The possible role of tissue-type plasminogen activator and the plasminogen system in the pathogenesis of major depression

Patent highlights December 2021-January 2022

A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.

A Comparison Study of Chaihu Shugan San and Fluoxetine on Antidepression and Regulating Blood Rheology Effects with Chronic Restrained Stress Rats

Chaihu Shugan San (CHSGS) is a traditional Chinese herbal formula that is often used in clinical practice to treat live Qi stagnation syndrome and depression. Fluoxetine is one of the commonly used drugs for the clinical treatment of depression. This study involved a comparison of CHSGS and fluoxetine on antidepression and regulating blood rheology effects with chronic restraint stress- (CRS-) induced depression rat models. Rats were induced depression models by CRS for 4 weeks. Upon successful induction of depression in the rats, the animal was administered CHSGS at 0.6 g/kg/d, 1.2 g/kg/d, or fluoxetine 1.8 mg/kg/d to corresponding groups by gavage for 2 weeks. The changes of CRS rats were determined by behavior observations and sucrose preference test and hypothalamic-pituitary-adrenal cortex (HPA) axis functional status. The changes in monoamine neurotransmitters and related indicators of blood status were detected by enzyme-linked immunosorbent assay (ELISA), blood rheometer, and other methods. The outcome shows that CHSGS is superior to fluoxetine in regulating the appearance and HPA axis function of model rats. In addition, CHSGS and fluoxetine have similar effects in improving blood rheology, and both can alleviate the hypercoagulable state of blood via the platelet 5-hydroxytryptamine receptor 2A (5-HT2A) pathway in rats of depression. It was also observed that CHSGS can improve the blood state of depressed rats by restoring liver coagulation-anticoagulation balance and endothelium-related functions.

Co-Expression Network Analysis Revealed That the ATP5G1 Gene Is Associated With Major Depressive Disorder

Major depressive disorder (MDD) is a leading cause of disability worldwide, although its etiology and mechanism remain unknown. The aim of our study was to identify hub genes associated with MDD and to illustrate the underlying mechanisms. A weighted gene co-expression network analysis (WGCNA) was performed to identify significant gene modules and hub genes associated with MDD in peripheral blood mononuclear cells (PBMCs) (n = 45). In the blue module (R ² = 0.95), five common hub genes in both co-expression network and protein-protein interaction (PPI) network were regarded as "real" hub genes. In another independent dataset, GSE52790, four genes were still significantly down-regulated in PBMCs from MDD patients compared with the controls. Furthermore, these four genes were validated by quantitative real-time polymerase chain reaction (qRT-PCR) in PBMCs from 33 MDD patients and 41 healthy controls. The qRT-PCR analysis showed that ATP synthase membrane subunit c locus 1 (ATP5G1) was significantly down-regulated in samples from MDD patients than in control samples (t = -2.89, p-value = 0.005). Moreover, this gene was significantly differentially expressed between patients and controls in the prefrontal cortex (z = -2.83, p-value = 0.005). Highly significant differentially methylated positions were identified in the Brodmann area 25 (BA25), with probes in the ATP5G1 gene being significantly associated with MDD: cg25495775 (t = 2.82, p-value = 0.008), cg25856120 (t = -2.23, p-value = 0.033), and cg23708347 (t = -2.24, p-value = 0.032). These findings indicate that the ATP5G1 gene is associated with the pathogenesis of MDD and that it could serve as a peripheral biomarker for MDD.

1,3,7-Trihydroxyxanthone, derived from Polygalae Radix, a herbal medicine, stimulates the expression of neurotrophic factors in rat astrocyte primary cultures via cAMP- and ERK-dependent pathways

1,3,7-Trihydroxyxanthone is a compound isolated from Polygalae Radix, a medicinal herb frequently applied for treatment of psychiatric disordres with symptoms of forgetfulness and depression in ancient China. In current research, this compound was applied onto rat astrocyte primary cultures in exploring the action mechanisms of 1,3,7-trihydroxyxanthone on regulating synthesis of neurotrophic factors. It was found that 1,3,7-trihydroxyxanthone could significantly stimulate the expression of NGF and BDNF in dose-dependent manners: the stimulation was both in mRNA and protein levels. Furthermore, 1,3,7-trihydroxyxanthone might fulfill this effect by regulating critical enzymes, such as plasminogen, tissue plasminogen activator, neuroserpin and tissue inhibitor of metalloproteinases in metabolic pathway of neurotrophic factors. Besides, inhibitors of cAMP- and ERK-dependent pathways, which implied the possible signaling pathway, could reverse this inducing effect. These results might support the potentiality of 1,3,7-trihydroxyxanthone in drug development in treating psychiatric disorders.

Role of tissue-type plasminogen activator and plasminogen activator inhibitor-1 in psychological stress and depression

Major depressive disorder is a common illness worldwide, but the pathogenesis of the disorder remains incompletely understood. The tissue-type plasminogen activator-plasminogen proteolytic cascade is highly expressed in the brain regions involved in mood regulation and neuroplasticity. Accumulating evidence from animal and human studies suggests that tissue-type plasminogen activator and its chief inhibitor, plasminogen activator inhibitor-1, are related to stress reaction and depression. Furthermore, the neurotrophic hypothesis of depression postulates that compromised neurotrophin brain-derived neurotrophic factor (BDNF) function is directly involved in the pathophysiology of depression. In the brain, the proteolytic cleavage of proBDNF, a BDNF precursor, to mature BDNF through plasmin represents one mechanism that can change the direction of BDNF action. We also discuss the implications of tissue-type plasminogen activator and plasminogen activator inhibitor-1 alterations as biomarkers for major depressive disorder. Using drugs that increase tissue-type plasminogen activator or decrease plasminogen activator inhibitor-1 levels may open new avenues to develop conceptually novel therapeutic strategies for depression treatment.

Kai-Xin-San series formulae alleviate depressive-like behaviors on chronic mild stressed mice via regulating neurotrophic factor system on hippocampus

Kai-xin-san (KXS) is a famous Chinese medicinal formula applied for treating stress-related psychiatric diseases with the symptoms such as depression, forgetfulness and dizziness. In clinic, the composition ratio of KXS is always varied and KXS series formulae are created. Here, we aim to compare the anti-depressive effect of different ratios of KXS and reveal its action mechanism on regulation of neurotrophic factor system. Firstly, daily intra-gastric administration of chemically standardized extracts of KXS series formulae for seven days significantly alleviated the depressive symptoms of chronic unpredictable mild stressed mice displayed by enhanced sucrose consumptions and decreased immobile time of forced swimming coupled with increased locomotor activities. KXS might fulfill this effect by up-regulating the expressions of NGF, BDNF and Trk receptors in hippocampus, which were confirmed by the treatment of corresponding blockers tPA-stop and K252a. The ratio with higher amounts of Ginseng Radix et Rhizoma and Polygalae Radix exerted most profound effect on anti-depression and regulation enzymes in metabolic pathway of neurotrophic factors. These findings suggested that KXS was beneficial for enhancing supplies, up-regulating receptors, and restoring the dysfunction of metabolic pathway of neurotrophic factors, which might account for its anti-depression effect.

Is plasminogen activator inhibitor-1 a physiological bottleneck bridging major depressive disorder and cardiovascular disease?

Major depressive disorder (MDD) is estimated to affect one in twenty people worldwide. MDD is highly comorbid with cardiovascular disease (CVD), itself one of the single largest causes of mortality worldwide. A number of pathological changes observed in MDD are believed to contribute to the development of cardiovascular disease, although no single mechanism has been identified. There are also no biological markers capable of predicting the future risk of developing heart disease in depressed individuals. Plasminogen activator inhibitor-1 (PAI-1) is a prothrombotic plasma protein secreted by endothelial tissue and has long been implicated in CVD. An expanding body of literature has recently implicated it in the pathogenesis of major depressive disorder as well. In this study, we review candidate pathways implicating MDD in CVD and consider how PAI-1 might act as a mediator by which MDD induces CVD development: chiefly through sleep disruption, adiposity, brain-derived neurotrophic factor (BDNF) metabolism, systemic inflammation and hypothalamic-pituitary-adrenal (HPA)-axis dysregulation. As both MDD and CVD are more prevalent in women than in men, and incidence of either condition is dramatically increased during reproductive milestones, we also explore hormonal and sex-specific associations between MDD, PAI-1 and CVD. Of special interest is the role PAI-1 plays in perinatal depression and in cardiovascular complications of pregnancy. Finally, we propose a theoretical model whereby PAI-1 might serve as a useful biomarker for CVD risk in those with depression, and as a potential target for future treatments.

The fibrinolytic system: A new target for treatment of depression with psychedelics

Current understanding of the neurobiology of depression has grown over the past few years beyond the traditional monoamine theory of depression to include chronic stress, inflammation and disrupted synaptic plasticity. Tissue plasminogen activator (tPA) is a key factor that not only promotes fibrinolysis via the activation of plasminogen, but also contributes to regulation of synaptic plasticity and neurogenesis through plasmin-mediated activation of a probrain derived neurotrophic factor (BDNF) to mature BDNF. ProBDNF activation could potentially be supressed by competition with fibrin for plasmin and tPA. High affinity binding of plasmin and tPA to fibrin could result in a decrease of proBDNF activation during brain inflammation leading to fibrosis further perpetuating depressed mood. There is a paucity of data explaining the possible role of the fibrinolytic system or aberrant extravascular fibrin deposition in depression. We propose that within the brain, an imbalance between tPA and urokinase plasminogen activator (uPA) and plasminogen activator inhibitor-1 (PAI-1) and neuroserpin favors the inhibitors, resulting in changes in neurogenesis, synaptic plasticity, and neuroinflammation that result in depressive behavior. Our hypothesis is that peripheral inflammation mediates neuroinflammation, and that cytokines such as tumor necrosis factor alpha (TNF-α) can inhibit the fibrinolytic system by up- regulating PAI-1 and potentially neuroserpin. We propose that the decrement of the activity of tPA and uPA occurs with downregulation of uPA in part involving the binding and clearance from the surface of neural cells of uPA/PAI-1 complexes by the urokinase receptor uPAR. We infer that current antidepressants and ketamine mitigate depressive symptoms by restoring the balance of the fibrinolytic system with increased activity of tPA and uPA with down-regulated intracerebral expression of their inhibitors. We lastly hypothesize that psychedelic 5-ht2a receptor agonists, such as psilocybin, can improve mood through anti- inflammatory and pro-fibrinolytic effects that include blockade of TNF-α activity leading to decreased PAI-1 activity and increased clearance. The process involves disinhibition of tPA and uPA with subsequent increased cleavage of proBDNF which promotes neurogenesis, decreased neuroinflammation, decreased fibrin deposition, normalized glial-neuronal cross-talk, and optimally functioning neuro-circuits involved in mood. We propose that psilocybin can alleviate deleterious changes in the brain caused by chronic stress leading to restoration of homeostatic brain fibrinolytic capacity leading to euthymia.

Effects of Kaixinjieyu, a Chinese herbal medicine preparation, on neurovascular unit dysfunction in rats with vascular depression

BACKGROUND

Kaixinjieyu (KJ), derived from Kaixin and Sini powder, is an effective Chinese herbal medicine preparation used in the treatment of vascular depression (VD). We hypothesize that broad antidepressant effect of KJ results from the improved neurovascular unit (NVU) function via neurogenesis, permeability of blood-brain barrier (BBB) and balance of the fibrinolytic system.

METHODS

A VD model of rat was established by chronic unpredictable mild stress and separation after ligation of the bilateral common carotid arteries. The rats were treated with KJ and fluoxetine hydrochloride (FLU) for 21 days, respectively. The behavior and cerebral perfusion were investigated and then NVU functions including neurogenesis, permeability of BBB and balance of the fibrinolytic system were studied using a number of biomarkers and TUNEL assay.

RESULTS

KJ significantly increased sucrose preference, moving distance, number of rearing and cortical blood flow. NVU functions measured by brain-derived neurotrophic factor (BDNF), tropomyosin receptor kinase B (TrkB) and tissue plasminogen activator (t-PA) proteins and mRNA, zona occludens protein-1 (ZO-1), occludin and claudin-5 proteins increased significantly, whereas, plasminogen activator inhibitor-1 (PAI-1), matrix metalloproteinase-2 (MMP-2) proteins, mRNA and apoptotic rates of neurons decreased significantly with treatment of KJ. FLU has a function similar to KJ in behavior, regulation of BDNF, TrkB, MMP-2, occludin and apoptotic rates of cells.

CONCLUSIONS

KJ has function of reducing depression-like behavior and improving cerebral hypoperfusion, which might be mediated by the up-regulation of neurogenesis and tight junction of BBB, and balance of the fibrinolytic system. The results imply that KJ is better than FLU in improving cerebral hypoperfusion and the fibrinolytic system.

Plasminogen activator inhibitor-1 as an early potential diagnostic marker for Alzheimer's disease

Alzheimer's disease (AD) is the most common cause of dementia in individuals over 65 years old. However, to date, no useful early diagnostic markers for AD have been discovered. We examined the utility of plasminogen activator inhibitor-1 (PAI-1) as a potential biomarker for AD in subjects with mild cognitive impairment (MCI) or AD, as well as in nondemented healthy controls. Plasma PAI-1 levels were measured by enzyme-linked immunosorbent assays (ELISAs) in samples collected from 76 patients with MCI, 74 patients with AD, and 76 healthy controls. Our results show that plasma PAI-1 levels gradually increased as dementia progressed. The mean levels of plasma PAI-1 in patients with MCI and AD patients were significantly higher than those of in healthy controls. Consistently, neuropsychological examination (e.g., MMSE, CDR) also demonstrated significant correlations between the plasma PAI-1 levels and cognitive function. In conclusion, the level of plasma PAI-1 is a potential biomarker for the early detection and diagnosis of AD.

2D-DIGE proteome analysis on the platelet proteins of patients with major depression

INTRODUCTION

Platelet activation is related to the psychopathology of major depression. We attempted to search and identify protein biomarkers from the platelets of patients with major depression. High resolution two-dimensional Differential Gel Electrophoresis (2D-DIGE), the matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), Western blot, and bioinformatic tools were applied to examine the platelet proteins of 10 patients with major depression and 10 healthy controls.

RESULTS

The levels of 8 proteins were significantly different between the patients with major depression in the acute phase and healthy controls. The levels of protein disulfide-isomerase A3 (PDIA3) and F-actin-capping protein subunit beta (CAPZB) were higher in patients with major depression than in healthy controls. The levels of fibrinogen beta chain (FIBB), fibrinogen gamma chain (FIBG), retinoic acid receptor beta (RARB), glutathione peroxidase 1 (GPX1), SH3 domain-containing protein 19 (SH319), and T-complex protein 1 subunit beta (TCPB) were lower in patients with major depression than in healthy controls.

CONCLUSIONS

Platelet provided valuable information about the pathways and processes of inflammation/immunity, oxidative stress, and neurogenesis, related to major depression.

Self-reported sleep disturbance is associated with elevated levels of PAI-1 in individuals with a recorded history of depressive symptoms

BACKGROUND

The majority of depressed individuals report insomnia. Self-reported symptoms of insomnia, in particular, more strongly predict adverse health effects than the actual measured sleep time. The physiological alterations in individuals with insomnia are complex, as both autonomic and endocrine dysfunctions are present. Plasminogen activator inhibitor (PAI)-1 is a stress-related acute-phase reactant that has also been suggested to regulate the circadian rhythm and sleep patterns. It has been suggested to contribute to both depressive symptoms and sleep disorders, although data on the relationships between these parameters are scarce.

OBJECTIVE

This study examined the role of self-reported sleep disturbance and its association with PAI-1 among individuals with a history of depressive symptoms.

METHODS

Differences in the serum levels of PAI-1 between two groups (group 1: moderate to very severe sleep disturbance, n=37; group 2: mild or no sleep disturbance, n = 90) were examined in a population-based sample of individuals with a recorded history of depressive symptoms.

RESULTS

Multivariate analysis controlling for potential confounding factors (age, sex, body mass index, depression severity) showed that each 1-unit increase in PAI-1 (μg/mL) increased the likelihood for belonging to the group with moderate to very severe sleep disturbance by 23% (OR = 1.23, C.I. 95% = 1.04-1.45, p = 0.016). This statistical significance remained after additional adjustments for regular smoking and the use of sleep or lipid-lowering medication.

CONCLUSION

Our observations may further clarify the physiological alterations related to sleep disturbance in depressive individuals. In the present study, self-reported sleep disturbance in individuals with a recorded history of depressive symptoms was associated with an elevation of PAI-1. This finding may illustrate the association of subjective sleep disturbance with sympathetic activation. Our study highlights the importance of effects of perceived sleep disturbance on individual homeostasis, and may provide potential directions for research on treatment options.

Is anxious-depression an inflammatory state?

For several years, the literature has examined the association of depression and anxiety with inflammatory states such as atherosclerosis and cardiovascular disease, yet this association remains inconclusive. Several possible immune and endocrinological pathways have been postulated that associate depression and anxiety with inflammation and immune dysregulation. Anxiety and depression have usually been envisioned as two separate psychiatric conditions yet they share similar symptoms and are frequently encountered together among individuals. Individuals suffering from anxious-depression are more refractory to treatment and have been reported to have greater disability compared to individuals with anxiety or depression alone. With the current changes in the diagnostic manual for psychiatric disorders placing more emphasis on a dimensional approach for the diagnosis of psychiatric illnesses, the hypothesis presented is that anxious-depression should be considered as a chronic inflammatory phenomenon since it shares common physiopathological pathways and pharmacological treatments with inflammatory states. This hypothesis might help to investigate how different levels of inflammatory biomarkers could be correlated with symptoms of anxious-depression.

Principle component analysis combined with matrix-assisted laser desorption ionization mass spectrometry for rapid diagnosing the sera of patients with major depression

BACKGROUND

Previously, we demonstrated that 6M HCl hydrolysis followed by matrix-assisted laser desorption/ionization (MALDI-TOF) mass spectrometry is a useful technique to detect potential protein biomarkers in the sera collected from major depression (MD) patients and from healthy controls.

METHODS

In this study, the effects of various organic acids in hydrolyzing proteins in serum were first examined. The organic matrixes commonly used in MALDI analysis were also examined for characterizing the hydrolyzed peptides. Finally, principle component analysis (PCA) was used to analyze the MALDI mass spectra of acid-hydrolyzed serum samples.

RESULTS

It was found that 20% TFA and sinapinic acid were the optimal reagents for hydrolysis and MALDI matrix. Samples collected from MD patients and healthy controls were readily classified through PCA analysis. A receiver operating characteristic (ROC) curve based on the ratio of the intensities of the two fragment ions (m/z 8606 and 9287) indicated by PCA plot was also constructed. The area under the curve was 0.845; the sensitivity and specificity were both 80%.

CONCLUSIONS

An analytical platform employing trifluoroacetic acid to hydrolyze serum proteins followed by MALDI-TOF/MS and PCA analysis was developed to rapidly differentiate the sera between MD patients and healthy controls.

Hippocampus-specific deletion of tissue plasminogen activator "tPA" in adult mice impairs depression- and anxiety-like behaviors

Anxiety and depression are multifactorial disorders that have become prominent health problems all over the world. Neurotrophic factors have emerged underlying pathogenesis of these diseases. Although a number of studies indicate that the hippocampus-brain-derived neurotrophic factor (BDNF) may be involved in these psychiatric illnesses, little is known about the molecular mediators of these disorders. In this study we further investigate the role of tissue plasminogen activator (tPA), a serine protease involved in pro-BDNF cleavage to BDNF, in depression and anxiety-like behaviors in adult mice. To address this issue, we investigated the effect of hippocampus tPA manipulation, using viral vectors, on anxiety- and depression-like behaviors, including the marble burying test (MBT), elevated plus maze (EPM), tail suspension test (TST), novelty suppressed feeding (NSF) and forced swim test (FST). Our results showed that tPA knock-down - using lentiviral vectors expressing specific short hairpin RNAs (LV-shRNA) - increased the number of buried marbles together with the digging time in the MBT and decreased the time spent in open the arms of an EPM. In addition, tPA-knock down in the hippocampus increased immobility in the FST and TST, and increased time to feed in the NSF test. These effects were reversed when tPA-over-expressing vectors (LV-tPA) were injected in the hippocampus. We also found that BDNF protein levels were elevated in the hippocampus of mice receiving tPA-expressing vectors. Together, our results imply that tPA manipulation may provide an effective therapeutic intervention for depression and anxiety disorders.

Promoter polymorphisms of SERPINE1 are associated with the antidepressant response to depression in Alzheimer's disease

Depression is one of the most frequent neuropsychiatric symptoms in Alzheimer's disease (AD). As the main regulator of the tissue plasminogen activator/brain-derived neurotrophic factor axis, plasminogen activator inhibitor-1 (PAI-1) is involved in the pathogenesis of both AD and depression. This suggests a potential role of the PAI-1 gene SERPINE1 in the development of AD-related depression and its response to antidepressant treatment. The purpose of this study was to explore the association between the SERPINE1 promoter polymorphisms (rs1799889 and rs2227631) and the risk of depression in AD and to determine the relationship between these 2 polymorphisms and the response to paroxetine treatment in AD patients with depressive symptoms. A total of 423 AD patients, all of which were inpatients, including 161 patients with obvious depressive symptoms, were recruited into this study, and the MassARRAY system was used for genotyping. We failed to detect any significant associations of these 2 polymorphisms with AD-related depression in the Chinese population (p>0.05). However, for the depressive symptoms in AD, the frequency of the 5G allele of rs1799889 was significantly higher (p=0.009 after Bonferroni correction) in responders than in non-responders to an 8-week paroxetine treatment. Our preliminary results suggest that the SERPINE1 promoter polymorphisms may be associated with antidepressant treatment, but not with the increased susceptibility to the depressive symptoms in AD.

Prenatal stress differentially alters brain-derived neurotrophic factor expression and signaling across rat strains

BACKGROUND

Psychiatric illness and anxiety disorders have strong neurodevelopmental components. Environmental insults such as prenatal exposure to stress and genetic differences in stress responses may affect brain development.

METHODS

A rat model of random variable prenatal stress was used to study the expression and processing of hippocampal brain-derived neurotrophic factor (BDNF) in the offspring of the stressed rat dams. To account for unknown genetic influences that may play a role in the outcome of this prenatal stress paradigm, three different rat strains with known differences in stress responsivity were studied: Fischer, Sprague-Dawley, and Lewis rats (n=132).

RESULTS

Multiple disparities in mRNA expression levels of BDNF, and transcripts related to its processing and signaling were found in the three strains. Of the numerous splice variants transcribed from the BDNF gene, the transcript containing BDNF exon VI was most aberrant in the prenatally stressed animals. Protein levels of both uncleaved proBDNF and mature BDNF were also altered, as was intra-cellular signaling by phosphorylation of the neurotrophic tyrosine kinase receptor type 2 (NTRK2, TrkB) and mitogen-activated protein kinase (Erk 1/2). Changes were not only dependent on prenatal stress, but were also strain dependent, demonstrating the importance of genetic background.

CONCLUSION

BDNF signaling provides both positive neurotrophic support for neurons and negative apoptotic effects, both of which may contribute to behavioral or neurochemical outcomes after prenatal exposure to stress. Differential processing of BDNF after prenatal stress in the three rat strains has implications for human subjects where genetic differences may protect or exacerbate the effects of an environmental stressor during fetal development.

Effects of BDNF polymorphisms on antidepressant action

Evidence suggests that the down-regulation of the signaling pathway involving brain-derived neurotrophic factor (BDNF), a molecular element known to regulate neuronal plasticity and survival, plays an important role in the pathogenesis of major depression. The restoration of BDNF activity induced by antidepressant treatment has been implicated in the antidepressant therapeutic mechanism. Because there is variability among patients with major depressive disorder in terms of response to antidepressant treatment and since genetic factors may contribute to this inter-individual variability in antidepressant response, pharmacogenetic studies have tested the associations between genetic polymorphisms in candidate genes related to antidepressant therapeutic action. In human BDNF gene, there is a common functional polymorphism (Val66Met) in the pro-region of BDNF, which affects the intracellular trafficking of proBDNF. Because of the potentially important role of BDNF in the antidepressant mechanism, many pharmacogenetic studies have tested the association between this polymorphism and the antidepressant therapeutic response, but they have produced inconsistent results. A recent meta-analysis of eight studies, which included data from 1,115 subjects, suggested that the Val/Met carriers have increased antidepressant response in comparison to Val/Val homozygotes, particularly in the Asian population. The positive molecular heterosis effect (subjects heterozygous for a specific genetic polymorphism show a significantly greater effect) is compatible with animal studies showing that, although BDNF exerts an antidepressant effect, too much BDNF may have a detrimental effect on mood. Several recommendations are proposed for future antidepressant pharmacogenetic studies of BDNF, including the consideration of multiple polymorphisms and a haplotype approach, gene-gene interaction, a single antidepressant regimen, controlling for age and gender interactions, and pharmacogenetic effects on specific depressive symptom-clusters.

Molecular actions and therapeutic potential of lithium in preclinical and clinical studies of CNS disorders

Lithium has been used clinically to treat bipolar disorder for over half a century, and remains a fundamental pharmacological therapy for patients with this illness. Although lithium's therapeutic mechanisms are not fully understood, substantial in vitro and in vivo evidence suggests that it has neuroprotective/neurotrophic properties against various insults, and considerable clinical potential for the treatment of several neurodegenerative conditions. Evidence from pharmacological and gene manipulation studies support the notion that glycogen synthase kinase-3 inhibition and induction of brain-derived neurotrophic factor-mediated signaling are lithium's main mechanisms of action, leading to enhanced cell survival pathways and alteration of a wide variety of downstream effectors. By inhibiting N-methyl-D-aspartate receptor-mediated calcium influx, lithium also contributes to calcium homeostasis and suppresses calcium-dependent activation of pro-apoptotic signaling pathways. In addition, lithium decreases inositol 1,4,5-trisphosphate by inhibiting phosphoinositol phosphatases, a process recently identified as a novel mechanism for inducing autophagy. Through these mechanisms, therapeutic doses of lithium have been demonstrated to defend neuronal cells against diverse forms of death insults and to improve behavioral as well as cognitive deficits in various animal models of neurodegenerative diseases, including stroke, amyotrophic lateral sclerosis, fragile X syndrome, as well as Huntington's, Alzheimer's, and Parkinson's diseases, among others. Several clinical trials are also underway to assess the therapeutic effects of lithium for treating these disorders. This article reviews the most recent findings regarding the potential targets involved in lithium's neuroprotective effects, and the implication of these findings for the treatment of a variety of diseases.

Plasma BDNF and tPA are associated with late-onset geriatric depression

AIMS

Studies in the recent decade have shown that brain-derived neurotrophic factor (BDNF) may play an important role in the pathogenesis of major depressive disorder (MDD). Tissue-type plasminogen activator (tPA) has been implicated in the control of the direction of BDNF action. The aim of the study was therefore to investigate the changes of BDNF/tPA levels and their clinical meanings in geriatric depression.

METHODS

Plasma BDNF and tPA levels were measured in late-onset geriatric depression (LGD) before treatment (n = 24) and after 6 weeks of antidepressant treatment (n = 24) compared with control subjects (n = 30) using enzyme-linked immunosorbent assay. The severity of depression was assessed with the Hamilton Depression Rating Scale.

RESULTS

Baseline plasma BDNF and tPA levels were significantly lower in LGD patients compared to controls (P = 0.037 and P = 0.000, respectively). There was a heightening tendency of plasma BDNF level after treatment.

CONCLUSIONS

Plasma BDNF and tPA levels are associated with LGD. The complex mechanism of BDNF and tPA in LGD should be further explored in future studies.

Increased Serum PAI-1 Levels in Subjects with Metabolic Syndrome and Long-Term Adverse Mental Symptoms: A Population-Based Study

Depression is an independent risk factor for cardiovascular diseases and is associated with metabolic syndrome (MetS). Levels of plasminogen activator inhibitor-1 (PAI-1), an inhibitor of tissue-type and urokinase-type plasminogen activators, are associated with MetS. To clarify the role of PAI-1 in subjects with long-term adverse mental symptomatology (LMS; including depression) and MetS, we measured circulating PAI-1 levels in controls (n = 111), in subjects with MetS and free of mental symptoms (n = 42), and in subjects with both MetS and long-term mental symptoms (n = 70). PAI-1 increased linearly across the three groups in men. In logistic regression analysis, men with PAI-1 levels above the median had a 3.4-fold increased likelihood of suffering from the comorbidity of long-term adverse mental symptoms and MetS, while no such associations were detected in women. In conclusion, our results suggest that in men high PAI-1 levels are independently associated with long-term mental symptomatology.

Acid hydrolysis followed by matrix-assisted laser desorption/ionization mass spectrometry for the rapid diagnosis of serum protein biomarkers in patients with major depression

We have developed a technique combining acid hydrolysis with matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) for the rapid study of the changes in the levels of positive and negative acute phase protein biomarkers in the sera of patients suffering from major depression. The serum proteins were first precipitated using an organic solvent; after separation, they were subjected to hydrochloric acid hydrolysis (6 M HCl) for 10 min. The resulting peptides were characterized using MALDI-TOF MS. Short-term treatment of the serum proteins with HCl efficiently removed interference from the abundant protein - albumin - and produced abundant peptide ion signals in the range of m/z 4000-10 000. This approach allowed us to rapidly detect the peptide ions originating from transferrin (a common negative acute phase protein) and fibrinogen (a common positive acute phase protein). The average ratios and (standard deviations) of the ion signals derived from transferrin/fibrinogen were 3.58 (+/-1.93) for the healthy control subjects and 1.02 (+/-0.52) for the patients suffering from major depression. The differences in transferrin/fibrinogen ratios between healthy controls and patients suggest that major depression will induce internal inflammation and cause either an increase in the level of fibrinogen or a decrease in the level of transferrin.

Lithium inhibits Smad3/4 transactivation via increased CREB activity induced by enhanced PKA and AKT signaling

Smad proteins are intracellular transducers for transforming growth factor-beta (TGF-beta) signaling and play a critical role in differentiation, tissue repair and apoptosis of the central nervous system. Both TGF-beta and its regulated gene, plasminogen activator inhibitor type-1 (PAI-1), have been implicated in the etiology and progression of neurodegenerative diseases and mood disorders. We previously reported that GSK-3beta protein depletion suppresses Smad3/4-dependent gene transcription and causes a reduction in PAI-1 expression. Here, we provide evidence that lithium, the drug for the treatment and prophylaxis of bipolar disorder, inhibits Smad-dependent signaling by regulating cAMP-protein kinase A (PKA), AKT-glycogen synthase kinase-3beta (GSK-3beta), and CRE-dependent signaling pathways in neuron-enriched cerebral cortical cultures of rats. We demonstrate that lithium-induced activation of these pathways inhibits Smad3/4-dependent gene transcription through an increase in pCREB(Ser133) protein levels, an enhanced interaction between pCREB(Ser133) and p300/CBP, which causes Smad3/4-p300/CBP complex disruption and transcriptional suppression of Smad3/4-dependent genes. Therapeutic implications of our findings are discussed.

The P11, tPA/plasminogen system and brain-derived neurotrophic factor: Implications for the pathogenesis of major depression and the therapeutic mechanism of antidepressants

Major depressive disorder (MDD) is a common disabling psychiatric illness with an unknown etiology. Evidence from animal and human studies suggests that a disturbance in serotonergic (5-HT) activity and/or brain-derived neurotrophic factor (BDNF) signaling may be implicated in the pathogenesis of MDD. Recently, a protein, p11, has been found to increase the number of 5-HT(1B) receptors on the surface of cells and enhance 5-HT(1B) receptor function. Furthermore, mice over-expressing p11 acted as if they were undergoing treatment with antidepressants and p11 knockout mice exhibit a depression-like phenotype and reduced behavioural reactions to an antidepressant. As tissue-type plasminogen activator (tPA)/plasminogen proteolytic cascade is implicated in the cleavage of proBDNF to BDNF, and p11, a component of the Annexin II, which can greatly enhance the activation of plasmin by tPA, it is proposed that p11 may act through the tPA/plasminogen/BDNF pathway to achieve its antidepressant effect. Attempts to confirm this hypothesis may lead to new directions in the study of the pathogenesis of MDD and the development of a novel intervention for this disorder. In addition, BDNF is also implicated in several psychiatric diseases such as schizophrenia, bipolar disorder, attention-deficit hyperactivity disorder and Alzheimer's disease; whether p11 and other components related to the tPA/plasminogen pathway may be related to the pathogenesis of these diseases needs further exploration.

Statins may enhance the proteolytic cleavage of proBDNF: implications for the treatment of depression

The family of hydroxymethylglutaryl coenzyme A reductase inhibitors, collectively known as statins, are used clinically to reduce plasma cholesterol levels. Recent reports indicate that statin therapy is associated with a reduced risk of depression, although the mechanism underlying this antidepressant effect is unknown. Evidence suggests that increasing central BDNF activity plays an important role in the treatment of major depression. In the nervous system, the proteolytic cleavage of pro-BDNF, a BDNF precursor, to BDNF through the tissue-type plasminogen activator (tPA)-plasmin pathway represents one mechanism that can regulate the action of BDNF. In vitro studies have demonstrated that statins can induce tPA and inhibit plasminogen activator inhibitor-1, the major inhibitor of tPA. It is therefore possible that statins could act through the tPA-plasminogen pathway to increase BDNF and achieve an antidepressant effect. It is suggested that statins could be of therapeutic potential for patients with major depression: especially those that have an abnormality in the tPA-plasminogen pathway or comorbidities relating to cardiovascular disease. Furthermore, BDNF dysfunction has also been implicated in several other neuropsychiatric diseases, such as Alzheimer's disease, attention-deficit hyperactivity disorder and Rett syndrome. The potential use of statins in these diseases may warrant further exploration.