Role of oxytocin/oxytocin receptor system in regulation of cell growth and neoplastic processes.

Novel sites of oxytocin receptor expression have recently been detected in central nervous system, cardiomyocytes, endothelial cells, various carcinoma cells, etc. These and other discoveries have greatly expanded the classical biological roles of oxytocin, which are stimulation of uterine smooth muscle contraction at parturition and milk ejection during lactation. It is becoming clear that the great diversity of oxytocin actions in the brain and peripheral organs is paralleled by activation of a diversity of signalling pathways. On the other hand, until now only one single oxytocin receptor type has been detected. This receptor belongs to G protein-coupled receptors and in dependence on cell conditions it binds to different G proteins; this phenomenon is called receptor-G protein promiscuity. Thus, in the same cells oxytocin can activate multiple responses at the same time. Recently, the oxytocinergic system has also been implicated in the growth modulation of various neoplastic cells, where it may inhibit or stimulate cell proliferation in dependence on cell type and activated metabolic pathways. The discovery of novel oxytocin receptor-linked signalling cascades brings interesting knowledge opening new avenues for research in oncology and molecular pharmacology with perspectives of finding new therapeutic agents.

Immune-glutamatergic dysfunction as a central mechanism of the autism spectrum disorders.

Despite the great number of observations being made concerning cellular and the molecular dysfunctions associated with autism spectrum disorders (ASD), the basic central mechanism of these disorders has not been proposed in the major scientific literature. Our review brings evidence that most heterogeneous symptoms of ASD have a common set of events closely connected with dysregulation of glutamatergic neurotransmission in the brain with enhancement of excitatory receptor function by pro-inflammatory immune cytokines as the underlying mechanism. We suggest that environmental and dietary excitotoxins, mercury, fluoride, and aluminum can exacerbate the pathological and clinical problems by worsening excitotoxicity and by microglial priming. In addition, each has effects on cell signaling that can affect neurodevelopment and neuronal function. Our hypothesis opens the door to a number of new treatment modes, including the nutritional factors that naturally reduce excitotoxicity and brain inflammation.

Alterations in calcium homeostasis as biological marker for mild Alzheimer's disease?

The calcium hypothesis of neurodegenerative disorders such as Alzheimer's disease (AD) suggests that altered cytosolic Ca(2+) levels ( Ca(2+) (i)) and/or disturbances in Ca2+ homeostasis concern cellular mechanisms underlying neuronal pathology. To search for a diagnostic marker of Alzheimer's disease, we measured cytosolic calcium concentrations in platelets of AD patients, age-matched control subjects (AMC), and vascular dementia (VD) patients. The ( Ca(2+) (i)) was determined using long wavelength indicator Fluo-3AM in 21 mild AD patients, 17 AMC, and 23 patients with VD. The basal values of [Ca(2+)](i) were significantly lower in AD compared to AMC. After the addition of 1 mM calcium, the [Ca(2+)](i) markedly increased in platelets of AD compared to AMC and VD. Measurement of calcium homeostasis could provide a very sensitive, but less specific biological marker of AD. These results support the hypothesis that influencing calcium homeostasis may provide a therapeutic strategy in dementia.

[Development of the views on the function of the pineal gland]. / Vývoj názoru na funkci sisinky.

Physiology has been collecting the knowledge about the functional significance of the pineal gland during the last 30 years. The recent scientific knowledge about the physiological functions of this gland is compared with the historical development of the views about the role of the pineal gland in the human body.

[Molecular mechanisms of biological effects of lithium]. / Molekulární mechanismy biologického úcinku lithia.

Lithium has the inhibitory effect on many enzymes and multiple effects on some physiological processes. Lithium is also highly effective in the treatment of bipolar disorder, however, the mechanism of lithium action in the treatment of this psychiatric disorder is still unknown. A number of lithium-sensitive enzymes and putative important biomolecules have been proposed as potential targets of lithium action and these mechanisms are discussed in this review.

Fluoride plus aluminum: useful tools in laboratory investigations, but messengers of false information.

Aluminofluoride complexes (AlF(x)) form spontaneously in aqueous solutions containing fluoride and traces of aluminum ions and appear to act as phosphate analogs. These complexes have become widely utilized in laboratory investigations of various guanine nucleotide-binding proteins. Reflecting on many laboratory studies, a new mechanism of fluoride and aluminum action on the cellular level is being suggested. The long-term synergistic effects of these ions in living environment and their hidden danger for human health are not yet fully recognized.

An ideal biological marker of Alzheimer's disease: dream or reality?

Senile dementia of Alzheimer's type (AD) is commonly characterized as a neurodegenerative disorder, which exhibits gradual changes of consciousness, loss of memory, perception and orientation as well as loss of personality and intellect. AD prevalence increases dramatically with age and is the fourth cause of death in Europe and in the USA. Currently, there are no available biological markers, which gives clinicians no other alternative than to rely upon clinical diagnosis by exclusion. There is no assay of objective ante mortem biochemical phenomena that relate to the pathophysiology of this disease. The pathophysiology of AD is connected with alterations in neurotransmission, plaque formation, cytoskeletal abnormalities and disturbances of calcium homeostasis. The search for a test, which is non-invasive, simple, cheap and user-friendly, should be directed at accessible body fluids. Only abnormalities replicated in large series across different laboratories fulfilling the criteria for a biological marker are likely to be of relevance in diagnosing AD. To date, only the combination of cerebrospinal fluid tau and Abeta42 most closely approximate an ideal biomarker of Alzheimer's disease. A short review on the role of biological markers in AD on the basis of the literature, contemporary knowledge and our own recent findings are presented.

[Cholinesterases and their importance in the etiology, diagnosis and therapy of Alzheimer's disease]. / Cholinesterázy a jejich význam v etiologii, diagnostice a terapii Alzheimerovy nemoci.

Cholinesterases belong to esterases and represent important animal enzymes with multiple biological function. Acetylcholinesterase (AChE) plays the key role in cholinergic neurotransmission, whereas the function of butyrylcholinesterase (BuChE) is still unrevealed. Both enzymes seem to act as neurogenic factors during the early embryogenesis and later on they may participate in some pathological alteration. In humans, these degenerative changes are related to the deposition of pathologic proteins in the brain and with the progress of the Alzheimer's dementia (AD). Both AChE) and BuChE become recently the target for the most frequently used therapy of AD--cholinesterase inhibitors.

Cytosolic calcium alterations in platelets of patients with early stages of Alzheimer's disease.

Alterations in calcium homeostasis might be implicated in the neuropathology of Alzheimer's disease (AD). To date it is not clear whether changes in cytosolic calcium level ([Ca2+ ]i) are the result or the cause of pathogenic effects. In platelets of patients with early stages of AD, the basal values of [Ca2+]i in the absence of extracellular Ca2+ were significantly lower in comparison with age-matched and young controls. After the addition of 1 mM calcium into the incubation medium the [Ca2+]i markedly increased in platelets of AD patients whereas the increase only to a smaller extent was observed in control age-matched and young subjects. The present study proposes that calcium dysregulation during the whole disease period could not be uniform and according to our results the [Ca2+]i is reduced in the first stages of AD. We suggest that the disturbed calcium homeostasis in AD is an "early defect."

The most important microtubule natural inhibitors.

Natural microtubule inhibitors represent chemically very variegated family of structures with strong effect on cytoskeletal functions and the use of them is one of the most frequent therapeutic strategies for carcinoma treatment. The survey of the most important natural microtubule inhibitors is summarized in this paper.

[Ion channels--target proteins for some animal toxins]. / Iontové kanály--cílové proteiny pro nekteré zivocisné toxiny.

Advances in molecular biology along with improvements in electrophysiological techniques have increased the knowledge in the structure and function of many ion channels. Voltage-gated Na+ and K+ channels may become sensitive to biologically active substances such as animal toxins. Study of animal toxins can help to understand the molecular mechanisms of their action, but it can also reveal the tools for the future study of molecular physiology of ion channels.

Phosphoinositide signalling system in platelets of schizophrenic patients and the effect of neuroleptic therapy.

Alterations in the phosphoinositide signalling system have been proposed as a possible biological marker of schizophrenia. We studied the levels of inositol 1,4,5-trisphosphate (IP3), cytosolic Ca2+ concentrations ([Ca2+]i), and the incorporation of [32P]-orthophosphate into inositol phospholipids and phosphatidic acid (PA) in blood platelets of neuroleptic-treated schizophrenics in comparison with controls. The [Ca2+]i was significantly higher in platelets of one month neuroleptic-treated patients (155+/-5.8 nM) in comparison with controls (95+/-5.4 nM). Neuroleptic therapy decreased the [Ca2+]i, but even after long-term therapy it remained significantly higher (114+/-5.7 nM) than in controls. Differences were also found in the level of IP3 between controls (30+/-4.0 pmol/10(9) platelets), drug-free schizophrenics (52+/-9.0 pmol/10(9) platelets) and treated patients (50+/-6.0 pmol/10(9) platelets). The increased turnover of PA was observed in platelets of neuroleptic-treated schizophrenic patients. The study suggests that the regulation of calcium homeostasis and pathways involved in the phosphoinositide signalling system are altered in the platelets of schizophrenics. Neuroleptic therapy did not remove the observed changes in [Ca2+]i and IP3 levels.

What can the investigation of phosphoinositide signaling system in platelets of schizophrenic patients tell us?

Disturbances in the regulation of the phosphoinositide signaling system have been proposed as a possible biological marker of schizophrenia. This review considers the laboratory investigations of phosphoinositide metabolism in platelets of schizophrenic patients. We suggest that alterations in the inositol phosphate level and a disturbance of calcium homeostasis may be common denominators for the multiple factors implicated in the pathogenesis of schizophrenia. In addition, these abnormalities may account for the diverse clinical and biochemical manifestations of schizophrenia.

[Reassessment of the role of aluminum in the development of Alzheimer's disease]. / Prehodnocení úcasti hliníku na vzniku Alzheimerovy nemoci.

The pathophysiology of Alzheimer's disease (AD) is related to the alterations in neurotransmission, beta-amyloid production, plaque formation and cytoskeletal abnormalities. The question of aluminium relevance to the etiology of AD cannot yet be adequately answered. Aluminium is currently regarded as the putative risk factor for the disease. Our paper shows that some of pathologic changes are not raised by aluminium alone, but by the aluminofluoride complexes. These complexes may act as the initial signal stimulating impairment of homeostasis, degeneration and death of the cells. By influencing energy metabolism these complexes can accelerate the aging and impair the functions of the nervous system. In respect to the etiology of AD, the long term action of aluminofluoride complexes may represent a serious and powerful risk factor for the development of AD.

Phospholipids and calcium alterations in platelets of schizophrenic patients.

Alterations in phospholipid metabolism in blood elements have been proposed as the possible biochemical marker of schizophrenia. In the present study, we investigated the composition and membrane distribution of phospholipids in platelets of drug-free schizophrenic patients and controls. We have demonstrated that platelets of drug-free schizophrenics have significantly higher cytosolic Ca2+ levels in comparison with healthy controls. Platelets of drug-free schizophrenic patients have a lower content of phosphatidylinositol (PI). After thrombin activation, PI is the target of phospholipase C instead of phosphatidylinositol 4,5-bisphosphate (PIP2), which is hydrolyzed in platelets of controls. Alterations in the distribution of phospholipids were found in the plasma membrane of platelets of schizophrenic patients. We suggest that alterations in phospholipid metabolism might be evoked by a disturbance of calcium homeostasis in schizophrenic patients.

Red blood cell age dependent modifications of inositol 1,4,5-trisphosphate.

The level of inositol 1,4,5-trisphosphate (Ins1,4,5P3) was determined in human and rabbit red blood cells of different ages. In human erythrocytes, fractionated by discontinuous density gradient centrifugation, Ins1,4,5P3 was 290 nM in the 0.3% low density (youngest) cells compared to values of 107 nM in the whole red blood cell population. A progressive increase in Ins1,4,5P3 was then observed during erythrocyte aging from values of 63 nM in mature erythrocytes to 128 nM in the oldest cells. Determinations of Ins1,4,5P3 in rabbit erythrocytes provided values of 180 nM. Phenylhydrazine was administered to three animals to induce reticulocytosis. Ins1,4,5P3 in rabbit reticulocytes was significantly lower than in the whole red cell population, remained lower in young red blood cells and then increased to normal values during cell maturation. These results provide evidence for an increase of Ins1,4,5P3 during red blood cell aging and could contribute to explain the age-dependent loss of deformability and of Ca2+ homeostasis of these cells.

Phosphoinositide signalling system in red blood cells of patients with hereditary spherocytosis.

Hereditary spherocytosis (HS) is characterised with many deviations of red blood cells properties. We investigated a group of 14 patients with mild HS, 7 of whom were splenectomised. We found changes in the content and/or turnover of polyphosphoinositides and phosphatidic acid accompanied by the higher generation of inositol 1,4,5-trisphosphate. We suggest that the activation of the phosphoinositide signalling system may be crucial for the manifestation of HS.

The effect of inositol 1,4,5-trisphosphate and inositol 1,4,5-trisphosphorothioate on calcium release and membrane skeleton organization in the human red blood cell.

The inositol 1,4,5-trisphosphate [Ins(1,4,5)P3] content of unstimulated human red blood cells (RBC) has been found to be 227 +/- 83 pmol of Ins(1,4,5)P3 per mL of packed cells. Ins (1,4,5)P3 at concentrations between 0.4-5.0 microM releases Ca2+ from RBC plasma membrane with an EC50 of 0.55 microM. Inositol 4,5-bisphosphate [Ins(4,5)P2] is less potent, but inositol 1-phosphate [Ins(1)P], inositol 1,4-bisphosphate [Ins (1,4)P2], and adenosine triphosphate (ATP) are inactive. The release was stereospecific for D-Ins(1,4,5)P3; 1 microM L-Ins(1,4,5)P3 released no more Ca2+ than the control. A nonhydrolyzable analog of Ins(1,4,5)P3, inositol 1,4,5-trisphosphorothioate [Ins(1,4,5)PS3] evokes sustained release of Ca2+ from isolated ghosts. Release of 45Ca2+ was also observed after the addition of AlF4-. Ionophore A23187 and AlF4- increase the level of Ins(1,4,5)P3 in intact RBC to 1004 +/- 533 and 455 +/- 74 pmol/mL of packed RBC, respectively. We have elaborated a method for visualization of spectrin by indirect immunofluorescence in smears of RBC. Ins(1,4,5)P3 evokes shape changes in permeabilized RBC and disorganization of the spectrin network. The shape changes are stereospecific for the D-enantiomer, since L-Ins(1,4,5)P3 and other compounds had no effect. Whereas the effect of Ins(1,4,5)P3 was reversible, as was the weaker effect of Ins(4,5)P2, Ins(1,4,5)PS3 evoked irreversible shape changes. Shape changes and spectrin disorganization were also observed after the action of AlF4- and ionophore A23187. We conclude that the phosphoinositide signaling system plays an important role in the shape maintenance of human RBC.

Calcium affects phosphoinositide turnover in human erythrocytes.

Changes in extracellular Ca2+ concentration ([Ca2+]) were observed to affect 32Pi incorporation into polyphosphoinositides (PPI) and phosphatidic acid (PA) of human erythrocytes. A decrease of extracellular [Ca2+] from 1.5 mmol/l to 0.04 mumol/l increased the specific radioactivity (S.A.) of phosphatidylinositol 4,5-bisphosphate to 182% and that of phosphatidylinositol 4-phosphate to 120% of controls. Simultaneously S.A. and concentration of PA decreased. Further decrease of the extracellular [Ca2+] from 0.04 mumol/l to lower values as well as depletion of intracellular Ca2+ using ionophore A 23187 in Ca2(+)-free medium did not accelerate the PPI turnover rates any more. None of the above changes in extracellular [Ca2+] had any effect on the phosphorylation pattern of erythrocyte membrane proteins. Isolated erythrocyte membranes were incubated in the presence of [gamma-32P]ATP in media with various [Ca2+]. The decrease of [Ca2+] from 0.04 mumol/l (physiological concentration inside the cell) to lower values did not influence the turnover of PPI and PA monoester phosphates. Only after [Ca2+] was increased to 1-5 mumol/l an increase of PPI and PA turnover was observed. Our data suggest that the changes in extracellular [Ca2+] affect the metabolism of PPI and PA (despite the intracellular location of the latter) and may thus influence the properties of red cell plasma membrane.

Phosphoinositide signalling system in human erythrocyte and its role in cell pathology.

Human erythrocytes contain 217.2 +/- 70.5 pmole of inositol 1,4,5-trisphosphate per ml of packed cells (n = 14). The increased generation of Ins 1,4,5P3, was induced by 1 microM A 23187, 20 microM Pb2+, and by AlF4-. Ins 1,4,5P3, Pb2+ and AlF4- evoke shape changes, disorganisation of spectrin network and vesiculation. In erythrocytes of patients with hereditary spherocytosis the level of Ins 1,4,5P3 was increased to 556.7 +/- 374 pmole per ml of packed cells. We suggest that activation of the phosphoinositide signalling system may represent a common denominator for many divergent stimuli and defects which affect shape changes of erythrocytes.