Leukotriene B4-induced permeability increase in postcapillary venules and its inhibition by three different antiinflammatory drugs

Absence of prostacyclin greatly relieves cyclophosphamide-induced cystitis and bladder pain in mice

Cyclophosphamide (CP) has been widely used in the treatment of various malignancies and autoimmune diseases, but acrolein, a byproduct of CP, causes severe hemorrhagic cystitis as the major side effect of CP. On the other hand, a large amount of prostacyclin (PGI₂ ) is produced in bladder tissues, and PGI₂ has been shown to play a critical role in bladder homeostasis. PGI₂ is biosynthesized from prostaglandin (PG) H₂ , the common precursor of PGs, by PGI₂ synthase (PTGIS) and is known to also be involved in inflammatory responses. However, little is known about the roles of PTGIS-derived PGI₂ in bladder inflammation including CP-induced hemorrhagic cystitis. Using both genetic and pharmacological approaches, we here revealed that PTGIS-derived PGI₂ -IP (PGI₂ receptor) signaling exacerbated CP-induced bladder inflammatory reactions. Ptgis deficiency attenuated CP-induced vascular permeability and chemokine-mediated neutrophil migration into bladder tissues and then suppressed hemorrhagic cystitis. Treatment with RO1138452, an IP selective antagonist, also suppressed CP-induced cystitis. We further found that cystitis-related nociceptive behavior was also relieved in both Ptgis^-/- mice and RO1138452-treated mice. Our findings may provide new drug targets for bladder inflammation and inflammatory pain in CP-induced hemorrhagic cystitis.

Angioedema and Fatty Acids

Angioedema is a life-threatening emergency event that is associated with bradykinin and histamine-mediated cascades. Although bradykinin-mediated angioedema currently has specific therapeutic options, angioedema is sometimes intractable with current treatments, especially histamine-mediated angioedema, suggesting that some other mediators might contribute to the development of angioedema. Fatty acids are an essential fuel and cell component, and act as a mediator in physiological and pathological human diseases. Recent updates of studies revealed that these fatty acids are involved in vascular permeability and vasodilation, in addition to bradykinin and histamine-mediated reactions. This review summarizes each fatty acid’s function and the specific receptor signaling responses in blood vessels, and focuses on the possible pathogenetic role of fatty acids in angioedema.

Bone marrow lesions and subchondral bone pathology of the knee

Bone marrow lesions (BMLs) around the knee are a common magnetic resonance imaging (MRI) finding. However, despite the growing interest on BMLs in multiple pathological conditions, they remain controversial not only for the still unknown role in the etiopathological processes, but also in terms of clinical impact and treatment. The differential diagnosis includes a wide range of conditions: traumatic contusion and fractures, cyst formation and erosions, hematopoietic and infiltrated marrow, developmental chondroses, disuse and overuse, transient bone marrow oedema syndrome and, lastly, subchondral insufficiency fractures and true osteonecrosis. Regardless the heterogeneous spectrum of these pathologies, a key factor for patient management is the distinction between reversible and irreversible conditions. To this regard, MRI plays a major role, leading to the correct diagnosis based on recognizable typical patterns that have to be considered together with coexistent abnormalities, age, and clinical history. Several treatment options have been proposed, from conservative to surgical approaches. In this manuscript the main lesion patterns and their management have been analysed to provide the most updated evidence for the differential diagnosis and the most effective treatment.

Hormonal control of inflammatory responses

Almost any stage of inflammatory and immunological responses is affected by hormone actions. This provides the basis for the suggestion that hormones act as modulators of the host reaction against trauma and infection. Specific hormone receptors are detected in the reactive structures in inflamed areas and binding of hormone molecules to such receptors results in the generation of signals that influence cell functions relevant for the development of inflammatory responses. Diversity of hormonal functions accounts for recognized pro- and anti-inflammatory effects exerted by these substances. Most hormone systems are capable of influencing inflammatory events. Insulin and glucocorticoids, however, exert direct regulatory effects at concentrations usually found in plasma. Insulin is endowed with facilitatory actions on vascular reactivity to inflammatory mediators and inflammatory cell functions. Increased concentrations of circulating glucocorticoids at the early stages of inflammation results in downregulation of inflammatory responses. Oestrogens markedly reduce the response to injury in a variety of experimental models. Glucagon and thyroid hormones exert indirect anti-inflammatory effects mediated by the activity of the adrenal cortex. Accordingly, inflammation is not only merely a local response, but a hormone-controlled process.

Beta-adrenergic stimulation contributes to maintenance of endothelial barrier functions under baseline conditions

OBJECTIVES

cAMP signaling within the endothelium is known to reduce paracellular permeability and to protect against loss of barrier functions under various pathological conditions. Because activation of β-adrenergic receptors elevates cellular cAMP, we tested whether β-adrenergic receptor signaling contributes to the maintenance of baseline endothelial barrier properties.

METHODS

We compared hydraulic conductivity of rat postcapillary venules in vivo with resistance measurements and with reorganization of endothelial adherens junctions in cultured microvascular endothelial cells downstream of β-adrenergic receptor-mediated changes of cAMP levels.

RESULTS

Inhibition of β-adrenergic receptors by propranolol increased hydraulic conductivity, reduced both cAMP levels and TER of microvascular endothelial cell monolayers and induced fragmentation of VE-cadherin staining. In contrast, activation by epinephrine both increased cAMP levels and TER and resulted in linearized VE-cadherin distribution, however this was not sufficient to block barrier-destabilization by propranolol. Similarly, PDE inhibition did not prevent propranolol-induced TER reduction and VE-cadherin reorganization whereas increased cAMP formation by AC activation enhanced endothelial barrier functions under baseline conditions and under conditions of propranolol treatment.

CONCLUSIONS

Our results indicate that generation of cAMP mediated by activation of β-adrenergic receptor signaling contributes to the maintenance of endothelial barrier properties under baseline conditions.

Outcome of painful bone marrow edema of the femoral head following treatment with parenteral iloprost

BACKGROUND

Bone marrow edema (BME) is a common cause of hip pain. The aim of the study was to assess the efficacy of the vasoactive drug iloprost in the treatment of BME of femoral head.

MATERIALS AND METHODS

We reviewed 27 patients (19 male, 8 female) with BME of the femoral head. Their mean age was 53.7 +/- 10.8 years. All patients were treated with iloprost, a vasoactive drug that dilates arterioles and venules, reduces capillary permeability and suppresses platelet aggregation. The therapy comprised a series of five infusions with 20 to 50 mug iloprost over 6 h on 5 consecutive days each. Weight bearing was reduced for up to 3 weeks, depending on the severity of symptoms. Pain at rest as well as under stress was assessed with a semi quantitative scale from before and 4 months after therapy. MRI investigations were done before and repeated 4 months after therapy.

RESULTS

At the clinical follow up of four months after therapy, the pain level at rest had diminished by a mean of 58.3% (P < 0.0001). Pain under stress decreased by a mean of 41.9% (P < 0.0001). On MRI, 20 patients had a significant reduction of BME size or complete normalization and 4 showed no change. Worsening of the MRI pattern was found in 3 patients.

CONCLUSION

The authors conclude that the use of parenteral iloprost might be a viable method in the treatment of BME of femoral head.

Rationale for prostaglandin I2 in bone marrow oedema--from theory to application

Introduction

Bone marrow oedema (BME) and avascular osteonecrosis (AVN) are disorders of unclear origin. Although there are numerous operative and non-operative treatments for AVN, pain management in patients with AVN remains challenging. Prostaglandins play an important role in inflammatory responses and cell differentiation. It is thought that prostaglandin I₂ ([PGI₂] or synonoma prostacyclin) and its analogues promote bone regeneration on a cellular or systemic level. The purpose of this study was to assess the curative and symptomatic efficacy of the prostacyclin analogue iloprost in BME and AVN patients.

Method

We are reporting on 50 patients (117 bones) affected by BME/AVN who were treated with iloprost. Pain levels before, during and 3 and 6 months after iloprost application were evaluated by a visual analogue scale (VAS). The short form(SF)-36 health survey served to judge general health status before and after treatment. Harris Hip Score (HHS) and Knee Society Score (KSS) were performed as functional scores and MRI and X-rays before and 3 and 6 months after iloprost application served as objective parameters for morphological changes of the affected bones.

Results

We found a significant improvement in pain, functional and radiological outcome in BME and early AVN stages after iloprost application, whereas patients with advanced AVN stages did not benefit from iloprost infusions. Mean pain level decreased from 5.26 (day 0) to 1.63 (6 months) and both HHS and KSS increased during follow-up. Moreover, the SF-36 increased from 353.2 (day 0) to 560.5 points (6 months). We found a significant decrease in BME on MRI scans after iloprost application.

Conclusions

In addition to other drugs, iloprost may be an alternative substance which should be considered in the treatment of BME/AVN-associated pain.

Areca nut extracts-activated secretion of leukotriene B4, and phosphorylation of p38 mitogen-activated protein kinase and elevated intracellular calcium concentrations in human polymorphonuclear leukocytes

BACKGROUND AND OBJECTIVE

Polymorphonuclear leukocytes are the major source of leukotriene B4, which is synthesized via the 5-lipoxygenase pathway. Activation of the 5-lipoxygenase pathway is regulated by intracellular calcium and the phosphorylation of p38 mitogen-activated protein kinase (MAPK). The impact of areca nut extracts on the biosynthesis of leukotriene B4 by human polymorphonuclear leukocytes was evaluated, and some of the possible mechanisms underlying the responses were examined.

MATERIAL AND METHODS

Polymorphonuclear leukocytes were treated with various concentrations of areca nut extracts. The concentrations of leukotriene B4 released into the supernatants were evaluated using enzyme immunoassay. The phosphorylation of p38 MAPK was monitored using immunoblotting, and the cytosolic calcium kinetics were assessed fluorometrically using Fura-2.

RESULTS

Exposure of polymorphonuclear leukocytes to areca nut extracts led to a dose-dependent increase in the production of leukotriene B4, with levels peaking at 30 min and decreasing thereafter. Areca nut extracts enhanced the phosphorylation of p38 MAPK, an enzyme known to activate 5-lipoxygenase. Incubation with areca nut extracts also resulted in a rapid elevation of intracellular calcium concentrations in polymorphonuclear leukocytes. The induction of leukotriene B4 by areca nut extracts was suppressed with the p38 MAPK inhibitor, SB203580, or with the intracellular calcium chelator, BAPTA-AM.

CONCLUSION

The interaction of areca nut extracts with polymorphonuclear leukocytes activated the arachidonic acid metabolic cascade. Incubation of polymorphonuclear leukocytes with areca nut extracts resulted in the activation of intracellular events, such as phosphorylation of p38 MAPK and Ca2+ mobilization, involved in the release of pro-inflammatory lipid mediators. The results of this study emphasize the potential importance of polymorphonuclear leukocytes as a source of leukotriene B4, which may modulate the inflammatory response in areca chewers.

Preparation of budesonide and budesonide-PLA microparticles using supercritical fluid precipitation technology

The objective of this study was to prepare and characterize microparticles of budesonide alone and budesonide and polylactic acid (PLA) using supercritical fluid (SCF) technology. A precipitation with a compressed antisolvent (PCA) technique employing supercritical CO2 and a nozzle with 100- microm internal diameter was used to prepare microparticles of budesonide and budesonide-PLA. The effect of various operating variables (temperature and pressure of CO2 and flow rates of drug-polymer solution and/or CO2) and formulation variables (0.25%, 0.5%, and 1% budesonide in methylene chloride) on the morphology and size distribution of the microparticles was determined using scanning electron microscopy. In addition, budesonide-PLA particles were characterized for their surface charge and drug-polymer interactions using a zeta meter and differential scanning calorimetry (DSC), respectively. Furthermore, in vitro budesonide release from budesonide-PLA microparticles was determined at 37 degrees C. Using the PCA process, budesonide and budesonide-PLA microparticles with mean diameters of 1 to 2 microm were prepared. An increase in budesonide concentration (0.25%-1% wt/vol) resulted in budesonide microparticles that were fairly spherical and less agglomerated. In addition, the size of the microparticles increased with an increase in the drug-polymer solution flow rate (1.4-4.7 mL/min) or with a decrease in the CO2 flow rate (50-10 mL/min). Budesonide-PLA microparticles had a drug loading of 7.94%, equivalent to approximately 80% encapsulation efficiency. Budesonide-PLA microparticles had a zeta potential of -37 +/- 4 mV, and DSC studies indicated that SCF processing of budesonide-PLA microparticles resulted in the loss of budesonide crystallinity. Finally, in vitro drug release studies at 37 degrees C indicated 50% budesonide release from the budesonide-PLA microparticles at the end of 28 days. Thus, the PCA process was successful in producing budesonide and budesonide-PLA microparticles. In addition, budesonide-PLA microparticles sustained budesonide release for 4 weeks.

Augmentation of allergic inflammation in prostanoid IP receptor deficient mice

1 To evaluate the role of prostaglandin I(2) (PGI(2)) in allergic inflammation, allergic responses in the airway, skin and T cells were studied in mice lacking the receptor for PGI(2) (the prostanoid IP receptor) through gene disruption. 2 Three inhalations of antigen caused an increase in plasma extravasation, leukocyte accumulation and cytokine (interleukin (IL)-4 and IL-5) production in the airway of sensitized mice. These airway inflammatory responses were significantly greater in IP receptor deficient mice than in wild-type mice. 3 The vascular leakage caused by passive cutaneous anaphylaxis, substance P and 5-hydroxytryptamine was markedly increased in the skin of IP receptor deficient mice, compared with comparably treated wild-type mice. 4 The inhalation of antigen in sensitized mice resulted in increased serum antigen specific IgE, total IgE and IgG levels. The magnitude of the elevations of each immunoglobulin level in IP receptor deficient mice is notably higher than that in wild-type mice. To elucidate the mechanism of an enhancement of immunoglobulin production, the activity of T cells in sensitized and non-sensitized mice was studied by means of the production of cytokines. The antigen-induced IL-4 production by spleen cells from sensitized IP receptor deficient mice was almost three times greater than that in wild-type mice. On the contrary, the anti-CD3 antibody-induced interferon-gamma production by CD4(+) T cells from non-sensitized IP receptor deficient mice was significantly lower than that in wild-type mice. 5 The present data indicate that IP receptor deficiency reinforced an allergic airway and skin inflammation by augmentation of vascular permeability increase and the T helper 2 cell function. These findings suggest a regulatory role of PGI(2) in allergic inflammation.

Bone marrow edema of the forefoot after chevron osteotomy--a rare cause of metatarsalgia: a case report

Treatment options of bone marrow edema syndrome, which is associated with vascular disturbances, are protracted nonoperative treatment or core decompression which still demands several weeks until complete recovery. We obtained excellent results by the use of the vasoactive drug iloprost, a stable prostacyclin analogue, leading to a complete relief of symptoms in cases of bone marrow edema which had initially suggested early avascular necrosis of the second metatarsal head. The bone marrow edema of the second metatarsal bone was thought to be due to altered biomechanics following a distal first metatarsal chevron osteotomy. During the five days of iloprost infusion, the patient reported relief of rest pain. After therapy, the pedobarogram was normalized. The AOFAS forefoot score improved from 44 to 85 points after one month, and to 95 points after three months. At that time, the marrow showed normal signals. Without additional intervention the patient was able to resume normal activities.

Preparation of budesonide and budesonide-PLA microparticles using supercritical fluid precipitation technology

The objective of this study was to prepare and characterize microparticles of budesonide alone and budesonide and polylactic acid (PLA) using supercritical fluid (SCF) technology. A precipitation with a compressed antisolvent (PCA) technique employing supercritical CO2 and a nozzle with 100- microm internal diameter was used to prepare microparticles of budesonide and budesonide-PLA. The effect of various operating variables (temperature and pressure of CO2 and flow rates of drug-polymer solution and/or CO2) and formulation variables (0.25%, 0.5%, and 1% budesonide in methylene chloride) on the morphology and size distribution of the microparticles was determined using scanning electron microscopy. In addition, budesonide-PLA particles were characterized for their surface charge and drug-polymer interactions using a zeta meter and differential scanning calorimetry (DSC), respectively. Furthermore, in vitro budesonide release from budesonide-PLA microparticles was determined at 37 degrees C. Using the PCA process, budesonide and budesonide-PLA microparticles with mean diameters of 1 to 2 microm were prepared. An increase in budesonide concentration (0.25%-1% wt/vol) resulted in budesonide microparticles that were fairly spherical and less agglomerated. In addition, the size of the microparticles increased with an increase in the drug-polymer solution flow rate (1.4-4.7 mL/min) or with a decrease in the CO2 flow rate (50-10 mL/min). Budesonide-PLA microparticles had a drug loading of 7.94%, equivalent to approximately 80% encapsulation efficiency. Budesonide-PLA microparticles had a zeta potential of -37 +/- 4 mV, and DSC studies indicated that SCF processing of budesonide-PLA microparticles resulted in the loss of budesonide crystallinity. Finally, in vitro drug release studies at 37 degrees C indicated 50% budesonide release from the budesonide-PLA microparticles at the end of 28 days. Thus, the PCA process was successful in producing budesonide and budesonide-PLA microparticles. In addition, budesonide-PLA microparticles sustained budesonide release for 4 weeks.

Budesonide reduces vascular endothelial growth factor secretion and expression in airway (Calu-1) and alveolar (A549) epithelial cells

Vascular endothelial growth factor (VEGF), a cytokine expressed in the respiratory epithelial cells, induces vascular hyperpermeability and edema, symptoms that are alleviated by budesonide, an anti-asthma corticosteroid. However, modulation of VEGF levels by budesonide in the respiratory epithelium has not been studied. In this study, we investigated the mechanisms of VEGF secretion using brefeldin A and monensin in human airway (Calu-1) and alveolar (A549) epithelial cells, and further determined whether budesonide inhibits VEGF secretion and mRNA expression through a glucocorticoid receptor-mediated mechanism. In both cell types, VEGF secretion was inhibited by brefeldin A and monensin, suggesting vesicular transport of VEGF through endoplasmic reticulum (ER)-golgi pathway. At concentrations devoid of cytotoxicity, budesonide reduced VEGF secretion and VEGF mRNA expression in both cell types and these effects were inhibited by mifepristone (RU 486), a glucocorticoid receptor antagonist, suggesting that budesonide reduces VEGF secretion and expression through its glucocorticoid receptor-mediated action. Also, budesonide-mediated inhibition of VEGF mRNA was time- and protein synthesis-dependent. Thus, budesonide may be of potential value in treating disorders of the respiratory tract that are associated with VEGF elevation.

Levels of leukotriene B4 in gingival crevicular fluid and gingival tissue in specific periodontal diseases

BACKGROUND

Leukotriene B4 (LTB4), a product of the lipoxygenase pathway of arachidonic acid metabolism, exhibits numerous activities that can account for most of the features of host responses seen in periodontal diseases. The aim of the present study was to examine the role of LTB4 in the pathogenesis of specific periodontal diseases.

METHODS

LTB4 levels were investigated in gingival crevicular fluid (GCF) and gingival tissue (GT) samples of 10 patients with chronic periodontitis (CP), 12 patients with generalized aggressive periodontitis (GAgP), 6 patients with localized aggressive periodontitis (LAgP), 6 patients with gingivitis (G), and 6 periodontally healthy subjects (H). Periodontal status was evaluated by measuring probing depth, gingival index, papillary bleeding index, and plaque index. LTB4 was extracted from the samples by solid-phase method using C18 cartridge and was purified by high performance liquid chromatographic method and then analyzed by radioimmunoassay.

RESULTS

All patient groups had significantly higher levels of GCF and GT LTB4 compared to the control group (P<0.005). The CP patients had the highest LTB4 levels compared to those in other patient groups (P<0.005). GAgP, LAgP, and G groups had similar amounts of GCF and GT LTB4 (P>0.005). When the data were expressed as concentration, the CP group was found to have higher concentration of LTB4, compared to that of control group (P<0.005). GAgP, LAgP, and G groups had similar LTB4 concentration compared to that of control group (P>0.005). No significant difference was found between GAgP, LAgP, and G groups (P>0.005). The CP group had higher LTB4 concentration compared to both GAgP and LAgP groups (P<0.005). Although the CP group had a higher GCF LTB4 concentration compared to G group, this difference did not reach significance (P>0.005). No significant correlation was found between GCF and GT LTB4 levels and clinical parameters.

CONCLUSIONS

The results of the present study indicate that LTB4 is likely to be an important mediator in regulating inflammatory responses in the human periodontal tissues. This lipid mediator may play an important role in the pathophysiology of periodontal disease.

Time course of endothelial cell proliferation and microvascular remodeling in chronic inflammation

Angiogenesis and vascular remodeling are features of many chronic inflammatory diseases. When diseases evolve slowly, the accompanying changes in the microvasculature would seem to be similarly gradual. Here we report that the rate of endothelial cell proliferation and the size of blood vessels increases rapidly after the onset of an infection that leads to chronic inflammatory airway disease. In C3H mice inoculated with Mycoplasma pulmonis, the tracheal microvasculature, made visible by perfusion of Lycopersicon esculentum lectin, rapidly enlarged from 4 to 7 days after infection and then plateaued. Diameters of arterioles, capillaries, and venules increased on average 148, 214, and 74%, respectively. Endothelial cell proliferation, measured by bromodeoxyuridine (BrdU) labeling, peaked at 5 days (18 times the pathogen-free value), declined sharply until day 9, but remained at approximately 3 times the pathogen-free value for at least 28 days. Remodeled capillaries and venules were sites of focal plasma leakage and extensive leukocyte adherence. Most systemic manifestations of the infection occurred well after the peak of endothelial proliferation, and the humoral immune response to M. pulmonis was among the latest, increasing after 14 days. These data show that endothelial cell proliferation and microvascular remodeling occur at an early stage of chronic airway disease and suggest that the vascular changes precede widespread tissue remodeling.

Croup. A current perspective

In the past decade, much progress has been made in the management of patients with croup. Where glucocorticoids have been adopted into practice, evidence shows that a decrease of health-care-service use is occurring in terms of fewer admissions to intensive care units and hospitals. The evidence may be summarized as follows. All children with croup symptoms who demonstrate increased work of breathing in the clinics or emergency departments should be treated with glucocorticoids. This treatment may be with nebulized budesonide (2 mg) or PO or IM dexamethasone (dose may be 0.15-0.6 mg/kg). Oral dexamethasone may be the best option because of its ease of administration, widespread availability, and lower cost. L-Epinephrine (5 mL of 1:1000) or racemic epinephrine (0.5 mL) should be considered for children with croup who have moderate or severe distress. No evidence supports the effectiveness of mist therapy, and physicians are in need of a randomized, controlled trial for this.

[Childhood croup]

Hoarseness, whooping cough and stridor are elements of a syndrome of upper airway obstruction. In childhood, acute laryngotracheobronchitis is by far the commonest cause of this syndrome. Yet, the differential diagnosis includes a number of rare and severe entities. In many cases, the traditional distinction between viral and spasmodic types is not possible. The value of humidifying therapy has not been established. In severe cases, nebulized adrenaline is of benefit but should be reserved for hospital. The effect lasts only two hours and at times a rebound effect is observed. It is now realized that some patients treated with adrenaline can safely be discharged after a two to three hours observation. There is a large body of evidence that all children arriving at the emergency department with croup should receive steroids without delay. This policy results in a much better outcome, with important reduction in hospitalizations, intensive care unit admissions and incubations. Oral dexamethasone is the drug of choice: it is as effective, easier to administer and cheaper than nebulised budesonide. In most studies, dexamethasone has been used at a dose of 0.6 mg/kg but there is some evidence that 0.15 mg/kg may be just as effective.

Investigations on the ability of clenbuterol hydrochloride to reduce clinical signs and inflammation associated with equine influenza A infection

Twenty-four Quarter Horse and Quarter Horse-cross yearlings were experimentally infected with influenza A virus (Influenza A/equine/Saskatoon/90 [H3N8]) by nebulisation. In a double blind controlled trial the horses were randomly assigned to 3 groups of 8 animals. Group 1 received a placebo, (carrier syrup), Group 2 the labelled dose and Group 3 twice the labelled dose of clenbuterol hydrochloride. All treatments were given per os b.i.d. for 10 days and started on the day of infection. The horses were monitored for clinical signs of influenza infection for 14 days. Bronchoalveolar lavages were performed 4 days prior to, and 5 and 13 days after infection. Cell counts and concentrations of prostaglandin E2 and prostaglandin F2alpha in the lavage fluid were determined. Blood samples for haematology and serology were taken 4 days before, on the day of infection, 5, 9 and 13 days after infection. All horses experienced a typical influenza infection with fever, coughing and secondary bacterial infections with mainly Actinobacillus spp. and Streptococcus spp. There was no statistically or clinically significant effect of treatment with clenbuterol hydrochloride on measured clinical or laboratory parameters within 14 days of infection.

In vivo stimulation of 12(S)-lipoxygenase in the rat skin by bradykinin and platelet activating factor: formation of 12(S)-HETE and hepoxilins, and actions on vascular permeability

In this study we set out to investigate whether the inflammatory agents, bradykinin (BK) and platelet activating factor (PAF), affect the lipoxygenase pathway in rat skin in vivo and whether the main products so formed may be involved in the inflammatory actions of these agents. In vitro preparations of epidermis were also investigated to determine whether lipoxygenases are stimulated by these agents. We also investigated the actions of arachidonic acid and 12(S)-HPETE as substrates for the lipoxygenases. Our results indicated that 12-lipoxygenase is actively and selectively stimulated in a dose-dependent way in both preparations by the administration of BK and PAF; the main product, 12-HETE, was shown by chiral analysis to be exclusively of the S-configuration, indicating that 12(S)-lipoxygenase was present in the rat skin and was stimulated by these inflammatory agents. Hepoxilins were also formed but to a lesser extent in both in vivo and in vitro preparations. In separate experiments, 12(S)-HETE administered intradermally on its own (40 ng/site), increased vascular permeability as also seen with bradykinin (100 ng/site) and PAF (10 ng/site). However, unlike previously observed with hepoxilin A3 administration, 12(S)-HETE did not stimulate the action of BK on vascular permeability, suggesting that the two compounds may have different mechanisms of action to enhance inflammation. These observations suggest that the vascular permeability and plasma extravasation observed with both inflammatory agents (BK and PAF) may be mediated at least in part through the activation of 12(S)-lipoxygenase, resulting in enhanced formation of 12(S)-HETE which causes acute inflammation.

Dopexamine attenuates endotoxin-induced microcirculatory changes in rat mesentery: role of beta2 adrenoceptors

OBJECTIVE

To investigate the influence of dopexamine on endotoxin-induced leukocyte adherence and on vascular permeability in postcapillary venules of rat mesentery.

DESIGN

Randomized, controlled trial.

SETTING

Experimental laboratory.

SUBJECTS

Twenty-seven male Wistar rats, weighing 250 to 350 g.

INTERVENTIONS

Rats received one of three treatments: a) infusion of Escherichia coli endotoxin without dopexamine pretreatment; b) infusion of endotoxin with dopexamine pretreatment; or c) infusion of endotoxin after pretreatment with dopexamine and ICI 118,551, a selective beta2-receptor antagonist.

MEASUREMENTS AND MAIN RESULTS

Leukocyte adherence, red blood cell velocity, and vessel diameters in postcapillary venules were evaluated using in vivo videomicroscopy. Vascular permeability was determined by measuring the extravasation of fluorescence-labeled albumin. Venular wall shear rate was calculated from red cell velocity and vessel diameter. Dopexamine attenuated both the increase in leukocyte adherence and vascular permeability during endotoxemia. The attenuating effect on leukocyte adherence could not be antagonized by the beta2-adrenoceptor antagonist. However, the attenuating effect on vascular permeability was antagonized by ICI 118,551. Dopexamine prevented a decrease in venular wall shear rate during endotoxemia. This effect was not influenced by ICI 118,551.

CONCLUSIONS

Dopexamine attenuates endotoxin-induced microcirculatory disturbances in rat mesentery. The attenuating effect on vascular permeability is a beta2-adrenoceptor-mediated process, whereas the beta2-adrenoceptor actions of dopexamine play no significant role in attenuating leukocyte adherence.

Inhaled flunisolide for acute severe asthma

This randomized, double-blind trial was designed to determine the benefit of high and cumulative doses of flunisolide added to salbutamol in patients with acute asthma in the emergency room (ER). Ninety-four patients who presented to an ER for treatment of an acute exacerbation of asthma were assigned in a randomized, double-blind fashion to receive salbutamol and placebo (n = 47) or salbutamol combined with flunisolide (n = 47). Both drugs were administered successively through a metered-dose inhaler and spacer at 10-min intervals for 3 h (400 microg of salbutamol and 1 mg of flunisolide every 10 min). In both groups, FEV1 and peak expiratory flow rate (PEFR) improved significantly over baseline values (p < 0.01). Results in the flunisolide group were significantly different from those in the placebo group at 90, 120, 150, and 180 min. Data analyzed separately in accord with the duration of the attack before presenting at the ER (< 24 or > or = 24 h) showed that the placebo > or = 24 h group produced a significantly lower FEV1 at 120, 150, and 180 min (p = 0.041) than did the remaining groups. Our data support the theory that high and cumulative doses of inhaled flunisolide administered by metered-dose inhaler with spacer and added to salbutamol are an effective therapy for patients with acute asthma and a prolonged duration of symptoms before ER presentation.

Effects of oral administration of purified micronized flavonoid fraction on increased microvascular permeability induced by various agents and on ischemia/reperfusion in the hamster cheek pouch

The effects of a clinically used purified micronized flavonoid fraction (S 5682) containing 90% diosmin and 10% hesperidin on increased microvascular permeability induced by histamine, bradykinin, and leukotriene B4 (LTB4) were investigated by intravital microscopy in the hamster cheek pouch preparation. The authors also investigated the effects of S 5682 on macromolecular permeability increase and leukocyte adhesion during ischemia-reperfusion by using the same preparation. S 5682, suspended in 10% lactose solution, or vehicle (10% lactose) was administered orally to male hamsters for ten days at 20 mg/kg/day (10 mg/kg twice a day). Fluorescein isothiocyanate (FITC)-labeled dextran (mol wt 150,000) was given intravenously, thirty minutes after completion of the cheek pouch preparation. The leukocytes were stained by continuous IV infusion of acridine orange (0.5 mg/kg/minute). Histamine (2 microM), bradykinin (1 microM), and LTB4 (0.01 microM), applied topically for five minutes, increased the number of fluorescent vascular leakage sites in postcapillary venules. A temporary ischemia with total circulatory arrest of the cheek pouch was obtained by clamping the neck of the everted pouch. The maximum number of leaky sites (per cm2 in the prepared area) that occurred either at five minutes after the beginning of each topical application or ten minutes after the onset of reperfusion was quantified in ultraviolet light microscopy. The results from 60 animals divided into 10 groups of 6 animals each are presented as means +/- SEM. In comparison with vehicle, S 5682 significantly inhibited the macromolecular permeability increasing effect of histamine (343.5 +/- 22.3 versus 207.5 +/- 32.0 leaks/cm2; P < 0.01), bradykinin (345.2 +/- 19.0 versus 206.2 +/- 21.6 leaks/cm2; P < 0.01), and LTB4 (353.3 +/- 27.5 versus 242.7 +/- 33.6 leaks/cm2; P < 0.05). At reperfusion, after thirty minutes of ischemia, S 5682 significantly decreased the observed macromolecular permeability (103.6 +/- 15.4 versus 42.6 +/- 9.3 leaks/cm2; P < 0.01). Flavonoid-treated animals also displayed a statistically significant lower number of adhering leukocytes to the venular endothelium (83.5 +/- 9.5 versus 48.4 +/- 12.3 per 6 mm2; P < 0.05). These results demonstrate that oral administration of S 5682 for ten days at 20 mg/kg body weight/day had a protective effect against leakage of macromolecules after application of permeability-increasing substances and during ischemia-reperfusion in the cheek pouch microvasculature. Since firm leukocyte attachment to the endothelial wall and subsequent emigration of leukocytes into the interstitium is a mechanism for tissue damage during inflammation, attenuation of this phenomenon during conditions of ischemia-reperfusion can in part explain previous observations that this purified micronized flavonoid fraction decreases edema formation. The present data illustrating the inhibitory effect of a clinically relevant dose of S 5682 on the inflammatory processes induced in this in vivo model of microcirculation may serve as a rational basis to explain its clinical efficacy.

Recent advances in the treatment of bronchiolitis and laryngitis

Progress has been made in the treatment for patients with croup and bronchiolitis in the past decade. By intervening with pharmacologic agents, a better outcome has been documented in children with these diseases. A lower probability of hospital admission means that fewer health care dollars need to be expended in this area. The present state of evidence substantiates the following. Bronchiolitis . Nebulized albuterol causes significant short-term improvement in clinical scores in bronchiolitic children, but there is no evidence that it reduces admission rates or decreases length of hospitalization. . Nebulized epinephrine results in significant improvement in clinical scores and airway resistance in children hospitalized with bronchiolitis and in the emergency department causes acute improvement in oxygenation, decreases length of time in the emergency department and admission rate to hospital. . There is no evidence to support the use of dexamethasone or other glucocorticosteroids for infants hospitalized with bronchiolitis. Croup . Nebulized budesonide or oral dexamethasone results in acute clinical improvement in outpatients with mild to moderate croup, reducing the need for hospitalization. . A combination of nebulized budesonide and oral dexamethasone may provide the best clinical outcome, although further evidence is needed to substantiate this . The required dose of oral dexamethasone may range from 0.15 mg/kg to 0.6 mg/kg for best clinical outcome. . Use of racemic epinephrine or L-epinephrine in the emergency department, especially when used concomitantly with glucocorticoids, does not require automatic hospital admission; a 3-hour observation period in the emergency department may suffice. . Use of intramuscular dexamethasone is difficult to justify in patients with croup who are able to ingest oral medications. Future studies need to examine dosing of glucocorticoids for inpatients with croup. In addition, an important question remains as to whether very mild croup patients (those with no evidence of respiratory distress) might benefit from glucocorticoids administered in the physician's office or the emergency department.

Prostacyclin counteracts the increase in capillary permeability induced by tumour necrosis factor-alpha

OBJECTIVE

To analyse how prostacyclin interferes with the short-term local circulatory effects of tumour necrosis factor-alpha (TNF alpha) in a skeletal muscle.

DESIGN

An autoperfused sympathectomised cat gastrocnemius muscle enclosed in a plethysmograph.

INTERVENTIONS

Arterial blood flow, total and segmental vascular resistances (large-bore arterial vessels, arterioles and veins), hydrostatic capillary pressure, tissue volume and capillary filtration coefficient were followed during local intra-arterial infusion of TNF alpha at various rates (2.5, 5.0 and 7.5 micrograms/kg per min) and during intra-arterial infusion of prostacyclin simultaneously with the highest dose of TNF alpha. The capillary filtration coefficient reflects the capillary surface for fluid exchange.

RESULTS

Arterial infusion of TNFx had no influence on vascular resistance up to 5.0 micrograms/kg per min but induced vasodilation at 7.5 micrograms/kg per min. No effects on the recorded hydrostatic capillary pressure were observed. The capillary filtration coefficient and the capillary filtration increased with the infusion rate of TNF alpha, the former by 55%. Simultaneous arterial infusion of prostacyclin (350 ng/kg per min) caused further vasodilation and an increase in hydrostatic capillary pressure and completely restored the capillary filtration coefficient to control. The TNF alpha-induced filtration was partly restored.

CONCLUSIONS

The local circulatory effect of TNF alpha is small apart from a graded increase in the capillary filtration coefficient, most likely reflecting an increase in the capillary permeability. The prostacyclin-induced decrease in capillary filtration coefficient most likely reflects a restoration of capillary permeability. The TNF alpha-induced transcapillary filtration is not fully reduced by prostacyclin due to a simultaneous increase in hydrostatic capillary pressure.

Dermal inflammation in primates, mice, and guinea pigs: attenuation by second-generation leukotriene B4 receptor antagonist, SC-53228

Granulocyte infiltration is a prominent feature of human psoriasis. Psoriatic lesional skin contains abnormally high amounts of immunoreactive leukotriene B4 (LTB4), a potent granulocyte chemotaxin in vivo and in vitro. SC-53228 [(+)-(S)-7-(3-}2-(cyclopropylmethyl)-3-methoxy-4- [(methylamino)carbonyl]phenoxy}propoxy}-3,4-dihydro-8-propyl-2H-1- benzopyran-2-propanoic acid], a second-generation LTB4 receptor antagonist, was tested topically and orally in phorbol ester-induced dermal inflammation in three species. Skin inflammation was induced by topical application of phorbol-12-myristate-13-acetate-(PMA/TPA) and assessed by ear thickness, levels of the neutrophil marker enzyme myeloperoxidase (MPO) and histological examination. In mice, SC-53228 inhibited inflammation with a topical ED50 value of 200 +/- 18 micrograms. When applied to guinea pigs, SC-53228 (100 micrograms) inhibited the MPO increase by 86%, while 1000 micrograms abrogated inflammation in rhesus macaques with no plasma accumulation of the drug. A 1% gel formulation was also efficacious in guinea pig PMA-induced epidermal inflammation. Furthermore, single oral dose administration to mice was efficacious (ED50 < 2.5 mg/kg) as was multidose administration to rhesus macaques. PMA-induced skin inflammation possesses some of the attributes of human psoriasis and an agent such as SC-53228 may have utility in the medical management of this condition.

In vivo effects of prostacyclin on segmental vascular resistances, on myogenic reactivity, and on capillary fluid exchange in cat skeletal muscle

OBJECTIVE

To analyze the local circulatory effects of prostacyclin in skeletal muscle.

DESIGN

A prospective experimental study.

SETTING

A university laboratory.

SUBJECTS

Twelve adult cats.

INTERVENTIONS

The study was performed on autoperfused, sympathectomized gastrocnemius muscle.

MEASUREMENTS AND MAIN RESULTS

Arterial blood flow, total and segmental vascular resistances (arterial vessels of > 25 microns, arterioles of < 25 microns, and veins), hydrostatic capillary pressure, tissue volume, myogenic reactivity, and the capillary filtration coefficient were followed. The capillary filtration coefficient reflects the functional capillary fluid exchange area. Myogenic reactivity was evaluated as the arteriolar resistance increase after a standardized decrease in extravascular pressure. Arterial infusion of prostacyclin decreased vascular resistance by approximately 50% at the highest dose given (500 ng/kg/min). This effect was more pronounced on the arterial side, especially in arterial vessels of > 25 microns. Hydrostatic capillary pressure increased by 1.9 +/- 0.3 mm Hg, causing fluid filtration. The relative fluid filtration was less than that value shown for some other vasodilator drugs (isoprenaline, calcium-channel blockers, thiopental) in this muscle preparation. Capillary filtration coefficient decreased by 25%. Myogenic reactivity was depressed but to a lesser extent than previously observed for other vasodilator mechanisms (muscle exercise, beta-adrenergic receptor stimulation, thiopental infusion, nifedipine infusion).

CONCLUSIONS

Prostacyclin is a vasodilator, both on the arterial and venous side, that restricts the increase in hydrostatic capillary pressure. The decrease in capillary filtration coefficient most likely reflects a decrease in capillary permeability, explaining the smaller relative filtration rate. The relatively well-preserved myogenic reactivity may imply a better preserved microvascular flow distribution and peripheral oxygen uptake.

Nebulized budesonide for children with mild-to-moderate croup

BACKGROUND

Although recent evidence has strongly supported the use of glucocorticoid therapy in children hospitalized with croup, the benefit of this therapy in children with less severe croup has not been documented. This randomized, double-blind trial compared a nebulized glucocorticoid, budesonide, with placebo in outpatients with mild-to-moderate croup.

METHODS

Children three months to five years of age were eligible for the study if their croup scores fell in the mild-to-moderate range (scores of 2 to 7 out of a possible 17). The patients were randomly assigned to receive either 2 mg (4 ml) of nebulized budesonide (27 children) or 4 ml of nebulized normal saline (27 children); they were then assessed hourly for up to four hours by investigators who were unaware of the assigned treatments.

RESULTS

The median croup score at entry into the study was 4 in both groups. At the final study assessment, the median score was significantly lower in the budesonide group than in the placebo group (1 vs. 3, P = 0.005). The patients in the budesonide group were discharged from the emergency department significantly earlier than those in the placebo group (P = 0.002). One week after enrollment, 21 patients assigned to placebo had received dexamethasone, as compared with 15 patients assigned to budesonide (P = 0.10), and 7 patients assigned to placebo had been admitted to the hospital, as compared with 1 patient assigned to budesonide (P = 0.05).

CONCLUSIONS

We conclude that nebulized budesonide leads to a prompt and important clinical improvement in children with mild-to-moderate croup who come to the emergency department.

Effects of two vasodilatory phosphodiesterase inhibitors on bradykinin-induced permeability increase in the hamster cheek pouch

Two inhibitors with selective effect on cyclic nucleotide phosphodiesterases (PDEs, preferentially hydrolyzing cAMP), milrinone (cGMP-inhibited PDE) and rolipram (cAMP-specific PDE) were studied for their effects on bradykinin-induced plasma leakage in comparison with the beta 2-receptor stimulant terbutaline. The dilation of arterioles induced by milrinone and rolipram was studied in the concentration range 10(-7)-10(-4) M. Maximal arteriolar dilation was 53% for milrinone at 10(-4) M and 28% for rolipram at 10(-4) M. The hamster cheek pouch preparation was used as prepared for intravital microscopy of fluorescein-labelled dextran, FITC-dextran. Bradykinin was applied topically to the cheek pouch at a final concentration of 4 x 10(-7) M and caused rapid and reversible increase in plasma leakage (number of leakage sites) from postcapillary venules. Milrinone (M), rolipram (R) and terbutaline (T) were also applied topically starting 5 min prior to bradykinin application and at final concentration of 10(-4) and 10(-5) M (M), 10(-5) and 10(-6) M (R) and 10(-7) M (T). These local concentrations resulted in significant (p < 0.05) and reversible inhibition of the bradykinin-induced response by 44% and 33% (M), 77% and 67% (R) and 46% (T). Combining M and R individually with T resulted in a significantly larger inhibition of the bradykinin response than with each of the drugs given separately.(ABSTRACT TRUNCATED AT 250 WORDS)

Profiling of eicosanoids in inflamed gall bladder wall by gas chromatography with selected-ion monitoring

The profiling of eicosanoids, including prostaglandin E2 (PGE2), prostaglandin F2 alpha (PGF2 alpha), 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), thromboxane B2 (TXB2) and leukotriene B4 (LTB4), in dog and human gall bladders was carried out by a combination of an effective and convenient clean-up procedure and gas chromatography with selected-ion monitoring. The clean-up procedure was based on the stepwise elution of their methyl ester derivatives from a silica gel column with n-hexane-ethyl acetate and ethyl acetate-methanol in various ratios. The LTB4 methyl ester was eluted with an n-hexane-ethyl acetate (2:1, v/v) fraction because LTB4 is more lipophilic than the other eicosanoids. The present method permitted the quantitation of trace amounts of eicosanoids, including LTB4, present in tissues in the order of pg/mg of protein, without interference from other endogenous substances. In experimental acalculous cholecystitis produced in dog, the levels of eicosanoids (except LTB4) were significantly changed. Of these eicosanoids, the level of 6-keto-PGF1 alpha was significantly higher in the seromuscular layer and correlated with the observed severe morphological changes. In human chronic cholecystitis with gallstones, the level of 6-keto-PGF1 alpha in the mucosal layer was significantly higher than that in the seromuscular layer. These data suggest that prostaglandin I2 may play an important pathophysiological role in the course of cholecystitis.

Modification of postischemic increase of leukocyte adhesion and vascular permeability in the hamster by Iloprost

This study of the postischemic events in the hamster cheek pouch showed that there is an increase in number of leukocytes adhering to the venular endothelium after reperfusion. It also showed that the stable prostacyclin analogue Iloprost could counteract both the postischemic increase in leukocyte adhesion and the postischemic increase in vascular permeability to macromolecules. The hamsters were anesthetized and the cheek pouch was everted and prepared for intravital microscopy. Temporary ischemia (30 min) was obtained using an expandable cuff placed around the proximal part of the cheek pouch. Fluorescein labelled dextran (FITC-dextran, Mw 150,000) was used as a tracer of macromolecular leakage from the postcapillary venules. Iloprost, given either topically (0.1 nM) or as an intravenous infusion (40 ng/kg/min), reduced the postischemic permeability increase (P less than 0.05) but did not affect the hemodynamics or the permeability response induced by histamine. It is proposed that these effects could be due to inhibition of leukocyte activation by Iloprost, indicating that these cells could play a role in the permeability increase during reperfusion after ischemia.

Inflammation of guinea pig dermis. Effects of leukotriene B4 receptor antagonist, SC-41930

Neutrophil (PMNL) infiltration is a prominent feature of human psoriasis. Psoriatic skin lesions contain abnormally high amounts of leukotriene B4 (LTB4), itself a potent PMNL chemoattractant both in vivo and in vitro. SC-41930 (7-[3-(4-acetyl-3-methoxy-2-propylphenoxy)-propoxy]-3,4-dihydro-8- propyl-2H-1-benzopyran-2-carboxylic acid), an orally active LTB4 receptor antagonist, was tested topically in models of skin inflammation induced by 200 nmol of the calcium ionophore A23187 or 200 micrograms phorbol-12-myristate-13-acetate (PMA) applied topically to the guinea pig ear as assessed by ear weight, levels of the PMNL marker enzyme myeloperoxidase (MPO), and histological examination (PMA model) at 4 and 18 h respectively. When coapplied topically with A23187 or PMA, SC-41930 significantly inhibited epidermal inflammation with ED50 values of 0.6 and 4 mg, respectively. SC-41930 treatment also was associated with lowered dermal LTB4 levels in both models. The PMA-induced skin inflammation model also was assessed histologically and revealed acanthosis, edema, PMNL infiltration, and rete ridge prominence as long as 96 h after a single application that was completely inhibited by SC-41930 topical coapplication. Furthermore, oral treatment (40 mg/kg) significantly reduced edema and inflammatory cell infiltration in both models. These models possess many of the characteristics of human psoriasis, and agents such as SC-41930 that demonstrate activity in these models may well have therapeutic utility in the treatment of human psoriasis.

Superoxide dismutase as an inhibitor of postischemic microvascular permeability increase in the hamster

The purpose was to elucidate the involvement of superoxide radical (O2-.) in the postischemic increase in the vascular permeability in the hamster cheek pouch. Cheek pouches of anesthetized hamsters were everted, prepared for intravital microscopy, and superfused with a bicarbonate buffered saline solution. Local ischemia for 30 min was obtained using a cuff placed around the proximal part of the cheek pouch. The vascular permeability in the postcapillary venules was quantified as leakage of intravenously injected fluorescein labeled dextran (FITC-dextran, Mw 150,000), using intravital microscopy and fluorimetry. There was a significant and reversible permeability increase after the reperfusion started. In the first series of experiments, combined intravenous infusion and topical application of human recombinant extracellular superoxide dismutase C (EC-SOD C) reduced the postischemic permeability response by 80%. Bovine CuZn-SOD given in exactly the same way reduced the response by 60%. In the second series of experiments, inactivated EC-SOD C was given to the control animals and active EC-SOD C was given to the treated animals. The topical treatment was excluded. Only active EC-SOD C reduced significantly the postischemic permeability increase when present during the ischemic period. Treatment with mannitol (i.v.) did not alter the postischemic response. Since active EC-SOD C and CuZn-SOD but not inactivated EC-SOD C effectively inhibited the response, we suggest that the superoxide anion is involved in the mediation of the postischemic permeability increase in the hamster.