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Rajendran NK, Liu W, Cahill PA, Redmond EM. Caveolin-1 inhibition mediates the opposing effects of alcohol on γ-secretase activity in arterial endothelial and smooth muscle cells. Physiol Rep 2023; 11:e15544. [PMID: 36635975 PMCID: PMC9837422 DOI: 10.14814/phy2.15544] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2022] [Revised: 12/01/2022] [Accepted: 12/04/2022] [Indexed: 04/18/2023] Open
Abstract
Notch is important to vessel homeostasis. We investigated the mechanistic role of caveolin-1 (Cav-1) in mediating the effects of alcohol (Ethanol/EtOH) on the γ-secretase proteolytic activity necessary for Notch signaling in vascular cells. Human coronary artery endothelial cells (HCAEC) were treated with EtOH (0-50 mM), Notch ligand delta-like ligand 4 (Dll4), and the γ-secretase inhibitor DAPT. EtOH stimulated Notch signaling in HCAEC as evidenced by increased Notch receptor (N1, N4) and target gene (hrt2, hrt3) mRNA levels with the most robust response achieved at 25 mM EtOH. Ethanol (25 mM) stimulated γ-secretase proteolytic activity, to the same extent as Dll4, in HCAEC membranes. Ethanol inhibited Cav-1 mRNA and protein levels in HCAEC. Caveolin-1 negatively regulated γ-secretase activity in HCAEC as Cav-1 knockdown stimulated it, while Cav-1 overexpression inhibited it. Moreover, Cav-1 overexpression blocked the stimulatory effect of EtOH on γ-secretase activity in HCAEC. Although EtOH also inhibited Cav-1 expression in human coronary artery smooth muscle cells (HCASMC), EtOH inhibited γ-secretase activity in HCASMC in contrast to its effect in HCAEC. The inhibitory effect of EtOH on γ-secretase in HCASMC was mimicked by Cav-1 knockdown and prevented by Cav-1 overexpression, suggesting that in these cells Cav-1 positively regulates γ-secretase activity. In conclusion, EtOH differentially regulates γ-secretase activity in arterial EC and SMC, being stimulatory and inhibitory, respectively. These effects are both mediated by caveolin-1 inhibition which itself has opposite effects on γ-secretase in the two cell types. This mechanism may underlie, in part, the effects of moderate drinking on atherosclerosis.
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Affiliation(s)
- Naresh K. Rajendran
- Department of SurgeryUniversity of Rochester Medical CenterRochesterNew YorkUSA
| | - Weimin Liu
- Department of SurgeryUniversity of Rochester Medical CenterRochesterNew YorkUSA
| | - Paul A. Cahill
- Vascular Biology and Therapeutics Laboratory, School of BiotechnologyDublin City UniversityDublinIreland
| | - Eileen M. Redmond
- Department of SurgeryUniversity of Rochester Medical CenterRochesterNew YorkUSA
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Zhang S, Zhu N, Li HF, Gu J, Zhang CJ, Liao DF, Qin L. The lipid rafts in cancer stem cell: a target to eradicate cancer. Stem Cell Res Ther 2022; 13:432. [PMID: 36042526 PMCID: PMC9429646 DOI: 10.1186/s13287-022-03111-8] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Accepted: 08/03/2022] [Indexed: 11/10/2022] Open
Abstract
Cancer stem cells (CSCs) are a subpopulation of cancer cells with stem cell properties that sustain cancers, which may be responsible for cancer metastasis or recurrence. Lipid rafts are cholesterol- and sphingolipid-enriched microdomains in the plasma membrane that mediate various intracellular signaling. The occurrence and progression of cancer are closely related to lipid rafts. Emerging evidence indicates that lipid raft levels are significantly enriched in CSCs compared to cancer cells and that most CSC markers such as CD24, CD44, and CD133 are located in lipid rafts. Furthermore, lipid rafts play an essential role in CSCs, specifically in CSC self-renewal, epithelial-mesenchymal transition, drug resistance, and CSC niche. Therefore, lipid rafts are critical regulatory platforms for CSCs and promising therapeutic targets for cancer therapy.
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Affiliation(s)
- Shuo Zhang
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China
| | - Neng Zhu
- Department of Urology, The First Hospital of Hunan University of Chinese Medicine, Changsha, China
| | - Hong Fang Li
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China
| | - Jia Gu
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China
| | - Chan Juan Zhang
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China
| | - Duan Fang Liao
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China
| | - Li Qin
- Laboratory of Stem Cell Regulation With Chinese Medicine and Its Application, School of Pharmacy, Hunan University of Chinese Medicine, 300 Xueshi Road, Hanpu Science and Education District, 410208, Changsha, Hunan, People's Republic of China. .,Institutional Key Laboratory of Vascular Biology and Translational Medicine in Hunan Province, Hunan University of Chinese Medicine, Changsha, China. .,Hunan Province Engineering Research Center of Bioactive Substance Discovery of Traditional Chinese Medicine, Hunan University of Chinese Medicine, Changsha, China.
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3
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Rajendran NK, Liu W, Chu CC, Cahill PA, Redmond EM. Moderate dose alcohol protects against serum amyloid protein A1-induced endothelial dysfunction via both notch-dependent and notch-independent pathways. Alcohol Clin Exp Res 2021; 45:2217-2230. [PMID: 34585422 DOI: 10.1111/acer.14706] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2021] [Revised: 08/24/2021] [Accepted: 08/27/2021] [Indexed: 01/26/2023]
Abstract
BACKGROUND Arterial endothelium plays a critical role in maintaining vessel homeostasis and preventing atherosclerotic cardiovascular disease (CVD). Low-to-moderate alcohol (EtOH) consumption is associated with reduced atherosclerosis and stimulates Notch signaling in endothelial cells. The aim of this study was to determine whether EtOH protects the endothelium against serum amyloid A1 (SAA1)-induced activation/injury, and to determine whether this protection is exclusively Notch-dependent. METHODS AND RESULTS Human coronary artery endothelial cells (HCAEC) were stimulated or not with "pro-atherogenic" SAA1 (1 μM) in the absence or presence of EtOH (25 mM), the Notch ligand DLL4 (3 μg/ml), or the Notch inhibitor DAPT (20 μM). EtOH stimulated Notch signaling in HCAEC, as evidenced by increased expression of the Notch receptor and hrt target genes. Treatment with EtOH alone or stimulation of Notch signaling by DLL4 increased eNOS activity and enhanced HCAEC barrier function as assessed by trans-endothelial electrical resistance. Moreover, EtOH and DLL4 both inhibited SAA1-induced monolayer leakiness, cell adhesion molecule (ICAM, VCAM) expression, and monocyte adhesion. The effects of EtOH were Notch-dependent, as they were blocked with DAPT and by Notch receptor (N1, N4) knockdown. In contrast, EtOH's inhibition of SAA1-induced inflammatory cytokines (IL-6, IFN-γ) and reactive oxygen species (ROS) was Notch-independent, as these effects were unaffected by DAPT or by N1 and/or N4 knockdown. CONCLUSIONS EtOH at moderate levels protects against SAA1-induced endothelial activation via both Notch-dependent and Notch-independent mechanisms. EtOH's maintenance of endothelium in a nonactivated state would be expected to preserve vessel homeostasis and protect against atherosclerosis development.
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Affiliation(s)
- Naresh K Rajendran
- Department of Surgery, University of Rochester Medical Center, Rochester, New York, USA
| | - Weimin Liu
- Department of Surgery, University of Rochester Medical Center, Rochester, New York, USA
| | - Charles C Chu
- Department of Medicine, University of Rochester Medical Center, Rochester, New York, USA
| | - Paul A Cahill
- Vascular Biology and Therapeutics Laboratory, School of Biotechnology, Dublin City University, Dublin, Ireland
| | - Eileen M Redmond
- Department of Surgery, University of Rochester Medical Center, Rochester, New York, USA
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4
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Shi M, Ren S, Chen H, Li J, Huang C, Li Y, Han Y, Li Y, Sun Z, Chen X, Xiong Z. Alcohol drinking inhibits NOTCH-PAX9 signaling in esophageal squamous epithelial cells. J Pathol 2021; 253:384-395. [PMID: 33314197 DOI: 10.1002/path.5602] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 11/22/2020] [Accepted: 12/08/2020] [Indexed: 01/04/2023]
Abstract
Alcohol drinking has been established as a major risk factor for esophageal diseases. Our previous study showed that ethanol exposure inhibited PAX9 expression in human esophageal squamous epithelial cells in vitro and in vivo. In this study, we aimed to investigate the molecular pathways through which alcohol drinking suppresses PAX9 in esophageal squamous epithelial cells. We first demonstrated the inhibition of NOTCH by ethanol exposure in vitro. NOTCH regulated PAX9 expression in KYSE510 and KYSE410 cells in vitro and in vivo. RBPJ and NOTCH intracellular domain (NIC) D1 ChIP-PCR confirmed Pax9 as a direct downstream target of NOTCH signaling in mouse esophagus. NOTCH inhibition by alcohol drinking was further validated in mouse esophagus and human tissue samples. In conclusion, ethanol exposure inhibited NOTCH signaling and thus suppressed PAX9 expression in esophageal squamous epithelial cells in vitro and in vivo. Our data support a novel mechanism of alcohol-induced esophageal injury through the inhibition of NOTCH-PAX9 signaling. © 2020 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
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Affiliation(s)
- Menghan Shi
- Beijing Stomatological Hospital, Capital Medical University, Beijing, PR China.,Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Shuang Ren
- Beijing Stomatological Hospital, Capital Medical University, Beijing, PR China.,Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Hao Chen
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Jing Li
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.,Department of Thoracic Surgery, Ningxia Medical University General Hospital, Yinchuan, PR China
| | - Caizhi Huang
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Yahui Li
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Yuning Han
- Department of Thoracic Surgery, Ningxia Medical University General Hospital, Yinchuan, PR China
| | - Yong Li
- Department of Thoracic Surgery, National Cancer Center, Cancer Hospital of Chinese Academy of Medical Sciences, Beijing, PR China
| | - Zheng Sun
- Beijing Stomatological Hospital, Capital Medical University, Beijing, PR China
| | - Xiaoxin Chen
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.,Center for Gastrointestinal Biology and Disease, Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA
| | - Zhaohui Xiong
- Cancer Research Program, Julius L Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
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5
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Li Y, Li Y, Chen X. NOTCH and Esophageal Squamous Cell Carcinoma. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1287:59-68. [PMID: 33034026 PMCID: PMC7895477 DOI: 10.1007/978-3-030-55031-8_5] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Esophageal squamous cell carcinoma (ESCC) is a deadly disease that requires extensive research on its mechanisms, prevention, and therapy. Recent studies have shown that NOTCH mutations are commonly seen in human ESCC. This chapter summarizes our current understanding of the NOTCH pathway in normal esophagus and in ESCC. In normal esophagus, NOTCH pathway regulates the development of esophageal squamous epithelium, in particular, squamous differentiation. Exposure to extrinsic and intrinsic factors, such as gastroesophageal reflux, alcohol drinking, and inflammation, downregulates the NOTCH pathway and thus inhibits squamous differentiation of esophageal squamous epithelial cells. In ESCC, NOTCH plays a dual role as both a tumor suppressor pathway and an oncogenic pathway. In summary, further studies are warranted to develop NOTCH activators for the prevention of ESCC and NOTCH inhibitors for targeted therapy of a subset of ESCC with activated NOTCH pathway.
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Affiliation(s)
- Yong Li
- Department of Thoracic Surgery, National Cancer Center, Cancer Hospital of Chinese Academy of Medical Sciences, Beijing, China
- Cancer Research Program, Julius L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Yahui Li
- Cancer Research Program, Julius L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA
| | - Xiaoxin Chen
- Cancer Research Program, Julius L. Chambers Biomedical Biotechnology Research Institute, North Carolina Central University, Durham, NC, USA.
- Center for Gastrointestinal Biology and Disease, Division of Gastroenterology and Hepatology, Department of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
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Reagan AM, Gu X, Paudel S, Ashpole NM, Zalles M, Sonntag WE, Ungvari Z, Csiszar A, Otalora L, Freeman WM, Stout MB, Elliott MH. Age-related focal loss of contractile vascular smooth muscle cells in retinal arterioles is accelerated by caveolin-1 deficiency. Neurobiol Aging 2018; 71:1-12. [PMID: 30059797 DOI: 10.1016/j.neurobiolaging.2018.06.039] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2018] [Revised: 06/28/2018] [Accepted: 06/29/2018] [Indexed: 10/28/2022]
Abstract
Cerebral microcirculation is critical for the preservation of brain health, and vascular impairment is associated with age-related neurodegenerative diseases. Because the retina is a component of the central nervous system, cellular changes that occur in the aging retina are likely relevant to the aging brain, and the retina provides the advantage that the entire vascular bed is visible, en face. In this study, we tested the hypothesis that normal, healthy aging alters the contractile vascular smooth muscle cell (VSMC) coverage of retinal arterioles. We found that aging results in a significant reduction of contractile VSMCs in focal patches along arterioles. Focal loss of contractile VSMCs occurs at a younger age in mice deficient in the senescence-associated protein, caveolin-1. Age-related contractile VSMC loss is not exacerbated by genetic depletion of insulin-like growth factor-1. The patchy loss of contractile VSMCs provides a cellular explanation for previous clinical studies showing focal microirregularities in retinal arteriolar responsiveness in healthy aged human subjects and is likely to contribute to age-related retinal vascular complications.
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Affiliation(s)
- Alaina M Reagan
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Xiaowu Gu
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Sijalu Paudel
- Department of Cell Biology, Cameron University, Lawton, OK, USA
| | - Nicole M Ashpole
- Department of BioMolecular Sciences, University of Mississippi, Oxford, MS, USA
| | - Michelle Zalles
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - William E Sonntag
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Zoltan Ungvari
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Anna Csiszar
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Laura Otalora
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Willard M Freeman
- Reynolds Oklahoma Center on Aging & Nathan Shock Center of Excellence in the Biology of Aging, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Geriatric Medicine, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA
| | - Michael B Stout
- Department of Nutritional Sciences, University of Oklahoma Health Sciences Center, Oklahoma city, OK, USA
| | - Michael H Elliott
- Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; Department of Ophthalmology, Dean McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA.
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Hatch E, Morrow D, Liu W, Cahill PA, Redmond EM. Differential effects of alcohol and its metabolite acetaldehyde on vascular smooth muscle cell Notch signaling and growth. Am J Physiol Heart Circ Physiol 2017; 314:H131-H137. [PMID: 29212792 DOI: 10.1152/ajpheart.00586.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Alcohol (EtOH) consumption can variously affect cardiovascular disease. Our aim was to compare the effects of EtOH and its primary metabolite acetaldehyde (ACT) on vascular smooth muscle Notch signaling and cell growth, which are important for atherogenesis. Human coronary artery smooth muscle cells (HCASMCs) were treated with EtOH (25 mM) or ACT (10 or 25 μM). As previously reported, EtOH inhibited Notch signaling and growth of HCASMCs. In contrast, ACT treatment stimulated HCASMC proliferation (cell counts) and increased proliferating cell nuclear antigen expression, concomitant with stimulation of Notch signaling, as determined by increased Notch receptor (N1 and N3) and target gene (Hairy-related transcription factor 1-3) mRNA levels. Interaction of the ligand with the Notch receptor initiates proteolytic cleavage by α- and γ-secretase, resulting in the release of the active Notch intracellular domain. Neither EtOH nor ACT had any significant effect on α-secretase activity. A fluorogenic peptide cleavage assay demonstrated almost complete inhibition by EtOH of Delta-like ligand 4-stimulated γ-secretase activity in solubilized HCASMCs (similar to the effect of the control inhibitor DAPT) but no effect of ACT treatment. EtOH, but not ACT, affected the association and distribution of the γ-secretase catalytic subunit presenilin-1 with lipid rafts, as determined by dual fluorescent labeling and confocal microscopic visualization. In conclusion, ACT stimulates vascular smooth muscle cell Notch signaling and growth, effects opposite to those of EtOH. These differential actions on vascular smooth muscle cells of EtOH and its metabolite ACT may be important in mediating the ultimate effects of drinking on cardiovascular disease. NEW & NOTEWORTHY Acetaldehyde stimulates, in a Notch-dependent manner, the vascular smooth muscle cell growth that contributes to atherogenesis; effects opposite to those of ethanol. These data suggest that in addition to ethanol itself, its metabolite acetaldehyde may also mediate some of the effects of alcohol consumption on vascular cells and, thus, cardiovascular health.
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Affiliation(s)
- Ekaterina Hatch
- Department of Surgery, University of Rochester Medical Center , Rochester, New York
| | - David Morrow
- Department of Surgery, University of Rochester Medical Center , Rochester, New York
| | - Weimin Liu
- Department of Surgery, University of Rochester Medical Center , Rochester, New York
| | - Paul A Cahill
- Vascular Biology and Therapeutics Laboratory, School of Biotechnology, Dublin City University , Dublin , Ireland
| | - Eileen M Redmond
- Department of Surgery, University of Rochester Medical Center , Rochester, New York
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Phytanic acid attenuates insulin-like growth factor-1 activity via nitric oxide-mediated γ-secretase activation in rat aortic smooth muscle cells: possible implications for pathogenesis of infantile Refsum disease. Pediatr Res 2017; 81:531-536. [PMID: 27886192 DOI: 10.1038/pr.2016.258] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/31/2016] [Accepted: 10/09/2016] [Indexed: 01/26/2023]
Abstract
BACKGROUND Infantile Refsum disease (IRD), a peroxisomal disease with defective phytanic acid oxidation, causes neurological impairment and development delay. Insulin-like growth factor-1 (IGF-1) regulates child development and to understand molecular mechanism(s) of IRD, we examined the effect of phytanic acid (PA) on IGF-1 activity. METHODS Bromodeoxyuridine (BrdU) incorporation was measured in rat aortic smooth muscle cell (SMC) cultures following treatment with fetal bovine serum (FBS), basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) or IGF-1 in the absence or presence of PA. Gene expression and protein contents of IGF-1 receptor (IGF-1R) and PDGF receptor (PDGFR) were examined using quantitative PCR and western blotting. RESULTS PA inhibited mitogenic activities of FBS, PDGF and IGF-1 with more pronounced effect on IGF-1-induced bromodeoxyuridine (BrdU) incorporation. Palmitic acid or lignoceric acids did not inhibit IGF-1 activity. PA had no effect on PDGFR mRNA/protein levels but markedly increased IGF-1R mRNA levels. PA and nitric oxide (NO) markedly decreased IGF-1R protein. L-NAME, a NO synthase inhibitor and DAPT, a γ-secretase inhibitor, alleviated PA-induced decrease in IGF-1R protein. Both PA and NO donor increased γ-secretase activity which was alleviated by L-NAME. CONCLUSION This study demonstrates that PA attenuates IGF-1 activity possibly through IGF-1R impairment and NO-mediated modulation of γ-secretase activity.
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