P2X7 Receptor Expression in Patients With Serositis Related to Systemic Lupus Erythematosus

Abstract

Introduction: P2X7R is an extracellular ATP-gated receptor involved in inflammatory and autoimmune processes mainly acting through NLPR3-inflammasome activation and IL-1β release, also implicated in lymphocyte proliferation and cellular apoptosis. Several observations from animal models and patients’ studies highlight a possible link between P2X7R-NLRP3 axis and Systemic Lupus Erythematosus (SLE) pathogenesis. The P2X7R-inflammasome axis in addition to the direct production of IL-1β and IL-18, indirectly mediates the release of other cytokines implicated in the pathogenesis of SLE, such as IL-6. The aim of this study was to investigate the role of P2X7R and NLRP3-inflammasome in SLE. Methods: Forty-eight SLE patients, 16 with (SLE-S) and 32 without (SLE-NS) history of serositis, and 20 healthy control (HC) subjects were enrolled. Demographic, clinical, and therapeutic data were collected. IL-1β and IL-6 plasma levels were evaluated by ELISA. Peripheral blood mononuclear cells (PBMCs) were isolated from venous blood by Ficoll gradient sedimentation and employed as follows: (1) evaluation of P2X7R and NLRP3 expression by RT-PCR; (2) determination of P2X7R activity as Benzoyl ATP (BzATP)-induced [Ca 2+ ] i increments using Fura-2-AM fluorescent probe; (3) isolation of monocytes/macrophages and assessment of in vitro IL-1β and IL-6 release following stimulation with lipopolysaccharide (LPS) and BzATP, either separately or in combination. Results: Plasma IL-1β levels were unmodified in SLE respect to HC whereas IL-6 levels were higher in SLE than in HC, resulting significantly increased in SLE-S. Macrophages isolated from SLE patients released lower quantities of IL-1β after stimulation with BzATP, whereas IL-6 release was significantly augmented in SLE-NS respect to both HC and SLE-S after all types of stimulation. The [Ca 2+ ]i increase following BzATP stimulation was significantly lower in PBMCs from SLE patients than in PBMCs from HC. RT-PCR showed significantly reduced P2X7R and significantly augmented NLRP3 expression in PBMCs from SLE patients. Conclusion: Our data indicate reduced P2X7R expression and function in SLE patients compared with HC and, conversely, increased IL-6 signaling. The possible consequences of reduced P2X7R, mainly on cytokines network deregulation and lymphocyte proliferation, will be further investigated as well as the role of IL-6 as a possible therapeutic target especially in lupus serositis.

Metabolic determinants of lupus pathogenesis

“…Interestingly, the generation on foreign antigen‐specific Tfh cells was not impaired by P2X7 deficiency. In accordance with these findings in mice, P2X7 expression and function are reduced in the PBMCs of lupus patients as compared to HCs . These results suggest that P2X7 may provide another metabolic therapeutic target to reduce the number of pathogenic cell types or redirect their function in lupus.…”

“…In accordance with these findings in mice, P2X7 expression and function are reduced in the PBMCs of lupus patients as compared to HCs. 232 These results suggest that P2X7 may provide another metabolic therapeutic target to reduce the number of pathogenic cell types or redirect their function in lupus. These results also support the hypothesis that autoreactive Tfh cells have unique metabolic requirements, which are fueled by glucose (see above), and dampened by extracellular ATP.…”

Ectonucleotidases in Acute and Chronic Inflammation

“…Down regulation of ADA activity is associated with increased anti-inflammatory Th2 response, whereas its up-regulation may promote Th1-dependent pro-inflammatory response. Compared to healthy control subjects, SLE patients present significantly higher levels of IL-6, IL-17, IL-12, and IL-23 ( Talaat et al, 2015 ; Furini et al, 2019 ), which correlate positively and significantly with SLE disease activity index (SLEDAI) score ( Talaat et al, 2015 ). Treg cells from SLE patients express lower levels of NTPDase1/CD39 than Tregs from control subjects, and nearly absent adenosine-dependent Treg-mediated suppression.…”

P2X7 Receptor (P2X7R) of Microglia Mediates Neuroinflammation by Regulating (NOD)-Like Receptor Protein 3 (NLRP3) Inflammasome-Dependent Inflammation After Spinal Cord Injury

“…No study has specifically explored the NLRP3/P2X7R interaction in neuroinflammation after SCI [ 15 , 16 ]. It is important to know that the role that P2X7R exhibits depends both on the degree of ATP activation (depending on the concentration and duration of stimulation) and on the expression of the receptor itself, which may vary between different cells [ 17 ]. Therefore, in this study, we set out to assess whether spinal cord P2X7R on MG regulates NLRP3 inflammasome to mediate neuroinflammation after SCI.…”