Abstract
This study was performed to determine whether EMAP II increases the permeability of the blood-tumor barrier (BTB) by affecting the expression of miR-330-3p as well as its possible mechanisms. We determined the over-expression of miR-330-3p in glioma microvascular endothelial cells (GECs) by Real-time PCR. Endothelial monocyte-activating polypeptide-II (EMAP-II) significantly decreased the expression of miR-330-3p in GECs. Pre-miR-330-3p markedly decreased the permeability of BTB and increased the expression of tight junction (TJ) related proteins ZO-1, occludin and claudin-5, however, anti-miR-330-3p had the opposite effects. Anti-miR-330-3p could enhance the effect of EMAP-II on increasing the permeability of BTB, however, pre-miR-330-3p partly reversed the effect of EMAP-II on that. Similarly, anti-miR-330-3p improved the effects of EMAP-II on increasing the expression levels of PKC-α and p-PKC-α in GECs and pre-miR-330-3p partly reversed the effects. MiR-330-3p could target bind to the 3′UTR of PKC-α. The results of in vivo experiments were similar to those of in vitro experiments. These suggested that EMAP-II could increase the permeability of BTB through inhibiting miR-330-3p which target negative regulation of PKC-α. Pre-miR-330-3p and PKC-α inhibitor decreased the BTB permeability and up-regulated the expression levels of ZO-1, occludin and claudin-5 while anti-miR-330-3p and PKC-α activator brought the reverse effects. Compared with EMAP-II, anti-miR-330-3p and PKC-α activator alone, the combination of the three combinations significantly increased the BTB permeability. EMAP-II combined with anti-miR-330-3p and PKCα activator could enhance the DOX’s effects on inhibiting the cell viabilities and increasing the apoptosis of U87 glioma cells. Our studies suggest that low-dose EMAP-II up-regulates the expression of PKC-α and increases the activity of PKC-α by inhibiting the expression of miR-330-3p, reduces the expression of ZO-1, occludin and claudin-5, and thereby increasing the permeability of BTB. The results can provide a new strategy for the comprehensive treatment of glioma.
Highlights
In the glioma, blood-tumor barrier (BTB) is the key factor to restrict the delivery of large therapeutic molecules into the tumor tissues, which affects the efficacy of chemotherapy
The cell viability of EMAP II+anti-miR-330-3p+PKCα activator+DOX group was significantly decreased compared with DOX group. These results suggested Endothelial monocyte-activating polypeptide-II (EMAP-II) combined with anti-miR-330-3p and PKCα activator could enhance the effect of DOX on inhibiting the cell viabilities of U87 glioma cells
We found that miR-330-3p was over-expressed in glioma microvascular endothelial cells (GECs) and EMAP-II could down-regulate the expression of miR-330-3p
Summary
Blood-tumor barrier (BTB) is the key factor to restrict the delivery of large therapeutic molecules into the tumor tissues, which affects the efficacy of chemotherapy. Selectively enhancing the permeability of BTB is an urgent problem to be solved to deliver anti-tumor drugs into tumor tissues effectively and to improve the therapeutic effect of glioma. Studies have reported that low-dose EMAP-II (0.05 nM) selectively increases the permeability of BTB via the cAMP/PKA signaling pathway and the PKC-ζ/PP2A signaling pathway (Li et al, 2015a,c). In vitro BTB model, low-dose EMAP-II can bind to α-ATP synthase on BMECs surface and open tight junction (TJ) to selectively increase the permeability of BTB by significantly decreasing the protein expression levels of TJ-related proteins ZO-1, occludin and claudin-5 (Xie et al, 2010; Li et al, 2011). The above studies suggest that PKC plays an important regulatory role in EMAP-II increasing the permeability of BTB. The mechanism of EMAP-II regulating the expression and activity of PKC is unclear
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