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Gong Z, Lao D, Wu Y, Li T, Lv S, Mo X, Huang W. Inhibiting PI3K/Akt-Signaling Pathway Improves Neurobehavior Changes in Anti-NMDAR Encephalitis Mice by Ameliorating Blood-Brain Barrier Disruption and Neuronal Damage. Cell Mol Neurobiol 2023; 43:3623-3637. [PMID: 37314618 PMCID: PMC10477152 DOI: 10.1007/s10571-023-01371-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2023] [Accepted: 05/31/2023] [Indexed: 06/15/2023]
Abstract
The disruption of the blood-brain barrier (BBB) is hypothesized to be involved in the progression of anti-N-methyl-D-aspartate receptor (NMDAR) encephalitis, but its mechanism is still unclear. Recently, the phosphatidylinositol 3-kinase (PI3K)/threonine kinase (Akt) pathway is involved in the regulation of the BBB in various diseases. This study is aimed to investigate the mechanism of BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. Female C57BL/6J mice were actively immunized to establish an anti-NMDAR encephalitis mouse model and evaluate the neurobehavior changes of mice. To study its potential mechanism, LY294002 (PI3K inhibitor, 8 mg/kg) and Recilisib (PI3K agonist, 10 mg/kg) were treated by intraperitoneal injection, respectively. Anti-NMDAR encephalitis mice showed neurological deficits, increased BBB permeability, open endothelial tight junctions (TJs), and decreased expression of TJ-related proteins zonula occludens (ZO)-1 and Claudin-5. However, administration of PI3K inhibitor significantly reduced the expression of p-PI3K and p-Akt, improved neurobehavior function, decreased BBB permeability, and upregulated the expressions of ZO-1 and Claudin-5. Furthermore, PI3K inhibition reversed the decline of NMDAR NR1 in the membranes of hippocampal neurons, which reduced the loss of neuron-specific nucleoprotein (NeuN) and microtubule-associated protein 2 (MAP2). In contrast, administration of the PI3K agonist Recilisib showed a tendency to exacerbate BBB breakdown and neurological deficits. Our results showed that the activation of PI3K/Akt, along with the changes in TJ-related proteins ZO-1 and Claudin-5, may be closely related to BBB damage and neurobehavior changes in anti-NMDAR encephalitis mice. PI3K inhibition attenuates BBB disruption and neuronal damage in mice, thereby improving neurobehavior.
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Affiliation(s)
- Zhuowei Gong
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
| | - Dayuan Lao
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
| | - Yu Wu
- University of Pittsburgh School of Medicine, Pittsburgh, PA USA
| | - Taiyan Li
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
| | - Sirao Lv
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
| | - Xuean Mo
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
| | - Wen Huang
- Department of Neurology, The First Affiliated Hospital of Guangxi Medical University, #6 Shuangyong Road, Nanning, 530021 Guangxi People’s Republic of China
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Cai J, Chen Y, Wang K, Li Y, Wu J, Yu H, Li Q, Wu Q, Meng W, Wang H, Lu A, Huang M, Wei G, Guan D. Decoding the key compounds and mechanism of Shashen Maidong decoction in the treatment of lung cancer. BMC Complement Med Ther 2023; 23:158. [PMID: 37189139 PMCID: PMC10184424 DOI: 10.1186/s12906-023-03985-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Accepted: 04/29/2023] [Indexed: 05/17/2023] Open
Abstract
BACKGROUND Lung cancer is a malignant tumour with the fastest increase in morbidity and mortality around the world. The clinical treatments available have significant side effects, thus it is desirable to identify alternative modalities to treat lung cancer. Shashen Maidong decoction (SMD) is a commonly used traditional Chinese medicine (TCM) formula for treating lung cancer in the clinic. While the key functional components (KFC) and the underlying mechanisms of SMD treating lung cancer are still unclear. METHODS We propose a new integrated pharmacology model, which combines a novel node-importance calculation method and the contribution decision rate (CDR) model, to identify the KFC of SMD and to deduce their mechanisms in the treatment of lung cancer. RESULTS The enriched effective Gene Ontology (GO) terms selected from our proposed node importance detection method could cover 97.66% of enriched GO terms of reference targets. After calculating CDR of active components in key functional network, the first 82 components covered 90.25% of the network information, which were defined as KFC. 82 KFC were subjected to functional analysis and experimental validation. 5-40 μM protocatechuic acid, 100-400 μM paeonol or caffeic acid exerted significant inhibitory activity on the proliferation of A549 cells. The results show that KFC play an important therapeutic role in the treatment of lung cancer by targeting Ras, AKT, IKK, Raf1, MEK, and NF-κB in the PI3K-Akt, MAPK, SCLC, and NSCLC signaling pathways active in lung cancer. CONCLUSIONS This study provides a methodological reference for the optimization and secondary development of TCM formulas. The strategy proposed in this study can be used to identify key compounds in the complex network and provides an operable test range for subsequent experimental verification, which greatly reduces the experimental workload.
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Affiliation(s)
- Jieqi Cai
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Yupeng Chen
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Kexin Wang
- Neurosurgery Center, Guangdong Provincial Key Laboratory on Brain Function Repair and Regeneration, Department of Cerebrovascular Surgery, Engineering Technology Research Center of Education Ministry of China on Diagnosis and Treatment of Cerebrovascular Disease, Zhujiang Hospital, Southern Medical University, Guangzhou, Guangdong, 510280, China
| | - Yi Li
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Jie Wu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Hailang Yu
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Qingping Li
- Division of Hepatobiliopancreatic Surgery, Department of General Surgery, Nanfang Hospital, Southern Medical University, Guangzhou, Guangdong, China
| | - Qi Wu
- Department of Burns, Nanfang Hospital, Southern Medical University, Guangzhou, China
| | - Wei Meng
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Handuo Wang
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China
| | - Aiping Lu
- Institute of Integrated Bioinformedicine and Translational Science, Hong Kong Baptist University, Hong Kong, China
| | - Mianbo Huang
- Department of Histology and Embryology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China.
| | - Genxia Wei
- Huiqiao Medical Center, Nanfang Hospital, Southern Medical University, Guangzhou, China.
| | - Daogang Guan
- Department of Biochemistry and Molecular Biology, School of Basic Medical Sciences, Southern Medical University, Guangzhou, Guangdong Province, China.
- Guangdong Provincial Key Laboratory of Single Cell Technology and Application, Guangzhou, Guangdong Province, China.
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Wang C, Li S, Liu J, Cheng M, Wang D, Wang Y, Lu B. Silencing of S-phase kinase-associated protein 2 enhances radiosensitivity of esophageal cancer cells through inhibition of PI3K/AKT signaling pathway. Genomics 2020; 112:3504-3510. [PMID: 32360515 DOI: 10.1016/j.ygeno.2020.04.029] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 04/26/2020] [Accepted: 04/27/2020] [Indexed: 01/14/2023]
Abstract
We investigated the effect of S-phase kinase-associated protein 2 (SKP2) on radiosensitivity of esophageal cancer (EC) cells. Expression of SKP2, PI3K, AKT, Bcl-2 and Bax were assayed in EC. EC cells were transfected with SKP2-siRNA/IGF-1 to detect expression of SKP2, PI3K, AKT, Bcl-2 and Bax. At last, the radiosensitivity of cells in different doses of X (0, 2, 4, 6, 8 Gy) irradiation and cell apoptosis were also detected. EC cells displayed a higher positive expression rate of SKP2, elevated mRNA and protein expression of SKP2, PI3K, AKT, Bcl-2 and Bax, as well as higher extent of PI3K and AKT phosphorylation. SKP2 silencing downregulated mRNA and protein expression of PI3K, AKT and Bcl-2 but increased p27 protein expression, and inhibited the cell survival rate while promoting cell apoptosis. Taken together, silencing SKP2 can inhibit the PI3K/AKT signaling pathway, thereby increasing the radiosensitivity of EC cells.
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Affiliation(s)
- Chunying Wang
- Department of Radiotherapy, Jingjiang People's Hospital, Jingjiang 214500, China.
| | - Shimeng Li
- Department of Oncology, Suqian First Hospital, Suqian 223800, China
| | - Jin Liu
- Department of Oncology, Suqian First Hospital, Suqian 223800, China
| | - Ming Cheng
- Department of Radiotherapy, Jingjiang People's Hospital, Jingjiang 214500, China
| | - Dewen Wang
- Department of Radiotherapy, Jingjiang People's Hospital, Jingjiang 214500, China
| | - Yuxin Wang
- Department of Traditional Chinese Medicine, Jingjiang People's Hospital, Jingjiang 214500, China
| | - Bin Lu
- Department of Radiotherapy, Jingjiang People's Hospital, Jingjiang 214500, China
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Elkahloun AG, Rodriguez Y, Alaiyed S, Wenzel E, Saavedra JM. Telmisartan Protects a Microglia Cell Line from LPS Injury Beyond AT1 Receptor Blockade or PPARγ Activation. Mol Neurobiol 2018; 56:3193-3210. [PMID: 30105672 DOI: 10.1007/s12035-018-1300-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2018] [Accepted: 08/02/2018] [Indexed: 01/12/2023]
Abstract
The Angiotensin II Receptor Blocker (ARB) Telmisartan reduces inflammation through Angiotensin II AT1 receptor blockade and peroxisome proliferator-activated receptor gamma (PPARγ) activation. However, in a mouse microglia-like BV2 cell line, imitating primary microglia responses with high fidelity and devoid of AT1 receptor gene expression or PPARγ activation, Telmisartan reduced gene expression of pro-injury factors, enhanced that of anti-inflammatory genes, and prevented LPS-induced increase in inflammatory markers. Using global gene expression profiling and pathways analysis, we revealed that Telmisartan normalized the expression of hundreds of genes upregulated by LPS and linked with inflammation, apoptosis and neurodegenerative disorders, while downregulating the expression of genes associated with oncological, neurodegenerative and viral diseases. The PPARγ full agonist Pioglitazone had no neuroprotective effects. Surprisingly, the PPARγ antagonists GW9662 and T0070907 were neuroprotective and enhanced Telmisartan effects. GW9226 alone significantly reduced LPS toxic effects and enhanced Telmisartan neuroprotection, including downregulation of pro-inflammatory TLR2 gene expression. Telmisartan and GW9662 effects on LPS injury negatively correlated with pro-inflammatory factors and upstream regulators, including TLR2, and positively with known neuroprotective factors and upstream regulators. Gene Set Enrichment Analysis (GSEA) of the Telmisartan and GW9662 data revealed negative correlations with sets of genes associated with neurodegenerative and metabolic disorders and toxic treatments in cultured systems, while demonstrating positive correlations with gene sets associated with neuroprotection and kinase inhibition. Our results strongly suggest that novel neuroprotective effects of Telmisartan and GW9662, beyond AT1 receptor blockade or PPARγ activation, include downregulation of the TLR2 signaling pathway, findings that may have translational relevance.
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Affiliation(s)
- Abdel G Elkahloun
- Microarray Core, Cancer Genetics and Comparative Genomics Branch, National Human Genome Research Institute, National Institutes of Health, 50 South Dr, MSC 4435, Bethesda, MD, 20892-4435, USA
| | - Yara Rodriguez
- Laboratory of Neuroprotection, Department of Pharmacology and Physiology, Georgetown University Medical Center, SE402 Med/Dent, 3900 Reservoir Road, Washington, DC, 20057, USA
| | - Seham Alaiyed
- Laboratory of Neuroprotection, Department of Pharmacology and Physiology, Georgetown University Medical Center, SE402 Med/Dent, 3900 Reservoir Road, Washington, DC, 20057, USA
| | - Erin Wenzel
- Laboratory of Neuroprotection, Department of Pharmacology and Physiology, Georgetown University Medical Center, SE402 Med/Dent, 3900 Reservoir Road, Washington, DC, 20057, USA
| | - Juan M Saavedra
- Laboratory of Neuroprotection, Department of Pharmacology and Physiology, Georgetown University Medical Center, SE402 Med/Dent, 3900 Reservoir Road, Washington, DC, 20057, USA.
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Bian ZM, Field MG, Elner SG, Elner VM. Expression and regulation of alarmin cytokine IL-1α in human retinal pigment epithelial cells. Exp Eye Res 2018; 172:10-20. [PMID: 29551335 DOI: 10.1016/j.exer.2018.03.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2018] [Accepted: 03/14/2018] [Indexed: 02/08/2023]
Abstract
Human retinal pigment epithelial (hRPE) cells play important immune-regulatory roles in a variety of retinal pathologic processes, including the production of inflammatory cytokines that are essential mediators of the innate immune response within the ocular microenvironment. The pro-inflammatory "alarmin" cytokine IL-1α has been implicated in both infectious and non-infectious retinal diseases, but its regulation in the retina is poorly understood. The purpose of this study was to elucidate the expression and regulation of IL-1α within hRPE cells. To do this, IL-1α mRNA and protein in hRPE cells was assessed by RT-PCR, qPCR, ELISA, Western blot, and immunofluorescence following treatment with a variety of stimuli and inhibitors. ER stress, LPS, IL-1β, and TLR2 activation all significantly increased intracellular IL-1α protein. Increasing intracellular calcium synergized both LPS- and Pam3CSK4-induced IL-1α protein production. Accordingly, blocking calcium signaling and calpain activity strongly suppressed IL-1α protein expression. Significant but more moderate inhibition occurred following blockage of TLR4, caspase-4, or caspase-1. Neutralizing antibodies to IL-1β and TLR2 partially eliminated LPS- and TLR2 ligand Pam3CSK4-stimulated IL-1α protein production. IFN-β induced caspase-4 expression and activation, and also potentiated LPS-induced IL-1α expression, but IFN-β alone had no effect on IL-1α protein production. Interestingly, all inhibitors targeting the PI3K/Akt pathway, with the exception of Ly294002, strongly increased IL-1α protein expression. This study improves understanding of the complex mechanisms regulating IL-1α protein expression in hRPE cells by demonstrating that TLR4 and TLR2 stimulation and exposure to IL-1β, ER stress and intracellular calcium all induce hRPE cells to produce intracellular IL-1α, which is negatively regulated by the PI3K/Akt pathway. Additionally, the non-canonical inflammasome pathway was shown to be involved in LPS-induced hRPE IL-1α expression through caspase-4 signaling.
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Affiliation(s)
- Zong-Mei Bian
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, United States
| | - Matthew G Field
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, United States.
| | - Susan G Elner
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, United States
| | - Victor M Elner
- Department of Ophthalmology, University of Michigan, Ann Arbor, MI, 48105, United States
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Liu J, Copland DA, Theodoropoulou S, Chiu HAA, Barba MD, Mak KW, Mack M, Nicholson LB, Dick AD. Impairing autophagy in retinal pigment epithelium leads to inflammasome activation and enhanced macrophage-mediated angiogenesis. Sci Rep 2016; 6:20639. [PMID: 26847702 PMCID: PMC4742917 DOI: 10.1038/srep20639] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2015] [Accepted: 01/06/2016] [Indexed: 01/06/2023] Open
Abstract
Age-related decreases in autophagy contribute to the progression of age-related macular degeneration (AMD). We have now studied the interaction between autophagy impaired in retinal pigment epithelium (RPE) and the responses of macrophages. We find that dying RPE cells can activate the macrophage inflammasome and promote angiogenesis. In vitro, inhibiting rotenone-induced autophagy in RPE cells elicits caspase-3 mediated cell death. Co-culture of damaged RPE with macrophages leads to the secretion of IL-1β, IL-6 and nitrite oxide. Exogenous IL-6 protects the dysfunctional RPE but IL-1β causes enhanced cell death. Furthermore, IL-1β toxicity is more pronounced in dysfunctional RPE cells showing reduced IRAK3 gene expression. Co-culture of macrophages with damaged RPE also elicits elevated levels of pro-angiogenic proteins that promote ex vivo choroidal vessel sprouting. In vivo, impaired autophagy in the eye promotes photoreceptor and RPE degeneration and recruitment of inflammasome-activated macrophages. The degenerative tissue environment drives an enhanced pro-angiogenic response, demonstrated by increased size of laser-induced choroidal neovascularization (CNV) lesions. The contribution of macrophages was confirmed by depletion of CCR2+ monocytes, which attenuates CNV in the presence of RPE degeneration. Our results suggest that the interplay between perturbed RPE homeostasis and activated macrophages influences key features of AMD development.
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Affiliation(s)
- Jian Liu
- School of Clinical Sciences, University of Bristol, Bristol, UK.,School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - David A Copland
- School of Clinical Sciences, University of Bristol, Bristol, UK.,School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | | | - Hsi An Amy Chiu
- School of Clinical Sciences, University of Bristol, Bristol, UK
| | | | - Ka Wang Mak
- School of Clinical Sciences, University of Bristol, Bristol, UK
| | - Matthias Mack
- Department of Internal Medicine II, University Hospital Regensburg, Regensburg, Germany
| | - Lindsay B Nicholson
- School of Clinical Sciences, University of Bristol, Bristol, UK.,School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK
| | - Andrew D Dick
- School of Clinical Sciences, University of Bristol, Bristol, UK.,School of Cellular and Molecular Medicine, University of Bristol, Bristol, UK.,Institute of Ophthalmology, University College London, London, UK.,National Institute for Health Research (NIHR) Biomedical Research Centre, London, UK
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Chen HF, Liu SJ, Chen G. Heat shock protein 27 phosphorylation in the proliferation and apoptosis of human umbilical vein endothelial cells induced by high glucose through the phosphoinositide 3‑kinase/Akt and extracellular signal‑regulated kinase 1/2 pathways. Mol Med Rep 2014; 11:1504-8. [PMID: 25373458 DOI: 10.3892/mmr.2014.2884] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 09/18/2014] [Indexed: 11/06/2022] Open
Abstract
In the present study, the effect of the heat shock protein 27 (HSP27) signaling pathway on the proliferation and apoptosis of human umbilical vein endothelial cells (HUVECs) induced by high glucose (HG) was investigated. HUVEC proliferation in the indicated conditions was measured by the alamarBlue® assay. Apoptosis in HUVECs cultured with HG was analyzed by an Annexin V‑fluorescein isothiocyanate/propidium iodide apoptosis detection kit. HSP27 activity was evaluated by western blotting with specific phospho‑HSP27 antibody. HUVEC proliferation induced by HG was observed to be reduced by the HSP27 inhibitor quercetin in a concentration‑dependent manner, with a concomitant increase in apoptosis. The phosphorylation of HSP27 induced by HG was blocked by the specific phosphoinositide 3‑kinase (PI3K) inhibitor LY294002 and the specific extracellular signal‑regulated kinase (ERK) 1/2 inhibitor U0126 in a concentration‑dependent manner, with peak inhibition rates of 62.6 and 56.1%, respectively. LY294002 and U0126 also reduced HUVEC proliferation with a concomitant increase in apoptotic rate. In conclusion, HSP27 phosphorylation is important in mediating the proliferation and apoptosis of HUVECs induced by high glucose, and PI3K/Akt and ERK1/2 are important signaling pathways that contribute to HSP27 phosphorylation.
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Affiliation(s)
- Hai-Feng Chen
- Department of Cardiology, Fujian Provincial Clinical College, Fujian Medical University, Fuzhou, Fujian 350001, P.R. China
| | - Shu-Juan Liu
- Department of Endocrinology, Fujian Provincial Clinical College, Fujian Medical University, Fuzhou, Fujian 350001, P.R. China
| | - Gang Chen
- Department of Endocrinology, Fujian Provincial Clinical College, Fujian Medical University, Fuzhou, Fujian 350001, P.R. China
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Endothelial Akt1 mediates angiogenesis by phosphorylating multiple angiogenic substrates. Proc Natl Acad Sci U S A 2014; 111:12865-70. [PMID: 25136137 DOI: 10.1073/pnas.1408472111] [Citation(s) in RCA: 109] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
The PI3K/Akt pathway is necessary for several key endothelial cell (EC) functions, including cell growth, migration, survival, and vascular tone. However, existing literature supports the idea that Akt can be either pro- or antiangiogenic, possibly due to compensation by multiple isoforms in the EC when a single isoform is deleted. Thus, biochemical, genetic, and proteomic studies were conducted to examine isoform-substrate specificity for Akt1 vs. Akt2. In vitro, Akt1 preferentially phosphorylates endothelial nitric oxide synthase (eNOS) and promotes NO release, whereas nonphysiological overexpression of Akt2 can bypass the loss of Akt1. Conditional deletion of Akt1 in the EC, in the absence or presence of Akt2, retards retinal angiogenesis, implying that Akt1 exerts a nonredundant function during physiological angiogenesis. Finally, proteomic analysis of Akt substrates isolated from Akt1- or Akt2-deficient ECs documents that phosphorylation of multiple Akt substrates regulating angiogenic signaling is reduced in Akt1-deficient, but not Akt2-deficient, ECs, including eNOS and Forkhead box proteins. Therefore, Akt1 promotes angiogenesis largely due to phosphorylation and regulation of important downstream effectors that promote aspects of angiogenic signaling.
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