Deficiency of protease-activated receptor (PAR) 1 and PAR2 exacerbates collagen-induced arthritis in mice via differing mechanisms

Abstract

Objectives Protease-activated receptor (PAR) 1 and PAR2 have been implicated in RA, however their exact role is unclear. Here, we detailed the mechanistic impact of these receptors on the onset and development of inflammatory arthritis in murine CIA and antigen-induced arthritis (AIA) models. Methods CIA or AIA was induced in PAR1 or PAR2 gene knockout (KO) and matched wild type mice. The onset and development of arthritis was monitored clinically and histologically. Immune cells, cytokines and MMPs were detected by ELISA, zymography, flow cytometry, western blot or immunohistochemistry. Results In CIA, PAR1KO and PAR2KO exacerbated arthritis, in opposition to their effects in AIA. These deficient mice had high plasma levels of IL-17, IFN-γ, TGF-β1 and MMP-13, and lower levels of TNF-α; T cells and B cells were higher in both KO spleen and thymus, and myeloid-derived suppressor cells were lower only in PAR1KO spleen, when compared with wild type cells. Th1, Th2 and Th17 cells were lower in PAR1KO spleens cells, whereas Th1 and Th2 cells were lower and Th17 cells higher in both KO thymus cells, when compared with wild type cells. PAR1KO synovial fibroblasts proliferated faster and produced the most abundant MMP-9 amongst three type cells in the control, lipopolysaccharides or TNF stimulated conditions. Conclusion This is the first study demonstrated that deficiency of PAR1 or PAR2 aggravates inflammatory arthritis in CIA. Furthermore, the protective functions of PAR1 and PAR2 in CIA likely occur via differing mechanisms involving immune cell differentiation and cytokines/MMPs.

Activated Protein C Protects against Murine Contact Dermatitis by Suppressing Protease-Activated Receptor 2

“…APC and PAR1 or PAR2 deficiency have been shown to affect Th cell phenotypes in a mouse model of human rheumatoid arthritis [ 14 , 28 ]. In this study, the effect of APC and the deficiency of PAR1 or PAR2 on the specific intracellular Th cytokines and Th cell phenotypes were examined using spleen cells isolated from mice with CHS.…”

“…In C. rodentium-induced colitis, PAR1 promotes disease progression by stimulating Th17-related immunity [ 35 ], whereas, during H. pylori infection, PAR1 protects the host against severe gastritis partly via inhibition of neutrophil infiltration [ 36 ]. Furthermore, in mouse models of human arthritis, lack of PAR1 or PAR2 exacerbates collagen-induced arthritis but reduces the severity of antigen-induced arthritis [ 14 ]. These studies reveal complex disease specific roles of PAR1 and PAR2 in modulating the immune response.…”

“…Six to eight week-old female PAR1KO, PAR2KO and matched WT mice (all with a C57 background) were bred and obtained from Kearns Facility as described previously [ 14 ]. CHS in these mice was induced via sensitization with 30 μL of 0.5% DNFB (Sigma-Aldrich, Merck KGaA, Darmstadt, Germany) on the flank skin on day zero and day one, 15 μL of 0.3% DNFB on the dorsum of both ears on day five to seven, and 15 μL of 0.1% DNFB on the ears on days eight–13 [ 26 ].…”

“…PARs are G-coupled transmembrane receptors. Among four members, PAR1 and PAR2 are expressed by most immune cells, epithelial and endothelial cells, and exert important roles in the regulation of innate and adaptive immunity [ 3 , 13 , 14 ]. In the skin, both PAR1 and PAR2 are abundantly present in the epidermis and dermis [ 15 , 16 ].…”

The protein C pathways

“…EPCR deficient (PROCR low ) mice exhibit enhanced proinflammatory Th17 cell generation and exacerbated disease in experimental autoimmune encephalomyelitis; Significantly, administration of APC to T cells isolated from PROCR low mice inhibits their differentiation to Th17 cells ex vivo [58]. Similarly, APC administration reduces Th1, Th17 and Treg populations in a preclinical atopic dermatitis model via PAR2dependent signaling [60] and dampens systemic inflammatory cytokine levels and Th1 and Th17 populations in collagen-induced arthritis models [61,62].…”