Study On The Expression And Role Of 12/15-lipoxygenase In The Brain Of Rats After Traumatic Brain Injury

Background and objectiveTraumatic brain injury is a common severe clinical emergency in neurosurgery, with high mortality and disability rate. Besides the uncontrollable primary impact damage, the secondary damage including oxidative stress caused by ROS, glutamate excitotoxicity, calcium imbalance, neuron apoptosis and cerebral inflammation do play significant roles after TBI. Among all the complicated pathogenesis of TBI, lipid metabolism plays a pivotal role. For example, cascade activation of arachidonic acid on cell membrane is closely related to the production of oxygen free radicals. And metabolites produced by lipid metabolism, such as phospholipase A2, prostaglandins and leukotrienes, cause different types of cell damage.12/15-lipoxygenase is one of the key enzymes of arachidonic acid metabolism, and is also confirmed to be one of the primary isoforms in central nervous system.12/15-lipoxygenase is proved to be involved in various nervous disorders, associated with oxidative stress, inflammation and apoptosis. However, whether 12/15-LOX metabolic pathway acts in the pathogenesis of TBI has not been clearly elucidated. This study included two experiments, the first experiment was designed to investigate time course of 12/15-LOX expression in injured cortex. And in the second experiment, we chose the maximum time point of 12/15-LOX expression and assessed the effect of baicalein (a direct 12/15-LOX inhibitor) in regulating neuron apoptosis and inflammation.Methods In Experiment 1,70 male Sprague-Dawley rats (250-300g, purchased from the animal center of Jinling Hospital) were randomly assigned to 7 groups:the control group, TBI 6h,12h, dayl, day2, day3, day7 group (n=10 for each group). Control rats underwent right parietal craniotomy surgically prepared alone, but did not receive TBI. Rats in later six groups were subjected to experimental TBI and killed separately at different time points after TBI. RT-PCR, Western blot analysis, and immunohistochemical study were performed to investigate 12/15-LOX expression. The groups in Experiment 2 consisted of control group, TBI group, TBI+DMSO group, and TBI+baicalein group (n=10 for each group). All rats in Experiment 2 were killed at day 2, which was the time point of the highest 12/15-LOX expression according to the result of Experiment 1. We use TUNEL for Apoptosis detection and ELISA for IL-6 and TNF-αdetection.Results(1) We observed that 12/15-LOX expression was significantly increased in the brain after TBI. The elevation started at 6h after TBI or even earlier, got its peak on day2, and gradually recovered to normal levels in 7 days. (2) Blocking 12/15-LOX dramatically reduced the levels of brain apoptosis and expression of IL-6, TNF-a compared with TBI groups.ConclusionOur findings suggest that 12/15-LOX is involved in the secondary damage after TBI, and 12/15-LOX inhibitors would thus be effective as neuroprotectants to combat TBI injury.