Ang-(1–7)/MasR axis promotes functional recovery after spinal cord injury by regulating microglia/macrophage polarization

Abstract

Background Inflammatory response is an essential part of secondary injury after spinal cord injury (SCI). During this period, the injury may be exacerbated through the release of a large number of inflammatory factors and the polarization of infiltrating macrophages and microglia towards M1. Ang-(1–7), mainly generated by Ang II via angiotensin-converting enzyme 2 (ACE2), can specifically bind to the G protein-coupled receptor Mas (MasR) and plays an important role in regulating inflammation and alleviating oxidative stress. Methods We aimed to investigate whether activating the Ang-(1–7)/MasR axis in rats after SCI can regulate local neuroinflammation to achieve functional recovery and obtain its potential mechanism. MasR expression of bone marrow-derived macrophages was determined by Western blot. Immunofluorescence, Western blot, Flow cytometry, and RT-qPCR were applied to evaluate the polarization of Ang-(1–7) on macrophages and the regulation of inflammatory cytokines. Previous evaluation of the spinal cord and bladder after SCI was conducted by hematoxylin–eosin staining, Basso, Beattie, and Bresnahan (BBB) score, inclined plate test, electrophysiology, and catwalk were used to evaluate the functional recovery of rats. Results MasR expression increased in macrophages under inflammatory conditions and further elevated after Ang-(1–7) treatment. Both in vivo and in vitro results confirmed that Ang-(1–7) could regulate the expression of inflammatory cytokines by down-regulating proinflammatory cytokines and up-regulating anti-inflammatory cytokines, and bias the polarization direction of microglia/macrophages to M2 phenotypic. After SCI, Ang-(1–7) administration in situ led to better histological and functional recovery in rats, and this recovery at least partly involved the TLR4/NF-κB signaling pathway. Conclusion As shown in our data, activating Ang-(1–7)/MasR axis can effectively improve the inflammatory microenvironment after spinal cord injury, promote the polarization of microglia/macrophages towards the M2 phenotype, and finally support the recovery of motor function. Therefore, we suggest using Ang-(1–7) as a feasible treatment strategy for spinal cord injury to minimize the negative consequences of the inflammatory microenvironment after spinal cord injury.

Bone marrow mesenchymal stem cell exosomes-derived microRNA-216a-5p on locomotor performance, neuronal injury, and microglia inflammation in spinal cord injury

“…In the current study, it was found that p-p65/p65 was decreased by BMSC-Exo-derived miR-216a-5p, which indicated that BMSC-Exo-derived miR-216a-5p inactivated the NF-κB pathway. In terms of the detection of TLR4/β-ACTIN and myD88/β-ACTIN, we used β-ACTIN as the internal reference to reflect the expression of TLR4 and myD88 proteins, which was in line with previous studies ( Liu et al, 2020 ; Rong et al, 2021 ; Gu et al, 2023 ). Overall, this study discovered that BMSC-Exo-derived miR-216a-5p reduced the TLR4/β-ACTIN, myD88/β-ACTIN, and p-p65/p65 in SCI rats, which indicated that BMSC-Exo-derived miR-216a-5p inactivated the TLR4/NF-κB pathway in SCI rats.…”

The Ang-(1–7)/MasR axis ameliorates neuroinflammation in hypothermic traumatic brain injury in mice by modulating phenotypic transformation of microglia

“…These results suggest that Ang-(1-7) can regulate microglia polarization toward the M2 type in vivo, which is consistent with the results of the in vitro experiment. In addition, MasR expression was also upregulated in the TS group, suggesting that the upregulation of MasR may be related to the macrophage activation status rather than to a specific phenotype [13]. Interestingly, HE staining revealed a more pronounced demarcation between the damaged area and the surrounding normal tissue in the TS+Ang-(1-7) group than in the TS group.…”

“…Recent studies have shown that the Ang-(1-7)/MasR axis is a protective arm of the renin-angiotensin system against inflammation and improves the prognosis of TBI [11,12]. Guangjin Gu et al suggested that Ang-(1-7) could regulate microglia polarization from M1 to M2 phenotype after spinal cord injury, thereby promoting functional recovery [13].…”

Myeloid ACE2 protects against septic hypotension and vascular dysfunction through Ang-(1–7)-Mas-mediated macrophage polarization

“…Interestingly, both ACE2 and MasR are primarily expressed on macrophages and are markedly reduced upon LPS stimulation in vitro . Activation of the Ang-(1–7)-MasR cascade can shift macrophages toward the M2 phenotype by inhibiting MAPK and TLR4-IKK–NF–κB signals in sepsis [ 34 , 56 ]. Moreover, administration of an ACE2 activator reduces the inflammatory effect in retinal pigment epithelium cells by blocking the MAPK–NF–κB pathway following LPS stimulation [ 57 ].…”