Hypertension-Causing Mutation in Peroxisome Proliferator–Activated Receptor γ Impairs Nuclear Export of Nuclear Factor-κB p65 in Vascular Smooth Muscle

Abstract

Selective expression of dominant negative (DN) peroxisome proliferator-activated receptor gamma (PPARγ) in vascular smooth muscle cells (SMC) results in hypertension, atherosclerosis, and increased NF-κB target gene expression. Mesenteric SMC were cultured from mice designed to conditionally express wild-type (WT) or DN-PPARγ in response to Cre-recombinase to determine how SMC PPARγ regulates expression of NF-κB-target inflammatory genes. SMC-specific overexpression of WT-PPARγ or agonist-induced activation of endogenous PPARγ blunted TNFα-induced NF-κB target gene expression and activity of a NF-κB responsive promoter. TNFα-induced gene expression responses were enhanced by DN-PPARγ in SMC. Although expression of NF-κB p65 was unchanged, nuclear export of p65 was accelerated by WT-PPARγ and prevented by DN-PPARγ in SMC. Leptomycin B, a nuclear export inhibitor, blocked p65 nuclear export and inhibited the anti-inflammatory action of PPARγ. Consistent with a role in facilitating p65 nuclear export, WT-PPARγ co-immunoprecipitated with p65, and WT-PPARγ was also exported from the nucleus after TNFα treatment. Conversely, DN-PPARγ does not bind to p65 and was retained in the nucleus after TNFα treatment. Transgenic mice expressing WT- or DN-PPARγ specifically in SMC (S-WT or S-DN) were bred with mice expressing luciferase controlled by a NF-κB-responsive promoter to assess effects on NF-κB activity in whole tissue. TNFα-induced NF-κB activity was decreased in aorta and carotid artery from S-WT, but was increased in vessels from S-DN mice. We conclude that SMC PPARγ blunts expression of pro-inflammatory genes by inhibition of NF-κB activity through a mechanism promoting nuclear export of p65, which is abolished by DN mutation in PPARγ.

Angiotensin II Signal Transduction: An Update on Mechanisms of Physiology and Pathophysiology

“…Expression of dominant negative PPAR␥ specifically in either smooth muscle or endothelium worsens atherosclerotic lesions in apoEϪ/Ϫ mice fed a western diet, although the cell type specific mechanism may differ (808). Increased expression of inflammatory markers was a consistent observation, and a recent study showed that wild-type PPAR␥ in smooth muscle cells limits NF-B activation by facilitating nuclear export of p65 (719). Expression of PPAR␦ is increased in the vasculature of LDLrϪ/Ϫ mice infused with ANG II, and treatment with a PPAR␦ agonist attenuates vascular inflammation and atherosclerosis possibly through a suppression of ERK and p38 MAPK activation (1030).…”

Inactivation of SERCA2 Cys674 accelerates aortic aneurysms by suppressing PPARγ

“…The activated PPARγ physically associates with NFAT and blocks NFAT DNA binding and transcriptional activity in T lymphocyte (Yang et al, 2000). In SMCs, PPARγ inhibits NF-κB activity by promoting nuclear export of p65NF-κB, which is abolished by dominant-negative mutation in PPARγ1 (Mukohda et al, 2017). In SKI SMCs, overexpression of PPARγ2 or activation of PPARγ inhibits the expression of phosphorylated p65NF-κB, further confirmed the mutual negative regulation between PPARγ and NF-κB.…”

RhoBTB1 protects against hypertension and arterial stiffness by restraining phosphodiesterase 5 activity

“…This hypothesis was confirmed by studies of transgenic mice, in which targeting the expression of the human hypertension-causing mutations in PPARγ selectively to either endothelium or vascular smooth muscle was done (16)(17)(18). PPARγ also was found to have antiinflammatory effects on endothelium and smooth muscle (19,20) as well as antioxidant effects on endothelium (21,22).…”

“…Western blot and IP analyses. Western blotting was performed using transfected HEK293 cells or aortic tissue as previously described (19,20). Lipofectamine (Thermo Fisher Scientific) was used to transfect HEK293 cells.…”