• Development and Reproduction
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• v.24 no.3
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• pp.177-185
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• 2020

Although many aquaporin (AQP) transcripts have been demonstrated to express in the female reproductive tract, the defined localizations and functions of AQP subtype proteins remain unclear. In this study, we investigated the expression of AQP1, AQP3, AQP5, AQP6, and AQP9 proteins in female reproductive tract of mouse and characterized their precise localizations at the cellular and subcellular levels. Immunofluorescence analyses for AQP1, AQP3, AQP6, and AQP9 showed that these proteins were abundantly expressed in female reproductive tract and that intense immunoreactivities were observed in mucosa epithelial cells with a subtype-specific pattern. The most abundant aquaporin in both vagina and uterine cervix was AQP3. Each of AQP1, AQP3, AQP6, and AQP9 exhibited its distinct distribution in stratified squamous or columnar epithelial cells. AQP9 expression was predominant in oviduct and ovary. AQP1, AQP3, AQP6, and AQP9 proteins were mostly seen in apical membrane of ciliated epithelial cells of the oviduct as well as in both granulosa and theca cells of ovarian follicles. Most of AQP subtypes were also expressed in surface epithelial cells and glandular cells of endometrium in the uterus, but their expression levels were relatively lower than those observed in the vagina, uterine cervix, oviduct and ovary. This is the first study to investigate the expression and localization of 5 AQP subtype proteins simultaneously in female reproductive tract of mouse. Our results suggest that AQP subtypes work together to transport water and glycerol efficiently across the mucosa epithelia for lubrication, proliferation, energy metabolism and pH regulation in female reproductive tract.

• International Journal of Oral Biology
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• v.45 no.4
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• pp.211-217
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• 2020

Molecular mimicry is the most common mechanism that breaches self-tolerance. We previously identified autoantibodies to aquaporin-5 (AQP5) in the sera of patients with Sjögren's syndrome and found that the aquaporin of Prevotella melaninogenica (PmAqp), an oral commensal, is highly homologous to human AQP5. This study aimed to test whether PmAqp can induce anti-AQP5 autoantibodies via molecular mimicry. From the amino acid sequence of PmAqp, an immunizing peptide; i.e., PmE-L, was designed, which contained both the B cell epitope "E" and T cell epitope. C57BL/6 and BALB/c mice were subcutaneously immunized with linear or cyclic forms of PmE-L emulsified in incomplete Freund's adjuvant. The concentrations of the antibodies in sera were measured using enzyme-linked immunosorbent assays. Both linear and cyclic PmE-L induced high levels of antibodies against not only the immunized peptides but also autoantibodies against AQP5E and antibodies against PmE, a Pm homolog of AQP5E. In C57BL/6 mice; however, the cyclic form of PmE-L was more efficient than the linear form in inducing autoantibodies against AQP5E that contained a cyclic epitope. The levels of anti-PmE antibodies and anti-AQP5E autoantibodies showed a strong positive correlation (r = 0.95, p < 0.0005), suggesting molecular mimicry. Collectively, the mice produced anti-AQP5E autoantibodies in response to a PmAqp-derived peptide. This model proved to be useful for studying the mechanisms of autoantibody production by molecular mimicry.

• The Korean Journal of Physiology and Pharmacology
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• v.3 no.2
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• pp.157-164
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• 1999

To determine molecular mechanisms of Aquaporin-CD (AQP2) gene regulation, the promoter region of the AQP2 gene was examined by transiently transfecting a promoter-luciferase reporter fusion gene into mouse renal collecting duct cell lines such as mIMCD-3, mIMCD-K2, and M-1 cells, and NIH3T3 mouse embryo fibroblast cells. PCR-Southern analysis reveals that mIMCD-3 and mIMCD-K2 cells express AQP2, but M-1 and NIH3T3 cells do not, and that the treatment with cpt-cAMP $(400\;{\mu}M)$) or forskolin/isobutylmethylxanthine (IBMX) increased the AQP2 expression in IMCD cells. In both IMCD and NIH3T3 cells, the constructs containing the promoter of AQP2 gene showed promoter activities, indicating lack of tissue-specific element in the 1.4 kb 5'-flanking region of the mouse AQP2 gene. Luciferase activity in the IMCD cells transfected with the construct containing 5-flanking region showed responsiveness to cpt-cAMP, indicating that the 1.4 kb 5'-flanking region contains the element necessary for the regulatory mechanism by cAMP. The promoter-luciferase constructs which do not have a cAMP-responsible element (CRE) still showed the cAMP responsiveness in IMCD cells, but not in NIH3T3 cells. Increase in medium osmolarity did not affect AQP2 promoter activity in mIMCD-K2 cells. These results demonstrate that AQP2 gene transcription is increased with cAMP treatment through multiple motifs including CRE in the 5'-flanking region of the gene in vitro, and the regulatory mechanism may be important for in vivo regulation of AQP2 expression.

• International Journal of Oral Biology
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• v.43 no.4
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• pp.185-191
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• 2018

Alcohol intake is known to affect various organs in the human body, causing reduction of salivation in the oral cavity. Hypo-salivation effect of alcohol is a common feature, but the mechanism in salivary glands is still poorly studied. Therefore, in this study, the changes in salivary secretion and water channel protein (aquaporin5, AQP5) in salivary glands of mice were investigated after ethanol administration. Animals were divided in to 4 groups with the control, 4 g/kg ethanol, 8 g/kg ethanol and 16 g/kg ethanol administration groups. One hour after ethanol administration, saliva was collected from the oral cavity, and the animals were killed and parotid and submandibular glands were extracted to analyze the histopathology, AQP5 immunihistochemistry and AQP5 protein level. According to the results, the salivation rate decreased irrespective of the ethanol dose in mice, and viscosities increased with increase in ethanol dose. However, there were no pathological changes in parotid and submandibular glands due to ethanol administration. Expression of AQP5 in parotid and submandibular glands decreased with increase ethanol administration These results indicate that the reduction of salivary secretion due to acute alcohol intake is closely related to decrease of the water channel protein such as AQP5 in parotid glands and submandibular glands, rather than the damage of salivary glands.

• Development and Reproduction
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• v.18 no.3
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• pp.153-160
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• 2014

Adaptive development of early stage embryo is well established and recently it is explored that the mammalian embryos also have adaptive ability to the stressful environment. However, the mechanisms are largely unknown. In this study, to evaluate the possible role of aquaporin in early embryo developmental adaptation, the expression of aquaporin (AQP) 5 gene which is detected during early development were examined by the environmental condition. To compare expression patterns between in vivo and in vitro, we conducted quantitative RT-PCR and analyzed localization of the AQP5 by whole mount immunofluorescence. At in vivo condition, Aqp5 expressed in oocyte and in all the stages of preimplantation embryo. It showed peak at 2-cell stage and decreased continuously until morula stage. At in vitro condition, Aqp5 expression pattern was similar with in vivo embryos. It expressed both at embryonic genome activation phase and second mid-preimplantation gene activation phase, but the fold changes were modified between in vivo embryos and in vitro embryos. During in vivo development, AQP5 was mainly localized in apical membrane of blastomeres of 4-cell and 8-cell stage embryos, and then it was localized in cytoplasm. However, the main localization area of AQP5 was dramatically shifted after 8-cell stage from cytoplasm to nucleus by in vitro development. Those results explore the modification of Aqp5 expression levels and location of its final products by in vitro culture. It suggests that expression of Aqp5 and the roles of AQP5 in homeostasis can be modulated by in vitro culture, and that early stage embryos can develop successfully by themselves adapting to their condition through modulation of the specific gene expression and localization.

• IMMUNE NETWORK
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• v.21 no.5
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• pp.34.1-34.16
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• 2021

Sjögren's syndrome (SS) is an autoimmune disease characterized by dryness of the mouth and eyes. The glandular dysfunction in SS involves not only T cell-mediated destruction of the glands but also autoantibodies against the type 3 muscarinic acetylcholine receptor or aquaporin 5 (AQP5) that interfere with the secretion process. Studies on the breakage of tolerance and induction of autoantibodies to these autoantigens could benefit SS patients. To break tolerance, we utilized a PmE-L peptide derived from the AQP5-homologous aquaporin of Prevotella melaninogenica (PmAqp) that contained both a B cell "E" epitope and a T cell epitope. Repeated subcutaneous immunization of C57BL/6 mice with the PmE-L peptide efficiently induced the production of Abs against the "E" epitope of mouse/human AQP5 (AQP5E), and we aimed to characterize the antigen specificity, the sequences of AQP5E-specific B cell receptors, and salivary gland phenotypes of these mice. Sera containing anti-AQP5E IgG not only stained mouse Aqp5 expressed in the submandibular glands but also detected PmApq and PmE-L by immunoblotting, suggesting molecular mimicry. Characterization of the AQP5E-specific autoantibodies selected from the screening of phage display Ab libraries and mapping of the B cell receptor repertoires revealed that the AQP5E-specific B cells acquired the ability to bind to the Ag through cumulative somatic hypermutation. Importantly, animals with anti-AQP5E Abs had decreased salivary flow rates without immune cell infiltration into the salivary glands. This model will be useful for investigating the role of anti-AQP5 autoantibodies in glandular dysfunction in SS and testing new therapeutics targeting autoantibody production.

• The Korean Journal of Physiology and Pharmacology
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• v.1 no.2
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• pp.195-200
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• 1997

Water transport in highly-permeable membranes is facilitated by some specialized pathways, which are called aquaporins (AQP). AQP1 (AQP-CHIP) is the first recognized aquaporin identified from red cells and renal proximal tubules. Up until now 4 other aquaporin homologs have been reported. Each aquaporin has its unique tissue distribution and regulatory mechanims. To elucidate molecular mechanisms for their transcription regulation and tissue-specific expression isolation of aquaporin genes is required. To clone promoters of the AQP family mouse genomic library was screened by the 1st exon-specific probe of AQP4, and 5 different plaques were positively hybridized. Phage DNAs were purified and characterized by restriction mapping and sequencing. One of them is the mouse AQP-CD gene. The gene was consisted of 4 exons and the exon-intron boundaries of mouse AQP-CD gene were identified at identical positions in other related genes. The 5'-flanking region of AQP-CD gene contains one classic TATA box, a GATA consensus sequence, an E-box and a cyclic AMP-responsive element. The cloning of the mouse AQP-CD gene, of which product is expressed in the collecting duct and is responsible for antidiuresis by vasopressin, will contribute to understand the molecular mechanisms of tissue-specific expression and regulation of AQP-CD gene under various conditions.

• The Korean Journal of Physiology and Pharmacology
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• v.10 no.4
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• pp.213-216
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• 2006

The present study was aimed to determine whether nitric oxide (NO) plays a role in the regulation of aquaporin (AQP) channels in the kidney. Male Brattleboro rats ($250{\sim}300\;g$ body weight) were used. The experimental group was treated with $N^G$-nitro-L-arginine methyl ester (L-NAME, 100 mg/L drinking water) for 1 week, and cotreated with indomethacin (5 mg/kg, twice a day, i.p.) for the last two days. Control groups were treated with either L-NAME for 1 week, indomethacin for 2 days, or without any drug treatment. The abundance of AQP1, AQP2 and AQP3 proteins in the kidney was determined by Western blot analysis. Indomethacin downregulated AQP channels, whereas L-NAME by itself showed no significant effects on them. The indomethacin-induced downregulation of AQP2 and AQP3 was significantly blunted in L-NAME-treated rats, while that of AQP1 was not affected. These results suggest that endogenous NO, when stimulated, may downregulate AQP channels that are specifically regulated by AVP/cAMP pathway in the kidney.

• Proceedings of the Korean Society of Developmental Biology Conference
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• 2003.10a
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• pp.61-61
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• 2003

Aquaporins (AQPs)는 다양한 상피세포와 내피세포에 존재하며 다량의 물 수송을 촉진하는 막성단백질로 현재 11개의 AQP가 (AQP0-10) 발견되었으나, 아직 생리적, 기능적 분석은 불충분한 상태이다. 생쥐의 자궁내막은 발정주기 동안 호르몬의 자극에 따라 부풀어오르거나 수축하는 변화를 보이며 에스트로젠과 몇몇 혈관에 작용하는 매개체에 의해 자궁 혈관의 투수성이 증가한다는 보고는 있으나, 자궁액의 수송 메커니즘에 대해서는 뚜렷하게 밝혀진 바가 없다. 발정기의 생쥐 자궁은 자궁내막세포의 증식과 함께 수화되는 특징을 보이며 자궁내강으로 물이 수송되어 luminal fluid의 점성이 낮아지는 현상이 나타나는데, 이 때 AQP가 water channel로서 중요한 역할을 할 것으로 보고 본 실험에서는 면역조직화학법(immunohistochemistry)과 역전사중합효소연쇄반응(Reverse-transcriptase polymerase chain reaction)을 통해 발정기 자궁의 수화와 AQP 발현의 상관성에 대해 알아보고자 하였다. 면역조직화학법의 결과 발정주기의 다른 시기에 비해 발정기(estrus phase)에 자궁상피세포에 AQP4, 5, 8 protein이 다량 존재하는 것으로 밝혀졌고, 근육층(myometrium)에서의 발현은 발정주기 동안 차이가 없었다. Whole uterus로 RT-PCR을 수행한 결과 AQP4, 5, 8 mRNA는 luteal phase에 비해 follicular phase에 더 많이 발현하는 것으로 확인되었다. 또한 LCM(Laser Capture Microdissection) system을 이용하여 luminal epithelium과 stromal cell을 분리하여 RT-PCR을 수행한 결과 AQP4, 5, 8 mRNA는 stromal cell 보다는 luminal epithelium에 더 많이 발현하며, 이 역시 follicular phase에 발현량이 증가함을 확인하였다. 이러한 결과로 미루어 생쥐 자궁에서 AQP4, 5, 8은 발정주기 내막에 발현이 증가하며 이는 자궁내강 안으로 수분을 수송하는데 주요한 기작으로 사료되며 estrogen에 의한 조절 가능성을 암시한다.

• Asian Pacific Journal of Cancer Prevention
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• v.13 no.5
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• pp.1971-1975
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• 2012

Overexpression of several aquaporins (AQPs) has been reported in different types of human cancer but their role in carcinogenesis, for example in the cervix, have yet to be clearly defined. In this study, expression of AQPs in cervical carcinomawas investigated by real-time PCR, immunofluorescent and immunohistochemical assays and evaluated for correlations with clinicopathologic variables. AQP1, 3, 8 exhibited differential expression in cervical carcinoma, corresponding CIN and mild cervicitis. AQP1 was predominantly localized in the microvascular endothelial cell in the stroma of mild cervicitis, CIN and cervical carcinoma. AQP3 and AQP8 were localized in the membrane of normal squamous epithelium and carcinoma cells, local signals being more common than diffuse staining. AQP1 and AQP3 expression was remarkably stronger in cervical cancer than in mild cervicitis and CIN2-3 (P<0.05). AQP8 expression was highest in CIN2-3 (91.7%), but levels in cervical carcinoma were also higher than in mild cervicitis. AQP1, AQP3, AQP8 expression significantly increased in advanced stage, deeper infiltration, metastatic lymph nodes and larger tumor volume (P<0.05). Our findings showed that AQPs might play important roles in cervical carcinogenesis and tumour progression in Uygur women.