Uric Acid Therapy Prevents Early Ischemic Stroke Progression

Association of serum uric acid to serum creatinine ratio with 1-year stroke outcomes in patients with acute ischemic stroke: A multicenter observational cohort study

BACKGROUND AND PURPOSE

Considering the reliance of serum uric acid (SUA) levels on renal clearance function, its role in stroke outcomes remains controversial. This study investigated the association of renal function-normalized SUA (SUA to serum creatinine ratio, SUA/SCr), a novel renal function index, with the 1-year outcomes in patients with acute ischemic stroke (AIS).

METHODS

This is a prospective, multicenter observational study. Renal function-normalized SUA levels were determined by calculating the ratio of SUA to SCr. One-year outcomes included stroke recurrence, all-cause mortality, and poor prognosis. Multivariable Cox regression analyses and restriction cubic splines for curve fitting were used to evaluate SUA/SCr's association with 1-year stroke outcomes.

RESULTS

Among 2294 enrolled patients, after adjustment for potential confounders, multivariable Cox regression analyses showed that each one-unit increase in SUA/SCr corresponded to a 19% decrease in 1-year stroke recurrence in patients with AIS. SUA/SCr was analyzed as a continuous variable and categorized into quartiles (Q1-Q4). Compared with the Q1 reference group, Q2, Q3, and Q4 showed significantly lower 1-year stroke recurrence risks. The trend test indicated significant differences in the 1-year stroke recurrence trend from Q1 to Q4. In these patients, SUA/SCr did not show a significant association with poor prognosis or all-cause mortality. Curve fitting revealed SUA/SCr had a negative but nonlinear association with 1-year stroke recurrence.

CONCLUSIONS

In patients with AIS, low SUA/SCr may be an independent risk factor for 1-year stroke recurrence. Changes in SUA/SCr had no significant impact on 1-year poor prognosis and all-cause mortality.

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.

Lower serum uric acid to serum creatinine ratio as a predictor of poor functional outcome after mechanical thrombectomy in acute ischaemic stroke

BACKGROUND AND PURPOSE

The ratio of serum uric acid (SUA) to serum creatinine (SCr), representing normalized SUA for renal function, is associated with functional outcome in acute ischaemic stroke (AIS) patients. However, its effect on AIS patients undergoing mechanical thrombectomy (MT) remains unknown. This study aimed to investigate the influence of the SUA/SCr ratio on clinical outcome in MT-treated AIS patients.

METHODS

Acute ischaemic stroke patients who underwent MT were continuously enrolled from January 2018 to June 2023. Upon admission, SUA and SCr levels were recorded within the initial 24 h. Stroke severity was determined using the National Institutes of Health Stroke Scale (NIHSS) score. Clinical outcome included poor functional outcome (modified Rankin Scale score >2) at 90 days, symptomatic intracranial haemorrhage and death.

RESULTS

Amongst 734 patients, 432 (58.8%) exhibited poor functional outcome at 90 days. The SUA/SCr ratio exhibited a negative correlation with NIHSS score (ρ = -0.095, p = 0.010). Univariate analysis revealed a significant association between SUA/SCr ratio and poor functional outcome. After adjusting for confounders, the SUA/SCr ratio remained an independent predictor of functional outcome (adjusted odds ratio 0.348, 95% confidence interval 0.282-0.428, p < 0.001). Receiver operating characteristic curve analysis highlighted the ability of the SUA/SCr ratio to predict functional outcome, with a cutoff value of 3.62 and an area under the curve of 0.757 (95% confidence interval 0.724-0.788, p < 0.001).

CONCLUSION

The SUA/SCr ratio is correlated with stroke severity and may serve as a predictor of 90-day functional outcome in AIS patients undergoing MT.

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.

The prognostic value of combined uric acid and neutrophil-to-lymphocyte ratio in acute ischemic stroke patients treated with intravenous thrombolysis

BACKGROUND

Serum uric acid (UA) and the neutrophil-to-lymphocyte ratio (NLR) have been reported to be associated with outcomes in acute ischemic stroke (AIS). However, whether UA is related to the prognosis of AIS patients undergoing intravenous thrombolysis (IVT) remains inconclusive. We sought to explore the combined effect of UA and NLR on the prognosis of AIS treated with IVT.

METHODS

A total of 555 AIS patients receiving IVT treatment were enrolled. Patients were categorized into four groups according to the levels of UA and NLR: LNNU (low NLR and normal UA), LNHU (low NLR and high UA), HNNU (high NLR and normal UA), and HNHU (high NLR and high UA). Multivariable logistic regression analysis was used to evaluate the value of serum UA level and NLR in predicting prognosis. The primary outcomes were major disability (modified Rankin scale (mRS) score 3-5) and death within 3 months.

RESULTS

After multivariate adjustment, a high NLR (≥ 3.94) increased the risk of 3-month death or major disability (OR, 2.23; 95% CI, 1.42 to 3.55, p < 0.001). However, there was no statistically significant association between a high UA level (≥ 313.00 µmol/L) and clinical outcome. HNHU was associated with a 5.09-fold increase in the risk of death (OR, 5.09; 95% CI, 1.31-19.83; P value = 0.019) and a 1.98-fold increase in the risk of major disability (OR, 1.98; 95% CI 1.07-3.68; P value = 0.030) in comparison to LNNU.

CONCLUSIONS

High serum UA levels combined with high NLR were independently associated with 3-month death and major disability in AIS patients after IVT.

Effects of the New Thrombolytic Compound LT3001 on Acute Brain Tissue Damage After Focal Embolic Stroke in Rats

LT3001 is a novel synthetic small molecule with thrombolytic and free radical scavenging activities. In this study, we tested the effects of LT3001 as a potential alternative thrombolytic in focal embolic ischemic stroke rat model. Stroked rats received intravenous injection of 10 mg/kg LT3001 or tPA at 1.5, 3, or 4.5 h after stroke, respectively, and the outcomes were measured at different time points after stroke by performing multi-parametric MRI, 2,3,5-triphenyltetrazolium chloride (TTC) staining, and modified neurological severity score. Lastly, we assessed the effect of LT3001 on the tPA activity in vitro, the international normalized ratio (INR), and the serum levels of active tPA and plasminogen activator inhibitor-1 (PAI-1). LT3001 treated at 1.5 h after stroke is neuroprotective by reducing the CBF lesion size and lowering diffusion and T2 lesion size measured by MRI, which is consistent with the reduction in TTC-stained infarction. When treated at 3 h after stroke, LT3001 had significantly better therapeutic effects regarding reduction of infarct size, swelling rate, and hemorrhagic transformation compared to tPA. When treated at 4.5 h after stroke, tPA, but not LT3001, significantly increased brain swelling and intracerebral hemorrhagic transformation. Lastly, LT3001 did not interfere with tPA activity in vitro, or significantly alter the INR and serum levels of active tPA and PAI-1 in vivo. Our data suggests that LT3001 is neuroprotective in focal embolic stroke rat model. It might have thrombolytic property, not interfere with tPA/PAI-1 activity, and cause less risk of hemorrhagic transformation compared to the conventional tPA. Taken together, LT3001 might be developed as a novel therapy for treating thrombotic ischemic stroke.

Scientific Landscape of Oxidative Stress in Stroke: From a Bibliometric Analysis to an in-Depth Review

Stroke is an acute cerebrovascular disease resulting from either obstruction or rupture of a blood vessel in the brain. Oxidative stress (OS), referred to a status where cellular oxidative capacities overwhelm antioxidative defenses, is involved in the pathophysiology of stroke. The bibliometric analysis and in-depth review aim to depict the research trend of OS in stroke. Relevant scientific publications were acquired from the Web of Science Core Collection database. Scientific landscape of OS in stroke was illustrated by general quantitative trend, impactful journals, and co-authorship of various academic units (i.e., countries/regions, organizations, and authors). Furthermore, theme analysis predicting the hot research issues and frontiers was performed. 15,826 documents regarding OS in stroke were obtained over a time span of more than 20 years from 1992 to 2021. The overall tendency of publication counts was continuously on the rise. Bibliometric analysis indicated China and the United States were predominant in this study field, as reflected by their high publication counts and intensive collaboration with other countries. Current key research areas of OS in stroke may lie in the investigation of neuroinflammation, and interaction among multiple cell death mechanisms including apoptosis, autophagy, and ferroptosis to search for effective treatments. Moreover, another hot topic could be the association between air pollution and stroke, and its underlying mechanisms. As the exploration of OS in stroke is speculated to be a continuous hot spot in the future, this article may be helpful for researchers to conduct future studies with the understanding of influential academic forces and research highlights.

Neuroprotective Strategies for Ischemic Stroke-Future Perspectives

Ischemic stroke is the main cause of death and the most common cause of acquired physical disability worldwide. Recent demographic changes increase the relevance of stroke and its sequelae. The acute treatment for stroke is restricted to causative recanalization and restoration of cerebral blood flow, including both intravenous thrombolysis and mechanical thrombectomy. Still, only a limited number of patients are eligible for these time-sensitive treatments. Hence, new neuroprotective approaches are urgently needed. Neuroprotection is thus defined as an intervention resulting in the preservation, recovery, and/or regeneration of the nervous system by interfering with the ischemic-triggered stroke cascade. Despite numerous preclinical studies generating promising data for several neuroprotective agents, successful bench-to-bedside translations are still lacking. The present study provides an overview of current approaches in the research field of neuroprotective stroke treatment. Aside from "traditional" neuroprotective drugs focusing on inflammation, cell death, and excitotoxicity, stem-cell-based treatment methods are also considered. Furthermore, an overview of a prospective neuroprotective method using extracellular vesicles that are secreted from various stem cell sources, including neural stem cells and bone marrow stem cells, is also given. The review concludes with a short discussion on the microbiota-gut-brain axis that may serve as a potential target for future neuroprotective therapies.

Therapeutic Induction of Collateral Flow

Therapeutic induction of collateral flow as a means to salvage tissue and improve outcome from acute ischemic stroke is a promising approach in the era in which endovascular therapy is no longer time-dependent but collateral-dependent. The importance of collateral flow enhancement as a therapeutic for acute ischemic stroke extends beyond those patients with large amounts of salvageable tissue. It also has the potential to extend the time window for reperfusion therapies in patients who are ineligible for endovascular thrombectomy. In addition, collateral enhancement may be an important adjuvant to neuroprotective agents by providing a more robust vascular route for which treatments can gain access to at risk tissue. However, our understanding of collateral hemodynamics, including under comorbid conditions that are highly prevalent in the stroke population, has hindered the efficacy of collateral flow augmentation for improving stroke outcome in the clinical setting. This review will discuss our current understanding of pial collateral function and hemodynamics, including vasoactivity that is critical for enhancing penumbral perfusion. In addition, mechanisms by which collateral flow can be increased during acute ischemic stroke to limit ischemic injury, that may be different depending on the state of the brain and vasculature prior to stroke, will also be reviewed.

Serum uric acid to serum creatinine ratio predicts neurological deterioration in branch atheromatous disease

Background and objective

Branch atheromatous disease (BAD) makes patients prone to early neurological deterioration (END), resulting in poor prognosis. The aim of this study was to investigate the association between SUA/SCr and END in BAD stroke patients.

Methods

We conducted a retrospective study that included 241 patients with BAD-stroke within 48 h of symptom onset. We divided the patients into the END group and the no END group. END was defined as an NIHSS score increase of more than 2 points within 1 week. SUA/SCr was calculated by the concentration of serum uric acid and creatine (serum uric acid/serum creatine) on admission. Univariate and multivariate analyses were used to identify independent predictors of END in BAD-stroke patients.

Results

END was observed in 24.1% (58/241) of the patients in our study. Multiple logistic regression analyses showed that SUA/SCr (aOR, 0.716; 95% CI, 0.538-0.952; P = 0.022) and female sex (aOR, 0.469; 95% CI, 0.245-0.898; P = 0.022) were associated with END after adjusting for confounding factors. The predicted value of SUA/Scr for END was a sensitivity of 79.3%, a specificity of 44.8%, and an AUC of 0.609 (95% CI, 0.527-0.691, P < 0.05). The optimal cut-off value was 4.76.

Conclusion

SUA/SCr was negatively associated with the risk of END in BAD stroke patients.

Ischemic stroke: From pathological mechanisms to neuroprotective strategies

Ischemic stroke (IS) has complex pathological mechanisms, and is extremely difficult to treat. At present, the treatment of IS is mainly based on intravenous thrombolysis and mechanical thrombectomy, but they are limited by a strict time window. In addition, after intravenous thrombolysis or mechanical thrombectomy, damaged neurons often fail to make ideal improvements due to microcirculation disorders. Therefore, finding suitable pathways and targets from the pathological mechanism is crucial for the development of neuroprotective agents against IS. With the hope of making contributions to the development of IS treatments, this review will introduce (1) how related targets are found in pathological mechanisms such as inflammation, excitotoxicity, oxidative stress, and complement system activation; and (2) the current status and challenges in drug development.

Elevated Serum Uric Acid Increases the Risk of Ischemic Stroke Recurrence and Its Inflammatory Mechanism in Older Adults

Background

Serum uric acid (UA) has been reported to be associated with ischemic stroke and inflammation. However, whether or not UA is related to the recurrence of ischemic stroke, and whether inflammation plays a role in the relationship between them remain inconclusive.

Objective

We sought to explore the relationship between UA and the recurrence of ischemic stroke and to define the role of neutrophil-to-lymphocyte ratio (NLR) in the aforementioned relationship.

Methods

A total of 8,995 patients were included in this study. Basic information and blood samples were collected, and whether or not each participant experienced ischemic stroke recurrence within 3 years was documented. Patients were stratified into three groups according to their UA level, as follows: ≤ 266, 267–339, and ≥ 340 μmol/L. COX regression and restricted cubic spline regression models were used to evaluate the clinical correlation between UA and ischemic stroke recurrence, mediation analysis and interaction and joint analysis were used to evaluate the role of NLR in the association of UA and ischemic stroke recurrence, and sensitivity and subgroup analyses were performed to test the robustness of the data.

Results

Ischemic stroke recurrence was related to male sex, older age, higher UA level, higher NLR, hypertension, diabetes, and cardiovascular disease. Following adjustment for potential confounders, a high level of UA (≥ 340 μmol/L) increased the risk of recurrence by 92.6% in patients with previous ischemic stroke. We also found that NLR affects the association between UA and the recurrence of ischemic stroke in older adults, suggesting that patients with high NLR and high UA levels are at greater risk for ischemic stroke recurrence.

Conclusion

UA level is non-linearly associated with recurrence, and NLR has an additive interaction between UA and ischemic stroke recurrence.

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.

Serum Uric Acid to Serum Creatinine Ratio and Risk of Stroke Recurrence in Young Adults with Ischemic Stroke

BACKGROUND AND AIM

Serum uric acid to serum creatinine ratio (SUA/SCr) is associated with metabolic and cardiovascular diseases. We aimed to investigate the association between SUA/SCr and stroke recurrence among young adults with ischemic stroke.

METHODS

A total of 428 young patients with ischemic stroke were included in the present study. SUA/SCr was calculated from the concentration of serum uric acid and creatine (uric acid/creatine). Cox proportional regression models were performed to evaluate the association between SUA/SCr and stroke recurrence. Kaplan-Meier curves were used to compare recurrence rates in different quantiles of SUA/SCr.

RESULTS

During a median follow-up of 3.14 years, 51 (10.7%) patients had stroke recurrence. Multivariable analyses indicated that SUA/SCr was associated with stroke recurrence after being adjusted for potential confounders (quantile four versus quantile one: hazard ratio: 3.420; 95% confidence interval: 1.426-8.200; P = 0.006). Kaplan-Meier curves revealed that patients with a high concentration of SUA/SCr had an increased stroke recurrence risk. The time-dependent receiver operating characteristic curve showed that the area under the curve for SUA/SCr was above 0.7 during follow-up. Restricted cubic spline presented an increasing trend for the link between SUA/SCr and stroke recurrence among young adults.

CONCLUSION

SUA/SCr was positively associated with the risk of stroke recurrence among young adults with ischemic stroke. Further prospective studies are warranted to assess the causality between SUA/SCr and the development of stroke recurrence among young adults.

Hyperuricemia, Gout, and the Brain-an Update

PURPOSE OF REVIEW

This review aims to summarize recent evidence regarding the complex relationship between uric acid (UA), gout, and brain diseases.

RECENT FINDINGS

Observational studies have suggested that patients with hyperuricemia or gout might have a decreased risk of neurodegenerative diseases. Conversely, they may be at increased risk of cerebrovascular disease. Mendelian randomization (MR) studies use a genetic score as an instrumental variable to address the causality of the association between a risk factor (here, UA or gout) and an outcome. So far, MR analyses do not support a causal relationship of UA or gout with Alzheimer's disease and dementia, and of UA with Parkinson's disease or stroke. Observation studies indicate a U-shaped association between UA and brain diseases, but MR studies do not support that this association is causal. Further studies should address the causal role of gout as well as the impact of urate-lowering therapy on these outcomes.

Adjunctive cytoprotective therapies in acute ischemic stroke: a systematic review

With the introduction of endovascular thrombectomy (EVT), a new era for treatment of acute ischemic stroke (AIS) has arrived. However, despite the much larger recanalization rate as compared to thrombolysis alone, final outcome remains far from ideal. This raises the question if some of the previously tested neuroprotective drugs warrant re-evaluation, since these compounds were all tested in studies where large-vessel recanalization was rarely achieved in the acute phase. This review provides an overview of compounds tested in clinical AIS trials and gives insight into which of these drugs warrant a re-evaluation as an add-on therapy for AIS in the era of EVT. A literature search was performed using the search terms "ischemic stroke brain" in title/abstract, and additional filters. After exclusion of papers using pre-defined selection criteria, a total of 89 trials were eligible for review which reported on 56 unique compounds. Trial compounds were divided into 6 categories based on their perceived mode of action: systemic haemodynamics, excitotoxicity, neuro-inflammation, blood-brain barrier and vasogenic edema, oxidative and nitrosative stress, neurogenesis/-regeneration and -recovery. Main trial outcomes and safety issues are summarized and promising compounds for re-evaluation are highlighted. Looking at group effect, drugs intervening with oxidative and nitrosative stress and neurogenesis/-regeneration and -recovery appear to have a favourable safety profile and show the most promising results regarding efficacy. Finally, possible theories behind individual and group effects are discussed and recommendation for promising treatment strategies are described.

The U-Shaped Association Between Serum Uric Acid and Red Blood Cell Distribution Width in Acute Ischemic Stroke

Objective: The U-shaped association between serum uric acid (SUA) and the functional outcome has been found in acute ischemic stroke (AIS). However, it is unclear if SUA is associated with red blood cell morphology in AIS. This study aimed to determine the relationship between SUA and red blood cell distribution width (RDW) in patients with AIS. Methods: A cross-sectional study including 438 consecutive patients with AIS was conducted. SUA and RDW, biochemical parameters that reflect the heterogeneity of red blood cell volume, were evaluated on admission. We evaluated the association between SUA and RDW through linear curve fitting analyses and two-piecewise regression analyses. Results: The association between SUA levels and RDW followed a U-shape in all patients. In females, the values of RDW significantly decreased with the increment of SUA (per mg/dl: β, -1.45; 95% CI: -2.15 to -0.75; p < 0.001) in patients with SUA <3.86 mg/dl and increased with the increment of SUA (per mg/dl: β, 0.60; 95% CI: 0.22-0.97; p = 0.002) in patients with SUA ≥ 3.86 mg/dl. Similar results were observed in males with the turning point of SUA = 4.82 mg/dl. After adjusting for potential confounders, a U-shaped association between SUA and RDW was maintained in females, but no statistical significance was maintained in patients with SUA ≥ 4.82 mg/dl in males (p = 0.206). Conclusion: In the sample of patients with AIS, we found a U-shaped relationship between SUA levels and RDW, with the turning point of SUA (3.96 mg/dl in females and 4.82 mg/dl in males) by the threshold effect analysis.

The biology of urate

Urate is the end-product of the purine metabolism in humans. The dominant source of urate is endogenous purines and the remainder comes through diet. Approximately two thirds of urate is eliminated via the kidney with the rest excreted in the feces. While the transporter BCRP, encoded by ABCG2, has been found to play a role in both the gut and kidney, SLC22A12 and SLC2A9 encoding URAT1 and GLUT9, respectively, are the two transporters best characterized. Only 8-12% of the filtered urate is excreted by the kidney. Renal elimination of urate depends substantially on specific transporters, including URAT1, GLUT9 and BCRP. Studies that have assessed the biologic effects of urate have produced highly variable results. Although there is a suggestion that urate may have anti-oxidant properties in some circumstances, the majority of evidence indicates that urate is pro-inflammatory. Hyperuricemia can result in the formation of monosodium urate (MSU) crystals that may be recognized as danger signals by the immune system. This immune response results in the activation of the NLRP3 inflammasome and ultimately in the production and release of interleukin-1β, and IL-18, that mediate both inflammation, pyroptotic cell death, and necroinflammation. It has also been demonstrated that soluble urate mediates effects on the kidney to induce hypertension and can induce long term epigenetic reprogramming in myeloid cells to induce "trained immunity." Together, these sequelae of urate are thought to mediate most of the physiological effects of hyperuricemia and gout, illustrating this biologically active molecule is more than just an "end-product" of purine metabolism.

Uric acid inhibits HMGB1-TLR4-NF-κB signaling to alleviate oxygen-glucose deprivation/reoxygenation injury of microglia

Mounting evidence has implicated inflammation in ischemia-reperfusion injury following acute ischemic stroke (AIS). Microglia remain the primary initiator and participant of brain inflammation. Emerging evidence has indicated that uric acid has promise for the treatment of AIS, but its explicit mechanisms remain elusive. Here, we observed that uric acid reduced the severity of cerebral infarction and attenuated the activation of microglia in the cerebral cortex in a mouse middle cerebral-artery occlusion/reperfusion model. Thus, we speculated that uric acid may play a role by directly interfering with the inflammatory response of microglia. First, we investigated whether the HMGB1-TLR4-NF-κB signaling plays a role in oxygen glucose deprivation and reperfusion (OGD/R) injury of BV2 cells. Inhibition of the signaling significantly reduced the release of the proinflammatory cytokines tumor necrosis factor α (TNF-α), interleukin 1β (IL1β), and IL6 caused by OGD/R in BV2 cells. Second, uric acid weakened the decreased cell viability and lactate dehydrogenase release induced by OGD/R in BV2 cells. Finally, uric acid reduced the release of the proinflammatory cytokines TNF-α, IL1β, and IL6 caused by OGD/R in BV2 cells by dampening HMGB1-TLR4-NF-κB signaling, which was reversed by probenecid treatment, an inhibitor of the uric acid channel. Hence, uric acid halted the release of inflammatory factors and the decreased cell viability induced by ODG/R via inhibiting the microglia HMGB1-TLR4-NF-κB signaling, thereby alleviating the damage to microglia. This may be part of the molecular mechanisms by which uric acid protects mice against the brain damage of middle cerebral-artery occlusion/reperfusion.

Effects of uric acid on oxidative and nitrosative stress and other related parameters in SH-SY5Y human neuroblastoma cells

Uric acid (UA) comprises about 65% of the total antioxidant capacity of plasma. In patients with acute ischemic stroke, UA reduces the incidence of early clinical worsening and improves patient outcomes compared with placebo. It also reduces infarct growth and improves functional outcomes in some patient subgroups, such as those with hyperglycemia pretreatment. Although UA is widely recognized as an important antioxidant in blood, its precise mechanism of action on the CNS is still unclear. Here, we assess how UA produces an antioxidant effect in neuroblastoma cells subjected to oxidative/nitrosative stress. We also evaluate its action on mitochondrial complexes I and III, as well as the capacity of UA to modify cell death induced by oxidative stress. Other related parameters such as BDNF and PGE₂ were also determined. We observed that UA is a very powerful antioxidant which efficiently reduces ROS/RNS stress signaling and cell death during oxidative/nitrosative neurotoxicity. This providing evidence that UA could be used to improve disorders in which ROS and RNS play important role, such as ischemic stroke and chronic neurodegeneration, as confirmed by BDNF results. PGE₂ results indicate that UA does not modify the inflammation in control neuroblastoma cells despite an increased in PGE₂ levels in ischemic situations.

Cross-sectional analysis of the association between serum uric acid levels and handgrip strength among Chinese adults over 45 years of age

Background

Sarcopenia is the decline in muscle strength and mass attributed to aging. The pathogenesis of sarcopenia may be triggered by oxidative stress; uric acid (UA) has strong antioxidant properties. This study aimed to examine if the serum UA level is associated with handgrip strength (HGS), which is a useful indicator of sarcopenia among Chinese participants aged over 45.

Methods

Our study included 992 eligible participants (583 males and 409 females). Based on serum UA quartiles and gender, the participants were divided into 8 groups. HGS was measured in kilograms using an electronic dynamometer. Face-to-face visits and fasting blood analyses were performed to determine the serum UA levels and various covariates. Univariate analysis of variance (ANOVA) and covariance (ANCOVA) was conducted to analyze the linear or quadratic trend between the UA levels and grip strength.

Results

Participants were grouped according to UA quartiles by gender. In both genders, ANOVA showed an inverted J-shaped association between serum UA levels and HGS (P for quadratic trend =0.004 in men, P for quadratic trend =0.003 in women). After adjusting for potential confounders, the association between the UA quartiles and HGS was unchanged, irrespective of gender.

Conclusions

The results suggest that a specific range of serum UA levels may be associated with better HGS among Chinese adults aged over 45.

Uric Acid and Clinical Outcomes Among Intracerebral Hemorrhage Patients: Results From the China Stroke Center Alliance

Background and Purpose: The effect of uric acid (UA) levels on severity and prognosis of spontaneous intracerebral hemorrhage (ICH) remains controversial. We aimed to explore the association of admission UA levels with stroke severity and outcomes in ICH patients.

Materials and Methods: The patients enrolled in this study were from the China Stroke Center Alliance study (CSCA). Patients were divided into four groups (Q1–Q4) according to the quartiles of UA levels at admission. The primary outcome was in-hospital mortality. The secondary outcomes included stroke severity, in-hospital complications, and discharge disposition. Multivariate logistic regression was adopted to explore the association of UA levels with outcomes after ICH.

Results: Patients (84,304) with acute ICH were included in the final analysis; the median (interquartile range) of UA was 277 (210, 354) μmol/L. The four groups were defined as follows: Q1 ≤ 210 μmol/L, 210 μmol/L < Q2 ≤ 277 μmol/L, 277 μmol/L < Q3 ≤ 354 μmol/L, Q4 > 354 μmol/L. There was no significant evidence indicating that UA levels were correlated with the discharge disposition and in-hospital mortality after ICH. However, compared to Q1, the patients with higher UA levels had decreased odds of severe stroke (NIHSS ≥ 16) at admission (OR 0.89, 95% CI 0.86–0.92). An L-shaped association was found between UA and severe stroke. Among in-hospital complications, decrease in pneumonia, poor swallow function, gastrointestinal bleeding, and deep vein thrombosis (DVT) were significantly associated with higher UA levels compared to Q1 (P for trend < 0.0001).

Conclusions: UA was a protective factor for stroke severity and in-hospital complications such as pneumonia, poor swallow function, gastrointestinal bleeding, and DVT. However, no significant evidence indicated that UA levels were predictive of the discharge disposition and in-hospital mortality after ICH.

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

Despite the promising neuroprotective effects of uric acid (UA) in acute ischemic stroke, the seemingly pleiotropic underlying mechanisms are not completely understood. Recent evidence points to transcription factors as UA targets. To gain insight into the UA mechanism of action, we investigated its effects on pertinent biomarkers for the most relevant features of ischemic stroke pathophysiology: (1) oxidative stress (antioxidant enzyme mRNAs and MDA), (2) neuroinflammation (cytokine and Socs3 mRNAs, STAT3, NF-κB p65, and reactive microglia), (3) brain swelling (Vegfa, Mmp9, and Timp1 mRNAs), and (4) apoptotic cell death (Bcl-2, Bax, caspase-3, and TUNEL-positive cells). Adult male Wistar rats underwent intraluminal filament transient middle cerebral artery occlusion (tMCAO) and received UA (16 mg/kg) or vehicle (Locke's buffer) i.v. at 20 min reperfusion. The outcome measures were neurofunctional deficit, infarct, and edema. UA treatment reduced cortical infarct and brain edema, as well as neurofunctional impairment. In brain cortex, increased UA: (1) reduced tMCAO-induced increases in Vegfa and Mmp9/Timp1 ratio expressions; (2) induced Sod2 and Cat expressions and reduced MDA levels; (3) induced Il6 expression, upregulated STAT3 and NF-κB p65 phosphorylation, induced Socs3 expression, and inhibited microglia activation; and (4) ameliorated the Bax/Bcl-2 ratio and induced a reduction in caspase-3 cleavage as well as in TUNEL-positive cell counts. In conclusion, the mechanism for morphological and functional neuroprotection by UA in ischemic stroke is multifaceted, since it is associated to activation of the IL-6/STAT3 pathway, attenuation of edematogenic VEGF-A/MMP-9 signaling, and modulation of relevant mediators of oxidative stress, neuroinflammation, and apoptotic cell death.

Strategies to prevent hemorrhagic transformation after reperfusion therapies for acute ischemic stroke: A literature review

BACKGROUND

Reperfusion therapies by tissue plasminogen activator (tPA) and mechanical thrombectomy (MT) have ushered in a new era in the treatment of acute ischemic stroke (AIS). However, reperfusion therapy-related HT remains an enigma.

AIM

To provide a comprehensive review focused on emerging concepts of stroke and therapeutic strategies, including the use of protective agents to prevent HT after reperfusion therapies for AIS.

METHODS

A literature review was performed using PubMed and the ClinicalTrials.gov database.

RESULTS

Risk of HT increases with delayed initiation of tPA treatment, higher baseline glucose level, age, stroke severity, episode of transient ischemic attack within 7 days of stroke onset, and hypertension. At a molecular level, HT that develops after thrombolysis is thought to be caused by reactive oxygen species, inflammation, remodeling factor-mediated effects, and tPA toxicity. Modulation of these pathophysiological mechanisms could be a therapeutic strategy to prevent HT after tPA treatment. Clinical mechanisms underlying HT after MT are thought to involve smoking, a low Alberta Stroke Program Early CT Score, use of general anesthesia, unfavorable collaterals, and thromboembolic migration. However, the molecular mechanisms are yet to be fully investigated. Clinical trials with MT and protective agents have also been planned and good outcomes are expected.

CONCLUSION

To fully utilize the easily accessible drug-tPA-and the high recanalization rate of MT, it is important to reduce bleeding complications after recanalization. A future study direction could be to investigate the recovery of neurological function by combining reperfusion therapies with cell therapies and/or use of pleiotropic protective agents.

Uric acid preconditioning alleviated doxorubicin induced JNK activation and Cx43 phosphorylation associated cardiotoxicity via activation of AMPK-SHP2 signaling pathway

Background

Doxorubicin is an anthracycline antibiotic, which is effective for treating various malignancies such as leukemias and lymphomas. However, its serious cumulative dose-dependent cardiotoxicity limits its clinical application. Previous studies have shown that doxorubicin-associated cardiotoxicity is closely related to adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK). Uric acid is known to exert a strong antioxidant function and moderate protection on the nerves. However, its cardioprotective properties have not been established. This study aimed to investigate the potential effect of uric acid preconditioning on doxorubicin-induced cardiotoxicity and the involvement of AMPK signaling in this process.

Methods

An acute cardiotoxicity model of doxorubicin was established by intraperitoneal injection of a single dose of doxorubicin (20 mg/kg) in mice. Uric acid (62.5, 125, and 250 mg/kg) was intragastrically administered to mice one day before doxorubicin treatment and then continuously administered every 24 h for 8 consecutive days. The mortality rate and weight of the mice were recorded every day. Electrocardiograms (ECG) and serum biochemicals were detected with an ECG instrument and enzyme-linked immunosorbent assay kit (Elisa) respectively. A real-time cell analyzer (RTCA) was used to investigate the cytotoxicity of doxorubicin in vitro. Cell signaling was assayed by western blotting.

Results

Uric acid (125 mg/kg) preconditioning increased the survival rate and body weight of doxorubicin-treated mice. Uric acid also effectively alleviated prolongation of the doxorubicin-induced QT interval, slowed heart rate, and reduced the plasma levels of aspartate aminotransferase (AST), lactate dehydrogenase (LDH) and creatine kinase (CK) in plasma in mice. Moreover, uric acid strongly activated AMPK and Src homology 2 domain-containing protein tyrosine phosphatase (SHP2), inhibiting doxorubicin-induced expression phosphorylated-c-Jun N-terminal kinases (JNK) and phosphorylated-connexin 43 (Cx43) in vitro and in vivo and effectively reversing the doxorubicin-induced decreased viability of H9C2 myocardial cells in vitro.

Conclusions

We demonstrated that uric acid preconditioning alleviated doxorubicin-induced cardiotoxicity through the AMPK-SHP2-JNK-Cx43 signaling pathway.

Higher uric acid is associated with better discharge recovery and short-term outcome in stroke patients treated with thrombolysis

BACKGROUND

Uric acid (UA) possesses antioxidant features and potential neuroprotective effects. However, conflicting results regarding the association between serum uric acid (SUA) levels and the prognosis of stroke have been obtained. We aimed to assess whether SUA is related to discharge recovery and short-term outcomes in patients who underwent thrombolysis therapy.

METHODS

We recruited 393 consecutive patients who were diagnosed with acute ischaemic stroke (AIS) and treated with thrombolysis. The demographic information, including sex and age, was collected. Haematology tests, including SUA, fasting plasma glucose (FPG), and blood lipid parameters, were performed under fasting conditions the morning after admission. The modified Rankin Scale (mRS) was used to assess the functional outcome of patients at discharge and 3 months after onset.

RESULTS

A negative correlation was observed between the levels of SUA and the National Institute of Health Stroke Scale (NIHSS) score at discharge (r = - 0.171, P = 0.003). Additionally, a positive correlation was observed between the levels of SUA and the difference between the baseline NIHSS and discharge NIHSS (r = 0.118, P = 0.032). The levels of SUA in the patients with good outcomes (353.76 ± 93.05) were higher than those in the patients with poor outcomes (301.99 ± 92.24; P = 0.015) at 3 months. The multivariate logistic regression analysis demonstrated that a higher SUA level (odds ratio 0.988, 95% confidence interval 0.985-0.991, P = 0.002) was an independent predictor of a good outcome at 3 months.

CONCLUSION

Higher SUA levels were associated with better discharge recovery and 3-month outcomes in patients with ischaemic stroke who received thrombolysis.

Emerging neuroprotective strategies for the treatment of ischemic stroke: An overview of clinical and preclinical studies

Stroke is the leading cause of disability and thesecond leading cause of death worldwide. With the global population aged 65 and over growing faster than all other age groups, the incidence of stroke is also increasing. In addition, there is a shift in the overall stroke burden towards younger age groups, particularly in low and middle-income countries. Stroke in most cases is caused due to an abrupt blockage of an artery (ischemic stroke), but in some instances stroke may be caused due to bleeding into brain tissue when a blood vessel ruptures (hemorrhagic stroke). Although treatment options for stroke are still limited, with the advancement in recanalization therapy using both pharmacological and mechanical thrombolysis some progress has been made in helping patients recover from ischemic stroke. However, there is still a substantial need for the development of therapeutic agents for neuroprotection in acute ischemic stroke to protect the brain from damage prior to and during recanalization, extend the therapeutic time window for intervention and further improve functional outcome. The current review has assessed the past challenges in developing neuroprotective strategies, evaluated the recent advances in clinical trials, discussed the recent initiative by the National Institute of Neurological Disorders and Stroke in USA for the search of novel neuroprotectants (Stroke Preclinical Assessment Network, SPAN) and identified emerging neuroprotectants being currently evaluated in preclinical studies. The underlying molecular mechanism of each of the neuroprotective strategies have also been summarized, which could assist in the development of future strategies for combinational therapy in stroke treatment.

The Predictive Value of Serum Uric Acid on Acute Kidney Injury following Traumatic Brain Injury

Backgrounds

Acute kidney injury (AKI) is a prevalent nonneurological complication in patients with traumatic brain injury (TBI). We designed this study to explore the association between serum uric acid (SUA) level and the occurrence of AKI following TBI.

Methods

This is a retrospective single-center study. A total of 479 patients admitted with TBI were included in this study. We utilized SUA and other risk factors for AKI to construct a predictive model by performing multivariate logistic regression. 374 patients and 105 patients were, respectively, divided into a training set and validation set. The predictive value of the single SUA and constructed model was evaluated by drawing a receiver operating characteristic (ROC) curve. AKI was diagnosed according to the KIDGO criteria.

Results

79 (21.12%) patients were diagnosed with AKI in the training cohort. The patients in the AKI group are older than those in the non-AKI group (p = 0.01). And the Glasgow Coma Scale (GCS) of the AKI group was lower than that of the non-AKI group (p < 0.001). In a multivariate logistic regression analysis, we found that heart rate (p = 0.041), shock (p = 0.018), serum creatinine (p < 0.001), and serum uric acid (SUA) (p < 0.001) were significant risk factors for AKI. Bivariate correlation analyses showed that serum creatinine was moderately positively correlated with SUA (r = 0.523, p < 0.001). Finally, the area under the receiver operating characteristic curve (AUC) of SUA for predicting AKI in the training set and validation set was 0.850 (0.805-0.895) and 0.869 (0.801-0.938), respectively.

Conclusions

SUA is an effective risk factor for AKI following TBI. Combining SUA with serum creatinine could more accurately identify TBI patients with high risk of developing AKI.

Design, synthesis, and biological evaluation of ligustrazine/resveratrol hybrids as potential anti-ischemic stroke agents

To search for potent anti-ischemic stroke agents, a series of tetramethylpyrazine (TMP)/resveratrol (RES) hybrids 6a-t were designed and synthesized. These hybrids inhibited adenosine diphosphate (ADP)- or arachidonic acid (AA)-induced platelet aggregation, among them, 6d, 6g-i, 6o and 6q were more active than TMP. The most active compound 6h exhibited more potent anti-platelet aggregation activity than TMP, RES, as well as positive control ticlopidine (Ticlid) and aspirin (ASP). Furthermore, 6h exerted strong antioxidative activity in a dose-dependent manner in rat pheochromocytoma PC12 cells which were treated with hydrogen peroxide (H₂O₂) or hydroxyl radical (·OH). Importantly, 6h significantly protected primary neuronal cells suffered from oxygen-glucose deprivation/reoxygenation (OGD/R) injury, comparable to an anti-ischemic drug edaravone (Eda). Together, our findings suggest that 6h may be a promising candidate warranting further investigation for the intervention of ischemic stroke.

Effect of renal function on association between uric acid and prognosis in acute ischemic stroke patients with elevated systolic blood pressure

BACKGROUND AND AIMS

The prognostic value of uric acid in ischemic stroke remains controversial, and it is unclear whether renal function status modifies the prognostic value of uric acid in ischemic stroke patients.

METHODS

A total of 3284 acute ischemic stroke patients from the China Antihypertensive Trial in Acute Ischemic Stroke (CATIS) with creatinine and uric acid measurements were included in this analysis. The primary outcome was a composite of death and major disability (modified Rankin Scale score ≥3) at 1 year after stroke.

RESULTS

The prognostic value of uric acid in ischemic stroke was appreciably modified by patients' renal function status (p for interaction <0.05). After multivariate adjustment, higher uric acid level was significantly associated with a better prognosis in patients with normal renal function (odds ratio, 0.61; 95% confidence interval, 0.45-0.83), but not in those with abnormal renal function (odds ratio, 0.87; 95% confidence interval, 0.48-1.55), when two extreme quartiles were compared. Linear association between uric acid and primary outcome was observed among patients with normal renal function (p for linearity = 0.023).

CONCLUSION

The present study suggests that high serum uric acid concentration is associated with better prognosis in ischemic stroke patients with normal renal function, but not in those with abnormal renal function. The establishment of causality between increased uric acid levels and better stroke prognosis needs more suitably designed randomized clinical trials.

J-shaped relationship between serum uric acid levels and the risk of ischemic stroke in high-risk individuals: A hospital-based observational study

OBJECTIVE

The relationship between serum uric acid (SUA) and the risk of ischemic stroke (IS) has been fully elucidated in previous studies. Therefore, we further investigated the relationship between SUA levels and the risk of IS.

PATIENTS AND METHODS

2195 patients at the Beijing Hospital, between February 2012 and May 2018, were enrolled in our hospital-based cross-sectional study. The patients were divided into an IS group and a (non-IS) control group, based on their medical records. SUA level was measured using the enzymatic uricase method. Univariate and multivariable logistic regression models were used for the analysis.

RESULTS

A total of 300 patients with IS [176 men; age (mean ± SD): 71.38 ± 10.66 years] and 1895 control patients [1060 men; age (mean ± SD): 66.12 ± 12.04 years] were enrolled in this study. IS patients had higher concentrations of SUA, compared with control group patients [6.11 ± 1.92 vs. 5.77 ± 1.62 (mg/dL)]; P = 0.004). We observed a J-shaped association between SUA levels and the risk of IS. Both the univariate and multivariate logistic regression analyses found a significantly elevated risk of IS in the bottom and upper SUA levels both in quartiles and deciles, compared with the intermediate SUA levels.

CONCLUSION

These results indicate a J-shaped, independent association between SUA levels and the risk of IS in high-risk individuals.

Low levels of serum urate are associated with a higher prevalence of depression in older adults: a nationwide cross-sectional study in Korea

Background

Soluble urate has been shown to serve as an antioxidant, especially in the central nervous system. Although there are intriguing data suggesting that low levels of serum urate are associated with worse outcomes in neurodegenerative diseases, its impact on mental health has not been adequately assessed. Thus, we aimed to investigate the association between serum urate and depression using a large, nationally representative sample.

Methods

Information on participants’ socio-demographic characteristics as well as physical and mental health conditions were retrieved from the Korea National Health and Nutrition Examination Survey (KNHANES) 2016 dataset. The Patient Health Questionnaire (PHQ)-9 was applied to identify depressive symptoms. Analyses were stratified by age: young adults (aged 19–39 years), middle-aged adults (aged 40–59 years), and older adults (aged 60 years and older).

Results

A total of 5332 participants were included. Serum urate concentrations were divided into sex-specific quartiles based on their distribution: ≤ 4.9 (Q1), 5.0–5.7 (Q2), 5.8–6.6 (Q3), and ≥ 6.7 (Q4) mg/dL in men and ≤ 3.7 (Q1), 3.8–4.3 (Q2), 4.4–4.9 (Q3), and ≥ 5.0 (Q4) mg/dL in women. There was a significant negative linear relationship between serum urate quartiles and PHQ-9 scores in older adults (p for trend = 0.020 in men and p for trend = 0.048 in women). Compared to high levels (Q3 and Q4) of serum urate, low levels (Q1 and Q2) were significantly associated with the overall burden of depression in older women (OR 1.78, 95% CI 1.21, 2.61) and clinically relevant depression in older men (OR 3.35, 95% CI 1.16, 9.70), even after adjustment.

Conclusions

Based on the KNHANES data, low levels of serum urate are associated with a higher prevalence of depression in older adults. This may have clinical implications for mental health.

Uric acid level and risk of symptomatic intracranial haemorrhage in ischaemic stroke treated with endovascular treatment

BACKGROUND AND PURPOSE

There are limited data on the association between uric acid (UA) and symptomatic intracranial haemorrhage (SICH) in patients who have undergone mechanical thrombectomy [endovascular treatment (EVT)]. In the present study, we aimed to investigate the role of serum UA level in SICH after EVT in a real-world practice.

METHODS

Patients were selected from the Endovascular Treatment for Acute Anterior Circulation Ischemic Stroke (ACTUAL) registry. SICH was identified using the Heidelberg Bleeding Classification. Multivariable logistic regression analysis was performed to explore the relationship between serum UA and SICH.

RESULTS

Among 611 enrolled patients, 90 (14.7%) were diagnosed with SICH within 72 h after EVT. Patients with SICH had a significantly higher level of serum UA (median, 341.0 vs. 302.0 μmol/L; P = 0.003) than those without SICH. Univariate logistic regression analysis indicated that patients with UA levels in the fourth quartile, compared with the first quartile, were more likely to have SICH (odds ratio, 2.846; 95% confidence intervals, 1.429-6.003; P = 0.003). The association remained significant after multivariable adjustment for potential confounders. Furthermore, the multiple-adjusted spline regression model showed an inverted U-shaped association between UA and SICH (P = 0.047 for non-linearity).

CONCLUSION

Our study indicated that increased serum UA level was independently associated with SICH after EVT in acute ischaemic stroke.

Pre-clinical to Clinical Translational Failures and Current Status of Clinical Trials in Stroke Therapy: A Brief Review

In stroke (cerebral ischemia), despite continuous efforts both at the experimental and clinical level, the only approved pharmacological treatment has been restricted to tissue plasminogen activator (tPA). Stroke is the leading cause of functional disability and mortality throughout worldwide. Its pathophysiology starts with energy pump failure, followed by complex signaling cascade that ultimately ends in neuronal cell death. Ischemic cascade involves excessive glutamate release followed by raised intracellular sodium and calcium influx along with free radicals' generation, activation of inflammatory cytokines, NO synthases, lipases, endonucleases and other apoptotic pathways leading to cell edema and death. At the pre-clinical stage, several agents have been tried and proven as an effective neuroprotectant in animal models of ischemia. However, these agents failed to show convincing results in terms of efficacy and safety when the trials were conducted in humans following stroke. This article highlights the various agents which have been tried in the past but failed to translate into stroke therapy along with key points that are responsible for the lagging of experimental success to translational failure in stroke treatment.

Interleukin 1 alpha administration is neuroprotective and neuro-restorative following experimental ischemic stroke

Background

Stroke remains a leading cause of death and disability worldwide despite recent treatment breakthroughs. A primary event in stroke pathogenesis is the development of a potent and deleterious local and peripheral inflammatory response regulated by the pro-inflammatory cytokine interleukin-1 (IL-1). While the role of IL-1β (main released isoform) has been well studied in stroke, the role of the IL-1α isoform remains largely unknown. With increasing utilization of intravenous tissue plasminogen activator (t-PA) or thrombectomy to pharmacologically or mechanically remove ischemic stroke causing blood clots, respectively, there is interest in pairing successful cerebrovascular recanalization with neurotherapeutic pharmacological interventions (Fraser et al., J Cereb Blood Flow Metab 37:3531–3543, 2017; Hill et al., Lancet Neurol 11:942–950, 2012; Amaro et al., Stroke 47:2874–2876, 2016).

Methods

Transient stroke was induced in mice via one of two methods. One group of mice were subjected to tandem ipsilateral common carotid artery and middle cerebral artery occlusion, while another group underwent the filament-based middle cerebral artery occlusion. We have recently developed an animal model of intra-arterial (IA) drug administration after recanalization (Maniskas et al., J Neurosci Met 240:22–27, 2015). Sub groups of the mice were treated with either saline or Il-1α, wherein the drug was administered either acutely (immediately after surgery) or subacutely (on the third day after stroke). This was followed by behavioral and histological analyses.

Results

We now show in the above-mentioned mouse stroke models (transient tandem ipsilateral common carotid artery (CCA) and middle cerebral artery occlusion (MCA) occlusion, MCA suture occlusion) that IL-1α is neuroprotective when acutely given either intravenously (IV) or IA at low sub-pathologic doses. Furthermore, while IV administration induces transient hemodynamic side effects without affecting systemic markers of inflammation, IA delivery further improves overall outcomes while eliminating these side effects. Additionally, we show that delayed/subacute IV IL-1α administration ameliorates functional deficit and promotes neurorepair.

Conclusions

Taken together, our present study suggests for the first time that IL-1α could, unexpectedly, be an effective ischemic stroke therapy with a broad therapeutic window.

The potential of drug repurposing combined with reperfusion therapy in cerebral ischemic stroke: A supplementary strategy to endovascular thrombectomy

Stroke is the major cause of adult disability and the second or third leading cause of death in developed countries. The treatment options for stroke (thrombolysis or thrombectomy) are restricted to a small subset of patients with acute ischemic stroke because of the limited time for an efficacious response and the strict criteria applied to minimize the risk of cerebral hemorrhage. Attempts to develop new treatments, such as neuroprotectants, for acute ischemic stroke have been costly and time-consuming and to date have yielded disappointing results. The repurposing approved drugs known to be relatively safe, such as statins and minocycline, may provide a less costly and more rapid alternative to new drug discovery in this clinical condition. Because adequate perfusion is thought to be vital for a neuroprotectant to be effective, endovascular thrombectomy (EVT) with advanced imaging modalities offers the possibility of documenting reperfusion in occluded large cerebral vessels. An examination of established medications that possess neuroprotective characters using in a large-vessel occlusive disorder with EVT may speed the identification of new and more broadly efficacious medications for the treatment of ischemic stroke. These approaches are highlighted in this review along with a critical assessment of drug repurposing combined with reperfusion therapy as a supplementary means for halting or mitigating stroke-induced brain damage.

Serum Uric Acid and Risk of Hemorrhagic Transformation in Patients with Acute Ischemic Stroke

Uric acid (UA) is an antioxidant with neuroprotective effects in experimental stroke models. Whether serum UA plays a role in hemorrhagic transformation (HT) remains unclear. We aimed to explore the association between serum UA and HT in patients with acute ischemic stroke (AIS). AIS patients within 7 days after stroke onset were consecutively enrolled between January 2016 and October 2017. Patients were categorized into three groups according to serum UA tertiles by sex. HT was detected by follow-up CT or MRI within 7 days after admission. The multivariate logistic analysis was performed to assess the association of serum UA with HT. We included 1230 patients (mean age 64.1 years, 63.5% males) and 133 (10.8%) patients experienced HT. After adjusting confounders, patients in the second and third UA tertiles showed a significant decrease in HT compared with those in the lowest tertile (OR 0.432, 95% CI 0.266-0.702; OR 0.033, 95% CI 0.013-0.086, respectively). Similar results were observed for sex-based subgroups. Males with higher UA had lower risk of HT compared with the lowest UA tertile (OR 0.332, 95% CI 0.170-0.651; OR 0.008, 95% CI 0.001-0.070, respectively). In females, the highest UA tertile was inversely associated with HT (OR 0.148, 95% CI 0.058-0.376). Multiple-adjusted spline regression analyses further confirmed the dose-response relationship between UA levels and HT. Higher serum UA is independently associated with lower HT following stroke. More studies are needed to elucidate the potential neuroprotective mechanism of serum UA and its link to HT.

Relationship between infarct size and serum uric acid levels during the acute phase of stroke

Introduction

Uric acid has gained considerable attention as a potential neuroprotective agent in stroke during the last decades, however, its role in the pathophysiology of ischemic stroke remains poorly understood. A serial evaluation of uric acid levels during the acute phase of stroke and its association with infarct size on magnetic resonance imaging is lacking.

Methods

We present a cohort study of 31 patients with ischemic stroke who were not candidates for thrombolysis according to current criteria at the time. We performed daily measurements of serum uric acid and total antioxidant capacity of plasma during the first week after symptoms onset and 30 days after. Infarct size was determined in the acute phase by a DWI sequence and the final infarct size with a control MRI (FLAIR) at day 30.

Results

Uric acid significantly decreases between days 2 to 6 compared to day 1, after adjustment by sex, age and DWI at diagnosis, with a nadir value at 72h. A mixed model analysis showed a negative association between DWI at diagnosis and uric acid evolution during the first week after stroke. Moreover, multivariable linear regression of uric acid values during follow up on DWI volumes demonstrated that DWI volume at diagnosis is negatively associated with uric acid levels at day 3 and 4. There were no significant associations between total antioxidant capacity of plasma and DWI at diagnosis, or FLAIR at any point.

Discussion

Patients with larger infarcts exhibited a significant decrease in serum uric acid levels, accounting for a more prominent reactive oxygen species scavenging activity with subsequent consumption and decay of this antioxidant. The different kinetics of total antioxidant capacity of plasma and serum uric acid levels suggests a specific role of uric acid in the antioxidant response in ischemic stroke.

Impact of Collateral Status on Neuroprotective Effect of Cyclosporine A in Acute Ischemic Stroke

BACKGROUND

Neuroprotection for acute ischemic stroke remains an elusive goal. Intracranial collaterals may favor neuroprotective drugs delivery at the acute stage of ischemic stroke. A recent phase 2 study showed that cyclosporine A (CsA) reduced ischemic damage in patients with a proximal occlusion who experienced effective recanalization. Collateral flow may improve this benefit.

MATERIALS & METHODS

Collateral supply was assessed using dynamic susceptibility contrast MRI in 47 patients among the 110 patients from the original study and were graded in two groups: good collaterals and poor collaterals. Patients with good collaterals had significantly smaller initial infarct in both CsA group (p = 0.003) and controls (p = 0.016). Similarly, the final lesion volume was significantly lower in patients with good collaterals in both groups.

RESULTS

In patients with either good or poor collaterals CsA showed no additional benefit on ischemic lesion progression and final infarct size at day 30.

CONCLUSION

We failed to demonstrate any significant additional benefit of CsA in patients with good collateral circulation.

Uric acid therapy for vasculoprotection in acute ischemic stroke

Uric acid (UA) is a product of the catabolism of purine nucleotides, the principal constituents of DNA, RNA, and cellular energy stores, such as adenosine triphosphate. The main properties of UA include scavenging of hydroxyl radicals, superoxide anion, hydrogen peroxide, and peroxynitrite that make this compound to be the most potent antioxidant in the human plasma. As the result of two silencing mutations in the gene of the hepatic enzyme uricase which degrades UA to allantoin, humans have higher levels of UA than most mammals. However, these levels rapidly decrease following an acute ischemic stroke (AIS), and this decrement has been associated to worse stroke outcomes. This review highlights the safety and potential clinical value of UA therapy in AIS, particularly in patients more exposed to redox-mediated mechanism following the onset of ischemia, such as women, hyperglycemic patients, or patients treated with mechanical thrombectomy. The clinical findings are supported by preclinical data gathered in different laboratories, and in assorted animal species which include male and female individuals or animals harboring comorbidities frequently encountered in patients with AIS, such as hyperglycemia or hypertension. A remarkable finding in these studies is that UA targets its main effects in the brain vasculature since available evidence suggests that does not seem to cross the blood–brain barrier. Altogether, the available data with UA therapy extend the importance of vasculoprotection for effective neuroprotection at the bedside and reinforce the role of endothelial cells after brain ischemia for an increased survival of the whole neurovascular unit.

tPA Helpers in the Treatment of Acute Ischemic Stroke: Are They Ready for Clinical Use?

Tissue plasminogen activator (tPA) is the only therapeutic agent approved to treat patients with acute ischemic stroke. The clinical benefits of tPA manifest when the agent is administered within 4.5 hours of stroke onset. However, tPA administration, especially delayed administration, is associated with increased intracranial hemorrhage (ICH), hemorrhagic transformation (HT), and mortality. In the ischemic brain, vascular remodeling factors are upregulated and microvascular structures are destabilized. These factors disrupt the blood brain barrier (BBB). Delayed recanalization of the vessels in the presence of relatively matured infarction appears to damage the BBB, resulting in HT or ICH, also known as reperfusion injury. Moreover, tPA itself activates matrix metalloproteases, further aggravating BBB disruption. Therefore, attenuation of edema, HT, or ICH after tPA treatment is an important therapeutic strategy that may enable clinicians to extend therapeutic time and increase the probability of excellent outcomes. Recently, numerous agents with various mechanisms have been developed to interfere with various steps of ischemia/ reperfusion injuries or BBB destabilization. These agents successfully reduce infarct volume and decrease the incidence of ICH and HT after delayed tPA treatment in various animal stroke models. However, only some have entered into clinical trials; the results have been intriguing yet unsatisfactory. In this narrative review, I describe such drugs and discuss the problems and future directions. These “tPA helpers” may be clinically used in the future to increase the efficacy of tPA in patients with acute ischemic stroke.

Association between Pretreatment Serum Uric Acid Levels and Progression of Newly Diagnosed Primary Angle-Closure Glaucoma: A Prospective Cohort Study

Purpose

Increased evidence reveals that uric acid (UA) may have an important neuroprotective effect through its antioxidant properties. The aim of the present study was to investigate the relationship between pretreatment serum UA levels and the progression of newly diagnosed primary angle-closure glaucoma (PACG).

Methods

This prospective observational cohort study included 64 patients with newly diagnosed PACG who were followed up for a mean period of 12.77 months (range: 3–28 months). All subjects underwent a complete ophthalmological examination during the baseline and final follow-up visits, together with the acquisition of blood samples for UA measurements. During the follow-up period, the progression of PACG was defined as a clinical diagnosis of medically uncontrolled intraocular pressure and a loss of visual field with a mean deviation of >1 dB/year. Univariable and multivariable Cox regression models were used to investigate the association between baseline serum UA levels and the progression of PACG. The cumulative probability of progression of glaucoma was analyzed using the Kaplan-Meier method.

Results

During follow-up, 32 subjects were defined as progressive PACG, among whom baseline UA values were significantly higher in nonprogressing subjects than in progressing subjects (0.314 ± 0.069 mmol/l versus [vs.] 0.258 ± 0.069 mmol/l, respectively; P = 0.002). Similar results were also observed in male and female subgroups (P < 0.05). In a multivariable model, a decreased baseline serum UA level was associated with an increased risk for progressing PACG: both in male (hazard ratio [HR] 6.088 [95% confidence interval (CI) 1.163–31.8638]; P = 0.032) and female subjects (HR 3.565 [95% CI 1.131–11.236]; P = 0.030). Subjects with high UA levels demonstrated higher cumulative probabilities of nonprogressing PACG than those with low UA levels (male [16.67% vs. 80.00%; P = 0.0084] and female [29.41% vs. 68.00%; P = 0.0182]).

Conclusion

An association between high baseline serum UA levels and a decreased risk for progressing PACG was found. This primary finding suggests that high serum UA levels may have a protective role against PACG and could slow disease progression.

Uric acid enhances longevity and endurance and protects the brain against ischemia

Among mammals, there is a positive correlation between serum uric acid (UA) levels and life span. Humans have high levels of UA because they lack a functional urate oxidase (UOX) enzyme that is present in shorter lived mammals. Here, we show that male and female mice with UOX haploinsufficiency exhibit an age-related elevation of UA levels, and that the life span of female but not male UOX+/- mice is significantly increased compared to wild-type mice. Serum UA levels are elevated in response to treadmill exercise in UOX+/- mice, but not wild-type mice, and the endurance of the UOX+/- mice is significantly greater than wild-type mice. UOX+/- mice exhibit elevated levels of brain-derived neurotrophic factor, reduced brain damage and improved functional outcome in a model of focal ischemic stroke. Levels of oxidative protein nitration and lipid peroxidation are reduced in muscle and brain tissues of UOX+/- mice under conditions of metabolic and oxidative stress (running in the case of muscle and ischemia in the case of the brain), consistent with prior evidence that UA can scavenge peroxynitrite and hydroxyl radical. Our findings reveal roles for UA in life span determination, endurance and adaptive responses to brain injury, and suggest novel approaches for protecting cells against injury and for optimizing physical performance.

Sex differences in stroke: Challenges and opportunities

Biologic sex influences many variables that are important to brain health in general, and to stroke or cerebral ischemia in particular, such as general health status, cerebrovascular anatomy and function, unique risk factors such as pregnancy and preeclampsia, symptomatology, and therapeutic response. A more complete understanding of the scale and depth of sexual dimorphism in the brain and the role of more general sex-based factors is crucial to reducing the burden of stroke in women and men. This focused review highlights recent findings in stroke, including sex differences in epidemiology, risk factor reduction, comparative use of stroke therapeutics in both sexes, the importance of frailty in women, and the biologic basis for sex differences in stroke. Such findings show tremendous promise for the future of personalized medicine in stroke prevention and treatment.

Uric acid enhances alteplase-mediated thrombolysis as an antioxidant

Uric acid (UA) therapy may prevent early ischemic worsening after acute stroke in thrombolysis patients. The aim of this study was to examine the influence of UA on the thrombolytic efficacy of alteplase in human blood samples by measuring thrombolysis under flow conditions using a newly developed microchip-based flow-chamber assay. Human blood samples from healthy volunteers were exposed to UA, alteplase, or a combination of UA and alteplase. Whole blood and platelet-rich plasma were perfused over a collagen- and thromboplastin-coated microchip, and capillary occlusion was monitored with a video microscope and flow-pressure sensor. The area under the curve (extent of thrombogenesis or thrombolysis) at 30 minutes was 92% lower in the UA-alteplase-treated group compared with the alteplase-treated group. D-dimers were measured to evaluate these effects in human platelet-poor plasma samples. Although hydrogen peroxide significantly decreased the elevation of D-dimers by alteplase, UA significantly inhibited the effect of hydrogen peroxide. Meanwhile, rat models of thromboembolic cerebral ischemia were treated with either alteplase or UA-alteplase combination therapy. Compared with alteplase alone, the combination therapy reduced the infarct volume and inhibited haemorrhagic transformation. UA enhances alteplase-mediated thrombolysis, potentially by preventing oxidative stress, which inhibits fibrinolysis by alteplase in thrombi.

Uric Acid Treatment After Stroke Prevents Long-Term Middle Cerebral Artery Remodelling and Attenuates Brain Damage in Spontaneously Hypertensive Rats

Hypertension is the most important modifiable risk factor for stroke and is associated with poorer post-stroke outcomes. The antioxidant uric acid is protective in experimental normotensive ischaemic stroke. However, it is unknown whether this treatment exerts long-term protection in hypertension. We aimed to evaluate the impact of transient intraluminal middle cerebral artery (MCA) occlusion (90 min)/reperfusion (1-15 days) on brain and vascular damage progression in adult male Wistar-Kyoto (WKY; n = 36) and spontaneously hypertensive (SHR; n = 37) rats treated (i.v./120 min post-occlusion) with uric acid (16 mg kg^-1) or vehicle (Locke's buffer). Ischaemic brain damage was assessed longitudinally with magnetic resonance imaging and properties of MCA from both hemispheres were studied 15 days after stroke. Brain lesions in WKY rats were associated with a transitory increase in circulating IL-18 and cerebrovascular oxidative stress that did not culminate in long-term MCA alterations. In SHR rats, more severe brain damage and poorer neurofunctional outcomes were coupled to higher cortical cerebral blood flow at the onset of reperfusion, a transient increase in oxidative stress and long-lasting stroke-induced MCA hypertrophic remodelling. Thus, stroke promotes larger brain and vascular damage in hypertensive rats that persists for long-time. Uric acid administered during early reperfusion attenuated short- and long-term brain injuries in both normotensive and hypertensive rats, an effect that was associated with abolishment of the acute oxidative stress response and prevention of stroke-induced long-lasting MCA remodelling in hypertension. These results suggest that uric acid might be an effective strategy to improve stroke outcomes in hypertensive subjects.

Emergent Uric Acid Treatment is Synergistic with Mechanical Recanalization in Improving Stroke Outcomes in Male and Female Rats

Preclinical and clinical studies support a promising, albeit not definitive, neuroprotective effect of emergent uric acid (UA) administration in ischemic stroke. We assessed the effects of UA in an ischemic stroke model relevant to the current treatment paradigm of mechanical thrombectomy within the STAIR/RIGOR recommendations. A cohort of male and female Wistar rats was subjected to ischemic stroke with mechanical recanalization under physiological monitoring. The effects of transient middle cerebral artery occlusion (tMCAO) with adjunctive UA (IV, 16 mg/kg) or vehicle treatment were assessed at 24 h and 7 days. Outcomes included neurofunctional impairment, brain infarct (TTC staining, MRI imaging and cresyl violet staining) and edema. At 24 h after tMCAO, neurofunctional scores and brain infarct were significantly reduced in rats subjected to UA treatment compared to vehicle, with a selective effect of UA on cortical infarct. No differential effect of UA between male and female rats was evidenced, as no significant interaction of sex with stroke outcomes was found. Rats achieving higher reperfusion levels after tMCAO showed superior reduction of neurofunctional impairment, cortical infarct and edema by UA. After a 7-day follow-up, male rats subjected to UA treatment still showed reductions in neurofunctional impairment and infarct size, compared to vehicle treatment. In conclusion, UA treatment immediately after transient ischemia results in a sex-independent, maintained reduction of brain damage and neurological impairment, better manifested in hyperperfusion conditions. This synergistic effect of UA with mechanical recanalization supports additional clinical testing of UA as an adjunctive treatment to mechanical thrombectomy.

Advances in stroke pharmacology

Stroke occurs when a cerebral blood vessel is blocked or ruptured, and it is the major cause of death and adult disability worldwide. Various pharmacological agents have been developed for the treatment of stroke either through interrupting the molecular pathways leading to neuronal death or enhancing neuronal survival and regeneration. Except for rtPA, few of these agents have succeeded in clinical trials. Recently, with the understanding of the pathophysiological process of stroke, there is a resurrection of research on developing neuroprotective agents for stroke treatment, and novel molecular targets for neuroprotection and neurorestoration have been discovered to predict or offer clinical benefits. Here we review the latest major progress of pharmacological studies in stroke, especially in ischemic stroke; summarize emerging potential therapeutic mechanisms; and highlight recent clinical trials. The aim of this review is to provide a panorama of pharmacological interventions for stroke and bridge basic and translational research to guide the clinical management of stroke therapy.