Specific gene blockade shows that peptide nucleic acids readily enter neuronal cells in vivo

Abstract

Peptide nucleic acids (PNAs) are DNA analogs that can hybridize to complementary sequences with high affinity and stability. Here, we report the first evidence of intracellular delivery of PNAs in vivo. Two CNS receptors, an opioid (mu) and a neurotensin (NTR-1), were targeted independently by repeated microinjection of PNAs into the periaqueductal gray. Behavioral responses to neurotensin (antinociception and hypothermia) and morphine (antinociception) were lost in a specific manner. Binding studies confirmed a large reduction in receptor sites. The loss of behavioral responses was long lasting but did fully recover. The implications of specifically and readily turning off gene expression in vivo are profound.z 1998 Federation of European Biochemical Societies.

Potent Spinal Analgesia Elicited through Stimulation of NTS2 Neurotensin Receptors

“…Some of these effects are likely mediated via NTS1, because mice deficient in NTS1 expression exhibited reduced antinociception in the hotplate test (Tyler et al, 1998;Pettibone et al, 2002). However, the extensive anatomical association found here between NTS2 and spinal nociceptive pathways, together with the evidence for a role of NTS2 in the mediation of the supraspinal analgesic actions of NT (Dubuc et al, 1999;Maeno et al, 2004), prompted us to investigate whether this receptor subtype might also be involved in the mediation of the antinociceptive effects of NT at the spinal level.…”

“…Two of these, NTS1 and NTS2, correspond to G-protein-coupled receptors, whereas the third one, NTS3, is a single transmembrane spanning receptor that shares 100% homology with the sorting protein, gp95/sortilin (Hermans and Maloteaux, 1998;. Although some of the antinociceptive effects of NT appear to be exerted through the highaffinity NTS1 receptor (Tyler et al, 1998;Pettibone et al, 2002), the fact that various NT analogs exhibit analgesic potencies that do not correlate with their binding affinity for NTS1 suggests that other receptors are also involved. Several lines of evidence point to the levocabastine-sensitive low-affinity NTS2 subtype as a pos-sible antinociceptor .…”

“…Indeed, whereas neurons expressing NTS1 mRNA had been reported in DRG neurons (Zhang et al, 1995) and high concentrations of NTS1 binding sites, and NTS1-immunoreactive nerve cell bodies and fibers had been detected in the substantia gelatinosa of the dorsal horn (Ninkovic et al, 1981;Kar and Quirion, 1995;Fassio et al, 2000), nothing was known about the distribution of NTS2 receptors in these two areas. Likewise, recent studies using knock-down strategies had suggested that NTS1 receptors may be implicated in spinal antinociception (Tyler et al, 1998;Pettibone et al, 2002), but whether NTS2 receptors were also involved in this process was still an open question.…”

The Effects of Deleting the Mouse Neurotensin Receptor NTR1 on Central and Peripheral Responses to Neurotensin

“…A role for NTR2 in NT-induced analgesia (but not hypothermia) was further suggested by Dubuc et al (1999b) by using an NTR2 antisense knock-down strategy. On the other hand, use of peptide nucleic acids to downregulate NTR1 expression provided evidence for involvement of NTR1 in the antinociception and hypothermia (Tyler et al, 1998a). Other studies showed that the highly NTR2-selective levocabastine had no effect on baseline core body temperature or NT-induced hypothermia or baseline analgesia (Tyler et al, 1998b;Dubuc et al, 1999a), but either partially inhibited NT-induced analgesia at low (but not high) doses (Tyler et al, 1998b) or completely blocked it (Dubuc et al, 1999a).…”

Artificial (Pseudo)peptides for Molecular Recognition and Catalysis

“…Finally, in a very exciting and controversial study Richelson and coworkers have claimed that antigene and antisense PNA can pass the blood-brain barrier and can bind in-vivo to the neurotensin receptor (NTR1) in rats [52,53]. Specifically, intraperitoneal injection of PNA inhibited the hypothermic and antinociceptive activities of neurotensin microinjected in the brain.…”