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Murine CD14 gene expression in vivo: extramyeloid synthesis and regulation by lipopolysaccharide
C Fearns1, V V Kravchenko, R J Ulevitch
1Department of Vascular Biology, Scripps Research Institute, La Jolla, California 92037.
Abstract:
A murine model system was used to study the distribution and regulation of CD14 gene expression in vivo. Western blot analysis failed to detect CD14 in plasma from untreated CB6 (BALB/c x C57Bl6) mice, but showed markedly increased levels of CD14 in plasma from mice treated with lipopolysaccharide (LPS). Plasma levels of CD14 increased in a time- and dose-dependent manner, reaching a maximum between 8 and 16 h. Northern blot analysis of total RNA extracted from mouse tissues revealed low, but significant, levels of CD14 mRNA in many tissues of untreated animals with the highest levels in uterus, adipose tissue, and lung. After intraperitoneal injection of LPS, induction of CD14 gene expression was detected in all organs examined with the extent of induction varying between organs. Induction of CD14 mRNA was both time and dose dependent. Maximum induction in the heart and lung was observed 2-4 h after injection of LPS, while liver and kidney showed maximal induction between 8 and 16 h. In situ hybridization showed that CD14 mRNA was expressed in myeloid cells in many tissues, and that expression in these cells was upregulated by LPS. Unexpectedly, CD14 mRNA was also detected in other cells within tissues, including epithelial cells, and expression in these cell types also was upregulated by LPS. Immunochemical analysis revealed that CD14 antigen colocalized to the cytoplasm of cells expressing CD14 mRNA. These studies demonstrate that CD14 gene expression is not restricted to myeloid cells, and that the level of expression of CD14 is influenced by exposure to LPS.
Insights
Lipopolysaccharide (LPS) significantly increases CD14 gene expression in mice, affecting various tissues and cell types beyond myeloid cells. This regulation is time- and dose-dependent, highlighting LPS as a key influence on CD14 levels.
Area of Science:
- Immunology
- Molecular Biology
- Genetics
Background:
- CD14 is a key receptor involved in innate immunity.
- Its expression patterns and regulation in vivo are not fully understood.
Purpose of the Study:
- To investigate the distribution and regulation of CD14 gene expression in a murine model.
- To determine the effect of lipopolysaccharide (LPS) on CD14 expression.
Main Methods:
- Western blot analysis for plasma CD14 protein levels.
- Northern blot analysis for tissue CD14 mRNA expression.
- In situ hybridization and immunochemical analysis for cellular localization.
Main Results:
- Plasma CD14 levels increased significantly after LPS treatment in a time- and dose-dependent manner.
- CD14 mRNA was detected in multiple tissues, with highest basal levels in uterus, adipose tissue, and lung.
- LPS induced CD14 gene expression in all examined organs, with varying kinetics.
- CD14 mRNA and protein were found in myeloid cells, epithelial cells, and other cell types, all upregulated by LPS.
Conclusions:
- CD14 gene expression is not exclusively limited to myeloid cells.
- LPS exposure significantly influences CD14 expression levels in various cell types and tissues.
- These findings expand the understanding of CD14's role in innate immune responses.