Circulating neutrophil extracellular trap remnants as a biomarker to predict outcomes in lupus nephritis

Abstract

Objective: To determine if the serum levels of neutrophil extracellular trap (NET) remnants (Elastase-DNA and HMGB1-DNA complexes) at the time of a lupus nephritis (LN) flare predict renal outcomes in the following 24 months.

Methods: This was a retrospective study performed in prospectively followed cohorts. The study included two cohorts: an exploratory cohort to assess the association between NET remnant levels and the presence of active LN, and a separate LN cohort to determine the utility of NET remnants to predict renal outcomes over the subsequent 24 months.

Results: Ninety-two individuals were included in the exploratory cohort (49 active systemic lupus erythematosus (SLE), 23 inactive SLE and 20 healthy controls (HC)). NET remnants were significantly higher in patients with SLE patients compared with HC (p<0.0001 for both complexes) and those with active LN (36%) had significantly higher levels of NET remnants compared with active SLE without LN (Elastase-DNA: p=0.03; HMGB1-DNA: p=0.02). The LN cohort included 109 active LN patients. Patients with proliferative LN had significantly higher levels of NET remnants than non-proliferative LN (Elastase-DNA: p<0.0001; HMGB1-DNA: p=0.0003). Patients with higher baseline levels of NET remnants had higher odds of not achieving complete remission (Elastase-DNA: OR 2.34, p=0.007; HMGB1-DNA: OR 2.61, p=0.009) and of progressing to severe renal impairment (Elastase-DNA: OR 2.84, p=0.006; HMGB1-DNA: OR 2.04, p=0.02) at 24 months after the flare.

Conclusions: Elastase-DNA and HMGB1-DNA complexes predict renal outcomes, suggesting they could be used to identify patients requiring more aggressive therapy at flare onset.

Keywords: lupus erythematosus, systemic; lupus nephritis; outcome assessment, health care.

Figure 1

NET remnant levels in patients with SLE and HC. Comparison of NET remnant levels between (A) active SLE (n=49), inactive SLE (n=23) and HC (n=20); (B) active SLE patients stratified for the presence (n=18) or absence of active LN (n=31); (C) proliferative (n=7) and non-proliferative LN (n=6) in the exploratory cohort. (D) Correlation between the levels of Elastase-DNA and HMGB1-DNA in the exploratory cohort. (E) Comparison of NET remnant levels between proliferative (n=62) and non-proliferative LN (n=23) in the LN cohort. For all graphs, the symbols represent the determination from a single individual, columns the median and the bars IQR. The p values for all comparisons between groups are shown and were calculated as outlined in the Methods. HC, healthy control; LN, lupus nephritis; NET, neutrophil extracellular trap.

Figure 2

Linear relationship between the amount of NET remnants and decline in kidney function 24 months after the LN flare. Regression analyses were adjusted for ethnicity, adherence to treatment, serum creatinine at the time of the flare, history of a prior LN flare, immunosuppressive therapy received in the prior 3 months to the sample collection and the time in months from the sample collection to the NET remnants quantification. eGFR, estimated glomerular filtration rate; LN, lupus nephritis; NET, neutrophil extracellular trap.