Vasopressin-oxytocin-type signaling is ancient and has a conserved water homeostasis role in euryhaline marine planarians

Vasopressin/oxytocin (VP/OT)-related peptides are essential for mammalian antidiuresis, sociosexual behavior, and reproduction. However, the evolutionary origin of this peptide system is still uncertain. Here, we identify orthologous genes to those for VP/OT in Platyhelminthes, intertidal planarians that have a simple bilaterian body structure but lack a coelom and body-fluid circulatory system. We report a comprehensive characterization of the neuropeptide derived from this VP/OT-type gene, identifying its functional receptor, and name it the "platytocin" system. Our experiments with these euryhaline planarians, living where environmental salinities fluctuate due to evaporation and rainfall, suggest that platytocin functions as an "antidiuretic hormone" and also organizes diverse actions including reproduction and chemosensory-associated behavior. We propose that bilaterians acquired physiological adaptations to amphibious lives by such regulation of the body fluids. This neuropeptide-secreting system clearly became indispensable for life even without the development of a vascular circulatory system or relevant synapses.

Variation of pro-vasopressin processing in parvocellular and magnocellular neurons in the paraventricular nucleus of the hypothalamus: Evidence from the vasopressin-related glycopeptide copeptin

Arginine vasopressin (AVP) is synthesized in parvocellular- and magnocellular neuroendocrine neurons in the paraventricular nucleus (PVN) of the hypothalamus. Whereas magnocellular AVP neurons project primarily to the posterior pituitary, parvocellular AVP neurons project to the median eminence (ME) and to extrahypothalamic areas. The AVP gene encodes pre-pro-AVP that comprises the signal peptide, AVP, neurophysin (NPII), and a copeptin glycopeptide. In the present study, we used an N-terminal copeptin antiserum to examine copeptin expression in magnocellular and parvocellular neurons in the hypothalamus in the mouse, rat, and macaque monkey. Although magnocellular NPII-expressing neurons exhibited strong N-terminal copeptin immunoreactivity in all three species, a great majority (~90%) of parvocellular neurons that expressed NPII was devoid of copeptin immunoreactivity in the mouse, and in approximately half (~53%) of them in the rat, whereas in monkey hypothalamus, virtually all NPII-immunoreactive parvocellular neurons contained strong copeptin immunoreactivity. Immunoelectron microscopy in the mouse clearly showed copeptin-immunoreactivity co-localized with NPII-immunoreactivity in neurosecretory vesicles in the internal layer of the ME and posterior pituitary, but not in the external layer of the ME. Intracerebroventricular administration of a prohormone convertase inhibitor, hexa-d-arginine amide resulted in a marked reduction of copeptin-immunoreactivity in the NPII-immunoreactive magnocellular PVN neurons in the mouse, suggesting that low protease activity and incomplete processing of pro-AVP could explain the disproportionally low levels of N-terminal copeptin expression in rodent AVP (NPII)-expressing parvocellular neurons. Physiologic and phylogenetic aspects of copeptin expression among neuroendocrine neurons require further exploration.

Drosophila Sex Peptide controls the assembly of lipid microcarriers in seminal fluid

Seminal fluid plays an essential role in promoting male reproductive success and modulating female physiology and behavior. In the fruit fly, Drosophila melanogaster, Sex Peptide (SP) is the best-characterized protein mediator of these effects. It is secreted from the paired male accessory glands (AGs), which, like the mammalian prostate and seminal vesicles, generate most of the seminal fluid contents. After mating, SP binds to spermatozoa and is retained in the female sperm storage organs. It is gradually released by proteolytic cleavage and induces several long-term postmating responses, including increased ovulation, elevated feeding, and reduced receptivity to remating, primarily signaling through the SP receptor (SPR). Here, we demonstrate a previously unsuspected SPR-independent function for SP. We show that, in the AG lumen, SP and secreted proteins with membrane-binding anchors are carried on abundant, large neutral lipid-containing microcarriers, also found in other SP-expressing Drosophila species. These microcarriers are transferred to females during mating where they rapidly disassemble. Remarkably, SP is a key microcarrier assembly and disassembly factor. Its absence leads to major changes in the seminal proteome transferred to females upon mating. Males expressing nonfunctional SP mutant proteins that affect SP's binding to and release from sperm in females also do not produce normal microcarriers, suggesting that this male-specific defect contributes to the resulting widespread abnormalities in ejaculate function. Our data therefore reveal a role for SP in formation of seminal macromolecular assemblies, which may explain the presence of SP in Drosophila species that lack the signaling functions seen in Dmelanogaster.

Oxytocin Influences Male Sexual Activity via Non-synaptic Axonal Release in the Spinal Cord

Oxytocinergic neurons in the paraventricular nucleus of the hypothalamus that project to extrahypothalamic brain areas and the lumbar spinal cord play an important role in the control of erectile function and male sexual behavior in mammals. The gastrin-releasing peptide (GRP) system in the lumbosacral spinal cord is an important component of the neural circuits that control penile reflexes in rats, circuits that are commonly referred to as the "spinal ejaculation generator (SEG)." We have examined the functional interaction between the SEG neurons and the hypothalamo-spinal oxytocin system in rats. Here, we show that SEG/GRP neurons express oxytocin receptors and are activated by oxytocin during male sexual behavior. Intrathecal injection of oxytocin receptor antagonist not only attenuates ejaculation but also affects pre-ejaculatory behavior during normal sexual activity. Electron microscopy of potassium-stimulated acute slices of the lumbar cord showed that oxytocin-neurophysin-immunoreactivity was detected in large numbers of neurosecretory dense-cored vesicles, many of which are located close to the plasmalemma of axonal varicosities in which no electron-lucent microvesicles or synaptic membrane thickenings were visible. These results suggested that, in rats, release of oxytocin in the lumbar spinal cord is not limited to conventional synapses but occurs by exocytosis of the dense-cored vesicles from axonal varicosities and acts by diffusion-a localized volume transmission-to reach oxytocin receptors on GRP neurons and facilitate male sexual function.

Glutamine deprivation alters the origin and function of cancer cell exosomes

Exosomes are secreted extracellular vesicles carrying diverse molecular cargos, which can modulate recipient cell behaviour. They are thought to derive from intraluminal vesicles formed in late endosomal multivesicular bodies (MVBs). An alternate exosome formation mechanism, which is conserved from fly to human, is described here, with exosomes carrying unique cargos, including the GTPase Rab11, generated in Rab11-positive recycling endosomal MVBs. Release of Rab11-positive exosomes from cancer cells is increased relative to late endosomal exosomes by reducing growth regulatory Akt/mechanistic Target of Rapamycin Complex 1 (mTORC1) signalling or depleting the key metabolic substrate glutamine, which diverts membrane flux through recycling endosomes. Vesicles produced under these conditions promote tumour cell proliferation and turnover and modulate blood vessel networks in xenograft mouse models in vivo. Their growth-promoting activity, which is also observed in vitro, is Rab11a-dependent, involves ERK-MAPK-signalling and is inhibited by antibodies against amphiregulin, an EGFR ligand concentrated on these vesicles. Therefore, glutamine depletion or mTORC1 inhibition stimulates release from Rab11a compartments of exosomes with pro-tumorigenic functions, which we propose promote stress-induced tumour adaptation.

Vasopressin gene products are colocalised with corticotrophin-releasing factor within neurosecretory vesicles in the external zone of the median eminence of the Japanese macaque monkey (Macaca fuscata)

Arginine vasopressin (AVP), when released into portal capillaries with corticotrophin-releasing factor (CRF) from terminals of parvocellular neurones of the hypothalamic paraventricular nucleus (PVH), facilitates the secretion of adrenocorticotrophic hormone (ACTH) in stressed rodents. The AVP gene encodes a propeptide precursor containing AVP, AVP-associated neurophysin II (NPII), and a glycopeptide copeptin, although it is currently unclear whether copeptin is always cleaved from the neurophysin and whether the NPII and/or copeptin have any functional role in the pituitary. Furthermore, for primates, it is unknown whether CRF, AVP, NPII and copeptin are all colocalised in neurosecretory vesicles in the terminal region of the paraventricular CRF neurone axons. Therefore, we investigated, by fluorescence and immunogold immunocytochemistry, the cellular and subcellular relationships of these peptides in the CRF- and AVP-producing cells in unstressed Japanese macaque monkeys (Macaca fuscata). Reverse transcription-polymerase chain reaction analysis showed the expression of both CRF and AVP mRNAs in the monkey PVH. As expected, in the magnocellular neurones of the PVH and supraoptic nucleus, essentially no CRF immunoreactivity could be detected in NPII-immunoreactive (AVP-producing) neurones. Immunofluorescence showed that, in the parvocellular part of the PVH, NPII was detectable in a subpopulation (approximately 39%) of the numerous CRF-immunoreactive neuronal perikarya, whereas, in the outer median eminence, NPII was more prominent (approximately 52%) in the CRF varicosities. Triple immunoelectron microscopy in the median eminence demonstrated the presence of both NPII and copeptin immunoreactivity in dense-cored vesicles of CRF-containing axons. The results are consistent with an idea that the AVP propeptide is processed and NPII and copeptin are colocalised in hypothalamic-pituitary CRF axons in the median eminence of a primate. The CRF, AVP and copeptin are all co-packaged in neurosecretory vesicles in monkeys and are thus likely to be co-released into the portal capillary blood to amplify ACTH release from the primate anterior pituitary.

Double superior venae cavae with absence of the coronary sinus and anomalies of the azygos venous system

The superior vena cava is formed during the fetal period by the development of anastomoses between the right and left anterior cardinal veins, and the regression of the central part of the left anterior cardinal vein. The persistence of this part of the left anterior cardinal vein causes the formation of a left superior vena cava, which is a rare anomaly in cadaver dissection. We report the case of a persistent left superior vena cava with a normal right superior vena cava in a 95-year-old male cadaver, which was discovered during anatomical dissection for medical students at Kawasaki Medical School in 2016. The left superior vena cava was formed by the confluence of the left internal jugular and left subclavian veins and terminated in the right atrium via what would normally be the coronary sinus. The right and left superior venae cavae received intercostal veins via a right and left azygos vein, respectively. However, the right azygos vein was shorter than the normal azygos vein and received only the second to fifth intercostal veins, whereas the left azygos vein received the fifth to eleventh left intercostal veins and the sixth to eleventh right intercostal veins. We consider that the anomalies of the azygos venous system were the result of regression of right supracardinal vein and the persistence of the left supracardinal vein during development. An awareness of such variations of major thoracic veins is important for the interpretation of unusual CT images.

Multistate Outbreak of Human Salmonella Typhimurium Infections Linked to Pet Hedgehogs - United States, 2011-2013

Zoonotic Salmonella infections cause approximately 130 000 illnesses annually in the United States. Of 72.9 million US households owning at least one pet, five million own small mammals; 3000 hedgehogs were documented by USDA in USDA-licensed breeding facilities and pet stores in 2012. State health department collaborators and PulseNet, the national bacterial subtyping network, identified human infections of a Salmonella Typhimurium outbreak strain, which were investigated by CDC, USDA-APHIS and state public and animal health officials. A case was defined as an illness in a person infected with the outbreak strain identified between 1 December 2011 and 3 June 2013. Investigators collected information on patient exposures, cultured animal and environmental specimens for Salmonella, and conducted traceback investigations of USDA-licensed hedgehog facilities. There were 26 cases in 12 states. Illness onset dates ranged from 26 December 2011 to 8 April 2013. The median patient age was 15 years (range = <1-91 years); 58% were female. Among 23 persons with available information, 8 (35%) were hospitalized and one outbreak strain-associated death was reported. Of 25 patients with available information, 20 (80%) reported pet hedgehog contact in the week before illness onset. The outbreak strain was isolated from animal and environmental samples collected from three ill persons' homes in three states. Hedgehogs were purchased in geographically distant states from USDA-licensed breeders (10/17, 59%); a USDA-licensed pet store (1/17, 6%); unlicensed or unknown status breeders (3/17, 18%); and private individuals (3/17, 18%). Traceback investigations of USDA-licensed facilities did not reveal a single source of infection. Public and animal health collaboration linked pet hedgehog contact to human infections of Salmonella Typhimurium, highlighting the importance of a One Health investigative approach to zoonotic salmonellosis outbreaks. More efforts are needed to increase awareness among multiple stakeholders on the risk of illness associated with pet hedgehogs.

Fine-Tuning of PI3K/AKT Signalling by the Tumour Suppressor PTEN Is Required for Maintenance of Flight Muscle Function and Mitochondrial Integrity in Ageing Adult Drosophila melanogaster

Insulin/insulin-like growth factor signalling (IIS), acting primarily through the PI3-kinase (PI3K)/AKT kinase signalling cassette, plays key evolutionarily conserved regulatory roles in nutrient homeostasis, growth, ageing and longevity. The dysfunction of this pathway has been linked to several age-related human diseases including cancer, Type 2 diabetes and neurodegenerative disorders. However, it remains unclear whether minor defects in IIS can independently induce the age-dependent functional decline in cells that accompany some of these diseases or whether IIS alters the sensitivity to other aberrant signalling. We identified a novel hypomorphic allele of PI3K’s direct antagonist, Phosphatase and tensin homologue on chromosome 10 (Pten), in the fruit fly, Drosophila melanogaster. Adults carrying combinations of this allele, Pten⁵, combined with strong loss-of-function Pten mutations exhibit subtle or no increase in mass, but are highly susceptible to a wide range of stresses. They also exhibit dramatic upregulation of the oxidative stress response gene, GstD1, and a progressive loss of motor function that ultimately leads to defects in climbing and flight ability. The latter phenotype is associated with mitochondrial disruption in indirect flight muscles, although overall muscle structure appears to be maintained. We show that the phenotype is partially rescued by muscle-specific expression of the Bcl-2 homologue Buffy, which in flies, maintains mitochondrial integrity, modulates energy homeostasis and suppresses cell death. The flightless phenotype is also suppressed by mutations in downstream IIS signalling components, including those in the mechanistic Target of Rapamycin Complex 1 (mTORC1) pathway, suggesting that elevated IIS is responsible for functional decline in flight muscle. Our data demonstrate that IIS levels must be precisely regulated by Pten in adults to maintain the function of the highly metabolically active indirect flight muscles, offering a new system to study the in vivo roles of IIS in the maintenance of mitochondrial integrity and adult ageing.

BMP-regulated exosomes from Drosophila male reproductive glands reprogram female behavior

Male Drosophila reproductive glands secrete exosomes in a BMP-dependent manner that fuse with sperm after mating and suppress female remating.

Male reproductive glands secrete signals into seminal fluid to facilitate reproductive success. In Drosophila melanogaster, these signals are generated by a variety of seminal peptides, many produced by the accessory glands (AGs). One epithelial cell type in the adult male AGs, the secondary cell (SC), grows selectively in response to bone morphogenetic protein (BMP) signaling. This signaling is involved in blocking the rapid remating of mated females, which contributes to the reproductive advantage of the first male to mate. In this paper, we show that SCs secrete exosomes, membrane-bound vesicles generated inside late endosomal multivesicular bodies (MVBs). After mating, exosomes fuse with sperm (as also seen in vitro for human prostate-derived exosomes and sperm) and interact with female reproductive tract epithelia. Exosome release was required to inhibit female remating behavior, suggesting that exosomes are downstream effectors of BMP signaling. Indeed, when BMP signaling was reduced in SCs, vesicles were still formed in MVBs but not secreted as exosomes. These results demonstrate a new function for the MVB–exosome pathway in the reproductive tract that appears to be conserved across evolution.

Vascular endothelial growth factor secretion from pituitary folliculostellate cells: role of KATP channels

Vascular endothelial growth factor (VEGF) is an endothelial cell mitogen responsible for physiological and pathological angiogenesis. Abnormal regulation of VEGF expression in anterior pituitary folliculostellate (FS) cells has been implicated in pituitary tumour progression. FS and endocrine cells express VEGF, which is considered to be secreted by the constitutive pathway. The present study investigated the mechanism of VEGF secretion in TtT/GF cells, a mouse FS cell line. TtT/GF cells were shown to express VEGF(164), the most potent and bioavailable isoform of VEGF. Immunofluorescence and immunogold electron microscopy localised VEGF to the cytoplasm and small electron-lucent vesicles. Pituitary adenylate cyclase-activating polypeptide (PACAP), a well-documented stimulant of VEGF secretion, caused a robust increase in VEGF secretion over 24 h. Glyburide, an ABCA1 and K(ATP) channel blocker, also caused an increase in VEGF secretion when applied alone, and amplified the response to PACAP. Other ABCA1 transport blockers did not affect VEGF secretion. Exposure of TtT/GF cells to cycloheximide with PACAP or glyburide inhibited the increased secretion of VEGF, consistent with control of secretion at the transcription level. The SUR2B/Kir6.1 form of K(ATP) channels was shown to be expressed by TtT/GF cells. Diazoxide, a K(ATP) activator, inhibited PACAP- and PACAP + glyburide-stimulated VEGF secretion but not that of glyburide alone. These data suggest that K(ATP) channels are expressed by FS cells and play a significant role in the control of VEGF secretion, and also that activation of K(ATP) channels inhibits the secretion of VEGF at the level of transcription.

Free surface flow between two horizontal concentric cylinders

Results are reported on a combined experimental and numerical investigation of a free surface flow at small Reynolds numbers. The flow is driven by the rotation of the inner of two horizontal concentric cylinders, with an inner to outer radius ratio of 0.43. The outer cylinder is stationary. The annular gap is partially filled, from 0.5 to 0.95 full, with a viscous liquid leaving a free surface. When the fraction of the annular volume filled by liquid is 0.5, a thin liquid film covers the rotating inner cylinder and reenters the liquid pool. For relatively low rotation speeds, the evolution of the film thickness is consistent with the theory for a plate being withdrawn from an infinite liquid pool. The overall liquid flow pattern at this condition consists of two counter-rotating cells: one is around the inner cylinder and the other with weaker circulation rate is in the bottom part of the annulus and nearly symmetric about the vertical axis. With increasing rotation rate, the free surface becomes more deformed, and the dynamics of the stagnation line and the cusp line dividing the cells are tracked as quantitative measures of the interface shape. In addition, the recirculating flow cells lose symmetry and the cusp deforms the free surface severely. A comparison of numerically computed flow which describes the interface by a phase-field method confirms the dynamics of the two cells and the interface deformation. For filling fraction 0.75, the liquid level is slightly above the inner cylinder and a significant decrease in size of the bottom cell with increasing rotation rate is found. For filling fractions approaching unity, the liquid flow consists of one single cell and the surface deformation remains small.

Roles of pre-treatment time and junctional proteins in Caco-2 cell microparticle uptake

Microparticle uptake in the small intestine is relevant to both the delivery of pharmaceutics and exposure to environmental pollutants. The Caco-2 enterocyte model is a useful tool to study the parameters that affect epithelial microparticle permeability and the mechanisms controlling them. The current study used this model to explore further the different effects of 10% ethanol v/v or ice on transepithelial resistance (TER), microparticle uptake and immunofluorescent labelling of intercellular junctions. The same exposure times for both treatments were used, rather than those shown in the literature to produce demonstrable changes induced by each. The effects of both pre-treatments were greater after 60 min than after 15 min. Ethanol pre-treatment for 60 min decreased TER, increased particle uptake and was associated with a disorganisation of tight and adhering junctional proteins. Pre-treatment with ice for 60 min however, increased TER, decreased particle uptake and was associated with concentration of intercellular junctional proteins in a more constrained manner. These findings on the effects of pre-treatment with ethanol or ice for 60 min suggest that the extent of uptake is influenced by changes in the distribution of intercellular junctional proteins.

Macrophages increase microparticle uptake by enterocyte-like Caco-2 cell monolayers

Caco-2 cells form an enterocyte-like monolayer that has been used to explore small intestinal microparticle uptake. They are a useful functional model for the investigation of in vivo drug delivery systems and the uptake of particulate environmental pollutants. The aim of this paper was to determine if the previously reported decrease in Caco-2 transepithelial resistance following exposure to macrophages was matched by increased microparticle uptake, especially as macrophage phagocytosis simulates removal of particles from the subepithelial compartment. Caco-2 cells were grown as a monoculture for 21 days on insert membranes. A compartmentalised model involved Caco-2 cells in the upper compartment, with THP-1-derived macrophages adhering to the base of the underlying well, the two cell populations communicating only through the shared culture medium. Caco-2 cells were also cultured in macrophage-conditioned medium and all groups were exposed apically to 2 μm latex particles for 5 or 60 min. Parameters measured were: transepithelial resistance; cytokine levels; cell dimensions and the distribution of nuclei, actin and junctional proteins. Subepithelial particle numbers, defined as those located below the insert membrane, were also counted and were significantly increased in the Caco-2/macrophage model, with over 90% associated with the macrophages. Other changes induced by the presence of macrophages included decreased transepithelial resistance levels, diffuse localisation of some junctional proteins, higher proinflammatory cytokine levels, disorganisation of cell shape and decreased cell height associated with actin reorganisation. Macrophage-conditioned medium produced a smaller transepithelial resistance decrease than the Caco-2/macrophage model and there were few other changes. In conclusion, culture of Caco-2 cells with underlying macrophages produced a lower, less organised epithelium and greater microparticle uptake.

Gerota and Brâncuşi: Romanian anatomy and art face to face

Gerota's name is associated with two eponyms and two histochemical methods, but he was also Brâncuşi's teacher and supervisor. When Brâncuşi was a student in Bucharest, he produced an 'écorché' (flayed man), of which six plaster replicas still exist, two in apparently the original shape and four which have been modified/'cosmetized'. The two are in the University of Arts in Bucharest, one in the main hall, the other in the classroom used for teaching students. Of the other four, one is in the Museum of Arts and one in the Museum of Natural Sciences of Carol I National College in Craiova (where Gerota graduated in 1885), and one each in the Faculties of Medicine in Cluj Napoca and Iassy. One more probably existed in the Faculty of Medicine in Bucharest, and one in the Faculty of Fine Arts in Iassy but no trace of them could be found. The original clay model was lost (or destroyed during transportation) in the 1930s or 1956. Two variants of the écorché exist: one 'artistic' (slender and smoother) in the University of Arts in Bucharest; the other more 'anatomical' (muscular, robust, athletic) in Craiova, Cluj and Iassy. Both variants are a very realistic representation of the human muscular system, but with that extra which only a master artist can add. Interestingly, the head of the écorché bears a striking resemblance in attitude and curves to that of Brâncuşi's famous head of Mademoiselle Pogany. The replicas appear to have been distributed to embellish the capitals of four of the six historical Romanian provinces: Muntenia (Bucharest), Oltenia (Craiova), Moldavia (Iassy), and Transylvania (Cluj).

Direct investigation of anisotropic suspension structure in pressure-driven flow

Evidence is presented to show the microstructural anisotropy responsible for normal stress in sheared suspensions. Particle velocimetry is combined with three-dimensional particle locations obtained via confocal microscopy at rest. A range of volume fractions phi and local shear rates gamma are investigated in a weakly Brownian pressure-driven suspension. At high gamma, the pairwise distribution shows a strong probability along the axis of compression similar to observations from Stokesian dynamics simulation at phi=0.32. At the channel center where gamma-->0, the concentrated suspension at phi=0.56 behaves as a confined isotropic fluid.

The long lifespan and low turnover of human islet beta cells estimated by mathematical modelling of lipofuscin accumulation

AIMS/HYPOTHESIS

Defects in pancreatic beta cell turnover are implicated in the pathogenesis of type 2 diabetes by genetic markers for diabetes. Decreased beta cell neogenesis could contribute to diabetes. The longevity and turnover of human beta cells is unknown; in rodents <1 year old, a half-life of 30 days is estimated. Intracellular lipofuscin body (LB) accumulation is a hallmark of ageing in neurons. To estimate the lifespan of human beta cells, we measured beta cell LB accumulation in individuals aged 1-81 years.

METHODS

LB content was determined by electron microscopical morphometry in sections of beta cells from human (non-diabetic, n = 45; type 2 diabetic, n = 10) and non-human primates (n = 10; 5-30 years) and from 15 mice aged 10-99 weeks. Total cellular LB content was estimated by three-dimensional (3D) mathematical modelling.

RESULTS

LB area proportion was significantly correlated with age in human and non-human primates. The proportion of human LB-positive beta cells was significantly related to age, with no apparent differences in type 2 diabetes or obesity. LB content was low in human insulinomas (n = 5) and alpha cells and in mouse beta cells (LB content in mouse <10% human). Using 3D electron microscopy and 3D mathematical modelling, the LB-positive human beta cells (representing aged cells) increased from >or=90% (<10 years) to >or=97% (>20 years) and remained constant thereafter.

CONCLUSIONS/INTERPRETATION

Human beta cells, unlike those of young rodents, are long-lived. LB proportions in type 2 diabetes and obesity suggest that little adaptive change occurs in the adult human beta cell population, which is largely established by age 20 years.

Culture conditions and treatments affect Caco-2 characteristics and particle uptake

Small intestinal microparticle uptake via a paracellular route is relevant to oral drug delivery and environmental pollution. In vitro investigation uses latex microparticle passage across a confluent Caco-2 cell epithelium. This paper examines the influence of culture conditions on transepithelial resistance (TER); cell dimensions from confocal microscopy; and number of particles below the epithelium. Variables investigated include level of initial TER; multiple TER measurements; involvement of medium; cell source; and pretreatment with ethanol or a range of temperatures. Data were collected after exposure to 2 microm latex particles for 5-120 min: sham groups were exposed to pretreatment but not particles. The results highlight the importance of very precise control of the experimental environment; confirm the pattern of sequential-TER increase/decrease in groups exposed only to particles and show accompanying increases in cell dimensions. Greater particle uptake was associated with ethanol-induced decreased TER, decreased cell height and increased intercellular spaces, similar to previous findings for external irradiation. Low temperatures raised TER but, despite this, cooling did not alter particle uptake. In conclusion, culture microenvironment and sham treatment are crucial considerations in studies of epithelial microparticle uptake in vitro.

Changes produced by external radiation in parameters influencing intestinal permeability and microparticle uptake in vitro

PURPOSE

To determine the interaction between X-irradiation and in vitro intestinal microparticle uptake through Caco-2 epithelial cells.

METHODS

Caco-2 cells were cultured on 3 microm porous membranes for 21 days, X-irradiated with 2 Gy or sham-irradiated, then incubated for 5 or 30 min and exposed apically for 30 min to 2 microm latex microparticles. Measurements included cell dimensions, from confocal microscope 'optical slices'; transepithelial resistance (TER) for tight junction (TJ) permeability; particle aggregation; and particle numbers on (adsorbed), in (intraepithelial) and through (submembranous) the epithelium.

RESULTS

Irradiation alone reduced TJ permeability more than sham-treatment, more so 5 min than 30 min after treatment. Irradiated epithelia were more permeable to particles than the equivalent sham-irradiated or previously untreated (particle only) groups: the latter two were similar. Irradiation altered adsorbed particle numbers and increased submembranous counts: particle uptake correlated best with cell height.

CONCLUSIONS

2 Gy X-irradiation increased particle uptake and translocation through the epithelium. This correlated well with the TJ opening seen after particle exposure in irradiated samples and changes in cell morphology. New data on cell dimensions underlined the similarity in particle uptake between this in vitro epithelium and that in an in vivo model, highlighting the translational significance of the work.

Expression of G protein-coupled receptor-30, a G protein-coupled membrane estrogen receptor, in oxytocin neurons of the rat paraventricular and supraoptic nuclei

The regulatory actions of estrogens on magnocellular oxytocin (OT) neurons of the paraventricular and supraoptic nuclei are well documented. Although the expression and distribution of nuclear estrogen receptor-beta, but not estrogen receptor-alpha, in the OT neuron has been described, the nuclear receptors may not explain all aspects of estrogen function in the hypothalamic OT neuron. Recently a G protein-coupled receptor (GPR) for estrogens, GPR30, has been identified as a membrane-localized estrogen receptor in several cancer cell lines. In this study, we therefore investigated the expression and localization of GPR30 in magnocellular OT neurons to understand the mode of rapid estrogen actions within these neurons. Here we show that, in the paraventricular nucleus and supraoptic nucleus, GPR30 is expressed in magnocellular OT neurons at both mRNA and protein levels but is not expressed in vasopressin neurons. Specific markers for intracellular organelles and immunoelectron microscopy revealed that GPR30 was localized mainly in the Golgi apparatus of the neurons but could not be detected at the cell surface. In addition, the expression of GPR30 is also detected in the neurohypophysis. These results suggest that GPR30 may serve primarily as a nongenomic transducer of estrogen actions in the hypothalamo-neurohypophyseal system.

Thyrotrophin-releasing hormone, vasoactive intestinal peptide, prolactin-releasing peptide and dopamine regulation of prolactin secretion by different lactotroph morphological subtypes in the rat

In the male rat anterior pituitary, three morphological subtypes of cells secreting primarily prolactin (PRL) (lactotrophs) have been described. Type I contain predominantly large irregularly shaped granules, whereas type II and type III lactotrophs contain smaller spherical granules. We have previously shown that oestradiol and testosterone exert a rapid stimulatory effect selectively on type II lactotrophs but it is not known how the lactotroph subtypes respond to peptide secretagogues. We have therefore examined which cell subtype(s) release PRL in response to vasoactive intestinal peptide (VIP), thyrotrophin-releasing hormone (TRH) and prolactin-releasing peptide (PrRP-31). Pituitary segments were incubated in medium containing tannic acid (to capture exocytosis of secretory granules), either alone or with secretagogue peptide. VIP (1-10 nM), TRH (10 nM) and PrRP-31 (10 nM) all caused a significant increase (P < 0.05) in the amount of PRL granule exocytosis from type II and III lactotrophs, but had no effect on PRL exocytosis from type I. Dopamine (100 nM) inhibited basal exocytosis of immunoreactive (ir)-PRL from type I, II and III lactotrophs and PrRP-31-stimulated ir-PRL granule exocytosis from II and III lactotrophs. Treatment of lactating female rats with the dopamine D(2) receptor antagonist sulpiride (40 microg/kg) produced a significant increase (P < 0.05) in PRL granule exocytosis from type I and type III lactotrophs and a significant increase (P < 0.05) in the proportion of type I and II cells undergoing exocytosis of PRL. In conclusion, VIP, TRH and PrRP-31 selectively stimulate exocytosis from type II and III lactotrophs in the male rat, whereas all three lactotroph types are sensitive to dopamine inhibition of exocytosis in male and female rats.

Parameters influencing intestinal epithelial permeability and microparticle uptake in vitro

The hypothesis that, in vivo in situ, villous uptake of 2 microm latex microparticles involves changes at enterocyte tight junctions (TJs) was tested using Caco-2 cells on porous membranes. Epithelial permeability was measured by transepithelial resistance (TER) and particle numbers in surface, intraepithelial and sub-epithelial compartments by microscopy. Apical particle or medium addition initially closed TJs, but this was subsequently reversed in particle-treated groups. Peristaltic onward movement of a bolus was simulated by removing apical particles after an exposure period and leaving the remaining particles to interact with the epithelium: this produced marked TJ loosening during the interaction period. For particle exposure groups, the early similarity with particle numbers in vivo taken up in young adult rats became less marked with time, although bolus removal counteracted this tendency. The TJ response to vasoactive intestinal polypeptide (VIP) was time-dependent. Adsorbed and intraepithelial particle numbers increased with particle exposure time; epithelial-associated microparticle aggregation varied with treatment and submembranous particles were seen in all groups. Correlation between TER changes and particle numbers suggests TJ loosening may be important in microparticle uptake. This Caco-2 model gives epithelial particle numbers that approximate well to published figures for microparticle uptake in vivo and allows effective microenvironmental manipulation.

Expression and externalization of annexin 1 in the adrenal gland: structure and function of the adrenal gland in annexin 1-null mutant mice

Annexin 1 (ANXA1) is a member of the annexin family of phospholipid- and calcium-binding proteins with a well demonstrated role in early delayed (30 min to 3 h) inhibitory feedback of glucocorticoids in the hypothalamus and pituitary gland. This study used adrenal gland tissue from ANXA1-null transgenic mice, in which a beta-galactosidase (beta-Gal) reporter gene was controlled by the ANXA1 promoter, and wild-type control mice to explore the potential role of ANXA1 in adrenal function. RT-PCR and Western blotting revealed strong expression of ANXA1 mRNA and protein in the adrenal gland. Immunofluorescence labeling of ANXA1 in wild-type and beta-Gal expression in ANXA1-null adrenals localized intense staining in the outer perimeter cell layers. Immunogold electron microscopy identified cytoplasmic and nuclear ANXA1 labeling in outer cortical cells and capsular cells. Exposure of adrenal segments in vitro to dexamethasone (0.1 mum, 3 h) caused an increase in the amount of ANXA1 in the intracellular compartment and attached to the surface of the cells. The N-terminal peptide ANXA1(Ac2-26) inhibited corticosterone release. Corticosterone release was significantly greater from ANXA1-null adrenal cells compared with wild type in response to ACTH (10 pm to 5 nm). In contrast, basal and ACTH-stimulated aldosterone release from ANXA1-null adrenal cells was not different from wild type. Morphometry studies demonstrated that ANXA1 null adrenal glands were smaller than wild-type, and the cortical/medullary area ratio was significantly reduced. These results suggest ANXA1 is a regulator of adrenocortical size and corticosterone secretion.

The influence of 17beta-estradiol on annexin 1 expression in the anterior pituitary of the female rat and in a folliculo-stellate cell line

Annexin 1 (ANXA1) is a Ca2+- and phospholipid-binding protein that plays an important role as a mediator of glucocorticoid action in the host-defence and neuroendocrine systems. Sex differences in hypothalamo-pituitary-adrenal (HPA) axis activity are well documented and a number of studies have demonstrated that gonadal steroids act as regulators of HPA activity. The aim of this study was to investigate the effect of ovariectomy and 17beta-estradiol replacement, and estrous cycle stage, on anterior pituitary ANXA1 content. The amount of anterior pituitary ANXA1 determined by western blotting varied with estrous cycle stage with a peak at estrus declining to a trough at proestrus. Ovariectomy resulted in a significant (P<0 x 05) decrease in anterior pituitary ANXA1 content. Administration of 17beta-estradiol (1 microg/100 g) significantly (P<0 x 01) increased anterior pituitary ANXA1 expression in the ovariectomized animals. In contrast, there was no change in pituitary ANXA1 content in response to 17beta-estradiol in adrenalectomized and adrenalectomized/ovariectomized rats. Treatment of TtT/GF cells, a folliculo-stellate cell line, with 17beta-estradiol (1 x 8-180 nM) increased ANXA1 mRNA expression and increased the amount of ANXA1 protein externalized in response to a dexamethasone stimulus. These results indicate that 17beta-estradiol stimulates ANXA1 expression in the anterior pituitary and in vivo an adrenal factor contributes to the mechanism of action.

Time-specific effects of perinatal glucocorticoid treatment on anterior pituitary morphology, annexin 1 expression and adrenocorticotrophic hormone secretion in the adult female rat

Perinatal glucocorticoid (GC) treatment is increasingly associated with long-term disturbances in hypothalamo-pituitary-adrenocortical function. In the male rat, such treatment induces profound molecular, morphological and functional changes in the anterior pituitary gland at adulthood. To determine whether these effects are sex-specific, we have examined the effects of perinatal dexamethasone treatment on the female pituitary gland, focusing on (i) the integrity of the annexin 1 (ANXA1) dependent regulatory effects of GCs on adrenocorticotrophic hormone (ACTH) release and (ii) corticotroph and folliculo-stellate (FS) cell morphology. Dexamethasone was given to pregnant (gestational days 16-19) or lactating (days 1-7 post partum) rats via the drinking water (1 microg/ml); controls received normal drinking water. Pituitary tissue from the female offspring was examined ex vivo at adulthood (60-90 days). Both treatment regimes reduced the intracellular and cell surface ANXA1 expression, as determined by western blot analysis and quantitative immunogold electron microscopic histochemistry. In addition, they compromised the ability of dexamethasone to suppress the evoked release of ACTH from the excised tissue in vitro, a process which requires the translocation of ANXA1 from the cytoplasm to the cell surface of FS cells. Although neither treatment regime affected the number of FS cells or corticotrophs, both altered the subcellular morphology of these cells. Thus, prenatal dexamethasone treatment increased while neonatal treatment decreased FS cell size and cytoplasmic area. By contrast, corticotroph size was unaffected by either treatment, as also was the size of the secretory granules. Corticotroph granule density and margination were, however, increased markedly by the prenatal treatment, while the neonatal treatment had no effect on granule density but decreased granule margination. Thus, perinatal dexamethasone treatment exerts long-term effects on the female pituitary gland, altering gene expression, cell morphology and the ANXA1-dependent GC regulation of ACTH secretion. The changes are similar but not identical to those reported in the male.

Gene deletion reveals roles for annexin A1 in the regulation of lipolysis and IL-6 release in epididymal adipose tissue

In this study, epididymal adipose tissue from male annexin 1 (ANXA1)-null and wild-type control mice were used to explore the potential role of ANXA1 in adipocyte biology. ANXA1 was detected by Western blot analysis in wild-type tissue and localized predominantly to the stromal-vascular compartment. Epididymal fat pad mass was reduced by ANXA1 gene deletion, but adipocyte size was unchanged, suggesting that ANXA1 is required for the maintenance of adipocyte and/or preadipocyte cell number. Epididymal tissue from wild-type mice responded in vitro to noradrenaline and isoprenaline with increased glycerol release, reduced IL-6 release, and increased cAMP accumulation. Qualitatively similar but significantly attenuated responses to the catecholamines were observed in tissue from ANXA1-null mice, an effect that was not associated with changes in beta-adrenoceptor mRNA expression. Lipopolysaccharide (LPS) also stimulated lipolysis in vitro, but its effects were muted by ANXA1 gene deletion. By contrast, LPS failed to influence IL-6 release from wild-type tissue but stimulated the release of the cytokine from tissue from ANXA1-null mice. ANXA1 gene deletion did not affect glucocorticoid receptor expression or the ability of dexamethasone to suppress catecholamine-induced lipolysis. It did, however, augment IL-6 expression and modify the inhibitory effects of glucocorticoids on IL-6 release. Collectively, these studies suggest that ANXA1 supports aspects of adipose tissue mass and alters the sensitivity of epididymal adipose tissue to catecholamines, glucocorticoids, and LPS, thereby modulating lipolysis and IL-6 release.

Lack of annexin 1 results in an increase in corticotroph number in male but not female mice

Annexin 1 (ANXA1) is a member of the annexin family of phospholipid- and calcium-binding proteins with a well demonstrated role in early delayed (30 min to 3 h) inhibitory feedback of glucocorticoids in the pituitary. We have examined corticotrophs in wild-type and ANXA1 knockout mice to determine the effects of lack of ANXA1 in male and female animals. Anterior pituitary tissue from ANXA1 wild-type, heterozygote and null mice was fixed and examined (i) by confocal immunocytochemistry to determine the number of corticotrophs and (ii) by electron microscopy to examine the size, secretory granule population and secretory machinery of corticotrophs. No differences in these parameters were detected in female mice. In male ANXA1 null mice, there were approximately four-fold more corticotrophs than in wild-type animals. However, the corticotrophs in ANXA1 null mice were smaller and had reduced numbers of secretory granules (the reduction in granules paralleled the reduction in cell size). No differences in the numerical density of folliculo-stellate, gonadotroph, lactotroph or somatotroph cells were detected in male ANXA1 null mice. Plasma corticosterone, adrenocorticotrophic hormone (ACTH) and pituitary pro-opiomelanocortin mRNA were unchanged but pituitary ACTH content was increased in male ANXA1 null mice. Interleukin (IL)-6 pituitary content was significantly elevated in male and reduced in female ANXA1 null mice compared to wild-type. In conclusion, these data indicate that ANXA1 deficiency is associated with gender-specific changes in corticotroph number and structure, via direct actions of ANXA1 and/or indirect changes in factors such as IL-6.

Evidence for the role of adenosine 5'-triphosphate-binding cassette (ABC)-A1 in the externalization of annexin 1 from pituitary folliculostellate cells and ABCA1-transfected cell models

Annexin 1 (ANXA1), a 37-kDa protein, is a member of the superfamily of Ca(2+)- and phospholipid-binding annexin proteins. In the anterior pituitary, ANXA1 is expressed mainly by folliculostellate (FS) cells and mediates the early delayed feedback inhibition exerted by glucocorticoids on the release of ACTH and other pituitary hormones. It has been previously demonstrated that TtT/GF cells (a FS cell line) express and externalize ANXA1 in response to glucocorticoid treatment. However, ANXA1 lacks a cleavable signal sequence and externalization is not affected by inhibitors of the secretory pathway. We have previously shown that glyburide, an ATP-binding cassette (ABC) transporter inhibitor, inhibits the externalization of ANXA1 from TtT/GF cells and pituitary tissue. Here we investigated whether ABCA1 is involved in ANXA1 externalization. The use of the ABCA1-transporter inhibitors geranyl-geranyl pyrophosphate and sulfobromophthalein significantly inhibited ANXA1 externalization. Partial silencing of ABCA1 expression in TtT/GF cells by siRNA also significantly decreased the amount of cell surface ANXA1. However, anterior pituitary tissue from ABCA1-null mice was found to externalize ANXA1 normally. Because compensation by other ABC family members may occur in vivo, ANXA1 externalization was studied in two transfection models: Xenopus oocytes injected with ABCA1 mRNA and AtT20 D1 corticoctroph cells cotransfected with ABCA1-green fluorescent protein and ANXA1. ABCA1-expressing oocytes, but not water-injected controls, were found to externalize ANXA1. Expression of ABCA1 in AtT20 D1 cells significantly increased the amount of cell surface ANXA1, compared with mock-transfected and ANXA1-only transfected controls. Together these data provide evidence for a role of ABCA1 in ANXA1 export.

Perinatal glucocorticoid treatment disrupts the hypothalamo-lactotroph axis in adult female, but not male, rats

This study aimed to test the hypothesis that the tuberoinfundibular dopaminergic neurons of the arcuate nucleus and/or the lactotroph cells of the anterior pituitary gland are key targets for the programming effects of perinatal glucocorticoids (GCs). Dexamethasone was administered noninvasively to fetal or neonatal rats via the mothers' drinking water (1 mug/ml) on embryonic d 16-19 or neonatal d 1-7, and control animals received normal drinking water. At 68 d of age, the numbers of tyrosine hydroxylase-positive (TH+) cells in the arcuate nucleus and morphometric parameters of pituitary lactotrophs were analyzed. In control animals, striking sex differences in TH+ cell numbers, lactotroph cell size, and pituitary prolactin content were observed. Both pre- and neonatal GC treatment regimens were without effect in adult male rats, but in females, the overriding effect was to abolish the sex differences by reducing arcuate TH+ cell numbers (pre- and neonatal treatments) and reducing lactotroph cell size and pituitary prolactin content (prenatal treatment only) without changing lactotroph cell numbers. Changes in circulating prolactin levels represented a net effect of hypothalamic and pituitary alterations that exhibited independent critical windows of susceptibility to perinatal GC treatments. The dopaminergic neurons of the hypothalamic periventricular nucleus and the pituitary somatotroph populations were not significantly affected by either treatment regimen in either sex. These data show that the adult female hypothalamo-lactotroph axis is profoundly affected by perinatal exposure to GCs, which disrupts the tonic inhibitory tuberoinfundibular dopaminergic pathway and changes lactotroph morphology and prolactin levels in the pituitary and circulation. These findings provide new evidence for a long-term disruption in prolactin-dependent homeostasis in females, but not males, after inappropriate GC exposure in perinatal life.

Disruption of the transmembrane dense core vesicle proteins IA-2 and IA-2beta causes female infertility

Female infertility is a worldwide problem affecting 10-15% of the population. The cause of the infertility in many cases is not known. In the present report, we demonstrate that alterations in two transmembrane structural proteins, IA-2 and IA-2beta, located in dense core secretory vesicles (DCV) of many endocrine and neuroendocrine cells, can result in female infertility. IA-2 and IA-2beta are best known as major autoantigens in type 1 diabetes, but their normal function has remained an enigma. Recently we showed in mice that deletion of IA-2 and/or IA-2beta results in impaired insulin secretion and glucose intolerance. We now report that double knockout (DKO), but not single knockout, female mice are essentially infertile. Vaginal smears showed a totally abnormal estrous cycle, and examination of the ovaries revealed normal-appearing oocytes but the absence of corpora lutea. The LH surge that is required for ovulation occurred in wild-type mice but not in DKO mice. Additional studies showed that the LH level in the pituitary of DKO female mice was decreased compared with wild-type mice. Treatment of DKO females with gonadotropins restored corpora lutea formation. In contrast to DKO female mice, DKO male mice were fertile and LH levels in the serum and pituitary were within the normal range. From these studies we conclude that the DCV proteins, IA-2 and IA-2beta, play an important role in LH secretion and that alterations in structural proteins of DCV can result in female infertility.

Perinatal glucocorticoid treatment produces molecular, functional, and morphological changes in the anterior pituitary gland of the adult male rat

Stress or glucocorticoid (GC) treatment in perinatal life can induce long-term changes in the sensitivity of the hypothalamo-pituitary-adrenocortical axis to the feedback actions of GCs and, hence, in GC secretion. These changes have been ascribed largely to changes in the sensitivity of the limbic system, and possibly the hypothalamus, to GCs. Surprisingly, the possibility that early life stress/GC treatment may also exert irreversible effects at the pituitary level has scarcely been addressed. Accordingly, we have examined the effects of pre- and neonatal dexamethasone treatment on the adult male pituitary gland, focusing on the following: 1) the integrity of the acute annexin 1 (ANXA1)-dependent inhibitory actions of GCs on ACTH secretion, a process requiring ANXA1 release from folliculostellate (FS) cells; and 2) the morphology of FS cells and corticotrophs. Dexamethasone was given to pregnant (d 16-19) or lactating (d 1-7 postpartum) rats via the drinking water (1 microg/ml); controls received normal drinking water. Pituitary tissue from the offspring was examined ex vivo at d 90. Both treatment regimens reduced ANXA1 expression, as assessed by Western blotting and quantitative immunogold labeling. In particular, the amount of ANXA1 located on the outer surface of the FS cells was reduced. By contrast, IL-6 expression was increased, particularly by the prenatal treatment. Pituitary tissue from untreated control rats responded to dexamethasone with an increase in cell surface ANXA1 and a reduction in forskolin-induced ACTH release. In contrast, pituitary tissue from rats treated prenatally or neonatally with dexamethasone was unresponsive to the steroid, although, like control tissue, it responded readily to ANXA1, which readily inhibited forskolin-driven ACTH release. Prenatal dexamethasone treatment reduced the size but not the number of FS cells. It also caused a marked reduction in corticotroph number and impaired granule margination without affecting other aspects of corticotroph morphology. Similar but less marked effects on pituitary cell morphology and number were evident in tissue from neonatally treated rats. Our study shows that, when administered by a noninvasive process, perinatal GC treatment exerts profound effects on the adult pituitary gland, impairing the ANXA1-dependent GC regulation of ACTH release and altering the cell profile and morphology.

Somatotroph to thyrotroph cell transdifferentiation during experimental hypothyroidism - a light and electron-microscopy study

Somatotroph and thyrotroph pituitary cells share a common precursor cell expressing the transcription factor Pit1 in ontogeny. Cells expressing both thyrotropin (TSH) and growth-hormone (GH) are found in adult rat pituitary and in human pituitary adenomas in acromegaly, and these tumors contain both thyrotropin-releasing hormone (TRH) and the TRH receptors (TRHR). It has been shown that stimulation of TSH expression in primary hypothyroidism promotes changes suggestive of somatotroph to thyrotroph cell transdifferentiation. We tested this hypothesis and the role of TRH in experimental primary hypothyroidism in rats. Adult female Long-Evans rats, 6 months old, were administered the antithyroid drug methimazole (0.1% w/v) in the drinking water for 42 days. Animals were sacrificed by perfusion fixation under anaesthesia at weekly intervals and pituitary tissue processed in acrylic resin for immunofluorescence and immuno-electronmicroscopy for TSH, GH and TRHR. In the hypothyroid rat pituitary immunofluorescent somatotrophs were greatly reduced in number and gradually replaced by thyrotrophs during methimazole administration. Colocalization of GH and TSH in the same cell was noted. Immunoelectronmicroscopy demonstrated the development of enlarged thyrotrophs with dilated rough endoplasmic reticulum containing an electron-dense material and intracisternal granules, both of which are immunoreactive for TSH ('thyroidectomy cells'). The somatotrophs showed reduced GH immunoreactivity and also the presence of TSH-type, small-size secretory granules. This suggests that the greatly increased number of TSH-cells in methimazole-induced-hypothyroidism is due, at least partially, to the transdifferentiation of somatotroph into thyrotroph cells. TRHR immunofluorescence was expressed in many somatotrophs in normal rat pituitary and unlike immunoreactive GH, its expression was enhanced during hypothyroidism. The number of TRHR-immunoreactive cells increased in parallel with the number of TSH-immunoreactive cells. This indicates a role for TRH stimulation in the transdifferentiation process. Taken together, these data suggest that, in addition to the cell mutation mechanism involving an early totipotential progenitor cell, transdifferentiation of existing somatotroph cells also plays a part in the pathogenesis of multihormonal GH-secreting adenomas.

Magnocellular dendrites: prototypic receiver/transmitters

The hypothalamic magnocellular neurones of the supraoptic and paraventricular nuclei of mammals are among the best understood of all peptidergic neurones, and therefore serve as a model for understanding the functions of other peptidergic neurones. The release of vasopressin- and oxytocin-containing neurosecretory vesicles from their dendrites was first established 15 years ago. This local release is now known to have many functions, including controlling the interactions between oxytocin neurones and their surrounding glia, and facilitating and inhibiting the electrical activation of the neurones. Technical advances now permit dynamic analysis of dendritic release. Here, we review recent studies that focus on the conditional priming of dendritic peptide release by peptide-induced liberation of intracellular calcium, and the role of dendritic protein synthesis in the dendritic peptide release and the control of receptive properties of the neurones.

Annexin 1 and the regulation of endocrine function

Annexin 1 (ANXA1) was first identified as a mediator of the anti-inflammatory actions of glucocorticoids in the host defence system. Subsequent work revealed that this protein fulfils a wider brief and it is now recognized as an important signalling intermediate in a variety of other systems. Here, we consider the role of ANXA1 in the endocrine system, placing particular emphasis on new insights into the mechanisms and functional significance of the secondary processing of ANXA1, the processes that control the intracellular and transmembrane trafficking of the molecule and the molecular mechanisms of ANXA1 action that have identified a novel role for the protein as a paracrine/juxtacrine mediator of the non-genomic actions of glucocorticoids in the neuroendocrine system.

Expression, subcellular localization and phosphorylation status of annexins 1 and 5 in human pituitary adenomas and a growth hormone-secreting carcinoma

OBJECTIVE

Annexin 1 (ANXA1), a 37-kDa protein, plays an important role as a mediator of glucocorticoid action in the anterior pituitary gland and has been implicated in the processes of tumorigenesis in a number of other tissues. As a prelude to examining the potential role of ANXA1 in the pathophysiology of pituitary tumours, this study examined the expression, phosphorylation status and distribution of ANXA1 and the closely related protein, annexin 5 (ANXA5), in a series of pituitary adenomas and in two carcinomas.

PATIENTS AND DESIGN

Forty-two human pituitary adenomas were examined. Parallel studies were performed on normal pituitary tissue, obtained postmortem, a GH-secreting carcinoma and a grade 4 astrocytoma.

MEASUREMENTS

The tissue was processed for analysis of ANXA1 mRNA and protein expression by reverse transcriptase polymerase chain reaction (RT-PCR), Western blot analysis and immunogold electron-microscopic histochemistry. Parallel measures of ANXA5 mRNA and protein were also made.

RESULTS

ANXA1 mRNA and protein were detected in all but three adenomas studied; the protein was localized mainly, but not exclusively, to nonendocrine cells. ANXA5 expression was more variable and was contained within both endocrine and nonendocrine cells of these tumours. In comparison with the adenomas, the GH-secreting carcinoma showed abundant expression of both ANXA1 and ANXA5, with intense ANXA1 staining in some but not all tumour/endocrine cells. A serine-phosphorylated species of ANXA1 was detected in all pituitary tumours studied; by contrast, tyrosine-phosphorylated ANXA1 was detected in only four adenomas and in the GH carcinoma. ANXA1 and ANXA5 were also expressed in abundance in the astrocytoma.

CONCLUSIONS

The results demonstrate expression of both ANXA1 and ANXA5 in human pituitary tumours and thus raise the possibility that these proteins influence the growth and/or functional activity of the tumours.

Evidence from studies on co-cultures of TtT/GF and AtT20 cells that Annexin 1 acts as a paracrine or juxtacrine mediator of the early inhibitory effects of glucocorticoids on ACTH release

Annexin 1 (ANXA1) is a key mediator of the inhibitory effects of glucocorticoids on adrenocorticotropic hormone (ACTH) release, which develop within 1-2 h of a steroid challenge. Our previous studies, which showed that (i) ANXA1 is expressed principally by the nonsecretory folliculo-stellate cells in the pituitary gland; (ii) glucocorticoids cause the exportation of ANXA1 from these cells; and (iii) corticotrophs express specific ANXA1 binding sites, led us to propose that ANXA1 serves as a paracrine or juxtacrine mediator of glucocorticoids. To address this hypothesis, we examined ANXA1-dependent glucocorticoid actions in co-cultures of murine corticotroph (AtT20 clone D1) and folliculo-stellate (TtT/GF) cell lines. ANXA1 mRNA and protein were found in abundance in TtT/GF cells but neither was detectable in the AtT20 cells. AtT20 cells (alone and in co-culture with TtT/GF cells) responded to corticotropin-releasing hormone (CRH) (0.1-1 micro m) with increased ACTH release. The CRH-stimulated release of ACTH from AtT20 cells cultured alone was unaffected by preincubation with dexamethasone (Dex, 100 nm); by contrast, in co-cultures of AtT20 and TtT/GF cells, the steroid readily inhibited the secretory response to CRH. The effects of Dex on ACTH release were mimicked by N-terminal ANXA1 fragments (ANXA1Ac2-26, 2 micro g/ml and ANXA11-188, 0.1 ng/ml) and reversed by mifepristone (1 micro m) and by an antisense oligodeoxynucleotide (ODN) to ANXA1 (50 nm) but not by control ODNs. The antisense ODN also specifically blocked the Dex-induced externalization of ANXA1 from TtT/GF cells. Immunofluorescence imaging of the co-cultures localized the exported protein to the vicinity of the AtT20 cells and identified ANXA1 binding sites on these cells. These results provide functional and histological evidence to support our premise that the early inhibitory effects of glucocorticoids on ACTH release are dependent upon paracrine/juxtacrine actions of ANXA1 derived from folliculo-stellate cells.

Spread of injectate with superficial cervical plexus block in humans: an anatomical study

BACKGROUND

This study was undertaken to investigate why the superficial cervical plexus block for carotid endarterectomy is so effective. Initial consideration would suggest that a superficial injection would be unlikely to block all terminal fibres of relevant nerves. One possibility is that the local anaesthetic crosses the deep cervical fascia and blocks the cervical nerves at their roots.

METHODS

Superficial cervical plexus blocks (injections just below the investing fascia) were performed using methylene blue (30 ml) in four cadavers. In one additional control cadaver, a deep cervical plexus injection was performed. In a second control cadaver, a subcutaneous injection (superficial to investing fascia) was performed at the posterior border of the sternomastoid muscle.

RESULTS

Anatomical dissection showed that with superficial block there was spread of the dye to structures beneath the deep cervical fascia. In the first control, dye remained in the deep cervical space. In the second control, dye remained subcutaneous.

CONCLUSIONS

The superficial cervical space communicates with the deep cervical space and this may explain the efficacy of the superficial block. The method of communication remains unknown. Our findings also indicate that the suitable site of injection for the superficial cervical plexus block is below the investing fascia of the neck, and not just subcutaneous.

Kinase-dependent regulation of the secretion of thyrotrophin and luteinizing hormone by glucocorticoids and annexin 1 peptides

Our previous studies have identified a role for annexin 1 (ANXA1), a protein produced by the pituitary folliculostellate cells, as a paracrine/juxtacrine mediator of the acute regulatory effects of glucocorticoids on the release of adrenocorticotropic hormone and other pituitary hormones. In the present study, we focused on the secretion of thyroid stimulating hormone (TSH) and luteinizing hormone (LH) and used a battery of ANXA1-derived peptides to identify the key domains in the ANXA1 molecule that are critical to the inhibition of peptide release. In addition, as ANXA1 is a substrate for protein kinase C (PKC) and tyrosine kinase, we examined the roles of these kinases in the manifestation of the ANXA1-dependent inhibitory actions of dexamethasone on TSH and LH release. Dexamethasone suppressed the forskolin-induced release of TSH and LH from rat anterior pituitary tissue in vitro. Its effects were mimicked by human recombinant ANXA1 (hrANXA1) and a truncated protein, ANXA1(1-188). ANXA1(Ac2-26), also suppressed stimulated peptide release but it lacked both the potency and the efficacy of the parent protein. Shorter N-terminal ANXA1 sequences were without effect. The PKC inhibitor PKC(19-36) abolished the inhibitory actions of dexamethasone on the forskolin-evoked release of TSH and LH; it also attenuated the inhibitory actions of ANXA1(Ac2-26). Similar effects were produced by annexin 5 (ANXA5) which sequesters PKC in other systems. By contrast, the tyrosine kinase inhibitors, p60v-src (137-157) and genistein, had no effect on the secretion of TSH or LH alone or in the presence of forskolin and/or dexamethasone. Dexamethasone caused the translocation of a tyrosine-phosphorylated species of ANXA1 to the surface of pituitary cells. The total amount of ANXA1 exported from the cells in response to the steroid was unaffected by tyrosine kinase blockade. However, the degree of tyrosine-phosphorylation of the exported protein was markedly reduced by genistein. These results suggest that (i) the ANXA1-dependent inhibitory actions of dexamethasone on the release of TSH and LH require PKC and sequences in the N-terminal domain of ANXA1, but are independent of tyrosine kinase, and (ii) while dexamethasone induces the cellular exportation of a tyrosine-phosphorylated species of ANXA1, tyrosine phosphorylation per se is not critical to the steroid-induced passage of ANXA1 across the membrane.

Dexamethasone induces rapid serine-phosphorylation and membrane translocation of annexin 1 in a human folliculostellate cell line via a novel nongenomic mechanism involving the glucocorticoid receptor, protein kinase C, phosphatidylinositol 3-kinase, and mitogen-activated protein kinase

Our recent studies on rat pituitary tissue suggest that the annexin 1 (ANXA1)-dependent inhibitory actions of glucocorticoids on ACTH secretion are effected via a paracrine mechanism that involves protein kinase C (PKC)-dependent translocation of a serine-phosphorylated species of ANXA1 (Ser-P-ANXA1) to the plasma membrane of the nonsecretory folliculostellate cells. In the present study, we have used a human folliculostellate cell line (PDFS) to explore the signaling mechanisms that cause the translocation of Ser-P-ANXA1 to the membrane together with Western blot analysis and flow cytometry to detect the phosphorylated protein. Exposure of PDFS cells to dexamethasone caused time-dependent increases in the expression of ANXA1 mRNA and protein, which were first detected within 2 h of steroid contact. This genomic response was preceded by the appearance within 30 min of substantially increased amounts of Ser-P-ANXA1 and by translocation of the phosphorylated protein to the cell surface. The prompt membrane translocation of Ser-P-ANXA1 provoked by dexamethasone was inhibited by the glucocorticoid receptor, antagonist, mifepristone, but not by actinomycin D or cycloheximide, which effectively inhibit mRNA and protein synthesis respectively in our preparation. It was also inhibited by a nonselective PKC inhibitor (PKC(9-31)), by a selective inhibitor of Ca(2+)-dependent PKCs (Go 6976) and by annexin 5 (which sequesters PKC in other systems). In addition, blockade of phosphatidylinositiol 3-kinase (wortmannin) or MAPK pathways with PD 98059 or UO 126 (selective for MAPK kinse 1 and 2) prevented the steroid-induced translocation of Ser-P-ANXA1 to the cell surface. These results suggest that glucocorticoids induce rapid serine phosphorylation and membrane translocation of ANXA1 via a novel nongenomic, glucocorticoid receptor-dependent mechanism that requires MAPK, phosphatidylinositiol 3-kinase, and Ca(2+)-dependent PKC pathways.

Evidence for a role of the adenosine 5'-triphosphate-binding cassette transporter A1 in the externalization of annexin I from pituitary folliculo-stellate cells

Annexin 1 (ANXA1) has a well-demonstrated role in early delayed inhibitory feedback of glucocorticoids in the pituitary. ANXA1 is located in folliculo-stellate (FS) cells, and glucocorticoids act on these cells to externalize and stimulate the synthesis of ANXA1. However, ANXA1 lacks a signal sequence so the mechanism by which ANXA1 is externalized from FS cells was unknown and has been investigated. The ATP-binding cassette (ABC) transporters are a large group of transporters with varied roles that include the externalization of proteins. Glucocorticoid-induced externalization of ANXA1 from an FS cell line (TtT/GF) and rat anterior pituitary was blocked by glyburide, which inhibits ABC transporters. Glyburide also blocked the glucocorticoid inhibition of forskolin-stimulated ACTH release from pituitary tissue in vitro. RT-PCR revealed mRNA and Western blotting demonstrated protein for the ATP binding cassette A1 (ABCA1) transporter in mouse FS, TtT/GF, and A549 lung adenocarcinoma cells from which glucocorticoids also induce externalization of ANXA1. In TtT/GF cells, immunofluorescence labeling revealed a near total colocalization of cell surface ANXA1 and ABCA1. We conclude that ANXA1, which mediates the early delayed feedback of glucocorticoids in the anterior pituitary, is externalized from FS cells by an ABC transporter and that the ABCA1 transporter is a likely candidate.

Aberrant inflammation and resistance to glucocorticoids in annexin 1-/- mouse

The 37-kDa protein annexin 1 (Anx-1; lipocortin 1) has been implicated in the regulation of phagocytosis, cell signaling, and proliferation and is postulated to be a mediator of glucocorticoid action in inflammation and in the control of anterior pituitary hormone release. Here, we report that mice lacking the Anx-1 gene exhibit a complex phenotype that includes an altered expression of other annexins as well as of COX-2 and cPLA2. In carrageenin- or zymosan-induced inflammation, Anx-1-/- mice exhibit an exaggerated response to the stimuli characterized by an increase in leukocyte emigration and IL-1beta generation and a partial or complete resistance to the antiinflammatory effects of glucocorticoids. Anx-1-/- polymorphonuclear leucocytes exhibited increased spontaneous migratory behavior in vivo whereas in vitro, leukocytes from Anx-1-/- mice had reduced cell surface CD 11b (MAC-1) but enhanced CD62L (L-selectin) expression and Anx-1-/- macrophages exhibited anomalies in phagocytosis. There are also gender differences in activated leukocyte behavior in the Anx-1-/- mice that are not seen in the wild-type animals, suggesting an interaction between sex hormones and inflammation in Anx-1-/- animals.

Transition to turbulence in particulate pipe flow

We investigate experimentally the influence of suspended particles on the transition to turbulence. The particles are monodisperse and neutrally buoyant with the liquid. The role of the particles on the transition depends upon both the pipe to particle diameter ratios and the concentration. For large pipe-to-particle diameter ratios the transition is delayed while it is lowered for small ratios. A scaling is proposed to collapse the departure from the critical Reynolds number for pure fluid as a function of concentration into a single master curve.

Externalization of annexin I from a folliculo-stellate-like cell line

Our recent studies on rat pituitary tissue suggest that the annexin I-dependent inhibitory actions of glucocorticoids may not be exerted directly on endocrine cells but indirectly via folliculo-stellate (FS) cells. FS cells contain glucocorticoid receptors and abundant annexin I. We have studied the localization of annexin I in FS cells and the ability of dexamethasone to induce annexin I secretion by an FS (TtT/GF) cell line, using Western blotting and immunofluorescence microscopy. Exposure of TtT/GF cells to dexamethasone (0.1 micro M, 3 h) caused an increase in the amount of annexin I protein in the intracellular compartment and attached to the surface of the cells. In nonpermeabilized cells, immunofluorescence labeling revealed that annexin I immunoreactivity was associated with the cell surface and concentrated in focal patches on the ends of cytoplasmic processes; dexamethasone (0.1 micro M, 3 h) increased both the number and intensity of these foci. Immunogold electron microscopy confirmed in anterior pituitary tissue the presence of immunoreactive-annexin at the surface of FS cell processes contacting endocrine cells. These data support our hypothesis that annexin I is released by FS cells in response to glucocorticoids to mediate glucocorticoid inhibitory actions on pituitary hormone release via a juxtacrine mechanism.