ABSTRACT
Norcantharidin (NCTD), the demethylated analog of cantharidin isolated from Mylabris, is known to inhibit renal fibrosis. However, the underlying mechanism is largely unknown. The present study investigates whether NCTD exerts this effect through regulation of the protein phosphatase 2A catalytic subunit (PP2Ac)-Smad3 pathway. HK-2 human renal proximal tubule cells exposed to transforming growth factor (TGF)-ß1 were used as an in vitro model of renal fibrosis. The levels of total Smad3, C-terminal-phosphorylated Smad3 (p-Smad3), PP2Ac, and fibronectin (Fn) were evaluated by Western blotting. A PP2Ac overexpression plasmid and the PP2Ac inhibitor okadaic acid (OA) were used for functional analyses. The subcellular localization of Smad3 was visualized by immunofluorescence labeling. The results showed that PP2Ac overexpression increased Smad3 phosphorylation and nuclear translocation in HK-2 cells, while pharmacologic inhibition of PP2Ac with OA had the opposite effect. NCTD suppressed Fn and p-Smad3 expression and TGF-ß1-induced nuclear entry of Smad3, but these effects were abrogated by inhibition of PP2Ac. Thus, the anti-renal interstitial fibrosis effect of NCTD is exerted through inhibition of PP2Ac-mediated C-terminal phosphorylation of Smad3. These findings highlight the therapeutic potential of NCTD for the treatment of renal interstitial fibrosis.
Subject(s)
Active Transport, Cell Nucleus/drug effects , Bridged Bicyclo Compounds, Heterocyclic/pharmacology , Protein Phosphatase 2/metabolism , Smad3 Protein/metabolism , Catalytic Domain , Cell Line , Fibronectins/metabolism , Humans , Okadaic Acid/pharmacology , Phosphorylation/drug effects , Protein Phosphatase 2/antagonists & inhibitors , Protein Phosphatase 2/genetics , Transforming Growth Factor beta1/pharmacologyABSTRACT
Prenatal ethanol exposure (PEE) induces hypothalamic-pituitary-adrenal (HPA) axis-related neuroendocrine metabolic programming alteration in the first generation (F1) rats. In this study, the HPA hormones and glucose/lipid phenotypes under basal state and stressed condition induced by a fortnight ice-water swimming were examined in F2 to verify the intergenerational effect. Under the basal state, serum corticosterone (CORT) and glucose of some PEE groups were lowered while those of serum triglycerides (TG) were increased comparing with controls. Following chronic stress, the percentage increase in CORT from the basal state tended to be greater for some PEE groups compared with controls while the percentage reduction of glucose and percentage elevation of TG were smaller. These results revealed that the low basal activity and hyper-responsiveness of the HPA axis as well as glucocorticoid-associated glucose and lipid phenotypic alterations were partially retained in F2, which indicates PEE-induced neuroendocrine metabolic programming alteration may have an intergenerational effect.
Subject(s)
Ethanol/toxicity , Prenatal Exposure Delayed Effects , Animals , Blood Glucose/analysis , Cholesterol/blood , Corticosterone/blood , Female , Hypothalamo-Hypophyseal System/drug effects , Lipid Metabolism/drug effects , Male , Maternal-Fetal Exchange , Pituitary-Adrenal System/drug effects , Pregnancy , Rats, Wistar , Stress, Physiological , Triglycerides/bloodABSTRACT
It's known that blood leptin level is reduced in intrauterine growth retardation (IUGR) fetus, and placental leptin is the major source of fetal blood leptin. This study aimed to investigate the decreased fetal blood leptin level by prenatal caffeine exposure (PCE) and its underlying placental mechanisms. Pregnant Wistar rats were intragastrically administered caffeine (30-120 mg/kg day) from gestational day 9 to 20. The level of fetal serum leptin and the expression of placental leptin-related genes were analyzed. Furthermore, we investigated the molecular mechanism of the reduced placental leptin's expression by treatment with caffeine (0.8-20 µM) in the BeWo cells. In vivo, PCE significantly decreased fetal serum leptin level in caffeine dose-dependent manner. Meanwhile, placental mRNA expression of adenosine A2a receptor (Adora2a), cAMP-response element binding protein (CREB), a short-type leptin receptor (Ob-Ra) and leptin was reduced in the PCE groups. In vitro, caffeine significantly decreased the mRNA expression of leptin, CREB and ADORA2A in concentration and time-dependent manners. The addition of ADORA2A agonist or adenylyl cyclase (AC) agonist reversed the inhibition of leptin expression induced by caffeine. PCE induced a lower level of fetal blood leptin, which the primary mechanism is that caffeine inhibited antagonized Adora2a and AC activities to decreased cAMP synthesis, thus inhibited the expression of the transcription factor CREB and target gene leptin in the placenta. Meantime, the reduced transportation of maternal leptin by placental Ob-Ra also contributed to the reduced fetal blood leptin. Together, PCE decreased fetal blood leptin mainly via reducing the expression and transportation of leptin in the placenta.
Subject(s)
Caffeine/adverse effects , Leptin/blood , Maternal Exposure , Placenta/drug effects , Receptor, Adenosine A2A/metabolism , Adenylyl Cyclases/genetics , Adenylyl Cyclases/metabolism , Animals , Caffeine/administration & dosage , Cells, Cultured , Colforsin/pharmacology , Cyclic AMP Response Element-Binding Protein/genetics , Cyclic AMP Response Element-Binding Protein/metabolism , Down-Regulation , Female , Fetal Blood/chemistry , Fetal Development/drug effects , Fetal Growth Retardation/chemically induced , Fetal Growth Retardation/pathology , Fetus/drug effects , Humans , Leptin/genetics , Leptin/metabolism , Male , Pregnancy , RNA, Messenger/genetics , RNA, Messenger/metabolism , Rats , Rats, Wistar , Receptor, Adenosine A2A/genetics , Receptors, Leptin/genetics , Receptors, Leptin/metabolismABSTRACT
A simple channel estimator for space-time coded orthogonal frequency division multiplexing (OFDM) systems in rapid fading channels is proposed. The channels at the training bauds are estimated using the EM (expectation-maximization) algorithm, while the channels at the data bauds are estimated based on the method for modelling the time-varying channel as the linear combination of several time-invariant "Doppler channels". Computer simulations showed that this estimator outperforms the decision-directed tracking in rapid fading channels and that the performance of this method can be improved by iteration.