THE IN VITRO AND IN VIVO CYTOTOXICITY OF LIPOSOME-ENCAPSULATED DICHLOROMETHYLENE-DIPHOSPHONATE ON CHICKEN MACROPHAGES AND THE POTENTIAL OF USING MACROPHAGE-DEPLETED CHICKENS AS A MODEL FOR REOVIRUS INFECTION

The liposome-encapsulated dichloromethylene-diphosphonate ([Formula: see text]) is known to be toxic to the cultured macrophages and has selective cytotoxic effects on macrophages in rats and mice, but has minimal adverse effects on the non-phagocytic cells following various administration routes. In this study, the cytotoxicity of [Formula: see text] on chicken macrophages was investigated. Similar to findings related to other mammals, the [Formula: see text] was toxic to the macrophages originating from the chicken peripheral blood mononuclear cells as indicated by the MTT (3-(4, 5-dimethylthiazole-2-yl) 2, 5-diphonyltetrazolium bromide) cleavage assays. After administered with [Formula: see text], chicken spleens were rapidly and progressively reduced in sizes. This reduction was more severely gross than with the experimental course. One day post-treatment, the histopathology showed that most of the macrophages around the peri-ellipsoid white pulp had undergone marked cellular necrosis and lysis, and more severe lesions appeared with the loss of lymphoid and reticuloendothelial tissues at 3 and 5 days post-treatment. White pulp which has been replaced by red pulp in the spleen were noticed at 3 and 5 days post-treatment. The flow cytometric assays further confirmed the depletion of the macrophages in the chicken spleens following the administration of [Formula: see text], when compared with those of the controls. Furthermore, the replication of the avian reovirus (ARV) in the spleens was significantly reduced in the macrophage-depleted chickens administered with [Formula: see text]. Thus, depletion of the macrophages with [Formula: see text] followed by functional assesses in the macrophage-depleted chicken could be used as a model to confirm the involvement of the macrophages in ARV replication.

Inflammation-induced impairment of enteric nerve function in nematode-infected mice is macrophage dependent

Trichinella spiralis infection in rodents is associated with suppression of ACh release from myenteric plexus that can be mimicked by macrophage-derived cytokines. We verified the presence of a macrophage infiltrate in the intestine during T. spiralis infection and determined the extent to which this cell type is responsible for the neural changes. C57BL/6 mice were infected with 375 T. spiralis larvae by gavage, and the presence of macrophages (F4/80 positive) in the jejunum was determined immunohistochemically. In another experiment, infected mice were treated intravenously with liposomes containing dichloromethylene diphosphonate (clodronate, Cl2MDP), which causes apoptosis of macrophages, and killed at postinfection day 6, and jejunal tissues were evaluated for the presence of F4/80-positive cells and for [3H]ACh release from the myenteric plexus. Infection caused an infiltration of F4/80-positive cells into the intestinal mucosa, muscle layers, and myenteric plexus region and a significant suppression of ACh release (50%). Depletion of F4/80-positive macrophages using Cl2MDP-containing liposomes prevented the suppression in [3H]ACh release, identifying macrophages as the cell type involved in the functional impairment of enteric cholinergic nerves.