Blum Brian, Kaushal Shivani, Khan Sara, Kim Jae H, Alvarez Villalba Clara L
Psychiatry, Aventura Hospital and Medical Center, Aventura, USA.
Medicine, Nova Southeastern University Dr. Kiran C. Patel College of Allopathic Medicine, Davie, USA.
Cureus. 2021 Sep 6;13(9):e17776. doi: 10.7759/cureus.17776. eCollection 2021 Sep.
Traumatic brain injury (TBI) is a leading cause of long-term disability and mortality in young adults. The devastating effects of TBI on emotion regulation, executive functioning, and cognition have been well-established, and recent research links TBI as a risk factor for neurodegenerative diseases such as Alzheimer's disease. Despite an increased focus on the long-term cognitive dysfunction associated with TBI, research into potential treatments has not yet generated consistent successful results in human subjects. Many foundational studies have analyzed the cellular and molecular events involved in the inflammatory and healing processes following TBI, enhancing our understanding of the mechanisms that may contribute to the progression of dementia and cognitive decline in these patients. In this review, we will discuss the emergent research on melatonin within the framework of neuroinflammation and oxidative stress resulting from TBI and possibly preventing further sequelae such as Alzheimer's disease. A literature review was conducted using standard search strategies to query the PubMed database. The following search terms were used with qualifiers of various combinations: TBI, traumatic brain injury, melatonin, treatment, dementia, Alzheimer's, cognition, and neurodegeneration. Selected studies included meta-analyses, literature reviews, and randomized controlled trials (RCT) that evaluated melatonin's role as a potential therapy to prevent post-TBI neurodegeneration, specifically the development of dementia and deficits in memory and cognition. Three independent reviewers assessed all articles for eligibility. After assessment for eligibility, 11 total studies were included. Much of the available data on melatonin in TBI has highlighted its significant neuroprotective and antiinflammatory effects, which can be significant in fighting against the neuroinflammatory processes indicated in neurodegeneration. In animal models, immunohistochemistry and histopathology have allowed researchers to study measures of cell injury such as inflammatory cytokines, edema, and markers of oxidative stress. Though the effects of melatonin in TBI appear to be mediated through mostly indirect mechanisms on inflammatory processes, some research has explored potential mechanisms that could be specific to melatonin. Animal model studies support that melatonin treatment after TBI significantly improves cognition and behavioral outcomes. However, clinical studies with human subjects are scarce. Beyond the apparent general antiinflammatory and antioxidant actions of melatonin, a review of the evidence identified some preliminary research that has suggested the significance of melatonin receptors specifically in TBI. While there is some evidence to suggest that melatonin is able to reduce post-TBI cognitive decline as measured by subject performance on memory tasks, there is a lack of longitudinal data on whether melatonin decreases the risk of developing dementia after TBI. Considering melatonin therapy's promising preclinical data, favorable safety profile, and accessibility, further studies are warranted to assess the effects of melatonin as a post-TBI therapy on human subjects.
创伤性脑损伤(TBI)是导致年轻人长期残疾和死亡的主要原因。TBI对情绪调节、执行功能和认知的破坏性影响已得到充分证实,最近的研究将TBI列为神经退行性疾病(如阿尔茨海默病)的一个风险因素。尽管人们越来越关注与TBI相关的长期认知功能障碍,但针对潜在治疗方法的研究尚未在人体试验中取得一致的成功结果。许多基础研究分析了TBI后炎症和愈合过程中涉及的细胞和分子事件,加深了我们对可能导致这些患者痴呆和认知衰退进展的机制的理解。在这篇综述中,我们将讨论褪黑素在TBI引起的神经炎症和氧化应激框架内的新兴研究,以及其可能预防诸如阿尔茨海默病等进一步后遗症的作用。使用标准搜索策略对PubMed数据库进行了文献检索。使用了以下搜索词及各种组合的限定词:TBI、创伤性脑损伤、褪黑素、治疗、痴呆、阿尔茨海默病、认知和神经退行性变。选定的研究包括荟萃分析、文献综述和随机对照试验(RCT),这些研究评估了褪黑素作为预防TBI后神经退行性变(特别是痴呆的发展以及记忆和认知缺陷)的潜在疗法的作用。三位独立评审员评估了所有文章的 eligibility。经过资格评估,共纳入11项研究。关于TBI中褪黑素的现有许多数据突出了其显著的神经保护和抗炎作用,这在对抗神经退行性变中指出的神经炎症过程中可能具有重要意义。在动物模型中,免疫组织化学和组织病理学使研究人员能够研究细胞损伤的指标,如炎性细胞因子、水肿和氧化应激标志物。尽管褪黑素在TBI中的作用似乎主要通过对炎症过程的间接机制介导,但一些研究探索了可能特定于褪黑素的潜在机制。动物模型研究支持TBI后褪黑素治疗可显著改善认知和行为结果。然而,人体试验的临床研究很少。除了褪黑素明显的一般抗炎和抗氧化作用外,对证据的综述还发现了一些初步研究,表明褪黑素受体在TBI中具有特殊意义。虽然有一些证据表明褪黑素能够降低TBI后认知衰退(通过记忆任务中的受试者表现来衡量)但缺乏关于褪黑素是否能降低TBI后患痴呆风险的纵向数据。考虑到褪黑素疗法有前景的临床前数据、良好的安全性和可及性,有必要进一步研究评估褪黑素作为TBI后疗法对人体受试者的影响。