Amifostine activates Nrf2 by binding to Keap1, suppressing lung inflammation

Abstract

Abstract Although intracellular reactive oxygen species (ROS) produced during phagocytosis function as a key arsenal for innate immunity, inordinate production of ROS is detrimental to host cells, exacerbating inflammation. Nrf2/Keap1 axis is a key countering measure against ROS. Keap1 senses ROS via its thiols, resulting in Nrf2 activation and subsequent production of enzymes that nullify ROS. Amifostine is a cytoprotective thiophosphate that scavenges intracellular free radicals by donating hydrogen ions. Therefore, we tested whether amifostine can be used to suppress inflammation that involves intracellular ROS. Our results show that amifostine down-regulated the production of intracellular ROS induced by LPS. Interestingly, amifostine activated Nrf2 and suppressed the ubiquitination of Nrf2. Amifostine bound to Keap1 at S273, suggesting that amifostine suppresses the ubiquitination of Nrf2 by forming a complex with Keap1, which results in Nrf2 activation. In an LPS-induced acute lung injury mouse model, amifostine suppressed neutrophilic lung inflammation with decreased production of prototypic pro-inflammatory cytokines. Amifostine ameliorated lung damage and protected mice from LPS-induced sepsis. Together, our findings suggest that along with directly scavenging ROS, amifostine contributes to suppressing inflammation by activating Nrf2.