Cationic lipid:pDNA complexes

Chu, Q., Tousignant, J., Fang, S., Jiang, C., Chen, L., Cheng, S., Scheule, R. and Eastman, S. (1999) Binding and uptake of cationic lipid pDNA complexes by polarized airway epithelial cells. Hum. Gene Ther., 10,25-36. 

Eastman, S.J., Tousignant, J.D.,Lukason, M.J., Chu, Q., Cheng, S.H. andScheule, R.K. (1998) Aerosolization of cationic lipid pDNA complexes In vitro optimization of nebulizer parameters for human clinical studies. Hum. Gene Then, 9, 43-52. 

Cationic lipid pDNA complexes (lipoplexes) generally are prepared by the simple mixing together of the two components however, it is also important to consider that the applied protocols for complex formation and subsequent modifications strongly influence the properties of the transfection particle. Also, the order of addition of components to form the lipoplex affects considerably lipofection activity. 

Yew NS, Wang KX, Przyhylska M, Bagley RG, Stedman M, Marshall J, Scheule RK, Cheng SH. Contribution of plasmid DNA to inflammation in the lung after administration of cationic lipid pDNA complexes. Hum Gene Ther 1999, 10, 223-234. 

Given the polyionic nature and size of cationic lipid pDNA complexes, it should not come as a surprise that they can bind exogenous proteins that might subsequently affect their stability and biodistribution. Indeed, several studies have pointed to the ability of complexes to bind serum proteins such as albumin (23,24,35). In addition, complexes appear to interact with cellular components in vivo such as lymphocytes (36) and red blood cells (37). Thus, although some of the effects of semm protein binding on activity might be assessed in vitro, it would be extremely difficult to mimic in vitro all the important interactions of complexes with the biological environment that would be required to predict in vivo activity. 

When instilled into the luminal aspect of rodent lungs, cationic lipid pDNA complexes have resulted in variable distributions of expression. This should not be too surprising, since there are multiple physical variables associated with any instillation, for examples, details of the instillation procedure (lobar, intratracheal, intianasal), volume, identity of the vehicle, rate of delivery, that are superimposed on other sources of variability, such as the identity of the cationic lipid and the lipid pDNA ratio. Not surprisingly, intralobar instillation in rodents resulted in multifocal expression largely in the distal, alveolar aspect of the lung, presumably due to the physical pooling of the bolus instillate in this anatomical locale. Lung... 

II. The Delivery System—Cationic Lipid pDNA Complexes... 

III. Cationic Lipid pDNA Complexes and Transfection of the Lung... 

We examined the biodistribution of cationic liposomes/pDNA complex following intravenous injection in mice and pharmacokinetically analyzed the data based on the clearance concept (Mahato etal., 1995a, 1997). These analyses showed that the pharmacokinetics of 32P-pDNA complexes depend on their mixing (charge) ratio, the type of cationic and helper lipids (Mahato et al., 1998). When analyzed using radioactivity counting following the injection of the complex prepared with 32P-pDNA, the tissue uptake clearance per g... 

Yet another component of the toxicity was found to be the elevation of seram transantinases (e.g., aspartate aminotransferase, or AST), which is consistent with the accumulation of significant amounts of systemically administered complex in the liver (see above). These toxicities are not simply a consequence of the presence of plasmid DNA in the blood, which is rapidly degraded and much less toxic. Rather it is a consequence of the stabilization of the pDNA in the serum by cationic lipid and the subsequent interaction of tins complexed DNA with host blood components and cells (72,73). 

Figure 7 Pharmacokinetic properties and in vivo gene expression of stabilized plasmid-lipid particles (SPLP). (A) The levels of intact plasmid DNA (pDNA) in the circulation resulting from IV injection of naked plamid pDNA ( ), lipoplexes (O), and SPLP ( ) were determined by Southern blot analysis of plasma samples (100 pg pDNA/mouse). (B) Transgene expression at a distal tumor site resulting from rv injection of naked plamid pDNA ( ), plamid pDNA-cationic liposome complexes (O), and SPLP ( ).

---