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LPA‐induced activation of LPA 1 receptor leads to the loss of NO‐mediated flow‐induced dilation in human microvessels
Author(s) -
Chabowski Dawid S.,
AitAissa Karima,
Kadlec Andrew O.,
Hockenberry Joseph H.,
Beyer Andreas M.,
Gutterman David D.
Publication year - 2018
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2018.32.1_supplement.713.15
Subject(s) - lysophosphatidic acid , receptor , medicine , antagonist , endocrinology , chemistry , receptor antagonist , nitric oxide , endothelium , mediator , biology
Flow‐induced dilation (FID) in arterioles from patients with coronary artery disease (CAD) is dependent on hydrogen peroxide (H 2 O 2 ) 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 H 2 O 2 , 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 H 2 O 2 as the mediator of FID is mediated by LPA 1 receptor, and the shift can be prevented by blocking the receptor prior to LPA challenge. Methods Human arterioles from discarded adipose tissue were isolated and prepared for videomicroscopy. Arterioles from subjects without CAD were treated with LPA (10uM, 30 min) +Ki16425 (LPA 1/3 receptor antagonist, 10μM, 30 min) or LPA+H2L5186303 (LPA 2 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 H 2 O 2 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 LPA 1–3 receptor target sequences. Values were normalized to 18s. Results mRNA levels of LPA 1 and LPA 2 receptors were expressed at the same level in vessels from CAD and non‐CAD patients. There was no detection of LPA 3 receptor in either CAD or non‐CAD arterioles. Blocking LPA 1/3 receptors prevented the switch to H 2 O 2 ‐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 LPA 2 receptor did not alter the LPA‐induced shift to H 2 O 2 ‐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. Conclusion Blockade of LPA 1/3 receptors before exposing the vessels to pathophysiological levels of LPA preserved NO‐mediated dilation in non‐CAD arterioles, whereas blocking LPA 2 receptors did not protect LPA‐exposed vessels from shifting to H 2 O 2 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 LPA 1 receptor. Blocking LPA 1 receptor may be an effective strategy to preserve NO‐mediated FID in the arterioles of patients with elevated levels of LPA. Support or Funding Information This 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 .