Laser photosensitization of cells by hypericin.
ABSTRACT Administering a light dose of 90 J/cm2 at 599 nm during incubation with hypericin to a highly differentiated normal epithelial cell line (FRTL-5), derived from Fisher rat thyroid, and to a neoplastic cell line (MPTK-6), derived from the lung metastases of a thyroid carcinoma induced in Fisher rats, produces cell kill at drug doses 1000 times lower than those necessary to cause the same mortality in the dark. The photocytocidal activity of this polycyclic quinone drug on neoplastic cells is superior to that of antitumor anthraquinone drugs, such as daunomycin and mitoxanthrone, and to the photosensitized antiviral activity previously reported for hypericin.
Article: Behavioral and Biochemical Adaptations of Generalist and Specialist Herbivorous Insects Feeding on Hypericum perforatum (Guttiferae)[show abstract] [hide abstract]
ABSTRACT: The behavior and biochemical adaptations of 3 generalist insect species (Tettigonia viridissima L., Ruspolia nitidula Scopoli, and Conocephalus discolor Thunberg) and 3 specialists (Galeruca tanaceti L., Chrysolina geminata Payrtull, and Cloantha perspicillaris Boisduval) to the hypericin-containing leaves of Hypericum perforatum were investigated in southwestern France. The generalists preferentially fed on the part of the leaf lacking the phototoxic, hypericin-laden dark glands. The specialists showed no discriminatory feeding pattern but exhibited a negative phototaxis that is presumed to be an efficient strategy to circumvent the light-induced toxicity of hypericin. The constitutive and hypericin-inducible activities of glutathione reductase and glutathione S-transferase, 2 antioxidant enzymes which are considered to be biochemical adaptations used by phytophagous insects to attenuate the oxidative stress caused by photosensitization, were determined in the fatbody and midgut of T. viridissima, C. discolor, G. tanaceti, and G. geminata. The specialist insects had lower constitutive activities of glutathione S-transferase and glutathione reductase than the generalists, although the application of hypericin induced the activity of glutathione S-transferase in specialist insects only. Insects with different lifestyles therefore are capable of circumventing the phototoxic effects of hypericin by appropriate behavioral and biochemical strategies.Environmental Entomology 01/2009; · 1.56 Impact Factor
Article: Interaction of hypericin with serum albumins: surface-enhanced Raman spectroscopy, resonance Raman spectroscopy and molecular modeling study.[show abstract] [hide abstract]
ABSTRACT: Surface-enhanced Raman spectroscopy, resonance Raman spectroscopy and molecular modeling were employed to study the interaction of hypericin (Hyp) with human (HSA), rat (RSA) and bovine (BSA) serum albumins. The identification of the binding site of Hyp in serum albumins as well as the structural model for Hyp/HSA complex are presented. The interactions mainly reflect: (1) a change of the strength of H bonding at the N1-H site of Trp; (2) a change of the Trp side-chain conformation; (3) a change of the hydrophobicity of the Trp environment; and (4) a formation of an H-bond between the carbonyl group of Hyp and a proton donor in HSA and RSA which leads to a protonated-like carbonyl in Hyp. Our results indicate that Hyp is rigidly bound in IIA subdomain of HSA close to Trp214 (distance 5.12 A between the centers of masses). In the model presented the carbonyl group of Hyp is hydrogen bonded to Asn458. Two other candidates for hydrogen bonds have been identified between the bay-region hydroxyl group of Hyp and the carbonyl group of the Trp214 peptidic link and between the peri-region hydroxyl group of Hyp and the Asn458 carbonyl group. It is shown that the structures of the Hyp/HSA and Hyp/RSA complexes are similar to, and in some aspects different from, those found for the Hyp/BSA complex. The role of aminoacid sequence in the IIA subdomains of HSA, RSA and BSA is discussed to explain the observed differences.Photochemistry and Photobiology 09/2001; 74(2):172-83. · 2.41 Impact Factor
Article: Light-induced photoactivation of hypericin affects the energy metabolism of human glioma cells by inhibiting hexokinase bound to mitochondria.[show abstract] [hide abstract]
ABSTRACT: Glucose-dependent energy required for glioma metabolism depends on hexokinase, which is mainly bound to mitochondria. A decrease in intracellular pH leads to a release of hexokinase-binding, which in turn decreases glucose phosphorylation, ATP content, and cell proliferation. Thus, intracellular pH might be a target for therapy of gliomas, and a search for agents able to modulate intracellular pH was initiated. Hypericin, a natural photosensitizer, displays numerous biological activities when exposed to light. Its mechanism and site of action at the cellular level remain unclear, but it probably acts by a type II oxygen-dependent photosensitization mechanism producing singlet oxygen. Hypericin is also able to induce a photogenerated intracellular pH drop, which could constitute an alternative mechanism of hypericin action. In human glioma cells treated for 1 h with 2.5 microg/ml hypericin, light exposure induced a fall in intracellular pH. In these conditions, mitochondria-bound hexokinase was inhibited in a light- and dose-dependent manner, associated with a decreased ATP content, a decrease of mitochondrial transmembrane potential, and a depletion of intracellular glutathione. Hexokinase protein was effectively released from mitochondria, as measured by an ELISA using a specific anti-hexokinase antibody. In addition to decreased glutathione, a response to oxidative stress was confirmed by the concomitant increase in mRNA expression of gamma-glutamyl cysteine synthetase, which catalyzes the rate-limiting step in overall glutathione biosynthesis, and is subject to feedback regulation by glutathione. Hypericin also induced a dose- and light-dependent inhibition of [3H]thymidine uptake and induced apoptosis, as demonstrated by annexin V-FITC binding and cell morphology. This study confirmed the mitochondria as a primary target of photodynamic action. The multifaceted action of hypericin involves the alteration of mitochondria-bound hexokinase, initiating a cascade of events that converge to alter the energy metabolism of glioma cells and their survival. In view of the complex mechanism of action of hypericin, further exploration is warranted in a perspective of its clinical application as a potential phototoxic agent in the treatment of glioma tumors.Cancer Research 01/1999; 58(24):5777-86. · 7.86 Impact Factor