Apolipoprotein E Expression Of Peripheral Blood And Monocyte In Systemic Lupus Erythematosus Patients

Objective To detect apolipoprotein E (apoE)mRNA expression inperipheral blood monocytes , apoE protein in blood and evaluate the role of apoE in SLE.Methods A total of 47 SLE patients and 14 healthy subjects were enrolled.According to clinical characteristics, SLE patients were classified into 2 groups: lupus nephritis (LN) and SLE without LN. Twelve patients underwent renal biopsy, among them, there were 7 patients who suffered from diffuse LN(International Society of Nephrology/Renal Pathology Society, 2003, Class IV LN) and 5 with mesangial proliferative LN(class II LN). ApoE mRNA in peripheral blood monocyte was measured by reverse transcription polymerase chain reaction, concentration of apoE in blood was examined by enzyme-linked immunosorbent assay (ELISA).Results (1) Nonparameter test showed that concentration of apoE in bloodwas different between LN, SLE without LN patients and normal controls, LN > SLE without LN (P =0.002), LN > normal control (P =0.002). LN patients bore higher level of blood triglyceride (TG) than normal controls (P=0.000), and so do SLE without LN patients (P=0.007). When it comes to concentration of total cholesterol (TC), it increased only in LN patients by contrast to normal controls (P=0.019). (2) For all SLE patients, positive correlation appeared between blood apoE level and SLEDAI (r=0. 568, P=0.002) , TG level and SLEDAI (r=0.537, P=0.002) , but not TC level and SLEDAI (P=0.319) . Blood apoE level in SLE also did not correlate with TG and TC concentration(P>0.05 for both) . (3) Patients suffering from LN had higher level of apoE mRNA in monocytes than SLE without LN (P=0.035) and normal controls(P=0.006) , however, distinction did not occur between the latter two groups (P=0.171) . (4) For all SLE cases, factors such as SLEDAI, concentration of serum apoE , TG, TC did not correlate with apoE mRNA level in monocytes (P>0. 05). (5) Median of apoE mRNA abundance was much higher in class IV LN than in any other groups (P <0. 05), and in class II LN, it was also higher when compared to patients from SLE without LN(P=0.020) and normal control group (P=0.004). No difference was found between SLE without LN and normal control group (P=0.171). (6) In view of pathologic findings, seven cases with LN of class IV-G(A) (diffuse global proliferative LN with active lesions) were found, among them, one case which presented normal level of apoE mRNA abundance showed remarkable sclerotic lesions and severe kidney involvement with high activity, while the other six patients with LN of class IV-G(A) displayed no sclerosis but more extensive renal inflammation, as well as apparently higher apoE mRNA content in monocyte. At the same time, five patients with class II LN also showed no sclerotic lesions in their renal tissue, but exhibited moderate increment of apoE mRNA abundance and low degree of mesangial hypercellurity and mesangial matrix expansion.Conclusions (1) Both ApoE and TG in blood may serve as markers of SLEactivity. (2) Serum apoE level rises as LN presents. (3) Up-regulation of apoE mRNA in blood monocyte may be found in some classes of LN, such as class IV and class II LN. (4) Down-regulation of apoE mRNA in blood monocyte may relate to sclerotic lesions in kidney, while increment of apoE mRNA in blood monocyte may associate with active renal disease.