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1.
Arch Toxicol ; 2024 Apr 08.
Artigo em Inglês | MEDLINE | ID: mdl-38589558

RESUMO

Oxaliplatin (OHP) is effective in colorectal cancer treatment but induces peripheral neurotoxicity (OHP-induced peripheral neurotoxicity, OIPN), diminishing survivor quality of life. Organic cation transporter 2 (OCT2) is a key OHP uptake pathway in dorsal root ganglia. Competing for OCT2-mediated OHP uptake, such as with the tyrosine kinase inhibitor dasatinib, may mitigate OHP side effects. We investigated OHP and dasatinib interaction with OCT2 in human embryonic kidney 293 (HEK293) cells expressing OCT2 within a 10-3 to 10-7 M concentration range. Uptake competition experiments using fluorescent organic cation 4-(4-dimethylaminostyryl)-N-methylpyridinium (ASP+, 1 µM) and mass spectrometry (MS) to determine cellular platinum content indicated that OHP (100 µM) is an OCT2 substrate, mediating OHP cellular toxicity. ASP+ and MS analysis revealed dasatinib as a non-transported inhibitor of hOCT2 (IC50 = 5.9 µM) and as a regulator of OCT2 activity. Dasatinib reduced transporter Vmax, potentially via Y544 phosphorylation suppression. MS analysis showed cellular dasatinib accumulation independent of hOCT2. Although 3 µM dasatinib reduced 100 µM OHP accumulation in hOCT2-HEK293 cells, co-incubation with dasatinib and OHP did not prevent OHP toxicity, possibly due to dasatinib-induced cell viability reduction. In summary, this study demonstrates OHP as an OCT2 substrate and dasatinib as a non-transported inhibitor and regulator of OCT2, offering potential for OIPN mitigation.

2.
Int J Mol Sci ; 25(5)2024 Mar 02.
Artigo em Inglês | MEDLINE | ID: mdl-38474165

RESUMO

Cisplatin (CDDP) stands out as an effective chemotherapeutic agent; however, its application is linked to the development of significant adverse effects, notably nephro- and ototoxicity. The human organic cation transporter 2 (hOCT2), found in abundance in the basolateral membrane domain of renal proximal tubules and the Corti organ, plays a crucial role in the initiation of nephro- and ototoxicity associated with CDDP by facilitating its uptake in kidney and ear cells. Given its limited presence in cancer cells, hOCT2 emerges as a potential druggable target for mitigating unwanted toxicities associated with CDDP. Potential strategies for mitigating CDDP toxicities include competing with the uptake of CDDP by hOCT2 or inhibiting hOCT2 activity through rapid regulation mediated by specific signaling pathways. This study investigated the interaction between the already approved cationic drugs disopyramide, imipramine, and orphenadrine with hOCT2 that is stably expressed in human embryonic kidney cells. Regarding disopyramide, its influence on CDDP cellular transport by hOCT2 was further characterized through inductively coupled plasma isotope dilution mass spectrometry. Additionally, its potential protective effects against cellular toxicity induced by CDDP were assessed using a cytotoxicity test. Given that hOCT2 is typically expressed in the basolateral membrane of polarized cells, with specific regulatory mechanisms, this work studied the regulation of hOCT2 that is stably expressed in Madin-Darby Canine Kidney (MDCK) cells. These cells were cultured in a matrix to induce the formation of cysts, exposing hOCT2 in the basolateral plasma membrane domain, which was freely accessible to experimental solutions. The study specifically tested the regulation of ASP+ uptake by hOCT2 in MDCK cysts through the inhibition of casein kinase II (CKII), calmodulin, or p56lck tyrosine kinase. Furthermore, the impact of this manipulation on the cellular toxicity induced by CDDP was examined using a cytotoxicity test. All three drugs-disopyramide, imipramine, and orphenadrine-demonstrated inhibition of ASP+ uptake, with IC50 values in the micromolar (µM) range. Notably, disopyramide produced a significant reduction in the CDDP cellular toxicity and platinum cellular accumulation when co-incubated with CDDP. The activity of hOCT2 in MDCK cysts experienced a significant down-regulation under inhibition of CKII, calmodulin, or p56lck tyrosine kinase. Interestingly, only the inhibition of p56lck tyrosine kinase demonstrated the capability to protect the cells against CDDP toxicity. In conclusion, certain interventions targeting hOCT2 have demonstrated the ability to reduce CDDP cytotoxicity, at least in vitro. Further investigations in in vivo systems are warranted to ascertain their potential applicability as co-treatments for mitigating undesired toxicities associated with CDDP in patients.


Assuntos
Cistos , Ototoxicidade , Humanos , Animais , Cães , Transportador 2 de Cátion Orgânico , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Cisplatino/metabolismo , Disopiramida , Calmodulina/metabolismo , Imipramina , Orfenadrina , Células Madin Darby de Rim Canino , Proteínas Tirosina Quinases/metabolismo
4.
Int J Mol Sci ; 24(18)2023 Sep 13.
Artigo em Inglês | MEDLINE | ID: mdl-37762353

RESUMO

Endogenous positively charged organic substances, including neurotransmitters and cationic uremic toxins, as well as exogenous organic cations such as the anti-diabetic medication metformin, serve as substrates for organic cation transporters (OCTs) and multidrug and toxin extrusion proteins (MATEs). These proteins facilitate their transport across cell membranes. Vectorial transport through the OCT/MATE axis mediates the hepatic and renal excretion of organic cations, regulating their systemic and local concentrations. Organic cation transporters are part of the remote sensing and signaling system, whose activity can be regulated to cope with changes in the composition of extra- and intracellular fluids. Glucose, as a source of energy, can also function as a crucial signaling molecule, regulating gene expression in various organs and tissues. Its concentration in the blood may fluctuate in specific physiological and pathophysiological conditions. In this work, the regulation of the activity of organic cation transporters was measured by incubating human embryonic kidney cells stably expressing human OCT1 (hOCT1), hOCT2, or hMATE1 with high glucose concentrations (16.7 mM). Incubation with this high glucose concentration for 48 h significantly stimulated the activity of hOCT1, hOCT2, and hMATE1 by increasing their maximal velocity (Vmax), but without significantly changing their affinity for the substrates. These effects were independent of changes in osmolarity, as the addition of equimolar concentrations of mannitol did not alter transporter activity. The stimulation of transporter activity was associated with a significant increase in transporter mRNA expression. Inhibition of the mechanistic target of rapamycin (mTOR) kinase with Torin-1 suppressed the transporter stimulation induced by incubation with 16.7 mM glucose. Focusing on hOCT2, it was shown that incubation with 16.7 mM glucose increased hOCT2 protein expression in the plasma membrane. Interestingly, an apparent trend towards higher hOCT2 mRNA expression was observed in kidneys from diabetic patients, a pathology characterized by high serum glucose levels. Due to the small number of samples from diabetic patients (three), this observation must be interpreted with caution. In conclusion, incubation for 48 h with a high glucose concentration of 16.7 mM stimulated the activity and expression of organic cation transporters compared to those measured in the presence of 5.6 mM glucose. This stimulation by a diabetic environment could increase cellular uptake of the anti-diabetic drug metformin and increase renal tubular secretion of organic cations in an early stage of diabetes.


Assuntos
Metformina , Proteínas de Transporte de Cátions Orgânicos , Humanos , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Transportador 2 de Cátion Orgânico/genética , Metformina/farmacologia , Metformina/metabolismo , Cátions/metabolismo , RNA Mensageiro
5.
Int J Mol Sci ; 24(14)2023 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-37511245

RESUMO

Cisplatin (CDDP) is an efficient chemotherapeutic agent broadly used to treat solid cancers. Chemotherapy with CDDP can cause significant unwanted side effects such as renal toxicity and peripheral neurotoxicity. CDDP is a substrate of organic cation transporters (OCT), transporters that are highly expressed in renal tissue. Therefore, CDDP uptake by OCT may play a role in causing unwanted toxicities of CDDP anticancer treatment. In this study, the contribution of the mouse OCT2 (mOCT2) to CDDP nephro- and peripheral neurotoxicity was investigated by comparing the effects of cyclic treatment with low doses of CDDP on renal and neurological functions in wild-type (WT) mice and mice with genetic deletion of OCT2 (OCT2-/- mice). This CDDP treatment protocol caused significant impairment of kidneys and peripherical neurological functions in WT mice. These effects were significantly reduced in OCT2-/- mice, however, less profoundly than what was previously measured in mice with genetic deletion of both OCT1 and 2 (OCT1-2-/- mice). Comparing the apparent affinities (IC50) of mOCT1 and mOCT2 for CDDP, the mOCT1 displayed a higher affinity for CDDP than the mOCT2 (IC50: 9 and 558 µM, respectively). Also, cellular toxicity induced by incubation with 100 µM CDDP was more pronounced in cells stably expressing mOCT1 than in cells expressing mOCT2. Therefore, in mice, CDDP uptake by both OCT1 and 2 contributes to the development of CDDP undesired side effects. OCT seem to be suitable targets for establishing treatment protocols aimed at decreasing unwanted CDDP toxicity and improving anticancer treatment with CDDP.


Assuntos
Cisplatino , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Animais , Camundongos , Transporte Biológico , Cisplatino/toxicidade , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/metabolismo , Rim/metabolismo , Proteínas de Transporte de Cátions Orgânicos/genética , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Transportador 2 de Cátion Orgânico/genética , Transportador 2 de Cátion Orgânico/metabolismo
6.
Int J Mol Sci ; 24(8)2023 Apr 13.
Artigo em Inglês | MEDLINE | ID: mdl-37108379

RESUMO

This editorial summarizes the 22 scientific papers published in the Special Issue "Overcoming Biological Barriers: Importance of Membrane Transporters in Homeostasis, Disease, and Disease Treatment" of the International Journal of Molecular Sciences [...].


Assuntos
Proteínas de Membrana Transportadoras , Homeostase
7.
Biomolecules ; 13(3)2023 03 03.
Artigo em Inglês | MEDLINE | ID: mdl-36979408

RESUMO

In late 2019, the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) as the causative agent of coronavirus disease 2019 (COVID-19) emerged in China and spread rapidly around the world, causing an ongoing pandemic of global concern. COVID-19 proceeds with moderate symptoms in most patients, whereas others experience serious respiratory illness that requires intensive care treatment and may end in death. The severity of COVID-19 is linked to several risk factors including male sex, comorbidities, and advanced age. Apart from respiratory complications, further impairments by COVID-19 affecting other tissues of the human body are observed. In this respect, the human kidney is one of the most frequently affected extrapulmonary organs and acute kidney injury (AKI) is known as a direct or indirect complication of SARS-CoV-2 infection. The aim of this work was to investigate the importance of the protein angiotensin-converting enzyme 2 (ACE2) for a possible cell entry of SARS-CoV-2 into human kidney cells. First, the expression of the cellular receptor ACE2 was demonstrated to be decisive for viral SARS-CoV-2 cell entry in human AB8 podocytes, whereas the presence of the transmembrane protease serine 2 (TMPRSS2) was dispensable. Moreover, the ACE2 protein amount was well detectable by mass spectrometry analysis in human kidneys, while TMPRSS2 could be detected only in a few samples. Additionally, a negative correlation of the ACE2 protein abundance to male sex and elderly aged females in human kidney tissues was demonstrated in this work. Last, the possibility of a direct infection of kidney tubular renal structures by SARS-CoV-2 was demonstrated.


Assuntos
COVID-19 , Idoso , Feminino , Humanos , Masculino , Enzima de Conversão de Angiotensina 2 , Rim/metabolismo , Peptidil Dipeptidase A/genética , Peptidil Dipeptidase A/metabolismo , SARS-CoV-2/metabolismo
8.
Int J Mol Sci ; 23(24)2022 Dec 14.
Artigo em Inglês | MEDLINE | ID: mdl-36555515

RESUMO

Cisplatin (CDDP) is an efficient chemotherapeutic drug, whose use is associated with the development of serious undesired toxicities, such as nephrotoxicity. The human organic cation transporter 2 (hOCT2), which is highly expressed in the basolateral membrane domain of renal proximal tubules seems to play an important role in the development of CDDP nephrotoxicity. The role of angiotensin II (AII) signaling by binding to the AII receptor type 1 (AT1R) in the development and/or progression of CDDP nephrotoxicity is debated. Therefore, in this work, the regulation of hOCT2 activity by AII and its role in the development of CDDP cellular toxicity was investigated. To do this, hOCT2 was overexpressed by viral transduction in Madin-Darby Canine Kidney (MDCK) cells which were cultivated on a filter. This approach allows the separation of an apical and a basolateral membrane domain, which are easily accessible for experimentation. In this system, hOCT2 was mainly localized on the basolateral plasma membrane domain of the cells. The transporter was functional since a specific uptake of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) with an affinity (Km) of 35 µM was only detectable by the addition of ASP+ to the basolateral compartment of hOCT2 expressing MDCK (hOCT2-MDCK) cells. Similarly, CDDP toxicity was evident mainly by CDDP addition to the basolateral compartment of hOCT2-MDCK cells cultivated on a filter. The addition of 1 nM AII stimulated hOCT2 function via PKC activation and worsened CDDP cytotoxicity via binding to AT1R. Therefore, the AII signaling pathway may be implicated in the development and/or progression of CDDP nephrotoxicity. This signaling pathway may be a target for protective interventions for example by blocking AT1R in the kidneys. However, it should be further investigated whether these findings obtained in a cell culture system may have translational relevance for the clinical situation. For toxicity experiments, a 100 µM CDDP concentration was used, which is high but allows us to identify clearly toxic effects due to hOCT2. In summary, down-regulation of hOCT2 activity by the inhibition of the AII signaling pathway may protect against CDDP nephrotoxicity.


Assuntos
Angiotensina II , Cisplatino , Humanos , Animais , Cães , Transportador 2 de Cátion Orgânico/genética , Cisplatino/toxicidade , Cisplatino/metabolismo , Angiotensina II/farmacologia , Angiotensina II/metabolismo , Túbulos Renais/metabolismo , Rim/metabolismo , Proteínas de Transporte de Cátions Orgânicos/metabolismo
9.
Int J Mol Sci ; 23(22)2022 Nov 16.
Artigo em Inglês | MEDLINE | ID: mdl-36430667

RESUMO

Tyrosine kinase inhibitors (TKI) such as Masitinib were reported to be useful as therapeutic options in malignant disorders and nonmalignant diseases, like coronavirus disease 2019 (COVID-19). Most kinases must be translocated into targeted cells by the action of specific transport proteins, as they are hydrophilic and not able to cross cell membranes freely. Accordingly, the efficacy of TKI in target cells is closely dependent on the expression of their transporters. Specifically, Masitinib is an organic cation and is expected to interact with organic cation transporters (OCT and Multidrug and Toxin Extrusion proteins-MATE-). The aim of this work was to characterize the interaction of Masitinib with different OCTs. Human embryonic kidney 293 cells stably transfected with murine or human OCT were used for the experiments. The interaction of Masitinib with OCTs was investigated using quenching experiments. The intracellular accumulation of this drug was quantified using high performance liquid chromatography. Our results identified interactions of Masitinib with almost all investigated mouse (m) and human (h) OCTs and hMATE1 and indicated OCT1 and hOCT2 to be especially potent Masitinib translocators across cell membranes. Interestingly, some important differences were observed for the interaction with murine and human OCTs. In the future, investigations concerning further in vitro and in vivo properties of Masitinib and its efficacy related to transporter-related uptake mechanisms under pathophysiological conditions should be performed. Clinical trials in humans and other animals with Masitinib have already shown promising results. However, further research is necessary to understand the disease specific transport mechanisms of Masitinib to contribute to a successful and responsible therapy employment.


Assuntos
COVID-19 , Proteínas de Transporte de Cátions Orgânicos , Humanos , Camundongos , Animais , Proteínas de Transporte de Cátions Orgânicos/metabolismo , Transportador 2 de Cátion Orgânico , Tiazóis
10.
Int J Mol Sci ; 23(11)2022 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-35683007

RESUMO

This editorial summarizes the 12 scientific papers published in the Special Issue "Physiology, Biochemistry, and Pharmacology of Transporters for Organic Cations 2 [...].


Assuntos
Bioquímica , Farmacologia , Cátions , Proteínas de Membrana Transportadoras
12.
Viruses ; 14(4)2022 03 30.
Artigo em Inglês | MEDLINE | ID: mdl-35458456

RESUMO

The Na+/taurocholate co-transporting polypeptide (NTCP, gene symbol SLC10A1) is both a physiological bile acid transporter and the high-affinity hepatic receptor for the hepatitis B and D viruses (HBV/HDV). Virus entry via endocytosis of the virus/NTCP complex involves co-factors, but this process is not fully understood. As part of the innate immunity, interferon-induced transmembrane proteins (IFITM) 1-3 have been characterized as virus entry-restricting factors for many viruses. The present study identified IFITM3 as a novel protein-protein interaction (PPI) partner of NTCP based on membrane yeast-two hybrid and co-immunoprecipitation experiments. Surprisingly, IFITM3 knockdown significantly reduced in vitro HBV infection rates of NTCP-expressing HuH7 cells and primary human hepatocytes (PHHs). In addition, HuH7-NTCP cells showed significantly lower HDV infection rates, whereas infection with influenza A virus was increased. HBV-derived myr-preS1 peptide binding to HuH7-NTCP cells was intact even under IFITM3 knockdown, suggesting that IFITM3-mediated HBV/HDV infection enhancement occurs in a step subsequent to the viral attachment to NTCP. In conclusion, IFITM3 was identified as a novel NTCP co-factor that significantly affects in vitro infection with HBV and HDV in NTCP-expressing hepatoma cells and PHHs. While there is clear evidence for a direct PPI between IFITM3 and NTCP, the specific mechanism by which this PPI facilitates the infection process remains to be identified in future studies.


Assuntos
Hepatite B , Simportadores , Células Hep G2 , Vírus da Hepatite B/fisiologia , Vírus Delta da Hepatite/genética , Hepatócitos , Humanos , Proteínas de Membrana/genética , Proteínas de Membrana/metabolismo , Transportadores de Ânions Orgânicos Dependentes de Sódio/genética , Transportadores de Ânions Orgânicos Dependentes de Sódio/metabolismo , Proteínas de Ligação a RNA/metabolismo , Simportadores/genética , Simportadores/metabolismo , Internalização do Vírus
13.
Front Mol Biosci ; 9: 792829, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-35252349

RESUMO

Pals1 is part of the evolutionary conserved Crumbs polarity complex and plays a key role in two processes, the formation of apicobasal polarity and the establishment of cell-cell contacts. In the human kidney, up to 1.5 million nephrons control blood filtration, as well as resorption and recycling of inorganic and organic ions, sugars, amino acids, peptides, vitamins, water and further metabolites of endogenous and exogenous origin. All nephron segments consist of polarized cells and express high levels of Pals1. Mice that are functionally haploid for Pals1 develop a lethal phenotype, accompanied by heavy proteinuria and the formation of renal cysts. However, on a cellular level, it is still unclear if reduced cell polarization, incomplete cell-cell contact formation, or an altered Pals1-dependent gene expression accounts for the renal phenotype. To address this, we analyzed the transcriptomes of Pals1-haploinsufficient kidneys and the littermate controls by gene set enrichment analysis. Our data elucidated a direct correlation between TGFß pathway activation and the downregulation of more than 100 members of the solute carrier (SLC) gene family. Surprisingly, Pals1-depleted nephrons keep the SLC's segment-specific expression and subcellular distribution, demonstrating that the phenotype is not mainly due to dysfunctional apicobasal cell polarization of renal epithelia. Our data may provide first hints that SLCs may act as modulating factors for renal cyst formation.

14.
Int J Mol Sci ; 23(3)2022 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-35163014

RESUMO

The human organic cation transporter 2 (hOCT2) mediates renal and neuronal cellular cisplatin and oxaliplatin uptake, and therefore plays a significant role in the development of side effects associated with these chemotherapeutic drugs. Autophagy is induced by cisplatin and oxaliplatin treatment and is believed to promote cell survival under stressful conditions. We examined in vitro the role of hOCT2 on autophagy induced by cisplatin and oxaliplatin. We also explored the effect of autophagy on toxicities of these platinum derivatives. Our results indicate that autophagy, measured as LC3 II accumulation and reduction in p62 expression level, is induced in response to cisplatin and oxaliplatin in HEK293-hOCT2 but not in wild-type HEK293 cells. Furthermore, inhibition of autophagy is associated with higher toxicity of platinum derivatives, and starvation was found to offer protection against cisplatin-associated toxicity. In conclusion, activation of autophagy could be a potential strategy to protect against unwanted toxicities induced by treatment with platinum derivatives.


Assuntos
Proteínas Associadas aos Microtúbulos/metabolismo , Transportador 2 de Cátion Orgânico/genética , Platina/toxicidade , Proteína Sequestossoma-1/metabolismo , Autofagia , Biomarcadores/metabolismo , Cisplatino/toxicidade , Regulação da Expressão Gênica/efeitos dos fármacos , Células HEK293 , Humanos , Mutação , Oxaliplatina/toxicidade
15.
Biomolecules ; 11(11)2021 11 04.
Artigo em Inglês | MEDLINE | ID: mdl-34827636

RESUMO

The discovery of the anticancer properties of platinum derivatives by Rosenberg represents a milestone in the development of chemotherapeutic protocols for tumor treatment [...].


Assuntos
Antineoplásicos/farmacologia , Platina/farmacologia , Animais , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Humanos , Imunidade/efeitos dos fármacos , Morte Celular Imunogênica/efeitos dos fármacos
16.
Biochem Pharmacol ; 194: 114840, 2021 12.
Artigo em Inglês | MEDLINE | ID: mdl-34774844

RESUMO

The human organic cation transporter 2 (OCT2) is a multispecific transporter with cholesterol-dependent allosteric features. The present work elucidates the role of evolutionarily conserved cholesterol recognition/interaction amino acid consensus sequences (CRAC and CARC) in the allosteric binding to 1-methyl-4-phenylpyridinium (MPP+) in human embryonic kidney 293 cells stably or transiently expressing OCT2. Molecular blind simulations docked two mirroring cholesterol molecules in the 5th putative transmembrane domain, where a CARC and a CRAC sequence lie. The impact of the conserved amino acids that may constitute the CARC/CRAC mirror code was studied by alanine-scanning mutagenesis. At a saturating extracellular concentration of substrate, at which the impact of cholesterol depletion is maximal, five mutants transported MPP+ at a significantly lower rate than the wild-type OCT2 (WT), resembling the behavior of the WT upon cholesterol depletion. MPP+ influx rate as a function of the extracellular concentration of substrate was measured for the mutants R234A, R235A, L252A and R263A. R234A kinetic behavior was similar to that of the WT, whereas R235A, L252A and R263A activity shifted from allosteric to one-binding site kinetics, very much like the WT upon cholesterol depletion. The impact of cholesterol on protein thermal stability was assessed for WT, R234A and R263A. While the thermal stability of WT and R234A was improved by the supplementation with cholesterol, R263A was not sensitive to the presence of cholesterol. To conclude, the disruption of the CARC/CRAC mirror code in the 5th putative transmembrane domain is sufficient to abolish the allosteric interaction between OCT2 and MPP+.


Assuntos
Colesterol/metabolismo , Transportador 2 de Cátion Orgânico/metabolismo , Regulação Alostérica/fisiologia , Sequência de Aminoácidos , Colesterol/genética , Células HEK293 , Humanos , Transportador 2 de Cátion Orgânico/química , Transportador 2 de Cátion Orgânico/genética , Estrutura Secundária de Proteína
17.
Int J Mol Sci ; 22(17)2021 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-34502566

RESUMO

The renal secretory clearance for organic cations (neurotransmitters, metabolism products and drugs) is mediated by transporters specifically expressed in the basolateral and apical plasma membrane domains of proximal tubule cells. Here, human organic cation transporter 2 (hOCT2) is the main transporter for organic cations in the basolateral membrane domain. In this study, we stably expressed hOCT2 in Madin-Darby Canine Kidney (MDCK) cells and cultivated these cells in the presence of an extracellular matrix to obtain three-dimensional (3D) structures (cysts). The transport properties of hOCT2 expressed in MDCK cysts were compared with those measured using human embryonic kidney cells (HEK293) stably transfected with hOCT2 (hOCT2-HEK cells). In the MDCK cysts, hOCT2 was expressed in the basolateral membrane domain and showed a significant uptake of the fluorescent organic cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) with an affinity (Km) of 3.6 ± 1.2 µM, similar to what was measured in the hOCT2-HEK cells (Km = 3.1 ± 0.2 µM). ASP+ uptake was inhibited by tetraethylammonium (TEA+), tetrapentylammonium (TPA+), metformin and baricitinib both in the hOCT2-HEK cells and the hOCT2- MDCK cysts, even though the apparent affinities of TEA+ and baricitinib were dependent on the expression system. Then, hOCT2 was subjected to the same rapid regulation by inhibition of p56lck tyrosine kinase or calmodulin in the hOCT2-HEK cells and hOCT2- MDCK cysts. However, inhibition of casein kinase II regulated only activity of hOCT2 expressed in MDCK cysts and not in HEK cells. Taken together, these results suggest that the 3D cell culture model is a suitable tool for the functional analysis of hOCT2 transport properties, depending on cell polarization.


Assuntos
Técnicas de Cultura de Células/métodos , Polaridade Celular/fisiologia , Células Epiteliais/metabolismo , Transportador 2 de Cátion Orgânico/metabolismo , Animais , Transporte Biológico/fisiologia , Cátions/metabolismo , Cães , Células Epiteliais/citologia , Células Epiteliais/fisiologia , Proteínas de Fluorescência Verde/genética , Proteínas de Fluorescência Verde/metabolismo , Células HEK293 , Humanos , Células Madin Darby de Rim Canino , Metilaminas/metabolismo , Microscopia de Fluorescência/métodos , Transportador 2 de Cátion Orgânico/genética , Compostos de Piridínio/metabolismo
18.
Front Physiol ; 12: 707175, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34393825
19.
Front Cell Dev Biol ; 9: 688885, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34124075

RESUMO

Organic cation transporters (OCT) play an important role in mediating cellular uptake of several pharmaceuticals, such as the antidiabetic drug metformin and the platinum-derived chemotherapeutics. Since these drugs can also affect the pancreas, here it was investigated whether these transporters are expressed in this organ. An interaction between OCT2 and the glucose transporter 2 (GLUT2), which is expressed with important functional consequences in the kidneys and in the pancreas, has already been demonstrated elsewhere. Therefore, here it was further investigated whether the two proteins have a functional relationship. It was demonstrated that OCT2 is expressed in pancreas, probably in ß cells of Langerhans islets, together with GLUT2. However, a co-localization was only evident in a cell-line model of rat pancreatic ß cells under incubation with high glucose concentration. High glucose stimulated OCT2 expression and activity. On the other side, studies conducted in human embryonic kidney cells stably expressing OCT2, showed that overexpression of GLUT2 decreased OCT2 activity. Unfortunately, pull-down experiments aimed to confirm a physical OCT2/GLUT2 interaction were not successful. Renal glucose excretion was reduced in mice with genetic deletion of OCT2. Nonetheless, in these mice no regulation of known kidney glucose transporters was measured. Therefore, it may be speculated that OCT2 may influence cellular trafficking of GLUT2, without changing its amount. OCT2 may play a role in drug uptake of the pancreas, and its activity may be regulated by glucose and GLUT2. Vice versa, GLUT2 activity may be regulated through an interaction with OCT2.

20.
Front Oncol ; 11: 607574, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-33718160

RESUMO

After more than four decades of post-approval, cisplatin is still an important treatment for numerous cancers. However, acute kidney injury (AKI), defined as significant impairment of renal filtration as discussed below, is the major limiting side effect of cisplatin, occurring in approximately 30% of patients (25-33% after the first course). Cisplatin also damages the kidneys' ability to reabsorb magnesium in 40-100% of patients, with collateral health risks due to subsequent hypomagnesemia. Multiple methods and drugs have been proposed for preventing cisplatin-induced AKI, including saline infusion with or without mannitol, which has not always prevented AKI and has been found to activate a cellular stress response in renal tubular cells. While numerous reports and trials, as well as the National Comprehensive Cancer Network (NCCN), support premedication with magnesium and hydration, this practice has not been universally accepted. Many clinics administer intravenous magnesium (IV) only after identification of hypomagnesemia post-cisplatin treatment, thus placing patients at risk for AKI and chronic renal loss of magnesium. We present the following case report and additional supporting evidence identifying the immediate effect of IV magnesium prior to intraperitoneal cisplatin for cycle 4 because of documented hypomagnesemia resulting in normalization of oliguria, which had been experienced for the first three cycles. The patient subsequently requested and received IV magnesium before cisplatin for the next two cycles with continuation of normal urinary output. The effect of pretreatment with IV magnesium on urine output following cisplatin has not been previously reported and further supports pre-cisplatin administration. In addition, two recent meta-analyses of clinical trials and pre-clinical research are reviewed that demonstrate effectiveness of magnesium pretreatment to preventing AKI without reducing its chemotherapeutic efficacy. This case report with additional evidence supports the adoption of administration of 1-3 g IV magnesium before cisplatin as best practice to prevent cisplatin induced AKI and hypomagnesemia regardless of patient baseline serum magnesium levels.

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