GRK2 inhibits Flt-1^(+)macrophage infiltration and its proangiogenic properties in rheumatoid arthritis

Rheumatoid arthritis(RA)is an autoimmune disease with a complex etiology.Monocyte-derived macrophages(MDMs)infiltration are associated with RA severity.We have reported the deletion of G-protein-coupled receptor kinase 2(GRK2)reprograms macrophages toward an anti-inflammatory phenotype by recovering G-protein-coupled receptor signaling.However,as more GRK2-interacting proteins were discovered,the GRK2 interactome mechanisms in RA have been understudied.Thus,in the collagen-induced arthritis mouse model,we performed genetic GRK2 deletion using GRK2^(f/f)Lyz2-Cre^(+/−)mice.Synovial inflammation and M1 polarization were improved in GRK2^(f/f)Lyz2-Cre^(+/−)mice.Supporting experiments with RNA-seq and dual-luciferase reporter assays identified peroxisome proliferator-activated receptorγ(PPARγ)as a new GRK2-interacting protein.We further confirmed that fms-related tyrosine kinase 1(Flt-1),which promoted macrophage migration to induce angiogenesis,was inhibited by GRK2-PPARγsignaling.Mechanistically,excess GRK2 membrane recruitment in CIA MDMs reduced the activation of PPARγligand-binding domain and enhanced Flt-1 transcription.Furthermore,the treatment of mice with GRK2 activity inhibitor resulted in significantly diminished CIA pathology,Flt-1^(+)macrophages induced-synovial inflammation,and angiogenesis.Altogether,we anticipate to facilitate the elucidation of previously unappreciated details of GRK2-specific intracellular signaling.Targeting GRK2 activity is a viable strategy to inhibit MDMs infiltration,affording a distinct way to control joint inflammation and angiogenesis of RA.