Plasma levels of soluble Axl correlate with severity of community-acquired pneumonia

Abstract

Abstract. The aim of this study was to examine the plasma level changes of soluble Axl (sAxl) prior to and following treatment with antibiotics in hospitalized adult patients with community-acquired pneumonia (CAP), and to investigate the correlating clinical and laboratory manifestations of CAP with plasma sAxl levels. Blood samples were obtained from 61 adult CAP patients (prior to and following treatment with antibiotics) and 60 healthy controls in order to measure the plasma concentrations of sAxl using the enzyme-linked immunosorbent assay. The plasma-soluble Axl concentration level was markedly elevated in patients with CAP prior to treatment, compared with the controls, and decreased markedly following treatment. The levels of white blood cells, neutrophils, and C-reactive protein decreased markedly following treatment with antibiotics and did not correlate with the concentration level of sAxl. However, the plasma concentration of sAxl correlated with the severity of CAP with the pneumonia severity index score (r=0.350, P=0.006, n=61), the CURB-65 score (r=0.281, P=0.028, n=61) and the acute physiology and chronic health evaluation II score (r=0.313, P=0.014, n=61). In conclusion, plasma sAxl may be involved in the clinical assessment of the severity of CAP, which may guide the development of treatment strategies and predict the clinical outcome.

Diversification of TAM receptor tyrosine kinase function

“…We found that this cleavage, which generates a ‘soluble Axl’ (sAxl), also occurred when Axl was activated by cross-linking antibodies. Elevated sAxl in blood has recently been reported to mark multiple human disease and trauma states, including aortic aneurysm 37 , lupus flares 38 , pneumonia infection 39 , preeclampsia 40 , coronary bypass 41 , and insulin resistance 42 . We suggest that Axl cleavage, and the generation of a sAxl-GAS-6 complex, is triggered by the inflammation-induced exposure of PtdSer in these settings, and may be a broadly useful diagnostic biomarker for inflammation in human disease.…”

Differential TAM receptor–ligand–phospholipid interactions delimit differential TAM bioactivities

“…Elevated blood levels of soluble Axl have recently been reported to mark a variety of human disease and trauma states, including aortic aneurysm ( Ekman et al, 2010b ), lupus flares ( Zhu et al, 2014 ), pneumonia infection ( Ko et al, 2014 ), preeclampsia ( Liu et al, 2014 ), coronary bypass ( Lee et al, 2013 ), obesity and insulin resistance ( Hsiao et al, 2013 ), and limb ischemia ( Ekman et al, 2010a ). We suggest that the generation of a soluble Axl–Gas6 complex is triggered by the induced cellular exposure of PtdSer in many of these settings.…”

Diminished airway macrophage expression of the Axl receptor tyrosine kinase is associated with defective efferocytosis in asthma

“…The extracellular domain of Axl is cleaved upon engagement, and alterations in soluble Axl (sAxl) levels have been reported in inflammatory conditions. 7 We compared the levels of sAxl in serum and sputum from HDs and patients with moderate-to-severe asthma (British Thoracic Society steps 3-5). Although no difference in sAxl was detected in serum samples between the 2 groups (Fig 2, A), the levels of sAxl in sputum samples were significantly elevated in patients with asthma compared with controls (Fig 2, B), suggesting increased Axl shedding at the site of inflammation.…”