Injured pancreatic β cells enhance the release of miR-375-3p into the extracellular space.

miR-375-3p is a highly expressed microRNA in pancreatic β cells. We have previously reported that when mice were exposed to 7 Gy X-ray irradiation, miR-375-3p was increased in the serum and there was cytotoxicity in pancreatic β cells. However, it was unknown whether miR-375-3p is then released from injured pancreatic β cells to the extracellular space. The present study investigated the effect of ionizing radiation and streptozotocin (STZ) treatment on the expression of extracellular miR-375-3p into culture supernatants using the rat pancreatic β cell line RIN-5F. Cell growth was reduced, and cell death was increased at 24 h following exposure to 7 Gy irradiation as well as 24 h following treatment with 30 mM STZ compared with the control. Expression levels of miR-375-3p were significantly increased 24 h after 30 mM STZ treatment, yet this was only observed at 48 h following exposure to 7 Gy compared with the control. This suggests that the mechanism of cell death in RIN-5F is different between 7 Gy irradiation and 30 mM STZ treatment. The results of the present study suggest that injured pancreatic β cells enhance the release of miR-375-3p from cells into extracellular space.