MAPK3 and acute kidney injury: Phosphorylation of ERK1/2 and p38 was augmented in AKI mice, whereas a significant decrease in their activity was observed only in pan-PPAR-iMSC-EV-treated mice compared to those in vehicle-treated mice (phospho-ERK1/2, p < 0.001; phospho-p38, p < 0.001; Fig. 3C).