Measurement of the Estradiol Concentration in Cerebrospinal Fluid from Infants and Its Correlation with Serum Estradiol and Exosomal MicroRNA-126-5p

Multidimensional Effects of Stress on Neuronal Exosome Levels and Simultaneous Transcriptomic Profiles

Background

An excess of exosomes, nanovesicles released from all cells and key regulators of brain plasticity, is an emerging therapeutic target for stress-related mental illnesses. The effects of chronic stress on exosome levels are unknown; even less is known about molecular drivers of exosome levels in the stress response.

Methods

We used our state-of-the-art protocol with 2 complementary strategies to isolate neuronal exosomes from plasma, ventral dentate gyrus, basolateral amygdala, and olfactory bulbs of male mice to determine the effects of chronic restraint stress (CRS) on exosome levels. Next, we used RNA sequencing and bioinformatic analyses to identify molecular drivers of exosome levels.

Results

We found that CRS leads to an increase in the levels of neuronal exosomes but not total (i.e., not neuronally enriched) exosome levels assayed in plasma and the ventral dentate gyrus, whereas CRS leads to a decrease in neuronal exosome levels but not total exosome levels in the basolateral amygdala. There was a further specificity of effects as shown by a lack of changes in the levels of neuronal exosomes assayed in the olfactory bulbs. In pursuit of advancing translational applications, we showed that acetyl-L-carnitine administration restores the CRS-induced increase in neuronal exosome levels assayed in plasma (the most accessible specimen). Furthermore, the CRS-induced changes in neuronal exosome levels in the ventral dentate gyrus and basolateral amygdala mirrored the opposite pattern of CRS-induced transcriptional changes in these key brain areas, with β-estradiol signaling as a potential upstream driver of neuronal exosome levels.

Conclusions

This study provides a foundation for future studies of new forms of local and distant communication in stress neurobiology by demonstrating specific relationships between neuronal exosome levels assayed in plasma and the brain and providing new candidate targets for the normalization of exosome levels.

Sex-Specific MicroRNAs in Neurovascular Units in Ischemic Stroke

Accumulating evidence pinpoints sex differences in stroke incidence, etiology and outcome. Therefore, more understanding of the sex-specific mechanisms that lead to ischemic stroke and aggravation of secondary damage after stroke is needed. Our current mechanistic understanding of cerebral ischemia states that endothelial quiescence in neurovascular units (NVUs) is a major physiological parameter affecting the cellular response to neuron, astrocyte and vascular smooth muscle cell (VSMC) injury. Although a hallmark of the response to injury in these cells is transcriptional activation, noncoding RNAs such as microRNAs exhibit cell-type and context dependent regulation of gene expression at the post-transcriptional level. This review assesses whether sex-specific microRNA expression (either derived from X-chromosome loci following incomplete X-chromosome inactivation or regulated by estrogen in their biogenesis) in these cells controls NVU quiescence, and as such, could differentiate stroke pathophysiology in women compared to men. Their adverse expression was found to decrease tight junction affinity in endothelial cells and activate VSMC proliferation, while their regulation of paracrine astrocyte signaling was shown to neutralize sex-specific apoptotic pathways in neurons. As such, these microRNAs have cell type-specific functions in astrocytes and vascular cells which act on one another, thereby affecting the cell viability of neurons. Furthermore, these microRNAs display actual and potential clinical implications as diagnostic and prognostic biomarkers in ischemic stroke and in predicting therapeutic response to antiplatelet therapy. In conclusion, this review improves the current mechanistic understanding of the molecular mechanisms leading to ischemic stroke in women and highlights the clinical promise of sex-specific microRNAs as novel diagnostic biomarkers for (silent) ischemic stroke.