Maureen R. Horton

The kinase mTOR regulates the differentiation of helper T cells through the selective activation of signaling by mTORC1 and mTORC2

The kinase mTOR has emerged as an important regulator of the differentiation of helper T cells. Here we demonstrate that differentiation into the TH1 and TH17 subsets of helper T cells was selectively regulated by signaling from mTOR complex 1 (mTORC1) that was dependent on the small GTPase Rheb. Rheb-deficient T cells failed to generate TH1 and TH17 responses in vitro and in vivo and did not induce classical experimental autoimmune encephalomyelitis (EAE). However, they retained their ability to become TH2 cells. Alternatively, when mTORC2 signaling was deleted from T cells, they failed to generate TH2 cells in vitro and in vivo but preserved their ability to become TH1 and TH17 cells. Our data identify mechanisms by which two distinct signaling pathways downstream of mTOR regulate helper cell fate in different ways. These findings define a previously unknown paradigm that links T cell differentiation with selective metabolic signaling pathways.

Hyaluronan Fragments Act as an Endogenous Danger Signal by Engaging TLR2

Upon tissue injury, high m.w. hyaluronan (HA), a ubiquitously distributed extracellular matrix component, is broken down into lower m.w. (LMW) fragments, which in turn activate an innate immune response. In doing so, LMW HA acts as an endogenous danger signal alerting the immune system of a breach in tissue integrity. In this report, we demonstrate that LMW HA activates the innate immune response via TLR-2 in a MyD88-, IL-1R-associated kinase-, TNFR-associated factor-6-, protein kinase Cζ-, and NF-κB-dependent pathway. Furthermore, we show that intact high m.w. HA can inhibit TLR-2 signaling. Finally, we demonstrate that LMW HA can act as an adjuvant promoting Ag-specific T cell responses in vivo in wild-type but not TLR-2null mice.

Regulation of immune responses by mTOR.

mTOR is an evolutionarily conserved serine/threonine kinase that plays a central role in integrating environmental cues in the form of growth factors, amino acids, and energy. In the study of the immune system, mTOR is emerging as a critical regulator of immune function because of its role in sensing and integrating cues from the immune microenvironment. With the greater appreciation of cellular metabolism as an important regulator of immune cell function, mTOR is proving to be a vital link between immune function and metabolism. In this review, we discuss the ability of mTOR to direct the adaptive immune response. Specifically, we focus on the role of mTOR in promoting differentiation, activation, and function in T cells, B cells, and antigen-presenting cells.

Egr-2 and Egr-3 are negative regulators of T cell activation.

T cell receptor engagement in the absence of proper accessory signals leads to T cell anergy. E3 ligases are involved in maintaining the anergic state. However, the specific molecules responsible for the induction of anergy have yet to be elucidated. Using microarray analysis we have identified here early growth response gene 2 (Egr-2) and Egr-3 as key negative regulators of T cell activation. Overexpression of Egr2 and Egr3 was associated with an increase in the E3 ubiquitin ligase Cbl-b and inhibition of T cell activation. Conversely, T cells from Egr3−/− mice had lower expression of Cbl-b and were resistant to in vivo peptide-induced tolerance. These data support the idea that Egr-2 and Egr-3 are involved in promoting a T cell receptor–induced negative regulatory genetic program.

Hyaluronan Fragments Induce Nitric-oxide Synthase in Murine Macrophages through a Nuclear Factor κB-dependent Mechanism

Activated macrophages play a critical role in controlling chronic tissue inflammation through the release of a variety of mediators including cytokines, chemokines, growth factors, active lipids, reactive oxygen, and nitrogen species. The mechanisms that regulate macrophage activation in chronic inflammation are poorly understood. A hallmark of chronic inflammation is the turnover of extracellular matrix components, and recent work has suggested that interactions with the extracellular matrix can exert important influences on macrophage effector functions. We have examined the effect of low molecular weight fragments of the extracellular matrix glycosaminoglycan hyaluronan (HA) on the induction of nitric-oxide synthase (iNOS) in macrophages. We found that HA fragments induce iNOS mRNA, protein and activity alone, and markedly synergize with interferon-γ to induce iNOS gene expression in murine macrophages. In addition, we found that resident tissue alveolar macrophages respond minimally, but inflammatory alveolar macrophages exhibit a marked induction in iNOS expression in response to HA fragments. Finally, we demonstrate that the mechanism of HA fragment-induced expression of iNOS requires activation of the transcriptional regulator nuclear factor κB. These data support the hypothesis that HA may be an important regulator of macrophage activation at sites of chronic tissue inflammation.

Thalidomide for the Treatment of Cough in Idiopathic Pulmonary Fibrosis: A Randomized Trial

BACKGROUND Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal disorder of unknown cause with no effective treatment. Cough affects up to 80% of patients with IPF, is frequently disabling, and lacks effective therapy. OBJECTIVE To determine the efficacy of thalidomide in suppressing cough in patients with IPF. DESIGN 24-week, double-blind, 2-treatment, 2-period crossover trial. (ClinicalTrials.gov registration number: NCT00600028) SETTING 1 university center. PARTICIPANTS 98 participants were screened, 24 were randomly assigned, 23 received treatment (78.3% men; mean age, 67.6 years; mean FVC, 70.4% predicted), and 20 completed both treatment periods. MEASUREMENTS The primary end point was cough-specific quality of life measured by the Cough Quality of Life Questionnaire (CQLQ). Secondary end points were visual analogue scale of cough and the St. Georges Respiratory Questionnaire (SGRQ). For all measures, lower scores equaled improved cough or respiratory quality of life. RESULTS CQLQ scores significantly improved with thalidomide (mean difference vs. placebo, -11.4 [95% CI, -15.7 to -7.0]; P < 0.001). Thalidomide also significantly improved scores on the visual analogue scale of cough (mean difference vs. placebo, -31.2 [CI, -45.2 to -17.2]; P < 0.001). In participants receiving thalidomide, scores from the total SGRQ, SGRQ symptom domain, and SGRQ impact domain improved compared with those of participants receiving placebo. Adverse events were reported in 74% of patients receiving thalidomide and 22% receiving placebo; constipation, dizziness, and malaise were more frequent with thalidomide. LIMITATION This was a single-center study of short duration and small sample size focused on symptom-specific quality of life. CONCLUSION Thalidomide improved cough and respiratory quality of life in patients with IPF. A larger trial is warranted to assess these promising results. PRIMARY FUNDING SOURCE Celgene Corporation.

Threat matrix : Low-molecular-weight hyaluronan (HA) as a danger signal

Whether or not T cell receptor engagement leads to full activation or tolerance is determined by the context in which the antigen is encountered. Antigen presented by activated APCs in the presence of costimulation leads to full T cell activation, while antigen presented by resting APCs leads to tolerance. Pathogen-associated molecular patterns in the form of toll-like receptor ligands play a critical role in activating APCs and promoting T cell activation. In this review we hypothesize that low-molecular-weight species of the extracellular matrix polymer hyaluronan also performs this function by acting as an endogenous danger signal.

The AGC kinase SGK1 regulates TH1 and TH2 differentiation downstream of the mTORC2 complex

Serum- and glucocorticoid-regulated kinase 1 (SGK1) is an AGC kinase that regulates membrane sodium channel expression in renal tubular cells in an mTORC2-dependent manner. We hypothesized that SGK1 might represent a novel mTORC2-dependent regulator of T cell differentiation and function. Here we demonstrate that upon activation by mTORC2, SGK1 promoted TH2 differentiation by negatively regulating the NEDD4-2 E3 ligase-mediated destruction of transcription factor JunB. Simultaneously, SGK1 repressed the production of interferon-γ (IFN-γ) by controlling the expression of the long isoform of transcription factor TCF-1. Consistent with these findings, mice with a selective deletion of SGK1 in T cells were resistant to experimentally induced asthma, generated robust amounts of IFN-γ in response to viral infections and more readily rejected tumors.SGK1 is an AGC kinase that regulates the expression of membrane sodium channels in renal tubular cells in a manner dependent on the metabolic checkpoint kinase complex mTORC2. We hypothesized that SGK1 might represent an additional mTORC2-dependent regulator of the differentiation and function of T cells. Here we found that after activation by mTORC2, SGK1 promoted T helper type 2 (TH2) differentiation by negatively regulating degradation of the transcription factor JunB mediated by the E3 ligase Nedd4-2. Simultaneously, SGK1 repressed the production of interferon-γ (IFN-γ) by controlling expression of the long isoform of the transcription factor TCF-1. Consistent with those findings, mice with selective deletion of SGK1 in T cells were resistant to experimentally induced asthma, generated substantial IFN-γ in response to viral infection and more readily rejected tumors.

Ascertainment of collagen vascular disease in patients presenting with interstitial lung disease

INTRODUCTION Previous studies of interstitial lung disease (ILD) suggest that prognosis and therapeutic response are influenced by the presence of underlying collagen vascular disease (CVD). Yet, what proportion of patients presenting with ILD have CVD is largely unknown. We sought to determine the frequency of a new CVD diagnosis in an ILD referral population. MATERIALS/PATIENTS AND METHODS We retrospectively studied 114 consecutive patients evaluated at the Johns Hopkins Interstitial Lung Disease Clinic for the development of CVD. RESULTS In this retrospective cohort, nearly one-third of the 114 patients with confirmed ILD satisfied published criteria for a CVD diagnosis. Seventeen (15%) patients were diagnosed with a new CVD as a direct consequence of their ILD evaluation. Patients with new CVD diagnosis were younger than those without new CVD diagnosis: 51.4years (95% CI 45-58years) and 60years (95% CI 57-63), respectively (p=0.01). Moreover, an ANA>or=1:640 (p=0.03) and elevated levels of creatine phosphokinase (CPK) or aldolase (p<0.001) were associated with a new CVD diagnosis. CONCLUSIONS Unrecognized collagen vascular disease may be more common than previously appreciated among patients referred with ILD. High titer ANA and an elevated CPK or aldolase are associated with a CVD diagnosis in this referral population.

Enhancement of tumor immunotherapy by deletion of the A2A adenosine receptor

The A2A adenosine receptor plays a critical and non-redundant role in suppressing inflammation at sites of hypoxia and tissue damage. The tumor microenvironment has high levels of adenosine as a result of hypoxia and ectopic expression of enzymes responsible for the generation of extracellular adenosine. Thus, we sought to determine the ability of A2A receptor null mice to immunologically reject tumors. We observed that mice lacking the A2A adenosine receptor showed significantly delayed growth of lymphoma cells when compared to WT mice. Furthermore, when immunized with a low dose of tumor or with an irradiated GM-CSF–secreting tumor vaccine, A2A receptor null mice showed significantly enhanced protection from a subsequent high-dose challenge from both immunogenic and poorly immunogenic tumor lines. This increase in protection was accompanied by an increase in the number of tumor-antigen-specific CD8 T cells at the vaccine-site draining lymph node. Finally, we found that A2A receptor null mice displayed more robust anti-tumor responses than WT mice when they were treated with a soluble B7-DC/Fc fusion protein designed to antagonize B7-H1-mediated co-inhibition. This combinatorial immunotherapy strategy could also be recapitulated with pharmacological A2A receptor blockade paired with B7-DC/Fc administration. In light of these data, we believe that blockade of the A2A adenosine receptor is an attractive target for tumor immunotherapy that synergizes with other immunomodulatory approaches currently in clinical trials.