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    Apelin has inhibitory effect of endothelium-independent relaxation in the human internal mammary artery
    (2019) Kacar, Emine; Burma, Oktay; Serhatlioglu, Ihsan; Ulker, Nazife; Uysal, Ayhan; Yardimci, Ahmet; Kelestimur, Haluk
    Aim: Apelin has important effects on the circulatory system and heart. The main aim of this study was to investigate the effects of apelin-13 on the contraction induced by norepinephrine (NE), and the endothelium-independent relaxation induced by sodium nitroprusside (SNP) in human internal mammary artery (IMA) obtained from patients undergoing coronary artery bypass grafting (CABG) surgery. Material and Methods: IMA rings, obtained from patients undergoing CABG surgery, were suspended in isolated tissue baths containing Krebs-Henseleit solution, which were continuously gassed with 95% O2 and 5% CO2 at 37°C. Results: The IMA rings were pre-contracted with increasing concentrations of norepinephrine (NE 10-9–10-4 mol/l) and the endothelium-independent relaxation responses to sodium nitroprusside (SNP) were studied. Apelin-13 (10 μM) caused a dosedependent relaxation in NE pre-contracted IMA rings. Apelin also facilitated the endothelium-independent relaxation induced by SNP. Conclusion: According to the results, apelin facilitated the endothelium-independent relaxation and inhibited the contractile activity of IMA. These results suggest that apelin may be a physiological agent against the deterioration of vascular elasticity caused by endothelial damage especially in atherosclerotic cardiac patients and hypertensive patients.
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    Effects of Peripheral Administration of Kisspeptin on Pubertal Maturation and Serum Leptin Levels in Female Rats
    (Ortadogu Ad Pres & Publ Co, 2011) Alcin, Ergul; Ozcan, Mete; Ayar, Ahmet; Yilmaz, Bayram; Turkoz, Yusuf; Kelestimur, Haluk
    Objective: The aim of this study was to investigate the effects of exogenous kisspeptin on pubertal maturation in immature female rats. Material and Methods: Wistar female rats were weaned when they were 21 days old. The rats were divided into two groups. Controls (n=10) received saline only (1 ml/kg). Experimental rats (n=9) were intraperitoneally injected with daily 100 nmol kisspeptin-10 between 09.00h-10.00h a.m. starting from the day 26. Body weight and food intake were daily determined, and vaginal opening (VO) was daily monitored starting from day 26. The animals were decapitated when the first diestrus was determined by vaginal smears. Upon decapitation, serum was separated and stored at -20 degrees C until measurement of leptin, luteinizing hormone (LH) and estradiol. Uterus and ovaries were dissected out and weighed. Results: Intraperitoneal injection of 100 nmol kisspeptin-10 did not change median VO ages. There were no differences in food intake, and percentages of body weight change, between control and kisspeptin groups during the experimental period. Kisspeptin administration elicited significant (P<0.01) increases in uterus weight over control values. Serum leptin levels were significantly lower (P<0.05) in kisspeptin-treated group compared to vehicle group. Kisspeptin administration increased (P<0.05) serum LH and estradiol levels. Conclusion: Chronic peripheral administration of kisspeptin-10 does not advance puberty onset as estimated from the date of vaginal opening, but potentiates other conventional indices of maturation of reproductive axis such as elevated uterine weight and increased serum levels of LH and estradiol.
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    Kisspeptin antagonist prevents RF9-induced reproductive changes in female rats
    (Bioscientifica Ltd, 2015) Sahin, Zafer; Canpolat, Sinan; Ozcan, Mete; Ozgocer, Tuba; Kelestimur, Haluk
    The aim of this study was to determine the modulatory effects of peptide 234 (p234) (an antagonist of GPR54 receptors) on kisspeptin and RF9 (an RFamide-related peptide antagonist)-induced changes in reproductive functions and energy balance in female rats. Female Sprague-Dawley rats were weaned on postnatal day (pnd) 21. The animals were intracerebroventricularly cannulated under general anesthesia on pnd 23. Groups of female rats were injected with kisspeptin, RF9, p234, kisspeptin plus p234, or RF9 plus p234, daily. The experiments were ended on the day of first diestrus following pnd 60. Kisspeptin or RF9 alone advanced vaginal opening (VO), which was delayed by administration of kisspeptin antagonist alone. In the rats given kisspeptin plus p234 or RF9 plus p234, VO was not different from control rats. Kisspeptin and RF9 elicited significant elevations in circulating LH levels. Coadministrations of kisspeptin or RF9 with p234 decreased LH levels significantly. The use of p234 alone did not cause any significant change in LH secretion. Kisspeptin decreased both food intake and body weight while RF9 decreased only food intake without affecting body weight. The effects of kisspeptin on energy balance were also reversed by central administration of p234. In conclusion, kisspeptin antagonist, p234, modulates the effects of kisspeptin on reproductive functions and energy balance, whereas RF9 seems to exert only its effects on reproductive functions by means of GPR54 signaling in female rats.
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    Kisspeptin-10 elicits triphasic cytosolic calcium responses in immortalized GT1-7 GnRH neurones
    (Elsevier Ireland Ltd, 2011) Ozcan, Mete; Alcin, Ergul; Ayar, Ahmet; Yilmaz, Bayram; Sandal, Suleyman; Kelestimur, Haluk
    Kisspeptins, which are alternatively called as metastin since they were originally identified as products of metastasis suppressor gene KiSS-1, are the natural ligands for the G protein-coupled receptor 54 (GPR54). Kisspeptins are the most potent activators of hypothalamic-pituitary-gonadal (HPG) axis reported to date. The pulsatile pattern of GnRH release, which results in the intermittent release of gonadotropic hormones from the pituitary, has a critical importance for reproductive function but the factors responsible from this release pattern are not known. Therefore, the pattern of kisspeptin-induced intracellular signaling and the role of PKC in the intracellular signaling cascade were investigated by fluorescence calcium imaging using the immortalized GnRH-secreting GT1-7 hypothalamic neurons. Kisspeptin-10 caused a triphasic change characterized by an initial small increase followed by a significant decrease and increase in intracellular free calcium concentrations ([Ca2+](i)). The changes in [Ca2+](i) were significantly attenuated by pre-treatment with protein kinase C inhibitor. The compatibility of appeared mirrored-patterns of kisspeptin-10-induced changes in [Ca2+](i) concentrations in these neurons and GnRH secretion confirm the importance of intracellular calcium flux downstream from GPR54 through PKC signaling pathway. (C) 2011 Elsevier Ireland Ltd. All rights reserved.
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    Melatonin elicits protein kinase C-mediated calcium response in immortalized GT1-7 GnRH neurons
    (Elsevier Science Bv, 2012) Kelestimur, Haluk; Ozcan, Mete; Kacar, Emine; Alcin, Ergul; Yilmaz, Bayram; Ayar, Ahmet
    Melatonin is suggested to have effects on hypothalamic-pituitary-gonadal (HPG) axis. The pulsatile pattern of GnRH release, which results in the intermittent release of gonadotropic hormones from the pituitary, has a critical importance for reproductive function but the factors responsible from this release pattern are not known. Calcium is a second messenger involved in hormone release. Therefore, investigation of the effects of melatonin on intracellular free calcium levels ([Ca2+](i)) would provide critical information on hormone release in immortalized GnRH neurons. The pattern of melatonin-induced intracellular calcium signaling was investigated by fluorescence calcium imaging using the immortalized GnRH-secreting GT1-7 hypothalamic neurons. Melatonin caused a significant increase in [Ca2+](i), which was greatly blocked by luzindole, a melatonin antagonist, or attenuated by pre-treatment with protein kinase C inhibitor. This study suggests that melatonin seems to have a direct effect on GnRH neurons. (C) 2011 Elsevier B.V. All rights reserved.
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    Oxytocin activates calcium signaling in rat sensory neurons through a protein kinase C-dependent mechanism
    (Springer, 2014) Ayar, Ahmet; Ozcan, Mete; Alcin, Ergul; Serhatlioglu, Ihsan; Ozcan, Sibel; Kutlu, Selim; Kelestimur, Haluk
    In addition to its well-known effects on parturition and lactation, oxytocin (OT) plays an important role in modulation of pain and nociceptive transmission. But, the mechanism of this effect is unclear. To address the possible role of OT on pain modulation at the peripheral level, the effects of OT on intracellular calcium levels ([Ca2+](i)) in rat dorsal root ganglion (DRG) neurons were investigated by using an in vitro calcium imaging system. DRG neurons were grown in primary culture following enzymatic and mechanical dissociation of ganglia from 1- or 2-day-old neonatal Wistar rats. Using the fura-2-based calcium imaging technique, the effects of OT on [Ca2+](i) and role of the protein kinase C (PKC)-mediated pathway in OT effect were assessed. OT caused a significant increase in basal levels of [Ca2+](i) after application at the doses of 30 nM (n=34, p<0.01), 100 nM (n=41, p<0.001) and 300 nM (n=46, p<0.001). The stimulatory effect of OT (300 nM) on [Ca2+](i) was persistent in Ca2+-free conditions (n=56, p<0.01). Chelerythrine chloride, a PKC inhibitor, significantly reduced the OT-induced increase in [Ca2+](i) (n=28, p<0.001). We demonstrated that OT activates intracellular calcium signaling in cultured rat primary sensory neurons in a dose-and PKC-dependent mechanism. The finding of the role of OT in peripheral pain modification may serve as a novel target for the development of new pharmacological strategies for the management of pain.
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    Pinealectomy alters ıfn-gamma and ıl-10 levels in primary thymocyte culture of rats
    (C m b assoc, 34 boulevard solferıno, 86000 poıtıers, france, 2018) Sahin, Zafer; Sandal, Suleyman; Yilmaz, Bayram; Bulmus, Ozgur; Ozdemir, Gokcen; Kutlu, Selim; Godekmerdan, Ahmet; Kelestimur, Haluk
    Melatonin, produced mainly by the pineal gland, has an immunomodulatory role. However, the effects of the pineal gland and/or melatonin on thymus cytokine levels such as interferon-gamma (IFN-gamma), interleukin (IL)-4, and IL-10 are not well known. Twenty-one male Wistar rats (220-250 gr) were randomly divided into three groups (n=7): intact control, sham, and pinealectomy. Primary thymocyte cultures were prepared from each group and dispensed into well plates as Control, DMSO (or vehicle), Sham-pinealectomy, Pinealectomy, Pinealectomy+10 mu M melatonin, and Pinealectomy+100 mu M melatonin. IFN-gamma, IL-4, and IL-10 concentrations were measured in the thymocytes (as nonstimulated and Concanavalin A-stimulated) after 24 h. IFN-gamma levels significantly increased and IL-10 levels significantly decreased in both media prepared from pinealectomized rats. There was no significant difference between the groups in terms of IL-4. In the pinealectomy+100 mu M melatonin group, IFN-gamma and IL-10 levels did not differ from the pinealectomy group. However, the dose of 100 mu M melatonin caused a decrease in levels of IFN-gamma in both thymocyte media and an increase in the concentration of IL-10 in Concanavalin A-stimulated thymocytes. In conclusion, pineal gland and or melatonin affect IFN-gamma and IL-10 levels in the thymus gland.