The transmembrane glycoprotein CD38 catalyzes the synthesis of the calcium mobilizing molecule cyclic ADP-ribose from NAD. In human airway smooth muscle (HASM) cells, the expression and function of CD38 are augmented by the inflammatory cytokine tumor necrosis factor-alpha (TNF-alpha), leading to increased intracellular calcium response to agonists. A glucocorticoid response element in the CD38 gene has been computationally described, providing evidence for transcriptional regulation of its expression. In the present study, we investigated the effects of dexamethasone, a glucocorticoid, on CD38 expression and ADP-ribosyl cyclase activity in HASM cells stimulated with TNF-alpha. In HASM cells, TNF-alpha augmented CD38 expression and ADP-ribosyl cyclase activity, which were attenuated by dexamethasone. TNF-alpha increased NF-kappaB expression and its activation, and dexamethasone partially reversed these effects. TNF-alpha increased the expression of IkappaBalpha, and dexamethasone increased it further. An inhibitor of NF-kappaB activation or transfection of cells with IkappaB mutants decreased TNF-alpha-induced CD38 expression. The results indicate that TNF-alpha-induced CD38 expression involves NF-kappaB expression and its activation and dexamethasone inhibits CD38 expression through NF-kappaB-dependent and -independent mechanisms.

Achievement of long-term survival of patients with lung cancer treated with conventional chemotherapy is still difficult for treatment of metastatic and advanced tumors. Despite recent progress in investigational therapies, survival rates are still disappointingly low and novel adjuvant and systemic therapies are urgently needed. A recently elucidated secretory pathway is attracting considerable interest as a promising anticancer target. The cis-Golgi matrix protein, GOLGA2/GM130, plays an important role in glycosylation and transport of protein in the secretory pathway. In this study, the effects of short hairpin RNA (shRNA) constructs targeting GOLGA2/GM130 (shGOLGA2) on autophagy and lung cancer growth were evaluated in vitro and in vivo. Downregulation of GOLGA2/GM130 led to induction of autophagy and inhibition of glycosylation in A549 cells and in the lungs of K-ras(LA1) mice. Furthermore, downregulation of GOLGA2/GM130 decreased angiogenesis and cancer cell invasion in vitro and suppressed tumorigenesis in lung cancer mice model. The tumor specificity of sequence targeting GOLGA2/GM130 was also demonstrated. Taken together, these results suggest that induction of autophagy by shGOLGA2 may induce cell death rather than cell survival. Therefore, downregulation of GOLGA2/GM130 may be a potential therapeutic option for lung cancer.

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Methylmercury (MeHg) is a well-known human neurotoxic agent whose exposure sources are mainly environmental and aquatic-derived food. MeHg is reported to induce central nervous system disability. However, the exact mechanism of MeHg-induced neurotoxicity is still unknown. In this study, to investigate which cell death signaling pathway is related with MeHg-induced cytotoxicity, the effects of MeHg on apoptosis and autophagy were evaluated in HB1.F3 human neural stem cells (NSCs). Human NSCs were treated with 1 μM of MeHg for 48 hr and the effect of MeHg on cell signaling pathway was elucidated. MeHg inhibited Akt1/mTOR signaling that led to induction of caspase-dependent apoptosis and autophagy in the NSCs. Furthermore, retinoic acid (RA)-induced neuronal differentiation was inhibited by MeHg. Taken together, these results suggest that MeHg inhibits the differentiation of human NSCs by induction of caspase-dependent apoptosis and autophagy.

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