Double-stranded DNA (dsDNA) sensor cyclic-GMP-AMP synthase (cGAS) along with the downstream stimulator of interferon genes (STING) acting as essential immune-surveillance mediators have become hot ...topics of research. The intrinsic function of the cGAS-STING pathway facilitates type-I interferon (IFN) inflammatory signaling responses and other cellular processes such as autophagy, cell survival, senescence. cGAS-STING pathway interplays with other innate immune pathways, by which it participates in regulating infection, inflammatory disease, and cancer. The therapeutic approaches targeting this pathway show promise for future translation into clinical applications. Here, we present a review of the important previous works and recent advances regarding the cGAS-STING pathway, and provide a comprehensive understanding of the modulatory pattern of the cGAS-STING pathway under multifarious pathologic states.
ABSTRACT
In this study, we strove to substantiate the ability of linc‐MAF‐4 to act as a regulator of pathogenesis during multiple sclerosis (MS). We recruited 34 patients who were diagnosed with MS ...according to the revised McDonald criteria. Six patients with MS and 5 healthy volunteers contributed peripheral blood mononuclear cells for microarray analysis. Subsequent knockdown and overexpression of linc‐MAF‐4 in naive CD4+ T cells from the additional 28 patients with MS was performed to track changes in CD4+ T‐cell subsets and their function, as well as to confirm results from the prior microarray analysis. Expression of linc‐MAF‐4 increased significantly in peripheral blood mononuclear cells of patients with MS compared with those of control participants. In addition, linc‐MAF‐4 regulated encephalitogenic T helper (Th)1‐cell differentiation in patients with MS. Transfection of synthetic linc‐MAF‐4 into naive CD4+ T cells facilitated Th1‐cell differentiation and inhibited Th2‐cell differentiation by directly inhibiting MAF, which is a Th2‐cell transcription factor. Linc‐MAF‐4 also promoted activation of CD4+ T cells from patients with MS. Expression level of linc‐MAF‐4 correlated with the annual relapse rate in patients with MS. Our results suggest that linc‐MAF‐4 is involved in the pathogenesis of MS, specifically via regulation of encephalitogenic T cells.—Zhang, F., Liu, G., Wei, C., Gao, C., Hao, J. Linc‐MAF‐4 regulates Th1/Th2 differentiation and is associated with the pathogenesis of multiple sclerosis by targeting MAF. FASEB J. 31, 519–525 (2017). http://www.fasebj.org
Ischemic stroke (IS) is a detrimental neurological disease with limited treatments options. It has been challenging to define the roles of brain cell subsets in IS onset and progression due to ...cellular heterogeneity in the CNS. Here, we employed single-cell RNA sequencing (scRNA-seq) to comprehensively map the cell populations in the mouse model of MCAO (middle cerebral artery occlusion). We identified 17 principal brain clusters with cell-type specific gene expression patterns as well as specific cell subpopulations and their functions in various pathways. The CNS inflammation triggered upregulation of key cell type-specific genes unpublished before. Notably, microglia displayed a cell differentiation diversity after stroke among its five distinct subtypes. Importantly, we found the potential trajectory branches of the monocytes/macrophage’s subsets. Finally, we also identified distinct subclusters among brain vasculature cells, ependymal cells and other glia cells. Overall, scRNA-seq revealed the precise transcriptional changes during neuroinflammation at the single-cell level, opening up a new field for exploration of the disease mechanisms and drug discovery in stroke based on the cell-subtype specific molecules.
Cytosolic double‐stranded DNA (dsDNA) is a danger signal that is tightly monitored and sensed by nucleic acid‐sensing pattern recognition receptors. We study the inflammatory cascade on dsDNA ...recognition and investigate the neuroprotective effect of cyclic GMP‐AMP (cGAMP) synthase (cGAS) antagonist A151 and its mechanisms of neuroprotection in a mouse model of experimental stroke. Here, we found that cerebral ischemia promoted the release of dsDNA into the cytosol, where it initiated inflammatory responses by activating the cGAS. A151 effectively reduced the expression of cGAS, absent in melanoma 2 (AIM2) inflammasome, and pyroptosis‐related molecules, including caspase‐1, gasdermin D, IL‐1β, and IL‐18. Furthermore, mice treated with A151 showed a dampened immune response to stroke, with reduced counts of neutrophils, microglia, and microglial production of IL‐6 and TNF‐α after MCAO. Moreover, A151 administration significantly reduced infarct volume, attenuated neurodeficits, and diminished cell death. Notably, the protective effect of A151 was blocked in a microglia‐specific cGAS knockout mouse. These findings offer unique perspectives on stroke pathogenesis and indicate that inhibition of cGAS could attenuate brain inflammatory burden, representing a potential therapeutic opportunity for stroke.
Synopsis
Inflammation is involved in the progression of ischemic brain injury. This study focuses on the inflammatory cascade on double‐strand DNA (dsDNA) recognition and highlights the possibility of inhibiting dsDNA‐sensing cyclic GMP‐AMP synthase (cGAS) for treatment of ischemic stroke.
The release of dsDNA from necrotic tissue during brain infarction triggers an innate inflammatory cascade.
A synthetic oligonucleotide A151 that antagonizes cGAS regulates the microglial immune response and pyroptosis after ischemic stroke.
Inhibition of cGAS leads to a decline in neutrophil infiltration into the brain.
Suppression of the dsDNA‐sensing cGAS pathway reduces ischemic brain injury via mitigating neuroinflammation.
Inflammation is involved in the progression of ischemic brain injury. This study focuses on the inflammatory cascade on double‐strand DNA (dsDNA) recognition and highlights the possibility of inhibiting dsDNA‐sensing cyclic GMP‐AMP synthase (cGAS) for treatment of ischemic stroke.
Inflammation that complicates many autoimmune diseases, such as multiple sclerosis (MS), has been correlated to abnormal differentiation of Th17 cells. However, the reasons that promote Th17 ...cell-driven autoimmunity are yet to be discovered. In this study, we sought evidence that DNA-damage-inducible transcript 4 (DDIT4) and its associated long noncoding RNA DDIT4 (lncDDIT4) inhibit Th17 cell differentiation. We recruited 36 patients. Six MS patients and five healthy volunteers (controls) contributed PBMCs as material for microarray analysis. Microarray assays of lncDDIT4 and DDIT4 RNA expression identified outstanding differences between MS and control subjects, which were verified with real-time quantitative PCR. We then interrupted the expression of lncDDIT4 and DDIT4 mRNA in MS patients' naive CD4
T cells and observed the resulting changes in Th17 cells. The expression of lncDDIT4 and DDIT4 mRNA were higher both in PBMCs and CD4
T cells of MS patients than in healthy controls. DDIT4 (2.79-fold upregulation) was then recognized as a candidate for the
-regulated target of lncDDIT4 (4.32-fold upregulation). Isolation of naive CD4
T cells revealed enhanced levels of lncDDIT4 and DDIT4 after stimulated with Th17-inducing cytokines, but not after Th1, Th2, or T regulatory cell induction. Overexpression of lncDDIT4 in naive CD4
T cells inhibited IL-17 transcription through increased DDIT4 expression and decreased activation of the DDIT4/mTOR pathway. Consistently, silencing lncDDIT4 in naive CD4
T cells enhanced Th17 differentiation through increased activation of the DDIT4/mTOR pathway. However, these results vanished when DDIT4 was silenced. This outcome suggests that lncDDIT4 regulates Th17 cell differentiation by directly targeting DDIT4.
Guillain-Barré syndrome (GBS) is an acute, post-infectious, immune-mediated, demyelinating disease of peripheral nerves and nerve roots. Dimethyl fumarate (DMF), a fumaric acid ester, exhibits ...various biological activities, including multiple immunomodulatory and neuroprotective effects. However, the potential mechanism underlying the effect of DMF in GBS animal model experimental autoimmune neuritis (EAN) is unclear.
Using EAN, an established GBS model, we investigated the effect of DMF by assessing clinical score, histological staining and electrophysiological studies. Then, we further explored the potential mechanism by Western blot analysis, flow cytometry, fluorescence immunohistochemistry, PCR, and ELISA analysis. The Mann-Whitney U test was used to compare differences between control group and treatment groups where appropriate.
DMF treatment reduced the neurological deficits by ameliorating inflammatory cell infiltration and demyelination of sciatic nerves. In addition, DMF treatment decreased the level of pro-inflammatory M1 macrophages while increasing the number of anti-inflammatory M2 macrophages in the spleens and sciatic nerves of EAN rats. In RAW 264.7, a shift in macrophage polarization from M1 to M2 phenotype was demonstrated to be depended on DMF application. In sciatic nerves, DMF treatment elevated the level of the antioxidant transcription factor nuclear factor erythroid-derived 2-related factor 2 (Nrf2) and its target gene hemoxygenase-1 (HO-1) which could facilitate macrophage polarization toward M2 type. Moreover, DMF improved the inflammatory milieu in spleens of EAN rats, characterized by downregulation of messenger RNA (mRNA) of IFN-γ, TNF-α, IL-6, and IL-17 and upregulation of mRNA level of IL-4 and IL-10.
Taken together, our data demonstrate that DMF can effectively suppress EAN, and the mechanism involves altering the balance of M1/M2 macrophages and attenuating inflammation.
Background:
Combined central and peripheral demyelination (CCPD) is a disease of inflammatory demyelination that affects central and peripheral nerves simultaneously or temporally separated.
...Objectives:
This study evaluated the clinical characteristics and the existence of antinodal/paranodal antibodies in patients with CCPD.
Methods:
We reviewed the clinical manifestations, laboratory tests, electrophysiological examinations, neuroimaging findings, treatment, and prognosis of 31 patients with CCPD. Using a live cell–based assay, we tested antinodal/paranodal antibodies.
Results:
The most common symptoms were motor weakness (83.3%), hyporeflexia (63.3%), and sphincter disturbance (58.1%). In total, 16.6% of patients had impaired vision symptoms, whereas 33.3% of patients had abnormal visual-evoked potentials (VEPs). A total of 21.1% (4/19) of patients were positive for anti-AQP4 (aquaporin 4) antibodies, 20.0% (2/10) of patients were positive for anti-NF155 (neurofascin-155) antibodies, and 10.0% (1/10) of patients were positive for anti-MAG (myelin-associated glycoprotein) antibodies. The effective rates of intravenous corticosteroids, intravenous immunoglobulins, and rituximab were 72.2%, 37.5%, and 100%, respectively. At the illness peak, 75% of patients with CCPD had an mRS (modified Rankin Scale) score of 4 or greater. In remission, 37.5% had an mRS score of 4 or greater.
Conclusion:
The clinical manifestations of patients with CCPD are highly heterogeneous. We recommend testing antinodal/paranodal antibodies for patients with CCPD.
Astrocytes are believed to bridge interactions between infiltrating lymphocytes and neurons during brain ischemia, but the mechanisms for this action are poorly understood. Here we found that ...interleukin-15 (IL-15) is dramatically up-regulated in astrocytes of postmortem brain tissues from patients with ischemic stroke and in a mouse model of transient focal brain ischemia. We generated a glial fibrillary acidic protein (GFAP) promoter-controlled IL-15–expressing transgenic mouse (GFAP–IL-15tg) line and found enlarged brain infarcts, exacerbated neurodeficits after the induction of brain ischemia. In addition, knockdown of IL-15 in astrocytes attenuated ischemic brain injury. Interestingly, the accumulation of CD8⁺ T and natural killer (NK) cells was augmented in these GFAP–IL-15tg mice after brain ischemia. Of note, depletion of CD8⁺ T or NK cells attenuated ischemic brain injury in GFAP–IL-15tg mice. Furthermore, knockdown of the IL-15 receptor α or blockade of cell-to-cell contact diminished the activation and effector function of CD8⁺ T and NK cells in GFAP–IL-15tg mice, suggesting that astrocytic IL-15 is delivered in trans to target cells. Collectively, these findings indicate that astrocytic IL-15 could aggravate postischemic brain damage via propagation of CD8⁺ T and NK cell-mediated immunity.
Peripheral lymphocytes entering brain ischemic regions orchestrate inflammatory responses, catalyze tissue death, and worsen clinical outcomes of acute ischemic stroke (AIS) in preclinical studies. ...However, it is not known whether modulating brain inflammation can impact the outcome of patients with AIS. In this open-label, evaluator-blinded, parallel-group clinical pilot trial, we recruited 22 patients matched for clinical and MRI characteristics, with anterior cerebral circulation occlusion and onset of stroke that had exceeded 4.5 h, who then received standard management alone (controls) or standard management plus fingolimod (FTY720, Gilenya, Novartis), 0.5 mg per day orally for 3 consecutive days. Compared with the 11 control patients, the 11 fingolimod recipients had lower circulating lymphocyte counts, milder neurological deficits, and better recovery of neurological functions. This difference was most profound in the first week when reduction of National Institutes of Health Stroke Scale was 4 vs. −1, respectively ( P = 0.0001). Neurological rehabilitation was faster in the fingolimod-treated group. Enlargement of lesion size was more restrained between baseline and day 7 than in controls (9 vs. 27 mL, P = 0.0494). Furthermore, rT1%, an indicator of microvascular permeability, was lower in the fingolimod-treated group at 7 d (20.5 vs. 11.0; P = 0.005). No drug-related serious events occurred. We conclude that in patients with acute and anterior cerebral circulation occlusion stroke, oral fingolimod within 72 h of disease onset was safe, limited secondary tissue injury from baseline to 7 d, decreased microvascular permeability, attenuated neurological deficits, and promoted recovery.
Significance In patients with acute ischemic stroke (AIS), the abrupt and massive influx of lymphocytes from the periphery to the ischemic region orchestrates focal inflammatory responses, catalyzes tissue death, and worsens clinical outcomes. In this early phase clinical study, we reduced lymphocyte migration to the brain during the first 72 h of AIS via oral administration of three doses of fingolimod. This administration led to a significant reduction of secondary lesion enlargement, microvascular permeability, and better clinical outcomes during the acute phase and 3-mo follow-up visit. This study will provoke new investigations on the efficacy of modulation of brain inflammation in AIS.
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