Dapsone Suppresses Disease in Preclinical Murine Models of Pemphigoid Diseases.

Epidermolysis bullosa acquisita and mucous membrane pemphigoid are autoimmune blistering diseases characterized by mucocutaneous blisters elicited by an autoantibody-mediated immune response against specific proteins of the epidermal basement membrane. The antibiotic dapsone is frequently used to treat both diseases, but its therapeutic effectiveness is uncertain, and its mode of action in these diseases is largely unknown. We evaluated the effect of dapsone in antibody transfer mouse models of epidermolysis bullosa acquisita and mucous membrane pemphigoid, which do not allow the drawing of conclusions on clinical treatment regimens but can be instrumental to partially uncover the mode(s) of action of dapsone in these diseases. Dapsone significantly mitigated inflammation in both models, reducing the recruitment of neutrophils into the skin and disrupting their release of leukotriene B4 (LTB4) and ROS in response to immune complexes. LTB4 has been implicated in numerous diseases, but effective LTB4 inhibitors for clinical use are not available. Our findings indicate that the mode of action of dapsone in these models may be based on the inhibition of LTB4 and ROS release from neutrophils. Moreover, they encourage testing the use of dapsone as an effective, albeit nonspecific, inhibitor of LTB4 biosynthesis in other LTB4-driven diseases.

Calcium-dependent cytosolic phospholipase A2 activation is implicated in neuroinflammation and oxidative stress associated with ApoE4.

BACKGROUND: Apolipoprotein E4 (APOE4) is associated with a greater response to neuroinflammation and the risk of developing late-onset Alzheimer's disease (AD), but the mechanisms for this association are not clear. The activation of calcium-dependent cytosolic phospholipase A2 (cPLA2) is involved in inflammatory signaling and is elevated within the plaques of AD brains. The relation between APOE4 genotype and cPLA2 activity is not known. METHODS: Mouse primary astrocytes, mouse and human brain samples differing by APOE genotypes were collected for measuring cPLA2 expression, phosphorylation, and activity in relation to measures of inflammation and oxidative stress. RESULTS: Greater cPLA2 phosphorylation, cPLA2 activity and leukotriene B4 (LTB4) levels were identified in ApoE4 compared to ApoE3 in primary astrocytes, brains of ApoE-targeted replacement (ApoE-TR) mice, and in human brain homogenates from the inferior frontal cortex of patients with AD carrying APOE3/E4 compared to APOE3/E3. Greater cPLA2 phosphorylation was also observed in human postmortem frontal cortical synaptosomes and primary astrocytes after treatment with recombinant ApoE4 ex vivo. In ApoE4 astrocytes, the greater levels of LTB4, reactive oxygen species (ROS), and inducible nitric oxide synthase (iNOS) were reduced after cPLA2 inhibition. CONCLUSIONS: Our findings implicate greater activation of cPLA2 signaling system with APOE4, which could represent a potential drug target for mitigating the increased neuroinflammation with APOE4 and AD.

Synthesis and structure-activity relationships of novel 5-(hydroxamic acid)methyl oxazolidinone derivatives as 5-lipoxygenase inhibitors.

Oxazolidinone hydroxamic acid derivatives were synthesised and evaluated for inhibitory activity against leukotriene (LT) biosynthesis in three in vitro cell-based test systems and on direct inhibition of recombinant human 5-lipoxygenase (5-LO). Thirteen of the 19 compounds synthesised were considered active ((50% inhibitory concentration (IC50) ≤ 10 µM in two or more test systems)). Increasing alkyl chain length on the hydroxamic acid moiety enhanced activity and morpholinyl-containing derivatives were more active than N-acetyl-piperizinyl derivatives. The IC50 values in cell-based assay systems were comparable to those obtained by direct inhibition of 5-LO activity, confirming that the compounds are direct inhibitors of 5-LO. Particularly, compounds PH-249 and PH-251 had outstanding potencies (IC50 < 1 µM), comparable to that of the prototype 5-LO inhibitor, zileuton. Pronounced in vivo activity was demonstrated in zymosan-induced peritonitis in mice. These novel oxazolidinone hydroxamic acid derivatives are, therefore, potent 5-LO inhibitors with potential application as anti-allergic and anti-inflammatory agents.

Design and synthesis of Leukotriene A4 hydrolase inhibitors to alleviate idiopathic pulmonary fibrosis and acute lung injury.

Idiopathic pulmonary fibrosis (IPF) and acute lung injury (ALI) are considered two severe public health issues, attributed to malfunctions of neutrophils. They can cause chronic inflammation and have association with subsequent tissue damages. There have been rare drugs applying to the efficient treatment in clinical practice. Existing research revealed that Leukotriene B4 (LTB4) is the critical endogenous molecule to induce neutrophil inflammatory response. LTB4 blocking biosynthesis is the potential strategy treating IPF and ALI. In the present study, 45 hydroxamic acid derivatives were produced, and compound 26 was screened out as a highly selective Lead compound of Leukotriene A4 Hydrolase (LTA4H), i.e., an enzyme critical to the biosynthesis of LTB4. This compound is capable of relieving neutrophilic inflammation in an IPF mouse model at early stage, as well as mitigating LPS-induced acute lung injury via a mechanism of LTB4 blocking biosynthesis in vivo. Whether this compound acts as the potential lead compound for the treatment of IPF and ALI requires further verification.

HMGB1-C1q complexes regulate macrophage function by switching between leukotriene and specialized proresolving mediator biosynthesis.

Macrophage polarization is critical to inflammation and resolution of inflammation. We previously showed that high-mobility group box 1 (HMGB1) can engage receptor for advanced glycation end product (RAGE) to direct monocytes to a proinflammatory phenotype characterized by production of type 1 IFN and proinflammatory cytokines. In contrast, HMGB1 plus C1q form a tetramolecular complex cross-linking RAGE and LAIR-1 and directing monocytes to an antiinflammatory phenotype. Lipid mediators, as well as cytokines, help establish a milieu favoring either inflammation or resolution of inflammation. This study focuses on the induction of lipid mediators by HMGB1 and HMGB1 plus C1q and their regulation of IRF5, a transcription factor critical for the induction and maintenance of proinflammatory macrophages. Here, we show that HMGB1 induces leukotriene production through a RAGE-dependent pathway, while HMGB1 plus C1q induces specialized proresolving lipid mediators lipoxin A4, resolvin D1, and resolvin D2 through a RAGE- and LAIR-1-dependent pathway. Leukotriene exposure contributes to induction of IRF5 in a positive-feedback loop. In contrast, resolvins (at 20 nM) block IRF5 induction and prevent the differentiation of inflammatory macrophages. Finally, we have generated a molecular mimic of HMGB1 plus C1q, which cross-links RAGE and LAIR-1 and polarizes monocytes to an antiinflammatory phenotype. These findings may provide a mechanism to control nonresolving inflammation in many pathologic conditions.

Dietary coconut oil ameliorates skin contact hypersensitivity through mead acid production in mice.

Coconut oil is used as a dietary oil worldwide, and its healthy effects are recognized by the fact that coconut oil is easy to digest, helps in weight management, increases healthy cholesterol, and provides instant energy. Although topical application of coconut oil is known to reduce skin infection and inflammation, whether dietary coconut oil has any role in decreasing skin inflammation is unknown. In this study, we showed the impact of dietary coconut oil in allergic skin inflammation by using a mouse model of contact hypersensitivity (CHS). Mice maintained on coconut oil showed amelioration of skin inflammation and increased levels of cis-5, 8, 11-eicosatrienoic acid (mead acid) in serum. Intraperitoneal injection of mead acid inhibited CHS and reduced the number of neutrophils infiltrating to the skin. Detailed mechanistic studies unveiled that mead acid inhibited the directional migration of neutrophils by inhibiting the filamentous actin polymerization and leukotriene B4 production required for secondary recruitment of neutrophils. Our findings provide valuable insights into the preventive roles of coconut oil and mead acid against skin inflammation, thereby offering attractive therapeutic possibilities.

Leukotriene A4 Hydrolase Activation and Leukotriene B4 Production by Eosinophils in Severe Asthma.

Asthma is associated with the overproduction of leukotrienes (LTs), including LTB4. Patients with severe asthma can be highly responsive to 5-lipoxygenase (5-LO) inhibition, which blocks production of both the cysteinyl LTs and LTB4. Production of LTB4 has traditionally been ascribed to neutrophils, mononuclear phagocytes, and epithelial cells, and acts as a chemoattractant for inflammatory cells associated with asthma. The source of LTB4 is unclear, especially in eosinophilic asthma. We speculated that the benefit of 5-LO inhibition could be mediated in part by inhibition of eosinophil-derived LTB4. LTB4 concentrations were assayed in BAL fluid from patients with severe asthma characterized by isolated neutrophilic, eosinophilic, and paucigranulocytic inflammation. Expression of LTA4 hydrolase (LTA4H) by airway eosinophils was determined by immunohistochemistry (IHC). Subsequently, peripheral blood eosinophils were activated and secreted LTB4 was quantified by enzyme immunoassay. Blood eosinophil LTA4H expression was determined by flow cytometry, qPCR, and IHC. LTB4 concentrations were elevated in BAL fluid from patients with severe asthma, including those with isolated eosinophilic inflammation, and these eosinophils displayed LTA4H via IHC. LTA4H expression by blood eosinophils was confirmed by flow cytometry, IHC, and qPCR. Robust LTB4 production by blood eosinophils was observed in response to some, but not all, stimuli. We demonstrated that eosinophils express LTA4H transcripts and protein, and can be stimulated to secrete LTB4. We speculate that in many patients with asthma, eosinophil-derived LTB4 is increased, and this may contribute to the efficacy of 5-LO inhibition.

5-lipoxygenase-dependent biosynthesis of novel 20:4 n-3 metabolites with anti-inflammatory activity.

5-lipoxygenase (5-LO) catalyzes the conversion of arachidonic acid (AA) into pro-inflammatory leukotrienes. N-3 PUFA like eicosapentaenoic acid are subject to a similar metabolism and are precursors of pro-resolving mediators. Stearidonic acid (18:4 n-3, SDA) is a plant source of n-3 PUFA that is elongated to 20:4 n-3, an analogue of AA. However, no 5-LO metabolites of 20:4 n-3 have been reported. In this study, control and 5-LO-expressing HEK293 cells were stimulated in the presence of 20:4 n-3. Metabolites were characterized by LC-MS/MS and their anti-inflammatory properties assessed using AA-induced autocrine neutrophil stimulation and leukotriene B4-mediated chemotaxis. 8­hydroxy­9,11,14,17-eicosatetraenoic acid (Δ17-8-HETE) and 8,15-dihydroxy-9,11,13,17-eicosatetraenoic acid (Δ17-8,15-diHETE) were identified as novel metabolites. Δ17-8,15-diHETE production was inhibited by the leukotriene A4 hydrolase inhibitor SC 57461A. Autocrine neutrophil leukotriene stimulation and neutrophil chemotaxis, both BLT1-dependent processes, were inhibited by Δ17-8,15-diHETE at low nM concentrations. These data support an anti-inflammatory role for Δ17-8,15-diHETE, a novel 5-LO product.

Occurrence of azo food dyes and their effects on cellular inflammatory responses.

OBJECTIVES: The aim of this study was to examine the occurrence of five azo food dyes-tartrazine, sunset yellow, carmoisine, allura red, and ponceau 4 R-in the food supply chain of Singapore and their effects on the in vitro synthesis of leukotriene B4 (LTB4) and F2-isoprostanes. METHODS: Trained personnel recorded the names of foods and beverages sold in a local supermarket that contained at least one of the five azo dyes. The occurrence of the azo dyes in the local food supply was computed. The synthesis of LTB4 and F2-isoprostanes from freshly isolated blood neutrophils were measured using gas chromatography-mass spectrometry. RESULTS: Of the 1681 processed food items, 194 (11.54%) contained at least one of the five azo dyes. Tartrazine was most prevalent in food and beverage products sold in Singapore, followed by allura red, sunset yellow, ponceau 4 R, and carmoisine. The five azo dyes augmented the in vitro synthesis of LTB4 and F2-isoprostanes from blood neutrophils. Tartrazine was significantly more potent in increasing LTB4 synthesis than the other dyes, which exhibited similar potencies. The five food dyes increased the formation of F2-isoprostanes from blood neutrophils at all tested concentrations. CONCLUSION: The high prevalence of azo dyes in the food supply of Singapore and their ability to elicit proinflammatory responses in vitro suggest a potential health risk to the local population.

Early Production of the Neutrophil-Derived Lipid Mediators LTB4 and LXA4 Is Modulated by Intracellular Infection with Leishmania major.

Recruitment of neutrophil granulocytes to sites of infectious tissue damage is an early event in innate immune responses. Following chemotactic signals neutrophils establish a first line of defense in a swarm-like manner. Intracellular pathogens such as Leishmania major can, however, evade neutrophil-mediated killing and survive inside neutrophils. To achieve this the parasites evolved potent evasion mechanisms. Since neutrophils are a major source of inflammation regulating lipid mediators, we hypothesized that intracellular infection modifies the release of pro- and anti-inflammatory lipid mediators like leukotriene B4 (LTB4) and lipoxin A4 (LXA4), respectively. In the present study, we demonstrated in vitro that L. major-infected primary human neutrophils release an increased amount of LTB4, whereas LXA4 liberation is reduced during the first hours of infection. To investigate whether lipid mediator modulation is a common feature in intracellular infections, we tested the impact of an infection with Anaplasma phagocytophilum. Similarly to L. major, neutrophil infection with A. phagocytophilum led to an enhanced release of LTB4 and decreased LXA4 production. Together, our findings indicate that intracellular infections modulate the lipid mediator profile of neutrophils. This effect is likely to contribute to the survival of the pathogens in neutrophils and to the outcome of the infections.

Stereocontrolled synthesis and investigation of the biosynthetic transformations of 16(S),17(S)-epoxy-PDn-3 DPA.

PD1n-3 DPA is a specialized pro-resolving lipid mediator that displays potent anti-inflammatory properties and pro-resolving bioactivities. Such naturally occurring compounds are of current interest in biomolecular chemistry and drug discovery. To investigate the involvement of an epoxide intermediate in the biosynthesis of PD1n-3 DPA from n-3 docosapentaenoic acid, the epoxy acid 16(S),17(S)-epoxy-PDn-3 DPA, herein named ePDn-3 DPA, was prepared by stereoselective total synthesis. The synthetic material of ePDn-3 DPA allowed investigations of its role in the biosynthesis of PD1n-3 DPA. The obtained results establish that the biosynthesis of PD1n-3 DPA in neutrophils occurs with ePDn-3 DPA as the intermediate, and that 15-LOX produces ePDn-3 DPA from n-3 docosapentaenoic acid. Furthermore, support for the involvement of a hydrolytic enzyme in the biosynthetic conversion of ePDn-3 DPA to PD1n-3 DPA was found. In addition, ePDn-3 DPA was found to regulate the formation of the potent neutrophil chemoattractant LTB4 with equal potencies to that obtained with PD1n-3 DPA.

Biosynthesis of leukotriene B4.

Leukotriene B4 (LTB4) is a lipid mediator derived from arachidonic acid (AA) by the sequential action of 5-lipoxygenase (5-LOX), 5-lipoxygenase-activating protein (FLAP) and LTA4 hydrolase (LTA4H). It was initially recognized for its involvement in the recruitment of neutrophils and is one of the most potent chemotactic agents known to date. A large body of data has indicated that LTB4 plays a significant role in many chronic inflammatory diseases, such as arthritis, chronic obstructive pulmonary disease (COPD), cardiovascular disease, cancer and more recently, metabolic disorder. In this review, we focus on the biosynthesis of LTB4 and its biological effects. In particular, we will describe a basic biochemical understanding integrated with recent developments in the field of structural biology of the three key enzymes (5-LOX, FLAP and LTA4H) in LTB4 biosynthesis, and also summarize the most outstanding work on in vivo biological and pathogenic roles of these enzymes and the development of enzyme inhibitors.

Modulating effect of inositol hexaphosphate on arachidonic acid-dependent pathways in colon cancer cells.

Cyclooxygenase (COX) and lipoxygenase (LOX) are key enzymes of arachidonic acid metabolism. Their products, prostaglandins and leukotrienes, are involved in the pathogenesis of inflammatory bowel diseases and colorectal cancer. The aim of the study was to examine the influence of inositol hexaphosphate (IP6), a naturally occurring phytochemical, on the expression of genes encoding COX and LOX isoforms and synthesis of their products (PGE2 and LTB4) in colon cancer cell line Caco-2 stimulated with pro-inflammatory agents (IL-1ß/TNFα). Real-time RT-qPCR was used to validate mRNAs level of examined genes. The concentrations of COX-2 and 5-LOX proteins as well as PGE2 and LTB4 were determined by the ELISA method. Based on these studies it may be concluded that IP6 may limit inflammatory events in the colonic epithelium and prevent colon carcinomas by modulating the expression of genes encoding COX and LOX isoforms at both mRNA and protein levels as well as by affecting the synthesis and secretion of prostaglandins and leukotrienes.

Capturing LTA4 hydrolase in action: Insights to the chemistry and dynamics of chemotactic LTB4 synthesis.

Human leukotriene (LT) A4 hydrolase/aminopeptidase (LTA4H) is a bifunctional enzyme that converts the highly unstable epoxide intermediate LTA4 into LTB4, a potent leukocyte activating agent, while the aminopeptidase activity cleaves and inactivates the chemotactic tripeptide Pro-Gly-Pro. Here, we describe high-resolution crystal structures of LTA4H complexed with LTA4, providing the structural underpinnings of the enzyme's unique epoxide hydrolase (EH) activity, involving Zn2+, Y383, E271, D375, and two catalytic waters. The structures reveal that a single catalytic water is involved in both catalytic activities of LTA4H, alternating between epoxide ring opening and peptide bond hydrolysis, assisted by E271 and E296, respectively. Moreover, we have found two conformations of LTA4H, uncovering significant domain movements. The resulting structural alterations indicate that LTA4 entrance into the active site is a dynamic process that includes rearrangement of three moving domains to provide fast and efficient alignment and processing of the substrate. Thus, the movement of one dynamic domain widens the active site entrance, while another domain acts like a lid, opening and closing access to the hydrophobic tunnel, which accommodates the aliphatic tale of LTA4 during EH reaction. The enzyme-LTA4 complex structures and dynamic domain movements provide critical insights for development of drugs targeting LTA4H.

Phospholipase A2 Inhibitor from Crotalus durissus terrificus rattlesnake: Effects on human peripheral blood mononuclear cells and human neutrophils cells.

Crotalus Neutralizing Factor (CNF) is an inhibitor of phospholipase A2 (PLA2), present in the blood plasma of Crotalus durissus terrificus snake. This inhibitor neutralizes the lethal and enzymatic activity of crotoxin, the main neurotoxin from this venom. In this study, we investigated the effects of CNF on the functionality of human peripheral blood mononuclear cells (PBMCs) and human neutrophils. The following parameters were evaluated: viability and proliferation, chemotaxis, cytokines and LTB4 production, cytosolic PLA2s activity, myeloperoxidase (MPO) and superoxide anion (O2-) production. CNF showed no toxicity on PBMCs or neutrophils, and acts by stimulating the release of TNF-α and LTB4, but neither stimulates IL-10 and IL-2 nor affects PBMCs proliferation and O2- release. In neutrophils, CNF induces chemotaxis but does not induce the release of both MPO and O2-. However, it induces LTB4 and IL-8 production. These data show the influence of CNF on PBMCs' function by inducing TNF-α and LTB4 production, and on neutrophils, by stimulating chemotaxis and LTB4 production, via cytosolic PLA2 activity, and IL-8 release. The inflammatory profile produced by CNF is shown for the first time. Our present results suggest that CNF has a role in activation of leukocytes and exert proinflammatory effects on these cell.

Dioxin-induced increase in leukotriene B4 biosynthesis through the aryl hydrocarbon receptor and its relevance to hepatotoxicity owing to neutrophil infiltration.

Dioxin and related chemicals alter the expression of a number of genes by activating the aryl hydrocarbon receptors (AHR) to produce a variety of disorders including hepatotoxicity. However, it remains largely unknown how these changes in gene expression are linked to toxicity. To address this issue, we initially examined the effect of 2,3,7,8-tetrachrolodibenzo-p-dioxin (TCDD), a most toxic dioxin, on the hepatic and serum metabolome in male pubertal rats and found that TCDD causes many changes in the level of fatty acids, bile acids, amino acids, and their metabolites. Among these findings was the discovery that TCDD increases the content of leukotriene B4 (LTB4), an inducer of inflammation due to the activation of leukocytes, in the liver of rats and mice. Further analyses suggested that an increase in LTB4 comes from a dual mechanism consisting of an induction of arachidonate lipoxygenase-5, a rate-limiting enzyme in LTB4 synthesis, and the down-regulation of LTC4 synthase, an enzyme that converts LTA4 to LTC4. The above changes required AHR activation, because the same was not observed in AHR knock-out rats. In agreement with LTB4 accumulation, TCDD caused the marked infiltration of neutrophils into the liver. However, deleting LTB4 receptors (BLT1) blocked this effect. A TCDD-produced increase in the mRNA expression of inflammatory markers, including tumor-necrosis factor and hepatic damage, was also suppressed in BLT1-null mice. The above observations focusing on metabolomic changes provide novel evidence that TCDD accumulates LTB4 in the liver by an AHR-dependent induction of LTB4 biosynthesis to cause hepatotoxicity through neutrophil activation.

Naringenin improves the healing process of thermally-induced skin damage in rats.

Objective To evaluate the effect of the phenolic compound naringenin on thermal burn-induced inflammatory responses and oxidative stress in rats. Methods First degree thermal burn injuries were induced in shaved rats by 10 s immersion of the back surface in water at 90℃. Naringenin treatment (25, 50 and 100 mg/kg/day) was initiated 24 h following burn injury, and continued for 7 days. On treatment day 7, serum tumour necrosis factor (TNF)-α, interleukin (IL)-1ß, IL-6, nitric oxide (NO), prostaglandin (PG)E2, caspase-3, leukotriene (LT)-B4 and nuclear factor (NF)-κB levels were quantified. Skin sample glutathione (GSH) and thiobarbituric acid reactive substances (TBARS) levels, and catalase, superoxide dismutase (SOD), glutathione-S-transferase (GST) and glutathione peroxidase (GPx) activities, were also measured. Results Serum inflammatory biomarkers were significantly increased in thermal-burn injured rats versus uninjured controls. Naringenin significantly inhibited the increased proinflammatory markers at day 7 of treatment. Increased TBARS levels and decreased GSH levels in wounded skin were significantly restored by naringenin treatment at day 7. SOD, catalase, GPx and GST activities were markedly inhibited in wounded skin tissues, and were significantly increased in naringenin-treated rats. Conclusion Naringenin treatment showed anti-inflammatory and antioxidant effects in rats with thermal burn-induced injury.

The development of novel LTA4H modulators to selectively target LTB4 generation.

The pro-inflammatory mediator leukotriene B4 (LTB4) is implicated in the pathologies of an array of diseases and thus represents an attractive therapeutic target. The enzyme leukotriene A4 hydrolase (LTA4H) catalyses the distal step in LTB4 synthesis and hence inhibitors of this enzyme have been actively pursued. Despite potent LTA4H inhibitors entering clinical trials all have failed to show efficacy. We recently identified a secondary anti-inflammatory role for LTA4H in degrading the neutrophil chemoattractant Pro-Gly-Pro (PGP) and rationalized that the failure of conventional LTA4H inhibitors may be that they inadvertently prevented PGP degradation. We demonstrate that these inhibitors do indeed fail to discriminate between the dual activities of LTA4H, and enable PGP accumulation in mice. Accordingly, we have developed novel compounds that potently inhibit LTB4 generation whilst leaving PGP degradation unperturbed. These novel compounds could represent a safer and superior class of LTA4H inhibitors for translation into the clinic.

Ceruloplasmin-derived peptide is the strongest regulator of oxidative stress and leukotriene synthesis in neutrophils.

Ceruloplasmin, an acute-phase protein, can affect the activity of leukocytes through its various enzymatic activities and protein-protein interactions (with lactoferrin, myeloperoxidase, eosinophil peroxidase, serprocidins, and 5-lipoxygenase (5-LOX), among others). However, the molecular mechanisms of ceruloplasmin activity are not clearly understood. In this study, we tested the ability of two synthetic peptides, RPYLKVFNPR (883-892) (P1) and RRPYLKVFNPRR (882-893) (P2), corresponding to the indicated fragments of the ceruloplasmin sequence, to affect neutrophil activation. Leukotriene (LT) B4 is the primary eicosanoid product of polymorphonuclear leukocytes (PMNLs, neutrophils). We studied leukotriene synthesis in PMNLs upon interaction with Salmonella enterica serovar Typhimurium. Priming of neutrophils with phorbol 12-myristate 13-acetate (PMA) elicited the strong regulatory function of P2 peptide as a superoxide formation inducer and leukotriene synthesis inhibitor. Ceruloplasmin-derived P2 peptide appeared to be a strong inhibitor of 5-LOX product synthesis under conditions of oxidative stress.