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Fitzgerald HK, O’Rourke SA, Desmond E, Neto NGB, Monaghan MG, Tosetto M, Doherty J, Ryan EJ, Doherty GA, Nolan DP, Fletcher JM, Dunne A. The Trypanosoma brucei-Derived Ketoacids, Indole Pyruvate and Hydroxyphenylpyruvate, Induce HO-1 Expression and Suppress Inflammatory Responses in Human Dendritic Cells. Antioxidants (Basel) 2022; 11:antiox11010164. [PMID: 35052669 PMCID: PMC8772738 DOI: 10.3390/antiox11010164] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 01/11/2022] [Accepted: 01/12/2022] [Indexed: 02/04/2023] Open
Abstract
The extracellular parasite and causative agent of African sleeping sickness Trypanosoma brucei (T. brucei) has evolved a number of strategies to avoid immune detection in the host. One recently described mechanism involves the conversion of host-derived amino acids to aromatic ketoacids, which are detected at relatively high concentrations in the bloodstream of infected individuals. These ketoacids have been shown to directly suppress inflammatory responses in murine immune cells, as well as acting as potent inducers of the stress response enzyme, heme oxygenase 1 (HO-1), which has proven anti-inflammatory properties. The aim of this study was to investigate the immunomodulatory properties of the T. brucei-derived ketoacids in primary human immune cells and further examine their potential as a therapy for inflammatory diseases. We report that the T. brucei-derived ketoacids, indole pyruvate (IP) and hydroxyphenylpyruvate (HPP), induce HO-1 expression through Nrf2 activation in human dendritic cells (DC). They also limit DC maturation and suppress the production of pro-inflammatory cytokines, which, in turn, leads to a reduced capacity to differentiate adaptive CD4+ T cells. Furthermore, the ketoacids are capable of modulating DC cellular metabolism and suppressing the inflammatory profile of cells isolated from patients with inflammatory bowel disease. This study therefore not only provides further evidence of the immune-evasion mechanisms employed by T. brucei, but also supports further exploration of this new class of HO-1 inducers as potential therapeutics for the treatment of inflammatory conditions.
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Affiliation(s)
- Hannah K. Fitzgerald
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
| | - Sinead A. O’Rourke
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (N.G.B.N.); (M.G.M.)
| | - Eva Desmond
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
| | - Nuno G. B. Neto
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (N.G.B.N.); (M.G.M.)
| | - Michael G. Monaghan
- Trinity Centre for Biomedical Engineering, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (N.G.B.N.); (M.G.M.)
| | - Miriam Tosetto
- Centre for Colorectal Disease, St. Vincent’s University Hospital, School of Medicine, University College Dublin, D04 YN26 Dublin, Ireland; (M.T.); (J.D.); (G.A.D.)
| | - Jayne Doherty
- Centre for Colorectal Disease, St. Vincent’s University Hospital, School of Medicine, University College Dublin, D04 YN26 Dublin, Ireland; (M.T.); (J.D.); (G.A.D.)
| | - Elizabeth J. Ryan
- Department of Biological Sciences, Health Research Institute, University of Limerick, V94 T9PX Limerick, Ireland;
| | - Glen A. Doherty
- Centre for Colorectal Disease, St. Vincent’s University Hospital, School of Medicine, University College Dublin, D04 YN26 Dublin, Ireland; (M.T.); (J.D.); (G.A.D.)
| | - Derek P. Nolan
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
| | - Jean M. Fletcher
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
- School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland
| | - Aisling Dunne
- School of Biochemistry and Immunology, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland; (H.K.F.); (S.A.O.); (E.D.); (D.P.N.); (J.M.F.)
- School of Medicine, Trinity Biomedical Sciences Institute, Trinity College Dublin, D02 R590 Dublin, Ireland
- Correspondence:
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Alfituri OA, Quintana JF, MacLeod A, Garside P, Benson RA, Brewer JM, Mabbott NA, Morrison LJ, Capewell P. To the Skin and Beyond: The Immune Response to African Trypanosomes as They Enter and Exit the Vertebrate Host. Front Immunol 2020; 11:1250. [PMID: 32595652 PMCID: PMC7304505 DOI: 10.3389/fimmu.2020.01250] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2020] [Accepted: 05/18/2020] [Indexed: 12/14/2022] Open
Abstract
African trypanosomes are single-celled extracellular protozoan parasites transmitted by tsetse fly vectors across sub-Saharan Africa, causing serious disease in both humans and animals. Mammalian infections begin when the tsetse fly penetrates the skin in order to take a blood meal, depositing trypanosomes into the dermal layer. Similarly, onward transmission occurs when differentiated and insect pre-adapted forms are ingested by the fly during a blood meal. Between these transmission steps, trypanosomes access the systemic circulation of the vertebrate host via the skin-draining lymph nodes, disseminating into multiple tissues and organs, and establishing chronic, and long-lasting infections. However, most studies of the immunobiology of African trypanosomes have been conducted under experimental conditions that bypass the skin as a route for systemic dissemination (typically via intraperitoneal or intravenous routes). Therefore, the importance of these initial interactions between trypanosomes and the skin at the site of initial infection, and the implications for these processes in infection establishment, have largely been overlooked. Recent studies have also demonstrated active and complex interactions between the mammalian host and trypanosomes in the skin during initial infection and revealed the skin as an overlooked anatomical reservoir for transmission. This highlights the importance of this organ when investigating the biology of trypanosome infections and the associated immune responses at the initial site of infection. Here, we review the mechanisms involved in establishing African trypanosome infections and potential of the skin as a reservoir, the role of innate immune cells in the skin during initial infection, and the subsequent immune interactions as the parasites migrate from the skin. We suggest that a thorough identification of the mechanisms involved in establishing African trypanosome infections in the skin and their progression through the host is essential for the development of novel approaches to interrupt disease transmission and control these important diseases.
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Affiliation(s)
- Omar A. Alfituri
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Juan F. Quintana
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Annette MacLeod
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Paul Garside
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Robert A. Benson
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - James M. Brewer
- Wellcome Centre for Integrative Parasitology, College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
| | - Neil A. Mabbott
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Liam J. Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, United Kingdom
| | - Paul Capewell
- College of Medical, Veterinary and Life Sciences, Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, United Kingdom
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