Cytokine production in lipopolysaccharide-exposed rat lung pericytes

Vessels of the pulmonary microvasculature are composed of two cell types: endothelial cells and pericytes. Pericytes are crucial to the development of capillary leak and pulmonary edema seen in acute respiratory distress syndrome (ARDS). Pericytes express toll-like receptor-4, and is upregulated in response to lipopolysaccharide (LPS). The objective of this study was to evaluate secretory cytokine production by rat microvascular pericytes. It is our hypothesis that pericytes secrete interleukin (IL)-1B, IL-6, and tumor necrosis factor (TNF)-A in response to LPS.

Rat lung pericytes (RLPs) were isolated and grown either alone or in coculture with rat endothelial cells. Cells from passages 3 to 5 were used and treated with LPS (control, 10 ng/mL, and 100 ng/mL) for varying amounts of time. Immunoblotting and reverse transcriptase polymerase chain reaction (RT-PCR) was used for detection and quantification of NF-kB. Enzyme-linked immunosorbent assay and RT-PCR were used for detection and quantification of cytokines.

The protein and mRNA for NF-kB was detected in RLPs. Additionally, NF-kB mRNA increased with exposure to LPS. The supernatant of RLPs exposed to LPS contained IL-1B, and IL-1B increased in a time- and dose-dependant manner. An increase in mRNA for IL-1B, IL-6, and TNF-A was seen in a dose-dependant fashion. Cocultures produced significantly less IL-1B when exposed to similar concentrations of LPS.

Pericytes contain the machinery necessary, and produce pro-inflammatory cytokines. Cocultures manufacture less IL-1B then pericytes alone, which is similar to previous coculture observations. Pericyte activation and cytokine production may play a role in capillary leak seen in gram-negative sepsis.