OBJECTIVETo establish the method for cotransferring human A20 gene and human heme oxygenase-1 (HO-1) gene into the isolated rat islets using lentiviral transfection system, and to study the protective effect of A20 and HO-1 protein against the apoptosis induced by cycloheximide (CHX) and TNF-α, and finally to explore the underlying mechanism.

METHODThe A20 gene and HO-1 gene were cloned and inserted into the lentiviral transfection system. The efficacy of gene transfer was measured by the intensity of the enhanced green fluorescent protein (EGFP) fluorescence-positive islets. Western blot was applied to verify the expression of the A20 and HO-1 genes. To induce apoptosis in vitro, the isolated islets were treated with CHX+TNF-α, terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) and the fluorescence-activated cell sorting (FACS) methods were used to evaluate the apoptosis of the islet cells and Western blot was used to detect caspase-3 activation.

RESULT(1) A20 and HO-1 genes were introduced into the isolated islets by lentiviral transfection, both of the genes were highly expressed in the islets after 96 hours culture detected by Western blot method. (2) The insulin levels in the cell culture medium from A20 and/or HO-1 transgenic islets were significantly higher than that in non-transgenic controls (P < 0.01). (3)After CHX + TNF-alpha treatment, the cell culture medium insulin concentration in the A20 gene transfected group [(93.58 ± 4.12)µg/ml], HO-1 gene transfected group [(88.98 ± 4.77) µg/ml ] and A20/HO-1 co-transfected group [(103.33 ± 3.16) µg/ml] were significantly higher than that in the EGFP group [(9.03 ± 0.65) µg/ml ] and the control group [(8.86 ± 0.38) µg/ml] (P < 0.001). Minimum expression level of the activated caspase-3 was found in the A20/HO-1 co-transfected group.

CONCLUSIONThe lentiviral gene transfer system was an efficient and stable gene transfer vector, the over-expressed A20 and HO-1 protein delivered via lentivirus could preserve rats' islets function and act against the apoptosis induced by CHX and TNF-α.

Animals ; Apoptosis ; drug effects ; Caspase 3 ; metabolism ; Cell Line ; DNA-Binding Proteins ; genetics ; metabolism ; Female ; Flow Cytometry ; Genetic Vectors ; Heme Oxygenase-1 ; genetics ; metabolism ; Humans ; Insulin ; metabolism ; Intracellular Signaling Peptides and Proteins ; genetics ; metabolism ; Islets of Langerhans ; drug effects ; enzymology ; physiology ; Lentivirus ; genetics ; Male ; Nuclear Proteins ; genetics ; metabolism ; Rats ; Rats, Sprague-Dawley ; Transfection ; methods ; Tumor Necrosis Factor alpha-Induced Protein 3 ; Tumor Necrosis Factor-alpha ; pharmacology

BACKGROUNDMu opioid receptor plays an important role in many physiological functions. Fentanyl is a widely used opioid receptor agonist for analgesia. This study was conducted to test the role of mu-opioid receptor on insulin release by determining whether fentanyl affected insulin release from freshly isolated rat pancreatic islets and if small interfering RNAs (siRNA) targeting mu-opioid receptor in the islets could knock down mu-opioid receptor expression.

METHODSIslets were isolated from ripe SD rats' pancreas by common bile duct intraductal collagenase V digestion and purified by discontinuous Ficoll density gradient centrifugation. The siRNA knock-down of mu-opioid receptor mRNA and protein in islet cells was analyzed by semi-quantitative real time-PCR and Western blotting. After siRNA-transfection for 48 hours, the islets were co-cultured with fentanyl as follows: 0 ng/ml, 3 ng/ml and 30 ng/ml for 48 hours. Then glucose-evoked insulin release was performed. As a control, the insulin release was also analyzed in islets without siRNA-trasfection after being co-cultured with fentanyl for 48 hours.

RESULTSAfter 48 hours of transfections, specific siRNA targeting of mu-opioid receptors produced significant reduction of mu-opioid receptor mRNA and protein (P < 0.01). Fentanyl significantly inhibited glucose-evoked insulin release in islets in a concentration dependent manner (P < 0.01). But after siRNA-transfection for 48 hours, the inhibition on glucose-evoked insulin release was reversed (P < 0.01).

CONCLUSIONSRNA interference specifically reduces mu-opioid receptor mRNA and protein expression, leading to reversal of the fentanyl-induced inhibition on glucose-evoked insulin release of rat islets. The activation of opioid receptor induced by fentanyl functions to inhibit insulin release. The use of RNAi presents a promising tool for future research in diabetic mechanisms and a novel therapy for diabetes.

Analgesics, Opioid ; pharmacology ; Animals ; Cell Survival ; drug effects ; Cells, Cultured ; Fentanyl ; pharmacology ; Glucose ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; secretion ; Male ; RNA Interference ; RNA, Messenger ; analysis ; Rats ; Rats, Sprague-Dawley ; Receptors, Opioid, mu ; antagonists & inhibitors ; genetics ; physiology

AIMTo investigate the chronic effect of palmitic acid (PA) on apoptosis of pancreatic islet beta-cells and the possible mechanism.

METHODSInsulinoma cell line (MIN6 cells) were used in this study. After being incubated in PA (0.1 - 1.6 mml/L) for 24 and 48 hours, MTT method was used to evaluate the livability. After being incubated for 48 h, Hoechst-PI and Annexin-V-FTTC/PI FACS were used to estimate the apoptosis in each group, Western-blotting assay was used to estimate the protein level of p-Akt, Akt, Bax and Bcl-2.

RESULTSChronic PA dose-dependently (1) decreased the availability and increased the apoptosis of MIN6 cells; (2) decreased the phosphorylation of Akt and Bcl-2, but had no significant effects on Akt and Bax.

CONCLUSIONChronic PA dose-dependently induced apoptosis of MIN6 cells, and this effect was possibly regulated by Akt/Bcl-2.

Animals ; Apoptosis ; drug effects ; Cell Line, Tumor ; Cells, Cultured ; Insulinoma ; pathology ; Islets of Langerhans ; pathology ; Mice ; Oxidative Stress ; physiology ; Palmitic Acid ; pharmacology ; Proto-Oncogene Proteins ; metabolism ; Proto-Oncogene Proteins c-akt ; metabolism ; Proto-Oncogene Proteins c-bcl-2 ; Signal Transduction ; drug effects ; physiology ; bcl-2-Associated X Protein ; metabolism

AIMTo investigate the protective role of HO/CO systems in IL-1beta induced islest apoptosis and to explore the mechanisms of the protective effect of fructose-1, 6-disphosphate (FDP).

METHODSThe pancreases of the rats were removed to collect islets cells. The cells were incubated with IL-1beta with/or FDP. Cell activity, insulin secretion, HO-1 activity, CO content and apoptotic percentage were detected.

RESULTSHO-1 activity and CO content of the normal control group were low. IL-1beta induced a significant decrease of cell activity and insulin release, flow cytometry analysis showed that apoptotic percentage of islet cells remarkably increased following the addition of IL-1beta, FDP obviously improved the islets cellular activity damaged by IL-1beta, and basic amount of insulin secretion and stimulated by high glucose were improved (P < 0.01). Content of CO and activity of HO-1 were higher in the IL-1beta group than the normal control group (P < 0.05), and there were significant differences between the FDP groups and IL-1beta group. FDP decreased cell apoptotic percentage. Activities of HO-1 and content of CO were higher than that in the IL-1beta group (P < 0.01).

CONCLUSIONFDP can attenuate the IL-1beta induced apoptosis of cultured beta cells, the mechanism of which may be improved HO-1 activity and CO content.

Animals ; Animals, Newborn ; Apoptosis ; drug effects ; Carbon Monoxide ; metabolism ; Cells, Cultured ; Female ; Fructosediphosphates ; pharmacology ; Heme Oxygenase (Decyclizing) ; metabolism ; physiology ; Insulin ; secretion ; Interleukin-1beta ; antagonists & inhibitors ; pharmacology ; Islets of Langerhans ; cytology ; Male ; Rats ; Rats, Wistar

OBJECTIVETo establish the method for isolation, culture, and differentiation induction of nestin-positive cells in fetal rat hepatic cells.

METHODSHepatic cells were obtained from fetal rats by means of mechanical separation and hanging-drop culture, and after two days of primary culture, the medium was changed for further cell culture in the presence of 20% fetal bovine serum (containing glucose 25 ml/L, mycillin 100 U/ml, pH 7.6), 10 mmol/L nicotinamide, 1 mg/L insulin, affix N2, basic fibroblast growth factor, stem cell factor, epidermal growth factor and leukemia inhibitory factor.

RESULT AND CONCLUSIONNestin-positive cells were obtained from fetal rat liver, which can differentiate into islet beta cells after culture and expansion in vitro.

Animals ; Cell Differentiation ; drug effects ; physiology ; Cell Separation ; methods ; Cell Transdifferentiation ; drug effects ; physiology ; Cells, Cultured ; Epidermal Growth Factor ; pharmacology ; Female ; Fetus ; Fibroblast Growth Factor 2 ; pharmacology ; Hepatocytes ; cytology ; metabolism ; Insulin ; pharmacology ; Intermediate Filament Proteins ; biosynthesis ; Islets of Langerhans ; cytology ; drug effects ; Leukemia Inhibitory Factor ; pharmacology ; Liver ; Male ; Nerve Tissue Proteins ; biosynthesis ; Nestin ; Rats ; Rats, Wistar ; Stem Cell Factor ; pharmacology

OBJECTIVETo investigate the feasibility and benefits of co-culture of cryopreserved islets with small intestinal submucosa (SIS).

METHODSPurified rat islets cryopreserved for one month were divided into SIS group and control group, and after culture in standard islet culture media RPMI1640 for 1 week, the morphology and function of the islets were assessed.

RESULTSThe SIS protects the fragile islets from damage by cryopreservation, and increased the recovery from (60.6-/+3.3)% to (91.7-/+1.8) % (P<0.05). Compared with the control group, incubation of the islets of the SIS group in high-glucose (16.7 mmol/L) solution resulted in significantly enhanced insulin secretion (23.7-/+1.6 vs 12.5-/+1.1 mU/L, P<0.05). When the islets were incubated in high-glucose solution containing theophylline, the calculated stimulation index of SIS group was about 3-fold higher than that of the control group.

CONCLUSIONCo-culture of cryopreserved rat islets with SIS can increase the recovery of islet cells and improve their function.

Animals ; Coculture Techniques ; Cryopreservation ; methods ; Glucose ; pharmacology ; Insulin ; secretion ; Intestinal Mucosa ; cytology ; drug effects ; physiology ; Intestine, Small ; cytology ; drug effects ; physiology ; Islets of Langerhans ; cytology ; drug effects ; physiology ; Male ; Rats ; Rats, Wistar ; Theophylline ; pharmacology

BACKGROUNDIslet transplantation represents an ideal therapeutic approach for treatment of type 1 diabetes but islet function and regeneration may be influenced by necrosis or apoptosis induced by oxidative stress and other insults. Heme oxygenase-1 (HO-1) is the rate-limiting enzyme in the catabolism of heme into biliverdin, releasing free iron and carbon monoxide. It has also been reported to be an antioxidant enzyme which can improve the function of grafted islets by cytoprotection via free radical scavenging and apoptosis prevention. In the present study, we investigated whether transduction of HO-1 genes into human islets with an adenovirus vector has cytoprotective action on islets cultured in vitro and discuss this method of gene therapy for clinical islet transplantation.

METHODSCadaveric pancreatic islets were isolated and purified in vitro. Transduction efficiency of islets was determined by infecting islets with adenovirus vector containing the enhanced green fluorescent protein gene (Ad-EGFP) at multiplicities of infection (MOI) of 2, 5, 10, or 20. Newly isolated islets were divided into three groups: EGFP group, islets transduced with Ad-EGFP using MOI = 20; HO-1 group, transduced with adenovirus vectors containing the human HO-1 gene using MOI = 20; and control group, mock transduced islets. Insulin release after glucose stimulation of the cell lines was determined by a radioimmunoassay kit and the stimulation index was calculated. Flow cytometry was used to detect apoptotic cells in the HO-1 group and in the control group after induction by recombinant human tumor necrosis factor-alpha (rTNFalpha) and cycloheximide (CHX) for 48 hours.

RESULTSAdenovirus vectors have a high efficiency of gene transduction into adult islet cells. Transduction of islets with the Ad-EGFP was most successful at MOI 20, at which MOI fluorescence was very intense on day 7 after transduction and EGFP was expressed in cultured islet cells for more than four weeks in vitro. The insulin release in the control group was (182.36 +/- 58.96) mIU/L after stimulation by high glucose media (16.7 mmol/L), while insulin release from the HO-1 group and the EGFP group were (270.09 +/- 89.37) mIU/L and (175.95 +/- 75.05) mIU/L respectively. Compared to the control group and the EGFP group, insulin release in the HO-1 group increased significantly (P < 0.05). After treatment with rTNFalpha and CHX the apoptotic ratio of islet cells was (63.09 +/- 10.86)% in the HO-1 group, significantly lower than (90.86 +/- 11.25)% in the control group (P < 0.05).

CONCLUSIONSTransduction of human islets with Ad-HO-1 can protect against TNF-alpha and CHX mediated cytotoxicity. The HO-1 gene also appears to facilitate insulin release from human islets. Transduction of donor islets with the adenovirus vector containing an HO-1 gene might have potential value in clinical islet transplantation.

Adenoviridae ; genetics ; Apoptosis ; drug effects ; Cycloheximide ; pharmacology ; Cytoprotection ; Genetic Therapy ; Heme Oxygenase-1 ; genetics ; physiology ; Humans ; Insulin ; secretion ; Islets of Langerhans ; physiology ; Transduction, Genetic ; Tumor Necrosis Factor-alpha ; pharmacology

Dysfunction of the pancreatic beta-cell is an important defect in the pathophysiological changes of type 2 diabetes, and type 2 diabetes is evidently associated with obesity. But the role of the adipocyte in the dysfunction of the pancreatic beta-cell remains unknown. In the present study, we examined the direct effects of 3T3-L1 adipocytes on the expression of ATP-sensitive potassium channels (K(ATP) channels) in MIN6 insulin-secreting cells. MIN6 cells were divided into two groups as control group, where MIN6 cells were cultured in normal culture medium, and coculture group, where MIN6 cells were cocultured with differentiated 3T3-L1 adipocytes for 1 week. Semi-quantitative RT-PCR was employed to measure the expression of K(ATP) channel subunit Kir6.2 in MIN6 cells. Fura-2 was used to reflect changes in intracellular calcium concentration ([Ca(2+)](i)) in MIN6 cells. The secretary function of MIN6 cells from both groups was estimated by radioimmunoassay method. The results showed that the Kir6.2 cDNA levels corrected by GAPDH cDNA levels after densitometric analysis were 0.989+/-0.035 in control group and 0.726+/-0.087 in coculture group. The expression of Kir6.2 was significantly decreased in MIN6 cells in the coculture group as compared with that in control. MIN6 cells cocultured with 3T3-L1 adipocytes lost the ability to increase [Ca(2+)](i) when stimulated by tolbutamide (0.1 mmol/L), a highly selective KATP channel closer. In contrast, MIN6 cells in control group had typical responses to tolbutamide with a significant increase in [Ca(2+)](i). The magnitudes to basal levels of [Ca(2+)](i) after tolbutamide stimulation were 1.520+/-0.203 in control and 1.114+/-0.097 in coculture group (P<0.05, n=6). MIN6 cells in control showed a significant increase in insulin secretion from 0.38+/-0.099 mU/min to 2.87+/-0.248 mU/min after being stimulated by tolbutamide, whereas MIN6 cells in coculture group did not increase insulin secretion when stimulated by tolbutamide (0.21+/-0.055 mU/min to 0.22+/-0.082 mU/min). It is demonstrated that 3T3-L1 adipocytes decrease the expression of K(ATP) channels in MIN6 cells through secreting certain factors, which impair the secretary function of MIN6 cells. The present results indicate that adipocytes are directly involved in pancreatic beta-cell dysfunction, which may facilitate the development of type 2 diabetes.
3T3 Cells ; Adipocytes ; cytology ; Animals ; Cell Differentiation ; physiology ; Cells, Cultured ; Coculture Techniques ; Gene Expression ; Hypoglycemic Agents ; pharmacology ; Insulin ; biosynthesis ; Insulin Resistance ; Islets of Langerhans ; cytology ; metabolism ; Mice ; Potassium Channels, Inwardly Rectifying ; biosynthesis ; genetics ; physiology ; Tolbutamide ; pharmacology ; Transcription, Genetic ; drug effects

OBJECTIVETo investigate whether HIV-1 protease inhibitor nelfinavir alters the insulin stimulated phosphorylation of insulin signaling parameters in rat insulinoma INS-1 cells.

METHODSINS-1 cells were incubated with nelfinavir for 48 h and stimulated with 100 nmol/L insulin for 2 min. Immunoprecipitation and Western blot analysis of the insulin stimulated insulin receptor substrate (IRS)-1,-2 and Akt-Thr(308) phosphorylation were performed on cell lysates. Cytotoxic effects of nelfinavir were measured by cell count with trypan blue and MTT reduction test.

RESULTNelfinavir decreased insulin stimulated phosphorylation of IRS-2 and Akt-Thr(308) in a dose-dependent manner; for 10 micromol/L of nelfinavir, the decrease was 52% and 55%, respectively.

CONCLUSIONTreatment with nelfinavir might impair IRS-2-mediated signaling in pancreatic beta cells.

Animals ; Cell Line, Tumor ; Cell Survival ; drug effects ; HIV Protease Inhibitors ; pharmacology ; Insulin Receptor Substrate Proteins ; Insulinoma ; metabolism ; Intracellular Signaling Peptides and Proteins ; Islets of Langerhans ; drug effects ; physiology ; Nelfinavir ; pharmacology ; Pancreatic Neoplasms ; metabolism ; Phosphoproteins ; analysis ; physiology ; Protein-Serine-Threonine Kinases ; analysis ; Proto-Oncogene Proteins ; analysis ; Proto-Oncogene Proteins c-akt ; Rats ; Signal Transduction ; drug effects

To study the effects of free fatty acids on insulin secretion and expression of SUR1 gene in rat pancreatic B cells in vitro, and to explore the molecular mechanisms in lipotoxicity inducing insulin secretion dysfunction, pancreatic islet cells were isolated and digested from male SD rats. Purified islets were incubated with either 0.25 mmol/L palmitate or 0.125 mmol/L oleate for 48 h in vitro. Then islets were stimulated with either 5.6 mmol/L or 16.7 mmol/L glucose for 1 h. Insulin release was measured by using radioimmunoassay, and the expression of SUR1 gene mRNA was quantified by reserve transcription-polymerase chain reaction (RT-PCR). The islets exposed to both palmitate and oleate for 48 h showed an increased basal and a decreased glucose-indused insulin release as compared with control islets. Palmitate increased basal insulin secretion by 110% (P< 0.01), decreased glucose stimulated insulin secretion by 43% (P<0.01); while oleate increased basal insulin secretion by 80% (P<0.01) and decreased glucose stimulated insulin secretion by 32 % (P<0.05). RT-PCR showed that oleate significantly suppressed SUR1 gene expression by 64 % (P<0.01) as compared with the control group, while palmitate group manifested a light decrease of 15% (P>0.05) of SUR1 gene expression. Our results suggested that chronic exposure to free fatty acids of pancreatic beta cells inhibited glucose stimulated insulin secretion. Regulation of SUR1 gene expression may be involved in such effects, which may also be one of the molecular mechanisms in lipotoxocity inducing beta cells secretion dysfunction.
ATP-Binding Cassette Transporters ; biosynthesis ; genetics ; Animals ; Cells, Cultured ; Fatty Acids ; pharmacology ; Insulin ; secretion ; Islets of Langerhans ; drug effects ; physiology ; Male ; Potassium Channels ; biosynthesis ; genetics ; Potassium Channels, Inwardly Rectifying ; biosynthesis ; genetics ; RNA, Messenger ; biosynthesis ; genetics ; Rats ; Rats, Sprague-Dawley ; Receptors, Drug ; biosynthesis ; genetics ; Sulfonylurea Receptors