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Inflammation and Immunity in Human Hypertension and Vascular Dysfunction

Final Report Summary - IMMUNOTENSION (Inflammation and Immunity in Human Hypertension and Vascular Dysfunction.)

Hypertension is a major cause of death and disability in Europe and in the rest of the World. It affects 30% of adults, and additional 30% are at very high risk of developing hypertension. It is the main cause of death worldwide according to WHO, accounting for nearly 8 million deaths every year. This is an enormous health problem as it is a cause of subsequent renal failure, stroke, myocardial infarction and heart failure. Despite extensive research, the mechanisms of most cases of hypertension remain unclear. In spite of therapies available, over 40% of treated patients do not reach treatment goals and present with uncontrolled disease. Since the mid-1980s, no new classes of drugs have been successfully developed to treat hypertension. We and others have recently made observations providing a novel mechanism for hypertension involving activation of the immune system, with involvement of T lymphocytes, monocytes and dendritic cells. Mice lacking T cells or monocytes are protected from severe hypertension and renal/vascular dysfunction. Perivascular and renal infiltration of these cells producing cytokines such as IL-17 and TNF-alpha has been implicated. The exact mechanisms or relevance of these observations for human hypertension is unclear. Therefore, we proposed to investigate the involvement of the immune system in human hypertension. First, we proposed to analyse in depth the characteristics of leukocytes in hypertensive patients in comparison to normotensive controls. Subsequently we proposed to focus on leukocytes infiltrating perivascular adipose tissue and cortex and medulla of the kidney in hypertension in relation to detailed clinical phenotypes of the disease such as ambulatory blood pressure monitoring or vascular dysfunction. Subsequently we aimed to perform ex vivo functional studies by co-incubation of reporter vessels with hypertensive T cells (other leukocytes) to examine their role in vascular dysfunction. These interdisciplinary studies of hypertension have the potential of providing a new understanding and possibly treatment of this otherwise devastating disease. We have reviewed major progress and our contribution to it in two recent reviews that we have written (Antioxid Redox Signal. 2018 Jul 20;29(3):257-274 and Cardiovasc Res. 2017 Jul; 113(9): 1009–1023; Hypertension. 2017 Oct;70(4):660-667).
Studies were successfully conducted in accordance with proposal plan. T cells and their characteristics were characterised in depth using high density immunophenotyping developed by the University of Glasgow team. This wa performed in peripheral blood samples hypertensive patients and normotensive control subjects; in renal segments (cortex and medulla of hypertensive and normotensive subjects). This is important as it allowed us to build upon further mechanistic and clinical observations. The main observation published in our paper in Hypertension (Hypertension, 2016; Jul;68(1):123-32.) was that primarily memory CD4+ and CD8+ circulating T cells are increased in hypertension. In line with experimental data human T cells produce increased IL-17A, IFN-γ and TNFα. In vitro studies performed to complement these demonstrated that pre-hypertensive angiotensin II is not sufficient to cause changes in profile of T cell activation, which suggests participation of other hypertension specific factors.
As our earlier studies have defined a key role for monocyte derived dendritic cells in immune activation in hypertension, within this project we have performed studies of the mechanisms of monocyte participation in hypertension in relation to the role if IL-6 and STAT3 (Cardiovasc Res. 2018 Sep 1;114(11):1547-1563). In this study, we have shown the links between monocyte subsets circulating in hypertensive patients and clinical characteristics of the disease, namely blood pressure values.
To investigate the mechanisms of local target organ involvement in inflammation we have continued studies of perivascular and renal T cell infiltration in both models of Ang II induced hypertension and in human samples. In animal models we have demonstrated that chemokine and in particular RANTES (Regulated upon Activation Normal T cell Expressed and Secreted) is critical for the recruitment of CCR5+, CCR1+ and CCD3+ T cells producing IFN-g and TNF-a to perivascular adipose tissue. The overexertion of this chemokine is associated with endothelial and vascular dysfunction in hypertension in humans both locally (perivascular AT in IMA) and in plasma (published in FASEB J, 2016). Moreover, RANTES levels are increased at early stages of atherosclerotic disease in humans (published in J Physiol Pharmacol, 2016). We are now continuing characterisation of these cells in human hypertension and aiming to understand the mechanisms of their effects on vascular dysfunction and regulation of blood pressure in patients. Within the project 130 kidney samples from subjects with and without hypertension were collected and immunophenotyped. The data is currently undergoing bioinformatics analysis. Our studies of atherosclerotic vessels showed similar immunopathogenetic phenotype with greater effect of local pathology (such as aneurysm and atherosclerosis). In order to address this we used early atherosclerosis assessment in early ApoE-/- model of atherosclerosis, which showed that before vascular inflammation appears a prominent infiltration of perivascular fat and adventitia occurs (Br J Pharmacol. 2017 Nov;174(22):4055-4069) and the role of MMP-9 in the process of propagation of such perivascular inflammation has been recently proposed by us (Circ Res, 2018, Sep)
Further studies to understand consequences of immune cell activation andf target organ infiltration were published in relation to understanding vascular injury (Clin Immunol. 2018 Sep;194:26-33) where we demonstrated for the first time that typical for hypertension immune cells CD8+CD28nullCD57+ are preferentially recruited to vascular injury sites in patients with atherosclerosis. Moreover, we have extended these findings by characterising microvascular dysfunction in patients with one pf prototypic disorders associated with immune activation – ankylosing spondylitis. We described that microvascular dysfunction is linked to disease activity and is cured by blockade of TNF alopa with anti-TNF treatments (Sci Rep. 2018 Sep 4;8(1):13205).
This Marie Sklodowska Curie project has enabled to develop a mature and internationally competitive research program looking at inflammatory mechanisms of hypertension and its links to vascular dysfunction and disease in Glasgow while keeping close European collaborations.
PI further developed his expertise through interactions with European immunologists such as the Immunology group at Glasgow (I McInnes; C Monaco, G. Caliguri, A Habenicht). Final results have significant impact on several levels: Scientifically these help to fill in a gap in the understanding of inflammatory mechanisms in human hypertension. Socio-exconomically - hypertension is a major cause of death and disability (renal failure, stroke, myocardial infarction and heart failure) worldwide. Defining new mechanisms of this devastating disease is therefore vital as may lead to important discovery of new biomarkers.
In summary, this project has provided important stimulus for technological development of biomarkers and treatment of hypertension or at least enable understanding if and how inflammatory mechanisms described in animals play a role in humans. The studies described allowed the Fellow to establish independent tenured position at the University of Glasgow as Regius Professor of Physiology and Cardiovascular Pathobiology, attract independent competitive funding, including awarded ERC Consolidator grant and new members of his research group. CIG from Marie Sklodowska-Curie Program enabled a good balance between research teaching and other responsibilities and helped to establish new productive research group.