Advanced Glycation End Products and Activation of Toll-like Receptor-2 and -4 Induced Changes in Aquaporin-3 Expression in Mouse Keratinocytes.

Prolonged inflammation and impaired re-epithelization are major contributing factors to chronic non-healing diabetic wounds; diabetes is also characterized by xerosis. Advanced glycation end products (AGEs), and the activation of toll-like receptors (TLRs), can trigger inflammatory responses. Aquaporin-3 (AQP3) plays essential roles in keratinocyte function and skin wound re-epithelialization/re-generation and hydration. Suberanilohydroxamic acid (SAHA), a histone deacetylase inhibitor, mimics the increased acetylation observed in diabetes. We investigated the effects of TLR2/TLR4 activators and AGEs on keratinocyte AQP3 expression in the presence and absence of SAHA. Primary mouse keratinocytes were treated with or without TLR2 agonist Pam3Cys-Ser-(Lys)4 (PAM), TLR4 agonist lipopolysaccharide (LPS), or AGEs, with or without SAHA. We found that (1) PAM and LPS significantly upregulated AQP3 protein basally (without SAHA) and PAM downregulated AQP3 protein with SAHA; and (2) AGEs (100 µg/mL) increased AQP3 protein expression basally and decreased AQP3 levels with SAHA. PAM and AGEs produced similar changes in AQP3 expression, suggesting a common pathway or potential crosstalk between TLR2 and AGEs signaling. Our findings suggest that TLR2 activation and AGEs may be beneficial for wound healing and skin hydration under normal conditions via AQP3 upregulation, but that these pathways are likely deleterious in diabetes chronically through decreased AQP3 expression.

A potential link between AQP3 and SLC14A1 gene expression level and clinical parameters of maintenance hemodialysis patients.

BACKGROUND: The transport of water and urea through the erythrocyte membrane is facilitated by aquaporins such as aquaglyceroporin (AQP3), and type B urea transporters (UT-B). As they may play an important role in osmotic balance of maintenance hemodialysis (HD) patients, the aim of the present study was to determine whether any relationship exists between the expression of their genes and the biochemical / clinical parameters in HD patients. METHODS: AQP3 and UT-B (SLC14A1) gene expression was evaluated using RT-qPCR analysis in 76 HD patients and 35 participants with no kidney failure. RESULTS: The HD group demonstrated significantly higher median expression of AQP3 and UT-B (Z = 2.16; P = 0.03 and Z = 8.82; p < 0.0001, respectively) than controls. AQP3 negatively correlated with pre-dialysis urea serum concentration (R = -0.22; P = 0.049) and sodium gradient (R = -0.31; P = 0.04); however, no significant UT-B correlations were observed. Regarding the cause of end-stage kidney disease, AQP3 expression positively correlated with erythropoietin dosages in the chronic glomerulonephritis (GN) subgroup (R = 0.6; P = 0.003), but negatively in the diabetic nephropathy subgroup (R = -0.59; P = 0.004). UT-B positively correlated with inter-dialytic weight gain% in the GN subgroup (R = 0.47; P = 0.03). CONCLUSION: Maintenance hemodialysis seems significantly modify AQP3 and UT-B expression but their link to clinical and biochemical parameters needs further large-scale evaluation.

Aquaporin 3 promotes human extravillous trophoblast migration and invasion.

PROBLEM: Does aquaporin 3 (AQP3) affect the migration and invasion of human extravillous trophoblast (HTR8/Svneo) cells? METHOD OF STUDY: A lentivirus infection system was used to construct stable cell lines with either AQP3 knockdown or overexpression. RT-PCR and western blotting were used to verify the efficiencies of AQP3 knockdown or overexpression in HTR8/Svneo cells at mRNA and protein levels, respectively. Cell Counting Kit-8 and flow cytometry assays were used to detect the influence of AQP3 knockdown or overexpression on proliferation and apoptosis of HTR8/Svneo cells. In addition, wound healing and Transwell invasion assays were used to detect the effects of AQP3 knockdown or overexpression on migration and invasion capabilities of HTR8/Svneo cells. An Agilent gene chip was used to screen for significant differentially expressed genes after AQP3 knockdown. Finally, mechanisms by which AQP3 influences the migration and invasion of HTR8/Svneo cells were explored using bioinformatic analysis. RESULTS: Compared with controls, migration and invasion capabilities of HTR8/Svneo cells were significantly reduced after AQP3 knockdown, and significantly increased after AQP3 overexpression. Subsequent bioinformatic analysis of gene chip expression profiles indicated downregulation of genes related to adhesion such as PDGF-B, as well as signaling pathways (such as PIK3/AKT, NF-κB, and TNF) after AQP3 knockdown. CONCLUSIONS: AQP3 could significantly promote migration and invasion capabilities of human extravillous trophoblasts, it may mediate embryo invasion and adhesion to endometrium by regulating PDGF-B, PIK3/AKT signaling pathways, although this requires further verification.

Glycerol Improves Skin Lesion Development in the Imiquimod Mouse Model of Psoriasis: Experimental Confirmation of Anecdotal Reports from Patients with Psoriasis.

Glycerol is used in many skin care products because it improves skin function. Anecdotal reports by patients on the National Psoriasis Foundation website also suggest that glycerol may be helpful for the treatment of psoriasis, although to date no experimental data confirm this idea. Glycerol entry into epidermal keratinocytes is facilitated by aquaglyceroporins like aquaporin-3 (AQP3), and its conversion to phosphatidylglycerol, a lipid messenger that promotes keratinocyte differentiation, requires the lipid-metabolizing enzyme phospholipase-D2 (PLD2). To evaluate whether glycerol inhibits inflammation and psoriasiform lesion development in the imiquimod (IMQ)-induced mouse model of psoriasis, glycerol's effect on psoriasiform skin lesions was determined in IMQ-treated wild-type and PLD2 knockout mice, with glycerol provided either in drinking water or applied topically. Psoriasis area and severity index, ear thickness and ear biopsy weight, epidermal thickness, and inflammatory markers were quantified. Topical and oral glycerol ameliorated psoriasiform lesion development in wild-type mice. Topical glycerol appeared to act as an emollient to induce beneficial effects, since even in PLD2 knockout mice topical glycerol application improved skin lesions. In contrast, the beneficial effects of oral glycerol required PLD2, with no improvement in psoriasiform lesions observed in PLD2 knockout mice. Our findings suggest that the ability of oral glycerol to improve psoriasiform lesions requires its PLD2-mediated conversion to phosphatidylglycerol, consistent with our previous report that phosphatidylglycerol itself improves psoriasiform lesions in this model. Our data also support anecdotal evidence that glycerol can ameliorate psoriasis symptoms and therefore might be a useful therapy alone or in conjunction with other treatments.

Keratinocyte aquaporin-3 expression induced by histone deacetylase inhibitors is mediated in part by peroxisome proliferator-activated receptors (PPARs).

The water and glycerol channel, aquaporin-3 (AQP3), plays an important role in the skin epidermis, with effects on hydration, permeability barrier repair and wound healing; therefore, information about the mechanisms regulating its expression is important for a complete understanding of skin function physiologically and in disease conditions. We previously demonstrated that histone deacetylase inhibitors (HDACi) induce the mRNA and protein expression of AQP3, in part through the p53 family, transcription factors for which acetylation is known to affect their regulatory activity. Another set of transcription factors previously shown to induce AQP3 expression and/or regulate skin function are the peroxisome proliferator-activated receptors (PPARs). Since there are reports that PPARs are also acetylated, we examined the involvement of these nuclear hormone receptors in HDACi-induced AQP3 expression. We first verified that a PPARγ agonist upregulated AQP3 mRNA and protein levels and that this increase was blocked by a PPARγ antagonist. We then showed that the PPARγ antagonist also inhibited AQP3 expression induced both by a broad-spectrum HDACi and an HDAC3-selective inhibitor. Interestingly, a PPARα antagonist also inhibited HDACi-induced AQP3 expression. These antagonist effects were observed in both primary mouse and normal human keratinocytes. Furthermore, PPARγ overexpression enhanced HDACi-stimulated AQP3 mRNA levels. Thus, our results suggest that PPARγ and/or PPARα may play a role in regulating AQP3 levels in the skin; based on the ability of PPAR agonists to promote epidermal differentiation and/or inhibit proliferation, topical PPAR agonists might be considered as a therapy for hyperproliferative skin disorders, such as psoriasis.

[Attenuation mechanism of gamboges during processing based on inflammatory toxicity and AQP3, AQP4 protein and mRNA expressions in rat gastric and duodenal tissues].

To expand the clinical application of gamboges, it is necessary to study crude gamboges' toxicity after oral administration and attenuation mechanism during processing. In this study, crude gamboges' toxicity was judged by multiple assays, including inflammatory mediums [such as nitric oxide (NO), tumor necrosis factor alpha (TNF-α), and interleukin 6 (IL-6)] released by macrophage RAW264.7, and pathological manifestations of rat stomach and duodenal tissues after oral administration with crude and processed gamboges. The attenuation mechanism during processing was studied by detecting AQP3, AQP4 protein and mRNA expression in rat gastric and duodenal tissues using immunohistochemical assay and real-time fluorescent quantitative PCR technique. According to the results, crude gamboges group showed promotion in release of NO, TNF-α and IL-6 by macrophage RAW264.7 in a dose-dependent manner; Compared with crude gamboges group, processed gamboges group showed reduction in release of NO and IL-6, with increase in TNF-α. Crude gamboges could cause rat diarrhea, white blood cells increase, lymphocytes decrease, hyperemia and edema in rat gastric mucosa, duodenal mucosal necrosis and inflammatory cells infiltration. All of these results proved that gamboges had the inflammatory toxicity in gastric and duodenal tissues after oral administration in a dose-dependent manner, which however reduced after processing. In addition to the inflammatory toxicity, the mRNA and protein expressions of aquaporin 3 (AQP3), aquaporin 4 (AQP4) in gastric and duodenal tissues of high-dose crude gamboges group were increased significantly (P<0.05), while the protein and mRNA expressions of AQP3, AQP4 were weakened in processed gamboges group. The results showed that AQP3, AQP4 protein and mRNA expressions were positively correlated with the inflammatory toxicity. In conclusion, down-regulation of AQP3, AQP4 protein and mRNA expressions may be one of attenuation mechanisms in processing gamboges.

Loss of AQP3 protein expression is associated with worse progression-free and cancer-specific survival in patients with muscle-invasive bladder cancer.

PURPOSE: Urothelial carcinoma has recently been shown to express several aquaporins (AQP), with AQP3 being of particular interest as its expression is reduced or lost in tumours of higher grade and stage. Loss of AQP3 expression was associated with worse progression-free survival (PFS) in patients with pT1 bladder cancer. The objective of this study was to investigate the prognostic value of AQP3 expression in patients with muscle-invasive bladder carcinoma (MIBC). METHODS: Retrospective single-centre analysis of the oncological outcome of patients following radical cystectomy (Cx) due to MIBC. Immunohistochemistry was used to assess AQP3 protein expression in 100 Cx specimens. Expression levels of AQP3 were related to clinicopathological variables. The impact of biomarker expression on progression-free, cancer-specific and overall survival was determined by multivariate Cox regression analysis (MVA). RESULTS: High expression of AQP3 by the tumour was associated with a statistically significantly improved PFS (75 vs. 19 %, p = 0.043) and CSS (75 vs. 18 %, p = 0.030) and, alongside lymph node involvement, was an independent predictor of PFS (HR 2.871, CI 1.066-7.733, p = 0.037), CSS (HR 3.325, CI 1.204-8.774, p = 0.019) and OS (HR 2.001, CI 1.014-3.947) in MVA. CONCLUSIONS: Although the results of the study would be strengthened by a larger, more appropriately powered, prospective, multi-institutional study, our findings strongly suggest that AQP3 expression status may represent an independent predictor of PFS and CSS in MIBC and may help select patients in need for (neo-)adjuvant chemotherapy.

Phosphatidylglycerol to Treat Chronic Skin Wounds in Diabetes.

This review proposes the use of dioleoylphosphatidylglycerol (DOPG) to enhance diabetic wound healing. Initially, the characteristics of diabetic wounds are examined, focusing on the epidermis. Hyperglycemia accompanying diabetes results in enhanced inflammation and oxidative stress in part through the generation of advanced glycation end-products (AGEs), in which glucose is conjugated to macromolecules. These AGEs activate inflammatory pathways; oxidative stress results from increased reactive oxygen species generation by mitochondria rendered dysfunctional by hyperglycemia. These factors work together to reduce the ability of keratinocytes to restore epidermal integrity, contributing to chronic diabetic wounds. DOPG has a pro-proliferative action on keratinocytes (through an unclear mechanism) and exerts an anti-inflammatory effect on keratinocytes and the innate immune system by inhibiting the activation of Toll-like receptors. DOPG has also been found to enhance macrophage mitochondrial function. Since these DOPG effects would be expected to counteract the increased oxidative stress (attributable in part to mitochondrial dysfunction), decreased keratinocyte proliferation, and enhanced inflammation that characterize chronic diabetic wounds, DOPG may be useful in stimulating wound healing. To date, efficacious therapies to promote the healing of chronic diabetic wounds are largely lacking; thus, DOPG may be added to the armamentarium of drugs to enhance diabetic wound healing.

[Effect of acupuncture and moxibustion on skin barrier function in guinea pigs with eczema of skin damp-heat accumulation].

OBJECTIVE: To observe the effect of acupuncture and moxibustion on the water content of stratum corneum (WCSC), expression of serum inflammatory factors and aquaporin 3 (AQP3) in skin, lung and rectum in guinea pigs with eczema of skin damp-heat accumulation, and to explore the possible mechanism of acupuncture and moxibustion for regulating skin barrier function. METHODS: A total of 24 male albino guinea pigs were randomly divided into a blank group (n=6) and a modeling group (n=18). The guinea pigs in the modeling group were induced by 2,4-dinitrochlorobenzene (DNCB) to establish the eczema model of skin damp-heat accumulation. The guinea pigs with successful modeling were further randomly divided into a model group, a medication group and an acupuncture-moxibustion group, 6 guinea pigs in each group. The guinea pigs in the medication group were treated with loratadine tablets (0.8 mg/kg) by gavage, once a day for 7 days; the guinea pigs in the acupuncture-moxibustion group were treated with acupuncture at "Feishu" (BL 13), "Pishu" (BL 20), "Quchi" (LI 11), "Zusanli" (ST 36) and "Xuehai" (SP 10); at the same time, moxibustion was applied at "Feishu" (BL 13) and "Zusanli" (ST 36), moxibustion intervention for 10 min and needle retaining for 15 min at each acupoint, once a day for 7 days. The eczema area and severity index (EASI) score was evaluated before and After intervention, and WCSC and trans-epidermal water loss (TEWL) were measured by skin tester. After intervention, The HE staining was used to observe the changes of skin histomorphology in each group; ELISA was used to measure the contents of serum immunoglobulin E (IgE), interleukin (IL)-4 and IL-17; Western blot was used to measure the protein expression of AQP3 in skin, lung and rectum. RESULTS: Before the intervention, compared with the blank group, the EASI scores and TEWL were increased in the remaining groups (P<0.01), and the WCSC was decreased (P<0.01). After the intervention, compared with the model group, the EASI scores and TEWL were decreased (P<0.05, P<0.01), and WCSC was increased (P<0.01) in the medication group and the acupuncture-moxibustion group. The epidermal structure in the blank group was complete and the fibers in the dermis were arranged orderly; in the model group, epidermal hyperkeratosis, proliferation of granular layer, spinous cell layer and basal layer, and disordered arrangement of dermal fibers and infiltration of inflammatory cells were observed. The morphological performance in the medication group and the acupuncture-moxibustion group was better than that in the model group. Compared with the blank group, the contents of serum IgE and IL-17 were increased (P<0.01), and the content of serum IL-4 and the protein expression of AQP3 in skin, lung and rectum were decreased in the model group (P<0.01, P<0.05). Compared with the model group, the contents of serum IgE and IL-17 were decreased and the contents of serum IL-4 were increased in the medication group and the acupuncture-moxibustion group (P<0.01), and the protein expression of AQP3 in skin, lung and rectum in the acupuncture- moxibustion group were increased (P<0.05). Compared with the medication group, the contents of serum IgE and IL-17 were increased (P<0.01), and the content of serum IL-4 was decreased (P<0.01) in the acupuncture-moxibustion group. CONCLUSION: Acupuncture and moxibustion could improve the epidermal water metabolism and skin tissue morphology in guinea pigs with eczema of skin damp-heat accumulation. Its mechanism may be related to regulating inflammatory factors, up-regulating the expression of AQP3, and then repairing the skin barrier function.

Citric Acid-Enriched Extract of Ripe Prunus mume (Siebold) Siebold & Zucc. Induces Laxative Effects by Regulating the Expression of Aquaporin 3 and Prostaglandin E2 in Rats with Loperamide-Induced Constipation.

Previously, we demonstrated that extracts of the ripe fruit (rPM) and unripe fruit (uPM) of Prunus mume (Siebold) Siebold & Zucc. and citric acid have a laxative effect, which is at least partially mediated by the increase in fecal parameters as seen in the low-fiber diet-induced constipation model rats. This study aims at investigating the laxative effects of citric acid-enriched aqueous extracts of rPM, uPM, and its active compounds, such as citric acid and malic acid, on loperamide-induced constipation rat models. Animal studies were conducted with loperamide-induced constipation animal models. The results showed that rPM and citric acid, the major organic acid compounds, significantly improved stool parameters (number, weight, and water content of the stools) generated in loperamide-induced constipation rats, without adverse effects of diarrhea. The gastrointestinal (GI) motility was activated fully in the rPM- and citric acid-treated rats than in rats treaded with loperamide alone. In addition, when rPM and citric acid were added to RAW264.7 cells and used to treat loperamide-induced constipation model rats, the secretion of prostaglandin E2 (PGE2) increased significantly in cells and tissue. Furthermore, rPM and citric acid decreased the expression of the aquaporin 3 (AQP3) in the rat colons. Our results demonstrated that rPM and citric acid, the major organic acid compound in rPM, can effectively promote defecation frequency and regulate PGE2 secretion and AQP3 expression in the colon, providing scientific evidence to support the use of rPM as a therapeutic application.

Histological examination of carotid artery tissue in cases of ligature strangulation and hanging.

Violence against the neck can result in a range of macromorphological and micromorphological findings. However, the forensic relevance of the carotid sinus in cases of violence against the neck remains controversial. In this follow-up study of 22 cases of suicidal and accidental strangulations, carotid bifurcations were examined histologically for morphological changes implying direct trauma, including haemorrhage and immunohistochemical expression of heat-shock proteins 27, 60, and 70 and aquaporin-3. These cases were compared with a control group (82 cases) without neck compression or head trauma and with variable causes of death. No relevant histopathological findings implying direct trauma of the carotid bifurcation were found. No cases showed positive aquaporin-3 staining and only five cases showed positive heat-shock protein-27 staining, all of which were hangings. Without massive trauma of the carotid bifurcation, histological alterations cannot be expected. Without signs of rapid death, findings of acute circulatory failure, macromorphological and micromorphological findings of neck compression, and reliable markers indicating relevant impact on the carotid bifurcation the diagnosis of a lethal reflex cannot be verified.Key pointsAmong 22 cases of strangulation causing death, there were 16 cases of hanging and 6 cases of ligature strangulationFew cases showed small haemorrhages located predominantly in the surrounding fat and connective tissues; however, the haemorrhages did not have any effects on the tissuesNeck compression had minimal effects on heat shock protein 27 expression in carotid artery tissueAquaporin-3 staining suggested it is not a useful marker for relevant neck pressure, or that there had not been any relevant neck impactOur findings suggested no direct evidence for reflex cardiac death resulting from a brief force against the neck.

Possible Role of Phosphatidylglycerol-Activated Protein Kinase C-ßII in Keratinocyte Differentiation.

BACKGROUND: The epidermis is a continuously regenerating tissue maintained by a balance between proliferation and differentiation, with imbalances resulting in skin disease. We have previously found that in mouse keratinocytes, the lipid-metabolizing enzyme phospholipase D2 (PLD2) is associated with the aquaglyceroporin, aquaporin 3 (AQP3), an efficient transporter of glycerol. Our results also show that the functional interaction of AQP3 and PLD2 results in increased levels of phosphatidylglycerol (PG) in response to an elevated extracellular calcium level, which triggers keratinocyte differentiation. Indeed, we showed that directly applying PG can promote keratinocyte differentiation. OBJECTIVE: We hypothesized that the differentiative effects of this PLD2/AQP3/PG signaling cascade, in which AQP3 mediates the transport of glycerol into keratinocytes followed by its PLD2-catalyzed conversion to PG, are mediated by protein kinase CßII (PKCßII), which contains a PG-binding domain in its carboxy-terminus. Method: To test this hypothesis we used quantitative RT-PCR, western blotting and immunocytochemistry. RESULTS: We first verified the presence of PKCßII mRNA and protein in mouse keratinocytes. Next, we found that autophosphorylated (activated) PKCßII was redistributed upon treatment of keratinocytes with PG. In the unstimulated state phosphoPKCßII was found in the cytosol and perinuclear area; treatment with PG resulted in enhanced phosphoPKCßII localization in the perinuclear area. PG also induced translocation of phosphoPKCßII to the plasma membrane. In addition, we observed that overexpression of PKCßII enhanced calcium- and PG-induced keratinocyte differentiation without affecting calcium-inhibited keratinocyte proliferation. CONCLUSION: These results suggest that the PG produced by the PLD2/AQP3 signaling module may function by activating PKCßII.

Forensic diagnosis of ante- and postmortem burn based on aquaporin-3 gene expression in the skin.

In order to diagnose death associated with fire, it is essential to show that the person was exposed to heat while still alive. We investigated both AQP1 and AQP3 expression in the skin of an experimental burn model, as well as in forensic autopsy cases, and discuss its role in the differential diagnosis of ante- and postmortem burns. In animal experiments, there was no difference in AQP1 gene expression among four groups (n=4): antemortem burn, postmortem burn, mechanical wound, and control. However, AQP3 expression in the antemortem burn was increased significantly compared with that of the other groups even at 5min after burn. Water content of the skin was decreased significantly by the burn procedure. Consistent with animal experiments, AQP3 gene expression in the skin of antemortem burn cases was increased significantly compared with postmortem burns, mechanical wounds, and controls (n=12 in each group). These observations suggest that dermal AQP3 gene expression was increased to maintain water homeostasis in response to dehydration from burn. Finally, our results suggest that AQP3 gene expression may be useful for forensic molecular diagnosis of antemortem burn.