# M1 macrophage inhibits ferroptosis in Pseudomonas aeruginosa-induced kidney epithelial cell injury through the iNOS/ NO pathway without thiol

## TL;DR

Macrophages protect kidney cells from Pseudomonas aeruginosa damage by preventing a type of cell death called ferroptosis through a specific pathway.

## Contribution

The study reveals a new intercellular mechanism where macrophages inhibit ferroptosis via the iNOS/NO pathway without relying on thiol.

## Key findings

- P. aeruginosa induces ferroptosis in kidney cells via ploxA and by reducing GPx4/GSH defenses.
- Macrophages protect epithelial cells by inhibiting lipid peroxidation through iNOS/NO.
- Pharmacological inhibition of iNOS reduces the protective effect against ferroptosis.

## Abstract

Pseudomonas aeruginosa (PA) is one of the common pathogens of urinary tract infection. It can lead to urosepsis and renal damage. However, the mechanism by which P. aeruginosa affects epithelial cells is not clear.

HK2 cells were treated with extracted PA supernatant (PA.sup). Different pathway inhibitors were added, and similar treatments were applied to HK2 cells co-cultured with macrophages. Cell viability, ferroptosis-related markers, and lipid peroxidation levels were measured.

We found that PA induced lipid peroxidation using its specially secreted 15-lipoxygenase (ploxA), thereby triggering ferroptosis in epithelial cells. And PA can also damage the GPx4/GSH defense system of epithelial cells. This effect is not through the proteasome pathway but through activating lysosomal chaperone-mediated autophagy (CMA) to reduce the host's GPx4 expression. Then macrophages inhibited lipid peroxidation and protected cells lacking GPx4/GSH through iNOS/NO•.

We demonstrated that NO• produced by macrophages can remotely prevent PA-induced ferroptosis of renal epithelial cells. When iNOS, which is responsible for NO• production, is pharmacologically inhibited, the antiferroptotic effect of NO• is reduced. In conclusion, our study reveals an intercellular mechanism for inhibiting ferroptosis, which may provide a new strategy for the host to combat P. aeruginosa -induced ferroptosis.