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Toll‐like Receptor 4 Mutation Moderates Hyperhomocysteinemia‐ Induced Hypertension
Author(s) -
Familtseva Anastasia,
Chaturvedi Pankaj,
Kalani Anuradha,
Metreveli Naira,
Kunkel George H,
Tyagi Suresh C
Publication year - 2016
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.30.1_supplement.969.13
Subject(s) - inflammation , endocrinology , medicine , apoptosis , hyperhomocysteinemia , innate immune system , receptor , pathogenesis , cytokine , immune system , tlr4 , immunology , biology , homocysteine , biochemistry
Hyperhomocysteinemia (HHcy) has been observed to promote hypertension, but the mechanisms are unclear. Toll‐like receptor 4 (TLR‐4) is a cellular membrane protein that is expressed on immune cells and non‐immune cells (endothelial cells, vascular smooth muscle cells). TLR‐4 activation has been known to promote innate immune system response with inflammatory cytokine up‐regulation. TLR‐4‐ driven inflammatory cascade has been shown to be involved in pathogenesis of hypertension and atherosclerosis. In this study, we hypothesize that HHcy‐ induced TLR‐4 activation promotes inflammatory cytokine up‐regulation (IL‐1β, TNF‐α) and initiation of mitochondrial‐ dependent apoptosis leading to cell death and chronic vascular inflammation that predispose to hypertension. To test this hypothesis, we used 12 week old C57BL/6J mice (WT); Cystathionine‐β‐synthase deficient mice (CBS+/−) with genetic HHcy; C3H/HeJ (C3H) mice with TLR‐4 mutation and CBS+/−/C3H mice. Blood pressure measurement, western blotting (Caspase‐9, Caspase‐3, HSP60, TLR‐4), q‐PCR (Bax, IL‐1β, TNF‐α, NF‐kB), immunohistochemistry (cleaved Caspase‐3) and TUNEL assay were used. Blood pressure was up‐regulated in CBS+/− mice (systolic: 156.54 ± 10.2 mmHg; mean: 132.4 ± 11.16 mmHg) compared to WT mice (systolic: 121.8 ± 3.6 mmHg; mean: 97.2 ± 6.5 mmHg). Interestingly, blood pressure values were significantly decreased in CBS+/−/C3H mice (systolic: 130.13 ± 9.3 mmHg; mean: 105.8 ± 12.6 mmHg) compared to CBS+/− mice. q‐PCR showed significant up‐regulation of Bax, IL‐1β, TNF‐α mRNA expression in the mesenteric artery of CBS+/− mice compared to control and C3H mice. In addition, Bax, IL‐1β, TNF‐α mRNA expression was decreased in the mesenteric artery of CBS+/−/C3H mice compared to CBS+/− mice. Western blotting validated increase of Caspase‐9 and Caspase‐3 protein expression in the mesenteric artery of CBS+/−mice compared to WT and C3H mice. Immunohistochemistry confirmed cleaved Caspase‐3 up‐regulation in the mesenteric artery of CBS+/− mice compared to control and C3H mice. TUNEL assay showed DNA fragmentation in the mesenteric artery of CBS+/− mice compared to control and C3H mice. In addition, active Caspase‐3 and DNA fragmentation were significantly decreased in the mesenteric artery of CBS+/−/C3H mice compared to CBS+/− mice. In conclusion, our data suggested that HHcy‐induced TLR‐4 activation promotes inflammatory cytokine (IL‐1β, TNF‐α) and Bax up‐regulation followed by mitochondrial apoptosis leading to cell loss and chronic vascular inflammation that contributes to hypertension. Therefore, TLR‐4 mutation abates vascular inflammation and mitochondrial‐dependent apoptosis that moderate hypertension. Support or Funding Information This work was supported by NIH grants: HL‐74185