Non-steroidal Anti-inflammatory Drugs Regulate The Role And Mechanisms Of The A-type Transient Outward Potassium Current

Cell structure and normal function of ion channels is to maintain basic life processes. The genetic variation and dysfunction are related to the occurrence and development of many diseases. Potassium channel plays an important role during signal transduction of all excitable and non-excitable cells. Changes of lesions in potassium channels lead to the occurrence or the body to correct some of the pathophysiological changes. Such as senile dementia (Alzheimers'disease, AD), a large number of studies have found pathogenicity of some endogenous substances of AD patients is closely related to dysfunctions of potassium channel and calcium channel, and involved in AD patients with early memory loss, cognitive decline and other symptoms appeared through affecting the structure of potassium channel and calcium channel or processes of modulation. Extensive research has been shown that:non-steroidal anti-inflammatory drugs (NSAIDs) can selectively reduce the production of AD in vitro and in vivo, NSAIDs have some protective effect against AD by acting on COX and so. We chose two different cell models, using the whole cell patch clamp recording, cell transfection and other methods to get further understanding of the mechanisms regulated by NSAIDs on the potassium ion channels. The research is divided into the following two sections, the results show that NSAIDs bi-directionally modulated voltage-dependent transient outward K+ channel on rat cerebellar granule cells and HEK293 cells.Part One:It is observed that NSAIDs can regulate membrane ion channels in different cell models in previous experiments. In this part of the study, we selected two NSAIDs:Mefenamic acid (MA) and flufenamic acid(FFA). Take FFA for example, results show that at a higher concentration FFA reversibly inhibited IA in a dose-dependent manner. However, FFA at a low concentration significantly increased the current amplitude of IA. A higher concentration of FFA had a significant effect on the kinetic parameters of the steady-state activation and inactivation process, suggesting that the binding affinity of FFA to IA channels may be state-dependent. Intracellular application of FFA could significantly increase the IA amplitude but did not alter the inhibited effect induced by extracellular application of FFA, implying that FFA may exert its effect from both the inside and outside sites of the channel. Furthermore, the activation of current induced by intracellular application of FFA could mimic other cyclooxygenase inhibitors and arachidonic acid. Our data demonstrate how FFA is able to bidirectionally modulate IA channels in neurons at different concentrations and by different methods of application and that two different mechanisms may be involved.Part Two:The results showed that IA in cultured rat cerebellar granule neurons and Kv4.2, Kv4.3 expressed in HEK293 cells both displayed "A"-type current properties. Appropriate concentration of FFA/MA reversibly inhibited IA but significantly increased the current amplitude of IA at lower concentration. Intracellular application of FFA/MA could significantly increase the IA amplitude and can be mimicked by intracellular arachidonic acid application. Comparitive of its activation parameters, Kv4.2 channel kinetics is more sensitive than that of the granule cells no matter of before and after administration, or intracellular and extracellular administration, while less sensitive to that of Kv4.3. Extracellular FFA/MA on the Kv4.2 channel IA current in steady-state activation parameters and steady-state inactivation parameters consistent with the changes. This suggests that FFA and MA have similar mechanisms on the Kv4.2 channel extracellularly, it is also consistent with the effect of FFA/MA on cerebellar granule cells extracellularly. When exposed to a certain concentration of FFA, steady-state activation parameters and inactivation parameters consistent with the changes on the Kv4.2 channel and granule neurons of the IA channel current. This suggests that Kv4.2 channel subtypes play a major role in the regulation of FFA/MA on the intracellular granule neurons, mainly involved in regulation of granule neurons IA channel electrophysiological gating.