Differential intracellular signaling of the GalR1 and GalR2 galanin receptor subtypes

The diverse physiological functions exerted by the neuropeptide galanin may be regulated by multiple G protein-coupled receptor subtypes and intracellular signaling pathways. Three galanin receptor subtypes (GalRs) have been recently cloned, but the G protein coupling profiles of these receptors are not completely understood. We have generated GalR1- and GalR2-expressing Chinese hamster ovary (CHO) cell lines and systematically examined the potential for these two receptors to couple to the Gs, Gi, Go, and Gq proteins. Galanin did not stimulate an increase in cAMP levels in GalR1/CHO or GalR2/CHO cells, suggesting an inability of either receptor to couple to Gs. Galanin inhibited forskolin-stimulated cAMP production in GalR1/CHO cells by 70% and in GalR2/CHO cells by 30%, suggesting a strong coupling of GalR1 to Gi and a more modest coupling between GalR2 and Gi. GalR1 and GalR2 both mediated pertussis toxin-sensitive MAPK activity (2-3-fold). The stimulation mediated by GalR1 was inhibited by expression of the C-terminus of beta-adrenergic receptor kinase (beta ARKct), which specifically inhibits G beta gamma signaling, but was not affected by the protein kinase C (PKC) inhibitor, bis[indolylmaleimide], or cellular depletion of PKC. In contrast, GalR2-mediated MAPK activation was not affected by beta ARKct expression but was abolished by inhibition of PKC activity. The data demonstrate that GalR1 is coupled to a Gibetagamma signaling pathway to mediate MAPK activation. In contrast, GalR2 utilizes a distinct signaling pathway to mediate MAPK activation, which is consistent with Go-mediated MAPK activation in CHO cells. Galanin was unable to stimulate inositol phosphate (IP) accumulation in CHO or COS-7 cells expressing GalR1. In contrast, galanin stimulated a 7-fold increase in IP production in CHO or COS-7 cells expressing GalR2. The GalR2-mediated IP production was not affected by pertussis toxin, suggesting a linkage of GalR2 with Gq/G11. Thus, the GalR1 receptor appears to activate only the Gi pathway. By contrast, GalR2 is capable of stimulating signaling which is consistent with activation of Go, Gq/G11, and Gi. The differential signaling profiles and the tissue distribution patterns of GalR1 and GalR2 may underlie the functional spectra of galanin action mediated by these galanin receptors and regulate the diverse physiological functions of galanin.

Maternal hyperthermia and the risk for neural tube defects in offspring: systematic review and meta-analysis

BACKGROUND

In animals, excessive core body temperatures have been documented to cause malformations; neural tube defects (NTDs) are among the most frequently reported. In humans, data are inconclusive and often conflicting. The objective of our report is to determine the risk for neural tube defects associated with maternal hyperthermia in early pregnancy.

METHODS

We conducted a systematic review and meta-analysis to evaluate available evidence on this topic in humans. MEDLINE, EMBASE, references from published reports, and biologic abstracts from meetings were searched for relevant studies. Reviewers evaluated all the retrieved articles and extracted the relevant data. Individual and summary odds ratios and relative risks were calculated using the Mantel-Haenszel method.

RESULTS

Fifteen studies, reporting on 1,719 cases and 37,898 noncases, were included in the meta-analysis. The overall odds ratio for neural tube defects associated with maternal hyperthermia was 1.92 (95% confidence interval = 1.61-2.29). When analyzed separately, the 9 case-control studies had an odds ratio of 1.93 (1.53-2.42). The summary relative risk for the 6 cohort studies was 1.95 (1.30-2.92).

CONCLUSIONS

Maternal hyperthermia in early pregnancy is associated with increased risk for neural tube defects and may be a human teratogen.

The melanin-concentrating hormone receptor couples to multiple G proteins to activate diverse intracellular signaling pathways

The receptor for melanin-concentrating hormone (MCH) was recently identified as the orphan G protein-coupled receptor SLC-1. In this study, a CHO cell line expressing the MCH receptor (Kd = 1.3 nM; binding capacity, 3.6 pmol/mg protein) is used to assess the ability of the MCH receptor to couple to Gi, Go, and Gq proteins. The results demonstrate that MCH inhibits forskolin-stimulated cAMP production in a pertussis toxin- (PTX)-sensitive manner in CHO-MCHR cells (EC50 = 100 pM), indicating that the MCH receptor couples to one or more members of the Gi subfamily of G proteins. In addition, MCH stimulates increases in phosphoinositide metabolism (EC50 = 50 nM) and in intracellular free Ca2+ levels (EC50 = 10 nM). MCH-stimulated inositol phosphate production and increases in intracellular free Ca2+ are partially inhibited (60% and 40%, respectively) by PTX pretreatment, demonstrating that there are at least two components of each of these signaling pathways. One component is PTX sensitive and therefore mediated through a Gi/Go protein. A distinct G protein-coupled (probably Gq type) mediates the PTX-insensitive component. To distinguish Gi vs. Go coupling, MCH-stimulated mitogen-activated protein (MAP) kinase activity was examined. Gi and Go use separate signaling pathways to mediate MAP kinase activation in CHOcells. Protein kinase C (PKC) activity is essential in the Go-dependent MAP kinase signaling pathway, but is not required in the GC-dependent MAP kinase signaling pathway. MCH stimulated MAP kinase activity is decreased (50%), but not abolished, by inhibition of PKC activity or depletion of cellular PKC, indicating that MCH-stimulated MAP kinase activity is mediated through both Gi- and Go-dependent signaling mechanisms. The results of this study are the first to clearly demonstrate that the MCH receptor couples to multiple G proteins to mediate several diverse intracellular signaling pathways.

Malformation Rates in Children of Women with Untreated Epilepsy

BACKGROUND

It is widely quoted that women with epilepsy have a higher than baseline risk for giving birth to a child with malformations, independent of the effects of antiepileptic drugs.

OBJECTIVE

To determine, based on available evidence, if epilepsy per se represents a teratogenic risk. To systematically review all studies investigating the occurrence of major malformation rates among children of treated or untreated women with epilepsy and non-exposed controls who do not have epilepsy.

METHODS

A meta-analysis, using a random effects model, was conducted of all cohort and case-control studies reporting malformation rates in children of women with epilepsy exposed or unexposed to antiepileptic drugs compared with that of children of nonepileptic women. Medline (1966-2001), EMBASE, the Cochrane database as well as REPROTOX (an information system on environmental hazards to human reproduction and development) databases were accessed.

RESULTS

We found ten studies reporting results of untreated epilepsy (n = 400) and their non-epileptic healthy controls (n = 2492). Nine out of ten studies also reported results on 1443 patients exposed to antiepileptic drugs and their 2526 unexposed healthy controls. The risk for congenital malformations in the offspring of women with untreated epilepsy was not higher than among nonepileptic controls (odds ratio [OR] = 1.92; 95% CI 0.92-4.00). There was evidence of publication bias, thus with bias removed the OR was 0.99 (95% CI 0.49-2.01). In contrast, the offspring of epileptic women who received antiepileptic drugs had higher incidences of malformation than controls (OR 3.26; 95% CI 2.15-4.93).

CONCLUSION

Our study does not support the commonly held view that epilepsy per se represents a teratogenic risk. Our study suggests that this view is the result of a publication bias, with several small (< 100 participants) positive studies leading to a premature conclusion.

Identification and pharmacological characterization of a novel human melanin-concentrating hormone receptor, mch-r2

Melanin-concentrating hormone (MCH) is a neuropeptide highly expressed in the brain that regulates several physiological functions mediated by receptors in the G protein-coupled receptor family. Recently an orphan receptor, SLC-1, has been identified as an MCH receptor (MCH-R1). Herein we identify and characterize a novel receptor for human MCH (MCH-R2). The receptor is composed of 340 amino acids encoded by a 1023-base pair cDNA and is 35% homologous to SLC-1. (125)I-MCH specifically bound to Chinese hamster ovary cells stably expressing MCH-R2. MCH stimulated dose-dependent increases in intracellular free Ca(2+) and inositol phosphate production in these cells but did not affect cAMP production. The pharmacological profile for mammalian MCH, [Phe(13),Tyr(19)]MCH, and salmon MCH at MCH-R2 differed compared with MCH-R1 as assessed by intracellular signaling and radioligand binding assays. The EC(50) in signaling assays and the IC(50) in radioligand binding assays of salmon MCH was an order of magnitude higher than mammalian MCH at MCH-R2. By comparison, the EC(50) and IC(50) values of salmon MCH and mammalian MCH at MCH-R1 were relatively similar. Blot hybridization revealed exclusive expression of MCH-R2 mRNA in several distinct brain regions, particularly in the cortical area, suggesting the involvement of MCH-R2 in the central regulation of MCH-mediated functions.

Nociceptin (ORL-1) and mu-opioid receptors mediate mitogen-activated protein kinase activation in CHO cells through a Gi-coupled signaling pathway: evidence for distinct mechanisms of agonist-mediated desensitization

The recently identified 17-amino acid peptide nociceptin (orphanin FQ) is the endogenous ligand for the opioid receptor-like-1 (ORL-1) receptor. A physiologic role for nociceptin (OFQ) activation of the ORL-1 receptor (OFQR) may be to modulate opioid-induced analgesia. The molecular mechanism by which nociceptin (OFQ) and ORL-1 (OFQR) modify opioid-stimulated effects, however, is unclear. Both ORL-1 (OFQR) and opioid receptors mediate pertussis toxin (PTX)-sensitive signal transduction, indicating these receptors are capable of coupling to Gi/Go proteins. This study determines that nociceptin stimulates an intracellular signaling pathway, leading to activation of mitogen-activated protein (MAP) kinase in CHO cells expressing ORL-1 receptor (OFQR). Nociceptin (OFQ)-stimulated MAP kinase activation was inhibited by PTX or by expression of the carboxyl terminus of beta-adrenergic receptor kinase (betaARKct), which specifically blocks Gbetagamma-mediated signaling. Expression of the proline-rich domain of SOS (SOS-PRO), which inhibits SOS interaction with p21ras, also attenuated nociceptin (OFQ)-stimulated MAP kinase activation. The phosphatidylinositol 3-kinase (PI-3K) inhibitors wortmannin and LY294002 reduced nociceptin (OFQ)-stimulated MAP kinase activation, whereas inhibition of protein kinase C (PKC) activity by bisindolylmaleimide I or cellular depletion of PKC had no effect. In a similar manner, in cells expressing mu-opioid receptor, [D-Ala2,N-Me-Phe4,Gly-ol]-enkephalin (DAMGO; a mu-opioid receptor-selective agonist) stimulated PTX-sensitive MAP kinase activation that was inhibited by wortmannin, LY294002, betaARKct expression, or SOS-PRO expression but not affected by inhibition of PKC activity. These results indicate that both ORL-1 (OFQR) and mu-opioid receptors mediate MAP kinase activation via a signaling pathway using the betagamma-subunit of Gi, a PI-3K, and SOS, independent of PKC activity. In cells expressing both ORL-1 (OFQR) and mu-opioid receptors, pretreatment with nociceptin decreased subsequent nociceptin (OFQ)- or DAMGO-stimulated MAP kinase activation. In contrast, pretreatment of cells with DAMGO decreased subsequent DAMGO-stimulated MAP kinase but had no effect on subsequent nociceptin (OFQ)-stimulated MAP kinase activation. These results demonstrate that nociceptin (OFQ) activation of ORL-1 (OFQR) can modulate mu-opioid receptor signaling in a cellular system.

Neurodevelopment of children exposed in utero to treatment of maternal malignancy

Cancer is the second most common cause of death during the reproductive years, complicating approximately 1/1000 pregnancies. The occurrence of cancer during gestation is likely to increase as a result of a woman's tendency to delay childbearing. Improved diagnostic techniques for malignancies increases detection of cancer during pregnancy. Malignant conditions during gestation are believed to be associated with an increase in poor perinatal and fetal outcomes that are often due to maternal treatment. Physicians should weigh the benefits of treatment against the risks of fetal exposure. To date, most reports have focused on morphologic observations made very close to the time of delivery with little data collected on children's long-term neurodevelopment following in utero exposure to malignancy and treatment. Because the brain differentiates throughout pregnancy and in early postnatal life, damage may occur even after first trimester exposure. The possible delayed effects of treatment on a child's neurological, intellectual and behavioural functioning have never been systematically evaluated. The goal of this report was to summarize all related issues into one review to facilitate both practitioners' and patients' access to known data on fetal risks and safety.

Binge alcohol consumption by non-alcohol-dependent women during pregnancy affects child behaviour, but not general intellectual functioning; a prospective controlled study

Effects of binge ethanol consumption during early gestation on child neurodevelopment have not been elucidated. To study whether binge drinking affects cognitive abilities and behavior of exposed children, a prospective observational study comparing 51 children exposed to binge drinking during the first trimester of pregnancy to 51 children not exposed to any teratogens was conducted. The children's physical development, intelligence, language abilities and behavior were assessed. Temperament test results showed that children exposed in utero to maternal binge drinking displayed a greater degree of disinhibited behavior and that this behavior was associated with early drinking variables. Although binge alcohol drinking by non-alcohol-dependent women during the first trimester of pregnancy does not appear to affect intelligence or cognitive and language development of young children, binge drinking in pregnancy does increase the likelihood of certain behavioral characteristics that might predispose these children to later behavioral dysfunction.

Lipoprotein lipase and leptin are accumulated in different secretory compartments in rat adipocytes

Adipose cells produce and secrete several physiologically important proteins, such as lipoprotein lipase (LPL), leptin, adipsin, Acrp30, etc. However, secretory pathways in adipocytes have not been characterized, and vesicular carriers responsible for the accumulation and transport of secreted proteins have not been identified. We have compared the intracellular localization of two proteins secreted from adipose cells: leptin and LPL. Adipocytes accumulate large amounts of both proteins, suggesting that neither of them is targeted to the constitutive secretory pathway. By means of velocity centrifugation in sucrose gradients, equilibrium density centrifugation in iodixanol gradients, and immunofluorescence confocal microscopy, we determined that LPL and leptin were localized in different membrane structures. LPL was found mainly in the endoplasmic reticulum with a small pool being present in low density membrane vesicles that may represent a secretory compartment in adipose cells. Virtually all intracellular leptin was localized in these low density secretory vesicles. Insulin-sensitive Glut4 vesicles did not contain either LPL or leptin. Thus, secretion from adipose cells is controlled both at the exit from the endoplasmic reticulum as well as at the level of "downstream" secretory vesicles.

Ectopic adenine nucleotide translocase activity controls extracellular ADP levels and regulates the F1-ATPase-mediated HDL endocytosis pathway on hepatocytes

Ecto-F₁-ATPase is a complex related to mitochondrial ATP synthase which has been identified as a plasma membrane receptor for apolipoprotein A-I (apoA-I), the major protein of high-density lipoprotein (HDL), and has been shown to contribute to HDL endocytosis in several cell types. On hepatocytes, apoA-I binding to ecto-F₁-ATPase stimulates extracellular ATP hydrolysis into ADP, which subsequently activates a P2Y₁₃-mediated HDL endocytosis pathway. Interestingly, other mitochondrial proteins have been found to be expressed at the plasma membrane of several cell types. Among these, adenine nucleotide translocase (ANT) is an ADP/ATP carrier but its role in controlling extracellular ADP levels and F₁-ATPase-mediated HDL endocytosis has never been investigated. Here we confirmed the presence of ANT at the plasma membrane of human hepatocytes. We then showed that ecto-ANT activity increases or reduces extracellular ADP level, depending on the extracellular ADP/ATP ratio. Interestingly, ecto-ANT co-localized with ecto-F₁-ATPase at the hepatocyte plasma membrane and pharmacological inhibition of ecto-ANT activity increased extracellular ADP level when ecto-F₁-ATPase was activated by apoA-I. This increase in the bioavailability of extracellular ADP accordingly translated into an increase of HDL endocytosis on human hepatocytes. This study thus uncovered a new location and function of ANT for which activity at the cell surface of hepatocytes modulates the concentration of extracellular ADP and regulates HDL endocytosis.

Retention of Plutonium and Americium by Rock

The relative migration ratio of plutonium in various rocks is approximately 100 micrometers per meter of waterflow; the corresponding migration ratio for americium is about 500 micrometers per meter of water flow. Under these conditions radioactive decay will have taken place to such an extent that little plutonium and americium can reach the external environment from a well-designed and isolated geological repository site.

Carbon dioxide laser use in wound sealing and epikeratophakia

This paper presents current clinical and experimental uses of the carbon dioxide laser and the results of our human and animal tissue fusion investigations. Trials were conducted with human scleral and corneal eye bank tissue and in albino rabbits. With power settings of 100 to 200 mW, optimal laser effect consisting of slight whitening and minimal edge shrinkage occurred between 10 and 70 mJ of total energy. No tissue adherence could be demonstrated with the parameters tested. A final study was made on the feasibility of sealing an epikeratophakia lenticle to its recipient bed using the carbon dioxide laser. The average force required to remove the button in the control experiments was 6.45 g and this increased to 6.99 g after laser treatment although no fusion was apparent. This was statistically significant (P less than .05).