Sirolimus (rapamycin, Rapamune) and combination therapy with cyclosporin A in the rat developing adjuvant arthritis model: correlation with blood levels and the effects of different oral formulations.

OBJECTIVE AND DESIGN: To determine whole blood levels of sirolimus, a macrolide antibiotic in the rat developing adjuvant arthritis (AA) model after dosing orally with two different vehicles, and whether combinational doses of sirolimus and cyclosporin A (CsA) produced additive or synergistic inhibitory effects in this model. MATERIAL: Male Lewis rats (150-180g). TREATMENT: Arthritis was induced by the injection (0.5 mg/ rat) of heat-killed Mycobacterium butyricum suspended in light mineral oil. Drugs were administered orally either in fine suspension (0.5% Tween 80) or in emulsion (phosal 50 PG in 1% Tween 80) at doses of 0.1 to 5 mg/kg in a 7 day, MWF or daily regimen. METHOD: Paw volumes (ml) were measured by automated mercury plethysmograph and sirolimus concentrations in whole blood were quantitated by liquid chromatography/ mass spectroscopy. RESULTS: At 72h (7 days after adjuvant) after receiving the third oral dose (4.5 mg/kg p.o.), the phosal vehicle resulted in higher sirolimus blood levels (2.5 ng/ml) than in Tween 80 (1.6 ng/ml). After the rats received the last oral dose on day 14, (7 total doses of sirolimus at 4.5 mg/kg) the sirolimus blood levels (2h after the last dose) were about 2 times higher for the phosal dosed rats (9.8 ng/ml) compared to Tween 80 dosed rats (4.6ng/ml). Even 24h after the last dose, sirolimus blood levels were still elevated in the phosal dosed rats (0.8 ng/ml) relative to 0.5% Tween 80 dosed rats (0.5 ng/ml). At day 16 in the rat developing model, sirolimus, when given in phosal vehicle, produced an ED50 of 0.28 mg/ kg (i.e. inhibition of uninjected paw edema) that was about 5.5 times lower than using 0.5% Tween 80 as the suspending agent (ED50 = 1.6mg/kg). When combining sirolimus and CsA using precalculated doses for producing an additive effect in this adjuvant model, an additive inhibitory effect on uninjected paw edema was observed at equal combinational doses of 0.5 and 2 mg/kg, respectively. CONCLUSIONS: The phosal vehicle used in administering sirolimus increases the absorption and whole blood levels in the rat and the elevated blood levels correlated positively with the therapeutic effect in the rat developing AA model. In addition, combination therapy using sirolimus and CsA produced an additive effect in rat developing AA.

The effects of antiinflammatory and antiallergic drugs on cytokine release after stimulation of human whole blood by lipopolysaccharide and zymosan A.

IL-1 beta, IL-8, IL-6 and TNF alpha, derived from infiltrating leukocytes, are important mediators of inflammation in arthritic and allergic diseases. Heparinized human whole blood was evaluated as a model to study the effects of various classes of antiinflammatory drugs on cytokine release/biosynthesis from leukocytes. Whole blood was stimulated with zymosan A (1.5 mg/ml) or LPS (5 micrograms/ml) for 4 h to induce cytokine release. Dexamethasone was the most potent inhibitor of TNF alpha, IL-1 beta, IL-6 and IL-8 release from LPS stimulated blood leukocytes (IC50s of 0.19, 0.11 microM, 0.16 and 0.07 respectively). In LPS stimulated blood, SKF-86002, a 5-lipoxygenase/cytooxygenasae inhibitor, and rolipram, a PDE IV inhibitor, also inhibited the release of TNF alpha (IC50s of 33 and 11 microM, respectively), IL-1 beta (IC50s of 11 and 30 microM, respectively), IL-6 (IC50s of 56 and > 30, respectively) and IL-8 (IC50s of 6.7 and 15, respectively), whereas isoproterenol (1 microM) inhibited significantly only TNF alpha release. Nonsteroidal antiinflammatory drugs, 5-lipoxygenase inhibitors and immuno-suppressive drugs were inactive at 30 microM against LPS and zymosan A stimulation of cytokine release. Using zymosan A as the stimulus, only SKF-86002 (30 microM) showed significant inhibition of IL-1 beta (-59%). This 4 h human blood assay has the potential to identify novel inhibitors and sites of actions (e.g. transcription, post-transcriptional and secretion) of new antiinflammatory drugs.

Inhibition of endotoxin-induced hypothermia and serum TNF-alpha levels in CD-1 mice by various pharmacological agents.

Intraperitoneal injection of lipopolysaccharide (LPS) was used to elicit a sublethal, shock-like condition in mice. LPS, 2.5 mg/kg i.p., induced hypothermia, elevated serum TNF-alpha levels and lethality over a 48 h period in male CD-1 mice. The 5-lipoxygenase (LO) inhibitors, WY-50,295 tromethamine and zileuton (100 mg/kg p.o), significantly inhibited hypothermia at 4, 24 and 48 h after LPS. Interestingly, whereas cyclooxygenase (CO) inhibitors (ibuprofen, etodolac, naproxen and tenidap) at 40-80 mg/kg p.o. stimulated hypothermia at 4 h, they significantly reduced the later stages of hypothermia at 24-48 h. Rolipram (PDE-IV inhibitor) and dexamethasone significantly reduced hypothermia at 4-24 h and 1-24 h, respectively. All the anti-inflammatory agents significantly reduced elevated TNF-alpha levels at approximately 70 min post-LPS, except for ibuprofen. In conclusion, these anti-inflammatory standards indicate that LPS-induced shock involves multiple lipid mediators (PG's, LT's and possibly PAF) and secondary cytokine generation. This sublethal model of LPS-induced shock represents a sensitive model for estimating the efficacy of potential drug candidates for the treatment of endotoxic shock.

The effects of anti-inflammatory and antiallergic drugs on the release of IL-1 beta and TNF-alpha in the human whole blood assay.

Heparinized human whole blood was evaluated as a model to study the effects of various classes of anti-inflammatory drugs on IL-1 beta and TNF-alpha release from leukocytes. Human whole blood was stimulated with zymosan (1.5 mg/ml) or LPS (5 micrograms/ml) to induce significant cytokine release. As previously reported, the 5-lipoxygenase/cyclooxygenase (5-LO/CO) inhibitor, SKF86002 (30 microM), significantly inhibited both IL-1 beta and TNF-alpha release using either stimulus. In contrast, the cyclooxygenase (CO) inhibitors (naproxen and ibuprofen) and the lipoxygenase (5-LO) inhibitors (zileuton, L-663536 and BWA4C) did not effect IL-1 beta or TNF-alpha release/biosynthesis. Isoproterenol (beta-agonist), rolipram (a PDE-IV inhibitor), and IBMX (a nonselective PDE inhibitor), significantly inhibited TNF-alpha but not IL-1 beta in the LPS model while having no effect in the zymosan model. This human whole blood assay is a unique and rapid method which can be used to identify novel inhibitors of IL-1 beta and TNF-alpha release/biosynthesis.