Chronobiological regulation of psychosocial and physiological outcomes in multiple sclerosis.

There is mounting scientific evidence showing the importance of innate biological rhythms on disease onset and progression. Perhaps the most important of these is the circadian rhythm, a cycle of oscillations lasting approximately 24 h. Recent work has shown that circadian rhythms are intrinsically linked to the immune system in a bidirectional fashion, and that disruption of these cycles can contribute to changes in pathology and quality of life (including fatigue, mood, and disability). This is particularly true in diseases of the nervous and immune systems. We review here the current preclinical and clinical literature to highlight interactions between circadian rhythms and multiple sclerosis, as well as its animal model, experimental autoimmune encephalomyelitis. We highlight potential benefits of chronotherapy (the temporal administration of immunomodulatory drugs) in an effort to increase treatment efficacy and reduce the negative side-effects of the drugs that often burden those suffering from the disease.

Circadian control of pain and neuroinflammation.

The importance of a neuroinflammatory response to the development and maintenance of inflammatory and neuropathic pain have been highlighted in recent years. Inflammatory cells contributing to this response include circulating immune cells such as monocytes, T and B lymphocytes, and neutrophils, as well as microglia in the central nervous system. Pain signals are transmitted via sensory neurons in the peripheral nervous system, which express various receptors and channels that respond to mediators secreted from these inflammatory cells. Chronobiological rhythms, which include the 24-hr circadian cycle, have recently been shown to regulate both nervous and immune cell activity and function. This review examines the current literature on chronobiological control of neuroinflammatory processes, with a focus on inflammatory and neuropathic pain states. While the majority of this work has stemmed from observational studies in humans, recent advances in using animal models have highlighted distinct mechanisms underlying these interactions. Better understanding interactions between the circadian and neuroimmune systems can help guide the development of new treatments and provide improved care for patients suffering from acute and chronic pain.