Arja, R. D. | bioRxiv Science

bioRxiv2022

Two subsets of circulating Ly6Clo monocytes distinguished by CD138 (syndecan-1) expression and Nr4a1 dependence in pristane-treated mice

Chronic peritoneal inflammation following pristane injection induces lupus with diffuse alveolar hemorrhage (DAH) and pulmonary capillaritis in C57BL/6 mice. The pathogenesis involves pristane-induced microvascular lung injury. BALB/c mice are resistant to endothelial injury and DAH. Lung disease in C57BL/6 mice is abolished by depleting monocytes/macrophages. The objective of this study was to define the role of myeloid subsets in DAH. Hemorrhage and vasculitis were abolished in Ccr2-/- mice, indicating involvement of bone marrow-derived monocytes/macrophages. Along with Ly6Chi monocytes, we found two subsets of circulating Ly6Clo monocytes: one CD138- and a novel CD138+ subset. Nr4a1-dependent patrolling Ly6Clo monocytes maintain vascular integrity after endothelial injury. Circulating Ly6CloCD138+ monocytes were associated with DAH and were absent in mice without DAH. They also were absent in Nr4a1-/- mice, whereas Ly6CloCD138- monocytes were unaffected. However, Nr4a1-/- mice were susceptible to pristane-induced DAH and lung vasculitis, suggesting that disease onset does not require Ly6CloCD138- monocytes. Peritoneal Ly6CloCD138+ M{phi} were unchanged in Nr4a1-/- mice, indicating that they are not derived from Ly6CloCD138+ monocytes. We conclude that pristane-induced lung microvascular lung injury stimulates a wave of Nr4h1-dependent Ly6CloCD138+ patrolling monocytes in an ineffectual effort to maintain vascular integrity in the face of ongoing endothelial damage.

immunology↗

bioRxiv2021

Compensatory changes in contralesional node strength, brain wide modularity and cross-modular functional interactions in a rat model of traumatic brain injury

Penetrating cortical impact injuries alter neuronal communication beyond the injury epicenter, across regions involved in affective, sensorimotor, and cognitive processing. Understanding how traumatic brain injury (TBI) reorganizes local and brain wide nodal functional interactions may provide valuable quantitative parameters for monitoring pathological progression and functional recovery. To this end, we investigated spontaneous fluctuations in the functional magnetic resonance imaging (fMRI) signal obtained at 11.1 Tesla in rats sustaining controlled cortical impact (CCI) and imaged at 2- and 30-days post-injury. Graph theory-based calculations were applied to weighted undirected matrices constructed from 12,879 pairwise correlations between fMRI signals from 162 regions. Our data indicate that on days 2 and 30 post-CCI there is a significant increase in connectivity strength in nodes located in contralesional cortical, thalamic, and basal forebrain areas. Rats imaged on day 2 post-injury had significantly greater network modularity than controls, with influential nodes (with high eigenvector centrality) contained within the contralesional module and participating less in cross-modular interactions. By day 30, modularity and cross-modular interactions recover, although a cluster of nodes with low strength and low eigenvector centrality remain in the ipsilateral cortex. Our results suggest that changes in node strength, modularity, eigenvector centrality, and participation coefficient track early and late TBI effects on brain functional connectivity. We propose that the observed compensatory functional connectivity reorganization in response to CCI may be unfavorable to brain wide communication in the early post-injury period.

neuroscience↗