Activation of cAMP-dependent signaling pathway induces mouse organic anion transporting polypeptide 2 expression

Rodent Oatp2 is a hepatic uptake transporter for such compounds as cardiac glycosides. In the present study, we found that fasting resulted in a 2-fold induction of Oatp2 expression in liver of mice. Because the cAMP-protein kinase A (PKA) signaling pathway is activated during fasting, the role of this pathway in Oatp2 induction during fasting was examined. In Hepa-1c1c7 cells, adenylyl cyclase activator forskolin as well as two cellular membrane-permeable cAMP analogs, dibutyryl cAMP and 8-bromo-cAMP, induced Oatp2 mRNA expression in a time- and dose-dependent manner. These three chemicals induced reporter gene activity in cells transfected with a luciferase reporter gene construct containing a 7.6-kilobase (kb) 5'-flanking region of mouse Oatp2. Transient transfection of cells with 5'-deletion constructs derived from the 7.6-kb Oatp2 promoter reporter gene construct, as well as 7.6-kb constructs in which a consensus cAMP response element (CRE) half-site CGTCA (-1808/-1804 bp) was mutated or deleted, confirms that this CRE site was required for the induction of luciferase activity by forskolin. Luciferase activity driven by the Oatp2 promoter containing this CRE site was induced in cells cotransfected with a plasmid encoding the protein kinase A catalytic subunit. Cotransfection of cells with a plasmid encoding the dominant-negative CRE binding protein (CREB) completely abolished the inducibility of the reporter gene activity by forskolin. In conclusion, induction of Oatp2 expression in liver of fasted mice may be caused by activation of the cAMP-dependent signaling pathway, with the CRE site (-1808/-1804) and CREB being the cis- and trans-acting factors mediating the induction, respectively.     

CCK-8抗炎作用中DAG-PKC信号通路对cAMP-PKA信号通路的影响

目的探讨CCK-8抗炎作用中DAG-PKC信号通路对cAMP-PKA信号通路的影响。方法分离纯化大鼠PIMs,分别用LPS、CCK、LPS+CCK、PMA、SC-3088、LPS+PMA、LPS+SC-3088、CCK+PMA、CCK+SC-3088、LPS+CCK+PMA、LPS+CCK+SC-3088孵育一定时间,采用125I-cAMP放射免疫分析法测定细胞内cAMP含量,用放射激酶法测定PKA活性。结果单独应用PMA和SC-3088孵育大鼠PIMs,细胞内cAMP含量和PKA活性与正常对照组相比无明显变化(P>0.05)。PMA可升高LPS作用下的细胞内cAMP含量和PKA活性(P<0.01),SC-3088则可使LPS作用下的细胞内cAMP含量和PKA活性降低(P<0.01)。分别应用PMA、SC-3088与CCK共同孵育,则CCK+PMA组细胞内cAMP含量和PKA活性高于单独应用CCK组(P<0.01),CCK+SC-3088组则降低(P<0.01)。与LPS+CCK组相比,PMA+LPS+CCK组细胞内cAMP含量和PKA活性升高(P<0.01),而SC-3088+LPS+CCK组细胞内cAMP含量和PKA活性降低(P<0.01)。结论在LPS诱导的大鼠PIMs,CCK-8可通过激活cAMP-PKA信号通路发挥抗炎作用;DAG-PKC信号通路的活化对cAMP-PKA信号通路有正性调节作用。     

Fenvalerate induces germ cell apoptosis in mouse testes through the Fas/FasL signaling pathway

Fenvalerate has a potentially adverse effect on male reproduction and spermatogenesis, whereas the precise mechanism remains obscure. The present study investigated the effects of fenvalerate on germ cell apoptosis in testes. Adult male mice were administered with fenvalerate (15 or 60 mg/kg) by gavage for 28 days. Germ cell apoptosis was determined by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL). The number of TUNEL+ germ cells per tubule and the percentage of tubules with TUNEL+ germ cells were significantly increased in testes of mice treated with fenvalerate in a dose-dependent manner. TUNEL+ germ cells were observed mainly in stages VII–VIII and also stages IX–XII seminiferous tubules in testes. Additional experiments showed that fenvalerate increased the level of active caspase-8 and caspase-3 in testes. In addition, fenvalerate upregulated the expression of Fas and FasL in testes. No significant difference on the expression of Bcl-2 and Bax in testes was observed between fenvalerate-treated mice and controls. Fenvalerate did not affect the leakage of cytochrome c from mitochondria into cytoplasm. In addition, fenvalerate did not cause the activation of caspase-9 in testes. Taken together, these results suggest that fenvalerate induces germ cell apoptosis in testes through the Fas/FasL signaling pathway.     

cAMP-PKA signaling pathway regulates bone resorption mediated by processing of cathepsin K in cultured mouse osteoclasts

Cathepsin K (Cat K) is the major cysteine protease expressed in osteoclast and is thought to play a key role in matrix degradation during bone resorption. It is shown that the intracellular maturation of Cat K was prevented by the cAMP antagonist, Rp-cAMP, and the protein kinase A (PKA) inhibitors of KT5720 and H89. In contrast, forskolin, an adenylate cyclase agonist, rather induced Cat K processing and maturation in osteoclast. Furthermore, to determine whether Cat K processing and maturation signaling involves protein kinase C (PKC), mouse total bone cells were treated with calphostin C, a specific inhibitor of PKC, however, no effect was observed, indicating that PKC calphostin C did not affect to osteoclast-mediated Cat K processing and maturation in osteoclast. Thus, it is indicated that the cAMP-PKA signaling pathway regulate Cat K maturation in osteoclast. Since secreted proenzymes have the potential to reenter the cell via M6P receptor, to prevent this possibility, we tested cAMP antagonist Rp-cAMP and the PKA inhibitors KT5720 and H89 in the absence or presence of M6P. Inhibition of Cat K processing by Rp-cAMP, KT5720 or H89 was observed in a dose-dependent manner. Furthermore, the addition of M6P resulted in enhanced potency of Rp-cAMP, KT5720 and H89, which dose-dependently inhibited in vitro bone resorption with potency similar to that observed for inhibition of Cat K processing.     

Sphingosine-1-phosphate induces VEGF-C expression through a MMP-2/FGF-1/FGFR-1-dependent pathway in endothelial cells in vitro

Aim:

To investigate whether sphingosine-1-phosphate (S1P), a potent angiogenic factor, induced vascular endothelial growth factor-C (VEGF-C) expression in endothelial cells in vitro and to examine its underlying mechanisms.

Methods:

Human umbilical vein endothelial cells (HUVECs) were examined. VEGF-C mRNA expression in the cells was assessed using real-time PCR. VEGF-C protein and FGFR-1 phosphorylation in the cells were measured with ELISA. RNA interference was used to downregulate the expression of matrix metalloproteinase-2 (MMP-2), fibroblast growth factor-1 (FGF-1) and FGF receptor-1 (FGFR-1).

Results:

Incubation of HUVECs with S1P (1, 5, and 10 μmol/L) significantly increased VEGF-C expression. The effect was blocked by pretreatment with the MMP inhibitor GM6001 or the FGFR inhibitor SU5402, but not the EGFR inhibitor AG1478. The effect was also blocked in HUVECs that were transfected with FGFR-1 or MMP-2 siRNA. Furthermore, incubation of HUVECs with S1P (5 μmol/L) significantly increased FGFR-1 phosphorylation, which was blocked by GM6001. Moreover, knockdown of FGF-1, not FGF-2, in HUVECs with siRNAs, blocked S1P-induced VEGF-C expression.

Conclusion:

S1P induces VEGF-C expression through a MMP-2/ FGF-1/FGFR-1-dependent pathway in HUVECs.     

Glabridin induces apoptosis and cell cycle arrest in oral cancer cells through the JNK1/2 signaling pathway

Glabridin, a flavonoid extracted from licorice (Glycyrrhiza glabra), possesses various biological properties, including anticancer activities. However, the effect of glabridin on oral cancer cell apoptosis and the underlying molecular mechanisms has not been elucidated. In this study, we demonstrated that glabridin treatment significantly inhibits cell proliferation in human oral cancer SCC‐9 and SAS cell lines. Flow cytometric assays demonstrated that glabridin induced several features of apoptosis, such as sub‐G1 phase cell increase and phosphatidylserine externalization. Furthermore, glabridin induced apoptosis dose‐dependently in SCC‐9 cells through caspase‐3, −8, and −9 activation and poly (ADP‐ribose) polymerase cleavage. Moreover, glabridin increased the phosphorylation of the extracellular signal–regulated kinase, p38, and c‐Jun N‐terminal kinase (JNK) pathways in a dose‐dependent manner. Moreover, the inhibition of the JNK1/2 inhibitor significantly reversed the glabridin‐induced activation of the caspase pathway. In conclusion, our findings suggest that glabridin induces oral cancer cell apoptosis through the JNK1/2 pathway and is a potential therapeutic agent for oral cancer.     

Calcium changes in rabbit CSF during endotoxin, IL-1 beta, and PGE2 fever.

New Zealand rabbits were chronically incannulated in the lateral ventricle and cisterna magna to assess the hypothesis that calcium concentration (Ca) of cerebrospinal fluid (CSF) varies during fevers of diverse origin. In normothermic and febrile animals recovering from surgery, CSF Ca was positively and significantly correlated to rectal temperature (TR). IV injection of E. coli endotoxin and ICV injection of human recombinant interleukin 1 beta (hrIL-1 beta) induced a TR rise of 1.7 +/- 0.3 degrees C (mean +/- SEM) and 1.45 +/- 0.25 degrees C, respectively, accompanied by significant increases in CSF Ca. After endotoxin administration, maximal Ca increases ranged between 0.21 and 0.48 mM above basal values in individual animals (p < 0.01), whereas after administration of hrIL-1 beta increases were 0.17 and 0.25 mM (p < 0.05). Acetylsalicylic acid (ASA) countered the fever induced by both endotoxin and hrIL-1 beta administrations and concomitantly antagonized the Ca increase in CSF. HrIL-1 beta-derived nonapeptide was characteristically devoid of pyrogenic effect and did not modify CSF Ca. Although ICV injection of prostaglandin E2 (PGE2) increased TR by 2.1 +/- 0.77 degrees C, it failed to have any effect on CSF Ca. Differently from the other Ca enhancers, PGE2, however, increased CSF protein concentration (protein). These findings suggest that brain calcium metabolism plays a role in fever development and that prostaglandin involvement is only engaged once changes in CSF calcium concentration have taken place.     

Effects of cinnamaldehyde on PGE2 release and TRPV4 expression in mouse cerebral microvascular endothelial cells induced by interleukin-1beta

Cinnamaldehyde is a principle compound isolated from Guizhi-Tang (GZT), which is a famous traditional Chinese medical formula used to treat influenza, common cold and other pyretic conditions. Transient receptor potential vanilloid subtype 4 (TRPV4) is expressed in the anterior hypothalamus and may act as thermosensor. The purpose of the present study was to investigate the effects of cinnamaldehyde on the production of prostaglandin E2 (PGE2) and the expression of TRPV4 in mouse cerebral microvascular endothelial cell strain (b.End3). In the research work, the b.End3 cells were cultured in DMEM medium containing interleukin-1beta (IL-1beta) in the presence or absence of ruthenium red (RR), a kind of known TRPV4 inhibitor, or different concentrations of cinnamaldehyde. The results suggested that IL-1beta significantly increase production of PGE2 and cinnamaldehyde evidently decrease IL-1beta-induced PGE2 production, while RR showed no inhibitory effect on PGE2 production. Moreover, it was identified that TRPV4 was expressed at the mRNA and protein levels in b.End3 cells. IL-1beta could up-regulate the expression of TRPV4, RR and cinnamaldehyde could down-regulate the high expression of mRNA and protein of TRPV4 by IL-1beta induced in b.End3 cells. In conclusion, cinnamaldehyde decreased the production of PGE2 and the expression of TRPV4 in b.End3 cells induced by IL-1beta.     

Kaempferol induces chondrogenesis in ATDC5 cells through activation of ERK/BMP-2 signaling pathway

Endochondral bone formation occurs when mesenchymal cells condense to differentiate into chondrocytes, the primary cell types of cartilage. The aim of the present study was to identify novel factors regulating chondrogenesis. We investigated whether kaempferol induces chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Kaempferol treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. Kaempferol-treated ATDC5 cells stained more intensely with alcian blue staining than control cells, suggesting greater synthesis of matrix proteoglycans in the kaempferol-treated cells. Similarly, kaempferol induced greater activation of alkaline phosphatase activity than control cells, and it enhanced the expression of chondrogenic marker genes, such as collagen type I, collagen type X, OCN, Runx2, and Sox9. Kaempferol induced an acute activation of extracellular signal-regulated kinase (ERK) but not c-jun N-terminal kinase or p38 MAP kinase. PD98059, an inhibitor of MAPK/ERK, decreased in stained cells treated with kaempferol. Furthermore, kaempferol greatly expressed the protein and mRNA levels of BMP-2, suggesting chondrogenesis was stimulated via a BMP-2 pathway. Taken together, our results suggest that kaempferol has chondromodulating effects via an ERK/BMP-2 signaling pathway and could potentially be used as a therapeutic agent for bone growth disorders.     

黄连素调节鞘氨醇激酶-1-磷酸鞘氨醇信号通路抗糖尿病小鼠肾损伤的研究

目的研究黄连素对四氧嘧啶诱导的糖尿病小鼠肾损伤的保护作用及其对糖尿病小鼠肾脏鞘氨醇激酶-1-磷酸鞘氨醇(SphK-S1P)信号通路的抑制效应。方法四氧嘧啶诱导的糖尿病小鼠采用黄连素(300 mg.kg-1.d-1)灌胃给药12周,正常组和糖尿病组小鼠给予同体积的溶媒。采用Re-al-time PCR技术检测肾组织中SphK1、TGF-β1、FN、ColⅣ的基因;Western blot法检测肾脏组织中SphK1、FN、ColⅣ的蛋白表达;LC-MS/MS检测肾脏组织中SphK1活性和S1P含量。结果黄连素明显抑制糖尿病小鼠血糖,肾重/体重比、血尿素氮、血肌酐和24 h尿蛋白异常增高;抑制肾脏肥大、纤维连接蛋白和Ⅳ型胶原积聚。此外,黄连素明显减少肾脏SphK1活性、mRNA和蛋白表达,降低S1P的生成。结论黄连素发挥抗糖尿病小鼠肾损伤的作用可能与抑制肾脏SphK-S1P信号通路的激活相关联。     

Furazolidone induces apoptosis through activating reactive oxygen species-dependent mitochondrial signaling pathway and suppressing PI3K/Akt signaling pathway in HepG2 cells

Furazolidone (FZD), a synthetic nitrofuran with a broad spectrum of antimicrobial activities, has been shown to be genotoxic and potentially carcinogenic in several types of cells. However, the proper molecular mechanisms of FZD toxicity remain unclear. This study was aimed to explore the effect of FZD on apoptosis in HepG2 cells and uncover signaling pathway underlying the cytotoxicity of FZD. The results showed that FZD induced apoptosis in HepG2 cells in a dose-dependent manner characterized by nuclei morphology changes, cell membrane phosphatidylserine translocation, poly (ADP-ribose) polymerase (PARP) cleavage and a cascade activation of caspase-9 and -3. FZD could enhance reactive oxygen species (ROS) generation, up-regulate Bax/Bcl-2 ratio, disrupt mitochondrial membrane potential (MMP) and subsequently cause cytochrome c release. Both ROS scavenger (N-acetyl cysteine, NAC) and caspase inhibitors suppressed FZD-induced apoptosis. Furthermore, NAC attenuated FZD-induced ROS generation and mitochondrial dysfunction. Meanwhile, FZD treatment inhibited both the activation and expression of Akt, and PI3K/Akt inhibitor LY294002 promoted FZD-induced apoptosis. On the contrary, PI3K/Akt activator insulin-like growth factor-1 (IGF-1) attenuated lethality of FZD in HepG2 cells. In conclusion, it is first demonstrated that FZD-induced apoptosis in HepG2 cells might be mediated through ROS-dependent mitochondrial signaling pathway and involves PI3K/Akt signaling.     

The snake venom metalloproteinase BaP1 induces joint hypernociception through TNF-alpha and PGE2-dependent mechanisms

BACKGROUND AND PURPOSE: Matrix metalloproteinases (MMPs) have been implicated in joint tissue destruction in arthritis. However, MMPs have not been assigned a role in joint pain. We investigated the ability of BaP1, a metalloproteinase from Bothrops asper snake venom, with structural homology to MMPs, to induce joint hypernociception. EXPERIMENTAL APPROACH: Animals received intra-articular (i.art.) BaP1. Hypernociception was assessed using the rat-knee joint articular incapacitation test. Cell influx, prostaglandin E(2) (PGE(2)), and TNF-alpha levels were assessed in joint exudates following BaP1 injection. KEY RESULTS: BaP1 (5 microg per joint) provoked hypernociception between 1 and 6 h after i.art. injection. Cell influx, mostly neutrophils, was maximal 3 h after BaP1 i.art. injection. BaP1 also led to increase in PGE(2) and TNF-alpha levels in the joint exudates. Pretreatment with either indomethacin (4 mg.kg(-1) i.p.) or with an anti-TNF-alpha antiserum (i.art.) significantly inhibited both BaP1-induced joint hypernociception and cell influx. In isolated rat peritoneal macrophages, BaP1 increased cyclooxygenase (COX)-2 expression, while not altering that of COX-1. CONCLUSIONS AND IMPLICATIONS: This is the first demonstration that a metalloproteinase promotes joint hypernociception. This effect involves local release of PGE(2) and TNF-alpha. BaP1-induced increase in PGE(2) is associated to increased COX-2 expression in macrophages. Blocking PGE(2) or TNF-alpha inhibits BaP1-induced hypernociception. In addition to unravelling a hitherto unknown mechanism whereby TNF blockade provides analgesia in arthritis, the data show, for the first time that MMPs are involved in inflammatory joint hypernociception and induce COX-2 expression.     

TIMP-1 expression induced by IL-32 is mediated through activation of AP-1 signal pathway

Hepatic fibrosis is a necessarily stage from the progression of chronic liver diseases to cirrhosis, even hepatocellular carcinoma (HCC). Hepatic fibrosis is characterized by the progressive accumulation of extracellular matrix (ECM). The balance between ECM production and degradation is mediated by matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs). TIMP-1 is an important regulator in the synthesis and degradation of ECM. IL-32, a multi-function cytokine, could induce IL-1β, IL-6, IL-8 and other cytokine expressions by activating AP-1, NF-κβ, p38MAPK signal pathways. IL-32 expression is increased in liver tissues of hepatic fibrosis. However, the role of IL-32 in the pathogenesis of liver fibrosis is not thoroughly clear. Recently, it is demonstrated that TIMP-1 expression is induced by the activation of AP-1 signal pathway. So we assayed the effect of IL-32 on TIMP-1 expression by LX-2 cells (one of HSCs cell lines) in the present study. We found that IL-32 could induce TIMP-1 expression by LX-2 cells at a dose-dependent manner. IL-32 could increase TIMP-1 promoter activity and induce TIMP-1 expression by activating AP-1 signal pathway. Moreover, the increase of TIMP-1 expression could promote the migration of LX-2 cells. In conclusion, we believe that IL-32 might be involved in the pathogenesis of hepatic fibrosis by inducing TIMP-1 expression.     

Toosendanin induces apoptosis through suppression of JNK signaling pathway in HL-60 cells

Toosendanin (TSN), a triterpenoid isolated from Melia toosendan Sieb. et Zucc., has been found to suppress proliferation and induce apoptosis in a variety of human cancer cells. However, the mechanism how TSN induces apoptosis remains poorly understood. In this study, we examined the effects of TSN on the growth, cell cycle arrest, induction of apoptosis and the involved signaling pathway in human promyelocytic leukemia HL-60 cells. Proliferation of HL-60 cells was inhibited in a dose-dependent manner with the IC_{50 (48h)} of 28 ng/mL. The growth inhibition was due primarily to the S phase arrest and cell apoptosis. Cell apoptosis induced by TSN was confirmed by Annexin V-FITC/propidium iodide staining. The increase of the pro-apoptotic protein Bax, cleaved PARP and caspase-3, and the decrease of anti-apoptotic protein Bcl-2 were observed. Western blot analysis indicated that TSN inhibits the CDC42/MEKK1/JNK pathway. Taken together, our study suggested, for the first time, that the pro-apoptotic effects of TSN on HL-60 cells were mediated through JNK signaling pathway.