Human chronic lymphocytic leukemia B cells can escape DNA damage-induced apoptosis through the nonhomologous end-joining DNA repair pathway

Nonhomologous end-joining (NHEJ) DNA factors maintain genomic stability through their DNA double-strand break (DSB) repair and telomere-associated activities. Unrepaired or misrepaired DSBs can lead to apoptotic death or chromosomal damage. The B cells of some B-chronic lymphocytic leukemia (B-CLL) patients are resistant to radiation-induced apoptosis in vitro. We show here that the novel DNA-dependent protein kinase (DNA-PK) inhibitor, NU7026 (2-(morpholin-4-yl)-benzo[h]chomen-4-one), and the phosphatidylinositol 3 (PI-3) kinase inhibitor, wortmannin, restored sensitivity to DNA damage-induced apoptosis of otherwise resistant cells. These resistant malignant B cells also escaped DSB-induced apoptosis following exposure to etoposide or neocarzinostatin. We found that at 15 minutes after irradiation, the levels of NHEJ (as measured by an in vitro DSB end-ligation assay) and DNA-PK catalytic subunit (DNA-PKcs) activity were, respectively, 2-fold and 4-fold higher in radio-resistant than in radio-sensitive B-CLL cells or Epstein-Barr virus (EBV)-transformed B cells. Ku70/Ku80 heterodimer DNA end-binding activity was also 2- to 3-fold higher in the resistant B-CLL cell subset compared with the sensitive B-CLL cell subset. Our results provide the first evidence that overactivating the NHEJ DNA repair pathway impairs DNA damage-induced apoptosis in malignant B cells and that this may contribute to their resistance to current chemotherapy.     

Induction of long-term potentiation is associated with major ultrastructural changes of activated synapses.

Long-term potentiation (LTP), an increase in synaptic efficacy believed to underlie learning and memory mechanisms, has been proposed to involve structural modifications of synapses. Precise identification of the morphological changes associated with LTP has however been hindered by the difficulty in distinguishing potentiated or activated from nonstimulated synapses. Here we used a cytochemical method that allowed detection in CA1 hippocampus at the electron microscopy level of a stimulation-specific, D-AP5-sensitive accumulation of calcium in postsynaptic spines and presynaptic terminals following application of high-frequency trains. Morphometric analyses carried out 30-40 min after LTP induction revealed dramatic ultrastructural differences between labeled and nonlabeled synapses. The majority of labeled synapses (60%) exhibited perforated postsynaptic densities, whereas this proportion was only 20% in nonlabeled synaptic contacts. Labeled synaptic profiles were also characterized by a larger apposition zone between pre- and postsynaptic structures, longer postsynaptic densities, and enlarged spine profiles. These results add strong support to the idea that ultrastructural modifications and specifically an increase in perforated synapses are associated with LTP induction in field CA1 of hippocampus and they suggest that a majority of activated contacts may exhibit such changes.     

Analysis of Th1 and Th2 cytokines expressing CD4+ and CD8+ T cells in rheumatoid arthritis by flow cytometry

OBJECTIVE: A Th1/Th2 cytokine imbalance with a predominance of Th1 cytokines has been suggested to be of pathogenetic importance in rheumatoid arthritis (RA). To evaluate the role of Th1/Th2 cytokines in RA, we used intracellular cytokine flow cytometry to determine cytokine profiles of CD4+ and CD8+ T cells in 34 peripheral blood (PB) and 10 synovial fluid (SF) samples from patients with RA. Results were compared with 10 PB samples from healthy controls (HC) and 5 SF samples from patients with non-RA synovitis. METHODS: After stimulating cells with PMA and ionomycin or alternatively with anti-CD3/CD28 in the presence of brefeldin A, intracellular levels of Th1 [interleukin 2 (IL-2), interferon-gamma (IFN-gamma)] and Th2 cytokines (IL-4, IL-5, IL-10, IL-13) were determined for CD3+CD8- (i.e., CD4+ Th1 and Th2 cells) and CD3+CD8+ (i.e., CD8+ Tc1 and Tc2 cells) T cells. RESULTS: The percentages of CD4+ and CD8+ Th1 and Th2 cytokines producing T cells (PB) were similar in patients with RA and healthy controls (HC), with a clear predominance of Th1 cytokines expressing, T cells. With regard to T cell subsets, IFN-gamma-producing T cells were significantly more frequently detected in the CD8+ subset [CD8+: median 45.1% (RA; p < 0.001), 38.2% (HC; p = 0.009) vs CD4+: 10.8%(RA), 17.0% (HC)]. Conversely, IL-2 was found in a higher percentage of CD4+ T cells [CD4+: median 33.4% (RA), 17.9% (HC) vs CD8+: 23.6% (RA), 12.3% (HC)]. Patients not in disease remission tended to have more IFN-gamma-producing CD8+ and IL-2-producing CD4+ T cells than patients in remission [CD8+: median 45.9% (IFN-gamma) vs 23.0% (IFN-gamma); CD4+: median 34.1% (IL-2) vs 18.2% (IL-2)1. In all PB samples, the proportion of T cells producing the Th2 cytokines IL-4, IL-5, IL-10, and IL-13 did not exceed 2%. Cytokine profiles did not differ between patients receiving immunosuppressive treatment and patients treated only with nonsteroidal antiinflammatory drugs. In comparison to PB, RA SF analysis revealed a significant increase in the percentage of IFN-gamma-producing CD4+ (p < 0.001) and CD8+ T cells (p < 0.001). In addition, the percentage of IL-10-producing CD4+ (p < 0.001) as well as CD8+ T cells (p = 0.001) was significantly elevated in SF. However, production of the other Th2 cytokines (IL-4, IL-5, IL-13) was similar in SF and PB. CONCLUSION: These data indicate similar cytokine profiles of T cells in PB of RA patients and healthy controls, with a strong predominance of Th1 cytokines producing T cells in the CD4+ and CD8+ T cell subset of both groups. PB cytokine profiles did not significantly differ in patients with active and non-active disease or between patients receiving and those not receiving immunosuppressive medication. In SF, the proportion of Th1 and Tcl cells was significantly elevated compared to PB, emphasizing the local importance of these cells for inflammation. CD8+ T cells (Tc1 cells) mainly contributed to the production of IFN-gamma, indicating an underestimated role of this cell subset for local cytokine production. The upregulation of IL-10-producing Th2 and Tc2 cells in SF may reflect an insufficient effort to down-regulate chronic inflammation in the joint. Modifying this cytokine imbalance in the joints may be a promising therapeutic approach in RA.     

Corticotropin-releasing activity of the renin-angiotensin system peptides in rat and in man

In this study we investigated in the rat the binding and corticotropin-releasing factor (CRF) activity of various constituents of the renin-angiotensin system and the possible angiotensin II receptor changes following procedures known to alter plasma renin activity. We investigated also the CRF activity of angiotensin II in vitro and in vivo in humans. The CRF activity of peptides was studied by their ability to stimulate ACTH release from pituitary cells. Deleting amino acids from the N-terminus of angiotensin II resulted in decreased CRF activity; while the ED50 for angiotensin II was 2 nM, it increased to about 10 nM for the (2-8)-heptapeptide. Angiotensin I had a weak CRF activity, whereas the substrate angiotensinogen had no stimulatory effect even at a concentration of 100 nM. There was a strong correlation between the activation and binding properties of all peptides tested. Dietary salt load or depletion as well as dexamethasone treatment did not affect the number nor the affinity of pituitary angiotensin II receptors. Angiotensin II had a CRF activity on human pituitary cells in vitro. However, peripherally injected agiotensin II at a pressive dose of 7 ng/kg/min did not produce any ACTH release in normal male volunteers. These data suggest that angiotensin II may play a modulatory role in the physiological regulation of ACTH secretion, but this role might be attributed to the endogenous brain angiotensin II as it is not closely dependent on the angiotensin II plasma levels.     

Matrix metalloproteinases and diabetic foot ulcers: the ratio of MMP-1 to TIMP-1 is a predictor of wound healing

Aims Matrix metalloproteinases (MMPs) play a major role in wound healing: they can degrade all components of the extracellular matrix. In diabetic foot ulcers there is an excess of MMPs and a decrease of the tissue inhibitors of MMPs (TIMPs). This imbalance is probably one cause of impaired healing. However, little is known about changes in MMPs during wound healing. Methods Sixteen patients with neuropathic diabetic foot ulcers participated. Wound fluid was collected regularly during the 12-week follow-up period, for measurement of MMP-1, MMP-2, MMP-8, MMP-9 and TIMP-1. Results were analysed by the degree of wound healing: good healers (defined by a reduction of at least 82% in initial wound surface at 4 weeks) and poor healers (reduction of less than 82% in wound surface at 4 weeks). Results In good healers, levels of MMP-8 and -9 secreted by inflammatory cells decreased earlier. The initial levels of MMP-1 were similar in good and poor healers (P = 0.1) but rose significantly at week 2 in good healers (P = 0.039). There was a significant correlation between a high ratio of MMP-1/TIMP-1 and good healing (r = 0.65, P = 0.008). Receiver Operator Curve (ROC) analysis showed that an MMP-1/TIMP-1 ratio of 0.39 best predicted wound healing (sensitivity = 71%, specificity = 87.5%). Conclusions A high level of MMP-1 seems essential to wound healing, while an excess of MMP-8 and -9 is deleterious, and could be a target for new topical treatments. The MMP-1/TIMP-1 ratio is a predictor of wound healing in diabetic foot ulcers.     

Abnormal function of the bone marrow microenvironment in chronic myelogenous leukemia: role of malignant stromal macrophages

The bone marrow microenvironment supports and regulates the proliferation and differentiation of hematopoietic cells. Dysregulated hematopoiesis in chronic myelogenous leukemia (CML) is caused, at least in part, by abnormalities in CML hematopoietic progenitors leading to altered interactions with the marrow microenvironment. The role of the microenvironment itself in CML has not been well characterized. We examined the capacity of CML stroma to support the growth of long-term culture-initiating cells (LTC-IC) obtained from normal and CML marrow. The growth of normal LTC-IC on CML stroma was significantly reduced compared with normal stroma. This did not appear to be related to abnormal production of soluble factors by CML stroma because normal LTC- IC grew equally well in Transwells above CML stroma as in Transwells above normal stroma. In addition, CML and normal stromal supernatants contained similar quantities of both growth-stimulatory (granulocyte colony-stimulating factor (CSF), interleukin-6, stem cell factor, granulocyte-macrophage CSF, and interleukin-1 beta) and growth- inhibitory cytokines (transforming growth factor-beta, macrophage inflammatory protein-1 alpha, and tumor necrosis factor-alpha). The relative proportion of different cell types in CML and normal stroma was similar. However, polymerase chain reaction and fluorescence in situ hybridization studies showed the presence of bcr-abl-positivo cells in CML stroma, which were CD14+ stromal macrophages. To assess the effect of these malignant macrophages on stromal function, CML and normal stromal cells were separated by fluorescence-activated cell sorting into stromal mesenchymal cell (CD14-) and macrophage (CD14+) populations. CML and normal CD14- cells supported the growth of normal LTC-IC equally well. However, the addition of CML macrophages to normal or CML CD14- mesenchymal cells resulted in impaired progenitor support. This finding indicates that the abnormal function of CML bone marrow stroma is related to the presence of malignant macrophages. In contrast to normal LTC-IC, the growth of CML LTC-IC on allogeneic CML stromal layers was not impaired and was significantly better than that of normal LTC-IC cocultured with the same CML stromal layers. These studies demonstrate that, in addition to abnormalities in CML progenitors themselves, abnormalities in the CML marrow microenvironment related to the presence of malignant stromal macrophages may contribute to the selective expansion of leukemic progenitors and suppression of normal hematopoiesis in CML.     

Alström Syndrome: Mutation Spectrum of ALMS1

Alström Syndrome (ALMS), a recessive, monogenic ciliopathy caused by mutations in ALMS1, is typically characterized by multisystem involvement including early cone‐rod retinal dystrophy and blindness, hearing loss, childhood obesity, type 2 diabetes mellitus, cardiomyopathy, fibrosis, and multiple organ failure. The precise function of ALMS1 remains elusive, but roles in endosomal and ciliary transport and cell cycle regulation have been shown. The aim of our study was to further define the spectrum of ALMS1 mutations in patients with clinical features of ALMS. Mutational analysis in a world‐wide cohort of 204 families identified 109 novel mutations, extending the number of known ALMS1 mutations to 239 and highlighting the allelic heterogeneity of this disorder. This study represents the most comprehensive mutation analysis in patients with ALMS, identifying the largest number of novel mutations in a single study worldwide. Here, we also provide an overview of all ALMS1 mutations identified to date.