The aim of this project was to study ATP binding cassette (ABC) transporters in the human placenta, in particular their regulation and role in trophoblast differentiation and survival. The presence and localisation of four major placental drug transporters, multidrug resistance gene product 1 and 3 (MDR1 and 3)/ABC subfamily B members 1 and 4 (ABCB1 and 4), multidrug resistance associated proteins 1 and 2 (MRP1 and 2)/ABCC1 and 2 and breast cancer resistance protein (BCRP)/ABCG2 was initially studied in term human placenta, cultured primary trophoblast and BeWo and Jar trophoblast-like cell lines. Jar cells were found to be more similar to nondifferentiated cytotrophoblast with respect to their ABC protein expression profile, whereas BeWo cells more closely reflected differentiated syncytiotrophoblast. Treatment of primary term trophoblasts in vitro with cytokines (TNF- or IL-1) decreased expression and activity of apical transporters ABCB1/MDR1 and ABCG2/BCRP. Growth factors, on the other hand, increased BCRP expression and activity, while estradiol stimulated BCRP, MDR1 and MDR3 expression MDR1/3 functional activity. The ability of BCRP/ABCG2 to abrogate the apoptotic effects of TNF- and ceramides was studied in primary trophoblast and BeWo cells using pharmacological and molecular (siRNA) approaches. The results suggest that BCRP/ABCG2 contributes to the resistance of trophoblast cells to cytokine-induced (extrinsic) apoptosis, whereas its effects on apoptosis activated via the intrinsic mitochondrial pathway is minimal. This altered resistance was associated with increased intracellular accumulation of ceramides and reduced ability to maintain phosphatidylserine in the inner leaflet of the plasma membrane. A role for BCRP/ABCG2 in cell protection from differentiation-induced stressors was also demonstrated during the process of cell fusion associated with transient loss of plasma membrane lipid asymmetry. Finally, expression of BCRP/ABCG2 (and 9 other genes) was studied in 50 placentas from normal pregnancy and pregnancies complicated with fetal growth restriction (FGR). A marked reduction of BCRP/ABCG2 and MDR1/ABCB1 expression was observed in FGR placentas, while other transporter genes were unaffected. Collectively these data suggest that BCRP/ABCG2 and probably other ABC transporters may play a hitherto unrecognised survival role in the placenta, conferring a “stress resistance” to trophoblast cells.

The aim of this project was to study ATP binding cassette (ABC) transporters in the human placenta, in particular their regulation and role in trophoblast differentiation and survival. The presence and localisation of four major placental drug transporters, multidrug resistance gene product 1 and 3 (MDR1 and 3)/ABC subfamily B members 1 and 4 (ABCB1 and 4), multidrug resistance associated proteins 1 and 2 (MRP1 and 2)/ABCC1 and 2 and breast cancer resistance protein (BCRP)/ABCG2 was initially studied in term human placenta, cultured primary trophoblast and BeWo and Jar trophoblast-like cell lines. Jar cells were found to be more similar to nondifferentiated cytotrophoblast with respect to their ABC protein expression profile, whereas BeWo cells more closely reflected differentiated syncytiotrophoblast. Treatment of primary term trophoblasts in vitro with cytokines (TNF- or IL-1) decreased expression and activity of apical transporters ABCB1/MDR1 and ABCG2/BCRP. Growth factors, on the other hand, increased BCRP expression and activity, while estradiol stimulated BCRP, MDR1 and MDR3 expression MDR1/3 functional activity. The ability of BCRP/ABCG2 to abrogate the apoptotic effects of TNF- and ceramides was studied in primary trophoblast and BeWo cells using pharmacological and molecular (siRNA) approaches. The results suggest that BCRP/ABCG2 contributes to the resistance of trophoblast cells to cytokine-induced (extrinsic) apoptosis, whereas its effects on apoptosis activated via the intrinsic mitochondrial pathway is minimal. This altered resistance was associated with increased intracellular accumulation of ceramides and reduced ability to maintain phosphatidylserine in the inner leaflet of the plasma membrane. A role for BCRP/ABCG2 in cell protection from differentiation-induced stressors was also demonstrated during the process of cell fusion associated with transient loss of plasma membrane lipid asymmetry. Finally, expression of BCRP/ABCG2 (and 9 other genes) was studied in 50 placentas from normal pregnancy and pregnancies complicated with fetal growth restriction (FGR). A marked reduction of BCRP/ABCG2 and MDR1/ABCB1 expression was observed in FGR placentas, while other transporter genes were unaffected. Collectively these data suggest that BCRP/ABCG2 and probably other ABC transporters may play a hitherto unrecognised survival role in the placenta, conferring a “stress resistance” to trophoblast cells.

The aim of this project was to study ATP binding cassette (ABC) transporters in the human placenta, in particular their regulation and role in trophoblast differentiation and survival. The presence and localisation of four major placental drug transporters, multidrug resistance gene product 1 and 3 (MDR1 and 3)/ABC subfamily B members 1 and 4 (ABCB1 and 4), multidrug resistance associated proteins 1 and 2 (MRP1 and 2)/ABCC1 and 2 and breast cancer resistance protein (BCRP)/ABCG2 was initially studied in term human placenta, cultured primary trophoblast and BeWo and Jar trophoblast-like cell lines. Jar cells were found to be more similar to nondifferentiated cytotrophoblast with respect to their ABC protein expression profile, whereas BeWo cells more closely reflected differentiated syncytiotrophoblast. Treatment of primary term trophoblasts in vitro with cytokines (TNF- or IL-1) decreased expression and activity of apical transporters ABCB1/MDR1 and ABCG2/BCRP. Growth factors, on the other hand, increased BCRP expression and activity, while estradiol stimulated BCRP, MDR1 and MDR3 expression MDR1/3 functional activity. The ability of BCRP/ABCG2 to abrogate the apoptotic effects of TNF- and ceramides was studied in primary trophoblast and BeWo cells using pharmacological and molecular (siRNA) approaches. The results suggest that BCRP/ABCG2 contributes to the resistance of trophoblast cells to cytokine-induced (extrinsic) apoptosis, whereas its effects on apoptosis activated via the intrinsic mitochondrial pathway is minimal. This altered resistance was associated with increased intracellular accumulation of ceramides and reduced ability to maintain phosphatidylserine in the inner leaflet of the plasma membrane. A role for BCRP/ABCG2 in cell protection from differentiation-induced stressors was also demonstrated during the process of cell fusion associated with transient loss of plasma membrane lipid asymmetry. Finally, expression of BCRP/ABCG2 (and 9 other genes) was studied in 50 placentas from normal pregnancy and pregnancies complicated with fetal growth restriction (FGR). A marked reduction of BCRP/ABCG2 and MDR1/ABCB1 expression was observed in FGR placentas, while other transporter genes were unaffected. Collectively these data suggest that BCRP/ABCG2 and probably other ABC transporters may play a hitherto unrecognised survival role in the placenta, conferring a “stress resistance” to trophoblast cells.

The aim of this project was to study ATP binding cassette (ABC) transporters in the human placenta, in particular their regulation and role in trophoblast differentiation and survival. The presence and localisation of four major placental drug transporters, multidrug resistance gene product 1 and 3 (MDR1 and 3)/ABC subfamily B members 1 and 4 (ABCB1 and 4), multidrug resistance associated proteins 1 and 2 (MRP1 and 2)/ABCC1 and 2 and breast cancer resistance protein (BCRP)/ABCG2 was initially studied in term human placenta, cultured primary trophoblast and BeWo and Jar trophoblast-like cell lines. Jar cells were found to be more similar to nondifferentiated cytotrophoblast with respect to their ABC protein expression profile, whereas BeWo cells more closely reflected differentiated syncytiotrophoblast. Treatment of primary term trophoblasts in vitro with cytokines (TNF- or IL-1) decreased expression and activity of apical transporters ABCB1/MDR1 and ABCG2/BCRP. Growth factors, on the other hand, increased BCRP expression and activity, while estradiol stimulated BCRP, MDR1 and MDR3 expression MDR1/3 functional activity. The ability of BCRP/ABCG2 to abrogate the apoptotic effects of TNF- and ceramides was studied in primary trophoblast and BeWo cells using pharmacological and molecular (siRNA) approaches. The results suggest that BCRP/ABCG2 contributes to the resistance of trophoblast cells to cytokine-induced (extrinsic) apoptosis, whereas its effects on apoptosis activated via the intrinsic mitochondrial pathway is minimal. This altered resistance was associated with increased intracellular accumulation of ceramides and reduced ability to maintain phosphatidylserine in the inner leaflet of the plasma membrane. A role for BCRP/ABCG2 in cell protection from differentiation-induced stressors was also demonstrated during the process of cell fusion associated with transient loss of plasma membrane lipid asymmetry. Finally, expression of BCRP/ABCG2 (and 9 other genes) was studied in 50 placentas from normal pregnancy and pregnancies complicated with fetal growth restriction (FGR). A marked reduction of BCRP/ABCG2 and MDR1/ABCB1 expression was observed in FGR placentas, while other transporter genes were unaffected. Collectively these data suggest that BCRP/ABCG2 and probably other ABC transporters may play a hitherto unrecognised survival role in the placenta, conferring a “stress resistance” to trophoblast cells.

Pancreatic cancer (PC) is known to be highly resistant to chemotherapy. Transporters, which regulate the influx and efflux of substrates across the plasma membrane, may play a role in PC drug resistance. ABC transporters are a large family of transmembrane proteins with diverse physiological functions, several of which play major roles in cancer drug resistance. Given that 90% of PC express a mutant K-ras oncogene and that PC are highly hypoxic, I postulated that constitutive K-ras activation and/or hypoxia may correlate with ABC transporter expression, which in turn may promote drug resistance in PC. Using normal and PC cell lines either overexpressing mutant K-ras or subjected to hypoxic treatment, mRNA expression was profiled for 48 ABC transporters. My findings indicate that expression of mutant K-ras and hypoxic treatment, as well as long-term exposure to chemotherapy, may contribute to the development of drug resistance in PC cells in part by inducing the expression of ABC transporters. Similar to ABC transporters, I investigated whether amino acid transporters would mediate drug resistance in PC. The Xc⁻ amino acid transporter (Xc⁻) mediates cellular uptake of cystine for the biosynthesis of glutathione, a major detoxifying agent. Because the Xc⁻ has been regulates the growth of various cancer cell types, and Xc⁻ is expressed in the pancreas, I postulated that the Xc⁻ may be involved in growth and drug resistance in PC. The Xc⁻ transporter is differentially expressed in normal pancreatic tissues and is overexpressed in PC in vivo. Using PC cell lines, I found that cystine uptake via the Xc⁻ was required for growth and survival in response to oxidative stress, and that expression of the Xc⁻ correlated with gemcitabine resistance. Accordingly, inhibition of Xc⁻ expression via siRNA reduced PC cell proliferation and restored sensitivity to gemcitabine. I also identified the anti-inflammatory drug sulfasalazine as a mixed inhibitor of the Xc⁻, which acts to inhibit cell proliferation via reducing Xc⁻ activity and not by reducing NFKB activity. My findings thus indicate that the Xc⁻ plays a role in PC growth in partby contributing to glutathione synthesis to promote PC cell proliferation, survival, and drug resistance. / Medicine, Faculty of / Medicine, Department of / Experimental Medicine, Division of / Graduate

No description available.

The objective of the first study was to characterize amino peptidase N (APN), peptide (PepT1), amino acid (ASCT1, bo,+AT, CAT1, EAAT3, LAT1, y+LAT2), and sugar transporter expression (GLUT2, GLUT5, SGLT1) in the small intestine of male and female turkeys. Small intestine samples were collected during embryonic development (E21, E24) and DOH. In a separate experiment during post-hatch development (DOH, D7, D14, D21, D28). APN, bo,+AT, PepT1, y+LAT2, GLUT5 and SGLT1 were expressed most on DOH. Post-hatch, all genes except GLUT2 and SGLT1 were expressed greater in females than males. SGLT1 was expressed greater in males. Basolateral transporters were expressed more during early development; while there was more expression of brush border transporters EAAT3, GLUT5 and SGLT1 later in development. In chickens, there are alternatively spliced exons of the PepT2 gene that encode proteins with four different N-termini (Variants 5-8). The objective of this study was to characterize the patterns of expression of these PepT2 variants. Brain, kidney, liver and intestine were analyzed at E18 and D7 (n=5). Expression of Variant 5 was most prominent in the brain and variant 6 was most prominent in the kidney. Variant 8 appeared in all tissues on E18 and D7. Variant 7 was only expressed in late embryonic development in the ileum. Results from these studies demonstrate that there are differences in gene expression of nutrient transporters in two agriculturally important avian species from the same order Galliformes. These differences can be used to improve feed efficiency and enhance the growth of both species. / Master of Science

The transporters primarily responsible for transporting important nutrients involved in energy metabolism have a wide substrate specificity setting up the potential for drug-nutrient transporter interactions. Pharmacological inhibition of nutrient transport across the lactating mammary and neonatal intestinal epithelial barrier can directly and indirectly affect growth and maturation of the developing neonate by either reducing the uptake of important nutrients by the neonate or by disrupting epithelial barrier integrity. My thesis focused on two transporters, OCTN2 and MCT1, expressed in immortalized intestinal and mammary epithelial cell cultures to assess the effects of their pharmacological inhibition on L-carnitine and butyrate flux, respectively, and polarized epithelial barrier integrity. Human colorectal adenocarcinoma (Caco-2) and bovine mammary (BME-UV) cell lines were grown into monolayers on 12-well tissue culture plates and subsequently exposed to the presence or absence of OCTN2 and MCT1 inhibitors for 6, 12, and 24 hours as well as 7 days. Failure to obtain a polarized mammary monolayer prevented the analysis of the direct effects of nutrient transport inhibition on nutrient flux forcing the focus on the indirect effects. To assess polarized epithelial barrier integrity, transepithelial electrical resistance and Lucifer yellow rejection rates were measured at each time point. No trend was noted between control and treated groups. To assess the acute and chronic effects of pharmacological exposure on polarized epithelial function, a limited appraisal of nutrient transporter expression and cellular homeostasis parameters was conducted. Following exposure at each time point, mRNA expression of OCTN1, OCTN2, MCT1, MCT2 and GADPH were measured using qPCR. Low mRNA yields resulted in an inability to assess transporter expression levels in the epithelial systems. Cellular homeostasis parameters were analyzed using the CellTiter-Glo Luminescent Cell Viability Assay, pH-Xtra Glycolysis Assay and MitoXpress Xtra Oxygen Consumption Assay. These assays measured ATP synthesis, glycolytic flux and cellular respiration, respectively. No significant trend was noted in ATP synthesis between control and treated groups. An upward trend in both glycolytic flux and cellular respiration was noted in treatment with both inhibitors in both cell lines. Complications in obtaining polarized monolayer forced the focus on the indirect affects, therefore, obtaining and utilizing a more accurate portrayal of the lactating mammary and neonatal intestinal epithelium is critical in answering this research question as both of these systems are highly synthetic and complex. By doing so, a more accurate representation of the effects of pharmacological inhibition of nutrient transporters essential for energy metabolism can be identified.

No description available.

No description available.