Hemokinin 1 (mouse)

Hemokinin 1 (mouse) is a selective agonist of neurokinin-1 receptor, with Ki of 0.175 nM and 560 nM for human NK1 receptor and human NK2 receptor, respectively. Sequence: Arg-Ser-Arg-Thr-Arg-Gln-Phe-Tyr-Gly-Leu-Met-NH2.

In Vitro:Hemokinin 1 (mouse) (1 nM-3 μM) produces concentration-dependent contraction of RUB averaging 66±3% (n=6) of the maximal contraction produced by KCl (80 mM). Hemokinin 1 (mouse) (10 nM-10 μM) induces a quickly-developing contractile responses of GPI, as does the tachykinin NK3 receptor selective agonist senktide or neurokinin B (NKB). Hemokinin 1 (mouse) induces full agonist responses but with a 500 fold lower potency as compared to NKB[1].

In Vivo:Hemokinin 1 (mouse) (0.01-100 nmol/kg i.v., n=10) induces a dose-related hypotension that is maximal at the dose of 10 nmol/kg. For systolic blood pressure (SBP), the ED50 value is 0.2 nmol/kg (0.1-0.4 nmol/kg) for Hemokinin 1 (mouse). For diastolic blood pressure (DBP), the ED50 value is 0.1 nmol/kg (0.07-0.2 nmol/kg) for Hemokinin 1 (mouse). Hemokinin 1 (mouse) (0.1-100 nmol/kg, i.v.) induces a dose-related salivary secretion in atropine-pretreated rats[1].

References:
[1]. Francesca Bellucci, et al. Pharmacological profile of the novel mammalian tachykinin, hemokinin 1. Br J Pharmacol. 2002 Jan; 135(1): 266-274

Study on the distribution sites and the molecular mechanism of analgesia after intracerebroventricular injection of rat/mouse hemokinin-1 in mice.[Pubmed:23470255]

Peptides. 2013 May;43:113-20.

Hemokinin-1 is a peptide encoded by Pptc, which belongs to the family of mammalian tachykinins. Our previous results showed that rat/mouse hemokinin-1 (r/m HK-1) produced striking analgesia after intracerebroventricular (i.c.v.) injection in mice, and the analgesia could be blocked by the NK1 receptor antagonist and the opioid receptor antagonist, respectively. However, the precise distribution sites and the molecular mechanism involved in the analgesic effect after i.c.v. administration of r/m HK-1 are needed to be further investigated deeply. Using the fluorescence labeling method, our present results directly showed that r/m HK-1 peptides were mainly distributed at the ventricular walls and several juxta-ventricular structures for the first time. Our results showed that the mRNA expressions of NK1 receptor, PPT-A, PPT-C, KOR, PDYN, DOR and PENK were not changed markedly, as well as the protein expression of NK1 receptor was hardly changed. However, both the transcripts and proteins of MOR and POMC were up-regulated significantly, indicating that the analgesic effect induced by i.c.v. administration of r/m HK-1 is related to the activation of NK1 receptor first, then it is related to the release of endogenous proopiomelanocortin, as well as the increased expression level of mu opioid receptor. These results should facilitate further the analysis of the analgesia of r/m HK-1 in the central nerval system in acute pain and may open novel pharmacological interventions.

Hemokinin-1 is an important mediator of endotoxin-induced acute airway inflammation in the mouse.[Pubmed:25541043]

Peptides. 2015 Feb;64:1-7.

OBJECTIVE: Hemokinin-1, the newest tachykinin encoded by the preprotachykinin C (Tac4) gene, is predominatly produced by immune cells. Similarly to substance P, it has the greatest affinity to the tachykinin NK1 receptor, but has different binding site and signaling mechanisms. Furthermore, several recent data indicate the existence of a not yet identified own receptor and divergent non-NK1-mediated actions. Since there is no information on its functions in the airways, we investigated its role in endotoxin-induced pulmonary inflammation. METHODS: Acute pneumonitis was induced in Tac4 gene-deleted (Tac4(-/-)) mice compared to C57Bl/6 wildtypes by intranasal E. coli lipopolysaccharide (LPS). Airway responsiveness to inhaled carbachol was measured with unrestrained whole body plethysmography 24h later. Semiquantitative histopathological scoring was performed; reactive oxygen species (ROS) production was measured with luminol bioluminescence, myeloperoxidase activity with spectrophotometry, and inflammatory cytokines with Luminex. RESULTS: All inflammatory parameters, such as histopathological alterations (perivascular edema, neutrophil/macrophage accumulation, goblet cell hyperplasia), myeloperoxidase activity, ROS production, as well as interleukin-1beta, interleukin-6, tumor necrosis factor alpha, monocyte chemoattractant protein-1 and keratinocyte chemoattractant concentrations were significantly diminished in the lung of Tac4(-/-) mice. However, bronchial hyperreactivity similarly developed in both groups. Interestingly, in LPS-treated Tac4(-/-) mouse lungs, bronchus-associated, large, follicle-like lymphoid structures developed. CONCLUSIONS: We provide the first evidence that hemokinin-1 plays a crucial pro-inflammatory role in the lung by increasing inflammatory cell activities, and might also be a specific regulator of lymphocyte functions.

[Particularities of Spatial Organization of Human Hemokinin-1 and Mouse/Rat Hemokinin-1 Molecules].[Pubmed:26349209]

Biofizika. 2015 May-Jun;60(3):457-70.

By molecular mechanics method the conformational properties of two molecules of the tachykinin family, human hemokinin-1 and mouse/rat hemokinin-1, each consisting of 11 amino acids, have been investigated. On the basis of a step-by-step approach we determined the energetically favorable spatial structures of these molecules and their fragments represented as a set of conformations characterized by the relatively labile N-terminal tripeptide and conformationally rigid C-terminal segment. It was shown that conformationally conservative C-terminal octapeptide of the molecules preferably forms two conformations with different structural types of the peptide chain. One of these conformations has an alpha-helical structure, and the other forms the chain's turn that led to an alpha helical turn at the C-terminus. As a result of calculations the energetically favorable ranges of the values of the dihedral angles and orientations of all the residues in low energy conformational states of the molecules were shown. Due to conformational analysis of separate fragments it was possible to trace the process of the second structure formation in these molecules. Based on the results obtained the contribution of inter-residues interaction energy was determined and the role of the each residue in the formation of the optimal spatial structures of hemokinin-1 molecules was estimated.

Effects of rat/mouse hemokinin-1, human hemokinin-1 and human hemokinin-1(4-11), mammalian tachykinin peptides, on rate and perfusion pressure in the isolated guinea pig heart.[Pubmed:20471676]

Neuropeptides. 2010 Oct;44(5):437-44.

Rat/mouse hemokinin-1 (r/m HK-1), human hemokinin-1 (h HK-1) and human hemokinin-1(4-11) (h HK-1(4-11)) are members of the tachykinin family. In the present study, the coronary vascular activities and cardiac functions of r/m HK-1, h HK-1 and h HK-1(4-11) were investigated in isolated, spontaneously beating guinea pig hearts. Bolus injections of r/m HK-1 caused decrease in perfusion pressure indicative of coronary vasodilation, which was primarily due to the action on tachykinin NK1 receptors on vascular endothelial cells, causing the release of nitric oxide that relaxed the coronary vessels. H HK-1 caused biphasic perfusion pressure changes that were coronary vasodilation followed by coronary vasoconstriction. The mechanisms involved in the vasodilation induced by h HK-1 were similar to that of r/m HK-1 while the mechanisms for coronary vasoconstriction were mediated through the activation of tachykinin NK2 receptors on coronary sympathetic neurons to release catecholamines. H HK-1(4-11) only produced coronary vasoconstriction and the mechanisms involved in this effect were similar to that of h HK-1 in vasoconstriction. Moreover, r/m HK-1 and h HK-1 produced similar decreases in heart rate indicative of negative chronotropic responses and the decreases were mainly mediated through the activation of tachykinin NK1 receptors to release ACh acting on muscarinic receptors. H HK-1(4-11) also produced negative chronotropic response, which was mainly mediated through tachykinin NK2 receptors and muscarinic receptors. Our present results provide evidence that all of the three tachykinins could influence cardiac function and coronary vascular activity in the isolated guinea pig heart.

Pharmacological profile of the novel mammalian tachykinin, hemokinin 1.[Pubmed:11786503]

Br J Pharmacol. 2002 Jan;135(1):266-74.

1. The effects of the novel mammalian tachykinin, hemokinin 1 (HEK-1), have been investigated by radioligand binding and functional in vitro and in vivo experiments. 2. Similar to SP (K(i)=0.13 nM), HEK-1 inhibited in a concentration-dependent manner and with high affinity [(3)H]-substance P (SP) binding to human NK(1) receptor (K(i)=0.175 nM) while its affinity for [(125)I]-neurokinin A (NKA) binding at human NK(2) receptor was markedly lower (K(i)=560 nM). 3. In isolated bioassays HEK-1 was a full agonist at tachykinin NK(1), NK(2) and NK(3) receptors. In the rat urinary bladder (RUB) HEK-1 was about 3 fold less potent than SP. In the rabbit pulmonary artery (RPA) HEK-1 and in the guinea-pig ileum (GPI), HEK-1 was about 500 fold less potent than NKA and NKB, respectively. 4. The responses to HEK-1 were antagonized by GR 82334 in RUB (pK(B)=5.6+/-0.07), by nepadutant in RPA (pK(B)=8.6+/-0.04) and by SR 142801 in GPI (pK(B)=9.0+/-0.2) with apparent affinities comparable to that measured against tachykinin NK(1), NK(2) and NK(3) receptor-selective agonists, respectively. 5. Intravenous HEK-1 produced dose-related decrease of blood pressure in anaesthetized guinea-pigs (ED(50)=0.1 nmol kg(-1)) and salivary secretion in anaesthetized rats (ED(50)=6 nmol kg(-1)) with potencies similar to that of SP. All these effects were blocked by the selective tachykinin NK(1) receptor antagonist, SR 140333. 6. We conclude that HEK-1 is a full agonist at tachykinin NK(1), NK(2) and NK(3) receptors, possesses a remarkable selectivity for NK(1) as compared to NK(2) or NK(3) receptors and acts in vivo experiments with potency similar to that of SP.

Hemokinin is a hematopoietic-specific tachykinin that regulates B lymphopoiesis.[Pubmed:11062498]

Nat Immunol. 2000 Nov;1(5):392-7.

We report here the molecular cloning of a newly identified preprotachykinin gene, Pptc, which specifies the sequence for a new preprotachykinin protein and bioactive peptide designated hemokinin 1 (HK-1). PPT-C mRNA was detected primarily in hematopoietic cells in contrast to the previously described Ppta and Pptb genes, which are predominantly expressed in neuronal tissues. HK-1 has several biological activities that are similar to the most studied tachykinin, substance P, such as induction of plasma extravasation and mast cell degranulation. However, HK-1 also has properties that are indicative of a critical role in mouse B cell development. HK-1 stimulated the proliferation of interleukin 7-expanded B cell precursors, whereas substance P had no effect. HK-1, but not substance P, promoted the survival of freshly isolated bone marrow B lineage cells or cultured, lipopolysaccharide-stimulated pre-B cells. N-acetyl-L-trytophan-3,5-bistrifluromethyl benzyl ester, a tachykinin receptor antagonist, increased apoptosis of these cells and in vivo administration of this antagonist led to specific reductions of the B220lowCD43 population (the pre-B cell compartment) in the bone marrow and the IgMhighIgDlow population (the newly generated B cells) in the spleen. Thus, HK-1 may be an autocrine factor that is important for the survival of B cell precursors at a critical phase of development.

Hemokinin 1 (mouse) is a selective agonist of neurokinin-1 receptor, with Ki of 0.175 nM and 560 nM for human NK1 receptor and human NK2 receptor, respectively.

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