Paroxetine prevented the down-regulation of astrocytic L-Glu transporters in neuroinflammation

Modulation of microglial activation by antidepressants

BACKGROUND

Recent studies have suggested that microglial activation plays a key role in the pathogenesis of depression. In fact, neuroinflammation is associated with a phenotypic change of microglia, consisting of morphological differences, increased release of cytokines and oxidative stress products, which may contribute to the development and maintenance of depression. Antidepressants, including selective serotonin re-uptake inhibitors and serotonin-norepinephrine reuptake inhibitors, have been shown to act on the immune and oxidative stress mechanisms commonly found to be disrupted in depression. Thus, the inhibition of microglial activation may be one of the mechanisms through which they exert an antidepressant action.

AIM

This is the first review summarising in vitro and ex vivo studies investigating the effects of different classes of antidepressants on microglia activation, by examining cellular changes and/or via measuring the production of immune and/or oxidative stress signalling molecules, in microglia models of neuroinflammation with either lipopolysaccharide (LPS) or cytokines. A total of 23 studies were identified, 18 using LPS stimulation and 5 using cytokines stimulation.

RESULTS

Overall, the studies show that antidepressants, such as selective serotonin re-uptake inhibitors, serotonin-norepinephrine reuptake inhibitors, monoamine oxidase inhibitors and tricyclic antidepressants prevented microglial activation, including reduced microglial reactivity and decreased immune and oxidative stress products, in both models. However, specific antidepressants, such as bupropion and agomelatine did not prevent interferon-gamma (IFN-γ)-induced microglial activation; and for other antidepressants, including phenelzine, venlafaxine and sertraline, the results of different studies were inconsistent.

CONCLUSIONS

Overall, results summarised in this review support the hypothesis that the action of at least certain classes of antidepressants may involve regulation of microglial activation, especially when in presence of increased levels of inflammation.

Kampo formulas alleviate aging-related emotional disturbances and neuroinflammation in male senescence-accelerated mouse prone 8 mice

Aging-induced neuroinflammation, also known as neuroinflammaging, plays a pivotal role in emotional disturbances, including depression and anxiety, in older individuals, thereby leading to cognitive dysfunction. Although numerous studies have focused on therapeutic strategies for cognitive impairment in older individuals, little research has been performed on treating its preceding emotional disturbances. Here, we examined whether Kampo formulas (kososan [KS], nobiletin-rich kososan [NKS], and hachimijiogan [HJG]) can ameliorate aging-induced emotional disturbances and neuroinflammation in mice. The depression-like behaviors observed in SAMP8 mice, relative to normally aging SAMR1 mice, were significantly prevented by treatment with Kampo formulas for 13 weeks. Western blot analysis revealed that hippocampal neuroinflammation was significantly abrogated by Kampo formulas. KS and NKS also significantly attenuated the hippocampal neuroinflammatory priming induced by lipopolysaccharide (LPS, 0.33 mg/kg, i.p.) challenge in SAMP8 mice. Hippocampal IL-1β, IL-6, and MCP-1 levels were significantly decreased in NKS-treated SAMP8 mice. KS and NKS showed significantly reduced tau accumulation in the brains of SAMP8 mice. RNA-sequencing revealed that each Kampo formula led to unique dynamics of hippocampal gene expression and appeared to abrogate hippocampal inflammatory responses. HJG significantly blocked the LPS-induced increase in serum IL-6 and MCP-1. These results suggest that Kampo formulas would be useful for treating aging-induced depression, in part by regulating neuroinflammatory pathways. This finding may pave the way for the development of therapeutic strategies for aging-related emotional disturbances, which may contribute to the prevention of cognitive dysfunction in older individuals.

Identifying the effectual-combination ingredients of Zhi-zi-Hou-po decoction based on metabolic difference-oriented network regulation strategy

Zhi-zi-Hou-po decoction (ZZHPD) has been used to treat depression in the clinic for thousand years in China. However, the pharmacodynamic substance of ZZHPD is still not totally clear due to its complex components. The objective of this study was to identify the effectual combination ingredients (ECIs) of ZZHPD, which could represent the antidepressant effect of the original formula. Firstly, differential plasma absorbed components with different variable importance in projection (VIP) value in chronic unpredictable mild stress (CUMS)-induced depression and control rat were revealed by untargeted metabolomics-driven strategy based on HPLC-ESI-TOF/MS, XCMS online and SIMCA-p software. Secondly, network topology scores (NTS) of plasma absorbed components were exposed by protein-protein interaction (PPI) network analysis based on components-related genes and depression-related genes, which were performed by network pharmacology tools. Finally, the ECIs were screened by considered of VIP value and NTS. Then the bioactivity was evaluated by cell viability and expression of glial fibrillary acid protein (GFAP), tumor necrosis factor α (TNFα) and interleukin 1β (IL-1β) of a lipopolysaccharide-induced astrocyte depression model. An effective combination composed with 12 components was filtrated as ECIs of ZZHPD, exposed to which the cell viability effect, the expression of GFAP and IL-1β in astrocytes were essentially equivalent with original ZZHPD (p > 0.05), and that both characteristic constituents and trace compounds of ZZHPD might exert synergistic actions through multi-targets. The result of this study provided useful information for the clinical application and modern development of ZZHPD, and the proposed strategy could be regard as an alternative solution for effective combination screening of herbal medicines.

Emotional Impairments and Neuroinflammation are Induced in Male Mice Invulnerable to Repeated Social Defeat Stress

Prolonged stress triggers neuroinflammation, which plays a significant role in the development of depression; however, stressed people do not always suffer from depression because of individual differences in stress vulnerability. Negative cognitive bias (NCB) toward pessimistic judgment often underlies depressive episodes. However, a relationship between stress vulnerability, neuroinflammation, and NCB remains elusive. In addition, an animal model with all the traits would be a powerful tool for studying the etiology of depression and its therapeutic approaches. Accordingly, this study evaluated the effect of stress vulnerability on neuroinflammation and depression-related behaviors, including NCB in males, using a modified version of repeated social defeat stress (mRSDS) paradigm, a validated animal model of psychosocial stress. Exposure to mRSDS, consisting of 5 min of social defeat by unfamiliar CD-1 aggressor mice for five consecutive days, caused NCB, which co-occurred with depressive- and anxiety-like behaviors, and neuroinflammation in male BALB/c mice. Treatment with minocycline, an antibiotic with anti-inflammatory property, blocked mRSDS-induced depressive-like behaviors and neuroinflammation, but not NCB, indicating the limited effect of an anti-inflammatory intervention. In addition, marked differences were found in neuroinflammatory profiles and hippocampal gene expression patterns between resilient and unstressed mice, as well as between susceptible and resilient mice. Therefore, mice resilient to mRSDS are indeed not intact. Our findings provide insights into the unique features of the mRSDS model in male BALB/c mice, which could be used to investigate the etiological mechanisms underlying depression as well as bridge the gap in the relationship between stress vulnerability, neuroinflammation, and NCB in males.

Paroxetine suppresses reactive microglia-mediated but not lipopolysaccharide-induced inflammatory responses in primary astrocytes

BACKGROUND

Astrocytes are the most abundant glial cells in a brain that mediate inflammatory responses and provide trophic support for neurons. We have previously disclosed that paroxetine, a common selective serotonin reuptake inhibitor, ameliorates LPS-induced microglia activation. However, it remains elusive for the role of paroxetine in astrocytic responses.

METHODS

Isolated primary astrocytes were pretreated with paroxetine and stimulated with different stimuli, lipopolysaccharide (LPS) or microglia conditioned medium pre-activated with LPS (M/Lps). Inflammatory and neurotrophic responses, underlying mechanisms and the impact on neuronal survival were assessed.

RESULTS

Paroxetine had no impact on LPS-stimulated iNOS, TNF-α, and IL-1β expression, but inhibited M/Lps-induced TNF-α and IL-1β expression in primary astrocytes. Paroxetine suppressed M/Lps- but not LPS-induced activation of NF-κB and had no impact on the activation of MAPKs and STAT3. Incubation with the resulted astrocyte conditioned media caused no change in the viability of SH-SY5Y cells. BDNF and MANF mRNA expressions were upregulated by M/Lps and paroxetine, respectively. However, M/Lps- or LPS-induced extracellular releases of NO, TNF-α, and/or BDNF in astrocytes were in minor amount compared to those by microglia.

CONCLUSIONS

Paroxetine ameliorates the reactive microglia-mediated inflammatory responses in astrocytes partially via inhibition of the NF-κB pathway but has no impact on LPS-stimulated astrocyte activation. While the effects of paroxetine on secondary astrocytic responses are not robust compared to its effect on the innate immune responses of microglia, the results together may implicate a therapeutic potential of paroxetine against neuroinflammation-associated neurological disorders such as Parkinson's disease.