Minocycline Ameliorates Depressive-Like Behavior and Demyelination Induced by Transient Global Cerebral Ischemia by Inhibiting Microglial Activation

Microglial activation in the medial prefrontal cortex after remote fear recall participates in the regulation of auditory fear extinction

Excessive or inappropriate fear responses can lead to anxiety-related disorders, such as post-traumatic stress disorder (PTSD). Studies have shown that microglial activation occurs after fear conditioning and that microglial inhibition impacts fear memory. However, the role of microglia in fear memory recall remains unclear. In this study, we investigated the activated profiles of microglia after the recall of remote-cued fear memory and the role of activated microglia in the extinction of remote-cued fear in adult male C57BL/6 mice. The results revealed that the expression of the microglia marker Iba1 increased in the medial prefrontal cortex (mPFC) at 10 min and 1 h following remote-cued fear recall, which was accompanied by amoeboid morphology. Inhibiting microglial activation through PLX3397 treatment before remote fear recall did not affect recall, reconsolidation, or regular extinction but facilitated recall-extinction and mitigated spontaneous recovery. Moreover, our results demonstrated reduced co-expression of Iba1 and postsynaptic density protein 95 (PSD95) in the mPFC, along with decreases in the p-PI3K/PI3K ratio, p-Akt/Akt ratio, and KLF4 expression after PLX3397 treatment. Our results suggest that microglial activation after remote fear recall impedes fear extinction through the pruning of synapses in the mPFC, accompanied by alterations in the expression of the PI3K/AKT/KLF4 pathway. This finding can help elucidate the mechanism involved in remote fear extinction, contributing to the theoretical foundation for the intervention and treatment of PTSD.

Hyperforin ameliorates neuroinflammation and white matter lesions by regulating microglial VEGFR2 /SRC pathway in vascular cognitive impairment mice

AIM

To explore the neuroprotective potential of hyperforin and elucidate its underlying molecular mechanisms involved in its therapeutic effects against vascular cognitive impairment (VCI).

METHODS

The active compounds and possible targets of Hypericum perforatum L. that may be effective against VCI were found by network pharmacology in this research. We utilized bilateral common carotid artery occlusion (BCCAO) surgery to induce a VCI mouse model. Morris water maze (MWM) and Y-maze tests were used to assess VCI mice's cognitive abilities following treatment with hyperforin. To evaluate white matter lesions (WMLs), we utilized Luxol fast blue (LFB) stain and immunofluorescence (IF). Neuroinflammation was assessed using IF, western blot (WB), and enzyme-linked immunosorbent assay (ELISA). The effects of hyperforin on microglia were investigated by subjecting the BV2 microglial cell line to oxygen-glucose deprivation/reperfusion (OGD/R) stimulation. The expressions of VEGFR2 , p-SRC, SRC, VEGFA, and inflammatory markers including IL-10, IL-1β, TNF-α, and IL-6 were subsequently assessed.

RESULTS

The VEGFR2 /SRC signaling pathway is essential for mediating the protective properties of hyperforin against VCI according to network pharmacology analysis. In vivo findings demonstrated that hyperforin effectively improved BCCAO-induced cognitive impairment. Furthermore, staining results showed that hyperforin attenuated WMLs and reduced microglial activation in VCI mice. The hyperforin treatment group's ELISA results revealed a substantial decrease in IL-1β, IL-6, and TNF-α levels. According to the results of in vitro experiments, hyperforin decreased the release of pro-inflammatory mediators (TNF-α, IL-6, and IL-1β) and blocked microglial M1-polarization by modulating the VEGFR2 /SRC signaling pathway.

CONCLUSION

Hyperforin effectively modulated microglial M1 polarization and neuroinflammation by inhibiting the VEGFR2 /SRC signaling pathways, thereby ameliorating WMLs and cognitive impairment in VCI mice.

Integrative Analyses of scRNA-seq, Bulk mRNA-seq, and DNA Methylation Profiling in Depressed Suicide Brain Tissues

BACKGROUND

Suicidal behaviors have become a serious public health concern globally due to the economic and human cost of suicidal behavior to individuals, families, communities, and society. However, the underlying etiology and biological mechanism of suicidal behavior remains poorly understood.

METHODS

We collected different single omic data, including single-cell RNA sequencing (scRNA-seq), bulk mRNA-seq, DNA methylation microarrays from the cortex of Major Depressive Disorder (MDD) in suicide subjects' studies, as well as fluoxetine-treated rats brains. We matched subject IDs that overlapped between the transcriptome dataset and the methylation dataset. The differential expression genes and differentially methylated regions were calculated with a 2-group comparison analysis. Cross-omics analysis was performed to calculate the correlation between the methylated and transcript levels of differentially methylated CpG sites and mapped transcripts. Additionally, we performed a deconvolution analysis for bulk mRNA-seq and DNA methylation profiling with scRNA-seq as the reference profiles.

RESULTS

Difference in cell type proportions among 7 cell types. Meanwhile, our analysis of single-cell sequence from the antidepressant-treated rats found that drug-specific differential expression genes were enriched into biological pathways, including ion channels and glutamatergic receptors.

CONCLUSIONS

This study identified some important dysregulated genes influenced by DNA methylation in 2 brain regions of depression and suicide patients. Interestingly, we found that oligodendrocyte precursor cells (OPCs) have the most contributors for cell-type proportions related to differential expression genes and methylated sites in suicidal behavior.

Minocycline in depression not responding to first-line therapy: A systematic review and meta-analysis

BACKGROUND

Major depressive disorder is often resistant to first-line treatment, with around 30% failing to respond to traditional therapy. Treatment-resistant depression results in prolonged hospitalization and healthcare costs. Anti-inflammatory drugs have shown promising results in depression not responding to initial therapy. Minocycline has anti-inflammatory properties and crosses the blood-brain barrier. It has demonstrated varied results in several randomized controlled trials (RCTs).

METHODS

We assessed the efficacy of minocycline compared to placebo in depression not responding to one first-line antidepressant via a systematic review and meta-analysis. We performed a comprehensive literature search across PubMed, Cochrane, and Scopus for RCTs. We visualized the results using forest plots and drapery plots. We assessed and explored heterogeneity using I2, prediction interval, and meta-regression. Then, we rated the certainty of the evidence.

RESULTS

Four RCTs revealed a non-significant difference in depression severity [-3.93; 95% CI: -16.14 to 8.28], rate of response [1.15; 0.33-4.01], and rate of remission [0.94; 0.44-2.01]. However, the reduction in depression severity is significant at a trend of P < .1. The high between-study heterogeneity (I2 = 78%) for depression severity could be answered by meta-regression (P = .02) for the duration of therapy.

CONCLUSION

There is no significant difference with minocycline compared to placebo for depression not responding to first-line antidepressant therapy. However, the treatment response varies with treatment duration and patients' neuroinflammatory state. Thus, larger and longer RCTs, especially in diverse disease subgroups, are needed for further insight. This is needed to allow greater precision medicine in depression and avoid elevated healthcare expenditure associated with hit-and-trial regimens.

REGISTRATION

CRD42023398476 (PROSPERO).

Ferroptosis-related genes as diagnostic markers for major depressive disorder and their correlations with immune infiltration

Background

Major depression disorder (MDD) is a devastating neuropsychiatric disease, and one of the leading causes of suicide. Ferroptosis, an iron-dependent form of regulated cell death, plays a pivotal role in numerous diseases. The study aimed to construct and validate a gene signature for diagnosing MDD based on ferroptosis-related genes (FRGs) and further explore the biological functions of these genes in MDD.

Methods

The datasets were downloaded from the Gene Expression Omnibus (GEO) database and FRGs were obtained from the FerrDb database and other literatures. Least absolute shrinkage and selection operator (LASSO) regression and stepwise logistic regression were performed to develop a gene signature. Receiver operating characteristic (ROC) curves were utilized to assess the diagnostic power of the signature. Gene ontology (GO) enrichment analysis was used to explore the biological roles of these diagnostic genes, and single sample gene set enrichment analysis (ssGSEA) algorithm was used to evaluate immune infiltration in MDD. Animal model of depression was constructed to validate the expression of the key genes.

Results

Eleven differentially expressed FRGs were identified in MDD patients compared with healthy controls. A signature of three FRGs (ALOX15B, RPLP0, and HP) was constructed for diagnosis of MDD. Afterwards, ROC analysis confirmed the signature's discriminative capacity (AUC = 0.783, 95% CI = 0.719-0.848). GO enrichment analysis revealed that the differentially expressed genes (DEGs) related to these three FRGs were mainly involved in immune response. Furthermore, spearman correlation analysis demonstrated that these three FRGs were associated with infiltrating immune cells. ALOX15B and HP were significantly upregulated and RPLP0 was significantly downregulated in peripheral blood of the lipopolysaccharide (LPS)-induced depressive model.

Conclusion

Our results suggest that the novel FRG signature had a good diagnostic performance for MDD, and these three FRGs correlated with immune infiltration in MDD.

Lower 25-hydroxyvitamin D is associated with severer white matter hyperintensity and cognitive function in patients with non-disabling ischemic cerebrovascular events

OBJECTIVES

This study aimed to investigate the potential correlations among serum 25-hydroxyvitamin D [25(OH)D] levels, white matter hyperintensity (WMH) and cognitive function in patients with non-disabling ischemic cerebrovascular events (NICE).

METHODS

This was a prospective investigation of 160 NICE patients with age of 40 years or older. Cognitive function was evaluated by the Montreal Cognitive Assessment (MoCA). White matter lesions were evaluated by WMH using Fazekas scores. Spearman correlation analysis and linear regression models were used to identify the associations between serum 25(OH)D levels and cognitive function. Binary logistic regression analysis models were used to evaluate the predictable value of serum 25(OH)D levels and WMH for cognitive impairment.

RESULTS

Patients with inadequate 25(OH)D levels had lower MoCA score (P=0.008), and a higher proportion of severe WMH (P=0.043). Spearman correlation analysis demonstrated that serum 25(OH)D concentrations were positively associated with MoCA score (rs=0.185, P=0.019) while negatively related to the proportion of severe WMH (sWMH) (rs=-0.166, P=0.036).The association between 25(OH)D concentrations and MoCA score remained significant in linear regression (adjusted β=0.012, 95%CI:0.001-0.203).Adjusted binary logistic regression analysis showed that the odds ratio of cognitive impairment with insufficient 25(OH)D concentration was 5.038 (95%CI:1.154-21.988) compared with the sufficient group and the sWMH (OR=2.728, 95%CI:1.230-6.051) was identified as an independent risk factor for cognitive decline in NICE patients.

CONCLUSION

Serum 25(OH)D levels and white matter lesions were independently and significantly associated with cognitive impairment in NICE patients.

The mechanisms of minocycline in alleviating ischemic stroke damage and cerebral ischemia-reperfusion injury

Stroke is a group of diseases resulting from cerebral vascular rupture or obstruction and subsequent brain blood circulation disorder, leading to rapid neurological deficits. Ischemic stroke accounts for the majority of all stroke cases. The current treatments for ischemic stroke mainly include t-PA thrombolytic therapy and surgical thrombectomy. However, these interventions aimed at recanalizing cerebral vessels can paradoxically lead to ischemia-reperfusion injury, which exacerbates the severity of brain damage. Minocycline, a semi-synthetic tetracycline antibiotic, has been shown to possess a wide range of neuroprotective effects independent of its antibacterial activity. Here we summarize the mechanisms underlying the protective effects of minocycline against cerebral ischemia-reperfusion injury based on the pathogenesis of cerebral ischemia-reperfusion injury, including its modulation of oxidative stress, inflammatory response, excitotoxicity, programmed cell death and blood-brain barrier injury, and also introduce the role of minocycline in alleviating stroke-related complications, in order to provide a theoretical basis for the clinical application of minocycline in cerebral ischemia-reperfusion injury.

Inhibiting microglia exacerbates the early effects of cuprizone in males in a rat model of multiple sclerosis, with no effect in females

Hyper-activity of the brain's innate immune cells, microglia, is a hallmark of multiple sclerosis (MS). However, it is not clear whether this involvement of microglia is beneficial or detrimental or whether manipulating microglial activity may be therapeutic. We investigated if inhibiting microglial activity with minocycline prevents the early changes in oligodendrocyte and myelin-related markers associated with a demyelinating challenge in adult female and male rats. Cuprizone reduced the expression of myelin and oligodendrocyte genes in both females and males, reflective of cuprizone intoxication and the early phases demyelination, and reduced the number of oligodendrocytes in the corpus callosum. However, we see notable differences in the role for microglia in this response between females and males. In males, myelin and oligodendrocyte genes, as well as oligodendrocytes were also reduced by minocycline treatment; an effect that was not seen in females. In males, but not females, early changes in oligodendrocyte and myelin-related genes were associated with microglial proliferation in corpus callosum, and this increase was reversed by minocycline. These data indicate sex-specific effects of inhibiting microglia on the early changes leading to demyelination in an MS model and suggest microglia may play a key role in myelin stability in males but not in females. This highlights a strong need for sex-specific understanding of disease development in MS and suggest that treatments targeting microglia may be more effective in males than in females due to differing mechanisms of disease progression.

Global Cerebral Ischemia-induced Depression Accompanies Alteration of Neuronal Excitability in the Infralimbic Cortex Layer 2/3 Pyramidal Neurons

Cerebral ischemia can lead to a range of sequelae, including depression. The pathogenesis of depression involves neuronal change of the medial prefrontal cortex (mPFC). However, how cerebral ischemia-induced changes manifest across subregions and layers of the mPFC is not well understood. In this study, we induced cerebral ischemia in mice via transient bilateral common carotid artery occlusion (tBCCAO) and observed depressive-like behavior. Using whole-cell patch clamp recording, we identified changes in the excitability of pyramidal neurons in the prelimbic cortex (PL) and infralimbic cortex (IL), the subregions of mPFC. Compared to sham control mice, tBCCAO mice showed significantly reduced neuronal excitability in IL layer 2/3 but not layer 5 pyramidal neurons, accompanied by increased rheobase current and decreased input resistance. In contrast, no changes were observed in the excitability of PL layer 2/3 and layer 5 pyramidal neurons. Our results provide a new direction for studying the pathogenesis of depression following ischemic damage by showing that cerebral ischemia induces subregion- and layer-specific changes in the mPFC pyramidal neurons.

Ramelteon improves blood-brain barrier of focal cerebral ischemia rats to prevent post-stroke depression via upregulating occludin

Post-stroke depression (PSD) negatively affects the prognosis of post-stroke animals. Ramelteon has neuroprotection for chronic ischemia animals, but the effect and the biological mechanism of it on PSD is still unclear. This study explored the effects of ramelteon with prophylactic administration on blood-brain barrier in rats with middle cerebral artery occlusion (MCAO) and the oxygen-glucose deprivation/reperfusion (OGD/R) bEnd.3 cells and found that ramelteon pretreatment improved the depressive-like behaviors and decreased infarct area in MCAO rats. Also, this study found ramelteon pretreatment improved viability and inhibited permeability in OGD/R cells. In addition, this study found that MCP-1, TNF-α, and IL-1 levels were raised in the MCAO rats and that occludin protein and mRNA levels were decreased in the MCAO and the OGD/R models, while the Egr-1 level was up-regulated. All of these were antagonized by ramelteon pretreatment. In addition, overexpression of Egr-1 could reverse the effect of 100nM ramelteon pretreatment on FITC and occludin levels in OGD/R cells. In short, this study has demonstrated that the protective effect on PSD of ramelteon pretreatment on MCAO rats is related to the development of BBB permeability and that ramelteon regulates occludin to protect the BBB by inhibiting Egr-1.

Ebselen alleviates white matter lesions and improves cognitive deficits by attenuating oxidative stress via Keap1/Nrf2 pathway in chronic cerebral hypoperfusion mice

Oxidative stress is crucial in cerebral white matter lesions (WMLs) induced by chronic cerebral hypoperfusion. Therefore, ameliorating oxidative damage is considered to be a beneficial strategy for the treatment of WMLs. Ebselen (EbSe), a small lipid organoselenium compound, its lipid peroxidation activity is mediated through the glutathione peroxidase-mimetic properties. This study aimed to investigate the role of EbSe in WMLs after bilateral common carotid artery stenosis (BCAS). The BCAS model can moderately reduce cerebral blood flow, and mimics white matter damage caused by chronic cerebral hypoperfusion or small vessel disease. Laser Speckle Contrast Imaging (LSCI) was used to monitor the cerebral blood flow of mice. The spatial learning and memory were tested by using the eight-arm maze. LFB staining was used to detect demyelination. The expression of MBP, GFAP and Iba1 was assayed by immunofluorescence. The demyelination was assessed by Transmission Electron Microscope (TEM). The activities of MDA, SOD and GSH-Px were detected by assay kits. The mRNA levels of SOD, GSH-Px and HO-1 was detected by realtime PCR. The activation of the Nrf2/ARE pathway and the expression of SOD, GSH-Px and HO-1was assessed by Western blot. EbSe ameliorated cognitive deficits and white matter lesions induced by bilateral common carotid artery stenosis (BCAS). The expression of GFAP and Iba1 was decreased in the corpus callosum of BCAS mice after EbSe treatment. Moreover, EbSe alleviated the level of MDA by elevating the expression and mRNA of SOD, GSH-Px and HO-1 in BCAS mice. Furthermore, EbSe promoted the dissociation of the Keap1/Nrf2 complex, resulting in the accumulation of Nrf2 in the nucleus. This study demonstrates a favorable effect of EbSe on cognitive impairment in a chronic cerebral hypoperfusion model, and the improvement of EbSe's antioxidant property is mediated by Keap1/Nrf2 pathway.

Effect of Minocycline on Depressive Symptoms in Patients With Treatment-Resistant Depression: A Randomized Clinical Trial

IMPORTANCE

Insufficient treatment response and resulting chronicity constitute a major problem in depressive disorders. Remission rates range as low as 15% to 40% and treatment-resistant depression (TRD) is associated with low-grade inflammation, suggesting anti-inflammatory interventions as a rational treatment strategy. Minocycline, which inhibits microglial activation, represents a promising repurposing candidate in the treatment of TRD.

OBJECTIVE

To determine whether 6 weeks of minocycline as add-on to antidepressant treatment as usual can significantly reduce depressive symptoms in patients with TRD.

DESIGN, SETTING, AND PARTICIPANTS

The study was conducted in Germany and designed as a multicenter double-blind randomized clinical trial (RCT) of 200 mg/d minocycline treatment over a course of 6 weeks with a 6-month follow-up. Participants were recruited from January 2016 to August 2020 at 9 university hospitals that served as study sites. Key inclusion criteria were a diagnosis of major depressive disorder (according to Diagnostic and Statistical Manual of Mental Disorders [Fifth Edition] criteria), severity of depressive symptoms on the Hamilton Depression Rating Scale (HAMD-17) greater than or equal to 16 points, aged 18 to 75 years, body mass index 18 to 40, Clinical Global Impression Scale (CGI-S) greater than or equal to 4, failure to adequately respond to an initial antidepressant standard medication as per Massachusetts General Hospital Antidepressant Treatment History Questionnaire, and stable medication for at least 2 weeks. A total of 258 patients were screened, of whom 173 were randomized and 168 were included into the intention-to-treat population. Statistical analysis was performed from April to November 2020.

INTERVENTIONS

Participants were randomized (1:1) to receive adjunct minocycline (200 mg/d) or placebo for 6 weeks.

MAIN OUTCOMES AND MEASURES

Primary outcome measure was the change in Montgomery-Åsberg Depression Rating Scale (MADRS) score from baseline to week 6 analyzed by intention-to-treat mixed model repeated measures. Secondary outcome measures were response, remission, and various other clinical rating scales.

RESULTS

Of 173 eligible and randomized participants (84 randomized to minocycline and 89 randomized to placebo), 168 formed the intention-to-treat sample (79 [47.0%] were women, 89 [53.0%] were men, 159 [94.6%] were White, 9 [6.4%] were of other race and ethnicity, including Asian and unknown ethnicity), with 81 in the minocycline group and 87 in the placebo group. The mean (SD) age was 46.1 (13.1) years, and the mean (SD) MADRS score at baseline was 26.5 (5.0). There was no difference in rates of completion between the minocycline (83.3% [70 of 81]) and the placebo group (83.1% [74 of 87]). Minocycline treatment did not alter the course of depression severity compared with placebo as assessed by a decrease in MADRS scores over 6 weeks of treatment (1.46 [-1.04 to 3.96], P = .25). Minocycline treatment also exhibited no statistically significant effect on secondary outcomes.

CONCLUSIONS AND RELEVANCE

In this large randomized clinical trial with minocycline at a dose of 200 mg/d added to antidepressant treatment as usual for 6 weeks, minocycline was well tolerated but not superior to placebo in reducing depressive symptoms in patients with TRD. The results of this RCT emphasize the unmet need for therapeutic approaches and predictive biomarkers in TRD.

TRIAL REGISTRATION

EU Clinical Trials Register Number: EudraCT 2015-001456-29.

Microglia Involves in the Immune Inflammatory Response of Poststroke Depression: A Review of Evidence

Poststroke depression (PSD) does not exist before and occurs after the stroke. PSD can appear shortly after the onset of stroke or be observed in the weeks and months after the acute or subacute phase of stroke. The pathogenesis of PSD is unclear, resulting in poor treatment effects. With research advancement, immunoactive cells in the central nervous system, particularly microglia, play a role in the occurrence and development of PSD. Microglia affects the homeostasis of the central nervous system through various factors, leading to the occurrence of depression. The research progress of microglia in PSD has been summarized to review the evidence regarding the pathogenesis and treatment target of PSD in the future.

Depressive-like behaviors induced by chronic cerebral hypoperfusion associate with a dynamic change of GABAB1/B2 receptors expression in hippocampal CA1 region

Cerebral ischemia could induce depressive-like behaviors; however, the alteration of gamma-aminobutyric acid receptors type B (GABA_B) receptors in these pathological processes has not been extensively investigated. The aim of the current study was to document the behavioral change and the alteration of GABA_B receptors in chronic cerebral hypoperfusion. The permanent occlusion of the bilateral common carotid arteries (two-vessel occlusion, 2VO) was performed to induce chronic cerebral ischemia (CCH). The depressive-like behaviors were evaluated with sucrose preference test, novelty suppress feeding test as well as forced swim test at 4, 8, and 12 weeks after the 2VO surgery. The total, surface and intracellular expressions of GABA_B subunit 1 (GABA_B1) and subunit 2 (GABA_B2) in hippocampal CA1 were quantified by western blot. The depressive-like behaviors were observed in rats suffered from 4, 8, and 12 weeks 2VO in sucrose preference test, novelty suppress feeding test and forced swim test. In addition, the surface and total expression of GABA_B1 in CA1 was reduced at 4 weeks after 2VO rather than 8 or 12 weeks. While the surface and total expression of GABA_B2 in CA1 was decreased throughout the ischemia timeline (4, 8, and 12 weeks). Taken together, our findings suggested the potential roles of GABA_B1 and GABA_B2 subunits involved in depressive-like behaviors caused by chronic cerebral hypoperfusion.

Vascular cognitive impairment and dementia: An early career researcher perspective

The field of vascular contributions to cognitive impairment and dementia (VCID) is evolving rapidly. Research in VCID encompasses topics aiming to understand, prevent, and treat the detrimental effects of vascular disease burden in the human brain. In this perspective piece, early career researchers (ECRs) in the field provide an overview of VCID, discuss past and present efforts, and highlight priorities for future research. We emphasize the following critical points as the field progresses: (a) consolidate existing neuroimaging and fluid biomarkers, and establish their utility for pharmacological and non-pharmacological interventions; (b) develop new biomarkers, and new non-clinical models that better recapitulate vascular pathologies; (c) amplify access to emerging biomarker and imaging techniques; (d) validate findings from previous investigations in diverse populations, including those at higher risk of cognitive impairment (e.g., Black, Hispanic, and Indigenous populations); and (e) conduct randomized controlled trials within diverse populations with well-characterized vascular pathologies emphasizing clinically meaningful outcomes.

Reduced myelin density in unmedicated major depressive disorder: An inhomogeneous magnetization transfer MRI study

OBJECTIVES

To detect the whole-brain reduced myelin density in unmedicated patients with major depressive disorder (MDD) using the inhomogeneous magnetization transfer (ihMT) imaging technology. Compared to other technologies, the ihMT provides high specificity and sensitivity to detect myelin.

METHOD

In this prospective study, fifty unmedicated patients (mean age 25.36 years, 40% men) with MDD and 57 age- and sex-matched healthy controls (HCs) (mean age 25.02 years, 53% men) were recruited between January 2019 and December 2019. All participants underwent ihMT imaging, and pseudo-quantitative ihMT (qihMT) and ihMT ratio (ihMTR) were obtained. The mean values of qihMT and ihMTR extracted from the 50 WM masks (extracted from the International Consortium for Brain Mapping, ICBM-152) in each participant were compared between participants in the MDD and HCs groups. The symptoms of patients were evaluated using the 24-item Hamilton Depression Rating scale (HDRS).

RESULTS

Compared with the HC group, the MDD group showed significantly decreased qihMT and ihMTR values in the left inferior fronto-occipital fasciculus (IFOF) (t = -4.057, p < 0.001; t = -3.662, p < 0.001) and the left uncinate fasciculus (UF) (t = -4.776, p < 0.001; t = -3.800, p < 0.001) after Bonferroni correction. The correlation analysis displayed a significant negative correlation between qihMT values of the left IFOF and HDRS total scores in patients with MDD (r = -0.390, p = 0.012).

LIMITATIONS

This was a cross-sectional study with a relative small sample.

CONCLUSIONS

These findings suggest the reduced myelin density in the IFOF and UF in patients with MDD, which might be associated with the pathophysiology of MDD.

N6-methyladenosine (m6A) modification and its clinical relevance in cognitive dysfunctions

BACKGROUND

N6 adenosine methylation (m6A) is the most abundant internal RNA modification in eukaryotic cells. Dysregulation of m6A has been associated with the perturbations of cell proliferation and cell death in different diseases. However, the roles of m6A in the neurodegenerative process and cognitive dysfunction are unclear.

METHODS

We systematically investigated the molecular alterations of m6A regulators and their clinical relevance with cognitive dysfunctions using published datasets of Alzheimer's Disease (AD), vascular dementia, and mild cognitive impairment (MCI).

FINDINGS

The expressions of m6A regulators vary in different tissues and closely correlate with neurodegenerative pathways. We identified co-expressive m6A regulators SNRPG and SNRPD2 as potential biomarkers to predict transformation from MCI to AD. Moreover, we explored correlations between Apolipoprotein E4 and m6A methylations.

INTERPRETATION

Collectively, these findings suggest that m6A methylations as potential biomarkers and therapeutic targets for cognitive dysfunction.

FUNDING

This work was supported by the National Natural Science Foundation of China (81871040) and the Shanghai Health System Talent Training Program (2018BR29).

Minocycline attenuation of rat corpus callosum abnormality mediated by low-dose lipopolysaccharide-induced microglia activation

Background

Microglia are resident innate immune cells in the brain, and activation of these myeloid cells results in secretion of a variety of pro-inflammatory molecules, leading to the development of neurodegenerative disorders. Lipopolysaccharide (LPS) is a widely used experimental stimulant in microglia activation. We have previously shown that LPS produced microglia activation and evoked detectable functional abnormalities in rat corpus callosum (CC) in vitro. Here, we further validated the effects of low-dose LPS-induced microglia activation and resultant white matter abnormality in the CC in an animal model and examined its attenuation by an anti-inflammatory agent minocycline.

Methods

Twenty-four SD rats were divided randomly into three groups and intra-peritoneally injected daily with saline, LPS, and LPS + minocycline, respectively. All animals were subject to MRI tests 6 days post-injection. The animals were then sacrificed to harvest the CC tissues for electrophysiology, western blotting, and immunocytochemistry. One-way ANOVA with Tukey’s post-test of all pair of columns was employed statistical analyses.

Results

Systemic administration of LPS produced microglial activation in the CC as illustrated by Iba-1 immunofluorescent staining. We observed that a large number of Iba-1-positive microglial cells were hyper-ramified with hypertrophic somata or even amoeba like in the LPS-treated animals, and such changes were significantly reduced by co-administration of minocycline. Electrophysiological recordings of axonal compound action potential (CAP) in the brain slices contained the CC revealed an impairment on the CC functionality as detected by a reduction in CAP magnitude. Such an impairment was supported by a reduction of fast axonal transportation evidenced by β-amyloid precursor protein accumulation. These alterations were attenuated by minocycline, demonstrating minocycline reduction of microglia-mediated interruption of white matter integrity and function in the CC.

Conclusions

Systemic administration of LPS produced microglia activation in the CC and resultant functional abnormalities that were attenuated by an anti-inflammatory agent minocycline.

Tetracyclines, a promise for neuropsychiatric disorders: from adjunctive therapy to the discovery of new targets for rational drug design in psychiatry

Major mental disorders, such as schizophrenia, bipolar disorder, and major depressive disorder, represent the leading cause of disability worldwide. Nevertheless, the current pharmacotherapy has several limitations, and a large portion of patients do not respond appropriately to it or remain with disabling symptoms overtime. Traditionally, pharmacological interventions for psychiatric disorders modulate dysfunctional neurotransmitter systems. In the last decades, compelling evidence has advocated for chronic inflammatory mechanisms underlying these disorders. Therefore, the repurposing of anti-inflammatory agents has emerged as an attractive therapeutic tool for mental disorders. Minocycline (MINO) and doxycycline (DOXY) are semisynthetic second-generation tetracyclines with neuroprotective and anti-inflammatory properties. More recently, the most promising results obtained in clinical trials using tetracyclines for major psychiatric disorders were for schizophrenia. In a reverse translational approach, tetracyclines inhibit microglial reactivity and toxic inflammation by mechanisms related to the inhibition of nuclear factor kappa B signaling, cyclooxygenase 2, and matrix metalloproteinases. However, the molecular mechanism underlying the effects of these tetracyclines is not fully understood. Therefore, the present review sought to summarize the latest findings of MINO and DOXY use for major psychiatric disorders and present the possible targets to their molecular and behavioral effects. In conclusion, tetracyclines hold great promise as (ready-to-use) agents for being used as adjunctive therapy for human neuropsychiatric disorders. Hence, the understanding of their molecular mechanisms may contribute to the discovery of new targets for the rational drug design of novel psychoactive agents.

Higher inflammation and cerebral white matter injury associated with cognitive deficit in asthmatic patients with depression

OBJECTIVE

Depression is a common co-morbidity in asthma, worsening asthma control and impairing quality of life. Previous studies have reported a higher risk of cognitive deficit in depression, yet little research has focused on the level of cognition in asthmatic patients with depression. Evidence shows that inflammation may play an important role in both asthma and depression. Cerebral white matter injury, possibly induced by inflammation, has been associated with depression. This study assesses cognitive function in patients with asthma and a depression comorbidity, compared to patients with asthma only or depression only.

METHODS

Four groups were studied: Asthma comorbid Depression group (A + D, n = 26), Depression group (D, n = 25), Asthma group (A, n = 33) and Normal controls (N, n = 28). Cognitive function was evaluated using Montreal Cognitive Assessment (MoCA). Inflammatory cytokines were measured, including interleukin-1β (IL-1β), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), high-mobility group box 1(HMGB1) and Netrin-1. Cerebral white matter injury was assessed by serum myelin basic protein (MBP) and myelin oligodendrocyte glycoprotein (MOG), and their correlations with cognitive performance were calculated.

RESULTS

A + D group showed the highest incidence of cognitive deficit, with the cognitive domain particularly affected. Compared to N group, serum levels of IL-6, HMGB1, Netrin-1, MBP and MOG were significantly elevated in A + D group. MOG level negatively correlated with the MoCA score.

CONCLUSION

Patients with comorbidities presented with more severe cognitive deficits and higher levels of inflammatory cytokines. Cerebral white matter injury may account for the cognitive deficit in patients and MOG could be a potential biomarker for this process.

Window of opportunity for human amnion epithelial stem cells to attenuate astrogliosis after umbilical cord occlusion in preterm fetal sheep

There is increasing evidence that administration of many types of stem cells, including human amnion epithelial cells (hAECs), can reduce hypoxic-ischemic injury, including in the perinatal brain. However, the therapeutic window for single dose treatment is not known. We compared the effects of early and delayed intracerebroventricular administration of hAECs in fetal sheep at 0.7 gestation on brain injury induced by 25 minutes of complete umbilical cord occlusion (UCO) or sham occlusion. Fetuses received either 1 × 10⁶ hAECs or vehicle alone, as an infusion over 1 hour, either 2 or 24 hours after UCO. Fetuses were killed for brain histology at 7 days post-UCO. hAEC infusion at both 2 and 24 hours had dramatic anti-inflammatory and anti-gliotic effects, including significantly attenuating the increase in microglia after UCO in the white and gray matter and the number of astrocytes in the white matter. Both protocols partially improved myelination, but had no effect on total or immature/mature numbers of oligodendrocytes. Neuronal survival in the hippocampus was increased by hAEC infusion at either 2 or 24 hours, whereas only hAECs at 24 hours were associated with improved neuronal survival in the striatum and thalamus. Neither protocol improved recovery of electroencephalographic (EEG) power. These data suggest that a single infusion of hAECs is anti-inflammatory, anti-gliotic, and neuroprotective in preterm fetal sheep when given up to 24 hours after hypoxia-ischemia, but was associated with limited white matter protection after 7 days recovery and no improvement in the recovery of EEG power.

The Anti-Depressive Effects of Hesperidin and the Relative Mechanisms Based on the NLRP3 Inflammatory Signaling Pathway

There is increasing evidence showing that inflammation is associated with depression in humans. Hesperidin, a natural bioflavonoid, has performed excellent effects on depression. The aim of this research was to investigate the therapeutic effect of hesperidin on chronic unpredictable mild stress (CUMS)-induced rats. The sucrose preference test (SPT), forced swimming test (FST), and open field test (OFT) were performed to measure the depression-related symptoms. The enzyme-linked immunosorbent assay (ELISA) was used to determine the concentrations of interleukin (IL)-1β, IL-6, and tumor necrosis factor (TNF)-α in the prefrontal cortex (PFC) of rats and cellular supernatant. PCR and Western blot were used to monitor the differences of NLRP3, caspase-1, ASC activation in the levels of genes and proteins in the PFC of rats and microglia. The activation of microglia was determined using immunofluorescence staining and flow cytometry assay. Our results show that hesperidin treatment significantly relieved depressive like behaviors in CUMS rats. In addition, hesperidin decreased the expression levels of IL-1β, IL-6, TNF-α, NLRP3, caspase-1, and ASC in the PFC and microglia. This study investigated that hesperidin treatment ameliorated CUMS-induced depression by suppressing microglia and inflammation.

Anti-mouse CX3CR1 Antibody Alleviates Cognitive Impairment, Neuronal Loss and Myelin Deficits in an Animal Model of Brain Ischemia

White matter lesions are common when global cerebral ischemia (GCI) occurs in the elderly, and cause damage to neurological and psychological functions. Remyelination often fails because of the limited recruitment of oligodendrocyte progenitor cells (OPCs) to the demyelinated site or the inefficient differentiation of OPCs to mature oligodendrocytes (OLs). The activation of microglia, the most important immune cells in the central nervous system, and subsequent inflammation have been implicated in myelination repair disorder. Little is known about the role of the Fractalkine/CX3CR1 signaling pathway, the key regulator of microglia activation, on myelin in microglia. In this study, a GCI animal model was generated through bilateral common carotid artery occlusion to induce ischemic inflammation and white matter damage; then, we downregulated CX3CR1 by intracerebroventricular administration of neutralizing antibody anti-FKR. Downregulation of CX3CR1 significantly reversed the depression-like behavior and cognitive impairment in GCI mice. Activation of microglia was inhibited, and the peripheral inflammatory responses were also ameliorated as revealed by decreased serum levels of IL-1β, IL-6 and TNF-α. CX3CR1 block substantially reversed demyelination in striatum, cortex and hippocampus and promoted differentiation and maturation of OPCs into mature OLs in the hippocampus. No effect was found on myelin in the corpus callosum. Besides, hippocampal neurons were protected by anti-FKR treatment after GCI. Collectively, our data demonstrated that downregulating of the Fractalkine/CX3CR1 signaling pathway had an anti-depressant and cognition-improvement effect by inhibiting microglia activation, promoting OPCs maturation and remyelination.

Dystrophy of Oligodendrocytes and Adjacent Microglia in Prefrontal Gray Matter in Schizophrenia

BACKGROUND

Some evidence support the notion that microglia activation in acute state of schizophrenia might contribute to damage of oligodendrocytes and myelinated fibers. Previously we found dystrophic changes of oligodendrocytes in prefrontal white matter in schizophrenia subjects displaying predominantly positive symptoms as compared to controls. The aim of the study was to verify whether microglial activation might contribute to dystrophic changes of oligodendrocytes in prefrontal gray matter in this clinical subgroup.

METHODS

Transmission electron microscopy and morphometry of microglia and adjacent oligodendrocytes were performed in layer 5 of the prefrontal cortex (BA10) in the schizophrenia subjects displaying predominantly positive symptoms (SPPS, n = 12), predominantly negative symptoms (SPNS, n = 9) and healthy controls (n = 20).

RESULTS

Qualitative study showed microglial activation and dystrophic alterations of microglia and oligodendrocytes adjacent to each other in both subgroups as compared to controls. A significant reduction in volume density (Vv) and the number (N) of mitochondria and an increase in N of lipofuscin granules were found in oligodendrocytes and adjacent microglia in both subgroups. Vv of lipofuscin granules, Vv and N of vacuoles of endoplasmic reticulum in microglia were increased significantly in the SPPS subgroup as compared to controls. In the SPPS subgroup Vv and N of mitochondria in microglia were correlated with N of vacuoles in microglia (r = -0.61, p < 0.05) and with Vv (r = 0.79, p < 0.01) and N (r = 0.59, p < 0.05) of mitochondria in oligodendrocytes. Vv of mitochondria in microglia was also correlated with Vv and N of vacuoles in oligodendrocytes in the SPPS subgroup (r = 0.76, p < 0.01). Area of nucleus of microglial cells was correlated negatively with age (r = -0.76, p < 0.01) and age at illness onset (r = -0.65, p < 0.05) in the SPPS subgroup. In the SPNS subgroup N of mitochondria in microglia was correlated with Vv of lipofuscin granules in oligodendrocytes (r = -0.9, p < 0.01). There were no significant correlations between these parameters in the control group.

DISCUSSION

Microglial dystrophy might contribute to oligodendrocyte dystrophy in the schizophrenia subjects with predominantly positive symptoms during relapse. Mitochondria in microglia and oligodendrocytes may be a target for treatment strategy of schizophrenia.