Proinflammatory molecules, including IFN-γ and IL-12, play a crucial role in the elimination of causative agents. To allow healing, potent anti-inflammatory processes are required to down-regulate the inflammatory response. In this study, we first show that CD47/integrin-associated protein, a ubiquitous multispan transmembrane protein highly expressed on T cells, interacts with signal-regulator protein (SIRP)-α, an immunoreceptor tyrosine-based inhibition motif-containing molecule selectively expressed on myelomonocytic cells, and next demonstrate that this pair of molecules negatively regulates human T and dendritic cell (DC) function. CD47 ligation by CD47 mAb or L-SIRP-α transfectants inhibits IL-12R expression and down-regulates IL-12 responsiveness of activated CD4+ and CD8+ adult T cells without affecting their response to IL-2. Human CD47-Fc fusion protein binds SIRP-α expressed on immature DC and mature DC. SIRP-α engagement by CD47-Fc prevents the phenotypic and functional maturation of immature DC and still inhibits cytokine production by mature DC. Finally, in allogeneic MLR between mDC and naive T cells, CD47-Fc decreases IFN-γ production after priming and impairs the development of a Th1 response. Therefore, CD47 on T cells and its cognate receptor SIRP-α on DC define a novel regulatory pathway that may be involved in the maintenance of homeostasis by preventing the escalation of the inflammatory immune response.

Abstract-Thrombospondin-1 (TSP1) limits the angiogenic and vasodilator activities of NO. This activity of TSP1 can be beneficial in some disease states, but endogenous TSP1 limits recovery of tissue perfusion following fixed ischemic injury in dorsal skin flaps in mice. Using mice lacking the TSP1 receptors CD36 or CD47, we now show that CD47 is the necessary receptor for limiting NO-mediated vascular smooth muscle relaxation and tissue survival following ischemic injury in skin flaps and hindlimbs. We further show that blocking CD47 or TSP1 using monoclonal antibodies and decreasing CD47 expression using an antisense morpholino oligonucleotide are effective therapeutic approaches to dramatically increase survival of soft tissue subjected to fixed ischemia. These treatments facilitate rapid vascular remodeling to restore tissue perfusion and increase skin and muscle viability. Thus, limiting CD47-dependent antagonism of NO-mediated vasodilation and vascular remodeling is a promising therapeutic modality to preserve tissues subject to ischemic stress. (Circ Res. 2007;100:712-720.)Key Words: nitric oxide Ⅲ thrombospondin-1 Ⅲ ischemic tissue survival Ⅲ CD47 Ⅲ therapeutics T issue viability requires continuous perfusion, which in turn depends on vascular tone, sufficient intravascular volume, and adequate blood oxygenation. 1-3 The contractile status of arterial smooth muscle is the major determinant of vascular tone, with venous tone playing a lesser role. 4,5 Underperfusion of soft tissues is the leading cause of tissue necrosis and secondary delayed wound healing in surgical patients. 6 The complications incurred can be substantial and life threatening. 7 Complications of inadequate tissue perfusion are multiplied in the elderly and patients with hypertension and diabetes because of the general vasculopathies associated with these disease processes. 8,9 Current therapies to improve vascular perfusion combine surgical vessel manipulation/bypass with vasodilators that relax vascular smooth muscle cells (VSMCs). 10,11 The bioactive gas NO is a potent vasodilator 12 that activates soluble guanylate cyclase. The increased cGMP activates cGMPdependent protein kinases and thereby decreases VSMC sensitivity to intracellular Ca 2ϩ , leading to relaxation of contractile proteins. [13][14][15][16] We recently reported that NO/cGMP signaling in VSMCs and endothelial cells is potently inhibited by the secreted protein thrombospondin-1 (TSP1). [17][18][19] We further showed that endogenous TSP1 limits the ability of NO to increase skeletal muscle perfusion and blood oxygen levels in vivo. 20 Following surgically induced acute ischemia in random dorsal skin flaps, endogenous TSP1 also limits tissue survival and recovery of tissue oxygenation. Ischemic tissue survival could be improved by increasing NO levels using isosorbide dinitrate, but the degree of tissue necrosis in treated wild-type mice remained higher than in TSP1-null mice, which achieved essentially complete flap survival following this treatment.To further improve s...

Activity-dependent transcription influences neuronal connectivity, but the roles and mechanisms of inactivation of activity-dependent genes have remained poorly understood. Genome-wide analyses in the mouse cerebellum revealed that the nucleosome remodeling and deacetylase (NuRD) complex deposits the histone variant H2A.z at promoters of activity-dependent genes, thereby triggering their inactivation. Purification of translating mRNAs from synchronously developing granule neurons (Sync-TRAP) showed that conditional knockout of the core NuRD subunit Chd4 impairs inactivation of activity-dependent genes when neurons undergo dendrite pruning. Chd4 knockout or expression of NuRD-regulated activity genes impairs dendrite pruning. Imaging of behaving mice revealed hyperresponsivity of granule neurons to sensorimotor stimuli upon Chd4 knockout. Our findings define an epigenetic mechanism that inactivates activity-dependent transcription and regulates dendrite patterning and sensorimotor encoding in the brain.

Neuronal activity-dependent transcription couples sensory experience to adaptive responses of the brain including learning and memory. Mechanisms of activity-dependent gene expression including alterations of the epigenome have been characterized1–8. However, the fundamental question of whether and how sensory experience remodels chromatin architecture in the adult brain in vivo to induce neural code transformations and learning and memory remains to be addressed. Here, in vivo calcium imaging, optogenetics, and pharmacological approaches reveal that granule neuron activation in the anterior dorsal cerebellar vermis (ADCV) plays a crucial role in a novel delay tactile startle learning paradigm in mice. Strikingly, using large-scale transcriptome and chromatin profiling, we have discovered that activation of the motor learning-linked granule neuron circuit reorganizes neuronal chromatin including through long-distance enhancer-promoter and transcriptionally active compartment interactions to orchestrate distinct granule neuron gene expression modules. Conditional CRISPR knockout of the chromatin architecture regulator Cohesin in ADCV granule neurons in adult mice disrupts enhancer-promoter interactions, activity-dependent transcription, and motor learning. These findings define how sensory experience patterns chromatin architecture and neural circuit coding in the brain to drive motor learning.