Ginell R. Post

Telomerase Activation in Atherosclerosis and Induction of Telomerase Reverse Transcriptase Expression by Inflammatory Stimuli in Macrophages

Objective—Telomerase serves as a critical regulator of tissue renewal. Although telomerase activity is inducible in response to various environmental cues, it remains unknown whether telomerase is activated during the inflammatory remodeling underlying atherosclerosis formation. To address this question, we investigated in the present study the regulation of telomerase in macrophages and during atherosclerosis development in low-density lipoprotein receptor–deficient mice. Methods and Results—We demonstrate that inflammatory stimuli activate telomerase in macrophages by inducing the expression of the catalytic subunit telomerase reverse transcriptase (TERT). Reporter and chromatin immunoprecipitation assays identified a previously unrecognized nuclear factor-&kgr;B (NF-&kgr;B) response element in the TERT promoter, to which NF-&kgr;B is recruited during inflammation. Inhibition of NF-&kgr;B signaling completely abolished the induction of TERT expression, characterizing TERT as a bona fide NF-&kgr;B target gene. Furthermore, functional experiments revealed that TERT deficiency results in a senescent cell phenotype. Finally, we demonstrate high levels of TERT expression in macrophages of human atherosclerotic lesions and establish that telomerase is activated during atherosclerosis development in low-density lipoprotein receptor–deficient mice. Conclusion—These results characterize TERT as a previously unrecognized NF-&kgr;B target gene in macrophages and demonstrate that telomerase is activated during atherosclerosis. This induction of TERT expression prevents macrophage senescence and may have important implications for the development of atherosclerosis.

sarA-mediated repression of protease production plays a key role in the pathogenesis of Staphylococcus aureus USA300 isolates.

Mutation of staphylococcal accessory regulator (sarA) results in increased production of extracellular proteases in Staphylococcus aureus, which has been correlated with decreased biofilm formation and decreased accumulation of extracellular toxins. We used murine models of implant‐associated biofilm infection and S. aureus bacteraemia (SAB) to compare virulence of USA300 strain LAC, its isogenic sarA mutant, and derivatives of each of these strains with mutations in all 10 of the genes encoding recognized extracellular proteases. The sarA mutant was attenuated in both models, and this was reversed by eliminating production of extracellular proteases. To examine the mechanistic basis, we identified proteins impacted by sarA in a protease‐dependent manner. We identified 253 proteins where accumulation was reduced in the sarA mutant compared with the parent strain, and was restored in the sarA/protease mutant. Additionally, in SAB, the LAC protease mutant exhibited a hypervirulent phenotype by comparison with the isogenic parent strain, demonstrating that sarA also positively regulates production of virulence factors, some of which are subject to protease‐mediated degradation. We propose a model in which attenuation of sarA mutants is defined by their inability to produce critical factors and simultaneously repress production of extracellular proteases that would otherwise limit accumulation of virulence factors.

PAX-5: A Valuable Immunohistochemical Marker in the Differential Diagnosis of Lymphoid Neoplasms

Objective: Undifferentiated tumors and hematolymphoid neoplasms can be diagnostically challenging due to potential overlap of morphologic features and variant antigen expression. PAX-5, a transcription factor expressed throughout B-cell maturation, is detected in most B-cell neoplasms including those that lack expression of mature B-cell markers, such as classical Hodgkin lymphoma (cHL), B-lymphoblastic leukemia and B-cell lymphomas following rituximab therapy. The lack of PAX-5 expression in most CD30-positive non-hematopoietic malignancies (embryonal carcinoma and seminoma) and T-cell lymphomas, such as anaplastic large cell lymphoma (ALCL), suggests that the absence of PAX-5 may be used to confirm non-B-cell lineage. The goal of this study was to retrospectively assess PAX-5 immunoreactivity in diagnostic samples of hematolymphoid and other non-hematopoietic malignancies. Design: Diagnostic lymph node, decalcified core bone marrow biopsies and tissue sections from 111 archived paraffin-embedded tissue blocks and a tissue lymphoma microarray were immunostained using a monoclonal antibody to PAX-5. The corresponding hematoxylin and eosin stained tissue sections and additional immunostains were simultaneously evaluated. PAX-5 immunoreactivity in neoplastic cells was scored as positive or negative. This study was exempted by the Institutional Review Board for Human Research. Results: Nuclear PAX-5 immunoreactivity was detected in 88% (36/41) of Hodgkin lymphoma, all cases of diffuse large B-cell lymphoma (n=72), small B-cell lymphomas (n=5), B-lymphoblastic leukemia/lymphoma and mixed phenotype acute leukemia with B-cell lineage (n=5). PAX-5 was not detected in ALCL (n=22), T-cell lymphoblastic leukemia/lymphoma, mixed phenotype acute leukemia with T-cell lineage (n=5), acute myeloid leukemia (n=4), carcinoid tumors with typical morphology (n=5), melanoma (n=3), and undifferentiated/metastatic tumors (n=8). Non-neoplastic bone marrow sections showed scattered nuclear staining in small B-cell lymphocytes/hematogones. The detection of PAX-5 immunoreactivity resulted in the reclassification of two cases of ALCL to cHL. Conclusion: Overall, our results demonstrate that including PAX-5 in a panel with other immunomarkers helps establish B-cell lineage and increases diagnostic yield.

A comparison of washed and volume-reduced platelets with respect to platelet activation, aggregation, and plasma protein removal.

BACKGROUND: Washed or volume‐reduced platelets (PLTs) are occasionally requested for patients with a history of allergic or anaphylactic transfusion reactions. However, conclusive data are not available as to which method is more suitable.

UTP but not ATP causes hypertrophic growth in neonatal rat cardiomyocytes

Addition of ATP to neonatal rat cardiomyocytes has been reported to inhibit hypertrophic growth responses, even though G(q)-coupled receptors are activated. In the current study, we investigated hypertrophic responses to activation of G(q)-coupled-purinergic receptors on cardiomyocytes using UTP as an alternative agonist to ATP. UTP (100 microM) activated phospholipase C via G(q) similarly to ATP, and responses to the two agonists were not additive. Similarly, UTP and ATP both induced phosphorylation of extracellular signal-regulated kinase (ERK1/2), while having little effect on p38 mitogen-activated protein kinase or c-Jun NH(2)-terminal kinase. However, addition of UTP (100 microM) to cardiomyocytes caused hypertrophic growth indicated by increased protein content without DNA synthesis. ATP (100 microM) caused no increase in protein. We conclude that activation of purinergic receptors on neonatal cardiomyocytes initiates hypertrophic signaling pathways, but that prolonged exposure to ATP, but not UTP, has growth-inhibitory effects.

Pathways and roadblocks in muscarinic receptor-mediated growth regulation

In some cell systems muscarinic receptor stimulation can induce proliferation or transformation. This phenomenon is subtype-specific (only m1 and m3 receptors are effective) and cell type dependent. In 1321N1 astrocytoma cells activation of m3 receptors stimulates phospholipase C, but does not induce DNA synthesis. In contrast the thrombin receptor, which also couples to phospholipase C, is strongly mitogenic and induces AP-1-dependent gene expression. Various experimental findings indicate that this discrepancy is not due to muscarinic receptor desensitization or blockade of growth stimulatory pathways. Muscarinic receptor number may be limiting, in particular for receptor coupling to the pertussis toxin-insensitive G-protein G12. This G-protein is required for thrombin-induced mitogenesis in 1321N1 cells and may couple selectively to the thrombin versus muscarinic receptor. In cardiomyocytes hypertrophic cell growth is induced by heterologously expressed m1 or m3 receptors but not by the endogenous m2 receptors. Studies using chimeric receptors confirm that induction of hypertrophy requires signalling through phospholipase C, but indicate that additional signals are needed to induce the morphological features of this response. We suggest that small G-proteins of the Rho subfamily, in addition to G12, mediate growth responses to G-protein-coupled receptors.

Pancytopenia with myelodysplasia due to copper deficiency.

We present a case of pancytopenia in a 9‐month‐old infant with total parenteral nutrition (TPN) dependence due to short bowel syndrome. Bone marrow examination revealed left‐shifted myeloid maturation, erythroid and myeloid dysplasia with normal iron stores. Serum copper level was 2 µm/dl (normal range 90–190 mcg/dl). After supplementation, copper levels normalized at 143 mcg/dl, and the macrocytic anemia, neutropenia, and thrombocytopenia resolved. Copper deficiency should be considered in the differential diagnosis of cytopenias and myelodsyplasia, particularly in the growing number of pediatric patients with TPN dependency or malabsorption. Pediatr Blood Cancer 2008;51:693–695.

Impact of the functional status of saeRS on in vivo phenotypes of Staphylococcus aureus sarA mutants

We investigated the in vivo relevance of the impact of sarA and saeRS on protease production using derivatives of the USA300 strain LAC. The results confirmed that mutation of saeRS or sarA reduces virulence in a bacteremia model to a comparable degree. However, while eliminating protease production restored virulence in the sarA mutant, it had little impact in the saeRS mutant. Additionally, constitutive activation of saeRS (saeRSC) enhanced the virulence of LAC and largely restored virulence in the isogenic sarA mutant. Based on these results, together with our analysis of the representative virulence factors alpha toxin, protein A (Spa), and extracellular nucleases, we propose a model in which the attenuation of saeRS mutants is defined primarily by decreased production of such factors, while constitutive activation of saeRS increases virulence, and reverses the attenuation of sarA mutants, because it results in both increased production and decreased protease‐mediated degradation of these same factors. This regulatory balance was also apparent in a murine model of catheter‐associated infection, with the results suggesting that the impact of saeRS on nuclease production plays an important role during the early stages of these infections that is partially offset by increased protease production in sarA mutants.

Metastatic chest wall malignant schwannoma responding to sorafenib: case report and literature review

Malignant schwannomas or malignant peripheral nerve sheath tumors (MPNST) represent approximately 10% of all soft tissue sarcomas. Metastatic disease from chest wall MPNST is very rare. We present a case of a major clinical response to the tyrosine kinase inhibitor (TKI) sorafenib in a patient with metastatic MPNST. A 42-year-old female with a prior history of neurofibromas developed MPNST, which later metastasized to the lungs and brain. She was initially placed on sorafenib with significant clinical response to lung metastases. MPNST show high levels of Ras activity and hence these tumors are promising targets for TKIs. Studies are ongoing and the results are eagerly awaited regarding the responses to these medications and whether they can positively impact on the natural history of this disease.

Cytopenia, Dysplasia, and Monocytosis: A Precursor To Chronic Myelomonocytic Leukemia or a Distinct Subgroup? Case Reports and Review of Literature

Chronic myelomonocytic leukemia (CMML) consists of disorders with overlapping dysplastic and proliferative features. The diagnosis of CMML requires absolute monocytosis (> 1000/μL) in addition to other criteria outlined by the World Health Organization (WHO) classification.(1) Monocytosis not reaching 1000/μL has been observed in myelodysplastic syndrome (MDS) and presents a diagnostic challenge in classification especially if increases in leukocyte count occurring during disease shifts the monocyte count into the absolute range. We discuss the laboratory and clinical features of 3 patients with myelodysplasia and associated monocytosis. Absolute neutropenia was the dominant feature at presentation, with mild anemia, thrombocytopenia, monocytosis (as a percentage), multilineage dysplasia, and increased myeloblasts, consistent with a diagnosis of refractory anemia with excess blasts (RAEB). Absolute monocytosis fulfilling the diagnostic criteria for CMML developed over 6-8 months, prompting a change in diagnosis. Two of 3 patients had normal cytogenetic examinations. JAK2 V617F mutation was detected after transformation to CMML in 1 of them; in the other, a novel translocation t(5;12)(p13;q24) was observed at the time of progression to acute leukemia. The use of different diagnostic terminologies--MDS, dysplasia with reactive monocytosis, myeloproliferative, and myeloproliferative/myelodysplastic syndromes by different and even the same pathologists at different times created confusion among the clinicians and patients. The disease course in these 3 patients was characterized by better survival and prolonged time to progression to acute leukemia, than predicted based on the original diagnosis of RAEB, suggesting that MDS with monocytosis may represent a subgroup distinct from MDS or CMML.