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TNF-alpha downregulates the peroxisome proliferator activated receptor-alpha and the mRNAs encoding peroxisomal
1Institut für Anatomie und Zellbiologie II, Universität Heidelberg, Germany. konstantin.beier@urz.uni-heidelberg.de
Abstract:
We have studied the effects of TNF-alpha on the mRNAs coding for the peroxisome proliferator activated receptor alpha (PPAR-alpha), and for catalase (Cat), acyl-CoA oxidase (AOX), multifunctional enzyme (PH), and beta-actin in rat liver. Total RNA was isolated from livers of male SD-rats 16 h after administration of a single dose of 25 microg TNF-alpha and mRNAs were analyzed by a novel dot blot RNase protection assay. The mRNAs for PPAR-alpha and for Cat, AOX and PH were significantly reduced by TNF-treatment. In addition, the level of PPAR-alpha protein was also decreased after TNF. In contrast, the mRNA for beta-actin was markedly increased implying that the effect of TNF on PPAR-alpha and the peroxisomal mRNAs is highly selective. This effect may have important implications in perturbation of the lipid metabolism induced by TNF-alpha.
Insights
Tumor necrosis factor-alpha (TNF-alpha) selectively reduces key liver mRNAs, including peroxisome proliferator-activated receptor alpha (PPAR-alpha), impacting lipid metabolism.
Area of Science:
- Biochemistry
- Molecular Biology
- Toxicology
Background:
- Tumor necrosis factor-alpha (TNF-alpha) is a pro-inflammatory cytokine with diverse physiological roles.
- TNF-alpha's impact on specific gene expression in the liver, particularly concerning lipid metabolism, requires further elucidation.
Purpose of the Study:
- To investigate the effects of TNF-alpha on the expression of peroxisome proliferator-activated receptor alpha (PPAR-alpha) and related peroxisomal genes in rat liver.
- To determine the selectivity of TNF-alpha's effects on gene expression by examining beta-actin mRNA levels.
Main Methods:
- Male Sprague-Dawley rats were administered a single dose of TNF-alpha.
- Liver total RNA was isolated 16 hours post-administration.
- mRNA levels for PPAR-alpha, catalase (Cat), acyl-CoA oxidase (AOX), multifunctional enzyme (PH), and beta-actin were quantified using a dot blot RNase protection assay.
Main Results:
- TNF-alpha treatment significantly reduced the mRNA levels of PPAR-alpha, Cat, AOX, and PH in rat liver.
- The protein level of PPAR-alpha was also decreased following TNF-alpha administration.
- In contrast, beta-actin mRNA levels were markedly increased, indicating a selective effect of TNF-alpha.
Conclusions:
- TNF-alpha exhibits selective downregulation of PPAR-alpha and peroxisomal mRNAs in the liver.
- These findings suggest TNF-alpha may perturb lipid metabolism through its effects on PPAR-alpha signaling.
- The selective nature of these changes highlights a specific mechanism of TNF-alpha action in hepatic gene regulation.