Dexamethasone protected human glioblastoma U87MG cells from temozolomide induced apoptosis by maintaining Bax:Bcl-2 ratio and preventing proteolytic activities

BACKGROUND: Glioblastoma is the deadliest and most prevalent brain tumor. Dexamethasone (DXM) is a commonly used steroid for treating glioblastoma patients for alleviation of vasogenic edema and pain prior to treatment with chemotherapeutic drugs. Temozolomide (TMZ), an alkylating agent, has recently been introduced in clinical trials for treating glioblastoma. Here, we evaluated the modulatory effect of DXM on TMZ induced apoptosis in human glioblastoma U87MG cells. RESULTS: Freshly grown cells were treated with different doses of DXM or TMZ for 6 h followed by incubation in a drug-free medium for 48 h. Wright staining and ApopTag assay showed no apoptosis in cells treated with 40 μM DXM but considerable amounts of apoptosis in cells treated with 100 μM TMZ. Apoptosis in TMZ treated cells was associated with an increase in intracellular free [Ca(2+)], as determined by fura-2 assay. Western blot analyses showed alternations in the levels of Bax (pro-apoptotic) and Bcl-2 (anti-apoptotic) proteins resulting in increased Bax:Bcl-2 ratio in TMZ treated cells. Western blot analyses also detected overexpression of calpain and caspase-3, which cleaved 270 kD α-spectrin at specific sites for generation of 145 and 120 kD spectrin break down products (SBDPs), respectively. However, 1-h pretreatment of cells with 40 μM DXM dramatically decreased TMZ induced apoptosis, decreasing Bax:Bcl-2 ratio and SBDPs. CONCLUSION: Our results revealed an antagonistic effect of DXM on TMZ induced apoptosis in human glioblastoma U87MG cells, implying that treatment of glioblastoma patients with DXM prior to chemotherapy with TMZ might result in an undesirable clinical outcome

A putative role for calpain in demyelination associated with optic neuritis

Calcium activated neutral proteinase (calpain) is an endopeptidase present in the central nervous system which degrades myelin proteins. To examine the role of calpain in demyelination associated with optic neuritis, immunocytochemical expression of calpain was evaluated in Lewis rats with experimental optic neuritis. Calpain expression was increased in activated microglia, infiltrating macrophages, activated T cells, and reactive astrocytes in experimental optic neuritis compared to controls. Calpain activity and translational expression were also examined by Western blotting studies measuring the extent of myelin protein degradation, calpain-specific fodrin proteolysis, axonal neurofilament degradation, and calpain proenzyme content. Results showed myelin associated glycoprotein and 68 kD neurofilament protein levels were significantly decreased while calpain translational expression and calpain-autolyzed fodrin levels were significantly increased in experimental optic neuritis compared to controls. Thus, increased activity and translational expression of calpain in optic neuritis may be integral to the pathogenesis of this disorder

Sequential hTERT knockdown and apigenin treatment inhibited invasion and proliferation and induced apoptosis in human malignant neuroblastoma SK-N-DZ and SK-N-BE2 cells. Journal of molecular neuroscience : MN

Abstract Human telomerase reverse transcriptase (hTERT) plays a key role in conferring immortality to human malignant neuroblastomas. We first determined differential expression of hTERT in four human malignant neuroblastoma SH-SY5Y, SK-N-DZ, SK-N-BE2, and IMR-32 cell lines. We then used SK-N-DZ and SK-N-BE2 cell lines, which showed the highest expression of hTERT, to investigate the therapeutic effects of sequential hTERT knockdown and apigenin (APG) treatment. We performed cell invasion assay and studied alterations in expression of matrix metalloproteinases and cell cycle regulatory molecules after this combination therapy. We also investigated induction of apoptosis by using in situ Wright staining, Annexin V staining, and Western blotting. Sequential hTERT knockdown and APG treatment significantly downregulated expression of hTERT so as to cause over 90 % inhibition of cell invasion and 70 % induction of apoptosis in both SK-N-DZ and SK-N-BE2 cell lines. Western blotting demonstrated downregulation of the molecules involved in cell invasion and proliferation, but upregulation of the cell cycle inhibitor and apoptosis-inducing molecules. In conclusion, our current results clearly showed that sequential hTERT knockdown and APG treatment could be a promising therapeutic strategy for effective inhibition of invasion and proliferation and induction of apoptosis in hTERT overexpressing malignant neuroblastoma cells

Sequential hTERT knockdown and apigenin treatment inhibited invasion and proliferation and induced apoptosis in human malignant neuroblastoma SK-N-DZ and SK-N-BE2 cells. Journal of molecular neuroscience : MN

Abstract Human telomerase reverse transcriptase (hTERT) plays a key role in conferring immortality to human malignant neuroblastomas. We first determined differential expression of hTERT in four human malignant neuroblastoma SH-SY5Y, SK-N-DZ, SK-N-BE2, and IMR-32 cell lines. We then used SK-N-DZ and SK-N-BE2 cell lines, which showed the highest expression of hTERT, to investigate the therapeutic effects of sequential hTERT knockdown and apigenin (APG) treatment. We performed cell invasion assay and studied alterations in expression of matrix metalloproteinases and cell cycle regulatory molecules after this combination therapy. We also investigated induction of apoptosis by using in situ Wright staining, Annexin V staining, and Western blotting. Sequential hTERT knockdown and APG treatment significantly downregulated expression of hTERT so as to cause over 90 % inhibition of cell invasion and 70 % induction of apoptosis in both SK-N-DZ and SK-N-BE2 cell lines. Western blotting demonstrated downregulation of the molecules involved in cell invasion and proliferation, but upregulation of the cell cycle inhibitor and apoptosis-inducing molecules. In conclusion, our current results clearly showed that sequential hTERT knockdown and APG treatment could be a promising therapeutic strategy for effective inhibition of invasion and proliferation and induction of apoptosis in hTERT overexpressing malignant neuroblastoma cells