The anti-inflammatory action of the analgesic kyotorphin neuropeptide derivatives: insights of a lipid-mediated mechanism
Recently, a designed class of efficient analgesic drugs derived from an endogenous neuropeptide, kyotorphin (KTP, Tyr-Arg) combining C-terminal amidation (KTP-NH2) and N-terminal conjugation to ibuprofen (Ib), IbKTP-NH2, was developed. The Ib moiety is an enhancer of KTP-NH2 analgesic action. In the present study, we have tested the hypothesis that KTP-NH2 is an enhancer of the Ib anti-inflammatory action. Moreover, the impact of the IbKTP-NH2 conjugation on microcirculation was also evaluated by a unified approach based on intravital microscopy in the murine cremasteric muscle. Our data show that KTP-NH2 and conjugates do not cause damage on microcirculatory environment and efficiently decrease the number of leukocyte rolling induced by lipopolysaccharide (LPS). Isothermal titration calorimetry showed that the drugs bind to LPS directly thus contributing to LPS aggregation and subsequent elimination. In a parallel study, molecular dynamics simulations and NMR data showed that the IbKTP-NH2 tandem adopts a preferential “stretched” conformation in lipid bilayers and micelles, with the simulations indicating that the Ib moiety is anchored in the hydrophobic core, which explains the improved partition of IbKTP-NH2 to membranes and the permeability of lipid bilayers to this conjugate relative to KTP-NH2. The ability to bind glycolipids concomitant to the anchoring in the lipid membranes through the Ib residue explains the analgesic potency of IbKTP-NH2 given the enriched glycocalyx of the blood–brain barrier cells. Accumulation of IbKTP-NH2 in the membrane favors both direct permeation and local interaction with putative receptors as the location of the KTP-NH2 residue of IbKTP-NH2 and free KTP-NH2 in lipid membranes is the same.
KeywordsKyotorphin Kyotorphin amide Ibuprofen Analgesia Microcirculation
Fundação para a Ciência e Tecnologia (Portugal) is acknowledged for funding (Grant Nos. SFRH/BD/65709/2009, PTDC/BIA-PRO/104378/2008 and PEst-OE/EQB/LA0004/2011). Katia Conceição and Vasanthakumar Ramu were recipients of Marie Curie IAPP fellowships. Marie Curie Industry-Academia Partnerships and Pathways (European Commission) is acknowledged for funding (FP7-PEOPLE-2007-3-1-IAPP. Project 230654). The financial contributions of the Deutsche Forschungsgemeinschaft (to MM), the Agence Nationale de la Recherche (projects TRANSPEP, ProLipIn, membrane DNP and the LabEx Chemistry of Complex Systems), the University of Strasbourg, the CNRS, the Région Alsace and the RTRA International Center of Frontier Research in Chemistry are gratefully acknowledged.
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Conflict of interest
The authors declare that they have no conflict of interest.
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