Necrosis of murine tail skin following photodynamic treatment with meso-tetra-(p-sulphophenyl) porphine (TPPS)

Mouse skin photosensitization with benzoporphyrin derivatives and Photofrin: macroscopic and microscopic evaluation

A comparative study, at both the macroscopic and microscopic level, of skin photosensitivity caused by four isomeric forms of benzoporphyrin derivative (BPD) has been carried out, and compared to effects of Photofrin. Animals injected intravenously with BPD analogues and exposed to light 3 h later showed extensive photosensitivity. Animals receiving the monoacid derivatives of BPD (BPD-MA and BPD-MB) showed markedly more photosensitivity than those receiving the diacid derivatives (BPD-DA and BPD-DB). Animals receiving BPD analogues which were exposed to light 24 h or more later showed only minimal reactivity. Histological examination of biopsies taken after photosensitizer injection and light exposure showed extensive changes in epidermis and dermis, including epidermal erosion, degranulation of the stratum granulosum, spongiosis, depletion in cellularity and mast cell degranulation. These changes were noted to be similar to changes caused by Photofrin.

Cutaneous photosensitizing and immunosuppressive effects of a series of tumor localizing porphyrins

A series of tumor localizing porphyrins was evaluated with respect to their ability to elicit cutaneous photosensitivity and systemic immunosuppression, two of the most common side effects associated with photodynamic therapy. Using the murine ear swelling response as an indicator, it was found that all the non-metalloporphyrins caused cutaneous photosensitization. Immunosuppressive effects were noted using hematoporphyrin derivative (HPD) and meso-tetra(4-sulfonatophenyl)porphine if sensitization occurred immediately after photoirradiation, but none were evident using Photofrin II (PII) or meso-tetra(4-carboxyphenyl)porphine (TCPP). Subsequent studies indicated that PII and TCPP manifested a delayed type immunosuppression similar to that found following UVB photoirradiation. Manganese (III) meso-tetra(4-sulfonatophenyl)porphine, a prototype magnetic resonance imaging contrast agent, was also evaluated because of its reported demetallation in vivo. It was found to cause neither cutaneous photosensitivity nor immunosuppression.

Mouse skin photosensitivity with dihaematoporphyrin ether (DHE) and aluminium sulphonated phthalocyanine (AlSPc): a comparative study

Skin photosensitivity of sun exposed sites is the major side effect of dihaematoporphyrin ether (DHE) photodynamic therapy (PDT). Reports of severe oedema and erythema have generally been anecdotal. We have studied aluminium sulphonated phthalocyanine (AlSPc) as a potential photosensitiser for PDT. In this paper we report our work comparing the skin photosensitivity reactions of DHE and AlSPc. We have studied: (i) the time course of the skin reactions, (ii) the effect of increasing time from administration of photosensitiser to irradiation, (iii) drug-skin reaction dose response. Groups of Skh I female hairless albino mice were given an intravenous bolus dose of either 0.9% saline solution, AlSPc or DHE (Photofrin II). Drug doses ranged from 0.5 to 50 mg/kg. At times ranging from 1 h to 1 month animals were irradiated with a range of doses of solar simulated radiation (SSR). The skin reaction was observed over a 2 week period. DHE reactions were always more severe than those with AlSPc. Peak skin reaction was seen at 3 h for DHE and 6 h for AlSPc. DHE reactions were still visible 2 weeks after irradiation whereas the AlSPc reaction disappeared by 48 h. Irradiation evoked a reaction up to 2 months after administration of DHE but only up to 2 weeks with AlSPc. The mean SSR dose at which a skin reaction was seen decreased with increasing dose of both agents. The rate of decrease was slower with AlSPc than DHE. This study suggests that in PDT, AlSPc will cause much less skin photosensitivity than DHE.

The photodynamic effects of photofrin II, hematoporphyrin derivative, hematoporphyrin, and tetrasodium-mesotetra(4-sulfonatophenyl)porphine in vitro: clonogenic cell survival and drug uptake studies

The human colon adenocarcinoma cell line, WiDr, was exposed to Photofrin II, hematoporphyrin derivative (HPD), hematoporphyrin (HP) or tetrasodium-meso-tetra(4-sulfonatophyenyl)porphine (TPPS4) followed by irradiation with light. Clonogenicity was determined and the resultant survival curves compared and shown to be qualitatively similar in shape. However, for equal amounts of drug in the medium, there were large differences in photosensitizing efficiency with Photofrin II approximately 5, 25 and 50 fold more effective than HPD, HP and TTPS4, respectively. For the same power used, all drugs were less efficient photosensitizers under red light (600-1100 nm) than under white light (300-110 nm). For all drugs this could be explained in terms of changes in light absorption over the two wavelength ranges. Differences in clonogenic cell survival could not be explained in terms of differences in singlet oxygen production (from published values). A reduction in drug uptake into the cells was sufficient to explain the differences between Photofrin II, HPD and HP, while TPPS4 was 5-fold less effective compared to other drugs than would be expected from drug uptake measurements. Two methods for measuring drug uptake were compared and shown to give different results for Photofrin II. Measurements of drug fluorescence in 0.1 N NaOH yielded 5-fold lower values than when measurements were in 1 N HCl following heat treatment to monomerise aggregated drug. Clearly the reliability of the method used in determining drug uptake must be carefully ascertained.

Cell survival characteristics of a human colon adenocarcinoma cell line after photodynamic treatment: a comparison of Photofrin II and TPPS

A comparison has been made of the in vitro light-activated drug cytotoxicities of two different porphyrin compounds, Photofrin II and TPPS4. An early passage human colon adenocarcinoma cell line, WiDr, has been exposed to either drug for 24 h, the excess drug washed from the cells and the cells irradiated with light using quartz-tungsten-halogen lamps. Neither light nor drug alone under the experimental conditions employed was toxic to WiDr cells. Together, considerable cytotoxicity could be seen and the shapes of the cell survival curves following exposure to either drug then irradiation with light, were similar. For equal amounts of drug in the medium, Photofrin II was a more efficient photosensitizer of WiDr cells than TPPS4, and differences in cellular uptake could only partly explain this. When the experimental procedure was changed by reducing the temperature of irradiation, a reduction in photosensitizing efficiency could be demonstrated. This was more pronounced for Photofrin II, and was seen as a change in the slope of the final portion of the survival curve; and as a change in the shoulder for TPPS4. Two different batches of the two drugs were compared and shown to give slightly different results for Photofrin II (change in shoulder) but not to differ for TPPS4.

The effect of fractionation of light treatment on necrosis and vascular function of normal skin following photodynamic therapy

Sparing of normal tissue, mouse tail skin, by fractionation of light treatment in photodynamic therapy has been demonstrated in BDF1 mice injected with 2 mg tetrasodium-meso-tetra(4-sulphophenyl)porphine dodecahydrate i.v. When the time between 2 fractions of 67.5 J cm-2 and 90 J cm-2 was increased to 2 and 4 days respectively the incidence of necrosis fell to that expected after a single fraction. Blood flow in the tail skin 5 days after the second light fraction, as measured by the clearance of an intradermally injected solution of 133xenon in 0.9% saline, returned to control values when the time between 2 fractions was 2 days with 67.5 J cm-2 fractions, and 3 days with 90 J cm-2 fractions. The time course of recovery of normal mouse tail skin from photodynamic therapy, as shown by these split dose experiments, was found to be similar to the time course for the recovery of blood flow following a single light treatment.

Vascular function and the probability of skin necrosis after photodynamic therapy: an experimental study

The clearance of an intradermally-injected solution of 133Xenon in 0.9% saline has been used to study the impairment and recovery of blood flow in mouse tail for 5 days following photodynamic therapy (PDT) with 2mg TPPS i.v. per mouse and a range of doses of white light. Impairment of blood flow was observed within 10 min of light exposure. Blood flow increased between day 1 and day 5 at light doses less than 151J cm-2 and had returned to control levels by day 5 at light doses less than 129J cm-2. In mice treated with a light dose that caused a 50% incidence of necrosis, there was no significant difference in the initial xenon clearance half-time (measured at 10 min and 1 day after PDT) between those mice which developed tail necrosis and those which healed. However, the latter showed significantly greater improvement in vascular function on days 2, 3 and 4. This suggests that the timing and extent of recovery of blood flow determined the risk of necrosis in individual mice.