Donna B. Farley

Luteal maintenance during early pregnancy in the pig: Role for prostaglandin E2

We previously demonstrated that prostaglandin E2 (PGE) directly inhibits prostaglandin F2 alpha (PGF)-induced regression of individual pig corpora lutea (CL) in a dose dependent manner. The present experiments were conducted to 1) characterize and compare uterine secretion of PGE and PGF during the estrous cycle and early pregnancy and 2) evaluate the local effect of the conceptus on uterine prostaglandin secretion and associated CL function in unilaterally pregnant pigs. In Experiment 1, utero-ovarian venous blood samples were collected from two nonpregnant and two pregnant gilts at 3-h intervals from day 10 through 16 (first day of estrus or mating = day 0) for quantitation of uterine PGE and PGF secretion. In Experiment 2, gilts (n = 4) were made unilaterally pregnant on day 2, and utero-ovarian venous catheters were placed bilaterally to determine if differences in PGE and/or PGF secretion might account for the known luteotrophic/antiluteolytic effect of the gravid uterine horn on the CL of the ipsilateral ovary. During the estrous cycle (Experiment 1), pulsatile secretion of PGF increased markedly on day 13 and continued to increase through day 16. PGE secretion also increased from day 13 to 16 of the estrous cycle; however, concentrations of PGE remained at least 3-fold lower than those of PGF. In contrast to changes in non-mated gilts, prostaglandin secretion in mated gilts peaked earlier (day 11-12), with PGE predominating. Thereafter, both PGE and PGF secretion declined to basal levels where they remained through day 16 of pregnancy. During unilateral pregnancy (Experiment 2), PGF concentration in nongravid and gravid horns was similar (P > 0.8). In contrast, PGE concentrations were greater (P < 0.06) in utero-ovarian venous blood draining the gravid uterine horn. This increase in PGE was associated with enhanced CL function on the ipsilateral ovary as evidenced by an elevated progesterone content and concentration as well as increased CL weights. These data are consistent with a role for conceptus-associated increases in uterine PGE secretion in the local stimulation of luteal function during early pregnancy in the pig.

Social isolation is associated with elevated tumor norepinephrine in ovarian carcinoma patients

Noradrenergic pathways have been implicated in growth and progression of ovarian cancer. Intratumoral norepinephrine (NE) has been shown to increase with stress in an animal cancer model, but little is known regarding how tumor NE varies with disease stage and with biobehavioral factors in ovarian cancer patients. This study examined relationships between pre-surgical measures of social support, depressed mood, perceived stress, anxiety, tumor histology and tumor catecholamine (NE and epinephrine [E]) levels among 68 ovarian cancer patients. We also examined whether associations observed between biobehavioral measures and tumor catecholamines extended to other compartments. Higher NE levels were found in advanced stage (p=0.006) and higher grade (p=0.001) tumors. Adjusting for stage, grade, and peri-surgical beta blockers, patients with a perceived lack of social support had significantly higher tumor NE (β=-0.29, p=0.012). A similar trend was seen for social support and ascites NE (adjusting for stage, peri-surgical beta blockers and caffeine: β=-0.50, p=0.075), but not for plasma NE. Other biobehavioral factors were not related to tumor, ascites, or plasma NE (p values >0.21). Tumor E was undetectable in the majority of tumors and thus E was not further analyzed. In summary, these results suggest that tumor NE provides distinct information from circulating plasma concentrations. Tumor NE levels were elevated in relationship to tumor grade and stage. Low subjective social support was associated with elevated intratumoral NE. As beta-adrenergic signaling is related to key biological pathways involved in tumor growth, these findings may have implications for patient outcomes in ovarian cancer.

Furosemide induced release of prostaglandin E to increase renal blood flow.

Summary Levels of PGE in renal venous blood were found to be significantly elevated at the time RBF was increased by furosemide. Following indomethacin, a second dose of furosemide failed to increase RBF and levels of PGE in renal venous blood were not elevated. Levels of PGF and PGA were not affected by furosemide. The increase of PGE in renal venous blood at the time of renal dilation supports the hypothesis that furosemide increases RBF by releasing PGE. An intrarenal action of the released PGE is implied by this mechanism.

Dopamine Blocks Stress-Mediated Ovarian Carcinoma Growth

Purpose: Increased adrenergic activity in response to chronic stress is known to promote tumor growth by stimulating the tumor microenvironment. The focus of the current study was to determine whether dopamine, an inhibitory catecholamine, could block the effects of chronic stress on tumor growth. Experimental Design: Expression of dopamine receptors (DR1–DR5) was analyzed by reverse transcriptase-PCR and by Western blotting. In vitro effects of dopamine on cell viability, apoptosis, and migration were examined. For in vivo therapy, murine and human DR2-siRNAs were incorporated into chitosan nanoparticles (CH-NP). Results: In this model of chronic stress, tumoral norepinephrine levels remained elevated whereas dopamine levels were significantly decreased compared with nonstressed animals. Daily restraint stress resulted in significantly increased tumor growth in both immunodeficient (SKOV3ip1 and HeyA8) and immunocompetent (ID8) ovarian cancer models. This increase was completely blocked with daily dopamine treatment. Dopamine treatment also blocked the stress-induced increase in angiogenesis. Endothelial and ovarian cancer cells expressed all dopamine receptors except for the lack of DR3 expression in ovarian cancer cells. DR2 was responsible for the inhibitory effects of dopamine on tumor growth and microvessel density as well as the stimulatory effect on apoptosis, as the DR2 antagonist eticlopride reversed these effects. Dopamine significantly inhibited cell viability and stimulated apoptosis in vitro. Moreover, dopamine reduced cyclic AMP levels and inhibited norepinephrine and vascular permeability factor/VEGF-induced Src kinase activation. Conclusions: Dopamine depletion under chronic stress conditions creates a permissive microenvironment for tumor growth that can be reversed by dopamine replacement. Clin Cancer Res; 17(11); 3649–59. ©2011 AACR.

Angiotensin II acts through the angiotensin 1a receptor to upregulate pendrin

Pendrin is an anion exchanger expressed in the apical regions of B and non-A, non-B intercalated cells. Since angiotensin II increases pendrin-mediated Cl(-) absorption in vitro, we asked whether angiotensin II increases pendrin expression in vivo and whether angiotensin-induced hypertension is pendrin dependent. While blood pressure was similar in pendrin null and wild-type mice under basal conditions, following 2 wk of angiotensin II administration blood pressure was 31 mmHg lower in pendrin null than in wild-type mice. Thus pendrin null mice have a blunted pressor response to angiotensin II. Further experiments explored the effect of angiotensin on pendrin expression. Angiotensin II administration shifted pendrin label from the subapical space to the apical plasma membrane, independent of aldosterone. To explore the role of the angiotensin receptors in this response, pendrin abundance and subcellular distribution were examined in wild-type, angiotensin type 1a (Agtr1a) and type 2 receptor (Agtr2) null mice given 7 days of a NaCl-restricted diet (< 0.02% NaCl). Some mice received an Agtr1 inhibitor (candesartan) or vehicle. Both Agtr1a gene ablation and Agtr1 inhibitors shifted pendrin label from the apical plasma membrane to the subapical space, independent of the Agtr2 or nitric oxide (NO). However, Agtr1 ablation reduced pendrin protein abundance through the Agtr2 and NO. Thus angiotensin II-induced hypertension is pendrin dependent. Angiotensin II acts through the Agtr1a to shift pendrin from the subapical space to the apical plasma membrane. This Agtr1 action may be blunted by the Agtr2, which acts through NO to reduce pendrin protein abundance.

Role of pendrin in iodide balance: going with the flow

Pendrin is expressed in the apical regions of type B and non-A, non-B intercalated cells, where it mediates Cl(-) absorption and HCO3(-) secretion through apical Cl(-)/HCO3(-) exchange. Since pendrin is a robust I(-) transporter, we asked whether pendrin is upregulated with dietary I(-) restriction and whether it modulates I(-) balance. Thus I(-) balance was determined in pendrin null and in wild-type mice. Pendrin abundance was evaluated with immunoblots, immunohistochemistry, and immunogold cytochemistry with morphometric analysis. While pendrin abundance was unchanged when dietary I(-) intake was varied over the physiological range, I(-) balance differed in pendrin null and in wild-type mice. Serum I(-) was lower, while I(-) excretion was higher in pendrin null relative to wild-type mice, consistent with a role of pendrin in renal I(-) absorption. Increased H2O intake enhanced differences between wild-type and pendrin null mice in I(-) balance, suggesting that H2O intake modulates pendrin abundance. Raising water intake from approximately 4 to approximately 11 ml/day increased the ratio of B cell apical plasma membrane to cytoplasm pendrin label by 75%, although circulating renin, aldosterone, and serum osmolality were unchanged. Further studies asked whether H2O intake modulates pendrin through the action of AVP. We observed that H2O intake modulated pendrin abundance even when circulating vasopressin levels were clamped. We conclude that H2O intake modulates pendrin abundance, although not likely through a direct, type 2 vasopressin receptor-dependent mechanism. As water intake rises, pendrin becomes increasingly critical in the maintenance of Cl(-) and I(-) balance.

Role of prostaglandins in estrogen-induced uterine hyperemia

Abstract Estrogen-induced uterine hyperemia is known to result from some other mechanism than direct vasodilatation produced by the hormone. Prostaglandin E 1 has been shown to exhibit properties consistent with a role as a vasodilator intermediate in estrogen-induced hyperemia. In the present study performed on rats the hyperemic response to estrogen as estimated by changes in uterine blood volume was blocked by two different prostaglandin synthesis inhibitors, indomethacin and meclofenamic acid. There was a parallel block of the increase in uterine PGE and PGF activity (radioimmunoassay) produced by estrogen. These results demonstrate that estrogen induces formation of uterine prostaglandins which appear to play a role in promoting the increase in blood supply to the uterus.

Ethacrynic acid induced release of prostaglandin E to increase renal blood flow.

Ethacrynic acid administered to anesthetized dogs was found to increase the level of prostaglandin E as determined by radioimmunoassay in renal venous blood at the time when renal blood flow was increased by this agent. No change was found in the renal venous level of prostaglandin F. When ethacrynic acid was administered after treatment with indomethacin, which blocks the increase in renal blood flow induced by the natriuretic agent, no increase in the renal venous level of prostaglandin E was seen. Thus, the dilation of the renal vasculature would appear to be caused by a stimulation of synthesis and release of prostaglandin E by ethacrynic acid.

Role of endogenous prostaglandins in regulation of uterine blood flow and adrenergic neurotransmission

Earlier studies from these laboratories have demonstrated that prostaglandins (PGs) of the A and E series are potent uterine vasodilators whereas PGFs do not significantly alter uterine vascular resistance. In addition, PGEs and PGFs are also able to modify adrenergic vasoconstrictor responses in the canine uterus. In the present study the role of endogenous prostaglandins in regulating uterine vascular resistance and adrenergic neurotransmission was evaluated. Intra-arterial infusion of the prostaglandin synthesis inhibitor meclofenamate resulted in a significant reduction in PGE levels in uterine venous plasma and increased vascular resistance. Uterine vasoconstrictor responses produced by sympathetic nerve stimulation and norepinephrine were enhanced when endogenous PG synthesis was inhibited. During sympathetic nerve stimulation, uterine venous plasma levels of radioimmunoassayable prostaglandins of the E of F series did not change, suggesting that the adrenergic activation of PG synthesis is not detectable in uterine venous efferent. These data suggest that endogenous prostaglandins of the E series appear to play an important role in regulating uterine blood flow (I) by relaxing uterine vascular smooth muscle and (2) by depressing adrenergic vasoconstrictor responses.

Effect of prostacyclin inhibition by tranylcypromine on uterine 6-keto-PGF1α levels during estrogen hyperemia in rats

A role for prostacyclin (PGI2) as a mediator of estrogen-induced increases in uterine blood volume (UBV) was investigated by measuring uterine tissue levels of 6-keto-prostaglandin F1 alpha (6-keto-PGF 1 alpha), and testing estrogen responses in rats pretreated with the PGI2 synthesis inhibitor, tranylcypromine (TCP). Uterine 6-keto-PGF1 alpha content was determined by radioimmunoassay of tissue extracts purified through the use of high-performance liquid chromatography (HPLC). Estrogen treatment of castrate rats resulted in a significant increase of uterine 6-keto-PGF 1 alpha was compared to saline treated controls (9.3 ng/uterine horn vs 6.7 ng/uterine horn, p=0.01). Pretreatment with TCP (20 mg/kg) markedly reduced the uterine content of 6-keto-PGF 1 alpha (2.5 ng/uterine horn). The typical 50% increase in UBV observed after estrogen was unaffected by tranylcypromine pretreatment. It was concluded that the increased PGI2 synthesis, as indicated by elevated levels of 6-keto-PGF1 alpha, may function as an amplifying mechanism for the uterine vasodilation-induced by estrogen in castrate rats, but that production of this prostanoid is not essential for the estrogen response.