Arundic acid (ONO-2526) inhibits stimulated-S100B secretion in inflammatory conditions

Persistence of post-stress blood pressure elevation requires activation of astrocytes

The reflexive excitation of the sympathetic nervous system in response to psychological stress leads to elevated blood pressure, a condition that persists even after the stress has been alleviated. This sustained increase in blood pressure, which may contribute to the pathophysiology of hypertension, could be linked to neural plasticity in sympathetic nervous activity. Given the critical role of astrocytes in various forms of neural plasticity, we investigated their involvement in maintaining elevated blood pressure during the post-stress phase. Specifically, we examined the effects of arundic acid, an astrocytic inhibitor, on blood pressure and heart rate responses to air-jet stress. First, we confirmed that the inhibitory effect of arundic acid is specific to astrocytes. Using c-Fos immunohistology, we then observed that psychological stress activates neurons in cardiovascular brain regions, and that this stress-induced neuronal activation was suppressed by arundic acid pre-treatment in rats. By evaluating astrocytic process thickness, we also confirmed that astrocytes in the cardiovascular brain regions were activated by stress, and this activation was blocked by arundic acid pre-treatment. Next, we conducted blood pressure measurements on unanesthetized, unrestrained rats. Air-jet stress elevated blood pressure, which remained high for a significant period during the post-stress phase. However, pre-treatment with arundic acid, which inhibited astrocytic activation, suppressed stress-induced blood pressure elevation both during and after stress. In contrast, arundic acid had no significant impact on heart rate. These findings suggest that both neurons and astrocytes play integral roles in stress-induced blood pressure elevation and its persistence after stress, offering new insights into the pathophysiological mechanisms underlying hypertension.

Palmitic acid, but not other long-chain saturated fatty acids, increases S100B protein and TNF-α secretion by astrocytes

Obesity is a health problem that involves fat accumulation in adipose and other tissues and causes cell dysfunction. Long-chain saturated fatty acids can induce and propagate inflammation, which may also contribute to the brain alterations found in individuals with obesity. Fatty acids accumulate in astrocytes in situations of blood‒brain barrier disruption, such as inflammatory conditions. Furthermore, the increase in tumor necrosis factor-alpha (TNF-α) and S100 calcium-binding protein B (S100B) secretion is considered an essential component of the inflammatory response. We hypothesize that through their action on astrocytes, long-chain saturated fatty acids mediate some of the brain alterations observed in individuals with obesity. Here, we investigate the direct effect of long-chain fatty acids on astrocytes. Primary astrocyte cultures were incubated for 24 hours with myristic, palmitic, stearic, linoleic, or α-linolenic acids (25-100 µM). All saturated fatty acids tested led to an increase in TNF-α secretion, but only palmitic acid, one of the most common fatty acids, increased S100B secretion, indicating that S100B secretion is probably not caused in response to TNF-α release. Palmitic acid also caused nuclear migration of nuclear factor kappa B. Long-chain saturated fatty acids did not alter cell viability or redox status. In conclusion, long-chain saturated fatty acids can alter astrocytic homeostasis and may contribute to brain disorders associated with obesity, such as neuroinflammation.

Lipopolysaccharide impairs neurodevelopment and induces changes in astroglial reactivity, antioxidant defenses and bioenergetics in the cerebral cortex of neonatal rats

Neonates have an immature immune system, which increases their vulnerability to infectious agents and inflammatory insults. The administration of the immunostimulatory agent lipopolysaccharide (LPS) has been shown to induce the expression of pro-inflammatory cytokines and cause behavior alterations in rodents at different ages. However, the effects of LPS administration during the neonatal period and its consequences during immune system maturation remain to be elucidated. We showed here that a single intraperitoneal administration of LPS in rats on postnatal day (PND) 7 caused early and variable alterations in TNF-α, S100B and GFAP levels in the cerebral cortex, CSF and serum of the animals, indicating long-term induction of neuroinflammation and astroglial reactivity. However, on PND 21, only GFAP levels were increased by LPS. Additionally, LPS induced oxidative stress and altered energy metabolism enzymes in the cerebral cortex on PND 21, and caused neurodevelopment impairment over time. These data suggest that neuroinflammation induction during the neonatal period induces glial reactivity, oxidative stress and bioenergetic disruption that may lead to neurodevelopment impairment and cognitive deficit in adult life.

Arundic acid (ONO-2506) downregulates neuroinflammation and astrocyte dysfunction after status epilepticus in young rats induced by Li-pilocarpine

Astrocytes, the most abundant glial cells, have several metabolic functions, including ionic, neurotransmitter and energetic homeostasis for neuronal activity. Reactive astrocytes and their dysfunction have been associated with several brain disorders, including the epileptogenic process. Glial Fibrillary Acidic Protein (GFAP) and S100 calcium-binding protein B (S100B) are astrocyte biomarkers associated with brain injury. We hypothesize that arundic acid (ONO-2506), which is known as an inhibitor of S100B synthesis and secretion, protects the hippocampal tissue from neuroinflammation and astrocyte dysfunction after status epileptics (SE) induction by Li-pilocarpine in young rats. Herein, we investigated the effects of arundic acid treatment, at time points of 6 or 24 h after the induction of SE by Li-pilocarpine, in young rats. In SE animals, arundic acid was able to prevent the damage induced by Li-pilocarpine in the hippocampus, decreasing neuroinflammatory signaling (reducing IL-1β, COX2, TLR4 and RAGE contents), astrogliosis (decreasing GFAP and S100B) and astrocytic dysfunction (recovering levels of GSH, glutamine synthetase and connexin-43). Furthermore, arundic acid improved glucose metabolism and reduced the glutamate excitotoxicity found in epilepsy. Our data reinforce the role of astrocytes in epileptogenesis development and the neuroprotective role of arundic acid, which modulates astrocyte function and neuroinflammation in SE animals.

ONO-2506 Can Delay Levodopa-induced Dyskinesia in the Early Stage

BACKGROUND

Levodopa-induced dyskinesia (LID) is a common motor complication of levodopa (L-DOPA) treatment for Parkinson's disease (PD). In recent years, the role of astrocytes in LID has increasingly attracted attention.

OBJECTIVE

To explore the effect of an astrocyte regulator (ONO-2506) on LID in a rat model and the potential underlying physiological mechanism.

METHODS

Unilateral LID rat models, established by administering 6-hydroxydopamine (6-OHDA) into the right medial forebrain bundle through stereotactic injection, were injected with ONO-2506 or saline into the striatum through brain catheterization and were administered L-DOPA to induce LID. Through a series of behavioral experiments, LID performance was observed. Relevant indicators were assessed through biochemical experiments.

RESULTS

In the LID model of 6-OHDA rats, ONO-2506 significantly delayed the development and reduced the degree of abnormal involuntary movement in the early stage of L-DOPA treatment and increased glial fibrillary acidic protein and glutamate transporter 1 (GLT-1) expression in the striatum compared to saline. However, there was no significant difference in the improvement in motor function between the ONO-2506 and saline groups.

CONCLUSIONS

ONO-2506 delays the emergence of L-DOPA-induced abnormal involuntary movements in the early stage of L-DOPA administration, without affecting the anti-PD effect of L-DOPA. The delaying effect of ONO-2506 on LID may be linked to the increased expression of GLT-1 in the rat striatum. Interventions targeting astrocytes and glutamate transporters are potential therapeutic strategies to delay the development of LID.

Diagnostic and prognostic value of serum S100B in sepsis-associated encephalopathy: A systematic review and meta-analysis

Background

In sepsis, brain dysfunction is known as Sepsis-associated encephalopathy (SAE), which often results in severe cognitive and neurological sequelae and increases the risk of death. Our systematic review and meta-analysis aimed to explore the diagnostic and prognostic value of serum S100 calcium-binding protein B (S100B) in SAE patients.

Methods

We conducted a systematic search of the databases PubMed, Web of Science, Embase, Cochrane databases, CNKI, VIP, and WFSD from their inception dates until August 20, 2022. A Meta-analysis of the included studies was also performed using Review Manager version 5.4 and Stata16.0.

Results

This meta-analysis included 28 studies with 1401 serum samples from SAE patients and 1591 serum samples from no-encephalopathy septic (NE) patients. The Meta-Analysis showed that individuals with SAE had higher serum S100B level than NE controls (MD, 0.49 [95% CI (0.37)-(0.60), Z =8.29, P < 0.00001]), and the baseline level of serum S100B in septic patients with burn was significantly higher than average (1.96 [95% CI (0.92)-(2.99), Z =3.71, P < 0.0002]) In addition, septic patients with favorable outcomes had lower serum S100B levels than those with unfavorable outcomes (MD, -0.35 [95% CI (-0.50)-(-0.20), Z =4.60, P < 0.00001]).

Conclusion

Our Meta-Analysis indicates that higher serum S100B level in septic patients are moderately associated with SAE and unfavorable outcomes (The outcomes here mainly refer to the mortality). The serum S100B level may be a useful diagnostic and prognostic biomarker of SAE.

Early effects of LPS-induced neuroinflammation on the rat hippocampal glycolytic pathway

Neuroinflammation is a common feature during the development of neurological disorders and neurodegenerative diseases, where glial cells, such as microglia and astrocytes, play key roles in the activation and maintenance of inflammatory responses in the central nervous system. Neuroinflammation is now known to involve a neurometabolic shift, in addition to an increase in energy consumption. We used two approaches (in vivo and ex vivo) to evaluate the effects of lipopolysaccharide (LPS)-induced neuroinflammation on neurometabolic reprogramming, and on the modulation of the glycolytic pathway during the neuroinflammatory response. For this, we investigated inflammatory cytokines and receptors in the rat hippocampus, as well as markers of glial reactivity. Mitochondrial respirometry and the glycolytic pathway were evaluated by multiple parameters, including enzymatic activity, gene expression and regulation by protein kinases. Metabolic (e.g., metformin, 3PO, oxamic acid, fluorocitrate) and inflammatory (e.g., minocycline, MCC950, arundic acid) inhibitors were used in ex vivo hippocampal slices. The induction of early inflammatory changes by LPS (both in vivo and ex vivo) enhanced glycolytic parameters, such as glucose uptake, PFK1 activity and lactate release. This increased glucose consumption was independent of the energy expenditure for glutamate uptake, which was in fact diverted for the maintenance of the immune response. Accordingly, inhibitors of the glycolytic pathway and Krebs cycle reverted neuroinflammation (reducing IL-1β and S100B) and the changes in glycolytic parameters induced by LPS in acute hippocampal slices. Moreover, the inhibition of S100B, a protein predominantly synthesized and secreted by astrocytes, inhibition of microglia activation and abrogation of NLRP3 inflammasome assembly confirmed the role of neuroinflammation in the upregulation of glycolysis in the hippocampus. Our data indicate a neurometabolic glycolytic shift, induced by inflammatory activation, as well as a central and integrative role of astrocytes, and suggest that interference in the control of neurometabolism may be a promising strategy for downregulating neuroinflammation and consequently for diminishing negative neurological outcomes.

Acute Methylglyoxal-Induced Damage in Blood-Brain Barrier and Hippocampal Tissue

Methylglyoxal (MG) is a reactive dicarbonyl compound formed mostly via the glycolytic pathway. Elevated blood glucose levels can cause MG accumulation in plasma and cerebrospinal fluid in patients with diabetes mellitus and Alzheimer's disease. Under these disease conditions, the high reactivity of MG leads to modification of proteins and other biomolecules, generating advanced glycation end products (AGEs), which are considered mediators in neurodegenerative diseases. We investigated the integrity of the blood-brain barrier (BBB) and astrocyte response in the hippocampus to acute insult induced by MG when it was intracerebroventricularly administered to rats. Seventy-two hours later, BBB integrity was lost, as assessed by the entry of Evans dye into the brain tissue and albumin in the cerebrospinal fluid, and a decrease in aquaporin-4 and connexin-43 in the hippocampal tissue. MG did not induce changes in the hippocampal contents of RAGE in this short interval, but decreased the expression of S100B, an astrocyte-secreted protein that binds RAGE. The expression of two important transcription factors of the antioxidant response, NF-κB and Nrf2, was unchanged. However, hemeoxigenase-1 was upregulated in the MG-treated group. These data corroborate the idea that hippocampal cells are targets of MG toxicity and that BBB dysfunction and specific glial alterations induced by this compound may contribute to the behavioral and cognitive alterations observed in these animals.

Glioprotective Effects of Resveratrol Against BMAA-Induced Astroglial Dysfunctions

Astroglial cells play important roles in maintaining central nervous system (CNS) homeostasis. The neurotoxin β-N-methylamino-L-alanine (BMAA) has usually been associated with neurodegeneration due to its toxic effects on neurons. However, little is known about the effects of BMAA on astroglial cells. Resveratrol, a natural polyphenol, represents a potential protective strategy against brain injuries. In the present study, we sought to investigate BMAA-induced astroglial dysfunctions and the glioprotective roles of resveratrol. BMAA did not impair astroglial cellular viability, but increased glutamate uptake, glutamate metabolism into glutamine, and reactive oxygen species production, while decreased glutathione (GSH) and superoxide dismutase (SOD)-based antioxidant defenses and triggers an inflammatory response. In contrast, resveratrol was able to prevent most of these BMAA-induced functional changes in astroglial cells. Moreover, both BMAA and resveratrol modulated the gene expression of molecular pathways associated with glutamate metabolism, redox homeostasis, and inflammatory response, which characterize their roles on astroglial functions. In this regard, BMAA downregulated adenosine receptors, peroxisome proliferator-activated receptor-gamma coactivator 1-alpha (PGC-1α), phosphoinositide-3-kinase (PI3K), and Akt, while resveratrol prevented these effects and upregulated nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1). Our study, for the first time, demonstrates that BMAA directly impacts key astroglial functions, contributing to elucidating the cellular and molecular mechanisms of this toxin in the CNS. In addition, we reinforce the glioprotective effects of resveratrol against BMAA-induced astroglial dysfunctions.