Water Channel Protein Research Articles

Review: Recent advances in the understanding of the pathophysiology of neuromyelitis optica spectrum disorder.

Neuromyelitis optica is an autoimmune inflammatory disorder of the central nervous system that preferentially targets the spinal cord and optic nerve. Following the discovery of circulating antibodies against the astrocytic aquaporin 4 (AQP4) water channel protein, recent studies have expanded our knowledge of the unique complexities of the pathogenesis of neuromyelitis optica and its relationship with the immune response. This review describes and summarizes the recent advances in our understanding of the molecular mechanisms underlying neuromyelitis optica disease pathology and examines their potential as therapeutic targets. Additionally, we update the most recent research by proposing major unanswered questions regarding how peripheral AQP4 antibodies are produced and their entry into the central nervous system, the causes of AQP4-IgG-seronegative disease, why peripheral AQP4-expressing organs are spared from damage, and the impact of this disease on pregnancy.

Identification, Expression Patterns and RNA Interference of Aquaporins in Dendroctonus armandi (Coleoptera: Scolytinae) Larvae During Overwintering.

The ability to survive annual temperature minima could be a key determinant of distribution limits for insects under global climate change. Recent studies have suggested that insect aquaporins are indispensable for cellular water management under conditions that lead to dehydration and cold stress. Aquaporins are integral membrane water channel proteins in the major intrinsic protein superfamily and promote selected solutes and the movement of water across biological membranes. We cloned and characterized nine full-length aquaporins from Dendroctonus armandi (DaAqps), the most destructive forest pest in the Qinling Mountains of Shaanxi Province, China. Eight of the DaAqps belong to three classical aquaporin grades, including the Drosophila integral protein, the Pyrocoelia rufa integral protein, the entomoglyceroporins and one that belongs to the unorthodox grade of aquaporin 12-like channels. The DaAqps were increasingly expressed during different developmental stages and in different larval tissues, and expression peaked in mid-winter. They were tested under cold conditions for different lengths of time, and the expression of almost all DaAqps was down regulated with decreasing temperatures and long-term exposure to cold conditions. However, when the lowest temperatures were reached, the levels were immediately upregulated. These genes indicate that cold tolerance can improve through mortality responses at low temperatures after RNA interference of DaAqps. In our study, we analyzed the molecular response, expression patterns, and RNA interference of DaAqps and clarified the crucial role of protective compounds (aquaporins) underlying D. armandi cold tolerance and provide a new pest control method.

ASTAXANTHIN INCREASE AQP-5 MRNA LEVEL, SALIVARY FLOW RATE AND REDUCE F2-ISOPROSTANE LEVEL ON SUBMANDIBULAR GLAND OF WISTAR RATS WHICH IRRADIATED GAMMA RAYS

Aquaporin-5 (AQP5) is a water channel protein expressed on the apical membrane of serous acini in salivary gland. Previous study have shown that the level of mRNA AQP5 is decreased in irradiated rat that result in decreased salivary flow rate; however, the mechanism has not been reported. It’s maybe due to presence of free radicals. The purpose of this study was to determine the effects of antioxidant on level of mRNA AQP5, salivary flow rate and F2 Isoprostane level (as biomarker of oxidative stress) on salivary gland of rats irradiated with g rays. All experiments were performed using Male Wistar Rat (Rattus Norvegicus, ages 3-4 month,  weight 200 – 300 g) were randomly divided into 2 groups: the experimental group and the control group. Twenty two rats were irradiated with single dose (10 Gy) of Co60 Gamma rays at ventral surface at their neck. Before irradiated, the experimental group (11 rats) were given 0.5 mg Astaxanthin® for 4 days but not  the control group (11 rats). Saliva secretion, saliva flow rate, and blood were collected after 24 hours. After that, submandibular glands were extirpated for analized mRNA AQP5 using Real Time-RT PCR. Level of F2 Isoprostane  was analyzed by ELISA. Using independet t-test showed that mRNA AQP5 level and Flow rate saliva were significanly increased at experimental group (p<0,05), plasma F2 Isoprostance level were significanly decreased at experimental group (p<0,05). Pearson correlation test demonstrate a strong correlation between levels of AQP5 mRNA with levels of F2-isoprostane,  mRNA AQP5 levels with salivary secretion,  levels of mRNA AQP5 with salivary secretion rate, levels of F2-isoprostane with the salivary secretion, and the levels of F2 -isoprostane with salivary secretion rate. Using regression test showed a significant influence of level F2 Isoprostane toward the levels of mRNA AQP5 and the levels of mRNA AQP5 toward differences of salivary flow rate on submandibular gland. It can be conclude that antioxidant (Astaxanthin®) increased mRNA AQP5 levels, salivary flow rate and reduce levels of isoprostane F2 at Wistar rat irradiated with gamma-rays.

New insights into the transcriptional regulation of aquaporin-2 and the treatment of X-linked hereditary nephrogenic diabetes insipidus.

The kidney collecting duct (CD) is a tubular segment of the kidney where the osmolality and final flow rate of urine are established, enabling urine concentration and body water homeostasis. Water reabsorption in the CD depends on the action of arginine vasopressin (AVP) and a transepithelial osmotic gradient between the luminal fluid and surrounding interstitium. AVP induces transcellular water reabsorption across CD principal cells through associated signaling pathways after binding to arginine vasopressin receptor 2 (AVPR2). This signaling cascade regulates the water channel protein aquaporin-2 (AQP2). AQP2 is exclusively localized in kidney connecting tubules and CDs. Specifically, AVP stimulates the intracellular translocation of AQP2-containing vesicles to the apical plasma membrane, increasing the osmotic water permeability of CD cells. Moreover, AVP induces transcription of the Aqp2 gene, increasing AQP2 protein abundance. This review provides new insights into the transcriptional regulation of the Aqp2 gene in the kidney CD with an overview of AVP and AQP2. It summarizes current therapeutic approaches for X-linked nephrogenic diabetes insipidus caused by AVPR2 gene mutations.

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.

Cerebrospinal Fluid Level of Aquaporin4: A New Window on Glymphatic System Involvement in Neurodegenerative Disease?

Aquaporin4 (AQP4) is a water channel protein located at astrocyte foot processes that plays a role in glymphatic system, a highly organized fluid transport pathway which seems to be involved in Alzheimer's disease (AD) and normal pressure hydrocephalus (NPH) pathophysiology. Cerebrospinal fluid (CSF) AQP4 levels were determined in 11 patients with AD, 10 patients with NPH, and 9 controls. We found significantly reduced AQP4 in AD patients, a trend in reduction in NPH patients, and a correlation between AQP4 and amyloid-β CSF levels. This study indicates the potential role of AQP4 and glymphatic system in neurodegenerative diseases pathophysiology.

Current Status and Prospects of Complement-Targeting Therapy for Neuromyelitis Optica

Neuromyelitis optica (NMO) is clinically characterized by severe optic neuritis and long myelitis; and is associated with aquaporin-4 immunoglobulin-G (AQP4-IgG), an autoantibody directed against aquaporin-4 (AQP4), which is an astrocytic water channel protein. Until recent years, the treatment of NMO has mainly focused on the suppression of lymphocytes and depletion of autoantibodies. However, several studies on the pathogehesis of the disease in human pathology, cultured cells, and animal models have revealed that astrocyte injury in NMO is mainly caused by the complement-dependent cytotoxicity following AQP4-IgG binding to AQP4. Moreover, complement-targeting therapy has recently been translated into practical applications in several hematological disorders. and similary, also in the cases of NMO. In this article, we review the relevance of the complement system in the pathogenesis of NMO. Additionally, we review the current status and prospects of the complement-targeting therapy for NMO, including the clinical trials of eculizumab and C1 inhibitor for NMO, and the experimental studies on C1 inhibition by monoclonal antibodies.

Comparative Analysis of the aquaporin Gene Family in 12 Fish Species.

Simple SummaryAquaporins (Aqps) are a group of membrane proteins. In this study, 166 Aqp genes were identified in 12 fish species. Gene organization, motif distribution, recombination, and selection pressure were performed to investigate their evolutionary characteristics. In addition, expression profiles of Aqps were also examined under pathogens infection and organophosphorus pesticide stress. This study will provide a useful reference for further functional study.Aquaporins (Aqps) are a class of water channel proteins that play key roles in many physiological functions and cellular processes. Here, we analyzed 166 putative Aqp genes in 12 fish species and divided them into four groups. Gene organization and motif distribution analyses suggested potentially conserved functions in each group. Several recombination events were identified in some members, which accelerate their divergence in evolution. Furthermore, a few positive selection sites were identified, and mutations at these sites could alter the stability of Aqp proteins. In addition, expression profiles of some Aqp genes under pathogen infection and organophosphorus pesticide stress were also investigated. The result implied that several Aqp genes may affect different immune responses and osmoregulation. This study provides a comparative analysis of the fish Aqp gene family to facilitate further functional analyses.

Targeting Water in the Brain: Role of Aquaporin-4 in Ischemic Brain Edema.

Brain edema primarily occurs as a consequence of various cerebral injuries including ischemic stroke. Excessive accumulation of brain water content causes a gradual expansion of brain parenchyma, decreased blood flow and increased intracranial pressure and, ultimately, cerebral herniation and death. Current clinical treatment for ischemic edema is very limited, therefore, it is urgent to develop novel treatment strategies. Mounting evidence has demonstrated that AQP4, a water channel protein, is closely correlated with brain edema and could be an optimal therapeutic target for the reduction of ischemic brain edema. AQP4 is prevalently distributed in the central nervous system, and mainly regulates water flux in brain cells under normal and pathological conditions. This review focuses on the underlying mechanisms of AQP4 related to its dual role in edema formation and elimination.

A bell-shaped pattern of urinary aquaporin-2-bearing extracellular vesicle release in an experimental model of nephronophthisis.

The DBA/2‐FG pcy (pcy) mouse is a model of human nephronophthisis, a recessive cystic kidney disease. Renal expression of aquaporin‐2 (AQP2), a water channel protein, has been shown to be altered in pcy mice. However, the relationship between the renal expression and its release in urinary extracellular vesicles (uEV‐AQP2), which account for most urinary AQP2, in pcy mice has remained largely unknown. In this study, we examined age‐related alterations of this relationship in pcy mice. In comparison with control mice, pcy mice after the age of 14 weeks showed defective urinary concentration ability with an increase in urinary volume. Interestingly, the release of uEV‐AQP2 increased progressively up to the age of 16 weeks, but at 21 weeks the release did not significantly differ from that in control mice (i.e., a bell‐shaped pattern was evident). Similar results were obtained for uEV marker proteins, including tumor susceptibility gene 101 (TSG101) protein and apoptosis‐linked gene 2‐interacting protein X (Alix). Immunoblot analysis revealed that renal AQP2 expression increased progressively from 11 weeks, and immunohistochemistry showed that this increase was possibly due to an increase in the number of AQP2‐positive cells. Analysis of mRNAs for seven types of AQP expressed in the kidney supported this notion. These data suggest that the level of uEV‐AQP2 does not simply mirror the renal expression of AQP2 and that the altered release of uEV‐AQP2 in pcy mice depends on the numbers of both renal AQP2‐positive cells and EVs released into the urine.

AQP4 Aggregation State Is a Determinant for Glioma Cell Fate

The glial water channel protein aquaporin-4 (AQP4) forms heterotetramers in the plasma membrane made of the M23-AQP4 and M1-AQP4 isoforms. The isoform ratio controls AQP4 aggregation into supramolecular structures called orthogonal arrays of particles (AQP4-OAP). The role of AQP4 aggregation into OAP in malignant gliomas is still unclear. In this study, we demonstrate that AQP4 aggregation/disaggregation into OAP influences the biology of glioma cells. Selective expression of the OAP-forming isoform M23-AQP4 (AQP4-OAP) triggered cell shape changes in glioma cells associated with alterations to the F-actin cytoskeleton that affected apoptosis. By contrast, expression of M1-AQP4 (AQP4-tetramers), which is unable to aggregate into OAP, ameliorated glioma cell invasiveness, improved cell migration, and increased methalloproteinase-9 activity. Two prolines (254 and 296) at the C-terminus tail were shown to be important in mediating the relationship between the actin cytoskeleton and AQP4-OAP and AQP4-tetramers. In conclusion, this study demonstrates that AQP4 aggregation state might be an important determinant in orienting glioma cells to persist or perish. AQP4 disaggregation may potentiate invasiveness potential, whereas AQP4 aggregation may activate the apoptotic path. This study shows a new perspective on the role of AQP4 in brain tumors not necessarily associated with edema formation but with AQP4 aggregation/disaggregation dynamics and their link with the actin cytoskeleton. SIGNIFICANCE: This study demonstrates how AQP4 aggregation influences plasma membrane dynamics to alter cell proliferation, invasiveness, migration, and apoptotic potential in glioma cells.

Rutin protects mercuric chloride‐induced nephrotoxicity via targeting of aquaporin 1 level, oxidative stress, apoptosis and inflammation in rats

ObjectiveMercury is a dangerous industrial and environmental pollutant which induces severe damage in diverse organs in animal and humans. The aim of this study was to investigate the protective effect of rutin (50 and 100 mg/kg body weight) against mercuric chloride (HgCl2) (1.23 mg/kg b.w.) toxicity in rats. MethodsThe experiment was carried out in male Sprague Dawley rats (n = 35) which was divided into five groups as follow: control, rutin-100, HgCl2, HgCl2 + rutin-50 and HgCl2 + rutin-100. ResultsThe results showed that HgCl2 caused a marked increase in the malondialdehyde (MDA) level and significantly decreased antioxidant enzyme activities (p < 0.05). HgCl2 also provoked inflammatory responses by elevating the levels of tumor necrosis factor-α (TNF-α), B-cell lymphoma-3 (Bcl-3), interleukin-1β (IL-1β), nuclear factor kappa B (NF-κB), interleukin-33 (IL-33), and activities of mitogen-activated protein kinase 14 (MAPK 14) and myeloperoxidase (MPO) (p < 0.05). HgCl2 also prompted the apoptotic pathway by increasing the levels of Bcl-2 associated X protein (Bax) and p53, expression of terminal deoxynucleotidyl transferase dUNT nick end labeling (TUNEL) and cysteine aspartate specific protease-3 (caspase-3). HgCl2 changed histological integrity of kidney and expression of 8-hydroxy-2′-deoxyguanosine (8–OHdG) while caused a decrease in aquaporin 1 (AQP1) water channel protein level. In contrast to this, rutin significantly decreased oxidative stress, apoptosis, inflammation and histopathological alterations while increased AQP1 levels in kidney tissues (p < 0.05). ConclusionThe present study indicated that rutin has a nephroprotective effect due to its anti-inflammatory, antioxidant and antiapoptotic properties.

Small GTPase Rab7 Mediates Aquaporin‐2 Recycling and Apical Trafficking

Water permeability of the kidney collecting ducts is regulated by the abundance of the molecular water channel protein aquaporin‐2 (AQP2) in the apical plasma membrane of the collecting duct cells. The apical AQP2 abundance in turn is regulated by trafficking of AQP2‐containing intracellular vesicles to and from the apical membrane by the peptide hormone vasopressin. Here we used confocal microscopy to follow how AQP2 trafficked among biotin‐labeled apical membrane, Rab5+ early endosome, Rab7+ late endosome, and Rab11+ recycling endosome in response to vasopressin. Before vasopressin stimulation, most AQP2 stayed in Rab5+ early endosome and Rab11+ recycling endosome. In response to vasopressin, AQP2 in the Rab11+ recycling endosome trafficked first to the apical membrane followed by AQP2 in the Rab5+ early endosome. Upon vasopressin withdrawal, apical AQP2 returned to the Rab5+ early endosome before joining the Rab11+ recycling endosome. Rab5 knockdown slowed APQ2 internalization upon vasopressin withdrawal. Rab7 knockdown resulted in AQP2 accumulation in the Rab5+ early endosome upon vasopressin withdrawal, consistent with a role of Rab7 in AQP2 sorting to the late endosome. However, Rab7 knockdown also reduced AQP2 in the Rab11+ recycling endosome upon vasopressin withdrawal, suggesting that Rab7 participates in AQP2 sorting from the early endosome to the recycling endosome. In fact, in the Rab7 knockdown cells vasopressin‐stimulated apical AQP2 trafficking was greatly impaired. These results indicate that internalizing AQP2 first arrives at the early endosome where Rab7 sorts it to the recycling endosome where it waits for the next vasopressin signal for apical trafficking. Rab11 knockdown did not affect vasopressin‐induced apical AQP2 trafficking as reported previously. In contrast, Vps35 (vacuolar protein sorting‐associated protein 35) knockdown trapped AQP2 in the Rab11+ recycling endosome and reduced apical AQP2 trafficking. We conclude that Rab7 plays an important role in AQP2 sorting from the early endosome to the recycling endosome where vasopressin excites its apical trafficking mediated by Vps35.Support or Funding InformationThis work was supported by the Ministry of Science and Technology, TAIWAN (MOST 107‐2320‐B‐002‐057‐MY3).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Non‐Polarized mpkCCD Cell Model for Aquaporin‐2 Phosphorylation and Membrane Trafficking Study

Aquaporin‐2 (AQP2) is a water channel protein expressed in the kidney collecting duct principal cells responsible for water reabsorption. AQP2's ability to regulate water reabsorption depends on its phosphorylation states and trafficking to and from the apical plasma membrane regulated by the peptide hormone vasopressin. The mpkCCD cells have been an instrumental collecting duct cell model for studying AQP2 phosphorylation and trafficking. However, the cells require a time‐consuming polarization process before they can respond to vasopressin. We sought to circumvent this issue by examining AQP2 phosphorylation and trafficking in non‐polarized AQP2‐overexpressing mpkCCD cells treated with forskolin, which elevates intracellular cyclic AMP (cAMP), a second messenger of vasopressin. We found that forskolin induced AQP2 phosphorylation at serine 269 (S269) by 1.6 folds as observed in polarized mpkCCD and isolated rat inner medullary collecting duct cells treated with vasopressin. Before forskolin stimulation, most AQP2 was intracellular and was not phosphorylated at S269 by confocal immunofluorescence microscopy. In response to forskolin, AQP2 was found in the plasma membrane and was phosphorylated at S269, similar to those observed in the polarized mpkCCD cells and native collecting duct cells stimulated with vasopressin. As a proof of principle, we found that small hairpin RNA‐mediated protein kinase A knockdown reduced AQP2 phosphorylation at S269 and membrane localization in the non‐polarized mpkCCD cells treated with forskolin. Thus, non‐polarized AQP2‐overexpressing mpkCCD cells can be used in lieu of polarized mpkCCD cells when time is a limiting factor including transient small hairpin RNA‐mediated gene knockdown experiments.Support or Funding InformationThis work was supported by the Ministry of Science and Technology, TAIWAN (MOST 107‐2320‐B‐002‐057‐MY3).This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

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.

Biomimetic and bioinspired membranes for water purification: A critical review and future directions

Various types of channel proteins, broadly named porins, present in the cell membrane of gram‐negative bacteria have specific functionalities depending on their selectivity toward different nutrients or toward water. The high selectivity of porins has led to their incorporation into synthetic systems, in a field called biomimetics. An example is the addition of water channel proteins, or aquaporins, to polymeric separations membranes in order to enhance their performance in terms of selectivity and permeability. The concept of incorporating aquaporins into synthetic membranes has been studied for the last 10 years; however, there are still limitations such as costs, alignment into the membrane assembly, and scalability of membrane fabrication. Therefore, in recent years, there has been an increase in the study of synthesizing molecules with similar structure–function relationships of porins. These artificial channels attempt to mimic the biological porins, while being synthesized using simpler chemistry, being solvent compatible, and requiring less space on the membrane surface which helps to incorporate more channels into the membrane assembly. In summary, the future of biomimetic and bioinspired membranes depends on the design strategies, level of nature imitation, and the performance of these systems on a commercial scale. © 2019 American Institute of Chemical Engineers Environ Prog, 38:e13215, 2019

Comparative phylogenetic analysis of aquaporins provides insight into the gene family expansion and evolution in plants and their role in drought tolerant and susceptible chickpea cultivars

Aquaporins (AQPs) are water channel proteins that play a significant role in drought stress. Although the AQPs identified in multiple plant species, there is no detailed evolutionary and comparative study of AQPs regarding chickpea plant. The current study involved evolutionary analyses coupled with promoter and expression analyses of chickpea AQPs (CaAQPs). A total of 924 non-redundant AQPs were studied in 24 plant species including algae, mosses, lycophytes, monocots and dicots. Phylogenetic analysis demonstrated a clear divergence of eight AQP subfamilies (LIPs, SIPs, GIPs, NIPs, XIPs, PIPs, HIPs and TIPs). The comparative phylogenetic trees of AQP subfamilies among Arabidopsis, soybean, common bean, maize and chickpea demonstrated that the AQPs were highly species-specific. Interestingly, the dual NPA motif was conserved in all species. However, the ar/R selectivity filter signatures [W/T/S/N/G/A]-[V/S/L/I/A]-[S/G/A]-R (in NIPs), F-H-T-R (in PIPs), [H/N/Q/S]-[A/I/L/S/V]-[A/G]-[A/C/L/M/R/V] (in TIPs) and [V/I/L/M]-[V/I/A/F/M]-[A/S/F/C]-[N/F/L/I/A/S (in SIPs) were found in five species. Moreover, the Froger's positions (P1-P5) were found as [F/L/Y]-[S/T]-A-Y-[L/I/M/V/F] (in NIPs), [Q/E/M]-S-A-F-W (in PIPs), [A/L/S/T/V]-[A/C/N/S/T/V]-[P/R/S]-[Y/N/F]-[W/Q] (in TIPs) and [I/M/F]-[A/V]-[A/V]-Y-W (in SIPs). The MEME motif analyses showed that most of the motifs were specific to subfamily and subgroups. Tissue-specific expression profiling of CaAQPs revealed that CaTIPs and CaPIPs are highly expressed in most of the tissues, while CaNIPs and CaSIPs have low expression. In promoter analysis of CaAQPs, multiple stress-related cis-acting elements e.g. MYB, MYC, ABRE, etc. were found. Semi-quantitative RT-PCR analysis showed that CaPIP2;3 and CaNIP3;1 are positive regulator, while CaSIP1;1 and CaPIP2;1 have a negative role in drought tolerance. The findings and implications of this study are discussed in detail.

Aquaporins Respond to Chilling in the Phloem by Altering Protein and mRNA Expression.

Previous experiments using heat exchangers (liquid cooled blocks) to chill a portion of plant stem have shown a transient stoppage in phloem translocation and an increase in measured phloem pressure. Although a chilled-induced stoppage of phloem transport has been known for over 100 years, the mechanism of this phenomenon is still poorly understood. Recently, work has highlighted that aquaporins occur within the plasma membrane of the sieve tubes along the entire source-to-sink pathway, and that isoforms of these water channel proteins may change dynamically. Aquaporins show regulatory roles in controlling tissue and cellular water status in response to environmental hardships. Thus, we tested if protein localization and mRNA transcript abundance changes occur in response to chilling in balsam poplar (Populus balsamifera) using immunohistochemistry and qrtPCR. The results of the immunolocalization experiments show that the labeling intensity of the sieve elements treated for only 2 min of chill time significantly increased for PIP2. After 10 min of chilling, this signal declined significantly to lower than that of the pre-chilled sieve elements. Overall, the abundance of mRNA transcript increased for the tested PIP2s following cold application. We discuss the implication that aquaporins are responsible for the alleviation of sieve tube pressure and the resumption of flow following a cold-induced blockage event.

Intravaginal treatment with Marantodes pumilum (Kacip Fatimah) ameliorates vaginal atrophy in rats with post-menopausal condition

Ethnopharmacological relevanceMarantodes pumilum (MP) (Kacip Fatimah) is used to maintain the well-being of post-menopausal women. However, its role in ameliorating post menopause-related vaginal atrophy (VA) is unknown. AimsTo investigate the ability of intravaginal MP gel treatment to ameliorate VA in sex-steroid deficient condition, mimicking post-menopause. MethodsOvariectomized female Sprague-Dawley rats received MP (100 μg/ml, 250 μg/ml and 500 μg/ml) and estriol (E) gels intravaginally for seven consecutive days. Rats were then euthanized and vagina was harvested and subjected for histological and protein expression and distribution analyses. Vaginal ultrastructure was observed by transmission electron microscopy (TEM). ResultsThickness of vaginal epithelium increased with increasing intravaginal MP doses. Additionally, increased in expression and distribution of proliferative protein i.e. PCNA, tight junction protein i.e. occludin, water channel proteins i.e. AQP-1 and AQP-2 and proton extruder protein i.e. V-ATPase A1 were observed in the vagina following intravaginal MP and E gels treatment. Intravaginal MP and E gels also induced desmosome formation and approximation of the intercellular spaces between the vaginal epithelium. ConclusionsIntravaginal MP was able to ameliorate features associated with VA; thus, it has potential to be used as an agent to treat this condition.

Increasing Salt Rejection of Polybenzimidazole Nanofiltration Membranes via the Addition of Immobilized and Aligned Aquaporins.

Aquaporins are water channel proteins in cell membrane, highly specific for water molecules while restricting the passage of contaminants and small molecules, such as urea and boric acid. Cysteine functional groups were installed on aquaporin Z for covalent attachment to the polymer membrane matrix so that the proteins could be immobilized to the membranes and aligned in the direction of the flow. Depth profiling using x-ray photoelectron spectrometer (XPS) analysis showed the presence of functional groups corresponding to aquaporin Z modified with cysteine (Aqp-SH). Aqp-SH modified membranes showed a higher salt rejection as compared to unmodified membranes. For 2 M NaCl and CaCl2 solutions, the rejection obtained from Aqp-SH membranes was 49.3 ± 7.5% and 59.1 ± 5.1%. On the other hand, the rejections obtained for 2 M NaCl and CaCl2 solutions from unmodified membranes were 0.8 ± 0.4% and 1.3 ± 0.2% respectively. Furthermore, Aqp-SH membranes did not show a significant decrease in salt rejection with increasing feed concentrations, as was observed with other membranes. Through simulation studies, it was determined that there was approximately 24% capping of membrane pores by dispersed aquaporins.