Modulating the Activity of the Human Organic Cation Transporter 2 Emerges as a Potential Strategy to Mitigate Unwanted Toxicities Associated with Cisplatin Chemotherapy.

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.

Contrast medium free selective adrenal vein sampling in the management of primary aldosteronism.

BACKGROUND: To analyze contrast free adrenal vein sampling (AVS) for differentiating unilateral from bilateral disease in patients diagnosed with hypertension due to primary aldosteronism (PA). METHODS: Consecutive patients with PA and subsequent contrast medium free AVS between April 2015 and March 2020 were retrospectively included. Cross-sectional imaging (CSI), AVS and clinical data were analyzed regarding diagnostic performance. In addition, patients with lateralisation receiving adrenalectomy were compared to a control group treated with mineralocorticoid antagonists. RESULTS: In total 186 patients with AVS were included. The success rate for bilateral catheterization was 88% (median effective dose 2.8 mSv). CSI had an accuracy of 60% (CI: 0.52-0.67) in the detection of lateralization compared to AVS. Patients with bilateral adrenal hyperplasia and those with aldosterone-producing adenoma did not differ in systolic blood pressure (sBP) (p = 0.63) or number of antihypertensive drugs (NAD) (p = 0.11). After adrenalectomy, 28 patients were cured (51%; sBP ≤130 mmHg, NAD = 0), 18 were improved (33%; decrease of sBP ≥20 mmHg and NAD), and 8 were unchanged (15%). Serum renin increased significantly after treatment (p < 0.01). CONCLUSION: Contrast medium free AVS is a reliable procedure in the diagnostic management of patients with PA with high technical success rate. The accordance between CSI and results from AVS was only moderate indicating the central role of AVS in the diagnostic work-up of patients with PA. Patients with predominant disease diagnosed with AVS had a high cure rate and/or significant improvement after adrenalectomy.

How acute renal failure led to the diagnosis of aortic coarctation.

The present case report focuses on a rare presentation of aortic coarctation. A 38-year-old man with well-controlled arterial hypertension, minimal change glomerulonephritis and colitis ulcerosa was suffering from recurrent acute renal failure episodes during viral gastroenteritis. No other symptoms at rest or during physical activity were present. The workup included renal duplex sonography, which unmasked tardus parvus profile in both kidneys without any acceleration of blood flow in the renal arteries. Further examination included CT angiography, which confirmed the diagnosis of aortic coarctation. The observed narrowing of the aorta measured 4 mm and was treated with percutaneous transluminal angioplasty and stent implantation (final diameter 12 mm). After the procedure, the patient had normal blood pressure values without the need of any medication; duplex sonography showed improved renal perfusion. The present case confirms the importance of evaluation for secondary hypertension and thorough workup of acute renal failure in young patients.

The Effect of Renal Denervation on T Cells in Patients with Resistant Hypertension.

(1) Background: Sympathetic overactivity is a major contributor to resistant hypertension (RH). According to animal studies, sympathetic overactivity increases immune responses, thereby aggravating hypertension and cardiovascular outcomes. Renal denervation (RDN) reduces sympathetic nerve activity in RH. Here, we investigate the effect of RDN on T-cell signatures in RH. (2) Methods: Systemic inflammation and T-cell subsets were analyzed in 17 healthy individuals and 30 patients with RH at baseline and 6 months after RDN. (3) Results: The patients with RH demonstrated higher levels of pro-inflammatory cytokines and higher frequencies of CD4+ effector memory (TEM), CD4+ effector memory residential (TEMRA) and CD8+ central memory (TCM) cells than the controls. After RDN, systolic automated office blood pressure (BP) decreased by -17.6 ± 18.9 mmHg. Greater BP reductions were associated with higher CD4+ TEM (r -0.421, p = 0.02) and CD8+ TCM (r -0.424, p = 0.02) frequencies at baseline. The RDN responders, that is, the patients with ≥10mmHg systolic BP reduction, showed reduced pro-inflammatory cytokine levels, whereas the non-responders had unchanged inflammatory activity and higher CD8+ TEMRA frequencies with increased cellular cytokine production. (4) Conclusions: The pro-inflammatory state of patients with RH is characterized by altered T-cell signatures, especially in non-responders. A detailed analysis of T cells might be useful in selecting patients for RDN.

Factors Associated With Vaccine-Induced T-Cell Immune Responses Against Severe Acute Respiratory Syndrome Coronavirus 2 in Kidney Transplant Recipients.

Vaccination against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an important prophylactic measure in kidney transplant recipients (KTRs), but the immune response is often impaired. Here, we examined the T-cell immune response against SARS-CoV-2 in 148 KTRs after 3 or 4 vaccine doses, including 35 KTRs with subsequent SARS-CoV-2 infection. The frequency of spike-specific T cells was lower in KTRs than in immunocompetent controls and was correlated with the level of spike-specific antibodies. Positive predictors for detection of vaccine-induced T cells were detection of spike-specific antibodies, heterologous immunization with messenger RNA and a vector vaccine, and longer time after transplantation. In vaccinated KTRs with subsequent SARS-CoV-2 infection, the T-cell response was greatly enhanced and was significantly higher than in vaccinated KTRs without SARS-CoV-2 infection. Overall, the data show a correlation between impaired humoral and T-cell immunity to SARS-CoV-2 vaccination and provide evidence for greater robustness of hybrid immunity in KTRs.

Exacerbation of Cisplatin Cellular Toxicity by Regulation of the Human Organic Cation Transporter 2 through Angiotensin II.

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.

Development and validation of multivariable prediction models of serological response to SARS-CoV-2 vaccination in kidney transplant recipients.

Repeated vaccination against SARS-CoV-2 increases serological response in kidney transplant recipients (KTR) with high interindividual variability. No decision support tool exists to predict SARS-CoV-2 vaccination response to third or fourth vaccination in KTR. We developed, internally and externally validated five different multivariable prediction models of serological response after the third and fourth vaccine dose against SARS-CoV-2 in previously seronegative, COVID-19-naïve KTR. Using 20 candidate predictor variables, we applied statistical and machine learning approaches including logistic regression (LR), least absolute shrinkage and selection operator (LASSO)-regularized LR, random forest, and gradient boosted regression trees. For development and internal validation, data from 590 vaccinations were used. External validation was performed in four independent, international validation cohorts comprising 191, 184, 254, and 323 vaccinations, respectively. LASSO-regularized LR performed on the whole development dataset yielded a 20- and 10-variable model, respectively. External validation showed AUC-ROC of 0.840, 0.741, 0.816, and 0.783 for the sparser 10-variable model, yielding an overall performance 0.812. A 10-variable LASSO-regularized LR model predicts vaccination response in KTR with good overall accuracy. Implemented as an online tool, it can guide decisions whether to modulate immunosuppressive therapy before additional active vaccination, or to perform passive immunization to improve protection against COVID-19 in previously seronegative, COVID-19-naïve KTR.

Immune response to third SARS-CoV-2 vaccination in seronegative kidney transplant recipients: Possible improvement by mycophenolate mofetil reduction.

Modification of vaccination strategies is necessary to improve the immune response to SARS-CoV-2 vaccination in kidney transplant recipients (KTRs). This multicenter observational study analyzed the effects of the third SARS-CoV-2 vaccination in previously seronegative KTRs with the focus on temporary mycophenolate mofetil (MMF) dose reduction within propensity matched KTRs. 56 out of 174 (32%) previously seronegative KTRs became seropositive after the third vaccination with only three KTRs developing neutralizing antibodies against the omicron variant. Multivariate logistic regression revealed that initial antibody levels, graft function, time after transplantation and MMF trough levels had an influence on seroconversion (P < .05). After controlling for confounders, the effect of MMF dose reduction before the third vaccination was calculated using propensity score matching. KTRs with a dose reduction of ≥33% showed a significant decrease in MMF trough levels to 1.8 (1.2-2.5) µg/ml and were more likely to seroconvert than matched controls (P = .02). Therefore, a MMF dose reduction of 33% or more before vaccination is a promising approach to improve success of SARS-CoV-2 vaccination in KTRs.

Improved heart failure after closure of arteriovenous fistula.

The population of patients with end-stage renal disease is rapidly growing and hemodialysis remains the most common treatment option. We present a case of a young patient with arteriovenous fistula (AVF)-related heart failure, and a review of the main hemodynamic changes after AVF formation and ligation procedures.

Serum Calcification Propensity and Calcification of the Abdominal Aorta in Patients With Primary Aldosteronism.

Patients with primary aldosteronism (PA) are more susceptible to cardiovascular disease and mortality than patients with primary hypertension. This is mostly attributed to excess production of aldosterone and its effects on the development of vascular injury. A novel functional test (T50) measures serum calcification propensity. Lower T50-values predict higher cardiovascular risk. We investigated serum calcification propensity and vascular calcification in PA and resistant hypertension (RH). T50 measurement was performed in patients with PA (n = 66) and RH (n = 28) at baseline and after 403 (279-640) and 389 (277-527) days of treatment. No significant differences in T50-values were observed between the groups (371 ± 65 and 382 ± 44 min, in PA and RH group, respectively, p > 0.05). However, higher aldosterone-to-renin ratios were associated with lower T50-values in PA-patients (r -0.282, p < 0.05). Furthermore, lower T50-values were associated with increased abdominal aortic calcification measured by Agatston score in PA (r -0.534, p < 0.05). In both, PA and RH, higher atherosclerotic cardiovascular disease (ACSVD) scores (r -0.403, p < 0.05) and lower HDL (r 0.469, p < 0.05) was related to lower T50-values in a linear regression model. Adrenalectomy or medical treatment did not increase T50-values. In comparison to patients with stable T50-values, PA patients with a decrease in T50 after intervention had higher serum calcium concentrations at baseline (2.24 ± 0.11 vs. 2.37 ± 0.10 mmol/l, p < 0.05). This decline of T50-values at follow-up was also associated with a decrease in serum magnesium (-0.03 ± 0.03 mmol/l, p < 0.05) and an increase in phosphate concentrations (0.11 ± 0.11 mmol/l, p < 0.05). Resistant hypertension patients with a decrease in T50-values at follow-up had a significantly lower eGFR at baseline. In summary, these data demonstrate an association between a high aldosterone-to-renin ratio and low T50-values in PA. Moreover, lower T50-values are associated with higher ACSVD scores and more pronounced vascular calcification in PA. Thus, serum calcification propensity may be a novel modifiable risk factor in PA.

Intensity of mycophenolate mofetil treatment is associated with an impaired immune response to SARS-CoV-2 vaccination in kidney transplant recipients.

Kidney transplant recipients (KTRs) are extremely vulnerable to SARS-CoV-2 infection and show an impaired immune response to SARS-CoV-2 vaccination. We analyzed factors related to vaccination efficiency in KTRs. In a multicenter prospective observational study (NCT04743947), IgG antibodies levels against SARS-CoV-2 spike S1 subunit and their neutralization capacity after SARS-CoV-2 vaccination were analyzed in 225 KTRs and compared to 176 controls. After the vaccination, 56 (24.9%) KTRs became seropositive of whom 68% had neutralizing antibodies. This immune response was significantly lower compared to controls (239 [78-519] BAU/ml versus 1826 [560-3180] BAU/ml for KTRs and controls, p < .0001). The strongest predictor for an impaired response was mycophenolate mofetil (MMF) treatment. Multivariate regression analysis revealed that MMF-free regimen was highly associated with seroconversion (OR 13.25, 95% CI 3.22-54.6; p < .001). In contrast, other immunosuppressive drugs had no significant influence. 187 out of 225 KTRs were treated with MMF of whom 26 (13.9%) developed antibodies. 23 of these seropositive KTRs had a daily MMF dose ≤1 g. Furthermore, higher trough MMF concentrations correlated with lower antibody titers (R -0.354, p < .001) supporting a dose-dependent unfavorable effect of MMF. Our data indicate that MMF dose modification could lead to an improved immune response.

Rapid Regulation of Human Multidrug and Extrusion Transporters hMATE1 and hMATE2K.

Vectorial transport of organic cations (OCs) in renal proximal tubules is mediated by sequential action of human OC transporter 2 (hOCT2) and human multidrug and toxic extrusion protein 1 and 2K (hMATE1 and hMATE2K), expressed in the basolateral (hOCT2) and luminal (hMATE1 and hMATE2K) plasma membranes, respectively. It is well known that hOCT2 activity is subjected to rapid regulation by several signaling pathways, suggesting that renal OC secretion may be acutely adapted to physiological requirements. Therefore, in this work, the acute regulation of hMATEs stably expressed in human embryonic kidney cells was characterized using the fluorescent substrate 4-(4-(dimethylamino)styryl)-N-methylpyridinium (ASP+) as a marker. A specific regulation of ASP+ transport by hMATE1 and hMATE2K measured in uptake and efflux configurations was observed. In the example of hMATE1 efflux reduction by inhibition of casein kinase II, it was also shown that this regulation is able to modify transcellular transport of ASP+ in Madin-Darby canine kidney II cells expressing hOCT2 and hMATE1 on the basolateral and apical membrane domains, respectively. The activity of hMATEs can be rapidly regulated by some intracellular pathways, which sometimes are common to those found for hOCTs. Interference with these pathways may be important to regulate renal secretion of OCs.

Histopathological Classification-A Prognostic Tool for Rapidly Progressive Glomerulonephritis.

Background: Recently proposed histopathological classification may predict patient outcome in pauci-immune glomerulonephritis. This study sought to prove that the prognostic effect could be extended to all types of rapidly progressive glomerulonephritis. Methods: Retrospective analysis of patients diagnosed with rapidly progressive glomerulonephritis between April 1999 and August 2015 was performed. Epidemiological and clinical data were collected from medical records. The descriptions of renal biopsies were reviewed and classified into focal, sclerotic, crescentic and mixed class according to classification proposed by Berden et al. The study end points were end stage renal disease (ESRD) or death. Survival analyses were modelled using Cox regression. Results: 73 renal biopsies with diagnosis of rapidly progressive glomerulonephritis were included in the study. 25 (34.2%), 16 (21.9%), 24 (32.9%) and 8 (11%) patients were assigned to focal, crescentic, mixed and sclerotic class, respectively. Thirty-two (42.5%) patients were anti-neutrophil cytoplasmic antibody (ANCA) negative, of which eight (10.9%) were anti⁻glomerular basement membrane antibody (anti⁻GBM) positive and 24 (32.8%) were negative for autoimmune antibodies. Six (8.2%) patients died within one year. Among patients who survived, median change in estimated glomerular filtration rate (eGFR) values were: -10.5 mL/min in focal, 4.2 mL/min in crescentic, -4.3 mL/min in mixed and 4.1 mL/min in sclerotic group, p > 0.05. In the Cox regression model, there was no significant predictor of patient survival whereas the sclerotic group (HR 3.679, 95% CI, 1.164⁻11.628, p < 0.05) and baseline eGFR of <15 mL/min (HR 4.832, 95% CI, 1.55⁻15.08, p < 0.01) had an unfavorable effect for renal survival. Conclusions: Predominant glomerular sclerosis and low eGFR at baseline are associated with higher risk of ESRD in cases with crescentic glomerulonephritis. Therefore, despite the origin of injury, histological classification might aid in prediction of patient outcomes in rapidly progressive glomerulonephritis.

Interaction of the New Monofunctional Anticancer Agent Phenanthriplatin With Transporters for Organic Cations.

Cancer treatment with platinum compounds is an important achievement of modern chemotherapy. However, despite the beneficial effects, the clinical impact of these agents is hampered by the development of drug resistance as well as dose-limiting side effects. The efficacy but also side effects of platinum complexes can be mediated by uptake through plasma membrane transporters. In the kidneys, plasma membrane transporters are involved in their secretion into the urine. Renal secretion is accomplished by uptake from the blood into the proximal tubules cells, followed by excretion into the urine. The uptake process is mediated mainly by organic cation transporters (OCT), which are expressed in the basolateral domain of the plasma membrane facing the blood. The excretion of platinum into the urine is mediated by exchange with protons via multidrug and toxin extrusion proteins (MATE) expressed in the apical domain of plasma membrane. Recently, the monofunctional, cationic platinum agent phenanthriplatin, which is able to escape common cellular resistance mechanisms, has been synthesized and investigated. In the present study, the interaction of phenanthriplatin with transporters for organic cations has been evaluated. Phenanthriplatin is a high affinity substrate for OCT2, but has a lower apparent affinity for MATEs. The presence of these transporters increased cytotoxicity of phenanthriplatin. Therefore, phenanthriplatin may be especially effective in the treatment of cancers that express OCTs, such as colon cancer cells. However, the interaction of phenanthriplatin with OCTs suggests that its use as chemotherapeutic agent may be complicated by OCT-mediated toxicity. Unlike cisplatin, phenanthriplatin interacts with high specificity with hMATE1 and hMATE2K in addition to hOCT2. This interaction may facilitate its efflux from the cells and thereby decrease overall efficacy and/or toxicity.