Pietro Antonio Bernabei

HERG potassium channels are constitutively expressed in primary human acute myeloid leukemias and regulate cell proliferation of normal and leukemic hemopoietic progenitors.

An important target in the understanding of the pathogenesis of acute myeloid leukemias (AML) relies on deciphering the molecular features of normal and leukemic hemopoietic progenitors. In particular, the analysis of the mechanisms involved in the regulation of cell proliferation is decisive for the establishment of new targeted therapies. To gain further insight into this topic we report herein a novel approach by analyzing the role of HERG K+ channels in the regulation of hemopoietic cell proliferation. These channels, encoded by the human ether-a-gò-gò-related gene (herg), belong to a family of K+ channels, whose role in oncogenesis has been recently demonstrated. We report here that herg is switched off in normal peripheral blood mononuclear cells (PBMNC) as well as in circulating CD34+ cells, however, it is rapidly turned on in the latter upon induction of the mitotic cycle. Moreover, hergappears to be constitutively activated in leukemic cell lines as well as in the majority of circulating blasts from primary AML. Evidence is also provided that HERG channel activity regulates cell proliferation in stimulated CD34+ as well as in blast cells from AML patients. These results open new perspectives on the pathogenetic role of HERG K+ channels in leukemias.

Natural fluorescence of white blood cells: spectroscopic and imaging study

Autofluorescence has been proved to be an intrinsic parameter of biological substrates that may aid in both the characterization of the physiological state and the discrimination of pathological from normal conditions of cells, tissues and organs. In this work, the fluorescence properties of human white blood cells have been studied in suspension and on single cells at microscopy. The results indicate that suspensions of agranulocytes and granulocytes differ in the amplitude of the fluorescence signal on excitation at wavelengths in the range 250-370 nm. The differences are particularly enhanced when excitation is performed in the 250-265 nm range. Microspectrofluorometric analysis, performed on single cells, allows several leukocyte families to be characterized. Lymphocytes, monocytes, neutrophils and eosinophils can be distinguished according to the intensity and spectral shape of the autofluorescence emission in the visible range from 440 to 580 nm. Both the nature and extent of the differences change when the excitation wavelength is moved from 366 to 436 nm. Differences in the intrinsic metabolic engagement, rather than in the cell dimensions, seem to be responsible for the differences observed between the leukocyte populations. The results identify interesting perspectives for autofluorescence as a discriminating parameter in the differential counting of human white blood cells.

Platelet-derived growth factor(s) mitogenic activity in patients with myeloproliferative disease

Summary. Platelet‐derived growth factor has been invoked in the pathogenesis of medullary fibrosis during myeloproliferative disorders. In this study we compared the mitogenic activity of heat‐stable platelet‐derived growth factor(s) from 13 patients suffering from myeloproliferative disorders with that of a normal group. The test was carried out on G0 growth arrested Balb/c 3T3 fibroblasts incubated with various concentrations of platelet extracts, determining the entrance into the S phase by means of [14C]thymidine uptake. The incorporation curves of [14C]thymidine by the fibroblast culture, under the effect of pathological extracts, were consistently lower than the control curve, indicating a lower level of PDGF(s) in platelets from patients. The greatest depression of this activity was found to be associated with highest degree of medullary fibrosis (agnogenic myeloid metaplasia patient group), in agreement with the hypothesis that fibroblast activation within bone marrow during myeloproliferative disorders might be correlated with a PDGF(s) release in the bone marrow environment.

Multispectral imaging autofluorescence microscopy for the analysis of lymph-node tissues.

Abstract Although histochemical and immunohistochemical methods are the standard procedures in diagnosis of lymphoproliferative disorders, useful improvements in evidencing histopathologic manifestations can be obtained with the introduction of tissue autofluorescence analyses. We used microspectrofluorometry and a Multispectral Imaging Autofluorescence Microscopy (MIAM) technique to analyze lymph-node biopsies from patients with lymphoadenopathy of different origins. Images of tissue autofluorescence were obtained by excitation at 365 nm of lymph-node sections and sequential detection with interference filters (50 nm bandwidth) peaked at 450, 550 and 658 nm. Monochrome images were combined together in a single red–green–blue color image. Most of the fluorescence was observed within the blue spectral band because of large contributions from extracellular collagen and elastin fibers as well as from reduced form of intracellular nicotinamide adenine dinucleotide (phosphate). Autofluorescence imaging shows morphological differences between neoplastic and non-neoplastic tissues. The reactive hyperplasia samples show the typical lymph-node organization with weak fluorescent follicles separated by high fluorescent connective trabeculae. In the neoplastic lymph nodes the loss of follicle organization is observed. Consequently, MIAM permits to discriminate between non-neoplastic and neoplastic tissues on the basis of their autofluorescence pattern. Multispectral imaging of tissue autofluorescence may present some advantages with respect to standard histochemical microscopy since it (1) does not require any chemical manipulation of samples; (2) gives real-time results performing the analysis immediately upon specimen resection; and (3) supplies a representation of the biological structure organization linked to endogenous fluorophores.

Modeled gravitational unloading triggers differentiation and apoptosis in preosteoclastic cells

Gravity acts permanently on organisms as either static or dynamic stimulation. Understanding the influence of gravitational and mechanical stimuli on biological systems is an intriguing scientific problem. More than two decades of life science studies in low g, either real or modeled by clinostats, as well as experimentation with devices simulating different types of controlled mechanical stimuli, have shown that important biological functions are altered at the single cell level. Here, we show that the human leukemic line FLG 29.1, characterized as an osteoclastic precursor model, is directly sensitive to gravitational unloading, modeled by a random positioning machine (RPM). The phenotypic expression of cytoskeletal proteins, osteoclastic markers, and factors regulating apoptosis was investigated using histochemical and immunohistochemical methods, while the expression of the corresponding genes was analyzed using RT‐PCR. A quantitative bone resorption assay was performed. Autofluorescence spectroscopy and imaging were applied to gain information on cell metabolism. The results show that modeled hypogravity may trigger both differentiation and apoptosis in FLG 29.1 cells. Indeed, when comparing RPM versus 1 × g cultures, in the former we found cytoskeletal alterations and a marked increase in apoptosis, but the surviving cells showed an osteoclastic‐like morphology, overexpression of osteoclastic markers and the ability to resorb bone. In particular, the overexpression of both RANK and its ligand RANKL, maintained even after return to 1 × g conditions, is consistent with the firing of a differentiation process via a paracrine/autocrine mechanism. J. Cell. Biochem. 98: 65–80, 2006.

Functional and structural interactions between osteoblastic and preosteoclastic cells in vitro

Osteoblasts are involved in the bone resorption process by regulating osteoclast maturation and activity. In order to elucidate the mechanisms underlying osteoblast/preosteoclast cell interactions, we developed an in vitro model of co-cultured human clonal cell lines of osteoclast precursors (FLG 29.1) and osteoblastic cells (Saos-2), and evaluated the migratory, adhesive, cytochemical, morphological, and biochemical properties of the co-cultured cells. In Boyden chemotactic chambers, FLG 29.1 cells exhibited a marked migratory response toward the Saos-2 cells. Moreover, they preferentially adhered to the osteoblastic monolayer. Direct co-culture of the two cell types induced: (1) positive staining for tartrate-resistant acid phosphatase in FLG 29.1 cells; (2) a decrease of the alkaline phosphatase activity expressed by Saos-2 cells; (3) the appearance of typical ultrastructural features of mature osteoclasts in FLG 29.1 cells; (4) the release into the culture medium of granulocyte-macrophage colony stimulating factor. The addition of parathyroid hormone to the co-culture further potentiated the differentiation of the preosteoclasts, the cells tending to fuse into large multinucleated elements. These in vitro interactions between osteoblasts and osteoclast precursors offer a new model for studying the mechanisms that control osteoclastogenesis in bone tissue.

Dependence of leukemic cell autofluorescence patterns on the degree of differentiation

The characterisation of leukemic cell autofluorescence during differentiation, induced by 12-O-tetradecanoylphorbol 13-acetate and all-trans retinoic acid, was performed by autofluorescence microspectroscopy and multispectral imaging autofluorescence microscopy. We have found that a dependence exists between the cell autofluorescence pattern and the degree of cell differentiation. When cells differentiate, their autofluorescence emission changes, following the morphological and functional rearrangement of cell structures. A decrease in emission intensity and a different distribution of endogenous fluorophores are observed. Thus, autofluorescence monitoring on living cells is a potentially useful tool for in vitro study of the differentiation processes. Furthermore, different maturation steps can be distinguished on the basis of the cell fluorescence pattern, leading the way to future application of the technique in diagnostics.

Effects of fludarabine and gemcitabine on human acute myeloid leukemia cell line HL 60 : Direct comparison of cytotoxicity and cellular Ara-C uptake enhancement

This study was designed to compare the effects of fludarabine and gemcitabine on cytosine arabinoside (Ara-C) uptake and retention, and their specific cytotoxicity on HL 60 human acute myeloid leukemia cells. The leukemic blasts were exposed to either drug at equimolar concentrations (10 microM) for 3 h and further incubated with Ara-C (5 microM), added immediately (day 0) or after an interval of 24 h in cells were kept in a drug free medium (day 1). On day 0, leukemic cells exposed to fludarabine 10 microM had a significant (P<0.01) increase in Ara-C uptake (297 +/- 11 pmol/10(7) cells) with respect to control cells (not pre-treated: 195 +/- 10 pmol/10 (7) cells). After treatment of leukemic cells with fludarabine, cytoplasmic Ara-C peaked after 180 min of exposure, as well as nuclear bound Ara-C. At the same time, a significant decrease in the number of S-phase leukemic cells, consistent with depressed [3 H]TdR uptake was observed. Although on day 0 gemcitabine 10 microM did not have potentiating effects on Ara-C uptake, it showed a high degree of intrinsic cytotoxicity as a single agent(clear from cell cycle distribution, [3H]TdR uptake, plating efficiency (PE) data and percentage of apoptotic cells). Cells exposed to gemcitabine, on the other hand, showed on day 1 a significant increase in Ara-C uptake (2.4 x control values in the cytoplasmic and 3x in the nuclear fractions) and a reduced number of S-phase blasts, [3H]TdR uptake and PEs, as well as an increased apoptotic cell death. Evidently, it is possible to modulate Ara-C uptake by leukemic cells with gemcitabine. Although this effect is similar to that demonstrated with fludarabine, its kinetics and time of efficacy are different and also, because of its intrinsic higher cytoxicity and lack of important side effects, gemcitabine could be considered a suitable candidate for Ara-C association therapy in acute leukemia.

In Vitro Activity of Vinorelbine on Human Leukemia Cells

Abstract Vinorelbine (VNR) is a semi-synthetic Vinca rosea alkaloid that has been employed both as a single agent and in combination, and has shown significant antitumor activity. As little is known about VNR activity on human leukemia, we studied its In Vitro cytotoxic effect on human leukemia cell lines (FLG 29.1, HL60, K562, Balm 4, CEM and Daudi) and on fresh leukemia cells from 28 patients: 2 acute myeloid leukemia (AML); 3 chronic myeloid leukemia in blas-tic phase (CML-BP); 5 acute lymphoblastic leukemia (ALL); 18 B-chronic lymphatic leukemia (B-CLL), employing the colorimetric INT assay and determining the IC50. We observed that VNR exerts its cytotoxic activity on leukemic cell lines in a dose-dependent fashion. The lymphoid cell lines appear more sensitive than the myeloid ones to the VNR-dependent growth inhibition. A similar pattern was noticed for leukemia cells in primary cultures. VNR is not effective on CML-BP cells, shows variable activity on the AML and ALL cells and is very effective against B-CLL cells. VNR inhibited the growth of fresh B-CLL cells from 15 of 18 patients, the IC50 doses ranging from 4 ng/ml to 83 μg/ml (doses coinciding with the plasma levels obtained in clinics). These observations strongly suggest that VNR could be useful in clinics for the treatment of B-CLL.

A new method based on contact surface profilometry for quantitative measurement of resorbed bone volume.

Bone is a dynamic tissue. Its continuous remodeling depends on the balance between bone formation and bone resorption. These two processes are carried out by specialized cells called osteoblast and ostreoclast respectively. The osteoclastic bone resorption consists in degradation of the mineral and collagen components of bone. The study of bone turnover requires accurate assessment of osteoclastic bone resorption, that becomes even more important in pathologic bone loss due to the uncoupling between bone formation and bone resorption. Osteoclastic activity is diffucult to measure. Many techniques, generally based on the detection of the resorbing lacunae (lacunae (pits) due to the bone degradation, allow to estimate bone resorption, but none of them quantitatively and directly measures the volume of resorbed bone. We propose a reliable and relatively simple method, based on contact surfact profilometry, to evaluate directly and quantitatively the volume of resorbed bone. The method has the following advantages: