Heme Oxygenase and the Kidney

Heme oxygenases (HOs) are the enzymes responsible for the breakdown of heme and the generation of biliverdin/bilirubin and carbon monoxide (CO). The kidney is a complex organ consisting of many different cell types all working together for the single purpose of filtering the blood to eliminate waste products and conserving ions, minerals, and water necessary for life. HO enzymes and their products play a critical role in the normal function of the kidney as well as protecting the kidney from various insults including ischemia and exposure to nephrotoxins. For example, the HO metabolite, bilirubin, is a potent antioxidant which can limit damage to renal tubular epithelial cells following exposure to nephrotoxins associated with chemotherapy or traumatic injury. Another HO metabolite, CO, is an important vasodilator of renal blood vessels and helps protect against severe decreases in renal blood flow in conditions as diverse as exposure to radiocontrast agents and in hypertension-induced kidney disease. HO and its metabolites also play an important role in the survival of kidney cells after acute and chronic injuries by regulating important cell growth and programmed cell death pathways. The intent of this volume is to highlight the important role that HO enzymes and their related metabolites, bilirubin and CO, play in the regulation of renal function and in the response of the kidney to both acute and chronic pathologies.