Abstract
Microvascular inflammation occurs during sepsis and the endogenous opioid-like peptide nociceptin/orphanin FQ (N/OFQ) is known to regulate inflammation. This study aimed to determine the inflammatory role of N/OFQ and its receptor NOP (ORL1) within the microcirculation, along with anti-inflammatory effects of the NOP antagonist UFP-101 (University of Ferrara Peptide-101) in an animal model of sepsis (endotoxemia).Male Wistar rats (220 to 300 g) were administered lipopolysaccharide (LPS) for 24 h (-24 h, 1 mg kg-1; -2 h, 1 mg kg-1 i.v., tail vein). They were then either anesthetised for observation of the mesenteric microcirculation using fluorescent in vivo microscopy, or isolated arterioles (~200 µm) were studied in vitro with pressure myography.200 nM kg-1 fluorescently labelled N/OFQ (FITC-N/OFQ, i.a., mesenteric artery) bound to specific sites on the microvascular endothelium in vivo, indicating sparse distribution of NOP receptors. In vitro, arterioles (~200 µm) dilated to intraluminal N/OFQ (10-5M) (32.6 + 8.4%) and this response was exaggerated with LPS (62.0 +7.9%, p=0.031). In vivo, LPS induced macromolecular leak of FITC-BSA (0.02 g kg-1 i.v.) (LPS: 95.3 (86.7 to 97.9)%, p=0.043) from post-capillary venules (<40 µm) and increased leukocyte rolling as endotoxemia progressed (p=0.027), both being reduced by 150 nmol kg-1 UFP-101 (i.v., jugular vein).Firstly, the rat mesenteric microcirculation expresses NOP receptors and secondly, NOP function (ability to induce dilation) is enhanced with LPS. UFP-101 also reduced microvascular inflammation to endotoxemia in vivo. Hence inhibition of the microvascular N/OFQ-NOP pathway may have therapeutic potential during sepsis and warrants further investigation.
Highlights
The presence of bacteria in the bloodstream, or sepsis, results in generalised inflammation of blood vessels, hypotension and hypovolemia, which together cause tissue damage and poor perfusion of organs, potentially resulting in multiple organ failure
Nociceptin/orphanin FQ (N/OFQ) is an opioid-like peptide and an endogenous ligand for the NOP receptor, which is coupled to the Gi/Go signalling pathway [2]
As anticipated the high affinity binding of Fluoroscein isothiocyanate (FITC)-N/OFQ resulted in a high potency stimulation of the binding of GTPγ[35S] to membranes prepared from cells expressing NOP (Figure 1B)
Summary
The presence of bacteria in the bloodstream, or sepsis, results in generalised inflammation of blood vessels, hypotension and hypovolemia, which together cause tissue damage and poor perfusion of organs, potentially resulting in multiple organ failure. NOP is expressed on aortic endothelium [3], and following intravenous (i.v.) and intracerebroventricular (i.c.v.) administration, N/OFQ caused both hypotension and bradycardia [4,5,6]. N/OFQ increased aortic blood flow and induced dilation of large blood vessels >200 μm [4,7]. Within smaller blood vessels (15 to 40 μm) N/OFQ induces dilation, along with inflammatory responses such as increased permeability and leukocyte-endothelial interactions within postcapillary venules [9]. We labelled N/OFQ with a fluorescent marker (fluoroscein isothiocyanate, FITC) to produce FITC-N/ OFQ, which could be injected locally at high concentrations to identify the distribution of NOP in small vessels
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
