Redox processes are major regulators of leukotriene synthesis in neutrophils exposed to bacteria Salmonella typhimurium; the way to manipulate neutrophil swarming

Neutrophils play a primary role in protecting our body from pathogens. When confronted with invading bacteria, neutrophils begin to produce leukotriene B4, a potent chemoattractant that, in cooperation with the primary bacterial chemoattractant fMLP, stimulates the formation of swarms of neutrophils surrounding pathogens. Here we describe a complex redox regulation that either stimulates or inhibits fMLP-induced leukotriene synthesis in an experimental model of neutrophils interacting with Salmonella typhimurium. The scavenging of mitochondrial reactive oxygen species by mitochondria-targeted antioxidants MitoQ and SkQ1, as well as inhibition of their production by mitochondrial inhibitors, inhibit the synthesis of leukotrienes regardless of the cessation of oxidative phosphorylation. On the contrary, antioxidants N-acetylcysteine and sodium hydrosulfide promoting reductive shift in the reversible thiol-disulfide system stimulate the synthesis of leukotrienes. Diamide that oxidizes glutathione at high concentrations inhibits leukotriene synthesis, and the glutathione precursor S-adenosyl-L-methionine prevents this inhibition. Diamide-dependent inhibition is also prevented by diphenyleneiodonium, presumably through inhibition of NADPH oxidase and NADPH accumulation. Thus, during bacterial infection, maintaining the reduced state of glutathione in neutrophils plays a decisive role in the synthesis of leukotriene B4. Suppression of excess leukotriene synthesis is an effective strategy for treating various inflammatory pathologies. Our data suggest that the use of mitochondria-targeted antioxidants may be promising for this purpose, whereas known thiol-based antioxidants, such as N-acetylcysteine, may dangerously stimulate leukotriene synthesis by neutrophils during severe pathogenic infection.

Effects of total alkaloids from Alstonia scholaris (L.) R. Br. on ovalbumin-induced asthma mice

ETHNOPHARMACOLOGICAL RELEVANCE

More than 300 million people worldwide suffer from asthma, a chronic respiratory inflammatory disease. Total alkaloids (TA) were extracted from the ethnic medicinal plant Alstonia solaris (L.) R.Br., which is used to treat respiratory diseases. They may be effective drugs for treating asthma, but research is still needed to determine their effectiveness and mechanism in treating asthma.

AIM OF THE STUDY

To further understand TA's role in the treatment of asthma and to support the phase II trial of the drug.

MATERIALS AND METHODS

In this study, we investigated the effects of TA in a mouse asthma model produced by Ovalbumin (OVA). H&E and PAS staining were used to observe the histopathological features of lung. airway hyperresponsiveness (AHR) was detected by ventilator; The expression of interleukin (IL)-33, suppression of tumorigenicity 2 (ST2) and E-cadherin in the lungs was evaluated by IHC. The concentrations of Mucin5AC (MUC5AC), eotaxin, IL-4, IL-5, IL-9, IL-13, interferon (IFN)-γ, IL-6, IL-8, IL-17A, IL-33, IL-25, thymic stromal lymphopoietin (TSLP), monocyte chemoattractant protein 1 (MCP-1), leukotriene (LT) B4, LTC4, LTD4, LTE4 in bronchoalveolar lavage fluid (BALF) and total IgE (tIgE), OVA-Specific IgE (OVA-IgE) in serum were measured by ELISA. ILC2s and eosinophils were detected in lung tissue by flow cytometry. The gene expression levels of IL-33 and ST2 were detected by RT-qPCR.

RESULTS

Administration of TA reduced pulmonary inflammatory symptoms, MUC5AC production in the BALF, and AHR. At the same time, TA inhibited eotaxin production and eosinophil recruitment. Moreover, TA significantly decreased Th2 and Th17 cytokines and increased Th1 cytokines, contributing to restore the balance between Th1 and Th2 and Th17 cytokines. TA may reduce ILC2s numbers by inhibiting IL-33, IL-25, and TSLP levels in BALF and IL-33/ST2 signaling in lung tissue. Finally, TA decreased tIgE, OVA-IgE, and MCP-1 levels and subsequently inhibited mast cell activation and leukotriene release.

CONCLUSIONS

These findings imply that TA may be an effective immunoregulatory medication for the management and prevention of asthma.

A review of the therapeutic potential of the cysteinyl leukotriene antagonist Montelukast in the treatment of bronchiolitis obliterans syndrome following lung and hematopoietic-stem cell transplantation and its possible mechanisms

Lung and hematopoietic stem cell transplantation are therapeutic modalities in chronic pulmonary and hematological diseases, respectively. One of the complications in these patients is the development of bronchiolitis obliterans syndrome (BOS). The efficacy and safety of available treatment strategies in BOS remain a challenge. A few mechanisms have been recognized for BOS in lung transplant and graft-versus-host disease (GVHD) patients involving the TH-1 and TH-2 cells, NF-kappa B, TGF-b, several cytokines and chemokines, and cysteinyl leukotrienes (CysLT). Montelukast is a highly selective CysLT receptor antagonist that has been demonstrated to exert anti-inflammatory and anti-fibrotic effects in abundant experiments. One area of interest for the use of montelukast is lung transplants or GVHD-associated BOS. Herein, we briefly review data regarding the mechanisms involved in BOS development and montelukast administration as a treatment modality for BOS, and finally, the possible relationship between CysLTs antagonism and BOS improvement will be discussed.

The Multifarious Functions of Leukotrienes in Bone Metabolism

Leukotrienes (LTs) are derived from arachidonic acid metabolism by the 5-lipoxygenase (5-LO) enzyme. The production of LTs is stimulated in the pathogenesis of rheumatoid arthritis (RA), osteoarthritis, and periodontitis, with a relevant contribution to bone resorption. However, its role in bone turnover, particularly the suppression of bone formation by modulating the function of osteoclasts and osteoblasts, remains unclear. We investigated the effects of LTs on bone metabolism and their impact on osteogenic differentiation and osteoclastogenesis using a 5-LO knockout (KO) mouse model. Results from micro-computed tomography (μCT) analysis of femur from 8-week-old 5-LO-deficient mice showed increased cortical bone and medullary region in females and males and decreased trabecular bone in females. In the vertebra, we observed increased marrow area in both females and males 5-LO KO and decreased trabecular bone only in females 5-LO KO. Immunohistochemistry (IHC) analysis showed higher levels of osteogenic markers tissue-nonspecific alkaline phosphatase (TNAP) and osteopontin (OPN) and lower expression of osteoclastogenic marker tartrate-resistant acid phosphatase (TRAP) in the femurs of 5-LO KO mice versus wild-type (WT). Alkaline phosphatase activity and mineralization assay results showed that the 5-LO absence enhances osteoblasts differentiation and mineralization but decreases the proliferation. Alkaline phosphatase (ALP), Bglap, and Sp7 gene expression were higher in 5-LO KO osteoblasts compared to WT cells. Eicosanoids production was higher in 5-LO KO osteoblasts except for thromboxane 2, which was lower in 5-LO-deficient mice. Proteomic analysis identified the downregulation of proteins related to adenosine triphosphate (ATP) metabolism in 5-LO KO osteoblasts, and the upregulation of transcription factors such as the adaptor-related protein complex 1 (AP-1 complex) in long bones from 5-LO KO mice leading to an increased bone formation pattern in 5-LO-deficient mice. We observed enormous differences in the morphology and function of osteoclasts with reduced bone resorption markers and impaired osteoclasts in 5-LO KO compared to WT osteoclasts. Altogether, these results demonstrate that the absence of 5-LO is related to the greater osteogenic profile. © 2023 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Distribution of the cysteinyl leukotriene system components in the human, rat and mouse eye

The cysteinyl leukotrienes (CysLTs) have important functions in the regulation of inflammation and cellular stress. Blocking the CysLT receptors (CysLTRs) with specific antagonists is beneficial against progression of retinopathies (e.g. diabetic retinopathy, wet AMD). However, the exact cellular localization of the CysLTRs and their endogenous ligands in the eye have not been elucidated in detail yet. It is also not known whether the expression patterns differ between humans and animal models. Therefore, the present study aimed to describe and compare the distribution of two important enzymes in CysLT biosynthesis, 5-lipoxygenase (5-LOX) and 5-lipoxygenase-activating protein (FLAP), and of CysLTR1 and CysLTR2 in healthy human, rat and mouse eyes. Human donor eyes (n = 10) and eyes from adult Sprague Dawley rats (n = 5) and CD1 mice (n = 8) of both sexes were collected. The eyes were fixed in 4% paraformaldehyde and cross-sections were investigated by immunofluorescence with specific antibodies against 5-LOX, FLAP (human tissue only), CysLTR1 and CysLTR2. Flat-mounts of the human choroid were prepared and processed similarly. Expression patterns were assessed and semiquantitatively evaluated using a confocal fluorescence microscope (LSM710, Zeiss). We observed so far unreported expression sites for CysLT system components in various ocular tissues. Overall, we detected expression of 5-LOX, CysLTR1 and CysLTR2 in the human, rat and mouse cornea, conjunctiva, iris, lens, ciliary body, retina and choroid. Importantly, expression profiles of CysLTR1 and CysLTR2 were highly similar between human and rodent eyes. FLAP was expressed in all human ocular tissues except the lens. Largely weak immunoreactivity of FLAP and 5-LOX was observed in a few, yet unidentified, cells of diverse ocular tissues, indicating low levels of CysLT biosynthesis in healthy eyes. CysLTR1 was predominantly detected in ocular epithelial cells, supporting the involvement of CysLTR1 in stress and immune responses. CysLTR2 was predominantly expressed in neuronal structures, suggesting neuromodulatory roles of CysLTR2 in the eye and revealing disparate functions of CysLTRs in ocular tissues. Taken together, we provide a comprehensive protein expression atlas of CysLT system components in the human and rodent eye. While the current study is purely descriptive and therefore does not allow significant functional conclusions yet, it represents an important basis for future studies in diseased ocular tissues in which distribution patterns or expression levels of the CysLT system might be altered. Furthermore, this is the first comprehensive study to elucidate expression patterns of CysLT system components in human and animal models that will help to identify and understand functions of the system as well as mechanisms of action of potential CysLTR ligands in the eye.

Targeting the Leukotriene Pathway for Colon Cancer Interception

The role of chronic inflammation and arachidonic acid (AA) metabolism in tumor progression has been well characterized for variety of cancers, with compelling data for colon cancer. Several preclinical and clinical studies primarily focused on inhibiting the cyclooxygenase pathways using NSAIDs and aspirin for colon cancer prevention. However, emerging evidence clearly supports the pro-tumorigenic role of 5-lipoxygenase and its downstream leukotriene pathway within AA metabolism. As discussed in the current issue, targeting the leukotriene pathway by cysteinyl leukotriene receptor antagonist (LTRA) montelukast suppressed formation of aberrant crypt foci (ACF) and cell proliferation in colonic epithelium, suggesting the potential of LTRAs for colon cancer prevention. Although this is a short clinical chemoprevention trial to explore the effects of LTRAs against ACF development, it is a significant and timely study opening avenues to further explore the possibilities of using LTRAs in other inflammation-associated precancerous lesions as well. In this spotlight commentary, we highlight the implications of their data and the opportunities for developing LTRAs as potential candidates for colorectal cancer interception. See related article by Higurashi et al., p. 661.

The influence of arachidonic acid metabolites on PPAR and RXR expression in bovine uterine cells

Peroxisome proliferator-activated receptors (PPARs) are ligand-activated transcription factors belonging to the superfamily of nuclear receptors. Three isoforms have been described: alpha (PPARα), delta (PPARδ), and gamma (PPARγ). PPARs heterodimerize with retinoid X receptors (RXRs: RXRα, RXRβ and RXRγ). PPAR activity can be modulated by several ligands, including arachidonic acid (AA) metabolites. The aims of the study were to determine the effect of AA metabolites (prostaglandin [PG]E₂, PGF_2α, leukotriene [LT]B₄, and LTC₄) on mRNA (real-time PCR) and protein expression (Western blotting) of PPARα, PPARδ, and PPARγ, and on mRNA expression of RXRα, RXRβ, and RXRγ, in bovine epithelial, stromal, and myometrial primary uterine cells and in bovine stromal cells with silenced PPAR genes (N = 10). All PPAR and RXR isoforms were expressed. Prostaglandins affected expression of PPARs only in stromal cells, whereas LTs modulated PPARγ mRNA expression in epithelial and myometrial primary cells. Blockade of signal transduction through PPARs prevented interactions between AA metabolites and PPARs and changed RXR expression comparing with primary stromal cells. In primary stromal uterine cells, mRNA expression of RXRs was higher than that of PPARs. In uterine stromal cells in which intracellular signaling through PPARs was blocked, RXRs seem to take over the role of PPARs and are pivotal for cell functions. This study revealed the reaction of PPARs and RXRs to agonists which naturally occur in the bovine uterus.

Proresolving lipid mediators and diabetic wound healing

PURPOSE OF REVIEW

Defective wound healing is one of the most prominent clinical manifestations of both type 1 and type 2 diabetes. As the global rates of diabetes increase, a detailed understanding of the molecular and cellular defects that give rise to unresolved inflammation and delayed wound healing in diabetes is urgently required. Emerging evidence indicates that timely resolution of inflammation is mediated in part by endogenous proresolving lipid mediators, such as resolvins. Here, we review recent advances in the area of resolution and diabetes and highlight the potential of novel proresolving strategies for promoting wound healing in diabetes.

RECENT FINDINGS

Macrophage dysfunction is a critical underlying feature of altered wound healing in diabetic patients. This is associated with defective clearance of apoptotic cells, increased risk of infection, and altered angiogenesis. Diabetes and obesity are associated with chronic inflammation and altered biosynthesis of bioactive lipid mediators that promote the resolution of inflammation. Stimulating resolution with proresolving lipid mediators improves metabolic parameters in diabetes, blunts systemic inflammation, restores defective macrophage phagocytosis, and accelerates wound healing in animal models of obesity and diabetes.

SUMMARY

Stimulating resolution with proresolving lipid mediators may represent a novel strategy for promoting wound healing in diabetes.

Cysteinyl leukotrienes regulate TGF-β(1) and collagen production by bronchial fibroblasts obtained from asthmatic subjects

BACKGROUND

Cysteinyl leukotrienes (CysLTs) play an important role in airway inflammation in asthma but their role in airway remodeling is not completely known.

METHODS

CysLTs receptors and procollagen I(α(1)) mRNA were determined by qPCR. Procollagen protein production was measured by RIA and TGF-β(1) expression was determined by ELISA. TGF-β receptor expression was assessed by western blots.

RESULTS

CysLT1R, TGF-β-R1 and active TGF-β(1) are highly expressed in cells from asthmatics compared to normal controls. LTD(4) increased significantly procollagen I(α(1)) mRNA and protein expression in fibroblasts from asthmatics. This increase was blocked by CysLTs receptor antagonist. LTD(4) increased significantly mRNA expression of TGF-β(1) and active form production in fibroblasts from asthmatics. Inhibition of TGF-β(1) signaling blocked LTD(4)-induced procollagen I(α(1)) expression.

CONCLUSIONS

Fibroblasts from asthmatic subjects express high level of CysLT1R. LTD(4) regulates procollagen I(α(1)) transcription in fibroblasts derived from asthmatic patients by modulating TGF-β(1) expression. This suggests that CysLTs may play a role in regulating collagen deposition in asthma.

Inhibition of renin release by arachidonic acid metabolites, 12(s)-HPETE and 12-HETE: role of TRPV1 channels

We test the hypothesis that 12-hydroperoxyeicosatetraenoic acid (12(s)-HPETE) and 12-hydroxyeicosatetraenoic acid (12-HETE) perfused into the renal pelvis increase afferent renal nerve activity (ARNA) and suppress renin release in rats fed a low-salt (LS) diet via activation of the transient receptor potential vanilloid type 1 (TRPV1) expressed in renal sensory nerves. 12(s)-HPETE or 12-HETE given into the left renal pelvis dose-dependently increased ARNA, which was abolished by AMG9810, a selective TRPV1 antagonist, or by RP67580, a selective neurokinin 1 receptor antagonist, in normal salt or LS-treated rats. 12(s)-HPETE, 12-HETE, or substance P perfused into the left renal pelvis suppressed plasma angiotensin I (Ang I) levels in LS rats, which was abolished by AMG9810 or attenuated by ipsilateral renal denervation (RD). 12(s)-HPETE or 12-HETE increased release of substance P and calcitonin gene-related peptide from the ipsilateral kidney, which was abolished by AMG9810 but not RP67580, RD, or RP67580 plus RD. Immunofluorescence staining showed that TRPV1-positive nerve fibers located in the renal cortex, medulla, and pelvis, and that the sympathetic nerve marker, neuropeptide Y, but not neurokinin 1 receptors expressed in the juxtaglomerular region colocalized with renin. Thus, our data show that 12(s)-HPETE and 12-HETE enhance ARNA and substance P/calcitonin gene-related peptide release but suppress renin activity in LS rats, and these effects are abolished when TRPV1 is blocked. These results indicate that TRPV1 mediates 12(s)-HPETE and 12-HETE action in the kidney in such a way that dysfunction in TRPV1 may lead to disintegrated regulation of renin and renal function.

Cysteinyl leukotrienes impair hypoxic pulmonary vasoconstriction in endotoxemic mice

BACKGROUND

Sepsis impairs hypoxic pulmonary vasoconstriction (HPV) in patients and animal models, contributing to systemic hypoxemia. Concentrations of cysteinyl leukotrienes are increased in the bronchoalveolar lavage fluid of patients with sepsis, but the contribution of cysteinyl leukotrienes to the impairment of HPV is unknown.

METHODS

Wild-type mice, mice deficient in leukotriene C(4) synthase, the enzyme responsible for cysteinyl leukotriene synthesis, and mice deficient in cysteinyl leukotriene receptor 1 were studied 18 h after challenge with either saline or endotoxin. HPV was measured by the increase in left pulmonary vascular resistance induced by left mainstem bronchus occlusion. Concentrations of cysteinyl leukotrienes were determined in the bronchoalveolar lavage fluid.

RESULTS

In the bronchoalveolar lavage fluid of all three strains, cysteinyl leukotrienes were not detectable after saline challenge; whereas endotoxin challenge increased cysteinyl leukotriene concentrations in wild-type mice and mice deficient in cysteinyl leukotriene receptor 1, but not in mice deficient in leukotriene C(4) synthase. HPV did not differ among the three mouse strains after saline challenge (120 ± 26, 114 ± 16, and 115 ± 24%, respectively; mean ± SD). Endotoxin challenge markedly impaired HPV in wild-type mice (41 ± 20%) but only marginally in mice deficient in leukotriene C(4) synthase (96 ± 16%, P < 0.05 vs. wild-type mice), thereby preserving systemic oxygenation. Although endotoxin modestly decreased HPV in mice deficient in cysteinyl leukotriene receptor 1 (80 ± 29%, P < 0.05 vs. saline challenge), the magnitude of impairment was markedly less than in endotoxin-challenged wild-type mice.

CONCLUSION

Cysteinyl leukotrienes importantly contribute to endotoxin-induced impairment of HPV in part via a cysteinyl leukotriene receptor 1-dependent mechanism.

Control of experimental pulmonary tuberculosis depends more on immunostimulatory leukotrienes than on the absence of immunosuppressive prostaglandins

Prostaglandins (PGs) and leukotrienes (LTs) are produced in Mycobacterium tuberculosis (Mtb)-infected lungs and have immune suppressive and protective effects, respectively. Considering that both of these mediators are produced during mycobacterial infection, we investigated the specific and relative biological importance of each in regulating host response in experimental tuberculosis. Administration of celecoxib, which was found to reduce lung levels of PGE(2) and increase LTB(4), enhanced the 60-day survival of Mtb-infected mice in 14%. However administration of MK-886, which reduced levels of LTB(4) but did not enhance PGE(2), reduced 60-day survival from 86% to 43% in Mtb-infected mice, and increased lung bacterial burden. MK-886 plus celecoxib reduced survival to a lesser extent than MK-886 alone. MK-886- and MK-886 plus celecoxib-treated animals exhibited reduced levels of the protective interleukin-12 and gamma-interferon. Our findings indicate that in this model, the protective effect of LTs dominates over the suppressive effect of PGs.

High extracellular Ca2+ stimulates Ca2+-activated Cl- currents in frog parathyroid cells through the mediation of arachidonic acid cascade

Elevation of extracellular Ca(2+) concentration induces intracellular Ca(2+) signaling in parathyroid cells. The response is due to stimulation of the phospholipase C/Ca(2+) pathways, but the direct mechanism responsible for the rise of intracellular Ca(2+) concentration has remained elusive. Here, we describe the electrophysiological property associated with intracellular Ca(2+) signaling in frog parathyroid cells and show that Ca(2+)-activated Cl(-) channels are activated by intracellular Ca(2+) increase through an inositol 1,4,5-trisphophate (IP(3))-independent pathway. High extracellular Ca(2+) induced an outwardly-rectifying conductance in a dose-dependent manner (EC(50) ∼6 mM). The conductance was composed of an instantaneous time-independent component and a slowly activating time-dependent component and displayed a deactivating inward tail current. Extracellular Ca(2+)-induced and Ca(2+) dialysis-induced currents reversed at the equilibrium potential of Cl(-) and were inhibited by niflumic acid (a specific blocker of Ca(2+)-activated Cl(-) channel). Gramicidin-perforated whole-cell recording displayed the shift of the reversal potential in extracellular Ca(2+)-induced current, suggesting the change of intracellular Cl(-) concentration in a few minutes. Extracellular Ca(2+)-induced currents displayed a moderate dependency on guanosine triphosphate (GTP). All blockers for phospholipase C, diacylglycerol (DAG) lipase, monoacylglycerol (MAG) lipase and lipoxygenase inhibited extracellular Ca(2+)-induced current. IP(3) dialysis failed to induce conductance increase, but 2-arachidonoylglycerol (2-AG), arachidonic acid and 12S-hydroperoxy-5Z,8Z,10E,14Z-eicosatetraenoic acid (12(S)-HPETE) dialysis increased the conductance identical to extracellular Ca(2+)-induced conductance. These results indicate that high extracellular Ca(2+) raises intracellular Ca(2+) concentration through the DAG lipase/lipoxygenase pathway, resulting in the activation of Cl(-) conductance.

Fatty acid-derived lipid mediators and blood platelet aggregation

Polyunsaturated fatty acids of nutritional value may affect cell functions after their release from cell lipid storage sites, especially phospholipids, and specific oxygenation by cyclooxygenases, lipoxygenases and cytochrome P(450). The end-products, namely prostanoids, leukotrienes, and mono-, di- and tri-hydroxy derivatives exhibit a variety of biological effects, especially on vascular cells, leukocytes and platelets. This paper reviews some results obtained with blood platelets as target cells, showing that various lipoxygenase end-products, mainly mono- and di-hydroxy derivatives, are inhibitors (IC(50) in microM range) of arachidonic acid-induced aggregation either at the cycloxygenase or thromboxane receptor site level.

Interactions between CB(1) receptors and TRPV1 channels mediated by 12-HPETE are cytotoxic to mesencephalic dopaminergic neurons

BACKGROUND AND PURPOSES

We recently proposed the existence of neurotoxic interactions between the cannabinoid type 1 (CB(1)) receptor and transient receptor potential vanilloid 1 (TRPV1) channels in rat mesencephalic cultures. This study seeks evidence for the mediator(s) and mechanisms underlying the neurotoxic interactions between CB(1) receptors and TRPV1 in vitro and in vivo.

EXPERIMENTAL APPROACH

The mediator(s) and mechanism(s) for the interactions between CB(1) receptors and TRPV1 were evaluated by cell viability assays, immunocytochemistry, Fura-2 calcium imaging, mitochondrial morphology assay, ELISA and Western blot assay in vitro in neuron-enriched mesencephalic cultures. Injections into the substantia nigra and subsequent cell counts were also used to confirm these interactions in vivo.

KEY RESULTS

The neurotoxic interactions were mediated by 12(S)-hydroperoxyeicosatetraenoic acid (12(S)-HPETE), an endogenous TRPV1 agonist. CB(1) receptor agonists (HU210 and WIN55,212-2) increased the level of 12(S)-hydroxyeicosatetraenoic acid (12(S)-HETE), a downstream metabolite of 12(S)-HPETE, which stimulates TRPV1-mediated death of mesencephalic neurons, both in vitro and in vivo. The neurotoxicity was mediated by increased intracellular Ca(2+) concentration ([Ca(2+)](i)) through TRPV1, consequently leading to mitochondrial damage and was attenuated by baicalein, a 12-lipoxygenase inhibitor.

CONCLUSION AND IMPLICATIONS

Activation of CB(1) receptors in rat mesencephalic neurons was associated with biosynthesis of 12(S)-HPETE, which in turn stimulated TRPV1 activity, leading to increased [Ca(2+)](i), mitochondrial damage and neuronal death.

Selenium inhibits 15-hydroperoxyoctadecadienoic acid-induced intracellular adhesion molecule expression in aortic endothelial cells

Increased intracellular adhesion molecule 1 (ICAM-1) expression and enhanced monocyte recruitment to the endothelium are critical steps in the early development of atherosclerosis. The 15-lipoxygenase 1 (15-LOX1) pathway can generate several proinflammatory eicosanoids that are known to enhance ICAM-1 expression within the vascular endothelium. Oxidative stress can exacerbate endothelial cell inflammatory responses by modifying arachidonic acid metabolism through the 15-LOX1 pathway. Because selenium (Se) influences the oxidant status of cells and can modify the expression of eicosanoids, we investigated the role of this micronutrient in modifying ICAM-1 expression as a consequence of enhanced 15-LOX1 activity. Se supplementation reduced ICAM-1 expression in bovine aortic endothelial cells, an effect that was reversed with 15-LOX1 overexpression or treatment with exogenous 15-hydroperoxyoctadecadienoic acid (15-HPETE). ICAM-1 expression increased proportionately when intracellular15-HPETE levels were allowed to accumulate. However, changes in intracellular 15-HETE levels did not seem to affect ICAM-1 expression regardless of Se status. Our results indicate that Se supplementation can reduce 15-HPETE-induced expression of ICAM-1 by controlling the intracellular accumulation of this fatty acid hydroperoxide in endothelial cells.

Cysteinyl leukotrienes enhance tumour necrosis factor-alpha-induced matrix metalloproteinase-9 in human monocytes/macrophages

BACKGROUND

Matrix metalloproteinase-9 (MMP-9) is an important enzyme responsible for airway remodelling. Monocytes/macrophages have a cysteinyl leukotriene 1 (cysLT1) receptor, but its function is poorly understood.

OBJECTIVE

To elucidate the function of the cysLT1 receptor of human monocytes/macrophages in MMP-9 production.

METHODS

We examined the effect of cysLTs (LTC4, -D4 and -E4) on TNF-alpha-induced MMP-9 production in THP-1 cells, a human monocytic leukaemia cell line and peripheral blood CD14+ monocytes/macrophages. In addition, we examined the effect of pranlukast, a cysLT1 receptor antagonist, on the enhancement of TNF-alpha-induced MMP-9 production by cysLTs.

RESULTS

ELISA revealed that LTC4 and -D4, but not -E4, enhanced TNF-alpha-induced MMP-9 production in THP-1 cells and peripheral blood CD14+ monocytes/macrophages. Real-time polymerase chain reaction demonstrated that LTC4 and -D4, but not -E4, increased MMP-9 mRNA expression induced by TNF-alpha in THP-1 cells. Moreover, we demonstrated that pranlukast completely inhibited the enhancement of TNF-alpha-induced MMP-9 production by LTC4 and -D4 in THP-1 cells and peripheral blood CD14+ monocytes/macrophages.

CONCLUSION

LTC4 and -D4 enhanced the TNF-alpha-induced MMP-9 production via binding the cysLT1 receptor in human monocytes/macrophages. Pranlukast inhibited the enhancements by LTC4 and D4.

Establishment of a progesterone-sensitive cell line from human lung cancer

For deveplopment and function of the lung, progesterone (Prog) fulfils important roles. In a recent report, immunolocalization of Prog and estrogen receptors in non-small cell lung carcinomas were examined and it was shown that the Prog receptor might be a potent prognostic factor. In the present study, a cell line with the sensitivity to Prog was established from a human lung cancer and the growth mechanism was analyzed. The proliferation of established SN96-42 cells was sensitive to Prog and antiprogesterone RU38486 inhibited their proliferation stimulated by Prog. Exposure of these cells to Prog resulted in a decreased formation of leukotriene (LT). The 5-lipoxygenase inhibitor (5-LOX), AA861, effectively stimulated SN96-42 cell proliferation and 5-LOX-catalyzed product(s), especially LTC4, inhibited SN96-42 cell proliferation caused by Prog. Prog-sensitive enhancement of SN96-42 cell proliferation is at least partly mediated through an inhibition of LT formation and these data suggest that 5-LOX and LTs play important roles in SN96-42 cell proliferation stimulated by Prog.

CysLT2 receptors interact with CysLT1 receptors and down-modulate cysteinyl leukotriene dependent mitogenic responses of mast cells

Cysteinyl leukotrienes (cys-LTs) induce inflammation through 2 G protein-coupled receptors (GPCRs), CysLT(1) and CysLT(2), which are coexpressed by most myeloid cells. Cys-LTs induce proliferation of mast cells (MCs), transactivate c-Kit, and phosphorylate extracellular signal-regulated kinase (ERK). Although MCs express CysLT(2), their responses to cys-LTs are blocked by antagonists of CysLT(1). We demonstrate that CysLT(2) interacts with CysLT(1), and that knockdown of CysLT(2) increases CysLT(1) surface expression and CysLT(1)-dependent proliferation of cord blood-derived human MCs (hMCs). Cys-LT-mediated responses were absent in MCs from mice lacking CysLT(1) receptors, but enhanced by the absence of CysLT(2) receptors. CysLT(1) and CysLT(2) receptors colocalized to the plasma membranes and nuclei of a human MC line, LAD2. Antibody-based fluorescent lifetime imaging microscopy confirmed complexes containing both receptors based on fluorescence energy transfer. Negative regulation of CysLT(1)-induced mitogenic signaling responses of MCs by CysLT(2) demonstrates physiologically relevant functions for GPCR heterodimers on primary cells central to inflammation.

IFN-gamma induces cysteinyl leukotriene receptor 2 expression and enhances the responsiveness of human endothelial cells to cysteinyl leukotrienes

Cysteinyl leukotrienes (cysLTs) are important mediators of cell trafficking and innate immune responses, involved in the pathogenesis of inflammatory processes, i.e., atherosclerosis, pulmonary fibrosis, and bronchial asthma. The aim of this study was to examine the regulation of cysLT signaling by IFN-gamma in human primary endothelial cells. IFN-gamma increased cysLT receptor 2 (CysLTR2) mRNA expression and CysLTR2-specific calcium signaling in endothelial cells. IFN-gamma signaled through Jak/STAT1, as both AG490, a Jak2 inhibitor, and expression of a STAT1 dominant-negative construct, significantly inhibited CysLTR2 mRNA expression in response to IFN-gamma. To determine mechanisms of IFN-gamma-induced CysLTR2 expression, the human CysLTR2 gene structure was characterized. The CysLTR2 gene has a TATA-less promoter, with multiple transcription start sites. It consists of six variably spliced exons. Eight different CysLTR2 transcripts were identified in endothelial and monocytic cells. Gene reporter assay showed potent basal promoter activity of a putative CysLTR2 promoter region. However, there were no significant changes in gene reporter and mRNA t(1/2) assays in response to IFN-gamma, suggesting transcriptional control of CysLTR2 mRNA up-regulation by IFN-gamma response motifs localized outside of the cloned CysLTR2 promoter region. Stimulation of endothelial cells by cysLTs induced mRNA and protein expression of early growth response genes 1, 2, and 3 and cycloxygenase-2. This response was mediated by CysLTR2 coupled to G(q/11), activation of phospholipase C, and inositol-1,4,5-triphosphate, and was enhanced further 2- to 5-fold by IFN-gamma stimulation. Thus, IFN-gamma induces CysLTR2 expression and enhances cysLT-induced inflammatory responses.

Effect of 15-lipoxygenase metabolites, 15-(S)-HPETE and 15-(S)-HETE on chronic myelogenous leukemia cell line K-562: reactive oxygen species (ROS) mediate caspase-dependent apoptosis

Growth inhibitory effects of 15-lipoxygenase-1 [13-(S)-HPODE and 13-(S)-HODE] and 15-lipoxygenase-2 [15-(S)-HPETE and 15-(S)-HETE] (15-LOX-1 and LOX-2) metabolites and the underlying mechanisms were studied on chronic myeloid leukemia cell line (K-562). The hydroperoxy metabolites, 15-(S)-HPETE and 13-(S)-HPODE rapidly inhibited the growth of K-562 cells by 3h with IC(50) values, 10 and 15microM, respectively. In contrast, the hydroxy metabolite of 15-LOX-2, 15-(S)-HETE, showed 50% inhibition only at 40microM by 6h and 13-(S)-HODE, hydroxy metabolite of 15-LOX-1, showed no significant effect up to 160microM. The cells exposed to 10microM of 15-(S)-HPETE and 40microM of 15-(S)-HETE showed typical apoptotic features like release of cytochrome c, caspase-3 activation and PARP-1 (poly(ADP) ribose polymerase-1) cleavage. A flow cytometry based DCFH-DA analysis and inhibitory studies with DPI, a pharmacological inhibitor of NADPH oxidase, NAC (N-acetyl cysteine) and GSH revealed that NADPH oxidase-mediated generation of ROS is responsible for caspase-3 activation and subsequent induction of apoptosis in the K-562 cell line.

12(S)-HPETE induces itch-associated scratchings in mice

The itch-associated responses evoked by intradermal injection of 12(S)-HPETE and leukotriene B4 were compared in ICR-mice. 12(S)-HPETE and leukotriene B4 (0.01-0.2 nmol/site) induced scratching of the injected site, respectively; the dose-responses were a peak at 0.05 nmol/site (12(S)-HPETE) or 0.03 nmol/site (leukotriene B4). The scratching response by 12(S)-HPETE (0.05 nmol/site) started within 1 min, peaked in the first 10 min period, had almost subsided by 25 min whereas the effect of leukotriene B4 peaked in the second 10 min. The effect of leukotriene B4 is slightly stronger than that of 12(S)-HPETE in 40 min of count. The scratching induced by 12(S)-HPETE was inhibited by capsaicin, naltrexon, and LY255283. These results suggest the possibility that 12-lipoxygenase product can be added to a new member of an endogenous itch mediator in the skin.

Nonsteroidal anti-inflammatory drugs: cyclooxygenase 2 inhibitors

OBJECTIVES

To analyze selective COX 2 inhibitor nonsteroidal anti-inflammatory drugs (NSAID) in terms of their mechanism of action, principal indications, posology and most common adverse effects.

SOURCES

MEDLINE and LILACS databases and Food and Drug Administration (FDA) and National Agency for Sanitary Vigilance (ANVISA - Agência Nacional de Vigilância Sanitária) websites. The most important articles were selected and preference was given to articles published within the last 5 years.

SUMMARY OF THE FINDINGS

The principal indications for NSAID are for control of pain and acute and chronic inflammation. There is no overwhelming evidence that demonstrates the superiority of one NSAID over another in terms of effectiveness. To date none of the COX 2 inhibitors has been liberated for use in the pediatric age group. Only meloxicam and etoricoxib can be prescribed for adolescents (13 and 16 years, respectively). Selective COX 2 inhibitors are indicated for patients with adverse effects that have proven to be associated with nonselective NSAID use. Selective COX 2 inhibitors can be prescribed in some cases of allergy to aspirin, but they must be used with care. Principal adverse effects include cardiovascular events and thrombotic phenomena.

CONCLUSIONS

Selective COX 2 inhibitors are medicines that have been used in certain well-defined clinical situations and which may offer certain advantages over nonselective NSAID. Nevertheless, taking into consideration the higher cost involved and the potential for adverse cardiovascular effects, they should be employed only in accordance with strict criteria.

Leukotrienes are essential for the control of Leishmania amazonensis infection and contribute to strain variation in susceptibility

Leukotrienes (LTs) are known to be produced by macrophages when challenged with Leishmania, but it is not known whether these lipid mediators play a role in host defense against this important protozoan parasite. In this study, we investigated the involvement of LTs in the in vitro and in vivo response to Leishmania amazonensis infection in susceptible (BALB/c) and resistant (C3H/HePAS) mice. Pharmacologic or genetic deficiency of LTs resulted in impaired leishmanicidal activity of peritoneal macrophages in vitro. In contrast, addition of LTB4 increased leishmanicidal activity and this effect was dependent on the BLT1 receptor. LTB4 augmented NO production in response to L. amazonensis challenge, and studies with a NO synthesis inhibitor revealed that NO was critical for the enhancement of macrophage leishmanicidal activity. Interestingly, macrophages from resistant mice produced higher levels of LTB4 upon L. amazonensis challenge than did those from susceptible mice. In vivo infection severity, as assessed by footpad swelling following s.c. promastigote inoculation, was increased when endogenous LT synthesis was abrogated either pharmacologically or genetically. Taken together, these results for the first time reveal an important role for LTB4 in the protective response to L. amazonensis, identify relevant leishmanicidal mechanisms, and suggest that genetic variation in LTB4 synthesis might influence resistance and susceptibility patterns to infection.