Vitamin C is known as a potent antioxidant. We studied vitamin C as a radioprotective agent, focusing on its antioxidative effect. When the body is exposed to radiation, free radicals and reactive oxygen species (ROS) are produced and oxidize cell components, resulting in cell damage. Vitamin C has the potential to scavenge these radical products, thereby protecting against radiation-induced cell damage. We investigated the effects of vitamin C on radiation-induced gastrointestinal (GI) syndrome in mice. The mice received whole-body irradiation followed by bone marrow transplantation 24 h after exposure. Despite avoiding bone marrow failure, the mice eventually died of GI syndrome. Pretreatment with per os administration of high-dose vitamin C effectively mitigated radiation-induced GI syndrome and improved mouse survivals, while per os post-treatment with vitamin C was ineffective, presumably due to impaired absorption from the radiation-damaged intestine. We also investigated the effect of post-exposure treatment with intraperitoneal administration of vitamin C on radiation-induced bone marrow dysfunction in mice. Intraperitoneal administration with high-dose vitamin C, even at 24 h after whole-body irradiation, was still effective in avoiding bone marrow dysfunction, thereby increasing mouse survival after radiation. In conclusion, administration of high-dose vitamin C effectively reduced the radiation lethality in mice.
Part of the book: Vitamin C
The liver has long been recognized as important in digestion. However, the liver’s abundance of innate immune cells strongly suggests that it has specific defense mechanisms. A characteristic anatomical feature of the liver is its large blood flow. The blood flowing out from the whole alimentary tract is transported to the liver via the portal vein and distributed to peripheral structures called sinusoids. Kupffer cells, a typical example of resident macrophages, are located in sinusoids and are in continuous contact with various portal blood components. They have vigorous phagocytic activity and eliminate bacteria coming from the gut before they enter systemic circulation. Based on this framework, Kupffer cells were considered a filter for portal blood pathogens. However, recent evidence reveals that they exert crucial functions in systemic host defense against bacterial infection. To defend against various sources of bacterial pathogens, Kupffer cells construct an efficient surveillance system for systemic circulation, cooperating aggressively with other immune cells. They collaborate with non-immune cells such as hepatocytes and platelets to potentiate defense function. In conclusion, Kupffer cells coordinate immune cell activity to efficiently defend against infections, making them crucial players in systemic antibacterial immunity.
Part of the book: Antimicrobial Immune Response