tretinoin and pyrrolidine-dithiocarbamic-acid

Cryptococcus neoformans, a basidiomycetous yeast, is a fungal pathogen that can colonize the lungs of humans causing pneumonia and fungal meningitis in severely immunocompromised individuals. Recent studies have implied that the antifungal drug fluconazole (FLC) can induce oxidative stress in C. neoformans by increasing the production of reactive oxygen species (ROS), as presence of the antioxidant ascorbic acid (AA) could reverse the inhibitory effects of FLC on C. neoformans. However, in Candida albicans, AA has been shown to stimulate the expression of genes essential for ergosterol biosynthesis. Hence, the contribution of ROS in FLC-mediated growth inhibition remains unclear.. In order to determine whether counteracting ROS generated by FLC in C. neoformans can contribute to diminishing inhibitory effects of FLC, we tested three other antioxidants in addition to AA, namely, pyrrolidine dithiocarbamate (PDTC), retinoic acid (RA), and glutathione (GSH). Our data confirm that there is an increase in ROS in the presence of FLC in C. neoformans. Importantly, all four antioxidants reversed FLC-mediated growth inhibition of C. neoformans to various extents. We further verified the involvement of increased ROS in FLC-mediated growth inhibition by determining that ROS-scavenging proteins, metallothioneins (CMT1 and CMT2), contribute to growth recovery by PDTC and AA during treatment with FLC.. Our study suggests that ROS contributes to FLC-mediated growth inhibition and points to a complex nature of antioxidant-mediated growth rescue in the presence of FLC.

Topics: Antifungal Agents; Ascorbic Acid; Cryptococcus neoformans; Fluconazole; Fungal Proteins; Gene Expression Regulation, Fungal; Glutathione; Metallothionein; Microbial Viability; Pyrrolidines; Reactive Oxygen Species; Thiocarbamates; Tretinoin

We recently demonstrated that the constitutive expression of cyclooxygenase (COX)-2 protein and prostaglandin E(2) (PGE(2)) biosynthesis were significantly enhanced in human skin epidermal cancer cells and that cancer cell growth was effectively inhibited by the suppression of COX-2 expression by transfection with COX-2 antisense oligonucleotide. The purpose of this study was to search for agents which suppress COX-2 expression and examine their effects on cell growth. Since retinoids and antioxidants have been used for chemoprevention of cancers in several tissues, the effects of these agents on COX-2 expression and PGE(2) biosynthesis in skin squamous carcinoma cells were investigated. Treatment with a retinoid (9-cis-retinoic acid (9-cis-RA)) or an antioxidant (pyrrolidinedithiocarbamate (PDTC)) suppressed COX-2 expression and PGE(2) biosynthesis in a concentration-dependent manner. Cell growth was significantly inhibited by 9-cis-RA and PDTC. These results suggest that 9-cis-RA and PDTC may be useful in preventing skin cancer growth and that COX-2 is involved in their protective effects on skin carcinogenesis.

Topics: Acetylcysteine; Alitretinoin; Antineoplastic Agents; Antioxidants; Blotting, Western; Carcinoma, Squamous Cell; Cell Division; Cell Line; Cyclooxygenase 2; Dinoprostone; Dose-Response Relationship, Drug; Free Radical Scavengers; Humans; Isoenzymes; Keratinocytes; Membrane Proteins; Oligonucleotides, Antisense; Prostaglandin-Endoperoxide Synthases; Pyrrolidines; Retinoids; Skin Neoplasms; Thiocarbamates; Time Factors; Transfection; Tretinoin; Tumor Cells, Cultured