Brain expression of the water channels aquaporin-1 and -4 in mice with acute liver injury, hyperammonemia and brain edema

Cerebral edema is a feared complication to acute liver failure (ALF), but the pathogenesis is still poorly understood. The water channels Aquaporin-1 (Aqp1) and -4 (Aqp4) has been associated with brain edema formation in several neuropathological conditions, indicating a possible role of Aqp1 and/or Aqp4 in ALF mediated brain edema. We induced acute liver injury and hyperammonemia in mice, to evaluate brain edema formation and the parallel expression of Aqp1 and Aqp4 in ALF. Liver injury and hyperammonemia were induced by +D-galactosamine (GLN) plus lipopolysaccharide (LPS) intraperitoneally and intravenous ammonia-acetate (NH(4)(+)), the GLN+LPS+NH(4)(+) group. The vehicle control group (CONTROL) was treated with NaCl and phosphate-buffered saline. The GLN+LPS+NH(4)(+) group showed significantly elevated p-alanine aminotransferase, p-INR and p-ammonium vs. CONTROL (p < 0.001). Cortical brain water content was significantly elevated in the GLN+LPS+NH(4)(+) group vs. CONTROL, mean (SEM) 80.8(0.3) vs 80.0(0.1) % (p < 0.05). Western blot of membrane enriched cortical brain tissue showed significantly upregulation of Aqp4 in the GLN+LPS+NH(4)(+) group vs. CONTROL, mean AU (SEM) 100775(14820) vs. 58857(6266) (p < 0.05), and stationary levels for Aqp1. Aqp1 and Aqp4 mRNA were stationary. This study indicates that Aqp4, but not Aqp1, may be of importance in the pathogenesis of cortical brain edema in mice with ALF.

Aquaporin-4 water channel expression by thymoma of patients with and without myasthenia gravis

BACKGROUND

Neuromyelitis optica (NMO) is a serious idiopathic inflammatory demyelinating disorder characterized by acute transverse myelitis and optic neuritis. A significant proportion of NMO patients are seropositive for NMO-IgG, an autoantibody targeting aquaporin-4 (AQP4) water channel. Paraneoplastic NMO associated various tumors were recently reported.

AIM

We studied the expression of AQP4 by thymoma from patients with and without myasthenia gravis (MG).

METHODS

Thymoma obtained from thymomectomy in patients with and without MG were studied by immunohistochemistry and western blot.

RESULTS

Ten thymoma patients (9 with MG) and two control patients without thymoma or MG were studied. Immunohistochemistry revealed AQP4 immunoreactivity in cell membrane of thymoma cells from all ten thymoma specimens whereas thymic tissues from patients without thymoma or MG were negative for AQP4 immunoreactivity. Western blot revealed that lysates of nine of the ten thymoma specimens reacted with anti-human AQP4 antibody with a band of ~30 kDa compatible with the molecular weight of AQP4. Interestingly, immunofluorescence revealed that IgG isolated from 2 NMO patients seropositive for NMO-IgG bound to cell membrane of thymoma cells from all ten thymoma specimens while IgG from healthy control subject did not.

CONCLUSION

Thymoma cells of patients with and without MG express AQP4. AQP4 autoantibodies from serum of NMO patients bound to AQP4 expressed on thymoma cell membrane.

Ammonia induces upregulation of aquaporin-4 in neocortical astrocytes of rats through the p38 mitogen-activated protein kinase pathway

BACKGROUND

Astrocyte swelling is an important consequence of hepatic encephalopathy, and aquaporin-4 has been reported to play a vital role in this swelling. Ammonia causes astrocyte swelling and is also known to modulate aquaporin-4 expression in the astrocyte foot processes. The purpose of this study was to explore the mechanism of ammonia-induced aquaporin-4 expression, which has been suggested to involve the p38 mitogen-activated protein kinase pathway.

METHODS

We exposed cultured astrocytes to ammonium chloride, an in vitro model of hepatic encephalopathy. The purity of cultured astrocytes was evaluated by fluorescent glial fibrillary acidic protein labeling; cell morphology was assessed by light microscopy; the expression of aquaporin-4, phospho-p38, and p38 were detected by Western blotting analysis. Statistical analysis was performed by one-way factorial analysis of variance, and the relationship between variables was calculated by linear regression using SPSS version 13.0 program for Windows (SPSS, Chicago, IL, USA).

RESULTS

The purity of cultured astrocytes was (96.6 +/- 1.4)%. Astrocytes swelled significantly when exposed to 5 mmol/L ammonium chloride for 24 hours as compared to non-exposed astrocytes. Co-treatment with 10 micromol/L SB203580 (an inhibitor of p38) attenuated the degree of ammonium chloride induced astrocyte swelling. Western blotting analysis revealed that the expression levels of phospho-p38 and aquaporin-4 in ammonium chloride treated cells were significantly increased relative to the control group (P < 0.001); SB203580 co-treatment inhibited the increased expression of phospho-p38 and aquaporin-4 relative to the ammonium chloride treated group (P = 0.002 and P = 0.015 respectively). The phosphorylation of p38 and upregulation of aquaporin-4 were highly correlated (r = 0.909). There were no significant differences in total p38 expression among the groups (P = 0.341).

CONCLUSIONS

Ammonium chloride induced upregulation of aquaporin-4 in astrocytes is regulated by the p38 mitogen-activated protein kinase pathway. Inhibiting p38 activation prevented ammonium chloride induced aquaporin-4 protein upregulation.

Differential expression of aquaporin-4 isoforms localizes with neuromyelitis optica disease activity

Neuromyelitis optica (NMO) is a devastating neuroinflammatory disorder that specifically targets the spinal cord and optic nerves. Aquaporin-4 (AQP4) is the target of the NMO-IgG biomarker. AQP4 is expressed as two isoforms: M1 and M23, which have different functions in the central nervous system (CNS). We characterized the expression pattern of these AQP4 isoform mRNAs in humans and found a pattern of AQP4 expression that correlates with NMO disease localization. The ratio of M1:M23 mRNA is highest in the optic nerve and spinal cord, followed by brainstem, then the cerebral and cerebellar cortices.

[Construction and clinical application of lentivirus-AQP4 expressing vector]

OBJECTIVE

To construct the human aquaporin-4 (AQP4) expressing vector and detect anti-AQP4 antibody in serum of patients with neuromyelitis optica (NMO).

METHODS

RNA was extracted from human glioblastoma and AQP4 cDNA obtained through RT-PCR.The fragment was cloned into the lentiviral expressing vector (iDUET101) and transformed into competent strain Hb101 for later amplification; plasmids were extracted from the amplified positive-bacteria-colony, sequenced and transfected into HEK-293T cells. Expression of AQP4 was identified by RT-PCR, Western blot and immunofluorescence assay. And anti-AQP4 antibody in human serum was tested.

RESULTS

The sequence of target fragment matched with that of human AQP4 fragment sequences (NM_001650) completely. The constructed AQP4 fragment transfected in HEK-293T cell was tested by immunofluorescent examination and it exhibited obvious fluorescence located in cell membrane. Western blot test was positive. And the fragment was about 34 KD. Cellular immunofluorescence examination showed 11 examples of 12 NMO patient serums (91.7%) were positive, 4 in 34 multiple sclerosis (11.8%) positive and negative in all 50 serum samples of healthy controls.

CONCLUSION

The HEK-293T cell transfected with lentivirus-AQP4 vector can express stably. And the expressed fragment may be applied in clinical examination.

[Clinical spectrum associated with aquaporin-4 antibodies (NMO-IgG)]

INTRODUCTION

The description of a highly sensitive and specific biomarker for neuromyelitis optica (NMO-IgG/aquaporin-4 antibody) extended the clinical spectrum of NMO to limited forms such as optic neuritis (ON) and longitudinally extensive myelitis (LEM).

OBJECTIVE

To asses the sensitivity and specificity of our assay, and to describe the clinical characteristics of the patients who were tested for NMO-IgG.

METHODS

NMO-IgG was analysed by immunohistochemistry and confirmed by assay on HEK cells transfected with aquaporin-4. The clinical information was obtained from forms filled in by the referring neurologists.

RESULTS

A total of 580 samples from 518 patients were analysed from November 2005 to September 2008. Clinical information was available from 358 (68%) patients. All 33 (100%) positive cases were followed up. Twenty-eight of the 43 (65%) patients diagnosed with NMO by the revised criteria of 2006 were positive; the sensitivity was 62.5% when applying the same criteria, but discounting the criterion of NMO-IgG status, or 57% when applying the criteria of 1999. NMO-IgG was detected in 3 (13%) of the recurrent LEM and 2 (4%) of the recurrent ON. NMO-IgG was not detected in the remaining patients (96 with a final diagnosis of multiple sclerosis; 80 with myelitis; 28 with non-recurrent ON; and 33 other diagnosis).

CONCLUSIONS

No false positive cases were found in this large and non-selected study. NMO-IgG positive cases were mostly associated with NMO, and only in a low percentage with recurrent ON or LEM.

[Regulating effects of aquaporin 4 expression in LoVo cells by serum containing total anthraquinone in rheum]

OBJECTIVE

To investigate the regulating effects of serum containing total anthraquinone in rheum on the expression of AQP4 in cultured LoVo cells in vitro.

METHOD

Sixteen SD rats were randomly divided into 4 groups respectively treated with 0, 1.4, 2.5, 4.5 g x kg(-1) x d(-1) of total anthraquinone in rheum by intragastric administration. After 7 days of treatment, the rats were anesthetized and celiotomized to prepare the serum containing total anthraquinone in rheum. LoVo cells cultured in vitro were treated with different concentrations of total anthraquinone in rheum for 24 h. The expression levels of protein and mRNA of AQP4 IN LoVo cells were decided by Western blot and semiquantive RT-PCR.

RESULT

Western blot and semiquantive RT-PCR showed that serum containing total anthraquinone in rheum prepared from rats treated with 4.5 g x kg(-1) x d(-1) of total anthraquinone in rheum could inhibit the expression of mRNA and protein levels of AQP 4 in LoVo cells (P<0.01).

CONCLUSION

Serum containing total anthraquinone in rheum can inhibit both the transcription and translation of AQP4 gene, indicating that the regulation mechanism of rhubarb on the expression of AQP4 can be related to the cathartic effect of rhubarb.

Regulation of water permeability through aquaporin-4

Aquaporin-4 (AQP4) is a predominant water channel protein in mammalian brains that is distributed with the highest density in the perivascular and subpial astrocyte end-feet. AQP4 is a critical component of an integrated water and potassium homeostasis. Expression and regulation of AQP4 have been studied to understand the roles of AQP4 in physiology and several pathological conditions. Indeed, AQP4 has been implicated in several neurological conditions, such as brain edema and seizure. AQP4 is dynamically regulated at different levels: channel gating, subcellular distribution, phosphorylation, protein-protein interactions and orthogonal array formation. In this review, we focus on the short-term regulation of AQP4. Phosphorylation of AQP4 is important; AQP4 is inhibited when Ser180 is phosphorylated and activated when Ser111 is phosphorylated. AQP4 is also regulated by several metal ions. These metal ions inhibit AQP4 by interacting with the Cys178 residue located in the cytoplasmic loop D, suggesting that AQP4 is regulated by intracellular signaling pathways in response to extracellular stimuli. Recently, it was demonstrated that AQP4 may be inhibited by arylsulfonamides, antiepileptic drugs and other related chemical compounds. Structural analysis of AQP4 may guide a drug design for AQP4.

[A aquaporin 4 expression and effects in rat hippocampus after microwave radiation]

OBJECTIVE

To investigate the expression of aquaporin 4 (AQP4) after microwave exposure and the correlation with the brain injury by radiation.

METHODS

70 male rats were exposed to microwave whose average power density was 0, 10, 30 and 100 mW/cm(2) respectively. Rats were sacrificed at 6 h, 1 d, 3 d and 7 d after exposure. Immunohistochemistry and Western blot were used to detect the expression of AQP4 in protein level in rat hippocampus, and the expression of AQP4 in gene level was measured by in situ hybridization and RT-PCR.

RESULTS

The expression of AQP4 in rat hippocampus was abnormal after 10, 30, 100 mW/cm(2) microwave exposure. The protein level showed increased at first and then recovered at 10 and 30 mW/cm(2) groups, while increased progressively in 100 mW/cm(2) group within 14 d (P < 0.01). The gene expression of AQP4 was increased (0.51 +/- 0.02) at the beginning (6 h) and then regained after 10 mW/cm(2) microwave exposure, while in 30 and 100 mW/cm(2) groups, it rose to the peak at 7 d (0.46 +/- 0.02 and 0.43 +/- 0.08) and didn't get back (P = 0.004; P = 0.012).

CONCLUSION

Microwave radiation can increase the expression of AQP4 in rat hippocampus. The change might participate in the process of increasing permeability of blood-brain barrier and lead to the brain edema after microwave radiation.

[Effect of MAPK signal transduction pathway inhibitor U0126 on aquaporin 4 expression in alveolar type II cells in rats with oleic acid-induced acute lung injury]

OBJECTIVE

To investigate the relationship between aquaporin 4 (AQP4) in alveolar type II (AT-II) cells and MAPK signaling pathway in rats with early-stage oleic acid-induced acute lung injury (ALI) and acute respiratory distress syndrome (ARDS).

METHODS

Three groups of rats, namely the normal control, ALI and U0126 treatment group were used in this study. After oleic acid-induced ALI in the latter two groups, the rats in the treatment group received 100 micromol/L U0126 treatment at the dose of 10 micro, and dimethyl sulfoxide (DMSO) were given in the normal control and ALI groups. Arterial blood gas and the extravascular lung water (EVLW) content were measured after the treatments, and pathological changes in the lung tissues were observed microscopically. ATII cells were isolated from the lung tissues and identified using tannic acid staining and alkaline phosphatase (APK) staining. The expression of AQP-4 mRNA in the cells was detected with RT-PCR.

RESULTS

Blood gas analysis, HE staining and EVLW content measurement revealed severer injury of the lung tissues in ALI group than in the normal control group, but the severity was comparable between the treatment and ALI groups. RT-PCR demonstrated significantly increased AQP-4 mRNA expression in ALI group as compared with that in the normal control group, and U0126 treatment resulted in obvious reduction in AQP-4 mRNA expression in the U0126 treatment group.

CONCLUSION

Oleic acid-induced ALI results in the activation of MAPK signaling pathway and up-regulation of AQP-4 mRNA expression in the ATII cells of rats.

Identification of binding sites for anti-aquaporin 4 antibodies in patients with neuromyelitis optica

OBJECTIVE

Anti-aquaporin 4 antibodies (AQP4-Ab) are specifically detected in patients with neuromyelitis optica. To investigate the role of AQP4-Ab, we examined the antibody binding epitope using human and mouse mutant AQP4.

METHODS

We constructed human and mouse amino acid substitution AQP4 mutants and compared the reactivity with wild-form of human, mouse and rat AQP4.

RESULTS

The decreased intensity of AQP4-Ab staining with mouse AQP4 was recovered to that of human AQP4 with the mouse mutant A228E for 9 of the 10 sera.

CONCLUSIONS

The third extracellular loop of AQP4 is considered to be the major epitope for AQP4-Ab in NMO.

[Effect of rhubarb on expressions of aquaporin-2 and -4 in rat's kidney]

OBJECTIVE

To investigate the effect of rhubarb on expressions of aquaporin-2 and 4 (AQP2 and AQP4) in rat's kidney.

METHODS

Thirty-two SD rats were randomly divided into 4 groups, the normal control group, and the three rhubarb groups medicated via gastrogavage with low, mid and high dose of rhubarb extract (total anthraquinone) respectively. The 6 h and 24 h urine volume were measured, and the protein and mRNA expressions of AQP2 and AQP4 in renal tissue were determined with immunohistochemistry, Western blot and RT-PCR.

RESULTS

No significant difference between the control group and the low dose rhubarb treated group was found in urine volume, as well as in AQP2 and AQP4 protein and mRNA expressions. But the urine volume was obviously higher, the protein and mRNA expressions of AQP2 and AQP4 were markedly lower in rats after mid/high dose rhubarb medication respectively when compared with those in the normal controls (all P < 0.01).

CONCLUSION

Rhubarb can inhibit the protein and mRNA expressions of AQP2 and AQP4 in rats' kidney, which probably is one of the mechanisms of rhubarb for diuresis.

[The relationship between the aquaporin-4 and brain edema, pathologic change, ultrastructure in peri-hematoma tissue in patients with intracerebral hemorrhage]

OBJECTIVE

To observe the expression of aquaporin-4 (AQP-4) mRNA and study the relationship between AQP-4, brain edema, pathological changes and ultrastructure of peri-hematoma tissue in intracerebral hemorrhage (ICH) patients.

METHODS

Intracranial operation was performed via nonfunctional area with a funnel-like approach on 30 ICH patients. The brain tissue which must be removed 1 cm away the hematoma was removed within 12 hours for observation as normal brain tissue and taken as the control group (7 patients), and which of the brain tissue within 1 cm around hematoma was taken as the study specimens. The experimental group was subdivided into five groups according to the time interval after ICH: <6 hours (6 cases), 6-12 hours (7 cases), 12-24 hours (5 cases), 24-72 hours (6 cases), and >72 hours ( 6 cases ). Expression of the AQP-4 mRNA, brain edema, pathological and ultrastructural changes were observed with reverse transcription-polymerase chain reaction (RT-PCR), light microscope and electron microscope.

RESULTS

The expression of the AQP-4 mRNA was not remarkable, the morphology and construction were basically normal in control group. The expression of AQP-4 mRNA was mild (1.17+/-0.41)and there was edema of neuroglia in the <6 hours group. After 6 hours, besides neuroglial edema, the expression of the AQP-4 mRNA was gradually obvious, capillary endothelial cells began to swell too, and tight junctions gradually began to loosen. In the 12-72 hours group the expression of the AQP-4 mRNA reached its peak (3.50+/-0.55, 3.60+/-0.55, both P<0.01), and brain edema was most prominent, and electron microscopy showed that neurons, neuroglia, and capillary endothelial cells were markedly deformed. After 72 hours, the expression of AQP-4 mRNA gradually recovered, and brain cells showed less damage. On the 5th day the damage began to repair, and on the 8th day, the damage was basically repaired. The correlation analysis showed that there was a remarkable positive correlation between the expression of the AQP-4 mRNA and the degree of brain edema and the size of hematoma (r(1)=0.67, P<0.01; r(2)=0.44, P<0.05) .

CONCLUSION

Secondary edema and brain damage may correlate with the expression of the AQP-4 mRNA in the peri-hematoma brain edema area. Removal of hematoma will help decrease the AQP-4 mRNA expression and brain edema damage in the early stage.

Detection of anti-aquaporin-4 antibodies in neuromyelitis optica: current status of the assays

BACKGROUND

Neuromyelitis optica (NMO) is a severe inflammatory demyelinating disease that predominantly affects the optic nerve and spinal cord. Since the discovery of a specific serum marker for NMO in 2004, and its subsequent identification as an antibody to aquaporin-4 (AQP-4), various methods have been developed to test for the antibodies in patients sera.

OBJECTIVE

To assess the principal methods used to measure AQP-4 antibodies in patients sera, describe their contribution to neuromyelitis spectrum disease and examine their value in the early detection of disease.

METHODS

We compared the published data on each assay and used the relapsing NMO cohort as a uniform patient group for direct assay comparison.

RESULTS

The indirect immunofluorescence assay, a cellbased assay (CBA) and a fluorescence-based immunoprecipitation assay have broadly similar high sensitivities (86%, 91% and 83%) in the relapsing cohort, but the indirect immunofluorescence has a lower specificity (91%) compared with the other two (both 100% specific).

CONCLUSIONS

The indirect immunofluorescence assay for NMO-IgG allows the detection of antibodies in routine screening, but the CBA for AQP-4 antibodies is the most sensitive. The fluoroimmunoprecipitation assay is a potentially high-throughput test for identifying positive sera and for serial estimations of antibody levels, but in its present form is slightly less sensitive. Overall, these assays are proving very useful in helping to diagnose those patients with longitudinally extensive transverse myelitis or recurrent optic neuritis who are likely to have relapsing NMO, including patients with myelopathy and Sjogrens syndrome, but it appears to be less often positive in patients with monophasic NMO.

[Regulatory effect of anthraquinone derivatives from rhubarb on aquaporin 4 expression in colon of rats and in LoVo cell line]

OBJECTIVE

To investigate the cathartic effect of total anthraquinone (AQ) from rhubarb on SD rats and its regulatory effect on aquaporin 4 (AQP4) expression in rat colon and in vitro cultured LoVo cell line.

METHODS

Twenty-four SD rats were randomly divided into the normal control group treated with distilled water, and the two AQ groups administered with AQ suspension in cathartic and high dose (AQcd and AQhd) respectively via gastrogavage for 5 days. Water content in colonic stool was detected and the expression of AQP4 in rat's proximal colon was measured using Western blot and RT-PCR. LoVo cells cultured in vitro were used in the experimental study. The AQP4 protein and mRNA expressions in the cells were detected by Western blot and semiquantitative RT-PCR after they were cultured for 24 h with RPMI-1640 medium containing rhein/emodin in different concentrations, and those cultured with RPMI-1640 containing 20 mg/L rhein/emodin for different time points.

RESULTS

After treatment, the stool water content in the AQcd and AQhd groups was higher than that in the control group and the AQP4 expression in rats treated with AQ decreased in a dose-dependent manner. The study showed that rhein/emodin could significantly down-regulate the protein and mRNA expressions of AQP4 in cultured LoVo cells, with the effectiveness related with dose and acting time.

CONCLUSION

At the same time of playing cathartic action, total AQ of rhubarb can effectively down-regulate the expression of AQP4 in rat's proximal colon; rhein/emodin can suppress the AQP4 expression in LoVo cells in vitro. One mechanism of cathartic effect of rhubarb AQ is possibly its down-regulation on AQP4 expression.

A postpartum model in rat: behavioral and gene expression changes induced by ovarian steroid deprivation

BACKGROUND

Postpartum depression (PPD) affects approximately 10% to 20% of women during the first 4 weeks of the postpartum period and is characterized by labile mood with prominent anxiety and irritability, insomnia, and depressive mood. During the postpartum period, elevated ovarian hormones abruptly decrease to the early follicular phase levels that are postulated to play a major role in triggering PPD. However, the underlying neurobiological mechanisms that contribute to PPD have not been determined.

METHODS

In the present study, we examined the effect of ovarian steroids, administered at levels that occur during human pregnancy followed by rapid withdrawal to simulate postpartum conditions, on behavior and gene expression in the rat.

RESULTS

The results of behavioral testing reveal that the hormone-simulated postpartum treatment results in the development of a phenotype relevant to PPD, including vulnerability for helplessness, increased anxiety, and aggression. Real-time quantitative polymerase chain reaction (PCR) demonstrated transient regulation of several genes, including Ca(2+)/calmodulin-dependent protein kinase II (CAMKII), serotonin transporter (SERT), myocyte enhancer factor 2A (MEF2A), brain-derived neurotrophic factor (BDNF), gamma-aminobutyric acid type A receptor alpha 4 (GABAARA4), mothers against decapentaplegic homolog 4 (SMAD4), and aquaporin 4 (AQP4) that could underlie these behavioral effects.

CONCLUSIONS

These studies provide an improved understanding of the effects of withdrawal from high doses of ovarian hormones on behavior and gene expression changes in the brain that could contribute to the pathophysiology of PPD.

Hypersensitivity of aquaporin 4-deficient mice to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine and astrocytic modulation

Aquaporin 4 (AQP4) is a predominant water channel protein in mammalian brains, which is localized in the astrocyte plasma membrane. AQP4 has gained much attraction due to its involvement in the physiopathology of cerebral disorders including stroke, tumor, infection, hydrocephalus, epilepsy, and traumatic brain injury. But there is almost no evidence whether abnormal AQP4 levels are associated with degenerative diseases, such as Parkinson's disease (PD). In our studies, we established PD animal models by administration of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine to test the hypothesis that abnormal AQP4 expression is involved in the pathophysiology of this disease. We show that mutant mice lacking AQP4 were significantly more prone to MPTP-induced neurotoxicity than their wild-type littermates. Furthermore, after administration of MPTP, astroglial proliferation and GDNF protein synthesis were inhibited by AQP4 deficiency. This study demonstrates that AQP4 is important in the MPTP neurotoxic process and indicates that the therapeutic strategy targeted to astrocytic modulation with AQP4 may offer a great potential for the development of new treatment for PD.

Skeletal muscle syntrophin interactors revealed by yeast two-hybrid assay

Syntrophins are the cytoplasmic peripheral proteins of dystrophin glycoprotein complex, of which five (alpha l, beta 1, beta 2, gamma 1 and gamma 2) isoforms have been identified so far. Respective syntrophin isoforms are encoded by different genes but have similar domain structures. At the sarcolemma of skeletal muscle, the most abundant alpha l-syntrophin was shown to interact at its PDZ domain with many membrane proteins. Among them, the AQP4 interaction with alpha 1-syntrophin PDZ domain was demonstrated by a Tg mouse study, prompting us to investigate the interaction between mouse alpha l-syntrophin (BC018546: nt.267-492, PDZ domain) pEXP-AD502 as prey vector and mouse AQP4 (NM009700: nt.805-969) pDBLeu as bait vector by the yeast two-hybrid assay, resulting in a negative study. We further studied the binding partner of another sarcolemma located beta 1-syntrophin, and performed a yeast two-hybrid experiment. With human beta 1-syntrophin as bait and human skeletal muscle cDNA library as prey, we obtained one positive clone which turned out to be alpha-dystrobrevin. Although the interaction of human beta 1-syntrophin with alpha-dystrobrevin has already been shown by immunoprecipitation assay, we have here confirmed this interaction by a yeast two-hybrid experiment.

[Regulative effects of aquaporin 4 expression by rhein in rhubarb to intestinal epithelial cell line LoVo]

OBJECTIVE

To investigate the effects of rhein on regulating aquaporin4 (AQP4) to LoVo cells cultured with RPMI-1640 medium containing rhein.

METHODS

LoVo cells were cultured with RPMI-1640 medium containing different concentration rhein for 24 hours and were cultured with RPMI-1640 containing rhein (20 mg/L) for different time. Four groups were assigned as LoVo cells were cultured respectively with RPMI-1640 medium containing different concentration rhein (40, 20, 10 mg/L and control group), while six groups were assigned as LoVo cells were cultured with RPMI-1640 medium containing rhein (20 mg/L) for different time (3, 6, 12, 24, 48 h and control group). The location of AQP4 protein in LoVo cells was definited by immuocytochemistry dying. Western blotting and semiquantitative RT-PCR were adopted to detect the relative expression of AQP4 protein and mRNA.

RESULTS

AQP4 was located mainly in plasma membrane of LoVo cells while partly in cytoplasm. The relative expression of AQP4 protein and mRNA decreased with the increasing of rhein concentration; there was no significant difference of the relative expression of AQP4 in 10 mg/L group compared with that in control group, but it decreased significantly in 40 and 20 mg/L groups. The relative expression of AQP4 in 3 and 6 h groups was lower than that in control group but there was no statistical significance, however that in 12, 24, 48 h groups was lower significantly compared with that in control group.

CONCLUSION

Rhein can inhibit the genetic transcription and the translation of AQP4 gene in LoVo cells, which demonstrates that the change of AQP4 expression regulated by rhein may be related to the cathartic effect of rhubarb.

[Role of AQP-4 in pulmonary water metabolism in rats in early stage of oleic acid-induced acute lung injury]

OBJECTIVE

To evaluate the capacity of alveolar type II (AT II) cells for water and sodium transport in rats with early-stage oleic acid-induced acute lung injury (ALI)/acute respiratory distress syndrome (ARDS).

METHODS

AT II cells were isolated and purified from rats with ALI/ARDS induced by oleic acid, and their morphology was observed using electron microscopy and optical microscopy. The extravascular lung water (EVLW) content in the rats was measured by gravimetric method. The distribution of aquaporin-4 (AQP-4) on the cell membrane was observed with immunohistochemistry, and the expression of AQP-4 mRNA was detected with RT-PCR.

RESULTS

Microscopic examination and blood gas analysis indicated severe injury of the lung tissues in ALI group. Smith lung injury score and EVLW in ALI group were significantly higher in ALI group than in the control group (P<0.05). Immunohistochemistry identified intensified AQP-4 expression in rat lung tissues and RT-PCR also demonstrated increased AQP-4 mRNA expression as compared with the control group. The level of APQ-4 whole-cell currents was decreased in AT II cell membrane and increased in cytoplasm in ALI group (P<0.05 ).

CONCLUSIONS

Pathophysiological changes occurs in early stage of oleic acid-induced AMI, and AQP-4 mRNA expression is up-regulated on the AT II cell membrane to regulate the exchange of fluid between the alveolar space and alveolar epithelium barrier and play an important compensational role in pulmonary liquid clearance in the event of sodium transport damages in ALI.

Modulation of AQP4 expression by the selective V1a receptor antagonist, SR49059, decreases trauma-induced brain edema

BACKGROUND

Currently, there are no pharmacological treatments available for traumatically induced brain edema and the subsequent rise of ICP. Evidence indicates that Aquaporin-4 (AQP4) plays a significant role in the pathophysiology of brain edema. Previously we have reported that SR49059 reduced brain edema secondary to ischemia. We, therefore, examined whether the selective V1a receptor antagonist, SR49059, reduces brain edema by modulating AQP4 expression following cortical contusion injury (CCI).

METHODS

Traumatic brain injury (TBI) was produced in thirty-two adult male Sprague-Dawley rats by lateral CCI (6.0 m/sec, 3 mm depth). Animals were randomly assigned to vehicle (n=16) or SR49059 treatment (n=16) groups and administered drug (960 microl/hr i.v.) immediately after injury over a 5 hr period. Animals were sacrificed for assessment of brain water content by Wet/Dry method and AQP4 protein expression by immunoblotting expressed as the ratio of AQP4 and Cyclophilin-A densitometries.

FINDINGS

Elevated AQP4 expression levels and water content were observed on the right injured side in both the right anterior (RA) and right posterior (RP) section compared to the left non-injured side inclusive of the left anterior (LA) and right anterior (RA) sections. The average AQP4 expression levels in contused areas for animals receiving SR drug treatment (RA: 1.313 +/- 0.172, RP: 1.308 +/- 0.175) were significantly decreased from vehicle-treated animals (RA: 2.181 +/- 0.232, RP: 2.303 +/- 0.370, p = 0.001, p= 0.003). Water content levels on SR treatment (78.89 +/- 0.14) was also significantly decreased from vehicle levels (80.38 +/- 0.38, p < 0.01) in the traumatized hemisphere.

CONCLUSIONS

SR49059 significantly reduced trauma-induced AQP4 up-regulation in the contused hemisphere. Moreover, brain water content was also significantly reduced paralleling the AQP4 suppression. These data provide further support that vasopressin (AVP) and V1a receptors can control water flux through astrocytic plasma membranes by regulating AQP4 expression. Taken in concert, these results affirm our laboratories contention that AQP4 can be effectively modulated pharmacologically.

Transgenic mice for conditional gene manipulation in astroglial cells

Astrocytes are thought to exert diverse functions in the brain, but it has been difficult to prove this in vivo because of a scarcity of tools to manipulate these cells. Here, we report the generation of new transgenic mouse lines that allow for conditional gene ablation in astrocytes using the tamoxifen- (TAM-) inducible CreER(T2)/loxP system and bacterial artificial chromosome (BAC)-based transgenesis. In adult transgenic mice, where CreER(T2) expression is driven by the promoter of the sodium-dependent glutamate/aspartate transporter (Glast/Slc1a3) or of connexin 30 (Cx30/Gjb6), intraperitoneal TAM-injection induced Cre-mediated recombination in astroglial cells throughout the brain. Targeting efficacies varied in a region-specific manner from 20 to 90% as indicated by enzyme-based reporter lines and immunohistochemical staining. In addition, the Glast-line allowed to target retinal Müller cells and adult neural stem/progenitor cells in neurogenic regions of the adult brain. Transgenic mice expressing CreER(T2) under the control of the apolipoprotein e (ApoE) or aquaporin 4 (Aqp4) promoter showed inducible recombination in different areas of the central nervous system (CNS) albeit at low levels. Transgenic lines showed TAM-induced recombination in specific peripheral organs. These new mouse lines should help to further explore the relevance of astrocytes for brain function, as well as their contribution to pathological conditions because of aging, disease or injury.

[Study on correlation between aquaporin 3, 4 gene expression in gastric mucosa and severity of Pi-Wei damp-heat syndrome in patients with chronic superficial gastritis]

OBJECTIVE

To explore the relationship between aquaporin 3,4 (AQP3, AQP4) gene expression in gastric mucosa and severity of Pi-Wei damp-heat syndrome (PWDHS) in patients with chronic superficial gastritis (CSG).

METHODS

Gastric mucosa taken from the upper part of gastric corpus was collected under gastroscope and preserved in liquid nitrogen. The gene expression of AQP3 and AQP4 was determined quantitatively by fluorescent PCR.

RESULTS

The gene expression of AQP3 and AQP4 in patients with PWDHS of moderate and severe degree was higher than that in those of mild degree and in healthy persons respectively (P <0.05 and P <0.01); and the gene expression of AQP3 in patients with PWDHS of severe degree was higher than that in those of moderate degree (P<0.05).

CONCLUSION

The gene expression of AQP3 and AQP4 in gastric mucosa was correlative with the severity of PWDHS in patients with chronic superficial gastritis, the severer the syndrome, the higher the gene expression.

Aquaporin 1 and aquaporin 4 overexpression in bovine spongiform encephalopathy in a transgenic murine model and in cattle field cases

Aquaporins (AQP) are a family of transmembrane proteins that act as water selective channels. AQP1 and AQP4 are widely expressed in the central nervous system where they play several roles. Overexpression of AQP has been reported in some human and animal transmissible spongiform encephalopathies, but information is scanty about their distribution in the central nervous system in bovine spongiform encephalopathy (BSE). Double immunohistochemistry for AQP1, AQP4 and GFAP was developed in a transgenic mouse line overexpressing the bovine cellular prion protein (BoTg110), intracerebrally infected with cattle BSE. Western blot for AQP1 and AQP4, and immunohistochemistry for both AQP and GFAP were carried out in cases of BSE-diagnosed cattle as part of surveillance plan in Catalonia (Spain). A marked increase in AQP1 and AQP4 was observed in mice at the terminal stage of the disease, when they had a wide range of clinical signs, whereas no increase could be observed in the early stage before the onset of the clinical signs. In cattle which did not show evidence of clinical signs, both AQP already showed a great increase. The AQP overexpression correlated with GFAP-immunoreactive astrocytes and PrPres deposition in both cases. The results of this study suggest that AQP overexpression in glial cells could lead to an imbalance in water and ion homeostasis which could contribute to triggering the typical histopathological changes of BSE.

Can variation in aquaporin 4 gene be associated with different outcomes in traumatic brain edema?

In traumatic brain injury (TBI), cerebral edema and hemorrhage are factors involved in the determination of the clinical presentation and outcome. The aquaporin 4 (AQP4) water channel is abundant in mammalian brain and there is a growing body of evidence suggesting that this protein plays a major role in the control of water flow within the central nervous system. Previous studies examined the influence of genetic variants in cerebral edema of TBI. However, to our knowledge, there are no previous studies of molecular variations of the AQP4 gene and its association with TBI. Thus, we sought to investigate if the clinical presentation and outcome of TBI could be influenced by the presence of mutations on exon 4 of the AQP4 gene. One hundred and two patients were enrolled in this study. A neurologist assessed the clinical severity at admission according to the GCS followed by a brain computer tomography (CT) scan. Then, DNA was extracted from blood cells and exon 4 of the AQP4 gene amplified by the polymerase chain reaction and directly sequenced. On discharge, GOS was assigned by a neurologist blind to the CGS on admission. We did not find any variation in exon 4 of the AQP4 gene in our considerable large sample. Despite this negative result, there is a strong biological rationale for the involvement of AQP4 gene in brain edema regulation and, as consequence, in TBI. Therefore, further studies should be performed, including the assessment of the other three exons of the AQP4 gene.