A derivative of vitamin B3 applied several days after exposure reduces lethality of severely irradiated mice

Most, if not all, of the hitherto tested substances exert more or less pronounced pro-survival effects when applied before or immediately after the exposure to high doses of ionizing radiation. In the present study we demonstrate for the first time that 1-methyl nicotinamide (MNA), a derivative of vitamin B-3, significantly (1.6 to 1.9 times) prolonged survival of BALB/c mice irradiated at LD30/30 (6.5 Gy), LD50/30 (7.0 Gy) or LD80/30 (7.5 Gy) of gamma -rays when the MNA administration started as late as 7 days post irradiation. A slightly less efficient and only after the highest dose (7.5 Gy) of gamma -rays was another vitamin B-3 derivative, 1-methyl-3-acetylpyridine (1,3-MAP) (1.4-fold prolonged survival). These pro-survival effects did not seem to be mediated by stimulation of haematopoiesis, but might be related to anti-inflammatory and/or anti-thrombotic properties of the vitamin B-3 derivatives. Our results show that MNA may represent a prototype of a radioremedial agent capable of mitigating the severity and/or progression of radiation-induced injuries when applied several hours or days after exposure to high doses of ionizing radiation.

Automated summary

The study demonstrated that the vitamin B-3 derivative 1-methyl nicotinamide significantly prolonged the survival of mice irradiated at high doses of gamma rays when administered 7 days post-irradiation. Another vitamin B-3 derivative, 1-methyl-3-acetylpyridine, also showed some level of effectiveness, particularly after the highest dose of radiation. These pro-survival effects may be related to anti-inflammatory and anti-thrombotic properties of the vitamin B-3 derivatives.