Melatonin improves functional outcome via inhibition of matrix metalloproteinases-9 after photothrombotic spinal cord injury in rats

Impact of commonly administered drugs on the progression of spinal cord injury: a systematic review

BACKGROUND

Complications arising from acute traumatic spinal cord injury (SCI) are routinely managed by various pharmacological interventions. Despite decades of clinical application, the potential impact on neurological recovery has been largely overlooked. This study aims to highlight commonly administered drugs with potential disease-modifying effects.

METHODS

This systematic literature review included studies referenced in PubMed, Scopus and Web of Science from inception to March 31st, 2021, which assess disease-modifying properties on neurological and/or functional recovery of drugs routinely administered following spinal cord injury. Drug effects were classified as positive, negative, mixed, no effect, or not (statistically) reported. Risk of bias was assessed separately for animal, randomized clinical trials, and observational human studies.

RESULTS

We analyzed 394 studies conducting 486 experiments that evaluated 144 unique or combinations of drugs. 195 of the 464 experiments conducted on animals (42%) and one study in humans demonstrate positive disease-modifying properties on neurological and/or functional outcomes. Methylprednisolone, melatonin, estradiol, and atorvastatin are the most common drugs associated with positive effects. Two studies on morphine and ethanol report negative effects on recovery.

CONCLUSION

Despite a large heterogeneity observed in study protocols, research from bed to bench and back to bedside provides an alternative approach to identify new candidate drugs in the context of SCI. Future research in human populations is warranted to determine if introducing drugs like melatonin, estradiol, or atorvastatin would contribute to enhancing neurological outcomes after acute SCI.

Teriparatide: an innovative and promising strategy for protecting the blood-spinal cord barrier following spinal cord injury

The blood-spinal cord barrier (BSCB) is disrupted within minutes of spinal cord injury, leading to increased permeability and secondary spinal cord injury, resulting in more severe neurological damage. The preservation of blood-spinal cord barrier following spinal cord injury plays a crucial role in determining the prognosis. Teriparatide, widely used in clinical treatment for osteoporosis and promoting fracture healing, has been found in our previous study to have the effect of inhibiting the expression of MMP9 and alleviating blood-brain barrier disruption after ischemic stroke, thereby improving neurological damage symptoms. However, there are limited research on whether it has the potential to improve the prognosis of spinal cord injury. This article summarizes the main pathological mechanisms of blood-spinal cord barrier disruption after spinal cord injury and its relationship with Teriparatide, and explores the therapeutic potential of Teriparatide in improving the prognosis of spinal cord injury by reducing blood-spinal cord barrier disruption.

Melatonin, a natural antioxidant therapy in spinal cord injury

Spinal cord injury (SCI) is a sudden onset of disruption to the spinal neural tissue, leading to loss of motor control and sensory function of the body. Oxidative stress is considered a hallmark in SCI followed by a series of events, including inflammation and cellular apoptosis. Melatonin was originally discovered as a hormone produced by the pineal gland. The subcellular localization of melatonin has been identified in mitochondria, exhibiting specific onsite protection to excess mitochondrial reactive oxygen species and working as an antioxidant in diseases. The recent discovery regarding the molecular basis of ligand selectivity for melatonin receptors and the constant efforts on finding synthetic melatonin alternatives have drawn researchers' attention back to melatonin. This review outlines the application of melatonin in SCI, including 1) the relationship between the melatonin rhythm and SCI in clinic; 2) the neuroprotective role of melatonin in experimental traumatic and ischemia/reperfusion SCI, i.e., exhibiting anti-oxidative, anti-inflammatory, and anti-apoptosis effects, facilitating the integrity of the blood-spinal cord barrier, ameliorating edema, preventing neural death, reducing scar formation, and promoting axon regeneration and neuroplasticity; 3) protecting gut microbiota and peripheral organs; 4) synergizing with drugs, rehabilitation training, stem cell therapy, and biomedical material engineering; and 5) the potential side effects. This comprehensive review provides new insights on melatonin as a natural antioxidant therapy in facilitating rehabilitation in SCI.

Intrathecal administration of naringenin improves motor dysfunction and neuropathic pain following compression spinal cord injury in rats: relevance to its antioxidant and anti-inflammatory activities

Background

Spinal cord injury (SCI) is one of the most debilitating disorders throughout the world, causing persistent sensory-motor dysfunction, with no effective treatment. Oxidative stress and inflammatory responses play key roles in the secondary phase of SCI. Naringenin (NAR) is a natural flavonoid with known anti-inflammatory and antioxidative properties. This study aims at evaluating the effects of intrathecal NAR administration on sensory-motor disability after SCI.

Methods

Animals underwent a severe compression injury using an aneurysm clip. About 30 minutes after surgery, NAR was injected intrathecally at the doses of 5, 10, and 15 mM in 20 µL volumes. For the assessment of neuropathic pain and locomotor function, acetone drop, hot plate, inclined plane, and Basso, Beattie, Bresnahan tests were carried out weekly till day 28 post-SCI. Effects of NAR on matrix metalloproteinase (MMP)-2 and MMP-9 activity was appraised by gelatin zymography. Also, histopathological analyses and serum levels of glutathione (GSH), catalase and nitrite were measured in different groups.

Results

NAR reduced neuropathic pain, improved locomotor function, and also attenuated SCI-induced weight loss weekly till day 28 post-SCI. Zymography analysis showed that NAR suppressed MMP-9 activity, whereas it increased that of MMP-2, indicating its anti-neuroinflammatory effects. Also, intrathecal NAR modified oxidative stress related markers GSH, catalase, and nitrite levels. Besides, the neuroprotective effect of NAR was corroborated through increased survival of sensory and motor neurons after SCI.

Conclusions

These results suggest intrathecal NAR as a promising candidate for medical therapeutics for SCI-induced sensory and motor dysfunction.

Neuroprotection of melatonin on spinal cord injury by activating autophagy and inhibiting apoptosis via SIRT1/AMPK signaling pathway

The effect of melatonin (MT) on spinal cord injury (SCI) has attracted increasing research attention. However, the specific role and molecular mechanism of MT on SCI have not been elucidated. An experiment was performed to investigate the effect and molecular mechanism of MT on the neuronal autophagy after SCI and its effect on the recovery of nerve function. The rats were randomly divided into four treatment groups: the SCI+MT+EX527 (SIRT1 inhibitor), SCI+MT, SCI, and sham operation groups. On the 14th day after SCI, MT significantly promoted the recovery of motor function in the hind limbs according to the results of Basso, Beattie, and Bresnahan scores. At the same time, MT treatment resulted in reduced activation of cleaved-caspase-3, cleaved-caspase-9, and terminal deoxynucleotidyl transferase dUTP nick end labeling-positive neurons and increased the survival of motoneurons in the anterior horn of the spinal cord on the 14th day after SCI, which exerted its neuroprotection. Furthermore, western blot and immunofluorescence double staining were performed to verify the molecular mechanism of effect of MT on SCI, and results showed the significantly upregulated expressions of Beclin-1, light chain-3B, SIRT1, p-AMPK proteins in the spinal cord tissue of MT-treated rats on the 14th day after SCI, however, the effect of MT on autophagy was reversed by EX527 (SIRT1 inhibitor), which implied that MT activated autophagy via SIRT1/AMPK signaling pathway after SCI. Similarly, the neuroprotective effects of MT on SCI were also inhibited after the SIRT1/AMPK signaling pathway was suppressed by EX527. Taken together, these results suggest that MT inhibits the apoptosis and activates autophagy of nerve cells after SCI and ultimately exerts the neuroprotective effect by SIRT1/AMPK signaling pathway.

Biomaterial strategies for limiting the impact of secondary events following spinal cord injury

The nature of traumatic spinal cord injury (SCI) often involves limited recovery and long-term quality of life complications. The initial injury sets off a variety of secondary cascades, which result in an expanded lesion area. Ultimately, the native tissue fails to regenerate. As treatments are developed in the laboratory, the management of this secondary cascade is an important first step in achieving recovery of normal function. Current literature identifies four broad targets for intervention: inflammation, oxidative stress, disruption of the blood-spinal cord barrier, and formation of an inhibitory glial scar. Because of the complex and interconnected nature of these events, strategies that combine multiple therapies together show much promise. Specifically, approaches that rely on biomaterials to perform a variety of functions are generating intense research interest. In this review, we examine each target and discuss how biomaterials are currently used to address them. Overall, we show that there are an impressive amount of biomaterials and combinatorial treatments which show good promise for slowing secondary events and improving outcomes. If more emphasis is placed on growing our understanding of how materials can manage secondary events, treatments for SCI can be designed in an increasingly rational manner, ultimately improving their potential for translation to the clinic.

Low-Dose Evans Blue Dye for Near-Infrared Fluorescence Imaging in Photothrombotic Stroke Model

Background: Evans blue dye (EBD) is the most common indicator to analyze the extent of blood-brain barrier (BBB) breakdown in several neurological disease models. However, the high-dose of EBD (51.9 mg/kg) is usually required for visualization of blue color by the human eye that brings potential safety issues. Methods: To solve this problem, low-dose of EBD was applied for the near-infrared (NIR) fluorescence-assisted quantitation of BBB breakdown in photothrombotic stoke model. Animals were allocated to seven dose groups ranging from 1.35 nmol (5.19 μg/kg) to 13.5 μmol (51.9 mg/kg) EBD. Results: EBD was undetectable in the non-ischemic brain tissue, and the fluorescence signals in the infarcted hemisphere seemed proportional to the injected dose in the dose range. Although the maximum fluorescence signals in brain tissue were obtained with the injections of 1.35 nmol ~ 13.5 μmol EBD, the background signals in the neighboring brain tissues were significantly increased as well. Since the high concentration of EBD is necessary for color-based identification of the infarcted lesion in brain tissues, even 10-fold diluted could not be distinguished visually by naked eye. Conclusions: NIR fluorescence-assisted method could potentially provide new opportunities to study BBB leakage just using small amount of EBD in different pathological conditions and to test the efficacy of various therapeutic strategies to protect the BBB.

Melatonin for the treatment of spinal cord injury

Spinal cord injury (SCI) from trauma or disease severely impairs sensory and motor function. Neurorehabilitation after SCI is a complex medical process that focuses on improving neurologic function and repairing damaged connections in the central nervous system. An increasing number of preclinical studies suggest that melatonin may be useful for the treatment of SCI. Melatonin is an indolamine that is primarily secreted by the pineal gland and known to be regulated by photoperiodicity. However, it is also a versatile hormone with antioxidative, antiapoptotic, neuroprotective, and anti-inflammatory properties. Here, we review the neuroprotective properties of melatonin and the potential mechanisms by which it might be beneficial in the treatment of SCI. We also describe therapies that combine melatonin with exercise, oxytetracycline, and dexamethasone to attenuate the secondary injury after SCI and limit potential side effects. Finally, we discuss how injury at different spinal levels may differentially affect the secretion of melatonin.

Regulation function of MMP-1 downregulated by siRNA on migration of heat-denatured dermal fibroblasts

Cutaneous wound healing is a complex physiological process that requires the efforts of various cell types and signaling pathways and often results in thickened collagen-enriched healed tissue called a scar. Therefore, the identification of the mechanism of cutaneous wound healing is necessary and has great value in providing better treatment. Here, we demonstrated that MMP-1 inhibition could promote cell proliferation in dermal fibroblasts via the MTT assay. Meanwhile, we investigated cell migration by flow cytometry and tested type I collagenase activity. We found that MMP-1 inhibition promoted cell proliferation and inhibited cell migration and type I collagenase activity. In conclusion, our study demonstrated that MMP-1 might be a potential therapeutic target in cutaneous wound healing.

Propofol protects against blood-spinal cord barrier disruption induced by ischemia/reperfusion injury

Propofol has been shown to exert neuroprotective effects on the injured spinal cord. However, the effect of propofol on the blood-spinal cord barrier (BSCB) after ischemia/reperfusion injury (IRI) is poorly understood. Therefore, we investigated whether propofol could maintain the integrity of the BSCB. Spinal cord IRI (SCIRI) was induced in rabbits by infrarenal aortic occlusion for 30 minutes. Propofol, 30 mg/kg, was intravenously infused 10 minutes before aortic clamping as well as at the onset of reperfusion. Then, 48 hours later, we performed histological and mRNA/protein analyses of the spinal cord. Propofol decreased histological damage to the spinal cord, attenuated the reduction in BSCB permeability, downregulated the mRNA and protein expression levels of matrix metalloprotease-9 (MMP-9) and nuclear factor-κB (NF-κB), and upregulated the protein expression levels of occludin and claudin-5. Our findings suggest that propofol helps maintain BSCB integrity after SCIRI by reducing MMP-9 expression, by inhibiting the NF-κB signaling pathway, and by maintaining expression of tight junction proteins.

Targeting the blood-spinal cord barrier: A therapeutic approach to spinal cord protection against ischemia-reperfusion injury

One of the principal functions of physical barriers between the blood and central nervous system protects system (i.e., blood brain barrier and blood-spinal cord barrier) is the protection from toxic and pathogenic agents in the blood. Disruption of blood-spinal cord barrier (BSCB) plays a key role in spinal cord ischemia-reperfusion injury (SCIRI). Following SCIRI, the permeability of the BSCB increases. Maintaining the integrity of the BSCB alleviates the spinal cord injury after spinal cord ischemia. This review summarizes current knowledge of the structure and function of the BSCB and its changes following SCIRI, as well as the prevention and cure of SCIRI and the role of the BSCB.

Adoptive transfer of M2 macrophages promotes locomotor recovery in adult rats after spinal cord injury

Classically activated pro-inflammatory (M1) and alternatively activated anti-inflammatory (M2) macrophages populate the local microenvironment after spinal cord injury (SCI). The former type is neurotoxic while the latter has positive effects on neuroregeneration and is less toxic. In addition, while the M1 macrophage response is rapidly induced and sustained, M2 induction is transient. A promising strategy for the repair of SCI is to increase the fraction of M2 cells and prolong their residence time. This study investigated the effect of M2 macrophages induced from bone marrow-derived macrophages on the local microenvironment and their possible role in neuroprotection after SCI. M2 macrophages produced anti-inflammatory cytokines such as interleukin (IL)-10 and transforming growth factor β and infiltrated into the injured spinal cord, stimulated M2 and helper T (Th)2 cells, and produced high levels of IL-10 and -13 at the site of injury. M2 cell transfer decreased spinal cord lesion volume and resulted in increased myelination of axons and preservation of neurons. This was accompanied by significant locomotor improvement as revealed by Basso, Beattie and Bresnahan locomotor rating scale, grid walk and footprint analyses. These results indicate that M2 adoptive transfer has beneficial effects for the injured spinal cord, in which the increased number of M2 macrophages causes a shift in the immunological response from Th1- to Th2-dominated through the production of anti-inflammatory cytokines, which in turn induces the polarization of local microglia and/or macrophages to the M2 subtype, and creates a local microenvironment that is conducive to the rescue of residual myelin and neurons and preservation of neuronal function.