Expression of aquaporin 1 and 5 and their regulation by ovarian hormones, arachidonic acid, forskolin and cAMP during implantation in pigs

The In Vitro Effect of Steroid Hormones, Arachidonic Acid, and Kinases Inhibitors on Aquaporin 1, 2, 5, and 7 Gene Expression in the Porcine Uterine Luminal Epithelial Cells during the Estrous Cycle

Aquaporins (AQPs) are integral membrane proteins, which play an important role in water homeostasis in the uterus. According to the literature, the expression of aquaporins in reproductive structures depends on the local hormonal milieu. The current study investigated the effect of selected PKA kinase inhibitor H89 and MAPK kinase inhibitor PD98059, on the expression of AQP1, 2, 5, and 7, and steroid hormones (E₂), progesterone (P₄), and arachidonic acid (AA) in the porcine endometrium on days 18–20 and 2–4 of the estrous cycle (the follicular phase where estrogen and follicle-stimulating hormone (FSH) are secreted increasingly in preparation for estrus and the luteal phase where the ovarian follicles begin the process of luteinization with the formation of the corpus luteum and progesterone secretion, respectively). The luminal epithelial cells were incubated in vitro in the presence of the aforementioned factors. The expression of mRNA was determined by the quantitative real-time PCR technique. In general, in Experiment 1, steroid hormones significantly increased expression of AQP1, 2, and 5 while arachidonic acid increased expression of AQP2 and AQP7. On the other hand, MAPK kinase inhibitor significantly decreased the expression of AQP1 and 5. In Experiment 2, E₂, P₄, or AA combined with kinase inhibitors differentially affected on AQPs expression. E₂ in combination with PKA inhibitor significantly decreased expression of AQP1 but E₂ or P₄ combined with this inhibitor increased the expression of AQP5 and 7. On the contrary, E₂ with PD98059 significantly increased AQP5 and AQP7 expression. Progesterone in combination with MAPK kinase inhibitor significantly downregulated the expression of AQP5 and upregulated AQP7. Arachidonic acid mixed with H89 or PD98059 caused a decrease in the expression of AQP5 and an increase of AQP7. The obtained results indicate that estradiol, progesterone, and arachidonic acid through PKA and MAPK signaling pathways regulate the expression of AQP1 and AQP5 in the porcine luminal epithelial cells in the periovulatory period.

N-Glycanase 1 Transcriptionally Regulates Aquaporins Independent of Its Enzymatic Activity

Patients with pathogenic mutations in NGLY1 cannot make tears and have global developmental delay and liver dysfunction. Traditionally, NGLY1 cleaves intact N-glycans from misfolded, retrotranslocated glycoproteins before proteasomal degradation. We demonstrate that Ngly1-null mouse embryonic fibroblasts, NGLY1 knockout human cells, and patient fibroblasts are resistant to hypotonic lysis. Ngly1-deficient mouse embryonic fibroblasts swell slower and have reduced aquaporin1 mRNA and protein expression. Ngly1 knockdown and overexpression confirms that Ngly1 regulates aquaporin1 and hypotonic cell lysis. Patient fibroblasts and NGLY1 knockout cells show reduced aquaporin11 mRNA, supporting NGLY1 as regulating expression of multiple aquaporins across species. Complementing Ngly1-deficient cells with catalytically inactive NGLY1 (p.Cys309Ala) restores normal hypotonic lysis and aquaporin1 protein. We show that transcription factors Atf1/Creb1 regulate aquaporin1 and that the Atf1/Creb1 signaling pathway is disrupted in Ngly1-deficient mouse embryonic fibroblasts. These results identify a non-enzymatic, regulatory function of NGLY1 in aquaporin transcription, possibly related to alacrima and neurological symptoms.

The Role of TREK-1 and AQP5 in Gonadocorticoid-Related Voice Disorders

OBJECTIVES

TWIK-related potassium channel-1 (TREK-1) and Aquaporin 5 (AQP5) are involved in epithelial integrity and fluid transport, respectively. In this study, we aimed to compare physiological and gestational patterns of TREK-1 and AQP5 location and expression in rat larynx. Our secondary objective was to reveal the effect of estradiol (E2) and progesterone (PG) on these two biomolecules.

METHODS

This study was conducted on 20 Wister albino female rats which were assigned as control (group A) and pregnant group (group B). The rats were sacrificed at 20th day of pregnancy. Blood was obtained directly from the ventricle for detection of serum E2 and PG levels. Larynx was resected for immunohistochemical analyses and real-time polymerase chain reaction testing for detection of TREK-1 and AQP5 staining and expression, respectively.

RESULTS

Relative TREK-1 (P = 0.035) and AQP5 (P = 0.019) expression was found to be significantly high in group B when compared with group A. We found positive correlation between serum E2 levels and both biomolecules (TREK-1; P = 0.018, AQP5; P = 0.016). We also found positive correlation between serum PG levels and both biomolecules (TREK-1; P = 0.001, AQP5; P = 0.019). TREK-1 immunostaining was found to be higher in surface epithelium and lamina propria of vocal cord mucosa. AQP5 was particularly found to be located in basement membrane and adjacent superficial lamina propria. We revealed the physiological and gestational pattern of laryngeal TREK-1 and AQP5 expression for the first time. Gestational expression of both TREK-1 and AQP5 was found to be increased. Stimulatory effect of E2 and PG on laryngeal TREK-1 and AQP5 expression was also revealed.

CONCLUSIONS

We revealed upregulatory effect of E2 and PG on laryngeal TREK-1 and AQP5 expression. Based on this finding, it can be suggested that TREK-1 and AQP5 play role in biomolecular processes leading gonadocorticoid-related voice changes.

Expression of Selected Connexin and Aquaporin Genes and Real-Time Proliferation of Porcine Endometrial Luminal Epithelial Cells in Primary Culture Model

Luminal epithelial cells are the first embryonic-maternal contact site undergoing very specific changes associated with reproductive processes. Cells prepare for embryo development by increasing their volume, with the help of aquaporins that provide a transcellular path of rapid water movement during the secretion and absorption of fluids, as well as connexins enabling the flow of inorganic ions and small molecules. In this work, we have examined how AQPs and Cx's behave in luminal epithelium primary cell culture. Cells obtained from porcine specimen during slaughter were primarily in vitro cultured for 7 days. Their proliferation patterns were then analyzed using RTCA, with the expression of genes of interest evaluated with the use of immunofluorescence and RT-qPCR. The results of these changes of gene of interest expression were analyzed on each of the seven days of the porcine luminal primary cell culture. Our study showed that the significant changes were noted in the case of Cx43, whose level of protein expression and distribution increases after 120 hours of culture, when the cells enter the lag phase, and maintains an upward trend until the end of the culture. We noted an increase in AQP4, AQP7, AQP8, and AQP11 levels throughout the entire culture period, while the largest differences in expression were found in AQP3, AQP4, and AQP10. The obtained results could become a point of reference for further in vivo and clinical research. Experiments conducted with these proteins showed that they influence the endometrial fluid content during the oestrous cycle and participate in the process of angiogenesis, which intensifies during endometrial development.

Pituitary Hormones (FSH, LH, PRL, and GH) Differentially Regulate AQP5 Expression in Porcine Ovarian Follicular Cells

This study aimed to examine the effect of follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL), and growth hormone (GH) on Aquaporin 5 (AQP5) expression in granulosa (Gc) and theca cells (Tc) from medium (MF) and large (LF) ovarian follicles of pigs. The results showed that GH significantly decreased the expression of AQP5 in Gc from MF in relation to the control. In the Gc of large follicles, PRL stimulated the expression of AQP5. However, the increased expression of AQP5 in the Tc of LF was indicated by GH and PRL in relation to the control. A significantly higher expression of the AQP5 protein in the Gc from MF and LF was indicated by FSH and PRL. In co-cultures, an increased expression of AQP5 was observed in the Gc from LF incubated with LH, PRL, and GH. A significantly increased expression of AQP5 was also observed in co-cultures of Tc from all type of follicles incubated with LH, whereas PRL stimulated the expression of AQP5 in Tc from MF. Moreover, AQP5 protein expression increased in the co-culture isolated from MF and LF after treatment with FSH, LH, PRL, and GH. AQP5 immunoreactivity was observed in the cytoplasm, mainly in the perinuclear region and endosomes, as well as in the cell membranes of Gc and Tc from the LF and MF.

Effects of AQP5 gene silencing on proliferation, migration and apoptosis of human glioma cells through regulating EGFR/ERK/ p38 MAPK signaling pathway

We investigated the effects of aquaporin 5 (AQP5) gene silencing on the proliferation, migration and apoptosis of human glioma cells through regulating the EGFR/ERK/p38MAPK signaling pathway. qRT-PCR was applied to examine the mRNA expressions of AQP5 in five human glioma cell lines. U87-MG, U251 and LN229 cells were selected and assigned into blank, vector, AQP5 siRNA and FlagAQP5 groups. MTT assay was used to measure cell proliferation. Flow cytometry (FCM) with AnnexinV-FITC/PI double staining and PI staining were employed to analyze cell apoptosis and cell cycle respectively. Scratch test was used to detect cell migration. Western blotting was performed to determine the EGFR/ERK/p38 MAPK signaling pathway-related proteins. Results showed that the positive expression of AQP5 in primary glioblastoma was associated with the tumor size and whether complete excision was performed. The mRNA expressions of AQP5 in cell lines of U87-MG, U251 and LN229 were significantly higher than in U373 and T98G. The proliferation rates of U87-MG, U251 and LN229 cells in the AQP5 siRNA group were lower than in the vector and blank groups. The apoptosis rate increased in the AQP5 siRNA group compared with the vector group. Scratch test demonstrated that AQP5 gene silencing could suppress cell migration. Compared with the vector and blank groups, the AQP5 siRNA group showed decreased expressions of the ERK1/2, p38 MAPK, p-ERK1/2 and p-p38 MAPK proteins. AQP5 gene silencing could inhibit the cell proliferation, reduce cell migration and promote the cell apoptosis of U87-MG, U251 and LN229 by suppressing EGFR/ERK/p38 MAPK signaling pathway.

Pituitary Gonadotropins, Prolactin and Growth Hormone Differentially Regulate AQP1 Expression in the Porcine Ovarian Follicular Cells

The present in vitro study analyzed whether the hormones that affect the ovarian follicular steroidogenesis process also participate in the regulation of AQP1 mRNA and protein expression. Granulosa (Gc) and theca cells (Tc) of medium and large porcine ovarian follicles were exposed to follicle-stimulating hormone (FSH), luteinizing hormone (LH), prolactin (PRL) and growth hormone (GH) for 24 h in separated cells and co-cultures of these cells. Real-time PCR, Western blotting, immunofluorescence and volumetric analysis were then performed. Gonadotropins, PRL and GH had a stimulatory impact on AQP1 mRNA and protein expression in Gc and Tc of medium and large ovarian cells. Moreover, swelling assays, in response to a hypotonic environment, demonstrated the functional presence of AQPs in porcine Gc and Tc. Immunofluorescence analysis showed that AQP1 protein was mainly localized in the perinuclear region of the cytoplasm, endosomes and cell membranes of Gc and Tc from medium and large follicles. It seems possible that AQP1 present in Gc and Tc cells may be implicated not only in the regulation of water homeostasis required for follicle development but also in cell proliferation and migration.

Aquaporins during Pregnancy: Their Function and Significance

Water is the major component of cells and tissues, and the movement of water across the cell membrane is a fundamental property of life. Until the discovery of the first water channel, aquaporin, it was long assumed that the transport of water was due to simple diffusion through the lipid bilayer membrane that encloses cells. Aquaporin (AQP) molecules were first discovered in the human uterus in 1994, and since then several studies have investigated these channels in the female reproductive system. The expressions of AQPs have been proven in the reproductive system. Their levels are altered during the implantation process, both in the uterus and the fetal cells, and participate in the control of the flow of amniotic fluid. They seem to be very important for the normal placental functions. AQPs are present during parturition, participating in the control of pregnant myometrial contractions and cervical ripening. However, most of the physiological and regulatory roles of AQPs are not clarified in the reproductive tract. Furthermore, no satisfactory knowledge is available about their sensitivities to different drugs. AQP-selective ligands may contribute to the development of new drug candidates and the therapy of several reproductive disorders.