Secreted frizzled related protein 5 (SFRP5) is a recognized cardioprotective protein with diminished expression in atrial fibrillation (AF). This study investigates SFRP5's function in AF-related cardiac fibrosis and cardiomyocyte apoptosis, exploring the underlying dysregulation causes. Utilizing C57BL/6 mice, mouse cardiac fibroblasts (CFs), and HC-1 mouse atrial myocyte cell line, AF models were induced by angiotensin Ⅱ (Ang Ⅱ). SFRP5 levels were consistently decreased in plasma samples from clinical patients, modeled mice, and CF culture supernatants. Treatment with recombinant SFRP5 restored its levels, mitigating Ang Ⅱ-induced AF in mice and ameliorating atrial tissue fibrosis and oxidative stress. In vitro , SFRP5 recombinant protein suppressed CF activation and fibrosis-related markers. The study identified Sp1 transcription factor (SP1) binding to the SFRP5 promoter, causing transcriptional repression. SP1 knockdown reinstated SFRP5 levels in mice and CFs, thus suppressing fibrosis. Additionally, SP1 knockdown attenuated Ang Ⅱ-induced apoptosis in HC-1 cells, but this effect was counteracted by concurrent SFRP5 knockdown. In conclusion, this investigation underscores that SP1 mediates SFRP5 loss during AF by transcriptional repression, contributing to fibrosis and myocyte apoptosis. These findings illuminate potential therapeutic interventions targeting the SFRP5-SP1 axis in AF-related cardiac complications.
Allergic rhinitis (AR) is tightly associated with type 2 inflammation. SFRP5 combined with WNT5A mainly inhibits chronic inflammatory response, atherosclerosis , and other metabolic disorders . However, the effect of SFRP5/WNT5A axis on recombinant human interleukin-13 (rhIL-13)-induced inflammation has not been studied. In this study, we aimed to investigate whether secreted frizzled-related protein 5 (SFRP5) could modulate the production of cytokines relevant to eosinophil infiltration and mucin secretion through blocking the activation of Wnt family 5A (WNT5A) signaling pathway . A mouse model of AR demonstrated low expression of SFRP5 and high expression of WNT5A, and indicated that the number of eosinophil and goblet cells was increased, concomitant with elevated IL-13, colony stimulating factor 2 (CSF2), chemokine ligand 11 (CCL11), Mucin 4 , and Mucin 5AC levels. Furthermore, lentivirus-SFRP5 overexpression up-regulated the expression of SFRP5 but down-regulated WNT5A level, and inhibited the activation of JNK pathway via decreasing p-JNK1/2 (Thr183/Tyr185) and p-c-Jun (Ser73) protein expressions in rhIL-13-treated human nasal epithelial cells (HNEpCs). Noticeably, SFRP5 overexpression markedly reduced rhIL-13-induced inflammatory protein and mucin generation through lowered CSF2, CCL11, Mucin 4, as well as Mucin 5AC levels. Taken together, these findings confirmed the regulatory role of SFRP5/WNT5A axis in rhIL-13-mediated inflammatory response in HNEpCs.
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