanoate (5-HD), a selective mitoK(ATP) blocker, on neurotoxin 3-nitropropionic acid (3-NPA)-induced ischemic tolerance to transient focal cerebral ischemia in rats.

METHODS

Male Wistar rats were administrated 3-NPA (20 mg/kg IP; n=16) or vehicle (saline; n=16) 3 days before temporary occlusion (120 minutes) of the middle cerebral artery; 5-HD (40 mg/kg IP; n=16) was injected 20 minutes before 3-NPA administration. Infarct volumes were measured 4 days after reperfusion. To directly investigate whether chemical preconditioning activates mitoK(ATP), we tested the effect of prior incubation with 1 mmol/L 5-HD on 300 micromol/L 3-NPA-induced alterations of mitochondrial membrane potential (Delta(Psi)m) in cultured neurons and astrocytes using the fluorescent dye tetramethylrhodamine ethyl ester.

RESULTS

Treatment with 3-NPA exhibited a 16% reduction (P<0.05) and 23% reduction in infarct volume (P<0.01) for total brain and cortex, respectively. Pretreatment with 5-HD completely abolished the neuroprotective effect of chemical preconditioning. In cultured cells, 3-NPA resulted in mitochondrial depolarization. This change of Delta(Psi)m was completely blocked by 5-HD pretreatment.

CONCLUSIONS

These results strongly suggest that opening of mitoK(ATP) plays a key role as the trigger in the development of 3-NPA-induced ischemic tolerance in brain.

Phosphorylation of activating transcription factor in murine splenocytes through delta opioid receptors

Delta opioid receptors (DORs) modulate TCR signaling through the mitogen-activated protein kinases (MAPKs), ERKs 1 and 2. These studies determined whether a DOR agonist alone ([D-Ala(2)-D-Leu(5)]enkephalin; DADLE) affects phosphorylation of the activating transcription factor (ATF-2) and its interaction with the MAPK, c-Jun NH(2)-terminal kinase (JNK). DOR expression was induced on murine splenocytes by anti-CD3 and then quiescent cells were treated with DADLE. DADLE, itself, dose-dependently induced maximal phosphorylation of ATF-2 within 5-10min; naltrindole, a specific antagonist, abolished this. Anti-ATF-2 immunoprecipitates from control and DADLE-treated splenocytes showed a dominant 59kDa phosphorylated band and a 71kDa band. DADLE stimulated phosphorylation of both bands, although the 71kDa band was selectively immunoprecipitated by anti-JNK. Thus, DADLE stimulated phosphorylation of 71kDa ATF-2 and its association with JNK, suggesting that JNK is activated through DORs. Along with previous observations, these studies suggest that lymphocyte DORs can affect the activation of MAPKs by TCR-independent stimulation (e.g., JNK) or indirectly by modulating TCR-dependent stimulation (e.g., ERK).

Up-regulation of c-jun mRNA in cardiac myocytes requires the extracellular signal-regulated kinase cascade, but c-Jun N-terminal kinases are required for efficient up-regulation of c-Jun protein

Cardiac hypertrophy, an important adaptational response, is associated with up-regulation of the immediate early gene, c- jun, which encodes the c-Jun transcription factor. c-Jun may feed back to up-regulate its own transcription and, since the c-Jun N-terminal kinase (JNK) family of mitogen-activated protein kinases (MAPKs) phosphorylate c-Jun(Ser-63/73) to increase its transactivating activity, JNKs are thought to be the principal factors involved in c- jun up-regulation. Hypertrophy in primary cultures of cardiac myocytes is induced by endothelin-1, phenylephrine or PMA, probably through activation of one or more of the MAPK family. These three agonists increased c- jun mRNA with the rank order of potency of PMA approximately endothelin-1>phenylephrine. Up-regulation of c- jun mRNA by endothelin-1 was attenuated by inhibitors of protein kinase C (GF109203X) and the extracellular signal-regulated kinase (ERK) cascade (PD98059 or U0126), but not by inhibitors of the JNK (SP600125) or p38-MAPK (SB203580) cascades. Hyperosmotic shock (0.5 M sorbitol) powerfully activates JNKs, but did not increase c- jun mRNA. These data suggest that ERKs, rather than JNKs, are required for c- jun up-regulation. However, endothelin-1 and phenylephrine induced greater up-regulation of c-Jun protein than PMA and phosphorylation of c-Jun(Ser-63/73) correlated with the level of c-Jun protein. Up-regulation of c-Jun protein by endothelin-1 was attenuated by inhibitors of protein kinase C and the ERK cascade, probably correlating with a primary input of ERKs into transcription. In addition, SP600125 inhibited the phosphorylation of c-Jun(Ser-63/73), attenuated the increase in c-Jun protein induced by endothelin-1 and increased the rate of c-Jun degradation. Thus whereas ERKs are the principal MAPKs required for c- jun transcription, JNKs are necessary to stabilize c-Jun for efficient up-regulation of the protein.

Distinct roles of mitogen-activated protein kinase pathways in GATA-4 transcription factor-mediated regulation of B-type natriuretic peptide gene

The expression of cardiac hormones, atrial natriuretic peptide and B-type natriuretic peptide, is induced by cardiac wall stretch and responds to various hypertrophic agonists such as endothelin-1. In cardiac myocytes, endothelin-1 induces GATA-4 binding to the B-type natriuretic peptide gene, but the signaling pathways involved in endothelin-1-induced GATA-4 activation are unknown. Mitogen-activated protein kinase pathways are stimulated in response to various extracellular stimuli, and they modulate the function of several transcription activators. Here we show that inhibition of p38 kinase with SB203580 inhibited endothelin-1-induced GATA-4 binding to B-type natriuretic peptide gene and serine phosphorylation of GATA-4. Inhibition of extracellular signal-regulated protein kinase with MEK1 inhibitor PD98059 reduced basal and p38-induced GATA-4 binding activity, but it had no significant effect on endothelin-1-induced GATA-4 binding activity. Overexpression of p38 kinase pathway, but not extracellular signal-regulated kinase or c-Jun N-terminal protein kinase, activated GATA-4 binding to B-type natriuretic peptide gene and induced rat B-type natriuretic peptide promoter activity via proximal GATA binding sites. In conclusion, these findings demonstrate that activation of p38 kinase is necessary for hypertrophic agonist-induced GATA-4 binding to B-type natriuretic peptide gene and sufficient for GATA-dependent B-type natriuretic peptide gene expression.

Cardiac expression and subcellular localization of the p38 mitogen-activated protein kinase member, stress-activated protein kinase-3 (SAPK3)

Despite the interest in the roles that mitogen-activated protein kinases (MAPKs) play in the heart, the role of the different MAPK isoforms has been relatively poorly defined. A third isoform of p38 MAPK, known variously as stress-activated protein kinase-3 (SAPK3), p38- gamma or ERK6, has been previously shown to differ from p38- alpha/ beta both in its molecular weight and its lack of inhibition by the compound SB203580. We have generated monoclonal antibodies with specificity for SAPK3 demonstrated by immunoblot analysis, immunofluorescence studies, and cloning of SAPK3 from a rat heart cDNA expression library. By immunoblotting, we confirmed high expression of SAPK3 in fast, slow and mixed fibre types of murine skeletal muscle and observed significant expression restricted to heart, lung, thymus and testes. In addition to expression in normal heart (human, mouse, rat, dog and pig), we observed constant expression in diseased human heart, as well as control and hypertrophic cultured neonatal rat cardiac myocytes. Immunolocalization in cultured cardiac myocytes followed by confocal microscopy showed punctate, non-nuclear SAPK3 staining. In contrast, p38- alpha/ beta staining was non-punctate and distributed throughout the cytosol and nucleus. Whereas treatment with Leptomycin B to prevent nuclear export processes promoted higher levels of p38- alpha/ beta staining in cardiac myocyte nuclei, there was no apparent change in SAPK3 localization under these conditions. These differences between p38- alpha/ beta and SAPK3 probably reflect the specialized functions of SAPK3 and emphasize the need to evaluate SAPK3 upstream activators and downstream targets in the heart.

p38 MAPK regulates group IIa phospholipase A2 expression in interleukin-1beta -stimulated rat neonatal cardiomyocytes

Group IIa phospholipase A(2) (GIIa PLA(2)) is released by some cells in response to interleukin-1beta. The purpose of this study was to determine whether interleukin-1beta would stimulate the synthesis and release of GIIa PLA(2) from cardiomyocytes, and to define the role of p38 MAPK and cytosolic PLA(2) in the regulation of this process. Whereas GIIa PLA(2) mRNA was not identified in untreated cells, exposure to interleukin-1beta resulted in the sustained expression of GIIa PLA(2) mRNA. Interleukin-1beta also stimulated a progressive increase in cellular and extracellular GIIa PLA(2) protein levels and increased extracellular PLA(2) activity 70-fold. In addition, interleukin-1beta stimulated the p38 MAPK-dependent activation of the downstream MAPK-activated protein kinase, MAPKAP-K2. Treatment with the p38 MAPK inhibitor, SB202190, decreased interleukin-1beta stimulated MAPKAP-K2 activity, GIIa PLA(2) mRNA expression, GIIa PLA(2) protein synthesis, and the release of extracellular PLA(2) activity. Infection with an adenovirus encoding a constitutively active form of MKK6, MKK6(Glu), which selectively phosphorylates p38 MAPK, induced cellular GIIa PLA(2) protein synthesis and the release of GIIa PLA(2) and increased extracellular PLA(2) activity 3-fold. In contrast, infection with an adenovirus encoding a phosphorylation-resistant MKK6, MKK6(A), did not result in GIIa PLA(2) protein synthesis or release by unstimulated cardiomyocytes. In addition, infection with an adenovirus encoding MKK6(A) abrogated GIIa PLA(2) protein synthesis and release by interleukin-1beta-stimulated cells. These results provide direct evidence that p38 MAPK activation was necessary for interleukin-1beta-induced synthesis and release of GIIa PLA(2) by cardiomyocytes.

Inclusion body myositis: genetic factors, aberrant protein expression, and autoimmunity

Sporadic inclusion body myositis (s-IBM) is an inflammatory myopathy mainly affecting elderly individuals. It has a chronic progressive course leading to severe disability. Immunosuppressive treatment is in most instances ineffective. S-IBM is morphologically characterized by mononuclear cell infiltrates and vacuolated muscle fibers with pathologic accumulation of a large number of different proteins. Recent research has focused on the expression of various factors that may contribute to the inflammatory reaction and the typical inclusions. This review summarizes the new information on genetic factors, abnormal protein expression and inflammation, which provides a basis for linking the different typical morphologic features of s-IBM to a cascade of pathogenic events.

Protein kinase Czeta activation mediates glucagon-like peptide-1-induced pancreatic beta-cell proliferation

Glucagon-like peptide-1 (GLP-1), an insulinotropic and glucoincretin hormone, is a potentially important therapeutic agent in the treatment of diabetes. We previously provided evidence that GLP-1 induces pancreatic beta-cell growth nonadditively with glucose in a phosphatidylinositol-3 kinase (PI-3K)-dependent manner. In the present study, we investigated the downstream effectors of PI-3K to determine the precise signal transduction pathways that mediate the action of GLP-1 on beta-cell proliferation. GLP-1 increased extracellular signal-related kinase 1/2, p38 mitogen-activated protein kinase (MAPK), and protein kinase B activities nonadditively with glucose in pancreatic beta(INS 832/13) cells. GLP-1 also caused nuclear translocation of the atypical protein kinase C (aPKC) zeta isoform in INS as well as in dissociated normal rat beta-cells as shown by immunolocalization and Western immunoblotting analysis. Tritiated thymidine incorporation measurements showed that the p38 MAPK inhibitor SB203580 suppressed GLP-1-induced beta-cell proliferation. Further investigation was performed using isoform-specific pseudosubstrates of classical (alpha, beta, and gamma) or zeta aPKC isoforms. The PKCzeta pseudosubstrate suppressed the proliferative action of GLP-1, whereas the inhibitor of classical PKC isoforms had no effect. Overexpression of a kinase-dead PKCzeta acting as a dominant negative protein suppressed GLP-1-induced proliferation. In addition, ectopic expression of a constitutively active PKCzeta mutant stimulated tritiated thymidine incorporation to the same extent as GLP-1, and the glucoincretin had no growth-promoting action under this condition. The data indicate that GLP-1-induced activation of PKCzeta is implicated in the beta-cell proliferative signal of the insulinotropic hormone. The results are consistent with a model in which GLP-1-induced PI-3K activation results in PKCzeta translocation to the nucleus, which may play a role in the pleiotropic effects (DNA synthesis, metabolic enzymes, and insulin gene expression) of the glucoincretin.

Nickel requires hypoxia-inducible factor-1 alpha, not redox signaling, to induce plasminogen activator inhibitor-1

Human epidemiological and animal studies have associated inhalation of nickel dusts with an increased incidence of pulmonary fibrosis. At the cellular level, particulate nickel subsulfide inhibits fibrinolysis by transcriptionally inducing expression of plasminogen activator inhibitor (PAI)-1, an inhibitor of the urokinase-type plasminogen activator. Because nickel is known to mimic hypoxia, the present study examined whether nickel transcriptionally activates PAI-1 through the hypoxia-inducible factor (HIF)-1 alpha signaling pathway. The involvement of the NADPH oxidase complex, reactive oxygen species, and kinases in mediating nickel-induced HIF-1 alpha signaling was also investigated. Addition of nickel to BEAS-2B human airway epithelial cells increased HIF-1 alpha protein levels and elevated PAI-1 mRNA levels. Pretreatment of cells with the extracellular signal-regulated kinase inhibitor U-0126 partially blocked HIF-1 alpha protein and PAI-1 mRNA levels induced by nickel, whereas antioxidants and NADPH oxidase inhibitors had no effect. Pretreating cells with antisense, but not sense, oligonucleotides to HIF-1 alpha mRNA abolished nickel-stimulated increases in PAI-1 mRNA. These data indicate that signaling through extracellular signal-regulated kinase and HIF-1 alpha is required for nickel-induced transcriptional activation of PAI-1.

A role for the extracellular signal-regulated kinase and p38 mitogen-activated protein kinases in interleukin-1 beta-stimulated delayed signal tranducer and activator of transcription 3 activation, atrial natriuretic factor expression, and cardiac myocyte morphology

We have demonstrated that two hypertrophic agents, interleukin-1 beta (IL-1 beta) and leukemic inhibitory factor (LIF), altered cardiac myocyte morphology with striking similarity and prompted us to investigate the common actions of these cytokines. We compared the phosphorylation/activation of signal tranducer and activator of transcription 3 (STAT3), extracellular signal-regulated kinase (ERK), p38(MAPK), and c-Jun N-terminal kinase mitogen-activated protein kinases (MAPKs). The phosphorylation of STAT3 by IL-1 beta was delayed (>60 min), whereas the response to LIF was rapid (<10 min) and transient. We confirmed that IL-1 beta potently stimulated all three MAPK subfamilies. In contrast, LIF promoted strong activation of ERKs, marginal activation of p38(MAPK), and no c-Jun N-terminal kinase activation. To test the roles of ERKs and p38(MAPK), myocytes were pretreated with PD98059 and SB203580. Either inhibitor alone prevented STAT3 phosphorylation, implicating ERKs and p38(MAPK) in the delayed STAT3 response to IL-1 beta. The interplay of MAPKs and STAT3 phosphorylation in regulating IL-1 beta-stimulated hypertrophy was investigated by evaluating the effect of MAPK inhibitors on atrial natriuretic factor (ANF) expression and myocyte morphology. The specific inhibition of either ERK or p38(MAPK) attenuated the IL-1 beta- or LIF-stimulated ANF expression by up to 70%. Inhibition was not further increased in the presence of both inhibitors. Furthermore, although individual inhibition of ERK or p38(MAPK) did not affect morphology, co-treatment with both inhibitors abrogated the hypertrophic morphology stimulated by IL-1 beta but not by LIF. Taken together, our data indicate that the activation of ERK and p38(MAPK) is essential in regulating a delayed STAT3 phosphorylation as well as changes in ANF expression and morphology that follow IL-1 beta treatment. Thus, the role of MAPKs in the hypertrophic response can be dictated at least partly by the nature of the hypertrophic agent employed.

Oxidant stress and endothelial cell dysfunction

Reactive oxygen species (ROS) are generated at sites of inflammation and injury, and at low levels, ROS can function as signaling molecules participating as signaling intermediates in regulation of fundamental cell activities such as cell growth and cell adaptation responses, whereas at higher concentrations, ROS can cause cellular injury and death. The vascular endothelium, which regulates the passage of macromolecules and circulating cells from blood to tissues, is a major target of oxidant stress, playing a critical role in the pathophysiology of several vascular diseases and disorders. Specifically, oxidant stress increases vascular endothelial permeability and promotes leukocyte adhesion, which are coupled with alterations in endothelial signal transduction and redox-regulated transcription factors such as activator protein-1 and nuclear factor-kappaB. This review discusses recent findings on the cellular and molecular mechanisms by which ROS signal events leading to impairment of endothelial barrier function and promotion of leukocyte adhesion. Particular emphasis is placed on the regulation of cell-cell and cell-surface adhesion molecules, the actin cytoskeleton, key protein kinases, and signal transduction events.

Roles of protein kinase C and Ca2+-dependent signaling in angiotensin II-induced adrenomedullin production in rat cardiac myocytes

OBJECTIVES

We showed that angiotensin II stimulates adrenomedullin production in cultured neonatal rat cardiac myocytes, and that the secreted adrenomedullin inhibits hypertrophy of the myocytes, although the intracellular mechanisms of adrenomedullin production are still unknown. Since protein kinase C (PKC) and the Ca2+ signaling system are involved in cardiac hypertrophy, we examined the roles of these intracellular signaling systems in the production of adrenomedullin by myocytes.

METHODS

Cultured neonatal rat cardiac myocytes were incubated with agonists or antagonists of PKC and Ca2+ signaling systems for 24 h. Adrenomedullin secreted into the medium and adrenomedullin mRNA expression were measured by radioimmunoassay and quantitative polymerase chain reaction, respectively.

RESULTS

Both phorbol-12-myristate-13-acetate (PMA), a PKC activator and A23187, a calcium ionophore, significantly increased adrenomedullin mRNA expression and secretion from the myocytes. The induction of adrenomedullin secretion by PMA was abolished by H7, a PKC inhibitor, and by downregulation of PKC induced by pre-incubation with PMA. Similarly, the stimulation of adrenomedullin secretion by 10(-6) mol/l angiotensin II was significantly reduced following the inhibition or downregulation of PKC activity in the myocytes. Blockade of the L-type Ca2+ channel and chelation of intracellular Ca2+ both resulted in a significant reduction of the stimulation of adrenomedullin secretion by angiotensin II. In addition, the secretion was significantly attenuated by inhibitors of calmodulin (W-7) and calmodulin kinase II (KN-62), and slightly attenuated by FK506, a calcineurin inhibitor.

CONCLUSIONS

These results suggest that PKC and the Ca2+/calmodulin signaling systems are involved in angiotensin II-induced adrenomedullin secretion from rat cardiac myocytes.

Corticosterone-induced rapid phosphorylation of p38 and JNK mitogen-activated protein kinases in PC12 cells

The present study showed that corticosterone (B) could induce a rapid activation of p38 and c-Jun NH(2)-terminal protein kinase (JNK) in PC12 cells. The dose-response and time-response curves were bell-shaped with maximal activation at 10(-9) M and at 15 min. RU38486 had no effect, and bovine serum albumin-coupled B could induce the activation. Genistein failed to block the phosphorylation, suggesting the pathway was not involved in tyrosine kinase activity. Phorbol 12-myristate 13-acetate could mimic, while Gö6976 could abolish the actions. These results demonstrated that B might act via a putative membrane receptor to activate p38 and JNK rapidly through a protein kinase C-dependent pathway.

Differential involvement of p38 mitogen-activated protein kinase and phosphatidyl inositol 3-kinase in the IL-1-mediated NF-κB and AP-1 activation

Interleukin-1 (IL-1) is a central regulator of the immune and inflammatory responses by which various inflammatory genes are induced. Although IL-1 signaling is known to involve PI3-kinase, p38 mitogen-activated protein (MAP) kinase and extracellular signal-regulated kinase (ERK), the crosstalk of these kinases on the IL-1-mediated signal transduction is not clear. We used two specific inhibitors, SB203580 which selectively inhibits p38 MAP kinase and LY294002 which inhibits PI3-kinase, respectively, to explore the involvement of these kinases in the IL-1-induced NF-kappa B activation, using a human glioblastoma cell line, T98G. Two kinase inhibitors decreased IL-1-induced IL-8 mRNA and protein levels markedly. IL-1 caused phosphorylation of p38 MAP kinase with concomitant recruitment of PI3-kinase to IL-1 receptor I (IL-1RI) and its activation. In this context, pretreatment of LY294002, but not SB203580, inhibited IL-1-induced NF-kappa B activation significantly. While IL-1 induced-AP-1 activation was moderate, both LY294002 and SB203580 suppressed IL-1-induced AP-1 activation. These observations were prominent particularly in the TRAF6 transfection system, in which overexpression of wild type TRAF6 augmented the IL-1 mediated NF-kappa B and AP-1 activation, while dominant negative TRAF6 construct (delta TRAF6) suppressed these activation. Namely, LY294002 inhibited TRAF6-mediated IL-1-induced NF-kappa B and AP-1 activation markedly, while SB203580 inhibited TRAF6-induced AP-1 activation but not NF-kappa B activation. Above results indicated that both PI3-kinase and p38 MAP kinase are differentially involved in IL-1-induced NF-kappa B and AP-1 activation.