Induction of Monocyte Chemoattractant Protein-1 (MCP-1) Expression by Angiotensin II (AngII) in the Pancreatic Islets and Beta Cells Galina Chipitsyna, Qiaoke Gong, Chance F. Gray et al. Endocrinology, May 2007 Type 1 (insulin-dependent) diabetes millitus Monocyte chemoattractant protein (MCP- 1) The circulating renin angiotensin system (RAS) Type 1 (insulin-dependent) diabetes millitus Type 1 diabetes develops as a consequence of autoimmunity, leading to beta cell destruction The early stages of insulitis cytokines Monocyte chemoattractant protein (MCP- 1) a protein from the chemotactic cytokines ( C-C chemokine) subfamily is expressed in human and rodent islets macrophages T-cells free radicals MCP-1 attracts monocytes, T-cells, and natural killer cells to the site of inflammation beta cell dysfunction and death play a role in the clinical outcome of islet allografts in type 1 diabetic patients high MCP-1 is negatively correlated with successful engraftment and long-lasting g insulin independence Transgenic mice expressing MCP-1 under control of the insulin promoter develop an intense insulitis The circulating renin angiotensin system (RAS) angiotensinogen critical Zn 2+ -dependent metallopeptidase angiotensin nsin I (AngI) angiotensin I-converting enzyme (ACE) the bioactive octapeptide AngII multiple G-protein-coupled receptor subtypes including AngII receptor 1 and 2 (AT1R, AT2R) 1
AngII PLC-β NF-kB γ α ß AT1R R R T T P K K P MAPK expression of proinflammatory genes such as MCP-1 Gene expression Hypothesis AngII may contribute to islet inflammation through induction of MCP-1 in the islets and beta cells MAPK=The mitogen-activated protein (MAP) kinases Cell culture -RINm5F insulinoma cell line -grown at 37 o C under a humidified -5% CO 2 atmosphere in RPMI 1640 medium -supplemented with -10% fetal bovine serum -2 mm glutamine -100 units/ml of penicillin -100 μg/ml of streptomycin -2.5 μg/ml of amphotericin B Cell culture Serum free media RINm5F AII 10-6 mol/l overnight AII 10-8 mol/l AII 10-7 mol/l 3 & 6 hrs IL-1β 0.1 ng/ml cells and media were harvested : MCP-1 & GAPDH = Reverse Transcription Polymerase Chain Reaction GAPDH= Glyceraldehyde 3-phosphate dehydrogenase RINm5F Cell Trizol reagent, DNase-digested RNAs Reverse Transcriptase cdnas EDAS 290 Electrophoresis semi-quantitative PCR Kodak Electrophoresis Documentation and Analysis System 290 (EDAS 290). AngII-induces MCP-1 mrna accumulation and secretion of MCP-1 in cultured beta cells MCP-1/GAPDH mr RNA (arbitrary units s) Cont. IL-1ß AII 10-8 10-7 10-6 3h 6h 2
To examine whether the increase in MCP-1 mrna levels in response to AngII is associated with MCP-1 production IL-1β 0.1 ng/ml AII 10-7 mol/l 6 & 12 hrs MCP-1 protein levels in the media rat-specific MCP-1 ELISA kit AngII-induces MCP-1 mrna accumulation and secretion of MCP-1 in cultured beta cells l (ng/ml) MCP-1 protein level ELISA -AngII - is a potent stimulator of MCP-1 expression -induced MCP-1 accumulation rapidly in the pancreatic islets and with significant magnitude -In beta cells, AngII (10-7 mol/l) significant induction of MCP-1 mrna and protein levels AngII-induced MCP-1 mrna expression in RINm5F cells is blocked by AT1R antagonist Losartan PD123319 1 hr 3 hrs AngII 10-7 mol/l Losartan AngII 10-7 mol/l AngII 10-7 mol/l PD123319 AT1R blocker=losartan and the AT2R blocker= PD123319 To determine the receptor that mediates the AngIIinduced MCP-1 gene expression in beta cells MCP-1/GAPDH mrna (arbitrary u nits) AngII Losartan PD123319 - MCP-1 GAPDH + + + + - - - + AngII induces MCP-1 promoter activity in RINm5F cells ORI luciferase expression vector pgl3 basic rat MCP-1 promoter -514(enh)luc TransFast reagent 24-well culture plates luciferase expression vector pgl3 basic pgfp vector (transfection control) 3
transfected cells AngII (10-7 mol/l) AngII induces MCP-1 promoter activity in RINm5F cells. 24 hrs 1 & 2 hrs luciferase activity in the cell lysates was measured Fold Inducti ion of Luciferase Activity P<0.05 control 1 hr P=0.005 2 hr -AT1R antagonist prevented the AngII-MCP-1 production -AngII addition to beta cells results in a concomitant increase in AT1R mrna expression -Assume that AngII itself could have a regulatory effect on AT1R in beta cells which could consequently contribute to AngII-MCP-1 induction -possible that AngII induces MCP-1 transcripts in the pancreatic islets and beta cells directly through acting on its promoter indirectly through AT1R upregulation -MCP-1 promoter was induced significantly as early as after 1 hour of stimulation. acute response to AngII -Further studies are required -analyze the AngII specific cis-elements on MCP-1 promoter -AngII-induced MCP-1 upregulation is mediated through NF-kB? To determine whether an increase in tyrosine phosphorylation induces MCP-1 mrna accumulation sodium orthovanadate 50 μm sodium orthovanadate 100 μm 3 hrs sodium orthovanadate 200 μm sodium orthovanadate = protein tyrosine phosphatase inhibitor 4
Result To determine the involvement of protein kinase in AngII-induced MCP-1 expression Genistein 60 μm mol/l MCP-1 /GADPH mrna (arbitrary unit ts) RINm5F cells 1 hr 3 hr genistein mol/l Genistein Sod.orthovanadate - 50µM 100µM 200µM RINm5F cells Genistein= specific tyrosine kinase inhibitor Result AngII-induced MCP-1 gene expression requires ERK1/2 MAP kinase activity RINm5F + mol/l 5 & 10 & 15 & 30 & 60 min NA MCP-1 /GADPH mrn (arbitrary units) Genistein - + - + - + protein Washing and lysed cells Western blot Protein isolation and Western blot analysis RINm5F cell modified RIPA lysis buffer protein incubate 4 o C overnight Protein gel loading buffer at 85 o C 5 min 10 % SDS-polyacrylamide slab gels transfered BCA protein assay reagent BCA =Bicinchoninic Acid primary antibody diluted in PBS/Tween 20 PVDF 5
Western blot analysis Western blot analysis anti-total and anti-phospho-p38 MAPK anti- total and anti-phospho-erk1/2mapk Substrate HRP Secondary Ab anti-total and anti phospho JNK/SAPK Primary Ab Proteins from beta cells treated with AngII Blot JNK/ SAPK =c-jun NH2-terminal protein kinase/ stress-activated protein kinases MAPK=The mitogen-activated protein (MAP) kinases Proteins from beta cells treated with AngII Blot -The protein bands were visualized with enhanced chemiluminescence reagents -analyzed and intensity quantified using EDAS 290 AngII-induced MCP-1 gene expression requires ERK1/2 MAP kinase activity AngII-induced MCP-1 gene expression requires ERK1/2 MAP kinase activity MEK1/2 selective inhibitor U0126 10 µm mol/l mol/l U0126 10 µm Western blot RINm5F MEK1/2 selective inhibitor U0126 30 µm 10 min 3 hrs U0126 30 µm mol/l U0126 30 µm ERK =extracellular signal regulated kinase RINm5F MCP-1 /G GADPH mrna (arbitr rary units) Statistical analysis Figure 4.A,B: Data represent three independent experiments. *p < 0.05 vs. AngII treated cells using one-way repeated ANOVA with subsequent all pairwise comparison procedure by student t-test - - - + + + - U0126 10µM U0126 =MEK1/2 selective inhibitor 30µM 30µM 6
-MAP kinases encoded by the extracellular signal regulated kinase (ERK) genes are a family of serine/threonine protein kinases -ERK referred to as p44 (ERK1), and p42 (ERK2) are activated by phosphorylation of threonine and tyrosine residues by MAP kinase kinase(mek) -Using U0126, a selective inhibitor for MEK activation -AngII-induced MCP-1 mrna occurs through a MEK-sensitive mechanism -Further studies -fully delineate the specific signaling pathway by which AngII ultimately modulates MCP-1 synthesis in the islets Mice NOD pancreatic AngII generating system expression correlates with hyperglycemia and progression to severe diabetes Female NOD pancreata (3 gr.) Female NOD mice ;n=5 1.prediabetic (2-4 wks) 2.diabetic FBG 200-250 mg/dl (13-15 wks) 3.diabetic FBG >350 mg/dl (20-22 wks) ICR mice normoglycemic; n=3 1. 2-4 wks 2. 13-15 wks 3. 20-22 wks : ACE mrna, GAPDH Clean Western blot : ACE protein Actin NOD pancreatic NOD pancreatic Western blot ACE protein/actin (arbitrary units) 2-4 wks 13-15 wks 20-22 wks ACE mrna/gapdh (arbitrary units) 2-4 wks 13-15 wks 20-22 wks 7
ICR mice pancreata (3 gr.) Clean Western blot ICR mice pancreata Western blot tin ACE protein/act arbitrary units 2-4 wks 13-15 wks 20-22 wks ICR mice pancreata ACE distribution in the diabetic pancreas and colocalization with MCP-1 in beta cells pancreata ACE mrna/ga APDH arbitrary un nit 2-4 wks 13-15 wks 20-22 wks Serial sections at 5 μm formaline fixed paraffin embedded tissue blocks stained -a goat polyclonal antibody against ACE -goat polyclonal antibody against human MCP-1 -antibodies against mouse insulin glucagon somatostatin -A vectastain universal elite ABC kit and diaminobenzedine i (DAB) chromogenic substrate -Insulin was visualize by alkaline phosphatase reaction (red) -DAB was used to visualize the rest of the islet hormones in addition to ACE and MCP-1 (brown) ACE distribution in the diabetic pancreas and colocalization with MCP-1 in beta cells. 8
Angiotensin II alone and in combination with IL-1β elicit an inflammatory response in the islets by stimulation of MCP-1 Islet cell normoglycemic female NOD mice clean digested in shaker-type water bath at 37 C culture in RPMI medium Islets cells AngII (10-7 -mol/l) IL-1ß ß (0.1 ng/ml) RPMI medium overnight 3 hrs AngII + IL- 1ß AngII+ losartan 100 μm /GAPDH MCP-1 / trary units) mrna (arbit IL-1ß(0.1 ng/ml) Losartan - + - + + - + + - - - + -The first time the presence of an active AngII generating system in the pancreata of NOD mice - As early as 2 weeks of age ACE mrna and protein were detectable in the non diabetic pancreata -Development of insulitis and progression to hyperglycemia and beta cell destruction expression levels of ACE -suggesting that AngII generation is an active ongoing process with diabetes advancement -ACE is constitutively expressed in most of the islet cells, colocalizing with MCP-1 -suggesting an endogenous autocrine / paracrine interaction -Using of angiotensin blockade therapies could improve islet function and glucose intolerance in type 2 diabetes patients and in animal models 9
adding ACE inhibitors in vitro to the islets leads to their protection against glucotoxcitiy and oxidative stress AngII g itself affects the islet short-term insulin release the long-term effects of AngII on the islet functions are yet to be determined -The novel data about the role of the local pancreatic renin angiotensin system as a source of islet inflammation -suggest that targeting g AngII could be used as a novel therapeutic strategy to -reduce MCP-1 levels in the islets -inhibit beta cell directed immunity in type 1 diabetes This research showed that 1.AngII elicits an inflammatory response in the islets and beta cells by stimulation of MCP-1 production through h an AT1R-ERK1/2-dependent nt mechanism 2.hyperglycemia and progression to diabetes correlate with upregulation of ACE 10