Targeting AQP9 enhanced the anti-TNF therapy response in Crohn's disease by inhibiting LPA-hippo pathway.

Although anti-TNF antibodies are extensively used to treat Crohn's disease (CD), a significant proportion of patients, up to 40%, exhibit an inadequate response to this therapy. Our objective was to identify potential targets that could improve the effectiveness of anti-TNF therapy in CD. Through the integration and analysis of transcriptomic data from various CD databases, we found that the expression of AQP9 was significantly increased in anti-TNF therapy-resistant specimens. The response to anti-TNF therapy in the CD mouse model was significantly enhanced by specifically inhibiting AQP9. Further experiments found that the blockade of AQP9, which is dominantly expressed in macrophages, decreased inflamed macrophage functions and cytokine expression. Mechanistic studies revealed that AQP9 transported glycerol into macrophages, where it was metabolized to LPA, which was further metabolized to LPA, resulting in the activation of the LPAR2 receptor and downstream hippo pathway, finally promoting the expression of cytokines, especially IL23 and IL1ß⊡ Taken together, the expansion of AQP9+ macrophages is associated with resistance to anti-TNF therapy in Crohn's disease. These findings indicated that AQP9 could be a potential target for enhancing anti-TNF therapy in Crohn's disease.

Aquaporin Inhibitors.

Aquaporins (AQP) working as membrane channels facilitated water transport, play vital roles in various physiological progress including cell migration, energy metabolism, inflammation, etc. They are quite important drug targets, but elusive for discovery due to their undruggable properties. In this chapter, we summarized most fluently used methods for screening AQP inhibitors, including cell swelling assay, cell shrinking assay, and stopped-flow assay. And three classes of AQP inhibitors have been discussed, including metal-related inhibitors, quaternary ammonium salts, and small molecule inhibitors which further divided into four parts, sulfanilamide analogies, TGN-020, antiepileptic drugs, and others. It has been suggested that although they showed inhibition effects on AQP1, AQP3, AQP4, AQP7, or AQP9 in some researches, none of them could be asserted as AQP inhibitors to some extent. Discovering AQP inhibitors is a big challenge, but if successful, it will be a great contribution for human health.

Contribution of aquaporins in the transamniotic water flux.

We explored the contribution of each aquaporin (AQP) expressed in human amnion in the transcellular water flux across the human amnion. Human amnion was placed between two lucite chambers and net water transport (Jw) was recorded by applying a hydrostatic (7 cm H2O) and an osmotic (40 mOsm PEG 8000) pressure gradients. The hydrostatic (Phydr) and osmotic (POsm) permeabilities were calculated before and after the blocking of AQPs. Phdr showed no significant difference after the blocking of AQPs, while POsm was dramatically reduced. Interestingly, we also found that the blocking of AQP1 produced the highest decrease of POsm (80 ± 1%). Our results strongly suggested that AQP1 seems to contribute more to the maintenance of AF volume homeostasis.

Xinshuitong Capsule extract attenuates doxorubicin-induced myocardial edema via regulation of cardiac aquaporins in the chronic heart failure rats.

Doxorubicin (Dox), an effective antineoplastic drug, was limited use for cardiotoxicity. Xinshuitong Capsule (XST), a patented herbal formula, showed desirable beneficial effects in the treatment of chronic heart failure (CHF) patients. However, the drug on Dox-induced cardiotoxicity remains unclear. Ninety male Sprague-Dawley rats were randomized into two groups: 15 rats were selected as the normal group and 75 rats were injected intraperitoneally with Dox to establish CHF rat models, the success ones were randomly divided into five groups: low XST (LXST), medium XST (MXST) or high XST (HXST) (4.9, 9.8, or 19.6 g/kg d) administrated intragastrically twice a day for 4 weeks, with the captopril-treated group and the model group as comparison. The model group showed the cardiac functions generally impaired, and CHF mortality rate higher (47%) than those in the XST-treated groups (averaged 24%, P < 0.05). Compared with XST-treated groups, myocardial remodeling, inflammation and desarcomerization, and higher water content more severe in the cardiac tissue in the model group (P < 0.05), which was associated with higher expressions of mRNA or protein levels of AQP1, 4 and 7. Dox-impaired cardiac functions, cardiac remodeling and myocardial edema could be dose-dependently reverted by XST treatment. XST could inhibit AQP1, 4 and 7 at mRNA levels or at protein levels, which was associated with the attenuation of myocardial edema and cardiac remodeling, decreasing the ventricular stiffness and improving the cardiac functions and rats' survival. AQPs is involved in cardiac edema composed one of the mechanisms of Dox-induced cardiotoxicity, XSTvia inhibition of AQPs relieved the Dox-induced side effects.

Mechanisms of irreversible aquaporin-10 inhibition by organogold compounds studied by combined biophysical methods and atomistic simulations.

The inhibition of glycerol permeation via human aquaporin-10 (hAQP10) by organometallic gold complexes has been studied by stopped-flow fluorescence spectroscopy, and its mechanism has been described using molecular modelling and atomistic simulations. The most effective hAQP10 inhibitors are cyclometalated Au(III) C^N compounds known to efficiently react with cysteine residues leading to the formation of irreversible C-S bonds. Functional assays also demonstrate the irreversibility of the binding to hAQP10 by the organometallic complexes. The obtained computational results by metadynamics show that the local arylation of Cys209 in hAQP10 by one of the gold inhibitors is mapped into a global change of the overall free energy of glycerol translocation across the channel. Our study further pinpoints the need to understand the mechanism of glycerol and small molecule permeation as a combination of local structural motifs and global pore conformational changes, which are taking place on the scale of the translocation process and whose study, therefore, require sophisticated molecular dynamics strategies.

Exploring the role of Aquaporins (AQPs) in LPS induced systemic inflammation and the ameliorative effect of Garcinia in male Wistar rat.

The Aquaporins (AQPs) could prove to be striking targets of inflammation. The aim of this study was to study the involvement of AQPs and explore the anti-inflammatory activity of Garcinia extract in LPS induced acute systemic inflammation in Wistar rats. Adult male Wistar rats (n = 6) were pretreated with Garcinia orally twice for 7 days, followed by a single intraperitoneal dose (5.5 mg/kgbw) of LPS. Serum ALT, AST, ALP, Creatinine, Urea and BUN, nitric oxide, prostaglandin, cytokine and chemokine levels were measured. LC-MS analysis of Garcinia was performed to identify the phytoconstituents present. The iNOS and COX enzyme activity were determined in the target tissues. qPCR analysis of inos, cox-2 and aqps was performed. Relative protein expression of AQPs was studied by Western blot analysis. Molecular docking studies were performed to study the interaction of garcinol and hydroxycitric acid, the two important phytoconstituents of Garcinia with AQP. The qPCR analysis showed tissue-specific up-regulation of aqp1, aqp3, aqp4 and aqp8 in LPS induced rats. Garcinia extract treatment effectively lowered the mRNA expression of these AQPs. Garcinia extract significantly inhibited the LPS-induced NO, prostaglandin, cytokine and chemokine production in serum and also decreased tissue-specific transcript level of inos and cox-2, thus suggesting the anti-inflammatory role of Garcinia. Also, docking studies revealed interactions of garcinol and hydroxycitric acid with AQP1, 3, 4 and 8. Therefore, the present study suggests the possible involvement of AQP1, 3, 4 and 8 in inflammation and the efficacy of Garcinia extract as an anti-inflammatory agent. Therefore, AQPs can act as prognostic markers of inflammation and can be targeted with Garcinia extract.

Diuretic effect of Lagopsis supina fraction in saline-loaded rats is mediated through inhibition of aquaporin and renin-angiotensin-aldosterone systems and up-regulation of atriopeptin.

Lagopsis supina (Steph. ex Willd.) lk. -Gal. ex Knorr. has been used as a diuretic agent in China for centuries with limited scientific evidence. This study investigated the diuretic efficacy and underlying mechanism of a macroporous adsorption resin with 30% ethanol elution fraction from L. supina (LSC) in saline-loaded rats and to identify its phytochemicals by ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-qTOF-MS/MS). As a result, 18 phenylpropanoids, 14 flavonoids and 15 others were identified in LSC, among which stachysoside A and acteoside could be the main bio-active constituents responsible for the diuretic effect. In parallel, the daily administration of LSC (16, 32 and 64 mg/kg) markedly promoted urinary excretion after 2 h of treatment. Moreover, LSC had no effect on urinary Na+ and K+ concentrations, as well as on serum Na+-K+-ATPase activity. Meanwhile, LSC significantly decreased the serum levels of angiotensin II (Ang II), anti-diuretic hormone (ADH), aldosterone (ALD), aquaporin (AQP) 1, AQP2 and AQP3, suppressed renal AQP1, AQP2, and AQP3 mRNA expressions, down-regulated AQP1, AQP2 and AQP3 protein levels, and up-regulated serum atriopeptin (ANP) level in a dose-dependent manner. These findings suggest that LSC has acute and prolonged diuretic effects by inhibiting the AQPs, RAAS, and upregulation of atriopeptin in saline-loaded rats, and this finding support LSC as a novel diuretic agent.

The chemical profiling of aqueous soluble fraction from Lagopsis supina and its diuretic effects via suppression of AQP and RAAS pathways in saline-loaded rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Lagopsis supina (Steph.) Ik. -Gal. ex Knorr. has been widely used as a remedy treatment for diuresis and edema in China over 2500 years. Our previous results showed that the aqueous soluble fraction from L. supina (LSB) possessed acute diuretic effect. AIM OF THE STUDY: The aim of this study was to appraise the acute (6 h) and prolonged (7 d) diuretic effects, underlying mechanisms, and chemical profiling of LSB. MATERIALS AND METHODS: The chemical profiling of LSB was performed by ultra-high-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry (UHPLC-qTOF-MS/MS). Then, oral administration of LSB (40, 80, 160 and 320 mg/kg) and furosemide (10 mg/kg) once daily for 7 consecutive days to evaluate the diuretic effects in saline-loaded rats. The body weight, food consumption, and water intake were recorded once daily. The urinary volume, pH and electrolyte concentrations (Na+, K+, Cl-, and Ca2+) were measured after administration drugs for acute and prolonged diuretic effects. In addition, the serum levels of Na+-K+-ATPase, angiotensin II (Ang II), anti-diuretic hormone (ADH), aldosterone (ALD), atriopeptin (ANP), aquaporins (AQPs)-1, 2 and 3 were determined by ELISA kits. The mRNA expressions and protein levels of AQPs-1, 2 and 3 were analyzed by real-time quantitative PCR and Western blot assays, respectively. RESULTS: 30 compounds were identified in LSB based on accurate mass and MS/MS fragmentation compared to literature, among which phenylpropanoids and flavonoids could be partly responsible for the major diuretic effect. Daily administration of LSB (160 or 320 mg/kg) prominently increased urinary excretion volume after the 2 h at the first day of treatment, remaining until the 7th day. LSB did not cause Na+ and K+ electrolyte abnormalities, and has minor effect on Cl- and Ca2+ concentrations at 320 mg/kg. Furthermore, LSB observably suppressed renin-angiotensin-aldosterone system (RAAS) activation, including decreased serum levels of Ang II, ADH, and ALD, and prominently increased serum level of ANP in rats. LSB treatment significantly down-regulated the serum levels, mRNA expressions and protein levels of AQP1, AQP2, and AQP3. CONCLUSION: LSB has a prominent acute and prolonged diuretic effects via suppression of AQP and RAAS pathways in saline-loaded rats, and support the traditional folk use of this plant. Taken together, LSB might be a potential diuretic agent.

HPV Infection Affects Human Sperm Functionality by Inhibition of Aquaporin-8.

Human sperm cells express different aquaporins (AQPs), AQP3, 7, 8, 11, which are localized both in the plasma membrane and in intracellular structures. Besides cell volume regulation and end stage of cytoplasm removal during sperm maturation, the role of AQPs extends also to reactive oxygen species (ROS) elimination. Moreover, oxidative stress has been shown to inhibit AQP-mediated H2O2 permeability. A decrease in AQPs functionality is related to a decrease in sperm cells number and motility. Here we investigate the possible effect of human Papillomavirus (HPV) on both expression and function of AQPs in human sperm cells of patients undergoing infertility couple evaluation. Stopped-flow light-scattering experiments demonstrated that HPV infection heavily reduced water permeability of sperm cells in normospermic samples. Confocal immunofluorescence experiments showed a colocalization of HPV L1 protein with AQP8 (Pearson's correlation coefficient of 0.61), confirmed by co-immunoprecipitation experiments. No interaction of HPV with AQP3 and AQP7 was observed. A 3D model simulation of L1 protein and AQP8 interaction was also performed. Present findings may suggest that HPV infection directly inhibits AQP8 functionality and probably makes sperm cells more sensitive to oxidative stress.

Effect of AQP Inhibition on Boar Sperm Cryotolerance Depends on the Intrinsic Freezability of the Ejaculate.

Aquaporins (AQPs) are transmembrane channels with permeability to water and small solutes that can be classified according to their structure and permeability into orthodox AQPs, aquaglyceroporins (GLPs), and superAQPs. In boar spermatozoa, AQPs are related to osmoregulation and play a critical role in maturation and motility activation. In addition, their levels differ between ejaculates with good and poor cryotolerance (GFE and PFE, respectively). The aim of this work was to elucidate whether the involvement of AQPs in the sperm response to cryopreservation relies on the intrinsic freezability of the ejaculate. With this purpose, two different molecules: phloretin (PHL) and 1,3-propanediol (PDO), were used to inhibit sperm AQPs in GFE and PFE. Boar sperm samples were treated with three different concentrations of each inhibitor prior to cryopreservation, and sperm quality and functionality parameters were evaluated in fresh samples and after 30 and 240 min of thawing. Ejaculates were classified as GFE or PFE, according to their post-thaw sperm viability and motility. While the presence of PHL caused a decrease in sperm quality and function compared to the control, samples treated with PDO exhibited better quality and function parameters than the control. In addition, the effects of both inhibitors were more apparent in GFE than in PFE. In conclusion, AQP inhibition has more notable consequences in GFE than in PFE, which can be related to the difference in relative levels of AQPs between these two groups of samples.

Unraveling the genetic architecture for carbon and nitrogen related traits and leaf hydraulic conductance in soybean using genome-wide association analyses.

BACKGROUND: Drought stress is a major limiting factor of soybean [Glycine max (L.) Merr.] production around the world. Soybean plants can ameliorate this stress with improved water-saving, sustained N2 fixation during water deficits, and/or limited leaf hydraulic conductance. In this study, carbon isotope composition (δ13C), which can relate to variation in water-saving capability, was measured. Additionally, nitrogen isotope composition (δ15N) and nitrogen concentration that relate to nitrogen fixation were evaluated. Decrease in transpiration rate (DTR) of de-rooted soybean shoots in a silver nitrate (AgNO3) solution compared to deionized water under high vapor pressure deficit (VPD) conditions was used as a surrogate measurement for limited leaf hydraulic conductance. A panel of over 200 genetically diverse soybean accessions genotyped with the SoySNP50K iSelect BeadChips was evaluated for the carbon and nitrogen related traits in two field environments (Athens, GA in 2015 and 2016) and for transpiration response to AgNO3 in a growth chamber. A multiple loci linear mixed model was implemented in FarmCPU to perform genome-wide association analyses for these traits. RESULTS: Thirty two, 23, 26, and nine loci for δ13C, δ15N, nitrogen concentration, and transpiration response to AgNO3, respectively, were significantly associated with these traits. Candidate genes that relate to drought stress tolerance enhancement or response were identified near certain loci that could be targets for improving and understanding these traits. Soybean accessions with favorable breeding values were also identified. Low correlations were observed between many of the traits and the genetic loci associated with each trait were largely unique, indicating that these drought tolerance related traits are governed by different genetic loci. CONCLUSIONS: The genomic regions and germplasm identified in this study can be used by breeders to understand the genetic architecture for these traits and to improve soybean drought tolerance. Phenotyping resources needed, trait heritability, and relationship to the target environment should be considered before deciding which of these traits to ultimately employ in a specific breeding program. Potential marker-assisted selection efforts could focus on loci which explain the greatest amount of phenotypic variation for each trait, but may be challenging due to the quantitative nature of these traits.

Inhibition of RIPK1-dependent regulated acinar cell necrosis provides protection against acute pancreatitis via the RIPK1/NF-κB/AQP8 pathway.

Currently, preliminary results have confirmed the existence of receptor-interacting protein kinase 3 (RIPK3) and mixed lineage kinase domain-like protein (MLKL)-dependent necroptosis of pancreatic acinar cells during early acute pancreatitis (AP), which might be a potential target for the effective regulation of necroinflammatory injury. However, the exact effect of receptor-interacting protein kinase 1 (RIPK1)-dependent regulated acinar cell necrosis on AP is still uncertain. In our study, we first explored the changes in the degree of local and systemic inflammation in AP rats when the activation of acinar cell RIPK1 was inhibited. The RIPK1 inhibitor Nec-1 was used to treat rats, and the levels of related inflammatory markers, necrosis indicators and apoptotic indicators were measured. Changes in pancreatic nuclear factor κB (NF-κB) and aquaporin 8 (AQP8) expression were noted. Next, the expression of AQP8 in AR42J cells was inhibited, and the degree of cell necrosis and inflammatory damage was found to be significantly reduced. Most importantly, we demonstrated that the RIPK1/NF-ĸB/AQP8 axis might be a potential regulatory pathway mediating RIPK1-dependent regulated acinar cell necrosis in early AP. Finally, we used the NF-κB inhibitor PDTC and Nec-1 to treat rats in different groups and measured the degree of pathological pancreatic injury, the activation of RIPK1, and the expression of NF-κB and AQP8. In summary, we hypothesized that there might be a RIPK1/NF-ĸB/AQP8 pathway controlling RIPK1-dependent regulated necrosis of acinar cells in AP, which might be a promising therapeutic target against AP-related injury.

Effects of major vein blockage and aquaporin inhibition on leaf hydraulics and stomatal conductance.

The density and architecture of leaf veins determine the network and efficiency of water transport within laminae and resultant leaf gas exchange and vary widely among plant species. Leaf hydraulic conductance ( Kleaf) can be regulated by vein architecture in conjunction with the water channel protein aquaporin. However, our understanding of how leaf veins and aquaporins affect leaf hydraulics and stomatal conductance ( gs) remains poor. By inducing blockage of the major veins and inhibition of aquaporin activity using HgCl2, we examined the effects of major veins and aquaporins on Kleaf and gs in species with different venation types. A vine species, with thick first-order veins and low vein density, displayed a rapidly declined gs with high leaf water potential in response to vein blockage and a greatly reduced Kleaf and gs in response to aquaporin inhibition, suggesting that leaf aquaporins are involved in isohydric/anisohydric stomatal behaviour. Across species, the decline in Kleaf and gs due to aquaporin inhibition increased linearly with decreasing major vein density, possibly indicating that a trade-off function between vein architecture (apoplastic pathway) and aquaporin activity (cell-to-cell pathway) affects leaf hydraulics.

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.

Identification and characterization of potent and selective aquaporin-3 and aquaporin-7 inhibitors.

The aquaglyceroporins are a subfamily of aquaporins that conduct both water and glycerol. Aquaporin-3 (AQP3) has an important physiological function in renal water reabsorption, and AQP3-mediated hydrogen peroxide (H2O2) permeability can enhance cytokine signaling in several cell types. The related aquaglyceroporin AQP7 is required for dendritic cell chemokine responses and antigen uptake. Selective small-molecule inhibitors are desirable tools for investigating the biological and pathological roles of these and other AQP isoforms. Here, using a calcein fluorescence quenching assay, we screened a library of 7360 drug-like small molecules for inhibition of mouse AQP3 water permeability. Hit confirmation and expansion with commercially available substances identified the ortho-chloride-containing compound DFP00173, which inhibited mouse and human AQP3 with an IC50 of ∼0.1-0.4 µm but had low efficacy toward mouse AQP7 and AQP9. Surprisingly, inhibitor specificity testing revealed that the methylurea-linked compound Z433927330, a partial AQP3 inhibitor (IC50, ∼0.7-0.9 µm), is a potent and efficacious inhibitor of mouse AQP7 water permeability (IC50, ∼0.2 µm). Stopped-flow light scattering measurements confirmed that DFP00173 and Z433927330 inhibit AQP3 glycerol permeability in human erythrocytes. Moreover, DFP00173, Z433927330, and the previously identified AQP9 inhibitor RF03176 blocked aquaglyceroporin H2O2 permeability. Molecular docking to AQP3, AQP7, and AQP9 homology models suggested interactions between these inhibitors and aquaglyceroporins at similar binding sites. DFP00173 and Z433927330 constitute selective and potent AQP3 and AQP7 inhibitors, respectively, and contribute to a set of isoform-specific aquaglyceroporin inhibitors that will facilitate the evaluation of these AQP isoforms as drug targets.

Lagopsis supina exerts its diuretic effect via inhibition of aquaporin-1, 2 and 3 expression in a rat model of traumatic blood stasis.

ETHNOPHARMACOLOGICAL RELEVANCE: Lagopsis supina has been used as a traditional medicinal herb for centuries in China. In folk medicine, it is used for promoting blood circulation and removing blood stasis (PBCRBS), anti-inflammatory and diuretic activities. Modern pharmacological investigation have shown that L. supina have an improvement in blood and lymphatic microcirculation, myocardioprotective, and antioxidative activities. Although the pharmacological research of L. supina was more, there was no report on the diuretic activity. AIM OF THE STUDY: This study was to evaluate the diuretic activity and the underlying mechanism of an ethanol extract of L. supina (LS) in a rat model of traumatic blood stasis (TBS). MATERIALS AND METHODS: There were 30 male Sprague-Dawley rats that were randomly assigned to the control group, TBS group, and LS group (10 animals in each group). LS was administered orally (460 mg/kg) once daily for 7 successive days. The control group and TBS group were given an equal amount of 0.3% sodium carboxymethyl cellulose (CMC-Na). For the efficacy evaluation, the urine output volume, the urinary electrolyte concentrations (Na+, K+, Cl- and Ca2+) and pH value, the levels of angiotensin II (Ang II), atriopeptin (ANP), anti-diuretic hormone (ADH) and aldosterone (ALD), as well as aquaporin (AQP)-1, 2 and 3 protein expressions were detected in a rat model of TBS. The protein expressions of AQP-1, 2 and 3 were detected by quantitative immunohistochemistry (IHC) and Western blot analysis. RESULTS: In the efficacy evaluation, rat models treated with LS showed a significant increase in the total urine output (p < 0.01). The urinary electrolyte and the acid-base disturbances, including the decrease of Na+ and Ca2+ levels and the Na+/K+ value together with the increase in the Cl- level and the pH value, in the urine of the LS group were compared with the TBS group. Moreover, the levels of Ang II, ADH and ALD of rat model were decreased after being treated with LS (p < 0.05 or p < 0.01), while the ANP level was increased (p < 0.05). In addition, the results of the quantitative IHC and the Western blot analysis showed that the expression levels of AQP-1, 2 and 3 proteins decreased significantly compared with those of the TBS group. CONCLUSIONS: This is the first reported notable diuretic effect by LS, which probably was through the suppression of the renin-angiotensin-aldosterone system (RAAS) and the regulation of the signaling pathways of AQP-1, 2 and 3 protein expressions. Based on our results, we conclude that L. supina carries out its diuretic effect mainly by down-regulating the levels of AQP-1, 2 and 3 expressions in TBS rat model. These data also embody the traditional Chinese medicine (TCM) application principle of Huo xue li shui. These findings suggest that LS may warrant further evaluation as a possible agent for the diuretic drug in clinical applications. Further research is underway to elucidate the active compounds responsible for the diuretic activity of LS.

Mitochondrial aquaporin-8 is involved in SREBP-controlled hepatocyte cholesterol biosynthesis.

Cholesterol, via sterol regulatory element-binding protein (SREBP) transcription factors, activates or represses genes involved in its hepatic biosynthetic pathway, and also modulates the expression of hepatocyte mitochondrial aquaporin-8 (mtAQP8), a channel that can function as peroxiporin by facilitating the transmembrane diffusion of H2O2. Here we tested the hypothesis that mtAQP8 is involved in the SREBP-mediated regulation of hepatocyte cholesterol biosynthesis. Using human hepatocyte-derived Huh-7 cells and primary rat hepatocytes, we found that mtAQP8 knockdown significantly downregulated de novo cholesterol synthesis as well as protein expressions of SREBP-2 and its target gene, a rate-limiting enzyme in cholesterol synthesis 3-Hydroxy-3-Methylglutaryl-CoA Reductase (HMGCR). In contrast, adenovirus-mediated human AQP8 mitochondrial expression significantly increased de novo cholesterol synthesis and protein expressions of SREBP-2 and HMGCR. In mtAQP8-overexpressed hepatocytes, mitochondrial H2O2 release was found to be increased; and a mitochondria-targeted antioxidant prevented the upregulation of mitochondrial H2O2 release and that of cholesterol synthesis. Our results suggest that peroxiporin mtAQP8 plays a role in the SREBP-controlled hepatocyte cholesterogenesis, a finding that might be relevant to cholesterol-related metabolic disorders.

Whole root system water conductance responds to both axial and radial traits and network topology over natural range of trait variation.

Current theory and supporting research suggests that radial transport is the most limiting factor to root water uptake, raising the question whether only absorbing root length and radial conductivity matter to water uptake. Here, we extended the porous pipe analytical model of root water uptake to entire root networks in 3D and analysed the relative importance of axial and radial characteristics to total uptake over parameter ranges reported in the literature. We found that network conductance can be more sensitive to axial than radial conductance of absorbing roots. When axial transport limits uptake, more dichotomous topology, especially towards the base of the network, increases water uptake efficiency, while the effect of root length is reduced. Whole root system conductance was sensitive to radial transport and length in model lupin (Lupinus angustifolius L.), but to axial transport and topology in wheat (Triticum aestivum L.), suggesting the root habit niche space of monocots may be constrained by their loss of secondary growth. A deep tap root calibrated to oak (Quercus fusiformis J. Buchholz) hydraulic parameters required 15 times more xylem volume to transport comparable amounts of water once recalibrated to parameters from juniper (Juniperus ashei Small 1901), showing that anatomical constraints on axial conductance can lead to significant trade-offs in woody roots as well. Root system water uptake responds to axial transport and can be limited by it in a biologically meaningful way.

Binding of a small molecule water channel inhibitor to aquaporin Z examined by solid-state MAS NMR.

Aquaporins are integral membrane proteins that facilitate water flow across biological membranes. Their involvement in multiple physiological functions and disease states has prompted intense research to discover water channel activity modulators. However, inhibitors found so far are weak and/or lack specificity. For organic compounds, which lack of high electron-dense atoms, the identification of binding sites is even more difficult. Nuclear magnetic resonance spectroscopy (NMR) requires large amounts of the protein, and expression and purification of mammalian aquaporins in large quantities is a difficult task. However, since aquaporin Z (AqpZ) can be purified and expressed in good quantities and has a high similarity to human AQP1 (~ 40% identity), it can be used as a model for studying the structure and function of human aquaporins. In the present study, we have used solid-state MAS NMR to investigate the binding of a lead compound [1-(4-methylphenyl)1H-pyrrole-2,5-dione] to AqpZ, through mapping of chemical shift perturbations in the presence of the compound.

Aquaporins: Novel Targets for Age-Related Ocular Disorders.

Aquaporins (AQPs), a large family of membrane protein channels that facilitate transport of water and other small solutes, play important roles in physiological functions and human diseases. Up till now, 13 types of AQPs, numbered 0 through 12, have been identified in various mammalian tissues. Homologous genes for AQPs in amphibians, insects, and bacteria highlight the evolutionary conservation and, thus, the importance of these membrane channels. Many members of the AQP family are expressed in the eye. AQP1, which is a water-selective channel, is expressed in the anterior chamber (cornea, ciliary body, trabecular meshwork) and posterior chamber (retina and microvessels in choroid), controlling the fluid homeostasis in the eye. Mice knockout studies have indicated that AQP1 plays an important function in the eye by suggesting its role in aqueous humor dynamics and retina angiogenesis. This review will focus on the role of AQP1 as a novel target for ocular disorders such as glaucoma and age-related macular degeneration, and it will discuss challenges and advances in identifying modulators of AQP1 function that could be useful in clinical applications.