| The blood-brain barrier (BBB) is a sophisticated organ between blood and brain tissue, which limits entry of bloodderived products, pathogens, and cells into the brain that is essential for normal neuronal functioning and information processing. BBB is composed of Brain Microvascular Endothelial Cells(BMEC), pericyte, basement membrance(BM), astrocyte and neurons. Any disruption of these components may result the leakage of BBB, followed by the compromise of healthy and normal function of central nerves system (CNS). Therefore, BBB study has been focused in medical research, and the regulation of its permeability is significance for us to learn the mechanism of brain disease and how to prevent these diseases. Although most BBB studies have been associated with the injury inside the brain, such as traumatic brain injury (TBI), stroke, ischemia etc. We cannot ignore the influence of peripheral trauma (surgery, burns, chronic wounds) on BBB permeability. While most previous studies supposed peripheral trauma followed by stress response and then cause the inflammation of central nerves system, finally break the integrity of BBB.The study of Mervyn in 2010 demonstrated that pretreated mice with anti-TNF-aneutralizing antibody can effectively maintain the BBB integrity. Our previous data also suggested that BBB permeability changed after peripheral surgery (abdominal surgery) in different age group (9 months old and 18 month old mice) and 18 months old mice have a higher BBB permeability than 9 months old mice. Also, old group (18 months) seemed more severe in their behavior changing compare to adult group (9 months). These studies indicate that peripheral circulation inflammation after surgery result an unstable BBB permeability. Therefore, identification the relationship between peripheral trauma and BBB permeability is crucial to prevent clinical post operate cognitive dysfunction (POCD). Based on these reports mentioned above, we designed the study into three parts:1. we aimed to identify the key factor that may cause high BBB permeability in our abdominal surgery model, include anesthesia process, peripheral circulation inflammation factor, the time point of BBB leakage and the choice of proper tracer; use Enzyme Linked Immunosorbent Assay (ELISA) detect the concentration of peripheral circulation and brain tissue inflammation factor (IL-6) caused by surgery, using 10 KDa Tracer (Dextran 10) to reveal age-dependent BBB leak out under fluorescence microscope and using spectrophotometer to quantify Dextran 10; Western Blotting (WB) showing the expression change of BBB endothelial cells tight junction (TJ) protein; Using Y Maze to demonstrate mice spatial memory changed in different group; 3. Using IL-6 gene knockout mice to verify our theory and investigate the effects of IL-6 blockade on BBB permeability.The result of this study showed:1. Peripheral inflammation factor IL-6 reach a peak at 6 hours following surgery, the level of 18 months old mice much higher than 9 months mice, while the serum IL-6 level and BBB permeability of anesthesia group had no difference compare to the sham group; only Dextran 10 was observed leak out from brain microvascular under fluorescence microscope, while Dextran 70 and Evans Blue were not detected; 2. Quantification of Dextran 10 indicated 9 months mice group is 1.3 times and 18 months old mice 1.6 times compared to sham group; both 9 and 18 months mice group behavior changed after surgery and 18 months group seemed more severe than 9 months group; 3. Systemic block of IL-6 and IL-6 gene knockout mice were observed no BBB leakage after surgery.Our results demonstrated that peripheral inflammation can profoundly affect the permeability of BBB and the function of the CNS, including memory and cognition and also suggest a unique therapeutic potential for preemptive treatment with anti-IL-6 antibody to prevent surgery-induced cognitive decline. |
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