Jolanta Gutkowska

B-Type Natriuretic Peptide Receptor Expression and Activity Are Hormonally Regulated in Rat Ovarian Cells1

Natriuretic peptides form a family of structurally related peptides known to regulate salt and water homeostasis and to cause vasodilation. Synthesis of atrial (ANP), brain (BNP), and C-type (CNP) natriuretic peptides occurs mainly in the heart and brain and has been identified recently in the female reproductive tract. The expression of ANP and CNP as well as their cognate guanylyl cyclase receptors (NPR-A and NPR-B, respectively) have been detected in the rat ovary. We have shown previously that the expression of the natriuretic peptides and their receptors in the rat ovary appears to be modulated by the estrous cycle. In the present study we have evaluated the expression of the natriuretic peptide system (peptide and receptor) in ovarian cells (granulosa and thecal-interstitial cells) obtained from immature female rats treated with either diethylstilbestrol (DES), an estrogen analog, or equine CG (eCG), a gonadotropin that possesses both LH and FSH activity. Using a whole cell RRA, we found that CNP bi...

Molecular mechanisms underlying oxytocin-induced cardiomyocyte protection from simulated ischemia-reperfusion.

Oxytocin (OT) stimulates cardioprotection. Here we investigated heart-derived H9c2 cells in simulated ischemia-reperfusion (I-R) experiments in order to examine the mechanism of OT protection. I-R was induced in an anoxic chamber for 2 hours and followed by 2u2009h of reperfusion. In comparison to normoxia, I-R resulted in decrease of formazan production by H9c2 cells to 63.5u2009±u20091.7% (MTT assay) and in enhanced apoptosis from 1.7u2009±u20090.3% to 2.8u2009±u20090.4% (Tunel test). Using these assays it was observed that treatment with OT (1-500u2009nM) exerted significant protection during I-R, especially when OT was added at the time of ischemia or reperfusion. Using the CM-H2DCFDA probe we found that OT triggers a short-lived burst in reactive oxygen species (ROS) production in cells but reduces ROS production evoked by I-R. In cells treated with OT, Western-blot revealed the phosphorylation of Akt (Thr 308, p-Akt), eNOS and ERK 1/2. Microscopy showed translocation of p-Akt and eNOS into the nuclear and perinuclear area and NO production in cells treated with OT. The OT-induced protection against I-R was abrogated by an OT antagonist, the Pi3K inhibitor Wortmannin, the cGMP-dependent protein kinase (PKG) inhibitor, KT5823, as well as soluble guanylate cyclase (GC) inhibitor, ODQ, and particulate GC antagonist, A71915. In conditions of I-R, the cells with siRNA-mediated reduction in OT receptor (OTR) expression responded to OT treatment by enhanced apoptosis. In conclusion, the OTR protected H9c2 cells against I-R, especially if activated at the onset of ischemia or reperfusion. The OTR-transduced signals include pro-survival kinases, such as Akt and PKG.

Atrial natriuretic peptide levels in brain venous outflow during cardiopulmonary bypass in humans: Evidence for extracardiac hormonal production☆

Atrial natriuretic peptide (ANP) is a hormone with an important role in the regulation of extracellular fluid volume. The ANP gene is not only expressed in the heart, but the high concentration of ANP in cardiac blood makes it difficult to demonstrate extraatrial hormonal secretion in vivo. This issue was addressed during complete cardiopulmonary bypass (CPB) in 13 patients undergoing elective cardiac surgery in whom ANP concentrations were followed in the internal jugular vein, representing largely brain venous outflow, as well as a peripheral vein and radial artery, after the heart and lungs were excluded from circulation. Plasma ANP levels in the peripheral venous circulation showed no significant changes during extracorporeal circulation, although they tended to decrease (from 6.75 +/- 2.16 fmol/mL to 4.76 +/- 0.69 fmol/mL; P greater than 0.05). ANP levels in the radial artery decreased significantly after the exclusion of the heart (from 16.84 +/- 3.51 fmol/mL to 6.83 +/- 0.97 fmol/mL; P less than 0.01). In contrast, ANP concentration in the internal jugular vein increased in 12 of 13 patients during the first 15 minutes of CPB (from 9.49 +/- 1.96 fmol/mL to 15.96 +/- 2.8 fmol/mL; P less than 0.01) and remained above the levels found simultaneously in other sampling sites during CPB. High-performance liquid chromatography analysis of plasma extracts showed multiple peaks of ANP, but the elution patterns of peripheral venous blood and brain outflow were similar. One of the immunoreactive peaks was located at the position of standard human ANP (Ser99-Met110-Tyr126).(ABSTRACT TRUNCATED AT 250 WORDS)

7A.02: CARDIOMYOPATHY IN OBESE AND DIABETIC MALE DB/DB MICE IS INHIBITED BY OXYTOCIN TREATMENT.

Objective: Obesity and diabetes enhance the risk of developing cardiovascular diseases and heart failure. The heart/cardiac oxytocin (OT) system was discovered by our group and shown to regulate cardiovascular cell survival pathways and cardioprotection. OT is also involved in the regulation of cardiac energy metabolism and cardiac OT receptor is downregulated in diabetes. Our hypothesis is that OT prevents development of diabetic cardiomyopathy. We evaluated whether chronic treatment with OT could prevent the metabolic and cardiac abnormalities associated with diabetes and obesity using the db/db mice. Design and method: Four-week-old C57BL/KsJ-db/db obese diabetic mice (db/db) and their lean control littermates (db/+) were treated with OT (125u200ang/kg/h) or saline during 12 weeks (nu200a=u200a10/group). Serial blood and tomography analysis were performed. Cardiac function was determined by echocardiography, and biochemical and histological heart and fat analysis were also performed. Results: Compared to db/+ mice, the saline-treated db/db mice developed obesity, hyperglycemia and hyperinsulinemia. These mice also exhibited a deficient cardiac OT/natriuretic system and developed systolic and diastolic dysfunction resulting from cardiomyocytes hypertrophy, fibrosis and apoptosis. These abnormalities were associated with increased ROS production, inflammation and suppressed AMP-kinase signaling pathway. The db/db mice displayed reduced serum levels of adiponectin and adipsin and elevated resistin. OT treatment increased circulating OT levels, significantly reduced serum resistin, body fat accumulation (19%: pu200a<u200a0.001), fasting blood glucose levels by (23%; pu200a<u200a0.001), and improved glucose tolerance and insulin sensitivity. OT also normalized cardiac OT receptors, ANP and BNP expressions and prevented systolic and diastolic dysfunction as well as cardiomyocytes hypertrophy, fibrosis and apoptosis. Furthermore, OT reduced cardiac oxidative stress and inflammation, and normalized the AMP-activated protein kinase signaling pathway. The complete normalization of cardiac structure and function by OT treatment in db/db mice contrasted with only partial improvement of hyperglycemia and hyperinsulinemia. Conclusions: The results indicate that chronic treatment with OT partially improves glucose and fat metabolism, reverses abnormal cardiac structural remodeling, preventing cardiac dysfunction in db/db mice. These observations clearly suggest a potential role for OT in replacement therapy for the prevention of cardiovascular complications of diabetes and obesity.