Hexyl‐aminolevulinate‐mediated photodynamic therapy: How to spare normal urothelium. An in vitro approach

Abstract

Background and Objectives: Photodynamic therapy (PDT) of superficial bladder cancer may cause damages to the normal surrounding bladder wall. Prevention of these is important for bladder healing. We studied the influence of photosensitizer concentration, irradiation parameters, and production of reactive oxygen species (ROS) on the photodynamically induced damage in the porcine urothelium in vitro. The aim was to determine the threshold conditions for the cell survival. Methods: Living porcine bladder mucosae were incubated with solution of hexylester of 5-aminolevulinic acid (HAL). The mucosae were irradiated with increasing doses and cell alterations were evaluated by scanning electron microscopy and by Sytox green fluorescence. The urothelial survival score was correlated with Protoporphyrin IX (PpIX) photobleaching and intracellular fluorescence of Rhodamine 123 reflecting the ROS production. Results: The mortality ratio was dependent on PpIX concentration. After 3 hours of incubation, the threshold radiant exposures for blue light were 0.15 and 0.75 J/cm 2 (irradiance 30 and 75 mW/cm 2 , respectively) and for white light 0.55 J/cm 2 (irradiance 30 mW/cm 2 ). Photobleaching rate increased with decreasing irradiance. Interestingly, the DHR123/R123 reporter system correlated well with the threshold exposures under all conditions used. Conclusions: We have determined radiant exposures sparing half of normal urothelial cells. We propose that the use of low irradiance combined with systems reporting the ROS production in the irradiated tissue could improve the in vivo dosimetry and optimize the PDT. Lasers Surg.

Membrane transport enhancement of chlorin e6‐polyvinylpyrrolidone and its photodynamic efficacy on the chick chorioallantoic model

“…This suggests that there is a light dose threshold for a photodynamic reaction to cause cell death using Ce6-PVP. As addressed by many researchers, the interdependence of photosensitizer concentration, route of administration, and incubation time determines the irradiance and radiant exposure required to cause PDT-induced tissue damage [26][27][28]. As such, a cautious extrapolation of PDT parameters obtained from the CAM model may provide a useful guide to establish a basis for the clinical use of Ce6-PVP for bladder cancer.…”

Advances in Management of Bladder Cancer—The Role of Photodynamic Therapy

“…Protoporphyrin IX (PPIX) is known as a precursor to haem. Haem itself is not a photosensitiser, due to the coordination of a paramagnetic ion in the centre of the macrocycle, causing significant reduction in excited state lifetimes [ 49 , 50 , 51 , 52 , 53 , 54 , 55 , 56 ].…”

“…On the other hand, photosensitizers obtained from natural sources and having a positive effect are hypericin [ 57 , 58 , 59 ] and chlorophyllin [ 60 , 61 ]. Photosensitizers should absorb light in the red or far-red wavelengths in order to penetrate tissue deeper [ 49 , 50 , 51 , 52 , 53 , 54 , 62 ].…”

Photodynamic therapy with hexyl aminolevulinate induces carbonylation, posttranslational modifications and changed expression of proteins in cell survival and cell death pathways

“…7- 18 The effect of illumination was examined in rat ovarian cancer and porcine bladder mucosa. 19,20 Moreover, tissue response to HAL-PDT was monitored in rat bladder. The results revealed a clear treatment response in vivo including decreased tissue oxygenation and immunoprecipitated with anti-DNP antibody prior to 2D-GE and MS. 31,32…”