High-throughput proteomics reveal alarmins as amplifiers of tissue pathology and inflammation after spinal cord injury

Abstract

Spinal cord injury is characterized by acute cellular and axonal damage followed by aggressive inflammation and pathological tissue remodelling. The biological mediators underlying these processes are still largely unknown. Here we apply an innovative proteomics approach targeting the enriched extracellular proteome after spinal cord injury for the first time. Proteomics revealed multiple matrix proteins not previously associated with injured spinal tissue, including small proteoglycans involved in cell-matrix adhesion and collagen fibrillogenesis. Network analysis of transcriptomics and proteomics datasets uncovered persistent overexpression of extracellular alarmins that can trigger inflammation via pattern recognition receptors. In mechanistic experiments, inhibition of toll-like receptor-4 (TLR4) and the receptor for advanced glycation end-products (RAGE) revealed the involvement of alarmins in inflammatory gene expression, which was found to be dominated by IL1 and NFκΒ signalling. Extracellular high-mobility group box-1 (HMGB1) was identified as the likely endogenous regulator of IL1 expression after injury. These data reveal a novel tissue remodelling signature and identify endogenous alarmins as amplifiers of the inflammatory response that promotes tissue pathology and impedes neuronal repair after spinal cord injury.

The soft mechanical signature of glial scars in the central nervous system

“…The softening of cortical glial scars can be partly explained by the specific composition of the ECM, whose expression is upregulated after injury4041. The ECM in scars outside the CNS is usually rich in collagen-1, which scales with tissue stiffness1.…”

Rat models of spinal cord injury: from pathology to potential therapies

“…Combining neuronal stem cells with ten different growth factors (Lu et al, 2012) is a promising example of such a combinatory approach. Systems-level studies also offer an alternative, genomic and proteomic view, and provide us with a better understanding of spinal cord injury at the molecular level (Anderson et al, 2016; Didangelos et al, 2016). However, few attempts have been made to date to understand the course of pathology that follows spinal cord injury, or the effects of treatment on this pathology, using tools such as RNAseq and advanced proteomics.…”

Modulation of Neuroinflammation by Taklisodok-um in a Spinal Cord Injury Model

“…TLR activation requires the presence of a co-receptor to initiate the signaling cascade; of these, CD14 is a well-studied candidate [28,29]. A previous study has described the upregulation of CD14 gene expression after SCI [8]. TLR4 signaling induces pro-inflammatory proteins, such as NF-κB, iNOS, and interferons [34][35][36].…”

“…CD14 expression was increased by 5.5-fold in control SCI mice compared to sham mice, and TLSDU treatment decreased CD14 expression by 2.0-fold as compared to control SCI mice. Finally, we examined iNOS, a pro-inflammatory protein induced by TLR4 signaling that is also increased by SCI [8]. As expected, iNOS expression was increased by 5.8-fold in the spinal cords of SCI mice compared to sham mice.…”

“…This suggests that neuroinflammation may also play a role in persistent pain after SCI, although there is insufficient clinical trial evidence to support this mechanism. As an alternative, several studies in rodent models of SCI have described neuroinflammation-associated pathway components as targets for treatment [8][9][10]. Neuroinflammatory proteins, including TNF-α, IL-1β, CD11b, MHC2, Iba-1, and CD81 are upregulated in rodents after SCI [10][11][12][13].…”