HMR 1883

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HMR 1883 (1-[5-[2-(5-chloro-o-anisamido)ethyl]-2-methoxyphenyl]sulfonyl-3 methylthiourea) and its sodium salt HMR 1098, are experimental anti-arrhythmic drugs classified as sulfonylthiourea compounds.[1] Their main purpose is to treat ventricular fibrillation caused by myocardial ischemia. They were synthesized via structural modifications to glibenclamide, an antidiabetic drug.[1] Both HMR 1883 and glibenclamide act by inactivating the ATP-sensitive potassium channels (KATP) responsible for potassium efflux.[2] Unlike glibenclamide, HMR 1883 has been suggested to target selectively the Kir6.2/SUR2A KATP subtype, found mostly in the membranes of cardiac cells.[3] However, data showing that HMR 1098 inhibits the Kir6.2/SUR1 KATP subtype found in insulin-secreting pancreatic beta cells challenges this view.[4]

Mechanism[edit]

Hypoxia provokes potassium efflux from cardiac muscles cells via the activation of ATP-sensitive potassium channels (KATP).[5] Potassium efflux from cardiac cells decreases action potential duration and results in non-uniform repolarization of the cardiac cells.[6] The heterogeneous repolarization of the cardiac tissue permits reentry of action potentials into conducting pathways, which manifests as malignant arrhythmias in the heart.[6] HMR 1883 is a cardioselective ATP-sensitive potassium channel antagonist that prevents the potassium efflux, hence correcting the non-uniform refractory period in the ischemic tissue. A uniform refractory period corrects the conductance problems in the heart and prevents the re-entry arrhythmias.

Side effects[edit]

HMR 1883 attenuates is chemically induced arrhythmias with little to no side effects as a result of having a higher affinity for the cardiac tissue KATP subtype than any other subtype found in the body.[2] In contrast, glibenclamide interacts with many KATP channels throughout the body resulting in many side effects. In particular its interaction with coronary smooth muscle cells and pancreatic-β cells cause decreased coronary blood flow, hyperinsulinemia, and hypoglycemia.[2] Since KATP channels only become activated during periods of low ATP and High ADP, HMR 1883 only affects hypoxic tissue and has no negative effect on the normal tissue.[2] Activation of the KATP channels on cardiac mitochondria is involved in ischemic preconditioning that results in protection for the heart.[7] It was shown that HMR 1883 did not interfere with the mitochondrial protective mechanisms in both rat[8] and rabbit[9] models. By not inhibiting the mitochondrial KATP channel subtype, HMR 1883 can treat cardiac arrhythmias while permitting mitochondrial protective mechanisms.

Research[edit]

HMR 1883 has been shown to attenuate and decrease ventricular fibrillation in anesthetized pigs,[10] rats[11] and conscious dogs.[10] Its sodium salt, HMR 1098, has been shown to decrease ventricular fibrillation in rabbit hearts,[12] anesthetized rats[13] and dogs.[14]

References[edit]

  1. ^ a b Heinrich C. Englert, Uwe Gerlach, Heinz Goegelein, Jens Hartung, Holger Heitsch, Dieter Mania, and Sabine Scheidler. 2001. Cardioselective KATP Channel Blockers Derived from a New Series of m-Anisamidoethylbenzenesulfonylthioureas J. Med. Chem. 44 (7):1085–1098
  2. ^ a b c d Billman, G. E., Englert, H. C., & Schoelkens, B. A. (1998) HMR 1883, a novel cardioselective inhibitor of the ATP- sensitive potassium channel; Part II: effects on susceptibility to ventricular fibrillation induced by myocardial ischemia in conscious dogs. J Pharmacol Exp Therap 286, 1465−1473
  3. ^ Suzuki, M., Li, R. A., Miki, T., Uemura, H., Sakamoto, N., Ohmoto-Sekine, Y., Tamagawa, M., Ogura, T., Seino, S., Marban, E., & Nakaya, H. (2001). Functional roles of cardiac and vascular ATP-sensitive potassium channels clarified by Kir6.2-knockout mice. Circ Res 88, 570−577.
  4. ^ Hai Xia Zhang, Alejandro Akrouh, Harley T Kurata, Maria Sara Remedi, Jennifer S Lawton, Colin G Nichols. 2011. HMR 1098 is not an SUR isotype specific inhibitor of heterologous or sarcolemmal KATP channels. J. Mol. Cell. Cardiol. 50(3):552-560
  5. ^ Wilde, A. A. M. (1993). Role of ATP-sensitive K+ channel current in ischemic arrhythmias. Cardiovasc Drugs Ther 7, 521−526.
  6. ^ a b Harris, A. S., Bisteni, A., Russell, R. A., Brigham, J. C., & Firestone, J. E. (1954). Excitory factors in ventricular tachycardia resulting from myocardial ischemia: potassium a major excitant. Science 119, 200−203
  7. ^ Gross, G. J., & Fryer, R. M. (1999). Sarcolemmal versus mitochondrial ATP-sensitive K+ channels and myocardial preconditioning. Circ Res 84, 973−979.
  8. ^ Fryer, R. M., Eells, J. T., Hsu, A. K., Henry, M. M., & Gross, G. J. (2000). Ischemic preconditioning in rats: role of mitochondrial KATP channel in preservation of mitochondrial function. Am J Physiol Heart Circ Physiol 278, H305−H312.
  9. ^ Sato, T., & Marban, E. (2000). The role of mitochondrial KATP channels in cardioprotection. Bas Res Cardiol 95, 285−289
  10. ^ a b Bohn, H., Englert, H. C., & Schoelkens, B. A. (1998). The KATP channel blocker HMR 1883 attenuates the effects of ischemia on MAP duration and improves survival during LAD occlusion in anesthetized pig. Br J Pharmacol 124, 23P.
  11. ^ Wirth, K. J., Klaus, E., Englert, H. G., Scholkens, B. A., & Linz, W. (1999b). HMR 1883, a cardioselective K(ATP) channel blocker, inhibits ischaemia- and reperfusioninduced ventricular fibrillation in rats. Naunyn-Schmiedeberg's Arch Pharmacol 360, 295−300.
  12. ^ Behrens, S., Zabel,M., Janssen, A., Barbierato,M., & Schultheiss, H. P. (2001). Influence of a new ATP-sensitive potassium-channel antagonist (HMR 1098) on ventricular fibrillation inducibility during myocardial ischemia. Eur Heart J 22(abstract suppl), 546.
  13. ^ Vajda, S., Baczko, I., & Lepran, I. (2007). Selective cardiac plasma-membrane KATP channel inhibition is defibrillatory and improves survival during acute myocardial ischemia and reperfusion. Eur J Pharmacol 577, 115−123.
  14. ^ Zhu, B. M., Miyamoto, S., Nagawa, Y., Wajima, T., & Hashimoto, K. (2003). Effect of sarcolemmal K-ATP blocker HMR 1098 on arrhythmias induced by programmed electrical stimulation in canine old myocardial infarction model: comparison with glibenclamide. J Pharmacol Sci 93, 106−113.
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