Modulating weak interactions for molecular recognition: a dynamic combinatorial analysis for assessing the contribution of electrostatics to the stability of CH-π bonds in water

Electrostatic and charge-transfer contributions to CH-π complexes can be modulated by attaching electron-withdrawing substituents to the carbon atom. While clearly stabilizing in the gas phase, the outcome of this chemical modification in water is more difficult to predict. Herein we provide a definitive and quantitative answer to this question employing a simple strategy based on dynamic combinatorial chemistry.

Non-ventricular, Clinical, and Functional Features of the RyR2(R420Q) Mutation Causing Catecholaminergic Polymorphic Ventricular Tachycardia

INTRODUCTION AND OBJECTIVES

Catecholaminergic polymorphic ventricular tachycardia is a malignant disease, due to mutations in proteins controlling Ca(2+) homeostasis. While the phenotype is characterized by polymorphic ventricular arrhythmias under stress, supraventricular arrhythmias may occur and are not fully characterized.

METHODS

Twenty-five relatives from a Spanish family with several sudden deaths were evaluated with electrocardiogram, exercise testing, and optional epinephrine challenge. Selective RyR2 sequencing in an affected individual and cascade screening in the rest of the family was offered. The RyR2(R420Q) mutation was generated in HEK-293 cells using site-directed mutagenesis to conduct in vitro functional studies.

RESULTS

The exercise testing unmasked catecholaminergic polymorphic ventricular tachycardia in 8 relatives (sensitivity = 89%; positive predictive value = 100%; negative predictive value = 93%), all of them carrying the heterozygous RyR2(R420Q) mutation, which was also present in the proband and a young girl without exercise testing, a 91% penetrance at the end of the follow-up. Remarkably, sinus bradycardia, atrial and junctional arrhythmias, and/or giant post-effort U-waves were identified in patients. Upon permeabilization and in intact cells, the RyR2(R420Q) expressing cells showed a smaller peak of Ca(2+) release than RyR2 wild-type cells. However, at physiologic intracellular Ca(2+) concentration, equivalent to the diastolic cytosolic concentration, the RyR2(R420Q) released more Ca(2+) and oscillated faster than RyR2 wild-type cells.

CONCLUSIONS

The missense RyR2(R420Q) mutation was identified in the N-terminus of the RyR2 gene in this highly symptomatic family. Remarkably, this mutation is associated with sinus bradycardia, atrial and junctional arrhythmias, and giant U-waves. Collectively, functional heterologous expression studies suggest that the RyR2(R420Q) behaves as an aberrant channel, as a loss- or gain-of-function mutation depending on cytosolic intracellular Ca(2+) concentration.

Ca(2+) handling alterations and vascular dysfunction in diabetes

More than 65% of patients with diabetes mellitus die from cardiovascular disease or stroke. Hyperglycemia, due to either reduced insulin secretion or reduced insulin sensitivity, is the hallmark feature of diabetes mellitus. Vascular dysfunction is a distinctive phenotype found in both types of diabetes and could be responsible for the high incidence of stroke, heart attack, and organ damage in diabetic patients. In addition to well-documented endothelial dysfunction, Ca(2+) handling alterations in vascular smooth muscle cells (VSMCs) play a key role in the development and progression of vascular complications in diabetes. VSMCs provide not only structural integrity to the vessels but also control myogenic arterial tone and systemic blood pressure through global and local Ca(2+) signaling. The Ca(2+) signalosome of VSMCs is integrated by an extensive number of Ca(2+) handling proteins (i.e. channels, pumps, exchangers) and related signal transduction components, whose function is modulated by endothelial effectors. This review summarizes recent findings concerning alterations in endothelium and VSMC Ca(2+) signaling proteins that may contribute to the vascular dysfunction found in the diabetic condition.

Ca(2+) fluxes involvement in gene expression during cardiac hypertrophy

Cardiac hypertrophy arises as a response of the heart to many different pathological stimuli that challenge its work. Regardless of the initial pathologic cause, cardiac hypertrophy shares some characteristics resulting from a genetic reprogramming of several proteins. Recent studies point to Ca2+ as a key signaling element in the initiation of this genetic reprogramming. In fact, besides its important role in excitation-contraction coupling, Ca2+ regulates cardiac growth by activation of Ca2+-dependent transcription factors. This mechanism has been termed excitation-transcription (ET) coupling. Some information about cardiac ET coupling is being gathered from the analysis of cardiac hypertrophy development, where two Ca2+ dependent enzymes are key actors: the Ca2+/calmodulin kinase II (CaMKII) and the phosphatase calcineurin, both activated by Ca2+/Calmodulin. In this review we focus on some neurohormonal signaling pathways involved in cardiac hypertrophy, which could be ascribed as activators of ET coupling, for instance, adrenergic stimulation and the renin-angiotensin-aldosterone system. β-adrenergic receptor (β-AR) produces cAMP, which directly, (through cAMP response element) or indirectly (through activating Epac) induces cardiac hypertrophy. α1 AR and angiotensin receptor type 1 are Gq protein coupled receptors, which when activated, stimulate phospholipase C producing inositol 1,4,5 triphosphate (IP3) and diacylglycerol (DAG). IP3 promotes elevation of [Ca2+] in the nucleus, activating CaMKII/MEF2 (myocyte enhancer factor 2) pathway and may indirectly induce Ca2+ entry through transient receptor potential channels (TRPC). Other TRPC channels are activated by DAG. Ca2+ entry activates calcineurin/NFAT hypertrophic signaling. By promoting L-type Ca2+ channel expression, aldosterone may also have an important role in the genetic reprogramming during hypertrophy.

[Glycemic variability and oxidative stress in children, with type 1 diabetes attending a summer camp]

OBJECTIVE

To assess glycemic variability, oxidative stress and their relationship in children and adolescents with type 1 diabetes (T1DM) attending a summer camp.

PATIENTS AND METHOD

Cross-sectional study that included 54 children and adolescents with T1DM aged 7-16, attending a 7 day summer camp. Sociodemographic information, clinical data, and blood glucose values measured using an Accu-Chek Nano® glucose meter were recorded. Glucose variability markers (standard deviation [SD], low blood glucose index [LBGI], high blood glucose index [HBGI], mean amplitude of glycemic excursions [MAGE] and mean of daily differences [MODD]) were calculated. Oxidative stress was assessed by the measurement of 8-iso-prostaglandin F2 alpha (PGF2α) in a 24-hour urine sample collected at the end of the camp in 14 children.

RESULTS

The Median SD, MAGE and MODD indexes were in the high range (61, 131 and 58 mg/dl, respectively), LBGI in the moderate range (3.3), and HBGI in the low range (4.5). The mean HbA1c was 7.6% and the median urinary excretion rate of 8-iso-PGF2α was 864.39 pg/mg creatinine. The Spearman correlation coefficients between markers of glycemic variability (SD, HBGI, MAGE, MODD) were significant. Non-significant correlations were found between markers of glycemic variability and urinary 8-iso-PGF2α.

CONCLUSIONS

High glycemic variability was observed in children and adolescents attending a summer camp. However, no correlations were found between markers of glycemic variability and oxidative stress measured by urinary 8-iso-PGF2α. Further studies are needed to address the relationship between oxidative stress and glycemic variability in children with T1DM.

A dynamic combinatorial approach for the analysis of weak carbohydrate/aromatic complexes: dissecting facial selectivity in CH/π stacking interactions

A dynamical combinatorial approach for the study of weak carbohydrate/aromatic interactions is presented. This methodology has been employed to dissect the subtle structure-stability relationships that govern facial selectivity in these supramolecular complexes.

The other side of cardiac Ca(2+) signaling: transcriptional control

Ca²⁺ is probably the most versatile signal transduction element used by all cell types. In the heart, it is essential to activate cellular contraction in each heartbeat. Nevertheless Ca²⁺ is not only a key element in excitation-contraction coupling (EC coupling), but it is also a pivotal second messenger in cardiac signal transduction, being able to control processes such as excitability, metabolism, and transcriptional regulation. Regarding the latter, Ca²⁺ activates Ca²⁺-dependent transcription factors by a process called excitation-transcription coupling (ET coupling). ET coupling is an integrated process by which the common signaling pathways that regulate EC coupling activate transcription factors. Although ET coupling has been extensively studied in neurons and other cell types, less is known in cardiac muscle. Some hints have been found in studies on the development of cardiac hypertrophy, where two Ca²⁺-dependent enzymes are key actors: Ca²⁺/Calmodulin kinase II (CaMKII) and phosphatase calcineurin, both of which are activated by the complex Ca²⁺/Calmodulin. The question now is how ET coupling occurs in cardiomyocytes, where intracellular Ca²⁺ is continuously oscillating. In this focused review, we will draw attention to location of Ca²⁺ signaling: intranuclear ([Ca²⁺]_n) or cytoplasmic ([Ca²⁺]_c), and the specific ionic channels involved in the activation of cardiac ET coupling. Specifically, we will highlight the role of the 1,4,5 inositol triphosphate receptors (IP₃Rs) in the elevation of [Ca²⁺]_n levels, which are important to locally activate CaMKII, and the role of transient receptor potential channels canonical (TRPCs) in [Ca²⁺]_c, needed to activate calcineurin (Cn).

Sustained Epac activation induces calmodulin dependent positive inotropic effect in adult cardiomyocytes

Cardiac actions of Epac (exchange protein directly activated by cAMP) are not completely elucidated. Epac induces cardiomyocytes hypertrophy, Ca(2+)/calmodulin protein kinase II (CaMKII) and excitation-transcription coupling in rat cardiac myocytes. Here we aimed to elucidate the pathway cascade involved in Epac sustained actions, as during the initiation of hypertrophy development, where β-adrenergic signaling is chronically stimulated. Rats were treated with the Epac selective activator 8-pCPT during 4 weeks and Ca(2+) signaling was analyzed in isolated cardiac myocytes by confocal microscopy. We observed a positive inotropic effect manifested by increased [Ca(2+)](i) transient amplitudes. In order to further analyze these actions, we incubated adult cardiomyocytes in the presence of 8-pCPT. The effects were similar to those obtained in-vivo and are blunted by Epac1 knock down. Interestingly, the increase in [Ca(2+)] transients was abolished by protein synthesis blockade or when the downstream effectors of calmodulin (CaMKII or calcineurin) were inhibited, pointing to calmodulin (CaM) as an important downstream protein in Epac sustained actions. In fact, CaM expression was enhanced by 8-pCPT treatment in isolated cells, as found by Western blots. Moreover, the 8-pCPT-induced, PKA-independent, positive inotropic effect was favored by enhanced extracellular Ca(2+) influx via L-type Ca(2+) channels. However, 8-pCPT also induced aberrant Ca(2+) release as Ca(2+) waves and extra [Ca(2+)](i) transients, suggesting proarrhythmic effect. These results provide new insights regarding Epac cardiac actions, suggesting an important role in the initial compensation of the heart to pathological stimuli during the initiation of cardiac hypertrophy, favoring contraction but also arrhythmia risk.

Unexpected stereocontrolled access to 1α,1'β-disaccharides from methyl 1,2-ortho esters

Mannopyranose-derived methyl 1,2-orthoacetates (R = Me) and 1,2-orthobenzoates (R = Ph) undergo stereoselective formation of 1α,1'β-disaccharides, upon treatment with BF(3)·Et(2)O in CH(2)Cl(2), rather than the expected acid-catalyzed reaction leading to methyl glycosides by way of a rearrangement-glycosylation process of the liberated methanol.

Epac enhances excitation-transcription coupling in cardiac myocytes

Epac is a guanine nucleotide exchange protein that is directly activated by cAMP, but whose cardiac cellular functions remain unclear. It is important to understand cardiac Epac signaling, because it is activated in parallel to classical cAMP-dependent signaling via protein kinase A. In addition to activating contraction, Ca(2+) is a key cardiac transcription regulator (excitation-transcription coupling). It is unknown how myocyte Ca(2+) signals are decoded in cardiac myocytes to control nuclear transcription. We examine Epac actions on cytosolic ([Ca(2+)](i)) and intranuclear ([Ca(2+)](n)) Ca(2+) homeostasis, focusing on whether Epac alters [Ca(2+)](n) and activates a prohypertrophic program in cardiomyocytes. Adult rat cardiomyocytes, loaded with fluo-3 were viewed by confocal microscopy during electrical field stimulation at 1Hz. Acute Epac activation by 8-pCPT increased Ca(2+) sparks and diastolic [Ca(2+)](i), but decreased systolic [Ca(2+)](i). The effects on diastolic [Ca(2+)](i) and Ca(2+) spark frequency were dependent on phospholipase C (PLC), inositol 1,4,5 triphosphate receptor (IP(3)R) and CaMKII activation. Interestingly, Epac preferentially increased [Ca(2+)](n) during both diastole and systole, correlating with the perinuclear expression pattern of Epac. Moreover, Epac activation induced histone deacetylase 5 (HDAC5) nuclear export, with consequent activation of the prohypertrophic transcription factor MEF2. These data provide the first evidence that the cAMP-binding protein Epac modulates cardiac nuclear Ca(2+) signaling by increasing [Ca(2+)](n) through PLC, IP(3)R and CaMKII activation, and initiates a prohypertrophic program via HDAC5 nuclear export and subsequent activation of the transcription factor MEF2.

A survey of Ley's reactivity tuning in oligosaccharide synthesis

This chapter summarizes the concepts and chemistry developed by Ley's group in relation to the relevance of reactivity tuning in oligosaccharide coupling reactions. The recognition that protecting groups affect the reactivity of glycosyl donors allowed Ley's group to make imaginative use of their 1,2-diacetal protecting groups. The combination of 1,2-diacetals with the presence of different anomeric leaving groups provides up to four different levels of reactivity. The exploitation of these reactivity levels in chemoselective glycosylation processes (reactivity tuning) has allowed the development of highly simplified routes to several complex oligosaccharides in step-wise or one-pot procedures.

More than one pulmonary resections or combined lung-liver resection in 79 patients with metastatic colorectal carcinoma

BACKGROUND

The way to select patients who will benefit from surgical resection of pulmonary metastases of colorectal carcinoma (CRC) remains unclear.

METHODS

We analyze overall survival and potential prognostic factors in 101 pulmonary resections of CRC metastases in 79 patients, focusing on cases with repeated pulmonary resection or with hepatic metastasectomy.

RESULTS

Number of pathological pulmonary metastases was higher than that of preoperatively suspected pulmonary nodules in 18% of the resections. Morbidity rate was 16.5%. There was no mortality. Five-year survival rates from the resection of the CRC and from the first pulmonary metastasectomy were 74.6% and 53.3%, respectively. Prognosis did not decrease in patients with history of hepatic metastasectomy or in those in which repeated pulmonary resection was performed. Age ≥70, preoperative carcinoembrionary antigen (CEA) ≥5 ng/dl and mediastinal lymph node involvement entailed worse prognosis. Pathological lymph node involvement and age were shown as independent prognostic factors in the multivariate analysis.

CONCLUSIONS

Resection of pulmonary metastases of CRC is a safe procedure, with 5-year survival rates over 50%. History of resected hepatic metastases or needs for more than one pulmonary resection do not seem to decrease survival rates. Only lymph node involvement and age seem to be clearly associated to worse prognosis.

Exercise training and cytokines in breast cancer survivors

The purpose of this randomized controlled trial was to determine the effects of an 8-week (aerobic+strength) exercise training program (3 sessions/week) on the circulating cytokine levels of breast cancer survivors. We randomly allocated 16 female survivors of breast cancer (mean±SD age: 50±5 years) to an intervention or usual care (control) group (N=8 in each group). The intervention group followed an 8-week exercise program consisting of 3 sessions/week (session duration: 90 min). We measured the levels of the following cytokines before and after the intervention: beta-NGF, CTACK, eotaxin, FGF basic, G-CSF, gmCSFα, HGF, ICAM1, IFNα2, IFNγ, IL1α, IL1ß, IL1ra, IL2, IL2ra, IL3, IL4, IL6, IL7, IL8, IL9, IL10, IL12, IL13, IL15, IL16, IL17, IL18, IP10, LIF, MCS-F, MIP1α, MIP1β, MIF, MCP1, MCP3, MIG, PDGF bb, SCF, SCGFβ, SDF1α, TRAIL, TNFα, TNFβ, VCAM1, and VEGF. We only observed a significant interaction (group*time) effect for CTACK ( P=0.016), with mean values remaining stable in the intervention group but increasing over time in controls. The intervention program did not induce a significant decrease in the main breast cancer-related cytokines such as IL6 and IL8. A combined (aerobic+strength) 8-week exercise training intervention did not induce major changes in the basal cytokine levels of breast cancer survivors.