The gasotransmitter carbon monoxide (CO) regulates fluid and electrolyte movements across epithelial tissues. However, its action on anion channels is incompletely understood. Here, we investigate the direct action of CO on the cystic fibrosis transmembrane conductance regulator (CFTR) by applying CO-releasing molecules (CORMs) to the intracellular side of excised inside-out membrane patches from cells heterologously expressing wild-type human CFTR. Addition of increasing concentrations of tricarbonyldichlororuthenium (II) dimer (CORM-2) (1 - 300 μM) inhibited CFTR channel activity, whereas the control RuCl₃ (100 μM) was without effect. CORM-2 predominantly inhibited CFTR by decreasing the frequency of channel openings and hence, open probability (P_o). But, it also reduced current flow through open channels with very fast kinetics, particularly at elevated concentrations. By contrast, the chemically distinct CO-releasing molecule CORM-3 inhibited CFTR by decreasing P_o without altering current flow through open channels. Neither depolarizing the membrane voltage nor raising the ATP concentration on the intracellular side of the membrane affected CFTR inhibition by CORM-2. Interestingly, CFTR inhibition by CORM-2, but not by CFTR_inh-172, was prevented by prior enhancement of channel activity by the clinically-approved CFTR potentiator ivacaftor. Similarly, when added after CORM-2, ivacaftor completely relieved CFTR inhibition. In conclusion, CORM-2 has complex effects on wild-type human CFTR consistent with allosteric inhibition and open-channel blockade. Inhibition of CFTR by CO-releasing molecules suggests that CO regulates CFTR activity and that the gasotransmitter has tissue-specific effects on epithelial ion transport. The action of ivacaftor on CFTR Cl^- channels inhibited by CO potentially expands the drug's clinical utility.

中文翻译：

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一氧化碳释放分子抑制囊性纤维化跨膜电导调节剂Cl-通道。

气体递质一氧化碳（CO）调节液体和电解质在上皮组织中的运动。但是，它对阴离子通道的作用尚不完全清楚。在这里，我们通过从异源表达野生型人类CFTR的细胞中将CO释放分子（CORM）应用于切除的内向外膜片的细胞内侧，研究了CO对囊性纤维化跨膜电导调节剂（CFTR）的直接作用。添加浓度越来越高的三羰基二氯钌（II）二聚体（CORM-2）（1-300μM）会抑制CFTR通道活性，而对照RuCl ₃（100μM）没有作用。CORM-2主要通过降低通道打开的频率并因此降低打开概率来抑制CFTR（P _o）。但是，它也以非常快的动力学降低了流经开放通道的电流，特别是在浓度升高的情况下。相比之下，化学上独特的CO释放分子CORM-3通过降低P _o而不改变通过明渠的电流来抑制CFTR 。使膜电压去极化或提高膜细胞内侧的ATP浓度都不会影响CORM-2对CFTR的抑制作用。有趣的是，CORM-2会抑制CFTR，但CFTR _inh不会临床认可的CFTR增强剂依伐卡托可通过预先增强通道活性来预防-172。同样，当在CORM-2之后添加时，依伐卡托可以完全缓解CFTR抑制作用。总之，CORM-2对野生型人CFTR具有复杂的作用，与变构抑制和明渠阻断相一致。释放CO的分子对CFTR的抑制作用表明，CO调节CFTR的活性，而气体递质对上皮离子的转运具有组织特异性作用。ivacaftor对CFTR Cl为基准的动作^-由CO抑制通道潜在扩大药物的临床效用。