Therapeutic Potentiality of Celtis choseniana Nakai on Androgenic Alopecia through Repression of Androgen Action and Modulation of Wnt/β-catenin Signaling

In this study, we investigated the efficacy of Celtis choseniana Nakai (C. choseniana) as complementary herbal medicine to ameliorate androgenic alopecia (AGA). The effects of C. choseniana on AGA were evaluated using testosterone propionate-induced AGA mouse model and dihydrotestosterone-treated human hair follicle dermal papilla cells. In vivo, C. choseniana treatment deactivated androgen signaling by reducing the concentration of serum dihydrotestosterone level and expressions of 5α-reductase 2 and androgen receptor. Next, C. choseniana treatment increased the hair regrowth rate. Histological studies demonstrated that C. choseniana induced the anagen phase in testosterone propionate-induced AGA mouse model. Cellular proliferation was promoted by C. choseniana treatment via increasing the expression of proliferation factors, such as proliferating cell nuclear antigen and cyclin D1. Furthermore, C. choseniana treatment increased the expression of proteins related to the Wnt/β-catenin signaling pathway. In addition, dickkopf-1, a Wnt inhibitor, was downregulated with C. choseniana treatment. Likewise, C. choseniana treatment promoted cellular proliferation in vitro. This study demonstrated the inhibitory effect of C. choseniana on androgen-induced AGA. Moreover, C. choseniana induced activation of Wnt/β-catenin signaling, resulting in prolonged anagen and cellular proliferation. Therefore, we suggest that C. choseniana can be used as a therapeutic agent to alleviate AGA.

The extract of Celtis choseniana Nakai alleviates testosterone-induced benign prostatic hyperplasia through inhibiting 5α reductase type 2 and the Akt/NF-κB/AR pathway / 中国天然药物

Benign prostatic hyperplasia (BPH) is a chronic male disease characterized by the enlarged prostate. Celtis chosenianaNakai (C. choseniana) is medicinally used to alleviate pain, gastric disease, and lung abscess. In this study, the effect of C. choseniana extract on BPH was investigated using testosterone-induced rats. Sprague Dawley rats were divided into five groups: control, BPH (testosterone 5 mg·kg-1), Fina (finasteride 2 mg·kg-1), and C. choseniana (50 and 100 mg·kg-1). After four weeks of TP treatment with finasteride or C. choseniana, prostate weights and DHT levels were measured. In addition, the prostates were histopathologically examined and measured for protein kinase B (Akt)/nuclear factor-κB (NF-κB)/AR signaling, proliferation, apoptosis, and autophagy. Prostate weight and epithelial thickness were reduced in the C. choseniana groups compared with that in the BPH group. The extract of C. choseniana acted as a 5α reductase inhibitor, reducing DHT levels in the prostate. Furthermore, the extract of C. choseniana blocked the activation of p-Akt, nuclear NF-κB activation and reduced the expression of AR and PSA compared with BPH. Moreover, the expression of Bax, PARP-1, and p53 increased, while the expression of bcl-2 decreased. The present study demonstrated that C. choseniana extract alleviated testosterone-induced BPH by suppressing 5α reductase and Akt/NF-κB activation, reducing AR signaling and inducing apoptosis and autophagy in the prostate. These results suggested that C. choseniana probably contain potential herbal agents to alleviate BPH.

Effects of Albizia julibrissin Durazz through Suppression of Mitochondrial Fission and Apoptosis in Cisplatin-induced Acute Kidney Injury

Albizia julibrissin Durazz. (AJ; family Minosaceae) is widely distributed worldwide, and its stem bark has been used as a traditional herbal medicine. Acute kidney injury (AKI) is a clinical syndrome that results in sudden loss of renal function. This study aimed to investigate the effects of AJ against cisplatin-induced AKI using a human kidney proximal tubule epithelial cell line (HK-2) and cisplatin-treated mice. In vitro, cisplatin treatment increased apoptosis in HK-2 cells. However, AJ treatment decreased apoptosis of cisplatin-treated HK-2 cells. In vivo, cisplatin treatment accelerated renal injury by increasing the levels of renal injury markers, such as blood urea nitrogen, creatinine, kidney injury molecule 1, and neutrophil gelatinase-associated lipocalin, which were reversed by AJ treatment. Histopathologically, AJ treatment resulted in decreased renal damage with less tubular necrosis and brush border desquamation compared with the AKI group. Additionally, cisplatin treatment upregulated mitochondrial fission, a pathological characteristic of AKI, which was downregulated by AJ treatment. Along with increased mitochondrial fission, AJ treatment also reduced cisplatin-induced apoptosis.These results suggest that AJ may be a potential therapeutic agent for cisplatin-induced AKI.

Albizzia julibrissin Suppresses Testosterone-induced Benign Prostatic Hyperplasia by Regulating 5α-Reductase Type 2 – Androgen Receptor Pathway

Albizzia julibrissin (AJ) is an herbal medicine that shows low toxicity, promotes promoting blood circulation and mitigates the inflammation and has mild side effects. Benign prostate hyperplasia (BPH) is one of the most common diseases that occurs in older males and often results in lower urinary tract symptoms. This study was conducted to evaluate the protective effect of AJ against BPH using LNCaP cells and Sprague Dawley rats treated with testosterone. Treatment with AJ extract reduced the expression of androgen receptor (AR) and prostate-specific antigen (PSA) in vitro. In vivo, rats were divided into 6 groups: 1 (Normal Control); 2 (Testosterone propionate (TP) alone); 3 (TP + finasteride); 4 (TP + AJ 10 mg/kg); 5 (TP + AJ 50 mg/kg); 6 (TP + AJ 300 mg/kg). The groups treated with AJ showed reduced the relative prostate weights and BPH-related proteins were altered, with decreased AR, PSA and proliferating cell nuclear antigen (PCNA) observed by western blot. Histopathological analysis revealed the therapeutic effect of AJ, with a decreased thickness of epithelial cells and reduced level of PCNA and 5α-reductase type 2. These results suggest that AJ extract could ameliorate testosterone-induced benign prostatic hyperplasia.

Autophagy localization and cytoprotective role in cisplatin-induced acute kidney injury / 대한수의학회지

Autophagy is a fundamental cellular process that maintains homeostasis and cell integrity, under stress conditions. Although the involvement of autophagy in various conditions has been elucidated, the role of autophagy in renal structure is not completely clarified. Our aim was to investigate the cytoprotective effect of autophagy against acute kidney injury (AKI) through cisplatin deteriorative pathway, which leads to AKI via renal cell degradation. For in vivo experiments, male Sprague Dawley rats were divided in to 2 groups (n = 6/group) as control, Cis-5D. Following a single intraperitoneal injection of cisplatin, rats were sacrificed after 5 days. Blood urea nitrogen (BUN), creatinine (Cr) and histological alterations were examined. Further, expression of key regulators of autophagy, light-clain 3 (LC3), p62, and Beclin1, was evaluated by immunohistochemistry (IHC). The rats exhibited severe renal dysfunction, indicated by elevated BUN, Cr. Hematoxylin and eosin staining revealed histological damages in cisplatin-treated rats. Furthermore, IHC analysis revealed increased expression of LC3, Beclin1 and decreased expression of p62. Furthermore, expression of aforementioned autophagy markers was restricted to proximal tubule. Taken together, our study demonstrated that cisplatin can cause nephrotoxicity and lead to AKI. This phenomenon accelerated autophagy in renal proximal tubules and guards against AKI.

Non-Alcoholic Fatty Liver Disease and Its Association with Depression in Korean General Population

BACKGROUND: Recent studies have indicated the significant association between non-alcoholic fatty liver disease (NAFLD) and depression. However, there is ongoing debate on whether the risk for depression is actually related with the presence and severity of NAFLD. Thus, this study was conducted to investigate the association between depression and NAFLD evaluated by diverse modalities. METHODS: A total of 112,797 participants from the Korean general population were enrolled. The study participants were categorized into three groups according to degree of NAFLD evaluated by ultrasonography, fatty liver index (FLI) and fibrosis-4 score (FIB-4). Depression was defined as a score of Center for Epidemiological Studies-Depression (CES-D) ≥ 16, and the odd ratios (ORs) and 95% confidence interval (CI) for depression (adjusted ORs [95% CI]) were assessed by multiple logistic regression analyses. RESULTS: In the unadjusted model, the presence and severity of NAFLD was not significantly associated with depressive symptoms. However, in the fully adjusted model, ORs for depression increased in proportion to the degree of ultrasonographically detected NAFLD (mild fatty liver: 1.14 [1.06–1.22]; and moderate to severe fatty liver: 1.32 [1.17–1.48]). An association was also observed between depression and FLI (30 ≤ FLI < 60: 1.06 [0.98–1.15]; FLI ≥ 60: 1.15 [1.02–1.29]). CONCLUSION: The presence and severity of NAFLD is significantly associated with depressive symptoms. In addition, this association was more distinct after adjusting for covariates including age, gender and insulin resistance. This finding indicates the necessity of further study evaluating the incidental relationship of depression with NAFLD.

NAD(P)H-quinone oxidoreductase-1 silencing modulates cytoprotection related protein expression in cisplatin cytotoxicity

NAD(P)H-quinone oxidoreductase-1 (NQO1) is a down-stream target gene of nuclear factor erythroid 2-related factor 2 (Nrf2), and performs diverse biological functions. Recently, NQO1 is recognized as an effective gene for the cytotoxic inserts with its diverse biological functions, which is focused on antioxidant properties. The aim of present study was to assess the impact of NQO1 knockdown on cytoprotection-related protein expression in cisplatin cytotoxicity by using small interfering (si) RNA targeted on NQO1 gene. Cytotoxicity of cisplatin on ACHN cells was assessed in a dose- and time-dependent manner after siScramble or siNQO1 treatment. After cisplatin treatment, cells were subjected to cell viability assay, western-blot analysis, and immunofluorescence study. The cell viability was decreased in the siNQO1 cells (50%) than the siScramble cells (70%) after 24 h of cisplatin (20 µM) treatment. Moreover, cytoprotection-related protein expressions were markedly suppressed in the siNQO1 cells after cisplatin treatment. The expression of Nrf2 and Klotho were decreased by 20% and 40%, respectively, of that in siScramble cells. Nrf2 and Klotho activation were also decreased in cisplatin treated siNQO1 cells, confirmed by cytoplasm-to-nuclear translocation. Our findings demonstrate that the increased cisplatin-induced cytotoxicity was accompanied by suppressed Nrf2 activation and Klotho expression in siNQO1 cells.

Erratum: Quatification of Flavonoid Contents in Chungsimyeonja-tang, a Multi-Herbal Decoction, and Its Protective Effect against Cisplatin-induced Nephrotoxicity

Correction for incorrect control groups (A, B, and C) at a Fig. 3. and Fig. 4. respectively. NPS 2014 20(4): 251-257.

Localization of Klotho in cisplatin induced acute kidney failure / 대한수의학회지

Klotho deficiency is an early event in acute kidney injury (AKI) that exacerbates acute kidney damage. The present study explored the expression of Klotho and inflammation related factors in cisplatin-induced AKI. Rats (n = 18) were treated with cisplatin intraperitoneal injection (5 mg/kg) or left untreated as controls (n = 6), then sacrificed at 5 (n = 6) and 10 days (n = 6) treatment. Five days after cisplatin injection, the serum kidney enzymes and kidney cell apoptosis were significantly increased. Moreover, the expression of Klotho was decreased when compared to the control group, especially in the cortex and outer medulla regions. In contrast, inflammation related signals including nuclear factor kappa B, tumor necrosis factor-alpha, and tumor necrosis factor-like weak inducer of apoptosis were enhanced. However, 10 days after cisplatin injection, Klotho expression was enhanced upon both IHC and Western blot analysis, with slightly recovered renal function and decreased apoptosis. Furthermore, inflammation related signals expression was decreased relative to the 5 days group. Overall, this study confirmed the opposite expression patterns between Klotho and inflammation related signals and their localization in cisplatin-induced AKI kidney.

Expression of CD133, CD44, CK7, and OCT4 in Animal Cancers / 대한수의학회지

Cancers are mainly sustained by a small pool of neoplastic cells, known as cancer stem cells or tumor-initiating cells. These cells possess the ability to self-renew and proliferate, and are thus able to form the tumor. In the present study cells that correspond to cancer stem cells in mammary and liver cancers in animals were identified by the expression of CD133, CD44, CK7, and OCT4 using immunochemistry. As a result, we found with CD133+ and CD44+ cancer stem cell-like phenotypes in mouse and canine hepatocellular carcinoma and canine mammary gland tumors. However, CK7+ and OCT4+ cells were not identified in animal mammary and liver cancer. CD133+ and CD44+ cells are wellknown stem cell lines and play key roles in development and metastasis in human cancer. These findings suggest that cancer stem cells are involved in animal tumorigenesis and may provide insight into mechanisms in cancer development as well as cancer diagnostics.

Chordoma in the Tail of a Ferret / 한국실험동물학회지

A chordoma is an uncommon tumor that originates from the remnants of the notochord and most commonly involves the cranial and caudal regions of the axial skeleton. Chordoma has been described in laboratory animals such as dogs, rats, minks, and ferrets. This report describes a case of a chordoma in the tail of a ferret. Grossly, a grayish-white, expansile, subcutaneous soft-tissue mass was observed in the tail. Histopathologically, the mass was a loosely placed, nodular, unencapsulated neoplasm within the dermis. In the mass, tumor lobules were intermingled with fibrous tissues. Fibrous tissues contained abundant extracellular basophilic material that was consistent with mucin. The tumor was composed of a close pack of adipocyte-like vacuolated cells (physaliferous cells). The cells were centrally or eccentrically located round nuclei and eosinophilic cytoplasm with large vacuoles. Immunohistologically, neoplastic cells were positive for vimentin and S-100 protein. Based on histopathologic findings and special staining characteristics, this case was diagnosed as chordoma.

Antifungal Effects of New Synthetic Materials, KAF-200522 and KAF-200522-HCl, on in vitro and in vivo Models / 한국실험동물학회지

KAF-200522 and its chloride form, KAF-200522-HCl, were invented in Chemon inc. as new triazole antifungal agents with excellent activities in vivo and in vitro against wide range of fungi. As a result of in vitro susceptibility measurements, 80% minimum inhibitory concentrations (MIC80) of both test articles against Candida albican sp. and Aspergillus fumigatus sp. were below 0.0156 microg/mL, which were over 4,100 times lower than those of fluconazole against fluconazole resistant C. albican sp. and A. fumigatus sp., and were over 16 times lower than those of amphotericin B against above same fungi. Additionally, against representative dermatophytes, Trichophyton sp., the MIC80s of both test articles were below 0.0156 microg/mL which were over 64 times lower than those of fluconazole and amphotericin B. As in vivo antifungal activities in A. fumigatus sp. infected mouse models, KAF-200522 treatment group at 600 mg/kg showed 80% survival rate which was 2 times higher than that of amphotericin B and showed 13.7 days in the mean survival time (MST) which was about 2.1 times higher than that of amphotericin B. But in KAF-200522-HCl treatment groups, all animals were found dead in contrast to 40% survival rate in amphotericin B treatment group, however dose dependent increases in MST was revealed. In conclusion, antifungal activities of KAF-200522 and its mimics, KAF-200522-HCl in vitro and in vivo were confirmed in this study, therefore the potentiality of the present compounds to be developed into new antifungal drug was expected.

Pharmacokinetic and Toxicokinetic Studies of Potential Antifungal Compounds, KAF-200522 and KAF-200522 . HCl, in Animal Models / 한국실험동물학회지

Recent researches on clinically used triazole antifungal reagents are focused on their pharmacokinetic disadvantage which increases the probability of inducing adverse effects in patients. For this point, in the present laboratory, Chemon Inc., has investigated new antifungal reactive compounds, KAF-200522 and its chloride form, KAF-200522 . HCl, which has a modified triazole structure. Pharmacokinetic data were measured with LC-MS/MS in male mice which were orally treated with the above compounds at 10 mg/kg. Tmax and t1/2 of KAF-200522 . HCl were comparable to KAF-200522, but AUC and Cmax were 1.4 and 1.6 times higher than those of KAF-200522, respectively. In beagle dogs, AUC and Cmax of KAF-200522 . HCl were 2.7 and 1.4 times higher than those of KAF-200522, and t1/2 was 3.5 times higher than that of KAF-200522. Moreover, in beagle dogs, the oral bioavailability value of KAF-200522 . HCl was revealed as 31.0% to contrast to 6.2% of KAF-200522. In 1-week repeated oral treatment toxicity study of KAF-200522 in male rats, inhibition of body weight gain was observed in 120 mg/kg treatment group, and loss of body weight was observed in 600 mg/kg treatment group. In the toxicokinetic study of KAF-200522, no accumulation after the systemic exposure was observed. In conclusion, as to the new antifungal drug development, KAF-200522 . HCl was considered to be advantageous in pharmacokinetic characteristics compared to KAF-200522.

Pneumocystis jiroveci Pneumonia Mimicking Miliary Tuberculosis in a Kidney Transplanted Patient / 결핵및호흡기질환

Bilateral interstitial infiltration in chest radiography, which may be fine granular, reticular or of ground glass opacity, is the typical radiographic findings of Pneumocystis jiroveci pneumonia. Recently, atypical radiographic features, including cystic lung disease, spontaneous pneumothorax or nodular opacity, have been reported intermittently in patients with P. jiroveci pneumonia. We report the case of a 29-year-old woman with a transplanted kidney whose simple chest radiography and HRCT scan showed numerous miliary nodules in both lungs, mimicking miliary tuberculosis (TB). Under the presumptive diagnosis of miliary TB, empirical anti-TB medication was started. However, Grocott methenamine silver nitrate staining of a transbronchial lung biopsy tissue revealed P. jiroveci infection without evidence of TB. These findings suggest that even in TB-endemic area other etiology such as P. jiroveci as well as M. tuberculosis should be considered as an etiology of miliary lung nodules in immunocompromised patients.

The Usefulness of Percutaneous Transhepatic Cholangioscopy for Identifying Malignancies in Distal Commom Bile Duct Strictures

The diagnostic accuracy of percutaneous transhepatic cholangioscopy (PTCS) was compared to that of three radiologic modalities in distal common bile duct (CBD) strictures for the evaluation of clinical application. Ninety-five patients who underwent PTCS for the evaluation of distal CBD strictures (35 malignant and 60 benign) whose masses were not obvious from radiologic imagings were included. Confirmative diagnosis could not be reached by endoscopic retrograde cholangiopancreatography (ERCP) or radiologic findings in all cases. Specific findings on the computed tomography (CT), magnetic resonance cholangiopancreatography (MRCP) and direct cholangiography were analyzed among 68 (25 malignant and 43 benign) out of the 95 patients in order to determine the sensitivity and specificity of three radiologic studies for the diagnosis of malignant distal CBD strictures, and to compare those results with those by a combination of PTCS-guided biopsy and tumor vessel observation on cholangioscopy. The sensitivity/specificity of CT, MRCP and direct cholangiography including ERCP in diagnosing malignant distal CBD strictures were 42.9%/65.8%, 53.3%/58.3%, and 70.8%/47.6% respectively, while it was 96%/100% for the combination of PTCS-guided biopsy and tumor vessel. PTCS is a useful method for differential diagnosis of distal CBD strictures, particularly when it is difficult to distinguish benign from malignant strictures by radiologic studies and when peroral approach is not feasible.

Localization of Heat Shock Protein 72 in Potassium-deprivated Rat Kidney / 대한해부학회지

Heat shock protein 72 (HSP72) appears to play an important role in cell survival in the hypertonic conditions of the renal medulla. The purpose of this study was to examine the effect of potassium deprivation on renal HSP72 expression. Male Sprague-Dawley rats were fed potassium deficient diet for 2 weeks. Kidney tissues were preserved by in vivo perfusion with paraformaldehyde-lysine-periodate (PLP) and processed for Western blot analysis and immunocytochemistry. Serum potassium concentration and urine osmolality decreased in potassium deprivated animals. In control kidneys, HSP72 immunostaining was observed mainly in the inner medulla in almost all cells including the inner medullary collecting duct and papillary surface epithelial cells. In potassium deprivated kidneys, HSP72 expression decreased dramatically in the inner medulla. However, strong HSP72 immunostaining remained in some inner medullary collecting duct and papillary surface epithelial cell. These results demonstrated that potassium deprivation induced down regulation of HSP72 in the renal medulla, at least in part, through cell-specific manner.

Immunolocalization of Aquaporin Water Channels in the Kidney of the Common Marmoset Monkey (Callithrix jacchus) / 대한해부학회지

Aquaporin (AQP) is a water channel protein that is of critical importance in the urinary concentrating process and the regulation of water balance in the kidney, and at least seven AQPs are expressed at distinct sites in the kidney. The common marmoset monkey is widely used as an experimental animal included in the primate order in the filed of renal system. However, nothing is known about the expression AQP in the common marmoset monkey kidney. The purpose of this study was to establish the distribution of AQP-1, AQP-2, AQP-3 and AQP-4 in the common marmoset monkey kidney. We used three male common marmoset monkeys (Callithrix jacchus) ranging in age from 2 to 3 years. AQP-1 was expressed in segments 1, 2 and 3 of the proximal tubule, particularly abundant in segment 1, and also observed in the descending thin limb of the medulla. AQP-2 immunoreactivity was observed in the apical plasma membrane of principal cells in the cortical and medullary collecting ducts. AQP-3 immunostaining was intense in the basolateral plasma membrane of connecting tubules as well as in the cortical and outer medullary collecting ducts. AQP-4 was expressed mainly in the cytoplasm of inner medullary collecting duct cells. These data suggest that AQPs of the common marmoset monkey kidney may play a similar role in urinary concentrating processes and the regulation of water balance to that of AQPs in rats, mice and humans.

The Role of Percutaneous Transhepatic Cholangioscopy in Patients with Hilar Strictures

BACKGROUND/AIMS: Various diagnostic advantages of percutaneous transhepatic cholangioscopy (PTCS) for the determination of the range of tumor and for the characterization of cholangioscopic findings have been reported. The aim of our study is to evaluate the diagnostic and therapeutic role of PTCS in patients with hilar strictures and to investigate its causes. METHODS: We retrospectively studied the medical records and cholangioscopic reports of 177 patients who received PTCS for hilar strictures between January 2000 and December 2005 at Asan Medical Center, Seoul. For each patient, cholagnioscopy, biopsy result, computed tomography (CT) and magnetic resonance cholangiopancreaticography (MRCP), operation, and pathologic reports were collected. RESULTS: Most patients had malignant hilar strictures or biliary papillomatosis while a few had benign hilar strictures. Presence of tumor vessel on PTCS was a useful diagnostic tool since direct observation of the tumor vessel strongly suggested a malignant tumor in the bile duct. The sensitivity of tumor vessel alone was 56.1%, and sensitivity of PTCS biopsy alone was 76.9%. However, sensitivity of biopsy combined with cholangioscopy of the tumor vessel was 88.4%, which was statistically significant compared with biopsy or tumor vessel alone. CONCLUSIONS: PTCS biopsy combined with cholangioscopic observation was useful in differential diagnosis of hilar strictures. PTCS also had a therapeutic role in some patients with incurable malignant hilar lesion.

Immunolocalization of anion exchanger 1 (Band 3) in the renal collecting duct of the common marmoset

The purpose of this study was to determine the expression and distribution of band 3 in the collecting duct and connecting tubules of the kidney of the marmoset monkey (Callithrix jacchus), and to establish whether band 3 is expressed in type A intercalated cells. The intracellular localization of band 3 in the different populations of intercalated cells was determined by double-labeling immunohistochemistry. Immunohistochemical microscopy demonstrated that band 3 is located in the basolateral plasma membranes of all type A intercalated cells in the connecting tubule (CNT), cortical collecting duct (CCD), and outer medullary collecting duct (OMCD) of the marmoset. However, type B intercalated cells and non-A/ non-B intercalated cells did not show band 3 labeling. Electron microscopy of the CNT, CCD and OMCD confirmed the light microscopic observation of the basolateral plasma membrane staining for band 3 in a subpopulation of interacted cells. Basolateral staining was seen on the plasma membrane and small coated vesicles in the perinuclear structure, some of which were located in the Golgi region. In addition, there was no labeling of band 3 in the mitochondria of the CNT, CCD and in OMCD cells. The intensity of the immunostaining of the basolateral membrane was less in the CNT than in the CCD and OMCD. In contrast, band 3 immunoreactivity was greater in the intracellular vesicles of the CNT. From these results, we suggest that the basolateral Cl-/HCO3- exchanger in the monkey kidney is in a more active state in the collecting duct than in the CNT.

Regulation of Urea Transporters by Tonicity-responsive Enhancer Binding Protein

Urea accumulation in the renal inner medulla plays a key role in the maintenance of maximal urinary concentrating ability. Urea transport in the kidney is mediated by transporter proteins that include renal urea transporter (UT-A) and erythrocyte urea transporter (UT-B). UT-A1 and UT-A2 are produced from the same gene. There is an active tonicity-responsive enhancer (TonE) in the promoter of UT-A1, and the UT-A1 promoter is stimulated by hypertonicity via tonicity-responsive enhancer binding protein (TonEBP). The downregulation of UT-A2 raises the possibility that TonEBP also regulates its promoter. There is some evidence that TonEBP regulates expression of UT-A in vivo; (1) during the renal development of the urinary concentrating ability, expression of TonEBP precedes that of UT-A1; (2) in transgenic mice expressing a dominant negative form of TonEBP, expression of UT-A1 and UT-A2 is severely impaired; (3) in treatment with cyclosporine A, TonEBP was significantly downregulated after 28 days. This downregulation involves mRNA levels of UT-A2; (4) in hypokalemic animals, downregulation of TonEBP contributed to the down regulation of UT-A in the inner medulla. These data support that TonEBP directly contributes to the urinary concentration and renal urea recycling by the regulation of urea transporters.