Elevated circulating procathepsin L as a potential biomarker of inflamm-aging

• Published in: Medical hypotheses 2024-05, Vol.186, p.111322, Article 111322
• Main Authors: Zhu, Cassie Shu, Chen, Weiqiang, Qiang, Xiaoling, Lou, Li, Li, Jianhua, Wang, Haichao
• Format: Article
• Language: English
• Subjects: Cytokines; Inflamm-aging; Inflammation; Procathepsin L (pCTS-L)
• ISSN: 0306-9877; 1532-2777
• DOI: 10.1016/j.mehy.2024.111322

•Procathepsin L (pCTS-L) has recently been identified as a secretory protein capable of stimulating inflammatory responses.•Extracellular pCTS-L serves as a mediator of lethal systemic inflammatory diseases such as sepsis.•There was a marked elevation of blood pCTS-L levels in aged mice, supporting a possible role of blood pCTS-L as a biomarker of inflamm-aging, a condition of low-grade and chronic systemic inflammation.•This hypothesis can be tested by developing more specific and sensitive immunoassays and respectively comparing blood pCTS-L levels between young and aged animal or human populations. Inflamm-aging is a condition of low-grade and chronic systemic inflammation characterized by a systemic increase in multiple inflammatory biomarkers such as tumor necrosis factor (TNF), interleukin 6 (IL-6), C-reactive protein (CRP), and CXCL9 (MIG) in experimental and clinical settings. However, despite the recent identification of extracellular procathepsin L (pCTS-L) as a novel mediator of inflammatory diseases such as sepsis, its possible role in inflamm-aging was previously not investigated. In the present study, we compared blood levels of pCTS-L and other 62 cytokines and chemokines between young and aged Balb/C mice by Western blotting and Cytokine Antibody Arrays. In light of the surprising finding of a marked increase in blood pCTS-L levels in aged mice, we propose that blood pCTS-L levels may serve as another biomarker of inflamm-aging. Given the capacity of pCTS-L in inducing various cytokines (e.g., TNF and IL-6), it will be important to test the hypothetic role of pCTS-L in inflamm-aging under experimental and clinical conditions.