Uric Acid Neuroprotection Associated to IL-6/STAT3 Signaling Pathway Activation in Rat Ischemic Stroke

Targeting uric acid: a promising intervention against oxidative stress and neuroinflammation in neurodegenerative diseases

Oxidative stress and neuroinflammation are recognized as key factors in the development of neurodegenerative diseases, yet effective interventions and biomarkers to address oxidative stress and neuroinflammation in these conditions are limited. Uric acid (UA), traditionally associated with gout, is now gaining prominence as a potential target in neurodegenerative diseases. Soluble UA stands out as one of the most vital antioxidant compounds produced by the human body, accounting for up to 55% of the extracellular capacity to neutralize free radicals. While there is increasing evidence supporting the neuroprotective properties of UA in Parkinson's disease and Alzheimer's disease, gaps in knowledge still exist regarding the underlying mechanisms and how to effectively translate these benefits into clinical practice. Moreover, the current UA elevation therapy exhibits unstable antioxidant properties, individual variability, and even adverse effects, limiting its potential clinical applications. This review consolidates recent advancements in understanding how UA exerts neuroprotective effects on neurodegenerative diseases and emphasizes the dual roles of UA in managing oxidative stress and neuroinflammation. Additionally, the review elucidates the mechanisms through which UA confers neuroprotection. Based on this, the review underscores the significance of UA as a potential biomarker and aims to provide a comprehensive understanding of its potential as a therapeutic target, while also addressing possible challenges to clinical implementation.

Role of uric acid in neurodegenerative diseases, focusing on Alzheimer and Parkinson disease: A new perspective

Neurodegenerative diseases (NDs) such as Alzheimer disease (AD) and Parkinson disease (PD) are group of diseases affecting the central nervous system (CNS) characterized by progressive neurodegenerations and cognitive impairment. Findings from different studies highlighted the beneficial and detrimental effects of serum uric acid on the development and progression of NDs. Therefore, this mini-review aims to discuss the beneficial and detrimental effects of uric on NDs. The neuroprotective effect of uric acid is mainly related to the antioxidant effect of uric acid which alleviates oxidative stress-induced neurodegeneration in AD and PD. However, long-term effect of hyperuricemia prompts for the development and progression of cognitive impairment. Hyperuricemia is associated with cognitive impairment and dementia, and gout increases dementia risk. In addition, hyperuricemia can cause cerebral vascular injury which is a risk factor for vascular dementia and cognitive impairment. Taken together, the relationship between uric acid and NDs risk remains conflicting. Hence, preclinical and clinical studies are indicated in this regard.

No causal relationship between serum urate and neurodegenerative diseases: A Mendelian randomization study

OBJECTIVE

Observational studies have shown that increased serum urate is associated with a lower risk of neurodegenerative diseases (NDs), but the causality remains unclear. We employed a two-sample Mendelian randomization (MR) approach to assess the causal relationship between serum urate and four common subtypes of NDs, including Parkinson's disease (PD), Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and multiple sclerosis (MS).

METHODS

Serum urate data came from the CKDGen Consortium. GWAS data for PD, AD, ALS, and MS were obtained from four databases in the primary analysis and then acquired statistics from the FinnGen consortium for replication and meta-analysis. Inverse variance weighted (IVW), weighted median (WM), and MR-Egger regression methods were applied in the MR analyses. Pleiotropic effects, heterogeneity, and leave-one-out analyses were evaluated to validate the results.

RESULTS

There was no evidence for the effect of serum urate on PD (OR: 1.00, 95 % CI: 0.90-1.11, P = 0.97), AD (OR: 1.02, 95 % CI: 1.00-1.04, P = 0.06), ALS (OR: 1.05, 95 % CI: 0.97-1.13, P = 0.22), and MS (OR: 1.01, 95 % CI: 0.89-1.14, P = 0.90) risk when combined with the FinnGen consortium, neither was any evidence of pleiotropy detected between the instrumental variables (IVs).

CONCLUSION

The MR analysis suggested that serum urate may not be causally associated with a risk of PD, AD, ALS, and MS.

Association between uric acid and the risk of hemorrhagic transformation in patients with acute ischemic stroke: a systematic review and meta-analysis

Background

The relationship between hemorrhagic transformation (HT) and uric acid (UA) remains controversial. This study aimed to investigate the relationship between UA concentrations and the risk of HT following acute ischemic stroke (AIS).

Methods

Electronic databases were searched for studies on HT and UA from inception to October 31, 2023. Two researchers independently reviewed the studies for inclusion. STATA Software 16.0 was used to compute the standardized mean difference (SMD) and 95% confidence interval (CI) for the pooled and post-outlier outcomes. Heterogeneity was evaluated using the I2 statistic and the Galbraith plot. Additionally, sensitivity analysis was performed. Lastly, Begg's funnel plot and Egger's test were used to assess publication bias.

Results

A total of 11 studies involving 4,608 patients were included in the meta-analysis. The pooled SMD forest plot (SMD = -0.313, 95% CI = -0.586--0.039, p = 0.025) displayed that low UA concentrations were linked to a higher risk of HT in post-AIS patients. However, heterogeneity (I2 = 89.8%, p < 0.001) was high among the studies. Six papers fell outside the Galbraith plot regression line, and there exclusive resulted in the absence of heterogeneity (I2 = 52.1%, p = 0.080). Meanwhile, repeated SMD analysis (SMD = -0.517, 95% CI = -0.748--0.285, p = 0.000) demonstrated that the HT group had lower UA concentrations. Finally, Begg's funnel plot and Egger's test indicated the absence of publication bias in our meta-analysis.

Conclusion

This meta-analysis illustrated a substantial connection between UA concentrations and HT, with lower UA concentrations independently linked with a higher risk of HT post-AIS. These results lay a theoretical reference for future studies.Systematic review registration:https://www.crd.york.ac.uk/PROSPERO/CRD42023485539.

Genetically predicted type 2 diabetes mellitus mediates the causal association between plasma uric acid and ischemic stroke

OBJECTIVE

This study conducts a systematic investigation into the causal relationships between plasma uric acid levels and subtypes of ischemic stroke (IS), as well as the extent to which Type 2 diabetes mellitus (T2DM) mediates this relationship.

BACKGROUND

There is a known association between Uric acid and IS but whether they have a causal relationship remains unclear. This study aims to determine whether a genetic predisposition to uric acid is causally linked to IS, including three subtypes, and to determine the mediating role of T2DM.

METHODS

Bidirectional Mendelian randomization (MR) analyses was initially used to explore the causal relationship between uric acid and three subtypes of IS. Two-step MR methods were then used to investigate the role of T2DM in mediating the effect of uric acid and IS with its subtypes.

RESULTS

A primary analysis showed uric acid had a markedly causal association with IS (IVW, OR 1.23; 95 % CI, 1.13 - 1.34; p = 6.39 × 10-9), and two subtypes of IS, Large-vessel atherosclerotic stroke LAS (IVW, OR 1.25; 95 % CI, 1.03 - 1.53; p = 0.026) and small vessel stroke (SVS) (IVW, OR 1.20; 95 % CI, 1.00 - 1.43; p = 0.049), but not with cardioembolic stroke (CES)(IVW, OR 1.00; 95 % CI, 0.87 - 1.15; p = 0.993). Two-step MR results showed that T2DM mediated the association between uric acid and LAS and SVS, accounting for 13.85 % (p = 0.025) and 13.57 % (p = 0.028), respectively.

CONCLUSIONS

The study suggests that genetic predisposition to uric acid is linked to a greater risk of IS, especially LAS and SVS. T2DM might mediate a significant proportion of the associations between uric acid and LAS as well as SVS.

Regulation of SOCS3-STAT3 in urate-induced cytokine production in human myeloid cells

OBJECTIVE

Hyperuricaemia is necessary for gout. High urate concentrations have been linked to inflammation in mononuclear cells. Here, we explore the role of the suppressor of cytokine signaling 3 (SOCS3) in urate-induced inflammation.

METHODS

Peripheral blood mononuclear cells (PBMCs) from gout patients, hyperuricemic and normouricemic individuals were cultured for 24h with varying concentrations of soluble urate, followed by 24h restimulation with lipopolysaccharides (LPS)±monosodium urate (MSU) crystals. Transcriptomic profiling was performed using RNA-Sequencing. DNA methylation was assessed using Illumina Infinium® MethylationEPIC BeadChip system (EPIC array). Phosphorylation of signal transducer and activator of transcription 3 (STAT3) was determined by flow cytometry. Cytokine responses were also assessed in PBMCs from patients with JAK2 V617F tyrosine kinase mutation.

RESULTS

PBMCs pre-treated with urate produced more interleukin-1beta (IL-1β) and interleukin-6 (IL-6) and less interleukin-1 receptor anatagonist (IL-1Ra) after LPS simulation. In vitro, urate treatment enhanced SOCS3 expression in control monocytes but no DNA methylation changes were observed at the SOCS3 gene. A dose-dependent reduction in phosphorylated STAT3 concomitant with a decrease in IL-1Ra was observed with increasing concentrations of urate. PBMCs with constitutively activated STAT3 (JAK2 V617F mutation) could not be primed by urate.

CONCLUSION

In vitro, urate exposure increased SOCS3 expression, while urate priming, and subsequent stimulation resulted in decreased STAT3 phosphorylation and IL-1Ra production. There was no evidence that DNA methylation constitutes a regulatory mechanism of SOCS3. Elevated SOCS3 and reduced pSTAT3 could play a role in urate-induced hyperinflammation since urate priming had no effect in PBMCs from patients with constitutively activated STAT3.

High serum uric acid levels are protective against cognitive impairment in amyotrophic lateral sclerosis

BACKGROUND

Uric acid (UA) has emerged as a factor that can modify cognitive function both in the general population and in people with neurodegenerative disorders. Since very few data are available concerning amyotrophic lateral sclerosis (ALS), we explored the correlation of UA levels and cognitive impairment in a large cohort of ALS patients.

METHODS

We enrolled ALS patients consecutively seen at the Turin ALS expert center in the 2007-2018 period who underwent both cognitive/behavioral and UA evaluation at diagnosis. Patients were classified in 5 categories: normal cognition (ALS-CN), isolated cognitive impairment (ALSci), isolated behavioural impairment (ALSbi), cognitive and behavioural impairment (ALScbi), frontotemporal dementia (ALS-FTD). For this study, ALSci, ALSbi and ALScbi were merged as ALS with intermediate cognitive impairment (ALS-INT).

RESULTS

Out of the 841 ALS patients, 422 had ALS-CN, 271 ALS-INT and 148 ALS-FTD. The mean values of UA were significantly different among the cognitive subgroups of patients, with the lowest values in the ALS-FTD (ALS-CN, 288.5 ± 78.0 (μmol/L; ALS-INT, 289.7 ± 75.5 μmol/L; ALS-FTD, 271.8 ± 74.9 μmol/L; p = 0.046). The frequency of ALS-FTD was significantly higher in the 1st tertile of UA. Lower UA levels were independently associated with FTD (OR 1.32, 95% c.i. 1.01-1.43; p = 0.038) in binary logistic regression.

CONCLUSIONS

We found that in ALS lower UA serum levels are correlated with reduced frequency of co-morbid FTD. Patients with intermediate cognitive impairment showed UA levels similar to ALS-CN but higher than ALS-FTD, implying that higher UA levels can prevent or delay cognitive function deterioration.

Emerging diagnostic markers and therapeutic targets in post-stroke hemorrhagic transformation and brain edema

Stroke is a devastating condition that can lead to significant morbidity and mortality. The aftermath of a stroke, particularly hemorrhagic transformation (HT) and brain edema, can significantly impact the prognosis of patients. Early detection and effective management of these complications are crucial for improving outcomes in stroke patients. This review highlights the emerging diagnostic markers and therapeutic targets including claudin, occludin, zonula occluden, s100β, albumin, MMP-9, MMP-2, MMP-12, IL-1β, TNF-α, IL-6, IFN-γ, TGF-β, IL-10, IL-4, IL-13, MCP-1/CCL2, CXCL2, CXCL8, CXCL12, CCL5, CX3CL1, ICAM-1, VCAM-1, P-selectin, E-selectin, PECAM-1/CD31, JAMs, HMGB1, vWF, VEGF, ROS, NAC, and AQP4. The clinical significance and implications of these biomarkers were also discussed.

Gut microbiota and transcriptome dynamics in every-other-day fasting are associated with neuroprotection in rats with spinal cord injury

Introduction

Every-other-day fasting (EODF) is a classical intermittent fasting (IF) mode with neuroprotective effects that promotes motor function recovery after spinal cord injury (SCI) in rats. However, its dynamic effects on the gut microbiota and spinal cord transcriptome remain unknown.

Methods

In this study, 16S rRNA sequencing and RNA-seq analysis were used to investigate the effects of ad libitum (AL) and EODF dietary modes on the structural characteristics of rat gut microbiota in rats and the spinal cord transcriptome at various time points after SCI induction.

Results

Our results showed that both dietary modes affected the bacterial community composition in SCI rats, with EODF treatment inducing and suppressing dynamic changes in the abundances of potentially anti-inflammatory and pro-inflammatory bacteria. Furthermore, the differentially expressed genes (DEGs) enriched after EODF intervention in SCI rats were associated with various biological events, including immune inflammatory response, cell differentiation, protein modification, neural growth, and apoptosis. In particular, significant spatiotemporal differences were apparent in the DEGs associated with neuroprotection between the EODF and AL interventions. These DGEs were mainly focused on days 1, 3, and 7 after SCI. The relative abundance of certain genera was significantly correlated with DEGs associated with neuroprotective effects in the EODF-SCI group.

Discussion

Our results showed that EODF treatment may exert neuroprotective effects by modulating the transcriptome expression profile following SCI in rats. Furthermore, gut microbiota may be partially involved in mediating these effects.

Neuroprotection for Nonarteritic Central Retinal Artery Occlusion: Lessons from Acute Ischemic Stroke

Nonarteritic central retinal artery occlusion (NA-CRAO) is a variant of acute ischemic stroke (AIS) and is a cause of sudden severe loss of vision. There are guidelines by the American Heart Association and the American Stroke Association for the care of CRAO patients. This review explores the basis of retinal neuroprotection for CRAO and its potential for improving the outcome of NA-CRAO. Recently, there have been significant advances in research into the use of neuroprotection to treat retinal diseases, including retinal detachment, age-related macular degeneration, and inherited retinal diseases. Also, neuroprotective research in AIS has been extensive, and newer drugs tested, including Uric acid, Nerinetide, and Otaplimastat, with promising results. Progress in cerebral neuroprotection after AIS offers hope for retinal neuroprotection after CRAO; and a possibility of extrapolating research findings from AIS into CRAO. Combining neuroprotection and thrombolysis can extend the therapeutic window for NA-CRAO treatment and potentially improve outcomes. Experimented neuroprotection for CRAO includes Angiopoietin (Comp Ang1), KUS 121, Gene therapy (XIAP), and hypothermia. Efforts in the field of neuroprotection for NA-CRAO should focus on better imaging to delineate the penumbra after an acute episode of NA-CRAO (using a combination of high-definition optical coherence angiography and electrophysiology). Also, research should explore details of pathophysiologic mechanisms involved in NA-CRAO, allowing for further neuroprotective intervention, and closing the gap between preclinical and clinical neuroprotection.

Nitration of cAMP-Response Element Binding Protein Participates in Myocardial Infarction-Induced Myocardial Fibrosis via Accelerating Transcription of Col1a2 and Cxcl12

Aims: Myocardial fibrosis after myocardial infarction (MI) leads to heart failure. Nitration of protein can alter its function. cAMP-response element binding protein (CREB) is a key transcription factor involved in fibrosis. However, little is known about the role of nitrated CREB in MI-induced myocardial fibrosis. Meanwhile, downstream genes of transcription factor CREB in myocardial fibrosis have not been identified. This study aims to verify the hypothesis that nitrated CREB promotes MI-induced myocardial fibrosis via regulating the transcription of Col1a2 and Cxcl12. Results: Our study showed that (1) the level of nitrative stress was elevated and nitrated CREB was higher in the myocardium after MI. Tyr182, 307, and 336 were the nitration sites of CREB; (2) with the administration of peroxynitrite (ONOO^-) scavengers, CREB phosphorylation, nuclear translocation, and binding activity to TORC2 (transducers of regulated CREB-2) were attenuated; (3) the expressions of extracellular matrix (ECM) proteins were upregulated and downregulated in accordance with the expression alteration of CREB both in vitro and in vivo; (4) CREB accelerated transcription of Col1a2 and Cxcl12 after MI directly. With the administration of ONOO^- scavengers, ECM protein expressions were attenuated; meanwhile, the messenger RNA (mRNA) levels of Col1a2 and Cxcl12 were alleviated as well. Innovation and Conclusion: Nitration of transcription factor CREB participates in MI-induced myocardial fibrosis through enhancing its phosphorylation, nuclear translocation, and binding activity to TORCs, among which CREB transcripts Col1a2 and Cxcl12 directly. These data indicated that nitrated CREB might be a potential therapeutic target against MI-induced myocardial fibrosis.

Ischemic Stroke, Lessons from the Past towards Effective Preclinical Models

Ischemic stroke is a leading cause of death worldwide, mainly in western countries. So far, approved therapies rely on reperfusion of the affected brain area, by intravenous thrombolysis or mechanical thrombectomy. The last approach constitutes a breakthrough in the field, by extending the therapeutic window to 16-24 h after stroke onset and reducing stroke mortality. The combination of pharmacological brain-protective strategies with reperfusion is the future of stroke therapy, aiming to reduce brain cell death and decrease patients' disabilities. Recently, a brain-protective drug-nerinetide-reduced brain infarct and stroke mortality, and improved patients' functional outcomes in clinical trials. The success of new therapies relies on bringing preclinical studies and clinical practice close together, by including a functional outcome assessment similar to clinical reality. In this review, we focused on recent upgrades of in vitro and in vivo stroke models for more accurate and effective evaluation of therapeutic strategies: from spheroids to organoids, in vitro models that include all brain cell types and allow high throughput drug screening, to advancements in in vivo preclinical mouse stroke models to mimic the clinical reality in surgical procedures, postsurgical care, and functional assessment.

The role of damage associated molecular pattern molecules (DAMPs) and permeability of the blood-brain barrier in depression and neuroinflammation

Depression is a heterogeneous mental disorder characterized by feelings of sadness and loss of interest that render the subject unable to handle basic daily activities such as sleeping, eating, or working. Neurobiological traits leading to depression include genetic background, early life abuse, life stressors, and systemic and central inflammatory profiles. Several clinical and preclinical reports documented that depression shows an increase in pro-inflammatory markers such as interleukin (IL-)1β, IL-6, IL-12, tumor necrosis factor (TNF), and interferon (IFN)-γ; and a decrease in anti-inflammatory IL-4, IL-10, and transforming growth factor (TGF)-β species. Inflammatory activation may trigger and maintain depression. Dynamic crosstalk between the peripheral immune system and the central nervous system (CNS) such as activated endothelial cells, monocytes, monocyte-derived dendritic cells, macrophages, T cells, and microglia has been proposed as a leading cause of neuroinflammation. Notably, pro-inflammatory cytokines disrupt the hypothalamic-pituitary-adrenal (HPA) axis and serotonergic, noradrenergic, dopaminergic, and glutamatergic neurotransmission. While still under investigation, peripheral cytokines can engage brain pathways and affect the central synthesis of HPA hormones and neurotransmitters through several mechanisms such as activation of the vagus nerve, increasing the permeability of the blood-brain barrier (BBB), altered cytokines transport systems, and engaging toll-like receptors (TLRs) by pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs). However, physiological mechanisms that favor time-dependent central inflammation before or during illness are not totally understood. This review will provide preclinical and clinical evidence of DAMPs and the BBB permeability as contributors to depression and neuroinflammation. We will also discuss pharmacologic approaches that could potentially modulate DAMPs and BBB permeability for future interventions against major depression.

Association of Total Calcium With Serum Uric Acid Levels Among United States Adolescents Aged 12-19 Years: A Cross-Sectional Study

Aims

Evidence of a link between total calcium (CA) and serum uric acid (SUA) is absent in adolescents. Thus, this study aimed to determine the relationship between total CA levels and SUA levels in United States adolescents.

Methods

A cross-sectional study analyzed a sample composed of 8,309 United States adolescents aged 12–19 years from the National Health and Nutrition Examination Survey database (1999–2006 survey cycle). Multivariable linear regression analyses and multivariable logistic regression analyses were used to assess the correlation of total CA with SUA levels and hyperuricemia. Furthermore, the dose-response relationship of total CA and SUA levels was analyzed using smooth curve fitting (penalized spline method).

Results

According to multivariable linear regression analysis, every 1 mg/dL increase in total CA level is associated with a 0.33 mg/dL (β = 0.33, 95% CI: 0.27–0.40, p < 0.001) increase in SUA. Multivariable logistic regression analyses showed that every 0.1 mg/dL increase in total CA level is linked with an 8% increased risk of hyperuricemia (OR = 1.08, 95% CI: 1.06–1.10, p < 0.001). The analyses of smooth curve fitting revealed that total CA levels were linearly correlated with SUA levels (P_{non–linearity} = 0.152). The results were highly stable in all subgroups. The interaction analysis results presented that race/ethnicity had an interactive role in associating total CA with SUA levels.

Conclusions

In United States adolescents, total CA levels were linearly and positively correlated with SUA levels.

Cyclo-(Phe-Tyr) as a novel cyclic dipeptide compound alleviated ischemic stroke reperfusion brain injury via JUNB/JNK/NF-κB and SOX5/PI3K/AKT pathways

Ischemic stroke reperfusion (IR) can cause adverse reactions including apoptosis, oxidative stress, and inflammation, but the existing therapeutic strategies have been limited. Moreover, the regulation of microglia plays an important role in brain injury after reperfusion. Hence, it is imperative to find new and effective drugs for modulating microglia to treat IR brain injury. Cyclic peptide compound cyclo-(Phe-Tyr) (Sparganin C, SC) is a compound isolated from Sparganii Rhizoma. However, the protective effects of SC on the central nervous system are rather unclear. In an attempt to elucidate the protective effects and mechanism of SC on cerebral damage induced by the IR, we used a middle cerebral artery occlusion reperfusion (MCAO/R) model in rats and discovered that SC significantly decreased the size of cerebral infarcts, improved neurological scores, and blocked inflammatory and oxidative factor release. Using RNA-Seq and metabolomics association analyses, SC was shown to have a protective impact through the JUNB and SOX5-related pathways. Metabolomic analysis revealed twenty-eight differentially expressed biomarkers. In addition, the detection of SC content in brain tissue using LC/MS revealed that SC had blood-brain barrier penetration. To investigate the mechanism, we established an in vitro BV2 cell oxygen-glucose deprived re-oxygenation (OGD/R) model and used siRNA as well as an inhibitor. The protective effects of SC were dependent on the JUNB and SOX5 to inhibit inflammation and apoptosis in microglia. Our findings revealed for the first that SC against IR injury by reducing inflammation and apoptosis while simultaneously acting as potential therapeutic lead compound for ischemic stroke.

Combination of Systems Pharmacology and Experimental Evaluation to Explore the Mechanism of Synergistic Action of Frankincense-Myrrh in the Treatment of Cerebrovascular Diseases

Frankincense-Myrrh is a classic drug pair that promotes blood circulation, and eliminates blood stasis. The combination of the two drugs has a definite clinical effect on the treatment of cerebrovascular diseases (CBVDs), but its mechanism of action and compatibility have not been elucidated. In this study, the bioactive components, core targets, and possible synergistic mechanisms of Frankincense-Myrrh in the treatment of CBVDs are explored through systems pharmacology combined with in vivo and in vitro experiments. Comparing target genes of components in Frankincense and Myrrh with CBVD-related genes, common genes were identified; 15 core target genes of Frankincense-Myrrh for the treatment of CBVDs were then identified using protein-protein interaction (PPI) analysis. It was also predicted through Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis that the molecular mechanism of Frankincense-Myrrh action on CBVDs was mainly related to the regulation of neurotrophic factors and inflammatory responses. Frankincense-Myrrh significantly improved neurological function, decreased infarct volume, alleviated histopathological damage, inhibited microglial expression, and promoted the expression of neurons in middle cerebral artery occlusion (MCAO)-induced rats. The results of this study not only provide important theoretical support and experimental basis for the synergistic effect of Frankincense-Myrrh, but also provide new ideas for the prevention and treatment of cerebral ischemic injuries.

Uric Acid and Clinical Outcomes in Young Patients with Ischemic Stroke

BACKGROUND AND PURPOSE

There is limited available evidence for the relationship between uric acid (UA) levels and ischemic stroke in young adults. We aimed to explore the association between UA levels and acute ischemic stroke (AIS) in young patients.

MATERIALS AND METHODS

This was a prospective and observational study. We recruited young patients aged 18-45 years with AIS at our tertiary hospital. Patients were categorized into four groups according to quartiles of UA levels. The primary outcome was functional outcome at 3 months. The secondary outcomes included stroke severity, in-hospital complications, and functional outcome at discharge. Modified Rankin Scale (mRS) scores were used to assess functional outcome as poor (mRS=2-6) or favorable(mRS=0-1).

RESULTS

A total of 636 patients were enrolled in the current analysis. The four groups were defined as follows: Q1≤289.8 µmol/L, 289.8 µmol/ L<Q2≤349.0 µmol/L, 349.0 µmol/L<Q3≤421 µmol/L, and Q4>421 µmol/L. Multiple logistic regression analysis showed that UA levels were not significantly predictive of functional outcome either at discharge or at 3 months after AIS. However, compared to Q1, higher UA levels were significantly negatively associated with the rate of moderate-severe stroke (NIHSS≥5) at admission (p for trend =0.016). Furthermore, a reduction in the risk for in-hospital pneumonia was significantly associated with higher UA levels compared to Q1 (P for trend < 0.0001).

CONCLUSION

Serum UA was a protective factor for stroke severity and in-hospital pneumonia after AIS in young patients. However, we were unable to identify the predictive significance of UA for functional outcome either at discharge or at 3 months after AIS.

The Influence of Serum Uric Acid on the Brain and Cognitive Dysfunction

Uric acid is commonly known for its bad reputation. However, it has been shown that uric acid may be actively involved in neurotoxicity and/or neuroprotection. These effects could be caused by oxidative stress or inflammatory processes localized in the central nervous system, but also by other somatic diseases or systemic conditions. Our interest was to summarize and link the current data on the possible role of uric acid in cognitive functioning. We also focused on the two putative molecular mechanisms related to the pathological effects of uric acid-oxidative stress and inflammatory processes. The hippocampus is a prominent anatomic localization included in expressing uric acid's potential impact on cognitive functioning. In neurodegenerative and mental disorders, uric acid could be involved in a variety of ways in etiopathogenesis and clinical presentation. Hyperuricemia is non-specifically observed more frequently in the general population and after various somatic illnesses. There is increasing evidence to support the hypothesis that hyperuricemia may be beneficial for cognitive functioning because of its antioxidant effects but may also be a potential risk factor for cognitive dysfunction, in part because of increased inflammatory activity. In this context, gender specificities must also be considered.

Transient Focal Cerebral Ischemia Leads to miRNA Alterations in Different Brain Regions, Blood Serum, Liver, and Spleen

Ischemic stroke is characterized by an occlusion of a cerebral blood vessel resulting in neuronal cell death due to nutritional and oxygen deficiency. Additionally, post-ischemic cell death is augmented after reperfusion. These events are paralleled by dysregulated miRNA expression profiles in the peri-infarct area. Understanding the underlying molecular mechanism in the peri-infarct region is crucial for developing promising therapeutics. Utilizing a tMCAo (transient Middle Cerebral Artery occlusion) model in rats, we studied the expression levels of the miRNAs (miR) 223-3p, 155-5p, 3473, and 448-5p in the cortex, amygdala, thalamus, and hippocampus of both the ipsi- and contralateral hemispheres. Additionally, the levels in the blood serum, spleen, and liver and the expression of their target genes, namely, Nlrp3, Socs1, Socs3, and Vegfa, were assessed. We observed an increase in all miRNAs on the ipsilateral side of the cerebral cortex in a time-dependent manner and increased miRNAs levels (miR-223-3p, miR-3473, and miR-448-5p) in the contralateral hemisphere after 72 h. Besides the cerebral cortex, the amygdala presented increased expression levels, whereas the thalamus and hippocampus showed no alterations. Different levels of the investigated miRNAs were detected in blood serum, liver, and spleen. The gene targets were altered not only in the peri-infarct area of the cortex but selectively increased in the investigated non-affected brain regions along with the spleen and liver during the reperfusion time up to 72 h. Our results suggest a supra-regional influence of miRNAs following ischemic stroke, which should be studied to further identify whether miRNAs are transported or locally upregulated.

Targeting neuroinflammation to treat cerebral ischemia - The role of TIGAR/NADPH axis

Cerebral ischemia is a disease of ischemic necrosis of brain tissue caused by intracranial artery stenosis or occlusion and cerebral artery embolization. Neuroinflammation plays an important role in the pathophysiology of cerebral ischemia. Microglia, astrocytes, leukocytes and other cells that release a variety of inflammatory factors involved in neuroinflammation may play a damaging or protective role during the process of cerebral ischemia. TP53-induced glycolysis and apoptotic regulators (TIGAR) may facilitate the production of nicotinamide adenine dinucleotide phosphoric acid (NADPH) via the pentose phosphate pathway (PPP) to inhibit oxidative stress and neuroinflammation. TIGAR can also directly inhibit NF-κB to inhibit neuroinflammation. TIGAR thus protect against cerebral ischemic injury. Exogenous NADPH can inhibit neuroinflammation by inhibiting oxidative stress and regulating a variety of signals. However, since NADPH oxidase (NOX) may use NADPH as a substrate to generate reactive oxygen species (ROS) to mediate neuroinflammation, the combination of NADPH and NOX inhibitors may produce more powerful anti-neuroinflammatory effects. Here, we review the cells and regulatory signals involved in neuroinflammation during cerebral ischemia, and discuss the possible mechanisms of targeting neuroinflammation in the treatment of cerebral ischemia with TIGAR/NADPH axis, so as to provide new ideas for the prevention and treatment of cerebral ischemia.

The future of neuroprotection in stroke

Investigators acknowledge the limitations of rodent or non-human primate stroke models, hundreds of putative neuroprotectants have been evaluated in preclinical models, but not one has entered the clinical realm. Initial studies focused on the neuron, but in recent years the focus has widened to also include other neural cells including astrocytes, pericytes and endothelial cells, which together form the neurovascular unit. Some new developments raise renewed hope for neuroprotection: the appearance of new compounds with multiple mechanisms of action, or the promulgation of new standards for a rigorous preclinical testing. At the bedside in the last 5 years, uric acid and nerinetide are the only compounds tested for clinical efficacy in randomised controlled trials (RCTs), where all patients had to receive reperfusion therapies, either intravenous thrombolysis and/or mechanical thrombectomy. In addition, otaplimastat, 3K3A-activated protein C (APC), intra-arterial verapamil and intra-arterial hypothermia were also assessed in combination with reperfusion therapy, but in RCTs that only included feasibility or safety outcomes. Some of these compounds yielded promising results which are discussed in this review. Altogether, a deeper knowledge of the mechanisms involved in the ischaemic death process at the neurovascular unit, an improved preselection and evaluation of drugs at the preclinical stage and the testing of putative neuroprotectants in enriched clinical studies of patients receiving reperfusion therapies, might prove more effective than in the past to reverse a dismal situation that has lasted already too long.