Caffeic acid acts as a potent senomorphic and alleviates inflammation and lung fibrosis by covalently targeting Annexin A5

Background and aims: The accumulation of senescent cells and their secretion of senescence-associated secretory phenotype (SASP) play important roles in pulmonary fibrosis (IPF). Small molecules, known as senolytics (compounds selectively eliminating senescent cells) or senomorphics (agents modulating the harmful secretory phenotype of senescent cells without killing them), some of them derived from foods, have been effective in targeting senescent cells. However, food-derived natural senomorphics with defined protein targets and their potential applications are rarely investigated.

Methods: The protein target for CA in senescent cells was determined by Activity-Based Protein Profiling (ABPP) technology. The binding affinity of CA to its target protein was measured by isothermal titration calorimetry. The effect of CA on lung fibrosis in vivo was evaluated in a bleomycin-induced pulmonary fibrosis mouse model.

Results: In the present study, we found that a widely sourced natural product, caffeic acid (CA), acts as a potent senomorphic that effectively inhibits the secretion of SASP in senescent lung cells as well as lung tissues. Using ABPP technology, we firstly demonstrated that CA covalently binds to the cysteine residue (Cys316) of Annexin A5 protein with the dissociation constant (kd) value of 3.68 μM. In the in vitro assays, CA at 25 μM was found to effectively trigger Annexin A5 degradation, PKCθ deactivation, and the inhibition of the NF-κB inflammatory pathway in senescent cells. Notably, CA exhibited a promising effect in limiting inflammation in the lung and circulatory system, alleviating pulmonary pathology and fibrosis, and improving physical function through reducing SASP secretion in a bleomycin-induced pulmonary fibrosis mouse model.

Conclusions: This study suggests that Annexin A5 could be used as the target for the precise intervention of aging-related fibrotic diseases, such as IPF, and that food-derived caffeic acid could act as a promising anti-fibrotic agent for fibrosis-related disorders.