• Archives of Pharmacal Research
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• v.29 no.8
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• pp.657-665
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• 2006

We recently reported that dimethylsphingosine (DMS), a metabolite of sphingolipids, increased intracellular pH and $Ca^{2+}$ concentration in U937 human monocytes. In the present study, we found that dimethylphytosphingosine (DMPH) induced the above responses more robustly than DMS. However, phytosphingosine, monomethylphytosphingosine or trimethylsphingosine showed little or no activity. Synthetic C3 deoxy analogues of sphingosine did show similar activities, with the C16 analogue more so than C18. The following structure-activity relationships were observed between DMS derivatives and the intracellular pH and $Ca^{2+}$ concentrations in U937 monocytes; 1) dimethyl modification is important for the DMS-induced increase of intracellular pH and $Ca^{2+}$, 2) the addition of an OH group on C4 enhances both activities, 3) the deletion of the OH group on C3 has a negligible effect on the activities, and 4) C16 appears to be more effective than C18. We also found that W-7, a calmodulin inhibitor, blocked the DMS-induced pH increase, whereas, KN-62, ML9, and MMPX, specific inhibitors for calmodulin-dependent kinase II, myosin light chain kinase, and $Ca^{2+}$-calmodulin-dependent phosphodiesterase, respectively, did not affect DMS-induced increases of pH in the U937 monocytes.

• Reproductive and Developmental Biology
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• v.36 no.3
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• pp.173-181
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• 2012

Sphingosine-1-phosphate (S1P) has a many function involved proliferation, differentiation and survival of many cells. In this study, to investigate whether S1P improve the developmental competence of porcine embryos, 50 nM of S1P were supplemented during in vitro maturation (with EGF or without EGF) medium and/or in vitro culture (IVC) medium. Addition of S1P was significantly increased the rate of oocytes reaching metaphase II (MII) compared to the control (83.5 vs. 64.1%) in without EGF medium, but not with EGF medium (89.5 vs. 84.6%). When treated with $1{\mu}M$ of N1N-dimethylsphingosine (DMS), a sphingosine kinase inhibitor which is blocked endogenous generation of S1P, the meiotic progression rates to MII stage (without EGF: 45.2 and with EGF: 66.7%) were significantly decreased and degeneration rates (without EGF: 51.2 and with EGF: 30.1%) were increased in both medium compared to control group during IVM periods. Also, the rates of blastocyst formation was significantly increased in the S1P treated group compared to control group (29.0 vs. 19.2%) of EGF supplemented medium, whereas there were no effect in the EGF free medium (9.0 vs. 10.5%). After 12 h IVM, the phosphorylation of ERK1 and ERK2, which is major signaling pathway of MAP kinase, were increased in the S1P group than that of control or DMS group. When supplemented of S1P during IVC, the rates of blastocyst formation and total cell number (30.2% and 40.6) were significantly increased in S1P-treated group compared with control (20.1% and 32.5), DMS (12.3% and 25.1), and S1P plus DMS group (24.7% and 33.6). The percentage of apoptosis nuclei in the S1P group was significantly decreased than other groups. Also, the rates of blastocyst formation (26.7 vs. 14%) and total cell number (42.8 vs. 32.5) were significantly increased in the S1P group than those of control group when S1P added during the entire IVM and IVC periods. Taken together, our results indicate that S1P supplementation in IVM and/or IVC medium affects beneficial effect of meiotic maturation and subsequent developmental competence of porcine embryos.

• The Korean Journal of Physiology and Pharmacology
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• v.2 no.6
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• pp.743-752
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• 1998

The atrial acetylcholine-activated $K^+\;(K_{ACh})$ channel is gated by the pertussis toxin-sensitive inhibitory G $(G_K)$ protein. Earlier studies revealed that ATP alone can activate the $K_{ACh}$ channel via transphosphorylation mediated by nucleoside-diphosphate kinase (NDPK) in atrial cells of rabbit and guinea pig. This channel can be activated by various agonists and also modulated its function by phosphorylation. ATP-induced $K_{ACh}$ channel activation (AIKA) was maintained in the presence of the NDPK inhibitor, suggesting the existence of a mechanism other than NDPK-mediated process. Here we hypothesized the phosphorylation process as another mechanism underlying AIKA and was undertaken to examine what kinase is involved in atrial cells isolated from the rat heart. Single application of 1 mM ATP gradually increased the activity of $K_{ACh}$ channels and reached its maximum $40{\sim}50$ sec later following adding ATP. AIKA was not completely reduced but maintained by half even in the presence of NDPK inhibitor. Neither ADP nor a non-hydrolyzable ATP analogue, AMP-PNP can cause AIKA, while a non-specific phosphatase, alkaline phosphatase blocked completely AIKA. PKC antagonists such as sphingosine or tamoxifen, completely blocked AIKA, whereas PKC catalytic domain increased AIKA. Taken together, it is suggested that the PKC-mediated phosphorylation is partly involved in AIKA.

• Development and Reproduction
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• v.2 no.1
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• pp.9-20
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• 1998

It has been wel known that phospholipase C(PLC) plays an important role in the intracellular signaling in a variety of cell types. However, involvement of PLC in mouse oocyte maturation and preimplantation embryo development remains unknown. The present study examined the expression patterns of the mouse PLC \beta 1 and \gamma 1 during oocyte maturatio and preimplantation embryo development study examined the expression patterns of the mouse PLC \beta 1 and \gamma 1 during oocyte maturation and preimplantation embryo development by the competitive reverse transcription-polymerase chain reaction (RT-PCR method). PLC \gamma 1 mRNA (0.1 fg) was readily detected in germinal vesicle (GV)-stage oocyte and its level was reduced as meiotic resumption proceeded. PLC-\beta 1 mRNA (<0.1 fg) as detected at low level at GV-stage oocytes and scarcely detected at germinal vescle breakdown (GVBD)-stage oocytes. After fertilization, both PLC \beta 1 and \gamma 1 mRNA levels began to increase at morula-stage embryos (0.2 fg) and were more prominent in blastocyst-stage embryos(1 fg). to elucidate the possible involvement of PLC via protein kinase C(PKC) pathway during oocyte maturation and preimplantation embryo development , the effects of sphingosine (PKC inhibitor), sn-$diC_{8}$(PKC activator) anc U73122 (PLC ingibitor) were examined. Treatment of GV-stage oocytes with sphingosine (20 \mu M) facilitated the meiotic resuption by 10-20 over the control within 1 h as judged by GVBD, whereas U73122 failed to show any significant effect. U73122 (10 \mu M) effectively blocked the compaction of morula, while sn-$diC_{8}$(50 \mu M). In summary, the present study shows that the mouse PLC \beta 1 and \gamma 1 are expressed in a developmental stage-specific manner and PLC-PKC pathway may be involved in early preimplantation embryo development.

• Biomolecules & Therapeutics
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• v.20 no.5
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• pp.470-476
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• 2012

Resveratrol, a chemopreventive agent, is rapidly metabolized in the intestine and liver via glucuronidation. Thus, the pharmacokinetics of resveratrol limits its efficacy. To improve efficacy, the activity of resveratrol was investigated in the context of sphingolipid metabolism in human gastric cancer cells. Diverse sphingolipid metabolites, including dihydroceramides (DHCer), were tested for their ability to induce resveratrol cytotoxicity. Exposure to resveratrol ($100{\mu}M$) for 24 hr induced cell death and cell cycle arrest in gastric cancer cells. Exposure to the combination of resveratrol and dimethylsphingosine (DMS) increased cytotoxicity, demonstrating that sphingolipid metabolites intensify resveratrol activity. Specifically, DHCer accumulated in a resveratrol concentration-dependent manner in SNU-1 and HT-29 cells, but not in SNU-668 cells. LC-MS/MS analysis showed that specific DHCer species containing C24:0, C16:0, C24:1, and C22:0 fatty acids chain were increased by up to 30-fold by resveratrol, indicating that resveratrol may partially inhibit DHCer desaturase. Indeed, resveratrol mildly inhibited DHCer desaturase activity compared to the specific inhibitor GT-11 or to retinamide (4-HPR); however, in SNU-1 cells resveratrol alone exhibited a typical cell cycle arrest pattern, which GT-11 did not alter, indicating that inhibition of DHCer desaturase is not essential to the cytotoxicity induced by the combination of resveratrol and sphingolipid metabolites. Resveratrol-induced p53 expression strongly correlated with the enhancement of cytotoxicity observed upon combination of resveratrol with DMS or 4-HPR. Taken together, these results show that DHCer accumulation is a novel lipid biomarker of resveratrol-induced cytotoxicity in human gastric cancer cells.

• Molecules and Cells
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• v.21 no.1
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• pp.42-51
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• 2006

We investigated the mechanism of contraction induced by S1P in esophageal smooth muscle cells. Western blot analysis demonstrated that $S1P_1$, $S1P_2$, $S1P_3$, and $S1P_5$ receptors existed in the cat esophagus. Only penetration of EDG-5 ($S1P_2$) antibody into permeabilized cells inhibited S1P-induced contraction. Pertussis toxin (PTX) also inhibited contraction, suggesting that it was mediated by $S1P_2$ receptors coupled to a PTXsensitive $G_i$ protein. Specific antibodies to $G_{i2}$, $G_q$ and $G_{\beta}$ inhibited contraction, implying that the S1P-induced contraction depends on PTX-insensitive $G_q$ and $G_{\beta}$ dimers as well as the PTX-sensitive $G_{i2}$. Contraction was not affected by the phospholipase $A_2$ inhibitor DEDA, or the PLD inhibitor ${\rho}$-chloromercuribenzoate, but it was abolished by the PLC inhibitor U73122. Incubation of permeabilized cells with $PLC{\beta}3$ antibody also inhibited contraction. Contraction involved the activation of a PKC pathway since it was affected by GF109203X and chelerythrine. Since $PKC{\varepsilon}$ antibody inhibited contraction, $PKC{\varepsilon}$ may be required. Preincubation of the muscle cells with the MEK inhibitor PD98059 blocked S1P-induced contraction, but the p38 MAP kinase inhibitor SB202190 did not. In addition, co-treatment of cells with GF 109203X and PD98059 did not have a synergistic effect, suggesting that these two kinases are involved in the same signaling pathway. Our data suggest that S1P-induced contraction in esophageal smooth muscle cells is mediated by $S1P_2$ receptors coupled to PTX-sensitive $G_{i2}$ proteins, and PTX-insensitive $G_q$ and $G_{\beta}$ proteins, and that the resulting activation of the $PLC{\beta}3$ and $PKC{\varepsilon}$ pathway leads to activation of a p44/p42 MAPK pathway.