Mutant Huntingtin Secretion in Neuro2A Cells and Rat Primary Cortical Neurons

The mammosphere-derived epithelial cell secretome modulates neutrophil functions in the bovine model

Background

Innovative therapies against bacterial infections are needed. One approach is to focus on host-directed immunotherapy (HDT), with treatments that exploit natural processes of the host immune system. The goals of this type of therapy are to stimulate protective immunity while minimizing inflammation-induced tissue damage. We use non-traditional large animal models to explore the potential of the mammosphere-derived epithelial cell (MDEC) secretome, consisting of all bioactive factors released by the cells, to modulate host immune functions. MDEC cultures are enriched for mammary stem and progenitor cells and can be generated from virtually any mammal. We previously demonstrated that the bovine MDEC secretome, collected and delivered as conditioned medium (CM), inhibits the growth of bacteria in vitro and stimulates functions related to tissue repair in cultured endothelial and epithelial cells.

Methods

The immunomodulatory effects of the bovine MDEC secretome on bovine neutrophils, an innate immune cell type critical for resolving bacterial infections, were determined in vitro using functional assays. The effects of MDEC CM on neutrophil molecular pathways were explored by evaluating the production of specific cytokines by neutrophils and examining global gene expression patterns in MDEC CM-treated neutrophils. Enzyme linked immunosorbent assays were used to determine the concentrations of select proteins in MDEC CM and siRNAs were used to reduce the expression of specific MDEC-secreted proteins, allowing for the identification of bioactive factors modulating neutrophil functions.

Results

Neutrophils exposed to MDEC secretome exhibited increased chemotaxis and phagocytosis and decreased intracellular reactive oxygen species and extracellular trap formation, when compared to neutrophils exposed to control medium. C-X-C motif chemokine 6, superoxide dismutase, peroxiredoxin-2, and catalase, each present in the bovine MDEC secretome, were found to modulate neutrophil functions.

Conclusion

The MDEC secretome administered to treat bacterial infections may increase neutrophil recruitment to the site of infection, stimulate pathogen phagocytosis by neutrophils, and reduce neutrophil-produced ROS accumulation. As a result, pathogen clearance might be improved and local inflammation and tissue damage reduced.

Structural insight into transmissive mutant huntingtin species by correlative light and electron microscopy and cryo-electron tomography

Aggregates of mutant huntingtin (mHTT) containing an expanded polyglutamine (polyQ) tract are hallmarks of Huntington's Disease (HD). Studies have shown that mHTT can spread between cells, leading to the propagation of misfolded protein pathology. However, the structure of transmissive mHTT species, and the molecular mechanisms underlying their transmission remain unknown. Using correlative light and electron microscopy (CLEM) and cryo-electron tomography (cryo-ET), we identified two types of aggregation-prone granules in conditioned medium from PC12 cells expressing a mHTT N-terminal fragment: densities enclosed by extracellular vesicles (EVs), and uncoated, amorphous meshworks of heterogeneous oligomers that co-localize with clusters of EVs. In vitro assays confirmed that liposomes induce condensation of polyQ oligomers into higher-order assemblies, resembling the uncoated meshworks observed in PC12 conditioned medium. Our findings provide novel insights into formation and architecture of transmissive mHTT proteins, and highlight the potential role of EVs as both carriers and modulators of transmissive mHTT proteins.

Distortion of protein analysis in primary neuronal cultures by serum albumin from culture medium: A methodological approach to improve target protein quantification

BACKGROUND

Primary neuronal cultures underpin diverse neuroscience experiments, including various protein analysis techniques, such as Western blotting, whereby protein extraction from cultured neurons is required. During immunoblotting experiments, we encountered problems due to a highly-abundant protein of 65-70 KDa present in the cell extracts, that interfered with total protein estimation, and immunodetection of target proteins of similar size. Previous research has suggested that serum proteins, specifically albumin, contained within commonly-used culture media, can bind to, or be adsorbed by, generic cell culture plasticware. This residual albumin may then be extracted along with cell proteins.

NEW METHOD

We made simple modifications to wash steps of traditional cell lysis/extraction protocols.

RESULTS

We report that a substantial amount of albumin, accumulated from the standard culture media, is extracted from primary neuronal cultures along with the cellular contents. This contamination can be reduced, without changing the culture conditions, by modifying wash procedures.

COMPARISON WITH EXISTING METHODS

Accumulated albumin from neuronal culture media, in amounts equivalent to cellular contents, can distort data from total protein assays and from the immunoreactive signal from nearby bands on Western blots. By altering wash protocols during protein extraction, these problems can be ameliorated.

CONCLUSIONS

We suggest that the standard extended culture periods for primary neuronal cultures, coupled with the requirement for successive medium changes, may leave them particularly susceptible to cumulative albumin contamination from the culture media used. Finally, we propose the implementation of simple alterations to wash steps in protein extraction protocols which can ameliorate this interference.