Central opioid inhibition of neuroendocrine stress responses in pregnancy in the rat is induced by the neurosteroid allopregnanolone.

The hypothalamus-pituitary-adrenal (HPA) axis is the major neuroendocrine stress response system. Corticotropin-releasing hormone (CRH) neurons in the parvocellular paraventricular nucleus (pPVN) play a key role in coordinating responses of this system to stressors. The cytokine interleukin-1beta (IL-1beta), mimicking infection, robustly activates these CRH neurons via a noradrenergic input arising from the nucleus tractus solitarii (NTS). In late pregnancy, HPA axis responses to stressors, including IL-1beta, are attenuated by a central opioid mechanism that auto-inhibits noradrenaline release in the PVN. Here we show that the neuroactive progesterone metabolite allopregnanolone induces these changes in HPA responsiveness to IL-1beta in pregnancy. In late pregnancy, inhibition of 5alpha-reductase (an allopregnanolone-synthesizing enzyme) with finasteride restored HPA axis responses (rapidly increased pPVN CRH mRNA expression, ACTH, and corticosterone secretion) to IL-1beta. Conversely, allopregnanolone reduced HPA responses in virgin rats. In late pregnancy, activity of the allopregnanolone-synthesizing enzymes (5alpha-reductase and 3alpha-hydroxysteroid dehydrogenase) was increased in the hypothalamus as was mRNA expression in the NTS and PVN. Naloxone, an opioid antagonist, restores HPA axis responses to IL-1beta in pregnancy but had no additional effect after finasteride, indicating a causal connection between allopregnanolone and the endogenous opioid mechanism. Indeed, allopregnanolone induced opioid inhibition over HPA responses to IL-1beta in virgin rats. Furthermore, in virgin rats, allopregnanolone treatment increased, whereas in pregnant rats finasteride decreased proenkephalin-A mRNA expression in the NTS. Thus, in pregnancy, allopregnanolone induces opioid inhibition over HPA axis responses to immune challenge. This novel opioid-mediated mechanism of allopregnanolone action may alter regulation of other brain systems in pregnancy.

Angiotensin receptors in hormone-independent prostate cancer cell line DU145: presence of two variants of angiotensin type 1 receptor.

BACKGROUND: Recently, the involvement of the renin-angiotensin system in the proliferation of prostate cancer has been suggested. There is increasing evidence that angiotensin II receptor type 1 (AT1) is expressed in a variety of cancer cells and tissues and may have a role in tumor growth, angiogenesis, and invasive activity of malignant lesions in vivo. The implications of data referring to an angiotensin receptor in hormone-independent human prostate cancer DU145 cells are unclear. Angiotensin II has been shown to inhibit the proliferation of DU145 cell lines. However, it is known that AT1 stimulates cell proliferation and that angiotensin II receptor type 2 (AT2) induces apoptosis and inhibits cell proliferation. MATERIAL/METHODS: The aim of our study was to investigate, by means of immunohistochemical and reverse transcriptase polymerase chain reaction assays, the type of angiotensin II receptor that is present in DU145 cells. RESULTS: In DU145-derived complementary deoxyribonucleic acid (cDNA), a polymerase chain reaction assay revealed 2 AT1-specific PCR products (93 bp and 126 bp). DU145-derived cDNA did not reveal AT2 expression at a level sufficient for detection by PCR. In cultured cells, immunohistochemical testing revealed a positive reaction in cultures immunostained with anti-AT1 antibody but not in those immunostained with AT2 antibody. CONCLUSIONS: The inhibitory effect of angiotensin II on the proliferation of DU145 cells is exerted via AT1. It is possible that presence of 2 variants of AT1 in that cancer cell line is essential to produce the biological effects of angiotensin.

Exposure to polychlorinated naphthalenes affects GABA-metabolizing enzymes in rat brain.

There is substantial evidence that polychlorinated naphthalenes (PCNs) are widespread global environmental pollutants, which accumulate in biota. The aim of our study was to characterize the effect of prolonged PCNs exposure on γ-aminobutyric acid (GABA) metabolism in rat brain regions with a high amount of GABAergic neurons (cerebellum, brain stem and basal ganglia). PCNs mixture was administered intragastrically for 7, 14 and 21 days in a dose 10mg/kg of body weight daily, and next the activity of glutamate decarboxylase (GAD), GABA-aminotransferase (GABA-T), succinic semialdehyde dehydrogenase (SDH) and succinate dehydrogenase (SSA-DH) was assayed. PCNs administration altered all examined activities in the selected brain areas, except GAD in basal ganglia. The results suggest the correlation between PCNs action and disturbance in GABA metabolism in rat brain. Moreover, the chronic PCNs intoxication increased SDH-mediated activation of TCA cycle, and it may be a kind of protective mechanism developed in nervous tissue in response to administration of toxic compounds.

Maternal and fetal hypothalamo-pituitary-adrenal axis: different response depends upon the mode of parturition.

OBJECTIVES: The changes in corticotropin releasing hormone (CRH), adrenocorticotropin hormone (ACTH), cortisol and dehydroepiandrosterone (DHEA) in maternal and fetal plasma were estimated in two group of women undergoing labour after oxytocin induction, or elective cesarean section to correlate changes in maternal and fetal HPA axis to the different stressor conditions. MATERIALS AND METHODS: Blood was sampled from a maternal peripheral vein two days before labour, during the second stage of labour and on the second postnatal day, and also from umbilical vessels just after delivery. Hormone concentrations were measured by RIA and ELSA methods. The maternal plasma CRH concentration before and after labour was similar in both studied groups. RESULTS: Plasma CRH levels measured before labour in both groups were similar, but during labour after oxytocin infusion declined, and was in group of women with elective cesarean section rose, after the delivery there was no difference between groups. The plasma ACTH prior to the delivery was at the same level in all subjects, during the third stage of labour ACTH rose in the both groups, but was statistically higher in group with oxytocin infusion. The concentrations of cortisol before delivery was similar in both groups, then rose to the same level during the delivery and then declined to the level observed before delivery. The DHEA concentration was similar in both groups, did not change during the labour, there was no difference between its level in the umbilical vein and artery. In the group with oxytocin-induction there was no correlation between maternal CRH and ACTH or cortisol concentration, but such a correlation occurred in the group with elective cesarean section. The concentration of ACTH and DHEA in umbilical artery was similar in both groups but the concentrations of CRH and cortisol in umbilical artery in group of newborns delivered after elective cesarean section were statistically higher. CONCLUSION: The activity of the mother's HPA axis is partially inhibited rather by psychological stressors, than events connected with mode of parturition. The newborn's HPA axis responds in a specific way to mother's HPA-axis. The communication between mother's and newborn's HPA is possibly related to many other factors than placental CRH and ACTH. It is necessary to consider effects of central CRH and ACTH on the fine-tune regulation of HPA axis in the late pregnancy and parturition, not detectable due to the high levels of placental hormones.

Steroid modulation of angiotensin II action in the rat anterior pituitary gland.

OBJECTIVES: The present study was designed to test whether various steroid hormones modulate differently angiotensin II (AngII) action in the anterior pituitary in males and females. MATERIAL AND METHODS: Adult female and male rats were treated with one of the following substances: oil (control), pregnenolone sulfate (PREG-S), 17beta-estradiol benzoate (E2,) progesterone (P), or dehydroepiandrosterone sulfate (DHEA-S), given in intraperitoneal injections for five days in dose of 50 microg per animal per day. Because AngII is known to act in the anterior pituitary through the phosphatidiloinositol breakdown, thus increasing the level of inositol-1,4,5-trisphosphate (IP3), the IP3 concentration was determined 24 hours after the injection in the anterior pituitary homogenate exposed to AngII. RESULTS: In control animals (without steroids) AngII stimulated concentration of IP(3) stronger in females than in males. E(2) and DHEA-S enhanced AngII effects in both males and females. PREG-S increased AngII-induced IP(3) concentration in females, but not males. Progesterone raised AngII effect on IP(3) concentration in males, only when high concentrations of peptide were used. CONCLUSION: These results indicate that pituitary sensitivity to AngII stimulation is modulated by steroid hormones and is related to the gender of the animal.

[Influence of interleukin-1 and interleukin-6 on modulation of hypothalamo-pituitary-adrenal axis in pregnancy at term and in spontaneous and oxytocin-induced delivery]. / Wplyw interleukiny-1 i interleukiny-6 na modulacje osi podwzgórze-przysadkanadnercza w ciazy donoszonej w porodzie samoistnym i indukowanym oksytocyna.

OBJECTIVES: During the pregnancy the placenta and hypothalamus produce trophic hormones for hypothalamo-pituitary-adrenal axis (HPA), i.e. corticotropin releasing hormone (CRH) and adrenocorticotropin (ACTH). The HPA axis of pregnant women is differentially modulated in comparison to non-pregnant ones. Beside steroids, the influence on CRH release may be modulated by cytokines, especially interleukin 1 (IL-1) and interleukin 6 (IL-6). DESIGN: To evaluate the effects of IL-1 and IL-6 on modulation of HPA axis in pregnancy, we have examined the group of women with spontaneous delivery, and second group consists of women delivered after intravenous oxytocin infusion. All women were at term and in the same pregnancy age. MATERIAL AND METHODS: Blood was sampled from a maternal peripheral vein days before labour, during the second stage of labour and on the second postnatal day, the levels of IL-1, IL-6, CRH, ACTH and cortisol were measured. The concentrations of hormones were measured using RIA method. RESULTS: The level of IL-1 before the delivery was significantly higher in the group with oxytocin-induction. CRH concentration before the labour was much higher in the group with spontaneous contractions. The levels of IL-1 and CRH in both groups decreased during the labour and were lowest after the delivery. Concentration of IL-6 did not changed dependently of group and time of blood sampling. Changes in CRH in time concentration did not correlate with changes in ACTH levels. ACTH concentrations were similar in both groups, low before delivery raised during the delivery and low again after labour. Cortisol concentration in spontaneous labour was much lower before delivery in comparison with second examined group, then lowered during and after the delivery. In group with oxytocin induction, cortisol levels raised during the delivery and maintained almost the same level after the labour. The time-changes in IL-1 concentration and ACTH and cortisol levels were similar in shape in group with spontaneous delivery. CONCLUSIONS: These results suggest that IL-6 is not involved in modulation of HPA axis in pregnancy at term. IL-1 may modulate mother's HPA axis, influencing the release of ACTH and cortisol, probably via stimulation of hypothalamic CRH.

[Modulation of hypothalamo-pituitary axis by stress during labor]. / Modulacja osi podwzgórze-przysadka podczas stresu zwiazanego z porodem w ciazy donoszonej.

OBJECTIVES: The present study is aimed to investigate the function of hypothalamo-pituitary-adrenal axis of women during late pregnancy and term labor. DESIGN: Levels of hormones were measured in blood of 34 women undergoing spontaneous labor and elective cesarean section, 2 days before and after delivery, and during labour. Additionally, blood from the umbilical vein and artery was also collected. MATERIALS AND METHODS: We have evaluated changes in corticotropin releasing hormone (CRH), adrenocorticotropin (ACTH) and dehydroepiandrosterone (DHEA) in vein blood of 34 subjects. The concentrations of hormones were measured by dint of RIA method. RESULTS: No significant correlation was found between hormone measurements and fetal outcome. CRH level in the umbilical vein was higher than in the umbilical artery, suggesting the placental origin of hormone. Prepartum CRH concentration was significantly higher in the group of spontaneously delivered patients. There were no correlations between CRH levels and ACTH and DHEA concentration in mother's blood plasma. In fetuses, higher prepartum CRH concentrations resulted in elevated levels of ACTH. No changes were found in DHEA concentration, in both mother and fetus. CONCLUSIONS: These results suggest that placental CRH may modulate a fetus's pituitary but not mother's. The observed high levels of this hormone play an important role mainly in preparation of mother and fetus for delivery.

The effect of angiotensin 1-7 on tyrosine kinases activity in rat anterior pituitary.

Angiotensin 1-7 (Ang 1-7) is a peptide originated from Ang II. It is known that in vessels Ang 1-7 shows opposite effects to Ang II. Ang 1-7 can modify processes of proliferation. However, Ang 1-7 action in pituitary gland cells was never studied. Moreover, the specific binding sites for Ang 1-7 are still unknown. The aim of this study was to examine the effects of Ang 1-7 on tyrosine kinases (PTKs) activity in the anterior pituitary. The reaction of phosphorylation was carrying out in presence of different concentration of Ang 1-7 and losartan (antagonist of AT1 receptor) and PD123319 (antagonist of AT2). Our results show that Ang 1-7 inhibited activity of PTK to 60% of basic activity. Losartan did not change the Ang 1-7-induced changes in PTKs activity. The presence of PD123319 together with Ang 1-7 caused stronger inhibition PTKs activity than Ang 1-7 alone. These observations suggest that Ang 1-7 binds to the novel, unknown, specific for this peptide receptor.

Endothelin-induced, long lasting, and Ca2+ influx-independent blockade of intrinsic secretion in pituitary cells by Gz subunits.

The G protein-coupled receptors in excitable cells have prominent roles in controlling Ca2+-triggered secretion by modulating voltage-gated Ca2+ influx. In pituitary lactotrophs, spontaneous voltage-gated Ca2+ influx is sufficient to maintain prolactin release high. Here we show that endothelin in picomolar concentrations can interrupt such release for several hours downstream of spontaneous and high K+-stimulated voltage-gated Ca2+ influx. This action occurred through the Gz signaling pathway; the adenylyl cyclase-signaling cascade could mediate sustained inhibition of secretion, whereas rapid inhibition also occurred at elevated cAMP levels regardless of the status of phospholipase C, tyrosine kinases, and protein kinase C. In a nanomolar concentration range, endothelin also inhibited voltage-gated Ca2+ influx through the G i/o signaling pathway. Thus, the coupling of seven-transmembrane domain endothelin receptors to Gz proteins provided a pathway that effectively blocked hormone secretion distal to Ca2+ entry, whereas the cross-coupling to G i/o proteins reinforced such inhibition by simultaneously reducing the pacemaking activity.

Gender differences in steroid modulation of angiotensin II-induced protein kinase C activity in anterior pituitary of the rat.

To investigate whether the various steroid hormones can modulate the basal and angiotensin II-induced protein kinase C (PKC) activity in the anterior pituitary of the rat, female and male intact and ovariectomized female Wistar rats were treated in vivo with estradiol (E2), progesterone (P), dehydroepiandrostendione sulfate (DHEA-S), and pregnenolone sulfate (PREG-S). Estradiol caused the increase of basal PKC activity in intact and ovariectomized females, but did not change the enzyme activity in males. In ovariectomized animals the increase of PKC activity was lower than in intact females. Progesterone decreased PKC activity only in intact animals. DHEA-S strongly enhanced activity of PKC in ovariectomized females. Pregnenolone sulfate did not significantly change PKC function of all studied groups. Incubation with AngII enhanced the PKC activity in intact (without steroid treatment) animals of both genders. In females, AngII and estradiol together rise the PKC-stimulated phosphorylation in greater degree than used separately. Treatment with other investigated steroids reduced the effect of AngII. In intact males every examined hormone turned back the stimulatory effect of AngII on PKC activity. These data suggest that gender differences in PKC activity are likely related to hormonal milieu of experimental animals and may depend in part on the basic plasma level of estrogens.