FCCP

FCCP, a proton carrier (H+ ionophore), is also a powerful phosphoric acid defusing coupling agent, which promotes the depolarization of plasma membrane and mitochondrial membrane.FCCP can affect various activities in which cellular calcium ions participate, inhibit K+ background current and induce small inward current, decrease 0.1 unit pH, and induce intracellular Na+ to increase. FCCP can stimulate Mg2+-ATPase activity, inhibit β-amyloid formation, and simulate the physiological effect of glutamate receptor agonist NMDA on mitochondrial superoxide.

Exposure of K695sw cells to the protonophore FCCP resulted in a concentration-dependent decrease in both Aβ release and the formation of the cell-associated C99 fragment. Production of the ectodomain fragment APPsα was only affected by exposure to the highest concentration of FCCP, whereas neither total cellular levels of APP nor the maturation of APP via N /O -linked glycosylation appeared to be affected by any concentration of FCCP used^[1]. Pre-exposure to 200 nM FCCP during 120 min protects and enhances the follicle integrity in cat ovarian tissue during short-term in vitro culture^[2]. Concentrations of FCCP that cause mitochondrial oxidation without depolarisation are cardioprotective. Higher FCCP concentrations dissipate mitochondrial membrane potential and exacerbate injury^[3]. FCCP activated ionic currents and depolarized the plasma membrane potential in a dose-dependent manner. Neither the removal of extracellular Ca2+ nor pretreatment with BAPTA/AM affected the FCCP-induced currents, implying that the currents are not associated with the FCCP-induced intracellular [Ca2+]i increase^[4]. Application of FCCP evoked a gradual increase in cell body [Ca2+]i that reached a level approximately 3-fold higher than baseline after 60 min. Moreover, FCCP released Ca2+ even when added after mitochondrial stores of Ca2+ had previously been emptied by an alternate method. FCCP, in addition to its recognized effect on mitochondrial Ca2+ sequestration, also releases Ca2+ from a non-mitochondrial store and is, therefore, unsuitable for use in an intact neuron to selectively inactivate mitochondrial Ca2+ uptake^[5]. A further analysis of this effect on BHK21 cells has shown that a decrease in the number of microtubules can be observed 15 min after adding FCCP and there is complete disruption after 60 min. Regrowth of microtubules was initiated 30 min after removal of FCCP, in marked contrast with the rapid reversion observed when microtubules are disrupted by nocodazole^[6].

References:
[1]. Connop BP, Thies RL, et,al. Novel effects of FCCP [carbonyl cyanide p-(trifluoromethoxy)phenylhydrazone] on amyloid precursor protein processing. J Neurochem. 1999 Apr;72(4):1457-65. doi: 10.1046/j.1471-4159.1999.721457.x. PMID: 10098849.
[2]. Tanpradit N, Chatdarong K, et,al. Carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) pre-exposure ensures follicle integrity during in vitro culture of ovarian tissue but not during cryopreservation in the domestic cat model. J Assist Reprod Genet. 2016 Dec;33(12):1621-1631. doi: 10.1007/s10815-016-0810-5. Epub 2016 Sep 17. PMID: 27639998; PMCID: PMC5171893.
[3]. Brennan JP, Berry RG, et,al. FCCP is cardioprotective at concentrations that cause mitochondrial oxidation without detectable depolarisation. Cardiovasc Res. 2006 Nov 1;72(2):322-30. doi: 10.1016/j.cardiores.2006.08.006. Epub 2006 Aug 16. PMID: 16979603.
[4]. Park KS, Jo I, et,al. FCCP depolarizes plasma membrane potential by activating proton and Na+ currents in bovine aortic endothelial cells. Pflugers Arch. 2002 Jan;443(3):344-52. doi: 10.1007/s004240100703. Epub 2001 Oct 6. PMID: 11810202.
[5]. Jensen JR, Rehder V. FCCP releases Ca2+ from a non-mitochondrial store in an identified Helisoma neuron. Brain Res. 1991 Jun 14;551(1-2):311-4. doi: 10.1016/0006-8993(91)90947-t. PMID: 1913158.
[6]. Maro B, Marty MC, et,al. In vivo and in vitro effects of the mitochondrial uncoupler FCCP on microtubules. EMBO J. 1982;1(11):1347-52. doi: 10.1002/j.1460-2075.1982.tb01321.x. PMID: 6765194; PMCID: PMC553215.

FCCP是一种质子载体（H+离子载体），也是一种强磷酸化解偶联剂，促进质膜和线粒体膜的去极化。FCCP可以影响细胞钙离子参与的各种活动，抑制K+背景电流并诱导小的内向电流，降低0.1个单位的pH值，诱导细胞内Na+增加。 FCCP可刺激Mg2+-ATP酶活性，抑制β-淀粉样蛋白形成，模拟谷氨酸受体激动剂NMDA对线粒体超氧化物的生理作用。

将 K695sw 细胞暴露于质子载体 FCCP 会导致 Aβ 释放和细胞相关 C99 片段形成的浓度依赖性降低。胞外域片段 APPsα 的产生仅受暴露于最高浓度 FCCP 的影响，而 APP 的总细胞水平和通过 N /O 连接糖基化的 APP 成熟似乎不受所用任何浓度 FCCP 的影响 ^[1]。在 120 分钟内预暴露于 200 nM FCCP 可在短期体外培养过程中保护和增强猫卵巢组织中的卵泡完整性^[2]。引起线粒体氧化而不去极化的 FCCP 浓度具有心脏保护作用。较高的 FCCP 浓度会耗散线粒体膜电位并加剧损伤^[3]。 FCCP 激活离子电流并以剂量依赖性方式去极化质膜电位。细胞外 Ca2+ 的去除和 BAPTA/AM 的预处理都不影响 FCCP 诱导的电流，这意味着电流与 FCCP 诱导的细胞内 [Ca2+]i 增加无关^[4]。 FCCP 的应用引起细胞体 [Ca2+]i 的逐渐增加，在 60 分钟后达到比基线高约 3 倍的水平。此外，即使在先前通过替代方法清空 Ca2+ 的线粒体储存后添加，FCCP 也会释放 Ca2+。 FCCP 除了公认的对线粒体 Ca2+ 螯合的作用外，还从非线粒体储存中释放 Ca2+，因此不适合在完整神经元中用于选择性灭活线粒体 Ca2+ 摄取^[5] .进一步分析这种对 BHK21 细胞的影响表明，在添加 FCCP 后 15 分钟可以观察到微管数量减少，60 分钟后完全破坏。微管在去除 FCCP 后 30 分钟开始再生，这与诺考达唑破坏微管时观察到的快速恢复形成鲜明对比^[6]。