Rho-kinase mediates lysophosphatidic acid-induced IL-8 and MCP-1 production via p38 and JNK pathways in human endothelial cells

Lysophosphatidic acid (LPA), an inflammatory mediator that is elevated in multiple inflammatory diseases, is a potent activator of Rho kinase (ROCK) signaling and of chemokine production in endothelial cells. In this study, LPA activated ROCK, p38, JNK and NF-κB pathways and induced interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) mRNA and protein expression in human endothelial cells. We mapped signaling events downstream of ROCK, driving chemokine production. In summary, MCP-1 production was partly regulated by ROCK acting upstream of p38 and JNK and mediated downstream by NF-κB. IL-8 production was largely driven by ROCK through p38 and JNK activation, but with no involvement of NF-κB.     

Vasoactive intestinal peptide inhibits IL-8 production in human monocytes

Vasoactive intestinal peptide (VIP), a neuropeptide present in the lymphoid microenvironment, acts as a potent anti-inflammatory agent that inhibits the function of activated macrophages. VIP was shown to inhibit IL-6, TNFalpha, IL-12, chemokine, and nitric oxide production in endotoxin-activated macrophages. The present study reports the effect of VIP on IL-8 production by stimulated human monocytes. VIP inhibits IL-8 production in a dose- and time-dependent manner at the mRNA level. The specific VPAC1 receptor mediates the inhibitory effect of VIP. Two transduction pathways appear to be involved, a major cAMP-independent pathway and a secondary cAMP-dependent pathway. Of obvious physiological significance is the fact that VIP, presumably through the inhibition of IL-8 production, dramatically reduces the monocyte-induced neutrophil chemotaxis, an important event in the pathogenesis of several inflammatory and autoimmune disorders. These findings support the proposed role of VIP as a key endogenous anti-inflammatory agent and describe a novel mechanism, i.e., the inhibition of the production of monocyte-derived IL-8.     

Modulatory effect of HHV-6 on MCP-1 production by human monocytes

Chemokines represent a large family of proinflammatory proteins that orchestrate leukocyte trafficking to sites of viral infection. Human Herpes virus type 6 (HHV-6) is a typical immunosuppressive agent, as suggested by its tropism. In this study the production of monocyte chemoattractant protein-1 (MCP-1) and interleukin-10 (IL-10) by human peripheral blood monocytes was evaluated during HHV-6 infection. Our results demonstrate that HHV-6 infection triggers monocytes to release MCP-1 and IL-10. The addition of exogenous recombinant MCP-1 upregulates the release of extracellular virus, whereas does not influence the percentage of viral-antigen positive cells. Furthermore, the addition of monoclonal antibodies anti-IL-10 down-regulates MCP-1 release induced by HHV-6. These findings indicate that IL-10 and MCP-1 production was closely related and that the marked amounts of MCP-1 were supported not only by virus but also by virus-induced IL-10.     

Synovial stromal cells from rheumatoid arthritis patients attract monocytes by producing MCP-1 and IL-8

Macrophages that accumulate in the synovium of rheumatoid arthritis patients play an important role in the pathogenesis of this inflammatory disease. However, the mechanism by which macrophages are attracted into the inflamed synovium and accumulate there has not been completely delineated. The results of this study show that rheumatoid arthritis synovial stromal cells produce the chemokines monocyte chemotactic protein-1 and IL-8, and these have the capacity to attract peripheral monocytes. These results suggest that one of the mechanisms by which macrophages accumulate in the inflamed synovium is by responding to the chemokines produced locally.     

Protein microarrays for multiplex analysis of signal transduction pathways

We have developed a multiplexed reverse phase protein (RPP) microarray platform for simultaneous monitoring of site-specific phosphorylation of numerous signaling proteins using nanogram amounts of lysates derived from stimulated living cells. We first show the application of RPP microarrays to the study of signaling kinetics and pathway delineation in Jurkat T lymphocytes. RPP microarrays were used to profile the phosphorylation state of 62 signaling components in Jurkat T cells stimulated through their membrane CD3 and CD28 receptors, identifying a previously unrecognized link between CD3 crosslinking and dephosphorylation of Raf-1 at Ser259. Finally, the potential of this technology to analyze rare primary cell populations is shown in a study of differential STAT protein phosphorylation in interleukin (IL)-2-stimulated CD4(+)CD25(+) regulatory T cells. RPP microarrays, prepared using simple procedures and standard microarray equipment, represent a powerful new tool for the study of signal transduction in both health and disease.     

IL-1 activates two separate signal transduction pathways in T helper type II cells

We have investigated the signal transduction pathways mediated by IL-1 in the Th 2 cell line D10.A, and we have made the following findings. Interaction of IL-1 with its receptor leads to the translocation of protein kinase C (PKC) from the cytosol to the membrane, phosphorylation of the 80-kDa protein that is substrate for PKC, as well as an increase in the level of cAMP. In addition, IL-1 induced IL-5 mRNA expression in these cells. We have established that the IL-5 gene is activated in D10.A cells in response to either phorbol esters or 8-Br cAMP, and that the two agents act as cofactors. IL-1 is able to synergize with phorbol esters and is additive with 8-Br cAMP for IL-5 mRNA expression. There are two possibilities to explain these results: 1) D10.A cells express two types of functional IL-1R, each linked to an independent signal transduction pathway; or 2) these cells have only one kind of IL-1R which, upon ligand interaction, mediates the activation of both the PKC and the adenylate cyclase pathway.     

Structure-function analysis of human IL-6 receptor: dissociation of amino acid residues required for IL-6-binding and for IL-6 signal transduction through gp130.

Here, we report the analysis of the structure-function relationship of the extracellular region of human interleukin 6 receptor (IL-6R). Upon binding of IL-6, IL-6R becomes associated extracellularly with a non-IL-6-binding but signal transducing molecule, gp130, and the IL-6 signal is generated. In this region, the cytokine receptor family domain, but not the immunoglobulin-like domain, was responsible both for IL-6 binding and for signal transduction through gp130. Because a soluble, extracellular portion of IL-6R (sIL-6R) could bind IL-6 and mediate IL-6 functions through gp130, amino acid substitutions were introduced into sIL-6R by site-directed mutagenesis. The results, together with the previously proposed tertiary structure model, suggested that the amino acid residues critical for IL-6 binding have a tendency to be distributed to the hinge region between the two 'barrel'-like fibronectin type III modules and to the same side of these two 'barrels'. Amino acid residues, of which substitutions barely affected the IL-6-binding but did abolish the IL-6 signalling capability of sIL-6R, were identified and found to be located mainly in the membrane proximal half of the second barrel. sIL-6R mutants carrying such substitutions lacked the capacity to associate with gp130 in the presence of IL-6.     

IL-4 receptor signal transduction in human monocytes is associated with protein kinase C translocation.

IL-4 regulates B cell differentiation and monocyte functions. Protein kinases, such as kinase C (PKC), transduce receptor signals. The involvement of PKC in IL-4R signaling was investigated in human monocytes. Treatment with IL-4 (10 ng/ml) for 10 min resulted in a significant redistribution of the PKC activity from cytosol to nuclear fraction. Total PKC activity localized in the nuclear fraction of IL-4-treated and control monocytes was, respectively, 68 and 19%. In contrast, similar PKC activity was found in membrane fraction of IL-4-treated and control cells. The kinetics of IL-4-mediated redistribution of PKC activity to the nuclear fraction were rapid. Within 30 s of IL-4 exposure, 29% of the total PKC activity localized in the nuclear fraction as compared to 15% in control monocytes and increased to 69% at 10 min. The PKC activity in the nuclear fraction appears to be a sequestered form. Extraction with Triton X-100 and additional sonication were required for functional assay of PKC activity. Additional support for PKC involvement in IL-4R signaling is provided by the dose-dependent effect of IL-4 on PKC activity and the abrogation of this effect after heat denature and immunoabsorption of IL-4. Furthermore, electron microscope examination and subcellular marker enzyme assays excluded significant contamination of the nuclear fraction by plasma membranes or subcellular organelles and IL-4 altering membrane disruption. The data presented indicate that IL-4R signaling in human monocytes involves PKC translocation to a nuclear fraction.     

HIV-1 Tat protein induces IL-10 production in monocytes by classical and alternative NF-kappaB pathways

The human immunodeficiency virus (HIV) transactivating Tat protein is not only critical for viral replication but also affects the host immune system by inducing the production of cytokines such as IL-10. This anti-inflammatory cytokine is upregulated during the course of HIV infection, representing an important pathway by which HIV may induce immunodeficiency. Here, we show that, by acting at the membrane, Tat induces IL-10 expression in primary monocytes and promonocytic U937 cells by NF-kappaB-dependent pathways. The trans-dominant negative mutants of NF-kappaB-inducing kinase (NIK), IKKalpha and IKKbeta expressed in our transactivation model, in accordance with the nuclear binding of p65 and p52 NF-kappaB subunits to the IL-10 promoter, suggest the involvement of both classical and alternative NF-kappaB pathways. In inactivated cells, IKKalpha is localized predominantly in the cytoplasm. Interestingly, Tat stimulates IKKalpha translocation from the cytoplasm to the nucleus in monocytes. Chromatin immunoprecipitation (ChIP) assay experiments, after Tat treatment, revealed IKKalpha and CBP/p300 recruitment to the IL-10 promoter and histone H3 phosphorylation (Ser 10) and acetylation (Lys 14) in this region, presumably leading to chromatin remodeling. We demonstrate that, upstream of NF-kappaB, PKC, ERK1/2 and p38 MAP kinases are involved in Tat-induced IKKalpha nuclear translocation and histone H3 modifications on the IL-10 promoter in accordance with the role of these three kinases in IL-10 production. As a whole, the study demonstrates that Tat activates at least three signaling pathways concurrently, including the classical, alternative and IKKalpha pathways, to promote production of IL-10.     

Absence of induction of IL-1 production in human monocytes by complement fragments

The ability of C fragments to induce IL-1 production in human monocytes was examined by using various approaches to carefully exclude the role of contaminating endotoxin. The presence of IL-1 activity in monocyte supernatants and lysates was assayed by the augmentation of PHA-induced proliferation of murine thymocytes. SRBC were opsonized with IgM rabbit antibodies and various human C components to prepare EAC reagents that contained less than 25 pg LPS/ml of EAC at 5 x 10(8) cells/ml. EAC1q, EAC4b, EAC4b2aoxy, EAC4b2aoxy C3b, EAC4b2aoxyC3bi, and EAC4b2aoxyC3d all failed to induce IL-1 production when incubated at 10- to 100-fold excess with adherent human monocytes. Similarly, LPS-free purified C3a, C5a, and C5a des Arg all showed no IL-1-inducing activities at concentrations up to 25 micrograms/ml. However, the same C5a preparations were active on human monocytes in the induction of chemotaxis, and C3a and C5a both induced skin-blueing in guinea pigs. Fragment Ba and Bb preparations purified by gel filtration chromatography contained approximately 100 pg LPS/micrograms Ba or Bb. These Ba and Bb preparations at 10 and 50 micrograms/ml, respectively, induced IL-1 production in the presence of 5 micrograms/ml polymyxin B (PMB). However, Ba and Bb preparations purified by affinity chromatography and HPLC contained lower levels of endotoxin contamination and displayed IL-1-inducing activities at Ba and Bb concentrations of 50 and 100 micrograms/ml, respectively, that were almost completely inhibited by PMB. To explore further the role of contaminating endotoxin, a Bb preparation was adsorbed with PMB-4B in the presence of a dialyzable detergent to remove LPS bound to the Bb. This LPS-free Bb preparation failed to induce IL-1 production while maintaining intact enzymatic activities. These results indicate that various solid phase or soluble C fragments, including C3b, iC3b, C3d, C3a, C5a, Ba or Bb do not induce IL-1 production in human monocytes in the absence of contaminating endotoxin.     

Altered signal transduction pathways and induction of autophagy in human myotonic dystrophy type 1 myoblasts

Congenital myotonic dystrophy type 1 (CDM1) affects patients from birth and is associated with mental retardation and impaired muscle development. CDM1 patients carry 1000–3000 CTG repeats in the DMPK gene and display defective skeletal muscles differentiation, resulting in reduced size of myotubes and decreased number of satellite cells. In this study, human myoblasts in culture deriving from control and DM1 embryos (3200 CTG repeats) were analyzed using both a biochemical and electron microscopic approach, in order to provide new insights into the molecular mechanisms underlying such alteration. Interestingly, electron microscopy analysis showed not only ultrastructural features of abnormal differentiation but also revealed the presence of autophagic vacuoles in DM1 myoblasts not undergoing differentiation. In accordance with the electron microscopic findings, the autophagic markers LC3 and ATG5, but not apoptotic markers, were significantly up regulated in DM1 myoblasts after differentiating medium addition. The induction of autophagic processes in DM1 myoblasts was concomitant to p53 over-expression and inhibition of the mTOR–S6K1 pathway, causatively involved in autophagy. Moreover biochemical alterations of the two main signal transduction pathways involved in differentiation were observed in DM1 myoblasts, in particular decreased activation of p38MAPK and persistent activation of the MEK–ERK pathway. This work, while demonstrating that major signaling pathways regulating myoblasts differentiation are profoundly deranged in DM1 myoblasts, for the first time provides evidence of autophagy induction, possibly mediated by p53 activation in response to metabolic stress which might contribute to the dystrophic alterations observed in the muscles of congenital DM1 patients.     

Non-infected preterm parturition is related to increased concentrations of IL-6, IL-8 and MCP-1 in human cervix

Background  

Human cervical ripening is an inflammatory process. In labour at term the mRNA-levels and protein concentrations for interleukin-6 (IL-6) and IL-8 in cervix significantly increase. The aim of this study was to investigate if there are differences in the inflammatory process of preterm and term cervical ripening.     

Scoparone inhibits PMA-induced IL-8 and MCP-1 production through suppression of NF-kappaB activation in U937 cells

Scoparone is a major component of the shoot of Artemisia capillaris (Compositae), which has been used for the treatment of hepatitis and biliary tract infection in oriental countries. In this study, the effects of scoparone on the expression of interleukin-8 (IL-8) and monocyte chemotactic protein-1 (MCP-1) and activation of nuclear factor-kappaB (NF-kappaB) were examined in U937 human monocytes activated with phorbol 12-myristate 13-acetate (PMA). Scoparone (5-100 microM) had no cytotoxic effect in unstimulated cells and concentration-dependently reversed PMA-induced toxicity in the cells stimulated with PMA. Scoparone concentration-dependently reduced the release of IL-8 and MCP-1 protein and expression of IL-8 and MCP-1 mRNA levels induced by PMA. Moreover, scoparone inhibited the levels of NF-kappaB-DNA complex and NF-kappaB activity in the cells stimulated with PMA in a concentration-dependent manner. Scoparone dose-dependently inhibited the phosphorylation of IkappaBalpha and nuclear translocation of NF-kappaB1 p50, RelA p65, and c-Rel p75. These data suggest that scoparone may inhibit the expression of chemokines (IL-8 and MCP-1) in PMA-stimulated U937 cells and a potential mechanism of scoparone may be inhibition of NF-kappaB activation, which is linked to inhibition of NF-kappaB subunits (NF-kappaB1 p50, RelA p65, and c-Rel p75) translocation via suppression of IkappaBalpha phosphorylation.