Anti-radiation damage effect of polyethylenimine as a toll-like receptor 5 targeted agonist

Hu, Zhiqiang; Xing, Yaling; Qian, Yuanyu; Chen, Xiaojuan; Tu, Jian; Ren, Lening; Wang, Kai; Chen, Zhongbin

Exposure to ionizing irradiation may result in tissue damage, and have negative impacts on our health and safety. Nuclear accidents can lead to serious social economic issues [1] . The toxicity of ionizing irradiation, described as acute radiation syndrome (ARS) or radiation sickness is caused by total-or partial-body exposure to a high dose of penetrating ionizing radiation over a short period of time. Even at low doses, ionizing irradiation is capable of causing illness, and ARS can occur within hours to days [2] . In clinical medicine, ARS often exists as the adverse side-effect of radiation therapy for cancer and other diseases. Administration of medicine for radiation damage control is one of the most effective and direct approaches to protect and treat the injuries caused by ionizing radiation. Thousands of compounds have been reported to offer potential for radiation protection, but most of them are not suitable for clinical application. There is only a small window of opportunity for administration of chemical drugs, which may be introduced prior to or immediately after irradiation exposure. Biological drugs have poor specificity. Most radio-protective agents have severe toxicity [3, 4] . Therefore, there is an urgent need to develop effective compounds that offer radiation protection. The human immune system is one of the most vulnerable systems targeted by radiation and has been a key target for research in radio-protective strategies [5] . Toll-like receptors (TLRs) are an important family of immune receptors. To date, at least 13 human TLRs have been identified and extensively investigated in the immune system of invertebrates. TLRs are important cell surface receptors in the innate immune system and play a vital role in the natural immune system at the initiation stage of multiple immune signaling pathways. It has been reported that TLRs can induce antigen-presenting cell maturation and secretion of inflammatory chemokines and cytokines, resulting in a connection between innate immunity and acquired immunity. TLRs can induce strong antigen-specific immune responses [6, 7] .