Hemopressin (Hp) is an alpha

hemoglobin Hemoglobin (haemoglobin BrE) (from the Greek word αἷμα, ''haîma'' 'blood' + Latin ''globus'' 'ball, sphere' + ''-in'') (), abbreviated Hb or Hgb, is the iron-containing oxygen-transport metalloprotein present in red blood cells (erythrocyte ...

fragment with the sequence PVNFKFLSH, originally identified in extracts of rat brain using an enzyme capture technique. It binds

cannabinoid receptors Cannabinoid receptors, located throughout the body, are part of the endocannabinoid system a class of cell membrane receptors in the G protein-coupled receptor superfamily. As is typical of G protein-coupled receptors, the cannabinoid recepto ...

, acting as an

inverse agonist In pharmacology, an inverse agonist is a drug that binds to the same receptor as an agonist but induces a pharmacological response opposite to that of the agonist. A neutral antagonist has no activity in the absence of an agonist or inverse agon ...

at CB₁ receptors. Longer forms of hemopressin containing 2-3 additional amino acids on the

N-terminus The N-terminus (also known as the amino-terminus, NH2-terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide, referring to the free amine group (-NH2) located at the end of a polypeptide. Within a peptide, the ami ...

have been identified in extracts of

mouse brain The mouse brain refers to the brain of Mus musculus. Various brain atlases exist. For reasons of reproducibility, genetically characterized, stable strains like C57BL/6 were chosen to produce high-resolution images and databases. Well known onli ...

. These longer hemopressin peptides, named RVD-Hpα and VD-Hpα, bind to CB1 receptors and were originally reported to be

agonist An agonist is a chemical that activates a receptor to produce a biological response. Receptors are cellular proteins whose activation causes the cell to modify what it is currently doing. In contrast, an antagonist blocks the action of the ago ...

s. In addition to the Hp peptides from alpha hemoglobin, a related peptide from beta hemoglobin has been found in mouse brain extracts; this peptide, named VD-Hpβ, is also an agonist at CB1 cannabinoid receptors. Hemopressin is not an endogenous peptide but rather an extraction artefact [Bauer M, Chicca A, Tamborrini M, Eisen D, Lerner R, Lutz B, Poetz O, Pluschke G, Gertsch J. Identification and quantification of a new family of peptide endocannabinoids (Pepcans) showing negative allosteric modulation at CB1 receptors. J Biol Chem. 2012 Oct 26;287(44):36944-67. doi: 10.1074/jbc.M112.382481. Epub 2012 Sep 5.]. The only endogenous peptide found endogenously at physiological conditions is RVD-hemopressin (pepcan-12), which has more recently been shown to be a negative allosteric modulator of CB1 receptors and positive allosteric modulator of CB2 receptors [Bauer M, Chicca A, Tamborrini M, Eisen D, Lerner R, Lutz B, Poetz O, Pluschke G, Gertsch J. Identification and quantification of a new family of peptide endocannabinoids (Pepcans) showing negative allosteric modulation at CB1 receptors. J Biol Chem. 2012 Oct 26;287(44):36944-67. doi: 10.1074/jbc.M112.382481. Epub 2012 Sep 5.] [Petrucci V, Chicca A, Glasmacher S, Paloczi J, Cao Z, Pacher P, Gertsch J. Pepcan-12 (RVD-hemopressin) is a CB2 receptor positive allosteric modulator constitutively secreted by adrenals and in liver upon tissue damage. Sci Rep. 2017 Aug 25;7(1):9560. doi: 10.1038/s41598-017-09808-8.]. RVD-hemopressin (pepcan-12) is generated from a pro-peptide called pepcan-23 and these peptides are exclusively found in noradrenergic neurons in the brain and in the adrenal medulla [Hofer SC, Ralvenius WT, Gachet MS, Fritschy JM, Zeilhofer HU, Gertsch J. Localization and production of peptide endocannabinoids in the rodent CNS and adrenal medulla. Neuropharmacology. 2015 Nov;98:78-89. doi: 10.1016/j.neuropharm.2015.03.021. Epub 2015 Mar 31.] The original Hp peptide reduces sensitivity to painful stimuli in an experimental model of hyperalgesia. Hp also reduces food intake in mice. However, it remains to be shown if Hp is an endogenous brain peptide. The original purification used boiling acid to extract the peptide from rat brain, and hot acid can specifically cleave D-P bonds. The N-terminally-extended forms RVD-Hpα and VD-Hpα may represent the true endogenous forms.

Role in diet

Scientists at the

University of Manchester , mottoeng = Knowledge, Wisdom, Humanity , established = 2004 – University of Manchester Predecessor institutions: 1956 – UMIST (as university college; university 1994) 1904 – Victoria University of Manchester 1880 – Victoria Univer ...

have discovered that hemopressin could be used as an

appetite suppressant An anorectic or anorexic is a drug which reduces appetite, resulting in lower food consumption, leading to weight loss. By contrast, an appetite stimulant is referred to as orexigenic. The term is (from the Greek ''ἀν-'' (an-) = "without" and ...

without having the side effects of many other drugs that are used for this purpose. In laboratory tests hemopressin was administrated to mice and rats, which significantly reduced food intake. Hemopressin works by affecting the reward centres of the brain which make us feel happy when we eat too much. A further research should be carried out in order to confirm these effects and the safety on people.

References

{{Cannabinoidergics Neuropeptides Cannabinoids

Role in diet

See also

References