• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.76.2-76.2
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• 2003

Although sphingosine-1-phosphate (S1P) is a well-known mitogen, our results show that S1P potently inhibits keratinocyte proliferation, and that this leads the inhibition of DNA synthesis. Interestingly, the prolonged activation of extracellular signal-regulated protein kinase (ERK) and the transient inactivation of Akt/protein kinase B (PKB) were also oberved in concert with the inhibition of keratinocyte proliferation by S1P. To further verify the anti-proliferative action of S1P, we examined changes in cell cycle related proteins. (omitted)

• Molecules and Cells
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• 제23권1호
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• pp.11-16
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• 2007

N,N-dimethyl-D-erythro-sphingosine (DMS) is an N-methyl derivative of sphingosine and an inhibitor of protein kinase C (PKC) and sphingosine kinase (SK). In the present study, we examined the effects of DMS on intracellular $Ca^{2+}$ concentration, pH, and glutamate uptake in human 1321N1 astrocytes. DMS increased intracellular $Ca^{2+}$ concentration and cytosolic pH in a concentration-dependent manner. Pretreatment of the cells with the $G_{i/o}$ protein inhibitor PTX and the PLC inhibitor U73122 had no obvious effect. However, removal of extracellular $Ca^{2+}$ with the $Ca^{2+}$ chelator EGTA or depletion of intracellular $Ca^{2+}$ stores with thapsigargin impeded the DMS-induced increase of intracellular $Ca^{2+}$ concentration. Pretreatment of cells with $NH_4Cl$ or monensin reduced the DMS-induced $Ca^{2+}$ increase. However, inhibition of the DMS-induced $Ca^{2+}$ increase with BAPTA did not influence the DMS-induced pH increase. DMS also inhibited glutamate uptake by the 1321N1 astrocytes in a concentration-dependent manner. It also increased intracellular $Ca^{2+}$ and pH in PC12 neuronal cells. Our observations on the effects of DMS on 1321N1 astrocytes and PC12 neuronal cells point to a physiological role of DMS in the brain.

• Journal of Photoscience
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• 제9권2호
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• pp.433-435
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• 2002

In the present study, we investigated the actions of sphingosine-I-phosphate (SPP) in Mel-Ab melanocytes. We observed the cytoprotective effect of SPP on UVB-induced cell death. Following exposure of cells to UVB, a significant protective effect was seen in cultures pretreated with SPP. Since SPP is well known as a mitogenic agent, it is possible that the mitogenic effect of SPP may contribute to cell survival. Surprisingly, we found that SPP inhibited DNA-synthesis significantly. We were next interested in the regulation of the extracellular signal-regulated protein kinase (ERK) and Akt pathways by SPP. We clearly observed that SPP potently stimulated the phosphorylation of both ERK and Akt against UVB-induced cell death. Based on these results, we conclude that SPP may show its cytoprotective effect through ERK and Akt activation.

• Biomolecules & Therapeutics
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• 제27권3호
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• pp.318-326
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• 2019

Sphingosine 1-phosphate (S1P) levels are often found to be elevated in serum, bronchoalveolar lavage, and lung tissue of idiopathic pulmonary fibrosis patients and experimental mouse models. Although the roles of sphingosine kinase 1 and S1P receptors have been implicated in fibrosis, the underlying mechanism of fibrosis via Sphingosine 1-phosphate receptor 2 ($S1P_2$) has not been fully investigated. Therefore, in this study, the roles of $S1P_2$ in lung inflammation and fibrosis was investigated by means of a bleomycin-induced lung fibrosis model and lung epithelial cells. Bleomycin was found to induce lung inflammation on day 7 and fibrosis on day 28 of treatment. On the $7^{th}$ day after bleomycin administration, $S1P_2$ deficient mice exhibited significantly less pulmonary inflammation, including cell infiltration and pro-inflammatory cytokine induction, than the wild type mice. On the $28^{th}$ day after bleomycin treatment, severe inflammation and fibrosis were observed in lung tissues from wild type mice, while lung tissues from $S1P_2$ deficient mice showed less inflammation and fibrosis. Increase in TGF-${\beta}1$-induced extracellular matrix accumulation and epithelial-mesenchymal transition were inhibited by JTE-013, a $S1P_2$ antagonist, in A549 lung epithelial cells. Taken together, pro-inflammatory and pro-fibrotic functions of $S1P_2$ were elucidated using a bleomycin-induced fibrosis model. Notably, $S1P_2$ was found to mediate epithelial-mesenchymal transition in fibrotic responses. Therefore, the results of this study indicate that $S1P_2$ could be a promising therapeutic target for the treatment of pulmonary fibrosis.

• BMB Reports
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• 제52권3호
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• pp.220-225
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• 2019

We have identified a mechanism to diminish the proliferative capacity of cells during cell expansion using human adipose-derived stromal cells (hAD-SCs) as a model of replicative senescence. hAD-SCs of high-passage numbers exhibited a reduced proliferative capacity with accelerated cellular senescence. Levels of key bioactive sphingolipids were significantly increased in these senescent hAD-SCs. Notably, the transcription of sphingosine kinase 1 (SPHK1) was down-regulated in hAD-SCs at high-passage numbers. SPHK1 knockdown as well as inhibition of its enzymatic activity impeded the proliferation of hAD-SCs, with concomitant induction of cellular senescence and accumulation of sphingolipids, as seen in high-passage cells. SPHK1 knockdown-accelerated cellular senescence was attenuated by co-treatment with sphingosine-1-phosphate and an inhibitor of ceramide synthesis, fumonisin $B_1$, but not by treatment with either one alone. Together, these results suggest that transcriptional down-regulation of SPHK1 is a critical inducer of altered sphingolipid profiles and enhances replicative senescence during multiple rounds of cell division.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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• pp.90.1-90.1
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• 2003

This study shows that sphingosine-1-phosphate (S1P) significantly inhibits melanin synthesis in a concentration-dependent manner, and that the activity of tyrosinase was also reduced in S1P-treated cells. In contrast, a specific extracellular signal-regulated protein kinase (ERK) pathway inhibitor, PD98059 increased tyrosinase activity and melanin production, and PD98059 restored the reduced tyrosinase activity and pigmentation induced by SIP. We also found that S1P induces the sustained activation of ERK and the subsequent degradation of microphthalmia-associated transcription factor (MITF), which plays a key role in melanogenesis. (omitted)

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.271.3-272
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• 2002

This study shows that sphingosine-1-phosphate (SPP) significantly inhibits melanin synthesis in a concentration-dependent manner, and that the activity of tyrosinase was also reduced in SPP-treated cells. In contrast. a specific extracellular signal-regulated protein kinase (ERK) pathway inhibitor, PD98059 increased tyrosinase activity and melanin production, and PD98059 restored the reduced tyrosinase activity and pigmentation induced by SPP. (omitted)

• Archives of Pharmacal Research
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• 제26권9호
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• pp.739-746
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• 2003

Ultraviolet B (UVB) is known to induce apoptosis in human melanocytes. Here we show the cytoprotective effect of sphingosine-1-phosphate (S1P) against UVB-induced apoptosis. We also show that UVB-induced apoptosis of melanocytes is mediated by caspase-3 activation and poly(ADP-ribose) polymerase (PARP) cleavage, and that S1P prevents apoptosis by inhibiting this apoptotic pathway. We further investigated three major mitogen-activated protein (MAP) kinases after UVB irradiation. UVB gradually activated c-Jun N-terminal kinase (JNK) and p38 MAP kinase, while extracellular signal-regulated protein kinase (ERK) was inactivated transiently. Blocking of the p38 MAP kinase pathway using SB203580 promoted cell survival and inhibited the activation of caspase-3 and PARP cleavage. These results suggest that p38 MAP kinase activation may play an important role in the UVB-induced apoptosis of human melanocytes. To explain this cytoprotective effect, we next examined whether S1P could inhibit UVB-induced JNK and p38 MAP kinase activation. However, S1P was not found to have any influence on UVB-induced JNK or p38 MAP kinase activation. In contrast, S1P clearly stimulated the phosphorylation of ERK, and the specific inhibition of the ERK pathway using PD98059 abolished the cytoprotective effect of S1P. Based on these results, we conclude that the activation of p38 MAP kinase plays an important role in UVB-induced apoptosis, and that S1P may show its cytoprotective effect through ERK activation in human melanocytes.

• Biomolecules & Therapeutics
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• 제30권6호
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• pp.553-561
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• 2022

Chronic myeloid leukemia (CML) is a slowly progressing hematopoietic cell disorder. Sphingosine kinase 1 (SPHK1) plays established roles in tumor initiation, progression, and chemotherapy resistance in a wide range of cancers, including leukemia. However, small-molecule inhibitors targeting SPHK1 in CML still need to be developed. This study revealed the role of SPHK1 in CML and investigated the potential anti-leukemic activity of hirsuteine (HST), an indole alkaloid obtained from the oriental plant Uncaria rhynchophylla, in CML cells. These results suggest that SPHK1 is highly expressed in CML cells and that overexpression of SPHK1 represents poor clinical outcomes in CML patients. HST exposure led to G2/M phase arrest, cellular apoptosis, and downregulation of Cyclin B1 and CDC2 and cleavage of Caspase 3 and PARP in CML cells. HST shifted sphingolipid rheostat from sphingosine 1-phosphate (S1P) towards the ceramide coupled with a marked inhibition of SPHK1. Mechanistically, HST significantly blocked SPHK1/S1P/S1PR1 and BCR-ABL/PI3K/Akt pathways. In addition, HST can be docked with residues of SPHK1 and shifts the SPHK1 melting curve, indicating the potential protein-ligand interactions between SPHK1 and HST in both CML cells. SPHK1 overexpression impaired apoptosis and proliferation of CML cells induced by HST alone. These results suggest that HST, which may serve as a novel and specific SPHK1 inhibitor, exerts anti-leukemic activity by inhibiting the SPHK1/S1P/S1PR1 and BCR-ABL/PI3K/Akt pathways in CML cells, thus conferring HST as a promising anti-leukemic drug for CML therapy in the future.

• 생명과학회지
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• 제21권2호
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• pp.183-193
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• 2011

중간엽 줄기세포의 이동과 분화는 손상된 조직의 재생을 위해 필수적이다. Sphingosine-1-phosphate (S1P)는 세포성장, 생존, 분화, 이동성 등 여러 가지 생명현상에 중요한 역할을 하는 생리활성 지질이다. 본 연구에서는 인체 골수유래 중간엽 줄기세포의 이동과 세포분화에 대한 S1P의 영향을 조사하였다. S1P는 중간엽 줄기세포의 이동을 증가시켰으며 pertussis toxin의 전처리는 S1P에 의한 세포이동을 억제하였다. 본 결과는 S1P에 의한 세포 이동과정에 Gi에 연결된 수용체가 관여함을 제시한다. $S1P_1$과 $S1P_3$ 수용체에 대한 길항제인 VPC23019의 전처리나 siRNA를 이용한 $S1P_1$ 수용체의 발현억제는 S1P에 의한 세포 내 칼슘 증가와 중간엽 줄기세포의 이동을 저해 하였다. 또한, S1P의 처리는 중간엽 줄기세포에서 평활근세포의 표지유전자인 $\alpha$-smooth muscle actin ($\alpha$-SMA)의 발현을 증가시켰으며 VPC23019의 전처리는 S1P에 의한 $\alpha$-SMA의 발현증가를 저해하였다. S1P는 중간엽 줄기세포에서 p38 mitogen-activated protein kinase (p38 MAPK)의 인산화를 촉진하였으며 p38 MAPK의 저해제인 SB202190의 전처리 또는 p38 MAPK의 dominant negative mutant의 과발현은 S1P에 의한 중간엽 줄기세포의 이동 $\alpha$-SMA 발현증가를 억제하였다. 본 연구결과는 S1P가 $S1P_1$-p38 MAPK 신호전달기전을 통해 중간엽 줄기세포의 이동과 평활근세포로의 분화를 촉진함으로써 중간엽 줄기세포를 이용한 조직재생에의 활용 가능성을 제시한다.