Modification of proinflammatory cytokine production by the antirheumatic agents tenidap and naproxen. A possible correlate with clinical acute phase response.

The cytokines IL-6, IL-1, and TNF play a key role in the pathogenesis of rheumatoid arthritis (RA) and initiate hepatic serum amyloid A (SAA) expression after injury. To provide a possible mechanistic explanation for the previous observation that plasma SAA concentrations decreased during treatment of RA patients with tenidap, but increased during treatment with naproxen, the present study compared the effects of tenidap and naproxen on the two stages of SAA expression: cytokine production by human PBMC and cytokine-stimulated SAA synthesis by human Hep3B hepatoma cells. Tenidap inhibited production of IL-6 greater than TNF greater than IL-1; the effect of naproxen on production of all three cytokines was lesser and least on IL-6. Indeed, an increase in IL-6 production was observed after exposure to naproxen. PBMC beta-2-microglobulin production and total protein synthesis were unaffected at concentrations and times at which effects on cytokine production were observed. Cell density was a significant factor in the extent to which cytokines were stimulated by LPS. Approximately physiologic cell densities, 0.5 to 1 x 10(6) cells/ml, were optimal for stimulation of IL-1-beta and IL-6 production by LPS; however, greater amounts of TNF were produced at lower cell densities. Because neither tenidap nor naproxen inhibited SAA synthesis by cytokine-stimulated Hep3B cells and because they differ most significantly in their effect on IL-6 production, the results support a role for IL-6 in the continued stimulation of SAA production during RA.     

The pharmacologic regulation of interleukin-1 production: the role of prostaglandins

The role of prostaglandins in the regulation of lipopolysaccharide (LPS)-induced interleukin-1 (IL-1) production by murine C3H/HeN resident peritoneal macrophages was studied. IL-1 production was initially studied in the presence of piroxicam and indomethacin, both inhibitors of prostaglandin biosynthesis. IL-1 was assayed using the IL-1-dependent proliferative response of C3H/HeJ thymocytes. LPS stimulation resulted in 15 to 20 ng/ml of prostaglandin E2 (PGE2) produced in the first hour of culture. IL-1-containing supernatants from drug-treated macrophages at dilutions of up to 1:32 resulted in enhanced thymocyte proliferation compared to control, non-drug-treated cultures and contained less than 2 ng/ml of PGE2. Similar enhancement of proliferation could be obtained by incubating non-drug-treated supernatants with monoclonal anti-PGE2 but not anti-thromboxane B2 (TxB2) antibody. Further dilutions of the drug-treated supernatants gave thymocyte proliferation responses which were indistinguishable from control cultures and, correspondingly, had identical values for IL-1 production. The absence of an effect on IL-1 production was confirmed by quantitation of intracellular IL-1 alpha using goat anti-IL-1 alpha antibody and by quantitation of supernatant IL-1 receptor competition assay. Exogenous PGE2, in the concentration range produced in macrophage supernatants (10-20 ng/ml), directly inhibited IL-1-stimulated thymocyte proliferation. Finally, when macrophages were stimulated with LPS for 24 hr in the presence of added PGE2, thymocyte proliferation was inhibited at the lowest supernatant dilutions, but as the IL-1-containing supernatants were diluted out, the assay curves were indistinguishable from non-PGE2-treated control. Thus, in this system, PGE2 has no effect on IL-1 synthesis, but rather has a direct inhibitory effect on thymocyte proliferation. Nonsteroidal anti-inflammatory drugs are not stimulating IL-1 production but are, in fact, relieving inhibition of the thymocyte IL-1 assay caused by the presence of prostaglandins.     

Selective macrophage suppression during sepsis

Polymicrobial sepsis induces suppression of macrophage function as determined by a reduction of pro-inflammatory cytokine production upon re-exposure to lipopolysaccharide (LPS) in vitro. We examined whether macrophages were refractory to only LPS challenge or if they were immunoparalyzed and unable to respond to other stimuli such as lipoteichoic acid (LTA) or zymosan (ZYM). This study evaluated the capacity of peritoneal macrophages to produce pro-inflammatory and anti-inflammatory cytokines as well as chemokines following mild or severe sepsis induced by cecal ligation and puncture (CLP). Peritoneal macrophages were isolated 29 h after CLP and challenged with different stimuli. LPS was a more potent stimulus for cytokine induction than LTA or ZYM in both mild and severe sepsis. In mild sepsis, the macrophage cytokine response to LPS was selective and less refractory than in severe sepsis. While production of IL-6 and KC was reduced, secretion of TNF-alpha and MIP-1alpha was enhanced in those cells isolated from mice with mild sepsis. Production of IL-10 and the IL-1 receptor antagonist , MIP-2, and MCP-1 in response to LPS stimulation was equivalent to the amount produced by naive macrophages. Our results indicate that macrophages are not immunoparalyzed during sepsis and may still be induced to secrete some inflammatory mediators.     

Leukotrienes do not regulate interleukin 1 production by activated macrophages

The objective of this work was to investigate the role of leukotrienes in the production of IL-1 by activated human peripheral blood monocytes and mouse peritoneal macrophages. Using overnight adherent macrophages, stimulation with lipopolysaccharide or zymosan caused a time-dependent increase in IL-1 production. LTC4 was detected and preceded IL-1 production only in zymosan-treated macrophages. Lipopolysaccharide did not stimulate macrophages to produce LTC4. Zymosan-stimulated LTC4 production was inhibited by the lipoxygenase inhibitors, ICI207968 (3.20 microM), nordihydroguaiaretic acid (0.22 microM), phenidone (4.60 microM), REV5901 (0.20 microM), and the Merck 5-lipoxygenase "translocation inhibitor" MK886 (0.02 microM) with IC50 values as shown in parenthesis. However, none of these inhibitors reduced IL-1 production at concentrations which completely inhibited leukotriene synthesis. Taken together, these results do not support a role for leukotrienes in the production of IL-1 by zymosan-activated macrophages.     

Modulation by propranolol of the uptake of ethidium bromide by rat submandibular acinar cells exposed to a P2X(7) agonist or to maitotoxin

We have compared the formation of pores in rat submandibular acinar cells in response to 2',3'-O-(4-benzoylbenzoyl) adenosine 5'-triphosphate (Bz-ATP) and maitotoxin. Bz-ATP (100 microM) permeabilized the cells to ethidium bromide. The uptake of ethidium increased to 29+/-1% of maximal uptake in 10 min. DL-Propranolol (300 microM) inhibited the Bz-ATP-induced uptake of ethidium bromide by 40% without affecting the P2X(7)-gated cation channel. The inhibitory effect of DL-propranolol on the formation of pores by Bz-ATP was reproduced by D-propranolol, an optical isomer with very poor beta-blocking activity. Tenidap, an antiinflammatory drug, enhanced the permeabilization in response to Bz-ATP. Propanolol inhibited the response to tenidap plus Bz-ATP. The effect of propranolol was reproduced by labetolol, a beta-adrenergic antagonist with membrane-stabilizing properties, but not by atenolol, which blocks beta-adrenergic receptors but has no effect on the stability of the membrane. In the presence of extracellular calcium, maitotoxin also increased the uptake of ethidium bromide. Tenidap had no effect on this response, which was delayed by propranolol. In conclusion, we have shown that propranolol, in a range of 10-300 microM, inhibits the pore-forming activity of the P2X(7) receptor without affecting the opening of the cation channel coupled to this receptor. This inhibition is not related to its beta-adrenergic blocking activity but rather to its membrane-stabilizing properties. Propranolol also delays the uptake of ethidium bromide in response to maitotoxin. This is in agreement with the current view that P2X(7) agonists and maitotoxin share a common pore.     

Over-expression of hsp-70 inhibits bacterial lipopolysaccharide-induced production of cytokines in human monocyte-derived macrophages

Cytokines released from monocytes and macrophages are major mediators of inflammation. Heat shock significantly inhibits cytokine production from these cells. To investigate whether this inhibitory effect was mediated by heat-shock proteins (HSP), we transfected human peripheral blood monocyte-derived macrophages (MDM) with HSP-70 cDNA and examined Brucella melitensis lipopolysaccharide (LPS)-induced cytokine production in transfected cells. Over-expression of HSP-70 protein in the gene-transfected MDM had no effect on cytokine synthesis unless LPS was added. LPS-induced increases in production of tumour necrosis factor alpha (TNF-alpha), interleukin 1beta (IL-1beta), IL-10 and IL-12 were significantly inhibited by the over-expression of HSP-70. However, over-expression of HSP-70 did not block LPS-induced increase in IL-6 synthesis. To further confirm these results, an antisense HSP-70 DNA oligomer was used to block HSP-70 synthesis. The inhibitory effect of HSP-70 on LPS-induced cytokine production in gene- transfected cells was completely reversed after treatment of cells with 5 microM antisense HSP-70. The same concentration of antisense HSP-70 also partially reversed heat-shock-induced inhibition of LPS-stimulated cytokine production. These results suggest that HSP-70 is involved in the regulation of LPS-induced cytokine production and that this family of proteins plays a role in mitigating adverse effects of endotoxin during infection or other pathological stresses.     

Ability of 15-hydroxyeicosatrienoic acid (15-OH-20:3) to modulate macrophage arachidonic acid metabolism

Mouse peritoneal macrophages metabolize dihomogammalinolenic acid (20:3n-6) primarily to 15-hydroxy-8,11,13-eicosatrienoic acid (15-OH-20:3). Since the biological properties of this novel trienoic eicosanoid remain poorly defined, the effects of increasing concentrations of 15-OH-20:3 and its arachidonic acid (20:4n-6) derived analogue. 15-hydroxy-5,8,11,13-eicosatetraenoic acid (15-HETE), on mouse macrophage 20:4n-6 metabolism were investigated. Resident peritoneal macrophages were prelabeled with [3H]-20:4n-6 and subsequently stimulated with zymosan in the presence of either 15-OH-20:3 or 15-HETE (1-30 microM). After 1 hr, the radiolabeled soluble metabolites were analyzed by reverse phase high performance liquid chromatography. 15-OH-20:3 inhibited zymosan-induced leukotriene C4 (IC50 = 2.4 microM) and 5-HETE (IC50 = 3.1 microM) synthesis. In contrast to the inhibition of macrophage 5-lipoxygenase, 15-OH-20:3 enhanced 12-HETE synthesis (5-30 microM) and had no measurable effect on cyclooxygenase metabolism (1-10 microM) i.e., 6-keto-prostaglandin F1 alpha and prostaglandin E2 synthesis. Addition of exogenous 15-HETE produced similar effects. These results suggest that the manipulation of macrophage 15-OH-20:3n-6 levels may provide a measure of cellular control over 20:4n-6 metabolism, specifically, leukotriene production.     

Surfactant protein A inhibits alveolar macrophage cytokine production by CD14-independent pathway

The lung collectin surfactant protein A (SP-A) has both anti-inflammatory and prophagocytic activities. We and others previously showed that SP-A inhibits the macrophage production of tumor necrosis factor (TNF)-alpha stimulated by the gram-negative bacterial component LPS. We propose that SP-A decreases the production of proinflammatory cytokines by alveolar macrophages via a CD14-independent mechanism. SP-A inhibited LPS-simulated TNF-alpha production in rat and mouse macrophages in the presence and absence of serum (72% and 42% inhibition, respectively). In addition, SP-A inhibited LPS-induced mRNA levels for TNF-alpha, IL-1 alpha, and IL-1 beta as well as NF-kappa B DNA binding activity. SP-A also diminished ultrapure LPS-stimulated TNF-alpha produced by wild-type and CD14-null mouse alveolar macrophages by 58% and 88%, respectively. Additionally, SP-A inhibited TNF-alpha stimulated by PMA in both wild-type and TLR4-mutant macrophages. These data suggest that SP-A inhibits inflammatory cytokine production in a CD14-independent manner and also by mechanisms independent of the LPS signaling pathway.     

Interleukin 1alpha activity of peritoneal and bone marrow macrophages infected with Leishmania major and Leishmania donovani in vitro

In this study, the pattern of interleukin-1alpha (IL-1alpha) production by both peritoneal (PM) and bone marrow macrophages (BMM) from resistant (C3H/HeJ) and susceptible (BALB/c) mice was investigated, using a bioassay and an IL-1alpha-specific ELISA kit. PM from normal uninfected mice showed either an initial high (C3H/HeJ) or a neglected (BALB/c) level of IL-1alpha activity, respectively, probably due to thioglycollate stimulation. Infection with Leishmania major induced only a marginal effect on IL-1 production by both cells. Normal, uninfected and unstimulated BMM from both mice did not produce IL-1alpha over a 7-day period of cultivation in vitro. Upon stimulation with either lipopolysaccharide (LPS) (BALB/c) or concanavalin A (Con A) (C3H/HeJ), both cell types produced IL-1alpha that peaked within the first 12-24 h following stimulation. BMM from C3H/HeJ and BALB/c mice failed to produce IL-1alpha when infected in vitro with L. major or L. donovani promastigotes. However, infection with these two parasites did not interfere with the capability of the host cell to produce IL-1alpha when stimulated with LPS or Con A. The level of IL-1alpha production was independent of the degree of parasitization of the macrophages. Similar results were observed with IL-1beta and IL-6 production by BMM, even though their levels were generally slightly higher than those obtained with IL-1alpha.     

IL-10 inhibits cytokine production by activated macrophages

IL-10 inhibits the ability of macrophage but not B cell APC to stimulate cytokine synthesis by Th1 T cell clones. In this study we have examined the direct effects of IL-10 on both macrophage cell lines and normal peritoneal macrophages. LPS (or LPS and IFN-gamma)-induced production of IL-1, IL-6, and TNF-alpha proteins was significantly inhibited by IL-10 in two macrophage cell lines. Furthermore, IL-10 appears to be a more potent inhibitor of monokine synthesis than IL-4 when added at similar concentrations. LPS or LPS- and IFN-gamma-induced expression of IL-1 alpha, IL-6, or TNF-alpha mRNA was also inhibited by IL-10 as shown by semiquantitative polymerase chain reaction or Northern blot analysis. Inhibition of LPS-induced IL-6 secretion by IL-10 was less marked in FACS-purified peritoneal macrophages than in the macrophage cell lines. However, IL-6 production by peritoneal macrophages was enhanced by addition of anti-IL-10 antibodies, implying the presence in these cultures of endogenous IL-10, which results in an intrinsic reduction of monokine synthesis after LPS activation. Consistent with this proposal, LPS-stimulated peritoneal macrophages were shown to directly produce IL-10 detectable by ELISA. Furthermore, IFN-gamma was found to enhance IL-6 production by LPS-stimulated peritoneal macrophages, and this could be explained by its suppression of IL-10 production by this same population of cells. In addition to its effects on monokine synthesis, IL-10 also induces a significant change in morphology in IFN-gamma-stimulated peritoneal macrophages. The potent action of IL-10 on the macrophage, particularly at the level of monokine production, supports an important role for this cytokine not only in the regulation of T cell responses but also in acute inflammatory responses.     

IL-1 beta is secreted by activated murine macrophages as biologically inactive precursor

IL-1 alpha and IL-beta are distinct cytokines, produced by activated macrophages. The temporal sequence in the processing and secretion as well as the mechanism(s) by which IL-1 is secreted from the cells remain undefined. Here we have studied the production of IL-1 from murine macrophages after stimulation with LPS or Listeria monocytogenes by two distinct methods: i) immunoprecipitation of radio-labeled IL-1 peptides from culture supernatants, and ii) determination of IL-1 activity by neutralization with monospecific antisera to either form of IL-1. We confirmed that precursor and mature forms of both IL-1 alpha and IL-1 beta can be detected in the culture supernatants after stimulation of the macrophages with 10 to 20 micrograms LPS/ml but, in addition, we report the novel finding that IL-1 beta is exclusively secreted in its unprocessed precursor form after stimulation of the cells with either 0.5 to 1 microgram LPS/ml or with L. monocytogenes. Exposure of the cells to increasing amounts of LPS led to the appearance of a 20-kDa IL-1 beta peptide in the culture supernatants concomitant with the release of a processing activity for the IL-1 beta precursor. These data therefore suggest that, in a first step, IL-1 beta is secreted as an unprocessed precursor protein that in a second, postsecretory step is cleaved by a LPS-inducible protease, thus generating the 20-kDa IL-1 beta peptide. The latter represents the biologically active IL-1 beta inasmuch as the generation of IL-1 beta activity in the culture supernatants strictly correlated with the appearance of the 20-kDa IL-1 beta peptide.     

15-Deoxy-delta(12,14)-prostaglandin J(2) inhibits IL-10 and IL-12 production by macrophages

15-Deoxy-Delta(12,14)-prostaglandin J(2) (dPGJ(2)) is a metabolite of prostaglandin D(2), that binds to peroxisome proliferator-activated receptor gamma (PPARgamma). PPARgamma and prostaglandin D(2) synthase, which is required for dPGJ(2) synthesis, are predominantly expressed in macrophages. In contrast, IL-10 and IL-12 produced by macrophages stimulate Th1 and Th2 immune response, respectively. This study investigated the effect of dPGJ(2) on IL-10 and IL-12 production by macrophages in response to lipopolysaccharide (LPS). Our data clearly demonstrated that dPGJ(2) inhibits LPS-induced IL-10 and IL-12 production by macrophages. A different agonist of PPARgamma, 13-hydroxyoctadecadienoic acid, similarly inhibited the production of IL-10 and IL-12 in response to LPS. Further, dPGJ(2) did not appear to act through the PGD(2) receptor. These results suggest that dPGJ(2) may inhibit LPS-induced IL-10 and IL-12 production by macrophages through PPARgamma.     

Modulator of intracellular Ca(2+), thapsigargin, interferes with in vitro secretion of cytokines and nitric oxide

Interference of thapsigargin (TG), an inhibitor of endoplasmic reticulum Ca(2+) ATPase, with immune reactivity of murine macrophages was investigated under conditions in vitro. The activation of cells with lipopolysaccharide (LPS), interferon-(gamma) (IFN-(gamma)), and with acyclic nucleoside phosphonate N(6)-isobutyl-9-[2-(phosphonomethoxy)ethyl]- 2,6-diaminopurine (N(6)-isobutyl-PMEDAP) resulted in enhanced production of cytokines TNF-alpha, IL-10, chemokines RANTES/CCL5 and MIP-1alpha/CCL3, as well as in substantially augmented production of nitric oxide (NO) triggered by IFN-(gamma). The effects were in a dual mode of action influenced by TG (1 microM). While TG upregulated secretion of TNF-alpha, it inhibited secretion of IL-10 and RANTES. The immune-stimulated secretion of MIP-1alpha remained virtually unaffected, though TG on its own activated expression of MIP-1alpha in macrophages. The high-output NO production induced by IFN-(gamma), high concentrations of LPS, or by combination of IFN-(gamma) plus LPS or N(6)-isobutyl-PMEDAP was inhibited by TG. On the other hand, production of NO which was marginally activated by low concentration of LPS was upregulated by TG.     

Lipopolysaccharide and interleukin 1 inhibit interferon-gamma-induced Fc receptor expression on human monocytes

The objectives of these studies were to study the effects of bacterial lipopolysaccharide (LPS) on interferon-gamma (IFN-gamma)-induced Fc receptor expression on human monocytes and to examine whether these effects were mediated through stimulation of interleukin 1 (IL-1) production. Fc receptor expression was determined by binding of monomeric monoclonal murine immunoglobulin (Ig)G2a and cytofluorographic analysis. IL-1 activity in monocyte supernatants and lysates was assayed by augmentation of mitogen-induced murine thymocyte proliferation. IFN-gamma induced the expression of Fc receptors on human monocytes that were specific for murine IgG2a. This induction was inhibited by the addition of LPS in amounts as low as 2 to 8 pg/ml. LPS inhibition of IFN-gamma-induced Fc receptor expression was paralleled by the appearance of IL-1 in monocyte lysates and supernatants. The addition of purified human or recombinant IL-1 beta at the initiation of culture similarly inhibited the expression of IFN-gamma-induced Fc receptors on the monocytes. LPS also inhibited Fc receptor expression on the human myelomonocytic cell line THP-1 after induction with IFN-gamma or phorbol myristate acetate alone or with both agents together. This inhibition also was paralleled by the production of IL-1 but the addition of exogenous IL-1 to the THP-1 cells had no effect on IFN-gamma-induced Fc receptor expression. Tumor necrosis factor (TNF) inhibited IFN-gamma-induced Fc receptor expression on human monocytes but was much less potent than comparable amounts of IL-1. TNF also did not inhibit Fc receptor expression on THP-1 cells. In fact, IL-1 or TNF led to an enhancement in IFN-gamma-induced Fc receptor expression on THP-1 cells. These results indicate that LPS can inhibit IFN-gamma-induced Fc receptor expression on human monocytes and that IL-1 and TNF may mediate these effects of LPS. Thus, an autocrine or paracrine role is suggested for these cytokines. The possibility exists that intracellular IL-1 resulting from LPS stimulation may be at least in part responsible for inhibition of Fc receptor expression.     

Selective regulation of cytokine induction by adenoviral gene transfer of IkappaBalpha into human macrophages: lipopolysaccharide-induced, but not zymosan-induced, proinflammatory cytokines are inhibited, but IL-10 is nuclear factor-kappaB independent

Macrophages are the major cytokine producers in chronic inflammatory diseases, but the biochemical pathways regulating cytokine production are poorly understood. This is because genetic tools to dissect signaling pathways cannot be used in macrophages because of difficulties in transfection. We have developed an adenoviral technique to achieve high efficiency gene delivery into macrophages and recently showed that spontaneous TNF-alpha production in rheumatoid arthritis joint cells, chiefly from macrophages, is 75% blocked by adenoviral transfer of IkappaBalpha. In this report we use the same adenovirus to investigate whether the production of a number of proinflammatory cytokines (e.g., TNF-alpha, IL-1beta, IL-6, and IL-8) from human macrophages depends on NF-kappaB. While the cytokine response to certain inducers, such as LPS, PMA, and UV light, is blocked by overexpression of IkappaBalpha, the response to zymosan is not. In contrast, anti-inflammatory mediators (IL-10 and IL-1 receptor antagonist) induced by LPS are only marginally inhibited by IkappaBalpha excess. These studies demonstrate several new points about macrophage cytokine production. First, there is heterogeneity of mechanisms regulating both the proinflammatory and anti-inflammatory cytokines within populations of a single cell type. In addition, the results confirm the utility of the adenoviral technique for functional analysis of cytokine induction. The results also confirm that there are autocrine and paracrine interactions regulating cytokine synthesis within a single cell type. The selectivity of NF-kappaB blockade for proinflammatory but not anti-inflammatory mediators indicates that in macrophages, NF-kappaB may be a good target for the treatment of chronic inflammatory diseases.     

Regulation of macrophage inflammatory protein-1 alpha expression and function by endogenous interleukin-10 in a model of acute inflammation

In this study we have determined the role of endogenous interleukin (IL)-10 on leucocyte recruitment and production of the CC chemokine macrophage inflammatory protein-1alpha (MIP-1alpha) in a murine model of acute inflammation. Intraperitoneal injection of zymosan produced a dose-dependent cellular infiltration which was concomitant with MIP-1alpha release in the lavage fluids. Release of this chemokine had a functional role since treatment of mice with a specific anti-MIP-1alpha antibody reduced both neutrophil and monocyte accumulation into the peritoneal cavity. An unexpected increase in cell influx and MIP-1alpha production was measured following depletion of resident peritoneal macrophages, as achieved by a 3-day liposome treatment. A similar result was obtained when the zymosan peritonitis response was elicited in IL-10 knock-out mice. In summary we propose a functional cross talk between endogenous IL-10 and this CC chemokine during the host inflammatory response.     

Differential expression and regulation of macrophage inflammatory protein (MIP)-1alpha and MIP-2 genes by alveolar and peritoneal macrophages in LPS-hyporesponsive C3H/HeJ mice

A point mutation in Toll-like receptor 4 (Tlr4) gene in C3H/HeJ mice underlies a defect in LPS-induced cytokine production by peritoneal macrophages (PMphi;). Whether the C-C and the C-X-C chemokines are induced differently by LPS between alveolar macrophages (AMphi;) and PMphi; in this mice remains unclear. Thus, we examined the expression and regulation of macrophage inflammatory protein-1alpha (MIP-1alpha) and macrophage inflammatory protein-2 (MIP-2) in C3H/HeJ macrophages. These results showed that the accumulation of MIP-1alpha and MIP-2 mRNA increased dose dependently in response to LPS. PMphi; responded to LPS to produce significantly higher levels of both chemokine mRNA and protein than AMphi;. In addition, both macrophages produced much more MIP-2 than MIP-1alpha by the same doses of LPS stimulation. Moreover, the chemokine production by C3H/HeN macrophages was significantly higher than that of the C3H/HeJ macrophages. IFN-gamma suppressed the LPS-induced MIP-1alpha release but enhanced the LPS-induced MIP-2 secretion in both macrophages. These results show that the chemokine production was induced and regulated differentially in AMphi; and PMphi;.     

Paradoxical anti-inflammatory actions of TNF-alpha: inhibition of IL-12 and IL-23 via TNF receptor 1 in macrophages and dendritic cells

IL-12 and TNF-alpha are central proinflammatory cytokines produced by macrophages and dendritic cells. Disregulation of TNF-alpha is associated with sepsis and autoimmune diseases such as rheumatoid arthritis. However, new evidence suggests an anti-inflammatory role for TNF-alpha. TNF-alpha-treated murine macrophages produced less IL-12p70 and IL-23, after stimulation with IFN-gamma and LPS. Frequency of IL-12p40-producing macrophages correspondingly decreased as measured by intracellular cytokine staining. IL-12p40 production was also inhibited in dendritic cells. TNFR1 was established as the main receptor involved in IL-12p40 regulation, because IL-12p40 levels were not affected by TNF-alpha in TNFR1(-/-)-derived macrophages. Macrophages activated during Listeria monocytogenes infection were more susceptible to inhibition by TNF-alpha than cells from naive animals, which suggests a regulatory role for TNF-alpha in later stages of infection. This nonapoptotic anti-inflammatory regulation of IL-12 and IL-23 is an important addition to the multitude of TNF-alpha-induced responses determined by cell-specific receptor signaling.