The design and delivery of a thermally responsive peptide to inhibit S100B-mediated neurodegeneration

Abstract

S100B, a glial secreted protein is believed to play a major role in neurodegeneration in Alzheimer's disease, Down syndrome, traumatic brain injury and spinocerebellar ataxia type 1 (SCA1). SCA1 is a trinucleotide repeat disorder in which the expanded polyglutamine mutation in the protein ataxin-1 primarily targets Purkinje cells (PCs) of the cerebellum. Currently, the exact mechanism of S100B mediated PC damage in SCA1 is not clear. However, here we show that S100B may act via the activation of the RAGE signaling pathway resulting in oxidative stress mediated injury to mutant ataxin-1 expressing neurons. To combat S100B mediated neurodegeneration, we have designed a selective thermally responsive S100B inhibitory peptide, Synb1-ELP-TRTK. Our therapeutic polypeptide was developed using three key elements: (1) the elastin-like polypeptide (ELP), a thermally responsive polypeptide, (2) the TRTK12 peptide, a known S100B inhibitory peptide and (3) a cell penetrating peptide, Synb1, to enhance intracellular delivery. Binding studies revealed that our peptide, Synb1-ELP-TRTK, interacts with its molecular target S100B and maintains a high S100B binding affinity as comparable with the TRTK12 peptide alone. In addition, in vitro studies revealed that Synb1-ELP-TRTK treatment reduces S100B uptake in SHSY5Y cells. Furthermore, the Synb1-ELP-TRTK peptide decreased S100B induced oxidative damage to mutant ataxin-1 expressing neurons. To test the delivery capabilities of ELP based therapeutic peptides to the cerebellum; we treated mice with fluorescently labeled Synb1-ELP and observed that thermal targeting enhanced peptide delivery to the cerebellum. Here, we have laid the framework for thermal based therapeutic targeting to regions of the brain, particularly the cerebellum. Overall, our data suggests that thermal targeting of ELP based therapeutic peptides to the cerebellum is a novel treatment strategy for cerebellar neurodegenerative disorders.

Cell penetrating peptides fused to a thermally targeted biopolymer drug carrier improve the delivery and antitumor efficacy of an acid-sensitive doxorubicin derivative

“…Heating consisted of a thermal cycling protocol previously shown to be effective (Dreher et al, 2007) and optimized by our lab (20 min heating, 10 min cooling × 4). Previously, this protocol was used to focus an infrared light to generate hyperthermia in the breast tissue (Bidwell et al, 2012) and in the cerebellum (Hearst et al, 2011). Using the heat cycling protocol, the tumor temperature repeatedly cycled in and out of the desired hyperthermia window (39 – 41 °C), which has been shown to be more effective than prolonged heating for ELP thermal targeting (Dreher et al, 2007).…”

Functions of S100 Proteins

“…Thus, it seems that at the levels found in the brain extracellular space in normal physiological conditions, S100B is trophic to neural cells. However, in a background of inflammation and/or neurodegenerative disorders, which is accompanied by enhanced expression levels of S100B and the S100B receptor, RAGE, in neural and inflammatory cells [7,320-322], S100B acts synergistically with proinflammatory cytokines and, at higher concentrations, behaves itself as a cytokine, amplifying and perpetuating inflammation and causing oxidative damage to neurons.…”

White matter damage after traumatic brain injury: A role for damage associated molecular patterns

“…As extracranial sources of S100β do not affect serum levels in humans [122], reduced tissue expression likely reflects increased extracellular release due to pathological conditions [111]. Functionally, S100β inhibition reduced neurodegeneration [123] and S100β −/− mice or antibody-mediated neutralization of S100β attenuated microglial reactivity and improved memory function after experimental TBI [124]. Thus, S100β may represent a predictive biomarker of outcomes and target for therapeutic development after TBI [125].…”