Na(+)/K(+)-ATPase DR region-specific antibody protects U251 cells against hypoxia reperfusion-induced injury via the PI3K/AKT and ERK pathways

Cerebral ischemia is a condition in which there is insufficient blood flow to the brain to meet metabolic demand. This leads to poor oxygen supply or cerebral hypoxia and to the death of brain tissue or cerebral infarction/ischemic stroke. In the present study, an Na(+)/K(+)-ATPase (NKA) DR region-specific antibody (DRSAb) was established and purified and it was demonstrated that DRSAb induced a protective effect on human astrocytes (U251) via the phosphoinositide 3-kinase (PI3K)/AKT and extracellular signal-regulated protein kinase (ERK) signaling pathways. The binding of DRSAb on NKA was revealed using flow cytometry. High signals were detected on U251 cells incubated with DRSAb, but not with control sera or BSA. The viability of the hypoxia/reperfusion (H/R)-treated cells was markedly increased by DRSAb administration of 0.3–0.5 µM. The optimal concentration of DRSAb was 0.4 µM for attenuation of the injury induced by H/R. The administration of 0.4 µM DRSAb markedly reduced the number of apoptotic cells compared with control sera. The application of PD98059, an ERK inhibitor, and LY-294002, an AKT inhibitor, attenuated the protective effect induced by DRSAb in the U251 cells subjected to H/R. Furthermore, the application of LY294002 prior to incubation with DRSAb eliminated the activation of ERK1/2, whereas the use of PD98059 failed to attenuate the effect of DRSAb on PI3K/AKT activation. These results indicated that the protective effects of DRSAb against H/R injury in U251 cells occurred via stimulation of the PI3K/AKT and ERK signaling pathways.