Experimental Photodynamic Laser Therapy for Rheumatoid Arthritis Using Photosan-3, 5-ALA-Induced PPIX and BPD Verteporfi
Photodynamic therapy (PDT) is the activation of a dye (photosensitizer) by means of light which evokes a cytotoxic effect using oxygen [6, 32]. Descriptions of photoactive effects have been known for nearly 100 years, while systematic examination of the s
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HENDRICH' G. HUTTMANN . G. DROGE'
J. SEARA . T. GOMILLE . C. LEHNERT' S. HOUSEREK . W. E. SIEBERT
Introduction
more in the red spectral range. Some of the new chemical compounds that seem to be of clinical use Photodynamic therapy (PDT) is the activation of a are the benzoporphyrin derivative BPD Verteporfin, dye (photosensitizer) by means of light which evokes zinc-II -phtalocyanin and the 5-aminolevulinic acida cytotoxic effect using oxygen [6, 32]. Descriptions induced protoporphyrin IX [IS, 23, 24]. 5-Aminoleof photo active effects have been known for nearly vulinic acid (ALA) has an exceptional position here 100 years, while systematic examination of the sub- because as an amino acid it is not photodynamically stances that are of therapeutic use today began in active itself, but causes an endogenous concentration the 1950s [4]. Different substances do work in differ- of the potent photosensitizer protoporphyrin IX ent ways, but the principal physicochemical process (PPIX) in certain cells [24]. In order to achieve the greatest possible deep is the absorption of photons by the photosensitizer, leading to singlet and triplet oxygen states which effect of PDT, red light between 600 and 800 nm is are highly energetic. The following transfer of energy used for stimulation, which is able to enter very and charge evokes activated states of oxygen that are deeply into human tissue. In principle there is no very reactive chemically and damage membranes and need for laser light to stimulate the photosensitizers, proteins [5]. The substantial cytotoxic effect is prob- but the intensities needed for endoscopic irradiation ably that of the singlet oxygen which is formed of the hollow organs cannot be coupled to a lightlocally at the area of irradiation [33]. The specialty conducting fiber or endoscopic optics by means of of PDT compared to other therapeutic methods is a conventional light source. Dye-lasers pumped by its double selectivity: there is only an effect if the argon ions emit monochromatic light at more than photo sensitizers are concentrated in the tissue 3 watts, which can be applied without problems aimed at and we have a sufficient photon density endoscopically because of its parallel nature. Besides on account of the irradiation. Because of the low toxi- this, the monochrome nature of the laser allows city in the dark, there are no systemic side effects easy calculation of the effective light dose. The exact wavelength is chosen for each sensitizer correapart from photosensitizing of the skin. The first generation of to day's established photo- sponding to its absorption maximum in this range. sensitizers are the derivatives of hematoporphyrin High-output laser diodes promise to become a low(HpD) and a cleaned fraction of the HpD, which price alternative to these lasers. Up to now the main field for photodynamic methhas a larger portion of the operative porphyrin dimers and is distributed under the names Porfimer ods of therapy was oncology [14]. Porfimer Sodium Sodium (formerly Photofrin II) and Photosa
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