Lithium inhibits the development of physical dependence to clonidine in mice

ErbB4 deletion in noradrenergic neurons in the locus coeruleus induces mania-like behavior via elevated catecholamines

Dysfunction of the noradrenergic (NE) neurons is implicated in the pathogenesis of bipolar disorder (BPD). ErbB4 is highly expressed in NE neurons, and its genetic variation has been linked to BPD; however, how ErbB4 regulates NE neuronal function and contributes to BPD pathogenesis is unclear. Here we find that conditional deletion of ErbB4 in locus coeruleus (LC) NE neurons increases neuronal spontaneous firing through NMDA receptor hyperfunction, and elevates catecholamines in the cerebrospinal fluid (CSF). Furthermore, Erbb4-deficient mice present mania-like behaviors, including hyperactivity, reduced anxiety and depression, and increased sucrose preference. These behaviors are completely rescued by the anti-manic drug lithium or antagonists of catecholaminergic receptors. Our study demonstrates the critical role of ErbB4 signaling in regulating LC-NE neuronal function, reinforcing the view that dysfunction of the NE system may contribute to the pathogenesis of mania-associated disorder.

Bipolar disorder is a mental illness that affects roughly 1 in 100 people worldwide. It features periods of depression interspersed with episodes of mania – a state of delusion, heightened excitation and increased activity. Evidence suggests that changes in a brain region called the locus coeruleus contribute to bipolar disorder. Cells within this area produce a chemical called norepinephrine, whose levels increase during mania and decrease during depression. But it is unclear exactly how norepinephrine-producing cells, also known as noradrenergic cells, contribute to bipolar disorder.

The answer may lie in a protein called ErbB4, which is found within the outer membrane of many noradrenergic neurons. ErbB4 is active in both the developing and adult brain, and certain people with bipolar disorder have mutations in the gene that codes for the protein. Might changes in ErbB4 disrupt the activity of noradrenergic neurons? And could these changes increase the risk of bipolar disorder?

To find out, Cao, Zhang et al. deleted the gene for ErbB4 from noradrenergic neurons in the locus coeruleus of mice. The mutant mice showed mania-like behaviors: compared to normal animals, they were hyperactive, less anxious, and consumed more of a sugary solution. Treating the mice with lithium, a medication used in bipolar disorder, reversed these changes and made the rodents behave more like non-mutant animals. Further experiments revealed that noradrenergic neurons in the mutant mice showed increased spontaneous activity. These animals also had more of the chemicals noradrenaline and dopamine in the fluid circulating around their brains and spinal cords.

The results thus suggest that losing ErbB4 enhances the spontaneous firing of noradrenergic neurons in the locus coeruleus. This increases release of noradrenaline and dopamine, which in turn leads to mania-like behaviors. Future research should examine whether drugs that target ErbB4 could treat mania and improve the lives of people with bipolar disorder and related conditions.

Lithium-responsive genes and gene networks in bipolar disorder patient-derived lymphoblastoid cell lines

Lithium (Li) is the mainstay mood stabilizer for the treatment of bipolar disorder (BD), although its mode of action is not yet fully understood nor is it effective in every patient. We sought to elucidate the mechanism of action of Li and to identify surrogate outcome markers that can be used to better understand its therapeutic effects in BD patients classified as good (responders) and poor responders (nonresponders) to Li treatment. To accomplish these goals, RNA-sequencing gene expression profiles of lymphoblastoid cell lines (LCLs) were compared between BD Li responders and nonresponders with healthy controls before and after treatment. Several Li-responsive gene coexpression networks were discovered indicating widespread effects of Li on diverse cellular signaling systems including apoptosis and defense response pathways, protein processing and response to endoplasmic reticulum stress. Individual gene markers were also identified, differing in response to Li between BD responders and nonresponders, involved in processes of cell cycle and nucleotide excision repair that may explain part of the heterogeneity in clinical response to treatment. Results further indicated a Li gene expression signature similar to that observed with clonidine treatment, an α2-adrenoceptor agonist. These findings provide a detailed mechanism of Li in LCLs and highlight putative surrogate outcome markers that may permit for advanced treatment decisions to be made and for facilitating recovery in BD patients.

Deficiency of diacylglycerol kinase η induces lithium-sensitive mania-like behavior

The η isozyme of diacylglycerol kinase (DGK) is highly expressed in the hippocampus and Purkinje cells in the central nervous system. Recently, several genome-wide association studies have implicated DGKη in the etiology of bipolar disorder (BPD). However, it is still unknown whether DGKη is indeed related to BPD. In this study, we generated DGKη-knockout (KO) mice and performed behavioral tests such as the open field test, the elevated plus maze test and tail suspension test using the KO mice to investigate the effects of DGKη deficits on psychomotor behavior. Intriguingly, DGKη-KO mice displayed an overall behavioral profile that is similar to human mania, including hyperactivity, less anxiety and less depression-like behavior. In addition, these phenotypes were significantly attenuated by the administration of a BPD (mania) remedy, namely, lithium. Moreover, DGKη-KO mice showed impairment in glycogen synthase kinase (GSK) 3β signaling, which is closely related to BPD. These findings clearly support the linkage between BPD and DGKη that is implicated by genome-wide association studies. Moreover, this study provides DGKη-KO mice as a previously unrecognized model that reflects several features of human BPD with manic episodes and revealed an important role for DGKη in regulating behavior and mood through, at least in part, GSK3β signaling. Several genome-wide association studies have implicated diacylglycerol kinase (DGK) η gene in the etiology of bipolar disorder (BPD). In this study, we revealed that DGKη-knockout (KO) mice displayed an overall behavioral profile that is similar to mania of BPD and is lithium (BPD (mania) remedy)-sensitive. DGKη may regulate behavior and mood through, at least in part, glycogen synthase kinase (GSK) 3β signaling.

Modeling bipolar disorder in mice by increasing acetylcholine or dopamine: chronic lithium treats most, but not all features

RATIONALE

Bipolar disorder (BD) is a disabling and life-threatening disease characterized by states of depression and mania. New and efficacious treatments have not been forthcoming partly due to a lack of well-validated models representing both facets of BD.

OBJECTIVES

We hypothesized that cholinergic- and dopaminergic-pharmacological manipulations would model depression and mania respectively, each attenuated by lithium treatment.

METHODS

C57BL/6 J mice received the acetylcholinesterase inhibitor physostigmine or saline before testing for "behavioral despair" (immobility) in the tail suspension test (TST) and forced swim test (FST). Physostigmine effects on exploration and sensorimotor gating were assessed using the cross-species behavioral pattern monitor (BPM) and prepulse inhibition (PPI) paradigms. Other C57BL/6 J mice received chronic lithium drinking water (300, 600, or 1200 mg/l) before assessing their effects alone in the BPM or with physostigmine on FST performance. Another group was tested with acute GBR12909 (dopamine transporter inhibitor) and chronic lithium (1000 mg/l) in the BPM.

RESULTS

Physostigmine (0.03 mg/kg) increased immobility in the TST and FST without affecting activity, exploration, or PPI. Lithium (600 mg/l) resulted in low therapeutic serum concentrations and normalized the physostigmine-increased immobility in the FST. GBR12909 induced mania-like behavior in the BPM of which hyper-exploration was attenuated, though not reversed, after chronic lithium (1000 mg/ml).

CONCLUSIONS

Increased cholinergic levels induced depression-like behavior and hyperdopaminergia induced mania-like behavior in mice, while chronic lithium treated some, but not all, facets of these effects. These data support a cholinergic-monoaminergic mechanism for modeling BD aspects and provide a way to assess novel therapeutics.

Protective effects of lithium chloride on seizure susceptibility: Involvement of α2-adrenoceptor

For more than 60years, lithium has been the mainstay in the treatment of mental disorders as a mood stabilizer. In addition to the antimanic and antidepressant responses, lithium also shows some anticonvulsant properties. In spite of the ascertained neuroprotective effects of this alkali metal, the underlying mechanisms through which lithium regulates behavior are still poorly understood. Among different targets, some authors suggest neuromodulatory effects of lithium are the consequences of interaction of this agent with the brain neurotransmitters including adrenergic system. In order to study the involvement of α2-adrenergic system in anticonvulsant effect of lithium, we used a model of clonic seizure induced by pentylenetetrazole (PTZ) in male NMRI mice. Injection of a single effective dose of lithium chloride (30mg/kg, i.p.) significantly increased the seizure threshold (p<0.01). The anticonvulsant effect of an effective dose of lithium was prevented by pre-treatment with low and per se non-effective dose of clonidine [α2-adrenoceptor agonist] (0.05, 0.1 and 0.25mg/kg). On the other hand, yohimbine [α2-adrenoceptor antagonist] augmented the anticonvulsant effect of sub-effective dose of lithium (10mg/kgi.p.) at relatively low doses (0.1, 0.5, 1 and 2.5mg/kg). Moreover, UK14304 [a potent and selective α2-adrenoceptor agonist] (0.05 and 0.1mg/kg) and RX821008 [a potent and selective α2D-adrenoceptor antagonist] (0.05, 0.1 and 0.25mg/kg) repeated the same results confirming that these modulatory effects are conducted specifically through the α2D-adrenoceptors. In summary, our findings demonstrated that α2-adrenoceptor pathway could be involved in the anticonvulsant properties of lithium chloride in the model of chemically induced clonic seizure.

The mood stabilizer lithium potentiates the antidepressant-like effects and ameliorates oxidative stress induced by acute ketamine in a mouse model of stress

BACKGROUND

Evidence suggests that mammalian target of rapamycin activation mediates ketamine's rapid but transient antidepressant effects and that glycogen synthase kinase-3β inhibits this pathway. However, ketamine has associated psychotomimetic effects and a high risk of abuse. The mood stabilizer lithium is a glycogen synthase kinase-3 inhibitor with strong antisuicidal properties. Here, we used a mouse stress model to investigate whether adjunct lithium treatment would potentiate ketamine's antidepressant-like effects.

METHODS

Mice received chronic restraint stress and long-term pre- or postketamine lithium treatment in drinking water. The effects of lithium on ketamine-induced antidepressant-like effects, activation of the mammalian target of rapamycin/brain-derived neurotrophic factor signaling pathways, oxidative stress, and dendritic spine density in the brain of mice were investigated.

RESULTS

Subtherapeutic (600 mg/L) lithium-pretreated mice exhibited an antidepressant-like response to an ineffective ketamine (2.5 mg/kg, intraperitoneally) challenge in the forced swim test. Both the antidepressant-like effects and restoration of dendritic spine density in the medial prefrontal cortex of stressed mice induced by a single ketamine (50 mg/kg) injection were sustained by postketamine treatment with 1200 mg/L of lithium for at least 2 weeks. These benefits of lithium treatments were associated with activation of the mammalian target of rapamycin/brain-derived neurotrophic factor signaling pathways in the prefrontal cortex. Acute ketamine (50 mg/kg) injection also significantly increased lipid peroxidation, catalase activity, and oxidized glutathione levels in stressed mice. Notably, these oxidative stress markers were completely abolished by pretreatment with 1200 mg/L of lithium.

CONCLUSIONS

Our results suggest a novel therapeutic strategy and justify the use of lithium in patients who benefit from ketamine.

Lithium protects against cartilage degradation in osteoarthritis

OBJECTIVE

To determine the actions of lithium chloride (LiCl) on catabolic events in human articular chondrocytes, and the effects of LiCl on the progression and severity of cartilage degradation in interleukin-1β (IL-1β)-treated mouse knee joints and after surgical induction of osteoarthritis (OA) in a mouse model.

METHODS

Human articular chondrocytes were treated with LiCl followed by IL-1β, and the expression levels of catabolic genes were determined by real-time polymerase chain reaction. To understand the mechanism by which LiCl affects catabolic events in articular chondrocytes after IL-1β treatment, the activation of NF-κB was determined using luciferase reporter assays, and the activities of MAPKs and the STAT-3 signaling pathway were determined by immunoblot analysis of total cell lysates. Cultures of mouse femoral head explants treated with IL-1β and a mouse model of surgically induced OA were used to determine the effects of LiCl on proteoglycan loss and cartilage degradation.

RESULTS

LiCl treatment resulted in decreased catabolic marker messenger RNA levels and activation of NF-κB, p38 MAPK, and STAT-3 signaling in IL-1β-treated articular chondrocytes. Furthermore, LiCl directly inhibited IL-6-stimulated activation of STAT-3 signaling. Consequently, the loss of proteoglycan and severity of cartilage destruction in LiCl-treated mouse knee joints 8 weeks after OA induction surgery or in LiCl-treated mouse femoral head explants after IL-1β treatment were markedly reduced compared to that in vehicle-treated joints or explants.

CONCLUSION

LiCl reduced catabolic events in IL-1β-treated human articular chondrocytes and attenuated the severity of cartilage destruction in IL-1β-treated mouse femoral head explants and in the knee joints of mice with surgically induced OA, acting via inhibition of the activities of the NF-κB, p38, and STAT-3 signaling pathways.

Fibronectin and beta-catenin act in a regulatory loop in dermal fibroblasts to modulate cutaneous healing

β-Catenin is an important regulator of dermal fibroblasts during cutaneous wound repair. However, the factors that modulate β-catenin activity in this process are not completely understood. We investigated the role of the extracellular matrix in regulating β-catenin and found an increase in β-catenin-mediated Tcf-dependent transcriptional activity in fibroblasts exposed to various extracellular matrix components. This occurs through an integrin-mediated GSK3β-dependent pathway. The physiologic role of this mechanism was demonstrated during wound repair in extra domain A-fibronectin-deficient mice, which exhibited decreased β-catenin-mediated signaling during the proliferative phase of healing. Extra domain A-fibronectin-deficient mice have wounds that fail at a lower tensile strength and contain fewer fibroblasts compared with wild type mice. This phenotype was rescued by genetic or pharmacologic activation of β-catenin signaling. Because fibronectin is a transcriptional target of β-catenin, this suggests the existence of a feedback loop between these two molecules that regulates dermal fibroblast cell behavior during wound repair.

Beta-catenin signaling plays a disparate role in different phases of fracture repair: implications for therapy to improve bone healing

BACKGROUND

Delayed fracture healing causes substantial disability and usually requires additional surgical treatments. Pharmacologic management to improve fracture repair would substantially improve patient outcome. The signaling pathways regulating bone healing are beginning to be unraveled, and they provide clues into pharmacologic management. The beta-catenin signaling pathway, which activates T cell factor (TCF)-dependent transcription, has emerged as a key regulator in embryonic skeletogenesis, positively regulating osteoblasts. However, its role in bone repair is unknown. The goal of this study was to explore the role of beta-catenin signaling in bone repair.

METHODS AND FINDINGS

Western blot analysis showed significant up-regulation of beta-catenin during the bone healing process. Using a beta-Gal activity assay to observe activation during healing of tibia fractures in a transgenic mouse model expressing a TCF reporter, we found that beta-catenin-mediated, TCF-dependent transcription was activated in both bone and cartilage formation during fracture repair. Using reverse transcription-PCR, we observed that several WNT ligands were expressed during fracture repair. Treatment with DKK1 (an antagonist of WNT/beta-catenin pathway) inhibited beta-catenin signaling and the healing process, suggesting that WNT ligands regulate beta-catenin. Healing was significantly repressed in mice conditionally expressing either null or stabilized beta-catenin alleles induced by an adenovirus expressing Cre recombinase. Fracture repair was also inhibited in mice expressing osteoblast-specific beta-catenin null alleles. In stark contrast, there was dramatically enhanced bone healing in mice expressing an activated form of beta-catenin, whose expression was restricted to osteoblasts. Treating mice with lithium activated beta-catenin in the healing fracture, but healing was enhanced only when treatment was started subsequent to the fracture.

CONCLUSIONS

These results demonstrate that beta-catenin functions differently at different stages of fracture repair. In early stages, precise regulation of beta-catenin is required for pluripotent mesenchymal cells to differentiate to either osteoblasts or chondrocytes. Once these undifferentiated cells have become committed to the osteoblast lineage, beta-catenin positively regulates osteoblasts. This is a different function for beta-catenin than has previously been reported during development. Activation of beta-catenin by lithium treatment has potential to improve fracture healing, but only when utilized in later phases of repair, after mesenchymal cells have become committed to the osteoblast lineage.

Mania-like behavior induced by disruption of CLOCK

Circadian rhythms and the genes that make up the molecular clock have long been implicated in bipolar disorder. Genetic evidence in bipolar patients suggests that the central transcriptional activator of molecular rhythms, CLOCK, may be particularly important. However, the exact role of this gene in the development of this disorder remains unclear. Here we show that mice carrying a mutation in the Clock gene display an overall behavioral profile that is strikingly similar to human mania, including hyperactivity, decreased sleep, lowered depression-like behavior, lower anxiety, and an increase in the reward value for cocaine, sucrose, and medial forebrain bundle stimulation. Chronic administration of the mood stabilizer lithium returns many of these behavioral responses to wild-type levels. In addition, the Clock mutant mice have an increase in dopaminergic activity in the ventral tegmental area, and their behavioral abnormalities are rescued by expressing a functional CLOCK protein via viral-mediated gene transfer specifically in the ventral tegmental area. These findings establish the Clock mutant mice as a previously unrecognized model of human mania and reveal an important role for CLOCK in the dopaminergic system in regulating behavior and mood.

Role for the Clock gene in bipolar disorder

Nearly all patients with bipolar disorder have severely disrupted circadian rhythms. Treatment with mood stabilizers can restore these daily rhythms, and this is correlated with patient recovery. However, it is still uncertain whether clock abnormalities are the cause of bipolar disorder or if these rhythm disruptions are secondary to alterations in other circuits. Furthermore, the mechanism by which the circadian clock might influence mood is still unclear. With cloning and characterization of the circadian genes and recent advances in molecular biology, we are starting to understand this strong association between circadian rhythms and bipolar disorder. Recent human genetic and mouse behavioral studies indicate that the Clock gene is particularly relevant in the mood disruptions associated with this disorder. Furthermore, it appears that Clock expression outside of the central pacemaker of the suprachiasmatic nucleus (SCN) is involved in mood regulation. In this chapter, the evidence linking circadian rhythms, the Clock gene, and bipolar disorder is discussed, along with the possible biology that underlies this connection.

Beta-catenin regulates wound size and mediates the effect of TGF-beta in cutaneous healing

After cutaneous injury, a variety of cell types are activated to reconstitute the epithelial and dermal components of the skin. beta-Catenin plays disparate roles in keratinocytes and fibroblasts, inhibiting keratinocyte migration and activating fibroblast proliferation, suggesting that beta-catenin could either inhibit or enhance the healing process. How beta-catenin functions in concert with other signaling pathways important in the healing process is unknown. Wound size was examined in mice expressing conditional null or conditional stabilized alleles of beta-catenin, regulated by an adenovirus expressing cre-recombinase. The size of the wounds in the mice correlated with the protein level of beta-catenin. Using mice expressing these conditional alleles, we found that the wound phenotype imparted by Smad3 deficiency and by the injection of TGFbeta before wounding is mediated in part by beta-catenin. TGFbeta was not able to regulate proliferation in beta-catenin null fibroblasts, whereas keratinocyte proliferation rate was independent of beta-catenin. When mice are treated with lithium, beta-catenin-mediated signaling was activated in cutaneous wounds, which healed with a larger size. These results demonstrate a crucial role for beta-catenin in regulating cutaneous wound size. Furthermore, these data implicate mesenchymal cells as playing a critical role regulating wound size.

Alpha2-adrenoceptor and NO mediate the opioid subsensitivity in isolated tissues of cholestatic animals

1. Our previous report showed that in acute cholestasis, the subsensitivity to morphine inhibitory effect on electrical-stimulated contractions develops significantly faster in guinea-pig ileum (GPI) and in mouse vas deferens (MVD) (45.2 and 29.9 times, respectively) compared with non-cholestatic subjects. 2. The possible contribution of alpha2-adrenoceptor and nitric oxide (NO) pathways on the development of tolerance was assessed in GPI and MVD of cholestatic subjects. 3. Daily administration of naltrexone (20 mg kg(-1)), yohimbine (5 mg kg(-1)), and Nomega-nitro-l-arginine methyl ester (l-NAME) (3 mg kg(-1)) to cholestatic animals significantly (P-value < 0.05) inhibited the process of subsensitivity in all groups. 4. Consistent with the literature, it was concluded that both the alpha2-adrenergic system and NO have close interaction with the opioid system and may underlie some of the mechanisms involved in the subsensitivity development to opioids in acute cholestatic states.

Endogenous opiates and behavior: 2002

This paper is the twenty-fifth consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2002 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Alpha-2-adrenoceptor hyporesponsiveness in isolated tissues of cholestatic animals: involvement of opioid and nitric oxide systems

In the present study, the status of alpha(2)-adrenoceptors during cholestasis was investigated by the inhibitory effect of clonidine on the electrically stimulated contractions of mice vas deferens (MVD) and guinea pig ileum (GPI). Clonidine inhibited the contractions in both tissues in a dose-dependent manner. Compared to unoperated animals, there was a significant right-shift in the clonidine concentration-curves of both tissues obtained from 5-day bile-duct ligated (BDL) animals (p < 0.01), implying the hyporesponsiveness of alpha(2)-adrenoceptors during cholestasis. Chronic treatment with naltrexone (3 mg/kg/day) reversed the right-shift induced by cholestasis in both tissues. Administration of N(omega)-nitro-L-arginine methyl ester (20 mg/kg/day) also partially reversed cholestasis-induced effect on IC(50) of clonidine. These two treatments had no effect on IC(50) of tissues from controls. Chronic yohimbine treatment (5 mg/kg/day) recovered the effect of cholestasis on MVD, but sensitized the ileum of unoperated and BDL guinea pigs to clonidine to a similar extent, providing evidence for the role of the augmented adrenergic state of cholestasis in the hyporesponsiveness of norepinephrine-releasing neurons of MVD. We concluded that cholestasis is associated with the decreased responsiveness of alpha(2)-adrenoceptors and the cholestasis-associated augmented opioidergic tone and increased NO production contribute to this process.