Enantioselective binding of carvedilol to human serum albumin and alpha-1-acid glycoprotein

Carvedilol, a highly protein-bound beta-blocker, is used in therapy as a racemic mixture of its two enantiomers that exhibit different pharmacological activity. The aim of this study was to evaluate the stereoselective nature of its binding to the two major plasma proteins: albumin and alpha-1-acid glycoprotein. The determination of the plasma protein-binding degree for carvedilol and its enantiomers was achieved using ultrafiltration for the separation of the free fraction, followed by LC-MS/MS quantification, using two different developed and validated methods in terms of stationary phase: achiral C18 type and chiral ovomucoid type. Furthermore, molecular docking methods were applied in order to investigate and to better understand the mechanism of protein-binding for S-(-)- and R-(+)-carvedilol. A difference in the binding behavior of the two enantiomers to the plasma proteins was observed when taken individually, with R-(+)-carvedilol having a higher affinity for albumin and S-(-)-carvedilol for alpha-1-acid glycoprotein. However, in the case of the racemic mixture, the binding of the S enantiomer to alpha-1-acid glycoprotein seemed to be influenced by the presence of its antipode, although no such influence was observed in the case of albumin. The results raise the question of a binding competition between the two enantiomers for alpha-1-acid glycoprotein.

Real-Time Visualization of the Antioxidative Potency of Drugs for the Prevention of Myocardium Ischemia-Reperfusion Injury by a NIR Fluorescent Nanoprobe

The burst of the reactive oxygen species (ROS) is the culprit of myocardial ischemia-reperfusion injury. As direct ROS scavengers, antioxidants are clinically documented drugs for the prevention of reperfusion injury. However, some drugs give disappointing therapeutic performance despite their good in vitro effects. Therefore, in vivo assessments are necessary to screen the antioxidants before clinical trials. However, traditional methods such as histological study require invasive and complicated preprocessing of the biological samples, which may fail to reflect the actual level of the unstable ROS with a very short lifetime. Peroxynitrite (ONOO^-) is a characteristic endogenous ROS produced during reperfusion. Here, we modified the ONOO^--responsive near-infrared fluorescent probe on a myocardium-targeting silica cross-linked micelle to prepare a nanoprobe for the real-time monitoring of ONOO^- during coronary reperfusion. A ROS-stable cyanine dye was co-labeled as an internal reference to achieve ratiometric sensing. The nanoprobe can passively target the infarcted myocardium and monitor the generation of ONOO^- during reperfusion in real-time. The antioxidants, carvedilol, atorvastatin, and resveratrol, were used as model drugs to demonstrate the capability of the nanoprobe to evaluate the antioxidative potency in situ. The drugs were either loaded and delivered by the nanoprobe to compare their in vivo efficacy under similar concentrations or administered intraperitoneally as a free drug to take their pharmacokinetics into account. The imaging results revealed that pharmacokinetics might be the determinant factor that influences the efficacy of the antioxidants.