In situ heparin-induced peroxisomal reticulum and biogenesis of peroxisomes in pulmonary intravascular macrophages (PIMs) of caprine lung: an ultrastructural and cytochemical study

A porcine model of complement-mediated infusion reactions to drug carrier nanosystems and other medicines

Intravenous administration of low (milligram) doses of nanoparticulate materials in pigs can lead to acute cardiopulmonary, hemodynamic, hematological, biochemical and dermatological changes within minutes, mimicking the human infusion (or anaphylactoid) reactions to many state-of-the-art (nano)medicines and biologicals. Because of the causal role of complement (C) activation, the phenomenon was called C activation-related pseudoallergy (CARPA). This review summarizes the available information on porcine CARPA caused by different liposomes and polymers. It provides methodical details of the model and addresses the quantitation, sensitivity, specificity, reproducibility and variability of symptoms caused by different reactogenic drugs. We describe a unique feature of the model: the rise of tachyphylaxis (self-induced tolerance) as a function of structural properties of reactogenic agents. For drugs that cause tachyphylactic CARPA, such as liposomal doxorubicin (Doxil), the review recapitulates a recently reported method of desensitization, which may prevent this, as well as many similar hypersensitivity reactions. In explaining the underlying mechanism of tachyphylactic CARPA, a new theory on "double hit" is outlined, wherein the pulmonary intravascular macrophages (PIM cells) of pigs give aggravated response to simultaneous stimulation of their anaphylatoxin and other surface receptors (e.g., toll-like, PAMP, DAMP or mannose) that recognize vesicle surface molecular patterns. The porcine CARPA model might provide unique advantages in studying the mechanism of severe hypersensitivity reactions in man to i.v. drugs, as well as in identifying drugs and drug carriers that may cause such reactions.

In vivo interaction of pulmonary intravascular macrophages with activated platelets in microvessels of equine lung after multiple exposures to halothane, isoflurane, and thiamylal: A comparative ultrastructural and cytochemical study

The pulmonary intravascular macrophages (PIMs) of equines contain a unique electron-dense surface coat that is predominantly composed of lipoproteins. A single exposure of inhalatory halothane causes mobilization of the surface coat into the endocytotic system of the PIMs, followed by expansion of the Golgi apparatus and its enrichment with acid phosphatase. Simultaneously, the cells of the lymphocytic series show hyperplasia in the form of mitotic changes inside the microvascular compartment of the lung. Halothane is known to cause acute and chronic hepatotoxicity because of its biotransformation into trifluoroacytelated polypeptides. The present study was designed to examine the comparative effects of reexposures of inhalatory doses of halothane, isoflurane, and the intravenous barbiturate thiamylal sodium in ponies to evoke a stronger response in the PIMs after four exposures at increasing intervals of 1, 2, and 6 weeks. Ultrastructural and cytochemical evidence is presented that halothane induced translocation of the surface coat into the vacuolar system of the PIMs, followed by expansion of the Golgi apparatus and its enrichment with acid phosphatase. The cell membrane was thrown into extraordinary lamellipodial extensions, which enabled the PIMs to interact with platelets within the narrow confines of the pulmonary capillaries. The relationship between PIMs and platelets developed into large platelet aggregates. Isoflurane and thiamylal sodium did not affect the circulating platelets, although the surface coat was translocated into the endolysosomes in both situations. Although isoflurane is a lipid-soluble inhalant anesthetic similar to halothane, it is subject to very little biotransformation after use and in the present model demonstrates no immune response.