Surfactant protein a attenuates generalized and localized neuroinflammation in neonatal mice

Abstract

Surfactant protein A (SP-A) has important roles in innate immunity and modulation of pulmonary and extrapulmonary inflammation. Given SP-A has been detected in rat and human brain, we sought to determine if SP-A has a role in modulating inflammation in the neonatal mouse brain. Neonatal wildtype (WT) and SP-A-deficient (SP-A^-/-) mice were subjected to three models of brain inflammation: systemic sepsis, intraventricular hemorrhage (IVH) and hypoxic-ischemic encephalopathy (HIE). Following each intervention, RNA was isolated from brain tissue and expression of cytokine and SP-A mRNA was determined by real-time quantitative RT-PCR analysis. In the sepsis model, expression of most cytokine mRNAs was significantly increased in brains of WT and SP-A^-/- mice with significantly greater expression of all cytokine mRNA levels in SP-A^-/- mice compared to WT. In the IVH model, expression of all cytokine mRNAs was significantly increased in WT and SP-A^-/- mice and levels of most cytokine mRNAs were significantly increased in SP-A^-/- mice compared to WT. In the HIE model, only TNF-α mRNA levels were significantly increased in WT brain tissue while all pro-inflammtory cytokine mRNAs were significantly increased in SP-A^-/- mice, and all pro-inflammatory cytokine mRNA levels were significantly higher in SP-A^-/- mice compared to WT. SP-A mRNA was not detectable in brain tissue of adult WT mice nor in WT neonates subjected to these models. These results suggest that SP-A^-/- neonatal mice subjected to models of neuroinflammation are more susceptible to both generalized and localized neuroinflammation compared to WT mice, thus supporting the hypothesis that SP-A attenuates inflammation in neonatal mouse brain.

Keywords: HIE; IVH; Neonatal; Neuroinflammation; Sepsis; Surfactant.