Ionizing radiation induces blockade of c-Jun N-terminal kinasedependent cell death pathway in amanner correlated with p21Cip/WAF1 induction in primary cultured normal human fibroblasts

During radiotherapy of cancer, neighboring normal cells may receive sub-lethal doses of radiation. To investigate whether such low levels of radiation modulate normal cell responses to death stimuli, primary cultured human fibroblasts were exposed to various doses of gamma-rays. Analysis of cell viability using an exclusion dye propidium iodide revealed that the irradiation up to 10 Gy killed the fibroblasts only to a minimal extent. In contrast, the cells efficiently lost their viability when exposed to 0.5-0.65 mM H2O2. This type of cell death was accompanied by JNK activation, and was reversed by the use of a JNK-specific inhibitor SP600125. Interestingly, H2O2 failed to kill the fibroblasts when these cells were pre-irradiated, 24 h before H2O2 treatment, with 0.25-0.5 Gy of gamma-rays. These cytoprotective doses of gamma-rays did not enhance cellular capacity to degrade H2O2, but elevated cellular levels of p21Cip/WAF1, a p53 target that can suppress H2O2-induced cell death by blocking JNK activation. Consistently, H2O2-induced JNK activation was dramatically suppressed in the pre-irradiated cells. The overall data suggests that ionizing radiation can impart normal fibroblasts with a survival advantage against oxidative stress by blocking the process leading to JNK activation.

Assessment of skin toxicity using living skin equivalents / 대한피부과학회지

BACKGROUND: There are various alternative in vitro irritancy tests for substituting animal experiment. However, there is no standardized method or guideline for assessing in vitro cytotoxicity. OBJECTIVES: In order to predict toxicity on human skin, an experimental model was evaluated for the cutaneous cytotoxicity using living skin equivalents(LSE). METHODS: After applying test substances (SLS, various plant extracts) on LSE, morphological examination and MTT reduction assay was done. RESULTS: The results showed that cytotoxicity of SLS using LSE was well correlated with the concentration of SLS. Furthermore, characteristic histologic findings were observed according to the increasing concentrations of test materials. CONCLUSION: These results showed that LSE can be used as an alternative model to replace animal model for cytotoxicity testing.