Regulation of aldose reductase activity by tubulin and phenolic acid derivates.

In this work we demonstrate that aldose reductase (AR) interacts directly with tubulin and, was subjected to microtubule formation conditions, enzymatic AR activity increased more than sixfold. Since AR interacts mainly with tubulin that has 3-nitro-tyrosine in its carboxy-terminal, we evaluated whether tyrosine and other phenolic acid derivatives could prevent the interaction tubulin/AR and the enzymatic activation. The drugs evaluated have two characteristics in common: the presence of an aromatic ring and a carboxylic substituent. The 9 drugs tested were able to prevent both the interaction tubulin/AR and the enzymatic activation. In addition, we found that the induction of microtubule formation by high concentrations of glucose and the consequent activation of AR in cultured cells can be inhibited by phenolic acid derivates that prevent the interaction tubulin/AR. These results suggest that tubulin regulates the activation of AR through a direct interaction which can be controlled with phenolic derivates of carboxylic acids.

Optimization of cellular uptake of zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine for maximal photoinactivation of Candida albicans.

Cellular uptake and photodynamic action of zinc(II) 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]phthalocyanine (ZnPPc4⁺) was examined in Candida albicans. In vitro investigations showed that ZnPPc4⁺ was rapidly bound to C. albicans cells. The binding of phthalocyanine to cells was dependent on ZnPPc4⁺ concentrations (1-10 µM) and cells densities (106-108 cells mL⁻¹). A high amount of ZnPPc4⁺ retained in the cells after two washing steps, indicating a strong interaction between the photosensitizer and C. albicans. The uptake was temperature dependent, although the difference between 37 °C and 4 °C was about 10 %. Also, the amount of ZnPPc bound to C. albicans was affected when the cells were incubated for a longer time with azide and 2,4-dinitrophenol (DNP) prior to treatment with ZnPP4⁺. Cell survival after irradiation was dependent on the irradiation period, ZnPPc4⁺ concentration and cells density. Photoinactivation of C. albicans cells was elevated even after two washing steps. The strong dependence of uptake on cell density reveals the strength and avidity of the binding of ZnPPc4⁺ to C. albicans cells. The accumulation behaviour of ZnPPc4⁺ suggests that mainly an affinity-mediated binding mechanism can be involved. Therefore, ZnPPc4⁺ is an interesting phthalocyanine for photodynamic inactivation (PDI) of yeasts in liquid suspensions.