Differential expression of vasoactive intestinal peptide and its functional receptors in human osteoarthritic and rheumatoid synovial fibroblasts

Abstract

Objective. Vasoactive intestinal peptide (VIP) hasshown potent antiinflammatory effects in murine arthritis and ex vivo in human rheumatoid arthritis (RA) synovial cells. To investigate the potential endogenous participation of this system in the pathogenesis of RA, we analyzed the expression and regulation of VIP and its functional receptors in human fibroblast-like synoviocytes (FLS) from patients with osteoarthritis (OA) and patients with RA.Methods. The expression of VIP was studied by reverse transcription-polymerase chain reaction (RT-PCR), enzyme immunoassay, and immunofluorescence in cultured FLS, and by immunohistochemical analysis in synovial tissue. The expression and function of the potential VIP receptors in FLS were studied by RT-PCR, determination of intracellular cAMP production, cell membrane adenylate cyclase (AC) activity, and interleukin-6, CCL2, and CXCL8 production in response to VIP or specific agonists and antagonists.Results. VIP expression was detected in human FLS at the messenger RNA and protein levels, and it was significantly decreased in RA FLS compared with OA FLS. VIP receptor type 1 (VPAC 1 ) was the dominant AC-coupled receptor in OA FLS, in contrast with RA FLS, in which VPAC 2 was dominant. Tumor necrosis factor ␣-treated OA FLS reproduced the VIP and VPAC receptor expression pattern of RA FLS. The antagonistic effects of VIP on FLS proinflammatory factor production were reproduced by VPAC 1 -and VPAC 2 -specific agonists in OA FLS and RA FLS, respectively.Conclusion. VIP expression is down-regulated in RA and in tumor necrosis factor ␣-treated FLS, suggesting that down-regulation of this endogenous antiinflammatory factor may contribute to the pathogenesis of RA. In RA FLS, VPAC 2 mediates the antiinflammatory effects of VIP, suggesting that VPAC 2 agonists may be an alternative to VIP as antiinflammatory agents.The vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating peptide (PACAP) system consists of 2 peptides and 3 receptors: VIP receptor type 1 (VPAC 1 ), VPAC 2 , and PACAP type 1 (PAC 1 ) receptor. These receptors belong to family 2 of the G proteincoupled receptors, which in recent years have shown remarkable antiinflammatory and immunomodulatory properties (1-3). VPAC 1 is constitutively expressed in macrophages and lymphocytes and binds VIP and PACAP with equal affinity (1,3). VPAC 2 has also been described in lymphocytes and macrophages as an inducible receptor after T cell receptor triggering or lipopolysaccharide (LPS) stimulation (1,3). The bestcharacterized effects of VIP/PACAP on immune cells are mediated by the adenylate cyclase (AC) pathway coupled to these receptors. Finally, the PAC 1 receptor is the PACAP-specific receptor, although at high concentrations VIP is a heterologous ligand (4). Endogenous VIP and PACAP can be produced by both neural and immune cells, but their regulation and participation in the pathogenesis of human inflammation are not known.

Role of PACAP and VIP Signalling in Regulation of Chondrogenesis and Osteogenesis

“…Similar results have been published in alveolar cells where both VIP and PACAP were able to decrease the expression of certain MMPs and reduced the activation and expression of caspase3 [ 69 ]. It is also important to note that VIP and its receptors in synovial fi broblasts [ 70 ] are able to regulate infl ammatory factors release [ 71 ]. These data all strongly suggest that PACAP is a promising future therapeutic agent in infl ammatory and degenerative joint diseases [ 72 ].…”

Monocytes from Sjögren's syndrome patients display increased vasoactive intestinal peptide receptor 2 expression and impaired apoptotic cell phagocytosis

“…Here we showed that the effect of LPS on VPAC2 expression occurred only in pSS but not in normal monocytes, and that it averaged a threefold increase, in line with previous observations in murine macrophages. Interestingly, a higher expression of VPAC2 was observed on fibroblast-like synovial cells from rheumatoid arthritis patients compared with osteoarthritis patients [48], suggesting that receptor differential expression might regulate VIP local effects in vivo. The increased expression of VPAC2 receptors in resting pSS monocytes shown here might reflect a compensating mechanism operating in vivo.…”

Healthy and Osteoarthritic Synovial Fibroblasts Produce a Disintegrin and Metalloproteinase with Thrombospondin Motifs 4, 5, 7, and 12

“…After three passages, residual contamination by macrophages was avoided, previously assessed by flow cytometry analysis of SF with a purity of 95%. 19 Monocultures of SF were used for experiments until passage 8. Despite the use of cells at varying passage numbers, all comparisons within a same experimentation were made on SF at an identical passage number and at 80% to 90% confluence.…”

“…For relative quantification, results were presented as the relative expression with respect to the untreated condition using the formula 2 ÀDDCt , as previously described. 19 …”