Development of a Novel Immunoassay for the Assessment of Plasma Gas6 Concentrations and Their Variation with Hormonal Status

Abstract

Background: Gas6 is a vitamin K-dependent antiapoptotic protein that has been implicated in cardiovascular pathophysiology. We report the development and validation of an ELISA for Gas6, and the variation of plasma Gas6 with hormonal status in a study designed to evaluate the effect of oral contraception on plasma markers. Methods: After validation of the main stages of the ELISA assay, we measured plasma Gas6 concentrations in 94 male and 88 female healthy volunteers ages 18 to 38 years. Forty-five of the women then received an oral contraceptive, which contained ethinylestradiol and levonorgestrel, for 3 months before a new measurement was performed at the same time point in their menstrual cycles. Results: Interassay imprecision was 5.8%-11.8%, and the detection limit was 5.9 g/L. Mean Gas6 plasma concentrations were significantly lower in men (52.0 g/L) than in women not receiving oral contraceptives (63.8 g/L, P <0.001). In the women who received oral contraceptives, Gas6 concentrations decreased after 3 months of therapy from 63.6 g/L to 51.9 g/L (P <0.001). Conclusions: We have developed a simple and reproducible ELISA assay for measuring plasma Gas6 con-

Elevated plasma gas6 levels are associated with venous thromboembolic disease

“…The mean gas6 concentration in the healthy volunteers in our study is 35 ng/ml with a sensitivity of detection up to 81 ng/ml, whereas in the Balogh et al study, the mean concentration was 18 ng/ml with a sensitivity up to 62.5 ng/ml. It should be noted however that the measurement of gas6 levels is quite variable, some studies showing a mean level as high as 50 ng/ml and others as low as 50 pg/ml, the variation possibly due to the lot of antibody used for the ELISA [23][24][25][26][27]. Moreover, in both our study and that of Balogh et al, patients taking warfarin had lower levels of gas6 [11].…”

Malignant cells fuel tumor growth by educating infiltrating leukocytes to produce the mitogen Gas6

“…Human recombinant Gas6 was produced as described. 36 As already described, human Gas6 binds to murine Axl. 8 Proliferation was measured by the use of the Cell Proliferation Reagent WST-1 (Roche).…”

Plasma concentrations of growth arrest specific protein 6 and the soluble form of its tyrosine kinase receptor Axl as markers of large abdominal aortic aneurysms

“…The Gas6 plasma concentrations have been reported to be decreased by Warfarin 24 and oral contraceptives 26 whereas increased levels have been found in patients suffering from sepsis 33,34 . To our knowledge, the plasma concentrations of sAxl have not previously been measured in patients with different diseases.…”

“…Gas6 is expressed in many cell types, including endothelial cells, vascular smooth muscle cells and fibroblasts 11 . However, expression is low in the liver, explaining the low concentration of Gas6 (approximately 0.2 nM) in plasma [24][25][26] . The affinity between Gas6 and the Axl receptor is in the subnanomolar range suggesting that Gas6 and sAxl in plasma may form a complex 27,28 .…”