Differential effects of adrenaline and noradrenaline on the hepatic expression of immediate early genes in mice

Adrenergic Mechanisms of Audiogenic Seizure-Induced Death in a Mouse Model of SCN8A Encephalopathy

Sudden unexpected death in epilepsy (SUDEP) is the leading cause of death amongst patients whose seizures are not adequately controlled by current therapies. Patients with SCN8A encephalopathy have an elevated risk for SUDEP. While transgenic mouse models have provided insight into the molecular mechanisms of SCN8A encephalopathy etiology, our understanding of seizure-induced death has been hampered by the inability to reliably trigger both seizures and seizure-induced death in these mice. Here, we demonstrate that mice harboring an Scn8a allele with the patient-derived mutation N1768D (D/+) are susceptible to audiogenic seizures and seizure-induced death. In adult D/+ mice, audiogenic seizures are non-fatal and have nearly identical behavioral, electrographical, and cardiorespiratory characteristics as spontaneous seizures. In contrast, at postnatal days 20–21, D/+ mice exhibit the same seizure behavior, but have a significantly higher incidence of seizure-induced death following an audiogenic seizure. Seizure-induced death was prevented by either stimulating breathing via mechanical ventilation or by acute activation of adrenergic receptors. Conversely, in adult D/+ mice inhibition of adrenergic receptors converted normally non-fatal audiogenic seizures into fatal seizures. Taken together, our studies show that in our novel audiogenic seizure-induced death model adrenergic receptor activation is necessary and sufficient for recovery of breathing and prevention of seizure-induced death.

An exaggerated epinephrine-adrenergic receptor signaling impairs uterine decidualization in mice

Our understanding of the relationship between stress-derived epinephrine and early pregnancy failure remains incomplete. Here, we explored the effect of epinephrine exposure on early pregnancy and pseudopregnancy in mice. Increased expression of adrenergic receptors Adra1b, Adra2b and Adrb2 was observed during decidualization and post-implantation embryogenesis was delayed or survival impaired. Epinephrine treatment also impaired decidualization in both the gravid and pseudopregnant uterus, suggesting the effect on decidualization was independent of the conceptus. This included a suppression of endometrial stroma cell proliferation and of key decidualization regulators, including COX2, BMP2 and WNT4. Collectively, these data demonstrate that maternal epinephrine exposure during early pregnancy impairs uterine decidualization and embryo development, underlying early pregnancy failure.

Food Perception Primes Hepatic ER Homeostasis via Melanocortin-Dependent Control of mTOR Activation

Adaptation of liver to the postprandial state requires coordinated regulation of protein synthesis and folding aligned with changes in lipid metabolism. Here we demonstrate that sensory food perception is sufficient to elicit early activation of hepatic mTOR signaling, Xbp1 splicing, increased expression of ER-stress genes, and phosphatidylcholine synthesis, which translate into a rapid morphological ER remodeling. These responses overlap with those activated during refeeding, where they are maintained and constantly increased upon nutrient supply. Sensory food perception activates POMC neurons in the hypothalamus, optogenetic activation of POMC neurons activates hepatic mTOR signaling and Xbp1 splicing, whereas lack of MC4R expression attenuates these responses to sensory food perception. Chemogenetic POMC-neuron activation promotes sympathetic nerve activity (SNA) subserving the liver, and norepinephrine evokes the same responses in hepatocytes in vitro and in liver in vivo as observed upon sensory food perception. Collectively, our experiments unravel that sensory food perception coordinately primes postprandial liver ER adaption through a melanocortin-SNA-mTOR-Xbp1s axis. VIDEO ABSTRACT.

A cautionary note for researchers treating mice with the neurotransmitter norepinephrine

The sympathetic nervous system plays a crucial role in metabolic function and glucose homeostasis. Norepinephrine is the main neurotransmitter released from sympathetic neurons. The major goal of our studies was to examine the impact of norepinephrine on metabolism related gene expression in obesity in vivo. Interestingly, we discovered that norepinephrine had a detrimental effect in our studies. C57BL6/J mice fed a high fat diet were intraperitoneally injected with 0.2 or 2 mg/kg/day norepinephrine. These doses of norepinephrine have been used previously by other researchers. Survival of the mice was documented. Kidney and bladder tissues were excised and fixed for histological studies. A subset of norepinephrine treated mice experienced unexpected adverse events which included bladder distension and reduced kidney perfusion as suggested by kidney discolouration. This eventuated in the mice having to be sacrificed or the mice succumbed to the pathological condition. To our knowledge, such an effect of norepinephrine has not been previously reported in mice. Morphological examination of kidney and bladder indicated marked detrimental architectural changes, which we postulate is associated with norepinephrine induced vasoconstriction, urinary retention and renal impairment. Our studies highlight that administration of norepinephrine to mice may trigger adverse effects relating predominantly to the urogenital tract which can result in decline in a subpopulation of these mice. Researchers administering norepinephrine in mouse models should be aware and look out for these unexpected adverse events associated with the use of norepinephrine.

Transient {beta}2-adrenoceptor activation confers pregnancy loss by disrupting embryo spacing at implantation

Pregnancy loss is a serious social and medical issue, with one important cause associated with aberrant embryo implantation during early pregnancy. However, whether and how the process of embryo implantation is affected by environmental factors such as stress-induced sympathetic activation remained elusive. Here we report an unexpected, transient effect of β₂-adrenoreceptor (β₂-AR) activation (day 4 postcoitus) in disrupting embryo spacing at implantation, leading to substantially increased midterm pregnancy loss. The abnormal embryo spacing could be prevented by pretreatment of β₂-AR antagonist or genetic ablation of β-AR. Similar β₂-AR activation at day 5 postcoitus, when implantation sites have been established, did not affect embryo spacing or pregnancy outcome, indicating that the adverse effect of β₂-AR activation is limited to the preimplantation period before embryo attachment. In vitro and in vivo studies demonstrated that the transient β₂-AR activation abolished normal preimplantation uterine contractility without adversely affecting blastocyst quality. The contractility inhibition is mediated by activation of the cAMP-PKA pathway and accompanied by specific down-regulation of lpa3, a gene previously found to be critical for uterine contraction and embryo spacing. These results indicated that normal uterine contraction-mediated correct intrauterine embryo distribution is crucial for successful ongoing pregnancy. Abnormal β₂-AR activation at early pregnancy provided a molecular clue in explaining how maternal stress at early stages could adversely affect the pregnancy outcome.

Sympathetic outflow activates the venom gland of the snakeBothrops jararacaby regulating the activation of transcription factors and the synthesis of venom gland proteins

The venom gland of viperid snakes has a central lumen where the venom produced by secretory cells is stored. When the venom is lost from the gland,the secretory cells are activated and new venom is produced. The production of new venom is triggered by the action of noradrenaline on bothα 1- and β-adrenoceptors in the venom gland. In this study, we show that venom removal leads to the activation of transcription factors NFκB and AP-1 in the venom gland. In dispersed secretory cells,noradrenaline activated both NFκB and AP-1. Activation of NFκB and AP-1 depended on phospholipase C and protein kinase A. Activation of NFκB also depended on protein kinase C. Isoprenaline activated both NFκB and AP-1, and phenylephrine activated NFκB and later AP-1. We also show that the protein composition of the venom gland changes during the venom production cycle. Striking changes occurred 4 and 7 days after venom removal in female and male snakes, respectively. Reserpine blocks this change,and the administration of α1- and β-adrenoceptor agonists to reserpine-treated snakes largely restores the protein composition of the venom gland. However, the protein composition of the venom from reserpinized snakes treated with α1- or β-adrenoceptor agonists appears normal, judging from SDS-PAGE electrophoresis. A sexual dimorphism in activating transcription factors and activating venom gland was observed. Our data suggest that the release of noradrenaline after biting is necessary to activate the venom gland by regulating the activation of transcription factors and consequently regulating the synthesis of proteins in the venom gland for venom production.

Genetic profiling of alpha 1-adrenergic receptor subtypes by oligonucleotide microarrays: coupling to interleukin-6 secretion but differences in STAT3 phosphorylation and gp-130

Alpha(1)-adrenoceptor subtypes (alpha(1A)-, alpha(1B)-, alpha(1D)-) are known to couple to similar signaling pathways, although differences among the subtypes do exist. As a more sensitive assay, we used oligonucleotide microarrays to identify gene expression changes in Rat-1 fibroblasts stably expressing each individual subtype. We report the gene expressions that change by at least a factor of 2 or more. Gene expression profiles significantly changed equally among all three subtypes, despite the unequal efficacy of the inositol phosphate response. Gene expressions were clustered into cytokines/growth factors, transcription factors, enzymes, and extracellular matrix proteins. There were also a number of individual subtype-specific changes in gene expression, suggesting a link to independent pathways. In addition, all three alpha(1)-AR subtypes robustly stimulated the transcription of the prohypertrophic cytokine interleukin (IL)-6, but differentially altered members of the IL-6 signaling pathway (gp-130 and STAT3). This was confirmed by measurement of secreted IL-6, activated STAT3, and gp-130 levels. Activation of STAT3 Tyr705 phosphorylation by the alpha(1)-ARs was not through IL-6 activation but was synergistic with IL-6, suggesting direct effects. Interestingly, alpha(1B)-AR stimulation caused the dimerization-dependent phosphorylation of Tyr705 on STAT3 but did not activate the transcriptional-dependent phosphorylation of Ser727. The alpha(1B)-AR also constitutively down-regulated the protein levels of gp-130. These results suggest that the alpha(1B)-AR has differential effects on the phosphorylation status of the STAT3 pathway and may not be as prohypertrophic as the other two subtypes.