Anti-apoptotic Effects Of Insulin-like Growth Factor-1 Research Articles

Anti-inflammatory effect of IGF-1 is mediated by IGF-1R cross talk with GPER in MPTP/MPP+-induced astrocyte activation

Insulin-like growth factor-1 (IGF-1) is a potent neuroprotective polypeptide that exerts neuroprotective effects via the IGF-1 receptor (IGF-1R). Our previous study reported that G protein-coupled estrogen receptor (GPER) was involved in the anti-apoptotic effect of IGF-1. The present study was designed to investigate the anti-inflammatory effect of IGF-1 in association with astrocyte activation and the molecular details of the interaction between IGF-1R and GPER. We showed that IGF-1 could improve 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced motor deficits and attenuate the upregulation of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) both in vivo and in vitro. The IGF-1R antagonist JB-1 and the GPER antagonist G15 could antagonize the anti-inflammatory effect of IGF-1. Silencing GPER abrogated the inhibitory effect of IGF-1 on 1-methyl-4-phenylpyridinium (MPP+)-induced upregulation of COX-2 and iNOS in primary astrocytes. Moreover, the MPP + -induced inflammatory response was related to the activation of mitogen-activated protein kinases (MAPKs) and NF-κB signaling pathways. The inhibitory effects of IGF-1 on the phosphorylation of p38, JNK and IκB could be blocked by JB-1. G15 antagonized the inhibitory effects of IGF-1 on p-JNK and p-IκB, but not p-p38. Furthermore, IGF-1 treatment alone increased the expression of GPER, which was blocked by JB-1, the phosphatidylinositol 3-kinase (PI3–K) antagonist LY294002 and the MEK antagonist PD98059 in primary astrocytes. Overall, we show for the first time that GPER may contribute to the anti-inflammatory effect of IGF-1 against MPTP/MPP + -induced astrocyte activation. IGF-1 could regulate the expression of GPER via the IGF-1R/PI3-K/MAPK signaling pathway in primary astrocytes.

Anti-Apoptotic Effect of IGF1 on Schwann Exposed to Hyperglycemia is Mediated by Neuritin, a Novel Neurotrophic Factor.

The aim of the present study is to explore the effects of exogenous insulin-like growth factor-1 (IGF1) on hyperglycemia-induced apoptosis of Schwann cells via neuritin-mediated pathway. Neuritin was identified with immunohistochemistry. Exogenous IGF1 was used to prevent possible changes in neuritin expression and apoptosis of Schwann cells isolated from rat sciatic nerves and cultured in high-glucose media. Neuritin silencing or overexpressing lentivirus transfection of Schwann cells was conducted. Expressions of neuritin at levels of transcription or translation were measured using quantitative PCR or Western blot. Caspase-3 and caspase-9 fluorometric assays were performed. Bcl-2 and Bax were assayed using Western blotting. Apoptosis of Schwann cells was measured using FACS analysis and TUNEL assay. A pathway of IGF1 action in relation to neuritin was explored. Neuritin and Bcl-2 protein were localized in Schwann cells of rats' sciatic nerves. In vitro, apoptosis increased with downregulated neuritin expression, which was prevented by exogenous IGF1 treatment in contrast to without, in Schwann cells isolated from rat sciatic nerve and cultured in high-glucose and serum-free media. A phosphatidylinositol-3-kinase (PI3K) inhibitor treatment blocked the action of IGF1. The inhibitor did not affect the apoptosis rate that decreased obviously after neuritin was overexpressed in Schwann cells. The apoptosis rate increased drastically after neuritin was silenced, and the resultant apoptosis was suppressed by a caspase inhibitor treatment but not affected by exogenous IGF1. The activities of caspase-3 and caspase-9 changed positively with apoptosis. An anti-apoptotic protein (Bcl-2) not Bax increased or decreased in neuritin-overexpressed or neuritin-silenced Schwann cells, respectively. Bcl-2-selective inhibitor blocked the anti-apoptotic effect of neuritin. IGF1 or neuritin was not found to affect glucose levels in media during the experiment. The anti-apoptotic effect of IGF1 on Schwann cells inflicted by hyperglycemia is mediated at least by neuritin, a novel neurotrophic factor, through PI3K and Bcl-2.

Down-regulation of microRNA-320 suppresses cardiomyocyte apoptosis and protects against myocardial ischemia and reperfusion injury by targeting IGF-1.

Insulin-like growth factor-1 (IGF-1) is an important regulator of cardiomyocyte homeostasis and cardiac structure, and the prosurvival and antiapoptotic effects of IGF-1 have been investigated. However, the effect of microRNA-320 (miR-320) in ischemia and reperfusion (I/R) by targeting IGF-1 is rarely discussed. We investigated the role of miR-320 in I/R injury. A total of 192 healthy female Wistar rats were divided into eight groups (n = 24). Rat heart I/R model was established. Hemodynamics, infarct size weight (ISW), heart function, and rat cardiomyocyte apoptosis were measured. Hypoxia-reoxygenation (H/R) in rat cardiomyocyte was used to simulate the I/R process. The mRNA levels of miR-320 and IGF-1, and proteins levels of IGF-1, IGF-1R, p-IGF-1R, p-ASK1, p-JNK, p-p38, Bcl-2, Bax and Caspase-3 were measured. In vivo inhibition of miR-320 expression significantly increased IGF-1 and IGF-1R mRNA levels, elevated the absolute values of SBP, DBP, MAP, ± dp/dtmax, LVEF and LVFS, decreased ISW, LVESD and LVEDd and the number of TUNEL positive cells, lowered the levels of p-ASK1, p-JNK, p-p38, Bax and Caspase-3 and increased expression of Bcl-2 compared to the I/R + NC group. Compared to H/R + NC group in vitro, miR-320 inhibition increased IGF-1 mRNA levels, inhibited cardiomyocyte apoptosis, down-regulated p-ASK, p-JNK, p-p38, Bax and Caspase-3 levels, and up-regulated Bcl-2 level. MiR-320 inhibition target elevated IGF-1 mRNA and protein levels, suppress early cardiomyocyte apoptosis of I/R, and inhibited ASK1-JNK/p38 pathway, which provides a new target for clinical study of I/R injury.

Obesity and Breast Cancer: A Multipartite Connection

Obesity and Breast Cancer: A Multipartite Connection

Potent Long-Term Cardioprotective Effects of Single Low-Dose Insulin-Like Growth Factor-1 Treatment Postmyocardial Infarction

Insulin-like growth factor-1 (IGF-1) is recognized as an important regulator of cardiac structure and cardiomyocyte homeostasis. The prosurvival and antiapoptotic effects of IGF-1 have been investigated in vitro and in rodent models of myocardial infarction (MI). However, the clinical application of IGF-1 has been hampered by dose-dependent side effects both acutely and during chronic administration. We hypothesized that single, low-dose IGF-1 (LD-IGF-1) administered locally and early in the reperfusion phase after acute MI in a large animal model would avoid significant side effects but would have prosurvival effects that would manifest in long-term structural and functional improvement after MI treatment. Forty-four female Landrace pigs underwent intracoronary administration of LD-IGF-1 or saline 2 hours into the reperfusion phase of acute left anterior descending artery occlusion MI. In the area of infarction, IGF-1 receptor and signaling responses were activated at 30 minutes and cardiomyocyte cell death attenuated at 24 hours after LD-IGF-1 but not saline treatment. Hemodynamic and structural studies using pressure-volume loop, CT, and triphenyltetrazolium chloride analysis 2 months post-MI confirmed a marked reduction in infarct size, attenuation of wall thinning, and augmentation of wall motion in the LD-IGF-1-treated but not in the saline-treated animals. These regional structural benefits were associated with global reductions in left ventricular volumes and significant improvement in left ventricular systolic and diastolic function. One-time LD-IGF-1 effects potent acute myocardial salvage in a preclinical model of left anterior descending artery occlusive MI, extending to long-term benefits in MI size, wall structure, and function and underscoring its potential as an adjunctive therapeutic agent.

Insulin like growth factor-1 prevents 1-mentyl-4-phenylphyridinium-induced apoptosis in PC12 cells through activation of glycogen synthase kinase-3beta

Dopaminergic neurons are lost mainly through apoptosis in Parkinson's disease. Insulin like growth factor-1 (IGF-1) inhibits apoptosis in a wide variety of tissues. Here we have shown that IGF-1 protects PC12 cells from toxic effects of 1-methyl-4-phenylpyridiniumion (MPP +). Treatment of PC12 cells with recombinant human IGF-1 significantly decreased apoptosis caused by MPP + as measured by acridine orange/ethidium bromide staining. IGF-1 treatment induced sustained phosphorylation of glycogen synthase kinase-3beta (GSK-3beta) as shown by western blot analysis. The anti-apoptotic effect of IGF-1 was abrogated by LY294002, which indirectly inhibits phosphorylation of GSK-3beta. Lithium chloride (LiCl), a known inhibitor of GSK-3beta, also blocked MPP +-induced apoptosis. Finally, although IGF-1 enhanced phosphorylation of extracellular signal-regulated kinases ERK1 and 2 (ERK1/2), PD98059, a specific inhibitor of ERK1/2, did not alter the survival effect of IGF-1. Thus, our findings indicate that IGF-1 protects PC12 cells exposed to MPP + from apoptosis via the GSK-3beta signaling pathway.

Abstract 5441: The Roles for MicroRNA-221 and IGF-1 Signaling in Regulation of High Glucose-Induced Endothelial Dysfunction and Apoptosis

Persistent hyperglycemia represents a major metabolic complication of diabetes, which may cause endothelial cell dysfunction and apoptosis. microRNAs are novel biomarkers, modulators and therapeutic targets for disease. The microRNA miR-221 is expressed in human umbilical vein endothelial cells (HUVEC). Insulin-like growth factor 1 (IGF-1) is an important survival factor for multiple cell types. This study was to investigate whether high glucose (HG) induces endothelial dysfunction and apoptosis through altering the microRNA expression and IGF-1 signaling. The mirVana qRT-PCR miRNA detection assay showed that exposure to glucose for 24 h dose-dependently (up to 25 mM) increased miR-221 expression by 2.6 ± 0.5 folds (p<0.05). HG treatment decreased c-kit protein expression (58 ± 7 % decrease vs. control at 48 h) assessed by flow cytometry. The treated HUVEC had a reduced capacity for wound healing responded to stem cell factor (SCF, the ligand of c-kit). SCF-induced HUVEC migration potential was also reduced significantly by exposure to high dose of glucose. As estimated by prediction algorithms, c-kit, but not IGF-1, was identified as the target of miR-221. Transfection of HUVEC with 2′-O-methyl antisense inhibitory oligonucleotide (AMO-221) downregulation of miR-221 led to attenuation of the glucose’s effect on the c-kit expression, SCF-induced migration and wound healing in HUVEC. Prolonged glucose exposure (25 mM, 96 h) induced apoptosis of HUVEC assessed by Death ELISA (O.D. values = 0.49 ± 0.06 in glucose group vs. 0.12 ± 0.07 in control, p<0.01). Addition of IGF-1 (30 ng/ml) blocked the glucose-induced apoptosis, whereas AMO-221 did not attenuate the apoptosis. In addition, the anti-apoptotic effects of IGF-1 was attenuated by PI3 kinase inhibitor LY294002 (15 uM) (IGF-1 + glucose + PI3 kinase inhibitor vs. IGF-1 + glucose = 0.45 ± 0.07 vs. 0.15 ± 0.05 O.D. values). Our data demonstrate that downregulation of miR-221 attenuates HG-induced reduction of c-kit, wound healing and migration of HUVEC, and enhanced IGF-1 signaling prevents HG-induced apoptosis. Thus, reducing miR-221 expression and activating IGF-1 signaling pathway may be a useful strategy to prevent diabetic-induced endothelial dysfunction and apoptosis. This research has received full or partial funding support from the American Heart Association, AHA South Central Affiliate (Arkansas, New Mexico, Oklahoma & Texas).

Insulin-like growth factor-1 protects H9c2 cardiac myoblasts from oxidative stress-induced apoptosis via phosphatidylinositol 3-kinase and extracellular signal-regulated kinase pathways

Oxidative stress plays a critical role in cardiac injuries during ischemia/reperfusion. Insulin-like growth factor-1 (IGF-1) promotes cell survival in a number of cell types, but the effect of IGF-1 on the oxidative stress has not been elucidated in cardiac muscle cells. Therefore, we examined the role of IGF-1 signaling pathway in cell survival against H 2O 2-induced apoptosis in H9c2 cardiac myoblasts. H 2O 2 treatment induced apoptosis in H9c2 cells, and pretreatment of cells with IGF-1 suppressed apoptotic cell death. The antiapoptotic effect of IGF-1 was blocked by LY294002 (an inhibitor of phosphatidylinositol 3-kinase) and by PD98059 (an inhibitor of extracellular signal-regulated kinase (ERK)). The protective effect of IGF-1 was also blocked by rapamycin (an inhibitor of p70 S6 kinase). Furthermore, H9c2 cells stably transfected with constitutively active PI 3-kinase (H9c2-p110*) and Akt (H9c2-Gag-Akt) constructs were more resistant to H 2O 2 cytotoxicity than control cells. Although H 2O 2 activates both p38 mitogen-activated protein kinase (MAPK) and c-Jun N-terminal kinase (JNK), IGF-1 inhibited only JNK activation. Activated PI 3-kinase (H9c2-p110*) and pretreatment of cells with IGF-1 down-regulated Bax protein levels compared to control cells. Taken together, our results suggest that IGF-1 transmits a survival signal against oxidative stress-induced apoptosis in H9c2 cells via PI 3-kinase and ERK-dependent pathways and the protective effect of IGF-1 is associated with the inhibition of JNK activation and Bax expression.

Extracellular Regulated Kinase, but Not Protein Kinase C, Is an Antiapoptotic Signal of Insulin-like Growth Factor-1 on Cultured Cardiac Myocytes

This study aims to elucidate the signaling pathway for insulin-like growth factor-1 (IGF-1) in cultured neonatal rat cardiomyocytes and particularly the role of IGF-1 in cardiac apoptosis. IGF-1 stimulated polyphosphoinositide turnover, translocation of protein kinase C (PKC) isoforms (α, ε, and δ) from the soluble to the particulate fraction, activation of phospholipid-dependent and Ca2+-, phospholipid-dependent PKC, and activation of the extracellular-regulated kinase (ERK). IGF-1 attenuated sorbitol-induced cardiomyocyte viability and nuclear DNA fragmentation. These antiapoptotic effects of IGF-1 were blocked by PD-098059 (an MEK inhibitor) but not by bisindolylmaleimide I (BIM, a specific PKC inhibitor). The ERK pathway may therefore be an important component in the mechanism whereby IGF-1 exerts its antiapoptotic effect on the cardiomyocyte.