Paul D Jager

The role of 5-lipoxygenase products in preclinical models of asthma

BACKGROUND The action of 5-lipoxygenase on arachidonic acid generates potent inflammatory mediators that may contribute to the pathophysiology of asthma. METHODS Using the potent and selective 5-lipoxygenase inhibitor BI-L-239, we have examined the role of 5-lipoxygenase products in three animal models of asthma. RESULTS In vitro BI-L-239 inhibited 5-lipoxygenase product generation from human lung mast cells, alveolar macrophages, and peripheral blood leukocytes with a concentration that would provide 50% inhibition values of 28 to 340 nmol/L. A 36-fold selectivity for immunoreactive leukotriene C4 versus immunoreactive prostaglandin D2 inhibition was demonstrated in mast cells. In anesthetized cynomolgus monkeys, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced immunoreactive leukotriene C4 release (maximum, 73%; bronchoalveolar lavage [BAL], 20 minutes), late-phase bronchoconstriction (maximum, 41%; +6 to 8 hours), and neutrophil infiltration (maximum, 63%; BAL, +8 hours). In conscious sheep, inhaled BI-L-239 provided dose-dependent inhibition of the inhaled Ascaris-induced late-phase bronchoconstriction (maximum, 66%; +6 to 8 hours) and increase in airway responsiveness (maximum, 82%; carbachol, +24 hours). The acute bronchoconstriction was shortened, and neutrophil infiltration diminished (maximum, 61%; BAL, +8 hours) in this model. Finally in conscious actively sensitized guinea pigs pretreated with pyrilamine and indomethacin, inhaled BI-L-239 attenuated acute bronchoconstriction (maximum, 80%; +5 to 15 minutes), leukocyte infiltration (58%; BAL, +3 days) and increase in airway responsiveness (100%; methacholine, +3 days) induced by three alternate-day ovalbumin inhalations. CONCLUSIONS In conclusion, results in these three animal models indicate that 5-lipoxygenase products may be major contributors to the bronchoconstriction (especially late phase), leukocyte infiltration, and airway hyperresponsiveness that characterize asthma.

Assessment of Pharmaceutical Powder Flowability using Shear Cell-Based Methods and Application of Jenike’s Methodology

Jenikes approach to hopper design for a large-scale (3150 L) conical hopper was applied to pharmaceutical powders to evaluate flow issues, such as funnel flow or cohesive arching. Seven grades of microcrystalline cellulose (MCC) and six powder blends were tested. A Schulze Ring Shear Tester measured the flow function, wall friction (using stainless steel coupons with a #2B or #8 finish) and compressibility. Hopper Index (HI, maximum hopper angle required for mass flow) and Arching Index (AI, minimum hopper outlet size to prevent cohesive arch formation) were computed using Mathcad(©) . For MCC, a linear relationship was observed between median particle size and the Jenike flow function coefficient. A curvilinear relationship was observed for powder blends indicating more complex flow behavior than based on median particle size alone. Powder bulk density had a minimal effect on AI for MCC grades. Overestimation of AI can occur with this method for pharmaceutical powders because the true shape of the flow function is not defined at very low consolidation pressures and linear extrapolation becomes unrepresentative. This instrumental limitation underscores the need for a precise and accurate test method to determine powder flow functions at very low levels of consolidation stress for pharmaceutical applications.