Malondialdehyde Acetaldehyde Adducts (MAA-Adducts) Direct Distinctive Pro-Inflammatory Responses in Endothelial and Macrophage Cell Lines

Chronic inflammation plays a critical role in the pathogenesis of atherosclerosis. At present, the mechanism(s) by which inflammation contributes to this disease isnot entirely understood. Inflammation is known to induce oxidative stress, of which one consequence is lipid peroxidation. This process leads to the production of malondialdehyde (MDA), which can subsequently break down to form acetaldehyde (AA). These two aldehyde by-products can covalently interact with the ε-amino group of lysineswithin proteins and lipoproteins leading to the formation of highly immunogenic malondialdehyde-acetaldehyde adducts (MAA-adducts). The aim of this study was to determine the in-vitro cytokine response of endothelial cells and macrophages treated with MAA-modified human serum albumin (HSA-MAA) and low-density lipoprotein (LDL-MAA). In addition, cells isolated from mice with exposure to MAA and high fat diets were stained and imaged for uptake of the modified macromolecules of interest. We found that exposure of endothelial cells resulted in increased expression of IL-6, TNF-α, ICAM-1, VCAM-1, and MCP-1 in response to incubation with HSA-MAA; whereas, the same treatment of macrophages resulted in increased expression of IL-6, TNF-α, and IL-1b. LDL-MAA incubationresulted in increased TNF-α expression in macrophages, but MCP-1 was elevated in endothelial cells. Interestingly, the quantitative and qualitative uptake of triglycerides was increased in both endothelial and macrophage cells when exposed to LDL-MAA compared to LDL alone. The results of these studies demonstrate that different MAA-adducts elicit unique responses in different cell types. Additionally, the presence of MAA appears to modulate the cells leading to increased uptake of triglycerides and further progression of the inflammatory response.https://digitalcommons.unmc.edu/emet_posters/1003/thumbnail.jp

A Link among DNA Replication, Recombination, and Gene Expression Revealed by Genetic and Genomic Analysis of TEBICHI Gene of Arabidopsis thaliana

Spatio-temporal regulation of gene expression during development depends on many factors. Mutations in Arabidopsis thaliana TEBICHI (TEB) gene encoding putative helicase and DNA polymerase domains-containing protein result in defects in meristem maintenance and correct organ formation, as well as constitutive DNA damage response and a defect in cell cycle progression; but the molecular link between these phenotypes of teb mutants is unknown. Here, we show that mutations in the DNA replication checkpoint pathway gene, ATR, but not in ATM gene, enhance developmental phenotypes of teb mutants, although atr suppresses cell cycle defect of teb mutants. Developmental phenotypes of teb mutants are also enhanced by mutations in RAD51D and XRCC2 gene, which are involved in homologous recombination. teb and teb atr double mutants exhibit defects in adaxial-abaxial polarity of leaves, which is caused in part by the upregulation of ETTIN (ETT)/AUXIN RESPONSIVE FACTOR 3 (ARF3) and ARF4 genes. The Helitron transposon in the upstream of ETT/ARF3 gene is likely to be involved in the upregulation of ETT/ARF3 in teb. Microarray analysis indicated that teb and teb atr causes preferential upregulation of genes nearby the Helitron transposons. Furthermore, interestingly, duplicated genes, especially tandemly arrayed homologous genes, are highly upregulated in teb or teb atr. We conclude that TEB is required for normal progression of DNA replication and for correct expression of genes during development. Interplay between these two functions and possible mechanism leading to altered expression of specific genes will be discussed

Malondialdehyde-Acetaldehyde Modified (MAA) Proteins Differentially Effect the Inflammatory Response in Macrophage, Endothelial Cells and Animal Models of Cardiovascular Disease

Chronic inflammation plays a critical role in the pathogenesis of atherosclerosis. Currently, the mechanism(s) by which inflammation contributes to this disease are not entirely understood. Inflammation is known to induce oxidative stress, which can lead to lipid peroxidation. Lipid peroxidation can result in the production of reactive by-products that can oxidatively modify macromolecules including DNA, proteins, and lipoproteins. A major reactive by-product of lipid peroxidation is malondialdehyde (MDA). MDA can subsequently break down to form acetaldehyde (AA). These two aldehydes can covalently interact with the epsilon (ε)-amino group of lysines within proteins and lipoproteins leading to the formation of extremely stable, highly immunogenic malondialdehyde/acetaldehyde adducts (MAA-adducts). The aim of this study was to investigate the inflammatory response to MAA-modified human serum albumin (HSA-MAA) and low-density lipoprotein (LDL-MAA). We found that animals injected with LDL-MAA generate antibodies specific to MAA-adducts. The level of anti-MAA antibodies were further increased in an animal model of atherosclerosis fed a Western diet. An animal model that combined both high fat diet and immunization of MAA-modified protein resulted in a dramatic increase in antibodies to MAA-adducts and vascular fat accumulation compared with controls. In vitro exposure of endothelial cells and macrophages to MAA-modified proteins resulted in increased fat accumulation as well as increased expression of adhesion molecules and pro-inflammatory cytokines. The expression of cytokines varied between the different cell lines and was unique to the individual modified proteins. The results of these studies demonstrate that different MAA-modified proteins elicit unique responses in different cell types. Additionally, the presence of MAA-modified proteins appears to modulate cellular metabolism leading to increased accumulation of triglycerides and further progression of the inflammatory response