Ascorbic Acid Synergistically Potentiates Phloxine B‐induced Photocytotoxicity in Human Acute Promyelocytic Leukemia Cells

Ascorbic acid (AsA) is known as an antioxidant but concomitantly possesses a pro‐oxidant property. Because the impact of AsA on photodynamic therapy response is unclear, we investigated the effect of AsA on photocytotoxicity induced by phloxine B in human acute promyelocytic leukemia HL‐60 cells. AsA synergistically enhanced phloxine B‐induced photocytotoxic effects, including inhibition of cell proliferation, DNA ladder formation, and caspase‐3 activation, whereas AsA itself showed no photocytotoxicity. AsA also enhanced the consumption of the reduced glutathione level compared with the cells treated with phloxine B alone under the light condition. Combination of AsA with phloxine B under the light condition enhanced the phosphorylation of c‐Jun N‐terminal kinase and p38 mitogen‐activated protein kinase (MAPK). These effects were completely cancelled by catalase. These results suggest that AsA synergistically enhances phloxine B‐induced photocytotoxicity, possibly through the extracellular oxidative stress‐dependent MAPK pathway activation.     

Light-activated cytotoxic compounds from Malaysian microorganisms for photodynamic therapy of cancer

Photodynamic therapy (PDT) is a promising cancer treatment which involves activation of a photosensitizing drug with light to produce reactive oxygen species that kill tumors without causing damage to unirradiated normal tissues. To date, only Photofrin^®, Foscan^® and Levulan^® have been approved for clinical treatment of cancer. Tropical habitats such as those found in Malaysia are attractive sources of new therapeutic compounds as tremendous chemical diversity is found in a large number of plants, animals, marine- and micro-organisms. In our screening program for novel photosensitizers from nature, colorful strains of fungi (from Aspergillus and Penicillium genus) and bacteria (including actinomycetes and photosynthetic bacteria) were collected from various habitats in Peninsular Malaysia, such as coastal soil, peat soil, marine sponges and wastewater ponds. Methanolic extracts from a total of 85 different species were evaluated with a short-term cell viability assay for photo-cytotoxicity, where a promyelocytic leukemia cell-line, HL60 incubated with 20 μg/ml of extracts was irradiated with 9.6 J/cm² of a broad spectrum light. Two of these extracts, one from Rhodobacter sphaeroides (PBUM003) and one from Rhodopseudomonas palustris (PBUM001) showed moderate to strong photo-cytotoxicity. Subsequent bioassay guided isolation of the PBUM001 extract yielded known photosensitisers that are based on bacteriochlorophyll-a by comparing their molecular weight data, HPLC profiles and UV–vis absorption spectra with literature values, thereby demonstrating the validity of our screening approach.     

Cationic porphyrin–quinoxaline conjugate as a photochemically triggered novel cytotoxic agent

A novel cationic porphyrin–quinoxaline conjugate 8 was prepared in good yield by the coupling of activated quinoxaline carboxylic acid 5 with an appropriate aminoporphyrin. The UV–vis spectra of conjugate 8 with the addition of ctDNA shows substantial hypochromicity (39%) and a red shift (12 nm) in the Soret band indicating intercalation and self stacking along the surface. The binding constant of conjugate 8 with ctDNA was determined to be 1.26 × 10⁶ M^?1. The porphyrin–quinoxaline conjugate 8 displayed enhanced photocytotoxicity (IC₅₀ = 0.06 μM) when compared to TMPyP against A549 cancer cells.     

Synthesis of β-functionalized temoporfin derivatives for an application in photodynamic therapy

The synthesis of novel β-functionalized derivatives of the clinically used photosensitizer Temoporfin has been achieved by nucleophilic addition reactions to a corresponding diketo chlorin. The β-substituted dihydroxychlorin products exhibit a strong absorption in the red spectral region, a high singlet oxygen quantum yield, and were found to be highly effective in in vitro assays against HT-29 tumor cells.     

Synthesis,characterization, and photodynamic therapy activity of 5,10,15,20-Tetrakis(carboxyl)porphyrin

Water-soluble porphyrins are considered promising drug candidates for photodynamic therapy (PDT). This study investigated the PDT activity of a new water-soluble, anionic porphyrin (1-Zn), which possesses four negative charges. The photodynamic anticancer activity of 1-Zn was investigated by the MTT assay, with mTHPC as a positive control. The cellular distribution was determined by fluorescence microscopy. Holographic and phase contrast images were recorded after 1-Zn treatment with a HoloMonitor™ M3 instrument. The inhibition of A549 cell growth achieved by inducing apoptosis was investigated by flow cytometry and fluorescence microscopy. DNA damage was investigated by the comet assay. The expression of apoptosis-related proteins was also measured by western blot assays. 1-Zn had better phototoxicity against A549 cells than HeLa and HepG2 cancer cells. Interestingly, 1-Zn was clearly located almost entirely in the cell cytoplasmic region/organelles. The late apoptotic population was less than 1.0% at baseline in the untreated and only light-treated cells and increased to 40.5% after 1-Zn treatment and irradiation (P < 0.05). 1-Zn triggered significant ROS generation after irradiation, causing ΔΨm disruption (P < 0.01) and DNA damage. 1-Zn induced A549 cell apoptosis via the mitochondrial apoptosis pathway. In addition, 1-Zn bound in the groove of DNA via an outside binding mode by pi-pi stacking and hydrogen bonding. 1-Zn exhibits good photonuclease activity and might serve as a potential photosensitizer (PS) for lung cancer cells.     

Photocytotoxicity and near-IR light DNA cleavage activity of oxovanadium(IV) Schiff base complexes having phenanthroline bases

Oxovanadium(IV) complexes [VO(L)(B)] (1-3), where H₂L is a Schiff base ligand 2-(2-hydroxybenzylideneamino)phenol and B is 1,10-phenanthroline (phen for 1), dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq for 2) or dipyrido[3,2-a:2′,3′-c]phenazine (dppz for 3), have been prepared, characterized and their DNA binding property and photo-induced DNA cleavage activity studied. Complex 3 which is structurally characterized by X-ray crystallography shows the presence of an oxovanadium(IV) moiety in a six coordinate VO₃N₃ coordination geometry. The complexes show a d-d band within 800-850 nm in DMF. The complexes display an oxidative response near 0.7 V versus SCE for V(V)-V(IV) and a reductive response within −1.1 to −1.3 V due to V(IV)-V(III) couple in DMF-0.1 M TBAP. The complexes are avid binders to calf thymus DNA giving binding constant values of 4.2 × 10⁴ to 1.2 × 10⁵ M⁻¹. The complexes do not show any “chemical nuclease” activity in dark. The dpq and dppz complexes are photocleavers of plasmid DNA in UV-A light of 365 nm via ¹O₂ pathway and in near-IR light (752.5 to 799.3 nm IR optics) by HO^• pathway. Complex 3 exhibits significant photocytotoxicity in visible light in HeLa cells giving IC₅₀ value of 13 μM, while it is less toxic in dark (IC₅₀ = 97 μM).     

Synthesis,photophysical properties,and photodynamic activity of positional isomers of TFPP-glucose conjugates

The synthesis and characterization of a ‘complete set’ of positional isomers of tetrakis(perfluorophenyl)porphyrins (TFPP)-glucose conjugates (1OH, 2OH, 3OH, 4OH, and 6OH) are reported herein. The cellular uptake and photocytotoxicity of these conjugates were examined in order to investigate the influence of location of the TFPP moiety on the d-glucose molecule on the biological activity of the conjugates. An In vitro biological evaluation revealed that the certain of these isomers have a greater effect on cellular uptake and cytotoxicity than others. The TFPP-glucose conjugates 1OH, 3OH, and 4OH were found to exert exceptional photocytotoxicity in several types of cancer cells compared to 2OH and 6OH substituted isomers.