FSTL1 Promotes Macrophage M2 Polarization and Its Role in Allergic Rhinitis

Allergic rhinitis (AR) is a prevalent inflammatory condition characterized by an overactive immune response to allergens. Recent studies have highlighted the role of macrophage polarization in modulating immune responses. This study investigates the role of Follistatin-like 1 (FSTL1) in promoting macrophage M2 polarization and its implications in AR. Using in vitro and in vivo models, we demonstrate that FSTL1 significantly enhances the expression of M2 macrophage markers, including Arg1, CD206, and IL-10, while concurrently reducing M1 markers such as iNOS and TNF-a. Furthermore, FSTL1-treated macrophages exhibited increased anti-inflammatory properties, contributing to the attenuation of allergic inflammation in a murine model of AR. Our findings suggest that FSTL1-mediated M2 polarization plays a crucial role in mitigating allergic responses, providing a potential therapeutic target for AR management. Overall design: The aim of this study is to investigate the effects and mechanisms of FSTL1 on the polarization of THP-1-derived macrophages.Experimental Design: THP-1 cells were differentiated into M0 macrophages using phorbol 12-myristate 13-acetate (PMA). The cells were then divided into three groups: a blank control, a negative control (transfected with si-NC or pcDNA3.1 (+)-NC), and an experimental group (transfected with FSTL1 or pcDNA3.1 (+)-FSTL1). M1 polarization was induced in all groups using LPS, IFN-?, and IL-6, while M2 polarization was achieved with IL-4, IL-13, and IL-6. Flow cytometry was used to assess CD206 and CD86 expression levels in each group.Vector Construction Method:The FSTL1 overexpression construct was generated by amplifying cDNA via PCR and inserting it into the pcDNA3.1 (+) vector.The small-interfering RNA (siRNA) targeting FSTL1 along with a scrambled negative control siRNA, were synthesized as single-stranded primers and annealed to form double-stranded RNA, which was subsequently cloned into the pLKO.1-puro vector.High-throughput sequencing design: RNA-seq analysis was performed on M0 macrophages transfected with si-FSTL1 and M0 macrophages transfected with pcDNA3.1(+)-FXTL1.