Long-term exposure to muscarinic agonists decreases expression of contractile proteins and responsiveness of rabbit tracheal smooth muscle cells

Efficacy of tiotropium bromide combined with different doses of fluticasone plus salmeterol DPI in the treatment of stable COPD

OBJECTIVE

To explore the efficacy of tiotropium bromide combined with different doses of fluticasone plus salmeterol DPI (dry powder for inhalation) in treating stable moderate to severe chronic obstructive pulmonary disease (COPD) and its influence on pulmonary function.

METHODS

From August 2017 to November 2019, 105 patients with stable moderate to severe COPD in our hospital were enrolled and divided into three groups: group A (GA), group B (GB) and group C (GC). In GA, patients received tiotropium bromide combined with low dose of fluticasone plus salmeterol. In GB, patients received tiotropium bromide combined with medium dose of fluticasone plus salmeterol. In GC, patients received tiotropium bromide combined with high dose of fluticasone plus salmeterol. The baseline data and adverse reactions were observed in each group. After therapy, the improvement of clinical symptoms, quality of life, pulmonary function index and therapeutic effect were observed in each group.

RESULTS

There was no difference in the general data of patients among the groups (P>0.05). The improvement of clinical symptoms in GB was better than that in GA, and that in GC was better than that in GB (P<0.05). There was no difference in adverse reactions among the groups (P>0.05). After treatment, IL-8, MPO, LTB4 and the number of inflammatory cells in sputum in the three groups decreased; the four in GB group were dramatically lower than those in GA group, and those in GC group were dramatically lower than those in GB group. The lung function indexes of patients in GB were better than those in GA, and those in GC were better than those in GB (P<0.05). The efficacy in GB was better than that in GA, and that in GC was better than that in GB (P<0.05). The quality of life scores in GB were higher than those in GA, and those in GC were higher than those in GB (P<0.05).

CONCLUSION

Tiotropium bromide combined with high dose of salmeterol xinafoate (SX) and fluticasone propionate (FP) powder for inhalation can effectively improve the pulmonary function of patients with moderate to severe stable COPD.

Role of Airway Smooth Muscle in Inflammation Related to Asthma and COPD

Airway smooth muscle contributes to both contractility and inflammation in the pathophysiology of asthma and COPD. Airway smooth muscle cells can change the degree of a variety of functions, including contraction, proliferation, migration, and the secretion of inflammatory mediators (phenotype plasticity). Airflow limitation, airway hyperresponsiveness, β₂-adrenergic desensitization, and airway remodeling, which are fundamental characteristic features of these diseases, are caused by phenotype changes in airway smooth muscle cells. Alterations between contractile and hyper-contractile, synthetic/proliferative phenotypes result from Ca²⁺ dynamics and Ca²⁺ sensitization. Modulation of Ca²⁺ dynamics through the large-conductance Ca²⁺-activated K⁺ channel/L-type voltage-dependent Ca²⁺ channel linkage and of Ca²⁺ sensitization through the RhoA/Rho-kinase pathway contributes not only to alterations in the contractile phenotype involved in airflow limitation, airway hyperresponsiveness, and β₂-adrenergic desensitization but also to alteration of the synthetic/proliferative phenotype involved in airway remodeling. These Ca²⁺ signal pathways are also associated with synergistic effects due to allosteric modulation between β₂-adrenergic agonists and muscarinic antagonists. Therefore, airway smooth muscle may be a target tissue in the therapy for these diseases. Moreover, the phenotype changing in airway smooth muscle cells with focuses on Ca²⁺ signaling may provide novel strategies for research and development of effective remedies against both bronchoconstriction and inflammation.

MicroRNA-221 is overexpressed in the equine asthmatic airway smooth muscle and modulates smooth muscle cell proliferation

Airway wall remodeling, including hyperplasia and hypertrophy of smooth muscle (ASM) cells leading to an increased smooth muscle mass, is considered central to asthma. However, molecular pathways responsible for ASM remodeling remain poorly understood. MicroRNAs (miRNAs) have emerged as key regulators of inflammatory and repair processes affecting the lungs and can downregulate protein expression by inhibiting target mRNA translation. We therefore hypothesized that miRNAs are involved in ASM remodeling in asthma by modulating ASM proliferation. We have analyzed the expression of miRNAs in bronchial smooth muscle from asthmatic horses during disease exacerbation and remission and from controls. Their involvement in ASM cell proliferation was then studied. Our results shown that miR-26a, miR-133, and miR-221 were upregulated in ASM from horses with asthma exacerbation compared with asthma remission and controls. MiR-221 induced cell hyperproliferation and reduced the expression of contractile gene markers in ASM cells. These changes were associated with the decreased mRNA expression of cell cycle regulatory genes (p53, p21, and p27). In conclusion, we demonstrated for the first time an upregulation of miR-221 in asthmatic airway smooth muscle and confirm the involvement of miR-221 in ASM cell proliferation by regulation of the cell cycle arrest genes. Targeting miR-221 network genes may represent a novel approach for the treatment of ASM remodeling in asthma.

L-Alpha-glycerylphosphorylcholine can be cytoprotective or cytotoxic in neonatal rat cardiac myocytes: a double-edged sword phenomenon

l-Alpha-glycerylphosphorylcholine (GPC) is a widely used food supplement. GPC has been shown to exert beneficial effects in several organs; however, the cardiac effects of GPC have yet to be investigated. The aim of the present study was therefore to map out the effects of GPC on cardiac myocytes, with or without ischemia–reperfusion insult. Neonatal rat cardiac myocytes were treated with GPC at 1, 10, 80, and 100 µM concentrations for 15 min, 3 h, or 24 h, respectively. Cell viability by calcein assay and the degree of oxidative stress by DHE (superoxide level) and H₂DCF (total ROS accumulation) staining were measured. In separate experiments, cardiomyocytes were pre-treated with the optimal concentration of GPC for 3 h and then cells were exposed to 4 h of simulated ischemia followed by 2 h of reperfusion (SI/R). Cell viability was measured at the end of the SI/R protocol. In normoxic conditions, the 15-min and the 3-h GPC treatment did not affect cell viability, total ROS, and superoxide levels. Under SI/R conditions, the 3-h GPC treatment protected the cardiac myocytes from SI/R-induced cell death and did not alter the level of oxidative stress. The 24-h GPC treatment in normoxic conditions resulted in significant cell death and increased oxidative stress at each concentration. Here we provide the first evidence for the cytoprotective effect of short-term GPC treatment. However, long-term administration of GPC may exert cytotoxicity in a wide concentration range in cardiac myocytes. These results may draw attention to a comprehensive cardiac safety protocol for the testing of GPC.

The muscarinic antagonist gallamine induces proliferation of airway smooth muscle cells regardless of the cell phenotype

BACKGROUND

Muscarinic receptor antagonists are a usual treatment for chronic airway diseases, with increased bronchoconstriction, like asthma and chronic obstructive pulmonary disease. These diseases are usually accompanied by airway remodeling, involving airway smooth muscle cell (ASMC) proliferation. The purpose of this study was to examine the effect of the muscarinic receptor modulator gallamine on rabbit tracheal ASMC proliferation.

METHODS

ASMCs were incubated with gallamine (1 nM-10 mM), atropine (1 fM-10 mM), and/or acetylcholine (1 nM-1 mM), in the presence or absence of FBS (1% or 10%). Cell proliferation was estimated by incorporation of radioactive thymidine, the Cell Titer AQueous One Solution method and cell number counting after Trypan blue exclusion. The mechanisms mediating cell proliferation were studied using the PI3K and MAPK inhibitors LY294002 (20 μM) and PD98059 (100 μM), respectively. Cell phenotype was studied by indirect immunofluorescence for α-actin, Myosin Heavy Chain and desmin.

RESULTS

ASMC incubation with the muscarinic receptor allosteric modulator gallamine or the muscarinic receptor antagonist atropine increased methyl-[³H]thymidine incorporation and cell number in a dose-dependent manner. ASMC proliferation was mediated via PI3K and MAPK activation and was transient. Gallamine antagonized the mitogenic effect of 1% FBS. Furthermore, gallamine had a similar effect on contractile ASMCs, without synergizing with or affecting acetylcholine induced proliferation, or altering the percentage of ASMCs expressing contractile phenotype marker proteins.

CONCLUSIONS

Gallamine, in the absence of any agonist, has a transient mitogenic effect on ASMCs, regardless of the cell phenotype, mediated by the PI3K and the MAPK signaling pathways.

Lifetime of muscarinic receptor-G-protein complexes determines coupling efficiency and G-protein subtype selectivity

G-protein-coupled receptors (GPCRs) are essential for the detection of extracellular stimuli by cells and transfer the encoded information via the activation of functionally distinct subsets of heterotrimeric G proteins into intracellular signals. Despite enormous achievements toward understanding GPCR structures, major aspects of the GPCR-G-protein selectivity mechanism remain unresolved. As this can be attributed to the lack of suitable and broadly applicable assays, we set out to develop a quantitative FRET-based assay to study kinetics and affinities of G protein binding to activated GPCRs in membranes of permeabilized cells in the absence of nucleotides. We measured the association and dissociation kinetics of agonist-induced binding of Gi/o, Gq/11, Gs, and G12/13 proteins to muscarinic M1, M2, and M3 receptors in the absence of nucleotides between fluorescently labeled G proteins and receptors expressed in mammalian cells. Our results show a strong quantitative correlation between not the on-rates of G-protein-M3-R interactions but rather the affinities of Gq and Go proteins to M3-Rs, their GPCR-G-protein lifetime and their coupling efficiencies determined in intact cells, suggesting that the G-protein subtype-specific affinity to the activated receptor in the absence of nucleotides is, in fact, a major determinant of the coupling efficiency. Our broadly applicable FRET-based assay represents a fast and reliable method to quantify the intrinsic affinity and relative coupling selectivity of GPCRs toward all G-protein subtypes.

Human trachealis and main bronchi smooth muscle are normoresponsive in asthma

RATIONALE

Airway smooth muscle (ASM) plays a key role in airway hyperresponsiveness (AHR) but it is unclear whether its contractility is intrinsically changed in asthma.

OBJECTIVES

To investigate whether key parameters of ASM contractility are altered in subjects with asthma.

METHODS

Human trachea and main bronchi were dissected free of epithelium and connective tissues and suspended in a force-length measurement set-up. After equilibration each tissue underwent a series of protocols to assess its methacholine dose-response relationship, shortening velocity, and response to length oscillations equivalent to tidal breathing and deep inspirations.

MEASUREMENTS AND MAIN RESULTS

Main bronchi and tracheal ASM were significantly hyposensitive in subjects with asthma compared with control subjects. Trachea and main bronchi did not show significant differences in reactivity to methacholine and unloaded tissue shortening velocity (Vmax) compared with control subjects. There were no significant differences in responses to deep inspiration, with or without superimposed tidal breathing oscillations. No significant correlations were found between age, body mass index, or sex and sensitivity, reactivity, or Vmax.

CONCLUSIONS

Our data show that, in contrast to some animal models of AHR, human tracheal and main bronchial smooth muscle contractility is not increased in asthma. Specifically, our results indicate that it is highly unlikely that ASM half-maximum effective concentration (EC50) or Vmax contribute to AHR in asthma, but, because of high variability, we cannot conclude whether or not asthmatic ASM is hyperreactive.

Role of epidermal growth factor in pathogenesis of uterine leiomyomas

OBJECTIVE

To investigate the role of epidermal growth factor (EGF) in the pathogenesis of uterine leiomyomas.

METHODS

Human myometrial smooth muscle cells (HM-SMCs) and smooth muscle cells of human uterine leiomyomas (HL-SMCs) were separated from patients' specimens and cultured. After processed by EGF or PD98059 (inhibitor of MKK/MEK) +EGF, the proliferation rate of both SMCs was detected by BrdU method and the phosphorylation level of p44/42 mitogen-activated protein kinase (MAPK) was determined by Western-blot. After different processing time by EGF, the phosphorylation levels of p44/42 MAPK and AKT and p27 expression level in both SMCs were detected by Western-blot.

RESULTS

EGF could significantly promote HL-SMCs proliferation and PD98059 could inhibit this effect (P<0.05); besides, PD98059 could inhibit the increase of the phosphorylation level of p44/42 MAPK in both SMCs induced by EGF. When the processing time by EGF was over 15min, the phosphorylation levels of p44/42 MAPK and AKT in both SMCs decreased sharply and were close to zero; p27 expression in HM-SMCs raised significantly while the upregulation in HL-SMCs was little.

CONCLUSIONS

EGF could not cause activation of EGFR because of the dephosphorylation of p44/42 MAPK and AKT in HL-SMCs, which caused p27 expression insufficiently and cell cycle dysregulation.