Limb Ischemic Conditioning Induces Oxidative Stress Followed by a Correlated Increase of HIF-1α in Healthy Volunteers

Background: Local and remote ischemic preconditioning has been used as a protective intervention against ischemia/reperfusion (I/R) damage in several preclinical and clinical studies. However, its physiological mechanisms are not completely known. I/R increases the production of reactive oxygen species, which also serve as messengers for a variety of functions. Hypoxia-inducible factor 1 alpha (HIF-1 alpha) is probably the most important transcription factor mediator of hypoxic signaling. Objective: We hypothesized that limb ischemic conditioning (LIC) induces a local oxidative/nitrosative stress and a correlated increase of HIF-1 alpha plasma levels. Methods: An observational, prospective, and single-center study has been conducted in 27 healthy volunteers. LIC was applied: three cycles (5 min of ischemia followed by 5 min of reperfusion) using an ischemia cuff placed on the upper left arm. Time course of 8-isoprostane, nitrite, and HIF-1 alpha levels was measured in blood plasma. Venous blood was sampled from the left arm before tourniquet inflation (basal) and after LIC: 1 min and 2 hr for 8-isoprostane and nitrite; and 1 min, 2 hr, 8 hr, 24 hr, and 48 hr for HIF-1 alpha. Results: After LIC, we have found an early increase of 8-isoprostane and nitrite. HIF-1 alpha increased at 2 and 8 hr after LIC. We found a direct correlation between HIF-1 alpha and 8-isoprostane and nitrite plasma levels. Conclusions: We concluded that LIC induces an early oxidative/nitrosative stress in the arm followed by an increase of HIF-1 alpha plasma levels correlated with 8-isoprostane and nitrite levels, possibly as a local response.