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Starr A, Sand CA, Heikal L, Kelly PD, Spina D, Crabtree M, Channon KM, Leiper JM, Nandi M. Overexpression of GTP cyclohydrolase 1 feedback regulatory protein is protective in a murine model of septic shock. Shock 2014; 42:432-9. [PMID: 25046538 PMCID: PMC4851220 DOI: 10.1097/shk.0000000000000235] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2014] [Accepted: 07/10/2014] [Indexed: 11/26/2022]
Abstract
Overproduction of nitric oxide (NO) by inducible NO synthase contributes toward refractory hypotension, impaired microvascular perfusion, and end-organ damage in septic shock patients. Tetrahydrobiopterin (BH4) is an essential NOS cofactor. GTP cyclohydrolase 1 (GCH1) is the rate-limiting enzyme for BH4 biosynthesis. Under inflammatory conditions, GCH1 activity and hence BH4 levels are increased, supporting pathological NOS activity. GCH1 activity can be controlled through allosteric interactions with GCH1 feedback regulatory protein (GFRP). We investigated whether overexpression of GFRP can regulate BH4 and NO production and attenuate cardiovascular dysfunction in sepsis. Sepsis was induced in mice conditionally overexpressing GFRP and wild-type littermates by cecal ligation and puncture. Blood pressure was monitored by radiotelemetry, and mesenteric blood flow was quantified by laser speckle contrast imaging. Blood biochemistry data were obtained using an iSTAT analyzer, and BH4 levels were measured in plasma and tissues by high-performance liquid chromatography. Increased BH4 and NO production and hypotension were observed in all mice, but the extents of these pathophysiological changes were attenuated in GFRP OE mice. Perturbations in blood biochemistry were similarly attenuated in GFRP OE compared with wild-type controls. These results suggest that GFRP overexpression regulates GCH1 activity during septic shock, which in turn limits BH4 bioavailability for iNOS. We conclude that the GCH1-GFRP axis is a critical regulator of BH4 and NO production and the cardiovascular derangements that occur in septic shock.
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Affiliation(s)
- Anna Starr
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Claire A. Sand
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Lamia Heikal
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Peter D. Kelly
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Domenico Spina
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Mark Crabtree
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Keith M. Channon
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - James M. Leiper
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
| | - Manasi Nandi
- *Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King’s College London; and MRC Clinical Sciences Centre, Faculty of Medicine, Imperial College London, London; and British Heart Foundation Centre of Research Excellence, Division of Cardiovascular Medicine, University of Oxford, John Radcliffe Hospital, Oxford, United Kingdom
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Abstract
6R l-erythro-5,6,7,8-tetrahydrobiopterin (BH4) is an essential cofactor for several enzymes including phenylalanine hydroxylase and the nitric oxide synthases (NOS). Oral supplementation of BH4 has been successfully employed to treat subsets of patients with hyperphenylalaninaemia. More recently, research efforts have focussed on understanding whether BH4 supplementation may also be efficacious in cardiovascular disorders that are underpinned by reduced nitric oxide bioavailability. Whilst numerous preclinical and clinical studies have demonstrated a positive association between enhanced BH4 and vascular function, the efficacy of orally administered BH4 in human cardiovascular disease remains unclear. Furthermore, interventions that limit BH4 bioavailability may provide benefit in diseases where nitric oxide over production contributes to pathology. This review describes the pathways involved in BH4 bio-regulation and discusses other endogenous mechanisms that could be harnessed therapeutically to manipulate vascular BH4 levels.
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Affiliation(s)
- Anna Starr
- Pharmacology and Therapeutics Group, Institute of Pharmaceutical Science, School of Biomedical Sciences, King's College London, Franklin Wilkins Building, 150 Stamford Street,London SE1 9NH, United Kingdom
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Shanmuganathan MV, Krishnan S, Fu X, Prasadarao NV. Attenuation of biopterin synthesis prevents Escherichia coli K1 invasion of brain endothelial cells and the development of meningitis in newborn mice. J Infect Dis 2013; 207:61-71. [PMID: 23100563 PMCID: PMC3523800 DOI: 10.1093/infdis/jis656] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2012] [Accepted: 08/10/2012] [Indexed: 11/12/2022] Open
Abstract
Elevated levels of pterins and nitric oxide (NO) are observed in patients with septic shock and bacterial meningitis. We demonstrate that Escherichia coli K1 infection of human brain microvascular endothelial cells (HBMECs) induces the expression of guanosine triphosphate cyclohydrolase (GCH1), the rate-limiting enzyme in pterin synthesis, thereby elevating levels of biopterin. DAHP (2,4-diamino hydroxyl pyrimidine), a specific inhibitor of GCH1, prevented biopterin and NO production and invasion of E. coli K1 in HBMECs. GCH1 interaction with Ecgp96, the receptor for outer membrane protein A of E. coli K1, also increases on infection, and suppression of Ecgp96 expression prevents GCH1 activation and biopterin synthesis. Pretreatment of newborn mice with DAHP prevented the production of biopterin and the development of meningitis. These results suggest a novel role for biopterin synthesis in the pathogenesis of E. coli K1 meningitis.
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Affiliation(s)
| | | | - Xiaowei Fu
- Department of Pathology and Laboratory Medicine, Children's Hospital Los Angeles, California
- Keck School of Medicine, University of Southern California, Los Angeles
| | - Nemani V. Prasadarao
- Division of Infectious Diseases, Department of Pediatrics
- Department of Surgery
- Keck School of Medicine, University of Southern California, Los Angeles
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