Oxidative stress in kidney transplantation: causes, consequences, and potential treatment.

Oxidative stress is a major mediator of adverse outcomes throughout the course of transplantation. Transplanted kidneys are prone to oxidative stress-mediated injury by pre-transplant and post-transplant conditions that cause reperfusion injury or imbalance between oxidants and antioxidants. Besides adversely affecting the allograft, oxidative stress and its constant companion, inflammation, cause cardiovascular disease, cancer, metabolic syndrome, and other disorders in transplant recipients. Presence and severity of oxidative stress can be assessed by various biomarkers produced from interaction of reactive oxygen species with lipids, proteins, nucleic acids, nitric oxide, glutathione, etc. In addition, expression and activities of redox-sensitive molecules such as antioxidant enzymes can serve as biomarkers of oxidative stress. Via activation of nuclear factor kappa B, oxidative stress promotes inflammation which, in turn, amplifies oxidative stress through reactive oxygen species generation by activated immune cells. Therefore, inflammation markers are indirect indicators of oxidative stress. Many treatment options have been evaluated in studies conducted at different stages of transplantation in humans and animals. These studies have provided useful strategies for use in donors or in organ preservation solutions. However, strategies tested for use in post-transplant phase have been largely inconclusive and controversial. A number of therapeutic options have been exclusively examined in animal models and only a few have been tested in humans. Most of the clinical investigations have been of short duration and have provided no insight into their impact on the long-term survival of transplant patients. Effective treatment of oxidative stress in transplant population remains elusive and awaits future explorations.