Metabolic Reprogramming of Trophoblast Cells in Response to Hypoxia.

Hypoxia of trophoblast cells is an important regulator of normal development of the placenta. However, some pathological states associated with hypoxia, e.g. preeclampsia, impair the functions of placental cells. Oxyquinoline derivative inhibits HIF-prolyl hydroxylase by stabilizing HIF-1 transcription complex, thus modeling cell response to hypoxia. In human choriocarcinoma cells BeWo b30 (trophoblast model), oxyquinoline increased the expression of a core hypoxia response genes along with up-regulation of NOS3, PDK1, and BNIP3 genes and down-regulation of the PPARGC1B gene. These changes in the expression profile attest to activation of the metabolic cell reprogramming mechanisms aimed at reducing oxygen consumption by enabling the switch from aerobic to anaerobic glucose metabolism and the respective decrease in number of mitochondria. The possibility of practical use of the therapeutic properties of oxyquinoline derivatives is discussed.

New Experimental Models of Retinal Degeneration for Screening Molecular Photochromic Ion Channel Blockers.

Application of molecular photochromic ion channel blockers to recover the visual function of a degenerated retina is one of the promising trends in photopharmacology. To this day, several photochromic azobenzene-based compounds have been proposed and their functionality has been demonstrated on cell lines and knockout mouse models. Further advance necessitates testing of the physiological activity of a great number of new compounds. The goal of this study is to propose animal models of photoreceptor degeneration that are easier to obtain than knockout mouse models but include the main features required for testing the physiological activity of molecular photoswitches. Two amphibian-based models were proposed. The first model was obtained by mechanical deletion of the photoreceptor outer segments. The second model was obtained by intraocular injection of tunicamycin to induce the degeneration of rods and cones. To test our models, we used 2-[(4-{(E)-[4-(acryloylaminophenyl]diazenyl}phenyl)amino]-N,N,N-triethyl-2-oxoethanammonium chloride (AAQ), one of the compounds that have been studied in other physiological models. The electroretinograms recorded from our models before and after AAQ treatment are in agreement with the results obtained on knockout mouse models and reported in other studies. Hence, the proposed models can be used for primary screening of molecular photochromic ion channel blockers.

[Role of dopamine as a regulator of vertebrate photoreceptors].

Numerous and profound cyclical changes in retina functioning during a 24-hour daily cycle are largely determined by the influence of two neuromodulators--melatonin and dopamine. Do- pamine and melatonin form a reciprocal pair by mutually inhibiting the synthesis of each other, and they release into extracellular space of the retina approximately in antiphase. Dopamine is cyclically synthesized by special populations of dopaminergic amacrine cells in the retina and its content increases during the day and decreases at night. Like melatonin, dopamine affects all the major cell types of the outer and inner retinal layers. Activation of dopamine D1- and D2-type receptors regulate the activity of protein kinase A and the intracellular concentration of cAMP, and may trigger other regulatory pathways, including activation of phospholipase C. In photorecep- tors, dopamine acting on D2-type receptors reduces cAMP concentration, suppresses melatonin synthesis and regulates the conduction of gap junctions between rods and cones, depending on the phase ofthe light cycle. By decreasing the concentration of cAMP, dopamine could also be a regu- lator of the phototransduction cascade and other cellular functions of the photoreceptor. Here we review some of these possibilities. Key words: dopamine, dopamine receptors, cAMP, retina, photoreceptor, circadian rhythms, protein kinase A.

[cAMP as a regulator of the phototransduction cascade].

Until recently, it has generally been believed that cyclic AMP plays an important role in supporting circadian cycles in the vertebrate retina, but does not directly control the photoreceptors' phototransduction cascade. However, the cAMP levels in photoreceptors oscillate during the day/night cycle, and the cAMP turnover in photoreceptors may be light-dependent. Thus it is natural to suggest that the cAMP-dependent protein phosphorylation may be a mechanism of tuning phototransduction to lighting conditions. In the present review, we summarize available information on the structure and operation of the retinal pacemaker, role(s) of cAMP in its functioning, and identified intracellular targets that could be controlled by cAMP. We discuss our recent results that show that cAMP changes do regulate the phototransduction cascade. This regulation may substantially extend the range of photoreceptor's adaptation by increasing its sensitivity at night, and reducing the sensitivity in bright light.