Crosslinked nanocarriers based upon poly(ethylene imine) for systemic plasmid delivery: in vitro characterization and in vivo studies in mice.

Crosslinked poly(ethylene imine) (PEI) polyplexes for intracellular DNA release were generated using a low molecular weight crosslinking reagent, Dithiobis(succinimidyl propionate) (DSP). Disulfide bonds of the crosslinked polyplexes were susceptible to intracellular redox conditions and DNA release was observed using an ethidium bromide exclusion assay and dynamic light scattering. Transfection experiments were performed to elucidate the effect of extra- and intracellular redox conditions.

PEGylation of poly(ethylene imine) affects stability of complexes with plasmid DNA under in vivo conditions in a dose-dependent manner after intravenous injection into mice.

The influence of PEGylation on polyplex stability from poly(ethylene imine), PEI, and plasmid DNA was investigated both in vitro and after intravenous administration in mice. Polyplexes were characterized with respect to particle size (dynamic light scattering), zeta-potential (laser Doppler anemometry), and morphology (atomic force microscopy). Pharmacokinetics and organ accumulation of both polymers and pDNA were investigated using 125I and 32P radioactive labels, respectively.

The sympathetic control of blood supply is different in the spleen and lymph nodes.

Objectives: The noradrenergic innervation of lymphoid organs controls several immune cell functions and local blood perfusion. Considering that cell and antigen uptake depend on the blood supply to lymphoid organs, the hypothesis was tested that feedback signals from activated immune cells control sympathetic vasomotor activity.

Methods: We determined the blood flow in spleen and mesenteric lymph nodes (mLN) of Wistar Kyoto rats during immune stimulation with endotoxin (LPS; 10 microg/kg) and following disruption of the noradrenergic transmission.

Local and systemic autonomic nervous effects on cell migration to the spleen.

This work is based on the hypothesis that sympathetic nerves regulate the uptake of circulating cells by the spleen by affecting splenic blood flow and that the quantity of cells sequestered depends on whether changes in noradrenergic transmission occur at local or systemic levels. Fluorescently labeled lymphoid cells were injected into rats, and organ blood flow was measured by the microsphere method. Increased retention of cells in the spleen paralleled by increased blood flow was detected after local denervation of this organ or administration of bacterial endotoxin.