Sexually dimorphic extracellular vesicle responses after chronic spinal cord injury are associated with neuroinflammation and neurodegeneration in the aged brain

Blocking the p38 MAPK Signaling Pathway in the Rat Hippocampus Alleviates the Depressive-like Behavior Induced by Spinal Cord Injury

Patients with spinal cord injury (SCI) may develop depression, which can affect their rehabilitation. However, the underlying mechanism of depression in SCI patients remains unclear. Previous studies have revealed increased p38 MAPK phosphorylation in the rat hippocampus after SCI, accompanied by depression-like behaviors. However, the role of the p38 MAPK signaling pathway in SCI-induced depression remains unclear. In this study, we used an aneurysm clip-induced rat SCI model to investigate whether p38 MAPK phosphorylation in the hippocampus is associated with depression-like behaviors in rats after SCI. Behavioral testing revealed that SB203580, a p38 MAPK signaling inhibitor, reduced depression-like behaviors. Western blotting and morphological analyses showed that SB203580 inhibited the activation of microglia and astrocytes in the hippocampus after SCI. Additionally, SB203580 reduced the expression of tumor necrosis factor α and increased p38 MAPK phosphorylation and the number of bromodeoxyuridine-positive cells in the hippocampus. These findings suggest that SB203580 can inhibit hippocampal remodeling and the neuroimmune response in the rat hippocampus after SCI. Therefore, the phosphorylation of p38 MAPK in the hippocampus plays a key role in the depression-like behaviors induced by SCI. The inhibition of p38 MAPK phosphorylation may represent a mechanism to protect against hippocampal injury induced by SCI.

Sex as a biological variable in ageing: insights and perspectives on the molecular and cellular hallmarks

Sex-specific differences in lifespan and ageing are observed in various species. In humans, women generally live longer but are frailer and suffer from different age-related diseases compared to men. The hallmarks of ageing, such as genomic instability, telomere attrition or loss of proteostasis, exhibit sex-specific patterns. Sex chromosomes and sex hormones, as well as the epigenetic regulation of the inactive X chromosome, have been shown to affect lifespan and age-related diseases. Here we review the current knowledge on the biological basis of sex-biased ageing. While our review is focused on humans, we also discuss examples of model organisms such as the mouse, fruit fly or the killifish. Understanding these molecular differences is crucial as the elderly population is expected to double worldwide by 2050, making sex-specific approaches in the diagnosis, treatment, therapeutic development and prevention of age-related diseases a pressing need.

Spinal cord injury disrupts plasma extracellular vesicles cargoes leading to neuroinflammation in the brain and neurological dysfunction in aged male mice

Aged individuals with spinal cord injury (SCI) are prevalent with increased mortality and worse outcomes. SCI can cause secondary brain neuroinflammation and neurodegeneration. However, the mechanisms contributing to SCI-induced brain dysfunction are poorly understood. Cell-to-cell signaling through extracellular vesicles (EVs) has emerged as a critical mediator of neuroinflammation, including at a distance through circulation. We have previously shown that SCI in young adult (YA) male mice leads to robust changes in plasma EV count and microRNAs (miRs) content. Here, our goal was to investigate the impact of old age on EVs and brain after SCI. At 24 h post-injury, there was no difference in particle count or size distribution between YA and aged mice. However, aged animals increased expression of EV marker CD63 with SCI. Using the Fireplex® miRs assay, Proteomics, and mass spectrometry-based Lipidomics, circulating EVs analysis identified distinct profiles of miRs, proteins, and lipid components in old and injury animals. In vitro, plasma EVs from aged SCI mice, at a lower concentration comparable to those of YA SCI mice, induced the secretion of pro-inflammatory cytokines and neuronal apoptosis. Systemic administration of plasma EVs from SCI animals was sufficient to impair general physical function and neurological function in intact animals, which is associated with pro-inflammatory changes in the brain. Furthermore, plasma EVs from young animals had rejuvenating effects on naïve aged mice. Collectively, these studies identify the critical changes in circulating EVs cargoes after SCI and in aged animals and support a potential EV-mediated mechanism for SCI-induced brain changes.

Old age alters inflammation and autophagy signaling in the brain, leading to exacerbated neurological outcomes after spinal cord injury in male mice

Older patients with spinal cord injury (SCI) have different features with regard to neurological characteristics after injury. Recent large-scale longitudinal population-based studies showed that individuals with SCI are at a higher risk of developing dementia than non-SCI patients, indicating that SCI is a potential risk factor for dementia. Aging is known to potentiate inflammation and neurodegeneration at the injured site leading to impaired recovery from SCI. However, no research has been aimed at studying the mechanisms of SCI-mediated cognitive impairment in the elderly. The present study examined neurobehavioral and molecular changes in the brain and the underlying mechanisms associated with brain dysfunction in aged C57BL/6 male mice using a contusion SCI model. At 2 months post-injury, aged mice displayed worse performance in locomotor, cognitive and depressive-like behavioral tests compared to young adult animals. Histopathology in injured spinal cord tissue was exacerbated in aged SCI mice. In the brain, transcriptomic analysis with NanoString neuropathology panel identified activated microglia and dysregulated autophagy as the most significantly altered pathways by both age and injury. These findings were further validated by flow cytometry, which demonstrated increased myeloid and lymphocytes infiltration at both the injured site and brain of aged mice. Moreover, SCI in aged mice altered microglial function and dysregulated autophagy in microglia, resulting in worsened neurodegeneration. Taken together, our data indicate that old age exacerbates neuropathological changes in both the injured spinal cord and remote brain regions leading to poorer functional outcomes, at least in part, through altered inflammation and autophagy function.

Caffeic acid phenethyl ester inhibits neuro-inflammation and oxidative stress following spinal cord injury by mitigating mitochondrial dysfunction via the SIRT1/PGC1α/DRP1 signaling pathway

BACKGROUND

The treatment of spinal cord injury (SCI) has always been a significant research focus of clinical neuroscience, with inhibition of microglia-mediated neuro-inflammation as well as oxidative stress key to successful SCI patient treatment. Caffeic acid phenethyl ester (CAPE), a compound extracted from propolis, has both anti-inflammatory and anti-oxidative effects, but its SCI therapeutic effects have rarely been reported.

METHODS

We constructed a mouse spinal cord contusion model and administered CAPE intraperitoneally for 7 consecutive days after injury, and methylprednisolone (MP) was used as a positive control. Hematoxylin-eosin, Nissl, and Luxol Fast Blue staining were used to assess the effect of CAPE on the structures of nervous tissue after SCI. Basso Mouse Scale scores and footprint analysis were used to explore the effect of CAPE on the recovery of motor function by SCI mice. Western blot analysis and immunofluorescence staining assessed levels of inflammatory mediators and oxidative stress-related proteins both in vivo and in vitro after CAPE treatment. Further, reactive oxygen species (ROS) within the cytoplasm were detected using an ROS kit. Changes in mitochondrial membrane potential after CAPE treatment were detected with 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-imidacarbocyanine iodide. Mechanistically, western blot analysis and immunofluorescence staining were used to examine the effect of CAPE on the SIRT1/PGC1α/DRP1 signaling pathway.

RESULTS

CAPE-treated SCI mice showed less neuronal tissue loss, more neuronal survival, and reduced demyelination. Interestingly, SCI mice treated with CAPE showed better recovery of motor function. CAPE treatment reduced the expression of inflammatory and oxidative mediators, including iNOS, COX-2, TNF-α, IL-1β, 1L-6, NOX-2, and NOX-4, as well as the positive control MP both in vitro and in vivo. In addition, molecular docking experiments showed that CAPE had a high affinity for SIRT1, and that CAPE treatment significantly activated SIRT1 and PGC1α, with down-regulation of DRP1. Further, CAPE treatment significantly reduced the level of ROS in cellular cytoplasm and increased the mitochondrial membrane potential, which improved normal mitochondrial function. After administering the SIRT1 inhibitor nicotinamide, the effect of CAPE on neuro-inflammation and oxidative stress was reversed.On the contrary, SIRT1 agonist SRT2183 further enhanced the anti-inflammatory and antioxidant effects of CAPE, indicating that the anti-inflammatory and anti-oxidative stress effects of CAPE after SCI were dependent on SIRT1.

CONCLUSION

CAPE inhibits microglia-mediated neuro-inflammation and oxidative stress and supports mitochondrial function by regulating the SIRT1/PGC1α/DRP1 signaling pathway after SCI. These effects demonstrate that CAPE reduces nerve tissue damage. Therefore, CAPE is a potential drug for the treatment of SCI through production of anti-inflammatory and anti-oxidative stress effects.

Melatonin Protects Injured Spinal Cord Neurons From Apoptosis by Inhibiting Mitochondrial Damage via the SIRT1/Drp1 Signaling Pathway

Spinal cord injuries (SCIs) often result in limited prospects for recovery and a high incidence of disability. Melatonin (Mel), a hormone, is acknowledged for its neuroprotective attributes. Mel was examined in this study to discover if it alleviates SCIs via the sirtuin1/dynamin-related protein1 (SIRT1/Drp1) signaling pathway. SCIs were simulated in mice by inducing cord contusion at the T9-T10 vertebrae and causing inflammation in primary spinal neurons using lipopolysaccharide (LPS). The findings of our study demonstrated that Mel treatment effectively promoted neuromotor recovery through multiple mechanisms, including the reduction of neuronal death, suppression of astrocyte and microglia activation, and attenuation of neuroinflammation. Moreover, Mel therapy significantly upregulated the expression of SIRT1 in both spinal cord tissues and spinal neurons of mice. Additionally, Mel exhibited the potential to mitigate neuronal mitochondrial dysfunction by modulating the levels of Drp1 and TOMM20, thereby addressing the underlying factors contributing to this dysfunction. Furthermore, when SIRT1 was downregulated, it reversed the positive effects of Mel. Overall, our present study suggests that Mel has the capacity to modulate the SIRT1/Drp1 pathway, thereby ameliorating mitochondrial dysfunction, attenuating inflammation and apoptosis, and enhancing neural function subsequent to SCIs.