Poly-Arginine and Arginine-Rich Peptides are Neuroprotective in Stroke Models

Abstract

Using cortical neuronal cultures and glutamic acid excitotoxicity and oxygen-glucose deprivation (OGD) stroke models, we demonstrated that poly-arginine and arginine-rich cell-penetrating peptides (CPPs), are highly neuroprotective, with efficacy increasing with increasing arginine content, have the capacity to reduce glutamic acid-induced neuronal calcium influx and require heparan sulfate preotoglycan-mediated endocytosis to induce a neuroprotective effect. Furthermore, neuroprotection could be induced with immediate peptide treatment or treatment up to 2 to 4 hours before glutamic acid excitotoxicity or OGD, and with poly-arginine-9 (R9) when administered intravenously after stroke onset in a rat model. In contrast, the JNKI-1 peptide when fused to the (non-arginine) kFGF CPP, which does not rely on endocytosis for uptake, was not neuroprotective in the glutamic acid model; the kFGF peptide was also ineffective. Similarly, positively charged poly-lysine-10 (K10) and R9 fused to the negatively charged poly-glutamic acid-9 (E9) peptide (R9/E9) displayed minimal neuroprotection after excitotoxicity. These results indicate that peptide positive charge and arginine residues are critical for neuroprotection, and have led us to hypothesize that peptide-induced endocytic internalization of ion channels is a potential mechanism of action. The findings also question the mode of action of different neuroprotective peptides fused to arginine-rich CPPs.

Inhibition of N-Methyl-d-aspartate-induced Retinal Neuronal Death by Polyarginine Peptides Is Linked to the Attenuation of Stress-induced Hyperpolarization of the Inner Mitochondrial Membrane Potential

“…Increasing evidence demonstrates that Arg-rich peptides are neuroprotective in excitotoxic models (49,50). In in vitro studies, cell-penetrating peptides were recently reported to protect dissociated cortical neurons against excitotoxic doses of NMDA (50,51).…”

“…In in vitro studies, cell-penetrating peptides were recently reported to protect dissociated cortical neurons against excitotoxic doses of NMDA (50,51). Furthermore, Meloni et al (49) reported that only long Arg-rich peptides, containing nine or more arginines, demonstrated neuroprotective properties. Extending these studies, we show using an in vivo retinal neuroprotection model in which the retina is subjected to a strong NMDA insult (20 nmol of NMDA into the vitreal chamber corresponding to ϳ300 M) that the Arg-rich peptides Tat, Tat-NR2B9c, R(7), C-R(7), both D-and L-isoforms of C-s-s-C-R(7) and the cyclic peptides that were linked via a disulfide bridge to C-R(7), including CN2097, all blocked "short term" NMDA-induced LPMS.…”

The neuroprotective potential of arginine-rich peptides for the acute treatment of traumatic brain injury

“…Moreover, substantial safety and efficacy in the administration of TAT-NR2B9c in humans and non-human primates has been established [24]. To this end, studies in our laboratory have shown that a poly-arginine-18 peptide is more neuroprotective than TAT-NR2B9c in both in vitro [11] and in vivo (unpublished observation) stroke models. Therefore, based on the TAT-NR2B9c, and APOE-and APPderived peptide studies, plus the superior efficacy of polyarginine peptides compared with the three aforementioned peptides, it is possible that poly-arginine, or other argininerich peptides, may be effective agents following TBI.…”

“…Furthermore, studies revealed that arginine residues were the critical elements for neuroprotection, with peptide efficacy increasing with arginine content [11]. In addition, arginine-rich peptides were shown to be neuroprotective in a rat stroke model and also capable of reducing neuronal calcium influx following glutamate excitotoxicity [11].…”

“…Furthermore, studies revealed that arginine residues were the critical elements for neuroprotection, with peptide efficacy increasing with arginine content [11]. In addition, arginine-rich peptides were shown to be neuroprotective in a rat stroke model and also capable of reducing neuronal calcium influx following glutamate excitotoxicity [11]. Finally, mounting evidence suggests that the neuroprotective actions of TAT-fused neuroprotective peptides is largely mediated by the arginine residues and to a lesser extent lysine and tryptophan residues within the TAT and/or cargo peptide [12].…”