Data_Sheet_2_Increased lipocalin-2 expression in pulmonary inflammation and fibrosis.PDF

IntroductionIdiopathic 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.MethodsIn 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 discussionIncreased 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.

特发性肺纤维化（IPF）是一种慢性、进行性的间质性肺疾病，其预后堪忧。其潜在的致病机制尚不明确，导致缺乏有效的治疗方案。然而，反复的上皮损伤被认为是疾病起始和持续的关键因素，这通过分泌可溶性因子放大炎症，进而导致成纤维细胞活化以及细胞外基质（ECM）成分的过度沉积。脂质运载蛋白-2（LCN2）是一种与中性粒细胞明胶酶相关的脂质运载蛋白（NGAL），曾被提议作为肾脏损伤的生物标志物。研究表明，LCN2能够调节先天免疫，包括中性粒细胞的募集，并通过隔离铁质来保护免受细菌感染。研究方法包括：对公开可用的转录组数据集进行计算机模拟分析；对人类IPF患者的支气管肺泡灌洗液（BALFs）进行酶联免疫吸附测定（ELISA）；在老鼠中诱导博莱霉素（BLM）所致的肺炎症和纤维化，以及脂多糖（LPS）所致的急性肺损伤（ALI）：进行肺功能测试、组织学检查、定量逆转录聚合酶链反应（Q-RT-PCR）、蛋白质印迹和流式细胞术分析。结果与讨论：在IPF患者的肺组织中检测到LCN2 mRNA表达增加，这与呼吸功能呈负相关，同样在IPF患者队列中观察到支气管肺泡灌洗液（BALF）中LCN2蛋白水平增加。在BLM诱导的肺炎症和纤维化过程中，也检测到Lcn2表达增加，尤其是在急性期，与中性粒细胞浸润相关，以及在LPS诱导的ALI中，一个以中性粒细胞浸润为特征的老鼠模型。令人惊讶的是，尽管研究存在局限性，且观察到某些趋势，但发现Lcn2−/−老鼠仍然会发展为BLM或LPS诱导的肺炎症和纤维化，从而对LCN2在老鼠中的主要致病作用提出质疑。然而，LCN2被视为肺炎症的替代生物标志物，以及肺功能受损的可能指标，这迫切需要更大规模的研究。