Quantifying Cell Viability with CCK8 and LDH Assays

Cell Counting Kit-8 (CCK8; Dojindo Laboratories, Tokyo, Japan) or LDH (Beyotime, Shanghai, China) assay was used to determine cell viability. For CCK8 assay, 24 h after OGD, 10 μl CCK8 was added into each well of 96-well plates, which were incubated at 37 °C for 2 h. Optical density was measured at 450 nm using a plate reader (ELX 800; Bio-Tek, Winooski, VT, USA). For LDH assay, the neurons and culture medium were lysed in PBS containing 1% Triton X-100 at 37 °C for 30 min, respectively. The LDH activities in both the cell lysates and the culture mediums were assayed with the assay kit following the manufacturer’s instructions. LDH leakage was calculated as follows: LDH leakage (%)=LDH culture medium/(LDH culture medium+LDH cell lysates) × 100%.^{73 (link)}