In vitro effects of binuclear (eta (6)-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

Abstract

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 {[}\{RuCl2(eta(6)-p-cym)\}(2)mu-((NN)-N-a (c))] ((NN)-N-a (c) = bis(nicotinate)- and bis(iso-nicotinate)-polyethylene glycol esters; (3-py)COO(CH2CH2O) (n) CO(3-py) and (4-py)COO(CH2CH2O) (n) CO(4-py); n = 1-4), as well as {[}RuCl2(eta(6)-p-cym)(nic)] (R1, nic = nicotinate) and {[}RuCl2(eta(6)-p-cym)(inic)] (R2, inic = isonicotinate) as an immunomodulatory agents capable to direct Th cell differentiation. From all investigated complexes, {[}\{RuCl2(eta(6)-p-cym)\}(2)mu-\{(3-py)COO(CH2CH2O)(4)CO(3-py)\}] (4) was selected for further study because it did not affect splenocyte viability (in concentration up to 50 mu M), but significantly reduced secretion of representative Th1 cytokine, IFN-gamma induced by T cell mitogen. Besides IFN-gamma, 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 CD4(+)CD25(+)FoxP3(+) 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.