PHPB ameliorates memory deficits and reduces oxidative injury in Alzheimer's disease mouse model by activating Nrf2 signaling pathway.

Alzheimer's disease (AD), a progressive neurodegenerative disorder, is the most common cause of dementia in elderly people and substantially affects patient quality of life. Oxidative stress is considered a key factor in the development of AD. Nrf2 plays a vital role in maintaining redox homeostasis and regulating neuroinflammatory responses in AD. Previous studies show that potassium 2-(1-hydroxypentyl)-benzoate (PHPB) exerts neuroprotective effects against cognitive impairment in a variety of dementia animal models such as APP/PS1 transgenic mice. In this study we investigated whether PHPB ameriorated the progression of AD by reducing oxidative stress (OS) damage. Both 5- and 13-month-old APP/PS1 mice were administered PHPB (100 mg·kg-1·d-1, i.g.) for 10 weeks. After the cognition assessment, the mice were euthanized, and the left hemisphere of the brain was harvested for analyses. We showed that 5-month-old APP/PS1 mice already exhibited impaired performance in the step-down test, and knockdown of Nrf2 gene only slightly increased the impairment, while knockdown of Nrf2 gene in 13-month-old APP/PS1 mice resulted in greatly worse performance. PHPB administration significantly ameliorated the cognition impairments and enhanced antioxidative capacity in APP/PS1 mice. In addition, PHPB administration significantly increased the p-AKT/AKT and p-GSK3ß/GSK3ß ratios and the expression levels of Nrf2, HO-1 and NQO-1 in APP/PS1 mice, but these changes were abolished by knockdown of Nrf2 gene. In SK-N-SH APPwt cells and primary mouse neurons, PHPB (10 µM) significantly increased the p-AKT/AKT and p-GSK3ß/GSK3ß ratios and the level of Nrf2, which were blocked by knockdown of Nrf2 gene. In summary, this study demonstrates that PHPB exerts a protective effect via the Akt/GSK3ß/Nrf2 pathway and it might be a promising neuroprotective agent for the treatment of AD.

Caffeic acid alleviates cerebral ischemic injury in rats by resisting ferroptosis via Nrf2 signaling pathway.

There are few effective and safe neuroprotective agents for the treatment of ischemic stroke currently. Caffeic acid is a phenolic acid that widely exists in a number of plant species. Previous studies show that caffeic acid ameliorates brain injury in rats after cerebral ischemia/reperfusion. In this study we explored the protective mechanisms of caffeic acid against oxidative stress and ferroptosis in permanent cerebral ischemia. Ischemia stroke was induced on rats by permanent middle cerebral artery occlusion (pMCAO). Caffeic acid (0.4, 2, 10 mg·kg-1·d-1, i.g.) was administered to the rats for 3 consecutive days before or after the surgery. We showed that either pre-pMCAO or post-pMCAO administration of caffeic acid (2 mg·kg-1·d-1) effectively reduced the infarct volume and improved neurological outcome. The therapeutic time window could last to 2 h after pMCAO. We found that caffeic acid administration significantly reduced oxidative damage as well as neuroinflammation, and enhanced antioxidant capacity in pMCAO rat brain. We further demonstrated that caffeic acid down-regulated TFR1 and ACSL4, and up-regulated glutathione production through Nrf2 signaling pathway to resist ferroptosis in pMCAO rat brain and in oxygen glucose deprivation/reoxygenation (OGD/R)-treated SK-N-SH cells in vitro. Application of ML385, an Nrf2 inhibitor, blocked the neuroprotective effects of caffeic acid in both in vivo and in vitro models, evidenced by excessive accumulation of iron ions and inactivation of the ferroptosis defense system. In conclusion, caffeic acid inhibits oxidative stress-mediated neuronal death in pMCAO rat brain by regulating ferroptosis via Nrf2 signaling pathway. Caffeic acid might serve as a potential treatment to relieve brain injury after cerebral ischemia. Caffeic acid significantly attenuated cerebral ischemic injury and resisted ferroptosis both in vivo and in vitro. The regulation of Nrf2 by caffeic acid initiated the transcription of downstream target genes, which were shown to be anti-inflammatory, antioxidative and antiferroptotic. The effects of caffeic acid on neuroinflammation and ferroptosis in cerebral ischemia were explored in a primary microglia-neuron coculture system. Caffeic acid played a role in reducing neuroinflammation and resisting ferroptosis through the Nrf2 signaling pathway, which further suggested that caffeic acid might be a potential therapeutic method for alleviating brain injury after cerebral ischemia.

[Pathogenic role of leukotriene B4 in pulmonary microvascular endothelial cell hyper- permeability induced by one lung ventilation in rabbits].

OBJECTIVE: To elucidate the pathogenic role of leukotriene B4 (LTB4) in increased pulmonary microvascular endothelial cell permeability induced by one lung ventilation (OLV) in rabbits. METHODS: Forty-eight healthy Japanese white rabbits were randomly divided into control group (group C), saline pretreatment group (group S), bestatin (a leukotriene A4 hydrolase (LTA4H) inhibitor) plus saline pretreatment group (group B), OLV group (group O), saline pretreatment plus OLV group (group SO) and bestatin plus saline pretreatment with OLV group (group BO). ELISA was used to detect LTB4 content in the lung tissues, and LTA4H and phospholipase Cεl (PLCEl) expressions were examined by Western blotting and quantitative PCR. The wet/dry weight (W/D) ratio of the lung, lung permeability index and the expressions of myosin light chain kinase (MLCK) protein and mRNA in the lung tissues were determined to evaluate the permeability of the pulmonary microvascular endothelial cells (PMVECs). The severities of lung injury were evaluated by lung histomorphological scores. RESULTS: No significant differences were found among groups C, S and B except that LTA4H expressions was significantly lower in group B than in groups C and S (P<0.05). OLV significantly increased the expressions of LTA4H (P<0.05) and resulted in LTB4 overproduction in the lungs (P<0.05) accompanied by significantly enhanced PLCE1 expression and PMVEC permeability (P<0.05). Pretreatment with bestatin, significantly reduced the expression of LTA4H and LTB4 production (P<0.05) and down-regulated the expression of PLCE1 in the lungs of the rabbits receiving OLV (P<0.05). CONCLUSION: Bestatin plays a protective role in OLV-induced rabbit lung injury by downregulating LTA4H to reduce the production of LTB4 in the lungs. LTB4 can increase PMVEC permeability by up-regulating PLCE1 expression in rabbits with OLV-induced lung injury.

[Relationship between cytoplasmic phospholipase A2 and nuclear factor κB in one lung ventilation-induced lung injury in rabbits].

OBJECTIVE: To elucidate the mechanisms of up regulated expression of cytoplasmic phospholipase A2 (CPLA2) induced by one lung ventilation (OLV) by investigating the interactions between nuclear factor kappaB (NF-κB) and C-PLA2. METHODS: Forty-eight healthy Japanese white rabbits were randomized into control group, solvent treatment group (group S), NF-κB inhibitor (PDTC)/solvent treatment group ( group PS), C-PLA2 inhibitor (AACOCF3)/solvent treatment group (group AS), OLV group (group O), solvent treatment plus OLV group (SO group), NFκB inhibitor (PDTC)/solvent treatment plus OLV group (group PSO) and CPLA2 inhibitor (AACOCF3)/solvent treatment plus OLV group (group ASO). ELISA was used to detect arachidonic acid (AA) content in the lung tissues, and NFκB and CPLA2 expressions were detected by Western blotting and quantitative PCR. Lung injuries were assessed based on the lung histological score, and the polymorphonuclear leukocyte count in the bronchial alveolar lavage fluid, myeloperoxidase (MPO) content in the lung tissues, and lung wet/dry weight (W/D) raito were determined. RESULTS: Treatment of the rabbits with the solvent did not produce any adverse effects. OLV caused obvious lung injury in the rabbits and up regulated the expressions of CPLA2 and NFκB in the lung tissues (P<0.05). In rabbits without OLV, treatment with AACOCF3 or PDTC significantly down regulated both CPLA2 and NFκB expressions without affecting the other parameters. In rabbits with OLV, treatment with AACOCF3 or PDTC obviously lowered CPLA2 and NFκB expressions and lessened the OLV-induced lung injuries. CONCLUSION: Both C-PLA2 and NF-κB play important roles and show interactions in OLV-induced lung injury in rabbits.

Spinal TRPC6 channels contributes to morphine-induced antinociceptive tolerance and hyperalgesia in rats.

The chronic administration of opioids results in the development of morphine analgesic tolerance and withdrawl-induced hyperalgesia, which limits their clinical utility in pain treatment. However, the cellular mechanisms underlying opioid-induced tolerance and hyperalgesia are not fully understood. The transient receptor potential canonical channel TRPC6 is important for brain development and function, as it regulates cytosolic, endoplasmic reticulum, and mitochondrial Ca2+ levels in neural cells. Here, we report that TRPC6 expression in the spinal cord was up-regulated after chronic morphine treatment. Furthermore, inhibition of TRPC6 in the spinal cord blocked the induction of morphine tolerance and hyperalgesia without affecting basal pain perception. These effects were attributed to the attenuation of morphine-induced neuroimmune activation and increased levels of CaMKIIα and nNOS in the spinal cord. This data suggests that specific TRPC6 inhibitors could be utilized for the prevention of morphine-induced antinociceptive tolerance and hyperalgesia in chronic pain management.

Determination and pharmacokinetic study of catechin in rat plasma by HPLC.

A high performance liquid chromatographic method was developed and validated for the quantitative determination of catechin in rat plasma and its pharmacokinetic study after intragastric administration of Catechu and Xiongdanjiangre Wan into SD rats. Plasma samples were prepared by protein precipitation using methanol-5% aqueous zinc sulfate (70:30, v/v) as precipitant. Chromatographic separation was achieved on Hypersil C18 column (250 mm×4.6 mm, 10 µm) with acetonitrile-water-triethylamine (6:94:0.3, v/v/v, pH 4.0±0.1, adjusted with phosphoric acid) as mobile phase, followed by a UV detection at 207 nm. Good linearity was obtained over the range of 0.143-7.15 mg/L of catechin, with correlation coefficient of 0.9992. The method was simple, sensitive, accurate and reproducible and has been successfully applied to the pharmacokinetic study of catechin in rat plasma.