Cardiovascular Division

Ajay Shah graduated from the University of Wales College of Medicine in 1982. His postgraduate doctoral training was undertaken with Dirk Brutsaert in Belgium and Andrew Henderson in Cardiff, his thesis being awarded with Distinction in 1990. Subsequent academic training included a British Heart Foundation Intermediate Fellowship, a period at the National Institutes of Health in the USA, and a Medical Research Council Senior Clinical Fellowship. He was appointed to the Chair of Cardiology at King's College London in 1998.
 
He is an elected Fellow of the Academy of Medical Sciences, the European Society of Cardiology, the American Heart Association, and the International Academy of Cardiovascular Sciences, and a member of the Association of Physicians of Great Britain and Ireland. He is the current Chairman of the European Society of Cardiology Working Group on Myocardial Function and the Chairman of the Basic Science section of the Heart Failure Association of the European Society of Cardiology (2006- ). He is on the editorial board of Heart, European Heart Journal, Cardiovascular Research, Journal of Molecular & Cellular Cardiology, European Journal of Heart Failure, Basic Research in Cardiology, Heart Lung & Circulation, and Heart & Vessels. He has also led the establishment of the annual Winter Congress on Translational Basic Science of the Heart Failure Association of the ESC. 
 
Research Group: Academic Cardiology, Denmark Hill
(PIs: A Shah, A Brewer)

The group is based within the new £30M James Black Centre at the Denmark Hill campus of King’s College London. We study the role of NADPH oxidases and redox-regulated pathways involved in the development of cardiac hypertrophy, failure and vascular dysfunction. We employ an integrative multidisciplinary approach to address this focused area, with molecular, cellular, biochemical, physiological and clinical techniques and a strong emphasis on carefully phenotyped relevant gene-modified models, several of which have been generated within the group. With respect to translational research and clinical application, we are well integrated with the clinical cardiac unit at King’s College Hospital and have established access to patients, clinical material and excellent clinical research facilities. Our work is funded through British Heart Foundation programme and project grants, EU grants and a range of other awards.

The main current areas of research are:
 
(a) NADPH oxidases in cardiac hypertrophy, remodelling and heart failure
The mechanisms underlying the development of cardiac hypertrophy in response to increased workload or of adverse remodelling post-MI, and the subsequent transition to heart failure, remain incompletely understood. Our work focuses on the role of reactive oxygen species (ROS, such as superoxide and hydrogen peroxide) and redox-regulated pathways in this process. Although there are several potential sources of ROS in the heart, we have focussed specifically on the NADPH oxidase family of enzymes as these proteins appear to be specifically designed for redox signalling. NADPH oxidases are complex multi-subunit enzymes in which a Nox catalytic subunit facilitates the transfer of electrons from NADPH to molecular oxygen, thereby resulting in the formation of superoxide and then hydrogen peroxide. Of the 5 Nox isoforms identified to date, Nox2 and Nox4 are co-expressed in endothelial cells, cardiomyocytes and fibroblasts. ROS production by NADPH oxidases may be stimulated in an isoform-specific manner by agonists such as angiotensin II and other G-protein coupled receptor agonists, growth factors, cytokines and mechanical stimuli. Our previous work includes the first definitive evidence for the presence of NADPH oxidases in cardiomyocytes and endothelial cells, as well as significant contributions to defining its mechanisms of regulation and role in redox signalling in these cells. We discovered that Nox2 is involved in both experimental and human heart failure and found that it has a pivotal role in signalling angiotensin II- and aldosterone-induced hypertrophy and fibrosis. Subsequently, we found that not only are Nox2 and 4 differentially activated in cardiac hypertrophy but that they modulate distinct components of the overall cardiac hypertrophic response, suggesting that these different facets may be amenable to independent regulation.

Our key objectives now are to: (a) define the distinct Nox2- and Nox4-activated pathways that influence specific facets of the cardiac and vascular responses to chronic overload (eg, hypertrophy, fibrosis, contractile dysfunction), so that detrimental pathways might be specifically targetted; (b) investigate the molecular and cellular mechanisms of Nox4 versus Nox2 activation and coupling to downstream signalling pathways; (c) elucidate molecular mechanisms responsible for the transcriptional regulation of the Noxs; and (d) investigate the involvement of Noxs in human cardiovascular disease.
 
(b) NADPH oxidases and endothelial dysfunction
Endothelial dysfunction is a key early event in atherogenesis and a powerful predictor of future cardiovascular morbidity and mortality. A major factor in the development of endothelial dysfunction is redox imbalance involving excess ROS production which leads not only to the inactivation of nitric oxide (NO) but also modulates the activity of redox-sensitive intracellular signalling pathways. We and others have shown that a Nox2-based NADPH oxidase is a major source of endothelial ROS but that endothelial cells also express Nox4. In studies complementary to those addressing the role of Noxs in cardiac hypertrophy and remodelling, we are also addressing the relative roles of Nox2 and Nox4 in endothelial cells both in vitro and in vivo. The relative roles of Nox-derived ROS and NOS-derived NO are also of interest.

Confocal image showing colocalisation of the NADPH oxidase subunit gp91phox and tubulin in endothelial cells
 

(c) Autocrine/paracrine regulation of contractile function
A long-standing interest has been in the cardiac contractile actions of locally-released mediators such as NO, both in the physiological setting and in heart failure. This question has been addressed with a wide range of techniques and models, ranging from sarcomere length and intracellular calcium measurements in isolated cardiomyocytes to invasive cardiac catheterisation laboratory-based studies in humans. More recently, we have focussed on the role of the myofilament protein troponin I in these effects, using among other models the transgenic replacement of cardiac troponin I by slow skeletal troponin I. Our current work is addressing the effects of ROS and NO on contractile function both experimentally and in humans in vivo.

Lecturer
 * Dr N Melikian (Clin)
 
Senior Research Fellow
* Dr A Brewer
 
Postdoctoral Fellows
* Dr N Anilkumar 
* Dr X Dong
* Dr M Marshall
* Dr C Murdoch
* Dr T Murray
* Dr A Protti
* Dr B Yu
* Dr M Zhang
 
PhD Students
* Ms S Alom Ruiz
* Dr S Chaubey (Clin)
* Ms K Curtis
* Ms S Mushemi
* Dr R Ray (Clin)
* Dr A Sirker (Clin)
* Ms M Wang
 
Clinical Research Fellow
* Dr H Shabeeh
 
Lab Manager
* Mr K Roberts
 
Research Assistants
* Mr S Walker

1. Seddon M, Melikian N, Dworakowski R, Shabeeh H, Jiang B, Byrne J, Casadei B, Chowienczyk P, Shah AM. Effects of neuronal nitric oxide synthase (nNOS) on human coronary artery diameter and blood flow in vivo. Circulation. 2009;119:2656-2662.
2. Anilkumar N, Sirker A, Shah AM. Redox sensitive modulation of signaling pathways in cardiac remodeling, hypertrophy and failure. Frontiers Biosc. 2009;14:3168-3187.
3. Anilkumar N, Weber R, Zhang M, Brewer A, Shah AM. Nox4 and Nox2 NADPH oxidases mediate distinct cellular redox signaling responses to agonist stimulation. Arterioscler Thromb Vasc Biol. 2008;28:1347-1354.
4. Seddon MR, Chowienczyk PJ, Brett SE, Casadei B, Shah AM. Neuronal nitric oxide synthase (nNOS) regulates basal microvascular tone in humans in vivo. Circulation. 2008;117:1991-1996.
5. Dworakowski R, Walker S, Momin A, Desai J, El-Gamel A, Wendler O, Kearney MT, Shah AM. Reduced NADPH oxidase-derived superoxide and vascular endothelial dysfunction in human heart failure. J Am Coll Cardiol. 2008; 51:1349–56.
6. Duncan E, Crossey P, Walker S, Anilkumar N, Poston L, Douglas G, Ezzat V, Wheatcroft S, Shah AM, Kearney MT. The effect of endothelium specific insulin resistance on endothelial function in vivo. Diabetes. 2008;57:3307-3314.
7. Looi YH, Grieve DJ, Siva A, Walker SJ, Anilkumar N, Cave AC, Marber MS, Monaghan MJ, Shah AM. Involvement of Nox2 NADPH oxidase in adverse cardiac remodeling following myocardial infarction. Hypertension. 2008;51:319-325.
8. Zhang M, Kho AL, N Anilkumar, Chibber R, Pagano PJ, Shah AM, Cave AC. Glycated proteins stimulate reactive oxygen species production in cardiac myocytes: Involvement of Nox2(gp91phox)- containing NADPH oxidase. Circulation. 2006;113: 1235-1243.
9. Grieve DJ, Byrne JA, Siva A, Layland J, Johar S, Cave AC, Shah AM. Involvement of the NADPH oxidase isoform Nox2 in cardiac contractile dysfunction occurring in response to pressure-overload. J Am Coll Cardiol. 2006;47:817-826.
10. Li J-M, Fan LM, Christie MR, Shah AM. Acute TNFa signaling via NADPH oxidase in microvascular endothelial cells: Role of p47phox phosphorylation and binding to TRAF4. Mol Cell Biol. 2005;25:2320-2330.
11. Li J-M, Wheatcroft S, Fan LM, Kearney MT, Shah AM. Opposing roles of p47phox in basal versus angiotensin II-stimulated alterations in vascular O2- production, vascular tone, and mitogen-activated protein kinase activation. Circulation. 2004;109:1307-1313.
12. Byrne JA, Grieve DJ, Bendall JK, Li J-M, Gove C, Lambeth JD, Cave AC, Shah AM. Contrasting roles of NADPH oxidase isoforms in pressure overload versus angiotensin II-induced cardiac hypertrophy. Circ Res. 2003;93:802-804.
13. Li J-M, Shah AM. Mechanism of endothelial cell NADPH oxidase activation by angiotensin II: Role of the p47phox subunit. J Biol Chem. 2003;278:12094-12100.
14. Heymes C, Bendall JK, Ratajczak P, Cave AC, Samuel J-L, Hasenfuss G, Shah AM. Increased myocardial NADPH oxidase activity in human heart failure. J Am Coll Cardiol. 2003;41:2164-2171.
15. Bendall JK, Cave AC, Heymes C, Gall N, Shah AM. Pivotal role of gp91phox-containing NADPH oxidase in angiotensin II-induced cardiac hypertrophy. Circulation. 2002;105:293-296.
16. Li J-M, Mullen AM, Yun S, Wientjes F, Brouns GY, Thrasher AJ, Shah AM. Essential role of the NADPH oxidase subunit p47phox in endothelial cell superoxide production in response to phorbol ester and tumor necrosis factor-a. Circ Res. 2002; 90:143-150.
17. Cotton JM, Kearney MT, MacCarthy PA, Grocott-Mason RM, McClean DR, Heymes C, Richardson PJ, Shah AM. Effects of nitric oxide synthase inhibition on basal function and the force-frequency relationship in the normal and failing human heart in vivo. Circulation. 2001;104:2318-2323.
18. MacCarthy PA, Shah AM. Impaired endothelium-dependent regulation of ventricular relaxation in pressure-overload cardiac hypertrophy. Circulation. 2000;101:1854-1860.
19. Bayraktutan U, Blayney L, Shah AM. Molecular characterization and localization of the NAD(P)H oxidase components, gp91-phox and p22-phox, in endothelial cells. Arterioscler Thromb Vasc Biol. 2000;20:1903-1911.
20. MacCarthy PA, Grocott-Mason R, Prendergast BD, Shah AM. Contrasting inotropic effects of endogenous endothelin in the normal and failing human heart: Studies with an intracoronary ETA receptor antagonist. Circulation. 2000;101:142-147.