RESUMEN
BACKGROUND: Cystic fibrosis (CF) is a genetic disease affecting multiple organ systems of the body and is characterized by mutation in the gene coding for the cystic fibrosis transmembrane conductance regulator (CFTR). Previous work has shown that a single dose of aß-agonist increases cardiac output (Q) and stroke volume (SV) and decreases systemic vascular resistance (SVR) in healthy subjects. This effect is attenuated in patients with CF; however, the mechanism is unknown. Potential explanations for this decreased cardiovascular response to a ß-agonist in CF include inherent cardiovascular deficits secondary to the CFTR mutation, receptor desensitization from prolonged ß-agonist use as part of clinical care, or inhibited drug delivery to the bloodstream due to mucus buildup in the lungs. This study sought to determine the effects of endogenous epinephrine (EPI) and norepinephrine (NE) on cardiovascular function in CF and to evaluate the relationship between cardiovascular function and CFTR F508del mutation. METHODS: A total of 19 patients with CF and 31 healthy control subjects completed an assessment of Q (C2H2 rebreathing), SV (calculated from Q and heart rate [HR]), Q and SV indexed to body surface area (BSA, QI, and SVI, respectively), SVR (through assessment of Q and mean arterial blood pressure [MAP]), and HR (from 12-lead electrocardiogram [ECG]) at rest along with plasma measures of EPI and NE. We compared subjects by variables of cardiovascular function relative to EPI and NE, and also based on genetic variants of the F508del mutation (homozygous deletion for F508del, heterozygous deletion for F508del, or no deletion of F508del). RESULTS: Cystic fibrosis patients demonstrated significantly lower BSA (CF = 1.71 ± 0.05 m2 vs healthy = 1.84 ± 0.04 m2, P = .03) and SVI (CF = 30.6 ± 2.5 mL/beat/m2 vs healthy = 39.9 ± 2.5 mL/beat/m2, P = .02) when compared with healthy subjects. Cystic fibrosis patients also demonstrated lower Q (CF = 4.58 ± 0.36 L/min vs healthy = 5.71 ± 0.32 L/min, P = .03) and SV (CF = 54 ± 5.5 mL/beat vs healthy = 73.3 ± 4.5 mL/beat, P = .01), and a higher HR (CF = 93.2 ± 3.9 bpm vs healthy = 80.5 ± 2.7 bpm, P < .01) and SVR (CF = 2082 ± 156 dynes*s/cm-5 vs healthy = 1616 ± 74 dynes*s/cm-5, P = .01) compared with healthy subjects. Furthermore, CF patients demonstrated a lower SV (P < .01) corrected for NE when compared with healthy subjects. No significant differences were seen in HR or Q relative to NE, or SVR relative to EPI. Differences were seen in SV (F(2,14) = 7.982, P < .01) and SV index (F(2,14) = 2.913, P = .08) when patients with CF were stratified according to F508del mutation (number of deletions). CONCLUSIONS: Individuals with CF have lower cardiac and peripheral hemodynamic function parameters at rest. Furthermore, these results suggest that impairment in cardiovascular function is likely the result of F508del CFTR genotype, rather than receptor desensitization or inhibited drug delivery.
RESUMEN
Carvedilol functions as a nonselective ß-adrenergic receptor (AR)/α1-AR antagonist that is used for treatment of hypertension and heart failure. Carvedilol has been shown to function as an inverse agonist, inhibiting G protein activation while stimulating ß-arrestin-dependent signaling and inducing receptor desensitization. In the present study, short-circuit current (Isc) measurements using human airway epithelial cells revealed that, unlike ß-AR agonists, which increase Isc, carvedilol decreases basal and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate-stimulated current. The decrease in Isc resulted from inhibition of the cystic fibrosis transmembrane conductance regulator (CFTR). The carvedilol effect was abolished by pretreatment with the ß2-AR antagonist ICI-118551, but not the ß1-AR antagonist atenolol or the α1-AR antagonist prazosin, indicating that its inhibitory effect on Isc was mediated through interactions with apical ß2-ARs. However, the carvedilol effect was blocked by pretreatment with the microtubule-disrupting compound nocodazole. Furthermore, immunocytochemistry experiments and measurements of apical CFTR expression by Western blot analysis of biotinylated membranes revealed a decrease in the level of CFTR protein in monolayers treated with carvedilol but no significant change in monolayers treated with epinephrine. These results demonstrate that carvedilol binding to apical ß2-ARs inhibited CFTR current and transepithelial anion secretion by a mechanism involving a decrease in channel expression in the apical membrane.
Asunto(s)
Antagonistas Adrenérgicos beta/farmacología , Carbazoles/farmacología , Regulador de Conductancia de Transmembrana de Fibrosis Quística/metabolismo , Células Epiteliales/efectos de los fármacos , Propanolaminas/farmacología , Receptores Adrenérgicos beta 2/efectos de los fármacos , Aniones/metabolismo , Arrestinas/metabolismo , Carvedilol , Células Cultivadas , AMP Cíclico/metabolismo , Células Epiteliales/metabolismo , Humanos , Transducción de Señal , beta-ArrestinasRESUMEN
Human mammary epithelial (HME) cells express several P2Y receptor subtypes located in both apical and basolateral membranes. Apical UTP or ATP-γ-S stimulation of monolayers mounted in Ussing chambers evoked a rapid, but transient decrease in short circuit current (I(sc)), consistent with activation of an apical K+ conductance. In contrast, basolateral P2Y receptor stimulation activated basolateral K+ channels and increased transepithelial Na+ absorption. Chelating intracellular Ca2+ using the membrane-permeable compound BAPTA-AM, abolished the effects of purinoceptor activation on I(sc). Apical pretreatment with charybdotoxin also blocked the I(sc) decrease by >90% and similar magnitudes of inhibition were observed with clotrimazole and TRAM-34. In contrast, iberiotoxin and apamin did not block the effects of apical P2Y receptor stimulation. Silencing the expression of K(Ca)3.1 produced â¼70% inhibition of mRNA expression and a similar reduction in the effects of apical purinoceptor agonists on I(sc). In addition, silencing P2Y2 receptors reduced the level of P2Y2 mRNA by 75% and blocked the effects of ATP-γ-S by 65%. These results suggest that P2Y2 receptors mediate the effects of purinoceptor agonists on K+ secretion by regulating the activity of K(Ca)3.1 channels expressed in the apical membrane of HME cells. The results also indicate that release of ATP or UTP across the apical or basolateral membrane elicits qualitatively different effects on ion transport that may ultimately determine the [Na+]/[K+] composition of fluid within the mammary ductal network.