Mouse organic cation transporter 1 determines properties and regulation of basolateral organic cation transport in renal proximal tubules.

The proximal tubule of mouse kidney expresses mouse organic cation transporter 1 (mOCT1), mOCT2, and much less mOCT3. Therefore, mOCT-mediated transport across the basolateral membrane of proximal tubules reflects properties of at least mOCT1 and mOCT2. Here, we unraveled substrate affinities and modulation of transport activity by acute regulation by protein kinases on mOCT1 and mOCT2 separately and compared these findings with those from isolated proximal tubules of male and female mOCT2−/− mice. These data are also compared to our recent reports on isolated tubules from wild-type and mOCT1/2 double knockout (mOCT1/2−/−) mice. OCT-mediated transport in proximal tubules of mOCT2−/− mice was only 20 % lower compared to those isolated from wild-type mice. While mOCT1 was regulated by all five pathways examined [protein kinase A (PKA), protein kinase C (PKC), p56lck, phosphoinositide 3-kinase (PI3K), and calmodulin (CaM)], mOCT2 activity was modulated by PKA, p56lck, and CaM only, however, in the same direction. As mOCT-mediated transport across the basolateral membrane of mOCT2−/− mice expressing only mOCT1 and to a small amount mOCT3 was identical to that observed for tubules isolated from wild-type mice and to that observed for human embryonic kidney 293 (HEK293) cells stably expressing mOCT1, mOCT1 represents the relevant paralog for OCT-dependent organic cation transport in the mouse kidney. Gender does not play a major role in expression and activity of renal OCT-mediated transport in the mouse. Properties of mouse OCT considerably differ from those of rat or human origin, and thus, observations made in these rodents cannot directly be transferred to the human situation

The organic cation transporter 3 (OCT3) as molecular target of psychotropic drugs: transport characteristics and acute regulation of cloned murine OCT3.

The organic cation transporter 3 (OCT3) is a widely expressed transporter for endogenous and exogenous organic cations. Of particular interest is OCT3 expression and function in the brain, where it plays a role in serotonin clearance and influences mood and behavior. Protein kinase signaling mediates rapid modulation of cerebral processes, but little is known about acute regulation of OCT3 by protein kinases. Therefore, we cloned mouse OCT3 (mOCT3) and generated a human embryonic kidney cell line stably expressing the transporter to study transport characteristics, acute regulation by protein kinases, and interaction with psychotropic drugs. Uptake measurement was performed using the fluorescent cation 4-(4-(dimethylamino)styryl)-N-methylpyridinium iodide (ASP(+), 1 µM) as a substrate. The translational value of these findings was determined by comparing results obtained with cloned mouse and human OCT3. mOCT3-mediated transport is membrane potential dependent and pH independent. ASP(+) uptake by mOCT3 and human OCT3 (hOCT3) was efficiently inhibited by 1-methyl-4-phenylpyridinium, tetrapentylammonium (TPA(+)), corticosterone, serotonin, and histamine and by the drugs ketamine, fluoxetine, and diazepam. The half maximal inhibitory concentrations of mOCT3 and hOCT3 for TPA(+), serotonin, diazepam, and ketamine are significantly different. Diazepam is a non-transported inhibitor. Furthermore, the activities of mOCT3 and hOCT3 are acutely regulated by the p56 (lck) tyrosine kinase by decreasing their V max. Studies with freshly isolated renal proximal tubules from mOCT1/2(-/-) mice, in which mOCT3 is the only OCT present, confirmed this regulation pathway. Only the activity of hOCT3 is regulated by calmodulin. These findings suggest that even though many transport properties of mOCT3 and hOCT3 are similar, there are also species-specific aspects of OCT3 function.

Reduced splenic uptake on 68Ga-Pentixafor-PET/CT imaging in multiple myeloma - a potential imaging biomarker for disease prognosis.

Beyond being a key factor for tumor growth and metastasis in human cancer, C-X-C motif chemokine receptor 4 (CXCR4) is also highly expressed by a number of immune cells, allowing for non-invasive read-out of inflammatory activity. With two recent studies reporting on prognostic implications of the spleen signal in diffusion-weighted magnetic resonance imaging in patients with plasma cell dyscrasias, the aim of this study was to correlate splenic 68Ga-Pentixafor uptake in multiple myeloma (MM) with clinical parameters and to evaluate its prognostic impact. Methods: Eighty-seven MM patients underwent molecular imaging with 68Ga-Pentixafor-PET/CT. Splenic CXCR4 expression was semi-quantitatively assessed by peak standardized uptake values (SUVpeak) and corresponding spleen-to-bloodpool ratios (TBR) and correlated with clinical and prognostic features as well as survival parameters. Results:68Ga-Pentixafor-PET/CT was visually positive in all MM patients with markedly heterogeneous tracer uptake in the spleen. CXCR4 expression determined by 68Ga-Pentixafor-PET/CT corresponded with advanced disease and was inversely associated with the number of previous treatment lines as compared to controls or untreated smouldering multiple myeloma patients (SUVpeakSpleen 4.06 ± 1.43 vs. 6.02 ± 1.16 vs. 7.33 ± 1.40; P < 0.001). Moreover, reduced splenic 68Ga-Pentixafor uptake was linked to unfavorable clinical outcome. Patients with a low SUVpeakSpleen (<3.35) experienced a significantly shorter overall survival of 5 months as compared to 62 months in patients with a high SUVpeakSpleen >5.79 (P < 0.001). Multivariate Cox analysis confirmed SUVpeakSpleen as an independent predictor of survival (HR 0.75; P = 0.009). Conclusion: These data suggest that splenic 68Ga-Pentixafor uptake might provide prognostic information in pre-treated MM patients similar to what was reported for diffusion-weighted magnetic resonance imaging. Further research to elucidate the underlying biologic implications is warranted.

Improved Primary Staging of Marginal-Zone Lymphoma by Addition of CXCR4-Directed PET/CT.

PET/CT with 18F-FDG is an integral component in the primary staging of most lymphomas. However, its utility is limited in marginal-zone lymphoma (MZL) because of inconsistent 18F-FDG avidity. One diagnostic alternative could be the targeting of C-X-C motif chemokine receptor 4 (CXCR4), shown to be expressed by MZL cells. This study investigated the value of adding CXCR4-directed 68Ga-pentixafor PET/CT to conventional staging. Methods: Twenty-two newly diagnosed MZL patients were staged conventionally and with CXCR4 PET/CT. Lesions identified exclusively by CXCR4 PET/CT were biopsied as the standard of reference and compared with imaging results. The impact of CXCR4-directed imaging on staging results and treatment protocol was assessed. Results: CXCR4 PET/CT correctly identified all patients with viable MZL and was superior to conventional staging (P < 0.001). CXCR4-directed imaging results were validated by confirmation of MZL in 16 of 18 PET-guided biopsy samples. Inclusion of CXCR4 PET/CT in primary staging significantly impacted staging results in almost half of patients and treatment protocols in a third (upstaging, n = 7; downstaging, n = 3; treatment change, n = 8; P < 0.03). Conclusion: CXCR4 PET/CT is a suitable tool in primary staging of MZL and holds the potential to improve existing diagnostic algorithms.

English version of the self-administered Fabry Pain Questionnaire for adult patients.

BACKGROUND: Pain is an early symptom of Fabry disease (FD) and is characterized by a unique phenotype with mainly episodic acral and triggerable burning pain. Recently, we designed and validated the first pain questionnaire for adult FD patients in an interview and a self-administered version in German: the Würzburg Fabry Pain Questionnaire (FPQ). We now report the validation of the English version of the self-administered FPQ (enFPQ). METHODS: After two forward-backward translations of the FPQ by native German and native English speakers, the enFPQ was applied at The Mark Holland Metabolic Unit, Manchester, UK for validation. Consecutive patients with genetically ascertained FD and current or previous FD pain underwent a face-to-face interview using the enFPQ. Two weeks later, patients filled in the self-administered enFPQ at home. The agreement between entries collected by supervised administration and self-administration of the enFPQ was assessed via Gwet's AC1-statistics (AC1) for nominal-scaled scores and intraclass correlation coefficient (ICC) for interval-scaled elements. RESULTS: Eighty-three FD patients underwent the face-to-face interview and 54 patients sent back a completed self-administered version of the enFPQ 2 weeks later. We found high agreement with a mean AC1-statistics of 0.725 for 55 items, and very high agreement with a mean ICC of 0.811 for 9 items. CONCLUSIONS: We provide the validated English version of the FPQ for self-administration in adult FD patients. The enFPQ collects detailed information on the individual FD pain phenotype and thus builds a solid basis for better pain classification and treatment in patients with FD.