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DOCK2 contributes to endotoxemia-induced acute lung injury in mice by activating proinflammatory macrophages
Xiaotao Xu1, Yang Su2, Kaixuan Wu1
1Department of Anesthesiology, Affiliated Shanghai Sixth People's Hospital, Shanghai Jiao Tong University, Shanghai 200233, China.
Abstract:
Dedicator of cytokinesis 2 (DOCK2), an atypical Rac activator, has important anti-inflammatory properties in blepharitis, enteric bacterial infection and colitis. However, the roles of DOCK2 in macrophage activation and acute lung injury (ALI) are still poorly elucidated. In vitro studies demonstrated that DOCK2 was essential for the nucleotide-sensing Toll-like receptor (TLR) 4-mediated inflammatory response in macrophages. We also confirmed that exposure of macrophages to LPS induced Rac activation through a TLR4-independent, DOCK2-dependent mechanism. Phosphorylation of IκB kinase (IKK) β and nuclear translocation of transcription factor nuclear factor kappa B (NF-κB) were impaired in Ad-shDOCK2-expressing macrophages, resulting in a decreased inflammatory response. Similar results were obtained when EHop-016 (a Rac inhibitor) was used to treat uninfected macrophages. In summary, these data indicate that the DOCK2-Rac signaling pathway acts in parallel with TLR4 engagement to control IKKβ activation for inflammatory cytokine release. Next, we investigated whether pharmacological inhibition of DOCK2 protects against endotoxemia-induced lung injury in mice. Treatment with 4-[3'-(2″-chlorophenyl)-2'-propen-1'-ylidene]-1-phenyl-3,5-pyrazolidinedione (CPYPP), a small-molecule inhibitor of DOCK2, reduced the severity of lung injury, as indicated by decreases in the lung injury score and myeloperoxidase (MPO) activity. Moreover, CPYPP attenuated LPS-induced proinflammatory cytokine release in mice. Our studies suggest that inhibition of DOCK2 may suppress LPS-induced macrophage activation and that DOCK2 may be a novel target for treating endotoxemia-related ALI.
Insights
Dedicator of cytokinesis 2 (DOCK2) is crucial for macrophage inflammatory responses and acute lung injury (ALI). Inhibiting DOCK2 with CPYPP reduces lung inflammation, suggesting DOCK2 as a therapeutic target for ALI.
Area of Science:
- Immunology
- Cell Biology
- Molecular Medicine
Background:
- Dedicator of cytokinesis 2 (DOCK2) is an atypical Rac activator with known anti-inflammatory roles.
- The specific functions of DOCK2 in macrophage activation and acute lung injury (ALI) remain largely unknown.
- Understanding DOCK2's role is critical for developing new treatments for inflammatory lung conditions.
Purpose of the Study:
- To investigate the role of DOCK2 in macrophage activation and inflammatory responses.
- To determine if DOCK2 inhibition can protect against lipopolysaccharide (LPS)-induced acute lung injury (ALI).
- To explore DOCK2 as a potential therapeutic target for ALI.
Main Methods:
- In vitro studies using macrophages to assess DOCK2's role in Toll-like receptor 4 (TLR4)-mediated and LPS-induced inflammatory pathways.
- Assessing Rac activation, IκB kinase (IKK) β phosphorylation, and nuclear factor kappa B (NF-κB) translocation in DOCK2-deficient macrophages.
- In vivo studies using a mouse model of LPS-induced ALI, treated with the DOCK2 inhibitor CPYPP.
Main Results:
- DOCK2 is essential for TLR4-mediated inflammatory responses in macrophages and also mediates LPS-induced Rac activation via a TLR4-independent pathway.
- Impaired IKKβ phosphorylation and NF-κB nuclear translocation were observed in DOCK2-deficient macrophages, leading to reduced inflammatory cytokine release.
- Pharmacological inhibition of DOCK2 with CPYPP significantly reduced lung injury severity, myeloperoxidase (MPO) activity, and pro-inflammatory cytokine levels in mice with ALI.
Conclusions:
- The DOCK2-Rac signaling pathway functions independently of TLR4 to regulate inflammatory cytokine release by controlling IKKβ activation.
- Inhibition of DOCK2 effectively suppresses LPS-induced macrophage activation and ameliorates endotoxemia-related ALI in mice.
- DOCK2 represents a promising novel therapeutic target for the treatment of acute lung injury.
