Download bone marrow targeting and targeting to lysosomal

BONE MARROW TARGETING AND
TARGETING TO LYSOSOMAL DISEASES
By
SOMESHWAR.K
M.PHARM.
II - SEMESTER
Department of Pharmaceutics
University College of Pharmaceutical
Sciences,
KAKATIYA UNIVERSITY
Warangal - 506009
CONTENTS
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Introduction
Physiology of bone marrow
Bone marrow targets for drug delivery
Colloidal carriers for bone marrow targeting
Nanospheres/nanoparticles
Liposomes
Lysosomal storage diseases
Targeting exogenous enzymes
Conclusion
References
INTRODUCTION
The main problems currently associated with systemic
drug administration are:
1. Even biodistribution of pharmaceuticals throughout
the body;
2. The lack of drug specific affinity toward a pathological
site;
3. The necessity of a large total dose of a drug;
4. Non-specific toxicity and other adverse side-effects.
Drug targeting
Targeted drug delivery (TDD) is an event
where, a drug-carrier complex or conjugate delivers the
drug(s) exclusively to preselected cells in a specified manner.
TDD implies for selective and effective
localization of pharmacologically active moiety at a
predetermined target in a therapeutic concentration, while
restricting its access to non-target normal cellular linings,
thus minimizing the toxic effects and maximizing therapeutic
index.
The concept of drug targeting includes a
coordinated behavior of three components:
(a) Drug;
(b) Targeting moiety - cell, tissue, inside of a cell,
etc.
(c) Pharmaceutical carrier colloidal carriers, cellular carriers, polymer
based systems, macromolecular carriers.
LEVELS OF TARGETING
Passive targeting
Inverse targeting
Active targeting
- First order targeting
- Second order targeting
- Third order targeting
Physical targeting
Dual targeting
PHYSIOLOGY OF BONE MARROW
Bone marrow is the flexible tissue found in the hollow
interior of bones. In adults, marrow in large bones produces
new blood cells. It constitutes 4% of total body weight, i.e.
approximately 2.6 kg in adults.
There are two types of bone marrow:
- Red marrow
- Yellow marrow
 Red bone marrow consists of hematopoietic or blood forming
tissue which produces white blood cells and red blood cells.
 Within the marrow haemopoietic progenitor cells at various
stages of development replenish the peripheral blood cells
populations.
 The major vascular constituents of bone marrow are called as
sinuses.
 These blood vessels are relatively large forming a barrier i.e.
Marrow Blood Barrier (MBB) between the Hematopoietic
compartment and the circulation.
 The walls of MBB consists of continuous endothelium and a
discontinuous adventitial cell layer . The MBB serves to
control cellular traffic in and out of the marrow.
BONE MARROW TARGETS FOR DRUG
DELIVERY
1. Reticuloendothelial system (RES)
 The RES of organism is usually very effective in
removing small foreign colloidal particles
administered intravenously.
 The kupffer cells of liver and the macrophages of the
spleen constitute 80-95% of phagocytic cells of this
system and it is here that the particles are normally
deposited.
 For the particles to reach the bone marrow this uptake
by kupffer cells and macrophages should be
prevented.
2. Sinusoidal capillaries
 The endothelium of bone marrow sinusoids removes
particulate materials from the blood.
 The endothelium is not only capable of phagocytic
uptake and storage of particles but also provides for
the transmural passage of particulate material to the
extra vascular spaces where the particles are
phagocytosed by central macrophages.
.
Capillary endothelial barrier
MARROW (STEM CELL) TRANSPLANTATION
The homing of progenitor cells to the marrow has
provided the basis for treatment of certain diseases of
haemopoietic origin by bone marrow transplantation.
Certain genetic diseases which are characterised
by a generalized absence of a specific enzyme such as
adenosine deaminase (ADA) deficiency in severe combined
immunodeficiency, and glucose cerebrosidase deficiency in
Gaucher’s disease are treated.
COLLOIDAL CARRIERS FOR
BONE MARROW TARGETING
The ability of the bone marrow to remove the
particulate matters from the circulation, opens up an idea for
the delivery of therapeutic agents by means of colloidal drug
carrier systems such as
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Liposomes
Nanospheres
Emulsions
Microspheres
 With all these carrier systems a high proportions of the
dose still reaches the liver and spleen within few minutes
after intravenous administration.
 Since intravenously administered colloidal particles are
normally removed efficiently by RES cells of liver and
spleen , only a small fraction of these particles reaches
the bone marrow.
 Modification of the surfaces of the particles by a polymer
in order to provide a hydrophilic barrier minimize the
uptake of the plasma components.
E.g. poly(ethylene oxide) (PEO),
polysorbate (Tween-80) and lauryl ethers (Brij-35).
NANOSPHERES/NANOPARTICLES
Poloxomer 407
 Non-ionic block copolymer.
 It contains a central block of hydrophobic polyoxypropylene
( POP) flanked by blocks of hydrophilic polyoxyethylene
(POE).
 Polystyrene microspheres are surface labeled with iodine131 .these labeled particles are incubated for 24hours with a
2% w/v solution of poloxomer 407.
 This provides a coating layer over the particles
 Both the coated and uncoated particles were administered
intravenously to rabbits.
 The blood samples were taken and radioactivity was
measured using gamma counter.
 Gamma camera scans of rabbits clearly demonstrated that
the uncoated polystyrene particles were largely taken up
by liver and spleen after injection while the Poloxomer
407 coated particles were apparently deposited in bone
marrow.
 The uptake of uncoated particles by liver/spleen region
occurred rapidly and efficiently with 90% of the particles
being deposited in these organs within 2 min.
 The Poloxomer 407 coated particles showed a marked
decreased liver/spleen activity.
Polyalkylcyanoacrylate nanoparticles
(Gibaud Et al., 1999)
 Doxorubicin & stimulating growth factor (rhG-CSF) are the
model compounds
 Histological studies showed rapid capture of nanoparticles by
bone marrow macrophages as soon as 15 min after injection
 Doxorubicin nanoparticles administered were more toxic than
free doxorubicin on all blood and marrow cells
LIPOSOMES
 Phospholipids vesicles (Liposomes) have been widely
investigated as potential carriers for drugs, genes , proteins
because their capsular structure permits encapsulation of
various therapeutic agents.
 Advantage of using Liposomes as drug delivery carriers is
that their pharmacokinetics can be controlled by modifying
surface characteristics.
 Liposomes composed of equimolar amounts of cholesterol
and either saturated phospholipids or sphingomyelin
exhibited low tendency for accumulation in kupffer cells
following intravascular administration.
 Their uptake from blood to spleen and bone marrow remains
relatively high.
 25% of the injected dose of vesicles, formed from equimolar
amounts of cholesterol and disteroyl phosphatidylcholine ,
were localized in rat bone marrow 72 hours post intravenous
administration.
Immunoliposomes
Liposomes appended with antibodies or their fragments,
as target oriented moieties are known as immunoliposomes.
Immunoliposomes bearing poly-(ethylene glycol)coupled monoclonal antibody linked via cleavable disulphide
bond can be used for ex vivo applications as sorting of
hematopoietic stem cells
LYSOSOMAL STORAGE DISEASES
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Lysosomal storage diseases (LSDs) are a group of
approximately 40 rare inherited metabolic disorders that
result from defects in lysosomal function.
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LSDs are caused by lysosomal dysfunction usually as a
consequence of deficiency of a single enzyme required for
the metabolism of lipids, glycoproteins (sugar containing
proteins) or mucopolysaccharides.
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Like other genetic diseases, individuals inherit lysosomal
storage diseases from their parents. Although each disorder
results from different gene mutations that translate into a
deficiency in enzyme activity, they all share a common
biochemical characteristic – all lysosomal disorders
originate from an abnormal accumulation of substances
inside the lysosome.
Based on the chemical nature of the
accumulating materials LSDs are categorized into:

Lipid storage disorders (Sphingolipidoses) Sphingolipidoses are caused by genetic defects in a series
of lysosomal enzymes and other proteins essential for the
catabolism of sphingolipids.
E.g. Gaucher’s disease, Niemann -Pick disease,
Fabry’s disease, Tay-sach’s disease.

Mucopolysaccharidoses - Mucopolysaccharidoses are
caused by genetic enzymatic defects in the degradation of
carbohydrate chains of glycosaminoglycans.
E.g. Hurler Syndrome, Hunter syndrome,
Mucolipidosis.

Glycogen storage disorders - Glycoprotein disorders result
from defects in lysosomal hydrolases.
E.g. Pompe disease, Sialidosis.
Principal manifestations, stored lipids in sphingolipidoses
DISEASE
SIGNS AND
SYMPTOMS
MAJOR LIPID
ACCUMULATION
ENZYME DEFECT
Faber’s
disease
Gaucher’s
disease
Mental retardation,
dermatitis
ceramide
ceramidase
Spleen and liver
enlargement, erosion
of long bones
glucoceribroside
Glucoceribroside
β- glucosidase
Niemann pick disease
Fabry’s
disease
Spleen and liver
enlargement
sphingomyelin
sphingomyelinase
Reddish purple skin
ceramidetrihexoside
rashes, kidney failure
Ceramidetrihexoside
α- galactosidase
Tay-sach’s
disease
Red spot in retina,
blindness, muscular
weakness
Hexosaminidase A
ganglioside
TARGETING EXOGENOUS ENZYMES
Direct the major portion of enzymes to the
storage cells.
Intracellular trafficking of the enzyme.
Conclusion
Improvement of existing approaches to
diagnosis and treatment of various diseases
involving bone marrow.
Combination with gene delivery and controlled
expression of enzymes and carrier proteins is a
promising strategy.
References
S.P.Vyas and Roop K. Khar; targeted &
Controlled drug delivery: Novel Carrier Systems,
S.P.Vyas and V.K.Dixit; pharmaceutical
biotechnology,
James Swarbrick and James C.Boylan;
Encyclopedia of pharmaceutical technology; third
edition; volume2,
 Garret M. Ihler; methods of drug delivery.
S.M. Moghimi; Exploiting bone marrow
microvascular structure for drug delivery and future
therapies; Advanced Drug Delivery Reviews 17
(1995) 61-73,
P.B. Malafaya, G.A. Silva, E.T. Baran, R.L. Reis;
Drug delivery therapies I: General trends and its
importance on bone tissue engineering applications;
Current Opinion in Solid State and Materials
Science 6 (2002) 283–295
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 www.wikipedia.org
 www.informaworld.com