Photodynamic Effects of Hypericin on Lipid Peroxidation and Antioxidant Status in Melanoma Cells

Abstract

Photodynamic-induced cytotoxicity by hypericin (HYP) was studied on three human melanoma cell lines: one pigmented cell line (G361) and two amelanotic cell lines (M18 and M6). No significant variation in the rate of uptake and in the maximum level of HYP incorporation for the different cells was observed. In the dark, no cytotoxicity was observed in the range 0-10-6 M HYP for the three cell lines. Amelanotic cells were found to be more sensitive than pigmented cells to irradiation of HYP with visible light (lambda > 590 nm). In addition, for the three cell lines HYP-induced photocytotoxicity was found to be drug-dose and light-dose dependent. Under the conditions used, thiobarbituric acid-reacting substances (TBARs) were significantly increased in amelanotic cells after irradiation (P < 0.0001). By contrast, the amount of TBARS remained unchanged in pigmented cells. Antioxidant defenses including enzymes and glutathione (GSH) were assayed before and after HYP photosensitization. Significantly increased total SOD activity was observed after photosensitizaton for amelanotic cells (P < 0.05), while glutathione peroxidase (GSHPx) and catalase (Cat) activities but also GSH levels were significantly decreased (P < 0.01). In pigmented cells a significantly increased Cat activity was found (P < 0.05), whereas GSHPx was unaffected after irradiation. It can be inferred that (a) HYP may be an effective PDT agent for melanoma and (b) there is a relationship between melanin content and sensitivity to HYP phototoxicity in human melanoma cells.

Melanoma resistance to photodynamic therapy: new insights

“…One explanation for this phenomenon is that melanin may act as a filter by preventing any in-depth penetration of light, shielding certain cellular targets from light as well as absorbing and scattering therapeutic light (Hadjur, Richard et al 1996). It has been showed in a study that in 500-600 nm interval, melanin is the dominant absorber and the optical penetration depth demonstrated that light transmittance of melanotic melanomas occurs only above 700-nm (Kollias, Sayre et al 1991).…”

“…However, several resistance mechanisms such as; optical interference (Hadjur, Richard et al 1996;Busetti, Soncin et al 1999), anti-oxidant defense mechanisms of melanin (Hadjur, Richard et al 1996;Davids, Kleemann et al 2009), cytoprotective response through induction of autophagy (Davids, Kleemann et al 2009), melanosomes protecting melanocytes and melanoma cells against harmful effects of toxic intermediates (Davids, Kleemann et al 2009) and lastly ABCG2 transporters acting as efflux pumps making cells capable of eliminating toxic amounts of porphyrins (Bebes, Nagy et al 2011) cause reduction in efficacy of PDT on melanoma cells.…”

“…Due to melanoma's intrinsic resistance to radiation and chemotherapeutic drugs, PDT has been suggested as an alternative therapeutic modality, which involved light induced destruction of cells or target tissues through sensitization to light by various photosensitizing agents; hypericin (Hadjur, Richard et al 1996), benzoporphyrin derivatives (Busetti, Soncin et al 1999) or protophorphyrin IX (PPIX) being just a few examples (Kiesslich, Krammer et al 2006). However, several resistance mechanisms such as; optical interference (Hadjur, Richard et al 1996;Busetti, Soncin et al 1999), anti-oxidant defense mechanisms of melanin (Hadjur, Richard et al 1996;Davids, Kleemann et al 2009), cytoprotective response through induction of autophagy (Davids, Kleemann et al 2009), melanosomes protecting melanocytes and melanoma cells against harmful effects of toxic intermediates (Davids, Kleemann et al 2009) and lastly ABCG2 transporters acting as efflux pumps making cells capable of eliminating toxic amounts of porphyrins (Bebes, Nagy et al 2011) cause reduction in efficacy of PDT on melanoma cells.…”

Novel Neuroprotective Formulations Based on St. John’s Wort Extract

“…as photosensitizer for the photodynamic therapy of cancer by mean its single oxygen production, or it can be used for the photo-diagnosis of early epithelial cancer by taking advantage of its specific accumulation in various types of tumor cells (Kah et al, 2008;Ritz et al, 2008). Among different targets, tumor melanocytes (Hadjur et al, 1996), glioma cells (Huntosova et al, 2012), isolated crayfish neuron (Uzdensky et al, 2003) and hepatocellular carcinoma cells (Fadel et al, 2010) were quoted and reported as cell models for the study of the photodynamic efficacy of hypericin after photoirradiation.…”

Visualization and Photodynamic Therapy in Malignant Glioma - An Overview and Perspectives

“…It has a high triplet quantum yield and a high efficiency in the formation of ROS. (Diwu & Lown 1993;Ehrenberg, Anderson, & Foote 1998;Hadjur et al 1996) The excessive production of the so called ROS leads to oxidative stress to many biomolecules, e.g. proteins, causing cell death by induction of apoptosis, necrosis or autophagy associated cell death.…”