Department of Kinesiology, University of Massachusetts Amherst, MA, USA.
Department of Kinesiology, University of Massachusetts Amherst, MA, USA; Diabetes and Metabolism Research Center, University of Utah, UT, USA.
Free Radic Biol Med. 2024 Nov 1;224:325-334. doi: 10.1016/j.freeradbiomed.2024.08.024. Epub 2024 Aug 22.
Oxidative stress plays a critical role in cellular dysfunction associated with cigarette smoke exposure and aging. Some chemicals from tobacco smoke have the potential to amplify mitochondrial ROS (mROS) production, which, in turn, may impair mitochondrial respiratory function. Accordingly, the present study tested the hypothesis that a mitochondria-targeted antioxidant (MitoTEMPO, MT) would attenuate the inhibitory effects of cigarette smoke on skeletal muscle respiratory capacity of middle-aged mice. Specifically, mitochondrial oxidative phosphorylation was assessed using high-resolution respirometry in permeabilized fibers from the fast-twitch gastrocnemius muscle of middle-aged C57Bl/6J mice. Before the assessment of respiration, tissues were incubated for 1hr with a control buffer (CON), cigarette smoke condensate (2 % dilution, SMOKE), or MitoTEMPO (10 μM) combined with cigarette smoke condensate (MT + SMOKE). Cigarette smoke condensate (CSC) decreased maximal-ADP stimulated respiration (CON: 60 ± 15 pmolO.s.mg and SMOKE: 33 ± 8 pmolO.s.mg; p = 0.0001), and this effect was attenuated by MT (MT + SMOKE: 41 ± 7 pmolO.s.mg; p = 0.02 with SMOKE). Complex-I specific respiration was inhibited by CSC, with no significant effect of MT (p = 0.35). Unlike CON, the addition of glutamate (ΔGlutamate) had an additive effect on respiration in fibers exposed to CSC (CON: 0.9 ± 1.1 pmolO.s.mg and SMOKE: 5.4 ± 3.7 pmolO.s.mg; p = 0.008) and MT (MT + SMOKE: 8.2 ± 3.8 pmolO.s.mg; p ≤ 0.01). Complex-II specific respiration was inhibited by CSC but was partially restored by MT (p = 0.04 with SMOKE). Maximal uncoupled respiration induced by FCCP was inhibited by CSC, with no significant effect of MT. These findings underscore that mROS contributes to cigarette smoke condensate-induced inhibition of mitochondrial respiration in fast-twitch gastrocnemius muscle fibers of middle-aged mice thus providing a potential target for therapeutic treatment of smoke-related diseases. In addition, this study revealed that CSC largely impaired muscle respiratory capacity by decreasing metabolic flux through mitochondrial pyruvate transporter (MPC) and/or the enzymes upstream of α-ketoglutarate in the Krebs cycle.
氧化应激在与吸烟和衰老相关的细胞功能障碍中起着关键作用。烟草烟雾中的一些化学物质有可能放大线粒体 ROS（mROS）的产生，这反过来可能损害线粒体呼吸功能。因此，本研究检验了这样一个假设，即一种靶向线粒体的抗氧化剂（MitoTEMPO，MT）将减轻香烟烟雾对中年小鼠骨骼肌呼吸能力的抑制作用。具体来说，使用快速抽搐比目鱼肌的透化纤维中的高分辨率呼吸计评估线粒体氧化磷酸化。在评估呼吸之前，组织在对照缓冲液（CON）、香烟烟雾冷凝物（2%稀释，SMOKE）或 MitoTEMPO（10 μM）与香烟烟雾冷凝物（MT+SMOKE）结合孵育 1 小时。香烟烟雾冷凝物（CSC）降低了最大 ADP 刺激的呼吸（CON：60±15 pmolO.s.mg 和 SMOKE：33±8 pmolO.s.mg；p=0.0001），并且 MT 减弱了这种作用（MT+SMOKE：41±7 pmolO.s.mg；p=0.02 与 SMOKE）。CSC 抑制了复合物 I 特异性呼吸，而 MT 没有明显影响（p=0.35）。与 CON 不同，谷氨酸（ΔGlutamate）的添加对暴露于 CSC 的纤维的呼吸有相加作用（CON：0.9±1.1 pmolO.s.mg 和 SMOKE：5.4±3.7 pmolO.s.mg；p=0.008）和 MT（MT+SMOKE：8.2±3.8 pmolO.s.mg；p≤0.01）。CSC 抑制了复合物 II 特异性呼吸，但 MT 部分恢复了这种作用（p=0.04 与 SMOKE）。FCCP 诱导的最大解偶联呼吸被 CSC 抑制，而 MT 没有明显影响。这些发现强调了 mROS 有助于香烟烟雾冷凝物诱导的中年小鼠快肌比目鱼肌纤维中线粒体呼吸的抑制，从而为治疗与吸烟有关的疾病提供了一个潜在的治疗靶点。此外，本研究表明，CSC 主要通过降低线粒体丙酮酸转运体（MPC）和/或三羧酸循环中α-酮戊二酸上游的酶的代谢通量来降低肌肉呼吸能力。
