A Pd ²⁺-Free Near-Infrared Fluorescent Probe Based on Allyl Ether Isomerization for Tracking CORM-3 with High Contrast Imaging in Living Systems

Carbon monoxide (CO) is increasingly being accepted as a cytoprotective and homeostatic molecule with important signalling capabilities in physiological and pathophysiological situations. The endogenous production of CO occurs through the activity of constitutive (haem oxygenase 2) and inducible (haem oxygenase 1) haem oxygenases, enzymes that are responsible for the catabolism of haem. Through the generation of its products, which in addition to CO includes the bile pigments biliverdin, bilirubin and ferrous iron, the haem oxygenase 1 system also has an obligatory role in the regulation of the stress response and in cell adaptation to injury. This Review provides an overview of the physiology of CO, summarizes the effects of CO gas and CO-releasing molecules in preclinical animal models of cardiovascular disease, inflammatory disorders and organ transplantation, and discusses the development and therapeutic options for the exploitation of this simple gaseous molecule.

The long wavelength (far-red to NIR) analyte-responsive fluorescent probes are advantageous for in vivo bioimaging because of minimum photo-damage to biological samples, deep tissue penetration, and minimum interference from background auto-fluorescence by biomolecules in the living systems. Thus, great interest in the development of new long wavelength analyte-responsive fluorescent probes has emerged in recent years. This review highlights the advances in the development of far-red to NIR fluorescent probes since 2000, and the probes are classified according to their organic dye platforms into various categories, including cyanines, rhodamine analogues, BODIPYs, squaraines, and other types (240 references).

The heme oxygenases, which consist of constitutive and inducible isozymes (HO-1, HO-2), catalyze the rate-limiting step in the metabolic conversion of heme to the bile pigments (i.e., biliverdin and bilirubin) and thus constitute a major intracellular source of iron and carbon monoxide (CO). In recent years, endogenously produced CO has been shown to possess intriguing signaling properties affecting numerous critical cellular functions including but not limited to inflammation, cellular proliferation, and apoptotic cell death. The era of gaseous molecules in biomedical research and human diseases initiated with the discovery that the endothelial cell-derived relaxing factor was identical to the gaseous molecule nitric oxide (NO). The discovery that endogenously produced gaseous molecules such as NO and now CO can impart potent physiological and biological effector functions truly represented a paradigm shift and unraveled new avenues of intense investigations. This review covers the molecular and biochemical characterization of HOs, with a discussion on the mechanisms of signal transduction and gene regulation that mediate the induction of HO-1 by environmental stress. Furthermore, the current understanding of the functional significance of HO shall be discussed from the perspective of each of the metabolic by-products, with a special emphasis on CO. Finally, this presentation aspires to lay a foundation for potential future clinical applications of these systems.