5-Hydroxytryptamine receptor 2B (5-HT2B) also known as serotonin receptor 2B is a protein that in humans is encoded by the HTR2Bgene.[5][6] 5-HT2B is a member of the 5-HT2 receptor family that binds the neurotransmitterserotonin (5-hydroxytryptamine, 5-HT).
Tissue distribution and function
First discovered in the stomach of rats, 5-HT2B was challenging to characterize initially because of its structural similarity to the other 5-HT2 receptors, particularly 5-HT2C.[7] The 5-HT2 receptors (of which the 5-HT2B receptor is a subtype) mediate many of the central and peripheral physiologic functions of serotonin. Cardiovascular effects include contraction of blood vessels and shape changes in platelets; central nervous system (CNS) effects include neuronal sensitization to tactile stimuli and mediation of some of the effects of hallucinogenicsubstituted amphetamines. The 5-HT2B receptor is expressed in several areas of the CNS, including the dorsal hypothalamus, frontal cortex, medial amygdala, and meninges.[8] However, it is most important role is in the peripheral nervous system (PNS) where it maintains the viability and efficiency of the cardiac valve leaflets.[9]
The 5-HT2B receptor subtype is involved in:
CNS: inhibition of serotonin and dopamine uptake, behavioural effects[10]
Cardiac: The 5-HT2B receptor regulates cardiac structure and functions, as demonstrated by the abnormal cardiac development observed in 5-HT2B receptor null mice.[12] Excessive stimulation of this receptor causes pathological proliferation of cardiac valve fibroblasts,[13] with chronic overstimulation leading to valvulopathy.[14][15] These receptors are also overexpressed in human failing heart and antagonists of 5-HT2B receptors were uncovered to prevent both angiotensin II or beta-adrenergic agonist-induced pathological cardiac hypertrophy in mouse.[16][17][18]
Serotonin transporter: 5-HT2B receptors regulate serotonin release via the serotonin transporter, and are important both to normal physiological regulation of serotonin levels in blood plasma,[19] and with the abnormal acute serotonin release produced by drugs such as MDMA.[10] Surprisingly however 5-HT2B receptor activation appears to be protective against the development of serotonin syndrome following elevated extracellular serotonin levels,[20] despite its role in modulating serotonin release.
Clinical significance
5-HT2B receptors have been strongly implicated in causing drug-induced valvular heart disease.[21][22][23] The Fen-Phen scandal in the 80s and 90s revealed the cardiotoxic effects of 5-HT2B stimulation.[24] Today, 5-HT2B agonism is considered a toxicity signal precluding further clinical development of a compound.[25]
Ligands
The structure of the 5-HT2B receptor was resolved in a complex with the valvulopathogenic drug ergotamine.[26] As of 2009, few highly selective 5-HT2B receptor ligands have been discovered, although numerous potent non-selective compounds are known, particularly agents with concomitant 5-HT2C binding. Research in this area has been limited due to the cardiotoxicity of 5-HT2B agonists, and the lack of clear therapeutic application for 5-HT2B antagonists, but there is still a need for selective ligands for scientific research.[27]
Agonists
Selective
BW-723C86:[28] fair functional subtype selectivity; almost full agonist. Anxiolytic in vivo.[29]
Ro60-0175[28] functionally selective over 5-HT2A, potent agonist at both 5-HT2B/C
5-HT2B antagonists have previously been proposed as treatment for migraine headaches, and RS-127,445 was trialled in humans up to Phase I for this indication, but development was not continued.[47] More recent research has focused on possible application of 5-HT2B antagonists as treatments for chronic heart disease.[48][49] Research claims serotonin 5-HT2B receptors have effect on liver regeneration.[50] Antagonism of 5-HT2B may attenuate fibrogenesis and improve liver function in disease models in which fibrosis is pre-established and progressive.
^Kennett GA, Trail B, Bright F (Dec 1998). "Anxiolytic-like actions of BW 723C86 in the rat Vogel conflict test are 5-HT2B receptor mediated". Neuropharmacology. 37 (12): 1603–10. doi:10.1016/S0028-3908(98)00115-4. PMID9886683. S2CID7310462.
^Görnemann T, Hübner H, Gmeiner P, Horowski R, Latté KP, Flieger M, Pertz HH (Mar 2008). "Characterization of the molecular fragment that is responsible for agonism of pergolide at serotonin 5-Hydroxytryptamine2B and 5-Hydroxytryptamine2A receptors". The Journal of Pharmacology and Experimental Therapeutics. 324 (3): 1136–45. doi:10.1124/jpet.107.133165. PMID18096760. S2CID24907300.
^Millan MJ, Gobert A, Lejeune F, Dekeyne A, Newman-Tancredi A, Pasteau V, Rivet JM, Cussac D (Sep 2003). "The novel melatonin agonist agomelatine (S20098) is an antagonist at 5-hydroxytryptamine2C receptors, blockade of which enhances the activity of frontocortical dopaminergic and adrenergic pathways". The Journal of Pharmacology and Experimental Therapeutics. 306 (3): 954–64. doi:10.1124/jpet.103.051797. PMID12750432. S2CID18753440.
^Hofmann C, Penner U, Dorow R, Pertz HH, Jähnichen S, Horowski R, Latté KP, Palla D, Schurad B (2006). "Lisuride, a dopamine receptor agonist with 5-HT2B receptor antagonist properties: absence of cardiac valvulopathy adverse drug reaction reports supports the concept of a crucial role for 5-HT2B receptor agonism in cardiac valvular fibrosis". Clinical Neuropharmacology. 29 (2): 80–6. doi:10.1097/00002826-200603000-00005. PMID16614540. S2CID33849447.
^Egan CT, Herrick-Davis K, Miller K, Glennon RA, Teitler M (Apr 1998). "Agonist activity of LSD and lisuride at cloned 5HT2A and 5HT2C receptors". Psychopharmacology. 136 (4): 409–14. doi:10.1007/s002130050585. PMID9600588. S2CID3021798.
^Kovács A, Gacsályi I, Wellmann J, Schmidt E, Szücs Z, Dubreuil V, Nicolas JP, Boutin J, Bózsing D, Egyed A, Tihanyi K, Spedding M, Szénási G (2003). "Effects of EGIS-7625, a selective and competitive 5-HT2B receptor antagonist". Cardiovascular Drugs and Therapy. 17 (5–6): 427–34. doi:10.1023/B:CARD.0000015857.96371.43. PMID15107597. S2CID11532969.
^Dunlop J, Lock T, Jow B, Sitzia F, Grauer S, Jow F, Kramer A, Bowlby MR, Randall A, Kowal D, Gilbert A, Comery TA, Larocque J, Soloveva V, Brown J, Roncarati R (Mar 2009). "Old and new pharmacology: positive allosteric modulation of the alpha7 nicotinic acetylcholine receptor by the 5-hydroxytryptamine(2B/C) receptor antagonist SB-206553 (3,5-dihydro-5-methyl-N-3-pyridinylbenzo[1,2-b:4,5-b']di pyrrole-1(2H)-carboxamide)". The Journal of Pharmacology and Experimental Therapeutics. 328 (3): 766–76. doi:10.1124/jpet.108.146514. PMID19050173. S2CID206500076.
^Moss N, Choi Y, Cogan D, Flegg A, Kahrs A, Loke P, Meyn O, Nagaraja R, Napier S, Parker A, Thomas Peterson J, Ramsden P, Sarko C, Skow D, Tomlinson J, Tye H, Whitaker M (Apr 2009). "A new class of 5-HT2B antagonists possesses favorable potency, selectivity, and rat pharmacokinetic properties". Bioorganic & Medicinal Chemistry Letters. 19 (8): 2206–10. doi:10.1016/j.bmcl.2009.02.126. PMID19307114.
Kursar JD, Nelson DL, Wainscott DB, Baez M (Aug 1994). "Molecular cloning, functional expression, and mRNA tissue distribution of the human 5-hydroxytryptamine2B receptor". Molecular Pharmacology. 46 (2): 227–34. PMID8078486.
Schmuck K, Ullmer C, Engels P, Lübbert H (Mar 1994). "Cloning and functional characterization of the human 5-HT2B serotonin receptor". FEBS Letters. 342 (1): 85–90. doi:10.1016/0014-5793(94)80590-3. PMID8143856. S2CID11232259.
Slominski A, Pisarchik A, Zbytek B, Tobin DJ, Kauser S, Wortsman J (Jul 2003). "Functional activity of serotoninergic and melatoninergic systems expressed in the skin". Journal of Cellular Physiology. 196 (1): 144–53. doi:10.1002/jcp.10287. PMID12767050. S2CID24534729.
Lin Z, Walther D, Yu XY, Drgon T, Uhl GR (Dec 2004). "The human serotonin receptor 2B: coding region polymorphisms and association with vulnerability to illegal drug abuse". Pharmacogenetics. 14 (12): 805–11. doi:10.1097/00008571-200412000-00003. PMID15608559.
External links
"5-HT2B". IUPHAR Database of Receptors and Ion Channels. International Union of Basic and Clinical Pharmacology.
