Hashimoto S, Pittet JF, Hong K, Folkesson H, Bagby G, Kobzik L, Frevert C, Wanatabe K, Tsurufuji S, Weiner-Kronish, J.
Depletion of alveolar macrophages decreases neutrophil chemotaxis to Pseudomonas airspace infections.
American Journal of Physiology – Lung Cellular and Molecular Physiology. 1996 May 1;270(5):L819 –L828.
[toggle_content title=”Abstract”] The mechanism for neutrophil (PMN) influx into infected airspaces of the lung is not known. To determine whether alveolar macrophage products are important in the initiation of chemotaxis, we depleted rats of alveolar macrophages by aerosolizing negatively charged oligolamellar liposomes complexed to clodronate disodium. Ninety-five percent of the alveolar macrophages were depleted, and lung injury and inflammation were minimized with this depletion technique. Rats depleted of alveolar macrophages were then anesthetized, and either 5 x 106 colony-forming units (CFU) or 5 x 107 CFU of Pseudomonas aeruginosa were instilled into the airspaces of these animals. When recombinant macrophage inflammatory protein (MIP-2) was intratracheally instilled into rats depleted of alveolar macrophages, PMN were recruited to their airspaces. Nonetheless, PMN numbers were decreased in the lavage fluids when moderate or large inoculums of bacteria were instilled into depleted rats, although the PMN response appeared dose dependent. Levels of bioactive tumor necrosis factor-α and immunoreactive proteins CINC/gro (cytokine-induced PMN chemoattractant) in the lavage fluids obtained from infected rats depleted of alveolar macrophages were significantly decreased compared with the levels in the lavage fluids obtained from normal infected rats. MIP-2 mRNA expression, as detected by Northern analysis, was also decreased in the infected lungs of depleted rats, and the lavage fluid from these rats had significantly decreased chemotactic activity. Therefore these results suggest that alveolar macrophage products play a direct role in the initial recruitment of PMN into infected lungs. [/toggle_content] [toggle_content title=”Clodronate Liposome Parameters”] [custom_table]
Clodronate Concentration Total Lipid Concentration Lipid Composition Lipid Mole % Liposome Type Control Liposomes
7 mg/ml 33.4 mg/ml EPC/BPS/Chol 55/9/36 REV PBS(-)
[/custom_table] [/toggle_content] [toggle_content title=”Animals and Dosing”] [custom_table]
Animal Description Clodronate Dose Dosing Site/Method Target Phagocytes Systemic Dosing? Systemic Results
Sprague Dawley rats, male, 300-375 g 0.05-0.25 µmoles aerosol / lungs alveolar macrophages (AM) no no change in peripheral moncytes or PMN detected
[/custom_table] [/toggle_content] [toggle_content title=”Notes”]
  1. The authors state that liposomes were “extruded” through 0.2 µm syringe filters. A syringe filter is not a substitute for extrusion therefore the resulting size distribution is questionable. Liposomes >400 nm have been shown to be disrupted by aerosolization, therefore it’s likely that there was free clodronate in the aerosol.
  2. Aerotech II nebulizer at 10 L/min. MMAD = 1.6 µm; GSD = 2.5. Fluorescent liposome aerosol delivery experiments indicated that 0.1-0.5% of the dose was delivered to the lung. This value was used to estimate the clodronate dose delivered to the lungs. The authors estimate that 26X more drug is delivered by this method than by liquid installation.
[/toggle_content] [toggle_content title=”Results”]
  1. >95% of the AM were depleted (BAL cell counts via light microscopy).
  2. The authors further state that clodronate liposome delivery by aerosol prevents neutrophilia often observed when direct instillation is used.