Background/Purpose: Neutrophils and neutrophil death (NETosis) have a role in the pathogenesis of SLE. A neutrophil gene signature (NGS) exists in SLE, although its association with the clinical phenotype is unknown. We explored the association of a neutrophil gene signature comprised of genes significantly upregulated in low-density granulocytes (LDGs) with both future disease activity and long-term outcomes.

Methods:

292 SLE patients (91.1% female; 58.9% Caucasian, 33.9% African-American, mean age (SD) 46.5 (±11.9) years were included.  Gene expression levels were assessed in peripheral blood RNA samples using microarray (Affymetrix). The LDG-associated gene signature was comprised of 8 genes reported in the literature to be significantly upregulated in LDGs relative to normal-density neutrophils. The LDG–associated NGS “score” was calculated for each patient based on the geometric mean of the expression levels (chip signal intensity) of the 8 genes in the signature. Three groups based on NGS scores were compared. GEE models (to account for repeated measures) were used.

 

Results:

The mean LDG-associated NGS was somewhat lower in African Americans (mean=5.4) relative to Caucasians (mean=5.8) and other ethnicities (mean=6.4), p=0.0087.  It was also somewhat higher in men than women (mean 6.2 vs. 5.7, p=0.067). The NGS was strongly associated with global disease activity over the next year, serologies (anti-dsDNA and low complement), and future organ-specific activity (renal, cutaneous and arthritis) (Table 1). An elevated LDG-associated NGS was also strongly associated with a history of poor outcomes (myocardial infarction, deep venous thrombosis, diabetes, malignancy).

Table 1. %visits with various types of disease activity over 1 year, by LDG-associated NGS tertiles

 

Variable	1st Tertile Neutrophil Patient n=97 visit n=406	2nd Tertile Neutrophil Patient n=98 visit n=395	3rd Tertile Neutrophil  Patient n=97 visit n=409	P-value	Adjusted P-value for Ethnicity	Adjusted P-value for Trend
Physician Global Assessment >1	13%	17%	24%	0.057	0.045	0.0064
SLEDAI ≥2	48%	53%	62%	0.054	0.0034	0.0010
Urine Protein/Creatinine Ratio (≥0.5)	8%	7%	14%	0.16	0.11	0.037
Anti-dsDNA ≥ 10	9%	23%	32%	<0.0001	<0.0001	0.0006
C3 <79	9%	7%	19%	0.014	0.022	0.0012
C4 <12	9%	7%	16%	0.088	0.14	0.0046
ESR >20	41%	51%	59%	0.014	0.0007	0.0005
Any SLEDAI Renal	5%	6%	11%	0.073	0.052	0.0038
SLEDAI Arthritis	1%	2%	6%	0.020	0.020	0.0031
Any SLEDAI Skin	25%	30%	30%	0.57	0.030	0.016
Any SLEDAI Heme	6%	4%	4%	0.69	0.67	0.31

Table 2. Association between SLICC/ACR Damage Index and the LDG-associated NGS in SLE

 

Variable	Low Neutrophil (<5) (%, N=107)	Med Neutrophil (5-6) (%, N=92)	High Neutrophil (>6) (%, N=93)	Adjusted P-value for Ethnicity
Myocardial Infarction	0.0	6.5	5.4	0.0056
Deep Venous Thrombosis	1.9	0.0	6.5	0.016
Diabetes	4.7	6.5	14.1	0.024
Malignancy	2.8	12.1	15.2	0.0043

Conclusion: The LDG-associated NGS associates with SLE clinical and serologic activity over the next year. This is the first gene signature to be associated with myocardial infarction, deep venous thrombosis and malignancy. The NGS may be a promising biomarker of disease activity. Given that atherosclerotic disease is the major cause of death in late SLE, this gene signature may be the “missing link” in understanding how SLE accelerates atherosclerosis.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/association-of-a-neutrophil-gene-signature-comprised-of-low-density-granulocyte-ldg-enriched-genes-with-both-future-systemic-lupus-erythematosus-disease-activity-and-poor-longterm-outcomes/