Role of SOCS-1 Gene on Melanoma Cell Growth and Tumor Development

Melanoma is the most aggressive form of skin cancer, and its incidence has increased dramatically over the years. The murine B16F10 melanoma in syngeneic C57Bl/6 mice has been used as a highly aggressive model to investigate tumor development. Presently, we demonstrate in the B16F10-Nex2 subclone that silencing of SOCS-1, a negative regulator of Jak/Stat pathway, leads to reversal of the tumorigenic phenotype and inhibition of melanoma cell metastasis. SOCS-1 silencing with short hairpin RNA affected tumor growth and cell cycle regulation with arrest at the S phase with large-sized nuclei, reduced cell motility, and decreased melanoma cell invasion through Matrigel. A clonogenic assay showed that SOCS-1 acted as a modulator of resistance to anoikis. In addition, down-regulation of SOCS-1 decreased the expression of epidermal growth factor receptor ( mainly the phosphorylated-R), Ins-R alpha, and fibroblast growth factor receptor. In vivo, silencing of SOCS-1 inhibited subcutaneous tumor growth and metastatic development in the lungs. Because SOCS-1 is expressed in most melanoma cell lines and bears a relation with tumor invasion, thickness, and stage of disease, the present results on the effects of SOCS-1 silencing in melanoma suggest that this regulating protein can be a target of cancer therapy.

Impaired dendritic cell differentiation and maturation in the absence of C3

Human monocytes can be differentiated into immature dendritic cells (DCs) in the presence of serum and cytokines. One of the main functions of immature DCs is to capture and process antigens. Following maturation, they differentiate into antigen presenting cells. The role of complement in the differentiation process from monocytes towards immature DCs remains elusive. Here we demonstrate that complement 3 (C3) has a regulatory impact on the expression of specific DC surface molecules and DC-derived cytokine production during DC differentiation. We isolated human adherent peripheral blood mononuclear cells, which were cultured in the presence of GM-CSF plus IL-4 in medium supplemented with normal human serum or C3 deficient serum. The lack of C3 during DC differentiation negatively impacted the expression of C-type lectin receptor DC-SIGN, the antigen presenting molecules HLA-DR and CD1a, and the costimulatory molecules CD80 and CD86. Further, the spontaneous production of IL-6 and IL-12 was reduced in the absence of C3. Moreover, the maturation of immature DCs in response to LPS challenge was impaired in the absence of C3 as evidenced by reduced MHC-II, co-stimulatory molecule expression as well as modulated IL-12 and TNF-alpha production. Collectively, our results provide evidence for a novel role of C3 as a critical cofactor in human DC differentiation and maturation. (C) 2007 Elsevier Ltd. All rights reserved.

Up-regulation of NADPH oxidase components and increased production of interferon-gamma by leukocytes from sickle cell disease patients

We have previously demonstrated that mononuclear leukocytes from patients with sickle cell disease (SCD) release higher amounts of superoxide compared with normal controls. The aim of this study was to further study the NADPH oxidase system in these patients by investigating gene expression of NADPH oxidase components, phosphorylation of p47(phox) component, and the release of cytokines related to NADPH oxidase activation in mononuclear leukocytes from patients with SCD. gp91(phox) gene expression was significantly higher in monocytes from SCD patients compared with normal controls (P = 0.036). Monocytes from SCD patients showed higher levels of p47 phox phosphorylation compared with normal controls. INF-gamma release by lymphocytes from SCD patients was significantly higher compared with normal controls, after 48 h culture with phytohemagglutinin (P = 0.02). The release of TNF-alpha by monocytes from SCD patients and normal controls was similar after 24 and 48 h culture with lipopolysaccharide (P > 0.05). We conclude that monocytes from SCD patients show higher levels of gp91(phox) gene expression and p47(phox) phosphorylation, along with increased IFN-gamma release by SCD lymphocytes. These findings help to explain our previous observation showing the increased respiratory burst activity of mononuclear leukocytes from SCD patients and may contribute to inflammation and tissue damage in these patients.

Insulin suppresses LPS-induced iNOS and COX-2 expression and NF-kappa B activation in alveolar macrophages

The development of septic shock is a common and frequently lethal consequence of gram-negative infection. Mediators released by lung macrophages activated by bacterial products such as lipopolysaccharide (LPS) contribute to shock symptoms. We have shown that insulin downregulates LPS-induced TNF production by alveolar macrophages (AMs). In the present study, we investigated the effect of insulin on the LPS-induced production of nitric oxide (NO) and prostaglandin (PG)-E(2), on the expression of inducible nitric oxide synthase ( iNOS) and cyclooxygenase (COX)-2, and on nuclear factor kappa B (NF-kappa B) activation in AMs. Resident AMs from male Wistar rats were stimulated with LPS (100 ng/mL) for 30 minutes. Insulin (1 mU/mL) was added 10 min before LPS. Enzymes expression, NF-kappa B p65 activation and inhibitor of kappa B (I-kappa B) a phosphorylation were assessed by immunobloting; NO by Griess reaction and PGE(2) by enzyme immunoassay (EIA). LPS induced in AMs the expression of iNOS and COX-2 proteins and production of NO and PGE(2), and, in parallel, NF-kappa B p65 activation and cytoplasmic I-kappa B alpha phosphorylation. Administration of insulin before LPS suppressed the expression of iNOS and COX-2, of NO and PGE(2) production and Nuclear NF-kappa B p65 activation. Insulin also prevented cytoplasmic I-kappa Ba phosphorylation. These results show that in AMs stimulated by LPS, insulin prevents nuclear translocation of NF-kappa B, possibly by blocking I-kappa Ba degradation, and supresses the production of NO and PGE(2), two molecules that contribute to septic shock. Copyright (C) 2008 S. Karger AG, Basel.

Mannose-binding lectin complement pathway plays a key role in complement activation by Paracoccidioides brasiliensis

Paracoccidioides brasiliensis (Pb) is a dimorphic fungal pathogen that causes paracoccidioidomycosis the most severe deep mycosis from South America Although cell mediated immunity is considered the most efficient protective mechanism against Pb infection mechanisms of innate immunity are poorly defined Herein we investigated the interaction of the complement system with high and low virulence isolates of Pb We demonstrated that Pb18 a high virulence Pb Isolate when incubated with normal human serum (NHS) induces consumption of hemolytic complement and when immobilized promotes binding of C4b C3b and C5b-C9 Both low virulence (Pb265) and high virulence (Pb18) isolates consumed C4 C3 and mannose-binding learn (MBL) of MBL-sufficient but not of MBL-deficient serum as revealed by deposition of residual C4 C3 and MBL on immune complexes and mannan However higher complement components consumption was observed with Pb265 as compared with Pb18 The suggested relationship between low virulence and significant complement activation properties of Pb isolates was confirmed by the demonstration that virulence attenuation of Pb 18 results in acquisition of the ability to activate complement Conversely reactivation of attenuated Pb18 results in loss of the ability to activate complement Our results demonstrate for the first time that Pb yeasts activate the complement system by the lectin pathway and there is an Inverse correlation between complement activating ability and Pb virulence These differences could exert an influence on Innate immunity and severity of the disease developed by infected hosts (C) 2010 Elsevier Ltd All rights reserved

A Novel Pathway for Inducible Nitric-oxide Synthase Activation through Inflammasomes

Innate immune recognition of flagellin is shared by transmembrane TLR5 and cytosolic Nlrc4 (NOD-like receptor family CARD (caspase activation recruitment domain) domain containing 4)/Naip5 (neuronal apoptosis inhibitory protein 5). TLR5 activates inflammatory genes through MYD88 pathway, whereas Nlrc4 and Naip5 assemble multiprotein complexes called inflammasomes, culminating in caspase-1 activation, IL-1 beta/IL-18 secretion, and pyroptosis. Although both TLR5 and Naip5/Nlrc4 pathways cooperate to clear infections, little is known about the relative anti-pathogen effector mechanisms operating through each of them. Here we show that the cytosolic flagellin (FLA-BSDot) was able to activate iNOS, an enzyme previously associated with TLR5 pathway. Using Nlrc4- or Naip5-deficient macrophages, we found that both receptors are involved in iNOS activation by FLA-BSDot. Moreover, distinct from extracellular flagellin (FLA-BS), iNOS activation by intracellular flagellin is completely abrogated in the absence of caspase-1. Interestingly, IL-1 beta and IL-18 do not seem to be important for FLA-BSDot-mediated iNOS production. Together, our data defined an additional anti-pathogen effector mechanism operated through Naip5 and Nlrc4 inflammasomes and illustrated a novel signaling transduction pathway that activates iNOS.

Sustained activation of p53 in confluent nucleotide excision repair-deficient cells resistant to ultraviolet-induced apoptosis

p53 activation is one of the main signals after DNA damage, controlling cell cycle arrest, DNA repair and apoptosis. We have previously shown that confluent nucleotide excision repair (NER)-deficient cells are more resistant to apoptosis induced by ultraviolet irradiation (UV). Here, we further investigated the effect of cell confluence on UV-induced apoptosis in normal and NER-deficient (XP-A and XP-C) cells, as well as the effects of treatments with the ATWATR inhibitor caffeine, and the patterns of p53 activation. Strong p53 activation was observed in either proliferating or confluent cells. Caffeine increased apoptosis levels and inhibited p53 activation in proliferating cells, suggesting a protective role for p53. However, in confluent NER-deficient cells no effect of caffeine was observed. Transcription recovery measurements showed decreased recovery in proliferating XPA-deficient cells, but no recovery was observed in confluent cells. The levels of the cyclin/Cdk inhibitor, p21(Waf1/Cip1), correlated well with p53 activation in proliferating cells. Surprisingly, confluent cells also showed similar activation of p21(Waf1/Cip1). These results indicate that reduced apoptosis in confluent cells is associated with the deficiency in DNA damage removal, since this effect is not clearly observed in NER-proficient cells. Moreover, the strong activation of p53 in confluent cells, which barely respond to apoptosis, suggests that this protein, under these conditions, is not linked to UV-induced cell death signaling. (c) 2008 Elsevier B.V. All rights reserved.

Inhibitory Signals Mediated by Programmed Death-1 Are Involved With T-Cell Function in Chronic Periodontitis

Background: Inhibitory signals mediated via molecules such as programmed death-1 (PD-1) play a critical role in downmodulating immune responses and maintaining peripheral tolerance. We investigated the involvement of cytokines and PD-1 engagement in mediating the T-cell unresponsiveness to bacterial and ubiquitous antigens in periodontal diseases. Methods: Gingival and peripheral blood samples from healthy individuals and patients with chronic periodontitis were collected and used for the subsequent assays. Leukocytes in the lesion site and blood were evaluated using flow cytometry. The production of interferon-gamma, interleukin-10, and transforming growth factor-P proteins was evaluated by enzyme-linked immunosorbent assay (ELISA), and the presence of PD-1+cells in the inflamed gingiva was confirmed by immunofluorescence confocal microscopy for CD4 and PD-1 colocalization. Results: T cells from patients with chronic periodontitis proliferated poorly in response to Aggregatibacter actinomycetem comitans (previously Actinobacillus actinomycetemcomitans) antigen. T-cell unresponsiveness was not associated with imbalanced cytokine production. However, T cells from patients with chronic periodontitis expressed significantly higher levels of PD-1 either upon isolation or after culture with antigens. Moreover, PD-1 blocking did not result in significant T-cell proliferation in cells cultured with phytohemagglutinin or bacterial antigens. The blockade of PD-1 resulted in the increased production of IFN-gamma. In addition, CD4+ and CD8+ T cells expressing PD-1 accumulated in lesions with chronic periodontitis. Conclusion: These data show that PD-1 engagement could be involved in the modulation of IFN-gamma production by T cells in patients with chronic periodontitis. J Periodontol 2009,80:1833-1844.

Peptide gomesin triggers cell death through L-type channel calcium influx, MAPK/ERK, PKC and PI3K signaling and generation of reactive oxygen species

Gomesin is an antimicrobial peptide isolated from hemocytes of a common Brazilian tarantula spider named Acanthoscurriagomesiana. This peptide exerts antitumor activity in vitro and in vivo by an unknown mechanism. In this study, the cytotoxic mechanism of gomesin in human neuroblastoma SH-SY5Y and rat pheochromocytoma PC12 cells was investigated. Gomesin induced necrotic cell death and was cytotoxic to SH-SY5Y and PC12 cells. The peptide evoked a rapid and transient elevation of intracellular calcium levels in Fluo-4-AM loaded PC12 cells, which was inhibited by nimodipine, an L-type calcium channel blocker. Preincubation with nimodipine also inhibited cell death induced by gomesin in SH-SY5Y and PC12 cells. Gomesin-induced cell death was prevented by the pretreatment with MAPK/ERK, PKC or PI3K inhibitors, but not with PKA inhibitor. In addition, gomesin generated reactive oxygen species (ROS) in SH-SY5Y cells, which were blocked with nimodipine and MAPK/ERK, PKC or PI3K inhibitors. Taken together, these results suggest that gomesin could be a useful anticancer agent, which mechanism of cytotoxicity implicates calcium entry through L-type calcium channels, activation of MAPK/ERK, PKC and PI3K signaling as well as the generation of reactive oxygen species. (C) 2010 Elsevier Ireland Ltd. All rights reserved.

CD8(+) T cell adjuvant effects of Salmonella FliCd flagellin in live vaccine vectors or as purified protein

Salmonella flagellin, the flagellum structural subunit, has received particular interest as a vaccine adjuvant conferring enhanced immunogenity to soluble proteins or peptides, both for activation of antibody and cellular immune responses. In the present study, we evaluated the Salmonella enterica FliCd flagellin as a T cell vaccine adjuvant using as model the 9-mer (SYVPSAEQI) synthetic H2(d)-restricted CD8(+) T cell-specific epitope (CS(280-288)) derived from the Plasmodium yoelii circumsporozoite (G) protein. The FliCd adjuvant effects were determined under two different conditions: (i) as recombinant flagella, expressed by orally delivered live S. Dublin vaccine strains expressing the target CS(280-288) peptide fused at the central hypervariable domain, and (ii) as purified protein in acellular vaccines in which flagellin was administered to mice either as a recombinant protein fused or admixed with the target CS(280-288) peptide. The results showed that CS(280-288)-specific cytotoxic CD8(+) T cells were primed when BALB/c mice were orally inoculated with the expressing the CS280-288 epitope S. Dublin vaccine strain. In contrast, mice immunized with purified FliCd admixed with the CS280-288 peptide and, to a lesser extent, fused with the target peptide developed specific cytotoxic CD8(+) T cell responses without the need of a heterologous booster immunization. The CD8(+) T cell adjuvant effects of flagellin, either fused or not with the target peptide, correlated with the in vivo activation of CD11c(+) dendritic cells. Taken together, the present results demonstrate that Salmonella flagellins are flexible adjuvant and induce adaptative immune responses when administered by different routes or vaccine formulations. (C) 2009 Elsevier Ltd. All rights reserved.

Increased Activation of Stromal Interaction Molecule-1/Orai-1 in Aorta From Hypertensive Rats A Novel Insight Into Vascular Dysfunction

Disturbances in the regulation of cytosolic calcium (Ca(2+)) concentration play a key role in the vascular dysfunction associated with arterial hypertension. Stromal interaction molecules (STIMs) and Orai proteins represent a novel mechanism to control store-operated Ca(2+) entry. Although STIMs act as Ca(2+) sensors for the intracellular Ca(2+) stores, Orai is the putative pore-forming component of Ca(2+) release-activated Ca(2+) channels at the plasma membrane. We hypothesized that augmented activation of Ca(2+) release-activated Ca(2+)/Orai-1, through enhanced activity of STIM-1, plays a role in increased basal tonus and vascular reactivity in hypertensive animals. Endothelium-denuded aortic rings from Wistar-Kyoto and stroke-prone spontaneously hypertensive rats were used to evaluate contractions because of Ca(2+) influx. Depletion of intracellular Ca(2+) stores, which induces Ca(2+) release-activated Ca(2+) activation, was performed by placing arteries in Ca(2+) free-EGTA buffer. The addition of the Ca(2+) regular buffer produced greater contractions in aortas from stroke-prone spontaneously hypertensive rats versus Wistar-Kyoto rats. Thapsigargin (10 mu mol/L), an inhibitor of the sarcoplasmic reticulum Ca(2+) ATPase, further increased these contractions, especially in stroke-prone spontaneously hypertensive rat aorta. Addition of the Ca(2+) release-activated Ca(2+) channel inhibitors 2-aminoethoxydiphenyl borate (100 mu mol/L) or gadolinium (100 mu mol/L), as well as neutralizing antibodies to STIM-1 or Orai-1, abolished thapsigargin-increased contraction and the differences in spontaneous tone between the groups. Expression of Orai-1 and STIM-1 proteins was increased in aorta from stroke-prone spontaneously hypertensive rats when compared with Wistar-Kyoto rats. These results support the hypothesis that both Orai-1 and STIM-1 contribute to abnormal vascular function in hypertension. Augmented activation of STIM-1/Orai-1 may represent the mechanism that leads to impaired control of intracellular Ca(2+) levels in hypertension. (Hypertension. 2009; 53[part 2]: 409-416.)

Intracellular peptides as natural regulators of cell signaling

Protein degradation by the ubiquitin proteasome system releases large amounts of oligopeptides within cells. To investigate possible functions for these intracellularly generated oligopeptides, we fused them to a cationic transactivator peptide sequence using reversible disulfide bonds, introduced them into cells, and analyzed their effect on G protein-coupled receptor (GPCR) signal transduction. A mixture containing four of these peptides (20-80 mu M) significantly inhibited the increase in the extracellular acidification response triggered by angiotensin II (ang II) in CHO-S cells transfected with the ang II type 1 receptor (AT1R-CHO-S). Subsequently, either alone or in a mixture, these peptides increased luciferase gene transcription in AT1R-CHO-S cells stimulated with ang II and in HEK293 cells treated with isoproterenol. These peptides without transactivator failed to affect GPCR cellular responses. All four functional peptides were shown in vitro to competitively inhibit the degradation of a synthetic substrate by thimet oligopeptidase. Overexpression of thimet oligopeptidase in both CHO-S and HEK293 cells was sufficient to reduce luciferase activation triggered by a specific GPCR agonist. Moreover, using individual peptides as baits in affinity columns, several proteins involved in GPCR signaling were identified, including alpha-adaptin A and dynamin 1. These results suggest that before their complete degradation, intracellular peptides similar to those generated by proteasomes can actively affect cell signaling, probably representing additional bioactive molecules within cells.

Differential expression of new LTA splice variants upon lymphocyte activation

Lymphotoxin alpha (LTA) is a member of the TNF cytokine superfamily, produced principally by lymphocytes. It plays an important role in immune and inflammatory responses. Many TNF superfamily members have functionally important isoforms generated by alternative splicing but alternative splicing of LTA has never been studied. The known LTA protein is encoded by a transcript containing four exons. Here we report seven new LTA splice variants, three of them evolutionary conserved. We demonstrate their presence in cytoplasmic RNA suggesting that they could be translated into new LTA isoforms. We observed that their expression is differentially regulated upon activation of peripheral blood mononuclear cells and lymphocyte subpopulations (CD4+, CD8+, and CD19+). Our data suggest that the new LTA splice variants might play a role in the regulation of the immune response. (C) 2007 Elsevier Ltd. All rights reserved.

Mycoplasma synoviae cell invasion: Elucidation of the Mycoplasma pathogenesis in chicken

Fluorochrome-labelled cells of two field isolates and Mycoplasma synoviae (Ms) were inoculated onto monolayer cultures of fluorochrome-labelled HEp-2 cells and monitored by confocal laser scanning microscopy (CLSM). Ms was detected initially adhered to and subsequently inside the host cells. Between 24 and 48 h of infection, Ms was detected in the perinuclear region, and after 72 h of infection was confirmed by gentamicin invasion assay. High and low passage Ms strains showed no differences in adherence or invasion. The morphology and the actin filaments of the infected HEp-2 cells were preserved throughout the study period. The observed invasion by Ms is consistent with the biology of Mollicutes, and could explain the difficulties in recovering field isolates of the mycoplasma and in controlling the infection in birds even after long-term antibiotic treatment. (C) 2009 Elsevier Ltd. All rights reserved.

Melatonin triggers PKA activation in the rodent malaria parasite Plasmodium chabaudi

Calcium (Ca2+) is a critical regulator of many aspects of the Plasmodium reproductive cycle. In particular, intra-erythrocyte Plasmodium parasites respond to circulating levels of the melatonin in a process mediated partly by intracellular Ca2+. Melatonin promotes the development and synchronicity of parasites, thereby enhancing their spread and worsening the clinical implications. The signalling mechanisms underlying the effects of melatonin are not fully established, although both Ca2+ and cyclic AMP (cAMP) have been implicated. Furthermore, it is not clear whether different strains of Plasmodium use the same, or divergent, signals to control their development. The aim of this study was to explore the signalling mechanisms engaged by melatonin in P. chabaudi, a virulent rodent parasite. Using parasites at the throphozoite stage acutely isolated from mice erythrocytes, we demonstrate that melatonin triggers cAMP production and protein kinase A (PKA) activation. Interestingly, the stimulation of cAMP/PKA signalling by melatonin was dependent on elevation of Ca2+ within the parasite, because buffering Ca2+ changes using the chelator BAPTA prevented cAMP production in response to melatonin. Incubation with melatonin evoked robust Ca2+ signals within the parasite, as did the application of a membrane-permeant analogue of cAMP. Our data suggest that P. chabaudi engages both Ca2+ and cAMP signalling systems when stimulated by melatonin. Furthermore, there is positive feedback between these messengers, because Ca2+ evokes cAMP elevation and vice versa. Melatonin more than doubled the observed extent of parasitemia, and the increase in cAMP concentration and PKA activation was essential for this effect. These data support the possibility to use melatonin antagonists or derivates in therapeutic approach.