Quercetin prevents necroptosis of oligodendrocytes by inhibiting macrophages/microglia polarization to M1 phenotype after spinal cord injury in rats

Abstract

BackgroundOligodendrocytes (OLs) death after spinal cord injury (SCI) contributes to demyelination, even leading to a permanent neurological deficit. Besides apoptosis, our previous study demonstrated that OLs underwent receptor-interacting serine-threonine kinase 3(RIP3)/mixed lineage kinase domain-like protein (MLKL)-mediated necroptosis. Considering that necroptosis is always accompanied with pro-inflammatory response and quercetin has long been used as anti-inflammatory agent, in the present study we investigated whether quercetin could inhibit necroptosis of OLs and suppress the M1 macrophages/microglia-mediated immune response after SCI as well as the possible mechanism.MethodsIn this study, we applied quercetin, an important flavonoid component of various herbs, to treat rats with SCI and rats injected with saline were employed as the control group. Locomotor functional recovery was evaluated using Basso-Beattie-Bresnahan (BBB) scoring and rump-height Index (RHI) assay. In vivo, the necroptosis, apoptosis, and regeneration of OLs were detected by immunohistochemistry, 5′-bromo-2′-deoxyuridine (BrdU) incorporation. The loss of myelin and axons after SCI were evaluated by Luxol fast blue (LFB) staining, immunohistochemistry, and electron microscopic study. The polarization of macrophages/microglia after SCI and the underlying mechanisms were detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and immunohistochemistry. In vitro, the ATP and reactive oxygen species (ROS) level examination, propidium iodide (PI) labeling, and Western blotting were used to analyze the necroptosis of cultured OLs, while the signaling pathways-mediated polarization of cultured macrophages/microglia was detected by qRT-PCR and Western blotting.ResultsWe demonstrated that quercetin treatment improved functional recovery in rats after SCI. We then found that quercetin significantly reduced necroptosis of OLs after SCI without influencing apoptosis and regeneration of OLs. Meanwhile, myelin loss and axon loss were also significantly reduced in quercetin-treated rats, as compared to SCI + saline control. Further, we revealed that quercetin could suppress macrophages/microglia polarized to M1 phenotype through inhibition of STAT1 and NF-κB pathway in vivo and in vitro, which contributes to the decreased necroptosis of OLs.ConclusionsQuercetin treatment alleviated necroptosis of OLs partially by inhibiting M1 macrophages/microglia polarization after SCI. Our findings suggest that necroptosis of OLs may be a potential therapeutic target for clinical SCI.

Cell Clearing Systems as Targets of Polyphenols in Viral Infections: Potential Implications for COVID-19 Pathogenesis

“…Neuroprotective effects of quercetin and kaempferol are widely documented in various experimental models, which are associated, either directly or indirectly, with modulation of autophagy and immunoproteasome pathways. These include reduction of oxidative stress and neuroinflammation, induction of M2 microglia polarization, improvement of BBB function, prevention of AGE/RAGE-related neuronal damage, inhibition of HMBG1/TLR4 axis, and activation of AMPK and Nrf2 [ 200 , 201 , 202 , 203 , 204 , 205 , 206 ]. Both quercetin and kaempferol, through inhibition of cytochrome P-450-dependent catalysis, prevent the hepatic metabolism of 17 beta-estradiol [ 207 ], whose effects are bound to autophagy activity [ 208 ] and are potentially relevant in the frame of either influenza virus or COVID-19 pathogenesis [ 209 , 210 ].…”

Inhibiting HMGB1-RAGE axis prevents pro-inflammatory macrophages/microglia polarization and affords neuroprotection after spinal cord injury

“…Microglial cells were obtained from neonatal (about 3-day-old) SD rats, as described previously [ 4 ]. Microglial cells were cultured in DMEM supplemented with 3% FBS, penicillin-streptomycin (100 U/ml–100 μg/ml) and 4 mM L-glutamine.…”

“…Preservation of motor function after SCI is one of the most concerned issues during treatment and rehabilitation, which is mainly depended on the neuronal survival and myelin maintenance [2,3]. That the relationship between neuronal or myelin loss and pro-inflammatory response after SCI has been proven by other research and our previous study [4,5]. SCI triggers a dominant pro-inflammatory response, and resident microglia and recruited macrophages are central players in innate immune response following SCI [6,7].…”

“…Luxol fast blue (LFB) staining was performed as described previously [4]. Serial transverse cryosections (12 μm thickness) were incubated in 0.1% Luxol fast blue (Sigma) in acidified 95% ethanol overnight at 60°C.…”

Biomaterial-supported MSC transplantation enhances cell–cell communication for spinal cord injury

“…Transplanted Schwann cells can myelinate axons and enhance endogenous Schwann cell myelination. At the same time, Schwann cells were shown to migrate from peripheral nervous structures resulting from a disruption of the barrier integrity, to participate not only in remyelination of central axons in the area of injury but also in the restoration of conduction [138][139][140][141]. Therefore, it is not known to what extent spared axons are remyelinated by transplanted Schwann cells, nor is the contribution of this myelin to functional improvements proven.…”