KPV (Lys-Pro-Val): PepT1 Transport and NF-κB Signaling Research

KPV is the C-terminal tripeptide of α-melanocyte-stimulating hormone, a 13-residue neuropeptide with the sequence Ac-Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-NH2. Lysine, proline and valine occupy positions 11, 12 and 13. PubChem records the fragment under CID 125672 with the formula C16H30N4O4 and a molecular weight of 342.43 g/mol.

Three residues is unusually small for a research peptide, and the computed properties reflect that. PubChem lists a monoisotopic mass of 342.2267 Da, an XLogP of -3.5, a topological polar surface area of 139 Ų, nine rotatable bonds, four hydrogen bond donors and six acceptors. Those values describe a compact, strongly hydrophilic solid rather than a membrane-partitioning molecule, which is why transporter biology rather than passive diffusion dominates the mechanistic literature.

The lysine side chain carries a positive charge at neutral pH and the C-terminal carboxylate carries a negative one, so the free acid form is zwitterionic. Proline in the central position constrains the backbone through its pyrrolidine ring, limiting conformational freedom across the middle of the molecule. Some suppliers list an acetylated, amidated variant, Ac-KPV-NH2, which is a chemically distinct entity from the free acid recorded under CAS 67727-97-3.

Naming across the literature is inconsistent enough to cause confusion. The same molecule appears as KPV, Lys-Pro-Val, α-MSH (11-13), MSH (11-13) and tripeptide KPV. A related but separate fragment, KdPT, substitutes D-proline and threonine and belongs to a different line of work; the two are frequently discussed side by side in review articles and should not be conflated.

KPV enters cells through PepT1, the proton-coupled di- and tripeptide transporter encoded by SLC15A1. Dalmasso and colleagues measured uptake directly in 2008 using tritiated KPV alongside competition with unlabeled peptide, reporting transporter-mediated accumulation in human intestinal epithelial cells and in T cells rather than nonspecific entry across the plasma membrane.

The distribution of PepT1 is what makes this route interesting to the intestinal literature. The transporter is abundant in small intestine under normal conditions and is induced in colonic tissue during inflammatory bowel disease, and it is also expressed by immune cells. A tripeptide that depends on PepT1 therefore concentrates preferentially in exactly the tissue compartments where the transporter is upregulated, which supplies a mechanism for tissue selectivity without any targeting ligand attached to the molecule.

Transporter dependence has been probed genetically as well as pharmacologically. Viennois and colleagues reported in 2016 that transgenic mice overexpressing human PepT1 developed larger tumors, greater tumor burden and increased intestinal inflammation in a colitis-associated cancer model, while PepT1 knockout mice showed significantly decreased tumor number, tumor size and intestinal inflammation. KPV delivered to wild-type animals limited carcinogenesis in the same model through a PepT1-dependent route.

KPV research centers on two signaling readouts: nuclear factor kappa B and the mitogen-activated protein kinase cascade. Dalmasso and colleagues reported that nanomolar concentrations of the tripeptide inhibited activation of both pathways in cytokine-stimulated human intestinal epithelial cells and T cells, and reduced secretion of pro-inflammatory cytokines.

Where in the NF-κB pathway the fragment acts has been addressed separately. Land reported in 2012 that KPV and γ-MSH each produced concentration-dependent inhibition of NF-κB signaling, matrix metalloproteinase-9 activity, and IL-8 and eotaxin secretion in human bronchial epithelial cells challenged with TNF-α or respiratory syncytial virus. The two peptides diverged mechanistically: KPV blocked nuclear import of the p65RelA subunit, whereas γ-MSH acted through MC3R.

MAP kinase branches recur in the more recent cell work. Sung and colleagues reported in 2025 that KPV limited reactive oxygen species production in HaCaT keratinocytes, and that the reduction in oxidant signal was upstream of extracellular signal-regulated kinase and p38 activation. The same study tracked NF-κB as a redox-sensitive transcription factor and reported reduced expression of Bax, Bcl-2 and cleaved caspase-3.

Inflammasome output appears as a third readout. In the keratinocyte work, KPV blocked reactive oxygen species-mediated caspase-1 activation and lowered IL-1β secretion, a sequence the authors describe as mitigation of pyroptosis. Getting and colleagues had earlier reported IL-1β inhibition as a candidate route in a rodent crystal-induced peritonitis model, so the cytokine recurs across two decades and two very different systems.

KPV lacks the His-Phe-Arg-Trp core that gives α-MSH its affinity for melanocortin receptors. That message sequence occupies residues 6 to 9 of the parent hormone, while KPV is drawn from residues 11 to 13, so the fragment carries none of the pharmacophore that MC1R through MC5R recognize. The structural argument is straightforward, and two experimental lines support it.

The first is genetic. Kannengiesser and colleagues ran DSS colitis in mice carrying a nonfunctional melanocortin-1 receptor, the MC1Re/e strain, and reported that KPV rescued all animals in the peptide arm from death during the challenge. Activity in an animal lacking functional MC1R indicates a mechanism at least partially independent of that receptor.

The second is biochemical. Getting and colleagues compared KPV against α-MSH and the melanocortin agonist MTII in crystal-induced peritonitis. All three reduced polymorphonuclear leukocyte accumulation in the peritoneal cavity, but MTII raised cyclic AMP while KPV did not, and the authors concluded that KPV is unlikely to act through melanocortin receptors.

This matters for how the compound is positioned in reviews. Gravina and colleagues surveyed the melanocortin system in inflammatory bowel disease in 2023 and describe a family of mediators and receptors spanning melanogenesis, steroidogenesis and neuromodulation. KPV occupies an odd position inside that family: derived from the prototypical melanocortin agonist, yet apparently operating through transporter-mediated uptake and intracellular signaling rather than receptor occupancy.

KPV appears in the 2023 to 2026 literature across three model families: colonic inflammation in rodents, keratinocyte and reconstructed skin models challenged with particulate matter, and metabolic cell lines. Working concentrations in the recent cell studies cluster at 50 to 100 µg/mL, far above the nanomolar range reported for NF-κB inhibition in intestinal epithelium.

The 2025 keratinocyte study supplies the most detailed cell-model numbers. PM10 particulate matter suppressed HaCaT proliferation and raised IL-1β secretion; KPV at 50 µg/mL restored viability and lowered IL-1β, acting through reduced oxidant production, blunted ERK and p38 activation, and suppressed NF-κB. A three-dimensional reconstructed skin model showed attenuated inflammatory cell death under the same challenge.

Two 2026 papers from overlapping Korean groups moved the fragment into lipid-handling cell models. In HepG2 hepatic epithelial cells challenged with oleic acid, KPV at 100 µg/mL lowered lipid accumulation and fatty acid synthase expression without cytotoxicity, with reduced reactive oxygen species, blunted ERK activation, lower AKT and mTORC1 phosphorylation, and altered PPARγ phosphorylation. In 3T3-L1 preadipocytes under MDI differentiation, KPV at 100 µg/mL reduced Oil Red O staining intensity by roughly 55% and intracellular triglyceride content by roughly 38% against the MDI comparator, again with lower PPARγ and fatty acid synthase expression.

Delivery chemistry produced the newest intestinal result. Cheng and colleagues published a self-immolative conjugate platform in Science Advances in 2026 in which the linker is cleaved by the inflammatory environment itself. The KPV-based conjugate, designated proKPV, reached 3.8-fold greater colonic accumulation than the free tripeptide in colitis models while retaining activity at a lower delivered amount.

Review coverage has kept pace. Adnan and colleagues surveyed tripeptides in skin repair across studies published from 2016 to 2025, and record KPV-loaded hydrogels as reducing inflammation, supporting tissue regeneration and acting against methicillin-resistant Staphylococcus aureus.

KPV formulation research responds to a practical problem: a three-residue peptide clears rapidly and distributes broadly, so most published work encapsulates or conjugates it. Xiao and colleagues loaded the tripeptide into hyaluronic acid-functionalized polymeric nanoparticles of roughly 272.3 nm with a zeta potential near -5.3 mV, then embedded those particles in a chitosan and alginate hydrogel.

That construct was reported to release nanoparticles in the colonic lumen, penetrate colitis tissue, and internalize into colonic epithelial cells and macrophages, showing greater capacity to limit mucosal damage and lower TNF-α than the unfunctionalized comparator. Marotti and colleagues extended the surface-design logic in 2023 with hybrid lipid hyaluronate-KPV conjugated nanoparticles carrying teduglutide, reporting that immunomodulation depended on whether the hyaluronan-KPV functionalization was present.

Carrier-free approaches have also been described. Zhang and colleagues reported in 2024 that KPV and rapamycin self-assemble into nanoparticles without an added carrier material, and that the resulting construct inhibited vascular calcification in cell and rodent systems through combined suppression of inflammatory signaling and activation of autophagy. A separate 2024 report co-assembled KPV with the immunosuppressant FK506 into a PepT1-targeted nanodrug evaluated against acute and chronic DSS colitis.

Skin delivery has been studied physically rather than chemically. Pawar and colleagues measured transdermal transport of KPV across microporated human skin, reporting permeation of 4.4 µg/cm² per hour with microneedle poration alone and roughly 35-fold enhancement when iontophoresis was combined with poration, with confocal imaging confirming migration beyond 100 µm of depth.

KPV is supplied as a lyophilized powder, and its computed profile matches that format. An XLogP of -3.5, a topological polar surface area of 139 Ų and a zwitterionic free-acid form describe a highly water-soluble solid with no lipophilic character. Published methods prepare working solutions in aqueous buffer, saline or culture medium.

Working concentrations in the literature span roughly six orders of magnitude by model type, so a concentration quoted without its model system is close to meaningless. Signaling inhibition in cytokine-stimulated intestinal epithelial cells and T cells was reported at nanomolar concentrations, while recent keratinocyte, hepatocyte and preadipocyte work used 50 to 100 µg/mL, equivalent to roughly 146 to 292 µM at a molecular weight of 342.43 g/mol.

Stability is unusually well characterized for a compound of this size. A validated reversed-phase HPLC method on a C18 column, 4.6 × 250 mm with 5 µm silica, running a gradient of 0.1% trifluoroacetic acid in water against 0.1% trifluoroacetic acid in acetonitrile, achieved a correlation coefficient of 0.9999 with limits of detection and quantification at 0.01 and 0.25 µg/mL. Forced degradation under acid, alkali and hydrogen peroxide produced Lys-Pro-diketopiperazine as the major breakdown product, formed by intramolecular cyclization of the lysine and proline residues, and the method resolves that product from intact peptide.

Identity confirmation follows standard peptide practice: electrospray mass spectrometry against a monoisotopic mass of 342.2267 Da, giving a singly protonated ion near m/z 343.2, with purity determined by reversed-phase HPLC and reported on the lot certificate of analysis. Lyophilized material is normally kept frozen, protected from light and moisture, with aqueous stock solutions aliquoted so that repeated freeze-thaw cycles are avoided. Because the diketopiperazine pathway is pH sensitive, aqueous stocks held at extremes of pH are the condition most likely to degrade.

This material is offered for laboratory research use only. It is not a drug, not a food, and not intended for human or veterinary use.