The suppression of rat collagen-induced arthritis and inhibition of macrophage derived mediator release by liposomal methotrexate formulations.
OBJECTIVE
This study was designed to determine whether liposomes are suitable vehicles for the delivery of methotrexate (MTX-gamma-DMPE) for arthritis therapy.


METHODS
Liposomal formulations containing either egg lecithin (EPC), cholesterol (CHOL) and phosphatidic acid (PA) (MTX-EPC) or distearoylphosphatidylcholine (DSPC), CHOL and distearoylphosphatidylethanolamine conjugated to polyethyleneglycol (PEG) (MTX-PEG) were employed. Rat peritoneal macrophages (rPM phi) were used to test the mechanism of action of these liposomes in vitro, whilst, the rat collagen-induced arthritis (CIA) model was used to evaluate the in vivo efficacy of MTX-EPC and MTX-PEG.


METHODS
In vitro, rPM phi were incubated with liposomal MTX concentrations ranging from 0 to 15 microg/well. In vivo, rats were given 4 daily intravenous injections of liposomal MTX (2.5 mg/Kg).


METHODS
IL-1beta and prostaglandin-E2 (PGE2) release from rPM phi were quantified by immunoradiometric assay. Arthritis progression, in vivo, was measured by serial clinical score and hind paw diameter measurements.


RESULTS
MTX-EPC and MTX-PEG respectively (15 microg of MTX and 0.15 mg of lipid) were powerful inhibitors of both IL-1beta (77 +/- 2.3%; 79 +/- 4.0%) and PGE2 (75.5 +/- 4.9%; 68.5 +/- 2.3%) release (mean +/- SEM % inhibition) from lipopolysaccaride stimulated rPM phi. In vivo, only MTX-EPC exerted an anti-inflammatory effect, clinical score (p < 0.001) and paw diameter (p < 0.001) measurements being significantly lower than in control rats, after 2 days treatment.


CONCLUSIONS
MTX-EPC and MTX-PEG are potent inhibitors of pro-inflammatory mediators in vitro, but liposomes with long circulation times do not appear to have therapeutic potential for treating arthritis in vivo.
Williams
A
A
Rheumatology Research Laboratory, University of Wales College of Medicine, Cardiff, UK. wmdasw@cardiff.ac.uk
Goodfellow
R
R
Topley
N
N
Amos
N
N
Williams
B
B
D000818:Animals; D018501:Antirheumatic Agents / Q000008:administration & dosage / Q000494:pharmacology*; D001168:Arthritis / Q000139:chemically induced / Q000188:drug therapy*; D001772:Blood Cell Count; D003094:Collagen; D016207:Cytokines / Q000096:biosynthesis; D015232:Dinoprostone / Q000096:biosynthesis; D004337:Drug Carriers; D066298:In Vitro Techniques; D007375:Interleukin-1 / Q000096:biosynthesis; D008081:Liposomes; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008727:Methotrexate / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D011917:Rats, Inbred Lew
D018501:Antirheumatic Agents; D016207:Cytokines; D004337:Drug Carriers; D007375:Interleukin-1; D008081:Liposomes; D003094:Collagen; D015232:Dinoprostone; D008727:Methotrexate