scholarly journals Ammonia induced microglia activation was associated with limited effects on connexin 43 and aquaporin 4 expression in an astrocyte-microglia co-culture model

2021 ◽  
Vol 22 (1) ◽  
Author(s):  
Fatme Seval Ismail ◽  
Timo Jendrik Faustmann ◽  
Franco Corvace ◽  
Anamariya Tsvetanova ◽  
Zahra Moinfar ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Microglial Activation ◽  
Neurological Complication ◽  
Microglia Activation ◽  
Aquaporin 4 ◽  
Cx43 Expression ◽  
Aqp4 Expression ◽  
Astrocyte Swelling ◽  
Culture Model

Abstract Background Hepatic encephalopathy (HE) is a neurological complication resulting from acute or chronic liver disease. Hyperammonemia leading to astrocyte swelling and cerebral edema in combination with neuroinflammation including microglia activation, mainly contribute to the pathogenesis of HE. However, little is known about microglia and their inflammatory response, as well as their influence on astrocytic channels and astrocyte swelling under hyperammonemia. Objective To investigate the effects of ammonia on the microglial activation and morphology in different set-ups of an in vitro astrocyte-microglia co-culture model. Further, potential effects on glial viability, connexin 43 (Cx43) and aquaporin 4 (AQP4) expression were tested. Methods Primary rat glial co-cultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) of microglia were incubated with 3 mM, 5 mM, 10 mM and 20 mM ammonium chloride (NH4Cl) for 6 h and 24 h in order to mimic the conditions of HE. An MTT assay was performed to measure the viability, proliferation and cytotoxicity of cells. The microglial phenotypes were analyzed by immunocytochemistry. The expression of Cx43 and AQP4 were quantified by immunoblot analysis. Results A significant reduction of glial viability was observed in M30 co-cultures after incubation with 20 mM NH4Cl for 6 h, whereas in M5 co-cultures the viability remained unchanged. Microglial activation was detected by immunocytochemistry after incubation with 3 mM, 5 mM and 10 mM NH4Cl for 6 h and 24 h in M5 as well as in M30 co-cultures. The Cx43 expression was slightly increased in M30 co-cultures after 6 h incubation with 5 mM NH4Cl. Also, the AQP4 expression was slightly increased only in M5 co-cultures treated with 10 mM NH4Cl for 6 h. Under the other conditions, Cx43 and AQP4 expression was not affected by NH4Cl. Conclusions The novel aspect of our study was the significant microglial activation and decrease of viability after NH4Cl incubation in different set-ups of an in vitro astrocyte-microglia co-culture model, contributing to better understanding of pathophysiological mechanisms of HE. Hyperammonemia led to limited effects on Cx43 and AQP4 expression, the relevance of these minimal changes should be viewed with caution.

scholarly journals Ammonia Induced Microglial Activation Modulates Connexin 43 and Aquaporin 4 Expression in Astrocyte-microglia Co-culture Model

2020 ◽  
Author(s):  
Fatme Seval Ismail ◽  
Timo Jendrik Faustmann ◽  
Anamariya Tsvetanova ◽  
Zahra Moinfar ◽  
Pedro M. Faustmann
Keyword(s):  
Connexin 43 ◽  
Microglial Activation ◽  
Neurological Complication ◽  
Microglia Activation ◽  
Aquaporin 4 ◽  
Cx43 Expression ◽  
Aqp4 Expression ◽  
Astrocyte Swelling ◽  
Culture Model

Abstract Background Hepatic encephalopathy (HE) is a neurological complication resulting from acute or chronic liver disease. Hyperammonemia leading to astrocyte swelling and cerebral edema in combination with neuroinflammation including microglia activation, mainly contribute to the pathogenesis of HE. However, little is known about microglia and their inflammatory response, as well as their influence on astrocytic channels and astrocyte swelling under hyperammonemia.Objective To investigate the effects of ammonia on the microglial activation, glial viability, connexin 43 (Cx43) and aquaporin 4 (AQP4) expression in astrocytes in in vitro astrocyte-microglia co-culture model.Methods Primary rat glial cocultures of astrocytes containing 5% (M5, representing "physiological" conditions) or 30% (M30, representing "pathological" conditions) of microglia were incubated with 3 mM, 5 mM, 10 mM and 20 mM ammonium chloride (NH4Cl) for 6 h and 24 h in order to mimic the conditions of HE. An MTT assay was performed to measure the viability, proliferation and cytotoxicity of cells. The microglial phenotypes were analysed by immunocytochemistry. The expression of Cx43 and AQP4 were quantified by immunoblot analysis.Results A significant reduction of glial viability was observed in M30 co-cultures after incubation with 20 mM NH4Cl for 6 h, whereas in M5 co-cultures the viability remained unchanged. Microglial activation was detected by immunocytochemistry after incubation with 3 mM, 5 mM and 10 mM NH4Cl for 6 h and 24 h in M5 as well as in M30 co-cultures. The Cx43 expression was increased significantly in M30 co-cultures after 6 h incubation with 5 mM NH4Cl. The AQP4 expression was increased significantly in M5 co-cultures treated with 10 mM NH4Cl for 6 h.Conclusions Our findings showed a significant microglial activation, decrease of viability and increase in Cx43 and AQP4 expression after NH4Cl incubation in astrocyte-microglia co-culture model. Based on previous in vitro studies suggesting that microglia activation influences astrocytic networks, it can be assumed that the microglial activation under hyperammonemia can modulate the Cx43 and AQP4 expression in astrocytes in a dynamic way and this can contribute to astrocytic dysfunction in HE.

Expression of connexin 43 (Cx43) is critical for normal hematopoiesis

Blood ◽  
2000 ◽  
Vol 96 (3) ◽  
pp. 917-924 ◽  
Author(s):  
Encarnacion Montecino-Rodriguez ◽  
Hyosuk Leathers ◽  
Kenneth Dorshkind
Keyword(s):  
Bone Marrow ◽  
T Cell ◽  
Blood Cell ◽  
Gap Junctions ◽  
Connexin 43 ◽  
Cell Formation ◽  
Cx43 Expression ◽  
Hematopoietic System ◽  
Blood Cell Formation

Abstract Gap junctions are intercellular channels, formed by individual structural units known as connexins (Cx), that allow the intercellular exchange of various messenger molecules. The finding that numbers of Cx43-type gap junctions in bone marrow are elevated during establishment and regeneration of the hematopoietic system has led to the hypothesis that expression of Cx43 is critical during the initiation of blood cell formation. To test this hypothesis, lymphoid and myeloid development were examined in mice with a targeted disruption of the gene encoding Cx43. Because Cx43−/− mice die perinatally, initial analyses were performed on Cx43−/−, Cx43+/−, and Cx43+/+ embryos and newborns. The data indicate that lack of Cx43 expression during embryogenesis compromises the terminal stages of primary T and B lymphopoiesis. Cx43−/− embryos and neonates had a reduced frequency of CD4+ and T-cell receptor-expressing thymocytes and surface IgM+cells compared to their Cx43+/+ littermates. Surprisingly, Cx43+/− embryos/neonates also showed defects in B- and T-cell development similar to those observed in Cx43−/− littermates, but their hematopoietic system was normal at 4 weeks of age. However, the regeneration of lymphoid and myeloid cells was severely impaired in the Cx43+/− mice after cytoablative treatment. Taken together, these data indicate that loss of a single Cx43 allele can affect blood cell formation. Finally, the results of reciprocal bone marrow transplants between Cx43+/+ and Cx43+/− mice and examination of hematopoietic progenitors and stromal cells in vitro indicates that the primary effects of Cx43 are mediated through its expression in the hematopoietic microenvironment.

scholarly journals Targeting connexin 43 provides anti-inflammatory effects after intracerebral hemorrhage injury by regulating YAP signaling

2020 ◽  
Vol 17 (1) ◽  
Author(s):  
Hailong Yu ◽  
Xiang Cao ◽  
Wei Li ◽  
Pinyi Liu ◽  
Yuanyuan Zhao ◽  
...  
Keyword(s):  
Intracerebral Hemorrhage ◽  
Connexin 43 ◽  
Nuclear Translocation ◽  
Neurological Deficits ◽  
Proximity Ligation Assay ◽  
Neuroprotective Effects ◽  
Cx43 Expression ◽  
Anti Inflammatory

Abstract Background In the central nervous system (CNS), connexin 43 (Cx43) is mainly expressed in astrocytes and regulates astrocytic network homeostasis. Similar to Cx43 overexpression, abnormal excessive opening of Cx43 hemichannels (Cx43Hcs) on reactive astrocytes aggravates the inflammatory response and cell death in CNS pathologies. However, the role of excessive Cx43Hc opening in intracerebral hemorrhage (ICH) injury is not clear. Methods Hemin stimulation in primary cells and collagenase IV injection in C57BL/6J (B6) mice were used as ICH models in vitro and in vivo. After ICH injury, the Cx43 mimetic peptide Gap19 was used for treatment. Ethidium bromide (EtBr) uptake assays were used to measure the opening of Cx43Hcs. Western blotting and immunofluorescence were used to measure protein expression. qRT-PCR and ELISA were used to determine the levels of cytokines. Coimmunoprecipitation (Co-IP) and the Duolink in situ proximity ligation assay (PLA) were applied to measure the association between proteins. Results In this study, Cx43 expression upregulation and excessive Cx43Hc opening was observed in mice after ICH injury. Delayed treatment with Gap19 significantly alleviated hematoma volume and neurological deficits after ICH injury. In addition, Gap19 decreased inflammatory cytokine levels in the tissue surrounding the hematoma and decreased reactive astrogliosis after ICH injury in vitro and in vivo. Intriguingly, Cx43 transcriptional activity and expression in astrocytes were significantly increased after hemin stimulation in culture. However, Gap19 treatment downregulated astrocytic Cx43 expression through the ubiquitin-proteasome pathway without affecting Cx43 transcription. Additionally, our data showed that Gap19 increased Yes-associated protein (YAP) nuclear translocation. This subsequently upregulated SOCS1 and SOCS3 expression and then inhibited the TLR4-NFκB and JAK2-STAT3 pathways in hemin-stimulated astrocytes. Finally, the YAP inhibitor, verteporfin (VP), reversed the anti-inflammatory effect of Gap19 in vitro and almost completely blocked its protective effects in vivo after ICH injury. Conclusions This study provides new insight into potential treatment strategies for ICH injury involving astroglial Cx43 and Cx43Hcs. Suppression of abnormal astroglial Cx43 expression and Cx43Hc opening by Gap19 has anti-inflammatory and neuroprotective effects after ICH injury.

scholarly journals Sympathetic Overactivity in CKD Disrupts Buffering of Neurotransmission by Endothelium-Derived Hyperpolarizing Factor and Enhances Vasoconstriction

2020 ◽  
Vol 31 (10) ◽  
pp. 2312-2325
Author(s):  
Wei Cao ◽  
Liling Wu ◽  
Xiaodong Zhang ◽  
Jing Zhou ◽  
Jian Wang ◽  
...  
Keyword(s):  
Gap Junction ◽  
Vascular Resistance ◽  
Connexin 43 ◽  
Structural Changes ◽  
Ex Vivo ◽  
Resistance Arteries ◽  
Cx43 Expression ◽  
Neurovascular Transmission

BackgroundHypertension commonly complicates CKD. Vascular smooth muscle cells (VSMCs) of resistance arteries receive signals from the sympathetic nervous system that induce an endothelial cell (EC)–dependent anticontractile response that moderates vasoconstriction. However, the specific role of this pathway in the enhanced vasoconstriction in CKD is unknown.MethodsA mouse model of CKD hypertension generated with 5/6-nephrectomy (5/6Nx) was used to investigate the hypothesis that an impaired anticontractile mechanism enhances sympathetic vasoconstriction. In vivo, ex vivo (isolated mesenteric resistance arteries), and in vitro (VSMC and EC coculture) models demonstrated neurovascular transmission and its contribution to vascular resistance.ResultsBy 4 weeks, 5/6Nx mice (versus sham) had augmented increases in mesenteric vascular resistance and mean arterial pressure with carotid artery occlusion, accompanied by decreased connexin 43 (Cx43) expression at myoendothelial junctions (MEJs), impaired gap junction function, decreased EC-dependent hyperpolarization (EDH), and enhanced contractions. Exposure of VSMCs to NE for 24 hours in a vascular cell coculture decreased MEJ Cx43 expression and MEJ gap junction function. These changes preceded vascular structural changes evident only at week 8. Inhibition of central sympathetic outflow or transfection of Cx43 normalized neurovascular transmission and vasoconstriction in 5/6Nx mice.Conclusions5/6Nx mice have enhanced neurovascular transmission and vasoconstriction from an impaired EDH anticontractile component before vascular structural changes. These neurovascular changes depend on an enhanced sympathetic discharge that impairs the expression of Cx43 in gap junctions at MEJs, thereby interrupting EDH responses that normally moderate vascular tone. Dysregulation of neurovascular transmission may contribute to the development of hypertension in CKD.

Abstract TP97: Improved Long-Term Outcome after Transient Cerebral Ischemia in Aquaporin-4 Knockout Mice

Stroke ◽  
2013 ◽  
Vol 44 (suppl_1) ◽  
Author(s):  
Andrew M Fukuda ◽  
Lorenz Hirt ◽  
Kamalakar Ambadipudi ◽  
Alan S Verkman ◽  
Devin K Binder ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Aquaporin 4 ◽  
Lesion Volume ◽  
Post Injury ◽  
Edema Formation ◽  
Cx43 Expression ◽  
Long Term Outcome ◽  
Junction Protein ◽  
Network Properties

Introduction: Aquaporin-4 (AQP4) is an abundant aquaporin in brain that has been hypothesized to play a central role in edema formation. Furthermore, AQP4 downregulation has been correlated with connexin 43 (Cx43) downregulation, a gap junction protein important for ion and water transport through astrocyte networks. AQP4 deletion in mice was shown to be beneficial at 24 hours after permanent occlusion of the middle cerebral artery (MCAO). However, the long-term consequences of AQP4 deletion on behavior, edema, and tissue properties after stroke have not been studied. Objective: Following transient MCAO, behavior, lesion volumes, blood brain barrier (BBB) integrity, neuroinflammation, and astrocyte network properties with Cx43 expressions were assessed for 14 days in wild type (WT) and AQP4 -/- mice. Methods: Transient (30-min) filament MCAO was performed on AQP4 -/- (n=5) and WT (n=8) mice on a CD1 genetic background. Behavioral outcomes were assessed by rotarod, beam balance, and foot fault tests from 1 to 14 days (d) post injury. Temporal magnetic resonance imaging (MRI) was undertaken to assess lesion volume. Mice were transcardially perfused at 15 d and the brains were extracted and frozen to perform immunohistochemical analysis for IgG, AQP4, Cx43, and glial fibrillary acidic protein (GFAP). Results: MRI showed significantly smaller lesion volume in AQP4 -/- at 1, 3, 7, and 14d. AQP4 -/- mice also had improved motor function recovery with 54% and 75% decreased number of foot-faults than WT mice respectively at 1 and 3 d; and 60% increased time spent on the rotarod compared to WT over the 14 days after stroke onset. AQP4 -/- mice had reduced IgG extravasation and Cx43 expression but increased GFAP staining compared to WT at 14d, suggesting, respectively, less BBB disruption and modified astrocyte network properties combined with altered neuroinflammation fates. Conclusion: AQP4 deletion resulted in improved long-term functional recovery associated with decreased lesion volumes and improved BBB integrity. Although more work must be done, the beneficial outcomes in AQP4 -/- may partly be due to decreased Cx43 as well, resulting in not only decreased edema formation through AQP4, but also in decreased spread of edema through the astrocyte network.

scholarly journals PDTC ameliorates neuropathic pain by inhibiting microglial activation via blockage of the TNFα-CX3CR1 pathway

2021 ◽  
Vol 65 (1) ◽  
Author(s):  
Xilei Li ◽  
Zhi Ye ◽  
Qulian Guo ◽  
E Wang ◽  
Yundan Pan
Keyword(s):  
Neuropathic Pain ◽  
Sciatic Nerve ◽  
Microglial Activation ◽  
Thermal Hyperalgesia ◽  
Microglia Activation ◽  
Pyrrolidine Dithiocarbamate ◽  
Mechanical Stimuli ◽  
Necrosis Factor Alpha ◽  
Intrathecal Infusion

Previous studies have suggested that pyrrolidine dithiocarbamate (PDTC), a nuclear factor κB (NF-κB) inhibitor, play a role in deterring nerve injury-induced neuropathic pain (NP) The activation of NF-κB pathway may contribute to spinal microglial activation, CX3CR1 and tumor necrosis factor-alpha (TNF-a) up-regulation. The aim of this study was to clarify whether PDTC could inhibit the development of neuropathic pain via decreasing TNF-a-induced CX3CR1 up-regulation. Sprague-Dawley rats were randomly divided into sham group and NP group. Rats in each group were treated with intrathecal infusion of PDTC (100 or 1000 pmol/d) or saline. The sciatic nerve chronic constriction injury (CCI) model was used to induce NP in rats. Mechanical stimuli and radiant heat were used to evaluate mechanical allodynia and thermal hyperalgesia. Spinal microglial marker OX42 and TNF-a were detected by immunohistochemistry. In vitro BV-2 microglia activation was induced by TNF-a incubation, and the levels of CX3CR1 were assessed by Western blot and reverse transcription-polymerase chain reaction. Pain behavior and immunohistochemistry results showed that intrathecal infusion of PDTC at 100 or 1000 pmol/d prevented the development of mechanical and thermal hyperalgesia, spinal microglial activation and TNF-a expression induced by sciatic nerve CCI in rats. In vitro experiment results showed that PDTC inhibited the TNF-a-induced CX3CR1 up-regulation in BV-2 microglial cells. In conclusion, intrathecal infusion of PDTC could attenuate the pain-related behaviors induced by sciatic nerve CCI through suppressing the spinal microglia activation and TNF-a up-regulation in rats. The NF-κB activation might be responsible for TNF-a-induced CX3CR1 up-regulation in microglia.

scholarly journals Propofol Mediated Protection of the Brain From Ischemia/Reperfusion Injury Through the Regulation of Microglial Connexin 43

2021 ◽  
Vol 9 ◽  
Author(s):  
Tingting Zhang ◽  
Yanyan Wang ◽  
Qin Xia ◽  
Zhiyi Tu ◽  
Jiajun Sun ◽  
...  
Keyword(s):  
Connexin 43 ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Neuronal Population ◽  
Neuronal Morphology ◽  
Microglial Cells ◽  
Cx43 Expression ◽  
The Brain

Cerebral ischemia/reperfusion (I/R) injury is a serious condition that leads to increased apoptosis of microglial and neurons in the brain. In this study, we identified that Cx43 expression level is significantly increased in the microglial cells during I/R injury. Using an in vitro model (hypoxia/reoxygenation-H/R injury), we observed that H/R injury leads to an increase in activation of microglial cells and increase in levels of pro-inflammatory markers such as IL-1β, IL-6, and TNF-α. Additionally, we could also observe significant increase in phosphorylation of Cx43 and Cav3.2 levels. To assess the role of H/R injured microglial cells on neuronal population, we cultured the neurons with conditioned media (MCS) from H/R injured microglial cells. Interestingly, we observed that microglial H/R injury significantly decreased Map2 expression and affected neuronal morphology. Further, we aimed to assess the effects of propofol on cerebral H/R injury, and observed that 40 μM propofol significantly decreased Cx43, Cx43 phosphorylation, and CaV3.2 levels. Additionally, propofol decreased apoptosis and increased Map2 expression levels in H/R injured neurons. Using silencing experiments, we confirmed that siCx43 could significantly improve the propofol’s rescue after H/R injury in both microglia and neurons. We further developed an in vivo MCAO (middle cerebral artery occlusion) rat model to understand the effect of propofol in I/R injury. Interestingly, propofol treatment and downregulation of Cx43 significantly decreased the infract volume and apoptosis in these MCAO rats. Thus, this study clearly establishes that propofol protects the brain against I/R injury through the downregulation of Cx43 in microglial cells.

scholarly journals The Potential Impact of Connexin 43 Expression on Bcl-2 Protein Level and Taxane Sensitivity in Head and Neck Cancers–In Vitro Studies

Cancers ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1848 ◽  
Author(s):  
Bianka Gurbi ◽  
Diána Brauswetter ◽  
Attila Varga ◽  
Pál Gyulavári ◽  
Kinga Pénzes ◽  
...  
Keyword(s):  
Squamous Cell Carcinoma ◽  
Cell Viability ◽  
Cell Carcinoma ◽  
Head And Neck ◽  
Squamous Cell ◽  
Connexin 43 ◽  
Carcinoma Cells ◽  
Cx43 Expression ◽  
Cx43 Protein

The poor prognosis of head and neck squamous cell carcinoma (HNSCC) is partly due to the lack of reliable predictive markers. Connexin 43 (Cx43) protein and its cell-communication channels have been assigned tumor suppressor functions while the anti-apoptotic Bcl-2 (B-cell lymphoma-2) protein has been associated with negative prognostic significance in cancer. This study aimed to test the role of Cx43 protein on Bcl-2 expression, tumor progression and response to taxane-based treatment in HNSCC. Human papillomavirus (HPV) negative HNSCC cell lines were tested for paclitaxel sensitivity through measuring apoptosis induction, cell viability and changes in Cx43 and Bcl-2 levels using flow cytometry, cell viability assay, immunocytochemistry and western blot. Inhibition of Cx43 expression using siRNA increased Bcl-2 protein levels in SCC25 (tongue squamous cell carcinoma) cells, while forced Cx43 expression reduced Bcl-2 levels and supported paclitaxel cytotoxicity in FaDu (hypopharynx squamous cell carcinoma) cells. In vitro results were in line with protein expression and clinicopathological features tested in tissue microarray samples of HNSCC patients. Our data demonstrate that elevated Cx43 and reduced Bcl-2 levels may indicate HNSCC sensitivity to taxane-based treatments. On the contrary, silencing of the Cx43 gene GJA1 (gap junction protein alpha-1) can result in increased Bcl-2 expression and reduced paclitaxel efficiency. Clinical tumor-based analysis also confirmed the inverse correlation between Cx43 and Bcl-2 expression.

scholarly journals The important role of connexin 43 in subarachnoid hemorrhage-induced cerebral vasospasm

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Le Yang ◽  
Jian Yan ◽  
Jin-An Zhang ◽  
Xin-Hui Zhou ◽  
Chao Fang ◽  
...  
Keyword(s):  
Subarachnoid Hemorrhage ◽  
Cerebral Vasospasm ◽  
Connexin 43 ◽  
Delayed Cerebral Ischemia ◽  
Dye Transfer ◽  
Cx43 Expression ◽  
Gf 109203X ◽  
Pkc Inhibitors

Abstract Background Gap junctions are involved in the development of cerebral vasospasm (CVS) after subarachnoid hemorrhage (SAH). However, the specific roles and regulatory functions of related connexin isoforms remain unknown. The aim of this study was to investigate the importance of connexin 43 (Cx43) in CVS and determine whether Cx43 alterations are modulated via the protein kinase C (PKC) signaling transduction pathway. Methods Oxyhemoglobin (OxyHb)-induced smooth muscle cells of basilar arterial and second-injection model in rat were used as CVS models in vitro and in vivo. In addition, dye transfer assays were used for gap junction-mediated intercellular communication (GJIC) observation in vitro and delayed cerebral ischemia (DCI) was observed in vivo by perfusion-weighted imaging (PWI) and intravital fluorescence microscopy. Results Increase in Cx43 mediated the development of SAH-induced CVS was found in both in vitro and in vivo CVS models. Enhanced GJIC was observed in vitro CVS model, this effect and increased Cx43 were reversed by preincubation with specific PKC inhibitors (chelerythrine or GF 109203X). DCI was observed in vivo on day 7 after SAH. However, DCI was attenuated by pretreatment with Cx43 siRNA or PKC inhibitors, and the increased Cx43 expression in vivo was also reversed by Cx43 siRNA or PKC inhibitors. Conclusions These data provide strong evidence that Cx43 plays an important role in CVS and indicate that changes in Cx43 expression may be mediated by the PKC pathway. The current findings suggest that Cx43 and the PKC pathway are novel targets for developing treatments for SAH-induced CVS.

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