Effects of alpha lipoic acid on apoptosis and oxidative stress of Schwann cell induced by high glucose in vitro

Objective To investigate the effects of alpha lipoic acid (ALA) on apoptosis and oxidative stress of Schwann cells cultured with high glucose medium in vitro. Methods Schwann cells were primarily cultured and purified from the sciatic nerves of newborn Sprague-Dawley rats. S-100 protein immunohistochemical method was adopted for the identification. Schwann cells of the 3rd and 4th passage were collected and divided into normal group (5.6 mmol/L glucose) and high glucose group (50 mmol/L glucose). Various concentrations of ALA (10, 100 and 500 μmol/L) were added into high glucose medium to establish high glucose+10 ALA group, high glucose+100 ALA group, and high glucose+500 ALA group, respectively. After 48-hour intervention, methyl thiazolyl tetrazolium (MTT) was adopted to detect the activity of Schwann cells. Apoptosis was confirmed by the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL). Western blot was performed to detect the expression of B cell lymphoma/leukemia associationed x protein (Bax protein). In addition, the oxidative stress indices in Schwann cells, such as the content of malondialdehyde (MDA) and the activity of superoxide dismutase (SOD) were also measured. Results The survival rates of Schwann cells in high glucose group, high glucose+10 ALA group, high glucose+100 ALA group, and high glucose+500 ALA group were significantly lower than the control group (all P0.05), while the proportion of cell apoptosis in high glucose groups was significantly higher than that in the control group (P0.05). The survival rates of Schwann cells in high glucose +10 ALA group, high glucose+100 ALA group and high glucose+500 ALA group were significantly higher than high glucose group (all P0.05), while the proportion of cell apoptosis was significantly lower than high glucose group (all P0.05). MDA level in high glucose group was significantly higher than the control group (P0.05), but SOD activity in high glucose group was significantly lower than the control group (P0.05). MDA levels in high glucose+10 ALA group, high glucose +100 ALA group and high glucose +500 ALA group were significantly higher than the control group (all P0.05), but the MDA levels in these ALA groups were significantly lower than the high glucose group (all P0.05). On the contrary, SOD activity in the ALA groups was significantly lower than the control group (all P0.05), but the SOD activity was significantly higher than the high glucose group (P0.05). Bax protein expression in the high glucose group and the ALA groups were significantly higher than that in the control group (all P0.05). But Bax protein expression in the ALA groups were significantly lower than the high glucose group (all P0.05). Conclusion ALA can antagonize high glucose induced apoptosis in Schwann cells through inhibiting oxidative stress, which may play a key role in improving diabetic peripheral neuropathy.