Topogenesis and homeostasis of fatty acyl-CoA reductase 1.

Peroxisomal fatty acyl-CoA reductase 1 (Far1) is essential for supplying fatty alcohols required for ether bond formation in ether glycerophospholipid synthesis. The stability of Far1 is regulated by a mechanism that is dependent on cellular plasmalogen levels. However, the membrane topology of Far1 and how Far1 is targeted to membranes remain largely unknown. Here, Far1 is shown to be a peroxisomal tail-anchored protein. The hydrophobic C terminus of Far1 binds to Pex19p, a cytosolic receptor harboring a C-terminal CAAX motif, which is responsible for the targeting of Far1 to peroxisomes. Far1, but not Far2, was preferentially degraded in response to the cellular level of plasmalogens. Experiments in which regions of Far1 or Far2 were replaced with the corresponding region of the other protein showed that the region flanking the transmembrane domain of Far1 is required for plasmalogen-dependent modulation of Far1 stability. Expression of Far1 increased plasmalogen synthesis in wild-type Chinese hamster ovary cells, strongly suggesting that Far1 is a rate-limiting enzyme for plasmalogen synthesis.

Exploring the Physiological and Psychological Effects of Digital Shinrin-Yoku and Its Characteristics as a Restorative Environment.

This study investigated the physiological and psychological therapeutic effects of a digital Shinrin-yoku environment constructed indoors in an urban facility as well as the characteristics of the environment that contribute to restorativeness (restorative traits). We measured the fluctuations in the physical and mental states of 25 subjects by obtaining both before-after measurements and continuous measurements while exposed to a digital Shinrin-yoku environment that reproduced visual, auditory, and olfactory elements. The results demonstrated that the parasympathetic nerve activity was significantly increased and that the heart rate was significantly decreased during the exposure compared with that during the resting state. As for mood, five of the six Profile of Mood States (POMS) scales ("Tension-Anxiety," "Depression," "Anger-Hostility," "Fatigue," and "Confusion") were significantly decreased after the experience. In addition, psychological restorative effects were also confirmed, with a significant decrease in "negative affect" (measured using the Positive and Negative Affect Schedule (PANAS)) and a significant increase in the sense of restorativeness (Restorative Outcome Scale (ROS)) after the experience. In contrast, comparing the digital Shinrin-yoku environment with the actual forest environment and the urban environment using POMS, PANAS, ROS, and Perceived Restorativeness Scale (PRS), the psychological effects and environmental traits of the digital Shinrin-yoku were found to be considerably similar to those of the actual forest environment.

The inhibitory effect of connexin 32 gene on metastasis in renal cell carcinoma.

We have previously reported that connexin (Cx) 32 gene, a member of gap junctions, was specifically downregulated in human renal cell carcinoma (RCC) and it acts as a tumor suppressor against RCC. Because there is no standard therapy for advanced RCC, we investigated the anti-metastatic effect of Cx32 to seek a possibility of new RCC therapy. In this study, we used human metastatic RCC cell (Caki-1), and established Cx32-expressed cell clone (Caki-1T) or only mock-transfected cell clone (Caki-1W). For experimental production of metastases, the cells were injected into the lateral tail vein of SCID mice. Seventy days after inoculation, metastatic colonies were observed in Caki-1W inoculated group, though none of them were in Caki-1T inoculated group. The plasma VEGF concentration was significantly lower in Caki-1T group compared to Caki-1W group. To investigate where Cx32 effects on, we also tried in vitro analysis and found that the malignant phenotypes involving metastasis steps were significantly decreased in Caki-1T under hypoxia, a mimic condition of internal tumor environment. After hypoxia treatment, the protein level of HIF-2alpha, which plays main role for hypoxia adaptation, was observed to increase in Caki-1W, whereas no expression was observed in Caki-1T. We investigated the activation of Src, which is required for stabilization of HIF-2alpha, is suppressed in Caki-1T compared to Caki-1W. These results suggest that Cx32 inhibits hypoxia adaptation governed by HIF-2alpha, and this may help to reduce the metastasis of RCC cells.

Enhancing effect of connexin 32 gene on vinorelbine-induced cytotoxicity in A549 lung adenocarcinoma cells.

PURPOSE: Connexin (Cx) genes exert negative growth effects on tumor cells with certain cell specificity, and tumor-suppressive effects of the Cx genes contribute to enhancement of chemotherapeutical agents-induced cytotoxicity in some cancer cells. Since we and others have been reported that Cx32 acts as a tumor suppressor gene in lung adenocarcinomas, this study was undertaken to estimate if the combination of Cx32-dependent tumor-suppressive effect and vinorelbine (VBN), a chemotherapeutic agent which has been utilized for clinical lung adenocarcinoma treatment, could be effective in enhancing the sensitivity of the lung cancer to VBN treatment. METHODS: We established the A549 cells (a human lung adenocarcinoma cell line) which had stable expression of Cx32 and estimated effect of Cx32 on VBN-induced cytotoxicity in the established cells. RESULTS: Cx32 expression in A549 cells significantly potentiated VBN-induced cytotoxicity on the cells due to enhancement of apoptosis induction. The enhancing cytotoxicity in A549 cells by Cx32 mainly depended on a decrease in expression of multi-drug resistance-1 (MDR-1) gene responsible for reduction of VBN accumulation into the cells. We also observed that silencing of Cx32 by siRNA treatment elevated the expression level of MDR-1 mRNA in A549 cells and that inhibition of MDR-1 gene product-dependent function enhanced VBN-induced cytotoxicity in the cells. CONCLUSION: These results suggest that Cx32 contributes to the enhancement of VBN-induced cytotoxicity in A549 cells via the reduction of MDR-1 expression.

Connexin32 as a tumor suppressor gene in a metastatic renal cell carcinoma cell line.

Connexin genes expressing gap junction proteins have tumor-suppressive effects on primary cancers with certain cell specificity, but the suppressive effects on metastatic cancers are still conflicting. In this study, we show that connexin32 (Cx32) has a strong tumor-suppressive effect on a human metastatic renal cell carcinoma cell line (Caki-1 cell). Cx32 expression in Caki-1 cells reduced in vitro malignant phenotypes of the cells such as anchorage independency and invasion capacity. Furthermore, the Cx32 expression drastically reduced the development of Caki-1 cells in nude mice. We also determined that Cx32 reduced the malignant phenotypes in Caki-1 cells mainly through the inactivation of Src signaling. Especially, Cx32-dependent inactivation of Src decreased the production of vascular epithelial growth factor (VEGF) via the suppression of signal transducers and activators of transcription 3 (Stat3) activation, and we confirmed this result using short interfering RNA. In nude mice, Cx32-transfected Caki-1 cells showed lower serum level of VEGF comparing mock transfectant, and the development of the cells in nude mice positively related to the VEGF level. These data suggest that Cx32 acts as a tumor suppressor gene in Caki-1 cells and that the tumor-suppressive effect partly depends on the inhibition of Src-Stat3-VEGF signal pathway.

Connexin 32 down-regulates the fibrinolytic factors in metastatic renal cell carcinoma cells.

Fibrinolytic factors have an important role in tumor progression through the degradation of extracellular matrix. The increased levels of urokinase-type plasminogen activator (uPA), uPA-receptor (uPAR) and type-1 PA inhibitor (PAI-1) are reported in human renal cell carcinoma (RCC). Connexin (Cx) gene, a member of gap junction, is known to act as a tumor suppressor gene. We have reported that Cx32 improves malignant phenotypes of metastatic RCC cells via the inhibition of Src-dependent signaling. In this study, we examined the effect of expression of Cx32 gene on the production of uPA, uPAR and PAI-1, and on the induction of PAI-1 stimulated by hypoxia in a human metastatic RCC cell line, Caki-1 cells. Cx32 expression decreased both mRNA level and production of PAI-1, uPA and uPAR in Caki-1 cells. Cx32 also decreased hypoxia-inducible factor (HIF)-1alpha and HIF-2alpha mRNA level. PP1, a Src inhibitor, significantly decreased PAI-1, uPA, uPAR and HIF-alpha mRNA levels in Caki-1 cells. Furthermore, Cx32 suppressed the induction of HIF-2alpha protein in Caki-1 cells under hypoxia. PAI-1 mRNA level in Cx32-transfected Caki-1 cells was lower than that of mock transfectant under hypoxic conditions. These results suggest that Cx32 might reduce PAI-1, uPA and uPAR production in metastatic RCC cells via the inhibition of Src-dependent induction of HIF-1alpha and HIF-2alpha gene expression and that Cx32 might suppress hypoxia-inducible gene expression under hypoxic conditions.

Expression patterns of connexin 26 and connexin 43 mRNA in canine benign and malignant mammary tumours.

The expression patterns of connexin (Cx) genes, encoding gap junctional proteins, are tissue- and cell-specific and, as their expression is mostly suppressed during carcinogenic processes, they are appropriate for monitoring tumour development. In this study, using reverse transcriptase-coupled polymerase chain reaction (RT-PCR), the expression of Cx mRNAs was examined in seven normal canine mammary glands and in 31 mammary gland tumour samples. Cx26 and Cx43 gene expression was studied in all normal tissues using specific Cx26 and Cx43 primers. When the expression patterns of Cx26 and Cx43 genes were analyzed in several types of canine mammary gland tumours, it was noted that it was the loss of Cx26 expression rather than the occurrence of Cx43 expression that was associated with malignancy. These results suggest that Cx26 plays an important role in tumourigenesis of canine mammary gland.

Peroxisome proliferator-activated receptor delta as a molecular target to regulate lung cancer cell growth.

It has been assumed that prostaglandin (PG)I2 signaling contributes to the negative growth control of lung cancer cells; however, the mechanism remains unresolved. PGI2 functions through a cell surface G protein-coupled receptor (prostaglandin I2-binding receptor, IP) and also exerts an effect by interacting with a nuclear hormone receptor, peroxisome proliferator-activated receptor delta (PPARdelta). We found that PPARdelta was a key molecule of PGI2 signaling to give negative growth control of lung cancer cells (A549), using carbarprostacyclin, a PGI2 agonist for IP and PPARdelta, and L-165041, a PPARdelta agonist. Furthermore, PPARdelta-induced cell growth control was reinforced by the inhibition of cyclooxygenase. These results suggest that PPARdelta activation under the suppression of PG synthesis is important to regulate lung cancer cell growth.

A Src family inhibitor (PP1) potentiates tumor-suppressive effect of connexin 32 gene in renal cancer cells.

Connexin (Cx) genes exert negative growth effects on tumor cells with certain cell specificity. We have recently reported that Cx32 acts as a tumor suppressor gene in renal cancer cells due to the inhibition of Src-dependent signaling. In line with the previous study, here we examined if a Src family inhibitor (PP1) could potentiate tumor-suppressive effect of Cx32 in Caki-2 cell from human renal cell carcinoma. In order to clarify the potentialization of PP1, using Cx32-transfected Caki-2 cells and mock-transfected Caki-2 cells, we estimated difference in cytotoxic effect of PP1 on the two cell clones in vitro as well as in vivo. PP1 showed more cytotoxic effect on Caki-2 cells having Cx32 positive expression than that of Cx32 negative expression at lower doses. This potentialization was also observed in xenograft model of nude mice. The potentialization of the effect mainly depended on the induction of apoptosis but not the control of cell growth. In conjugation with this event, the reduction of anti-apoptotic molecules (Bcl-2 and Bcl-xL) was caused by the combination of Cx32 expression and PP1 treatment in Caki-2 cells. These results suggest that PP1 potentiates tumor-suppressive effect of connexin 32 gene in renal cancer cells through the reduction of anti-apoptotic molecules.

Connexin 32 potentiates vinblastine-induced cytotoxicity in renal cell carcinoma cells.

We have reported that connexin (Cx) 32 gene, a member of gap junction protein family, acts as a tumor suppressor gene in human renal cell carcinoma (RCC). Of solid tumors, RCC is one of the most chemoresistant cancers, and there is no effective cancer chemotherapy against RCC at present. In this study, we examined if the combination of Cx32-dependent tumor-suppressive effect and vinblastine (VBL), a chemotherapeutic agent which has been utilized for clinical RCC treatment, could be effective in enhancing the sensitivity of RCC to VBL treatment. Cx32 expression in a human metastatic RCC cell (Caki-1 cell) significantly enhanced in vitro and in vivo VBL-induced cytotoxicity on the cell. Cx32 expression in the RCC cells potentiated VBL-induced apoptosis compared to the Cx32-negative RCC cells in vitro as well as in vivo. The enhancing apoptosis in the RCC cells by Cx32 mainly depended on the decrease of P-glycoprotein (P-gp), a multidrug resistance gene-1 (MDR-1) product responsible for reduction of VBL accumulation into the cells. We also observed that silencing of Cx32 by short interfering RNA (siRNA) treatment elevated the level of P-gp in Caki-1 cells and that inhibition of P-gp function enhanced VBL-induced apoptosis in the RCC cells. These results suggest that Cx32 is effective to enhance VBL-induced cytotoxicity in Caki-1 cells via the reduction of P-gp. Overall, it seems that the combination of Cx32-dependent tumor-suppressive effect and VBL is promising as a new cancer therapy against RCC.

Induction of cytotoxicity in human lung adenocarcinoma cells by 6-O-carboxypropyl-alpha-tocotrienol, a redox-silent derivative of alpha-tocotrienol.

Tocotrienols are one of the most potent anticancer agents of all natural compounds and the anticancer property may be related to the inactivation of Ras family molecules. The anticancer potential of tocotrienols, however, is weakened due to its short elimination half life in vivo. To overcome the disadvantage and reinforce the anticancer activity in tocotrienols, we synthesized a redox-silent analogue of alpha-tocotrienol (T3), 6-O-carboxypropyl-alpha-tocotrienol (T3E). We estimated the possibility of T3E as a new anticancer agent against lung adenocarcinoma showing poor prognosis based on the mutation of ras gene. T3E showed cytotoxicity against A549 cells, a human lung adenocarcinoma cell line with a ras gene mutation, in a dose-dependent manner (0-40 microM), whereas T3 and a redox-silent analogue of alpha-tocopherol (T), 6-O-carboxypropyl-alpha-tocopherol (TE), showed much less cytotoxicity in cells within 40 microM. T3E cytotoxicity was based on the accumulation of cells in the G1-phase of the cell-cycle and the subsequent induction of apoptosis. Similar to this event, 24-hr treatment of A549 cells with 40 microM T3E caused the inhibition of Ras farnesylation, and a marked decrease in the levels of cyclin D required for G1/S progression in the cell-cycle and Bcl-xL, a key anti-apoptotic molecule. Moreover, the T3E-dependent inhibition of RhoA geranyl-geranylation is an inducing factor for the occurrence of apoptosis in A549 cells. Our results suggest that T3E suppresses Ras and RhoA prenylation, leading to negative growth control against A549 cells. In conclusion, a redox-silent analogue of T3, T3E may be a new candidate as an anticancer agent against lung adenocarcinoma showing poor prognosis based on the mutation of ras genes.

Cytotoxic effect of the Her-2/Her-1 inhibitor PKI-166 on renal cancer cells expressing the connexin 32 gene.

We have reported that connexin (Cx) 32 acts as a tumor suppressor gene in renal cancer cells partly due to Her-2 inactivation. Here, we determined if a Her-2/Her-1 inhibitor (PKI-166) can enhance the tumor-suppressive effect of Cx32 in Caki-2 cells from human renal cell carcinoma. The expression of Cx32 in Caki-2 cells was required for PKI-166-induced cytotoxic effect at lower doses. The cyctotoxicity was dependent on the occurrence of apoptosis and partly mediated by Cx32-driven gap junction intercellular communications. These results suggest that PKI-166 further supports the tumor-suppressive effect of the Cx32 gene in renal cancer cells through the induction of apoptosis.

Contribution of the Src family of kinases to the appearance of malignant phenotypes in renal cancer cells.

Although the constitute activation of the Src family of kinases (Src) has been established as a poor prognostic factor in several types of cancer, the role of Src in renal cell carcinoma (RCC) has not been defined. This study aimed to determine whether Src could contribute to the appearance of malignant phenotypes in RCC. The role of Src in the appearance of malignant phenotypes in RCC was examined in two human renal cancer cell lines, Caki-1 from human metastatic RCC and ACHN from human primary RCC. Src activity in Caki-1 cells was higher than that in ACHN cells, and this difference corresponded to the difference of PP1 (a Src family inhibitor)-induced cytotoxicity on the two cells. The difference in cytotoxicity between the cells did not depend on cell cycle regulation but on the induction of apoptosis, and the difference in apoptosis particularly related to the reduction of the Bcl-xL level. Furthermore, in Caki-1 cells with higher Src activity, Src stimulated the production of vascular endothelial growth factor (VEGF), partially via the activation of Stat3, and the inhibition of Src activity caused a reduction of the VEGF level in serum, angiogenesis, and tumor development in a xenograft model. These results suggested that Src contributed to the appearance of malignant phenotypes in renal cancer cells, particularly due to the resistance against apoptosis by Bcl-xL and angiogenesis stimulated by Src-Stat3-VEGF signaling.