Signaling mechanisms in endothelial monocyte-activating polypeptide-Ⅱ-enhanced permeability of the blood-tumor barrier / 中国药理学通报

ABSTRACT

Aim To investigate the signaling mecha-nisms in endothelial monocyte-activating polypeptide-Ⅱ( EMAP-Ⅱ)-induced increase in blood-tumor barri-er ( BTB ) permeability. Methods Relatively pure cerebral microvessel fragments were obtained from the cortex of 3-5 days old Wistar rats by using careful dis-section, enzyme digestion, and dextran centrifugation. Then, these fragments were seeded on dishes and cul-tured primarily. In vitro BTB models were constructed by co-cultivation of rat brain microvascular endothelial cells ( BMECs) with C6 glioma cells. Confluent mono-layers of co-cultured BMECs were divided randomly in-to 5 groups ( each n=6 ): control, EMAP-Ⅱ, H7 +EMAP-Ⅱ, C3 exoenzyme + EMAP-Ⅱ, and C3 ex-oenzyme + H7 + EMAP-Ⅱ groups. Transendothelial electric resistance values and horseradish peroxidase flux were measured to evaluate changes in the BTB permeability . The expression levels of tight junction-re-lated protein occludin and ZO-1 in BMECs were meas-ured by Western blot. Immunofluorescence was used to identify the expression and distribution of occludin and ZO-1 in BMECs. Also, Western blot were used to de-tect the expression levels of myosin light chain ( MLC) and phosphomyosin light chain ( pMLC ) in BMECs. Results Compared with control group, the BTB per-meability of EMAP-Ⅱ group was increased significant-ly. The expression levels of occludin and ZO-1 in BMECs were significantly decreased, accompanied with marked increase in the expression level of pMLC. These above-mentioned effects of EMAP-Ⅱ were sig-nificantly inhibited by pretreatment with H7 ( an inhib-itor of PKC ) or/and C3 exoenzyme ( an inhibitor of RhoA ) . Conclusion Signaling molecules PKC and RhoA play important roles in EMAP-Ⅱ-induced in-crease in BTB permeability; signaling pathways PKC-pMLC and RhoA-pMLC are involved in this process.