TNF deficiency causes alterations in the spatial organization of neurogenic zones and alters the number of microglia and neurons in the cerebral cortex.

BACKGROUND: Although tumor necrosis factor (TNF) inhibitors are used to treat chronic inflammatory diseases, there is little information about how long-term inhibition of TNF affects the homeostatic functions that TNF maintains in the intact CNS. MATERIALS AND METHODS: To assess whether developmental TNF deficiency causes alterations in the naïve CNS, we estimated the number of proliferating cells, microglia, and neurons in the developing neocortex of E13.5, P7 and adult TNF knock out (TNF-/-) mice and wildtype (WT) littermates. We also measured changes in gene and protein expression and monoamine levels in adult WT and TNF-/- mice. To evaluate long-term effects of TNF inhibitors, we treated healthy adult C57BL/6 mice with either saline, the selective soluble TNF inhibitor XPro1595, or the nonselective TNF inhibitor etanercept. We estimated changes in cell number and protein expression after two months of treatment. We assessed the effects of TNF deficiency on cognition by testing adult WT and TNF-/- mice and mice treated with saline, XPro1595, or etanercept with specific behavioral tasks. RESULTS: TNF deficiency decreased the number of proliferating cells and microglia and increased the number of neurons. At the same time, TNF deficiency decreased the expression of WNT signaling-related proteins, specifically Collagen Triple Helix Repeat Containing 1 (CTHRC1) and Frizzled receptor 6 (FZD6). In contrast to XPro1595, long-term inhibition of TNF with etanercept in adult C57BL/6 mice decreased the number of BrdU+ cells in the granule cell layer of the dentate gyrus. Etanercept, but not XPro1595, also impaired spatial learning and memory in the Barnes maze memory test. CONCLUSION: TNF deficiency impacts the organization of neurogenic zones and alters the cell composition in brain. Long-term inhibition of TNF with the nonselective TNF inhibitor etanercept, but not the soluble TNF inhibitor XPro1595, decreases neurogenesis in the adult mouse hippocampus and impairs learning and memory after two months of treatment.

T-cells and macrophages peak weeks after experimental stroke: Spatial and temporal characteristics.

The activities of the central and peripheral immune systems impact neurological outcome after ischemic stroke. However, studies investigating the temporal profile of leukocyte infiltration, especially T-cell recruitment, are sparse. Our aim was to investigate leukocyte infiltration at different time points after experimental stroke in mice. Permanent middle cerebral artery occlusion was performed on 11 weeks old C57BL/6J mice, allowed to survive for 1, 3, 8, 14 or 28 days. In addition to infarct size measurements, detailed immunohistochemical analyses of T-cell and macrophage influx were performed. A recently introduced F-19 MR probe (V-sense), designed to track macrophages, was furthermore tested. Fourteen and 28 days after permanent middle cerebral artery occlusion a significant increase in CD3+ T-cells was found within the ipsilateral hemisphere compared to controls, especially within the infarct core and the corpus callosum. The number of CD68+ cells within the infarct core was significantly increased at days 8, 14 and 28. This temporal pattern was also seen in MRI. After experimental stroke within the infarcted cortex we found a delayed (day 14) infiltration of T-cells and macrophages. Furthermore, our data show that T-cells are present in higher numbers in the corpus callosum compared to the rest of the brain (except from the infarct core where they were highest).

Development of a 64Cu-labeled CD4+ T cell targeting PET tracer: evaluation of CD4 specificity and its potential use in collagen-induced arthritis.

BACKGROUND: CD4+ T cells are central inflammatory mediators in the pathogenesis of autoimmune rheumatoid arthritis (RA), as they are one of the dominating cell types in synovial inflammation. Molecular imaging of CD4+ T cells has potential role for early detection and monitoring of RA. Here, we developed a new radiotracer for in vivo immunoPET imaging of murine CD4+ T cells and tested it in the collagen-induced arthritis (CIA) mouse model of human RA. RESULTS: The tracer, [64Cu]Cu-NOTA-CD4-F(ab)'2 ([64Cu]Cu-NOTA-CD4), was generated from F(ab)'2 fragments of R-anti-mouse CD4 antibodies conjugated to the 2-S-(isothiocyanatbenzyl)-1,4,7-triazacyclononane-1,4,7-triacetic acid (p-SCN-Bn-NOTA) chelator and radiolabeled with copper-64. Accumulation of the tracer and isotype control was evaluated in the CIA model and mice receiving whole-body irradiation (WBI) (5 Gy). The potential of [64Cu]Cu-NOTA-CD4 for response assessment was evaluated in CIA induced mice treated with dexamethasone (DXM). Imaging data were compared with flow cytometry and immunohistochemistry (IHC) of inflammatory cells including CD4+ T cells. [64Cu]Cu-NOTA-CD4 showed increased accumulation in T cell-rich tissues compared with isotype control (p < 0.0001). In addition, reduced accumulation of [64Cu]Cu-NOTA-CD4 was observed in T cell-depleted tissue (p < 0.0001). Flow cytometry and IHC confirmed the increased infiltration of CD4+ T cells in CIA mice. CONCLUSIONS: We developed and evaluated a new radiotracer, [64Cu]Cu-NOTA-CD4, for immunoPET imaging of murine CD4+ T cells. [64Cu]Cu-NOTA-CD4 was successfully synthesized by F(ab)'2 fragments of R-anti-mouse CD4 antibodies conjugated to a chelator and radiolabeled with copper-64. We found that our novel CD4 PET tracer can be used for noninvasive visualization of murine CD4+ T cells.

Noninvasive Molecular Imaging of the Enhanced Permeability and Retention Effect by 64Cu-Liposomes: In vivo Correlations with 68Ga-RGD, Fluid Pressure, Diffusivity and 18F-FDG.

BACKGROUND: The accumulation of liposome encapsulated chemotherapy in solid cancers is dependent on the presence of the enhanced permeability and retention (EPR) effect. Positron emission tomography (PET) imaging with a liposome encapsulated radioisotope, such as liposome encapsulated Cu-64 (64Cu-liposome) may help to identify tumors with high liposome accumulation, and thereby stratify patients based on expected benefit from liposomal chemotherapy. However, intravenous administration of liposomes without a cytotoxic content is complicated by the accelerated blood clearance (ABC) phenomenon for succeeding therapeutic liposome dosing. Alternative markers for assessing the tumor's EPR level are therefore warranted. MATERIALS AND METHODS: To increase our understanding of EPR variations and to ultimately identify an alternative marker for the EPR effect, we investigated the correlation between 64Cu-liposome PET/CT (EPR effect) and 68Ga-RGD PET/CT (neoangiogenesis), 18F-FDG PET/CT (glycolysis), diffusion-weighted MRI (diffusivity) and interstitial fluid pressure in two experimental cancer models (CT26 and COLO 205). RESULTS: 64Cu-liposome and 68Ga-RGD SUVmax displayed a significant moderate correlation, however, none of the other parameters evaluated displayed significant correlations. These results indicate that differences in neoangiogenesis may explain some EPR variability, however, as correlations were only moderate and not observed for SUVmean, 68Ga-RGD is probably insufficient to serve as a stand-alone surrogate marker for quantifying the EPR effect and stratifying patients.