Bi-directional effects of the elevation of intracellular calcium on the expression of inducible nitric oxide synthase in J774 macrophages exposed to low and to high concentrations of endotoxin. Biochem J. 2001;354:351-358. [PMID: 11171114 DOI: 10.1042/bj3540351]

Mevalonate kinase of Leishmania donovani promotes its survival and plays a pivotal role in pathogenesis

The infectivity of Leishmania is determined by its ability to invade and evade host and its thriving capacity within the macrophage. Our study revealed the role of Leishmania donovani mevalonate kinase (MVK), an enzyme of mevalonate pathway in visceral leishmaniasis pathogenesis. Peritoneal exudate cells (PEC)-derived macrophages from BALB/c mice were infected with wild type (WT), MVK over expressing (MVK OE) and knockdown (KD) parasites and MVK OE parasites were found to be more infective than WT and MVK KD parasites. Incubation of macrophages with MVK OE parasites declined inducible nitric oxide synthase (iNOS) expression as well as nitric oxide (NO) production, both by 2 times in comparison to WT parasites. Moreover, ∼3 fold increase in Arginase1 expression indicated that MVK might induce polarization of macrophage towards M2, favouring the survival of parasite within the macrophages. Post 24 h infection of the macrophages with mutant strains, the levels of different cytokines (TNF-α, IL-12, IL-10 and IFN-γ) were measured. Infection of macrophages with MVK OE parasites showed an increase in the level of anti-inflammatory cytokine: IL-10 while infection with MVK KD parasites exhibited an increase in the level of pro-inflammatory cytokines: TNF-α, IL-12, and IFN-γ. Hence, Leishmania donovani mevalonate kinase (LdMVK) modulates macrophage functions and has a significant role in pathogenesis.

Sarco/Endoplasmic Reticulum Calcium ATPase Inhibitors: Beyond Anticancer Perspective

The sarco/endoplasmic reticulum calcium ATPase (SERCA), which plays a key role in the maintenance of Ca²⁺ ion homeostasis, is an extensively studied enzyme, the inhibition of which has a considerable impact on cell life and death decision. To date, several SERCA inhibitors have been thoroughly studied and the most notable one, a derivative of the sesquiterpene lactone thapsigargin, is gradually approaching a clinical application. Meanwhile, new compounds with SERCA-inhibiting properties of natural, synthetic, or semisynthetic origin are being discovered and/or developed; some of these might also be suitable for the development of new drugs with improved performance. This review brings an up-to-date comprehensive overview of recently discovered compounds with the potential of SERCA inhibition, discusses their mechanism of action, and highlights their potential clinical applications, such as cancer treatment.

Transient Receptor Potential Ankyrin 1 (TRPA1) Mediates Lipopolysaccharide (LPS)-Induced Inflammatory Responses in Primary Human Osteoarthritic Fibroblast-Like Synoviocytes

Transient receptor potential ankyrin 1 (TRPA1) is a membrane-associated cation channel, widely expressed in neuronal and non-neuronal cells. Recently, emerging evidences suggested the crucial role of TRPA1 in the disease progression of osteoarthritis (OA). Therefore, we aimed to investigate whether TRPA1 mediate lipopolysaccharide (LPS)-induced inflammatory responses in primary human OA fibroblast-like synoviocytes (OA-FLS). The expression of TRPA1 in LPS-treated OA-FLS was assessed by polymerase chain reaction (PCR) and western blot (WB), and the functionality of TRPA1 channel by Ca²⁺ influx measurements. Meanwhile, production of interleukin (IL)-1β, tumor necrosis factor (TNF)-α, IL-6, matrix metalloproteinase (MMP)-1, and MMP-3 in LPS-treated cells was measured by immunoassay. Histological observation after inhibition of TRPA1 was also performed in rats with LPS-induced inflammatory arthritis. After being induced by LPS, the gene and protein expression of TRPA1 was increased in the time-dependent or dose-dependent manner. Meanwhile, Ca²⁺ influx mediated by TRPA1 in human OA-FLS was also enhanced. In addition, pharmacological inhibition and gene silencing of TRPA1 downregulated the production of IL-1β, TNF-α, IL-6, MMP-1, and MMP-3 in LPS-treated FLS. Finally, synovial inflammation and cartilage degeneration were also reduced by the TRPA1 antagonist. We found the LPS caused the increased functional expression of TRPA1, the activation of which involved in LPS-reduced inflammatory responses in primary human OA-FLS, and the inhibition of TRPA1 produces protective effect in LPS-induced arthritis.

NFAT1 Regulates Systemic Autoimmunity through the Modulation of a Dendritic Cell Property

The transcription factor NFAT1 plays a pivotal role in the homeostasis of T lymphocytes. However, its functional importance in non-CD4⁺ T cells, especially in systemic immune disorders, is largely unknown. In this study, we report that NFAT1 regulates dendritic cell (DC) tolerance and suppresses systemic autoimmunity using the experimental autoimmune myasthenia gravis (EAMG) as a model. Myasthenia gravis and EAMG are T cell-dependent, Ab-mediated autoimmune disorders in which the acetylcholine receptor is the major autoantigen. NFAT1-knockout mice showed higher susceptibility to EAMG development with enhanced Th1/Th17 cell responses. NFAT1 deficiency led to a phenotypic alteration of DCs that show hyperactivation of NF-κB-mediated signaling pathways and enhanced binding of NF-κB (p50) to the promoters of IL-6 and IL-12. As a result, NFAT1-knockout DCs produced much higher levels of proinflammatory cytokines such as IL-1β, IL-6, IL-12, and TNF-α, which preferentially induce Th1/Th17 cell differentiation. Our data suggest that NFAT1 may limit the hyperactivation of the NF-κB-mediated proinflammatory response in DCs and suppress autoimmunity by serving as a key regulator of DC tolerance.

Transient receptor potential ankyrin 1 (TRPA1) is functionally expressed in primary human osteoarthritic chondrocytes

BACKGROUND

Transient receptor potential ankyrin 1 (TRPA1) is a membrane-associated cation channel, widely expressed in neuronal cells and involved in nociception and neurogenic inflammation. We showed recently that TRPA1 mediates cartilage degradation and joint pain in the MIA-model of osteoarthritis (OA) suggesting a hitherto unknown role for TRPA1 in OA. Therefore, we aimed to investigate whether TRPA1 is expressed and functional in human OA chondrocytes.

METHODS

Expression of TRPA1 in primary human OA chondrocytes was assessed by qRT-PCR and Western blot. The functionality of the TRPA1 channel was assessed by Ca(2+)-influx measurements. Production of MMP-1, MMP-3, MMP-13, IL-6, and PGE2 subsequent to TRPA1 activation was measured by immunoassay.

RESULTS

We show here for the first time that TRPA1 is expressed in primary human OA chondrocytes and its expression is increased following stimulation with inflammatory factors IL-1β, IL-17, LPS, and resistin. Further, the TRPA1 channel was found to be functional, as stimulation with the TRPA1 agonist AITC caused an increase in Ca(2+) influx, which was attenuated by the TRPA1 antagonist HC-030031. Genetic depletion and pharmacological inhibition of TRPA1 downregulated the production of MMP-1, MMP-3, MMP-13, IL-6, and PGE2 in osteoarthritic chondrocytes and murine cartilage, respectively.

CONCLUSIONS

The TRPA1 cation channel was found to be functionally expressed in primary human OA chondrocytes, which is an original finding. The presence and inflammatory and catabolic effects of TRPA1 in human OA chondrocytes propose a highly intriguing role for TRPA1 as a pathogenic factor and drug target in OA.

DMSO Modifies Structural and Functional Properties of RPMI-8402 Cells by Promoting Programmed Cell Death

Apoptosis in lymphoid cells can be induced in different ways depending on cell type and acquired signal. Biochemical modifications occur at an early phase of cell death while at late times the typical morphological features of apoptosis can be visualized. The aim of this study is to verify by multiparametric analyses the plasma membrane fluidity, the intracellular Ca2+ concentration and the nitric oxide synthase (NOS) activity during cell death progression induced by DMSO treatment. The RPMI-8402 human pre-T lymphoblastoid cell line was induced to cell death by DMSO. Analyses rescued at early times of treatment prove a substantial modification of plasma membrane fluidity associated with an increase of intracellular Ca2+. Moreover, these modifications are associated with an up regulation of NOS activity. Our results are consistent with the hypothesis that programmed cell death can be induced by up regulation of the intracellular Ca2+ associated with an increase of cell membrane fluidity. The apoptotic mechanisms seem to involve not only membrane damage and increased intracellular calcium levels but also production of nitric oxide.

Influence of the culture medium on the production of nitric oxide and expression of inducible nitric oxide synthase by activated macrophages in vitro

Macrophages play an important role in immune and inflammatory responses, and have been extensively studied in vitro using culture media such as RPMI1640 medium, Dulbecco's modified Eagle medium (DMEM), and Ham's F-12 medium (F-12). We found that the activation phenotypes of a murine macrophage-like cell line, J774.1/JA-4, were obviously different in two distinct culture media (F-12 and DMEM), both of which were supplemented with 10% of the same fetal bovine serum (FBS). Among these phenotypes, nitric oxide (NO) production as well as inducible NO synthase (iNOS) expression, induced by lipopolysaccharide (LPS) and interferon-γ (IFN-γ), were remarkably different. iNOS expression was higher in the macrophages cultured in DMEM than in F-12 for 20 h, while no significant differences were shown in NO production between in F-12 and DMEM. It might be the reason why DMEM have reduced NO production by the induced iNOS. Besides, [Formula: see text]-generating activity, and production of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in the activated macrophages were also different between the cultures in F-12 and DMEM. These results suggest that F-12 and DMEM contain certain components responsible for modification of macrophage activation processes and/or macrophage functions. Our present results provide evidence that the choice of culture medium is important in the study and analysis of macrophage activation.

Monosodium iodoacetate-induced inflammation and joint pain are reduced in TRPA1 deficient mice--potential role of TRPA1 in osteoarthritis

OBJECTIVES

Intra-articularly injected monosodium iodoacetate (MIA) induces joint pathology mimicking osteoarthritis (OA) and it is a widely used experimental model of OA. MIA induces acute inflammation, cartilage degradation and joint pain. Transient Receptor Potential Ankyrin 1 (TRPA1) is an ion channel known to mediate nociception and neurogenic inflammation. Here, we tested the hypothesis that TRPA1 would be involved in the development of MIA-induced acute inflammation, cartilage changes and joint pain.

METHODS

The effects of pharmacological blockade (by TCS 5861528) and genetic depletion of TRPA1 were studied in MIA-induced acute paw inflammation. Cartilage changes (histological scoring) and joint pain (weight-bearing test) in MIA-induced experimental OA were compared between wild type and TRPA1 deficient mice. The effects of MIA were also studied in primary human OA chondrocytes and in mouse cartilage.

RESULTS

MIA evoked acute inflammation, degenerative cartilage changes and joint pain in wild type mice. Interestingly, these responses were attenuated in TRPA1 deficient animals. MIA-induced paw inflammation was associated with increased tissue levels of substance P; and the inflammatory edema was reduced by pretreatment with catalase, with the TRPA1 antagonist TCS 5861528 and with the neurokinin 1 receptor antagonist L703,606. In chondrocytes, MIA enhanced interleukin-1 induced cyclooxygenase-2 (COX-2) expression, an effect that was blunted by pharmacological inhibition and genetic depletion of TRPA1.

CONCLUSIONS

TRPA1 was found to mediate acute inflammation and the development of degenerative cartilage changes and joint pain in MIA-induced experimental OA in the mouse. The results reveal TRPA1 as a potential mediator and drug target in OA.

Urate crystal induced inflammation and joint pain are reduced in transient receptor potential ankyrin 1 deficient mice--potential role for transient receptor potential ankyrin 1 in gout

Introduction

In gout, monosodium urate (MSU) crystals deposit intra-articularly and cause painful arthritis. In the present study we tested the hypothesis that Transient Receptor Poten-tial Ankyrin 1 (TRPA1), an ion channel mediating nociceptive signals and neurogenic in-flammation, is involved in MSU crystal-induced responses in gout by utilizing three experi-mental murine models.

Methods

The effects of selective pharmacological inhibition (by HC-030031) and genetic depletion of TRPA1 were studied in MSU crystal-induced inflammation and pain by using 1) spontaneous weight-bearing test to assess MSU crystal-induced joint pain, 2) subcutaneous air-pouch model resembling joint inflammation to measure MSU crystal-induced cytokine production and inflammatory cell accumulation, and 3) MSU crystal-induced paw edema to assess acute vascular inflammatory responses and swelling.

Results

Intra-articularly injected MSU crystals provoked spontaneous weight shift off from the affected limb in wild type but not in TRPA1 knock-out mice referring alleviated joint pain in TRPA1 deficient animals. MSU crystal-induced inflammatory cell infiltration and accumulation of cytokines MCP-1, IL-6, IL-1beta, MPO, MIP-1alpha and MIP-2 into subcu-taneous air-pouch (resembling joint cavity) was attenuated in TRPA1 deficient mice and in mice treated with the selective TRPA1 inhibitor HC-030031 as compared to control animals. Further, HC-030031 treated and TRPA1 deficient mice developed tempered inflammatory edema when MSU crystals were injected into the paw.

Conclusions

TRPA1 mediates MSU crystal-induced inflammation and pain in experimental models supporting the role of TRPA1 as a potential mediator and a drug target in gout flare.

Identification of a receptor for neuropeptide VGF and its role in neuropathic pain

VGF (nonacronymic) is a neuropeptide precursor that plays multiple roles in regulation of energy balance, reproduction, hippocampal synaptic plasticity, and pain. Data from a number of pain models showed significant up-regulation of VGF in sensory neurons. TLQP-21, one of the VGF-derived neuropeptides, has been shown to induce a hyperalgesic response when injected subcutaneously into the hind paw of mice. However, the precise role of VGF-derived neuropeptides in neuropathic pain and the molecular identity of the receptor for VGF-derived peptides are yet to be investigated. Here we identified gC1qR, the globular heads of the C1q receptor, as the receptor for TLQP-21 using chemical cross-linking combined with mass spectrometry analysis. TLQP-21 caused an increase in intracellular Ca²⁺ levels in rat macrophages and microglia. Inoculation of TLQP-21-stimulated macrophages into rat hind paw caused mechanical hypersensitivity. The increase in intracellular Ca²⁺ levels in macrophages was attenuated by either siRNA or neutralizing antibodies against gC1qR. Furthermore, application of the gC1qR-neutralizing antibody to rats with partial sciatic nerve ligation resulted in a delayed onset of nerve injury-associated mechanical hypersensitivity. These results indicate that gC1qR is the receptor for TLQP-21 and plays an important role in chronic pain through activation of macrophages. Because direct association between TLQP-21 and gC1qR is required for activation of macrophages and causes hypersensitivity, disrupting this interaction may be a useful new approach to develop novel analgesics.

Attenuation of the acute inflammatory response by dual specificity phosphatase 1 by inhibition of p38 MAP kinase

Dual specificity phosphatase 1 (DUSP1) dephosphorylates and, hence, regulates the activity of MAP kinases. The present study investigated the effect of DUSP1 on inflammatory gene expression and on the development of carrageenan-induced inflammation. It was found that DUSP1 expression was increased by LPS, and the down-regulation of DUSP1 by siRNA enhanced the phosphorylation of p38 MAPK, while JNK phosphorylation was not affected in murine macrophages. LPS-induced interleukin (IL)-6, tumor-necrosis factor (TNF) and cyclooxygenase-2 (COX2) expression were enhanced in bone marrow-derived macrophages (BMMs) from DUSP1(-/-) mice as compared to those from wild-type mice. In addition, down-regulation of DUSP1 by siRNA enhanced IL-6, TNF and COX2 expression in J774 macrophages, while p38 MAPK inhibitors SB202190 and BIRB 796 inhibited the expression of those inflammatory factors. In vivo, the intensity of the carrageenan-induced paw edema reaction was increased in DUSP1(-/-) mice as compared to the wild-type animals. In conclusion, DUSP1 is an important negative regulator of the acute inflammatory response by limiting p38 MAPK, and compounds which enhance DUSP1 expression or activity may hold a promise as anti-inflammatory drugs.

Multi-system disorders of glycosphingolipid and ganglioside metabolism

Glycosphingolipids (GSLs) and gangliosides are a group of bioactive glycolipids that include cerebrosides, globosides, and gangliosides. These lipids play major roles in signal transduction, cell adhesion, modulating growth factor/hormone receptor, antigen recognition, and protein trafficking. Specific genetic defects in lysosomal hydrolases disrupt normal GSL and ganglioside metabolism leading to their excess accumulation in cellular compartments, particularly in the lysosome, i.e., lysosomal storage diseases (LSDs). The storage diseases of GSLs and gangliosides affect all organ systems, but the central nervous system (CNS) is primarily involved in many. Current treatments can attenuate the visceral disease, but the management of CNS involvement remains an unmet medical need. Early interventions that alter the CNS disease have shown promise in delaying neurologic involvement in several CNS LSDs. Consequently, effective treatment for such devastating inherited diseases requires an understanding of the early developmental and pathological mechanisms of GSL and ganglioside flux (synthesis and degradation) that underlie the CNS diseases. These are the focus of this review.

The role of nitric oxide in osteoarthritis

Elevated levels of markers of nitric oxide (NO) production are found in osteoarthritic joints suggesting that NO is involved in the pathogenesis of osteoarthritis (OA). In OA, NO mediates many of the destructive effects of interleukin-1 (IL-1) and tumour necrosis factor-alpha (TNF-alpha) in the cartilage, and inhibitors of NO synthesis have demonstrated retardation of clinical and histological signs and symptoms in experimentally induced OA and other forms of arthritis. As an important factor in cartilage, the regulation of inducible nitric oxide synthase (iNOS) expression and activity, and the effects of NO are reviewed, especially in relation to the pathogenesis of OA.

Induction of TLR4-target genes entails calcium/calmodulin-dependent regulation of chromatin remodeling

Upon toll-like receptor 4 (TLR4) signaling in macrophages, the mammalian Swi/Snf-like BAF chromatin remodeling complex is recruited to many TLR4 target genes where it remodels their chromatin to promote transcription. Here, we show that, surprisingly, recruitment is not sufficient for chromatin remodeling; a second event, dependent on calcium/calmodulin (CaM), is additionally required. Calcium/CaM directly binds the HMG domain of the BAF57 subunit within the BAF complex. Calcium/CaM antagonists, including a CaM-binding peptide derived from BAF57, abolish BAF-dependent remodeling and gene expression without compromising BAF recruitment. BAF57 RNAi and BAF57 dominant negative mutants defective in CaM binding similarly impair the induction of BAF target genes. Our data implicate calcium/CaM in TLR4 signaling, and reveal a previously undescribed, recruitment-independent mode of regulation of the BAF complex that is probably achieved through a direct CaM-BAF interaction.

Reactive oxygen and nitrogen species are involved in sorbitol-induced apoptosis of human erithroleukaemia cells K562

In this study, we found that production of both reactive oxygen (ROS) and nitrogen (RNS) species is a very early event related to treatment with hyperosmotic concentration of sorbitol. The production of nitric oxide (NO) was paralleled by the increase of the mRNA and protein level of the inducible form of the nitric oxide synthase (iNOS). ROS and RNS enhancement, process concomitant to the failure of mitochondrial trans-membrane potential (DeltaPsi), was necessary for the induction of apoptosis as demonstrated by the protection against sorbitol-mediated toxicity observed after treatment with ROS scavengers or NOS inhibitors. The synergistic action of ROS and RNS was finally demonstrated by pre-treatment with rosmarinic acid that, by powerfully buffering both these species, prevents impairment of DeltaPsi and cell death. Overall results suggest that the occurrence of apoptosis upon sorbitol treatment is an event mediated by oxidative/nitrosative stress rather than a canonical hyperosmotic shock.

Genetic diseases of sphingolipid metabolism: pathological mechanisms and therapeutic options

Although diseases in the pathway of sphingolipid degradation have been known for decades, the first disease in the biosynthetic pathway was only reported in 2004, when a form of infantile-onset symptomatic epilepsy was described as a genetic defect in GM3 synthase. Presumably other diseases in the sphingolipid biosynthetic pathway will yet be discovered, although many may remain undetected due to their putative lethal phenotypes. In contrast, diseases are known for essentially every step in the pathway of SL degradation, caused by the defective activity of one or other of the lysosomal hydrolases in this pathway. Despite the fact that some of these storage disorders were first discovered in the 19th century, the cellular and biochemical events that cause pathology are still poorly delineated. In this review, we focus on recent advances in our understanding of how defects in the pathways of sphingolipid metabolism may lead to pathology. In addition, we discuss currently-available and emerging therapeutic options.

Aurothiomalate and hydroxychloroquine inhibit nitric oxide production in chondrocytes and in human osteoarthritic cartilage

OBJECTIVES

Nitric oxide (NO) is a destructive mediator produced by activated chondrocytes. The aim of the present study was to investigate the effect of disease-modifying anti-rheumatic drugs (DMARDs) on interleukin-1beta (IL-1beta)-induced NO production in chondrocyte cultures, and in human osteoarthritic cartilage.

RESULTS

Aurothiomalate, hydroxychloroquine, methotrexate and leflunomide inhibited IL-1beta-induced inducible NO synthase (iNOS) expression and NO production in immortalized H4 chondrocytes, while penicillamine and sulfasalazine had no effect. This can be explained by the fact that the four effective DMARDs also suppressed IL-1beta-induced activation of nuclear factor kappa B (NF-kappaB), which is a crucial transcription factor for iNOS. Aurothiomalate and hydroxychloroquine also inhibited IL-1beta-induced NO production in OA cartilage whereas methotrexate and leflunomide had no effect.

CONCLUSION

Aurothiomalate and hydroxychloroquine suppressed IL-1beta-induced NO production in chondrocyte cultures and in OA cartilage. The results suggest an additional anti-inflammatory mechanism for aurothiomalate and hydroxychloroquine and indicates their possible therapeutic value in the treatment of osteoarthritis (OA).

Simultaneously multi-parameter determination of hematonosis cell apoptosis by two-photon and confocal laser scanning microscopy

Flow cytometry (FCM), TdT-mediated dUTP Nick End Labeling (TUNEL), and DNA ladder are conventional methods to detect apoptosis of drug-treated cells. However, the assumption of cell number restricts their applications in clinics. In this paper, we report a cell-saving imaging method for quick identification of the hematonosis cell apoptosis induced by chemotherapeutic drugs. By the combination of two-photon and confocal microscopy, three main apoptosis parameters (the change of nuclear morphology, collapse of mitochondrial membrane potential, and increase of intracellular calcium) were recorded simultaneously for single As2O3-induced Molt-4 cells. The results are highly in accordance with those produced by classical flow cytometry. This work suggests that this new imaging method would be promising in the quick identification of hematonosis cell apoptosis.

P2X7 nucleotide receptor activation enhances IFN gamma-induced type II nitric oxide synthase activity in BV-2 microglial cells

Under normal and pathological conditions, brain cells release nucleotides that regulate a wide range of cellular responses due to activation of P2 nucleotide receptors. In this study, the effect of extracellular nucleotides on IFN gamma-induced NO release in murine BV-2 microglial cells was investigated. BV-2 cells expressed mRNA for metabotropic P2Y and ionotropic P2X receptors. Among the P2 receptor agonists tested, ATP, ADP, 2',3'-O-(4-benzoylbenzoyl)-ATP (BzATP), and 2-methylthio-ATP (2-MeSATP), but not UTP, enhanced IFN gamma-induced iNOS expression and NO production, suggesting that the uridine nucleotide receptors P2Y2 and P2Y6 are not involved in this response. U0126, an antagonist for MEK1/2, a kinase that phosphorylates the extracellular signal-regulated kinases ERK1/2, decreased IFN gamma-induced NO production. BzATP, a potent P2X7 receptor agonist, was more effective than ATP, ADP, or 2-MeSATP at enhancing IFN gamma-induced ERK1/2 phosphorylation. Consistent with activation of the P2X7 receptor, periodate-oxidized ATP, a P2X7 receptor antagonist, and suramin, a non-specific P2 receptor antagonist, inhibited the effect of ATP or BzATP on IFN gamma-induced NO production, whereas pyridoxal-phosphate-6-azophenyl-2',4'-disulfonic acid (PPADS), an antagonist of several P2X receptor subtypes, was ineffective. These results suggest that activation of P2X7 receptors may contribute to inflammatory responses in microglial cells seen in neurodegenerative diseases.

Macrophage endothelial nitric-oxide synthase autoregulates cellular activation and pro-inflammatory protein expression

Expression of inducible nitric-oxide (NO) synthase (iNOS) and "high-output" production of NO by macrophages mediates many cytotoxic actions of these immune cells. However, macrophages have also been shown to express a constitutive NOS isoform, the function of which remains obscure. Herein, bone marrow-derived macrophages (BMDMØs) from wild-type and endothelial NOS (eNOS) knock-out (KO) mice have been used to assess the role of this constitutive NOS isoform in the regulation of macrophage activation. BMDMØs from eNOS KO animals exhibited reduced nuclear factor-kappaB activity, iNOS expression, and NO production after exposure to lipopolysaccharide (LPS) as compared with cells derived from wild-type mice. Soluble guanylate cyclase (sGC) was identified in BMDMØs at a mRNA and protein level, and activation of cells with LPS resulted in accumulation of cyclic GMP. Moreover, the novel non-NO-based sGC activator, BAY 41-2272, enhanced BMDMØ activation in response to LPS, and the sGC inhibitor 1H-(1,2,4)oxadiazolo(4,3-a)quinoxalin-1-one attenuated activation. These observations provide the first demonstration of a pathophysiological role for macrophage eNOS in regulating cellular activation and suggest that NO derived from this constitutive NOS isoform, in part via activation of sGC, is likely to play a pivotal role in the initiation of an inflammatory response.

The bacterial redox protein azurin induces apoptosis in J774 macrophages through complex formation and stabilization of the tumor suppressor protein p53

Two redox proteins, azurin and cytochrome c(551) elaborated by Pseudomonas aeruginosa, demonstrate significant cytotoxic activity towards macrophages. Azurin can enter macrophages, localize in the cytosol and nuclear fractions, and induce apoptosis. Two redox-negative mutants of azurin have less cytotoxicity than does wild-type (wt) azurin. Azurin has been shown to form a complex with the tumor suppressor protein p53, a known inducer of apoptosis, thereby stabilizing it and enhancing its intracellular level. A higher level of reactive oxygen species (ROS), generated during treatment of macrophages with wt azurin, correlates with its cytotoxicity. Treatment with some ROS-removing antioxidants greatly reduces azurin-mediated cytotoxicity, thus demonstrating a novel virulence property of this bacterial redox protein.

Nitric oxide and calcium ions in apoptotic esophageal carcinoma cells induced by arsenite

AIM: To Quantitatively analyze the nitri oxide (NO) and Ca²⁺ in apoptosis of esophageal carcinoma cells induced by arsenic trioxide (As₂O₃).

METHODS: The cell line SHEEC1, a malignant esophageal epithelial cell induced by HPV in synergy with TPA in our laboratory, was cultured in a serum-free medium and treated with As₂O₃. Before and after administration of As₂O₃, NO production in cultured medium was detected quantitatively using the Griess Colorimetric method. Intracellular Ca²⁺ was labeled by using the fluorescent dye Fluo3-AM and detected under confocal laser scanning microscope (CLSM), which was able to acquire data in real-time enabling Ca²⁺ dynamics of individual cells in vitro. The apoptotic cells were examined under electron microscopy.

RESULTS: Intracellular concentration of Ca²⁺ increased from 1.00 units to 1.09-1.38 units of fluorescent intensity at As₂O₃ treatment and NO products subsequently released from As₂O₃-treated cells increased from 0.98-1.00 × 10^-2μmol·L^-1 up to 1.48-1.52 × 10^-2μmol·L^-1 and maintained in a high level continuously. Finally apoptosis of cells occurred, chromatin being agglutinated, cells shrunk, nuclei became round and mitochondria swelled.

CONCLUSION: Ca²⁺ and NO increased with cell damage and apoptosis in cells treated by As₂O₃. The Ca²⁺ is an initial messenger to the apoptotic pathway. To investigate Ca²⁺ and NO will be a new direction for studying the apoptotic signaling messenger of the esophageal carcinoma cells induced by As₂O₃.