Evidence of Positive Selection of Aquaporins Genes from Pontoporia blainvillei during the Evolutionary Process of Cetaceans

BACKGROUND

Marine mammals are well adapted to their hyperosmotic environment. Several morphological and physiological adaptations for water conservation and salt excretion are known to be present in cetaceans, being responsible for regulating salt balance. However, most previous studies have focused on the unique renal physiology of marine mammals, but the molecular bases of these mechanisms remain poorly explored. Many genes have been identified to be involved in osmotic regulation, including the aquaporins. Considering that aquaporin genes were potentially subject to strong selective pressure, the aim of this study was to analyze the molecular evolution of seven aquaporin genes (AQP1, AQP2, AQP3, AQP4, AQP6, AQP7, and AQP9) comparing the lineages of cetaceans and terrestrial mammals.

RESULTS

Our results demonstrated strong positive selection in cetacean-specific lineages acting only in the gene for AQP2 (amino acids 23, 83, 107,179, 180, 181, 182), whereas no selection was observed in terrestrial mammalian lineages. We also analyzed the changes in the 3D structure of the aquaporin 2 protein. Signs of strong positive selection in AQP2 sites 179, 180, 181, and 182 were unexpectedly identified only in the baiji lineage, which was the only river dolphin examined in this study. Positive selection in aquaporins AQP1 (45), AQP4 (74), AQP7 (342, 343, 356) was detected in cetaceans and artiodactyls, suggesting that these events are not related to maintaining water and electrolyte homeostasis in seawater.

CONCLUSIONS

Our results suggest that the AQP2 gene might reflect different selective pressures in maintaining water balance in cetaceans, contributing to the passage from the terrestrial environment to the aquatic. Further studies are necessary, especially those including other freshwater dolphins, who exhibit osmoregulatory mechanisms different from those of marine cetaceans for the same essential task of maintaining serum electrolyte balance.

Generation of muscle aquaporin 4 overexpressing transgenic mouse: Its characterization at RNA and protein levels including freeze-fracture study

We generated the muscle aquaporin 4 (AQP4) overexpressing transgenic mice in order to investigate the skeletal muscle pathology at RNA and protein levels. At RNA level, the AQP4 mRNA expression of soleus, EDL and cardiac muscles in Tg mice was statistically significantly higher than that in wild mice by the real-time reverse transcription polymerase chain reaction method. At protein level examinations, we used the immunoblot, immunohistochemistry and freeze-fracture electron microscopy. The immunoblot showed the single band of 31kDa with anti-AQP4 antibody in the extracts of soleus and EDL muscles of wild mice but not in extract of wild cardiac muscle; while the reaction band was noted in cardiac muscle of Tg mice and the reaction band was stronger in the extracts of soleus and EDL muscles of Tg mice. The immunohistochemistry showed that the expression of AQP4 at the myofiber surface of soleus and EDL muscles of Tg mice was more marked than that of wild mice and, interestingly, the AQP4 expression of these muscles of Tg mice appeared to be more remarkable in type 1 slow twitch myofibers as judged by the positive slow myosin immunostaining of adjacent serial sections. The immunofluorescence staining with anti-AQP4 antibody of cardiac muscles of wild mice revealed the scarcely immunopositive myofibers; whereas the immunostaining cardiac muscles of Tg mice contained the numerous AQP4 immunopositive myofibers. The freeze-fracture electron microscopy demonstrated that the orthogonal array densities in soleus and EDL muscle plasma membranes of Tg mice were significantly higher than those of wild mice and that the orthogonal array like particle density of cardiac muscle plasma membranes of Tg mice appeared to be more numerous than that of cardiac myofibers of wild mice. Finally the clinical phenotype of Tg mice appeared to be similar to that of wild mice. Further physiological examination with devices may suggest some about the physiological difference.

Mechanisms of aquaporin-4 vesicular trafficking in mammalian cells

The aquaporin-4 (AQP4) water channel is abundantly expressed in the glial cells of the central nervous system and facilitates brain swelling following diverse insults, such as traumatic injury or stroke. Lack of specific and therapeutic AQP4 inhibitors highlights the need to explore alternative routes to control the water permeability of glial cell membranes. The cell surface abundance of AQP4 in mammalian cells fluctuates rapidly in response to changes in oxygen levels and tonicity, suggesting a role for vesicular trafficking in its translocation to and from the cell surface. However, the molecular mechanisms of AQP4 trafficking are not fully elucidated. In this work, early and recycling endosomes were investigated as likely candidates of rapid AQP4 translocation together with changes in cytoskeletal dynamics. In transiently transfected HEK293 cells a significant amount of AQP-eGFP colocalised with mCherry-Rab5-positive early endosomes and mCherry-Rab11-positive recycling endosomes. When exposed to hypotonic conditions, AQP4-eGFP rapidly translocated from intracellular vesicles to the cell surface. Co-expression of dominant negative forms of the mCherry-Rab5 and -Rab11 with AQP4-eGFP prevented hypotonicity-induced AQP4-eGFP trafficking and led to concentration at the cell surface or intracellular vesicles respectively. Use of endocytosis inhibiting drugs indicated that AQP4 internalisation was dynamin-dependent. Cytoskeleton dynamics-modifying drugs also affected AQP4 translocation to and from the cell surface. AQP4 trafficking mechanisms were validated in primary human astrocytes, which express high levels of endogenous AQP4. The results highlight the role of early and recycling endosomes and cytoskeletal dynamics in AQP4 translocation in response to hypotonic and hypoxic stress and suggest continuous cycling of AQP4 between intracellular vesicles and the cell surface under physiological conditions.

Aquaporin 4 regulation by ginsenoside Rb1 intervenes with oxygen-glucose deprivation/reoxygenation-induced astrocyte injury

BACKGROUND

Spinal cord ischemia-reperfusion injury (SCII) is a common complication of spinal surgery as well as thoracic and abdominal surgery. Acute cytotoxic edema is the key pathogenic alteration. Therefore, avoiding or decreasing cellular edema has become the major target for SCII treatment.

METHODS

The antiedema activity of ginsenoside Rb1 on aquaporin (AQP) 4, nerve growth factor (NGF), and brain-derived neurotrophic factor expression was detected by western blot and real-time polymerase chain reaction under conditions of oxygen-glucose deprivation/reoxygenation (OGD/R) in a rat astrocyte model in vitro. In addition, the cellular membrane permeability of AQP4 overexpressing cells or AQP4 small interfering RNA-transfected cells was detected.

RESULTS

Ginsenoside Rb1 significantly prevented OGD/R-induced AQP4 downregulation in rat astrocytes. In addition, ginsenoside Rb1 treatment or AQP4 overexpression in rat astrocytes significantly attenuated the OGD/R-induced increase of cellular membrane permeability. Moreover, ginsenoside Rb1 obviously prevented the OGD/R-induced decrease of NGF and BDNT expression in rat astrocytes.

CONCLUSION

These findings demonstrate that ginsenoside Rb1 can relieve spinal cord edema and improve neurological function by increasing AQP4 expression.

Linkage disequilibrium in aquaporin 4 gene and association study with schizophrenia

Aquaporin 4 (AQP4) has an important role in water homeostasis of human brain and a dysfunction of AQP4 could induce pathological conditions in neuronal activity. Several genome scan studies for schizophrenia found a suggestive linkage on 18q, where human AQP4 (18q11.2-12.1) is located nearby. A case-control study was performed which comprised 261 schizophrenia subjects and 278 controls from the Japanese population with four SNP markers. We found strong linkage disequilibrium (LD) and an LD block in the AQP4 gene but found no association between AQP4 and schizophrenia, both single SNP and haplotype analyses. The present study shows that AQP4 is not directly associated with schizophrenia in these Japanese patients.

Aquaporin 4 is not present in normal porcine and human lamina cribrosa

Aquaporin 4 is absent from astrocytes in the rodent optic nerve head, despite high expression in the retina and myelinated optic nerve. The purpose of this study was to quantify regional aquaporin channel expression in astrocytes of the porcine and human mouse optic nerve (ON). Ocular tissue sections were immunolabeled for aquaporins 1(AQP1), 4(AQP4), and 9(AQP9), myelin basic protein (MBP), glial fibrillary acidic protein (GFAP) and alpha-dystroglycan (αDG) for their presence in retina, lamina, myelin transition zone (MTZ, region just posterior to lamina) and myelinated ON (MON). Semi- quantification of AQP4 labeling & real-time quantitative PCR (qPCR) data were analyzed in retina and ON tissue. Porcine and control human eyes had abundant AQP4 in Müller cells, retinal astrocytes, and myelinated ON (MON), but minimal expression in the lamina cribrosa. AQP1 and AQP9 were present in retina, but not in the lamina. Immunolabeling of GFAP and αDG was similar in lamina, myelin transition zone (MTZ) and MON regions. Semi-quantitative AQP4 labeling was at background level in lamina, increasing in the MTZ, and highest in the MON (lamina vs MTZ, MON; p≤0.05, p≤0.01, respectively). Expression of AQP4 mRNA was minimal in lamina and substantial in MTZ and MON, while GFAP mRNA expression was uniform among the lamina, MTZ, and MON regions. Western blot assay showed AQP4 protein expression in the MON samples, but none was detected in the lamina tissue. The minimal presence of AQP4 in the lamina is a specific regional phenotype of astrocytes in the mammalian optic nerve head.

A hydrogen sulfide donor suppresses pentylenetetrazol-induced seizures in rats via PKC signaling

Epilepsy is a serious neurological disorder. Available antiepileptic drugs are still lacking. Hydrogen sulfide (H2S), a neuron-protective endogenous gasotransmitter, is reported to have effect on epilepsy. But it remains to be determined for its mechanism. In the present study, we found that a novel carbazole-based H2S donor could effectively suppress pentylenetetrazol-induced seizures in rats. The H2S donor could alleviate not only the epileptic behavior of animals but also the hippocampal EEG activity of seizures. The H2S donor down-regulated the expression of aquaporin 4 in the hippocampus of epilepsy rats. The H2S donor also decreased the seizure-induced release of inflammatory cytokines including IL-1β, IL-6 and TNF-α. In addition, the H2S donor increased protein kinase C (PKC) expression in the hippocampus of epilepsy rats. These effects of the H2S donor on epilepsy rats were attenuated after blockade of PKC signaling by Go6983, suggesting that PKC signaling participated in the antiepileptic process of H2S donor. Taken together, the H2S donor has a beneficial effect on epilepsy control in a PKC-dependent manner.

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.

The Readthrough Isoform AQP4ex Is Constitutively Phosphorylated in the Perivascular Astrocyte Endfeet of Human Brain

AQP4ex is a recently discovered isoform of AQP4 generated by a translational readthrough mechanism. It is strongly expressed at the astrocyte perivascular endfeet as a component of the supramolecular membrane complex, commonly called orthogonal array of particles (OAP), together with the canonical isoforms M1 and M23 of AQP4. Previous site-directed mutagenesis experiments suggested the potential role of serine331 and serine335, located in the extended peptide of AQP4ex, in water channel activity by phosphorylation. In the present study we evaluated the effective phosphorylation of human AQP4ex. A small scale bioinformatic analysis indicated that only Ser335 is conserved in human, mouse and rat AQP4ex. The phosphorylation site of Ser335 was assessed through generation of phospho-specific antibodies in rabbits. Antibody specificity was first evaluated in binding phosphorylated peptide versus its unphosphorylated analog by ELISA, which was further confirmed by site-directed mutagenesis experiments. Western blot and immunofluorescence experiments revealed strong expression of phosphorylated AQP4ex (p-AQP4ex) in human brain and localization at the perivascular astrocyte endfeet in supramolecular assemblies identified by BN/PAGE experiments. All together, these data reveal, for the first time, the existence of a phosphorylated form of AQP4, at Ser335 in the extended sequence exclusive of AQP4ex. Therefore, we anticipate an important physiological role of p-AQP4ex in human brain water homeostasis.

A Single Amino Acid Substitution Prevents Recognition of a Dominant Human Aquaporin-4 Determinant in the Context of HLA-DRB1*03:01 by a Murine TCR

Background

Aquaporin 4 (AQP4) is considered a putative autoantigen in patients with Neuromyelitis optica (NMO), an autoinflammatory disorder of the central nervous system (CNS). HLA haplotype analyses of patients with NMO suggest a positive association with HLA-DRB1* 03:01. We previously showed that the human (h) AQP4 peptide 281–300 is the dominant immunogenic determinant of hAQP4 in the context of HLA-DRB1*03:01. This immunogenic peptide stimulates a strong Th₁ and Th₁₇ immune response. AQP4_281-300-specific encephalitogenic CD4⁺ T cells should initiate CNS inflammation that results in a clinical phenotype in HLA-DRB1*03:01 transgenic mice.

Methods

Controlled study with humanized experimental animals. HLA-DRB1*03:01 transgenic mice were immunized with hAQP4_281-300, or whole-length hAQP4 protein emulsified in complete Freund’s adjuvant. Humoral immune responses to both antigens were assessed longitudinally. In vivo T cell frequencies were assessed by tetramer staining. Mice were followed clinically, and the anterior visual pathway was tested by pupillometry. CNS tissue was examined histologically post-mortem. Flow cytometry was utilized for MHC binding assays and to immunophenotype T cells, and T cell frequencies were determined by ELISpot assay.

Results

Immunization with hAQP4_281-300 resulted in an in vivo expansion of antigen-specific CD4⁺ T cells, and an immunoglobulin isotype switch. HLA-DRB1*03:01 TG mice actively immunized with hAQP4_281-300, or with whole-length hAQP4 protein were resistant to developing a neurological disease that resembles NMO. Experimental mice show no histological evidence of CNS inflammation, nor change in pupillary responses. Subsequent analysis reveals that a single amino acid substitution from aspartic acid in hAQP4 to glutamic acid in murine (m)AQP4 at position 290 prevents the recognition of hAQP4_281-300 by the murine T cell receptor (TCR).

Conclusion

Induction of a CNS inflammatory autoimmune disorder by active immunization of HLA-DRB1*03:01 TG mice with human hAQP4_281-300 will be complex due to a single amino acid substitution. The pathogenic role of T cells in this disorder remains critical despite these observations.

1,2-Dichloroethane induces cortex demyelination by depressing myelin basic protein via inhibiting aquaporin 4 in mice

1,2-Dichloroethane (1,2-DCE) is a pervasive environmental pollutant, and overexposure to this hazardous material causes brain edema and demyelination in humans. We found that 1,2-DCE inhibits aquaporin 4 (AQP4) and is a primary pathogenic effector of 1,2-DCE-induced brain edema in animals. However, AQP4 down-regulation's link with cortex demyelination after 1,2-DCE exposure remains unclear. Thus, we exposed wild-type (WT) CD-1 mice and AQP4 knockout (AQP4-KO) mice to 0, 100, 350 and 700 mg/m³ 1,2-DCE by inhalation for 28 days. We applied label-free proteomics and a cell co-culture system to elucidate the role of AQP4 inhibition in 1,2-DCE-induced demyelination. The results showed that 1,2-DCE down-regulated AQP4 in the WT mouse cortexes. Both 1,2-DCE exposure and AQP4 deletion induced neurotoxicity in mice, including increased brain water content, abnormal pathological vacuolations, and neurobehavioral damage. Tests for interaction of multiple regression analysis highlighted different effects of 1,2-DCE exposure level depending on the genotype, indicating the core role of AQP4 in regulation on 1,2-DCE-caused neurotoxicity. We used label-free quantitative proteomics to detect differentially expressed proteins associated with 1,2-DCE exposure and AQP4 inhibition, and identified down-regulation in myelin basic protein (MBP) and tyrosine-protein kinase Fyn (FYN) in a dose-dependent manner in WT mice but not in AQP4-KO mice. 1,2-DCE and AQP4 deletion separately resulted in demyelination, as detected by Luxol fast blue staining, and manifested as disordered nerve fibers and cavitation in the cortexes. Western blot and immunofluorescence confirmed the decreased AQP4 in the astrocytes and the down-regulated MBP in the oligodendrocytes by 1,2-DCE exposure and AQP4 inhibition, respectively. Finally, the co-culture results of SVG p12 and MO3.13 cells showed that 1,2-DCE-induced AQP4 down-regulation in the astrocytes was responsible for demyelination, by decreasing MBP in the oligodendrocytes. In conclusion, 1,2-DCE induced cortex demyelination by depressing MBP via AQP4 inhibition in the mice.

Estimated prevalence of AQP4 positive neuromyelitis optica spectrum disorder and MOG antibody associated disease in São Paulo, Brazil

BACKGROUND

Numerous studies addressed the prevalence of multiple sclerosis, but prevalence studies of NMOSD and, particularly, MOGAD are scarce. We aimed to estimate the prevalence of NMOSD and MOGAD in the city of São Paulo, based on the known prevalence of MS.

METHODS

In this observational study, we determined the total number of patients with central nervous system demyelinating disease on regular follow-up in a university referral center in São Paulo, from May 2019 to May 2021 according to the diagnosis of multiple sclerosis (MS), NMOSD and MOGAD using the current diagnostic criteria for these diseases. We used the MS: NMOSD and MS: MOGAD ratios to estimate the ratio of these diseases in São Paulo, Brazil.

RESULTS

We identified 968 patients with MS, 133 patients with AQP4 positive NMOSD, and 28 patients with MOGAD. We found the MS: NMOSD ratio of 7,28 and the MS: MOGAD ratio of 34,57. We estimated a prevalence of 2,1 per 100,000 inhabitants for NMOSD and of 0,4 per 100,000 inhabitants for MOGAD.

CONCLUSION

The prevalence of NMOSD is high in São Paulo, but the prevalence of MOGAD is low when compared with the prevalence found in most of the studies reported to date.

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.

Predictive Value of Serum Antibodies and Point Mutations of AQP4, AQP1 and MOG in A Cohort of Spanish Patients with Neuromyelitis Optica Spectrum Disorders

The detection of IgG aquaporin-4 antibodies in the serum of patients with Neuromyelitis optica (NMO) has dramatically improved the diagnosis of this disease and its distinction from multiple sclerosis. Recently, a group of patients have been described who have an NMO spectrum disorder (NMOsd) and who are seronegative for AQP4 antibodies but positive for IgG aquaporin-1 (AQP1) or myelin oligodendrocyte glycoprotein (MOG) antibodies. The purpose of this study was to determine whether AQP1 and MOG could be considered new biomarkers of this disease; and if point mutations in the gDNA of AQP4, AQP1 and MOG genes could be associated with the etiology of NMOsd. We evaluated the diagnostic capability of ELISA and cell-based assays (CBA), and analyzed their reliability, specificity, and sensitivity in detecting antibodies against these three proteins. The results showed that both assays can recognize these antigen proteins under appropriate conditions, but only anti-AQP4 antibodies, and not AQP1 or MOG, appears to be a clear biomarker for NMOsd. CBA is the best method for detecting these antibodies; and serum levels of AQP4 antibodies do not correlate with the progression of this disease. So far, the sequencing analysis has not revealed a genetic basis for the etiology of NMOsd, but a more extensive analysis is required before definitive conclusions can be drawn.

Expression of Olig2, Nestin, NogoA and AQP4 have no impact on overall survival in IDH-wildtype glioblastoma

Despite many years of research efforts and clinical trials the prognosis of patients diagnosed with glioblastoma remains very poor. The oligodendrocyte transcription factor 2 (Olig2) was identified as a marker for glioma stem cells, which are believed to be responsible for glioma recurrence and therapy resistance. In this retrospective analysis we assessed the prognostic value of oligodendroglial and glioma stem cell markers in 113 IDH-wildtype glioblastomas. Immunohistochemical staining for Olig2, NogoA, AQP4 and Nestin was performed in combination with sequencing of IDH1 and IDH2 as well as promotor methylation analysis of the MGMT gene. Even though differences in overall survival according to Olig2 expression were observed, univariate and multivariate survival analysis did not reveal a firm significant prognostic impact of Olig2, NogoA, AQP4 or Nestin expression. Additionally, no differences in the expression of these markers depending on clinical status, age or gender were found. The established independent prognostic factors age<65, Karnofsky Performance Status> = 70 and methylated MGMT gene promoter were significant in the multivariate analysis. In conclusion expression of oligodendroglial and glioma stem cell markers do not have an independent prognostic effect in IDH-wildtype glioblastoma.

Expression of aquaporin 4 in the chicken oviduct following tamoxifen treatment

This study was designed to examine whether aquaporin 4 (AQP4) is present in the chicken oviduct, and if so, whether its expression changes during pause in laying induced by tamoxifen (TMX; oestrogen receptor modulator) treatment. The control chickens were injected with a vehicle (ethanol) and the experimental ones with TMX at a dose of 6 mg/kg of body weight. Birds were treated daily until complete cessation of egg laying. The oviductal parts, that is the infundibulum, magnum, isthmus, shell gland and vagina were isolated from hens on day 8 of the experiment, and subsequently, the gene and protein expressions of AQP4 in tissues were examined by real-time PCR and Western blot, respectively. Immunohistochemical localization of AQP4 in the wall of the chicken oviduct was also investigated. Both mRNA and protein of AQP4 were found in all segments of the chicken oviduct. The relative expression [RQ] of AQP4 was the highest in the infundibulum and the vagina and the lowest, less detectable, in the magnum and isthmus. The pattern of AQP4 protein expression was similar to that of mRNA. Treatment of hens with TMX decreased the mRNA and protein levels of AQP4 in the oviduct. Immunohistochemistry demonstrated tissue and cell-dependent localization of AQP4 protein in the oviductal wall. The intensity of the immunopositive reaction was as follows: the infundibulum > vagina > shell gland ≥ isthmus >˃ magnum. In the control chickens, the immunoreactivity for AQP4 in all oviductal segments was stronger compared with the TMX-treated hens. The results obtained indicate that AQP4 takes part in the regulation of water transport required for the formation of egg in the chicken oviduct. Moreover, a relationship between oestrogen action and AQP4 gene and protein expression is suggested.

Potential molecular mechanism of Guiqi Baizhu Decoction in radiation-induced intestinal edema by regulating HIF-1a, AQP4 and Na+/K+-ATPase

BACKGROUND

Guiqi Baizhu Decoction (GQBZD) has a good protective effect on radiation-induced intestinal edema (RIIE). However, the underlying molecular mechanisms need further elucidation.

PURPOSE

To reveal the potential mechanism of RIIE and GQBZD treatment.

METHODS

SD rats were irradiated with 6Gy X-ray to establish RIIE model. The general condition of the rats was observed; the dry/wet weight ratio of colon tissue was detected; the morphological changes of colon tissue were observed by HE staining; the expressions of ROS, HIF-1α and AQP4 in colon tissue were detected by confocal laser scanning; the expression of edema-related proteins was detected by Western blot. In addition, human colon epithelial cells (NCM460) was irradiated with 2Gy X-ray, and HIF-1α expression in NCM460 was knocked down by small interfering RNA (siRNA) transfection, and the activity of Na⁺/K⁺-ATPase was detected by enzyme activity kit; the ROS expression was detected by flow cytometer; the AQP4 expression was detected by laser confocal microscopy; and the expression of edema-related proteins were detected by Western blot.

RESULTS

We found that after irradiation, the colon tissue of rats was significantly edema, mainly manifested as mucosal and submucosal edema, and the ultrastructure was reflected in the structural damage of nucleus and mitochondria. ROS, HIF-1α and AQP4 were significantly expressed, and Na⁺/K⁺-ATPase expression/activity was decreased. After the intervention of GQBZD, the edema of the colon tissue of the rats was improved, the expressions of ROS, HIF-1α and AQP4 were decreased, and the expression/activity of Na⁺/K⁺-ATPase was increased.

CONCLUSION

Ionizing radiation (IR) can cause significant intestinal edema. AQP4 and Na⁺/K⁺-ATPase are the key factors of RIIE, which are regulated by ROS and HIF-1α. GQBZD can improve hypoxia and oxidative stress, regulate the expression of AQP4 and Na⁺/K⁺-ATPase, and achieve a protective effect on RIIE. This study is the first to reveal the mechanism of RIIE.

Oryeongsan (Goreisan) Ameliorates Experimental Autoimmune Encephalomyelitis

Objective Oryeongsan (Goreisan), a formula composed of five herbal medicines, has long been used to treat impairments of the regulation of body fluid homeostasis. Goreisan has been revealed to have anti-inflammatory actions and inhibit a water channel, the aquaporin (AQP). We herein report the therapeutic effect of Goreisan on experimental autoimmune encephalomyelitis (EAE in, an animal model of inflammatory demyelinating diseases. Materials and Methods EAE mice immunized with MOG_35-55 peptide were divided into Goreisan- and sham-treated groups. The clinical EAE score and histopathological finding of the central nervous system (CNS) were analyzed. For the proliferation assay, prepared spleen cells from immunized mice were cultured and analyzed for the [³H]-thymidine uptake and cytokine concentrations of the culture supernatant. The relative quantification of AQP4 mRNA in the CNS of EAE mice was analyzed quantitatively. Results The EAE score of the Goreisan-treated mice was significantly lower than that of the sham-treated mice. The CD4-positive cell number in the CNS of Goreisan-treated mice was lower than that of sham-treated mice. In the recall response to MOG_35-55 peptide, the cell proliferation did not differ markedly between the spleen cells from Goreisan- and sham-treated mice. Furthermore, Goreisan decreased the mRNA level of AQP4 in the spinal cord during EAE. Conclusion Goreisan prevented the disease activity of EAE by inhibiting the migration of pathogenic cells into the CNS by suppressing the AQP4 expression in the CNS. Goreisan may have a therapeutic effect on inflammatory demyelinating diseases.

CU06-1004 (endothelial dysfunction blocker) ameliorates astrocyte end-feet swelling by stabilizing endothelial cell junctions in cerebral ischemia/reperfusion injury

Cerebral ischemia, or stroke, is widespread leading cause of death and disability. Surgical and pharmacological interventions that recover blood flow are the most effective treatment strategies for stroke patients. However, restoring the blood supply is accompanied by severe reperfusion injury, with edema and astrocyte end-feet disruption. Here, we report that the oral administration of CU06-1004 (previously Sac-1004), immediately after onset of ischemia/reperfusion (I/R), ameliorated cerebral damage. CU06-1004 stabilized blood‑brain barrier by inhibiting the disruption of the tight junction-related protein zona occludens-1 and the cortical actin ring in endothelial cells (ECs) after I/R. Interestingly, CU06-1004 significantly suppressed astrocyte end-feet swelling following I/R, by reducing aquaporin 4 and connexin 43 levels, which mediates swelling. Furthermore, the degradation of β1-integrin and β-dystroglycan, which anchors to the cortical actin ring in ECs, was inhibited by CU06-1004 administration after I/R. Consistently, CU06-1004 administration following I/R also suppressed the loss of laminin and collagen type IV, which bind to the cortical actin ring anchoring proteins. Unlike the protective effects of CU06-1004 in ECs, astrocyte viability and proliferation were not directly affected. Taken together, our observations suggest that CU06-1004 inhibits I/R-induced cerebral edema and astrocyte end-feet swelling by maintaining EC junction stability. KEY MESSAGES: • CU06-1004 ameliorates I/R-induced cerebral injury. • EC junction integrity was stabilized by CU06-1004 treatment after I/R. • CU06-1004 reduces astrocyte end-feet swelling following I/R. • EC junction stability affects astrocyte end-feet structure maintenance after I/R.

Generation of Periventricular Reactive Astrocytes Overexpressing Aquaporin 4 Is Stimulated by Mesenchymal Stem Cell Therapy

Aquaporin-4 (AQP4) plays a crucial role in brain water circulation and is considered a therapeutic target in hydrocephalus. Congenital hydrocephalus is associated with a reaction of astrocytes in the periventricular white matter both in experimental models and human cases. A previous report showed that bone marrow-derived mesenchymal stem cells (BM-MSCs) transplanted into the lateral ventricles of hyh mice exhibiting severe congenital hydrocephalus are attracted by the periventricular astrocyte reaction, and the cerebral tissue displays recovery. The present investigation aimed to test the effect of BM-MSC treatment on astrocyte reaction formation. BM-MSCs were injected into the lateral ventricles of four-day-old hyh mice, and the periventricular reaction was detected two weeks later. A protein expression analysis of the cerebral tissue differentiated the BM-MSC-treated mice from the controls and revealed effects on neural development. In in vivo and in vitro experiments, BM-MSCs stimulated the generation of periventricular reactive astrocytes overexpressing AQP4 and its regulatory protein kinase D-interacting substrate of 220 kDa (Kidins220). In the cerebral tissue, mRNA overexpression of nerve growth factor (NGF), vascular endothelial growth factor (VEGF), hypoxia-inducible factor-1 (HIF1α), and transforming growth factor beta 1 (TGFβ1) could be related to the regulation of the astrocyte reaction and AQP4 expression. In conclusion, BM-MSC treatment in hydrocephalus can stimulate a key developmental process such as the periventricular astrocyte reaction, where AQP4 overexpression could be implicated in tissue recovery.

Aquaporin 4 Silencing Aggravates Hydrocephalus Induced by Injection of Autologous Blood in Rats

BACKGROUND Aquaporin 4 (AQP4), the most abundant aquaporin in the brain, is a type of bidirectional water channel controlling the brain-water balance and plays a critical role in physiologic and pathologic water balance in the brain. AQP4 was reported to be elevated in hydrocephalus; therefore, we hypothesized that AQP4 contributes to hydrocephalus. In this study, the role of AQP4 in hydrocephalus was explored. MATERIAL AND METHODS The hydrocephalus rat model was established by injection of autologous blood. On Day 1 and Day 3 after injection of autologous blood, magnetic resonance imaging (MRI) and hematoxylin-eosin (HE) staining were performed to detect the changes in ventricles, and quantitative real-time PCR (qRT-PCR) and immunohistochemistry were carried out to detect the changes in AQP4 level. Thereafter, an AQP4-specific siRNA was used to downregulate AQP4. Then, on Day 3 after injection of autologous blood, the levels of AQP4 and connexin-43 were detected by qRT-PCR, immunohistochemistry, immunofluorescence, or Western blot analysis. MRI and HE staining were performed to detect the changes in ventricles, and Evans blue extravasation assay was used to assess blood-brain barrier integrity. RESULTS The hydrocephalus rat model was established successfully, and hydrocephalus rats showed a higher AQP4 level. Silencing AQP4 aggravated the hydrocephalus, with enlarged lateral ventricles and destruction of ependymal integrity and blood-brain barrier. CONCLUSIONS Our study demonstrates that silencing AQP4 aggravates hydrocephalus, indicating that AQP4 protects against hydrocephalus.

Targeting chemoattractant chemokine (C-C motif) ligand 2 derived from astrocytes is a promising therapeutic approach in the treatment of neuromyelitis optica spectrum disorders

Introduction

Aquaporin-4 immunoglobulin G (AQP4-IgG)-induced astrocytes injury is a key mechanism in the pathogenesis of neuromyelitis spectrum disorder (NMOSD), and although CCL2 is involved, its specific role has not been reported. We aimed to further investigate the role and potential mechanisms of CCL2 in AQP4-IgG-induced astrocyte injury.

Methods

First, we evaluated CCL2 levels in paired samples of subject patients by automated microfluidic platform, Ella®. Second, we knock down astrocyte's CCL2 gene in vitro and in vivo to define the function of CCL2 in AQP4-IgG-induced astrocyte injury. Third, astrocyte injury and brain injury in live mice were assessed by immunofluorescence staining and 7.0T MRI, respectively. Western blotting and high-content screening were conducted to clarify the activation of inflammatory signaling pathways, and changes in CCL2 mRNA and cytokine/chemokines were measured by qPCR technique and flow cytometry, respectively.

Results

There were greatly higher CSF-CCL2 levels in NMOSD patients than that in other non-inflammatory neurological diseases (OND) groups. Blocking astrocyte CCL2 gene expression can efficiently mitigate AQP4-IgG-induced damage in vitro and in vivo. Interestingly, prevention of CCL2 expression could decrease other inflammatory cytokines released, including IL-6 and IL-1β. Our data suggest that CCL2 involves in the initiation and plays a pivotal role in AQP4-IgG-damaged astrocytes.

Discussion

Our results indicate that CCL2 may serve as a promising candidate target for inflammatory disorder therapy, including NMOSD.

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

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