Interleukin-17 and -22 synergy linking inflammation and EMT-dependent fibrosis in Sjögren's syndrome.

Primary Sjögren's syndrome (pSS) is a chronic inflammatory, autoimmune and systemic disorder commonly associated with dry eyes and a dry mouth. Recently, the hypothetical link between epithelial-mesenchymal transition (EMT)-dependent salivary gland (SG) fibrosis and chronic inflammatory conditions has been suggested. In this study, we present data demonstrating a negative correlation of the epithelial marker E-cadherin expression and a positive correlation of mesenchymal vimentin and collagen type I expression with increasing degrees of tissue inflammation in pSS SG specimens. In addition, as it is not clear whether dysregulated cytokines in pSS, interleukin (IL)-17 and IL-22 may also contribute to the EMT-dependent fibrosis process, the effect of IL-17 and IL-22 treatment on EMT-dependent SG fibrosis was evaluated in primary human salivary gland epithelial cells (SGEC) isolated from healthy subjects. Here we present data demonstrating that IL-17 and IL-22 can induce SGEC to undergo a morphological and phenotypical transition to a mesenchymal phenotype. In support of this, vimentin and collagen type I were up-regulated while a decreased expression of E-cadherin occurs after interleukin treatment, and co-operation between IL-17 and Il-22 was required to induce the EMT.

Downstream activation of NF-κB in the EDA-A1/EDAR signalling in Sjögren's syndrome and its regulation by the ubiquitin-editing enzyme A20.

Sjögren's syndrome (SS) is an autoimmune disease and the second most common chronic systemic rheumatic disorder. Prevalence of primary SS in the general population has been estimated to be approximately 1-3%, whereas secondary SS has been observed in 10-20% of patients with rheumatoid arthritis, systemic lupus erythematosus (SLE) and scleroderma. Despite this, its exact aetiology and pathogenesis are largely unexplored. Nuclear factor-kappa B (NF-κB) signalling mechanisms provide central controls in SS, but how these pathways intersect the pathological features of this disease is unclear. The ubiquitin-editing enzyme A20 (tumour necrosis factor-α-induced protein 3, TNFAIP3) serves as a critical inhibitor on NF-κB signalling. In humans, polymorphisms in the A20 gene or a deregulated expression of A20 are often associated with several inflammatory disorders, including SS. Because A20 controls the ectodysplasin-A1 (EDA-A1)/ectodysplasin receptor (EDAR) signalling negatively, and the deletion of A20 results in excessive EDA1-induced NF-κB signalling, this work investigates the expression levels of EDA-A1 and EDAR in SS human salivary glands epithelial cells (SGEC) and evaluates the hypothesis that SS SGEC-specific deregulation of A20 results in excessive EDA1-induced NF-κB signalling in SS. Our approach, which combines the use of siRNA-mediated gene silencing and quantitative pathway analysis, was used to elucidate the role of the A20 target gene in intracellular EDA-A1/EDAR/NF-κB pathway in SS SGEC, holding significant promise for compound selection in drug discovery.

Sjögren's syndrome pathological neovascularization is regulated by VEGF-A-stimulated TACE-dependent crosstalk between VEGFR2 and NF-κB.

We explore the involvement of tumor necrosis factor α (TNF-α)-converting enzyme (TACE) in vascular endothelial growth factor (VEGF) and its receptor 2 (VEGFR2) (VEGF-A/VEGFR2)-mediated angiogenesis in Sjögren's syndrome (SS), one of the most common autoimmune rheumatic diseases. To test the hypothesis that SS autoantibodies (Abs) regulate VEGF-A/VEGFR2 expression by a TACE-dependent nuclear factor-κB (NF-κB) activation pathway, their effects on the expression and activation of the VEGF-A/TACE/VEGFR2/NF-κB pathway were determined in human salivary gland epithelial cells (SGEC). An enhanced angiogenesis in SS salivary gland biopsies was observed, associated with an increased VEGF-A expression and activation of VEGF-A/VEGFR2 signaling. Human cytokine array analysis of the pro-inflammatory and pro-angiogenic protein response in SGEC treated with SS Abs revealed an overexpression of multiple pro-angiogenic factors. TACE RNA knockdown, the use of anti-VEGF-A monoclonal antibody and the inhibition of NF-κB activity significantly abrogated the release of pro-angiogenic factors, demonstrating that VEGF-A/TACE/VEGFR2/NF-κB axis dysfunction may be contributory to pathogenesis and exacerbation of this autoimmune condition.

Possible role of oral ibandronate administration in Osteonecrosis of the Jaw: a case report.

We describe a case of Osteonecrosis of the Jaw (ONJ) that developed in a 65-year-old Caucasian woman with osteopenia and other risk factors who was receiving low doses of oral bisphosphonate therapy (ibandronate, 150 mg monthly). Computed tomography (CT), panoramic radiographs (OPT), 99mTc-Sn-MDP scintigraphy, and magnetic resonance imaging (MRI) were performed to study the diseased area; cytological examination also revealed the presence of suppurative material around the area of exposed bone. A diagnosis of bisphosphonate-related osteonecrosis of the jaw complicated by osteomyelitis was made. The patient was prescribed a drug protocol consisting of metronidazole 250 mg 2 times daily, chlorhexidine mouthwashes 3 times daily and chewing exercises for two months. Ibandronate was stopped and replaced with strontium ranelate. The symptoms improved and the patient is still under close follow-up. Assessment of the benefits versus risks is particularly necessary in patients with several risk factors to ascertain their eligibility for treatment with antiresorptive drugs and when this is not possible to choose alternative medications.

Anti-Ro/SSA autoantibody-mediated regulation of extracellular matrix fibulins in human epithelial cells of the salivary gland.

OBJECTIVES: The fibulins are a family of extracellular matrix (ECM) molecules that regulate the organ shape along with other growth factors and stromal cells and have recently been shown to be involved in a variety of cellular functions including proliferation, migration, differentiation, and survival. Important changes in acinar and ductal morphology and function, together with pronounced ECM remodelling, are detectable in the labial salivary glands (LSGs) of patients with Sjögren's syndrome (SS). Here we report the in vitro expression of the recently identified ECM proteins fibulin-6 and fibulin-7 by human salivary gland epithelial cells (SGECs). The ability of anti-Ro/SSA autoantibodies (Abs) to modulate fibulin-6 and fibulin-7 expression was investigated. METHODS: Semiquantitative reverse transcription polymerase chain reaction (RT-PCR) and real-time PCR were used to analyse fibulin-6 and fibulin-7 mRNA expression. Confocal microscopy and fluorescence-activated cell sorting (FACS) were used to study expression of the proteins in primary human SGEC cultures, established from biopsies of minor LSGs, in both untreated control cells and anti-Ro/SSA Abs-treated cells. RESULTS: The methods used show the expression of fibulin-6 and fibulin-7 in SGECs. Treatment of cells with anti-Ro/SSA Abs results in a down-regulation of fibulin-6 mRNA expression whereas no significant differences were observed in fibulin-7 expression between untreated and treated cells. CONCLUSION: Dysregulation of fibulin expression in SGECs by anti-Ro/SSA Abs may contribute to disorganization of the ECM environment and thus cause injury to the salivary gland architecture and functionality observed in SS.

Hashimoto's thyroiditis in Melkersson-Rosenthal syndrome patient: casual association or related diseases?

Melkersson-Rosenthal syndrome (MRS) is a rare disorder of unknown etiology. MRS is classically defined as a triad of recurrent orofacial edema, relapsing paralysis of the facial nerve, and fissured tongue. The authors present the case of a 52-year-old woman with orofacial swelling and facial pain attacks. The patient reported to suffer of hypothyroidism and laboratory findings disclosed free triiodothyronine (FT(3)), free thyroxine (FT(4)), and thyrotropin (TSH) altered. Endocrinological consult led to the diagnosis of Hashimoto's thyroiditis. Antithyroper-oxidase antibodies (anti-TPO) were highly elevated and thyroid function tests had evidenced a clinically significant hypothyroidism. A link between MRS and immunological disorders such as sarcoidosis, Crohn's disease, unilateral anterior uveitis and multiple sclerosis was documented. The literature did not report any association between Hashimoto's thyroiditis and Melkersson-Rosenthal syndrome. The presence of the anti-TPO antibodies in the case reported here could suggest a possible correlation between immunological alteration characteristic of autoimmune thyroiditis and MRS.

Siögren's syndrome: anti-Ro and anti-La autoantibodies trigger apoptotic mechanism in the human salivary gland cell line, A-253.

AIM: The Sjögren's syndrome (SS) is an autoimmune rheumatic disease that targets salivary and lacrimal glands, characterized by a high concentration of autoantibodies in the serum. The anti-Ro and anti-La autoantibodies are present in approximately 70-90% of the patients with primary SS and this presence is correlated to extraglandular manifestations. The objective of this work was to explore the cellular apoptotic pathway triggered by binding and penetration of anti-Ro and anti-La autoantibodies, isolated from the total IgG fraction of patients with primary SS, in the human salivary gland cell line A-253. METHODS: The sera were obtained from 13 healthy volunteers and 13 patients with primary SS. The IgG was obtained from sera through precipitation with ammonium sulfate and the anti-La and anti-Ro autoantibodies were purified using Sepharose 4B-Ro and Sepharose 4B-La affinity columns. The methods used to evaluate the apoptosis were: DNA fragmentation, immunofluorescence and immunoenzymatic tests. RESULTS: In the salivary gland cells, the anti-Ro and anti-La autoantibodies: 1) are able to penetrate; 2) induce DNA fragmentation and cleavage and activation of the effector caspase-3. In the same experimental condition, IgG purified from healthy sera did not have any apoptotic effect on the human salivary gland cell line. CONCLUSION: Anti-Ro and anti-La autoantibodies mediate the apoptosis the human salivary gland cells A-253 in a caspase-3 dependent manner.

Anti-Ro and anti-La autoantibodies induce TNF-alpha production by human salivary gland cells: an in vitro study.

In this report, we demonstrate that both TNFR1 and the TNFR2 are expressed on the salivary gland cell line A-253 cell membrane. Furthermore, cell treatment with anti-Ro and anti-La autoantibodies from Sjögren IgG determined TNF-alpha production, clarifying which could be the inducer of the extrinsic pathway of apoptosis in salivary gland cells.

Transcatheter closure of an unligated vertical vein with an Amplatzer Vascular Plug-II device.

: The usual surgical practice after repair of a Total Anomalous Pulmonary Venous Connection (TAPVC) is to ligate the vertical vein (VV). Many surgeons find it expedient to leave the VV unligated to reduce pulmonary arterial pressure, decrease perioperative pulmonary hypertensive crisis, provide better hemodynamics postoperatively (1), and enable the adaptation of cardiac chambers to a new workload. Afterwards, the unligated VV may cause significant left-to-right shunt, likewise an atrial septal defect, mandating later surgical ligation or device closure (2). This report details transcatheter occlusion of a patent VV using a device Amplatzer Vascular Plug II, after TAPVC repair in early infancy. The transcatheter occlusion of an unligated VV after repair of supracardiac TAPVC represents an effective alternative to surgical redo. The device Amplatzer Vascular Plug II achieves great results.

HER-2/neu in bladder carcinoma.

A total of 66 bladder cancer patients were studied to verify possible relationships between HER-2/neu alterations and pathological characteristics, and to define a poor prognosis patient subgroup with respect to time to recurrence, time to progression and survival. Tumor and healthy tissue specimens were analyzed for HER-2/neu DNA amplification and protein overexpression by Southern and Western blot techniques and evaluated statistically. 13% of cases were amplified and 39% were overexpressed. HER-2/neu alterations were not significantly associated with pathological staging or tumor grading. Multifocal tumors had a higher percentage and overexpression with respect to monofocal tumors. Actuarial analyses did not show a significant statistical correlation between HER-2/neu amplification and overexpression and clinical outcome. Clinical evaluation of HER-2/neu status showed that this gene is not related to tumor relapse, progression or patient survival.

Evidences for iNOS expression and nitric oxide production in the human macrophages.

Nitric oxide (NO) is a pleiotropic mediator of numerous biological processes, including smooth muscle relaxation, neurotransmission and defence against pathogens. In addition, NO is involved in the pathogenesis and control of inflammation, tumors, autoimmunity, and infectious and chronic degenerative diseases. NO, a highly reactive radical, is produced from L-arginine and oxygen by the enzyme NO synthase (NOS). Three NOS isoforms have been identified: two distinct NOS isoforms are constitutively expressed in cells, whereas a third isoform, inducible NOS (iNOS), is transcribed in response to specific stimuli. In particular, iNOS is responsible for the discontinuous synthesis of high amounts of NO and was originally characterized in murine macrophages after exposure to cytokines and/or microbial products. A wide range of microorganisms is sensibly inhibited in its development by NO, like fungi, bacteria, protozoa and viruses. Although NO production and its antimicrobial effect appear well established in rodent macrophages, the existence of L-arginine pathway in human mononuclear phagocytes has long been disputed. Recently, evidences showing the iNOS activity and NO production in other animal models, including humans, are now emerging, even if the NO induction has been more difficult to demonstrate. The present observations provide evidence for the occurrence of iNOS protein expression and NO production in human macrophages cultured in vitro.

Embryonal cardiotoxicity of the Helicobacter pylori lipopolysaccharide.

Helicobacter (H.) pylori is the causative agent of the peptic ulcer disease and a co-factor in the development of gastric malignancies. Recently, it has been maintained that chronic H. pylori infections in adults are linked to a higher risk of coronary heart diseases. In this respect, the acute toxic effects of the H. pylori lipopolysaccharide (LPS) on embryonal cardiomyocytes at different developmental stages was evaluated. White Leghorn chick embryos and smooth (S)--form NCTC 11637 strain H. pylori organisms were used. Both whole heath-killed H. pylori suspensions (3.10(6) bacteria/egg) and isolated S-LPS (500 ng/egg) or S-Lipid A (500 ng/egg) were non-lethal to 4-day embryos, becoming moderately lethal (5% to 30%) to 6- and 8-day embryos and highly lethal (> 90%) to 10- to 17-day embryos. The contractile activity of isolated atrial fragments from 10-day embryos was completely inhibited, within 5 min, following treatments with heath-killed H. pylori (3 x 10(6)/ml), or S-LPS (500 ng/ml), or S-Lipid A (500 ng/ml); the block determined by S-LPS and S-Lipid A was irreversible, while the block by bacterial suspensions was completely reversible upon withdrawal. Following a 24-hour treatment with S-LPS or S-Lipid A of single-cell cultures of cardiomyocytes (isolated from 10-day embryos) a dose-dependent cell loss was observed, as assessed by total protein dosage and direct counting of adherent cells. Propidium Iodide/Annexin V FACS-analysis confirmed the occurrence of cellular necrosis, but did not show any evidence of apoptotic processes. The release of superoxide anion radicals by cultured cardiomyocytes was as follows: S-Lipid A (25 micrograms/ml) > S-LPS (25 micrograms/ml) > heath killed H. pylori suspensions (3 x 10(6)/ml); control cultures did not release detectable amounts of superoxide anion radicals. Furthermore, cultured cardiomyocytes produced increased amounts of NO (N-monomethylarginine-inhibitable) following stimulation with S-LPS (25 micrograms/ml) or S-Lipid A (25 micrograms/ml) (but not heath killed H. pylori 3 x 10(6)/ml suspensions). Under all the above experimental conditions S-polysaccharide proved to be non-toxic. Concluding, H. pylori LPS is relatively non-toxic to the less differentiated cardiomyocytes; cardiomyocytes which are more advanced in their biochemical differentiation become highly sensitive to LPS and produce ROS and NO. ROS are probably responsible for the early toxic actions, while both ROS and NO are likely to be involved in the later degenerative/necrotic effects.

Using NMR to study full intact wine bottles.

A nuclear magnetic resonance (NMR) probe and spectrometer capable of investigating full intact wine bottles is described and used to study a series of Cabernet Sauvignons with high resolution 1H NMR spectroscopy. Selected examples of full bottle 13C NMR spectra are also provided. The application of this full bottle NMR method to the measurement of acetic acid content, the detection of complex sugars, phenols, and trace elements in wine is discussed.

Nitric oxide production by macrophages of dogs vaccinated with killed Leishmania infantum promastigotes.

Human visceral leishmaniosis is endemic in Southern Italy, where the dog is the main reservoir of viscerotropic strains of Leishmania infantum. The release of nitric oxide (NO) by interferon (IFN)-gamma-activated macrophages is an important leishmanicidal mechanism in several animal species. In this work NO production, phagocytosis and killing capacity of monocyte-derived dog macrophages were evaluated in vitro before and after administration of a vaccine composed of killed Leishmania infantum promastigotes. Moreover, IFN-gamma content was measured in concanavalin A-activated dog peripheral blood mononuclear cell (PBMC) supernatants employed for macrophage stimulation. Phagocytosis, killing capacity and NO production by canine macrophages increased significantly 1 month after vaccine administration, and the increase also persisted 5 months later. In addition, the amount of IFN-gamma in PBMC supernatants was significantly higher after vaccination. Overall, our results suggest the usefulness of evaluating the in vivo protective role of this promastigote preparation in dogs.

Inducible nitric oxide synthase expression in Leishmania-infected dog macrophages.

Nitric oxide (NO) production by the inducible NO synthase (iNOS or NOS2) represents one of the main microbicidal mechanisms of murine macrophages, but its role in other animal models is poorly investigated. Therefore, the aim of this work was to evaluate NOS2 expression in dog macrophages infected with Leishmania infantum. Macrophages obtained from peripheral blood of healthy dogs were activated with recombinant human interferon (rhIFN)-gamma and bacterial lipopolysaccharide (LPS) and then infected with L. infantum promastigotes. zymodeme MONI. For the immunofluorescence assay fixed macrophages were incubated with polyclonal rabbit anti-NOS2 and then with rhodamine F(ab')2 goat anti-rabbit IgG. For immunoblotting, cell lysates were submitted to SDS-PAGE and blots were incubated with polyclonal rabbit anti-NOS2 and then with horseradish peroxidase-conjugated goat anti-rabbit IgG. Results demonstrated that L. infantum-infected cells, after stimulation with rhIFN-gamma and LPS, displayed high levels of fluorescence for the NOS2 in their cytoplasm, unlike unstimulated uninfected macrophages. In western blotting, polyclonal anti-NOS2 reacted specifically with a protein band corresponding to 130 kDa. The signal produced in Leishmania-infected cells stimulated with rhIFN-gamma and LPS was higher than that produced in Leishmania-infected unstimulated cells. No band was detected in cellular lysates from uninfected unstimulated cells. These results indicate that dog macrophages can express NOS2, and suggest a role for IFN-gamma and LPS in NOS2 induction also in this animal model.

Nitric oxide production by Leishmania-infected macrophages and modulation by prostaglandin E2.

Nitric oxide (NO), produced by the nitric oxide synthase (iNOS) enzyme, is the most-important molecule responsible for the killing of Leishmania parasites by macrophages. In previous work we have demonstrated that, after activation with recombinant human interferon-gamma and/or bacterial lipopolysaccharide, human macrophages infected with Leishmania infantum are able to produce nitric oxide and to express nitric oxide synthase. The arachidonate derivative prostaglandin E2 has been shown to modulate various macrophage activities, and in particular nitric oxide production, sometimes with opposite effects, related to experimental conditions. In this work we have evaluated nitric oxide release and parasite killing by peripheral blood-derived L. infantum-infected human macrophages in vitro stimulated with lipopolysaccharide and simultaneously treated with prostaglandin E2. Experiments were also performed in the presence of the nitric oxide synthase inhibitor L-NGmonomethylarginine (L-NMMA) and of the cyclooxygenase inhibitor indomethacin. Nitric oxide release in supernatants of macrophage cultures was measured by the Griess reaction for nitrites. Parasite killing was microscopically evaluated by fluorescent dyes. Results demonstrated that macrophages stimulated with lipopolysaccharide and treated with prostaglandin E2 exhibited increased nitric oxide production and parasite killing, which were significantly reduced by either L-NMMA or indomethacin. In indomethacin-treated macrophages, nitric oxide production and leishmanicidal ability were partially restored by the addition of exogenous prostaglandin E2. Taken together, these results indicate that prostaglandin E2 may be involved in nitric oxide production, and possibly in the host-protective immune response against Leishmania. Moreover, the demonstration of a stimulatory role of prostaglandin E2 on nitric oxide production induced by intracellular pathogens in humans is interesting in the light of a possible pharmacological regulation of nitric oxide by modulation of prostaglandin E2 synthesis.

Macrophage chemotactic protein-1 and macrophage inflammatory protein-1 alpha induce nitric oxide release and enhance parasite killing in Leishmania infantum-infected human macrophages.

Chemokines are a group of structurally defined small proteins that act as chemoattractants for leukocytes and are involved in many different biological activities, including leukocyte activation for antimicrobial mechanisms. We studied the effect of the chemokines monocyte chemotactic protein (MCP)-1 and macrophage inflammatory protein (MIP)-1 alpha on nitric oxide release and parasitocidal ability of peripheral blood-derived human macrophages in vitro infected with Leishmania infantum, zymodeme MON1. In infected human macrophages, treatment with MCP-1 or MIP-1 alpha significantly enhanced nitric oxide production and leishmanicidal ability, compared with untreated cells, to the same levels induced by interferon-gamma. Both nitric oxide release and parasitocidal ability of macrophages were significantly reduced by addition of L- N(G)monomethylarginine ( L-NMMA), which is a competitive inhibitor of the L-arginine nitric oxide pathway. These data suggest that MCP-1 and MIP-1 alpha mediate macrophage activation for nitric oxide release and subsequent parasite clearance, and thus may play a role in the containment of Leishmania infection.

Reduced expression of the chemokine receptor CCR1 in human macrophages and U-937 cells in vitro infected with Leishmania infantum.

Chemokines exert their actions through G-proteinlinked receptors, which are expressed to variable extents by different cell types. In accordance with the chemokine classification, these receptors are designated as CXC, CC, XC, and CX(3)C, followed by R and a number. The purpose of this investigation was to evaluate CCR1 expression in human peripheral blood-derived macrophages and the human monocytic U-937 cell line. Cells in vitro were infected with live Leishmania infantum promastigotes (zymodeme MON1); cell lysates were then subjected to SDS-PAGE and immunoblotting, by using an anti-CCR1 affinity purified polyclonal antibody. The expression of the CCR1 gene was analyzed by RT-PCR, using specific human primers. The results of both immunoblotting and RT-PCR showed that CCR1 expression in Leishmania-infected cells was lower than in uninfected control cells. These results indicate that Leishmania infantum infection causes a down-regulation of the CCR1 gene and protein expression, suggesting that reduced phagocyte recruitment at the inflammation sites could favor parasite progression and the spread of Leishmania infection.

Interactions between Leishmania parasites and host cells.

Several species of protozoa belonging to the genus Leishmania are pathogenic for humans, causing visceral and cutaneous diseases. They are transmitted by phlebotomine sandflies as flagellated promastigotes to mammals hosts, where they live as aflagellated amastigotes mainly within macrophages. Studies performed on mice infected with Leishmania major demonstrated that host defence against this infection depends on the interleukin-12-driven expansion of the T helper 1 cell subset, with production of cytokines such as interferon-gamma, which activate macrophages for parasite killing through the release of nitric oxide. The parasitocidal role of this radical is now emerging also in the human and canine model. Healing or progression of the infection is related to the genetic and immune status of the host, and to the virulence of different species and strains of Leishmania. The parasite survival ultimately depends on the ability to evade the host immune response by several mechanisms. Among them, inhibition of the signal transduction pathway of the host cells is particularly important. In fact, promastigotes inhibit protein kinase C activation, cause Ca++ influx into the host cell and decrease the levels of myristoylated alanine-rich C kinase substrate-related proteins, which are substrates for PKC. In addition, Leishmania infection blocks IFN-gamma-induced tyrosine kinase phosphorylation, with consequent impairment of signalling for IL-12 and nitric oxide production. Finally, Leishmania activates protein phosphotyrosine phosphatases, which down-regulate mitogen-activated protein kinase signalling and c-fos and nitric oxide synthase expression. New pharmacological applications, including protein tyrosine phosphatase and protein farnesyltransferase inhibitors, are being evaluated against leishmaniosis in vitro and in vivo in the murine model.

Nitric oxide production by Leishmania-infected macrophages and modulation by cytokines and prostaglandins.

Nitric oxide (NO) produced by an inducible nitric oxide synthase (iNOS or NOS2) plays a major microbicidal role in murine macrophages and its importance is now emerging also in the dog and human models. In dogs we demonstrated that macrophages in vitro infected with Leishmania infantum produced NO, after stimulation with cytokine-enriched peripheral blood mononuclear cell supernatants. In addition, parasite killing was reduced by the NOS inhibitor L-NG monomethylarginine. On the contrary, canine blood monocytes before macrophage differentiation did not release NO, and their leishmanicidal activity was instead correlated with superoxide anion and interferon (IFN)-gamma production. In human macrophage cultures, after infection with Leishmania infantum, we showed both iNOS expression by immunofluorescence and western blotting and NO release by the Griess reaction for nitrites. Various cytokines and prostaglandins can differently modulate NO synthesis. In our experiments, stimulation by recombinant human IFN-gamma and bacterial lipopolysaccharide greatly enhanced iNOS expression and NO production in human macrophages. In addition, the prostaglandin E2 increased NO release in activated, Leishmania-infected human macrophages. These results are interesting in the light of a possible immunological or pharmacological regulation of NO synthesis and microbicidal functions of macrophages.