Kinin

Group of peptides

Not to be confused with Knin.

A kinin is any of various structurally related peptides, such as bradykinin and kallidin.[1] They are members of the autacoid family.[2] Kinins are peptides that are cleaved from kininogens by the process of kallikreins. Kallikreins activate kinins when stimulated.[3]

It is a component of the kinin-kallikrein system.

Their precursors are kininogens.[4] Kininogens contain a 9-11 amino acid bradykinin sequence.[5]

In botany, the plant hormones known as cytokinins were first called kinins; the name was changed to avoid confusion.[6]

## Effects of kinins

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Kinins are short-lived peptides that cause pain sensation, arteriolar dilation, increase vascular permeability, and cause contractions in smooth muscle. Kinins transmit their effects through G protein-coupled receptors.[5]

Kinins act on axons to block nerve impulses, which leads to distal muscle relaxation. They are also potent nerve stimulators which are mostly responsible for the pain sensation (and sometimes itching). Kinins increase vascular permeability by acting on vascular endothelial cells to cause cell contraction. Concomitantly, they induce local expression of adhesive molecules. Together they increase white blood cell adhesion and extravasation. Kinins are rapidly inactivated by the proteases generated locally during the aforementioned processes.[7]

They act locally to induce vasodilation and contraction of smooth muscle.[8] Kinins function as mediators for inflammatory responses by triggering the immune system. They are also able to regulate cardiovascular and renal (kidney) function by mediating the effects of ACE inhibitors.[9] Reduced kinin activity can result in high blood pressure, sodium retention, and the narrowing of blood vessels.[3]

Aspirin inhibits the activation of kallenogen by interfering with the formation of the kallikrein enzyme, which is essential in the process of activation.

## Where kinins are produced

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Kinins are mostly produced at inflamed or injured tissues of the body and human body fluids. Kinin peptides (kallidin and bradykinin) are located in human blood and urine.[10]

## Kinin receptors

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There are two types of kinin receptors: B1 and B2. Both are G-protein coupled receptors in which B2 are expressed in various tissues and B1 are induced from inflammation, tissue injuries, and stress.[11] The human body contains more B2 receptors than B1 receptors.[10]

B1 and B2 receptors are essentially related as homologous genes.[12] Both have the same cellular signaling pathways, although their patterns are different in intensity and duration; the B1 signaling pathway lasts longer than the B2 signaling pathway.[13]

## History

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Kinin was initially discovered by J.E. Abelous and E. Bardier in 1909 while performing experiments where human body fluids, such as urine, were injected into dogs. The resulting observations state that the urine caused a reduction in blood pressure.[3][clarification needed]

## References

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1. ^ Kinins. De Gruyter. 2011. ISBN 978-3-11-025235-4.
2. ^ Kinins at the U.S. National Library of Medicine Medical Subject Headings (MeSH)
3. ^ a b c Sharma, Jagdish N., ed. (2014). Recent Developments in the Regulation of Kinins. doi:10.1007/978-3-319-06683-7. ISBN 978-3-319-06682-0. S2CID 38701984.
4. ^ Online Medical Dictionary
5. ^ a b Bader, Michael (2011-01-16), Bader, Michael (ed.), "1 Kinins: History and outlook", Kinins, Berlin, Boston: DE GRUYTER, pp. 1–6, doi:10.1515/9783110252354.1, ISBN 978-3-11-025235-4, retrieved 2021-04-30
6. ^ Galuszka P, Spíchal L, Kopečný D, Tarkowski P, Frébortová J, Šebela M, Frébort I (2008). "Metabolism of plant hormones cytokinins and their function in signaling, cell differentiation and plant development". Bioactive Natural Products (Part N). Studies in Natural Products Chemistry. Vol. 34\. pp. 203–64\. doi:10.1016/S1572-5995(08)80028-2. ISBN 978-0-444-53180-3.
7. ^ Textbook Immunology: a short course, 5th ed, Coico R, Sunshine G, Benjamini E.Wiley-Liss
8. ^ "Kinin" at Dorland's Medical Dictionary
9. ^ Rhaleb NE, Yang XP, Carretero OA (April 2011). "The kallikrein-kinin system as a regulator of cardiovascular and renal function". Comprehensive Physiology. 1 (2): 971–93\. doi:10.1002/cphy.c100053. ISBN 9780470650714. PMC 4685708. PMID 23737209.
10. ^ a b Duncan, Ann-Maree; Kladis, Athena; Jennings, Garry L.; Dart, Anthony M.; Esler, Murray; Campbell, Duncan J. (2000-04-01). "Kinins in humans". American Journal of Physiology. Regulatory, Integrative and Comparative Physiology. 278 (4): R897 – R904. doi:10.1152/ajpregu.2000.278.4.r897. ISSN 0363-6119. PMID 10749777.
11. ^ Soley, Bruna da Silva; Morais, Rafael Leite Tavares de; Pesquero, João Bosco; Bader, Michael; Otuki, Michel Fleith; Cabrini, Daniela Almeida (2016-05-01). "Kinin receptors in skin wound healing". Journal of Dermatological Science. 82 (2): 95–105\. doi:10.1016/j.jdermsci.2016.01.007. ISSN 0923-1811. PMID 26817699.
12. ^ Girolami, Jean-Pierre; Bouby, Nadine; Richer-Giudicelli, Christine; Alhenc-Gelas, Francois (March 2021). "Kinins and Kinin Receptors in Cardiovascular and Renal Diseases". Pharmaceuticals. 14 (3): 240. doi:10.3390/ph14030240. ISSN 1424-8247. PMC 8000381. PMID 33800422.
13. ^ da Costa, Patrícia L. N.; Sirois, Pierre; Tannock, Ian F.; Chammas, Roger (2014-04-01). "The role of kinin receptors in cancer and therapeutic opportunities". Cancer Letters. 345 (1): 27–38\. doi:10.1016/j.canlet.2013.12.009. ISSN 0304-3835. PMID 24333733.

## External links

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* The kinin-forming system at nic.sav.sk

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Intercellular signaling peptides and proteins / ligands

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* Epidermal growth factor
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Ephrin|

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see also extracellular ligand disorders

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Autacoids

Kinins|

* Kininogen (HMWK, LMWK)
* Bradykinin
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Peptides: neuropeptides

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Other
neuropeptides|

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Bradykinins
Tachykinins: mammal

* Substance P
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amphibian

* Kassinin
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