The Role of Proinflammatory Cytokine Interleukin-18 in Radiation Injury

Massive radiation-induced inflammatory factors released from injured cells may cause innate and acquired immune reactions that can further result in stress response signal activity-induced local and systemic damage. IL‐1 family members IL‐1β, IL‐18, and IL‐33 play key roles in inflammatory and immune responses and have been recognized to have significant influences on the pathogenesis of diseases. IL‐1β, IL‐18, and IL‐33 share similarities of cytokine biology, but differences exist in signaling pathways. A key component of the inflammatory reaction is the inflammasome, which is a caspase‐1‐containing multiprotein oligomer. Pathological stimuli such as radiation can induce inflammasome and caspase‐1 activation, and subsequently cause maturation (activation) of pro-forms of IL‐1 and IL‐18 upon caspase‐1 cleavage. This caspase‐1 dependent and IL‐1 and IL‐18 associated cell damage is defined as pyroptosis. Activated IL‐1 and IL‐18 as proinflammatory cytokines drive pathology at different immune and inflammatory disorders through Toll-like receptor (TLR) signaling. While the mechanisms of IL‐1β-induced pathophysiology of diseases have been well studied, IL‐18 has received less attention. The author recently reported that gamma radiation highly increased IL‐1β, IL‐18 and IL‐33 expression in mouse thymus, spleen and/or bone marrow cells; also circulating IL‐18 can be used as a radiation biomarker to track radiation injury in mice, minipigs, and nonhuman primates. This mini-review focuses on the role of IL‐18 in response to gamma radiation-induced injury.