Selective effects of pentamidine on cytosolic and granule-associated enzyme release from zymosan-activated human neutrophilic granulocytes

Complement inhibition reduces material-induced leukocyte activation with PEG modified polystyrene beads (Tentagel™) but not polystyrene beads

With isolated leukocytes, inhibiting complement reduced material-induced leukocyte activation (CD11b) with polyethylene glycol modified polystyrene beads (PS-PEG), but not with polystyrene beads (PS). The PS-PEG beads (TentaGel) were complement activating as measured by SC5b-9 levels consistent with the sensitivity of these beads to leukocyte inhibition with complement inhibitors. Following contact with PS and PS-PEG beads, isolated leukocytes in plasma and in the absence in platelets were found to significantly upregulate CD11b, while TF expression and exposure of phosphatidylserine remained at background levels. Complement inhibition by means of sCR1 partially reduced CD11b upregulation on PS-PEG beads, but had no effect with PS beads. Pyridoxal-5-phosphate (P5P) was able to significantly reduce both CD11b upregulation and exposure of phosphatidylserine with PS-PEG beads, although it did not appear to inhibit SC5b-9 production. Pentamidine and NAAGA inhibited complement and were effective in reducing CD11b upregulation with both PS and PS-PEG. However, they also had an inhibitory effect on leukocyte signaling mechanisms, precluding their utility for further study in this context. Leukocyte adhesion occurred to similar extents on both PS and PS-PEG beads. While sCR1 and P5P blocked adhesion and activation (for adherent leukocytes) on PS-PEG beads, they had no effect on leukocytes adherent to PS beads. The role of complement in leukocyte activation and adhesion was found to be material-dependent. Thus, leukocyte-material compatibility may be resolved by complement inhibition in some but not all cases. For these other materials (example here was PS), other mechanisms, such as fibrinogen adsorption and direct leukocyte release, may need exploitation to minimize leukocyte activation and adhesion.

Drug resistance and Acanthamoeba keratitis: the quest for alternative antiprotozoal chemotherapy

Trophozoites and cysts of 20 isolates of Acanthamoeba from the cornea and five from related samples were tested in vitro for sensitivity to ten drugs (three aromatic diamidines, two aminoglycosides, two macrolides, a polyene macrolide antibiotic, an organoarsenical and an antimetabolite) and two cationic antiseptics (chlorhexidine and polyhexamethylene biguanide, PHMB). Only chlorhexidine and PHMB showed uniform amoebacidal activity. Aromatic diamidines (pentamidine isethionate, propamidine isethionate and diminazene aceturate) generally proved effective against both forms of the amoeba; only pentamidine gave synergy with the biguanide while propamidine gave an additive effect. Other drugs tested proved erratic or ineffective against different isolates. Chlorhexidine alone, or together with propamidine, was subsequently used in two patients with proven Acanthamoeba keratitis; the causative isolates were sensitive to the individual compounds and to the combination in vitro. The treatment provided resolution of the clinical disease; amoebae were shown to be nonviable by histology and culture. The combination of chlorhexidine and propamidine is recommended for treatment of proven Acanthamoeba keratitis.