TASK1 modulates inflammation and neurodegeneration in autoimmune inflammation of the central nervous system

We provide evidence that TWIK-related acid-sensitive potassium channel 1 (TASK1), a member of the family of two-pore domain potassium channels relevant for setting the resting membrane potential and balancing neuronal excitability that is expressed on T cells and neurons, is a key modulator of T cell immunity and neurodegeneration in autoimmune central nervous system inflammation. After induction of experimental autoimmune encephalomyelitis, an experimental model mimicking multiple sclerosis, TASK1(-/-) mice showed a significantly reduced clinical severity and markedly reduced axonal degeneration compared with wild-type controls. T cells from TASK1(-/-) mice displayed impaired T cell proliferation and cytokine production, while the immune repertoire is otherwise normal. In addition to these effects on systemic T cell responses, TASK1 exhibits an independent neuroprotective effect which was demonstrated using both a model of acutely prepared brain slices cocultured with activated T cells as well as in vitro cultivation experiments with isolated optic nerves. Anandamide, an endogenous cannabinoid and inhibitor of TASK channels, reduced outward currents and inhibited effector functions of T cells (IFN-gamma production and proliferation); an effect completely abrogated in TASK1(-/-) mice. Accordingly, preventive blockade of TASK1 significantly ameliorated experimental autoimmune encephalomyelitis after immunization. Therapeutic application of anandamide significantly reduced disease severity and was capable of lowering progressive loss of brain parenchymal volume as assessed by magnetic resonance imaging. These data support the identification and characterization of TASK1 as potential molecular target for the therapy of inflammatory and degenerative central nervous system disorders.

Altered neuronal expression of TASK1 and TASK3 potassium channels in rodent and human autoimmune CNS inflammation

Multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE) are characterized by T cell-mediated autoimmune inflammation of the central nervous system (CNS) leading to oligodendrocyte loss and demyelination accompanied by neuronal cell death. Neuronal TWIK-related acid-sensitive potassium (TASK) channels allow the regulated efflux of potassium ions. These channels might either protect neurons in the inflamed CNS by modulating electrical excitability or even contribute to inflammatory neurodegeneration mediating intracellular potassium depletion. Using a combination of in-situ-hybridisation and immunofluorescence staining, we found increased neuronal expression of TASK1 and TASK3 channels in the optic nerve and decreased expression in the spinal cord and thalamus of rats undergoing MOG-induced EAE. Inflammatory plaques of human MS patients displayed profoundly lowered expression of both TASK isoforms. Thus, regulated expression of TASK channels might contribute to a molecular switch between death and survival of neurons in autoimmune CNS inflammation.

The neuroprotective impact of the leak potassium channel TASK1 on stroke development in mice

Oxygen depletion (O(2)) and a decrease in pH are initial pathophysiological events in stroke development, but secondary mechanisms of ischemic cell death are incompletely understood. By patch-clamp recordings of brain slice preparations we show that TASK1 and TASK3 channels are inhibited by pH-reduction (42+/-2%) and O(2) deprivation (36+/-5%) leading to membrane depolarization, increased input resistance and a switch in action potential generation under ischemic conditions. In vivo TASK blockade by anandamide significantly increased infarct volumes at 24 h in mice undergoing 30 min of transient middle cerebral artery occlusion (tMCAO). Moreover, blockade of TASK channels accelerated stroke development. Supporting these findings TASK1(-/-) mice developed significantly larger infarct volumes after tMCAO accompanied by worse outcome in functional neurological tests compared to wild type mice. In conclusion, our data provide evidence for an important role of functional TASK channels in limiting tissue damage during cerebral ischemia.

Left ventricular volumes and mass in marathon runners and their association with cardiovascular risk factors

BACKGROUND

To assess left ventricular volumes and mass by cardiac magnetic resonance imaging in relation to conventional cardiovascular risk factors and coronary atherosclerotic plaque burden in master marathon runners aged > or =50 years.

METHODS

Cardiac MRI was performed in 105 clinically healthy male marathon runners (mean age 57.3 +/- 5.7 years, range 50-71 years) on a 1.5 T MR system (Avanto, Siemens, Germany). Cine steady state free precession images in standard long and short axes views were acquired to assess left ventricular volumes and mass. Cardiovascular risk factors (blood pressure, HDL/LDL cholesterol, smoking, body mass index) were assessed and coronary artery calcification (CAC) was quantified by electron beam computed tomography.

RESULTS

Left ventricular muscle mass (mean LVMM = 140 +/- 27 g; 73 +/- 13 g/m(2)) increased with increasing left ventricular end-diastolic volume (mean LVEDV = 137 +/- 32 ml; 72 +/- 15 ml/m(2)) (r = 0.41, P < 0.0001) and with systolic (r = 0.33, P = 0.005) and diastolic (r = 0.28, P = 0.005) blood pressures. Left ventricular EDV increased up to the age of 55 years, but decreased thereafter. Runners with LVMM > or =150 g had significantly higher CAC scores than runners with LVMM <150 g (median CAC score 110 vs. 25, P = 0.04).

CONCLUSIONS

Increases in LVMM and LVEDV may not only represent a response to exercise but are dependent on age and blood pressure, also. In addition, a left ventricular hypertrophy without an increase in volume may be an indicator for early subclinical cardiac alterations in response to risk factor exposure.

Correlation of T-channel coding gene expression, IT, and the low threshold Ca2+ spike in the thalamus of a rat model of absence epilepsy

T-type Ca(2+) current-dependent burst firing of thalamic neurons is thought to be involved in the hyper-synchronous activity observed during absence seizures. Here we investigate the correlation between the expression of T-channel coding genes (alpha1G, -H, -I), T-type Ca(2+) current, and the T-current-dependent low threshold Ca(2+) spike in three functionally distinct thalamic nuclei (lateral geniculate nucleus; centrolateral nucleus; reticular nucleus) in a rat model of absence epilepsy, the WAG/Rij rats, and a non-epileptic control strain, the ACI rats. The lateral geniculate nucleus and centrolateral nucleus were found to primarily express alpha1G and alpha1I, while the reticular thalamic nucleus expressed alpha1H and alpha1I. Expression was higher in WAG/Rij when compared to ACI. The T-type Ca(2+) current properties matched the predictions derived from the expression pattern analysis. Current density was larger in all nuclei of WAG/Rij rats when compared to ACI and correlated with LTS size and the minimum LTS generating slope, while T-type Ca(2+) current voltage dependency correlated with the LTS onset potential.

[Primary Coronary Intervention (PCI) within the myocardial infarction network system in a German city (Essen)]

In a German city (Essen, 490,000 people), a new network system for patients with ST elevation myocardial infarction (STEMI) was established in 2004. This included a so-called integrated care model (IV model) by participation of insurance companies. In a cooperative structure between invasive and noninvasive hospitals, general practitioners and cardiologists as well as emergency systems it could be realized, that every patient with STEMI will be treated by primary percutaneous coronary intervention (PCI) as soon as possible according to the current guidelines. The patient characteristics (age, gender, comorbidity, medication) were comparable to other trials and registries. The primary success rate was high (96.4%). The acute in-hospital results demonstrated a low mortality (7.6%). The time periods of delay were comparable to other registries. The symptom-to-balloon time was 239 min, the medical contact-to-balloon time 95 min, the door-to-balloon time 60 min, and the puncture-to-balloon time 18 min (median values). The STEMI network system in Essen demonstrates the possibility of modern therapy in patients with myocardial infarction (primary PCI) in a cooperative modality between all participants in the health-care system.

[STEMI network Essen--results after 1 year]

The myocardial infarction network "Herzinfarktverbund Essen" was initiated on September 1, 2004 in order to establish a standardized strategy and therapy for patients with ST elevation myocardial infarction (STEMI) in the city of Essen. The primary goal is the immediate reopening of the infarcted vessel by direct transfer of the patient to a hospital with 24-h stand-by catheter laboratory. The first 1-year follow-up, completed on August 31, 2006, showed a low 1-year mortality rate (11.2%), whereby 7.6% of the patients died in hospital. There was a significant dependency of mortality on age, the prehospital stability of cardiovascular circulation, the amount of left ventricular damage, the TIMI flow after intervention, and the duration of interventional therapy ("puncture-to-balloon" time). The coronary status, anticoagulation therapy as well as diabetes mellitus were also dependent variables, whereas the type of stent showed no influence. The rate of restenosis was greater with bare-metal stents (BMS) compared to the use of drug-eluting stents (DES). There was a low rate of repeated STEMI or NSTEMI (non-ST elevation myocardial infarction; 1.8%, 1.7%). These first long-term data confirm the successful implementation of treatment guidelines for STEMI patients within a standardized strategy in an urban environment.

[STEMI network Essen-in-hospital results]

BACKGROUND AND PURPOSE

The myocardial infarction network "Herzinfarktverbund Essen", existing since 2004, was designed to introduce guideline therapy of ST elevation myocardial infarction (STEMI) into everyday clinical practice using primary percutaneous coronary intervention (PCI) as the preferred reperfusion strategy, early prescribing recommended medication and optimizing patient's pathway from the first symptom to rehabilitation in a city of 580,000 inhabitants.

PATIENTS AND METHODS

In the 1st year, 489 patients were treated in five high-volume PCI centers. 444 primary PCIs were performed (90.8%).

RESULTS

In-hospital mortality was 7.6% and thus lower than in other, historical STEMI registers with similar baseline characteristics but lower PCI rate. The best risk predictor was left ventricular function. Patients with an ejection fraction (EF) <or= 30% had a 27 times higher mortality risk than those with normal EF. Guideline-recommended medication was prescribed in 75% of patients (acetylsalicylic acid [ASS], clopidogrel, beta-blockers, and statins) and in 71%, respectively, with additional ACE inhibitor (five drugs). 72% of these patients were referred to rehabilitation therapy.

CONCLUSION

The "Herzinfarktverbund Essen" demonstrates, that implementing guideline-conformal therapy into an urban area may result in a lower in-hospital mortality, a higher rate of patients prescribed recommended medication and a stronger patient adherence to ambulant therapy.

TWIK-related acid-sensitive K+ channel 1 (TASK1) and TASK3 critically influence T lymphocyte effector functions

Two major K(+) channels are expressed in T cells, (i) the voltage-dependent K(V)1.3 channel and (ii) the Ca(2+)-activated K(+) channel KCa 3.1 (IKCa channel). Both critically influence T cell effector functions in vitro and animal models in vivo. Here we identify and characterize TWIK-related acid-sensitive potassium channel 1 (TASK1) and TASK3 as an important third K(+) conductance on T lymphocytes. T lymphocytes constitutively express TASK1 and -3 protein. Application of semi-selective TASK blockers resulted in a significant reduction of cytokine production and cell proliferation. Interference with TASK channels on CD3(+) T cells revealed a dose-dependent reduction ( approximately 40%) of an outward current in patch clamp recordings indicative of TASK channels, a finding confirmed by computational modeling. In vivo relevance of our findings was addressed in an experimental model of multiple sclerosis, adoptive transfer experimental autoimmune encephalomyelitis. Pretreatment of myelin basic protein-specific encephalitogenic T lymphocytes with TASK modulators was associated with significant amelioration of the disease course in Lewis rats. These data introduce K(2)P channels as novel potassium conductance on T lymphocytes critically influencing T cell effector function and identify a possible molecular target for immunomodulation in T cell-mediated autoimmune disorders.

[New health care delivery model in cardiology -- Myocardial Infarction Network Essen]

Current guidelines favor primary percutaneous coronary intervention (PCI) as the strategy of choice for the treatment of acute ST segment elevation myocardial infarction (STEMI). Already in its 1st year, the myocardial infarction network "Herzinfarktverbund Essen" demonstrates with 489 patients the feasibility of an exhaustive urban STEMI network with preference to patient transfer to high-volume PCI centers. Furthermore, integrated health care as an optional part of the "Herzinfarktverbund" offers reimbursement for modern and innovative diagnostic procedures, therapies, and rehabilitation.

The two-pore domain potassium channel TASK3 functionally impacts glioma cell death

Two-pore domain K(+) channels, a recently discovered family of ion channels with a unique membrane topology, have been shown to be critically involved in cell death. We here address the functional role of TASK3 (TWIK-related acid-sensitive K(+) channel, KCNK9) in human glioblastoma in vitro and in vivo. Human glioma cell lines (n = 5) as well as glioma specimens (n = 5) constitutively express TASK3 mRNA and protein. The functional impact of the potassium channel on cell survival was investigated using a medium with high (25 mM) extracellular potassium over 7 days. Using flow cytometric assessment, we show that under these culture conditions 97 +/- 0.76% of all glioma cells survived. Application of the TASK channel opener isoflurane (1 vol%) resulted in a 30 +/- 4% reduction of cell survival in different glioma cell lines. Simultaneous application of isoflurane and the TASK channel blockers bupivacaine (20 microM) and spermine (500 microM) completely reversed this effect. Our results demonstrate the expression of TASK3 in glioma cells in vitro and in vivo and provide a direct link between the TASK3 channel function and glioma cell survival. This implies that TASK3 channels may possibly represent a novel molecular target for the treatment of this type of cancer.

Specific expression of low-voltage-activated calcium channel isoforms and splice variants in thalamic local circuit interneurons

It has been suggested that the specific burst firing patterns of thalamic neurons reflect differential expression of low-voltage-activated (LVA) Ca(2+) channel subtypes and their splice variants. By combining electrophysiological, molecular biological, immunological, and computational modeling techniques we here show that diverging LVA Ca(2+) currents of thalamocortical relay (TC) and GABAergic interneurons of the dLGN correlate with a differential expression of LVA Ca(2+) channel splice variations and isoforms (alpha1G-a in TC; alpha1G-bc and alpha1I in interneurons). Implementation of the observed LVA Ca(2+) current differences into a TC neuron model changed the burst firing from TC-like to interneuron-like. We conclude that alternative splicing of the alpha1G isoform in dLGN TC and interneurons, and the exclusive expression of the alpha1I isoform in interneurons play a prominent role in setting the different LVA Ca(2+) current properties of TC and interneurons, which critically contribute to the diverging burst firing behavior of these neurons.

T-current related effects of antiepileptic drugs and a Ca2+ channel antagonist on thalamic relay and local circuit interneurons in a rat model of absence epilepsy

Channel blocking, anti-oscillatory, and anti-epileptic effects of clinically used anti-absence substances (ethosuximide, valproate) and the T-type Ca2+ current (IT) blocker mibefradil were tested by analyzing membrane currents in acutely isolated local circuit interneurons and thalamocortical relay (TC) neurons, slow intrathalamic oscillations in brain slices, and spike and wave discharges (SWDs) occurring in vivo in Wistar Albino Glaxo rats from Rijswijk (WAG/Rij). Substance effects in vitro were compared between WAG/Rij and a non-epileptic control strain, the ACI rats. Ethosuximide (ETX) and valproate were found to block IT in acutely isolated thalamic neurons. Block of IT by therapeutically relevant ETX concentrations (0.25-0.75 mM) was stronger in WAG/Rij, although the maximal effect at saturating concentrations (>or=10 mM) was stronger in ACI. Ethosuximide delayed the onset of the low threshold Ca2+ spike (LTS) of neurons recorded in slice preparations. Mibefradil (>or=2 microM) completely blocked IT and the LTS, dampened evoked thalamic oscillations, and attenuated SWDs in vivo. Computational modeling demonstrated that the complete effect of ETX can be replicated by a sole reduction of IT. However, the necessary degree of IT reduction was not induced by therapeutically relevant ETX concentrations. A combined reduction of IT, the persistent sodium current, and the Ca2+ activated K+ current resulted in an LTS alteration resembling the experimental observations. In summary, these results support the hypothesis of IT reduction as part of the mechanism of action of anti-absence drugs and demonstrate the ability of a specific IT antagonist to attenuate rhythmic burst firing and SWDs.

[Current studies on the progression of coronary calcification]

The quantification of coronary calcification facilitates improved prediction of cardiovascular diseases, in particular in persons with intermediate risk. The importance of serial measurement of coronary calcium in one to two-year intervals for evaluating the course of the disease and therapeutic monitoring after risk modification is unclear. The precise quantification of the progression of arteriosclerosis could contribute to the non-invasive detection of the chronic, often subclinical development of coronary heart disease at an asymptomatic stage of the disease, long before an irreversible clinical event in the pathogenetic cascade, such as sudden cardiac death or myocardial infarction, occurs. An important prerequisite for evaluating changes in the coronary calcium load is detailed knowledge of reproducibility or variability. In addition to a rapid image acquisition time and the use of calibration phantoms, low heart rate and breathing variability, image acquisition in the late systole, overlapping layers (at the expense of radiation dose) and optimized analysis algorithms also contribute to improvement in reproducibility. The limits of variability however are, above all, dependent upon the calcium load itself. Reproducibility is on the average about 10% and thus lies below the highest expected progression, which is about 10-50% per year, depending upon the initial value and pre-existing conditions Only a few studies have identified calcium score progression as an independent predictor for later events. In several studies, calcium score progression was related to the rate of events, but was not independent of other variables. The most important determinant appears to be the calcium score itself. Other relevant determinants are age, gender, diabetes, obesity and renal failure. Whether lipid values significantly influence the progression has not been clarified.

CONCLUSION

Further studies on the natural course of coronary heart disease, particularly in the early disease stages, the determinants of progression and the extent to which the calcification progress can be modified are necessary to assess the benefit of serial score measurement for risk stratification. Until then, the repeated radiation exposure cannot be recommended outside of clinical studies.

[Assessment of the natural history of coronary artery calcification and identification of its determinants. Rationale of the 2nd part of the Heinz Nixdorf Recall Study]

The Heinz Nixdorf Recall Study, which was inaugurated in 2000, is an ongoing population-based study to evaluate the prediction of cardiovascular events by integrating new imaging and nonimaging modalities in risk assessment. A focus is the additional prognostic value of coronary artery calcification (CAC). Currently used risk stratification algorithms often describe the individuals' risk based on few established risk factors only inaccurately. Using noninvasive quantification of CAC progression, the natural history of atherosclerosis with its repetitive, frequently subclinical plaque ruptures, may detect an unstable course of the disease long before the disease irreversibly manifests in sudden death or myocardial infarction. While the independent additional prognostic value of CAC quantification has been shown in asymptomatic patients at intermediate risk, only few studies provided evidence for an independent prognostic value of serial CAC measurements. In the Heinz Nixdorf Recall Study, the impact of established and new risk factors, e.g., the metabolic syndrome, psychosocial and environmental risk factors, or genetic variables, can be assessed. Further, the association of CAC progression with the incidence of other cardiovascular diseases such as heart failure or aortic or aortic valve calcification can be described. Since April 2006, the participants of the study return to the study center 5 years after baseline recruitment to assess health status and to determine the risk factor profile. Based on recently published data, serial CAC measurements have been granted allowing for (1) characterization of the natural history of CAC progression, and (2) identification of its determinants. The rationale of serial CAC quantification is discussed in this article.The Heinz Nixdorf Recall Study will contribute to the appraisal of new imaging modalities in risk stratification.

AICD treatment in 2004--state of the art

Primary and secondary prevention of sudden cardiac death is not sufficiently assured by medication. The (automatic) implantable cardioverter/defibrillator ((A)ICD) is able to terminate life-threatening arrhythmias (ventricular fibrillation/flutter, ventricular tachycardia) reliably. The identification and care of risk patients is of crucial importance. Initially, only survived resuscitation for ventricular fibrillation or ventricular tachycardia was regarded as a confirmed indication. Several studies (CABG patch, MADIT, MADIT II, MUSTT, DINAMIT, CAT AMIOVIRT, DEFINITE, COMPANION, SCD-HeFT) have examined the prophylactic indication for ICD therapy in risk groups. Patients with chronic state after myocardial infarction with markedly impaired left ventricular function and/or spontaneous, non-sustained ventricular tachycardia have been documented to benefit. Patients with moderately severe or severe heart failure also profit from ICD implantation, where appropriate in combination with cardiac resynchronization therapy in conduction disorders. There is divergent data on dilated cardiomyopathy. ICD is not indicated in patients with acute infarctions or undergoing elective bypass surgery.

Coronary Atherosclerosis and Cardiovascular Risk in Masters Male Marathon Runners

BACKGROUND

Regular physical exercise is recommended to reduce cardiovascular mortality. And yet, atherosclerosis is the main cause of exercise-associated death in persons beyond age 35. The need for risk stratification in marathon runners is under discussion. The predictive value of modern imaging- and non-imaging-based markers of risk that can be used for risk stratification in masters endurance athletes still deserves exploration.

METHODS

Male runners > 50 years who have completed at least five marathon races during the preceding 3 years and do not suffer from coronary artery disease, angina nor diabetes mellitus are studied to assess the predictive value of established and modern imaging- based and biochemical cardiovascular risk factors. Laboratory parameters including clinical chemistry, hematology and hormone measurements are determined. Lifestyle-related risk factors, psychosocial and socioeconomic variables are explored using standardized questionnaires. Coronary, carotid, femoral and aortic atherosclerosis is measured using electronbeam computed tomography and ultrasound. In addition, a resting ECG, a bicycle stress test and heart rate variability are performed. Myocardial morphology and function are assessed using echocardiography and magnetic resonance imaging. Participants are invited to compete in a marathon race to quantify the association of coronary atherosclerosis with marathon-related changes of cardiac troponin levels and the extent of marathon-induced inflammation. At the cellular level, the effect on the amount of circulating progenitor cells (EPCs) is determined by FACS analysis. Changes in laboratory parameters and hormone levels are also studied. Annual long-term follow-up including hospital records and death certificates is performed. Data are compared with those from a general unselected cohort from the Heinz Nixdorf Recall Study.

CONCLUSION

This study should contribute to cardiovascular risk assessment in the growing number of masters marathon runners with a focus on assessing the predictive value of modern imaging techniques and biochemical markers for comprehensive risk stratification.

Membrane Resting Potential of Thalamocortical Relay Neurons Is Shaped by the Interaction Among TASK3 and HCN2 Channels

By combining molecular biological, electrophysiological, immunological, and computer modeling techniques, we here demonstrate a counterbalancing contribution of TASK channels, underlying hyperpolarizing K+ leak currents, and HCN channels, underlying depolarizing Ih, to the resting membrane potential of thalamocortical relay (TC) neurons. RT-PCR experiments revealed the expression of TASK1, TASK3, and HCN1–4. Quantitative determination of mRNA expression levels and immunocytochemical staining demonstrated that TASK3 and HCN2 channels represent the dominant thalamic isoforms and are coexpressed in TC neurons. Extracellular acidification, a standard procedure to inhibit TASK channels, blocked a TASK current masked by additional action on HCN channels. Only in the presence of the HCN blocker ZD7288 was the pH-sensitive component typical for a TASK current, i.e., outward rectification and current reversal at the K+ equilibrium potential. In a similar way extracellular acidification was able to shift the activity pattern of TC neurons from burst to tonic firing only during block of Ih or genetic knock out of HCN channels. A single compartmental computer model of TC neurons simulated the counterbalancing influence of TASK and HCN on the resting membrane potential. It is concluded that TASK3 and HCN2 channels stabilize the membrane potential by a mutual functional interaction, that the most efficient way to regulate the membrane potential of TC neurons is the converse modulation of TASK and HCN channels, and that TC neurons are potentially more resistant to insults accompanied by extracellular pH shifts in comparison to other CNS regions.

Effects of divalent cations and spermine on the K+ channel TASK-3 and on the outward current in thalamic neurons

The potassium channels TASK-1 and TASK-3 show high sequence homology but differ in their sensitivity to extracellular divalent cations. Heterologous expression in HEK293 cells showed that the single-channel conductance of TASK-3 increased approximately four-fold after removal of external divalent cations, whereas the conductance of TASK-1 was unaffected. Replacing the glutamate at position 70 of TASK-3 by a lysine or arginine residue abolished the sensitivity to divalent cations. The reverse mutation in TASK-1 (K70E) induced sensitivity to divalent cations. The organic polycations spermine and ruthenium red modulated the conductance of TASK-3 in a similar way as Ca2+ or Mg2+. Our data suggest that these effects were mediated by shielding of the negative charges in the extracellular loops of TASK-3. Whole-cell currents carried by TASK-3 channels were inhibited by spermine and ruthenium red even in the presence of external divalent cations. These data suggest that, in addition to their effect on single-channel conductance, spermine and ruthenium red decreased the open probability of TASK-3 channels, probably by binding to residue E70. The standing outward current in thalamocortical relay neurons, which is largely carried by TASK channels, was also inhibited by divalent cations and spermine. Using the differential sensitivity of TASK-1 and TASK-3 to divalent cations and spermine we found that about 20% of the standing outward current in thalamocortical relay neurons flows through TASK-3 channels. We conclude from our results that inhibition of TASK-3 channels may contribute to the neuromodulatory effect of spermine released from neurons during repetitive activity or during hypoxia.

Effects of lifestyle modification on the progression of coronary atherosclerosis, autonomic function, and angina--the role of GNB3 C825T polymorphism

BACKGROUND

Given the multimodal medical and interventional treatment options in coronary artery disease, the additional value of intensified lifestyle modification is unclear. We have therefore examined the effects of lifestyle modification on top of current treatment and also associated with the GNB3 C825T polymorphism, which has established association to sympathetic activation and the precipitation of angina.

METHODS

One hundred one patients with established coronary artery disease were randomized to a 1-year lifestyle modification group (lifestyle group [LG]) or an advice group. Risk factors, coronary calcification (electron beam tomography), heart rate variability, baroreflex sensitivity, anginal symptoms, and quality of life (QOL) were assessed on entry and after 1 year.

RESULTS

Patients in LG had excellent program adherence, but lifestyle modification had no impact on metabolic risk factors and coronary calcification. Changes in heart rate, heart rate variability, and blood pressure were only slightly favoring LG. Baroreflex sensitivity increased by 2 (0.79-3.13) ms/mm Hg in the LG but decreased by -0.10 (-1.11 to 0.92) in the advice group (P = .013). Lifestyle modification led to improved physical QOL, reductions of anginal attacks (-54% vs 11%, P = .01), and dose reductions in 30% of anti-ischemic medications (P = .004). *825T allele carriers had a more pronounced reduction of heart rate and improvement of angina and QOL. The beneficial effect on reduction of medication was seen in *825T allele carriers only.

CONCLUSIONS

In the presence of modern treatments, comprehensive lifestyle modification provides no additional benefits on progression of atherosclerosis but improves autonomic function, angina, and QOL with concomitant reduced need of medication. These responses are more pronounced in GNB3*825T allele carriers.

The Contribution of TWIK-Related Acid-Sensitive K+-Containing Channels to the Function of Dorsal Lateral Geniculate Thalamocortical Relay Neurons

A genetic knockout was used to determine the specific contribution of TWIK-related acid-sensitive K+ (TASK)-1 channels to the function of dorsal lateral geniculate nucleus (DLG) thalamocortical relay (TC) neurons. Disruption of TASK-1 function produced an approximately 19% decrease in amplitude of the standing outward current (ISO) and a 3 +/- 1-mV depolarizing shift in resting membrane potential (Vrest) of DLG neurons. We estimated that current through TASK-1 homodimers or TASK-1/TASK-3 heterodimers contribute(s) approximately one third of the current sensitive to TASK channel modulators in DLG TC neurons. The effects of the TASK channel blocker bupivacaine (20 microM), of muscarine (50 microM), and of H+ on ISO were reduced to approximately 60%, 59%, and shifted to more acidic pH values, respectively. The blocking effect of anandamide on ISO [30 microM; 23 +/- 3% current decrease in wild type (WT)] was absent in TASK-1 knockout (TASK-1-/-) mice (9 +/- 6% current increase). Comparable results were obtained with the more stable anand-amide derivative methanandamide (20 microM; 20 +/- 2% decrease in WT; 4 +/- 6% increase in TASK-1-/-). Current-clamp recordings revealed a muscarine-induced shift in TC neuron activity from burst to tonic firing in both mouse genotypes. Electrocorticograms and sleep/wake times were unchanged in TASK-1-/- mice. In conclusion, our findings demonstrate a significant contribution of TASK-1 channels to ISO in DLG TC neurons, although the genetic knockout of TASK-1 did not produce severe deficits in the thalamocortical system.