Abstract
BackgroundFibroblast-like synoviocytes (FLS) and CCR7− effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA). In particular, FLS become highly invasive, whereas TEM cells proliferate and secrete proinflammatory cytokines, during RA. FLS and T cells may also interact and influence each other’s phenotypes. Inhibition of the pathogenic phenotypes of both FLS and TEM cells can be accomplished by selectively blocking the predominant potassium channels that they upregulate during RA: KCa1.1 (BK, Slo1, MaxiK, KCNMA1) upregulated by FLS and Kv1.3 (KCNA3) upregulated by activated TEM cells. In this study, we investigated the roles of KCa1.1 and Kv1.3 in regulating the interactions between FLS and TEM cells and determined if combination therapies of KCa1.1- and Kv1.3-selective blockers are more efficacious than monotherapies in ameliorating disease in rat models of RA.MethodsWe used in vitro functional assays to assess the effects of selective KCa1.1 and Kv1.3 channel inhibitors on the interactions of FLS isolated from rats with collagen-induced arthritis (CIA) with syngeneic TEM cells. We also used flow cytometric analyses to determine the effects of KCa1.1 blockers on the expression of proteins used for antigen presentation on CIA-FLS. Finally, we used the CIA and pristane-induced arthritis models to determine the efficacy of combinatorial therapies of KCa1.1 and Kv1.3 blockers in reducing disease severity compared with monotherapies.ResultsWe show that the interactions of FLS from rats with CIA and of rat TEM cells are regulated by KCa1.1 and Kv1.3. Inhibiting KCa1.1 on FLS reduces the ability of FLS to stimulate TEM cell proliferation and migration, and inhibiting Kv1.3 on TEM cells reduces TEM cells’ ability to enhance FLS expression of KCa1.1 and major histocompatibility complex class II protein, as well as stimulates their invasion. Furthermore, we show that combination therapies of selective KCa1.1 and Kv1.3 blockers are more efficacious than monotherapies at reducing signs of disease in two rat models of RA.ConclusionsOur results demonstrate the importance of KCa1.1 and Kv1.3 in regulating FLS and TEM cells during RA, as well as the value of combined therapies targeting both of these cell types to treat RA.
Highlights
Fibroblast-like synoviocytes (FLS) and CCR7− effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA)
TEM cells migrated in equivalent amounts toward unstimulated collagen-induced arthritis (CIA)-FLS and Collagen-induced arthritis fibroblast-like synoviocytes (CIA-FLS) that had been treated for 72 h with paxilline
Significantly more TEM cells migrated toward the CIA-FLS that had been pretreated with IFN-γ for 72 h
Summary
Fibroblast-like synoviocytes (FLS) and CCR7− effector memory T (TEM) cells are two of the major cell types implicated in the progression of rheumatoid arthritis (RA). T cells have a role in disease pathogenesis; in particular, CD4+CD45RA−CCR7− effector memory T lymphocytes (TEM cells) are a primary effector T cell population responsible for the inflammatory aspect of this disease, with characteristic phenotypes of being highly proliferative and the secretion of proinflammatory cytokines within the synovium, leading to joint inflammation [5,6,7]. Selective blockade of Kv1.3 reduces TEM cell proliferation and cytokine secretion while leaving naïve and central memory T cells able to become activated. ShK-186 (Dalazatide; Kv1.3 Therapeutics, Inc., Seattle, WA, USA), an analog of a venom peptide from the sea anemone Stichodactyla helianthus, is a highly potent and selective Kv1.3 blocker that has shown promise in early clinical trials for the treatment of TEM cell-mediated autoimmune disease [12, 13]. It is likely that other cell types involved in the pathogenesis of RA and its animal models that do not express Kv1.3 are still active following Kv1.3 block and continue to cause disease progression
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