Arthur Sung

Rapid Mechanotransduction in Situ at the Luminal Cell Surface of Vascular Endothelium and Its Caveolae

The vascular endothelium is uniquely positioned between the blood and tissue compartments to receive directly the fluid forces generated by the blood flowing through the vasculature. These forces invoke specific responses within endothelial cells and serve to modulate their intrinsic structure and function. The mechanisms by which hemodynamic forces are detected and converted by endothelia into a sequence of biological and even pathological responses are presently unknown. By purifying and subfractionating the luminal endothelial cell plasma membrane from tissue, we show, for the first time, that not only does mechanotransduction occur at the endothelial cell surface directly exposed to vascular flow in vivo but also increased flowin situ induces rapid tyrosine phosphorylation of luminal endothelial cell surface proteins located primarily in the plasmalemmal invaginations called caveolae. Increased flow induces the translocation of signaling molecules primarily to caveolae, ultimately activating the Ras-Raf-mitogen-activated protein kinase pathway. This signaling appears to require intact caveolae. Filipin-induced disassembly of caveolae inhibits both proximal signaling events at the cell surface and downstream activation of the mitogen-activated protein kinase pathway. With the molecular machinery required for mediating rapid flow-induced responses as seen in endothelium, caveolae may be flow-sensing organelles converting mechanical stimuli into chemical signals transmitted into the cell.

Relapsing Polychondritis and Airway Involvement

OBJECTIVE To assess the prevalence and characteristics of airway involvement in relapsing polychondritis (RP). METHODS Retrospective chart review and data analysis of RP patients seen in the Rheumatology Clinic and the Complex Airway Center at Beth Israel Deaconess Medical Center from January 2004 through February 2008. RESULTS RP was diagnosed in 145 patients. Thirty-one patients had airway involvement, a prevalence of 21%. Twenty-two patients were women (70%), and they were between 11 and 61 years of age (median age, 42 years) at the time of first symptoms. Airway symptoms were the first manifestation of disease in 17 patients (54%). Dyspnea was the most common symptom in 20 patients (64%), followed by cough, stridor, and hoarseness. Airway problems included the following: subglottic stenosis (n = 8; 26%); focal and diffuse malacia (n = 15; 48%); and focal stenosis in different areas of the bronchial tree in the rest of the patients. Twelve patients (40%) required and underwent intervention including balloon dilatation, stent placement, tracheotomy, or a combination of the above with good success. The majority of patients experienced improvement in airway symptoms after intervention. One patient died during the follow-up period from the progression of airway disease. The rest of the patients continue to undergo periodic evaluation and intervention. CONCLUSION In this largest cohort described in the English language literature, we found symptomatic airway involvement in RP to be common and at times severe. The nature of airway problems is diverse, with tracheomalacia being the most common. Airway intervention is frequently required and in experienced hands results in symptom improvement.

A Multicenter RCT of Zephyr® Endobronchial Valve Treatment in Heterogeneous Emphysema (LIBERATE)

Rationale: This is the first multicenter randomized controlled trial to evaluate the effectiveness and safety of Zephyr Endobronchial Valve (EBV) in patients with little to no collateral ventilation out to 12 months. Objectives: To evaluate the effectiveness and safety of Zephyr EBV in heterogeneous emphysema with little to no collateral ventilation in the treated lobe. Methods: Subjects were enrolled with a 2:1 randomization (EBV/standard of care [SoC]) at 24 sites. Primary outcome at 12 months was the &Dgr;EBV‐SoC of subjects with a post‐bronchodilator FEV1 improvement from baseline of greater than or equal to 15%. Secondary endpoints included absolute changes in post‐bronchodilator FEV1, 6‐minute‐walk distance, and St. Georges Respiratory Questionnaire scores. Measurements and Main Results: A total of 190 subjects (128 EBV and 62 SoC) were randomized. At 12 months, 47.7% EBV and 16.8% SoC subjects had a &Dgr;FEV1 greater than or equal to 15% (P < 0.001). &Dgr;EBV‐SoC at 12 months was statistically and clinically significant: for FEV1, 0.106 L (P < 0.001); 6‐minute‐walk distance, +39.31 m (P = 0.002); and St. Georges Respiratory Questionnaire, −7.05 points (P = 0.004). Significant &Dgr;EBV‐SoC were also observed in hyperinflation (residual volume, −522 ml; P < 0.001), modified Medical Research Council Dyspnea Scale (−0.8 points; P < 0.001), and the BODE (body mass index, airflow obstruction, dyspnea, and exercise capacity) index (−1.2 points). Pneumothorax was the most common serious adverse event in the treatment period (procedure to 45 d), in 34/128 (26.6%) of EBV subjects. Four deaths occurred in the EBV group during this phase, and one each in the EBV and SoC groups between 46 days and 12 months. Conclusions: Zephyr EBV provides clinically meaningful benefits in lung function, exercise tolerance, dyspnea, and quality of life out to at least 12 months, with an acceptable safety profile in patients with little or no collateral ventilation in the target lobe. Clinical trial registered with www.clinicaltrials.gov (NCT 01796392).

Statins for Treatment of Pulmonary Hypertension

By virtue of their multiple actions, including anti-inflammatory, antiproliferative, and pro-apoptotic traits and the ability to restore endothelial vasoactive mediator production, statins have been proposed as potential therapies for pulmonary hypertension. In experimental studies in rats with pulmonary hypertension induced either by either monocrotaline or hypoxia, statins have blunted the severity of pulmonary hypertension, right ventricular hypertrophy, and pulmonary vascular remodeling, sometimes in association with the restoration of the endothelial cell production of nitric oxide. Pending trials that demonstrate the efficacy of statins in pulmonary arterial hypertension in humans, however, the clinical use of statins should be considered investigational.