Structure–activity relationship of coordinated catecholamine in the [RuIII(NH3)4(catecholamine)]+ complex

Vascular tone and angiogenesis modulation by catecholamine coordinated to ruthenium

Catecholamines participate in angiogenesis, an important tumor development process. However, the way catecholamines interact with their receptors has not been completely elucidated, and doubts still remain as to whether these interactions occur between catechol and/or amine sites and particular amino acid residues on the catecholamine receptors. To evaluate how catechol and amine groups contribute to angiogenesis, we immobilized the catechol site through ruthenium ion (Ru) coordination, to obtain species with the general formula [Ru(NH₃)₄(catecholamine-R)]Cl. We then assessed the angiogenic activity of the complexes in a chorioallantoic membrane model (CAM) and examined vascular reactivity and calcium mobilization in rat aortas and vascular cells. [Ru(NH₃)₄(catecholamine-R)]Cl acted as partial agonists and/or antagonists of their respective receptors and induced calcium mobilization. [Ru(NH₃)₄(isoproterenol)]⁺ [Ru(NH₃)₄(noradrenaline)]⁺, and [Ru(NH₃)₄(adrenaline)]⁺ behaved as antiangiogenic complexes, whereas [Ru(NH₃)₄(dopamine)]⁺ proved to be a proangiogenic complex. In conclusion, catecholamines and [Ru(NH₃)₄(catecholamine-R)]Cl can modulate angiogenesis, and catechol group availability can modify the way these complexes impact the vascular tone, suggesting that catecholamines and their receptors interact differently after catecholamine coordination to ruthenium.

Antifungal mechanism of [RuIII(NH3)4catechol]+ complex on fluconazole-resistant Candida tropicalis

Candidiasis, a major opportunistic mycosis caused by Candida sp., may comprise life-threatening systemic infections. The incidence of non-albicans species is rising, particularly in South America and they are frequently drug resistant, causing unresponsive cases. Thus, novel antimycotic agents are required. Here we tested the antifungal activity of [RuIII(NH3)4catechol]+ complex (RuCat), approaching possible action mechanisms on fluconazole-resistant Candida tropicalis. RuCat significantly (P < 0.05) inhibited the growth and viability of C. tropicalis dose-dependently (IC50 20.3 μM). Cytotoxicity of RuCat upon murine splenocytes was lower (Selectivity Index = 16). Scanning electron microscopy analysis showed pseudohyphae formation, yeast aggregation and surface damage. RuCat-treated samples investigated by transmission electron microscopy showed melanin granule trafficking to cell surfaces and extracellular milieu. Surface-adherent membrane fragments and extracellular debris were also observed. RuCat treatment produced intense H2DCFDA labeling, indicating reactive oxygen species (ROS) production which caused increased lipoperoxidation. ROS are involved in the fungicidal effect as N-acetyl-L-cysteine completely restored cell viability. Calcofluor White chitin staining suggests that 70 or 140 μM RuCat treatment for 2 h affected cell-wall structure. PI labeling indicated necrotic cell death. The present data indicate that RuCat triggers ROS production, lipoperoxidation and cell surface damage, culminating in selective necrotic death of drug-resistant C. tropicalis.