Robust Central Nervous System Pathology in Transgenic Mice following Peripheral Injection of α-Synuclein Fibrils

Abstract

Misfolded ␣-synuclein (␣S) is hypothesized to spread throughout the central nervous system (CNS) by neuronal connectivity leading to widespread pathology. Increasing evidence indicates that it also has the potential to invade the CNS via peripheral nerves in a prion-like manner. On the basis of the effectiveness following peripheral routes of prion administration, we extend our previous studies of CNS neuroinvasion in M83 ␣S transgenic mice following hind limb muscle (intramuscular [i.m.]) injection of ␣S fibrils by comparing various peripheral sites of inoculations with different ␣S protein preparations. Following intravenous injection in the tail veins of homozygous M83 transgenic (M83 ϩ/ϩ ) mice, robust ␣S pathology was observed in the CNS without the development of motor impairments within the time frame examined. Intraperitoneal (i.p.) injections of ␣S fibrils in hemizygous M83 transgenic (M83 ϩ/Ϫ ) mice resulted in CNS ␣S pathology associated with paralysis. Interestingly, injection with soluble, nonaggregated ␣S resulted in paralysis and pathology in only a subset of mice, whereas soluble Δ71-82 ␣S, human ␤S, and keyhole limpet hemocyanin (KLH) control proteins induced no symptoms or pathology. Intraperitoneal injection of ␣S fibrils also induced CNS ␣S pathology in another ␣S transgenic mouse line (M20), albeit less robustly in these mice. In comparison, i.m. injection of ␣S fibrils was more efficient in inducing CNS ␣S pathology in M83 mice than i.p. or tail vein injections. Furthermore, i.m. injection of soluble, nonaggregated ␣S in M83 ϩ/Ϫ mice also induced paralysis and CNS ␣S pathology, although less efficiently. These results further demonstrate the prion-like characteristics of ␣S and reveal its efficiency to invade the CNS via multiple routes of peripheral administration. IMPORTANCEThe misfolding and accumulation of ␣-synuclein (␣S) inclusions are found in a number of neurodegenerative disorders and is a hallmark feature of Parkinson's disease (PD) and PD-related diseases. Similar characteristics have been observed between the infectious prion protein and ␣S, including its ability to spread from the peripheral nervous system and along neuroanatomical tracts within the central nervous system. In this study, we extend our previous results and investigate the efficiency of intravenous (i.v.), intraperitoneal (i.p.), and intramuscular (i.m.) routes of injection of ␣S fibrils and other protein controls. Our data reveal that injection of ␣S fibrils via these peripheral routes in ␣S-overexpressing mice are capable of inducing a robust ␣S pathology and in some cases cause paralysis. Furthermore, soluble, nonaggregated ␣S also induced ␣S pathology, albeit with much less efficiency. These findings further support and extend the idea of ␣S neuroinvasion from peripheral exposures.

‘Prion‐like’ propagation of the synucleinopathy of M83 transgenic mice depends on the mouse genotype and type of inoculum

“…; Ayers et al . ). Our data extend these observations, showing that extracts from a brain with synucleinopathy also accelerate M83 disease after IP inoculation.…”

α-Synuclein fibril-induced inclusion spread in rats and mice correlates with dopaminergic Neurodegeneration

“…Injection of α-syn fibrils into the rodent striatum, somatosensory cortex, entorhinal cortex, olfactory bulb, substantia nigra pars compacta (SNpc), or muscle, show that the fibrils induce inclusions that resemble those found in PD and LBD (Luk et al, 2012) (Masuda-Suzukake et al, 2014; Masuda-Suzukake et al, 2013; Rey et al, 2016) (Ayers et al, 2017; Paumier et al, 2015). In vivo imaging of cortical neurons previously exposed to fibrils demonstrates the overall cytotoxic nature of the inclusion (Osterberg et al, 2015).…”

Neurodegeneration and the ordered assembly of α-synuclein

“…Moreover, the peripheral injection of α-synuclein aggregates assembled from recombinant protein caused α-synuclein pathology and neurodegeneration in the central nervous system of transgenic but not wild-type, mice (Breid et al 2016; Ayers et al 2017). Using long-term in vivo imaging, aggregated recombinant α-synuclein was shown to seed the ordered assembly of expressed α-synuclein in brain (Osterberg et al 2015).…”