Shear stress blunts tubuloglomerular feedback partially mediated by primary cilia and nitric oxide at the macula densa.
The present study tested whether primary cilia on macula densa serve as a flow sensor to enhance nitric oxide synthase 1 (NOS1) activity and inhibit tubuloglomerular feedback (TGF). Isolated perfused macula densa was loaded with calcein red and 4,5-diaminofluorescein diacetate to monitor cell volume and nitric oxide (NO) generation. An increase in tubular flow rate from 0 to 40 nl/min enhanced NO production by 40.0 ± 1.2%. The flow-induced NO generation was blocked by an inhibitor of NOS1 but not by inhibition of the Na/K/2Cl cotransporter or the removal of electrolytes from the perfusate. NO generation increased from 174.8 ± 21 to 276.1 ± 24 units/min in cultured MMDD1 cells when shear stress was increased from 0.5 to 5.0 dynes/cm(2). The shear stress-induced NO generation was abolished in MMDD1 cells in which the cilia were disrupted using a siRNA to ift88. Increasing the NaCl concentration of the tubular perfusate from 10 to 80 mM NaCl in the isolated perfused juxtaglomerular preparation reduced the diameter of the afferent arteriole by 3.8 ± 0.1 μm. This response was significantly blunted to 2.5 ± 0.2 μm when dextran was added to the perfusate to increase the viscosity and shear stress. Inhibition of NOS1 blocked the effect of dextran on TGF response. In vitro, the effects of raising perfusate viscosity with dextran on tubular hydraulic pressure were minimized by reducing the outflow resistance to avoid stretching of tubular cells. These results suggest that shear stress stimulates primary cilia on the macula densa to enhance NO generation and inhibit TGF responsiveness.
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Lei
L
Wang
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida; Department of Forensic Pathology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and.
Chunyu
C
Shen
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Haifeng
H
Liu
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Shaohui
S
Wang
Department of Forensic Pathology, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China; and.
Xinshan
X
Chen
Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi.
Richard J
RJ
Roman
Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi.
Luis A
LA
Juncos
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida; Department of Physiology/Pharmacology, University of Mississippi Medical Center, Jackson Mississippi.
Yan
Y
Lu
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Jin
J
Wei
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Jie
J
Zhang
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida;
Kay-Pong
KP
Yip
Department of Molecular Pharmacology and Physiology, University of South Florida College of Medicine, Tampa, Florida; ruisheng@health.usf.edu.
Ruisheng
R
Liu
D000818:Animals; D002452:Cell Count; D002460:Cell Line; D002923:Cilia / Q000502:physiology*; D025461:Feedback, Physiological / Q000502:physiology*; D006863:Hydrogen-Ion Concentration; D007678:Kidney Glomerulus / Q000098:blood supply / Q000378:metabolism* / Q000502:physiology*; D007684:Kidney Tubules / Q000098:blood supply / Q000378:metabolism* / Q000502:physiology*; D008297:Male; D009569:Nitric Oxide / Q000096:biosynthesis / Q000378:metabolism*; D052248:Nitric Oxide Synthase Type I / Q000378:metabolism; D034741:RNA, Small Interfering / Q000494:pharmacology; D011817:Rabbits; D013314:Stress, Mechanical; D014783:Viscosity
D034741:RNA, Small Interfering; D009569:Nitric Oxide; D052248:Nitric Oxide Synthase Type I
macula densa; nitric oxide; primary cilia; tubuloglomerular feedback