Protective effect of thyroid hormone on spinal cord injury neurons in rats

Abstract

Objective To investigate the protective effect of thyroid hormone on spinal cord injury neurons and its molecular mechanism. Methods A DMEM culture medium with a volume fraction of 10% fetal bovine serum was cultured with the dorsal ridge neurons of RN- dsc rats. The neurons were inoculated in the culture plate after the digestion of trypsin and treated differently as follows: (1) control group: DMEM treatment with no drugs or serum; (2) H2O2 group: serum-free DMEM treatment containing 100 μmol/L H2O2; (3) H2O2+ 10-6mol/L triiodothyronine (T3) group: serum-free DMEM treatment containing 100 μmol/L H2O2 and 10-6mol/L T3 ; (4) H2O2+ 10-5mol/L T3 group: serum-free DMEM treatment containing 100 μmol/L H2O2 and 10-5mol/L T3; (5) negative control group: transfection of negative control mimics with Lipofectamine™2000 reagent; (6) miR-210 group: transfection of miR-210 mimics with Lipofectamine™2000 reagent. Cell viability, apoptosis number, and expressions of nuclear factor E2 correlation factor 2 (Nrf-2) antioxidant pathway molecules and miR-210 were determined. After transfection of miR-210 mimics and negative control mimics, expressions of Nrf-2 antioxidant pathway molecules were determined. Results The cell proliferation activity and protein expressions of Nrf-2, antioxidant reaction elements (ARE), superoxide dismutase 2 (SOD2), and heme oxygenase (HO-1) in H2O2 group (0.39±0.06, 0.52±0.08, 0.31±0.08, 0.25±0.05, respectively) were significantly lower than those in control group (1.00±0.15, 1.00±0.17, 1.00±0.13, 1.00±0.11, respectively) (P<0.05), while the apoptosis numbers and the expressions of miR-210 were significantly higher than those in control group (P<0.05). The cell proliferation activity and protein expressions of Nrf-2, ARE, SOD2, HO-1 in H2O2+ 10-6mol/L T3 group and H2O2+ 10-5mol/L T3 group were significantly higher than those in the H2O2 group (P<0.05), while apoptosis numbers and expressions of miR-210 were significantly lower than those in H2O2 group (P<0.05). The cell proliferation activity and protein expressions of Nrf-2, ARE, SOD2, HO-1 in H2O2+ 10-5mol/L T3 group (0.88±0.14, 0.84±0.12, 0.72±0.09, 0.69±0.09) were significantly higher than those in H2O2+ 10-6mol/L T3 group (0.73±0.09, 0.71±0.08, 0.58±0.09, 0.52±0.08)(P<0.05), while apoptosis numbers and expressions of miR-210 were significantly lower than those in H2O2+ 10-6mol/L T3 group. The protein expressions of Nrf-2, ARE, SOD2, and HO-1 in miR-210 group (0.37±0.06, 0.24±0.05, 0.45±0.08, 0.49±0.07, respectively) were significantly lower than those in negative control group (1.00±0.13, 1.00±0.19, 1.00±0.15, 1.00±0.14, respectively) (P<0.05). Conclusion Thyroid hormone can inhibit the expression of Nrf-2 in oxidative stress injury process of neurons by inhibiting the expression of miR-210, and hence reduce the oxidative stress injury of spinal cord neurons. Key words: Triiodothyronine; Spinal cord injuries; Nf-E2-related factor 2