Acetylsalicylic acid provides cerebrovascular protection from oxidant damage in salt-loaded stroke-prone rats

Estimating the therapeutic potential of NSAIDs and linoleic acid-isomers supplementation against neuroinflammation

Nonsteroidal anti-inflammatory drugs (NSAIDs) regulate inflammation, which is associated with their role in preventing neurodegenerative diseases in epidemiological studies. It has sparked interest in their unconventional application for reducing neuroinflammation, opening up new avenues in biomedical research. However, given the pharmacological drawbacks of NSAIDs, the development of formulations with naturally antioxidant/anti-inflammatory dietary fatty acids has been demonstrated to be advantageous for the clinical translation of anti-inflammatory-based therapies. It includes improved blood-brain barrier (BBB) permeability and reduced toxicity. It permits us to speculate about the value of linoleic acid (LA)-isomers in preventing and treating neuroinflammatory diseases compared to NSAIDs. Our research delved into the impact of various factors, such as administration route, dosage, timing of intervention, and BBB permeability, on the efficacy of NSAIDs and LA-isomers in preclinical and clinical settings. We conducted a systematic comparison between NSAIDs and LA-isomers regarding their therapeutic effectiveness, BBB compatibility, and side effects. Additionally, we explored their underlying mechanisms in addressing neuroinflammation. Through our analysis, we've identified challenges and drawn conclusions that could propel advancements in treating neurodegenerative diseases and inform the development of future alternative therapeutic strategies.

CNS border-associated macrophages in the homeostatic and ischaemic brain

CNS border-associated macrophages (BAMs) are a small population of specialised macrophages localised in the choroid plexus, meningeal and perivascular spaces. Until recently, the function of this elusive cell type was poorly understood and largely overlooked, especially in comparison to microglia, the primary brain resident immune cell. However, the recent single cell immunophenotyping or transcriptomic analysis of BAM subsets in the homeostatic brain, coupled with the rapid emergence of new studies exploring BAM functions in various cerebral pathologies, including Alzheimer's disease, hypertension-induced neurovascular and cognitive dysfunction, and ischaemic stroke, has unveiled previously unrecognised heterogeneity and spatial-temporal complexity in BAM populations as well as their contributions to brain homeostasis and disease. In this review, we discuss the implications of this new-found knowledge on our current understanding of BAM function in ischaemic stroke. We first provide a comprehensive overview and discussion of the cell-surface expression profiles, transcriptional signatures and potential functional phenotypes of homeostatic BAM subsets described in recent studies. Evidence for their putative physiological roles is examined, including their involvement in immunological surveillance, waste clearance, and vascular permeability. We discuss the evidence supporting the accumulation and genetic transformation of BAMs in response to ischaemia and appraise the experimental evidence that BAM function might be deleterious in the acute phase of stroke, while considering the mechanisms by which BAMs may influence stroke outcomes in the longer term. Finally, we review the therapeutic potential of immunomodulatory strategies as an approach to stroke management, highlighting current challenges in the field and key issues relating to BAMs, and how BAMs could be harnessed experimentally to support future translational research.

Thromboxane A2 receptor antagonist (ONO-8809) attenuates renal disorders caused by salt overload in stroke-prone spontaneously hypertensive rats

Epidemiological and clinical studies have demonstrated that excessive salt intake causes severe hypertension and exacerbates organ derangement, such as in chronic kidney disease (CKD). In this study, we focused on evaluating the histological and gene expression effects in the kidneys of stroke‐prone spontaneously hypertensive rats (SHRSP) with a high salt intake and the thromboxane A₂/ prostaglandin H₂ receptor (TPR) blocker ONO‐8809. Six‐week‐old SHRSPs were divided into three groups and were fed normal chow containing 0.4% NaCl, 2.0%NaCl or 2.0%NaCl + ONO‐8809 (0.6 mg/kg p.o. daily). Histological analyses with immunohistochemistry and a gene expression assay with a DNA kidney microarray were performed after 8 weeks. The following changes were observed in SHRSPs with the high salt intake. Glomerular sclerotic changes were remarkably observed in the juxtamedullary cortex areas. The ED1, monocyte chemoattractant protein‐1 (MCP‐1), nitrotyrosine and hypoxia inducible factor 1α (HIF‐1α) staining areas were increased in the glomeruli and interstitial portion of the kidneys. The genes Tbxa2r (that encodes TPR), Prcp and Car7 were significantly underexpressed in the kidneys. The plasma 8‐isoprostane level was significantly elevated and was attenuated with the ONO‐8809 treatment. Thromboxane A₂ (TXA₂) and oxidative stress exaggerated renal dysfunction in the salt‐loaded SHRSPs, and ONO‐8809 as a TPR blocker suppressed these changes. Therefore, ONO‐8809 is a candidate drug to prevent CKD in hypertensive patients when CKD is associated with a high salt intake.

Monocyte Transmodulation: The Next Novel Therapeutic Approach in Overcoming Ischemic Stroke?

The immune response following neuroinflammation is a vital element of ischemic stroke pathophysiology. After the onset of ischemic stroke, a specialized vasculature system that effectively protects central nervous system tissues from the invasion of blood cells and other macromolecules is broken down within minutes, thereby triggering the inflammation cascade, including the infiltration of peripheral blood leukocytes. In this series of processes, blood-derived monocytes have a significant effect on the outcome of ischemic stroke through neuroinflammatory responses. As neuroinflammation is a necessary and pivotal component of the reparative process after ischemic stroke, understanding the role of infiltrating monocytes in the modulation of inflammatory responses may offer a great opportunity to explore new therapies for ischemic stroke. In this review, we discuss and highlight the function and involvement of monocytes in the brain after ischemic injury, as well as their impact on tissue damage and repair.

Evaluation of the neuroprotective and antioxidant effects of Dorema aucheri extract on cerebral ischaemia-reperfusion injury in rats

CONTEXT

The hydroalcoholic extract of Dorema aucheri Bilhar (Umbelliferae) (DA) leaves, a medicinal plant, has powerful antioxidant properties.

OBJECTIVE

This study evaluates the neuroprotective effects of pre-treatment with DA leaves extract against cerebral ischaemia-induced brain injury through alteration of the antioxidant capacity.

MATERIALS AND METHODS

The study was conducted in three groups of Wistar rats (N = 47) as follows; sham, control ischaemic and pre-treated ischaemic groups. Rats were administered a fresh hydroalcoholic extract of DA leaves at a dosage of 200 mg/kg/day for 14 days. Then, the middle cerebral artery (MCA) of the right hemisphere was occluded for 90 min to achieve cerebral ischaemia. After 24 h reperfusion, cerebral infarction and superoxide dismutase (SOD) and catalase activities, as well as malondialdehyde (MDA), glutathione, and NOx contents were determined in the right hemispheres.

RESULTS

Occlusion of the right MCA caused noticeable cerebral infarction (298 ± 21 mm³) in control ischaemic group, but pre-treatment with DA extract considerably attenuated it (92 ± 14 mm³) in the pre-treated ischaemic group. DA extract significantly decreased the levels of MDA by 28% and NOx by 11% in pre-treated ischaemic group compared to the control ischaemic group. DA extract also enhanced glutathione content by 7%, SOD activity by 16% and catalase activity by 46% in pre-treated ischaemic rats compared to control ischaemic rats.

DISCUSSION AND CONCLUSIONS

DA is able to improve the antioxidant capacity and injuries of ischaemic brain. It is proposed as a neuroprotectant following cerebral ischaemia to decrease the injuries of ischaemic stroke.

Fullerenol nanoparticles decrease ischaemia-induced brain injury and oedema through inhibition of oxidative damage and aquaporin-1 expression in ischaemic stroke

BACKGROUND

We examined the possible protective effects of fullerenol nanoparticles on brain injuries and oedema in experimental model of ischaemic stroke through inhibition of oxidative damage and aquaporin-1 (AQP-1) expression.

METHODS

Experiment was done in three groups of rats (N = 66): sham, control ischaemia and ischaemic treatment. Ischaemia was induced by 90-minutes middle cerebral artery occlusion (MCAO) followed by 24 hours of reperfusion. Rats received a dose of 10 mg/kg of fullerenol 30 minutes before MCAO. Infarction, brain oedema, malondialdehyde (MDA) and nitrate contents as well as mRNA level of AQP-1 were determined 24 hours after termination of MCAO.

RESULTS

Administration of fullerenol before MCAO significantly reduced the infarction of cortex and striatum by 72 and 77%, respectively. MCAO induced brain oedema in control ischaemic rats (3.83 ± 0.53%), whereas, fullerenol significantly reduced it (0.91 ± 0.55%). The contents of MDA and nitrate increased in ischaemic hemispheres by 86 and 41%, respectively. Fullerenol considerably reduced the MDA and nitrate contents by 83 and 48%, respectively. Moreover, MCAO noticeably increased the mRNA level of AQP-1 in ischaemic hemispheres by 22%, whereas fullerenol significantly decreased it by 29%.

DISCUSSION

Fullerenol is able to reduce ischaemia-induced brain injuries and oedema possibly through inhibition of oxidative damage and AQP-1 expression in ischaemic stroke.

Interaction of incidental microbleeds and prior use of antithrombotics with early hemorrhagic transformation: Causative or protective?

BACKGROUND

Gradient echo (GRE) sequence of magnetic resonance imaging (MRI) is a sensitive tool to detect hemorrhagic transformation (HT) and old cerebral microbleeds (CMBs). Presence of CMBs and prior use of antithrombotics pose a risk of HT in ischemic stroke. We evaluated the association of CMBs and antithrombotic use with resultant HT in acute ischemic stroke (AIS).

METHODS

This retrospective study included AIS patients admitted to our center between January 2009 and August 2010 who underwent GRE-weighted MRI within 48 h of admission. Demographic and clinical data including diabetes mellitus, hypertension, hyperlipidemia, prior intake of antiplatelets/anticoagulants/statins, and presence of CMBs at admission were collected and compared between patients who developed HT and those who did not. We did a multivariate analysis using logistic regression to assess the effect of CMBs and prior use of antithrombotic agents on the risk of development for early HT in ischemic stroke.

RESULTS

Of 529 AIS patients, 81 (15%) were found to have HT during the initial hospital course. CMBs were found in only 9 of 81 patients (11%) with HT and in 40 out of remaining 448 patients (9%) who did not develop HT. The presence of CMBs was not associated with increased risk of HT (P = 0.53). However, prior use of antiplatelets (33% vs. 47% in the patients without HT, P = 0.02) was associated with decreased risk of HT in ischemic stroke.

CONCLUSION

Presence of incidental CMBs was not associated with increased risk for early HT of an ischemic stroke. Interestingly, the prior intake of antiplatelets was found to be protective against HT of ischemic stroke.

Polyhydroxylated fullerene nanoparticles attenuate brain infarction and oxidative stress in rat model of ischemic stroke

Oxidative stress is the common underlying mechanism of damage in ischemic stroke. Therefore, we aimed to evaluate the possible protective effects of polyhydroxylated fullerene derivatives on brain infarction and oxidative/nitrosative stress in a rat model of ischemic stroke. The experiment was performed by four groups of rats (each; n=12); Sham, Control ischemia, and ischemic treatment groups (Pretreatment and Posttreatment). Brain ischemia was induced by 90 min middle cerebral artery occlusion (MCAO) followed by 24 hours reperfusion. Rats received fullerene nanoparticles at dose of 1 mg/kg 30 min before MCAO and immediately after beginning of reperfusion. Infarct volume, contents of malondialdehyde (MDA), glutathione (GSH) and nitrate as well as superoxide dismutase (SOD) activity were assessed 24 hours after termination of MCAO. Brain infarct volume was 310 ± 21 mm³ in control group. Administration of fullerene nanoparticles before and after MCAO significantly decreased the infarct volume by 53 % (145 ± 45 mm³) and 81 % (59 ± 13 mm³), respectively. Ischemia also enhanced MDA and nitrate contents of ischemic hemispheres by 45 % and 25 % , respectively. Fullerene nanoparticles considerably reduced the MDA and nitrate contents of ischemic hemispheres before MCAO by 58 % and 17 % , respectively, and after MCAO by 38 % and 21 % , respectively. Induction of MCAO significantly decreased GSH content (19 % ) and SOD activity (52 % ) of ischemic hemispheres, whereas fullerene nanoparticles increased the GSH content and SOD activity of ischemic hemispheres by 19 % and 52 % before MCAO, respectively, and 21 % and 55 % after MCAO, respectively. Our findings indicate that fullerene nanoparticles, as a potent scavenger of free radicals, protect the brain cells against ischemia/reperfusion injury and inhibit brain oxidative/nitrosative damage.

Aspirin and multiple sclerosis

Aspirin is widely used to lessen the risks of cardiovascular events. Some studies suggest that patients with multiple sclerosis have an increased risk for some cardiovascular events, for example, venous thromboembolism and perhaps ischemic strokes, raising the possibility that aspirin could lessen these increased risks in this population or subgroups (patients with limited mobility and/or antiphospholipid antibodies). However, aspirin causes a small increased risk of hemorrhagic stroke, which is a concern as it could potentially worsen a compromised blood-brain barrier. Aspirin has the potential to ameliorate the disease process in multiple sclerosis (for example, by limiting some components of inflammation), but aspirin also has the potential to inhibit mitochondrial complex I activity, which is already reduced in multiple sclerosis. In an experimental setting of a cerebral ischemic lesion, aspirin promoted the proliferation and/or differentiation of oligodendrocyte precursors, raising the possibility that aspirin could facilitate remyelination efforts in multiple sclerosis. Other actions by aspirin may lead to small improvements of some symptoms (for example, lessening fatigue). Here we consider potential benefits and risks of aspirin usage by patients with multiple sclerosis.

Association of renin and aldosterone with ethnicity and blood pressure: the Multi-Ethnic Study of Atherosclerosis

BACKGROUND

Although variations in plasma renin activity (PRA) and aldosterone have been examined in whites and blacks, the association of these hormones with blood pressure in multiethnic populations has not been described.

METHODS

We measured PRA and aldosterone in 1,021 participants in the Multi-Ethnic Study of Atherosclerosis not taking antihypertensives and examined the association between ethnicity and PRA/aldosterone and the association between PRA/aldosterone with systolic blood pressure (SBP).

RESULTS

Average age was 62 (SD = 9) years, and 49% of participants were women. Median PRA was 0.51 (interquartile range (IQR) = 0.29-0.87) ng/ml/hour, and median aldosterone was 12.6 (IQR = 9.1-17.1) ng/dl. After age and sex adjustment, compared with whites, blacks had 28% lower PRA and 17.4% lower aldosterone, and Hispanics had 20.1% higher PRA but similar aldosterone levels. After multivariable adjustment, compared with whites, only Hispanic ethnicity independently associated with higher PRA (0.18ng/ml/hour; 95% confidence interval (CI) = 0.06-0.31). Blacks had lower aldosterone (-1.7ng/dl; 95% CI = -3.2 to -0.2) compared with whites. After multivariable adjustment, PRA was associated with lower SBP in whites (-3.2mm Hg; 95% CI = -5.2 to -1.2 per standardized unit PRA), Chinese (-3.5mm Hg; 95% CI = -6.2 to -0.80 per standardized unit), and Hispanics (-2.3mm Hg; 95% CI = -4.1 to -0.6 per standardized unit) but not blacks. Aldosterone was associated with higher SBP only in Hispanics (2.5mm Hg; 95% CI = 0.4-4.5 per SD).

CONCLUSIONS

Compared with whites, blacks have lower aldosterone and Hispanics have higher PRA. Aldosterone had significant associations with higher SBP in Hispanics compared with other groups, a finding that may suggest a different mechanism of hypertension.

The proapoptotic effect of traditional and novel nonsteroidal anti-inflammatory drugs in mammalian and yeast cells

Nonsteroidal anti-inflammatory drugs (NSAIDs) have long been used to treat pain, fever, and inflammation. However, mounting evidence shows that NSAIDs, such as aspirin, have very promising antineoplastic properties. The chemopreventive, antiproliferative behaviour of NSAIDs has been associated with both their inactivation of cyclooxygenases (COX) and their ability to induce apoptosis via pathways that are largely COX-independent. In this review, the various proapoptotic pathways induced by traditional and novel NSAIDs such as phospho-NSAIDs, hydrogen sulfide-releasing NSAIDs and nitric oxide-releasing NSAIDs in mammalian cell lines are discussed, as well as the proapoptotic effects of NSAIDs on budding yeast which retains the hallmarks of mammalian apoptosis. The significance of these mechanisms in terms of the role of NSAIDs in effective cancer prevention is considered.

Pivotal roles of monocytes/macrophages in stroke

Stroke is an important issue in public health due to its high rates both of morbidity and mortality, and high rate of disability. Hypertension, cardiovascular disease, arterial fibrillation, diabetes mellitus, smoking, and alcohol abuse are all risk factors for stroke. Clinical observations suggest that inflammation is also a direct risk factor for stroke. Patients with stroke have high levels of inflammatory cytokines in plasma, and immune cells, such as macrophages and T-lymphocytes, are noted within stroke lesions. These inflammatory events are considered as a result of stroke. However, recent studies show that plasma levels of inflammatory cytokines or soluble adhesion molecules are high in patients without stroke, and anti-inflammatory therapy is effective at reducing stroke incidence in not only animal models, but in humans as well. Statins have been shown to decrease the stroke incidence via anti-inflammatory effects that are both dependent and independent of their cholesterol-lowering effects. These reports suggest that inflammation might directly affect the onset of stroke. Microglial cells and blood-derived monocytes/macrophages play important roles in inflammation in both onset and aggravation of stroke lesions. We review the recent findings regarding the role of monocytes/macrophages in stroke.

Interleukin-1β accelerates the onset of stroke in stroke-prone spontaneously hypertensive rats

High blood levels of inflammatory biomarkers and immune cells in stroke lesions have been recognized as results of stroke. However, recent studies have suggested that inflammation occurs prior to stroke onset. In this study, we aimed to clarify the role of inflammation in stroke onset among stroke-prone spontaneously hypertensive rats (SHRSP). At 4 weeks of age (before stroke onset), the plasma level of IL-1β was significantly higher in SHRSP (153.0 ± 49.7 pg/ml) than in Wistar Kyoto rats (WKY) (7.7 ± 3.4 pg/ml, P < 0.001 versus SHRSP) or spontaneously hypertensive rats (SHR) (28.0 ± 9.1 pg/ml, P < 0.001 versus SHRSP) (n = 6 per strain). Stimulated IL-1β signal was also observed in cerebrovascular endothelial cells of SHRSP. Gene expressions of IL-1β, IL-1 receptors, caspase-1, and downstream genes (MCP-1 and ICAM-1), which associated with immune cell recruitment, were significantly greater in SHRSP than in WKY or SHR, coincident with greater NFκB protein levels in SHRSP compared to WKY or SHR. In addition, continuous administration of IL-1β (2 μg/day) using an osmotic pump slightly increased the incidence of stroke in SHR (P = 0.046) and significantly accelerated the onset of stroke in SHRSP (P = 0.006) compared to each control (n = 10 per group). These results suggest that a stimulated IL-1β signal might be a cause of stroke onset when concomitant with severe hypertension.

Low-Dose Aspirin Therapy Does not Increase the Severity of Acute Radiation Proctitis

Background

Although anticoagulation therapy is commonly used in the prostate cancer population, there are only a few studies about the correlation between radiation proctitis and anticoagulation therapy. The purpose of the present study was to determine whether low-dose aspirin increases the severity of acute radiation proctitis in an experimental animal model.

Methods

Wistar rats were used in the present study. The rats were administered either aspirin at doses of 5, 10, and 20 mg/kg, or saline, daily before and after irradiation. The rats were irradiated to the rectum as a single fraction of 25 Gy. The rectal mucosal changes of each rat were evaluated macroscopically and pathologically on the tenth day following irradiation. The findings of proctitis were graded from 0 to 4, and then were compared with regard to the status.

Results

No apparent correlations were observed between the administration of aspirin and the severity of radiation proctitis in the macroscopic findings and in the morphological mucosal damage in the pathological examination. The proportion of rats with a severe degree of mucosal inflammation was 90.0%, 100.0%, 16.7% and 100.0% at 5 mg/kg, 10 mg/kg, and 20 mg/kg of aspirin, or saline, respectively. The rats receiving aspirin at the dose of 20 mg/kg showed significantly milder inflammation than the other groups (P < 0.05).

Conclusions

In the present study, low-dose aspirin did not increase the severity of acute radiation proctitis. In addition, aspirin might decrease the severity of radiation-induced mucosal inflammation in the rectum.

Anti-inflammatory effects of chronic aspirin on brain arachidonic acid metabolites

Pro-inflammatory and anti-inflammatory mediators derived from arachidonic acid (AA) modulate peripheral inflammation and its resolution. Aspirin (ASA) is a unique non-steroidal anti-inflammatory drug, which switches AA metabolism from prostaglandin E₂ (PGE₂) and thromboxane B₂ (TXB₂) to lipoxin A₄ (LXA₄) and 15-epi-LXA₄. However, it is unknown whether chronic therapeutic doses of ASA are anti-inflammatory in the brain. We hypothesized that ASA would dampen increases in brain concentrations of AA metabolites in a rat model of neuroinflammation, produced by a 6-day intracerebroventricular infusion of bacterial lipopolysaccharide (LPS). In rats infused with LPS (0.5 ng/h) and given ASA-free water to drink, concentrations in high-energy microwaved brain of PGE₂, TXB₂ and leukotriene B₄ (LTB₄) were elevated. In rats infused with artificial cerebrospinal fluid, 6 weeks of treatment with a low (10 mg/kg/day) or high (100 mg/kg/day) ASA dose in drinking water decreased brain PGE₂, but increased LTB₄, LXA₄ and 15-epi-LXA₄ concentrations. Both doses attenuated the LPS effects on PGE₂, and TXB₂. The increments in LXA₄ and 15-epi-LXA₄ caused by high-dose ASA were significantly greater in LPS-infused rats. The ability of ASA to increase anti-inflammatory LXA₄ and 15-epi-LXA₄ and reduce pro-inflammatory PGE₂ and TXB₂ suggests considering aspirin further for treating clinical neuroinflammation.

Alterations in the modulation of cerebrovascular tone and blood flow by nitric oxide synthases in SHRsp with stroke

AIMS

The modulation of myogenic function and cerebral blood flow (CBF) by nitric oxide (NO) synthases (NOS) was assessed in the middle cerebral arteries (MCAs) of Kyoto Wistar stroke prone hypertensive rats (SHRsp) in relation to haemorrhagic stroke development.

METHODS AND RESULTS

MCAs were studied with a pressure myograph. CBF in MCA perfusion domain was measured using laser Doppler techniques. NOS isozymes were identified using immunohistochemistry. MCAs expressed endothelial, neuronal, and inducible NOS (eNOS, nNOS, and iNOS, respectively) in the endothelium, nNOS and traces of iNOS in smooth muscle and adventitial cells. Before stroke, MCA pressure-dependent constriction (PDC) was superimposed over basal non-pressure-dependent tone (BNPDT). Endothelial NO generation and non-endothelial nNOS but not iNOS reduced BNPDT and increased the lumen diameter at which PDC initiated without altering the amplitude of PDC. NOS inhibition decreased CBF and increased the upper blood pressure limit of autoregulation. PDC, CBF autoregulation, and NOS dilatory influence were lost, and BNPDT was increased in MCAs from SHRsp with stroke. The expression of NOS isozymes and MCA reactivity to NO donors was not altered. NOS activity was not recovered by in vitro l-arginine or tetrahydrobiopterin supplementation, l-arginase inhibition or superoxide scavengers.

CONCLUSION

The loss of PDC and CBF autoregulation during hypertension may facilitate over-perfusion and cerebral haemorrhage formation in SHRsp. NOS dysfunction in MCAs preceded stroke and involved the inactivation of eNOS and nNOS in areas not subjected to hyper-distension. The elevation in BNPDT due to NOS inactivation may oppose over-perfusion in the absence of CBF autoregulation.