Aquaporin-11 Research Articles

MiR-152–3p facilitates cell adhesion and hepatic metastases in colorectal cancer via targeting AQP11

BackgroundTumor metastasis is a fundamental reason for the poor prognosis of colorectal cancer (CRC) patients. Publications suggested that upregulated Aquaporin-11 (AQP11) can improve CRC patients’ prognoses, but few articles investigated the regulation of AQP11 in CRC cell adhesion and hepatic metastases. Therefore, this study will explore the regulatory mechanism of AQP11 regulating CRC cell adhesion and hepatic metastases at the molecular level. MethodsAQP11 and miR-152–3p expression were analyzed based on The Cancer Genome Atlas-Colon Adenocarcinoma/Rectum Adenocarcinoma (TCGA-COAD/READ) dataset and several other datasets. The upstream genes of AQP11 were predicted via StarBase and MicroRNA Data Integration Portal (mirDIP) databases. The signaling pathways in which the downregulated AQP11 enriched were analyzed via Gene Set Enrichment Analysis (GSEA). Cell proliferation, migration, invasion, and adhesion were respectively tested via western blot, Transwell, and cell adhesion assays. The expression of adhesion-related proteins was determined via enzyme-linked immunosorbent assay (ELISA). AQP11 protein level was examined via western blot, and AQP11 functions were validated via nude mice xenograft experiment. ResultsAQP11 was downregulated in CRC, and the upregulated AQP11 remarkably repressed cell proliferation, migration, invasion, and adhesion. The silenced AQP11 notably facilitated the above cell functions in CRC. In addition, AQP11 was negatively regulated by miR-152–3p. In vitro cellular assays revealed that miR-152–3p, by targeting AQP11, facilitated CRC cell proliferation, migration, invasion, and adhesion. An in vivo assay suggested that AQP11 could notably repress CRC growth and metastasis. ConclusionThe above results confirmed that miR-152–3p/AQP11 axis could regulate CRC hepatic metastases and would be a promising target in anti-cancer treatment.

Aquaporin 11 alleviates retinal Müller intracellular edema through water efflux in diabetic retinopathy

Retinal Müller glial dysfunction and intracellular edema are important mechanisms leading to diabetic macular edema (DME). Aquaporin 11 (AQP11) is primarily expressed in Müller glia with unclear functions. This study aims to explore the role of AQP11 in the pathogenesis of intracellular edema of Müller glia in diabetic retinopathy (DR). Here, we found that AQP11 expression, primarily located at the endfeet of Müller glia, was down-regulated with diabetes progression, accompanied by intracellular edema, which was alleviated by intravitreal injection of lentivirus-mediated AQP11 overexpression. Similarly, intracellular edema of hypoxia-treated rat Müller cell line (rMC-1) was aggravated by AQP11 inhibition, while attenuated by AQP11 overexpression, accompanied by enhanced function in glutamate metabolism and reduced cell death. The down-regulation of AQP11 was also verified in the Müller glia from the epiretinal membranes (ERMs) of proliferative DR (PDR) patients. Mechanistically, down-regulation of AQP11 in DR was mediated by the HIF-1α-dependent and independent miRNA-AQP11 axis. Overall, we deciphered the AQP11 down-regulation, mediated by miRNA-AQP11 axis, resulted in Müller drainage dysfunction and subsequent intracellular edema in DR, which was partially reversed by AQP11 overexpression. Our findings propose a novel mechanism for the pathogenesis of DME, thus targeting AQP11 regulation provides a new therapeutic strategy for DME.

The therapeutic prospect of zinc oxide nanoparticles in experimentally induced diabetic nephropathy

ABSTRACT Diabetic nephropathy (DN) is the most frequent cause of end-stage renal failure. Zinc oxide nanoparticles (ZnO-NPs) are promising antidiabetic agents. Our aim was to evaluate the prospective efficacy of ZnO-NPs in treating DN in streptozotocin-induced diabetic rats. Rats were randomly dispersed into three sets: control group, DN group and DN + ZnO-NPs group. ZnO-NPs were given at a dose of 10 mg/kg/day by oral gavage for 4 weeks. Urine and blood samples were processed for biochemical analyses. Kidney samples were managed for light and electron microscopy studies. Immune histochemical staining of P53, aquaporin11 (AQP11) and mechanistic target of rapamycin (mTOR) were performed. Gene analyses of nephrin, podocin, beclin-1, LC3 and p62 were done. Administration of ZnO-NPs ameliorated the functional and histopathological alterations of the kidney in a rat model of diabetic nephropathy. ZnO-NPs retained the constancy of the glomerular filtration barrier and restored almost normal renal structure. This was confirmed by upregulation of mRNA expression of podocyte markers (nephrin and podocin) and AQP11 immune histochemical expression in the renal tubules. The beneficial outcomes of ZnO-NPs might be attributed to activation of autophagy through inhibiting mTOR signaling pathway. ZnO-NPs enhanced beclin-1 and LC3 mRNA expressions and reduced p62 mRNA expression. ZnO-NPs also exerted anti-apoptotic potential (evidenced by the decrease in p53 immune expression), anti-inflammatory and anti-oxidant effect [endorsed by suppression of serum cyclooxygenase-2 (COX-2) enzyme activity, tissue nuclear factor kappa beta (NF-κB) level and blood hypoxia-inducible factors (HIF-1α) level]. These results may point the way to an effective therapy of DN. Abbreviations: AQP11 Aquaporin11; BUN: Blood urea nitrogen; COX-2: Cyclooxygenase-2; DAB: 3, 3’-diaminobenzidine; DM: Diabetes mellitus; DN: Diabetic nephropathy; ELISA: Enzyme-linked immunosorbent assay; H&E: Hematoxylin & eosin; HIF-1α: Hypoxia-inducible factors; iNOS: inducible nitric oxide synthase; LC3: Microtubule-associated protein 1 light chain 3; mTOR: Mechanistic target of rapamycin; NF-κB: Nuclear factor kappa beta; NPs: Nanoparticles; PAS: Periodic acid Schiff; PCR: Polymerase chain reaction; PGE2: Prostaglandin E2; ROS: Reactive oxygen species; STZ: Streptozotocin; X ± SEM: Mean ± standard error of means; Zn: Zinc; ZnO-NPs: Zinc oxide nanoparticles.

Aquaporin-11 Contributes to TGF-β1-Induced Endoplasmic Reticulum Stress in Human Visceral Adipocytes: Role in Obesity-Associated Inflammation.

Aquaporin-11 (AQP11) is expressed in human adipocytes, but its functional role remains unknown. Since AQP11 is an endoplasmic reticulum (ER)-resident protein that transports water, glycerol, and hydrogen peroxide (H2O2), we hypothesized that this superaquaporin is involved in ER stress induced by lipotoxicity and inflammation in human obesity. AQP11 expression was assessed in 67 paired visceral and subcutaneous adipose tissue samples obtained from patients with morbid obesity and normal-weight individuals. We found that obesity and obesity-associated type 2 diabetes increased (p < 0.05) AQP11 mRNA and protein in visceral adipose tissue, but not subcutaneous fat. Accordingly, AQP11 mRNA was upregulated (p < 0.05) during adipocyte differentiation and lipolysis, two biological processes altered in the obese state. Subcellular fractionation and confocal microscopy studies confirmed its presence in the ER plasma membrane of visceral adipocytes. Proinflammatory factors TNF-α, and particularly TGF-β1, downregulated (p < 0.05) AQP11 mRNA and protein expression and reinforced its subcellular distribution surrounding lipid droplets. Importantly, the AQP11 gene knockdown increased (p < 0.05) basal and TGF-β1-induced expression of the ER markers ATF4 and CHOP. Together, the downregulation of AQP11 aggravates TGF-β1-induced ER stress in visceral adipocytes. Owing to its “peroxiporin” properties, AQP11 overexpression in visceral fat might constitute a compensatory mechanism to alleviate ER stress in obesity.

MiR-27b-mediated suppression of aquaporin-11 expression in hepatocytes reduces HCV genomic RNA levels but not viral titers

BackgroundMicroRNAs (miRNAs) have gained much attention as cellular factors regulating hepatitis C virus (HCV) infection. miR-27b has been shown to regulate HCV infection in the hepatocytes via various mechanisms that have not been fully elucidated. In this study, therefore, we examined the mechanisms of miR-27b-mediated regulation of HCV infection.MethodsIn silico screening analysis, transfection with miR-27b mimic, and a cell-based reporter assay were performed to identify miR-27b target genes. Cell cultured-derived HCV (HCVcc) was added to Huh7.5.1 cells knocked down for aquaporin (AQP) 11 (AQP11) and overexpressing AQP11. HCV replication levels were evaluated by real-time RT-PCR analysis of HCVcc genome.ResultsInfection of Huh7.5.1 cells with HCVcc resulted in significant elevation in miR-27b expression levels. In silico analysis revealed that AQP11, which is an AQP family member and is mainly localized in the endoplasmic reticulum (ER), was a candidate for a target gene of miR-27b. Transfection of a miR-27b mimic significantly reduced AQP11 expression, but a cell-based reporter assay demonstrated that miR-27b did not suppress the expression of a reporter gene containing the 3′-untranslated region of the AQP11 gene, suggesting that miR-27b indirectly suppressed AQP11 expression. AQP11 expression levels were significantly reduced by infection with HCVcc in Huh7.5.1 cells. Knockdown and over-expression of AQP11 significantly reduced and increased HCVcc genome levels in the cells following infection, respectively, however, AQP11 knockdown did not show significant effects on the HCVcc titers in the culture supernatants.ConclusionsThese results indicated that HCV infection induced a miR-27b-mediated reduction in AQP11 expression, leading to a modest reduction in HCV genome levels in the cells, not HCV titers in the culture supernatants.

Involvement of the NADPH oxidase 2 pathway in renal oxidative stress in Aqp11-/- mice

Aquaporin-11 (AQP11) is an intracellular AQP. Several studies with Aqp11-/- mice have shown that AQP11 has a role in normal development of the kidney after birth. Our previous studies have suggested that alteration of oxygen homeostasis may be involved in the kidney injury caused by AQP11 deficiency, although the underlying mechanism is largely unknown. To clarify this issue, we examined genes that are related to oxygen homeostasis in Aqp11-/- mice. Among 62 genes that are involved in oxygen homeostasis, 35 were upregulated by more than 2-fold in Aqp11-/- mice in comparison with wild-type mice. Pathway analysis using these genes extracted the pathway responsible for production of reactive oxygen species in macrophages. As expression of the genes involved in the NADPH oxidase 2 (NOX2) complex was dramatically increased by more than 14-fold, we further analyzed NOX2 at the protein level. Immunoblotting analysis demonstrated a dramatic increase of NOX2 protein in the kidney of Aqp11-/- mice, and immunohistochemistry showed that NOX2 protein and a marker protein for macrophages were increased in the renal interstitium. These results indicate that NOX2-induced oxidative stress accompanied by macrophage infiltration plays an important role in alteration of oxygen homeostasis in Aqp11-/- mice.

MiR-27a-3p protects against blood–brain barrier disruption and brain injury after intracerebral hemorrhage by targeting endothelial aquaporin-11

Previous studies have reported that miR-27a-3p is down-regulated in the serum of patients with intracerebral hemorrhage (ICH), but the implication of miR-27a-3p down-regulation in post-ICH complications remains elusive. Here we verified miR-27a-3p levels in the serum of ICH patients by real-time PCR and observed that miR-27a-3p is also significantly reduced in the serum of these patients. We then further investigated the effect of miR-27a-3p on post-ICH complications by intraventricular administration of a miR-27a-3p mimic in rats with collagenase-induced ICH. We found that the hemorrhage markedly reduced miR-27a-3p levels in the hematoma, perihematomal tissue, and serum and that intracerebroventricular administration of the miR-27a-3p mimic alleviated behavioral deficits 24 h after ICH. Moreover, ICH-induced brain edema, vascular leakage, and leukocyte infiltration were also attenuated by this mimic. Of note, miR-27a-3p mimic treatment also inhibited neuronal apoptosis and microglia activation in the perihematomal zone. We further observed that the miR-27a-3p mimic suppressed the up-regulation of aquaporin-11 (AQP11) in the perihematomal area and in rat brain microvascular endothelial cells (BMECs). Moreover, miR-27a-3p down-regulation increased BMEC monolayer permeability and impaired BMEC proliferation and migration. In conclusion, miR-27a-3p down-regulation contributes to brain edema, blood-brain barrier disruption, neuron loss, and neurological deficits following ICH. We conclude that application of exogenous miR-27a-3p may protect against post-ICH complications by targeting AQP11 in the capillary endothelial cells of the brain.

Aquaporin 11 rs2276415 variant and progression of chronic kidney disease.

The Aquaporin 11 (AQP11) rs2276415 variant has been implicated in kidney disease in Type 2 diabetes. Association of the AQP11 variant with chronic kidney disease (CKD) beyond diabetic nephropathy is unknown, with no studies reported in the Chinese population. We explored the risk of CKD progression associated with the AQP11 rs2276415 variant in a population-based study in China. We conducted a prospective cohort study of 620 participants with CKD (Stages 2-5 and who were not receiving dialysis) at the Nephrology Center of First Affiliated Hospital of Jiaxing University between July 2011 and December 2014 and followed up for 3 years. Incident CKD progression, defined as an increase in creatinine levels of at least 0.4 mg/dL (35 µmol/L) above baseline or maintenance dialysis initiation or transplantation, was examined by AQP11 genotypes. During the follow-up period, CKD progression developed in 170 individuals. Cumulative events-free survival was significantly dependent on AQP11 genotypes with an apparent gene-dose effect (log-rank P < 0.001). Adjusting for sex, age and major CKD risk factors, the A allele of AQP11 gene (GA + AA) increased the risk of CKD progression by 1.92 (95% confidence interval 1.31- 2.84). The AQP11 rs2276415 variant predicts CKD progression in the Chinese population, independent of traditional risk factors. Exploring the pathways mediating the association may shed light on novel therapeutic targets in the pathophysiology of CKD.

Abstract 2620: Aquaporin 11 as a new predictive biomarker of overall survival and platinum-based chemotherapy response in lung adenocarcinoma patients

Abstract Background: Biomarkers predictive of response to chemotherapy are critically needed for the precise selection of treatment protocols in lung adenocarcinoma (LUAD). Aquaporins (AQPs), transmembrane water channels, are emerging targets in cancer. Recently discovered, non-ubiquitous family member aquaporin 11 (AQP11), a tissue-specific endoplasmic reticulum (ER) resident, was identified as a cellular pro-survival factor implicated in the maintenance of ER homeostasis. AQP11 is mapped to 11q13-q14 amplicon harboring oncogenic drivers and associated with poor prognosis in cancer patients. We recently showed that high AQP11 expression is an in-vitro therapeutic biomarker of cisplatin therapy, which directly interferes with AQP11 functional structure. In addition, silencing of AQP11 expression in human lung cancer cell lines significantly increased response to cisplatin treatment. We hypothesized that LUAD tumors expressing high levels of AQP11 depend on AQP11-mediated cytoprotection and would be more responsive to platinum-based chemotherapy targeting AQP11. Method: We downloaded and curated matched mRNA expression, survival, and drug response data from The Cancer Genome Atlas (TCGA) LUAD dataset (N=369). Results: Analysis of PRECOG and TCGA databases showed that high AQP11 mRNA expression is negatively prognostic in patients with LUAD. TCGA LUAD cases were categorized by AQP11 mRNA levels into high and low expression (high = AQP11 mRNA expression mean + 1 standard deviation). Patients with high tumor AQP11 mRNA expression (10.3%) had significantly worse overall survival (OS) compared to patients with low AQP11 expression (p=0.0015). An analysis of patients treated with platinum-based chemotherapy (N=74) showed that patients with high AQP11 mRNA expression (7%) had significantly higher OS then patients with LUAD expressing low levels of AQP11 (p=0.0263). Conclusions: This study identifies AQP11 as a new biomarker of OS and chemotherapy in LUAD patients. It is conceivable that lung tumors expressing high levels of AQP11 are dependent on its function and elevated AQP11 expression renders tumor resistance to microenvironment and therapy-induced stress and associates with lower OS of patients. At the same time, as cisplatin efficiently targets AQP11 functional multimeric structure, these AQP11-depending tumors are more prone to platinum based chemotherapy. This study provides a rationale for combination anti-AQP11 and chemotherapy in LUAD tumors with high AQP11 expression. Citation Format: Michael Sharpnack, David P. Carbone, Mikhail M. Dikov, Elena E. Tchekneva. Aquaporin 11 as a new predictive biomarker of overall survival and platinum-based chemotherapy response in lung adenocarcinoma patients [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2620.

Aquaporin 11 is related to cryotolerance and fertilising ability of frozen-thawed bull spermatozoa.

Aquaporins (AQPs) are channel proteins involved in the transport of water and solutes across biological membranes. In the present study we identified and localised aquaporin 11 (AQP11) in bull spermatozoa and investigated the relationship between the relative AQP11 content, sperm cryotolerance and the fertilising ability of frozen-thawed semen. Bull ejaculates were classified into two groups of good and poor freezability and assessed through immunofluorescence and immunoblotting analyses before and after cryopreservation. AQP11 was localised throughout the entire tail and along the sperm head. These findings were confirmed through immunoblotting, which showed a specific band of approximately 50 kDa corresponding to AQP11. The relative amount of AQP11 was significantly (P<0.05) higher in both fresh and frozen-thawed spermatozoa from bull ejaculates with good freezability compared with those with poorer freezability. In addition, in vitro oocyte penetration rates and non-return rates 56 days after AI were correlated with the relative AQP11 content in fresh spermatozoa. In conclusion, AQP11 is present in the head and tail of bull spermatozoa and its relative amount in fresh and frozen-thawed spermatozoa is related to the resilience of the spermatozoa to withstand cryopreservation and the fertilising ability of frozen-thawed spermatozoa. Further research is needed to elucidate the actual role of sperm AQP11 in bovine fertility.

Proteomic analysis of AQP11-null kidney: Proximal tubular type polycystic kidney disease

Autosomal Dominant Polycystic Kidney Disease (ADPKD) is caused by the mutation of polycystins (PC-1 or PC-2), in which cysts start from the collecting duct to extend to all nephron segments with eventual end stage renal failure. The cyst development is attenuated by a vasopressin V2 receptor antagonist tolvaptan which, however, will not affect proximal tubule cysts devoid of V2 receptor. Aquaporin-11 (AQP11) is expressed selectively in the proximal tubule of the kidney and AQP11-null kidneys have a disruptive PC-1 trafficking to the plasma membrane to develop polycystic kidneys. Here, we analyzed AQP11-null kidneys at the beginning of cyst formation by quantitative proteomic analysis using Tandem Mass Tag (TMT). Among ~ 1200 identified proteins, 124 proteins were differently expressed by > 1.5 or < 0.8 fold change. A pancreatic stone inhibitor or a growth factor, lithostathine-1 (Reg1) was most enhanced by 5 folds which was confirmed by western blot, while mitochondria-related proteins were downregulated. The identified proteins will be new target molecules for the treatment of proximal tubular cysts and helpful to explore the functional roles of AQP11 in the kidney.

Abstract 5468: Expression of aquaporin 11 as a potential predictor of cisplatin sensitivity

Abstract Platinum-based combination is a standard of care treatment for lung cancer patients. Accumulating evidence indicates that aquaporins are emerging targets in cancer. Aquaporin 11 (AQP11), a non-ubiquitous member of aquaporins family, is an endoplasmic reticulum (ER)-specific water channel mostly present in epithelial cells and is implicated in the maintenance of ER homeostasis. In our recent publications, we demonstrated that under the stress the reduction of AQP11 expression is a pro-apoptotic factor in normal epithelial cells. We revealed that under normal conditions AQP11 is heavily S-nitrosylated forming functionally important multimeric structures (&amp;gt; 1000 kDa), whereas cisplatin treatment interferes with AQP11 causing its structural and post-translational modification. We hypothesized that if tumor cells express AQP11 then cells with lower levels of AQP11 are not protected from cisplatin-associated ER stress and develop higher sensitivity to drug treatment. In normal lung AQP11 is expressed at low levels. We evaluated the expression of AQP11 in lung cancer cells to determine whether the AQP11 expression correlates with cisplatin sensitivity and whether lower AQP11 expression in lung tumor associates with positive overall survival in patients with lung adenocarcinoma. A strong link between the level of AQP11 protein expression and cell sensitivity to CP was detected using MTT assay. Screening lung cancer cell lines we found that all tested cancer cell lines expressed AQP11 protein at various levels. Western blot of stress markers showed that cisplatin-treated cells with higher AQP11 expression had lowered cellular and ER stress. Reduction of AQP11 expression using shRNA AQP11 silencing in cispaltin-resistant A549 and HCC827 cell lines, resulted in the significantly increased up to 3-fold sensitivity to cisplatin compared with control shRNA transfected or parental non-transfected cells (p&amp;lt;0.001). In sensitive H460 cells, knocking down AQP11 did not change sensitivity to cisplatin. TCGA database analysis of previously untreated lung adenocarcinoma, detected 13% tumors with elevated AQP11 mRNA expression. Lower AQP11 expression was significantly associated with higher OS and higher median survival rate (52.5 vs. 34.47 mo) than in patients with high AQP11 expression (p&amp;lt;0.05). AQP11 gene is located within oncogenic 11q13-q14 amplicon, which is a common aberration in solid tumors associated with poor prognosis. The AQP11 is a pro-survival factor protecting tumor cells from cisplatin-induced stress. Low AQP11 expression associates with higher OS in lung adenocarcinoma patients and with higher cispaltin sensitivity in lung cancer cell. The ER stress aggravation via interference with AQP11 could become a prospective therapeutic approach in anti-tumor treatment. Citation Format: Jason V. Evans, Anwari Akhter, David P. Carbone, Mikhail M. Dikov, Elena E. Tchekneva. Expression of aquaporin 11 as a potential predictor of cisplatin sensitivity [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 5468. doi:10.1158/1538-7445.AM2017-5468

P2.03b-082 AQP11 as a Novel Factor of Lung Cancer Cell Resistance to Cisplatin: Topic: Biomarkers

Platinum-based combination treatment is a standard of care treatment for lung cancer patients. Aquaporin 11 (AQP11), a non-ubiquitous member of aquaporins family, is an ER-specific water channel mostly present in epithelial cells and is implicated in the maintenance of ER homeostasis. We demonstrated that the induction of AQP11 expression is a pro-survival factor in normal epithelial cells under the stress and that cispaltin interacts with AQP11, as a non-DNA target, causing AQP11 structural and post-translational modification. This study evaluated the expression of AQP11 in lung cancer cells to determine whether the AQP11 expression correlates with cisplatin resistance and whether AQP11 expression in lung tumor associates with overall survival in patients with lung adenocarcinoma. 18 lung cancer cell lines were tested for AQP11 expression using Western blotting. Growth inhibitory effect of cisplatin was examined using MTT assay and IC50 values were determined. AQP11 knockdown cell lines were generated using a lentiviral vector with shRNA targeting AQP11; efficiency of AQP11 blockage was assessed by Western blotting. We analyzed TCGA database to identify connection between AQP11 mRNA expression and overall survival (OS) in lung adenocarcinoma patients. All tested cancer cell lines expressed AQP11 and correlation analysis revealed significant association of AQP11 expression with cisplatin resistance (Spearman’s r=0.82, p=0.008). Analysis of stress markers showed that cisplatin-treated cells with higher AQP11 expression had lower stress. Using shRNA, we knocked down AQP11 in cispaltin resistant A549 and HCC827 cells and cisplatin sensitive H460 cells. Resulting knockdown A549 and HCC827 cells became 2.6- to 2.9-fold more sensitive to cisplatin compared to parental and control vector transduced cells. In sensitive H460 cells, knocking down AQP11 did not change sensitivity to cisplatin. Results suggest that high expression AQP11 contributes to cisplatin resistance. TCGA database analysis of previously untreated lung adenocarcinoma, detected 13% tumors with elevated AQP11 mRNA expression (6.18±0.55 vs. 4.28±0.77, p<0.001). Increased AQP11 expression was significantly associated with decreased OS. These patients showed lower median survival rate of 34.47 versus 52.5 months in patients with low AQP11 expression (longrank test p<0.05). AQP11 is the cispaltin non-DNA target that may significantly contribute to the development of resistance. High AQP11 level is a pro-survival factor protecting tumor cells from cisplatin-induced stress. High AQP11 expression associates with lower OS in lung adenocarcinoma patients and with cispaltin resistance in lung cancer cell lines. With further validation, AQP11 level might be a predictor of cisplatin resistance and overall survival in lung cancer.

Enhanced Autophagy in Polycystic Kidneys of AQP11 Null Mice.

Aquaporin-11 (AQP11) is an intracellular water channel expressed at the endoplasmic reticulum (ER) of the proximal tubule. Its gene disruption in mice leads to intracellular vacuole formation at one week and the subsequent development of polycystic kidneys by three weeks. As the damaged proximal tubular cells with intracellular vacuoles form cysts later, we postulated that autophagy may play a role in the cyst formation and examined autophagy activity before and after cyst development in AQP11(−/−) kidneys. PCR analysis showed the increased expression of the transcript encoding LC3 (Map1lc3b) as well as other autophagy-related genes in AQP11(−/−) mice. Using green fluorescent protein (GFP)-LC3 transgenic mice and AQP11(−/−) mice, we found that the number of GFP-LC3–positive puncta was increased in the proximal tubule of AQP11(−/−) mice before the cyst formation. Interestingly, they were also observed in the cyst-lining epithelial cell. Further PCR analyses revealed the enhanced expression of apoptosis-related and ER stress–related caspase genes before and after the cyst formation, which may cause the enhanced autophagy. These results suggest the involvement of autophagy in the development and maintenance of kidney cysts in AQP11(−/−) mice.

Temporal deletion of Aqp11 in mice is linked to the severity of cyst-like disease.

Aquaporin 11 (AQP11) is a channel protein with unknown biological function that is expressed in multiple tissues, including the kidney proximal tubule (PT) epithelium. Constitutive deletion of Aqp11 in mice (Aqp11-/-) results in early postnatal vacuolization in the PT and development of apparent cysts at 2 wk of age. Electron microscopy of adult Aqp11-/- mouse PT cells revealed a dilated rough endoplasmic reticulum. These changes may cause renal failure and premature death. This study examined 1) whether postnatal deletion of Aqp11 affects PT injury and cyst formation, 2) the temporal role of Aqp11 deletion on cyst development, and 3) the nature of apparent cysts. Tamoxifen-inducible Aqp11-/- mice were generated (Ti-Aqp11-/-). Deletion of Aqp11 at postnatal days (P) P2, P4, P6, P8, and P12 was investigated. Deranged renal development, especially in kidney cortex, PT cell vacuolization, and apparent tubular cysts developed only in mice where Aqp11 gene disruption was induced until P8. Aqp11 gene deletion from P12 onward did not result in a clear deficiency in renal development, PT injury, or cyst formation. Intraperitoneal injection of biotinylated-dextran (10 kDa) into adult mice resulted in extensive endocytic dextran uptake in both cystic Aqp11-/- and control PT epithelium, respectively. This suggests that apparent cysts are not membrane-enclosed structures but represent PT dilations. We conclude that Aqp11-/- mice develop cyst-like dilated proximal tubules without documented cysts at time of death.

Aquaporin-11 (AQP11) Expression in the Mouse Brain.

Aquaporin-11 (AQP11) is an intracellular aquaporin expressed in various tissues, including brain tissues in mammals. While AQP11-deficient mice have developed fatal polycystic kidneys at one month old, the role of AQP11 in the brain was not well appreciated. In this study, we examined the AQP11 expression in the mouse brain and the brain phenotype of AQP11-deficient mice. AQP11 messenger ribonucleic acid (mRNA) and protein were expressed in the brain, but much less than in the thymus and kidney. Immunostaining showed that AQP11 was localized at the epithelium of the choroid plexus and at the endothelium of the brain capillary, suggesting that AQP11 may be involved in water transport at the choroid plexus and blood-brain barrier (BBB) in the brain. The expression of AQP4, another brain AQP expressed at the BBB, was decreased by half in AQP11-deficient mice, thereby suggesting the presence of the interaction between AQP11 and AQP4. The brain of AQP11-deficient mice, however, did not show any morphological abnormalities and the function of the BBB was intact. Our findings provide a novel insight into a water transport mechanism mediated by AQPs in the brain, which may lead to a new therapy for brain edema.

Aquaporin 11, a regulator of water efflux at retinal Müller glial cell surface decreases concomitant with immune-mediated gliosis.

BackgroundMüller glial cells are important regulators of physiological function of retina. In a model disease of retinal inflammation and spontaneous recurrent uveitis in horses (ERU), we could show that retinal Müller glial cells significantly change potassium and water channel protein expression during autoimmune pathogenesis. The most significantly changed channel protein in neuroinflammatory ERU was aquaporin 11 (AQP11). Aquaporins (AQP, 13 members) are important regulators of water and small solute transport through membranes. AQP11 is an unorthodox member of this family and was assigned to a third group of AQPs because of its difference in amino acid sequence (conserved sequence is only 11 %) and especially its largely unknown function.MethodsIn order to gain insight into the distribution, localization, and function of AQP11 in the retina, we first developed a novel monoclonal antibody for AQP11 enabling quantification, localization, and functional studies.ResultsIn the horse retina, AQP11 was exclusively expressed at Müller glial cell membranes. In uveitic condition, AQP11 disappeared from gliotic Müller cells concomitant with glutamine synthase. Since function of AQP11 is still under debate, we assessed the impact of AQP11 channel on cell volume regulation of primary Müller glial cells under different osmotic conditions. We conclude a concomitant role for AQP11 with AQP4 in water efflux from these glial cells, which is disturbed in ERU. This could probably contribute to swelling and subsequent severe complication of retinal edema through impaired intracellular fluid regulation.ConclusionsTherefore, AQP11 is important for physiological Müller glia function and the expression pattern and function of this water channel seems to have distinct functions in central nervous system. The significant reduction in neuroinflammation points to a crucial role in pathogenesis of autoimmune uveitis.

Aberrant glycosylation and localization of polycystin-1 cause polycystic kidney in an AQP11 knockout model.

We previously reported that disruption of the aquaporin-11 (AQP11) gene in mice resulted in cystogenesis in the kidney. In this study, we aimed to clarify the mechanism of cystogenesis in AQP11(-/-) mice. To enable the analyses of AQP11 at the protein level in vivo, AQP11 BAC transgenic mice (Tg(AQP11)) that express 3×HA-tagged AQP11 protein were generated. This AQP11 localized to the endoplasmic reticulum (ER) of proximal tubule cells in Tg(AQP11) mice and rescued renal cystogenesis in AQP11(-/-) mice. Therefore, we hypothesized that the absence of AQP11 in the ER could result in impaired quality control and aberrant trafficking of polycystin-1 (PC-1) and polycystin-2 (PC-2). Compared with kidneys of wild-type mice, AQP11(-/-) kidneys exhibited increased protein expression levels of PC-1 and decreased protein expression levels of PC-2. Moreover, PC-1 isolated from AQP11(-/-) mice displayed an altered electrophoretic mobility caused by impaired N-glycosylation processing, and density gradient centrifugation of kidney homogenate and in vivo protein biotinylation revealed impaired membrane trafficking of PC-1 in these mice. Finally, we showed that the Pkd1(+/-) background increased the severity of cystogenesis in AQP11(-/-) mouse kidneys, indicating that PC-1 is involved in the mechanism of cystogenesis in AQP11(-/-) mice. Additionally, the primary cilia of proximal tubules were elongated in AQP11(-/-) mice. Taken together, these data show that impaired glycosylation processing and aberrant membrane trafficking of PC-1 in AQP11(-/-) mice could be a key mechanism of cystogenesis in AQP11(-/-) mice.

Human aquaporin-11 is a water and glycerol channel and localizes in the vicinity of lipid droplets in human adipocytes.

For a long time Aquaporin-7 has been the only aquaporin associated with the adipose tissue, and its dysregulation has been linked to the underlying mechanisms of obesity. However, the presence of alternative glycerol channels within the adipose tissue has been postulated, which has prompted us to the search of alternate glycerol transport routes in adipocytes. In view of this, it is hypothesized that Aquaporin-11 (AQP11) would have a role in adipocyte cell biology. The expression, the localization and the function of human AQP11 (hAQP11) in cultured differentiated adipocytes were investigated. Gene expression analysis revealed the presence of AQP11 in both subcutaneous and visceral human mature adipocytes. It is found that hAQP11 is primarily located intracellularly in human adipocytes and partially colocalizes with perilipin, pointing towards AQP11 preferential location in the vicinity of lipid droplets. Overexpression of hAQP11 in 3T3-L1 adipocytes enabled to validate its function as a water channel and reveal its glycerol permeation activity. hAQP11 permeates both water and glycerol, localizing in the vicinity of lipid droplets in human adipocytes.

Aquaporin 11 deletion results in induceable proximal tubule injury in response to metabolic challenge (LB837)

Aquaporin 11 (AQP11) is a channel protein with unknown biological function expressed intracellularly in multiple tissues, among others in kidney proximal tubule epithelium. The neonate Aqp11 gene knockout (KO) mice show injury of the proximal tubule (PT) cells, manifesting as dilatation of RER cisterns, leading to apoptosis of the PT epithelial cells (Morishita et al, Mol Cell Biol. 2005). The mice develop cortical cysts within the first weeks of life and die due to kidney failure. It is unclear if the kidney failure is caused by functional insufficiency of the PT in the absence of AQP11, or by the abnormal development of the nephron and resulting structural malformation of the kidney. We have developed an inducible Aqp11 KO mouse model, where we can temporally control the time point of Aqp11 gene disruption by injection of tamoxifen. We performed microscopic analyses of the PT morphology after induction of AQP11 mutation in unchallenged mice and after different metabolic challenges (fasting/re‐feeding, administration of free amino acids). In mice where AQP11 deletion was induced after the completion of kidney development we observe no cellular damage of PT cells and no cyst formation for up to 4 months after disruption of the Aqp11 gene. When the mice are metabolically stressed (fasting/re‐feeding, administration of free amino acids) the PT cells suffer acute injury with development of giant vacuoles, similar to those observed in neonatal total AQP11 KO mice. In conclusion, we propose that AQP11 function is necessary for proper PT cell function during states of increased protein/amino acid supply, such as during the neonatal period, when mice feed on protein‐rich milk, and in adults subject to high amino acid metabolism challenge. We hypothesize that continuous PT injury during neonatal period results in abnormal development of more distal tubule segments and cyst formation, possibly by impairment of fluid flow in the tubule.