Institute of Brain Science, School of Life Sciences and State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai 200433, China.
Biochem J. 2011 Aug 15;438(1):203-15. doi: 10.1042/BJ20110569.
AA (arachidonic acid), which possesses both neurotoxic and neurotrophic activities, has been implicated as a messenger in both physiological and pathophysiological processes. In the present study, we investigated the effects of both extracellular and intracellular application of AA on the activity of Na(V) (voltage-gated Na(+) channels) in rat cerebellar GCs (granule cells). The extracellular application of AA inhibited the resultant I(Na) (Na(V) current), wherein the current-voltage curve shifted to a negative voltage direction. Because this effect could be reproduced by treating the GCs with ETYA (eicosa-5,8,11,14-tetraynoic acid) or a membrane-impermeable analogue of AA, AA-CoA (arachidonoyl coenzyme A), we inferred that AA itself exerted the observed modulatory effects on I(Na). In contrast, intracellular AA significantly augmented the elicited I(Na) peak when the same protocol that was used for extracellular AA was followed. The observed I(Na) increase that was induced by intracellular AA was mimicked by the AA cyclo-oxygenase metabolite PGE(2) (prostaglandin E(2)), but not by ETYA. Furthermore, cyclo-oxygenase inhibitors decreased I(Na) and quenched AA-induced channel activation, indicating that the effect of intracellular AA on Na(V) was possibly mediated through AA metabolites. In addition, the PGE2-induced activation of I(Na) was mimicked by cAMP and quenched by a PKA (protein kinase A) inhibitor, a G(s) inhibitor and EP (E-series of prostaglandin) receptor antagonists. The results of the present study suggest that extracellular AA modulates Na(V) channel activity in rat cerebellar GCs without metabolic conversion, whereas intracellular AA augments the I(Na) by PGE(2)-mediated activation of cAMP/PKA pathways. These observations may explain the dual character of AA in neuronal pathogenesis.
AA（花生四烯酸）具有神经毒性和神经营养活性，被认为是生理和病理生理过程中的信使。在本研究中，我们研究了细胞外和细胞内应用 AA 对大鼠小脑颗粒细胞（GCs）中 Na(V)（电压门控 Na(+)通道）活性的影响。细胞外应用 AA 抑制了产生的 I(Na)（Na(V)电流），其中电流-电压曲线向负电压方向移动。因为这种效应可以通过用 ETYA（二十碳五烯酸）或 AA 的不可渗透膜类似物 AA-CoA（花生四烯酰辅酶 A）处理 GCs 来重现，我们推断 AA 本身对 I(Na) 产生了观察到的调节作用。相比之下，当遵循与细胞外 AA 相同的方案时，细胞内 AA 显着增加了诱发的 I(Na)峰值。细胞内 AA 诱导的 I(Na)增加被 AA 环氧化酶代谢产物 PGE(2)（前列腺素 E(2)）模拟，但不是 ETYA。此外，环氧化酶抑制剂降低了 I(Na)并抑制了 AA 诱导的通道激活，表明细胞内 AA 对 Na(V)的作用可能通过 AA 代谢物介导。此外，PGE2 诱导的 I(Na)激活被 cAMP 模拟，并被 PKA（蛋白激酶 A）抑制剂、G(s)抑制剂和 EP（E 系列前列腺素）受体拮抗剂抑制。本研究的结果表明，细胞外 AA 调节大鼠小脑 GCs 中的 Na(V)通道活性而无需代谢转化，而细胞内 AA 通过 PGE(2)介导的 cAMP/PKA 途径激活来增加 I(Na)。这些观察结果可能解释了 AA 在神经元发病机制中的双重特征。
