Effects of hypoxia on production of ATP and expression of mitochrome C in human meningothelial cells as the cerebral fluid-optic nerve barrier

Background BackgroundMeningothelial cells (MECs) are major cell type in the meningeal sheath around optic nerve,which form a fluid barrier between optic nerve and the cerebral spinal fluid.The impairment of the cerebral fluid-optic nerve barrier probably affects the balance of cerebral fluid components.Currently,the investigation on the role of MECs in neuropathy is less performed.Objective This study attempted to explore hypoxia-induced function changes of MECs,and to shed a new clus for the future research of optic nerve disorders.Methods Human MECs strains were cultured in vitro and cell suspension was prepared with the cell densities of 2.5 ×103/hole,5.0× 103/hole and 1 x 104 /hole,respectively.The suspensions of 100 μl were separately collected to incubate in 96-well plates and cultivated for 2 days in 21％ O2(normoxia group) or 1％ O2(hypoxia group).MTS was used to detect and compare the proliferative value (A490) of MECs between the normoxia group and the hypoxia group.The changes of MECs diameter and volume were measured by CASY1 assay.ATP product in the cells after MECs exposed to different oxygen environments with or without substrate (100 mmol/L pyruvate and 100 mmol/L malate) for 1,2 days were assayed by Luminometer method.The expression and distribution of cytochrome C in the cells of the normoxia group and the hypoxia group were determined by immunofluorescence.Results A490 of MECs in the 2.5× 103/hole,5.0× 103/hole and 1 × 104/hole were 0.399±0.009,0.393±0.009 and 0.496±0.026 in the hypoxia group,which were lower than 0.424±0.131,0.413±0.111 and 0.537±0.021 in the normoxia group (t =3.777,P =0.004 ; t =3.251,P =0.009 ; t =3.037,P =0.013).Compared with the normoxia group,the diameter and volume were significantly increased in the hypoxia group ([20.970 ±0.127] μm vs.[21.198 ±0.048] μm,t =-3.762,P=0.006; [5805±73] fl vs.[6026±106] fl,t=-4.124,P=0.002).ATP products were (0.900±0.225)mmol/(L· g) and (0.952± 0.075) mmol/(L · g) in the hypoxia group and the hypoxia+substrate group,which were significantly lower than (1.389±0.145) mmol/(L · g) and (1.401±0.122) mmol/(L · g) in the normoxia group and the normoxia +substrate group (P =0.001,0.002,0.001).Immunofluorescense staining showed that the green fluorescence of cytochrome C located at mitochondria of MECs in the normoxia group,but in the hypoxia group,cytochrome C distributed in the cytoplasm extensively.Conclusions Hypoxia induces malfunction of MECs,which might impact the intact of the cerebral spinal fluid-optic nerve barrier and therefore influence the microenvironment of the subarachnoid space and neuronal function. Key words: Hypoxia;  Meningothelial cells;  Mitochondria;  Cytochrome C;  Cerebral spinal fluid-optic nerve barrier