Complement activation by PEGylated single-walled carbon nanotubes is independent of C1q and alternative pathway turnover.
We have investigated the interaction between long circulating poly(ethylene glycol)-stabilized single-walled carbon nanotubes (SWNTs) and the complement system. Aminopoly(ethylene glycol)(5000)-distearoylphosphatidylethanolamine (aminoPEG(5000)-DSPE) and methoxyPEG(5000)-DSPE coated as-grown HIPco SWNTs activated complement in undiluted normal human serum as reflected in significant rises in C4d and SC5b-9 levels, but not the alternative pathway split-product Bb, thus indicating activation exclusively through C4 cleavage. Studies in C2-depleted serum confirmed that PEGylated nanotube-mediated elevation of SC5b-9 was C4b2a convertase-dependent. With the aid of monoclonal antibodies against C1s and human serum depleted from C1q, nanotube-mediated complement activation in C1q-depleted serum was also shown to be independent of classical pathway. Nanotube-mediated C4d elevation in C1q-depleted serum, however, was inhibited by N-acetylglucosamine, Futhan (a broad-spectrum serine protease inhibitor capable of preventing complement activation through all three pathways) and anti-MASP-2 antibodies; this strongly suggests a role for activation of MASP-2 in subsequent C4 cleavage and assembly of C4b2a covertases. Intravenous injection of PEGylated nanotubes in some rats was associated with a significant rise in plasma thromboxane B2 levels, indicative of in vivo nanotube-mediated complement activation. The clinical implications of these observations are discussed.
Hamad
Islam
I
Molecular Targeting and Polymer Toxicology Group, School of Pharmacy, University of Brighton, Brighton BN2 4GJ, UK.
Christy Hunter
A
A
Rutt
Kenneth J
KJ
Liu
Zhuang
Z
Dai
Hongjie
H
Moein Moghimi
S
S
D000328:Adult; D002244:Carbon / Q000276:immunology; D003167:Complement Activation / Q000502:physiology*; D015922:Complement C1q / Q000276:immunology* / Q000378:metabolism; D050577:Complement C3-C5 Convertases / Q000276:immunology / Q000378:metabolism; D003181:Complement C4 / Q000037:antagonists & inhibitors / Q000276:immunology / Q000378:metabolism; D003170:Complement Pathway, Alternative / Q000276:immunology*; D006801:Humans; D008297:Male; D043942:Nanotubes / Q000737:chemistry*; D011092:Polyethylene Glycols / Q000378:metabolism*
D003181:Complement C4; D011092:Polyethylene Glycols; D002244:Carbon; D015922:Complement C1q; D050577:Complement C3-C5 Convertases