Novel treatment for joint inflammation

Intra-articular nanodrug delivery strategies for treating osteoarthritis

Osteoarthritis (OA) is characterized by progressive cartilage degeneration. Pharmaceutical intervention remains a main treatment approach. However, drug delivery via intra-articular administration (IA) can be restricted by rapid clearance, the dense and highly negatively charged extracellular matrix (ECM) of cartilage, and uneven distribution of diseased chondrocytes. Nanodrug delivery systems, such as liposomes, micelles, and nanoparticles (NPs), have shown great potential to prolong intra-articular residence, penetrate the ECM, and achieve diseased chondrocyte-specific delivery. In this review, we discuss the challenges associated with intra-articular drug delivery in OA and the nanodrug delivery strategies developed to overcome these challenges. It is anticipated that these nanodrug delivery strategies will advance IA of drugs into broader applications in OA treatment.

Overcoming barriers for intra-articular delivery of disease-modifying osteoarthritis drugs

Despite four decades of research in intra-articular drug delivery systems (DDS) and two decades of advances in disease-modifying osteoarthritis drugs (DMOADs), there is still no clinically available disease-modifying therapy for osteoarthritis (OA). Multiple barriers compromise intra-articular DMOAD delivery. Although multiple exciting approaches have been developed to overcome these barriers, there are still outstanding questions. We make several recommendations that can help in fully overcoming these barriers. Considering OA heterogeneity, we also propose a patient-centered, bottom-up workflow to guide preclinical development of DDS-based intra-articular DMOAD therapies. Overall, we expect this review to inspire paradigm-shifting innovations for developing next-generation DDS that can enable clinical translation of intra-articular DMOADs.

Fate of Biodegradable DL-Lactic Acid Oligomer Microspheres in the Articulus

The objective of the present study was to investigate the biodegradation and tissue responses of dl-lactic acid oligomer microspheres in the knee articulus. Different-sized microspheres containing a fluorescent dye were prepared from oligomers with different molecular weights (Mw) by a solvent evaporation method. Following intra-articular injection into the kneejoint of rabbits, the microspheres were localized at the popliteal fat tissue, irrespective of the microsphere size and oligomer Mw. When degradation of the microspheres injected intra-articularly was evaluated based on the decrease in the fluorescent intensity of microspheres remaining, the microspheres were degraded with time to finally disappear in the articular cavity. The degradation periods of microsphere prepared from 3,000, 5,600, and 7,000 Mw oligomers were 5, 10, and 17 days, respectively, whereas no size dependence on microsphere degradation was observed. No inflammatory response to the microspheres by the synovial tissue was observed; however, there was a temporary increase in the number of white blood cells in the articular cavity, irrespective of the microsphere size.

Roles of Sterol Derivatives in Regulating the Properties of Phospholipid Bilayer Systems

Liposomes are considered an ideal biomimetic environment and are potential functional carriers for important molecules such as steroids and sterols. With respect to the regulation of self-assembly via sterol insertion, several pathways such as the sterol biosynthesis pathway are affected by the physicochemical properties of the membranes. However, the behavior of steroid or sterol molecules (except cholesterol (Chl)) in the self-assembled membranes has not been thoroughly investigated. In this study, to analyze the fundamental behavior of steroid molecules in fluid membranes, Chl, lanosterol, and ergosterol were used as representative sterols in order to clarify how they regulate the physicochemical properties of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) liposomes. Membrane properties such as surface membrane fluidity, hydrophobicity, surface membrane polarity, inner membrane polarity, and inner membrane fluidity were investigated using fluorescent probes, including 1-(4-trimethylammoniumphenyl)-6-phenyl-1,3,5-hexatriene, 8-anilino-1-naphthalenesulfonic acid, 6-propionyl-2-(dimethylamino) naphthalene, 6-dodecanoyl-2-dimethylaminonaphthalene, and 1,6-diphenyl-1,3,5-hexatriene. The results indicated that each sterol derivative could regulate the membrane properties in different ways. Specifically, Chl successfully increased the packing of the DOPC/Chl membrane proportional to its concentration, and lanosterol and ergosterol showed lower efficiencies in ordering the membrane in hydrophobic regions. Given the different binding positions of the probes in the membranes, the differences in membrane properties reflected the relationship between sterol derivatives and their locations in the membrane.

Application of liposomes in treatment of rheumatoid arthritis: quo vadis

The most common treatments for rheumatoid arthritis include nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids, disease modifying antirheumatic drugs (DMARDs), and some biological agents. However, none of the treatments available is able to achieve the ultimate goal of treatment, that is, drug-free remission. This limitation has shifted the focus of treatment to delivery strategies with an ability to deliver the drugs into the synovial cavity in the proper dosage while mitigating side effects to other tissues. A number of approaches like microemulsions, microspheres, liposomes, microballoons, cocrystals, nanoemulsions, dendrimers, microsponges, and so forth, have been used for intrasynovial delivery of these drugs. Amongst these, liposomes have proven to be very effective for retaining the drug in the synovial cavity by virtue of their size and chemical composition. The fast clearance of intra-synovially administered drugs can be overcome by use of liposomes leading to increased uptake of drugs by the target synovial cells, which in turn reduces the exposure of nontarget sites and eliminates most of the undesirable effects associated with therapy. This review focuses on the use of liposomes in treatment of rheumatoid arthritis and summarizes data relating to the liposome formulations of various drugs. It also discusses emerging trends of this promising technology.

Preparation and evaluation of lidocaine hydrochloride-loaded TAT-conjugated polymeric liposomes for transdermal delivery

Transactivation transcriptional activator (TAT) peptides were conjugated on the octadecyl-quaternized, lysine-modified chitosan to form polymeric liposomes (TAT-PLs) with cholesterol for improving transdermal delivery of local anesthetic lidocaine hydrochloride (LID). In this study, the LID loaded TAT-conjugated polymeric liposomes (LID-TAT-PLs) have been successfully prepared. LID-TAT-PLs were characterized by determination of their particle size, polydispersity, morphology, drug encapsulation efficiency, drug release behavior in vitro, and storage-stability. The skin permeation of LID-TAT-PLs was examined using a Franz diffusion cell mounted with depilated mouse skin in vitro, and penetration of TAT-PLs was visualized by confocal laser scanning microscopy (CLSM). The results showed that LID-TAT-PLs were spherical in solution, with substantially smaller mean diameter (154.7±10.7 nm), higher encapsulation efficiency (80.05±2.64%) and better stability in contrast to conventional liposomes (CLs). From the in vitro skin permeation results, transdermal flux of LID-TAT-PLs was approximately 4.17 and 1.75 times higher than that of LID solution and LID CLs (P<0.05). CLSM studies also confirmed that TAT-PLs reached viable layers of the skin. Hence, the results indicate that LID-TAT-PLs are effective and potential alternative for the LID transdermal formulation.

Accumulation of Polyvinylpyrrolidone within the Inflamed Paws of Adjuvant-induced Arthritic Rats

125I-Labelled polyvinylpyrrolidone ([125I]PVP) of a range of molecular weights (mol. wt 10, 40 and 360 kDa) was injected i.v. into adjuvant-induced arthritic and normal rats and the blood clearance and tissue distribution of the polymers determined. The half-life of PVP in the circulation increased with increasing mol. wt; 10, 40 and 360 kDa polymers had mean terminal half-lives of 2·2, 6·9 and 16·4 h, respectively. Tissue uptake was also found to be mol. wt dependent, the largest PVP molecule accumulating to a greater extent in the spleen, liver, lungs and paws in both normal and arthritic rats (P &lt; 0·01) than the two lower mol. wt polymers. Accumulation of the polymer in inflamed paws (g tissue)−1 greatly exceeded that of normal paws (P &lt; 0·01). This difference was particularly noticeable with 360 kDa PVP, where arthritic paws amassed 7 times more PVP than normal paws.

Efficacy of chitosan microspheres for controlled intra-articular delivery of celecoxib in inflamed joints

The use of polymeric carriers in formulations of therapeutic drug delivery systems has gained widespread application, due to their advantage of being biodegradable and biocompatible. In this study, we aimed to prepare celecoxib-loaded chitosan microspheres for intra-articular administration and to compare the retention of the celecoxib solution and chitosan microspheres in the joint cavity. The microspheres were characterized for entrapment efficiency, particle size and surface morphology by scanning electron microscopy. In-vitro drug release studies of microspheres revealed that the microspheres are able to control the release of celecoxib over a period of 96 h. Biodistribution studies of celecoxib and chitosan microspheres were performed by radiolabelling with 99mTc and injecting intra-articularly in rats. The study indicated that following intra-articular administration the distribution of the drug to the organs, like liver and spleen, is very rapid compared with that of the microspheres. Compared with the drug solution, a 10-fold increase in the concentration of the drug in the joint was observed 24 h post intra-articular injection (P &lt; 0.005) when drug was encapsulated in microspheres.

Role of in vitro release models in formulation development and quality control of parenteral depots

This review article provides an assessment of advantages/limitations of the use of current in vitro release models to predict in vivo performance of parenteral sustained release products (injectable depots). As highlighted, key characteristics influencing the in vivo drug fate may vary with the route of administration and the type of sustained release formulation. To this end, an account is given on three representative injection sites (intramuscular, subcutaneous and intra-articular) as well as on in vitro release mechanism(s) of drugs from five commonly investigated depot principles (suspensions, microspheres, hydrogels, lipophilic solutions, and liposomes/other nano-size formulations). Current in vitro release models are, to a different extent, able to mimic the rate, transport and equilibrium processes that the drug substance may experience in the environment of the administration site. Their utility for the purpose of quality control including in vitro-in vivo correlations and formulation design is discussed.

Intra-articular depot formulation principles: role in the management of postoperative pain and arthritic disorders

The joint cavity constitutes a discrete anatomical compartment that allows for local drug action after intra-articular injection. Drug delivery systems providing local prolonged drug action are warranted in the management of postoperative pain and not least arthritic disorders such as osteoarthritis. The present review surveys various themes related to the accomplishment of the correct timing of the events leading to optimal drug action in the joint space over a desired time period. This includes a brief account on (patho)physiological conditions and novel potential drug targets (and their location within the synovial space). Particular emphasis is paid to (i) the potential feasibility of various depot formulation principles for the intra-articular route of administration including their manufacture, drug release characteristics and in vivo fate, and (ii) how release, mass transfer and equilibrium processes may affect the intra-articular residence time and concentration of the active species at the ultimate receptor site.

New Dosage Formulations for Targeted Delivery of Cyclo-Oxygenase-2 Inhibitors

NSAIDs are a widely used class of analgesic and anti-inflammatory drugs that act by inhibiting the cyclo-oxygenase (COX) enzyme. However, because of their nonspecificity of action, use of these agents as long-term therapy for chronic pain in diseases such as rheumatoid arthritis (RA) and osteoarthritis (OA) is often discouraged. Among NSAIDs, COX-2 inhibitors are promising candidates for long-term therapy of chronic diseases, particularly in the elderly, because of their reduced incidence of gastrointestinal adverse effects. However, in recent times these agents have also been shown to cause adverse effects such as cardiovascular effects (myocardial infarction, stroke and hypertension) and renal effects (decreased renal blood flow/glomerular filtration rate), which in 2004 led to the withdrawal of rofecoxib and in 2005 the withdrawal of valdecoxib from the US market. Importantly, these adverse effects can be effectively reduced by achieving site specific/targeted delivery through new formulation approaches. These formulations not only restrict the drug supply to specific organs but also reduce the dose required. As a result, use of new delivery systems such as nanoparticles, microparticles, microemulsions and nanogels has gained widespread applicability in the management of chronic disease, especially in the elderly, and particularly when there is a need to decrease dose-dependent adverse effects (as is the case with COX-2 inhibitors). This article reviews various new approaches to the delivery of COX-2 inhibitors and highlights issues related to the development of delivery systems for these agents for RA, OA, cancer (familial adenomatous polyposis, prostate, breast and non-small cell lung cancer), ocular diseases (such as diabetic retinopathy) and inflammatory diseases of the skin, with emphasis on their potential for use in the elderly. Emphasis is also placed on the preparation of these particulate systems, their release profile and behaviour in biological systems.

Celecoxib incorporated chitosan microspheres: in vitro and in vivo evaluation

Recently, considerable interest has been focussed on the use of biodegradable polymers for specialized applications such as controlled release of drug formulations; meanwhile, microsphere drug delivery systems using various kinds of biodegradable polymers have been studied extensively during the past two decades. In the present investigation, it was aimed to prepare microsphere formulations of celecoxib using a natural polymer, chitosan as a carrier for intra-articular administration to extend the retention of the drug in the knee joint. Microsphere formulations were evaluated in vitro for particle size, entrapment efficiency, surface morphology and in vitro drug release. For in vivo studies, (99m)Technetium- labeled glutathione was used as a radiopharmaceutical to demonstrate arthritic lesions by gamma scintigraphy. Evaluation of arthritic lesions post therapy in rats showed a significant difference (P < 0.005) in the group treated with celecoxib solution compared to the group treated with celecoxib loaded chitosan microspheres.

Drug targeting by long-circulating liposomal glucocorticosteroids increases therapeutic efficacy in a model of multiple sclerosis

High-dose glucocorticosteroid hormones are a mainstay in the treatment of relapses in multiple sclerosis. We searched for a way to deliver ultra high doses of glucocorticosteroids to the CNS of rats with experimental autoimmune encephalomyelitis (EAE) using a novel formulation of polyethylene glycol (PEG)-coated long-circulating liposomes encapsulating prednisolone (predni solone liposomes, PL). 3H-labelled PL showed selective targeting to the inflamed CNS, where up to 4.5-fold higher radioactivity was achieved than in healthy control animals. HPLC revealed much higher and more persistent levels of prednisolone in spinal cord after PL compared with an equal dose of free prednisolone. Gold-labelled liposomes could be detected in the target tissue, mostly taken up by macrophages (Mphi), microglial cells and astrocytes. Blood-brain barrier disruption was greatly reduced by 10 mg/kg PL, which was superior to a 5-fold higher dose of free methylprednisolone (MP). PL was also superior to MP in diminishing T-cell infiltration by induction of T-cell apoptosis in spinal cord. Mphi infiltration was clearly decreased only by PL. The percentage of tumour necrosis factor-alpha (TNF-alpha)-positive T cells or Mphi was greatly reduced by PL and by MP. No adverse effects on glial cells were detected. A single injection of PL clearly ameliorated the course of adoptive transfer EAE and EAE induced by immunization. In conclusion, PL is a highly effective drug in treatment of EAE, and is superior to a 5-fold higher dose of free MP, possibly by means of drug targeting. These findings may have implications for future therapy of autoimmune disorders such as multiple sclerosis.

Prolonged anti-inflammatory action of DL-lactide/glycolide copolymer nanospheres containing betamethasone sodium phosphate for an intra-articular delivery system in antigen-induced arthritic rabbit

PURPOSE

The objective of the present study was to develop prolonged anti-inflammatory action of DL-lactide/glycolide copolymer (PLGA) nanosphere incorporating a water-soluble corticosteroid (betamethasone sodium phosphate; BSP). Another aim was to demonstrate the biocompatibility and biologic efficacy of these BSP-loaded nanospheres directly administered into ovalbumin-induced chronic synovitis in the rabbit.

METHODS

BSP-loaded nanospheres were prepared by an emulsion solvent diffusion method in oil (caprylate and caprate triglyceride). The drug releasing properties of the nanospheres were measured in vitro in phosphate buffer saline (PBS: pH7.4), and in vivo in rat air-pouch (pseudo synovial fluid). The BSP-loaded nanosphere suspensions were administered into the joint cavity in a model of antigen-induced arthritic rabbit and evaluated by measuring the joint swelling, and the biocompatibility was appraised by histologic microscopy.

RESULTS

The BSP-nanospheres were a unimodally-dispersed particulate system with a mean diameter ranging from 300 to 490 nm, and BSP was efficiently entrapped in the lipophilic copolymer (PLGA), although its hydrophilic properties. The drug release-rate from the nanospheres in PBS was controlled by the molecular weight and the lactic/glycolic acid (LA/GA) ratio of the polymers. The in vitro releasing study demonstrated that sustained drug release occurred for over three weeks. In the antigen-induced arthritic rabbit, the joint swelling decreased significantly by administering BSP-loaded nanospheres during a 21-day period after intra-articular challenge. With regards to the prolonged anti-inflammatory efficacy, serum antibody to ovalbumin showed a sustained reduction during the period, and the steroidal effect appeared by the degradation of the polymer in the synovium. The BSP-nanosphere administered was phagocytosed by the synovial activated-cells and the cartilage degradation was almost prevented.

CONCLUSIONS

Direct intra-articular injection of a PLGA nanosphere system with a water-soluble steroid provided a prolonged pharmacological efficacy in the joints of arthritic rabbits. The local anesthetic in the knee-joints was evaluated to be safe and without biologic damage.

Gelatin/chondroitin 6-sulfate microspheres for the delivery of therapeutic proteins to the joint

OBJECTIVE

To develop a biodegradable, inflammation-responsive microsphere system for the intraarticular delivery of therapeutic proteins.

METHODS

Microspheres were synthesized by complex coacervation. Radiolabeled protein release and microsphere degradation were assessed by exposing the microspheres to human synovial fluids (SF) and recombinant gelatinase. Microsphere degradation was confirmed by scanning electron microscopy (SEM). Microsphere biocompatibility was evaluated in vitro by incubating the microspheres with human synoviocytes, and in vivo by injection into mouse joints.

RESULTS

Optimal microsphere formulation was developed. Significant (up to 100%) release of encapsulated protein occurred in SF samples with measurable metalloprotease activity, while release was minimal in SF with negligible activity. Dissolution of microspheres exposed to gelatinase was confirmed by SEM. Microspheres were found to be noncytotoxic in vitro, and noninflammatory in vivo.

CONCLUSION

Microsphere encapsulation is an inflammation-responsive and biocompatible system of protein delivery that holds promise for use in the delivery of therapeutic proteins to the joint.

Influence of chitosan microspheres on the transport of prednisolone sodium phosphate across HT-29 cell monolayers

PURPOSE

The present study was performed to investigate the influence of chitosan microspheres on transport of the hydrophilic, antiinflammatory drug prednisolone sodium phosphate (PSP) across the epithelial barrier.

METHODS

Microspheres were prepared using a precipitation method and loaded with PSP. Transport studies were performed in a diffusion cell chamber using the polarized human cell line HT-29B6. Porcine small intestine and fluorescence-labeled microspheres were used to investigate penetration ability of microspheres.

RESULTS

It was shown that transport of PSP drug solution was not saturable across the cell monolayers (P = 8.68 +/- 8.24 x 10(-6) cm sec-1) and no sodium dependency could be established. EGTA treatment resulted in an increased permeability (P = 18.69 +/- 1.09 x 10(-6) cm sec-1). After binding of prednisolone to chitosan microspheres its permeability was enhanced drastically compared with the drug solution (P = 35.37 +/- 3.21 x 10(-6) cm sec-1). This effect was prevented by EGTA treatment (P = 15.11 +/- 2.57 x 10(-6) cm sec-1). Furthermore the supporting effect of chitosan microspheres was impaired by pH and ion composition of the medium, whereas the effect remained unchanged in cells treated with bacterial lipopolysaccharides. In vitro incubation of fluorescence-labeled microspheres in the lumen of freshly excised intestine revealed a significant amount of the spheres in the submucosa.

CONCLUSIONS

Chitosan microspheres are a useful tool to improve the uptake of hydrophilic substances like PSP across epithelial layers. The effect is dependent on the integrity of the intercellular cell contact zones and the microparticles are able to pass the epithelial layer. Their potential benefit under inflammatory conditions like in inflammatory bowel disease, in order to establish high drug doses at the region of interest, remains to be shown.

Liposome-incorporated dexamethasone palmitate inhibits in-vitro lymphocyte response to mitogen

The use of liposomes for the pulmonary delivery of corticosteroid is an area that is under active investigation. We have recently developed a novel liposomal corticosteroid preparation based on the incorporation of dexamethasone palmitate (DMP) within the bilayer of small unilamellar vesicles (SUVs) made of egg yolk phosphatidylcholine (EPC) and cholesterol; molar ratio EPCC:cholesterol: DMP, 4:3:0.3. In the present study, the biological activity of DMP-SUVs was evaluated using the lymphocyte transformation test with peripheral blood mononuclear cells (PBMCs) and a gamma-interferon production assay. Results showed that DMP-SUVs (but not empty SUVs) inhibited [3H]thymidine uptake and gamma-interferon production by concanavalin A-stimulated PBMCs by 94 and 96%, respectively, at a concentration corresponding to 10(-6) M dexamethasone. The inhibition by DMP-SUVs was found to require a 24-h pre-incubation with unstimulated PBMCs, suggesting that interaction of SUVs with lymphocytes may be altered by mitogen stimulation. We conclude that our DMP liposomal preparation is biologically active and may be considered a promising alternative to conventional local glucocorticoid therapy.

Intra-articular therapy of experimental arthritis with a derivative of triamcinolone acetonide incorporated in liposomes

Triamcinolone acetonide-21-palmitate was synthesized and incorporated into liposomes for intra-articular treatment of an experimentally-induced arthritis in the knee joints of rabbits. The liposomal formulation was more efficient than free triamcinolone acetonide in solution in suppressing the arthritis. Using radioactive tracers, it was found that triamcinolone acetonide-21-palmitate incorporated into liposomes was retained in the articular cavity, together with the liposomal lipids, for a much longer period than free triamcinolone acetonide, and this correlated with its anti-inflammatory effect.

Kupffer cells and liver metastasis. Optimization and limitation of activation of tumoricidal activity

Kupffer cells, tissue-fixed macrophages located in the sinusoids of the liver, represent the highest concentration of mononuclear phagocytes in the body. Their ability to act as scavengers of particulate material in the blood has given rise to speculation that they play a role in controlling hepatic metastases derived from blood-borne tumor cells. Circumstantial evidence for such a role has been obtained from animal studies where Kupffer cell function has been compromised or inhibited, and from anecdotal clinical observations. Current evidence suggests that Kupffer cells are capable of nonspecifically eliminating some circulating tumor cells from the circulation via phagocytosis. This surveillance mechanism would appear to be limited in capacity, and subject to a number of external factors. Recent studies have demonstrated that Kupffer cells can be activated to a tumoricidal state via the administration of biological response modifiers such as gamma interferon or muramyl peptides. The localization of liposomes within Kupffer cells after systemic administration has provided a considerable stimulus for the efficient targeting of macrophage-activating compounds to these cells. Such therapeutic intervention, while capable of inducing Kupffer cell tumoricidal activity in situ and inhibiting tumor growth, is limited with respect to the location of the tumor cells (sinusoidal versus parenchymal) and to the size of the metastatic nodule. Therapeutic intervention using liposomes containing macrophage-activating agents may only be of benefit in patients with minimal tumor load who are at risk for hepatic metastases, rather than those patients who already have clinically detectable liver tumors.

Corticosteroids in rheumatoid arthritis

This report has presented evidence to support a disease-modifying role for corticosteroids in rheumatoid arthritis. It would appear that the efficacy of these agents in retarding the destructive course of rheumatoid disease has been substantially underestimated. Consideration for more liberal use of corticosteroids in the management of rheumatoid arthritis is warranted. Further study on new approaches to corticosteroid delivery is proposed.

Evaluation of reconstituted Sendai virus envelopes as intra-articular drug vectors: effects on normal and experimentally arthritic rabbit knee joints

Fusogenic vesicles reconstituted from the envelopes of Sendai virus particles were injected into rabbit knee joints (both normal and experimentally arthritic) to evaluate the in-vivo biocompatibility of these putative drug carriers. The reconstituted Sendai virus envelopes (RSVE) were greater than 80% retained within the arthritic knee joints after 24 h and studies with 125I- and fluorescein-labelled RSVE both showed association of the vesicles with the synovia of arthritic and healthy joints. However, RSVE were found to cause inflammation after intra-articular injection, as judged by joint swelling and histological assessment, and these effects were exacerbated by successive administrations. RSVE-entrapped methotrexate, whether free or conjugated to human serum albumin, was ineffective in preventing the irritancy of RSVE or in reducing the chronic inflammation in joints affected by an experimentally induced arthritis.

Association of liposome-entrapped [3H]methotrexate with thioglycollate-elicited macrophages in-vitro

The association of free or liposome-entrapped [3H]methotrexate [( 3H]MTX) with thioglycollate-elicited macrophages was investigated in-vitro. [14C]Cholesteryl oleate was incorporated into the liposomes as a lipid marker. [3H]MTX association with the macrophages was 5 to 9-fold higher with liposome-entrapped [3H]MTX than with the free drug. Macrophage-liposome association was biphasic, temperature-dependent and saturable at high liposomal lipid concentration. A high liposome cholesterol (CH) content or the presence of 2,4-dinitrophenol or colchicine also reduced macrophage-liposome association.

Preparation and use of liposomes in the treatment of microbial infections

The potential application of liposomes to drug delivery has been apparent since 1965, when these phospholipid vesicles were first described by Bangham. Since then, experiments on animals have shown that liposome encapsulation can dramatically alter the distribution of drugs in the body and their rate of clearance. These pharmacokinetic differences, as well as other less well-understood effects, can result in reduced toxicity and enhanced efficacy of the encapsulated drug. The vast majority of studies on the therapeutic use of liposomes have involved the delivery of drugs used in cancer chemotherapy and metabolic storage diseases, but there is now more literature on the use of liposomes for the delivery of antimicrobial drugs and immunomodulating agents. This review briefly discusses the general properties of liposomes and the rationale for their use in antimicrobial drug delivery and immunomodulation, as well as the encapsulation of specific agents and the effect of encapsulation on the treatment of infectious diseases.

Albumin microspheres for intra-articular drug delivery: investigation of their retention in normal and arthritic knee joints of rabbits

The retention of 131I-labelled albumin microspheres and microsphere-entrapped [131I]rose bengal was investigated in normal and experimentally arthritic knee joints of rabbits. Albumin microspheres were cleared slowly from the joint cavity and no significant difference was observed between normal and inflamed joints. Entrapment of rose bengal within albumin microspheres was found to delay the clearance of the drug from the joint when compared with a solution of rose bengal. In addition, the retention time for entrapped rose bengal was dependent on the degree of inflammation present.

Studies of pharmacokinetics and therapeutic effects of glucocorticoids entrapped in liposomes after intraarticular application in healthy rabbits and in rabbits with antigen-induced arthritis

Dexamethasone palmitate (DMP) entrapped in liposomes of defined sizes was administered intraarticularly in healthy rabbits and in rabbits with antigen-induced arthritis. The pharmacokinetics and therapeutic effect of liposomal DMP were measured and compared with corresponding experiments using microcrystalline triamcinolone acetonide (TAC). The small DMP liposomes (diameter 160 nm) showed a greater decrease in joint circumference than the 3-times-higher dose of microcrystalline TAC. Moreover, about 98% of administered TAC had already disappeared from the joint 6 h after injection, whereas about 36% of liposomal DMP was still measured in synovial fluid and synovium at the same time. Increasing the vesicle diameter from 160 to 750 nm (large liposomes) improved the retention of DMP by a factor of 2.6 within 48 h after injection in healthy rabbits. In addition, none of the liposomal glucocorticoid preparations ever suppressed the endogenous plasma cortisol level, which is in contrast to the suppression measured after administration of the microcrystalline preparation.

Liposomes and tear fluid. I. Release of vesicle-entrapped carboxyfluorescein

The successful application of liposomes as a topical ophthalmic drug delivery device requires knowledge of vesicle stability in the presence of tear fluid. The release of 5-carboxyfluorescein from large unilamellar liposomes in the presence of rabbit tear fluid was studied in vitro as a function of bilayer cholesterol content. Reverse evaporation vesicles were prepared from egg phosphatidylcholine, stearylamine and varying amounts of cholesterol. Both the rate and the extent of fluorescent dye release were significantly increased in the presence of rabbit tear fluid at all cholesterol levels. However, by incorporating increasing amounts of cholesterol in the vesicle bilayers, tear-induced leakage was reduced. The release kinetics reported in this study are similar to those observed in the presence of human serum. While serum-induced leakage is attributed to high-density lipoprotein-mediated destabilization, reported differences in tear protein composition suggest some other, as yet unidentified, factor.

Liposomes as drug carriers for oral ulcers

The aim of this study was to test the potential of liposomes as drug carriers to the ulcerated oral mucosa. Radioactive triamcinolone acetonide palmitate (3H-TRMAp) was encapsulated in large multilamellar lipid vesicles and served as the test lotion. 3H-TRMAp in solution served as control. Forty-six hamsters were divided into three groups. In group I, multiple confluent ulcers in both cheek pouches were treated by topical application. In group II, single ulcers on the cheeks were treated by intramucosal injection. In group III, multiple confluent ulcers were produced in the cheek pouch on one side, with a single ulcer in the contralateral cheek pouch; no drug was applied, and the tissues were prepared for histology. Hamsters were killed at three and 24 hours, respectively, after treatment. Pouches were divided into ulcerated and intact adjacent mucosa. Cheeks were divided into ulcerated mucosa and distant mucosa. Drug levels in the four mucosal portions as well as in the blood, liver, spleen, brain, and thalamic region were determined by radioactive tracer technique. At three hours, liposomal drug concentrations were lower than in control animals in the brain and the thalamic region. At 24 hours, liposomal drug values were higher than in control animals in the ulcerated mucosa and lower than in control animals in the thalamic region. Mean drug concentrations in the ulcerated mucosa were higher in group II than group I. The results parallel those of Mezei and Gulasekharam (1980, 1982); liposomes increase local and decrease systemic drug concentration.(ABSTRACT TRUNCATED AT 250 WORDS)

Preparation and evaluation of biodegradable polymeric systems for the intra-articular delivery of drugs

Colloidal suspensions of four biodegradable polymers, polylactic acid (PLA), polybutylcyanoacrylate (PBCA), gelatin (PG) and albumin (PA) were prepared within the size range 1-10 micron. In-vivo biocompatibility tests with synovial tissues were carried out to assess the irritancy of the polymers following intra-articular injection into rabbit knee joints. PLA, PBCA and PG were found to cause joint inflammation whereas PA was well tolerated by the tissues. PA microspheres may provide a means of sustaining the release and reducing the rate of clearance of drugs from the knee joint.

A hypothesis on the pathogenesis of rheumatoid and other non-specific synovitides. IV A. The possible intermediate role of local hypoxia and metabolic alterations

According to the original hypothesis, synovial tissue (ST) oedema and synovial fluid (SF) volume increase contribute to local hypoxia and metabolic alterations and to inflammation (A 1). Studies on biochemical mechanisms (A 2) in synovitides show that the SF volume correlates to SF hypoxia that correlates to lactate increase, acidosis and to some decrease in glucose. Normal ST produces lactate by glycolytic and pentose phosphate pathway activity, both, as well as the normally low oxygen utilization, being increased in synovitides . In ST very little carbohydrate seems to pass directly into the citric acid cycle and oxidation of fat may be involved, but it is not known if the fat is carried to ST by the blood or if it is synthetized locally (B). ST oedema and effusions may be most important as causes of local hypoxia (C). Acidosis alters physico-chemical properties of proteins, possibly changing their chemotactic and antigenic qualities, etc. Hypoxia and fuel supply might be related to fibroblast, macrophage and neutrophil reactions, and, in view of the high metabolic demands of villi, they may contribute to, e.g., ST necroses, and to erosions (D). I shall summarize some essentials of my present views on the pathogenesis (E 1 a) and causes in single cases (E 3 b) of synovitis, and comment on two other new hypotheses on rheumatoid arthritis (E 2) and on therapeutic (E 4) and other implications of this concept (E).