Current scientific projects

Role of ion channels and calcium signaling in malignant transformation and carcinogenesis

This direction of the research is pursued in close collaboration with the Laboratoire de Physiologie Cellulaire, Inserm U1003, Universite de Lille1 (France) headed by Prof. Natalia Prevarskaya. Studies within this direction were supported by two grants from International Association for the Promotion of Co-operation with Scientists from the New Independent States of the Former Soviet Union (INTAS) – INTAS-99-01248 (2000-2003) and INTAS-05-1000008-8223 (2006-2009), and now are continued on initiative basis.

Due to the ability to transport ions through a cell membrane, the activation of various types of ion channels can significantly contribute to the regulation of cell volume, and in the event when they transport calcium ions, also to the changes of intracellular calcium concentration, which plays an important signaling role. The same factors, namely the regulation of cell volume and the changes in calcium signaling, affect the progression of processes that determine cell fate, such as proliferation, differentiation, migration and apoptosis. Since the deregulation of these processes towards enhanced proliferation, loss of differentiation, accelerated migration and increased resistance to apoptosis are characteristic features (also referred to as cancer hallmarks) of malignant transformation of cells, the function of ion channels becomes key to either promotion or prevention of the development of these features. In our studies, the properties and carcinogenic potential of several types of chloride- and calcium-permeable ion channels in prostate cancer cells were described, and suggestions were made regarding their potential as therapeutic targets for cancer treatment. The results of these studies are widely presented in the scientific literature (see relevant publications).

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Involvement of thermo- and mechanosensitive ion channels in the functioning of smooth muscles of the male urogenital system

The opening and closing (i.e. gating) of the most known types ion channels is governed by such classical stimuli as membrane potential and/or endogenous chemical ligands called neurotransmitters. However, since the end of 1990s many new types of ion channels which are gated by non-classical stimuli, including temperature changes and mechanical stress, have been discovered. In the framework of this research direction, we asked how the channels activated by heat (TRPV family), cold (TRPA1, TRPM8) or mechanical stress (PIEZO family) are involved in the regulation of contractile activity of smooth muscles (SM) of the male urogenital system – the detrusor, the prostate, the vas deferens and tunica dartos, which are distinguished by a high degree of sensitivity to the thermal and mechanical (stretching) insults. These studies are conducted within the institutional budgetary funding from the National Academy of Sciences of Ukraine (NASU), as well as funding from NASU's specialized programs such as "Genome" and "Biotechnology". In these studies we not only elucidate normal expression and function of the thermo- and mechano-gated channels in these SM tissues at the cellular and subcellular levels, but also try to get an idea on their possible changes as a result of complications caused by diabetes (see relevant publications).

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The influence of diabetes on neuromuscular transmission and excitation-contraction coupling in smooth muscles of the male urogenital system

The impairment of the autonomic nervous system, peripheral diabetic neuropathy, is a frequent and serious complication of diabetes mellitus (DM). The weakening of the autonomic regulation of the lower urinary tract in patients with DM provokes the development of diabetic cystopathies, the main symptom of which is urinary incontinence. However, literature data on the impact of DM on neuromuscular synaptic transmission in visceral smooth muscle, and in particular the bladder detrusor smooth muscle (DSM), are quite controversial. The dominant view is that in diabetes, the expression of muscarinic m-cholinergic receptors (mAChR) and DSM sensitivity to their agonists is increased. Moreover, mAChR antagonists are considered to be effective in alleviating the symptoms of hyperactive urinary bladder and urge incontinence of different etiologies, although such therapy should be applied with caution due to significant side effects. Recently, potentially new determinants of bladder hyperactivity amongst ion channels from Transient Receptor Potential (TRP) family, TRPV1 and TRPA1, acting as receptors of burning and cooling temperatures, respectively, have been identified. The degree of severity and direction of urological complications in diabetes can also largely depend on inflammation and/or infection of the lower urinary tract that often accompany this disease. In this regard, we aimed to investigate how TRPV1 and TRPA1 are involved in changes of DSM contractility in diabetes and how DSM contractility in diabetic bladder is influenced by accompanying inflammation or infection. These studies are carried out within the institutional budgetary funding from the National Academy of Sciences of Ukraine (NASU), as well as funding from NASU's specialized "Genome" program (see relevant publications).

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Targets of pharmacological action of new openers of ATP-dependent potassium channels (K_ATP) and their selectivity towards tissue-specific K_ATP subtypes of these channels

ATP-dependent potassium channels (K_ATP) play pivotal role in the coupling of physiological activity of cells with their intracellular energetics: when cell energy metabolism is compromised (i.e., the intracellular ATP to ADP ration is low), these channels become activated, leading to hyperpolarization of the membrane potential and suppression of cellular activity (i.e., the cell is turned into resting mode of operation). Thus, pharmacological agents, the so-called K_ATP-openers, are potentially very important protective therapeutic agents. Depending on their subunit composition, K_ATP-s are subdivided into three tissue-specific subtypes, cardiac, vascular and pancreatic. In the framework of this research direction, we investigate the peculiarities of the pharmacological action of the newly developed Ukrainian K_ATP-opener, flocalin. Flocalin is fluorine-containing derivative of a well known K_ATP-opener, pinacidil, which is positioned as cardioprotective agent against ischemic heart injury. Our data show that flocalin is indeed an effective opener of cardiac-type K_ATP-s, and that this effect underlies its cardioprotective properties. However, flocalin is also able to partially block sodium and calcium channels, which should be considered when establishing its therapeutic doses. The data obtained in native cardiomyocytes and bladder smooth muscle cells have already been published (see relevant publications). As a next step we aim to test the specificity of the flocalin action on different subtypes of recombinant, heterologously expressed K_ATP-channels.

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Expression, biophysical properties, pharmacology and epigenetic regulation of low-threshold calcium channels in norm and in experimental abscess epilepsy

Low voltage-activated (LVA) calcium channels, also referred to as T-type calcium channels, are characterized by a number of biophysical properties that significantly differentiate them from other types of voltage-gated calcium channels (VGCCs). Three subtypes of LVA channels, namely Cav3.1, Cav3.2 and Cav3.3, have been identified on molecular level, each of which is encoded by a separate gene with specific expression in various tissues and cell types. Accordingly, the functional significance of each LVA-channel subtype may be quite unique and not always obvious, which makes the study of these channels very important. In our interest to the LVA calcium channels, we focused on three main directions:

1. The study of how LVA channels discriminate various polyvalent cations in terms of either passing them through or being blocked by them;
2. Determining potential factors that may regulate expression of LVA-channel subtypes;
3. Establishing the role of LVA channels in epileptogenesis.

Our data obtained on Cav3.1, Cav3.2, Cav3.3 channels heterologously expressed in Xenopus oocytes revealed that these channels nearly similar pass Ca²⁺, Sr²⁺ and Ba²⁺, and that under physiological conditions they are also noticeably permeable to Na+. Blockade of these channels by some of the transition polyvalent cations, particularly Ni²⁺, require interaction with at least three channel's binding sites. Studies of different LVA-channel subtypes in the thalamus nuclei of normal rats in ontogenesis and rats with absence epilepsy phenotype (WAG/Rij strain) showed that the latter is accompanied by an increase in the expression of predominantly Cav3.1 channel and that the regulation of expression of various subtypes, both in ontogenesis and in pathologies, may be regulated by microRNA, miR-1 (see relevant publications).

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