Glucose-6-phosphate dehydrogenase deficiency accelerates arterial aging in diabetes.

AIMS: High glucose levels and Glucose-6-Phosphate Dehydrogenase deficiency (G6PDd) have both tissue inflammatory effects. Here we determined whether G6PDd accelerates arterial aging (information linked stiffening) in diabetes. METHODS: Plasma glucose, interleukin 6 (IL6), and arterial stiffness (indexed as carotid-femoral Pulse Wave Velocity, PWV) and red blood cell G6PD activity were assessed in a large (4448) Sardinian population. RESULTS: Although high plasma glucose in diabetics, did not differ by G6DP status (178.2 ± 55.1 vs 169.0 ± 50.1 mg/dl) in G6DPd versus non-G6PDd subjects, respectively, IL6, and PWV (adjusted for age and glucose) were significantly increased in G6PDd vs non-G6PDd subjects (PWV, 8.0 ± 0.4 vs 7.2 ± 0.2 m/sec) and (IL6, 6.9 ± 5.0 vs 4.2 ± 3.0 pg/ml). In non-diabetics, neither fasting plasma glucose, nor IL6, nor PWV were impacted by G6PDd. CONCLUSION: G6PDd in diabetics is associated with increased inflammatory markers and accelerated arterial aging.

Computer-aided detection of arrhythmogenic sites in post-ischemic ventricular tachycardia.

Nowadays, catheter-based ablation in patients with post-ischemic ventricular tachycardia (VT) is performed in arrhythmogenic sites identified by electrophysiologists by visual inspection during electroanatomic mapping. This work aims to present the development of machine learning tools aiming at supporting clinicians in the identification of arrhythmogenic sites by exploiting innovative features that belong to different domains. This study included 1584 bipolar electrograms from nine patients affected by post-ischemic VT. Different features were extracted in the time, time scale, frequency, and spatial domains and used to train different supervised classifiers. Classification results showed high performance, revealing robustness across the different classifiers in terms of accuracy, true positive, and false positive rates. The combination of multi-domain features with the ensemble tree is the most effective solution, exhibiting accuracies above 93% in the 10-time 10-fold cross-validation and 84% in the leave-one-subject-out validation. Results confirmed the effectiveness of the proposed features and their potential use in a computer-aided system for the detection of arrhythmogenic sites. This work demonstrates for the first time the usefulness of supervised machine learning for the detection of arrhythmogenic sites in post-ischemic VT patients, thus enabling the development of computer-aided systems to reduce operator dependence and errors, thereby possibly improving clinical outcomes.

Arterial stiffness and multiple organ damage: a longitudinal study in population.

AIMS: Previous cross-sectional observation identified arterial aging, indexed as pulse-wave velocity (PWV), as a key determinant of the simultaneous multiple organ damage (heart, carotid artery, and kidney). The aim of the present cohort study is to investigate trajectories of repeated measures of PWV and traditional CV risk factors in subjects who eventually presented clinical evidence of multiple organ damage in the SardiNIA study. METHODS AND RESULTS: Organ damage was measured in the heart (left ventricular hypertrophy, LVH), the common carotid artery (intima-media thickness > 0.9 mm and/or plaque), and the kidney (eGFR < 60 ml/min/1.73 m2) of 2130 men and women of a broad age range participating the SardiNIA study. SHATS was defined as the simultaneous occurrence of all the three-organ damages. Trajectory in traditional CV risk factors and PWV was analyzed retrospectively (four observations over 9 years) according to the number of organ damage (from 0 to 3). Compared to subjects with no organ damage, after controlling for traditional CV risk factors, each 1 m/s increase in baseline PWV was accompanied by a 93% higher odds of developing SHATS; and each 1 cm/s (0.01 m/s) annual increase in PWV by a 31% greater odds of developing SHATS. CONCLUSIONS: Arterial stiffness, a proxy of arterial aging that can be measured clinically as PWV, is an integrated predictive marker of multiple age-associated organ damage recognized as clinical diseases.

Equilibrative nucleoside transporter ENT1 as a biomarker of Huntington disease.

The initial goal of this study was to investigate alterations in adenosine A2A receptor (A2AR) density or function in a rat model of Huntington disease (HD) with reported insensitivity to an A2AR antagonist. Unsuspected negative results led to the hypothesis of a low striatal adenosine tone and to the search for the mechanisms involved. Extracellular striatal concentrations of adenosine were measured with in vivo microdialysis in two rodent models of early neuropathological stages of HD disease, the Tg51 rat and the zQ175 knock-in mouse. In view of the crucial role of the equilibrative nucleoside transporter (ENT1) in determining extracellular content of adenosine, the binding properties of the ENT1 inhibitor [3H]-S-(4-Nitrobenzyl)-6-thioinosine were evaluated in zQ175 mice and the differential expression and differential coexpression patterns of the ENT1 gene (SLC29A1) were analyzed in a large human cohort of HD disease and controls. Extracellular striatal levels of adenosine were significantly lower in both animal models as compared with control littermates and striatal ENT1 binding sites were significantly upregulated in zQ175 mice. ENT1 transcript was significantly upregulated in HD disease patients at an early neuropathological severity stage, but not those with a higher severity stage, relative to non-demented controls. ENT1 transcript was differentially coexpressed (gained correlations) with several other genes in HD disease subjects compared to the control group. The present study demonstrates that ENT1 and adenosine constitute biomarkers of the initial stages of neurodegeneration in HD disease and also predicts that ENT1 could constitute a new therapeutic target to delay the progression of the disease.

Local Control of Extracellular Dopamine Levels in the Medial Nucleus Accumbens by a Glutamatergic Projection from the Infralimbic Cortex.

It is generally assumed that infralimbic cortex (ILC) and prelimbic cortex, two adjacent areas of the medial prefrontal cortex (mPFC) in rodents, provide selective excitatory glutamatergic inputs to the nucleus accumbens (NAc) shell and core, respectively. It is also generally believed that mPFC influences the extracellular levels of dopamine in the NAc primarily by an excitatory collateral to the ventral tegmental area (VTA). In the present study, we first established the existence of a selective functional connection between ILC and the posteromedial portions of the VTA (pmVTA) and the mNAc shell (pmNAc shell), by measuring striatal neuronal activation (immunohistochemical analysis of ERK1/2 phosphorylation) and glutamate release (in vivo microdialysis) upon ILC electrical stimulation. A novel optogenetic-microdialysis approach allowed the measurement of extracellular concentrations of glutamate and dopamine in the pmNAc shell upon local light-induced stimulation of glutamatergic terminals from ILC. Cortical electrical and local optogenetic stimulation produced significant increases in the extracellular concentrations of glutamate and dopamine in the pmNAc shell. Local blockade of glutamate release by perfusion of an adenosine A2A receptor antagonist in the pmNAc shell blocked the dopamine release induced by local optogenetic stimulation but only partially antagonized dopamine release induced by cortical electrical stimulation. The results demonstrate that ILC excitatory afferents directly modulate the extracellular concentration of dopamine in the pmNAc shell, but also support the involvement of an indirect mechanism of dopamine control, through a concomitant ILC-mediated activation of the pmVTA. Significance statement: We established the existence of a functional connection between the infralimbic cortex (ILC) and the posteromedial portions of the ventral tegmental area (pmVTA) and the medial nucleus acumbens shell (pmNAc shell). A novel optogenetic-microdialysis approach allowed us to demonstrate that local glutamate release from glutamatergic terminals from the ILC exert a significant modulation of extracellular concentration of dopamine in the pmNAc shell. This mechanism provides the frame for a selective cortical-mediated tonic dopaminergic modulation of specific striatal compartments.

Arterial stiffness and influences of the metabolic syndrome: a cross-countries study.

Specific clusters of metabolic syndrome (MetS) components impact differentially on arterial stiffness, indexed as pulse wave velocity (PWV). Of note, in several population-based studies participating in the MARE (Metabolic syndrome and Arteries REsearch) Consortium the occurrence of specific clusters of MetS differed markedly across Europe and the US. The aim of the present study was to investigate whether specific clusters of MetS are consistently associated with stiffer arteries in different populations. We studied 20,570 subjects from 9 cohorts representing 8 different European countries and the US participating in the MARE Consortium. MetS was defined in accordance with NCEP ATPIII criteria as the simultaneous alteration in ≥3 of the 5 components: abdominal obesity (W), high triglycerides (T), low HDL cholesterol (H), elevated blood pressure (B), and elevated fasting glucose (G). PWV measured in each cohort was "normalized" to account for different acquisition methods. MetS had an overall prevalence of 24.2% (4985 subjects). MetS accelerated the age-associated increase in PWV levels at any age, and similarly in men and women. MetS clusters TBW, GBW, and GTBW are consistently associated with significantly stiffer arteries to an extent similar or greater than observed in subjects with alteration in all the five MetS components--even after controlling for age, sex, smoking, cholesterol levels, and diabetes mellitus--in all the MARE cohorts. In conclusion, different component clusters of MetS showed varying associations with arterial stiffness (PWV).

Psychostimulant pharmacological profile of paraxanthine, the main metabolite of caffeine in humans.

Caffeine induces locomotor activation by its ability to block adenosine receptors. Caffeine is metabolized to several methylxanthines, with paraxanthine being the main metabolite in humans. In this study we show that in rats paraxanthine has a stronger locomotor activating effect than caffeine or the two other main metabolites of caffeine, theophylline and theobromine. As previously described for caffeine, the locomotor activating doses of paraxanthine more efficiently counteract the locomotor depressant effects of an adenosine A(1) than an adenosine A(2A) receptor agonist. In drug discrimination experiments in rats trained to discriminate a maximal locomotor activating dose of caffeine, paraxanthine, unlike theophylline, generalized poorly to caffeine suggesting the existence of additional mechanisms other than adenosine antagonism in the behavioral effects of paraxanthine. Pretreatment with the nitric oxide inhibitor N(G)-nitro-l-arginine methyl ester (l-NAME) reduced the locomotor activating effects of paraxanthine, but not caffeine. On the other hand, pretreatment with the selective cGMP-preferring phosphodiesterase PDE9 inhibitor BAY 73-6691, increased locomotor activity induced by caffeine, but not paraxanthine. Ex vivo experiments demonstrated that paraxanthine, but not caffeine, can induce cGMP accumulation in the rat striatum. Finally, in vivo microdialysis experiments showed that paraxanthine, but not caffeine, significantly increases extracellular levels of dopamine in the dorsolateral striatum, which was blocked by l-NAME. These findings indicate that inhibition of cGMP-preferring PDE is involved in the locomotor activating effects of the acute administration of paraxanthine. The present results demonstrate a unique psychostimulant profile of paraxanthine, which might contribute to the reinforcing effects of caffeine in humans.

Paraxanthine: Connecting Caffeine to Nitric Oxide Neurotransmission.

Recent results obtained in our laboratory indicate that paraxanthine, the main metabolite of caffeine in humans, produces a significantly stronger locomotor activation in rats than caffeine. Furthermore, paraxanthine also produced a very significant increase in striatal extracellular concentrations of dopamine. Searching for an additional mechanism other than adenosine antagonism responsible for these psychostimulant-like effects, it was found that paraxanthine, but not caffeine, inhibited cGMP-preferring phosphodiesterases. Furthermore, interrupting nitric oxide neurotransmision (inhibiting nitric oxide synthase) significantly decreased both the locomotor-activating and the dopamine-releasing effects of paraxanthine. These results open up some obvious questions about the role of paraxanthine in the pharmacological effects of caffeine.

Functional changes in postsynaptic adenosine A(2A) receptors during early stages of a rat model of Huntington disease.

Huntington disease (HD) is a neurodegenerative disorder involving preferential loss of striatal GABAergic medium spiny neurons. Adenosine A(2A) receptors (A(2A)Rs) are present in the striatum at both presynaptic and post-synaptic levels. Blocking pre-synaptic A(2A)Rs, localized in glutamatergic terminals that contact striatal GABAergic dynorphinergic neurons, reduces glutamate release, which could be beneficial in HD. On the other hand, blockade of post-synaptic A(2A)Rs, localized in striatal GABAergic enkephalinergic neurons, could exacerbate the motor dysfunction. To evaluate the function of pre- or post-synaptic A(2A)Rs in HD we used selective antagonists for these receptors in a transgenic rat model of HD. Locomotor activity after systemic administration of the postsynaptic A(2A)R antagonist KW-6002 was used to investigate the function of post-synaptic A(2A)Rs. The role of pre-synaptic A(2A)Rs was instead evaluated by measuring the reduction of the electromyographic response of mastication muscles during electrical stimulation of the orofacial motor cortex after the systemic administration of the presynaptic A(2A)R antagonist SCH-442416. The ability of KW-6002 to produce locomotor activation was lost at 6 and 12 month-old of age in heterozygous and homozygous transgenic rats, but not in wild-type littermates. Nevertheless, no significant changes were observed up to 12 months of age in the potency of SCH-442416 to decrease the electromyographic response after cortical electrical stimulation. These results agree with a selective impairment of the striatal GABAergic enkephalinergic neuronal function during pre-symptomatic stages in HD. Since presynaptic A(2A)R function is not impaired, this receptor could probably be used as a target for the symptomatic treatment of the disease.

Adenosine A(2A) Receptors and A(2A) Receptor Heteromers as Key Players in Striatal Function.

A very significant density of adenosine A(2A) receptors (A(2A)Rs) is present in the striatum, where they are preferentially localized postsynaptically in striatopallidal medium spiny neurons (MSNs). In this localization A(2A)Rs establish reciprocal antagonistic interactions with dopamine D(2) receptors (D(2)Rs). In one type of interaction, A(2A)R and D(2)R are forming heteromers and, by means of an allosteric interaction, A(2A)R counteracts D(2)R-mediated inhibitory modulation of the effects of NMDA receptor stimulation in the striatopallidal neuron. This interaction is probably mostly responsible for the locomotor depressant and activating effects of A(2A)R agonist and antagonists, respectively. The second type of interaction involves A(2A)R and D(2)R that do not form heteromers and takes place at the level of adenylyl cyclase (AC). Due to a strong tonic effect of endogenous dopamine on striatal D(2)R, this interaction keeps A(2A)R from signaling through AC. However, under conditions of dopamine depletion or with blockade of D(2)R, A(2A)R-mediated AC activation is unleashed with an increased gene expression and activity of the striatopallidal neuron and with a consequent motor depression. This interaction is probably the main mechanism responsible for the locomotor depression induced by D(2)R antagonists. Finally, striatal A(2A)Rs are also localized presynaptically, in cortico-striatal glutamatergic terminals that contact the striato-nigral MSN. These presynaptic A(2A)Rs heteromerize with A(1) receptors (A(1)Rs) and their activation facilitates glutamate release. These three different types of A(2A)Rs can be pharmacologically dissected by their ability to bind ligands with different affinity and can therefore provide selective targets for drug development in different basal ganglia disorders.

Pharmacological evidence for different populations of postsynaptic adenosine A2A receptors in the rat striatum.

Adenosine A(2A) receptors (A(2A)Rs) are highly concentrated in the striatum. Two pharmacological different functional populations of A(2A)Rs have been recently described based on their different affinities for the A(2A)R antagonist SCH-442416. This compound has high affinity for A(2A)Rs not forming heteromers or forming heteromers with adenosine A(1) receptors (A(1)Rs) while showing very low affinity for A(2A)Rs forming heteromers with dopamine D(2) receptors (D(2)Rs). It has been widely described that striatal A(1)R-A(2A)R heteromers are preferentially localized presynaptically in the glutamatergic terminals that contact GABAergic dynorphinergic neurons, and that A(2A)R-D(2)R heteromers are localized postsynaptically in GABAergic enkephalinergic neurons. In the present study we provide evidence suggesting that SCH-442416 also targets postsynaptic A(2A)R not forming heteromers with D(2)R, which are involved in the motor depressant effects induced by D(2)R antagonists. SCH-442416 counteracted motor depression in rats induced by the D(2)R antagonist raclopride at a dose that did not produce motor activation or that blocked motor depression induced by an A(2A)R agonist. Furthermore, we re-evaluated the recently suggested key role of cannabinoid CB(1) receptors (CB(1)Rs) in the effects of A(2A)R antagonists acting at postsynaptic A(2A)Rs. By recording locomotor activity and monitoring striatal glutamate release induced by cortical electrical stimulation in rats after administration of A(2A)R and CB(1)R antagonists, we did not find evidence for any significant role of endocannabinoids in the post- or presynaptic effects of A(2A)R antagonists. The present results further suggest the existence of at least two functionally and pharmacologically different populations of striatal postsynaptic A(2A)Rs.

Striatal pre- and postsynaptic profile of adenosine A(2A) receptor antagonists.

Striatal adenosine A(2A) receptors (A(2A)Rs) are highly expressed in medium spiny neurons (MSNs) of the indirect efferent pathway, where they heteromerize with dopamine D(2) receptors (D(2)Rs). A(2A)Rs are also localized presynaptically in cortico-striatal glutamatergic terminals contacting MSNs of the direct efferent pathway, where they heteromerize with adenosine A(1) receptors (A(1)Rs). It has been hypothesized that postsynaptic A(2A)R antagonists should be useful in Parkinson's disease, while presynaptic A(2A)R antagonists could be beneficial in dyskinetic disorders, such as Huntington's disease, obsessive-compulsive disorders and drug addiction. The aim or this work was to determine whether selective A(2A)R antagonists may be subdivided according to a preferential pre- versus postsynaptic mechanism of action. The potency at blocking the motor output and striatal glutamate release induced by cortical electrical stimulation and the potency at inducing locomotor activation were used as in vivo measures of pre- and postsynaptic activities, respectively. SCH-442416 and KW-6002 showed a significant preferential pre- and postsynaptic profile, respectively, while the other tested compounds (MSX-2, SCH-420814, ZM-241385 and SCH-58261) showed no clear preference. Radioligand-binding experiments were performed in cells expressing A(2A)R-D(2)R and A(1)R-A(2A)R heteromers to determine possible differences in the affinity of these compounds for different A(2A)R heteromers. Heteromerization played a key role in the presynaptic profile of SCH-442416, since it bound with much less affinity to A(2A)R when co-expressed with D(2)R than with A(1)R. KW-6002 showed the best relative affinity for A(2A)R co-expressed with D(2)R than co-expressed with A(1)R, which can at least partially explain the postsynaptic profile of this compound. Also, the in vitro pharmacological profile of MSX-2, SCH-420814, ZM-241385 and SCH-58261 was is in accordance with their mixed pre- and postsynaptic profile. On the basis of their preferential pre- versus postsynaptic actions, SCH-442416 and KW-6002 may be used as lead compounds to obtain more effective antidyskinetic and antiparkinsonian compounds, respectively.

Independent and additive effects of cytokine patterns and the metabolic syndrome on arterial aging in the SardiNIA Study.

OBJECTIVE: Metabolic syndrome (MetS) and its components accelerate age-associated increases in arterial stiffness and thickness. We investigated whether specific proinflammatory cytokines contribute to arterial aging, independent of age, sex, MetS, and other traditional CV risk factors. RESEARCH DESIGN AND METHODS: MetS components (ATP III criteria) and arterial properties were assessed in 6148 subjects, aged 14-102 in Sardinia, Italy. Common carotid artery (CCA) diameter, intima-media thickness (IMT), and aortic pulse wave velocity (PWV), adiponectin, leptin, high-sensitivity C reactive protein (hsCRP), monocyte chemoattractant protein 1 (MCP1), and interleukin 6 (IL6) were measured. RESULTS: While cytokine levels - except for MCP1 - were significantly higher (lower for adiponectin) in MetS than in control subjects, and the increased PWV and CCA IMT with aging were associated with MetS, this association was independent of cytokine levels (p<0.001 for both PWV and CCA IMT). Specific cytokines, however, were significantly associated with arterial stiffness (higher leptin, p<0.001, and higher hsCRP, p<0.001) or thickness (lower adiponectin, p<0.05, and higher IL6, p<0.001) - independent of age, sex, MetS and other traditional CV risk factors. The co-occurrence of both MetS and higher cytokines levels was associated with greater increases in arterial stiffness and thickness. CONCLUSION: While MetS and specific cytokine patterns associated with arterial aging, the increases in arterial stiffness and thickness are greater when both MetS and higher cytokine levels are present, suggesting a possible synergistic effect of MetS and inflammation on the arterial wall.

Adenosine-cannabinoid receptor interactions. Implications for striatal function.

Adenosine and endocannabinoids are very ubiquitous non-classical neurotransmitters that exert a modulatory role on the transmission of other more 'classical' neurotransmitters. In this review we will focus on their common role as modulators of dopamine and glutamate neurotransmission in the striatum, the main input structure of the basal ganglia. We will pay particular attention to the role of adenosine A(2A) receptors and cannabinoid CB(1) receptors. Experimental results suggest that presynaptic CB(1) receptors interacting with A(2A) receptors in cortico-striatal glutamatergic terminals that make synaptic contact with dynorphinergic medium-sized spiny neurons (MSNs) are involved in the motor-depressant and addictive effects of cannabinoids. On the other hand, postsynaptic CB(1) receptors interacting with A(2A) and D(2) receptors in the dendritic spines of enkephalinergic MSNs and postsynaptic CB(1) receptors in the dendritic spines of dynorphinergic MSN are probably involved in the cataleptogenic effects of cannabinoids. These receptor interactions most probably depend on the existence of a variety of heteromers of A(2A), CB(1) and D(2) receptors in different elements of striatal spine modules. Drugs selective for the different striatal A(2A) and CB(1) receptor heteromers could be used for the treatment of neuropsychiatric disorders and drug addiction and they could provide effective drugs with fewer side effects than currently used drugs.

Key modulatory role of presynaptic adenosine A2A receptors in cortical neurotransmission to the striatal direct pathway.

Basal ganglia processing results from a balanced activation of direct and indirect striatal efferent pathways, which are controlled by dopamine D1 and D2 receptors, respectively. Adenosine A2A receptors are considered novel antiparkinsonian targets, based on their selective postsynaptic localization in the indirect pathway, where they modulate D2 receptor function. The present study provides evidence for the existence of an additional, functionally significant, segregation of A2A receptors at the presynaptic level. Using integrated anatomical, electrophysiological, and biochemical approaches, we demonstrate that presynaptic A2A receptors are preferentially localized in cortical glutamatergic terminals that contact striatal neurons of the direct pathway, where they exert a selective modulation of corticostriatal neurotransmission. Presynaptic striatal A2A receptors could provide a new target for the treatment of neuropsychiatric disorders.

Common variants at ten loci modulate the QT interval duration in the QTSCD Study.

The QT interval, a measure of cardiac repolarization, predisposes to ventricular arrhythmias and sudden cardiac death (SCD) when prolonged or shortened. A common variant in NOS1AP is known to influence repolarization. We analyze genome-wide data from five population-based cohorts (ARIC, KORA, SardiNIA, GenNOVA and HNR) with a total of 15,842 individuals of European ancestry, to confirm the NOS1AP association and identify nine additional loci at P < 5 x 10(-8). Four loci map near the monogenic long-QT syndrome genes KCNQ1, KCNH2, SCN5A and KCNJ2. Two other loci include ATP1B1 and PLN, genes with established electrophysiological function, whereas three map to RNF207, near LITAF and within NDRG4-GINS3-SETD6-CNOT1, respectively, all of which have not previously been implicated in cardiac electrophysiology. These results, together with an accompanying paper from the QTGEN consortium, identify new candidate genes for ventricular arrhythmias and SCD.