scholarly journals Hyperglycemia downregulates Connexin36 in pancreatic islets via the upregulation of ICER-1/ICER-1γ

2013 ◽  
Vol 51 (1) ◽  
pp. 49-58 ◽  
Author(s):  
Jacques-Antoine Haefliger ◽  
Françoise Rohner-Jeanrenaud ◽  
Dorothée Caille ◽  
Anne Charollais ◽  
Paolo Meda ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Chronic Exposure ◽  
Prolonged Exposure ◽  
Mrna Levels ◽  
Adult Rats ◽  
Junction Protein ◽  
And Function

Channels formed by the gap junction protein Connexin36 (CX36) contribute to the proper control of insulin secretion. We previously demonstrated that chronic exposure to glucose decreases Cx36 levels in insulin-secreting cells in vitro. Here, we investigated whether hyperglycemia also regulates Cx36 in vivo. Using a model of continuous glucose infusion in adult rats, we showed that prolonged (24–48 h) hyperglycemia reduced the Cx36 gene Gjd2 mRNA levels in pancreatic islets. Accordingly, prolonged exposure to high glucose concentrations also reduced the expression and function of Cx36 in the rat insulin-producing INS-1E cell line. The glucose effect was blocked after inhibition of the cAMP/PKA pathway and was associated with an overexpression of the inducible cAMP early repressor ICER-1/ICER-1γ, which binds to a functional cAMP-response element in the promoter of the Cx36 gene Gjd2. The involvement of this repressor was further demonstrated using an antisense strategy of ICER-1 inhibition, which prevented glucose-induced downregulation of Cx36. The data indicate that chronic exposure to glucose alters the in vivo expression of Cx36 by the insulin-producing β-cells through ICER-1/ICER-1γ overexpression. This mechanism may contribute to the reduced glucose sensitivity and altered insulin secretion, which contribute to the pathophysiology of diabetes.

Mice pancreatic islets protection from oxidative stress induced by single-walled carbon nanotubes through naringin

2018 ◽  
Vol 37 (12) ◽  
pp. 1268-1281 ◽  
Author(s):  
A Ahangarpour ◽  
S Alboghobeish ◽  
AA Oroojan ◽  
MA Dehghani
Keyword(s):  
Oxidative Stress ◽  
Carbon Nanotubes ◽  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Mtt Assay ◽  
Antioxidant Defense System ◽  
Protective Effects ◽  
Cell Functions

The growing use of carbon nanotubes (CNTs) emphasizes the importance of its potential toxic effects on the human health. Previous studies proved that CNTs caused oxidative stress and decreased cell viability. On the other hand, reactive oxygen species (ROS) and oxidative stress impaired β-cell functions and reduced the insulin secretion. However, there is not any study on the effects of CNTs on islets and β-cells. Therefore, the present study aimed to evaluate the effects of single-walled CNTs (SWCNTs) on oxidative stress in islets in addition to the protective effects of naringin (NRG) as an antioxidant . We examined the effects of SWCNTs and naringin on islets by 3,4 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) assay; measurement of insulin secretion, ROS, and malondialdehyde (MDA); activities of superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) peroxidase (GSH-Px); and content of GSH and mitochondrial membrane potential (MMP). The MTT assay demonstrated that decreased viability of islets cells was dose-dependent with exposure to SWCNTs. Further studies revealed that SWCNTs decreased insulin secretion and MMP, induced the formation of ROS, increased the level of MDA, and decreased the activities of SOD, GSH-Px, and CAT and content of GSH. Furthermore, the pretreatment of islets with naringin significantly reverted back these changes. These findings revealed that SWCNTs might induce the oxidative stress to pancreatic islets, causing the occurrence of diabetes, and the protective effects of naringin that was mediated by augmentation of the antioxidant defense system of islets. Our research indicated the necessity for further in vivo and in vitro researches on the effects of SWCNTs and naringin on diabetes.

scholarly journals Connexin 43 confers chemoresistance through activating PI3K

Oncogenesis ◽  
2022 ◽  
Vol 11 (1) ◽  
Author(s):  
Kevin J. Pridham ◽  
Farah Shah ◽  
Kasen R. Hutchings ◽  
Kevin L. Sheng ◽  
Sujuan Guo ◽  
...  
Keyword(s):  
Poor Prognosis ◽  
Connexin 43 ◽  
Therapeutic Potential ◽  
Mrna Levels ◽  
Phosphatidylinositol 3 Kinase ◽  
Junction Protein ◽  
Gap Junction Protein ◽  
Cx43 Mrna

AbstractCircumventing chemoresistance is crucial for effectively treating cancer including glioblastoma, a lethal brain cancer. The gap junction protein connexin 43 (Cx43) renders glioblastoma resistant to chemotherapy; however, targeting Cx43 is difficult because mechanisms underlying Cx43-mediated chemoresistance remain elusive. Here we report that Cx43, but not other connexins, is highly expressed in a subpopulation of glioblastoma and Cx43 mRNA levels strongly correlate with poor prognosis and chemoresistance in this population, making Cx43 the prime therapeutic target among all connexins. Depleting Cx43 or treating cells with αCT1–a Cx43 peptide inhibitor that sensitizes glioblastoma to the chemotherapy temozolomide–inactivates phosphatidylinositol-3 kinase (PI3K), whereas overexpression of Cx43 activates this signaling. Moreover, αCT1-induced chemo-sensitization is counteracted by a PI3K active mutant. Further research reveals that αCT1 inactivates PI3K without blocking the release of PI3K-activating molecules from membrane channels and that Cx43 selectively binds to the PI3K catalytic subunit β (PIK3CB, also called PI3Kβ or p110β), suggesting that Cx43 activates PIK3CB/p110β independent of its channel functions. To explore the therapeutic potential of simultaneously targeting Cx43 and PIK3CB/p110β, αCT1 is combined with TGX-221 or GSK2636771, two PIK3CB/p110β-selective inhibitors. These two different treatments synergistically inactivate PI3K and sensitize glioblastoma cells to temozolomide in vitro and in vivo. Our study has revealed novel mechanistic insights into Cx43/PI3K-mediated temozolomide resistance in glioblastoma and demonstrated that targeting Cx43 and PIK3CB/p110β together is an effective therapeutic approach for overcoming chemoresistance.

scholarly journals Chronic Exposure to High Doses of Bisphenol A Exhibits Significant Atrial Proarrhythmic Effects in Healthy Adult Rats

2021 ◽  
Vol 31 (3) ◽  
pp. 587-595
Author(s):  
Vasile Bogdan HALATIU ◽  
◽  
Alkora Ioana BALAN ◽  
Dan Alexandru COZAC ◽  
Remus BOBARNAC ◽  
...  
Keyword(s):  
Bisphenol A ◽  
Chronic Exposure ◽  
Atrial Pacing ◽  
Autonomic Tone ◽  
Adult Rats ◽  
Female Wistar Rats ◽  
High Doses ◽  
Premature Beats

Objectives: We aimed to evaluate the effects of chronic exposure to bisphenol A (BPA) on atrial fibrillation (AF) occurrence in rats. Methods: Twenty-two healthy female Wistar rats were randomized into three groups: Control (no BPA; n=7), BPA (exposed to usual BPA doses; 50 μg/kg/day, 9 weeks; n=7), and hBPA (exposed to high BPA doses; 25 mg/kg/day, 9 weeks; n=8). 24-h ECG monitoring was performed using radiotelemetry ECG devices prior to and after transesophageal atrial pacing. Spontaneous and pacing-induced atrial arrhythmias, autonomic tone, and in vivo an in vitro atrial arrhythmogenicity-related parameters were evaluated. Results: All studied parameters were similar between Control and BPA (all p>0.05). However, compared to Control, hBPA presented more atrial premature beats both at baseline (p=0.04) and after pacing (p=0.03), more AF episodes (p<0.001) and of longer duration (p=0.02) following transesophageal stimulation, and significantly higher vagal tone (all p<0.05). Conclusions: Chronic exposure to high, but not usual BPA doses induced significant atrial proarrhythmic effects in healthy rats, and this may be at least partially due to BPA-induced vagal hyperactivation. Exposure to high BPA doses, such as that occurring in plastics industry workers, could favor AF occurrence even in the absence of underlying cardiovascular disease.

scholarly journals Sitagliptin and the Blood-Retina Barrier: Effects on Retinal Endothelial Cells Manifested Only after Prolonged Exposure

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Anja Jäckle ◽  
Focke Ziemssen ◽  
Eva-Maria Kuhn ◽  
Jürgen Kampmeier ◽  
Gerhard K. Lang ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Endothelial Cells ◽  
Prolonged Exposure ◽  
Diabetic Patients ◽  
Barrier Dysfunction ◽  
Fibronectin Receptor ◽  
Retinal Endothelial Cells ◽  
Junction Protein

Inhibitors of dipeptidyl peptidase-4 (DPP-4) are widely used to treat diabetes mellitus, but data concerning their effects on the barrier stability of retinal endothelial cells (REC) in vivo and in vitro are inconsistent. Therefore, we studied whether the barrier properties of immortalized endothelial cells of the bovine retina (iBREC) were affected by the inhibitors of DPP-4 sitagliptin (10-1000 nM) and diprotin A (1-25 μM). Their effects were also investigated in the presence of VEGF-A165 because diabetic patients often develop macular edema caused by VEGF-A-induced permeability of REC. To detect even transient or subtle changes of paracellular and transcellular flow as well as adhesion of the cells to the extracellular matrix, we continuously monitored the cell index (CI) of confluent iBREC grown on gold electrodes. Initially, the CI remained stable but started to decline significantly and persistently at 40 h or 55 h after addition of sitagliptin or diprotin A, respectively. Both inhibitors did not modulate, prevent, or revert the persistent VEGF-A165-induced reduction of the CI. Interestingly, sitagliptin and diprotin A increased the expression of the tight-junction protein claudin-1 which is an important component of a functional barrier formed by iBREC. In contrast, expressions of CD29—a subunit of the fibronectin receptor—or of the tetraspanin CD9 were lower after extended treatment with the DPP-4 inhibitors; less of the CD9 was seen at the plasma membrane after prolonged exposure to sitagliptin. Because both associated proteins are important for adhesion of iBREC to the extracellular matrix, the observed low CI might be caused by weakened attachment of the cells. From our results, we conclude that extended inhibition of DPP-4 destabilizes the barrier formed by microvascular REC and that DPP-4 inhibitors like sitagliptin do not counteract or enhance a VEGF-A165-induced barrier dysfunction as frequently observed in DME.

scholarly journals ECM-enriched alginate hydrogels for bioartificial pancreas: an ideal niche to improve insulin secretion and diabetic glucose profile

2019 ◽  
Vol 17 (4) ◽  
pp. 228080001984892 ◽  
Author(s):  
Joana Crisóstomo ◽  
Ana M Pereira ◽  
Sílvia J Bidarra ◽  
Ana C Gonçalves ◽  
Pedro L Granja ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Beta Cells ◽  
Diabetic Patients ◽  
Bioartificial Pancreas ◽  
Multicellular Spheroids ◽  
Rgd Peptides ◽  
Alginate Hydrogels ◽  
And Function

Introduction: The success of a bioartificial pancreas crucially depends on ameliorating encapsulated beta cells survival and function. By mimicking the cellular in vivo niche, the aim of this study was to develop a novel model for beta cells encapsulation capable of establishing an appropriate microenvironment that supports interactions between cells and extracellular matrix (ECM) components. Methods: ECM components (Arg-Gly-Asp, abbreviated as RGD) were chemically incorporated in alginate hydrogels (alginate-RGD). After encapsulation, INS-1E beta cells outcome was analyzed in vitro and after their implantation in an animal model of diabetes. Results: Our alginate-RGD model demonstrated to be a good in vitro niche for supporting beta cells viability, proliferation, and activity, namely by improving the key feature of insulin secretion. RGD peptides promoted cell–matrix interactions, enhanced endogenous ECM components expression, and favored the assembly of individual cells into multicellular spheroids, an essential configuration for proper beta cell functioning. In vivo, our pivotal model for diabetes treatment exhibited an improved glycemic profile of type 2 diabetic rats, where insulin secreted from encapsulated cells was more efficiently used. Conclusions: We were able to successfully introduce a novel valuable function in an old ally in biomedical applications, the alginate. The proposed alginate-RGD model stands out as a promising approach to improve beta cells survival and function, increasing the success of this therapeutic strategy, which might greatly improve the quality of life of an increasing number of diabetic patients worldwide.

Hyperoxic stress elevates p52(PAI-1) mRNA abundance in cultured cells and adult rat pulmonary tissue

1993 ◽  
Vol 265 (2) ◽  
pp. L121-L126
Author(s):  
J. E. White ◽  
M. P. Ryan ◽  
M. F. Tsan ◽  
P. J. Higgins
Keyword(s):  
Cultured Cells ◽  
Rat Kidney ◽  
Mrna Abundance ◽  
In Vivo Studies ◽  
Mrna Levels ◽  
Adult Rats ◽  
Pulmonary Tissue ◽  
Pai 1

Hyperoxic stress alters expression of genes involved in extracellular matrix (ECM) remodeling. To identify novel ECM-associated gene products positively regulated by hyperoxia, rat kidney cells were exposed to 95% O2, and the complement of [35S]methionine-labeled, saponin-resistant, ECM-associated proteins was compared with normoxic controls. O2-stressed cells accumulated significantly greater ECM levels (approximately 3- to 4-fold that of control cells) of a 52-kDa glycoprotein (p52), recently identified as the matrix form of plasminogen activator inhibitor type 1 (PAI-1) (P.J. Higgins, P. Chaudhari, and M.P. Ryan. Biochem. J. 273: 651-658, 1991; P. J. Higgins, M. P. Ryan, R. Zeheb, T. D. Gelehrter, P. Chaudhari. J. Cell. Physiol. 143:321-329, 1990), which peaked at 48 h of exposure. Hyperoxia-associated increases in ECM p52(PAI-1) content reflected parallel elevations in p52(PAI-1) mRNA abundance. Similar results were obtained using secondary cultures of rat pulmonary fibroblasts. This 48-h period of maximal hyperoxia-induced p52(PAI-1) expression in vitro was used to design subsequent in vivo studies. Adult rats were exposed to 99% O2 for 24–50 h, and RNA was extracted from the pulmonary tissue of stressed and control animals. A 5- to 8-fold and 6- to 15-fold increase in lung p52(PAI-1) mRNA content was evident in hyperoxia-treated rats at 24 and 50 h, respectively. All of this increase occurred in the defined 3.2-kb species of rat p52(PAI-1) mRNA. Actin mRNA levels increased three- to sevenfold as a function of hyperoxic stress, whereas catalase and glyceraldehyde-3-phosphate dehydrogenase mRNA abundance was unchanged.(ABSTRACT TRUNCATED AT 250 WORDS)

EFFECTS OF GASTRIN ON THE RELEASE OF INSULIN IN VITRO

1969 ◽  
Vol 43 (3) ◽  
pp. 371-375 ◽  
Author(s):  
A. LERNMARK ◽  
B. HELLMAN ◽  
H. G. COORE
Keyword(s):  
Insulin Secretion ◽  
Pancreatic Islets ◽  
Glucose Concentration ◽  
Gastrointestinal Hormones ◽  
Mouse Pancreas ◽  
Low Glucose ◽  
Isolated Pancreas ◽  
Stimulation Of

SUMMARY Several investigations in vivo and in vitro have shown that gastrointestinal hormones stimulate insulin secretion. Whether gastrin also has such an effect was tested both with the isolated mouse pancreas and with micro-dissected pancreatic islets from obese-hyperglycaemic mice. A fairly low concentration of human synthetic gastrin I (0·15 μg./ml.) was found to inhibit the stimulation of insulin release normally obtained with increasing glucose concentrations. However, when a higher concentration of gastrin was tested on the isolated pancreas in the presence of a low glucose concentration there was a stimulation of insulin secretion.

Lack of long-term β-cell glucotoxicity in vitro in pancreatic islets isolated from two mouse strains (C57BL/6J; C57BL/KsJ) with different sensitivities of the β-cells to hyperglycaemia in vivo

1993 ◽  
Vol 136 (2) ◽  
pp. 289-296 ◽  
Author(s):  
C. Svensson ◽  
S. Sandler ◽  
C. Hellerström
Keyword(s):  
Insulin Secretion ◽  
Glucose Metabolism ◽  
Pancreatic Islets ◽  
Insulin Release ◽  
Insulin Biosynthesis ◽  
Mouse Strains ◽  
Β Cells ◽  
Insulin Mrna

ABSTRACT Previous studies have shown that 4 weeks after syngeneic transplantation of a suboptimal number of islets into either C57BL/6J (BL/6J) or C57BL/KsJ (BL/KsJ) diabetic mice there is an impaired insulin secretion by the perfused grafts. After normalization of the blood glucose level with a second islet graft, the BL/6J strain showed restored insulin secretion whilst that of the BL/KsJ strain remained impaired. The aim of the present work was to study the effects of glucose on the in-vitro function of islet β-cells from these two mouse strains, with different sensitivities of their β-cells to glucose in vivo. Isolated pancreatic islets from each strain were kept for 1 week in tissue culture at 5·6, 11, 28 or 56 mmol glucose/l and were subsequently analysed with regard to insulin release, (pro)-insulin and total protein biosynthesis, insulin, DNA and insulin mRNA contents and glucose metabolism. Islets from both strains cultured at 28 or 56 mmol glucose/l showed an increased accumulation of insulin in the culture medium and an enhanced glucose-stimulated insulin release compared with corresponding control islets cultured at 11 mmol glucose/l. After culture at either 5·6 or 56 mmol/l, rates of (pro)insulin biosynthesis were decreased in BL/KsJ islets in short-term incubations at 17 mmol glucose/l, whereas islets cultured at 56 mmol glucose/l showed a marked increase at 1·7 mmol glucose/l. In BL/6J islets, the (pro)insulin biosynthesis rates were similar to those of the BL/KsJ islets with one exception, namely that no decrease was observed at 56 mmol glucose/l. Islets of both strains showed a decreased insulin content after culture with 56 mmol glucose/l. Insulin mRNA content was increased in islets cultured in 28 or 56 mmol glucose/l from both mouse strains. Glucose metabolism showed no differences in the rates of glucose oxidation, however, in islets cultured in 56 mmol glucose/l the utilization of glucose was increased in both BL/6J and BL/KsJ animals. There were no differences in DNA content in islets cultured at different glucose concentrations, suggesting no enhancement of cell death. The present study indicates that, irrespective of genetic background, murine β-cells can adapt to very high glucose concentrations in vitro without any obvious signs of so-called glucotoxicity. Previously observed signs of glucotoxicity in vivo in BL/KsJ islets appear not to be related only to glucose but rather to an additional factor in the diabetic environment. Journal of Endocrinology (1993) 136, 289–296

scholarly journals Delayed Puberty in Spontaneously Hypertensive Rats Involves a Primary Ovarian Failure Independent of the Hypothalamic KiSS-1/GPR54/GnRH System

Endocrinology ◽  
2009 ◽  
Vol 150 (6) ◽  
pp. 2889-2897 ◽  
Author(s):  
L. Pinilla ◽  
J. M. Castellano ◽  
M. Romero ◽  
M. Tena-Sempere ◽  
F. Gaytán ◽  
...  
Keyword(s):  
Ovarian Function ◽  
Follicular Development ◽  
Experimental Models ◽  
Gnrh Receptor ◽  
Delayed Puberty ◽  
Mrna Levels ◽  
Spontaneously Hypertensive ◽  
And Function

Spontaneously hypertensive (SH) rats, extensively used as experimental models of essential human hypertension, display important alterations in the neuroendocrine reproductive axis, which manifest as markedly delayed puberty onset in females but whose basis remains largely unknown. We analyze herein in female SH rats: 1) possible alterations in the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems, 2) the integrity of feedback mechanisms governing the hypothalamic-pituitary-ovarian axis, and 3) the control of ovarian function by gonadotropins. Our data demonstrate that, despite overtly delayed puberty, no significant decrease in hypothalamic KiSS-1, GPR54, or GnRH mRNA levels was detected in this strain. Likewise, in vivo gonadotropin responses to ovariectomy and systemic kisspeptin-10 or GnRH administration, as well as in vitro gonadotropin responses to GnRH, were fully preserved in SH rats. Moreover, circulating LH levels were grossly conserved during prepubertal maturation, whereas FSH levels were even enhanced from d 20 postpartum onwards. In striking contrast, ovarian weight and hormone (progesterone and testosterone) responses to human chorionic gonadotropin (CG) in vitro were profoundly decreased in SH rats, with impaired follicular development and delayed ovulation at puberty. Such reduced hormonal responses to human CG could not be attributed to changes in LH/CG or FSH-receptor mRNA expression but might be linked to blunted P450scc, 3β-hydroxy steroid dehydrogenase, and aromatase mRNA levels in ovaries from SH rats. In conclusion, our results indicate that the expression and function of KiSS-1/GPR54 and GnRH/GnRH-receptor systems is normal in SH rats, whereas ovarian development, steroidogenesis, and responsiveness to gonadotropins are strongly compromised.

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