Intracellular Damage in Yeast Cells Caused by Photodynamic Treatment With Toluidine Blue

Abstract

The positively charged photosensitizer toluidine blue (TB) can induce loss of clonogenicity in Kluyveromyces marxianus. Previous studies have revealed that, as a consequence of the localization of this dye at the cell surface, photodynamic action results in extensive damage at the level of the plasma membrane. In this paper, a study is reported on the effect of photodynamic treatment with TB on intracellular enzymes. It is shown that treatment with TB and light resulted in the inhibition of alcohol dehydrogenase, cytochrome c oxidase, glyceraldehyde-3-phosphate dehydrogenase and hexokinase. Photodynamic treatment also lowered the ATP levels. The ATP levels could be partially restored in the presence of glucose but not with ethanol. Toluidine blue binding experiments revealed that photodynamic treatment caused a rapid increase in the amount of cell-associated dye. Moreover, it also appeared that this treatment decreased the binding of TB to the cell surface. It is concluded that TB enters the cell during the first minutes of illumination, whereafter intracellular enzymes are inactivated. The data indicate that photodynamic damage of intracellular sites contributes to the loss of viability.

Mechanistic Study of the Photodynamic Inactivation of Candida albicans by a Cationic Porphyrin

“…Our observations are very similar to those obtained for the PDI of K. maxianus with toluidine blue (30,31) and the PDI of C. albicans with hematoporphyrin (3,4). In both cases it was concluded that the plasma membrane became permeable during PDI, but the cell inactivation was attributed to more subtle forms of membrane damage, followed by damage to intracellular targets.…”

“…In order to optimize the PDI of microorganisms, knowledge of the underlying mechanisms is indispensable. However, in the majority of studies investigating the mechanisms of yeast PDI, the anionic hematoporphyrin and its derivatives (3,39), the hydrophobic chloroaluminum phthalocyanine (29,32) or the cationic thiazine dye toluidine blue (6,13,28,30), are used as photosensitizers.…”

Antimicrobial Photodynamic Inactivation Inhibits Candida albicans Virulence Factors and Reduces In Vivo Pathogenicity

“…Cellular metabolism can be reduced after APDI due to decreased transport of carbohydrates, amino acids, or phosphate through membrane-bound carrier proteins (30). Photodynamic action can also disturb carbon metabolism and ATP production by knocking out intracellular enzymes (e.g., alcohol dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, hexokinase, and cytochrome c oxidase) (31). In addition, photodynamic damage of mitochondria can increase the expression of p21, an inhibitor of cyclin-dependent kinases, leading to growth inhibition (29).…”

In Vivo Killing of Porphyromonas gingivalis by Toluidine Blue-Mediated Photosensitization in an Animal Model

“…PDT can be defined as eradication of target cells by reactive oxygen species (ROS) produced by means of a photosensitizing compound and light of an appropriate wavelength (6). Although PDT is more widely known for its application to the treatment of neoplasms, there is also interest in antimicrobial PDT, as a large number of microorganisms (including oral species) have been reported to be killed in vitro by this approach (21,27,31,40,43,46,47). Furthermore, the potencies of some key virulence factors (lipopolysaccharide and proteases) have also been shown to be reduced by photosensitization (18,32).…”