Comparative transcriptome and metabolome analyses revealed quality difference between beauty tea processed through indoor withering and outdoor solar withering

BACKGROUND

Withering is the first processing procedure of beauty tea, and there are few reports on the impact of withering methods on the quality of beauty tea and its regulatory mechanisms.

RESULTS

Through comparison of fresh tea leaves (FT) with the leaves after indoor natural withering for 18 h (IWT-18) and outdoor solar withering for 6 h (OWT-6), which were collected at the end of the two withering processes, 17 282 and 13 984 differentially expressed genes (DEGs) were respectively screened and 267 and 154 differential metabolites (DMs) were respectively identified. The coexpression network revealed that a large number of DEGs and DMs were enriched in phenylpropanoid, flavonoid, and adenosine triphosphate binding cassette (ABC) transporter pathways, and the number of DMs and DEGs in IWT-18 versus FT exceeded that in OWT-6 versus FT. Both withering methods promoted a significant increase in content of phenylalanine and upregulation of β-glucoside expression in the phenylpropanoid metabolism pathway. Five theaflavin-type proanthocyanidins in the flavonoid synthesis pathway were more significantly accumulated in FT versus IWT-18 than in FT versus OWT-6. Meanwhile, both withering methods can affect the ABC transporter pathway to promote the accumulation of amino acids and their derivatives, but different withering methods affect different ABC transporter families. Outdoor withering with more severe abiotic stress has a greater impact on the ABCG family, whereas indoor withering has a more significant effect on the ABCC family. Sensory evaluation results showed that the dry tea of IWT-18 was slightly better than that of OWT-6 because of the longer withering time and more thorough substance transformation.

CONCLUSION

In conclusion, the formation of honey flavor in beauty tea may be closely related to the DEGs and DMs in these three pathways. Our research provides theoretical data support for further revealing the mechanism of quality formation during the withering process of beauty tea. © 2023 Society of Chemical Industry.

Super-resolution imaging of flat-mounted whole mouse cornea

Super-resolution microscopy revolutionized biomedical research with significantly improved imaging resolution down to the molecular scale. To date, only limited studies reported multi-color super-resolution imaging of thin tissue slices mainly because of unavailable staining protocols and incompatible imaging techniques. Here, we show the first super-resolution imaging of flat-mounted whole mouse cornea using single-molecule localization microscopy (SMLM). We optimized immunofluorescence staining protocols for β-Tubulin, Vimentin, Peroxisome marker (PMP70), and Histone-H4 in whole mouse corneas. Using the optimized staining protocols, we imaged these four intracellular protein structures in the epithelium and endothelium layers of flat-mounted mouse corneas. We also achieved simultaneous two-color spectroscopic SMLM (sSMLM) imaging of β-Tubulin and Histone-H4 in corneal endothelial cells. The spatial localization precision of sSMLM in these studies was around 20-nm. This work sets the stage for investigating multiple intracellular alterations in corneal diseases at a nanoscopic resolution using whole corneal flat-mount beyond cell cultures.

Mass spectrometry-based abundance atlas of ABC transporters in human liver, gut, kidney, brain and skin

ABC transporters (ATP-binding cassette transporter) traffic drugs and their metabolites across membranes, making ABC transporter expression levels a key factor regulating local drug concentrations in different tissues and individuals. Yet, quantification of ABC transporters remains challenging because they are large and low-abundance transmembrane proteins. Here, we analysed 200 samples of crude and membrane-enriched fractions from human liver, kidney, intestine, brain microvessels and skin, by label-free quantitative mass spectrometry. We identified 32 (out of 48) ABC transporters: ABCD3 was the most abundant in liver, whereas ABCA8, ABCB2/TAP1 and ABCE1 were detected in all tissues. Interestingly, this atlas unveiled that ABCB2/TAP1 may have TAP2-independent functions in the brain and that biliary atresia (BA) and control livers have quite different ABC transporter profiles. We propose that meaningful biological information can be derived from a direct comparison of these data sets.

1H, 13C, 15N backbone resonance assignments of the apo and holo forms of the ABC transporter solute binding protein PiuA from Streptococcus pneumoniae

Streptococcus pneumoniae is a Gram-positive human pathogen that causes millions of infections worldwide with an increasing occurrence of antibiotic resistance. Iron acquisition is essential for its survival and virulence, especially under host-imposed nutritional immunity. S. pneumoniae expresses several ATP-binding cassette (ABC) transporters to facilitate acquisition under iron limitation, including PitABCD, PiaABCD, and PiuBCDA. The substrate specificity of PiuBCDA is not fully established. Herein, we report the backbone ¹H, ¹³C and ¹⁵N resonance assignments of the 31 kDa soluble, extracellular domain of the substrate binding protein PiuA in the apo form and in complex with Ga(III) and the catechol siderophore-mimic 4-LICAM. These studies provide valuable information for further functional studies of interactions with other proteins, metals, and small molecules.

Developmental patterns in human blood-brain barrier and blood-cerebrospinal fluid barrier ABC drug transporter expression

When drugs exert their effects in the brain, linear extrapolation of doses from adults could be harmful for children as the blood-brain barrier (BBB) and blood-CSF barrier (BCSFB) function is still immature. More specifically, age-related variation in membrane transporters may impact brain disposition. As human data on brain transporter expression is scarce, age dependent [gestational age (GA), postnatal age (PNA), and postmenstrual age (PMA)] variation in immunohistochemical localization and staining intensity of the ABC transporters P-glycoprotein (Pgp), breast cancer resistance protein (BCRP), and multidrug resistance-associated proteins 1, 2, 4, and 5 (MRP1/2/4/5) was investigated. Post mortem brain cortical and ventricular tissue was derived from 23 fetuses (GA range 12.9-39 weeks), 17 neonates (GA range 24.6-41.3 weeks, PNA range 0.004-3.5 weeks), 8 children (PNA range 0.1-3 years), and 4 adults who died from a wide variety of underlying conditions. In brain cortical BBB, immunostaining increased with age for Pgp and BCRP, while in contrast, MRP1 and MRP2 staining intensity appeared higher in fetuses, neonates, and children, as compared to adults. BCSFB was positively stained for Pgp, MRP1, and MRP2 and appeared stable across age, while BCRP was not detected. MRP4 and MRP5 were not detected in BBB or BCSFB. In conclusion, human BBB and BCSFB ABC membrane transporters show brain location and transporter-specific maturation.

Initiation of the ABCD3-I algorithm for expediated evaluation of transient ischemic attack patients in an emergency department

BACKGROUND

The use of ABCD3-I score for Transient ischemic attack (TIA) evaluation has not been widely investigated in the ED. We aim to determine the performance and cost-effectiveness of an ABCD3-I based pathway for expedited evaluation of TIA patients in the ED.

METHODS

We conducted a single-center, pre- and post-intervention study among ED patients with possible TIA. Accrual occurred for seven months before (Oct. 2016-April 2017) and after (Oct. 2017-April 2018) implementing the ABCD3-I algorithm with a five-month wash-in period (May-Sept. 2017). Total ED length of stay (LOS), admissions to the hospital, healthcare cost, and 90-day ED returns with subsequent stroke were analyzed and compared.

RESULTS

Pre-implementation and post-implementation cohorts included 143 and 118 patients respectively. A total of 132 (92%) patients were admitted to the hospital in the pre-implementation cohort in comparison to 28 (24%) patients admitted in the post-implementation cohort (p < 0.001) with similar 90-day post-discharge stroke occurrence (2 in pre-implementation versus 1 in post-implementation groups, p > 0.05). The mean ABCD2 scores were 4.5 (1.4) in pre- and 4.1 (1.3) in post-implementation cohorts (p = 0.01). The mean ABCD3-I scores were 4.5 (1.8) in post-implementation cohorts. Total ED LOS was 310 min (201, 420) in pre- and 275 min (222, 342) in post-implementation cohorts (p > 0.05). Utilization of the ABCD3-I algorithm saved an average of over 40% of total healthcare cost per patient in the post-implementation cohort.

CONCLUSIONS

The initiation of an ABCD3-I based pathway for TIA evaluation in the ED significantly decreased hospital admissions and cost with similar 90-day neurological outcomes.

Chromate detoxification potential of Staphylococcus sp. isolates from an estuary

Chromium (Cr) pollution is an emerging environmental problem. The present study was carried out to isolate Cr-resistant bacteria and characterize their Cr detoxification and resistance ability. Bacteria screened by exposure to chromate (Cr⁶⁺) were isolated from Mandovi estuary Goa, India. Two isolates expressed high resistance to Cr⁶⁺ (MIC ≥ 300 µg mL^-1), Cr³⁺ (MIC ≥ 900 µg mL^-1), other toxic heavy metals and displayed a pattern of resistance to cephalosporins and ß-lactams. Biochemical and 16 S rRNA gene sequence analysis indicated that both isolates tested belonged to the Staphylococcus genus and were closely related to S. saprophyticus and S. arlettae. Designated as strains NIOER176 and NIOER324, batch experiments demonstrated that both removed 100% of 20 and 50 µg mL^-1 Cr⁶⁺ within 4 and 10 days, respectively. The rate of reduction in both peaked at 0.260 µg mL^-1 h^-1. ATP-binding cassette (ABC) transporter gene involved in transport of a variety of substrates including efflux of toxicants was present in strain NIOER176. Through SDS-PAGE analysis, whole-cell proteins extracted from both strains indicated chromium-induced specific induction and up-regulation of 24 and 40 kDa proteins. Since bacterial ability to ameliorate Cr⁶⁺ is of practical significance, these findings demonstrate strong potential of some estuarine bacteria to detoxify Cr⁶⁺ even when its concentrations far exceed the concentrations reported from many hazardous effluents and chromium contaminated natural habitats. Such potential of salt tolerant bacteria would help in Cr⁶⁺ bioremediation efforts.

Differentiation of Pythium spp. from vegetable crops with molecular markers and sensitivity to azoxystrobin and mefenoxam

BACKGROUND

Pythium species attack various vegetable crops causing seed, stem and root rot, and 'damping-off' after germination. Pythium diseases are prevalently controlled by two classes of fungicides, QoIs with azoxystrobin and phenlyamides with mefenoxam as representatives. The present study aimed to test the sensitivity of six Pythium species from different vegetable crops to azoxystrobin and mefenoxam and differentiating species based on ITS, cytochrome b and RNA polymerase I gene sequences.

RESULTS

The inter- and intra-species sensitivity to azoxystrobin was found to be stable, with the exception of one Pythium paroecandrum isolate, which showed reduced sensitivity and two cytochrome b amino acid changes. For mefenoxam, the inter-species sensitivity was quite variable and many resistant isolates were found in all six Pythium species, but no RNA polymerase I amino acid changes were observed in them. ITS and cytochrome b phylogenetic analyses permitted a clear separation of Pythium species corresponding to globose- and filamentous-sporangia clusters.

CONCLUSION

The results document the necessity of well-defined chemical control strategies adapted to different Pythium species. Since the intrinsic activity of azoxystrobin among species was stable and no resistant isolates were found, it may be applied without species differentiation, provided it is used preventatively to also control highly aggressive isolates. For a reliable use of mefenoxam, precise identification and sensitivity tests of Pythium species are crucial because its intrinsic activity is variable and resistant isolates may exist. Appropriate mixtures and/or alternation of products may help to further delay resistance development. © 2018 Society of Chemical Industry.

Effect of praziquantel on the differential expression of mouse hepatic genes and parasite ATP binding cassette transporter gene family members during Schistosoma mansoni infection

Schistosomiasis is a chronic parasitic disease caused by sexually dimorphic blood flukes of the genus Schistosoma. Praziquantel (PZQ) is the only drug widely available to treat the disease but does not kill juvenile parasites. Here we report the use of next generation sequencing to study the transcriptional effect of PZQ on murine hepatic inflammatory, immune and fibrotic responses to Schistosoma mansoni worms and eggs. An initial T helper cell 1 (Th1) response is induced against schistosomes in mice treated with drug vehicle (Vh) around the time egg laying begins, followed by a T helper cell 2 (Th2) response and the induction of genes whose action leads to granuloma formation and fibrosis. When PZQ is administered at this time, there is a significant reduction in egg burden yet the hepatic Th1, Th2 and fibrotic responses are still observed in the absence of granuloma formation suggesting some degree of gene regulation may be induced by antigens released from the dying adult worms. Quantitative real-time PCR was used to examine the relative expression of 16 juvenile and adult S. mansoni genes during infection and their response to Vh and PZQ treatment in vivo. While the response of stress genes in adult parasites suggests the worms were alive immediately following exposure to PZQ, they were unable to induce transcription of any of the 9 genes encoding ATP-binding cassette (ABC) transporters tested. In contrast, juvenile schistosomes were able to significantly induce the activities of ABCB, C and G family members, underscoring the possibility that these efflux systems play a major role in drug resistance.

Purified Human Bone Marrow Multipotent Mesenchymal Stem Cells Regenerate Infarcted Myocardium in Experimental Rats

Recent findings suggest the feasibility of cardiac repair by transplantation of bone marrow mesenchymal stem cell (MSCs). However, it remains controversial regarding which cell type is the best source for transplanting into the ischemic heart because of lack of well-defined cell markers. In this study, we investigated the in vitro and in vivo effects of the novel multipotent marrow mesenchymal stem cells (MMSCs) from human bone marrow. Pluripotent markers (Oct4, Bmi1, and Abcg2) and vascular endothelial growth factor (VEGF) were detected by RT-PCR and immunofluorescence in MMSCs. Myocardial differentiation was induced in the expanded MMSC cultures by treatment with 5-azacyline. Expressions of VEGF in the animals transplanted with MMSCs were markedly increased in comparison with the animals injected with fibroblasts or saline at both mRNA and protein levels. VEGF expression was observed in both transplanted MMSCs and recipient cardiomyocytes by immunofluorescence. Confocal immunofluorescence microscopy revealed the specific markers for cardiomyocytes and endothelial cells in transplanted MMSCs 14 days after transplantation. Vessel count was increased and left ventricular function improved post-MMSC transplantation. These results indicate that transplantation of purified MMSCs from human bone marrow upregulated VEGF expression, enhanced angiogenesis, and improved the functional recovery following myocardial infarction in rats.

Mechanisms of drug resistance in colon cancer and its therapeutic strategies

Drug resistance develops in nearly all patients with colon cancer, leading to a decrease in the therapeutic efficacies of anticancer agents. This review provides an up-to-date summary on over-expression of ATP-binding cassette (ABC) transporters and evasion of apoptosis, two representatives of transport-based and non-transport-based mechanisms of drug resistance, as well as their therapeutic strategies. Different ABC transporters were found to be up-regulated in colon cancer, which can facilitate the efflux of anticancer drugs out of cancer cells and decrease their therapeutic effects. Inhibition of ABC transporters by suppressing their protein expressions or co-administration of modulators has been proven as an effective approach to sensitize drug-resistant cancer cells to anticancer drugs in vitro. On the other hand, evasion of apoptosis observed in drug-resistant cancers also results in drug resistance to anticancer agents, especially to apoptosis inducers. Restoration of apoptotic signals by BH3 mimetics or epidermal growth factor receptor inhibitors and inhibition of cancer cell growth by alternative cell death pathways, such as autophagy, are effective means to treat such resistant cancer types. Given that the drug resistance mechanisms are different among colon cancer patients and may change even in a single patient at different stages, personalized and specific combination therapy is proposed to be more effective and safer for the reversal of drug resistance in clinics.

Application of image cytometry to characterize heterologous lipid flippases in yeast

Lipid flippases are integral membrane proteins that play a central role in moving lipids across cellular membranes. Some of these transporters are ATPases that couple lipid translocation to ATP hydrolysis, whereas others function without any discernible metabolic energy input. A growing number of lipid flippases has been identified but key features of their activity remain to be elucidated. A well-established method to characterize ATP-driven flippases is based on their heterologous expression in yeast, followed by incubation of the cells with fluorescent lipids. Internalization of these probes is typically monitored by flow cytometry, a costly and maintenance-intensive method. Here, we have optimized a protocol to use an automated image-based cell counter to accurately measure lipid uptake by heterologous lipid flippases expressed in yeast. The method was validated by comparison with the classical flow cytometric evaluation of lipid-labeled cells. In addition, we demonstrated that expression of fluorescently tagged flippase complexes can be directly co-related with fluorescent lipid uptake using the image-based cell counter system. The method extends the number of techniques available for characterization of lipid flippase activity, and should be readily adaptable to analyze a variety of other transport systems in yeast, parasites, and mammalian cells. © 2016 International Society for Advancement of Cytometry.

[Effect of ferulic acid on cholesterol efflux in macrophage foam cell formation and potential mechanism]

The formation of macrophage-derived foam cells is a typical feature of atherosclerosis (AS). Reverse cholesterol efflux (RCT) is one of important factors for the formation of macrophage foam cells. In this study, macrophage form cells were induced by oxidized low density lipoprotein (ox-LDL) and then treated with different concentrations of ferulic acid, so as to observe the effect of ferulic acid on the intracellular lipid metabolism in the ox-LDL-induced macrophage foam cell formation, the cholesterol efflux and the mRNA expression and protein levels of ATP binding cassette transporter A1 (ABCA1) and ATP binding cassette transporter G1 (ABCG1) that mediate cholesterol efflux, and discuss the potential mechanism of ferulic acid in resisting AS. According to the findings, compared with the control group, the ox-LDL-treated group showed significant increase in intracellular lipid content, especially for the cholesterol content; whereas the intracellular lipid accumulation markedly decreased, after the treatment with ferulic acid. The data also demonstrated that the mRNA and protein expressions of ABCA1 and ABCG1 significantly increased after macrophage foam cells were treated with different concentrations of ferulic acid. In summary, ferulic acid may show the anti-atherosclerosis effect by increasing the surface ABCA1 and ABCG1 expressions of macrophage form cells and promoting cholesterol efflux.

Discordance between protein and transcript levels detected by selected reaction monitoring

Expression levels between transcript and protein are not always correlated. In the present study, the abundance of protein PDR9/ABCG37 in 3 Arabidopsis pdr9/abcg37 mutant alleles was evaluated using selected reaction monitoring analysis. The results showed that protein and mRNA expression levels were similar in 2 mutant alleles. The mRNA expression levels in another mutant, determined by both semi-quantitative and quantitative RT-PCR, were similar to the wild-type, although the abundance of protein was about half the abundance of the wild-type. These results suggested that using only mRNA expression levels to infer protein abundance, compare mutants or responses to various stimuli may lead to incorrect interpretation and conclusions.

The ABC transporter ABCG1 is required for suberin formation in potato tuber periderm

The lipid biopolymer suberin plays a major role as a barrier both at plant-environment interfaces and in internal tissues, restricting water and nutrient transport. In potato (Solanum tuberosum), tuber integrity is dependent on suberized periderm. Using microarray analyses, we identified ABCG1, encoding an ABC transporter, as a gene responsive to the pathogen-associated molecular pattern Pep-13. Further analyses revealed that ABCG1 is expressed in roots and tuber periderm, as well as in wounded leaves. Transgenic ABCG1-RNAi potato plants with downregulated expression of ABCG1 display major alterations in both root and tuber morphology, whereas the aerial part of the ABCG1-RNAi plants appear normal. The tuber periderm and root exodermis show reduced suberin staining and disorganized cell layers. Metabolite analyses revealed reduction of esterified suberin components and hyperaccumulation of putative suberin precursors in the tuber periderm of RNA interference plants, suggesting that ABCG1 is required for the export of suberin components.

Quantitative colocalization analysis of fluorescence microscopy images

Colocalization is an important finding in many cell biological studies. This unit describes a protocol for quantitative evaluation of fluorescence microscopy images with colocalization based on calculation of a number of specialized coefficients. Images of double-stained sections are first subjected to background correction, and then various coefficients are calculated. Meanings of the coefficients and a guide to interpretation of the results of calculations based on the use of linguistic variables are given. Success in colocalization studies depends on the quality of images analyzed, proper preparation of the images for coefficients calculations, and correct interpretation of results obtained. This protocol helps ensure reliability of colocalization coefficient calculations.

Intravital multiphoton microscopy can model uptake and excretion of fluorescein in hepatic ischemia-reperfusion injury

The liver is important in the biotransformation of various drugs, where hepatic transporters facilitate uptake and excretion. Ischemia-reperfusion (I/R) injury is a common occurrence in liver surgery, and the developing oxidative stress can lead to graft failure. We used intravital multiphoton tomography, with fluorescence lifetime imaging, to characterize metabolic damage associated with hepatic I/R injury and to model the distribution of fluorescein as a measure of liver function. In addition to measuring a significant increase in serum alanine transaminase levels, characteristic of hepatic I/R injury, a decrease in the averaged weighted lifetime of reduced nicotinamide adenine dinucleotide phosphate was observed, which can be attributed to a changed metabolic redox state of the hepatocytes. I/R injury was associated with delayed uptake and excretion of fluorescein and elevated area-under-the-curve within the hepatocytes compared to sham (i.e., untreated control) as visualized and modeled using images recorded by intravital multiphoton tomography. High-performance liquid chromatography analysis showed no differences in plasma or bile concentrations of fluorescein. Finally, altered fluorescein distribution was associated with acute changes in the expression of liver transport proteins. In summary, multiphoton intravital imaging is an effective approach to measure liver function and is more sensitive in contrasting the impact of I/R injury than measuring plasma and bile concentrations of fluorescein.

Lack of prognostic significance of neuroendocrine differentiation and stem cell antigen co-expression in resected early-stage non-small cell lung cancer

BACKGROUND

Neuroendocrine (NE) carcinomas of the lung exhibit expression of various stem cell antigens, and except for carcinoid tumours, carry a poor prognosis. Despite the fact that 10%-30% of all non-small cell lung carcinomas (NSCLC) which are not classified as NE carcinomas also show expression of NE markers, data on their prognostic significance are conflicting and analyses of the expression and relevance of stem cell antigens in this subgroup are lacking.

MATERIALS AND METHODS

Tissue specimens of 100 resected early-stage NSCLC were analyzed by immunohistochemistry for the expression and prognostic significance of NE markers. Moreover, the subgroup of NSCLC with NE differentiation (ND) were assessed for the expression and prognostic significance of the stem cell antigens CD117, CD133 and breast cancer resistance protein-1 (ABCG2).

RESULTS

ND correlated significantly with adenocarcinoma histology (p=0.035), but not with prognosis. In the subgroup of ND-NSCLC (n=80), the stem cell antigens CD117, CD133 and ABCG2 were expressed in 51%, 14% and 33% of the cases, but likewise, showed no association with prognosis or clinicopathological characteristics.

CONCLUSION

This study indicates that neither ND, nor co-expression of the stem cell antigens CD117, CD133 or ABCG2, have a prognostic significance in resected early-stage NSCLC.

An evaluation of the mechanism of ABCA7 on cellular lipid release in ABCA7-HEC293 cell

BACKGROUND

ABCA7 is a member of the ABCA subfamily that shows a high degree of homology to ABCA1 and, like ABCA1, mediates cellular cholesterol and phospholipid release by apolipoproteins when transfected in vitro. However, expression of ABCA7 has been shown to be downregulated by increased cellular cholesterol while ABCA1 was upregulated.

METHODS

The underlying mechanism for this effect was examined in ABCA1 or ABCA7-transfected HEC293. Lipid content in the medium and cells was determined by enzymatic assays. Gene expression was quantitated by real time PCR, and protein content was determined by Western blotting.

RESULTS

While ABCA7 mRNA was decreased by 25-hydroxycholesterol treatment, ABCA1 was apparently increased. Treatment with the synthetic LXR agonist T0901317 (T09) upregulated ABCA1 expression and apoAI-mediated cellular lipid release in ABCA1-transfected HEC293 cells, but ABCA7 expression and cellular lipid release in ABCA7-transfected HEC293 cells showed no obvious changes.

CONCLUSION

The ABCA7 gene is regulated by sterol in a direction opposite to that of ABCA1.

Measurement of transporter associated with antigen processing 1 and tumor necrosis factor alpha expression in hepatitis B virus-related hepatocellular carcinoma and peritumor cirrhosis tissues using tissue chip technology

BACKGROUND/AIMS

The objective of this study was to explore the associations of expression of transporter associated with antigen processing 1 (TAP1) and tumor necrosis factor alpha (TNF-α with the occurrence and development of HBV-related hepatocellular carcinoma (HCC).

METHODOLOGY

The expression of TAP1 and TNF-α in 38 HCC, 32 peritumor liver cirrhosis and 28 normal liver tissues, were assessed by immunohistochemical assay using tissue microarray technology.

RESULTS

TAP1 and TNF-α were negative in normal liver tissue hut positive in HCC and peritumor cirrhosis tissue. There were no significant differences in the rates of positivity for TAP1 and TNF-α between HCC and peritumor cirrhosis tissue (p>0.05), but there was a significant difference when rates in HCC and peritumor cirrhosis tissue were compared with those in normal liver tissue (p<0.0001, p<0.01, respectively). The degree of differentiation of HCC was correlated with TNF-α expression (p<0.05), but not TAP1 expression (p>0.05), CONCLUSIONS: Major histocompatibility complex class I molecules are involved in HBV-related HCC. TNF-α plays an important role in liver cirrhosis and in formation and development of HCC following HBV infection. TNF-α can be used as an indicator of the degree of differentiation of HCC.

Shifting the paradigm: the putative mitochondrial protein ABCB6 resides in the lysosomes of cells and in the plasma membrane of erythrocytes

ABCB6, a member of the adenosine triphosphate–binding cassette (ABC) transporter family, has been proposed to be responsible for the mitochondrial uptake of porphyrins. Here we show that ABCB6 is a glycoprotein present in the membrane of mature erythrocytes and in exosomes released from reticulocytes during the final steps of erythroid maturation. Consistent with its presence in exosomes, endogenous ABCB6 is localized to the endo/lysosomal compartment, and is absent from the mitochondria of cells. Knock-down studies demonstrate that ABCB6 function is not required for de novo heme biosynthesis in differentiating K562 cells, excluding this ABC transporter as a key regulator of porphyrin synthesis. We confirm the mitochondrial localization of ABCB7, ABCB8 and ABCB10, suggesting that only three ABC transporters should be classified as mitochondrial proteins. Taken together, our results challenge the current paradigm linking the expression and function of ABCB6 to mitochondria.

miR-33a modulates ABCA1 expression, cholesterol accumulation, and insulin secretion in pancreatic islets

Changes in cellular cholesterol affect insulin secretion, and β-cell-specific deletion or loss-of-function mutations in the cholesterol efflux transporter ATP-binding cassette transporter A1 (ABCA1) result in impaired glucose tolerance and β-cell dysfunction. Upregulation of ABCA1 expression may therefore be beneficial for the maintenance of normal islet function in diabetes. Studies suggest that microRNA-33a (miR-33a) expression inversely correlates with ABCA1 expression in hepatocytes and macrophages. We examined whether miR-33a regulates ABCA1 expression in pancreatic islets, thereby affecting cholesterol accumulation and insulin secretion. Adenoviral miR-33a overexpression in human or mouse islets reduced ABCA1 expression, decreased glucose-stimulated insulin secretion, and increased cholesterol levels. The miR-33a-induced reduction in insulin secretion was rescued by cholesterol depletion by methyl-β-cyclodextrin or mevastatin. Inhibition of miR-33a expression in apolipoprotein E knockout islets and ABCA1 overexpression in β-cell-specific ABCA1 knockout islets rescued normal insulin secretion and reduced islet cholesterol. These findings confirm the critical role of β-cell ABCA1 in islet cholesterol homeostasis and β-cell function and highlight modulation of β-cell miR-33a expression as a means to influence insulin secretion.

Detection of cancer stem cell markers in sarcomas

The identification of cancer stem cell markers represents one of the very relevant research topics because cancer stem cells play important roles in tumour initiation and progression, as well as during metastasis formation and in relapse of the disease. This article summarises recent knowledge on well-known and putative cancer stem cell markers in various types of bone and soft-tissue sarcomas. Special attention is paid to the detection of CD133, ABC transporters, nestin and aldehyde dehydrogenase that have been intensively studied both in tumour tissues and in sarcoma cell lines during the past few years. Finally, an overview is given of the possible CSC phenotypes provided by functional assays of tumourigenicity.

Role of sorafenib and sunitinib in the induction of expressions of NKG2D ligands in nasopharyngeal carcinoma with high expression of ABCG2

BACKGROUND

Sorafenib and sunitinib are novel small molecule tyrosine kinase inhibitors with multiple targets on tumor cells, which have been demonstrated to be beneficial in the treatment of several carcinomas. Combining the usage of molecular targeted agents and adoptive cellular immunotherapy (ACI) against drug-resistant relapse nasopharyngeal carcinoma which had no standard therapeutic regimen was investigated by our research in order to study whether synergistic effects exist and related mechanisms.

METHODS

Human multidrug-resistant nasopharyngeal carcinoma cell line CNE2/DDP with high and low expressions of ABCG(2) (abbreviated to ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP) cells and NK cells were isolated by magnetic activated cell sorting, and the purity of isolated cells was detected by flow cytometry. mRNA expressions of drug-resistant gene ABCG(2), Bcl-2, MDR1, MRP and MGMT in ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP cells were detected by reverse transcription polymerase chain reaction (RT-PCR). Drug sensitivity of two kinds of cells to fluorouracil, cisplatin, vincristine, carboplatin, epirubicin, daunorubicin, paclitaxel, mitomycin, sorafenib, and sunitinib were detected by MTT assay. FCM was used to evaluate the expressions of NKG2D ligands (NKG2DLs,) on target cells before and after incubated with sorafenib and sunitinib. Subsequently, the cytotoxic sensitivity of incubated and un-incubated ABCG (2) (High) CNE2/DDP and ABCG (2) (Low) CNE2/DDP cells to NK cells was measured by CytoTox 96(®) Non-Radioactive Cytotoxicity Assay.

RESULTS

The results revealed that target cells' cytotoxic sensitivity to natural killer (NK) cells increased in association with up-regulation of NKG2DLs on tumor cells after incubation with sorafenib and sunitinib. Furthermore, up-regulation in sunitinib group was much higher than in sorafenib group when it came to the expressions of NKG2DLs on tumor cells. For another, ABCG (2) (High) CNE2/DDP was much more sensitive to the regulation than ABCG (2) (Low) CNE2/DDP.

CONCLUSIONS

Our research revealed for the first time that sorafenib and sunitinib could up-regulate NKG2DLs on tumor cells resulting in markedly increased tumor cells cytotoxic sensitivity to NK cells, which suggested that combining usage of molecular targeted agents and ACI may result in great benefits in clinical practice for the therapy-resistant cases and drug-resistant relapse.

Identification of stem-like cells in head and neck cancer cell lines

This study investigated the existence of stem-like cells in established head and neck squamous cell carcinoma (HNSCC) lines, HSC3 and HSC4. Flow cytometric analysis confirmed the presence of side population (SP) cells excluding Hoechst 33342 in HSC4 cells (0.37+/-0.06%) but not HSC3 cells in a reserpine-sensitive manner. After sorting, the SP cells generated both SP and main population (MP) cells in culture while MP cells generated MP cells only. Higher expression of stem cell markers was detected in SP than in MP cells. These results suggest that cancer stem-like cells exist in head and neck squamous cell carcinoma.

A novel ABC transporter: the first insight into zebrafish (Danio rerio) ABCH1

Abch1 is a novel ATP binding cassette (ABC) transporter found in fish. This study represents an initial characterisation of this transporter using phylogenetic analyses, membrane topology prediction and determination of its tissue expression pattern in adult zebrafish (Danio rerio). Blast search showed that Abch1 orthologs are not present in genomes of other vertebrate taxa and similar genes are found only in invertebrate genomes. Abch1 is most closely related to the ABCG subfamily, although it shares only 12-14% of amino acid sequence identity with ABCG subfamily members. Topology analysis indicated that Abch1 is a half transporter that consists of six transmembrane domains with reverse domain arrangement (NBD-TMD), like ABCG subfamily members, but with differences in loop organization. Tissue distribution pattern revealed the highest Abch1 expression in brain, gills and kidney, followed by lower expression in intestine, gonads, skeletal muscle and liver. Considering moderate similarity in topology and tissue distribution pattern between Abch1 and ABCG subfamily members, we speculate that Abch1 is either involved in sterol transport similar to ABCG1, or is a part of the multidrug/multixenobiotic defence like ABCG2. These hypotheses remain to be addressed in further research.

Recurrence of bile salt export pump deficiency after liver transplantation

Severe bile salt export pump (BSEP) deficiency is a hereditary cholestatic condition that starts in infancy and leads to end-stage liver disease. Three children who underwent orthotopic liver transplantation for severe BSEP deficiency had post-transplantation episodes of cholestatic dysfunction that mimicked the original disease. Remission of all episodes was achieved by intensifying the immunosuppressive regimen. The phenotypic recurrence of the disease correlated with the presence of circulating high-titer antibodies against BSEP that inhibit transport by BSEP in vitro. When administered to rats, these antibodies targeted the bile canaliculi and impaired bile acid secretion.

Breast Cancer Resistance Protein (BCRP) in Acute Leukaemia

Multidrug resistance, cross-resistance to structurally and functionally unrelated drugs, is an important cause of treatment failure in acute leukemia. Multidrug resistance can result from the overexpression of ATP-dependent efflux pumps, such as P-glycoprotein and members of the multidrug resistance associated protein (MRP) family. Recently a novel transporter has been identified, which is called breast cancer resistance protein (BCRP), ABCG2 or mitoxantrone resistance protein. BCRP confers resistance to chemotherapeutic agents, such as mitoxantrone, doxorubicin and daunorubicin. This review describes BCRP detection techniques and the normal physiology of BCRP. The role of BCRP in the physiology of hematopoietic stem cells is addressed as well as the involvement of BCRP in multidrug resistance in acute leukemia. In AML and ALL, several studies showed that BCRP is expressed and functionally active at low, but variable levels. However, further studies are warranted to investigate its effect on clinical outcome, and explore whether patients could benefit from the combination of BCRP inhibitors and chemotherapy.

Characterisation of the hepatic progenitor cell compartment in normal liver and in hepatitis: an immunohistochemical comparison between dog and man

The liver progenitor cell compartment in the normal canine liver and in spontaneous canine acute (AH) and chronic hepatitis (CH) was morphologically characterised and compared to its human equivalents. Immunohistochemistry was performed for cytokeratin-7 (CK7), human hepatocyte marker (Hep Par 1), multidrug resistance-associated protein-2 (MRP2), and breast cancer resistance protein (BCRP) on paraffin and frozen sections from canine and human tissues. Normal liver showed similar morphology and immunohistochemical reaction of the progenitor cell compartment/canal of Hering in man and dog. In addition, a ductular reaction, comparable in terms of severity, location and immunohistochemical characteristics, was observed in canine and human AH and CH. CK7 was a good marker for canine progenitor cells, including intermediate cells, which were positively identified in cases of AH and CH. In both species, BCRP was expressed in both hepatocytes and bile ducts of the normal liver, and in ductular reaction in AH and CH. MRP2 detected bile canalicular membranes in man and dog. These findings underline the similarities between canine and human liver reaction patterns and may offer mutual advantage for comparative research in human and canine spontaneous liver diseases.

Proteomic analysis in the lichen Physcia adscendens exposed to cadmium stress

This work was undertaken to explore the potential of proteomics to dissect parallel and consecutive events of cadmium stress response in the lichen Physcia adscendens (Fr.) H. Olivier. Thalli were exposed to 0 (control) and 36 microM Cd for 6, 18, 24 and 48 h. Two-dimensional electrophoresis and mass spectrometry analyses showed an 80-85% spot identity between 6 and 18 h vs. 24 and 48 h of Cd exposure. Putative heat-shock proteins and glutathione S-transferase generally increased their expression all over the Cd treatments. By contrast, ABC transporters were underexpressed after 6-18 h, but in some cases induced after 24-48 h of Cd exposure. The cytochrome P450 appeared to have a variable expression pattern over time. Overall these data suggest that a considerable importance in the response of P. adscendens thalli to Cd stress can be assumed by differential expression of various protein families.

Influence of feeder layer on the expression of stem cell markers in cultured limbal corneal epithelial cells

BACKGROUND & OBJECTIVE

The limbus is enriched with the stem cells of corneal epithelium. Auto- and allograft limbal transplantations are effective in restoring the corneal epithelium and inhibiting inflammation and neovascularization. Preserved human amniotic membrane (AM) is now widely used as a substrate for ocular surface reconstruction. The combination of limbal and AM transplantation has been shown to improve the surgical outcome in patients with total limbal stem cell deficiency (LSCD). The purpose of this study was to compare the expression of putative stem cell markers ATP binding cassette protein (ABCG2) and keratinocyte stem cell marker: p63 and differentiation markers. (connexin 43 and keratin 3 / keratin 12) on the limbal epithelial cells cultured over the denuded AM with and without the 3T3 murine fibroblast cells as feeder layer.

METHODS

Human limbal tissues obtained from the cadaveric donor eyes were cultured over the denuded human amniotic membrane in the presence of mitomycin C treated 3T3 fibroblasts and the cultured cells studied for the expression of ABCG2 and p63 by immunohistochemistry and Western blot. Semi-quantitative reverse transcriptase polymerase chain reaction (RT-PCR) was done on the cultured cells at varying intervals of time for expression of ABCG2, p63, connexin43 (Cnx43), and keratin 3 (K3) and keratin 12 (K12).

RESULTS

The growth rates were similar in both denuded AM and denuded AM + 3T3. The cells cultured over AM + 3T3 showed the expression of p63 and ABCG2 till 21 days of incubation by immunohistochemistry and Western blot. The expression of p63 and ABCG2 were retained till 21 days of incubation on the cells cultured over denuded AM + 3T3, whereas it was expressed only till day 8 on the cells cultured over the denuded membrane by semi quantitative RT-PCR. Cnx43 and K3/K12 were observed in both the conditions.

INTERPRETATION & CONCLUSION

The limbal epithelial cells cultured in the presence of mitomycin C treated 3T3 feeder layer were able to maintain the expression of putative stem cell markers. Further in vitro studies using feeder layer will enable us to understand the factors, which play a role in maintaining the limbal stem cell niche.

Detection and characterization of CD133+ cancer stem cells in human solid tumours

BACKGROUND

Osteosarcoma is the most common primary tumour of bone. Solid tumours are made of heterogeneous cell populations, which display different goals and roles in tumour economy. A rather small cell subset can hold or acquire stem potentials, gaining aggressiveness and increasing expectancy of recurrence. The CD133 antigen is a pentaspan membrane glycoprotein, which has been proposed as a cancer stem cell marker, since it has been previously demonstrated to be capable of identifying a cancer initiating subpopulation in brain, colon, melanoma and other solid tumours. Therefore, our aim was to observe the possible presence of cells expressing the CD133 antigen within solid tumour cell lines of osteosarcoma and, then, understand their biological characteristics and performances.

METHODOLOGY AND PRINCIPAL FINDINGS

In this study, using SAOS2, MG63 and U2OS, three human sarcoma cell lines isolated from young Caucasian subjects, we were able to identify and characterize, among them, CD133+ cells showing the following features: high proliferation rate, cell cycle detection in a G2\M phase, positivity for Ki-67, and expression of ABCG2 transporters. In addition, at the FACS, we were able to observe the CD133+ cell fraction showing side population profile and forming sphere-clusters in serum-free medium with a high clonogenic efficiency.

CONCLUSIONS

Taken together, our findings lead to the thought that we can assume that we have identified, for the first time, CD133+ cells within osteosarcoma cell lines, showing many features of cancer stem cells. This can be of rather interest in order to design new therapies against the bone cancer.

Effects of combined PPARgamma and PPARalpha agonist therapy on reverse cholesterol transport in the Zucker diabetic fatty rat

AIM

We investigated the effects of the combined therapy of PPARgamma and PPARalpha agonists on HDL metabolism, especially concerning reverse cholesterol transport (RCT), using Zucker diabetic fatty rats (ZDF/Crl-Lepr fa rats) that are the rodent model for type 2 diabetes with obesity, hyperlipidaemia and insulin resistance.

METHODS

The ZDF rats were divided into four medicated groups as follows: pioglitazone as a PPARgamma agonist (5 mg/kg/day; P group, n = 6), fenofibrate as a PPARalpha agonist (30 mg/kg/day; F group, n = 6), both these medications (P + F group, n = 6) and no treatment (UNT group, n = 6). Non-diabetic rats (ZDF/GmiCrl-lean, CON group, n = 6) served as controls. We evaluated HDL particle size and messenger RNA (mRNA) levels of the following factors: liver X receptor alpha (L x R alpha), ATP-binding cassette A1 (ABCA1) and ABCG1 which are regulated by PPARs and are related to early stage RCT.

RESULTS

The significant increase in HDL particle size was demonstrated in rats of the F and P + F groups, although changes in plasma HDL-cholesterol levels were not significant. In accordance with this finding, mRNA levels of ABCG1 in the liver increased significantly.

CONCLUSIONS

These findings suggest the efficacy of combined therapy with PPARgamma and PPARalpha in improving lipid metabolism, partly through the enhanced RCT, and insulin resistance in type 2 diabetes mellitus.

Up-regulation of MRP4 and down-regulation of influx transporters in human leukemic cells with acquired resistance to 6-mercaptopurine

To investigate the mechanism of cellular resistance to 6-MP, we established a 6-MP resistant cell line (CEM-MP5) by stepwise selection of the human T-lymphoblastic leukemia cell line (CEM). CEM-MP5 cells were about 100-fold resistant to 6-MP compared with parental CEM cells. Western blot analysis demonstrated that multidrug resistant protein 4 (MRP4) was increased in CEM-MP5 cells, whereas the levels of the nucleoside transporters hENT1, hCNT2 and hCNT3 were decreased compared with those of parental CEM cells. Consistent with the operation of an efflux pump, accumulation of [14C]6-MP and/or its metabolites was reduced, and ATP-dependent efflux was increased in CEM-MP5 cells. Taken together these results showed that up-regulation of MRP4 and down-regulation of influx transporters played a major role in 6-MP resistance of CEM-MP5 cells.

ME3738 protects against lithocholic acid-induced hepatotoxicity, which is associated with enhancement of biliary bile acid and cholesterol output

ME3738 (22beta-methoxyolean-12-ene-3beta, 24(4beta)-diol), a derivative of soyasapogenol, attenuates liver disease in several models of chronic liver inflammation. In the present study, we have investigated a protective effect of ME3738 in a typical bile acid-induced cholestatic liver model, lithocholate (LCA) feeding mouse. Co-administration of ME3738 resulted in decreases in plasma alanine aminotransferase (ALT) and alkaline phosphatase (ALP) activities and hepatic bile acid level, and increases in biliary outputs of bile acid and cholesterol, as compared with the results in mice treated with LCA alone. LCA sulfation by hydroxysteroid sulfotransferase 2a and hydroxylation have been reported to be involved in protection against LCA-induced hepatotoxicity. ME3738-treatment, however, had no clear influence on the hydroxysteroid sulfotransferase 2a protein level and LCA 6alpha-, 6beta- and 7alpha-hydroxylase activities, but increased biliary cholesterol output. Cholate (CA)-treatment has been shown to induce hepatotoxicity in farnesoid X receptor-null mice, which is scarcely dependent on bile acid sulfation and hydroxylation but associated with decreased biliary bile acid output. Co-administration of ME3738 decreased the ALT and ALP activities and hepatic bile acid level, and increased biliary outputs of bile acid and cholesterol in farnesoid X receptor-null mice, as compared with the results in the mice treated with CA. Moreover, a clear correlation between biliary outputs of cholesterol and bile acid was observed in these two bile acid-induced hepatotoxicity mouse models. These results suggest that ME3738 protects against bile acid-induced hepatotoxicity through increased biliary bile acid output that is not related to bile acid metabolism but associated with cholesterol output.

Use of arrays to investigate the contribution of ATP-binding cassette transporters to drug resistance in cancer chemotherapy and prediction of chemosensitivity

Multidrug resistance (MDR) is a major problem in cancer chemotherapy. One of the best known mechanisms of MDR is the elevated expression of ATP-binding cassette (ABC) transporters. While some members of human ABC transporters have been shown to cause drug resistance with elevated expression, it is not yet known whether the over-expression of other members could also contribute to drug resistance in many model cancer cell lines and clinics. The recent development of microarrays and quantitative PCR arrays for expression profiling analysis of ABC transporters has helped address these issues. In this article, various arrays with limited or full list of ABC transporter genes and their use in identifying ABC transporter genes in drug resistance and chemo-sensitivity prediction will be reviewed.

Molecular interaction between caveolin-1 and ABCA1 on high-density lipoprotein-mediated cholesterol efflux in aortic endothelial cells

OBJECTIVE

Caveolin-1 and ATP-binding cassette transporter A1 (ABCA1) are proteins that are involved in cellular cholesterol efflux. In this study, we analyzed the relationships between caveolin-1 and ABCA1 on high-density lipoprotein (HDL)-mediated cholesterol efflux in rat aortic endothelial cells.

METHODS AND RESULTS

Overexpression of caveolin-1 by transfection with caveolin-1 cDNA in aortic endothelial cells up-regulated ABCA1 expression and enhanced cholesterol efflux. Suppression of caveolin-1 by siRNA decreased ABCA1 expression and reduced cholesterol efflux. The number of caveolae increased after transfection with caveolin-1 into cells. Immunoprecipitation assays revealed a molecular interaction between caveolin-1 and ABCA1 in the plasma membrane and in the cytoplasm after HDL incubation. Immunoelectron microscopy demonstrated that caveolin-1 colocalized with ABCA1 in the caveolae and in the cytoplasmic vesicles; it was also found that caveolin-1 and ABCA1 colocalized with cellular cholesterol by immunofluorescence microscopy. Blocking of intracellular lipid transport by inhibitors disrupted the interaction between caveolin-1 and ABCA1 and reduced cholesterol to methyl-beta-cyclodextrin and HDL.

CONCLUSIONS

The molecular interaction between caveolin-1 and ABCA1 is associated with the HDL-mediated cholesterol efflux pathway in aortic endothelial cells.

Human ABCB6 Localizes to Both the Outer Mitochondrial Membrane and the Plasma Membrane

Expression of the ATP-binding cassette transporter ABCB6 has been associated with multiple cellular functions, including resistance to several cytotoxic agents, iron homeostasis, and porphyrin transport. To further elucidate its physiological function and/or role in drug resistance, we determined the subcellular location of ABCB6. Using three novel ABCB6-specific antibodies, Western blot analysis of cells expressing cDNA-derived or endogenous ABCB6 revealed two distinct molecular weight forms. Confocal microscopy indicates that the protein localizes to both mitochondria and the plasma membrane. Differential centrifugation revealed that the lower molecular weight form predominantly resides in the mitochondria, while the larger protein form is more abundant in the plasma membrane. Preliminary studies indicate that ABCB6 is functionally relevant in the plasma membrane, where its expression prevents the accumulation of specific porphyrins in the cell. Digitonin solubilization of mitochondria demonstrated that ABCB6 is present in the outer mitochondrial membrane, while back-titration assays with the ABCB6-specific antibodies reveal that the nucleotide binding domain of ABCB6 is cytoplasmic. These studies are the first to demonstrate that ABCB6 exists in two molecular weight forms, is localized to both the outer mitochondrial membrane and the plasma membrane, and plays a functional role in the plasma membrane.

Placental ABCA1 Expression is Reduced in Primary Antiphospholipid Syndrome Compared to Pre-eclampsia and Controls

The ATP binding cassette transporter A1 (ABCA1) mediates cellular cholesterol and phospholipid efflux, and is implicated in phosphatidylserine translocation and apoptosis. Loss of functional ABCA1 in null mice results in severe placental malformation. This study aimed to establish the placental localisation of ABCA1 and to investigate whether ABCA1 expression is altered in placentas from pregnancies complicated by pre-eclampsia and antiphospholipid syndrome. ABCA1 mRNA and protein localisation studies were carried out using in situ hybridization and immunohistochemistry. Comparisons of gene expression were performed using real-time PCR and immunoblotting. ABCA1 mRNA and protein was localised to the apical syncytium of placental villi and endothelia of fetal blood vessels within the villi. ABCA1 mRNA expression was reduced in placentas from women with APS when compared to controls (p<0.001), and this was paralleled by reductions in ABCA1 protein expression. There were no differences in ABCA1 expression between placentas from pre-eclamptic pregnancies and controls. The localisation of ABCA1 in human placenta is consistent with a role in cholesterol and phospholipid transport. The decrease in ABCA1 protein in APS may reflect reduced cholesterol transport to the fetus affecting the formation of cell membranes and decreasing the level of substrate available for steroidogenesis.

Gene expression profiles of ATP-binding cassette transporter A and C subfamilies in mouse retinal vascular endothelial cells

The purpose of this study was to quantify gene expression levels of the ATP-binding cassette (ABC) transporter A and C subfamilies ABCA1-A9, and ABCC1-6/Mrp1-6, C10/Mrp7 in mouse retinal vascular endothelial cells (RVEC) using a combination of a magnetic isolation method for mouse RVEC and real-time quantitative PCR analysis. The transcript level of endothelial cell markers, such as CD31, Tie-2, claudin-5, occludin, ABCB1a/mdr1a, and ABCG2, were more than 20-fold higher than those in the non-RVEC fraction, suggesting that RVEC in the RVEC fraction are concentrated at least 20-fold compared with those of the non-RVEC fraction. In the ABCA1 to A9 families, the transcript level of ABCA3 and A9 in the RVEC fraction was 1.2- and 32-fold higher than that in the non-RVEC fraction. Although ABCA3 was expressed in both the RVEC and non-RVEC fractions, A9 is predominantly expressed in the RVEC fraction. In the ABCC1 to C6 and C10 families, the transcript level of ABCC3, C4, and C6 in the RVEC fraction was 27-, 251-, and 242-fold higher, respectively, than that in the non-RVEC fraction, suggesting that ABCC3, C4, and C6 are predominantly expressed in the RVEC. In conclusion, ABCA3, ABCA9, ABCC3, ABCC4, and ABCC6 mRNAs are predominantly expressed at the inner blood-retina barrier (inner BRB) and appear to play a major role in the efflux transport of their substrates at the inner BRB.

The challenges of targeting chronic myeloid leukemia stem cells

Chronic myeloid leukemia (CML) is sustained by a clonally amplified population of Bcr Abl-positive pluripotent stem cells. Persistence of a large, functionally intact yet suppressed residual normal hematopoietic stem cell population in most patients with CML has made it possible to aim at the development of curative therapies. However, achieving this goal requires the identification of agents that will eradicate the leukemic stem cell population. Several potent Bcr-Abl-targeted drugs have now been introduced into clinical practice with remarkable effects. Nevertheless, accumulating data indicate that the leukemic CML stem cells in patients with chronic phase CML are less responsive to these agents than the bulk of the neoplastic cells. In this article, we review emerging evidence that CML stem cells have a number of unusual properties that underlie their relative insensitivity to treatment, including those that specifically target the Bcr-Abl oncoprotein. The biology of the neoplastic stem cells in patients with CML is clearly important to the future attainment of cures and might also prove a paradigm relevant to other types of malignancies that are sustained by transformed stem cell populations.

Physiologically regulated transgenic ABCA1 does not reduce amyloid burden or amyloid-β peptide levels in vivo

ABCA1-deficient mice have low levels of poorly lipidated apolipoprotein E (apoE) and exhibit increased amyloid load. To test whether excess ABCA1 protects from amyloid deposition, we crossed APP/PS1 mice to ABCA1 bacterial artificial chromosome (BAC) transgenic mice. Compared with wild-type animals, the ABCA1 BAC led to a 50% increase in cortical ABCA1 protein and a 15% increase in apoE abundance, demonstrating that this BAC supports modest ABCA1 overexpression in brain. However, this was observed only in animals that do not deposit amyloid. Comparison of ABCA1/APP/PS1 mice with APP/PS1 controls revealed no differences in levels of brain ABCA1 protein, amyloid, Abeta, or apoE, despite clear retention of ABCA1 overexpression in the livers of these animals. To further investigate ABCA1 expression in the amyloid-containing brain, we then compared ABCA1 mRNA and protein levels in young and aged cortex and cerebellum of APP/PS1 and ABCA1/APP/PS1 animals. Compared with APP/PS1 controls, aged ABCA1/APP/PS1 mice exhibited increased ABCA1 mRNA, but not protein, selectively in cortex. Additionally, ABCA1 mRNA levels were not increased before amyloid deposition but were induced only in the presence of extensive Abeta and amyloid levels. These data suggest that an induction of ABCA1 expression may be associated with late-stage Alzheimer's neuropathology.

Decreased expression of breast cancer resistance protein in the duodenum in patients with obstructive cholestasis

BACKGROUND/AIMS

The expression of transporters involved in bile acid homeostasis is differentially regulated during obstructive cholestasis. Since the drug efflux transporter breast cancer resistance protein (BCRP) is known to transport bile acids, we investigated whether duodenal BCRP expression could be altered during cholestasis.

METHODS

Using real-time RT-PCR analysis we determined mRNA expression levels in duodenal tissue of 19 cholestatic patients. Expression levels were compared to 14 healthy subjects. BCRP protein staining was determined in biopsies of 6 cholestatic and 6 healthy subjects by immunohistochemistry.

RESULTS

We found that in patients with obstructive cholestasis mean duodenal BCRP mRNA levels were significantly reduced to 53% and mean protein staining was reduced to 57%.

CONCLUSIONS

BCRP, a transporter for bile acids and numerous drugs, appears to be down-regulated in the human duodenum during cholestasis. The clinical impact of these results has to be investigated in further studies.

Ethanol consumption alters expression and colocalization of bile salt export pump and multidrug resistance protein 2 in the rat

Chronic ethanol consumption elicits detrimental changes of liver metabolism. By employing a 12-week-long feeding regimen, we investigated the effects of chronic ethanol consumption on the expression and localization of bile salt export pump (Bsep), a major canalicular exporter of bile salts, and multidrug resistance protein 2 (Mrp2), a canalicular organic anion transporter, in the rat liver. RT-PCR, confocal immunofluorescence microscopy, immunoblotting, and quantitative colocalization analysis were used to examine their gene and protein expression, and changes in the distribution of antigenic sites. Bsep mRNA was upregulated, while Mrp2 mRNA responded by downregulation. In agreement with mRNA, the expression of Bsep protein increased, while the expression of Mrp2 protein responded with a decrease, suggesting that the expression of both of them is transcriptionally regulated. Confocal immunofluorescence microscopy showed disruption of the colocalization of Bsep and Mrp2 proteins at the hepatocyte canalicular membrane and their relocation intracellularly. Quantitative colocalization analysis of Bsep and Mrp2 proteins revealed a steady decrease in the degree of colocalization and Mrp2 expression, indicating that although the properties of both transporters are affected, Mrp2 is altered more. These findings provide evidence that ethanol alters Bsep and Mrp2 canalicular transporters in the rat liver, at both the mRNA and protein levels. Mrp2 shows deeper involvement. Eight weeks appears to be a critical time point in this process.

Imatinib mesylate potentiates topotecan antitumor activity in rhabdomyosarcoma preclinical models

High levels of PDGFR expression in primary rhabdomyosarcoma (RMS) have been associated with disease progression. To date however, there are no reports on the activity of imatinib mesylate, a selective PDGFR inhibitor, in RMS preclinical models. A panel of 5 RMS cell lines was used to investigate the expression of PDGFRalpha and PDGFRbeta, c-Kit and the multidrug transporter ABCG2 (also inhibited by imatinib). In vitro and in vivo experiments were performed using RD (embryonal) and RH30 (alveolar) cell lines to determine the efficacy of imatinib as single agent and in combination with topotecan (TPT). PDGFRbeta was significantly expressed in all cell lines, with the highest levels in RD, while PDGFR alpha and ABCG2 were significantly expressed only in RH30 and RMZ-RC2. c-Kit was not detected. PDGFRbeta signaling was active in RD but not in RH30, whilst PDGFRalpha signaling was not active in either cell lines. Significant ABCG2-mediated extrusion of Hoechst 33342 was demonstrated in RH30 but not in RD, and was inhibited by imatinib and the specific ABCG2 inhibitor Ko143. In vitro, imatinib was not active as a single agent at therapeutic concentrations, but significantly potentiated TPT antitumor activity in both cell lines. In vivo experiments using tumor xenografts confirmed the synergistic interaction in both cell lines. These results suggest that at least 2 different mechanisms--inhibition of ABCG2 and/or PDGFRbeta--are involved in the synergistic interaction between imatinib and TPT, and support the use of this combination for the treatment of high-risk RMS patients.

Phytosterol-mediated inhibition of intestinal cholesterol absorption is independent of ATP-binding cassette transporter A1

An increased activity of ATP-binding cassette transporter (ABC) A1 has been proposed as a mechanism underlying the hypocholesterolaemic effect of phytosterols. In the present study, ABCA1-deficient mice (ABCA1−/− mice) were used to examine the involvement of the ABCA1 in the reduction of intestinal cholesterol absorption in response to a phytosterol-enriched diet. A decrease in intestinal cholesterol absorption of 39 and 35% was observed after phytosterol treatment in ABCA1+/+ mice and in ABCA1−/− mice, respectively. No statistically significant changes in plasma lipoprotein profile or in intestinal ABCG5, ABCG8 and Niemann-Pick C1-Like 1 gene expression levels were found when phytosterol-treated ABCA1−/− mice and untreated ABCA1−/− mice were compared. We conclude that phytosterol inhibition of cholesterol absorption in mice is independent of ABCA1

Fluctuation of the SP/non-SP phenotype in the C6 glioma cell line

Using the C6 glioma cell as a paradigm, we found that (i) the clonogenicity of C6 cells is several orders of magnitude higher than the percentage of SP cells; (ii) non-SP cells are able to generate SP cells, and conversely SP cells generate non-SP cells; (iii) non-SP sorted cells behave as tumorigenic cells. Hence, in C6 cells cultured in serum-containing medium, SP cells can be generated from non-SP cells. This dynamic equilibrium explains in C6 cells the maintenance of the SP phenotype with cell passaging and demonstrates the existence of tumorigenic non-SP cells.

Effects of genetic backgrounds on hyperbilirubinemia in radixin-deficient mice due to different expression levels of Mrp3

ERM (ezrin/radixin/moesin) proteins are organizers of apical actin cortical layer in general. We previously reported that the knockout of radixin resulted in Rdx(-/-) mice with displacement/loss of the canalicular transporter Mrp2, giving rise to Dubin-Johnson syndrome-like conjugated hyperbilirubinemia in the mixed genetic background (C57BL/6-129/Sv) (Kikuchi, et al. (2002) Nature Genetics 31, 320-325). However, when these mice were kept under mixed genetic background for years (late mixed backgrounds; LMB), the conjugated hyperbilirubinemia gradually became inconspicuous, while evidence of liver injury increased. We examined the effect of genetic background by backcrossing LMB Rdx(-/-) mice to C57BL/6 and 129/Sv wild type mice with the result that the Rdx(-/-) congenic mice regained hyperbilirubinemia with reduced hepatocellular damage. As revealed by immunofluorescence and western blots, the localization/expression of apical transporters, Mrp2, CD26, P-gps, and Bsep were not influenced by backcrossing, though those of a basolateral transporter, Mrp3, were strikingly increased by backcrossing.

ΔF508 Mutation Results in Impaired Gastric Acid Secretion

The cystic fibrosis transmembrane conductance regulator (CFTR) is recognized as a multifunctional protein that is involved in Cl(-) secretion, as well as acting as a regulatory protein. In order for acid secretion to take place a complex interaction of transport proteins and channels must occur at the apical pole of the parietal cell. Included in this process is at least one K(+) and Cl(-) channel, allowing for both recycling of K(+) for the H,K-ATPase, and Cl(-) secretion, necessary for the generation of concentrated HCl in the gastric gland lumen. We have previously shown that an ATP-sensitive potassium channel (K(ATP)) is expressed in parietal cells. In the present study we measured secretagogue-induced acid secretion from wild-type and DeltaF508-deficient mice in isolated gastric glands and whole stomach preparations. Secretagogue-induced acid secretion in wild-type mouse gastric glands could be significantly reduced with either glibenclamide or the specific inhibitor CFTR-inh172. In DeltaF508-deficient mice, however, histamine-induced acid secretion was significantly less than in wild-type mice. Furthermore, immunofluorescent localization of sulfonylurea 1 and 2 failed to show expression of a sulfonylurea receptor in the parietal cell, thus further implicating CFTR as the ATP-binding cassette transporter associated with the K(ATP) channels. These results demonstrate a regulatory role for the CFTR protein in normal gastric acid secretion.

Establishing a Method to Isolate Rat Brain Capillary Endothelial Cells by Magnetic Cell Sorting and Dominant mRNA Expression of Multidrug Resistance-associated Protein 1 and 4 in Highly Purified Rat Brain Capillary Endothelial Cells

PURPOSE

To establish a method for isolating highly purified brain capillary endothelial cells (BCECs) from rat brain by using magnetic cell sorting, and clarify the expression levels of multidrug resistance-associated protein (Mrp) subtypes in these highly purified BCECs.

METHODS

The cells were prepared from the capillary enriched-fraction by enzyme digestion, and reacted with anti-PECAM-1 antibody. The cell sorting was performed by autoMACS. The mRNA levels were measured by quantitative real-time PCR analysis.

RESULTS

From five rats, 2.3 x 10(6) cells were isolated in the PECAM-1(+) fraction and the percentage of labeled cells in this was 85.9%. PECAM-1, claudin-5 and Tie-2 mRNA were concentrated in the PECAM-1(+) fraction compared with rat brain. The contamination by neurons and astrocytes was markedly less than in the brain capillary fraction prepared by the glass bead column method. Mrp1 and 4 were predominantly expressed in the PECAM-1(+) fraction at similar levels to Mdr1a. The mRNA levels of Mrp5 and 3 were 10.6 and 7.60% of that of Mrp1, respectively.

CONCLUSIONS

This new purification method provides BCECs with less contamination by neural cells. In the isolated BCECs, Mrp1 and 4 are predominantly expressed, suggesting that they play an important role at the rat blood-brain barrier.