In vitro effects of binuclear ( η- p-cymene)ruthenium(II) complex containing bridging bis(nicotinate)-polyethylene glycol ester ligand on differentiation pathways of murine Th lymphocytes activated by T cell mitogen.

T cell differentiation into distinct T helper (Th) subpopulations is crucial in governing acquired immune responses as well as some inflammatory and autoimmune disorders. This study investigated potential of the novel neutral binuclear ruthenium(II) complexes 1- 8 with general formula [{RuCl(η- p-cym)}μ-(NN)] (NN = bis(nicotinate)- and bis(iso-nicotinate)-polyethylene glycol esters; (3-py)COO(CHCHO)CO(3-py) and (4-py)COO(CHCHO)CO(4-py); n = 1-4), as well as [RuCl(η- p-cym)(nic)] ( R1, nic = nicotinate) and [RuCl(η- p-cym)(inic)] ( R2, inic = isonicotinate) as an immunomodulatory agents capable to direct Th cell differentiation. From all investigated complexes, [{RuCl(η- p-cym)}μ-{(3-py)COO(CHCHO)CO(3-py)}] ( 4) was selected for further study because it did not affect splenocyte viability (in concentration up to 50 μM), but significantly reduced secretion of representative Th1 cytokine, IFN-γ induced by T cell mitogen. Besides IFN-γ, 4 inhibited dose dependently expression and production of representative Th17 cytokine, IL-17, in these cells. Otherwise, the production of anti-inflammatory cytokines IL-4 and IL-10 was upregulated. Also, 4 significantly increased CD4CD25FoxP3 Treg cell frequency in the activated splenocytes. Moreover, ConA-induced expression of Th1 transcription factors, T-bet and STAT1, as well as of Th17-related protein STAT3 was attenuated upon exposure to 4, while the expression of Th2-related transcription factor GATA3 remained stable. In conclusion, ruthenium(II) complex 4 modulates immune system cell functions in vitro by inhibiting T cell differentiation towards pathogenic Th1/Th17 phenotype and inducing a regulatory phenotype characterized by IL-10 and IL-4 production, which may provide novel therapeutic opportunities for immune-inflammatory and/or autoimmune disorders. [ABSTRACT FROM AUTHOR]