NADPH oxidase mediates TNF-α-evoked in vitro brain barrier dysfunction: roles of apoptosis and time.
The pro-inflammatory cytokine TNF-α severely perturbs the integrity of the blood-brain barrier (BBB). This study explored the specific roles of NADPH oxidase and associated downstream effectors by using human brain microvascular endothelial cells (HBMECs) and human astrocytes (HAs), the key components of BBB, alone or in co-cultures to mimic human BBB. Exposure to TNF-α (6h) impaired BBB integrity as evidenced by marked decreases in transendothelial electrical resistance and concurrent increases in paracellular flux which appeared to subside with time (24h). Increased barrier dysfunction concurred with increases in endothelial NADPH oxidase activity, O2(-) production, actin stress fibre formation, MMP-2/9 activities and concomitant decreases in antioxidant (CuZn-SOD and catalase) and tight junction (claudin-5 and occludin) protein expressions. Conversely, TNF-α did not affect astrocytic MMP activities and antioxidant enzyme expressions. Unlike BBB damage, rates of HBMEC and HA apoptosis increased by time. Suppression of NADPH oxidase by apocynin or diphenyleneiodonium prevented TNF-α-evoked morphological changes and apoptosis, attenuated endothelial MMP activity and helped retain usual tight junction protein expression and barrier function. In conclusion, HBMECs constitute the main source of oxidative stress and basement-membrane degrading endopeptidases in inflammatory conditions associated with excessive release of TNF-α where targeting NADPH oxidase may prove extremely beneficial in maintaining proper barrier activity through prevention of cytoskeletal and tight junction reorganisations.
['Abdullah|Zuraidah|Z|', 'Bayraktutan|Ulvi|U|']
D000098:Acetophenones D017209:Apoptosis D001253:Astrocytes D002374:Catalase D018920:Coculture Techniques D045304:Cytochromes c D017097:Electric Impedance D042783:Endothelial Cells D004791:Enzyme Inhibitors D005786:Gene Expression Regulation D006801:Humans D066298:In Vitro Techniques D020778:Matrix Metalloproteinase 2 D020780:Matrix Metalloproteinase 9 D019255:NADPH Oxidases D009861:Onium Compounds D010100:Oxygen D017382:Reactive Oxygen Species D013482:Superoxide Dismutase D013997:Time Factors D014409:Tumor Necrosis Factor-alpha
NADPH oxidase TNF-α MMP Blood–brain barrier Cytoskeleton