Psycho-Neuro-Endocrine-Immunology: A Role for Melatonin in This New Paradigm

Abstract

Psychoneuroendocrinoimmunology is the area of study of the intimate relationship between immune, physical, emotional, and psychological aspects. This new way of studying the human body and its diseases was initiated in the last century's first decades. However, the molecules that participate in the communication between the immune, endocrine, and neurological systems are still being discovered. This paper aims to describe the development of psychoneuroendocrinoimmunology, its scopes, limitations in actual medicine, and the extent of melatonin within it.

Keywords: endocrinology; immunology; melatonin; neurology; psychology.

Figure 1

Relationships among hypothalamic hormones, pituitary hormones, and target organs. Neurohypophysis secretion is controlled by nerve signals originating from the hypothalamus, unlike adenohypophysis secretion, which is controlled by hormones or releasing factors from the median eminence. Hormones released from the adenohypophysis are transported to their target organs through the bloodstream. Abbreviations: TRH—thyrotropin-releasing hormone; CRH—corticotropin-releasing hormone; GHRH—growth hormone-releasing hormone; GnRH—gonadotropin-releasing hormone; DA—dopamine; SST—somatostatin; GH—growth hormone; TSH—thyroid-stimulating hormone; ACTH—adrenocorticotropic hormone; LH—luteinizing hormone; FSH—follicle-stimulating hormone; ADH—antidiuretic hormone.

Figure 2

General adaptation syndrome. The general adaptation syndrome is divided into three phases. In the presence of a stressor, phase 1 begins, where the body activates the hypothalamic-pituitary-adrenal axis with the consequent release of hormones to defend itself; in phase 2, symptoms are reduced, and anabolic functions are increased. Phase 3 is exhaustion.

Figure 3

Opiates and cannabinoid system. The activation of the opiate system results in immunosuppression; in contrast, the cannabinoid system results in immunostimulation. Torres-Sanchez ED modified this image, which was obtained from Creative Commons BY based on an unknown author.

Figure 4

The effect of pleasure on the sympathetic and parasympathetic response induces immunosuppression or immunostimulation, respectively. ED Torres-Sánchez modified this image, obtained from the Creative Commons BY base of an unknown author.

Figure 5

MLT is synthesized in the pineal gland. It has proinflammatory and anti-inflammatory effects and multiple functions, among which the adaptive immune response stands out. ED Torres-Sánchez modified this image, obtained from the Creative Commons BY base of an unknown author.

Figure 6

Effects of melatonin in major depressive disorder and cognitive impairments. The pathological process of neurological diseases involves an increase in oxidative stress and an increase in proinflammatory cytokines that stimulate astrocytes and activate microglia. In contrast, by interacting with M2 receptors, melatonin decreases oxidative stress and neuroinflammation. ED Torres-Sánchez modified this image, obtained from the Creative Commons BY base of an unknown author and QIAGEN’s original.