Age-dependent regulation of depression-like behaviors through modulation of adrenergic receptor α1A subtype expression revealed by the analysis of interleukin-1 receptor antagonist knockout mice

IL-1ra treatment prevents chronic social defeat stress-induced depression-like behaviors and glutamatergic dysfunction via the upregulation of CREB-BDNF

BACKGROUND

Proinflammatory cytokines IL-1β has been proposed to be a key mediator in the pathophysiology of mood-related disorders. However, the IL-1 receptor antagonist (IL-1ra) is a natural antagonist of IL-1 and plays a key role in the regulation of IL-1-mediated inflammation, the effects of IL-1ra in stress-induced depression has not been well elucidated.

METHODS

Chronic social defeat stress (CSDS) and lipopolysaccharide (LPS) were used to investigate the effects of IL-1ra. ELISA kit and qPCR were used to detect IL-1ra levels. Golgi staining and electrophysiological recordings were used to investigate glutamatergic neurotransmission in the hippocampus. Immunofluorescence and western blotting were used to analyze CREB-BDNF pathway and synaptic proteins.

RESULTS

Serum levels of IL-1ra increased significantly in two animal models of depression, and there was a significant correlation between serum IL-1ra levels and depression-like behaviors. Both CSDS and LPS induced the imbalance of IL-1ra and IL-1β in the hippocampus. Furthermore, chronic intracerebroventricular (i.c.v.) infusion of IL-1ra not only blocked CSDS-induced depression-like behaviors, but also alleviated CSDS-induced decrease in dendritic spine density and impairments in AMPARs-mediated neurotransmission. Finally, IL-1ra treatment produces antidepressant-like effects through the activation of CREB-BDNF in the hippocampus.

LIMITATION

Further studies need to investigate the effect of IL-1ra in the periphery in CSDS-induced depression.

CONCLUSION

Our study suggests that the imbalance of IL-1ra and IL-1β reduces the expression of the CREB-BDNF pathway in the hippocampus, which dysregulates AMPARs-mediated neurotransmission, ultimately leading to depression-like behaviors. IL-1ra could be a new potential candidate for the treatment of mood disorders.

Graves' disease as a driver of depression: a mechanistic insight

Graves' disease (GD) is characterized by diffuse enlargement and overactivity of the thyroid gland, which may be accompanied by other physical symptoms. Among them, depression can dramatically damage patients' quality of life, yet its prevalence in GD has not received adequate attention. Some studies have established a strong correlation between GD and increased risk of depression, though the data from current study remains limited. The summary of mechanistic insights regarding GD and depression has underpinned possible pathways by which GD contributes to depression. In this review, we first summarized the clinical evidence that supported the increased prevalence of depression by GD. We then concentrated on the mechanistic findings related to the acceleration of depression in the context of GD, as mounting evidence has indicated that GD promotes the development of depression through various mechanisms, including triggering autoimmune responses, inducing hormonal disorders, and influencing the thyroid-gut-microbiome-brain axis. Finally, we briefly presented potential therapeutic approaches to decreasing the risk of depression among patients with GD.

Involvement of IL-6 and GSK3β in impaired sensorimotor gating induced by high-fat diet

Increased levels of proinflammatory cytokines have been implicated in schizophrenia; however, their pathophysiological roles in abnormal brain dysfunctions remain unclear. We evaluated the effect of proinflammatory cytokines on a high-fat diet (HFD)-induced prepulse inhibition (PPI) deficits in the acoustic startle response. Eight-week-old male C57BL/6J mice were fed a HFD for 3 weeks and then PPI was examined. HFD significantly induced PPI deficits and increased plasma IL-6, but not TNFα, levels. Interestingly, MR16-1 administration during the HFD period ameliorated PPI deficits. Further, in the striatum of HFD-fed mice, phosphorylation of GSK3β, but not GSK3α, was significantly increased; this increase was attenuated by MR16-1, although the protein levels of GSK3α and β were not altered. There were no significant differences in either phosphorylation or protein levels of GSK3α, β in the PFC during the HFD period. These results suggest that increased IL-6 levels during HFD may induce sensorimotor gating deficits, likely through the alteration of striatal GSK3β phosphorylation. MR16-1 might have a beneficial effect on such HFD-induced sensorimotor gating deficits.

Molecular mechanism of noradrenaline during the stress-induced major depressive disorder

Chronic stress-induced depression is a common hallmark of many psychiatric disorders with high morbidity rate. Stress-induced dysregulation of noradrenergic system has been implicated in the pathogenesis of depression. Lack of monoamine in the brain has been believed to be the main causative factor behind pathophysiology of major depressive disorder (MDD) and several antidepressants functions by increasing the monoamine level at the synapses in the brain. However, it is undetermined whether the noradrenergic receptor stimulation is critical for the therapeutic effect of antidepressant. Contrary to noradrenergic receptor stimulation, it has been suggested that the desensitization of β-adrenoceptor is involved in the therapeutic effect of antidepressant. In addition, enhanced noradrenaline (NA) release is central response to stress and thought to be a risk factor for the development of MDD. Moreover, fast acting antidepressant suppresses the hyperactivation of noradrenergic neurons in locus coeruleus (LC). However, it is unclear how they alter the firing activity of LC neurons. These inconsistent reports about antidepressant effect of NA-reuptake inhibitors (NRIs) and enhanced release of NA as a stress response complicate our understanding about the pathophysiology of MDD. In this review, we will discuss the role of NA in pathophysiology of stress and the mechanism of therapeutic effect of NA in MDD. We will also discuss the possible contributions of each subtype of noradrenergic receptors on LC neurons, hypothalamic-pituitary-adrenal axis (HPA-axis) and brain derived neurotrophic factor-induced hippocampal neurogenesis during stress and therapeutic effect of NRIs in MDD.

Type-7 metabotropic glutamate receptors negatively regulate α1-adrenergic receptor signalling

We studied the interaction between mGlu7 and α₁-adrenergic receptors in heterologous expression systems, brain slices, and living animals. L-2-Amino-4-phosphonobutanoate (L-AP4), and l-serine-O-phosphate (L-SOP), which activate group III mGlu receptors, restrained the stimulation of polyphosphoinositide (PI) hydrolysis induced by the α₁-adrenergic receptor agonist, phenylephrine, in HEK 293 cells co-expressing α₁-adrenergic and mGlu7 receptors. The inibitory action of L-AP4 was abrogated by (i) the mGlu7 receptor antagonist, XAP044; (ii) the C-terminal portion of type-2 G protein coupled receptor kinase; and (iii) the MAP kinase inhibitors, UO126 and PD98059. This suggests that the functional interaction between mGlu7 and α₁-adrenergic receptors was mediated by the βγ-subunits of the G_i protein and required the activation of the MAP kinase pathway. Remarkably, activation of neither mGlu2 nor mGlu4 receptors reduced α₁-adrenergic receptor-mediated PI hydrolysis. In mouse cortical slices, both L-AP4 and L-SOP were able to attenuate norepinephrine- and phenylephrine-stimulated PI hydrolysis at concentrations consistent with the activation of mGlu7 receptors. L-AP4 failed to affect norepinephrine-stimulated PI hydrolysis in cortical slices from mGlu7^-/- mice, but retained its inhibitory activity in slices from mGlu4^-/- mice. At behavioural level, i.c.v. injection of phenylephrine produced antidepressant-like effects in the forced swim test. The action of phenylephrine was attenuated by L-SOP, which was inactive per se. Finally, both phenylephrine and L-SOP increased corticosterone levels in mice, but the increase was halved when the two drugs were administered in combination. Our data demonstrate that α₁-adrenergic and mGlu7 receptors functionally interact and suggest that this interaction might be targeted in the treatment of stress-related disorders.

Possible role of the dopamine D1 receptor in the sensorimotor gating deficits induced by high-fat diet

RATIONALE

High-fat diet (HFD) has been recently reported to induce sensorimotor gating deficits, but the underlying mechanisms are not well understood.

OBJECTIVE

The purpose of this study is to determine whether HFD induces long-lasting deficits in sensorimotor gating and to examine the involvement of altered dopamine (DA) function.

METHODS

C57BL/6J mice were fed HFD for 10 weeks and then normal diet (ND) for 4 weeks. DA D2 receptor (D2R) knockout (KO) mice were also fed HFD for 10 weeks. The mice were evaluated for prepulse inhibition (PPI) of acoustic startle after HFD and the subsequent 4-week ND. We evaluated the effect of SCH23390, a D1 receptor (D1R) antagonist, on PPI and measured protein expression levels of D1R and D2R in the prefrontal cortex (PFC) in HFD mice. The concentrations of monoamines and their metabolites in the cortices of 10-week HFD or ND mice were measured using high performance liquid chromatography.

RESULTS

Long-term HFD-induced PPI disruption in WT and D2R KO mice. Even after 4 weeks of subsequent ND, PPI remained to be disrupted. SCH23390 mitigated the PPI disruption. In HFD animals, D1R protein expression in the PFC was significantly decreased, while DA, homovanillic acid, and 3,4-dihydroxyphenylacetic acid levels in the cortex were increased.

CONCLUSION

This is the first evidence that HFD can induce long-lasting deficits in sensorimotor gating through alteration of cortical levels of DA and its metabolites. Our data suggest that HFD-induced PPI deficits are related to altered D1R signaling and that D1R antagonists may have therapeutic effects on the deficits.

The potential of metabolomic analysis techniques for the characterisation of α1-adrenergic receptors in cultured N1E-115 mouse neuroblastoma cells

Several studies of neuropathic pain have linked abnormal adrenergic signalling to the development and maintenance of pain, although the mechanisms underlying this are not yet fully understood. Metabolomic analysis is a technique that can be used to give a snapshot of biochemical status, and can aid in the identification of the mechanisms behind pathological changes identified in cells, tissues and biological fluids. This study aimed to use gas chromatography-mass spectrometry-based metabolomic profiling in combination with reverse transcriptase-polymerase chain reaction and immunocytochemistry to identify functional α1-adrenergic receptors on cultured N1E-115 mouse neuroblastoma cells. The study was able to confirm the presence of mRNA for the α1D subtype, as well as protein expression of the α1-adrenergic receptor. Furthermore, metabolomic data revealed changes to the metabolite profile of cells when exposed to adrenergic pharmacological intervention. Agonist treatment with phenylephrine hydrochloride (10 µM) resulted in altered levels of several metabolites including myo-inositol, glucose, fructose, alanine, leucine, phenylalanine, valine, and n-acetylglutamic acid. Many of the changes observed in N1E-115 cells by agonist treatment were modulated by additional antagonist treatment (prazosin hydrochloride, 100 µM). A number of these changes reflected what is known about the biochemistry of α1-adrenergic receptor activation. This preliminary study therefore demonstrates the potential of metabolomic profiling to confirm the presence of functional receptors on cultured cells.

Effects of environmental manipulations in genetically targeted animal models of affective disorders

Mental illness is the leading cause of disability worldwide. We are only just beginning to reveal and comprehend the complex interaction that exists between the genetic makeup of an organism and the potential modifying effect of the environment in which it lives, and how this translates into mediating susceptibility to neurological and psychiatric conditions. The capacity to address this issue experimentally has been facilitated by the availability of rodent models which allow the precise manipulation of genetic and environmental factors. In this review, we discuss the valuable nature of animal models in furthering our understanding of the relationship between genetic and environmental factors in affective illnesses, such as anxiety and depressive disorders. We first highlight the behavioral impairments exhibited by genetically targeted animal models of affective disorders, and then provide a discussion of the underlying neurobiology, focusing on animal models that involve exposure to stress. This is followed by a review of recent studies that report of beneficial effects of environmental manipulations such as environmental enrichment and enhanced physical activity and discuss the likely mechanisms that mediate those benefits.