Secretion of leukotrienes by senescent lung fibroblasts promotes pulmonary fibrosis.
Level 5 - mechanism / opinion, no new human data
Preclinical in vitro, animal model, and human tissue explant study
PubMed 31687975 · doi:10.1172/jci.insight.130056
What was done
Researchers evaluated whether profibrotic leukotrienes (LTs) are components of the senescence-associated secretory phenotype (SASP). They analyzed conditioned medium, lipid extracts, and synthase gene expression in senescent human lung fibroblasts (IMR-90) and tested naive fibroblast profibrotic responses with ALOX5 inhibitors. They tested bleomycin-induced pulmonary fibrosis, bronchoalveolar lavage cysteinyl LT levels, and synthase gene expression in mouse models with genetic senescent cell clearance or senolytic pharmacotherapy. They also examined ALOX5 and p16Ink4a co-expression in lung explants from idiopathic pulmonary fibrosis (IPF) patients and compared lipid secretion between irradiated normal donor fibroblasts and senescent IPF fibroblasts.
What was found
Senescent cells secreted LTs across different cell origins and senescence induction methods in a biphasic pattern followed by prostaglandin (PG) secretion. LT-rich conditioned medium triggered profibrotic signaling in naive fibroblasts, which was blocked by ALOX5 inhibition. In bleomycin-treated mice, clearing senescent cells genetically or with senolytics reduced LT/PG synthase gene expression, bronchoalveolar cysteinyl LT levels, and total fibrosis. In human IPF lung explants, half of ALOX5+ cells were also p16Ink4a+. Senescent IPF fibroblasts secreted LTs but lacked the PG synthesis seen in normal donor fibroblasts. The abstract reports no exact numeric values or statistical measures.
Why it matters
This study identifies leukotriene secretion as a functional component of the SASP that drives fibrotic signaling in lung tissue. It suggests that targeting leukotriene biosynthesis via ALOX5 inhibitors or clearing senescent cells via senolytics may offer therapeutic strategies for idiopathic pulmonary fibrosis.
Limits
The findings rely on cell cultures and an acute bleomycin animal model, which do not fully replicate human IPF disease progression. Human data were restricted to descriptive ex vivo explant histology and primary cell cultures, with no patient sample sizes or clinical intervention outcomes provided in the abstract.
Cited by
- supports Senescent cells secrete bioactive lipids, specifically prostaglandins and leukotrienes, which modulate inflammation, fibrosis, and tissue repair.