The effect of some peptides from the hibernating brain on Ca2+ current in cardiac cells and on the activity of septal neurons

CARDIOPROTECTIVE EFFECT OF ENKEPHALINS UNDER IMMOBILIZATION STRESS

Objective: The aim of this study was to investigate the cardioprotective effect of dalargin, a synthetic leu-enkephalin. Methods: The induction of myocardial infarction in rats, which were kept on a diet with excess fat and calcium/sodium salts for two months, by the use of immobilization stress. The experimental results indicated that the applied model allowed to induce the development of myocardial infarction within one three days, which was confirmed by electrocardiography, enzyme-linked immunosorbent assay and histological examination. Results: Pre-treatment of rats with dalargin had no prevented myocardial infarction, however, it increased the resistance to immobilization stress and reduced infarction-induced myocardial lesions. Simultaneous administration of naloxone, an opiate receptor antagonist, together with dalargin eliminated its cardioprotective effect in experimental animals. Conclusion: The use of synthetic leu-enkephalin dalargin significantly reduced the risk of myocardial infarction caused by excessive neuromuscular stress. The dalargin effect on the myocardium was mediated by opiate receptors.

Mass spectrometric analysis of activity-dependent changes of neuropeptide profile in the snail, Helix pomatia

Terrestrial snails are able to transform themselves into inactivity ceasing their behavioral activity under unfavorable environmental conditions. In the present study, we report on the activity-dependent changes of the peptide and/or polypeptide profile in the brain and hemolymph of the snail, Helix pomatia, using MALDI TOF and quadrupole mass spectrometry. The present data indicate that the snails respond to low temperature by increasing or decreasing the output of selected peptides. Average mass spectra of the brain and hemolymph revealed numerous peaks predominantly present during the active state (19 and 10 peptides/polypeptides, respectively), while others were observed only during hibernation (11 and 13). However, there were peptides and/or polypeptides or their fragments present irrespective of the activity states (49 and 18). The intensity of fourteen peaks that correspond to previously identified neuropeptides varied in the brain of active snails compared to those of hibernating animals. Among those the intensity of eight peptides increased significantly in active animals while in hibernated animals the intensity of another six peptides increased significantly. A new peptide or peptide fragment at m/z 1110.7 was identified in a brain of the snail with the following suggested amino acid sequence: GSGASGSMPATTS. This peptide was found to be more abundant in active animals because the intensity of the peptide was significantly higher compared to hibernating animals. In summary, our results revealed substantial differences in the peptide/polypeptide profile of the brain and hemolymph of active and hibernating snails suggesting a possible contribution of peptides in the process of hibernation.

Peptidomics: a logical sequel to proteomics

Rapid progress of separation techniques as well as methods of structural analysis provided conditions in the past decade for total screening of complex biologic mixtures for any given class of biomolecules. The present review updates the reader with the modern state of peptidomics, a chapter of chemical biology that deals with structure and biologic properties of sets of peptides present in biologic tissues, cells or fluids. Scope and limitations of currently employed experimental techniques are considered and the main results are outlined. Considerable attention will be afforded to the biologic role of peptides formed in vivo by proteolysis of nonspecialized precursor proteins with other well-defined functions. In conclusion, the connection is discussed between peptidomics and the much more mature and still closely related field of proteomics.

Stimulation of fibroblast proliferation by neokyotorphin requires Ca2+ influx and activation of PKA, CaMK II and MAPK/ERK

Neokyotorphin [TSKYR, hemoglobin alpha-chain fragment (137-141)] has previously been shown to enhance fibroblast proliferation, its effect depending on cell density and serum level. Here we show the dependence of the effect of neokyotorphin on cell type and its correlation with the effect of protein kinase A (PKA) activator 8-Br-cAMP, but not the PKC activator 4beta-phorbol 12-myristate, 13-acetate (PMA). In L929 fibroblasts, the proliferative effect of neokyotorphin was suppressed by the Ca2+ L-type channel inhibitors verapamil or nifedipine, the intracellular Ca2+ chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid acetoxymethyl ester, kinase inhibitors H-89 (PKA), KN-62 (Ca2+/calmodulin-dependent kinase II) and PD98059 (mitogen-activated protein kinase). The proliferative effect of 8-Br-cAMP was also suppressed by KN-62 and PD98059. PKC suppression (downregulation with PMA or inhibition with bisindolylmaleimide XI) did not affect neokyotorphin action. The results obtained point to a cAMP-like action for neokyotorphin.

Potential for discovery of neuroprotective factors in serum and tissue from hibernating species

Hibernation is a unique phenotype displayed by a phylogenetically diverse group of organisms including several species of mammals and one species of primate. Here we review evidence for blood and tissue borne signaling molecules in hibernating animals, achievements in isolating and characterizing these molecules, and potential medicinal applications.

The paradoxically high reactivity of septal neurons in hibernating ground squirrels to endogenous neuropeptides is lost after chronic deafferentation of the septum from the preopticohypothalamic areas

The effect of neuropeptides (TSKYR, TSKY and DY) and neurotransmitters (serotonin and noradrenaline) on the activity of medial septum (MS) neurons from the brain of summer wakening ground squirrels (WGS), hibernating ground squirrels (HGS), and hibernating ground squirrels with the undercut septum (UHGS) was studied. It was shown that in HGS, the neuropeptides were substantially more effective in modulating the spontaneous activity of MS neurons than in WGS. The undercutting of MS led to the disappearance of the increased responsiveness to the neuropeptides: in UHGS, neuropeptide-induced changes in the spontaneous activity became nearly identical to those in WGS. The decrease in MS responsiveness in UHGS is due mainly to pacemaker neurons, which cease to respond to the peptides. It was shown that the neuropeptides have a dual effect: they change the level of spontaneous activity through direct modulation of pacemaker potential and control responses to electrical stimulation by modulating the synaptic transmission. Contrary to neuropeptides, neurotransmitters were highly effective in neurons of all groups of animals. Presumably, the enhanced excitability of MS during hibernation, which is necessary for performing the 'sentry post' function, is formed under the influence of the preopticohypothalamic area, and this influence is mediated by peptides.

Norepinephrine induces slow calcium signalling in murine brown preadipocytes through the beta-adrenoceptor/cAMP/protein kinase A pathway

The mechanism of adrenergically activated calcium signalling in isolated murine brown preadipocytes (stromal-vascular fraction) was studied with Fura-2. Norepinephrine (NE) generated in preadipocytes a slow Ca(2+)-response ( approximately 10 nM/min) without a burst and a maximum, whereas in mature brown adipocytes, the quick burst reached 1.5 microM [Ca(2+)](i). Thapsigargin, which is known to discharge Ca(2+) ions from the IP(3)-sensitive stores, initiated a huge capacitative calcium entry in mature brown adipocytes but failed to stimulate a response in preadipocytes. The beta-selective antagonist nadolol almost completely prevented the effect of NE on [Ca(2+)](i), while the antagonist of alpha-adrenoceptors phentolamine caused only a approximately 25% reduction of the cellular response. Forskolin or the cell-permeable Br-cAMP caused [Ca(2+)](i) rise, which were even higher than with NE. The protein kinase A (PKA) inhibitor N-[2-(p-bromocynnamylamino)ethyl]-5-isoquinolinesulfonamide (H-89) reduced and the phosphodiesterase inhibitors 3-isobutyl-1-methylxanthine (IBMX), N-cyclohexyl-N-(2-hydroxyethyl)-4-(6-(1,2-dihydro-2-oxoquinolyloxy))butyramide (OPC-3911), 4-(3-butoxy-4-methoxybenzyl)-2-imidazolidone (Ro 20-1724) or the protein phosphatase inhibitor okadaic acid enhanced the NE-, isoproterenol- or forskolin-initiated cellular calcium responses. It was concluded that (i) brown preadipocytes lacked a trigger mechanism of initiation of [Ca(2+)](i) rises and (ii) the cAMP- and protein kinase A-mediated phosphorylation played an important role in the beta-adrenoceptor-initiated calcium signalling in these cells. All these features distinguish brown adipocyte precursors from differentiated brown adipocytes, where calcium signalling is initiated exclusively via alpha(1)-adrenoceptors and the trigger mechanism.

What to synthesize? from Emil Fischer to peptidomics

The driving forces, incentives and strategic targets of peptide synthesis have undergone considerable evolution during the centenary following the pioneer work of Emil Fischer. In those days peptide synthesis was considered as a way of confirming the polypeptide theory of protein structure. The scientific community also expected (naively) that the synthesis would eventually lead to the creation of artificial living organisms. Only in the 1950s, when the first exact amino acid sequences were established did peptide chemistry obtain firmer ground and clearly defined targets. The total synthesis of peptide hormones and antibiotics became possible, providing valuable material for elucidating structure-functional relationships and the mechanisms of biological action. In the following years the number of peptides isolated from various biological sources grew with impressive speed and peptides became known as the most abundant, ubiquitous group of low molecular bioregulators. The design and synthesis of novel peptide based pharmaceuticals became an important area of peptide chemistry. At present we are facing the challenge of analysing the structures and bioactivities of total sets of peptides, i.e. peptidoms, present in concrete tissues or groups of cells. The results obtained along these lines at the IBCH RAS Institute of Bioorganic Chemistry are briefly considered in the review.

Endogenous fragment of hemoglobin, neokyotorphin, as cell growth factor

It is shown that neokyotorphin (the alpha-globin fragment 137-141) stimulates proliferation of normal cells (murine embryonic fibroblasts, red bone marrow and spleen cells) and tumor cells (murine melanoma and transformed fibroblasts L929) in the absence or in the presence of fetal bovine serum. In contrast to serum deprivation conditions, the ability to potentiate L929 cell growth in the presence of fetal serum is strongly cell density dependent. The peptide also enhances the viability of L929 cells, murine embryonic fibroblasts and of the primary cultures of murine red bone marrow cells and splenocytes under serum-deprivation conditions for at least 72 h. The results of flow cytometry analysis suggest that the effect of neokyotorphin on survival of L929 cells in serum-free culture medium is due to maintenance of cell proliferation in the absence of growth factors. Along with cell cycle progression the peptide induces reversible reduction of L929 cell size.

The effects of afferent stimulation on neurons in slices of the medial septal area and their modulation by biologically active substances in hibernating and awake ground squirrels

Evoked neuron activity in slices of the medial septal area and its modulation by neuropeptides and monoamines was studied in two groups of ground squirrels--hibernating and awake animals. Electrical stimulation of the medial forebrain bundle evoked predominantly inhibitory effects of different durations. In addition, responses were seen consisting of resetting of the phase of background volleys to the stimulus after initial inhibition: there were also small numbers of short-latency single-spike responses. All the neuropeptides tested. which had been identified from the brains of hibernating animals, induced differentiated reversible effects consisting of modulation of responses; changes in evoked activity were seen significantly more often than shifts in spontaneous activity. The effects depended on the state of the animal. Thus. peptide TSKYR increased the duration of inhibition in hibernating ground squirrels but shortened inhibition in awake animals. Peptide TSKY. which had little effect in hibernating animals, increased the duration of inhibition in awake animals. Dipeptide DY. which decreased the duration of inhibition and increased the amplitude of the activatory components of responses in hibernating ground squirrels. had little effect in awake animals. The effects of noradrenaline and serotonin correlated to a large extent with their effects on spontaneous activity. It is suggested that endogenous substances are involved in creating the conditions required for increasing the latent excitability and reactivity of septal neurons during hibernation. This allows the medial septal area to function as a "sentry post," allowing the receipt of signals and urgent arousal during hibernation.

State-dependent effects of some neuropeptides and neurotransmitters on neuronal activity of the medial septal area in brain slices of the ground squirrel, Citellus undulatus

Neuronal activity of the medial septal area was recorded extracellularly in brain slices taken from hibernating (winter) and waking (summer) ground squirrels. The effects of neuropeptides identified in the brain tissue of hibernators (Thr-Ser-Lys-Tyr, Thr-Ser-Lys-Tyr-Arg and Asp-Tyr) on the background activity and responses to electrical stimulation of the median forebrain bundle were analysed. For comparison, the effects of bath application of noradrenaline and serotonin were also tested. Spontaneous activity in half of all neurons (47-56%) was changed under the influence of neuropeptides in hibernating ground squirrels, while in waking ground squirrels the proportion of responsive neurons was significantly lower (25-30%). The tendency for higher efficacy in hibernating ground squirrels was observed for serotonin; only noradrenaline was equally effective in both groups of animals. Electrically evoked responses of the medial septal nucleus-nucleus of the diagonal band neurons were also strongly modulated by neuropeptides; their changes could occur in the absence of shifts in the level and pattern of spontaneous activity. All three neuropeptides had differential action on the level of spontaneous activity, as well as on inhibitory and excitatory components of electrically evoked responses. Thus, the character and distribution of the effects were state dependent and differed greatly in hibernating and waking ground squirrels. The experiments confirmed that medial septal nucleus-nucleus of the diagonal band neurons have higher excitability and responsiveness to some neuropeptides and neurotransmitters in hibernating ground squirrels.The data obtained suggest an increased latent excitability and responsiveness of septal neurons during hibernation and their possible active participation in urgent arousal under the influence of sensory signals.