Recent studies suggest the effect of radiation is observed not only in irradiated cells but also in adjacent non-irradiated cells (bystander effect), although the mechanism has not yet been fully revealed. This bystander effect may be caused by intercellular communication via a gap junction or by messengers released from irradiated cells, such as reactive oxygen species, nitric oxide, or cytokines. However, an unknown mechanism is also possible in the bystander effect. On the other hand, it is known that extracellular ATP, ADP, uridine 5′-triphosphate (UTP), and uridine 5′-diphosphate (UDP), which are released from cells, act as intercellular signaling molecules by activating purinergic P2X and P2Y receptors (purinergic signaling). Recently, I have suggested these extracellular nucleotides may be novel mediators of a radiation-induced bystander effect, because our recent studies indicated that purinergic signaling is involved in important cellular responses to radiation. Our data indicate that ionizing irradiation causes activation of the transient receptor potential melastatin type 2 (TRPM2) channel, and then ATP is released from cells through the anion channel or connexin43 hemichannel mediated by the activation of a P2X7 receptor. The released nucleotides activate P2Y6 and P2Y12 receptors, which are involved in the DNA damage response after irradiation. Activation of the P2Y6 receptor is also involved in radiation-induced activation of the epithelial growth factor receptor-extracellular signal regulated protein kinase (EGFR-ERK)1/2 pathway and subsequent nuclear translocation of EGFR, which plays a role in DNA repair. Further, the induction of an antioxidant after irradiation is also mediated by the activation of the P2Y receptor. In conclusion, purinergic signaling could play an important role in the protective cellular response to ionizing irradiation.
Adipokines, hormones predominantly produced from adipose tissue, have been shown to impart dynamic functions in the liver. Emerging evidence has shown that adipokines are also involved in modulating liver cell survival and/or death. Among the various adipokines, adiponectin and leptin directly regulate proliferation of hepatocytes, Kupffer cells, and hepatic stellate cells. Moreover, these adipokines control apoptosis and cell cycle of hepatic cancer cells in a complex manner. Adiponectin possesses both pro- and anti-proliferative properties, whereas leptin appears to play roles as a pro-survival hormone. Recent studies have revealed that regulation of cell death and proliferation is one of the critical factors regulating liver physiology by adipokines. In this review, we summarize the effects of adipokines on apoptosis and survival of liver cells and also demonstrate their implications in regulating various liver functions and decipher the underlying molecular mechanisms.
Sestrin2 (Sesn2), a highly conserved antioxidant protein, is induced by various stresses, including oxidative and energetic stress, and protects cells against those stresses. In normal physiological conditions, redox-homeostasis plays an essential role in cell survival and performs the cellular functions to protect the cells against oxidative damage. The liver is susceptible to oxidative stress, since it is responsible for xenobiotic detoxification and energy metabolism. For this reason, oxidative stress is associated with the pathogenesis of liver diseases. Recently, the role of Sesn2 has been investigated in liver injury and related diseases. In this paper, we review the role of Sesn2 in the pathophysiology of liver diseases and the potential clinical applications of Sesn2 as a therapeutic target to prevent/treat liver diseases. This article promotes our understanding of liver disease progression and advances the development of strategies for pharmacological intervention.
Methionine is an essential sulfur-containing amino acid that is metabolized mainly in the liver, where it is converted to S-adenosylmethionine (SAM) by methionine adenosyltransferase. Importantly, SAM is a metabolically pleiotropic molecule that participates in three types of biochemical reactions; transmethylation, transsulfuration (which results in the transfer of sulfur from methionine to serine to form cysteine), and amino propylation (to synthesize polyamines). Critical roles of SAM in the liver have been extensively studied using transgenic animals with chronically reduced or increased hepatic SAM levels. Interestingly, both models with abnormal hepatic SAM concentrations develop liver disease suggesting that SAM homeostasis plays a pivotal role in liver disease. The transsulfuration pathway is connected to the production of glutathione (GSH), which has potent antioxidant capacity in the liver. Accumulating data show that GSH depletion renders the liver vulnerable to oxidative stress and prone to progression of liver disease. In this review, we highlight the importance of homeostasis in the metabolism of sulfur-containing amino acids with a particular focus on the transsulfuration pathway which could be a promising therapeutic target in liver injury.
Phosphorylation of proteins on serine or threonine residues preceding proline is a pivotal signaling mechanism regulating cell proliferation. The recent identification and characterization of the enzyme peptidyl–prolyl cis/trans isomerase never in mitosis A (NIMA)-interacting 1 (PIN1) has led to the discovery of a new mechanism regulating phosphorylation in cell signaling. PIN1 specifically binds phosphorylated serine or threonine residues immediately preceding proline (pSer/Thr-Pro) and then regulates protein functions, including catalytic activity, phosphorylation status, protein interactions, subcellular location, and protein stability, by promoting cis/trans isomerization of the peptide bond. Recent results have indicated that such conformational changes following phosphorylation represent a novel signaling mechanism in the regulation of many cellular functions. Understanding this mechanism also provides new insight into the pathogenesis and treatment of human hepatocellular carcinoma. A better understanding of the role of PIN1 in the pathogenesis of hepatocellular carcinoma may lead to the identification of molecular targets for prevention and therapeutic intervention.
Liver fibrosis is a wound healing process that includes inflammation, deposition of extracellular matrix molecules, and pathological neovascularization. Angiogenesis, which is defined by the formation of new blood vessels from pre-existing vessels, is a complex and dynamic process under both physiological and pathological conditions. Although whether angiogenesis can induce or occur in parallel with the progression of hepatic fibrosis has not yet been determined, intrahepatic sinusoidal formation and remodeling are key features of liver fibrosis. Some recent evidence has suggested that experimental inhibition of angiogenesis ameliorates the development of liver fibrosis, while other recent studies indicate that neutralization or genetic ablation of vascular endothelial growth factor (VEGF) in myeloid cells can delay tissue repair and fibrosis resolution in damaged liver. In this review, we briefly summarize the current knowledge about the differential roles of angiogenesis in the induction of fibrogenesis and the resolution of fibrosis in damaged livers. Possible strategies for the prevention and treatment of liver fibrosis are also discussed.
Hepatocellular carcinoma (HCC) is the sixth most common cancer and the third most lethal neoplasm, causing an estimated 700000 deaths annually. Currently HCC has only one systemic molecular targeted therapy, the multi-kinase inhibitor, sorafenib. The standard-of-care for advanced liver cancer is limited because sorafenib can expand the median life expectancy of patients for only 1 year. Thus there is an urgent need to develop a novel molecular targeted therapy to improve therapeutic outcomes for HCC. HCCs are phenotypically and genetically heterogeneous tumors driven by diverse molecular mechanisms. However, HCCs exhibit certain common traits selected through genetic and epigenetic alterations. The identification of common molecular alterations may provide an opportunity to develop more effective anticancer treatment through targeted therapy. Recent studies in liver cancer biology have revealed a limited number of molecular targets responsible for initiating and maintaining dysregulated cell proliferation, including vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), fibroblast growth factor receptor (FGFR), platelet-derived growth factor receptor (PDGFR), c-mesenchymal-epithelial transition factor-1 (c-Met), mammalian target of rapamycin (mTOR) and histone deacetylases (HDACs). New treatments involving inhibitors targeting several of these critical pathways are in development. This review describes the current understanding of target pathways, ongoing clinical trials using HCC-targeted agents, and future directions in the treatment of HCC.
We previously showed that anthraquinones (including rhein, emodin, aloe-emodin, chrysophanol and physcion) were inhibitors of human organic anion transporter 1 (hOAT1) and hOAT3, causing transporter-mediated drug–drug interactions in rats. In this study, the time-dependent inhibition (TDI) of hOAT1 and hOAT3 by anthraquinones was investigated. Madin–Darby canine kidney (MDCK)-hOAT1, HEK293-hOAT3 and their parental cells were used. Preincubation with chrysophanol or physcion for 30 min significantly increased the inhibition of hOAT1, but preincubation with rhein, emodin, aloe-emodin or probenecid had no effect on hOAT1 activity. By contrast, preincubation of hOAT3 with emodin, aloe-emodin, chrysophanol or physcion for 30 min significantly increased its inhibition, but preincubation with rhein or probenecid had no effect on activity. As the incubating time lengthened, from 0 to 60 min, both the inhibition of hOAT1 by chrysophanol and physcion and the inhibition of hOAT3 by emodin, aloe-emodin, chrysophanol and physcion were observed to increase in a time-dependent manner. In conclusion, our results suggest that some anthraquinones contribute to the TDI of hOAT1 and hOAT3. An inhibition study without the preincubation procedure may underestimate the inhibitory potential of anthraquinones against hOAT1 and hOAT3. The underlying mechanisms of TDI of hOAT1 and hOAT3 need to be further investigated.
Pharmacokinetic research in China on the use of voriconazole in critically ill adult patients with different pulmonary diseases remains to be explored. This study evaluated the population pharmacokinetics of the use of voriconazole (VRC) in critically ill patients to determine covariate effects on VRC pharmacokinetics by NONMEM, which could further optimize VRC dosing in this population. A one-compartment model with first-order absorption and elimination best fit the data, giving 4.28 L/h clearance and 93.4 L volume of distribution of VRC. The model variability, described as an approximate percentage coefficient of interindividual variability in clearance and volume of distribution, was 72.94% and 26.50%, respectively. A significant association between Cmin and drug response or grade 2 hepatotoxicity was observed (p=0.002, <0.001, respectively, 1.5–4.0 µg/mL) via logistic multivariate regression. Monte Carlo simulations at 100, 150, 200, and 250 mg dosage predicted effectiveness at 45.99%, 99.76%, 98.76%, and 67.75% within the 1.5–4.0 µg/mL range, suggesting that a 150 or 200 mg intravenous dose twice daily is best suited to achieve the target steady state trough concentration range in critically ill patients with pulmonary disease.
Nonalcoholic fatty liver disease (NAFLD) is the most common chronic liver disease worldwide. Paeoniflorin, a natural product and active ingredient of Paeonia lactiflora, has been demonstrated to have many pharmacological effects including antiinflammatory and antihyperglycemic activity. We investigated the effects of paeoniflorin on NAFLD in mice and its underlying mechanisms. We examined this hypothesis using a well-established animal model of NAFLD. The effects of paeoniflorin on inflammation and glucolipid metabolism disorder were evaluated. The corresponding signaling pathways were measured using real-time polymerase chain reaction (PCR). We demonstrated that the mice developed obesity, dyslipidemia, and fatty liver, which formed the NAFLD model. Paeoniflorin attenuated NAFLD and exhibited potential cardiovascular protective effects in vivo by lowering body weight, hyperlipidemia, and insulin resistance; blocking inflammation; and inhibiting lipid ectopic deposition. Further investigation revealed that the antagonistic effect on hyperlipidemia and lipid ectopic deposition was related to lowering the lipid synthesis pathway (de novo pathway, 3-hydroxy-3-methyl glutaryl coenzyme A reductase (HMG-CoAR)), promoting fatty acid oxidation [peroxisome proliferator-activated receptor-alpha (PPARα), carnitine palmitoyltransferase-1, etc.] and increasing cholesterol output (PPARγ-liver X receptor-α-ATP-binding cassette transporter-1); the inhibitory effects on inflammation and hyperglycemia were mediated by blocking inflammatory genes activation and reducing gluconeogenic genes expression (phosphoenolpyruvate carboxykinase and G6Pase). These results suggest that paeoniflorin prevents the development of NAFLD and reduces the risks of atherosclerosis through multiple intracellular signaling pathways. It may therefore be a potential therapeutic compound for NAFLD.
Sphingosine-1-phosphate type-1 receptor (S1P1) agonists have the potential to inhibit the egress of lymphocytes, and have been demonstrated to provide protective effects on some acute inflammatory diseases. However, the value of S1P1 agonists on acute pancreatitis (AP) remains unclear. The aim of this study was to explore the effect of SEW2871, a S1P1-selective agonist, on caerulein-induced AP in mice. AP was induced by giving eight intraperitoneal injections of caerulein (50 µg/kg/h) at hourly intervals. SEW2871 was administered by gavage, at a dose of 20 mg/kg, at 0 h and 12 h after the first intraperitoneal injection of caerulein. The mice were sacrificed at 24 h. Severity of AP, serum amylase and lipase activity, levels of serum cytokines, pancreatic myeloperoxidase (MPO) activity, CD45+CD4+ T lymphocytes in blood, CD4+ T cell infiltration in the pancreas, and proinflammatory cytokine production were assessed. Furthermore, the expression of signal transducer and activator of transcription (STAT) 3 and phospho-STAT3 (p-STAT3) in the pancreas was also evaluated. The results revealed that the administration of SEW2871 ameliorated the severity of AP, by a reduction of serum pancreatic enzyme activity and levels of cytokines, decreased pancreatic MPO activity, depletion of CD4+CD45+ T lymphocytes in the blood and a reduction of CD4+ T cell infiltration in the pancreas. Furthermore, the expression of proinflammatory cytokines mRNA and p-STAT3 were also suppressed by SEW2871 treatment. These results suggest that SEW2871 treatment attenuates the severity of caerulein-induced AP in mice, which may provide a new therapeutic approach for AP therapy.
When local anesthetics are used, the administration of dexmedetomidine (DEX) can prolong analgesic duration. However, the effect of caudal DEX on high volume/low concentration (HVLC) local anesthetics has not been studied. We investigated the analgesic effect of DEX added to a HVLC of ropivacaine for caudal block in children. Eighty children (the American Society of Anesthesiologists (ASA) status I; age, 1–6 years) undergoing ambulatory orchiopexy were enrolled in the study. Children were randomly assigned to undergo a caudal block with 1.5 mL/kg of 0.15% ropivacaine and either 1 µg/kg of DEX (DEX group, n=40) or the same amount of saline (Control group, n=40) under general anesthesia. The results showed that the time to first analgesic request was significantly longer in the DEX group than in the control group. The sevoflurane requirement for anesthesia and frequency of emergence agitation (EA) were also significantly lower in the DEX group. There was no difference in adverse events between the two groups. In conclusion, a dose of 1 µg/kg of caudal DEX prolonged the first analgesic request time, although the immediate postoperative pain scores were comparable in both groups. Furthermore, caudal DEX significantly reduced the sevoflurane requirement and the frequency of EA.
The oral absorption of dronedarone (DRN), a benzofuran derivative with anti-arrhythmic activity, is significantly affected by food intake. The absolute bioavailability of the marketed product (Multaq®, Sanofi, U.S.) was about 4% without food, but increased to 15% when administered with a high fat meal. Therefore, to reduce the food-effect on the intestinal absorption of DRN, a novel self-microemulsifying drug delivery system (SMEDDS) was formulated and the comparative in vivo absorption studies with the marketed product were carried out using male beagle dogs either in the fasted or fed state. The SMEDDS consisted of the drug, Labrafil M 1944CS, and Kolliphor EL in a weight ratio of 1 : 1 : 2, rapidly formed a fine oil-in-water emulsion with a droplet size less than 50 nm. An in vivo absorption study revealed that the area-under-curve (AUC0–24 h) and maximal plasma concentration (Cmax) were 10.4-fold (p<0.05) and 8.6-fold (p<0.05) higher, respectively, after the marketed product was orally administered to beagles in the fed state when compared to those in the fasted state. This food-effect were remarkably alleviated by SMEDDS formulation, with AUC0–24 h and Cmax 2.9-fold (p<0.05) and 2.6-fold (p<0.05) higher in the fed state when compared to the fasted state, by facilitating intestinal absorption of DRN in the fasted state. The results of this study suggest that SMEDDS may decrease the differences in oral absorption of DRN between the prandial states, improving therapeutic efficacy as well as patient compliance.
To develop a novel solid dispersion of clopidogrel napadisilate monohydrate (CNM) with improved stability and oral bioavailability, surface-modified solid dispersions were prepared by spray-drying using water as a solvent, Tween 80 as a surfactant, and hydroxypropylmethyl cellulose (HPMC) as a hydrophilic polymer, and optimized according to drug solubility. Its solid-state characterization was evaluated by scanning electron microscopy (SEM), powder X-ray diffraction (PXRD) and differential scanning calorimetry (DSC). The stability study was performed at 50°C/75% RH over a period of 6 weeks. Its dissolution profiles and oral bioavailability in rats were also compared with that of CNM and clopidogrel bisulfate (CB). The solid dispersion, composed of CNM/HPMC/Tween80 at a weight ratio of 10/2.5/2.5, in which CNM was in the crystalline state, increased the drug solubility approximately 4.6-fold. It showed a significantly better dissolution profile than that of CNM in all the dissolution media, and gave either similar or higher dissolution compared to that of CB. This solubility and dissolution enhancement was attributed to improved wetting and solubilization of CNM crystals due to hydrophilic carriers attached on the drug surface. It had excellent stability, thereby addressing the stability problem of CB powder. Furthermore, it increased the area under curve (AUC) values by about 4-fold and 1.6-fold compared to CNM and CB, respectively, suggesting that it improved the oral bioavailability of the drug in rats. Thus, this solid dispersion system prepared with water, HPMC and Tween 80 can be used to enhance the bioavailability of CNM as well as to solve the stability problem of CB.
In this study we describe the design, synthesis, and antibacterial activity of novel pleuromutilin analogs. A series of new compounds containing piperazine and alkylamino or arylamino groups was synthesized. The new compounds were characterized via1H-NMR, 13C-NMR, Fourier transform (FT)-IR and MS, and were further evaluated for their in vitro activity against seven Gram-positive, and one Gram-negative, pathogens. Antibacterial data revealed that all compounds exhibited moderate to good antibacterial activities against sensitive Gram-positive pathogens. Specifically, 9d displayed the best activity: its activity to Staphylococcus aureus (ATCC25923) is 0.125 µg/mL, which is equal to the control compound tiamulin. The antibacterial activities of 9d to Streptococcus suis (minimum inhibitory concentration (MIC) of 2 µg/mL), Streptococcus agalactiae (MIC of 0.5 µg/mL), and Streptococcus dysgalactiae (MIC of 0.5 µg/mL) were also excellent compared with the control drug erythromycin (MIC of >128 µg/mL). The binding modes of these compounds with active sites were calculated using the programs of Molecular Operating Environment (MOE) and Pymol.
Paraquat is one of the most widely used herbicides in the world and is highly toxic to humans and animals. In this study, we developed a serum metabolomic method based on GC/MS to evaluate the effects of acute paraquat poisoning on rats. Pattern recognition analysis, including both principal component analysis and partial least squares-discriminate analysis revealed that acute paraquat poisoning induced metabolic perturbations. Compared with the control group, the level of octadecanoic acid, L-serine, L-threonine, L-valine, and glycerol in the acute paraquat poisoning group (36 mg/kg) increased, while the levels of hexadecanoic acid, D-galactose, and decanoic acid decreased. These findings provide an overview of systematic responses to paraquat exposure and metabolomic insight into the toxicological mechanism of paraquat. Our results indicate that metabolomic methods based on GC/MS may be useful to elucidate the mechanism of acute paraquat poisoning through the exploration of biomarkers.
Due to health concerns about phthalate esters, the use of alternative plasticizers is being considered. Phthalate esters enhance skin sensitization to fluorescein isothiocyanate (FITC) in mouse models. We have demonstrated that phthalate esters stimulate transient receptor potential ankyrin 1 (TRPA1) cation channels expressed on sensory neurons. We also found a correlation between TRPA1 activation and the enhancing effect on FITC-induced contact hypersensitivity (CHS) when testing various types of phthalate esters. Here we investigated the effects of an alternative plasticizer, diisopropyl adipate (DIA). Activation of TRPA1 by DIA was demonstrated by calcium mobilization using Chinese hamster ovary cells expressing TRPA1 in vitro. The effect of DIA was inhibited by a TRPA1-specific antagonist, HC-030031. The presence of DIA or dibutyl phthalate (DBP; positive control) during skin sensitization of BALB/c mice to FITC augmented the CHS response, as revealed by the level of ear-swelling. The enhancing effect of DIA was inhibited by in vivo pretreatment with HC-030031. FITC-presenting CD11c+ dendritic cell (DC)-trafficking to draining lymph nodes was facilitated both by DIA and by DBP. DBP and DIA were similarly active in the enhancement of interferon-γ production by draining lymph nodes, but the effect on interleukin-4 production was weaker with DIA. Overall, DIA activated TRPA1 and enhanced FITC-induced CHS, as DBP did. The adjuvant effects of adipate esters may need to be considered because they are used as ingredients in cosmetics and drug formulations topically applied to the skin.
Hypercalcemia is often observed in postmenopausal women as well as in patients with primary hyperparathyroidism or malignant tumors. In this study, we investigated the relationship between calcium ion (Ca2+) levels in lacrimal fluid and the rate of corneal wound healing in hypercalcemia using ovariectomized (OVX) rat debrided corneal epithelium. We also determined the effects of Ca2+ levels on cell adhesion, proliferation and viability in a human cornea epithelial cell line (HCE-T). The calcium content in bones of OVX rats decreased after ovariectomy. Moreover, the Ca2+ content in the blood of OVX rats was increased 1 month after ovariectomy, and decreased. The Ca2+ content in the lacrimal fluid of OVX rats was also increased after ovariectomy, and then decreased similarly as in blood. Corneal wound healing in OVX rats was delayed in comparison with Sham rats (control rats), and a close relationship was observed between the Ca2+ levels in lacrimal fluid and the rate of corneal wound healing in Sham and OVX rats (y=−0.7863x+8.785, R=0.78, n=25). In addition, an enhancement in Ca2+ levels caused a decrease in the viability in HCE-T cells. It is possible that enhanced Ca2+ levels in lacrimal fluid may cause a decrease in the viability of corneal epithelial cells, resulting in a delay in corneal wound healing. These findings provide significant information that can be used to design further studies aimed at reducing corneal damage of patients with hypercalcemia.
We have developed a simple protocol for inducing the myocardial differentiation of human induced pluripotent stem (iPS) cells. Human iPS cell-derived embryonic bodies (EBs) were treated with a combination of activin-A, bone morphogenetic protein-4 and wnt-3a for one day in serum-free suspension culture, and were subsequently treated with noggin for three days. Thereafter, the EBs were subjected to adherent culture in media with 5% serum. All EBs were differentiated into spontaneously beating EBs, which were identified by the presence of striated muscles in transmission electron microscopy and the expression of the specific cardiomyocyte markers, NKX2-5 and TNNT2. The beating rate of the beating EBs was decreased by treatment with a rapidly activating delayed rectifier potassium current (Ikr) channel blocker, E-4031, an Ikr trafficking inhibitor, pentamidin, and a slowly activating delayed rectifier potassium current (Iks) channel blocker, chromanol 293B, and was increased by treatment with a beta-receptor agonist, isoproterenol. At a low concentration, verapamil, a calcium channel blocker, increased the beating rate of the beating EBs, while a high concentration decreased this rate. These findings suggest that the spontaneously beating EBs were myocardial cell clusters. This simple protocol for myocardial differentiation would be useful in providing a sufficient number of the beating myocardial cell clusters for studies requiring human myocardium.
Endoplasmic reticulum stress has been reported to be involved in the pathogenesis of retinitis pigmentosa, macular degeneration and diabetic retinopathy. In the present study, we examined the effects of deferiprone, an iron chelator, on photoreceptor degeneration induced by tunicamycin (300 nmol/eye), an endoplasmic reticulum stress inducer, in the rat retina. Scotopic electroretinogram measurement and morphometric evaluation were done 7 d after the injection of tunicamycin. In the scotopic electroretinogram, intravitreal deferiprone (5 nmol/eye) injected simultaneously with tunicamycin significantly reduced the decreases in a- and b-wave amplitudes induced by tunicamycin. Morphometric evaluation showed that deferiprone significantly reduced thinning of the outer nuclear layer, the inner segment and the outer segment. These results suggest that iron chelation therapy may be a good candidate for the treatment of eye diseases related to endoplasmic reticulum stress.
To identify bioactive natural products possessing anti-inflammatory activity, the potential of fulgidic acid from the rhizomes of Cyperus rotundus and the underlying mechanisms involved in its anti-inflammatory activity were evaluated in this study. Fulgidic acid reduced the production of nitric oxide (NO), prostaglandin E2 (PGE2), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) in lipopolysaccharide (LPS)-induced RAW264.7 macrophages. Consistent with these findings, fulgidic acid suppressed the LPS-induced expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) at the protein level, as well as iNOS, COX-2, TNF-α, and IL-6 at mRNA levels. Fulgidic acid suppressed the LPS-induced transcriptional activity of activator protein-1 (AP-1) as well as the phosphorylation of c-Fos and c-Jun. On the other hand, fulgidic acid did not show any effect on LPS-induced nuclear factor κB (NF-κB) activity. Taken together, these results suggest that the anti-inflammatory effect of fulgidic acid is associated with the suppression of iNOS, COX-2, TNF-α, and IL-6 expression through down-regulating AP-1 activation in LPS-induced RAW264.7 macrophages.
The purpose of this study was to elucidate the transport mechanism(s) of L-glutamate (L-Glu), a neuroexcitatory neurotransmitter, in the inner blood–retinal barrier (BRB). The L-Glu transport was evaluated by an in vitro uptake study with a conditionally-immortalized rat retinal capillary endothelial cell line, TR-iBRB2 cells. L-Glu uptake by TR-iBRB2 exhibited time- and concentration-dependence, and was composed of high- and low-affinity processes with Michaelis–Menten constants (Km) of 19.3 µM and 275 µM, respectively. Under Na+-free conditions, L-Glu uptake by TR-iBRB2 involved one-saturable kinetics with a Km of 190 µM, which is similar to that of the low-affinity process of L-Glu uptake under normal conditions. Moreover, substrates/inhibitors of system Xc−, which is involved in blood-to-retina transport of compounds across the inner BRB, strongly inhibited the L-Glu uptake under Na+-free conditions, suggesting that Na+-independent low-affinity L-Glu transport at the inner BRB is carried out by system Xc−. Regarding the Na+-dependent high affinity process of L-Glu transport at the inner BRB, L-Glu uptake by TR-iBRB2 under normal conditions was significantly inhibited by substrates/inhibitors of excitatory amino acid transporter (EAAT) 1–5, but not alanine-serine-cysteine transporters. Reverse-transcription polymerase chain reaction (RT-PCR) analysis and immunoblot analysis demonstrated that mRNA and protein of EAAT1 are expressed in TR-iBRB2 cells, whereas mRNAs and/or proteins of EAAT2-5 are not. Immunohistochemical analysis revealed that EAAT1 protein is localized on the abluminal membrane of the retinal capillaries. In conclusion, EAAT1 most likely mediates Na+-dependent high-affinity L-Glu transport at the inner BRB and appears to take part in L-Glu elimination from the retina across the inner BRB.