The Isolation and In Vitro Differentiation of Primary Fetal Baboon Tracheal Epithelial Cells for the Study of SARS-CoV-2 Host-Virus Interactions

The mucociliary airway epithelium lines the human airways and is the primary site of host-environmental interactions in the lung. Following virus infection, airway epithelial cells initiate an innate immune response to suppress virus replication. Therefore, defining the virus-host interactions of the mucociliary airway epithelium is critical for understanding the mechanisms that regulate virus infection, including Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Non-human primates (NHP) are closely related to humans and provide a model to study human disease. However, ethical considerations and high costs can restrict the use of in vivo NHP models. Therefore, there is a need to develop in vitro NHP models of human respiratory virus infection that would allow for rapidly characterizing virus tropism and the suitability of specific NHP species to model human infection. Using the olive baboon (Papio anubis), we have developed methodologies for the isolation, in vitro expansion, cryopreservation, and mucociliary differentiation of primary fetal baboon tracheal epithelial cells (FBTECs). Furthermore, we demonstrate that in vitro differentiated FBTECs are permissive to SARS-CoV-2 infection and produce a potent host innate-immune response. In summary, we have developed an in vitro NHP model that provides a platform for the study of SARS-CoV-2 infection and other human respiratory viruses.

Early and mid-gestation Zika virus (ZIKV) infection in the olive baboon (Papio anubis) leads to fetal CNS pathology by term gestation

Zika virus (ZIKV) infection in pregnancy can produce catastrophic teratogenic damage to the developing fetus including microcephaly and congenital Zika syndrome (CZS). We previously described fetal CNS pathology occurring by three weeks post-ZIKV inoculation in Olive baboons at mid-gestation, including neuroinflammation, loss of radial glia (RG), RG fibers, neuroprogenitor cells (NPCs) resulting in disrupted NPC migration. In the present study, we explored fetal brain pathologies at term gestation resulting from ZIKV exposure during either first or second trimester in the Olive baboon. In all dams, vRNA in whole blood resolved after 7 days post inoculation (dpi). One first trimester infected dam aborted at 5 dpi. All dams developed IgM and IgG response to ZIKV with ZIKV IgG detected in fetal serum. Placental pathology and inflammation were observed including disruption of syncytiotrophoblast layers, delayed villous maturation, partially or fully thrombosed vessels, calcium mineralization and fibrin deposits. In the uterus, ZIKV was detected in ¾ first trimester but not in second trimester infected dams. While ZIKV was not detected in any fetal tissue at term, all fetuses exhibited varying degrees of neuropathology. Fetal brains from ZIKV inoculated dams exhibited a range of gross brain pathologies including irregularities of the major gyri and sulci of the cerebral cortex and cerebellar pathology. Frontal cortices of ZIKV fetuses showed a general disorganization of the six-layered cortex with degree of disorganization varying among the fetuses from the two groups. Frontal cortices from ZIKV inoculation in the first but not second trimester exhibited increased microglia, and in both trimester ZIKV inoculation, increased astrocyte numbers (white matter). In the cerebellum, increased microglia were observed in fetuses from both first and second trimester inoculation. In first trimester ZIKV inoculation, decreased oligodendrocyte precursor cell populations were observed in fetal cerebellar white matter. In general, our observations are in accordance with those described in human ZIKV infected fetuses.

Western diet-induced shifts in the maternal microbiome are associated with altered microRNA expression in baboon placenta and fetal liver

Maternal consumption of a high-fat, Western-style diet (WD) disrupts the maternal/infant microbiome and contributes to developmental programming of the immune system and nonalcoholic fatty liver disease (NAFLD) in the offspring. Epigenetic changes, including non-coding miRNAs in the fetus and/or placenta may also underlie this risk. We previously showed that obese nonhuman primates fed a WD during pregnancy results in the loss of beneficial maternal gut microbes and dysregulation of cellular metabolism and mitochondrial dysfunction in the fetal liver, leading to a perturbed postnatal immune response with accelerated NAFLD in juvenile offspring. Here, we investigated associations between WD-induced maternal metabolic and microbiome changes, in the absence of obesity, and miRNA and gene expression changes in the placenta and fetal liver. After ~8-11 months of WD feeding, dams were similar in body weight but exhibited mild, systemic inflammation (elevated CRP and neutrophil count) and dyslipidemia (increased triglycerides and cholesterol) compared with dams fed a control diet. The maternal gut microbiome was mainly comprised of Lactobacillales and Clostridiales, with significantly decreased alpha diversity (P = 0.0163) in WD-fed dams but no community-wide differences (P = 0.26). At 0.9 gestation, mRNA expression of IL6 and TNF in maternal WD (mWD) exposed placentas trended higher, while increased triglycerides, expression of pro-inflammatory CCR2, and histological evidence for fibrosis were found in mWD-exposed fetal livers. In the mWD-exposed fetus, hepatic expression levels of miR-204-5p and miR-145-3p were significantly downregulated, whereas in mWD-exposed placentas, miR-182-5p and miR-183-5p were significantly decreased. Notably, miR-1285-3p expression in the liver and miR-183-5p in the placenta were significantly associated with inflammation and lipid synthesis pathway genes, respectively. Blautia and Ruminococcus were significantly associated with miR-122-5p in liver, while Coriobacteriaceae and Prevotellaceae were strongly associated with miR-1285-3p in the placenta; both miRNAs are implicated in pathways mediating postnatal growth and obesity. Our findings demonstrate that mWD shifts the maternal microbiome, lipid metabolism, and inflammation prior to obesity and are associated with epigenetic changes in the placenta and fetal liver. These changes may underlie inflammation, oxidative stress, and fibrosis patterns that drive NAFLD and metabolic disease risk in the next generation.

Characterization of the SARS-CoV-2 Host Response in Primary Human Airway Epithelial Cells from Aged Individuals

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the causative agent of coronavirus disease 2019 (COVID-19), a global pandemic characterized by an exaggerated immune response and respiratory illness. Age (>60 years) is a significant risk factor for developing severe COVID-19. To better understand the host response of the aged airway epithelium to SARS-CoV-2 infection, we performed an in vitro study using primary human bronchial epithelial cells from donors >67 years of age differentiated on an air–liquid interface culture. We demonstrate that SARS-CoV-2 infection leads to early induction of a proinflammatory response and a delayed interferon response. In addition, we observed changes in the genes and pathways associated with cell death and senescence throughout infection. In summary, our study provides new and important insights into the temporal kinetics of the airway epithelial innate immune response to SARS-CoV-2 in older individuals.

Long term hypoxia during gestation alters perirenal adipose tissue gene expression in the lamb

We previously reported that following long-term hypoxia (LTH), the ovine foetus exhibits enhanced expression of brown/beige adipose genes. This study was designed to determine if these changes are preserved after birth. Pregnant ewes were divided among three groups, 1) Control, sea level, 2) LTH, high altitude (3,820 m, LTH-HA) from ~ day 40 of gestation through ~14 days post-delivery and 3) LTH from ⁓ day 40 through day 137 of gestation then returned to the laboratory where atory reduced maternal PO₂ was maintained by nitrogen infusion. Following delivery, lambs remained at sea level (LTH-SL). Perirenal adipose tissue was collected at ~day 14, and qRT-PCR was used to quantify mRNA. Uncoupling protein 1 (UCP-1), PPAR gamma coactivator 1 (PGC1α), and deiodinase-2 (DIO2) mRNA levels were significantly lower in both LTH groups while PR domain containing 16 (PRDM16) levels did not differ. Peroxisome proliferator-activated receptor (PPARγ) was maintained in the LTH-HA group and significantly increased in the LTH-SL group, compared to control. Unlike our previous LTH foetal studies, the brown/beige fat phenotype was rapidly lost by day 14 postpartum compared to control, while PPARγ was maintained. This loss of the brown fat phenotype may promote obesity due to decreased energy expenditure, favouring fat deposition.

Zika virus infection at mid-gestation results in fetal cerebral cortical injury and fetal death in the olive baboon

Zika virus (ZIKV) infection during pregnancy in humans is associated with an increased incidence of congenital anomalies including microcephaly as well as fetal death and miscarriage and collectively has been referred to as Congenital Zika Syndrome (CZS). Animal models for ZIKV infection in pregnancy have been developed including mice and non-human primates (NHPs). In macaques, fetal CZS outcomes from maternal ZIKV infection range from none to significant. In the present study we develop the olive baboon (Papio anubis), as a model for vertical transfer of ZIKV during pregnancy. Four mid-gestation, timed-pregnant baboons were inoculated with the French Polynesian ZIKV isolate (10⁴ ffu). This study specifically focused on the acute phase of vertical transfer. Dams were terminated at 7 days post infection (dpi; n = 1), 14 dpi (n = 2) and 21 dpi (n = 1). All dams exhibited mild to moderate rash and conjunctivitis. Viremia peaked at 5–7 dpi with only one of three dams remaining mildly viremic at 14 dpi. An anti-ZIKV IgM response was observed by 14 dpi in all three dams studied to this stage, and two dams developed a neutralizing IgG response by either 14 dpi or 21 dpi, the latter included transfer of the IgG to the fetus (cord blood). A systemic inflammatory response (increased IL2, IL6, IL7, IL15, IL16) was observed in three of four dams. Vertical transfer of ZIKV to the placenta was observed in three pregnancies (n = 2 at 14 dpi and n = 1 at 21 dpi) and ZIKV was detected in fetal tissues in two pregnancies: one associated with fetal death at ~14 dpi, and the other in a viable fetus at 21 dpi. ZIKV RNA was detected in the fetal cerebral cortex and other tissues of both of these fetuses. In the fetus studied at 21 dpi with vertical transfer of virus to the CNS, the frontal cerebral cortex exhibited notable defects in radial glia, radial glial fibers, disorganized migration of immature neurons to the cortical layers, and signs of pathology in immature oligodendrocytes. In addition, indices of pronounced neuroinflammation were observed including astrogliosis, increased microglia and IL6 expression. Of interest, in one fetus examined at 14 dpi without detection of ZIKV RNA in brain and other fetal tissues, increased neuroinflammation (IL6 and microglia) was observed in the cortex. Although the placenta of the 14 dpi dam with fetal death showed considerable pathology, only minor pathology was noted in the other three placentas. ZIKV was detected immunohistochemically in two placentas (14 dpi) and one placenta at 21 dpi but not at 7 dpi. This is the first study to examine the early events of vertical transfer of ZIKV in a NHP infected at mid-gestation. The baboon thus represents an additional NHP as a model for ZIKV induced brain pathologies to contrast and compare to humans as well as other NHPs.

Zika virus is endemic in the Americas, primarily spread through mosquitos and sexual contact. Zika virus infection during pregnancy in women is associated with a variety of fetal pathologies now referred to as Congenital Zika Syndrome (CZS), with the most severe pathology being fetal microcephaly. Developing model organisms that faithfully recreate Zika infection in humans is critical for future development of treatments and preventions. In our present study, we infected Olive baboons at mid-gestation with Zika virus and studied the acute period of viremia and transfer of Zika virus to the fetus during the first three weeks after infection to better understand the timing and mechanisms of transfer of ZIKV across the placenta, leading to CZS. We observed Zika virus transfer to fetuses resulting in fetal death in one pregnancy and in a second pregnancy, significant damage to the frontal cortex of the fetal brain at a critical period of neurodevelopment in primates. Thus, the baboon provides a promising new non-human primate model to further compare and contrast the consequences of Zika virus infection in pregnancy to humans and other non-human primates.

Clinical Insights for Cervical Ripening and Labor Induction Using Prostaglandins

Cervical ripening is often the first component of labor induction and is used to facilitate the softening and thinning of the cervix in preparation for labor. Common methods used for cervical ripening include both mechanical (e.g., Foley or Cook catheters) and pharmacologic (e.g., prostaglandins) methods. The choice of method(s) for ripening should take into account the patient's medical and obstetric history, clinical characteristics, and risk of adverse effects if uterine tachysystole were to occur. In this narrative review, we highlight the differences between the prostaglandins dinoprostone and misoprostol with respect to pharmacology and pharmacokinetics, efficacy, and potential safety concerns. Practical guidance on choosing an appropriate prostaglandin agent for cervical ripening and labor induction is provided via the use of clinical vignettes. Considering the advantages and disadvantages of each preparation allows clinicians to individualize treatment, depending on the indications for induction and unique characteristics of each patient.

Translational Model of Zika Virus Disease in Baboons

Zika virus (ZIKV) is an emerging mosquito-borne flavivirus with devastating outcomes seen recently in the Americas due to the association of maternal ZIKV infection with fetal microcephaly and other fetal malformations not previously associated with flavivirus infections. Here, we have developed the olive baboon (Papio anubis) as a nonhuman primate (NHP) translational model for the study of ZIKV pathogenesis and associated disease outcomes to contrast and compare with humans and other major NHPs, such as macaques. Following subcutaneous inoculation of adult male and nonpregnant female baboons, viremia was detected at 3 and 4 days postinfection (dpi) with the concordant presentation of a visible rash and conjunctivitis, similar to human ZIKV infection. Furthermore, virus was detected in the mucosa and cerebrospinal fluid. A robust ZIKV-specific IgM and IgG antibody response was also observed in all the animals. These data show striking similarity between humans and the olive baboon following infection with ZIKV, suggesting our model is a suitable translational NHP model to study ZIKV pathogenesis and potential therapeutics.IMPORTANCE ZIKV was first identified in 1947 in a sentinel rhesus monkey in Uganda and subsequently spread to Southeast Asia. Until 2007, only a small number of cases were reported, and ZIKV infection was relatively minor until the South Pacific and Brazilian outbreaks, where more severe outcomes were reported. Here, we present the baboon as a nonhuman primate model for contrast and comparison with other published animal models of ZIKV, such as the mouse and macaque species. Baboons breed year round and are not currently a primary nonhuman primate species used in biomedical research, making them more readily available for studies other than human immunodeficiency virus studies, which many macaque species are designated for. This, taken together with the similarities baboons have with humans, such as immunology, reproduction, genetics, and size, makes the baboon an attractive NHP model for ZIKV studies in comparison to other nonhuman primates.

Gestational hypoxia disrupts the neonatal leptin surge and programs hyperphagia and obesity in male offspring in the Sprague-Dawley rat

The effect of gestational hypoxia on the neonatal leptin surge, development of hypothalamic arcuate nuclei (ARH) projections and appetite that could contribute to the programming of offspring obesity is lacking. We examined the effect of 12% O₂ from gestational days 15–19 in the Sprague-Dawley rat on post-weaning appetite, fat deposition by MRI, adipose tissue cytokine expression, the neonatal leptin surge, ARH response to exogenous leptin, and αMSH projections to the paraventricular nucleus (PVN) in response to a high fat (HFD) or control diet (CD) in male offspring. Normoxia (NMX) and Hypoxia (HPX) offspring exhibited increased food intake when fed a HFD from 5–8 weeks post-birth; HPX offspring on the CD had increased food intake from weeks 5–7 vs. NMX offspring on a CD. HPX offspring on a HFD remained hyperphagic through 23 weeks. Body weight were the same between offspring from HPX vs. NMX dams from 4–12 weeks of age fed a CD or HFD. By 14–23 weeks of age, HPX offspring fed the CD or HFD as well as male NMX offspring fed the HFD were heavier vs. NMX offspring fed the CD. HPX offspring fed a CD exhibited increased abdominal adiposity (MRI) that was amplified by a HFD. HPX offspring fed a HFD exhibited the highest abdominal fat cytokine expression. HPX male offspring had higher plasma leptin from postnatal day (PN) 6 through 14 vs. NMX pups. HPX offspring exhibited increased basal c-Fos labeled cells in the ARH vs. NMX pups on PN16. Leptin increased c-Fos staining in the ARH in NMX but not HPX offspring at PN16. HPX offspring had fewer αMSH fibers in the PVN vs. NMX offspring on PN16. In conclusion, gestational hypoxia impacts the developing ARH resulting in hyperphagia contributing to adult obesity on a control diet and exacerbated by a HFD.

Interaction Between Progesterone and Interleukin-1β in Modulating Progesterone Receptor Expression and the Inflammatory Phenotype in Human Cervical Fibroblasts

Progesterone helps maintain cervical structure during pregnancy via the progesterone receptor (PR). Two PR isoforms exist, PR-A and PR-B, which have overlapping as well as isoform-specific target genes. During late gestation, leukocytes infiltrate the cervical stroma accompanied by increased cervical cytokine levels, resembling an inflammatory process. We examined interleukin (IL)-1β regulation of the expression of PR-A, PR-B, and genes governing prostaglandin synthesis in human cervical fibroblasts (HCFs). Since progesterone has been shown to exert anti-inflammatory actions, we also examined the capacity of progesterone (R5020) to ameliorate the actions of IL-1β in HCFs. Interleukin-1β induced both PR-A and PR-B mRNA in HCFs. Interleukin-1β induced a rapid and transient loss of both PR-A and PR-B protein, followed by a latent (24 hours) increase in both PR isoforms. R5020 negated the IL-1β-induced increase in PR-A and PR-B mRNA and protein as well as the rapid IL-1β-induced downregulation of nuclear PR. Interleukin-1β induced prostaglandin G/H synthase-2 (PGHS-2), but not prostaglandin G/H synthase-1 (PGHS-1), as well as prostaglandin E synthase-1 (PGES-1), but not prostaglandin F synthase (PGFS). R5020 did not ameliorate IL-1β induction of PGHS-2 or PGES-1. Blockade of prostaglandin synthesis (indomethacin) prevented both the IL-1β-induced increase in PR mRNA and the acute decrease in PR-A and PR-B protein, implicating a role for prostaglandins in regulating PR expression in HCFs. Although progesterone may function to maintain PR expression in a milieu of increasing cytokines in the late gestation human cervix, it does not exert an anti-inflammatory role with regard to prostaglandin E₂ (PGE2) production.

Expression of StAR and Key Genes Regulating Cortisol Biosynthesis in Near Term Ovine Fetal Adrenocortical Cells: Effects of Long-Term Hypoxia

We previously demonstrated decreased expression of key genes regulating cortisol biosynthesis in long-term hypoxic (LTH) sheep fetal adrenals compared to controls. We also showed that inhibition of the extracellular signal-regulated kinases (ERKs) with the mitogen-activated protein kinase (MEK)/ERK inhibitor UO126 limited adrenocorticotropic (ACTH)-induced cortisol production in ovine fetal adrenocortical cells (FACs), suggesting a role for ERKs in cortisol synthesis. This study was designed to determine whether the previously observed decrease in LTH cytochrome P45011A1/cytochrome P450c17 (CYP11A1/CYP17) in adrenal glands was maintained in vitro, and whether ACTH alone with or without UO126 treatment had altered the expression of CYP11A1, CYP17, and steroidogenic acute regulatory protein (StAR) in control versus LTH FACs. Ewes were maintained at high altitude (3820 m) from ∼40 days of gestation (dG). At 138 to 141 dG, fetal adrenal glands were collected from LTH (n = 5) and age-matched normoxic controls (n = 6). Fetal adrenocortical cells were challenged with ACTH (10^-8 M) with or without UO126 (10 µM) for 18 hours. Media samples were collected for cortisol analysis and messenger RNA (mRNA) for CYP11A1, CYP17, and StAR was quantified by quantitative real-time polymerase chain reaction. Cortisol was higher in the LTH versus control ( P < .05). StAR mRNA was decreased in LTH versus control ( P < .05). U0126 alone had no effect on mRNA in either group. UO126 prevented the increase in CYP11A1 and CYP17 in control FACs. Basal CYP11A1 and CYP17 were not different in LTH versus control. ACTH increased CYP11A1 and CYP17 only in control FACs ( P < .05). U1026 attenuated the ACTH response indicative of a role for ERK in CYP11A1 and CYP17 expression. ACTH may require additional factors in FACs to fully regulate StAR expression.

Gestational hypoxia modulates expression of corticotropin-releasing hormone and arginine vasopressin in the paraventricular nucleus in the ovine fetus

Maturation of the fetal hypothalamo–pituitary–adrenocortical (HPA) axis is critical for organ maturation necessary for the fetus to transition to the ex‐utero environment. Intrauterine stressors can hasten maturation of the HPA axis leading to fetal growth restriction and in sheep, premature birth. We have previously reported that high‐altitude mediated, long‐term‐moderate gestational hypoxia (LTH) during gestation has a significant impact on the fetal HPA axis. Significant effects were observed at the level of both the anterior pituitary and adrenal cortex resulting in elevated plasma ACTH during late gestation with decreased adrenocortical expression of enzymes rate limiting for cortisol synthesis. As such, these fetuses exhibited the normal ontogenic rise in fetal plasma cortisol but an exaggerated cortisol response to acute stress. This study extended these findings to ACTH secretagogue expression in the PVN using in situ hybridization. We report that the expression of AVP but not CRH was increased in the medial parvocellular PVN (mpPVN) in the LTH fetus. This represented an increase in both AVP mRNA per neuron as well as an increase in AVP hybridizing neurons with no increase in mpPVN CRH neurons. LTH had no effect on PVN volume, area of CRH or AVP hybridization, thus LTH did not have a trophic effect on the size of the nucleus. In conclusion, there appears to be a switch from CRH to AVP as a primary ACTH secretagogue in response to LTH, supporting our previous findings of increased anterior pituitary sensitivity to AVP over CRH in the LTH fetus.

Fetal endocrine and metabolic adaptations to hypoxia: the role of the hypothalamic-pituitary-adrenal axis

In utero, hypoxia is a significant yet common stress that perturbs homeostasis and can occur due to preeclampsia, preterm labor, maternal smoking, heart or lung disease, obesity, and high altitude. The fetus has the extraordinary capacity to respond to stress during development. This is mediated in part by the hypothalamic-pituitary-adrenal (HPA) axis and more recently explored changes in perirenal adipose tissue (PAT) in response to hypoxia. Obvious ethical considerations limit studies of the human fetus, and fetal studies in the rodent model are limited due to size considerations and major differences in developmental landmarks. The sheep is a common model that has been used extensively to study the effects of both acute and chronic hypoxia on fetal development. In response to high-altitude-induced, moderate long-term hypoxia (LTH), both the HPA axis and PAT adapt to preserve normal fetal growth and development while allowing for responses to acute stress. Although these adaptations appear beneficial during fetal development, they may become deleterious postnatally and into adulthood. The goal of this review is to examine the role of the HPA axis in the convergence of endocrine and metabolic adaptive responses to hypoxia in the fetus.

Adrenocorticotropic Hormone and PI3K/Akt Inhibition Reduce eNOS Phosphorylation and Increase Cortisol Biosynthesis in Long-Term Hypoxic Ovine Fetal Adrenal Cortical Cells

This study was designed to determine the role of the MEK/ERK1/2 and PI3K/Akt pathways in cortisol production and endothelial nitric oxide synthase (eNOS) phosphorylation (peNOS) in the ovine fetal adrenal in response to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for the last 100 days of gestation (dGa). At 138 to 142 dGa, fetal adrenal cortical cells (FACs) were collected from LTH and age-matched normoxic fetuses. Cortisol production and peNOS were measured in response to pretreatment with the MEK/ERK1/2 pathway inhibitor UO126 (UO) and adrenocorticotropic hormone (ACTH) stimulation. UO126 reduced ACTH-stimulated cortisol in both normoxic and LTH FACs. UO126 alone or in combination with ACTH reduced peNOS in the normoxic group, while ACTH alone or ACTH + UO inhibited peNOS in LTH FACs. Additionally, cortisol was measured in response to pretreatment with UO and treatment with 22R-hydroxycholesterol (22R-OHC) or water-soluble cholesterol (WSC) with and without ACTH stimulation. UO126 had no effect on 22R-OHC-treated cells, but reduced cortisol in cells treated with WSC and/or ACTH. Cortisol and peNOS were also measured in response to pretreatment with PI3K/Akt pathway inhibitor Wortmannin (WT) and ACTH stimulation. Wortmannin further increased cortisol under ACTH-stimulated conditions and, like ACTH, reduced peNOS in LTH but not normoxic FACs. Together, these data suggest that in LTH FACs MEK/ERK1/2 does not regulate peNOS but that UO acts downstream from eNOS, possibly at cholesterol transport, to affect cortisol production in LTH FACs, while the PI3K/Akt pathway, along with ACTH, regulates peNOS and plays a role in the fetal adaptation to LTH in FACs.

Long-Term Gestational Hypoxia Modulates Expression of Key Genes Governing Mitochondrial Function in the Perirenal Adipose of the Late Gestation Sheep Fetus

We previously reported that long-term hypoxia (LTH) increases expression of brown adipose tissue (BAT) genes in the perirenal adipose in the ovine fetus. The mechanisms with which hypoxia mediates the enhanced BAT phenotype are unresolved. This study was designed to examine the effects of LTH on (1) the expression of endothelial cell nitric oxide synthase (eNOS) and (2) indicators of mitochondrial biogenesis (transcription factors mitochondrial transcription factor A (mtTFA), nuclear respiratory factor (NRF) 1, and NRF-2; cytochrome c oxidase (COX) I, II, and IV and mitochondrial DNA content). Pregnant ewes were maintained at high altitude (3820 m) from ∼40 to 137 to 140 days of gestation and perirenal adipose was collected from normoxic control and LTH fetuses. There was no effect of LTH on fetal body weight or perirenal adipose mass. Long-term hypoxia increased (P < .05) perirenal eNOS and phospho-eNOS, messenger RNA (mRNA) for NRF1, NRF-2, mtTFA as well as COX-I, COX-II, and COX-IV mRNA. In contrast, mRNA for 2 markers for cellular proliferation (Ki67 and proliferating cell nuclear antigen [PCNA]) was lower in perirenal adipose from LTH fetuses compared to controls (P < .05), while mitochondrial to nuclear DNA ratio did not differ between groups. In conclusion, nitric oxide may function as a mechanism via which LTH enhances the BAT phenotype in fetal sheep prior to birth. Although there is an apparent increase in genes supporting mitochondrial function and adaptive thermogenesis in response to LTH, there does not appear to be an increased mitochondrial biogenesis per se. Such adaptive changes may provide a mechanism for the prominence of the BAT phenotype observed in the late gestation LTH fetus.

Up-regulation of the fetal baboon hypothalamo-pituitary-adrenal axis in intrauterine growth restriction: coincidence with hypothalamic glucocorticoid receptor insensitivity and leptin receptor down-regulation

Intrauterine growth restriction (IUGR) is an important fetal developmental problem resulting from 2 broad causes: maternal undernutrition and/or decreased fetal nutrient delivery to the fetus via placental insufficiency. IUGR is often accompanied by up-regulation of the hypothalamo-pituitary-adrenal axis (HPAA). Sheep studies show fetal HPAA autonomy in late gestation. We hypothesized that IUGR, resulting from poor fetal nutrient delivery, up-regulates the fetal baboon HPAA in late gestation, driven by hypothalamo-pituitary glucocorticoid receptor (GR) insensitivity and decreased fetal leptin in peripheral plasma. Maternal baboons were fed as ad libitum controls or nutrient restricted to produce IUGR (fed 70% of the control diet) from 0.16 to 0.9 gestation. Peripheral ACTH, cortisol, and leptin were measured by immunoassays. CRH, arginine vasopressin (AVP), GR, leptin receptor (ObRb), and pro-opiomelanocortin peptide expression were determined immunohistochemically. IUGR fetal peripheral cortisol and ACTH, but not leptin, were increased (P < .05). IUGR increased CRH peptide expression, but not AVP, in the fetal hypothalamic paraventricular nucleus (PVN) and median eminence (P < .05). PVN ObRb peptide expression, but not GR, was decreased (P < .05) with IUGR. ObRb and pro-opiomelanocortin were robustly expressed in the anterior pituitary gland, but ∼1% of cells showed colocalization. We conclude that (1) CRH, not AVP, is the major releasing hormone driving ACTH and cortisol secretion during primate IUGR, (2) fetal HPAA activation was aided by GR insensitivity and decreased ObRb expression in the PVN, and (3) the anterior pituitary is not a site for ObRb effects on the HPAA.

Extracellular signal-regulated kinases (ERK1/2) signaling pathway plays a role in cortisol secretion in the long-term hypoxic ovine fetal adrenal near term

This study assessed the role of the extracellular signal-regulated kinase (ERK) signaling pathway on the previously observed enhanced cortisol secretion in response to adrenocorticotropic hormone (ACTH) treatment in fetal adrenocortical cells (FACs) from long-term hypoxic (LTH) ovine fetuses. Ewes were maintained at high altitude (3,820 m) from ~40 to 138-141 days gestation when FACs were collected and challenged with either ACTH (10 nM) or 8-bromoadenosine 3',5'-cyclic monophosphate (8-bromo-cAMP, 10 mM) in the presence or absence of the mitogen-activated protein kinase/extracellular signal-regulated protein kinase (MEK)/ERK inhibitor UO126 (10 μM). FACs from age-matched normoxic fetuses served as controls. Media and FACs were collected at selected time intervals after ACTH or 8-bromo-cAMP stimulation for cortisol measurement and Western analysis of ERK1/2 and phospho-ERK1 and -2 (pERK1/2). After ACTH or 8-bromo-cAMP treatment, cortisol production was greater in the LTH group compared with control (P < 0.05). UO126 reduced ACTH and 8-bromo-cAMP-mediated cortisol output in both groups (P < 0.01 vs. ACTH or 8-bromo-cAMP alone). Under basal conditions, ERK1/2 and pERK1/2 were not different between LTH and normoxic fetuses. In response to ACTH or 8-bromo-cAMP treatment, ERK1/2 were not different between groups; however, pERK1/2 were elevated in the LTH FACs compared with normoxic control FACs. ERK1/2 phosphorylation declined following ACTH treatment in the control group, but UO126 had no effect on ERK1/2 compared with untreated levels. Both ACTH and 8-bromo-cAMP treatment resulted in a decline of protein levels. UO126 pretreatment virtually eliminated pERK1/2 expression. We conclude that basal ERK signaling in FACs is necessary for normal cortisol production and sustained pERK in LTH adrenals enhances cortisol production.

Leptin receptor antagonist treatment ameliorates the effects of long-term maternal hypoxia on adrenal expression of key steroidogenic genes in the ovine fetus

We previously reported elevated adipose leptin expression, plasma leptin concentrations, and adrenocortical leptin receptor expression in the long-term hypoxic (LTH) ovine fetus. This study addressed whether leptin antagonist (LA) administration to LTH fetal sheep altered expression of key genes governing cortisol synthesis. Ewes were maintained at high altitude (3,820 meters) from 40 to 130 days gestation (dG), returned to Loma Linda University, and implanted with a maternal tracheal catheter. Reduced Po2 was maintained by nitrogen infusion. On 132 dG, LTH (n = 11) and age-matched, normoxic control (n = 11) fetuses underwent vascular catheter implantation. At 138 dG, fetuses were continuously infused with either saline or the LA (1.5 mg·kg(-1)·day(-1)) for 4 days and samples collected for blood gases, ACTH, and cortisol. Fetal adrenal cortex was collected for determination of steriodogenic acute regulatory protein (StAR), ACTH, and leptin receptor, cholesterol side-chain cleavage (CYP11A1), cytochrome P-450 11β-hydroxylase (CYP11B1), 17α-hydroxylase (CYP17), 21-hydroxylase (CYP21), signal transducer and activator of transcription 3 (STAT3), pSTAT3, and 17β-hydroxysteroid dehydrogenase (HSD3B) expression. In the saline-infused LTH fetuses, StAR, ACTH receptor, CYP11A1, and CYP17 expression was significantly lower compared with control (P < 0.05), whereas levels of CYP11B1, CYP21, and HSD3B mRNA were similar between groups. LA infusion restored expression of StAR, pSTAT3, CYP11A1, and CYP17, but not ACTH receptor, to normal ontogenic levels in the LTH group while having no effect on control fetuses. Neither fetal plasma ACTH nor cortisol concentrations were altered by LA infusion. We speculate that while leptin plays a role in governing expression of key enzymes and StAR in response to LTH, other factors play a role in modulating cortisol synthesis in these fetuses.

eNOS activation and NO function: differential control of steroidogenesis by nitric oxide and its adaptation with hypoxia

Nitric oxide (NO) plays a role in a wide range of physiological processes. Aside from its widely studied function in the regulation of vascular function, NO has been shown to impact steroidogenesis in a number of different tissues. The goal of this review is to explore the effects of NO on steroid production and further, to discern its source(s) and mechanism of action. Attention will be given to the regulation of NO synthases in specific endocrine tissues including ovaries, testes, and adrenal glands. The effects of hypoxia on generation of NO and subsequent effects on steroid biosynthesis will also be examined. Finally, a potential model for the interaction of hypoxia on NO synthesis and steroid production is proposed.

Long-term hypoxia enhances cortisol biosynthesis in near-term ovine fetal adrenal cortical cells

This study was designed to determine the potential mechanism/mechanisms of previously observed enhanced fetal cortisol secretion following exposure to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for approximately the last 100 days of gestation. Between the gestation days of 138 and 141, adrenal glands were collected from LTH and age-matched normoxic control fetuses. Cyclic adenosine monophosphate (cAMP), cortisol, and steroidogenic acute regulatory (StAR) protein were measured in response to adrenocorticotropic hormone (ACTH) stimulation. Cortisol responses to ACTH were also measured in the presence of the protein kinase (PKA) inhibitor H-89, proopiomelanocortin (POMC), or 22-kDa pro-ACTH. Cortisol output was higher in the LTH group compared to the control (P < .05), following ACTH treatment while the cAMP response was similar in both groups. Although PKA inhibition decreased cortisol production in both groups, however no differences were observed between groups. Western analysis revealed a significant increase in protein expression for StAR in the LTH group (P < .05, compared to control). Proopiomelanocortin and 22-kDa pro-ACTH did not alter the cortisol response to ACTH treatment. Results from the present study taken together with those of previous in vivo studies suggest that the enhanced cortisol output in the LTH group is not the result of differences in cAMP generation or PKA. We conclude that enhanced cortisol production in LTH adrenals is the result of enhanced protein expression of StAR and potential downstream signaling pathways.

Nitric oxide inhibits ACTH-induced cortisol production in near-term, long-term hypoxic ovine fetal adrenocortical cells

We previously reported that in the sheep fetus, long-term hypoxia (LTH) resulted in elevated basal plasma adrenocorticotropic hormone (ACTH(1- 39)) whereas the cortisol levels were not different from normoxic controls. We also showed that LTH enhances endothelial nitric oxide synthase (eNOS) expression in the fetal adrenal. This study was designed to determine the effect of NO on cortisol production in adrenocortical cells from LTH fetal sheep. Ewes were maintained at high altitude (3820 m) from ∼40 days' gestation (dG) to near term. Between 138 and 141 dG, fetal adrenal glands were collected from LTH and age-matched normoxic control fetuses. Adrenal cortical cells were pretreated with sodium nitroprusside (SNP), nitro-L-arginine methyl ester (L-NAME), L-arginine, or diethyleneamine NO (DETA-NO) and then challenged with 10 nmol/L ACTH. Cortisol responses were compared after 1 hour. Adrenocorticotropic hormone -induced cortisol secretion was significantly higher in LTH versus control (P < .01). Enhancement of NO with L-arginine resulted in a significant reduction of ACTH-mediated cortisol production in the LTH group. DETA-NO also caused a significant decrease in ACTH-mediated cortisol production (P < .05). Inhibition of NOS with L-NAME significantly increased cortisol production in the LTH group (P < .05 compared to ACTH alone), whereas the effect on the control group was not significant. Nitric oxide synthase activity was significantly higher in the LTH group compared to control, but this difference was eliminated following ACTH treatment. These data indicate that LTH enhances adrenal cortical sensitivity to the inhibitory effects of NO on cortisol production. Nitric oxide may, therefore, play an important role in regulating ACTH-induced cortisol production in the LTH fetal adrenal.

Long-term hypoxia enhances ACTH response to arginine vasopressin but not corticotropin-releasing hormone in the near-term ovine fetus

This study tested the hypothesis that long-term hypoxia (LTH) results in enhanced fetal corticotrope sensitivity to the ACTH secretagogues, corticotropin-releasing hormone (CRH), and AVP. Ewes were maintained at high altitude (3,820 m) from 40 to 130-131 days of gestation. Upon return to the laboratory, hypoxia was maintained by maternal nitrogen infusion. Vascular catheters were placed in both LTH (n = 4) and normoxic controls (n = 4). Each fetus received a 15-min infusion of either saline, 100 ng/kg of ovine CRH, or 20 ng/kg of AVP/min over 3 consecutive days in a randomized order. Fetal blood samples were collected at 0, 15, 30, 60, and 90 min after the start of infusion and analyzed for ACTH(1-39), ACTH precursors, and cortisol. Anterior pituitaries were collected from additional noninstrumented fetuses for analysis of vasopressin receptor 1b (V1b) mRNA and protein. Basal plasma concentrations of both ACTH(1-39) and ACTH precursors were higher in LTH fetuses and were not altered by saline infusion. In response to CRH, ACTH(1-39) increased in both groups and was higher in the LTH group compared with control (P < 0.05). When analyzed as sum of ACTH(1-39) released (Delta0-90 min) above basal, CRH released equal amounts of ACTH(1-39) in both groups. In LTH fetuses, AVP evoked a greater ACTH(1-39) release (P < 0.05) when analyzed as an increased sum of ACTH(1-39) (Delta0-90 min) above basal. Both CRH and AVP elicited a release of ACTH precursors with no differences observed between LTH and control. AVP and CRH elicited significant increases in cortisol, which were higher in response to AVP than CRH. V1b mRNA and protein were elevated in the anterior pituitary of LTH fetuses compared with control. LTH significantly increases pituitary sensitivity to AVP. This enhanced sensitivity may be a mechanism of our previously observed enhanced corticotrope function.

Long-term hypoxia increases endothelial nitric oxide synthase expression in the ovine fetal adrenal

This study was designed to test the hypothesis that fetal adrenal nitric oxide synthase (NOS) is elevated in response to long-term hypoxia (LTH). Pregnant ewes were maintained at high altitude (3820 m) for approximately the last 100 days of gestation. Between days 138 and 141 of gestation, adrenal glands were collected from LTH fetuses and age-matched normoxic controls. Quantitative real-time polymerase chain reaction (qRT-PCR) and Western analysis were used to quantify NOS expression, and NOS distribution was examined by immunohistochemistry and double-staining immunofluorescence for endothelial NOS (eNOS) and 17alpha-hydroxylase (CYP17). Neuronal NOS (nNOS) was expressed at very low levels and with no differences between groups. Expression of eNOS was significantly greater in the LTH group compared with control. Neuronal NOS was distributed throughout the cortex while the greatest density of eNOS was observed in the zona fasciculata/reticularis area and eNOS co-localized with CYP17. We conclude that LTH enhances eNOS expression in the inner adrenal cortex which may play a role in regulation of cortisol biosynthesis in the LTH fetus.

Expression and distribution of glucocorticoid receptors in the ovine fetal adrenal cortex: effect of long-term hypoxia

This study was designed to determine if long-term hypoxia (LTH) alters adrenal glucocorticoid receptor (GR) expression in the ovine fetal adrenal cortex. Ewes were maintained at 3820 m from approximately 30 to 138 to 140 days' gestation, and fetal adrenals were collected. Western analysis revealed two approximately 94-kDa GR-alpha isoforms and a lower molecular weight (45 kDa) form. A decreasing trend in the ratio of 94-kDa/45-kDa bands following LTH suggested an increase in GR turnover. Immunohistochemistry demonstrated dense GR staining in the zona glomerulosa with minimal staining in the zona fasciculata in the control group, while dense staining was observed throughout the cortex in LTH. Western analysis and reverse transcription polymerase chain reaction confirmed that the GR- beta isoform is not present or expressed at extremely low levels in the fetal adrenal, hypothalamus, pituitary, and placenta. These data indicate that LTH alters GR-alpha function in the fetal adrenal cortex and suggest that GR-beta is not expressed in sheep.

Long-term hypoxia modulates expression of key genes regulating adipose function in the late-gestation ovine fetus

A major function of abdominal adipose in the newborn is nonshivering thermogenesis. Uncoupling protein (UCP) UCP1 and UCP2 play major roles in thermogenesis. The present study tested the hypothesis that long-term hypoxia (LTH) modulates expression of UCP1 and UCP2, and key genes regulating expression of these genes in the late-gestation ovine fetus. Ewes were maintained at high altitude (3,820 m) from 30 to 138 days gestation (dG); perirenal adipose tissue was collected from LTH and age-matched, normoxic control fetuses at 139-141 dG. Quantitative real-time PCR was used to analyze mRNA for UCP1, UCP2, 11beta hydroxysteroid dehydrogenase type 1 (HSD11B1) and 2 (HSD11B2), glucocorticoid receptor (GR), beta3 adrenergic receptor (beta3AR), deiodinase type 1 (DIO1) and DIO2, peroxisome proliferator activated receptor (PPAR) alpha and gamma and PPARgamma coactivator 1 (PGC1alpha). Concentrations of mRNA for UCP1, HSD11B1, PPARgamma, PGC1, DIO1, and DIO2 were significantly higher in perirenal adipose of LTH compared with control fetuses, while mRNA for HSD11B2, GR, or PPARalpha in perirenal adipose did not differ between control and LTH fetuses. The increased expression of UCP1 is likely an adaptive response to LTH, assuring adequate thermogenesis in the event of birth under oxygen-limiting conditions. Because both glucocorticoids and thyroid hormone regulate UCP1 expression, the increase in HSD11B1, DIO1, and DIO2 implicate increased adipose capacity for local synthesis of these hormones. PPARgamma and its coactivator may provide an underlying mechanism via which LTH alters development of the fetal adipocyte. These findings have important implications regarding fetal/neonatal adipose tissue function in response to LTH.

Strain differences in anxiety-like behavior: association with corticotropin-releasing factor

The purpose of the current study was to relate basal corticotropin-releasing factor (CRF) mRNA level in the central nucleus of the amygdala (CeA) with anxiety-like behavior using three strains of rat reported to exhibit a range of behavioral and neuroendocrine responses to stress. Anxiety-like behavior was determined for Fischer (F344), Wistar, and Wistar-Kyoto (WKY) rats with an elevated plus-maze and CRF mRNA level was measured using in situ hybridization. WKY rats exhibited more anxiety-like behavior on the elevated plus-maze than both F344 (p's < 0.01) and Wistar rats (p's < 0.05). WKY rats had higher basal levels of CRF mRNA in the CeA than F344 rats (p < 0.05) with a trend toward higher levels than Wistar rats (p = 0.06). Wistar rats had similar indices of anxiety with F344 rats and comparable levels of CRF mRNA in the CeA. Basal plasma corticosterone was similar for all three strains and repeated experience with the plus-maze had no effect on basal corticosterone levels or CRF mRNA levels in the paraventricular nucleus of the hypothalamus (PVN) for Wistar or WKY rats. Consistent with reported hyperactivity of the hypothalamopituitary adrenal axis of F344 rats with repeated stress, we observed elevated corticosterone following repeated exposure to the elevated plus-maze in F344 rats (p < 0.01) with a trend toward increased CRF mRNA levels in the PVN (p = 0.09). Heightened expression of CRF in the CeA of WKY rats may be involved in anxiety-like behaviors observed in this strain.

Long-term hypoxia modulates expression of key genes regulating adrenomedullary function in the late gestation ovine fetus

We previously communicated that long-term hypoxia (LTH) resulted in a selective reduction in plasma epinephrine following acute stress in fetal sheep. The present study tested the hypothesis that LTH selectively reduces adrenomedullary expression of phenylethanolamine-N-methyltransferase (PNMT), the rate-limiting enzyme for epinephrine synthesis. We also examined the effect of LTH on adrenomedullary nicotinic, muscarinic, and glucocorticoid receptor (GR) expression. Ewes were maintained at high altitude (3,820 m) from 30 to 138 days gestation (dGA); adrenomedullary tissue was collected from LTH and age-matched, normoxic control fetuses at 139-141 dGA. Contrary to our hypothesis, in addition to PNMT, adrenomedullary expression (mRNA, protein) of tyrosine hydroxylase (TH) and dopamine beta-hydroxylase (DBH) were reduced in the LTH fetus. Immunocytochemistry indicated that TH and DBH expression was lower throughout the medulla, while PNMT appeared to reflect a reduction in PNMT-expressing cells. Nicotinic receptor alpha 1, 2, 3, 5, 6, 7, beta 1, 2, and 4 subunits were expressed in the medulla of LTH and control fetuses. Messenger RNA for alpha 1 and 7 and beta 1 and 2 subunits was lower in LTH fetuses. Muscarinic receptors M1, M2, and M3 as well as the GR were also expressed, and no differences were noted between groups. In summary, LTH in fetal sheep has a profound effect on expression of key enzymes mediating adrenomedullary catecholamine synthesis. Further, LTH impacts nicotinic receptor subunit expression potentially altering cholinergic neurotransmission within the medulla. These findings have important implications regarding fetal cardiovascular and metabolic responses to stress in the LTH fetus.

Chronically elevated corticosterone in the amygdala increases corticotropin releasing factor mRNA in the dorsolateral bed nucleus of stria terminalis following duress

Elevated corticosterone in the amygdala leads to cautious avoidance behaviors on the elevated plus maze. The current study examined the effect of elevated corticosterone in the amygdala on corticotropin releasing factor (CRF) mRNA levels in the bed nuclei of stria terminalis (BNST). Exposure to the elevated plus maze increased CRF mRNA in both the dorsolateral and ventrolateral BNST. Corticosterone implants in the amygdala potentiated this effect in the dorsolateral, but not ventrolateral BNST. Corticosterone also resulted in an increased number of neurons expressing CRF in the dorsolateral BNST in response to the behavioral stimuli.

Long-term hypoxia increases leptin receptors and plasma leptin concentrations in the late-gestation ovine fetus

This study was designed to test the hypothesis that long-term hypoxia (LTH) increases fetal plasma leptin and fetal adipose or placental leptin expression and alters hypothalamic and adrenocortical leptin receptor (OB-R) expression. Pregnant ewes were maintained at high altitude (3,820 m) from day 30 to approximately 130 days of gestation. Reduced Po2 was maintained in the laboratory by nitrogen infusion through a maternal tracheal catheter. On day 132, normoxic control and LTH fetuses underwent surgical implantation of vascular catheters (n=6 for each group). Five days after surgery, maternal and fetal arterial blood samples were collected for leptin, insulin, and glucose analysis. Placental tissue, periadrenal fat, and fetal hypothalami and adrenal glands were collected from additional control (n=7) and LTH (n=8) fetuses for analysis of leptin mRNA by quantitative, real-time, RT-PCR (qRT-PCR). There was a significant (P<0.03) elevation in fetal plasma leptin in the LTH fetuses (3.5+/-0.7 ng/ml) vs. control (1.1+/-0.1 ng/ml). There were no differences in either glucose or insulin concentrations between the two groups. Periadrenal adipose leptin mRNA was significantly higher in the LTH group compared with control, as was placental leptin expression. The levels of leptin mRNA in adipose were approximately 70 times higher vs. placenta. LTH significantly reduced expression of OB-Ra (short-isoform) in the hypothalamus (P=0.0156), while resulting in a significant increase in adrenal OB-Rb (long-form) expression (P<0.03). Our data suggest that leptin is a hypoxia-inducible gene in the ovine fetus and OB-R expression is altered by LTH. These changes may be responsible in part, for our previously observed alterations in fetal hypothalamic-pituitary-adrenal function following LTH.

Long-term expression of corticotropin-releasing factor (CRF) in the paraventricular nucleus of the hypothalamus in response to an acute colonic inflammation

This study examined the long-term effects of an acute colitis on central corticotropin-releasing factor (CRF) expression. An increase in CRF mRNA in the paraventricular nucleus of the hypothalamus (PVN) and the central nucleus of the amygdala (CeA) was observed during active colitis, and the effect in the PVN was maintained following recovery. In summary, hypothalamic gene expression of CRF persists in the PVN despite resolution of an acute colitis.

Long-term hypoxia represses the expression of key genes regulating cortisol biosynthesis in the near-term ovine fetus

Basal plasma ACTH(1-39) concentrations are elevated in long-term hypoxic (LTH) fetal sheep. This study was designed to determine whether the expression of genes regulating cortisol biosynthesis was altered after LTH. Pregnant ewes were maintained at high altitude (3,820 m) from day 30 of gestation to near term, when the animals were transported to the laboratory. Reduced PO2 was maintained by nitrogen infusion through a maternal tracheal catheter. On days 137-141, fetal adrenal glands were collected from LTH and normoxic control fetuses. Real-time PCR was used to quantify mRNA for steroidogenic acute regulatory protein, 17alpha-hydroxylase (CYP17), 21-hydroxylase (CYP21), cholesterol side-chain cleavage (CYP11A1), 3beta-hydroxysteroid dehydrogenase type II (HSD3B2), and the ACTH receptor. We analyzed mRNA by slot-blot hybridization and also quantified mRNA for transcription factors necessary for adrenocortical development by quantitative real-time PCR: steroidogenic factor 1 and dosage-sensitive sex reversal, adrenal hypoplasia congenital, critical region on the X chromosome (DAX-1). Protein was quantified by Western blot analysis. Adrenal mRNAs for CYP17, CYP11A1, and the ACTH receptor were significantly reduced in LTH fetal sheep compared with levels shown in controls. Similarly, CYP11A1 protein and CYP17 protein were reduced in the LTH group. CYP21, steroidogenic acute regulatory protein, HSD3B2, steroidogenic factor 1, and DAX-1 expressions were not altered in response to LTH. We conclude that expression of two key steroidogenic enzymes (CYP17, CYP11A1) regulating cortisol biosynthesis and the ACTH receptor is lower in response to LTH. This likely represents an adaptive response to LTH, to prevent excessive cortisol production that would restrict fetal growth and potentially induce preterm delivery.

Proopiomelanocortin processing in the anterior pituitary of the ovine fetus after lesion of the hypothalamic paraventricular nucleus

The hypothalamic-pituitary-adrenocortical axis plays an essential role in the maturation of fetal organs and, in sheep, birth. Lesioning the paraventricular nucleus (PVN) in fetal sheep prevents adrenocortical maturation and parturition without altering plasma immunoreactive ACTH concentrations. The purpose of this study was to determine the effect of PVN lesion on anterior pituitary processing of proopiomelanocortin (POMC) to ACTH, plasma concentrations of ACTH and ACTH precursors (POMC; 22-kDa proACTH), and expression of subtilisin-like prohormone convertase 3 (SPC3) in corticotropes in fetal sheep. PVN lesion did not affect anterior pituitary POMC and 22-kDa proACTH levels, whereas ACTH was significantly affected. The ACTH precursor (POMC plus 22-kDa proACTH) to ACTH ratio in the anterior pituitary was significantly increased after PVN lesion. Post-PVN lesion, fetal plasma ACTH(1-39), was below the limit of detection, whereas ACTH precursors (POMC plus 22-kDa proACTH) were not affected. In the inferior region of the anterior pituitary, 40-50% of corticotropes had detectable SPC3 hybridization signal, and PVN lesion did not change the extent of colocalization of POMC and SPC3, or SPC3 mRNA levels within corticotropes. Neither the percent of corticotropes in the superior region containing SPC3 hybridization (7-12%) or hybridization signal strength was altered in response to PVN lesion. In conclusion, the fetal PVN is necessary for sustaining adequate anterior pituitary processing of POMC to ACTH and ACTH release needed for maturing the adrenal cortex in the sheep fetus.

Corticotropin-releasing factor 1 receptor-mediated mechanisms inhibit colonic hypersensitivity in rats

The potential relationship between stress and irritable bowel syndrome (IBS) symptomatology suggests a possible role for stress-mediating hormones, such as corticotropin-releasing factor (CRF), in the altered perception of stimuli in IBS patients. In previous studies, Wistar-Kyoto (WKY) rats with genetic indices of high anxiety demonstrated colonic hypersensitivity coupled with a high basal level of CRF within the central nervous system. In the current study we tested the hypothesis that a selective, non-peptide CRF1 receptor antagonist, antalarmin, would inhibit hypersensitivity in the WKY rat colon. Colonic sensitivity was determined by monitoring a visceromotor behavioural response during innocuous levels of colorectal distention (30 mmHg). In high anxiety WKY rats we found that antalarmin (20 mg kg-1, i.p.) significantly decreased the visceromotor response induced by colorectal distention. In a second study central administration (i.c.v.) of CRF was used to induce colonic hypersensitivity in lower anxiety Fischer 344 (F-344) rats, and in this model, antalarmin significantly inhibited the CRF-induced colonic hypersensitivity. In summary, a selective CRF1 receptor antagonist, antalarmin, inhibits colonic hypersensitivity apparent in WKY rats or in F-344 rats given a central administration of CRF. Our findings suggest that CRF1 receptor antagonism may represent a novel therapeutic approach for the treatment of IBS.

Corticosterone implants to the amygdala and type 1 CRH receptor regulation: effects on behavior and colonic sensitivity

Corticosterone (CORT) micropellets were stereotaxically placed bilaterally at the dorsal margin of the central nucleus of the amygdala (CeA). Both behavioral and physiological responses were recorded (plus maze and colonic discomfort) at 7 days post-implantation. Corticosterone reduced the exploration of the plus maze and increased colonic distress. The ability of a CRH type 1 receptor antagonist, antalarmin, to block behavioral and colonic effects of central placement of CORT was also examined. The diminished exploration in the plus maze and colon distress observed in response to CORT placement at the CeA were averted by the administration of antalarmin. These results provide further evidence for the role of the CRH type 1 receptor to ameliorate both behavioral and physiological functions.

Long-term hypoxia enhances proopiomelanocortin processing in the near-term ovine fetus

Secondary stressors in long-term hypoxic (LTH) fetal sheep lead to altered function of the hypothalamic-pituitary-adrenal axis. Although ACTH is considered the primary mediator of glucocorticoid production in fetal sheep, proopiomelanocortin (POMC) and 22-kDa pro-ACTH (22-kDa ACTH) have been implicated in the regulation of cortisol production in the ovine fetus. This study was designed to determine whether POMC expression and processing are altered after LTH. Pregnant ewes were maintained at high altitude (3,820 m) from day 30 of gestation to near term, when the animals were transported to the laboratory. Reduced Po2 was maintained by nitrogen infusion through a maternal tracheal catheter. On days 139-141, fetal anterior pituitaries were collected from normoxic control and LTH fetuses. We measured POMC and corticotrophin-releasing factor type 1 receptor (CRF1-R) mRNA using quantitative real-time PCR, and we used Western blot analysis for quantitation of ACTH, ACTH precursor, and CRF1-R proteins. We measured plasma ACTH1-39 using a two-site immunoradiometric assay specific for ACTH1-39. Plasma ACTH precursors were measured by ELISA. Anterior pituitary POMC mRNA levels were not different between groups, whereas CRF1-R levels were significantly higher in the LTH anterior pituitaries compared with control (P<0.05). In contrast, protein levels of POMC, CRF1-R, 22-kDa ACTH, and ACTH1-39 were significantly lower in the LTH group. Plasma concentrations of both ACTH precursors and ACTH1-39 were significantly elevated in LTH fetuses, whereas the ratio of plasma precursors to ACTH was significantly lower. We conclude that LTH results in enhanced POMC processing and/or release to ACTH and increased hypothalamic drive.

Corticosterone acts directly at the amygdala to alter spinal neuronal activity in response to colorectal distension

Administration of glucocorticoids to the amygdaloid nucleus facilitates visceromotor responses to colorectal distension in rats. The aim of this study was to determine if colorectal hypersensitivity develops through central modulation of spinal neuronal activity. Stereotaxic delivery of corticosterone (n = 10) or cholesterol (control, n = 10) onto the dorsal margin of the amygdala was performed on male Fischer-344 rats. Seven days later, extracellular potentials of single L(6)-S(1) spinal neurons were examined for responses to colorectal distension (CRD, 20-80 mmHg, 20 s) in sodium pentobarbital anesthetized and paralyzed animals. The proportions of neurons that responded to noxious CRD in corticosterone-implanted (62/186, 33%) and cholesterol-implanted (55/163, 34%) animals were virtually identical. However, the mean excitatory response of spinal neurons to CRD in corticosterone-treated rats was significantly greater (26.7 +/- 2.2 vs. 16.4 +/- 1.8 imp/s, P < 0.01) and the duration was longer (37.0 +/- 3.9 vs. 25.8 +/- 1.5 s, P < 0.05) than in the control group. No significant differences were found in neural responses to nonnoxious and noxious mechanical stimulation of somatic fields between corticosterone-implanted and control groups. In conclusion, our data support the hypothesis that central stimulation of the amygdala by corticosterone sensitizes the lumbosacral spinal neurons that mediate visceromotor reflexes to CRD.

Stereotaxic localization of corticosterone to the amygdala enhances hypothalamo-pituitary-adrenal responses to behavioral stress

The amygdala is involved in behavioral, autonomic, and neuroendocrine responses to stressful stimuli. The goal of the current study was to determine the effect of directly elevating glucocorticoids in the amygdala on hypothalamo-pituitary-adrenocortical (HPA) responses to the elevated plus maze, a behavioral stressor known to activate the amygdala. Micropellets (30 microg) of crystalline corticosterone or cholesterol (control) were implanted bilaterally at the dorsal margin of the CeA in male Wistar rats; vascular catheters were also placed at this time. Five days post-surgery, blood samples were drawn at 07:00 and 19:00 h to assess diurnal rhythm of plasma corticosterone. At 7 days post-implantation, rats were subjected to behavioral stress using an elevated plus maze and blood was collected 15 min prior to stress, and at 15, 45, and 90 min after the initiation of the stressor. Corticotropin releasing factor (CRF) and arginine vasopressin (AVP) mRNA levels were analyzed by in situ hybridization in the medial parvocellular division of the hypothalamic paraventricular nucleus (mpPVN) in corticosterone- and cholesterol-implanted rats either not exposed to the elevated plus maze (control) or 4 h post-behavioral stress. Localization of corticosterone to the amygdala had no effect on diurnal rhythm of corticosterone secretion. Behavioral stress significantly increased peak plasma corticosterone levels in both groups to a similar level. However, in the corticosterone implanted rats, plasma corticosterone concentrations at 45 and 90 min post-stress were significantly greater compared to control rats indicating a prolonged corticosterone response to behavioral stress. In non-stressed rats, corticosterone delivery to the amygdala elevated basal CRF mRNA in the mpPVN to levels similar to those observed post-stress in control animals; no further increase was observed in CRF mRNA following stress. Behavioral stress resulted in a significant elevation in CRF mRNA in cholesterol controls. Basal AVP mRNA levels were unaffected by corticosterone implants. AVP mRNA did not increase in cholesterol implanted rats in response to behavioral stress. However, AVP mRNA levels were higher in corticosterone implanted rats post stress compared to cholesterol treated controls. In conclusion, direct administration of corticosterone to the amygdala increases plasma corticosterone in response to a behavioral stressor without altering the diurnal rhythm in plasma corticosterone. Elevated basal levels of mpPVN CRF mRNA, and the induction of a mpPVN AVP mRNA response to the behavioral stressor implicate enhanced ACTH secretagogue expression in the increased HPA response to corticosterone modulation of amygdala function.

Anatomical distribution and cellular basis for high levels of aromatase activity in the brain of teleost fish: aromatase enzyme and mRNA expression identify glia as source

Although teleost fish have higher levels of brain aromatase activity than any other vertebrate group, its function remains speculative, and no study has identified its cellular basis. A previous study determined aromatase activity in a vocal fish, the plainfin midshipman (Porichthys notatus), and found highest levels in the telencephalon and lower levels in the sonic hindbrain, which was dimorphic between and within (males) sexes. We have now localized aromatase-containing cells in the midshipman brain both by immunocytochemistry using teleost-specific aromatase antibodies and by in situ hybridization using midshipman-specific aromatase probes. Aromatase-immuno-reactivity and mRNA hybridization signal are consistent with relative levels of aromatase activity in different brain regions: concentrated in the dimorphic sonic motor nucleus, in a band just beneath the periaqueductal gray in the midbrain, in ventricular regions in the hypothalamus, and highest levels in the telencephalon especially in preoptic and ventricular areas. Surprisingly, double-label immunofluorescence does not show aromatase-immunoreactive colocalization in neurons, but instead in radial glia throughout the brain. This is the first study to identify aromatase expression mostly, if not entirely, in glial cells under normal rather than brain injury-dependent conditions. The abundance of aromatase in teleosts may represent an adaptation linked to continual neurogenesis that is known to occur throughout an individual's lifetime among fishes. The localization of aromatase within the intersexually and intrasexually dimorphic vocal-motor circuit further implies a function in the expression of alternative male reproductive phenotypes and, more generally, the development of natural, individual variation of specific brain nuclei.

Regulation of proopiomelanocortin messenger ribonucleic acid levels in the ovine fetal anterior pituitary in vitro

Parturition in sheep is dependent upon maturation of the fetal hypothalamo-pituitary-adrenocortical (HPA) axis. Anterior pituitary expression of the ACTH precursor, proopiomelanocortin (POMC), increases during the final days of gestation in spite of exponentially increasing fetal plasma cortisol levels. Lesion of the hypothalamic paraventricular nucleus prevents the late gestation increase in POMC mRNA. The purpose of this study was to examine glucocorticoid, corticotropin releasing factor (CRF) and arginine vasopressin (AVP) regulation of POMC mRNA levels in fetal anterior pituitary corticotropes in vitro and to address potential interactions between glucocorticoids and neuropeptides in regulating POMC. Anterior pituitaries from fetal sheep at two gestational ages (dGA; 118-125 dGA, n=9; 140-144 dGA, n=7) were enzymatically dispersed. POMC mRNA levels were determined at 24, 48 and 72 h post-dispersion. CRF, AVP and dexamethasone (DEX) regulation of POMC mRNA were determined at 24 and 72 h post-dispersion. The capacity of CRF and AVP to modulate DEX suppression of POMC mRNA levels was also examined. POMC mRNA was elevated at 24 h (P<0.01) and 48 h (P<0.05) post-dispersion compared to 0 h (immediately post-dispersion) in 140-144 dGA but not 118-125 dGA corticotropes. DEX suppressed POMC mRNA in a dose-dependent manner (when administered at 24 h post-dispersion) in the 140-144 dGA anterior pituitary cells but not 118-125 dGA anterior pituitary cells. Administration of DEX (10 nM) at 0 h prevented the increase in POMC mRNA levels observed at 24 h post dispersion in the 140-144 dGA group. Neither CRF nor AVP (administered at either 24 or 72 h post-dispersion) altered POMC mRNA levels in either 118-125 or 140-144 dGA anterior pituitary cells. Continuous exposure of anterior pituitary cells with either CRF or AVP (50 pM) through 96 h increased (P<0.05) POMC mRNA. No synergistic or additive effects were observed with CRF and AVP. Four hour pretreatment with CRF but not AVP (100 nM at 24 h post-dispersion) attenuated (P<0.05) DEX suppression of POMC mRNA levels in 140-144 dGA corticotropes. In conclusion, our results indicate that direct glucocorticoid suppression of POMC expression in fetal sheep initiates between approximately 120 and approximately 140 dGA, coincident with the period of gestation when fetal plasma cortisol is exponentially rising. Further, while short duration exposure of fetal corticotropes to either CRF or AVP had no effect on POMC mRNA, CRF appears capable of interfering with glucocorticoid suppression of POMC mRNA. The latter observation provides a potential mechanism via which the fetal PVN may counter rising fetal plasma cortisol concentrations resulting in the previously observed late gestation increase in anterior pituitary POMC mRNA.

Evidence for visceral hypersensitivity in high-anxiety rats

In patients with irritable bowel syndrome, anxiety is often associated with visceral pain. Based on this information we hypothesized that rats genetically predisposed to anxiety have an increased visceral sensitivity. To test this hypothesis, visceromotor reflex recordings in response to colorectal distention were used to estimate the level of visceral stimulation in high; moderate-, and low-anxiety rats. We compared the effect of innocuous colorectal distension in rats with and without sensitized colons. In nonsensitized rats visceromotor responses were increased by colorectal distention with the greatest response in the high-anxiety Wistar-Kyoto strain. Sensitization of the colon significantly increased visceromotor responses to colorectal distention in all rat strains. In summary, our data suggested that a manifestation of a genetically determined anxiety level appeared to be abnormal neural responsiveness of the gastrointestinal tract leading to visceral hypersensitivity in high-anxiety animals.

Blunted stress cortisol response in abstinent alcoholic and polysubstance-abusing men

BACKGROUND

This study tested cortisol responses to a psychological stressor in controls (CT) versus patients who were diagnosed as alcohol dependent (AD) or alcohol and stimulant dependent (ADSD) by DSM-IV criteria and who were abstinent for 3 to 4 weeks from alcohol and illicit drugs. Alcohol increases cortisol secretion acutely and during withdrawal. However, there is little information about abnormalities of hypothalamic-pituitary-adrenocortical (HPA) reactivity in recovering alcoholics.

METHODS

Accordingly, we tested HPA function in the laboratory between 7:00 and 9:30 AM on control versus stress days. Stress consisted of a 20-min public speaking challenge with preparation and delivery of two short speeches, ostensibly evaluated for quality of delivery, whereas control involved relaxing for the same period. Cortisol was measured in saliva collected at baseline, stress or control, and recovery period, and also at home at 9:00 PM on one of the two days.

RESULTS

The three groups did not differ in diurnal patterns of cortisol secretion on the rest day and 9:00 PM sample, which indicated that AD and ADSD patients had intact diurnal HPA regulation at rest. During speech stress, the CT subjects showed the expected cortisol increase (p < 0.0001), whereas neither AD nor ADSD patients responded significantly. Cortisol values were not accounted for by covariates such as depression, posttraumatic stress disorder, glucose metabolism, or anthropometric or demographic characteristics.

CONCLUSIONS

The apparent stress hyporesponsiveness of the AD and ADSD patients suggests a persistent disruption of HPA function, perhaps due to incomplete recovery from prior abuse, or to a preexisting alteration in neural systems that regulate HPA responses to stress.

Corticosterone delivery to the amygdala increases corticotropin-releasing factor mRNA in the central amygdaloid nucleus and anxiety-like behavior

The present study examined the effects of stereotaxic delivery of corticosterone to the amygdala on anxiety-like behavior and corticotropin-releasing factor (CRF) mRNA level in the central nucleus of the amygdala (CeA). Micropellets (30 microg) of crystalline corticosterone or cholesterol (control) were implanted bilaterally at the dorsal margin of the CeA in Wistar rats. Seven days post-implantation, anxiety-like behavior was accessed using an elevated plus-maze. CRF mRNA level in the CeA was determined by in situ hybridization 4 h after being tested on the elevated plus-maze. Corticosterone implants increased indices of anxiety on the elevated plus-maze and produced a concomitant increase in both basal level of CRF mRNA per neuron and the number of neurons with CRF hybridization signal in the CeA. The plus-maze increased CRF mRNA levels in the CeA of cholesterol implanted rats to the elevated basal levels observed in corticosterone treated animals. Exposure to the plus-maze did not increase CRF mRNA level in the CeA of corticosterone implanted rats beyond elevated basal levels. Taken together, these findings support the involvement of the amygdala in anxiety-like behaviors in response to chronically elevated corticosterone and suggests that elevated glucocorticoids may increase anxiety by inducing CRF expression in the CeA.

Ontogeny of angiotensin II type 1 receptor and cytochrome P450(c11) in the sheep adrenal gland

In the present study we investigated the ontogeny of the expression of the type 1 angiotensin receptor (AT(1)R mRNA) and the zonal localization of AT(1)R immunoreactivity (AT(1)R-ir) and cytochrome P450(c11) (CYP11B-ir) in the sheep adrenal gland. In the adult sheep and in the fetus from as early as 90 days gestation, intense AT(1)R-ir was observed predominantly in the zona glomerulosa and to a lesser extent in the zona fasciculata, and it was not detectable in the adrenal medulla. AT(1)R mRNA decreased 4-fold between 105 days and 120 days, whereas AT(1)R mRNA levels remained relatively constant between 120 days and the newborn period. In contrast, both in the adult sheep and in the fetal sheep from as early as 90 days gestation, intense CYP11B-ir was consistently detected throughout the adrenal cortex and in steroidogenic cells that surround the central adrenal vein. In conclusion, we speculate that the presence of AT(1)R in the zona fasciculata, and the higher levels of expression of AT(1)R at around 100 days gestation, may suggest that suppression of CYP17 is mediated via AT(1)R at this time. The abundant expression of AT(1)R-ir and CYP11B-ir in the zona glomerulosa of the fetal sheep adrenal gland would also suggest that lack of angiotensin II stimulation of aldosterone secretion is not due to an absence of AT(1)R or CYP11B in the zona glomerulosa.

Corticotropin-releasing factor receptor expression in the pituitary of fetal sheep after lesion of the hypothalamic paraventricular nucleus

Both the capacity of CRF to release ACTH and the number of binding sites for CRF in the anterior pituitary decline during the final weeks of gestation in fetal sheep. The present study examined regulation of pituitary CRF receptor expression by the hypothalamic paraventricular nucleus (PVN) during late gestation in fetal sheep. Bilateral radiofrequency lesions of the PVN (PVN-Lx; n = 4) or sham lesions (SHAM; n = 5) were performed in fetal sheep at 118-122 days of gestational age (dGA). Pituitary glands from PVN-Lx and SHAM fetuses were collected at 139-142 dGA (term, approximately 148 dGA). Dual-label in situ hybridization was performed using a digoxigenin-labeled ovine POMC complementary RNA, together with a 35S-labeled ovine CRF type I (CRF1) receptor complementary RNA, to localize and quantify CRF1 receptor mRNA in POMC-hybridizing cells. Binding of [125I]-ovine CRF was also examined in the fetal pituitary of both PVN-Lx and SHAM fetuses using in situ autoradiography. The hybridization signal for the CRF1 receptor mRNA was primarily restricted to POMC-expressing cells in the anterior pituitary of both PVN-Lx and SHAM fetuses; no hybridization signal for the CRF1 receptor was observed in the neurointermediate lobe (NIL) in either group. The hybridization signal for CRF1 receptor mRNA in anterior pituitary corticotropes of PVN-Lx fetuses was significantly lower in both the inferior and superior regions of the anterior pituitary, compared with SHAM fetuses (P < 0.05). In the inferior region of the anterior pituitary, the percentage of POMC-hybridizing cells containing CRF1 receptor hybridization signal was significantly greater in PVN-Lx (90+/-7%; mean +/- SEM), compared with SHAM (67+/-6%; P < 0.05) fetuses. No differences in the percentage of POMC cells containing CRF1 receptor hybridization signal were observed in the superior region of the anterior pituitary between PVN-Lx (89+/-8%) and SHAM (87+/-9%). Binding of [125I]-ovine CRF (oCRF) was significantly greater in anterior pituitaries of PVN-Lx (140+/-19 mean arbitrary densitometry U +/- SEM), compared with SHAM (73+/-23; P < 0.05) fetuses. For both PVN-Lx and SHAM fetuses, there were no differences within group in [125I]-oCRF binding between the inferior and superior regions of the anterior pituitary. A weak, but significant (P < 0.05), autoradiographic signal for [125I]-oCRF binding was observed in the NIL of both SHAM and PVN-Lx fetal sheep. The level of [125I]-oCRF binding was significantly lower in the NIL, compared with anterior pituitary, for both SHAM (P < 0.01) and PVN-Lx fetuses. There were no differences in [125I]-oCRF binding in the NIL between SHAM and PVN-Lx fetal sheep. Our findings support a role for the PVN in regulating anterior pituitary CRF1 receptor expression in the late-gestation sheep fetus.

Expression of proopiomelanocortin and prohormone convertase-1 and -2 in the late gestation fetal sheep pituitary

The biological activity of fetal plasma immunoreactive ACTH has been reported to increase during the final weeks of gestation in fetal sheep, indicative of enhanced processing of POMC to ACTH. The present study was aimed at examining the expression and localization of the prohormone convertases, PC1 and PC2, in the pituitary of fetal sheep during the final weeks of gestation. Pituitaries were obtained from fetal sheep during the final 50 days gestation (dGA) at 100-107 dGA (n = 6), 117-121 dGA (n = 6), 126-130 dGA (n = 7), and 144-147 dGA (n = 8; term = approximately 148 dGA). Pituitaries were cryosectioned and subjected to dual labeling in situ hybridization using 35S-labeled PC1 and/or PC2 complementary RNA probes with a digoxigenin-labeled POMC complementary RNA to localize and quantify PC1 and PC2 messenger RNA (mRNA) in POMC-hybridizing cells. Immunocytochemistry was also performed to assess coexpression of PC1 and PC2 with ACTH in the fetal pituitary. PC1 mRNA was heterogeneously distributed in the anterior pituitary (AP) at all gestational ages examined, with hybridization signals observed over POMC-expressing cells (corticotropes) as well as over noncorticotrope phenotypes. The inferior region of the AP contained an approximately 3-fold greater (P < 0.01) percentage of POMC cells containing PC1 transcripts compared with the superior region of the AP. The proportion of POMC cells containing PC1 was significantly higher (P < 0.01) in the 100-107 dGA and 144-147 dGA groups than in the 117-121 dGA and 126-130 dGA groups in both inferior and superior AP. The intensity of the PC1 hybridization signal over POMC-expressing cells was also about 2- to 4-fold greater (P < 0.01) in the inferior compared with the superior region of the fetal AP; the intensity of the PC1 hybridization signal associated with POMC cells remained constant within the AP region and did not change over the gestational ages examined. Hybridization for PC1 was highly variable over regions of AP not hybridizing for POMC, probably due to differences in the level of mRNA for PC1 between phenotypes. Similar to POMC cells, the average hybridization signal for PC1 over non-POMC-hybridizing regions was about 2-fold greater in the inferior vs. superior AP. A weak PC2 hybridization signal was observed over a small number of unidentified phenotypes in the fetal AP at all ages examined; no POMC cells were found to contain PC2 hybridization signal. In the neurointermediate lobe, POMC, PC1, and PC2 were ubiquitously expressed at all ages. Levels of PC1 and PC2 mRNA in the fetal neurointermediate lobe did not change over the period of gestation examined. Immunocytochemical analysis of PC1 and PC2 with ACTH confirmed the pattern of expression and the extent of coexpression observed with in situ hybridization methods. We conclude that both PC1 and PC2 are likely to contribute to POMC processing in the fetal pituitary during the final weeks of gestation.

Structure and function of the ovine type 1 corticotropin releasing factor receptor (CRF1) and a carboxyl-terminal variant

Corticotropin releasing factor (CRF) is the major neuropeptide regulating the hypothalamo-pituitary-adrenocortical axis in most species. A pituitary receptor for CRF (designated CRF1) belonging to the seven-transmembrane helix, G-protein-coupled receptor superfamily has been cloned for human, rat, mouse and xenopus. Since ovine CRF shares only 84% identity to human/rat CRF (h/rCRF) we postulated that the sheep pituitary CRF1 receptor may have similarly diverged from the rodent and human CRF1. We report the molecular cloning of an ovine pituitary cDNA containing a 1245 bp open reading frame encoding a 415 amino acid sheep CRF1 receptor 78, 86, 94, and 95% homologous to xenopus, chicken, rat, mouse, and human CRF1, respectively. The divergence in primary structure between the sheep CRF1 and the other mammalian CRF1s is primarily localized to the extracellular amino terminal domain of the receptor (18 of 22 divergent residues, ovine vs human CRF1). A variant of the oCRF1 was also isolated (oCRF1var) with 133 bp deleted from nucleotide (nt) 1080 to nt 1213 of the open reading frame (ORF) resulting in a new ORF of 1176 nt predicting a 392 residue CRF1 variant receptor. The 133 bp deletion would cause a frame-shift at residue 358 within the carboxyl-third of the seventh transmembrane domain (TM7) resulting in a shortened cytoplasmic tail with a new amino acid sequence from residue 358 to 392. Scatchard analysis of saturation curves using membrane prepared from Cos 7 cells transfected with oCRF1 or oCRF1var indicated that both wild-type and variant receptors were expressed similarly (number of CRF binding sites) and both bound oCRF with high affinity [oCRF1 (Kd): 2.5 + 1.6 nM; oCRF1var: 5.1 + 2.3 nM]. The non-hydrolyzable GTP analogue (GTPgammaS) lowered the affinity of both wild-type and variant oCRF1 receptors to a similar extent (oCRF1: 18.2 nM; oCRF1var: 22.4 nM). Both wild-type and variant oCRF1 receptors exhibited approximately 10-fold greater selectivity for oCRF and sauvagine compared to h/rCRF or alpha-helical [9-41]oCRF. CRF effectively stimulated the accumulation of cAMP (EC50 = 51 pM) in Cos 7 cells transiently transfected with wild-type but not variant oCRF1 receptor. In Cos 7 cells transfected with oCRF1var, cAMP accumulation was only observed at the highest concentration of oCRF utilized (100 nM). Basal (unstimulated) levels of cAMP in Cos 7 cells transfected with oCRF1var (in the presence of 2 mM IBMX) were approximately 50% lower than for the wild-type oCRF1. Differences in cAMP accumulation could not be attributed to differences in receptor number since total binding sites in the transfected cells were not different between wild-type or variant oCRF1 receptors. Agonist-induced receptor internalization, determined as the percent of total [125I] Tyr0-oCRF bound located in the acid-resistant fraction of transfected Cos 7 cells, increased with time (0-60 min at 37 degrees C) for both wild-type and variant oCRF1. Wild-type CRF1 internalized approximately 2-fold greater percent of total [125I] Tyr0-oCRF bound compared to the variant receptor. In summary, an ovine CRF1 and a CRF1 cytoplasmic tail receptor variant displaying high affinity binding to oCRF as well as selectivity for oCRF vs h/rCRF, were cloned from an adult sheep pituitary cDNA library. GTPgammaS studies indicate that both variant and wild-type receptors couple efficiently to Galphas however, only the wild-type oCRF1 is capable of stimulating cAMP production at physiological levels of CRF. Agonist-induced internalization of the ovine CRF1var is also reduced compared to the wild-type CRF1 receptor. We suggest that the oCRF1var interacts efficiently with Galphas but is unable (post-hormonal binding) to effectively stimulate G-protein activation of adenylate cyclase, indicating that the cytoplasmic tail of the CRF1 can modulate receptor function related to signal transduction. (ABSTRACT TRUNCATED)