Involvement of p38 MAP Kinase in the inhibitory effects of phosphatidylserine liposomes on nitric oxide production from macrophages stimulated with LPS

Phosphatidylserine: A comprehensive overview of synthesis, metabolism, and nutrition

Phosphatidylserine (PtdS) is classified as a glycerophospholipid and a primary anionic phospholipid and is particularly abundant in the inner leaflet of the plasma membrane in neural tissues. It is synthesized from phosphatidylcholine or phosphatidylethanolamine by exchanging the base head group with serine, and this reaction is catalyzed by PtdS synthase-1 and PtdS synthase-2 located in the endoplasmic reticulum. PtdS exposure on the outside surface of the cell is essential for eliminating apoptotic cells and initiating the blood clotting cascade. It is also a precursor of phosphatidylethanolamine, produced by PtdS decarboxylase in bacteria, yeast, and mammalian cells. Furthermore, PtdS acts as a cofactor for several necessary enzymes that participate in signaling pathways. Beyond these functions, several studies indicate that PtdS plays a role in various cerebral functions, including activating membrane signaling pathways, neuroinflammation, neurotransmission, and synaptic refinement associated with the central nervous system (CNS). This review discusses the occurrence of PtdS in nature and biosynthesis via enzymes and genes in plants, yeast, prokaryotes, mammalian cells, and the brain, and enzymatic synthesis through phospholipase D (PLD). Furthermore, we discuss metabolism, its role in the CNS, the fortification of foods, and supplementation for improving some memory functions, the results of which remain unclear. PtdS can be a potentially beneficial addition to foods for kids, seniors, athletes, and others, especially with the rising consumer trend favoring functional foods over conventional pills and capsules. Clinical studies have shown that PtdS is safe and well tolerated by patients.

Involvement of splenic marginal zone macrophages in the recognition of systemically administered phosphatidylserine-coated liposomes in mice

Autoimmune diseases present a significant clinical problem, highlighting the need for the development of novel or improved therapeutic methods. One of the factors that causes autoimmune diseases is a defect in the clearance of apoptotic cells by phagocytes. Thus, improved apoptotic cell processing has been considered as a strategy to treat autoimmune diseases. However, therapeutic strategies focusing on apoptotic cell clearance have not been approved till date. We have reported that liposomes composed of phosphatidylserine (PS liposomes) exhibit anti-inflammatory or immunosuppressive effects in macrophages. A PS liposome display PS on its surface, which plays a crucial role in the phagocytosis of apoptotic cells by marginal zone macrophages (MZMs), a key player in the clearance of apoptotic cells, by recognizing PS exposed on the surface of apoptotic cells. Therefore, we hypothesized that PS liposomes could be used as "antigen delivery vesicles" to act as a substitute for apoptotic cells in the treatment of autoimmune diseases. In this study, we showed that systemically administered PS liposomes accumulated in the marginal zone of the spleen due to recognition of surface-displayed PS by MZMs because it was observed that liposomes without PS did not accumulate in the marginal zone. In conclusion, PS liposomes may be useful vehicles to function as active agents and/or antigens against autoimmune diseases.

Phosphatidylserine, inflammation, and central nervous system diseases

Phosphatidylserine (PS) is an anionic phospholipid in the eukaryotic membrane and is abundant in the brain. Accumulated studies have revealed that PS is involved in the multiple functions of the brain, such as activation of membrane signaling pathways, neuroinflammation, neurotransmission, and synaptic refinement. Those functions of PS are related to central nervous system (CNS) diseases. In this review, we discuss the metabolism of PS, the anti-inflammation function of PS in the brain; the alterations of PS in different CNS diseases, and the possibility of PS to serve as a therapeutic agent for diseases. Clinical studies have showed that PS has no side effects and is well tolerated. Therefore, PS and PS liposome could be a promising supplementation for these neurodegenerative and neurodevelopmental diseases.

Manufacture and characterization of anti-inflammatory liposomes from jumbo flying squid (Dosidicus gigas) skin phospholipid extraction

The anti-inflammation properties of marine phospholipids enriched with n-3 fatty acids contribute to anti-inflammatory and inflammation-resolving mediators. Functional squid-skin (SQ) liposomes were manufactured from squid-skin phospholipids, and their anti-inflammatory effects were investigated. SQ liposomes included phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidylethanolamine (PE), phosphatidylcholine (PC), and lysophosphatidylcholine (Lyso-PC), and had an approximate diameter of 100 mm. When RAW264.7 cells were treated with the SQ liposome, no (p > 0.05) cytotoxicity was observed below a concentration of 7.5 mg mL-1. An SQ-liposome pretreatment of lipopolysaccharide (LPS)-induced RAW 264.7 cells showed decreased (p < 0.05) prostaglandin E2 (PGE2), nitric oxide (NO), interleukin-1beta (IL-1β), IL-6, and tumor necrosis factor-alpha (TNF-α). The engulfment of SQ liposomes by the RAW264.7 cells resulted in lower (p < 0.05) LPS-induced intracellular levels of reactive oxygen species. Furthermore, an SQ-liposome administration ameliorated (p < 0.05) carrageenan-induced paw edema in mice. SQ liposomes may act via apoptotic mimicry to elicit the resolution of inflammation and prevent chronic inflammation-related diseases.

Therapeutic applications of reconstituted HDL: When structure meets function

Reconstituted forms of HDL (rHDL) are under development for infusion as a therapeutic approach to attenuate atherosclerotic vascular disease and to reduce cardiovascular risk following acute coronary syndrome and ischemic stroke. Currently available rHDL formulations developed for clinical use contain apolipoprotein A-I (apoA-I) and one of the major lipid components of HDL, either phosphatidylcholine or sphingomyelin. Recent data have established that quantitatively minor molecular constituents of HDL particles can strongly influence their anti-atherogenic functionality. Novel rHDL formulations displaying enhanced biological activities, including cellular cholesterol efflux, may therefore offer promising prospects for the development of HDL-based, anti-atherosclerotic therapies. Indeed, recent structural and functional data identify phosphatidylserine as a bioactive component of HDL; the content of phosphatidylserine in HDL particles displays positive correlations with all metrics of their functionality. This review summarizes current knowledge of structure-function relationships in rHDL formulations, with a focus on phosphatidylserine and other negatively-charged phospholipids. Mechanisms potentially underlying the atheroprotective role of these lipids are discussed and their potential for the development of HDL-based therapies highlighted.

Insulin-like growth factor-I induces arginase activity in Leishmania amazonensis amastigote-infected macrophages through a cytokine-independent mechanism

Leishmania (Leishmania) amazonensis exhibits peculiarities in its interactions with hosts. Because amastigotes are the primary form associated with the progression of infection, we studied the effect of insulin-like growth factor (IGF)-I on interactions between L. (L.) amazonensis amastigotes and macrophages. Upon stimulation of infected macrophages with IGF-I, we observed decreased nitric oxide production but increased arginase expression and activity, which lead to increased parasitism. However, stimulation of amastigote-infected macrophages with IGF-I did not result in altered cytokine levels compared to unstimulated controls. Because IGF-I is present in tissue fluids and also within macrophages, we examined the possible effect of this factor on phosphatidylserine (PS) exposure on amastigotes, seen previously in tissue-derived amastigotes leading to increased parasitism. Stimulation with IGF-I induced PS exposure on amastigotes but not on promastigotes. Using a PS-liposome instead of amastigotes, we observed that the PS-liposome but not the control phosphatidylcholine-liposome led to increased arginase activity in macrophages, and this process was not blocked by anti-TGF-β antibodies. Our results suggest that in L. (L.) amazonensis amastigote-infected macrophages, IGF-I induces arginase activity directly in amastigotes and in macrophages through the induction of PS exposure on amastigotes in the latter, which could lead to the alternative activation of macrophages through cytokine-independent mechanisms.

Phosphatidylserine-containing liposomes suppress inflammatory bone loss by ameliorating the cytokine imbalance provoked by infiltrated macrophages

Phosphatidylserine (PS)-containing liposomes (PSLs) strongly inhibit inflammatory bone loss in adjuvant arthritic (AA) rats. This effect was attributed to the inhibition of osteoclastogenesis through the secretion of prostaglandin E(2) and transforming growth factor-β1 by osteoclast precursors after the phagocytosis of PSLs. However, infiltrated macrophages are considered to secrete anti-inflammatory mediators after phagocytosis of PSLs, which also contribute to inhibiting osteoclastogenesis. In the present study, we have attempted to elucidate the effects of PSLs on the phenotype of infiltrated macrophages during inflammatory bone loss. In AA rats, the ankle joints swelled with the infiltration of both macrophages and helper T cells into the synovium after a complete Freund's adjuvant injection. In the ankle joints of AA rats, approximately half of the infiltrated macrophages underwent a phenotypic change from interleukin (IL)-1β-producing to IL-10-producing cells after the phagocytosis of PSLs. In lipopolysaccharide (LPS)-stimulated macrophages, PSLs also significantly decreased IL-1β production, but increased IL-10 production. Moreover, PSLs inhibited the rapid activation of p38 mitogen-activated protein kinases (MAPK) and nuclear factor (NF)-κB, but enhanced the delayed activation of extracellular signal-regulated kinase (ERK) in LPS-stimulated macrophages. PSL-induced different influence on the activities of p38 MAPK and ERK is a likely underlying mechanism for phenotypic change of infiltrated macrophages after the phagocytosis of PSLs. This phenotypic change may be responsible for a significant decrease in the mean mRNA level of the receptor activator of NF-κB (RANK) and the RANK ligand (RANKL) in the ankle joint of PSL-treated AA rats, resulting in the inhibition of inflammatory bone loss.

Oxaliplatin down-regulates survivin by p38 MAP kinase and proteasome in human colon cancer cells

Oxaliplatin, a platinum derivative cancer drug, has been used for treating human colorectal cancers. Survivin has been proposed as a cancer target, which highly expressed in most cancer cells but not normal adult cells. In this study, we investigated the regulation of survivin expression by exposure to oxaliplatin in human colon cancer cells. Oxaliplatin (3-9μM for 24h) markedly induced cytotoxicity, proliferation inhibition and apoptosis in the human RKO colon cancer cells. The survivin protein expression of RKO cells is dramatically reduced by oxaliplatin; however, the survivin gene expression is slightly altered. The survivin blockage of oxaliplatin elevated caspase-3 activation and apoptosis in RKO cells. Over-expression of survivin proteins by transfection with a survivin-expressed vector resisted the oxaliplatin-induced cancer cell death. Meantime, oxaliplatin elicited the phosphorylation of p38 mitogen-activated protein (MAP) kinase. SB202190, a specific p38 MAP kinase inhibitor, restored the survivin protein level and attenuated oxaliplatin-induced cancer cell death. In addition, oxaliplatin increased the levels of phospho-p53 (Ser-15) and total p53 proteins. Inhibition of p53 expression by a specific p53 inhibitor pifithrin-α reduced the phosphorylated p38 MAP kinase and active caspase-3 proteins in the oxaliplatin-exposed RKO cells. In contrast, SB202190 did not alter the oxaliplatin-induced p53 protein level. Furthermore, treatment with a specific proteasome inhibitor MG132 restored survivin protein level in the oxaliplatin-treated colon cancer cells. Taken together, our results demonstrate for the first time that survivin is down-regulated by p38 MAP kinase and proteasome degradation pathway after treatment with oxaliplatin in the human colon cancer cells.

Baicalein induces cancer cell death and proliferation retardation by the inhibition of CDC2 kinase and survivin associated with opposite role of p38 mitogen-activated protein kinase and AKT

The bioactive flavonoid baicalein has been shown to have in vitro growth-inhibitory activity in human cancer cells, although the mechanism of action is poorly understood. Baicalein (40-80 mumol/L for 24 h) more effectively induced cytotoxicity compared with other flavonoids (baicalin, catechin, genistein, quercetin, and rutin) in bladder cancer cells. Baicalein induced cell proliferation inhibition and apoptosis. The levels of cyclin B1 and phospho-CDC2 (Thr(161)) were reduced, whereas the G(2)-M phases were elevated by baicalein. Treatment of CDC2 kinase or CDC25 phosphatase inhibitors augments the baicalein-induced cytotoxicity. A variety of human bladder cancer cell lines expressed survivin proteins, which were located on the mitotic phases and regulated mitotic progression. Baicalein markedly reduced survivin protein expression. Transfection of a survivin small interfering RNA diminished the level of survivin proteins and increased the baicalein-mediated cell death. Overexpression of survivin enhanced cell proliferation and resisted the baicalein-induced cytotoxicity. Interestingly, baicalein induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and AKT. SB203580, a specific p38 MAPK inhibitor, attenuated proliferation inhibition and restored the protein levels of phospho-CDC2 (Thr(161)) and survivin in the baicalein-exposed cells; conversely, blockade of AKT activation enhanced cytotoxicity and the reduction of phospho-CDC2 (Thr(161)) and survivin proteins. As a whole, these findings provide that the opposite role of p38 MAPK and AKT regulates CDC2 kinase and survivin and the inhibition of CDC2-survivin pathway by baicalein contributes to apoptosis and proliferation retardation in cancer cells.

Involvement of phosphatidylinositol-3-kinase and ERK pathways in the production of TGF-beta1 by macrophages treated with liposomes composed of phosphatidylserine

We explored the involvement of phosphatidylinositol 3-kinase (PI3K) and ERK pathways in the production of TGF-beta1 by macrophages treated with liposomes composed of phosphatidylserine (PS-liposomes). PS-liposomes activated Akt, downstream of the PI3K signal cascade, and ERK which led to the expression of TGF-beta1. PI3K inhibitors, LY294002 and wortmannin, inhibited the activation of Akt and ERK following the treatment with PS-liposomes. These inhibitors also suppressed the production of TGF-beta1. Furthermore, PS-liposomes activated macrophages to induce TGF-beta1 expression through PS-specific receptors. These findings suggested that a PI3K-ERK signaling pathway via the PS-receptor is intimately involved in the production of TGF-beta1 which regulates macrophage functions.

Luteolin inhibits lipopolysaccharide actions on human gingival fibroblasts

Periodontal disease comprises a group of infections that lead to inflammation of the gingiva, periodontal tissue destruction, and in severe cases is accompanied by alveolar bone loss with tooth exfoliation. Actinobacillus actinomycetemcomitans is a Gram-negative microorganism, which possesses and produces lipopolysaccharide (LPS) molecules that play a key role in disease development. Human gingival fibroblasts are the major constituents of gingival connective tissue and may interact directly with bacteria and bacterial products including LPS. Flavonoids possess antioxidant and anti-inflammatory properties that reduce inflammatory molecule expression in macrophages and monocytes. In this study, we evaluated the ability of diverse flavonoids to regulate nitric oxide production of LPS-stimulated human gingival fibroblasts, and studied the effect of luteolin on diminish phosphorylation in mitogen-activated protein kinase (MAPK) family members as well as in protein kinase B (Akt), nuclear factor kappa B (NF-kappaB) activation, inducible nitric oxide synthase (NOS) expression, and nitric oxide (NO) synthesis. We also found that pretreatment with three flavonoids, including quercetin, genistein, and luteolin, blocked nitric oxide synthesis in a dose-dependent fashion. Luteolin exerted the strongest blocking action on expression of this inflammatory mediator. Luteolin pretreatment attenuated LPS-induced extracellular signal-regulated kinase, p38, and Akt phosphorylation. LPS treatment of human gingival fibroblasts resulted in NF-kappaB translocation. Cell pretreatment with luteolin abolished LPS effects on NF-kappaB translocation. In addition, luteolin treatment blocked LPS-induced cellular proliferation inhibition without affecting genetic material integrity. We concluded that luteolin interferes with LPS signaling pathways, reducing activation of several mitogen-activated protein kinase family members, and inhibits inflammatory mediator expression.

Adherence of uremic erythrocytes to vascular endothelium decreases endothelial nitric oxide synthase expression

BACKGROUND

High prevalence of atherosclerotic cardiovascular events accounts for much of the mortality among patients suffering from end-stage renal disease (ESRD). Endothelial dysfunction as a pathogenic mechanism might contribute to increasing the cardiovascular risk of ESRD. Reduced endothelium-dependent vasodilation has consistently been observed in chronic renal failure patients. Since nitric oxide (NO) is the principal endothelium-derived vasodilator, a reduction in the NO bioavailability may be envisaged in ESRD patients.

METHODS

To clarify whether exposure to erythrocytes from ESRD patients might modulate NO release by the endothelium, we evaluated endothelial NO synthase (eNOS) protein levels (Western blot), eNOS mRNA quantity (real-time PCR), and NOS activity (conversion of L-[3H] arginine in L-[3H] citruline) in endothelial cultures stimulated by erythrocytes from healthy subjects and ESRD patients.

RESULTS

A time-dependent decrease in eNOS protein levels was evident in cultures treated with erythrocytes from ESRD patients. This observation was consistent with the decreased eNOS mRNA quantities induced by erythrocytes from such patients. Moreover, compared to controls, NOS activity exhibited a significant reduction after incubation with erythrocytes from ESRD patients. The observed eNOS reduction induced by erytrocytes from ESRD patients was totally abolished by annexin V, able to mask red blood cell (RBC) surface-exposed phosphatidylserine.

CONCLUSION

These findings suggest that adhesion of erythrocytes from ESRD patients to vascular endothelium may cause a decrease in the levels of eNOS mRNA and protein, and inhibition of NOS activity. This might contribute to endothelial dysfunction, and may play a role in the pathogenesis of cardiovascular disease in ESRD patients.

Mycobacterium tuberculosis 6kDa early secreted antigenic target stimulates activation of J774 macrophages

The influence of the 6 kDa early-secreted antigenic target (ESAT-6) of Mycobacterium tuberculosis on macrophage activation was investigated using J774 macrophage cell line. While without effect if applied alone, ESAT-6 in a dose-dependent manner enhanced nitric oxide (NO) release by IFN-gamma-stimulated J774 cells. However, it completely failed to modulate NO production in J774 cells activated with E. coli lipopolysaccharide. The effect of ESAT-6 on NO synthesis in IFN-gamma-activated J774 cells was accompanied by up-regulated expression of inducible NO synthase (iNOS), an enzyme that catalyzes NO formation. ESAT-6-mediated enhancement of macrophage NO release was markedly suppressed by pharmacological agents that selectively inhibit iNOS enzymatic activity or protein tyrosine kinase and mitogen-activated protein kinase activation. Finally, treatment of J774 macrophages with ESAT-6 also enhanced IFN-gamma-induced expression of the surface molecules B7.1, MHC-II, and ICAM-1. Collectively, these data suggest that ESAT-6 might contribute to macrophage activation in tuberculosis.

Phosphatidylserine-Specific Receptor Contributes to TGF-.BETA. Production in Macrophages through a MAP Kinase, ERK

We explored the involvement of the phosphatidylserine (PS)-receptor in the production of TGF-beta by macrophages treated with PS-liposomes. The binding of anti-PS-receptor antibody to macrophages was specifically inhibited by PS-liposomes. The antibody led to an increase in the production of TGF-beta, and also activated ERK, a member of the MAP kinase. But no activations in p38 and JNK were observed. ERK inhibitor, U0126 completely prevented TGF-beta production. On the addition of a TGF-beta neutralizing antibody or U0126, the inhibitory effect of the anti-PS-receptor antibody on macrophage function, nitric oxide production, was restored. These findings suggested that TGF-beta is one of factors produced by PS-liposomes, and the ERK signaling pathway via the PS-receptor is intimately involved in the production of TGF-beta in macrophages.

Involvement of ERK, a MAP kinase, in the production of TGF-β by macrophages treated with liposomes composed of phosphatidylserine

We have already reported that TGF-beta could be involved in the inhibitory effects of negatively charged liposomes composed of phosphatidylserine (PS-liposome) on the production of nitric oxide (NO) by mouse peritoneal macrophages stimulated with LPS [Biochem. Biophys. Res. Commun. 281 (2001) 614]. In this paper, we explored the mechanism by which PS-liposomes promote the production of TGF-beta and the involvement of MAP kinases. When macrophages were treated with PS-liposomes, extracellular signal-regulated kinase (ERK), a member of MAP kinase superfamily, was activated quickly and potently. However, no activation was observed with p38 MAP kinase. TGF-beta production was completely inhibited by U0126, a specific inhibitor for ERK. Furthermore, TGF-beta neutralizing antibody and U0126 decreased the inhibitory effect of PS-liposomes on NO production by macrophages. These findings suggested that TGF-beta is the factor produced by PS-liposomes that suppresses production of NO, and the ERK signaling pathway is intimately involved in TGF-beta production by macrophages following treatment with PS-liposomes.

Evidence of a protective effect of phosphatidylserine-containing liposomes on lipopolysaccharide-induced impairment of long-term potentiation in the rat hippocampus

Lipopolysaccharide (LPS) has a negative impact on long-term potentiation (LTP) in the rat hippocampus, which has been correlated with increased concentration of interleukin-1 beta (IL-1 beta) and activation of p38 and c-Jun N-terminal kinase (JNK). It has been documented that phosphatidylserine (PS)-containing liposomes induce anti-inflammatory signals and we report that pre-treatment of rats with PS liposomes prevented these LPS-induced effects while also inhibiting microglial activation. We also observed increased concentration of the anti-inflammatory cytokine interleukin-10 (IL-10), whose intracerebroventricular injection administration mimicked the effects of PS liposomes on LTP. This suggests that administration of PS liposomes protects against the deleterious effects of LPS possibly through generation of the anti-inflammatory cytokine IL-10.

Down-regulation of survivin in nitric oxide-induced cell growth inhibition and apoptosis of the human lung carcinoma cells

Survivin is expressed in most tumor cells and has been associated with both anti-apoptosis and mitotic progression. However, the mechanism of regulation of the survivin expression remains unclear. In this study we investigated the expression and regulation of survivin in the nitric oxide (NO)-exposed human lung carcinoma cells. The lung carcinoma cell lines CL3, H1299, and A549 but not normal lung fibroblast expressed high levels of survivin proteins. NO donors S-nitroso-N-acetyl-penicillamine (SNAP) and sodium nitroprusside (SNP) decreased the survivin expression. SNAP (0.4 mm, 24h)and SNP (1 mm, 24 h) significantly induced cytotoxicity and apoptosis in lung carcinoma cells. Furthermore, SNAP inhibited the cell growth and increased the fractions of G(2)/M phase. The levels of cyclin B1 and phospho-cdc2-(Thr-161) proteins were inhibited in the NO-exposed cells. The cdc25 phosphatase inhibitors (Cpd 5 and NSC 663284) and the cdc2 kinase inhibitors (alsterpaullone and purvalanol A) enhanced SNP-induced cytotoxicity and the decrease in survivin expression. However, overexpression of survivin by a pOTB7-survivin vector reduced SNP-induced cell growth inhibition and cytotoxicity. In addition, SNP activated the phosphorylation of p38 mitogen-activated protein (MAP) kinase. The specific p38 MAP kinase inhibitor, SB202190, significantly decreased the cytotoxicity and increased the survivin levels in NO donor-treated and inducible NOS-transfected cells. Conversely, anticancer agents including quercetin, arsenite, and cisplatin but not genistein increased the levels of survivin protein. Our results indicated for the first time that NO inhibited the expression of survivin, which was down-regulated by the p38 MAP kinase pathway.

Quercetin suppresses proinflammatory cytokines production through MAP kinases andNF-kappaB pathway in lipopolysaccharide-stimulated macrophage

Quercetin is a flavonoid molecule ubiquitous in nature and functions as an anti-oxidant and anti-inflammatory agent with little toxicity in vivo and in vitro. Dose- and time-dependent effect of quercetin has been investigated on proinflammatory cytokine expression and NO production, focusing on its effects on the MAP kinases and the NF-kappaB signal transduction pathways in LPS-stimulated RAW 264.7 cells by using RT-PCR and immunoblotting. Quercetin strongly reduced activation of phosphorylated ERK kinase and p38 MAP kinase but not JNK MAP kinase by LPS treatment. In addition, quercetin treatment inhibited NF-kappaB activation through stabilization of the NF-kappaB/IkappaB complex and IkappaB degradation and proinflammatory cytokines and NO/iNOS expression. Quercetin may exert its anti-inflammatory and immunomodulatory properties in the effect molecules such as proinflammatory cytokines and NO/iNOS by suppressing the activation of ERK and p38 MAP kinase, and NF-kappaB/IkappaB signal transduction pathways.

Recombinant HBsAg, an apoptotic-like lipoprotein, interferes with the LPS-induced activation of ERK-1/2 and JNK-1/2 in monocytes

Yeast expressed Hepatitis B surface antigen (rHBsAg) binds to monocytes through interaction with the LPS binding protein (LBP) and the LPS receptor CD14. Charged phospholipids of rHBsAg determine the interaction with these proteins. Although attachment of rHBsAg resembles the pro-inflammatory binding of LPS to CD14, rHBsAg does not activate monocytes and even reduces the expression of pro-inflammatory cytokines by LPS-stimulated monocytes. It is reported here that addition of rHBsAg to LPS-stimulated PBMC often results in increased secretion of IL-10, suggesting a similarity between the interaction of monocytes with apoptotic cells and rHBsAg. Using THP-1 cells, it is shown that IL-10 is not necessary to reduce TNFalpha protein levels. Addition of rHBsAg to LPS-stimulated cells reduces TNFalpha mRNA levels, but does not affect phosphorylation of p65 NF-kappaB and p38 MAP kinase. Instead, a reduced phosphorylation of ERK-1/2 and JNK-1/2 MAP kinases is observed.

Mycobacteria-induced TNF-alpha and IL-10 formation by human macrophages is differentially regulated at the level of mitogen-activated protein kinase activity

The clinical course of mycobacterial infections is linked to the capacity of pathogenic strains to modulate the initial antimycobacterial response of the macrophage. To elucidate some of the mechanisms involved, we studied early signal transduction events leading to cytokine formation by human monocyte-derived macrophages (MDM) in response to clinical isolates of Mycobacterium avium. TNF-alpha production induced by M. avium was inhibited by anti-CD14 mAbs, but not by Abs against the macrophage mannose receptor. Analysis of mitogen-activated protein (MAP) kinase activation (extracellular signal-regulated kinase 1/2, p38, and c-Jun NH(2)-terminal kinase) showed a rapid phosphorylation of all three subfamilies in response to M. avium, which was inhibited by anti-CD14 Abs. Using highly specific inhibitors of p38 (SB203580) and MAP kinase kinase-1 (PD98059), we found that activation of the extracellular signal-regulated kinase pathway, but not of p38, was essential for the M. avium-induced TNF-alpha formation. In contrast, IL-10 production was abrogated by the p38 inhibitor, but not by the MAP kinase kinase-1 inhibitor. In conclusion, M. avium-induced secretion of TNF-alpha and IL-10 by human macrophages is differentially regulated at the level of MAP kinase activity.