Increased lipocalin-2 expression in pulmonary inflammation and fibrosis

Apostolos Galaris; Dionysios Fanidis; Eliza Tsitoura; Paraskevi Kanellopoulou; Ilianna Barbayianni; Konstantinos Ntatsoulis; Katerina Touloumi; Sofia Gramenoudi; Theodoros Karampitsakos; Argyrios Tzouvelekis; Katerina Antoniou; Vassilis Aidinis

doi:10.3389/fmed.2023.1195501

Increased lipocalin-2 expression in pulmonary inflammation and fibrosis

Front Med (Lausanne). 2023 Sep 7:10:1195501. doi: 10.3389/fmed.2023.1195501. eCollection 2023.

Affiliations

¹ Institute for Fundamental Biomedical Research, Biomedical Sciences Research Center Alexander Fleming, Athens, Greece.
² Department of Respiratory Medicine, School of Medicine, University of Crete, Heraklion, Greece.
³ Department of Respiratory Medicine, School of Medicine, University of Patras, Patras, Greece.

Abstract

Introduction: Idiopathic Pulmonary Fibrosis (IPF) is a chronic, progressive interstitial lung disease with dismal prognosis. The underlying pathogenic mechanisms are poorly understood, resulting in a lack of effective treatments. However, recurrent epithelial damage is considered critical for disease initiation and perpetuation, via the secretion of soluble factors that amplify inflammation and lead to fibroblast activation and exuberant deposition of ECM components. Lipocalin-2 (LCN2) is a neutrophil gelatinase-associated lipocalin (NGAL) that has been suggested as a biomarker of kidney damage. LCN2 has been reported to modulate innate immunity, including the recruitment of neutrophils, and to protect against bacterial infections by sequestering iron.

Methods: In silico analysis of publicly available transcriptomic datasets; ELISAs on human IPF patients' bronchoalveolar lavage fluids (BALFs); bleomycin (BLM)-induced pulmonary inflammation and fibrosis and LPS-induced acute lung injury (ALI) in mice: pulmonary function tests, histology, Q-RT-PCR, western blot, and FACS analysis.

Results and discussion: Increased LCN2 mRNA expression was detected in the lung tissue of IPF patients negatively correlating with respiratory functions, as also shown for BALF LCN2 protein levels in a cohort of IPF patients. Increased Lcn2 expression was also detected upon BLM-induced pulmonary inflammation and fibrosis, especially at the acute phase correlating with neutrophilic infiltration, as well as upon LPS-induced ALI, an animal model characterized by neutrophilic infiltration. Surprisingly, and non withstanding the limitations of the study and the observed trends, Lcn2^-/- mice were found to still develop BLM- or LPS-induced pulmonary inflammation and fibrosis, thus questioning a major pathogenic role for Lcn2 in mice. However, LCN2 qualifies as a surrogate biomarker of pulmonary inflammation and a possible indicator of compromised pulmonary functions, urging for larger studies.

Keywords: acute lung injury; bleomycin (BLM); idiopathic pulmonary fibrosis (IPF); lipocalin-2 (LCN2); transcriptomics.

Grants and funding

AG was supported by a fellowship from the Hellenic Foundation for Research and Innovation (#789). The research was further partly supported through the Hellenic Foundation for Research and Innovation (HFRI) under the 2nd Call for HFRI Research Projects to support Faculty Members and Researchers (#3565 to VA). The funders had no role in the design of the study, collection, analyses, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results.