LPA‐induced activation of LPA1 receptor leads to the loss of NO‐mediated flow‐induced dilation in human microvessels
Authors: Chabowski Dawid S. , Ait‐Aissa Karima , Kadlec Andrew O. , Hockenberry Joseph H. , Beyer Andreas M. , Gutterman David D. 
Published: June 2021

IntroductionFlow‐induced dilation (FID) in arterioles from patients with coronary artery disease (CAD) is dependent on hydrogen peroxide (H2O2) rather than the nitric oxide (NO)‐mediated mechanism observed in arterioles from patients without CAD. Circulating levels of lysophosphatidic acid (LPA), a bioactive lipid, range from low to high nanomolar levels in healthy individuals, but increase to micromolar levels in patients with risk factors for CAD as well as early and advanced stages of atherosclerosis. Studies from our laboratory show that acute (30 min) exposure to 10μM LPA in vessels from patients without CAD shifts the mediator of FID from NO to H2O2, recapitulating the CAD phenotype. LPA effects are mediated through cognate LPA receptors, but it is unknown which receptors are expressed in human arterioles and may be responsible for the observed LPA‐induced shift in the mediator of FID. Based on our observed expression pattern of LPA receptors in human arterioles, we hypothesized that LPA‐induced switch to H2O2 as the mediator of FID is mediated by LPA1 receptor, and the shift can be prevented by blocking the receptor prior to LPA challenge.MethodsHuman arterioles from discarded adipose tissue were isolated and prepared for videomicroscopy. Arterioles from subjects without CAD were treated with LPA (10uM, 30 min) +Ki16425 (LPA1/3 receptor antagonist, 10μM, 30 min) or LPA+H2L5186303 (LPA2 receptor antagonist, 1μM, 30 min). Diameters were measured at steady‐state during graded increases in intraluminal pressure gradients (flow) in the presence/absence of a NOS inhibitor (L‐NAME; 100μM) or H2O2 scavenger (Peg‐Catalase; 500 units/mL). Data are expressed as % maximal dilation. RT‐qPCR was performed on intact vessels from CAD and non‐CAD patients to examine LPA1–3 receptor target sequences. Values were normalized to 18s.ResultsmRNA levels of LPA1 and LPA2 receptors were expressed at the same level in vessels from CAD and non‐CAD patients. There was no detection of LPA3 receptor in either CAD or non‐CAD arterioles. Blocking LPA1/3 receptors prevented the switch to H2O2‐dependent FID from occurring (LPA+Ki16425 control: 81.9±4.1 vs Ki16425+LPA+L‐NAME: *23.8±8.7 vs Ki16425+LPA+Peg‐Cat: 79.1±4.4, n=8,7,7). Blocking LPA2 receptor did not alter the LPA‐induced shift to H2O2‐mediated FID (LPA+H2L5186303 control: 83.0±4.2 vs (LPA+H2L5186303+L‐NAME 84.2±3.0 vs (LPA+H2L5186303+Peg‐Cat *−9.72±2.0, n=6,6,6). *p<0.05, 2‐way ANOVA.ConclusionBlockade of LPA1/3 receptors before exposing the vessels to pathophysiological levels of LPA preserved NO‐mediated dilation in non‐CAD arterioles, whereas blocking LPA2 receptors did not protect LPA‐exposed vessels from shifting to H2O2 as the mediator of FID. Functional data and the expression pattern of the three receptors suggest that the LPA effect is mediated by activation of LPA1 receptor. Blocking LPA1 receptor may be an effective strategy to preserve NO‐mediated FID in the arterioles of patients with elevated levels of LPA.Support or Funding InformationThis work was supported by the AHA Predoctoral Fellowship ‐ Midwest Affiliate 17PRE33410986 (to D.S. Chabowski) and the National Institutes of Health RO1 HL135901‐01 (to D.D. Gutterman).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.