Impact of animal strain on gene expression in a rat model of acute cardiac rejection

<p>Abstract</p> <p>Background</p> <p>The expression levels of many genes show wide natural variation among strains or populations. This study investigated the potential for animal strain-related genotypic differences to confound gene expression profiles in acute cellular rejection (ACR). Using a rat heart transplant model and 2 different rat strains (Dark Agouti, and Brown Norway), microarrays were performed on native hearts, transplanted hearts, and peripheral blood mononuclear cells (PBMC).</p> <p>Results</p> <p>In heart tissue, strain alone affected the expression of only 33 probesets while rejection affected the expression of 1368 probesets (FDR 10% and FC ≥ 3). Only 13 genes were affected by both strain and rejection, which was < 1% (13/1368) of all probesets differentially expressed in ACR. However, for PBMC, strain alone affected 265 probesets (FDR 10% and FC ≥ 3) and the addition of ACR had little further effect. Pathway analysis of these differentially expressed strain effect genes connected them with immune response, cell motility and cell death, functional themes that overlap with those related to ACR. After accounting for animal strain, additional analysis identified 30 PBMC candidate genes potentially associated with ACR.</p> <p>Conclusion</p> <p>In ACR, genetic background has a large impact on the transcriptome of immune cells, but not heart tissue. Gene expression studies of ACR should avoid study designs that require cross strain comparisons between leukocytes.</p

Cooperative and redundant signaling of leukotriene B4 and leukotriene D4 in human monocytes

BACKGROUND: Leukotriene B(4) (LTB(4)) and cysteinyl leukotrienes (cysLTs) are important immune mediators, often found concomitantly at sites of inflammation. Although, some of the leukotriene-mediated actions are distinctive (e.g. bronchial constriction for cysLTs), many activities such as leukocyte recruitment to tissues and amplification of inflammatory responses are shared by both classes of leukotrienes. OBJECTIVE: We used human monocytes to characterize leukotriene specific signaling, gene expression signatures and functions and to identify interactions between LTB(4) and cysLTs induced pathways. METHODS: Responsiveness to leukotrienes was assessed using oligonucleotide microarrays, real-time PCR, calcium mobilization, kinase activation and chemotaxis assays. RESULTS: Human monocytes were found to express mRNA for high- and low-affinity LTB(4) receptors, BLT(1) and BLT(2), but signal predominantly through BLT(1) in response to LTB(4) stimulation as shown using selective agonists, inhibitors and gene knock-down experiments. LTB(4) acting through BLT(1) coupled to G protein α inhibitory subunit activated calcium signaling, p44/42 mitogen-activated protein kinase, gene expression and chemotaxis. Twenty-seven genes, including immediate-early genes, transcription factors, cytokines and membrane receptors were significantly upregulated by LTB(4). LTB(4) and LTD(4) had similar effects on signaling, gene expression and chemotaxis indicating redundant cell activation pathways but co-stimulation with both lipid mediators was additive for many monocyte functions. CONCLUSION: LTB(4) and LTD(4) display both redundant and cooperative effects on intracellular signaling, gene expression and chemotaxis in human monocytes. These findings suggest that therapies targeting either leukotriene alone may be less effective than approaches directed at both