Lanthanide(III) Lanthanide(III) Chelates Chelates of DTPA of DTPA - - Based Based Glycoconjugates Glycoconjugates : : Lectin Lectin - - Mediated Mediated Medical Imaging Agents Medical Imaging Agents João Paulo André Department Department of of Chemistry Chemistry , , University University of of Minho, Braga, Portugal Minho, Braga, Portugal
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Lanthanide(III) Chelates of DTPA-Based Glycoconjugates: Lectin … · 2018. 6. 26. · Summary 1. Objective: Develop new Lanthanide (III) glycoconjugate chelates of DPTA capable of
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Lanthanide(III) Lanthanide(III) ChelatesChelates of DTPAof DTPA--Based Based GlycoconjugatesGlycoconjugates: : LectinLectin--Mediated Mediated
1.1. Objective: Develop new Lanthanide (III) Objective: Develop new Lanthanide (III) glycoconjugateglycoconjugate chelateschelates of of DPTADPTA capable of targeting the liver capable of targeting the liver asialoglycoproteinasialoglycoprotein receptor receptor
(ASGPR)(ASGPR) - lectinlectin with with physicophysico--chemical and biological properties chemical and biological properties
capable ofcapable of making them potential agents for liver imagingmaking them potential agents for liver imaging2. 2. SynthesisSynthesis and and physicophysico--chemicalchemical characterizationcharacterization ofof dendrimericdendrimeric
Lectins : non-enzymatic proteins or glycoproteins which bind to carbohydrates and act as recognition determinants in many biological processes
TargetingTargeting LectinsLectins
-- ASGPASGP--R recognizes terminal R recognizes terminal ββ--galactosylgalactosyl residues on residues on desidesiaalylatedlylatedglycoproteinsglycoproteins
-- Control of intracellular traffic of Control of intracellular traffic of glycoproteinsglycoproteins and and liverliver clearanceclearance from the from the circulatory system of circulatory system of desialylateddesialylated glycoproteinsglycoproteins and apoptotic cells and apoptotic cells
-- Interactions of tumour cells with the immune system, masked by Interactions of tumour cells with the immune system, masked by sialylsialylterminalsterminals
-- Adhesion of infectious agents to host cellsAdhesion of infectious agents to host cells-- Recruitment of leucocytes to inflammatory sites (Recruitment of leucocytes to inflammatory sites (SelectinsSelectins) )
Molecular fit between pairs of complementary structuresMolecular fit between pairs of complementary structures::lectins lectins carbohydratescarbohydrates ((ligandsligands))
This action can be blocked by appropriate sugars This action can be blocked by appropriate sugars in vivoin vivo and and in vitroin vitro
-Composed of two homologous subunits, smaller H1 and bigger H2 in humans (ratio3:1).-Each subunit is a type II transmembrane lectin specific to Gal/N-AcGal.-Each subunit has a short aa cytoplasmatic N terminus, a hydrophobic membrane domain, and an exoplasmatic carboxy terminus exhibiting a carbohydrate recognition domain (CRD) which requires Ca2+ ions.
Models of subunit organization of rat ASGP-R (RHL)
Organization of membrane bound C-type lectins
Mannose macrophagereceptor
Chicken hepaticlectin
Kupffer cell receptor L-selectin
CrystCrystal al StructureStructure ofof CRD CRD ofof H1 H1 SubunitSubunit ofof ASGPASGP--RRCa(2) binding site (8 O atoms)
Gal binds at Ca(2) binding sitereplaces axial water molecules 11 and 13 by (3)OH and (4)OH groups of the carbohydrate
Overlay of sugar binding site of H1-CRD of ASGPR and CDR of MBP mutant containing N-AcGal
Ligands are cleared from the circulation by receptor-mediated endocytosis and degraded in lysosomes, while the receptor is recycled to the cell surface.
1. Ligand (L) binding2. Receptor (R)-ligand (L) internalization3. Uncoating4. Segregation of R and L5. L delivery to lysossomes6. L degradation7. Reactivation of R8. Recycling of R to cell surface9. Formation of new coated pits
Target ASGPTarget ASGP--R: attach R: attach galactosylgalactosyl target residues to a target residues to a carrier containing efficient reporter groupscarrier containing efficient reporter groups
-- SPECT quantification of SPECT quantification of asialoglasialoglyycoproteincoprotein receptorreceptor (ASGP(ASGP--R)R)correlated with hepatic function in normal vs. pathologycorrelated with hepatic function in normal vs. pathology
-- Tumours (Tumours (egeg. . hepatomahepatoma) have reduced ASGP) have reduced ASGP--R, uptake of R, uptake of targeted drugs much decreased vs. normal targeted drugs much decreased vs. normal
-- ASGPASGP--R present in hepatic carcinoma metastasesR present in hepatic carcinoma metastases-- Some of these findings also detected by MRISome of these findings also detected by MRI
Our approach:Our approach:-- GalactosylGalactosyl residues were employed as a targeting device as residues were employed as a targeting device as
part of part of dendrimericendrimeric glycoconjugateglycoconjugates where they were s where they were attached to reporter groups containing the attached to reporter groups containing the LnLn(III)(III)--bindingbindingmoiety, because moiety, because galactosegalactose binding binding ASGPASGP--RR are exposed on are exposed on the surface of liver the surface of liver parenchimalparenchimal cells (~500,000/cell)cells (~500,000/cell)
TTargetargetinging LLiveriver ASGP ASGP RReceptorseceptorsPreviousPrevious resultsresults and and oourur approachapproach
DOTAGalDOTAGal22 30 min30 min DOTAGlcDOTAGlc22 30 min30 min
- Gal conjugates target liverGal < Gal2 ~ Gal4
- Lac conjugates intermediate- Glc conjugates do not
Uptakes as % ID are small
Biodistribution in Wistar rats153Sm(III)-glycoconjugates
- Gal conjugates target liverGal < Gal2 < Gal4
Cluster effectbloo
d
kidn
ey
liver
sple
en
hear
t
lung
s. in
test
stom
ach
l. in
test
brai
n
gal 2gal 4
0
0.05
0.1
0.15
0.2
0.25
% ID
/g
at 1h
at 24h
-- A series of new DTPA glycosidaseA series of new DTPA glycosidase--resistant resistant dendrimericdendrimeric
glycoconjugatesglycoconjugates was synthesized and chemically characterizedwas synthesized and chemically characterized
-- The solution structure of some of their The solution structure of some of their LnLn complexes was studied by NMRcomplexes was studied by NMR
-- The water The water relaxivityrelaxivity of their of their Gd(IIIGd(III) ) chelateschelates was investigated by NMRDwas investigated by NMRD
-- Preliminary studies of the pharmacokinetics and Preliminary studies of the pharmacokinetics and biodistributionbiodistribution of theof the
153153SmSm--labeled labeled glycoconjugatesglycoconjugates in in WistarWistar rats shows selective liver rats shows selective liver uptake ofuptake of
the the glycoconjugatesglycoconjugates with with galactosegalactose terminal groups but not of the othersterminal groups but not of the others
-- These new These new glycoconjugateglycoconjugate ligandsligands may be selective to the liver ASGPRmay be selective to the liver ASGPR
and are potentially useful for liver targeting and imaging (and are potentially useful for liver targeting and imaging ( 153153SmSm3+3+, , 111111InIn3+3+ forfor
gamma gamma scintigraphyscintigraphy and and Gd(IIIGd(III) for MRI)) for MRI)
ConclusionsConclusions
Collaborations
-J. A. Martins, Paula Baía (Univ. Minho, Braga, PT)
- C. F. G. Geraldes (Dep. Biochemistry, Univ. Coimbra, PT)
- J.J P. Lima, I. Prata, A.C. Santos (Fac. Medicine, Univ. Coimbra, PT)
- M. Anjos Neves (ITN , Sacavém, PT)
- A. E. Merbach, E. Tóth, (EPFL, Lausanne, CH)
Support
F.C.T. (Portugal): grant POCTI/QUI/47005/2002
COST Chemistry D18 Program of the E.U “Chemistry of Metals in Medicine”