Stimulatory effect of methylglyoxal on capsaicin-sensitive lung vagal afferents in rats: role of TRPA1.

Methylglyoxal (MG), a reactive metabolic byproduct of glycolysis, is a causative of painful diabetic neuropathy. Patients with diabetes are associated with more frequent severe asthma exacerbation. Stimulation of capsaicin-sensitive lung vagal (CSLV) afferents may contribute to the pathogenesis of hyperreactive airway diseases such as asthma. However, the possibility of the stimulatory effect of MG on CSLV afferents and the underlying mechanisms remain unknown. Our results showed that intravenous injection of MG (25 mg/kg, MG25) in anesthetized, spontaneously breathing rats elicited pulmonary chemoreflexes characterized by apnea, bradycardia, and hypotension. The MG-induced apneic response was reproducible and dose dependent. MG25 no longer evoked these reflex responses after perineural capsaicin treatment of both cervical vagi to block C-fibers' conduction, suggesting that the reflexes were mediated through the stimulation of CSLV afferents. Pretreatment with HC030031 [an antagonist of transient receptor potential ankyrin subtype 1 protein (TRPA1)] or AP18 (another TRPA1 antagonist), but not their vehicle, markedly attenuated the apneic response induced by MG25. Consistently, electrophysiological results showed that pretreatment with HC030031 largely attenuated the intense discharge in CSLV afferents induced by injection of MG25 in open-chest and artificially ventilated rats. In isolated CSLV neurons, the perfusion of MG evoked an abrupt and pronounced increase in calcium transients in a concentration-dependent manner. This stimulatory effect on CSLV neurons was also abolished by HC030031 treatment but not by its vehicle. In conclusion, these results suggest that MG exerts a stimulatory effect on CSLV afferents, inducing pulmonary chemoreflexes, and such stimulation is mediated through the TRPA1 activation.NEW & NOTEWORTHY Methylglyoxal (MG) is implicated in the development of painful diabetic neuropathy. A retrospective cohort study revealed an increased incidence of asthma exacerbations in patients with diabetes. This study demonstrated that elevated circulating MG levels stimulate capsaicin-sensitive lung vagal afferents via activation of TRPA1, which in turn triggers respiratory reflexes. These findings provide new information for understanding the pathogenic mechanism of diabetes-associated hyperreactive airway diseases and potential therapy.

Premorbid use of selective beta-blockers improves sepsis incidence and course: Human cohort and animal model studies.

Introduction: Beta-blockers are widely prescribed to manage hypertension and cardiovascular diseases and have been suggested as an attractive therapy to improve the prognosis of sepsis. Herein, we investigated the potential benefits of premorbid selective beta-blocker use in sepsis with a real-world database and explored the underlying mechanism by in vivo and in vitro experiments. Methods: A total of 64,070 sepsis patients and 64,070 matched controls who were prescribed at least one anti-hypertensive drug for more than 300 days within 1 year were selected for the nested case-control study. Female C57BL/6 J mice and THP-1 cells stimulated with lipopolysaccharide (LPS) were used for studying systemic responses during sepsis to validate our clinical findings. Results: The risk of sepsis was lower in current selective beta-blocker users than in non-users (adjusted OR (aOR), 0.842; 95% CI, 0.755-0.939), and in recent users than in non-users (aOR, 0.773; 95% CI, 0.737-0.810). A mean daily dose of ≥0.5 DDD was associated with a lower risk of sepsis (aOR, 0.7; 95% CI, 0.676-0.725). Metoprolol, atenolol, and bisoprolol users had lower risk of sepsis than non-users. In a LPS-induced sepsis mouse model, mice pre-fed with atenolol had significantly reduced mortality. While atenolol had some mild effects on LPS-induced release of inflammatory cytokines in septic mice, it significantly reduced serum soluble PD-L1 levels. Notably, atenolol treatment reversed the negative correlation of sPD-L1 with inflammatory cytokines in septic mice. Moreover, atenolol markedly downregulated the PD-L1 expression on LPS-stimulated THP-1 monocytes/macrophages via targeting ROS-induced NF-κB and STAT3 activation. Conclusion: Atenolol pretreatment can reduce sepsis mortality in mice, and in vivo and in vitro studies of PD-L1 expression suggest a role for atenolol in the modulation of immune homeostasis. These findings may contribute to the reduced incidence of sepsis in hypertensive patients with premorbid treatment with selective beta-blockers, especially atenolol.

Inhibitory effect of sulfur dioxide inhalation on Hering-Breuer inflation reflex in mice: role of voltage-gated potassium channels.

Slowly adapting receptors (SARs), vagal mechanosensitive receptors located in the lung, play an important role in regulating the breathing pattern and Hering-Breuer inflation reflex (HBIR). Inhalation of high concentration of sulfur dioxide (SO2), a common environmental and occupational air pollutant, has been shown to selectively block the SAR activity in rabbits, but the mechanism underlying this inhibitory effect remained a mystery. We carried out this study to determine if inhalation of SO2 can inhibit the HBIR and change the eupneic breathing pattern, and to investigate further a possible involvement of voltage-gated K+ channels in the inhibitory effect of SO2 on these vagal reflex-mediated responses. Our results showed 1) inhalation of SO2 (600 ppm; 8 min) consistently abolished both the phasic activity of SARs and their response to lung inflation in anesthetized, artificially ventilated mice, 2) inhalation of SO2 generated a distinct inhibitory effect on the HBIR and induced slow deep breathing in anesthetized, spontaneously breathing mice, and these effects were reversible and reproducible in the same animals, 3) This inhibitory effect of SO2 was blocked by pretreatment with 4-aminopyridine (4-AP), a nonselective blocker of voltage-gated K+ channel, and unaffected by pretreatment with its vehicle. In conclusion, this study suggests that this inhibitory effect on the baseline breathing pattern and the HBIR response was primarily mediated through the SO2-induced activation of voltage-gated K+ channels located in the vagal bronchopulmonary SAR neurons.NEW & NOTEWORTHY This study demonstrated that inhaled sulfur dioxide completely and reversibly abolished the activity of vagal bronchopulmonary slowly adapting receptors, significantly inhibited the apneic response to lung inflation, and induced slow deep breathing in anesthetized mice. More importantly, our results further suggested that this inhibitory effect was mediated through an action of sulfur dioxide and its derivatives on the voltage-gated potassium channels expressed in the slowly adapting receptor sensory neurons innervating the lung.

Mechanisms Involved in the Stimulatory and Inhibitory Effects of 5-Hydroxytryptamine on Vagal Mechanosensitive Afferents in Rat Lung.

Mechanosensitive vagal afferents in the lung, rapidly and slowly adapting receptors (RARs and SARs, respectively), play an important role in eliciting the reflexes that regulate the normal airway function. A profound bronchoconstrictive effect of 5-hydroxytryptamine (5-HT) has been extensively reported in various animal species, but its influence on the SAR and RAR activity is not known. This study investigated the effect of 5-HT on these receptors, and the possible mechanisms involved. Single-fiber activities of these afferents were measured in anesthetized, open-chest, and mechanically ventilated rats. Our results showed that intravenous injection of 5-HT evoked a consistent and pronounced stimulation of phasic RARs. In contrast, 5-HT generated an inconsistent and paradoxical action on SARs: no effect in 29% (5 of 17) of the SARs; stimulation in 35% (6 of 17); and inhibition in the remainder. These responses of both RARs and SARs to 5-HT were reproducible and dose-dependent. After the injection of a high dose of 5-HT (16 µg/kg), the receptor responses slowly reached a peak (after ∼8 s) and returned toward the baseline in ∼20 s, accompanied by a consistent increase in total pulmonary resistance and a decrease in dynamic lung compliance in a temporal pattern very similar to the increased receptor activity. When these changes in lung mechanics induced by 5-HT were prevented by pretreatment with salbutamol, a ß2 adrenergic receptor agonist, the delayed responses of both RARs and SARs to 5-HT were also abolished, except that the immediate stimulatory effect on a subset of RARs, the silent RARs, was not affected. In conclusion, 5-HT generated a delayed stimulatory effect on RARs and a paradoxical effect on SARs, which resulted primarily from the 5-HT-induced changes in mechanical properties of the lung.

Airway Exposure to 1,3-Beta-d-Glucan Induces Airway Hyperresponsiveness in Guinea Pigs.

1,3-Beta-d-glucan (ß-glucan) is a component of mold cell walls and is frequently found in fungi and house dust mites. The studies of ß-glucan are inconsistent, although it has been implicated in airway adverse responses. This study was carried out to determine whether airway hyperresponsiveness was seen 24 h after airway exposure to ß-glucan in guinea pigs. Two matching guinea pigs were exposed intratracheally to either ß-glucan or its vehicle. Twenty-four hours after intratracheal instillation, there was no difference between these two groups in the baseline of the total pulmonary resistance (R L), dynamic lung compliance (C dyn), arterial blood pressure, and heart rate. In contrast, the responses of R L to capsaicin injection were significantly increased in ß-glucan animals; capsaicin at the same dose of 3.2 µg/kg increased R L by 184% in vehicle animals and by 400% in ß-glucan animals. The effective dose 200% to capsaicin injection was lower in the ß-glucan animals. Furthermore, the increases in R L were partially reduced after transient lung hyperinflation to recruit the occluding airways; however, the R L induced by capsaicin injection after lung hyperinflation was significantly larger than the baseline in ß-glucan animals; also, the lung wet-to-dry ratio in capsaicin-injected animals was augmented in the ß-glucan group. Moreover, the airway hyperresponsiveness was accompanied by increases in neutrophils in the bronchoalveolar lavage fluid in the ß-glucan animals. Furthermore, the levels of substance P and the calcitonin gene-related peptide in the bronchoalveolar lavage fluid collected after capsaicin injection were increased in ß-glucan animals. We provide definitive evidence that ß-glucan can induce airway hyperresponsiveness in guinea pigs, and the neuropeptide releases play an important role in this airway hyperresponsiveness.

Efficacy and safety of anti-interleukin-5 therapy in patients with chronic obstructive pulmonary disease: A meta-analysis of randomized, controlled trials.

BACKGROUND: Anti-interleukin-5 (IL-5) therapy has been proposed as a novel treatment option for patients with chronic obstructive pulmonary disease (COPD). However, its efficacy for preventing COPD exacerbation remains unclear. METHODS: A literature review was conducted to August 26th 2019. Only randomized controlled trials (RCTs) that investigated the clinical efficacy and adverse effects of anti-IL-5 therapy were included in the meta-analysis. The primary outcome was the risk of COPD exacerbation. RESULTS: A total of 3 articles containing 5 RCTs were included in the study. Overall, 2837 and 1442 patients received anti-IL-5 therapy (mepolizumab, n = 865; benralizumab, n = 1972) and placebo, respectively. In the pooled analysis, anti-IL-5 therapy was associated with a lower risk of COPD exacerbation compared with the placebo (rate ratio, 0.92; 95% CI, 0.86-0.97, I2 = 0%). In addition, no significant differences in the changes in SGRQ scores and FEV1 from baseline were found between the anti-IL-5 therapy and placebo (SGRQ, mean difference, -0.86, 95% CI, -1.92 - 0.19, I2 = 0%; FEV1, mean difference, 0.01, 95% CI, -0.01 - 0.03, I2 = 0%). Anti-IL-5 therapy had a similar risk of any adverse event (risk ratio, 1.02; 95% CI, 0.99-1.05), an event leading to treatment discontinuation (risk ratio, 1.04; 95% CI, 0.72-1.48) and any serious adverse events (risk ratio, 0.93; 95% CI, 0.85-1.01) when compared with the placebo. CONCLUSION: Anti-IL-5 therapy was associated with a lower rate of COPD exacerbation compared with placebo. In addition, anti-IL-5 therapy was well tolerated for COPD patients.

Coenzyme Q10 amends testicular function and spermatogenesis in male mice exposed to cigarette smoke by modulating oxidative stress and inflammation.

This study explored the effects of coenzyme Q10 (CoQ10) on the testicular functions of male mice exposed to cigarette smoke. Eight-week-old BALB/c male mice were divided into the following groups: the AV group (air with a vehicle), the AQ group (air with CoQ10), the SV group (smoke with a vehicle), and the SQ group (smoke with CoQ10). The results showed that the CoQ10 concentrations in the sera and testes were decreased in the groups subjected to smoke but they were improved after the administration of CoQ10. Neither smoke nor CoQ10 supplementation affected the serum or testis testosterone concentrations. Regarding the antioxidant system in the testis, the exposure to smoke induced malondialdehyde and hydrogen peroxide production and decreased the catalase and glutathione peroxidase activities. Oral CoQ10 administration reversed the oxidative damage. In apoptosis, the cytochrome c, c-caspase 9, and c-caspase 3 proteins were increased in the groups exposed to smoke but they were decreased after the CoQ10 administration. In mitochondrial biogenesis, smoke exposure led to decreases in the PGC1-α, NRF1, and NRF2 levels, but CoQ10 increased the expressions of these proteins. Additionally, oral CoQ10 administration improved the mitochondrial copy numbers that were reduced following the exposure to smoke. In summary, CoQ10 administration reduces smoke-induced testicular damage by regulating the antioxidant capacity, the cell apoptosis, the mitochondrial biogenesis, and the copy numbers in the testes.

The safety of nintedanib for the treatment of interstitial lung disease: A systematic review and meta-analysis of randomized controlled trials.

INTRODUCTION: Nintedanib can inhibit processes involved in the progression of fibrosis and can reduce the decline in forced vital capacity in patients with idiopathic pulmonary fibrosis (IPF) and fibrotic-interstitial lung disease (fibrotic-ILDs). Although the adverse events associated with nintedanib in IPF patients are well known, its safety in other fibrotic-ILD patients remained unclear. METHODS: We searched PubMed, EMBASE, Cochrane CENTRAL and Cochrane CDSR for randomized controlled studies which compared nintedanib with a placebo in ILD patients. We estimated pooled odds ratios (ORs) and 95% confidence intervals (CIs) for adverse events using the DerSimonian-Laird random-effects model. RESULTS: Six studies with a total of 2,583 patients were included in the meta-analysis. The pooled estimates showed that patients treated with nintedanib had a significantly higher likelihood of having any adverse events (OR = 2.39; 95% CI = 1.71-3.36) or adverse events leading to treatment discontinuation (OR = 1.73; 95% CI = 1.34-2.25). However, they had trend to lower likelihood of having fatal adverse events (OR = 0.69; 95% CI = 0.41-1.14) compared with the placebo group. Use of nintedanib was positively associated with diarrhea (OR = 5.96; 95% CI = 4.35-8.16), nausea (OR = 3.00; 95% CI = 1.93-4.66), vomiting (OR = 3.22; 95% CI = 2.17-4.76) and weight loss (OR = 3.38; 95% CI = 1.1.76-6.47). Whereas, patients treated with nintedanib were less likely to have a cough (OR = 0.73; 95% CI = 0.56-0.96) and dyspnea (OR = 0.70; 95% CI = 0.53-0.94). CONCLUSIONS: Compared to a placebo, nintedanib was associated with a higher risk of adverse events, especially for diarrhea, nausea, vomiting and weight loss, but it was also associated with a lower risk of cough and dyspnea in IPF and fibrotic-ILD patients.

HIF-1α-Mediated, NADPH Oxidase-Derived ROS Contributes to Laryngeal Airway Hyperreactivity Induced by Intermittent Hypoxia in Rats.

Obstructive sleep apnea, similar to intermittent hypoxia (IH) during sleep, is associated with laryngeal airway hyperreactivity (LAH). IH-induced laryngeal oxidative stress may contribute to LAH, but the underlying mechanism remains unknown. Conscious rats were subjected to repetitive 75 s cycles of IH for 7 or 14 consecutive days. Reflex apneic responses to laryngeal provocations with chemical stimulants were measured to reflect laryngeal reflex reactivity. Compared with control rats, rats exposed to IH for 14 days, but not for 7 days, displayed enhanced apneic response to laryngeal chemical stimulants. The apneic response to chemical stimulants, but not to mechanical stimulation, was totally abolished by perineural capsaicin treatment of superior laryngeal nerves (SLNs) or by the sectioning of the SLNs, suggesting that the reflex was mediated through capsaicin-sensitive SLNs. Daily intraperitoneal administration of N-acetyl-L-cysteine [NAC, a reactive oxygen species (ROS) scavenger], apocynin (an inhibitor of NADPH oxidase) or YC-1 (an inhibitor of HIF-1α), but not their vehicles, largely attenuated this augmented apneic response in 14 days IH rats. Laryngeal lipid peroxidation (an index of oxidative stress) was elevated in 7 days IH rats and 14 days IH rats, and was abolished by any of these three pharmacologic interventions. The protein expression of HIF-1α (an index of HIF-1 activation) and p47phox subunit in the membrane fraction (an index of NADPH oxidase activation) in the laryngeal tissues increased in 14 days IH rats; the former was reduced by NAC, whereas the latter was inhibited by YC-1. These results suggest that 14 days of IH exposure may sensitize capsaicin-sensitive SLNs and result in exaggerated apneic reflex response to laryngeal chemical stimulants. This phenomenon depends on the action of HIF-1α-mediated, NADPH oxidase-derived ROS.

Involvement of Capsaicin-Sensitive Lung Vagal Neurons and TRPA1 Receptors in Airway Hypersensitivity Induced by 1,3-ß-D-Glucan in Anesthetized Rats.

Airway exposure to 1,3-ß-D-glucan (ß-glucan), an essential component of the cell wall of several pathogenic fungi, causes various adverse responses, such as pulmonary inflammation and airway hypersensitivity. The former response has been intensively investigated; however, the mechanism underlying ß-glucan-induced airway hypersensitivity is unknown. Capsaicin-sensitive lung vagal (CSLV) afferents are very chemosensitive and stimulated by various insults to the lungs. Activation of CSLV afferents triggers several airway reflexes, such as cough. Furthermore, the sensitization of these afferents is known to contribute to the airway hypersensitivity during pulmonary inflammation. This study was carried out to determine whether ß-glucan induces airway hypersensitivity and the role of the CSLV neurons in this hypersensitivity. Our results showed that the intratracheal instillation of ß-glucan caused not only a distinctly irregular pattern in baseline breathing, but also induced a marked enhancement in the pulmonary chemoreflex responses to capsaicin in anesthetized, spontaneously breathing rats. The potentiating effect of ß-glucan was found 45 min later and persisted at 90 min. However, ß-glucan no longer caused the irregular baseline breathing and the potentiating of pulmonary chemoreflex responses after treatment with perineural capsaicin treatment that blocked the conduction of CSLV fibers. Besides, the potentiating effect of ß-glucan on pulmonary chemoreflex responses was significantly attenuated by N-acetyl-L-cysteine (a ROS scavenger), HC-030031 (a TRPA1 antagonist), and Laminarin (a Dectin-1 antagonist). A combination of Laminarin and HC-030031 further reduced the ß-glucan-induced effect. Indeed, our fiber activity results showed that the baseline fiber activity and the sensitivity of CSLV afferents were markedly elevated by ß-glucan instillation, with a similar timeframe in anesthetized, artificially ventilated rats. Moreover, this effect was reduced by treatment with HC-030031. In isolated rat CSLV neurons, the ß-glucan perfusion caused a similar pattern of potentiating effects on capsaicin-induced Ca2+ transients, and ß-glucan-induced sensitization was abolished by Laminarin pretreatment. Furthermore, the immunofluorescence results showed that there was a co-localization of TRPV1 and Dectin-1 expression in the DiI-labeled lung vagal neurons. These results suggest that CSLV afferents play a vital role in the airway hypersensitivity elicited by airway exposure to ß-glucan. The TRPA1 and Dectin-1 receptors appear to be primarily responsible for generating ß-glucan-induced airway hypersensitivity.

Hypersensitivity of Airway Reflexes Induced by Hydrogen Sulfide: Role of TRPA1 Receptors.

The activation of capsaicin-sensitive lung vagal (CSLV) afferents can elicit airway reflexes. Hypersensitivity of these afferents is known to contribute to the airway hypersensitivity during airway inflammation. Hydrogen sulfide (H2S) has been suggested as a potential therapeutic agent for airway hypersensitivity diseases, such as asthma, because of its relaxing effect on airway smooth muscle and anti-inflammatory effect. However, it is still unknown whether H2S affects airway reflexes. Our previous study demonstrated that exogenous application of H2S sensitized CSLV afferents and enhanced Ca2+ transients in CSLV neurons. The present study aimed to determine whether the H2S-induced sensitization leads to functional changes in airway reflexes and elevates the electrical excitability of the CSLV neurons. Our results showed that, first and foremost, in anesthetized, spontaneously breathing rats, the inhalation of aerosolized sodium hydrosulfide (NaHS, a donor of H2S; 5 mg/mL, 3 min) caused an enhancement in apneic response evoked by several stimulants of the CSLV afferents. This enhancement effect was found 5 min after NaHS inhalation and returned to control 30 min later. However, NaHS no longer enhanced the apneic response after perineural capsaicin treatment on both cervical vagi that blocked the conduction of CSLV fibers. Furthermore, the enhancing effect of NaHS on apneic response was totally abolished by pretreatment with intravenous HC-030031 (a TRPA1 antagonist; 8 mg/kg), whereas the potentiating effect was not affected by the pretreatment with the vehicle of HC-030031. We also found that intracerebroventricular infusion pretreated with HC-030031 failed to alter the potentiating effect of NaHS on the apneic response. Besides, the cough reflex elicited by capsaicin aerosol was enhanced by inhalation of NaHS in conscious guinea pigs. Nevertheless, this effect was entirely eliminated by pretreatment with HC-030031, not by its vehicle. Last but not least, voltage-clamp electrophysiological analysis of isolated rat CSLV neurons showed a similar pattern of potentiating effects of NaHS on capsaicin-induced inward current, and the involvement of TRPA1 receptors was also distinctly shown. In conclusion, these results suggest that H2S non-specifically enhances the airway reflex responses, at least in part, through action on the TRPA1 receptors expressed on the CSLV afferents. Therefore, H2S should be used with caution when applying for therapeutic purposes in airway hypersensitivity diseases.

Atrial arrhythmogenesis in a rabbit model of chronic obstructive pulmonary disease.

Chronic obstructive pulmonary disease (COPD) increases the risk of atrial fibrillation (AF), however, its arrhythmogenic mechanisms are unclear. This study investigated the effects of COPD on AF triggers (pulmonary veins, PVs) and substrates (atria), and their potential underlying mechanisms. Electrocardiographic, echocardiographic, and biochemical studies were conducted in control rabbits and rabbits with human leukocyte elastase (0.3 unit/kg)-induced COPD. Conventional microelectrode, Western blotting, and histological examinations were performed on PV, left atrium (LA), right atrium, and sinoatrial node (SAN) preparations from control rabbits and those with COPD. The rabbits with COPD had a higher incidence of atrial premature complexes, PV burst firing and delayed afterdepolarizations, higher sympathetic activity, larger LA, and faster PV spontaneous activity than did the control rabbits; but they exhibited a slower SAN beating rate. The LA of the rabbits with COPD had a shorter action potential duration and longer tachyarrhythmia induced by tachypacing (20 Hz) and isoproterenol (1 µM). Additionally, the rabbits with COPD had higher fibrosis in the PVs, LA, and SAN. H89 (10 µM), KN93 (1 µM), and KB-R7943 (10 µM) significantly suppressed burst firing and delayed afterdepolarizations in the PVs of the rabbits with COPD. Moreover, compared with the control rabbits, those with COPD had lower expression levels of the ß1 adrenergic receptor, Cav 1.2, and Na+/Ca2+ exchanger in the PVs; Cav 1.2 in the LA; and hyperpolarization-activated cyclic nucleotide-gated K+ channel 4 in the SAN. COPD increases atrial arrhythmogenesis by modulating the distinctive electrophysiological characteristics of the PVs, LA, and SAN.

Mechanisms underlying the stimulatory effect of inhaled sulfur dioxide on vagal bronchopulmonary C-fibres.

KEY POINTS: Brief inhalation of SO2 of concentration >500 p.p.m. triggered a pronounced stimulatory effect on vagal bronchopulmonary C-fibres in anaesthetized rats. This stimulatory effect was drastically diminished by a pretreatment with NaHCO3 that raised the baseline arterial pH, suggesting a possible involvement of acidification of airway fluid and/or tissue generated by inhaled SO2 . The stimulation was completely abolished by pretreatment with antagonists of both acid-sensing ion channels and transient receptor potential vanilloid type-1 receptors, indicating that this effect was caused by acid activation of these cation channels expressed in airway sensory nerves. This conclusion was further supported by the results obtained from studies in isolated rat vagal bronchopulmonary sensory neurones and also in the cough response to SO2 inhalation challenge in awake mice. These results provide new insight into the underlying mechanism of harmful irritant effects in the respiratory tract caused by accidental exposure to a high concentration of SO2 . ABSTRACT: Inhalation of sulfur dioxide (SO2 ) triggers coughs and reflex bronchoconstriction, and stimulation of vagal bronchopulmonary C-fibres is primarily responsible. However, the mechanism underlying this stimulatory effect is not yet fully understood. In this study, we tested the hypothesis that the C-fibre stimulation was caused by SO2 -induced local tissue acidosis in the lung and airways. Single-unit activities of bronchopulmonary C-fibres in response to inhalation challenges of SO2 (500-1500 p.p.m., 10 breaths) were measured in anaesthetized rats. Inhalation of SO2 reproducibly induced a pronounced and sustained stimulation (lasting for 15-60 s) of pulmonary C-fibres in a concentration-dependent manner. This stimulatory effect was significantly attenuated by an increase in arterial pH generated by infusion of sodium bicarbonate (NaHCO3 ), and completely abrogated by a combined pretreatment with amiloride (an antagonist of acid-sensing ion channels, ASICs) and AMG8910 (a selective antagonist of the transient receptor potential vanilloid type-1 receptor, TRPV1). Furthermore, in isolated rat vagal pulmonary sensory neurones, perfusion of an aqueous solution of SO2 evoked a transient increase in the intracellular Ca2+ concentration; this response was also markedly diminished by a pretreatment with amiloride and AMG8910. In addition, inhalation of SO2 consistently evoked coughs in awake mice; responses were significantly smaller in TRPV1-/- mice than in wild-type mice, and almost completely abolished after a pretreatment with amiloride in TRPV1-/- mice. These results suggested that the stimulatory effect of inhaled SO2 on bronchopulmonary C-fibres was generated by acidification of fluid and/or tissue in the lung and airways, which activated both ASICs and TRPV1 expressed in these sensory nerves.

Risk of sepsis among patients with COPD treated with fixed combinations of inhaled corticosteroids and long-acting Beta2 agonists.

This study aimed to compare the effect of budesonide/formoterol and fluticasone/salmeterol on the risk and outcomes of sepsis in COPD patients. We conducted this study using the Taiwan National Health Insurance Research Database. We included COPD patients prescribed with budesonide/formoterol or fluticasone/salmeterol between 2004 and 2011. Outcomes including sepsis and mortality were measured. 10,267 COPD patients who received fluticasone/salmeterol and 6,844 patients who received budesonide/formoterol were enrolled into this study and then subsequence were adjusted by propensity score weighting. The incidence of sepsis was 5.74 and 4.99 per 100 person-years for the patients receiving fluticasone/salmeterol and budesonide/formoterol, respectively. Fluticasone/salmeterol was associated with higher risk of sepsis (aHR, 1.15; 95%CI, 1.07-1.24) and septic shock (aHR, 1.14; 95%CI, 1.01-1.29) than budesonide/formoterol. Besides, fluticasone/salmeterol was associated with higher risk of death (aHR, 1.090; 95%CI, 1.01-1.18) than budesonide/formoterol. Patients receiving fluticasone/salmeterol had a significant higher risk of sepsis related respiratory organ dysfunction, lower respiratory tract infection, genitourinary tract infection, bacteremia and skin infection. In conclusion, long-term treatment with budesonide/formoterol was associated with lower rates of sepsis and deaths than fluticasone/salmeterol in patients with COPD.

Stimulatory Effect of 5-Hydroxytryptamine (5-HT) on Rat Capsaicin-Sensitive Lung Vagal Sensory Neurons via Activation of 5-HT3 Receptors.

5-hydroxytryptamine (5-HT) is an inflammatory mediator known to be released in lung. Capsaicin-sensitive lung vagal (CSLV) afferents function as a primary sensor for detecting chemical stimuli and produce consequent reflexes during lung inflammation. To characterize the effect of 5-HT on CSLV afferents, responses of cardiorespiratory reflexes and single-unit C-fiber afferents to right-atrial injections of 5-HT were investigated in anesthetized Sprague-Dawley rats. Bolus injection of 5-HT (8 µg/kg) caused an immediate augmented breath and apnea, accompanied by hypotension and bradycardia. These initial responses were then followed by a brief pressor response and a more sustained depressor response. After a perineural treatment of both cervical vagi with capsaicin to block the conduction of C fibers, 5-HT still triggered the augmented breath, but no longer evoked the apnea, bradycardia and hypotension, indicating an involvement of C-fiber activation. The remaining augmented breath induced by 5-HT after perineural capsaicin treatment was totally eliminated by vagotomy. To further study the effect of 5-HT on CSLV afferents, activities arising from these afferents were determined using the single-fiber recording technique. Right-atrial injection of 5-HT evoked an intense discharge in CSLV afferents in a dose-dependent manner. The highest dose of 5-HT (16 µg/kg) activated 79% (19/24) of CSLV afferents which were also sensitive to capsaicin (0.8 µg/kg). The pretreatment of tropisetron, a selective antagonist of the 5-HT3 receptor, completely blocked CSLV-afferents stimulation induced by 5-HT but did not affect that by capsaicin. Furthermore, a similar afferent response of CSLV afferents was mimicked by phenylbiguanide, a selective agonist of the 5-HT3 receptor. In isolated rat lung vagal C neurons, 5-HT induced intense calcium transients in a dose-dependent manner. The highest concentration (3 µM) of 5-HT activated 67% (18/27) of the CSLV neurons. The 5-HT-induced response was totally abolished by pretreatment of tropisetron. In conclusion, 5-HT exerts an intense stimulatory effect on lung C-fiber terminals mediated through an activation of the 5-HT3 receptor, which may contribute to the airway hypersensitivity under lung inflammation.

Immediate and delayed potentiating effects of tumor necrosis factor-α on TRPV1 sensitivity of rat vagal pulmonary sensory neurons.

We studied acute effects of tumor necrosis factor-α (TNFα) on the sensitivity of isolated rat vagal pulmonary sensory neurons. Our results showed the following. First, a brief pretreatment with a low dose of TNFα (1.44 nM, 9 min) enhanced the sensitivity of transient receptor potential vanilloid type 1 (TRPV1) receptors in these neurons in two distinct phases: the inward current evoked by capsaicin was amplified (Δ = 247%) immediately following the TNFα pretreatment, which gradually declined toward control and then increased again reaching another peak (Δ = 384%) after 60-90 min. Second, the immediate phase of this potentiating effect of TNFα was completely abolished by a pretreatment with a selective cyclooxygenase-2 (COX-2) inhibitor, NS-398, whereas the delayed potentiation was only partially attenuated. Third, in sharp contrast, TNFα did not generate any potentiating effect on the responses to non-TRPV1 chemical activators of these neurons. Fourth, the selectivity of the TNFα action on TRPV1 was further illustrated by the responses to acid (pH 6.0); TNFα did not affect the rapid transient current mediated by acid-sensing ion channels but significantly augmented the slow sustained current mediated by TRPV1 in the same neurons. Fifth, in anesthetized rats, a similar pattern of acute sensitizing effects of TNFα on pulmonary C-fiber afferents and the involvement of COX-2 were also clearly shown. In conclusion, a brief pretreatment with TNFα induced both immediate and delayed potentiating effects on the TRPV1 sensitivity in pulmonary sensory neurons, and the production of COX-2 arachidonic acid metabolites plays a major role in the immediate sensitizing effect of TNFα.

Inhaled Pharmacotherapy and Stroke Risk in Patients with Chronic Obstructive Pulmonary Disease: A Nationwide Population Based Study Using Two-Stage Approach.

BACKGROUND AND PURPOSE: Patients with chronic obstructive pulmonary disease (COPD) are at higher risk of stroke than those without COPD. This study aims to explore the impact of inhaled pharmacotherapy on stroke risk in COPD patients during a three-year follow-up, using a nationwide, population-based study and a matched cohort design. METHODS: The study cohort comprised 10,413 patients who had received COPD treatment between 2004 and 2006; 41,652 randomly selected subjects comprised the comparison cohort. Cox proportional hazard regressions and two-stage propensity score calibration were performed to determine the impact of various inhaled therapies including short-acting muscarinic antagonists, long-acting muscarinic antagonists, short-acting ß-agonists (SABAs), long-acting ß-agonists (LABAs), and LABA plus inhaled corticosteroid (ICS), on the risk after adjustment for patient demographic characteristics and comorbid disorders. RESULTS: Of the 52,065 sampled patients, 2,689 (5.2%) developed stroke during follow-up, including 727 (7.0%) from the COPD cohort and 1,962 (4.7%) from the comparison cohort (p < 0.001). Treatment with SABA was associated with 1.67-fold (95% CI 1.45-1.91; p < 0.001) increased risk of stroke in COPD patients. By contrast, the cumulative incidence of stroke was significantly lower in those treated with LABA plus ICS than those treated without (adjusted hazard ratio 0.75, 95% CI 0.60-0.94, p = 0.014). CONCLUSIONS: Among COPD patients, the use of inhaled SABA is associated with an increased risk of stroke, and combination treatment with inhaled LABA and ICS relates to a risk reduction. Further prospective research is needed to verify whether LABA plus ICS confers protection against stroke in patients with COPD.

Influence of serotonergic mechanisms on the urine flow rate in male rats.

This study extensively examined the role of a 5-HT(1A) receptor in controlling voiding function in anesthetized male rats. A simultaneous recording of the intravesical pressure (IVP), external urethral sphincter (EUS)-electromyography (EMG), and urine flow rate (UFR) during continuous cystometry was used. 8-Hydroxy-2-(di-n-propylamino)-tetralin (8-OH-DPAT), a 5-HT(1A) receptor agonist, significantly improved the voiding efficiency, as detected by increases in the evoked contraction amplitude, EUS burst period, and silent period, and decreases in the volume threshold, pressure threshold, and residual volume. Interestingly, the UFR during voiding was reduced by 8-OH-DPAT, as evidenced by decreases in the maximal UFR and mean UFRs of the voiding period, spike duration, and interspike interval. Conversely, treating rats with WAY-100635, a 5-HT(1A) antagonist, produced effects opposite to those produced by 8-OH-DPAT. These findings suggest that 8-OH-DPAT improved the voiding efficiency by enhancing the detrusor contractile ability and prolonging EUS burst period, which would compensate for the lower UFR, resulting from urethral smooth muscle contractions and longer EUS silent periods during voiding. The present study contributes to our understanding of the role of 5-HT(1A) receptors in controlling the urine flow rate in male rats.

Sexually dimorphic urethral activity in response to pharmacological activation of 5-HT1A receptors in the rat.

In this study, we examined the possibility that 5-HT1A receptors may underlie sexually dimorphic mechanisms affecting the regulation of urethral functions in anesthetized rats. Simultaneous recordings of intravesical pressure under isovolumetric conditions, external urethral sphincter-electromyography, and urethral perfusion pressure were used to examine the effects of a 5-HT1A receptor agonist [8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT)] and antagonist (WAY-100635) on bladder and urethral functions. This research also evaluated the effects of 8-OH-DPAT and α-bungarotoxin (a neuromuscular blockade agent) on urethral continence using leak point pressure testing, and the distribution of 5-HT1A receptors in the lower urinary tract was assessed by immunohistochemistry. The serotonergic mechanism that controls the urinary bladder and external urethral sphincter-electromyography activity showed no significant sexual differences, but urethral activity in urethral perfusion pressure and leak point pressure values exhibited some sexual differences. 8-OH-DPAT enhanced urethral pressure during continence in rats of both sexes, but the drug elevated the pressure during voiding in male rats and reduced it in female rats. The distribution of 5-HT1A receptors in the spinal cord also showed some sexual differences. The present study contributes to our understanding of the role of 5-HT1A receptors in physiological and immunohistochemical properties of urethral smooth muscle in rats of different sexes. These findings may be a basis for the future development of pharmacotherapies for stress urinary incontinence in men.