Ischemic-like And Excitotoxicity-induced Injuries Activate 5-lipoxygenase In PC12 Cells And The Protective Effect Of Minocycline

5-Lipoxygenase (5-LOX) is a key enzyme in the synthesis of leukotriens from arachidonic acid. Various pro-inflammatory stimuli activate 5-LOX then leukotrienes are produced. One of the important characteristics of 5-LOX activation is its translocation to nuclear membrane. Recently, most studies are focused on the roles of 5-LOX in peripheral organ diseases, such as the disease of respiration system. However, the possible roles of 5-LOX in the diseases of the central never system (CNS) are also investigated. Inflammation is one of the main pathological processes in pathogenesis of brain injuries including cerebral ischemia. The products of eicosanoid cascades (mainly including prostaglandins and leukotrienes) have been considered as the most important inflammatory mediators. Therefore, 5-LOX may be important in the CNS injuries. Currently, all the investigations of 5-LOX in the CNS are performed in animal models in vivo or in human brain samples, but none of cellular investigation is performed.In order to further clarify the pathogenesis of cerebral ischemia and post-ischemic inflammation, and to develop novel therapeutic treatments for cerebral ischemia or other brain injuries, this study was aimed to investigate the role of 5-LOX in ischemic-like and excitotoxicity-induced injuries in PC 12 cells, one of the neural cells, to evaluate the involvement of 5-LOX activation in neural cell injuries. In vitro ischemic-like injurywas induced by oxygen glucose deprivation (OGD), and excitotoxicity-induced injury was induced by N-methyl-D-aspartate (NMDA). OGD injury may cause metabolic disturbance and a series of pathological changes, such as release of excitory amino acids. So, OGD injury may well mimic in vivo cerebral ischemia. NMDA activates NMDA receptor and causes intracellular calcium ion elevation, then induces various lesions including cell necrosis and apoptosis. NMDA-induced injury is a common basic pathological process that is involved in various CNS diseases, such as cerebral ischemia, Alzheimer disease, Huntingdon disease and amyotrophic lateral sclerosis. Thus, this injury may mimic the common properties of various brain injuries.In these injury models, we used 5-LOX inhibitor caffeic acid and 12-LOX inhibitor baicalein as tools to confirm the involvement of 5-LOX in ischemic-like and excitotoxicity-induced injuries. NMDA receptor antagonist ketamine was also used to confirm the specificity of NMDA-induced injury. Since minocycline, a semi-synthetic second generation tetracycline antibiotic drug, has been reported to possess neuroprotective effects in many CNS diseases, we observed its protective effect on the ischemic-like and excitotoxicity-induced injuries in PC 12 cells, and analysed the relation of its effect and 5-LOX activation. Minocycline has been reported to protect the brain through inhibiting microglial activation and neuron apoptosis, however, the anti-inflammatory mechanisms and the involvement of 5-LOX in its effect are still unkown.The purpose of the present study was to explore the implication of 5-LOX in pathogenesis of brain injury, and to clarify whether pharmacological intervention for 5-LOX is a possible therapeutic way to treat cerebral ischemia and other brain injuries.Partâ… Ischemic-like injury activates 5-Iipoxygenase in PC 12 cells and theprotective effect of minocyclineAIM: To determine whether 5-LOX is involved in the ischemia-like injury in PC 12 cells, and whether minocycline has protective effect on the ischemic-like injury, if so, its effect is related to inhibiting 5-LOX activation. METHODS: PC 12 cells wereinjured by a glucose-free buffer in a hypoxia chamber that was gassed with a mixture of 95% N₂ and 5% CO₂ at 37°C (namely, oxygen glucose deprivation, OGD). OGD could mimic ischemic injury in vitro. Various concentrations of minocycline, caffeic acid (a 5-LOX inhibitor) and baicalein (a 12-LOX inhibitor) were added into the culture media 30 min before OGD to observe their protective effects on OGD insult. MTT reduction assay was used to evaluate PC 12 cell...