Primary meningococcal conjunctivitis: an unusual case of transmission by saliva.

A 49-year-old diabetic man presented with a 2-day history of a painful right eye associated with a purulent discharge. Prior to becoming symptomatic, he reported that someone spat at him, resulting in direct contact between the saliva and his affected eye. Gram stain revealed numerous leucocytes with Gram-negative diplococci, and culture yielded Neisseria meningitidis (serogroup C). There was no evidence of any systemic infection, and blood cultures were negative for any growth. He was treated for primary meningococcal conjunctivitis (PMC) with intensive topical antibiotic eyedrops as well as systemic antibiotics. One week after commencing treatment he remained systemically well and his symptoms had fully resolved.

Regulation of platelet lifespan in the presence and absence of thrombopoietin signaling.

UNLABELLED: Essentials We examined platelet survival in models of absent or enhanced thrombopoietin (TPO) signaling. Platelet lifespan is normal in transgenic mice with chronically enhanced TPO signaling. Mpl deficiency does not negatively affect platelet lifespan in the absence of thrombocytopenia. We conclude that TPO and its receptor Mpl are dispensable for platelet survival in adult mice. SUMMARY: Background It is well established that thrombopoietin (TPO), acting via its receptor Mpl, is the major cytokine regulator of platelet biogenesis. The primary mechanism by which TPO signaling stimulates thrombopoiesis is via stimulation of Mpl-expressing hematopoietic progenitors; Mpl on megakaryocytes and platelets acts to control the amount of TPO available. TPO could potentially reduce platelet and/or megakaryocyte apoptosis, and therefore increase the platelet count. However, the effect of TPO receptor signaling on platelet survival is unresolved. Methods and results Here, we investigated platelet survival in mouse models of absent or enhanced TPO signaling. In the absence of thrombocytopenia, Mpl deficiency did not negatively influence platelet lifespan, and nor was platelet survival affected in transgenic mice with chronically increased TPO signaling. Conclusions We conclude that TPO and its receptor Mpl are dispensable for platelet survival in adult mice.

BET inhibition represses miR17-92 to drive BIM-initiated apoptosis of normal and transformed hematopoietic cells.

The BET (bromodomain and extraterminal domain) bromodomain-containing proteins, such as BRD4, are highly promising targets for treating lymphoid and myeloid malignancies. They act to modulate the expression of multiple genes that control diverse cellular processes including proliferation, survival and differentiation that are consequentially disrupted by small-molecule BET bromodomain inhibitors such as JQ1. By assessing the impact of these inhibitors on normal mouse hematopoietic cells or their transformed counterparts, we establish definitively that their cytotoxic action in vitro and in vivo relies predominantly on the activation of BAX/BAK-dependent mitochondrial (intrinsic) apoptosis. In large part, this is triggered by marked upregulation of the BH3-only protein BIM when the BET inhibitors suppress miR-17-92, a key post-transcriptional repressor of BIM expression. Thus, our study strongly suggests that mutations that permit the evasion of apoptosis (for example, BCL2 overexpression, BIM inactivation) are likely to blunt the activity of the BET bromodomain inhibitors and should be anticipated when therapy resistance develops. Strikingly, we also found that certain normal hematopoietic cells, especially those of lymphoid origin, are as prone to apoptosis induced by the BET inhibitors as their transformed counterparts, indicating that their susceptibility to BET inhibitors did not arise from oncogenic transformation.

BCL-2 is dispensable for thrombopoiesis and platelet survival.

Navitoclax (ABT-263), an inhibitor of the pro-survival BCL-2 family proteins BCL-2, BCL-XL and BCL-W, has shown clinical efficacy in certain BCL-2-dependent haematological cancers, but causes dose-limiting thrombocytopaenia. The latter effect is caused by Navitoclax directly inducing the apoptotic death of platelets, which are dependent on BCL-XL for survival. Recently, ABT-199, a selective BCL-2 antagonist, was developed. It has shown promising anti-leukaemia activity in patients whilst sparing platelets, suggesting that the megakaryocyte lineage does not require BCL-2. In order to elucidate the role of BCL-2 in megakaryocyte and platelet survival, we generated mice with a lineage-specific deletion of Bcl2, alone or in combination with loss of Mcl1 or Bclx. Platelet production and platelet survival were analysed. Additionally, we made use of BH3 mimetics that selectively inhibit BCL-2 or BCL-XL. We show that the deletion of BCL-2, on its own or in concert with MCL-1, does not affect platelet production or platelet lifespan. Thrombocytopaenia in Bclx-deficient mice was not affected by additional genetic loss or pharmacological inhibition of BCL-2. Thus, BCL-2 is dispensable for thrombopoiesis and platelet survival in mice.

Hhex regulates Kit to promote radioresistance of self-renewing thymocytes in Lmo2-transgenic mice.

Lmo2 is an oncogenic transcription factor that is frequently overexpressed in T-cell acute leukemias, in particular poor prognosis early T-cell precursor-like (ETP-) acute lymphoblastic leukemia (ALL). The primary effect of Lmo2 is to cause self-renewal of developing CD4(-)CD8(-) (double negative, DN) T cells in the thymus, leading to serially transplantable thymocytes that eventually give rise to leukemia. These self-renewing thymocytes are intrinsically radioresistant implying that they may be a source of leukemia relapse after therapy. The homeobox transcription factor, Hhex, is highly upregulated in Lmo2-transgenic thymocytes and can phenocopy Lmo2 in inducing thymocyte self-renewal, implying that Hhex may be a key component of the Lmo2-induced self-renewal program. To test this, we conditionally deleted Hhex in the thymi of Lmo2-transgenic mice. Surprisingly, this did not prevent accumulation of DN thymocytes, nor alter the rate of overt leukemia development. However, deletion of Hhex abolished the transplantation capacity of Lmo2-transgenic thymocytes and overcame their radioresistance. We found that Hhex regulates Kit expression in Lmo2-transgenic thymocytes and that abrogation of Kit signaling phenocopied loss of Hhex in abolishing the transplantation capacity and radioresistance of these cells. Thus, targeting the Kit signaling pathway may facilitate the eradication of leukemia-initiating cells in immature T-cell leukemias in which it is expressed.

The Myb-p300-CREB axis modulates intestine homeostasis, radiosensitivity and tumorigenesis.

The gastrointestinal (GI) epithelium is constantly renewing, depending upon the intestinal stem cells (ISC) regulated by a spectrum of transcription factors (TFs), including Myb. We noted previously in mice with a p300 mutation (plt6) within the Myb-interaction-domain phenocopied Myb hypomorphic mutant mice with regard to thrombopoiesis, and here, changes in GI homeostasis. p300 is a transcriptional coactivator for many TFs, most prominently cyclic-AMP response element-binding protein (CREB), and also Myb. Studies have highlighted the importance of CREB in proliferation and radiosensitivity, but not in the GI. This prompted us to directly investigate the p300-Myb-CREB axis in the GI. Here, the role of CREB has been defined by generating GI-specific inducible creb knockout (KO) mice. KO mice show efficient and specific deletion of CREB, with no evident compensation by CREM and ATF1. Despite complete KO, only modest effects on proliferation, radiosensitivity and differentiation in the GI under homeostatic or stress conditions were evident, even though CREB target gene pcna (proliferating cell nuclear antigen) was downregulated. creb and p300 mutant lines show increased goblet cells, whereas a reduction in enteroendocrine cells was apparent only in the p300 line, further resembling the Myb hypomorphs. When propagated in vitro, crebKO ISC were defective in organoid formation, suggesting that the GI stroma compensates for CREB loss in vivo, unlike in MybKO studies. Thus, it appears that p300 regulates GI differentiation primarily through Myb, rather than CREB. Finally, active pCREB is elevated in colorectal cancer (CRC) cells and adenomas, and is required for the expression of drug transporter, MRP2, associated with resistance to Oxaliplatin as well as several chromatin cohesion protein that are relevant to CRC therapy. These data raise the prospect that CREB may have a role in GI malignancy as it does in other cancer types, but unlike Myb, is not critical for GI homeostasis.

SOCS2 is dispensable for BCR/ABL1-induced chronic myeloid leukemia-like disease and for normal hematopoietic stem cell function.

Suppressor of cytokine signaling 2 (SOCS2) is known as a feedback inhibitor of cytokine signaling and is highly expressed in primary bone marrow (BM) cells from patients with chronic myeloid leukemia (CML). However, it has not been established whether SOCS2 is involved in CML, caused by the BCR/ABL1 fusion gene, or important for normal hematopoietic stem cell (HSC) function. In this study, we demonstrate that although Socs2 was found to be preferentially expressed in long-term HSCs, Socs2-deficient HSCs were indistinguishable from wild-type HSCs when challenged in competitive BM transplantation experiments. Furthermore, by using a retroviral BCR/ABL1-induced mouse model of CML, we demonstrate that SOCS2 is dispensable for the induction and propagation of the disease, suggesting that the SOCS2-mediated feedback regulation of the JAK/STAT pathway is deficient in BCR/ABL1-induced CML.

Suppressor of cytokine signalling 1 (SOCS1) is a physiological regulator of the asthma response.

BACKGROUND: The molecular determinants of the severity and persistence of allergic asthma remain poorly understood. Suppressor of cytokine signalling 1 (SOCS1) is a negative regulator of IL-4-dependent pathways in vitro and might therefore control T-helper type 2 (Th2) immunity associated traits, such as IgE levels, mucin production, IL-5 and IL-13 induction, and eosinophilic mucosal inflammation, which are implicated in allergic asthma. OBJECTIVE: To investigate the role of SOCS1 in regulating Th2-associated disease traits in a murine sub-chronic aeroallergen-driven asthma model. METHODS: Following sensitization and challenge with ovalbumin (OVA), bronchoalveolar lavage and serum were collected from mice lacking the Socs1 gene on an IFN-gamma null background (Socs1(-/-)Ifngamma(-/-)). The composition of infiltrating cells in the lung, serum IgE and IgG1 levels and cytokine levels were analysed. RESULTS: Serum IgE levels and infiltrating eosinophils were considerably increased in the lungs of OVA-treated Socs1(-/-)Ifngamma(-/-) mice compared with Ifngamma(-/-) and C57BL/6 controls. Expression of the Th2 cytokines, IL-4, IL-5 and IL-13 was increased in CD4+ cells and lung tissue from OVA-treated Socs1(-/-)Ifngamma(-/-) mice. IgE, IL-5 levels and infiltrating eosinophils were also elevated in saline-treated Socs1(-/-)Ifngamma(-/-) mice, suggesting that in the absence of SOCS1, mice are already biased towards a Th2 response. It is at present unclear whether the elevated cytokine levels are sufficient to result in the exacerbated Th2 response to OVA challenge or whether enhanced intra-cellular signalling also contributes. Surprisingly, of the various IL-4/IL-13 responsive genes tested, only Arginase I appeared to be modestly up-regulated in the lungs of OVA-treated Socs1(-/-)Ifngamma(-/-) mice, suggesting that regulation by SOCS1 occurs primarily in haematopoietic cells and not in the airway epithelium. CONCLUSIONS: Together these results indicate that SOCS1 is an important regulator of the Th2 response.

Two distinct types of murine blast colony-forming cells are multipotential hematopoietic precursors.

Two types of blast colonies can be stimulated to develop in semisolid agar cultures of murine bone marrow cells. Typically, these are either multicentric colonies stimulated by stem cell factor (SCF) plus interleukin-6 (IL-6) or dispersed colonies stimulated by Flt3 ligand (FL) plus IL-6. Both types of blast colony-forming cells (BL-CFCs) can generate large numbers of lineage-committed granulocyte-macrophage progenitor cells and exhibit some capacity for self-generation and the formation of eosinophil and megakaryocyte progenitor cells. However, the two populations of BL-CFCs are largely distinct and partially separable by fluorescence-activated cell sorting and are distinguished by differing capacity to form granulocyte-committed progeny. Both types of BL-CFCs can generate dendritic cells and small numbers of lymphocytes but the FL-responsive BL-CFCs have a greater capacity to form both B and T lymphocytes. Both types of blast colonies offer remarkable opportunities to analyze multilineage commitment at a clonal level in vitro.

Suppressor of cytokine signaling 3 (SOCS3) limits damage-induced crypt hyper-proliferation and inflammation-associated tumorigenesis in the colon.

Intestinal injury or chronic inflammation induce cytokines that promote crypt regeneration and mucosal repair. If excessive or prolonged, such mechanisms may increase colon cancer risk. Factors that terminate or limit cytokine action in intestinal epithelial cells (IEC) may protect against crypt hyperplasia and neoplasia. We hypothesized that suppressor of cytokine signaling-3 (SOCS3) is such a factor. Mice with Vilin-promoter/Cre-recombinase (VC)-mediated IEC-specific SOCS3 gene disruption (VC/HO), WT/HO littermates with floxed but intact SOCS3 genes and VC/WT mice were studied. Colon was examined after acute dextran sodium sulfate (DSS)-induced mucosal injury or after azoxymethane (AOM) and chronic DSS. Signaling pathways were examined in colon, cultured IEC or colon cancer cell lines. VC/HO mice showed no basal phenotype. After acute DSS, VC/HO exhibited enhanced crypt proliferation and crypt hyperplasia and reduced transforming growth factor (TGF) beta expression in colon. Inflammation and mucosal damage were similar across genotypes. Following AOM/DSS, VC/HO mice had increased size, number and load of colonic tumors and increased STAT3 and nuclear factor-kappa B (NF-kappaB) activation in colon. In vitro, SOCS3 overexpression reduced proliferation, IL-6-mediated STAT3 activation and tumor necrosis factor (TNF) alpha-mediated NF-kappaB activation. We conclude that cytokine induction of SOCS3 normally provides an intrinsic mechanism to limit injury-induced crypt hyperproliferation and inflammation-associated colon cancer by regulating both STAT3 and NF-kappaB pathways.