1. 2024;27;273-282Melatonin: Evolving Physiological Understanding and Potential Therapeutic Role in Pain Medicine Including Intervertebral Disc Degeneration
   Systematic Review
   Alan D. Kaye, MD, PhD, Christopher J. File, MD Candidate, Grant E. Borne, BS, Charles P. Daniel, BS, Ramaswamy Sharma, PhD, Sahar Shekoohi, PhD, and Miguel A. Pappolla, MD, PhD.

BACKGROUND: Melatonin, one of the most versatile hormones in the body, is well appreciated in managing circadian rhythm and for antioxidant properties. Produced in the pineal gland and within mitochondria, melatonin influences many physiologic processes through receptor mediated and direct effects.

OBJECTIVE: The present investigation explores the evolving pharmacologic properties of melatonin, as well as current therapeutic uses in areas where mitigating oxidative stress, inflammation, and cellular senescence. This review also delves into novel therapeutic potential of melatonin and how current research is revealing a wide array of therapeutic promise in pain medicine.

STUDY DESIGN: A systematic review of randomized controlled trials (RCTs) and observational studies was performed using various search engines focused on melatonin and its role in pain medicine.

METHODS: The available literature on melatonin and pain medicine was reviewed. A comprehensive literature search of multiple databases from 1966 to July 2024, including manual searches of the bibliography of known review articles was performed. Quality assessment of the included studies and best evidence synthesis were incorporated into qualitative and quantitative evidence synthesis.

OUTCOME MEASURES: The primary outcome measure was the proportion of patients receiving melatonin with significant relief and functional improvement of greater than 50% of at least 3 months. Duration of relief was categorized as short-term (less than 6 months) and long-term (greater than 6 months).

RESULTS: Melatonin can affect intervertebral disc (IVD) health through the enhancement of survival and function of nucleus pulposus cells, primarily through activation of the ERK1/2 signaling pathway. Melatonin also influences the biochemical environment of the IVD by modulating inflammation and oxidative stress, crucial factors in the pathogenesis of disc degeneration. Melatonin has been shown to reduce senescence and promote autophagy within disc cells, vital for clearing out damaged cellular components, preserving cellular function and preventing deterioration associated with aging and degenerative diseases.

LIMITATIONS: Despite the availability of multiple studies, the paucity of clinical pain related literature is considered as the major drawback.

CONCLUSION: Based on the present systematic review, melatonin plays a critical role in sleep, but evolving studies have demonstrated substantive roles in mitigating degenerative conditions in various tissues, including IVD degeneration. Ongoing studies will better clarify the role of melatonin as a potential therapeutic agent, including the targeted delivery to various body regions.

KEY WORDS: Melatonin, 5-methoxy-N-acetyltryptamine, pineal gland, neurodegenerative disease, intervertebral disc disease