Measurement of Blood-Brain Barrier Disruption in Mice Following Ozone Exposure Using Highly Sensitive Radiotracer Assays

Impact of environmental pollutants on pediatric brain tumor incidence in New Jersey

OBJECTIVE

The relationship between environmental contaminants and brain tumor incidence in adults has been thoroughly explored but research into how these contaminants affect pediatric brain tumor (PBT) incidence has not been explored. Children, typically having more limited geographical movement and thus more consistent environmental contaminant exposure, might offer more reliable insights into which environmental contaminants affect the incidence of brain tumors. The present study is the first to focus on exploring whether a possible association exists between the incidence of PBTs and exposure to environmental pollutants in New Jersey (NJ).

METHODS

Linear regressions were run between PBT incidence and the concentration of air quality pollutants such as Ozone (O3), Particulate Matter 2.5 (PM2.5), Particulate Matter 10 (PM10), and Carbon Monoxide (CO). Similarly, linear regressions were run between PBT incidence and Elevated Blood Lead Levels (BLL).

RESULTS

The study observed a significant positive relationship between O3 and PBT incidence (β = 0.34, p = 0.028). However, the relationship between PBT incidence, and environmental pollutants such as CO (β = 0.0047, p = 0.098), PM2.5 (β = -0.2624, p = 0.74), and PM10 (β = -0.7353, p = 0.073) were found to be nonsignificant. For elevated BLL, nonsignificant relationships with PBT incidence were observed at 10-14 µg/dL (β = -39.38, p = 0.30), 15-19 µg/dL (β = -67.00, p = 0.21), and 20-44 µg/dL (β = -201.98, p = 0.12).

CONCLUSIONS

The results indicate a possible impact of O3 on the incidence of PBTs in NJ. In contrast to the significant links found in prior studies of adult brain tumors, the associations between PBT occurrence and particulate matter were not significant. These findings highlight the importance of further investigating how environmental factors, especially O3, relate to PBTs.

Peripheral HMGB1 is linked to O3 pathology of disease-associated astrocytes and amyloid

INTRODUCTION

Ozone (O3) is an air pollutant associated with Alzheimer's disease (AD) risk. The lung-brain axis is implicated in O3-associated glial and amyloid pathobiology; however, the role of disease-associated astrocytes (DAAs) in this process remains unknown.

METHODS

The O3-induced astrocyte phenotype was characterized in 5xFAD mice by spatial transcriptomics and proteomics. Hmgb1fl/fl LysM-Cre+ mice were used to assess the role of peripheral myeloid cell high mobility group box 1 (HMGB1).

RESULTS

O3 increased astrocyte and plaque numbers, impeded the astrocyte proteomic response to plaque deposition, augmented the DAA transcriptional fingerprint, increased astrocyte-microglia contact, and reduced bronchoalveolar lavage immune cell HMGB1 expression in 5xFAD mice. O3-exposed Hmgb1fl/fl LysM-Cre+ mice exhibited dysregulated DAA mRNA markers.

DISCUSSION

Astrocytes and peripheral myeloid cells are critical lung-brain axis interactors. HMGB1 loss in peripheral myeloid cells regulates the O3-induced DAA phenotype. These findings demonstrate a mechanism and potential intervention target for air pollution-induced AD pathobiology.

HIGHLIGHTS

Astrocytes are part of the lung-brain axis, regulating how air pollution affects plaque pathology. Ozone (O3) astrocyte effects are associated with increased plaques and modified by plaque localization. O3 uniquely disrupts the astrocyte transcriptomic and proteomic disease-associated astrocyte (DAA) phenotype in plaque associated astrocytes (PAA). O3 changes the PAA cell contact with microglia and cell-cell communication gene expression. Peripheral myeloid cell high mobility group box 1 regulates O3-induced transcriptomic changes in the DAA phenotype.

Transport of the Proinflammatory Chemokines C-C Motif Chemokine Ligand 2 (MCP-1) and C-C Motif Chemokine Ligand 5 (RANTES) across the Intact Mouse Blood-Brain Barrier Is Inhibited by Heparin and Eprodisate and Increased with Systemic Inflammation

One important function of the vascular blood-brain barrier (BBB) is to facilitate neuroimmune communication. The BBB fulfills this function, in part, through its ability to transport cytokines and chemokines. C-C motif chemokine receptor 2 (CCL2) (MCP-1) and C-C motif chemokine receptor 5 (CCL5) (RANTES) are proinflammatory chemokines that mediate neuroimmune responses to acute insults and aspects of brain injury and neurodegenerative diseases; however, a blood-to-brain transport system has not been evaluated for either chemokine in vivo. Therefore, we determined whether CCL2 and CCL5 in blood can cross the intact BBB and enter the brain. Using CD-1 mice, we found that ¹²⁵I-labeled CCL2 and CCL5 crossed the BBB and entered the brain parenchyma. We next aimed to identify the mechanisms of ¹²⁵I-CCL2 and ¹²⁵I-CCL5 transport in an in situ brain perfusion model. We found that both heparin and eprodisate inhibited brain uptake of ¹²⁵I-CCL2 and ¹²⁵I-CCL5 in situ, whereas antagonists of their receptors, CCR2 or CCR5, respectively, did not, suggesting that heparan sulfates at the endothelial surface mediate BBB transport. Finally, we showed that CCL2 and CCL5 transport across the BBB increased following a single injection of 0.3 mg/kg lipopolysaccharide. These data demonstrate that CCL2 and CCL5 in the brain can derive, in part, from the circulation, especially during systemic inflammation. Further, binding to the BBB-associated heparan sulfate is a mechanism by which both chemokines can cross the intact BBB, highlighting a novel therapeutic target for treating neuroinflammation. SIGNIFICANCE STATEMENT: Our work demonstrates that C-C motif chemokine ligand 2 (CCL2) and C-C motif chemokine ligand 5 (CCL5) can cross the intact blood-brain barrier and that transport is robustly increased during inflammation. These data suggest that circulating CCL2 and CCL5 can contribute to brain levels of each chemokine. We further show that the transport of both chemokines is inhibited by heparin and eprodisate, suggesting that CCL2/CCL5-heparan sulfate interactions could be therapeutically targeted to limit accumulation of these chemokines in the brain.