Farnesol-Induced Apoptosis in Candida albicans Is Mediated by Cdr1-p Extrusion and Depletion of Intracellular Glutathione

Farnesol is a key derivative in the sterol biosynthesis pathway in eukaryotic cells previously identified as a quorum sensing molecule in the human fungal pathogen Candida albicans. Recently, we demonstrated that above threshold concentrations, farnesol is capable of triggering apoptosis in C. albicans. However, the exact mechanism of farnesol cytotoxicity is not fully elucidated. Lipophilic compounds such as farnesol are known to conjugate with glutathione, an antioxidant crucial for cellular detoxification against damaging compounds. Glutathione conjugates act as substrates for ATP-dependent ABC transporters and are extruded from the cell. To that end, this current study was undertaken to validate the hypothesis that farnesol conjugation with intracellular glutathione coupled with Cdr1p-mediated extrusion of glutathione conjugates, results in total glutathione depletion, oxidative stress and ultimately fungal cell death. The combined findings demonstrated a significant decrease in intracellular glutathione levels concomitant with up-regulation of CDR1 and decreased cell viability. However, addition of exogenous reduced glutathione maintained intracellular glutathione levels and enhanced viability. In contrast, farnesol toxicity was decreased in a mutant lacking CDR1, whereas it was increased in a CDR1-overexpressing strain. Further, gene expression studies demonstrated significant up-regulation of the SOD genes, primary enzymes responsible for defense against oxidative stress, with no changes in expression in CDR1. This is the first study describing the involvement of Cdr1p-mediated glutathione efflux as a mechanism preceding the farnesol-induced apoptotic process in C. albicans. Understanding of the mechanisms underlying farnesol-cytotoxicity in C. albicans may lead to the development of this redox-cycling agent as an alternative antifungal agent

Expression of midkine in ameloblastomas and its correlation with clinicopathologic parameters

ObjectiveMidkine (MK) is a heparin-binding growth factor that is overexpressed in various human cancers. The aim of this study was to investigate the expression of MK in ameloblastomas and correlate the results with clinicopathologic parameters.Study DesignCases of ameloblastoma seen between 1999 and 2010 were identified. Clinical information was collected regarding age, gender, race, and location of tumor. Cases were classified as solid/multicystic, unicystic, and peripheral. The expression of midkine was assessed using immunohistochemistry. A significant difference was considered present at P < 0.05.ResultsA total of 34 cases of ameloblastoma and 4 cases of ameloblastic carcinomas were identified. MK was expressed in 67% of lesions (23.5% weak expression; 14.7% moderate expression; 29.4% strong expression). A significant difference was seen between solid/multicystic and unicystic lesions.ConclusionsMK is expressed in the majority of ameloblastomas, suggesting a role of the protein in the tumor's development, progression, and behavior