Cold-inducible RNA binding protein inhibits H2O2-induced apoptosis in rat cortical neurons

Objective: The expression cold-inducible RNA-binding protein (CIRP) is significantly enhanced in neurons under hypothermia, but its roles remain unclear. This study aims to investigate whether the cerebral protection under hypothermia is mediated by the CIRP-mediated inhibition of neuronal apoptosis. Methods: Primary rat cortical neurons were isolated, cultured, and transduced with lentiviral CIRP-RNAi. Apoptosis of the transduced neurons was induced with 100 μmol/L H2O2, the treated cells were divided into two groups, and cultured in 37 °C or 32 °C incubator respectively. Cell viability was detected by MTT colorimetric assay. Neuronal apoptosis was detected by flow cytometry after labeling the cells with Hoechst 33342 and Annexin V-FITC/PI. The protein expressions of CIRP, activated caspase-3, and thioredoxin (TRX) were detected by Western blot. Results: Under 32 °C, CIRP protein is significantly induced in cortical neurons; the expression of activated caspase-3 decreases, while the TRX expression increases. The rate of neuronal apoptosis is 4.5 ± 0.8%. Under 37 °C, CIRP expression is evidently reduced in cortical neurons; the expression of activated caspase-3 is significantly enhanced with reduced level of TRX expression. The rate of neuronal apoptosis reaches 53.5 ± 1.7% (P < 0.05, compared to that in 32 °C group). Conclusions: The induction of CIRP protein in rat cortical neurons under hypothermia inhibits H2O2-induced neuronal apoptosis and thereby exerts neuroprotective effect, which forms one of the cerebral protective pathways under hypothermia.

Highlight
► Hypothermia upregulates the synthesis of cold-inducible RNA-binding protein.
► CIRP affects the expression of TRX.
► CIRP reduces the activity of activated caspase-3.
► CIRP inhibits H2O2-induced neuronal apoptosis.
► Upregulation of CIRP expression may protect the brain from hypothermia-induced damage.