Rh-relaxin-2 attenuates degranulation of mast cells by inhibiting NF-\u03baB through PI3K-AKT/TNFAIP3 pathway in an experimental germinal matrix hemorrhage rat model

Peng Li,Yan Ding,Fanfan Chen,Jiping Tang,Weilin Xu,Jerry Flores,John H Zhang,Weitian Lu,Umut Ocak,Tongyu Zhang,Shengpeng Liu,Tianyi Wang,Gang Zhao

doi:10.1186/s12974-020-01926-x

Peng Li, Yan Ding + Show 11 more

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https://doi.org/10.1186/s12974-020-01926-x

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Abstract

BackgroundMast cells play an important role in early immune reactions in the brain by degranulation and the consequent inflammatory response. Our aim of the study is to investigate the effects of rh-relaxin-2 on mast cells and the underlying mechanisms in a germinal matrix hemorrhage (GMH) rat model.MethodsOne hundred seventy-three P7 rat pups were subjected to GMH by an intraparenchymal injection of bacterial collagenase. Clodronate liposome was administered through intracerebroventricular (i.c.v.) injections 24 h prior to GMH to inhibit microglia. Rh-relaxin-2 was administered intraperitoneally at 1 h and 13 h after GMH. Small interfering RNA of RXFP1 and PI3K inhibitor LY294002 were given by i.c.v. injection. Post-GMH evaluation included neurobehavioral function, Western blot analysis, immunofluorescence, Nissl staining, and toluidine blue staining.ResultsOur results demonstrated that endogenous relaxin-2 was downregulated and that RXFP1 level peaked on the first day after GMH. Administration of rh-relaxin-2 improved neurological functions, attenuated degranulation of mast cells and neuroinflammation, and ameliorated post-hemorrhagic hydrocephalus (PHH) after GMH. These effects were associated with RXFP1 activation, increased expression of PI3K, phosphorylated AKT and TNFAIP3, and decreased levels of phosphorylated NF-κB, tryptase, chymase, IL-6, and TNF-α. However, knockdown of RXFP1 and PI3K inhibition abolished the protective effects of rh-relaxin-2.ConclusionsOur findings showed that rh-relaxin-2 attenuated degranulation of mast cells and neuroinflammation, improved neurological outcomes, and ameliorated hydrocephalus after GMH through RXFP1/PI3K-AKT/TNFAIP3/NF-κB signaling pathway.

Highlights

Mast cells play an important role in early immune reactions in the brain by degranulation and the consequent inflammatory response
Endogenous relaxin-2 was downregulated and RXFP1 level peaked on the first day after germinal matrix hemorrhage (GMH) Western blot results showed that there was a significant decrease in the expression of endogenous relaxin-2 at 12 h after GMH (Fig. 1a, b)
The results showed that the total numbers of violet mast cells with rhrelaxin-2 treatment were decreased compared to the vehicle group in the perihematoma (Fig. 3b–d) and thalumic (Fig. 3f–h) areas

Summary

Introduction

Mast cells play an important role in early immune reactions in the brain by degranulation and the consequent inflammatory response. Our aim of the study is to investigate the effects of rh-relaxin-2 on mast cells and the underlying mechanisms in a germinal matrix hemorrhage (GMH) rat model. GMH is the most common neurological disorder of newborns. It is defined as the rupture of immature blood vessels in the subependymal brain tissue of the premature infant [1]. The activation of inflammatory cascades could be the main factor leading to post-hemorrhagic consequences, such as long-term morphological and functional impairment [4].

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