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2.
J Palliat Med ; 25(6): 915-924, 2022 06.
Article in English | MEDLINE | ID: mdl-35119311

ABSTRACT

Background: An increasing number of patients with end-of-life (EOL) conditions, particularly those with advanced cancer, are presenting to the emergency department (ED). Objectives: To assess the characteristics, management and short-term outcomes of ED patients with advanced cancer compared to patients with other EOL conditions. Methodology/Design: A secondary analysis of a prospective cohort study. Setting/Participants: Volunteer emergency physicians in two Canadian EDs identified presentations for advanced cancer and other EOL conditions with the aid of a modified screening tool March-August 2018. Results: Among the 663 presentations by patients with EOL conditions, 272 (41%) presented with advanced cancer. The majority of presentations for advanced cancer (81%) or other EOL conditions (77%) were by patients with unmet palliative care (PC) needs. Patients with advanced cancer were significantly less likely to have active goals of care (GOC) documented on their charts (53% vs. 75%; p < 0.001). While no significant differences were found between the groups, the majority of presentations involved imaging, investigations, consultations, and hospitalization. Presentations for advanced cancer were more likely to receive a postdischarge referral (38% vs. 23%; p < 0.001). Referrals to PC consultations or postdischarge referrals were infrequent. Regression analysis found that patients with advanced cancer were associated with shorter length of stay (LOS). Conclusions: The majority of presentations for advanced cancer or other EOL conditions involved significant resource use. Patients with cancer experienced shorter LOS; however, had less documentation of GOC and gaps in referrals to PC services were identified. Interventions should be explored to promote early GOC discussions and PC referrals in this patient group.


Subject(s)
Neoplasms , Terminal Care , Aftercare , Canada , Death , Emergency Service, Hospital , Humans , Neoplasms/therapy , Palliative Care , Patient Discharge , Prospective Studies
3.
PLoS One ; 16(9): e0257501, 2021.
Article in English | MEDLINE | ID: mdl-34570790

ABSTRACT

INTRODUCTION: This study examined emergency department (ED) presentations of patients with end of life (EOL) conditions and patients having met and unmet palliative care needs were compared. METHODS: Presentations for EOL conditions were prospectively identified and screened for palliative care needs. Descriptive data were reported as proportions, means or medians. Bi-variable analysis for dichotomous and continuous variables were performed by chi-squared and T-tests (p≤0.01), respectively. A multivariable logistic regression model identified factors associated with having unmet palliative needs and reported adjusted odds ratios (aOR) with 95% confidence intervals (CI). RESULTS: Overall, 663 presentations for EOL conditions were identified; 518 (78%) involved patients with unmet palliative care needs. Presentations by patients with unmet palliative needs were more likely to involve consultations (80% vs. 67%, p = 0.001) and result in hospitalization (69% vs. 51%, p<0.001) compared to patients whose palliative needs were met. Patients with unmet palliative care needs were more likely to have previous ED visits (73% unmet vs. 48% met; p<0.001). While medication, procedures, investigations and imaging ordering were high across all patients with EOL conditions, there were no significant differences between the groups. Consultations with palliative specialists in the ED (6% unmet vs. 1% met) and following discharge (29% unmet vs. 18% met) were similarly uncommon. Patients having two or more EOL conditions (aOR = 2.41; 95% CI: 1.16, 5.00), requiring hospitalization (aOR = 1.93; 95% CI: 1.30, 2.87), and dying during the ED visit (aOR = 2.15; 95% CI: 1.02, 4.53) were strongly associated with having unmet palliative care needs. CONCLUSIONS: Most ED presentations for EOL conditions were made by patients with unmet palliative care needs, who were significantly more likely to require consultation, hospitalization, and to die. Referrals to palliative care services during and after the ED visit were infrequent, indicating important opportunities to promote these services.


Subject(s)
Emergency Service, Hospital , Palliative Care , Adult , Emergency Service, Hospital/organization & administration , Female , Hospitalization/statistics & numerical data , Humans , Male , Middle Aged , Odds Ratio , Palliative Care/statistics & numerical data , Physicians/psychology , Prospective Studies , Referral and Consultation , Terminal Care , Tertiary Care Centers
4.
J Palliat Med ; 24(12): 1840-1848, 2021 12.
Article in English | MEDLINE | ID: mdl-34255578

ABSTRACT

Background: Presentations to the emergency department (ED) by patients with end-of-life (EOL) conditions for their acute care needs are common. Objectives: The objective of this study was to identify and describe the ED management across presentations to the ED for EOL conditions. Design: Prospective observational cohort study. Settings/Subjects: Emergency physicians in two Canadian ED's were asked to identify presentations by adult patients with EOL conditions using a modified screening tool. Measurements: Patient characteristics and ED management for each presentation were collected through chart review by trained research assistants. Descriptive analyses were conducted as appropriate and bivariate comparisons of dichotomous and continuous variables were completed using χ2 tests and using t test or Wilcoxon rank-sum test, respectively. Results: Physicians identified 663 ED presentations for EOL conditions, with advanced cancer (41%), dementia (23%), and chronic obstructive pulmonary disease (16%) being the most common EOL conditions. The majority of presentations involved consultations (77%), hospitalization (65%), and numerous investigations (97%), including blood work (97%) and imaging (92%). The majority of patients with EOL conditions had a history of ED visits (68%). Using a modified screening tool, 78% of presentations involved patients with unmet palliative care needs, but only 1% of presentations involved a palliative consultation or admission to a palliative care unit. Conclusion: Presentations to the ED for EOL conditions involve significant ED resources; however, only a handful of patients are referred to palliative services. Patients with EOL conditions are appropriate targets for palliative services and community support outside the ED.


Subject(s)
Emergency Service, Hospital , Terminal Care , Adult , Canada , Health Services Needs and Demand , Humans , Palliative Care , Prospective Studies
6.
Ann Surg Oncol ; 26(10): 3361-3367, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31342368

ABSTRACT

BACKGROUND: Long diagnostic intervals following abnormal breast imaging (DI) cause patient anxiety and possibly poorer prognosis. This study evaluates the effect of a provincial diagnostic pathway for BI-RADS 5 lesions on wait times and the patient-reported experience (PRE). METHODS: With multidisciplinary input, we developed a pathway for BI-RADS 5 lesions featuring expedited biopsy, early surgical referral, and nurse (RN) navigator support. Key diagnostic intervals were captured prospectively and compared with a prepathway control cohort. PRE data were obtained from a voluntary survey. RESULTS: 1205 patients were managed on the BI-RADS 5 pathway with 797 primary care physicians, 57 imaging centers, and 2 regional breast programs participating. Median duration from DI to biopsy was 6 days, from biopsy to pathology report was 5 days, DI to surgical referral was 6 days, and DI to surgical consult was 21 days. Compared with 128 prepathway controls, median intervals from DI to surgical referral and consult were significantly improved (15 vs. 6 days, 26 vs. 21 days, p < 0.001). Amongst 294 women who completed the survey, 92% experienced ≥ 1 anxiety complaint during assessment; prompt surgical consultation and multiple features of RN support reduced anxiety, and wait time satisfaction was high (70%). Patient preferences varied for receiving biopsy results from a surgeon (57%) vs. another provider (43%). CONCLUSIONS: A diagnostic pathway for BI-RADS 5 lesions reduced wait times and improved the patient experience through prompt surgical referral and RN navigator support. Differing preferences for receiving biopsy results emerged, and future iterations should incorporate individualized patient wishes.


Subject(s)
Breast Neoplasms/diagnosis , Diagnostic Services/statistics & numerical data , Early Detection of Cancer/methods , Health Plan Implementation , Mammography/methods , Ultrasonography, Mammary/methods , Waiting Lists , Breast Neoplasms/diagnostic imaging , Critical Pathways , Female , Humans , Prognosis , Time Factors
7.
Ann Surg Oncol ; 26(10): 3354-3360, 2019 Oct.
Article in English | MEDLINE | ID: mdl-31342384

ABSTRACT

BACKGROUND: Same-day surgery (SDS) following mastectomy is safe and well accepted. Overnight admission in patients fit for discharge is an inefficient use of health resources. In response to a national review highlighting SDS following mastectomy at 1.4% in Alberta, a perioperative pathway was conceived. METHODS: The pathway was implemented across Alberta at 13 hospitals beginning in 2016. A steering committee was assembled, and clinical and administrative leads at each site were identified. Opportunities along the patient care experience whereby action could be taken to promote uptake of SDS were identified. Provincially branded support materials including presentations, order sets, and standard operating procedures were developed. Nurse educators provided in-service teaching such as standardized drain care and discharge teaching. Educational booklets, group classes, and online resources were developed for patients and families. An audit of SDS rates, unscheduled return to the emergency department (ED), and readmission rates was reported to teams quarterly, allowing for iterative modifications. Patient-reported experience measures (PREMs) were collected. RESULTS: SDS following mastectomy increased from 1.7 to 47.8%, releasing an estimated 831 bed days per year. No differences in unexpected return to the ED or readmission to hospital existed between SDS patients and those admitted overnight. A total of 102 patients completed the PREM survey, of whom 90% felt "excellent or good" with the plan to go home, how to care for themselves once home, and who to contact should issues arise. CONCLUSIONS: Implementation of a provincial perioperative pathway improved uptake of SDS following mastectomy and demonstrated favorable PREMs.


Subject(s)
Ambulatory Surgical Procedures/methods , Breast Neoplasms/surgery , Mastectomy/methods , Patient Safety , Perioperative Care , Quality Improvement , Reoperation , Adolescent , Adult , Aged , Aged, 80 and over , Breast Neoplasms/pathology , Female , Follow-Up Studies , Humans , Middle Aged , Patient Discharge , Postoperative Complications , Treatment Outcome , Young Adult
8.
Head Neck ; 39(8): 1689-1695, 2017 08.
Article in English | MEDLINE | ID: mdl-28631342

ABSTRACT

BACKGROUND: The purpose of this study was to optimize an existing clinical care pathway (CCP) for head and neck cancer with a high-observation protocol (HOP) and to determine the effect on length of intensive care unit (ICU) admission and length of stay in hospital (LOS). METHODS: The HOP mandated initiation of spontaneous breathing trials before the conclusion of the surgery, weaning of sedation, and limiting mechanical ventilation. All patients with head and neck cancer undergoing primary surgery on the HOP were compared to a historical cohort regarding length of ICU admission, ICU readmissions, and LOS. RESULTS: Ninety-six and 52 patients were observed in "historical" and "HOP" cohorts. The length of ICU admission (1.9 vs 1.2 days; p = .021), LOS (20.3 vs 14.1 days; p = .020), and ICU readmissions (10.4% vs 1.9%; p = .013) were significantly decreased in the "HOP" cohort. CONCLUSION: Rapid weaning of sedation and limiting mechanical ventilation may contribute to a shorter length of ICU admission and LOS, as well as decreased ICU readmissions. © 2017 Wiley Periodicals, Inc. Head Neck 39: 1689-1695, 2016.


Subject(s)
Critical Pathways , Head and Neck Neoplasms/surgery , Monitoring, Physiologic/methods , Clinical Protocols , Female , Humans , Intensive Care Units , Length of Stay , Male , Middle Aged , Postoperative Care/methods , Prospective Studies , Respiration, Artificial , Time Factors
9.
Int J Biochem Cell Biol ; 44(8): 1366-76, 2012 Aug.
Article in English | MEDLINE | ID: mdl-22595283

ABSTRACT

Mitochondrial morphology is dynamic and controlled by coordinated fusion and fission pathways. The role of mitochondrial chaperones in mitochondrial morphological changes and pathology is currently unclear. Here we report that altered levels of DnaJA3 (Tid1/mtHsp40) a mitochondrial member of the DnaJ protein family, and heat shock protein (Hsp) co-chaperone of matrix 70 kDa Hsp70 (mtHsp70/mortalin/HSPA9), induces mitochondrial fragmentation. Suppression of DnaJA3 induced mitochondrial fragmentation in HeLa cells. Elevated levels of DnaJA3 in normal Hs68 fibroblast cells and HeLa, SKN-SH, U87 and U251 cancer cell lines induces mitochondrial fragmentation. Mitochondrial fragmentation induction was not observed in HeLa cells when other DnaJA family members, or mitochondrial DnaJ protein HSC20, were ectopically expressed, indicating that the effects on mitochondrial morphology were specific to DnaJA3. We show that the DnaJ domain (amino acids 88-168) of DnaJA3 is sufficient for the induction of mitochondrial fragmentation. Furthermore, an H121Q point mutation of the DnaJ domain, which abrogates interaction and activation of mtHsp70 ATPase, eliminates fragmentation induced by DnaJA3. This suggests that DnaJA3 interaction with mtHsp70 may be critical in mitochondrial morphological changes. DnaJA3-induced mitochondrial fragmentation was dependent on fission factor dynamin-related protein 1 (Drp1). Ectopic expression of the mitofusins (Mfn1 and Mfn2), however, does not rescue DnaJA3-induced mitochondrial fragmentation. Lastly, elevated levels of DnaJA3 inducing mitochondrial fragmentation were associated with reduction in cell viability. Taken together, elevated DnaJA3 induces Drp1-depedendent mitochondrial fragmentation and decreased cell viability.


Subject(s)
GTP Phosphohydrolases/metabolism , HSP40 Heat-Shock Proteins/metabolism , Microtubule-Associated Proteins/metabolism , Mitochondria/metabolism , Mitochondrial Proteins/metabolism , Molecular Chaperones/metabolism , Binding Sites/genetics , Cell Line, Tumor , Cell Survival , Cells, Cultured , Dynamins , Flow Cytometry , GTP Phosphohydrolases/genetics , Green Fluorescent Proteins/genetics , Green Fluorescent Proteins/metabolism , HSP40 Heat-Shock Proteins/genetics , HSP70 Heat-Shock Proteins/genetics , HSP70 Heat-Shock Proteins/metabolism , HeLa Cells , Humans , Immunoblotting , Membrane Potential, Mitochondrial , Microscopy, Fluorescence , Microtubule-Associated Proteins/genetics , Mitochondria/genetics , Mitochondrial Membrane Transport Proteins/genetics , Mitochondrial Membrane Transport Proteins/metabolism , Mitochondrial Proteins/genetics , Molecular Chaperones/genetics , Point Mutation , RNA Interference , Reactive Oxygen Species/metabolism
10.
Leuk Res ; 35(12): 1649-57, 2011 Dec.
Article in English | MEDLINE | ID: mdl-21798596

ABSTRACT

Although recent decades have seen a significant improvement in the treatment outcome of leukemia in the pediatric population, those who are treated for relapsed disease still face significant morbidity and mortality. However, current salvage regimens are often assembled with agents that have similar mode of activity as the chemotherapeutics used in the initial treatment. Hence, novel therapeutic agents that are capable of distinct and diverse mechanisms of activity in, now resistant, leukemia cells are of great interest. We have investigated the opioid agonist methadone for its anti-leukemic activity, initially reported in studies with cell lines derived from adult patients. Our findings show that, compared to normal cells, methadone has enhanced cytotoxicity against specimens and cell lines established from refractory childhood leukemia. In addition, methadone's activity synergized with that of the anti-Bcl-2 agent ABT-737 and was characterized by the induction of distinct changes in tumor cell mitochondria. Data presented also identify biological correlates and a potential mechanism for methadone activity by its effects on Mcl-1 and other members of the apoptosis cascade. We provide mechanistic data for the therapeutic potential of a family of agents that is largely unexplored for anti-leukemic activity.


Subject(s)
Antineoplastic Combined Chemotherapy Protocols/pharmacology , Apoptosis/drug effects , Biphenyl Compounds/pharmacology , Methadone/pharmacology , Nitrophenols/pharmacology , Precursor Cell Lymphoblastic Leukemia-Lymphoma/pathology , Proto-Oncogene Proteins c-bcl-2/antagonists & inhibitors , Sulfonamides/pharmacology , Age Factors , Age of Onset , Analgesics, Opioid/administration & dosage , Analgesics, Opioid/pharmacology , Antineoplastic Combined Chemotherapy Protocols/therapeutic use , Biphenyl Compounds/administration & dosage , Child , Child, Preschool , Drug Evaluation, Preclinical , Drug Synergism , Female , Humans , Infant , Male , Methadone/administration & dosage , Nitrophenols/administration & dosage , Piperazines/administration & dosage , Piperazines/pharmacology , Precursor Cell Lymphoblastic Leukemia-Lymphoma/drug therapy , Precursor Cell Lymphoblastic Leukemia-Lymphoma/epidemiology , Primary Cell Culture , Sulfonamides/administration & dosage , Treatment Outcome , Tumor Cells, Cultured , Up-Regulation/drug effects
11.
Cancer Res ; 70(8): 3013-9, 2010 Apr 15.
Article in English | MEDLINE | ID: mdl-20354179

ABSTRACT

Tamoxifen resistance is one of the overarching challenges in the treatment of patients with estrogen receptor (ER)-positive breast cancer. Through a genome-wide RNA interference screen to discover genes responsible for tamoxifen resistance in vitro, we identified insulin-like growth factor binding protein 5 (IGFBP5) as a determinant of drug sensitivity. Specific knockdown of IGFBP5 by retroviral infection with short hairpin RNA-expressing cassette in MCF7 human breast cancer cells (pRS-shIGFBP5) conferred tamoxifen resistance in vitro due to concomitant loss of ERalpha expression and signaling. IGFBP5 expression was also reduced in MCF7 cells selected for tamoxifen resistance in culture (TAMR). Both tamoxifen-resistant MCF7-TAMR and MCF7-pRS-shIGFBP5 cells could be resensitized to drug by treatment with exogenous recombinant IGFBP5 (rIGFBP5) protein. Treatment with rIGFBP5 protein in mouse tumor xenografts reversed the in vivo tamoxifen resistance of MCF7-pRS-shIGFBP5 cell-derived tumors by reducing tumor cell proliferation. IGFBP5 immunohistochemical staining in a cohort of 153 breast cancer patients showed that low IGFBP5 expression was associated with shorter overall survival after tamoxifen therapy. Thus, IGFBP5 warrants investigation as an agent to reverse tamoxifen resistance.


Subject(s)
Breast Neoplasms/metabolism , Gene Expression Regulation, Neoplastic , Insulin-Like Growth Factor Binding Protein 5/metabolism , Tamoxifen/pharmacology , Animals , Cell Line, Tumor , Cell Proliferation , Cell Survival , Cohort Studies , Drug Resistance, Neoplasm , Female , Humans , Mice , Mice, Nude , Neoplasm Transplantation
12.
Oncotarget ; 1(6): 396-404, 2010 Oct.
Article in English | MEDLINE | ID: mdl-21311096

ABSTRACT

The p53 tumor suppressor induces apoptosis in response to genotoxic and environmental stresses. Separately from its functions as a transcription factor, it is also capable to be translocated to the mitochondria and plays a critical role in transcription-independent mitochondrial apoptosis. We previously demonstrated that Tid1 interacts with p53, resulting in mitochondrial translocation of the complex and induction of intrinsic apoptosis [1]; however, the mechanism how they interact has been unknown. In this study, far western analyses demonstrated that Tid1 directly interacted with p53. Using domain deletion mutant constructs, we determined that DnaJ domain of Tid1 was necessary for the interaction, while either N- or C-terminal domains of p53 were sufficient for the interaction. In breast cancer cells, depletion of Tid1 by short hairpin RNA (shRNA) led to absence of p53 accumulation at mitochondria and resistance to apoptosis under hypoxic or genotoxic stresses. Our studies imply that Tid1 could be important in the potential combination chemotherapies of p53-related cancers.


Subject(s)
Apoptosis , Breast Neoplasms/metabolism , Breast Neoplasms/pathology , HSP40 Heat-Shock Proteins/metabolism , Mitochondria/metabolism , Tumor Suppressor Protein p53/metabolism , Blotting, Western , Breast Neoplasms/genetics , Female , HSP40 Heat-Shock Proteins/antagonists & inhibitors , HSP40 Heat-Shock Proteins/genetics , Humans , Immunoprecipitation , Protein Transport , RNA, Messenger/genetics , Reverse Transcriptase Polymerase Chain Reaction , Sequence Deletion , Subcellular Fractions , Tumor Cells, Cultured , Tumor Suppressor Protein p53/genetics
13.
Am J Physiol Renal Physiol ; 296(6): F1439-51, 2009 Jun.
Article in English | MEDLINE | ID: mdl-19297449

ABSTRACT

This study examined the roles of human nucleoside transporters (hNTs) in mediating transepithelial fluxes of adenosine, 2'-deoxyadenosine, and three purine nucleoside anti-cancer drugs across polarized monolayers of human renal proximal tubule cells (hRPTCs), which were shown in previous studies to have human equilibrative NT 1 (hENT1) and 2 (hENT2) and human concentrative NT 3 (hCNT3) activities (11). Early passage hRPTCs were cultured on transwell inserts under conditions that induced formation of polarized monolayers with experimentally accessible apical and basolateral domains. Polarized hRPTC cultures were monitored for inhibitor sensitivities and sodium-dependence of the following: 1) transepithelial fluxes of radiolabeled adenosine, 2'-deoxyadenosine, fludarabine (9-beta-d-arabinosyl-2-fluoroadenine), cladribine (2-chloro-2'-deoxyadenosine), and clofarabine (2-chloro-2'-fluoro-deoxy-9-beta-d-arabinofuranosyladenine); 2) mediated uptake of radiolabeled adenosine, 2'-deoxyadenosine, fludarabine, cladribine, and clofarabine from either apical or basolateral surfaces; and 3) relative apical cell surface hCNT3 protein levels. Transepithelial fluxes of adenosine were mediated from apical-to-basolateral sides by apical hCNT3 and basolateral hENT2, whereas transepithelial fluxes of 2'-deoxyadenosine were mediated from basolateral-to-apical sides by apical hENT1 and basolateral human organic anion transporters (hOATs). The transepithelial fluxes of adenosine, hCNT3-mediated cellular uptake of adenosine, and relative apical cell surface hCNT3 protein levels correlated positively in polarized hRPTCs. The purine nucleoside anti-cancer drugs fludarabine, cladribine, and clofarabine, like adenosine exhibited apical-to-basolateral fluxes. Collectively, this evidence suggested that apical hCNT3 and basolateral hENT2 are involved in proximal tubular reabsorption of adenosine and some nucleoside drugs and that apical hENT1 and basolateral hOATs are involved in proximal tubular secretion of 2'-deoxyadenosine.


Subject(s)
Adenosine/metabolism , Deoxyadenosines/metabolism , Equilibrative Nucleoside Transporter 1/metabolism , Equilibrative-Nucleoside Transporter 2/metabolism , Kidney Tubules, Proximal/cytology , Membrane Transport Proteins/metabolism , Adenosine/analogs & derivatives , Antineoplastic Agents/metabolism , Cells, Cultured , Epithelial Cells/metabolism , Equilibrative Nucleoside Transporter 1/genetics , Equilibrative-Nucleoside Transporter 2/genetics , Gene Expression Regulation/physiology , Humans , Membrane Transport Proteins/genetics , Organic Anion Transporters/genetics , Organic Anion Transporters/metabolism
14.
Cancer Chemother Pharmacol ; 63(2): 289-301, 2009 Jan.
Article in English | MEDLINE | ID: mdl-18500522

ABSTRACT

PURPOSE: Interpatient variability in renal elimination of fludarabine (9-beta-D-arabinosyl-2-fluoroadenine) by renal human nucleoside transporters (hNTs) may contribute to unpredictable toxicities including rare nephrotoxicities. This study assessed relationships between hNT levels and fludarabine uptake and cytotoxicity in cultures of human renal proximal tubule cells (hRPTCs) that produce multiple transporter types. METHODS: hRPTC cultures were established from ten different individuals and their hNT characteristics were assessed by measuring RNA expression by TaqMantrade mark reverse transcriptase polymerase chain reaction, protein abundance by quantitative immunoblotting of cell surface protein preparations, and uptake by radiolabeled nucleoside uptake assays. Fludarabine cytotoxicity against hRPTC cultures was quantified using methoxyphenyl tetrazolium inner salt (MTS) assays. RESULTS: RNA, protein and activities for human equilibrative NT 1 (hENT1) and 2 (hENT2) and human concentrative NT 3 (hCNT3) were identified in cultures of hRPTCs from ten different individuals. Significant differences in hCNT3 activities were exhibited among hRPTC cultures and correlated positively with cell surface levels of hCNT3 protein, but did not correlate with hCNT3 mRNA levels. CONCLUSIONS: Observed differences in hCNT3-mediated uptake activities, hNT-mediated fludarabine uptake activities, and fludarabine cytotoxicities correlated positively with each other, suggesting that hCNT3 is a primary determinant of fludarabine uptake and cytotoxicity in hRPTC cultures. Variations in hCNT3 abundance in renal proximal tubules, and hence nucleoside reabsorption, may explain interpatient variability in fludarabine's pharmacokinetics and toxicities.


Subject(s)
Antineoplastic Agents , Kidney Tubules, Proximal/metabolism , Membrane Transport Proteins/metabolism , Vidarabine/analogs & derivatives , Antineoplastic Agents/pharmacokinetics , Antineoplastic Agents/pharmacology , Cell Survival/drug effects , Cells, Cultured , Humans , Immunoblotting , Inhibitory Concentration 50 , Kidney Tubules, Proximal/cytology , Kidney Tubules, Proximal/drug effects , Reverse Transcriptase Polymerase Chain Reaction , Vidarabine/pharmacokinetics , Vidarabine/pharmacology
15.
Am J Physiol Renal Physiol ; 293(1): F200-11, 2007 Jul.
Article in English | MEDLINE | ID: mdl-17409283

ABSTRACT

Nucleoside transporters in kidney mediate renal reabsorption and secretion of nucleosides. Using RT-PCR, we demonstrated mRNAs encoding hENT1, hENT2, hCNT1, hCNT2, and hCNT3 in both cortex and medulla. Immunoblotting with crude membrane preparations revealed abundant hENT1 and hCNT3 in both cortex and medulla, and little, if any, hENT2, hCNT1, or hCNT2, indicating that the latter were either absent or below limits of detection of immunoassays. hENT1 immunostaining was observed on apical surfaces of proximal tubules and on both apical and basal surfaces of thick ascending loops of Henle and collecting ducts. Prominent hCNT3 immunostaining was observed on apical surfaces of proximal tubules and thick ascending loops of Henle in addition to some cytoplasmic staining. Equilibrium binding of [(3)H]nitrobenzylmercaptopurine ribonucleoside (NBMPR), a high-affinity inhibitor of hENT1, to brush-border membrane vesicles from cortex confirmed the presence of hENT1 on apical surfaces of proximal tubules. Uptake of [(3)H]uridine by polarized renal proximal tubule cells exhibited a sodium-dependent component that was inhibited by thymidine and inosine as well as a sodium-independent component that was partially inhibited by NBMPR and completely inhibited by dilazep, indicating high levels of hENT1 and hCNT3 and low levels of hENT2 activities. The presence of 1) transcripts for hENT1/2 and hCNT1/2/3 and the hENT1 and hCNT3 proteins in human kidneys and 2) hENT1, hENT2, and hCNT3 activities in cultured proximal tubule cells suggest involvement of hENT1, hCNT3, and possibly also hENT2 in renal handling of nucleosides and nucleoside drugs.


Subject(s)
Equilibrative Nucleoside Transporter 1/metabolism , Kidney/metabolism , Membrane Transport Proteins/metabolism , Antibodies, Monoclonal , Antibody Specificity , Biomarkers/metabolism , Blotting, Western , Cells, Cultured , Equilibrative Nucleoside Transporter 1/antagonists & inhibitors , Fluorescent Antibody Technique , Humans , Immunohistochemistry , Kidney/drug effects , Kidney Tubules, Collecting/metabolism , Kidney Tubules, Proximal/metabolism , Kinetics , Loop of Henle/metabolism , Membranes/drug effects , Membranes/metabolism , RNA, Messenger/biosynthesis , RNA, Messenger/isolation & purification , Reverse Transcriptase Polymerase Chain Reaction , Thioinosine/analogs & derivatives , Thioinosine/pharmacology , Uridine/metabolism
16.
Biochem Cell Biol ; 84(6): 844-58, 2006 Dec.
Article in English | MEDLINE | ID: mdl-17215872

ABSTRACT

Renal handling of physiological and pharmacological nucleosides is a major determinant of their plasma levels and tissue availabilities. Additionally, the pharmacokinetics and normal tissue toxicities of nucleoside drugs are influenced by their handling in the kidney. Renal reabsorption or secretion of nucleosides is selective and dependent on integral membrane proteins, termed nucleoside transporters (NTs) present in renal epithelia. The 7 known human NTs (hNTs) exhibit varying permeant selectivities and are divided into 2 protein families: the solute carrier (SLC) 29 (SLC29A1, SLC29A2, SLC29A3, SLC29A4) and SLC28 (SLC28A1, SLC28A2, SLC28A3) proteins, otherwise known, respectively, as the human equilibrative NTs (hENTs, hENT1, hENT2, hENT3, hENT4) and human concentrative NTs (hCNTs, hCNT1, hCNT2, hCNT3). The well characterized hENTs (hENT1 and hENT2) are bidirectional facilitative diffusion transporters in plasma membranes; hENT3 and hENT4 are much less well known, although hENT3, found in lysosomal membranes, transports nucleosides and is pH dependent, whereas hENT4-PMAT is a H+-adenosine cotransporter as well as a monoamine-organic cation transporter. The 3 hCNTs are unidirectional secondary active Na+-nucleoside cotransporters. In renal epithelial cells, hCNT1, hCNT2, and hCNT3 at apical membranes, and hENT1 and hENT2 at basolateral membranes, apparently work in concert to mediate reabsorption of nucleosides from lumen to blood, driven by Na+ gradients. Secretion of some physiological nucleosides, therapeutic nucleoside analog drugs, and nucleotide metabolites of therapeutic nucleoside and nucleobase drugs likely occurs through various xenobiotic transporters in renal epithelia, including organic cation transporters, organic anion transporters, multidrug resistance related proteins, and multidrug resistance proteins. Mounting evidence suggests that hENT1 may have a presence at both apical and basolateral membranes of renal epithelia, and thus may participate in both selective secretory and reabsorptive fluxes of nucleosides. In this review, the renal handling of nucleosides is examined with respect to physiological and clinical implications for the regulation of human kidney NTs and adenosine signaling, intracellular nucleoside transport, and nephrotoxicities associated with some nucleoside drugs.


Subject(s)
Kidney/metabolism , Nucleoside Transport Proteins/metabolism , Nucleosides/metabolism , Humans , Kidney/physiology , Models, Biological , Nucleoside Transport Proteins/genetics , Nucleosides/chemistry
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