sTNFR-IgGFc融合基因在内皮细胞中的表达及其对小鼠关节炎模型的基因治疗研究

可溶性肿瘤坏死因子受体(sTNFR)可以拮抗肿瘤坏死因子的活性,因此已被用来治疗与TNF相关的炎性疾病。本研究将sTNFR与IgGFc片段的融合蛋白基因克隆到真核表达载体pStar上,转染到人的内皮细胞中,获得了表达。表达的sTNFR-IgGFc能够拮抗TNFα对L929细胞的细胞毒活性。将该质粒DNA与脂质体混合,经尾静脉注射到Ⅱ型胶原诱导的关节炎小鼠体内后,应用RT-PCR在鼠的肝脏检测到了sTNFR-IgGFc的表达,并显著地改善了治疗组小鼠关节炎症状和病理反应。这表明抗TNF基因治疗有可能作为治疗类风湿性关节炎的新的途径。     

Comparison of cytokine production in cultures of whole human blood and purified mononuclear cells.

In order to examine inter- and intra-individual variations in cytokine production, blood was collected from 48 healthy subjects on each of 4 occasions separated by 4 weeks. Whole blood (diluted 1:10) and mononuclear cell (MNC) cultures were stimulated for 24 h with either concanavalin A (Con A) or bacterial lipopolysaccharide (LPS) and the concentrations of IL-1alpha, IL-1beta, IL-2, TNF-alpha, IL-10 and IFN-gamma in the culture medium measured. There were highly significant inter-individual variations in the production of each of the cytokines measured. However, the level of the production of each cytokine appeared to be characteristic of an individual. There were significant correlations between production of each cytokine in whole blood and MNC cultures. It is concluded that there is significant inter-individual variation in cytokine production which is unaffected by time or by the stimulus used to elicit cytokine production, and that whole blood cultures can be used instead of MNC cultures to measure cytokine production.     

A novel TNFalpha antagonizing peptide-Fc fusion protein designed based on CDRs of TNFalpha neutralizing monoclonal antibody

The variable regions of antibody molecules bind antigens with high affinity and specificity. The binding sites are imparted largely to the hypervariable portions (i.e., CDRs) of the variable region. Peptides derived from CDRs can bind antigen with similar specificity acting as mimic of antibody and become drug-designing core, although with markedly lower affinity. In order to increase the affinity and bioactivity, in this study, a novel peptide (PT) designed on CDRs of a TNFalpha neutralizing monoclonal antibody Z12 was linked with Fc fragment of human IgG1. The interaction mode of PT-linker-Fc (PLF) with TNFalpha was analyzed with computer-guided molecular modeling method. After expression in Escherichia coli and purification, recombinant PT-linker-Fc could bind directly with the TNFalpha coated on the ELISA plates. Furthermore, PLF could competitively inhibit the binding of Z12 to TNFalpha and also inhibit the TNFalpha-induced cytotoxicity on L929 cells. The TNFalpha antagonizing activity of PLF was significantly higher than that of the free peptide. This study highlights the potential of human Fc to enhance the potency of peptides designed on the CDRs of antibodies and could be useful in developing new TNFalpha antagonists.     

In humans, corticotropin releasing hormone antagonizes some of the negative immunoregulatory effects of serotonin

Both corticotropin releasing hormone (CRH) and serotonin (5-HT) participate in the stress response and are known to modulate cytokine release by human immune cells. Extracellular 5-HT concentrations at or above the serum values have negative immunoregulatory effects by inhibiting the production of interferon-gamma (IFNgamma), a pro-inflammatory cytokine produced by Th-1-like lymphocytes, whereas 5-HT has no significant effects on the production of interleukin-10 (IL-10), an anti-inflammatory cytokine. In one study, CRH significantly decreases IFNgamma production by cultured human peripheral blood immunocytes, whereas in other studies CRH increases the production of cytokines, such as IL-1, IL-2 and IL-6. The aims of the present study were to examine i) the effects of CRH, 10-9 M, 10(-8) M and 10(-7) M, on the stimulated production of IFNgamma, IL-10 and tumor necrosis factor-alpha (TNFalpha) by human whole blood; and ii) whether CRH, 10(-9) M, 10(-8) M and 10(-7) M, may antagonize some of the negative immunoregulatory effects of 5-HT, 1.5 microg/mL or 15 microg/mL. We found that CRH, 10(-9) M, 10(-8) M and 10(-7) M, had no significant effects either on the stimulated production of IFNgamma, IL-10 or TNFalpha or on the IFNg/IL-10 production ratio, which reflects the pro-inflammatory capacity of the culture. 5-HT, 1,5 microg/dL and 15 microg/dL, significantly suppressed the production of IFNgamma and TNFalpha and the IFNg/IL-10 production ratio. CRH, 10(-7) M, significantly reversed the 5-HT (1.5 microg/mL and 15 microg/mL)-induced suppression of IFNg production. CRH at all concentrations significantly blocked the 5-HT (1.5 microg/mL and 15 microg/mL)-induced suppression of TNFalpha production. The results suggest that CRH has no significant direct effects on the production of IFNgamma, IL-10 and TNFalpha, but antagonizes the negative immunoregulatory effects of 5-HT on the production of IFNgamma and TNFalpha and on the IFNgamma/IL-10 production ratio.     

Endosomal-lysosomal proteolysis mediates death signalling by TNFalpha,not by etoposide,in L929 fibrosarcoma cells: evidence for an active role of cathepsin D

In several 'in vitro' models of apoptosis, lysosomal proteolysis has been shown to play an active role in mediating the death signal by cytokines or antiblastic drugs. Depending on the experimental cell model and the cytotoxic stimulus applied, an increased expression and the cytosolic translocation of either cathepsin D or B have been reported in apoptotic cells. We have analysed the involvement of these lysosomal proteases in a canonical apoptotic cell model, namely L929 fibroblasts, in which apoptosis was induced by cytotoxic agents acting through different mechanisms: (i) the cytokine TNFalpha, which triggers the cell suicide via interaction with its membrane receptor, and (ii) the topoisomerase II-inhibitor etoposide (VP16), which directly causes DNA damage. In both cases the activity of cathepsins B and D increased in apoptosing cultures. CA074-Me, a specific inhibitor of cathepsin B, and Leupeptin, a broad inhibitor of serine and cysteine proteases (among which is cathepsin B), did not exert any protection from TNFalpha. In contrast, pre-loading the cells with pepstatin A, a specific inhibitor of cathepsin D, protected L929 cells from TNFalpha cytotoxicity by more than 50%. However, no protection was observed if pepstatin A was added concomitantly with the cytokine. Inhibition of either cathepsin B or D did not impede apoptosis induced by etoposide. Lysosomal integrity was preserved and cathepsin D remained still confined in vesicular structures in apoptotic cells treated with either TNFalpha or etoposide. It follows that proteolysis by cathepsin D is likely to represent an early event in the death pathway triggered by TNFalpha and occurs within the endosomal-lysosomal compartment.     

Pharmacologic inhibition of tpl2 blocks inflammatory responses in primary human monocytes, synoviocytes, and blood

Tumor necrosis factor alpha (TNFalpha) is a pro-inflammatory cytokine that controls the initiation and progression of inflammatory diseases such as rheumatoid arthritis. Tpl2 is a MAPKKK in the MAPK (i.e. ERK) pathway, and the Tpl2-MEK-ERK signaling pathway is activated by the pro-inflammatory mediators TNFalpha, interleukin (IL)-1beta, and bacterial endotoxin (lipopolysaccharide (LPS)). Moreover, Tpl2 is required for TNFalpha expression. Thus, pharmacologic inhibition of Tpl2 should be a valid approach to therapeutic intervention in the pathogenesis of rheumatoid arthritis and other inflammatory diseases in humans. We have developed a series of highly selective and potent Tpl2 inhibitors, and in the present study we have used these inhibitors to demonstrate that the catalytic activity of Tpl2 is required for the LPS-induced activation of MEK and ERK in primary human monocytes. These inhibitors selectively target Tpl2 in these cells, and they block LPS- and IL-1beta-induced TNFalpha production in both primary human monocytes and human blood. In rheumatoid arthritis fibroblast-like synoviocytes these inhibitors block ERK activation, cyclooxygenase-2 expression, and the production of IL-6, IL-8, and prostaglandin E(2), and the matrix metalloproteinases MMP-1 and MMP-3. Taken together, our results show that inhibition of Tpl2 in primary human cell types can decrease the production of TNFalpha and other pro-inflammatory mediators during inflammatory events, and they further support the notion that Tpl2 is an appropriate therapeutic target for rheumatoid arthritis and other human inflammatory diseases.     

Effect of a four-week course of interleukin-10 on cytokine production in a placebo-controlled study of HIV-1-infected subjects

Interleukin (IL)-10 suppresses synthesis of the pro-inflammatory cytokines tumor necrosis factor (TNF)alpha, IL-1beta, and interferon (IFN)gamma. Since pro-inflammatory cytokines have been implicated in the production of human immunodeficiency virus type 1 (HIV-1), cytokine synthesis in whole blood cultures were determined during a 4-week course of subcutaneous IL-10 injections in 33 HIV-1-infected patients. Patients were randomized into four groups: placebo (nine), IL-10 at 1 microg/kg/day (nine), IL-10 at 4 microg/kg/day (six) and IL-10 at 8 microg/kg three times per week (nine). Whole blood was obtained at the beginning and conclusion of the study and was stimulated for 24 hours with the combination of IL-18 plus lipopolysaccharide. TNFalpha production in stimulated whole blood was reduced three and six hours after the first injection of IL-10 compared to subjects injected with the placebo. After four weeks of treatment, production of IFNgamma was suppressed in a greater number of patients in the IL-10 treatment groups compared to subjects in the placebo group. Similarly, IL-1beta production was lower in the IL-10 treatment groups compared to subjects receiving placebo. In contrast, after four weeks of IL-10, circulating levels of the anti-inflammatory TNF soluble receptor p55 increased dose-dependently compared to placebo subjects. Patient heterogeneity and small sample size presented difficulties in establishing statistical significance. Although the cytokine changes in our study did not demonstrate statistically significant changes, the data nevertheless reveal that four weeks of IL-10 therapy in HIV-1 infected subjects produced the anticipated suppression of pro-inflammatory cytokines.     

Capsaicin inhibits the production of tumor necrosis factor alpha by LPS-stimulated murine macrophages, RAW 264.7: a PPARgamma ligand-like action as a novel mechanism

Capsaicin, a major ingredient of hot pepper, is considered to exhibit anti-inflammatory properties. Our previous study demonstrated that capsaicin inhibited the production of pro-inflammatory mediators through NF-kappaB inactivation in LPS-stimulated macrophages. In order to further clarify the mechanism underlying the anti-inflammatory action of capsaicin, we investigated whether capsaicin alters PPARgamma activity, which regulates the production of the pro-inflammatory cytokine TNFalpha. Capsaicin significantly inhibited the production of TNFalpha by macrophages in a dose-dependent manner. Simultaneous exposure of the cells to capsaicin and PPARgamma agonist troglitazone or RXR agonist LG100268 resulted in stronger inhibition of TNFalpha production compared to the cells treated with either capsaicin, troglitazone, or LG100268 alone. Luciferase reporter assay revealed that capsaicin induced GAL4/PPARgamma chimera and full length PPARgamma (PPRE) transactivations in a dose-dependent manner. Furthermore, a specific PPARgamma antagonist T0070907 abrogated the inhibitory action of capsaicin on LPS-induced TNFalpha production by RAW 264.7 cells, indicating that capsaicin acts like a ligand for PPARgamma. Our data demonstrate for the first time that the anti-inflammatory action of capsaicin may be mediated by PPARgamma activation in LPS-stimulated RAW 264.7 cells.     

Regulation of pro-inflammatory cytokine expression by curcumin in hyaline membrane disease (HMD)

Persistent expression of pro-inflammatory cytokines is believed to play a major role in the pathogenesis of chronic lung disease (CLD) in premature infants. Inhibition of pro-inflammatory cytokine production in the lungs of preterm newborns may result in the attenuation of CLD. Curcumin is a naturally occurring phenolic compound derived from the food spice tumeric with broad based in vitro anti-inflammatory properties. In this study lung inflammatory cells from preterm newborns at risk for the development of CLD were derived via modified broncho-alveolar lavage and stimulated ex vivo with lipopolysaccharide (LPS) (10 ng/ml). Curcumin was added to these cultures at 0, 0.5 and 20 uM concentrations. Pro-inflammatory cytokine, TNFalpha, IL-1beta and IL-8 protein was measured from the culture supernatants 12 hours post culture. For control, adult peripheral blood mononuclear cells (PBMC) were cultured under the same conditions. Both neonatal lung inflammatory cells and adult PBMC produced high levels of pro-inflammatory cytokines in response to LPS. Curcumin produced significant inhibition of IL-1beta and IL-8 but minimal inhibition of TNFalpha expression by preterm lung inflammatory cells at 20 uM concentrations. Adult PBMC expression of IL-8 was significantly inhibited by curcumin at 20 uM concentrations. Therefore, curcumin inhibits pro-inflammatory cytokine production (TNFalpha, IL-1beta and IL-8) by lung inflammatory cells ex vivo. Pathways involved with curcumin regulation of these cytokines are developmentally intact and functional in premature infants. Curcumin may be effective as a therapeutic agent in the attenuation of CLD.     

Inter-individual and intra-individual variability in TNF-alpha production by human peripheral blood cells in vitro

BACKGROUND: Two assays--isolated peripheral blood mononuclear cells (PBMC) and a whole blood assay (WBA)--are commonly used to study TNF-alpha production by an individual in order to distinguish between high and low cytokine producers. We assessed the reliability and reproducibility of these assays. METHODS: The PBMC assays (n=5) were performed weekly over a period of 6 weeks and the WBAs (n=4) weekly over a 4-week period. Polymethylmethacrylate particles (approx. 6 x 10(2) particles/cell) and optimal concentrations of endotoxin (6.25 and 12.5 ng/ml) were used as the stimulatory agents in PBMC and WBAs, respectively. TNF-alpha production was measured by ELISA. RESULTS: There was a high degree of both intra- and inter-individual variability of TNF-alpha secretion, with unpredictable changes in the amount of the cytokine produced by cells from the same donor. This variability could not be eliminated by correcting for cell numbers. CONCLUSION: The PBMC and WBA models of TNF-alpha production by human peripheral blood cells cannot be used for the evaluation of inter-individual variability in cytokine secretion due to the high intra-individual variability observed. In the case of PBMC this is partly due to differences in the confluency of the cells between individuals.     

CD45-induced tumor necrosis factor alpha production in monocytes is phosphatidylinositol 3-kinase-dependent and nuclear factor-kappaB-independent

The pro-inflammatory cytokine tumor necrosis factor (TNF)-alpha plays a pivotal role in the pathogenesis of rheumatoid arthritis. The mechanisms involved in regulating monocyte/macrophage TNFalpha production are not yet fully understood but are thought to involve both soluble factors and cell/cell contact with other cell types. Ligation of certain cell surface receptors, namely CD45, CD44, and CD58, can induce the production of TNFalpha in monocytes. In this paper, we investigate further the signaling pathways utilized by cell surface receptors (specifically CD45) to induce monocyte TNFalpha and compare the common/unique pathways involved with that of lipopolysaccharide. The results indicate that monocyte TNFalpha induced upon CD45 ligation or lipopolysaccharide stimulation is differentially modulated by phosphatidylinositol 3-kinase and nuclear factor-kappaB but similarly regulated by p38 mitogen-activated protein kinase. These results demonstrate that both common and unique signaling pathways are utilized by different stimuli for the induction of TNFalpha. These observations may have a major bearing on approaches to inhibiting TNFalpha production in disease where the cytokine has a pathogenic role.     

TNFalpha release from peripheral blood leukocytes depends on a CRM1-mediated nuclear export

Tumor necrosis factor-alpha (TNFalpha) is a potent pro-inflammatory cytokine that plays a major role in the pathogenesis of acute and chronic inflammatory disorders such as septic shock and arthritis, respectively. Leukocytes stimulated with inflammatory signals such as lipopolysaccharide (LPS) are the predominant producers of TNFalpha, and thus control of TNFalpha release from stimulated leukocytes represents a potential therapeutic target. Here, we report that leptomycin B (LMB), a specific inhibitor of CRM1-dependent nuclear protein export, inhibits TNFalpha release from LPS-stimulated human peripheral blood neutrophils and mononuclear cells. In addition, immunofluorescence confocal microscopy and immunoblotting analysis indicate that TNFalpha is localized in the nucleus of human neutrophils and mononuclear cells. This study demonstrates that the cellular release of TNFalpha from stimulated leukocytes is mediated by the CRM1-dependent nuclear export mechanism. Inhibition of CRM1-dependent cellular release of TNFalpha could thus provide a novel therapeutic approach for disorders involving excessive TNFalpha release.     

SPPL2a and SPPL2b promote intramembrane proteolysis of TNFalpha in activated dendritic cells to trigger IL-12 production

Homologues of signal peptide peptidase (SPPLs) are putative aspartic proteases that may catalyse regulated intramembrane proteolysis of type II membrane-anchored signalling factors. Here, we show that four human SPPLs are each sorted to a different compartment of the secretory pathway. We demonstrate that SPPL2a and SPPL2b, which are sorted to endosomes and the plasma membrane, respectively, are functional proteases that catalyse intramembrane cleavage of tumour necrosis factor alpha (TNFalpha). The two proteases promoted the release of the TNFalpha intracellular domain, which in turn triggers expression of the pro-inflammatory cytokine interleukin-12 by activated human dendritic cells. Our study reveals a critical function for SPPL2a and SPPL2b in the regulation of innate and adaptive immunity.     

(+)-Catechin inhibits tumour angiogenesis and regulates the production of nitric oxide and TNF-alpha in LPS-stimulated macrophages

The anti-angiogenic activity of (+)-catechin as well as its regulatory effect on the production of nitric oxide and TNFalpha were studied using in vivo and in vitro models. In vivo angiogenic activity was studied using B16F-10 melanoma cell-induced capillary formation in C57BL/6 mice. Administration of (+)-catechin significantly inhibited (36.09%) the number of tumour-directed capillaries induced by injecting B16F-10 melanoma cells on the ventral side of C57BL/6 mice. The cytokine profile in the serum of these animals showed a drastically increased level of proinflammatory cytokines such as IL-1 beta, IL-6, TNF-alpha, GM-CSF and the direct endothelial cell proliferating agent, VEGF. Administration of (+)-catechin could differentially regulate elevation of these cytokines. The differential elevation is further evidenced by the increased production of IL-2 and tissue inhibitor of metalloproteinase-1 (TIMP-1) in the B16F-10 injected, (+)-catechin-treated animals. In vitro L929 bioassay revealed the inhibition of TNF-alpha production by (+)-catechin treatment. In the rat aortic ring assay, (+)-catechin inhibited the microvessel outgrowth at non-toxic concentrations. (+)-Catechin at non-toxic concentrations (5-25 microg/ml) showed significant inhibition in the proliferation, migration and tube formation of endothelial cells, which are the key events in the process of angiogenesis. (+)-Catechin also showed inhibitory effect on VEGF mRNA levels in B16F-10 melanoma cells. (+)-Catechin inhibited the production of NO and TNF-alpha in LPS-stimulated primary macrophages. Taken together, these results demonstrate that (+)-catechin inhibits tumour-specific angiogenesis by regulating the production of pro- and anti-angiogenic factors such as pro-inflammatory cytokines, nitric oxide, VEGF, IL-2 and TIMP-1. These results also suggest that (+)-catechin could significantly inhibit nitrite and TNF-alpha production in LPS-stimulated macrophages.     

Whole blood assay to access T cell-immune responses to Mycobacterium tuberculosis antigens in healthy Brazilian individuals

The production of interferon gamma (IFNgamma) guarantees effective T cell-mediated immunity against Mycobacterium tuberculosis infection. In the present study, we simply compare the in vitro immune responses to Mycobacterium antigens in terms of IFNg production in a total of 10 healthy Brazilian volunteers. Whole blood and mononuclear cells were cultivated in parallel with PPD, Ag85B, and M. bovis hsp65, and five-days supernatants were harvested for cytokine detection by ELISA. The inter-assay result was that the overall profile of agreement in response to antigens was highly correlated (r(2) = 0.9266; p = 0.0102). Potential analysis is in current progress to dictate the usefulness of this method to access the immune responses also in tuberculosis patients and its contacts.     

IL-1 synergy with IL-2 in the generation of lymphokine activated killer cells is mediated by TNF-alpha and beta (lymphotoxin).

Interleukin 1 is a pleuripotent cytokine shown to synergize with IL-2 in the generation of lymphokine-activated killer (LAK) cells, when cultured with human peripheral blood mononuclear cells (PBMC) or peripheral blood lymphocytes (PBL). When IL-1 and low dose IL-2 are added in combination, both LAK cytotoxicity and proliferation are increased in short-term (5-6 day) and long-term (12-14 day) cultures compared with cells activated with IL-2 alone. The purpose of this study was to examine the contribution of tumor necrosis factor (TNF-alpha), lymphotoxin (LT, or TNF-beta) and the TNF receptor in the observed IL-1/IL-2 mediated synergy. Analysis of lymphocyte culture supernatants using the L929 bioassay and by specific ELISAs demonstrated an increased production of both TNF and LT in those cells cultured with IL-1 and IL-2. Utilizing specific neutralizing antisera, our experiments demonstrated the biologic activity of both cytokines, with LT-specific antibodies producing the greatest diminution of IL-1/IL-2 stimulated cell proliferation and cytotoxicity. The addition of IL-1 and IL-2 in combination markedly upregulated TNF-receptor expression (measured by Scatchard analysis) in comparison with cells stimulated with IL-2 alone. Characterization of the TNF-R by flow cytometric analysis revealed increased membrane expression of the 75 kDa, but not the 55 kDa, TNF binding protein as a result of IL-1 costimulation.     

Establishment of a consistent L929 bioassay system for TNF-alpha quantitation to evaluate the effect of lipopolysaccharide, phytomitogens and cytodifferentiation agents on cytotoxicity of TNF-alpha secreted by adherent human mononuclear cells

TUMOR necrosis factor-alpha (TNF-alpha) plays an important role in the pathogenesis of rheumatoid arthritis. The present study was to evaluate the effects of lipopolysaccharide (LPS), phytomitogens and cytodifferentiation agents on cytotoxicity of TNF-alpha secreted by adherent human mononuclear cells (AMC). TNF-alpha cytotoxicity in LPS-treated, phytomitogen-treated, and cytodifferentiation agent-treated AMC supernatants were analyzed by the L929 bioassay system. Our results showed that LPS could induce homogeneous TNF-alpha production by AMC whereas, in addition to TNF-alpha, phytomitogens could also induce other TNF-like factors. Neither methotrexate, retinoic acid nor sodium butyrate can inhibit TNF-alpha cytotoxicity, while hexamethylene bisacetamide could not only inhibit TNF-alpha cytotoxicity but also TNF-alpha inducing ability of LPS to AMC.     

CD36 Contributes to Malaria Parasite-Induced Pro-Inflammatory Cytokine Production and NK and T Cell Activation by Dendritic Cells

The scavenger receptor CD36 plays important roles in malaria, including the sequestration of parasite-infected erythrocytes in microvascular capillaries, control of parasitemia through phagocytic clearance by macrophages, and immunity. Although the role of CD36 in the parasite sequestration and clearance has been extensively studied, how and to what extent CD36 contributes to malaria immunity remains poorly understood. In this study, to determine the role of CD36 in malaria immunity, we assessed the internalization of CD36-adherent and CD36-nonadherent Plasmodium falciparum-infected red blood cells (IRBCs) and production of pro-inflammatory cytokines by DCs, and the ability of DCs to activate NK, and T cells. Human DCs treated with anti-CD36 antibody and CD36 deficient murine DCs internalized lower levels of CD36-adherent IRBCs and produced significantly decreased levels of pro-inflammatory cytokines compared to untreated human DCs and wild type mouse DCs, respectively. Consistent with these results, wild type murine DCs internalized lower levels of CD36-nonadherent IRBCs and produced decreased levels of pro-inflammatory cytokines than wild type DCs treated with CD36-adherent IRBCs. Further, the cytokine production by NK and T cells activated by IRBC-internalized DCs was significantly dependent on CD36. Thus, our results demonstrate that CD36 contributes significantly to the uptake of IRBCs and pro-inflammatory cytokine responses by DCs, and the ability of DCs to activate NK and T cells to produce IFN-γ. Given that DCs respond to malaria parasites very early during infection and influence development of immunity, and that CD36 contributes substantially to the cytokine production by DCs, NK and T cells, our results suggest that CD36 plays an important role in immunity to malaria. Furthermore, since the contribution of CD36 is particularly evident at low doses of infected erythrocytes, the results imply that the effect of CD36 on malaria immunity is imprinted early during infection when parasite load is low.     

ERK-dependent induction of TNFalpha expression by the environmental contaminant benzo(a)pyrene in primary human macrophages

Polycyclic aromatic hydrocarbons (PAHs) such as benzo(a)pyrene (BP) are toxic environmental contaminants known to enhance production of pro-inflammatory cytokines such as IL-1beta. The present study was designed in order to determine whether TNFalpha, another cytokine acting in inflammation, may also constitute a target for these chemicals. Both TNFalpha mRNA and TNFalpha secretion levels were found to be enhanced in human BP-treated macrophages. Dioxin, a contaminant activating the aryl hydrocarbon receptor (AhR) like PAHs, was also shown to increase TNFalpha expression. BP-mediated TNFalpha induction was however not suppressed by AhR antagonists, making unlikely the involvement of the typical AhR signalling pathway. BP-exposure of macrophages did not enhance NF-kappaB DNA binding activity, but it activated the MAP kinase ERK1/2. In addition, the use of chemical inhibitors of extracellular signal-regulated protein kinase (ERK) activation fully abrogated induction of TNFalpha production in BP-treated macrophages. These data likely indicate that PAHs enhance TNFalpha expression in human macrophages through an ERK-related mechanism. Such a regulation may contribute to confer pro-inflammatory properties to these widely-distributed environmental contaminants.