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Penetratins 39
2.4.4 IN VIVO INTERNALIZATION WITH PENETRATIN-DERIVED VECTORS
2.4.4.1 Immune System
Similarly, to Schutze-Redelmeier et al. with AntpHD, 40 Pietersz et al. have demonstrated
that penetratin efficiently targets antigenic peptides to the MHC-I complex. 74
Penetratin-coupled 9mer peptides corresponding to CTL epitopes have been successfully
and rapidly imported into the cytosol of peritoneal exudate cells (PEC).
Moreover, an 8mer peptide derived from ovalbumin (SIINFKEL) and coupled to
penetratin induced a T-cell response after injection in mice and protected them
against the development of tumor cell line E.G7-OVA expressing ovalbumin.
2.4.4.2 Delivery of Peptides in Blood Vessels
To appreciate further the role of caveolin-1 (the primary coat protein of caveolae)
in signal transduction, Bucci et al. synthesized a hybrid peptide containing penetratin
and the caveolin-1 scaffolding domain (19 aa). 75 Mice blood vessels and endothelial
cells efficiently took up the peptide ex vivo and in vivo. Consequently, acetylcholineinduced
vasodilatation and nitric oxyde production in isolated mouse aortic rings
were selectively inhibited. Moreover, systemic administration of the peptide in mice
suppressed acute inflammation and vascular leak as efficiently as a glucocorticoid
or endothelial nitric oxyde synthase (eNOS) inhibitors.
2.4.4.3 Direct Perfusion Inside the Central Nervous System
Bolton et al. have evaluated the brain response induced by fluorescent penetratin
after intrathecal injection into the striatum or the lateral ventricles of the rat brain. 76
Injection of 10 µg of penetratin in the striatum provoked neurotoxic cell death and
an inflammatory response. Injections of 1 µg or less resulted in low toxicity with
some spreading of the peptides, followed by its uptake, primarily by neurons.
Penetratin injected in the lateral ventricle was internalized by ependymal cells
bordering the ventricle but did not enter the parenchyme, or only very poorly. When
injected at the periphery, penetratin-1 did not disrupt the blood-brain barrier (BBB)
and Bolton et al. did not detect the peptide in rat brain 24 h after a 2-mg/kg
intravenous injection.
Penetratin has been used in vivo to deliver PNAs into the central nervous system
(CNS). 34,67 Galanin is a widely distributed neuropeptide involved in several biological
effects. Galanin receptor type 1 (Gal R1) is highly conserved between species
and abundant in the hypothalamus, hippocampus, and spinal cord. 77 PNAs designed
to down-regulate the expression of the Gal R1 gene were covalently coupled to the
N terminus of penetratin-1 by a disulfide bond. These PNAs down-regulated Gal R1
receptor expression by human Bowles melanoma cells and in vivo after intrathecal
delivery at the level of the dorsal spinal cord. Down-regulation in the spinal cord
decreased galanin binding and inhibited the C-fiber stimulation-induced facilitation
of the rat flexor reflex, a response monitoring Gal R1 activity.
2.4.4.4 The Blood–Brain Barrier
Following the intravenous injection of a doxorubicin-penetratin peptide, Rousselle
et al. have observed its passage into rat brain parenchyma. 78 These data are at odds