Postural hemodynamic parameters in older persons have a seasonal dependency : A pilot study

Aims

It is known that blood pressure regulation differs seasonally. It is unknown, however, how the cardiovascular system in patients with a stroke reacts to postural changes in different seasons. The aim was therefore to investigate how different temperatures in cold and warm seasons influence the reactions of haemodynamic mechanisms as well as heart rate variability during a sit-to-stand test in patients with stroke and a control group.

Methods

Hemodynamic responses were assessed in both groups during a sit-to-stand test (5 min sitting followed by 5 min standing) beat to beat within two different seasons. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean blood pressure (MBP), heart rate (HR), stroke index (SI), cardiac index (CI) and heart rate variability (HRV) were continuously monitored.

Results

During the sitting baseline period delta values of DBP (+15.1 [Standard error (SE) 3.75] mmHg, p < 0.05) and MBP (+14.35 [SE 4.18] mmHg, p < 0.05) were significantly higher in colder months compared to warmer months whereas SI (−3.86 [SE 1.43] ml/beat/m², p < 0.05) and CI (−0.4 [SE 0.11] l/min/m², p < 0.05) were lower in colder months compared to warmer months in non-stroke participants. In patients with stroke during sitting, baseline period delta values of DBP (+19.92 [SE 8.03] mmHg, p < 0.05) and MBP (+19.29 [SE 8.6] mmHg, p < 0.05) were significantly higher in colder months compared to warmer months but SI (−5.43 [SE 1.96] ml/beat/m², p < 0.05) was significantly lower in colder months compared to warmer months. After standing, there was a significant decrease in SBP in warmer months (−16.84 [SE 4.38] mmHg, p < 0.05) and a decrease in DBP in warmer months (−7.8 [SE 2.3] mmHg, p < 0.05) and colder months (−6.73 [SE 1.5] mmHg, p < 0.05) in non-stroke participants and a decrease in MBP in warmer months (−12.5 [SE 2.8] mmHg, p < 0.05) and colder months (−8.93 [SE 1.8] mmHg, p < 0.05) in non-stroke participants and in warmer months (−14.54 [SE 4.1] mmHg, p < 0.05) in patients with stroke.

Conclusion

Elderly with and without stroke respond to orthostatic stress with a greater drop in blood pressure in the warmer seasons.

Cannabinoids and Cardiovascular System

Cannabinoids influence cardiovascular variables in health and disease via multiple mechanisms. The chapter covers the impact of cannabinoids on cardiovascular function in physiology and pathology and presents a critical analysis of the proposed signalling pathways governing regulation of cardiovascular function by endogenously produced and exogenous cannabinoids. We know that endocannabinoid system is overactivated under pathological conditions and plays both a protective compensatory role, such as in some forms of hypertension, atherosclerosis and other inflammatory conditions, and a pathophysiological role, such as in disease states associated with excessive hypotension. This chapter focuses on the mechanisms affecting hemodynamics and vasomotor effects of cannabinoids in health and disease states, highlighting mismatches between some studies. The chapter will first review the effects of marijuana smoking on cardiovascular system and then describe the impact of exogenous cannabinoids on cardiovascular parameters in humans and experimental animals. This will be followed by analysis of the impact of cannabinoids on reactivity of isolated vessels. The article critically reviews current knowledge on cannabinoid induction of vascular relaxation by cannabinoid receptor-dependent and -independent mechanisms and dysregulation of vascular endocannabinoid signaling in disease states.

The quest for endothelial atypical cannabinoid receptor: BKCa channels act as cellular sensors for cannabinoids in in vitro and in situ endothelial cells

Endothelium-dependent component of cannabinoid-induced vasodilation has been postulated to require G-protein-coupled non-CB1/CB2 endothelial cannabinoid (eCB) receptor. GPR18 was proposed as a candidate for eCBR. To address the hypothesis that the effects attributed to eCBR are mediated by G-protein-coupled receptor (GPCR)-independent targets, we studied the electrical responses in endothelial cells, focusing on BKCa channels. In patches excised from endothelial-derived EA.hy926 cells, N-arachidonoyl glycine (NAGly) and abnormal cannabidiol (abn-cbd), prototypical agonists for eCB receptor, stimulate single BKCa activity in a concentration- and Ca2+-dependent manner. The postulated eCB receptor inhibitors rimonabant and AM251 were found to inhibit basal and stimulated by NAGly- and abn-cbd BKCa activity in cell-free patches. In isolated mice aortas, abn-cbd and NAGly produced endothelial cell hyperpolarization that was sensitive to paxilline, a selective BKCa inhibitor, but not to GPR18 antibody, and mimicked by NS1619, a direct BKCa opener. In excised patches from mice aortic endothelium, single channel activity with characteristics similar to BKCa was established by the addition of abn-cbd and NAGly. We conclude that the two cannabinoids abn-cbd and NAGly initiate a GPR18-independent activation of BKCa channels in mice aortic endothelial cells that might contribute to vasodilation to cannabinoids.

Ca2+-dependent potassium channels and cannabinoid signaling in the endothelium of apolipoprotein E knockout mice before plaque formation

Endothelial Ca2+-dependent K+ channels (KCa) regulate endothelial function. We also know that stimulation of type 2 cannabinoid (CB2) receptors ameliorates atherosclerosis. However, whether atherosclerosis is accompanied by altered endothelial KCa- and CB2 receptor-dependent signaling is unknown. By utilizing an in situ patch-clamp approach, we directly evaluated the KCa channel function and the CB2 receptor-dependent electrical responses in the endothelium of aortic strips from young ApoE-/- and C57Bl/6 mice. In the ApoE-/- group, the resting membrane potential (-30.1±1.1mV) was less negative (p<0.05) compared to WT (-38.9±1.4mV) and voltage ramps generated an overall KCa current of reduced amplitude. The peak hyperpolarization to 2μM Ach was not different between the groups. However, the sustained component was significantly reduced in ApoE-/- strips. In contrast, the peak hyperpolarization to 0.2μM Ach was increased in the ApoE-/- group, and SKA-31, a direct IKCa/SKCa channel opener, produced a hyperpolarization and whole-cell current of greater amplitude. The BKCa opener NS1619 produced hyperpolarization that was enhanced in ApoE-/- group. N-arachidonoyl glycine, a BKCa opener, produced a hyperpolarization of enhanced amplitude in ApoE-/- arteries. Selective CB2 receptor agonist AM1241 (5μM) had no effect on endothelial membrane potential in WT group; however, in ApoE-/- group, it elicited hyperpolarization that was inhibited by a selective CB2 receptor antagonist AM630. Conclusively, our data point to functional down-regulation of basal IKCa activity in unstimulated endothelium of ApoE-/- mice. Direct and indirect IKCa stimulation resulted in increased recruitment of the channels. In addition, our data point to up-regulation of endothelial BKCa channels and CB2 receptors in ApoE-/- arteries.

Big conductance calcium-activated potassium channel openers control spasticity without sedation

Background and Purpose

Our initial aim was to generate cannabinoid agents that control spasticity, occurring as a consequence of multiple sclerosis (MS), whilst avoiding the sedative side effects associated with cannabis. VSN16R was synthesized as an anandamide (endocannabinoid) analogue in an anti‐metabolite approach to identify drugs that target spasticity.

Experimental Approach

Following the initial chemistry, a variety of biochemical, pharmacological and electrophysiological approaches, using isolated cells, tissue‐based assays and in vivo animal models, were used to demonstrate the activity, efficacy, pharmacokinetics and mechanism of action of VSN16R. Toxicological and safety studies were performed in animals and humans.

Key Results

VSN16R had nanomolar activity in tissue‐based, functional assays and dose‐dependently inhibited spasticity in a mouse experimental encephalomyelitis model of MS. This effect occurred with over 1000‐fold therapeutic window, without affecting normal muscle tone. Efficacy was achieved at plasma levels that are feasible and safe in humans. VSN16R did not bind to known CB₁/CB₂/GPPR55 cannabinoid‐related receptors in receptor‐based assays but acted on a vascular cannabinoid target. This was identified as the major neuronal form of the big conductance, calcium‐activated potassium (BK_Ca) channel. Drug‐induced opening of neuronal BK_Ca channels induced membrane hyperpolarization, limiting excessive neural‐excitability and controlling spasticity.

Conclusions and Implications

We identified the neuronal form of the BK_Ca channel as the target for VSN16R and demonstrated that its activation alleviates neuronal excitability and spasticity in an experimental model of MS, revealing a novel mechanism to control spasticity. VSN16R is a potential, safe and selective ligand for controlling neural hyper‐excitability in spasticity.

GPR55 agonist lysophosphatidylinositol and lysophosphatidylcholine inhibit endothelial cell hyperpolarization via GPR-independent suppression of Na+-Ca2+ exchanger and endoplasmic reticulum Ca2+ refilling

Lysophosphatidylinositol (LPI) and lysophosphatidylcholine (LPC) are lipid signaling molecules that induce endothelium-dependent vasodilation. In addition, LPC suppresses acetylcholine (Ach)-induced responses. We aimed to determine the influence of LPC and LPI on hyperpolarizing responses in vitro and in situ endothelial cells (EC) and identify the underlying mechanisms. Using patch-clamp method, we show that LPI and LPC inhibit EC hyperpolarization to histamine and suppress Na⁺/Ca²⁺ exchanged (NCX) currents in a concentration-dependent manner. The inhibition is non-mode-specific and unaffected by intracellular GDPβS infusion and tempol, a superoxide dismutase mimetic. In excised mouse aorta, LPI strongly inhibits the sustained and the peak endothelial hyperpolarization induced by Ach, but not by SKA-31, an opener of Ca²⁺-dependent K⁺ channels of intermediate and small conductance. The hyperpolarizing responses to consecutive histamine applications are strongly reduced by NCX inhibition. In a Ca²⁺-re-addition protocol, bepridil, a NCX inhibitor, and KB-R7943, a blocker of reversed NCX, inhibit the hyperpolarizing responses to Ca²⁺-re-addition following Ca²⁺ stores depletion. These finding indicate that LPC and LPI inhibit endothelial hyperpolarization to Ach and histamine independently of G-protein coupled receptors and superoxide anions. Reversed NCX is critical for ER Ca²⁺ refilling in EC. The inhibition of NCX by LPI and LPC underlies diminished endothelium-dependent responses and endothelial dysfunction accompanied by increased levels of these lipids in the blood.

PRMT1-mediated methylation of MICU1 determines the UCP2/3 dependency of mitochondrial Ca(2+) uptake in immortalized cells

Recent studies revealed that mitochondrial Ca²⁺ channels, which control energy flow, cell signalling and death, are macromolecular complexes that basically consist of the pore-forming mitochondrial Ca²⁺ uniporter (MCU) protein, the essential MCU regulator (EMRE), and the mitochondrial Ca²⁺ uptake 1 (MICU1). MICU1 is a regulatory subunit that shields mitochondria from Ca²⁺ overload. Before the identification of these core elements, the novel uncoupling proteins 2 and 3 (UCP2/3) have been shown to be fundamental for mitochondrial Ca²⁺ uptake. Here we clarify the molecular mechanism that determines the UCP2/3 dependency of mitochondrial Ca²⁺ uptake. Our data demonstrate that mitochondrial Ca²⁺ uptake is controlled by protein arginine methyl transferase 1 (PRMT1) that asymmetrically methylates MICU1, resulting in decreased Ca²⁺ sensitivity. UCP2/3 normalize Ca²⁺ sensitivity of methylated MICU1 and, thus, re-establish mitochondrial Ca²⁺ uptake activity. These data provide novel insights in the complex regulation of the mitochondrial Ca²⁺ uniporter by PRMT1 and UCP2/3.

MICU1 is a regulatory subunit of mitochondrial Ca²⁺ channels that shields mitochondria from Ca²⁺ overload. Here the authors show that MICU1 methylation by PRMT1 reduces Ca²⁺ sensitivity, which is normalized by UCP2/3, re-establishing mitochondrial Ca²⁺ uptake activity.

Treatment with the GPR55 antagonist CID16020046 increases neutrophil activation in mouse atherogenesis

Endocannabinoids modulate atherogenesis by triggering different receptors. Recently, orphan G protein-coupled receptors (GPRs) were suggested to be activated by endocannabinoids, possibly regulating vasorelaxation. Here, we investigated whether GPR55 antagonism with CID16020046 would impact on atherosclerotic size and inflammation in two mouse models of early and more advanced atherogenesis. Eleven-week old ApoE^-/- mice were fed either a normal diet ([ND] for 16 weeks) or a high-cholesterol diet ([HD] for 11 weeks), resulting in different degrees of hypercholesterolaemia and size of atherosclerosis. CID16020046 (0.5 mg/kg) or vehicle were intraperitoneally administrated five times per week in the last three weeks before euthanasia. Treatment with CID1602004 was well-tolerated, but failed to affect atherosclerotic plaque and necrotic core size, fibrous cap thickness, macrophage and smooth muscle cell content as well as Th cell polarisation. In ND mice, treatment with CID1602004 was associated with increased chemokine production, neutrophil and MMP-9 intraplaque content as well as reduced collagen as compared to vehicle-treated animals. In HD mice, CID1602004 increased intraplaque MMP-9 and abrogated collagen content without affecting neutrophils. In vitro, serum from CID1602004-treated ND mice increased mouse neutrophil chemotaxis towards CXCL2 as compared to serum from vehicle-treated animals. CID1602004 dose-dependently induced neutrophil degranulation that was reverted by co-incubation with the GPR55 agonist Abn-CBD. In supernatants from degranulation experiments, increased levels of the endocannabinoid and putative GPR55 ligand anandamide (AEA) were found, suggesting its possible autocrine control of neutrophil activity. These results indicate that GPR55 is critical for the negative control of neutrophil activation in different phases of atherogenesis.

Assessment of mitochondrial Ca²⁺ uptake

Mitochondrial Ca(2+) uptake regulates mitochondrial function and contributes to cell signaling. Accordingly, quantifying mitochondrial Ca(2+) signals and elaborating the mechanisms that accomplish mitochondrial Ca(2+) uptake are essential to gain our understanding of cell biology. Here, we describe the benefits and drawbacks of various established old and new techniques to assess dynamic changes of mitochondrial Ca(2+) concentration ([Ca(2+)]mito) in a wide range of applications.

Endothelial atypical cannabinoid receptor: do we have enough evidence?

Cannabinoids and their synthetic analogues affect a broad range of physiological functions, including cardiovascular variables. Although direct evidence is still missing, the relaxation of a vast range of vascular beds induced by cannabinoids is believed to involve a still unidentified non-CB1 , non-CB2 Gi/o protein-coupled receptor located on endothelial cells, the so called endothelial cannabinoid receptor (eCB receptor). Evidence for the presence of an eCB receptor comes mainly from vascular relaxation studies, which commonly employ pertussis toxin as an indicator for GPCR-mediated signalling. In addition, a pharmacological approach is widely used to attribute the relaxation to eCB receptors. Recent findings have indicated a number of GPCR-independent targets for both agonists and antagonists of the presumed eCB receptor, warranting further investigations and cautious interpretation of the vascular relaxation studies. This review will provide a brief historical overview on the proposed novel eCB receptor, drawing attention to the discrepancies between the studies on the pharmacological profile of the eCB receptor and highlighting the Gi/o protein-independent actions of the eCB receptor inhibitors widely used as selective compounds. As the eCB receptor represents an attractive pharmacological target for a number of cardiovascular abnormalities, defining its molecular identity and the extent of its regulation of vascular function will have important implications for drug discovery. This review highlights the need to re-evaluate this subject in a thoughtful and rigorous fashion. More studies are needed to differentiate Gi/o protein-dependent endothelial cannabinoid signalling from that involving the classical CB1 and CB2 receptors as well as its relevance for pathophysiological conditions.

N-Arachidonoyl glycine suppresses Na⁺/Ca²⁺ exchanger-mediated Ca²⁺ entry into endothelial cells and activates BK(Ca) channels independently of GPCRs

Background and Purpose

N-arachidonoyl glycine (NAGly) is a lipoamino acid with vasorelaxant properties. We aimed to explore the mechanisms of NAGly's action on unstimulated and agonist-stimulated endothelial cells.

Experimental Approach

The effects of NAGly on endothelial electrical signalling were studied in combination with vascular reactivity.

Key Results

In EA.hy926 cells, the sustained hyperpolarization to histamine was inhibited by the non-selective Na⁺/Ca²⁺ exchanger (NCX) inhibitor bepridil and by an inhibitor of reversed mode NCX, KB-R7943. In cells dialysed with Cs⁺-based Na⁺-containing solution, the outwardly rectifying current with typical characteristics of NCX was augmented following histamine exposure, further increased upon external Na⁺ withdrawal and inhibited by bepridil. NAGly (0.3–30 μM) suppressed NCX currents in a URB597- and guanosine 5′-O-(2-thiodiphosphate) (GDPβS)-insensitive manner, [Ca²⁺]_i elevation evoked by Na⁺ removal and the hyperpolarization to histamine. In rat aorta, NAGly opposed the endothelial hyperpolarization and relaxation response to ACh. In unstimulated EA.hy926 cells, NAGly potentiated the whole-cell current attributable to large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels in a GDPβS-insensitive, paxilline-sensitive manner and produced a sustained hyperpolarization. In cell-free inside-out patches, NAGly stimulated single BK_Ca channel activity.

Conclusion and Implications

Our data showed that NCX is a Ca²⁺ entry pathway in endothelial cells and that NAGly is a potent G-protein-independent modulator of endothelial electrical signalling and has a dual effect on endothelial electrical responses. In agonist pre-stimulated cells, NAGly opposes hyperpolarization and relaxation via inhibition of NCX-mediated Ca²⁺ entry, while in unstimulated cells, it promotes hyperpolarization via receptor-independent activation of BK_Ca channels.

Effect of orthostasis on endothelial function: a gender comparative study

As the vascular endothelium has multiple functions, including regulation of vascular tone, it may play a role in the pathophysiology of orthostatic intolerance. We investigated the effect of orthostasis on endothelial function using EndoPAT®, a non-invasive and user-independent method, and across gender. As sex steroid hormones are known to affect endothelial function, this study examined the potential effect of these hormones on the endothelial response to orthostasis by including females at different phases of the menstrual cycle (follicular and luteal—where the hormone balance differs), and females taking an oral contraceptive. A total of 31 subjects took part in this study (11 males, 11 females having normal menstrual cycles and 9 females taking oral contraceptive). Each subject made two visits for testing; in the case of females having normal menstrual cycles the first session was conducted either 1–7 (follicular) or 14–21 days (luteal) after the start of menstruation, and the second session two weeks later, i.e., during the other phase, respectively. Endothelial function was assessed at baseline and following a 20-min orthostatic challenge (active standing). The EndoPAT® index increased from 1.71 ± 0.09 (mean ± SEM) at baseline to 2.07 ± 0.09 following orthostasis in females (p<0.001). In males, the index increased from 1.60 ± 0.08 to 1.94 ± 0.13 following orthostasis (p<0.001). There were no significant differences, however, in the endothelial response to orthostasis between females and males, menstrual cycle phases and the usage of oral contraceptive. Our results suggest an increased vasodilatatory endothelial response following orthostasis in both females and males. The effect of gender and sex hormones on the endothelial response to orthostasis appears limited. Further studies are needed to determine the potential role of this post orthostasis endothelial response in the pathophysiology of orthostatic intolerance.

Characterization of distinct single-channel properties of Ca²⁺ inward currents in mitochondria

Previous studies have demonstrated several molecularly distinct players involved in mitochondrial Ca²⁺ uptake. In the present study, electrophysiological recordings on mitoplasts that were isolated from HeLa cells were performed in order to biophysically and pharmacologically characterize Ca²⁺ currents across the inner mitochondrial membrane. In mitoplast-attached configuration with 105 mM Ca²⁺ as a charge carrier, three distinct channel conductances of 11, 23, and 80 pS were observed. All types of mitochondrial currents were voltage-dependent and essentially depended on the presence of Ca²⁺ in the pipette. The 23 pS channel exhibited burst kinetics. Though all channels were sensitive to ruthenium red, their sensitivity was different. The 11 and 23 pS channels exhibited a lower sensitivity to ruthenium red than the 80 pS channel. The activities of all channels persisted in the presence of cylosporin A, CGP 37187, various K⁺-channel inhibitors, and Cl⁻ channel blockers disodium 4,4′-diisothiocyanatostilbene-2,2′-disulfonate and niflumic acid. Collectively, our data identified multiple conductances of Ca²⁺ currents in mitoplasts isolated from HeLa cells, thus challenging the dogma of only one unique mitochondrial Ca²⁺ uniporter.

[The two-staged intervention for complicated colonic cancer]

The methods of colonic resection and a two-barrel colostomy closure, after performance of modified Mikulicz operation for complicated colonic cancer with formation of a two-staged extraperitoneal invagination duplicature anastomosis, were proposed. Postoperative complicationshave had occurred in 10 (10.9%) patients, including the anastomotic sutures insufficiency--in 2 (2.2%).

The endocannabinoid N-arachidonoyl glycine (NAGly) inhibits store-operated Ca2+ entry by preventing STIM1-Orai1 interaction

The endocannabiniod anandamide (AEA) and its derivate N-arachidonoyl glycine (NAGly) have a broad spectrum of physiological effects, which are induced by both binding to receptors and receptor-independent modulations of ion channels and transporters. The impact of AEA and NAGly on store-operated Ca(2+) entry (SOCE), a ubiquitous Ca(2+) entry pathway regulating many cellular functions, is unknown. Here we show that NAGly, but not AEA reversibly hinders SOCE in a time- and concentration-dependent manner. The inhibitory effect of NAGly on SOCE was found in the human endothelial cell line EA.hy926, the rat pancreatic β-cell line INS-1 832/13, and the rat basophilic leukemia cell line RBL-2H3. NAGly diminished SOCE independently from the mode of Ca(2+) depletion of the endoplasmic reticulum, whereas it had no effect on Ca(2+) entry through L-type voltage-gated Ca(2+) channels. Enhanced Ca(2+) entry was effectively hampered by NAGly in cells overexpressing the key molecular constituents of SOCE, stromal interacting molecule 1 (STIM1) and the pore-forming subunit of SOCE channels, Orai1. Fluorescence microscopy revealed that NAGly did not affect STIM1 oligomerization, STIM1 clustering, or the colocalization of STIM1 with Orai1, which were induced by Ca(2+) depletion of the endoplasmic reticulum. In contrast, independently from its slow depolarizing effect on mitochondria, NAGly instantly and strongly diminished the interaction of STIM1 with Orai1, indicating that NAGly inhibits SOCE primarily by uncoupling STIM1 from Orai1. In summary, our findings revealed the STIM1-Orai1-mediated SOCE machinery as a molecular target of NAGly, which might have many implications in cell physiology.

Mitochondrial Ca2+ uptake 1 (MICU1) and mitochondrial ca2+ uniporter (MCU) contribute to metabolism-secretion coupling in clonal pancreatic β-cells

In pancreatic β-cells, uptake of Ca²⁺ into mitochondria facilitates metabolism-secretion coupling by activation of various matrix enzymes, thus facilitating ATP generation by oxidative phosphorylation and, in turn, augmenting insulin release. We employed an siRNA-based approach to evaluate the individual contribution of four proteins that were recently described to be engaged in mitochondrial Ca²⁺ sequestration in clonal INS-1 832/13 pancreatic β-cells: the mitochondrial Ca²⁺ uptake 1 (MICU1), mitochondrial Ca²⁺ uniporter (MCU), uncoupling protein 2 (UCP2), and leucine zipper EF-hand-containing transmembrane protein 1 (LETM1). Using a FRET-based genetically encoded Ca²⁺ sensor targeted to mitochondria, we show that a transient knockdown of MICU1 or MCU diminished mitochondrial Ca²⁺ uptake upon both intracellular Ca²⁺ release and Ca²⁺ entry via L-type channels. In contrast, knockdown of UCP2 and LETM1 exclusively reduced mitochondrial Ca²⁺ uptake in response to either intracellular Ca²⁺ release or Ca²⁺ entry, respectively. Therefore, we further investigated the role of MICU1 and MCU in metabolism-secretion coupling. Diminution of MICU1 or MCU reduced mitochondrial Ca²⁺ uptake in response to d-glucose, whereas d-glucose-triggered cytosolic Ca²⁺ oscillations remained unaffected. Moreover, d-glucose-evoked increases in cytosolic ATP and d-glucose-stimulated insulin secretion were diminished in MICU1- or MCU-silenced cells. Our data highlight the crucial role of MICU1 and MCU in mitochondrial Ca²⁺ uptake in pancreatic β-cells and their involvement in the positive feedback required for sustained insulin secretion.

The vascular barrier-protecting hawthorn extract WS® 1442 raises endothelial calcium levels by inhibition of SERCA and activation of the IP3 pathway

WS® 1442 has been proven as an effective and safe therapeutical to treat mild forms of congestive heart failure. Beyond this action, we have recently shown that WS® 1442 protects against thrombin-induced vascular barrier dysfunction and the subsequent edema formation by affecting endothelial calcium signaling. The aim of the study was to analyze the influence of WS® 1442 on intracellular calcium concentrations [Ca(2+)](i) in the human endothelium and to investigate the underlying mechanisms. Using ratiometric calcium measurements and a FRET sensor, we found that WS® 1442 concentration-dependently increased basal [Ca(2+)](i) by depletion of the endoplasmic reticulum (ER) and inhibited a subsequent histamine-triggered rise of [Ca(2+)](i). Interestingly, the augmented [Ca(2+)](i) did neither trigger an activation of the contractile machinery nor led to a barrier breakdown (macromolecular permeability). It also did not impair endothelial cell viability. As assessed by patch clamp recordings, WS® 1442 did only slightly affect endothelial Na(+)/K(+)-ATPase, but increased [Ca(2+)](i) by inhibiting the sarcoplasmic/endoplasmic reticulum Ca(2+) ATPase (SERCA) and by activating the inositol 1,4,5-trisphosphate (IP(3)) pathway. Most importantly, WS® 1442 did not induce store-operated calcium entry (SOCE), but even irreversibly prevented histamine-induced SOCE. Taken together, WS® 1442 prevented the deleterious hyperpermeability-associated rise of [Ca(2+)](i) by a preceding, non-toxic release of Ca(2+) from the ER. WS® 1442 interfered with SERCA and the IP(3) pathway without inducing SOCE. The elucidation of this intriguing mechanism helps to understand the complex pharmacology of the cardiovascular drug WS® 1442.

Selective glycolysis blockade in guinea pig pulmonary artery and aorta reverses contractile and electrical responses to acute hypoxia

The goal of this study was to clarify the mechanisms of hypoxic pulmonary vasoconstriction (HPV) reversal following selective glycolysis blockade and to assess possible contribution of endothelial electrogenesis to this phenomenon as a trigger mechanism. We compared smooth muscle (SM) contractility and endothelial cell (EC) membrane potential (MP) during acute hypoxia before and after glycolysis blockade. MPs were recorded from the endothelium of guinea pig pulmonary artery (GPPA) and thoracic aorta (GPTA) using the patch-clamp technique. Acute hypoxia caused hyperpolarization in GPTA EC, while EC from GPPA were depolarized. Also, acute hypoxia elicited constriction in isolated GPPA and dilatation in GPTA. Selective glycolysis inhibition always reversed both electrical and contractile responses in GPPA to hypoxia, but in GPTA this only occurred in 30% of experiments. It is likely that an unknown glycolysis-driven mechanism in EC mediates vascular tone regulation under hypoxia and underlies the paradoxical difference in the response of pulmonary and systemic arterial SM to hypoxia. Our data suggest that HPV development in GPPA might, at least partially, be driven by EC depolarization spreading to the underlying SM cells.

Studying mitochondrial Ca(2+) uptake - a revisit

Mitochondrial Ca(2+) sequestration is a well-known process that is involved in various physiological and pathological mechanisms. Using isolated suspended mitochondria one unique mitochondrial Ca(2+) uniporter was considered to account ubiquitously for the transfer of Ca(2+) into these organelles. However, by applying alternative techniques for measuring mitochondrial Ca(2+) uptake evidences for molecularly distinct mitochondrial Ca(2+) carriers accumulated recently. Herein we compared different methodical approaches of studying mitochondrial Ca(2+) uptake. Patch clamp technique on mitoplasts from endothelial and HeLa cells revealed the existence of three and two mitoplast Ca(2+) currents (I(CaMito)), respectively. According to their conductance, these channels were named small (s-), intermediate (i-), large (l-) and extra-large (xl-) mitoplast Ca(2+) currents (MCC). i-MCC was found in mitoplasts of both cell types whereas s-MCC and l-MCC or xl-MCC were/was exclusively found in mitoplasts from endothelial cells or HeLa cells. The comparison of mitochondrial Ca(2+) signals, measured either indirectly by sensing extra-mitochondrial Ca(2+) or directly by recording changes of the matrix Ca(2+), showed different Ca(2+) sensitivities of the distinct mitochondrial Ca(2+) uptake routes. Subpopulations of mitochondria with different Ca(2+) uptake capacities in intact endothelial cells could be identified using Rhod-2/AM. In contrast, cells expressing mitochondrial targeted pericam or cameleon (4mtD3cpv) showed homogeneous mitochondrial Ca(2+) signals in response to cell stimulation. The comparison of different experimental approaches and protocols using isolated organelles, permeabilized and intact cells, pointed to cell-type specific and versatile pathways for mitochondrial Ca(2+) uptake. Moreover, this work highlights the necessity of the utilization of multiple technical approaches to study the complexity of mitochondrial Ca(2+) homeostasis.

Leucine zipper EF hand-containing transmembrane protein 1 (Letm1) and uncoupling proteins 2 and 3 (UCP2/3) contribute to two distinct mitochondrial Ca2+ uptake pathways

Cytosolic Ca²⁺ signals are transferred into mitochondria over a huge concentration range. In our recent work we described uncoupling proteins 2 and 3 (UCP2/3) to be fundamental for mitochondrial uptake of high Ca²⁺ domains in mitochondria-ER junctions. On the other hand, the leucine zipper EF hand-containing transmembrane protein 1 (Letm1) was identified as a mitochondrial Ca²⁺/H⁺ antiporter that achieved mitochondrial Ca²⁺ sequestration at small Ca²⁺ increases. Thus, the contributions of Letm1 and UCP2/3 to mitochondrial Ca²⁺ uptake were compared in endothelial cells. Knock-down of Letm1 did not affect the UCP2/3-dependent mitochondrial uptake of intracellularly released Ca²⁺ but strongly diminished the transfer of entering Ca²⁺ into mitochondria, subsequently, resulting in a reduction of store-operated Ca²⁺ entry (SOCE). Knock-down of Letm1 and UCP2/3 did neither impact on cellular ATP levels nor the membrane potential. The enhanced mitochondrial Ca²⁺ signals in cells overexpressing UCP2/3 rescued SOCE upon Letm1 knock-down. In digitonin-permeabilized cells, Letm1 exclusively contributed to mitochondrial Ca²⁺ uptake at low Ca²⁺ conditions. Neither the Letm1- nor the UCP2/3-dependent mitochondrial Ca²⁺ uptake was affected by a knock-down of mRNA levels of mitochondrial calcium uptake 1 (MICU1), a protein that triggers mitochondrial Ca²⁺ uptake in HeLa cells. Our data indicate that Letm1 and UCP2/3 independently contribute to two distinct, mitochondrial Ca²⁺ uptake pathways in intact endothelial cells.

[Preparation of magnetic latexes and their use for the immunodetection of microbial antigens]

The possibility of detecting antigens of plague, tularemia, and brucellosis microbes with magnetic latex (ML)-based test systems has been demonstrated. MLs were prepared from latexes (polyacroleine microspheres, 1.2-1.8 +/- 0.1 microm) by exposing the particles to a 25-35%-solution of ferrous sulfate for 0.5 h and then to a 15-25%-aqueous solution of ammonia for 0.5 h in a 100 degrees C water bath and dehydrating after each operation. The possibility of preparing magnetic latex immunosorbents (MLIS) by ligand immobilization on ML and using them in magnetic latex ELISA (ML-ELISA) for the detection of microbial antigens was demonstrated. The detection limit in ML-ELISA equaled 10(2)-10(3) microbial cells in 1 ml (cells/ml). Relative experimental error was not higher than 8%.

[The ultrastructural organization of Brucella L forms and revertant cultures]

The submicroscopic organization of Brucella cells in the process of L-transformation and reversion has been studied. As revealed in this study, at its initial stages L-transformation is accompanied by the loss of cell-wall peptidoglycan and by considerable polymorphism of Brucella cells. Further stages are characterized by the presence of a great number of closed annular membrane structures both in the cytoplasm and outside the cells. At late stages of L-transformation the destruction of the cytoplasm and the cells has been found to occur. In revertant cultures the restoration of the cell wall has been noted.

[Extraction of deuterated compounds from Chlorella sp. K. grown in D20]

A comparison of the three known methods made it possible to work out methods of complex extraction of deutero amino acids, deutero sugars and deutero vitamins from algae Chlorella sp. K., grown autotrophically in heavy water. An analysis of the isotopic composition of deutero amino acids by PMR indicates that treatment with HCl introduces 1H into side chains of some amino acids by chemical exchange (C2, 6H of tyrosine, C2H of histidine, rho-H of phenylalanin, beta-CH2-aspartate and gamma-CH2-glutamate. These exchanges made the amino acids convenient to be used as the substrates for the growth of heterotrophic selective deuterated organisms as a source of selective deuterated proteins.