Department of Cardiology & Cardiac Surgery Sections, VA Medical Center, University of Minnesota, Minneapolis, MN 55417, USA.
Transl Res. 2012 May;159(5):383-90. doi: 10.1016/j.trsl.2011.11.001. Epub 2011 Dec 2.
Myocardial uncoupling protein (UCP)-2 is increased with chronic peroxisome proliferator-activated receptor γ (PPARγ) stimulation, but the effect on membrane potential and superoxide is unclear. Wild-type (WT) and UCP-2 knockout (KO) mice were given a 3-week diet of control (C) or the PPARγ agonist pioglitazone (PIO; 50 μg/g-chow per day). In isolated mitochondria, UCP-2 content by Western blots, membrane potential (ΔΨm) by tetraphenylphosphonium (TPP), and relative superoxide levels by dihydroethidium (DHE) were measured. Oxygen respiration was determined at baseline and after 10 min anoxia-reoxygenation. PIO induced a 2-fold increase in UCP-2 and nuclear-bound PGC1α in WT mice with no UCP-2 expression in KO mice. Mitochondrial ΔΨm from WT mice on C and PIO diets was -166±4 mV and -147±6 mV, respectively (P<0.05). These values were lower than in UCP-2 KO mice on C and PIO (-180±4 mV and -180±4 mV, respectively; P<0.05). Maximal complex III inhibitable superoxide from WT mice on C and PIO diets was 22.5±1.3 and 17.8±1.1 AU, respectively (P<0.05), and were lower than UCP-2 KO on C and PIO (32.9±2.3 and 29.2±1.9 AU, respectively; P<0.05). Postanoxia, the respiratory control index (RCI) in mitochondria from WT mice with and without PIO was 2.5±0.3 and 2.4±0.2, respectively, and exceeded that of UCP-2 KO mice on C and PIO (1.2±0.1 and 1.4±0.1, respectively; P<0.05). In summary, chronic PPARγ stimulation leads to depolarization of the inner membrane and reduced superoxide of isolated heart mitochondria, which was critically dependent on increased expression of UCP-2. Thus, UCP-2 expression affords resistance to brief anoxia-reoxygenation.
心肌解偶联蛋白 (UCP)-2 随着慢性过氧化物酶体增殖物激活受体 γ (PPARγ) 刺激而增加，但对膜电位和超氧化物的影响尚不清楚。给予野生型 (WT) 和 UCP-2 敲除 (KO) 小鼠 3 周对照 (C) 或 PPARγ 激动剂吡格列酮 (PIO；每天 50 μg/g 饲料) 饮食。在分离的线粒体中，通过 Western blot 测量 UCP-2 含量、四苯基膦 (TPP) 的膜电位 (ΔΨm) 和二氢乙啶 (DHE) 的相对超氧化物水平。在基线和 10 分钟缺氧-再氧合后测定氧呼吸。PIO 在 WT 小鼠中诱导 UCP-2 和核结合 PGC1α 增加 2 倍，而 KO 小鼠中没有 UCP-2 表达。WT 小鼠在 C 和 PIO 饮食中的线粒体 ΔΨm 分别为-166±4 mV 和-147±6 mV（P<0.05）。这些值低于 C 和 PIO 饮食中的 UCP-2 KO 小鼠（分别为-180±4 mV 和-180±4 mV；P<0.05）。WT 小鼠在 C 和 PIO 饮食中的最大 III 复合物可抑制超氧化物分别为 22.5±1.3 和 17.8±1.1 AU（P<0.05），低于 C 和 PIO 的 UCP-2 KO（分别为 32.9±2.3 和 29.2±1.9 AU；P<0.05）。再氧合后，WT 小鼠有和没有 PIO 的线粒体呼吸控制指数 (RCI) 分别为 2.5±0.3 和 2.4±0.2，高于 C 和 PIO 的 UCP-2 KO 小鼠（分别为 1.2±0.1 和 1.4±0.1；P<0.05）。总之，慢性 PPARγ 刺激导致心脏线粒体内膜去极化和超氧化物减少，这主要依赖于 UCP-2 的增加表达。因此，UCP-2 的表达提供了对短暂缺氧-再氧合的抵抗。
