Impact of Mitochondrial Ca2+-Sensitive Potassium (mBKCa) Channels in Sildenafil-Induced Cardioprotection in Rats

Background

Mitochondrial large-conductance Ca²⁺-sensitive potassium (mBK_Ca) channels are involved in myocardial ischemic preconditioning. Their role in sildenafil-induced cardioprotection is unknown. We investigated whether sildenafil-induced acute cardioprotection is mediated by activation of mBK_Ca channels in the rat heart in vitro.

Methods

Male Wistar rats (n = 8 per group) were randomized and anesthetized with pentobarbital (90 mg/kg). Hearts were isolated, mounted on a Langendorff system and perfused with Krebs-Henseleit buffer at a constant pressure of 80 mmHg. Hearts underwent 30 min of global ischemia followed by 60 min of reperfusion. At the end of the experiments infarct size was determined by TTC staining. In the control group rats were not further treated. Sildenafil (3 μM) was administered over 10 min before the beginning of ischemia. The mBK_Ca channel inhibitor paxilline (1 μM) was administered with and without sildenafil before the onset of ischemia. The pathway underlying sildenafil-induced cardioprotection was further investigated with the protein kinase G blocker KT5823 (1 μM). Myocardial cGMP concentration was measured by ELISA. Data (mean±SD) were analysed with a one and two-way analysis of variance as appropriate.

Results

In control animals infarct size was 52±8%. Sildenafil increased cGMP concentration and reduced infarct size to 35±6% (P<0.05 vs. control). Paxilline and KT5823 completely blocked sildenafil-induced cardioprotection (paxilline+sildenafil: 50±8%, KT5823+sildenafil: 45±8%; both P<0.05 vs. sildenafil). Functional heart parameters and coronary flow were not different between the study groups.

Conclusion

This study shows that in male rats protein kinase G-dependent opening of mBK_Ca channels plays a pivotal role in sildenafil-induced cardioprotection.     

Prevention of bronchial hyperreactivity in a rat model of precapillary pulmonary hypertension

Background

The development of bronchial hyperreactivity (BHR) subsequent to precapillary pulmonary hypertension (PHT) was prevented by acting on the major signalling pathways (endothelin, nitric oxide, vasoactive intestine peptide (VIP) and prostacyclin) involved in the control of the pulmonary vascular and bronchial tones.

Methods

Five groups of rats underwent surgery to prepare an aorta-caval shunt (ACS) to induce sustained precapillary PHT for 4 weeks. During this period, no treatment was applied in one group (ACS controls), while the other groups were pretreated with VIP, iloprost, tezosentan via an intraperitoneally implemented osmotic pump, or by orally administered sildenafil. An additional group underwent sham surgery. Four weeks later, the lung responsiveness to increasing doses of an intravenous infusion of methacholine (2, 4, 8 12 and 24 μg/kg/min) was determined by using the forced oscillation technique to assess the airway resistance (Raw).

Results

BHR developed in the untreated rats, as reflected by a significant decrease in ED₅₀, the equivalent dose of methacholine required to cause a 50% increase in Raw. All drugs tested prevented the development of BHR, iloprost being the most effective in reducing both the systolic pulmonary arterial pressure (Ppa; 28%, p = 0.035) and BHR (ED₅₀ = 9.9 ± 1.7 vs. 43 ± 11 μg/kg in ACS control and iloprost-treated rats, respectively, p = 0.008). Significant correlations were found between the levels of Ppa and ED₅₀ (R = -0.59, p = 0.016), indicating that mechanical interdependence is primarily responsible for the development of BHR.

Conclusions

The efficiency of such treatment demonstrates that re-establishment of the balance of constrictor/dilator mediators via various signalling pathways involved in PHT is of potential benefit for the avoidance of the development of BHR.     

In vivo CD8+ T Cell Dynamics in the Liver of Plasmodium yoelii Immunized and Infected Mice

Plasmodium falciparum malaria remains one of the most serious health problems globally and a protective malaria vaccine is desperately needed. Vaccination with attenuated parasites elicits multiple cellular effector mechanisms that lead to Plasmodium liver stage elimination. While granule-mediated cytotoxicity requires contact between CD8+ effector T cells and infected hepatocytes, cytokine secretion should allow parasite killing over longer distances. To better understand the mechanism of parasite elimination in vivo, we monitored the dynamics of CD8+ T cells in the livers of naïve, immunized and sporozoite-infected mice by intravital microscopy. We found that immunization of BALB/c mice with attenuated P. yoelii 17XNL sporozoites significantly increases the velocity of CD8+ T cells patrolling the hepatic microvasculature from 2.69±0.34 μm/min in naïve mice to 5.74±0.66 μm/min, 9.26±0.92 μm/min, and 7.11±0.73 μm/min in mice immunized with irradiated, early genetically attenuated (Pyuis4-deficient), and late genetically attenuated (Pyfabb/f-deficient) parasites, respectively. Sporozoite infection of immunized mice revealed a 97% and 63% reduction in liver stage density and volume, respectively, compared to naïve controls. To examine cellular mechanisms of immunity in situ, naïve mice were passively immunized with hepatic or splenic CD8+ T cells. Unexpectedly, adoptive transfer rendered the motile CD8+ T cells from immunized mice immotile in the liver of P. yoelii infected mice. Similarly, when mice were simultaneously inoculated with viable sporozoites and CD8+ T cells, velocities 18 h later were also significantly reduced to 0.68±0.10 μm/min, 1.53±0.22 μm/min, and 1.06±0.26 μm/min for CD8+ T cells from mice immunized with irradiated wild type sporozoites, Pyfabb/f-deficient parasites, and P. yoelii CS_280–288 peptide, respectively. Because immobilized CD8+ T cells are unable to make contact with infected hepatocytes, soluble mediators could potentially play a key role in parasite elimination under these experimental conditions.     

A randomised dose-ranging study of tiotropium Respimat? in children with symptomatic asthma despite inhaled corticosteroids

Background

A considerable number of children with asthma remain symptomatic despite treatment with inhaled corticosteroids, resulting in significant morbidity, reduced quality of life, increased healthcare costs and lost school days. The aim of our study was to assess the efficacy, safety and tolerability of once-daily tiotropium Respimat® 5 μg, 2.5 μg and 1.25 μg add-on to medium-dose inhaled corticosteroids, with or without a leukotriene modifier, in children aged 6–11 years with symptomatic asthma.

Methods

In this Phase II, double-blind, placebo-controlled, incomplete-crossover, dose-ranging study, patients were randomised to receive three of the four treatments evaluated: once-daily tiotropium Respimat® 5 μg, 2.5 μg or 1.25 μg or placebo Respimat®, in the evening during the 12-week (three × 4-week) treatment period.

Results

In total, 76, 74, 75 and 76 patients aged 6–11 years received tiotropium Respimat® 5 μg, 2.5 μg, 1.25 μg and placebo Respimat®, respectively. For the primary end point (peak forced expiratory volume in 1 second measured within 3 hours post-dosing), the adjusted mean responses with tiotropium Respimat® 5 μg (272 mL), 2.5 μg (290 mL) and 1.25 μg (261 mL) were significantly greater than with placebo Respimat® (185 mL; p = 0.0002, p < 0.0001 and p = 0.0011, respectively). The safety and tolerability of all doses of tiotropium Respimat® were comparable with those of placebo Respimat®, with no serious adverse events and no events leading to discontinuation.

Conclusions

Tiotropium Respimat® add-on to medium-dose inhaled corticosteroids, with or without a leukotriene modifier, was efficacious in paediatric patients with symptomatic asthma and had comparable safety and tolerability with placebo Respimat®.

Trial registration

ClinicalTrials.gov identifier {"type":"clinical-trial","attrs":{"text":"NCT01383499","term_id":"NCT01383499"}}NCT01383499

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0175-9) contains supplementary material, which is available to authorized users.     

Iloprost-induced desensitization of the prostacyclin receptor in isolated rabbit lungs

Background

The rapid desensitization of the human prostacyclin (IP) in response to agonist binding has been shown in cell culture. Phosphorylation of the IP receptor by protein kinase C (PKC) has been suggested to be involved in this process.

Methods and results

In this study we investigated the vasodilatory effects of iloprost, a stable prostacyclin analogue, in perfused rabbit lungs. Continuous infusion of the thromboxane mimetic U46619 was employed to establish stable pulmonary hypertension. A complete loss of the vasodilatory response to iloprost was observed in experiments with continuous iloprost perfusion, maintaining the intravascular concentration of this prostanoid over a 180 min period. When lungs under chronic iloprost infusion were acutely challenged with inhaled iloprost, a corresponding complete loss of vasoreactivity was observed. This desensitization was not dependent on upregulation of cAMP-specific phosphodiesterases or changes in adenylate cyclase activity, as suggested by unaltered dose-response curves to agents directly affecting these enzymes. Application of a prostaglandin E1 receptor antagonist 6-isopropoxy-9-oxoxanthene-2-carboxylic acid (AH 6809) or the PKC inhibitor bisindolylmaleimide I (BIM) enhanced the vasodilatory response to infused iloprost and partially prevented tachyphylaxis.

Conclusion

A three-hour infusion of iloprost in pulmonary hypertensive rabbit lungs results in complete loss of the lung vasodilatory response to this prostanoid. This rapid desensitization is apparently not linked to changes in adenylate cyclase and phosphodiesterase activation, but may involve PKC function and co-stimulation of the EP1 receptor in addition to the IP receptor by this prostacyclin analogue.     

Acute Effects of Aerosolized Iloprost in COPD Related Pulmonary Hypertension - A Randomized Controlled Crossover Trial

Background

Inhaled iloprost potentially improves hemodynamics and gas exchange in patients with chronic obstructive pulmonary disease (COPD) and secondary pulmonary hypertension (PH).

Objectives

To evaluate acute effects of aerosolized iloprost in patients with COPD-associated PH.

Methods

A randomized, double blind, crossover study was conducted in 16 COPD patients with invasively confirmed PH in a single tertiary care center. Each patient received a single dose of 10 µg iloprost (low dose), 20 µg iloprost (high dose) and placebo during distinct study-visits. The primary end-point of the study was exercise capacity as assessed by the six minute walking distance.

Results

Both iloprost doses failed to improve six-minute walking distance (p = 0.36). Low dose iloprost (estimated difference of the means −1.0%, p = 0.035) as well as high dose iloprost (−2.2%, p<0.001) significantly impaired oxygenation at rest. Peak oxygen consumption and carbon dioxide production differed significantly over the three study days (p = 0.002 and p = 0.003, accordingly). As compared to placebo, low dose iloprost was associated with reduced peak oxygen consumption (−76 ml/min, p = 0.002), elevated partial pressure of carbon dioxide (0.27 kPa, p = 0.040) and impaired ventilation during exercise (−3.0l/min, p<0.001).

Conclusions

Improvement of the exercise capacity after iloprost inhalation in patients with COPD-associated mild to moderate PH is very unlikely.

Trial Registration

Controlled-Trials.com ISRCTN61661881     

Sildenafil Citrate for Prophylaxis of Nephropathy in an Animal Model of Contrast-Induced Acute Kidney Injury

Contrast-induced acute kidney injury (CIAKI) is one of the commonest complications associated with contrast media (CM). Although the exact etiology of CIAKI remains unclear, one hypothesis involves vasoconstriction of afferent arterioles resulting in renal ischemia. Increased renal blood flow, therefore, might represent an attractive target for the treatment of CIAKI. In this study we evaluated the protective effects of the phosphodiesterase type 5 (PDE5) inhibitor, sildenafil citrate, in a rabbit model of CIAKI. New Zealand white rabbits were used due to their susceptibility to CIAKI. To evaluate the effects of sildenafil, the drug was administered before CM infusion and repeatedly throughout the remainder of the experiment (6 mg/kg, p.o.). Animals were sacrificed after 48 hours and kidneys were prepared for histological evaluation. Intravenous administration of CM produced marked kidney injury. Serum creatinine concentrations were elevated within two hours of the infusion and remained elevated for the duration of the experiment. Histological evaluation of the kidneys revealed significant tubular necrosis. The effects of the CM were dose dependent. Treatment with sildenafil was associated with lesser degree of histological injury, attenuation in markers of acute kidney injury (48 hour creatinine 1.54±0.21 versus 4.42±1.31 mg/dl, p<0.05) and reduction in electrolyte derangement (percent change in serum K⁺ at 48 hours 2.55±3.80% versus 15.53±4.47%, p<0.05; serum Na⁺ at 48 hours −0.14±0.26% versus −1.97±1.29%, p = 0.20). The results suggest a possible role for PDE5 inhibitors in the treatment of CIAKI and warrant further evaluation to determine the exact mechanism of protection.     

Structural Basis for the Recognition of Tyrosine-based Sorting Signals by the μ3A Subunit of the AP-3 Adaptor Complex

Tyrosine-based signals fitting the YXXØ motif mediate sorting of transmembrane proteins to endosomes, lysosomes, the basolateral plasma membrane of polarized epithelial cells, and the somatodendritic domain of neurons through interactions with the homologous μ1, μ2, μ3, and μ4 subunits of the corresponding AP-1, AP-2, AP-3, and AP-4 complexes. Previous x-ray crystallographic analyses identified distinct binding sites for YXXØ signals on μ2 and μ4, which were located on opposite faces of the proteins. To elucidate the mode of recognition of YXXØ signals by other members of the μ family, we solved the crystal structure at 1.85 Å resolution of the C-terminal domain of the μ3 subunit of AP-3 (isoform A) in complex with a peptide encoding a YXXØ signal (SDYQRL) from the trans-Golgi network protein TGN38. The μ3A C-terminal domain consists of an immunoglobulin-like β-sandwich organized into two subdomains, A and B. The YXXØ signal binds in an extended conformation to a site on μ3A subdomain A, at a location similar to the YXXØ-binding site on μ2 but not μ4. The binding sites on μ3A and μ2 exhibit similarities and differences that account for the ability of both proteins to bind distinct sets of YXXØ signals. Biochemical analyses confirm the identification of the μ3A site and show that this protein binds YXXØ signals with 14–19 μm affinity. The surface electrostatic potential of μ3A is less basic than that of μ2, in part explaining the association of AP-3 with intracellular membranes having less acidic phosphoinositides.     

Inhibition of purine phosphoribosyltransferases of Ehrlich ascites-tumour cells by 6-mercaptopurine

1. The formation of adenosine 5′-phosphate, guanosine 5′-phosphate and inosine 5′-phosphate from [8-¹⁴C]adenine, [8-¹⁴C]guanine and [8-¹⁴C]hypoxanthine respectively in the presence of 5-phosphoribosyl pyrophosphate and an extract from Ehrlich ascites-tumour cells was assayed by a method involving liquid-scintillation counting of the radioactive nucleotides on diethylaminoethylcellulose paper. The results obtained with guanine were confirmed by a spectrophotometric assay which was also used to assay the conversion of 6-mercaptopurine and 5-phosphoribosyl pyrophosphate into 6-thioinosine 5′-phosphate in the presence of 6-mercaptopurine phosphoribosyltransferase from these cells. 2. At pH 7·8 and 25° the Michaelis constants for adenine, guanine and hypoxanthine were 0·9 μm, 2·9 μm and 11·0 μm in the assay with radioactive purines; the Michaelis constant for guanine in the spectrophotometric assay was 2·6 μm. At pH 7·9 the Michaelis constant for 6-mercaptopurine was 10·9 μm. 3. 25 μm-6-Mercaptopurine did not inhibit adenine phosphoribosyltransferase. 6-Mercaptopurine is a competitive inhibitor of guanine phosphoribosyltransferase (K_i 4·7 μm) and hypoxanthine phosphoribosyltransferase (K_i 8·3 μm). Hypoxanthine is a competitive inhibitor of guanine phosphoribosyltransferase (K_i 3·4 μm). 4. Differences in kinetic parameters and in the distribution of phosphoribosyltransferase activities after electrophoresis in starch gel indicate that different enzymes are involved in the conversion of adenine, guanine and hypoxanthine into their nucleotides. 5. From the low values of K_i for 6-mercaptopurine, and from published evidence that ascites-tumour cells require supplies of purines from the host tissues, it is likely that inhibition of hypoxanthine and guanine phosphoribosyltransferases by free 6-mercaptopurine is involved in the biological activity of this drug.     

Photosynthetic electron transport in isolated maize bundle sheath cells

Fragments of bundle sheath strands, free of mesophyll cells and showing a chlorophyll a/b ratio of 6.0 to 6.6 were prepared from Zea mays by a mechanical method. They were unable to photoreduce ferricyanide but were able to photoreduce the membrane-permeant 2,5-dimethylquinone at a rate of 250 to 420 microequivalents per hour per mg chlorophyll (μeq/hr · mg Chl) at 21 C. In the presence of the catalase inhibitor KCN, methylviologen catalyzed a Mehler reaction at a rate of 120 to 180 μeq/hr · mg Chl. This was increased to 200 to 350 μeq/hr · mg Chl when the uncoupler methylamine was added. The rate of endogenous pseudocyclic electron flow, detected as a Mehler reaction, was also considerable (100 to 150 μeq/hr · mg Chl with methylamine). Diaminodurene supported a high rate of photosystem I-mediated electron flow to methylviologen (400 to 750 μeq/hr · mg Chl).     

Sildenafil promotes adipogenesis through a PKG pathway

Sildenafil is the first oral PDE5 inhibitor for the treatment of erectile dysfunction and pulmonary arterial hypertension. In the present study, we investigated the effect of sildenafil on adipogenesis in 3T3L1 preadipocytes. Treatment with sildenafil for 8 days significantly promoted adipogenesis characterized by increased lipid droplet and triglyceride content in 3T3L1 cells. Meanwhile, sildenafil induced a pronounced up-regulation of the expression of adipocyte-specific genes, such as aP2 and GLUT4. The results by RT-PCR and Western blotting further showed that sildenafil increased the sequential expression of C/EBPβ, PPARγ and C/EBPα. Additionally, we found that the other two PDE5 inhibitors (vardenafil and tadalafil) and the cGMP analog 8-pCPT-cGMP also increased adipogenesis. Likewise, 8-pCPT-cGMP could up-regulate the expression of adipogenic and adipocyte-specific genes. Importantly, the PKG inhibitor Rp-8-pCPT-cGMP was able to inhibit both sildenafil and 8-pCPT-cGMP-induced adipogenesis. Furthermore, sildenafil promoted basal and insulin-mediated glucose uptake in 3T3L1 cells, which was counteracted by Rp-8-pCPT-cGMP. These results indicate that sildenafil could promote adipogenesis accompanied by increased glucose uptake through a PKG pathway at least partly.     

Impaired resolution of inflammatory response in the lungs of JF1/Msf mice following carbon nanoparticle instillation

Background

Declined lung function is a risk factor for particulate matter associated respiratory diseases like asthma and chronic obstructive pulmonary disease (COPD). Carbon nanoparticles (CNP) are a prominent component of outdoor air pollution that causes pulmonary toxicity mainly through inflammation. Recently we demonstrated that mice (C3H/HeJ) with higher than normal pulmonary function resolved the elicited pulmonary inflammation following CNP exposure through activation of defense and homeostasis maintenance pathways. To test whether CNP-induced inflammation is affected by declined lung function, we exposed JF1/Msf (JF1) mice with lower than normal pulmonary function to CNP and studied the pulmonary inflammation and its resolution.

Methods

5 μg, 20 μg and 50 μg CNP (Printex 90) were intratracheally instilled in JF1 mice to determine the dose response and the time course of inflammation over 7 days (20 μg dosage). Inflammation was assessed using histology, bronchoalveolar lavage (BAL) analysis and by a panel of 62 protein markers.

Results

24 h after instillation, 20 μg and 50 μg CNP caused a 25 fold and 19 fold increased polymorphonuclear leucocytes (PMN) respectively while the 5 μg represented the ''no observable adverse effect level'' as reflected by PMN influx (9.7 × 10E3 vs 8.9 × 10E3), and BAL/lung concentrations of pro-inflammatory cytokines. Time course assessment of the inflammatory response revealed that compared to day1 the elevated BAL PMN counts (246.4 × 10E3) were significantly decreased at day 3 (72.9 × 10E3) and day 7 (48.5 × 10E3) but did not reach baseline levels indicating slow PMN resolution kinetics. Strikingly on day 7 the number of macrophages doubled (455.0 × 10E3 vs 204.7 × 10E3) and lymphocytes were 7-fold induced (80.6 × 10E3 vs 11.2 × 10E3) compared to day1. At day 7 elevated levels of IL1B, TNF, IL4, MDC/CCL22, FVII, and vWF were detected in JF1 lungs which can be associated to macrophage and lymphocyte activation.

Conclusion

This explorative study indicates that JF1 mice with impaired pulmonary function also exhibits delayed resolution of particle mediated lung inflammation as evident from elevated PMN and accumulation of macrophages and lymphocytes on day7. It is plausible that elevated levels of IL1B, IL4, TNF, CCL22/MDC, FVII and vWF counteract defense and homeostatic pathways thereby driving this phenomenon.     

Pharmacokinetics and Tolerability of Inhaled Umeclidinium and Vilanterol Alone and in Combination in Healthy Chinese Subjects: A Randomized,Open-Label,Crossover Trial

Inhaled umeclidinium (UMEC) and the combination of inhaled UMEC with vilanterol (UMEC/VI) are approved maintenance treatments for chronic obstructive pulmonary disease in the US and EU. This was a randomized, open-label, three-period crossover, single- and repeat-dose study to assess the pharmacokinetics (PK), safety, and tolerability of inhaled UMEC/VI 62.5/25 μg (delivering 55/22 μg) and UMEC/VI 125/25 μg (delivering 113/22 μg) compared with their monotherapy components (UMEC 62.5 μg, UMEC 125 μg and, VI 25 μg [delivering 55, 113, and 22 μg, respectively]) in healthy Chinese subjects (n=20). UMEC and VI were rapidly absorbed following single and repeat dosing (time to maximum plasma concentration [t_max]: UMEC = 5 min; VI = 5 min). The median t_last was 2–4 h for UMEC and 1–2 h for VI following single doses of UMEC/VI and UMEC monotherapy (both doses). UMEC reached steady-state prior to Day 10; steady-state for VI could not be assessed. UMEC accumulation following repeat dosing was 11–34% based on C_max and 19–59% based on area under the concentration-time curve from time zero to 2 h (AUC_(0-2)). VI accumulation following repeat dosing was 25–66% based on C_max and 17–43% based on AUC_(0-2). The evidence was not sufficient to suggest that systemic exposure was substantially different between UMEC/VI combination therapy and the constituent monotherapies following single or repeat dosing. Following both single- and repeat-dose administration, the inter-subject coefficient of variation for all UMEC PK parameter estimates ranged from 12% to 165% for all treatments, indicating a wide range of variability in inhaled PK parameters. Twelve subjects experienced ≥1 adverse event (AE). Six subjects experienced ≥1 treatment-related AE; the most commonly reported treatment-related AE was chest discomfort (n=3 [15%]). No clinically important changes in vital signs or electrocardiogram parameters were reported. These data suggest that single- and repeat-dose administration of UMEC/VI combination therapy in healthy Chinese subjects did not result in substantial differences in systemic exposure compared with UMEC and VI as monotherapies.

Trial Registration

Clinicaltrials.gov NCT01899638 NCT01899638     

In Vivo Effects of Free Form Astaxanthin Powder on Anti-Oxidation and Lipid Metabolism with High-Cholesterol Diet

Astaxanthin extracted from Pomacea canaliculata eggs was made into free-form astaxanthin powder (FFAP) and its effects on lipid metabolism, liver function, antioxidants activities and astaxanthin absorption rate were investigated. 45 hamsters were split into 5 groups and fed with normal diet, high-cholesterol control (0.2% cholesterol), 1.6FFAP (control+1.6% FFAP), 3.2FFAP (control+3.2% FFAP) and 8.0FFAP (control+8.0% FFAP), respectively, for 6 weeks. FFAP diets significantly decreased the liver total cholesterol, triglyceride levels and increased liver fatty acids (C20:5n3; C22:6n3) compositions. It decreased plasma alanine aminotransferase and aspartate aminotransferase. In terms of anti-oxidative activities, we found 8.0 FFAP diet significantly decreased plasma and liver malonaldehyde (4.96±1.96 μg TEP eq./mL and 1.56±0.38 μg TEP eq./g liver) and liver 8-isoprostane levels (41.48±13.69 μg 8-ISOP/g liver). On the other hand, it significantly increased liver catalase activity (149.10±10.76 μmol/min/g liver), Vitamin C (2082.97±142.23 μg/g liver), Vitamin E (411.32±81.67 μg/g liver) contents, and glutathione levels (2.13±0.42 mg GSH eq./g liver). Furthermore, 80% of astaxanthin absorption rates in all FFAP diet groups suggest FFAP is an effective form in astaxanthin absorption. Finally, astaxanthin was found to re-distribute to the liver and eyes in a dose dependent manner. Taken together, our results suggested that the appropriate addition of FFAP into high cholesterol diets increases liver anti-oxidative activity and reduces the concentration of lipid peroxidase and therefore, it may be beneficial as a material in developing healthy food.     

Correlation of exhaled breath temperature with bronchial blood flow in asthma

In asthma elevated rates of exhaled breath temperature changes (Δe°T) and bronchial blood flow (Q_aw) may be due to increased vascularity of the airway mucosa as a result of inflammation.We investigated the relationship of Δe°T with Q_aw and airway inflammation as assessed by exhaled nitric oxide (NO). We also studied the anti-inflammatory and vasoactive effects of inhaled corticosteroid and β₂-agonist.Δe°T was confirmed to be elevated (7.27 ± 0.6 Δ°C/s) in 19 asthmatic subjects (mean age ± SEM, 40 ± 6 yr; 6 male, FEV₁ 74 ± 6 % predicted) compared to 16 normal volunteers (4.23 ± 0.41 Δ°C/s, p < 0.01) (30 ± 2 yr) and was significantly increased after salbutamol inhalation in normal subjects (7.8 ± 0.6 Δ°C/ s, p < 0.05) but not in asthmatic patients. Q_aw, measured using an acetylene dilution method was also elevated in patients with asthma compared to normal subjects (49.47 ± 2.06 and 31.56 ± 1.6 μl/ml/min p < 0.01) and correlated with exhaled NO (r = 0.57, p < 0.05) and Δe°T (r = 0.525, p < 0.05). In asthma patients, Q_aw was reduced 30 minutes after the inhalation of budesonide 400 μg (21.0 ± 2.3 μl/ml/min, p < 0.05) but was not affected by salbutamol.Δe°T correlates with Q_aw and exhaled NO in asthmatic patients and therefore may reflect airway inflammation, as confirmed by the rapid response to steroids.     

Hydrogel-Forming Microneedle Arrays Allow Detection of Drugs and Glucose In Vivo: Potential for Use in Diagnosis and Therapeutic Drug Monitoring

We describe, for the first time the use of hydrogel-forming microneedle (MN) arrays for minimally-invasive extraction and quantification of drug substances and glucose from skin in vitro and in vivo. MN prepared from aqueous blends of hydrolysed poly(methyl-vinylether-co-maleic anhydride) (11.1% w/w) and poly(ethyleneglycol) 10,000 daltons (5.6% w/w) and crosslinked by esterification swelled upon skin insertion by uptake of fluid. Post-removal, theophylline and caffeine were extracted from MN and determined using HPLC, with glucose quantified using a proprietary kit. In vitro studies using excised neonatal porcine skin bathed on the underside by physiologically-relevant analyte concentrations showed rapid (5 min) analyte uptake. For example, mean concentrations of 0.16 μg/mL and 0.85 μg/mL, respectively, were detected for the lowest (5 μg/mL) and highest (35 μg/mL) Franz cell concentrations of theophylline after 5 min insertion. A mean concentration of 0.10 μg/mL was obtained by extraction of MN inserted for 5 min into skin bathed with 5 μg/mL caffeine, while the mean concentration obtained by extraction of MN inserted into skin bathed with 15 μg/mL caffeine was 0.33 μg/mL. The mean detected glucose concentration after 5 min insertion into skin bathed with 4 mmol/L was 19.46 nmol/L. The highest theophylline concentration detected following extraction from a hydrogel-forming MN inserted for 1 h into the skin of a rat dosed orally with 10 mg/kg was of 0.363 μg/mL, whilst a maximum concentration of 0.063 μg/mL was detected following extraction from a MN inserted for 1 h into the skin of a rat dosed with 5 mg/kg theophylline. In human volunteers, the highest mean concentration of caffeine detected using MN was 91.31 μg/mL over the period from 1 to 2 h post-consumption of 100 mg Proplus^® tablets. The highest mean blood glucose level was 7.89 nmol/L detected 1 h following ingestion of 75 g of glucose, while the highest mean glucose concentration extracted from MN was 4.29 nmol/L, detected after 3 hours skin insertion in human volunteers. Whilst not directly correlated, concentrations extracted from MN were clearly indicative of trends in blood in both rats and human volunteers. This work strongly illustrates the potential of hydrogel-forming MN in minimally-invasive patient monitoring and diagnosis. Further studies are now ongoing to reduce clinical insertion times and develop mathematical algorithms enabling determination of blood levels directly from MN measurements.     

The Soluble Guanylate Cyclase Stimulator Riociguat Ameliorates Pulmonary Hypertension Induced by Hypoxia and SU5416 in Rats

Background

The nitric oxide (NO)–soluble guanylate cyclase (sGC)–cyclic guanosine monophosphate (cGMP) signal-transduction pathway is impaired in many cardiovascular diseases, including pulmonary arterial hypertension (PAH). Riociguat (BAY 63–2521) is a stimulator of sGC that works both in synergy with and independently of NO to increase levels of cGMP. The aims of this study were to investigate the role of NO–sGC–cGMP signaling in a model of severe PAH and to evaluate the effects of sGC stimulation by riociguat and PDE5 inhibition by sildenafil on pulmonary hemodynamics and vascular remodeling in severe experimental PAH.

Methods and Results

Severe angioproliferative PAH was induced in rats by combined exposure to the vascular endothelial growth factor receptor antagonist SU5416 and hypoxia (SUHx). Twenty-one days thereafter rats were randomized to receive either riociguat (10 mg/kg/day), sildenafil (50 mg/kg/day) or vehicle by oral gavage, for 14 days until the day of the terminal hemodynamic measurements. Administration of riociguat or sildenafil significantly decreased right ventricular systolic pressure (RVSP). Riociguat significantly decreased RV hypertrophy (RVH) (0.55±0.02, p<0.05), increased cardiac output (60.8±.8 mL/minute, p<0.05) and decreased total pulmonary resistance (4.03±0.3 mmHg min⁻¹ ml⁻¹ 100 g BW, p<0.05), compared with sildenafil and vehicle. Both compounds significantly decreased the RV collagen content and improved RV function, but the effects of riociguat on tricuspid annular plane systolic excursion and RV myocardial performance were significantly better than those of sildenafil (p<0.05). The proportion of occluded arteries was significantly lower in animals receiving riociguat than in those receiving vehicle (p<0.05); furthermore, the neointima/media ratio was significantly lower in those receiving riociguat than in those receiving sildenafil or vehicle (p<0.05).

Conclusion

Riociguat and sildenafil significantly reduced RVSP and RVH, and improved RV function compared with vehicle. Riociguat had a greater effect on hemodynamics and RVH than sildenafil.     

Pulmonary and anti-platelet effects of intravenous and inhaled prostacyclin in man

Prostacyclin in aerosol was inhaled by three healthy volunteers (0.3 – 30 μg) and by twelve patients with bronchial asthma (200 or 400 μg). Essentially, no changes in pulmonary function were noticed. Intravenous infusion of prostacyclin (2 – 20 ng/kg/min) into six healthy volunteers also remained without effects on respiratory indices studied. Inhaled prostacyclin impaired platelet aggregability to ADP, dispersed circulating platelet aggregates and produced vasodilation comparable to those observed following intravenous administration of the hormone. We suggest that aerosols of prostacyclin might be used in future in treatment of arterial thrombo-embolism.     

The Xanthine Derivative KMUP-1 Attenuates Serotonin-Induced Vasoconstriction and K+-Channel Inhibitory Activity via the PKC Pathway in Pulmonary Arteries

Serotonin (5-hydroxytryptamine, 5-HT) is a potent pulmonary vasoconstrictor that promotes pulmonary artery smooth muscle cell (PASMC) proliferation. 5-HT-induced K⁺ channel inhibition increases [Ca²⁺]_i in PASMCs, which is a major trigger for pulmonary vasoconstriction and development of pulmonary arterial hypertension (PAH). This study investigated whether KMUP-1 reduces pulmonary vasoconstriction in isolated pulmonary arteries (PAs) and attenuates 5-HT-inhibited K⁺ channel activities in PASMCs. In endothelium-denuded PA rings, KMUP-1 (1 μM) dose-dependently reduced 5-HT (100 μM) mediated contractile responses. Responses to KMUP-1 were reversed by K⁺ channel inhibitors (TEA, 10 mM, 4-aminopyridine, 5 mM, and paxilline, 10 μM). In primary PASMCs, KMUP-1 also dose-dependently restored 5-HT-inhibited voltage-gated K⁺-channel (Kv1.5 and Kv2.1) and large-conductance Ca²⁺-activated K⁺-channel (BK_Ca) proteins, as confirmed by immunofluorescent staining. Furthermore, 5-HT (10 μM)-inhibited Kv1.5 protein was unaffected by the PKA inhibitor KT5720 (1 μM) and the PKC activator PMA (1 μM), but these effects were reversed by KMUP-1 (1 μM), 8-Br-cAMP (100 μM), chelerythrine (1 μM), and KMUP-1 combined with a PKA/PKC activator or inhibitor. Notably, KMUP-1 reversed 5-HT-inhibited Kv1.5 protein and this response was significantly attenuated by co-incubation with the PKC activator PMA, suggesting that 5-HT-mediated PKC signaling can be modulated by KMUP-1. In conclusion, KMUP-1 ameliorates 5-HT-induced vasoconstriction and K⁺-channel inhibition through the PKC pathway, which could be valuable to prevent the development of PAH.     

Inhaled tolafentrine reverses pulmonary vascular remodeling via inhibition of smooth muscle cell migration

Background

The aim of the study was to assess the chronic effects of combined phosphodiesterase 3/4 inhibitor tolafentrine, administered by inhalation, during monocrotaline-induced pulmonary arterial hypertension (PAH) in rats.

Methods

CD rats were given a single subcutaneous injection of monocrotaline to induce PAH. Four weeks after, rats were subjected to inhalation of tolafentrine or sham nebulization in an unrestrained, whole body aerosol exposure system. In these animals (i) the acute pulmonary vasodilatory efficacy of inhaled tolafentrine (ii) the anti-remodeling effect of long-term inhalation of tolafentrine (iii) the effects of tolafentrine on the expression profile of 96 genes encoding cell adhesion and extracellular matrix regulation were examined. In addition, the inhibitory effect of tolafentrine on ex vivo isolated pulmonary artery SMC cell migration was also investigated.

Results

Monocrotaline injection provoked severe PAH (right ventricular systolic pressure increased from 25.9 ± 4.0 to 68.9 ± 3.2 after 4 weeks and 74.9 ± 5.1 mmHg after 6 weeks), cardiac output depression and right heart hypertrophy. The media thickness of the pulmonary arteries and the proportion of muscularization of small precapillary resistance vessels increased dramatically, and the migratory response of ex-vivo isolated pulmonary artery smooth muscle cells (PASMC) was increased. Micro-arrays and subsequent confirmation with real time PCR demonstrated upregulation of several extracellular matrix regulation and adhesion genes, such as matrixmetalloproteases (MMP) 2, 8, 9, 10, 11, 12, 20, Icam, Itgax, Plat and serpinb2. When chronically nebulized from day 28 to 42 (12 daily aerosol maneuvers), after full establishment of severe pulmonary hypertension, tolafentrine reversed about 60% of all hemodynamic abnormalities, right heart hypertrophy and monocrotaline-induced structural lung vascular changes, including the proportion of pulmonary artery muscularization. The upregulation of extracellular matrix regulation and adhesion genes was reduced by nearly 80% by inhalation of the tolafentrine. When assessed in vitro, tolafentrine blocked the enhanced PASMC migratory response.

Conclusion

In conclusion, we demonstrate for the first time that inhalation of combined PDE3/4 inhibitor reverses pulmonary hypertension fully developed in response to monocrotaline in rats. This "reverse-remodeling" effect includes structural changes in the lung vascular wall and key molecular pathways of matrix regulation, concomitant with 60% normalization of hemodynamics.