During the development of type 1 diabetes, interferons (IFN) are elaborated from islet-infiltrati... more During the development of type 1 diabetes, interferons (IFN) are elaborated from islet-infiltrating immune cells and/or from virally infected β-cells. They act via specific receptors to increase, acutely, the phosphorylation of the transcription factors STAT1 and 2. However, the longer-term impacts of chronic IFN stimulation are poorly understood and were investigated in the current study. Human EndoC-βH1 cells were treated with IFNα, IFNγ or IFNλ either acutely (<2 h) or chronically (≥24 h) and STAT phosphorylation, expression and activity were assessed by Western blotting and transcriptional reporter assays. Exposure of β-cells to IFNα or IFNλ induced a swift increase in the phosphorylation of both STAT1 and STAT2, whereas IFNγ increased only pSTAT1. Over more extended periods (≥24 h), STAT phosphorylation declined but STAT1 and STAT2 expression were enhanced in a sustained manner. All IFNs stimulated ISRE transcriptional activity (but with different time courses), whereas GAS ...
Additional file 1: Supplementary figure 1. The effect of exposing rodent β-cells to LC-SFA, incre... more Additional file 1: Supplementary figure 1. The effect of exposing rodent β-cells to LC-SFA, increasing in carbon chain length, at a concentration of 250µM for 24h, on viability.
Additional file 2: Raw datasets. Raw data (Figures 1–4, sup. fig.1) on which the conclusions of t... more Additional file 2: Raw datasets. Raw data (Figures 1–4, sup. fig.1) on which the conclusions of the manuscript rely.
In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islet... more In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islets. This milieu is generated via the enhanced secretion of proinflammatory cytokines and by the loss of anti-inflammatory molecules such as IL-4 and IL-13. While the actions of proinflammatory cytokines have been well-studied in beta cells, the effects of their anti-inflammatory counterparts have received relatively little attention and we have addressed this. Clonal beta cells, isolated human islets and pancreas sections from control individuals and those with type 1 diabetes were employed. Gene expression was measured using targeted gene arrays and by quantitative RT-PCR. Protein expression was monitored in cell extracts by western blotting and in tissue sections by immunocytochemistry. Target proteins were knocked down selectively with interference RNA. Cytoprotection achieved with IL-4 and IL-13 is mediated by the early activation of signal transducer and activator of transcription 6 ...
Background. Cameroon this last decade continues to present a low contribution ofM. africanumandM.... more Background. Cameroon this last decade continues to present a low contribution ofM. africanumandM. bovisin human tuberculosis (TB), whileM. boviswas prevalent in cattle but all these pieces of information only concerned West and Center regions.Methods. We carried out the first study in Adamaoua, one of the most rearing regions of Cameroon, on the genetic structure and drug susceptibility of the MTBC strains isolated from newly diagnosed sputum smear-positive patients aged 15 years and above. For that purpose, spoligotyping, a modified 15 standard MIRU/VNTR loci typing, and the proportion method were used.Results. Four hundred and thirty-seven MTBC isolates were analyzed by spoligotyping. Of these, 423 were identified asM. tuberculosis, within the Cameroon family being dominant with 278 (65.7%) isolates; twelve (2.75%) isolates were classified asM. africanumand two asM. bovis. MIRU/VNTR typing of the most prevalent sublineage (SIT 61) suggested that this lineage is not a unique clone ...
The generation of a human pancreatic beta cell line which reproduces the responses seen in primar... more The generation of a human pancreatic beta cell line which reproduces the responses seen in primary beta cells, but is amenable to propagation in culture, has long been an important goal in diabetes research. This is particularly true for studies focussing on the role of enteroviral infection as a potential cause of beta-cell autoimmunity in type 1 diabetes. In the present work we made use of a clonal beta cell line (1.1B4) available from the European Collection of Authenticated Cell Cultures, which had been generated by the fusion of primary human beta-cells with a pancreatic ductal carcinoma cell, PANC-1. Our goal was to study the factors allowing the development and persistence of a chronic enteroviral infection in human beta-cells. Since PANC-1 cells have been reported to support persistent enteroviral infection, the hybrid 1.1B4 cells appeared to offer an ideal vehicle for our studies. In support of this, infection of the cells with a Coxsackie virus isolated originally from the...
Obesity is a major risk factor for type 2 diabetes (T2D) although the causal links remain unclear... more Obesity is a major risk factor for type 2 diabetes (T2D) although the causal links remain unclear. A feature shared by both conditions however is systemic inflammation and raised levels of circulating fatty acids (FFA). It is widely believed that in obese individuals genetically prone to T2D, elevated levels of plasma FFA may contribute towards the death and dysfunction of insulin-producing pancreatic β-cells in a process of (gluco)lipotoxicity. In support of this, in vitro studies have shown consistently that long-chain saturated fatty acids (LC-SFA) are toxic to rodent β-cells during chronic exposure (>24h). Conversely, shorter chain SFA and unsaturated species are well tolerated, suggesting that toxicity is dependent on carbon chain length and/or double bond configuration. Despite the wealth of evidence implicating lipotoxicity as a means of β-cell death in rodents, the evidence that a similar process occurs in humans is much less substantial. Therefore, the present study has ...
Background. Cameroon this last decade continues to present a low contribution of M. africanum and... more Background. Cameroon this last decade continues to present a low contribution of M. africanum and M. bovis in human tuberculosis (TB), while M. bovis was prevalent in cattle but all these pieces of information only concerned West and Center regions. Methods. We carried out the first study in Adamaoua, one of the most rearing regions of Cameroon, on the genetic structure and drug susceptibility of the MTBC strains isolated from newly diagnosed sputum smear-positive patients aged 15 years and above. For that purpose, spoligotyping, a modified 15 standard MIRU/VNTR loci typing, and the proportion method were used. Results. Four hundred and thirty-seven MTBC isolates were analyzed by spoligotyping. Of these, 423 were identified as M. tuberculosis, within the Cameroon family being dominant with 278 (65.7%) isolates; twelve (2.75%) isolates were classified as M. africanum and two as M. bovis. MIRU/VNTR typing of the most prevalent sublineage (SIT 61) suggested that this lineage is not a unique clone as thought earlier but could constitute a group of strains implicated to different pocket of TB transmission. Only M. tuberculosis sublineages were associated with antituberculosis drug resistance. Conclusion. These results showed the weak contribution of M. africanum and M. bovis to human active pulmonary tuberculosis in Cameroon even in the rearing region.
Aims/hypothesis In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of... more Aims/hypothesis In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islets. This milieu is generated via the enhanced secretion of proinflammatory cytokines and by the loss of anti-inflammatory molecules such as IL-4 and IL-13. While the actions of proinflammatory cytokines have been well-studied in beta cells, the effects of their anti-inflammatory counterparts have received relatively little attention and we have addressed this. Methods Clonal beta cells, isolated human islets and pancreas sections from control individuals and those with type 1 diabetes were employed. Gene expression was measured using targeted gene arrays and by quantitative RT-PCR. Protein expression was monitored in cell extracts by western blotting and in tissue sections by immunocytochemistry. Target proteins were knocked down selectively with interference RNA. Results Cytoprotection achieved with IL-4 and IL-13 is mediated by the early activation of signal transducer and activator of transcription 6 (STAT6) in beta cells, leading to the upregulation of anti-apoptotic proteins, including myeloid leukaemia-1 (MCL-1) and B cell lymphoma-extra large (BCLXL). We also report the induction of signal regulatory protein-α (SIRPα), and find that knockdown of SIRPα is associated with reduced beta cell viability. These anti-apoptotic proteins and their attendant cytoprotective effects are lost following siRNA-mediated knockdown of STAT6 in beta cells. Importantly, analysis of human pancreas sections revealed that STAT6 is markedly depleted in the beta cells of individuals with type 1 diabetes, implying the loss of cytoprotective responses. Conclusions/interpretation Selective loss of STAT6 may contribute to beta cell demise during the progression of type 1 diabetes.
During the development of type 1 diabetes, interferons (IFN) are elaborated from islet-infiltrati... more During the development of type 1 diabetes, interferons (IFN) are elaborated from islet-infiltrating immune cells and/or from virally infected β-cells. They act via specific receptors to increase, acutely, the phosphorylation of the transcription factors STAT1 and 2. However, the longer-term impacts of chronic IFN stimulation are poorly understood and were investigated in the current study. Human EndoC-βH1 cells were treated with IFNα, IFNγ or IFNλ either acutely (<2 h) or chronically (≥24 h) and STAT phosphorylation, expression and activity were assessed by Western blotting and transcriptional reporter assays. Exposure of β-cells to IFNα or IFNλ induced a swift increase in the phosphorylation of both STAT1 and STAT2, whereas IFNγ increased only pSTAT1. Over more extended periods (≥24 h), STAT phosphorylation declined but STAT1 and STAT2 expression were enhanced in a sustained manner. All IFNs stimulated ISRE transcriptional activity (but with different time courses), whereas GAS ...
Additional file 1: Supplementary figure 1. The effect of exposing rodent β-cells to LC-SFA, incre... more Additional file 1: Supplementary figure 1. The effect of exposing rodent β-cells to LC-SFA, increasing in carbon chain length, at a concentration of 250µM for 24h, on viability.
Additional file 2: Raw datasets. Raw data (Figures 1–4, sup. fig.1) on which the conclusions of t... more Additional file 2: Raw datasets. Raw data (Figures 1–4, sup. fig.1) on which the conclusions of the manuscript rely.
In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islet... more In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islets. This milieu is generated via the enhanced secretion of proinflammatory cytokines and by the loss of anti-inflammatory molecules such as IL-4 and IL-13. While the actions of proinflammatory cytokines have been well-studied in beta cells, the effects of their anti-inflammatory counterparts have received relatively little attention and we have addressed this. Clonal beta cells, isolated human islets and pancreas sections from control individuals and those with type 1 diabetes were employed. Gene expression was measured using targeted gene arrays and by quantitative RT-PCR. Protein expression was monitored in cell extracts by western blotting and in tissue sections by immunocytochemistry. Target proteins were knocked down selectively with interference RNA. Cytoprotection achieved with IL-4 and IL-13 is mediated by the early activation of signal transducer and activator of transcription 6 ...
Background. Cameroon this last decade continues to present a low contribution ofM. africanumandM.... more Background. Cameroon this last decade continues to present a low contribution ofM. africanumandM. bovisin human tuberculosis (TB), whileM. boviswas prevalent in cattle but all these pieces of information only concerned West and Center regions.Methods. We carried out the first study in Adamaoua, one of the most rearing regions of Cameroon, on the genetic structure and drug susceptibility of the MTBC strains isolated from newly diagnosed sputum smear-positive patients aged 15 years and above. For that purpose, spoligotyping, a modified 15 standard MIRU/VNTR loci typing, and the proportion method were used.Results. Four hundred and thirty-seven MTBC isolates were analyzed by spoligotyping. Of these, 423 were identified asM. tuberculosis, within the Cameroon family being dominant with 278 (65.7%) isolates; twelve (2.75%) isolates were classified asM. africanumand two asM. bovis. MIRU/VNTR typing of the most prevalent sublineage (SIT 61) suggested that this lineage is not a unique clone ...
The generation of a human pancreatic beta cell line which reproduces the responses seen in primar... more The generation of a human pancreatic beta cell line which reproduces the responses seen in primary beta cells, but is amenable to propagation in culture, has long been an important goal in diabetes research. This is particularly true for studies focussing on the role of enteroviral infection as a potential cause of beta-cell autoimmunity in type 1 diabetes. In the present work we made use of a clonal beta cell line (1.1B4) available from the European Collection of Authenticated Cell Cultures, which had been generated by the fusion of primary human beta-cells with a pancreatic ductal carcinoma cell, PANC-1. Our goal was to study the factors allowing the development and persistence of a chronic enteroviral infection in human beta-cells. Since PANC-1 cells have been reported to support persistent enteroviral infection, the hybrid 1.1B4 cells appeared to offer an ideal vehicle for our studies. In support of this, infection of the cells with a Coxsackie virus isolated originally from the...
Obesity is a major risk factor for type 2 diabetes (T2D) although the causal links remain unclear... more Obesity is a major risk factor for type 2 diabetes (T2D) although the causal links remain unclear. A feature shared by both conditions however is systemic inflammation and raised levels of circulating fatty acids (FFA). It is widely believed that in obese individuals genetically prone to T2D, elevated levels of plasma FFA may contribute towards the death and dysfunction of insulin-producing pancreatic β-cells in a process of (gluco)lipotoxicity. In support of this, in vitro studies have shown consistently that long-chain saturated fatty acids (LC-SFA) are toxic to rodent β-cells during chronic exposure (>24h). Conversely, shorter chain SFA and unsaturated species are well tolerated, suggesting that toxicity is dependent on carbon chain length and/or double bond configuration. Despite the wealth of evidence implicating lipotoxicity as a means of β-cell death in rodents, the evidence that a similar process occurs in humans is much less substantial. Therefore, the present study has ...
Background. Cameroon this last decade continues to present a low contribution of M. africanum and... more Background. Cameroon this last decade continues to present a low contribution of M. africanum and M. bovis in human tuberculosis (TB), while M. bovis was prevalent in cattle but all these pieces of information only concerned West and Center regions. Methods. We carried out the first study in Adamaoua, one of the most rearing regions of Cameroon, on the genetic structure and drug susceptibility of the MTBC strains isolated from newly diagnosed sputum smear-positive patients aged 15 years and above. For that purpose, spoligotyping, a modified 15 standard MIRU/VNTR loci typing, and the proportion method were used. Results. Four hundred and thirty-seven MTBC isolates were analyzed by spoligotyping. Of these, 423 were identified as M. tuberculosis, within the Cameroon family being dominant with 278 (65.7%) isolates; twelve (2.75%) isolates were classified as M. africanum and two as M. bovis. MIRU/VNTR typing of the most prevalent sublineage (SIT 61) suggested that this lineage is not a unique clone as thought earlier but could constitute a group of strains implicated to different pocket of TB transmission. Only M. tuberculosis sublineages were associated with antituberculosis drug resistance. Conclusion. These results showed the weak contribution of M. africanum and M. bovis to human active pulmonary tuberculosis in Cameroon even in the rearing region.
Aims/hypothesis In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of... more Aims/hypothesis In type 1 diabetes, selective beta cell loss occurs within the inflamed milieu of insulitic islets. This milieu is generated via the enhanced secretion of proinflammatory cytokines and by the loss of anti-inflammatory molecules such as IL-4 and IL-13. While the actions of proinflammatory cytokines have been well-studied in beta cells, the effects of their anti-inflammatory counterparts have received relatively little attention and we have addressed this. Methods Clonal beta cells, isolated human islets and pancreas sections from control individuals and those with type 1 diabetes were employed. Gene expression was measured using targeted gene arrays and by quantitative RT-PCR. Protein expression was monitored in cell extracts by western blotting and in tissue sections by immunocytochemistry. Target proteins were knocked down selectively with interference RNA. Results Cytoprotection achieved with IL-4 and IL-13 is mediated by the early activation of signal transducer and activator of transcription 6 (STAT6) in beta cells, leading to the upregulation of anti-apoptotic proteins, including myeloid leukaemia-1 (MCL-1) and B cell lymphoma-extra large (BCLXL). We also report the induction of signal regulatory protein-α (SIRPα), and find that knockdown of SIRPα is associated with reduced beta cell viability. These anti-apoptotic proteins and their attendant cytoprotective effects are lost following siRNA-mediated knockdown of STAT6 in beta cells. Importantly, analysis of human pancreas sections revealed that STAT6 is markedly depleted in the beta cells of individuals with type 1 diabetes, implying the loss of cytoprotective responses. Conclusions/interpretation Selective loss of STAT6 may contribute to beta cell demise during the progression of type 1 diabetes.
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