Xplore mRNA assays for the quantification of IL-1 beta and TNF-alpha mRNA in lipopolysaccharide-induced mouse macrophages

Eicosapentaenoic Acid Prevents LPS-Induced TNF-α Expression by Preventing NF-κB Activation

BACKGROUND

Many studies have shown that fish oil supplementation inhibits tumor necrosis factor-alpha (TNF-alpha) production in mice and human subjects; however, the mechanisms remain unclear. Nuclear factor-kappaB (NF-kappaB) is a transcription factor that plays an important role in controlling the expression of pro-inflammatory genes including TNF-alpha. Activation of NF-kappaB has been shown to mediate the maximal expression of TNF-alpha in human monocytes. NF-kappaB is kept in an inactive form in the cytoplasm by IkappaB, the inhibitory subunit of NF-kappaB complex. Phosphorylation and subsequent degradation of IkappaB lead to NF-kappaB activation.

OBJECTIVES

The effect of eicosapentaenoic acid (EPA), a major n-3 fatty acid in fish oil, on the lipopolysaccharide (LPS)-induced expression of TNF-alpha and activation of NF-kappaB were investigated. The mechanism underlying EPA modulation of NF-kappaB activation was also studied.

METHODS

Human monocytic THP-1 cells were pre-incubated with EPA and stimulated with LPS. The levels of secreted TNF-alpha were determined by ELISA. The DNA binding activity of NF-kappaB was analyzed by EMSA. The degradation and phosphorylation of IkappaB-alpha were examined by Western blot analysis.

RESULTS

TNF-alpha production and expression induced by LPS were significantly decreased in cells pre-incubated with EPA. LPS-induced NF-kappaB activation, translocation of p65 subunit to the nucleus, phosphorylation and degradation of IkappaB-alpha were partially prevented by EPA.

CONCLUSIONS

The results suggest that suppression of the TNF-alpha expression by EPA is partly attributed to its inhibitory effect on NF-kappaB activation. EPA appears to prevent NF-kappaB activation by preventing the phosphorylation of IkappaB-alpha.

An invasive cleavage assay for direct quantitation of specific RNAs

RNA quantitation is becoming increasingly important in basic, pharmaceutical, and clinical research. For example, quantitation of viral RNAs can predict disease progression and therapeutic efficacy. Likewise, gene expression analysis of diseased versus normal, or untreated versus treated, tissue can identify relevant biological responses or assess the effects of pharmacological agents. As the focus of the Human Genome Project moves toward gene expression analysis, the field will require a flexible RNA analysis technology that can quantitatively monitor multiple forms of alternatively transcribed and/or processed RNAs (refs 3,4). We have applied the principles of invasive cleavage and engineered an improved 5'-nuclease to develop an isothermal, fluorescence resonance energy transfer (FRET)-based signal amplification method for detecting RNA in both total RNA and cell lysate samples. This detection format, termed the RNA invasive cleavage assay, obviates the need for target amplification or additional enzymatic signal enhancement. In this report, we describe the assay and present data demonstrating its capabilities for sensitive (<100 copies per reaction), specific (discrimination of 95% homologous sequences, 1 in > or =20,000), and quantitative (1.2-fold changes in RNA levels) detection of unamplified RNA in both single- and biplex-reaction formats.