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Hoffet MS, Tomov NS, Hupp S, Mitchell TJ, Iliev AI. Glucose and Oxygen Levels Modulate the Pore-Forming Effects of Cholesterol-Dependent Cytolysin Pneumolysin from Streptococcus pneumoniae. Toxins (Basel) 2024; 16:232. [PMID: 38922127 PMCID: PMC11209487 DOI: 10.3390/toxins16060232] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2024] [Revised: 05/08/2024] [Accepted: 05/16/2024] [Indexed: 06/27/2024] Open
Abstract
A major Streptococcus pneumoniae pathogenic factor is the cholesterol-dependent cytolysin pneumolysin, binding membrane cholesterol and producing permanent lytic or transient pores. During brain infections, vascular damage with variable ischemia occurs. The role of ischemia on pneumolysin's pore-forming capacity remains unknown. In acute brain slice cultures and primary cultured glia, we studied acute toxin lysis (via propidium iodide staining and LDH release) and transient pore formation (by analyzing increases in the intracellular calcium). We analyzed normal peripheral tissue glucose conditions (80 mg%), normal brain glucose levels (20 mg%), and brain hypoglycemic conditions (3 mg%), in combinations either with normoxia (8% oxygen) or hypoxia (2% oxygen). At 80 mg% glucose, hypoxia enhanced cytolysis via pneumolysin. At 20 mg% glucose, hypoxia did not affect cell lysis, but impaired calcium restoration after non-lytic pore formation. Only at 3 mg% glucose, during normoxia, did pneumolysin produce stronger lysis. In hypoglycemic (3 mg% glucose) conditions, pneumolysin caused a milder calcium increase, but restoration was missing. Microglia bound more pneumolysin than astrocytes and demonstrated generally stronger calcium elevation. Thus, our work demonstrated that the toxin pore-forming capacity in cells continuously diminishes when oxygen is reduced, overlapping with a continuously reduced ability of cells to maintain homeostasis of the calcium influx once oxygen and glucose are reduced.
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Affiliation(s)
- Michelle Salomé Hoffet
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland; (M.S.H.); (N.S.T.); (S.H.)
| | - Nikola S. Tomov
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland; (M.S.H.); (N.S.T.); (S.H.)
| | - Sabrina Hupp
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland; (M.S.H.); (N.S.T.); (S.H.)
| | - Timothy J. Mitchell
- School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK;
| | - Asparouh I. Iliev
- Institute of Anatomy, University of Bern, Baltzerstrasse 2, 3012 Bern, Switzerland; (M.S.H.); (N.S.T.); (S.H.)
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2
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Miserocchi G, Beretta E. A century of exercise physiology: lung fluid balance during and following exercise. Eur J Appl Physiol 2023; 123:1-24. [PMID: 36264327 DOI: 10.1007/s00421-022-05066-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 10/04/2022] [Indexed: 01/17/2023]
Abstract
PURPOSE This review recalls the principles developed over a century to describe trans-capillary fluid exchanges concerning in particular the lung during exercise, a specific condition where dyspnea is a leading symptom, the question being whether this symptom simply relates to fatigue or also implies some degree of lung edema. METHOD Data from experimental models of lung edema are recalled aiming to: (1) describe how extravascular lung water is strictly controlled by "safety factors" in physiological conditions, (2) consider how waning of "safety factors" inevitably leads to development of lung edema, (3) correlate data from experimental models with data from exercising humans. RESULTS Exercise is a strong edemagenic condition as the increase in cardiac output leads to lung capillary recruitment, increase in capillary surface for fluid exchange and potential increase in capillary pressure. The physiological low microvascular permeability may be impaired by conditions causing damage to the interstitial matrix macromolecular assembly leading to alveolar edema and haemorrhage. These conditions include hypoxia, cyclic alveolar unfolding/folding during hyperventilation putting a tensile stress on septa, intensity and duration of exercise as well as inter-individual proneness to develop lung edema. CONCLUSION Data from exercising humans showed inter-individual differences in the dispersion of the lung ventilation/perfusion ratio and increase in oxygen alveolar-capillary gradient. More recent data in humans support the hypothesis that greater vasoconstriction, pulmonary hypertension and slower kinetics of alveolar-capillary O2 equilibration relate with greater proneness to develop lung edema due higher inborn microvascular permeability possibly reflecting the morpho-functional features of the air-blood barrier.
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Affiliation(s)
- Giuseppe Miserocchi
- Dipartimento di Medicina e Chirurgia, Università Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy
| | - Egidio Beretta
- Dipartimento di Medicina e Chirurgia, Università Milano-Bicocca, Via Cadore 48, 20900, Monza, Italy.
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3
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Vacek L, Dvorak A, Bechynska K, Kosek V, Elkalaf M, Trinh MD, Fiserova I, Pospisilova K, Slovakova L, Vitek L, Hajslova J, Polak J. Hypoxia Induces Saturated Fatty Acids Accumulation and Reduces Unsaturated Fatty Acids Independently of Reverse Tricarboxylic Acid Cycle in L6 Myotubes. Front Endocrinol (Lausanne) 2022; 13:663625. [PMID: 35360057 PMCID: PMC8963465 DOI: 10.3389/fendo.2022.663625] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/03/2021] [Accepted: 02/16/2022] [Indexed: 11/29/2022] Open
Abstract
Obstructive sleep apnea syndrome, characterized by repetitive episodes of tissue hypoxia, is associated with several metabolic impairments. Role of fatty acids and lipids attracts attention in its pathogenesis for their metabolic effects. Parallelly, hypoxia-induced activation of reverse tricarboxylic acid cycle (rTCA) with reductive glutamine metabolism provides precursor molecules for de novo lipogenesis. Gas-permeable cultureware was used to culture L6-myotubes in chronic hypoxia (12%, 4% and 1% O2) with 13C labelled glutamine and inhibitors of glutamine uptake or rTCA-mediated lipogenesis. We investigated changes in lipidomic profile, 13C appearance in rTCA-related metabolites, gene and protein expression of rTCA-related proteins and glutamine transporters, glucose uptake and lactate production. Lipid content increased by 308% at 1% O2, predominantly composed of saturated fatty acids, while triacylglyceroles containing unsaturated fatty acids and membrane lipids (phosphatidylcholines, phosphatidylethanolamines, phosphatidylinositol) decreased by 20-70%. rTCA labelling of malate, citrate and 2-hydroxyglutarate increased by 4.7-fold, 2.2-fold and 1.9-fold in 1% O2, respectively. ATP-dependent citrate lyase inhibition in 1% O2 decreased lipid amount by 23% and increased intensity of triacylglyceroles containing unsaturated fatty acids by 56-80%. Lactate production increased with hypoxia. Glucose uptake dropped by 75% with progression of hypoxia from 4% to 1% O2. Protein expression remained unchanged. Altogether, hypoxia modified cell metabolism leading to lipid composition alteration and rTCA activation.
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Affiliation(s)
- Lukas Vacek
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Ales Dvorak
- Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University, Prague, Czechia
| | - Kamila Bechynska
- Institute of Food and Nutrition Analysis, Faculty of Food and Biochemical Technology, University of Chemistry and Technology in Prague, Prague, Czechia
| | - Vit Kosek
- Institute of Food and Nutrition Analysis, Faculty of Food and Biochemical Technology, University of Chemistry and Technology in Prague, Prague, Czechia
| | - Moustafa Elkalaf
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
- Department of Physiology, Faculty of Medicine in Hradec Králové, Charles University, Hradec Králové, Czechia
| | - Minh Duc Trinh
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Ivana Fiserova
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Katerina Pospisilova
- Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University, Prague, Czechia
| | - Lucie Slovakova
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
| | - Libor Vitek
- Institute of Medical Biochemistry and Laboratory Diagnostics, First Faculty of Medicine, Charles University, Prague, Czechia
- 4 Department of Internal Medicine, Faculty General Hospital and 1Faculty of Medicine, Charles University, Prague, Czechia
| | - Jana Hajslova
- Institute of Food and Nutrition Analysis, Faculty of Food and Biochemical Technology, University of Chemistry and Technology in Prague, Prague, Czechia
| | - Jan Polak
- Department of Pathophysiology, Third Faculty of Medicine, Charles University, Prague, Czechia
- *Correspondence: Jan Polak,
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4
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Saliakoura M, Rossi Sebastiano M, Pozzato C, Heidel FH, Schnöder TM, Savic Prince S, Bubendorf L, Pinton P, A Schmid R, Baumgartner J, Freigang S, Berezowska SA, Rimessi A, Konstantinidou G. PLCγ1 suppression promotes the adaptation of KRAS-mutant lung adenocarcinomas to hypoxia. Nat Cell Biol 2020; 22:1382-1395. [PMID: 33077911 PMCID: PMC7610419 DOI: 10.1038/s41556-020-00592-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Accepted: 09/15/2020] [Indexed: 12/25/2022]
Abstract
Mutant KRAS modulates the metabolic plasticity of cancer cells conferring growth advantage during hypoxia, but the molecular underpinnings are largely unknown. Using a lipidomic screen, we found that PLCγ1 is suppressed during hypoxia in KRAS-mutant human lung adenocarcinoma cancer cell lines. Suppression of PLCγ1 in hypoxia promotes a less oxidative cancer cell metabolism, reduces the formation of mitochondrial reactive oxygen species and switches tumor bioenergetics towards glycolysis by impairing Ca2+ entry into the mitochondria. This event prevents lipid peroxidation, antagonizes apoptosis and increases cancer cell proliferation. Accordingly, loss-of-function of Plcγ1 in a mouse model of KrasG12D-driven lung adenocarcinoma increased the expression of glycolytic genes, boosted tumor growth and reduced survival. In patients with mutant KRAS lung adenocarcinomas, low PLCγ1 expression correlates with increased expression of hypoxia markers and predicts poor patient survival. Thus, our work reveals a mechanism of cancer cell adaptation to hypoxia with potential therapeutic value.
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Affiliation(s)
- Maria Saliakoura
- Institute of Pharmacology, University of Bern, Bern, Switzerland
| | | | - Chiara Pozzato
- Institute of Pharmacology, University of Bern, Bern, Switzerland
| | - Florian H Heidel
- Internal Medicine II, Hematology and Oncology, University Hospital Jena, Jena, Germany.,Leibniz-Institute on Aging, Fritz-Lipmann-Institute, Jena, Jena, Germany
| | - Tina M Schnöder
- Internal Medicine II, Hematology and Oncology, University Hospital Jena, Jena, Germany.,Leibniz-Institute on Aging, Fritz-Lipmann-Institute, Jena, Jena, Germany
| | | | - Lukas Bubendorf
- Institute of Pathology, University Hospital Basel, Basel, Switzerland
| | - Paolo Pinton
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
| | - Ralph A Schmid
- Department of General Thoracic Surgery, Inselspital, Bern, Switzerland
| | | | - Stefan Freigang
- Institute of Pathology, University of Bern, Bern, Switzerland
| | | | - Alessandro Rimessi
- Department of Medical Sciences, Laboratory for Technologies of Advanced Therapies (LTTA), University of Ferrara, Ferrara, Italy
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5
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Bombelli S, Torsello B, De Marco S, Lucarelli G, Cifola I, Grasselli C, Strada G, Bovo G, Perego RA, Bianchi C. 36-kDa Annexin A3 Isoform Negatively Modulates Lipid Storage in Clear Cell Renal Cell Carcinoma Cells. THE AMERICAN JOURNAL OF PATHOLOGY 2020; 190:2317-2326. [PMID: 32861643 DOI: 10.1016/j.ajpath.2020.08.008] [Citation(s) in RCA: 61] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2020] [Revised: 07/28/2020] [Accepted: 08/18/2020] [Indexed: 11/26/2022]
Abstract
The adipocyte-like morphology of clear cell renal cell carcinoma (ccRCC) cells results from a grade-dependent neutral lipid accumulation; however, the molecular mechanism and role in renal cancer progression have yet to be clarified. ccRCC shows a gene expression signature consistent with adipogenesis, and the phospholipid-binding protein annexin A3 (AnxA3), a negative regulator of adipocyte differentiation, is down-regulated in RCC and shows a differential expression pattern for two isoforms of 36 and 33 kDa. Using primary cell cultures and cell lines, we investigated the involvement of AnxA3 isoforms in lipid storage modulation of ccRCC cells. We found that the increased accumulation of lipids into ccRCC cells correlated with a decrease of the 36/33 isoform ratio. Treatment with adipogenic medium induced a significant increment of lipid storage in ccRCC cells that had a low 36-kDa AnxA3 expression and 36/33 ratio. The 36-kDa AnxA3 silencing in ccRCC cells increased lipid storage induced by adipogenic medium. These data suggest that 36-kDa AnxA3 negatively modulates the response to adipogenic treatment and may act as negative regulator of lipid storage in ccRCC cells. The subcellular distribution of AnxA3 in the cellular endocytic compartment suggests its involvement in modulation of vesicular trafficking, and it might serve as a putative mechanism of lipid storage regulation in ccRCC cells, opening novel translational outcomes.
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Affiliation(s)
- Silvia Bombelli
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
| | - Barbara Torsello
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
| | - Sofia De Marco
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
| | - Giuseppe Lucarelli
- Department of Emergency and Organ Transplantation-Urology, University of Bari, Bari, Italy
| | - Ingrid Cifola
- Institute for Biomedical Technologies, National Research Council, Segrate, Italy
| | - Chiara Grasselli
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy
| | - Guido Strada
- Urology Unit, ASST North Milan, Bassini Hospital, Cinisello Balsamo, Italy
| | - Giorgio Bovo
- Pathology Unit, ASST North Milan, Vimercate Hospital, Vimercate, Italy
| | - Roberto A Perego
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
| | - Cristina Bianchi
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy.
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6
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Fuentes NR, Phan J, Huang Y, Lin D, Taniguchi CM. Resolving the HIF paradox in pancreatic cancer. Cancer Lett 2020; 489:50-55. [PMID: 32512024 DOI: 10.1016/j.canlet.2020.05.033] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Revised: 05/13/2020] [Accepted: 05/22/2020] [Indexed: 12/11/2022]
Abstract
Pancreatic ductal adenocarcinoma (PDAC) is currently the third leading cause of cancer-related deaths and has a 5-year survival rate of less than 10%, far below the ~70% national average for all cancers. This poor prognosis is driven by an extreme resistance to nearly all known cancer treatments, which has long been attributed to hypoxia driven interactions between tumor cells and the supporting stromal microenvironment. The cellular response to hypoxia is driven by the transcription factors known as the hypoxia inducible factors (HIFs), which have been hypothesized to play a role in the pathobiology of PDAC as well as a potential therapeutic target based on years of cell culture data. Attempts to validate the oncogenic role of HIF in PDAC through rigorous spontaneous tumor models have paradoxically shown that the HIFs may act as a tumor suppressor in epithelial cells. Here, we seek to resolve this paradox by discussing the roles of HIFs both in cancer cells and the supporting microenvironment and place them into context of current model systems that could be used to interrogate these interactions. We suggest that HIF may exert its oncogenic influences by modulating the form and function of the stroma rather than direct effects on cancer cells.
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Affiliation(s)
- Natividad R Fuentes
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Jae Phan
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Yanqing Huang
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Daniel Lin
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA
| | - Cullen M Taniguchi
- Department of Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX, 77030, USA.
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7
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Zuniga-Hertz JP, Patel HH. The Evolution of Cholesterol-Rich Membrane in Oxygen Adaption: The Respiratory System as a Model. Front Physiol 2019; 10:1340. [PMID: 31736773 PMCID: PMC6828933 DOI: 10.3389/fphys.2019.01340] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2019] [Accepted: 10/08/2019] [Indexed: 12/14/2022] Open
Abstract
The increase in atmospheric oxygen levels imposed significant environmental pressure on primitive organisms concerning intracellular oxygen concentration management. Evidence suggests the rise of cholesterol, a key molecule for cellular membrane organization, as a cellular strategy to restrain free oxygen diffusion under the new environmental conditions. During evolution and the increase in organismal complexity, cholesterol played a pivotal role in the establishment of novel and more complex functions associated with lipid membranes. Of these, caveolae, cholesterol-rich membrane domains, are signaling hubs that regulate important in situ functions. Evolution resulted in complex respiratory systems and molecular response mechanisms that ensure responses to critical events such as hypoxia facilitated oxygen diffusion and transport in complex organisms. Caveolae have been structurally and functionally associated with respiratory systems and oxygen diffusion control through their relationship with molecular response systems like hypoxia-inducible factors (HIF), and particularly as a membrane-localized oxygen sensor, controlling oxygen diffusion balanced with cellular physiological requirements. This review will focus on membrane adaptations that contribute to regulating oxygen in living systems.
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Affiliation(s)
- Juan Pablo Zuniga-Hertz
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
| | - Hemal H Patel
- Department of Anesthesiology, VA San Diego Healthcare System, University of California, San Diego, San Diego, CA, United States
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8
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Efremov YR, Proskurina AS, Potter EA, Dolgova EV, Efremova OV, Taranov OS, Ostanin AA, Chernykh ER, Kolchanov NA, Bogachev SS. Cancer Stem Cells: Emergent Nature of Tumor Emergency. Front Genet 2018; 9:544. [PMID: 30505319 PMCID: PMC6250818 DOI: 10.3389/fgene.2018.00544] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2018] [Accepted: 10/26/2018] [Indexed: 12/12/2022] Open
Abstract
A functional analysis of 167 genes overexpressed in Krebs-2 tumor initiating cells was performed. In the first part of the study, the genes were analyzed for their belonging to one or more of the three groups, which represent the three major phenotypic manifestation of malignancy of cancer cells, namely (1) proliferative self-sufficiency, (2) invasive growth and metastasis, and (3) multiple drug resistance. 96 genes out of 167 were identified as possible contributors to at least one of these fundamental properties. It was also found that substantial part of these genes are also known as genes responsible for formation and/or maintenance of the stemness of normal pluri-/multipotent stem cells. These results suggest that the malignancy is simply the ability to maintain the stem cell specific genes expression profile, and, as a consequence, the stemness itself regardless of the controlling effect of stem niches. In the second part of the study, three stress factors combined into the single concept of "generalized cellular stress," which are assumed to activate the expression of these genes, were defined. In addition, possible mechanisms for such activation were identified. The data obtained suggest the existence of a mechanism for the de novo formation of a pluripotent/stem phenotype in the subpopulation of "committed" tumor cells.
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Affiliation(s)
- Yaroslav R Efremov
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia.,Department of Natural Sciences, Novosibirsk State University, Novosibirsk, Russia
| | - Anastasia S Proskurina
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Ekaterina A Potter
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Evgenia V Dolgova
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Oksana V Efremova
- Department of Natural Sciences, Novosibirsk State University, Novosibirsk, Russia
| | - Oleg S Taranov
- The State Research Center of Virology and Biotechnology Vector, Koltsovo, Russia
| | - Aleksandr A Ostanin
- Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - Elena R Chernykh
- Research Institute of Fundamental and Clinical Immunology, Novosibirsk, Russia
| | - Nikolay A Kolchanov
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
| | - Sergey S Bogachev
- Institute of Cytology and Genetics, Siberian Branch of the Russian Academy of Sciences, Novosibirsk, Russia
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9
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Milani C, Corsetto PA, Farina F, Botto L, Lonati E, Massimino L, Rizzo AM, Bulbarelli A, Palestini P. Early evidence of stress in immortalized neurons exposed to diesel particles: the role of lipid reshaping behind oxidative stress and inflammation. Toxicology 2018; 409:63-72. [PMID: 30055298 DOI: 10.1016/j.tox.2018.07.017] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 07/18/2018] [Accepted: 07/24/2018] [Indexed: 01/10/2023]
Abstract
Diesel combustion is the major source of fine particle road emission, whose solid fraction is represented by diesel exhaust particles (DEP). Many studies indicate the contribution of DEP to the onset of different neurological diseases, such as Alzheimer's disease (AD), identifying oxidative stress and neuroinflammation as two cardinal processes of brain damage. This study aimed to investigate the effects of different concentrations of DEP (10 μg/ml and 50 μg/ml) on the mouse HT22 cells treated for 3 h or 24 h. Our results demonstrated that DEP contributed to an increased oxidative stress, defined by overexpression of HO-1, Hsp70 and Cyp1b1 protein levels. Moreover, an inflammatory-related processes were also observed, as COX-2 and iNOS levels were higher in treated cells when compared to the control. Furthermore, our investigations highlighted the alteration of fatty acid composition, total cholesterol content in cells and media, and of membrane fluidity, suggesting a lipid reshaping after DEP treatment. Finally, we detected APP and BACE1 increase after 24 h of treatment with 50 μg/ml of DEP. Indeed, our results propose a role of acute exposure in the onset of a deleterious mechanism for AD neurodegeneration, even though no differences were observed in p-APP Thr668 levels, BACE1 activity and APP C-terminal fragment beta amount.
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Affiliation(s)
- Chiara Milani
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy.
| | | | - Francesca Farina
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy; Polaris Research Centre, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Laura Botto
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy; Polaris Research Centre, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Elena Lonati
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy
| | - Luca Massimino
- Division of Neuroscience, San Raffaele scientific institute, Milan, Italy
| | - Angela Maria Rizzo
- Departments of Pharmacology and Biomolecular Science, University of Milan, Milan, Italy
| | - Alessandra Bulbarelli
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy; Polaris Research Centre, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
| | - Paola Palestini
- School of Medicine and Surgery, University of Milano-Bicocca, Monza, Italy; NeuroMi, Milan Centre for Neuroscience, Department of Neurology and Neuroscience, University of Milano-Bicocca, San Gerardo Hospital, Monza, Italy; Polaris Research Centre, Department of Earth and Environmental Sciences, University of Milano-Bicocca, Milan, Italy
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10
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Salminen A, Kauppinen A, Kaarniranta K. Hypoxia/ischemia activate processing of Amyloid Precursor Protein: impact of vascular dysfunction in the pathogenesis of Alzheimer's disease. J Neurochem 2017; 140:536-549. [DOI: 10.1111/jnc.13932] [Citation(s) in RCA: 111] [Impact Index Per Article: 15.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2016] [Revised: 12/05/2016] [Accepted: 12/10/2016] [Indexed: 12/13/2022]
Affiliation(s)
- Antero Salminen
- Department of Neurology; Institute of Clinical Medicine; University of Eastern Finland; Kuopio Finland
| | - Anu Kauppinen
- School of Pharmacy; Faculty of Health Sciences; University of Eastern Finland; Kuopio Finland
| | - Kai Kaarniranta
- Department of Ophthalmology; Institute of Clinical Medicine; University of Eastern Finland; Kuopio Finland
- Department of Ophthalmology; Kuopio University Hospital; Kuopio Finland
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11
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Zeitouni NE, Chotikatum S, von Köckritz-Blickwede M, Naim HY. The impact of hypoxia on intestinal epithelial cell functions: consequences for invasion by bacterial pathogens. Mol Cell Pediatr 2016; 3:14. [PMID: 27002817 PMCID: PMC4803720 DOI: 10.1186/s40348-016-0041-y] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 03/13/2016] [Indexed: 02/06/2023] Open
Abstract
The maintenance of oxygen homeostasis in human tissues is mediated by several cellular adaptations in response to low-oxygen stress, called hypoxia. A decrease in tissue oxygen levels is initially counteracted by increasing local blood flow to overcome diminished oxygenation and avoid hypoxic stress. However, studies have shown that the physiological oxygen concentrations in several tissues are much lower than atmospheric (normoxic) conditions, and the oxygen supply is finely regulated in individual cell types. The gastrointestinal tract has been described to subsist in a state of physiologically low oxygen level and is thus depicted as a tissue in the state of constant low-grade inflammation. The intestinal epithelial cell layer plays a vital role in the immune response to inflammation and infections that occur within the intestinal tissue and is involved in many of the adaptation responses to hypoxic stress. This is especially relevant in the context of inflammatory disorders, such as inflammatory bowel disease (IBD). Therefore, this review aims to describe the intestinal epithelial cellular response to hypoxia and the consequences for host interactions with invading gastrointestinal bacterial pathogens.
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Affiliation(s)
- Nathalie E. Zeitouni
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Sucheera Chotikatum
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Maren von Köckritz-Blickwede
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
- Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine Hannover, Hannover, Germany
| | - Hassan Y. Naim
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
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12
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Brambillaa A, Lonati E, Milani C, Rizzo AM, Farina F, Botto L, Masserini M, Palestini P, Bulbarelli A. Ischemic conditions and ß-secretase activation: The impact of membrane cholesterol enrichment as triggering factor in rat brain endothelial cells. Int J Biochem Cell Biol 2016; 69:95-104. [PMID: 27022655 DOI: 10.1016/j.biocel.2015.10.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Among harmful conditions damaging the blood–brain barrier, cerebral stroke and reperfusion injuries were proposed as contributing factors to Alzheimer's disease etiology. Indeed it was reported that ischemic conditions promote β-amyloid peptide production in brain endothelial cells, although implicated mechanisms are yet not fully understood.Oxidative injury related to ischemia affects membrane-lipids profile by altering their biochemical properties and structural dynamics, which are also believed to play significant role in the amyloid precursor protein processing, suggesting a link between alterations in lipid membrane composition and β-amyloid peptide production enhancement.Using brain microvascular endothelial cells, here we demonstrate how oxygen and glucose deprivation followed by normal conditions restoration, mimicking ischemic environment, increases cell cholesterol amount (+20%), reduces membrane fluidity and results in strong activation (+40%) of β-secretase 1 enzymatic activity. Moreover, we observed an increase of amyloid precursor protein and β-secretase 1 protein levels with altered localization in non-discrete (Triton X-100 soluble) membrane domains, leading to an enhanced production of amyloid precursor protein β-carboxyl-terminal fragment. Therefore, lipid alterations induced by oxygen and glucose deprivation enhance β-secretase 1 activity, favor its proximity to amyloid precursor protein and may concur to increased amyloidogenic cleavage. The latter, represents a detrimental event that may contribute to β-amyloid homeostasis impairment in the brain and to Alzheimer's disease-related BBB dysfunctions.
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13
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Zeitouni NE, Dersch P, Naim HY, von Köckritz-Blickwede M. Hypoxia Decreases Invasin-Mediated Yersinia enterocolitica Internalization into Caco-2 Cells. PLoS One 2016; 11:e0146103. [PMID: 26731748 PMCID: PMC4701670 DOI: 10.1371/journal.pone.0146103] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2015] [Accepted: 12/14/2015] [Indexed: 12/20/2022] Open
Abstract
Yersinia enterocolitica is a major cause of human yersiniosis, with enterocolitis being a typical manifestation. These bacteria can cross the intestinal mucosa, and invade eukaryotic cells by binding to host β1 integrins, a process mediated by the bacterial effector protein invasin. This study examines the role of hypoxia on the internalization of Y. enterocolitica into intestinal epithelial cells, since the gastrointestinal tract has been shown to be physiologically deficient in oxygen levels (hypoxic), especially in cases of infection and inflammation. We show that hypoxic pre-incubation of Caco-2 cells resulted in significantly decreased bacterial internalization compared to cells grown under normoxia. This phenotype was absent after functionally blocking host β1 integrins as well as upon infection with an invasin-deficient Y. enterocolitica strain. Furthermore, downstream phosphorylation of the focal adhesion kinase was also reduced under hypoxia after infection. In good correlation to these data, cells grown under hypoxia showed decreased protein levels of β1 integrins at the apical cell surface whereas the total protein level of the hypoxia inducible factor (HIF-1) alpha was elevated. Furthermore, treatment of cells with the HIF-1 α stabilizer dimethyloxalylglycine (DMOG) also reduced invasion and decreased β1 integrin protein levels compared to control cells, indicating a potential role for HIF-1α in this process. These results suggest that hypoxia decreases invasin-integrin-mediated internalization of Y. enterocolitica into intestinal epithelial cells by reducing cell surface localization of host β1 integrins.
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Affiliation(s)
- Nathalie E. Zeitouni
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Petra Dersch
- Helmholtz Center for Infection Research, Braunschweig, Germany
| | - Hassan Y. Naim
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
| | - Maren von Köckritz-Blickwede
- Department of Physiological Chemistry, University of Veterinary Medicine Hannover, Hannover, Germany
- Research Center for Emerging Infections and Zoonoses (RIZ), University of Veterinary Medicine Hannover, Hannover, Germany
- * E-mail:
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14
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Testai FD, Kilkus JP, Berdyshev E, Gorshkova I, Natarajan V, Dawson G. Multiple sphingolipid abnormalities following cerebral microendothelial hypoxia. J Neurochem 2014; 131:530-40. [PMID: 25060904 DOI: 10.1111/jnc.12836] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2014] [Revised: 07/21/2014] [Accepted: 07/21/2014] [Indexed: 01/01/2023]
Abstract
Hypoxia has been previously shown to inhibit the dihydroceramide (DHC) desaturase, leading to the accumulation of DHC. In this study, we used metabolic labeling with [3H]-palmitate, HPLC/MS/MS analysis, and specific inhibitors to show numerous sphingolipid changes after oxygen deprivation in cerebral microendothelial cells. The increased DHC, particularly long-chain forms, was observed in both whole cells and detergent-resistant membranes. This was reversed by reoxygenation and blocked by the de novo sphingolipid synthesis inhibitor myriocin, but not by the neutral sphingomyelinase inhibitor GW-4869. Furthermore, oxygen deprivation of microendothelial cells increased levels of dihydro-sphingosine (DH-Sph), DH-sphingosine1-phosphate (DH-S1P), DH-sphingomyelin (DH-SM), DH-glucosylceramide (DH-GlcCer), and S1P levels. In vitro assays revealed no changes in the activity of sphingomyelinases or sphingomyelin synthase, but resulted in reduced S1P lyase activity and 40% increase in glucosylceramide synthase (GCS) activity, which was reversed by reoxygenation. Inhibition of the de novo sphingolipid pathway (myriocin) or GCS (EtPoD4) induced endothelial barrier dysfunction and increased caspase 3-mediated cell death in response to hypoxia. Our findings suggest that hypoxia induces synthesis of S1P and multiple dihydro-sphingolipids, including DHC, DH-SM, DH-GlcCer, DH-Sph and DH-S1P, which may be involved in ameliorating the effects of stroke . Progressive hypoxia leads to the accumulation of several dihydrosphingolipids in cerebral microendothelial cells. Hypoxia also increases sphingosine-1-phosphate and the activity of glucosylceramide (Glc-Cer) synthase. These changes reverse by inhibiting the de novo sphingolipid synthesis, which worsens hypoxia-induced endothelial barrier dysfunction and apoptosis, suggesting that the identified sphingolipids may be vasculoprotective.
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Affiliation(s)
- Fernando D Testai
- Department of Neurology and Rehabilitation, University of Illinois at Chicago, Chicago, Illinois, USA
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15
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A bioreactor for subjecting cultured cells to fast-rate intermittent hypoxia. Respir Physiol Neurobiol 2012; 182:47-52. [DOI: 10.1016/j.resp.2012.01.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Revised: 12/30/2011] [Accepted: 01/02/2012] [Indexed: 01/02/2023]
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16
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A biophysical model of intracellular distribution and perinuclear accumulation of particulate matter. Biophys Chem 2011; 158:134-40. [DOI: 10.1016/j.bpc.2011.06.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2011] [Revised: 06/16/2011] [Accepted: 06/16/2011] [Indexed: 01/15/2023]
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17
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Barboni B, Bernabò N, Palestini P, Botto L, Pistilli MG, Charini M, Tettamanti E, Battista N, Maccarrone M, Mattioli M. Type-1 cannabinoid receptors reduce membrane fluidity of capacitated boar sperm by impairing their activation by bicarbonate. PLoS One 2011; 6:e23038. [PMID: 21829686 PMCID: PMC3150387 DOI: 10.1371/journal.pone.0023038] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2011] [Accepted: 07/05/2011] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Mammalian spermatozoa acquire their full fertilizing ability (so called capacitation) within the female genital tract, where they are progressively exposed to inverse gradients of inhibiting and stimulating molecules. METHODOLOGY/PRINCIPAL FINDINGS In the present research, the effect on this process of anandamide, an endocannabinoid that can either activate or inhibit cannabinoid receptors depending on its concentration, and bicarbonate, an oviductal activatory molecule, was assessed, in order to study the role exerted by the type 1 cannabinoid receptor (CB1R) in the process of lipid membrane remodeling crucial to complete capacitation. To this aim, boar sperm were incubated in vitro under capacitating conditions (stimulated by bicarbonate) in the presence or in the absence of methanandamide (Met-AEA), a non-hydrolysable analogue of anandamide. The CB1R involvement was studied by using the specific inhibitor (SR141716) or mimicking its activation by adding a permeable cAMP analogue (8Br-cAMP). By an immunocytochemistry approach it was shown that the Met-AEA inhibits the bicarbonate-dependent translocation of CB1R from the post-equatorial to equatorial region of sperm head. In addition it was found that Met-AEA is able to prevent the bicarbonate-induced increase in membrane disorder and the cholesterol extraction, both preliminary to capacitation, acting through a CB1R-cAMP mediated pathway, as indicated by MC540 and filipin staining, EPR spectroscopy and biochemical analysis on whole membranes (CB1R activity) and on membrane enriched fraction (C/P content and anisotropy). CONCLUSIONS/SIGNIFICANCE Altogether, these data demonstrate that the endocannabinoid system strongly inhibits the process of sperm capacitation, acting as membrane stabilizing agent, thus increasing the basic knowledge on capacitation-related signaling and potentially opening new perspectives in diagnostics and therapeutics of male infertility.
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Affiliation(s)
- Barbara Barboni
- Department of Biomedical Comparative Sciences, University of Teramo, Teramo, Italy.
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18
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Palestini P, Botto L, Rivolta I, Miserocchi G. Remodelling of membrane rafts expression in lung cells as an early sign of mechanotransduction-signalling in pulmonary edema. J Lipids 2011; 2011:695369. [PMID: 21785732 PMCID: PMC3139192 DOI: 10.1155/2011/695369] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/28/2010] [Accepted: 03/22/2011] [Indexed: 11/17/2022] Open
Abstract
Membrane rafts (MRs) are clusters of lipids, organized in a "quasicrystalline" liquid-order phase, organized on the cell surface and whose pattern of molecules and physicochemical properties are distinct from those of the surrounding plasma membrane. MRs may be considered an efficient and fairly rapid cell-activated mechanism to express or mask surface receptors aimed at triggering specific response pathways. This paper reports observations concerning the role of MRs in the control of lung extravascular water that ought to be kept at minimum to assure gas diffusion, supporting the hypothesis that MRs expression is a potential mechanism of sensing minor changes in the volume of extravascular water. We present the evidence that MRs expression specifically relates to signal-transduction processes evoked by mechanical stimuli arising in the interstitial lung compartment when a small increase in extravascular volume occurs. We further hypothesize that a differential expression of MRs might also reflect the damage to precise components of the extracellular matrix caused by the perturbation in water balance and thus can trigger a molecule-oriented specific matrix remodelling.
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Affiliation(s)
- Paola Palestini
- Department of Experimental Medicine, University of Milano-Bicocca, 48 Via Cadore, 20052 Monza, Italy
| | - Laura Botto
- Department of Experimental Medicine, University of Milano-Bicocca, 48 Via Cadore, 20052 Monza, Italy
| | - Ilaria Rivolta
- Department of Experimental Medicine, University of Milano-Bicocca, 48 Via Cadore, 20052 Monza, Italy
| | - Giuseppe Miserocchi
- Department of Experimental Medicine, University of Milano-Bicocca, 48 Via Cadore, 20052 Monza, Italy
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Botto L, Bernabò N, Palestini P, Barboni B. Bicarbonate induces membrane reorganization and CBR1 and TRPV1 endocannabinoid receptor migration in lipid microdomains in capacitating boar spermatozoa. J Membr Biol 2010; 238:33-41. [PMID: 21104238 DOI: 10.1007/s00232-010-9316-8] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2010] [Accepted: 10/28/2010] [Indexed: 10/18/2022]
Abstract
Mammalian spermatozoa acquire full fertilizing ability only after a morphofunctional maturation called "capacitation." During this process the high level of bicarbonate present within the upper female genital tract or in culture medium induces a marked reorganization of sperm membranes characterized by a biphasic behavior: In a few minutes, it promotes membrane phospholipid scrambling preliminary to the apical translocation of sterol that, 2-4 h later, enables spermatozoa to recognize zona pellucida after albumin-mediated cholesterol extraction. In the present research it was demonstrated that spermatozoa incubated with bicarbonate in protein-free media underwent a marked reorganization of lipid microdomains present in a detergent-resistant membrane fraction (DRM) isolated by ultracentrifugation on sucrose density gradient. In fact, bicarbonate exposed sperm (ES) cells, compared with ejaculated spermatozoa (nonexposed sperm [nES] cells), displayed an increase in protein DRM content and, in particular, in Cav-1 and CD55, markers of caveolae and lipid rafts, as well in acrosin-2, a marker of the outer acrosomal membrane (OAM). Moreover, the amount of certain proteins involved in capacitation, such as the endocannabinoid system receptors cannabinoid receptor type 1 (CBR1) and transient receptor potential cation channel 1 (TRPV1), increased in DRM obtained from ES. These data allow us to hypothesize that sperm membrane reorganization takes place even in the absence of extracellular proteins; that not only the plasma membrane but also the OAM participate in this process; and that important molecules playing a key role in inside-out signaling, such as the endocannbinoid receptors TRPV1 and CBR1, are involved in this event, with potentially important consequences on sperm function.
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Affiliation(s)
- Laura Botto
- Department of Experimental Medicine (DIMS), University of Milano-Bicocca, Via Cadore 48, 20052, Monza, Italy
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Mantecca P, Farina F, Moschini E, Gallinotti D, Gualtieri M, Rohr A, Sancini G, Palestini P, Camatini M. Comparative acute lung inflammation induced by atmospheric PM and size-fractionated tire particles. Toxicol Lett 2010; 198:244-54. [DOI: 10.1016/j.toxlet.2010.07.002] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Revised: 06/29/2010] [Accepted: 07/02/2010] [Indexed: 11/17/2022]
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21
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Current Opinion in Clinical Nutrition and Metabolic Care. Current world literature. Curr Opin Clin Nutr Metab Care 2010; 13:215-21. [PMID: 20145440 DOI: 10.1097/mco.0b013e32833643b4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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22
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Lee SH, Koo KH, Park JW, Kim HJ, Ye SK, Park JB, Park BK, Kim YN. HIF-1 is induced via EGFR activation and mediates resistance to anoikis-like cell death under lipid rafts/caveolae-disrupting stress. Carcinogenesis 2010; 30:1997-2004. [PMID: 19789263 DOI: 10.1093/carcin/bgp233] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The plasma membrane microdomains, lipid rafts, are involved in regulation of cellular functions such as cell survival and adhesion. Cholesterol is a critical component of lipid rafts in terms of their integrity and functions and rafts disruption by cholesterol depletion can induce detachment-induced cell death. Hypoxia inducible factor-1 (HIF-1) alpha is stabilized in hypoxia and transactivates numerous genes required for cellular adaptation to hypoxia. It is also induced by non-hypoxic stimuli and contributes to cell survival. Because hypoxia inhibits cholesterol synthesis and HIF-1alpha plays a role in this process, we here explored a possible connection between lipid rafts and HIF-1alpha. We investigated whether HIF-1alpha is regulated during cholesterol depletion/rafts disruption in A431 cells in normoxic conditions. Methyl-beta cyclodextrin (MbetaCD), which induces cholesterol depletion, upregulated HIF-1alpha even under normoxic conditions and this upregulation required epidermal growth factor receptor (EGFR) and extracellular signal-regulated kinase 1 and 2 activation, but not Akt activation. MbetaCD treatment induced HIF-1alpha upregulation at both the transcriptional and translational levels but not at the posttranslational levels. In addition, MbetaCD robustly induced vascular endothelial growth factor production and stimulated an hypoxia response element-driven luciferase reporter activity under normoxic conditions, indicating that MbetaCD-induced HIF-1alpha is functionally activated. Both EGFR activity and HIF-1alpha expression were higher in the attached cells than in the detached cells after MbetaCD treatment. Furthermore, inhibition of HIF-1alpha by RNA interference accelerated cell detachment, thus increasing cell death, indicating that HIF-1alpha expression attenuates MbetaCD-induced anoikis-like cell death. These data suggest that, depending on cholesterol levels, lipid rafts or membrane fluidity are probably to regulate HIF-1alpha expression in normoxia by modulating rafts protein activities such as EGFR, and this connection between lipid rafts and HIF-1alpha regulation may provide cell survival under membrane-disturbing stress.
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Affiliation(s)
- Seong-Hee Lee
- Pediatric Oncology Branch, Division of Translational & Clinical Research II, National Cancer Center, 809 Madu 1-dong, Ilsan-gu Goyang-si, Gyeonggi-do, 411-769, Korea
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