# RANKL Attenuates Sepsis‐Associated Acute Lung Injury Through the OPG/RANKL/RANK/TLR4 Pathway

## TL;DR

This study shows that RANKL pretreatment reduces lung damage in sepsis-related lung injury by reducing inflammation through a specific signaling pathway.

## Contribution

The study identifies the OPG/RANKL/RANK/TLR4 pathway as a potential therapeutic target for sepsis-associated acute lung injury.

## Key findings

- Recombinant RANKL pretreatment reduced inflammatory cytokines in serum and lung fluid.
- RANKL pretreatment alleviated lung tissue damage and modulated TLR4, RANK, and OPG levels.
- Anti-RANKL antibodies reversed the protective effects of RANKL, worsening lung damage.

## Abstract

Sepsis‐associated acute lung injury (SA‐ALI) is a critical disease marked by a dysregulated immune response to infection, causing organ dysfunction.

We explored the effect of receptor activator of nuclear factor‐κB ligand (RANKL) on SA‐ALI and the mechanism involving the osteoprotegerin (OPG)/RANKL/RANK (receptor activator of nuclear factor‐κB)/TLR4 (Toll‐like receptor 4) signaling pathway.

The SA‐ALI model was established in C57BL/6 mice. Recombinant RANKL or anti‐RANKL antibodies were administered intraperitoneally as pretreatment 2 h before modeling. After 24 h of modeling, ELISA measured the cytokine concentrations in the serum and bronchoalveolar lavage fluid. The TLR4, RANK, RANKL, and OPG levels in the lung tissues were analyzed using Western blot and real‐time quantitative PCR. HE staining assessed the pathological alterations in lung tissue.

Recombinant RANKL pretreatment had a protective effect on SA‐ALI mice and lowered the serum and bronchoalveolar lavage fluid concentrations of IL‐1β, TNF‐α, and IL‐6. It also reduced TLR4, RANK, and OPG levels in lung tissue while increasing RANKL levels. Moreover, lung tissue pathological changes were alleviated by recombinant RANKL. Conversely, treatment with anti‐RANKL antibodies reversed the changes in the above indicators and aggravated lung tissue pathological damage in mice.

Pretreatment with recombinant RANKL can reduce lung damage in SA‐ALI mice by inhibiting inflammation, with the underlying mechanism potentially associated with the OPG/RANKL/RANK/TLR4 pathway.

Pretreatment with recombinant RANKL can reduce lung damage in SA‐ALI mice by inhibiting inflammation. The mechanism may be related to the OPG/RANKL/RANK/TLR4 signaling pathway. These findings may provide new insights and targets for the treatment of SA‐ALI.