Deregulation of Tpl2 and NF-kappaB signaling and induction of macrophage apoptosis by the anti-depressant drug lithium

TNIP2 mediates GRβ-promoted inflammation and is associated with severity of major depressive disorder

In depression, continual activation of the hypothalamic-pituitaryadrenal (HPA) axis with excess cortisol release leads to impair sensitivity of the glucocorticoid receptor (GR) and increase activity of the pro-inflammatory immune responses. Aberrant expression of GR has been associated with inflammation in patients with major depressive disorder (MDD). Our previous studies showed that the aberrant expression of TNFAIP3 gene, which encodes the NF-κB regulatory protein A20, TNFAIP3-associated proteins and Toll-like receptors (TLRs) are involved in inflammation-associated depression. However, the link between desensitization of GR actions and negative regulation of the TLRs-mediated inflammatory pathway in MDD is yet to be established. Here, we examined the association of depression severity, measured via the 17-item Hamilton Depression Rating Scale (HAMD-17), with the mRNA expression profiling of GRα, GRβ, TNFAIP3-interacting proteins (TNIP), including TNIP1, TNIP2, and TNIP3, and TNFAIP3-like proteins, such as cezanne1, cezanne2, trabid, and valosin-containing protein p97/p47 complex-interacting protein p135 (VCIP135), in monocytes from 69 patients with MDD and 42 healthy controls. Herein we found the mRNA expressions of GRβ and TNIP2 were significantly higher in monocytes from patients with MDD. Notably, TNIP2 level was positively correlated with the GRβ expression and severity of depression, as determined via Pearson's correlation analysis. Mechanistically, we demonstrated that overexpression of GRβ promotes the mRNA levels of TNIP2 and tumor necrosis factor alpha (TNF-α) in human monocytes. The promoting effect of GRβ on TNF-α expression was partially attenuated upon depletion of TNIP2, suggesting that TNIP2 was required for GRβ-mediated enhancement of TNF-α levels. Together, these results suggest that activation of GRβ/TNIP2/TNF-α axis may induce inflammation in MDD patients and targeting this newly identified pathway may help in the development of better therapeutic approaches to reduce the development of MDD.

Lithium effects on serine-threonine kinases activity: High throughput kinomic profiling of lymphoblastoid cell lines from excellent-responders and non-responders bipolar patients

Objectives: Lithium is the leading mood stabiliser for maintenance treatment in bipolar disorder (BD). However, response to lithium is heterogeneous with more than 60% of patients experiencing partial or no response. In vitro and in vivo molecular studies have reported the implication of kinases in the pathophysiology of BD.Methods: Since kinases are putative targets for lithium therapeutic action, we conducted the first pilot study using kinase array technology to evaluate the global serine/threonine kinases (STK) profiles in cell lines from BD I subtype patients classified as lithium excellent-responders (ER) and non-responder (NR) to lithium treatment.Results: We found significant differences in the basal STK profiles between ER and NR to lithium. We also tested lithium influence on the global STK profile and found no significant difference between ER vs NR cell lines.Conclusions: The results obtained in this exploratory study suggest that multiplex kinase activity profiling could provide a complementary approach in the study of biomarkers of therapeutic response in BD.

Release of lithium from 3D printed polycaprolactone scaffolds regulates macrophage and osteoclast response

The immunomodulatory effects of lithium have been reported across a range of models and contexts. Lithium appears to have a positive effect on osteogenesis in vivo, while in vitro outcomes throughout the literature are varied. Tissue engineering approaches have rarely targeted local lithium delivery within a regenerative setting. We hypothesized that part of the positive effects of lithium in vivo may be due to an immunomodulatory effect manifesting in a local environment. To achieve a sustained lithium release from scaffold constructs, we blended lithium carbonate, a soluble salt of lithium, with the biomaterial polymer polycaprolactone (PCL). We printed constructs of PCL alone, and with 5% (5Li) and 10% (10Li) lithium carbonate. Mechanical testing revealed that mechanical properties were largely retained with lithium carbonate incorporation, and we measured a consistent release of the ion over a 7 day period. The efficacy of our construct system was then assessed using a primary mouse macrophage culture, and a differentiated osteoclast culture. We found that the lithium released from constructs had a great effect on macrophage polarization, resulting in pronounced upregulation of immunomodulatory (M2) genes, and a decrease in pro-inflammatory (M1) genes. This was reflected in cytokine expression, and illustrated through immunofluorescent staining. Osteoclast activity was greatly suppressed by the lithium incorporation, with a marked effect on gene expression and actin ring formation. Our work demonstrated an effective system for local lithium delivery, confirmed the pronounced effects that lithium has on macrophage and osteoclast response, and sets the stage for further innovations in ion release for targeted tissue engineering.

Transplantation of a Peripheral Nerve with Neural Stem Cells Plus Lithium Chloride Injection Promote the Recovery of Rat Spinal Cord Injury

Transplantation of neural stem cells (NSCs) holds great potential for the treatment of spinal cord injury (SCI). However, transplanted NSCs poorly survive in the SCI environment. We injected NSCs into tibial nerve and transplanted tibial nerve into a hemisected spinal cord and investigated the effects of lithium chloride (LiCl) on the survival of spinal neurons, axonal regeneration, and functional recovery. Our results show that most of the transplanted NSCs expressed glial fibrillary acidic protein, while there was no obvious expression of nestin, neuronal nuclei, or acetyltransferase found in NSCs. LiCl treatment produced less macrosialin (ED1) expression and axonal degeneration in tibial nerve after NSC injection. Our results also show that a regimen of LiCl treatment promoted NSC differentiation into NF200-positive neurons with neurite extension into the host spinal cord. The combination of tibial nerve transplantation with NSCs and LiCl injection resulted in more host motoneurons surviving in the spinal cord, more regenerated axons in tibial nerve, less glial scar area, and decreased ED1 expression. We conclude that lithium may have therapeutic potential in cell replacement strategies for central nervous system injury due to its ability to promote survival and neuronal generation of grafted NSCs and reduced host immune reaction.

Cytokine serum levels remain unchanged during lithium augmentation of antidepressants in major depression

Lithium augmentation (LA) of antidepressants is a first-line therapy in treatment-resistant depression. Immunomodulatory effects of lithium have been described. The cytokine hypothesis of depression postulates that cytokines play a key role in the pathophysiology of depression. Concordantly, it has been shown that proinflammatory cytokine serum levels decrease during antidepressant treatment. The aim of this study was to investigate changes in cytokine serum levels during LA. Serum concentrations of the cytokines interleukin (IL)-2, IL-4, IL-6, IL-8, IL-10, tumour necrosis factor alpha, interferon-gamma, granulocyte and monocyte colony stimulating factor were measured in a total of 95 acutely depressed patients before and after four weeks of LA. Changes in cytokine levels were corrected for the confounding factors severity of depression, treatment response, lithium serum level, gender, age and body mass index in a linear mixed-model analysis. We did not find a significant change in any of the measured cytokine serum levels during LA (p > 0.05). In conclusion, our study does not support the role of cytokine serum levels as a state marker in treatment of depression with LA.

β-elemene attenuates macrophage activation and proinflammatory factor production via crosstalk with Wnt/β-catenin signaling pathway

β-elemene, extracted from Rhizoma zedoariae, has been widely used as a traditional medicine for its antitumor activity against a broad range of cancers. However, the effect of β-elemene in inflammation disorders has yet to be determined. The present study was designed to investigate the anti-inflammatory effects and potential molecular mechanisms of β-elemene in lipopolysaccharide (LPS)-induced murine macrophage cells RAW264.7. We found that the production of pro-inflammatory mediators, including interleukin-6(IL-6), tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β), induced by LPS was significantly suppressed by β-elemene in a dose-dependent manner in RAW264.7 macrophage cell line. Also, β-elemene inhibited LPS-induced nitric oxide synthase (iNOS) and interleukin-10 (IL-10) expression by RAW264.7, which was related to the down-regulation of Wnt/β-catenin signaling pathway. Importantly, this study demonstrates that β-catenin was significantly inhibited by β-elemene, which appeared to be largely responsible for the down-regulation of Wnt/β-catenin signaling pathway. Accordingly, the deletion of β-catenin in primary macrophages reversed β-catenin-elicited inhibition of immune response. Furthermore, β-catenin expression and Wnt/β-catenin signaling pathway induced by LPS in RAW264.7 was also significantly inhibited by α-humulene, one isomeric sesquiterpene of β-elemene. α-humulene was also found to significantly inhibit LPS-induced production of proinflammatory cytokines. However, α-humulene showed more cytotoxic ability than β-elemene. Collectively, our data illustrated that β-elemene exerted a potent inhibitory effect on pro-inflammatory meditator and cytokines production via the inactivation of β-catenin, and also demonstrated the protective functions of β-elemene in endotoxin-induced inflammation. β-elemene may serve as potential nontoxic modulatory agents for the prevention and treatment of inflammatory diseases.

de Carvalho L, Ley SC, Wilson MS. TPL-2 Regulates Macrophage Lipid Metabolism and M2 Differentiation to Control TH2-Mediated Immunopathology

Persistent T_H2 cytokine responses following chronic helminth infections can often lead to the development of tissue pathology and fibrotic scarring. Despite a good understanding of the cellular mechanisms involved in fibrogenesis, there are very few therapeutic options available, highlighting a significant medical need and gap in our understanding of the molecular mechanisms of T_H2-mediated immunopathology. In this study, we found that the Map3 kinase, TPL-2 (Map3k8; Cot) regulated T_H2-mediated intestinal, hepatic and pulmonary immunopathology following Schistosoma mansoni infection or S. mansoni egg injection. Elevated inflammation, T_H2 cell responses and exacerbated fibrosis in Map3k8^–/–mice was observed in mice with myeloid cell-specific (LysM) deletion of Map3k8, but not CD4 cell-specific deletion of Map3k8, indicating that TPL-2 regulated myeloid cell function to limit T_H2-mediated immunopathology. Transcriptional and metabolic assays of Map3k8^–/–M2 macrophages identified that TPL-2 was required for lipolysis, M2 macrophage activation and the expression of a variety of genes involved in immuno-regulatory and pro-fibrotic pathways. Taken together this study identified that TPL-2 regulated T_H2-mediated inflammation by supporting lipolysis and M2 macrophage activation, preventing T_H2 cell expansion and downstream immunopathology and fibrosis.

Chronic helminth infections can cause significant morbidity and organ damage in their definitive mammalian hosts. Managing this collateral damage can reduce morbidity and preserve vital tissues for normal organ function. One particular consequence of some chronic helminth infections is the deposition of fibrotic scar tissue, following immune responses directed towards helminth material. In this study we tested the role of a particular signalling kinase, TPL-2, and identified that it critically regulated the magnitude of fibrotic scarring following infection. Using several murine models with genetic deletions of TPL-2 in either all cells or specific deletion in subsets of immune cells (Map3k8^–/–Map3k8^fl/fl) we identified that expression of TPL-2 in myeloid cells was essential to prevent severe immune-mediated pathology. Using genome-wide analyses and metabolic assays, we discovered that TPL-2 was required for normal lipid metabolism and appropriate activation of myeloid cells / macrophages to limit fibrosis. These results revealed a previously unappreciated role for TPL-2 in preventing severe pathology following infection. Thus, activating this pathway may limit immune mediated pathology following chronic helminth infection. More broadly, this pathway is being targeted to treat inflammatory diseases and cancer [1, 2]. This study would suggest that caution should be taken to prevent untoward co-morbidities and fibrosis-related pathologies in patients when targeting TPL-2.

Effect of the Chronic Use of Lithium Carbonate on Induced Tooth Movement in Wistar Rats

Patients who seek dental treatment may have bipolar disorder, and lithium carbonate (LC) is the drug of choice used in the treatment of this disorder. Taking into consideration the controversial results found in the literature, and the possible influence of LC on induced tooth movement, the objective was to evaluate tooth movement induced in rats after administration of lithium carbonate. One hundred and ninety-two rats were divided into 3 groups. In the L group, the animals received daily 60mg/kg of LC, they were not subjected to orthodontic movement, and they were euthanized after 33, 37, 44 or 51 days. In the LM group, the LC was administered for 30 days and during the subsequent 3, 7, 14 and 21 days, corresponding to the period of induced tooth movement, and they received a spring that produced a 30cN force. In the SM group, saline solution was applied. Measurements were made of tooth displacement, the numbers of osteoclasts and serum lithium phosphate (PO4), alkaline phosphatase (ALP) and creatinine levels. The tooth displacement was lower in the LM group compared to the SM group at 44 days. A tendency toward reduction in the number of osteoclasts was observed in the LM group compared to the SM group at 44 days. The average lithium were higher in the L and LM groups compared to the SM group. The opposite was observed for the PO4 group. A higher value for the ALP was found in the L group. The average creatinine level was lower in the LM group. LC inhibited tooth movement for 14 days, possibly due to the reduction in the number of osteoclasts.

Lithium chloride induces TNFα in mouse macrophages via MEK-ERK-dependent pathway

Lithium (Li) is one of the currently prescribed drugs for bipolar disorders (BPDs) and has many neuro-regulatory and immune-modulating properties. Because many neuro-pathological diseases including BPDs have been associated with some level of inflammation, Li's effect on inflammation may have some crucial consequences. Even though Li has been shown to have pro- and anti-inflammatory activities in different cell models, mechanisms involved in these effects are not well understood. Moreover, Li's effect on inflammation in the presence of activators of Toll-like receptors (TLRs), especially TLR-2 (that activates MyD88-dependent pathway) and TLR-3 (that activates TRIF-dependent pathway) is not known. Here we tested the role of Li in the presence and absence of TLR2, and TLR3 on MAPK and NFκB pathways and the consequent production of tumor necrosis factor-α (TNFα) in Raw264.7 macrophages. Our results indicate that Li enhances TNFα production both in the absence and presence of TLR stimulation. Interestingly, Li differentially modulates MAPK and NFκB pathways in the absence and presence of TLR2/3 ligands. Our results further indicate that the effect of Li on TNFα occurs at the post-transcriptional level. Together, these studies demonstrate that Li induces TNFα production in macrophages and that it modulates signaling at different levels depending on the presence or absence of TLR2/3 stimulation.

Regulation of macrophage biology by lithium: a new look at an old drug

Lithium (Li) continues to be a standard small compound used for the treatment of neurological disorders. Besides neuronal cells, Li is also known to affect immune cell function. In spite of its clinical use, potential mechanisms by which Li modulates immune cells, especially macrophages and its clinical relevance in bipolar patients are not well understood. Here, we provide an overview of the literature with regard to Li's effects on monocytes and macrophages. We have also included some of our results showing that Li differentially modulates chemokine gene expression in the absence and presence of Toll-like receptor-4 stimulation in a human macrophage model. Given that Li has a wide range of intracellular targets both in macrophages as well as in other cell types, more studies are needed to further understand the mechanistic basis of Li's effect in neurological and other inflammatory diseases. These studies could undoubtedly identify new therapeutic targets for treating such diseases.

Lithium chloride promotes host resistance against Pseudomonas aeruginosa keratitis

PURPOSE

To explore the role of lithium chloride (LiCl) in Pseudomonas aeruginosa (PA) keratitis.

METHODS

B6 mice were subconjunctivally injected with LiCl in contrast to appropriate control sodium chloride (NaCl), and then routinely infected with PA. Clinical score, slit-lamp photography, hematoxylin and eosin (H&E) staining, and bacterial plate counts were used to determine the role of LiCl in PA keratitis. Messenger ribonucleic acid and protein levels of inflammatory cytokines in PA-challenged mouse corneas and in vitro cultured macrophages and neutrophils were measured with real-time PCR and enzyme-linked immunosorbent assay (ELISA), respectively. Apoptosis of the infiltrating inflammatory cells in the PA-infected murine corneas was assessed using terminal deoxynucleotidyl transferase-mediated uridine 5'-triphosphate-biotin nick end labeling staining and propidium iodide staining associated with flow cytometry. In cultured murine macrophages and neutrophils, cell apoptosis was determined with annexin V/propidium iodide double staining associated with flow cytometry and western blot analysis for cleaved caspase-3 and cleaved poly(ADP-ribose) polymerase.

RESULTS

Treatment with LiCl reduced the severity of corneal disease by reducing corneal inflammatory response and bacterial burden. Moreover, LiCl increased anti-inflammatory cytokine interleukin-10 levels, decreased proinflammatory cytokine tumor necrosis factor-α levels, and enhanced apoptosis of infiltrating macrophages and neutrophils in the PA-infected mouse corneas. In vitro studies further confirmed that LiCl elevated anti-inflammatory cytokine expression but reduced proinflammatory cytokine production, as well as promoted cell apoptosis in murine macrophages and neutrophils.

CONCLUSIONS

This study demonstrates a protective role of LiCl in PA keratitis. LiCl promotes host resistance against PA infection by suppressing inflammatory responses, enhancing inflammatory cell apoptosis, and promoting bacterial clearance.

Lithium induces follicular atresia in rat ovary through a GSK-3β/β-catenin dependent mechanism

Lithium chloride (LiCl) is a drug used to treat bipolar disorder, but has side effects in the female reproductive system. Although lithium is known to decrease folliculogenesis and induce follicular atresia in rodent ovaries, its cellular and molecular effects in the ovary have not yet been addressed. To investigate these effects, 23-day-old immature female rats were injected with 10 IU pregnant mare serum gonadotropin (PMSG), followed by injections of 250 mg/kg LiCl every 12 hr for four doses. Ovaries were removed 40 and 48 hr after PMSG administration and prepared for histology, immunohistochemistry, Western blotting, and DNA laddering analysis. Our results showed that in the ovaries of LiCl-treated rats, few antral but more atretic follicles were present compared to those of the control rats. The induction of atresia by LiCl was further confirmed by the presence of DNA fragmentation, accompanied by a reduced level of 17β-estradiol in the serum. At the cellular level, lithium significantly decreased the number of proliferating cell nuclear antigen (PCNA)-positive cells and conversely increased the number of TUNEL-positive cells in the granulosa layer of the antral follicles. At the molecular level, lithium increased the level of phosphorylated glycogen synthase kinase-3β, and unexpectedly decreased the expression of active (stabilized) β-catenin. Altogether, our results indicate that lithium disrupts the balance between proliferation and apoptosis in granulosa cells, leading to follicular atresia possibly through the reduction in both the stabilized β-catenin and 17β-estradiol synthesis.

Inhibition of inositol monophosphatase by lithium chloride induces selective macrophage apoptosis in atherosclerotic plaques

BACKGROUND AND PURPOSE

Lithium chloride (LiCl) inhibits inositol monophosphatase (IMPase) at therapeutic concentrations. Given that LiCl induces death in cultured macrophages and that macrophages play an active role in atherosclerotic plaque destabilization, we investigated whether LiCl would induce selective macrophage death to stabilize the structure of the plaque.

EXPERIMENTAL APPROACH

The effect of LiCl was assessed on macrophages and smooth muscle cells (SMCs) in culture, in isolated atherosclerotic carotid arteries from rabbits and after local in vivo treatment via osmotic minipumps to rabbits with collared atherosclerotic carotid arteries. In addition, in vitro experiments were performed to elucidate the mechanism of LiCl-induced macrophage death.

KEY RESULTS

In vitro, whereas SMCs were highly resistant, LiCl induced macrophage death characterized by externalization of phosphatidylserine, caspase-3 cleavage and DNA fragmentation, all indicative of apoptosis. LiCl reduced inositol-1,4,5-trisphosphate levels in macrophages. Moreover, the IMPase inhibitor L-690 330 as well as IMPase gene silencing induced macrophage apoptosis. Both in vitro treatment of rabbit atherosclerotic carotid arteries with LiCl and local in vivo administration of LiCl to the plaques decreased plaque macrophages through apoptosis, as shown by terminal deoxynucleotidyl transferase deoxyuridine triphosphate (dUTP) nick-end labelling (TUNEL), without affecting SMCs. Vasomotor studies in vitro showed that LiCl did not affect the functionality of SMCs and endothelial cells.

CONCLUSIONS AND IMPLICATIONS

LiCl selectively decreased the macrophage load in rabbit atherosclerotic plaques via IMPase inhibition without affecting the viability or functionality of SMCs and endothelial cells. These data provide evidence for local administration of an IMPase inhibitor to stabilize atherosclerotic plaques.

Spinal cord injury therapies in humans: an overview of current clinical trials and their potential effects on intrinsic CNS macrophages

INTRODUCTION

Macrophage activation is a hallmark of spinal cord injury (SCI) pathology. CNS macrophages, derived from resident microglia and blood monocytes, are ubiquitous throughout the injured spinal cord, and respond to signals in the lesion environment by changing their phenotype and function. Depending on their phenotype and activation status, macrophages may initiate secondary injury mechanisms and/or promote CNS regeneration and repair.

AREAS COVERED

This review provides a comprehensive overview of current SCI clinical trials that are intended to promote neuroprotection, axon regeneration or cell replacement. None of these potential therapies were developed with the goal of influencing macrophage function; however, it is likely that each will have direct or indirect effects on CNS macrophages. The potential impact of each trial is discussed in the context of CNS macrophage biology.

EXPERT OPINION

Activation of CNS macrophages is an inevitable consequence of traumatic SCI. Given that these cells are exquisitely sensitive to changes in microenvironment, any intervention that affects tissue integrity and/or the composition of the cellular milieu will undoubtedly affect CNS macrophages. Thus, it is important to understand how current clinical trials will affect intrinsic CNS macrophages.

Docosahexaenoic acid suppresses neuroinflammatory responses and induces heme oxygenase-1 expression in BV-2 microglia: implications of antidepressant effects for ω-3 fatty acids

Accumulating evidence suggests that the pathophysiology of depression might be associated with neuroinflammation, which could be attenuated by pharmacological treatment for depression. Omega-3 polyunsaturated fatty acids (PUFAs) are anti-inflammatory and exert antidepressant effects. The aim of this study was to identify the molecular mechanisms through which docosahexaenoic acid (DHA), the main omega-3 PUFA in the brain, modulates oxidative reactions and inflammatory cytokine production in microglial and neuronal cells. The results of this study showed that DHA reduced expressions of tumor necrosis factor-α, interleukin-6, nitric oxide synthase, and cyclo-oxygenase-2, induced by interferon-γ, and induced upregulation of heme oxygenase-1 (HO-1) in BV-2 microglia. The inhibitory effect of DHA on nitric oxide production was abolished by HO-1 inhibitor zinc protoporphyrin IX. In addition, DHA caused AKT and ERK activation in a time-dependent manner, and the DHA-induced HO-1 upregulation could be attenuated by PI-3 kinase/AKT and MEK/ERK inhibitors. DHA also increased IKKα/β phosphorylation, IκBα phosphorylation, and IκBα degradation, whereas both nuclear factor-κB and IκB protease inhibitors could inhibit DHA-induced HO-1 expressions. The other major n-3 PUFA, eicosapentaenoic acid, showed similar effects of DHA on inflammation and HO-1 in repeated key experiments. In connecting with inflammation hypothesis of depression and clinical studies supporting the antidepressant effects of omega-3 PUFAs, this study provides a novel implication of the antidepressant mechanisms of DHA.