Precision imaging of Pantetheinase activity in a collagen-induced arthritis model via a Ratiometric fluorescent probe.

Rheumatoid arthritis (RA) is a highly disabling and relapsing chronic autoimmune disease with synovitis, pannus formation, and progressive bone erosion, which can lead to joint damage and functional loss. Although fluorescence imaging has emerged as an important tool for visualizing RA pathology, most fluorescent probes rely on the Carrageenan-Induced Paw Edema (CIPE) model due to its simple induction procedure. In contrast, the Collagen-Induced Arthritis (CIA) model is recognized as gold standard for preclinical RA research, because it involves an immune response against cartilage that closely mimics human RA pathology. Pantetheinase is a key enzyme involved in vitamin B5 recycling and inflammatory regulation, which may be a potential biomarker for arthritis. However, its activity in CIA model remains underexplored. In this study, we developed a ratiometric fluorescent probe for pantetheinase with large stokes shift, desirable sensitivity and high selectivity. Confocal imaging experiments demonstrated that the fluorescence intensity of the probe could accurately reflect pantetheinase activity in primary mouse chondrocytes. Furthermore, the probe realized in vivo fluorescence imaging of inflamed ankle joints in CIA mice, revealing elevated enzymatic activity. Histological and immunohistochemical analyses confirmed that high pantetheinase expression is correlated with cartilage destruction and synovial inflammation. Consequently, TMN-Pan provides a powerful chemical tool for elucidating the pathological role of pantetheinase in rheumatoid arthritis.