Curcumin induces autophagy to protect vascular endothelial cell survival from oxidative stress damage.

Our study first proposed that curcumin could protect human endothelial cells from the damage caused by oxidative stress via autophagy. Furthermore, our results revealed that curcumin causes some novel cellular mechanisms that promote autophagy as a protective effect. Pretreatment with curcumin remarkably improves the survival of human umbilical vein endothelial cells (HUVECs) from H 2O 2-induced viability loss, which specifically evokes an autophagic response. Exposed to H 2O 2, curcumin-treated HUVECs upregulate the level of microtubule-associated protein 1 light chain 3-II (LC3-II), the number of autophagosomes, and the degradation of p62. We show that this compound promotes BECN1 expression and inhibits the phosphatidylinositol 3-kinase (PtdIns3K)-AKT-mechanistic target of rapamycin (MTOR) signaling pathway. Curcumin can also reverse FOXO1 (a mediator of autophagy) nuclear localization along with causing an elevated level of cytoplasmic acetylation of FOXO1 and the interaction of acetylated FOXO1 and ATG7, under the circumstance of oxidative stress. Additionally, knockdown of FOXO1 by shRNA inhibits not only the protective effects that curcumin induced, but the autophagic process, from the quantity of LC3-II to the expression of RAB7. These results suggest that curcumin induces autophagy, indicating that curcumin has the potential for use as an autophagic-related antioxidant for prevention and treatment of oxidative stress. These data uncover a brand new protective mechanism involving FOXO1 as having a critical role in regulating autophagy in HUVECs, and suggest a novel role for curcumin in inducing a beneficial form of autophagy in HUVECs, which may be a potential multitargeted therapeutic avenue for the treatment of oxidative stress-related cardiovascular diseases.

Hypoxia-induced up-regulation of aquaporin-1 protein in prostate cancer cells in a p38-dependent manner.

BACKGROUND/AIMS: Aquaporin-1 (AQP1) is a glycoprotein that mediates osmotic water transport, its expression has been found to correlate with tumour stage in some tumours. However, the mechanism by which AQP1 protein expression is regulated in tumor cells remains to be fully elucidated. We hypothesized that hypoxia might play an important role in AQP1 induction during tumorigenesis and at the late stages of tumor development. METHODS: Isotonic and serum-free hypoxic models were used to investigate AQP1 expression in PC-3M human prostate cancer cells. RESULTS: AQP1 expression was up-regulated by density-induced pericellular hypoxia and cobalt(II) chloride (CoCl(2))-induced hypoxia at the transcriptional level. Moreover, phosphorylation of p38 mitogen-activated protein kinase (MAPK) was induced by density-induced pericellular hypoxia and CoCl(2)-induced hypoxia, specific inhibitors of p38 MAPK could concentration-dependently block those effects of hypoxia on AQP1 expression. Intracellular calcium ion (Ca(2+)) and protein kinase C (PKC) were shown to be responsible for the activation of p38 MAPK pathway. In addition, AQP1 induction in dense cultures was dependent on lowered oxygen (O(2)) tension. In high cell density culture, certain secretory proteins might induce AQP1 expression indirectly. CONCLUSION: These findings suggest that AQP1 could be induced by hypoxia at transcription level, and the regulation of AQP1 in PC-3M cells is dependent on calcium, PKC and p38 MAPK, as well as low oxygen tension.

Ginsenoside Rg3 attenuates cell migration via inhibition of aquaporin 1 expression in PC-3M prostate cancer cells.

Ginsenoside Rg3 (Rg3), one of the bioactive extracts found in ginseng root, was reported to have anti-cancer activity in various cancer models. The anti-proliferation effect of Rg3 on prostate cancer cells has been well reported. To test whether Rg3 has an anti-metastatic effect on prostate cancer, we treated a highly metastatic PC-3M prostate cancer cell line with Rg3. We found that Rg3 (10µM) led to remarkable inhibition of PC-3M cell migration. Simultaneously, exposure to Rg3 suppressed expression of the aquaporin 1 (AQP1) water channel protein, which has previously been reported to be involved in cell migration. Overexpression of AQP1 attenuated Rg3-induced inhibition of cell migration, and introduction of a shRNA targeting AQP1 abrogated the inhibitory effect of Rg3, although the basal level of cell migration was decreased by RNA interference. In mechanism study, estrogen receptor- and glucocorticoid receptor-dependent pathways are proved uninvolved in the AQP1 regulation by Rg3. However, Rg3 treatment triggered the activation of p38 MAPK; and SB202190, a specific inhibitor of p38 MAPK, antagonized the Rg3-induced regulation of AQP1 and cell migration, suggesting a crucial role for p38 in the regulation process. Deletion analysis of the promoter region of AQP1 was also conducted using dual-luciferase assay, which indicated that the -1000 bp to -200 bp promoter region was involved in the AQP1 regulation by Rg3. In all, we conclude that Rg3 effectively suppresses migration of PC-3M cells by down-regulating AQP1 expression through p38 MAPK pathway and some transcription factors acting on the AQP1 promoter.

Curcumin produces neuroprotective effects via activating brain-derived neurotrophic factor/TrkB-dependent MAPK and PI-3K cascades in rodent cortical neurons.

Curcumin is a major constituent of curcuma longa, a traditional medicine used to manage mental disorders effectively in China. The neuroprotective effects of curcumin have been demonstrated in our previous studies. In the present research, we confirmed this effect by showing that curcumin application promoted the viability of cultured rodent cortical neurons. Moreover, when neurons were pretreated with tyrosine kinase B (TrkB) antibody, known to inhibit the activity of brain-derived neurotrophic factor (BDNF), the protective effect of curcumin was blocked. Additionally, treatment of curcumin increased BDNF and phosphor-TrkB and both of these enhancements can be suppressed by ERK and PI-3K inhibitors. The administration of curcumin led to increased levels of phosphor-ERK and AKT, which were each blocked by MAPK and PI-3K inhibitors. Furthermore, the curcumin-induced increase in phosphorylated cyclic AMP response element binding protein (CREB), which has been implicated as a possible mediator of antidepressant actions, was prevented by MAPK and PI-3K inhibitors. Therefore, we hypothesize the neuroprotection of curcumin might be mediated via BDNF/TrkB-MAPK/PI-3K-CREB signaling pathway.