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Epigenetic contribution to individual variation in response to lipopolysaccharide in bovine dermal fibroblasts.

ABSTRACT: The innate immune signaling pathway plays a crucial role in the recognition and early response to pathogens associated with disease. Genetic analysis has been unable to completely account for individual variability in the strength of the innate immune response. The aim of this study was to determine the role of the epigenetic markers (DNA methylation or histone acetylation) in controlling bovine gene expression in relation to the response to lipopolysaccharide (LPS). To determine the impact epigenetics may have in controlling innate immunity, dermal fibroblasts from fifteen dairy heifers having previously displayed a differential response to LPS were exposed to 5-aza-2'-deoxycytidine (AZA) and trichostatin A (TSA); de-methylating and hyper-acetylating agents, respectively. The AZA-TSA exposure resulted in a loss of variability between individuals' response to LPS as measured by fibroblast IL-8 protein production. Transcriptomic analysis by microarray was used to elucidate the role of epigenetics in innate immune signaling at 2, 4, and 8h post-LPS exposure. A subset of genes displayed altered expression due to AZA-TSA alone, suggesting an epigenetic regulatory element modifying expression under normal conditions. Treatment with AZA-TSA also led to increased expression of IL-8 (7.0-fold), IL-6 (2.5-fold), TNF-? (1.6-fold), and serum amyloid A 3 (SAA3) (11.3-fold) among other genes compared to control cultures for at least one of the measured times following LPS exposure. These data support the conclusion that epigenetic regulation significantly alters LPS-induced responses and constitutive cytokine gene expression.

SUBMITTER: Green BB

PROVIDER: S-EPMC4228796 | biostudies-literature | 2014 Jan

REPOSITORIES: biostudies-literature

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Epigenetic contribution to individual variation in response to lipopolysaccharide in bovine dermal fibroblasts.

Green Benjamin B BB Kerr David E DE

Veterinary immunology and immunopathology 20131031 1-2

The innate immune signaling pathway plays a crucial role in the recognition and early response to pathogens associated with disease. Genetic analysis has been unable to completely account for individual variability in the strength of the innate immune response. The aim of this study was to determine the role of the epigenetic markers (DNA methylation or histone acetylation) in controlling bovine gene expression in relation to the response to lipopolysaccharide (LPS). To determine the impact epig ...[more]

PMID: 24268632

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Project description:The innate immune response plays a major role in defense against mastitis-causing pathogens. Identification of existing variation in innate immune signaling among cows and the underlying molecular causes for the variation may help in design of new mastitis control strategies. The dermal fibroblast has been used as a model cell type to explore between-cow variation in the ability of cells to produce IL-8 in response to lipopolysaccharide (LPS) treatment, and this response appears related to an animal's ability to respond to in vivo challenge with LPS or Escherichia coli mastitis. In this study, primary dermal fibroblast cultures of cows and microarray-based genomic analysis were used to investigate the cause(s) for the variable response to LPS. Fibroblast cultures from 2 cows, one with a low response phenotype (LR(array)) and another with a high response phenotype (HR(array)), were selected from our collection of fibroblast cultures established from 88 cows. The LR(array) fibroblast culture produced approximately 5-fold less IL-8 and IL-6 protein in response to 24-h LPS treatment than the HR(array) fibroblast culture. Genomic analysis of RNA obtained from 3 replicates of the 2 cultures before and after 8-h LPS treatment revealed a combined LPS-induced differential expression of 321 transcripts, indicating the robust response capability of the fibroblast cell. Under basal conditions, the microarray analysis revealed 2-fold less expression of toll-like receptor 4 (TLR4) in the LR(array) fibroblasts compared with the HR(array) fibroblasts, and this was associated with a marked reduction in expression of genes regulated by the TLR4-MyD88-dependent and TLR4-TRIF-dependent pathways (IL-8, IL-6, SAA3, CCL20, MX1, IRF1, and ISG20). The between-culture differential expression of TLR4 was confirmed and extended by quantitative PCR analysis (QPCR) that revealed a 33-fold lower expression of TLR4 in the LR(array) fibroblast culture. After LPS treatment, the difference in TLR4 expression increased to almost 50-fold and was associated with more than 8-fold lower expression of IL-8 and IL-6. No DNA sequence variations were identified in the proximal 1,300-bp promoter region of the TLR4 gene, and microarray analysis did not reveal a molecular explanation for the reduced TLR4 expression under either basal conditions or following exposure to LPS. The attenuated innate immune response of the LR(array) fibroblast culture to LPS may be caused by reduced TLR4 receptor expression. Also, the primary dermal fibroblast cells can be used to examine underlying causes for between-cow variations in key immune response pathways.

Dataset Information

Epigenetic contribution to individual variation in response to lipopolysaccharide in bovine dermal fibroblasts.

Publications

Epigenetic contribution to individual variation in response to lipopolysaccharide in bovine dermal fibroblasts.

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