The MAPK Signaling Pathway Presents Novel Molecular Targets for Therapeutic Intervention after Traumatic Spinal Cord Injury: A Comparative Cross-Species Transcriptional Analysis

Translational Relevance of Secondary Intracellular Signaling Cascades Following Traumatic Spinal Cord Injury

Traumatic spinal cord injury (SCI) is a life-threatening and life-altering condition that results in debilitating sensorimotor and autonomic impairments. Despite significant advances in the clinical management of traumatic SCI, many patients continue to suffer due to a lack of effective therapies. The initial mechanical injury to the spinal cord results in a series of secondary molecular processes and intracellular signaling cascades in immune, vascular, glial, and neuronal cell populations, which further damage the injured spinal cord. These intracellular cascades present promising translationally relevant targets for therapeutic intervention due to their high ubiquity and conservation across eukaryotic evolution. To date, many therapeutics have shown either direct or indirect involvement of these pathways in improving recovery after SCI. However, the complex, multifaceted, and heterogeneous nature of traumatic SCI requires better elucidation of the underlying secondary intracellular signaling cascades to minimize off-target effects and maximize effectiveness. Recent advances in transcriptional and molecular neuroscience provide a closer characterization of these pathways in the injured spinal cord. This narrative review article aims to survey the MAPK, PI3K-AKT-mTOR, Rho-ROCK, NF-κB, and JAK-STAT signaling cascades, in addition to providing a comprehensive overview of the involvement and therapeutic potential of these secondary intracellular pathways following traumatic SCI.

Network pharmacology analysis and experimental validation to explore the effect and mechanism of tetramethylpyrazine for spinal cord injury

OBJECTIVE

To investigate the effect and mechanism of Tetramethylpyrazine (TMP) in treating Spinal Cord Injury (SCI) using network pharmacology analysis and animal experiments.

METHODS

This study was based on public databases, including PharmMapper, BATMAN-TCM, and STRING, as well as KEGG pathway analysis and other methods of network pharmacology were used to preliminarily explore the molecular mechanism of TMP in the treatment of SCI. Using a mouse SCI compression injury model, the efficacy of TMP was evaluated, and the expression of predictive targets on the PI3K/AKT and MAPK signaling pathways was measured using Western blotting and q-PCR.

RESULTS

Network pharmacology analysis showed that TMP may exert therapeutic effects through the MAPK and PI3K/AKT signaling pathways. In animal experimental validation studies, it was shown that after treatment with TMP, the hind limb motor function scores and ramp test scores of the TMP-treated mice improved significantly. HE staining showed that after treatment with TMP, cavities decreased, fewer glial cells proliferated, and fewer inflammatory cells infiltrated; Nielsen staining showed less neuronal loss. Western blot studies showed that compared with the model group, expression of RAS, ERK1/2, RAF1, PI3K, and p-AKT proteins in the spinal cord tissue of mice treated with high-dose TMP was significantly lower. Accordingly, q-PCR studies showed that compared with the model group, the expression levels of RAS, ERK1/2, RAF1, PI3K, and p-AKT genes in the spinal cords of mice in the high-dose TMP group were significantly lower.

CONCLUSION

TMP exhibits a good neuroprotective effect after SCI, which may be related to inhibition of the MAPK and PI3K/AKT signaling pathways.

Elevation of NAD+ by nicotinamide riboside spares spinal cord tissue from injury and promotes locomotor recovery

Spinal cord injury (SCI)-induced tissue damage spreads to neighboring spared cells in the hours, days, and weeks following injury, leading to exacerbation of tissue damage and functional deficits. Among the biochemical changes is the rapid reduction of cellular nicotinamide adenine dinucleotide (NAD+), an essential coenzyme for energy metabolism and an essential cofactor for non-redox NAD+-dependent enzymes with critical functions in sensing and repairing damaged tissue. NAD+ depletion propagates tissue damage. Augmenting NAD+ by exogenous application of NAD+, its synthesizing enzymes, or its cellular precursors mitigates tissue damage. Nicotinamide riboside (NR) is considered to be one of the most promising NAD+ precursors for clinical application due to its ability to safely and effectively boost cellular NAD+ synthesis in rats and humans. Moreover, various preclinical studies have demonstrated that NR can provide tissue protection. Despite these promising findings, little is known about the potential benefits of NR in the context of SCI. In the current study, we tested whether NR administration could effectively increase NAD+ levels in the injured spinal cord and whether this augmentation of NAD+ would promote spinal cord tissue protection and ultimately lead to improvements in locomotor function. Our findings indicate that administering NR (500 mg/kg) intraperitoneally from four days before to two weeks after a mid-thoracic contusion-SCI injury, effectively doubles NAD+ levels in the spinal cord of Long-Evans rats. Moreover, NR administration plays a protective role in preserving spinal cord tissue post-injury, particularly in neurons and axons, as evident from the observed gray and white matter sparing. Additionally, it enhances motor function, as evaluated through the BBB subscore and missteps on the horizontal ladderwalk. Collectively, these findings demonstrate that administering NR, a precursor of NAD+, increases NAD+ within the injured spinal cord and effectively mitigates the tissue damage and functional decline that occurs following SCI.

miR-129-5p Induces Cell Apoptosis and Inhibits Inflammation by Inflammatory Signaling to Alleviate Spinal Cord Injury (SCI)

Spinal cord injury (SCI) is a spinal cord nerve dysfunction secondary to trauma. Until now, still no appropriate drug with unclear etiology. Therefore, it is to develop effective SCI treatment methods. Herein, we intended to detect the impact of miR-129-5p in SCI After establishment of a mouse SCI model, the animals received intrathecal injection of agomir-miR-129-5p or normal saline. Then, the miR-129-5p’s effect was evaluated by assessing motor function, spinal cord tissue edema, apoptosis and inflammation of mice upon treatments and potential targeted pathways of the miRNA were detected. Overexpressed miR-129-5p facilitated the wound healing with less spare tissue and water content. Additionally, overexpressed miR-129-5p suppressed the in vivo inflammation with decreased apoptotic rate of neurons. As SCI induced increased expression of HMGB1, TLR4, and NF-κB in tissues, but the presence of miR-129-5p reversed the expressions. Collectively, this study elucidate miR-129-5p significantly improves inflammatory response and apoptosis, thereby improving the condition of SCI. These findings might provide a new theory for the disorder, and promote the research progress on the disease.