| Objective To investigate the expression of PAD4 in neutrophils in patients with anti-neutrophil cytoplasmic myeloperoxidase antibody-associated vasculitis(MPO-AAV),and to analyze the relationship between the change and the disease activity.Methods Thirty-nine patients with untreated MPO-AAV(patient group)and thirty-nine healthy volunteers(control group)were involved in this study.Their PAD4 in neutrophils were detected by flow cytometry(FCM),and serum anti-neutrophil cytoplasmic myeloperoxidase antibody(MPO-ANCA)of patient group and C5 a of two groups were measured by ELISA.Their disease activity for every patient were valued by Birmingham vasculitis activity score(BVAS).The results were compared between the two groups,and relationships among the results in patient-group were also analyzed.Results(1)The clinical diagnosis of 39 MPO-AAV patients enrolled in the study was all MPA.The disease duration ranged from 1 to 125(4[1,24])months.The lung and kidney lesions were most common in multiple organ lesions,100%(39/39)and 87.2%(34/39)respectively.Other clinical lesions included 20.5%(8/39)of the nervous system,17.9%(7/39)of arthrosis and muscle,30.8%(12/39)of the cardiac system,15.4%(6/39)of the ear and nose,and 10.3%(4/ 39)of the mucous membrane.In the case group,BVAS scores ranged from 6 to 33(21.0 ± 6.0),renal BVAS scores ranged from 0 to 12(12 [8,12]),and lung BVAS scores ranged from 4 to 6(6 [6,6]).The age of patients in the case group ranged from 22 to 88(67.6 ± 12.7)years old,while that in the healthy control group was from 21 to 81(65.3 ± 10.3)years old.In the case group,there were 23 males and 16 females,while the control group had 22 males and 17 females.There was no significant difference in distribution of the age and sex between the case group and the healthy control group,both of which were comparable(P>0.05).(2)FCM test showed that,to compared with that in control group,the proportions of PAD4 in the Neutrophils and PAD4 MFI in patient group were significantly higher(70.5% ± 10.6% vs 25.9% ± 6.4%,P(27)0.001;32.9 ± 4.5 vs 14.3 ± 4.3,P(27)0.001),also,ELISA test showed the expressions of C5 a in patient group were markedly more intensive(4630.8 ± 1050.1 vs 2879.6 ± 967.5,P(27)0.001).(3)In patient group,the proportion of PAD4 was positively correlated with the level of C5 a,the level of MPO-ANCA,BVAS,and BVAS of kidney(r=0.443,P=0.005;r=0.783,P(27)0.001;r=0.992,P(27)0.001;r=0.508,P=0.001,respectively);meanwhile,PAD4 MFI was also positively correlated with the level of C5 a,the level of MPO-ANCA,BVAS,and BVAS of kidney(r=0.398,P=0.012;r=0.771,P(27)0.001;r=0.897,P(27)0.001;r=0.530,P=0.001,respectively).(4)The level of MPO-ANCA was positively associated with BVAS,and BVAS of kidney(r=0.872,P(27)0.001;r=0.550,P<0.001,respectively).Nevertheless,the expression of C5 a was negative correlated with BVAS of kidney(r=-0.354,P=0.027).Conclusions(1)Neutrophil intracellular PAD4 may increase the level of MPO-ANCA indirectly by promoting the release of NETs from activated neutrophils,leading to aggravation of the disease.Meanwhile,the elevated MPO-ANCA may promote the production of PAD4.(2)Neutrophil intracellular PAD4 Neutrophil intracellular PAD4 may excite the complement alternative pathway to activate more C5 a through activation of neutrophil-derived NETs,whereas C5 a may activate neutrophils through the C5a-C5 a R pathway,thereby promoting the expression of PAD4 in neutrophils.The formation of a vicious cycle between PAD4 in neutrophils and C5 a may be involved in the pathogenesis.(3)Neutrophil-derived PAD4 may release NETs to excite adaptive immunity and innate immunity by activating neutrophils,thereby participating in the pathogenesis and clinical damage of MPO-AAV through the vicious cycle of autoimmune reactions.PAD4 may become a potential clinical therapeutic target.(4)This experimental study supports the pathogenicity of MPO-ANCA for MPO-AAV and the involvement of C5 a in clinical injury. |
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