In vitro sepsis upregulates Nociceptin/Orphanin FQ receptor expression and function on human T- but not B-cells.

Background and Purpose

In animal models of sepsis, increased activation of the Nociceptin/Orphanin FQ (N/OFQ) receptor NOP is associated with mortality and NOP antagonists improved survival. We have explored the role of the N/OFQ-NOP system in freshly isolated volunteer human B- and T-cells incubated with lipopolysaccharide (LPS) and peptidoglycan G (PepG) as a model of in vitro sepsis.

Experimental Approach

B- and T-cell NOP expression was measured using the NOP fluorescent probe N/OFQATTO594, N/OFQ content was measured using immunofluorescence, N/OFQ release was tracked using a CHOhNOPGαiq5 biosensor assay, NOP function was measured using transwell migration and cytokine/chemokine release using a 25plex assay format. Cells were challenged with LPS/PepG.

Key Results

CD19 positive B-cells bound N/OFQATTO594; they also contain N/OFQ. Stimulation with CXCL13/IL-4 increased N/OFQ release. N/OFQ trended to reduced migration to CXCL13/IL4. Surface expression was unaffected by LPS/PepG but this treatment increased GM-CSF release in an N/OFQ sensitive manner. CD3 positive T-cells did not bind N/OFQATTO594; they did contain N/OFQ. Stimulation with CXCL12/IL-6 increased N/OFQ release. When incubated with LPS/PepG NOP surface expression was induced leading to N/OFQATTO594 binding. In LPS/PepG treated cells N/OFQ reduced migration to CXCL12/IL6. LPS/PepG increased GM-CSF release in an N/OFQ sensitive manner.

Conclusion and Implications

We suggest both a constitutive and sepsis-inducible N/OFQ-NOP receptor autocrine regulation of B- and T-cell function respectively. These NOP receptors variably inhibit migration and reduce GM-CSF release. These data provide mechanistic insights to the detrimental role for increased N/OFQ signalling in sepsis and suggest a potential role for NOP antagonists as treatments.