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Garfa Traoré M, Roccio F, Miceli C, Ferri G, Parisot M, Cagnard N, Lhomme M, Dupont N, Benmerah A, Saunier S, Delous M. Fluid shear stress triggers cholesterol biosynthesis and uptake in inner medullary collecting duct cells, independently of nephrocystin-1 and nephrocystin-4. Front Mol Biosci 2023; 10:1254691. [PMID: 37916190 PMCID: PMC10616263 DOI: 10.3389/fmolb.2023.1254691] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 09/15/2023] [Indexed: 11/03/2023] Open
Abstract
Renal epithelial cells are subjected to fluid shear stress of urine flow. Several cellular structures act as mechanosensors-the primary cilium, microvilli and cell adhesion complexes-that directly relay signals to the cytoskeleton to regulate various processes including cell differentiation and renal cell functions. Nephronophthisis (NPH) is an autosomal recessive tubulointerstitial nephropathy leading to end-stage kidney failure before adulthood. NPHP1 and NPHP4 are the major genes which code for proteins that form a complex at the transition zone of the primary cilium, a crucial region required for the maintenance of the ciliary composition integrity. These two proteins also interact with signaling components and proteins associated with the actin cytoskeleton at cell junctions. Due to their specific subcellular localization, we wondered whether NPHP1 and NPHP4 could ensure mechanosensory functions. Using a microfluidic set up, we showed that murine inner medullary collecting ductal cells invalidated for Nphp1 or Nphp4 are more responsive to immediate shear exposure with a fast calcium influx, and upon a prolonged shear condition, an inability to properly regulate cilium length and actin cytoskeleton remodeling. Following a transcriptomic study highlighting shear stress-induced gene expression changes, we showed that prolonged shear triggers both cholesterol biosynthesis pathway and uptake, processes that do not seem to involve neither NPHP1 nor NPHP4. To conclude, our study allowed us to determine a moderate role of NPHP1 and NPHP4 in flow sensation, and to highlight a new signaling pathway induced by shear stress, the cholesterol biosynthesis and uptake pathways, which would allow cells to cope with mechanical stress by strengthening their plasma membrane through the supply of cholesterol.
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Affiliation(s)
- Meriem Garfa Traoré
- Laboratory of Hereditary Kidney Disease, INSERM UMR 1163, Imagine Institute, Université Paris Cité, Paris, France
- Cell Imaging Platform, Structure Fédérative de Recherche Necker, INSERM US24/CNRS UMS3633, Université Paris Cité, Paris, France
| | - Federica Roccio
- Institut Necker Enfants-Malades (INEM), INSERM U1151/CNRS UMR 8253, Université Paris Cité, Paris, France
| | - Caterina Miceli
- Institut Necker Enfants-Malades (INEM), INSERM U1151/CNRS UMR 8253, Université Paris Cité, Paris, France
| | - Giulia Ferri
- Laboratory of Hereditary Kidney Disease, INSERM UMR 1163, Imagine Institute, Université Paris Cité, Paris, France
| | - Mélanie Parisot
- Genomics Core Facility, Institut Imagine-Structure Fédérative de Recherche Necker, INSERM U1163 et INSERM US24/CNRS UMS3633, Université Paris Cité, Paris, France
| | - Nicolas Cagnard
- Bioinformatic Platform, Institut Imagine-Structure Fédérative de Recherche Necker, INSERM U1163 et INSERM US24/CNRS UMS3633, Université Paris Cité, Paris, France
| | - Marie Lhomme
- ICAN Omics, IHU ICAN Foundation for Innovation in Cardiometabolism and Nutrition, Pitié-Salpêtrière Hospital, Paris, France
| | - Nicolas Dupont
- Institut Necker Enfants-Malades (INEM), INSERM U1151/CNRS UMR 8253, Université Paris Cité, Paris, France
| | - Alexandre Benmerah
- Laboratory of Hereditary Kidney Disease, INSERM UMR 1163, Imagine Institute, Université Paris Cité, Paris, France
| | - Sophie Saunier
- Laboratory of Hereditary Kidney Disease, INSERM UMR 1163, Imagine Institute, Université Paris Cité, Paris, France
| | - Marion Delous
- Laboratory of Hereditary Kidney Disease, INSERM UMR 1163, Imagine Institute, Université Paris Cité, Paris, France
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Yin J, Qu J, Liang X, Wang M. Prognostic significance of controlling nutritional status score for patients with gastric cancer: A systematic review and meta‑analysis. Exp Ther Med 2023; 25:202. [PMID: 37090072 PMCID: PMC10119667 DOI: 10.3892/etm.2023.11901] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2022] [Accepted: 03/03/2023] [Indexed: 04/25/2023] Open
Abstract
There is a need to identify potentially useful biomarker(s) for the prediction of prognostic outcomes in patients diagnosed with gastric cancer. This meta-analysis provided updated evidence on the association of controlling nutritional status (CONUT) score with survival and other clinicopathological outcomes in patients with gastric cancer. PubMed and Scopus databases were systematically searched. The review included studies, observational in design, that were conducted among patients with gastric cancer and had documented the association of CONUT score with outcomes of interest. The primary outcomes of interest were overall survival (OS), cancer-specific survival (CSS) and recurrence-free survival (RFS) along with tumour size and extent (T status), nodal status (N status) and tumour staging (TNM staging). STATA was used for statistical analysis. The meta-analysis was conducted with 17 studies. The 5-year OS [hazard ratio (HR), 1.75; 95% confidence interval (CI): 1.55, 1.96], RFS (HR, 1.58; 95% CI: 1.30, 1.91) and CSS (HR, 1.89; 95% CI: 1.01, 3.52) were comparatively poorer in the high CONUT group, than in low CONUT group. High CONUT score was associated with increased risk of having T3/T4 tumour [odds ratio (OR), 1.64; 95% CI: 1.16, 2.34], N2/N3 nodal status (OR, 1.44; 95% CI: 1.17, 1.77) and stage III/IV tumour (OR, 1.64; 95% CI: 1.43, 1.88). The risk of microvascular invasion (OR, 1.46; 95% CI: 1.20, 1.77) and post-operative complications (OR, 1.64; 95% CI: 1.31, 2.06) was higher in those with high CONUT. There were no differences in the risk of poorly differentiated tumour and need for adjuvant chemotherapy between the two groups. Findings suggested that preoperative assessment of CONUT score may be included in the routine assessment of patients with gastric cancer due to its association with survival and other clinical as well as pathological outcomes.
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Affiliation(s)
- Jian Yin
- Third Department of Chest Medicine, The Fifth People's Hospital of Dalian, Dalian, Liaoning 116021, P.R. China
| | - Jin Qu
- Third Department of Chest Medicine, The Fifth People's Hospital of Dalian, Dalian, Liaoning 116021, P.R. China
| | - Xiaoxiao Liang
- Third Department of Chest Medicine, The Fifth People's Hospital of Dalian, Dalian, Liaoning 116021, P.R. China
| | - Meimei Wang
- Third Department of Chest Medicine, The Fifth People's Hospital of Dalian, Dalian, Liaoning 116021, P.R. China
- Correspondence to: Dr Meimei Wang, Third Department of Chest Medicine, The Fifth People's Hospital of Dalian, 890 Huanghe Road, Dalian, Liaoning 116021, P.R. China
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Bergen J, Karasova M, Bileck A, Pignitter M, Marko D, Gerner C, Del Favero G. Exposure to dietary fatty acids oleic and palmitic acid alters structure and mechanotransduction of intestinal cells in vitro. Arch Toxicol 2023; 97:1659-1675. [PMID: 37117602 PMCID: PMC10182945 DOI: 10.1007/s00204-023-03495-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Accepted: 04/04/2023] [Indexed: 04/30/2023]
Abstract
Intestinal cells are continuously exposed to food constituents while adapting to peristaltic movement and fluid shear stress. Oleic acid (OA) and palmitic acid (PA) are among the most prevalent fatty acids with respect to dietary lipids. Despite the central importance of dietary lipids for a balanced diet, awareness about potential detrimental effects related to excessive consumption is increasing; this includes toxicity, metabolic deregulation, and, particularly for cancer cells, a benefit from the uptake of fatty acids related to promotion of metastasis. Expanding on this, we started elucidating the effects of OA and PA (25-500 µM) on non-transformed human intestinal epithelial cells (HCEC-1CT) in comparison to colon carcinoma cells (HCT116), with regard to the mechanosensory apparatus. Hence, intestinal cells' motility is on the one side essential to ensure adaption to peristaltic movement and barrier function, but also to enable metastatic progression. Incubation with both OA and PA (≥ 25 µM) significantly decreased membrane fluidity of HCT116 cells, whereas the effect on HCEC-1CT was more limited. Application of rhodamine-labelled PA demonstrated that the fatty acid is incorporated into the plasma membrane of HCT116, which could not be observed in the non-tumorigenic cell line. Down-streaming into the intracellular compartment, a pronounced rearrangement of actin cytoskeleton was evident in both cell lines (OA and PA; 25 and 100 µM). This was accompanied by a variation of translocation efficiency of the mechanosensitive co-transcription factor YAP1, albeit with a stronger effect seen for PA and the cancer cells. Untargeted proteomic analysis confirmed that exposure to OA and PA could alter the response capacity of HCT116 cells to fluid shear stress. Taken together, OA and PA were able to functionally modulate the mechanosensory apparatus of intestinal cells, implying a novel role for dietary fatty acids in the regulation of intestinal pathophysiology.
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Affiliation(s)
- Janice Bergen
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
- Core Facility Multimodal Imaging, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
| | - Martina Karasova
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
- Core Facility Multimodal Imaging, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
| | - Andrea Bileck
- Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
- Joint Metabolome Facility, University of Vienna, Medical University of Vienna, Vienna, Austria
| | - Marc Pignitter
- Department of Physiological Chemistry, Faculty of Chemistry, University of Vienna, Josef-Holaubek-Platz 2, 1090, Vienna, Austria
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
| | - Christopher Gerner
- Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria
- Joint Metabolome Facility, University of Vienna, Medical University of Vienna, Vienna, Austria
| | - Giorgia Del Favero
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria.
- Core Facility Multimodal Imaging, Faculty of Chemistry, University of Vienna, Währingerstr. 38-42, 1090, Vienna, Austria.
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Jobst M, Kiss E, Gerner C, Marko D, Del Favero G. Activation of autophagy triggers mitochondrial loss and changes acetylation profile relevant for mechanotransduction in bladder cancer cells. Arch Toxicol 2023; 97:217-233. [PMID: 36214828 PMCID: PMC9816236 DOI: 10.1007/s00204-022-03375-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Accepted: 09/05/2022] [Indexed: 01/19/2023]
Abstract
Bladder cells are constantly exposed to multiple xenobiotics and bioactive metabolites. In addition to this challenging chemical environment, they are also exposed to shear stress originating from urine and interstitial fluids. Hence, physiological function of bladder cells relies on a high biochemical and biomechanical adaptive competence, which, in turn, is largely supported via autophagy-related mechanisms. As a negative side of this plasticity, bladder cancer cells are known to adapt readily to chemotherapeutic programs. At the molecular level, autophagy was described to support resistance against pharmacological treatments and to contribute to the maintenance of cell structure and metabolic competence. In this study, we enhanced autophagy with rapamycin (1-100 nM) and assessed its effects on the motility of bladder cells, as well as the capability to respond to shear stress. We observed that rapamycin reduced cell migration and the mechanical-induced translocation potential of Krüppel-like transcription factor 2 (KLF2). These effects were accompanied by a rearrangement of cytoskeletal elements and mitochondrial loss. In parallel, intracellular acetylation levels were decreased. Mechanistically, inhibition of the NAD + -dependent deacetylase sirtuin-1 (SIRT1) with nicotinamide (NAM; 0.1-5 mM) restored acetylation levels hampered by rapamycin and cell motility. Taken together, we described the effects of rapamycin on cytoskeletal elements crucial for mechanotransduction and the dependency of these changes on the mitochondrial turnover caused by autophagy activation. Additionally, we could show that targeted metabolic intervention could revert the outcome of autophagy activation, reinforcing the idea that bladder cells can easily adapt to multiple xenobiotics and circumvent in this way the effects of single chemicals.
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Affiliation(s)
- Maximilian Jobst
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria
| | - Endre Kiss
- Core Facility Multimodal, Imaging, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria
| | - Christopher Gerner
- Department of Analytical Chemistry, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria ,Joint Metabolome Facility, University of Vienna and Medical University of Vienna, Vienna, Austria
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria
| | - Giorgia Del Favero
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria ,Core Facility Multimodal, Imaging, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090 Vienna, Austria
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5
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Foodborne compounds that alter plasma membrane architecture can modify the response of intestinal cells to shear stress in vitro. Toxicol Appl Pharmacol 2022; 446:116034. [DOI: 10.1016/j.taap.2022.116034] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 04/07/2022] [Accepted: 04/16/2022] [Indexed: 01/25/2023]
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Ridone P, Pandzic E, Vassalli M, Cox CD, Macmillan A, Gottlieb PA, Martinac B. Disruption of membrane cholesterol organization impairs the activity of PIEZO1 channel clusters. J Gen Physiol 2021; 152:151885. [PMID: 32582958 PMCID: PMC7398139 DOI: 10.1085/jgp.201912515] [Citation(s) in RCA: 80] [Impact Index Per Article: 26.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 05/12/2020] [Indexed: 11/20/2022] Open
Abstract
The human mechanosensitive ion channel PIEZO1 is gated by membrane tension and regulates essential biological processes such as vascular development and erythrocyte volume homeostasis. Currently, little is known about PIEZO1 plasma membrane localization and organization. Using a PIEZO1-GFP fusion protein, we investigated whether cholesterol enrichment or depletion by methyl-β-cyclodextrin (MBCD) and disruption of membrane cholesterol organization by dynasore affects PIEZO1-GFP's response to mechanical force. Electrophysiological recordings in the cell-attached configuration revealed that MBCD caused a rightward shift in the PIEZO1-GFP pressure-response curve, increased channel latency in response to mechanical stimuli, and markedly slowed channel inactivation. The same effects were seen in native PIEZO1 in N2A cells. STORM superresolution imaging revealed that, at the nanoscale, PIEZO1-GFP channels in the membrane associate as clusters sensitive to membrane manipulation. Both cluster distribution and diffusion rates were affected by treatment with MBCD (5 mM). Supplementation of polyunsaturated fatty acids appeared to sensitize the PIEZO1-GFP response to applied pressure. Together, our results indicate that PIEZO1 function is directly dependent on the membrane composition and lateral organization of membrane cholesterol domains, which coordinate the activity of clustered PIEZO1 channels.
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Affiliation(s)
- Pietro Ridone
- The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia
| | - Elvis Pandzic
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, Lowy Cancer Research Centre, The University of New South Wales, Sydney, NSW, Australia
| | - Massimo Vassalli
- Institute of Biophysics, National Research Council, Genova, Italy
| | - Charles D Cox
- The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW, Australia
| | - Alexander Macmillan
- Biomedical Imaging Facility, Mark Wainwright Analytical Centre, Lowy Cancer Research Centre, The University of New South Wales, Sydney, NSW, Australia
| | - Philip A Gottlieb
- Physiology and Biophysics, State University of New York at Buffalo, Buffalo, NY
| | - Boris Martinac
- The Victor Chang Cardiac Research Institute, Darlinghurst, NSW, Australia.,St. Vincent's Clinical School, University of New South Wales, Darlinghurst, NSW, Australia
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Exploring the dermotoxicity of the mycotoxin deoxynivalenol: combined morphologic and proteomic profiling of human epidermal cells reveals alteration of lipid biosynthesis machinery and membrane structural integrity relevant for skin barrier function. Arch Toxicol 2021; 95:2201-2221. [PMID: 33890134 PMCID: PMC8166681 DOI: 10.1007/s00204-021-03042-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 04/01/2021] [Indexed: 12/26/2022]
Abstract
Deoxynivalenol (vomitoxin, DON) is a secondary metabolite produced by Fusarium spp. fungi and it is one of the most prevalent mycotoxins worldwide. Crop infestation results not only in food and feed contamination, but also in direct dermal exposure, especially during harvest and food processing. To investigate the potential dermotoxicity of DON, epidermoid squamous cell carcinoma cells A431 were compared to primary human neonatal keratinocytes (HEKn) cells via proteome/phosphoproteome profiling. In A431 cells, 10 µM DON significantly down-regulated ribosomal proteins, as well as mitochondrial respiratory chain elements (OXPHOS regulation) and transport proteins (TOMM22; TOMM40; TOMM70A). Mitochondrial impairment was reflected in altered metabolic competence, apparently combined with interference of the lipid biosynthesis machinery. Functional effects on the cell membrane were confirmed by live cell imaging and membrane fluidity assays (0.1–10 µM DON). Moreover, a common denominator for both A431 and HEKn cells was a significant downregulation of the squalene synthase (FDFT1). In sum, proteome alterations could be traced back to the transcription factor Klf4, a crucial regulator of skin barrier function. Overall, these results describe decisive molecular events sustaining the capability of DON to impair skin barrier function. Proteome data generated in the study are fully accessible via ProteomeXchange with the accession numbers PXD011474 and PXD013613.
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Shin HY, Fukuda S, Schmid-Schönbein GW. Fluid shear stress-mediated mechanotransduction in circulating leukocytes and its defect in microvascular dysfunction. J Biomech 2021; 120:110394. [PMID: 33784517 DOI: 10.1016/j.jbiomech.2021.110394] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 03/03/2021] [Indexed: 11/16/2022]
Abstract
Leukocytes (neutrophils, monocytes) in the active circulation exhibit multiple phenotypic indicators for a low level of cellular activity, like lack of pseudopods and minimal amounts of activated, cell-adhesive integrins on their surfaces. In contrast, before these cells enter the circulation in the bone marrow or when they recross the endothelium into extravascular tissues of peripheral organs they are fully activated. We review here a multifaceted mechanism mediated by fluid shear stress that can serve to deactivate leukocytes in the circulation. The fluid shear stress controls pseudopod formation via the FPR receptor, the same receptor responsible for pseudopod projection by localized actin polymerization. The bioactivity of macromolecular factors in the blood plasma that interfere with receptor stimulation by fluid flow, such as proteolytic cleavage in the extracellular domain of the receptor or the membrane actions of cholesterol, leads to a defective ability to respond to fluid shear stress by actin depolymerization. The cell reaction to fluid shear involves CD18 integrins, nitric oxide, cGMP and Rho GTPases, is attenuated in the presence of inflammatory mediators and modified by glucocorticoids. The mechanism is abolished in disease models (genetic hypertension and hypercholesterolemia) leading to an increased number of activated leukocytes in the circulation with enhanced microvascular resistance and cell entrapment. In addition to their role in binding to biochemical agonists/antagonists, membrane receptors appear to play a second role: to monitor local fluid shear stress levels. The fluid shear stress control of many circulating cell types such as lymphocytes, stem cells, tumor cells remains to be elucidated.
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Affiliation(s)
- Hainsworth Y Shin
- F. Joseph Halcomb III, M.D. Department of Biomedical Engineering, University of Kentucky, Lexington, KY, United States; Division of Biology, Chemistry, and Materials Science, Office of Science and Engineering Laboratories Center for Devices and Radiological Health, The Food & Drive Administration, Silver Spring, MD, United States
| | - Shunichi Fukuda
- Department of Neurosurgery, National Hospital Organization Kyoto Medical Center, Kyoto, Japan
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Shear stress activates mitochondrial oxidative phosphorylation by reducing plasma membrane cholesterol in vascular endothelial cells. Proc Natl Acad Sci U S A 2020; 117:33660-33667. [PMID: 33318210 PMCID: PMC7776821 DOI: 10.1073/pnas.2014029117] [Citation(s) in RCA: 37] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022] Open
Abstract
The mechanotransduction of shear stress in vascular endothelial cells is still not completely understood. We show a pathway of shear stress signal transduction mediated by plasma membrane cholesterol-dependent mitochondrial oxidative phosphorylation. The latest imaging technology using domain 4 mutant-derived cholesterol biosensors and a fluorescence resonance energy transfer-based adenosine triphosphate (ATP) biosensor revealed that shear stress rapidly decreases cholesterol levels in the plasma membrane via both efflux and internalization, and reduction in plasma membrane cholesterol was linked to the activation of mitochondrial ATP production. The addition of cholesterol blocked these shear stress effects. Increased mitochondrial ATP production led to ATP release from the endothelial cells, thereby activating purinoceptors in the plasma membrane and leading to purinergic Ca2+ signaling in response to shear stress. Vascular endothelial cells (ECs) sense and respond to hemodynamic shear stress, which is critical for circulatory homeostasis and the pathophysiology of vascular diseases. The mechanisms of shear stress mechanotransduction, however, remain elusive. We previously demonstrated a direct role of mitochondria in the purinergic signaling of shear stress: shear stress increases mitochondrial adenosine triphosphate (ATP) production, triggering ATP release and Ca2+ signaling via EC purinoceptors. Here, we showed that shear stress rapidly decreases cholesterol in the plasma membrane, thereby activating mitochondrial ATP production. Imaging using domain 4 mutant-derived cholesterol biosensors showed that the application of shear stress to cultured ECs markedly decreased cholesterol levels in both the outer and inner plasma membrane bilayers. Flow cytometry showed that the cholesterol levels in the outer bilayer decreased rapidly after the onset of shear stress, reached a minimum (around 60% of the control level) at 10 min, and plateaued thereafter. After the shear stress ceased, the decreased cholesterol levels returned to those seen in the control. A biochemical analysis showed that shear stress caused both the efflux and the internalization of plasma membrane cholesterol. ATP biosensor imaging demonstrated that shear stress significantly increased mitochondrial ATP production. Similarly, the treatment of cells with methyl-β-cyclodextrin (MβCD), a membrane cholesterol-depleting agent, increased mitochondrial ATP production. The addition of cholesterol to cells inhibited the increasing effects of both shear stress and MβCD on mitochondrial ATP production in a dose-dependent manner. These findings indicate that plasma membrane cholesterol dynamics are closely coupled to mitochondrial oxidative phosphorylation in ECs.
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Hori A, Ishida F, Nakazawa H, Yamaura M, Morita S, Uehara T, Honda T, Hidaka H. Serum sphingomyelin species profile is altered in hematologic malignancies. Clin Chim Acta 2020; 514:29-33. [PMID: 33279503 DOI: 10.1016/j.cca.2020.11.024] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 11/12/2020] [Accepted: 11/26/2020] [Indexed: 01/27/2023]
Abstract
Sphingomyelin (SM) plays key roles in regulating cell membrane fluidity and in intracellular signal transduction. However, little is known as to whether alterations in SM concentration or SM species distribution are linked pathological conditions. The present study examined SM concentrations and species profiles in serum taken from patients with hematologic malignancies. Serum was collected from normal subjects and from patients with B-cell lymphoma, myelodysplastic syndrome (MDS), acute myeloid leukemia (AML) and acute lymphatic leukemia/ lymphoblastic lymphoma (ALL/LBL). Serum SM species distribution was analyzed using electrospray ionization mass spectrometry/ mass spectrometry (ESI MS/MS). Serum lipids concentration were measured using enzymatic assays. Normal and hematologic malignancy sera were similar in terms of total serum SM and phosphatidylcholine (PC) concentrations and SM/PC ratio. However, all hematologic malignancy sera had lower levels of SM species containing saturated odd chain fatty acids (OCFAs) in the side chain compared to normal serum. In addition, the proportion of SM species with saturated (C20 and C22) and mono unsaturated fatty acids (C18, C20, C22) were lower in MDS patient serum compared to normal serum. The present study revealed that the serum SM species profile in patients with hematologic malignancies differed from that of normal subjects despite total serum SM and PC concentrations and SM/PC ratios being similar between the various cancer groups and the normal group.
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Affiliation(s)
- Atsushi Hori
- Department of Biomedical Laboratory Sciences, School of Health Sciences, Shinshu University School of Medicine, Matsumoto, Japan; Department of Clinical Laboratory Medicine, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan; Center for Genomic and Regenerative Medicine, Juntendo University Graduate School of Medicine, Bunkyo-ku, Japan
| | - Fumihiro Ishida
- Department of Biomedical Laboratory Sciences, School of Health Sciences, Shinshu University School of Medicine, Matsumoto, Japan; Division of Hematology, Department of Internal Medicine, Shinshu University School of Medicine, Matsumoto, Japan
| | - Hideyuki Nakazawa
- Division of Hematology, Department of Internal Medicine, Shinshu University School of Medicine, Matsumoto, Japan
| | - Makoto Yamaura
- Department of Biomedical Laboratory Sciences, School of Health Sciences, Shinshu University School of Medicine, Matsumoto, Japan; Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan
| | - Sunao Morita
- Department of Medical Technology, Iida Municipal Hospital, Iida, Japan
| | - Takeshi Uehara
- Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan
| | - Takayuki Honda
- Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan
| | - Hiroya Hidaka
- Department of Laboratory Medicine, Shinshu University Hospital, Matsumoto, Japan.
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Zhang L, Zhao L, Ouyang PK, Chen P. Insight into the role of cholesterol in modulation of morphology and mechanical properties of CHO-K1 cells: An in situ AFM study. Front Chem Sci Eng 2019. [DOI: 10.1007/s11705-018-1775-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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12
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Del Favero G, Bialas F, Grabher S, Wittig A, Bräuer B, Gerthsen D, Echalier C, Kamalov M, Marko D, Becker CFW. Silica particles with a quercetin–R5 peptide conjugate are taken up into HT-29 cells and translocate into the nucleus. Chem Commun (Camb) 2019; 55:9649-9652. [DOI: 10.1039/c9cc02215e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Particles generated by biomimetic silica precipitation with a quercetin–R5 peptide enter the nucleus of HT-29 cells without inducing toxicity.
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13
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Del Favero G, Zaharescu R, Marko D. Functional impairment triggered by altertoxin II (ATXII) in intestinal cells in vitro: cross-talk between cytotoxicity and mechanotransduction. Arch Toxicol 2018; 92:3535-3547. [PMID: 30276433 PMCID: PMC6290659 DOI: 10.1007/s00204-018-2317-6] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2018] [Accepted: 09/19/2018] [Indexed: 12/22/2022]
Abstract
Intestinal cells are able to continuously integrate response to multiple stimuli/stressors; these include the concomitant activation of “chemically driven” pathways, of paramount importance in the response to toxicants, as well as physical stimulation derived from motility. Altertoxin II (ATXII, 0.1, 1 and 10 µM), a mycotoxin produced by the food contaminant fungus Alternaria alternata was studied in HT-29 intestinal adenocarcinoma cells and in non-transformed intestinal epithelial cells, HCEC. One-hour incubation with ATXII was sufficient to trigger irreversible cytotoxicity in both cell types, as well as to modify cellular responses to concomitant pro-oxidant challenge (H2O2, 100–500 µM, DCF-DA assay) suggesting that even relatively short-time exposure of the intestinal cells could be sufficient to alter their functionality. Combination of ATXII (1 µM) with physical stimulation typical of the intestinal compartment (shear stress) revealed differential response of tumor-derived epithelial cells HT-29 in comparison to HCEC, in particular in the localization of the transcription factor Nrf2 (NF-E2-related factor 2). Moreover, ATXII reduced the migratory potential of HCEC as well as their membrane fluidity, but had no respective impact on HT-29 cells. Taken together, ATXII appeared to alter predominantly membrane functionality in HCEC thus hampering crucial functions for cellular motility/turnover, as well as barrier function of healthy intestinal cells and had very limited activity on the tumor counterparts.
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Affiliation(s)
- Giorgia Del Favero
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090, Vienna, Austria.
| | - Ronita Zaharescu
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090, Vienna, Austria
| | - Doris Marko
- Department of Food Chemistry and Toxicology, Faculty of Chemistry, University of Vienna, Währingerstr. 38-40, 1090, Vienna, Austria
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The Unsolved Problem of How Cells Sense Micron-Scale Curvature. Trends Biochem Sci 2017; 42:961-976. [PMID: 29089160 DOI: 10.1016/j.tibs.2017.10.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Revised: 09/27/2017] [Accepted: 10/02/2017] [Indexed: 12/31/2022]
Abstract
Membrane curvature is a fundamental feature of cells and their organelles. Much of what we know about how cells sense curved surfaces comes from studies examining nanometer-sized molecules on nanometer-scale curvatures. We are only just beginning to understand how cells recognize curved topologies at the micron scale. In this review, we provide the reader with an overview of our current understanding of how cells sense and respond to micron-scale membrane curvature.
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15
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White MM, Geraghty P, Hayes E, Cox S, Leitch W, Alfawaz B, Lavelle GM, McElvaney OJ, Flannery R, Keenan J, Meleady P, Henry M, Clynes M, Gunaratnam C, McElvaney NG, Reeves EP. Neutrophil Membrane Cholesterol Content is a Key Factor in Cystic Fibrosis Lung Disease. EBioMedicine 2017; 23:173-184. [PMID: 28835336 PMCID: PMC5605378 DOI: 10.1016/j.ebiom.2017.08.013] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2017] [Revised: 08/09/2017] [Accepted: 08/14/2017] [Indexed: 01/13/2023] Open
Abstract
Background Identification of mechanisms promoting neutrophil trafficking to the lungs of patients with cystic fibrosis (CF) is a challenge for next generation therapeutics. Cholesterol, a structural component of neutrophil plasma membranes influences cell adhesion, a key step in transmigration. The effect of chronic inflammation on neutrophil membrane cholesterol content in patients with CF (PWCF) remains unclear. To address this we examined neutrophils of PWCF to evaluate the cause and consequence of altered membrane cholesterol and identified the effects of lung transplantation and ion channel potentiator therapy on the cellular mechanisms responsible for perturbed membrane cholesterol and increased cell adhesion. Methodology PWCF homozygous for the ΔF508 mutation or heterozygous for the G551D mutation were recruited (n = 48). Membrane protein expression was investigated by mass spectrometry. The effect of lung transplantation or ivacaftor therapy was assessed by ELISAs, and calcium fluorometric and μ-calpain assays. Findings Membranes of CF neutrophils contain less cholesterol, yet increased integrin CD11b expression, and respond to inflammatory induced endoplasmic reticulum (ER) stress by activating μ-calpain. In vivo and in vitro, increased μ-calpain activity resulted in proteolysis of the membrane cholesterol trafficking protein caveolin-1. The critical role of caveolin-1 for adequate membrane cholesterol content was confirmed in caveolin-1 knock-out mice. Lung transplant therapy or treatment of PWCF with ivacaftor, reduced levels of circulating inflammatory mediators and actuated increased caveolin-1 and membrane cholesterol, with concurrent normalized neutrophil adhesion. Interpretation Results demonstrate an auxiliary benefit of lung transplant and potentiator therapy, evident by a reduction in circulating inflammation and controlled neutrophil adhesion. This study explored neutrophil adhesion in cystic fibrosis. Altered membrane cholesterol lead to increased adhesion. Circulating inflammatory mediators caused increased calpain activity and reduced membrane cholesterol content.
In patients with cystic fibrosis (CF), chronic inflammation in the circulation, in part originating from the pulmonary compartment, leads to decreased membrane cholesterol in circulating neutrophils, resulting in increased cell adhesion. The mechanism of action involves proteolytic down-regulation of the cholesterol trafficking protein caveolin-1. The overall effect of lung transplant therapy, or CFTR potentiator treatment, was to significantly diminish the circulating inflammatory burden thereby permitting caveolin-1 expression, with concomitant decreased CF cell adhesion and significant clinical improvement.
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Affiliation(s)
- Michelle M White
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Patrick Geraghty
- Division of Pulmonary & Critical Care Medicine, Department of Medicine, State University of New York Downstate Medical Center, Brooklyn, NY, USA
| | - Elaine Hayes
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Stephen Cox
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - William Leitch
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Bader Alfawaz
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Gillian M Lavelle
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Oliver J McElvaney
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Ryan Flannery
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland; Coláiste Dhúlaigh College of Further Education, Dublin 17, Ireland
| | - Joanne Keenan
- National Institute for Cellular Biotechnology, Dublin City University, Dublin 9, Ireland
| | - Paula Meleady
- National Institute for Cellular Biotechnology, Dublin City University, Dublin 9, Ireland
| | - Michael Henry
- National Institute for Cellular Biotechnology, Dublin City University, Dublin 9, Ireland
| | - Martin Clynes
- National Institute for Cellular Biotechnology, Dublin City University, Dublin 9, Ireland
| | - Cedric Gunaratnam
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Noel G McElvaney
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland
| | - Emer P Reeves
- Irish Centre for Genetic Lung Disease, Department of Medicine, Royal College of Surgeons in Ireland, Beaumont Hospital, Dublin 9, Ireland.
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Ekpenyong AE, Toepfner N, Fiddler C, Herbig M, Li W, Cojoc G, Summers C, Guck J, Chilvers ER. Mechanical deformation induces depolarization of neutrophils. SCIENCE ADVANCES 2017; 3:e1602536. [PMID: 28630905 PMCID: PMC5470826 DOI: 10.1126/sciadv.1602536] [Citation(s) in RCA: 57] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/04/2023]
Abstract
The transition of neutrophils from a resting state to a primed state is an essential requirement for their function as competent immune cells. This transition can be caused not only by chemical signals but also by mechanical perturbation. After cessation of either, these cells gradually revert to a quiescent state over 40 to 120 min. We use two biophysical tools, an optical stretcher and a novel microcirculation mimetic, to effect physiologically relevant mechanical deformations of single nonadherent human neutrophils. We establish quantitative morphological analysis and mechanical phenotyping as label-free markers of neutrophil priming. We show that continued mechanical deformation of primed cells can cause active depolarization, which occurs two orders of magnitude faster than by spontaneous depriming. This work provides a cellular-level mechanism that potentially explains recent clinical studies demonstrating the potential importance, and physiological role, of neutrophil depriming in vivo and the pathophysiological implications when this deactivation is impaired, especially in disorders such as acute lung injury.
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Affiliation(s)
- Andrew E. Ekpenyong
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK
- Biotechnology Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, 01307 Dresden, Germany
- Department of Physics, Creighton University, Omaha, NE 68178, USA
| | - Nicole Toepfner
- Klinik und Poliklinik für Kinder-und Jugendmedizin, Universitätsklinikum Carl Gustav Carus, Technische Universität Dresden, Dresden, Germany
- Department of Medicine, Addenbrooke’s and Papworth Hospitals, University of Cambridge School of Clinical Medicine, Cambridge CB2 0QQ, UK
| | - Christine Fiddler
- Department of Medicine, Addenbrooke’s and Papworth Hospitals, University of Cambridge School of Clinical Medicine, Cambridge CB2 0QQ, UK
| | - Maik Herbig
- Biotechnology Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, 01307 Dresden, Germany
| | - Wenhong Li
- Biotechnology Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, 01307 Dresden, Germany
| | - Gheorghe Cojoc
- Biotechnology Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, 01307 Dresden, Germany
| | - Charlotte Summers
- Department of Medicine, Addenbrooke’s and Papworth Hospitals, University of Cambridge School of Clinical Medicine, Cambridge CB2 0QQ, UK
| | - Jochen Guck
- Cavendish Laboratory, Department of Physics, University of Cambridge, Cambridge CB3 0HE, UK
- Biotechnology Center for Molecular and Cellular Bioengineering, Technische Universität Dresden, 01307 Dresden, Germany
- Corresponding author.
| | - Edwin R. Chilvers
- Department of Medicine, Addenbrooke’s and Papworth Hospitals, University of Cambridge School of Clinical Medicine, Cambridge CB2 0QQ, UK
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17
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Akenhead ML, Fukuda S, Schmid-Schönbein GW, Shin HY. Fluid shear-induced cathepsin B release in the control of Mac1-dependent neutrophil adhesion. J Leukoc Biol 2017; 102:117-126. [PMID: 28389621 DOI: 10.1189/jlb.3a0716-317rr] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Revised: 02/23/2017] [Accepted: 03/20/2017] [Indexed: 11/24/2022] Open
Abstract
There is compelling evidence that circulatory hemodynamics prevent neutrophil activation, including adhesion to microvessels, in the microcirculation. However, the underlying mechanism or mechanisms by which that mechanoregulation occurs remain unresolved. Here, we report evidence that exposure to fluid shear stress (FSS) promotes neutrophils to release cathepsin B (ctsB) and that this autocrine regulatory event is antiadhesive for neutrophils on endothelial surfaces through Mac1-selective regulation. We used a combined cell-engineering and immunocytochemistry approach to find that ctsB was capable of cleaving Mac1 integrins on neutrophils and demonstrated that this proteolysis alters their adhesive functions. Under no-flow conditions, ctsB enhanced neutrophil migration though a putative effect on pseudopod retraction rates. We also established a flow-based cell detachment assay to verify the role of ctsB in the control of neutrophil adhesion by fluid flow stimulation. Fluid flow promoted neutrophil detachment from platelet and endothelial layers that required ctsB, consistent with its fluid shear stress-induced release. Notably, compared with leukocytes from wild-type mice, those from ctsB-deficient (ctsB -/- ) mice exhibited an impaired CD18 cleavage response to FSS, significantly elevated baseline levels of CD18 surface expression, and an enhanced adhesive capacity to mildly inflamed postcapillary venules. Taken together, the results of the present study support a role for ctsB in a hemodynamic control mechanism that is antiadhesive for leukocytes on endothelium. These results have implications in the pathogenesis of chronic inflammation, microvascular dysfunction, and cardiovascular diseases involving sustained neutrophil activation in the blood and microcirculation.
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Affiliation(s)
- Michael L Akenhead
- Department of Biomedical Engineering, University of Kentucky, Lexington, Kentucky, USA
| | - Shunichi Fukuda
- Department of Neurosurgery, National Hospital Organization Kyoto Medical Center, Kyoto, Japan; and.,Department of Bioengineering, University of California San Diego, La Jolla, California, USA
| | | | - Hainsworth Y Shin
- Department of Biomedical Engineering, University of Kentucky, Lexington, Kentucky, USA;
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18
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Silencing Triggering Receptors Expressed on Myeloid Cells-1 Impaired the Inflammatory Response to Oxidized Low-Density Lipoprotein in Macrophages. Inflammation 2016; 39:199-208. [PMID: 26277357 DOI: 10.1007/s10753-015-0239-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Atherosclerosis is a chronic progressive inflammatory disease characterized by the accumulation of lipid contents in arterial walls. Previous studies suggest participation of Toll-like receptors (TLRs) in lipid deposition and inflammatory response in vascular wall. The triggering receptor expressed on myeloid cells 1 (TREM-1) is a cell surface receptor of the immunoglobulin superfamily, which amplifies signal transduction of TLR pathway and enhances immune response to microbial infections. The aim of the present study was to investigate the effect of the oxidized low-density lipoprotein (oxLDL) on the expression of the TREM-1, as well as its engagement in proinflammatory cytokine production and foam cell formation in RAW264.7 mice macrophages. oxLDL enhanced TREM-1 and TLR-4, but not TLR-2 gene expression in macrophages; furthermore, silencing TREM-1 expression by short hairpin interfering RNA inhibited lipid phagocytosis and proinflammatory tumor necrosis factor-α (TNF-α) as well as interleukin-6 (IL-6) production in macrophages; moreover, application of synthetic antagonist, LP-17 polypeptide, reduced IL-6 production upon oxLDL stimulation in vitro and in vivo. In conclusion, in macrophages, oxLDL enhanced expression of TREM-1, which amplifies the innate immune response of TLR pathway; activation of TREM-1 contributes to atherogenesis process by enhancing proinflammatory cytokine production and foam cell formation.
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19
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A Abdel-Rahman E, Mahmoud AM, Khalifa AM, Ali SS. Physiological and pathophysiological reactive oxygen species as probed by EPR spectroscopy: the underutilized research window on muscle ageing. J Physiol 2016; 594:4591-613. [PMID: 26801204 DOI: 10.1113/jp271471] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2015] [Accepted: 12/04/2015] [Indexed: 12/18/2022] Open
Abstract
Reactive oxygen and nitrogen species (ROS and RNS) play crucial roles in triggering, mediating and regulating physiological and pathophysiological signal transduction pathways within the cell. Within the cell, ROS efflux is firmly controlled both spatially and temporally, making the study of ROS dynamics a challenging task. Different approaches have been developed for ROS assessment; however, many of these assays are not capable of direct identification or determination of subcellular localization of different ROS. Here we highlight electron paramagnetic resonance (EPR) spectroscopy as a powerful technique that is uniquely capable of addressing questions on ROS dynamics in different biological specimens and cellular compartments. Due to their critical importance in muscle functions and dysfunction, we discuss in some detail spin trapping of various ROS and focus on EPR detection of nitric oxide before highlighting how EPR can be utilized to probe biophysical characteristics of the environment surrounding a given stable radical. Despite the demonstrated ability of EPR spectroscopy to provide unique information on the identity, quantity, dynamics and environment of radical species, its applications in the field of muscle physiology, fatiguing and ageing are disproportionately infrequent. While reviewing the limited examples of successful EPR applications in muscle biology we conclude that the field would greatly benefit from more studies exploring ROS sources and kinetics by spin trapping, protein dynamics by site-directed spin labelling, and membrane dynamics and global redox changes by spin probing EPR approaches.
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Affiliation(s)
- Engy A Abdel-Rahman
- Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Ali M Mahmoud
- Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Abdulrahman M Khalifa
- Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
| | - Sameh S Ali
- Center for Aging and Associated Diseases, Helmy Institute of Medical Sciences, Zewail City of Science and Technology, Giza, Egypt
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20
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Yang Z, Wi Y, Yoon YM, Verwilst P, Jang JH, Kim TW, Kang C, Kim JS. BODIPY/Nile-Red-Based Efficient FRET Pair: Selective Assay of Endoplasmic Reticulum Membrane Fluidity. Chem Asian J 2015; 11:527-31. [PMID: 26537552 DOI: 10.1002/asia.201501060] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2015] [Revised: 10/31/2015] [Indexed: 12/26/2022]
Affiliation(s)
- Zhigang Yang
- Department of Chemistry; Korea University; Seoul 136-701 Korea
- Key Laboratory of optoelectronic devices and systems of ministry of education and Guangdong province, College of optoelectronic engineering; Shenzhen University; Shenzhen 518060 China
| | - Youngjin Wi
- The School of East-West Medical Science; Kyung Hee University; Yongin 446-701 Korea
| | - Young-Min Yoon
- The School of East-West Medical Science; Kyung Hee University; Yongin 446-701 Korea
| | - Peter Verwilst
- Department of Chemistry; Korea University; Seoul 136-701 Korea
| | - Joo Hee Jang
- Department of Chemistry; Korea University; Seoul 136-701 Korea
| | - Tae Woo Kim
- The School of East-West Medical Science; Kyung Hee University; Yongin 446-701 Korea
| | - Chulhun Kang
- The School of East-West Medical Science; Kyung Hee University; Yongin 446-701 Korea
| | - Jong Seung Kim
- Department of Chemistry; Korea University; Seoul 136-701 Korea
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21
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L. Akenhead M, Y. Shin H. The Contribution of Cell Surface Components to the Neutrophil Mechanosensitivity to Shear Stresses. AIMS BIOPHYSICS 2015. [DOI: 10.3934/biophy.2015.3.318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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22
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Rinninger F, Heine M, Singaraja R, Hayden M, Brundert M, Ramakrishnan R, Heeren J. High density lipoprotein metabolism in low density lipoprotein receptor-deficient mice. J Lipid Res 2014; 55:1914-24. [PMID: 24954421 DOI: 10.1194/jlr.m048819] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The LDL receptor (LDLR) and scavenger receptor class B type I (SR-BI) play physiological roles in LDL and HDL metabolism in vivo. In this study, we explored HDL metabolism in LDLR-deficient mice in comparison with WT littermates. Murine HDL was radiolabeled in the protein ((125)I) and in the cholesteryl ester (CE) moiety ([(3)H]). The metabolism of (125)I-/[(3)H]HDL was investigated in plasma and in tissues of mice and in murine hepatocytes. In WT mice, liver and adrenals selectively take up HDL-associated CE ([(3)H]). In contrast, in LDLR(-/-) mice, selective HDL CE uptake is significantly reduced in liver and adrenals. In hepatocytes isolated from LDLR(-/-) mice, selective HDL CE uptake is substantially diminished compared with WT liver cells. Hepatic and adrenal protein expression of lipoprotein receptors SR-BI, cluster of differentiation 36 (CD36), and LDL receptor-related protein 1 (LRP1) was analyzed by immunoblots. The respective protein levels were identical both in hepatic and adrenal membranes prepared from WT or from LDLR(-/-) mice. In summary, an LDLR deficiency substantially decreases selective HDL CE uptake by liver and adrenals. This decrease is independent from regulation of receptor proteins like SR-BI, CD36, and LRP1. Thus, LDLR expression has a substantial impact on both HDL and LDL metabolism in mice.
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Affiliation(s)
- Franz Rinninger
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Markus Heine
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Roshni Singaraja
- Translational Laboratories in Genetic Medicine, Agency for Science, Technology and Research National University of Singapore, Singapore 117609 Department of Medicine, National University of Singapore, Singapore 117609
| | - Michael Hayden
- Centre for Molecular Medicine and Therapeutics and Child and Family Research Institute, University of British Columbia, Vancouver, British Columbia V5Z 4H4, Canada
| | - May Brundert
- Department of Medicine, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
| | - Rajasekhar Ramakrishnan
- Department of Pediatrics, College of Physicians and Surgeons of Columbia University, New York, NY 10032
| | - Joerg Heeren
- Department of Biochemistry and Molecular Cell Biology, University Hospital Hamburg Eppendorf, 20246 Hamburg, Germany
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Zhang X, Cheng R, Rowe D, Sethu P, Daugherty A, Yu G, Shin HY. Shear-sensitive regulation of neutrophil flow behavior and its potential impact on microvascular blood flow dysregulation in hypercholesterolemia. Arterioscler Thromb Vasc Biol 2014; 34:587-93. [PMID: 24458712 DOI: 10.1161/atvbaha.113.302868] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
OBJECTIVE Shear stress-induced pseudopod retraction is an anti-inflammatory measure that minimizes neutrophil activity and is regulated by membrane cholesterol. We tested the hypothesis that a hypercholesterolemic impairment of shear mechanotransduction alters the neutrophil flow behavior leading to microvascular dysfunction. APPROACH AND RESULTS We examined the shear effects on the flow behavior of human leukocytes. When subjected to shearing during cone-plate viscometry, leukocyte suspensions exhibited parallel time-dependent reductions in viscosity and pseudopod activity. Shear-induced reductions in suspension viscosity were attenuated by membrane cholesterol enrichment. We also showed that enhanced pseudopod activity of leukocyte suspensions in 10% hematocrit significantly (P<0.05) raised the flow resistance of microvascular mimics. These results implicate an impaired neutrophil pseudopod retraction response to shear in hypercholesterolemic microvascular dysfunction. We confirmed this using near-infrared diffuse correlation spectroscopy to assess skeletal muscle blood flow regulation in the hindlimbs of mice subjected to reactive hyperemia. Using a custom protocol for the mouse, we extrapolated an adjusted peak flow and time to adjusted peak flow to quantify the early phase of the blood flow recovery response during reactive hyperemia when shear mechanobiology likely has a maximal impact. Compared with mice on normal diet, hypercholesterolemic mice exhibited significantly (P<0.05) reduced adjusted peak flow and prolonged time to adjusted peak flow which correlated (r=0.4 and r=-0.3, respectively) with neutrophil shear responsiveness and were abrogated by neutropenia. CONCLUSIONS These results provide the first evidence that the neutrophils contribute to tissue blood flow autoregulation. Moreover, a deficit in the neutrophil responsiveness to shear may be a feature of hypercholesterolemia-related microvascular dysfunction.
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Affiliation(s)
- Xiaoyan Zhang
- From the Department of Biomedical Engineering, University of Kentucky, Lexington (X.Z., R.C., D.R., G.Y., H.Y.S); Math, Science, and Technology Center, Paul L. Dunbar High School, Lexington, KY (D.R.); Division of Cardiovascular Disease, University of Alabama at Birmingham (P.S.); and Saha Cardiovascular Research Center, University of Kentucky, Lexington (A.D.)
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Akenhead ML, Zhang X, Shin HY. Characterization of the shear stress regulation of CD18 surface expression by HL60-derived neutrophil-like cells. Biomech Model Mechanobiol 2013; 13:861-70. [PMID: 24276331 DOI: 10.1007/s10237-013-0541-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2013] [Accepted: 11/12/2013] [Indexed: 10/26/2022]
Abstract
Shear stress-induced cleavage of cell surface CD18 integrins is reported to be part of an anti-inflammatory control mechanism that minimizes neutrophil activity in the blood under physiologic conditions. The cysteine protease, cathepsin B (catB), has been implicated in this mechanoregulatory mechanism, but its molecular dynamics remain to be elucidated. Moreover, attempts to do so using molecular approaches are hindered by the limited ex vivo life span of primary neutrophils. As an alternative, we explored the potential use of HL60-derived neutrophilic cells as a transfectable culture model that exhibits a shear-induced CD18 cleavage response comparable to primary neutrophils. HL60 cells were differentiated into neutrophil-like cells (dHL60-NCs) and exposed to laminar shear stress ([Formula: see text] for 10 min). Based on cytometric analyses, sheared cells cleaved CD18 and CD11a, but not CD11b, integrins. Treatment of cells with E64 or doxycycline prior to and during shear exposure inhibited CD18, but only attenuated CD11a, cleavage. Neither aprotinin nor pepstatin affected shear-induced CD18 or CD11a cleavage. Notably, dHL60-NCs expressed minimal catB. Thus, multiple cysteine proteases in addition to catB may cleave CD18 on sheared leukocytes. In fact, our findings indicate that multiple non-cysteine proteases also participate in the shear-related cleavage of CD11/CD18 heterodimers. Finally, shear-induced cleavage of CD18 and CD11a by dHL60-NCs was inhibited by fMLP concentrations of at least [Formula: see text]. Collectively, our findings indicate that shear-induced CD11/CD18 cleavage is phenotypic of neutrophilic cells, including those derived from HL60 cells. Moreover, our results verify shear stress as a key anti-inflammatory stimulus for neutrophils under physiologic conditions.
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Affiliation(s)
- M L Akenhead
- Department of Biomedical Engineering, University of Kentucky, 213 Wenner-Gren Research Laboratory, Lexington, KY, 40506-0070, USA
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Natsume T, Yoshimoto M. Membrane Permeability and Stability of Liposomes Suspended in Shear Flow. J DISPER SCI TECHNOL 2013. [DOI: 10.1080/01932691.2012.752712] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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26
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Naviaux RK. Metabolic features of the cell danger response. Mitochondrion 2013; 16:7-17. [PMID: 23981537 DOI: 10.1016/j.mito.2013.08.006] [Citation(s) in RCA: 136] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2013] [Revised: 08/12/2013] [Accepted: 08/16/2013] [Indexed: 12/12/2022]
Abstract
The cell danger response (CDR) is the evolutionarily conserved metabolic response that protects cells and hosts from harm. It is triggered by encounters with chemical, physical, or biological threats that exceed the cellular capacity for homeostasis. The resulting metabolic mismatch between available resources and functional capacity produces a cascade of changes in cellular electron flow, oxygen consumption, redox, membrane fluidity, lipid dynamics, bioenergetics, carbon and sulfur resource allocation, protein folding and aggregation, vitamin availability, metal homeostasis, indole, pterin, 1-carbon and polyamine metabolism, and polymer formation. The first wave of danger signals consists of the release of metabolic intermediates like ATP and ADP, Krebs cycle intermediates, oxygen, and reactive oxygen species (ROS), and is sustained by purinergic signaling. After the danger has been eliminated or neutralized, a choreographed sequence of anti-inflammatory and regenerative pathways is activated to reverse the CDR and to heal. When the CDR persists abnormally, whole body metabolism and the gut microbiome are disturbed, the collective performance of multiple organ systems is impaired, behavior is changed, and chronic disease results. Metabolic memory of past stress encounters is stored in the form of altered mitochondrial and cellular macromolecule content, resulting in an increase in functional reserve capacity through a process known as mitocellular hormesis. The systemic form of the CDR, and its magnified form, the purinergic life-threat response (PLTR), are under direct control by ancient pathways in the brain that are ultimately coordinated by centers in the brainstem. Chemosensory integration of whole body metabolism occurs in the brainstem and is a prerequisite for normal brain, motor, vestibular, sensory, social, and speech development. An understanding of the CDR permits us to reframe old concepts of pathogenesis for a broad array of chronic, developmental, autoimmune, and degenerative disorders. These disorders include autism spectrum disorders (ASD), attention deficit hyperactivity disorder (ADHD), asthma, atopy, gluten and many other food and chemical sensitivity syndromes, emphysema, Tourette's syndrome, bipolar disorder, schizophrenia, post-traumatic stress disorder (PTSD), chronic traumatic encephalopathy (CTE), traumatic brain injury (TBI), epilepsy, suicidal ideation, organ transplant biology, diabetes, kidney, liver, and heart disease, cancer, Alzheimer and Parkinson disease, and autoimmune disorders like lupus, rheumatoid arthritis, multiple sclerosis, and primary sclerosing cholangitis.
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Affiliation(s)
- Robert K Naviaux
- The Mitochondrial and Metabolic Disease Center, Departments of Medicine, Pediatrics, and Pathology, University of California, San Diego School of Medicine, 214 Dickinson St., Bldg CTF, Rm C102, San Diego, CA 92103-8467, USA; Veterans Affairs Center for Excellence in Stress and Mental Health (CESAMH), La Jolla, CA, USA.
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Lei L, Li H, Yan F, Xiao Y. Hyperlipidemia impaired innate immune response to periodontal pathogen porphyromonas gingivalis in apolipoprotein E knockout mice. PLoS One 2013; 8:e71849. [PMID: 23977160 PMCID: PMC3745424 DOI: 10.1371/journal.pone.0071849] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2013] [Accepted: 07/04/2013] [Indexed: 12/18/2022] Open
Abstract
A finely-tuned innate immune response plays a pivotal role in protecting host against bacterial invasion during periodontal disease progression. Hyperlipidemia has been suggested to exacerbate periodontal health condition. However, the underlying mechanism has not been addressed. In the present study, we investigated the effect of hyperlipidemia on innate immune responses to periodontal pathogen Porphyromonas gingivalis infection. Apolipoprotein E-deficient and wild-type mice at the age of 20 weeks were used for the study. Peritoneal macrophages were isolated and subsequently used for the study of viable P. gingivalis infection. ApoE−/− mice demonstrated inhibited iNOS production and impaired clearance of P. gingivalis in vitro and in vivo; furthermore, ApoE−/− mice displayed disrupted cytokine production pattern in response to P. gingivalis, with a decreased production of tumor necrosis factor-α, interleukin-6 (IL-6), IL-1β and monocyte chemotactic protein-1. Microarray data demonstrated that Toll-like receptor (TLR) and NOD-like receptor (NLR) pathway were altered in ApoE−/− mice macrophages; further analysis of pattern recognition receptors (PRRs) demonstrated that expression of triggering receptors on myeloid cells-1 (TREM-1), an amplifier of the TLR and NLR pathway, was decreased in ApoE−/− mice macrophages, leading to decreased recruitment of NF-κB onto the promoters of the TNF-α and IL-6. Our data suggest that in ApoE−/− mice hyperlipidemia disrupts the expression of PRRs, and cripples the host’s capability to generate sufficient innate immune response to P. gingivalis, which may facilitate immune evasion, subgingival colonization and establishment of P. gingivalis in the periodontal niche.
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MESH Headings
- Animals
- Apolipoproteins E/deficiency
- Apolipoproteins E/genetics
- Bacteroidaceae Infections/immunology
- Bacteroidaceae Infections/microbiology
- Cells, Cultured
- Cytokines/genetics
- Cytokines/metabolism
- Gene Expression Regulation/immunology
- Hyperlipidemias/complications
- Hyperlipidemias/immunology
- Immunity, Innate
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/microbiology
- Male
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Periodontal Diseases/immunology
- Periodontal Diseases/microbiology
- Phagocytosis
- Porphyromonas gingivalis/immunology
- Promoter Regions, Genetic
- Protein Binding
- Receptors, Pattern Recognition/genetics
- Receptors, Pattern Recognition/metabolism
- Transcription Factor RelA/metabolism
- Transcriptome
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Affiliation(s)
- Lang Lei
- School and Hospital of Stomatology, Fujian Medical University, Fuzhou, China
| | - Houxuan Li
- School and Hospital of Stomatology, Fujian Medical University, Fuzhou, China
| | - Fuhua Yan
- Institute and Hospital of Stomatology, Nanjing University Medical School, Nanjing, Jiangsu, China
- * E-mail: (FY); (YX)
| | - Yin Xiao
- Bone Research Lab, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Australia
- * E-mail: (FY); (YX)
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Jin K, Klima JC, Deane G, Dale Stokes M, Latz MI. Pharmacological investigation of the bioluminescence signaling pathway of the dinoflagellate Lingulodinium polyedrum: evidence for the role of stretch-activated ion channels. JOURNAL OF PHYCOLOGY 2013; 49:733-745. [PMID: 27007206 DOI: 10.1111/jpy.12084] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Accepted: 04/20/2013] [Indexed: 06/05/2023]
Abstract
Dinoflagellate bioluminescence serves as a whole-cell reporter of mechanical stress, which activates a signaling pathway that appears to involve the opening of voltage-sensitive ion channels and release of calcium from intracellular stores. However, little else is known about the initial signaling events that facilitate the transduction of mechanical stimuli. In the present study using the red tide dinoflagellate Lingulodinium polyedrum (Stein) Dodge, two forms of dinoflagellate bioluminescence, mechanically stimulated and spontaneous flashes, were used as reporter systems to pharmacological treatments that targeted various predicted signaling events at the plasma membrane level of the signaling pathway. Pretreatment with 200 μM Gadolinium III (Gd(3+) ), a nonspecific blocker of stretch-activated and some voltage-gated ion channels, resulted in strong inhibition of both forms of bioluminescence. Pretreatment with 50 μM nifedipine, an inhibitor of L-type voltage-gated Ca(2+) channels that inhibits mechanically stimulated bioluminescence, did not inhibit spontaneous bioluminescence. Treatment with 1 mM benzyl alcohol, a membrane fluidizer, was very effective in stimulating bioluminescence. Benzyl alcohol-stimulated bioluminescence was inhibited by Gd(3+) but not by nifedipine, suggesting that its role is through stretch activation via a change in plasma membrane fluidity. These results are consistent with the presence of stretch-activated and voltage-gated ion channels in the bioluminescence mechanotransduction signaling pathway, with spontaneous flashing associated with a stretch-activated component at the plasma membrane.
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Affiliation(s)
- Kelly Jin
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Jason C Klima
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Grant Deane
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Malcolm Dale Stokes
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
| | - Michael I Latz
- Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92093, USA
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Renò F, Carniato F, Rizzi M, Olivero F, Pittarella P, Marchese L. Flow cytometry evidence of human granulocytes interaction with polyhedral oligomeric silsesquioxanes: effect of nanoparticle charge. NANOTECHNOLOGY 2013; 24:185101. [PMID: 23574975 DOI: 10.1088/0957-4484/24/18/185101] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Nanoparticles (NPs) entering the human body are immediately confronted with the innate part of human immune system. In particular, monocyte and neutrophil granulocytes readily clear particles by phagocytosis, even if in the case of NPs the uptake mechanism may be classified as macropinocytosis. Among engineered nanoparticles, in the last years, siliceous materials have emerged as promising materials for several applications ranging from catalysis to biomedical. The polyhedral oligomeric silsesquioxanes (POSS) are nanodimensional, easily synthesizable molecular compounds and POSS-based systems are promising carriers for biological molecules. In this work, the ability of human granulocytes to uptake positively and negatively charged POSS was measured using a simple flow cytometry analysis based on cell size modifications. The data obtained showed that after a 30 min exposure only positive NPs were uptaken by human granulocyte using both macropinocytosis and clathrin-mediated mechanisms as demonstrated by uptake inhibition mediated by amiloride and chlorpromazine.
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Affiliation(s)
- Filippo Renò
- Innovative Research Laboratory for Wound Healing, Health Sciences Department, University of Eastern Piedmont A. Avogadro, via Solaroli, 17 I-28100 Novara, Italy.
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Effects of plasma membrane cholesterol level and cytoskeleton F-actin on cell protrusion mechanics. PLoS One 2013; 8:e57147. [PMID: 23451167 PMCID: PMC3579816 DOI: 10.1371/journal.pone.0057147] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2012] [Accepted: 01/17/2013] [Indexed: 12/12/2022] Open
Abstract
Protrusions are deformations that form at the surface of living cells during biological activities such as cell migration. Using combined optical tweezers and fluorescent microscopy, we quantified the mechanical properties of protrusions in adherent human embryonic kidney cells in response to application of an external force at the cell surface. The mechanical properties of protrusions were analyzed by obtaining the associated force-length plots during protrusion formation, and force relaxation at constant length. Protrusion mechanics were interpretable by a standard linear solid (Kelvin) model, consisting of two stiffness parameters, k0 and k1 (with k0>k1), and a viscous coefficient. While both stiffness parameters contribute to the time-dependant mechanical behavior of the protrusions, k0 and k1 in particular dominated the early and late stages of the protrusion formation and elongation process, respectively. Lowering the membrane cholesterol content by 25% increased the k0 stiffness by 74%, and shortened the protrusion length by almost half. Enhancement of membrane cholesterol content by nearly two-fold increased the protrusion length by 30%, and decreased the k0 stiffness by nearly two-and-half-fold as compared with control cells. Cytoskeleton integrity was found to make a major contribution to protrusion mechanics as evidenced by the effects of F-actin disruption on the resulting mechanical parameters. Viscoelastic behavior of protrusions was further characterized by hysteresis and force relaxation after formation. The results of this study elucidate the coordination of plasma membrane composition and cytoskeleton during protrusion formation.
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