# IL‐17A Promotes NETs Formation via the PKCζ–ERK–ROS–PAD4 Pathway in a Mouse Model of Ischemic Stroke

## TL;DR

This study shows how IL-17A worsens brain injury after stroke by promoting neutrophil extracellular traps through a specific molecular pathway.

## Contribution

The study identifies a novel PKCζ–ERK–ROS–PAD4 pathway through which IL-17A promotes NET formation in ischemic stroke.

## Key findings

- IL-17A increases PAD4 and NET formation via the PKCζ–ERK–ROS pathway in stroke.
- Blocking PAD4 or IL-17A reduces infarct size and improves neurological outcomes in mice.
- IL-17A−/− mice and IL-17mAb treatment decrease PAD4, MPO, and CitH3 expression.

## Abstract

Interleukin‐17A (IL‐17A) aggravates poststroke neurological damage and enhances neutrophil extracellular traps (NETs) formation, yet the underlying mechanism remains unclear. This study aimed to elucidate how IL‐17A regulates NETs generation after ischemic stroke.

Using a mouse middle cerebral artery occlusion (MCAO) model, we administered the Peptidylarginine deiminase 4 (PAD4) inhibitor GSK484 or an IL‐17A‐neutralizing antibody (IL‐17mAb). Infarct volume and neurological function were assessed, and protein expression of PAD4, myeloperoxidase (MPO), citrullinated histones H3 (CitH3), protein kinase Cζ (PKCζ), and phosphorylated extracellular signal‐regulated kinase (p‐ERK) was evaluated. IL‐17A−/− mice and primary neutrophils were used to further validate the signaling pathway.

Inhibiting PAD4 with GSK484 can significantly reduce infarct size, improve neurological outcomes, and decrease PAD4, MPO, and CitH3 protein levels. Subsequently, we found that IL‐17mAb treatment can reduce the expression of PAD4, MPO, and CitH3 in the peri‐infarct area, as well as the expression of PKC‐ζ and p‐ERK. Similarly, the expression of PAD4 and CitH3 decreased in the peri‐infarct area of IL‐17A−/− MCAO mice. Finally, we verified IL‐17A induced PAD4 upregulation via the PKCζ–ERK–ROS axis in vitro.

IL‐17A promotes NETs formation by upregulating PAD4 through the PKCζ–ERK–ROS pathway, exacerbating ischemic brain injury. Targeting this axis may offer a novel therapeutic strategy for stroke.

Our study demonstrates that IL‐17A promotes NET formation by upregulating PAD4 through the PKCζ–ERK–ROS pathway, thereby exacerbating ischemic brain injury. IL‐17A regulates NET formation through this newly identified molecular pathway, and targeting this pathway may offer a novel therapeutic strategy for stroke.