Fluoxetine enhances the antitumor effect of olfactory ensheathing cell-thymidine kinase/ganciclovir gene therapy in human glioblastoma multiforme cells through upregulation of Connexin43 levels.

Glioblastoma multiforme (GBM) is the most invasive form of primary brain astrocytoma, resulting in poor clinical outcomes. Herpes simplex virus thymidine kinase/ganciclovir (HSV-TK/GCV) gene therapy is considered a promising strategy for GBM treatment. Since Connexin43 (Cx43) expression is reduced in GBM cells, increasing Cx43 levels could enhance the effectiveness of gene therapy. The present study aims to examine the impact of fluoxetine on HSV-TK/GCV gene therapy in human GBM cells using human olfactory ensheathing cells (OECs) as vectors. The effect of fluoxetine on Cx43 levels was assessed using the western blot technique. GBM-derived astrocytes and OECs-TK were Cocultured, and the effect of fluoxetine on the Antitumor effect of OEC-TK/GCV gene therapy was evaluated using MTT assay and flow cytometry. Our results showed that fluoxetine increased Cx43 levels in OECs and GBM cells and augmented the killing effect of OECs-TK on GBM cells. Western blot data revealed that fluoxetine enhanced the Bax/Bcl2 ratio and the levels of cleaved caspase-3 in the coculture of OECs-TK and GBM cells. Moreover, flow cytometry data indicated that fluoxetine increased the percentage of apoptotic cells in the coculture system. This study suggests that fluoxetine, by upregulating Cx43 levels, could strengthen the Antitumor effect of OEC-TK/GCV gene therapy on GBM cells.

αCT1 peptide sensitizes glioma cells to temozolomide in a glioblastoma organoid platform.

Glioblastoma (GBM) is the most common form of brain cancer. Even with aggressive treatment, tumor recurrence is almost universal and patient prognosis is poor because many GBM cell subpopulations, especially the mesenchymal and glioma stem cell populations, are resistant to temozolomide (TMZ), the most commonly used chemotherapeutic in GBM. For this reason, there is an urgent need for the development of new therapies that can more effectively treat GBM. Several recent studies have indicated that high expression of connexin 43 (Cx43) in GBM is associated with poor patient outcomes. It has been hypothesized that inhibition of the Cx43 hemichannels could prevent TMZ efflux and sensitize otherwise resistance cells to the treatment. In this study, we use a three-dimensional organoid model of GBM to demonstrate that combinatorial treatment with TMZ and αCT1, a Cx43 mimetic peptide, significantly improves treatment efficacy in certain populations of GBM. Confocal imaging was used to visualize changes in Cx43 expression in response to combinatorial treatment. These results indicate that Cx43 inhibition should be pursued further as an improved treatment for GBM.

The protective effect of total glucosides of white paeony capsules on experimental autoimmune encephalomyelitis.

AIMS: To learn about the effect and mechanism of total glucosides of white peony capsule (TGP), on experimental autoimmune encephalomyelitis (EAE), an acknowledged animal model of multiple sclerosis (MS). METHODS: The rat model of EAE was induced by subcutaneous injection with guinea pig spinal cord homogenate. The severity of the disease model was assessed by clinical score, hematoxylin and eosin (H&E) and luxol fast blue (LFB). Immunohistochemical assay was used to observe the types of inflammatory cells and adhesive molecule expression. Enzyme-linked immunosorbent assay (ELISA) was applied to detect content of the stem cell growth factor / mast cell growth factor (scf/MGF), interleukin-6 (IL-6) and IL-2. Immunofluorescence assay was applied to observe the expression of connexin43 (Cx43), glial fibrillary acidic protein (GFAP), connexin47 (Cx47) and the monoclonal antibody anti-adenomatous polyposis coli (APC) clone CC1. RESULTS: Compare with the animals in EAE model group, TGP treated rats (particularly those treated with high doses) showed a significant decrease in morbidity, clinical scores, CNS infiltration of inflammatory cells (including mononuclear macrophages, CD4+ and CD8+ T cells) and demyelination. The key adhesion molecule ICAM-1, cytokines IL-2、IL-6 and scf/MGF were significantly decreased with TGP treatment. Oppositely, PD-1, connexin47 in oligodendrocytes and connexin43 in astrocytes were elevated with TGP treatment. CONCLUSION: To sum up, TGP exhibited a significantly prevention and treatment effect on EAE rat model, and this improvement was achieved through a combination way composed of glial and inflammatory cells, junction proteins, various factors including adhesion factors, interleukins and scf/MGF.

Normobaric hyperoxia plays a neuroprotective role after cerebral ischemia by maintaining the redox homeostasis and the level of connexin43 in astrocytes.

INTRODUCTION: Acute cerebral ischemia is caused by an insufficient blood supply to brain tissue. Oxygen therapy, which is able to aid diffusion to reach the ischemic region, has been regarded as a possible treatment for cerebral ischemia. Recent animal and pilot clinical studies have reported that normobaric hyperoxia (NBO) showed neuroprotective effects if started soon after the onset of stroke. However, little is known about the role and mechanism of NBO treatment in astrocytes. Connexin43, one of the main gap junction proteins in astrocytes, is extremely sensitive to hypoxia and oxidative stress after cerebral ischemia. AIMS: In the present study, we used sutures to develop an ischemia/reperfusion model in rats to mimic clinical recanalization and investigated the role of connexin43 in NBO-treated stroke rats, as well as the underlying mechanism of NBO therapy. RESULTS: Normobaric hyperoxia treatment maintained the homeostasis of oxidoreductases: glutathione peroxidase 4 (GPX4) and NADPH oxidase 4 (two important oxidoreductases) and rescued the ischemia/reperfusion-induced downregulation of connexin43 protein in astrocytes. Furthermore, NBO treatment attenuated cerebral ischemia-induced cytochrome c release from mitochondria and was involved in neuroprotective effects by regulating the GPX4 and connexin43 pathway, using Ferrostatin-1 (an activator of GPX4) or Gap27 (an inhibitor of connexin43). CONCLUSIONS: This study showed the neuroprotective effects of NBO treatment by reducing oxidative stress and maintaining the level of connexin43 in astrocytes, which could be used for the clinical treatment of ischemic stroke.

Mu and Delta Opioid Receptor Targeting Reduces Connexin 43-Based Heterocellular Coupling during Neuropathic Pain.

Chronic neuropathic pain emerges from either central or peripheral lesions inducing spontaneous or amplified responses to non-noxious stimuli. Despite different pharmacological approaches to treat such a chronic disease, neuropathic pain still represents an unmet clinical need, due to long-term therapeutic regimens and severe side effects that limit application of currently available drugs. A critical phenomenon involved in central sensitization is the exchange of signalling molecules and cytokines, between glia and neurons, driving the chronicization process. Herein, using a chronic constriction injury (CCI) model of neuropathic pain, we evaluated the efficacy of the mu (M-) and delta (D-) opioid receptor (-OR) targeting agent LP2 in modulating connexin-based heterocellular coupling and cytokine levels. We found that long-term efficacy of LP2 is consequent to MOR-DOR targeting resulting in the reduction of CCI-induced astrocyte-to-microglia heterocellular coupling mediated by connexin 43. We also found that single targeting of DOR reduces TNF and IL-6 levels in the chronic phase of the disease, but the peripheral and central discharge as the primary source of excitotoxic stimulation in the spinal cord requires a simultaneous MOR-DOR targeting to reduce CCI-induced neuropathic pain.

Peptide5 Attenuates rtPA Related Brain Microvascular Endothelial Cells Reperfusion Injury via the Wnt/ß-Catenin Signalling Pathway.

AIMS: Brain vascular endothelial cell dysfunction after rtPA treatment is a significant factor associated with poor prognosis, suggesting that alleviation of rtPA-related endothelial cell injury may represent a potential beneficial strategy along with rtPA thrombolysis. BACKGROUND: Thrombolysis with recombinant tissue plasminogen activator (rtPA) is beneficial for acute ischemic stroke but may increase the risk of Hemorrhagic Transformation (HT), which is considered ischemia-reperfusion injury. The underlying reason may contribute to brain endothelial injury and dysfunction related to rtPA against ischemic stroke. As previous studies have demonstrated that transiently blocked Cx43 using peptide5 (Cx43 mimetic peptide) during retinal ischemia reduced vascular leakage, it is necessary to know whether this might help decrease side effect of rtPA within the therapeutic time window. OBJECTIVE: This study aims to investigate the effects of peptide5 on rtPA-related cell injury during hypoxia/reoxygenation (H/R) within the therapeutic time window. METHODS: In this study, we established a cell hypoxia/reoxygenation H/R model in cultured primary Rat Brain Microvascular Endothelial Cells (RBMECs) and evaluated endothelial cell death and permeability after rtPA treatment with or without transient peptide5. In addition, we also investigated the potential signaling pathway to explore the underlying mechanisms preliminarily. RESULTS: The results showed that peptide5 inhibited rtPA-related endothelial cell death and permeability. It also slightly increased tight junction (ZO-1, occluding, claudin-5) and ß-catenin mRNA expression, demonstrating that peptide5 might attenuate endothelial cell injury by regulating the Wnt/ ß-catenin pathway. The following bioinformatic exploration from the GEO dataset GSE37239 was also consistent with our findings. CONCLUSION: This study showed that the application of peptide5 maintained cell viability and permeability associated with rtPA treatment, revealing a possible pathway that could be exploited to limit rtPA-related endothelial cell injury during ischemic stroke. Furthermore, the altered Wnt/ß- catenin signaling pathway demonstrated that signaling pathways associated with Cx43 might have potential applications in the future. This study may provide a new way to attenuate HT and assist the application of rtPA in ischemic stroke.

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

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.

Regulación de la plasticidad celular y senescencia encondrocitos articulares: conexina 43 como diana terapéutica para el tratamiento de la artrosis / A novel therapeutic target for osteoarthritis: control of cellular plasticity and senescence using connexin43

Introducción: La artrosis (OA) es una enfermedad musculo esquelética degenerativa que afecta aproximadamente al13% de la población occidental. A día de hoy no existe un tratamiento eficaz que evite el progreso de la misma o facilite la regeneración del cartílago articular. La conexina43 (Cx43) es una proteína transmembrana que se encuentra en niveles elevados en el cartílago y en la membrana sinovial de pacientes con OA. Esta proteína forma canales que permiten el intercambio de moléculas e iones entre dos células en contacto o entre la célula y su entorno, denominados uniones co‐municantes (UCs) y hemicanales, respectivamente. En este estudio se investigó la función de la Cx43 y de las UCs en la degradación del cartílago articular de pacientes con OA. Material y métodos: Se han aislado condrocitos primarios del cartílago de donantes OA y sanos. Se evaluaron los niveles proteicos mediante Western blot, inmunofluorescencia y citometría de flujo. La expresión génica se ha evaluado mediante RT‐qPCR, mientras que la comunicación celular se estudió mediante el ensayo scrape loading/dye transfer. La senescencia celular se evaluó midiendo la actividad de la β‐galactosidasa mediante citometría celular o microscopía. Resultados: Los resultados obtenidos indican que la sobre actividad de la Cx43 y de la comunicación intercelular a través de UCs detectadas en OA están implicadas con el progreso de la enfermedad al activar procesos de desdiferenciación celular hacia un estado inmaduro y senescencia celular. Utilizando condrocitos en cultivo aislados del cartílago de donantes con OA hemos demostrado que el incremento de la Cx43 activa factores implicados en la transición epitelio‐me sénquima (TEM), como el factor de transcripción Twist‐1. El incremento en el número de células desdiferenciadas y con altos índices de proliferación celular desencadena en senescencia celular vía p53/p16INK4a, activando el fenotipo secretor asociado a senescencia (SASP, del inglés Senescence-Associated Secretory Phenotype) que incluye la síntesis y liberación de factores inflamatorios como la interleuquina 6 (IL‐6). La disminución de los niveles de la Cx43 utilizando pequeñas moléculas como la oleuropeína o técnicas de edición genética como CRISPR/Cas9 revirtió el proceso dando lugar a re‐diferenciación celular, mejorando el fenotipo celular con incremento en proteínas implicadas en formación del tejido y diminuyendo la síntesis de MMPs y del componente inflamatorio y senescencia. Conclusiones: La disminución de la Cx43 en condrocitos artrósicos restaura regeneración tisular, por activación de re‐diferenciación celular y disminución de senescencia. Estos resultados corroboran el uso de la Cx43 como una diana terapéutica eficaz para restaurar regeneración del cartílago en pacientes con OA y evitar la progresión de la enfermedad

Introduction: Osteoarthritis (OA) is a degenerative musculoskeletal disease, which affects approximately the 13% of western population. Nowadays, there is no effective treatment for OA to avoid disease progression or to promote cartilage regeneration. Connexin43 (Cx43) is a transmembrane protein increased in cartilage and synovium from OA patients.Cx43 forms membrane channels that allow the exchange of molecules and ions between two adjacent cells through gapjunctions (GJs), or between a cell and its environment through hemichannels. In this study we investigated the involvement of Cx43 and GJ intercellular communication in the degradation of articular cartilage in chondrocytes from patientswith OA. Material and methods:Primary chondrocytes were obtained from cartilage from OA and healthy donors. Protein levelswere evaluated by western‐blot, immunofluorescence and flow cytometry. RNA expression was evaluated by RT‐qPCR.A scrape loading/dye transfer assay was used to evaluate cell communication. Cell senescence was analysed by flowcytometry or by light microscopy using β‐galactosidase assay.Results:Cx43 and GJs overactivities were correlated with the progression of OA, by promoting chronic cell dedifferen‐tiation and senescence in vitroassays. We found that Cx43 over expression activates factors involved in epithelial‐to‐me‐senchymal transition, such as Twist‐1. Increased levels of dedifferentiated cells, with high rates of cell proliferation, led to cell senescence via p53/p16INK4a, activating the senescence‐associated secretory phenotype (SASP) and promoting the synthesis and liberation of inflammatory factors, including the interleukin‐6 (IL‐6). Cx43 down regulation by using small molecules, such as oleuropein, or by genetic edition with CRISPR technology, led to the chondrocyte redifferentiation and an improved phenotype, with increased synthesis of extracellular matrix proteins such as Col2A1 and down‐regulating the synthesis of MMPs, inflammation and senescence. Conclusions: Down regulation of Cx43 in OA chondrocytes restores regeneration by activating chondrocyte re‐differentiation and decreasing cellular senescence. These results corroborate the use of Cx43 as an effective therapeutic target in order to restore cartilage regeneration and avoid OA progression

Involvement of Connexin Hemichannels in the Inflammatory Response of Chronic Diseases.

Over the last decade it has become evident that under normal conditions connexin hemichannels are either not expressed (e.g., skeletal muscle) or are expressed in very low numbers with low open probability in various mammalian tissues (e.g., liver and central nervous system (CNS)).[...].

TAT-Gap19 and Carbenoxolone Alleviate Liver Fibrosis in Mice.

Although a plethora of signaling pathways are known to drive the activation of hepatic stellate cells in liver fibrosis, the involvement of connexin-based communication in this process remains elusive. Connexin43 expression is enhanced in activated hepatic stellate cells and constitutes the molecular building stone of hemichannels and gap junctions. While gap junctions support intercellular communication, and hence the maintenance of liver homeostasis, hemichannels provide a circuit for extracellular communication and are typically opened by pathological stimuli, such as oxidative stress and inflammation. The present study was set up to investigate the effects of inhibition of connexin43-based hemichannels and gap junctions on liver fibrosis in mice. Liver fibrosis was induced by administration of thioacetamide to Balb/c mice for eight weeks. Thereafter, mice were treated for two weeks with TAT-Gap19, a specific connexin43 hemichannel inhibitor, or carbenoxolone, a general hemichannel and gap junction inhibitor. Subsequently, histopathological analysis was performed and markers of hepatic damage and functionality, oxidative stress, hepatic stellate cell activation and inflammation were evaluated. Connexin43 hemichannel specificity of TAT-Gap19 was confirmed in vitro by fluorescence recovery after photobleaching analysis and the measurement of extracellular release of adenosine-5'-triphosphate. Upon administration to animals, both TAT-Gap19 and carbenoxolone lowered the degree of liver fibrosis accompanied by superoxide dismutase overactivation and reduced production of inflammatory proteins, respectively. These results support a role of connexin-based signaling in the resolution of liver fibrosis, and simultaneously demonstrate the therapeutic potential of TAT-Gap19 and carbenoxolone in the treatment of this type of chronic liver disease.

Hyaluronic acid coated albumin nanoparticles for targeted peptide delivery in the treatment of retinal ischaemia.

Recent studies have shown that Connexin43 mimetic peptide (Cx43 MP) can prevent secondary damage following retinal ischaemic and inflammatory disorders by blocking uncontrolled Cx43 hemichannel opening. However, limitations in peptide stability and the presence of various intraocular barriers limit efficient retinal delivery in the clinical setting. The present study aimed to achieve targeted and sustained peptide delivery to the retina by encapsulating Cx43 MP into hyaluronic acid (HA) coated albumin nanoparticles (NPs). Intraocular biodistribution, particle retention, retinal targeting, and therapeutic efficacy of intravitreally injected NPs encapsulating Cx43 MP were evaluated in a rat model of retinal ischaemia-reperfusion injury. NPs rapidly diffused through the vitreous and specifically targeted CD44-expressing retinal cells. NPs remained at the target site for extended periods enabling sustained peptide release and thus prolonged therapeutic action. Compared to free Cx43 MP, Cx43 MP loaded NPs enabled enhanced therapeutic efficacy preventing thinning of retinal layers and disruption of retinal blood vessels. Immunohistochemical results confirm that Cx43 MP loaded NPs efficiently reduced Cx43 expression, thereby suppressing ongoing inflammation and preventing the loss of retinal ganglion cells. Overall, HA coated NPs could have great potential as a peptide delivery platform in the treatment of chronic retinal degenerative and inflammatory disorders.

A Multicenter Randomized Controlled Trial Evaluating a Cx43-Mimetic Peptide in Cutaneous Scarring.

The transmembrane protein Cx43 has key roles in fibrogenic processes including inflammatory signaling and extracellular matrix composition. aCT1 is a Cx43 mimetic peptide that in preclinical studies accelerated wound closure, decreased inflammation and granulation tissue area, and normalized mechanical properties after cutaneous injury. We evaluated the efficacy and safety of aCT1 in the reduction of scar formation in human incisional wounds. In a prospective, multicenter, within-participant controlled trial, patients with bilateral incisional wounds (≥10 mm) after laparoscopic surgery were randomized to receive acute treatment (immediately after wounding and 24 hours later) with an aCT1 gel formulation plus conventional standard of care protocols, involving moisture-retentive occlusive dressing, or standard of care alone. The primary efficacy endpoint was average scarring score using visual analog scales evaluating incision appearance and healing progress over 9 months. There was no significant difference in scar appearance between aCT1- or control-treated incisions after 1 month. At month 9, aCT1-treated incisions showed a 47% improvement in scar scores over controls (Vancouver Scar Scale; P = 0.0045), a significantly higher Global Assessment Scale score (P = 0.0009), and improvements in scar pigmentation, thickness, surface roughness, and mechanical suppleness. Adverse events were similar in both groups. aCT1 has potential to improve scarring outcome after surgery.

Connexin43 carboxyl-terminal peptides reduce scar progenitor and promote regenerative healing following skin wounding.

AIM: Gap-junctional connexin43 (Cx43) has roles in multiple aspects of skin wound healing - including scarring. The aim here was to study the effects of a cell-permeant peptide from the Cx43 carboxyl-terminus (CT) on scarring and regeneration following cutaneous injury. MATERIALS & METHODS: The effects of Cx43 CT peptide were studied in mouse and pig models of cutaneous injury. The parameters assessed included neutrophil density, wound closure, granulation, regeneration and skin tensile properties. RESULTS: Cx43 CT-peptide prompted decreases in area of scar progenitor tissue and promoted restoration of dermal histoarchitecture and mechanical strength following wounding of skin. These changes in healing were preceded by peptide-induced reduction in inflammatory neutrophil infiltration and alterations in the organization of epidermal Cx43, including increased connexon aggregation. CONCLUSION: Cx43 CT peptide promotes regenerative healing of cutaneous wounds and may have applications in tissues other than skin, including heart, cornea and spinal cord.

[Connexin 43 gene in the in vivo treatment of cerebral glioma in C6 rats].

OBJECTIVE: To study the role of connexin gene (Cx43) in the suppression of C6 glioma. METHODS: Cx43 gene depleted parental C6 rats (control group) and C6 cells transfected with Cx43 cDNA (transfection group) were implanted into the right caudate nucleus of SD rats. Rats bearing cerebral C6 gliomas were treated with Cx43 cDNA (treatment group) with another group treated with empty vector (empty vector group) serving as control. The general manifestation, survival time, MRI dynamic scanning and histopathological changes in all rats were observed. Cx43 mRNA and its protein were examined by in situ hybridization and immunohistochemistry. Proliferation activity was monitored by the average number of AgNOR stain. Cell apoptosis was examined by the Tolt-mediated x-duTP nick end labeling (TUNEL) method. RESULTS: All rats in the control and empty vector groups died of cerebral glioma within 3 weeks after implantation of C6 cells. Six in the transfection group and 8 in the treatment group were alive beyond 120 days with complete disappearance of the tumor foci, except one in this group having some residue of tumor. In the glioma of transfection and treatment groups, Cx43 gene expression was up-regulated, proliferation activity reduced while the apoptotic cells did not increase. CONCLUSION: The development of glioma is greatly suppressed by the transfection of Cx43 gene, which has great effectiveness in rats bearing cerebral malignant gliomas. This could become a target of choice in the gene treatment of malignant gliomas.