Chronic infection with the neurotropic parasite Toxoplasma gondii has been implicated in the risk for several neuropsychiatric disorders. The mechanisms, by which the parasite may alter neural function and behavior of the host, are not yet understood completely. Here, a novel proteomic approach using mass spectrometry was employed to investigate the alterations in synaptic protein composition in a murine model of chronic toxoplasmosis. In a candidate-based strategy, immunoblot analysis and immunohistochemistry were applied to investigate the expression levels of key synaptic proteins in glutamatergic signaling. A comparison of the synaptosomal protein composition revealed distinct changes upon infection, with multiple proteins such as EAAT2, Shank3, AMPA receptor, and NMDA receptor subunits being downregulated, whereas inflammation-related proteins showed an upregulation. Treatment with the antiparasitic agent sulfadiazine strongly reduced tachyzoite levels and diminished neuroinflammatory mediators. However, in both conditions, a significant number of latent cysts persisted in the brain. Conversely, infection-related alterations of key synaptic protein levels could be partly reversed by the treatment. These results provide evidence for profound changes especially in synaptic protein composition in T. gondii-infected mice with a downregulation of pivotal components of glutamatergic neurotransmission. Our results suggest that the detected synaptic alterations are a consequence of the distinct neuroinflammatory milieu caused by the neurotropic parasite.

Brain vascular health appears to be critical for preventing the development of amyotrophic lateral sclerosis (ALS) and slowing its progression. ALS patients often demonstrate cardiovascular risk factors and commonly suffer from cerebrovascular disease, with evidence of pathological alterations in their small cerebral blood vessels. Impaired vascular brain health has detrimental effects on motor neurons: vascular endothelial growth factor levels are lowered in ALS, which can compromise endothelial cell formation and the integrity of the blood–brain barrier. Increased turnover of neurovascular unit cells precedes their senescence, which, together with pericyte alterations, further fosters the failure of toxic metabolite removal. We here provide a comprehensive overview of the pathogenesis of impaired brain vascular health in ALS and how novel magnetic resonance imaging techniques can aid its detection. In particular, we discuss vascular patterns of blood supply to the motor cortex with the number of branches from the anterior and middle cerebral arteries acting as a novel marker of resistance and resilience against downstream effects of vascular risk and events in ALS. We outline how certain interventions adapted to patient needs and capabilities have the potential to mechanistically target the brain microvasculature towards favorable motor cortex blood supply patterns. Through this strategy, we aim to guide novel approaches to ALS management and a better understanding of ALS pathophysiology.

Collagen type XVIII (COL18) is an abundant heparan sulfate proteoglycan in vascular basement membranes. Here, we asked (i) if the loss of COL18 would result in blood-brain barrier (BBB) breakdown, pathological alterations of small arteries and capillaries and neuroinflammation as found in cerebral small vessel disease (CSVD) and (ii) if such changes may be associated with remodeling of synapses and neural extracellular matrix (ECM). We found that 5-month-old Col18a1^-/- mice had elevated BBB permeability for mouse IgG in the deep gray matter, and intravascular erythrocyte accumulations were observed brain-wide in capillaries and arterioles. BBB permeability increased with age and affected cortical regions and the hippocampus in 12-month-old Col18a1^-/- mice. None of the Col18a1^-/- mice displayed hallmarks of advanced CSVD, such as hemorrhages, and did not show perivascular space enlargement. Col18a1 deficiency-induced BBB leakage was accompanied by activation of microglia and astrocytes, a loss of aggrecan in the ECM of perineuronal nets associated with fast-spiking inhibitory interneurons and accumulation of the perisynaptic ECM proteoglycan brevican and the microglial complement protein C1q at excitatory synapses. As the pathway underlying these regulations, we found increased signaling through the TGF-ß1/Smad3/TIMP-3 cascade. We verified the pivotal role of COL18 for small vessel wall structure in CSVD by demonstrating the protein's involvement in vascular remodeling in autopsy brains from patients with cerebral hypertensive arteriopathy. Our study highlights an association between the alterations of perivascular ECM, extracellular proteolysis, and perineuronal/perisynaptic ECM, as a possible substrate of synaptic and cognitive alterations in CSVD.

Background: Chronic arterial hypertension restructures the vascular architecture of the brain, leading to a series of pathological responses that culminate in cerebral small‐vessel disease. Pericytes respond dynamically to vascular challenges; however, how they manifest under the continuous strain of hypertension has not been elucidated. Methods and Results: In this study, we characterized pericyte behavior alongside hypertensive states in the spontaneously hypertensive stroke‐prone rat model, focusing on their phenotypic and metabolic transformation. Flow cytometry was used to characterize pericytes by their expression of platelet‐derived growth factor receptor β, neuroglial antigen 2, cluster of differentiation 13–alanyl aminopeptidase, and antigen Kiel 67. Microvessels were isolated for gene expression profiling and in vitro pericyte expansion. Immunofluorescence validated the cell culture model. Plasma‐derived extracellular vesicles from hypertensive rodents were applied as a treatment to assess their effects on pericyte function and detailed metabolic assessments on enriched pericytes measured oxidative phosphorylation and glycolysis. Our results reveal a shift in platelet‐derived growth factor receptor β ⁺ pericytes toward increased neuroglial antigen 2 and cluster of differentiation 13–alanyl aminopeptidase coexpression, indicative of their critical role in vascular stabilization and inflammatory responses within the hypertensive milieu. Significant alterations were found within key pathways including angiogenesis, blood–brain barrier integrity, hypoxia, and inflammation. Circulating extracellular vesicles from hypertensive rodents distinctly influenced pericyte mitochondrial function, evidencing their dual role as carriers of disease pathology and potential therapeutic agents. Furthermore, a shift toward glycolytic metabolism in hypertensive pericytes was confirmed, coupled with ATP production dysregulation. Conclusions: Our findings demonstrate that cerebral pericytes undergo phenotypic and metabolic reprogramming in response to hypertension, with hypertensive‐derived plasma‐derived extracellular vesicles impairing their mitochondrial function. Importantly, plasma‐derived extracellular vesicles from normotensive controls restore this function, suggesting their potential as both therapeutic agents and precision biomarkers for hypertensive vascular complications. Further investigation into plasma‐derived extracellular vesicle cargo is essential to further explore their therapeutic potential in vascular health.

Background: Chronic arterial hypertension causes cerebral microvascular dysfunction and increases dementia risk in aging. However, cognitive health preservation by therapeutic blood pressure lowering alone is limited and depends on disease duration, the degree of irreversible tissue damage, and whether microvascular function can be restored. This study aimed to understand molecular and cellular temporospatial mechanisms of disease in the course of hypertension. Methods: We investigated the effects of initial, early chronic and late chronic hypertension in the frontal brain of spontaneously hypertensive stroke‐prone rats by applying behavioral tests, histopathology, immunofluorescence, fluorescence‐activated cell sorting, microvascular/neural tissue RNA sequencing, and ¹⁸ F‐fluorodeoxyglucose positron emission tomography imaging. Results: Chronic hypertension caused behavioral deficits associated with frontal cortex function. Our results highlight stage‐dependent responses to continuous microvascular stress and wounding by hypertension. Early chronic responses included a fast recruitment of activated microglia to the blood vessels, immigration of peripheral immune cells, blood–brain barrier breakdown and an energy‐demanding hypermetabolic state. Vascular adaptation mechanisms were observed in later stages and included angiogenesis and upregulation of cellular adhesion molecules and extracellular matrix. Among the top upregulated genes in blood vessels, we identified Igfbp‐5 , which attenuates protective insulin‐like growth factor 1 signaling. Conclusions: Our study provides new insight into mechanisms underlying hypertensive pathobiology and highlights its stage‐dependent nature. This groundwork will be helpful for basic and clinical research to identify stage‐dependent markers in the human disease course, investigate stage‐dependent interventions besides blood pressure lowering, and better understand the relationship between poor vascular health and neurodegenerative diseases.