Human subjects –From March 2016 to May 2018, 31 patients diagnosed with Gram-positive sepsis, 36 patients with Gram-negative sepsis and 45 healthy individuals were enrolled in the study. Written informed consent was obtained from each subject. Patients with sepsis were diagnosed in accordance with the guidelines on treatment of Chinese severe sepsis/septic shock (2014 version), issued by the Chinese society of Critical Care Medicine. The study was carried out according to the principles of the Declaration of Helsinki and was approved by the medical ethics committee of the Second Affiliated Hospital of Chongqing Medical University. The clinical characteristics of study subjects are demonstrated in Table 1.
Table 1
Clinical characteristics of subjects in this study
| Healthy individuals | Gram-positive sepsis | Gram-negative sepsis |
Number of subjects | 45 | 31 | 36 |
Age (year, ranger) | 22–67 | 15–88 | 18–95 |
(year, mean) | 45.1 | 56.4 | 51.9 |
Sex (male:female) | 22:23 | 21:10 | 24:11 |
NOX 2 (mean ± SD) pg/ml | 781.62 ± 441.53 | 2993.58 ± 821.14 | 2293.77 ± 726.63 |
sCD40L (mean ± SD) ng/ml | 3.93 ± 0.96 | 21.84 ± 6.00 | 20.30 ± 4.98 |
sP-Selectin (mean ± SD) ng/ml | 14.47 ± 4.04 | 56.62 ± 14.71 | 53.16 ± 12.36 |
WBC (mean ± SD) 109/L | 6.19 ± 1.29 | 10.31 ± 4.82 | 10.66 ± 3.86 |
CRP (mean ± SD) mg/L | 6.60 ± 5.81 | 109.39 ± 54.48 | 113.66 ± 43.88 |
IL-6 (mean ± SD) pg/ml | 1.81 ± 0.51 | 21.89 ± 9.24 | 23.68 ± 7.53 |
Complete blood count (CBC) –A Mindray BC6800 Hematology Analyzer (Mindray, Shenzhen, China) was used to perform complete blood cell counts including white cell differentials.
C - reactive protein (CRP) test –An automatic Immunofluorescence Analyzer Jet-iStar 3000 (Joinstar, Hangzhou, China) was employed to quantitatively detect CRP from EDTA-anticoagulated whole blood specimen.
Platelet preparation – Blood samples were drawn and mixed with 3.8% sodium citrate, then processed in a centrifuge for 15 minutes at 180 g to obtain platelet-rich plasma. As described by Violi and his colleagues, only the top 75% of the platelet-rich plasma was collected to avoid leukocyte contamination [15]. Next, to acquire platelet pellets, platelet-rich plasma was centrifuged for 10 minutes at 300g. In this process, acid citrate-dextrose (1:7 v/v) was added to avoid platelet activation. Platelet pellets were suspended in HEPES buffer in presence of albumin, pH 7.35 according to Carnevale et al [16]. Supernatant was collected by centrifugation for 5 minutes at 300 g and stored at -80°C until analysis.
Analysis of NOX2, sCD40L, sP-selectin and IL-6 –Soluble NOX2-derived peptide was measured by an ELISA method as previously described by Pignatelli and his colleagues [Pignatelli et al., 2010]. Here, it should be mentioned that we modified this protocol to evaluate the serum levels of NOX2 in HBV patients [19]. 100 µL of samples or standard were added into each capture antibody-coated well (Anti-NOX2/gp91phox antibody; Abcam, USA) and incubated 2 hours at room temperature. After aspirating and washing each well 3 times, 100 µL of diluted detection antibody-conjugated HRP (Rabbit anti-human IgG H&G antibody; Abcam, USA) was added and incubated 1 hour at room temperature while gentle shaking. Repeating the aspiration/wash of each well, 100 µL of substrate solution was added and incubated at room temperature for 20 minutes. Next, adding 50 µL of stop solution (1 mol/L H2SO4) to each well. The absorbance of the colored solution of NOX2 was measured at 450 nm by using a Multiskan™ FC microplate reader (Thermo Scientific, MA, USA).
Platelet soluble CD40L (sCD40L) and platelet soluble P-selectin (sP-selectin) were analyzed utilizing human sCD40L ELISA kit (Thermo Scientific, MA, USA) and human sP-selectin ELISA kit (Thermo Scientific, MA, USA), according to the manufacturer’s guideline. Serum IL-6 was analyzed utilizing human IL-6 ELISA kit (Multisciences, Hangzhou, China), according to the manufacturer’s guideline. The absorbance of sCD40L, sP-selectin and IL-6 was also read at 450 nm. All samples were run in triplicate and the mean value was used for statistical analysis.
Statistical analysis – Statistics were performed using SPSS software, version 19.0 for windows (SPSS Inc, IL, USA). The biological and clinical characteristics of human subjects were shown as means ± SD (standard deviation). Two groups were compared with a Mann-Whitney test. Spearman’s rank correlation analysis was employed to analyze association between two variables. The significance level was chosen to be P < 0.01.