Effects of apolipoprotein E gene polymorphism on the intracellular Ca2+ concentration of astrocytes in the early stages post injury

The present study aimed to investigate the correlation between apolipoprotein E (APOE) polymorphisms and the intracellular concentration of Ca2+ in astrocytes in the early stages after an injury. The chondroitin sulfate region of three APOE alleles (ε2, ε3 and ε4) was obtained by reverse transcription‑polymerase chain reaction (RT‑PCR). A recombinant plasmid, pEGFP‑N1‑APOE, was constructed and identified by sequencing, while astrocytes were isolated from APOE gene‑knockout mice and examined using immunocytochemistry. The recombinant plasmid was transfected into the astrocytes using the liposome‑mediated method and cell injury models were constructed by a scratch assay. Laser confocal scanning microscopy (LCSM) was used to detect dynamic alterations in intracellular Ca2+ concentration at 12, 24, 48 and 72 h after injury. Compared with the control group, cells transfected with any of the three alleles demonstrated significant increases in the fluorescence intensity of Ca2+ (P<0.05). The fluorescence intensity of Ca2+ was weak at 12 h after injury, with no statistically significant difference detected between any two groups at this time point (P>0.05). However, the fluorescence intensity increased in a time‑dependent manner and at 24, 48 and 72 h post injury, the fluorescence intensity of the ε4 allele‑containing cells was significantly higher when compared with that of cells harboring the other two alleles (P<0.05). These results indicate that intracellular Ca2+ overloading may contribute to the deterioration of brain cells and poor outcome subsequent to traumatic brain injury in APOE ε4 carriers.