Paricalcitol alleviates lipopolysaccharide-induced depressive-like behavior by suppressing hypothalamic microglia activation and neuroinflammation

Eldecalcitol protected osteocytes against ferroptosis of D-gal-induced senescent MLO-Y4 cells and ovariectomized mice

BACKGROUND

Active vitamin D analog eldecalcitol is clinically applied in treatment of postmenopausal osteoporosis. This study aims to determine the role of eldecalcitol in the protection of osteocytes from senescence and the associated ferroptosis.

METHODS

The MLO-Y4 osteocytes were exposed to D-gal inducing senescence. The ovariectomized (OVX) mice treated with D-gal using as an aging inducer were intraperitoneally injected with eldecalcitol. The multiplexed confocal imaging, fluorescence in situ hybridization and transmission electron microscopy were applied in assessing osteocytic properties. Immunochemical staining and immunoblotting were carried out to detect abundance and expression of molecules.

RESULTS

The ablation of vitamin D receptor led to a reduction in amounts of osteocytes, a loss of dendrites, an increase in mRNA expression of SASP factors and in protein expression of senescent factors, as well as changes in mRNA expression of ferroptosis-related genes (PTGS2 & RGS4). Eldecalcitol reversed senescent phenotypes of MLO-Y4 cells shown by improving cell morphology and density, decreasing β-gal-positive cell accumulation, and down-regulating protein expression (P16, P21 & P53). Eldecalcitol reduced intracellular ROS and MDA productions, elevated JC-1 aggregates, and up-regulated expression of Nrf2 and GPX4. Eldecalcitol exhibited osteopreserve effects in D-gal-induced aging OVX mice. The confocal imaging displayed its improvement on osteocytic network organization. Eldecalcitol decreased the numbers of senescent osteocytes at tibial diaphysis by SADS assay and attenuated mRNA expression of SASP factors as well as down-regulated protein expression of senescence-related factors and restored levels of ferroptotic biomarkers in osteocytes-enriched bone fraction. It reduced 4-HNE staining area, stimulated Nrf2-positive staining, and promoted nuclear translocation of Nrf2 in osteocytes of mice as well as inhibited and promoted protein expression of 4-HNE and Nrf2, respectively, in osteocytes-enriched bone fraction.

CONCLUSIONS

The present study revealed the ameliorative effects of eldecalcitol on senescence and the associated ferroptosis of osteocytes, contributing to its preservation against osteoporosis of D-gal-induced senescent ovariectomized mice.

A unique inflammation-related mechanism by which high-fat diets induce depression-like behaviors in mice

BACKGROUND

High-fat diet (HFD) consumption is an important reason for promoting depression, but the mechanism is unclear. The present study aims to explore the relationship between metabolic disturbance and HFD-induced depression-like behaviors.

METHODS

Depression models were established by HFD consumption and chronic unpredictable mild stress (CUMS) in mice. Enzyme-linked immunosorbent assay, western blotting, real-time polymerase chain reaction, gas chromatography and metabolomic analysis were undertaken to investigate the 5-hydroxytryptamine (5-HT) system, neuroinflammation and to identify altered lipid metabolic pathways.

RESULTS

Depression-like behaviors, impaired 5-HT neurotransmission and disordered lipid metabolism were observed upon HFD consumption. Despite a similar reduction of high-density lipoprotein cholesterol in CUMS and HFD group, high levels of body low-density lipoprotein cholesterol in the HFD group could help distinguish HFD from CUMS. Levels of interleukin (IL)-1β, IL-6, tumor necrosis factor (TNF)-α and inflammation-related metabolites were increased in HFD mice, so a link between depression and inflammation was postulated. Different metabolites were enriched in the two groups. The linoleic acid (LA) metabolic pathway and expression of fatty acid desaturase (FADS)1 and FADS2 (key enzymes in LA metabolic pathway) were enhanced significantly in HFD mice compared with the control group.

LIMITATIONS

Causality analyses for HFD and inflammation-related features were not undertaken.

CONCLUSIONS

HFD-induced depression-like behaviors was characterized by more severely disordered metabolism of lipids (especially in the LA metabolic pathway) and increased levels of inflammatory mediators, which might be the reasons for the disturbance of serotonergic system in hippocampus.

Targeting Underlying Inflammation in Carcinoma Is Essential for the Resolution of Depressiveness

In modern clinical practice and research on behavioral changes in patients with oncological problems, there are several one-sided approaches to these problems. Strategies for early detection of behavioral changes are considered, but they must take into account the specifics of the localization and phase in the course and treatment of somatic oncological disease. Behavioral changes, in particular, may correlate with systemic proinflammatory changes. In the up-to-date literature, there are a lot of useful pointers on the relationship between carcinoma and inflammation and between depression and inflammation. This review is intended to provide an overview of these similar underlying inflammatory disturbances in both oncological disease and depression. The specificities of acute and chronic inflammation are considered as a basis for causal current and future therapies. Modern therapeutic oncology protocols may also cause transient behavioral changes, so assessment of the quality, quantity, and duration of behavioral symptoms is necessary to prescribe adequate therapy. Conversely, antidepressant properties could be used to ameliorate inflammation. We will attempt to provide some impetus and present some unconventional potential treatment targets related to inflammation. It is certain that only an integrative oncology approach is justifiable in modern patient treatment.

Chronic lipopolysaccharide impairs motivation when delivered to the ventricles, but not when delivered peripherally in male rats

Increased neuroinflammation relative to controls is observed in major depression. Moreover, depressive disorders are significantly elevated in conditions which increase neuroinflammation (e.g., brain injury, Parkinson's disease, Alzheimer's disease). To better understand the relationship between neuroinflammation and depression, additional research is needed. The current set of studies made use of the progressive ratio (PR) task in male rats, a stable measure of motivation which can be evaluated daily and thus is ideally suited for examining a potential role for chronic neuroinflammation in depressive-like behavior. Lipopolysaccharide (LPS) was used to induce an inflammatory response. Experiment 1 confirmed prior acute LPS administration experiments for sensitivity of the PR task, with a large effect at 2 mg/kg, a partial effect at 1 mg/kg, and no effect at 0.5 mg/kg. Experiment 2 evaluated a dose-response of continuous s.c. LPS infusion but found no significant elevation in brain cytokines after 14 days at any doses of 0.1, 0.5, 1, or 2 mg/kg/week. Experiment 3 assessed motivation during continuous s.c. infusion of a large 5 mg/kg/week LPS dose and found no significant impairments in motivation, but transient decreases in rates of lever pressing (i.e., only motoric deficits). Experiment 4 measured motivation during continuous ICV infusion of 10.5 μg/kg/week LPS and found significantly decreased motivation without changes to rates of lever pressing (i.e., only motivational deficits). Together these results suggest that the PR task is efficient for evaluating models of chronic inflammation, and that the adaptive response to chronic LPS exposure, even when delivered centrally, may necessitate alternative strategies for generating long-term neuroinflammation.

Soy isoflavones alleviate lipopolysaccharide-induced depressive-like behavior by suppressing neuroinflammation, mediating tryptophan metabolism and promoting synaptic plasticity

Depression is highly prevalent in patients suffering from chronic inflammatory diseases. Dysregulated neuroinflammation and concomitant-activated microglia play a pivotal role in the pathogenesis of depression. As one of the biologically functional phytochemicals in soybeans, soy isoflavones (SI) have been reported to exhibit anti-inflammatory, antioxidant, estrogen-like and neuroprotective activities. However, there is no research on how SI administration affects the depressive-like behavior induced by neuroinflammation. Therefore, this study was conducted to evaluate the antidepressant-like action of SI in acute lipopolysaccharide (LPS)-treated mice and to explore its underlying mechanisms. An open field test, a sucrose preference experiment, a tail suspension test and a forced swimming task were conducted to assess the influence of SI on the depressive-like behavior induced by LPS injection. Then, the levels of the pro-inflammation cytokines, tryptophan (Trp) metabolism in the cortex and hippocampus, and the synaptic plasticity-related signal pathway in the hippocampus, which are involved in the pathophysiology of depression, were examined. The results showed that SI administration remarkably alleviated LPS-induced depressive-like behavior as indicated by the increased sucrose preference index and the decreased immobility time both in the tail suspension test and the forced swimming task. SI significantly suppressed neuroinflammation in the hippocampus of LPS mice, as indicated by a decrease in the levels of interleukin (IL)-1β, IL-10, tumor necrosis factor (TNF-α) and suppression of the signal pathway of TLR4/NF-κB. Additionally, SI administration regulated tryptophan (Trp) metabolism by increasing 5-hydroxytryptamine (5-HT) levels, inhibiting the release of kynurenine (KYN) in the cortex and hippocampus, and elevating the expressions of synaptic plasticity-related protein markers such as postsynaptic density-95 (PSD-95) and synaptophysin (SYN). The current study demonstrated that soy isoflavones could reverse LPS-induced depressive-like behavior by suppressing neuroinflammation, normalizing the Trp metabolism, up-regulating the expressions of synaptic plasticity-related proteins, and inhibiting the TLR4/NF-κB pathway activation in the hippocampus of mice, exerting their antidepressant-like action.

Night shift hormone: How does melatonin affect depression?

Melatonin is the main hormone secreted by the pineal gland that modulates the circadian rhythm and mood. Previous studies have shown the therapeutic effects of melatonin, or its important analogue, agomelatine, on depression. In this review study, we aimed to discuss the potential mechanisms of melatonin involved in the treatment of depression. It was noted that disrupted circadian rhythm can lead to depressive state, and melatonin via regulating circadian rhythm shows a therapeutic effect. It was also noted that melatonin induces antidepressant effects via promoting antioxidant system and neurogenesis, and suppressing oxidative stress, neuroinflammation, and apoptosis. The interaction effect between melatonin or agomelatine and serotonergic signaling has a significant effect on depression. It was noted that the psychotropic effects of agomelatine are induced by the synergistic interaction between melatonin and 5-HT_2C receptors. Agomelatine also interacts with glutamatergic signaling in brain regions involved in regulating mood and circadian rhythm. Interestingly, it was concluded that melatonin exerts both pro- and anti-inflammatory effects, depending on the grade of inflammation. It was suggested that synergistic interaction between melatonin and 5-HT_2C receptors may be able to induce therapeutic effects on other psychiatric disorders. Furthermore, dualistic role of melatonin in regulating inflammation is an important point that can be examined at different levels of inflammation in animal models of depression.

Chronic stress-induced depression requires the recruitment of peripheral Th17 cells into the brain

Background

Depression is a recurrent and devastating mental disease that is highly prevalent worldwide. Prolonged exposure to stressful events or a stressful environment is detrimental to mental health. In recent years, an inflammatory hypothesis has been implicated in the pathogenesis of stress-induced depression. However, less attention has been given to the initial phases, when a series of stress reactions and immune responses are initiated. Peripheral CD4⁺ T cells have been reported as the major contributors to the occurrence of mental disorders. Chronic stress exposure-evoked release of cytokines can promote the differentiation of peripheral CD4⁺ cells into various phenotypes. Among them, Th17 cells have attracted much attention due to their high pathogenic potential in central nervous system (CNS) diseases. Thus, we intended to determine the crucial role of CD4⁺ Th17 cells in the development of specific subtypes of depression and unravel the underpinnings of their pathogenetic effect.

Methods

In the present research, a daily 6-h restraint stress paradigm was employed in rats for 28 successive days to mimic the repeated mild and predictable, but inevitable environmental stress in our daily lives. Then, depressive-like symptoms, brain–blood barrier (BBB) permeability, neuroinflammation, and the differentiation and functional changes of CD4⁺ cells were investigated.

Results

We noticed that restrained rats showed significant depressive-like symptoms, concomitant BBB disruption and neuroinflammation in the dorsal striatum (DS). We further observed a time-dependent increase in thymus- and spleen-derived naïve CD4⁺ T cells, as well as the aggregation of inflammatory Th17 cells in the DS during the period of chronic restraint stress (CRS) exposure. Moreover, increased Th17-derived cytokines in the brain can further impair the BBB integrity, thus allowing more immune cells and cytokines to gain easy access to the CNS. Our findings suggested that, through a complex cascade of events, peripheral immune responses were propagated to the CNS, and gradually exacerbated depressive-like symptoms. Furthermore, inhibiting the differentiation and function of CD4⁺ T cells with SR1001 in the early stages of CRS exposure ameliorated CRS-induced depressive-like behaviour and the inflammatory response.

Conclusions

Our data demonstrated that inflammatory Th17 cells were pivotal in accelerating the onset and exacerbation of depressive symptoms in CRS-exposed rats. This subtype of CD4⁺ T cells may be a promising therapeutic target for the early treatment of stress-induced depression.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02543-6.

Vitamin D as a Risk Factor for Multiple Sclerosis: Immunoregulatory or Neuroprotective?

Vitamin D insufficiency during childhood has been linked to the development of multiple sclerosis (MS), typically an adult-onset inflammatory demyelinating disease of the central nervous system (CNS). Since vitamin D was known to have immunoregulatory properties on both innate and adaptive immunity, it was hypothesized that low vitamin D resulted in aberrant immune responses and the development of MS. However, vitamin D receptors are present on many cell types, including neurons, oligodendrocytes, astrocytes and microglia, and vitamin D has profound effects on development and function of the CNS. This leads to the possibility that low vitamin D may alter the CNS in a manner that makes it vulnerable to inflammation and the development of MS. This review analysis the role of vitamin D in the immune and nervous system, and how vitamin D insufficiency in children may contribute to the development of MS.

Antidepressant-like Effects of Renin Inhibitor Aliskiren in an Inflammatory Mouse Model of Depression

Depression is considered a neuropsychic disease that has global prevalence and is associated with disability. The pathophysiology of depression is not well understood; however, emerging evidence has indicated that neuroinflammation could contribute to developing depression symptoms. One of the factors that have a role in the development of neuroinflammation is the renin–angiotensin system. Therefore, the goal of the current study is to determine the antidepressant-like effects of Aliskiren, a renin inhibitor, against lipopolysaccharide (LPS)-induced depressive-like behavior in mice, glial cell activation, and the upregulation of proinflammatory cytokines in the prefrontal cortex. For behavioral studies, the open field test (OFT), tail suspension test (TST), forced swim test (FST), and sucrose preference test (SPT) were used. Inflammatory markers were assessed using real-time polymerase chain reaction (RT-PCR). LPS administration (0.5 mg/kg, intraperitoneal injection (i.p.)) sufficiently reduced the number of crossings in OFT, whereas Aliskiren pretreatment (10 mg/kg, i.p.) attenuated the LPS effect for two hours after LPS injection. The treatments did not show effects on locomotor activity in OFT 24 h after LPS administration. LPS increased the immobility time in TST and FST or reduced sucrose consumption in SPT after 24 h. Aliskiren reversed the effects induced by LPS in TST, FST, and SPT. CD11 b mRNA, a microglial marker, GFAP mRNA, an astroglial marker, and proinflammatory cytokines genes (TNF-α, IL-1β, and IL-6) were upregulated in the prefrontal cortex in LPS exposed animals. However, Aliskiren reduced LPS-induced inflammatory genes in the prefrontal cortex. Hence, the outcomes conclude that Aliskiren prevents depressive illness associated with neuroinflammation in humans.

Vitamin D/Vitamin D Receptor Signaling Attenuates Skeletal Muscle Atrophy by Suppressing Renin-Angiotensin System

The nutritional level of vitamin D may affect musculoskeletal health. We have reported that vitamin D is a pivotal protector against tissue injuries by suppressing local renin-angiotensin system (RAS). This study aimed to explore the role of the vitamin D receptor (VDR) in the protection against muscle atrophy and the underlying mechanism. A cross-sectional study on participants (n = 1034) in Shanghai (China) was performed to analyze the association between vitamin D level and the risk of low muscle strength as well as to detect the circulating level of angiotensin II (Ang II). In animal studies, dexamethasone (Dex) was applied to induce muscle atrophy in wild-type (WT) and VDR-null mice, and the mice with the induction of muscle atrophy were treated with calcitriol for 10 days. The skeletal muscle cell line C2C12 and the muscle satellite cells were applied in in vitro studies. The increased risk of low muscle strength was correlated to a lower level of vitamin D (adjusted odds ratio [OR] 0.58) accompanied by an elevation in serum Ang II level. Ang II impaired the myogenic differentiation of C2C12 myoblasts as illustrated by the decrease in the area of myotubes and the downregulation of myogenic factors (myosin heavy chain [MHC] and myogenic differentiation factor D [MyoD]). The phenotype of muscle atrophy induced by Dex and Ang II was aggravated by VDR ablation in mice and in muscle satellite cells, respectively, and mediated by RAS and its downstream phosphatidylinositol 3-kinase/protein kinase B/forkhead box O1 (PI3K/Akt/FOXO1) signaling. Calcitriol treatment exhibited beneficial effects on muscle function as demonstrated by the increased weight-loaded swimming time, grip strength, and fiber area, and improved fiber type composition via regulating ubiquitin ligases and their substrates MHC and MyoD through suppressing renin/Ang II axis. Taken together, VDR protects against skeletal muscle atrophy by suppressing RAS. Vitamin D could be a potential agent for the prevention and treatment of skeletal muscle atrophy. © 2021 American Society for Bone and Mineral Research (ASBMR).

RGFP966 is protective against lipopolysaccharide-induced depressive-like behaviors in mice by inhibiting neuroinflammation and microglial activation

Depression is a prevalent mental disorder. However, its pathophysiological mechanism has still remained elusive, and a limited number of effective treatments have been presented. Recent studies have shown that neuroinflammation and microglial activation are involved in the pathogenesis of depression. Histone deacetylase 3 (HDAC3) has neurotoxic effects on several neuropathological conditions. The inhibition of HDAC3 has been reported to induce anti-inflammatory and antioxidant effects. RGFP966 is a highly selective inhibitor of HDAC3. This study aimed to investigate the antidepressant effect of RGFP966 on lipopolysaccharide (LPS)-induced depressive-like behaviors in mice and to explore its possible mechanism. Adult male C57BL/6J mice were utilized in this study. The LPS and RGFP966 were injected intraperitoneally daily for 5 days. The behavior tests were performed to elucidate the depression-like behaviors. Western blot, ELISA and immunofluorescence staining were used to study the HDAC3/TLR4/NLRP3 pathway-related proteins. The results of behavioral tests showed that RGFP966 could improve the LPS-induced depressive-like behaviors in mice. The results of Western blotting showed that RGFP966 treatment downregulated the expression levels of toll-like receptor 4 (TLR4), nucleotide-binding oligomerization domain-like receptor pyrin domain-containing-3 (NLRP3), caspase-1, and interleukin-1β (IL-1β) (P < 0.05). Furthermore, the results of immunofluorescence staining showed that RGFP966 treatment inhibited microglial activation in the hippocampus of mice (P < 0.01). These findings suggested that RGFP966 could effectively ameliorate LPS-induced depressive-like behaviors in mice by inhibiting neuroinflammation and microglial activation. The anti-inflammatory mechanism of RGFP966 might be related to the inhibition of the HDAC3/TLR4/NLRP3 signaling pathway. Therefore, inhibition of HDAC3 using RGFP966 could serve as a potential treatment strategy for depression.

Beneficial effects of running exercise on hippocampal microglia and neuroinflammation in chronic unpredictable stress-induced depression model rats

Running exercise has been shown to relieve symptoms of depression, but the mechanisms underlying the antidepressant effects are unclear. Microglia and concomitant dysregulated neuroinflammation play a pivotal role in the pathogenesis of depression. However, the effects of running exercise on hippocampal neuroinflammation and the number and activation of microglia in depression have not been studied. In this study, rats were subjected to chronic unpredictable stress (CUS) for 5 weeks followed by treadmill running for 6 weeks. The depressive-like symptoms of the rats were assessed with a sucrose preference test (SPT). Immunohistochemistry and stereology were performed to quantify the total number of ionized calcium-binding adapter molecule 1 (Iba1)⁺ microglia, and immunofluorescence was used to quantify the density of Iba1⁺/cluster of differentiation 68 (CD68)⁺ in subregions of the hippocampus. The levels of proinflammatory cytokines in the hippocampus were measured by qRT-PCR and ELISA. The results showed that running exercise reversed the decreased sucrose preference of rats with CUS-induced depression. In addition, CUS increased the number of hippocampal microglia and microglial activation in rats, but running exercise attenuated the CUS-induced increases in the number of microglia in the hippocampus and microglial activation in the dentate gyrus (DG) of the hippocampus. Furthermore, CUS significantly increased the hippocampal levels of inflammatory factors, and the increases in inflammatory factors in the hippocampus were suppressed by running exercise. These results suggest that the antidepressant effects of exercise may be mediated by reducing the number of microglia and inhibiting microglial activation and neuroinflammation in the hippocampus.

Salidroside Improves Chronic Stress Induced Depressive Symptoms Through Microglial Activation Suppression

Depression is a severe neurological disorder highly associated with chronic mental stress stimulation, which involves chronic inflammation and microglial activation in the central nervous system (CNS). Salidroside (SLDS) has been reported to exhibit anti-neuroinflammatory and protective properties on neurological diseases. However, the mechanism underlying the effect of SLDS on depressive symptoms has not been well elaborated. In the present study, the effects of SLDS on depressive behaviors and microglia activation in mice CNS were investigated. Behavioral tests, including Forced swimming test (FST), Open field test (OFT) and Morris water maze (MWM) revealed that SLDS treatment attenuated the depressive behaviors in stress mice. SLDS treatment significantly reduced the microglial immunoreactivity for both Iba-1 and CD68, characteristic of deleterious M1 phenotype in hippocampus of stress mice. Additionally, SLDS inhibited microglial activation involving the suppression of ERK1/2, P38 MAPK and p65 NF-κB activation and thus reduced the expression and release of neuroinflammatory cytokines in stress mice as well as in lipopolysaccharide (LPS)-induced primary microglia. Also, SLDS changed microglial morphology, attachment and reduced the phagocytic ability in LPS-induced primary microglia. The results demonstrated that SLDS treatment could improve the depressive symptoms caused by unpredictable chronic stress, indicating a potential therapeutic application of SLDS in depression treatment by interfering microglia-mediated neuroinflammation.

Nootkatone improves anxiety- and depression-like behavior by targeting hyperammonemia-induced oxidative stress in D-galactosamine model of liver injury

Acute or chronic liver injury is closely related to hyperammonemia, which will result in oxidative stress and damage to nerve cells, and these factors are vital to the development of anxiety and depression. In this study, the effect of Nootkatone (NKT) on the anxiety- and depression-like behavioral changes in mice induced by liver injury was investigated. Liver injury was induced by D-galactosamine (D-GalN; 350 mg/kg) three times a week for 4 weeks. NKT (5 mg/kg or 10 mg/kg) was given as co-treatment daily for 4 weeks. NKT (5 mg/kg) co-treatment remarkably ameliorates D-GalN-induced anxiety- and depression-like behaviors as evident from the results of sucrose preference test, forced swimming test, tail suspension test, and novelty suppressed feeding test. Results showed that NKT could induce an elevation in serum alanine transaminase and aspartate transaminase level, alleviate the oxidative stress induced by hyperammonemia through activating Keap1/Nrf2/HO-1 antioxidant pathways, decrease the expression of inducible nitric oxide synthase and NOX2 in hippocampus and prefrontal cortex, enhance the vitality of superoxide dismutase, catalase, and glutathione levels in serum, liver, and brain, and significantly reduce the generation of malondialdehyde. At the same time, NKT also reduces the level of ammonia in serum and brain and upgrades the activity of glutamine synthetase in the hippocampus and prefrontal cortex. Taken together, the present results suggested that NKT has a significant antidepressant effect through modulation of oxidative stress induced by D-GalN administration.

Agomelatine effects on fat-enriched diet induced neuroinflammation and depression-like behavior in rats

Growing evidence suggests that a high fat diet (HFD) induces oxidative stress on the central nervous system (CNS), which predisposes to mood disorders and neuroinflammation. In this study we postulated that in addition to improving mood, antidepressant therapy would reverse inflammatory changes in the brain of rats exposed to a HFD. To test our hypothesis, we measured the effect of the antidepressant agomelatine (AGO) on anxiety- and depressive-like behaviors, as well as on CNS markers of inflammation in rats rendered obese. Agomelatine is an agonist of the melatonin receptors MT1 and MT2 and an antagonist of the serotonin receptors 5HT2B and 5HT2C. A subset of rats was also treated with lipopolysaccharides (LPS) to determine how additional neuroinflammation alters behavior and affects the response to the antidepressant. Specifically, rats were subjected to a 14-week HFD, during which time behavior was evaluated twice, first at the 10th week prior to LPS and/or agomelatine, and then at the 14th week after a bi-weekly exposure to LPS (250 μg/kg) and daily treatment with agomelatine (40 mg/kg). Immediately after the second behavioral testing we measured the proinflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6) and interleukin 1 beta (IL-1β), markers of oxidative stress thiobarbituric acid reactive substances (TABRS), catalase (CAT) and glutathione peroxidase (GPx), the growth factor BDNF, as well as the apoptosis marker caspase-3. Our results show that a HFD induced an anxiety-like behavior in the open field test (OFT) at the 10th week, followed by a depressive-like behavior in the forced swim test (FST) at the 14th week. In the prefrontal and hippocampal cortices of rats exposed to a HFD we noted an overproduction of TNF-α, IL-6, IL-1β, and TABRS, together with an increase in caspase-3 activity. We also observed a decrease in BDNF, as well as reduced CAT and GPx activity in the same brain areas. Treatment with agomelatine reversed the signs of anxiety and depression, and decreased the cytokines (TNF-α, IL-6 and IL-1β), TABRS, as well as caspase-3 activity. Agomelatine also restored BDNF levels and the activity of antioxidant enzymes CAT and GPx. Our findings suggest that the anxiolytic/antidepressant effect of agomelatine in obese rats could result from a reversal of the inflammatory and oxidative stress brought about by their diet.

S-equol, a metabolite of dietary soy isoflavones, alleviates lipopolysaccharide-induced depressive-like behavior in mice by inhibiting neuroinflammation and enhancing synaptic plasticity

Systemic injection with lipopolysaccharide can lead to depressive-like behavior in experimental animals by inducing neuroinflammation and is considered to be a classic model of depression. S-equol is a major metabolite of dietary soy isoflavones with antioxidant and anti-inflammatory effects, and it has many beneficial effects on human health, including alleviation of menopausal symptoms, osteoporosis, cancer, obesity, chronic kidney disease, and cognitive dysfunction. A recent study reported that S-equol inhibited lipopolysaccharide-stimulated neuroinflammation in astrocytes. However, there is no research on the antidepressant-like effects of S-equol. Therefore, the present study was conducted to evaluate the antidepressant-like effects of S-equol in a lipopolysaccharide-induced depression model in mice and explore its underlying mechanisms. Our results demonstrated that treatment with S-equol (10, 20 and 40 mg kg-1) for 19 days markedly reversed the behavior of acute LPS (1.0 mg kg-1) treated mice in sucrose preference, tail suspension and forced swimming tests, exerting antidepressant-like effects. In addition, S-equol administration significantly decreased the levels of pro-inflammatory cytokines (tumor necrosis factor, interleukin-6, interleukin-10, interleukin-1β), increased the levels of 5-hydroxytryptamine and norepinephrine, and normalized the release of tryptophan and kynurenine in the hippocampi of lipopolysaccharide-treated mice. Moreover, treatment with S-equol significantly up-regulated the expression of synaptic plasticity-related proteins (phospho synapsin, synapsin, postsynaptic density-95) and down-regulated the toll-like receptor 4/nuclear factor kappa B signaling pathway in the hippocampi of lipopolysaccharide-treated mice. These findings demonstrated that S-equol significantly alleviated the depressive-like behavior induced by acute systemic injection of LPS, and its antidepressant action was related to mediation of neuroinflammation via the TLR4/NF-κB signaling pathway, normalization of the monoamine neurotransmitter levels, reversal of tryptophan metabolism dysfunction, and enhancement of synaptic plasticity. The current study provides insight into the potential of S-equol in the prevention of depression.

Human torpor: translating insights from nature into manned deep space expedition

During a long-duration manned spaceflight mission, such as flying to Mars and beyond, all crew members will spend a long period in an independent spacecraft with closed-loop bioregenerative life-support systems. Saving resources and reducing medical risks, particularly in mental heath, are key technology gaps hampering human expedition into deep space. In the 1960s, several scientists proposed that an induced state of suppressed metabolism in humans, which mimics 'hibernation', could be an ideal solution to cope with many issues during spaceflight. In recent years, with the introduction of specific methods, it is becoming more feasible to induce an artificial hibernation-like state (synthetic torpor) in non-hibernating species. Natural torpor is a fascinating, yet enigmatic, physiological process in which metabolic rate (MR), body core temperature (T_b ) and behavioural activity are reduced to save energy during harsh seasonal conditions. It employs a complex central neural network to orchestrate a homeostatic state of hypometabolism, hypothermia and hypoactivity in response to environmental challenges. The anatomical and functional connections within the central nervous system (CNS) lie at the heart of controlling synthetic torpor. Although progress has been made, the precise mechanisms underlying the active regulation of the torpor-arousal transition, and their profound influence on neural function and behaviour, which are critical concerns for safe and reversible human torpor, remain poorly understood. In this review, we place particular emphasis on elaborating the central nervous mechanism orchestrating the torpor-arousal transition in both non-flying hibernating mammals and non-hibernating species, and aim to provide translational insights into long-duration manned spaceflight. In addition, identifying difficulties and challenges ahead will underscore important concerns in engineering synthetic torpor in humans. We believe that synthetic torpor may not be the only option for manned long-duration spaceflight, but it is the most achievable solution in the foreseeable future. Translating the available knowledge from natural torpor research will not only benefit manned spaceflight, but also many clinical settings attempting to manipulate energy metabolism and neurobehavioural functions.

Implications of Oxidative Stress and Potential Role of Mitochondrial Dysfunction in COVID-19: Therapeutic Effects of Vitamin D

Due to its high degree of contagiousness and like almost no other virus, SARS-CoV-2 has put the health of the world population on alert. COVID-19 can provoke an acute inflammatory process and uncontrolled oxidative stress, which predisposes one to respiratory syndrome, and in the worst case, death. Recent evidence suggests the mechanistic role of mitochondria and vitamin D in the development of COVID-19. Indeed, mitochondrial dynamics contribute to the maintenance of cellular homeostasis, and its uncoupling involves pathological situations. SARS-CoV-2 infection is associated with altered mitochondrial dynamics with consequent oxidative stress, pro-inflammatory state, cytokine production, and cell death. Furthermore, vitamin D deficiency seems to be associated with increased COVID-19 risk. In contrast, vitamin D can normalize mitochondrial dynamics, which would improve oxidative stress, pro-inflammatory state, and cytokine production. Furthermore, vitamin D reduces renin–angiotensin–aldosterone system activation and, consequently, decreases ROS generation and improves the prognosis of SARS-CoV-2 infection. Thus, the purpose of this review is to deepen the knowledge about the role of mitochondria and vitamin D directly involved in the regulation of oxidative stress and the inflammatory state in SARS-CoV-2 infection. As future prospects, evidence suggests enhancing the vitamin D levels of the world population, especially of those individuals with additional risk factors that predispose to the lethal consequences of SARS-CoV-2 infection.

Phenol glycosides extract of Fructus Ligustri Lucidi attenuated depressive-like behaviors by suppressing neuroinflammation in hypothalamus of mice

Depression is partially caused by inflammation in central nervous system. This study investigated the ameliorative effects of phenol glycosides (PG) from Ligustrum lucidum Ait. (Oleaceae) on neuroinflammation and depressive-like behavior in mice hypothalamus as well as the molecular mechanism. Mice were administered with PG extract for 2 weeks prior to treatment with LPS. The mice treated with PG extract showed resistance to LPS-induced reduction in body weight and LPS-induced depressive-like behaviors shown by sucrose preference, tail suspension test, forced swimming test and open field test. LPS-induced activation of microglial cells and elevation in protein expression of inflammatory cytokines including IL-1β, RANTES and MCP-1 in hypothalamus of mice were abrogated by pre-treatment with PG extract. This extract down-regulated expression of TLR4, MyD88, NLRP3, renin and angiotensin II and decreased proportional area of Iba-1⁺ microglias in hypothalamus. Pre-treatment with PG extract inhibited LPS-triggered activation of CaSR/G_α11 signaling, stimulated 1-OHase expression in hypothalamus, and enhanced circulating 1,25(OH)₂ D₃ level. Overall, pre-treatment with PG extract ameliorated LPS-induced depressive-like behaviors by repressing neuroinflammation in mice hypothalamus which was attributed to its suppression on activation of microglia and production of inflammatory cytokines via acting on TLR4 pathway, CaSR and RAS cascade associated with improving vitamin D metabolism.

Major depression accompanied with inflammation and multiple cytokines alterations: Evidences from clinical patients to macaca fascicularis and LPS-induced depressive mice model

BACKGROUND

Inflammation progress has been consistently implicated in the pathophysiology of major depressive disorder (MDD). However, the underlying mechanism of inflammation and depressive symptoms still far from being fully elucidated. In addition, studies on emotional disorders could also benefit from model of the non-human primates. To explore the difference of serum multi-cytokines levels among the MDD patients and depressed macaca fascicularis as well as LPS-treated mice, thus may find the reliable potential biomarkers for MDD.

METHODS

Serum multi-cytokines levels among MDD patients (n = 44) and depressed macaca fascicularis (n = 6) together with controls (n = 22 for human, n = 6 for macaques) were detected by the Bio-Plex cytokines panel. Then five of these serum cytokines in LPS-treated mice were measured via ELISA. Furthermore, these cytokines protein expressions were validated by western blotting in three depression-related regions of LPS-treated mice.

RESULTS

Here, we found that MDD patients displayed increased concentration of 13 proinflammatory and anti-inflammatory cytokines accompanied with one decreased cytokine in peripheral serum. Meanwhile, the naturally occurring depression (NOD) macaca fascicularis merely exhibited elevated concentration of 4 peripheral cytokines (IL-6, IL-8, MCP-1, VEGF), which were in accordance with the outcomes of MDD patients. Importantly, the serum and brain tissues of LPS-treated mice also emerged similar cytokines alterations.

CONCLUSION

In summary, our findings strengthen the evidence that cytokines were associated with the depression, and the IL-6 and VEGF may as predictive biomarkers for novel diagnostic as well as therapeutic of depression. The hypothalamus may as a key brain region involve in the inflammatory related depressive-like behaviors.

Muscone Ameliorates LPS-Induced Depressive-Like Behaviors and Inhibits Neuroinflammation in Prefrontal Cortex of Mice

Depression is partially caused by inflammation in the central nervous system. Early study demonstrated that musk, glandular secretion from male musk deer, exerted an antidepressant-like effect. The aim of this study was to investigate if muscone, a bioactive ingredient in musk, could ameliorate neuroinflammation and depressive-like behaviors as well as explore the potential action mechanism. Mice were intraperitoneally (i.p.) injected with muscone for 2 weeks prior to administration of lipopolysaccharides (LPS, 1mg/kg, i.p.). Pre-treatment with muscone reversed the LPS-induced decrease in body weight within 24h and ameliorated depressive-like behaviors shown by sucrose preference, tail suspension test, and forced swimming test. LPS-induced activation of microglial cells and elevation in expression of inflammatory cytokines including IL-1β, RANTES, and MCP-1 in the prefrontal cortex of mice were effectively abrogated by muscone, which significantly down-regulated expression of TLR4, MyD88, Caspase-1, NLRP3, renin, and Ang II. In addition, treatment of BV2 microglia cells with muscone markedly attenuated the LPS-induced rise in protein expression of TLR4, Ang II, and IL-1β. This study revealed that muscone could ameliorate LPS-induced depressive-like behaviors by repressing neuroinflammation in the prefrontal cortex of mice caused by its suppression on microglia activation and production of inflammatory cytokines via acting on TLR4 pathway and RAS cascade.

Bifidobacterium animalis subsp. lactis A6 Alleviates Obesity Associated with Promoting Mitochondrial Biogenesis and Function of Adipose Tissue in Mice

Probiotics are widely known for their health benefits. Mitochondrial dysfunction is related to obesity. The aim of this study was to illuminate whether Bifidobacterium animalis subsp. lactis A6 (BAA6) could improve obesity due to increased mitochondrial biogenesis and function of adipose tissues. Four-week-old male C57BL/6 mice were fed with a high-fat diet (HFD) for 17 weeks. For the final eight weeks, the HFD group was divided into three groups including HFD, HFD with BAA6 (HFD + BAA6 group), and HFD with Akkermansia muciniphila (AKK) (HFD + AKK group as positive control). The composition of the microbiota, serum lipopolysaccharides (LPS), and mitochondrial biosynthesis and function of epididymal adipose tissues were measured. Compared with the HFD group, body weight, relative fat weight, the relative abundance of Oscillibacter and Bilophila, and serum LPS were significantly decreased in the HFD + BAA6 and HFD + AKK groups (p < 0.05). Furthermore, the addition of BAA6 and AKK increased the expression of peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α) (by 21.53- and 18.51-fold), estrogen-related receptor α (ERRα) (by 2.83- and 1.24-fold), and uncoupling protein-1 (UCP-1) (by 1.51- and 0.60-fold) in epididymal adipose tissues. Our results suggest that BAA6 could improve obesity associated with promoting mitochondrial biogenesis and function of adipose tissues in mice.

An Update of Palmitoylethanolamide and Luteolin Effects in Preclinical and Clinical Studies of Neuroinflammatory Events

The inflammation process represents of a dynamic series of phenomena that manifest themselves with an intense vascular reaction. Neuroinflammation is a reply from the central nervous system (CNS) and the peripheral nervous system (PNS) to a changed homeostasis. There are two cell systems that mediate this process: the glia of the CNS and the lymphocites, monocytes, and macrophages of the hematopoietic system. In both the peripheral and central nervous systems, neuroinflammation plays an important role in the pathogenesis of neurodegenerative diseases, such as Parkinson’s and Alzheimer’s diseases, and in neuropsychiatric illnesses, such as depression and autism spectrum disorders. The resolution of neuroinflammation is a process that allows for inflamed tissues to return to homeostasis. In this process the important players are represented by lipid mediators. Among the naturally occurring lipid signaling molecules, a prominent role is played by the N-acylethanolamines, namely N-arachidonoylethanolamine and its congener N-palmitoylethanolamine, which is also named palmitoylethanolamide or PEA. PEA possesses a powerful neuroprotective and anti-inflammatory power but has no antioxidant effects per se. For this reason, its co-ultramicronization with the flavonoid luteolin is more efficacious than either molecule alone. Inhibiting or modulating the enzymatic breakdown of PEA represents a complementary therapeutic approach to treating neuroinflammation. The aim of this review is to discuss the role of ultramicronized PEA and co-ultramicronized PEA with luteolin in several neurological diseases using preclinical and clinical approaches.

Paricalcitol improves experimental autoimmune encephalomyelitis (EAE) by suppressing inflammation via NF-κB signaling

Multiple sclerosis (MS) is known as an autoimmune disease in the central nervous system (CNS) characterized by motor deficits, pain, fatigue, cognitive impairment, and sensory and visual dysfunction. MS is considered to be resulted from significant inflammatory response. Paricalcitol (Pari) is a vitamin D2 analogue, which has been indicated to show anti-inflammatory activities in kidney and heart diseases. In the present study, if Pari could ameliorate the experimental autoimmune encephalomyelitis (EAE) was investigated. Here, the C57BL/6 mice were immunized using myelin oligodendrocyte glycoprotein 35-55 (MOG_35-55). Subsequently, Pari was intraperitoneally injected into the mice. As for in vitro analysis, RAW264.7 and Jurkat cells were incubated with Pari together with corresponding stimulus. The results indicated that Pari administration reduced the paralytic severity, neuropathology and apoptosis in MOG-treated mice compared to the MOG single group. Pari also exhibited a significantly inhibitory effect on immune cell infiltration, glial cell activation, expression of pro-inflammatory factors and the activation of nuclear factor κB (NF-κB). The expression of pro-inflammatory regulators and the translocation of NF-κB from cytoplasm into nuclear in RAW264.7 and Jurkat cells under specific stimulation was clearly down-regulated by Pari incubation. Furthermore, we found that suppressing NF-κB with its inhibitor combined with Pari could further reduce the expression of pro-inflammatory factors and associated proteins. These data illustrated that Pari could diminish MOG-triggered EAE, as well as macrophages and T cells activation through blocking NF-κB activation. Collectively, Pari might have therapeutic effects in mouse models with MS.

Repetitive Transcranial Magnetic Stimulation Elicits Antidepressant- and Anxiolytic-like Effect via Nuclear Factor-E2-related Factor 2-mediated Anti-inflammation Mechanism in Rats

Repetitive transcranial magnetic stimulation (rTMS) treatment is widely accepted as an evidence-based treatment option for depression and anxiety. However, the underlying mechanism of this treatment maneuver has not been clearly understood. The chronic unpredictable mild stress (CUMS) procedure was used to establish depression and anxiety-like behavior in rats. The rTMS was performed with a commercially available stimulator for seven consecutive days, and then depression and anxiety-like behaviors were subsequently measured. The expression of nuclear factor-E2-related factor 2 (Nrf2) was measured by western-blot, and the level of tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), interleukin-1β (IL-1β), and interleukin-6 (IL-6) was measured with Enzyme-linked immunesorbent assay (ELISA) analyzing kits. Furthermore, a small interfering RNA was employed to knockdown Nrf2, after which the neurobehavioral assessment, Nrf2 nuclear expression, and the amount of inflammation factors were evaluated. Application of rTMS exhibited a significant antidepressant and anxiolytic-like effect, which was associated with the increased Nrf2 nuclear translocation and reduced level of TNF-α, iNOS, IL-1β, and IL-6 in the hippocampus. Following Nrf2 silencing, the antidepressant and anxiolytic-like effect produced by rTMS was abolished. Moreover, the elevated Nrf2 nuclear translocation, and the reduced production of TNF-α, iNOS, IL-1β, and IL-6 in hippocampus mediated by rTMS, were reversed by Nrf2 knockdown. Together, these results reveal that the Nrf2-induced anti-inflammation effect is crucial in regulating antidepressant-related behaviors produced by rTMS.

Gut microbiota-brain axis in depression: The role of neuroinflammation

Major depressive disorder (MDD) is a psychiatric condition that affects a large number of people in the world, and the treatment existents do not work for all individuals affected. Thus, it is believed that other systems or pathways which regulate brain networks involved in mood regulation and cognition are associated with MDD pathogenesis. Studies in humans and animal models have been shown that in MDD there are increased levels of inflammatory mediators, including cytokines and chemokines in both periphery and central nervous system (CNS). In addition, microglial activation appears to be a key event that triggers changes in signaling cascades and gene expression that would be determinant for the onset of depressive symptoms. Recent researches also point out that changes in the gut microbiota would lead to a systemic inflammation that in different ways would reach the CNS modulating inflammatory pathways and especially the microglia, which could influence responses to treatments. Moreover, pre- and probiotics have shown antidepressant responses and anti-inflammatory effects. This review will focus on studies that show the relationship of inflammation with the gut microbiota-brain axis and its relation with MDD.

Fucoidan exerts antidepressant-like effects in mice via regulating the stability of surface AMPARs

The inflammatory hypothesis is one of the most important mechanisms of depression. Fucoidan is a bioactive sulfated polysaccharide abundant in brown seaweeds with anti-inflammatory activity. However, the antidepressant effects of fucoidan on chronic stress-induced depressive-like behaviors have not been well elucidated. Here, we used two different depressive-like mouse models, lipopolysaccharide (LPS) and chronic restraint stress (CRS) models, to explore the detailed molecular mechanism underlying its antidepressant-like effects in C57BL/6J mice by combining multiple behavioral, molecular and immunofluorescence experiments. Adenovirus-mediated overexpression of caspase-1 and pharmacological inhibitors were also used to clarify the antidepressant mechanisms of fucoidan. We found that acute administration of fucoidan did not produce antidepressant effects in the tail suspension test (TST) and forced swim test (FST). Interestingly, chronic fucoidan administration not only dose-dependently reduced stress-induced depressive-like behaviors in the TST, FST, sucrose preference test (SPT), and novelty-suppressed feeding test (NSFT), but also alleviated the downregulation of brain-derived neurotrophic factor (BDNF)-dependent synaptic plasticity via inhibiting caspase-1-mediated inflammation in the hippocampus of mice. Moreover, fucoidan significantly ameliorated behavioral and synaptic plasticity abnormalities in the overexpression of caspase-1 in the hippocampus of mice. Furthermore, blocking BDNF abolished the antidepressant-like effects of fucoidan in mice. Therefore, our findings clearly indicate that fucoidan provides a potential supplementary noninvasive treatment for depression by inhibition of hippocampal inflammation.

Effects of vitamin D and paricalcitol on epileptogenesis and behavioral properties of WAG/Rij rats with absence epilepsy

AIM

Vitamin D (Vit D) has been considered as a neurosteroid and has a pivotal role in neuroprotection including epilepsy. Vit D regulator acts via a Vit D receptor (VDR). WAG/Rij rats have a genetically epileptic model of absence epilepsy with comorbidity of depression. The aim of the present study was to investigate the effect of Vit D and paricalcitol (PRC) on WAG/Rij rats.

MATERIAL AND METHODS

Sixty-three male WAG/Rij rats and seven male Wistar rats were used. The effects of acute and chronic treatment with Vit D (5.000 and 60.000 IU/kg, i.p) and PRC (0.5, 5 and 10 μg/kg, i.p) on absence seizures, and related psychiatric comorbidity were investigated in WAG/Rij rats. Depression-like behavior was assayed by using the forced swimming test (FST) and; anxiety-like behavior by using the open field test (OFT).

RESULTS

Acute Vit D treatments (5.000 and 60.000 IU/kg) similarly reduced the number and duration of spike-wave discharges (SWDs) and showed anxiolytic-antidepressive effect whereas there were no significant changes in other measured parameters between the daily and the bolus dose of Vit D. Acute administration of PRC (0.5, 5 and 10 μg/kg) showed anti-convulsive and anxiolytic-antidepressive effect. The dose (0.5 μg/kg) of PRC was the most effective dose. Chronic treatment was more effective than acute therapy in all parameters.

CONCLUSION

The results of the present study demonstrate that Vit D and PRC have antiepileptic and anxiolytic-antidepressive effects on the absence epilepsy in WAG/Rij rats.