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Williams BM, Cliff CL, Demirel I, Squires PE, Hills CE. Blocking connexin 43 hemichannel-mediated ATP release reduces communication within and between tubular epithelial cells and medullary fibroblasts in a model of diabetic nephropathy. Diabet Med 2022; 39:e14963. [PMID: 36256487 PMCID: PMC9828766 DOI: 10.1111/dme.14963] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/13/2022] [Revised: 09/08/2022] [Accepted: 09/19/2022] [Indexed: 01/18/2023]
Abstract
INTRODUCTION Fibrosis of renal tubules is the final common pathway in diabetic nephropathy and develops in the face of tubular injury and fibroblast activation. Aberrant connexin 43 (Cx43) hemichannel activity has been linked to this damage under euglycaemic conditions, however, its role in glycaemic injury is unknown. This study investigated the effect of a Cx43 blocker (Tonabersat) on hemichannel activity and cell-cell interactions within and between tubular epithelial cells and fibroblasts in an in vitro model of diabetic nephropathy. METHODS Human kidney (HK2) proximal tubule epithelial cells and medullary fibroblasts (TK173) were treated in low (5 mM) or high (25 mM) glucose ± transforming growth factor beta-1 (TGFβ1) ± Tonabersat in high glucose. Carboxyfluorescein dye uptake and ATPlite luminescence assessed changes in hemichannel-mediated ATP release, while immunoblotting determined protein expression. Co-incubation with the ATP-diphosphohydrolase apyrase or a P2X7R inhibitor (A438079) assessed ATP-P2X7R signalling. Indirect co-culture with conditioned media from the alternate cell type evaluated paracrine-mediated heterotypic interactions. RESULTS Tonabersat partially negated glucose/TGFβ1-induced increases in Cx43 hemichannel-mediated ATP release and downstream changes in adherens junction and extracellular matrix (ECM) protein expression in HK2 and TK173 cells. Apyrase and A438079 highlighted the role for ATP-P2X7R in driving changes in protein expression in TK173 fibroblasts. Indirect co-culture studies suggest that epithelial cell secretome increases Tonabersat-sensitive hemichannel-mediated dye uptake in fibroblasts and downstream protein expression. CONCLUSION Tonabersat-sensitive hemichannel-mediated ATP release enhances TGFβ1-driven heterotypic cell-cell interaction and favours myofibroblast activation. The data supports the potential benefit of Cx43 inhibition in reducing tubulointerstitial fibrosis in late-stage diabetic nephropathy.
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Affiliation(s)
| | | | - Isak Demirel
- School of Medical SciencesÖrebro UniversityÖrebroSweden
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Hotait ZS, Lo Cascio JN, Choos END, Shepard BD. The sugar daddy: the role of the renal proximal tubule in glucose homeostasis. Am J Physiol Cell Physiol 2022; 323:C791-C803. [PMID: 35912988 PMCID: PMC9448277 DOI: 10.1152/ajpcell.00225.2022] [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: 05/31/2022] [Revised: 07/26/2022] [Accepted: 07/26/2022] [Indexed: 11/22/2022]
Abstract
Renal blood flow represents >20% of total cardiac output and with this comes the great responsibility of maintaining homeostasis through the intricate regulation of solute handling. Through the processes of filtration, reabsorption, and secretion, the kidneys ensure that solutes and other small molecules are either returned to circulation, catabolized within renal epithelial cells, or excreted through the process of urination. Although this occurs throughout the renal nephron, one segment is tasked with the bulk of solute reabsorption-the proximal tubule. Among others, the renal proximal tubule is entirely responsible for the reabsorption of glucose, a critical source of energy that fuels the body. In addition, it is the only other site of gluconeogenesis outside of the liver. When these processes go awry, pathophysiological conditions such as diabetes and acidosis result. In this review, we highlight the recent advances made in understanding these processes that occur within the renal proximal tubule. We focus on the physiological mechanisms at play regarding glucose reabsorption and glucose metabolism, emphasize the conditions that occur under diseased states, and explore the emerging class of therapeutics that are responsible for restoring homeostasis.
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Affiliation(s)
- Zahraa S Hotait
- Department of Human Science, Georgetown University, Washington, District of Columbia
| | - Julia N Lo Cascio
- Department of Human Science, Georgetown University, Washington, District of Columbia
| | - Elijah N D Choos
- Department of Human Science, Georgetown University, Washington, District of Columbia
| | - Blythe D Shepard
- Department of Human Science, Georgetown University, Washington, District of Columbia
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Cliff CL, Williams BM, Chadjichristos CE, Mouritzen U, Squires PE, Hills CE. Connexin 43: A Target for the Treatment of Inflammation in Secondary Complications of the Kidney and Eye in Diabetes. Int J Mol Sci 2022; 23:600. [PMID: 35054783 PMCID: PMC8776095 DOI: 10.3390/ijms23020600] [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] [Subscribe] [Scholar Register] [Received: 11/26/2021] [Revised: 01/03/2022] [Accepted: 01/04/2022] [Indexed: 02/06/2023] Open
Abstract
Of increasing prevalence, diabetes is characterised by elevated blood glucose and chronic inflammation that precedes the onset of multiple secondary complications, including those of the kidney and the eye. As the leading cause of end stage renal disease and blindness in the working population, more than ever is there a demand to develop clinical interventions which can both delay and prevent disease progression. Connexins are membrane bound proteins that can form pores (hemichannels) in the cell membrane. Gated by cellular stress and injury, they open under pathophysiological conditions and in doing so release 'danger signals' including adenosine triphosphate into the extracellular environment. Linked to sterile inflammation via activation of the nod-like receptor protein 3 inflammasome, targeting aberrant hemichannel activity and the release of these danger signals has met with favourable outcomes in multiple models of disease, including secondary complications of diabetes. In this review, we provide a comprehensive update on those studies which document a role for aberrant connexin hemichannel activity in the pathogenesis of both diabetic eye and kidney disease, ahead of evaluating the efficacy of blocking connexin-43 specific hemichannels in these target tissues on tissue health and function.
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Affiliation(s)
- Chelsy L. Cliff
- Joseph Banks Laboratories, School of Life, Sciences University of Lincoln, Lincoln LN6 7DL, UK; (C.L.C.); (B.M.W.); (P.E.S.)
| | - Bethany M. Williams
- Joseph Banks Laboratories, School of Life, Sciences University of Lincoln, Lincoln LN6 7DL, UK; (C.L.C.); (B.M.W.); (P.E.S.)
| | - Christos E. Chadjichristos
- National Institutes for Health and Medical Research, UMR-S1155, Batiment Recherche, Tenon Hospital, 4 Rue de la Chine, 75020 Paris, France;
| | - Ulrik Mouritzen
- Ciana Therapeutics, Ole Maaloes Vej 3, 2200 Copenhagen N, Denmark;
| | - Paul E. Squires
- Joseph Banks Laboratories, School of Life, Sciences University of Lincoln, Lincoln LN6 7DL, UK; (C.L.C.); (B.M.W.); (P.E.S.)
| | - Claire E. Hills
- Joseph Banks Laboratories, School of Life, Sciences University of Lincoln, Lincoln LN6 7DL, UK; (C.L.C.); (B.M.W.); (P.E.S.)
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King DR, Sedovy MW, Leng X, Xue J, Lamouille S, Koval M, Isakson BE, Johnstone SR. Mechanisms of Connexin Regulating Peptides. Int J Mol Sci 2021; 22:ijms221910186. [PMID: 34638526 PMCID: PMC8507914 DOI: 10.3390/ijms221910186] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 12/22/2022] Open
Abstract
Gap junctions (GJ) and connexins play integral roles in cellular physiology and have been found to be involved in multiple pathophysiological states from cancer to cardiovascular disease. Studies over the last 60 years have demonstrated the utility of altering GJ signaling pathways in experimental models, which has led to them being attractive targets for therapeutic intervention. A number of different mechanisms have been proposed to regulate GJ signaling, including channel blocking, enhancing channel open state, and disrupting protein-protein interactions. The primary mechanism for this has been through the design of numerous peptides as therapeutics, that are either currently in early development or are in various stages of clinical trials. Despite over 25 years of research into connexin targeting peptides, the overall mechanisms of action are still poorly understood. In this overview, we discuss published connexin targeting peptides, their reported mechanisms of action, and the potential for these molecules in the treatment of disease.
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Affiliation(s)
- D. Ryan King
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
| | - Meghan W. Sedovy
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Translational Biology, Medicine, and Health Graduate Program, Virginia Tech, Blacksburg, VA 24061, USA
| | - Xinyan Leng
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
| | - Jianxiang Xue
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; (J.X.); (B.E.I.)
| | - Samy Lamouille
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Center for Vascular and Heart Research, Virginia Tech, Roanoke, VA 24016, USA
| | - Michael Koval
- Department of Medicine, Division of Pulmonary, Allergy, Critical Care and Sleep Medicine, Emory University School of Medicine, Atlanta, GA 30322, USA;
| | - Brant E. Isakson
- Robert M. Berne Cardiovascular Research Center, University of Virginia School of Medicine, Charlottesville, VA 22908, USA; (J.X.); (B.E.I.)
- Department of Molecular Physiology and Biophysics, University of Virginia School of Medicine, Charlottesville, VA 22908, USA
| | - Scott R. Johnstone
- Fralin Biomedical Research Institute at Virginia Tech Carilion School of Medicine, Virginia Tech, Roanoke, VA 24016, USA; (D.R.K.); (M.W.S.); (X.L.); (S.L.)
- Center for Vascular and Heart Research, Virginia Tech, Roanoke, VA 24016, USA
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA 24060, USA
- Correspondence:
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Collagen I Modifies Connexin-43 Hemichannel Activity via Integrin α2β1 Binding in TGFβ1-Evoked Renal Tubular Epithelial Cells. Int J Mol Sci 2021; 22:ijms22073644. [PMID: 33807408 PMCID: PMC8038016 DOI: 10.3390/ijms22073644] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Revised: 03/23/2021] [Accepted: 03/30/2021] [Indexed: 02/07/2023] Open
Abstract
Chronic Kidney Disease (CKD) is associated with sustained inflammation and progressive fibrosis, changes that have been linked to altered connexin hemichannel-mediated release of adenosine triphosphate (ATP). Kidney fibrosis develops in response to increased deposition of extracellular matrix (ECM), and up-regulation of collagen I is an early marker of renal disease. With ECM remodeling known to promote a loss of epithelial stability, in the current study we used a clonal human kidney (HK2) model of proximal tubular epithelial cells to determine if collagen I modulates changes in cell function, via connexin-43 (Cx43) hemichannel ATP release. HK2 cells were cultured on collagen I and treated with the beta 1 isoform of the pro-fibrotic cytokine transforming growth factor (TGFβ1) ± the Cx43 mimetic Peptide 5 and/or an anti-integrin α2β1 neutralizing antibody. Phase microscopy and immunocytochemistry observed changes in cell morphology and cytoskeletal reorganization, whilst immunoblotting and ELISA identified changes in protein expression and secretion. Carboxyfluorescein dye uptake and biosensing measured hemichannel activity and ATP release. A Cytoselect extracellular matrix adhesion assay assessed changes in cell-substrate interactions. Collagen I and TGFβ1 synergistically evoked increased hemichannel activity and ATP release. This was paralleled by changes to markers of tubular injury, partly mediated by integrin α2β1/integrin-like kinase signaling. The co-incubation of the hemichannel blocker Peptide 5, reduced collagen I/TGFβ1 induced alterations and inhibited a positive feedforward loop between Cx43/ATP release/collagen I. This study highlights a role for collagen I in regulating connexin-mediated hemichannel activity through integrin α2β1 signaling, ahead of establishing Peptide 5 as a potential intervention.
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