Effect of hyperbaric oxygen combined with temozolomide on the apoptosis of glioma U373MG cells

Objective To investigate the effect of hyperbaric oxygen (HBO) combined with temozolomide (TMZ) on the apoptosis of glioma U373MG cells and also to explore possible mechanism involved. Methods Upon completion of cell culture, they were divided into 4 groups, i. e. the control group, the TMZ group, the HBO group and the HBO + TMZ group. The control group received neither HBO nor drug treatment, the TMZ group only received 50 μmol/L TMZ, the HBO group just received 0.24 MPa HBO treatment for 3 hours and the HBO + TMZ group was given 50 μmol/L TMZ 3 hours after HBO pretreatment. CCK-8 method was used to detect the effects of HBO and TMZ alone or combined use of 2 treatment methods on the proliferation of glioma U373MG cells. Flow cytometry was used to detect HBO and TMZ alone or combined use of 2 treatment methods on glioma U373MG cells and changes in the level of reactive oxygen species (ROS). Western blotting was used to detect the expression of U373MG apoptosis-related proteins. Results The proliferation inhibition of U373MG cells in the HBO+ TMZ group was more obvious as compared with that of the TMZ group(P<0.05). U373MG cells in the TMZ group showed early and late apoptosis, the rate of apoptosis in the HBO+ TMZ group was significantly higher than that of the control group [(73.19±3.58)% vs.(30.5±2.27)%] (P<0.01). As compared with the blank control and HBO groups, the expression level of Bcl-2 in the TMZ group significantly decreased, while the expression level of Bax and caspase-3 markedly increased. Furthermore, more obvious changes could be detected, when the HBO+ TMZ group was compared with the TMZ group(P<0.05 or P<0.01). ROS level in the U373MG cells of the HBO+ TMZ group obviously increased(P<0.01). With the addition of ROS scavenger NAC, apoptosis was inhibited in the HBO+ TMZ group(P<0.01). Conclusion HBO combined with TMZ could enhance the inhibitory effect of TMZ on the proliferation of U373MG cells, and promote apoptosis induced by TMZ through up-regulating ROS levels in U373MG cells. Key words: Glioma; U373MG cell; Hyperbaric oxygen; Temozolomide