Overexpression of AQP3 Modifies the Cell Cycle and the Proliferation Rate of Mammalian Cells in Culture

The role of Aquaporins in tumorigenesis: implications for therapeutic development

Aquaporins (AQPs) are ubiquitous channel proteins that play a critical role in the homeostasis of the cellular environment by allowing the transit of water, chemicals, and ions. They can be found in many different types of cells and organs, including the lungs, eyes, brain, glands, and blood vessels. By controlling the osmotic water flux in processes like cell growth, energy metabolism, migration, adhesion, and proliferation, AQPs are capable of exerting their regulatory influence over a wide range of cellular processes. Tumour cells of varying sources express AQPs significantly, especially in malignant tumours with a high propensity for metastasis. New insights into the roles of AQPs in cell migration and proliferation reinforce the notion that AQPs are crucial players in tumour biology. AQPs have recently been shown to be a powerful tool in the fight against pathogenic antibodies and metastatic cell migration, despite the fact that the molecular processes of aquaporins in pathology are not entirely established. In this review, we shall discuss the several ways in which AQPs are expressed in the body, the unique roles they play in tumorigenesis, and the novel therapeutic approaches that could be adopted to treat carcinoma.

Blockage of aquaporin-3 peroxiporin activity by organogold compounds affects melanoma cell adhesion, proliferation and migration

Aquaporin-3 (AQP3) is a membrane channel with dual aquaglyceroporin/peroxiporin activity, facilitating the diffusion of water, glycerol and H2 O2 across cell membranes. AQP3 shows aberrant expression in melanoma and its role in cell adhesion, migration and proliferation is well described. Gold compounds were shown to modulate AQP3 activity with reduced associated toxicity, making them promising molecules for cancer therapy. In this study, we validated the phenotype resulting from AQP3-silencing of two melanoma cell lines, MNT-1 and A375, which resulted in decreased H2 O2 permeability. Subsequently, the AQP3 inhibitory effect of a new series of organogold compounds derived from Auphen, a potent AQP3 inhibitor, was first evaluated in red blood cells (RBCs) that highly express AQP3, and then in HEK-293T cells with AQP3 overexpression to ascertain the compounds' specificity. The first screening in RBCs unveiled two organogold compounds as promising blockers of AQP3 permeability. Moderate reduction of glycerol permeability but drastic inhibition of H2 O2 permeability was detected for some of the gold derivatives in both AQP3-overexpressing cells and human melanoma cell lines. Additionally, all compounds were effective in impairing cell adhesion, proliferation and migration, although in a cell type-dependent manner. In conclusion, our data show that AQP3 peroxiporin activity is crucial for melanoma progression and highlight organogold compounds as promising AQP3 inhibitors with implications in melanoma cell adhesion, proliferation and migration, unveiling their potential as anticancer drugs against AQP3-overexpressing tumours. KEY POINTS: AQP3 affects cellular redox balance. Gold compounds inhibit AQP3 permeability in melanoma cells. AQP3 is involved in cell adhesion, proliferation and migration of melanoma. Blockage of AQP3 peroxiporin activity impairs melanoma cell migration. Gold compounds are potential anticancer drug leads for AQP3-overexpressing cancers.

Population genomics analysis to identify ion and water transporter genes involved in the adaptation of Tibetan naked carps to brackish water

Understanding how evolutionary processes shape the genetic variations and influence the response of species to environmental alterations is critical for biodiversity conservation and molecular breeding. Gymnocypris przewalskii przewalskii is the only known cyprinid fish that dwells in the brackish water of Lake Qinghai on the Qinghai-Tibetan Plateau. To reveal the genetic basis of its adaptation to high salinity and alkalinity, whole-genome sequencing was performed in G. p. przewalskii and its freshwater relatives Gymnocypris eckloni and Gymnocypris przewalskii ganzihonensis. Compared with freshwater species, lower genetic diversity and higher linkage disequilibrium were observed in G. p. przewalskii. Selective sweep analysis identified 424 core-selective genes enriched in transport activities. Transfection analysis showed that genetic changes in the positively selected gene aquaporin 3 (AQP3) improved cell viability after salt treatment, suggesting its involvement in brackish water adaptation. Our analysis indicates that ion and water transporter genes experienced intensive selection, which might have contributed to the maintenance of high osmolality and ion content in G. p. przewalskii. The current study identified key molecules involved in the adaptation of fish to brackish water, providing valuable genomic resources for the molecular breeding of salt-tolerant fish.

Integrative analysis reveals marker genes for intestinal mucosa barrier repairing in clinical patients

This study aims to identify biomarkers of intestinal repair and provide potential therapeutic clues for improving functional recovery and prognostic performance after intestinal inflammation or injury. Here, we conducted a large-scale screening of multiple transcriptomic and scRNA-seq datasets of patients with inflammatory bowel disease (IBD), and identified 10 marker genes that potentially contribute to intestinal barrier repairing: AQP8, SULT1A1, HSD17B2, PADI2, SLC26A2, SELENBP1, FAM162A, TNNC2, ACADS, and TST. Analysis of a published scRNA-seq dataset revealed that expression of these healing markers were specific to absorptive cell types in intestinal epithelium. Furthermore, we conducted a clinical study where 11 patients underwent ileum resection demonstrating that upregulation of post-operative AQP8 and SULT1A1 expression were associated with improved recovery of bowel functions after surgery-induced intestinal injury, making them confident biomarkers of intestinal healing as well as potential prognostic markers and therapeutic targets for patients with impaired intestinal barrier functions.

Roles of hypoxia-inducible factor in hepatocellular carcinoma under local ablation therapies

Hepatocellular carcinoma (HCC) is one of the most common digestive malignancies. HCC It ranges as the fifth most common cause of cancer mortality worldwide. While The prognosis of metastatic or advanced HCC is still quite poor. Recently, locoregional treatment, especially local ablation therapies, plays an important role in the treatment of HCC. Radiofrequency ablation (RFA) and high-intensity focused ultrasound (HIFU) ablation are the most common-used methods effective and feasible for treating HCC. However, the molecular mechanisms underlying the actions of ablation in the treatments for HCC and the HCC recurrence after ablation still are poorly understood. Hypoxia-inducible factor (HIF), the key gene switch for adaptive responses to hypoxia, has been found to play an essential role in the rapid aggressive recurrence of HCC after ablation treatment. In this review, we summarized the current evidence of the roles of HIF in the treatment of HCC with ablation. Fifteen relevant studies were included and further analyzed. Among them, three clinical studies suggested that HIF-1α might serve as a crucial role in the RAF treatment of HCC or the local recurrence of HCC after RFA. The remainder included experimental studies demonstrated that HIF-1, 2α might target the different molecules (e.g., BNIP3, CA-IX, and arginase-1) and signaling cascades (e.g., VEGFA/EphA2 pathway), constituting a complex network that promoted HCC invasion and metastasis after ablation. Currently, the inhibitors of HIF have been developed, providing important proof of targeting HIF for the prevention of HCC recurrence after IRFA and HIFU ablation. Further confirmation by prospective clinical and in-depth experimental studies is still warranted to illustrate the effects of HIF in HCC recurrence followed ablation treatment in the future.

Non-Transport Functions of Aquaporins

Although it has been more than 20 years since the first aquaporin was discovered, the specific functions of many aquaporins are still under investigation, because various mice lacking aquaporins have no significant phenotypes. And in many studies, the function of aquaporin is not directly related to its transport function. Therefore, this chapter will focus on some unexpected functions of aquaporins, such the decreased tumor angiogenesis in AQP1 knockout mice, and AQP1 promotes cell migration, possibly by accelerating the water transport in lamellipodia of migrating cells. AQP transports glycerol, and water regulates glycerol content in epidermis and fat, thereby regulating skin hydration/biosynthesis and fat metabolism. AQPs may also be involved in neural signal transduction, cell volume regulation, and organelle physiology. AQP1, AQP3, and AQP5 are also involved in cell proliferation. In addition, AQPs have also been reported to play roles in inflammation in various tissues and organs. The functions of these AQPs may not depend on the permeability of small molecules such as water and glycerol, suggesting AQPs may play more roles in different biological processes in the body.

Critical Role of Aquaporins in Cancer: Focus on Hematological Malignancies

Simple Summary

Aquaporins are proteins able to regulate the transfer of water and other small substances such as ions, glycerol, urea, and hydrogen peroxide across cellular membranes. AQPs provide for a huge variety of physiological phenomena; their alteration provokes several types of pathologies including cancer and hematological malignancies. Our review presents data revealing the possibility of employing aquaporins as biomarkers in patients with hematological malignancies and evaluates the possibility that interfering with the expression of aquaporins could represent an effective treatment for hematological malignancies.

Abstract

Aquaporins are transmembrane molecules regulating the transfer of water and other compounds such as ions, glycerol, urea, and hydrogen peroxide. Their alteration has been reported in several conditions such as cancer. Tumor progression might be enhanced by aquaporins in modifying tumor angiogenesis, cell volume adaptation, proteases activity, cell–matrix adhesions, actin cytoskeleton, epithelial–mesenchymal transitions, and acting on several signaling pathways facilitating cancer progression. Close connections have also been identified between the aquaporins and hematological malignancies. However, it is difficult to identify a unique action exerted by aquaporins in different hemopathies, and each aquaporin has specific effects that vary according to the class of aquaporin examined and to the different neoplastic cells. However, the expression of aquaporins is altered in cell cultures and in patients with acute and chronic myeloid leukemia, in lymphoproliferative diseases and in multiple myeloma, and the different expression of aquaporins seems to be able to influence the efficacy of treatment and could have a prognostic significance, as greater expression of aquaporins is correlated to improved overall survival in leukemia patients. Finally, we assessed the possibility that modifying the aquaporin expression using aquaporin-targeting regulators, specific monoclonal antibodies, and even aquaporin gene transfer could represent an effective therapy of hematological malignancies.

Immune Cells Profiles in the Different Sites of COVID-19-Affected Lung Lobes in a Single Patient

Whereas the COVID-19 disease pathophysiology is under investigation, it is important to identify the pathways of viral transmission and inflammation from the pre-illness to the disease-onset stages. We analyzed five lung lobes from a patient with COVID-19 who finally died after prolonged lung protective ventilation. Pathological examination revealed moderate inflammation in upper lung lobes and uneven yet severe inflammation and diffuse alveolar damage in lower lung lobes. SARS-CoV-2 was detected at higher levels not in severely, but rather moderately inflamed middle lung lobes, and immunohistochemistry and bulk RNA-sequencing results showed that immune cells were detected at higher levels in lower lung lobes. The mRNA expression of cytokine families varied. We found an increase in keratin 5- or aquaporin 3-expressing basal cells in the severely inflamed lower lung lobes, and the alveolar stromal tissues were filled with them. Thus, this analysis of lung samples from a patient helps to determine the COVID-19 pathophysiology at a specific time point, and the virus localization and inflammatory responses at each site of the lungs provide various important indications.

Aquaporins in pancreatic ductal adenocarcinoma

Aquaporins are water channel proteins facilitating passive transport of water across cellular membranes. Aquaporins are over- or ectopically expressed in a multitude of cancers, including pancreatic ductal adenocarcinoma, which is a highly aggressive cancer with low survival rate. Evidence suggests that aquaporins can affect multiple cellular processes involved in cancer development and progression including epithelial-mesenchymal transition, cellular migration, cell proliferation, invasion, and cellular adhesions. In pancreatic ductal adenocarcinoma, aquaporin-1, aquaporin-3, and aquaporin-5 are overexpressed and have been associated with metastatic processes and poor survival. Thus, aquaporin expression has been suggested as diagnostic markers and therapeutic targets in pancreatic ductal adenocarcinoma.

Initial assessment of suitability of MCF-7 and HepG2 cancer cell lines for AQP3 research in cancer biology

Cancer cell lines are widely used as in vitro models to elucidate biological processes in cancer, and as a tool to evaluate anticancer agents. In fact, the use of an appropriate cancer cell line in cancer research is crucial for investigating new, potential factors involved in carcinogenesis. One of them is aquaporin-3 (AQP3), which is a small, hydrophobic, integral membrane protein with a predominant role in water and glycerol transport. Recently, altered expression of AQP3 has been reported in many types of cancer. Increasing evidence strongly suggests that AQP3 plays a key role in cancer cell proliferation, migration and invasion. In this study, we performed an insightful characteristic of AQP3 location and its protein expression in MCF-7 human breast adenocarcinoma and HepG2 hepatocellular carcinoma cell lines in the context of cancer biology using immunocytochemistry, immunofluorescence and Western blot analyses. AQP3 was found to be located in the cell membrane and cytoplasm of MCF-7 cells, and in the cytoplasm and nuclear membrane of HepG2 cells. Immunoblotting of proteins derived from both cell lines revealed a clear band with a molecular weight of approx. 30 kDa representing an unglycosylated form of AQP3. However, the expression of this protein was higher in MCF-7 than in HepG2. Concluding, our results clearly indicated variability in both the expression levels and subcellular location of the AQP3 protein in MCF-7 and HepG2 cell lines. This leads to the possibility that the expression patterns and subcellular location of AQP3 in the tested cancer cell lines are tissue-of-origin specific, and may be related to the aggressiveness of cancer cells and their mobility.

Aquaporins implicated in the cell proliferation and the signaling pathways of cell stemness

Aquaporins (AQPs) are water channel proteins facilitating passive transport of water and other small molecules across biomembranes. Regulation of osmotic homeostasis via AQPs is accompanied by dynamic participation of various cellular signaling pathways. Recently emerging evidence reveals that functional roles of AQPs are further extended from the osmotic regulation via water permeation into the cell proliferation and differentiation. In particular, anomalous expression of AQPs has been demonstrated in various types of cancer cells and cancer stem-like cells and it has been proposed as markers for proliferation and progression of cancer cells. Thus, a more comprehensive view on AQPs could bring a great interest in the cell stemness accompanied by the expression of AQPs. AQPs are broadly expressed across tissues and cells in a cell type- and lineage-specific manner during development via spatiotemporal transcriptional regulation. Moreover, AQPs are expressed in various adult stem cells and cells associated with a stem cell niche as well as cancer stem-like cells. However, the expression and regulatory mechanisms of AQP expression in stem cells have not been well understood. This review highlighted the AQPs expression in stem cell niches/stem cells and the involvement of AQPs in the cell proliferation and signaling pathways associated with cell stemness.

Characteristics of aquaporin 1, 3, and 5 expression during early murine salivary gland development

Aquaporins (AQPs) are essential to coordinate the transit of water and ions through the cell membrane. In salivary glands (SGs), AQPs have been associated with saliva formation, facilitating water absorption through the epithelium during the formation of hypotonic saliva, which is then secreted into the oral cavity. Different members of the AQP family have been suggested to play distinct roles during embryonic development, highlighted by their specific expression patterns. Here, we have investigated the expression patterns of AQP-1, AQP-3 and AQP-5 by immunofluorescence at key stages of salivary gland development, utilising cultured mouse embryonic submandibular (SMG) and sublingual (SLG) glands. The expression of AQPs was compared to a mitotic marker, phospho-histone 3 (PH3), a myoepithelial marker, smooth muscle actin (SMA), and a vascular marker, CD31. Qualitative analysis revealed that AQP-1 and AQP-3 were primarily expressed during the earlier phases of SG morphogenesis and were associated with cells undergoing mitotic processes (PH3-positive). AQP-5, in contrast, was not associated to mitotic figures, but was predominantly expressed during late stages of SG morphogenesis. Our results highlight that AQPs are expressed from early stages of SG morphogenesis and exhibit complimentary expression patterns that may contribute to the morphogenesis of salivary glands.

Role of Aquaporins in the Physiological Functions of Mesenchymal Stem Cells

Aquaporins (AQPs) are a family of membrane water channel proteins that control osmotically-driven water transport across cell membranes. Recent studies have focused on the assessment of fluid flux regulation in relation to the biological processes that maintain mesenchymal stem cell (MSC) physiology. In particular, AQPs seem to regulate MSC proliferation through rapid regulation of the cell volume. Furthermore, several reports have shown that AQPs play a crucial role in modulating MSC attachment to the extracellular matrix, their spread, and migration. Shedding light on how AQPs are able to regulate MSC physiological functions can increase our knowledge of their biological behaviours and improve their application in regenerative and reparative medicine.

Differential Expressions of Aquaporin Subtypes in Female Reproductive Tract of Mice

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.

Hypoxia-Induced Aquaporin-3 Changes Hepatocellular Carcinoma Cell Sensitivity to Sorafenib by Activating the PI3K/Akt Signaling Pathway

Purpose

Hypoxia-induced changes are primarily activated in patients with hepatocellular carcinoma (HCC) and long-term sorafenib exposure, thereby reducing the sensitivity to the drug. Aquaporin-3 (AQP3), a member of the aquaporin family, is a hypoxia-induced substance that affects the chemosensitivity of non-hepatocellular tumors. However, its expression and role in the sensitivity of hypoxic HCC cells to sorafenib-induced apoptosis remain unclear. The purpose of this study was to detect changes in AQP3 expression in hypoxic HCC cells and to determine whether these changes alter the sensitivity of these cells to sorafenib.

Materials and Methods

Huh7 and HepG2 hypoxic cell models were established and AQP3 expression was detected using quantitative real-time polymerase chain reaction (qPCR) and Western blotting. Furthermore, the role of AQP3 in cell sensitivity to sorafenib was evaluated via flow cytometry, Western blotting, and a CCK-8 assay.

Results

The results of qPCR and Western blotting showed that AQP3 was overexpressed in the Huh7 and HepG2 hypoxic cell models. Furthermore, AQP3 protein levels were positively correlated with hypoxia-inducible factor-1α (HIF-1α) levels. Compared with cells transfected with lentivirus-GFP (Lv-GFP), hypoxic cells transfected with lentivirus-AQP3 (Lv-AQP3) were less sensitive to sorafenib-induced apoptosis. However, the sensitivity to the drug increased in cells transfected with lentivirus-AQP3RNAi (Lv-AQP3RNAi). Akt and Erk phosphorylation was enhanced in Lv-AQP3-transfected cells. Compared with UO126 (a Mek1/2 inhibitor), LY294002 (a PI3K inhibitor) attenuated the AQP3-induced insensitivity to sorafenib observed in hypoxic cells transfected with Lv-AQP3. Combined with LY294002-treated cells, hypoxic cells transfected with Lv-AQP3RNAi were more sensitive to sorafenib.

Conclusion

The study results show that AQP3 is a potential therapeutic target for improving the sensitivity of hypoxic HCC cells to sorafenib.

Arctiin attenuates high glucose-induced human retinal capillary endothelial cell proliferation by regulating ROCK1/PTEN/PI3K/Akt/VEGF pathway in vitro

Diabetic retinopathy (DR) is one of the most prominent microvascular complications of diabetes, which remains the leading cause of legal blindness in the world. Arctiin, a bioactive compound from Arctium lappa L., has been reported to have antidiabetic activity. In this study, we investigated the effect of arctiin on a human retinal capillary endothelial cell (HRCEC) line and how arctiin inhibits cell proliferation in high glucose (HG)-induced HRCECs. Results showed that arctiin decreased HG-induced HRCECs proliferation in a dose-dependent manner by inducing cell cycle arrest at the G0/G1 phase. Tube formation assay and immunofluorescence staining indicated that arctiin abrogated tube formation induced by HG-induced HRCECs in a dose-dependent manner via down-regulation of VEGF expression. Mechanistic study indicated that perturbation of the ROCK1/PTEN/PI3K/Akt signalling pathway plays a vital role in the arctiin-mediated anti-proliferative effect. Furthermore, pre-incubation of HRCECs with Y-27632 attenuated arctiin-induced cell cycle arrest, cell proliferation and tube formation inhibition. Y-27632 also reversed the activation of PTEN, the inactivation/dephosphorylation of PI3K/Akt and down-regulation of VEGF. Taken together, the results demonstrated that arctiin inhibits the proliferation of HG-induced HRCECs through the activation of ROCK1 and PTEN and inactivation of PI3K and Akt, resulting in down-regulation of VEGF, which inhibits endothelial cell proliferation.

AQP3 Facilitates Proliferation and Adipogenic Differentiation of Porcine Intramuscular Adipocytes

The meat quality of animal products is closely related to the intramuscular fat content. Aquaglyceroporin (AQP) defines a class of water/glycerol channels that primarily facilitate the passive transport of glycerol and water across biological membranes. In this study, the AQP3 protein of the AQP family was mainly studied in the adipogenic function of intramuscular adipocytes in pigs. Here, we found that AQP3 was increased at both mRNA and protein levels upon adipogenic stimuli in porcine intramuscular adipocytes in vitro. Western blot results showed knockdown of AQP3 by siRNA significantly suppressed the expression of adipogenic genes (PPARγ, aP2, etc.), repressed Akt phosphorylation, as well as reducing lipid accumulation. Furthermore, deletion of AQP3 by siRNA significantly downregulated expression of cell cycle genes (cyclin D, E), and decreased the number of EdU-positive cells as well as cell viability. Collectively, our data indicate that AQP3 is of great importance in both adipogenic differentiation and proliferation in intramuscular adipocytes, providing a potential target for modulating fat infiltration in skeletal muscles.

Expression Pattern of Aquaporin 1 and Aquaporin 3 in Melanocytic and Nonmelanocytic Skin Tumors

OBJECTIVES

Study of aquaporin 1 (AQP1) and aquaporin 3 (AQP3) expression to understand its potential role in the pathophysiology of skin cancer.

METHODS

Analysis of AQP1 and AQP3 expression by immunohistochemistry of 72 skin biopsy specimens from melanocytic skin tumors, nonmelanocytic tumors, or healthy samples.

RESULTS

AQP1 showed strong labeling in 100% of benign common melanocytic nevi. Small blood vessels, stroma, and melanophages surrounding different types of melanomas tumors also were positive. Tumoral melanocytes in atypical nevi and melanomas were negative for AQP1. AQP3 showed strong labeling in 100% of melanocytic nevi, 100% of atypical melanocytic nevi, and 100% of melanomas. In all basal cell carcinomas and squamous cell carcinomas, staining for AQP3 was positive.

CONCLUSIONS

To our knowledge, this work represents the first demonstration of AQP1/AQP3 expression in human melanocytic skin tumors. More studies are needed to understand the underlying molecular mechanisms of expression of both AQPs in melanocytic tumors and their potential as molecular therapeutic targets.

Dysregulation of schizophrenia-related aquaporin 3 through disruption of paranode influences neuronal viability

Myelinated axons segregate the axonal membrane into four defined regions: the node of Ranvier, paranode, juxtaparanode, and internode. The paranodal junction consists of specific component proteins, such as neurofascin155 (NF155) on the glial side, and Caspr and Contactin on the axonal side. Although paranodal junctions are thought to play crucial roles in rapid saltatory conduction and nodal assembly, the role of their interaction with neurons is not fully understood. In a previous study, conditional NF155 knockout in oligodendrocytes led to disorganization of the paranodal junctions. To examine if disruption of paranodal junctions affects neuronal gene expression, we prepared total RNA from the retina of NF155 conditional knockout, and performed expression analysis. We found that the expression level of 433 genes changed in response to paranodal junction ablation. Interestingly, expression of aquaporin 3 (AQP3) was significantly reduced in NF155 conditional knockout mice, but not in cerebroside sulfotransferase knockout (CST-KO) mice, whose paranodes are not originally formed during development. Copy number variations have an important role in the etiology of schizophrenia (SCZ). We observed rare duplications of AQP3 in SCZ patients, suggesting a correlation between abnormal AQP3 expression and SCZ. To determine if AQP3 over-expression in NF155 conditional knockout mice influences neuronal function, we performed adeno-associated virus (AAV)-mediated over-expression of AQP3 in the motor cortex of mice and found a significant increase in caspase 3-dependent neuronal apoptosis in AQP3-transduced cells. This study may provide new insights into therapeutic approaches for SCZ by regulating AQP3 expression, which is associated with paranodal disruption.

The Expression of AQP1 IS Modified in Lung of Patients With Idiopathic Pulmonary Fibrosis: Addressing a Possible New Target

Activation of the epithelial-mesenchymal transition process (EMT) by which alveolar cells in human lung tissue undergo differentiation giving rise to a mesenchymal phenotype (fibroblast/miofibroblasts) has been well recognized as a key element in the origin of idiopathic pulmonary fibrosis (IPF). Here we analyzed expression of AQP1 in lung biopsies of patients diagnosed with IPF, and compared it to biopsies derived from patients with diverse lung pneumonies, such as hypersensitivity pneumonitis, sarcoidosis or normal lungs. Immunostaining for AQP1 showed a clear increment of AQP1 localized in the alveolar epithelium in biopsies from IPF patients alone. Moreover, to examine the possible participation of AQP1 in the pathophysiology of IPF, we evaluated its role in the pro-fibrotic transformation induced by transforming growth factor (TGF-β) in vitro. Human alveolar epithelial cells (A549), and fibroblasts derived from an IPF patient (LL29), or fibroblasts from healthy normal lung tissue (MRC-5), were treated with TGF-β, and levels of expression of AQP1, as well as those of E-cadherin, vimentin, α-SMA and collagen were analyzed by RT-qPCR, western blot and immunohistochemistry. An increase of AQP1 mRNA and protein after TGF-β treatment (4–72h) was observed either in A549 or IPF fibroblast-LL29 but not in MRC-5 fibroblasts. A gradual reduction of E-cadherin, and increased expression of vimentin, with no changes in α-SMA levels were observed in A549. Whereas in LL29 and MRC-5, TGF-β1 elicited a large production of collagen and α-SMA that was significantly greater in IPF fibroblast-LL29. Changes observed are consistent with activation of EMT by TGF-β, but whether modifications in AQP1 expression are responsible or independent events occurring at the same time is still unknown. Our results suggest that AQP1 plays a role in the pro-fibrotic TGF-β action and contributes to the etiology and pathophysiology of IPF. Understanding AQP1's role will help us comprehend the fate of this disease.

Aquaporin-3 in Cancer

Increasing evidence suggests that the water/glycerol channel aquaporin-3 (AQP3) plays a pivotal role in cancer metastasis. AQP3 knockout mice were resistant to skin tumor formation and overexpression correlated with metastasis and poor prognosis in patients with breast or gastric cancer. In cultured cancer cells, increased AQP3 expression stimulated several intracellular signaling pathways and resulted in increased cell proliferation, migration, and invasion as well as aggravation of epithelial-to-mesenchymal transition. Besides AQP facilitated water transport at the leading edge of migrating cells, AQP3 signaling mechanisms are beginning to be unraveled. Here, we give a thorough review of current knowledge regarding AQP3 expression in cancer and how AQP3 contributes to cancer progression via signaling that modulates cellular mechanisms. This review article will expand our understanding of the known pathophysiological findings regarding AQP3 in cancer.

Silencing of AQP3 induces apoptosis of gastric cancer cells via downregulation of glycerol intake and downstream inhibition of lipogenesis and autophagy

Gastric cancer (GC) has a poor prognosis and is a leading cause of cancer-related death. Optimal therapeutic targets have not been identified. AQP3 is capable of transporting glycerol across the cytomembrane. Previous studies have shown that AQP3 is involved in proliferation, invasion and migration by regulating glycerol and lipid metabolism in diverse cancer cell types. However, the potential roles of glycerol and lipid metabolism in AQP3-related cell apoptosis in GC remain unclear. In this study, we observed that AQP3 expression was upregulated in tumor tissues, and positively correlated with tumor size, lymph node metastasis and glycerol concentration in human GC samples. Silencing of AQP3 resulted in decreased glycerol intake and impaired lipid synthesis, which contributed to increased cell apoptosis. Furthermore, inhibition of autophagy induced by AQP3 knockdown promoted cell apoptosis. Administration of either glycerol or rapamycin restored cell viability, and overexpression of AQP3 increased cell viability by upregulating cellular glycerol metabolism and autophagy. Our study demonstrates that the increase in cell apoptosis of AQP3-deficient GC cells is a consequence of reduced glycerol uptake and lipogenesis and is associated with autophagy inhibition induced by AQP3 deficiency.

Differential regulation of the expression of aquaporins 3 and 9 by Auphen and dbcAMP in the SMMC-7721 hepatocellular carcinoma cell line

Aquaglycero-aquaporins (agAQPs) are the structural foundation of rapid water transport and they appear to participate in cancer proliferation and malignancy. AQP3 expression is increased and AQP9 expression is decreased in hepatocellular carcinoma (HCC) compared to normal liver, which suggests their possible use as targets for cancer treatment. AQP-based modifiers, such as Auphen and dibutyryladenosine 3', 5'-cyclic monophosphate (dbcAMP), might be used to treat several diseases and as chemical tools for assessing the functions of AQPs in biological systems. We investigated the effects of both Auphen on AQP3 and dbcAMP on AQP9 in SMMC-7721 cells. We used western blotting, real-time quantitative polymerase chain reaction (qPCR) and immunohistochemistry to evaluate changes in AQP3 and AQP9 expression in SMMC-7721 cells after culturing with Auphen and dbcAMP, respectively. We also determined the proliferation of SMMC-7721 cells. We found that compared to HL-7702 (L02) liver cells, Auphen increased AQP3 expression in tumor cells, whereas dbcAMP decreased expression of AQP9 in these cells. Also, high concentrations of Auphen and dbcAMP inhibited proliferation of SMMC-7721 cells in vitro. Auphen and dbcAMP may inhibit HCC development and could be considered targets for HCC diagnosis and therapy.

Implication of Renal Aquaporin-3 in Fructose-Induced Metabolic Syndrome and Melatonin Protection

INTRODUCTION

Metabolic Syndrome (MetS) can be induced by ingestion of large amounts of fructose as a consequence of oxidative stress and dyslipidemia.

AIM

We investigated the possible protective effects of melatonin administration on MetS induced in fructose-fed rats with special focus on the role of renal aquaporin-3 (AQP-3).

MATERIALS AND METHODS

Thirty rats were randomly divided into three groups; control, fructose, and fructose plus melatonin. MetS was induced by fructose rich diet and melatonin was injected at a dose of 5 mg/kg dissolved in 1% ethanol in normal saline. After the end of the 6-week experimental period, body weight and fat accretion were assessed. Invasive blood pressure and vascular reactivity were evaluated. Serum lipid profile, glucose, insulin levels, insulin resistance, malondialdehyde (MDA) and uric acid were measured, also underwent renal AQP-3 immunohistochemistry.

RESULTS

Fructose consumption significantly increased fat accretion, systolic blood pressure, serum lipids, insulin levels and insulin resistance, confirming successful establishment of the MetS model. Also serum MDA, uric acid and renal AQP-3 expression increased compared to the control group. Melatonin supplementation significantly decreased the previously measured parameters compared to fructose group.

CONCLUSION

Increased AQP-3 expression may be implicated in fructose induced MetS. Melatonin protective effect against metabolic consensus and vascular affection may be linked to its antioxidant and lipid lowering effect with reduced renal AQP-3 expression.

Role of aquaporins in cell proliferation: What else beyond water permeability?

In addition to the extensive data demonstrating the importance of mammalian AQPs for the movement of water and some small solutes across the cell membrane, there is now a growing body of evidence indicating the involvement of these proteins in numerous cellular processes seemingly unrelated, at least some of them in a direct way, to their canonical function of water permeation. Here, we have presented a broad range of evidence demonstrating that these proteins have a role in cell proliferation by various different mechanisms, namely, by allowing fast cell volume regulation during cell division; by affecting progression of cell cycle and helping maintain the balance between proliferation and apoptosis, and by crosstalk with other cell membrane proteins or transcription factors that, in turn, modulate progression of the cell cycle or regulate biosynthesis pathways of cell structural components. In the end, however, after discussing all these data that strongly support a role for AQPs in the cell proliferation process, it remains impossible to conclude that all these other functions attributed to AQPs occur completely independently of their water permeability, and there is a need for new experiments designed specifically to address this interesting issue.