ABSTRACT
Glioma is the most common type of brain tumors in adults, and treatment of high-grade gliomas is still palliative. Studies to date have revealed only modest effect in attenuating growth of these tumors with single agent therapy, but combination treatment appears to be more effective. Cyclophilin A (CypA), a target of immunosuppressive drugs cyclosporin A (CsA) and sanglifehrin A (SFA), is an intracellular protein that has peptidyl-prolyl cis-trans isomerase (PPIase) enzymatic activity. Previously, we showed that overexpressed CypA induced chemoresistance in cancer cells. Here we provide evidence that combination of cisplatin with either CsA or SFA synergistically enhances apoptotic cell death in C6 glioma cells, compared with single agent treatment. Enhanced apoptotic cell death is a result of an increase in ROS generation and a decrease in intracellular glutathione levels. Consistently, CypA knockdown by siRNA also enhances cisplatin-induced apoptosis. Immunohistochemical analysis showed increased expression of CypA in human glioblastoma multiforme, but not in normal human astrocytes. CypA was also shown to be up-regulated in C6 glioma cells during hypoxia. In conclusion, CsA or SFA in combination with cisplatin synergistically enhances cisplatin-induced apoptosis in C6 glioma cells via inhibition of PPIase activity of CypA, indicating that development of new drugs that selectively inhibit the CypA PPIase activity without immune suppression may facilitate alleviation of chemoresistance in treatment of high-grade glioma.
Subject(s)
Antineoplastic Agents/pharmacology , Brain Neoplasms/drug therapy , Cyclosporine/pharmacology , Glioma/drug therapy , Animals , Apoptosis/drug effects , Blotting, Western , Cell Line, Tumor , Cell Proliferation/drug effects , Cisplatin/pharmacology , Cyclophilin A/antagonists & inhibitors , Drug Synergism , Humans , Immunohistochemistry , Lactones/pharmacology , RNA, Small Interfering , Rats , Reactive Oxygen Species/metabolism , Spiro Compounds/pharmacologyABSTRACT
OBJECTIVE: While many factors contribute to aging, changes in calcium homeostasis and calcium related neuronal processes are likely to be important. High intracellular calcium is toxic to cells and alterations in calcium homeostasis are associated with changes in calcium-binding proteins, which confine free Ca(2+). We therefore assayed the expression of the calcium binding proteins calretinin and calbindin in the central auditory nervous system of rats. METHODS: Using antibodies to calretinin and calbindin, we assayed their expression in the cochlear nucleus, superior olivary nucleus, inferior colliculus, medial geniculate body and auditory cortex of young (4 months old) and aged (24 months old) rats. RESULTS: Calretinin and calbindin staining intensity in neurons of the cochlear nucleus was significantly higher in aged than in young rats (p<0.05) The number and staining intensity of calretinin-positive neurons in the inferior colliculus, and of calbindin-positive neurons in the superior olivary nucleus were greater in aged than in young rats (p<0.05). CONCLUSION: These results suggest that auditory processing is altered during aging, which may be due to increased intracellular Ca(2+) concentration, consequently leading to increased immunoreactivity toward calcium-binding proteins.
