ML171, a specific inhibitor of NOX1 attenuates formalin induced nociceptive sensitization by inhibition of ROS mediated ERK1/2 signaling.

Reactive oxygen species (ROS) have a key role in different etiologies of pain. At sub-cellular level, mitochondria and plasma membranes have been identified as endogenous sources of ROS required for pain generation. NADPH oxidase (NOX) is the main contributor of membrane associated ROS generation. Out of 7 isozymes, NOX1, NOX2 and NOX4 are reported to be associated with nociceptive sensitization. Therefore, it has been hypothesized that specific inhibition of the NOX isozymes could be putative strategy for treatment of pain. However, unavailability of specific inhibitors was the biggest obstacle to test this hypothesis. Here, we investigated anti-nociceptive potential of a newly identified specific NOX1 inhibitor ML171 in formalin induced inflammatory pain. ML171 administration decreased the paw lickings and flinching response in both phases of formalin test. Behavioral response was supported with decreased activation of c-Fos in spinal dorsal horn. The increased level of total NOX activity, ROS and pERK1/2 in dorsal root ganglion (DRG) and spinal dorsal horn of formalin induced nociception were reversed by ML171 administration. ML171 also inhibited the upregulated Tumor necrosis factor receptor 1 (TNFR1) expression in DRG, whereas did not show any effect in spinal dorsal horn which was unaltered after formalin insult. The study for the first time depicts anti-nociceptive potential of ML171 via regulation of ROS mediated ERK1/2 signaling by inhibition of NOX1 activity.