Validating MALDI-IMS Feasibility in Ex Vivo Brain Slices.

Matrix-assisted laser desorption ionization imaging mass spectrometry (MALDI-IMS) generates unique mass spectra in X/Y coordinates across a tissue sample, thus allowing for the spatial detection and relative quantification of biologic compounds in situ. The soft ionization of MALDI-IMS makes it an ideal technique for high-resolution imaging of complex lipid species. Lipid-based spatial chemical maps derived from MALDI-IMS provide critical insight into the unique molecular profiles of a variety of neurologic diseases. Ex vivo brain slice preparations are a prominent alternative to in vivo animal models for studying many different neurologic conditions. For the first time, we present a feasible protocol for achieving reproducible lipidomic MALDI-IMS data from ex vivo rat brain slices and provide evidence that ex vivo brain slices maintain spatiochemical lipidomic profiles representative of an intact whole brain. We conducted a methods comparison assessing the lipid profiles within the neocortex, striatum, and corpus callosum between coronal sections taken from ex vivo brain slices and the current gold standard tissue preparation method, fresh frozen whole brains. For the first time we demonstrate a technique by which 400 µm ex vivo brain slices can be extracted from an imaging chamber and prepared for MALDI-IMS in a way that preserves their lipidomic integrity. We demonstrate the feasibility of MALDI-IMS in ex vivo brain slices and provide a roadmap for MALDI-IMS utilization in uncharted neuroscience fields.

Expression of Neuronal Na+/K+-ATPase α Subunit Isoforms in the Mouse Brain Following Genetically Programmed or Behaviourally-induced Oxidative Stress.

The Na+/K+-ATPase is a transmembrane ion pump that has a critical homeostatic role within every mammalian cell; however, it is vulnerable to the effects of increased oxidative stress. Understanding how expression of this transporter is influenced by oxidative stress may yield insight into its role in the pathophysiology of neurological and neuropsychiatric diseases. In this study we investigated whether increased oxidative stress could influence Na+/K+-ATPase expression in various brain regions of mice. We utilized two different models of oxidative stress: a behavioural chronic unpredictable stress protocol and the Aldh2-/- mouse model of oxidative stress-based and age-related cognitive impairment. We identified distinct regional baseline mRNA and protein expression patterns of the Na+/K+-ATPase α1 and α3 isoforms within the neocortex, hippocampus, and brainstem of wildtype mice. Consistent with previous studies, there was a higher proportion of α3 expression relative to α1 in the brainstem versus neocortex, but a higher proportion of α1 expression relative to α3 in the neocortex versus the brainstem. The hippocampus had similar expression levels of both α1 and α3. Despite increased staining for oxidative stress in higher brain, no differences in α1 or α3 expression were noted in Aldh2-/- mice versus wildtype, or in mice exposed to a 28-day chronic unpredictable stress protocol. In both models of oxidative stress, gene and protein expression of Na+/K+-ATPase α1 and α3 isoforms within the higher and lower brain was remarkably stable. Thus, Na+/K+-ATPase function previously reported as altered by oxidative stress is not through induced changes in the expression of pump isoforms.

Improving the Social Relevance of Experimental Stroke Models: Social Isolation, Social Defeat Stress and Stroke Outcome in Animals and Humans.

The outcome of ischemic stroke varies across socioeconomic strata, even among countries with universal health care. Emerging evidence suggests that psychosocial aspects of low socioeconomic status such as social isolation and social defeat stress interact with, and contribute to, stroke pathophysiology. However, experimental investigations of stroke rarely account for such socioeconomic influences. Social isolation in stroke survivors is associated with increased infarction volume, increased risk of post-stroke depression, and worse long-term functional outcome. Social defeat is thought to contribute significantly to chronic stress in low socioeconomic status groups and is associated with poor health outcomes. Chronic stress is also associated with worse post-stroke functional outcome and greater disability even after accounting for stroke severity, vascular risk factors, and access to acute stroke care. Experimental stroke studies which incorporate social isolation or social defeat stress have shown that both tissue and functional stroke outcome is affected by the increased expression of TNF-α and IL-6, increased glucocorticoid production, and suppression of the protooncogene bcl-2. This review explores the consequences of social isolation and social defeat stress on stroke, preclinical stroke models that have been used to investigate these factors, and possible molecular mechanisms underlying the influence of socioeconomic disparities on stroke outcome.