What is KPV? The alpha-MSH tripeptide in published research

Where does KPV come from?

KPV comes from alpha-melanocyte stimulating hormone (alpha-MSH), a 13 amino acid peptide that the body cuts from a larger precursor protein called proopiomelanocortin (POMC). The full alpha-MSH sequence is SYSMEHFRWGKPV, and KPV is its last three residues, positions 11 to 13. For this reason the literature often writes it as alpha-MSH(11-13). Reviews of alpha-MSH biology describe it as a peptide with effects on inflammation and immune cells, and work from the late 1990s onward traced part of that activity, along with antimicrobial activity, to the C terminal tripeptide.

Structurally, KPV is a short linear chain of lysine, proline and valine. Lysine gives it a basic, positively charged side chain, and one study noted that KPV carries a positive charge below pH 7. Its molecular weight, calculated from the three residues, is about 342.4 g/mol. Researchers have also made variants: KP-D-V, which uses the D form of valine, and a dimer called (CKPV)2, in which two KPV units are joined by a Cys-Cys linker. The dimer was investigated for antimicrobial work, and its three dimensional structure was characterised by NMR.

Part of the research interest lies in what KPV lacks. Alpha-MSH has a pigmentary effect through melanocortin receptors, and reviews named that effect as one obstacle to studying the full hormone in inflammation research. One review noted that KPV lacks the sequence motif needed to bind any of the known melanocortin receptors, yet in the studies it summarised KPV kept most of the activity of the full hormone against inflammation, without pigmentary action. The same reviews describe a related tripeptide, KdPT, which corresponds to residues 193 to 195 of IL-1beta and has been studied alongside KPV.

How is it described at the molecular level?

Full alpha-MSH is known to act at melanocortin receptors, especially MC1R, and to raise cyclic AMP inside the cell. KPV appears to behave differently. In HaCaT and normal human keratinocytes, neither alpha-MSH nor KPV raised cyclic AMP, and calcium responses were seen only when an adenosine agonist was present. In Chinese hamster ovary cells engineered to express MC1R, KPV peptides did raise intracellular calcium. A mouse immunology study reported that KPV could bind MC1R on antigen presenting cells, which sits uneasily with the review statement that KPV lacks the receptor binding motif. In contrast, in mouse DSS colitis KPV still had an effect in animals with a nonfunctional MC1R, and the authors concluded that its effects were at least partly independent of that receptor.

Two routes inside the cell have been described in more detail. In human intestinal epithelial cells (Caco2-BBE and HT29-Cl.19A) and Jurkat T cells, KPV was taken up by PepT1, a transporter for di and tripeptides. Once inside, nanomolar concentrations reduced NF-kappaB and MAP kinase signalling and lowered the release of inflammatory cytokines. In immortalised human bronchial epithelial cells (16HBE14o-), KPV moved into the nucleus, stabilised the inhibitor protein IkappaBalpha and reduced the nuclear entry of the NF-kappaB subunit p65RelA. Competition tests pointed to an interaction with the site on p65RelA that binds importin-alpha3. Taken together, the published work describes KPV as a peptide that dampens NF-kappaB signalling, with the exact receptor contribution still open.

What has been observed in published research?

Most KPV research has been done in mouse models of intestinal inflammation, with smaller bodies of work on airway cells, skin immunology, the eye and microbes. The main findings are summarised below, with the model named in each case. Outcomes were measured as body weight, tissue histology, enzyme activity, cytokine levels or reporter gene signals, so each finding describes a laboratory measurement in that model rather than a clinical result.

• Mouse colitis, free peptide: in DSS colitis and in CD45RB(hi) T cell transfer colitis, mice that received KPV regained body weight sooner and showed fewer inflammatory infiltrates and lower myeloperoxidase activity in colon tissue. In mice with a nonfunctional MC1R given DSS, all animals in the KPV group survived.
• Mouse colitis, oral route: KPV added to drinking water reduced histological inflammation and inflammatory cytokine expression in both DSS and TNBS colitis, in the same study that described PepT1 uptake.
• Nanoparticle delivery to the colon: KPV loaded into nanoparticles inside an alginate and chitosan hydrogel, given orally, reduced inflammatory and histological signs of DSS colitis in mice. The authors reported a similar effect at a concentration about 12,000 times lower than free KPV in solution. A later study used hyaluronic acid coated nanoparticles that targeted colonic epithelial cells and macrophages, and reported less mucosal damage and lower TNF-alpha in mice.
• Tumour development linked to colitis: in the AOM plus DSS mouse model, KPV was followed by reduced tumour development in normal mice but had no such effect in mice lacking PepT1, which supports the transporter route described above.
• Airway epithelium: in human bronchial epithelial cells stimulated with TNF-alpha or a respiratory virus, KPV reduced NF-kappaB activity, matrix metalloproteinase 9 activity and release of the chemokines IL8 and eotaxin, with the effect increasing with concentration.
• Skin immunology: in a mouse model of contact hypersensitivity, systemic or topical alpha-MSH or KPV reduced both the sensitisation and elicitation phases and induced tolerance to the specific hapten.
• Corneal wounds: in rabbits whose corneal epithelium had been removed, all eight corneas that received topical KPV were fully covered by new epithelium at 60 hours, compared with none in the control group. Blocking nitric oxide synthase with L-NAME removed the effect, which points to a nitric oxide link.
• Microbes and viruses in vitro: alpha-MSH and KPV reduced Staphylococcus aureus colony formation and reduced viability and germ tube formation of Candida albicans. In separate work, KPV reduced HIV-1 expression in chronically infected U1 cells and reduced replication in acutely infected macrophages derived from monocytes.
• Endotoxin response: in human blood mononuclear cells stimulated with LPS, the dimer (CKPV)2 reduced TNF-alpha production and was more potent than KPV itself.
• Skin permeation: across donated human skin, KPV did not reach detectable levels by passive diffusion. Microneedle pretreatment and iontophoresis increased permeation, which is relevant to anyone designing topical delivery experiments.

What the evidence does not establish

The published record on KPV is almost entirely cell and animal work. No controlled human trials of KPV were found in PubMed, and human material appears only as cell lines, isolated blood cells and donated skin. Chemically induced and T cell transfer colitis in mice are useful models, but they do not reproduce the course of inflammatory bowel disease in people, and results in one model did not always carry over to another.

Several of the stronger colitis results used delivery systems, such as nanoparticles and hydrogels, so they cannot be read directly as properties of the free peptide. The receptor picture is also unresolved: MC1R binding, PepT1 transport and blocking of nuclear import have each been proposed, and the studies do not agree on how much each one contributes. Published data on plasma stability, distribution in the body and long term toxicology are limited, and the concentrations used in vitro vary widely between studies. The record therefore supports KPV as a tool for studying inflammatory signalling, not as an established therapy.

It is also worth noting the age and spread of the evidence. Most of the mouse colitis studies cited here were published between 2007 and 2017, and the antimicrobial and HIV findings date from 2000. Those studies used different peptide sources, vehicles and routes, and they rarely report peptide purity in the detail now expected. Researchers planning new work with KPV can make results easier to compare by reporting the source, purity and verified mass of the peptide, the solvent used, and the final concentration in each assay.

Which formats does Vitality Peps supply?

Vitality Peps supplies KPV as KPV 10 mg, a lyophilised powder in a sealed vial. For reconstitution, Vitality Peps also supplies bacteriostatic water in 10 ml vials. Both are sold for in vitro laboratory research only. The vial contains the free tripeptide, not a nanoparticle, hydrogel or dimer preparation like those used in some of the studies described above, so those delivery systems are not part of the product.

How is it handled in the laboratory?

Lyophilised KPV is stored cold and dark until it is needed. Before reconstitution the vial is allowed to reach room temperature, and the powder is dissolved in bacteriostatic water at room temperature by gentle swirling rather than shaking. The working concentration is calculated from the actual peptide mass in the vial, as stated on the certificate of analysis, not from the nominal label alone.

Once reconstituted, the solution is kept refrigerated, labelled with the concentration and dated on the day it was prepared. Repeated warming and cooling is avoided. Our guide to storing research peptides and our guide to reading a peptide certificate of analysis give more detail on both steps.

Research use only

KPV supplied by Vitality Peps is for in vitro laboratory research only. Not a medicine, not a supplement, not for human or veterinary consumption. Nothing above is instructions for use.