二甲基亚砜对生物膜的作用机理

二甲基亚砜被广泛应用于生物、化学和药学领域,这些应用大多与其增加生物膜的通透性、促进活性分子跨膜传输的作用密切相关。本文对二甲基亚砜增加生物膜通透性的理论及实验研究做简要综述,主要强调二甲基亚砜在生物膜中诱导水性孔道形成的分子动力学模拟及其相关的实验研究

脂多糖激活所致大鼠抑郁样行为及对海马神经细胞钾电流变化的影响

采用细胞因子刺激剂脂多糖(lipopolysaccharide,LPS)为免疫激活手段,研究LPS诱导的免疫激活产生的抑郁样行为及对海马神经细胞电压依赖钾电流变化的影响。应用膜片钳技术对海马神经细胞钾电流进行全细胞记录,比较抑郁样行为大鼠与正常大鼠钾离子通道电流密度和激活特性的变化。结果发现,与生理盐水对照组相比,一次LPS注射后2hr,实验组动物产生抑郁样行为,同时急性观察的海马神经细胞的钾离子通道的电流密度呈现显著升高(p<0.01);而一次LPS注射后24hr,动物的抑郁样行为消失,且急性观察的海马神经细胞的钾离子通道与对照组相比较,其电流密度和激活曲线没有显著性变化。结论:LPS诱导的抑郁样行为,与LPS诱导的海马神经细胞电压依赖钾电流的上调在时程上同步,提示钾离子通道可能参与免疫激活所致的抑郁样行为

Formaldehyde suppresses neuronal apoptosis via inhibition of outward K+ currents in rat hippocampus

National Basic Research Program of China [2005CB522804]; National Science Foundation of China [31070741]Formaldehyde (FA) is widely present in the environment, and is also a mammalian metabolite. However, its biological role has not been well understood. Here, we show that FA plays an anti-apoptotic role in cultured hippocampal neurons: FA suppressed staurosporine-induced neuronal apoptosis and inhibited the activity of apoptosis-associated caspase-3/7 proteases in a concentration-dependent manner. Moreover, FA suppressed outward K+ currents and attenuated the enhanced I-K currents that are associated with neuronal apoptosis. As an increase in outward K+ currents is critical for cell apoptosis, our results suggest that FA exerts its anti-apoptotic effects on neuronal cells, probably through its inhibitory effect on the outward K+ currents

Hypericin prolongs action potential duration in hippocampal neurons by acting on K plus channels

National Basic Research Program of China [2005CB522804]; Research Foundation of ShenzhenBackground and purpose: Synaptic deficiency is generally accepted to be involved in major depression, and accordingly classic antidepressants exert their effects through enhancing synaptic efficiency. Hypericin is one of the major active constituents of extracts of St. John's Wort (Hypericum perforatum L.) with antidepressive actions, but little is known about its therapeutic mechanisms. Our aim was to explore whether hypericin has a modulatory effect on neuronal action potential (AP) duration by acting on voltage-gated ion channels. Experimental approach: We used voltage-clamp and current-clamp techniques in a whole-cell configuration to study primary cultures of neonatal rat hippocampal neurones. We measured the effects of extracellularly applied hypericin on AP duration as well as on voltage-gated Na+, I(A) and I(K) currents. Key results: Extracellularly applied hypericin dose-dependently increased AP duration but barely affected its amplitude. Further analysis revealed that hypericin inhibited both transient I(A) and delayed rectifier I(K) potassium currents. In contrast, hypericin exerted no significant effect on both Na+ peak current and its decay kinetics. Conclusions and implications: Extracellularly applied hypericin increased AP duration, which might be ascribed to its effect on I(A) and I(K) currents. As a small increase in AP duration could lead to a dramatic increase in synaptic efficiency, our results imply that hypericin might exert its antidepressant effects by enhancing presynaptic efficiency

The effect of single cerebroside compounds on activation of BKCa channels

National Basic Research Program of China [2005CB522804]; National Science Foundation of China [31070741]We have previously shown that a mixture of cerebrosides obtained from dried tubers of herb Typhonium giganteum Engl. plays a neuroprotective role in the ischemic brain through its effect on activation of BKCa channels. It is very curious to know whether a single pure cerebroside compound could activate the BKCa channel as well. This study explored the possible effects of pure cerebroside compounds, termitomycesphins A and B, on the BKCa channel activation. Both termitomycesphins A and B activated the BKCa channels at micromole concentration without significant difference. Termitomycesphin A increased the single channel open probability of the BKCa channels in a dose-dependent manner without modifying the single channel conductance. Termitomycesphin A activated BKCa channel more efficiently when it was applied to the cytoplasmic face of the membrane, suggesting that binding site for termitomycesphin A is located at the cytoplasmic side. Termitomycesphin A shifted the voltage-dependent activation curve to less positive membrane potentials and the Ca2+-dependent activation curve of the channel upwards, suggesting that termitomycesphin A could activate the channels even without intracellular free Ca2+. Furthermore, STREX-deleted BKCa channels were completely insensitive to termitomycesphin A, indicating that STREX domain is required for the activation of the BKCa channel. These data provide evidence that termitomycesphins are potent in stimulating the activity of the BKCa channels. As BKCa channels are associated with pathology of many diseases, termitomycesphins might be used as therapeutic agents for treating these diseases through its regulatory effect on the BKCa channels

Electrostatic interaction in the NH2-terminus accelerates inactivation of the Kv14 channel

National Basic Research Program of China [2005CB522804]Inactivation of potassium channels plays an important role in shaping the electrical signalling properties of nerve and muscle cells. While it has been assumed that the rapid inactivation of the Kv1.4 channel is controlled by a "ball and chain" inactivation mechanism, the chain structure of the channel has not been well defined. Here, by conducting electrophysiological studies on variants containing mutations of the positively charged and negatively charged segments of the NH2-terminal of the channel protein, we show that neutralization or deletion of the positively charged segment (residues 83-98) significantly slowed the inactivation process. Replacement of this positively charged segment with the negatively charged segment (residues 123-137), and vice versa, so that both segments were simultaneously positively or negatively charged, also slowed the inactivation process. Furthermore, the inactivation process was not changed when the positively charged and the negatively charged segments were interchanged. In contrast, the voltage dependence of activation and inactivation of the channels was not significantly altered by these mutants. These results indicate that the electrostatic interaction between the positively and negatively charged segments plays a critical role in the inactivation process of the Kv1.4 channel. Taken together, we propose that the electrostatic interaction accelerates the inactivation of the Kv1.4 channel by making it easier for the inactivation ball to access its binding site. (C) 2010 Elsevier B.V. All rights reserved

Effect of inserting charged peptide at NH2-terminal on N-type inactivation of Kv14 channel

National Natural Science Foundation of China [31171059, 30970982, 31228013]; Program for Changjiang Scholars and Innovative Research Team in University [IRT1142]Rapid inactivation of voltage-gated potassium channel plays an important role in shaping the electrical signaling in neurons and other excitable cells. N-type ("ball and chain") inactivation, as the most extensively studied inactivation model, is assumed to be the inactivation mechanism of Kv1.4 channel. The inactivation ball inactivates the channel by interacting with the hydrophobic wall of inner pore and occluding it. Recently, we have proved that the electrostatic interaction between two charged segments in the NH2-termainal plays an important role through promoting the inactivation process of the Kv1.4 channel. This study investigates the effect of inserting negatively or positively charged short peptides at NH2-terminal on the inactivation of Kv1.4 channel. The results that inserting negatively-charged peptide (either myc or D-peptide) at different sites of NH2-terminal, deceleraes inactivation process of Kv1.4 channel to a different extent with inserting site changing and that the mutant Kv1.4-D50 exhibits a more slower inactivation rate than Kv1.4-K50 further identified the role of electrostatic interactions in the "ball and chain" inactivation mechanism. (C) 2012 Elsevier B.V. All rights reserved

Upregulation of K＋ Current in Hippocampal Neurons from Rat with Depressive-Like Behavior Induced by Lipopolysaccharide

采用细胞因子刺激剂脂多糖(lipopolysaccharide,LPS)为免疫激活手段,研究LPS诱导的免疫激活产生的抑郁样行为及对海马神经细胞电压依赖钾电流变化的影响。应用膜片钳技术对海马神经细胞钾电流进行全细胞记录,比较抑郁样行为大鼠与正常大鼠钾离子通道电流密度和激活特性的变化。结果发现,与生理盐水对照组相比,一次LPS注射后2hr,实验组动物产生抑郁样行为,同时急性观察的海马神经细胞的钾离子通道的电流密度呈现显著升高(p&lt;0.01);而一次LPS注射后24hr,动物的抑郁样行为消失,且急性观察的海马神经细胞的钾离子通道与对照组相比较,其电流密度和激活曲线没有显著性变化。结论:LPS诱导的抑郁样行为,与LPS诱导的海马神经细胞电压依赖钾电流的上调在时程上同步,提示钾离子通道可能参与免疫激活所致的抑郁样行为。;Lipopolysaccharide （LPS）-induced immunity activation can result in evident depressive-like behavior, such as anhedonia and reduced locomotion. Earlier studies have shown that K＋ channels, such as Kv7 and TREK-1, are involved in the development of depressive-like behavior in animal models. In the present study, we show that LPS （200 &mu;g/kg） could induce significant short-term depressive-like behavior in rat. In order to get insight into the underlying molecular mechanism, we investigated the potential involvement of rat hippocampal neuron voltage-dependent K＋ channels in the depressive-like behaviors induced by LPS. Methods： Twenty rats were randomly divided into LPS and control groups, each with ten rats. The rats in the LPS group were injected with LPS （200 ~tg/kg）, while saline was injected in the rats of the control group. The saccharin preference test and open field test were carried out 2 hours and 24 hours after injection of LPS to assess short-term or long-term effects on animal behavior, respectively. Next, 12 rats were randomly divided into LPS 2 hr, LPS 24 hr and control groups, each with four rats for assessing the effect of LPS on K＋ channel currents of hippocampal neurons by using whole-cell patch-clamp configuration. Results： The data showed that LPS induced depressive-like behavior in rat after 2 hours of single injection. However, this depressive-like behavior was recovered after 24 hours of single LPS injection. In agreement with these behavioral observations, voltage-dependent K＋ current density was increased in neurons isolated from rat after 2 hours of single LPS injection, whereas no significant change was found after 24 hours injection. Conclusion： Our results demonstrate that LPS-induced immunity activation can result in evident short term depressive-like behavior in rats, which are coincident with LPS induced up-regulation of voltage-dependent K＋ current in rat hippocampal neurons. This result suggests that voltage-dependent K＋ current might contribute to the development of the depressive-like behavior induced by LPS.</p