Measuring Cellular Stress Markers

After incubation period of heat stress, the fibroblasts were harvested and stored immediately at −80°C for further analyses. To measure LDH activity, the frozen cells (1 × 10⁶ cells) were homogenized with PBS by vortexing. LDH activity was measured using a colorimetric lactate dehydrogenase assay kit according to the manufacturer's instructions (Abnova, Walnut, CA. # cat- KA0878). The concentrations of nitrite and nitrate were determined using a colorimetric oxiselect™ in vitro nitric oxide (nitrite/nitrate) assay kit (Cell Biolabs, Inc., San Diego, USA). # Cat- STA-802) according to the manufacturer's instructions.