Acute Heat Exposure Protects Against Endothelial Ischemia-reperfusion Injury in Aged Humans

Non-pharmacological therapies that protect against endothelial ischemia-reperfusion injury (I/R) remain limited in aged adults. Acute heat exposure protects against endothelial I/R injury in young adults, but its efficacy has never been explored in aged adults. Therefore, we tested the hypothesis that acute heat exposure would protect endothelial-dependent vasodilation following I/R injury in aged adults. Nine (2 men, 69 ± 8 yrs) aged adults were exposed to a thermoneutral control condition or whole-body passive heating (water-perfused suit) sufficient to increase body core temperature by 1.2 °C. Experiments were separated by at least 7 days. Heat exposure was always performed first in order to time-match the thermoneutral control condition. Endothelium-dependent vasodilation was assessed via flow-mediated dilation of the brachial artery before (pre-I/R) and after I/R injury (post-I/R), which was induced by 20 min of arm ischemia followed by 20 min of reperfusion. Ischemia-reperfusion injury reduced flow-mediated dilation following the thermoneutral control condition (pre-I/R, 4.5 ± 2.9 % vs. post-I/R, 0.9 ± 2.8 %, P < 0.01), but was well maintained with prior heat exposure (pre-I/R, 4.4 ± 2.8 % vs. post-I/R, 3.5 ± 2.8 %, P = 0.5). Taken together, acute heat exposure protects against endothelial I/R injury in aged adults. These results highlight the therapeutic potential of heat therapy to prevent endothelial dysfunction associated with I/R injury in aged adults who are most at risk for an ischemic event.