Blocking Notch signal pathway suppresses the activation of neurotoxic A1 astrocytes after spinal cord injury

Abstract

Spinal cord injury (SCI) is a catastrophic disease which has complicated pathogenesis including inflammation, oxidative stress and glial scar formation. Astrocytes are the most abundant cells in central nervous system and fulfill homeostatic functions. Recent studies have described a new reactive phenotype of astrocytes, A1, induced by inflammation, which may have negative effects in SCI. As the Notch signaling pathway has been linked to cell differentiation and inflammation, we aimed to investigate its potential role in the differentiation of astrocytes in SCI. Contusive SCI rat model showed elevated A1 astrocyte numbers at the damage site 28 days after SCI and the expression levels of Notch signaling and its downstream genes were upregulated parallelly. Western blotting, RT-qPCR and immunofluorescence revealed that blocking of Notch pathway using γ-secretase blocker (DAPT) suppressed the differentiation of A1 astrocytes. Flow cytometry, and TUNEL staining indicated that DAPT alleviated neuronal apoptosis and axonal damage caused by A1 astrocytes likely through the Notch-dependent release of pro-inflammatory factors. CO-IP and western blotting revealed an interaction between Notch pathway and signal transducer and activator of transcription 3 (Stat3), which played a vital role in differentiation of A1 astrocytes. We conclude that phenotypic transition of A1 astrocytes and their neurotoxity were controlled by the Notch-Stat3 axis and that Notch pathway in astrocytes may serve as a promising therapeutic target for SCI.

Dissecting the Dual Role of the Glial Scar and Scar-Forming Astrocytes in Spinal Cord Injury

“…The in vivo blockade of A1 astrocyte formation through a total KO of C1qa/TNF/IL1a prevents the death of CNS neurons. Similar to the results in brain injury models, a recent study demonstrated the existence and neurotoxic function of A1 astrocytes in an SCI model (Qian et al, 2019). In this study, the immunofluorescence of C3 (a marker of A1 astrocytes) increases as early as 3 days after SCI.…”

“…The direct relationship between the reduction of A1 astrocytes and functional recovery also needs more proof. Qian et al (2019) changed the astrocytic state through interventions on the Notch-STAT3 axis, which was quite different from the study of Liddelow et al (2017). Regardless, these findings suggest that: (1) the existence of a neurotoxic/neuroprotective phenotype of astrocytes in the context of SCI is reasonable;…”

Exosome-shuttled miR-216a-5p from hypoxic preconditioned mesenchymal stem cells repair traumatic spinal cord injury by shifting microglial M1/M2 polarization

“…Primary microglia were obtained as previously reported [57,58]. Briefly, brains were removed from newborn mice (1-3 days old) and carefully cut into 0.5-1-mm 3 pieces.…”

Targeted Inhibition of STAT3 in Neural Stem Cells Promotes Neuronal Differentiation and Functional Recovery in Rats with Spinal Cord Injury

“…After SCI, the limited regenerative capacity of the adult mammalian spinal cord has been attributed to the formation of cavities and glial scars that interrupt the ascending and descending pathways [17][18][19]. Now, NSC transplantation is considered an appropriate choice for treating SCI [20].…”