Brain aging is associated with cognitive decline that is accompanied by progressive neuroinflammatory changes. The endocannabinoid system (ECS) is involved in the regulation of glial activity and influences the progression of age-related learning and memory deficits. Mice lacking the Cnr1 gene (Cnr1 −/− ), which encodes the cannabinoid receptor 1 (CB1), showed an accelerated agedependent deficit in spatial learning accompanied by a loss of principal neurons in the hippocampus. The age-dependent decrease in neuronal numbers in Cnr1 −/− mice was not related to decreased neurogenesis or to epileptic seizures. However, enhanced neuroinflammation characterized by an increased density of astrocytes and activated microglia as well as an enhanced expression of the inflammatory cytokine IL-6 during aging was present in the hippocampus of Cnr1 −/− mice. The ongoing process of pyramidal cell degeneration and neuroinflammation can exacerbate each other and both contribute to the cognitive deficits. Deletion of CB1 receptors from the forebrain GABAergic, but not from the glutamatergic neurons, led to a similar neuronal loss and increased neuroinflammation in the hippocampus as observed in animals lacking CB1 receptors in all cells. Our results suggest that CB1 receptor activity on hippocampal GABAergic neurons protects against age-dependent cognitive decline by reducing pyramidal cell degeneration and neuroinflammation.glial regulation | Morris water maze | stereological quantification | CD40 expression | telemetric EEG recording

Dendritic cells (DCs) are pivotal for the development of experimental autoimmune encephalomyelitis (EAE). However, the mechanisms by which they control disease remain to be determined. This study demonstrates that expression of CC chemokine receptor 4 (CCR4) by DCs is required for EAE induction. CCR4 −/− mice presented enhanced resistance to EAE associated with a reduction in IL-23 and GM-CSF expression in the CNS. Restoring CCR4 on myeloid cells in bone marrow chimeras or intracerebral microinjection of CCR4-competent DCs, but not macrophages, restored EAE in CCR4 −/− mice, indicating that CCR4 + DCs are cellular mediators of EAE development. Mechanistically, CCR4 −/− DCs were less efficient in GM-CSF and IL-23 production and also T H -17 maintenance. Intraspinal IL-23 reconstitution restored EAE in CCR4 −/− mice, whereas intracerebral inoculation using IL-23 −/− DCs or GM-CSF −/− DCs failed to induce disease. Thus, CCR4-dependent GM-CSF production in DCs required for IL-23 release in these cells is a major component in the development of EAE. Our study identified a unique role for CCR4 in regulating DC function in EAE, harboring therapeutic potential for the treatment of CNS autoimmunity by targeting CCR4 on this specific cell type.chemokines | neuroinflammation M ultiple sclerosis (MS) is a chronic demyelinating disease of the human CNS (1). Experimental autoimmune encephalomyelitis (EAE), the animal model of MS, is mediated by myelin-specific CD4 + T cells activated by professional antigenpresenting cells (APCs) in peripheral lymphoid tissues (2, 3). In recent studies, both peripherally derived macrophages and DCs have been shown to present myelin antigens to invading autoreactive T cells in the CNS. This presentation initiates the recruitment of a second wave of leukocytes that damage the target organ via demyelination and axonal degeneration (4-8). Understanding the mechanisms responsible for the recruitment of APCs to the CNS and their local function is essential for the development of therapeutic strategies targeting the effector phase and thereby controlling disease progression.Chemokines and their G protein-coupled receptors are key regulators of leukocyte trafficking (9, 10). The CC chemokine receptor 4 (CCR4) is the cognate receptor for the CC chemokines CCL17 and CCL22, and is expressed on functionally distinct subsets of T cells, including activated T cells, T H 2 cells, and Treg cells. CCR4 has also been found on platelets, NK cells, macrophages, and DCs (11-15). DCs are important cellular sources for CCL17 and, in concert with macrophages, produce CCL22 during both homeostasis and inflammation (16,17). Different studies have suggested a critical role for CCR4 in the pathogenesis of EAE and MS. For example, elevated levels of the CCR4 ligands CCL17 or CCL22 have been found in the cerebrospinal fluid of MS patients (18-20). CCL22 protein has been identified in CNS-infiltrating leukocytes and microglia of EAE-induced mice, and CCR4 is expressed by invading leukocyte subsets (21,22). However, it rema...

Cerebral malaria is a severe and often fatal complication of

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