Biology subjects

Griffin, M. N.

Publications and source records attributed to Griffin, M. N..

3 recordsLinked to original sources

bioRxiv2026

Stimulating microglial neuroinflammation with amyloid-beta oligomers compatible with solid-state NMR structural characterization

Soluble amyloid-{beta} (A{beta}) oligomers are considered the primary neurotoxic species in Alzheimer's disease, yet the relationship between oligomer structure and biological activity remains poorly understood. Oligomer sample preparations amenable to high-resolution structural characterization have not been tested in cell-based assays, mostly because detergents used to drive oligomer formation are toxic to cells. Here, we describe a detergent-free protocol in which size-exclusion chromatography-isolated A{beta}42 monomers spontaneously oligomerize at 37 {degrees}C in a concentration- and temperature-dependent manner. Biophysical characterization shows a {beta}-sheet structure by circular dichroism, a self-associating population above 100 kDa by silver-stained SDS-PAGE, and bead-like strings by negative-stain TEM resembling the previously characterized SDS-induced 150 kDa oligomer. Solid-state NMR spectroscopy of selectively 13C/15N-labeled 37 {degrees}C oligomers yields well-resolved spectra with {beta}-strand chemical shifts, and two-dimensional 13C-13C DARR and CHHC experiments provide initial inter-residue distance constraints that reveal both similarities to and differences from the 150 kDa oligomer. Treatment of mouse microglial cells (MMCs) with 50 nM 37 {degrees}C oligomers elicited a robust pro-inflammatory cytokine response that exceeded that of monomeric A{beta}42, as demonstrated by Luminex multiplex profiling and principal component analysis. hiPSC-derived microglia (iMGs) treated with 1 {micro}M oligomers also separated from vehicle, establishing activity in a human cellular model. Monomeric A{beta}42 was inactive in both systems, indicating that inflammatory activity depends on the assembly state of A{beta}42 rather than on the presence of peptide alone. These results establish a detergent-free A{beta}42 oligomer preparation that is simultaneously compatible with solid-state NMR structural characterization and biologically active in neuroinflammation assays, providing a platform for studying microglial immune responses to oligomers.

neuroscience↗

bioRxiv2026

Neuronal p38α knockout protects against neurological consequences following repetitive mild traumatic brain injury

Mild traumatic brain injuries (mTBI) can substantially impact quality of life, and repetitive mTBIs (rmTBI) can amplify injury effects compared to a single injury. However, effective clinical treatments remain elusive, largely due to an incomplete understanding of the underlying injury mechanisms. Neuroinflammation has emerged as a key contributor to worse functional outcomes after mTBI/rmTBI. While microglia are traditionally viewed as primary mediators of post-injury inflammation, accumulating evidence suggests neurons play an immunomodulatory role in initiating the rmTBI inflammatory cascade through activation of intracellular proinflammatory pathways like p38 MAPK and secretion of cytokines that, in turn, stimulate microglial activation. Here, we tested whether inducible neuronal p38 knockout protects against functional, immune, and cerebrovascular consequences of a weight-drop closed head injury model of rmTBI. A battery of functional assays was conducted 4 weeks post-injury, and tissues were collected at both 4 hours and 4 weeks following final CHI. In males, neuronal p38 knockout protected against injury-induced depressive-like behavior, hyperactivity, synaptic loss, microglial reactivity, cytokine upregulation, and reduction in cerebral blood flow. In females, neuronal p38 knockout protected against risk-taking behavior and partially protected against cytokine upregulation but had limited effect on microglial reactivity and cerebral blood flow. Together, these findings identify neuronal p38 as a sex-dependent driver of rmTBI-associated neurological consequences, and they support neuronal p38-immune signaling as a mechanistically relevant therapeutic target for future studies.

neuroscience↗

bioRxiv2025

Aβ-42 sidechain deamidation at Q15 and N27 modulate protein aggregation and microglial responses via altered cytokine production and CD68 expression

The progressive aggregation of amyloid beta (A{beta}) monomers into oligomers is a critical factor in Alzheimers disease (AD) pathogenesis. Although mutated forms of A{beta} have been shown to display altered aggregation dynamics, the specific effects of deamidated A{beta} on microglial function remain understudied. Our research group previously found that the deamidated variant A{beta}-42-N27D modified A{beta} aggregation, reduced neurotoxicity, and reduced microglial reactivity, but the impact of A{beta}-42 side chain deamidation in general on such parameters remained unclear. Here, we expanded on our prior work by investigating how two site-specific A{beta}-42 mutations (Q15E & N27D), where neutral amide side chains are replaced with negatively charged carboxylic acids, affect aggregation and microglial immune response using a mouse microglial cell line. Size exclusion chromatography revealed that A{beta}-42-Q15E and A{beta}-42-N27D exhibit distinct aggregation profiles compared to A{beta}-42 wild type (WT). Multiplexed analysis of 8 cytokines secreted into the culture medium revealed that A{beta}-42-Q15E and A{beta}-42-N27D decrease the expression of inflammatory cytokines such as IL-6, IP-10, and MIP-1 relative to A{beta}-42-WT. Immunocytochemistry revealed that A{beta}-42-Q15E and A{beta}-42-N27D decrease CD68 expression relative to A{beta}-42-WT. These findings demonstrate that deamidation significantly alters A{beta}-42 aggregation and microglial activation, suggesting structural modifications to A{beta}-42 modulate inflammatory signaling in AD. This work provides a foundation for future studies on A{beta}-42 post-translational modifications as potential therapeutic targets in AD.S

neuroscience↗