LAUSR

Hydrogen peroxide (H 2 O 2 ) has recently been identified as the earliest messenger released by damaged tissues and is crucial for the chemoattraction of neutrophils to sites of injury and infection. However, how neutrophils sense and respond to H 2 O 2 remains unresolved. Recently, we have identified the transient potential receptor melastatin-2 ion channel (TRPM2) as having a key role in directing the chemotaxis of neutrophils towards hydrogen peroxide (H 2 O 2 ), in both in vitro and in vivo models. We isolated neutrophils from wild-type and TRPM2 −/− mice and we observed that the genetic deletion of TRPM2 results in a reduction in both the speed and directionality of the neutrophil migration up a gradient of H 2 O 2 . We tested a diverse group of natural products, including a range of terpenes, alkaloids and flavonoids, for their effects on this H 2 O 2 -induced neutrophil chemotaxis using the Ibidi-chemotaxis system, which allows live-cell imaging in vitro of migration over time. From our screen, we have identified: beta-carotene, artemisinin, ferulic acid and N-acetylcysteine as compounds which reduce neutrophil chemotaxis in a comparable way to TRPM2 deletion, leading to the suggestion that they may be acting as TRPM2 inhibitors. Moreover, our compounds induce a more pronounced reduction in chemotaxis than the currently available TRPM2 inhibitors, which lack potency and selectivity. The natural compounds we have tested may have clinical applications; for example, in the treatment of inflammatory conditions, such as sepsis, which are characterised by excessive and damaging neutrophil migration.