No effect of ablation of surfactant protein-D on acute cerebral infarction in mice.

Kate L Lambertsen,Bjarne W Kristensen,Jan Stenvang,Bettina H Clausen,Michael Meldgaard,Bente Finsen,Pernille B Hansen,Grith L Sorensen,Kamilla Østergaard,Stine B Thorsen,Søren Hansen

doi:10.1186/1742-2094-11-123

Abstract

BackgroundCrosstalk between the immune system in the brain and the periphery may contribute to the long-term outcome both in experimental and clinical stroke. Although, the immune defense collectin surfactant protein-D (SP-D) is best known for its role in pulmonary innate immunity, SP-D is also known to be involved in extrapulmonary modulation of inflammation in mice. We investigated whether SP-D affected cerebral ischemic infarction and ischemia-induced inflammatory responses in mice.MethodsThe effect of SP-D was studied by comparing the size of ischemic infarction and the inflammatory and astroglial responses in SP-D knock out (KO) and wild type (WT) mice subjected to permanent middle cerebral artery occlusion. SP-D mRNA production was assessed in isolated cerebral arteries and in the whole brain by PCR, and SP-D protein in normal appearing and ischemic human brain by immunohistochemistry. Changes in plasma SP-D and TNF were assessed by ELISA and proximity ligation assay, respectively.ResultsInfarct volumetric analysis showed that ablation of SP-D had no effect on ischemic infarction one and five days after induction of ischemia. Further, ablation of SP-D had no effect on the ischemia-induced increase in TNF mRNA production one day after induction of ischemia; however the TNF response to the ischemic insult was affected at five days. SP-D mRNA was not detected in parenchymal brain cells in either naïve mice or in mice subjected to focal cerebral ischemia. However, SP-D mRNA was detected in middle cerebral artery cells in WT mice and SP-D protein in vascular cells both in normal appearing and ischemic human brain tissue. Measurements of the levels of SP-D and TNF in plasma in mice suggested that levels were unaffected by the ischemic insult. Microglial-leukocyte and astroglial responses were comparable in SP-D KO and WT mice.ConclusionsSP-D synthesis in middle cerebral artery cells is consistent with SP-D conceivably leaking into the infarcted area and affecting local cytokine production. However, there was no SP-D synthesis in parenchymal brain cells and ablation of SP-D had no effect on ischemic cerebral infarction.

Highlights

Surfactant protein-D (SP-D) is a C-type collectin mediating various effector mechanisms, such as opsonization of pathogenic microorganisms and cellular debris, chemotaxis of phagocytes [1], activation of phagocytosis [2,3] and modulation of toll-like receptor (TLR) activity [4,5]
Focal cerebral ischemia induced by permanent middle cerebral artery occlusion (pMCAO) caused a unilateral cortical infarct affecting the frontal and parietal cortices in both surfactant protein-D (SP-D) knock out (KO) and wild type (WT) mice (Figure 1A)
When performing direct infarct volume analysis, we found similar infarct volumes in SP-D KO (21.12 mm3 ± 10.89 mm3, n = 10) and WT (25.11 mm3 ± 10.64 mm3, n = 8) mice 1 day after pMCAO (P = 0.45, Figure 1B)

Summary

Introduction

Surfactant protein-D (SP-D) is a C-type collectin mediating various effector mechanisms, such as opsonization of pathogenic microorganisms and cellular debris, chemotaxis of phagocytes [1], activation of phagocytosis [2,3] and modulation of toll-like receptor (TLR) activity [4,5]. Studies of experimental and clinical stroke indicate that the complement system contributes to ischemic injury [13,14,15]. The collectin mannose-binding lectin (MBL) has been shown to play a central pathogenic role in ischemic injury through deposition and complement activation on ischemic endothelium [16,17,18]. Plasma proteins leak into the ischemic brain both after reperfusion-ischemia, and permanent focal cerebral ischemia, where leakage takes place through collaterals in the peri-infarct. We hypothesized that SP-D might leak into the ischemic area either from the circulation or from the deranged endothelium and reduce infarction after experimental stroke in mice. We investigated whether SP-D affected cerebral ischemic infarction and ischemia-induced inflammatory responses in mice

Methods

Results

Conclusion