Inactivation of astroglial NF-kappa B promotes survival of retinal neurons following ischemic injury

The impact of astrocytic NF-κB on healthy and Alzheimer's disease brains

Astrocytes play a role in healthy cognitive function and Alzheimer's disease (AD). The transcriptional factor nuclear factor-κB (NF-κB) drives astrocyte diversity, but the mechanisms are not fully understood. By combining studies in human brains and animal models and selectively manipulating NF-κB function in astrocytes, we deepened the understanding of the role of astrocytic NF-κB in brain health and AD. In silico analysis of bulk and cell-specific transcriptomic data revealed the association of NF-κB and astrocytes in AD. Confocal studies validated the higher level of p50 NF-κB and phosphorylated-p65 NF-κB in glial fibrillary acidic protein (GFAP)+-astrocytes in AD versus non-AD subjects. In the healthy mouse brain, chronic activation of astrocytic NF-κB disturbed the proteomic milieu, causing a loss of mitochondrial-associated proteins and the rise of inflammatory-related proteins. Sustained NF-κB signaling also led to microglial reactivity, production of pro-inflammatory mediators, and buildup of senescence-related protein p16INK4A in neurons. However, in an AD mouse model, NF-κB inhibition accelerated β-amyloid and tau accumulation. Molecular biology studies revealed that astrocytic NF-κB activation drives the increase in GFAP and inflammatory proteins and aquaporin-4, a glymphatic system protein that assists in mitigating AD. Our investigation uncovered fundamental mechanisms by which NF-κB enables astrocytes' neuroprotective and neurotoxic responses in the brain.

Polar lipids modify Alzheimer's Disease pathology by reducing astrocyte pro-inflammatory signaling through platelet-activating factor receptor (PTAFR) modulation

BACKGROUND

Pro-inflammatory processes triggered by the accumulation of extracellular amyloid beta (Aβ) peptides are a well-described pathology in Alzheimer's disease (AD). Activated astrocytes surrounding Aβ plaques contribute to inflammation by secreting proinflammatory factors. While astrocytes may phagocytize Aβ and contribute to Aβ clearance, reactive astrocytes may also increase Aβ production. Therefore, identifying factors that can attenuate astrocyte activation and neuroinflammation and how these factors influence pro-inflammatory pathways is important for developing therapeutic and preventive strategies in AD. Here, we identify the platelet-activating factor receptor (PTAFR) pathway as a key mediator of astrocyte activation. Intriguingly, several polar lipids (PLs) have exhibited anti-inflammatory protective properties outside the central nervous system through their inhibitory effect on the PTAFR pathway. Thus, we additionally investigated whether different PLs also exert inhibitory effects on the PAF pathway in astrocytes and whether their presence influences astrocytic pro-inflammatory signaling and known AD pathologies in vitro.

METHODS

PLs from salmon and yogurt were extracted using novel food-grade techniques and their fatty acid profile was determined using LC/MS. The effect of PLs on parameters such as astrocyte activation and generation of oxygen species (ROS) was assessed. Additionally, effects of the secretome of astrocytes treated with these polar lipids on aged neurons was measured.

RESULTS

We show that PLs obtained from salmon and yogurt lower astrocyte activation, the generation of reactive oxygen species (ROS), and extracellular Aβ accumulation. Cell health of neurons exposed to the secretome of astrocytes treated with salmon-derived PLs and Aβ was less affected than those treated with astrocytes exposed to Aβ only.

CONCLUSION

Our results highlight a novel underlying mechanism, why consuming PL-rich foods such as fish and dairy may reduce the risk of developing dementia and associated disorders.

Astrocyte KDM4A mediates chemokines and drives neutrophil infiltration to aggravate cerebral ischemia and reperfusion injury

Neutrophils plays a crucial role in acute ischemic brain injury and have emerged as potential treatment targets to mitigate such injuries. Lysine-specific demethylase 4 A (KDM4A), a member of the histone lysine demethylase family of enzymes involved in transcriptional regulation of gene expression, is upregulated during hypoxic events. However, the exact role of KDM4A in the pathological process of ischemic stroke remains largely unexplored. Our findings reveal that there was an upregulation of KDM4A levels in reactive astrocytes within both stroke mouse models and in vitro oxygen-glucose deprivation/regeneration (OGD/R) models. Using a conditional knockout mouse, we observed that astrocytic Kdm4a knockout regulates neutrophil infiltration and alleviates brain injury following middle cerebral artery occlusion reperfusion. Furthermore, Kdm4a deficiency astrocytes displayed lower chemokine C-X-C motif ligand 1 (CXCL1) level upon OGD/R and decreased neutrophil infiltration in a transwell system. Mechanistically, KDM4A, in cooperation with nuclear factor-kappa B (NF-κB), activates Cxcl1 gene expression by demethylating histone H3 lysine 9 trimethylation at Cxcl1 gene promoters in astrocytes upon OGD/R injury. Our findings suggest that astrocyte KDM4A-mediated Cxcl1 activation contributes to neutrophil infiltration via cooperation with NF-κB, and KDM4A in astrocytes may serve as a potential therapeutic target to modulate neutrophil infiltration after stroke.

Targeting blood-brain barrier for sepsis-associated encephalopathy: Regulation of immune cells and ncRNAs

Sepsis causes significant morbidity and mortality worldwide, most surviving patients show acute or chronic mental disorders, which are known as sepsis-associated encephalopathy (SAE). SAE involves many pathological processes, including the blood-brain barrier (BBB) damage. The BBB is located at the interface between the central nervous system and the surrounding environment, which protects the central nervous system (CNS) from the invasion of exogenous molecules, harmful substances or microorganisms in the blood. Recently, a growing number of studies have indicated that the BBB destruction was involved in SAE and played an important role in SAE-induced brain injury. In the present review, we firstly reveal the pathological processes of SAE such as the neurotransmitter disorders, oxidative stress, immune dysfunction and BBB destruction. Moreover, we introduce the structure of BBB, and describe the immune cells including microglia and astrocytes that participate in the BBB destruction after SAE. Furthermore, in view of the current research on non-coding RNAs (ncRNAs), we explain the regulatory mechanism of ncRNAs including long noncoding RNAs (lncRNAs), microRNAs (miRNAs) and circular RNAs (circRNAs) on BBB in the processes of SAE. Finally, we propose some challenges and perspectives of regulating BBB functions in SAE. Hence, on the basis of these effects, both immune cells and ncRNAs may be developed as therapeutic targets to protect BBB for SAE patients.

Cross-talk between bioactive lipid mediators and the unfolded protein response in ischemic stroke

Ischemic cerebral stroke is a severe medical condition that affects about 15 million people every year and is the second leading cause of death and disability globally. Ischemic stroke results in neuronal cell death and neurological impairment. Current therapies may not adequately address the deleterious metabolic changes and may increase neurological damage. Oxygen and nutrient depletion along with the tissue damage result in endoplasmic reticulum (ER) stress, including the Unfolded Protein Response (UPR), and neuroinflammation in the affected area and cause cell death in the lesion core. The spatio-temporal production of lipid mediators, either pro-inflammatory or pro-resolving, decides the course and outcome of stroke. The modulation of the UPR as well as the resolution of inflammation promotes post-stroke cellular viability and neuroprotection. However, studies about the interplay between the UPR and bioactive lipid mediators remain elusive and this review gives insights about the crosstalk between lipid mediators and the UPR in ischemic stroke. Overall, the treatment of ischemic stroke is often inadequate due to lack of effective drugs, thus, this review will provide novel therapeutical strategies that could promote the functional recovery from ischemic stroke.

Helicobacter pylori outer membrane vesicles induce astrocyte reactivity through nuclear factor-κappa B activation and cause neuronal damage in vivo in a murine model

BACKGROUND

Helicobacter pylori (Hp) infects the stomach of 50% of the world's population. Importantly, chronic infection by this bacterium correlates with the appearance of several extra-gastric pathologies, including neurodegenerative diseases. In such conditions, brain astrocytes become reactive and neurotoxic. However, it is still unclear whether this highly prevalent bacterium or the nanosized outer membrane vesicles (OMVs) they produce, can reach the brain, thus affecting neurons/astrocytes. Here, we evaluated the effects of Hp OMVs on astrocytes and neurons in vivo and in vitro.

METHODS

Purified OMVs were characterized by mass spectrometry (MS/MS). Labeled OMVs were administered orally or injected into the mouse tail vein to study OMV-brain distribution. By immunofluorescence of tissue samples, we evaluated: GFAP (astrocytes), βIII tubulin (neurons), and urease (OMVs). The in vitro effect of OMVs in astrocytes was assessed by monitoring NF-κB activation, expression of reactivity markers, cytokines in astrocyte-conditioned medium (ACM), and neuronal cell viability.

RESULTS

Urease and GroEL were prominent proteins in OMVs. Urease (OMVs) was present in the mouse brain and its detection coincided with astrocyte reactivity and neuronal damage. In vitro, OMVs induced astrocyte reactivity by increasing the intermediate filament proteins GFAP and vimentin, the plasma membrane α_Vβ₃ integrin, and the hemichannel connexin 43. OMVs also produced neurotoxic factors and promoted the release of IFNγ in a manner dependent on the activation of the transcription factor NF-κB. Surface antigens on reactive astrocytes, as well as secreted factors in response to OMVs, were shown to inhibit neurite outgrowth and damage neurons.

CONCLUSIONS

OMVs administered orally or injected into the mouse bloodstream reach the brain, altering astrocyte function and promoting neuronal damage in vivo. The effects of OMVs on astrocytes were confirmed in vitro and shown to be NF-κB-dependent. These findings suggest that Hp could trigger systemic effects by releasing nanosized vesicles that cross epithelial barriers and access the CNS, thus altering brain cells.

Activation of retinal glial cells contributes to the degeneration of ganglion cells in experimental glaucoma

Elevation of intraocular pressure (IOP) is a major risk factor for neurodegeneration in glaucoma. Glial cells, which play an important role in normal functioning of retinal neurons, are well involved into retinal ganglion cell (RGC) degeneration in experimental glaucoma animal models generated by elevated IOP. In response to elevated IOP, mGluR I is first activated and Kir4.1 channels are subsequently inhibited, which leads to the activation of Müller cells. Müller cell activation is followed by a complex process, including proliferation, release of inflammatory and growth factors (gliosis). Gliosis is further regulated by several factors. Activated Müller cells contribute to RGC degeneration through generating glutamate receptor-mediated excitotoxicity, releasing cytotoxic factors and inducing microglia activation. Elevated IOP activates microglia, and following morphological and functional changes, these cells, as resident immune cells in the retina, show adaptive immune responses, including an enhanced release of pro-inflammatory factors (tumor neurosis factor-α, interleukins, etc.). These ATP and Toll-like receptor-mediated responses are further regulated by heat shock proteins, CD200R, chemokine receptors, and metabotropic purinergic receptors, may aggravate RGC loss. In the optic nerve head, astrogliosis is initiated and regulated by a complex reaction process, including purines, transmitters, chemokines, growth factors and cytokines, which contributes to RGC axon injury through releasing pro-inflammatory factors and changing extracellular matrix in glaucoma. The effects of activated glial cells on RGCs are further modified by the interplay among different types of glial cells. This review is concluded by presenting an in-depth discussion of possible research directions in this field in the future.

The role of TIGAR in nervous system diseases

TP53-induced glycolysis and apoptosis regulator (TIGAR) mainly regulates pentose phosphate pathway by inhibiting glycolysis, so as to synthesize ribose required by DNA, promote DNA damage repair and cell proliferation, maintain cell homeostasis and avoid body injury. Its physiological functions include anti-oxidative stress, reducing inflammation, maintaining mitochondrial function, inhibiting apoptosis, reducing autophagy etc. This paper reviews the research of TIGAR in neurological diseases, including stroke, Parkinson’s disease (PD), Alzheimer’s disease (AD), seizures and brain tumors, aiming to provide reference for the development of new therapeutic targets.

Multiple types of programmed necrosis such as necroptosis, pyroptosis, oxytosis/ferroptosis, and parthanatos contribute simultaneously to retinal damage after ischemia-reperfusion

Ischemia-reperfusion (IR) injury is implicated in a large array of pathological conditions in the retina. Increasing experimental evidence suggests that programmed necrosis makes a significant contribution to inflammation and retinal damage triggered by IR. Since there are many types of programmed necrosis, it is important to identify those involved in retinal IR to determine the correct treatment. To this end, we used a mouse model of retinal IR and a variety of approaches including RNA-seq data analysis. Our RNA-seq data revealed the rapid development of ischemic pathology in the retina during the first 24 h after reperfusion. We found that at least four types of programmed necrosis including necroptosis, pyroptosis, oxytosis/ferroptosis, and parthanatos are simultaneously involved in retinal IR. Our data suggest that the high activity of the TNF pathway at the early stage of retinal IR leads to early activation of necroptosis while significant activity of other types of programmed necrosis appears later. Our results indicate that TNF, glutamate, and ferrous iron generated by Steap3 may be key players concurrently triggering at least necroptosis, oxytosis/ferroptosis, and parthanatos in ischemic retinal ganglion cells (RGCs). Thus, multiple signaling cascades involved in programmed necrosis should be synchronously targeted for therapeutic purposes to treat retinal IR.

Induction of distinct neuroinflammatory markers and gut dysbiosis by differential pyridostigmine bromide dosing in a chronic mouse model of GWI showing persistent exercise fatigue and cognitive impairment

AIMS

To characterize neuroinflammatory and gut dysbiosis signatures that accompany exaggerated exercise fatigue and cognitive/mood deficits in a mouse model of Gulf War Illness (GWI).

METHODS

Adult male C57Bl/6N mice were exposed for 28 d (5 d/wk) to pyridostigmine bromide (P.O.) at 6.5 mg/kg/d, b.i.d. (GW1) or 8.7 mg/kg/d, q.d. (GW2); topical permethrin (1.3 mg/kg), topical N,N-diethyl-meta-toluamide (33%) and restraint stress (5 min). Animals were phenotypically evaluated as described in an accompanying article [124] and sacrificed at 6.6 months post-treatment (PT) to allow measurement of brain neuroinflammation/neuropathic pain gene expression, hippocampal glial fibrillary acidic protein, brain Interleukin-6, gut dysbiosis and serum endotoxin.

KEY FINDINGS

Compared to GW1, GW2 showed a more intense neuroinflammatory transcriptional signature relative to sham stress controls. Interleukin-6 was elevated in GW2 and astrogliosis in hippocampal CA1 was seen in both GW groups. Beta-diversity PCoA using weighted Unifrac revealed that gut microbial communities changed after exposure to GW2 at PT188. Both GW1 and GW2 displayed systemic endotoxemia, suggesting a gut-brain mechanism underlies the neuropathological signatures. Using germ-free mice, probiotic supplementation with Lactobacillus reuteri produced less gut permeability than microbiota transplantation using GW2 feces.

SIGNIFICANCE

Our findings demonstrate that GW agents dose-dependently induce differential neuropathology and gut dysbiosis associated with cognitive, exercise fatigue and mood GWI phenotypes. Establishment of a comprehensive animal model that recapitulates multiple GWI symptom domains and neuroinflammation has significant implications for uncovering pathophysiology, improving diagnosis and treatment for GWI.

Neuroinflammation and Scarring After Spinal Cord Injury: Therapeutic Roles of MSCs on Inflammation and Glial Scar

Transected axons are unable to regenerate after spinal cord injury (SCI). Glial scar is thought to be responsible for this failure. Regulating the formation of glial scar post-SCI may contribute to axonal regrow. Over the past few decades, studies have found that the interaction between immune cells at the damaged site results in a robust and persistent inflammatory response. Current therapy strategies focus primarily on the inhibition of subacute and chronic neuroinflammation after the acute inflammatory response was executed. Growing evidences have documented that mesenchymal stem cells (MSCs) engraftment can be served as a promising cell therapy for SCI. Numerous studies have shown that MSCs transplantation can inhibit the excessive glial scar formation as well as inflammatory response, thereby facilitating the anatomical and functional recovery. Here, we will review the effects of inflammatory response and glial scar formation in spinal cord injury and repair. The role of MSCs in regulating neuroinflammation and glial scar formation after SCI will be reviewed as well.

Gap Junctional Coupling Between Retinal Astrocytes Exacerbates Neuronal Damage in Ischemia-Reperfusion Injury

Purpose

Retinal astrocytes abundantly express connexin 43 (Cx43), a transmembrane protein that forms gap junction (GJ) channels and unopposed hemichannels. While it is well established that Cx43 is upregulated in retinal injuries, it is unclear whether astrocytic Cx43 plays a role in retinal ganglion cell (RGC) loss associated with injury. Here, we investigated the effect of astrocyte-specific deletion of Cx43 (Cx43KO) and channel inhibitors on RGC loss in retinal ischemia/reperfusion (I/R) injury and assessed changes in expression and GJ channel and hemichannel function that occur in I/R injury. The effect of Cx43 deletion on neural function in the uninjured retina was also assessed.

Methods

Cx43 expression, astrocyte density and morphology, and RGC death in wild-type and Cx43KO mice after I/R injury were determined using immunohistochemistry and Western blotting. Visual function was assessed using ERG recordings. GJ coupling and hemichannel activity were evaluated using tracer coupling and uptake studies, respectively.

Results

Loss of RGCs in I/R injury was accompanied by an increase of Cx43 expression in astrocytes. Functional studies indicated that I/R injury augmented astrocytic GJ coupling but not Cx43 hemichannel activity. Importantly, deletion of astrocytic Cx43 improved neuronal survival in acute ischemia but did not affect RGC function in the absence of injury. In support, pharmacologic inhibition of GJ coupling provided neuroprotection in I/R injury.

Conclusions

The increase in Cx43 expression and GJ coupling during acute I/R injury exacerbates RGC loss. Inhibition of astrocytic Cx43 channels might represent a useful strategy to promote RGC survival in pathologic conditions.

Therapeutic Drugs and Devices for Tackling Ocular Hypertension and Glaucoma, and Need for Neuroprotection and Cytoprotective Therapies

Damage to the optic nerve and the death of associated retinal ganglion cells (RGCs) by elevated intraocular pressure (IOP), also known as glaucoma, is responsible for visual impairment and blindness in millions of people worldwide. The ocular hypertension (OHT) and the deleterious mechanical forces it exerts at the back of the eye, at the level of the optic nerve head/optic disc and lamina cribosa, is the only modifiable risk factor associated with glaucoma that can be treated. The elevated IOP occurs due to the inability of accumulated aqueous humor (AQH) to egress from the anterior chamber of the eye due to occlusion of the major outflow pathway, the trabecular meshwork (TM) and Schlemm’s canal (SC). Several different classes of pharmaceutical agents, surgical techniques and implantable devices have been developed to lower and control IOP. First-line drugs to promote AQH outflow via the uveoscleral outflow pathway include FP-receptor prostaglandin (PG) agonists (e.g., latanoprost, travoprost and tafluprost) and a novel non-PG EP2-receptor agonist (omidenepag isopropyl, Eybelis^®). TM/SC outflow enhancing drugs are also effective ocular hypotensive agents (e.g., rho kinase inhibitors like ripasudil and netarsudil; and latanoprostene bunod, a conjugate of a nitric oxide donor and latanoprost). One of the most effective anterior chamber AQH microshunt devices is the Preserflo^® microshunt which can lower IOP down to 10–13 mmHg. Other IOP-lowering drugs and devices on the horizon will be also discussed. Additionally, since elevated IOP is only one of many risk factors for development of glaucomatous optic neuropathy, a treatise of the role of inflammatory neurodegeneration of the optic nerve and retinal ganglion cells and appropriate neuroprotective strategies to mitigate this disease will also be reviewed and discussed.

Profiles of microRNA in aqueous humor of normal tension glaucoma patients using RNA sequencing

We aimed to identify and compare microRNAs (miRNAs) from individual aqueous humor samples between normal-tension glaucoma (NTG) patients and normal controls. Aqueous humor (80 to 120 µl) was collected before cataract surgery. Six stable NTG patients and seven age-matched controls were included in the final analysis. RNA sequencing was conducted for RNA samples extracted from the 13 aqueous humor samples, and bioinformatics analysis was employed for the miRNA targets and related pathways. Two hundred and twenty-eight discrete miRNAs were detected in the aqueous humor and consistently expressed in all samples. Eight significantly upregulated miRNAs were found in the NTG patients compared to the controls (fold-change > 2, p < 0.05). They were hsa-let-7a-5p, hsa-let-7c-5p, hsa-let-7f-5p, hsa-miR-192-5p, hsa-miR-10a-5p, hsa-miR-10b-5p, hsa-miR-375, and hsa-miR-143-3p. These miRNAs were predicted to be associated with the biological processes of apoptosis, autophagy, neurogenesis, and aging in the gene ontology categories. The related Kyoto encyclopedia of genes and genomes pathways were extracellular matrix-receptor interaction, mucin-type O-glycan biosynthesis, biotin metabolism, and signaling pathways regulating the pluripotency of stem cells. The differentially expressed miRNA in the NTG samples compared to the controls suggest the possible roles of miRNA in the pathogenesis of NTG. The underlying miRNA-associated pathways further imply novel targets for the pathogenesis of NTG.

Beyond the GFAP-Astrocyte Protein Markers in the Brain

The idea of central nervous system as one-man band favoring neurons is long gone. Now we all are aware that neurons and neuroglia are team players and constant communication between those various cell types is essential to maintain functional efficiency and a quick response to danger. Here, we summarize and discuss known and new markers of astroglial multiple functions, their natural heterogeneity, cellular interactions, aging and disease-induced dysfunctions. This review is focused on newly reported facts regarding astrocytes, which are beyond the old stereotypes. We present an up-to-date list of marker proteins used to identify a broad spectrum of astroglial phenotypes related to the various physiological and pathological nervous system conditions. The aim of this review is to help choose markers that are well-tailored for specific needs of further experimental studies, precisely recognizing differential glial phenotypes, or for diagnostic purposes. We hope it will help to categorize the functional and structural diversity of the astroglial population and ease a clear readout of future experimental results.

Upregulated Long Non-coding RNA ALMS1-IT1 Promotes Neuroinflammation by Activating NF-κB Signaling in Ischemic Cerebral Injury

BACKGROUND

ALMS1-IT1, a recently identified lncRNA, has been proven to play a crucial role in regulating tumor progression and predicting the survival time of tumor patients. Data analysis from the Human Body Map (HBM) revealed that ALMS1-IT1 is expressed mainly in brain tissues.

METHODS

In this study, the role of ALMS1-IT in regulating neuro-inflammation and functional recovery was investigated after ischemic cerebral damage. To this end, the rat model of transient middle cerebral artery occlusion (tMCAO) was constructed, the cell model of oxygen-glucose deprivation (OGD) was established using BV2 microglial cells, and the aberrant expression of ALMS1-IT1 was assessed in brain tissues. After ALMS1- IT1 knockdown through intrathecal injection of Lv-shALMS1-IT1, neuro-inflammatory response and functional tests including a modified neurological severity score (mNSS) and a foot-fault test were assessed.

RESULTS

The level of ALMS1-IT1 was promptly enhanced at 12 hours (h) following MCAO, peaking at 48 h, and remaining high at day 14 compared to the sham group. Pro-inflammatory cytokines (IL-1β, IL-6, and TNF- α) were increased after MCAO, whereas ALMS1-IT1 inhibition suppressed the expression of IL-1β, IL-6 and TNF-α in MCAO rats. The results from mNSS and foot-fault test showed that ALMS1-IT1 knockdown significantly improved spatial learning and sensorimotor function of MCAO rats. Mechanistically, ALMS1-IT1 knockdown suppressed the activation of NF-κB signaling in vitro and in vivo, as evidenced by decreased p65 expression and p65 nuclear translocation. ALMS1-IT1 overexpression facilitated pro-inflammatory cytokines expression in microglia, whereas the effect was blocked by treatment with JSH-23 (a specific NF-κB inhibitor).

CONCLUSION

These data demonstrated that ALMS1-IT1 inhibition improved neurological function of MCAO rats, at least in part by repressing NF-κB-dependent neuro-inflammation.

Immune Responses in the Glaucomatous Retina: Regulation and Dynamics

Glaucoma is a multifactorial disease resulting in progressive vision loss due to retinal ganglion cell (RGC) dysfunction and death. Early events in the pathobiology of the disease include oxidative, metabolic, or mechanical stress that acts upon RGC, causing these to rapidly release danger signals, including extracellular ATP, resulting in micro- and macroglial activation and neuroinflammation. Danger signaling also leads to the formation of inflammasomes in the retina that enable maturation of proinflammatory cytokines such IL-1β and IL-18. Chronic neuroinflammation can have directly damaging effects on RGC, but it also creates a proinflammatory environment and compromises the immune privilege of the retina. In particular, continuous synthesis of proinflammatory mediators such as TNFα, IL-1β, and anaphylatoxins weakens the blood–retina barrier and recruits or activates T-cells. Recent data have demonstrated that adaptive immune responses strongly exacerbate RGC loss in animal models of the disease as T-cells appear to target heat shock proteins displayed on the surface of stressed RGC to cause their apoptotic death. It is possible that dysregulation of these immune responses contributes to the continued loss of RGC in some patients.

Neuroinflammation in Post-Ischemic Neurodegeneration of the Brain: Friend, Foe, or Both?

One of the leading causes of neurological mortality, disability, and dementia worldwide is cerebral ischemia. Among the many pathological phenomena, the immune system plays an important role in the development of post-ischemic degeneration of the brain, leading to the development of neuroinflammatory changes in the brain. After cerebral ischemia, the developing neuroinflammation causes additional damage to the brain cells, but on the other hand it also plays a beneficial role in repair activities. Inflammatory mediators are sources of signals that stimulate cells in the brain and promote penetration, e.g., T lymphocytes, monocytes, platelets, macrophages, leukocytes, and neutrophils from systemic circulation to the brain ischemic area, and this phenomenon contributes to further irreversible ischemic brain damage. In this review, we focus on the issues related to the neuroinflammation that occurs in the brain tissue after ischemia, with particular emphasis on ischemic stroke and its potential treatment strategies.

Astrocyte Activation in Neurovascular Damage and Repair Following Ischaemic Stroke

Transient or permanent loss of tissue perfusion due to ischaemic stroke can lead to damage to the neurovasculature, and disrupt brain homeostasis, causing long-term motor and cognitive deficits. Despite promising pre-clinical studies, clinically approved neuroprotective therapies are lacking. Most studies have focused on neurons while ignoring the important roles of other cells of the neurovascular unit, such as astrocytes and pericytes. Astrocytes are important for the development and maintenance of the blood-brain barrier, brain homeostasis, structural support, control of cerebral blood flow and secretion of neuroprotective factors. Emerging data suggest that astrocyte activation exerts both beneficial and detrimental effects following ischaemic stroke. Activated astrocytes provide neuroprotection and contribute to neurorestoration, but also secrete inflammatory modulators, leading to aggravation of the ischaemic lesion. Astrocytes are more resistant than other cell types to stroke pathology, and exert a regulative effect in response to ischaemia. These roles of astrocytes following ischaemic stroke remain incompletely understood, though they represent an appealing target for neurovascular protection following stroke. In this review, we summarise the astrocytic contributions to neurovascular damage and repair following ischaemic stroke, and explore mechanisms of neuroprotection that promote revascularisation and neurorestoration, which may be targeted for developing novel therapies for ischaemic stroke.

Prophylactic inhibition of NF-κB expression in microglia leads to attenuation of hypoxic ischemic injury of the immature brain

Background

Periventricular leukomalacia (PVL), a devastating brain injury affecting premature infants, is the most common cause of cerebral palsy. PVL is caused by hypoxia ischemia (HI) and is characterized by white matter necrotic lesions, microglial activation, upregulation of NF-κB, and neuronal death. The microglia is the main cell involved in PVL pathogenesis. The goal of this study was to investigate the role of microglial NF-κB activity and its prophylactic inhibition in a neonate mouse model of HI.

Methods

Transgenic mice with specific knockout NF-κB in microglia and colony stimulating factor 1 receptor Cre with floxed IKKβ (CSF-1R Cre + IKKβ^flox/wt ) were used. Postnatal day 5 (P5) mice underwent sham or bilateral temporary carotid artery ligation followed by hypoxia. After HI insult, inflammatory cytokines, volumetric MRI, histopathology, and immunohistochemistry for oligodendroglia and microglial activation markers were analyzed. Long-term neurobehavioral assessment, including grip strength, rotarod, and open field testing, was performed at P60.

Results

We demonstrate that selective inhibition of NF-κB in microglia decreases HI-induced brain injury by decreasing microglial activation, proinflammatory cytokines, and nitrative stress. Rescue of oligodendroglia is evidenced by immunohistochemistry, decreased ventriculomegaly on MRI, and histopathology. This selective inhibition leads to attenuation of paresis, incoordination, and improved grip strength, gait, and locomotion.

Conclusion

We conclude that NF-κb activation in microglia plays a major role in the pathogenesis of hypoxic ischemic injury of the immature brain, and its prophylactic inhibition offers significant neuroprotection. Using a specific inhibitor of microglial NF-κB may offer a new prophylactic or therapeutic alternative in preterm infants affected by HI and possibly other neurological diseases in which microglial activation plays a role.

Inflammation in Glaucoma: From the back to the front of the eye, and beyond

The pathophysiology of glaucoma is complex, multifactorial and not completely understood. Elevated intraocular pressure (IOP) and/or impaired retinal blood flow may cause initial optic nerve damage. In addition, age-related oxidative stress in the retina concurrently with chronic mechanical and vascular stress is crucial for the initiation of retinal neurodegeneration. Oxidative stress is closely related to cell senescence, mitochondrial dysfunction, excitotoxicity, and neuroinflammation, which are involved in glaucoma progression. Accumulating evidence from animal glaucoma models and from human ocular samples suggests a dysfunction of the para-inflammation in the retinal ganglion cell layer and the optic nerve head. Moreover, quite similar mechanisms in the anterior chamber could explain the trabecular meshwork dysfunction and the elevated IOP in primary open-angle glaucoma. On the other hand, ocular surface disease due to topical interventions is the most prominent and visible consequence of inflammation in glaucoma, with a negative impact on filtering surgery failure, topical treatment efficacy, and possibly on inflammation in the anterior segment. Consequently, glaucoma appears as an outstanding eye disease where inflammatory changes may be present to various extents and consequences along the eye structure, from the ocular surface to the posterior segment, and the visual pathway. Here we reviewed the inflammatory processes in all ocular structures in glaucoma from the back to the front of the eye and beyond. Our approach was to explain how para-inflammation is necessary to maintain homoeostasis, and to describe abnormal inflammatory findings observed in glaucomatous patients or in animal glaucoma models, supporting the hypothesis of a dysregulation of the inflammatory balance toward a pro-inflammatory phenotype. Possible anti-inflammatory therapeutic approaches in glaucoma are also discussed.

Transgenic inhibition of astroglial NF-κB restrains the neuroinflammatory and neurodegenerative outcomes of experimental mouse glaucoma

BACKGROUND

Glia-driven neuroinflammation promotes neuron injury in glaucoma that is a chronic neurodegenerative disease of the optic nerve and a leading cause of irreversible blindness. Although therapeutic modulation of neuroinflammation is increasingly viewed as a logical strategy to avoid inflammatory neurotoxicity in glaucoma, current understanding of the molecular regulation of neuroinflammation is incomplete, and the molecular targets for immunomodulation remains unknown. Growing datasets pointed to nuclear factor-kappaB (NF-κB), a key transcriptional activator of inflammation, which was identified to be most affected in glaucomatous astroglia. Using a cell type-specific experimental approach, this study aimed to determine the value of astroglial NF-κB as a potential treatment target for immunomodulation in experimental mouse glaucoma.

METHODS

Neuroinflammatory and neurodegenerative outcomes of experimental glaucoma were comparatively analyzed in mice with or without cre/lox-based conditional deletion of astroglial IκKβ, which is the main activating kinase involved in IκB degradation through the canonical pathway of NF-κB activation. Glial responses and the inflammatory status of the retina and optic nerve were analyzed by cell morphology and cytokine profiling, and neuron structure and function were analyzed by counting retinal ganglion cell (RGC) axons and somas and recording pattern electroretinography (PERG) responses.

RESULTS

Analysis of glial inflammatory responses showed immunomodulatory outcomes of the conditional transgenic deletion of IκKβ in astroglia. Various pro-inflammatory cytokines known to be transcriptional targets for NF-κB exhibited decreased production in IκKβ-deleted astroglia, which included TNF-α that can induce RGC apoptosis and axon degeneration during glaucomatous neurodegeneration. Indeed, transgenic modulation of inflammatory responses by astroglial IκKβ deletion reduced neurodegeneration at different neuronal compartments, including both RGC axons and somas, and protected PERG responses.

CONCLUSIONS

The findings of this study support a key role for astroglial NF-κB in neuroinflammatory and neurodegenerative outcomes of experimental glaucoma and the potential of this transcriptional regulator pathway as a glial treatment target to provide neuroprotection through immunomodulation. By pointing to a potential treatment strategy targeting the astroglia, these experimental findings are promising for future clinical translation through transgenic applications to improve the treatment of this blinding disease.

Huoxue-Tongluo-Lishui-Decoction is visual-protective against retinal ischemia-reperfusion injury

Retinal ischemia reperfusion injury (IRI) is a leading cause of visual impairment or blindness, and an effective way to prevent the visual loss needs to be developed. Although decades of clinical application of Huoxue-Tongluo-Lishui-Decoction (HTLD) has demonstrated its reliable clinical efficacy against retinal IRI, no convincing randomized controlled trials were conducted in humans or animals, and the associated mechanism still needs to be explored. To confirm the protective effect of HTLD against retinal IRI and to explore its underlying mechanisms, a standard retinal IRI animal model, randomized controlled trials, objective evaluation and examination methods were adopted in this study. Flash visual evoked potentials (F-VEP) was performed 8 weeks post-reperfusion. The results showed that the medium dose of HTLD had better treatment effects than low dose of HTLD. High dose of HTLD did not further improve visual function relative to medium dose of HTLD, but had poor performance in the latency of P2 wave. The angio-optical coherence tomography (angio-OCT) examination showed that retinal nerve fiber layer (RNFL) became edematous in the early stage, then the edema subsided, and RNFL became thinning in the late stage. HTLD reduced the swelling of RNFL in the early stage and prevented the thinning of RNFL in the late stage. Similar to F-VEP, medium dose of HTLD has the best neural-protective effects against retinal IRI. In mechanisms, HTLD treatment not only enhanced autophagy at 6 h after reperfusion, but extended the enhancing effect until at least 24 h. HTLD treatment significantly reduced the cleaved Caspase-3, cleaved PARP and Caspase-3 activity at 48 h after reperfusion. HTLD inhibited neuro-toxic cytokines expression in retinal IRI by modulating Akt/NF-kB signaling. HTLD treatment enhanced the expressions of L-glutamate/L-aspartate transporter (GLAST) and glutamine synthetase (GS), and lower the concentration of free glutamate in retina after reperfusion. The phosphorylation of iNOS increased significantly in retinal IRI at 6 h, and HTLD treatment suppressed the phosphorylation of Inducible nitric oxide synthetase (iNOS). In conclusion, HTLD is visual-protective against retinal IRI, and the regulation of autophagy, apoptosis and neuro-toxic mediators may be the underlying mechanisms. These findings may provide new ideas for the clinical treatment of retinal IRI related diseases.

The role of microglia in neuroprogressive disorders: mechanisms and possible neurotherapeutic effects of induced ketosis

A comprehensive review of molecular mechanisms involved in the promotion and maintenance of distinct microglia phenotypes is provided. The acquisition and perpetuation of predominantly pro-inflammatory microglial phenotypes have been implicated in the pathophysiology of several neuroprogressive diseases and is associated with reduced ATP production via oxidative phosphorylation, increased ATP generation by glycolysis, elevated oxidative and nitrosative stress and other metabolic, inflammatory and hormonal insults. Microglia can also adopt a predominantly anti-inflammatory phenotypes with neuroprotective properties. Strategies that promote and maintain a predominantly anti-inflammatory phenotype may hold promise as novel therapeutic opportunities for neuroprogressive illness. Induced ketosis may promote a transition towards predominantly anti-inflammatory microglial states/phenotypes by several mechanisms, including inhibition of glycolysis and increased NAD⁺ production; engagement of microglial GPR109A receptors; histone deacetylase inhibition; and elevated n-3 polyunsaturated fatty acids levels. Since microglia activation can now be assessed in vivo, these data provide a clear rationale for the design of transdiagnostic randomized controlled trials of the ketogenic diet and other ketosis-inducing strategies for neuroprogressive diseases, which may also provide mechanistic insights through the assessment of "target engagement".

Glial Cells: Role of the Immune Response in Ischemic Stroke

Ischemic stroke, which accounts for 75-80% of all strokes, is the predominant cause of morbidity and mortality worldwide. The post-stroke immune response has recently emerged as a new breakthrough target in the treatment strategy for ischemic stroke. Glial cells, including microglia, astrocytes, and oligodendrocytes, are the primary components of the peri-infarct environment in the central nervous system (CNS) and have been implicated in post-stroke immune regulation. However, increasing evidence suggests that glial cells exert beneficial and detrimental effects during ischemic stroke. Microglia, which survey CNS homeostasis and regulate innate immune responses, are rapidly activated after ischemic stroke. Activated microglia release inflammatory cytokines that induce neuronal tissue injury. By contrast, anti-inflammatory cytokines and neurotrophic factors secreted by alternatively activated microglia are beneficial for recovery after ischemic stroke. Astrocyte activation and reactive gliosis in ischemic stroke contribute to limiting brain injury and re-establishing CNS homeostasis. However, glial scarring hinders neuronal reconnection and extension. Neuroinflammation affects the demyelination and remyelination of oligodendrocytes. Myelin-associated antigens released from oligodendrocytes activate peripheral T cells, thereby resulting in the autoimmune response. Oligodendrocyte precursor cells, which can differentiate into oligodendrocytes, follow an ischemic stroke and may result in functional recovery. Herein, we discuss the mechanisms of post-stroke immune regulation mediated by glial cells and the interaction between glial cells and neurons. In addition, we describe the potential roles of various glial cells at different stages of ischemic stroke and discuss future intervention targets.

Glaucoma: A Degenerative Optic Neuropathy Related to Neuroinflammation?

Glaucoma is one of the leading causes of irreversible blindness in the world and remains a major public health problem. To date, incomplete knowledge of this disease’s pathophysiology has resulted in current therapies (pharmaceutical or surgical) unfortunately having only a slowing effect on disease progression. Recent research suggests that glaucomatous optic neuropathy is a disease that shares common neuroinflammatory mechanisms with “classical” neurodegenerative pathologies. In addition to the death of retinal ganglion cells (RGCs), neuroinflammation appears to be a key element in the progression and spread of this disease. Indeed, early reactivity of glial cells has been observed in the retina, but also in the central visual pathways of glaucoma patients and in preclinical models of ocular hypertension. Moreover, neuronal lesions are not limited to retinal structure, but also occur in central visual pathways. This review summarizes and puts into perspective the experimental and clinical data obtained to date to highlight the need to develop neuroprotective and immunomodulatory therapies to prevent blindness in glaucoma patients.

Extracellular Signal-Regulated Kinase 1/2 Pathway Is Insufficiently Involved in the Neuroprotective Effect by Hydrogen Sulfide Supplement in Experimental Glaucoma

Purpose

Glaucoma is a neurodegenerative eye disease characterized by gradually impaired visual field and irreversible blindness due to retinal ganglion cell (RGC) loss. Our previous studies have confirmed that hydrogen sulfide (H2S) takes part in the glaucomatous process and contributes to RGC protection. The present study aimed to further investigate the role of extracellular signal-regulated kinase 1/2 (ERK 1/2) pathway underlying the impact of H2S, to better understand the mechanism through which H2S exerts neuroprotection in glaucoma.

Methods

An established rat glaucoma model was used and 168 rats were qualified to undergo sodium hydrosulfide (NaHS, a H2S donor)/PD98059 (an ERK inhibitor) treatment. Then the survival and apoptosis of RGC were evaluated through retrograde labeling and TUNEL staining, along with activity evaluations of ERK 1/2 pathway, intrinsic apoptotic pathway, glial activation, nuclear factor kappa B (NF-κB) pathway, nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, autophagy, and TNF-α production through immunohistochemistry, Western blotting, and ELISA.

Results

The study demonstrated that NaHS suppressed ERK 1/2 pathway activity similarly to PD98059 in retinas of experimental glaucoma rats, while PD98059 also similarly suppressed glial activation, NF-κB pathway, NADPH oxidase, and TNF-α production. However, PD98059 did not affect RGC survival, apoptotic regulation, or autophagy as NaHS did.

Conclusions

Our study indicated that inhibition of ERK 1/2 pathway might partly contribute to the neuroprotection by H2S in experimental glaucoma; however, it was insufficient to initiate the therapeutic effect on its own.

Astrocytic N-Myc Downstream-regulated Gene-2 Is Involved in Nuclear Transcription Factor κB-mediated Inflammation Induced by Global Cerebral Ischemia

BACKGROUND

Inflammation is a key element in the pathophysiology of cerebral ischemia. This study investigated the role of N-Myc downstream-regulated gene-2 in nuclear transcription factor κB-mediated inflammation in ischemia models.

METHODS

Mice (n = 6 to 12) with or without nuclear transcription factor κB inhibitor pyrrolidinedithiocarbamate pretreatment were subjected to global cerebral ischemia for 20 min. Pure astrocyte cultures or astrocyte-neuron cocultures (n = 6) with or without pyrrolidinedithiocarbamate pretreatment were exposed to oxygen-glucose deprivation for 4 h or 2 h. Astrocytic nuclear transcription factor κB and N-Myc downstream-regulated gene-2 expression, proinflammatory cytokine secretion, neuronal apoptosis and survival, and memory function were analyzed at different time points after reperfusion or reoxygenation. Proinflammatory cytokine secretion was also studied in lentivirus-transfected astrocyte lines after reoxygenation.

RESULTS

Astrocytic nuclear transcription factor κB and N-Myc downstream-regulated gene-2 expression and proinflammatory cytokine secretion increased after reperfusion or reoxygenation. Pyrrolidinedithiocarbamate pretreatment significantly reduced N-Myc downstream-regulated gene-2 expression and proinflammatory cytokine secretion in vivo and in vitro, reduced neuronal apoptosis induced by global cerebral ischemia/reperfusion (from 65 ± 4% to 47 ± 4%, P = 0.0375) and oxygen-glucose deprivation/reoxygenation (from 45.6 ± 0.2% to 22.0 ± 4.0%, P < 0.001), and improved memory function in comparison to vehicle-treated control animals subjected to global cerebral ischemia/reperfusion. N-Myc downstream-regulated gene-2 lentiviral knockdown reduced the oxygen-glucose deprivation-induced secretion of proinflammatory cytokines.

CONCLUSIONS

Astrocytic N-Myc downstream-regulated gene-2 is up-regulated after cerebral ischemia and is involved in nuclear transcription factor κB-mediated inflammation. Pyrrolidinedithiocarbamate alleviates ischemia-induced neuronal injury and hippocampal-dependent cognitive impairment by inhibiting increases in N-Myc downstream-regulated gene-2 expression and N-Myc downstream-regulated gene-2-mediated inflammation.

Neuroinflammation: friend and foe for ischemic stroke

Stroke, the third leading cause of death and disability worldwide, is undergoing a change in perspective with the emergence of new ideas on neurodegeneration. The concept that stroke is a disorder solely of blood vessels has been expanded to include the effects of a detrimental interaction between glia, neurons, vascular cells, and matrix components, which is collectively referred to as the neurovascular unit. Following the acute stroke, the majority of which are ischemic, there is secondary neuroinflammation that both promotes further injury, resulting in cell death, but conversely plays a beneficial role, by promoting recovery. The proinflammatory signals from immune mediators rapidly activate resident cells and influence infiltration of a wide range of inflammatory cells (neutrophils, monocytes/macrophages, different subtypes of T cells, and other inflammatory cells) into the ischemic region exacerbating brain damage. In this review, we discuss how neuroinflammation has both beneficial as well as detrimental roles and recent therapeutic strategies to combat pathological responses. Here, we also focus on time-dependent entry of immune cells to the ischemic area and the impact of other pathological mediators, including oxidative stress, excitotoxicity, matrix metalloproteinases (MMPs), high-mobility group box 1 (HMGB1), arachidonic acid metabolites, mitogen-activated protein kinase (MAPK), and post-translational modifications that could potentially perpetuate ischemic brain damage after the acute injury. Understanding the time-dependent role of inflammatory factors could help in developing new diagnostic, prognostic, and therapeutic neuroprotective strategies for post-stroke inflammation.

Immunomodulation as a Neuroprotective Strategy for Glaucoma Treatment

PURPOSE OF REVIEW

This review aims to highlight the current knowledge about inflammatory mechanisms of neurodegeneration in glaucoma with emphasis on potential immunomodulation strategies.

RECENT FINDINGS

Glaucomatous retina and optic nerve present multiple evidences of inflammatory responses of astroglia, microglia, and blood-born immune cells. Although adaptive/protective responses of resident or systemic immune cells can support neurons and promote tissue repair mechanisms after injurious insults, prolonged inflammatory processes can also produce neurotoxic mediators. Treatments targeting these neurodestructive outcomes may restore immune homeostasis and protect neurons from inflammatory injury. Due to widespread and chronic nature of neuroinflammation in glaucoma, immunomodulation offers a treatment strategy to protect different neuronal compartments of RGCs during the chronic and asynchronous course of neurodegeneration. Uncovering of distinct molecular responses and interactions of different immune cells that determine the neuroinflammatory phenotype and participate in neurodegenerative outcomes will be critical to develop effective strategies for immunomodulation in glaucoma.

SUMMARY

Neuroinflammation has increasingly been recognized to play an important role in glaucomatous neurodegeneration, and its modulation appears to be a promising treatment strategy for neuroprotection.

Reactive Astrocytes in Neurodegenerative Diseases

Astrocytes, the largest and most numerous glial cells in the central nervous system (CNS), play a variety of important roles in regulating homeostasis, increasing synaptic plasticity and providing neuroprotection, thus helping to maintain normal brain function. At the same time, astrocytes can participate in the inflammatory response and play a key role in the progression of neurodegenerative diseases. Reactive astrocytes are strongly induced by numerous pathological conditions in the CNS. Astrocyte reactivity is initially characterized by hypertrophy of soma and processes, triggered by different molecules. Recent studies have demonstrated that neuroinflammation and ischemia can elicit two different types of reactive astrocytes, termed A1s and A2s. However, in the case of astrocyte reactivity in different neurodegenerative diseases, the recently published research issues remain a high level of conflict and controversy. So far, we still know very little about whether and how the function or reactivity of astrocytes changes in the progression of different neurodegenerative diseases. In this review, we aimed to briefly discuss recent studies highlighting the complex contribution of astrocytes in the process of various neurodegenerative diseases, which may provide us with new prospects for the development of an excellent therapeutic target for neurodegenerative diseases.

The Effects of Sodium Dichloroacetate on Mitochondrial Dysfunction and Neuronal Death Following Hypoglycemia-Induced Injury

Our previous studies demonstrated that some degree of neuronal death is caused by hypoglycemia, but a subsequent and more severe wave of neuronal cell death occurs due to glucose reperfusion, which results from the rapid restoration of low blood glucose levels. Mitochondrial dysfunction caused by hypoglycemia leads to increased levels of pyruvate dehydrogenase kinase (PDK) and suppresses the formation of ATP by inhibiting pyruvate dehydrogenase (PDH) activation, which can convert pyruvate into acetyl-coenzyme A (acetyl-CoA). Sodium dichloroacetate (DCA) is a PDK inhibitor and activates PDH, the gatekeeper of glucose oxidation. However, no studies about the effect of DCA on hypoglycemia have been published. In the present study, we hypothesized that DCA treatment could reduce neuronal death through improvement of glycolysis and prevention of reactive oxygen species production after hypoglycemia. To test this, we used an animal model of insulin-induced hypoglycemia and injected DCA (100 mg/kg, i.v., two days) following hypoglycemic insult. Histological evaluation was performed one week after hypoglycemia. DCA treatment reduced hypoglycemia-induced oxidative stress, microglial activation, blood–brain barrier disruption, and neuronal death compared to the vehicle-treated hypoglycemia group. Therefore, our findings suggest that DCA may have the therapeutic potential to reduce hippocampal neuronal death after hypoglycemia.

Inflammasome Activation Induces Pyroptosis in the Retina Exposed to Ocular Hypertension Injury

Mechanical stress and hypoxia during episodes of ocular hypertension (OHT) trigger glial activation and neuroinflammation in the retina. Glial activation and release of pro-inflammatory cytokines TNFα and IL-1β, complement, and other danger factors was shown to facilitate injury and loss of retinal ganglion cells (RGCs) that send visual information to the brain. However, cellular events linking neuroinflammation and neurotoxicity remain poorly characterized. Several pro-inflammatory and danger signaling pathways, including P2X7 receptors and Pannexin1 (Panx1) channels, are known to activate inflammasome caspases that proteolytically activate gasdermin D channel-formation to export IL-1 cytokines and/or induce pyroptosis. In this work, we used molecular and genetic approaches to map and characterize inflammasome complexes and detect pyroptosis in the OHT-injured retina. Acute activation of distinct inflammasome complexes containing NLRP1, NLRP3 and Aim2 sensor proteins was detected in RGCs, retinal astrocytes and Muller glia of the OHT-challenged retina. Inflammasome-mediated activation of caspases-1 and release of mature IL-1β were detected within 6 h and peaked at 12–24 h after OHT injury. These coincided with the induction of pyroptotic pore protein gasdermin D in neurons and glia in the ganglion cell layer (GCL) and inner nuclear layer (INL). The OHT-induced release of cytokines and RGC death were significantly decreased in the retinas of Casp1^−/−Casp4(11)^del, Panx1^−/− and in Wild-type (WT) mice treated with the Panx1 inhibitor probenecid. Our results showed a complex spatio-temporal pattern of innate immune responses in the retina. Furthermore, they indicate an active contribution of neuronal NLRP1/NLRP3 inflammasomes and the pro-pyroptotic gasdermin D pathway to pathophysiology of the OHT injury. These results support the feasibility of inflammasome modulation for neuroprotection in OHT-injured retinas.

Genetic suppression of IKK2/NF-κB in astrocytes inhibits neuroinflammation and reduces neuronal loss in the MPTP-Probenecid model of Parkinson's disease

Neuroinflammatory activation of glia is considered a pathological hallmark of Parkinson's disease (PD) and is seen in both human PD patients and in animal models of PD; however, the relative contributions of these cell types, especially astrocytes, to the progression of disease is not fully understood. The transcription factor, nuclear factor kappa B (NFκB), is an important regulator of inflammatory gene expression in glia and is activated by multiple cellular stress signals through the kinase complex, IKK2. We sought to determine the role of NFκB in modulating inflammatory activation of astrocytes in a model of PD by generating a conditional knockout mouse (hGfapcre/Ikbk2^F/F) in which IKK2 is specifically deleted in astrocytes. Measurements of IKK2 revealed a 70% deletion rate of IKK2 within astrocytes, as compared to littermate controls (Ikbk2^F/F). Use of this mouse in a subacute, progressive model of PD through exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and probenecid (MPTPp) revealed significant protection in exposed mice to direct and progressive loss of dopaminergic neurons in the substantia nigra (SN). hGfapcre/Ikbk2^F/F mice were also protected against MPTPp-induced loss in motor activity, loss of striatal proteins, and genomic alterations in nigral NFκB gene expression, but were not protected from loss of striatal catecholamines. Neuroprotection in hGfapcre/Ikbk2^F/F mice was associated with inhibition of MPTPp-induced astrocytic expression of inflammatory genes and protection against nitrosative stress and apoptosis in neurons. These data indicate that deletion of IKK2 within astrocytes is neuroprotective in the MPTPp model of PD and suggests that reactive astrocytes directly contribute the potentiation of dopaminergic pathology.

Astroglia in Sepsis Associated Encephalopathy

Cellular pathophysiology of sepsis associated encephalopathy (SAE) remains poorly characterised. Brain pathology in SAE, which is manifested by impaired perception, consciousness and cognition, results from multifactorial events, including high levels of systemic cytokines, microbial components and endotoxins, which all damage the brain barriers, instigate neuroinflammation and cause homeostatic failure. Astrocytes, being the principal homeostatic cells of the central nervous system contribute to the brain defence against infection. Forming multifunctional anatomical barriers, astroglial cells maintain brain-systemic interfaces and restrict the damage to the nervous tissue. Astrocytes detect, produce and integrate inflammatory signals between immune cells and cells of brain parenchyma, thus regulating brain immune response. In SAE astrocytes are present in both reactive and astrogliopathic states; balance between these states define evolution of pathology and neurological outcomes. In humans pathophysiology of SAE is complicated by frequent presence of comorbidities, as well as age-related remodelling of the brain tissue with senescence of astroglia; these confounding factors further impact upon SAE progression and neurological deficits.

Storax Protected Oxygen-Glucose Deprivation/Reoxygenation Induced Primary Astrocyte Injury by Inhibiting NF-κB Activation in vitro

Stroke is the second leading cause of death and the leading cause of long-term disability in the world. There is an urgent unmet need to develop a range of neuroprotective strategies to restrain the damage that occurs in the hours and days following a stroke. Storax, a natural resin extracted from injuring Liquidambar orientalis Mill, has been used to treat acute stroke in traditional Chinese medicine for many centuries. Storax has demonstrated the neuroprotective effects in cerebrovascular diseases. However, the neuroprotective mechanisms activated by storax in ischemia/reperfusion-injured astrocytes have not been elucidated. In this study, we established an oxygen-glucose deprivation/reoxygenation (OGD/R)-induced astrocytes injury model to investigate the effects of storax on OGD/R-induced astrocytes injury and potential mechanisms. Experimental results showed that storax alleviated expression of inflammatory cytokines and protected primary cortical astrocytes injured by OGD/R. Furthermore, storax could inhibit NF-κB activation in injured astrocytes by OGD/R and inhibition of NF-κB with Bay-11-7082 obscured the neuroprotective effects of storax. In conclusion, storax alleviated expression of inflammatory cytokines and protected primary cortical astrocytes injured by OGD/R, which was partially mediated by NF-κB signaling pathway activation.

General Pathophysiology of Astroglia

Astroglial cells are involved in most if not in all pathologies of the brain. These cells can change the morpho-functional properties in response to pathology or innate changes of these cells can lead to pathologies. Overall pathological changes in astroglia are complex and diverse and often vary with different disease stages. We classify astrogliopathologies into reactive astrogliosis, astrodegeneration with astroglial atrophy and loss of function, and pathological remodelling of astrocytes. Such changes can occur in neurological, neurodevelopmental, metabolic and psychiatric disorders as well as in infection and toxic insults. Mutation in astrocyte-specific genes leads to specific pathologies, such as Alexander disease, which is a leukodystrophy. We discuss changes in astroglia in the pathological context and identify some molecular entities underlying pathology. These entities within astroglia may repent targets for novel therapeutic intervention in the management of brain pathologies.

Peripheral neuropathy and gastroenterologic disorders: an overview on an underrecognized association

BACKGROUND AND AIM OF THE WORK

Although peripheral neuropathies in children are often of genetic origin, acquired causes should be carefully looked for and ruled out also in the pediatric age. Gastroenterological disorders can be complicated by peripheral neuropathy as a result of micronutrients deficiency, drug toxicity or because of shared pathophysiological mechanisms.

METHODS

In this descriptive review we sought to give an overview on the most relevant clinical conditions in which peripheral neuropathies are associated with gastro-intestinal disorders or symptoms.

RESULTS

We describe the clinical, demographic, and electrophysiological features of peripheral neuropathy in three main clinical scenarios: in the context of common gastroenterological disorders (inflammatory bowel and celiac disease), in the context of micronutrients deficiencies arising from malabsorption irrespective of etiology, and in a rare degenerative mitochondrial disorder, mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) disorder.

CONCLUSIONS

The association between gastrointestinal and peripheral nervous system symptoms is probably still underrecognized but has to be actively sought, in order to provide prompt diagnosis resulting in optimal care and long-term management with the aim to improve quality of life and, at least in some conditions, try to impact on prognosis.

The roles of astrocyte in the brain pathologies following ischemic stroke

Aim: In this work, we systematically explored the physiological functions of astrocytes and their roles following ischemic stroke, additionally, the potential therapy strategy targeting the astrocytes was also discussed. Methods: This work searched the PubMed database (including MEDLINE) until 14 Feb 2018, and furthermore, the studies were identified through cross-referencing and by consulting the experts in this field. Results: This study indicated that the astrocytes can not only play harmful roles following ischemic stroke through release of inflammatory factors and formation of glial scar but also have protective effects through quenching glutamate excitotoxicity and maintaining the clearance function of glymphatic system in brain. Conclusion: Owing to their important roles in physiological functions of brain and in the pathological conditions following ischemic stroke, the astrocytes might be a potential but promising therapeutic target for treating the ischemic stroke in the future.

Potential immunotherapies for traumatic brain and spinal cord injury

Traumatic injury of the central nervous system (CNS) including brain and spinal cord remains a leading cause of morbidity and disability in the world. Delineating the mechanisms underlying the secondary and persistent injury versus the primary and transient injury has been drawing extensive attention for study during the past few decades. The sterile neuroinflammation during the secondary phase of injury has been frequently identified substrate underlying CNS injury, but as of now, no conclusive studies have determined whether this is a beneficial or detrimental role in the context of repair. Recent pioneering studies have demonstrated the key roles for the innate and adaptive immune responses in regulating sterile neuroinflammation and CNS repair. Some promising immunotherapeutic strategies have been recently developed for the treatment of CNS injury. This review updates the recent progress on elucidating the roles of the innate and adaptive immune responses in the context of CNS injury, the development and characterization of potential immunotherapeutics, as well as outstanding questions in this field.

Effects of Protocatechuic Acid (PCA) on Global Cerebral Ischemia-Induced Hippocampal Neuronal Death

Global cerebral ischemia (GCI) is one of the main causes of hippocampal neuronal death. Ischemic damage can be rescued by early blood reperfusion. However, under some circumstances reperfusion itself can trigger a cell death process that is initiated by the reintroduction of blood, followed by the production of superoxide, a blood⁻brain barrier (BBB) disruption and microglial activation. Protocatechuic acid (PCA) is a major metabolite of the antioxidant polyphenols, which have been discovered in green tea. PCA has been shown to have antioxidant effects on healthy cells and anti-proliferative effects on tumor cells. To test whether PCA can prevent ischemia-induced hippocampal neuronal death, rats were injected with PCA (30 mg/kg/day) per oral (p.o) for one week after global ischemia. To evaluate degenerating neurons, oxidative stress, microglial activation and BBB disruption, we performed Fluoro-Jade B (FJB), 4-hydroxynonenal (4HNE), CD11b, GFAP and IgG staining. In the present study, we found that PCA significantly decreased degenerating neuronal cell death, oxidative stress, microglial activation, astrocyte activation and BBB disruption compared with the vehicle-treated group after ischemia. In addition, an ischemia-induced reduction in glutathione (GSH) concentration in hippocampal neurons was recovered by PCA administration. Therefore, the administration of PCA may be further investigated as a promising tool for decreasing hippocampal neuronal death after global cerebral ischemia.

Notch signaling and neuronal death in stroke

Ischemic stroke is a leading cause of morbidity and death, with the outcome largely determined by the amount of hypoxia-related neuronal death in the affected brain regions. Cerebral ischemia and hypoxia activate the Notch1 signaling pathway and four prominent interacting pathways (NF-κB, p53, HIF-1α and Pin1) that converge on a conserved DNA-associated nuclear multi-protein complex, which controls the expression of genes that can determine the fate of neurons. When neurons experience a moderate level of ischemic insult, the nuclear multi-protein complex up-regulates adaptive stress response genes encoding proteins that promote neuronal survival, but when ischemia is more severe the nuclear multi-protein complex induces genes encoding proteins that trigger and execute a neuronal death program. We propose that the nuclear multi-protein transcriptional complex is a molecular mediator of neuronal hormesis and a target for therapeutic intervention in stroke.

The Role of Astrocytes in Multiple Sclerosis

The role traditionally assigned to astrocytes in the pathogenesis of multiple sclerosis (MS) lesions has been the formation of the glial scar once inflammation has subsided. Astrocytes are now recognized to be early and highly active players during lesion formation and key for providing peripheral immune cells access to the central nervous system. Here, we review the role of astrocytes in the formation and evolution of MS lesions, including the recently described functional polarization of astrocytes, discuss prototypical pathways for astrocyte activation, and summarize mechanisms by which MS treatments affect astrocyte function.

Progesterone treatment shows greater protection in brain vs. retina in a rat model of middle cerebral artery occlusion: Progesterone receptor levels may play an important role

BACKGROUND/OBJECTIVE

To determine whether inflammation increases in retina as it does in brain following middle cerebral artery occlusion (MCAO), and whether the neurosteroid progesterone, shown to have protective effects in both retina and brain after MCAO, reduces inflammation in retina as well as brain.

METHODS

MCAO rats treated systemically with progesterone or vehicle were compared with shams. Protein levels of cytosolic NF-κB, nuclear NF-κB, phosphorylated NF-κB, IL-6, TNF-α, CD11b, progesterone receptor A and B, and pregnane X receptor were assessed in retinas and brains at 24 and 48 h using western blots.

RESULTS

Following MCAO, significant increases were observed in the following inflammatory markers: pNF-κB and CD11b at 24 h in both brain and retina, nuclear NF-κB at 24 h in brain and 48 h in retina, and TNF-α at 24 h in brain.Progesterone treatment in MCAO animals significantly attenuated levels of the following markers in brain: pNF-κB, nuclear NF-κB, IL-6, TNF-α, and CD11b, with significantly increased levels of cytosolic NF-κB. Retinas from progesterone-treated animals showed significantly reduced levels of nuclear NF-κB and IL-6 and increased levels of cytosolic NF-κB, with a trend for reduction in other markers. Post-MCAO, progesterone receptors A and B were upregulated in brain and downregulated in retina.

CONCLUSION

Inflammatory markers increased in both brain and retina after MCAO, with greater increases observed in brain. Progesterone treatment reduced inflammation, with more dramatic reductions observed in brain than retina. This differential effect may be due to differences in the response of progesterone receptors in brain and retina after injury.

Hydrogen sulfide supplement attenuates the apoptosis of retinal ganglion cells in experimental glaucoma

Glaucoma is a group of neurodegenerative eye diseases characterized by progressive impairment of visual function due to loss of retinal ganglion cells (RGC). As hydrogen sulfide (H₂S) was reported to play a role in the process of glaucomatous neuropathy and improve RGC survival in experimental glaucoma, the authors aimed to investigate the anti-apoptosis effect of H₂S supplement in a rat glaucoma model, and further tried to explore the involved factors in the neuroprotection. A chronic ocular hypertension (COH) rat model induced by intracameral injection of cross-linking hydrogel was employed to simulate glaucoma and 288 rats were subjected to experimental procedures in the present study. After 4 weeks of sodium hydrosulfide (NaHS) administration following COH induction, the apoptosis of RGC isolated from experimented rats as well as apoptosis of neurons in ganglion cell layer (GCL), intrinsic apoptotic pathway activity, mitochondrial function, glial activation, NF-κB pathway activity, NADPH oxidase activity, autophagy activity and TNF-α level in retina were evaluated. The results showed that H₂S supplement effectively attenuated the apoptosis of RGC in experimental glaucoma, and the neuroprotection by H₂S might correlate with preservation of mitochondrial function, attenuation of oxidative stress, suppression of glial activation, inhibition of inflammatory pathways and downregulation of autophagy. Our study indicated that H₂S supplement resulted in significant neuroprotection through attenuation of RGC apoptosis which might be linked with multiple factors in experimental glaucoma. The new therapeutic strategy might potentially contribute to benefit glaucoma treatment, which is worth further concerns.

Understanding Retinal Changes after Stroke

Stroke is the fifth leading cause of death and disability in the United States. According to World Heart Federation, every year, 15 million people suffer from stroke worldwide out of which nearly 6 million people die and another 5 million people are disabled. Out of many organs affected after stroke, one of them is eye. Majority of the stroke victims suffer vision loss due to stroke-induced retinal damage. However, stroke-induced retinal damage and microvascular changes have not been given paramount importance in understanding stroke pathophysiology and predicting its occurrence. Retinal imaging can be a very powerful tool to understand and predict stroke. This review will highlight the importance of retinal changes in predicting occurrence of stroke, major retinal changes, the relationship between retinal diseases and stroke and moreover, molecular mechanisms delineating the stroke induced-retinal changes and therapeutics associated with it.

Risk Factors and Outcomes of Thalidomide-induced Peripheral Neuropathy in a Pediatric Inflammatory Bowel Disease Cohort

BACKGROUND

Thalidomide is an effective therapy in children with inflammatory bowel disease refractory to standard treatments, but thalidomide-induced peripheral neuropathy (TiPN) limits its long-term use. We aimed to investigate the risk factors and the outcome of TiPN in children with inflammatory bowel disease.

METHODS

Within a retrospective multicenter cohort study, we evaluated prevalence and evolution of TiPN. Clinical data and candidate genetic profiles of patients with and without TiPN were compared with detect predisposing factors.

RESULTS

One hundred forty-two patients were identified. TiPN was found in 72.5% of patients (38.7% clinical and instrumental alterations, 26.8% exclusive electrophysiological anomalies, and 7.0% exclusive neurological symptoms). Median TiPN-free period of treatment was 16.5 months; percentage of TiPN-free patients was 70.0% and 35.6% at 12 and 24 months of treatment, respectively. The risk of TiPN increased depending on the mean daily dose (50-99 mg/d adjusted hazard ratio 2.62; 95% confidence interval [CI], 1.31-5.21; 100-149 mg/d adjusted hazard ratio 6.16; 95% CI, 20.9-13.06; >150 mg/d adjusted hazard ratio 9.57; 95% CI, 2.6-35.2). Single nucleotide polymorphisms in ICAM1 (rs1799969) and SERPINB2 (rs6103) genes were found to be protective against TiPN (odds ratio 0.15; 95% CI, 0.03-0.82 and 0.36; 95% CI, 0.14-0.88, respectively). TiPN was the cause of drug suspension in 41.8% of patients. Clinical symptoms resolved in 89.2% of cases, whereas instrumental alteration persisted in more than half of the patients during a short follow-up.

CONCLUSIONS

In children with inflammatory bowel disease, TiPN is common but mild and generally reversible. Cumulative dose seems to be the most relevant risk factor, whereas polymorphisms in genes involved in neuronal inflammation may be protective.