Influence of redox activation of NAMI-A on affinity to serum proteins: transferrin and albumin

Abstract

Imidazolium trans-tetrachloridodimethylsulfoxideimidazoleruthenate(III), NAMI-A, is a ruthenium drug exhibiting unique properties under clinical studies such as ability to inhibit the process of metastases without exerting tumor toxicity. Its place of action is concentrated at the extracellular level, therefore, the transformation and fate of this drug upon injection is of great importance. This study focuses on evaluation of the reducing potency of blood stream on interaction with two serum proteins: albumin and transferrin. It was investigated by applying various simplified serum models preserving physiological concentration of proteins and the amount of Ru complex as found in patients. It was shown that ruthenation of albumin is slightly increased while transferrin decreased upon addition of reductant in blood stream (ascorbate, glutathione, and cysteine) at physiological concentration. Interestingly, in serum models comprising low-molecular-mass components the amount of the reductant in the solution had a pronounced effect on the Ru content, in particular in transferrin. Supplementation of serum models with glutathione at concentration enough for complete reduction of NAMI-A selectively enhanced the binding of Ru complex to transferrin while ruthenation of albumin was almost unchanged. Spectrofluorimetric studies revealed that reduction has a marginal effect on binding affinity, therefore, both Ru(III) and (II) derivatives equally can compete for binding to transferrin.

Graphical Abstract

Keywords:

• NAMI-A
• Transferrin
• Albumin
• Reducing agents
• ICP-MS
• ELISA

Acknowledgements

K.Ś. acknowledges the financial support from the National Science Center (grant no. 2013/09/N/ST5/00858). M.B. is thankful for financial support from National Science Center (grant no. N N204 247340). The research was carried out with equipment purchased with financial support from the European Regional Development Fund within the framework of the Polish Innovation Economy Operational Program (contract no. POIG.0 2.01.00-12-0 23/08). The authors gratefully acknowledge Wiesław Knap for performing the ICP-MS experiments.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the National Science Center [grant number 2013/09/N/ST5/00858], [grant number NN204 247340]; Regional Development Fund within the framework of the Polish Innovation Economy OperationalProgram [contract number POIG.0 2.01.00-12-0 23/08].