KPV

KPV is the tripeptide Lys-Pro-Val. It is the last three residues of alpha-melanocyte-stimulating hormone (alpha-MSH). Alpha-MSH is a 13-residue peptide cut from proopiomelanocortin. Papers from the 1980s onward call KPV alpha-MSH(11-13) or the C-terminal tripeptide of alpha-MSH. Interest in the fragment began with fever studies. Rabbits were made febrile with leukocytic pyrogen. KPV was then given centrally or peripherally. It showed part of the parent peptide's antipyretic activity, but was less potent.

The authors read this as evidence that residues 11 to 13 carry part of the message sequence (Richards and Lipton, 1984). Later work found that KPV keeps much of the parent peptide's activity in inflammation models. It does so without the pigmentary effect. It also does not seem to work through the classical melanocortin receptors.

The CAS number, sequence and aliases come from PubChem.

Published work on KPV falls into six areas. Each summary below states the model used. The indexed papers are preclinical throughout. They cover cell culture, rodent and rabbit models, plus formulation chemistry. No controlled human trials of KPV appear in PubMed. And a large share of the gut work comes from one lab group.

Early fragment studies in rodents and rabbits

The rabbit fever work came first (Richards and Lipton, 1984). The same lab then ran a mouse study. It tested graded amounts of KPV in picryl chloride-induced ear swelling. It compared them with saline and with a large amount of corticosteroid. KPV cut swelling in a concentration-related way. The authors read this as evidence of general anti-inflammatory activity for this part of alpha-MSH (Hiltz and Lipton, 1989).

Cell-culture signaling

One study used RAW 264.7 macrophages stimulated with bacterial lipopolysaccharide and interferon-gamma. Alpha-MSH, alpha-MSH(1-10) and alpha-MSH(11-13) all cut nitric oxide production. All three also cut nuclear translocation of NF-kappaB. Radioligand binding showed melanocortin-1 receptor sites on these cells. The full peptide and the 1-10 fragment competed for these sites. The 11-13 tripeptide did not, even at millimolar levels. It also did not raise cyclic AMP (Mandrika et al., 2001).

In human keratinocytes, neither alpha-MSH nor KPV raised cyclic AMP. Both caused rapid calcium transients inside the cells, which in HaCaT cells appeared only when the cyclic AMP pathway was inhibited with an adenosine agonist (Elliott et al., 2004). In immortalized human bronchial epithelial cells, KPV cut NF-kappaB reporter activity and chemokine secretion. The authors tied its action to interference with nuclear import of p65RelA, not to a melanocortin receptor (Land, 2012).

Receptor independence in vivo

A mouse study of crystal-induced peritonitis compared KPV with alpha-MSH. It also included the core melanocortin peptide and receptor-selective agonists. KPV lowered leukocyte accumulation. A melanocortin-3/4 receptor antagonist did not block this drop. In vitro, unlike the core peptides, KPV did not raise cyclic AMP. Nor did it curb macrophage cytokine release.

Its effect still held in mice with a non-functional melanocortin-1 receptor (Getting et al., 2003). A broad review of alpha-MSH and its tripeptides places this work in context. It notes that the missing pigmentary effect is the main reason the fragment has been pursued (Brzoska et al., 2008).

Intestinal models and peptide transport

The most developed line of work concerns the gut. In human intestinal epithelial and T cell lines, nanomolar levels of KPV cut NF-kappaB and MAP kinase signaling. It also cut cytokine secretion. Uptake tests with labeled peptide showed transport by PepT1. This is a di- and tripeptide transporter that is induced in inflamed colon. Given by mouth, KPV also lessened the severity of two chemically induced colitis models in mice (Dalmasso et al., 2008).

An outside German group studied two murine colitis models. It reported less weight loss, histological inflammation and myeloperoxidase activity. This included mice with a non-functional melanocortin-1 receptor (Kannengiesser et al., 2008). Follow-up work from the first group studied colitis-associated tumor formation in mice. It found that tumor formation tracked PepT1 expression. KPV lowered it in wild-type but not PepT1-deficient mice (Viennois et al., 2016).

Delivery and formulation

Free KPV is cleared and broken down quickly. So much of the recent work is on formulation. In one mouse colitis model, nanoparticles were released in the colon from an alginate and chitosan hydrogel. They carried the peptide to colonocytes. The peptide concentration was roughly four orders of magnitude below the free solution used for comparison (Laroui et al., 2010).

Hyaluronic acid-functionalized nanoparticles of about 272 nm were tested in the same model. They were reported to reach epithelial cells and macrophages (Xiao et al., 2017). Negatively charged double-network hydrogels were used to hold the peptide against inflamed colonic mucosa in rats (Zhao et al., 2022).

Other models and analytical chemistry

Reported work outside the gut spans several models. One is rabbit corneal epithelium after mechanical abrasion. There, topical use was linked to faster closure. A nitric oxide synthase inhibitor reduced the effect (Bonfiglio et al., 2006). Another is a controlled cortical impact model in mice. The peptide was given once, systemically. This was followed by smaller lesion volume and less microglial activation (Schaible et al., 2013).

There are also in vitro antimicrobial assays against Staphylococcus aureus and Candida albicans (Cutuli et al., 2000). And one study covers 3T3-L1 preadipocyte differentiation with a high-fat-diet mouse arm (An et al., 2026). A validated stability-indicating HPLC method found lys-pro-diketopiperazine to be the major degradation product. It formed under acid, alkali and peroxide stress (Pawar et al., 2015).