Different expressions of aquaporin water channels and macrophages infiltration in human cervix remodeling during pregnancy

Despite aquaporin water channels (AQPs) play a critical role in maintaining water homeostasis in female reproductive tract and prompt a gradual increase in water content in cervical edema as pregnancy progressed, their relationship with macrophage infiltration and collagen content in human cervical remodeling need to be further investigated. This is the first study to examine the expression and localization of AQP3, AQP4, AQP5, AQP8 and macrophages simultaneously in human cervical ripening. The immunoreactivity of these AQPs was 2.6 to 6-fold higher on gestational weeks 26 (GD26W) than that on GD6W and GD15W, but AQP4 expression on GD39W dropped a similar extent on GD15W, other AQPs continued to rise on GD39W. The AQP3, AQP4 and AQP5 intensity seemed more abundant in cervical stroma than in the perivascular area on GD26W; the distribution of AQP3, AQP5 and AQP8 in cervical stroma was equivalent to that in the perivascular area on GD39W. Macrophage numbers were 1.7-fold higher in subepithelium region and 3.0-fold higher in center area on GD26W than that on GD15W; such numbers remained elevated on GD39W. The electron micrographs showed that cervical extensibility increased significantly on GD26W and GD39W accompanied with increased macrophage infiltration, cervical water content and much more space among collagen fibers. These findings suggest that the upregulation of AQPs expression in human cervix is closely related to enhanced macrophage infiltration during pregnancy; there may be a positive feedback mechanism between them to lead the increase of water content and the degradation of collagen.

Altered mucins and aquaporins indicate dry eye outcome in patients undergoing Vitreo-retinal surgery

Vitreo-retinal (VR) surgeries induce conjunctival changes. However, there are no study reports regarding prevalence and severity of dry eye after these surgeries. This study evaluated dry eye outcome after VR surgery. Patients undergoing VR surgery classified as scleral buckle and microincision vitrectomy surgery (n = 44, mean age: 56.09±10.2 years) were recruited. Dry eye evaluation was done before and 8 weeks after surgery (2 weeks after omitting topical eye drops). Conjunctival imprint cytology for goblet cell count and tear Mucin 5AC (MUC5AC) protein estimation was done. Gene expressions of MUC5AC, MUC4, MUC16, Aquaporin 4 (AQP4) and AQP5 were analyzed in the conjunctival imprint cells by qPCR. None of the patients exhibited clinical signs of dry eye after VR surgery. But the conjunctival goblet cell density (GCD) was significantly lowered post-VR surgery (63% cases, **p = 0.012) with no alterations in the tear MUC5AC protein. Post-VR surgery, the conjunctival cell gene expression of MUC4, MUC16 and AQP4 were significantly increased (*p = 0.025, *p = 0.05 and *p = 0.02 respectively) and AQP5 was significantly lowered (*p = 0.037), with no change in MUC5AC expression. Tear cytokines were significantly increased post-VR surgery (anti-inflammatory: IL1RA, IL4, IL5, IL9, FGF; PDGFbb and pro-inflammatory: IL2, IL6, IL15, GMCSF and IFNg). Though clinical signs of dry eye were not observed after VR surgery, ocular surface changes in the form of reduced GCD, altered MUC5AC, MUC4, MUC16, AQP4, AQP5 and cytokines are suggestive of dry eye outcome at the molecular level especially inpatients aged above 51 years, especially female gender and those who are diabetic.

Anti-Neuronal Antibodies Within the IVIg Preparations: Importance in Clinical Practice

Our study objective was testing for anti-neuronal autoantibodies within commercially available intravenous immunoglobulin (IVIg) preparations. Sixteen samples from 5 different commercially available IVIg preparations were tested with cell-based assays (CBA) and enzyme-linked immunosorbent assay (ELISA) to detect and characterize common neuronal autoantibodies, and with immunohistochemistry on teased fibers from mouse sciatic nerve and on mouse brain sections to screen for nodal and not yet identified neuronal antigens. In 15/16 IVIg preparations, anti-GAD antibodies were detected in titers ranging from 40 to 1507 IU/mL, as typically seen in type 1 diabetes, but not in the range (> 2000 IU/mL) seen in GAD-positive neurological patients. None of the preparations was however positive with anti-GAD CBA. Antibodies to AQP4 were also detected by ELISA in 15/16 IVIg preparations with titers comparable to those seen in AQP4-seropositive NMO patients; with CBA, however, all IVIg samples were AQP4-negative. IVIg preparations contained IgG-anti-MAG antibodies by ELISA at statistically significant higher titers compared to controls. Two of the 16 IVIg samples were positive for human 3-hydroxy-3-methylglutaryl-coenzyme A reductase (HMGCR) antibodies. All IVIg preparations were negative for antibodies to MOG, NMDAR, anti-nodal, and other neuronal-specific proteins. IVIg preparations contain antibodies against GAD and AQP4 in titers comparable to those seen in autoimmune patients when tested by ELISA, but not by CBA or tissue immunohistochemistry, suggesting that the autoantibodies within the IVIg are against linear rather than structural epitopes, as part of the natural antibody immune repertoire. The information is clinically important for diagnosis when testing patients' sera after they have received therapy with IVIg to avoid false interpretation.

Anaplastic astrocytoma with aquaporin-4 positive in CSF: A case report

RATIONALE

An acute presentation with diffuse magnetic resonance imaging lesions can have a broad differential. Demyelination and malignancy are important considerations. Therefore, sometimes it is hard to differentiate glioma from some demyelinating diseases solely on imaging because of the similar clinical presentation and imaging features. Detection of highly specific serum autoantibody marker aquaporin-4 (AQP4)-IgG positivity has helped to define a category of neuromyelitis optica spectrum disorders (NMOSD), but the test of AQP4 antibody has not been reported in patients with glioma.

PATIENTS CONCERNS AND DIAGNOSES

We report a case of a 56-year-old woman with cerebrospinal fluid (CSF) positive aquaporin-4 antibodies with initial response to immune therapy and secondary deterioration. A surgical biopsy revealed an anaplastic astrocytoma.

INTERVENTIONS AND OUTCOMES

After the admission the patient was treated with a short course of intravenous steroid agents. After anaplastic astrocytoma was diagnosed, she began to receive a radiation treatment and soon later experienced a clinical deterioration with frequent epilepsy seizure and disturbance of consciousness within a few months.

LESSON

This case indicates that tumors could lead to polyclonal antibody responses as in this case with aquaporin-4 and myelin oligodendrocyte glycoprotein antibodies. The absence of a typical clinical phenotype and lack of sustained response to immunotherapy should alert the clinical suspicion of an alternative diagnosis. When AQP4 antibody was detected positive in CSF of a patient but negative in serum, differential diagnosis should especially be considered.

The Immunology of Neuromyelitis Optica-Current Knowledge, Clinical Implications, Controversies and Future Perspectives

Neuromyelitis optica (NMO) is an autoimmune, demyelinating disorder of the central nervous system (CNS) with typical clinical manifestations of optic neuritis and acute transverse myelitis attacks. Previously believed to be a variant of multiple sclerosis (MS), it is now considered an independent disorder which needs to be differentiated from MS. The discovery of autoantibodies against aquaporin-4 (AQP4-IgGs) changed our understanding of NMO immunopathogenesis and revolutionized the diagnostic process. AQP4-IgG is currently regarded as a specific biomarker of NMO and NMO spectrum disorders (NMOsd) and a key factor in its pathogenesis. Nevertheless, AQP4-IgG seronegativity in 10%-25% of NMO patients suggests that there are several other factors involved in NMO immunopathogenesis, i.e., autoantibodies against aquaporin-1 (AQP1-Abs) and antibodies against myelin oligodendrocyte glycoprotein (MOG-IgGs). This manuscript reviews current knowledge about NMO immunopathogenesis, pointing out the controversial issues and showing potential directions for future research. Further efforts should be made to broaden our knowledge of NMO immunology which could have important implications for clinical practice, including the use of potential novel biomarkers to facilitate an early and accurate diagnosis, and modern treatment strategies improving long-term outcome of NMO patients.

Ethanol-induced hyponatremia augments brain edema after traumatic brain injury

Alcohol consumption augments brain edema by expression of brain aquaporin-4 after traumatic brain injury. However, how ethanol induces brain aquaporin-4 expression remains unclear. Aquaporin-4 can operate with some of ion channels and transporters. Therefore, we hypothesized that ethanol may affect electrolytes through regulating ion channels, leading to express aquaporin-4. To clarify the hypothesis, we examined role of AQP4 expression in ethanol-induced brain edema and changes of electrolyte levels after traumatic brain injury in the rat. In the rat traumatic brain injury model, ethanol administration reduced sodium ion concentration in blood significantly 24 hr after injury. An aquaporin-4 inhibitor recovered sodium ion concentration in blood to normal. We observed low sodium ion concentration in blood and the increase of brain aquaporin-4 in cadaver with traumatic brain injury. Therefore, ethanol increases brain edema by the increase of aquaporin-4 expression with hyponatremia after traumatic brain injury.

Reperfusion of the rat brain tissues following acute ischemia: the correlation among diffusion-weighted imaging, histopathology, and aquaporin-4 expression

BACKGROUND

Although some studies have reported that aquaporin-4 (AQP4) plays a role in the post-ischemic edema formation and diffusion-weighted imaging (DWI), little is known about the AQP4 expression in stage of the reperfusion following acute cerebral ischemia, as well as the correlation between histopathology and DWI. The aim of the study was to investigate the correlation among DWI, histopathology and the AQP4 expression in the reperfused rat brain tissues following acute ischemia.

METHODS

Seventy Wistar rats were randomly divided into a control group (group A), and several occluded and reperfusion groups. They had their middle cerebral artery unilaterally occluded (MCAO) for 30 minutes (group B) followed by 30 minutes (group D) or 60 minutes (group E) of reperfusion, or 60 minutes of MCAO (group C) followed by 30 minutes (group F), or 60 minutes (group G) of reperfusion (n = 10 for each group). All rats underwent DWI scanning. The relative apparent diffusion coefficient (rADC) value of each rat was calculated. All the rats were sacrificed and the cerebral ischemic tissues were examined for histopathology. Real-time fluro-quantitative polymerase chain reaction (RT-PCR) and Western-blotting were performed. The amount of AQP4 mRNA (Ex(-ΔΔCt)) and AQP4 protein (Q) was statistically analyzed. The correlation between rADC values and AQP4 mRNA expression was analyzed with the Pearson correlation test.

RESULTS

In all the reperfusion groups, the areas of hyper-intensity signal in DWI were decreased, and the rADC value increased and the AQP4 expression decreased significantly compared with the occluded group (t = 26.89, t = 18.26, P < 0.01). There was a negative correlation between AQP4 mRNA expression and rADC values (r = -0.72, P < 0.01). A mixed edema, composed of cerebral intracelluar edema and vasogenic brain edema, was observed in all the reperfusion groups. It was more prevalent in groups D and F than in the groups E and G. With the reperfusion time postponed, the cerebral intracelluar edema of the rat was significantly mitigated, but the vasogenic brain edema was not significantly changed.

CONCLUSIONS

There is a close correlation between AQP4 expression and the cerebral intracellular edema. The change of ADC values may indirectly reflect the level of the AQP4 expression. DWI may become a promising, noninvasive imaging modality to predict early stroke and reperfusion injury.

Genetic deletion of laminin isoforms β2 and γ3 induces a reduction in Kir4.1 and aquaporin-4 expression and function in the retina

BACKGROUND

Glial cells such as retinal Müller glial cells are involved in potassium ion and water homeostasis of the neural tissue. In these cells, inwardly rectifying potassium (Kir) channels and aquaporin-4 water channels play an important role in the process of spatial potassium buffering and water drainage. Moreover, Kir4.1 channels are involved in the maintenance of the negative Müller cell membrane potential. The subcellular distribution of Kir4.1 and aquaporin-4 channels appears to be maintained by interactions with extracellular and intracellular molecules. Laminins in the extracellular matrix, dystroglycan in the membrane, and dystrophins in the cytomatrix form a complex mediating the polarized expression of Kir4.1 and aquaporin-4 in Müller cells.

METHODOLOGY/PRINCIPAL FINDINGS

The aim of the present study was to test the function of the β2 and γ3 containing laminins in murine Müller cells. We used knockout mice with genetic deletion of both β2 and γ3 laminin genes to assay the effects on Kir4.1 and aquaporin-4. We studied protein and mRNA expression by immunohistochemistry, Western Blot, and quantitative RT-PCR, respectively, and membrane currents of isolated cells by patch-clamp experiments. We found a down-regulation of mRNA and protein of Kir4.1 as well as of aquaporin-4 protein in laminin knockout mice. Moreover, Müller cells from laminin β2 and γ3 knockout mice had reduced Kir-mediated inward currents and their membrane potentials were more positive than those in age-matched wild-type mice.

CONCLUSION

These findings demonstrate a strong impact of laminin β2 and γ3 subunits on the expression and function of both aquaporin-4 and Kir4.1, two important membrane proteins in Müller cells.

Aquaporins in the brain: from aqueduct to "multi-duct"

The aquaporin channel family was first considered as a family of water channels, however it is now clear that some of these channels are also permeable to small solutes such glycerol, urea and monocarboxylates. In this review, we will consider AQP4 and AQP9 expressed in the rodent brain. AQP4 is present on astrocytic end-feet in contact with brain vessels and could be involved in ionic homeostasis. However, AQP4 may also be involved in cell adhesion. AQP4 expression is highly modified in several brain disorders and it can play a key role in the cerebral edema formation. However, the exact role of AQP4 in edema formation is still debated. Recently, AQP4 has been shown to be also involved in astrocyte migration during glial scar formation. AQP9 is expressed in astrocytes and in catecholaminergic neurons. Two isoforms of AQP9 are expressed in brain cells, the shortest isoform is localized in the inner membrane of mitochondria and the longest in the cell membrane. The level of expression of AQP9 is negatively regulated by high concentrations of insulin. Taken together, these results suggest that AQP9 could be involved in brain energy metabolism. The induction of AQP9 in astrocytes is observed with time after stroke onset suggesting participation in the clearance of excess lactate in the extracellular space. These recent exciting results suggest that AQPs may not only be involved in water homeostasis in the brain but could also participate in other important physiological functions.

Early upregulation in nasal epithelium and strong expression in olfactory bulb glomeruli suggest a role for Aquaporin-4 in olfaction

Aquaporin-4 (AQP4) has been reported to be upregulated post-partum in pregnancy and in early lung development. Several technical challenges exist in measuring AQP4 protein levels, among them sensitivity to detergent solubilization, sample heating and gel composition. Here we have optimized quantification of AQP4 using immuno-blots. Using improved methodology we find no evidence for AQP4 upregulation post-partum or in the early lung development. However, in the nasal epithelium AQP4 is upregulated as early as in the brain. Furthermore, AQP4 is strongly expressed in the glomerulus, the synaptic unit of the olfactory bulb, suggesting a role for AQP4 in olfactory function.

Distribution of aquaporin 4 on sarcolemma of fast-twitch skeletal myofibres

The aquaporin 4 (AQP4) water channel is present on the sarcolemma of fast-twitch-type skeletal myofibres. We have examined the distribution of AQP4 in relation to sarcolemmal domain structure and found that AQP4 protein is not evenly distributed on the sarcolemma. Immunofluorescence staining of isolated single myofibres indicated a punctate staining pattern overlapping with the dystrophin glycoprotein complex, but with the transverse tubule openings being left clear. Myotendinous and neuromuscular junctions also lacked AQP4, despite their high content of the dystrophin glycoprotein complex. The destruction of caveoli with methyl-beta-cyclodextrin did not change the distribution of AQP4 at the sarcolemma. Moreover, AQP4 did not float with the caveolar marker caveolin-3 in sucrose gradients after Triton X-100 extraction at 4 degrees C. These data indicated that AQP4 was not associated with caveoli. Surprisingly, m. flexor digitorum brevis fibres, although of the fast-twitch type, often lacked AQP4. Furthermore, those fibres harbouring AQP4 at the sarcolemma showed a regionalized distribution, suggesting that large areas were devoid of the protein. Blockage of the synthesized proteins in the endoplasmic reticulum with brefeldin A showed that, in spite of its regionalized sarcolemmal distribution, AQP4 was synthesized along the entire length of the fibres. These results suggest functional differences in the water permeability of the sarcolemma not only between the fast-twitch muscles, but also within single muscle fibres.

Loss of aquaporin 4 in lesions of neuromyelitis optica: distinction from multiple sclerosis

Neuromyelitis optica (NMO) is an inflammatory and necrotizing disease clinically characterized by selective involvement of the optic nerves and spinal cord. There has been a long controversy as to whether NMO is a variant of multiple sclerosis (MS) or a distinct disease. Recently, an NMO-specific antibody (NMO-IgG) was found in the sera from patients with NMO, and its target antigen was identified as aquaporin 4 (AQP4) water channel protein, mainly expressed in astroglial foot processes. However, the pathogenetic role of the AQP4 in NMO remains unknown. We did an immunohistopathological study on the distribution of AQP4, glial fibrillary acidic protein (GFAP), myelin basic protein (MBP), activated complement C9neo and immunoglobulins in the spinal cord lesions and medulla oblongata of NMO (n = 12), MS (n = 6), brain and spinal infarction (n = 7) and normal control (n = 8). The most striking finding was that AQP4 immunoreactivity was lost in 60 out of a total of 67 acute and chronic NMO lesions (90%), but not in MS plaques. The extensive loss of AQP4 accompanied by decreased GFAP staining was evident, especially in the active perivascular lesions, where immunoglobulins and activated complements were deposited. Interestingly, in those NMO lesions, MBP-stained myelinated fibres were relatively preserved despite the loss of AQP4 and GFAP staining. The areas surrounding the lesions in NMO had enhanced expression of AQP4 and GFAP, which reflected reactive gliosis. In contrast, AQP4 immunoreactivity was well preserved and rather strongly stained in the demyelinating MS plaques, and infarcts were also stained for AQP4 from the very acute phase of necrosis to the chronic stage of astrogliosis. In normal controls, AQP4 was diffusely expressed in the entire tissue sections, but the staining in the spinal cord was stronger in the central grey matter than in the white matter. The present study demonstrated that the immunoreactivities of AQP4 and GFAP were consistently lost from the early stage of the lesions in NMO, notably in the perivascular regions with complement and immunoglobulin deposition. These features in NMO were distinct from those of MS and infarction as well as normal controls, and suggest that astrocytic impairment associated with the loss of AQP4 and humoral immunity may be important in the pathogenesis of NMO lesions.

[Regulative effect of electroacupuncture on aquaporin-4 in rats with focal cerebral ischemia/reperfusion]

OBJECTIVE

To study the effect of electroacupuncture (EA) on changes of aquaporin-4 (AQP4) expression in rats with cerebral ischemia/reperfusion(CI/R).

METHODS

One hundred and seventy male Sprauge-Dawley rats were randomized into control (n = 50), CI/R model (n = 60) and EA (n = 60) groups, and the later 2 groups were further divided into 6 h, 12 h, 24 h, 48 h and 72 h subgroups, with 12 cases in each. CI/R model was established by occlusion of the middle cerebral artery (MCAO). EA (3.85/6.25 Hz, 0.8 - 1.0 mA) was applied to "Shuigou" (GV 26) and "Baihui" (GV 20) for 30 min. Transcardial perfusion was conducted with normal saline + paraformaldehyde in rats of different groups for taking brain tissue samples. The degree of brain edema was detected by cresyl violet stain method, permeability of the blood-brain barrier (BBB) reflected with IgG value in brain tissue was displayed by immunohistochemistry, and AQP4 protein and mRNA expression of corpora striata (CS) were detected by using immunohistochemistry (ABC) and RT-PCR techniques respectively.

RESULTS

Twelve hours after CI/R, the hemisphere of brain began to get swelling significantly and the exosmose state of IgG became evidently; compared with the corresponding phases of model group, the swell rates in 24 h, 48 h and 72 h subgroups of EA group were significantly lower (P < 0.05, 0.01), and nearly no IgG immunoreaction positive products were found in different phases of EA group. The expression of AQP4 protein and mRNA increased significantly from 12 h and 24 h on separately in model group, while the expression in EA group was markedly weaker. The ratios of AQP4 mRNA and beta-actin mRNA of CS on the affected side of the brain from 24 h to 72 h of EA group were significantly lower than those of model group (P < 0.05, 0.01).

CONCLUSION

EA can reduce the degree of brain edema induced by CI/R and improve the degree of BBB injury, which may be related to its effect in down-regulating AQP4 expression.

Different pattern of aquaporin-4 expression in extensor digitorum longus and soleus during early development

Aquaporin-4 (AQP4) is the neuromuscular water channel expressed at the sarcolemma of mammalian fast-twitch fibers that mediates a high water transport rate, which is important during muscle activity. Clinical interest in the neuromuscular expression of AQP4 has increased as it is associated with the protein complex formed by dystrophin, the product of the gene affected in Duchenne muscular dystrophy. The expression of AQP4 during development has not been characterized. In this study, we analyzed the expression of AQP4 in extensor digitorum longus (EDL) and soleus, a fast- and slow-twitch muscle, respectively, during the first weeks after birth. The results show that AQP4 expression in both types of skeletal muscle occurs postnatally. The time course of expression of AQP4 in the two types of muscles was also different. Whereas the expression of AQP4 protein levels in the EDL showed a progressive increase during the first month after birth, reaching levels found in adults by day 24, the levels of the protein in the soleus showed a transient peak between day 12 and day 24 and declined thereafter, an effect that may be related to the transient high number of fast motor units innervating the soleus muscle during this time. The results suggest that AQP4 expression in skeletal muscle is under neuronal influence and contribute to the understanding of the molecular events of fiber differentiation during development.

Effects of chronic treatment with statins and fenofibrate on rat skeletal muscle: a biochemical, histological and electrophysiological study

BACKGROUND AND PURPOSE

Skeletal muscle injury by hypolipidemic drugs is not fully understood. An extensive analysis of the effect of chronic treatment with fluvastatin (5 mgkg(-1) and 20 mgkg(-1)), atorvastatin (10 mgkg(-1)) and fenofibrate (60 mgkg(-1)) on rat skeletal muscle was undertaken.

EXPERIMENTAL APPROACH

Myoglobinemia as sign of muscle damage was measured by enzymatic assay. Histological and immunohistochemical techniques were used to estimate muscle integrity and the presence of aquaporin-4, a protein controlling water homeostasis. Electrophysiological evaluation of muscle Cl(-) conductance (gCl) and mechanical threshold (MT) for contraction, index of intracellular calcium homeostasis, was performed by the two-intracellular microelectrodes technique.

KEY RESULTS

Fluvastatin (20 mgkg(-1)) increased myoglobinemia. The lower dose of fluvastatin did not modify myoglobinemia, but reduced urinary electrolytes, suggesting direct effects on renal function. Atorvastatin also increased myoglobinemia, with slight effects on urinary parameters. No treatment caused any histological damage to muscle or modification in the number of fibres expressing aquaporin-4. Either fluvastatin (at both doses) or atorvastatin reduced sarcolemma gCl and changed MT. Both statins produced slight effects on total cholesterol, suggesting that the observed modifications occur independently of HMGCoA-reductase inhibition. Fenofibrate increased myoglobinemia and decreased muscle gCl, whereas it did not change the MT, suggesting a different mechanism of action from the statins.

CONCLUSIONS AND IMPLICATIONS

This study identifies muscle gCl and MT as early targets of drugs action that may contribute to milder symptoms of myotoxicity, such as muscle cramps, while the increase of myoglobinemia is a later phenomenon.

Redistribution of aquaporins 1 and 5 in the rat uterus is dependent on progesterone: a study with light and electron microscopy

During early pregnancy in the rat there is a dramatic reduction in luminal fluid which is associated with uterine receptivity for blastocyst implantation. This study investigates the presence and distributional changes of several members of the aquaporin (AQP) family in the rat uterus in response to hormonal regime. An increase in apical AQP5 protein expression was found in response to progesterone alone or in combination with oestrogen, which is similar to that seen at the time of implantation. AQP1 was found in endothelial cells of the endometrium and in the inner circular layer of smooth muscle, with maximal protein expression seen after three doses of progesterone plus 8 hr of oestrogen treatment. These results, for the first time, show that the up-regulation of AQP5 in the apical plasma membrane of uterine epithelial cells and AQP1 in the inner circular layer of myometrium, is dependent on progesterone. Furthermore, unlike during normal pregnancy, there is no differential gradient of AQP5 expression between mesometrial and antimesometrial poles of the progesterone treated uterus. Hence it is suggested that the differential gradient of AQP5 is dependent on the presence of a blastocyst, in addition to the appropriate hormonal environment.

Chronic cholinergic imbalances promote brain diffusion and transport abnormalities

Cholinergic imbalances occur after traumatic effects and in the initial stages of neurodegenerative diseases, but their long-lasting effects remained largely unexplained. To address this, we used TgS transgenic mice constitutively overexpressing synaptic acetylcholinesterase (AChE-S) and presenting a complex phenotype of progressive neurodeterioration. T1- and T2-weighted magnetic resonance (MR) brain images appeared similar. However, diffusion-weighted MRI showed decreased baseline water apparent diffusion coefficient in the brains of TgS animals. Furthermore, contrast-enhanced MRI after gadolinium diethylenetriaminepentaacetic acid (Gd-DTPA) injection demonstrated slower recovery of normal signals in the TgS brains than with controls. Perfusion MR imaging and difference T1 maps calculated from pre- postcontrast T1-weighted MR images indicated accumulation of more Gd-DTPA molecules in the TgS brains than in the parent strain, reflecting impaired blood-brain barrier (BBB) functioning in these transgenic mice. To explore the molecular mechanism(s) underlying these global phenotypes, we performed microarray analysis in the stress-controlling prefrontal cortex of TgS vs. strain-matched wild-type animals. Profound overexpression of numerous ion channels, transporters, and adhesion genes was confirmed by real time RT-PCR tests. Immunohistochemical and immunoblot analyses revealed corresponding increases in the level and cellular distributions of the chloride channel CLCN3 and the water channel AQP4, both of which contribute to BBB maintenance. Our study attributes to balanced cholinergic neurotransmission, a central role in the brain's maintenance of water diffusion and ion transport, and indicates that chronic impairments in this maintenance facilitate neurodeterioration through interference with BBB function.

Expression and distribution of aquaporin-1 in nasal polyps: does it have any significance in edema formation?

BACKGROUND

The aim of this study was to investigate the expression of Aquaporin 1 (AQP1) and AQP4 in polyp tissue.

METHODS

Nasal polyps were obtained from 34 patients with nasal polyposis during endoscopic sinus surgery. Bullous middle turbinates with normal-appearing mucosa of 10 patients were used as controls. Expression of AQP1 and AQP4 water channels were determined by immunohistochemical methods.

RESULTS

AQP1 has been found to be expressed in fibroblasts located in polyp tissue, especially in the subepithelial area, periphery of seromucous glands, and endothelial cells of venules.

CONCLUSION

We have established a high expression of AQP1 water channels in nasal polyp tissue and have suggested two mechanisms to explain this finding. Increased AQP1 expression may be a cause or a consequence of edema formation. Thus, additional studies are needed to elucidate the true mechanism underlying this relationship.

Expression of glucose transporter-1 and aquaporin-4 in the cerebral cortex of stroke-prone spontaneously hypertensive rats in relation to the blood-brain barrier function

BACKGROUND

Cerebral edema is an important initial event in cases of stroke among humans. Although hypertension is a major risk factor for endothelial injury, the precise mechanisms regulating brain microvascular changes are still unknown. To elucidate the pathogenesis of increases in vascular permeability in the cerebral cortex, we investigated the expression of glucose transporter-1 (GLUT-1) in endothelial cells and aquaporin-4 (AQP4) in astrocytes in relation to blood-brain barrier (BBB) function.

METHODS

Using male stroke-prone spontaneously hypertensive rats (SHRSP) and normotensive Wistar-Kyoto rats (WKY), the particular localization of both GLUT-1 and AQP4 was investigated by immunohistochemistry. Quantitative changes in these molecules were examined by Western blot analysis in these rats at 6 weeks and 20 weeks of age. Furthermore, to investigate the expression of these molecules at the mRNA level, reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was carried out using 20-week-old SHRSP and age-matched WKY.

RESULTS

We confirmed the localization of GLUT-1 in endothelial cells and that of AQP4 in the end feet of astrocytes around microvessels, as determined by electron immunohistochemistry. No significant differences were found in the expression of these molecules in rats at 6 weeks of age, whereas GLUT-1 expression was lower, but that of AQP4 was higher, in SHRSP after the establishment of hypertension. Furthermore, GLUT-1 mRNA expression was lower in SHRSP, and AQP4 mRNA expression was also lower in SHRSP than in WKY at 20 weeks of age.

CONCLUSIONS

These results indicate that AQP4 may play a much more important role in BBB function than GLUT-1, and thereby also in water distribution in the cerebral cortex of SHRSP with severe hypertension.

Enhanced expression of aquaporin 4 in human brain with inflammatory diseases

Aquaporin 4 (AQP4), one of the water channel proteins on the plasma membrane of astrocytes, is up-regulated in various conditions with brain edema. Possible participation of AQP4 in various inflammatory lesions, more or less associated with edema, was examined in human autopsied brains. Immunohistochemistry was used to investigate AQP4 expression in autopsied brains with multiple sclerosis (MS), human immunodeficiency virus encephalitis (HIVE) or progressive multifocal leukoencephalopathy (PML). The cellular localization of AQP4 and its relation to inflammatory lesions were then examined with double-labeling immunohistochemistry. AQP4 immunoreactivity (IR) was restricted to astrocytes and localized to their entire processes, including their endfeet facing the abluminal surface of capillaries. In MS brains, AQP4-positive astrocytes were more abundant at the periphery of plaques than in their center, as seen in ischemic foci. Quantification of fluorescent signal demonstrated that AQP4 IR was greatly increased around plaques relative to that in unaffected area. Although the white matter was severely involved in HIVE and PML, AQP4-positive astrocytes were rare in the white matter even around perivascular active inflammatory foci. They were abundant in the gray matter and most prominent in the boundary between the gray and white matter, without apparent relation to inflammatory foci. Some bizarre astrocytes in PML exhibited AQP4 IR. Up-regulation of AQP4 was consistently found in astrocytes in various inflammatory lesions. However, the distribution of AQP4-positve astrocytes differed markedly according to disease and was not necessarily related to brain edema, indicating that functions and regulation of AQP4 in human brains are multiple.

[Expression of aquaporin-4 in isolated and purified rat alveolar type II cells]

OBJECTIVE

To explore the expression of aquaporin-4 (AQP4) in isolated and purified rat alveolar type II cells.

METHODS

Rat alveolar type II cells were isolated, purified and identified by special staining and electron microscopy. The distribution of AQP4 in alveolar type II cells was observed by immunocytochemistry and immunoelectron microscope with affinity-purified antibodies to human AQP4.

RESULTS

Immunocytochemistry showed staining for AQP4 in rat alveolar type II cells, and immunoelectron microscope demonstrated the presence of AQP4 on the membrane of the cells.

CONCLUSION

AQP4 is expressed in alveolar type II cells in rats, and may play a role in water transportation in the respiratory system.

Ontogeny and the effects of corticosteroid pretreatment on aquaporin water channels in the ovine cerebral cortex

The aim of the present study was to determine the ontogeny and effects of corticosteroid pretreatment on aquaporin 4 (AQP4) channel mRNA and protein expression in the cerebral cortex of sheep during development. A portion of the cerebral cortex was snap-frozen from fetuses of dexamethasone- and placebo-treated ewes at 60%, 80% and 90% of gestation, dexamethasone- and placebo-treated newborn lambs and adult sheep. Cerebral cortical samples were obtained 18 h after the last of four 6 mg dexamethasone or placebo injections were given over 48 h to the ewes and adult sheep. Lambs were treated with 0.01 mg kg−1 dexamethasone or placebo in the same schedule as the ewes and adult sheep. Amplification of an ovine AQP4 cDNA fragment was accomplished by reverse transcription–polymerase chain reaction using primers based on a homologous bovine sequence. The resulting cDNA was used to determine AQP4 channel mRNA expression by Northern hybridisation using phosphorimaging. The relative abundance of AQP4 mRNA was normalised to the ovine ribosomal gene L32. A portion of the frontal cortex was also analysed for AQP4 protein expression by Western immunoblot. Densitometry was performed and the results expressed as a ratio to an adult brain pool. Aquaporin 4 channel mRNA and protein were detectable as early as at 60% gestation. There were no changes in AQP4 mRNA expression among the fetal, newborn and adult groups or after dexamethasone pretreatment in any age group. The expression of the AQP4 protein was higher (P < 0.05) in fetuses at 80% and 90% of gestation (2.9- and 3.3-fold, respectively), in lambs (3.2-fold) and in adult sheep (3.8-fold) compared with fetuses at 60% of gestation, as well as in adult sheep (1.3-fold) compared with fetuses at 80% of gestation. Dexamethasone pretreatment resulted in decreases (P < 0.05) in AQP4 protein expression in the lambs and adult sheep, but not in the fetal groups. We conclude that: (1) AQP4 mRNA and protein were expressed early in fetal and throughout ovine development; (2) protein, but not mRNA, expression increased between 60% and 80% of gestation and did not differ from adult levels by 90% of gestation; and (3) dexamethasone pretreatment resulted in decreases in AQP4 protein expression in lambs and adult sheep, but not in fetuses. The maturational increases in AQP4 protein expression and dexamethasone-related decreases in expression were post-transcriptional, because changes in AQP4 mRNA expression were not observed.