An in vitro evaluation of the antioxidant activities of necroptosis and apoptosis inhibitors: the potential of necrostatin-1 and necrostatin-1i to have radical scavenging activities

Abstract

Background: Necroptosis inhibitors, including necrostatin-1 (Nec-1), are attracting attention as potential therapeutic agents against various diseases, such as acute lung injury, chronic obstructive pulmonary disease, acute kidney injury, nonalcoholic fatty liver, and neurodegenerative disease, where necroptosis is thought to act as a contributing factor. Nec-1 suppresses necroptosis by inhibiting receptor-interacting protein (RIP) 1 kinase and can also reduce reactive oxygen species (ROS) production; however, the underlying molecular mechanisms mediating ROS reduction remain unclear.

Methods: The antioxidant effects of necroptosis inhibitors, including Nec-1 and apoptosis inhibitors, were quantified by performing a 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assay. Nec-1-related compounds were subsequently assayed for cupric ion-reducing capacity and superoxide dismutase (SOD)-like activity.

Results: Considering all examined apoptosis and necroptosis inhibitors, Nec-1and Nec-1i exhibited antioxidant activity in DPPH radical scavenging assay. In the cupric ion-reducing capacity assay, Nec-1i showed stronger antioxidant capacity than Nec-1. In the SOD-like activity assay, both Nec-1 and Nec-1i were found to have stronger antioxidant capacity than ascorbic acid (IC₅₀ = 4.6 ± 0.040 and 61 ± 0.54 µM, respectively).

Conclusion: These results suggest that Nec-1 and Nec-1i may exhibit direct radical scavenging ability against superoxide anions, independent of RIP1 inhibition.

Keywords: Antioxidant activity; Cupric ion-reducing capacity; DPPH radical scavenging activity; Necrostatin-1; SOD-like activity.