HOW DIETARY N-3 FATTY ACIDS PREVENT FATAL ARRHYTHMIAS

具体目的：我们已经证明，鱼油中的n-3多不饱和脂肪酸(PUFAs)可以防止心源性猝死，就像局部麻醉剂一样，抑制快速的电压依赖性钠电流(即，电压依赖性需要更负的静息膜电位来关闭钠通道，并使其恢复到静止的、可激活的状态)。目的1.确定这种效应的电压敏感性是否足以抑制心脏部分去极化区域的动作电位，但不影响保留正常退行性膜电位的非缺血心肌细胞。如果是这样的话，这可以解释n-3多不饱和脂肪酸抑制Ina在缺血诱导的心脏性猝死中的作用。目的2.在人类胚胎细胞系HEK 293T中，确定表达人心肌钠通道α亚基(HH1pha)的D-1、S6和D-IV、S6上的氨基酸突变是否阻断了n-3PUFAs对Na通道栅状突起的作用。LAS和n-3PUFAs的作用相似表明这可能是：a)两者都通过非竞争性抑制使BTX从其结合位置上移位到Na通道α亚基的激活状态。B)两者都通过延长Na通道的失活状态来抑制Ina。C)两者都是有效的抗心律失常药物。D-IV、S6为LA受体的推测部位，D-I、S6为BTX结合部位。阿尔法亚单位这两个区域的单个氨基酸突变使通道对BTX不敏感，并影响LA对Na通道的作用。这些研究将增加对n-3多不饱和脂肪酸如何在分子水平上抑制心肌细胞中的Ina的理解。这一作用对于这些n-3多不饱和脂肪酸预防缺血性致死性室性心律失常具有重要意义。每年有25万美国人和全球数百万人死于心脏病猝死，目前还没有安全有效的预防或治疗方法，PUFA的这一行动可能会给公共卫生带来巨大的好处。

Specific Aims: We have shown that the n-3 polyunsaturated fatty acids (PUFAs) in fish oils, which prevent sudden cardiac death, like local anesthetics, inhibit the fast, voltage dependent Na+ currents (i.e., a voltage-dependent need for a more negative resting membrane potential to close and return the Na+ channels to a resting, activatable state). Aim 1. Too determine if the voltage sensitivity of this effect is sufficient to inhibit action potentials in partially depolarized zones of the heart, but not affect non-ischemic cardiomyocytes that retain their normal resign membrane potentials. If so, this could explain the role of the inhibition of INa by n-3 PUFAS in ischemia-induced sudden cardiac death. Aim 2. To determine in a human embryonic cell line, HEK 293t, expressing alpha-subunits of the human myocardial sodium channel (hH1alpha), if point amino acid mutations in D-1, S6- the location of the putative batrachotoxin (BTX) binding site- and D-IV, S6- the location of the putative local anesthetic (LA) receptor-block the action of the n-3PUFAs on the Na+ channel grating process. Similarities between effects of Las and n-3 PUFAs indicates this to be likely: a) Both displace BTX, a potent cardiac and neural poison, from its binding site on the activated state of the Na+ channel alpha- subunit by non-competitive inhibition. B) Both inhibit INa by prolonging the inactivated state of the Na+ channel. C) Both are potent anti-arrhythmic agents. D-IV, S6 is the putative site of the LA receptor an D-I, S6 is the site of BTX binding. A single amino acid mutation in these two regions of the alpha-subunit renders the channel insensitive to BTX and affect LA action on the Na channel. These studies will add to understanding of how n-3 PUFAs act at a molecular level to inhibit the INa in cardiac myocytes. This effect is important for the preention by these n-3 PUFAs of ischemia-induced fatal ventricular arrhythmias. With 250,000 Americans, and millions more world wide, dying annually from cardiac sudden death for which there is no current safe and effective prevention or therapy, this action of the PUFAs has potentially great public health benefit.