Use of carbon monoxide in minimizing ischemia/reperfusion injury in transplantation

Although carbon monoxide (CO) is known to be toxic because of its ability to interfere with oxygen delivery at high concentrations, mammalian cells endogenously generate CO primarily via the catalysis of heme by heme oxygenases. Recent findings have indicated that heme oxygenases and generation of CO serve as a key mechanism to maintain the integrity of the physiological function of organs and supported the development of a new paradigm that CO, at low concentrations, functions as a signaling molecule in the body and exerts significant cytoprotection. Consequently, exogenously delivered CO has been shown to mediate potent protection in various injury models through its anti-inflammatory, vasodilating, and antiapoptotic functions. Ischemia/reperfusion (I/R) injury associated with organ transplantation is one of the major deleterious factors limiting the success of transplantation. Ischemia/reperfusion injury is a complex cascade of interconnected events involving cell damage, apoptosis, vigorous inflammatory responses, microcirculation disturbance, and thrombogenesis. Carbon monoxide has a great potential in minimizing I/R injury. This review will provide an overview of the basic physiology of CO, preclinical studies examining efficacy of CO in I/R injury models, and possible protective mechanisms. Carbon monoxide could be developed to be a valuable therapeutic molecule in minimizing I/R injury in transplantation.