A lipidome landscape of aging in mice.

Understanding the molecular mechanisms of aging is crucial for enhancing healthy longevity. We conducted untargeted lipidomics across 13 biological samples from mice at various life stages (2, 12, 19 and 24 months) to explore the potential link between aging and lipid metabolism, considering sex (male or female) and microbiome (specific pathogen-free or germ-free) dependencies. By analyzing 2,704 molecules from 109 lipid subclasses, we characterized common and tissue-specific lipidome alterations associated with aging. For example, the levels of bis(monoacylglycero)phosphate containing polyunsaturated fatty acids increased in various organs during aging, whereas the levels of other phospholipids containing saturated and monounsaturated fatty acids decreased. In addition, we discovered age-dependent sulfonolipid accumulation, absent in germ-free mice, correlating with Alistipes abundance determined by 16S ribosomal RNA gene amplicon sequencing. In the male kidney, glycolipids such as galactosylceramides, galabiosylceramides (Gal2Cer), trihexosylceramides (Hex3Cer), and mono- and digalactosyldiacylglycerols were detected, with two lipid classes-Gal2Cer and Hex3Cer-being significantly enriched in aged mice. Integrated analysis of the kidney transcriptome revealed uridine diphosphate galactosyltransferase 8A (UGT8a), alkylglycerone phosphate synthase and fatty acyl-coenzyme A reductase 1 as potential enzymes responsible for the male-specific glycolipid biosynthesis in vivo, which would be relevant to sex dependency in kidney diseases. Inhibiting UGT8 reduced the levels of these glycolipids and the expression of inflammatory cytokines in the kidney. Our study provides a valuable resource for clarifying potential links between lipid metabolism and aging.

Genetic deletion of Cyp4f18 disrupts the omega-3 epoxidation pathway and results in psoriasis-like dermatitis.

Cyp4f18 catalyzes the conversion of n-3 polyunsaturated fatty acids (PUFAs) into omega-3 epoxides, such as 17,18-epoxyeicosatetraenoic acid (17,18-EpETE) and 19,20-epoxydocosapentaenoic acid (19,20-EpDPE) from eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA), respectively. Cyp4f18-deficient mice spontaneously develop psoriasis-like dermatitis. A significant increase in the number of IL-17A-positive gamma delta (γδ) T cells in the skin and enlargement of draining lymph nodes was observed. These symptoms were drastically suppressed by antibiotic treatment. Cyp4f18 is highly expressed in dendritic cells (DCs), and Cyp4f18-deficient bone marrow-derived dendritic cells (BMDCs) show markedly increased expression levels of cytokines such as IL-23 and IL-1ß in response to lipopolysaccharide (LPS) stimulation. Lipidomic analysis of lymph nodes and BMDCs revealed a significant decrease in a series of omega-3 epoxidized metabolites. Among them, 17,18-dihydroxyeicosatetraenoic acid (17,18-diHETE), a vicinal diol derived from EPA omega-3 epoxidation suppressed IL-23 production in LPS-stimulated BMDCs in Cyp4f18-deficient mice. These results demonstrate that Cyp4f18 endogenously produces omega-3-epoxidized metabolites in the draining lymph nodes, and these metabolites contribute to skin homeostasis by suppressing the excessive activation of the IL-23/IL-17 axis initiated by DCs.

Eosinophils promote corneal wound healing via the 12/15-lipoxygenase pathway.

Lipid mediators play important roles in regulating inflammatory responses and tissue homeostasis. Since 12/15-lipoxygenase (12/15-LOX)-derived lipid mediators such as lipoxin A4 (LXA4 ) and protectin D1 (PD1) protect against corneal epithelial cell damage, the major cell types that express 12/15-LOX and contribute to the corneal wound healing process are of particular interest. Here, we found that eosinophils were the major cell type expressing 12/15-LOX during the corneal wound healing process. Eosinophils were recruited into the conjunctiva after corneal epithelium wounding, and eosinophil-deficient and/or eosinophil-specific 12/15-LOX knockout mice showed delayed corneal wound healing compared with wild-type mice. Liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based mediator lipidomics revealed that a series of 12/15-LOX-derived mediators were significantly decreased in eosinophil-deficient mice and topical application of 17-hydroxydocosahexaenoic acid (17-HDoHE), a major 12/15-LOX-derived product, restored the phenotype. These results indicate that 12/15-LOX-expressing eosinophils, by locally producing pro-resolving mediators, significantly contribute to the corneal wound healing process in the eye.

Successful Kidney Transplantation Alone With Severe Left Ventricular Systolic Dysfunction of Ejection Fraction 14%: A Case Report.

It is well known that correction of uremia by kidney transplantation alone (KTA) improves left ventricular systolic dysfunction (LVSD). However, for kidney transplant candidates with extremely severe LVSD, KTA is considered to be contraindicated because of the high risk of peri-operative management. We report a case of successful kidney transplantation with severe LVSD with an ejection fraction (EF) of 14% and low systolic blood pressure (SBP) of approximately 65 to 80 mm Hg. In this case, in spite of an extremely low EF and SBP, functional capacity was assessed using metabolic equivalents (METs) and showed a level of almost 4. The operation was performed carefully, considering the cardiac, operative, and anesthetic risks. No surgical complications occurred, and the patient received intensive care during the peri-operative period. His postoperative course was almost favorable, and he was discharged on postoperative day 29. The present report concludes that evaluation of METs may expand the indication for KTA in patients with extremely severe LVSD.

Cell-free and Concentrated Ascites Reinfusion Therapy for Refractory Ascites in Cirrhosis in Post-marketing Surveillance and the Role of Tolvaptan.

Objective Ascites becomes refractory to diuretics in cirrhotic patients, who then require repeated large-volume paracentesis or cell-free and concentrated ascites reinfusion therapy (CART). The objective of this study was to confirm the safety and efficacy of CART, evaluate the actual situations with respect to the prescription of diuretics and determine the role of diuretics after the introduction of CART. Patients and Methods We recruited 34 cirrhotic patients who received CART with concomitant diuretics using furosemide (76.2%), spironolactone (48.5%), thiazide (4.0%) and tolvaptan (53.5%) from a post-marketing surveillance of CART. Results CART improved the tested clinical indices, i.e., body weight, abdominal circumference, performance status, dietary intake, total protein and albumin. The intervals of CART sessions were significantly prolonged in patients who received tolvaptan (mean, 22.5 days) compared to those not receiving tolvaptan (mean, 10.8 days) (p<0.001). The drop-out rate was significantly decreased in patients receiving tolvaptan compared to those not receiving tolvaptan when drop-out was defined as paracentesis (p<0.05). Conclusion We confirmed that CART is an effective treatment for refractory ascites occurring in cirrhotic patients. The administration of tolvaptan in combination with CART leads to a significantly reduced rate of ascites accumulation.

Anatomical Variations of the Left Renal Vein During Laparoscopic Donor Nephrectomy.

OBJECTIVES: The aim of this study is to investigate the outcome of laparoscopic donor nephrectomy with vascular anomalies of the left renal vein. PATIENTS AND METHODS: Between August 2010 and September 2018, a total of 120 laparoscopic donor nephrectomies were performed at Kagoshima University. Among them, we experienced 7 cases of donors with anomalous left renal vein (circumaortic left renal vein n = 5, retroaortic left renal vein n = 1, left renal vein drainage into hemiazygos vein n = 1). We analyzed the following clinical outcomes: pneumoperitoneum time, estimated blood loss, warm ischemia time, length of hospital stay, and serum creatinine level of 1 month after surgery for evaluating the safety of laparoscopic donor nephrectomy. RESULTS: Among the 7 cases, 3 cases underwent transperitoneal approach, and 4 cases underwent retroperitoneal approach. The median pneumoperitoneum time was 168 (108-191) minutes. The median estimated blood loss was 90 (23-170) mL, and no donor required a blood transfusion. Median warm ischemia time was 4 (3-7) minutes. Length of hospital stay was 7 (6-9) days, and no readmission occurred. Median serum creatinine level of 1 month after surgery was 1.19 (0.84-1.74) mg/dL. Kidneys were transplanted successfully, and none of recipients required dialysis. CONCLUSIONS: Laparoscopic donor nephrectomy was safe for donors with an anomalous left renal vein. Preoperative recognition of anomalous left renal vein in computed tomography is important for avoiding hemorrhagic complication.

Omega-3 fatty acid-derived mediators that control inflammation and tissue homeostasis.

Omega-3 polyunsaturated fatty acids (PUFAs), including eicosapentaenoic acid, docosapentaenoic acid and docosahexaenoic acid, display a wide range of beneficial effects in humans and animals. Many of the biological functions of PUFAs are mediated via bioactive metabolites produced by fatty acid oxygenases such as cyclooxygenases, lipoxygenases and cytochrome P450 monooxygenases. Liquid chromatography-tandem mass spectrometry-based mediator lipidomics revealed a series of novel bioactive lipid mediators derived from omega-3 PUFAs. Here, we describe recent advances on omega-3 PUFA-derived mediators, mainly focusing on their enzymatic oxygenation pathway, and their biological functions in controlling inflammation and tissue homeostasis.

Efficacy of canagliflozin against nonalcoholic fatty liver disease: a prospective cohort study.

BACKGROUND: Nonalcoholic fatty liver disease (NAFLD) is a common cause of chronic liver disease worldwide and is characterized by insulin resistance, hepatic steatosis and often prediabetes or diabetes. Canagliflozin, a selective sodium glucose cotransporter 2 inhibitor, is a new oral anti-diabetic drug that reduces hyperglycaemia by promoting urinary glucose excretion. Glycosuria produced by canagliflozin is associated with weight loss, mainly due to reduced fat volume and improve insulin resistance. Reduced body weight and improvement of insulin resistance by canagliflozin may be an effective treatment for NAFLD. METHODS: Thirty-five patients with NAFLD (17 men and 18 women) were enrolled and administered canagliflozin (100 mg). Body weight and serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), gamma-glutamyl transferase (γ-GTP), low-density lipoprotein cholesterol, high-density lipoprotein cholesterol, triglycerides (TG), blood sugar (BS), glycated haemoglobin (HbA1C), uric acid (UA) and ferritin, and fibrosis-4 (FIB-4) index values were measured at baseline and at 3-month and 6-month follow-up visits. RESULTS: Body weight and serum levels of AST, ALT, γ-GTP, TG, UA, HbA1C, BS and ferritin decreased significantly after 3 and 6 months of canagliflozin treatment. Serum BS levels and FIB-4 index values decreased slightly following 3 months of treatment; these results reached significance after 6 months. Reduced serum ALT levels at 6 months were significantly correlated with baseline HbA1C and ferritin levels. Moreover, a significant correlation between reduced body weight and serum ALT levels was observed at 6 months. Decreased serum ALT levels were significantly correlated with decreased serum ferritin at 6 months. CONCLUSIONS: Canagliflozin significantly reduced the serum levels of BS, HbA1C, TG, UA and ferritin, as well as FIB-4 index values and body weight, with improved liver function. Sodium glucose cotransporter 2 inhibitors may be an important therapeutic modality for improving liver injury in NAFLD patients.

Identification of Protein Targets of 12/15-Lipoxygenase-Derived Lipid Electrophiles in Mouse Peritoneal Macrophages Using Omega-Alkynyl Fatty Acid.

The 12/15-lipoxygenase (12/15-LOX) enzyme introduces peroxyl groups, in a position-specific manner, into polyunsaturated fatty acids to form various kinds of bioactive lipid metabolites, including lipid-derived electrophiles (LDE). The resident peritoneal macrophage is the site of highest 12/15-LOX expression in the mouse. However, the role of the enzyme in the regulation of resident macrophages is not fully understood. Here, we describe a chemoproteomic method to identify the targets of enzymatically generated LDE. By treating mouse peritoneal macrophages with omega-alkynyl arachidonic acid (aAA), we identified a series of proteins adducted by LDE generated through a 12/15-LOX catalyzed reaction. Pathway analysis revealed a dramatic enrichment of proteins involved in energy metabolism and found that glycolytic flux and mitochondrial respiration were significantly affected by the expression of 12/15-LOX. Our findings thus highlight the utility of chemoproteomics using aAA for identifying intracellular targets of enzymatically generated LDE.

Protective and therapeutic effect of felodipine against bleomycin-induced pulmonary fibrosis in mice.

Idiopathic pulmonary fibrosis (IPF) involves alveolar epithelial injury and abnormal collagen production caused by activated fibroblasts; transforming growth factor (TGF)-ß1 is implicated in this activation. In this study, we screened for chemicals capable of inhibiting TGF-ß1-induced collagen production in cultured fibroblasts from medicines already in clinical use. We selected felodipine based on its extent of collagen production inhibition, clinical safety profile, and other pharmacological activity. Felodipine is a dihydropyridine Ca2+ channel blocker that has been used clinically to treat patients with high blood pressure. Felodipine suppressed collagen production within LL29 cells in the presence of TGF-ß1, but not in its absence. Intratracheal administration of felodipine prevented bleomycin-induced pulmonary fibrosis, alteration of lung mechanics and respiratory dysfunction. Felodipine also improved pulmonary fibrosis, as well as lung and respiratory function when administered after fibrosis development. Furthermore, administration of felodipine suppressed a bleomycin-induced increase in activated fibroblasts in the lung. We also found other dihydropyridine Ca2+ channel blockers (nifedipine and benidipine) inhibited collagen production in vitro and partially prevented bleomycin-induced pulmonary fibrosis, alteration of lung mechanics and respiratory dysfunction in vivo. We propose that these Ca2+ channel blockers may be therapeutically beneficial for IPF patients.

Safety and efficacy of cell-free and concentrated ascites reinfusion therapy (CART) in refractory ascites: Post-marketing surveillance results.

We performed post-marketing surveillance to evaluate the safety and efficacy of cell-free and concentrated ascites reinfusion therapy (CART). In total, 356 CART sessions in 147 patients at 22 centers were performed. The most common primary disease was cancer (128 cases, 300 sessions). Mean amount of ascites collected was 3.7 L, and mean concentration ratio was 9.2. Mean amount of reinfused protein was 67.8 g (recovery rate, 72.0%). Performance status, dietary intake, urine volume, body weight and abdominal circumference were significantly improved after CART. Body temperature increased significantly, by 0.3°C on average. Concomitant steroids and/or NSAIDs use before reinfusion was significantly and negatively associated with increases in body temperature. Most adverse events were fever and chills. This study examined a large number of patients compared with previous studies, and showed that CART is an effective and relatively safe treatment for refractory ascites, such as malignant ascites.

An Autophagic Flux Probe that Releases an Internal Control.

Macroautophagy is an intracellular degradation system that utilizes the autophagosome to deliver cytoplasmic components to the lysosome. Measuring autophagic activity is critically important but remains complicated and challenging. Here, we have developed GFP-LC3-RFP-LC3ΔG, a fluorescent probe to evaluate autophagic flux. This probe is cleaved by endogenous ATG4 proteases into equimolar amounts of GFP-LC3 and RFP-LC3ΔG. GFP-LC3 is degraded by autophagy, while RFP-LC3ΔG remains in the cytosol, serving as an internal control. Thus, autophagic flux can be estimated by calculating the GFP/RFP signal ratio. Using this probe, we re-evaluated previously reported autophagy-modulating compounds, performed a high-throughput screen of an approved drug library, and identified autophagy modulators. Furthermore, we succeeded in measuring both induced and basal autophagic flux in embryos and tissues of zebrafish and mice. The GFP-LC3-RFP-LC3ΔG probe is a simple and quantitative method to evaluate autophagic flux in cultured cells and whole organisms.

Identification of approved drugs that inhibit the binding of amyloid ß oligomers to ephrin type-B receptor 2.

Ephrin type-B receptor 2 (EphB2) is a member of the receptor tyrosine kinase family and plays an important role in learning and memory functions. In patients with Alzheimer's disease (AD) and in mouse models of AD, a reduction in the hippocampal EphB2 level is observed. It was recently reported that normalization of the EphB2 level in the dentate gyrus rescues memory function in a mouse model of AD, suggesting that drugs that restore EphB2 levels may be beneficial in the treatment of AD. Amyloid ß (Aß) oligomers, which are believed to be key molecules involved in the pathogenesis of AD, induce EphB2 degradation through their direct binding to EphB2. Thus, compounds that inhibit the binding of Aß oligomers to EphB2 may be beneficial. Here, we screened for such compounds from drugs already approved for clinical use in humans. Utilizing a cell-free screening assay, we determined that dihydroergotamine mesilate, bromocriptine mesilate, cepharanthine, and levonorgestrel inhibited the binding of Aß oligomers to EphB2 but not to cellular prion protein, another endogenous receptor for Aß oligomers. Additionally, these four compounds did not affect the binding between EphB2 and ephrinB2, an endogenous ligand for EphB2, suggesting that the compounds selectively inhibited the binding of Aß oligomers to EphB2. This is the first identification of compounds that selectively inhibit the binding of Aß oligomers to EphB2. These results suggest that these four compounds may be safe and effective drugs for treatment of AD.

Tumour-suppressive microRNA-29s directly regulate LOXL2 expression and inhibit cancer cell migration and invasion in renal cell carcinoma.

Here, we found that members of the microRNA-29 family (miR-29a/b/c; "miR-29s") were significantly reduced in clear cell renal cell carcinoma (ccRCC) tissues, suggesting that they functioned as tumour suppressors. Restoration of all mature members of the miR-29 family inhibited cancer cell proliferation, migration and invasion. LOXL2 was a direct target gene of miR-29s, as shown by genome-wide gene expression analysis and luciferase reporter assay. Overexpressed LOXL2 was confirmed in ccRCC clinical specimens, and silencing of LOXL2 inhibited cancer cell migration and invasion in ccRCC cell lines. Our data demonstrated that the miR-29s-LOXL2 axis contributed to cancer cell migration and invasion in ccRCC.

Drug Repositioning for Preeclampsia Therapeutics by In Vitro Screening: Phosphodiesterase-5 Inhibitor Vardenafil Restores Endothelial Dysfunction via Induction of Placental Growth Factor.

We screened a library of 528 approved drugs to identify candidate compounds with therapeutic potential as preeclampsia treatments via their proangiogenic properties. Using human umbilical vein endothelial cells (HUVECs), we assessed whether the screened drugs induced placental growth factor (PIGF) and restored damaged endothelial cell function. Enzyme-linked immunosorbent assays (ELISAs) were carried out to measure levels of PlGF in conditioned media treated with each drug (100 µmol/L) in the drug library. Tube formation assays were performed using HUVECs to evaluate the angiogenic effects of drugs that induced PlGF. We also performed ELISA, quantitative reverse transcription polymerase chain reaction, and tube formation assays after treatment with a range of concentrations of the candidate drug. Of the drugs that induced PlGF, vardenafil was the only compound that significantly facilitated tube formation in comparison with the control cells (P < .01). Treatment with vardenafil at concentrations of 50, 100, and 250 µmol/L increased expression of PlGF in a dose-dependent manner. Vardenafil (250 µmol/L) significantly improved tube formation which was inhibited in the presence of soluble fms-like tyrosine kinase 1 (100 ng/mL) and/or soluble endoglin (100 ng/mL). Production of PlGF from HUVECs in the presence of sera derived from patients with preeclampsia was significantly elevated by administration of vardenafil (250 µmol/L). By assessing drug repositioning through screening a library of approved drugs, we identified vardenafil as a potential protective agent against preeclampsia. The therapeutic mechanism of vardenafil may involve inhibition of the systemic maternal antiangiogenic state that leads to preeclampsia, in addition to its vasodilating effect. As concentrations used are high and unlikely to be useful clinically, further work is needed before testing it in humans.

Elevation of branched-chain amino acid levels in diabetes and NAFL and changes with antidiabetic drug treatment.

Diabetes mellitus (DM), non-alcoholic fatty liver (NAFL), and obesity are associated with elevated branched-chain amino acid (BCAA) levels, but the mechanism and significance of this has not been elucidated. Eighty-four subjects were enrolled including 43 with DM. Serum BCAA levels were positively correlated with waist-hip ratio and ALT. Serum BCAA levels in subjects with DM were higher than non-DM and those in subjects with NAFL were also higher than non-NAFL. Treatment with pioglitazone and alogliptin (19 of 43 DM subjects) improved serum haemoglobin A1c and decreased BCAA levels. The decrease in BCAAs with improved glucose metabolism suggests that abnormal glucose metabolism is also a factor in elevated BCAA levels.

Usefulness of Levocarnitine and/or Branched-Chain Amino Acids during Invasive Treatment for Hepatocellular Carcinoma.

Transarterial chemoembolization (TACE) and radiofrequency ablation (RFA) are effective treatments for hepatocellular carcinoma (HCC). However, the extent of treatment depends on hepatic functional reserve. L-Carnitine is a vitamin-like substance and several reports have described the usefulness of L-carnitine supplementation in cases of cirrhosis, with confirmed effectiveness against refractory hepatic encephalopathy. On the other hand, we have previously reported that in patients who underwent TACE or RFA, administration of branched-chain amino acids (BCAAs) pre-intervention significantly reduced inflammatory reactions. We first determined serum levels of total, free, and acyl-carnitine before and at 7 d after performing TACE in 10 HCC patients. We administered levocarnitine (L-carnitine chloride, a biologically active form of carnitine) at 900 mg/d to 69 consecutive HCC patients hospitalized to undergo TACE and/or RFA, and compared changes in blood test values with those in 119 consecutive patients not administered this drug. Sixty-seven patients had a history of using BCAAs at the time of admission. We found that after 7 d of TACE, serum levels of total and acyl-carnitine are significantly decreased. On comparing the four groups, the carnitine+BCAA, carnitine-alone, and BCAA-alone groups showed significantly higher values for changes in NH3 when compared with the non-dosed group. The decrease in albumin (Alb) was significantly suppressed in the carnitine+BCAA and BCAA-alone groups. We also conducted the same examinations in a subset of patients classified as Child-Pugh class A, and noted the same trends. Administration of levocarnitine and/or BCAAs during invasive treatments reduced blood NH3 concentrations and suppressed decreases in Alb.

Encapsulation of beraprost sodium in nanoparticles: analysis of sustained release properties, targeting abilities and pharmacological activities in animal models of pulmonary arterial hypertension.

Prostaglandin I2 (PGI2) and its analogues (such as beraprost sodium, BPS) are beneficial for the treatment of pulmonary arterial hypertension (PAH). The encapsulation of BPS in nanoparticles to provide sustained release and targeting abilities would improve both the therapeutic effect of BPS on PAH and the quality of life of patients treated with this drug. BPS was encapsulated into nanoparticles prepared from a poly(lactic acid) homopolymer and monomethoxy poly(ethyleneglycol)-poly(lactide) block copolymer. The accumulation of nanoparticles in damaged pulmonary arteries was examined using fluorescence-emitting rhodamine S-encapsulated nanoparticles. The monocrotaline-induced PAH rat model and the hypoxia-induced mouse model were used to examine the pharmacological activity of BPS-encapsulated nanoparticles. A nanoparticle, named BPS-NP, was selected among various types of BPS-encapsulated nanoparticles tested; this was based on the sustained release profile in vitro and blood clearance profile in vivo. Fluorescence-emitting rhodamine S-encapsulated nanoparticles were prepared in a similar manner to that of BPS-NP, and showed accumulation and prolonged residence in monocrotaline-damaged pulmonary peripheral arteries. Intravenous administration of BPS-NP (once per week, 20µg/kg) protected against monocrotaline-induced pulmonary arterial remodeling and right ventricular hypertrophy. The extent of this protection was similar to that observed with oral administration (once per day, 100µg/kg) of BPS alone. The once per week intravenous administration of BPS-NP (20µg/kg) also exhibited an ameliorative effect on hypoxia-induced pulmonary arterial remodeling and right ventricular hypertrophy. The beneficial effects of BPS-NP on PAH animal models seem to be mediated by its sustained release and tissue targeting profiles. BPS-NP may be useful for the treatment of PAH patients due to reduced dosages and frequency of BPS administration.

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.