Modification of gamma radiation induced response of peritoneal macrophages and splenocytes by Hippophae rhamnoides (RH-3) in mice

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Abstract
Alcoholic extract of Hippophae rhamnoides, RH-3, reported to render >80% survival against lethal whole body Co-60-gamma irradiation (10 Gy) in mice, was investigated for its immunostimulatory effects. In comparison with un-irradiated control, whole body irradiation did not reduce peritoneal macrophage counts at 24 h post-irradiation. RH-3 treatment (30 mg kg−1 body weight) alone or 30 min before whole-body irradiation enhanced viable counts of macrophages significantly (P≤0.05) compared with both un-irradiated control and irradiated groups. Whole-body irradiation reduced the number of viable splenocytes significantly (P≤0.05) compared with un-irradiated control at 24 h post-irradiation. RH-3 treatment alone or before whole-body irradiation appreciably countered radiation-induced decrease in splenocyte count. 3H-thymidine uptake method revealed that whole-body irradiation reduced splenocyte proliferation significantly (159 ± 45 counts min−1/106 cells; P±0.05) in comparison with control (607 ± 142 counts min−1) at 24 h after irradiation but RH-3 treatment before irradiation reduced the steep decrease and maintained it as 444 ± 153 counts-min−1. After whole-body irradiation, the ratio of spleen weight/mouse weight decreased to 1.5 ± 04 compared with 2.9 ± 0.32 in un-irradiated control at 24 h post-irradiation. Similarly, total protein content in splenocytes also decreased to 48 ± 6 μg/106 cells in comparison with 368 ± 16 μg/106 cells of un-irradiated control. RH-3 treatment before irradiation countered radiation-induced decrease in both spleen weight/mouse weight ratio (4.0 ± 0.35) and total protein content (360 ± 13 μg/106 splenocytes). In the supernatant of peritoneal macrophage cultures exposed to 2 Gy Co-60-gamma radiation ex-vivo, the total nitrite content was enhanced significantly (P<0.05) to 5.72 ± 0.09 μm in comparison with un-irradiated control (1.64 ± 0.09 μm). RH-3 treatment (30 μg mL−1) before irradiation reduced total nitrite significantly (0.93 ± 0.3; P≤0.05) in comparison with irradiated control group. At 24 h after whole body irradiation, the CD4+/CD8+ ratio reduced to 1.5 in comparison with un-irradiated control (1.9) but RH-3 treatment before irradiation restored the ratio to 2.1. These findings explicitly reveal the immunostimulatory activity of RH-3, which may play an important role in the manifestation of its radioprotective efficacy.