Topical Aspirin Administration Improves Cutaneous Wound Healing in Diabetic Mice Through a Phenotypic Switch of Wound Macrophages Toward an Anti-inflammatory and Proresolutive Profile Characterized by LXA4 Release.

Patients with diabetes present a persistent inflammatory process, leading to impaired wound healing. Since nonhealing diabetic wound management shows limited results, the introduction of advanced therapies targeting and correcting the inflammatory status of macrophages in chronic wounds could be an effective therapeutic strategy to stop the sustained inflammation and to return to a healing state. In an excisional skin injury in a diet-induced diabetic murine model, we demonstrate that topical administration of low-dose aspirin (36 µg/wound/day) improves cutaneous wound healing by increasing wound closure through the promotion of the inflammation resolution program of macrophages. This treatment increased efferocytosis of wound macrophages from aspirin-treated diabetic mice compared with untreated diabetic mice. We also show that aspirin treatment of high-fat-fed mice oriented the phenotype of wound macrophages toward an anti-inflammatory and proresolutive profile characterized by a decrease of LTB4 production. The use of diabetic mice deficient for 5-LOX or 12/15-LOX demonstrated that these two enzymes of acid arachidonic metabolism are essential for the beneficial effect of aspirin on wound healing. Thus, aspirin treatment modified the balance between pro- and anti-inflammatory eicosanoids by promoting the synthesis of proresolving LXA4 through 5-LOX, LTA4, 12/15-LOX signaling. In conclusion, the restoration of an anti-inflammatory and proresolutive phenotype of wound macrophages by the topical administration of low-dose aspirin represents a promising therapeutic approach in chronic wounds.

Bioactive fish collagen peptides weaken intestinal inflammation by orienting colonic macrophages phenotype through mannose receptor activation.

PURPOSE: Particular interest is now given to the potential of dietary supplements as alternative non-pharmacological approaches in intestinal inflammation handling. In this aim, this study evaluates the efficiency of fish collagen peptides, Naticol®Gut, on colonic inflammation. METHODS: Wild type and Mannose receptor-deficient in the myeloid lineage C57BL/6 mice were administered with Dextran Sodium Sulfate (DSS), Naticol®Gut, DSS, and Naticol®Gut or only water for 4 or 8 days. Inflammatory status was evaluated by establishing macroscopic and microscopic scores, by measuring cytokine and calprotectin production by ELISA and the myeloperoxidase activity by chemiluminescence. Colonic macrophages were phenotyped by measuring mRNA levels of specific markers of inflammation and oxidative status. Colonic immune populations and T-cell activation profiles were determined by flow cytometry. Mucosa-associated gut microbiota assessment was undertaken by qPCR. The phenotype of human blood monocytes from inflammatory bowel disease (IBD) subjects was characterized by RT-qPCR and flow cytometry and their oxidative activity by chemiluminescence. RESULTS: Naticol®Gut-treated DSS mice showed attenuated colonic inflammation compared to mice that were only exposed to DSS. Naticol®Gut activity was displayed through its ability to orient the polarization of colonic macrophage towards an anti-inflammatory and anti-oxidant phenotype after its recognition by the mannose receptor. Subsequently, Naticol®Gut delivery modulated CD4 T cells in favor of a Th2 response and dampened CD8 T-cell activation. This immunomodulation resulted in an intestinal eubiosis. In human monocytes from IBD subjects, the treatment with Naticol®Gut also restored an anti-inflammatory and anti-oxidant phenotype. CONCLUSION: Naticol®Gut acts as a protective agent against colitis appearing as a new functional food and an innovative and complementary approach in gut health.

Comparative study of the effects of ziram and disulfiram on human monocyte-derived macrophage functions and polarization: involvement of zinc.

Ziram, a zinc dithiocarbamate is widely used worldwide as a fungicide in agriculture. In order to investigate ziram-induced changes in macrophage functions and polarization, human monocytes-derived macrophages in culture were treated with ziram at 0.01-10 µmol.L-1 for 4-24 h. To characterize zinc involvement in these changes, we also determined the effects of disulfiram alone (dithiocarbamate without zinc) or in co-incubation with ZnSO4. We have shown that ziram and disulfiram at 0.01 µmol.L-1 increased zymosan phagocytosis. In contrast, ziram at 10 µmol.L-1 completely inhibited this phagocytic process, the oxidative burst triggered by zymosan and the production of TNF-α, IL-1ß, IL-6, and CCL2 triggered by LPS. Disulfiram had the same effects on these macrophages functions only when combined with zinc (10 µmol.L-1). In contrast, at 10 µmol.L-1 ziram and zinc associated-disulfiram induced expression of several antioxidants genes HMOX1, SOD2, and catalase, which could suggest the induction of oxidative stress. This oxidative stress could be involved in the increase in late apoptosis induced by ziram (10 µmol.L-1) and zinc associated-disulfiram. Concerning gene expression profiles of membrane markers of macrophage polarization, ziram at 10 µmol.L-1 had two opposite effects. It inhibited the gene expression of M2 markers (CD36, CD163) in the same way as the disulfiram-zinc co-treatment. Conversely, ziram induced gene expression of other M2 markers CD209, CD11b, and CD16 in the same way as treatment with zinc alone. Disulfiram-zinc association had no significant effects on these markers. These results taken together show that ziram via zinc modulates macrophages to M2-like anti-inflammatory phenotype which is often associated with various diseases.

IL13-Mediated Dectin-1 and Mannose Receptor Overexpression Promotes Macrophage Antitumor Activities through Recognition of Sialylated Tumor Cells.

Macrophage-mediated cytotoxicity is controlled by surface receptor expression and activation. Despite the numerous studies documenting the role of macrophage C-type lectin receptors (CLR) in pathogen elimination, little is known about their contribution to antitumor responses. Here, we report that IL13 inhibits T-cell lymphoma and ovarian adenocarcinoma development in tumor-bearing mice through the conversion of tumor-supporting macrophages to cytotoxic effectors, characterized by a CLR signature composed of dectin-1 and mannose receptor (MR). We show that dectin-1 and MR are critical for the recognition of tumor cells through sialic acid-specific glycan structure on their surface and for the subsequent activation of macrophage tumoricidal response. Finally, we validated that IL13 antitumor effect mediated by dectin-1 and MR overexpression on macrophages can extend to various types of human tumors. Therefore, these results identify these CLRs as potential targets to promote macrophage antitumor response and represent an attractive approach to elicit tumor-associated macrophage tumoricidal properties.

P17, an Original Host Defense Peptide from Ant Venom, Promotes Antifungal Activities of Macrophages through the Induction of C-Type Lectin Receptors Dependent on LTB4-Mediated PPARγ Activation.

Despite the growing knowledge with regard to the immunomodulatory properties of host defense peptides, their impact on macrophage differentiation and on its associated microbicidal functions is still poorly understood. Here, we demonstrated that the P17, a new cationic antimicrobial peptide from ant venom, induces an alternative phenotype of human monocyte-derived macrophages (h-MDMs). This phenotype is characterized by a C-type lectin receptors (CLRs) signature composed of mannose receptor (MR) and Dectin-1 expression. Concomitantly, this activation is associated to an inflammatory profile characterized by reactive oxygen species (ROS), interleukin (IL)-1ß, and TNF-α release. P17-activated h-MDMs exhibit an improved capacity to recognize and to engulf Candida albicans through the overexpression both of MR and Dectin-1. This upregulation requires arachidonic acid (AA) mobilization and the activation of peroxisome proliferator-activated receptor gamma (PPARγ) nuclear receptor through the leukotriene B4 (LTB4) production. AA/LTB4/PPARγ/Dectin-1-MR signaling pathway is crucial for P17-mediated anti-fungal activity of h-MDMs, as indicated by the fact that the activation of this axis by P17 triggered ROS production and inflammasome-dependent IL-1ß release. Moreover, we showed that the increased anti-fungal immune response of h-MDMs by P17 was dependent on intracellular calcium mobilization triggered by the interaction of P17 with pertussis toxin-sensitive G-protein-coupled receptors on h-MDMs. Finally, we also demonstrated that P17-treated mice infected with C. albicans develop less severe gastrointestinal infection related to a higher efficiency of their macrophages to engulf Candida, to produce ROS and IL-1ß and to kill the yeasts. Altogether, these results identify P17 as an original activator of the fungicidal response of macrophages that acts upstream PPARγ/CLRs axis and offer new immunomodulatory therapeutic perspectives in the field of infectious diseases.

LRH-1 mediates anti-inflammatory and antifungal phenotype of IL-13-activated macrophages through the PPARγ ligand synthesis.

Liver receptor homologue-1 (LRH-1) is a nuclear receptor involved in the repression of inflammatory processes in the hepatointestinal tract. Here we report that LRH-1 is expressed in macrophages and induced by the Th2 cytokine IL-13 via a mechanism involving STAT6. We show that loss-of-function of LRH-1 in macrophages impedes IL-13-induced macrophage polarization due to impaired generation of 15-HETE PPARγ ligands. The incapacity to generate 15-HETE metabolites is at least partially caused by the compromised regulation of CYP1A1 and CYP1B1. Mice with LRH-1-deficient macrophages are, furthermore, highly susceptible to gastrointestinal and systemic Candida albicans infection. Altogether, these results identify LRH-1 as a critical component of the anti-inflammatory and fungicidal response of alternatively activated macrophages that acts upstream from the IL-13-induced 15-HETE/PPARγ axis.

Extracts of Crinum latifolium inhibit the cell viability of mouse lymphoma cell line EL4 and induce activation of anti-tumour activity of macrophages in vitro.

ETHNOPHARMACOLOGICAL RELEVANCE: Crinum latifolium L. (CL) leaf extracts have been traditionally used in Vietnam and are now used all over the world for the treatment of prostate cancer. However, the precise cellular mechanisms of the action of CL extracts remain unclear. AIM OF THE STUDY: To examine the effects of CL samples on the anti-tumour activity of peritoneal murine macrophages. MATERIALS AND METHODS: The properties of three extracts (aqueous, flavonoid, alkaloid), one fraction (alkaloid), and one pure compound (6-hydroxycrinamidine) obtained from CL, were studied (i) for redox capacities (DPPH and bleaching beta-carotene assays), (ii) on murine peritoneal macrophages (MTT assay) and on lymphoma EL4-luc2 cells (luciferine assay) for cytotoxicity, (iii) on macrophage polarization (production of ROS and gene expression by PCR), and (iv) on the tumoricidal functions of murine peritoneal macrophages (lymphoma cytotoxicity by co-culture with syngeneic macrophages). RESULTS: The total flavonoid extract with a high antioxidant activity (IC50=107.36 mg/L, DPPH assay) showed an inhibitory action on cancer cells. Alkaloid extracts inhibited the proliferation of lymphoma cells either by directly acting on tumour cells or by activating of the tumoricidal functions of syngeneic macrophages. The aqueous extract induced mRNA expression of tumour necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß) and interleukin 6 (IL-6) indicating differentiation of macrophages into pro-inflammatory M1 polarized macrophages. The total flavonoid, alkaloid extracts and an alkaloid fraction induced the expression of the formyl peptide receptor (FPR) on the surface of the polarized macrophages that could lead to the activation of macrophages towards the M1 phenotype. Aqueous and flavonoid extracts enhanced NADPH quinine oxido-reductase 1 (NQO1) mRNA expression in polarized macrophages which could play an important role in cancer chemoprevention. All the samples studied were non-toxic to normal living cells and the pure alkaloid tested, 6-hydroxycrinamidine, was not active in any of the models investigated. CONCLUSIONS: Our results indicate that CL extracts and alkaloid fraction (but not pure 6-hydroxycrinamidine) inhibit the proliferation of lymphoma cells in multiple pathways. Our results are in accordance with traditional usage and encourage further studies and in vivo assays.

The C-type lectin receptors dectin-1, MR, and SIGNR3 contribute both positively and negatively to the macrophage response to Leishmania infantum.

Macrophages act as the primary effector cells during Leishmania infection through production of reactive oxygen species (ROS) and interleukin-1ß (IL-1ß). However, how macrophage-killing mechanisms are activated during Leishmania-macrophage interactions is poorly understood. Here, we report that the macrophage response against Leishmania infantum in vivo is characterized by an M2b-like phenotype and C-type lectin receptors (CLRs) signature composed of Dectin-1, mannose receptor (MR), and the DC-SIGN homolog SIGNR3 expression. Dectin-1 and MR were crucial for the microbicidal response as indicated by the fact that they activated Syk-p47phox and arachidonic acid (AA)-NADPH oxidase signaling pathways, respectively, needed for ROS production and also triggered Syk-coupled signaling for caspase-1-induced IL-1ß secretion. In contrast, SIGNR3 has divergent functions during Leishmania infantum pathogenesis; this CLR favored parasite resilience through inhibition of the LTB4-IL-1ß axis. These pathways also operated during infection of primary human macrophages. Therefore, our study promotes CLRs as potential targets for treatment, diagnosis, and prevention of visceral leishmaniasis.

Biomimetic nanocrystalline apatites: Emerging perspectives in cancer diagnosis and treatment.

Nanocrystalline calcium phosphate apatites constitute the mineral part of hard tissues, and the synthesis of biomimetic analogs is now well-mastered at the lab-scale. Recent advances in the fine physico-chemical characterization of these phases enable one to envision original applications in the medical field along with a better understanding of the underlying chemistry and related pharmacological features. In this contribution, we specifically focused on applications of biomimetic apatites in the field of cancer diagnosis or treatment. We first report on the production and first biological evaluations (cytotoxicity, pro-inflammatory potential, internalization by ZR-75-1 breast cancer cells) of individualized luminescent nanoparticles based on Eu-doped apatites, eventually associated with folic acid, for medical imaging purposes. We then detail, in a first approach, the preparation of tridimensional constructs associating nanocrystalline apatite aqueous gels and drug-loaded pectin microspheres. Sustained releases of a fluorescein analog (erythrosin) used as model molecule were obtained over 7 days, in comparison with the ceramic or microsphere reference compounds. Such systems could constitute original bone-filling materials for in situ delivery of anticancer drugs.

Double-walled carbon nanotubes trigger IL-1ß release in human monocytes through Nlrp3 inflammasome activation.

Because of their outstanding physical properties, carbon nanotubes (CNTs) are promising new materials in the field of nanotechnology. It is therefore imperative to assess their adverse effects on human health. Monocytes/macrophages that recognize and eliminate the inert particles constitute the main target of CNTs. In this article, we report our finding that double-walled CNTs (DWCNTs) synergize with Toll-like receptor agonists to enhance IL-1ß release in human monocytes. We show that DWCNTs-induced IL-1ß secretion is exclusively linked to caspase-1 and to Nlrp3 inflammasome activation in human monocytes. We also establish that this activation requires DWCNTs phagocytosis and potassium efflux, but not reactive oxygen specied (ROS) generation. Moreover, inhibition of lysosomal acidification or cathepsin-B activation reduces DWCNT-induced IL-1ß secretion, suggesting that Nlrp3 inflammasome activation occurs via lysosomal destabilization. Thus, DWCNTs present a health hazard due to their capacity to activate Nlrp3 inflammasome, recalling the inflammation caused by asbestos and hence demonstrating that they should be used with caution.

Contact sensitizers modulate the arachidonic acid metabolism of PMA-differentiated U-937 monocytic cells activated by LPS.

For the effective induction of a hapten-specific T cell immune response toward contact sensitizers, in addition to covalent-modification of skin proteins, the redox and inflammatory statuses of activated dendritic cells are crucial. The aim of this study was to better understand how sensitizers modulate an inflammatory response through cytokines production and COX metabolism cascade. To address this purpose, we used the human monocytic-like U-937 cell line differentiated by phorbol myristate acetate (PMA) and investigated the effect of 6 contact sensitizers (DNCB, PPD, hydroquinone, propyl gallate, cinnamaldehyde and eugenol) and 3 non sensitizers (lactic acid, glycerol and tween 20) on the production of pro-inflammatory cytokines (IL-1ß and TNF-α) and on the arachidonic acid metabolic profile after bacterial lipopolysaccharide (LPS) stimulation. Our results showed that among the tested molecules, all sensitizers specifically prevent the production of PMA/LPS-induced COX-2 metabolites (PGE(2,) TxB(2) and PGD(2)), eugenol and cinnamaldehyde inhibiting also the production of IL-1ß and TNF-α. We further demonstrated that there is no unique PGE(2) inhibition mechanism: while the release of arachidonic acid (AA) from membrane phospholipids does not appear do be a target of modulation, COX-2 expression and/or COX-2 enzymatic activity are the major steps of prostaglandin synthesis that are inhibited by sensitizers. Altogether these results add a new insight into the multiple biochemical effects described for sensitizers.

PPARγ ligands switched high fat diet-induced macrophage M2b polarization toward M2a thereby improving intestinal Candida elimination.

Obesity is associated with a chronic low-grade inflammation that predisposes to insulin resistance and the development of type 2 diabetes. In this metabolic context, gastrointestinal (GI) candidiasis is common. We recently demonstrated that the PPARγ ligand rosiglitazone promotes the clearance of Candida albicans through the activation of alternative M2 macrophage polarization. Here, we evaluated the impact of high fat diet (HFD)-induced obesity and the effect of rosiglitazone (PPARγ ligand) or WY14643 (PPARα ligand) both on the phenotypic M1/M2 polarization of peritoneal and cecal tissue macrophages and on the outcome of GI candidiasis. We demonstrated that the peritoneal macrophages and the cell types present in the cecal tissue from HF fed mice present a M2b polarization (TNF-α(high), IL-10(high), MR, Dectin-1). Interestingly, rosiglitazone induces a phenotypic M2b-to-M2a (TNF-α(low), IL-10(low), MR(high), Dectin-1(high)) switch of peritoneal macrophages and of the cells present in the cecal tissue. The incapacity of WY14643 to switch this polarization toward M2a state, strongly suggests the specific involvement of PPARγ in this mechanism. We showed that in insulin resistant mice, M2b polarization of macrophages present on the site of infection is associated with an increased susceptibility to GI candidiasis, whereas M2a polarization after rosiglitazone treatment favours the GI fungal elimination independently of reduced blood glucose. In conclusion, our data demonstrate a dual benefit of PPARγ ligands because they promote mucosal defence mechanisms against GI candidiasis through M2a macrophage polarization while regulating blood glucose level.

PPARγ controls Dectin-1 expression required for host antifungal defense against Candida albicans.

We recently showed that IL-13 or peroxisome proliferator activated receptor gamma (PPARgamma) ligands attenuate Candida albicans colonization of the gastrointestinal tract. Here, using a macrophage-specific Dectin-1 deficient mice model, we demonstrate that Dectin-1 is essential to control fungal gastrointestinal infection by PPARgamma ligands. We also show that the phagocytosis of yeast and the release of reactive oxygen intermediates in response to Candida albicans challenge are impaired in macrophages from Dectin-1 deficient mice treated with PPARgamma ligands or IL-13. Although the Mannose Receptor is not sufficient to trigger antifungal functions during the alternative activation of macrophages, our data establish the involvement of the Mannose Receptor in the initial recognition of non-opsonized Candida albicans by macrophages. We also demonstrate for the first time that the modulation of Dectin-1 expression by IL-13 involves the PPARgamma signaling pathway. These findings are consistent with a crucial role for PPARgamma in the alternative activation of macrophages by Th2 cytokines. Altogether these data suggest that PPARgamma ligands may be of therapeutic value in esophageal and gastrointestinal candidiasis in patients severely immunocompromised or with metabolic diseases in whom the prevalence of candidiasis is considerable.

Opposite roles of STAT and PPARgamma in the induction of p21WAF1 expression by IL-13 in human peripheral blood monocytes.

The cyclin kinase inhibitor p21WAF1 is expressed in most, if not all, differentiated cells in the human body and represents an important regulator of cell cycle control and terminal differentiation in the monocyte/macrophage lineage. It has been reported in macrophage cell lines that p21WAF1 expression is sensitive to numerous molecules including cytokines, but nothing was known about p21WAF1 regulation in human peripheral blood monocytes in response to Th2 cytokines. We report here, that IL-13 increases p21WAF1 expression in human blood monocytes. This induction is a transcription-dependent event, leading to an increase in mRNA content. We show that the signalling pathway for IL-13-induced p21WAF1 expression may involve the IL-4R alpha and the IL-13R alpha1 chains, and the tyrosine and JAK2 kinases. Also, p21WAF1 plasmid-based gene activation only requires a minimal p21WAF1 promoter, containing a putative PPRE. Since IL-13 signalisation involves PPARgamma, we tested PPARgamma involvement in p21WAF1 gene activation by using metabolic inhibitors of arachidonic acid metabolism, or by restoring PPARgamma expression in a defective cell line. We found that inhibition of PPARgamma increases IL-13-induced p21WAF1 gene expression in these models. These data argue that IL-13 upregulates p21WAF1 expression in monocytes via JAK/STAT pathway, and that the activation of PPARgamma by this cytokine can counteract this induction.

IL-13 attenuates gastrointestinal candidiasis in normal and immunodeficient RAG-2(-/-) mice via peroxisome proliferator-activated receptor-gamma activation.

We recently demonstrated that in vitro peroxisome proliferator-activated receptor-gamma (PPARgamma) activation of mouse peritoneal macrophages by IL-13 or PPARgamma ligands promotes uptake and killing of Candida albicans through mannose receptor overexpression. In this study, we demonstrate that i.p. treatment of immunocompetent and immunodeficient (RAG-2(-/-)) mice with natural and synthetic PPARgamma-specific ligands or with IL-13 decreases C. albicans colonization of the gastrointestinal (GI) tract 8 days following oral infection with the yeast. We also showed that Candida GI infection triggers macrophage recruitment in cecum mucosa. These mucosal macrophages, as well as peritoneal macrophages, overexpress the mannose receptor after IL-13 and rosiglitazone treatments. The treatments promote macrophage activation against C. albicans as suggested by the increased ability of peritoneal macrophages to phagocyte C. albicans and to produce reactive oxygen intermediates after yeast challenge. These effects on C. albicans GI infection and on macrophage activation are suppressed by treatment of mice with GW9662, a selective PPARgamma antagonist, and are reduced in PPARgamma(+/-) mice. Overall, these data demonstrate that IL-13 or PPARgamma ligands attenuate C. albicans infection of the GI tract through PPARgamma activation and hence suggest that PPARgamma ligands may be of therapeutic value in esophageal and GI candidiasis in immunocompromised patients.

n-3 and n-6 polyunsaturated fatty acids induce the expression of COX-2 via PPARgamma activation in human keratinocyte HaCaT cells.

Polyunsaturated fatty acids (PUFA) n-3 inhibit inflammation, in vivo and in vitro in keratinocytes. We examined in HaCaT keratinocyte cell line whether eicosapentaenoic acid (EPA) a n-3 PUFA, gamma-linoleic acid (GLA) a n-6 PUFA, and arachidic acid a saturated fatty acid, modulate expression of cyclooxygenase-2 (COX-2), an enzyme pivotal to skin inflammation and reparation. We demonstrate that only treatment of HaCaT with GLA and EPA or a PPARgamma ligand (roziglitazone), induced COX-2 expression (protein and mRNA). Moreover stimulation of COX-2 promoter activity was increased by those PUFAs or rosiglitazone. The inhibitory effects of GW9662 and T0070907 (PPARgamma antagonists), on COX-2 expression and on stimulation of COX-2 promoter activity by EPA and GLA suggest that PPARgamma is implicated in COX-2 induction. Finally, PLA2 inhibitor methyl arachidonyl fluorophosphonate blocked the PUFA effects on COX-2 induction, promoter activity and arachidonic acid mobilization suggesting involvement of AA metabolites in PPAR activation. These findings demonstrate that n-3 and n-6 PUFA increased PPARgamma activity is necessary for the COX-2 induction in HaCaT human keratinocyte cells. Given the anti-inflammatory properties of EPA, we suggest that induction of COX-2 in keratinocytes may be important in the anti-inflammatory and protective mechanism of action of PUFAs n-3 or n-6.

Tumor necrosis factor alpha and adalimumab differentially regulate CD36 expression in human monocytes.

In chronic inflammatory diseases, such as rheumatoid arthritis, inflammation acts as an independent cardiovascular risk factor and the use of anti-inflammatory drugs, such as anti-tumor necrosis factor alpha (anti-TNFalpha), may decrease this risk. The phagocytosis of oxidized low density lipoproteins (LDLs) accumulated in the subendothelium by mononuclear cells influences atherosclerosis and depends on CD36 expression. We investigated the role of TNFalpha and adalimumab, a human anti-TNFalpha monoclonal antibody widely used in human pathology, in CD36 expression in human monocytes. Human monocytes were prepared by adherence from whole-blood buffy-coat fractions from healthy donors. CD36 expression was assessed by RT-PCR and flow cytometry, with various TNFalpha or adalimumab concentrations. Implication of peroxisome proliferator-activated receptor (PPAR)gamma in the regulation of CD36 expression was assessed using specific inhibitor or gel shift assays. The impact of redox signaling was investigated using quantification of reactive oxygen species, antioxidant and a NADPH oxidase inhibitor. The F(ab')2 fragment of adalimumab was isolated and its effect was analyzed. TNFalpha inhibits both CD36 membrane expression and mRNA expression. This inhibition involves a reduction in PPARgamma activation. In contrast, adalimumab increases both CD36 membrane expression and mRNA expression. This induction is independent of the Fc portion of adalimumab and involves redox signaling via NADPH oxidase activation. CD36 expression on human monocytes is inhibited by TNFalpha and independently increased by adalimumab. These data highlight that pro-inflammatory cytokines and their specific neutralization influence the expression of cellular receptors implicated in atherosclerosis. Further studies are needed to investigate the clinical implications of these results in accelerated atherosclerosis observed in rheumatoid arthritis.

Tamoxifen is a potent inhibitor of cholesterol esterification and prevents the formation of foam cells.

Tamoxifen is a selective estrogen receptor modulator (SERM) used for the treatment and prevention of breast cancer. Tamoxifen has been reported to protect against the progression of coronary artery diseases in human and different atherosclerosis animal models by blocking the appearance of the atheromatous plaque. However, the molecular mechanism of this effect remains unknown. Acyl-CoA:cholesterol acyl transferase (ACAT) catalyzes the biosynthesis of cholesteryl esters, which are the major lipids found in the atheromatous plaque. In this paper we have tested whether ACAT might be inhibited by tamoxifen. We show, using molecular modeling, that tamoxifen displays three-dimensional structural homology with Sah 58-035 (3-[decyldimethylsilyl]-N-[2-(4-methylphenyl)-1-phenylethyl]-propanamide), a prototypical inhibitor of ACAT. We report that tamoxifen inhibits ACAT in a concentration-dependent manner on rat liver microsomal extract. We show that the presence on estrogen receptor ligands of a backbone isosteric to the diphenyl ethane backbone of Sah 58-035 constitutes a pharmacophore for ACAT inhibition. More importantly, tamoxifen was able to inhibit ACAT on intact macrophages stimulated with acetylated low-density lipoproteins and blocked the formation of foam cells, a step that precedes the formation of the atheromatous plaque. This work constitutes the first evidence that tamoxifen is an inhibitor of ACAT and foam cell formation at therapeutic doses and that this may account for its atheroprotective action.

PPARgamma promotes mannose receptor gene expression in murine macrophages and contributes to the induction of this receptor by IL-13.

Macrophage mannose receptor (MMR) is an important component of the innate immune system implicated in host defense against microbial infections such as candidiasis and in antigen presentation. We demonstrate here that the MMR expression is induced in mouse peritoneal macrophages following exposure to PPARgamma ligands or to interleukine-13 (IL-13) via a PPARgamma signaling pathway. Ligand activation of the PPARgamma in macrophages promotes uptake, killing of Candida albicans, and reactive oxygen intermediates production triggered by the yeasts through MMR overexpression. We also show that MMR induction by IL-13 via PPARgamma is dependent on phopholipase A2 activation and that IL-13 induces 15d-PGJ2 production and nuclear localization. These results reveal a novel signaling pathway controlling the MMR surface expression and suggest that endogenous PPARgamma ligand produced by phospholipase A2 activation may be an important regulator of MMR expression by IL-13.

A sub-inhibitory concentration of amphotericin B enhances candidastatic activity of interferon-gamma- and interleukin-13-treated murine peritoneal macrophages.

We studied the effects of interferon-gamma (IFN-gamma), a Th1 cytokine, and interleukin-13 (IL-13) or interleukin-4 (IL-4), Th2 cytokines, on the antifungal activity of resident murine peritoneal macrophages against Candida albicans 'in vitro'. IFN-gamma, IL-13 and IL-4 treatment enhanced the candidastatic functions of the macrophages. Reactive oxygen intermediates (ROIs) seem to be directly involved in the increase of anti-Candida activity in macrophages treated with Th1 or Th2 cytokines. Study of unopsonized C. albicans phagocytosis showed that IFN-gamma reduces the uptake process whereas the Th2 cytokines increase it. This difference is correlated to mannose receptor expression, which is decreased by IFN-gamma but increased by the Th2 cytokines. So, the effects on phagocytosis and candidastatic activity of IFN-gamma-treated macrophages are dissociated. In contrast, the phagocytic ability of macrophages pretreated 'in vitro' with IL-4 or IL-13 played a complementary role to the ROIs, in reduction of yeast proliferation by macrophages. In consequence, the macrophages treated with IL-13 and IL-4 develop a higher fungistatic activity than macrophages activated by IFN-gamma. Amphotericin B associated with IL-13 or IFN-gamma, but not with IL-4, enhanced the yeast growth inhibition activity of macrophages. The ROIs were involved in the additive effect of IFN-gamma with amphotericin B, whereas another mechanism was implicated in the increase of candidastatic activity of macrophages treated with IL-13 in association with amphotericin B.