Spinal Stenosis in Familial Transthyretin Amyloidosis.

Here we describe a patient with genetically confirmed ATTR, a family history of the disease and histological confirmation following carpal tunnel release surgery but no other manifestations. The first major neurological or systemic manifestation was cauda equina syndrome with ATTR deposits contributing to lumbar spinal stenosis. Recent gene therapy trials showed improvement in the neuropathy in TTR amyloidosis. This case highlights the need for awareness of the heterogeneous neurological phenotype seen in ATTR to aid earlier diagnosis especially now that disease modifying therapies are available.

A study of the neuropathy associated with transthyretin amyloidosis (ATTR) in the UK.

BACKGROUND: Hereditary transthyretin amyloidosis (ATTR) is usually characterised by a progressive peripheral and autonomic neuropathy often with associated cardiac failure and is due to dominantly inherited transthyretin mutations causing accelerated amyloid deposition. The UK population is unique in that the majority of patients have the T60A missense mutation in ATTR where tyrosine is replaced by adenine at position 60. This has been traced to a single founder mutation from north-west Ireland. The neuropathy phenotype is less well described than the cardiac manifestations in this group. METHODS: We present the findings from an observational cohort study of patients with ATTR attending the National Hospital Inherited Neuropathy Clinic between 2009 and 2013. Detailed clinical neurological and electrophysiological data were collected on all patients alongside correlating autonomic and cardiac assessments. Follow-up data were available on a subset. RESULTS: Forty-four patients with genetically confirmed ATTR were assessed; 37 were symptomatic; mean age at onset=62 years, range=38-75 years; 75.7% male. T60A was the most common mutation (17/37), followed by V30M (5/37). A severe, rapidly progressive, predominantly length dependent axonal sensorimotor neuropathy was the predominant phenotype. T60A patients were distinguished by earlier and more frequent association with carpal tunnel syndrome; a predominance of negative sensory symptoms at onset; significant vibration deficits; and a non-length dependent progression of motor deficit. Progression of the neuropathy was observed over a relatively short follow-up period (2 years) in 20 patients with evidence of clinically measurable annual change in Medical Research Council (MRC) sum score (-1.5 points per year) and Charcot Marie Tooth Neuropathy Score (CMTNS:2.7 points per year), and a congruent trend in the electrophysiological measures used. CONCLUSION: The description of the ATTR neuropathy phenotype, especially in the T60A patients, should aid early diagnosis as well as contribute to the understanding of its natural history.

Transthyretin V122I amyloidosis with clinical and histological evidence of amyloid neuropathy and myopathy.

Hereditary transthyretin amyloidosis (ATTR) is a genetically and clinically heterogeneous disease manifesting with predominant peripheral and autonomic neuropathy; cardiomyopathy, or both. ATTR V122I is the most common variant associated with non-neuropathic familial amyloid cardiomyopathy. We present an unusual case of V122I amyloidosis with features of amyloid neuropathy and myopathy, supported by histological confirmation in both sites and diffuse tracer uptake on (99m)Tc-3,3-Diphosphono-1,2-Propanodicarboxylic acid (DPD) scintigraphy throughout skeletal and cardiac muscle. A 64 year old Jamaican man presented with cardiac failure. Cardiac MR revealed infiltrative cardiomyopathy; abdominal fat aspirate confirmed the presence of amyloid, and he was homozygous for the V122I variant of transthyretin. He also described general weakness and EMG demonstrated myopathic features. Sural nerve and vastus lateralis biopsy showed TTR amyloid. The patient is being treated with diflunisal, an oral TTR stabilising agent. Symptomatic myopathy and neuropathy with confirmation of tissue amyloid deposition has not previously been described. Extracardiac amyloidosis has implications for diagnosis and treatment.

Oculoleptomeningeal Amyloidosis associated with transthyretin Leu12Pro in an African patient.

Oculoleptomeningeal amyloidosis is a rare manifestation of hereditary transthyretin (TTR) amyloidosis. Here, we present the first case of leptomeningeal amyloidosis associated with the TTR variant Leu12Pro mutation in an African patient. A 43-year-old right-handed Nigerian man was referred to our centre with rapidly progressive neurological decline. He presented initially with weight loss, confusion, fatigue, and urinary and erectile dysfunction. He then suffered recurrent episodes of slurred speech with right-sided weakness. He went on to develop hearing difficulties and painless paraesthesia. Neurological examination revealed horizontal gaze-evoked nystagmus, brisk jaw jerk, increased tone, brisk reflexes throughout and bilateral heel-shin ataxia. Magnetic resonance imaging showed extensive leptomeningeal enhancement. Cerebrospinal fluid analysis showed a raised protein of 6.4 g/dl. Nerve conduction studies showed an axonal neuropathy. Echocardiography was characteristic of cardiac amyloid. TTR gene sequencing showed that he was heterozygous for the leucine 12 proline mutation. Meningeal and brain biopsy confirmed widespread amyloid angiopathy. TTR amyloidosis is a rare cause of leptomeningeal enhancement, but should be considered if there is evidence of peripheral or autonomic neuropathy with cardiac or ocular involvement. The relationship between different TTR mutations and clinical phenotype, disease course, and response to treatment remains unclear.

A matched comparison of cyclophosphamide, bortezomib and dexamethasone (CVD) versus risk-adapted cyclophosphamide, thalidomide and dexamethasone (CTD) in AL amyloidosis.

Despite improvements in therapy amyloid light-chain (AL) amyloidosis, there are few studies comparing different regimens. Here we present a matched comparison with 69 patients in each cohort examining upfront therapy with cyclophosphamide, bortezomib and dexamethasone (CVD) vs cyclophosphamide, thalidomide and dexamethasone (CTD). On an intention-to-treat basis, the overall response rates were 71.0% vs 79.7% in the CVD and CTD arms, respectively, (P=0.32). A higher complete response (CR) rate was observed in the CVD arm (40.5%) vs CTD (24.6%), P=0.046. One-year overall survival (OS) was 65.2% and 66.7% for CVD and CTD, respectively (P=0.87). The median progression-free survival (PFS) was 28.0 and 14.0 m for CVD and CTD, respectively (P=0.039). In a landmark analysis assessing outcomes performed at 6 months, the CR rate with CVD was 59.6% vs 34.0% for CTD (P=0.03). The 1-year OS was 96% with CVD and 92% with CTD (P=0.40). The median PFS with CVD was not reached and was 19.2 m with CTD, P=0.028). In summary, both regimens are unable to overcome the high rate of early deaths in AL amyloidosis. However, CVD correlates with improved depth of response and superior PFS supporting its use in the frontline setting. Further optimisation and better supportive-care strategies are required to increase the proportion of patients fully benefiting from therapy.

Renal transplantation in systemic amyloidosis-importance of amyloid fibril type and precursor protein abundance.

Renal transplantation remains contentious in patients with systemic amyloidosis due to the risk of graft loss from recurrent amyloid and progressive disease. Outcomes were sought among all patients attending the UK National Amyloidosis Centre who received a renal transplant (RTx) between January 1978 and May 2011. A total of 111 RTx were performed in 104 patients. Eighty-nine percent of patients with end-stage renal disease (ESRD) due to hereditary lysozyme and apolipoprotein A-I amyloidosis received a RTx. Outcomes following RTx were generally excellent in these diseases, reflecting their slow natural history; median graft survival was 13.1 years. Only 20% of patients with ESRD due to AA, AL and fibrinogen amyloidosis received a RTx. Median graft survival was 10.3, 5.8 and 7.3 years in these diseases respectively, and outcomes were influenced by fibril precursor protein supply. Patient survival in AL amyloidosis was 8.9 years among those who had achieved at least a partial clonal response compared to 5.2 years among those who had no response (p = 0.02). Post-RTx chemotherapy was administered successfully to four AL patients. RTx outcome is influenced by amyloid type. Suppression of the fibril precursor protein is desirable in the amyloidoses that have a rapid natural history.

Solid organ transplantation in AL amyloidosis.

Vital organ failure remains common in AL amyloidosis. Solid organ transplantation is contentious because of the multisystem nature of this disease and risk of recurrence in the graft. We report outcome among all AL patients evaluated at the UK National Amyloidosis Centre who received solid organ transplants between 1984 and 2009. Renal, cardiac and liver transplants were performed in 22, 14 and 9 patients respectively, representing <2% of all AL patients assessed during the period. One and 5-year patient survival was 95% and 67% among kidney recipients, 86% and 45% among heart recipients and 33% and 22% among liver recipients. No renal graft failed due to recurrent amyloid during median (range) follow up of 4.8 (0.2-13.3) years. Median patient survival was 9.7 years among 8/14 cardiac transplant recipients who underwent subsequent stem cell transplantation (SCT) and 3.4 years in six patients who did not undergo SCT (p = 0.01). Amyloid was widespread in all liver transplant recipients. Solid organ transplantation has rarely been performed in AL amyloidosis, but these findings demonstrate feasibility and support a role in selected patients.

Evidence that 13-14 di-hydro, 15-keto prostaglandin D(2)-induced airway eosinophilia in guinea-pigs is independent of interleukin-5.

OBJECTIVE AND DESIGN: Prostaglandin D(2) (PGD(2)) has been shown to cause eosinophil, basophil and Th2 cell chemotaxis in vitro and in vivo through an action on the prostaglandin CRTH2 receptor. In the present study, the dependence of PGD(2)-induced eosinophil accumulation in vivo on interleukin-5 (IL-5) blood eosinophilia was investigated. MATERIALS: Guinea-pigs were exposed to aerosols of 13,14di-hydro 15-keto PGD(2) (DK-PGD(2)) or platelet activating factor (PAF) and the eosinophil content of the bronchoalveolar lavage fluid or blood determined. In some experiments, DK-PGD(2) was administered systemically and eosinophilia measured. RESULTS: Aerosols of DK-PGD(2) caused eosinophil accumulation in the lungs 24h after exposure. DK-PGD(2) (10 microg x ml(-1)) -induced airway eosinophilia was inhibited when animals were treated with the CRTH2 receptor antagonist ramatroban. 1-4h after exposure to DK-PGD(2) a significant decrease in blood eosinophil count was measured. The anti-IL-5 antibody TRFK-5 had no inhibitory effect of DK-PGD(2)-induced airway eosinophilia, but abolished airway eosinophilia induced by exposure of guinea-pigs to aerosols of PAF. Intracardiac injection of DK-PGD(2) induced a dose-related increase in blood eosinophil numbers. CONCLUSIONS: It is concluded that, in the guinea-pig, DK-PGD(2)-induced airway eosinophilia is mediated by an action on prostaglandin CRTH2 receptors and that this response appears to be independent of IL-5.

Characterisation of nicotine receptors on human peripheral blood mononuclear cells (PBMC).

AIM AND OBJECTIVE: The aim of the work was to characterise the nAChRs on human PBMC. METHOD: PBMC were isolated from human blood buffy coats provided by the blood transfusion service and were used for radioligand binding studies with [(3)H]-nicotine. RT-PCR experiments were used to determine nAChR subunit expression while immunoblotting experiments were used to confirm that nAChR subunits identified by RT-PCR were translated into protein. RESULTS: Binding studies suggested the presence of one binding site for (-)- nicotine on human peripheral blood lymphocytes. Competition studies showed that only (-)- nicotine, epibatidine and alpha-bungarotoxin, displaced radiolabelled nicotine from cells. RT-PCR studies demonstrated mRNA for alpha4, alpha5, alpha7, beta1 and beta2 nAChRs subunits in PBMC. Expression of mRNA for the a5 subunit of nAChR was observed in all lymphocyte samples tested. In contrast, the expression pattern of mRNAs for alpha4, alpha7, beta1, and beta2 mRNAs subunits of nAChRs, varied between samples. Western blot analysis showed that protein for alpha4, alpha5, and alpha7 and beta2 nAChR subunits was expressed in most, but not all of the PBMC samples tested but some of the bands obtained were faint. CONCLUSION: The results obtained suggest that human PBMC contain nAChRs containing alpha4beta2, alpha4beta2alpha5, and/or alpha7 subunits.

Investigation of nicotine binding to THP-1 cells: evidence for a non-cholinergic binding site.

Nicotine is known to modulate immune function, but reports have produced conflicting evidence as to whether nicotinic acetylcholine (nACh) receptors are responsible for these effects. This study was designed to examine the identity of nicotine-binding sites on immune cells using a human leukaemic monocytic cell line, THP-1, that is known to have functions that are modulated by nicotine. Binding studies were performed on THP-1 whole cells using [3H]nicotine as a probe to analyse any possible nicotine-binding sites on these cells. Saturation analysis of THP-1 cells revealed the presence of 2 distinct binding sites; one with a K(d1) of 3.5 +/- 2.1 x 10(-9) M and a B(max1) of 4100 +/- 560 sites/cell (designated the high-affinity site) and the other with a K(d2) of 27 +/- 9.2 x 10(-9) M and a B(max2) of 11,600 +/- 630 sites/cell (low-affinity site). Competition analysis revealed that one site had an affinity to a range of cholinergic ligands including epibatidine and cytisine. When saturation analysis of [3H](-)-nicotine to THP-1 cells was performed in the presence of 1 x 10(-6) M epibatidine, only one binding site was detected. Comparisons of K(d) and B(max) values showed that the high-affinity site was not occluded by epibatidine. No drugs tested displayed any affinity for the high-affinity site except the two enantiomers of nicotine. The high-affinity site was shown to be stereoselective for the (+)-enantiomer of nicotine as shown by K(i) values produced by competition analysis in the presence of 1 x 10(-6) M epibatidine. These values were 5.7 +/- 0.32 x 10(-11) M and 1.9 +/- 4.9 x 10(-9) M for (+)-nicotine and (-)-nicotine, respectively. This study presents evidence for a possible non-cholinergic binding site that may play a role in the mechanism of immunomodulation by nicotine.

Reactive oxygen species generation and histamine release by activated mast cells: modulation by nitric oxide synthase inhibition.

1. We have examined the generation of intracellular reactive oxygen species (ROS) and release of histamine by rat peritoneal mast cells (RPMC) in response to stimulation with antigen (ovalbumin), compound 48/80, nerve growth factor (NGF) and substance P (SP). 2. We have also examined the effects of the non-specific nitric oxide synthase inhibitor, L-NAME (100 microM) upon the release of histamine and generation of intracellular ROS in response to the named secretagogues. 3. Ovalbumin (100 - 1000 microg ml-1), compound 48/80 (0.1 - 100 microg ml-1), NGF (0.1 - 100 microg ml-1), and SP (5 - 50 microM), caused a concentration-dependent release of histamine from RPMC. 4. Ovalbumin (1 ng ml-1 - 0.1 microg ml-1), compound 48/80 (1 - 100 microg ml-1), NGF (1 pg ml-1 - 1 microg ml-1), and SP (0.005 - 50 microM) caused a concentration-dependent generation of intracellular ROS by RPMC. 5. Pre-incubation of RPMC with L-NAME (100 microM) caused a significant enhancement of both histamine release and intracellular ROS from RPMC in response to ovalbumin, compound 48/80, NGF and SP. 6. Our data demonstrate that NGF, SP and ovalbumin are capable of causing intracellular ROS generation by RPMC at lower concentrations than those causing significant histamine release and we speculate that this may contribute to the activation of cytokine production. 7. The data also show that NO modulates histamine release, and ROS generation in response to the secretagogues used. This may have significance in pathologies where NO synthesis is decreased, leading to an increased activation of mast cells.

A comparison of the inhibitory effects of budesonide, beclomethasone dipropionate, dexamethasone, hydrocortisone and tixocortol pivalate on cytokine release from leukocytes recovered from human bronchoalveolar lavage.

OBJECTIVE: The potency of budesonide, beclomethasone dipropionate (BDP), dexamethasone, hydrocortisone and tixocortol pivalate as inhibitors of interleukin-5 (IL-5) and interferon-gamma (IFNgamma) release from human bronchoalveolar lavage cells in vitro were compared. METHODS: BAL leukocytes were obtained from patients undergoing bronchoscopy for diagnostic purposes. BAL leukocytes were activated with PHA (10 microg/ml) and PMA (10 ng/ml) and cultured for 48 h in the presence or absence of glucocorticoids. Culture supernatants were assayed for cytokines by ELISA. RESULTS: Budesonide (10(-9) to 10(-7) M) and BDP (10(-8) to 10(-6) M) were the most potent glucocorticoids tested. Dexamethasone (10(-7) to 10(-5) M) was less potent, and the maximum inhibitory effect of dexamethasone was less than that produced by than budesonide or BDP. Tixocortol pivalate (10(-6) to 3 x 10(-5) M) caused a concentration-related inhibition of IL-5 release but only the highest concentration tested inhibited the release of IFNgamma. Hydrocortisone (10(-4) M) inhibited IL-5 and IFNgamma release. CONCLUSION: We conclude that, unlike the other glucocorticoids tested, tixocortol pivalate appeared to be a selective inhibitor of IL-5 release. Possible mechanisms for this selectivity are discussed.

Predator-mediated interactions between and within guilds of nesting songbirds: experimental and observational evidence.

Apparent competition (i.e., a mutually negative indirect interaction between prey species through shared predation) arises when predator abundance or foraging effort increases with total prey availability. We review and formalize several patch-use models from which we derive predictions for how the degree of coupling (from the predators' perspective) between nesting guilds (defined as species nesting within a vegetation stratum) affects the outcome of shared predation. We then determine which model best applies to nest predation on woodland songbirds and artificial nests by a natural population of raccoons. Using artificial nests, we showed that increasing the density of nests placed either in shrubs or on the ground increased overall predation (i.e., proportion of nests) on both types. We also tested for apparent competition between American robin and wood thrush, two coexisting woodland songbirds that commonly nest within the shrub stratum. Nest predation increased for wood thrushes but not robins as the combined density of robin and thrush nests within two individual substrate types, Lonicera and Rhamnus, increased. Thus, we documented apparent competition both within and among nesting guilds. We discuss the possible relevance of this interaction in determining species diversity, particularly in the light of increasing generalist nest predators through anthropogenically driven changes in human-altered landscapes.

Adenosine A3 receptors promote degranulation of rat mast cells both in vitro and in vivo.

OBJECTIVE: To investigate the effects of adenosine receptor agonists and antagonists on 5-HT release from rat isolated pleural mast cells and on plasma protein extravasation in the skin of conscious rats. In vitro METHODS: Rat isolated pleural mast cells were loaded with [14C] 5-HT, sensitised with mouse monoclonal anti-DNP and then challenged with human serum albumin-DNP. DNP-stimulated 5-HT release from mast cells was determined. In vivo METHODS: Rats, loaded intravenously with [125I] human serum albumin, were injected intradermally with adenosine agonists at sites on the back. 30 min later plasma protein extravasation at each injection site was determined. RESULTS: In isolated mast cells, each adenosine agonist enhanced DNP-induced 5-HT release, N6-(3-iodobenzyl)-5-(N-methyl-carboxamidoadenosine), (IB-MECA), being the most potent agonist. The adenosine A1/A2 antagonist, 8-phenyltheophylline (8-PT), had no effect on the response to IB-MECA. In contrast, 3-(4-amino-iodobenzyl)-8-[4-[[[carboxy]methyl]oxy]phenyl]-1-propylxanthi ne, (I-ABOPX), inhibited (pA2 6.2) the IB-MECA responses. In the skin of conscious rats, intradermal IB-MECA produced a marked plasma protein extravasation (PPE) which was mimicked by N6-2-(4-aminophenyl)-ethyladenosine (APNEA). The PPE produced by IB-MECA was not affected by either 8-PT or CGS15943A, but was virtually abolished by cyproheptadine and in rats pre-treated with Compound 48/80. CONCLUSIONS: These results indicate that stimulation of adenosine A3 receptors both enhances degranulation in vitro and directly produces degranulation of rat mast cells in vivo.

Inhibition of PAF-, LPS-, and cytokine-induced granulocyte accumulation in guinea pig lung by dexamethasone: evidence that inhibition of IL-5 release is responsible for the selective inhibition of eosinophilia by glucocorticoids in guinea-pigs.

The potency of dexamethasone has been determined as an inhibitor of intratracheally administered platelet activating factor- (PAF), or interleukin (IL)-5-induced eosinophilia, and of lipopolysaccharide-(LPS), tumour necrosis factor alpha-(TNF alpha) or cytokine-induced neutrophil chemoattractant- (CINC) induced neutrophilia in guinea-pig lungs. Dexamethasone was a potent inhibitor of PAF- induced eosinophil accumulation, but higher doses of dexamethasone were required to inhibit IL-5-induced eosinophilia. LPS-induced neutrophilia was less sensitive to the inhibitory effects of dexamethasone, than PAF-induced eosinophilia. Both LPS- and TNF alpha-induced neutrophilia were inhibited by the same doses of dexamethasone. In contrast, higher doses of dexamethasone were required to inhibit CINC-induced neutrophilia. Since data in the literature show that PAF-induced eosinophilia in guinea-pig lungs is dependent on the generation of IL-5, it is concluded that inhibition of this response, by dexamethasone, is due to inhibition of release of IL-5. Similarly, although data in the literature show that LPS-induced neutrophilia is dependent on the generation of TNF alpha, it is concluded that inhibition of this response, by glucocorticoids, is due to an action on an event which occurs after the release of TNF alpha, possibly through inhibition of chemokine release.

Inhibition of some aspects of acute inflammation of guinea-pig lung by intraperitoneal dexamethasone and mifepristone: demonstration of agonist activity of mifepristone in the guinea-pig.

We have determined the inhibitory activity of dexamethasone as an inhibitor of histamine-induced plasma protein extravasation (PPE) in guinea-pig lung and skin, and of lipopolysaccharide (LPS)-induced neutrophilia and platelet activating factor (PAF)-induced eosinophilia in guinea-pig lungs. Dexamethasone inhibited PAF-induced eosinophilia in guinea-pig lung (ED50 1.4 mg/kg i.p.). Higher doses of dexamethasone were required to inhibit LPS-induced neutrophilia (ED50 10.8 mg/kg i.p.). However, at doses up to 150 mg/kg i.p. dexamethasone did not inhibit histamine-induced plasma protein extravasation (PPE) in guinea-pig lung, but did inhibit PPE in guinea-pig skin. These preparations have previously been shown to be equally sensitive to inhibition by the beta 2-adrenoceptor agonist salmeterol. Dexamethasone inhibited PAF-induced eosinophilia (5 mg/kg) or LPS-induced neutrophilia (50 mg/kg) when given 3 h or 1 h prior to challenge. Inhibitory activity was lost when dexamethasone was administered 23 h prior to LPS or 1 h after PAF. The glucocorticoid antagonist mifepristone (1-100 mg/kg i.p.) caused dose-related inhibition of PAF-induced eosinophilia but not of LPS-induced neutrophilia. The highest dose of mifepristone used (100 mg/kg) did not reverse the inhibitory actions of dexamethasone (50 mg/kg) on LPS-induced neutrophilia. We suggest that the different inhibitory activity of dexamethasone in the preparations studied indicates differences in the sensitivity of the target cells involved to inhibition by dexamethasone. We also suggest that inhibition of PAF-induced eosinophilia by mifepristone reflects the partial agonist activity of this agent, demonstrated by others in different experimental systems.

Comparison of the anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung.

1. We have compared some anti-inflammatory properties of formoterol, salbutamol and salmeterol in guinea-pig skin and lung. 2. Intradermal formoterol (1 x 10(-10) to 1 x 10(-8) mol/site), salbutamol (1 x 10(-8) and 1 x 10(-7) mol/site) and salmeterol (1 x 10(-8) and 1 x 10(-7) mol/site) inhibited bradykinin-induced plasma protein extravasation (PPE) in guinea-pig skin. A maximally effective dose of formoterol (1 x 10(-9) mol/site) and salbutamol (1 x 10(-8) mol/site) inhibited PPE in guinea-pig skin for 2-4 h and 1-2 h respectively, whereas salmeterol (1 x 10(-8) mol/site) was effective for > 6 h. 3. Inhaled formoterol (nebuliser concentration 0.1 to 100 micrograms ml-1 inhibited histamine-induced plasma protein extravasation (PPE) in guinea-pig lung, with significant inhibition being observed at 10 and 100 micrograms ml-1. Formoterol (100 micrograms ml-1) inhibited PPE in guinea-pig lung for 2-4 h, a duration of action intermediate between that previously obtained for salbutamol (1 h) and salmeterol (> 6 h). 4. Formoterol, like salbutamol, had no effect on neutrophil accumulation or granulocyte-dependent PPE (zymosan-induced) in guinea-pig skin. Formoterol inhibited neutrophil accumulation (lipopolysaccharide-induced) in guinea-pig lung but at doses greater than those required to inhibit granulocyte-independent PPE (histamine-induced). In contrast, salmeterol inhibited neutrophil accumulation and granulocyte-dependent PPE in guinea-pig skin and inhibited neutrophil accumulation in guinea-pig lung at doses which inhibit granulocyte-independent PPE. 5. Inhaled formoterol (nebuliser concentration 100 microg ml-1) and salmeterol (100 microg ml-1) both inhibited PAF-induced eosinophil accumulation in guinea-pig lung. However, unlike salmeterol, this effect of formoterol was observed only at suprabronchodilator doses.6. We conclude that to inhibit neutrophil accumulation, at doses which inhibit granulocyte-independent PPE, agonists acting at beta-adrenoceptors on vascular endothelium require a duration of action greater than that of salbutamol and formoterol. However, we speculate that the mechanism of inhibition of eosinophil accumulation in guinea-pig lung by beta2-adrenoceptor agonists may involve an action on beta2-adrenoceptors on a cell type other than the endothelial cell.

The pharmacology of salmeterol.

Salmeterol was developed to provide prolonged bronchodilatation to control nocturnal symptoms and improve maintenance therapy in asthmatic patients. Salmeterol is > 10,000 times more lipophilic than salbutamol and has greater affinity for the beta 2-adrenoceptor. Membrane binding is non-competitive and dissociation is slow so that its effects last for many hours. Despite this, salmeterol does not accumulate in tissues. Its mechanism of action can be explained by binding to a specific exo-site domain of the beta 2-receptor protein to produce continuous stimulation of the active site of the receptor, which gives salmeterol a profile of pharmacological activity unlike that of other beta 2-agonists. Due to its potent and prolonged activation of beta 2-adrenoceptors in airway smooth muscle cells, endothelial cells, mast cells and epithelial cells, salmeterol induces prolonged bronchodilatation, reduced vascular permeability, inhibition of inflammatory mediators, stimulation of ciliary function and modulation of ion and water transport across the bronchial mucosa.