Abstract-The objective of this study was to test whether a glycosaminoglycan component of the surface glycocalyx layer is a fluid shear stress sensor on endothelial cells (ECs). Because enhanced nitric oxide (NO) production in response to fluid shear stress is a characteristic and physiologically important response of ECs, we evaluated NO x (NO 2 Ϫ and NO 3 Ϫ ) production in response to fluid shear stress after enzymatic removal of heparan sulfate, the dominant glycosaminoglycan of the EC glycocalyx, from cultured ECs. The significant NO x production induced by steady shear stress (20 dyne/cm 2 ) was inhibited completely by pretreatment with 15 mU/mL heparinase III (E.C.4.2.2.8) for 2 hours. Oscillatory shear stress (10Ϯ15 dyne/cm 2 ) induced an even greater NO x production than steady shear stress that was completely inhibited by pretreatment with heparinase III. Addition of bradykinin (BK) induced significant NO x production that was not inhibited by heparinase pretreatment, demonstrating that the cells were still able to produce abundant NO after heparinase treatment. Fluorescent imaging with a heparan sulfate antibody revealed that heparinase III treatments removed a substantial fraction of the heparan sulfate bound to the surfaces of ECs. In summary, these experiments demonstrate that a heparan sulfate component of the EC glycocalyx participates in mechanosensing that mediates NO production in response to shear stress. The full text of this article is available online at http://www.circresaha.org. Key Words: shear stress Ⅲ endothelial cells Ⅲ heparan sulfate Ⅲ nitric oxide Ⅲ glycocalyx T he inner surfaces of blood vessels are lined with a monolayer of endothelial cells (ECs) that is continually exposed to the mechanical shearing forces (stresses) of blood flow. Variations in shear stress magnitude as well as temporal and spatial distribution have been shown to induce alterations in endothelial permeability and hydraulic conductivity, 1-3 cytoskeletal structure, 4 -7 surface adhesion molecule expression, 8 and gene expression. 9,10 In addition, the exposure of endothelial cells to shear (both steady and oscillatory) has been shown to alter the production of vasoregulating agents of which nitric oxide (NO) is perhaps the most notable. [11][12][13] NO is a vasodilator produced by the conversion of L-arginine to L-citrulline that is catalyzed by endothelial nitric oxide synthase (eNOS). NO modulates vascular tone by eliciting relaxation of smooth muscle cells while inhibiting smooth muscle cell growth. 14 NO production responds to changes in shear stress in a biphasic manner in human umbilical vein endothelial cells (HUVECs) and bovine aortic endothelial cells (BAECs). 11,12 There is an initial rapid NO production phase that is G protein and Ca 2ϩ -dependent and is influenced by rate of change of shear and not the shear level per se. The subsequent phase is characterized by a lower rate of NO production rate that is G protein and Ca 2ϩ -independent but is shear level dependent. 12,15 Both phases of the NO respo...

To increase our understanding of important subject characteristics and design variables affecting the performance of oral moxifloxacin in thorough QT studies, population pharmacokinetic and concentration-QTc models were developed by pooling data from 20 studies. A 1-compartment model with first-order elimination described the pharmacokinetics. Absorption delay was modeled using 8 transit compartments. Mean (95% confidence interval) values for oral clearance, apparent volume of distribution, the first-order absorption rate constant, and mean transit time were 11.7 (11.5-11.9) L/h, 147 (144-150) L, 1.9 (1.7-2.1) 1/h, and 0.3 (0.28-0.34) hours, respectively. Overencapsulating the moxifloxacin tablet increased mean transit time by 138% and delayed time to maximum concentration by 0.5 hours but had a minimal effect on overall exposure. Administration with food decreased absorption rate constant by 27%. Women had higher moxifloxacin exposure compared with men, which was explained by lower body weights. A linear model described the concentration-QTc relationship with a mean slope of 3.1 (2.8-3.3) milliseconds per µg/mL moxifloxacin. Mean slopes for individual studies ranged from 1.6 to 4.8 milliseconds per µg/mL. Hysteresis between moxifloxacin plasma concentrations and QTc was modest, and incorporating this delay did not result in a different slope (3.3 milliseconds per µg/mL). There were no differences in slope estimates between men and women or among race categories.

IMPORTANCEThe US Food and Drug Administration (FDA) has provided guidance that sunscreen active ingredients with systemic absorption greater than 0.5 ng/mL or with safety concerns should undergo nonclinical toxicology assessment including systemic carcinogenicity and additional developmental and reproductive studies. OBJECTIVE To determine whether the active ingredients (avobenzone, oxybenzone, octocrylene, and ecamsule) of 4 commercially available sunscreens are absorbed into systemic circulation. DESIGN, SETTING, AND PARTICIPANTS Randomized clinical trial conducted at a phase 1 clinical pharmacology unit in the United States and enrolling 24 healthy volunteers. Enrollment started in July 2018 and ended in August 2018.INTERVENTIONS Participants were randomized to 1 of 4 sunscreens: spray 1 (n = 6 participants), spray 2 (n = 6), a lotion (n = 6), and a cream (n = 6). Two milligrams of sunscreen per 1 cm 2 was applied to 75% of body surface area 4 times per day for 4 days, and 30 blood samples were collected over 7 days from each participant. MAIN OUTCOMES AND MEASURESThe primary outcome was the maximum plasma concentration of avobenzone. Secondary outcomes were the maximum plasma concentrations of oxybenzone, octocrylene, and ecamsule. RESULTS Among 24 participants randomized (mean age, 35.5 [SD, 10.5] years; 12 [50%] women; 14 [58%] black or African American), 23 (96%) completed the trial. Systemic concentrations greater than 0.5 ng/mL were reached for all 4 products after 4 applications on day 1. The most common adverse event was rash (1 participant with each sunscreen).