Myocarditis and dilated cardiomyopathy (DCM) are often caused by viral infections and occur more frequently in men than in women, but the reasons for the sex difference remain unclear. The aim of this study was to assess whether gene changes in the heart during coxsackievirus B3 (CVB3) myocarditis in male and female BALB/c mice predicted worse DCM in males. Although myocarditis (P = 4.2 × 10(-5)) and cardiac dilation (P = 0.008) were worse in males, there was no difference in viral replication in the heart. Fibrotic remodeling genes, such as tissue inhibitor of metalloproteinase (TIMP)-1 and serpin A 3n, were upregulated in males during myocarditis rather than during DCM. Using gonadectomy and testosterone replacement, we showed that testosterone increased cardiac TIMP-1 (P = 0.04), serpin A 3n (P = 0.007), and matrix metalloproteinase (MMP)-8 (P = 0.04) during myocarditis. Testosterone increased IL-1β levels in the heart (P = 0.02), a cytokine known to regulate cardiovascular remodeling, and IL-1β in turn increased cardiac serpin A 3n mRNA (P = 0.005). We found that 39 of 118 (33%) genes identified in acute DCM patients were significantly altered in the heart during CVB3 myocarditis in mice, including serpin A 3n (3.3-fold change, P = 0.0001). Recombinant serpin A 3n treatment induced cardiac fibrosis during CVB3 myocarditis (P = 0.0008) while decreasing MMP-3 (P = 0.04) and MMP-9 (P = 0.03) levels in the heart. Thus, serpin A 3n was identified as a gene associated with fibrotic cardiac remodeling and progression to DCM in male myocarditis patients and mice.
Tracheal intubation can elicit reflex bronchoconstriction in patients with asthma or chronic obstructive pulmonary disease, complicating mechanical ventilation and weaning from mechanical support. In vitro studies of human and animal bronchial tissue indicate that alpha2-adrenoceptor stimulation can lead to smooth muscle relaxation and prevention of bronchoconstriction. Dexmedetomidine is a selective alpha2-adrenoceptor agonist approved for sedation in the intensive care unit. Whether dexmedetomidine can affect reflex bronchoconstriction is unknown.After the approval of the institutional animal care and use committee, five mongrel dogs were anesthetized with thiopental, endotracheally intubated, and ventilated, and their airways were challenged with histamine. High-resolution computed tomography was used to measure airway luminal areas at baseline and after nebulized histamine. After recovery to baseline, on separate days, dexmedetomidine (0.5 microg/kg) was administered either intravenously or as an aerosol, and the histamine challenge was repeated.At baseline, histamine constricted the airways to 66 +/- 27% (mean +/- SD) (P < 0.0001) and 59 +/- 30% (P < 0.0001) of maximum on the days dexmedetomidine was administered by intravenous and inhalational means, respectively. After recovery, intravenous administration of dexmedetomidine blocked the histamine-induced bronchoconstriction (87 +/- 30.4% of maximum, compared with histamine alone (P < 0.0001), whereas dexmedetomidine administered by inhalation showed no protective effect (45 +/- 30% of maximum; P < 0.0001 compared with histamine alone).alpha2-Adrenoceptor stimulation with intravenous dexmedetomidine completely blocked histamine-induced bronchoconstriction in dogs. Therefore, dexmedetomidine might be beneficial to decrease airway reactivity in patients with chronic obstructive pulmonary disease or asthma, particularly during weaning from mechanical ventilation, when neurally mediated airway reflexes may be elicited.
In recent decades the mouse has become the primary animal model of a variety of lung diseases. In models of emphysema or fibrosis, the essential phenotypic changes are best assessed by measurement of the changes in lung elasticity. To best understand specific mechanisms underlying such pathologies in mice, it is essential to make functional measurements that can reflect the developing pathology. Although there are many ways to measure elasticity, the classical method is that of the total lung pressure-volume (PV) curve done over the whole range of lung volumes. This measurement has been made on adult lungs from nearly all mammalian species dating back almost 100 years, and such PV curves also played a major role in the discovery and understanding of the function of pulmonary surfactant in fetal lung development. Unfortunately, such total PV curves have not been widely reported in the mouse, despite the fact that they can provide useful information on the macroscopic effects of structural changes in the lung. Although partial PV curves measuring just the changes in lung volume are sometimes reported, without a measure of absolute volume, the nonlinear nature of the total PV curve makes these partial ones very difficult to interpret. In the present study, we describe a standardized way to measure the total PV curve. We have then tested the ability of these curves to detect changes in mouse lung structure in two common lung pathologies, emphysema and fibrosis. Results showed significant changes in several variables consistent with expected structural changes with these pathologies. This measurement of the lung PV curve in mice thus provides a straightforward means to monitor the progression of the pathophysiologic changes over time and the potential effect of therapeutic procedures.
To examine whether hypoxia causes constriction of alveolar or extra-alveolar vessels, we determined the relationships among transpulmonary pressure, pulmonary arterial pressure (Ppa), blood flow (Q), and transvascular fluid filtration rate (W) during normoxia (PO2 = 200 Torr) and hypoxia (PO2 = 50 Torr) in isolated pig lungs perfused with autologous blood. Left atrial pressures were always subatmospheric. The effects of lung inflation and hypoxic vasoconstriction on the Ppa-Q relationship were similar; when transpulmonary pressure was greater than 5 Torr, both shifted the curve to higher pressures in a parallel fashion. When transpulmonary pressure was 0–5 Torr, however, inflation had no effect on the Ppa-Q relationship during either normoxia or hypoxia. During normoxia at a transpulmonary pressure of 3.5 Torr, the relationship between fluid filtration rate and flow was characterized by a W of zero at Q less than 1.5 l/min and a rapid increase in W with Q above this value. Both hypoxia and inflation shifted this relationship to higher filtration rates in a parallel fashion. Furthermore, the combined effects of hypoxia and inflation on filtration rate were additive. These results suggest that hypoxia caused constriction of both alveolar and extra-alveolar vessels, resulting in increased intraluminal pressure and filtration of fluid in vessels upstream from the sites of constriction.
The ability to successfully intubate the trachea of mice and control their ventilation is important for longitudinal studies requiring recovery from anesthesia and repeated pulmonary function measurements or other evaluations, such as the use of radiological imaging (e.g., computed tomography or magnetic resonance imaging). We describe a method for rapid and repeated intubation of mice, with subsequent pulmonary function measurements at baseline and after an agonist challenge. We describe a simply constructed metal blade used as a laryngoscope to facilitate oropharyngeal exposure, transillumination of the neck to facilitate visualization of the trachea through the oropharynx, readily available polyethylene tubing to intubate the trachea, and a simple solenoid ventilator to maintain physiological ventilation and assess respiratory resistance and compliance. Brief infusions of acetylcholine through a needle into the jugular vein are used to assess the responsiveness of the airway smooth muscle.
Pressure-volume (PV) curves constructed over the entire lung volume range can reliably detect functional changes in mouse models of lung diseases. In the present study, we constructed full-range PV curves in healthy and elastase-treated mice using either a classic manually operated technique or an automated approach using a computer-controlled piston ventilator [flexiVent FX; Scientific Respiratory Equipment (SCIREQ), Montreal, Quebec, Canada]. On the day of the experiment, subjects were anesthetized, tracheotomized, and mechanically ventilated. Following an initial respiratory mechanics scan and degassing of the lungs with 100% O2, full-range PV curves were constructed using either the classic or the automated technique. In control mice, superimposable curves were obtained, and statistical equivalence was attained between the two methodologies. In the elastase-treated ones, where significant changes in respiratory mechanics and lung volumes were expected, very small differences were observed between the two techniques, and the criteria for statistical equivalence were met in two out of four parameters assessed. The automated technique was adapted to rats and used to estimate the functional residual capacity (FRC) by volume subtraction. This novel approach generated FRC estimates consistent with the literature, with added accuracy relative to the existing method in diseased subjects. In conclusion, the automated technique generated full-range PV curves that were equivalent or very close to those obtained with the classic method under physiological or severe pathological conditions. The automation facilitated some technical aspects of the procedure, eased its use across species, and helped derive a more accurate estimate of FRC in preclinical models of respiratory disease.NEW & NOTEWORTHY Partial and full-range pressure-volume (PV) curves are frequently used to characterize lung disease models. Whereas automated techniques exist to construct partial PV curves, a manually operated approach is classically employed to build the full-range ones. In this study, the full-range PV curve technique was automated using a computer-controlled piston ventilator. The automation simplified the technique, facilitated its extension to other species, and inspired a novel way of estimating the functional residual capacity in laboratory rodents.
