Photobiomodulation inhibits the activation of neurotoxic microglia and astrocytes by inhibiting Lcn2/JAK2-STAT3 crosstalk after spinal cord injury in male rats

Abstract

Background Neurotoxic microglia and astrocytes begin to activate and participate in pathological processes after spinal cord injury (SCI), subsequently causing severe secondary damage and affecting tissue repair. We have previously reported that photobiomodulation (PBM) can promote functional recovery by reducing neuroinflammation after SCI, but little is known about the underlying mechanism. Therefore, we aimed to investigate whether PBM ameliorates neuroinflammation by modulating the activation of microglia and astrocytes after SCI. Methods Male Sprague–Dawley rats were randomly divided into three groups: a sham control group, an SCI + vehicle group and an SCI + PBM group. PBM was performed for two consecutive weeks after clip-compression SCI models were established. The activation of neurotoxic microglia and astrocytes, the level of tissue apoptosis, the number of motor neurons and the recovery of motor function were evaluated at different days post-injury (1, 3, 7, 14, and 28 days post-injury, dpi). Lipocalin 2 (Lcn2) and Janus kinase-2 (JAK2)-signal transducer and activator of transcription-3 (STAT3) signaling were regarded as potential targets by which PBM affected neurotoxic microglia and astrocytes. In in vitro experiments, primary microglia and astrocytes were irradiated with PBM and cotreated with cucurbitacin I (a JAK2-STAT3 pathway inhibitor), an adenovirus (shRNA-Lcn2) and recombinant Lcn2 protein. Results PBM promoted the recovery of motor function, inhibited the activation of neurotoxic microglia and astrocytes, alleviated neuroinflammation and tissue apoptosis, and increased the number of neurons retained after SCI. The upregulation of Lcn2 and the activation of the JAK2-STAT3 pathway after SCI were suppressed by PBM. In vitro experiments also showed that Lcn2 and JAK2-STAT3 were mutually promoted and that PBM interfered with this interaction, inhibiting the activation of microglia and astrocytes. Conclusion Lcn2/JAK2-STAT3 crosstalk is involved in the activation of neurotoxic microglia and astrocytes after SCI, and this process can be suppressed by PBM.

Sacsin Deletion Induces Aggregation of Glial Intermediate Filaments

“…Astroglia participates in neuroinflammation, where cytokine signaling plays a key role [ 23 ], and IFs are currently considered important scaffolds actively involved in signal transduction [ 24 ]. We hypothesized that sacsin deletion could interfere with specific signaling/inflammatory pathways, such as the Signal Transducer and Activator of Transcription 3 (STAT3) pathway, which play key roles in neuroinflammation [ 25 , 26 ]. Reference C6 cells responds poorly to LIF, IL-6 ( Figure 5 A) and Tumor Necrosis Factor alpha (data not shown).…”

Photobiomodulation promotes repair following spinal cord injury by restoring neuronal mitochondrial bioenergetics via AMPK/PGC-1α/TFAM pathway

“…Our group has developed an implantable optical fiber so that laser bioenergy could directly reach the surface of the spinal cord ( Wang et al, 2021a ; Wang et al, 2021b ; Ma et al, 2022 ). Compared with percutaneous irradiation, there is no skin or muscle barrier, which improves the efficacy of PBM.…”

“…Male Sprague Dawley rats were purchased from the Animal Center of the Air Force Medical University. SCI model, laser fiber embedding and photobiomodulation therapy were the same as our previous research ( Wang et al, 2021a ). After the rats were anesthetized with pentobarbital sodium, the lamina was excised, the T10 spinal cord was exposed and clamped with special pliers for 40 s to cause SCI.…”

Photobiomodulation for the treatment of neuroinflammation: A systematic review of controlled laboratory animal studies

“…Twenty seven articles reported experiments in rodents, of which 3 were performed on albino BALB/c mice (Salehpour et al, 2019a , b ; Hosseini et al, 2022 ), 6 used C57BL/6 mice (Khuman et al, 2012 ; Zhang et al, 2014 ; Gonçalves et al, 2016 ; Lee et al, 2016 , 2017 ; Duarte et al, 2018 ), 1 was conducted on the 5XFAD transgenic mice (pigmented C57BL/6 background) (Cho et al, 2020 ), 1 was performed on the APP/PS1 transgenic mice (Wu et al, 2021 ), 2 used the TgF344 transgenic mice (Yang et al, 2021b , 2022 ), 6 were performed using Wistar rats (Moreira et al, 2009 ; Prianti et al, 2014 ; Cardoso et al, 2021a , 2022 ; Gerace et al, 2021 ; Vogel et al, 2021 ), and 8 used Sprague-Dawley rats (Lu et al, 2017 ; Esenaliev et al, 2018 ; Yang et al, 2018 , 2021a ; O'Brien and Austin, 2019 ; Di Paolo, 2021 ; Wang et al, 2021 ; Tsai et al, 2022 ). In these laboratory rodent studies, the age of animals varied from 7 weeks old to 20 months old.…”

“…In these laboratory rodent studies, the age of animals varied from 7 weeks old to 20 months old. In order to analyze the anti-inflammatory effects of PBM on brain, we reviewed various animal models such as focal brain damage (Moreira et al, 2009 ), controlled cortical impact (Khuman et al, 2012 ), peripheral inflammation (Prianti et al, 2014 ), mild traumatic brain injury (Zhang et al, 2014 ), spinal cord injury (Wang et al, 2021 ), Aβ-treatment (Lu et al, 2017 ), Aβ and PS1 transgenic rodents (Cho et al, 2020 ), PS1 transgenic rodents (Wu et al, 2021 ), TgF344 transgenic rodents (Yang et al, 2021b , 2022 ), brain ischemia (Lee et al, 2016 , 2017 ; Gerace et al, 2021 ; Vogel et al, 2021 ), multiple sclerosis (Gonçalves et al, 2016 ), natural aging (Cardoso et al, 2021a , 2022 ), blast injury (Esenaliev et al, 2018 ), retinal degeneration (Di Paolo, 2021 ), induced aging (Hosseini et al, 2022 ), cuprizone-induced demyelination (Duarte et al, 2018 ), photothrombotic stroke (Yang et al, 2018 ), lipopolysaccharide-induced Parkinson's disease (O'Brien and Austin, 2019 ), experimental model of epilepsy (Tsai et al, 2022 ), restraint stress-induced depression experimental model (Salehpour et al, 2019a ), transient global brain ischemia and artificially aging (Salehpour et al, 2019b ), and neonatal hypoxic ischemia (Yang et al, 2021a ).…”