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Updated: Dec 28, 2025
Inducing Acute Lung Injury in Mice by Direct Intratracheal Lipopolysaccharide Instillation
Published on: July 6, 2019
Calreticulin Blockade Attenuates Murine Acute Lung Injury by Inducing Polarization of M2 Subtype Macrophages
Zhilong Jiang1, Zhihong Chen1, Lu Hu1
1Department of Pulmonary Medicine, Fudan University Zhongshan Hospital, Shanghai, China.
Abstract:
Calreticulin (CALR) has anti-tumor effects by increasing dendritic cell maturation and tumor antigen presentation. However, whether CALR affects macrophages and modulates progression of acute respiratory distress syndrome/acute lung injury (ARDS/ALI) remains unknown. In this study, we discovered that CALR protein was highly expressed in the mice with LPS-induced ALI and CALR expression level was positively correlated to the severity of ALI. Commercial anti-CALR antibody (aCALR) can neutralize recombinant CALR (rCALR) and suppress the expression of TNF-alpha and IL-6 in the rCALR-treated macrophages. Blocking CALR activity by intraperitoneal (i.p.) administration of aCALR significantly suppressed ALI, accompanied with lower total cell counts, neutrophil and T cell infiltration in bronchoalveolar lavage (BAL) and lung tissues. The expression of CXCL15, IL-6, IL-1beta, TNF-alpha, and CALR were significantly reduced, in association with more polarization of Siglec F+CD206+M2 subtype macrophages in the aCALR-treated mice. Pre-depletion of circulating monocytes did not abolish the aCALR-mediated suppression of ALI. Further analysis in bone marrow-derived macrophages (BMDMs) showed that aCALR suppressed the expression of CD80, IL-6, IL-1beta, IL-18, NLRP3, and p-p38 MAPK; but enhanced the expression of CD206 and IL-10. In addition, we observed more expression and phosphorylation of STAT6 in the aCALR-treated BMDM. Lack of STAT6 resulted in comparable and slightly higher expression of CALR, TNF-alpha and IL-6 in the aCALR-treated STAT6-/- BMDMs than the untreated cells. Therefore, we conclude that CALR is a novel biomarker in the evaluation of ALI. Blocking CALR activity by aCALR effectively suppressed ALI independent of circulating monocytes. Siglec F+CD206+M2 subtype macrophages and p38 MAPK/STAT6 signaling pathway played important role in the immune regulation of aCALR. Blocking CALR activity is a promising therapeutic approach in the treatment of ARDS/ALI.
Insights
Calreticulin (CALR) is highly expressed in acute lung injury (ALI) and blocking its activity with an anti-CALR antibody (aCALR) suppresses ALI progression. This approach shows promise for treating acute respiratory distress syndrome (ARDS/ALI).
Area of Science:
- Immunology
- Pulmonology
- Molecular Biology
Background:
- Calreticulin (CALR) exhibits anti-tumor properties by enhancing dendritic cell maturation and tumor antigen presentation.
- The role of CALR in macrophage function and its modulation of acute respiratory distress syndrome/acute lung injury (ARDS/ALI) progression remained unexplored.
Purpose of the Study:
- To investigate the role of CALR in LPS-induced ALI.
- To evaluate the therapeutic potential of blocking CALR activity in ALI.
Main Methods:
- Assessed CALR expression in mice with LPS-induced ALI.
- Utilized anti-CALR antibody (aCALR) to block CALR activity in vivo and in vitro.
- Analyzed immune cell infiltration, cytokine expression, and macrophage polarization in bronchoalveolar lavage (BAL) and lung tissues.
- Investigated the involvement of STAT6 signaling pathway in aCALR-mediated effects using bone marrow-derived macrophages (BMDMs).
Main Results:
- CALR expression was elevated in ALI mice and correlated with disease severity.
- aCALR treatment significantly reduced ALI severity, inflammatory cell infiltration, and pro-inflammatory cytokine levels (TNF-alpha, IL-6).
- aCALR promoted M2 macrophage polarization and modulated p38 MAPK/STAT6 signaling pathways.
Conclusions:
- CALR serves as a potential biomarker for ALI evaluation.
- Blocking CALR activity with aCALR is an effective therapeutic strategy for ALI, independent of circulating monocytes.
- The p38 MAPK/STAT6 signaling pathway and M2 macrophage polarization are crucial in aCALR's immunomodulatory effects.
