Expression Levels Of AQP1 Research Articles

AQP-4 in peritumoral edematous tissue is correlated with the degree of glioma and with expression of VEGF and HIF-alpha

It is recognized that expression of AQP4 protein is much greater in gliomas than in normal tissue. The relationship between AQP4 and glioma-associated brain edema is affected by osmotic pressure and hypoxia. In this study, we detected changes of AQP4 expression in tumor and peritumoral edematous tissues to analyze the relationship between AQP4 protein and the edema index (EI). We also detected expression of vascular endothelial growth factor (VEGF) and hypoxia-inducible factor-1α (HIF-1α) to investigate their relationship with AQP4 protein, and thus to uncover the molecular biological mechanisms of AQP4 expression in glioma-associated brain edema. Sixty-five patients with brain glioma were divided into tumor and peritumor groups. Fresh tumor specimens, including six cases of grade I glioma, 18 of grade II, 11 of grade III and 30 of grade IV, and peritumoral edematous tissue specimens (1 cm distant from the tumor) were resected from these patients, and AQP4 protein expression levels were detected by western blot. Different AQP4 expression in the tumor and peritumor groups were compared. The relationship between AQP4 expression levels and the degree of peritumoral edema, and expression differences in different grades, were analyzed. Immunofluorescence cytochemistry was used to detect positive expression of AQP4 protein, VEGF protein, and HIF-1α protein in tumor tissue, and differences between expression were analyzed. Western blot showed that AQP4 expression in the peritumor (0.7697 ± 0.0941) and tumor (0.6934 ± 0.0625) groups was higher than in the control group (0.6215 ± 0.0884), and was highest in the peritumor group (both P < 0.01). AQP4 expression level in the peritumor group was positively correlated with EI (r = 0.677, P < 0.001) whereas AQP4 expression level in the tumor group was not correlated with EI (r = 0.096, P > 0.05). AQP4 expression increased with higher tumor grades in the peritumor group, but differences were not significant in the tumor group. Immunofluorescence cytochemical staining revealed that AQP4 protein in normal brain tissue was mainly expressed in the cell membrane surface, and that cytoplasm and nuclear staining was shallow. In glioma cells, AQP4 was widely distributed in the cytoplasm, particularly in the edematous area around the tumor. AQP4 protein expression in the tumor was significantly positively correlated with both VEGF protein (r = 0.877, P < 0.001) and HIF-1α protein (r = 0.876, P < 0.001). AQP4 expression was higher in brain tumor, especially peritumor. The degree of peritumoral edema correlates with AQP4 protein expression only in peritumor, whereas AQP4 expression is in accordance with expression of VEGF and HIF-1α. In glioma-associated brain edema, AQP4 is coregulated by osmotic pressure and hypoxia, with predominance of osmotic regulation, and is redistributed in glioma cells, mainly in the cytoplasm, and its expression level increased with higher glioma grades.

Neuregulin attenuated cerebral ischemia–Creperfusion injury via inhibiting apoptosis and upregulating aquaporin-4

It has been demonstrated that neuregulin-1beta (NRG-1beta) plays a neuroprotective role in cerebral ischemic injury, however, its defined mechanisms and the perfect treatment window are still elusive. Therefore, we established the animal model of MCAO/R to evaluate cerebral damage. As a result, neurological deficit scores were increased, and a small infarction focus could be seen in ischemic cortex in the control group at ischemic 0.5h/reperfusion 24h. With the duration of ischemia time, deficit scores and infarction sizes obviously elevated in the control group. A large number of positive-apoptotic cells were widespread in the ischemic cortex. Simultaneously, the expression of AQP-4 mRNA and its protein increased. NRG-1beta significantly improved neurological function, decreased the infarction volume, and elevated the expression levels of AQP-4 compared with that in the control group. The therapeutic effect of NRG-1beta was notable, especially at the ischemic 1.0h. These results demonstrate that NRG-1beta might play a neuroprotective effect on cerebral ischemia and reperfusion by inhibiting mitochondrial apoptosis pathway and regulating the activation of AQP-4. The perfect treatment window is at ischemic 1.0h after MCAO.

Decreased expression of endometrial vessel AQP1 and endometrial epithelium AQP2 related to anovulatory uterine bleeding in premenopausal women

Aquaporins (AQPs) may be involved in the occurrence of abnormal uterine bleeding as the mediators between ovarian steroids and cyclic endometrial changes. The aim of the present study was to investigate the characteristics of endometrial AQPs in women with anovulatory uterine bleeding and explore the relationship between endometrial AQPs and ovarian steroids. Sixty-one women with premenopausal anovulatory uterine bleeding and 108 women with normal cycles were involved in this study. Endometrial biopsies were obtained from the women with anovulatory uterine bleeding and normal control women. Serum estradiol and progesterone concentrations were measured with enzyme-linked immunosorbent assay on the same day as an endometrial biopsy was performed. AQP1 and AQP2 mRNA expression was evaluated using reverse-transcriptase polymerase chain reaction. Immunohistochemistry was used to localize AQP1 and AQP2 in the endometrium, and their expression was quantified by an image analysis/measuring system. AQP1 was located in the endothelium of small vessels, whereas AQP2 was mainly found in luminal and glandular epithelium. The expression levels of AQP1 and AQP2 mRNA and protein were higher in the secretory phase than those in the proliferative phase (P < 0.01) in normal endometrium, and their expression was related to serum steroid hormones (P < 0.01). However, the expression of AQP1 and AQP2 decreased in the endometrium in anovulatory uterine bleeding comparing with normal endometrium (P < 0.01). The correlation between AQP expression and ovarian steroids vanished (P > 0.05) in anovulatory uterine bleeding. Our findings indicate that cyclic expression of endometrial AQP1/AQP2 correlated with steroid hormone levels may be essential to normal endometrial function and decreased AQP1/AQP2 expression in endometrial vessels or epithelium may be involved in the occurrence of anovulatory uterine bleeding.

Regional Expression of Aquaporin 1, 4, and 9 in the Brain During Pregnancy

Pregnancy is a state of physiologic adaptation, with significant changes in cardiovascular, renal, and hemodynamic systems. Aquaporins (AQPs) may play a role in facilitating these changes. While AQP expression has been assessed in several organs during pregnancy, little is known about its expression in the brain during pregnancy. Therefore, this study assesses the regional expression of AQP1, 4, and 9 during pregnancy and the postpartum period using real-time quantitative polymerase chain reaction. The authors show that AQP1, 4, and 9 are expressed in the anterior and posterior cerebrum, cerebellum, and brainstem of nonpregnant, midpregnant, late pregnant, and postpartum rats. The regional distribution pattern of AQP4 and 9 remained similar during gestation, whereas this pattern changed for AQP1. The expression levels of AQP1, 4, and 9 in the brainstem did not change with gestation, whereas changes were found in the anterior cerebrum for AQP4 and in the posterior cerebrum and cerebellum for all AQPs.

Lactic acid increases aquaporin 4 expression on the cell membrane of cultured rat astrocytes

The water channel protein aquaporin (AQP) may play roles in the homeostasis of water content in the brain and brain edema. One possible mechanism of brain edema is glial swelling due to lactic acidosis associated with ischemia. Here, we investigated the effect of lactic acid on the expression and cellular distribution of AQP 4 in cultured rat astrocytes. After 24 h of incubation, the AQP4 expression level increased maximally with 35 mM lactic acid. The AQP4 expression levels also increased with hydrochloric acid or acetic acid. In contrast, with sodium lactate, the AQP4 levels did not increase. The increase in AQP4 expression level occurred without a significant increase in AQP4 mRNA expression level by lactic acid. Under the conditions of de novo protein synthesis inhibition with cycloheximide, lactic acid increased the AQP4 expression level. Furthermore, lactic acid increased the AQP4 expression level on the cell surface of the astrocytes, as determined by a cell surface biotinylation assay and immunocytochemical examination. The increase in AQP4 expression level on the cell membrane of astrocytes induced by lactic acid may be a new regulation mechanism of AQP4 in the brain.

Aquaporin expression in the cerebral cortex is increased at early stages of Alzheimer disease

Abnormalities in the cerebral microvasculature are common in Alzheimer disease (AD). Expression levels of the water channels aquaporin 1 and aquaporin 4 (AQP1, AQP4) were examined in AD cases by gel electrophoresis and Western blotting, and densitometric values normalized with β-actin were compared with corresponding values in age-matched controls processed in parallel. In addition, samples of cases with Pick disease (PiD) were examined for comparative purposes. A significant increase in the expression levels of AQP1 was observed in AD stage II (following Braak and Braak classification). Individual variations were seen in advanced stages which resulted in non-significant differences between AD stages V–VI and age-matched controls. No differences in AQP1 levels were observed between familial AD cases (FAD, all of them at advanced stages) and corresponding age-matched controls. Immunohistochemistry showed increased AQP1 in astrocytes at early stages of AD. Double-labelling immunofluorescence and confocal microscopy disclosed AQP1 immunoreactivity at the cell surface of astrocytes which were recognized with anti-glial fibrillary acidic protein antibodies. No differences in the levels of AQP4 were observed in AD, FAD and PiD when compared with corresponding controls. These results indicate abnormal expression of AQP1 in astrocytes in AD, and they add support to the idea that abnormal regulation of mechanisms involved in the control of water fluxes occurs at early stages in AD.

Aquaporin in bleomycin induced lung injury

Background : Aquaporins (AQPs) may play a role in the pathogenesis of pulmonary inflammation and edema. This study investigated the role ofAQPs in acute lung injury following bleomycin inhalation in rats. Methods : Sprague-Dawley rats were treated via inhalation with 10 U/kg bleomycin hydrochloride dissolved in 5 ml of normal saline. The control rats were treated with 5 ml normal saline. The animals (n = 6-8 rats per group) were sacrificed at 4, 7, and 14 d. The changes in AQP1, AQP4, and AQP5 expression levels over time were analyzed by Western blotting. The nitrate and nitrite concentrations in the bronchoalveolar lavage fluid (BALF) were measured using a modified Griess reaction. ELISA was used to check cytokines. Results : The respiration rates were significantly higher 4 and 7 days after the bleomycin treatment compared with those of the control rats. The tidal volume was lower in rats at 4 days after the bleomycin treatment, and the wet/dry weights of the lung were significantly higher than those of the control group. The nitrite and nitrate concentrations in the BALF from the rats at 4 days after exposure to bleomycin were greater than those from the saline-treated rats. Immunoblotting studies demonstrated that the AQP1 and AQP4 expression levels were lower in the rats at 4 days. However, the AQP4 expression level was higher at 7 days. The AQP5 expression level increased at 4, 7 and 14 days after the bleomycin treatment. Conclusion : This study demonstrates that AQPs are expressed differently in bleomycin-induced pulmonary edema.

Aquaporin-1 channels in human retinal pigment epithelium: role in transepithelial water movement.

Aquaporin (AQP) is a hexahelical integral membrane protein that functions as a constitutive channel for water and regulated channel for cations in fluid transporting tissues, including many in the eye. Although AQP1 has been cloned from a cDNA library prepared from cultures of retinal pigment epithelial (RPE) cells isolated from human fetal tissue, three separate studies failed with various immunochemical techniques to detect AQP1 protein in adult human or rat RPE preparations. The purpose of this study was to examine specifically the expression and distribution of AQP1 in adult human RPE in situ by using alternative methodologies and model systems and to determine the contribution of AQP1 to water movement across cultured RPE cells isolated from human cadaveric and fetal eyes. AQP1 in human RPE in situ was determined after biotinylation of proteins on cell surfaces and streptavidin chromatography, followed by immunoblot analyses. AQP1 distribution in a polarized in vitro RPE model was determined with indirect immunofluorescence confocal microscopy. The role of channel-mediated transport of water across RPE cell monolayers on filters was assessed by osmotic challenge assay. Expression levels of AQP1 were controlled with an adenovirus expression system and monitored by immunoblot analyses. AQP1 protein was detected in human RPE in situ and in cultures of human adult and fetal RPE cells. In functional assays, AQP1 facilitated water movement across RPE monolayers in an expression-dependent manner in two complementary model systems. The expression of AQP1 by RPE in vivo probably contributes to the efficient transepithelial water transport across RPE, maintains retinal attachment, and prevents subretinal edema.

Downregulation of AQP1, -2, and -3 after ureteral obstruction is associated with a long-term urine-concentrating defect.

Previously, we demonstrated that 24 h of bilateral ureteral obstruction (BUO) and short-term release of BUO was associated with a decrease in the expression of aquaporin-2 (AQP2), polyuria, and a reduced urinary concentrating capacity (10). The purposes of the present study were to examine whether BUO and the long-term release of BUO (BUO-R) for 3, 14, and 30 days were associated with changes in the expression of renal AQP1, AQP2, and AQP3 and whether such changes were associated with parallel changes in urinary output and urinary concentrating capacity. Rats (n = 4-7 in each group) were kept in metabolic cages for measurements of urinary output. Kidneys were removed to determine the expression levels of AQP1, AQP2, and AQP3 by semiquantitative immunoblotting. AQP2 was downregulated after 24 h of BUO (42 +/- 3%). Downregulation of AQP2 persisted 3 (43 +/- 14%; P < 0.01) and 15 days after BUO-R (48 +/- 11%; P < 0.01) but was normalized 30 days after BUO-R. AQP3 showed a similar pattern. Moreover, AQP1 was downregulated in response to BUO (65 +/- 7%) and remained downregulated 3 days after BUO-R (41 +/- 5%), 14 days after BUO-R (57 +/- 8%), and 30 days after BUO-R (59 +/- 5%). BUO-R resulted in a significant polyuria that gradually decreased, although it remained significant at day 30. Urinary concentrating capacity remained significantly impaired when determined 3, 14, and 30 days after BUO-R in response to a 24-h period of thirst (1,712 +/- 270 vs. 2,880 +/- 91 mosmol/kgH2O at day 30, P < 0.05). In conclusion, the expression of AQP1, AQP2, and AQP3 were long-term downregulated after BUO-R, suggesting that dysregulation of aquaporins located at the proximal tubule, thin descending limb of the loop of Henle, and the collecting duct may contribute to the long-term polyuria and impairment of urinary concentrating capacity associated with obstructive nephropathy.

Alterations in the expression of the AQP family in cultured rat astrocytes during hypoxia and reoxygenation

Aquaporins (AQPs) are a family of water-selective transporting proteins with homology to the major intrinsic protein (MIP) of lens [Cell 39 (1984) 49], that increase plasma membrane water permeability in secretory and absorptive cells. In the central nervous system (CNS), we detected the transcripts of AQP3, 5 and 8 in addition to the previously reported transcripts of AQP4 and 9 in astrocytes, of AQP3, 5 and 8 in neurons, of AQP8 in oligodendrocytes, and none of them in microglia using RNase protection assay and the reverse transcription-polymerase chain reaction (RT-PCR). Hypoxia evoked a marked decrease in the expression levels of AQP4, 5 and 9, but not of AQP3 and 8 mRNAs, and in astrocytes in vitro subsequent reoxygenation elicited the restoration of the expression of AQP4 and 9 to their basal levels. Interestingly, AQP5 showed a transient up-regulation (about 3-fold) and subsequent down-regulation of its expression within 20 h of reoxygenation after hypoxia. The changes in the profiles of AQP expression during hypoxia and reoxygenation were also observed by Western blot analysis. These results suggest that AQP5 may be one of the candidates for inducing the intracranial edema in the CNS after ischemia injury.

Water and Glycerol Permeabilities of Aquaporins 1–5 and MIP Determined Quantitatively by Expression of Epitope-tagged Constructs inXenopus Oocytes

The goal of this study was to compare single channel water and glycerol permeabilities of mammalian aquaporins (AQP) 1-5 and the major intrinsic protein of lens fiber (MIP). Each of the six cloned cDNAs from rat was left untagged or was epitope-tagged with c-Myc or FLAG at either the N or C terminus so that results would not depend on epitope identity or location. The constructs were expressed in Xenopus oocytes for measurement of osmotic water permeability (Pf), [3H]glycerol uptake, and protein expression. Each of the 30 epitope-tagged constructs was expressed strongly at the oocyte plasma membrane. The 10-min uptake of [3H]glycerol was increased significantly (range of 4.5-8-fold over control) in oocytes expressing untagged AQP3 (GLIP) and each of the four tagged AQP3 constructs; [3H]glycerol uptake was not increased in oocytes expressing AQP1, AQP2, AQP4, AQP5, or MIP. In oocytes microinjected with 5 ng of cRNA, average Pf values (in cm/s x 10(-3)) were 0.67 +/- 0.06 (control), 19 +/- 2 (AQP1), 10 +/- 1 (AQP2), 8 +/- 2 (AQP3), 29 +/- 1 (AQP4), 10 +/- 1 (AQP5), and 1.3 +/- 0.2 (MIP), and they were relatively insensitive to the presence, identity, or location of the epitope tag. Pf values were not affected by protein kinase A or C activation. After normalization for plasma membrane expression by immunoprecipitation of microdissected plasma membranes, single channel water permeabilities (pf, referenced to the AQP1 pf of 6 x 10(-14) cm3/s) were (in cm3/s x 10(-14)) 3.3 +/- 0.2 (AQP2), 2.1 +/- 0.3 (AQP3), 24 +/- 0.6 (AQP4), 5.0 +/- 0.4 (AQP5), and 0.25 +/- 0.05 (MIP); pf values were insensitive to epitope identity and location. These results indicate very different intrinsic water permeabilities for the mammalian aquaporin homologs, with the pf value for AQP4 remarkably higher than those for the others. The pf values establish limits on aquaporin tissue densities required for physiological function and suggest significant structural and functional differences among the aquaporins.

Expression of Aquaporins in the Rat Ocular Tissue

The aquaporins (AQPs) are a rapid growing family of water channel proteins found in animals, plants and microorganisms that raise plasma membrane water permeability required for efficient isosmotic fluid transport. Five homologs of aquaporins (AQP1, AQP2, AQP3, AQP4 and AQP5) have been identified from various mammalian tissues; the expression of these aquaporins in ocular tissues was studied. Semiquantitative expression levels of these aquaporins were determined in ciliary body, cornea, lens, retina, iris and choroid using RT-PCR. Expression levels of AQP1 are highest among the known aquaporins in each rat ocular tissue examined. In cornea, AQP1 is expressed approximately three-fold higher than AQP3 and 2.5 fold higher than AQP5. However, the highest intraocular expressions of AQP3 and AQP5 are in the cornea. In the iris, expression levels of AQP1 are approximately 600–700 fold higher than AQP4 and AQP5. In the ciliary body, the expression levels of AQP1 are approximately ten-fold higher than AQP4, the only other aquaporin expressed. In the lens, the major water channel is AQP1 with detectable levels of AQP4 and AQP5 that are approximately 1000-fold lower than AQP1. In choroid, AQP1 is the only water channel expressed. In retina, AQP1 is expressed approximately six-fold higher than AQP4, the only other aquaporin expressed. However, the highest ocular expression of AQP4 is in retina. AQP2 is not detected in the eye. Finally, the possible physiological roles of aquaporins in maintaining and regulating the aqueous flow, and corneal and lens transparency are discussed.

Plants used in traditional medicine in lower Zambesia

Ziziphora clinopodioides has been frequently used as an anti asthmatic plant in traditional medication. Recent work explores the anti-asthmatic activity of Z. clinopodioides in allergen-induced asthmatic mice. Intraperitoneal sensitization followed by intranasal challenge were given with ovalbumin (allergen) to develop allergic asthma. Investigational groups of animals were administered with drug methylprednisolone (MP) (15 mg/kg body weight), n-hexane fraction, ethylacetate fraction, and methanolic extract of Z. clinopodioides extract (500 mg/kg b.w.) for successive 07 days. Hematoxyline and eosin (H&E) and periodic acid-Schiff (PAS) stains were used to evaluate histopathological parameters on lung tissues. As an index of lungs tissues edema, wet/dry weight ratio of lungs was determined. Evaluation of expression levels of AQP1, AQP5, IL4, and IL5 was conducted by using RT-PCR. The data exhibited that both Z. clinopodioides and MP attenuated differential and total leukocyte counts in hematological examination i.e. in BALF and blood. Treatment with Z. clinopodioides also caused suppression of inflammatory cell infiltration and expression levels of IL4 and IL5, the later could have caused attenuation of pulmonary inflammation. The study also found decline in lung wet/dry ratio and goblet cellh hyperplasia in treated groups which indicates amelioration of lung edema. Treatment with Z. clinopodioides significantly increased the expression levels of aquaporin-1 and -5, which could have led to reduction in lung edema. The treatment with MP showed comparable results to Z. clinopodioides. Current investigation revealed that Z. clinopodioides possessed anti-asthmatic property which might be accredited to upregulagted AQP1 and AQP5 levels and downregulated IL4 and IL5 levels.