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Objective:To investigate factors associated with the concentration of hydroxychloroquine (HCQ) and its metabolites in peripheral blood of patients with systemic lupus erythematosus (SLE) who were receiving long-term oral HCQ treatment.Methods:SLE patients who had been taking HCQ for more than 3 months were recruited. Clinical characteristics, laboratory test results and SLE disease activity index (SLEDAI) scores were examined. The concentrations of HCQ and its metabolites from peripheral blood were measured by high-performance liquid chromatography tandem mass spectrometry (HPLC-MS/MS). Student's-test and Nonpara-metric tests were used to compare quantitative data, Chi-square and Fisher's exact tests were used to analyze qualitative data. Correlation between the test results was assessed by correlation coefficient. Variables with P values less than 0.05 in univariate analysis were entered into a logistic regression model. Results:In total, 191 SLE patients on long-term HCQ treatment were included in the analysis. Medians of HCQ blood concentrations ([HCQ]), desethylhydroxychloroquine (DHCQ) blood concentrations ([DHCQ]), desethylchloroquine (DCQ) blood concentrations ([DCQ]) and bisdesethylchloroquine (BDCQ) blood concentrations ([BDCQ]) were 523.19 (402.63, 677.88) ng/ml, 291.79 (212.30, 432.51) ng/ml, 49.37 (35.00, 73.05) ng/ml, 21.78(14.37, 52.46) ng/ml respectively. On multivariate analysis, weight-adjusted oral HCQ dose [ OR(95% CI)=1.366 (1.053, 1.772) , P=0.019], the course of hydroxychloroquine [ OR (95% CI) =0.991 (0.984, 0.999), P=0.026], estimated glomerular filtration rate [ OR(95% CI)=0.984 (0.971, 0.997), P=0.014] and platelet count [ OR (95% CI)=1.010 (1.005, 1.015), P<0.001] were associated with [HCQ]. [HCQ], [DCQ], [BDCQ], [BDCQ]/[HCQ] were negatively correlated with estimated glomerular filtration rate (eGFR) ( r=-0.20, P=0.006; r=-0.19, P=0.010; r=-0.26, P<0.001; r=-0.15, P=0.044, respectively) after adjusted for age, course of disease, duration of HCQ treatment and weight adjusted HCQ dosage, [DHCQ]/[HCQ] was negatively correlated with the SLEDAI score ( r=-0.16, P=0.027) when the effects of glucocorticoid was controlled, [BDCQ]/[HCQ] among different renal function levels was statistically significant ( H=12.46, P=0.014). Conclusion:The factors associated with HCQ blood concentrations in SLE patients on long-term oral HCQ treatment are weight-adjusted HCQ dosage, duration of hydroxychloroquine intake and renal function. In addition, [BDCQ] is closely correlated with renal function, [DHCQ] is correlated with SLE disease activity.
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Objective:To investigate the expression and clinical significance of neutrophil myeloperoxidase (MPO) in patients with MPO-antibody associated vasculitis (AAV).Methods:Thirty-six newly diagnosed MPO-AAV patients who were hospitalized in the First Affiliated Hospital, Anhui Medical University from July 2018 to June 2021 were enrolled,and 36 age and sex matched healthy subjects were selected as controls. Neutrophil MPO level was detected by flow cytometry (FCM) and MPO mRNA was tested by real time quantitative polymerase chain reaction (RT-qPCR) in all subjects. Serum complement fragment C5 (C5a) and MPO in both groups and serum MPO-anti-antineutrophilic cytoplasmic antibody(ANCA) in MPO-AAV group were measured by enzyme linked immunosorbent assay (ELISA), while the disease activity was evaluated by Birmingham vasculitis activity score-V3 (BVAS-V3).Results:Compared with the heathy control group, the expression of MPO mRNA in neutrophils, serum MPO and complement C5a in MPO-AAV group were significantly higher[MPO mRNA:30.2±11.5 vs. 1.9±0.6, P<0.001;MPO:(112.0±68.7) IU/L vs. (87.4±22.9) IU/L, P=0.01; C5a:(187.3±90.3) ng/ml vs. (107.3±31.1) ng/ml, P<0.001; respectively], while the mean fluorescence intensity (MFI) of MPO in neutrophils were significantly lower [ 1 343.3±723.4 vs. 2 868.0±1 136.5, P<0.001]. In MPO-AAV group, the expression of neutrophil MPO mRNA was positively correlated with serum MPO-ANCA and MPO levels ( r=0.537, P=0.001 and r=0.358, P=0.032; respectively). Multiple regression analysis suggested that neutrophil MPO mRNA expression was positively correlated with serum MPO-ANCA level ( β=0.695, P=0.006); neutrophil MPO level was negatively correlated with serum MPO-ANCA, MPO and complement C5a levels ( r=-0.335, P=0.046; r=-0.372, P=0.026; r=-0.577, P<0.001; respectively). Further, neutrophil MPO level was negatively correlated with serum complement C5a level ( β=-0.374, P=0.043). BVAS-V3 was positively correlated with MPO mRNA expression in neutrophils, serum MPO-ANCA, MPO and complement C5a ( r=0.598, P<0.001; r=0.599, P<0.001; r=0.537, P=0.001; r=0.415, P=0.012; respectively) and negatively correlated with MPO level in neutrophils ( r=-0.342, P=0.041). In multiple regression analysis it suggested that BVAS-V3 was positively correlated with MPO mRNA expression in neutrophils ( β=0.511, P=0.002). Conclusion:In MPO-AAV patients, MPO synthesis and release in neutrophils are both significantly increased, which might be influenced by serum MPO-ANCA and C5a, respectively. Furthermore, MPO synthesis activity in neutrophils is an independent factor related to disease activity.