5-HT2B Receptor on Macrophages: What for?

Spa therapy and peripheral serotonin and dopamine function: a systematic review

“…More specifically, serotonin modulates (stimulating or inhibiting) the effector functions of granulocytes, B and T lymphocytes, monocytes, dendritic cells, and tissue-resident macrophages (Casas-Engel and Corbí 2014 ). Several immune cell types are able to synthesize, transport, store, and respond to serotonin through serotonin receptors expressed in these cells, although the exact role of many of these receptors is still unclear (Wu et al 2019 ) due to the tissue- and cell-specific pattern of expression as well as distinct signaling capacity of the different subtypes of serotonin receptors (Nieto et al 2021 ). Therefore, the pleiotropic, numerous actions of serotonin on immune cells and the inflammatory response can be different depending on the serotonin receptor subtype, and cell maturation stage... among several other factors (Casas-Engel and Corbí 2014 ).…”

“…Therefore, the pleiotropic, numerous actions of serotonin on immune cells and the inflammatory response can be different depending on the serotonin receptor subtype, and cell maturation stage... among several other factors (Casas-Engel and Corbí 2014 ). Indeed, peripheral serotonin modulates leukocyte migration into sites of inflammation, and the elevated levels of serotonin found at inflamed sites contribute to regulating cytokine production during inflammation promotion and resolution (Nieto et al 2021 ). In turn, activated immune cells can also influence serotonin synthesis and secretion in the gut (Spohn and Mawe 2017 ).…”

“…In turn, activated immune cells can also influence serotonin synthesis and secretion in the gut (Spohn and Mawe 2017 ). In this context, altered peripheral serotonin levels have been shown to be involved in the development and resolution of immunity/inflammation-related pathologies like pulmonary arterial hypertension, atopic dermatitis, allergic asthma, systemic sclerosis, amyotrophic lateral sclerosis, and inflammatory gut disorders and also regulate cancer angiogenesis, neuroendocrine neoplasms proliferation, and arthritis (Nieto et al 2020 , 2021 ). In rheumatoid arthritis (RA), synovial fluid and circulating serotonin levels are elevated; in fact, it has been reported that intra-articular injection of serotonin in models of arthritis causes joint inflammation and pain, while its depletion attenuates disease severity (Shajib and Khan 2015 ).…”

“…Serotonin (5-hydroxytryptamine, 5-HT) is a well-known neurotransmitter that mediates a diverse range of biological and behavioral processes such as circadian rhythms, food intake, sleep, reproductive activity, pain, cognition, mood, and anxiety/stress. Outside the central nervous system, peripheral serotonin acts as a hormone and also plays a fundamental, but lesser-known role, in many other physiological functions (bone mass, tissue regeneration—cell proliferation and wound healing—coagulation, angiogenesis, hematopoiesis gastrointestinal function, thermoregulation, and immunity) (Wu et al 2019 ; Nieto et al 2021 ). While the immune system was previously seen as unrelated to serotonin, recent findings have made it increasingly clear that peripheral serotonin plays a key part in the regulation of inflammation and immunity (Wu et al 2019 ).…”

“…While the immune system was previously seen as unrelated to serotonin, recent findings have made it increasingly clear that peripheral serotonin plays a key part in the regulation of inflammation and immunity (Wu et al 2019 ). In fact, the direct involvement of altered peripheral serotonin levels in the development and resolution of immunity/inflammation-related pathologies has been demonstrated (Nieto et al 2020 , 2021 ), although the exact role of peripheral serotonin in rheumatic diseases is yet to be elucidated.…”