Roles of aquaporin-3 in the epidermis. J Invest Dermatol. 2008;128:2145-2151. [PMID: 18548108 DOI: 10.1038/jid.2008.70]

Effects of Apigenin on RBL-2H3, RAW264.7, and HaCaT Cells: Anti-Allergic, Anti-Inflammatory, and Skin-Protective Activities

Apigenin (4',5,7-trihydroxyflavone, flavonoid) is a phenolic compound that is known to reduce the risk of chronic disease owing to its low toxicity. The first study on apigenin analyzed its effect on histamine release in the 1950s. Since then, anti-mutation and antitumor properties of apigenin have been widely reported. In the present study, we evaluated the apigenin-mediated amelioration of skin disease and investigated its applicability as a functional ingredient, especially in cosmetics. The effect of apigenin on RAW264.7 (murine macrophage), RBL-2H3 (rat basophilic leukemia), and HaCaT (human immortalized keratinocyte) cells were analyzed. Apigenin (100 μM) significantly inhibited nitric oxide (NO) production, cytokine expression (interleukin (IL)-1β, IL6, cyclooxygenase (COX)-2, and inducible nitric oxide synthase [iNOS]), and phosphorylation of mitogen-activated protein kinase (MAPK) signal molecules, including extracellular signal-regulated kinase (ERK) and c-Jun N-terminal protein kinase (JNK) in RAW264.7 cells. Apigenin (30 M) also inhibited the phosphorylation of signaling molecules (Lyn, Syk, phospholipase Cγ1, ERK, and JNK) and the expression of high-affinity IgE receptor FcεRIα and cytokines (tumor necrosis factor (TNF)-α, IL-4, IL-5, IL-6, IL-13, and COX-2) that are known to induce inflammation and allergic responses in RBL-2H3 cells. Further, apigenin (20 μM) significantly induced the expression of filaggrin, loricrin, aquaporin-3, hyaluronic acid, hyaluronic acid synthase (HAS)-1, HAS-2, and HAS-3 in HaCaT cells that are the main components of the physical barrier of the skin. Moreover, it promoted the expression of human β-defensin (HBD)-1, HBD-2, HBD-3, and cathelicidin (LL-37) in HaCaT cells. These antimicrobial peptides are known to play an important role in the skin as chemical barriers. Apigenin significantly suppressed the inflammatory and allergic responses of RAW264.7 and RBL cells, respectively, and would, therefore, serve as a potential prophylactic and therapeutic agent for immune-related diseases. Apigenin could also be used to improve the functions of the physical and chemical skin barriers and to alleviate psoriasis, acne, and atopic dermatitis.

Diagnosis and treatment of xerosis cutis - a position paper

BACKGROUND AND RATIONALE

Xerosis cutis (also referred to as xeroderma, dry skin, asteatosis) affects more than 10 million individuals in Germany. It is among the most common dermatological diagnoses and a cardinal symptom of many dermatological, internal and neurological diseases. Even though it has been established that basic skin care plays a significant role in the management of patients with xerosis cutis, there are as yet no evidence-based algorithms for diagnosis and treatment.

OBJECTIVE

The present position paper provides physicians across all specialties with a practical, symptom-based approach to the prevention, diagnosis and treatment of xerosis cutis.

METHODS

Within a structured decision-making process, a panel of experienced dermatologists first defined questions relevant to everyday clinical practice, which were then addressed by a systematic review of the literature. Based on the evidence available as well as expert consensus, diagnostic and treatment algorithms were subsequently developed and agreed upon.

RESULTS

Xerosis cutis is generally diagnosed on clinical grounds. Possible trigger factors must be avoided, and comorbidities should be adequately and specifically treated. Suitable skin care products should be chosen with a view to improving skin hydration and restoring its barrier function. They should therefore contain both rehydrating and lipid-replenishing components. The "drier" the skin appears, the greater the lipid content should be (preferably using water-in-oil formulations). The choice of ingredients is based on a patient's individual symptoms, such as scaling (e.g., urea), fissures/rhagades (e.g., urea or dexpanthenol), erythema (e.g., licochalcone A) and pruritus (e.g., polidocanol). Other factors to be considered include the site affected and patient age. Ingredients or rather combinations thereof for which there is good clinical evidence should be preferentially used. The best evidence by far is available for urea, whose efficacy in the treatment of xerosis is further enhanced by combining it with other natural moisturizing components and ceramides. The "xerosimeter" is a tool developed in an effort to facilitate patient management and for training purposes. It not only includes practical tools for diagnosis and follow-up but also a classification of ingredients and a structured treatment algorithm.

CONCLUSION

The structured symptom- and evidence-based approach proposed herein contains a road map for diagnosis and treatment of xerosis cutis. It aims to raise awareness in terms of prevention and early treatment of this condition and may thus improve quality of life and prevent potential sequelae.

Computational Modeling on Aquaporin-3 as Skin Cancer Target: A Virtual Screening Study

Aquaporin-3 (AQP3) is one of the aquaglyceroporins, which is expressed in the basolateral layer of the skin membrane. Studies have reported that human skin squamous cell carcinoma overexpresses AQP3 and inhibition of its function may alleviate skin tumorigenesis. In the present study, we have applied a virtual screening method that encompasses filters for physicochemical properties and molecular docking to select potential hit compounds that bind to the Aquaporin-3 protein. Based on molecular docking results, the top 20 hit compounds were analyzed for stability in the binding pocket using unconstrained molecular dynamics simulations and further evaluated for binding free energy. Furthermore, examined the ligand-unbinding pathway of the inhibitor from its bound form to explore possible routes for inhibitor approach to the ligand-binding site. With a good docking score, stability in the binding pocket, and free energy of binding, these hit compounds can be developed as Aquaporin-3 inhibitors in the near future.

Cartilage acidic protein 1 promotes increased cell viability, cell proliferation and energy metabolism in primary human dermal fibroblasts

Cartilage acidic protein 1 (CRTAC1) is an extracellular matrix protein of human chondrogenic tissue that is also present in other vertebrates, non-vertebrate eukaryotes and in some prokaryotes. The function of CRTAC1 remains unknown but the protein's structure indicates a role in cell-cell or cell-matrix interactions and calcium-binding. The aim of the present study was to evaluate the in vitro effects of hCRTAC1-A on normal human dermal fibroblasts (NHDF). A battery of in vitro assays (biochemical and PCR), immunofluorescence and a biosensor approach were used to characterize the protein's biological activities on NHDF cells in a scratch assay. Gene expression analysis revealed that hCRTAC1-A protein is associated with altered levels of expression for genes involved in the processes of cell proliferation (CXCL12 and NOS2), cell migration (AQP3 and TNC), and extracellular matrix-ECM regeneration and remodeling (FMOD, TIMP1, FN1) indicating a role for hCRTAC1-A in promoting these activities in a scratch assay. In parallel, the candidate processes identified by differential gene transcription were substantiated and extended using Electric cell-substrate impedance sensing (ECIS) technology, immunofluorescence and cell viability assays. Our findings indicate that hCRTAC1-A stimulated cell proliferation, migration and ECM production in primary human fibroblasts in vitro.

Effect of salinity fluctuation on the transcriptome of the Japanese mantis shrimp Oratosquilla oratoria

Salinity fluctuation may detrimentally affect the composition and biological processes of crustaceans. As a euryhaline crustacean, Oratosquilla oratoria can survive at salinities ranging from 20 psu to 40 psu. Therefore, we designed five salinity gradients (20, 25, 30, 35, and 40 psu) and 66.39 Gb clean transcriptome data were obtained after O. oratorias were exposed to each gradient for 24 h. All clean data were spliced into 50,482 unigenes and 17,035 unigenes were annotated in at least one database. Compared with 30 psu, 1010, 851, 1733 and 2188 differentially expressed genes were obtained at 20, 25, 35 and 40 psu, respectively. Results also showed that the osmoregulation of O. oratoria is primarily regulated by lipid and amino acid metabolism, amongst others. No significant up-regulated pathways were enriched at 25 psu and 35 psu, although more significant down-regulated pathways were obtained at 35 psu. Therefore, we assumed that the optimum survival salinity of O. oratoria may range from 25 psu to 35 psu. However, 35 psu may be more suitable for O. oratoria. In addition, 55 unigenes that encode putative inorganic ion exchanges were identified. This study aims to provide fundamental information for understanding the osmoregulation mechanisms of crustaceans.

An uncharacterized region within the N-terminus of mouse TMC1 precludes trafficking to plasma membrane in a heterologous cell line

Mechanotransduction by hair cell stereocilia lies at the heart of sound detection in vertebrates. Considerable effort has been put forth to identify proteins that comprise the hair cell mechanotransduction apparatus. TMC1, a member of the transmembrane channel-like (TMC) family, was identified as a core protein of the mechanotransduction complex in hair cells. However, the inability of TMC1 to traffic through the endoplasmic reticulum in heterologous cellular systems has hindered efforts to characterize its function and fully identify its role in mechanotransduction. We developed a novel approach that allowed for the detection of uncharacterized protein regions, which preclude trafficking to the plasma membrane (PM) in heterologous cells. Tagging N-terminal fragments of TMC1 with Aquaporin 3 (AQP3) and GFP fusion reporter, which intrinsically label PM in HEK293 cells, indicated that residues at the edges of amino acid sequence 138–168 invoke intracellular localization and/or degradation. This signal is able to preclude surface localization of PM protein AQP3 in HEK293 cells. Substitutions of the residues by alanine or serine corroborated that the information determining the intracellular retention is present within amino acid sequence 138–168 of TMC1 N-terminus. This novel signal may preclude the proper trafficking of TMC1 to the PM in heterologous cells.

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.

Aquaporin Channels in the Heart-Physiology and Pathophysiology

Mammalian aquaporins (AQPs) are transmembrane channels expressed in a large variety of cells and tissues throughout the body. They are known as water channels, but they also facilitate the transport of small solutes, gasses, and monovalent cations. To date, 13 different AQPs, encoded by the genes AQP0–AQP12, have been identified in mammals, which regulate various important biological functions in kidney, brain, lung, digestive system, eye, and skin. Consequently, dysfunction of AQPs is involved in a wide variety of disorders. AQPs are also present in the heart, even with a specific distribution pattern in cardiomyocytes, but whether their presence is essential for proper (electro)physiological cardiac function has not intensively been studied. This review summarizes recent findings and highlights the involvement of AQPs in normal and pathological cardiac function. We conclude that AQPs are at least implicated in proper cardiac water homeostasis and energy balance as well as heart failure and arsenic cardiotoxicity. However, this review also demonstrates that many effects of cardiac AQPs, especially on excitation-contraction coupling processes, are virtually unexplored.

Propolis Induces AQP3 Expression: A Possible Way of Action in Wound Healing

Propolis is the generic name of a complex of resinous compound collected by honeybees and it has been utilized for many years in folk medicine. As other products generated by honeybees (such as royal jelly, pollen, honey), propolis has great therapeutic properties, but very little scientific information is available. Therefore, this study was aimed at exploring the potential wound healing properties of propolis. To that end, we utilized an in vitro scratch wound healing model consisting of human immortalized keratinocytes. Our scratch wound data clearly demonstrated that propolis induced a pronounced increase in the wound repair abilities of keratinocytes. A cell migration assay showed that propolis stimulated keratinocytes to close the wound. We revealed the role of H₂O₂ as the main mediator of propolis regenerative properties. We showed that this extracellularly released H₂O₂ could pass across the plasma membrane through a specific aquaporin (i.e., AQP3) modulating intracellular responses. The data offer a biological characterization of propolis positive effects suggesting that propolis could also be utilized in wound treatment within clinical settings.

Inhibitors of Mammalian Aquaporin Water Channels

Aquaporins (AQPs) are water channel proteins that are essential to life, being expressed in all kingdoms. In humans, there are 13 AQPs, at least one of which is found in every organ system. The structural biology of the AQP family is well-established and many functions for AQPs have been reported in health and disease. AQP expression is linked to numerous pathologies including tumor metastasis, fluid dysregulation, and traumatic injury. The targeted modulation of AQPs therefore presents an opportunity to develop novel treatments for diverse conditions. Various techniques such as video microscopy, light scattering and fluorescence quenching have been used to test putative AQP inhibitors in both AQP-expressing mammalian cells and heterologous expression systems. The inherent variability within these methods has caused discrepancy and many molecules that are inhibitory in one experimental system (such as tetraethylammonium, acetazolamide, and anti-epileptic drugs) have no activity in others. Some heavy metal ions (that would not be suitable for therapeutic use) and the compound, TGN-020, have been shown to inhibit some AQPs. Clinical trials for neuromyelitis optica treatments using anti-AQP4 IgG are in progress. However, these antibodies have no effect on water transport. More research to standardize high-throughput assays is required to identify AQP modulators for which there is an urgent and unmet clinical need.

Mannosylerythritol lipids ameliorate ultraviolet A-induced aquaporin-3 downregulation by suppressing c-Jun N-terminal kinase phosphorylation in cultured human keratinocytes

Mannosylerythritol lipids (MELs) are glycolipids and have several pharmacological efficacies. MELs also show skin-moisturizing efficacy through a yet-unknown underlying mechanism. Aquaporin-3 (AQP3) is a membrane protein that contributes to the water homeostasis of the epidermis, and decreased AQP3 expression following ultraviolet (UV)-irradiation of the skin is associated with reduced skin moisture. No previous study has examined whether the skin-moisturizing effect of MELs might act through the modulation of AQP3 expression. Here, we report for the first time that MELs ameliorate the UVA-induced downregulation of AQP3 in cultured human epidermal keratinocytes (HaCaT keratinocytes). Our results revealed that UVA irradiation decreases AQP3 expression at the protein and messenger RNA (mRNA) levels, but that MEL treatment significantly ameliorated these effects. Our mitogen-activated protein kinase inhibitor analysis revealed that phosphorylation of c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase or p38, mediates UVA-induced AQP3 downregulation, and that MEL treatment significantly suppressed the UVA-induced phosphorylation of JNK. To explore a possible mechanism, we tested whether MELs could regulate the expression of peroxidase proliferator-activated receptor gamma (PPAR-γ), which acts as a potent transcription factor for AQP3 expression. Interestingly, UVA irradiation significantly inhibited the mRNA expression of PPAR-γ in HaCaT keratinocytes, whereas a JNK inhibitor and MELs significantly rescued this effect. Taken together, these findings suggest that MELs ameliorate UVA-induced AQP3 downregulation in HaCaT keratinocytes by suppressing JNK activation to block the decrease of PPAR-γ. Collectively, our findings suggest that MELs can be used as a potential ingredient that modulates AQP3 expression to improve skin moisturization following UVA irradiation-induced damage.

Honey-Mediated Wound Healing: H₂O₂ Entry through AQP3 Determines Extracellular Ca2+ Influx

Since Biblical times, honey has been utilized in “folk medicine”, and in recent decades the positive qualities of honey have been re-discovered and are gaining acceptance. Scientific literature states that honey has been successfully utilized on infections not responding to classic antiseptic and antibiotic therapy, because of its intrinsic H₂O₂ production. In our study, we demonstrated the involvement of H₂O₂ as a main mediator of honey regenerative effects on an immortalized human keratinocyte cell line. We observed that this extracellularly released H₂O₂ could pass across the plasma membrane through a specific aquaporin (i.e., AQP3). Once in the cytoplasm H₂O₂, in turn, induces the entry of extracellular Ca²⁺ through Melastatin Transient Receptor Potential 2 (TRPM2) and Orai1 channels. Honey-induced extracellular Ca²⁺ entry results in wound healing, which is consistent with the role played by Ca²⁺ signaling in tissue regeneration. This is the first report showing that honey exposure increases intracellular Ca²⁺ concentration ([Ca²⁺]_i), due to H₂O₂ production and redox regulation of Ca²⁺-permeable ion channels, opening up a new horizon for the utilization of the honey as a beneficial tool.

Aquaporin water channels: New perspectives on the potential role in inflammation

Aquaporins (AQPs) are a family of membrane water channel proteins that osmotically modulate water fluid homeostasis in several tissues; some of them also transport small solutes such as glycerol. At the cellular level, the AQPs regulate not only cell migration and transepithelial fluid transport across membranes, but also common events that are crucial for the inflammatory response. Emerging data reveal a new function of AQPs in the inflammatory process, as demonstrated by their dysregulation in a wide range of inflammatory diseases including edematous states, cancer, obesity, wound healing and several autoimmune diseases. This chapter summarizes the discoveries made so far about the structure and functions of the AQPs and provides updated information on the underlying mechanisms of AQPs in several human inflammatory diseases. The discovery of new functions for AQPs opens new vistas offering promise for the discovery of mechanisms and therapeutic opportunities in inflammatory disorders.

Histopathological evaluation of oral membranous substance in bedridden elderly persons without oral intake in Japan

OBJECTIVES

The aim of this study was to clarify by histopathological examination the origin of oral membranous substances deposited on the palate, tongue, buccal mucosa and teeth.

BACKGROUND

Several investigators have reported membranous substances deposited in the mouths of bedridden elderly persons requiring nursing care without oral intake. However, the precise nature and origin of the substances are poorly understood.

METHODS

Sixty-nine specimens were taken from the oral cavity of bedridden patients, that is, the palate, dorsum of the tongue, the cheek and teeth. Sections were stained with haematoxylin and eosin stain, alcian-blue and periodic acid-Schiff stain (AB-PAS) and antibodies for pankeratin (AE1AE3) and leukocyte common antigen (LCA).

RESULTS

All specimens showed a film-like nature coloured from tan to white, accompanied by a mucous substance. Histologically, specimens of all sites had a similar feature of the combination of basophilic amorphous and eosinophilic lamellar features. The basophilic substance was positive for AB-PAS, and PAS-positive glycogen granules were also noted in the lamellar structure. Immunochemistry revealed various degrees of pankeratin positive substance and LCA-positive inflammatory cell infiltration.

CONCLUSION

The oral membranous substance was composed of keratin and mucin with inflammation. These results suggest that the deposition of the oral membranous substance is a pathological condition or oral mucositis caused by dry mouth.

Water transport proteins-aquaporins (AQPs) in cancer biology

As highly conserved ubiquitous proteins, aquaporins (AQPs) play an imperative role in the development and progression of cancer. By trafficking water and other small molecules, AQPs play a vital role in preserving the cellular environment. Due to their critical role in cell stability and integrity, it would make sense that AQPs are involved in cancer progression. When AQPs alter the cellular environment, there may be several downstream effects such as alterations in cellular osmolality, volume, ionic composition, and signaling pathways. Changes in the intracellular levels of certain molecules serving as second messengers are synchronized by AQPs. Thus AQPs regulate numerous downstream effector signaling molecules that promote cancer development and progression. In numerous cancer types, AQP expression has shown a correlation with tumor stage and prognosis. Furthermore, AQPs assist in angiogenic and oxidative stress related damaging processes critical for cancer progression. This indicates that AQP proteins may be a viable therapeutic target or biomarker of cancer prognosis.

CEGP-003 Spray Has a Similar Hemostatic Effect to Epinephrine Injection in Cases of Acute Upper Gastrointestinal Bleeding

BACKGROUND

Endoscopically applicable hemostatic agents have been demonstrated to have high initial hemostasis rates in cases of upper gastrointestinal bleeding (UGIB).

AIMS

The authors developed a new hemostatic powder (CEGP-003) and evaluated its hemostatic and ulcer healing effects in UGIB.

METHODS

Patients with peptic ulcer or post-endoscopic resection bleeding were randomly assigned to be treated by epinephrine injection or CEGP-003 spray. All patients were placed under observation for 3 days and underwent second-look endoscopy. The primary outcome was initial hemostasis rate, and the secondary outcomes were rebleeding rate and ulcer healing effect.

RESULTS

Seventy-two patients with UGIB were enrolled in this study. Causes of bleeding were peptic ulcer (15, 20.5%), post-endoscopic mucosal resection (11, 15.1%), and post-endoscopic submucosal dissection bleeding (47, 64.4%). Initial hemostasis was achieved in 89.2% (34/37) of patients in the epinephrine group and in 100% (35/35) in the CEGP-003 group (p = 0.115). Rebleeding occurred in 2.7% (1/37) and 8.6% (3/35) in the epinephrine and CEGP-003 groups, respectively (p = 0.35). Three days after endoscopic hemostasis, the ulcer healing effects of epinephrine and CEGP-003 were similar (p = 0.79).

CONCLUSION

This study shows that CEGP-003 spray has a hemostatic effect similar to epinephrine in terms of initial hemostasis and rebleeding rates. The authors consider CEGP-003 a potential therapeutic tool for UGIB as a definitive or bridge therapy and that it is particularly useful for oozing lesions after endoscopic resection.

Protein biomarker for psoriasis: A systematic review on their role in the pathomechanism, diagnosis, potential targets and treatment of psoriasis

Psoriasis is defined as a long-lasting multifactorial inflammatory autoimmune skin condition precisely characterized by delimited, erythematic papules with adherent shiny scales. The conditions are led by hyperproliferative responses of epidermis due to hyperactivation and immature keratinocytes production. The psoriatic skin consists of the thickened epidermal layer, in concurrence with inflammatory exudates in the dermis mainly of dendritic cells, neutrophils, T cells, and macrophages, contributing to the distinct manifestation of psoriatic lesions. It consents to multifaceted and discrete pathology due to the genetic and immunological alteration resulting from abnormal expression of various regulatory and structural proteins. These proteins are associated with various cellular and sub-cellular activities. Therefore, the presence of protein in a pathological cellular environment in the psoriatic lesions as well as in serum could be a great avenue for the insight of pathomechanism, anticipation and diagnosis of psoriasis. Research of protein biomarker in psoriasis is yet a developing realm to be explored by both fundamental and clinical researchers. This review is an attempt to assimilate the current discoveries and revelations of different proteins as a biomarker and their importance in pathogenesis, diagnosis, treatment, and anticipation of both the inflammatory and other dermatological aspects of psoriasis.

Nonclinical and human pharmacology of the potent and selective topical retinoic acid receptor-γ agonist trifarotene

BACKGROUND

First- and third-generation retinoids are the main treatment for acne. Even though efficacious, they lack full selectivity for retinoic acid receptor (RAR) γ, expressed in the epidermis and infundibulum.

OBJECTIVES

To characterize the in vitro metabolism and the pharmacology of the novel retinoid trifarotene.

MATERIALS AND METHODS

In vitro assays determined efficacy, potency and selectivity on RARs, as well as the activity on the expression of retinoid target genes in human keratinocytes and ex vivo cultured skin. In vivo studies investigated topical comedolytic, anti-inflammatory and depigmenting properties. The trifarotene-induced gene expression profile was investigated in nonlesional skin of patients with acne and compared with ex vivo and in vivo models. Finally, the metabolic stability in human keratinocytes and hepatic microsomes was established.

RESULTS

Trifarotene is a selective RARγ agonist with > 20-fold selectivity over RARα and RARβ. Trifarotene is active and stable in keratinocytes but rapidly metabolized by human hepatic microsomes, predicting improved safety. In vivo, trifarotene 0·01% applied topically is highly comedolytic and has anti-inflammatory and antipigmenting properties. Gene expression studies indicated potent activation of known retinoid-modulated processes (epidermal differentiation, proliferation, stress response, retinoic acid metabolism) and novel pathways (proteolysis, transport/skin hydration, cell adhesion) in ex vivo and in vivo models, as well as in human skin after 4 weeks of topical application of trifarotene 0·005% cream.

CONCLUSIONS

Based on its RARγ selectivity, rapid degradation in human hepatic microsomes and pharmacological properties including potent modulation of epidermal processes, topical treatment with trifarotene could result in good efficacy and may present a favourable safety profile in acne and ichthyotic disorders.

Downregulation of aquaporin 3 inhibits cellular proliferation, migration and invasion in the MDA-MB-231 breast cancer cell line

Aquaporins are membrane proteins that regulate cellular water flow. Recently, aquaporins have been proposed as mediators of cancer cell biology. A subset of aquaporins, referred to as aquaglyceroporins are known to facilitate the transport of glycerol. The present study describes the effect of gene knockdown of the aquaglyceroporin AQP3 on MDA-MB-231 breast cancer cell proliferation, migration, invasion, adherence and response to the chemotherapeutic agent 5-fluorouracil. shRNA mediated AQP3 gene knockdown induced a 28% reduction in cellular proliferation (P<0.01), a 39% decrease in migration (P<0.0001), a 24% reduction in invasion (P<0.05) and a 25% increase in cell death at 100 µM 5-FU (P<0.01). Analysis of cell permeability to water and glycerol revealed that MDA-MB-231 cells with knocked down AQP3 demonstrated a modest decrease in water permeability (17%; P<0.05) but a more marked decrease in glycerol permeability (77%; P<0.001). These results suggest that AQP3 has a role in multiple aspects of breast cancer cell pathophysiology and therefore represents a novel target for therapeutic intervention.

Forensic application of epidermal AQP3 expression to determination of wound vitality in human compressed neck skin

In forensic practices, it is often difficult to determine wound vitality in compression marks of the neck with naked eyes. AQP1 and AQP3 are the major water channels associated with skin. Thus, we immunohistochemically examined the expression of AQP1 and AQP3 in neck skin samples to discuss their forensic applicability to determination of the wound vitality. Skin samples were obtained from 56 neck compression cases (hanging, 35 cases; strangulation, 21 cases). The intact skin from the same individual was taken as a control. Although AQP1 was immnunostained in dermal capillaries in both the neck compression marks and intact skin samples, there was no significant difference in the magnitude of AQP1 expression between both groups. On the contrary, AQP3-positive signals could be faintly detected in uninjured skin samples, and the positive signals seemed more intense in the keratinocytes in compression regions. Morphometrical analyses revealed that the ratio of AQP3-expressed keratinocytes was significantly enhanced in neck compression regions, compared with control groups. From the viewpoints of forensic pathology, immunohistochemical detection of AQP3 in the neck skin can be considered a valuable marker to diagnose the trace of antemortem compression.

Circadian rhythm in atopic dermatitis-Pathophysiology and implications for chronotherapy

Circadian rhythm is a biological clock that controls a wide range of physiological functions throughout the body, including various skin functions. A 24-h diurnal cycle, governed by an endogenous clock in the brain, largely controls cutaneous diurnal rhythm, which external factors, including temperature, humidity, diet, and stress, also modulate locally. Circadian rhythm influences cutaneous blood flow and properties of skin barrier function, such as transepidermal water loss and capacitance, and has important implications in atopic dermatitis (AD). This review explores how aberrations in circadian rhythm may play a role in the pathogenesis of AD and proposes implementation of chronotherapy to improve treatment outcomes in patients with AD.

Immunohistochemical analysis on aquaporin-1 and aquaporin-3 in skin wounds from the aspects of wound age determination

Immunohistochemical investigation of aquaporin (AQP)1 and AQP3 was performed in human skin wounds obtained from forensic autopsy cases. A total of 55 human skin wounds of different postinfliction intervals were collected as follows: group I, 0-3 days (n = 16); II, 4-7 days (n = 11); III, 9-14 days (n = 16); and IV, 17-21 days (n = 12). In uninjured skin samples, AQP1 and AQP3 could be slightly detected in dermal vessels and keratinocytes, respectively. The percentage of AQP1⁺ vessels and the number of AQP3⁺ keratinocytes were apparently elevated in accordance with wound ages. The number of AQP3⁺ keratinocytes was distinctly evident in groups II and III. Morphometrically, both AQP1⁺ vessel area and AQP3⁺ cell number were markedly increased in group II, compared with other three groups. With regard to forensic safety, AQP1⁺ vessel area of over 5% would imply wound ages of 4-12 days. Moreover, the positive area of > 15% would suggest wound age of 7-10 days. Especially, most samples of skin wounds aged 5-10 days except for only one sample (a 10-day-old wound) showed AQP3⁺ cell number of > 300, and the remaining other samples had that of < 300. Thus, the AQP3⁺ cell number of > 300 would indicate wound ages of 5-10 days. Collectively, immunohistochemical analyses of AQP1 and AQP3 in human skin wounds would support the objective accuracy of wound age determination.

Quantification of the Intracellular Life Time of Water Molecules to Measure Transport Rates of Human Aquaglyceroporins

Orthodox aquaporins are transmembrane channel proteins that facilitate rapid diffusion of water, while aquaglyceroporins facilitate the diffusion of small uncharged molecules such as glycerol and arsenic trioxide. Aquaglyceroporins play important roles in human physiology, in particular for glycerol metabolism and arsenic detoxification. We have developed a unique system applying the strain of the yeast Pichia pastoris, where the endogenous aquaporins/aquaglyceroporins have been removed and human aquaglyceroporins AQP3, AQP7, and AQP9 are recombinantly expressed enabling comparative permeability measurements between the expressed proteins. Using a newly established Nuclear Magnetic Resonance approach based on measurement of the intracellular life time of water, we propose that human aquaglyceroporins are poor facilitators of water and that the water transport efficiency is similar to that of passive diffusion across native cell membranes. This is distinctly different from glycerol and arsenic trioxide, where high glycerol transport efficiency was recorded.

18ß-glycyrrhetinic acid derivative promotes proliferation, migration and aquaporin-3 expression in human dermal fibroblasts

Licorice (Glycyrrhiza) species have been widely used as a traditional medicine and a natural sweetener in foods. The 18β-glycyrrhetinic acid (18β-GA) is a bioactive compound in licorice that exhibits potential anti-cancer, anti-inflammatory, and anti-microbial activities. Many synthesized derivatives of 18β-GA have been reported to be cytotoxic and suggested for the treatment of malignant diseases. In this study, we explored the possible pharmacological roles of an 18β-GA derivative in skin biology using primary human dermal fibroblasts and HaCaT keratinocytes as cell models. We found that this 18β-GA derivative did not cause cell death, but significantly enhanced the proliferation of dermal fibroblasts and HaCaT keratinocytes. A scratch wound healing assay revealed that the 18β-GA derivative promoted the migration of fibroblasts. Due to the important role of aquaporin-3 in cell migration and proliferation, we also investigated the expression of aquaporin-3 and found this compound up-regulated the expression of aquaporin-3 in dermal fibroblasts and HaCaT keratinocytes. In dermal fibroblasts, the 18β-GA derivative induced the phosphorylation of Akt, ERK, and p38. The inhibitor of Akt predominantly suppressed the 18β-GA derivative-induced expression of aquaporin-3. Collectively, this compound had a positive effect on the proliferation, migration, and aquaporin-3 expression of skin cells, implying its potential role in the treatment of skin diseases characterized by impaired wound healing or dermal defects.

Is Aquaporin-3 a Determinant Factor of Intrinsic and Extrinsic Aging? An Immunohistochemical and Morphometric Study

Aquaporin-3 (AQP3) is an aquaglyceroporin that plays a role in skin hydration, cell proliferation, and migration. The aim of this work was to investigate the expression of AQP3 in sun-exposed and sun-protected human skin from different age groups to understand the relationship between AQP3 and skin aging. Using standard immunohistochemical techniques, sun-exposed and sun-protected skin biopsies were taken from 60 normal individuals. AQP3 was expressed in the basal and the suprabasal layers, sparing the stratum corneum, in all specimens. Dermal expression was detected in fibroblasts, endothelial cells, and adnexa. Sun-protected skin showed a significantly higher epidermal H-score and percentage of expression (P=0.002 and <0.001, respectively) compared with sun-exposed skin. The AQP3 expression intensity showed a gradual decrease from the 20 to 35-year-old group to the 35 to 50-year-old group, with the least immunoreactivity in the above 50-year-old group. A significant difference was detected in the H-score in favor of the 20 to 35-year-old group in sun-exposed and sun-protected skin (P<0.001 for both). A significant negative correlation was noted between the AQP3 expression percentage and the age in sun-exposed (r=-0.64, P<0.001) and sun-protected skin (r=-0.53, P<0.001). In conclusion, the skin dryness observed in intrinsic and extrinsic aged skin may be explained, at least in part, by AQP3 downregulation. This may open new avenues sufficient to control skin texture and beauty. Its interaction in skin protein organization and gene polymorphism can also be tackled in future research. In addition, clinical trials using AQP3 topical applications should be carried out to evaluate its effectiveness in the reversal of age-related skin changes.

Biological properties of mud extracts derived from various spa resorts

Spa resorts are known for thousands of years for their healing properties and have been empirically used for the treatment of many inflammatory conditions. Mud is one of the most often used natural materials for preventive, healing and cosmetic reasons and although it has been used since the antiquity, little light has been shed on its physical, chemical and biological properties. In this study we examined the effect of mud extracts on the expression of adhesion molecules (CAMs) by endothelial cells as well as their effects on monocyte adhesion to activated endothelial cells. Most of mud extracts inhibited the expression of VCAM-1 by endothelial cells and reduced monocyte adhesion to activated endothelial cells, indicating a potent anti-inflammatory activity. Furthermore, the mud extracts were tested for their antimicrobial activity; however, most of them appeared inactive against S. aureus and S. epidermidis. One of the mud extracts (showing the best stabilization features) increased significantly the expression of genes involved in cell protection, longevity and hydration of human keratinocytes, such as, collagen 6A1, forkhead box O3, sirtuin-1, superoxide dismutase 1 and aquaporin-3. The present study reveals that mud exerts important beneficial effects including anti-inflammatory and anti-aging activity as well as moisturizing effects, implicating important cosmeceutical applications.

Topical Erythropoietin Treatment Accelerates the Healing of Cutaneous Burn Wounds in Diabetic Pigs Through an Aquaporin-3-Dependent Mechanism

We have previously reported that the topical application of erythropoietin (EPO) to cutaneous wounds in rats and mice with experimentally induced diabetes accelerates their healing by stimulating angiogenesis, reepithelialization, and collagen deposition, and by suppressing the inflammatory response and apoptosis. Aquaporins (AQPs) are integral membrane proteins whose function is to regulate intracellular fluid hemostasis by enabling the transport of water and glycerol. AQP3 is the AQP that is expressed in the skin where it facilitates cell migration and proliferation and re-epithelialization during wound healing. In this report, we provide the results of an investigation that examined the contribution of AQP3 to the mechanism of EPO action on the healing of burn wounds in the skin of pigs with experimentally induced type 1 diabetes. We found that topical EPO treatment of the burns accelerated their healing through an AQP3-dependent mechanism that activates angiogenesis, triggers collagen and hyaluronic acid synthesis and the formation of the extracellular matrix (ECM), and stimulates reepithelialization by keratinocytes. We also found that incorporating fibronectin, a crucial constituent of the ECM, into the topical EPO-containing gel, can potentiate the accelerating action of EPO on the healing of the burn injury.

Retinoic acid receptor-related orphan receptor RORα regulates differentiation and survival of keratinocytes during hypoxia

Low O₂ pressures present in the microenvironment of epidermis control keratinocyte differentiation and epidermal barrier function through hypoxia inducible factors (HIFs) dependent gene expression. This study focuses on investigating relations of the retinoic acid receptor-related orphan receptor alpha (RORα) to HIF-1α in keratinocytes under hypoxic conditions. The expression level of RORα is significantly elevated under hypoxia in both human and murine keratinocytes. Gene silencing of RORA attenuates hypoxia-stimulated expression of genes related to late differentiation and epidermal barrier function, and leads to an enhanced apoptotic response. While the hypoxic induction of RORα is dependent on HIF-1α, RORα is in turn critical for nuclear accumulation of HIF-1α and activation of HIF transcriptional activity. These results collectively suggest that RORα functions as an important mediator of HIF-1α activities in regulating keratinocyte differentiation/survival and epidermal barrier function during the oxygen sensing stage.

N-Acetylglutaminoyl-S-farnesyl-L-cysteine (SIG-1191): an anti-inflammatory molecule that increases the expression of the aquaglyceroporin, aquaporin-3, in human keratinocytes

Isoprenylcysteine (IPC) small molecules were discovered as signal transduction modulating compounds ~25 years ago. More recently, IPC molecules have demonstrated antioxidant and anti-inflammatory properties in a variety of dermal cells as well as antimicrobial activity, representing a novel class of compounds to ameliorate skin conditions and disease. Here, we demonstrate a new IPC compound, N-acetylglutaminoyl-S-farnesyl-L-cysteine (SIG-1191), which inhibits UVB-induced inflammation blocking pro-inflammatory cytokine interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) production. To investigate further the previously reported hydrating potential of IPC compounds, SIG-1191 was tested for its ability to modulate aquaporin expression. Specifically, aquaporin 3 (AQP3) the most abundant aquaporin found in skin has been reported to play a key role in skin hydration, elasticity and barrier repair. Results show here for the first time that SIG-1191 increases AQP3 expression in both cultured normal human epidermal keratinocytes as well as when applied topically in a three-dimensional (3D) reconstructed human skin equivalent. Additionally, SIG-1191 dose dependently increased AQP3 protein levels, as determined by specific antibody staining, in the epidermis of the 3D skin equivalents. To begin to elucidate which signaling pathways SIG-1191 may be modulating to increase AQP3 levels, we used several pharmacological pathway inhibitors and determined that AQP3 expression is mediated by the Mitogen-activated protein kinase/Extracellular signal-regulated kinase kinase (MEK) pathway. Altogether, these data suggest SIG-1191 represents a new IPC derivative with anti-inflammatory activity that may also promote increased skin hydration based on its ability to increase AQP3 levels.

Aquaporin modulators: a patent review (2010-2015)

INTRODUCTION

Since the discovery of aquaporin-1 (AQP1) as a water channel, more than 2,000 articles, reviews and chapters have been published. The wide tissue expression, functional and biological roles have documented the major and essential physiological importance of these channels both in health and disease. Thus, over the years, studies have revealed essential importance of aquaporins in mammalian pathophysiology revealing aquaporins as potential drug targets. Areas covered: Starting from a brief description of the main structural and functional features of aquaporins, their roles in physiology and pathophysiology of different human diseases, this review describes the main classes of small molecules and biologicals patented, published from 2010 to 2015, able to regulate AQPs for diagnostic and therapeutic applications. Expert opinion: Several patents report on AQP modulators, mostly inhibitors, and related pharmaceutical formulations, to be used for treatments of water imbalance disorders, such as edema. Noteworthy, a unique class of gold-based compounds as selective inhibitors of aquaglyceroporin isoforms may provide new chemical tools for therapeutic applications, especially in cancer. AQP4-targeted therapies for neuromyelitis optica, enhancement of AQP2 function for nephrogenic diabetes insipidus and AQP1-5 gene transfer for the Sjogren's syndrome represent promising therapies that deserve further investigation by clinical trials.

Expression and localization of aqua-glyceroporins AQP3 and AQP9 in rat oral epithelia

Aquaporins (AQPs) are a family of small integral membrane proteins made up of 6 hydrophobic, a-helical, membrane-spanning domains surrounding a highly selective aqueous pore. AQP3, AQP7, and AQP9, termed aqua-glyceroporins, are known to be involved in the transport of water, glycerol, and other small molecules. In this study, we investigated the expression and localization of aqua-glyceroporins in rat oral stratified squamous epithelia of the palate, the buccal mucosa, the inferior aspect of the tongue, and the oral floor by using RT-PCR, immunofluorescence, and immunogold electron microscopy. AQP3 and AQP9 mRNAs were expressed in whole oral epithelium. Immunostaining for AQP3 was recognized in each type of epithelium. The results suggest that AQP3 synthesis begins predominantly in the cytoplasm of the basal cells. During the process of epithelial cell differentiation, AQP3 protein appears to accumulate and be transported to the plasma membrane, from where it is incorporated into the cornified or surface layers. The intracellular localization of AQP3 appears to correlate with the differentiation of keratinocytes, suggesting that it acts as an enhancer of the physiological permeability barrier together with membrane coating granules. The distribution pattern of AQP9 was limited to the marginal areas of the basal and suprabasal layers, which was different from that of AQP3. This difference in distribution between AQP3 and AQP9 suggests that AQP9 in rat oral epithelia acts as a channel by facilitating glycerol uptake from the blood through the endothelial cells of the capillary vessels to the oral stratified squamous epithelium. AQP3 and AQP9 facilitate both transcellular osmotic water flow and glycerol transport as pore-like passive transporters in the keratinocytes of oral epithelia, and may play a key role in not only hydration and the permeability barrier, but also cell proliferation, differentiation, migration, development, and wound healing by generating ATP.

Endothelial Aquaporin-1 (AQP1) Expression Is Regulated by Transcription Factor Mef2c

Aquaporin 1 (AQP1) is expressed in most microvasculature endothelial cells and forms water channels that play major roles in a variety of physiologic processes. This study aimed to delineate the transcriptional regulation of AQP1 by Mef2c in endothelial cells. Mef2c cooperated with Sp1 to activate human AQP1 transcription by binding to its proximal promoter in human umbilical cord vein endothelial cells (HUVEC). Over-expression of Mef2c, Sp1, or Mef2c/Sp1 increased HUVEC migration and tube-forming ability, which can be abolished AQP1 knockdown. These data indicate that AQP1 is a direct target of Mef2c in regulating angiogenesis and vasculogenesis of endothelial cells.

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.

Aquaporin 3 is regulated by estrogen in the chicken oviduct and is involved in progression of epithelial cell-derived ovarian carcinomas

Aquaporins (AQPs) are membrane proteins that passively deliver water across the plasma membrane to play an important role in maintaining cell shape. Members of the AQP family are distributed in most of the tissues in the human body and perform a variety of functions based on the water homeostasis suitable for each organ. However, there is little known about the expression and regulation of AQP family members in chickens. Therefore, we determined the expression of AQPs in various tissues of chickens. Among 13 isotypes, AQP3 was highly expressed in the chicken oviduct. Expression of AQP3 messenger RNA (mRNA) increased in the magnum (P < 0.001) and isthmus (P < 0.001) of chick oviducts treated with diethylstilbestrol. Consistent with these results, the localization of AQP3 was detected in the glandular and luminal epithelia of the magnum and isthmus of oviducts of diethylstilbestrol-treated chicks. In addition, the pattern of expression of AQP3 changed in an estrogen-dependent manner during the molting period. During the regenerative period of the oviduct after molting, expression of AQP3 mRNA increased coordinately with increasing concentrations of estradiol (P < 0.001), whereas expression of AQP3 mRNA decreased as concentrations of estradiol in plasma decreased in response to induced molting (P < 0.001). Also, expression of the AQP3 increased (P < 0.001) in cancerous ovaries of laying hens. In conclusion, AQP3 does not simply function to transport water into and out of cells but also appears to be closely involved in development of the chicken oviduct, which is regulated by estrogens. Furthermore, our results suggest AQP3 as a new diagnostic for early detection and treatment of epithelial cell-derived ovarian carcinomas.

Auphen and dibutyryl cAMP suppress growth of hepatocellular carcinoma by regulating expression of aquaporins 3 and 9 in vivo

AIM: To investigate whether the regulation of aquaporin 3 (AQP3) and AQP9 induced by Auphen and dibutyryl cAMP (dbcAMP) inhibits hepatic tumorigenesis.

METHODS: Expression of AQP3 and AQP9 was detected by Western blot, immunohistochemistry (IHC), and RT-PCR in HCC samples and paired non-cancerous liver tissue samples from 30 hepatocellular carcinoma (HCC) patients. A xenograft tumor model was used in vivo. Nine nude mice were divided into control, Auphen-treated, and dbcAMP-treated groups (n = 3 for each group). AQP3 and AQP9 protein expression after induction of xenograft tumors was detected by IHC and mRNA by RT-PCR analysis. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling assay and histological evaluation were used to detect apoptosis of tumor cells, and the concentration of serum α-fetoprotein (AFP) was measured using RT-PCR and an ELISA kit.

RESULTS: The volumes and weights of tumors decreased significantly in the Auphen- and dbcAMP-treated mice compared with the control mice (P < 0.01). The levels of AQP3 were significantly lower in the Auphen treatment group, and levels of AQP9 were significantly higher in thedbcAMP treatment mice than in the control mice (P < 0.01). The reduction of AQP3 by Auphen and increase of AQP9 by dbcAMP in nude mice suppressed tumor growth of HCC, which resulted in reduced AFP levels in serum and tissues, and apoptosis of tumor cells in the Auphen- and dbcAMP-treated mice, when compared with control mice (P < 0.01). Compared with para-carcinoma tissues, AQP3 expression increased in tumor tissues whereas the expression of AQP9 decreased. By correlating clinicopathological and expression levels, we demonstrated that the expression of AQP3 and AQP9 was correlated with clinical progression of HCC and disease outcomes.

CONCLUSION: AQP3 increases in HCC while AQP9 decreases. Regulation of AQP3 and AQP9 expression by Auphen and dbcAMP inhibits the development and growth of HCC.

Aquaporin-3 Controls Breast Cancer Cell Migration by Regulating Hydrogen Peroxide Transport and Its Downstream Cell Signaling

Most breast cancer mortality is due to clinical relapse associated with metastasis. CXCL12/CXCR4-dependent cell migration is a critical process in breast cancer progression; however, its underlying mechanism remains to be elucidated. Here, we show that the water/glycerol channel protein aquaporin-3 (AQP3) is required for CXCL12/CXCR4-dependent breast cancer cell migration through a mechanism involving its hydrogen peroxide (H2O2) transport function. Extracellular H2O2, produced by CXCL12-activated membrane NADPH oxidase 2 (Nox2), was transported into breast cancer cells via AQP3. Transient H2O2 accumulation was observed around the membrane during CXCL12-induced migration, which may be facilitated by the association of AQP3 with Nox2. Intracellular H2O2 then oxidized PTEN and protein tyrosine phosphatase 1B (PTP1B) followed by activation of the Akt pathway. This contributed to directional cell migration. The expression level of AQP3 in breast cancer cells was related to their migration ability both in vitro and in vivo through CXCL12/CXCR4- or H2O2-dependent pathways. Coincidentally, spontaneous metastasis of orthotopic xenografts to the lung was reduced upon AQP3 knockdown. These findings underscore the importance of AQP3-transported H2O2 in CXCL12/CXCR4-dependent signaling and migration in breast cancer cells and suggest that AQP3 has potential as a therapeutic target for breast cancer.