Mechanistic insight of the photodynamic effect induced by tri- and tetra-cationic porphyrins on Candida albicans cells

Abstract

The photodynamic mechanism of action induced by 5-(4-trifluorophenyl)-10,15,20-tris(4-N,N,N-trimethylammoniumphenyl)porphyrin (TFAP(3+)), 5,10,15,20-tetrakis(4-N,N,N-trimethylammoniumphenyl)porphyrin (TMAP(4+)) and 5,10,15,20-tetrakis(4-N-methylpyridyl)porphyrin (TMPyP(4+)) was investigated on Candida albicans cells. These cationic porphyrins are effective photosensitizers, producing a ~5 log decrease of cell survival when the cultures are incubated with 5 μM photosensitizer and irradiated for 30 min with visible light. Studies under anoxic conditions indicated that oxygen is necessary for the mechanism of action of photodynamic inactivation of this yeast. Furthermore, photoinactivation of C. albicans cells was negligible in the presence of 100 mM azide ion, whereas the photocytotoxicity induced by these porphyrins increased in D(2)O. In contrast, the addition of 100 mM mannitol produced a negligible effect on the cellular phototoxicity. On the other hand, in vitro direct observation of singlet molecular oxygen, O(2)((1)Δ(g)) phosphorescence at 1270 nm was analyzed using C. albicans in D(2)O. A shorter lifetime of O(2)((1)Δ(g)) was found in yeast cellular suspensions. These cationic porphyrins bind strongly to C. albicans cells and the O(2)((1)Δ(g)) generated inside the cells is rapidly quenched by the biomolecules of the cellular microenvironment. Therefore, the results indicate that these cationic porphyrins appear to act as photosensitizers mainly via the intermediacy of O(2)((1)Δ(g)).

Mechanistic Aspects of Photoinactivation of Candida albicans by Exogenous Porphyrins†

“…Porphyrin binding to the cytoplasmic membrane and penetration into the yeast cell is a prerequisite for effective ROS production in the yeast cells, which result from effective photoinactivation. In a recent study (43) on tri and tetra cationic porphyrins, it was also shown that these porphyrins bind strongly to C. albicans cells, and the ROS, which is effective in cellular damage, is generated inside the cells. However, the microenvironment in which the yeasts are found during photosensitization can induce failure of this treatment, as found in this study and the above‐mentioned recent study (43).…”

“…In a recent study (43) on tri and tetra cationic porphyrins, it was also shown that these porphyrins bind strongly to C. albicans cells, and the ROS, which is effective in cellular damage, is generated inside the cells. However, the microenvironment in which the yeasts are found during photosensitization can induce failure of this treatment, as found in this study and the above‐mentioned recent study (43). The effectiveness of this new mode of therapy is dependent on the protein quantity and quality in the different biological milieus (tissues or body fluids), and this must be taken into account.…”

Photodynamic Antifungal Chemotherapy†

“…Cormick et al. (53) investigated the susceptibility of C. albicans to two tetracationic porphyrins (TMPγP 4+ ) and 5,10,15,20‐tetrakis(4‐N,N,N‐trimethylammoniumphenyl)porphyrin (TMAP 4+ ) and a tricationic porphyrin 5‐(4‐trifluorophenyl)‐10,15,20‐tris(4‐N,N,N‐trimethylammoniumphenyl) porphyrin (TFAP 3+ ). All the PSs had amphiphilic character of the structure and high affinity for C. albicans .…”

Ion-induced stacking of photosensitizer molecules can remarkably affect the luminescence detection of singlet oxygen inCandida albicanscells

“…[39][40][41][42][43] Many porphyrins are lipophilic and hence should accumulate in cellular membranes but the high water-solubility of XF73 suggests localization in the cytoplasm as well. In this context it is important to have a detection procedure that provides reliable data from inside such cells, in particular when knowing that cellular constituents can substantially affect singlet oxygen luminescence.…”