Spectroscopic studies of hematoporphyrin-derivative in culture medium

Photodynamic activity of lutetium-texaphyrin in a mouse tumor system

BACKGROUND AND OBJECTIVE

New photosensitizers proposed for photodynamic therapy (PDT) treatment of tumors need to be evaluated in animal models to determine the parameters needed for treatment. They also need to be compared with existing photosensitizers for efficacy. We examined the PDT response to lutetium-texaphyrin (PCI-0123) in a mouse mammary adenocarcinoma model and compared it with the PDT response seen when using Photofrin.

STUDY DESIGN/MATERIALS AND METHODS

DBA/2 mice with SMT-F tumors were used to explore PCI-0123 toxicity, laser light dose, and drug dose effects on PDT response and to determine the most effective time for light application. The PDT response of PCI-0123-treated tumors was compared with that of Photofrin-treated tumors.

RESULTS

Treatment of tumors with 150 J/cm2 of 740 nm laser light 5-6 hr after PCI-0123 administration (40 mg/kg) resulted in a 100% response rate and a 55% cure rate. Tumors treated with 150 J/cm2 of 630 nm laser light 24 hr after Photofrin administration (10 mg/kg) resulted in a 67% response rate and a 16% cure rate.

CONCLUSION

PCI-0123 was found to be a more effective photosensitizer than Photofrin.

A review of in vivo studies of porphyrins and unexpected fluorescences. An interpretation of the results

Clinical applications of porphyrins lead research biologists to characterize these compounds according to their fluorescence. These measurements revealed unexpected fluorescence spectra in addition to those of the injected porphyrins. The general characteristics of the spectra of porphyrins are reviewed. The technique permitting studies on animals in a waking state and the advantages of this method are shown. The studies in this field are reviewed and spectra reproduced. Among the observed fluorescences, those which cannot be attributed to injected porphyrins are divided into two groups. The first group, above 580 nm, seems to result from molecular associations (polymers or micelles of injected porphyrins). The second group, from 560-575 nm, seems to belong to a natural compound. Some spectroscopic observations and some medical reports lead us to identify it as an unusual natural porphyrin and perhaps as metalloporphyrin. Some authors have mentioned a Zn porphyrin. Finally, the importance of continuing the study of this natural porphyrin is discussed.

Probing the structure of HPD by fluorescence spectroscopy

Fluorescence emission spectra indicate that oligomers containing both hematoporphyrin and its dehydration products (vinyl porphyrins) comprise the tumor-localizing fraction of HPD. In the relatively polar solvent methanol, the vinyl porphyrins exhibit reduced fluorescence yields while the hematoporphyrin residues are relatively resistant to fluorescence quenching by Fe+3. In the less polar solvent tetrahydrofuran, fluorescence from oligomeric vinyl porphyrins was enhanced, and Fe+3-induced quenching of oligomeric hematoporphyrin promoted. These, together with other studies in biological systems, suggest a substantial degree of interaction among the porphyrin units contained in these oligomers, as a function of the polarity of the environment.

Effects of hematoporphyrin-derivative on mouse erythroleukemia cells in the absence of light irradiation

This paper concerns a general study on the effects of hematoporphyrin-derivative (HpD) on mouse erythroleukemia (MEL) cells, in the absence of light irradiation. In particular, HpD intrinsic cytotoxicity was evaluated at different doses and the results correlated with those referring to membrane functional and morphological changes. HpD uptake and release processes were also studied and compared with the above-mentioned results. In order to have an overall picture of HpD-cell interactions, time-resolved fluorescence measurements were performed on both undifferentiated and differentiated MEL cells. The results obtained indicate that, even at HpD doses exhibiting neither any cytotoxicity nor any morphological damage (1-10 micrograms/ml), membrane permeability alterations are observed. Thirty minutes of treatment are sufficient for HpD to develop its toxic effect: indeed, no differences in HpD influence on cell viability can be observed after 30 min, 60 min or 5 days of treatment. HpD cytotoxicity is reduced by high protein content in the incubation culture medium. The presence of both monomeric species and 580 nm emitting species was observed at cellular level. The latter is likelier in undifferentiated MEL cells, which also exhibit higher overall HpD uptake, as compared with differentiated MEL cells.

Time-resolved fluorescence spectroscopy of hematoporphyrin-derivative in human lymphocytes

This paper reports on time-resolved microfluorimetric measurements on hematoporphyrin-derivative (HpD)-treated lymphocytes. HpD is at present widely used as a tumor-locating and photosensitizing drug. It is therefore of great importance to study the extent to which the HpD uptake process depends on cell functional and structural properties. Time-resolved fluorescence measurements in single cells are very useful in this respect, since they give information on the content of fluorescent molecules through fluorescence peak-intensity, and, indirectly, on the binding properties through the fluorescence decay times. In particular, we studied the dependence of HpD fluorescence on the cellular functional state. To this end, we performed in-cell fluorescence measurements on human lymphocytes, both in quiescent conditions and in the pre-replicative phase, after stimulation with phytohemagglutinin (PHA). We found a higher HpD content in stimulated lymphocytes. Moreover, we found a spectral band around 575 nm, corresponding to a particular porphyrin species, in which the differences between normal and stimulated lymphocytes are more striking. The porphyrin species emitting in this band seems to play a role in the specific interaction of HpD with tumors, since a similar emission band has also been found in tumor cells containing HpD.