Fatty acids suppress voltage-gated Na+ currents in HEK293t cells transfected with the alpha-subunit of the human cardiac Na+ channel

Omega-3 Fatty Acids and Arrhythmias

The pro- and antiarrhythmic effects of omega-3 polyunsaturated fatty acids (n-3 PUFAs) have been extensively studied in preclinical and human trials. Despite early evidence of an antiarrhythmic role of n-3 PUFA in the prevention of sudden cardiac death and postoperative and persistent atrial fibrillation (AF), subsequent well-designed randomized trials have largely not shown an antiarrhythmic benefit. Two trials that tested moderate and high-dose n-3 PUFA demonstrated a reduction in sudden cardiac death, but these findings have not been widely replicated, and the potential of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) to reduce arrhythmic death in combination, or as monotherapy, remains uncertain. The accumulated clinical evidence does not support supplementation of n-3 PUFA for postoperative AF or secondary prevention of AF. Several large, contemporary, randomized controlled trials of high-dose n-3 PUFA for primary or secondary cardiovascular prevention have demonstrated a small, significant, dose-dependent increased risk of incident AF compared with mineral oil or corn oil comparator. These findings were reproduced with both icosapent ethyl monotherapy and a mixed EPA+DHA formulation. The proarrhythmic mechanism of increased AF in contemporary cohorts exposed to high-dose n-3 PUFA is unknown. EPA and DHA and their metabolites have pleiotropic cardiometabolic and pro- and antiarrhythmic effects, including modification of the lipid raft microenvironment; alteration of cell membrane structure and fluidity; modulation of sodium, potassium, and calcium currents; and regulation of gene transcription, cell proliferation, and inflammation. Further characterization of the complex association between EPA, EPA+DHA, and DHA and AF is needed. Which formulations, dose ranges, and patient subgroups are at highest risk, remain unclear.

Eicosapentaenoic Acid Rescues Cav1.2-L-Type Ca2+ Channel Decline Caused by Saturated Fatty Acids via Both Free Fatty Acid Receptor 4-Dependent and -Independent Pathways in Cardiomyocytes

Dietary intake of omega-3 polyunsaturated fatty acids (eicosapentaenoic acid, EPA) exerts antiarrhythmic effects, although the mechanisms are poorly understood. Here, we investigated the possible beneficial actions of EPA on saturated fatty acid-induced changes in the L-type Ca2+ channel in cardiomyocytes. Cardiomyocytes were cultured with an oleic acid/palmitic acid mixture (OAPA) in the presence or absence of EPA. Beating rate reduction in cardiomyocytes caused by OAPA were reversed by EPA. EPA also retrieved a reduction in Cav1.2 L-type Ca2+ current, mRNA, and protein caused by OAPA. Immunocytochemical analysis revealed a distinct downregulation of the Cav1.2 channel caused by OAPA with a concomitant decrease in the phosphorylated component of a transcription factor adenosine-3',5'-cyclic monophosphate (cAMP) response element binding protein (CREB) in the nucleus, which were rescued by EPA. A free fatty acid receptor 4 (FFAR4) agonist TUG-891 reversed expression of Cav1.2 and CREB mRNA caused by OAPA, whereas an FFAR4 antagonist AH-7614 abolished the effects of EPA. Excessive reactive oxygen species (ROS) accumulation caused by OAPA decreased Cav1.2 and CREB mRNA expressions, which was reversed by an ROS scavenger. Our data suggest that EPA rescues cellular Cav1.2-Ca2+ channel decline caused by OAPA lipotoxicity and oxidative stresses via both free fatty acid receptor 4-dependent and -independent pathways.

Effect of local administration of eicosapentaenoic acid on the jaw-opening reflex in rats

Although eicosapentaenoic acid (EPA) application in vitro inhibits voltage-gated Na⁺ (Nav) channels in excitable tissues, the acute local effect of EPA on the jaw-opening reflex in vivo remains unknown. The aim of the present study was to determine whether local administration of EPA to adult male Wistar rats could attenuate the excitability of the jaw-opening reflex in vivo, including nociception. The jaw-opening reflex evoked by electrical stimulation of the tongue was recorded by a digastric muscle electromyogram (dEMG) in pentobarbital-anesthetized rats. The amplitude of the dEMG response was significantly increased in proportion to the electrical stimulation intensity (1×-5× threshold). At 3×, local administration of EPA dose-dependently inhibited the dEMG response, lasting 60 min, with maximum inhibition observed within approximately 10 min. The mean magnitude of dEMG signal inhibition by EPA was almost equal to that observed with a local anesthetic, 1% lidocaine, and with a half dose of lidocaine plus a half dose of EPA. These findings suggest that EPA attenuates the jaw-opening reflex, possibly by blocking Nav channels of primary nerve terminals, and strongly support the idea that EPA is a potential therapeutic agent and complementary alternative medicine for the prevention of acute trigeminal nociception.

State-Dependent Inhibition of Voltage-Gated Sodium Channels in Neuroblastoma Neuro-2A Cells by Arachidonic Acid from Halichondria okadai

Voltage-gated sodium channels (Na_v) are closely associated with epilepsy, cardiac and skeletal muscle diseases, and neuropathic pain. Several toxic compounds have been isolated from the marine sponge Halichondria okadai; however, toxic substances that modulate Na_v are yet to be identified. This study aimed to identify Na_v inhibitors from two snake venoms and H. okadai using mouse neuroblastoma Neuro-2A cells (N2A), which primarily express the specific Na_v subtype Na_v1.7, using whole-cell patch-clamp recordings. We successfully isolated arachidonic acid (AA, 1) from the hexane extract of H. okadai, and then the fatty acid-mediated modulation of Na_v in N2A was investigated in detail for the first time. Octanoic acid (2), palmitic acid (3), and oleic acid (4) showed no inhibitory activity at 100 μM, whereas AA (1), dihomo-γ-linolenic acid (DGLA, 5), and eicosapentaenoic acid (EPA, 6) showed IC₅₀ values of 6.1 ± 2.0, 58 ± 19, and 25 ± 4.0 μM, respectively (N = 4, mean ± SEM). Structure and activity relationships were investigated for the first time using two ω-3 polyunsaturated fatty acids (PUFAs), EPA (6) and eicosatetraenoic acid (ETA, 7), and two ω-6 PUFAs, AA (1) and DGLA (5), to determine their effects on a resting state, activated state, and inactivated state. Steady-state analysis showed that the half inactivation potential was largely hyperpolarized by 10 μM AA (1), while 50 μM DGLA (5), 50 μM EPA (6), and 10 μM ETA (7) led to a slight change. The percentages of the resting state block were 24 ± 1, 22 ± 1, 34 ± 4, and 38 ± 9% in the presence of AA (1), DGLA (5), EPA (6), and ETA (7), respectively, with EPA (6) and ETA (7) exhibiting a greater inhibition than both AA (1) and DGLA (5), and their inhibitions did not increase in the following depolarization pulses. None of the compounds exhibited the use-dependent block. The half recovery times from the inactivated state for the control, AA (1), DGLA (5), EPA (6), and ETA (7) were 7.67 ± 0.33, 34.3 ± 1.10, 15.5 ± 1.10, 10.7 ± 0.31, and 3.59 ± 0.18 ms, respectively, with AA (1) exhibiting a distinctively large effect. Overall, distributed binding to the resting and the inactivated states of Na_v would be significant for the inhibition of Na_v, which presumably depends on the active structure of each PUFA.

Clinical significance of polyunsaturated fatty acids in the prevention of cardiovascular diseases

Cardiovascular diseases are one of the most important problems of modern medicine. They are associated with a large number of health care visits, hospitalizations and mortality. Prevention of atherosclerosis is one of the most effective strategies and should start as early as possible. Correction of lipid metabolism disorders is associated with definite clinical successes, both in primary prevention and in the prevention of complications of many cardiovascular diseases. A growing body of evidence suggests a multifaceted role for polyunsaturated fatty acids. They demonstrate a variety of functions in inflammation, both participating directly in a number of cellular processes and acting as a precursor for subsequent biosynthesis of lipid mediators. Extensive clinical data also support the importance of polyunsaturated fatty acids, but all questions have not been answered to date, indicating the need for further research.

Pharmacological and nutritional targeting of voltage-gated sodium channels in the treatment of cancers

Voltage-gated sodium (NaV) channels, initially characterized in excitable cells, have been shown to be aberrantly expressed in non-excitable cancer tissues and cells from epithelial origins such as in breast, lung, prostate, colon, and cervix, whereas they are not expressed in cognate non-cancer tissues. Their activity was demonstrated to promote aggressive and invasive potencies of cancer cells, both in vitro and in vivo, whereas their deregulated expression in cancer tissues has been associated with metastatic progression and cancer-related death. This review proposes NaV channels as pharmacological targets for anticancer treatments providing opportunities for repurposing existing NaV-inhibitors or developing new pharmacological and nutritional interventions.

Chronotropic effects and mechanisms of long-chain omega-3 polyunsaturated fatty acids on heartbeat: the latest insights

The roles of the resting heart rate (RHR) have been actively investigated and increasingly recognized in recent decades, because of the growing evidence that fast RHR is associated with and predicts the risk of developing cardiovascular and metabolic disorders, as well as all-cause mortality. Long-chain omega-3 polyunsaturated fatty acids (PUFAs) (eg, eicosapentaenoic acid and docosahexaenoic acid) have been shown to have chronotropic effects on heartbeat in both healthy people and patients with various disease conditions. The aims of this review are (1) to briefly summarize the importance of elevated RHR in disease pathogenesis and mortality; (2) to provide an update on the negative chronotropic effect of omega-3 PUFAs on the heart; (3) to highlight how omega-3 PUFAs regulate heart rate through the autonomic nervous system - a central control mechanism; and (4) to highlight how omega-3 PUFAs modulate the trans-membrane ionic channels in cardiomyocytes - a fundamental mechanism of cardiac automaticity. Eicosapentaenoic acid and docosahexaenoic acid are nutrients derived from some aquatic organisms, and they can also be converted from digested oily seeds and nuts of some terrestrial plants in the body. The consumption of omega-3 PUFAs for RHR reduction represents a lifestyle modification for risk factor management and promises nutritional benefits for public health improvement.

Anti-arrhythmic properties of non-antiarrhythmic medications

Traditional anti-arrhythmic drugs are classified by the Vaughan-Williams classification scheme based on their mechanisms of action, which includes effects on receptors and/or ion channels. Some known anti-arrhythmic drugs do not perfectly fit into this classification scheme. Other medications/molecules with established non-anti-arrhythmic indications have shown anti-arrhythmic properties worth exploring. In this narrative review, we discuss the molecular mechanisms and evidence base for the anti-arrhythmic properties of traditional non-antiarrhythmic drugs such as inhibitors of the renin angiotensin system (RAS), statins and polyunsaturated fatty acids (PUFAs). In summary, RAS antagonists, statins and PUFAs are 'upstream target modulators' that appear to have anti-arrhythmic roles. RAS blockers prevent the downstream arrhythmogenic effects of angiotensin II - the main effector peptide of RAS - and the angiotensin type 1 receptor. Statins have pleiotropic effects including anti-inflammatory, immunomodulatory, modulation of autonomic nervous system, anti-proliferative and anti-oxidant actions which appear to underlie their anti-arrhythmic properties. PUFAs have the ability to alter ion channel function and prevent excessive accumulation of calcium ions in cardiac myocytes, which might explain their benefits in certain arrhythmic conditions. Clearly, whilst a number of anti-arrhythmic drugs exist, there is still a need for randomised trials to establish whether additional agents, including those already in clinical use, have significant anti-arrhythmic effects.

Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome

The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings.

Omega-3 Polyunsaturated Fatty Acids: Benefits and Endpoints in Sport

The influence of nutrition has the potential to substantially affect physical function and body metabolism. Particular attention has been focused on omega-3 polyunsaturated fatty acids (n-3 PUFAs), which can be found both in terrestrial features and in the marine world. They are responsible for numerous cellular functions, such as signaling, cell membrane fluidity, and structural maintenance. They also regulate the nervous system, blood pressure, hematic clotting, glucose tolerance, and inflammatory processes, which may be useful in all inflammatory conditions. Animal models and cell-based models show that n-3 PUFAs can influence skeletal muscle metabolism. Furthermore, recent human studies demonstrate that they can influence not only the exercise and the metabolic response of skeletal muscle, but also the functional response for a period of exercise training. In addition, their potential anti-inflammatory and antioxidant activity may provide health benefits and performance improvement especially in those who practice physical activity, due to their increased reactive oxygen production. This review highlights the importance of n-3 PUFAs in our diet, which focuses on their potential healthy effects in sport.

Does Supplementation with Omega-3 PUFAs Add to the Prevention of Cardiovascular Disease?

PURPOSE OF REVIEW

Omega-3 fatty acids are increasingly used for the protection of cardiovascular disease. The main but not the sole mechanism of action is the reduction of triglyceride levels. In this review, we summarize the effect of omega-3 supplements on all-cause and cardiovascular mortality, myocardial infarction, and stroke from the relevant randomized controlled trials.

RECENT FINDINGS

Twenty-one randomized controlled trials assessed omega-3 supplementation on mortality and cardiovascular-related outcomes. From these studies, as well as from the relevant meta-analyses, we found that omega-3 supplements do not exert a consistent benefit for cardiovascular protection. There is uncertainty of a clear profit from omega-3 supplementation in cardiovascular disease.

Actions and Mechanisms of Polyunsaturated Fatty Acids on Voltage-Gated Ion Channels

Polyunsaturated fatty acids (PUFAs) act on most ion channels, thereby having significant physiological and pharmacological effects. In this review we summarize data from numerous PUFAs on voltage-gated ion channels containing one or several voltage-sensor domains, such as voltage-gated sodium (Na_V), potassium (K_V), calcium (Ca_V), and proton (H_V) channels, as well as calcium-activated potassium (K_Ca), and transient receptor potential (TRP) channels. Some effects of fatty acids appear to be channel specific, whereas others seem to be more general. Common features for the fatty acids to act on the ion channels are at least two double bonds in cis geometry and a charged carboxyl group. In total we identify and label five different sites for the PUFAs. PUFA site 1: The intracellular cavity. Binding of PUFA reduces the current, sometimes as a time-dependent block, inducing an apparent inactivation. PUFA site 2: The extracellular entrance to the pore. Binding leads to a block of the channel. PUFA site 3: The intracellular gate. Binding to this site can bend the gate open and increase the current. PUFA site 4: The interface between the extracellular leaflet of the lipid bilayer and the voltage-sensor domain. Binding to this site leads to an opening of the channel via an electrostatic attraction between the negatively charged PUFA and the positively charged voltage sensor. PUFA site 5: The interface between the extracellular leaflet of the lipid bilayer and the pore domain. Binding to this site affects slow inactivation. This mapping of functional PUFA sites can form the basis for physiological and pharmacological modifications of voltage-gated ion channels.

The pro- or antiarrhythmic actions of polyunsaturated fatty acids and of cholesterol

In this review, the pro- and anti-arrhythmic effects of a diet rich in fish oil fatty acids and of hypercholesterolemia will be discussed in relation to two major mechanisms of arrhythmogenesis (triggered activity and re-entry). Whereas a diet rich in fish oil is pro-arrhythmic in relation to re-entry based arrhythmias (as occur in acute myocardial ischemia) and anti-arrhythmic in relation to triggered activity based arrhythmias (as occur in heart failure), the reverse is true for hypercholesterolemia. Changing the lipid composition of cardiomyocytes likely has powerful pro- or anti-arrhythmic consequences, depending on the mechanism of arrhythmias, and has corresponding therapeutic potential.

Fatty Acid Regulation of Voltage- and Ligand-Gated Ion Channel Function

Free fatty acids (FFA) are essential components of the cell, where they play a key role in lipid and carbohydrate metabolism, and most particularly in cell membranes, where they are central actors in shaping the physicochemical properties of the lipid bilayer and the cellular adaptation to the environment. FFA are continuously being produced and degraded, and a feedback regulatory function has been attributed to their turnover. The massive increase observed under some pathological conditions, especially in brain, has been interpreted as a protective mechanism possibly operative on ion channels, which in some cases is of stimulatory nature and in other cases inhibitory. Here we discuss the correlation between the structure of FFA and their ability to modulate protein function, evaluating the influence of saturation/unsaturation, number of double bonds, and cis vs. trans isomerism. We further focus on the mechanisms of FFA modulation operating on voltage-gated and ligand-gated ion channel function, contrasting the still conflicting evidence on direct vs. indirect mechanisms of action.

Inhibition of TRPV1 channels by a naturally occurring omega-9 fatty acid reduces pain and itch

The transient receptor potential vanilloid 1 (TRPV1) ion channel is mainly found in primary nociceptive afferents whose activity has been linked to pathophysiological conditions including pain, itch and inflammation. Consequently, it is important to identify naturally occurring antagonists of this channel. Here we show that a naturally occurring monounsaturated fatty acid, oleic acid, inhibits TRPV1 activity, and also pain and itch responses in mice by interacting with the vanilloid (capsaicin)-binding pocket and promoting the stabilization of a closed state conformation. Moreover, we report an itch-inducing molecule, cyclic phosphatidic acid, that activates TRPV1 and whose pruritic activity, as well as that of histamine, occurs through the activation of this ion channel. These findings provide insights into the molecular basis of oleic acid inhibition of TRPV1 and also into a way of reducing the pathophysiological effects resulting from its activation.

TRPV1 channels are known to mediate pathological pain and itch. Here, the authors find a naturally occurring fatty acid, oleic acid, acts as a TRPV1 antagonist and can modulate capsaicin and histamine-mediated pain and itch response in mouse models.

Lipid Regulation of Sodium Channels

The lipid landscapes of cellular membranes are complex and dynamic, are tissue dependent, and can change with the age and the development of a variety of diseases. Researchers are now gaining new appreciation for the regulation of ion channel proteins by the membrane lipids in which they are embedded. Thus, as membrane lipids change, for example, during the development of disease, it is likely that the ionic currents that conduct through the ion channels embedded in these membranes will also be altered. This chapter provides an overview of the complex regulation of prokaryotic and eukaryotic voltage-dependent sodium (Nav) channels by fatty acids, sterols, glycerophospholipids, sphingolipids, and cannabinoids. The impact of lipid regulation on channel gating kinetics, voltage-dependence, trafficking, toxin binding, and structure are explored for Nav channels that have been examined in heterologous expression systems, native tissue, and reconstituted into artificial membranes. Putative mechanisms for Nav regulation by lipids are also discussed.

The nutraceutical potential of omega-3 alpha-linolenic acid in reducing the consequences of stroke

Stroke is a worldwide major cause of mortality and morbidity. Preclinical studies have identified over 1000 molecules with brain-protective properties. More than 200 clinical trials have evaluated neuroprotective candidates for ischemic stroke yet, to date almost all failed, leading to a re-analysis of treatment strategies against stroke. An emerging view is to seek combinatory therapy, or discovering molecules able to stimulate multiple protective and regenerative mechanisms. A pertinent experimental approach to identify such candidates is the study of brain preconditioning, which refers to how the brain protects itself against ischemia and others stress-inducing stimuli. The recent discovery that nutrients like alpha-linolenic acid (ALA is an essential omega-3 polyunsaturated fatty acid required as part of our daily diet), may be an efficient brain preconditionner against stroke fosters the novel concept of brain preconditioning by nutraceuticals. This review stresses the underestimated role of nutrition in preventing and combating stroke. Although there is a consensus that increased consumption of salt, fatty foods and alcoholic beverages may promote pathologies like hypertension, obesity and alcoholism - all of which are well known risk factors of stroke - few risk factors are attributed to a deficiency in an essential nutrient in the diet. The ALA deficiency observed in the Western modern diets may itself constitute a risk factor. This review outlines how ALA supplementation by modification of the daily diet prevented mortality and cerebral damage in a rodent model of ischemic stroke. It also describes the pleiotropic ability of ALA to trigger responses that are multicellular, mechanistically diverse, resulting in neuronal protection, stimulation of neuroplasticity, and brain artery vasodilation. Overall, this review proposes a promising therapeutic opportunity by integrating a nutritional-based approach focusing on enriching the daily diet in ALA to prevent the devastating damage caused by stroke.

Oral consumption of α-linolenic acid increases serum BDNF levels in healthy adult humans

Background aims

Dietary omega-6 and omega-3 fatty acids have remarkable impacts on the levels of DHA in the brain and retina. Low levels of DHA in plasma and blood hamper visual and neural development in children and cause dementia and cognitive decline in adults. The level of brain-derived neurotrophic factors (BDNF) changes with dietary omega-3 fatty acid intake. BDNF is known for its effects on promoting neurogenesis and neuronal survival.

Methods

In this study, we examined the effect of the oral consumption of α-Linolenic acid (ALA) on blood levels of BDNF and Malondialdehyde (MDA) in healthy adult humans. 30 healthy volunteers, 15 men and 15 women, were selected randomly. Each individual served as his or her own control. Before consuming the Flaxseed oil capsules, 5cc blood from each individual was sampled in order to measure the plasma levels of BDNF and MDA as baseline controls. During the experiment, each individual was given 3 oral capsules of flaxseed oil, containing 500mg of alpha linolenic acid, daily for one week. Then, plasma levels of BDNF and MDA were tested.

Results

The plasma levels of BDNF and MDA significantly (P < 0.05) increased in individuals who received the oral capsules of ALA. Plasma levels of BDNF increased more in the women in comparison with the men.

Conclusion

ALA treatment could be a feasible approach to reduce size of infarcts in stroke patients. Thus, ALA could be used in adjunction with routine stroke therapies to minimize brain lesions caused by stroke.

Alpha-linolenic acid: an omega-3 fatty acid with neuroprotective properties-ready for use in the stroke clinic?

Alpha-linolenic acid (ALA) is plant-based essential omega-3 polyunsaturated fatty acids that must be obtained through the diet. This could explain in part why the severe deficiency in omega-3 intake pointed by numerous epidemiologic studies may increase the brain's vulnerability representing an important risk factor in the development and/or deterioration of certain cardio- and neuropathologies. The roles of ALA in neurological disorders remain unclear, especially in stroke that is a leading cause of death. We and others have identified ALA as a potential nutraceutical to protect the brain from stroke, characterized by its pleiotropic effects in neuroprotection, vasodilation of brain arteries, and neuroplasticity. This review highlights how chronic administration of ALA protects against rodent models of hypoxic-ischemic injury and exerts an anti-depressant-like activity, effects that likely involve multiple mechanisms in brain, and may be applied in stroke prevention. One major effect may be through an increase in mature brain-derived neurotrophic factor (BDNF), a widely expressed protein in brain that plays critical roles in neuronal maintenance, and learning and memory. Understanding the precise roles of ALA in neurological disorders will provide the underpinnings for the development of new therapies for patients and families who could be devastated by these disorders.

SKF-96365 strongly inhibits voltage-gated sodium current in rat ventricular myocytes

SKF-96365 (1-(beta-[3-(4-methoxy-phenyl) propoxy]-4-methoxyphenethyl)-1H-imidazole hydrochloride) is a general TRPC channel antagonist commonly used to characterize the potential functions of TRPC channels in cardiovascular system. Recent reports showed that SKF-96365 induced a reduction in cardiac conduction. The present study investigates whether the reduced cardiac conduction caused by SKF-96365 is related to the blockade of voltage-gated sodium current (I Na) in rat ventricular myocytes using the whole-cell patch voltage-clamp technique. It was found that SKF-96365 inhibited I Na in rat ventricular myocytes in a concentration-dependent manner. The compound (1 μM) negatively shifted the potential of I Na availability by 9.5 mV, increased the closed-state inactivation of I Na, and slowed the recovery of I Na from inactivation. The inhibition of cardiac I Na by SKF-96365 was use-dependent and frequency-dependent, and the IC₅₀ was decreased from 1.36 μM at 0.5 Hz to 1.03, 0.81, 0.61, 0.56 μM at 1, 2, 5, 10 Hz, respectively. However, the selective TRPC3 antagonist Pyr3 decreased cardiac I Na by 8.5% at 10 μM with a weak use and frequency dependence. These results demonstrate that the TRPC channel antagonist SKF-96365 strongly blocks cardiac I Na in use-dependent and frequency-dependent manners. Caution should be taken for interpreting the alteration of cardiac electrical activity when SKF-96365 is used in native cells as a TRPC antagonist.

Retinoic acid induces changes in electrical properties of adult neurons in a dose- and isomer-dependent manner

The electrical activity of neurons is known to play a role in neuronal development, as well as repair of adult nervous tissue. For example, the extension of neurites and motility of growth cones can be modulated by changes in the electrical firing of neurons. The vitamin A metabolite retinoic acid also plays a critical role during nervous system development and is also known to elicit regenerative responses, namely the induction, enhancement, and directionality of neurite outgrowth. However, no studies have previously reported the ability of retinoic acid to modify the electrical activity of neurons. In this study, we determined whether retinoic acid might exert effects on the nervous system by altering the electrical properties of neurons. Using cultured adult neurons from Lymnaea stagnalis, we showed that acute application of retinoic acid can rapidly elicit changes in neuronal firing properties. Retinoic acid caused the presence of atypical firing behavior such as rhythmic bursting and altered the shape of action potentials, causing increases in half-amplitude duration and decay time. Retinoic acid also caused cell silencing, whereby neuronal activity was halted within an hour. These effects of retinoic acid were shown to be both dose and isomer dependent. We then showed that the effects of retinoic acid on cell firing (but not silencing) were significantly reduced in the presence of an retinoid X receptor pan-antagonist HX531. This study suggests that some of the effects of retinoic acid during neuronal development or regeneration might possibly occur as a result of changes in electrical activity of neurons.

The effects of omega-3 polyunsaturated fatty acids on cardiac rhythm: a critical reassessment

Although epidemiological studies provide strong evidence for an inverse relationship between omega-3 polyunsaturated fatty acids (n-3 PUFAs) and cardiac mortality, inconsistent and often conflicting results have been obtained from both animal studies and clinical prevention trials. Despite these heterogeneous results, some general conclusions can be drawn from these studies: 1) n-PUFAs have potent effects on ion channels and calcium regulatory proteins that vary depending on the route of administration. Circulating (acute administration) n-3 PUFAs affect ion channels directly while incorporation (long-term supplementation) of these lipids into cell membranes indirectly alter cardiac electrical activity via alteration of membrane properties. 2) n-3 PUFAs reduce baseline HR and increase HRV via alterations in intrinsic pacemaker rate rather than from changes in cardiac autonomic neural regulation. 3) n-3 PUFAs may be only effective if given before electrophysiological or structural remodeling has begun and have no efficacy against atrial fibrillation. 5) Despite initial encouraging results, more recent clinical prevention and animal studies have not only failed to reduce sudden cardiac death but actually increased mortality in angina patients and increased rather than decreased malignant arrhythmias in animal models of regional ischemia. 6) Given the inconsistent benefits reported in clinical and experimental studies and the potential adverse actions on cardiac rhythm noted during myocardial ischemia, n-3 PUFA must be prescribed with caution and generalized recommendations to increase fish intake or to take n-3 PUFA supplements need to be reconsidered.

Do omega-3 polyunsaturated fatty acids reduce risk of sudden cardiac death and ventricular arrhythmias? A meta-analysis of randomized trials

INTRODUCTION

Omega-3 polyunsaturated fatty acids (PUFA) have demonstrated to have antiarrhythmic properties. However, randomized studies have shown inconsistent results.

OBJECTIVE

We aimed to analyze the effect of omega-3 PUFA on preventing potentially fatal ventricular arrhythmias and sudden cardiac death.

METHODS

Randomized trials comparing omega-3 PUFA to placebo and reporting sudden cardiac death (SCD) or first implanted cardioverter-defibrillator (ICD) event for ventricular tachycardia or fibrillation were included in this study. A meta-analysis using a random effects model was performed and results were expressed in terms of Odds Ratio (OR) and 95% Confidence Interval (CI) after evaluating for interstudy heterogeneity using I(2). The reported data were extracted on the basis of the intention-to-treat principle.

RESULTS

A total of 32,919 patients were included in nine trials; 16,465 patients received omega-3 PUFA and 16,454 received placebo. When comparing omega-3 PUFA to placebo, there was nonsignificant risk reduction of SCD or ventricular arrhythmias (OR = 0.82 [95% CI: 0.60-1.21], p = 0.21 I(2) = 49.7%).

CONCLUSION

Dietary supplementation with omega-3 PUFA does not affect the risk of SCD or ventricular arrhythmias.

Anxiolytic-like actions of fatty acids identified in human amniotic fluid

Eight fatty acids (C12–C18) were previously identified in human amniotic fluid, colostrum, and milk in similar proportions but different amounts. Amniotic fluid is well known to be the natural environment for development in mammals. Interestingly, amniotic fluid and an artificial mixture of fatty acids contained in amniotic fluid produce similar anxiolytic-like actions in Wistar rats. We explored whether the lowest amount of fatty acids contained in amniotic fluid with respect to colostrum and milk produces such anxiolytic-like effects. Although a trend toward a dose-response effect was observed, only an amount of fatty acids that was similar to amniotic fluid fully mimicked the effect of diazepam (2 mg/kg, i.p.) in the defensive burying test, an action devoid of effects on locomotor activity and motor coordination. Our results confirm that the amount of fatty acids contained in amniotic fluid is sufficient to produce anxiolytic-like effects, suggesting similar actions during intrauterine development.

Current evidence and future perspectives of omega-3 polyunsaturated fatty acids for the prevention of cardiovascular disease

Omega-3 fatty acids have been traditionally used for the prevention of major cardiovascular events in patients with or without a history of cardiovascular disease. Their main mechanism of action is to lower triglyceride levels, but they also exert anti-arrythmic and anti-inflammatory properties, they reduce blood pressure levels and stabilize the atherosclerotic plaques. There is a vast amount of evidence derived from randomized studies that seems to question their benefit for the prevention of major cardiovascular events. Upcoming trials will help to better clarify their use in certain indications.

A meta-analysis of omega-3 fatty acids and incidence of atrial fibrillation

OBJECTIVES

Atrial fibrillation (AF) is associated with higher health care costs. Although omega-3 (n-3) fatty acids have been associated with a decreased risk of coronary heart disease, their effects on the risk of AF are inconsistent. We therefore sought to review the relation between n-3 fatty acids and the risk of AF.

METHODS

Using an extensive online search, we conducted a meta-analysis of new onset incident/recurrent AF following exposure to fish/fish oil or long-chain n-3 polyunsaturated fatty acids. A random-effect model was used and between-studies heterogeneity was estimated with I(2). The quality of studies was assessed using Jadad and United States Preventive Services Task Force (USPSTF) scoring systems. All analyses were performed with RevMan (version 5.0.20).

RESULTS

Seven cohort studies and 11 randomized controlled trials (RCTs) were included in this meta-analysis. The pooled odds ratio (OR) was 0.79 (95% confidence interval [CI] = 0.56-1.12; p = 0.19) for RCTs and 0.83 (95% CI = 0.59-1.16; p = 0.27) for cohort studies. On sensitivity analysis, no statistically significant difference was noted when stratified by study design or quality of the studies (as graded by Jadad or USPSTF scoring systems).

CONCLUSION

This study does not suggest a major effect of fish/fish oil or n-3 fatty acids on the risk of AF.

Dampening of hyperexcitability in CA1 pyramidal neurons by polyunsaturated fatty acids acting on voltage-gated ion channels

A ketogenic diet is an alternative treatment of epilepsy in infants. The diet, rich in fat and low in carbohydrates, elevates the level of polyunsaturated fatty acids (PUFAs) in plasma. These substances have therefore been suggested to contribute to the anticonvulsive effect of the diet. PUFAs modulate the properties of a range of ion channels, including K and Na channels, and it has been hypothesized that these changes may be part of a mechanistic explanation of the ketogenic diet. Using computational modelling, we here study how experimentally observed PUFA-induced changes of ion channel activity affect neuronal excitability in CA1, in particular responses to synaptic input of high synchronicity. The PUFA effects were studied in two pathological models of cellular hyperexcitability associated with epileptogenesis. We found that experimentally derived PUFA modulation of the A-type K (K_A) channel, but not the delayed-rectifier K channel, restored healthy excitability by selectively reducing the response to inputs of high synchronicity. We also found that PUFA modulation of the transient Na channel was effective in this respect if the channel's steady-state inactivation was selectively affected. Furthermore, PUFA-induced hyperpolarization of the resting membrane potential was an effective approach to prevent hyperexcitability. When the combined effect of PUFA on the K_A channel, the Na channel, and the resting membrane potential, was simulated, a lower concentration of PUFA was needed to restore healthy excitability. We therefore propose that one explanation of the beneficial effect of PUFAs lies in its simultaneous action on a range of ion-channel targets. Furthermore, this work suggests that a pharmacological cocktail acting on the voltage dependence of the Na-channel inactivation, the voltage dependences of K_A channels, and the resting potential can be an effective treatment of epilepsy.

The ΔF508-CFTR mutation inhibits wild-type CFTR processing and function when co-expressed in human airway epithelia and in mouse nasal mucosa

BACKGROUND

Rescue or correction of CFTR function in native epithelia is the ultimate goal of CF therapeutics development. Wild-type (WT) CFTR introduction and replacement is also of particular interest. Such therapies may be complicated by possible CFTR self-assembly into an oligomer or multimer.

RESULTS

Surprisingly, functional CFTR assays in native airway epithelia showed that the most common CFTR mutant, ΔF508-CFTR (ΔF-CFTR), inhibits WT-CFTR when both forms are co-expressed. To examine more mechanistically, both forms of CFTR were transfected transiently in varying amounts into IB3-1 CF human airway epithelial cells and HEK-293 human embryonic kidney cells null for endogenous CFTR protein expression. Increasing amounts of ΔF-CFTR inhibited WT-CFTR protein processing and function in CF human airway epithelial cells but not in heterologous HEK-293 cells. Stably expressed ΔF-CFTR in clones of the non-CF human airway epithelial cell line, CALU-3, also showed reduction in cAMP-stimulated anion secretion and in WT-CFTR processing. An ultimate test of this dominant negative-like effect of ΔF-CFTR on WT-CFTR was the parallel study of two different CF mouse models: the ΔF-CFTR mouse and the bitransgenic CFTR mouse corrected in the gut but null in the lung and airways. WT/ΔF heterozygotes had an intermediate phenotype with regard to CFTR agonist responses in in vivo nasal potential difference (NPD) recordings and in Ussing chamber recordings of short-circuit current (ISC) in vitro on primary tracheal epithelial cells isolated from the same mice. In contrast, CFTR bitransgenic +/- heterozygotes had no difference in their responses versus +/+ wild-type mice.

CONCLUSIONS

Taken altogether, these data suggest that ΔF-CFTR and WT-CFTR co-assemble into an oligomeric macromolecular complex in native epithelia and share protein processing machinery and regulation at the level of the endoplasmic reticulum (ER). As a consequence, ΔF-CFTR slows WT-CFTR protein processing and limits its expression and function in the apical membrane of native airway epithelia. Implications of these data for the relative health of CF heterozygous carriers, for CFTR protein processing in native airway epithelia, and for the relative efficacy of different CF therapeutic approaches is significant and is discussed.

Comparison of eicosapentaenoic acid concentrations in plasma between patients with ischemic stroke and control subjects

OBJECTIVE

ω-3 fatty acids, including eicosapentaenoic acid (EPA), prevent ischemic stroke. However, the clinical importance of EPA for ischemic stroke and its subtype has not been fully elucidated.

METHODS

In a cross-sectional study, we determined whether ω-3 fatty acids were predictive factors for ischemic stroke. We compared common clinical parameters among 65 patients with ischemic stroke and 65 control subjects. The parameters included blood chemistry data; concentrations of EPA, docosahexaenoic acid, and arachidonic acid (AA); EPA/AA ratio; smoking; alcohol intake; fish consumption more than four times per week; and the incidence of underlying diseases. The comparisons were performed using the Mann-Whitney U test, and multiple logistic regression analysis was applied to the significant factors in the non-parametric test. We also applied the same approach to the ischemic stroke subtypes, cardioembolism and large-artery atherosclerosis.

RESULTS

In the multiple logistic regression analysis after the Mann-Whitney U test, a lower EPA concentration was one of the significant risk factors for ischemic stroke, as were a lower body mass index, lower high-density lipoprotein cholesterol, and smoking (sensitivity 0.846, specificity 0.831, positive predictive value 0.833). In the analysis of subtypes, a lower EPA/AA ratio and a lower body mass index were the significant risk factors for cardioembolism (sensitivity 0.800, specificity 0.733, positive predictive value 0.750). However, large-artery atherosclerosis was not related to the EPA concentration or the EPA/AA ratio.

CONCLUSIONS

In this study, the plasma EPA concentration and the EPA/AA ratio were potential predictive risk factors for ischemic stroke, especially for cardioembolism. Further prospective studies are necessary.

Polyunsaturated Fatty acids in atrial fibrillation: looking for the proper candidates

Atrial fibrillation (AF) is the most common sustained arrhythmia encountered in clinical practice with growing prevalence in developed countries. Several medical and interventional therapies, such as atrial specific drugs and pulmonary vein isolation, have demonstrated prevention of recurrences. However, their suboptimal long-term success and significant rate of secondary effects have led to intensive research in the last decade focused on novel alternative and supplemental therapies. One such candidate is polyunsaturated fatty acids (PUFAs). Because of their biological properties, safety, simplicity, and relatively cheap cost, there is a special clinical interest in omega-3 PUFAs as a possible antiarrhythmic agent. Obtained from diets rich in fish, they represent one of the current supplemental therapies. At the cellular level, an increasing body of evidence has shown that n-3 PUFAs exert a variety of effects on cardiac ion channels, membrane dynamic properties, inflammatory cascade, and other targets related to AF prevention. In this article, we review the current basic and clinical evidence pertinent to n-3 PUFAs in AF treatment and prevention. We also discuss controversial outcomes among clinical studies and propose specific subsets of AF patients who will benefit most from n-3 PUFAs.

Effect of Omega-3 Polyunsaturated Fatty Acid Supplementation in Patients with Atrial Fibrillation

Atrial fibrillation (AF) is the most common sustained atrial arrhythmia conferring a higher morbidity and mortality. Despite the increasing incidence of AF; available therapies are far from perfect. Dietary fish oils, containing omega 3 fatty acids, also called polyunsaturated fatty acid [PUFA] have demonstrated beneficial electrophysiological, autonomic and anti-inflammatory effects on both atrial and ventricular tissue. Multiple clinical trials, focusing on various subsets of patients with AF, have studied the role of PUFA and their potential role in reducing the incidence of this common arrhythmia. While PUFA appears to have a beneficial effect in the primary prevention of AF in the elderly with structural heart disease, this benefit has not been universally observed. In the secondary prevention of AF, PUFA seems to have a greater impact in the reducing AF in patients with paroxysmal or persistent AF, stages of AF associated with less atrial fibrosis and negative structural remodeling. However, AF suppression has not been consistently demonstrated in clinical trials. In patients undergoing heart surgery, increasing PUFA intake has yielded mixed results in terms of AF prevention post-operatively; however, increased PUFA has been associated with a reduction in hospital stay. Therefore recommending the use of PUFA for the purpose of AF reduction remains controversial. This is in part attributable to the complexity of AF. Other conflicting variables include: heterogeneous patient populations studied; variable dosing; duration of follow-up; comorbidities; and, concomitant pharmacotherapy. This review article reviews in detail available basic and clinical research studies of fish oil in the treatment of AF, and its role in the treatment of this common disorder.

ABBREVIATIONS

AF=Atrial fibrillation, CHS=Cardiovascular Health Study,CABG=Coronary artery bypass surgery, d=Day, DHA=Docosahexaenoic acid, EPA=Eicosapentaenoic acid, ERP= Effective refractory period, g=Gram, PAF= Paroxysmal atrial fibrillation, PeAF= Persistent atrial fibrillation PUFA= Polyunsaturated fatty acid.

Effects of n-3 Polyunsaturated Fatty Acids on Cardiac Ion Channels

Dietary n−3 polyunsaturated fatty acids (PUFAs) have been reported to exhibit antiarrhythmic properties, and these effects have been attributed to their capability to modulate ion channels. In the present review, we will focus on the effects of PUFAs on a cardiac sodium channel (Na_v1.5) and two potassium channels involved in cardiac atrial and ventricular repolarization (K_v) (K_v1.5 and K_v11.1). n−3 PUFAs of marine (docosahexaenoic, DHA and eicosapentaenoic acid, EPA) and plant origin (alpha-linolenic acid, ALA) block K_v1.5 and K_v11.1 channels at physiological concentrations. Moreover, DHA and EPA decrease the expression levels of K_v1.5, whereas ALA does not. DHA and EPA also decrease the magnitude of the currents elicited by the activation of Na_v1.5 and calcium channels. These effects on sodium and calcium channels should theoretically shorten the cardiac action potential duration (APD), whereas the blocking actions of n−3 PUFAs on K_v channels would be expected to produce a lengthening of cardiac action potential. Indeed, the effects of n−3 PUFAs on the cardiac APD and, therefore, on cardiac arrhythmias vary depending on the method of application, the animal model, and the underlying cardiac pathology.

Why Do We Still Need Large Scale Clinical Trial: The Case of n-3 PUFA

After the first reports about a protective effect on coronary heart disease (CHD) published more than 40 years ago, wide interest in the therapeutic use of n-3 polyunsaturated fatty acids (n-3 PUFA) aroused. Since then, many studies and meta-analyses have reported a significantly reduced risk of CHD and CV death due to fish and n-3 PUFA intake. Some of the overviews reported a significant reduction of risk of sudden cardiac death, all-cause death, and nonfatal CV events. On the other side, recent clinical trials had mixed findings, raising concern about the consistency of the evidence on n-3 PUFA. We critically reviewed recent large clinical trials reporting data on the antiarrhythmic effects of n-3 PUFA in different clinical settings, i.e., patients with CHD, heart failure, with implantable cardioverter defibrillator, and at risk of atrial fibrillation, in order to summarize the results which are available up to date and possibly give "substantiated" fuel to the debate on the conflicting results of n-3 PUFA.

Fish, Marine n-3 Fatty Acids, and Atrial Fibrillation - Experimental Data and Clinical Effects

Marine n−3 polyunsaturated fatty acids (PUFA) may have beneficial effects in relation to atrial fibrillation (AF) with promising data from experimental animal studies, however, results from studies in humans have been inconsistent. This review evaluates the mechanisms of action of marine n−3 PUFA in relation to AF based on experimental data and provides a status on the evidence obtained from observational studies and interventional trials. In conclusion, there is growing evidence for an effect of marine n−3 PUFA in prevention and treatment of AF. However, further studies are needed to establish which patients are more likely to benefit from n−3 PUFA, the timing of treatment, and dosages.

The effects of supplementation with omega-3 polyunsaturated Fatty acids on cardiac rhythm: anti-arrhythmic, pro-arrhythmic, both or neither? It depends…

Supplementation of omega-3 fatty acids (Ω-3) has been associated with a decreased cardiovascular risk, thereby concentrating attention on a potentially preventive effect regarding tachyarrhythmias and sudden cardiac death. However, recent randomized controlled trials challenge the efficacy of the additional application of Ω-3 and its anti-arrhythmic effect under certain clinical conditions. The present paper reflects the results of earlier and recent clinical studies with respect to the individual background conditions that may determine the clinical outcome of Ω-3 supplementation and thereby explain apparently conflicting clinical results. It is concluded that the efficacy of Ω-3 supplementation to prevent cardiac arrhythmias strongly depends on the underlying clinical and pharmacological conditions, a hypothesis that also is supported by data from experimental animal studies and by molecular interactions of Ω-3 at the cellular level.

RACK1 suppresses gastric tumorigenesis by stabilizing the β-catenin destruction complex

BACKGROUND & AIMS

Dysregulation of Wnt signaling has been involved in gastric tumorigenesis by mechanisms that are not fully understood. The receptor for activated protein kinase C (RACK1, GNB2L1) is involved in development of different tumor types, but its expression and function have not been investigated in gastric tumors.

METHODS

We analyzed expression of RACK1 in gastric tumor samples and their matched normal tissues from 116 patients using immunohistochemistry. Effects of knockdown with small interfering RNAs or overexpression of RACK1 in gastric cancer cell lines were evaluated in cell growth and tumor xenograft. RACK1 signaling pathways were investigated in cells and zebrafish embryos using immunoblot, immunoprecipitation, microinjection, and in situ hybridization assays.

RESULTS

Expression of RACK1 was reduced in gastric tumor samples and correlated with depth of tumor infiltration and poor differentiation. Knockdown of RACK1 in gastric cancer cells accelerated their anchorage-independent proliferation in soft agar, whereas overexpression of RACK1 reduced their tumorigenicity in nude mice. RACK1 formed a complex with glycogen synthase kinase Gsk3β and Axin to promote the interaction between Gsk3β and β-catenin and thereby stabilized the β-catenin destruction complex. On stimulation of Wnt3a, RACK1 repressed Wnt signaling by inhibiting recruitment of Axin by Dishevelled 2 (Dvl2). Moreover, there was an inverse correlation between expression of RACK1 and localization of β-catenin to the cytoplasm/nucleus in human gastric tumor samples.

CONCLUSIONS

RACK1 negatively regulates Wnt signaling pathway by stabilizing the β-catenin destruction complex and act as a tumor suppressor in gastric cancer cells.

Novel nonphosphorylated peptides with conserved sequences selectively bind to Grb7 SH2 domain with affinity comparable to its phosphorylated ligand

The Grb7 (growth factor receptor-bound 7) protein, a member of the Grb7 protein family, is found to be highly expressed in such metastatic tumors as breast cancer, esophageal cancer, liver cancer, etc. The src-homology 2 (SH2) domain in the C-terminus is reported to be mainly involved in Grb7 signaling pathways. Using the random peptide library, we identified a series of Grb7 SH2 domain-binding nonphosphorylated peptides in the yeast two-hybrid system. These peptides have a conserved GIPT/K/N sequence at the N-terminus and G/WD/IP at the C-terminus, and the region between the N-and C-terminus contains fifteen amino acids enriched with serines, threonines and prolines. The association between the nonphosphorylated peptides and the Grb7 SH2 domain occurred in vitro and ex vivo. When competing for binding to the Grb7 SH2 domain in a complex, one synthesized nonphosphorylated ligand, containing the twenty-two amino acid-motif sequence, showed at least comparable affinity to the phosphorylated ligand of ErbB3 in vitro, and its overexpression inhibited the proliferation of SK-BR-3 cells. Such nonphosphorylated peptides may be useful for rational design of drugs targeted against cancers that express high levels of Grb7 protein.

Chemical structures of odorants that suppress ion channels in the olfactory receptor cell

It has been proposed that odorant suppression of the cyclic nucleotide-gated (CNG) channel is responsible for olfactory masking. In this study, the effect of odorant chain length and functional group on this suppression was investigated. Because similar suppression has been observed for voltage-gated channels also, we used voltage-gated Na channels in the olfactory receptor cell as a tool for substance screening. These features were then re-examined using CNG channels. Interestingly, both CNG and Na channels were suppressed in a similar manner-carboxylic acids had little effect and suppression became stronger when the chain length of the alcohol or ester was increased. Degree of suppression was correlated with the distribution coefficients (Log D), irrespective of the molecules used. Results obtained here may provide information for the development of novel masking agents based on molecular architecture.

Binding of sodium channel inhibitors to hyperpolarized and depolarized conformations of the channel

Sodium channels are inhibited by a chemically diverse group of compounds. In the last decade entirely new structural classes with superior properties have been discovered, and novel therapeutic uses of sodium channel inhibitors (SCIs) have been suggested. Many promising novel drug candidates have been described and characterized. Published structure-activity relationship studies, pharmacophore models, and mutagenesis studies seem to lag behind, dealing with only a limited group of inhibitor compounds. The abundance of novel compounds requires an organized comparison of drug potencies. The affinity of sodium channel inhibitors can vary typically ten- to thousand-fold depending on the voltage protocol; therefore comparison of electrophysiology data is difficult. In this study we describe a method for standardization of these data with the help of a simple model of state-dependence. We derived hyperpolarized (resting) and depolarized (generally termed "inactivated") state affinities for the studied drugs, which made the measurements comparable. We show a rank order of SCIs based on resting and inactivated affinity values. In an attempt to define basic chemical requirements for sodium channel inhibitor activity we investigated the dependence of both resting and inactivated state affinities on individual chemical descriptors. Lipophilicity (most often expressed by the logP value) is the single most important determinant of SCI potency. We investigated the independent impact of several other calculated chemical properties by standardizing drug potencies for logP values. By combining these two approaches: standardization of affinity values, and standardization of potencies, we concluded that while resting affinity is mostly determined by lipophilicity, inactivated state affinity is determined by a more complex interaction of chemical properties, including hydrogen bond acceptors, aromatic rings, and molecular weight.

Cardiovascular effects of marine omega-3 fatty acids

Much evidence shows that the marine omega-3 fatty acids eicosapentaenoic acid and docosahexaenoic acid have beneficial effects in various cardiac disorders, and their use is recommended in guidelines for management of patients after myocardial infarction. However, questions have been raised about their usefulness alongside optimum medical therapies with agents proven to reduce risk of cardiac events in high-risk patients. Additionally, there is some evidence for a possible pro-arrhythmic effect in subsets of cardiac patients. Some uncertainly exists about the optimum dose needed to obtain beneficial effects and the relative merit of dietary intake of omega-3 polyunsaturated fatty acids versus supplements. We review evidence for the effects of omega-3 polyunsaturated fatty acids on various cardiac disorders and the risk factors for cardiac disease. We also assess areas of uncertainty needing further research.

Cardioprotection by omega-3 fatty acids: involvement of PKCs?

It has been known since the 1970s that an increased consumption of n-3 long chain polyunsaturated fatty acids such as eicosapentaenoic acid and docosahexaenoic acid has cardioprotective effects. Epidemiological studies have reported that this effect is due to the prevention of the arrhythmias responsible for sudden cardiac death. Mechanistically, different hypotheses have been put forward to give an explanation. Among them, there are a direct effect of the polyunsaturated fatty acids on ion channels and/or a modification of the regulation of ion channels by protein kinase C's.

Subchronic alpha-linolenic acid treatment enhances brain plasticity and exerts an antidepressant effect: a versatile potential therapy for stroke

Omega-3 polyunsaturated fatty acids are known to have therapeutic potential in several neurological and psychiatric disorders. However, the molecular mechanisms of action underlying these effects are not well elucidated. We previously showed that alpha-linolenic acid (ALA) reduced ischemic brain damage after a single treatment. To follow-up this finding, we investigated whether subchronic ALA treatment promoted neuronal plasticity. Three sequential injections with a neuroprotective dose of ALA increased neurogenesis and expression of key proteins involved in synaptic functions, namely, synaptophysin-1, VAMP-2, and SNAP-25, as well as proteins supporting glutamatergic neurotransmission, namely, V-GLUT1 and V-GLUT2. These effects were correlated with an increase in brain-derived neurotrophic factor (BDNF) protein levels, both in vitro using neural stem cells and hippocampal cultures and in vivo, after subchronic ALA treatment. Given that BDNF has antidepressant activity, this led us to test whether subchronic ALA treatment could produce antidepressant-like behavior. ALA-treated mice had significantly reduced measures of depressive-like behavior compared with vehicle-treated animals, suggesting another aspect of ALA treatment that could stimulate functional stroke recovery by potentially combining acute neuroprotection with long-term repair/compensatory plasticity. Indeed, three sequential injections of ALA enhanced protection, either as a pretreatment, wherein it reduced post-ischemic infarct volume 24 h after a 1-hour occlusion of the middle cerebral artery or as post-treatment therapy, wherein it augmented animal survival rates by threefold 10 days after ischemia.