Hypertension and diabetes resulting in diabetic nephropathy (DN) are amongst the leading causes of chronic kidney disease (CKD) and end-stage kidney disease. Renoprotective effects the inhibitors of the renin-angiotensin-aldosterone system in patients with DN and CKD is well recognised. However, underlying mechanisms are not well defined and are likely to be complex involving functional and structural changes in both the renal microvasculature, the glomerulus and renal tubules (1). Recent evidence suggests that levels of adenosine, a key extracellular mediator of the tubuloglomerular feedback, are increased in diabetic kidney (2). Synergistic effect between angiotensin II and adenosine in the perfused renal afferent arteriole which supplies blood to the glomerulus has been demonstrated previously, however cellular mechanisms of this synergism and its specificity in respect to other important renal vasoconstrictors such as endothelin and noradrenaline remains not well understood (3).
This project will investigate the interaction between G-protein-coupled receptors (GPCRs) activated by adenosine and angiotensin II in isolated renal microvessels of the rat and mouse using the gel-perfused methodology (4-5). This unique methodology allows to study cell signalling in intact preglomerular (afferent and interlobular) and post-glomerular (efferent) arterioles with or without attached glomeruli. This project will study functional interactions between different receptor types using selective pharmacological agents in renal preparations loaded with calcium-sensitive fluorescent dyes. Distribution of adenosine and angiotensin receptor subtypes which is thought to be heterogeneous along the renal microvascular tree, and their colocalisation will be determined with immunolabelling and high resolution fluorescent and electron microscopy imaging and compared with gene expression in specific cell types using single cell qPCR. Changes in membrane potential and ion currents will be assessed using electrophysiological techniques in intact vessels and single smooth muscle cells isolated from arterioles.
Based in the Department of Pharmacy & Pharmacology within the Drug & Target Discovery research theme which provides a multidisciplinary interactive research environment. The project provides an excellent opportunity for training in molecular, imaging, electrophysiological and cell signalling methods. The University hosts a Microscopy and Analysis Suite with specialist training in multiphoton imaging, electron microscopy and hypoxic facilities (http://www.bath.ac.uk/facilities/mas
) which will be used in this study.
1. Thomas MC, Brownlee M, Susztak K, et al. Diabetic kidney disease. Nat. Rev. Dis. Primers 1: 15018, 2015.
2. Peleli M and Carlstrom M. Adenosine signaling in diabetes mellitus and associated cardiovascular and renal complications. Mol. Aspects Med. 55: 62-74, 2017.
3. Schnermann J. Concurrent activation of multiple vasoactive signaling pathways in vasoconstriction caused by tubuloglomerular feedback: a quantitative assessment. Annu Rev Physiol 77: 301-322, 2015.
4. Smirnov SV, Loutzenhiser K and Loutzenhiser R. Voltage-activated Ca2+ channels in rat renal afferent and efferent myocytes: No evidence for the T-type Ca2+ current. Cardiovasc. Res. 97: 293-301, 2013.
5. Chilton L, Smirnov SV, Loutzenhiser K, et al. Segment-specific differences in the inward rectifier K+ current along the renal interlobular artery. Cardiovasc. Res. 92: 169-177, 2011.