MiR-137 Boosts the Neuroprotective Effect of Endothelial Progenitor Cell Derived-Exosomes in Oxyhemoglobin Treated SH-SY5Y Cells Partially via COX2/PGE2 Pathway

Abstract

Background: We have previously verified the beneficial effects of exosomes from endothelial progenitor cells (EPC-EXs) in ischemic stroke. However, the effects of EPC-EXs in hemorrhagic stroke have not been investigated. Additionally, miR-137 is reported to regulate ferroptosis and to be involved in the neuroprotection against ischemic stroke. Hence, the present work explored the effects of miR-137-overexpressing EPC-EXs on apoptosis, mitochondrial dysfunction, and ferroptosis in oxyhemoglobin (oxyHb)-injured neurons.Methods: The lentiviral miR-137 was transfected into EPCs and then the EPC-EXs were collected. RT-PCR was used to detect the miR-137 level in EPCs, EXs and neurons. The uptake mechanisms of EPC-EXs in neurons were explored by the co-incubation of Dynasore, Pitstop 2, Ly294002 and Genistein. After the transfection of different types of EPC-EXs, flow cytometry and expression of cytochrome c and cleaved caspase-3 were used to detect the apoptosis of oxyHb-injured neurons. Neuronal mitochondrial function was assessed by reactive oxygen species (ROS) level, mitochondrial membrane potential (MMP) depolarization, and cellular ATP content. Cell ferroptosis was measured by lipid peroxidation, iron overload, degradation of glutathione and glutathione peroxidase 4. Additionally, recombinational PGE2 was used to detect if activation of COX2/PGE2 pathway could reverse the protection of miR-137 overexpression.Results: The present work showed 1) EPC-EXs could be taken in by SH-SY5Y cells via caveolin-/clathrin-mediated pathways and macropinocytosis; 2) miR-137 was decreased in neurons after oxyHb treatment, and EXs miR-137 could restore the miR-137 levels; 3) EXs miR-137 worked better than EXs in reducing the number of apoptotic neurons and pro-apoptotic protein expression after oxyHb treatment; 4) EXs miR-137 are more effective in improving the cellular MMP, ROS and ATP level; 5) EXs miR-137 , but not EXs, protected oxyHb-treated neurons against lipid peroxidation, iron overload, degradation of glutathione and glutathione peroxidase 4; 6) EXs miR-137 suppressed the expression of the COX2/PGE2 pathway, and activation of the pathway could partially reverse the neuroprotective effects of EXs miR-137 .Conclusion: MiR-137 overexpression boosts the neuroprotective effects of EPC-EXs against apoptosis and mitochondrial dysfunction in oxyHb-treated neurons. Furthermore, EXs miR-137 rather than EXs can restore the decrease in miR-137 levels and inhibit ferroptosis, and the protection mechanism might involve the miR-137-COX2/PGE2 signaling pathway.