Regulation of Renal Pericyte Claire Peppia*- Wildman Urinary System Physiology Unit

Transcription

1 Regulation of Renal Pericyte Claire Peppia- Wildman Urinary System Physiology Unit Medway School of Pharmacy, The Universi8es of Kent and Greenwich at Medway, UK.

2 What are Pericytes? Pericytes Perivascular cells express α-sma and myosin like VSMCs. composed of a cell body and claw like processes vasa recta pericyte Acta Physiologica Sept 212 functionally significant - angiogenesis, vessel stabilisation, macrophage activity and contractile capabilities

3 Regula;on of blood flow in ;ssue smooth muscle arteriole endothelial cells pericyte capillary Now established that there are 2 levels of blood flow control : 1. constric8on/dila8on of vascular smooth muscle at the arteriole level conven8onal understanding for blood flow regula8on

4 Regulation of blood flow in tissue smooth muscle arteriole endothelial cells pericyte capillary 2. constric8on and dila8on by pericytes at the capillary level. Pericytes are also a locus for local blood flow control. CNS studies, Peppia/ et al., Nature 26

5 Renal Pericytes cortex arteriolar smooth muscle G G G Pericytes Identified at regular intervals along vasa recta capillaries in the medulla medulla Pericytes DVR nerve Ang - II ATP NO NA ATP AVR Collec;ng Duct DVR Regula8ng vasa recta blood flow is key preserve the C- M gradients (NaCl & urea) maintain O 2 and nutrient delivery ensuring metabolic clearance

6 Renal medulla = hos8le environment cortex Inters88al Osmolarity (mosmol/l) 3 Inters88al PO 2 (mmhg) 5 G G Blood flow (ml/min/g) 5 outer medulla inner medulla Loop Of Henle DVR AVR Collecting Duct

7 Outcomes of dysregulated MBF? Ischemia Papillary necrosis AKI Inters88al fibrosis Progression to CKD short term long term Condi;ons in which dysregulated MBF may play a key role: Diabe8c nephropathy Drug- induced nephrotoxicity (NSAIDs, an8- cancer agents, an8- retrovirals and an8bio8cs) Renal fibrosis (CKD) Hypertension

8 How can we investigate regulation of this microcirculatory bed? Isolated perfused vasa recta used to inves8gate poten8al mediators of vessel diameter (luminal and extra- luminal) Vasa recta diameter changed in response to endogenous vasoac8ve agents: Ang- II, Endothelin- 1, Vasopressin, NO and PGE 2 Localised constric8on and dila8on associated with presence of contrac8le pericytes.

9 Can we measure pericyte-mediated changes in in situ vasa recta diameter? bath application of vasoactive agents to live kidney slices: NA (1 nm) ET 1 (1 nm) Ang II (1 µm) pericyte non-pericyte SNAP (1 µm) Contractile pericytes regulate in situ vasa recta diameter

10 Do nucleotides act at pericytes to regulate vasa recta diameter? ATP (1 µm) BzATP (1 µm) 2meSATP (1 µm) UTP (1 µm) Extracellular nucleo8des evoke pericyte- mediated vasoconstric8on

11 Do nucleotides contribute to basal tone? suramin PPADS RB-2 P2R antagonists è vasoconstriction revealed endogenous tonic vasodilation - Low [ATP] = pericyte-mediated dilation - High [ATP] = pericyte-mediated constriction

12 Well established that epithelial and endothelial cells are a source of ATP Both ATP and NE act at pericytes to constrict vasa recta ATP (1 µm) pericyte non-pericyte NE (1 nm) Sympathetic nerves release ATP as a co-transmitter with NE

13 Do sympathetic nerves act to regulate vasa recta pericytes? Tyramine (1 µm) Stimulating endogenous production of NE in kidney slices Tyramine evoked a pericyte-mediated constriction of vasa recta Neuro-vascular coupling???

14 Are sympathetic nerves in close proximity to pericytes? TH-labelled renal sympathetic nerves (green) are in close proximity to pericytes (red) Dense innervation of vasa recta pericytes Sympathetic nerves could be directly regulating medullary pericytes

15 What happens when we manipulate other endogenous signalling pathways? SNAP (NO donor) pericyte-mediated vasodilation L-NAME (1 mm) PSS wash Inhibit NOS - inhibit endogenous NO production constriction of vasa recta Removal of L-NAME surge in endogenous NO production - dilation - What is the source of endogenous NO epithelia or endothelia? - Does this demonstrate tubulovascular cross talk?

16 What is tubulovascular cross-talk? G G How the kidney matches medullary blood flow with filtrate flow rate and dynamics of solute transport? How is this achieved? Pericytes DVR Loop Of Henle AVR Collecting Duct How can we demonstrate this in our model?? % osmolarity Hypotonic shock to stimulate ATP release from tubules è pericyte-mediated vasodilation

17 Manipulating other endogenous signalling pathways demonstrated tubulovascuar cross talk PGE 2 (1 µm) Indomethacin (3 µm) PGE 2 potent vasodilator & predominant prostanoid produced by medullary COX Inhibit COX blocks endogenous PGE 2 production è constriction of vasa recta by pericytes Indomethacin is a NSAID - hence is there a clinical implication for pericytes?

18 How do NSAIDs mediate nephrotoxicity? In vivo studies describe ê MBF 2%... how? è NSAIDs inhibit COXs and production of PGE 2 è Chronic use = AKI and CKD DVR RMIC PGE 2 NSAIDs T PGE 2 PGE 2 Loop of Henle T tubules are a known source of PGE 2 tubulovascular crosstalk pericyte-mediated dilation of vasa recta T Collecting duct T NSAID è constriction

19 Role of pericytes in NSAID s-induced nephrotoxicity vessel diameter (%) NS Indomethacin (3 µm) COX1 COX2 COX2 SC-56 (1 µm) Meloxicam (1mM) Celecoxib (3 µm) NSAIDs è constriction of vasa recta via pericytes

20 What is the potency of the NSAIDmediated vasoconstriction 15 Pericyte Non- pericyte 15 Pericyte Non- pericyte SNAP (1 µm) SNAP (1 µm) & Indomethacin (3 µm) SNAP (1 µm) Bradykinin (1 nm) Bradykinin (1 nm) & Indomethacin (3 µm) Bradykinin (1 nm) endogenous compensatory vasodilatory mechanisms are not able to overcome constriction

21 What might the consequences of NSAID action at pericytes be? RMIC PGE 2 T Loop of Henle T NSAIDs T Collecting duct DVR T è reduced MBF and solute transport throughout the nephron è inability to concentrate urine, hypoxia, papillary necrosis è Does this exacerbate tubular toxicity or primary mechanism??

22 What about other nephrotoxic drugs? Calcinuerin inhibitors (CNIs) - immunosuppressant's Cyclosporine A (12 ng/ml) (36 ng/ml) (.6 mg/ml) (1.2 mg/ml) Vasoconstriction (%) Pericyte Non-pericyte Pericytes CNI sè constriction of vasa recta via pericytes More details - Mark Kelly s talk 1.1 Sunday

23 Role of pericytes in nephrotoxicity Lithium bipolar treatment vessel diameter (%), 2, 4, 6, 8, 1, Lithium (1 µm) pericyte non- pericyte Lithium è constriction of vasa recta via pericytes Are pericytes a novel therapeutic target site?

24 Now for something new!!!

25 Does GABA and Glutamate act at renal pericytes? Both act at CNS pericytes and both found in kidney Pericytes pericytemediated constriction GABA 3 µm pericytemediated dilation Glutamate 1 µm More info - Kadeishia Dunn s talk 16.5 Saturday

26 Conclusion Renal pericytes are regulated by endogenous vasoac;ve mediators and in turn regulate vasa recta capillaries and MBF Novel data suggest pericytes are also regulated by GABA and glutamate although the physiological mechanism needs to be defined Pericytes play an integral in tubulovascular cross talk Mul8ple nephrotoxic agents act at pericytes to regulate vasa recta diameter. The ensuing adenua8on of MBF may be a primary nephrotoxic mechanism or may compound established tubular toxicity. Pericytes might represent an appropriate drug target site when considering novel therapies or adjuvant treatment stratergies.

27 ACKNOWLEDGEMENTS USPU University of Kent Sco. S.P. Wildman Stephen Kelley Kadeshia Dunn Mark Kelly Carol Crawford Holly Courtneidge Gary Mabbu Kirs; Robertson Collaborators Edward Inschco (Georgia Reagents University) Kent Kidney Group Nephrology Team (Kent and Canterbury Hospital) Centre for Nephrology (UCL) Andrew Hall (University of Zurich)

28 Thank you for your aden8on

29 NSAID-induced nephrotoxicity ex vivo tissue slices chronic effects 4h control 4h incubation 3 µm indomethacin cortex NADH TMRM Altered PT morphology and mitochondrial Ψm, redox state, distribution

30 mrna expression in isolated vasa recta A mrna ra;o P2X vs. GAPDH P2X 1 P2X 2 P2X 3 P2X 4 P2X 5 P2X 6 P2X 7 B mrna ra;o P2Y vs. GAPDH P2Y 1 P2Y 2 P2Y 4 P2Y 6 P2Y 12 P2Y 13 P2Y 14

31 1 nm Ang- II evoked 18% mean constric8on at pericyte sites Using Poiseuille s law as an approxima8on: - 55% decrease in blood flow fold increase in resistance 2% decrease in diameter 1 μm Significantly impede passage of RBCs Medulla borderline hypoxic 55% decrease in flow ischemic injury and necrosis AKI??

32 Potential signalling cascades in renal pericytes GABA Cl - Ca 2+ GABA A R vocc GABA B R G α βϒ pericyte CaM [Ca 2+ ] i PLC IP 3 IP 3 R Ca 2+ Ca 2+ Ca 2+ Ca 2+ ER MLCK endothelial cell MLC αsma CONSTRICTION Blood vessel

33 1 nm Ang- II evoked 18% mean constric8on at pericyte sites Using Poiseuille s law as an approxima8on: - 55% decrease in blood flow fold increase in resistance Rela;ng change in vasa recta diameter to flow 1 μm 2% decrease in diameter Significantly impede passage of RBCs Medulla borderline hypoxic 55% decrease in flow ischemic injury and necrosis AKI??