Disruption of the 5-lipoxygenase pathway attenuates atherogenesis consequent to COX-2 deletion in mice.

Suppression of cyclooxygenase 2 (COX-2)-derived prostacyclin (PGI(2)) is sufficient to explain most elements of the cardiovascular hazard from nonsteroidal antinflammatory drugs (NSAIDs). However, randomized trials are consistent with the emergence of cardiovascular risk during chronic dosing with NSAIDs. Although deletion of the PGI(2) receptor fosters atherogenesis, the importance of COX-2 during development has constrained the use of conventional knockout (KO) mice to address this question. We developed mice in which COX-2 was deleted postnatally, bypassing cardiorenal defects exhibited by conventional KOs. When crossed into ApoE-deficient hyperlipidemic mice, COX-2 deletion accelerated atherogenesis in both genders, with lesions exhibiting leukocyte infiltration and phenotypic modulation of vascular smooth muscle cells, as reflected by loss of α-smooth muscle cell actin and up-regulation of vascular cell adhesion molecule-1. Stimulated peritoneal macrophages revealed suppression of COX-2-derived prostanoids and augmented 5-lipoxygenase product formation, consistent with COX-2 substrate rediversion. Although deletion of the 5-lipoxygenase activating protein (FLAP) did not influence atherogenesis, it attenuated the proatherogeneic impact of COX-2 deletion in hyperlipidemic mice. Chronic administration of NSAIDs may increasingly confer a cardiovascular hazard on patients at low initial risk. Promotion of atherogenesis by postnatal COX-2 deletion affords a mechanistic explanation for this observation. Coincident inhibition of FLAP may offer an approach to attenuating such a risk from NSAIDs.

Maternal allergy increases susceptibility to offspring allergy in association with TH2-biased epigenetic alterations in a mouse model of peanut allergy.

BACKGROUND: Although maternal atopy is a risk factor for the development of peanut allergy, this phenomenon has not been well characterized experimentally, and the mechanisms underlying offspring risk are unclear. OBJECTIVE: We sought to determine whether offspring of mothers with peanut allergy (O-PAM mice) are more susceptible to peanut allergy than offspring of naive mothers (O-NM mice) in a murine model and, if so, whether the susceptibility is linked to TH2-biased epigenetic alterations. METHODS: Five-week-old O-PAM and O-NM mice were intragastrically sensitized to and challenged with peanut. Serum peanut-specific IgE levels, plasma histamine levels, anaphylactic reactions, and splenocyte and MLN cell cytokine production were measured. DNA methylation levels of the Il4 gene promoter from splenocytes and MLN cells from sensitized offspring and splenocytes from unsensitized neonatal offspring were determined by means of pyrosequencing. RESULTS: O-PAM mice exhibited 3-fold higher peanut-specific IgE levels after peanut sensitization, as well as 5-fold higher histamine levels and significantly higher anaphylactic symptom scores after challenge than O-NM mice (P < .05-.01). Cultured splenocytes and MLNs from O-PAM mice produced significantly more TH2 cytokines than cells from O-NM mice (P < .05-.01). Cells from O-PAM mice exhibited significantly reduced DNA methylation at CpG sites of the Il4 gene promoter than cells from O-NM mice. DNA methylation levels were inversely correlated with IL-4 and IgE production. O-PAM neonatal splenocyte hypomethylation of the Il4 gene promoter was also present. CONCLUSION: This study is the first to demonstrate that increased susceptibility to peanut allergy in O-PAM mice is associated with epigenetic alteration of the Il4 gene promoter. This finding might provide insight into preventing the development of early-life allergy.

Phellinus tropicalis abscesses in a patient with chronic granulomatous disease.

Chronic Granulomatous Disease (CGD), caused by genetic defects in components of the phagocyte NADPH oxidase pathway, leads to recurrent life-threatening bacterial and invasive fungal infections. While a number of unique pathogens have been associated with this disease, the causative organisms may be difficult to identify. Here, we present a 24 year old male with known X-linked CGD who concurrently developed a cervical abscess and an abscess in the subcutaneous tissues of the right hip, both of which were surgically drained. Cultures failed to identify any organisms. He was treated empirically with ertapenem but the hip abscess recurred at the original site and in contiguous dependent areas in the posterior thigh and knee. A filamentous organism was observed microscopically, initially considered a contaminant, but on culture yielded a mold growth, identified as Phellinus tropicalis (synonym: Inonotus tropicalis) based on phenotypic and molecular methods. This is the third case report of human infection with P. tropicalis, all in subjects with CGD. The patient was treated with voriconazole with resolution of his symptoms.

Cardiomyocyte cyclooxygenase-2 influences cardiac rhythm and function.

Nonsteroidal anti-inflammatory drugs selective for inhibition of COX-2 increase heart failure and elevate blood pressure. The COX-2 gene was floxed and crossed into merCremer mice under the alpha-myosin heavy-chain promoter. Tamoxifen induced selective deletion of COX-2 in cardiomyocytes depressed cardiac output, and resulted in weight loss, diminished exercise tolerance, and enhanced susceptibility to induced arrhythmogenesis. The cardiac dysfunction subsequent to pressure overload recovered progressively in the knockouts coincident with increasing cardiomyocyte hypertrophy and interstitial and perivascular fibrosis. Inhibition of COX-2 in cardiomyocytes may contribute to heart failure in patients receiving nonsteroidal anti-inflammatory drugs specific for inhibition of COX-2.

Targeted deletions of cyclooxygenase-2 and atherogenesis in mice.

BACKGROUND: Although the dominant product of vascular Cyclooxygenase-2 (COX-2), prostacyclin (PGI(2)), restrains atherogenesis, inhibition and deletion of COX-2 have yielded conflicting results in mouse models of atherosclerosis. Floxed mice were used to parse distinct cellular contributions of COX-2 in macrophages and T cells (TCs) to atherogenesis. METHODS AND RESULTS: Deletion of macrophage-COX-2 (Mac-COX-2KOs) was attained with LysMCre mice and completely suppressed lipopolysaccharide-stimulated macrophage prostaglandin (PG) formation and lipopolysaccharide-evoked systemic PG biosynthesis by approximately 30%. Lipopolysaccharide-stimulated COX-2 expression was suppressed in polymorphonuclear leukocytes isolated from MacKOs, but PG formation was not even detected in polymorphonuclear leukocyte supernatants from control mice. Atherogenesis was attenuated when MacKOs were crossed into hyperlipidemic low-density lipoprotein receptor knockouts. Deletion of Mac-COX-2 appeared to remove a restraint on COX-2 expression in lesional nonleukocyte (CD45- and CD11b-negative) vascular cells that express vascular cell adhesion molecule and variably alpha-smooth muscle actin and vimentin, portending a shift in PG profile and consequent atheroprotection. Basal expression of COX-2 was minimal in TCs, but use of CD4Cre to generate TC knockouts depressed its modest upregulation by anti-CD3epsilon. However, biosynthesis of PGs, TC composition in lymphatic organs, and atherogenesis in low-density lipoprotein receptor knockouts were unaltered in TC knockouts. CONCLUSIONS: Macrophage-COX-2, primarily a source of thromboxane A(2) and prostaglandin (PG)E(2), promotes atherogenesis and exerts a restraint on enzyme expression by lesional cells suggestive of vascular smooth muscle cells, a prominent source of atheroprotective prostacyclin. TC COX-2 does not detectably influence TC development or function or atherogenesis in mice.

Deletion of microsomal prostaglandin E synthase-1 does not alter ozone-induced airway hyper-responsiveness.

Nonsteroidal anti-inflammatory drugs ameliorate pain and fever by inhibiting cyclooxygenase (COX) and suppressing prostanoid formation. Microsomal prostaglandin E synthase-1 (mPGES-1) catalyzes formation of PGE(2) from the COX product PGH(2) and has emerged as a therapeutic target. Inhibition of mPGES-1, however, renders the PGH(2) substrate available for diversion to other PG synthases. To address the possibility that substrate diversion augments formation of PGs that might modulate bronchial tone, we assessed the impact of mPGES-1 deletion in a mouse model of ozone-induced airway hyper-responsiveness. Ozone exposure increased total lung resistance to inhaled methacholine in wild-type mice. Deletion of mPGES-1 had little effect on total lung resistance in either naive or ozone-exposed animals. The carbachol-induced narrowing of luminal diameter in intrapulmonary airways of lung slices from acute ozone-exposed mice was also unaltered by mPGES-1 deletion. Likewise, although concentrations of PGE(2) were reduced in bronchoalveolar lavage fluid, whereas 6-keto-PGF(1alpha), PGD(2), and PGF(2alpha), all were increased, deletion of mPGES-1 failed to influence cell trafficking into the airways of either naive or ozone-exposed animals. Despite biochemical evidence of PGH(2) substrate diversion to potential bronchomodulator PGs, deletion of mPGES-1 had little effect on ozone-induced airway inflammation or airway hyper-responsiveness. Pharmacologically targeting mPGES-1 may not predispose patients at risk to airway dysfunction.

Hemoptysis in a Patient with Elevated Immunoglobulin E.

Recurrent pneumonia with cavitation leading to pneumatoceles, secondary fungal infections, and hemoptysis are major causes of mortality and morbidity in patients with hyper-IgE syndrome. Prevention and aggressive treatment of pneumonia in these patients are essential to prevent further lung damage, but treatment may be delayed because the classic signs/symptoms of infection such as fever, chills, or rigors may be lacking. Early imaging to identify infection is essential for diagnosis and treatment. The mainstay of therapy is continuous, full-dose daily trimethoprim-sulfamethoxazole and commonly fungal coverage. Because hyper-IgE syndrome is a progressive disease, patients' condition may worsen despite compliance with prophylactic therapy.

Directed vascular expression of human cysteinyl leukotriene 2 receptor modulates endothelial permeability and systemic blood pressure.

BACKGROUND: The proinflammatory and vascular actions of cysteinyl leukotrienes (CysLTs) are mediated by 2 receptors: cysteinyl leukotriene 1 receptor (CysLT1R) and cysteinyl leukotriene 2 receptor (CysLT2R). However, the distinct contribution of CysLT2R to the vascular actions of CysLTs has not been addressed. METHODS AND RESULTS: We generated an endothelial cell-specific human CysLT2R (EC-hCysLT2R) transgenic (TG) mouse model using the Tie2 promoter/enhancer. Strong expression of hCysLT2R in TG lung and endothelial cells, detected by real-time polymerase chain reaction, markedly enhanced CysLT-stimulated intracellular calcium mobilization compared with endogenous expression in cells from nontransgenic mice. The permeability response to exogenous LTC4 and to endogenous CysLTs evoked by passive cutaneous anaphylaxis was augmented in TG mice. The rapid, systemic pressor response to intravenous LTC4 was also diminished in TG mice coincidentally with augmented production of nitric oxide. CONCLUSIONS: The development of EC-hCysLT2R mice has permitted detection of distinct vascular effects of CysLTs, which can be mediated via the CysLT2R in vivo.

Cysteinyl leukotriene receptors.

Cysteinyl leukotrienes (CysLTs) are important inflammatory mediators in asthma and allergic disorders. Two types of CysLT receptors, CysLT(1) and CysLT(2), which were originally defined pharmacologically based on their sensitivity to CysLT(1) specific antagonists, are responsible for most of the known CysLT biological actions. The regulation of CysLT receptor expression and signaling in disease processes is largely unclear. Recent molecular cloning of both receptor subtypes from several different species will greatly facilitate future research in understanding CysLT signal transduction mechanisms. Expression of the relatively better-studied CysLT(1) is verified in lung tissues and peripheral blood cells. Elucidating how this receptor mediates airway inflammation will deepen our understanding of asthma etiology. On the other hand, detection of CysLT(2) in the heart, brain, and adrenal glands will inject new excitement into the search for novel CysLT functions. This review summarizes receptor cloning, ligand binding, expression, signaling, and functions in an effort to bridge early pharmacological studies to future studies at the molecular level.

Targeted cyclooxygenase gene (ptgs) exchange reveals discriminant isoform functionality.

The prostaglandin G/H synthase enzymes, commonly termed COX-1 and COX-2, differ markedly in their responses to regulatory stimuli and their tissue expression patterns. COX-1 is the dominant source of "housekeeping" prostaglandins, whereas COX-2 synthesizes prostaglandins of relevance to pain, inflammation, and mitogenesis. Despite these distinctions, the two enzymes are remarkably conserved, and their subcellular distributions overlap considerably. To address the functional interchangeability of the two isozymes, mice in which COX-1 is expressed under COX-2 regulatory elements were created by a gene targeting "knock-in" strategy. In macrophages from these mice, COX-1 was shown to be lipopolysaccharide-inducible in a manner analogous to COX-2 in wild-type macrophages. However, COX-1 failed to substitute effectively for COX-2 in lipopolysaccharide-induced prostaglandin E2 synthesis at low concentrations of substrate and in the metabolism of the endocannabinoid 2-arachidonylglycerol. The marked depression of the major urinary metabolite of prostacyclin in COX-2 null mice was only partially rescued by COX-1 knock-in, whereas the main urinary metabolite of prostaglandin E2 was rescued totally. Replacement with COX-1 partially rescued the impact of COX-2 deletion on reproductive function. The renal pathology consequent to COX-2 deletion was delayed but not prevented, whereas the corresponding peritonitis was unaltered. Insertion of COX-1 under the regulatory sequences that drive COX-2 expression indicated that COX-1 can substitute for some COX-2 actions and rescue only some of the consequences of gene disruption. Manipulation of COX-2 also revealed a preference for coupling with distinct downstream prostaglandin synthases in vivo. These mice will provide a valuable reagent with which to elucidate the distinct roles of the COX enzymes in mammalian biology.

Deletion of microsomal prostaglandin E synthase-1 augments prostacyclin and retards atherogenesis.

Prostaglandin (PG) E(2) is formed from PGH(2) by a series of PGE synthase (PGES) enzymes. Microsomal PGES-1(-/-) (mPGES-1(-/-)) mice were crossed into low-density lipoprotein receptor knockout (LDLR(-/-)) mice to generate mPGES-1(-/-) LDLR(-/-)s. Urinary 11alpha-hydroxy-9, 15-dioxo-2,3,4,5-tetranor-prostane-1,20-dioic acid (PGE-M) was depressed by mPGES-1 deletion. Vascular mPGES-1 was augmented during atherogenesis in LDLR(-/-)s. Deletion of mPGES-1 reduced plaque burden in fat-fed LDLR(-/-)s but did not alter blood pressure. mPGES-1(-/-) LDLR(-/-) plaques were enriched with fibrillar collagens relative to LDLR(-/-), which also contained small and intermediate-sized collagens. Macrophage foam cells were depleted in mPGES-1(-/-) LDLR(-/-) lesions, whereas the total areas rich in vascular smooth muscle cell (VSMC) and matrix were unaltered. mPGES-1 deletion augmented expression of both prostacyclin (PGI(2)) and thromboxane (Tx) synthases in endothelial cells, and VSMCs expressing PGI synthase were enriched in mPGES-1(-/-) LDLR(-/-) lesions. Stimulation of mPGES-1(-/-) VSMC and macrophages with bacterial LPS increased PGI(2) and thromboxane A(2) to varied extents. Urinary PGE-M was depressed, whereas urinary 2,3-dinor 6-keto PGF(1alpha), but not 2,3-dinor-TxB(2), was increased in mPGES-1(-/-) LDLR(-/-)s. mPGES-1-derived PGE(2) accelerates atherogenesis in LDLR(-/-) mice. Disruption of this enzyme retards atherogenesis, without an attendant impact on blood pressure. This may reflect, in part, rediversion of accumulated PGH(2) to augment formation of PGI(2). Inhibitors of mPGES-1 may be less likely than those selective for cyclooxygenase 2 to result in cardiovascular complications because of a divergent impact on the biosynthesis of PGI(2).