Border-associated macrophages mediate the neuroinflammatory response in an alpha-synuclein model of Parkinson disease.

Dopaminergic cell loss due to the accumulation of α-syn is a core feature of the pathogenesis of Parkinson disease. Neuroinflammation specifically induced by α-synuclein has been shown to exacerbate neurodegeneration, yet the role of central nervous system (CNS) resident macrophages in this process remains unclear. We found that a specific subset of CNS resident macrophages, border-associated macrophages (BAMs), play an essential role in mediating α-synuclein related neuroinflammation due to their unique role as the antigen presenting cells necessary to initiate a CD4 T cell response whereas the loss of MHCII antigen presentation on microglia had no effect on neuroinflammation. Furthermore, α-synuclein expression led to an expansion in border-associated macrophage numbers and a unique damage-associated activation state. Through a combinatorial approach of single-cell RNA sequencing and depletion experiments, we found that border-associated macrophages played an essential role in immune cell recruitment, infiltration, and antigen presentation. Furthermore, border-associated macrophages were identified in post-mortem PD brain in close proximity to T cells. These results point to a role for border-associated macrophages in mediating the pathogenesis of Parkinson disease through their role in the orchestration of the α-synuclein-mediated neuroinflammatory response.

Role of expanded clay and porous ceramic amendments on plant establishment in minespoils.

Greenhouse experiments were conducted to examine the impact of expanded clay (Turface) or porous ceramic (Isolite) amendments on germination, biomass production, plant Zn concentration, and Zn accumulation by Festuca arundinacea grown in mine tailings. Because previous studies have demonstrated that fertilization is essential for plant growth in these tailings, manure was also added to the tailings. Plant growth and germination were greatest if the expanded clay was added topically to the tailings. To a lesser extent, plant growth and germination was also stimulated by topical additions of porous ceramic. However, no benefit was observed if either amendment was mixed into the top 10 cm of the mine tailings. The concentration of Zn in F. arundinacea tissues was lowest if the expanded clay was added topically to the mine tailings. Roots growing in the layer of clay or ceramic amendment appeared to be smaller, finer, and more abundant than the large, coarse roots found throughout the tailings-manure mixture. These results suggest that topical application of an expanded clay or porous ceramic product will increase seed germination and improve plant establishment and growth in contaminated minespoils.

The influence of mycorrhizal symbiosis and fertilizer amendments on establishment of vegetation in heavy metal mine spoil.

Biomass production of Andropogon gerardii and Festuca arundinacea was assessed in mine tailings (chat), a material containing high levels of zinc. The effects of organic and inorganic fertilizer amendments, the addition of an expanded clay material, and mycorrhizal fungi on the revegetation of chat were assessed. Plant growth in chat was best with mycorrhizal inoculation combined with nitrogen (either organic or inorganic) and phosphorus fertilization. Plant growth was also achieved if the chat material was amended with expanded clay and N and P fertilizer. However, the biomass produced in contaminated soil did not equal that of similarly fertilized uncontaminated soil. Regression analysis and canonical discriminate analysis revealed significant differences in the responses of the two plant species to the various chat amendments. Although F. arundinacea generally produced greater biomass than A. gerardii, it tended to accumulate more zinc in the shoots than A. gerardii. Therefore, if plant cover is to be used as forage or if wind-blown plant dry matter is of concern, A. gerardii may be more appropriate than F. arundinacea for revegetation of these toxic sites. Alternatively, if maximum plant cover is of primary importance to reduce wind or water erosion from contaminated soils, F. arundinacea may be the species of choice.

Effects of mycorrhizae and other soil microbes on revegetation of heavy metal contaminated mine spoil.

The effects of mycorrhizal fungi and other soil microorganisms on growth of two grasses, Andropogon gerardii Vitm. and Festuca arundinacea Schreb., in heavy metal-contaminated soil and mine tailings were investigated. A. gerardii is highly dependent on mycorrhizal fungi in native prairie, while F. arundinacea is a facultative mycotroph and relies on mycorrhizal symbiosis only in extremely infertile soils. Regardless of microbial amendments, neither plant species was able to establish and grow in the mine tailings. Both plant species grew in the moderately contaminated or non-contaminated soils, although A. gerardii grew in these soils only when mycorrhizal. Other soil microbes significantly improved growth of A. gerardii only in uncontaminated soil, but to a lesser extent than mycorrhizae. Although F. arundinacea was more highly colonized by mycorrhizal fungi than A. gerardii, neither microbial amendment affected growth of fescue in any soil. In several treatments mycorrhizal fungi adapted to uncontaminated soil stimulated plant growth more than mycorrhizae adapted to the moderately contaminated soil. However, mycorrhizal fungi adapted to contaminated soil did not increase the productivity of plant growth in contaminated soil more than fungi adapted to uncontaminated soil. A. gerardii plants inoculated with mycorrhizal fungi retained more Zn in roots than in shoots, confirming earlier reports that mycorrhizal fungi alter the translocation pattern of heavy metals in host plants. In contrast, mycorrhizae did not affect translocation patterns in F. arundinaceae, suggesting that the mycorrhizal dependence of a plant species is correlated with the retention of metals in roots. The correlation between mycorrhizal dependence of a plant species and mycorrhizal alteration of translocation pattern may also explain the inconsistent reports of mycorrhizal effects on translocation of heavy metals in plants. Plant response to mycorrhizal symbiosis may therefore provide a useful criterion for the selection of the plant species to be used in revegetation of contaminated sites.