Melatonin exerts differential actions on X-ray radiation-induced apoptosis in normal mice splenocytes and Jurkat leukemia cells

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Published on Wednesday, 29 June 2016

Abstract

The ability of melatonin as a potent antioxidant was used as a rationale for testing its antiapoptotic ability in normal cells.

Recently, melatonin was shown to possess proapoptotic action by increasing reactive oxygen species in certain cancer cells.

The modification of radiation-induced apoptosis by melatonin and the expression of apoptosis-associated upstream regulators were studied in normal mice splenocytes and Jurkat T leukemia cells.

C57BL/6 mice were exposed to a single whole body X-ray radiation dose of 2 Gy with or without 250 mg/kg melatonin pretreatment.

The Jurkat cells were divided into four groups of control, 1 mm melatonin alone, 4 Gy irradiation-only and melatonin pretreatment before irradiation.

The highest level of apoptosis in the normal splenic white pulp was detected by TUNEL assay at 8 hr after irradiation. At this time, the apoptotic index of irradiation-only and melatonin pretreatment groups were 35.6% and 20.7%, respectively. This reduced apoptosis by melatonin was associated with the increase of Bcl-2 expression and a reduction of Bax/Bcl-2 ratio through a relative decrease of p53 mRNA and protein.

In the Jurkat cells treated with a combination of melatonin and radiation, both Annexin V-FITC(+)/PI(-) and Annexin V-FITC(+) cells were increased at 48 hr after irradiation when compared with irradiation-only or melatonin alone. The expressions of p53 between groups were well correlated with the results of Annexin V binding. The irradiation or melatonin did not influence the JNK1 expression in Jurkat cells. The present results suggest that melatonin enhances radiation-induced apoptosis in Jurkat leukemia cells, while reducing radiation-induced apoptosis in normal mice splenocytes.

These differential effects on radiation-induced apoptosis by melatonin might involve the regulation of p53 expression.

 

 

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See also:

- About Melatonin;

- Chronic Lymphocytic Leukemia: Long-Lasting Remission with Combination of Cyclophosphamide, Somatostatin, Bromocriptine, Retinoids, Melatonin, and ACTH.