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Anti-Ischemic Effects of PIK3IP1 Are Mediated through Its Interactions with the ETA-PI3Kγ-AKT Axis
Jei Hyoung Park1, Kyoung Jin Nho1, Ji Young Lee1
1School of Life Sciences, Gwangju Institute of Science and Technology (GIST), 123 Cheomdangwagi-ro, Buk-gu, Gwangju 61005, Korea.
Abstract:
Oxidative stress, caused by the accumulation of reactive oxygen species (ROS) during acute myocardial infarction (AMI), is one of the main factors leading to myocardial cell damage and programmed cell death. Phosphatidylinositol-3-kinase-AKT (PI3K-AKT) signaling is essential for regulating cell proliferation, differentiation, and apoptosis. Phosphoinositide-3-kinase (PI3K)-interacting protein 1 (PIK3IP1) is an intrinsic inhibitor of PI3K in various tissues, but its functional role during AMI remains unknown. In this study, the anti-ischemic role of PIK3IP1 in an in vitro AMI setting was evaluated using H9c2 cells. The MTT assay demonstrated that cell viability decreased significantly via treatment with H2O2 (200-500 μM). The TUNEL assay results revealed substantial cellular apoptosis following treatment with 200 μM H2O2. Under the same conditions, the expression levels of hypoxia-inducible factor (HIF-1α), endothelin-1 (ET-1), bcl-2-like protein 4 (BAX), and cleaved caspase-3 were elevated, whereas those of PIK3IP1, LC3II, p53, and Bcl-2 decreased significantly. PIK3IP1 overexpression inhibited H2O2-induced and PI3K-mediated apoptosis; however, PIK3IP1 knockdown reversed this effect, suggesting that PIK3IP1 functions as an anti-apoptotic molecule. To identify both the upstream and downstream molecules associated with PIK3IP1, ET-1 receptor type-specific antagonists (BQ-123 and BQ-788) and PI3K subtype-specific antagonists (LY294002 and IPI-549) were used to determine the participating isoforms. Co-immunoprecipitation was performed to identify the binding partners of PIK3IP1. Our results demonstrated that ROS-induced cardiac cell death may occur through the ETA-PI3Kγ-AKT axis, and that PIK3IP1 inhibits binding with both ETA and PI3Kγ. Taken together, these findings reveal that PIK3IP1 plays an anti-ischemic role by reducing the likelihood of programmed cell death via interaction with the ETA-PI3Kr-AKT axis.
Insights
Phosphoinositide-3-kinase (PI3K)-interacting protein 1 (PIK3IP1) protects against oxidative stress and cell death in acute myocardial infarction (AMI) models. PIK3IP1 inhibits the ETA-PI3Kγ-AKT pathway, reducing cardiac cell apoptosis.
Area of Science:
- Cardiovascular Biology
- Cellular Signaling
- Oxidative Stress Research
Background:
- Oxidative stress from reactive oxygen species (ROS) significantly contributes to myocardial cell damage and apoptosis during acute myocardial infarction (AMI).
- Phosphatidylinositol-3-kinase-AKT (PI3K-AKT) signaling is crucial for cell survival and apoptosis regulation.
- The role of Phosphoinositide-3-kinase (PI3K)-interacting protein 1 (PIK3IP1), an intrinsic PI3K inhibitor, in AMI remains largely uncharacterized.
Purpose of the Study:
- To investigate the anti-ischemic function of PIK3IP1 in an in vitro model of AMI.
- To elucidate the molecular mechanisms underlying PIK3IP1's role in regulating cardiac cell apoptosis.
- To identify upstream and downstream signaling pathways associated with PIK3IP1 during oxidative stress.
Main Methods:
- Utilized H9c2 cells exposed to hydrogen peroxide (H2O2) to simulate AMI conditions.
- Assessed cell viability using MTT assays and apoptosis via TUNEL assays.
- Quantified protein expression levels (HIF-1α, ET-1, BAX, cleaved caspase-3, PIK3IP1, LC3II, p53, Bcl-2) and employed receptor/kinase antagonists (BQ-123, BQ-788, LY294002, IPI-549) and co-immunoprecipitation.
Main Results:
- H2O2 treatment significantly reduced cell viability and induced apoptosis, increasing pro-apoptotic markers and decreasing anti-apoptotic markers.
- PIK3IP1 overexpression conferred protection against H2O2-induced apoptosis, while PIK3IP1 knockdown exacerbated it, confirming PIK3IP1's anti-apoptotic role.
- Findings suggest ROS-induced cardiac cell death involves the endothelin-1 receptor type A (ETA)-PI3Kγ-AKT axis, with PIK3IP1 inhibiting interactions between ETA and PI3Kγ.
Conclusions:
- PIK3IP1 exerts an anti-ischemic effect by mitigating programmed cell death in cardiomyocytes.
- PIK3IP1 functions as a protective molecule by modulating the ETA-PI3Kγ-AKT signaling pathway.
- Targeting PIK3IP1 may offer a novel therapeutic strategy for managing acute myocardial infarction.
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