The promotive effect of activation of the Akt/mTOR/p70S6K signaling pathway in oligodendrocytes on nerve myelin regeneration in rats with spinal cord injury

Moderate-Intensity Treadmill Exercise Promotes mTOR-Dependent Motor Cortical Neurotrophic Factor Expression and Functional Recovery in a Murine Model of Crush Spinal Cord Injury (SCI)

Treadmill exercise is widely considered an effective strategy for restoration of skilled motor function after spinal cord injury (SCI). However, the specific exercise intensity that optimizes recovery and the underlying mechanistic basis of this recovery remain unclear. To that end, we sought to investigate the effect of different treadmill exercise intensities on cortical mTOR activity, a key regulator of functional recovery following CNS trauma, in an animal model of C5 crush spinal cord injury (SCI). Following injury, animals were subjected to treadmill exercise for 4 consecutive weeks at three different intensities (low intensity [LEI]; moderate intensity [MEI]; and high intensity [HEI]). Motor function recovery was assessed by horizontal ladder test, cylinder rearing test, and electrophysiology, while neurotrophic factors and cortical mechanistic target of rapamycin (mTOR) pathway-related proteins were assessed by Western blotting. The activation of the cortical mTOR pathway and axonal sprouting was evaluated by immunofluorescence and the changes of plasticity in motor cortex neurons were assessed by Golgi staining. In keeping with previous studies, we found that 4 weeks of treadmill training resulted in improved skilled motor function, enhanced nerve conduction capability, increased neuroplasticity, and axonal sprouting. Importantly, we also demonstrated that when compared with the LEI group, MEI and HEI groups demonstrated elevated expression of brain-derived neurotrophic factor (BDNF), insulin-like growth factor 1 (IGF-1), phosphorylated ribosomal S6 protein (p-S6), and protein kinase B (p-Akt), consistent with an intensity-dependent activation of the mTOR pathway and neurotrophic factor expression in the motor cortex. We also observed impaired exercise endurance and higher mortality during training in the HEI group than in the LEI and MEI groups. Collectively, our findings suggest that treadmill exercise following SCI is an effective means of promoting recovery and highlight the importance of the cortical mTOR pathway and neurotrophic factors as mediators of this effect. Importantly, our findings also demonstrate that excessive exercise can be detrimental, suggesting that moderation may be the optimal strategy. These findings provide an important foundation for further investigation of treadmill training as a modality for recovery following spinal cord injury and of the underlying mechanisms.

Mechanism of erythropoietin-induced M2 microglia polarization via Akt / Mtor / P70S6k signaling pathway in the treatment of brain injury in premature mice and its effect on biofilm

We investigated the mechanism of erythropoietin (EPO) in brain injury in premature mice based on Akt/mTOR/p70S6K signaling pathway. The brain injury model group of premature mice was obtained by intraperitoneal injection of lipopolysaccharide during pregnancy. Normal mice were taken as the control group. The model mice were divided into low-dose EPO (1,000 IU/kg, L-EPO), medium-dose EPO (2,500 IU/kg, M-EPO), and high-dose EPO groups (5,000 IU/kg, H-EPO) by intraperitoneal injection. The levels of malondialdehyde (MDA) and total superoxide dismutase (T-SOD) were detected. TUNEL staining and Western blotting were used to detect the differences in neuronal apoptosis index (AI), microglial polarization marker protein, and Akt/mTOR/p70S6K-related protein expression levels in each group. Compared with the control group, the protein levels of AI, MDA, Bax, and iNOS in the model, L-EPO, and M-EPO groups were significantly increased, while the T-SOD level and Bcl-2, ARG1, p-Akt, p-mTOR, and p-70S6K protein levels were significantly decreased (P < 0.05). Compared with the model group, AI, MAD levels and Bax, iNOS protein expression levels in L-EPO, M-EPO, and H-EPO groups were significantly decreased, while T-SOD level and Bcl-2, ARG1, p-Akt, p-mTOR, and p-70S6K protein levels were significantly increased. The changes were dose-dependent. In summary, EPO can activate microglia transformation from M1 to M2 through Akt/mTOR/p70S6K signaling pathway.

METTL14 promotes apoptosis of spinal cord neurons by inducing EEF1A2 m6A methylation in spinal cord injury

Spinal cord injury (SCI) is a devastating traumatic condition. METTL14-mediated m6A modification is associated with SCI. This study was intended to investigate the functional mechanism of RNA methyltransferase METTL14 in spinal cord neuron apoptosis during SCI. The SCI rat model was established, followed by evaluation of pathological conditions, apoptosis, and viability of spinal cord neurons. The neuronal function of primary cultured spinal motoneurons of rats was assessed after hypoxia/reoxygenation treatment. Expressions of EEF1A2, Akt/mTOR pathway-related proteins, inflammatory cytokines, and apoptosis-related proteins were detected. EEF1A2 was weakly expressed and Akt/mTOR pathway was inhibited in SCI rat models. Hypoxia/Reoxygenation decreased the viability of spinal cord neurons, promoted LDH release and neuronal apoptosis. EEF1A2 overexpression promoted the viability of spinal cord neurons, inhibited neuronal apoptosis, and decreased inflammatory cytokine levels. Silencing METTL14 inhibited m6A modification of EEF1A2 and increased EEF1A2 expression while METTL14 overexpression showed reverse results. EEF1A2 overexpression promoted viability and inhibited apoptosis of spinal cord neurons and inflammation by activating the Akt/mTOR pathway. In conclusion, silencing METTL14 repressed apoptosis of spinal cord neurons and attenuated SCI by inhibiting m6A modification of EEF1A2 and activating the Akt/mTOR pathway.

Quercetin promotes locomotor function recovery and axonal regeneration through induction of autophagy after spinal cord injury

Quercetin (Que), one of the flavonoids, exerts numerous actions on the central nervous system. However, the roles and underlying mechanism of Que in locomotor function recovery and axonal regeneration following spinal cord injury (SCI) have not been fully elucidated. A rat model of spinal cord injury (SCI) was established at T10 using the modified Allen's method. The results in our study indicated that Basso, Beattie and Bresnahan (BBB) locomotor scores were significantly higher after Que treatment. Additionally, Que administration cut down the latency of somatosensory evoked potentials (SEP) and motor evoked potentials (MEP), increased the amplitude of MEP and SEP following SCI. Hematoxylin-eosin (HE) staining demonstrated that Que administration reduced lesion size and cavity formation. Biotinylated dextran amine (BDA) anterograde tracing revealed that BDA positive fibres were increased by Que following SCI. Immunofluorescence staining revealed that Que elevated 5-hydroxytryptamine (5-HT) positive nerve fibres and neurofilament-200 (NF-200) positive neurons, reduced glial fibrillary acidic protein (GFAP) positive astrocytes. In addition, Que inhibited GFAP expression, increased both NeuN and NF-200 expression and facilitated the spinal cord energy metabolism. Moreover, Que increased 18 F-FDG uptake in a time-dependent manner. Furthermore, Que increased Beclin 1 and LC3 II expression, blocked the phosphorylation of Akt, mTOR and p70S6K. 3-methyladenine (3-MA) partly abolished the neuro-protective roles of Que following SCI. Taken together, our study suggested that Que might promote locomotor function recovery, axonal regeneration and energy metabolism through induction of autophagy via Akt/mTOR/p70S6K pathway.