School of Pharmacy
alpha-synuclein, Lewy body disorders, heat shock protein, microglia, sex differences, intranasal, chaperone, glia
Lewy body disorders are a group of neurodegenerative conditions characterized by the pathological misfolding and aggregation of the abundant protein, α-synuclein. The most common Lewy body disorders are Parkinson’s disease and dementia with Lewy bodies. Apart from ageing, male sex is a major risk factor for Lewy body disorders, as men are at ~1.5-fold higher risk for these diseases than women. Yet, preclinical studies on Lewy body disorders rarely examine sex as a biological variable, and the mechanisms underlying sex-skewedness in disease risk remain undetermined.
Here, we developed a sex-stratified model of Lewy body disorders by exposing primary neurons harvested from male versus female rat pups to aggregated, fibrillar α-synuclein in vitro. In Aim 1, we tested if the sex-skewedness in the ensuing α-synucleinopathy was mediated by sex differences in intrinsic defenses that regulate protein homeostasis, such as the Hsp70 disaggregation machinery. Using primary rodent cultures as well as postmortem age- and sex-matched human tissue from subjects with Lewy body disorders, data from Aim 1 suggest that male cells may be more dependent on Hsp70 defenses under α-synucleinopathic disease conditions than female cells.
In Aim 2, we tested the therapeutic potential of Hsp70 via the intranasal route of drug delivery. Exogenously delivered Hsp70 (eHsp70) entered the aged male mouse brain within 3 hours, but, unexpectedly, eHsp70 did not penetrate the aged female mouse brain. Consistent with its nose-to-brain uptake, eHsp70 also mitigated pathology and behavior deficits in aged male mice injected with fibrillar α-synuclein. In contrast to its inability to permeate the female brain after intranasal delivery, eHsp70 was taken up by and reduced α-synuclein pathology in primary male and female neurons, via a mechanism that was partly dependent on its chaperone activities.
In Aim 3, we observed that eHsp70 increased the ability of primary microglia to engulf particles, but pretreatment of microglia with eHsp70 did not improve their ability to protect neighboring neurons from α-synucleinopathy. Rather, the mere presence of microglia in neuron/microglia co-cultures was protective against α-synucleinopathy—at least in male cells. In a final series of in vivo studies, we noted that partial depletion of microglia in aged male mice injected with fibrillar α-synuclein led to hyperactive and anxiety-like behaviors—effects that were not reversed post-microglial repopulation. In contrast, microglial repopulation improved spatial reference memory only in aged female mice injected with fibrillar α-synuclein, due perhaps to reversal of the ageing and diseased microglial phenotype. Thus, repopulating microglia may induce nootropic effects in aged female, but not male mice injected with fibrillar α-synuclein.
Collectively, this body of work reveals previously unrecognized sex differences in endogenous defenses and in the sex-skewed therapeutic benefits afforded by Hsp70 and microglia in α-synucleinopathic disease.
Bhatia, T. (2022). Sex-specific Effects of Chaperone and Glial Defenses on Experimental Lewy Body Disease (Doctoral dissertation, Duquesne University). Retrieved from https://dsc.duq.edu/etd/2120
Bhatia, T. N., Clark, R. N., Needham, P. G., Miner, K. M., Jamenis, A. S., Eckhoff, E. A., Abraham, N., Hu, X., Wipf, P., Luk, K. C., Brodsky, J. L., & Leak, R. K. (2021). Heat Shock Protein 70 as a Sex-Skewed Regulator of α-Synucleinopathy. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics, 18(4), 2541–2564. https://doi.org/10.1007/s13311-021-01114-6