Involvement of complement activation in the pulmonary vasoactivity of polystyrene nanoparticles in pigs: unique surface properties underlying alternative pathway activation and instant opsonization.
Background
It has been proposed that many hypersensitivity reactions to nanopharmaceuticals represent complement (C)-activation-related pseudoallergy (CARPA), and that pigs provide a sensitive animal model to study the phenomenon. However, a recent study suggested that pulmonary hypertension, the pivotal symptom of porcine CARPA, is not mediated by C in cases of polystyrene nanoparticle (PS-NP)-induced reactions.


Goals
To characterize PS-NPs and reexamine the contribution of CARPA to their pulmonary reactivity in pigs.


Study design
C activation by 200, 500, and 750 nm (diameter) PS-NPs and their opsonization were measured in human and pig sera, respectively, and correlated with hemodynamic effects of the same NPs in pigs in vivo.


Methods
Physicochemical characterization of PS-NPs included size, ζ-potential, cryo-transmission electron microscopy, and hydrophobicity analyses. C activation in human serum was measured by ELISA and opsonization of PS-NPs in pig serum by Western blot and flow cytometry. Pulmonary vasoactivity of PS-NPs was quantified in the porcine CARPA model.


Results
PS-NPs are monodisperse, highly hydrophobic spheres with strong negative surface charge. In human serum, they caused size-dependent, significant rises in C3a, Bb, and sC5b-9, but not C4d. Exposure to pig serum led within minutes to deposition of C5b-9 and opsonic iC3b on the NPs, and opsonic iC3b fragments (C3dg, C3d) also appeared in serum. PS-NPs caused major hemodynamic changes in pigs, primarily pulmonary hypertension, on the same time scale (minutes) as iC3b fragmentation and opsonization proceeded. There was significant correlation between C activation by different PS-NPs in human serum and pulmonary hypertension in pigs.


Conclusion
PS-NPs have extreme surface properties with no relevance to clinically used nanomedicines. They can activate C via the alternative pathway, entailing instantaneous opsonization of NPs in pig serum. Therefore, rather than being solely C-independent reactivity, the mechanism of PS-NP-induced hypersensitivity in pigs may involve C activation. These data are consistent with the "double-hit" concept of nanoparticle-induced hypersensitivity reactions involving both CARPA and C-independent pseudoallergy.
['Mészáros|Tamás|T|', 'Kozma|Gergely Tibor|GT|', 'Shimizu|Taro|T|', 'Miyahara|Koga|K|', 'Turjeman|Keren|K|', 'Ishida|Tatsuhiro|T|', 'Barenholz|Yechezkel|Y|', 'Urbanics|Rudolf|R|', 'Szebeni|János|J|']
D000818:Animals D003167:Complement Activation D003179:Complement C3b D004342:Drug Hypersensitivity D006801:Humans D007155:Immunologic Factors D008081:Liposomes D008297:Male D053758:Nanoparticles D011137:Polystyrenes D011652:Pulmonary Circulation D013499:Surface Properties D013552:Swine
nanoparticles pseudoallergy PIM cells adverse drug reactions anaphyla-toxins immunotoxicity phagocytosis