Biology subjects

Lawless, S.

Publications and source records attributed to Lawless, S..

3 recordsLinked to original sources

bioRxiv2022

A single closed head injury in mice induces chronic, progressive white matter atrophy and increased phospho-tau expressing oligodendrocytes

Traumatic brain injury (TBI) acutely damages the brain; this injury can evolve into chronic neurodegeneration. While much is known about the chronic effects arising from multiple mild TBIs, far less is known about the long-term effects of a single moderate to severe TBI. We found that a single moderate closed head injury to mice induces diffuse axonal injury within 1-day post-injury (DPI). At 14 DPI, injured animals have atrophy of ipsilesional cortex, thalamus, and corpus callosum, with bilateral atrophy of the dorsal fornix. Atrophy of the ipsilesional corpus callosum is accompanied by decreased fractional anisotropy and increased mean and radial diffusivity that remains unchanged between 14 and 180 DPI. Injured animals increased density of phospho-tau immunoreactive (pTau+) cells in the ipsilesional cortex and thalamus, and bilaterally in corpus callosum. Between 14 and 180 DPI, atrophy occurs in the ipsilesional ventral fornix, contralesional corpus callosum, and bilateral internal capsule. Diffusion tensor MRI parameters remain unchanged in white matter regions with delayed atrophy. Between 14 and 180 DPI, pTau+ cell density increases bilaterally in corpus callosum, but decreases in cortex and thalamus. The location of pTau+ cells within the ipsilesional corpus callosum changes between 14 and 180 DPI; density of all cells increases including pTau+ or pTau- cells. Greater than 90% of the pTau+ cells are in the oligodendrocyte lineage in both gray and white matter. Density of thioflavin-S+ cells in thalamus increases by 180 DPI. These data suggest a single closed head impact produces multiple forms of chronic neurodegeneration. Gray and white matter regions proximal to the impact site undergo rapid atrophy. More distal white matter regions undergo chronic, progressive white matter atrophy with an increasing density of oligodendrocytes containing pTau. These data suggest that the chronic neurodegeneration arising from a single moderate CHI differs greatly from the chronic traumatic encephalopathy produced by multiple mild head injuries. HighlightsGray and white matter atrophy begins within 14 days after a single closed head injury White matter atrophy progresses between 14 and 180 days post injury with minimal changes in diffusion tensor MRI parameters. CHI increases the density of oligodendrocytes with perinuclear accumulation of phosphorylated tau Thioflavin-S+ cells increase in thalamus at 180 days post injury

neuroscience↗

bioRxiv2022

In macrophages fatty acid oxidation spares glutamate for use in diverse metabolic pathways required for alternative activation

Fatty acid oxidation (FAO) is upregulated in IL-4-stimulated (alternatively activated) macrophages (M(IL-4)). We examined the effect of loss of function of the enzyme Cpt1a, which facilitates the entry of long chain fatty acids (FA) into mitochondria for FAO, on alternative activation. Expression of M(IL-4) markers ARG1, CD301 and RELM, was impaired in tamoxifen-treated ERT2Cre x Cpt1afl/fl macrophages and in macrophages expressing shRNA targeting Cpt1a (Cpt1a-shRNA). In contrast, VaviCre x Cpt1afl/fl and LysmCre x Cpt1afl/fl M(IL-4) responded normally to IL-4. Reduced alternative activation due to Cpt1a loss of function was linked to decreased cellular pools of -ketoglutarate, glutamate, and glutathione, diminished commitment of glucose carbon to serine/glycine synthesis, and decreased expression of genes in the Nrf2-oxidative stress response pathway. Consistent with this, reactive oxygen species were increased. Restoration of glutathione pools with N-acetyl cysteine normalized oxidative stress and allowed alternative activation in the face of Cpt1a-deficiency, pointing to a role for FAO in the control of ROS and as being important for alternative activation. In VaviCre x Cpt1afl/fl M(IL-4), glutamine uptake was increased, compensating for the loss of FAO to meet necessary metabolic demands, to allow alternative activation. The data indicate that macrophages are able to regulate glutamine metabolism to compensate for chronic disruption of FAO to meet metabolic needs.

immunology↗

bioRxiv2021

Chronic and progressive deficits after a single closed head injury in mice

BackgroundAcute injury following brain trauma may evolve into a chronic and progressive disorder. Chronic consequences of TBI have been understudied, in part, due to the lack of robust behavioral changes that are delayed in onset as well as chronic and progressive. Assessment of the chronic consequences of TBI also must distinguish behavioral changes that arises due to age vs those that develop and evolve over time due to injury. MethodsC57BL/6 mice receive single closed head injury (CHI) and are analyzed at 7DPI, 14DPI or 180DPI on neurological severity score, open field, rotarod, beam walk, and simple-complex wheel. ResultsIn the center of open field, injured mice have a turn bias at 180 days post-injury (DPI) not present at 7DPI. On rotarod, injured mice have shorter latencies at 7DPI, but not at 180DPI due to a large age effect in sham-injured mice. On beam walk at 180DPI, both sham and injured groups more slowly traverse a 2cm and 1cm beam than at 7DPI. Foot-faults show no significant effects of age or injury. On simple wheel injury affects speed at 14DPI with no effect on distance travelled. The lack of injury-dependent effects on beam walk or simple-complex wheel despite visible impairment was the impetus to assess limb position using Deeplabcut markerless tracking. Custom Python scripts were then developed to compute beam walk absition or foot fault severity (integral of limb displacement over time), and step frequency and quadrupedal limb coordination in simple-complex wheel. On the 2cm beam, age increased absition in all limbs of uninjured mice and both forelimbs of injured mice. On the 1cm beam both forelimbs and the left hindlimb of injured mice at 180DPI have larger absition than uninjured mice at 180DPI or injured mice at 7DPI. On a simple wheel injury affected speed only at 14 DPI with no effect on distance travelled. In contrast, injured mice at 180DPI developed a compensatory running strategy by increasing step frequency variability. This allowed injured mice at 180 DPI to reach sham-level quadrupedal limb coordination and improve running speed as compared to 14 DPI assessment. On complex wheel, injured mice at 180DPI do not express this compensatory running strategy resulting in impaired quadrupedal limb coordination. These data suggest chronic and progressive motor deficits of injured mice at 180DPI. ConclusionsA single impact produces chronic and progressive motor deficits. Quantitative motor analysis using DeepLabCut tracking reveals deficits not seen using standard outcomes.

neuroscience↗