Plasma levels of soluble intercellular adhesion molecule-1 as a biomarker for disease severity of patients with community-acquired pneumonia.

BACKGROUND: Community-acquired pneumonia (CAP) is characterized as an acute inflammation of the lung associated with the activation of macrophages and neutrophils. Intercellular adhesion molecule-1 (ICAM-1) is an essential adhesion molecule involved in immune cell recruitment in lung inflammation. We investigated whether ICAM-1 is a useful biomarker for assessing the disease severity of hospitalized adult patients with CAP.

METHODS: Plasma soluble ICAM-1 (sICAM-1) levels were measured in 78 patients with CAP and 69 healthy controls by using a commercial enzyme-linked immunosorbent assay. The pneumonia severity index scores were used to determine CAP severity in patients upon initial hospitalization.

RESULTS: The sICAM-1 and C-reactive protein (CRP) levels decreased significantly in patients with CAP after antibiotic treatment. The plasma concentration of sICAM-1 alone, but not CRP, was correlated with CAP severity according to the pneumonia severity index scores (r=0.431, p<0.001). The sICAM-1 levels in patients with CAP with high mortality risk were significantly higher than those in patients with CAP with medium or low mortality risk. Moreover, the sICAM-1 level showed a significant correlation with the length of hospital stay (r=0.488, p<0.001). Mechanistic investigations found that bacterial lipopolysaccharide induced upregulation of ICAM-1 expression through the c-Jun N-terminal kinase pathway in RAW264.7 macrophages.

CONCLUSIONS: Plasma sICAM-1 levels may play a role in the diagnosis and clinical assessment of CAP severity.