Macrophages acquire distinct phenotypes during tissue stress and inflammatory responses, but the mechanisms that regulate the macrophage polarization are poorly defined. Here we show that tuberous sclerosis complex 1 (TSC1) is a critical regulator of M1 and M2 phenotypes of macrophages. Mice with myeloid-specific deletion of TSC1 exhibit enhanced M1 response and spontaneously develop M1-related inflammatory disorders. However, TSC1-deficient mice are highly resistant to M2-polarized allergic asthma. Inhibition of the mammalian target of rapamycin (mTOR) fails to reverse the hypersensitive M1 response of TSC1-deficient macrophages, but efficiently rescues the defective M2 polarization. Deletion of mTOR also fails to reverse the enhanced inflammatory response of TSC1-deficient macrophages. Molecular studies indicate that TSC1 inhibits M1 polarization by suppressing the Ras GTPase-Raf1-MEK-ERK pathway in mTOR-independent manner, whereas TSC1 promotes M2 properties by mTOR-dependent CCAAT/enhancer-binding protein-b pathways. Overall, these findings define a key role for TSC1 in orchestrating macrophage polarization via mTOR-dependent and independent pathways.

In the mammalian brain, the specificity of excitatory synaptic transmission depends on rapid diffusion of glutamate away from active synapses and the powerful uptake capacity of glutamate transporters in astrocytes. The extent to which neuronal glutamate transporters influence the lifetime of glutamate in the extracellular space remains unclear. Here we show that EAAC1, the predominant neuronal glutamate transporter at excitatory synapses in hippocampal area CA1, buffers glutamate released during synaptic events and prolongs the time course of its clearance by astrocytes. EAAC1 does not significantly alter activation of receptors in the synaptic cleft. Instead, it reduces recruitment of perisynaptic/extrasynaptic NR2B-containing NMDARs, thereby facilitating induction of long-term potentiation by short burstsofhigh-frequencystimulation.WedescribenovelrolesofEAAC1inregulatingglutamatediffusionandproposethatNMDARsatdifferent subsynaptic locations can make distinct contributions to the regulation of synaptic strength.

Autoreactive B lymphocytes first encountering self-antigens in peripheral tissues are normally regulated by induction of anergy or apoptosis. According to the “two-signal” model, antigen recognition alone should render B cells tolerant unless T cell help or inflammatory signals such as lipopolysaccharide are provided. However, no such signals seem necessary for responses to T-independent type 2 (TI-2) antigens, which are multimeric antigens lacking T cell epitopes and Toll-like receptor ligands. How then do mature B cells avoid making a TI-2–like response to multimeric self-antigens? We present evidence that TI-2 antigens decorated with ligands of inhibitory sialic acid–binding Ig-like lectins (siglecs) are poorly immunogenic and can induce tolerance to subsequent challenge with immunogenic antigen. Two siglecs, CD22 and Siglec-G, contributed to tolerance induction, preventing plasma cell differentiation or survival. Although mutations in CD22 and its signaling machinery have been associated with dysregulated B cell development and autoantibody production, previous analyses failed to identify a tolerance defect in antigen-specific mutant B cells. Our results support a role for siglecs in B cell self-/nonself-discrimination, namely suppressing responses to self-associated antigens while permitting rapid “missing self”–responses to unsialylated multimeric antigens. The results suggest use of siglec ligand antigen constructs as an approach for inducing tolerance.

Treatment dropout is a problem of great prevalence and stands as an obstacle to recovery in cocaine-dependent (CD) individuals. Treatment attrition in CD individuals may result from impairments in cognitive control, which can be reliably measured by the Stroop color-word interference task. The present analyses contrasted baseline performance on the color-naming, word-reading, and interference subtests of the Stroop task in CD subjects who completed a cocaine treatment trial (completers: N ¼ 50) and those who dropped out of the trial before completion (non-completers: N ¼ 24). A logistic regression analysis was used to predict trial completion using three models with the following variables: the Stroop task subscale scores (Stroop model); the Hamilton depression rating scale (HDRS) scores (HDRS model); and both the Stroop task subscale scores and HDRS scores (Stroop and HDRS model). Each model was able to significantly predict group membership (completers vs non-completers) better than a model based on a simple constant (HDRS model p ¼ 0.02, Stroop model p ¼ 0.006, and Stroop and HDRS model p ¼ 0.003). Models using the Stroop preformed better than the HDRS model. These findings suggest that the Stroop task can be used to identify cocaine-dependent subjects at risk for treatment dropout. The Stroop task is a widely available, reliable, and valid instrument that can be easily employed to identify and tailor interventions of at risk individuals in the hope of improving treatment compliance.

Objectives: The aim of this study was to compare changes in brain ␥-aminobutyric (GABA) levels associated with an acute yoga session versus a reading session. It was hypothesized that an individual yoga session would be associated with an increase in brain GABA levels. Design: This is a parallel-groups design. Settings/location: Screenings, scan acquisitions, and interventions took place at medical school-affiliated centers. Subjects: The sample comprised 8 yoga practitioners and 11 comparison subjects. Interventions: Yoga practitioners completed a 60-minute yoga session and comparison subjects completed a 60-minute reading session. Outcome measures: GABA-to-creatine ratios were measured in a 2-cm axial slab using magnetic resonance spectroscopic imaging immediately prior to and immediately after interventions. Results: There was a 27% increase in GABA levels in the yoga practitioner group after the yoga session (0.20 mmol/kg) but no change in the comparison subject group after the reading session (Ϫ0.001 mmol/kg) (t ϭ Ϫ2.99, df ϭ 7.87, p ϭ 0.018). Conclusions: These findings demonstrate that in experienced yoga practitioners, brain GABA levels increase after a session of yoga. This suggests that the practice of yoga should be explored as a treatment for disorders with low GABA levels such as depression and anxiety disorders. Future studies should compare yoga to other forms of exercise to help determine whether yoga or exercise alone can alter GABA levels.

Catecholamine neurotransmitters are synthesized by hydroxylation of tyrosine to L-dihydroxyphenylalanine (L-Dopa) by tyrosine hydroxylase (TH). The elimination of TH in both pigmented and albino mice described here, like pigmented TH-null mice reported previously (Kobayashi et al., 1995; Zhou et al., 1995), demonstrates the unequivocal requirement for catecholamines during embryonic development. Although the lack of TH is fatal, TH-null embryos can be rescued by administration of catecholamine precursors to pregnant dams. Once born, TH-null pups can survive without further treatment until weaning. Given the relatively rapid half-life of catecholamines, we expected to find none in postnatal TH-null pups. Despite the fact that the TH-null pups lack TH and have not been supplemented with catecholamine precursers, catecholamines are readily detected in our pigmented line of TH-null mice by glyoxylic acid-induced histofluorescence at postnatal day 7 (P7) and P15 and quantitatively at P15 in sympathetically innervated peripheral organs, in sympathetic ganglia, in adrenal glands, and in brains. Between 2 and 22% of wild-type catecholamine concentrations are found in these tissues in mutant pigmented mice. To ascertain the source of the catecholamine, we examined postnatal TH-null albino mice that lack tyrosinase, another enzyme that converts tyrosine to L-Dopa but does so during melanin synthesis. In contrast to the pigmented TH-null mice, catecholamine histofluorescence is undetectable in postnatal albino mutants, and the catecholamine content of TH-null pups lacking tyrosinase is 18% or less than that of TH-null mice with tyrosinase. Thus, these extraordinary circumstances reveal that tyrosinase serves as an alternative pathway to supply catecholamines.Key words: catecholamines; tyrosine hydroxylase-null mutation; tyrosinase; tyrosine hydroxylase; tyrosinase and catecholamine synthesis; catecholamines in development; catecholamine synthesisThe catecholamines dopamine, norepinephrine, and epinephrine are synthesized from dietary tyrosine in selected central and peripheral neurons and in the adrenal medulla by the sequential action of enzymes in a synthetic pathway first postulated by Blaschko (1939) and finally f ully demonstrated by Nagatsu et al. (1964) with the isolation of tyrosine hydroxylase (TH). Tyrosine hydroxylase, the first and rate-limiting enzyme in catecholamine synthesis, catalyzes the conversion of tyrosine to L-dihydroxyphenylalanine (L-Dopa), a substrate for Dopa decarboxylase (DDC) (aromatic amino acid decarboxylase), which converts L-Dopa to dopamine. DDC is ubiquitously distributed but is particularly abundant in the kidney and in catecholamineproducing cells. Dopamine serves as a neurotransmitter in cell groups in the brain and in a few peripheral groups. In noradrenergic neurons in the sympathetic nervous system, in the brainstem, and in adrenal chromaffin cells, dopamine is converted to norepinephrine by dopamine ␤ hydroxylase (D␤H), whose expression is primarily restricted to these cells. Nor...

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CD22 is a member of the sialic acid-binding Ig-like lectin (Siglec) family that is known to be a regulator of B cell signaling. Its B cell-specific expression makes it an attractive target for immunotoxin-mediated B cell depletion therapy for the treatment of B cell lymphomas and autoimmune diseases. Although CD22 is well documented to be an endocytic receptor, it is believed that after internalization, it is targeted for degradation. We show in this study that CD22 is instead constitutively recycled to the cell surface. We also find that glycan ligand-based cargo is released from CD22 and accumulates intracellularly as CD22 recycles between the cell surface and endosomal compartments. In contrast, Abs to CD22 do not accumulate but remain bound to CD22 and recycle to the cell surface. The results have implications for development of agents that target CD22 as an endocytic receptor for delivery of cytotoxic cargo to B cells.