Department of Pharmacology and Toxicology, College of Medicine, Taif University, Taif, 21944, Kingdom of Saudi Arabia.
Department of Clinical Pharmacology and Medicine, College of Medicine, Mustansiriyah University, P.O. Box 14132, Baghdad, Iraq.
Neurotox Res. 2024 Aug 23;42(5):38. doi: 10.1007/s12640-024-00716-0.
Melatonin (MTN) is a neuro-hormone released from the pineal gland. MTN secretion is regulated by different neuronal circuits, including the retinohypothalamic tract and suprachiasmatic nucleus (SCN), which are affected by light. MTN is neuroprotective in various neurodegenerative diseases, including Parkinson's disease (PD). MTN circulating level is highly blunted in PD. However, the underlying causes were not fully clarified. Thus, the present review aims to discuss the potential causes of blunted MTN levels in PD. Distortion of MTN circadian rhythmicity in PD patients causies extreme daytime sleepiness. The underlying mechanism for blunted MTN response may be due to reduction for light exposure, impairment of retinal light transmission, degeneration of circadian pacemaker and dysautonomia. In conclusion, degeneration of SCN and associated neurodegeneration together with neuroinflammation and activation of NF-κB and NLRP3 inflammasome, induce dysregulation of MTN secretion. Therefore, low serum MTN level reflects PD severity and could be potential biomarkers. Preclinical and clinical studies are suggested to clarify the underlying causes of low MTN in PD.
褪黑素（MTN）是松果腺分泌的神经激素。MTN 的分泌受不同的神经元回路调节，包括视网膜下丘脑束和视交叉上核（SCN），它们受光的影响。MTN 在包括帕金森病（PD）在内的各种神经退行性疾病中具有神经保护作用。PD 患者的 MTN 循环水平显著降低。然而，其根本原因尚未完全阐明。因此，本综述旨在讨论 PD 中 MTN 水平降低的潜在原因。PD 患者 MTN 昼夜节律性紊乱导致极度日间嗜睡。MTN 反应迟钝的潜在机制可能是由于光照减少、视网膜光传输受损、昼夜节律起搏器变性和自主神经功能障碍。总之，SCN 的变性及其相关的神经退行性变以及神经炎症和 NF-κB 和 NLRP3 炎性小体的激活，导致 MTN 分泌失调。因此，血清 MTN 水平降低反映了 PD 的严重程度，可能是潜在的生物标志物。建议进行临床前和临床研究以阐明 PD 中 MTN 降低的潜在原因。
