scholarly journals IGF-I Signaling Is Essential for FSH Stimulation of AKT and Steroidogenic Genes in Granulosa Cells

2013 ◽  
Vol 27 (3) ◽  
pp. 511-523 ◽  
Author(s):  
Ping Zhou ◽  
Sarah C. Baumgarten ◽  
Yanguang Wu ◽  
Jill Bennett ◽  
Nicola Winston ◽  
...  
Keyword(s):  
Granulosa Cells ◽  
Akt Phosphorylation ◽  
Akt Activation ◽  
In Vivo Experiments ◽  
Igf I ◽  
First Time ◽  
Cyp19 Expression ◽  
Stimulation Of ◽  
Steroidogenic Genes

Abstract FSH and IGF-I synergistically stimulate gonadal steroid production; conversely, silencing the FSH or the IGF-I genes leads to infertility and hypogonadism. To determine the molecular link between these hormones, we examined the signaling cross talk downstream of their receptors. In human and rodent granulosa cells (GCs), IGF-I potentiated the stimulatory effects of FSH and cAMP on the expression of steroidogenic genes. In contrast, inhibition of IGF-I receptor (IGF-IR) activity or expression using pharmacological, genetic, or biochemical approaches prevented the FSH- and cAMP-induced expression of steroidogenic genes and estradiol production. In vivo experiments demonstrated that IGF-IR inactivation reduces the stimulation of steroidogenic genes and follicle growth by gonadotropins. FSH or IGF-I alone stimulated protein kinase B (PKB), which is also known as AKT and in combination synergistically increased AKT phosphorylation. Remarkably, blocking IGF-IR expression or activity decreased AKT basal activity and abolished AKT activation by FSH. In GCs lacking IGF-IR activity, FSH stimulation of Cyp19 expression was rescued by overexpression of constitutively active AKT. Our findings demonstrate, for the first time, that in human, mouse, and rat GCs, the well-known stimulatory effect of FSH on Cyp19 and AKT depends on IGF-I and on the expression and activation of the IGF-IR.

scholarly journals Prostaglandin F2α Represses IGF-I-Stimulated IRS1/Phosphatidylinositol-3-Kinase/AKT Signaling in the Corpus Luteum: Role of ERK and P70 Ribosomal S6 Kinase

2010 ◽  
Vol 24 (3) ◽  
pp. 632-643 ◽  
Author(s):  
Edward Arvisais ◽  
Xiaoying Hou ◽  
Todd A. Wyatt ◽  
Koumei Shirasuna ◽  
Heinrich Bollwein ◽  
...  
Keyword(s):  
Corpus Luteum ◽  
Prostaglandin F2α ◽  
Serine Phosphorylation ◽  
Phosphatidylinositol 3 Kinase ◽  
Akt Activation ◽  
Diminished Capacity ◽  
Igf I ◽  
In Vitro Treatment

Abstract Little is known about the early intracellular events that contribute to corpus luteum regression. Experiments were designed to determine the effects of prostaglandin F2α (PGF2α) on phosphatidylinositol-3-kinase (PI3K)/Akt signaling in the corpus luteum in vivo and in vitro. Treatment of midluteal-phase cows with a luteolytic dose of PGF2α resulted in a rapid increase in ERK and mammalian target of rapamycin (mTOR)/p70 ribosomal protein S6 kinase (p70S6K1) signaling and a rapid suppression of Akt phosphorylation in luteal tissue. In vitro treatment of primary cultures of luteal cells with PGF2α also resulted in an increase in ERK and mTOR/p70S6K1 signaling and a diminished capacity of IGF-I to stimulate PI3K, Akt, and protein kinase C ζ activation. Accounting for the reductions in PI3K and Akt activation observed in response to PGF2α treatment, we found that PGF2α promoted the phosphorylation of serine residues (307, 612, 636) in the insulin receptor substrate 1 (IRS1) peptide sequence in vivo and in vitro. Serine phosphorylation of IRS1 was associated with reduced formation of IGF-I-stimulated IRS1/PI3Kp85 complexes. Furthermore, treatment with inhibitors of the MAPK kinase 1/ERK or mTOR/p70S6K1 signaling pathways prevented PGF2α-induced serine phosphorylation of IRS1 and abrogated the inhibitory actions of PGF2α on Akt activation. Taken together, these experiments provide compelling evidence that PGF2α treatment stimulates IRS1 serine phosphorylation, which may contribute to a diminished capacity to respond to IGF-I. It seems likely that the rapid changes in phosphorylation events are among the early events that mediate PGF2α-induced corpus luteum regression.

scholarly journals Fitness of Isolates of Phytophthora capsici Resistant to Mefenoxam from Squash and Pepper Fields in North Carolina

Plant Disease ◽  
2008 ◽  
Vol 92 (10) ◽  
pp. 1439-1443 ◽  
Author(s):  
Adalberto C. Café-Filho ◽  
Jean Beagle Ristaino
Keyword(s):  
North Carolina ◽  
Phytophthora Capsici ◽  
Colony Growth ◽  
Relative Fitness ◽  
In Planta ◽  
Phytophthora Blight ◽  
In Vivo Experiments ◽  
First Time

Despite the wide adoption of mefenoxam (Ridomil Gold EC) for vegetables in North Carolina, the incidence of Phytophthora blight on pepper (Capsicum annuum) and squash (Cucurbita pepo) is high. Seventy-five isolates of Phytophthora capsici were collected in five pepper and one squash field in order to assess mefenoxam sensitivity. The relative fitness of resistant and sensitive isolates was contrasted in vitro by their respective rates of colony growth and their ability to produce sporangia in unamended V8 juice agar medium. In in vivo experiments, the aggressiveness of isolates on pepper was evaluated. The frequency of resistant isolates in North Carolina populations was 63%, considerably higher than resistance levels in areas where mefenoxam is not widely adopted. Resistant isolates grew on amended media at rates >80 to 90% and >100% of the nonamended control at 100 μg ml-1 and 5 μg ml-1, respectively. Sensitive isolates did not growth at 5 or 100 μg ml-1. All isolates from three fields, including two pepper and a squash field, were resistant to mefenoxam. Populations from other fields were composed of either mixes of sensitive and resistant isolates or only sensitive isolates. Response to mefenoxam remained stable during the course of in vitro and in planta experiments. Occurrence of a mefenoxam-resistant population of P. capsici on squash is reported here for the first time in North Carolina. When measured by rate of colony growth, sporulation in vitro, or aggressiveness in planta, fitness of resistant isolates was not reduced. Mefenoxam-resistant isolates from squash were as aggressive on pepper as sensitive or resistant pepper isolates. These results suggest that mefenoxam-resistant populations of P. capsici are as virulent and fit as sensitive populations.

scholarly journals Activation of the Lutropin/Choriogonadotropin Receptor Inhibits Apoptosis of Immature Leydig Cells in Primary Culture

Endocrinology ◽  
2009 ◽  
Vol 150 (8) ◽  
pp. 3766-3773 ◽  
Author(s):  
Ping Tai ◽  
Koji Shiraishi ◽  
Mario Ascoli
Keyword(s):  
Leydig Cells ◽  
Thymidine Incorporation ◽  
Primary Cultures ◽  
Drug Induced ◽  
Immature Rat ◽  
Akt Phosphorylation ◽  
Igf I ◽  
Epidermal Growth ◽  
Induced Apoptosis ◽  
Stimulation Of

We used proliferating primary cultures of immature rat Leydig cells expressing the recombinant human LH/choriogonadotropin (CG) receptor (LHR) to test the hypothesis that activation of this receptor inhibits apoptosis. We also compared the effects of LH/CG with epidermal growth factor (EGF) and IGF-I because these have been previously shown to stimulate proliferation and/or inhibit apoptosis in Leydig cells. Human CG (hCG), EGF, and IGF-I stimulated the phosphorylation of ERK1/2 and Akt in primary cultures of immature rat Leydig cells. These three hormones also robustly stimulated thymidine incorporation and inhibited drug-induced apoptosis. Using selective inhibitors of ERK1/2 (UO126) or Akt phosphorylation (LY294002), we show that the ERK1/2 and Akt cascades are both involved in the hCG- and EGF-dependent proliferation of Leydig cells, but only the ERK1/2 cascade is involved in their antiapoptotic actions. The same strategy showed that the proliferative and antiapoptotic actions of IGF-I are mediated entirely by the Akt pathway. These results show that activation of the LHR inhibits apoptosis in Leydig cells and that it does so through stimulation of the ERK1/2 pathway.

scholarly journals A Novel Inhibitory Protein in Adipose Tissue, the Aldo-Keto Reductase AKR1B7: Its Role in Adipogenesis

Endocrinology ◽  
2007 ◽  
Vol 148 (5) ◽  
pp. 1996-2005 ◽  
Author(s):  
Julien Tirard ◽  
Johann Gout ◽  
Anne Marie Lefrançois-Martinez ◽  
Antoine Martinez ◽  
Martine Begeot ◽  
...  
Keyword(s):  
Stromal Cells ◽  
Primary Cultures ◽  
Inhibitory Protein ◽  
Adipose Stromal Cells ◽  
Adipose Tissues ◽  
Detoxification Enzyme ◽  
In Vivo Experiments ◽  
First Time

The aldo-keto reductase 1B7 (AKR1B7) encodes an aldose-reductase that has been reported as a detoxification enzyme until now. We have demonstrated that AKR1B7 is differently expressed in various mouse white adipose tissues depending on their location. Its expression is associated with a higher ratio of preadipocytes vs. adipocytes. The cells that express AKR1B7 did not contain lipid droplets, and the expression level of akr1b7 was very low in mature adipocytes. We have defined the role of AKR1B7 in adipogenesis using either primary cultures of adipose stromal cells (containing adipocyte precursors) or the 3T3-L1 cell line. Under the same differentiation conditions, adipose stromal cells from tissues that expressed AKR1B7 had a decreased capacity to accumulate lipids compared with those that did not express it. Moreover, the overexpression of sense or antisense AKR1B7 in 3T3-L1 preadipocytes inhibited or accelerated, respectively, their rate of differentiation into adipocytes. In vivo experiments demonstrated that AKR1B7-encoding mRNA expression decreased in adipose tissues from mice where obesity was induced by a high-fat diet. All these results attributed for the first time a novel role to AKR1B7, which is the inhibition of adipogenesis in some adipose tissues.

scholarly journals Cyclo-oxygenase 2 expression impairs serum-withdrawal-induced apoptosis in liver cells

2006 ◽  
Vol 398 (3) ◽  
pp. 371-380 ◽  
Author(s):  
Amalia Fernández-Martínez ◽  
Belén Mollá ◽  
Rafael Mayoral ◽  
Lisardo Boscá ◽  
Marta Casado ◽  
...  
Keyword(s):  
Fluorescent Protein ◽  
Liver Cells ◽  
Cell Cycle Distribution ◽  
Hepatitis C Infection ◽  
Extrinsic Pathway ◽  
Akt Phosphorylation ◽  
Liver Cancers ◽  
Cox 2 ◽  
Stimulation Of

We have investigated the mechanism of COX-2 (cyclo-oxygenase 2)-dependent inhibition of apoptosis in liver, a key pathway underlying proliferative actions of COX-2 in liver cancers, cirrhosis, chronic hepatitis C infection and regeneration after partial hepatectomy. Stable expression of COX-2 in CHL (Chang liver) cells induced proliferation, with an increase in the proportion of cells in S-phase, but no other significant changes in cell-cycle distribution. This was associated with a marked inhibition of the apoptotic response to serum deprivation, an effect mimicked by treating empty-vector-transfected control cells (CHL-V cells) with prostaglandin E2 and prevented in COX-2-expressing cells (CHL-C cells) treated with selective inhibitors of COX-2. Serum-deprived CHL-V cells displayed several indicators of activation of intrinsic apoptosis: caspases 9 and 3 activated within 6 h and caspase 8 within 18 h, Bax expression was induced, cytochrome c was released to the cytosol, and PARP-1 [poly(ADP-ribose) polymerase 1] cleavage was evident in nuclei. COX-2 expression blocked these events, concomitant with reduced expression of p53 and promotion of Akt phosphorylation, the latter indicating activation of survival pathways. CHL cells were resistant to stimulation of the extrinsic pathway with anti-Fas antibody. Moreover, in vivo expression of GFP (green fluorescent protein)-labelled COX-2 in mice by hydrodynamics-based transient transfection conferred resistance to caspase 3 activation and apoptosis induced by stimulation of Fas.

scholarly journals Blood pressure changes alter tracheobronchial cough: computational model of the respiratory-cough network and in vivo experiments in anesthetized cats

2011 ◽  
Vol 111 (3) ◽  
pp. 861-873 ◽  
Author(s):  
Ivan Poliacek ◽  
Kendall F. Morris ◽  
Bruce G. Lindsey ◽  
Lauren S. Segers ◽  
Melanie J. Rose ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Motor Pattern ◽  
Esophageal Pressure ◽  
Respiratory Neurons ◽  
Cycle Duration ◽  
In Vivo Experiments ◽  
Arterial Blood ◽  
Posterior Cricoarytenoid ◽  
Stimulation Of

We tested the hypothesis, motivated in part by a coordinated computational cough network model, that alterations of mean systemic arterial blood pressure (BP) influence the excitability and motor pattern of cough. Model simulations predicted suppression of coughing by stimulation of arterial baroreceptors. In vivo experiments were conducted on anesthetized spontaneously breathing cats. Cough was elicited by mechanical stimulation of the intrathoracic airways. Electromyograms (EMG) of inspiratory parasternal, expiratory abdominal, laryngeal posterior cricoarytenoid (PCA), and thyroarytenoid muscles along with esophageal pressure (EP) and BP were recorded. Transiently elevated BP significantly reduced cough number, cough-related inspiratory, and expiratory amplitudes of EP, peak parasternal and abdominal EMG, and maximum of PCA EMG during the expulsive phase of cough, and prolonged the cough inspiratory and expiratory phases as well as cough cycle duration compared with control coughs. Latencies from the beginning of stimulation to the onset of cough-related diaphragm and abdominal activities were increased. Increases in BP also elicited bradycardia and isocapnic bradypnea. Reductions in BP increased cough number; elevated inspiratory EP amplitude and parasternal, abdominal, and inspiratory PCA EMG amplitudes; decreased total cough cycle duration; shortened the durations of the cough expiratory phase and cough-related abdominal discharge; and shortened cough latency compared with control coughs. Reduced BP also produced tachycardia, tachypnea, and hypocapnic hyperventilation. These effects of BP on coughing likely originate from interactions between barosensitive and respiratory brainstem neuronal networks, particularly by modulation of respiratory neurons within multiple respiration/cough-related brainstem areas by baroreceptor input.

scholarly journals Granulosa cells of the cumulus oophorus are different from mural granulosa cells in their response to gonadotrophins and IGF-I

2001 ◽  
Vol 170 (3) ◽  
pp. 565-573 ◽  
Author(s):  
F Khamsi ◽  
S Roberge
Keyword(s):  
Granulosa Cells ◽  
Cumulus Cells ◽  
Saline Control ◽  
Cell Replication ◽  
Progesterone Secretion ◽  
Igf I ◽  
Negative Effect ◽  
Positive Effect

There are two types of granulosa cells: those which surround the oocyte are cumulus cells (CC) and those which surround the antrum are mural granulosa cells (MGC). These cells are under the influence of several hormones and growth factors, the most important of which are gonadotrophins and IGF-I. In this article, we report novel observations on the differences between these two types of granulosa cells and their interaction with gonadotrophins and IGF-I. We were able to conduct physiological studies on the role of IGF-I by using an analogue of IGF-I which does not bind to IGF-I-binding proteins (LR3-IGF-I). Immature rats received saline, equine chorionic gonadotrophin (eCG), LR3-IGF-I or eCG plus LR3-IGF-I by infusion using a pump from 24-29 days of age. The rats were killed and the ovaries removed. Surface follicles were punctured and MGC and oocyte cumulus complexes were removed. These were cultured in saline (control) and in three different doses of FSH. Cell replication was assessed by 3H-thymidine incorporation and differentiation was evaluated by the measurement of progesterone secretion. It was noted that CC replicated ten times more than MGC. Similarly, progesterone secretion by CC was six times more than by MGC. In vivo exposure to gonadotrophins (eCG) positively influenced in vitro treatment with FSH in both cell types. This phenomenon was observed in both cell replication and progesterone secretion. The IGF-I analogue had a positive effect on cell replication of MGC but a negative effect on the cell replication of CC. With respect to progesterone secretion, the IGF-I analogue had a negative effect on CC but a positive effect on MGC. In conclusion, CC behaved differently from MGC in response to gonadotrophins and the IGF-I analogue. IGF-I and FSH acted additively, synergistically or antagonistically in different circumstances.

scholarly journals beta-Naphthoflavone abolishes interrenal sensitivity to ACTH stimulation in rainbow trout

1998 ◽  
Vol 157 (1) ◽  
pp. 63-70 ◽  
Author(s):  
JM Wilson ◽  
MM Vijayan ◽  
CJ Kennedy ◽  
GK Iwama ◽  
TW Moon
Keyword(s):  
Cytochrome P450 ◽  
Rainbow Trout ◽  
Acth Stimulation ◽  
Rainbow Trout Oncorhynchus Mykiss ◽  
Treated Fish ◽  
First Time ◽  
Hepatic Cytochrome ◽  
Stimulation Of

We report for the first time that beta-naphthoflavone (BNF) abolishes ACTH stimulation of cortisol production in rainbow trout (Oncorhynchus mykiss). There was significantly higher hepatic cytochrome P450 content and ethoxyresorufin O-de-ethylase and uridine-5'-diphosphoglucuronic acid transferase activities in BNF-treated fish than in sham-treated controls. BNF did not significantly affect either plasma turnover or tissue distribution of [3H]cortisol-derived radioactivity. Hepatic membrane fluidity and hepatocyte capacity for cortisol uptake were not altered by BNF as compared with the sham-treated fish. These results taken together suggest that BNF does not affect cortisol-clearance mechanisms in trout. A 3 min handling disturbance period elicited a plasma cortisol response in the sham-treated fish; however, the response in the BNF-treated fish was muted and significantly lower than in the sham fish. This in vivo response corroborates the lack of interrenal sensitivity to ACTH in vitro in the BNF-treated fish, suggesting that BNF affects the ACTH pathway in trout. Our results suggest the possibility that cytochrome P450-inducing compounds may affect cortisol dynamics by decreasing interrenal responsiveness to ACTH stimulation in fish, thereby impairing the physiological responses that are necessary for the animal to cope with the stressor.

β-Adrenoceptors mediate inhibition of lipolysis in adipocytes of tilapia (Oreochromis mossambicus)

2002 ◽  
Vol 282 (2) ◽  
pp. E318-E325 ◽  
Author(s):  
Gerjanne J. Vianen ◽  
Peter P. Obels ◽  
Guido E. E. J. M. van den Thillart ◽  
Johan Zaagsma
Keyword(s):  
Adipose Tissue ◽  
Fatty Acid ◽  
Free Fatty Acid ◽  
Plasma Free Fatty Acid ◽  
Oreochromis Mossambicus ◽  
Plasma Norepinephrine ◽  
In Vivo Experiments ◽  
First Time

The regulation of triglyceride mobilization by catecholamines was investigated in the teleost fish Oreochromis mossambicus (tilapia) in vivo and in vitro. In vitro experiments were carried out with adipocytes that were isolated for the first time from fish adipose tissue. For the in vivo experiments, cannulated tilapia were exposed to stepwise decreasing oxygen levels (20, 10, and 5% air saturation; 3.9, 1.9, and 1.0 kPa Po 2, respectively), each level being maintained for 2 h. Blood samples were taken at timed intervals and analyzed for plasma lactate, glucose, free fatty acids, epinephrine, norepinephrine, and cortisol. Hypoxia exposure did not change plasma epinephrine levels. In contrast, the plasma norepinephrine concentration markedly increased at all hypoxia levels. Over the same period, plasma free fatty acid levels showed a significant continuous decrease, suggesting that norepinephrine is responsible for the reduced plasma free fatty acid concentration, presumably through inhibition of lipolysis in adipose tissue. To elucidate the mechanism, adipocytes were isolated from mesenteric adipose tissue of tilapia and incubated with 1) norepinephrine, 2) norepinephrine + phentolamine (α1,α2-antagonist), 3) isoproterenol (nonselective β-agonist), 4) isoproterenol + timolol (β1,β2-antagonist), 5) norepinephrine + timolol, and 6) BRL-35135A (β3-agonist). The results demonstrate for the first time that norepinephrine and isoproterenol suppress lipolysis in isolated adipocytes of tilapia. The effect of norepinephrine is not mediated through α2-adrenoceptors but, like isoproterenol, via β-adrenoceptors. Furthermore, this study provides strong indications that β3-adrenoceptors are involved.

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