Lophirones B and C Extenuate AFB1‐Mediated Oxidative Onslaught on Cellular Proteins,Lipids, and DNA through Nrf‐2 Expression

The capability of lophirones B and C to extenuate aflatoxin B₁ (AFB₁)‐mediated onslaught on cellular proteins, lipids, and DNA was investigated for 6 weeks. Lophirones B and C significantly (P < 0.05) increase the expression and specific activity of cytoprotective enzymes (glutathione‐S‐trans‐ferase, nioctinamide adenine dicludeotide:quinone oxidoreductase‐1, epoxide hydrolase, and uridyl glucuronosyl transferase). There was significant (P < 0.05) reduction in the level of antioxidant system in AFB₁‐induced hepatocarcinogenesis. Furthermore, lophirones B and C significantly (P < 0.05) attenuated AFB₁‐mediated decrease in the specific activities of antioxidant enzymes. Oxidative stress biomarkers, malondialdehyde, lipid hydroperoxides, conjugated dienes, protein carbonyl, and fragmented DNA were significantly (P < 0.05) elevated in AFB₁‐treated rats. Although lophirones B and C did not significantly (P < 0.05) alter these biomarkers, an AFB₁‐mediated increase in these biomarkers was significantly attenuated. Results obtained showed that lophirones B and C extenuate AFB₁‐mediated onslaught on cellular proteins, lipids, and DNA by enhancing nuclear erythroid–related factor‐2 expression.     

Epinephrine increases DNA synthesis via ERK1/2s through cAMP, Ca(2+)/PKC, and PI3K/Akt signaling pathways in mouse embryonic stem cells

Epinephrine is a catecholamine that plays important roles in regulating a wide variety of physiological systems by acting through the adrenergic receptors (ARs). The cellular responses to AR stimulation are mediated through various signaling pathways. Therefore, this study examined the effects of epinephrine on DNA synthesis and related signaling molecules in mouse embryonic stem cells (ESCs). Epinephrine increased DNA synthesis in a dose- and time-dependent manner, as determined by the level of [(3)H]-thymidine incorporation. AR subtypes (alpha1(A), alpha2(A), beta1, beta2, and beta3) were expressed in mouse ESCs and their expression levels were increased by epinephrine. In this experiment, epinephrine increased cAMP levels, intracellular Ca(2+) concentration ([Ca(2+)](i)), and translocation of protein kinase C (PKC) from the cytosol to the membrane compartment. In addition, we observed Akt phosphorylation in response to epinephrine; this was stimulated by phosphorylation of the epidermal growth factor receptor (EGFR). Epinephrine also induced phosphorylation of ERK1/2 (p44/42 MAPKs), while inhibition of PKC or Akt blocked this phosphorylation. Epinephrine increased the mRNA levels of proto-oncogenes (c-fos, c-jun, c-myc), while inhibition of ERK1/2 decreased these mRNA levels. In experiments aimed at examining the involvement of cell cycle regulatory proteins, epinephrine increased the levels of cyclin E/cyclin-dependent kinase 2 (CDK2) and cyclin D1/cyclin-dependent kinase 4 (CDK4). In conclusion, epinephrine stimulates DNA synthesis via ERK1/2 through cAMP, Ca(2+)/PKC, and PI3K/Akt signaling pathways in mouse ESCs.     

Antioxidant protection by β‐selenoamines against thioacetamide‐induced oxidative stress and hepatotoxicity in mice

Thioacetamide (TAA) is a hepatotoxin that rapidly triggers the necrotic process and oxidative stress in the liver. Nevertheless, organic selenium compounds, such as β‐selenoamines, can be used as pharmacological agents to diminish the oxidative damage. Thus, the aim of this study was to investigate the protective effect of the antioxidant β‐selenoamines on TAA‐induced oxidative stress in mice. Here, we observed that a single intraperitoneal injection of TAA (200 mg/kg) dramatically elevated some parameters of oxidative stress, such as lipid peroxidation and reactive oxygen species (ROS) production, as well as depleted cellular antioxidant defenses. In addition, TAA‐induced edema and morphological changes in the liver, which correlate with high serum aspartate and alanine aminotransferase enzyme activities, and a decrease in cell viability. Conversely, a significant reduction in liver lipid peroxidation, ROS production, and edema was observed in animals that received an intraperitoneal injection of β‐selenoamines (15.6 mg/kg) 1 h after TAA administration.     

High glucose regulates cyclin D1/E of human mesenchymal stem cells through TGF‐β1 expression via Ca2+/PKC/MAPKs and PI3K/Akt/mTOR signal pathways

The elucidation of factors that support human mesenchymal stem cells (hMSCs) growth has remained unresolved partly because of the reliance of many researchers on ill‐defined, proprietary medium formulation. Thus, we investigated the effects of high glucose (D ‐glucose, 25 mM) on hMSCs proliferation. High glucose significantly increased [³H]‐thymidine incorporation and cell‐cycle regulatory protein expression levels compared with 5 mM D ‐glucose or 25 mM L ‐glucose. In addition, high glucose increased transforming growth factor‐β1 (TGF‐β₁) mRNA and protein expression levels. High glucose‐induced cell‐cycle regulatory protein expression levels and [³H]‐thymidine incorporation, which were inhibited by TGF‐β₁ siRNA transfection and TGF‐β₁ neutralizing antibody treatment. High glucose‐induced phosphorylation of protein kinase C (PKC), p44/42 mitogen‐activated protein kinases (MAPKs), p38 MAPK, Akt, and mammalian target of rapamycin (mTOR) in a time‐dependent manner. Pretreatment of PKC inhibitors (staurosporine, 10^?6 M; bisindolylmaleimide I, 10^?6 M), LY 294002 (PI3 kinase inhibitor, 10^?6 M), Akt inhibitor (10^?5 M), PD 98059 (p44/42 MAPKs inhibitor, 10^?5 M), SB 203580 (p38 MAPK inhibitor, 10^?6 M), and rapamycin (mTOR inhibitor, 10^?8 M) blocked the high glucose‐induced cellular proliferation and TGF‐β₁ protein expression. In conclusion, high glucose stimulated hMSCs proliferation through TGF‐β₁ expression via Ca²⁺/PKC/MAPKs as well as PI3K/Akt/mTOR signal pathways. J. Cell. Physiol. 224:59–70, 2010 © 2010 Wiley‐Liss, Inc.     

Prolactin induces chitotriosidase expression in human macrophages through PTK,PI3‐K,and MAPK pathways

We previously reported that prolactin (PRL) induces chitotriosidase (CHIT‐1) mRNA expression in human macrophages. In this investigation we determined the signaling pathways involved in CHIT‐1 induction in response to PRL. The CHIT‐1 induction PRL‐mediated was reduced by wortmannin and LY‐294002, inhibitors of phosphatidylinositol 3‐kinase (PI3‐K) and by genistein an inhibitor of protein tyrosine kinase (PTK). Pre‐treatment of macrophages with SB203580, a specific inhibitor of the mitogen‐activated kinases (MAPK) p38, or with U0126, an inhibitor of MAPK p44/42, prevented both basal and exogenous PRL‐mediated CHIT‐1 expression. No significant effects on CHIT‐1 induction PRL‐mediated were observed with a protein kinase C inhibitor (PKC), rottlerin, or with an Src inhibitor, PP2, or with JAK2 inhibitor, AG490. In addition, PRL induced a phosphorylation of AKT that was prevented both by the two MAPK inhibitors SB203580 and U0126 and by the PI3‐K inhibitors wortmannin and LY‐294002. In conclusion, our results indicate that PRL up‐regulated CHIT‐1 expression via PTK, PI3‐K, MAPK, and signaling transduction components. J. Cell. Biochem. 107: 881–889, 2009. © 2009 Wiley‐Liss, Inc.     

Fisetin induces apoptosis in breast cancer MDA‐MB‐453 cells through degradation of HER2/neu and via the PI3K/Akt pathway

Overexpression of human epidermal growth factor receptor 2 (HER2) is observed in breast cancer. The major snag faced by the human population is the development of chemoresistance to HER2 inhibitors by advanced stage breast cancer cells. Moreover, recent researchers focussed on fisetin as an antiproliferative and chemotherapeutic agent. Therefore, this study was intended to analyze the effects of fisetin on HER2/neu‐overexpressing breast cancer cell lines. Our results depicted that fisetin induced apoptosis of these cells by various mechanisms, such as inactivation of the receptor, induction of proteasomal degradation, decreasing its half‐life, decreasing enolase phosphorylation, and alteration of phosphatidylinositol 3‐kinase/Akt signaling.     

L-leucine increases [3H]-thymidine incorporation in chicken hepatocytes: involvement of the PKC, PI3K/Akt, ERK1/2, and mTOR signaling pathways

This study examined how L-leucine affected DNA synthesis and cell cycle regulatory protein expression in cultured primary chicken hepatocytes. L-Leucine promoted DNA synthesis in a dose- and time-dependent manner, with concomitant increases in cyclin D1 and cyclin E expression. Phospholipase C (PLC) and protein kinase C (PKC) mediated the L-leucine-induced increases in [3H]-thymidine incorporation and cyclin D1/CDK4 and cyclin E/CDK2 expression, as U73122 (a PLC inhibitor) or bisindolylmaleimide I (a PKC blocker) inhibited these effects. L-Leucine also increased PKC phosphorylation and intracellular Ca2+ levels. L-Leucine-mediated increases in [3H]-thymidine incorporation and cyclin/CDK expression were sensitive to LY 294002 (PI3K inhibitor), Akt inhibitor, PD 98059 (MEK inhibitor). It was also observed that L-leucine-induced increases of cyclin/CDK expression were inhibited by PI3K siRNA and ERK siRNA; L-leucine increased extracellular signal-regulated kinases 1/2 (ERK1/2) and Akt phosphorylation levels. Bisindolylmaleimide I attenuated L-leucine-induced phosphorylation of ERK1/2 but did not influence Akt phosphorylation, and PI3K siRNA and LY 294002 inhibited L-leucine-induced ERK1/2 phosphorylation, suggesting some cross-talk between the PKC and ERK1/2 or PI3K/Akt and ERK1/2 pathways. L-Leucine also increased the levels of phosphorylated molecular target of rapamycin (mTOR) and two of its targets, ribosomal protein S6 kinase (p70S6K), and 4E binding protein 1 (4E-BP1); furthermore, rapamycin (an mTOR inhibitor) blocked all of the mitogenic effects of L-leucine. In addition, Akt inhibitor blocked L-leucine-induced mTOR phosphorylation. In conclusion, L-leucine stimulated DNA synthesis and promoted cell cycle progression in primary cultured chicken hepatocytes through PKC, ERK1/2, PI3K/Akt, and mTOR.     

Simvastatin preparations promote PDGF‐BB secretion to repair LPS‐induced endothelial injury through the PDGFRβ/PI3K/Akt/IQGAP1 signalling pathway

Endothelial barrier dysfunction is a critical pathophysiological process of sepsis. Impaired endothelial cell migration is one of the main reasons for endothelial dysfunction. Statins may have a protective effect on endothelial barrier function. However, the effect and mechanism of statins on lipopolysaccharide (LPS)‐induced endothelial barrier dysfunction remain unclear. Simvastatin (SV) was loaded in nanostructured lipid carriers to produce SV nanoparticles (SV‐NPs). Normal SV and SV‐NPs were used to treat human umbilical vein vascular endothelial cells (HUVECs) injured by LPS. Barrier function was evaluated by monitoring cell monolayer permeability and transendothelial electrical resistance, and cell migration ability was measured by a wound healing assay. LY294002 and imatinib were used to inhibit the activity of PI3K/Akt and platelet‐derived growth factor receptor (PDGFR) β. IQ‐GTPase‐activating protein 1 (IQGAP1) siRNA was used to knockdown endogenous IQGAP1, which was used to verify the role of the PDGFRβ/PI3K/Akt/IQGAP1 pathway in SV/SV‐NPs‐mediated barrier protection in HUVECs injured by LPS. The results show that SV/SV‐NPs promoted the migration and decreased the permeability of HUVECs treated with LPS, and the efficacy of the SV‐NPs exceeded that of SV significantly. LY294002, imatinib and IQGAP1 siRNA all suppressed the barrier protection of SV/SV‐NPs. SV/SV‐NPs promoted the secretion of platelet‐derived growth factor‐BB (PDGF‐BB) and activated the PDGFRβ/PI3K/Akt/IQGAP1 pathway. SV preparations restored endothelial barrier function by restoring endothelial cell migration, which is involved in the regulation of the PDGFRβ/PI3K/Akt/IQGAP1 pathway and PDGF‐BB secretion. As an appropriate formulation for restoring endothelial dysfunction, SV‐NPs may be more effective than SV.     

(−)‐Epicatechin rescues the As2O3‐induced HERG K+ channel deficiency possibly through upregulating transcription factor SP1 expression

(?)‐Epicatechin (EPI) has beneficial effects on the cardiovascular disease. The human ether‐a‐go‐go‐related gene (HERG) potassium channel is crucial for repolarization of cardiac action potential. Dysfunction of the HERG channel can cause long QT syndrome type 2 (LQT2). Arsenic trioxide (As₂O₃) has shown efficacy in the treatment of acute promyelocytic leukemia. However, As₂O₃ can induce the deficiency of HERG channel and cause LQT2. In this study, we examined whether EPI could rescue the As₂O₃‐induced HERG channel deficiency. We found that 3 μM EPI obviously increased protein expression and current of HERG channel. EPI was able to recover the protein expression and current of HERG channel disrupted by As₂O₃. EPI was able to increase the expression of SP1 protein and recover the expression of SP1 protein disrupted by As₂O₃. In addition, EPI significantly shortened action potential duration prolonged by As₂O₃. Our data suggest that EPI rescues As₂O₃‐induced HERG channel deficiency through upregulating SP1 expression.     

5′‐N‐ethylcarboxamide induces IL‐6 expression via MAPKs and NF‐κB activation through Akt,Ca2+/PKC,cAMP signaling pathways in mouse embryonic stem cells

Many studies suggest that adenosine modulates cell responses in a wide array of tissues through potent and selective regulation of cytokine production. This study examined the effects of adenosine on interleukin (IL)‐6 expression and its related signal pathways in mouse embryonic stem (ES) cells. In this study, the adenosine analogue 5′‐N‐ethylcarboxamide (NECA) increased IL‐6 protein expression level. Mouse ES cells expressed the A₁, A_2A, A_2B, and A₃ adenosine receptors (ARs), whose expression levels were increased by NECA and NECA‐induced increase of IL‐6 mRNA expression or secretion level was inhibited by the non‐specific AR inhibitor, caffeine. NECA increased Akt and protein kinase C (PKC) phosphorylation, intracellular Ca²⁺ and cyclic adenosine monophosphate (cAMP) levels, which were blocked by caffeine. On the other hand, NECA‐induced IL‐6 secretion was partially inhibited by Akt inhibitor, bisindolylmaleimide I (PKC inhibitor), SQ 22536 (adenylate cyclate inhibitor) and completely blocked by the 3 inhibitor combination treatment. In addition, NECA increased mitogen activated protein kinase' (MAPK) phosphorylation, which were partially inhibited by the Akt inhibitor, bisindolylmaleimide I, and SQ 22536 and completely blocked by the 3 inhibitor combination treatment. NECA‐induced increases of IL‐6 protein expression and secretion levels were inhibited by MAPK inhibition. NECA‐induced increase of nuclear factor (NF)‐κB phosphorylation was inhibited by MAPK inhibitors. NECA also increased cAMP response element‐binding protein (CREB) phosphorylation, which was blocked by MAPK or NF‐κB inhibitors. Indeed, NECA‐induced increase of IL‐6 protein expression and secretion was blocked by NF‐κB inhibitors. In conclusion, NECA stimulated IL‐6 expression via MAPK and NF‐κB activation through Akt, Ca²⁺/PKC, and cAMP signaling pathways in mouse ES cells. J. Cell. Physiol. 219: 752–759, 2009. © 2009 Wiley‐Liss, Inc.