Endoplasmic reticulum stress in bipolar disorder? - BiP and CHOP gene expression- and XBP1 splicing analysis in peripheral blood

The Effect of Electroconvulsive Therapy on Hippocampal Endoplasmic Reticulum Stress in a Rat Model of Depression

OBJECTIVE

The mechanisms underlying the effectiveness of electroconvulsive therapy (ECT), one of the most effective treatments for depression, are still unknown. While the increasing endoplasmic reticulum (ER) stress in depression can retrieve with pharmacological agents, ECT's effectiveness has not been examined yet. In this study, we tested how hippocampal ER stress parameters change after repeated ECT in rats in the chronic unpredictable mild stress (CUMS) model.

METHODS

Rats were divided into 4 groups. Two groups were included in the experimental group, where the CUMS model was applied for 21 days. Then, the experimental ECT model was applied to 2 groups, one experimental and 1 control group, for 21 days. Weight changes results were evaluated at the end of the 21st and 42nd day. In the final step, 3 prominent ER stress-related proteins (Grp-78, Xbp1, and Atf-4) were measured by western blot in the removed hippocampus.

RESULTS

We found that rats administered CUMS exhibited depression-like behavioral responses such as weight loss. In CUMS-treated rats (group 3), Grp-78 levels increased, ATF4 levels did not change, and Xbp1 levels decreased. While ECT increased Grp-78 levels in normal rats, it did not change Atf-4 levels and reduced Xbp1 levels (group 2). When ECT was applied to rats undergoing the CUMS model, Grp-78 and Xbp1 levels decreased, while Atf-4 levels did not change (group 4).

CONCLUSIONS

These findings show that increased ER stress may play a role in the pathophysiology of depression and that this increase can be reversed with ECT treatment. These findings need to be confirmed by clinical studies in humans.

Potential antidepressant-like effects of N-3 polyunsaturated fatty acids through inhibition of endoplasmic reticulum stress

RATIONALE

The growing evidence has demonstrated the importance of endoplasmic reticulum stress (ERS) in the pathophysiology of depression. ERS genes were considered to be potential novel therapeutic targets for depression.

OBJECTIVES

To clarify the mechanisms of the chronic unpredictable mild stress (CUMS)-induced ERS response and the potential contributing pathways in depression, and further investigate the potential link between N-3 polyunsaturated fatty acids (PUFAs) and stress-induced ERS disturbances.

METHODS

This study analyzed the expression of ERS-related genes including GRP78, ATF-4, ATF-6, XBP-1, and CHOP, and sigma-1R with real-time PCR in peripheral blood mononuclear cell (PBMC) RNA samples from participants. All of the rats except for those in the control groups were subjected to 5 consecutive weeks of CUMS to establish the depression model, and the antidepressant effects of N-3 PUFAs were observed by behavior tests. Moreover, the effect of diet and stress on the ERS pathways was also investigated using the western blot.

RESULTS

Blood CHOP, ATF-4, and XBP-1 levels were notably elevated in depressed patients relative to healthy individuals. Moreover, increased sigma-1R and decreased ATF-6 implied the protective role of sigma-1R through modulating ERS in patients with depression. Animal studies disclosed the novel findings that supplementary N-3 PUFAs in rats alleviated CUMS-induced disturbance of ERS through the ATF-4/XBP-1/CHOP pathway, implying its potential strategy for depression.

CONCLUSION

CUMS-induced depressive-like behaviors are related to the disturbance of ERS. Furthermore, supplementary N-3 PUFAs might be an effective way to alleviate ERS.

Neurological Effects of Combining Low Toxic Dose of Tramadol and Nicotine: An Animal Model Evidence of Endoplasmic Reticulum Stress

Tramadol abuse is a common problem in the Middle East in conjunction with smoking. The current study applied immunohistochemistry, western blot, real-time PCR, and ELISA to test the combination toxicity. Low toxic doses of tramadol induced animal brain cortex inflammation and hippocampus injury. Adding nicotine reverted hippocampus pathological changes without triggering marked brain injury. The expression of CHOP protein with real-time PCR showed mild endoplasmic reticulum stress (ER) in rat's brain. Histological, immunohistochemical, and western blotting analysis of CHOP (CCAAT-enhancer-binding protein homologous protein) and BIP (immunoglobulin heavy chain-binding protein) chaperones demonstrated endoplasmic reticulum stress in the brains of animals. Furthermore, the levels of apoptosis and autophagy markers demonstrated a mild reaction. The blood level of serotonin was high in all study groups, with a marked increase in the combined one. The high serotonin levels in the blood can be critical and associated with a high risk of serious withdrawal and pathological consequences. Serotonin receptor blockers such as olanzapine may increase systemic serotonin levels and need further investigation to utterly pinpoint their roles in managing mood disorders. In conclusion, the combination of tramadol and nicotine is less harmful than expected. However, serious withdrawal effects can occur as a result of high systemic serotonin effects.

Endo-Lysosomal and Autophagy Pathway and Ubiquitin-Proteasome System in Mood Disorders: A Review Article

Mood disorders are disabling conditions that cause significant functional impairment. Due to the clinical heterogeneity and complex nature of these disorders, diagnostic and treatment strategies face challenges. The etiology of mood disorders is multifactorial, involving genetic and environmental aspects that are associated with specific biological pathways including inflammation, oxidative stress, and neuroprotection. Alterations in these pathways may reduce the cell's ability to recover from stress conditions occurring during mood episodes. The endo-lysosomal and autophagy pathway (ELAP) and the ubiquitin-proteasome system (UPS) play critical roles in protein homeostasis, impacting neuroplasticity and neurodevelopment. Thus, emerging evidence has suggested a role for these pathways in mental disorders. In the case of neurodegenerative diseases (NDDs), a deeper understanding in the role of ELAP and UPS has been critical to discover new treatment targets. Since it is suggested that NDDs and mood disorders share clinical symptomatology and risk factors, it has been hypothesized that there might be common underlying molecular pathways. Here, we review the importance of the ELAP and UPS for the central nervous system and for mood disorders. Finally, we discuss potential translational strategies for the diagnosis and treatment of major depressive disorder and bipolar disorder associated with these pathways.

The regulatory role of endoplasmic reticulum chaperone proteins in neurodevelopment

The endoplasmic reticulum (ER) is the largest tubular reticular organelle spanning the cell. As the main site of protein synthesis, Ca2+ homeostasis maintenance and lipid metabolism, the ER plays a variety of essential roles in eukaryotic cells, with ER molecular chaperones participate in all these processes. In recent years, it has been reported that the abnormal expression of ER chaperones often leads to a variety of neurodevelopmental disorders (NDDs), including abnormal neuronal migration, neuronal morphogenesis, and synaptic function. Neuronal development is a complex and precisely regulated process. Currently, the mechanism by which neural development is regulated at the ER level remains under investigation. Therefore, in this work, we reviewed the recent advances in the roles of ER chaperones in neural development and developmental disorders caused by the deficiency of these molecular chaperones.

Gene expression analysis of MAOA and the clock gene ARNTL in individuals with bipolar disorder compared to healthy controls

INTRODUCTION

Circadian rhythms are associated with bipolar disorder (BD). This cross-sectional study aimed at investigating ARNTL and MAOA gene expression differences (1) between individuals with BD and controls, (2) between affective episodes, and (3) the relationship between ARNTL and MAOA expression.

METHODS

ARNTL and MAOA gene expression in peripheral mononuclear blood cells were analysed from fasting blood samples (BD n =  81, controls n = 54) with quantitative real-time PCR operating on TaqMan® assays (normalised to 18S RNA expression). ANCOVAs corrected for age, sex, body mass index, and medication was used to evaluate expression differences and correlation analyses for the relation between ARNTL and MAOA expression.

RESULTS

ARNTL gene expression differed between affective episodes (F(2,78) = 3.198, p = 0.047, Partial Eta2= 0.083), but not between BD and controls (n.s.). ARNTL and MAOA expression correlated positively in BD (r = 0.704, p < 0.001) and in controls (r = 0.932, p < 0.001). MAOA expression differed neither between BD and controls nor between affective episodes (n.s.).

DISCUSSION

Clock gene expression changes were observed in different affective states of BD. More precisely, ARNTL gene expression was significantly higher in euthymia than in depression. ARNTL and MAOA gene expression correlated significantly in BD and in controls, which emphasises the strong concatenation between circadian rhythms and neurotransmitter breakdown.

A Perspective on the Potential Involvement of Impaired Proteostasis in Neuropsychiatric Disorders

Recent genetic approaches have demonstrated that genetic factors contribute to the pathologic origins of neuropsychiatric disorders. Nevertheless, the exact pathophysiological mechanism for most cases remains unclear. Recent studies have demonstrated alterations in pathways of protein homeostasis (proteostasis) and identified several proteins that are misfolded and/or aggregated in the brains of patients with neuropsychiatric disorders, thus providing early evidence that disrupted proteostasis may be a contributing factor to their pathophysiology. Unlike neurodegenerative disorders in which massive neuronal and synaptic losses are observed, proteostasis impairments in neuropsychiatric disorders do not lead to robust neuronal death, but rather likely act via loss- and gain-of-function effects to disrupt neuronal and synaptic functions. Furthermore, abnormal activation of or overwhelmed endoplasmic reticulum and mitochondrial quality control pathways may exacerbate the pathophysiological changes initiated by impaired proteostasis, as these organelles are critical for proper neuronal functions and involved in the maintenance of proteostasis. This perspective article reviews recent findings implicating proteostasis impairments in the pathophysiology of neuropsychiatric disorders and explores how neuronal and synaptic functions may be impacted by disruptions in protein homeostasis. A greater understanding of the contributions by proteostasis impairment in neuropsychiatric disorders will help guide future studies to identify additional candidate proteins and new targets for therapeutic development.

The Role of the UPR Pathway in the Pathophysiology and Treatment of Bipolar Disorder

Bipolar disorder (BD) is a mood disorder that affects millions worldwide and is associated with severe mood swings between mania and depression. The mood stabilizers valproate (VPA) and lithium (Li) are among the main drugs that are used to treat BD patients. However, these drugs are not effective for all patients and cause serious side effects. Therefore, better drugs are needed to treat BD patients. The main barrier to developing new drugs is the lack of knowledge about the therapeutic mechanism of currently available drugs. Several hypotheses have been proposed for the mechanism of action of mood stabilizers. However, it is still not known how they act to alleviate both mania and depression. The pathology of BD is characterized by mitochondrial dysfunction, oxidative stress, and abnormalities in calcium signaling. A deficiency in the unfolded protein response (UPR) pathway may be a shared mechanism that leads to these cellular dysfunctions. This is supported by reported abnormalities in the UPR pathway in lymphoblasts from BD patients. Additionally, studies have demonstrated that mood stabilizers alter the expression of several UPR target genes in mouse and human neuronal cells. In this review, we outline a new perspective wherein mood stabilizers exert their therapeutic mechanism by activating the UPR. Furthermore, we discuss UPR abnormalities in BD patients and suggest future research directions to resolve discrepancies in the literature.

The Unfolded Protein Response and Autophagy as Drug Targets in Neuropsychiatric Disorders

Neurons are polarized in structure with a cytoplasmic compartment extending into dendrites and a long axon that terminates at the synapse. The high level of compartmentalization imposes specific challenges for protein quality control in neurons making them vulnerable to disturbances that may lead to neurological dysfunctions including neuropsychiatric diseases. Synapse and dendrites undergo structural modulations regulated by neuronal activity involve key proteins requiring strict control of their turnover rates and degradation pathways. Recent advances in the study of the unfolded protein response (UPR) and autophagy processes have brought novel insights into the specific roles of these processes in neuronal physiology and synaptic signaling. In this review, we highlight recent data and concepts about UPR and autophagy in neuropsychiatric disorders and synaptic plasticity including a brief outline of possible therapeutic approaches to influence UPR and autophagy signaling in these diseases.

Weight Gain During Treatment of Bipolar Disorder (BD)-Facts and Therapeutic Options

Bipolar disorder (BPD) is a mood disorder, which is characterized by alternating affective states, namely (hypo)mania, depression, and euthymia. Evidence is growing that BPD has indeed a biologic substrate characterized by chronic inflammation, oxidative stress, and disturbed energy metabolism. Apart from this, there is obviously a hereditary component of this disease with multi-genetic factors. Most probably a susceptibility threshold favors the outbreak of clinical disease after a cascade of stress events that remain to be elucidated in more detail. Evidence is also growing that weak points in brain energy metabolism contribute to outbreak and severity of BPD. Conventional psychopharmacologic therapy must be reassessed under the aspects of weight cycling and development of central obesity as a deterioration factor for a worse clinical course leading to early cardiovascular events in BPD subgroups.