Infections are a major contributor to lupus disease. Uropathogenic E. coli (UPEC) is responsible for the majority of urinary tract infections in both healthy individuals and lupus patients. We have previously demonstrated that bacterial amyloid curli complexes of curli/DNA, produced by E.coli, can accelerate disease in mouse models of lupus. Moreover we have extended these findings to human lupus and demonstrate that curli/DNA complexes mimic lupus autoantigens and that patients with chronic bacteriuria and high levels of anti-curli/DNA have higher levels of anti-dsDNA, more flares and a proinflammatory profile. These findings suggest that curli/DNA complexes and subclinical chronic urinary bacterial infections might be a trigger and a propagator of autoimmunity via activation of the innate and adaptive immune system. Based on our previous results, we hypothesize that exposure to UPEC containing curli/eDNA complexes could also activate neutrophils, the first responders to bacterial infections, and specifically via generation of neutrophil extracellular traps (NETs), a fundamental mechanism to clear bacteria and a recently appreciated pathogenic mechanism in lupus. Neutrophil extracellular traps (NETs) are part of the innate immune system and are pathogenic in SLE. We therefore investigated 56 lupus patients who met at least 4 SLICC criteria. Results were compared to 20 age, sex, and race matched healthy controls. We found that curli/eDNA induced more NETs in SLE PMNs compared to healthy controls. In SLE, patients who were high inducers of NETs triggered by curli/eDNA complexes were also a high inducer of NETs triggered by LPS and PMA. Interestingly, patients who were anti- dsDNA positive made more NETs in response to curli/eDNA complexes. Moreover, we found patients who are anti-dsDNA positive responded highly to curli/eDNA complexes and LPS. We did not observe this in patients who were anti-dsDNA negative. Mechanistically, we found that curli/eDNA induce NETs via NADPH oxidase. Finally, we found patients who had bacteriuria had a higher amount of NET production in response to curli/eDNA complexes and PMA compared to patients with no bacteriuria. We conclude
1) that lupus PMNs are in a chronic inflammatory state. And 2) that curli/eDNA complexes can activate neutrophils and exposure to UPECs could be a mechanism to sustain autoantigens in the form of neutrophil extracellular traps.
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