Durable Response to Enfortumab Vedotin Compared to Re-challenging Chemotherapy in Metastatic Urothelial Carcinoma After Checkpoint Inhibitors.

BACKGROUND: Enfortumab vedotin (EV), an antibody-drug conjugate targeting Nectin-4, has been used for patients with metastatic urothelial carcinoma (mUC) after progressing on checkpoint inhibitors (CPIs). Re-challenging chemotherapy with platinum agents and continuing CPIs beyond progressive disease (PD) have often been chosen following PD on CPIs, and several studies indicate favorable treatment effects of re-challenging chemotherapy. There is little evidence for comparing EV and re-challenging chemotherapy in real-world clinical practice. OBJECTIVE: The aim was to reveal the real-world treatment outcomes of EV, re-challenging chemotherapy, and continuing CPIs beyond PD in mUC patients. PATIENTS AND METHODS: A multi-institutional dataset of 350 mUC patients treated with CPIs was utilized. Overall survival (OS), progression-free survival (PFS), objective response rate (ORR), and duration of response (DOR) were evaluated to compare the treatment arms. RESULTS: One hundred and nine mUC patients were treated with EV with a median follow-up of 6.4 months. The ORR and disease control rate (DCR) were 48% and 70%, respectively. The OS from PD on pembrolizumab exhibited significant differences among the three groups, with a median OS of 8, 14, and 29 months in continuing pembrolizumab beyond PD, re-challenging chemotherapy, and EV, respectively. When comparing the survival outcomes from the initiation of the treatment, there is neither a difference in OS (p = 0.124), PFS (p = 0.936), nor ORR (p = 0.816) between EV and re-challenging chemotherapy. Notably, the DOR in patients who achieved an objective response was significantly longer in the EV group than the re-challenging chemotherapy group (a median of 11 and 5 months, p = 0.049). For OS, the difference was not statistically significant (27 and 11 months in EV and re-challenging chemotherapy, respectively: p = 0.05). CONCLUSIONS: A superior effect of EV on patient survival compared to re-challenging chemotherapy and continuing pembrolizumab beyond PD was observed in our real-world analysis, which is attributed to the durable DOR in EV treatment despite the similar ORR to re-challenging chemotherapy.

Enfortumab vedotin (EV) is an antibody­drug conjugate targeting Nectin-4 and is now utilized for patients with metastatic urothelial carcinoma following treatment with checkpoint inhibitors (CPIs). Until recently, repeating chemotherapy using platinum drugs or continuing CPIs were often the treatments used for these patients. In the present study, we reported real-world treatment outcomes, mainly focusing on EV and repeating chemotherapy. Although the objective responses to the treatments were comparable, the duration of response for patients responding to the treatment was significantly longer in patients treated with EV than in those repeating chemotherapy, resulting in extended survival time with EV treatment.

Pattern of expression of microRNA in patients with radiation induced bladder injury.

INTRODUCTION: Bladder cancer (BC) is sensitive to radiation treatment and a subset of patient experiences radiation induced injuries including shrinkage of bladder due to bladder fibrosis. METHODS: Using a micro-RNA (miRNA) array comparing patient's samples with, or without radiation induced injuries, we have checked the clustering of miRNA expression. RESULTS: Hsa-miR-130a, hsa-miR-200c, hsa-miR-141, and hsa-miR-96 were found to be highly expressed (>50 times) in patients with fibrotic bladder shrinkage (FBS) compared to those with intact bladder (IB) function. In patients with FBS, hsa-miR-6835, hsa-miR-4675, hsa-miR-371a, and hsa-miR-6885 were detected to have lesser than half expression to IB patients. We have analyzed the significance of these genes in relation to overall survival of 409 BC patients retrieved from TCGA data set. We have run combined survival analysis of mean expression of these four miRNAs highly expressed in FBS patients. 175 patients with high expression had longer median survival of 98.47 months than 23.73 months in 233 patients with low expression (HR: 0.53; 0.39 - 0.72, logrank P value: 7.3e-0.5). Combination analysis of all 8 genes including hsa-miR-6835, hsa-miR-4675, hsa-miR-371a, and hsa-miR-6885 showed the same HR for OS. Target scanning for these miRNAs matched specific cytokines known as an early biomarker to develop radiation induced fibrosis. CONCLUSIONS: BC patients with fibrotic radiation injury have specific miRNA expression profile targeting pro-fibrotic cytokines and these miRNAs possibly renders to favorable survival.

Predicting Objective Response of Pembrolizumab in Platinum-Refractory Urothelial Carcinoma Based on NLR Fluctuation and Liver Metastases.

BACKGROUND AND PURPOSE: It is well known that patients with objective response to pembrolizumab have a durable duration of response leading to favorable survival outcomes. We investigated the possibility of predicting the objective response with concise indicators obtained from daily clinical practice. Methods In our multi-institutional cohort, 220 platinum-refractory metastatic urothelial carcinomas (mUC) treated with pembrolizumab for at least six weeks with complete information of objective response were investigated. Results The median follow-up was 7.3 months, and 119 patients deceased during the follow-up. A multivariate logistic regression analysis exhibited two independent variables predicting the objective response, including the neutrophil-lymphocyte ratio (NLR) change at six weeks of treatment and liver metastasis. We proposed a risk group using these two indicators. Patients with no predictive indicators / one of those were assigned to favorable (42%) / intermittent (47%) risk groups. Patients with both indicators were assigned to poor risk (11%). Notably, the objective response rate was well delineated in 41%, 25%, and 0% for favorable, intermediate, and poor risk groups, respectively (p<0.001). Distinct overall survival (OS) between the risk groups was also confirmed with the median OS of 14.1, 11.7, and 4.2 months in favorable, intermediate, and poor risk groups, respectively. CONCLUSIONS: At the six weeks of the pembrolizumab treatment, our risk model predicts the objective response rate precisely. Notably, those classified as 'poor risk'-marked by liver metastasis and a heightened NLR-should be considered for alternative therapy with a different mode of action, highlighting a critical decision point in treatment optimization.

Optimal Time Point for Evaluation of Response to Pembrolizumab Treatment in Japanese Patients With Metastatic Urothelial Carcinoma.

BACKGROUND/AIM: The duration of pembrolizumab use in actual daily practice might be shorter than that in clinical trials because termination of pembrolizumab therapy is at the discretion of the physician. We retrospectively reviewed the response to pembrolizumab in Japanese patients with metastatic urothelial carcinoma (mUC) in relation to the time to response (TTR). PATIENTS AND METHODS: The records of 165 patients treated with pembrolizumab for mUC were retrospectively analyzed. Response was evaluated at 2, 4, 6 and 8 months. TTR along with time to best response were analyzed. Phase II-III clinical trials were also reviewed to compare the TTR and time to best overall response. RESULTS: The median patient age was 70 years. The objective response rate in the total cohort was 27.1% (42 out of 155 patients). Median TTR was 2.4 months and the time to best response was 3.1 months. Radiological evaluation at each time point significantly predicted overall survival (OS). Considering the evaluation of response at 2, 4, 6 and 8 months, the response at later time points tended to predict OS better. Multivariate analysis showed that the evaluation of response at 8 months (hazard ratio=1.91, 95% confidence interval=1.16-3.16 months; p<0.01) and best response during the treatment (hazard ratio=1.69, 95% confidence interval=1.17-2.44; p<0.01) independently predicted improved OS. CONCLUSION: Given that response when evaluated at a later point during pembrolizumab treatment more favorably reflected improved survival than when assessed earlier, physicians may be encouraged to wait until at least the termination of pembrolizumab treatment to determine the best response.

Tissue Distribution of Cisplatin by Intra-arterial Infusion Route in Comparison to Systemic Route: Implication to Therapy for Node-positive Bladder Cancer.

BACKGROUND/AIM: In clinical practice, platinum-based systemic chemotherapy works to shrink pelvic lymph nodes. Intra-arterial (IA) bolus infusion may result in more favorable results than systemic chemotherapy. In the present study, we investigated the distribution of cisplatin administrated by IA infusion in varying organs, specifically focusing on the node tissue, in comparison with the intravenous (IV) route. MATERIALS AND METHODS: Under anesthesia, cisplatin 0.42 mg/body was administrated by IA or IV infusion in rats to mimic a balloon-occluded arterial infusion model used in clinical practice. The kidney, bladder, lymphatic tissue, and peripheral blood were extracted to analyze the amount of cisplatin by inductively coupled plasma-mass spectrometry. RESULTS: Concertation of cisplatin by IA infusion was higher than that by the IV route in the peripheral blood and kidney. IA infusion led to a significantly high concentration of cisplatin in the bladder compared to IV infusion (1.3±0.452 vs. 0.2 ppb/mg ± 0.055, p=0.050). Furthermore, the IA method led to an extremely high concentration of cisplatin in the lymphatic tissue compared to the IV method (0.1±0.036 vs. 13.3±5.36, p=0.048). CONCLUSION: High cisplatin accumulation in the lymphatic tissue and bladder by IA administration may have a potential role for treating patients with node-positive bladder cancer.

Re-challenging chemotherapy after pembrolizumab in platinum-refractory urothelial carcinoma.

OBJECTIVES: To assess the real-world clinical benefit of re-challenging chemotherapy after pembrolizumab in patients with metastatic urothelial carcinoma (mUC), as there have been several reports suggesting that programmed cell death protein-1/programmed death-ligand 1inhibitors can restore platinum sensitivity. PATIENTS AND METHODS: Of 236 patients treated with pembrolizumab, we excluded 45 patients who did not experience progressive disease (PD) for pembrolizumab during the follow-up and 86 patients who discontinued pembrolizumab by the diagnosis of PD followed by the best supportive care. A total of 105 patients were identified for a logistic regression propensity score model to compare the survival outcomes between patients treated with continuing pembrolizumab (80) and re-challenging chemotherapy (25) after the diagnosis of PD for pembrolizumab. RESULTS: A median overall survival (OS) from PD for pembrolizumab was 11 months in 105 patients. Of 25 patients treated with re-challenging chemotherapy, platinum-including chemotherapy (gemcitabine and cisplatin; gemcitabine/cisplatin/paclitaxel [GCP]; methotrexate and vinblastine and adriamycin and cisplatin; and methotrexate and carboplatin and vinblastine MCAVI) was offered in 20 patients (80%). The objective response rate (ORR) for the first-line chemotherapy in the 105 patients was 30%, with a comparable ORR in 25 patients treated with re-challenging chemotherapy of 28%. GCP as a re-challenging regimen was offered in 12 of 25 (48%) patients. The ORR for the GCP regimen was 50%. Propensity score matching was performed using putative clinical factors, from which 34 patients were identified as pair-matched groups. The OS for patients treated with re-challenging chemotherapy was significantly longer than continuing pembrolizumab (a median of 13.9 and 5.8 months, respectively: P = 0.048). CONCLUSION: Re-challenging chemotherapy including platinum agents after PD with pembrolizumab offers clinical benefits in patients with mUC.

Prognostic value of the fluctuation in the neutrophil-lymphocyte ratio at 6 weeks of pembrolizumab treatment is specific to the clinical response in metastatic urothelial carcinoma.

PURPOSE: Most patients with metastatic urothelial carcinoma experience no objective response to pembrolizumab and have poor overall survival (OS). Here, we investigated the prognostic value of fluctuation in the neutrophil-lymphocyte ratio (NLR) at 6 weeks of pembrolizumab treatment, focusing on its association with the achievement of objective response. MATERIALS AND METHODS: The clinical records of 177 metastatic urothelial carcinoma patients treated with pembrolizumab were retrospectively analyzed. RESULTS: The median age was 72 years, and the median OS was 14 months. The objective response rate in the total cohort was 26.5% (47 of 177 patients). Multivariable analysis showed that objective response achievement (hazard ratio 0.3 [95% confidence interval 0.15-0.59], P < 0.001) and decline in NLR from that at baseline at 6 weeks of treatment (0.54 [0.34-0.88], P = 0.013) were independent prognostic factors for improved OS. For 47 (26.5%) patients who achieved an objective response, OS was similar regardless of NLR fluctuation at 6 weeks of treatment (P = 0.723). Intriguingly, of the 130 (73.5%) patients with no objective response, those who showed a decreased NLR at 6 weeks of pembrolizumab treatment (57 patients) from that at baseline had significantly longer OS than those with elevated NLR (73 patients) (14 vs. 6 months, P = 0.007). CONCLUSIONS: The fluctuation in NLR from that at baseline at 6 weeks of pembrolizumab treatment may be useful for patients without an objective response. This could potentially aid decision-making for post pembrolizumab therapies.

Efficacy of pembrolizumab and comprehensive CD274/PD-L1 profiles in patients previously treated with chemoradiation therapy as radical treatment in bladder cancer.

BACKGROUND: Chemoradiation therapy (CRT) has been increasingly reported as a possible alternative to total cystectomy (TC) for localized bladder cancer (BC). Pembrolizumab is the standard of care for platinum-refractory metastatic urothelial carcinoma, although it is unknown whether the efficacy of pembrolizumab in patients previously treated with curative CRT varies from the results of benchmark trials. METHODS: We retrospectively assessed whether the survival benefit of pembrolizumab differs between patients previously treated with TC or CRT as radical treatment. A total of 212 patient records were collected for a logistic regression propensity score model. An independent dataset with next-generation sequencing (n=289) and PD-L1 Combined Positive Score (CPS: n=266) was analyzed to assess whether CRT-recurrent tumor harbors distinct CD274/PD-L1 profiles. RESULTS: Propensity score matching was performed using putative clinical factors, from which 30 patients in each arm were identified as pair-matched groups. There was no significant difference in overall survival from the initiation of pembrolizumab (p=0.80) and objective response rate (p=0.59) between CRT and TC treatment groups. In the independent 289 BC cohort, 22 samples (7.6%) were collected as CRT-recurrent tumors. There was no significant difference in CD274 mRNA expression level between CRT-naïve and CRT-recurrent tumors. The compositions of CD274 isoforms were comparable among all isoforms detected from RNAseq between CRT-naïve (n=267) and CRT-recurrent (n=22) tumors. No actionable exonic mutation in CD274 was detected in CRT-recurrent tumors. PD-L1 CPS was positively correlated with CD274 mRNA expression level, and PD-L1 CPS was comparable between CRT-naïve and CRT-recurrent tumors. CONCLUSIONS: The efficacy of pembrolizumab for patients previously treated with CRT was similar to those treated with TC. The enhanced tumor regression by combining programmed cell death protein 1/PD-L1 inhibitor and CRT might be expected only in the concurrent administration.

Eicosapentaenoic Acid and Prevalence of Cardiovascular Disease in Hemodialysis Patients.

Eicosapentaenoic acid (EPA)/arachidonic acid (AA) ratio showed inverse associations with cardiovascular disease (CVD) in general population. However, this has not been examined enough in dialysis patients. We cross-sectionally investigated the relationship between EPA/AA ratio and prevalence of CVD in 321 chronic hemodialysis patients (64 ± 11 years old; 110 women; dialysis vintage 10 ± 8 years) in an urban area of Tokyo. CVD was defined as a composite of ischemic heart disease, ischemic stroke and hemorrhagic stroke. The frequency of dietary fish intake was also examined. Logistic regression was used to quantify the association of EPA/AA ratio with CVD. EPA/AA ratio was 0.31 ± 0.19 and 154 patients (48%) consumed fish once or less weekly. One hundred and thirty patients (41%) had CVD, including 65 with ischemic heart disease, 70 with ischemic stroke, and 20 with hemorrhagic stroke. Age (odds ratio [OR], 1.04; P = 0.01), hypertension (OR, 2.25; P = 0.002), and dialysis vintage (OR, 1.04; P = 0.02) were associated with CVD; however, EPA/AA was not after adjustment for other risk factors. A similar relationship was observed between fish intake and CVD prevalence. We did not find any significant association between EPA/AA ratio and prevalence of CVD, although traditional risk factors such as age, hypertension and dialysis vintage were associated with CVD. These results might have been influenced by the fact that only a small proportion of our patients showed a high EPA/AA ratio.

Analysis of Aprotinin, a Protease Inhibitor, Action on the Trafficking of Epithelial Na+ Channels (ENaC) in Renal Epithelial Cells Using a Mathematical Model.

BACKGROUND/AIM: Epithelial Na+ channels (ENaC) play a crucial role in control of blood pressure by regulating renal Na+ reabsorption. Intracellular trafficking of ENaC is one of the key regulators of ENaC function, but a quantitative description of intracellular recycling of endogenously expressed ENaC is unavailable. We attempt here to provide a model for intracellular recycling after applying a protease inhibitor under hypotonic conditions. METHODS: We simulated the ENaC-mediated Na+ transport in renal epithelial A6 cells measured as short-circuit currents using a four-state mathematical ENaC trafficking model. RESULTS: We developed a four-state mathematical model of ENaC trafficking in the cytosol of renal epithelial cells that consists of: an insertion state of ENaC that can be trafficked to the apical membrane state (insertion rate); an apical membrane state of ENaC conducting Na+ across the apical membrane; a recycling state containing ENaC that are retrieved from the apical membrane state (endocytotic rate) and then to the insertion state (recycling rate) communicating with the apical membrane state or to a degradation state (degradation rate). We studied the effect of aprotinin (a protease inhibitor) blocking protease-induced cleavage of the extracellular loop of γ ENaC subunit on the rates of intracellular ENaC trafficking using the above-defined four-state mathematical model of ENaC trafficking and the recycling number relative to ENaC staying in the apical membrane. We found that aprotinin significantly reduced the insertion rate of ENaC to the apical membrane by 40%, the recycling rate of ENaC by 81%, the cumulative time of an individual ENaC staying in the apical membrane by 32%, the cumulative life-time after the first endocytosis of ENaC by 25%, and the cumulative Na+ absorption by 31%. The most interesting result of the present study is that cleavage of ENaC affects the intracellular ENaC trafficking rate and determines the residency time of ENaC, indicating that more active cleaved ENaCs stay longer at the apical membrane contributing to transcellular Na+ transport via an increase in recycling of ENaC to the apical membrane. CONCLUSION: The extracellular protease-induced cleavage of the extracellular loop of γ ENaC subunit increases transcellular epithelial Na+ transport by elevating the recycling rate of ENaC due to an increase in the recycling rate of ENaCs associated with increases in the insertion rate of ENaC.

Distinct action of flavonoids, myricetin and quercetin, on epithelial Cl⁻ secretion: useful tools as regulators of Cl⁻ secretion.

Epithelial Cl(-) secretion plays important roles in water secretion preventing bacterial/viral infection and regulation of body fluid. We previously suggested that quercetin would be a useful compound for maintaining epithelial Cl(-) secretion at a moderate level irrespective of cAMP-induced stimulation. However, we need a compound that stimulates epithelial Cl(-) secretion even under cAMP-stimulated conditions, since in some cases epithelial Cl(-) secretion is not large enough even under cAMP-stimulated conditions. We demonstrated that quercetin and myricetin, flavonoids, stimulated epithelial Cl(-) secretion under basal conditions in epithelial A6 cells. We used forskolin, which activates adenylyl cyclase increasing cytosolic cAMP concentrations, to study the effects of quercetin and myricetin on cAMP-stimulated epithelial Cl(-) secretion. In the presence of forskolin, quercetin diminished epithelial Cl(-) secretion to a level similar to that with quercetin alone without forskolin. Conversely, myricetin further stimulated epithelial Cl(-) secretion even under forskolin-stimulated conditions. This suggests that the action of myricetin is via a cAMP-independent pathway. Therefore, myricetin may be a potentially useful compound to increase epithelial Cl(-) secretion under cAMP-stimulated conditions. In conclusion, myricetin would be a useful compound for prevention from bacterial/viral infection even under conditions that the amount of water secretion driven by cAMP-stimulated epithelial Cl(-) secretion is insufficient.

AP-VAS 2012 case report: two patients with rheumatoid arthritis suspected of relapsed microscopic polyangiitis after initiation of dialysis.

We report two patients with rheumatoid arthritis (RA) who were suspected of microscopic polyangiitis during maintenance dialysis. Case 1 was a 52-year-old woman with RA diagnosed at the age of 38 years and treated successfully with gold compounds. At the age of 43 years, she presented with progressive renal dysfunction and abnormal urine sediments, and a renal biopsy revealed crescentic nephritis with advanced glomerular sclerosis. Myeloperoxidase antineutrophil cytoplasmic antibody (MPO-ANCA) was not measured on that occasion. She reached end-stage renal failure within 4 months and started peritoneal dialysis. Eight years later, soon after she was switched to hemodialysis, she developed fever of unknown origin. MPO-ANCA was elevated to 37 EU, although there were no other signs or symptoms suggestive of vasculitis. After taking prednisolone orally (10 mg/day), her fever withdrew, and MPO-ANCA became undetectable. Case 2 was a 71-year-old woman with RA diagnosed at the age of 60 years and treated with gold compounds. She developed renal failure of unknown cause (no biopsy was performed), and started hemodialysis at the age of 69 years. One year later, she presented with fever and subsequently developed cough with hemoptysis. MPO-ANCA was elevated to 62 EU. Treatment with azathioprine 50 mg and prednisolone 35 mg daily brought remarkable clinical improvement, and MPO-ANCA became undetectable. These cases highlight the importance of measuring ANCA even in RA patients on dialysis who present with fever of unknown origin or with underlying kidney disease of uncertain etiology.

Regulation of epithelial sodium transport via epithelial Na+ channel.

Renal epithelial Na+ transport plays an important role in homeostasis of our body fluid content and blood pressure. Further, the Na+ transport in alveolar epithelial cells essentially controls the amount of alveolar fluid that should be kept at an appropriate level for normal gas exchange. The epithelial Na+ transport is generally mediated through two steps: (1) the entry step of Na+ via epithelial Na+ channel (ENaC) at the apical membrane and (2) the extrusion step of Na+ via the Na+, K+-ATPase at the basolateral membrane. In general, the Na+ entry via ENaC is the rate-limiting step. Therefore, the regulation of ENaC plays an essential role in control of blood pressure and normal gas exchange. In this paper, we discuss two major factors in ENaC regulation: (1) activity of individual ENaC and (2) number of ENaC located at the apical membrane.

Regulation of paracellular Na+ and Cl(-) conductances by hydrostatic pressure.

The effect of hydrostatic pressure on the paracellular ion conductance (Gp) composed of the Na(+) conductance (G(Na)) and the Cl(-) conductance (G(Cl)) has been Investigated. Gp, G(Na) and G(Cl) were time-dependently increased after applying an osmotic gradient generated by NaCl with basolateral hypotonicity. Hydrostatic pressure (1-4cm H2O) applied from the basolateral side enhanced the osmotic gradient-induced increase in Gp, G(Na) and G(Cl) in a magnitude-dependent manner, while the hydrostatic pressure applied from the apical side diminished the osmotic gradient-induced increase in Gp, G(Na) and G(Cl). How the hydrostatic pressure influences Gp, G(Na) and G(Cl) under an isosmotic condition was also investigated. Gp, G(Na) and G(Cl) were stably constant under a condition with basolateral application of sucrose canceling the NaCl-generated osmotic gradient (an isotonic condition). Even under this stable condition, the basolaterally applied hydrostatic pressure drastically elevated Gp, G(Na) and G(Cl), while apically applied hydrostatic pressure had little effect on Gp, G(Na) or G(Cl). Taken together, these observations suggest that certain factors controlled by the basolateral osmolality and the basolaterally applied hydrostatic pressure mainly regulate the Gp, G(Na) and G(Cl).

Efficacy of once-weekly intravenous administration of epoetin-beta as a maintenance treatment for anemia in Japanese hemodialysis patients: a multicenter, open-label clinical study.

Epoetin-beta is extremely useful as a drug for treating anemia in hemodialysis (HD) patients and is widely used for that purpose. The aim of this study was to determine whether once-weekly intravenous administration of epoetin-beta is as effective in maintaining hemoglobin (Hb) concentration as the same weekly dose administered 2 or 3 times per week as maintenance treatment of anemia in HD patients. The subjects were stable HD patients who had been receiving HD for at least 12 months. Using a fixed weekly dose of 3000 or 6000 IU of epoetin-beta, this study evaluated maintenance of improvement of anemia by comparing Hb concentration in the study period (once-weekly) with Hb concentration in the prestudy period (2 or 3 times per week). Of the 112 patients treated with epoetin-beta, 111 patients (full analysis set; 3000 IU, 52 patients; 6000 IU, 59 patients) were evaluated, after excluding one patient whose dose was changed immediately before study initiation. The change in the Hb concentration was maintained within +/-1.5 g/dL in 89.2% of patients (3000 IU, 88.5%; 6000 IU, 89.8%). The mean Hb concentration was 10.42 +/- 0.73 g/dL at study initiation and 10.14 +/- 1.00 g/dL at study completion. Adverse reactions occurred in 9.8% of patients (11 out of 112 patients). The main adverse reactions were malaise and increased blood pressure. Once-weekly intravenous administration of epoetin-beta is useful as maintenance treatment of anemia in HD patients and may be a treatment option.

Abnormal expression of ENaC and SGK1 mRNA induced by dietary sodium in Dahl salt-sensitively hypertensive rats.

Epithelial sodium channel (ENaC) plays a crucial role in controlling sodium reabsorption in the kidney keeping the normal blood pressure. We previously reported that the expression of ENaC mRNA in the kidney of Dahl salt-sensitive (DS) rats was abnormally regulated by aldosterone, however it is unknown if dietary sodium affects the expression of ENaC and serum and glucocorticoid-regulated kinase 1 (SGK1), which plays an important role in ENaC activation, in DS rats. In the present study, we investigated whether dietary sodium abnormally affects the expression of ENaC and SGK1 mRNA in DS rats. DS and Dahl salt-resistant (DR) rats (8 weeks old) were divided into three different groups, respectively: (1) low sodium diet (0.005% NaCl), (2) normal sodium diet (0.3% NaCl), and (3) high sodium diet (8% NaCl). The high sodium diet for 4 weeks in DS rats elevated the systolic blood pressure, but did not in any other groups. The expression of alpha-ENaC mRNA in DS rats was abnormally increased by high sodium diet in contrast to DR rats, while it was normally increased by low sodium diet in DS rats similar to DR rats. The expression of beta- and gamma-ENaC mRNA in DS rats was also abnormally increased by high sodium diet unlike DR rats. The expression of SGK1 mRNA was elevated by high sodium diet in DS rats, but it was decreased in DR rats. These observations indicate that the expression of ENaC and SGK1 mRNA is abnormally regulated by dietary sodium in salt-sensitively hypertensive rats, and that this abnormal expression would be one of the factors causing salt-sensitive hypertension.

Cross talk of cAMP and flavone in regulation of cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel and Na+/K+/2Cl- cotransporter in renal epithelial A6 cells.

We have reported that in renal epithelial A6 cells flavones stimulate the transepithelial Cl- secretion by activating the cystic fibrosis transmembrane conductance regulator (CFTR) Cl- channel and/or the Na+/K+/2Cl- cotransporter. On the other hand, it has been established that cAMP activates the CFTR Cl- channel and the Na+/K+/2Cl- cotransporter. However, no information is available on the interaction between cAMP and flavones on stimulation of the CFTR Cl- channel and the Na+/K+/2Cl- cotransporter. To clarify the interaction between cAMP and flavones, we studied the regulatory mechanism of the CFTR Cl- channel and the Na+/K+/2Cl- cotransporter by flavones (apigenin, luteolin, kaempherol, and quercetin) under the basal and cAMP-stimulated conditions in renal epithelial A6 cells. Under the basal (cAMP-unstimulated) condition, these flavones stimulated the Cl- secretion by activating the Na+/K+/2Cl- cotransporter without any significant effects on the CFTR Cl- channel activity. On the other hand, these flavones diminished the activity of the cAMP-stimulated Na+/K+/2Cl- cotransporter without any significant effects on the CFTR Cl- channel activity. Interestingly, the level of the flavone-induced Cl- secretion under the basal condition was identical to that under the cAMP-stimulated condition. Based on these results, it is suggested that although both cAMP and flavones activate the Na+/K+/2Cl- cotransporter, these flavones have more powerful effects than cAMP on the Na+/K+/2Cl- cotransporter.

Activation of CFTR Cl(-) channel by tyrphostins via a protein tyrosine kinase-independent pathway in forskolin-stimulated renal epithelial A6 cells.

We studied effects of tyrphostin A23 (an inhibitor of protein tyrosine kinase; PTK) and tyrphostin A63 (an inactive analog of tyrphostin A23) on forskolin-activated cystic fibrosis transmembrane conductance regulator (CFTR) Cl(-) channels and Cl(-) secretion in renal epithelial A6 cells. Tyrphostin A23 and A63 had no effects on the basal CFTR Cl(-) channel and Cl(-) secretion. However, under the forskolin-stimulated condition, tyrphostin A23 and A63 stimulated Cl(-) secretion by activating CFTR Cl(-) channels. These observations suggest that: 1) tyrphostin A23 and A63 stimulate the cAMP-activated CFTR Cl(-) channel via a PTK-independent, structure-dependent mechanism, and 2) tyrphostin A23 and A63 do not stimulate the basal CFTR Cl(-) channel. These lead us to an idea that: 1) cAMP might cause a conformational change of CFTR Cl(-) channel which is accessible by tyrphostins, and 2) tyrphostins would stimulate translocation of the cAMP-modified channel to the apical membrane by binding to the channel.