Lower serum uric acid levels in cerebral amyloid angiopathy: a pilot study

Uric Acid Mitigates Cognitive Deficits via TFEB-Mediated Microglial Autophagy in Mice Models of Alzheimer's Disease

Clinical trials have demonstrated the potential neuroprotective effects of uric acid (UA) in Alzheimer's disease (AD). However, the specific mechanism underlying the neuroprotective effect of UA remains unclear. In the present study, we investigated the neuroprotective effect and underlying mechanism of UA in AD mouse models. Various behavioral tests including an elevated plus maze, Barnes maze, and Morris water maze were conducted to evaluate the impact of UA on cognitive function in β-amyloid (Aβ) microinjection and APP23/PS45 double transgenic mice models of AD. Immunohistochemical staining was employed to visualize pathological changes in the brains of AD model mice. Western blotting and immunofluorescence techniques were used to assess levels of autophagy-related proteins and transcription factor EB (TFEB)-related signaling pathways. BV2 cells were used to investigate the association between UA and microglial autophagy. We reported that UA treatment significantly alleviated memory decline in Aβ-induced AD model mice and APP23/PS45 double transgenic AD model mice. Furthermore, UA activated microglia and upregulated the autophagy-related proteins such as LC3II/I ratio, Beclin-1, and LAMP1 in the hippocampus of AD model mice. Similarly, UA protected BV2 cells from Aβ toxicity by upregulating the expressions of Beclin-1, LAMP1, and the LC3II/I ratio, whereas genetic inhibition of TFEB completely abolished these protective effects. Our results indicate that UA may serve as a novel activator of TFEB to induce microglia autophagy and facilitate Aβ degradation, thereby improving cognitive function in AD model mice. Therefore, these findings suggest that UA may be a novel therapeutic agent for AD treatment.

Relationship between uric acid and cerebral amyloid angiopathy

Purpose: To explored Relationship between uric acid and cerebral amyloid angiopathy; Materials and methods: ZO-1 and RAGE in HBMECs were detected by western blotting, and then, we analyzed ZO-1, occludin, and RAGE mRNA expression levels in different treatment groups using RTPCR. Cell counts and the relative αSMA fluorescence intensity were measured in order to evaluate the protective effect of uric acid against injury to HBVSMCs. Analysis of variance showed that LDH leakage rate was used to verify the uric acid protective effect on the injury induced by Aβ1-40. After that, the level of uric acid in serum and Aβ1-40 in brain tissue was analyzed by western blotting and immunohistochemistry to evaluate the protective effect of uric acid in the brain of APP23 mice. Meanwhile, Occludin, ZO-1, and RAGE protein levels were measured by western blotting; Results: Uric acid reduced the negative effects of Aβ on the vascular endothelium and smooth muscle cells and protected the vascular wall in vitro. In APP23 mice, Aβ_1-40 and Aβ_1-42 levels were significantly elevated in brain tissues and further increased after uric acid concentration was decreased. In APP23 mice, ZO-1 and occludin expression levels were both significantly lower than those in wild-type animals. After uric acid concentration was lowered in APP23 mice, ZO-1 and occludin expression levels were significantly lower than those in untreated animals; Conclusions: Uric acid in the blood protects the blood vessels from CAA damage to the blood vessel wall, and reduces the occurrence of cerebral hemorrhage.

Relationship of Serum Uric Acid to Hematoma Volume and Prognosis in Patients with Acute Supratentorial Intracerebral Hemorrhage

BACKGROUND

Oxidative stress and inflammation play important roles in the neuronal injury caused by intracerebral hemorrhage (ICH). Uric acid (UA), an important natural antioxidant, might reduce the neuronal injury caused by ICH. Delineating the relationship between UA and ICH will enhance our understanding of antioxidative mechanisms in recovery from ICH.

METHODS

We conducted a retrospective study of 325 patients with acute supratentorial ICH to investigate the relationship between serum UA levels and hematoma volumes and prognosis. A hematoma volume of ≥30 mL was defined as a large hematoma. An unfavorable outcome was defined as a modified Rankin scale score of 4-6 on day 30.

RESULTS

The serum UA level was significantly lower in the patients with a large hematoma volume (median, 306 μmol/L; 25th to 75th percentile, 243-411 μmol/L) than in those with a small hematoma volume (median, 357 μmol/L; 25th to 75th percentile, 271-442 μmol/L; P = 0.012). Similarly, the unfavorable outcome group had had lower serum UA levels (median, 309 vs. 363 μmol/L; P = 0.009) compared with the favorable outcome group. The results of the multivariate logistic analysis indicated that a lower serum UA level was associated with a larger hematoma volume (odds ratio, 0.996; P = 0.006) and an unfavorable outcome (odds ratio, 0.997; P = 0.030).

CONCLUSIONS

The results from the present study have indicated that in patients with acute supratentorial ICH, a low serum UA level might indicate that the patient has a large hematoma volume and might be a risk factor for a poor day 30 functional prognosis.

Sex as a biological variable in the pathology and pharmacology of neurodegenerative and neurovascular diseases

The incidence of dementia, most commonly caused by cerebrovascular and neurodegenerative diseases, continues to grow as our population ages. Alzheimer disease (AD) and vascular cognitive impairment (VCI) are responsible for more than 80% of all cases of dementia. There are few effective, long-term treatments for AD and VCI-related conditions (e.g., stroke and cerebral amyloid angiopathy (CAA)). This review focuses on AD (as the most common "neurodegenerative" cause of dementia), CAA (as an "emerging" cause of dementia), and stroke (as the most common cause of "vascular" dementia). We will discuss the available literature on the pharmacological therapies that demonstrate sex differences, which refer to any combination of structural, chromosomal, gonadal, or hormonal differences between males and females. We will emphasize the importance of considering sex as a biological variable in the design of preclinical and clinical studies that investigate underlying pathologies or response to pharmacological interventions in dementia. LINKED ARTICLES: This article is part of a themed section on The Importance of Sex Differences in Pharmacology Research. To view the other articles in this section visit http://onlinelibrary.wiley.com/doi/10.1111/bph.v176.21/issuetoc.

Serum uric acid concentrations and risk of intracerebral hemorrhage: A systematic review and meta-analysis

BACKGROUND AND AIMS

The relationship between serum uric acid (UA) and the risk of intracerebral hemorrhage (ICH) remains controversial. The aim of our systematic review and meta-analysis was to ascertain the association between serum UA concentrations and the risk of ICH.

METHODS

We systematically searched databases of Embase, Pubmed, Web of Science and Cochrane Library up to December 30, 2017, and additional papers were identified through a manual search. Mean difference (MD) for serum UA levels with 95% confidence intervals (CI) was calculated. Six studies, including 345 ICH patients, 574 ischemic stroke patients and 535 healthy controls, were identified for meta-analysis.

RESULTS

Our results revealed no statistically significant differences in the comparison of UA between ICH and healthy controls (95% CI = -9.04-15.61); UA levels in patients with ischemic stroke were significantly higher than those in healthy controls (95% CI = 3.91-56.32); further subgroup analysis of age showed higher UA levels in ICH patients over 65 years than healthy controls (age≥65: 95% CI = 1.44-35.96). Subgroup of ethnicity (Asians: CI = -9.06-21.00; Caucasians: 95% CI = -68.43-8.43), gender (Men: 95% CI = -56.08-4.73; Women: 95% CI = -27.19-35.91) and sample size (large samples: 95% CI = -20.54-41.05; small samples: 95% CI = -25.41-13.78) with respect to UA levels between ICH and healthy controls did not change these results.

CONCLUSIONS

This meta-analysis showed that serum UA levels did not increase the risk of ICH probably because of the dual roles of UA, i.e. pro-oxidant and antioxidant, in the progression of atherosclerosis. However, serum UA may be a potential risk factor for ICH in the elderly. There were no race-specific differences in UA levels between Asians and Caucasians as well as gender-related differences between men and women in the risk of ICH.

Organic Anion Transporter 1 Deficiency Accelerates Learning and Memory Impairment in tg2576 Mice by Damaging Dendritic Spine Morphology and Activity

To investigate whether and how organic anion transporter 1 (OAT1) is involved in the process of Alzheimer's disease (AD), we crossbred OAT1 knockout mice with tg2576, the widely used AD model mice. Results here showed the heterozygous OAT1-deficient tg2576 mice developed a learning- and memory-related behavior deficiency and higher soluble Abeta amount in early stage (3 months old). Furthermore, the heterozygous mice brain slice also showed impaired long-term potentiation (LTP) and spontaneous excitatory postsynaptic currents (sEPSC). By crossbreeding heterozygous OAT1-deficient tg2576 mice with Thy-1 YFP mice, we got autofluoresced (layer 4/5 cortical neuron) heterozygous mice. By using two-photon microscope in the direct observation of mice brain in vivo or single photon confocal on slices, compared with control tg2576 mice, we found that the OAT1-deficient mice showed a higher spine numbers but with a much lesser maturity extent. Finally, by using glutamate uncaging method, we induced chemical LTP in brain slices and found that OAT1-deficient mice showed abnormal chemical-induced LTP, which meant that the deficient behavior may be caused by abnormal spine morphology and activity. Our results indicated OAT1 may be involved in AD process by regulating spine morphology and activity.