1
|
Bellato F, Feola S, Dalla Verde G, Bellio G, Pirazzini M, Salmaso S, Caliceti P, Cerullo V, Mastrotto F. Mannosylated Polycations Target CD206 + Antigen-Presenting Cells and Mediate T-Cell-Specific Activation in Cancer Vaccination. Biomacromolecules 2022; 23:5148-5163. [PMID: 36394394 DOI: 10.1021/acs.biomac.2c00993] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Immunotherapy is deemed one of the most powerful therapeutic approaches to treat cancer. However, limited response and tumor specificity are still major challenges to address. Herein, mannosylated polycations targeting mannose receptor- are developed as vectors for plasmid DNA (pDNA)-based vaccines to improve selective delivery of genetic material to antigen-presenting cells and enhance immune cell activation. Three diblock glycopolycations (M15A12, M29A25, and M58A45) and two triblock copolymers (M29A29B9 and M62A52B32) are generated by using mannose (M), agmatine (A), and butyl (B) derivatives to target CD206, complex nucleic acids, and favor the endosomal escape, respectively. All glycopolycations efficiently complex pDNA at N/P ratios <5, protecting the pDNA from degradation in a physiological milieu. M58A45 and M62A52B32 complexed with plasmid encoding for antigenic ovalbumin (pOVA) trigger the immune activation of cultured dendritic cells, which present the SIINFEKL antigenic peptide via specific major histocompatibility complex-I. Importantly, administration of M58A45/pOVA elicits SIINFEKL-specific T-cell response in C56BL/6 mice bearing the melanoma tumor model B16-OVA, well in line with a reduction in tumor growth. These results qualify mannosylation as an efficient strategy to target immune cells in cancer vaccination and emphasize the potential of these glycopolycations as effective delivery vehicles for nucleic acids.
Collapse
Affiliation(s)
- Federica Bellato
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| | - Sara Feola
- Drug Research Program ImmunoViroTherapy Lab (IVT), Faculty of Pharmacy, Helsinki University, Viikinkaari 5E, 00790Helsinki, Finland.,iCAN Digital Precision Cancer Medicine Flagship, FI-00014Helsinki, Finland
| | - Gloria Dalla Verde
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| | - Greta Bellio
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| | - Marco Pirazzini
- Department of Biomedical Sciences, University of Padova, Via Ugo Bassi 58/B, 35131Padova, Italy
| | - Stefano Salmaso
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| | - Paolo Caliceti
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| | - Vincenzo Cerullo
- Drug Research Program ImmunoViroTherapy Lab (IVT), Faculty of Pharmacy, Helsinki University, Viikinkaari 5E, 00790Helsinki, Finland.,iCAN Digital Precision Cancer Medicine Flagship, FI-00014Helsinki, Finland
| | - Francesca Mastrotto
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131Padova, Italy
| |
Collapse
|
2
|
Zhuang A, Yap FYT, Borg DJ, McCarthy D, Fotheringham A, Leung S, Penfold SA, Sourris KC, Coughlan MT, Schulz BL, Forbes JM. The AGE receptor, OST48 drives podocyte foot process effacement and basement membrane expansion (alters structural composition). Endocrinol Diabetes Metab 2021; 4:e00278. [PMID: 34277994 PMCID: PMC8279619 DOI: 10.1002/edm2.278] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2021] [Revised: 05/16/2021] [Accepted: 05/22/2021] [Indexed: 11/17/2022] Open
Abstract
AIMS The accumulation of advanced glycation end products is implicated in the development and progression of diabetic kidney disease. No study has examined whether stimulating advanced glycation clearance via receptor manipulation is reno-protective in diabetes. Podocytes, which are early contributors to diabetic kidney disease and could be a target for reno-protection. MATERIALS AND METHODS To examine the effects of increased podocyte oligosaccharyltransferase-48 on kidney function, glomerular sclerosis, tubulointerstitial fibrosis and proteome (PXD011434), we generated a mouse with increased oligosaccharyltransferase-48kDa subunit abundance in podocytes driven by the podocin promoter. RESULTS Despite increased urinary clearance of advanced glycation end products, we observed a decline in renal function, significant glomerular damage including glomerulosclerosis, collagen IV deposition, glomerular basement membrane thickening and foot process effacement and tubulointerstitial fibrosis. Analysis of isolated glomeruli identified enrichment in proteins associated with collagen deposition, endoplasmic reticulum stress and oxidative stress. Ultra-resolution microscopy of podocytes revealed denudation of foot processes where there was co-localization of oligosaccharyltransferase-48kDa subunit and advanced glycation end-products. CONCLUSIONS These studies indicate that increased podocyte expression of oligosaccharyltransferase-48 kDa subunit results in glomerular endoplasmic reticulum stress and a decline in kidney function.
Collapse
Affiliation(s)
- Aowen Zhuang
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
- Faculty of MedicineUniversity of QueenslandSt LuciaQldAustralia
- Baker Heart and Diabetes InstituteMelbourneVicAustralia
| | | | - Danielle J. Borg
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
| | - Domenica McCarthy
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
| | - Amelia Fotheringham
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
| | - Sherman Leung
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
| | | | - Karly C. Sourris
- Baker Heart and Diabetes InstituteMelbourneVicAustralia
- Department of DiabetesCentral Clinical SchoolMonash UniversityMelbourneVicAustralia
| | - Melinda T. Coughlan
- Baker Heart and Diabetes InstituteMelbourneVicAustralia
- Department of DiabetesCentral Clinical SchoolMonash UniversityMelbourneVicAustralia
| | - Benjamin L. Schulz
- School of Chemistry and Molecular BiosciencesUniversity of QueenslandSt LuciaQldAustralia
| | - Josephine M. Forbes
- Glycation and Diabetes ComplicationsMater Research Institute – The University of QueenslandTranslational Research InstituteWoolloongabbaQldAustralia
- Faculty of MedicineUniversity of QueenslandSt LuciaQldAustralia
| |
Collapse
|
3
|
Tully M, Wedepohl S, Kutifa D, Weise C, Licha K, Schirner M, Haag R. Prolonged activity of exenatide: Detailed comparison of Site-specific linear polyglycerol- and poly(ethylene glycol)-conjugates. Eur J Pharm Biopharm 2021; 164:105-113. [PMID: 33957224 DOI: 10.1016/j.ejpb.2021.04.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2021] [Revised: 04/15/2021] [Accepted: 04/26/2021] [Indexed: 12/23/2022]
Abstract
Exenatide is a small therapeutic peptide being currently used in clinic for the treatment of diabetes mellitus type II, however, displaying a short blood circulation time which makes two daily injections necessary. Covalent polymer modification of a protein is a well-known approach to overcome this limitation, resulting in steric shielding, an increased size and therefore a longer circulation half-life. In this study, we employed site-selective C-terminal polymer ligation of exenatide via copper-catalyzed azide-alkyne-cycloaddition (CuAAC) to yield 1:1-conjugates of either poly(ethylene glycol) (PEG) or linear polyglycerol (LPG) of different molecular weights. Our goal was to compare the impact of the two polymers on size, structure and activity of exenatide on the in vitro and in vivo level. Both polymers did not alter the secondary structure of exenatide and expectedly increased its hydrodynamic size, where the LPG-versions of exenatide showed slightly smaller values than their PEG-analogs of same molecular weight. Upon conjugation, GLP-1 receptor activation was diminished, however, still enabled maximum receptor response at slightly higher concentrations. Exenatide modified with a 40 kDa LPG (Ex-40-LPG) showed significant reduction of the blood glucose level in diabetic mice for up to 72 h, which was comparable to its PEG-analog, but 9-fold longer than native exenatide (8 h).
Collapse
Affiliation(s)
- Michael Tully
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Stefanie Wedepohl
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Daniel Kutifa
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Christoph Weise
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Kai Licha
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Michael Schirner
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Rainer Haag
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany.
| |
Collapse
|
4
|
Tully M, Dimde M, Weise C, Pouyan P, Licha K, Schirner M, Haag R. Polyglycerol for Half-Life Extension of Proteins-Alternative to PEGylation? Biomacromolecules 2021; 22:1406-1416. [PMID: 33792290 DOI: 10.1021/acs.biomac.0c01627] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Since several decades, PEGylation is known to be the clinical standard to enhance pharmacokinetics of biotherapeutics. In this study, we introduce polyglycerol (PG) of different lengths and architectures (linear and hyperbranched) as an alternative polymer platform to poly(ethylene glycol) (PEG) for half-life extension (HLE). We designed site-selective N-terminally modified PG-protein conjugates of the therapeutic protein anakinra (IL-1ra, Kineret) and compared them systematically with PEG analogues of similar molecular weights. Linear PG and PEG conjugates showed comparable hydrodynamic sizes and retained their secondary structure, whereas binding affinity to IL-1 receptor 1 decreased with increasing polymer length, yet remained in the low nanomolar range for all conjugates. The terminal half-life of a 40 kDa linear PG-modified anakinra was extended 4-fold compared to the unmodified protein, close to its PEG analogue. Our results demonstrate similar performances of PEG- and PG-anakinra conjugates and therefore highlight the outstanding potential of polyglycerol as a PEG alternative for half-life extension of biotherapeutics.
Collapse
Affiliation(s)
- Michael Tully
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Mathias Dimde
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Christoph Weise
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Paria Pouyan
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Kai Licha
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Michael Schirner
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| | - Rainer Haag
- Freie Universität Berlin, Institute of Chemistry and Biochemistry, Takustr. 3, 14195 Berlin, Germany
| |
Collapse
|
5
|
Rippe B. Does an Endothelial Surface Layer Contribute to the Size Selectivity of the Permeable Pathways of the Three-Pore Model? Perit Dial Int 2020. [DOI: 10.1177/089686080802800104] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
Affiliation(s)
- Bengt Rippe
- Department of Nephrology Lund University University Hospital of Lund Lund, Sweden
| |
Collapse
|
6
|
Voinova M, Repin N, Sokol E, Tkachuk B, Gorelik L. Physical Processes in Polymeric Filters Used for Dialysis. Polymers (Basel) 2019; 11:E389. [PMID: 30960373 PMCID: PMC6473866 DOI: 10.3390/polym11030389] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2018] [Revised: 02/06/2019] [Accepted: 02/12/2019] [Indexed: 01/03/2023] Open
Abstract
The key physical processes in polymeric filters used for the blood purification include transport across the capillary wall and the interaction of blood cells with the polymer membrane surface. Theoretical modeling of membrane transport is an important tool which provides researchers with a quantification of the complex phenomena involved in dialysis. In the paper, we present a dense review of the most successful theoretical approaches to the description of transport across the polymeric membrane wall as well as the cell⁻polymer surface interaction, and refer to the corresponding experimental methods while studying these phenomena in dialyzing filters.
Collapse
Affiliation(s)
- Marina Voinova
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
- Department of Industrial and Biomedical Electronics, Kharkiv Polytechnical Institute, National Technical University, 61002 Kharkov, Ukraine.
| | - Nikolay Repin
- Department of Cryomorphology, Institute for Problems of Cryobiology and Cryomedicine, 61015 Kharkov, Ukraine.
| | - Evgen Sokol
- Department of Industrial and Biomedical Electronics, Kharkiv Polytechnical Institute, National Technical University, 61002 Kharkov, Ukraine.
| | - Bogdan Tkachuk
- Department of Hemodialysis, Municipal Noncommercial Enterprise of Kharkiv Regional Council "Regional Medical Clinical Center of Urology and Nephrology n.a. V.I. Shapoval", 61037 Kharkov, Ukraine.
| | - Leonid Gorelik
- Department of Physics, Chalmers University of Technology, 41296 Gothenburg, Sweden.
| |
Collapse
|
7
|
Palit S, Yethiraj A. Dynamics and cluster formation in charged and uncharged Ficoll70 solutions. J Chem Phys 2017; 147:074901. [DOI: 10.1063/1.4986366] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- Swomitra Palit
- Department of Physics and Physical Oceanography, Memorial University, St. John’s, Newfoundland and Labrador A1B3X7, Canada
| | - Anand Yethiraj
- Department of Physics and Physical Oceanography, Memorial University, St. John’s, Newfoundland and Labrador A1B3X7, Canada
| |
Collapse
|
8
|
Rusinga FI, Weis DD. Soft interactions and volume exclusion by polymeric crowders can stabilize or destabilize transient structure in disordered proteins depending on polymer concentration. Proteins 2017; 85:1468-1479. [PMID: 28425679 DOI: 10.1002/prot.25307] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2017] [Revised: 04/07/2017] [Accepted: 04/17/2017] [Indexed: 01/19/2023]
Abstract
The effects of macromolecular crowding on the transient structure of intrinsically disordered proteins is not well-understood. Crowding by biological molecules inside cells could modulate transient structure and alter IDP function. Volume exclusion theory and observations of structured proteins suggest that IDP transient structure would be stabilized by macromolecular crowding. Amide hydrogen exchange (HX) of IDPs in highly concentrated polymer solutions would provide valuable insights into IDP transient structure under crowded conditions. Here, we have used mass spectrometry to measure HX by a transiently helical random coil domain of the activator of thyroid and retinoid receptor (ACTR) in solutions containing 300 g L-1 and 400 g L-1 of Ficoll, a synthetic polysaccharide, using a recently-developed strong cation exchange-based cleanup method [Rusinga, et al., Anal Chem 2017;89:1275-1282]. Transiently helical regions of ACTR exchanged faster in 300 g L-1 Ficoll than in dilute buffer. In contrast, one transient helix exchanged more slowly in 400 g L-1 Ficoll. Nonspecific interactions destabilize ACTR helicity in 300 g L-1 Ficoll because ACTR engages with the Ficoll polymer mesh. In contrast, 400 g L-1 Ficoll is a semi-dilute solution where ACTR cannot engage the Ficoll mesh. At this higher concentration, volume exclusion stabilizes ACTR helicity because ACTR is compacted in interstitial spaces between Ficoll molecules. Our results suggest that the interplay between nonspecific interactions and volume exclusion in different cellular compartments could modulate IDP function by altering the stability of IDP transient structures. Proteins 2017; 85:1468-1479. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Farai I Rusinga
- Department of Chemistry and R. N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas, USA
| | - David D Weis
- Department of Chemistry and R. N. Adams Institute for Bioanalytical Chemistry, University of Kansas, Lawrence, Kansas, USA
| |
Collapse
|
9
|
Öberg CM, Groszek JJ, Roy S, Fissell WH, Rippe B. A distributed solute model: an extended two-pore model with application to the glomerular sieving of Ficoll. Am J Physiol Renal Physiol 2017; 314:F1108-F1116. [PMID: 28424207 DOI: 10.1152/ajprenal.00066.2017] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
One of the many unresolved questions regarding the permeability of the glomerular filtration barrier is the reason behind the marked difference in permeability between albumin and polysaccharide probe molecules such as Ficoll and dextran of the same molecular size. Although the differences in permeability have been mainly attributed to charge effects, we have previously shown that this would require a highly charged filtration barrier, having a charge density that is ~10 times more than that on the albumin molecule. In this article, the classic two-pore model was extended by introducing size distributions on the solute molecules, making them conformationally flexible. Experimental sieving data for Ficoll from the rat glomerulus and from precision-made silicon nanopore membranes were analyzed using the model. For the rat glomerulus a small-pore radius of 36.2 Å and a geometric standard deviation (gSD) for the Ficoll size-distribution of 1.16 were obtained. For the nanopore membranes, a gSD of 1.24 and a small-pore radius of 43 Å were found. Interestingly, a variation of only ~16% in the size of the polysaccharide molecule is sufficient to explain the difference in permeability between albumin and Ficoll. Also, in line with previous data, the effects of applying a size distribution on the solute molecule are only evident when the molecular size is close to the pore size. Surely there is at least some variation in the pore radii, and, likely, the gSD obtained in the current study is an overestimation of the "true" variation in the size of the Ficoll molecule.
Collapse
Affiliation(s)
- Carl M Öberg
- Lund University, Skane University Hospital, Department of Nephrology , Lund , Sweden
| | - Joseph J Groszek
- Nephrology and Hypertension, Vanderbilt University , Nashville, Tennessee
| | - Shuvo Roy
- Bioengineering & Therapeutic Sciences, University of California , San Francisco, California
| | - William H Fissell
- Nephrology and Hypertension, Vanderbilt University , Nashville, Tennessee
| | - Bengt Rippe
- Lund University, Skane University Hospital, Department of Nephrology , Lund , Sweden
| |
Collapse
|
10
|
Kostka L, Etrych T. High-molecular-weight HPMA-based polymer drug carriers for delivery to tumor. Physiol Res 2017; 65:S179-S190. [PMID: 27762584 DOI: 10.33549/physiolres.933420] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
Abstract
In this work, design and synthesis of high-molecular-weight N-(2-hydroxypropyl)methacrylamide-based polymer drug delivery systems tailored for cancer therapy is summarized. Moreover, the influence of their architecture on tumor accumulation and in vivo anti-cancer efficacy is discussed. Mainly, the high-molecular-weight delivery systems, such as branched, grafted, multi-block, star-like or micellar systems, with molecular weights greater than the renal threshold are discussed and reviewed in detail.
Collapse
Affiliation(s)
- L Kostka
- Department of Biomedicinal Polymers, Institute of Macromolecular Chemistry of the Czech Academy of Sciences, Prague, Czech Republic.
| | | |
Collapse
|
11
|
MCO Membranes: Enhanced Selectivity in High-Flux Class. Sci Rep 2015; 5:18448. [PMID: 26669756 PMCID: PMC4680880 DOI: 10.1038/srep18448] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2015] [Accepted: 11/18/2015] [Indexed: 12/02/2022] Open
Abstract
Novel MCO high-flux membranes for hemodialysis have been developed with optimized permeability, allowing for filtration close to that of the natural kidney. A comprehensive in vitro characterization of the membrane properties by dextran filtration is presented. The sieving profile of pristine membranes, as well as that of membranes exposed to blood for 40 minutes, are described. The effective pore size (Stokes-Einstein radius) was estimated from filtration experiments before and after blood exposure, and results were compared to hydrodynamic radii of middle and large uremic toxins and essential proteins. The results indicate that the tailored pore sizes of the MCO membranes promote removal of large toxins while ensuring the retention of albumin.
Collapse
|
12
|
Lubbad L, Öberg CM, Dhanasekaran S, Nemmar A, Hammad F, Pathan JY, Rippe B, Bakoush O. Reduced glomerular size selectivity in late streptozotocin-induced diabetes in rats: application of a distributed two-pore model. Physiol Rep 2015; 3:3/5/e12397. [PMID: 26009635 PMCID: PMC4463827 DOI: 10.14814/phy2.12397] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Microalbuminuria is an early manifestation of diabetic nephropathy. Potential contributors to this condition are reduced glomerular filtration barrier (GFB) size- and charge selectivity, and impaired tubular reabsorption of filtered proteins. However, it was recently reported that no significant alterations in charge selectivity of the GFB occur in early experimental diabetic nephropathy. We here aimed at investigating the functional changes in the GFB in long-term type-1 diabetes in rats, applying a novel distributed two-pore model. We examined glomerular permeability in 15 male Wistar rats with at least 3 months of streptozotocin (STZ)-induced diabetes (blood glucose ∼20 mmol/L) and in age-matched control rats. The changes in glomerular permeability were assessed by determining the glomerular sieving coefficients (θ) for FITC-Ficoll (molecular radius 20–90 Å) using size exclusion HPLC. The values of θ for FITC-Ficoll of radius >50 Å were significantly increased in STZ-diabetic rats compared to age-matched controls (θ for 50–69 Å = 0.001 vs. 0.0002, and θ for 70–90 Å = 0.0007 vs. 0.00006, P < 0.001), while θ for FITC-Ficoll <50 Å tended to be lower in diabetic rats than in controls (θ for 36–49 Å = 0.013 vs. 0.016, ns). According to the distributed two-pore model, there was primarily an increase in macromolecular transport through large pores in the glomerular filter of diabetic rats associated with a loss of small-pore area. Deterioration in the glomerular size selectivity due to an increase in the number and size-spread of large pores, with no changes in the permeability of the small-pore system, represent the major functional changes observed after 3 months of induced experimental diabetes.
Collapse
Affiliation(s)
- Loay Lubbad
- Department of Surgery, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Carl M Öberg
- Department of Nephrology, Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Subramanian Dhanasekaran
- Department of Pharmacology and Therapeutics, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Abderrahim Nemmar
- Department of Physiology, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Fayez Hammad
- Department of Surgery, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Javed Y Pathan
- Department of Internal Medicine, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| | - Bengt Rippe
- Department of Nephrology, Clinical Sciences Lund, Lund University, Lund, Sweden
| | - Omran Bakoush
- Department of Internal Medicine, College of Medicine & Health Sciences, United Arab Emirates University, Al Ain, United Arab Emirates
| |
Collapse
|
13
|
Kumar P, Shenoi RA, Lai BFL, Nguyen M, Kizhakkedathu JN, Straus SK. Conjugation of Aurein 2.2 to HPG Yields an Antimicrobial with Better Properties. Biomacromolecules 2015; 16:913-23. [DOI: 10.1021/bm5018244] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Affiliation(s)
- Prashant Kumar
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Rajesh A. Shenoi
- Centre
for Blood Research, Department of Pathology and Laboratory Medicine, University of British Columbia, 2350 Health Sciences Mall, Life Sciences Centre, Vancouver, BC V6T 1Z3, Canada
| | - Benjamin F. L. Lai
- Centre
for Blood Research, Department of Pathology and Laboratory Medicine, University of British Columbia, 2350 Health Sciences Mall, Life Sciences Centre, Vancouver, BC V6T 1Z3, Canada
| | - Michael Nguyen
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| | - Jayachandran N. Kizhakkedathu
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
- Centre
for Blood Research, Department of Pathology and Laboratory Medicine, University of British Columbia, 2350 Health Sciences Mall, Life Sciences Centre, Vancouver, BC V6T 1Z3, Canada
| | - Suzana K. Straus
- Department
of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, BC V6T 1Z1, Canada
| |
Collapse
|
14
|
Öberg CM, Rippe B. Letter to the Editor: "Can early plasma elimination rate be used to quantify renal clearance of macromolecules?". Am J Physiol Renal Physiol 2015; 308:F164-5. [PMID: 25560050 DOI: 10.1152/ajprenal.00491.2014] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Affiliation(s)
- Carl M Öberg
- Department of Nephrology, Lund University, Lund, Sweden
| | - Bengt Rippe
- Department of Nephrology, Lund University, Lund, Sweden
| |
Collapse
|
15
|
Affiliation(s)
- Bengt Rippe
- Department of Nephrology, Lund University, Lund, Sweden
| | - Carl M Öberg
- Department of Nephrology, Lund University, Lund, Sweden
| |
Collapse
|
16
|
Saxton MJ. Wanted: scalable tracers for diffusion measurements. J Phys Chem B 2014; 118:12805-17. [PMID: 25319586 PMCID: PMC4234437 DOI: 10.1021/jp5059885] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/03/2014] [Indexed: 12/02/2022]
Abstract
Scalable tracers are potentially a useful tool to examine diffusion mechanisms and to predict diffusion coefficients, particularly for hindered diffusion in complex, heterogeneous, or crowded systems. Scalable tracers are defined as a series of tracers varying in size but with the same shape, structure, surface chemistry, deformability, and diffusion mechanism. Both chemical homology and constant dynamics are required. In particular, branching must not vary with size, and there must be no transition between ordinary diffusion and reptation. Measurements using scalable tracers yield the mean diffusion coefficient as a function of size alone; measurements using nonscalable tracers yield the variation due to differences in the other properties. Candidate scalable tracers are discussed for two-dimensional (2D) diffusion in membranes and three-dimensional diffusion in aqueous solutions. Correlations to predict the mean diffusion coefficient of globular biomolecules from molecular mass are reviewed briefly. Specific suggestions for the 3D case include the use of synthetic dendrimers or random hyperbranched polymers instead of dextran and the use of core-shell quantum dots. Another useful tool would be a series of scalable tracers varying in deformability alone, prepared by varying the density of crosslinking in a polymer to make say "reinforced Ficoll" or "reinforced hyperbranched polyglycerol."
Collapse
Affiliation(s)
- Michael J. Saxton
- Department of Biochemistry
and Molecular Medicine, University of California, One Shields Ave., Davis, California 95616, United States
| |
Collapse
|
17
|
Sverrisson K, Axelsson J, Rippe A, Asgeirsson D, Rippe B. Dynamic, size-selective effects of protamine sulfate and hyaluronidase on the rat glomerular filtration barrier in vivo. Am J Physiol Renal Physiol 2014; 307:F1136-43. [PMID: 25209861 DOI: 10.1152/ajprenal.00181.2014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The proteinuric actions of protamine sulfate (PS) have classically been, at least partly, attributed to alterations of the negatively charged glomerular endothelial glycocalyx. To investigate whether the charge-selective properties of the glomerular filtration barrier (GFB) would be altered by PS, we assessed the glomerular sieving of conventional, uncharged, polydispersed Ficoll (n-Ficoll) compared with charge modified, conformationally intact, anionic (carboxymethylated) Ficoll (a-Ficoll) before and after systemic infusions of PS in rats. For comparison, we also investigated the impact of hyaluronidase (hyase), which partially degrades the glycocalyx, on GFB permeability. In anaesthetized Wistar rats, blood access was achieved, and the left ureter was cannulated for urine collection. Rats were infused with either n-Ficoll or a-Ficoll before and during systemic infusions with either PS or hyase. Plasma and urine samples were taken repeatedly and analyzed by high-performance size exclusion chromatography to assess glomerular sieving coefficients (θ) for Ficoll (radius 10-80 Å). The GFB showed a significant glomerular charge selectivity for Ficoll molecules of radius 20-35 Å. PS and hyase infusions reversibly increased θ for large Ficoll molecules (Ficoll molecules of radius 50-80 Å). Thus, for PS, θ for a-Ficoll molecules of radius 70 Å increased from 2.47 × 10(-5) ± 1.1(-5) to 7.25 × 10(-5) ± 1.1(-5) (P < 0.05) at 15 min. For hyase, changes in a-Ficoll molecules of radius 50-80 Å were, however, not statistically significant. Neither PS nor hyase had any effect on θ for n-Ficoll molecules of radius 20-45 Å or a-Ficoll molecules of radius 20-45 Å. It is concluded that systemically administered PS and hyase in moderate doses dynamically decreased the size selectivity of the rat GFB without affecting its charge selective properties.
Collapse
Affiliation(s)
| | | | - Anna Rippe
- Department of Nephrology, Lund University, Lund, Sweden
| | | | - Bengt Rippe
- Department of Nephrology, Lund University, Lund, Sweden
| |
Collapse
|
18
|
Sandoval RM, Molitoris BA. Letter to the editor: "Quantifying albumin permeability with multiphoton microscopy: why the difference?". Am J Physiol Renal Physiol 2014; 306:F1098-100. [PMID: 24785957 PMCID: PMC5243215 DOI: 10.1152/ajprenal.00652.2013] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Affiliation(s)
- Ruben M Sandoval
- Indiana Univ. School of Medicine, 1120 South Dr., Indianapolis, IN 46202-5116.
| | | |
Collapse
|
19
|
Affiliation(s)
- Wayne D Comper
- SalAqua Diagnostics Inc., Suite 277, 331 West 57th Street, New York, NY 10019, USA
| |
Collapse
|
20
|
Challenges for PEGylated Proteins and Alternative Half-Life Extension Technologies Based on Biodegradable Polymers. ACTA ACUST UNITED AC 2013. [DOI: 10.1021/bk-2013-1135.ch013] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/08/2023]
|
21
|
Sandoval RM, Molitoris BA. Quantifying glomerular permeability of fluorescent macromolecules using 2-photon microscopy in Munich Wistar rats. J Vis Exp 2013. [PMID: 23628966 DOI: 10.3791/50052] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Kidney diseases involving urinary loss of large essential macromolecules, such as serum albumin, have long been thought to be caused by alterations in the permeability barrier comprised of podocytes, vascular endothelial cells, and a basement membrane working in unison. Data from our laboratory using intravital 2-photon microscopy revealed a more permeable glomerular filtration barrier (GFB) than previously thought under physiologic conditions, with retrieval of filtered albumin occurring in an early subset of cells called proximal tubule cells (PTC)(1,2,3). Previous techniques used to study renal filtration and establishing the characteristic of the filtration barrier involved micropuncture of the lumen of these early tubular segments with sampling of the fluid content and analysis(4). These studies determined albumin concentration in the luminal fluid to be virtually non-existent; corresponding closely to what is normally detected in the urine. However, characterization of dextran polymers with defined sizes by this technique revealed those of a size similar to serum albumin had higher levels in the tubular lumen and urine; suggesting increased permeability(5). Herein is a detailed outline of the technique used to directly visualize and quantify glomerular fluorescent albumin permeability in vivo. This method allows for detection of filtered albumin across the filtration barrier into Bowman's space (the initial chamber of urinary filtration); and also allows quantification of albumin reabsorption by proximal tubules and visualization of subsequent albumin transcytosis(6). The absence of fluorescent albumin along later tubular segments en route to the bladder highlights the efficiency of the retrieval pathway in the earlier proximal tubule segments. Moreover, when this technique was applied to determine permeability of dextrans having a similar size to albumin virtually identical permeability values were reported(2). These observations directly support the need to expand the focus of many proteinuric renal diseases to included alterations in proximal tubule cell reclamation.
Collapse
|
22
|
Wen H, Hao J, Li SK. Characterization of human sclera barrier properties for transscleral delivery of bevacizumab and ranibizumab. J Pharm Sci 2013; 102:892-903. [PMID: 23212655 PMCID: PMC3787849 DOI: 10.1002/jps.23387] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2012] [Revised: 10/21/2012] [Accepted: 10/26/2012] [Indexed: 01/20/2023]
Abstract
The objectives of this study were to (a) investigate transscleral permeation of antivascular endothelial growth factor drugs bevacizumab and ranibizumab and (b) examine the effects of molecular structures of macromolecules upon permeation across human sclera using bevacizumab, ranibizumab, fluorescein isothiocyanate (FITC)-labeled bovine serum albumin (FITC-BSA), FITC-labeled ficoll (FITC-ficoll), and FITC-labeled dextrans (FITC-dextrans) in vitro. The hydrodynamic radii of the macromolecules were measured using dynamic light scattering, their partition coefficients to sclera were determined in uptake experiments, and their permeability coefficients and transport lag times across sclera were evaluated in transport experiments of side-by-side diffusion cells. Macromolecules showed relatively low partition coefficients to sclera. The partition coefficient of FITC-BSA was found to be related to its concentration in the equilibration solution, whereas for other macromolecules, no specific concentration dependency was observed. The macromolecules displayed relatively low permeability coefficients and long transport lag times because of their molecular sizes and hindered diffusion. Bevacizumab, ranibizumab, and FITC-BSA exhibited lower transscleral permeability and longer transport lag times than FITC-dextrans and FITC-ficoll of comparable molecular weights possibly because of the flexible structures of the polysaccharides. Thus, the polysaccharides may not be good surrogate permeants to model transscleral transport of therapeutic proteins in transscleral delivery studies.
Collapse
Affiliation(s)
- He Wen
- Division of Pharmaceutical Sciences, James L. Winkle College of Pharmacy, University of Cincinnati, Cincinnati, Ohio 45267, USA.
| | | | | |
Collapse
|
23
|
Etrych T, Šubr V, Strohalm J, Šírová M, Říhová B, Ulbrich K. HPMA copolymer-doxorubicin conjugates: The effects of molecular weight and architecture on biodistribution and in vivo activity. J Control Release 2012; 164:346-54. [DOI: 10.1016/j.jconrel.2012.06.029] [Citation(s) in RCA: 99] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2012] [Revised: 06/08/2012] [Accepted: 06/21/2012] [Indexed: 10/28/2022]
|
24
|
Imran ul-haq M, Lai BF, Chapanian R, Kizhakkedathu JN. Influence of architecture of high molecular weight linear and branched polyglycerols on their biocompatibility and biodistribution. Biomaterials 2012; 33:9135-47. [DOI: 10.1016/j.biomaterials.2012.09.007] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2012] [Accepted: 09/04/2012] [Indexed: 10/27/2022]
|
25
|
Axelsson J, Öberg CM, Rippe A, Krause B, Rippe B. Size-selectivity of a synthetic high-flux and a high cut-off dialyzing membrane compared to that of the rat glomerular filtration barrier. J Memb Sci 2012. [DOI: 10.1016/j.memsci.2012.03.001] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
|
26
|
Dufresne SF, Datta K, Li X, Dadachova E, Staab JF, Patterson TF, Feldmesser M, Marr KA. Detection of urinary excreted fungal galactomannan-like antigens for diagnosis of invasive aspergillosis. PLoS One 2012; 7:e42736. [PMID: 22900046 PMCID: PMC3416763 DOI: 10.1371/journal.pone.0042736] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2012] [Accepted: 07/12/2012] [Indexed: 02/06/2023] Open
Abstract
Mortality associated with invasive aspergillosis (IA) remains high, partly because of delayed diagnosis. Detection of microbial exoantigens, released in serum and other body fluids during infection, may help timely diagnosis. In course of IA, Aspergillus galactomannan (GM), a well established polysaccharide biomarker, is released in body fluids including urine. Urine is an abundant, safely collected specimen, well-suited for point-of-care (POC) testing, which could play an increasing role in screening for early disease. Our main objective was to demonstrate GM antigenuria as a clinically relevant biological phenomenon in IA and establish proof-of-concept that it could be translated to POC diagnosis. Utilizing a novel IgM monoclonal antibody (MAb476) that recognizes GM-like antigens from Aspergillus and other molds, we demonstrated antigenuria in an experimental animal IA model (guinea pig), as well as in human patients. In addition, we investigated the chemical nature of the urinary excreted antigen in human samples, characterized antigen detection in urine by immunoassays, described a putative assay inhibitor in urine, and indicated means of alleviation of the inhibition. We also designed and used a lateral flow immunochromatographic assay to detect urinary excreted antigen in a limited number of IA patient urine samples. In this study, we establish that POC diagnosis of IA based on urinary GM detection is feasible. Prospective studies will be necessary to establish the performance characteristics of an optimized device and define its optimal clinical use.
Collapse
Affiliation(s)
- Simon F. Dufresne
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- Département de Microbiologie et Immunologie, Université de Montréal, Montréal, Quebec, Canada
| | - Kausik Datta
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Xinming Li
- Albert Einstein College of Medicine, Bronx, New York, United States of America
- China Medical University, Shenyang, People's Republic of China
| | - Ekaterina Dadachova
- Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Janet F. Staab
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
| | - Thomas F. Patterson
- University of Texas Health Science Center and South Texas Veterans Healthcare System, San Antonio, Texas, United States of America
| | - Marta Feldmesser
- Albert Einstein College of Medicine, Bronx, New York, United States of America
| | - Kieren A. Marr
- Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America
- The Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins Medical Institutions, Baltimore, Maryland, United States of America
- * E-mail:
| |
Collapse
|
27
|
Statistical modelling of the interplay between solute shape and rejection in porous membranes. Sep Purif Technol 2012. [DOI: 10.1016/j.seppur.2012.01.032] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
|
28
|
Axelsson J, Sverrisson K, Rippe A, Fissell W, Rippe B. Reduced diffusion of charge-modified, conformationally intact anionic Ficoll relative to neutral Ficoll across the rat glomerular filtration barrier in vivo. Am J Physiol Renal Physiol 2011; 301:F708-12. [PMID: 21775478 DOI: 10.1152/ajprenal.00183.2011] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The glomerular filtration barrier (GFB) is commonly conceived as a negatively charged sieve to proteins. Recent studies, however, indicate that glomerular charge effects are small for anionic, carboxymethylated (CM) dextran vs. neutral dextran. Furthermore, two studies assessing the glomerular sieving coefficients (θ) for negative CM-Ficoll vs. native Ficoll have demonstrated an increased glomerular permeability for CM-Ficoll (Asgeirsson D, Venturoli D, Rippe B, Rippe C. Am J Physiol Renal Physiol 291: F1083-F1089, 2006; Guimarães M, Nikolovski J, Pratt L, Greive K, Comper W. Am Physiol Renal Physiol 285: F1118-F1124, 2003.). The CM-Ficoll used, however, showed a larger Stokes-Einstein radius (a(e)) than neutral Ficoll, and it was proposed that the introduction of negative charges in the Ficoll molecule had made it more flexible and permeable. Recently, a negative FITC-labeled CM-Ficoll (CMI-Ficoll) was produced with a conformation identical to that of neutral FITC-Ficoll. Using these probes, we determined their θ:s in anesthetized Wistar rats (259 ± 2.5 g). After blood access had been achieved, the left ureter was cannulated for urine sampling. Either polysaccharide was infused (iv) together with a filtration marker, and urine and plasma were collected. Assessment of θ FITC-Ficoll was achieved by high-performance size-exclusion chromatography (HPSEC). CMI-Ficoll and native Ficoll had identical elugrams on the HPSEC. Diffusion of anionic Ficoll was significantly reduced compared with that of neutral Ficoll across the GFB for molecules of a(e) ∼20-35 Å, while there were no charge effects for Ficoll of a(e) = 35-80 Å. The data are consistent with a charge effect present in "small pores," but not in "large pores," of the GFB and mimicked those obtained for anionic membranes in vitro for the same probes.
Collapse
Affiliation(s)
- Josefin Axelsson
- Dept. of Nephrology, Univ. of Lund, Univ. Hospital of Lund, S-221 85 Lund, Sweden.
| | | | | | | | | |
Collapse
|
29
|
Rippe B, Davies S. Permeability of Peritoneal and Glomerular Capillaries: What are the Differences According to Pore Theory? Perit Dial Int 2011; 31:249-58. [DOI: 10.3747/pdi.2010.00124] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Pore and fiber-matrix theory can both be used to model the peritoneal and glomerular filtration barriers in an attempt to shed light on their differing structure–function relationships. The glomerular filtration barrier (GFB) is structurally more specialized, morphologically complex, and also highly dynamic; but paradoxically, because of its uniformity, it conforms more closely to the predictions of pore theory than does the peritoneum, and it in fact resembles a more simple synthetic membrane. Compared with the peritoneal capillary wall, the GFB has no transcellular “third” pores (aquaporins), and it is far less leaky and more size-selective to proteins, mainly as a result of having far fewer “large” pores. It does have charge-selective properties, although these are considered much less important in excluding albumin than was once thought, and it is also able to select polymers according to their shape and flexibility. Even this property might reflect the relative uniformity of the GFB, which has a high diffusion area and short diffusion distances, compared with the peritoneal barrier, which behaves more like a gel filtration column. Furthermore, the length of the diffusion path across the peritoneal membrane is much greater for small solutes, given the relatively high ultrafiltration coefficient for that membrane compared with the GFB—a situation that reflects both the tortuosity of the interendothelial clefts and the distribution of peritoneal capillaries within the interstitium. These comparisons reveal the peritoneal barrier as a relatively complex structure to model; and yet this model may be more representative of the general microcirculation, and thus shed light on systemic endothelial function in renal failure.
Collapse
Affiliation(s)
- Bengt Rippe
- Department of Nephrology, Lund University, Sweden Stoke-on-Trent, Staffordshire, U.K
| | - Simon Davies
- Department of Nephrology, University Hospital of North Staffordshire, Stoke-on-Trent, Staffordshire, U.K
| |
Collapse
|
30
|
Hoppe T, Yuan JM. Protein Folding with Implicit Crowders: A Study of Conformational States Using the Wang−Landau Method. J Phys Chem B 2011; 115:2006-13. [DOI: 10.1021/jp107809r] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Travis Hoppe
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| | - Jian-Min Yuan
- Department of Physics, Drexel University, Philadelphia, Pennsylvania 19104, United States
| |
Collapse
|
31
|
Fodeke AA, Minton AP. Quantitative characterization of polymer-polymer, protein-protein, and polymer-protein interaction via tracer sedimentation equilibrium. J Phys Chem B 2010; 114:10876-80. [PMID: 20677765 PMCID: PMC3488767 DOI: 10.1021/jp104342f] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Quantitative analysis of the composition dependence of the concentration gradient of each species of macromolecule within a solution mixture at sedimentation equilibrium permits the quantitative characterization of self- and heterointeractions between sedimenting solutes. Sedimentation equilibrium experiments were conducted on solutions containing a trace concentration of FITC-labeled BSA in varying concentrations of Ficoll 70 and on solutions containing a trace concentration of FITC-labeled Ficoll 70 in varying concentrations of BSA. The equilibrium gradient of each solute component in each mixture was measured independently. Analysis of the resulting gradients resulted in evaluation of the dependence of the activity coefficient of Ficoll upon the concentrations of Ficoll and BSA at concentrations of up to 100 g/L and the dependence of the activity coefficient of BSA upon the concentrations of Ficoll and BSA at concentrations of up to 100 g/L. The activity coefficients of both species increase significantly with increasing Ficoll and BSA concentration and do not vary with temperature, to within the precision of measurement, over the temperature range of 5-37 degrees C, indicating that the dominant interaction between Ficoll molecules and between BSA and Ficoll molecules is repulsive and probably due to steric volume exclusion. The measured dependences may be accounted for quantitatively by a simple model in which BSA and Ficoll 70 are represented by equivalent rigid particles.
Collapse
Affiliation(s)
| | - Allen P. Minton
- Section on Physical Biochemistry, Laboratory of Biochemistry and Genetics, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, U.S. Department of Health and Human Services, Bethesda, Maryland 20892
| |
Collapse
|
32
|
Axelsson J, Rippe A, Rippe B. Acute hyperglycemia induces rapid, reversible increases in glomerular permeability in nondiabetic rats. Am J Physiol Renal Physiol 2010; 298:F1306-12. [PMID: 20237233 DOI: 10.1152/ajprenal.00710.2009] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This study was performed to investigate the impact of acute hyperglycemia (HG) on the permeability of the normal glomerular filtration barrier in vivo. In anesthetized Wistar rats (250-280 g), the left ureter was catheterized for urine collection, while simultaneously blood access was achieved. Rats received an intravenous (iv) infusion of either 1) hypertonic glucose to maintain blood glucose at 20-25 mM (G; n = 8); 2) hypertonic glucose as in 1) and a RhoA-kinase inhibitor (Y-27632; Rho-G; n = 8); 3) 20% mannitol (MANN; n = 7) or 4) hypertonic (12%) NaCl to maintain plasma crystalloid osmotic pressure (pi(cry)) at approximately 320-325 mosmol/l (NaCl; n = 8) or 5) physiological saline (SHAM; n = 8). FITC-Ficoll 70/400 was infused iv for at least 20 min before termination of the experiments, and plasma and urine were collected to determine the glomerular sieving coefficients (theta) for polydisperse Ficoll (molecular radius 15-80 A) by high-performance size-exclusion chromatography. In G there was a marked increase in for Ficoll(55-80A) at 20 min, which was completely reversible within 60 min and abrogated by a Rho-kinase (ROCK) inhibitor, while glomerular permeability remained unchanged in MANN and NaCl. In conclusion, acute HG caused rapid, reversible increases in for large Ficolls, not related to the concomitant hyperosmolarity, but sensitive to ROCK inhibition. The changes observed were consistent with the formation of an increased number of large pores in the glomerular filter. The sensitivity of the permeability changes to ROCK inhibition strongly indicates that the cytoskeleton of the cells in the glomerular barrier may be involved in these alterations.
Collapse
|
33
|
Fissell WH, Hofmann CL, Smith R, Chen MH. Size and conformation of Ficoll as determined by size-exclusion chromatography followed by multiangle light scattering. Am J Physiol Renal Physiol 2009; 298:F205-8. [PMID: 19846572 DOI: 10.1152/ajprenal.00312.2009] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The characteristics of the glomerular filtration barrier (GFB) are challenging to measure, as macromolecular solutes in blood may be metabolized or transported by various cells in the kidney. Urinary solute concentrations generally reflect the cumulative influence of multiple transport processes rather than the intrinsic behavior of the GFB alone. Synthetic tracer molecules which are not secreted, absorbed, or modified by the kidney are useful tools. Ficoll, a globular polymer of epichlorohydrin and sucrose, is round, physiologically inert, and easily labeled, making it a nearly ideal glomerular probe. Fissell et al. reported filtration data suggesting that Ficoll was not as spherical as had been previously suggested (Fissell WH, Manley S, Dubnisheva A, Glass J, Magistrelli J, Eldridge AN, Fleischman AJ, Zydney AL, Roy S. Am J Physiol Renal Physiol 293: F1209-F1213, 2007). More recently, two investigators published comparisons of neutral and anionic Ficoll clearance that suggest Ficoll may undergo conformational changes when chemically derivatized (Asgeirsson D, Venturoli D, Rippe B, Rippe C. Am J Physiol Renal Physiol 291: F1083-F1089, 2006; Guimaraes MAM, Nikolovski J, Pratt LM, Greive K, Comper WD. Am J Physiol Renal Physiol 285: F1118-F1124, 2003). To investigate Ficoll's characteristics further, we examined two commercial preparations, Ficoll 70 and Ficoll 400, by size-exclusion chromatography using a differential refractive index detector combined with light-scattering and viscosity detectors. A slope of 0.45 was obtained from the plot of the logarithm of molecular mass against the logarithm of root-mean square radius. The Mark-Houwink exponent values of 0.34 and 0.36 were calculated for Ficoll 70 and Ficoll 400, respectively. These results suggest Ficoll's conformation in physiological saline solution is likely intermediate between a solid sphere and a well-solvated linear random coil. The measurements help explain our previous observations and guide interpretation of in vivo experiments.
Collapse
|
34
|
The glomerular filter: an imperfect barrier is required for perfect renal function. Curr Opin Nephrol Hypertens 2009; 18:336-42. [PMID: 19474730 DOI: 10.1097/mnh.0b013e32832cb96a] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
PURPOSE OF REVIEW There is currently a major debate on the mechanisms of albuminuria, and this review appraises recent studies in this area. RECENT FINDINGS The traditional view of albuminuria is that it is the result of damage to an essentially impermeable glomerular barrier. However, over the years, critical evidence for this traditional model has been shown to be flawed. An alternative explanation has evolved in which the glomerular filter governs albumin permeability by size selectivity alone. This means that the filter offers a significant barrier to albumin, but it is imperfect - the barrier leaks albumin. The virtue of this leakage is that it endows the filter an in-built anticlogging mechanism. The filtered albumin, if not rescued, would be excreted at nephrotic levels in the urine. There is evidence that proximal tubular cells participate in retrieving most of this filtered albumin to return it back to the blood supply intact. A small amount of the filtered albumin is not retrieved but directed toward lysosomal degradation, and the peptide products are exocytosed into the tubular lumen and excreted. SUMMARY In acquired and chemically induced kidney disease, albuminuria is the result of dysfunction in proximal tubular cell processing of albumin rather than alterations in glomerular permeability.
Collapse
|
35
|
Fox ME, Szoka FC, Fréchet JMJ. Soluble polymer carriers for the treatment of cancer: the importance of molecular architecture. Acc Chem Res 2009; 42:1141-51. [PMID: 19555070 DOI: 10.1021/ar900035f] [Citation(s) in RCA: 563] [Impact Index Per Article: 37.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Chemotherapy can destroy tumors and arrest cancer progress. Unfortunately, severe side effects (treatment is usually a series of injections of highly toxic drugs) often restrict the frequency and size of dosages, much to the detriment of tumor inhibition. Most chemotherapeutic drugs have pharmacokinetic profiles with tremendous potential for improvement. Water-soluble polymers offer the potential to increase drug circulation time, improve drug solubility, prolong drug residence time in a tumor, and reduce toxicity. Cytotoxic drugs that are covalently attached to water-soluble polymers via reversible linkages more effectively target tumor tissue than the drugs alone. Macromolecules passively target solid tumor tissue through a combination of reduced renal clearance and exploitation of the enhanced permeation and retention (EPR) effect, which prevails for fast-growing tumors. Effective drug delivery involves a balance between (i) elimination of the polymeric drug conjugate from the bloodstream by the kidneys, liver, and other organs and (ii) movement of the drug out of the blood vasculature and into the tumor (that is, extravasation). Polymers are eliminated in the kidney by filtration through pores with a size comparable to the hydrodynamic diameter of the polymer; in contrast, the openings in the blood vessel structures that traverse tumors are an order of magnitude greater than the diameter of the polymer. Thus, features that may broadly be grouped as the "molecular architecture" of the polymer, such as its hydrodynamic volume (or molecular weight), molecular conformation, chain flexibility, branching, and location of the attached drug, can greatly impact elimination of the polymer from the body through the kidney but have a much smaller effect on the extravasation of the polymer into the tumor. Molecular architecture can in theory be adjusted to assert essentially independent control over elimination and extravasation. Understanding how molecular architecture affects passage of a polymer through a pore is therefore essential for designing polymer drug carriers that are effective in passively delivering a drug payload while conforming to the requirement that the polymers must eventually be eliminated from the body. In this Account, we discuss examples from in vivo studies that demonstrate how polymer architectural features impact the renal filtration of a polymer as well as tumor penetration and tumor accumulation. In brief, features that inhibit passage of a polymer through a pore, such as higher molecular weight, decreased flexibility, and an increased number of polymer chain ends, help prevent elimination of the polymer by the kidneys and can improve blood circulation times and tumor accumulation, thus improving therapeutic effectiveness.
Collapse
Affiliation(s)
- Megan E. Fox
- College of Chemistry, University of California, Berkeley, California 94720-1460
| | - Francis C. Szoka
- Department of Biopharmaceutical Sciences and Pharmaceutical Chemistry, University of California, San Francisco, California 94143-0446
| | - Jean M. J. Fréchet
- College of Chemistry, University of California, Berkeley, California 94720-1460
| |
Collapse
|
36
|
Asgeirsson D, Axelsson J, Rippe C, Rippe B. Similarity of permeabilities for Ficoll, pullulan, charge-modified albumin and native albumin across the rat peritoneal membrane. Acta Physiol (Oxf) 2009; 196:427-33. [PMID: 19141139 DOI: 10.1111/j.1748-1716.2009.01955.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
AIM Compared to neutral globular proteins, neutral polysaccharides, such as dextran, pullulan and Ficoll, appear hyperpermeable across the glomerular filtration barrier. This has been attributed to an increased flexibility and/or asymmetry of polysaccharides. The present study investigates whether polysaccharides are hyperpermeable also across the continuous capillaries in the rat peritoneum. METHODS In anaesthetized Wistar rats, FITC-Ficoll or FITC-pullulan together with (125)I-human serum albumin (RISA) or neutralized (125)I-bovine serum albumin (nBSA) were given intravenously, after which peritoneal dialysis (PD) using conventional PD fluid (Gambrosol 1.5%) was performed for 120 min. Concentrations of FITC-polysaccharides and radioactive albumin species in plasma and dialysis fluid were analysed with high-performance size exclusion chromatography and a gamma counter respectively. Transperitoneal clearance values were calculated for polysaccharides in the molecular radius range 36-150 A, and for RISA and nBSA. RESULTS Ficoll and pullulan showed more or less identical permeabilities, compared to RISA and nBSA, across the peritoneal membrane. Although RISA-clearance, 5.50 +/- 0.28 (microL min(-1); +/-SEM), tended to be lower than the clearances of Ficoll(36A) (6.55 +/- 0.25), pullulan(36A) (6.08 +/- 0.22) and nBSA (6.56 +/- 0.23), the difference was not statistically significant. This is in contrast to the hyperpermeability exhibited by polysaccharides across the glomerular filtration barrier and also contrasts with the charge selectivity of the latter. CONCLUSION The phenomenon of molecular flexibility is more important for a macromolecule's permeability through the glomerular filter than across the continuous peritoneal capillary endothelium. Furthermore, it seems that charge plays a subordinate role in the steady-state transport across the combined peritoneal capillary-interstitial barrier.
Collapse
Affiliation(s)
- D Asgeirsson
- Department of Nephrology, Clinical Sciences, Lund University, Lund, Sweden
| | | | | | | |
Collapse
|
37
|
Abstract
PURPOSE OF REVIEW The nephrology community lacks a unified view of protein sieving through the glomerular capillary wall. The glomerular capillary wall consists of three distinct but closely interacting layers: the fenestrated endothelium, with its glycocalyx; the podocytes, with their interdigitated foot processes and slit diaphragms; and the intervening glomerular basement membrane. Proteinuria is associated with abnormalities in any one layer, suggesting that each contributes to the glomerular filtration barrier (GFB). Proteinuria can also be induced in the context of a normal glomerular capillary wall. Here, we review some classic studies as well as some newer concepts and present competing hypotheses about the GFB. RECENT FINDINGS Two almost forgotten concepts have recently emerged. One group has challenged the exquisite selectivity of the GFB to albumin and suggested that proteinuria is the result of abnormal tubular uptake. There has also been a reemphasis on diffusion through the glomerular basement membrane as the driving force behind macromolecular filtration. New evidence suggests that the endothelial glycocalyx is an important charge-selective barrier. SUMMARY We suggest viewing the GFB as a dynamic rather than as a rigid barrier, requiring three healthy layers and a hemodynamic steady state. Multiple challenges to studying the endothelium, the tubular handling of albumin, and the role of hemodynamic forces will require new tools, new hypotheses, and open minds.
Collapse
|
38
|
|
39
|
Tsuruta K, Kodama T, Serada M, Hori K, Inaba A, Miyake T, Kohira T. Pharmacokinetics of recombinant human soluble thrombomodulin, thrombomodulin alfa in the rat. Xenobiotica 2009; 39:125-34. [DOI: 10.1080/00498250802604074] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
|
40
|
Russo LM, Sandoval RM, Campos SB, Molitoris BA, Comper WD, Brown D. Impaired tubular uptake explains albuminuria in early diabetic nephropathy. J Am Soc Nephrol 2008; 20:489-94. [PMID: 19118149 DOI: 10.1681/asn.2008050503] [Citation(s) in RCA: 196] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
Understanding the pathogenesis of albuminuria in diabetic nephropathy is important to improve methods for early diagnosis and treatment. In this study, we addressed whether albuminuria in diabetes results from altered glomerular filtration and/or altered processing of filtered albumin by the proximal tubule. Type 1 diabetic Munich Wistar rats developed albuminuria after 12 wk of diabetes. Intravital two-photon microscopy revealed similar glomerular permeability in the diabetic and control animals, assessed using both albumin-Alexa568 and 69-kD FITC-dextran; however, diabetic animals demonstrated significantly less filtered fluorescent albumin in renal proximal tubule (PT) cells compared with control animals. We also observed increased albumin-derived urinary peptide excretion in diabetic animals, and hyperglycemia modulated this peptideuria. In conclusion, in the early stages of diabetic nephropathy, the PT plays a major role in the development of albuminuria, which may be preceded by peptideuria.
Collapse
Affiliation(s)
- Leileata M Russo
- Program in Membrane Biology, Division of Nephrology, Massachusetts General Hospital/Harvard Medical School, Simches Research Center, Boston, MA 02114, USA.
| | | | | | | | | | | |
Collapse
|
41
|
Sarin H, Kanevsky AS, Wu H, Brimacombe KR, Fung SH, Sousa AA, Auh S, Wilson CM, Sharma K, Aronova MA, Leapman RD, Griffiths GL, Hall MD. Effective transvascular delivery of nanoparticles across the blood-brain tumor barrier into malignant glioma cells. J Transl Med 2008; 6:80. [PMID: 19094226 PMCID: PMC2639552 DOI: 10.1186/1479-5876-6-80] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2008] [Accepted: 12/18/2008] [Indexed: 11/29/2022] Open
Abstract
BACKGROUND Effective transvascular delivery of nanoparticle-based chemotherapeutics across the blood-brain tumor barrier of malignant gliomas remains a challenge. This is due to our limited understanding of nanoparticle properties in relation to the physiologic size of pores within the blood-brain tumor barrier. Polyamidoamine dendrimers are particularly small multigenerational nanoparticles with uniform sizes within each generation. Dendrimer sizes increase by only 1 to 2 nm with each successive generation. Using functionalized polyamidoamine dendrimer generations 1 through 8, we investigated how nanoparticle size influences particle accumulation within malignant glioma cells. METHODS Magnetic resonance and fluorescence imaging probes were conjugated to the dendrimer terminal amines. Functionalized dendrimers were administered intravenously to rodents with orthotopically grown malignant gliomas. Transvascular transport and accumulation of the nanoparticles in brain tumor tissue was measured in vivo with dynamic contrast-enhanced magnetic resonance imaging. Localization of the nanoparticles within glioma cells was confirmed ex vivo with fluorescence imaging. RESULTS We found that the intravenously administered functionalized dendrimers less than approximately 11.7 to 11.9 nm in diameter were able to traverse pores of the blood-brain tumor barrier of RG-2 malignant gliomas, while larger ones could not. Of the permeable functionalized dendrimer generations, those that possessed long blood half-lives could accumulate within glioma cells. CONCLUSION The therapeutically relevant upper limit of blood-brain tumor barrier pore size is approximately 11.7 to 11.9 nm. Therefore, effective transvascular drug delivery into malignant glioma cells can be accomplished by using nanoparticles that are smaller than 11.7 to 11.9 nm in diameter and possess long blood half-lives.
Collapse
Affiliation(s)
- Hemant Sarin
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
- Diagnostic Radiology Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Ariel S Kanevsky
- Diagnostic Radiology Department, Clinical Center, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Haitao Wu
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kyle R Brimacombe
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Steve H Fung
- Neuroradiology Department, Massachusetts General Hospital, Boston, Massachusetts 02114, USA
| | - Alioscka A Sousa
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Sungyoung Auh
- Biostatistics, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Colin M Wilson
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Kamal Sharma
- Metabolism Branch, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
- Division of Biologic Drug Products, Office of Oncology Products, Center for Drug Evaluation and Research, U.S. Food & Drug Administration, Silver Spring, Maryland 20993, USA
| | - Maria A Aronova
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Richard D Leapman
- National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Gary L Griffiths
- Imaging Probe Development Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| | - Matthew D Hall
- Laboratory of Cell Biology, National Cancer Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
| |
Collapse
|
42
|
Abstract
The classic mechanism to explain albumin excretion in diabetes has been permeability defects in the glomerular filter. However, a new concept has emerged that albuminuria can be explained by the two major pathways the proximal tubular cell uses to process filtered albumin. Specifically, albumin permeability through the glomerular filter is only governed by size selectivity. Most of the filtered albumin is retrieved by the proximal tubular cell and returned to the peritubular blood supply. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-beta1, whose production is stimulated by hyperglycemic environments. Dysfunction in this degradation pathway may lead to albuminuria below the nephrotic range.
Collapse
Affiliation(s)
- Wayne D Comper
- Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia.
| | | |
Collapse
|
43
|
Abstract
PURPOSE OF REVIEW The glomerular filtration barrier consists of fenestrated glomerular endothelium, podocyte foot processes/slit diaphragms, and intervening glomerular basement membrane. Its characterization as both a size and charge-selective barrier emerged from studies conducted decades ago. The charge selectivity phenomenon is receiving renewed attention now that the identities and mechanisms of synthesis of relevant molecules are known. Here we summarize studies employing genetic or other in-vivo strategies to investigate glomerular charge. RECENT FINDINGS Attention has focused on glomerular basement membrane heparan sulfate proteoglycans, long considered primary charge barrier components. Agrin contributes significantly to glomerular basement membrane charge but, like perlecan and collagen XVIII, is dispensable for glomerular structure and function. Disruption of glomerular heparan sulfate through transgenic methods or administration of heparanase in vivo provides further evidence against a role for heparan sulfate in glomerular function. Disruption of glomerular sialoproteins, however, causes proteinuria and indicates a critical role for these cell-associated glycoproteins in glomerular filtration. SUMMARY Recent in-vivo manipulations of glomerular heparan sulfate proteoglycans fail to reveal a crucial role for either them or their anionic charge in glomerular filtration. In contrast, cell-associated sialoproteins are clearly important, but whether their functions actually involve contributions to the charge barrier is unknown.
Collapse
|
44
|
Comper WD, Hilliard LM, Nikolic-Paterson DJ, Russo LM. Disease-dependent mechanisms of albuminuria. Am J Physiol Renal Physiol 2008; 295:F1589-600. [PMID: 18579704 DOI: 10.1152/ajprenal.00142.2008] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The mechanism of albuminuria is perhaps one of the most complex yet important questions in renal physiology today. Recent studies have directly demonstrated that the normal glomerulus filters substantial amounts of albumin and that charge selectivity plays little or no role in preventing this process. This filtered albumin is then processed by proximal tubular cells by two distinct pathways; dysfunction in either one of these pathways gives rise to discrete forms of albuminuria. Most of the filtered albumin is returned to the peritubular blood supply by a retrieval pathway. Albuminuria in the nephrotic range would arise from retrieval pathway dysfunction. The small quantities of filtered albumin that are not retrieved undergo obligatory lysosomal degradation before urinary excretion as small peptide fragments. This degradation pathway is sensitive to metabolic factors responsible for hypertrophy and fibrosis, particularly molecules such as angiotensin II and transforming growth factor-beta1, whose production is stimulated by hyperglycemic and hypertensive environments. Dysfunction in this degradation pathway leads to albuminuria below the nephrotic range. These new insights into albumin filtration and processing argue for a reassessment of the role of podocytes and the slit diaphragm as major direct determinants governing albuminuria, provide information on how glomerular morphology and "tubular" albuminuria may be interrelated, and offer a new rationale for drug development.
Collapse
Affiliation(s)
- Wayne D Comper
- Dept. of Biochemistry and Molecular Biology, Monash Univ., Clayton, Victoria, Australia.
| | | | | | | |
Collapse
|
45
|
Rippe B. Free water transport, small pore transport and the osmotic pressure gradient three-pore model of peritoneal transport. Nephrol Dial Transplant 2008; 23:2147-53. [PMID: 18388123 DOI: 10.1093/ndt/gfn049] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Bengt Rippe
- Department of Nephrology, University Hospital of Lund, Sweden.
| |
Collapse
|