Barbro Näsman-Glaser

Inhibitory effects of helenalin and related compounds on 5-lipoxygenase and leukotriene C4 synthase in human blood cells

The sesquiterpene lactone helenalin, which can be isolated from several plant species of the Asteraceae family, is a potent anti-inflammatory and antineoplastic agent. In agreement, alcohol extracts of these plants are used for local external treatment of inflammatory conditions. Since leukotrienes are important mediators in inflammatory processes, the inhibitory effects of helenalin and some derivatives on leukotriene (LT) biosynthesis were studied. Treatment of human platelets with helenalin provoked irreversible inhibition of LTC(4) synthase in a concentration- and time-dependent manner with an IC(50) of 12 microM after a 60 min preincubation. 11alpha,13-Dihydrohelenalin acetate was less potent. Interestingly, individual donors could be divided into two distinct groups with respect to the efficacy of helenalin to suppress platelet LTC(4) synthase. In human granulocytes, helenalin inhibited both the 5-lipoxygenase (IC(50) 9 microM after 60 min preincubation) and LTC(4) synthase in a concentration- and time-dependent fashion. In contrast, the drug was without effect on LTA(4) hydrolase. The GSH-containing adducts (2beta-(S-glutathionyl)-2,3-dihydrohelenalin and 2beta-(S-glutathionyl)-2,3,11alpha,13-tetra hydrohelenalin acetate) did not significantly inhibit LTC(4) synthase. The present results indicate a mechanism for the anti-inflammatory effect of helenalin and related compounds.

T cells in chronic lymphocytic leukemia display dysregulated expression of immune checkpoints and activation markers

Chronic lymphocytic leukemia is characterized by impaired immune functions largely due to profound T-cell defects. T-cell functions also depend on co-signaling receptors, inhibitory or stimulatory, known as immune checkpoints, including cytotoxic T-lymphocyte-associated antigen-4 (CTLA-4) and programmed death-1 (PD-1). Here we analyzed the T-cell phenotype focusing on immune checkpoints and activation markers in chronic lymphocytic leukemia patients (n=80) with different clinical characteristics and compared them to healthy controls. In general, patients had higher absolute numbers of CD3+ cells and the CD8+ subset was particularly expanded in previously treated patients. Progressive patients had higher numbers of CD4+ and CD8+ cells expressing PD-1 compared to healthy controls, which was more pronounced in previously treated patients (P=0.0003 and P=0.001, respectively). A significant increase in antigen-experienced T cells was observed in patients within both the CD4+ and CD8+ subsets, with a significantly higher PD-1 expression. Higher numbers of CD4+ and CD8+ cells with intracellular CTLA-4 were observed in patients, as well as high numbers of proliferating (Ki67+) and activated (CD69+) CD4+ and CD8+ cells, more pronounced in patients with active disease. The numbers of Th1, Th2, Th17 and regulatory T cells were substantially increased in patients compared to controls (P<0.05), albeit decreasing to low levels in pre-treated patients. In conclusion, chronic lymphocytic leukemia T cells display increased expression of immune checkpoints, abnormal subset distribution, and a higher proportion of proliferating cells compared to healthy T cells. Disease activity and previous treatment shape the T-cell profile of chronic lymphocytic leukemia patients in different ways.

Inverse relationship between myeloid maturation and leukotriene C4 synthase expression in normal and leukemic myelopoiesis—consistent overexpression of the enzyme in myeloid cells from patients with chronic myeloid leukemia

OBJECTIVE Leukotriene (LT) C(4) synthase (LTC(4)S) is the key enzyme in the biosynthesis of LTC(4), which has been reported to stimulate the growth of human myeloid progenitor cells and is specifically overproduced in chronic myeloid leukemia (CML). The aim of this study was to clarify the expression of LTC(4)S during normal and leukemic myelopoiesis and to investigate the correlation between abnormal LTC(4)S expression in CML myeloid cells and the activity of the disease-specific tyrosine kinase p210 BCR-ABL. MATERIALS AND METHODS Immature and mature myeloid cell subpopulations were isolated with magnetic cell sorting from healthy volunteer bone marrow (n = 11) and CML patient peripheral blood (n = 8), respectively. The cells were subjected to analysis of LTC(4)S protein expression and activity. Expression of LTC(4)S was investigated in CD16(+) neutrophils from CML patients before and after 1 month of medication with imatinib mesylate (STI571), which is a specific inhibitor of p210 BCR-ABL. RESULTS Among normal cells, the highest enzyme activity was observed in the most immature, CD34(+) progenitor cell-enriched and CD15(+) myelocyte-enriched fractions. Subsequently, LTC(4)S activity decreased with increasing maturity, with only negligible amounts of LTC(4) produced in CD16(+) neutrophils. LTC(4)S was expressed at the protein level in the immature myeloid cell fractions but not in CD16(+) cells. In CML cells, LTC(4)S activity and expression were consistently elevated. Thus, the CML CD34(+) and CD15(+) cell fractions, as well as the CD11b(+) myelocyte/metamyelocyte-enriched fractions, produced 6 to 10 times as much LTC(4) as the corresponding normal cells. Again, enzyme expression was highest in the most immature cells, although evident LTC(4)S expression and activity remained in CML CD16(+) neutrophils. Interestingly, treatment of five CML patients with imatinib mesylate down-regulated the abnormal neutrophil LTC(4)S expression and activity. CONCLUSIONS Expression of LTC(4)S in immature myelopoid cells is in line with a role for this enzyme in myelopoiesis. In addition, consistent overexpression of LTC(4)S in CML and the correlation to p210 BCR-ABL activity suggests that LTC(4)S may be involved in leukemic pathogenesis.

Long-term effects of idiotype vaccination on the specific T-cell response in peripheral blood and bone marrow of multiple myeloma patients.

Objectives:  To elucidate long‐term effects of idiotype (Id) vaccination on Id‐specific T cells of multiple myeloma (MM) patients and compare Id‐specific T‐cell responses of peripheral blood with those of bone marrow (BM).

Metabolism of Granulocyte-Derived Leukotriene A4 in Human Platelets and Respiratory Tissue: Transcellular Formation of Lipoxins and Leukotrienes

Leukotriene (LT)A4, the unstable intracellular intermediate in leukotriene biosynthesis, may be released to the extracellular space by activated leukocytes (1). As a consequence, the metabolism of LTA4 is not restricted to cells with 5-lipoxygenase activity, but can also be exerted by other cell types equipped with LTA4-metabolizing enzymes. Thus, LTA4, released by 5-lipoxygenase expressing cells, may be converted to LTB4 by surrounding erythrocytes (2), endothelial cells (3) or lymphocytes (4), all possessing LTA4 hydrolase activity. Similarly, mast cells (1), endothelial cells (3, 5) and smooth muscle cells (6) have been demonstrated to convert LTA4 to cysteinyl-containing leukotrienes. The present chapter describes some of our recent data regarding the metabolism of synthetic or granulocyte-derived LTA4 in human platelets and respiratory tissue leading to formation of cysteinyl-containing leukotrienes and lipoxins (LX).

Lenalidomide as immune adjuvant to a dendritic cell vaccine in chronic lymphocytic leukemia patients

We previously showed that immunization with ex vivo‐ generated autologous dendritic cells loaded with apoptotic tumor cells (Apo‐DC) potentiated tumor‐specific immunity in chronic lymphocytic leukemia (CLL) patients. Here, we evaluated safety and immunogenicity of Apo‐DC in combination with lenalidomide, granulocyte‐macrophage colony‐stimulating factor (GM‐CSF), and low‐dose cyclophosphamide (CTX).

Modulation of leukotriene signaling inhibiting cell growth in chronic myeloid leukemia

Abstract Although tyrosine kinase inhibitors (TKIs) have dramatically improved clinical outcome in chronic myeloid leukemia (CML), cure rarely occurs. This may be due to BCR-ABL-independent, aberrant signaling pathways, one of which leads to leukotriene (LT) formation. Well-recognized as inflammatory mediators, LT can also affect oncogenic mechanisms of several tumors. We have previously discovered elevated LT-synthesis and up-regulated cysteinyl-LT-inducing enzyme in CML. Here we report on dose-dependent inhibition of CML cell growth exerted by specific blockers of LT-signaling. Thus, the cysteinyl-LT1-receptor-antagonist montelukast significantly reduced the growth of K562, KCL22, and KU812 cells, as well as primary CD34+ blood cells from two CML patients. Adding montelukast to the TKI imatinib caused combined inhibition. No effect was seen on normal bone marrow cells. Similarly, growth inhibition was also observed with the 5-lipoxygenase (LO)-inhibitor BWA4C, the 5-LO-activating-protein-(FLAP)-inhibitor licofelone and the LTB4(BLT1)-receptor-antagonist LY293111. Thus, blocking of aberrant LT-signaling may provide an additional, novel therapeutic possibility in CML.