Dietary constituents modulate the healing response through the action of amine oxidases

Lead Research Organisation: University of Birmingham
Department Name: Immunity and Infection


The maintenance of health and wellbeing requires the complex interaction between biological systems and environmental factors. Dysregulation of the processes governing repair of damaged tissue can result in a loss of tissue function, a process that underpins organ failure in many chronic disorders and aging. It is clear that tackling the problems posed by impaired wound healing responses presents a major socio-economic and health challenge.

The repair and replacement of damaged tissue is a multistep process. Firstly clearance of dead/dying cells and scaffolding proteins that provide a framework for cellular growth is facilitated by specialised immune cells in blood that patrol the circulatory system. This is followed by a co-ordinated invasion by fibroblast cells that form a temporary framework to support the growth of replacement tissue. Once the damaged site has been replaced with healthy tissues the temporary scaffold is then degraded through the programmed cell death of the fibroblasts following further interactions with specialised immune cells. The delicate balance of these processes can be affected by factors such as diet, age and even the type of bacteria present in the gut. This can lead to impairment of responses to tissue injury and the rapidity of age-related scarring.

Natural products present in the diet can regulate the function of amine oxidases, a family of proteins that are present in many cells of the body. They are implicated in the development of chronic disorders and the development of tumours. It is thought that an increased level of these proteins leads to the build-up of damaging immune cells and the production of highly rigid cellular scaffolds. This results in excessive scar formation and impaired function, potentially leading to life threatening disorders. Dietary constituents that are used by amine oxidases can be found in diverse foodstuffs such as fish, meat, vegetables, coffee and wine. They can also be produced by bacteria present in the gut and transported to other parts of the body through the circulation. However it is not clear what impact regulation of these proteins by the diet has on the wound healing process. This project will seek to identify specific dietary components that modulate amine oxidase activity. In this context we will also investigate which members of the amine oxidase protein family can promote immune cell recruitment and exacerbate scar formation.

The identification of dietary mediators of amine oxidase activity will have important implications in tailoring the formulation of diets for individuals such as those with chronic disorders. Understanding the function of each amine oxidase in the maintenance of healthy tissue will have far-reaching consequences for both the long-term goal of development and deployment of medical therapeutic interventions.

Technical Summary

Tissue homeostasis requires a coordinated programme of inflammation, regeneration and replacement. The maintenance of homeostasis is underpinned by tightly controlled inflammatory and stromal cell responses. Dysregulation of these processes can result in loss of tissue function and integrity, and is a feature of both humans and animals suffering from chronic conditions such as progressive organ failure. There is mounting evidence that dietary factors and the composition of the gut microbiome can affect an individual's response to tissue injury and the rapidity of age-related scarring. Therefore an understanding of the dietary factors that control of inflammation and wound healing responses is critical to the development of strategies to alleviate these conditions.

The amine oxidases are a group of enzymes that deaminate primary amines such as those found in the diet, or those generated as a consequence of metabolism by gut bacteria. Amine oxidases have been implicated in inflammatory and stromal responses to tissue damage through recruitment of distinct immune cell subsets, stromal cell activation and cross-linking of ECM. Whilst it is known that certain dietary amines are substrates for these enzymes their effects on tissue homeostasis are poorly understood. Furthermore the precise roles of individual members of the amine oxidase family in this process have not been fully described.

This project aims to define the substrate specificity of amine oxidases and their impact on i) wound healing mediated by stromal cells and ii) the recruitment of inflammatory cells. This project will also study systemic effects of amine oxidases mediated by circulating forms of the proteins and highly reactive products of the deamination reaction such as advanced glycation end products. It is anticipated that this project will provide novel data linking diet and health through the action of amine oxidase activity, and inform future approaches to improve the healing response.

Planned Impact

Dysregulated tissue repair and homeostasis underlies most chronic conditions and age-related disorders. Despite major health and socio-economic implications the cellular and molecular determinants of impaired responses to wound healing are currently limited. The primary goal of this study is to define dietary regulators of amine oxidases that have an impact on tissue homeostasis.

This study will benefit both academic and non-academic groups with impact expected to come from several main streams:
1. Increase in fundamental knowledge of the function of individual amine oxidases and their interactions with biogenic amines will benefit the wider academic community.
2. Understanding the mechanisms by which amine oxidases modulate wound healing responses will be of interest to researchers such as those studying immune cell-stroma interactions in multiple organ systems.
3. Methodological development in the detection of advanced glycation end products (AGE) will be made available for researchers from diverse streams such as clinical science, pharmacology and biomedical science.
4. Translational potential from the identification of key players in tissue homeostasis will benefit the pharmaceutical and drug-development industries, and in the long-term individuals suffering from related disorders.
5. Identification of dietary components that regulate amine oxidase activity will be relevant to nutritionists and food manufacturers.

Who will benefit from this research and how?
1. Academic research groups at local, national and international level working on nutrition, wound healing, immune responses, ageing and reactive intermediates (such as AGE). Research findings will be disseminated via both Open Access publication and presentation at research meetings and congresses.
2. Students/early career researchers. Students will be engaged through lectures/tutorials and laboratory-based sessions provided by the PI as part of the College of Medical and Dental School teaching programme. Clinical and non-clinical students will be exposed to cutting-edge research and novel methodologies, thereby increasing their knowledge of processes fundamental for health and wellbeing.
3. Research staff. Training in research techniques and professional development opportunities will be provided for the technician employed by this project. This will also benefit other members of the group through development of a broad spectrum of generic and project-specific research skills that align with the BBSRC Skills Statement for research training.
4.Drug-development Industry. Determination of specific amine oxidase proteins responsible for disruption of tissue homeostasis will shape the development and use of therapeutic agents for related disorders.
5. Clinical practitioners and patients. The investigation of dietary substrates for amine oxidases and the consequences for tissue homeostasis is of clear interest to the clinical community in terms of medical research and practice.
6. Wider socio-economic impacts. Development of effective therapeutic strategies may ultimately have a significant impact on the health and wellbeing of patients, enhancing quality of life and improving socio-economic status.
7. Methodology development. This project will develop methods to detect AGE in biological samples that will be of enormous benefit to the global research community, thus increasing the competitiveness of UK science.
8. Food manufacturers and distributors. A number of methods have been developed to control the levels of biogenic amines in the manufacture and storage of foods. The interaction between amine oxidases and these compounds, and their effects on health will have direct impact on the monitoring of biogenic amine levels in foodstuffs.
9. Public. The project will support public engagement to promote dialogue with the wider non-academic community, thereby communicating research outcomes and their relevance to society.
Description 1) We have discovered that a protein (VAP-1) that we thought was restricted to tissue is also present on circulating neutrophils. These cells are highly important in fighting infections and are the first responders to a site of injury. We suspect that the protein contributes to the detection of pathogens and/or damaged cells, which promotes the recruitment of other cells of the immune system enabling the clearance of the injurious agent. We are continuing to explore this exciting new angle using fluorescently-tagged VAP-1 constructs in the pro-myelocytic cell line HL-60, exploring the effects of different mutations and impact on cell survival and migration.
2) This grant has allowed us to collaborate with the University of Edinburgh on a project looking at single-cell RNA sequencing of normal and diseased livers, where we have identified markers that can discriminate different macrophage and endothelial populations. We have extended this to further collaborations with Imperial College London and University of Basel, Switzerland.
3) We have detected the expression of a family of lysyl oxidase enzymes in both diseased human and murine livers (using archived samples). These enzymes have been implicated in cross-linking of ECM and malignancy. We have observed differences between human and murine samples that may have implications for dissecting disease mechanisms, particularly in the field of fibrosis. We discovered that there is a lack of good reagents to probe the functions of the lysyl oxidases and so have focused mainly on the AOC genes (AOC1 [DAO], AOC2 [RAO] and AOC3 [VAP-1])
4) We have also used some of the funds to identify the expression of amine oxidases in rare neuroendocrine tumours, and we suspect that circulating amines may contribute to the progression of disease. Such tumours occur in the gut and pancreas and have impact on cardiac function through alterations in heart valves, suggesting that the effects of VAP-1 biology are systemic.
5) Work on the impact of amine oxidase activity on cell metabolism is ongoing - these processes are central to responses to e.g. infection and we have been trying to unpick the mechanisms that might influence how fibroblasts and immune cells might react to the presence of amine oxidases in the circulation, or the products of their enzyme reactions.
Exploitation Route Our studies will help to inform pre-clinical models and clinical trials targeting amine oxidases in different organ systems.
However on a more fundamental level our data will help to develop a more mechanistic insight into the development of inflammation and fibrosis and identify key molecular players (both proteins and dietary constituents) that regulate these pathways.
Sectors Chemicals,Environment,Healthcare,Manufacturing, including Industrial Biotechology,Pharmaceuticals and Medical Biotechnology

Description Wellcome Trust Four Year PhD Programme in Inflammation (MIDAS Scheme, University of Birmingham)
Amount £71,784 (GBP)
Funding ID 203824/Z/16/Z 
Organisation Wellcome Trust 
Sector Charity/Non Profit
Country United Kingdom
Start 10/2017 
End 10/2020
Description Boehringer Ingelheim 
Organisation Boehringer Ingelheim
Country Germany 
Sector Private 
PI Contribution We have engaged with Boehringer Ingelheim to test the efficacy of their compounds in treating liver disease, with a view to investigate the mechanisms behind the function of the target protein.
Collaborator Contribution Boehringer Ingelheim have provided additional funding and resources to support in vivo and in vitro experiments that are able to run alongside our current research focus
Impact No outputs yet - collaboration started early but contracts only formally in place from mid-2018.
Start Year 2017
Description Macrophage phenotype and function 
Organisation University of Basel
Country Switzerland 
Sector Academic/University 
PI Contribution We have worked closely with Dr Christine Bernsmeier's team in Basel investigating the regulation of macrophage markers during fibrosis. My research team have some data to suggest that amine oxidases may regulate macrophage polarity and/or function and so a deeper understanding of the plasticity of these cells in the liver will inform our research pathway.
Collaborator Contribution Their lab has access to high quality biopsy specimens and expertise in looking at a subset of macrophage markers, in particular Axl. The collaboration has generated a published paper and we have contributed intellectually to a Swiss National Science Foundation grant that was awarded to Dr Bernsmeier to continue the work for 4 years.
Impact Manuscript: Life Sci Alliance. 2019 Dec 10;3(1). pii: e201900465. doi: 10.26508/lsa.201900465. Print 2020 Jan. Expression of AXL receptor tyrosine kinase relates to monocyte dysfunction and severity of cirrhosis. Brenig R1,2, Pop OT2,3, Triantafyllou E3,4, Geng A1, Singanayagam A3,4, Perez-Shibayama C2,5, Besse L6, Cupovic J5, Künzler P2, Boldanova T1, Brand S2, Semela D2, Duong FH1, Weston CJ7, Ludewig B5, Heim MH1, Wendon J3, Antoniades CG3,4, Bernsmeier C8,2. Funding to Dr Bernsmeier from Swiss National Science Foundation - no link to award currently available
Start Year 2018
Description Modulation of immune cell function - Imperial College London 
Organisation Imperial College London
Country United Kingdom 
Sector Academic/University 
PI Contribution We have established a collaboration with a liver research group from Imperial College with whom we have carried out other projects outside of this current funding stream. This particular aspect of the project is focused on understanding the consequences of exposing immune cells to amine oxidases and measuring the impact on the presence of co-stimulatory/checkpoint/exhaustion/maturation markers as a means to better understand the influence of these enzyme on inflammatory cell biology.
Collaborator Contribution The collaborators have provided access to liver samples and expertise in flow cytometry analysis following exposure of immune cells to purified amine oxidase protein.
Impact None to date - data generated but not yet able to interpret consequences.
Start Year 2019
Description Single cell RNASeq of cirrhotic liver 
Organisation University of Edinburgh
Department MRC Centre for Inflammation Research
Country United Kingdom 
Sector Academic/University 
PI Contribution We have contributed to a study of cell populations that have been identified in diseased human livers by RNAseq technology. We have provided the primary human liver tissue and know how to isolate cell populations and carry out functional assays that complement the work.
Collaborator Contribution The researchers at University of Edinburgh initiated the study and then contacted us following the requirement for revisions to their manuscript. Their main focus was on the RNAseq angle of the paper whereas we have been able to carry out the majority of the functional assays
Impact Manuscript nearing completion for resubmission. However we expect the collaboration to continue beyond the duration of this award as the work has identified some novel pathways that we wish to investigate.
Start Year 2018
Description Patient engagement NETs VAP-1 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach Regional
Primary Audience Patients, carers and/or patient groups
Results and Impact Research awareness days for patients with neuroendocrine tumours - describing our work on amine oxidases and how knowledge of the basic mechanisms of these enzymes could be applied to abberant tissue repair and support of tumour environments such as that observed in their rare disease.
Year(s) Of Engagement Activity 2019,2020