Induction of lipoprotein lipase gene expression in Chlamydia pneumoniae-infected macrophages is dependent on Ca2+ signaling events
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A. A. Azenabor
Abstract
Unregulated uptake of low density lipoprotein (LDL) in macrophages is the hallmark of early atherogenic lesions, and Chlamydia pneumoniae infection of macrophages induces this process by an unknown mechanism. It was therefore aimed in this study to investigate (i) the role of C. pneumoniae in macrophage expression of the lipoprotein lipase (LpL) gene, (ii) the probable role of Ca[2+] influx signals and (iii) the effect of the process on LDL uptake. Lipoprotein lipase mRNA expression and LpL activity in infected RAW-264.7 cells were significantly upregulated. A biphasic Ca[2+] influx signal was observed in infected cells with a moderate influx (303 nM Ca[2+]) favoring optimal LpL gene expression. Also, the antagonists of Ltype Ca[2+] channel in macrophages significantly downregulated LpL gene expression and the biomolecular content of C. pneumoniae responsible for the observed events was in part found to be Chlamydia lipopolysaccharide (cLPS). Investigations aimed at determining the specific relevance of Ca[2+]dependent lipoprotein lipase gene expression in C. pneumoniae-infected macrophages showed that the condition caused enhanced uptake of LDL which was abrogated by Calphostin-C-mediated downregulation of LpL. This discovery of a specialized Ca[2+] influx signal-mediated LpL upregulation in C. pneumoniae-infected macrophages provides a mechanistic insight into early events involving C. pneumoniae in macrophage foam cell formation resulting from LDL uptake.
Copyright © 2004 by Walter de Gruyter GmbH & Co. KG
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Articles in the same Issue
- The chemistry of nitrosative stress induced by nitric oxide and reactive nitrogen oxide species. Putting perspective on stressful biological situations
- Til cell death do us part: nitric oxide and mechanisms of hepatotoxicity
- Singlet oxygen-mediated damage to cellular DNA determined by the comet assay associated with DNA repair enzymes
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- Structural destabilization of the recombinant thermophilic TthL11 ribosomal protein by a single amino acid substitution
- Relevance of the kinetic equilibrium of forces to the control of the cell cycle by Ras proteins
- N-linked glycosylation of the human bradykinin B2 receptor is required for optimal cell-surface expression and coupling
- Identification of sialic acids on Leishmania donovani amastigotes
- Induction of lipoprotein lipase gene expression in Chlamydia pneumoniae-infected macrophages is dependent on Ca2+ signaling events
- Induction of MMP-10 and MMP-1 in a squamous cell carcinoma cell line by ultraviolet radiation
- Monitoring human parvovirus B19 virus-like particles and antibody complexes in solution by fluorescence correlation spectroscopy
- In vitro folding and characterization of the p53 DNA binding domain
