Apoptosis of human lung cancer cells by curcumin mediated through up-regulation of "growth arrest and DNA damage inducible genes 45 and 153".

The expression of "growth arrest and DNA damage inducible genes 45 and 153" is related to apoptotic induction of cells. GADD45 is an effector gene of the tumor suppressor p53, and GADD153 is associated with cellular function of cancer prevention. Curcumin, isolated from the plant Curcuma longa (LINN), has been investigated as a promising cancer preventive in food because curcumin, a phenolic and coloring compound, is widely ingested in the Indian subcontinent. However, the exact mechanisms of action of curcumin have not yet been clearly elucidated. Based on our successful results with green tea catechins as cancer preventive, we studied the relationship between the expression of GADD45 and 153 and apoptotic induction in human lung cancer cell line PC-9. In our study curcumin increased the expression of GADD45 and 153 in a p53-independent manner. Curcumin also inhibited the growth of PC-9 cells and induced G(1)/S arrest of the cell-cycle followed by strong induction of apoptosis. Treatment with GADD45 and 153 small interfering RNAs (siRNAs) inhibited the apoptotic induction in PC-9 cells by curcumin. Moreover, curcumin induced the expression of cyclin dependent kinase inhibitor genes p21 and p27, while it inhibited the expression of numerous genes, including Bcl-2, cyclin D1, CDK2, CDK4 and CDK6. All the results with PC-9 cells suggest that the up-regulation of GADD45 and 153 by curcumin is a prime mechanism in the anticancer activity of curcumin.

New role of (-)-epicatechin in enhancing the induction of growth inhibition and apoptosis in human lung cancer cells by curcumin.

Curcumin, a phenolic compound isolated from the plant Curcuma longa (Linn), is ingested every day in the Indian subcontinent and is well reported to possess cancer-preventive activity. To achieve effective cancer prevention with curcumin, we need to find a new method to enhance the effects of curcumin in the diet. Based on our evidence that (-)-epicatechin (EC), an inert catechin, enhances the cancer-preventive activity of green tea catechins, we studied the enhancing effects of EC on inductions of growth inhibition and apoptosis in human lung cancer cell lines PC-9 and A549 with curcumin. The combination of curcumin with EC significantly increased the inhibition of cell growth compared with curcumin or EC alone. The combination similarly increased both apoptosis and expression of GADD153 and GADD45 genes, associated with their enhanced protein production. Knockdown of GADD153 or GADD45 by small interfering RNA abrogated the apoptosis induction and growth inhibition induced by the combination, indicating the crucial role of their upregulation. Treatments of PC-9 cells with c-Jun-NH(2)-kinase inhibitor SP600125, with p38 mitogen-activated protein kinase inhibitor SB202190 and with PD98059 (extracellular signal-regulated kinase 1/2 inhibitor) all increased the upregulation of GADD153 and GADD45 genes by the combination. Because EC was previously shown to enhance the incorporation of EGCG into PC-9 cells, we think that EC has similar effects on curcumin. This report is the first report on the enhancing effects of EC on curcumin, and the data suggest that EC plays a significant role in the enhancement of the cancer-preventive activity of curcumin in the diet.

Identification of a vesicular aspartate transporter.

Aspartate is an excitatory amino acid that is costored with glutamate in synaptic vesicles of hippocampal neurons and synaptic-like microvesicles (SLMVs) of pinealocytes and is exocytosed and stimulates neighboring cells by binding to specific cell receptors. Although evidence increasingly supports the occurrence of aspartergic neurotransmission, this process is still debated because the mechanism for the vesicular storage of aspartate is unknown. Here, we show that sialin, a lysosomal H(+)/sialic acid cotransporter, is present in hippocampal synaptic vesicles and pineal SLMVs. RNA interference of sialin expression decreased exocytosis of aspartate and glutamate in pinealocytes. Proteoliposomes containing purified sialin actively accumulated aspartate and glutamate to a similar extent when inside positive membrane potential is imposed as the driving force. Sialin carrying a mutation found in people suffering from Salla disease (R39C) was completely devoid of aspartate and glutamate transport activity, although it retained appreciable H(+)/sialic acid cotransport activity. These results strongly suggest that sialin possesses dual physiological functions and acts as a vesicular aspartate/glutamate transporter. It is possible that people with Salla disease lose aspartergic (and also the associated glutamatergic) neurotransmission, and this could provide an explanation for why Salla disease causes severe neurological defects.

Identification of a vesicular nucleotide transporter.

ATP is a major chemical transmitter in purinergic signal transmission. Before secretion, ATP is stored in secretory vesicles found in purinergic cells. Although the presence of active transport mechanisms for ATP has been postulated for a long time, the proteins responsible for its vesicular accumulation remains unknown. The transporter encoded by the human and mouse SLC17A9 gene, a novel member of an anion transporter family, was predominantly expressed in the brain and adrenal gland. The mouse and bovine counterparts were associated with adrenal chromaffin granules. Proteoliposomes containing purified transporter actively took up ATP, ADP, and GTP by using membrane potential as the driving force. The uptake properties of the reconstituted transporter were similar to that of the ATP uptake by synaptic vesicles and chromaffin granules. Suppression of endogenous SLC17A9 expression in PC12 cells decreased exocytosis of ATP. These findings strongly suggest that SLC17A9 protein is a vesicular nucleotide transporter and should lead to the elucidation of the molecular mechanism of ATP secretion in purinergic signal transmission.