Improvement of astrocytic gap junction involves the anti-depressive effect of celecoxib through inhibition of NF-κB.

CONTEXT: Celecoxib, a selective cyclooxygenase-2 (COX-2) inhibitor, has been shown to exhibit anti-depressive effects in clinical trials. However, the direct mechanism underlying its effect on neuroinflammation remains unclear. Neuroinflammatory reaction from astrocytes leads to depression, and our previous study found that gap junction disorder between astrocytes aggravated neuroinflammatory reaction in depressed mice. OBJECTIVE: To investigate the potential mechanism of celecoxib's effects on astrocytic gap junctions during the central nervous inflammation-induced depression. MATERIALS & METHODS: Stereotaxic injection of lipopolysaccharide (LPS) into the prefrontal cortex (PFC) to establish a model of major depressive disorder (MDD). Celecoxib was administrated into PFC 15 min after LPS injection. The depressive performance was tested by tail suspension test and forced swimming test, and the levels of proinflammation cytokines were determined at mRNA and protein levels. Resting-state functional connection (rsFC) was employed to assess changes in the default mode network (DMN). Additionally, astrocytic gap junctions were also determined by lucifer yellow (LY) diffusion and transmission electron microscope (TEM), and the expression of connexin 43 (Cx43) was measured by western blotting, quantitative polymerase chain reaction, and immunofluorescence. RESULTS: LPS injection induced significant depressive performance, which was ameliorated by celecoxib treatment. Celecoxib also improved rsFC in the DMN. Furthermore, celecoxib improved astrocytic gap junctions as evidenced by increased LY diffusion, shortened gap junction width, and normalized levels of phosphorylated Cx43. Celecoxib also blocked the phosphorylation of p65, and inhibition of p65 abolished the improvement of Cx43. DISCUSSION & CONCLUSION: Anti-depressive effects of celecoxib are mediated, at least in part, by the inhibition of nuclear factor- kappa B (NF-κB) and the subsequent improvement of astrocytic gap junction function.

CKLF induces microglial activation via triggering defective mitophagy and mitochondrial dysfunction.

Although microglial activation is induced by an increase in chemokines, the role of mitophagy in this process remains unclear. This study aimed to elucidate the role of microglial mitophagy in CKLF/CKLF1 (chemokine-like factor 1)-induced microglial activation and neuroinflammation, as well as the underlying molecular mechanisms following CKLF treatment. This study determined that CKLF, an inducible chemokine in the brain, leads to an increase in mitophagy markers, such as DNM1L, PINK1 (PTEN induced putative kinase 1), PRKN, and OPTN, along with a simultaneous increase in autophagosome formation, as evidenced by elevated levels of BECN1 and MAP1LC3B (microtubule-associated protein 1 light chain 3 beta)-II. However, SQSTM1, a substrate of autophagy, was also accumulated by CKLF treatment, suggesting that mitophagy flux was reduced and mitophagosomes accumulated. These findings were confirmed by transmission electron microscopy and confocal microscopy. The defective mitophagy observed in our study was caused by impaired lysosomal function, including mitophagosome-lysosome fusion, lysosome generation, and acidification, resulting in the accumulation of damaged mitochondria in microglial cells. Further analysis revealed that pharmacological blocking or gene-silencing of mitophagy inhibited CKLF-mediated microglial activation, as evidenced by the expression of the microglial marker AIF1 (allograft inflammatory factor 1) and the mRNA of proinflammatory cytokines (Tnf and Il6). Ultimately, defective mitophagy induced by CKLF results in microglial activation, as observed in the brains of adult mice. In summary, CKLF induces defective mitophagy, microglial activation, and inflammation, providing a potential approach for treating neuroinflammatory diseases.Abbreviation: 3-MA: 3-methyladenine; AIF1: allograft inflammatory factor 1; ANOVA: analysis of variance; BAF: bafilomycin A1; BSA: bovine serum albumin; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; cGAMP: cyclic GMP-AMP; CGAS: cyclic GMP-AMP synthase; CKLF/CKLF1: chemokine-like factor 1; CNS: central nervous system; DMEM: Dulbecco's Modified Eagle Medium; DNM1L: dynamin 1 like; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; GFP: green fluorescence protein; IRF3: interferon regulatory factor 3; IgG: immunoglobulin G; LAMP1: lysosomal-associated membrane protein 1; LAPTM4A: lysosomal-associated protein transmembrane 4A; MAP1LC3B: microtubule-associated protein 1 light chain 3 beta; Mdivi-1: mitochondrial division inhibitor 1; mRFP: monomeric red fluorescent protein; mtDNA: mitochondrial DNA; MTORC1: mechanistic target of rapamycin kinase complex 1; OPTN: optineurin; PBS: phosphate-buffered saline; PCR: polymerase chain reaction; PINK1: PTEN induced putative kinase 1; PLL: poly-L-lysine; PRKN: parkin RBR E3 ubiquitin protein ligase; qPCR: quantitative polymerase chain reaction; ROS: reactive oxygen species; SQSTM1: sequestosome 1; TBK1: TANK-binding kinase 1; TFEB: transcription factor EB; VDAC: voltage-dependent anion channel.

A small molecule 20C from Gastrodia elata inhibits α-synuclein aggregation and prevents progression of Parkinson's disease.

Parkinson's disease (PD) is pathologically manifested by the aggregation of α-synuclein, which has been envisioned as a promising disease-modifying target for PD. Here, we identified 20C, a bibenzyl compound derived from Gastrodia elata, able to inhibit the aggregation of A53T variants of α-synuclein directly in vitro. Computational analysis revealed that 20C binds to cavities in mature α-synuclein fibrils, and it indeed displays a strong interaction with α-synuclein and reduced their ß-sheet structure by microscale thermophoresis and circular dichroism, respectively. Moreover, incubating neural cells with 20C reduced the amounts of α-synuclein inclusions significantly. The treatment of A53T α-Syn transgenic mice with 20C significantly reduces the toxic α-synuclein levels, improves behavioral performance, rescues dopaminergic neuron, and enhances functional connections between SNc and PD associated brain areas. The transcriptome analysis of SNc demonstrated that 20C improves mitochondrial dynamics, which protects mitochondrial morphology and function against α-synuclein induced degeneration. Overall, 20C appears to be a promising candidate for the treatment of PD.

A breakdown of metabolic reprogramming in microglia induced by CKLF1 exacerbates immune tolerance in ischemic stroke.

Ischemic stroke is characterized by the presence of reactive microglia. However, its precise involvement in stroke etiology is still unknown. We used metabolic profiling and showed that chemokine like factor 1 (CKLF1) causes acute microglial inflammation and metabolic reprogramming from oxidative phosphorylation to glycolysis, which was reliant on the AMP-activated protein kinase (AMPK)-mammalian target of rapamycin (mTOR)-hypoxia inducible factor 1α (HIF-1α) signaling pathway. Once activated, microglia enter a chronic tolerant state as a result of widespread energy metabolism abnormalities, which reduces immunological responses, including cytokine release and phagocytosis. Metabolically dysfunctional microglia were also found in mice using genome-wide RNA sequencing after chronic administration of CKLF1, and there was a decrease in the inflammatory response. Finally, we showed that the loss of CKLF1 reversed the defective immune response of microglia, as indicated by the maintenance its phagocytosis to neutrophils, thereby mitigating the long-term outcomes of ischemic stroke. Overall, CKLF1 plays a crucial role in the relationship between microglial metabolic status and immune function in stroke, which prepares a potential therapeutic strategy for ischemic stroke.

Regulatory T cells in ischemic stroke.

Recent evidence shows that when ischemic stroke (IS) occurs, the BBB would be destructed, thereby promoting the immune cells to migrate into the brain, suggesting that the immune responses can play a vital role in the pathology of IS. As an essential subpopulation of immunosuppressive T cells, regulatory T (Treg) cells are involved in maintaining immune homeostasis and suppressing immune responses in the pathophysiological conditions of IS. During the past decades, the regulatory role of Treg cells has attracted the interest of numerous researchers. However, whether they are beneficial or detrimental to the outcomes of IS remains controversial. Moreover, Treg cells exert distinctive effects in the different stages of IS. Therefore, it is urgent to elucidate how Treg cells modulate the immune responses induced by IS. In this review, we describe how Treg cells fluctuate and play a role in the regulation of immune responses after IS in both experimental animals and humans, and summarize their biological functions and mechanisms in both CNS and periphery. We also discuss how Treg cells participate in poststroke inflammation and immunodepression and the potential of Treg cells as a novel therapeutic approach.

Flavin-containing monooxygenase 1 deficiency promotes neuroinflammation in dopaminergic neurons in mice.

A growing body of evidence indicates an association between flavin-containing monooxygenase (FMO) and neurodegeneration, including Parkinson's disease (PD); however, the details of this association are unclear. We previously showed that the level of Fmo1 mRNA is decreased in an in vitro rotenone model of parkinsonism. To further explore the potential involvement of FMO1 deficiency in parkinsonism, we generated Fmo1 knockout (KO) mice and examined the survival of dopaminergic neurons and relative changes. Fmo1 KO mice exhibited loss of tyrosine hydroxylase-positive neurons, decreased levels of tyrosine hydroxylase and Parkin proteins, and increased levels of pro-inflammatory cytokines (IL1ß and IL6) in the nigrostriatal region. Moreover, the protein levels of PTEN induced kinase 1 (PINK1) and p62, and the Microtubule associated protein 1 light chain 3 (LC3)-II/I ratio were not significantly altered in Fmo1 KO mice (P > 0.05). FMO1 deficiency promotes neuroinflammation in dopaminergic neurons in mice, thus may plays a potential pathological role in dopaminergic neuronal loss. These findings may provide new insight into the pathogenesis of PD.

The progress of chemokines and chemokine receptors in autism spectrum disorders.

Autism spectrum disorders (ASD) are a group of neurodevelopmental disorders and the main symptoms of ASD are impairments in social communication and abnormal behavioral patterns. Studies have shown that immune dysfunction and neuroinflammation play a key role in ASD patients and experimental models. Chemokines are groups of small proteins that regulate cell migration and mediate inflammation responses via binding to chemokine receptors. Thus, chemokines/chemokine receptors may be involved in neurodevelopmental disorders and associated with ASD. In this review, we summarize the research progress of chemokine aberrations in ASD and also review the recent progress of clinical treatment of ASD and pharmacological research related to chemokines/chemokine receptors. This review highlights the possible connection between chemokines/chemokine receptors and ASD, and provides novel potential targets for drug discovery of ASD.