Pyrene conjugation and spectroscopic analysis of hydroxypropyl methylcellulose compounds successfully demonstrated a local dielectric difference associated with in vivo anti-prion activity

Improvement of anti-prion efficacy with stearoxy conjugation of hydroxypropyl methylcellulose in prion-infected mice

Prion diseases are fatal transmissible neurodegenerative disorders. Among known anti-prions, hydroxypropyl methylcellulose compounds (HPMCs) are unique in their chemical structure and action. They have several excellent anti-prion properties but the effectiveness depends on the prion-infected mouse model. In the present study, we investigated the effects of stearoxy-modified HPMCs on prion-infected cells and mice. Stearoxy modification improved the anti-prion efficacy of HPMCs in prion-infected cells and significantly prolonged the incubation period in a lower HPMC-responding mouse model. However, stearoxy modification showed no improvement over nonmodified HPMCs in an HPMC-responding mouse model. These results offer a new line of inquiry for use with prion-infected mice that do not respond well to HPMCs.

Combination of Styrylbenzoazole Compound and Hydroxypropyl Methylcellulose Enhances Therapeutic Effect in Prion-Infected Mice

Prion diseases are fatal transmissible neurodegenerative disorders. Tremendous efforts have been made for prion diseases; however, no effective treatment is available. Several anti-prion compounds have a preference for which prion strains or prion-infected animal models to target. Styrylbenzoazole compound called cpd-B is effective in RML prion-infected mice but less so in 263K prion-infected mice, whereas hydroxypropyl methylcellulose is effective in 263K prion-infected mice but less so in RML prion-infected mice. In the present study, we developed a combination therapy of cpd-B and hydroxypropyl methylcellulose expecting synergistic effects in both RML prion-infected mice and 263K prion-infected mice. A single subcutaneous administration of this combination had substantially a synergistic effect in RML prion-infected mice but had no additive effect in 263K prion-infected mice. These results showed that the effect of cpd-B was enhanced by hydroxypropyl methylcellulose. The complementary nature of the two compounds in efficacy against prion strains, chemical properties, pharmacokinetics, and physical properties appears to have contributed to the effective combination therapy. Our results pave the way for the strategy of new anti-prion agents.

Cellulose ether treatment inhibits amyloid beta aggregation, neuroinflammation and cognitive deficits in transgenic mouse model of Alzheimer's disease

Alzheimer's disease (AD) is an incurable, progressive and devastating neurodegenerative disease. Pathogenesis of AD is associated with the aggregation and accumulation of amyloid beta (Aβ), a major neurotoxic mediator that triggers neuroinflammation and memory impairment. Recently, we found that cellulose ether compounds (CEs) have beneficial effects against prion diseases by inhibiting protein misfolding and replication of prions, which share their replication mechanism with Aβ. CEs are FDA-approved safe additives in foods and pharmaceuticals. Herein, for the first time we determined the therapeutic effects of the representative CE (TC-5RW) in AD using in vitro and in vivo models. Our in vitro studies showed that TC-5RW inhibits Aβ aggregation, as well as neurotoxicity and immunoreactivity in Aβ-exposed human and murine neuroblastoma cells. In in vivo studies, for the first time we observed that single and weekly TC-5RW administration, respectively, improved memory functions of transgenic 5XFAD mouse model of AD. We further demonstrate that TC-5RW treatment of 5XFAD mice significantly inhibited Aβ oligomer and plaque burden and its associated neuroinflammation via regulating astrogliosis, microgliosis and proinflammatory mediator glial maturation factor beta (GMFβ). Additionally, we determined that TC-5RW reduced lipopolysaccharide-induced activated gliosis and GMFβ in vitro. In conclusion, our results demonstrate that CEs have therapeutic effects against Aβ pathologies and cognitive impairments, and direct, potent anti-inflammatory activity to rescue neuroinflammation. Therefore, these FDA-approved compounds are effective candidates for developing therapeutics for AD and related neurodegenerative diseases associated with protein misfolding.

Therapeutic development of polymers for prion disease

Prion diseases, also known as transmissible spongiform encephalopathies, are caused by the accumulation of abnormal isoforms of the prion protein (scrapie isoform of the prion protein, PrPSc) in the central nervous system. Many compounds with anti-prion activities have been found using in silico screening, in vitro models, persistently prion-infected cell models, and prion-infected rodent models. Some of these compounds include several types of polymers. Although the inhibition or removal of PrPSc production is the main target of therapy, the unique features of prions, namely protein aggregation and assembly accompanied by steric structural transformation, may require different strategies for the development of anti-prion drugs than those for conventional therapeutics targeting enzyme inhibition, agonist ligands, or modulation of signaling. In this paper, we first overview the history of the application of polymers to prion disease research. Next, we describe the characteristics of each type of polymer with anti-prion activity. Finally, we discuss the common features of these polymers. Although drug delivery of these polymers to the brain is a challenge, they are useful not only as leads for therapeutic drugs but also as tools to explore the structure of PrPSc and are indispensable for prion disease research.

Polymorphisms in glia maturation factor β gene are markers of cellulose ether effectiveness in prion-infected mice

Anti-prion effects of cellulose ether (CE) are reported in rodents, but the molecular mechanism is fully unknown. Here, we investigated the genetic background of CE effectiveness by proteomic and genetic analysis in mice. Proteomic analysis in the two mouse lines showing a dramatic difference in CE effectiveness revealed a distinct polymorphism in the glia maturation factor β gene. This polymorphism was significantly associated with the CE effectiveness in various prion-infected mouse lines. Sequencing of this gene and its vicinity genes also revealed several other polymorphisms that were significantly related to the CE effectiveness. These polymorphisms are useful as genetic markers for finding more suitable mouse lines and exploring the genetic factors of CE effectiveness.

Administration of FK506 from Late Stage of Disease Prolongs Survival of Human Prion-Inoculated Mice

Human prion diseases are etiologically categorized into three forms: sporadic, genetic, and infectious. Sporadic Creutzfeldt-Jakob disease (sCJD) is the most common type of human prion disease that manifests as subacute progressive dementia. No effective therapy for sCJD is currently available. Potential therapeutic compounds are frequently tested in rodents infected with mouse-adapted prions that differ from human prions. However, therapeutic effect varies depending on the prion strain, which is one of the reasons why candidate compounds have shown little effect in sCJD patients. We previously reported that intraperitoneal administration of FK506 was able to prolong the survival of mice infected with a mouse-adapted prion by suppressing the accumulation of abnormal prion protein (PrP) and inhibiting the activation of microglia. In this study, we tested oral administration of FK506 in knock-in mice expressing chimeric human prion protein (KiChM) that were infected with sCJD to determine if this compound is also effective against a clinically relevant human prion, i.e., one that has not been adapted to mice. Treatment with FK506, started either just before or just after disease onset, suppressed typical sCJD pathology (gliosis) and slightly but significantly prolonged the survival of sCJD-inoculated mice. It would be worthwhile to conduct a clinical trial using FK506, which has been safety-approved and is widely used as a mild immunosuppressant.

Preparation and Characterization of Cellulose Ether Liposomes for the Inhibition of Prion Formation in Prion-Infected Cells

Prion accumulation in the brain and lymphoreticular system causes fatal neurodegenerative diseases. Our previous study revealed that cellulose ethers (CE) have anti-prion activities in vivo and in prion-infected cells when administered at high doses. This study aims to improve the bioavailability of a representative CE using a liposomal formulation and characterized CE-loaded liposomes in cultured cells. The liposomal formulation reduced the EC₅₀ dose of CE by <1/200-fold in prion-infected cells. Compared to empty liposomes, CE-loaded liposomes were taken up much more highly by prion-infected cells and less by macrophage-like cells. Phosphatidylserine modification reduced the uptake of CE-loaded liposomes in prion-infected cells and did not change the anti-prion activity, whereas increased the uptake in macrophage-like cells. Polyethylene glycol modification reduced the uptake of CE-loaded liposomes in both types of cells and reduced the anti-prion activity in prion-infected cells. These results suggest that a liposomal formulation of CE is more practical than unformulated CE and showed that the CE-loaded liposome uptake levels in prion-infected cells were not associated with anti-prion activity. Although further improvement of the stealth function against phagocytic cells is needed, the liposomal formulation is useful to improve CE efficacy and elucidate the mechanism of CE action.