Protective Effect of 4-Methoxy Benzyl Alcohol on the Blood–Brain Barrier after Cerebral Ischemia Reperfusion Injury

Pharmacokinetics of 4-Hydroxybenzaldehyde in Normal and Cerebral Ischemia-Reperfusion Injury Rats Based on Microdialysis Technique

AIM

4-Hydroxybenzaldehyde (4-HBd) is used for the treatment of headaches, dizziness, and convulsions. The objective of this study was to characterize the pharmacokinetics of 4-HBd in cerebral ischemia-reperfusion injury (CIRI) rats by microdialysis technology with high-performance liquid chromatography with diode-array detection (HPLC-DAD) and ultra-performance liquid chromatography-mass spectrometry (UPLC-MS).

METHODS

Microdialysis was used to collect blood, feces, and urine of normal and CIRI model rats. Pharmacokinetic parameters were determined using HPLC-DAD and 4-HBd metabolites were determined using UPLC-MS.

RESULTS

After gavage of 4-HBd in normal and middle cerebral artery occlusion/reperfusion (MCAO/R) rats, it was widely distributed to all tissues (heart, liver, spleen, lung, kidney, and brain) in both the equilibrium and elimination phases, and the distribution pattern was basically the same; the highest concentration was found in the brain. The absolute bioavailability of 4-HBd was 5.33%; however, after intragastric administration in normal and MCAO/R rats, fecal and urinary excretion of 4-HBd accounted for 0.02% and 0.01% and for 0.01% and 0.03% of the dosage, respectively. Furthermore, 4-HBd was rapidly metabolized into 4-hydroxybenzoic acid (4-HBA) after administration in both the control and MCAO/R groups. Compared with the control, the peak time of 4-HBd plasma concentration in the MCAO/R rats decreased from 10.67 min to 8.83 min, the area under the concentration-time curve decreased significantly, and the half-life increased from 31.81 min to 78.85 min.

CONCLUSIONS

The rapid absorption and low absolute bioavailability of 4-HBd by gavage in rats are followed by rapid and wide distribution to various tissues and organs, including the brain. The prototype drug is excreted in the feces and urine in low amounts, and it is metabolized to 4-HBA in large amounts in vivo; the pathological state of the MCAO/R model mainly affects its absorption degree and metabolism rate.

De Novo Biosynthesis of Anisyl Alcohol and Anisyl Acetate in Engineered Escherichia coli

Anisyl alcohol and its ester anisyl acetate are both important fragrance compounds and have a wide range of applications in the cosmetics, perfumery, and food industries. The currently commercially available anisyl alcohol and anisyl acetate are based on chemical synthesis. However, consumers increasingly prefer natural fragrance compounds. Therefore, it is of great significance to construct microbial cell factories to produce anisyl alcohol and anisyl acetate. In this study, we first established a biosynthetic pathway in engineered Escherichia coli MG1655 for the production of anisyl alcohol from simple carbon sources. We further increased the anisyl alcohol production to 355 mg/L by the increasing availability of erythrose-4-phosphate and phosphoenolpyruvate. Finally, we further demonstrated the production of anisyl acetate by overexpressing alcohol acetyltransferase ATF1 for the subsequent acetylation of anisyl alcohol to produce anisyl acetate. To our knowledge, this is the first report on the biosynthesis of anisyl alcohol and anisyl acetate directly from a renewable carbon source.

Angiogenesis effects of 4-methoxy benzyl alcohol on cerebral ischemia-reperfusion injury via regulation of VEGF-Ang/Tie2 balance

Angiogenesis facilitates the formation of microvascular networks and promotes neurological deficit recovery after cerebral ischemia-reperfusion injury (CIRI). This study investigated the angiogenesis effects of 4-methoxy benzyl alcohol (4-MA) on CIRI. The angiogenesis effects of 4-MA and the potential underlying mechanisms were assessed based on a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model and a hind limb ischemic (HLI) mouse model. Immunofluorescence was conducted to detect microvessel density, and Western blotting and polymerase chain reaction were performed to determine the expression of angiogenesis-promoting factors. In addition, we investigated whether the angiogenesis effects of 4-MA caused damage to the blood-brain barrier (BBB). After treatment with 4-MA (20 mg/kg) for 7 days, the neurological deficits recovered and microvessel density in the cerebral cortex increased in the MCAO/R rats. Additionally, 4-MA also regulated the expression of angiogenesis factors, with an increase in vascular endothelial growth factor (VEGF) and vascular endothelial growth factor receptor 2 (VEGFR-2) expression and a decrease in angiopoietin 1 (Ang-1), Ang-2, and Tie-2 expression in both MCAO/R rats and HLI mice. Moreover, 4-MA increased the expression of angiogenesis-promoting factors without exacerbating BBB cascade damage in MCAO/R rats. Our results indicated that 4-MA may contribute to the formation of microvascular networks, thus promoting neurological deficit recovery after CIRI.

Neuroprotective effects of four different fluids on cerebral ischaemia/reperfusion injury in rats through stabilization of the blood-brain barrier

Protecting the blood–brain barrier (BBB) is a potential strategy to treat cerebral ischaemic injury. We previously reported that hypertonic sodium chloride hydroxyethyl starch 40 (HSH) treatment alleviates brain injury induced by transient middle cerebral artery occlusion (tMCAO). However, other fluids, including 20% mannitol (MN), 3% hypertonic sodium chloride (HTS) and hydroxyethyl starch 130/0.4 solution (HES), have the same effect as HSH in cerebral ischaemia/reperfusion injury (CI/RI) remains unclear. The present study evaluated the protective effects of these four fluids on the BBB in tMCAO rats. Sprague–Dawley (SD) rats were randomly assigned to six groups. A CI/RI rat model was established by tMCAO for 120 min followed by 24 h of reperfusion. The sham and tMCAO groups were treated with normal saline (NS), whereas the other four groups were treated with the four fluids. After 24 h of reperfusion, neurological function, brain oedema, brain infarction volume, permeability of the BBB, cortical neuron loss and protein and mRNA expression were assessed. The four fluids (especially HSH) alleviated neurological deficits and decreased the infarction volume, brain oedema, BBB permeability and cortical neuron loss induced by tMCAO. The expression levels of GFAP, IL‐1β, TNF‐α, MMP‐9, MMP‐3, AQP4, MMP‐9, PDGFR‐β and RGS5 were decreased, whereas the expression levels of laminin and claudin‐5 were increased. These data suggested that small‐volume reperfusion using HSH, HES, MN and HTS ameliorated CI/RI, probably by attenuating BBB disruption and postischaemic inflammation, with HSH exerting the strongest neuroprotective effect.

Neuroprotective Phytochemicals in Experimental Ischemic Stroke: Mechanisms and Potential Clinical Applications

Ischemic stroke is a challenging disease with high mortality and disability rates, causing a great economic and social burden worldwide. During ischemic stroke, ionic imbalance and excitotoxicity, oxidative stress, and inflammation are developed in a relatively certain order, which then activate the cell death pathways directly or indirectly via the promotion of organelle dysfunction. Neuroprotection, a therapy that is aimed at inhibiting this damaging cascade, is therefore an important therapeutic strategy for ischemic stroke. Notably, phytochemicals showed great neuroprotective potential in preclinical research via various strategies including modulation of calcium levels and antiexcitotoxicity, antioxidation, anti-inflammation and BBB protection, mitochondrial protection and antiapoptosis, autophagy/mitophagy regulation, and regulation of neurotrophin release. In this review, we summarize the research works that report the neuroprotective activity of phytochemicals in the past 10 years and discuss the neuroprotective mechanisms and potential clinical applications of 148 phytochemicals that belong to the categories of flavonoids, stilbenoids, other phenols, terpenoids, and alkaloids. Among them, scutellarin, pinocembrin, puerarin, hydroxysafflor yellow A, salvianolic acids, rosmarinic acid, borneol, bilobalide, ginkgolides, ginsenoside Rd, and vinpocetine show great potential in clinical ischemic stroke treatment. This review will serve as a powerful reference for the screening of phytochemicals with potential clinical applications in ischemic stroke or the synthesis of new neuroprotective agents that take phytochemicals as leading compounds.

4-Methoxybenzylalcohol protects brain microvascular endothelial cells against oxygen-glucose deprivation/reperfusion-induced injury via activation of the PI3K/AKT signaling pathway

Damage to the blood-brain barrier (BBB) during the process of cerebral ischemic injury is a key factor that affects the treatment of this condition. The present study aimed to assess the potential effects of 4-methoxybenzyl alcohol (4-MA) on brain microvascular endothelial cells (bEnd.3) against oxygen-glucose deprivation/reperfusion (OGD/Rep) using an in vitro model that mimics in vivo ischemia/reperfusion injury. In addition, the present study aimed to explore whether this underlying mechanism was associated with the inhibition of pro-inflammatory factors and the activation status of the PI3K/Akt signaling pathway. bEnd.3 cells were subjected to OGD/Rep-induced injury before being treated with 4-MA, following which cell viability, lactate dehydrogenase (LDH) release and levels of nitric oxidase (NO) were detected by colorimetry, pro-inflammatory factors including tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6, were detected by ELISA. The expression levels of occluding and claudin-5were evaluated by immunofluorescence staining. The expression levels of AKT, phosphorylated (p)-Akt, endothelial nitric oxide synthase (eNOS) and p-eNOS were also measured by western blot analysis. After bEnd.3 cells were subjected to OGD/Rep-induced injury, cell viability and NO levels were significantly decreased, whilst LDH leakage and inflammatory factor (TNF-α, IL-1β and IL-6) levels were significantly increased. Treatment with 4-MA significantly ameliorated cell viability, LDH release and the levels of NO and pro-inflammatory factors TNF-α, IL-1β and IL-6 as a result of OGD/Rep. Furthermore, treatment with 4-MA upregulated the expression of occludin, claudin-5, Akt and eNOS, in addition to increasing eNOS and AKT phosphorylation in bEnd.3 cells. These results suggest that 4-MA can alleviate OGD/Rep-induced injury in bEnd.3 cells by inhibiting inflammation and by activating the PI3K/AKT signaling pathway as a possible mechanism. Therefore, 4-MA can serve as a potential candidate for treating OGD/Rep-induced injury.

Anti-neuroinflammatory effect of 3,4-dihydroxybenzaldehyde in ischemic stroke

BACKGROUND

Increasing evidence from human and animal studies suggests that cerebral ischemic diseases are associated with nerve dysfunction and neuroinflammation. Therefore, alleviating neuroinflammation is a potential way to treat ischemic stroke. Gastrodia elata Blume (GEB) is a traditional Chinese medicine used to treat central nervous system diseases and related conditions, such as vertigo, headache, epilepsy. We have previously shown that GEB has a protective effect in ischemic stroke, and that the underlying mechanism is related to anti-neuroinflammation. 3,4-Dihydroxybenzaldehyde (DBD) is a phenolic component of GEB and may be responsible for the neuroprotective effect of GEB; however, the detailed molecular mechanisms underlying the effects of DBD are unknown.

METHODS

The anti-neuroinflammatory effect of DBD and the potential mechanisms underlying it were assessed. We using a rat model of middle cerebral artery occlusion/reperfusion and lipopolysaccharide-treated BV2 microglial cells.

RESULTS

DBD (10 mg/kg) significantly decreased infarct volume. Additionally, it alleviated neurological deficits in the rats by inhibiting microglia activation. DBD (0.01, 0.1, and 1 μM) also significantly decreased the levels of inflammatory mediators and cytokines such as tumor necrosis factor-α, interleukin (IL)-1β, IL-6, prostaglandin E2. Furthermore, phenotypic analysis of the BV2 cells showed that DBD significantly down-regulated the expression of M1 marker but significantly up-regulated the expression of M2 marker. Moreover, it suppressed nuclear factor (NF)-κB activation and inhibited the phosphorylation of p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase, and extracellular signal-regulated protein kinases 1/2.

CONCLUSIONS

The neuroprotective and anti-inflammatory effects of DBD are associated with selective modulation of microglia polarization and reduction in the production of inflammatory mediators and cytokines through inhibition of MAPK and NF-κB activation. These findings suggest that DBD may be a potential treatment for ischemic stroke and other neuroinflammatory diseases.

Exploring the effects of Gastrodia elata Blume on the treatment of cerebral ischemia-reperfusion injury using UPLC-Q/TOF-MS-based plasma metabolomics

Gastrodia elata Blume (Orchidaceae, GEB) is a medicinal plant that has been widely used in the treatment of cerebrovascular disease. This study explored the protective effects of GEB against cerebral ischemia-reperfusion using Information-Dependent Acquisition (IDA)-mediated UPLC-Q/TOF-MS-based plasma metabolomics. Cerebral ischemia-reperfusion (IR) injury was induced in male Wistar rats using the Zea Longa method. Biochemical and histological assays were performed to evaluate the therapeutic effects of GEB on IR rats. We found that the neurobehavioral scores and infarction areas of GEB and nimodipine treated groups were dramatically lower than those of the IR groups. Hematoxylin and Eosin (HE) staining and TdT-mediated dUTP Nick-End Labeling (TUNEL) showed that GEB significantly improved neuronal injury and prevented neuronal apoptosis. Biochemical analysis revealed that GEB prevented cerebral ischemia-reperfusion injury by regulating inflammation and oxidative injury. Through ultra-high-performance liquid chromatography-quadrupole time-of-flight mass spectrometry-metabolomics-based approaches, 43 plasma metabolites related to GEB treatment were detected, 6 of which significantly differed (p < 0.05) between the model and GEB groups. The levels of l-histidine, sphinganine, thymine, spermidine and deoxycytidine in the IR group were significantly higher than those in the sham group, but decreased following GEB treatment. Arachidonic acid levels were lower in the IR group, but dramatically increased in response to GEB. Pharmacodynamics and metabolomics confirmed that the mechanism of GEB in the treatment of cerebral ischemia was not only related to the reduction of inflammation, oxidation, neurotoxicity, and apoptosis, but also mediated through arachidonic acid metabolism, histidine metabolism, pyrimidine metabolism, arginine and proline metabolism, sphingolipid metabolism, and glycerophospholipid metabolism in vivo.

Protective effect of 4-Methoxy benzyl alcohol on the neurovascular unit after cerebral ischemia reperfusion injury

OBJECTIVE

Cerebral ischemia reperfusion injury (CIRI) is a major cause of ischemic stroke (IS) deterioration. Considering the intricate mechanism of the pathological process of CIRI, most drugs only work on one target. The neurovascular unit (NVU) puts forward the concept of neuroprotection from nerve protection to global stabilization. The NVU plays an important role in maintaining the brain microenvironment. This would promote neuronal survival and overall neurological recovery, which would likely lead to the reduction of mortality rate. Previous studies have shown that 4-methoxy benzyl alcohol (4-MA) ameliorated neurological score and cerebral infarct volume and reduced the concentration of Evans blue (EB) in brain tissue. In this research, we investigated the effects of 4-MA on NVU microenvironment improvement in rats impaired by middle cerebral artery occlusion/reperfusion (MCAO/R).

METHODS

First, we established a rat model of middle cerebral artery occlusion (MCAO) so as to use Western blot analysis, immunofluorescence and transmission electron microscopy (TEM) evaluating the NVU's protection of 4-MA. Then we established a primary cortical neuron model of oxygen glucose deprivation and re-oxygenation (OGD/R) with the objective of identifying whether 4-MA exhibited anti-oxidant and anti-apoptotic effects on neurons.

RESULTS

NVU ultra structural changes were improved by 4-MA. Immunofluorescence and western blot showed that 4-MA protected NVUs through enhancement of the expression of the symbolic neuronal proteins Microtubule Associated Protein-2(MAP-2), and attenuation of protein expression of Asy symbolic protein Glial Fibrillary Acidic Protein(GFAP). Furthermore, in the OGD/R model of I/R injury in vitro, 4-MA significantly increased Superoxide dismutase(SOD), Nitric Oxide(NO), B-cell lymphoma-2(Bcl-2), decreased Bcl-2-Associated X(Bax) and increased Bcl-2/Bax.

CONCLUSION

4-MA can play the role of anti-ischemic stroke drug by ameliorating the microenvironment of NVUs while its neuroprotective effects will contribute towards the inhibition of the antioxidant and anti-apoptotic activities.

1, 25-D3 Protects From Cerebral Ischemia by Maintaining BBB Permeability via PPAR-γ Activation

The blood-brain barrier (BBB) is a physical and biochemical barrier that maintains cerebral homeostasis. BBB dysfunction in an ischemic stroke, results in brain injury and subsequent neurological impairment. The aim of this study was to determine the possible protective effects of 1, 25-dihydroxyvitamin D3 [1, 25(OH)2D3, 1, 25-D3, vit D] on BBB dysfunction, at the early stages of an acute ischemic brain injury. We analyzed the effects of 1, 25-D3 on BBB integrity in terms of histopathological changes, the neurological deficit, infarct size and the expression of brain derived neurotrophic factor (BDNF), in a middle cerebral artery occlusion/reperfusion (MCAO/R) rat model. BBB permeability and the expression of permeability-related proteins in the brain were also evaluated by Evans blue (EB) staining and Western blotting respectively. To determine the possible mechanism underlying the role of 1, 25-D3 in BBB maintenance, after MCAO/R, the rats were treated with the specific peroxisome proliferator-activated receptor gamma (PPARγ) inhibitor GW9662. Supplementation with 1, 25-D3 markedly improved the neurological scores of the rats, decreased the infarct volume, prevented neuronal deformation and upregulated the expression of the tight junction (TJ) and BDNF proteins in their brains. Furthermore, it activated PPARγ but downregulated neuro-inflammatory cytokines such as nuclear factor kappa-B (NF-κB) and tumor necrosis factor-α (TNF-α), after MCAO/R. Taken together, 1, 25-D3 protects against cerebral ischemia by maintaining BBB permeability, upregulating the level of BDNF and inhibiting PPARγ-mediated neuro-inflammation.

Picroside II Exerts a Neuroprotective Effect by Inhibiting mPTP Permeability and EndoG Release after Cerebral Ischemia/Reperfusion Injury in Rats

Mitochondrial membrane permeability is closely related to cerebral ischemia/reperfusion (I/R) injury. This paper explored the neuroprotective effect of picroside II (Picr), which inhibits the permeability of mitochondrial permeability transition pore (mPTP) and endonuclease G (EndoG) release from mitochondria into cytoplasm after cerebral I/R in rats. After 2 h of cerebral ischemia and 24 h of reperfusion in rats with different intervention measures, the neurobehavioral function, infarction volume, and reactive oxygen species (ROS) content in brain tissues were observed by modified neurological severity scale (mNSS), triphenyl tetrazolium chloride (TTC) staining, and enzyme-linked immunosorbent assay, respectively. The permeability of mPTP was assayed using spectrophotometry. The morphology and apoptotic cells of brain tissues were observed by hematoxylin-eosin staining and terminal deoxynucleotidyl transferase dUTP nick end labeling assay, respectively. The expressions of EndoG and voltage-dependent anion channel 1 (VDAC1) were determined by immunohistochemical assay and western blot. The Picr group exhibited clear decreases in mNSS scores, ROS content, number of apoptotic cells, mPTP permeability and expression of VDAC1, and EndoG in cytoplasm and nuclei, and the morphology of brain tissue was improved as compared with the model group (P < 0.05). Picr could attenuate cerebral I/R injury by downregulating the expression of VDAC1 and decreasing the permeability of mPTP, thereby inhibiting EndoG release from mitochondria into cytoplasm.