The relationship between folate/homocysteine metabolism and inflammatory markers in vitro and in vivo / Zhi-Yong Lu.

Format:

Book

Manuscript

Microformat

Thesis/Dissertation

Author/Creator:

Lu, Zhi-Yong.

Contributor:

Whitehead, Steve, advisor.

Blair, Ian A., advisor.

University of Pennsylvania.

Language:

English

Subjects (All):

Penn dissertations--Pharmacological sciences.

Pharmacological sciences--Penn dissertations.

Pharmacological Sciences.

Academic Dissertations as Topic.

Medical Subjects:

Pharmacological Sciences.

Academic Dissertations as Topic.

Local Subjects:

Penn dissertations--Pharmacological sciences.

Pharmacological sciences--Penn dissertations.

Physical Description:

xvi, 166 pages : illustrations ; 29 cm

Production:

2008.

Summary:

Hyperhomocysteinemia (HHcy), caused by common functional polymorphisms in folate/homocysteine (Hcy) metabolism-related genes and/or environmental factors (e.g. low B vitamins status), has long been regarded as a risk marker for cardiovascular disease, neural tube defects, rheumatoid arthritis, and a number of other pathologies. The mechanism by which HHcy contributes etiologically to these pathologies is still not fully understood. To study the long-term effects of dysregulation of folate/Hcy metabolism in endothelial cells, an endothelial cell model was established by knocking down methylenetetrahydrofolate reductase (MTHFR). MTHFR knockdown cells showed an altered folate derivative profile without elevated extracellular or intracellular Hcy levels. This study suggests that folate concentration is a more important determinant of Hcy levels than MTHFR functional status.

Besides being a common determinant of HHcy, our laboratory has found that chronic folate insufficiency independently can induce Ea.hy 926 endothelial cells to produce elevated amounts of monocyte chemoattractant protein-1 (MCP-1), an important player in early atherogenesis, relative to folate replete cells. To further understand the potential role of chronic folate insufficiency in atherogenesis, the mechanisms by which chronic folate insufficiency modified MCP-1 synthesis were investigated. Cells maintained in conditions of chronic folate insufficiency (LO cells) had upregulated transcription of CCL2, the gene encoding MCP-1, as compared to folate replete controls (HI cells). However, there was no significant difference in MCP-1 mRNA stability between LO and HI cells, suggesting that the former had more active CCL2 transcription. This transcriptional advantage was associated with elevated levels of both total p38 and phospho-p38, but not with NF-kappaB activity, and was retained after massive induction of MCP-1 by TNF-alpha treatment (via increased NF-kappaB activity). This study suggests that folate insufficiency induces elevated expression levels of p38, which is the primary determinant of increased baseline CCL2 transcription. Folate insufficiency also primes Ea.hy 926 endothelial cells to have a quantitatively more vigorous MCP-1 synthetic response to cytokine-mediated inflammatory stress.

To further test the hypothesis that folate modulates MCP-1 synthesis in vivo, the relationships between MCP-1, folate derivatives, Hcy, MTHFR 6770>T genotype and CCL2 --2518A>G genotype were investigated in healthy women of childbearing age (the "Comparator study") and rheumatoid arthritis (RA) patients treated with methotrexate (MTX) (the "MTX study"). The Comparator study showed that MCP-1 levels were significantly associated with MTHFR 6770>T genotype and red blood cell (RBC) tetrahydrofolate levels. In the MTX study, MTX treatment led to reduced disease activity and better clinical status as well as to elevated MCP-1 levels. Prior to MTX treatment MTHFR 677C carriers had significantly more MCP-1 than TT homozygotes, and following MTX treatment MCP-1 concentrations became significantly higher in C carriers, but not in TT homozygotes. These two studies indicate that folate metabolism is a determinant of circulating levels of the potent pro-inflammatory chemokine MCP-1 in healthy individuals and in the context of inflammatory disease.

Notes:

Advisers: Steve Whitehead; Ian A. Blair.

Thesis (Ph.D. in Pharmacological Sciences) -- University of Pennsylvania, 2008.

Includes bibliographical references.

Local Notes:

University Microfilms order no.: 3346161