An adolescent girl diagnosed with IgA nephropathy following the first dose of the COVID-19 vaccine.

There has been growing interest in reported cases of IgA nephropathy (IgAN) flare-up following administration of the coronavirus disease 2019 (COVID-19) vaccine. Our patient is a previously healthy 17-year-old girl who presented with a 10-year history of microscopic hematuria. Because there were no abnormal findings in blood examination or ultrasonography, we followed her up twice per year as asymptomatic hematuria. Although she never developed gross hematuria when she had upper respiratory infections or received an influenza vaccine, she presented with gross hematuria and proteinuria within a few days after receiving the first dose of the Pfizer vaccine. We performed renal biopsy 2 weeks after the first vaccination. It revealed minor glomerular abnormalities with diffuse mesangial IgA deposits, and we diagnosed her with mild IgAN. Gross hematuria was detected after both the first and second doses, although it changed to microscopic hematuria within 1 week. Additionally, her proteinuria resolved spontaneously approximately 10 days after the second dose of the vaccine. Therefore, we opted to observe her without administering medication. The causation between COVID-19 vaccination and IgAN flare-up remains unclear. Several reports showed IgAN patients presenting gross hematuria following the second dose of the Pfizer or Moderna vaccines. However, our patient developed gross hematuria and proteinuria even after the first dose and without known severe acute respiratory syndrome coronavirus 2 exposure. Nephrologists should inform both patients with IgAN and those with asymptomatic hematuria that this side effect can occur even after the first vaccination.

Structural Development of Salicylanilide-Based SPAK Inhibitors as Candidate Antihypertensive Agents.

Hypertension is an important target for drug discovery. We have focused on the with-no-lysine kinase (WNK)-oxidative stress-responsive 1 (OSR1) and STE20/SPS1-related proline-alanine-rich protein kinase (SPAK)-NaCl cotransporter (NCC) signal cascade as a potential target, and we previously developed a screening system for inhibitors of WNK-OSR1/SPAK-NCC signaling. Herein we used this system to examine the structure-activity relationship (SAR) of salicylanilide derivatives as SPAK kinase inhibitors. Structural design and development based on our previous hit compound, aryloxybenzanilide derivative 2, and the veterinary anthelmintic closantel (3) led to the discovery of compound 10 a as a potent SPAK inhibitor with reduced toxicity. Compound 10 a decreased the phosphorylation level of NCC in mouse kidney in vivo, and appears to be a promising lead compound for a new class of antihypertensive drugs.

Association between Immunoglobulin M and Steroid Resistance in Children with Nephrotic Syndrome: A Retrospective Multicenter Study in Japan.

Background: The prognosis of steroid-resistant nephrotic syndrome (SRNS) in children is poorer than steroid-sensitive cases. Diagnosis of SRNS is made after observing the response to the initial 4-week corticosteroid therapy, which might be accompanied by side effects. However, predictive indicators at initial diagnosis remain unknown. We aimed to investigate whether selectivity index (SI) and other indicators at initial diagnosis-for example, serum IgM and total serum protein-albumin ratio (TA ratio, total serum protein level over albumin level)-can predict SRNS. Methods: A total of 80 children were enrolled from seven hospitals in Japan between January 2008 and December 2019 (mean age, 4.7 years; 65% male). Of the children enrolled, 13 (16%, M/F=5:8) had been diagnosed as steroid resistant after initial treatment with steroids. The association between serum IgM (tertile categories: low, 24-133; middle, 134-169; and high, 169.1-510 mg/dl), SI (<0.2 or ≥0.2), and TA ratio (tertile categories: low, 1.8-2.6; middle, 2.62-3.75; and high, 3.8-15.3) at initial diagnosis and steroid resistance was evaluated with logistic regression, adjusting for age and sex. Results: Low levels of serum IgM were significantly associated with steroid resistance (adjusted odds ratio, 6.94; 95% CI, 1.12 to 43.11). TA ratio and SI were not significantly associated with steroid resistance. Conclusions: Low levels of serum IgM at initial diagnosis might predict steroid resistance among Japanese children with idiopathic nephrotic syndrome.

Structural development of N-(4-phenoxyphenyl)benzamide derivatives as novel SPAK inhibitors blocking WNK kinase signaling.

We report here structural development of N-(4-phenoxyphenyl)benzamide derivatives as novel SPAK (STE20/SPS1-related proline/alanine-rich kinase) inhibitors. Abnormal activation of the signal cascade of with-no-lysine kinase (WNK) with OSR1 (oxidative stress-responsive kinase 1)/SPAK and NCC (NaCl cotransporter) results in characteristic salt-sensitive hypertension, and therefore inhibitors of the WNK-OSR1/SPAK-NCC cascade are candidates for antihypertensive drugs. Based on the structure of lead compound 2, we examined the SAR of N-(4-phenoxyphenyl)benzamide derivatives, and developed compound 20l as a potent SPAK inhibitor. Compounds 20l is a promising candidate for a new class of antihypertensive drugs.

Glyoxalase 1 gene is highly expressed in basal-like human breast cancers and contributes to survival of ALDH1-positive breast cancer stem cells.

Glyoxalase 1 (GLO1) is a ubiquitous enzyme involved in the detoxification of methylglyoxal, a cytotoxic byproduct of glycolysis that induces apoptosis. In this study, we found that GLO1 gene expression correlates with neoplasm histologic grade (χ 2 test, p = 0.002) and is elevated in human basal-like breast cancer tissues. Approximately 90% of basal-like cancers were grade 3 tumors highly expressing both GLO1 and the cancer stem cell marker ALDH1A3. ALDH1high cells derived from the MDA-MB 157 and MDA-MB 468 human basal-like breast cancer cell lines showed elevated GLO1 activity. GLO1 inhibition using TLSC702 suppressed ALDH1high cell viability as well as the formation of tumor-spheres by ALDH1high cells. GLO1 knockdown using specific siRNAs also suppressed ALDH1high cell viability, and both TLSC702 and GLO1 siRNA induced apoptosis in ALDH1high cells. These results suggest GLO1 is essential for the survival of ALDH1-positive breast cancer stem cells. We therefore conclude that GLO1 is a potential therapeutic target for treatment of basal-like breast cancers.

Development of WNK signaling inhibitors as a new class of antihypertensive drugs.

Pseudohypoaldosteronism type II (PHAII) is characterized by hyperkalemia and hypertension despite a normal glomerular filtration rate. Abnormal activation of the signal cascade of with-no-lysine kinase (WNK) with OSR1 (oxidative stress-responsive kinase 1)/SPAK (STE20/SPS1-related proline/alanine-rich kinase) and NCC (NaCl cotransporter) results in characteristic salt-sensitive hypertension. Thus, inhibitors of the WNK-OSR1/SPAK-NCC cascade are candidates for a new class of antihypertensive drugs. In this study, we developed novel inhibitors of this signal cascade from the 9-aminoacridine lead compound 1, one of the hit compounds obtained by screening our chemical library for WNK-SPAK binding inhibitors. Among the synthesized acridine derivatives, several acridine-3-amide and 3-urea derivatives, such as 10 (IC50: 6.9µM), 13 (IC50: 2.6µM), and 20 (IC50: 4.8µM), showed more potent inhibitory activity than the lead compound 1 (IC50: 15.4µM). Compounds 10 and 20 were confirmed to inhibit phosphorylation of NCC in vivo.

Drug-Repositioning Screening for Keap1-Nrf2 Binding Inhibitors using Fluorescence Correlation Spectroscopy.

The Kelch-like ECH-associating protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-antioxidant response element (ARE) signaling pathway is the major regulator of cytoprotective responses to oxidative and electrophilic stress. The Cul3/Keap1 E3 ubiquitin ligase complex interacts with Nrf2, leading to Nrf2 ubiquitination and degradation. In this study, we focused on the disruption of the Keap1-Nrf2 interaction to upregulate Nrf2 expression and the transcription of ARE-controlled cytoprotective oxidative stress response enzymes, such as HO-1. We completed a drug-repositioning screening for inhibitors of Keap1-Nrf2 protein-protein interactions using a newly established fluorescence correlation spectroscopy (FCS) screening system. The binding reaction between Nrf2 and Keap1 was successfully detected with a KD of 2.6 µM using our FCS system. The initial screening of 1,633 drugs resulted in 12 candidate drugs. Among them, 2 drugs significantly increased Nrf2 protein levels in HepG2 cells. These two promising drugs also upregulated ARE gene promoter activity and increased HO-1 mRNA expression, which confirms their ability to dissociate Nrf2 and Keap1. Thus, drug-repositioning screening for Keap1-Nrf2 binding inhibitors using FCS enabled us to find two promising known drugs that can induce the activation of the Nrf2-ARE pathway.

Wnt5a induces renal AQP2 expression by activating calcineurin signalling pathway.

Heritable nephrogenic diabetes insipidus (NDI) is characterized by defective urine concentration mechanisms in the kidney, which are mainly caused by loss-of-function mutations in the vasopressin type 2 receptor. For the treatment of heritable NDI, novel strategies that bypass the defective vasopressin type 2 receptor are required to activate the aquaporin-2 (AQP2) water channel. Here we show that Wnt5a regulates AQP2 protein expression, phosphorylation and trafficking, suggesting that Wnt5a is an endogenous ligand that can regulate AQP2 without the activation of the classic vasopressin/cAMP signalling pathway. Wnt5a successfully increases the apical membrane localization of AQP2 and urine osmolality in an NDI mouse model. We also demonstrate that calcineurin is a key regulator of Wnt5a-induced AQP2 activation without affecting intracellular cAMP level and PKA activity. The importance of calcineurin is further confirmed with its activator, arachidonic acid, which shows vasopressin-like effects underlining that calcineurin activators may be potential therapeutic targets for heritable NDI.

Generation and analysis of knock-in mice carrying pseudohypoaldosteronism type II-causing mutations in the cullin 3 gene.

Pseudohypoaldosteronism type II (PHAII) is a hereditary hypertensive disease caused by mutations in four different genes: with-no-lysine kinases (WNK) 1 and 4, Kelch-like family member 3 (KLHL3), and cullin 3 (Cul3). Cul3 and KLHL3 form an E3 ligase complex that ubiquitinates and reduces the expression level of WNK4. PHAII-causing mutations in WNK4 and KLHL3 impair WNK4 ubiquitination. However, the molecular pathogenesis of PHAII caused by Cul3 mutations is unclear. In cultured cells and human leukocytes, PHAII-causing Cul3 mutations result in the skipping of exon 9, producing mutant Cul3 protein lacking 57 amino acids. However, whether this phenomenon occurs in the kidneys and is responsible for the pathogenesis of PHAII in vivo is unknown. We generated knock-in mice carrying a mutation in the C-terminus of intron 8 of Cul3, c.1207-1G>A, which corresponds to a PHAII-causing mutation in the human Cul3 gene. Heterozygous Cul3(G(-1)A/+) knock-in mice did not exhibit PHAII phenotypes, and the skipping of exon 9 was not evident in their kidneys. However, the level of Cul3 mRNA expression in the kidneys of heterozygous knock-in mice was approximately half that of wild-type mice. Furthermore, homozygous knock-in mice were nonviable. It suggested that the mutant allele behaved like a knockout allele and did not produce Cul3 mRNA lacking exon 9. A reduction in Cul3 expression alone was not sufficient to develop PHAII in the knock-in mice. Our findings highlighted the pathogenic role of mutant Cul3 protein and provided insight to explain why PHAII-causing mutations in Cul3 cause kidney-predominant PHAII phenotypes.

Impaired degradation of WNK by Akt and PKA phosphorylation of KLHL3.

Mutations in with-no-lysine kinase (WNK) 1, WNK4, Kelch-like 3 (KLHL3), and Cullin3 result in an inherited hypertensive disease, pseudohypoaldosteronism type II. WNK activates the Na-Cl cotransporter (NCC), increasing sodium reabsorption in the kidney. Further, KLHL3, an adapter protein of Cullin3-based E3 ubiquitin ligase, has been recently found to bind to WNK, thereby degrading them. Insulin and vasopressin have been identified as powerful activators of WNK signaling. In this study, we investigated effects of Akt and PKA, key downstream substrates of insulin and vasopressin signaling, respectively, on KLHL3. Mass spectrometry analysis revealed that KLHL3 phosphorylation at S433. Phospho-specific antibody demonstrated defective binding between phosphorylated KLHL3 and WNK4. Consistent with the fact that S433 is a component of Akt and PKA phosphorylation motifs, in vitro kinase assay demonstrated that Akt and PKA can phosphorylate KLHL3 at S433, that was previously reported to be phosphorylated by PKC. Further, forskolin, a representative PKA stimulator, increased phosphorylation of KLHL3 at S433 and WNK4 protein expression in HEK293 cells by inhibiting the KLHL3 effect that leads to WNK4 degradation. Insulin also increased phosphorylation of KLHL3 at S433 in cultured cells. In conclusion, we found that Akt and PKA phosphorylated KLHL3 at S433, and phosphorylation of KLHL3 by PKA inhibited WNK4 degradation. This could be a novel mechanism on how insulin and vasopressin physiologically activate the WNK signal.

[WNK-SPAK-SLC12A signal cascade is a new therapeutic target for hypertension].

WNK-oxidative stress-responsive 1 (OSR1) /STE20/SPS1-related proline-alanine-rich protein kinase(SPAK)-SLC12A transporters cascade regulates blood pressure through NaCl reabsorption in kidney and vasoconstriction. Furthermore, we recently reported that this cascade is positively regulated by insulin, which may contribute to hypertension in patients with hyperinsulinemia. Therefore, drugs that inhibit this signal cascade could become new antihypertensive drugs that have dual effects as a diuretic and vasodilator and be particularly beneficial for patients with hyperinsulinemia such as metabolic syndrome and obesity. In this review, we provide an overview about the current understanding about WNK-SPAK-SLC12A signal cascade and show some prospects for drug discovery that blocks this signal cascade.

Discovery of Novel SPAK Inhibitors That Block WNK Kinase Signaling to Cation Chloride Transporters.

Upon activation by with-no-lysine kinases, STE20/SPS1-related proline-alanine-rich protein kinase (SPAK) phosphorylates and activates SLC12A transporters such as the Na(+)-Cl(-) cotransporter (NCC) and Na(+)-K(+)-2Cl(-) cotransporter type 1 (NKCC1) and type 2 (NKCC2); these transporters have important roles in regulating BP through NaCl reabsorption and vasoconstriction. SPAK knockout mice are viable and display hypotension with decreased activity (phosphorylation) of NCC and NKCC1 in the kidneys and aorta, respectively. Therefore, agents that inhibit SPAK activity could be a new class of antihypertensive drugs with dual actions (i.e., NaCl diuresis and vasodilation). In this study, we developed a new ELISA-based screening system to find novel SPAK inhibitors and screened >20,000 small-molecule compounds. Furthermore, we used a drug repositioning strategy to identify existing drugs that inhibit SPAK activity. As a result, we discovered one small-molecule compound (Stock 1S-14279) and an antiparasitic agent (Closantel) that inhibited SPAK-regulated phosphorylation and activation of NCC and NKCC1 in vitro and in mice. Notably, these compounds had structural similarity and inhibited SPAK in an ATP-insensitive manner. We propose that the two compounds found in this study may have great potential as novel antihypertensive drugs.

Chemical library screening for WNK signalling inhibitors using fluorescence correlation spectroscopy.

WNKs (with-no-lysine kinases) are the causative genes of a hereditary hypertensive disease, PHAII (pseudohypoaldosteronism type II), and form a signal cascade with OSR1 (oxidative stress-responsive 1)/SPAK (STE20/SPS1-related proline/alanine-rich protein kinase) and Slc12a (solute carrier family 12) transporters. We have shown that this signal cascade regulates blood pressure by controlling vascular tone as well as renal NaCl excretion. Therefore agents that inhibit this signal cascade could be a new class of antihypertensive drugs. Since the binding of WNK to OSR1/SPAK kinases was postulated to be important for signal transduction, we sought to discover inhibitors of WNK/SPAK binding by screening chemical compounds that disrupt the binding. For this purpose, we developed a high-throughput screening method using fluorescent correlation spectroscopy. As a result of screening 17000 compounds, we discovered two novel compounds that reproducibly disrupted the binding of WNK to SPAK. Both compounds mediated dose-dependent inhibition of hypotonicity-induced activation of WNK, namely the phosphorylation of SPAK and its downstream transporters NKCC1 (Na/K/Cl cotransporter 1) and NCC (NaCl cotransporter) in cultured cell lines. The two compounds could be the promising seeds of new types of antihypertensive drugs, and the method that we developed could be applied as a general screening method to identify compounds that disrupt the binding of two molecules.

Impaired KLHL3-mediated ubiquitination of WNK4 causes human hypertension.

Mutations in WNK kinases cause the human hypertensive disease pseudohypoaldosteronism type II (PHAII), but the regulatory mechanisms of the WNK kinases are not well understood. Mutations in kelch-like 3 (KLHL3) and Cullin3 were also recently identified as causing PHAII. Therefore, new insights into the mechanisms of human hypertension can be gained by determining how these components interact and how they are involved in the pathogenesis of PHAII. Here, we found that KLHL3 interacted with Cullin3 and WNK4, induced WNK4 ubiquitination, and reduced the WNK4 protein level. The reduced interaction of KLHL3 and WNK4 by PHAII-causing mutations in either protein reduced the ubiquitination of WNK4, resulting in an increased level of WNK4 protein. Transgenic mice overexpressing WNK4 showed PHAII phenotypes, and WNK4 protein was indeed increased in Wnk4(D561A/+) PHAII model mice. Thus, WNK4 is a target for KLHL3-mediated ubiquitination, and the impaired ubiquitination of WNK4 is a common mechanism of human hereditary hypertension.

Hereditary nephrogenic diabetes insipidus in Japanese patients: analysis of 78 families and report of 22 new mutations in AVPR2 and AQP2.

BACKGROUND: Familial form of nephrogenic diabetes insipidus (NDI) is a rare hereditary disease caused by arginine vasopressin type 2 receptor (AVPR2) or water channel aquaporin 2 (AQP2) gene mutations. It is speculated that 90% of NDI families carry disease-causing mutations in AVPR2 and 10% carry the mutations in AQP2; however, these percentages have not been supported by actual data. It is also unknown whether these percentages vary in different ethnic groups. METHODS: Gene mutation analyses were performed for 78 Japanese NDI families. All exons and intron-exon boundaries of the AVPR2 and AQP2 genes were directly sequenced. RESULTS: A total of 62 families (79%) carried disease-causing mutations in AVPR2, while nine families (12%) carried mutations in AQP2. We identified 22 novel putatively disease-causing mutations (19 in AVPR2 and 3 in AQP2). Regarding AVPR2, 52 disease-causing mutations were identified. Among them, missense mutations were most common (54%), followed by deletion mutations. In the 64 women who had monoallelic disease-causing AVPR2 mutations, 16 (25%) had NDI symptoms, including 4 complete NDI subjects. Regarding AQP2, 9 disease-causing mutations were identified in nine families. Two missense mutations and one deletion mutation showed a recessive inheritance, while one missense mutation and five small deletion mutations in the C-terminus of AQP2 showed a dominant inheritance. CONCLUSIONS: Most Japanese NDI families carry disease-causing mutations in AVPR2 and 12% carry mutations in AQP2. A total of 22 novel putatively disease-causing mutations were identified. The relatively high occurrence of symptomatic carriers of AVPR2 mutations needs attention.

Acute encephalopathy and tubulointerstitial nephritis associated with Yersinia pseudotuberculosis.

We report the case of a 28-month-old boy with encephalopathy and acute tubulointerstitial nephritis possibly associated with Yersinia pseudotuberculosis (Yp) infection. He was transferred to our center because of impairment of renal function and altered consciousness. He had fever for 5 days after recurrent vomiting and diarrhea. Computed tomography scan was normal, but electroencephalogram (EEG) analyses showed generalized slow wave patterns. Continuous hemodialysis was undergone and then his renal function was improved, but altered consciousness persisted. Single photon emission computed tomography (SPECT) revealed abnormally low signals at entire field, which suggested that he was suffered from encephalopathy. Phenobarbital administration and post-encephalopathy rehabilitation were started, and he recovered in fully premorbid state with normal EEG and SPECT findings on the 33rd hospital day. Various bacterial cultures were negative, but both Yp antibody and Yp-derived mitogen (YPM) antibody, the antibody of a specific Yp exotoxin, had an extremely high titer. This is the first report of encephalopathy potentially caused by Yp, indicated by the presence of a high Yp and YPM antibody titer.

ABO-incompatible renal transplantation in Epstein syndrome.

Epstein syndrome (ES) is an autosomal dominant hereditary disease characterized by hereditary nephritis, sensory deafness, and thrombocytopenia. We herein report the case of a 20-yr-old man with ES who underwent ABO blood type-incompatible living-donor kidney transplantation from his mother. He was given platelet transfusion, and his pre-operative number of platelets were 108 x 10(3)/microL. After transplantation, urine output and the decrease in serum creatinine (sCr) were within the acceptable ranges. On the seventh post-operative day (POD), sCr had risen and urine output decreased. Anti-type A antibody rapidly elevated from <2 times (x2) just before transplantation to 64 times (x64), and the patient required hemodialysis again. Resistance index (RI) by ultrasound increased from an average of 0.5 approximately 0.6 on POD 1 to an average of 0.7 approximately 0.8 on POD 7. However, several biopsies (POD 4, 7, and 10) showed no obvious findings of acute rejection except for intense C4d deposition. Because acute antibody-mediated rejection was not completely ruled out, he was treated with methyl-prednisolone pulse therapy, plasma exchange, cyclophosphamide, and immunoglobulin. Regardless, his titer of anti-type A antibody was still high, and he still presented oliguria. We performed an emergent splenectomy. Consequently, the levels of anti-type A antibody decreased, the RI also dropped to an average of 0.6. However, on POD 19 and 25 (platelets were 27 x 10(3)/microL and 36 x 10(3)/microL), he developed a massive intraperitoneal hematoma around the graft and region of the removed spleen, which pushed the graft out and caused acute tubular necrosis, resulting in anuria. The RI rose to an average of 0.8 approximately 1.0 after these episodes. He also experienced bleeding from a duodenal ulcer on POD 21. However, his renal function has fully recovered after acute hemodialysis for 35 d. The latest sCr was 1.5 mg/dL with a recovery in RI to 0.6. Although his platelet count was maintained at a minimum of 50 x 10(3)/microL, he had several severe bleeding episodes, concluding that sufficient platelets are necessary after transplantation in ES.