Effect Of Cell Adhesion Molecule Nb3 On Brain Microvascular Endothelial Cells In Hypoxia

High altitude cerebral edema(HACE) is central nervous system serious disorder caused by acute hypoxia. The main clinical manifestations include severe headache, vomiting, ataxia, coma and death. There is a mortality rate more than 40%. High altitude cerebral edema includes vasogenic edema and cytotoxic edema.Vasogenic edema is a main cause of high altitude cerebral edema. In HACE, blood-brain barrier(BBB) dysfunctions have been described, not only as a late event, but involved in the early stages of the progression of HACE. BBB is a highly specialized brain endothelial structure of the fully differentiated neurovascular system. Normal BBB maintains a unique microenvironment within the central nervous system(CNS). The main types of BBB dysfunction in HACE have been documented below:(1) increased BBB permeability through disruption of TJs and(2) massive cellular infiltration across the BBB. In addition, the disruption of the vascular endothelial barrier is a central factor in the regulation of BBB. Therefore, the study on the mechanism of hypoxia on blood-brain barrier is of great significance for the prevention and treatment of HACE.Cell adhesion molecule NB3, as also known contactin 6, with is one of the F3/ contactin neural recognition molecule family members.Previous studies show that NB3 has an important role in motor function, neurological development, NPC differentiation and synapse formation. In our previous study, the survival rate of NB3 knockout mice was obviously decreased after acute hypoxia exposure. Evans blue permeability was significantly higher in NB3 knockout mice, suggesting that NB3 may have a protective effect on the blood brain barrier. In this study, we explored whether neural adhesion molecule NB3 maintein integrity of BBB by regulating tight junction?In this study, we firstly investigated the expression and localization of NB3 in neurovascular unit. Then, we cultured mouse primary brain microvascular endothelial cells and measured Trans-endothelial electrical resistant(TEER) and observed theexpression of tight junctions proteins in hypoxic injury. Next, we observed the alteration of NB3-deficient brain microvascular endothelial cell on permeability in hypoxic injury. Finally, we investigated the possible molecular mechanisms of NB3 in hypoxic injury. Results: 1.Neurons and brain microvascular endothelial cells but not astrocytes expressed NB3. 2.Hypoxia decreased TEER and permeability of brain microvascular endothelial cells and reduced the expression of NB3, ZO-1, Occludin, Claudin5 and VE-cadherin proteins. 3.NB3-deficient aggravates hypoxia injury by disrupting tight junctions andincreasing the permeability of BMECs. 4. NB3 protein has obvious protective effect on brain microvascular endothelial cells under hypoxia injury Conclusions:We firstly identify that NB3 expressed in brain microvascular endothelial cells. NB3 deficiency increased the damage of hypoxia to tight junctions and vascular permeability.NB3 protein can effectively reduce the damage of hypoxia on brain microvascular endothelial cells. These results show that NB3 is an important endogenous protective molecule to brain microvascular endothelial cells. It provides a new therapeutic approachfor investigate the mechanism of HACE and develops a new way on the prevention and treatmentof the neurovascular unit in brain injury.