Leptin is a hormone primarily secreted by adipocytes and participating in the regulation of food intake and energy expenditure. Its blood levels usually correlate with adiposity. The secretion of this hormone is affected, among others, by food consumption, insulin, fasting and cold exposure. Regulation of leptin secretion depends on many intracellular events. It is known that the activation of mTOR (the mamma lian target of rapamycin) as well as increase in ATP and malonyl-CoA content in adipocytes enhance secretion of leptin. The rise in intracellular cAMP and fatty acids is thought to evoke the opposite effect. Moreover, the undisturbed action of endogenous adenosine in adipocytes and the proper intracellular Ca2+ concentration in these cells were also found to have an important function in leptin release. The role of mTOR, ATP, cAMP, fatty acids, malonyl-CoA, adenosine and Ca2+ in the regulation of leptin secretion from adipocytes is discussed., T. Szkudelski., and Obsahuje bibliografii a bibliografické odkazy
Dipeptidyl peptidase-IV (DPP-IV, CD26) is a serine protease almost ubiquitously expressed on cell surface and present in body fluids. DPP-IV has been suggested to proteolytically modify a number of biologically active peptides including substance P (SP) and the chemokine stro mal cell derived factor-1α (SDF-1α, CXCL12). SP and SDF-1α have been implicated in the regulation of multiple biological processes and also induce responses that may be relevant for glioma progression. Both SP and SDF-1α are signaling through cell surface receptors and use intracellular calcium as a second messenger. The effect of DPP-IV on intracellular calcium mobilization mediated by SP and SDF- α was monitored in suspension of wild type U373 and DPP-IV transfected U373DPPIV glioma cells using indicator FURA-2. Nanomolar concentrations of SP triggered a transient dose dependent increase in intracellular calcium rendering the cells refractory to repeated stimulation, while SDF-1α had no measurable effect. SP signaling in DPP-IV overexpressing U373DPPIV cells was not substantially different from that in wild type cells. However, preincubation of SP with the DPP-IV overexpressing cells lead to the loss of its signaling potential, which could be prevented with DPP-IV inhibitors. Taken together, DPP-IV may proteolytically inactivate local mediators involved in gliomagenesis., P. Bušek, J, Stremeňová, E. Křepela, A. Šedo., and Obsahuje bibliografii a bibliografické odkazy
Glutamate is a well-characterized excitatory neurotransmitter in the central nervous system (CNS). Recently, glutamate receptors (GluRs) were also found in peripheral tissues, including the heart. However, the function of GluRs in peripheral organs remains poorly understood. In the present study, we found that N-methyl-D-aspartate (NMDA) could increase intracellular calcium ([Ca2+]i) level in a dose-dependent manner in cultured neonatal rat cardiomyocytes. NMDA at 10-4 M increased the levels of reactive oxygen species (ROS), cytosolic cytochrome c (cyto c), and 17-kDa caspase-3, but depolarized mitochondrial membrane potential, leading to cardiomyocyte apoptosis. In addition, NMDA treatment induced an increase in ba x mRNA but a decrease in bcl-2 mRNA expression in the cardiomyocytes. The above effects of NMDA were bloc ked by the NMDA receptor antagonist (+)-5-methyl- 10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5,10-imine hydrogen maleate (MK-801), and by ROS scavengers glutathione (GSH) and N-acetylcystein (NAC). These results suggest that stimulation of NMDA receptor in the cardiomyocyte may lead to apoptosis via a Ca2+, ROS, and caspase-3 mediated pathway. These findings suggest that NMDA receptor may play an important role in myocardial pathogenesis., X. Gao, X. Xu, J. Pang, C. Zhang, J. M. Ding, X. Peng, Y. Liu, J.-M. Cao., and Obsahuje bibliografii a bibliografické odkazy
Orexins (orexin A and B) are initially known to be a hypothalamic peptide critical for feeding and normal wakefulness. In addition, emerging evidence from behavioral tests suggests that orexins are also involved in the regulation of nociceptive processing, suggesting a novel potential therapeutic approach for pain treatment. Both spinal and supraspinal mechanisms appear to contribute to the role of orexin in nociception. In the spinal cord, dorsal root ganglion (DRG) neurons are primary afferent neurons that transmit peripheral stimuli to the pain-processing areas. Morphological results show that both orexin A and orexin-1 receptor are distributed in DRG neurons. Moreover, by using whole-cell patch-clamp recordings and calcium imaging measurements we found that orexin A induced excitability and intracellular calcium concentration elevation in the isolated rat DRG neurons, which was mainly dependent on the activation of spinal orexin-1 receptor. Based on these findings, we propose a hypothesis that the direct effect of orexin A on DRG neurons would represent a possible mechanism for the orexinergic modulation of spinal nociceptive transmission., J.-A. Yan, L. Ge, W. Huang, B. Song, X.-W. Chen, Z.-P. Yu., and Obsahuje bibliografii a bibliografické odkazy
We present a review about the relationship between ryanodine receptors and voltage-gated calcium channels in myocardium, and also how both of them are related to protein kinase A. Ryanodine receptors, which have three subtypes (RyR1-3), are located on the membrane of sarcoplasmic reticulum. Different subtypes of voltage-gated calcium channels interact with ryanodine receptors in skeletal and cardiac muscle tissue. The mechanism of excitation-contraction coupling is therefore different in the skeletal and cardiac muscle. However, in both tissues ryanodine receptors and voltage-gated calcium channels seem to be physically connected. FK-506 binding proteins (FKBPs) are bound to ryanodine receptors, thus allowing their concerted activity, called coupled gating. The activity of both ryanodine receptors and voltage-gated calcium channels is positively regulated by protein kinase A. These effects are, therefore, components of the mechanism of sympathetic stimulation of myocytes. The specificity of this enzyme’s targeting is achieved by using different A kinase adapting proteins. Different diseases are related to inborn or acquired changes in ryanodine receptor activity in cardiac myocytes. Mutations in the cardiac ryanodine receptor gene can cause catecholamine-provoked ventricular tachycardia. Changes in phosphorylation state of ryanodine receptors can provide a credible explanation for the development of heart failure. The restoration of their normal level of phosphorylation could explain the positive effect of beta-blockers in the treatment of this disease. In conclusion, molecular interactions of ryanodine receptors and voltage-gated calcium channels with PKA have a significant physiological role. However, their defects and alterations can result in serious disturbances., M. M. Petrovič, K. Valeš, B. Putnikovič, V. Djulejič, D. M. Mitrovič., and Obsahuje bibliografii a bibliografické odkazy
Plasma endothelin-1 (ET-1) levels are elevated in spinal cord injury (SCI), and ET-1 may be involved in the pathophysiology of this condition. However, its effects on contractile function of the heart of SCI rats are still unknown. To define more clearly the possiblel role of ET-1 following SCI, we investigated the effect of ET-1 on the contraction, calcium transients and L-type calcium current (ICa,L) in the cardiomyocytes of control and SCI rats. Sixteen Sprague-Dawley male rats aged 80-100 days and weighing 250-350 g were randomized into control and SCI groups. Fourteen days following compression injury to the spinal cord, effects of ET-1 on the contraction, calcium transients and ICa,L were studied in the cardiomyocytes of control and SCI rats by the technique of simultaneous measurement of intracellular Ca2+ and contraction and by whole-cell configuration of the patch-clamp technique. In myocytes from control rats, ET-1 significantly increased contraction, the magnitude of Ca2+ transients and the peak amplitude of ICa,L. However, ET-1 had little effect on the amplitude of contraction, calcium transients and ICa,L in myocytes from SCI rats. These results suggest that the positive inotropic effects of ET-1 on control myocardial contraction may be altered in pathological states such as SCI., Y.-F. Guo ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Chronic kidney disease (CKD) is associated with increased concentration of intracellular calcium, which is pathological and may lead to irreversible damage of cell functions and structures. The aim of our study was to investigate the impact of 6 months vitamin D3 supplementation (14 000 IU/week) on free cytosolic calcium concentration ([Ca2+]i) and on the plasma membrane calcium ATPase (PMCA) activity of patients with CKD stage 2-3. PMCA activity of patients was also compared to that of healthy volunteers. Vitamin D3 supplementation of CKD patients resulted in the decrease of [Ca2+]i (119.79±5.87 nmol/l vs. 105.36± 3.59 nmol/l, n=14, P<0.001), whereas PMCA activity of CKD patients (38.75±22.89 nmol Pi/mg/h) remained unchanged after vitamin D3 supplementation (40.96±17.74 nmol Pi/mg/h, n=14). PMCA activity of early stage CKD patients before supplementation of vitamin D3, was reduced by 34 % (42.01±20.64 nmol Pi/mg/h) in comparison to healthy volunteers (63.68±20.32 nmol Pi/mg/h, n=28, P<0.001). These results indicate that vitamin D3 supplementation had a lowering effect on [Ca2+]i and negligible effect on PMCA activity in CKD patients., M. Morvová Jr., I. Lajdová, V. Spustová, M. Zvarík, L. Šikurová., and Obsahuje bibliografii
ncreased systemic vascular resistance is responsible for blood pressure (BP) elevation in most forms of human or experimental hypertension. The enhanced contractility of structurally remodeled resistance arterioles is mediated by enhanced calcium entry (through L type voltagedependent calcium channels - L-VDCC) and/or augmented calcium sensitization (mediated by RhoA/Rho kinase pathway). It is rather difficult to evaluate separately the role of these two pathways in BP control because BP response to the blockade of either pathway is always dependent on the concomitant activity of the complementary pathway. Moreover, vasoconstrictor systems enhance the activity of both pathways, while vasodilators attenuate them. The basal fasudil-sensitive calcium sensitization determined in rats deprived of endogenous renin-angiotensi n system (RAS) and sympathetic nervous system (SNS) in wh ich calcium entry was dose- dependently increased by L-VDCC opener BAY K8644, is smaller in spontaneously hypertensive rats (SHR) than in normotensive Wistar-Kyoto (WKY) rats. In co ntrast, if endogenous RAS and SNS were present in intact rats, fasudil caused a greater BP fall in SHR than WKY rats. Our in vivo experiments indicated that the endogenous pressor systems (RAS and SNS) augment calcium sensitization mediated by RhoA/Rho kinase pathway, whereas the endogenous vasodilator systems (such as nitric oxide) attenuate this pathway. However, the modulation of calcium entry and calcium sensitization by nitric oxide is strain-dependent because NO deficiency significan tly augments low calcium entry in WKY and low calcium sensitization in SHR. Further in vivo and in vitro experiments should clarify the interrelationships between endogenous vasoactive systems an d the contribution of calcium entry and/or calcium sensitization to BP maintenance in various forms of experimental hypertension., J. Zicha ... [et al.]., and Obsahuje bibliografii a bibliografické odkazy
Oxid dusnatý (NO) je známy ako signálna molekula, ktorá hrá dôležitú úlohu v patofyziológii mnohých neurodegeneratívnych ochorení. Málo sa však vie o úlohe NO v patogenéze cauda equina syndrómu. V práci sme sledovali aktivitu kalciovo-závislej syntázy oxidu dusnatého (NOS) v Th1?Th12, L1?L3 a L4?L7 segmentoch miechy, rozdelenej na dorzálnu, mediálnu a prednú časť a neurónovú NOS imunoreaktivitu (nNOS-IR) v L4?L7 segmentoch po chirurgicky navodenej mnohonásobnej konstrikcii cauda equina (MCEC) u psa a po prežívaní experimentálnych zvierat po dobu 2 a 5 dní. Signifikantné zvýšenie kalciovo-závislej NOS aktivity bolo zaznamenané v zadnej časti torakálnych a horných lumbálnych segmentov 2 dni po MCEC, kým na piaty deň enzýmová aktivita v zadnej časti vyššie uvedených miechových segmentov sa signifikantne znížila. Nevýrazné rozdiely sa zaznamenali v zadnej časti L4?L6 segmentov. V mediálnej časti L4?L7 segmentov odobranej 2 dni po MCEC, bola kalciovo-závislá NOS aktivita zvýšená len prechodne; hodnota sa vrátila takmer na úroveň kontroly piaty deň po konstrikcii. 2 dni trvajúca MCEC nespôsobila zmeny v enzýmovej aktivite v mediálnej časti torakálnych a horných lumbálnych segmentov. Signifikantné rozdiely sa zaznamenali len 5 dní po MCEC. Vplyv MCEC na kalciovo-závislú NOS aktivitu vo ventrálnej časti torakálnych, horných a dolných lumbálnych segmentov bol podobný, pričom sa zistilo signifikantné zvýšenie enzýmovej aktivity v sledovaných segmentoch avšak s výnimkou jej zníženia v horných lumbálnych segmentoch 5 dní po konstrikcii. Zvýšenie kalciovo-závislej NOS aktivity v dolných lumbálnych segmentoch korelovalo so zvýšeným počtom NOS-IR neurónov lokalizovaných v laminae VIII a IX a so zvýšenou expresiou NOS-IR axónov vo ventrolaterálnom povrazci., Jozef Kafka, N. Lukáčová, D. Čížková, J. Maršala, and Lit.: 37