Pentraxin 3 regulates neutrophil infiltration to the brain during neuroinflammation.

Ivana Rajkovic,Raymond Wong,Eloise Lemarchand,Emmanuel Pinteaux,Stuart M Allan,Rory Tinker

doi:10.12688/amrcopenres.12875.1

Abstract

Introduction: The acute phase protein pentraxin 3 (PTX3) is known for its anti-inflammatory effects through downregulating neutrophil transmigration during peripheral inflammation. Furthermore, we have previously demonstrated a neuroprotective and neuroreparative effect of PTX3 after cerebral ischaemia. Here we investigated, to our knowledge for the first time, the role of PTX3 in neutrophil transmigration and neurotoxicity following lipopolysaccharide (LPS)-induced cerebral inflammation and cerebral ischaemia. Methods: Neutrophil transmigration through interleukin-1β (IL-1β) activated brain endothelium and neurotoxicity of neutrophils isolated from wild-type (WT) or PTX3 knock-out (KO) mice was assessed in vitro. Primary cortical neuronal death after treatment with transmigrated neutrophils was quantified by lactate dehydrogenase (LDH) assay. Cerebral inflammation or ischemia was induced in WT and PTX3 KO mice via intrastriatal LPS injection or by transient middle cerebral artery occlusion (MCAo) respectively. Subsequent neutrophil infiltration in the brain was assessed by immunohistochemistry and the expression of pro-inflammatory cytokines interleukin-6 (IL-6) and IL-1β by enzyme-linked immunosorbent assay (ELISA). Results: Neutrophils isolated from WT mice after intrastriatal LPS injection transmigrated significantly more through IL-1β activated brain endothelium compared to neutrophils from PTX3 KO mice. Transmigrated WT and PTX3 KO neutrophils were significantly more neurotoxic than corresponding non-transmigrated neutrophils; however, no significant differences in neurotoxicity between genotypes were observed. PTX3 reduced the number of transmigrated neutrophils to the brain after intrastriatal LPS injection. Furthermore, PTX3 KO mice showed significantly increased levels of neutrophils in the brain after LPS administration or in the ischaemic hemisphere after MCAo, compared to WT mice. Conclusion: Our study shows that PTX3 regulates neutrophil transmigration in the CNS during neuroinflammation, demonstrating the potential of PTX3 as an effective therapeutic target in neuroinflammatory conditions.

Highlights

The acute phase protein pentraxin 3 (PTX3) is known for its anti-inflammatory effects through downregulating neutrophil transmigration during peripheral inflammation
The acute-phase protein PTX3 has been extensively described as a biomarker in major inflammatory disorders such as stroke, cancer or cardiovascular disease (Bonacina et al, 2013; Ryu et al, 2012; Shindo et al, 2014), and several studies indicate that PTX3 regulates neutrophil transmigration during peripheral inflammation via interaction with P-selectin (Deban et al, 2010; Salio et al, 2008)
We demonstrate that neurotoxicity upon neutrophil transmigration is totally independent of neutrophil-derived PTX3

Summary

Introduction

The acute phase protein pentraxin 3 (PTX3) is known for its anti-inflammatory effects through downregulating neutrophil transmigration during peripheral inflammation. Methods: Neutrophil transmigration through interleukin-1β (IL-1β) activated brain endothelium and neurotoxicity of neutrophils isolated from wild-type (WT) or PTX3 knock-out (KO) mice was assessed in vitro. Results: Neutrophils isolated from WT mice after intrastriatal LPS injection transmigrated significantly more through IL-1β activated brain endothelium compared to neutrophils from PTX3 KO mice. PTX3 reduced the number of transmigrated neutrophils to the brain after intrastriatal LPS injection. PTX3 KO mice showed significantly increased levels of neutrophils in the brain after LPS administration or in the ischaemic hemisphere after MCAo, compared to WT mice. PTX3 knock-out (KO) mice demonstrated greater myocardial injury, which was associated with greater neutrophil infiltration when compared to wild type (WT) mice (Salio et al, 2008). A previous published study indicated that PTX3 is stored in neutrophil granules, localised in neutrophil extracellular traps (NETs) (Jaillon et al, 2007), which could contribute to the regulation of neutrophil infiltration

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