Retinal Alterations Predict Early Prodromal Signs of Neurodegenerative Disease

Neurodegenerative diseases are an increasingly common group of diseases that occur late in life with a significant impact on personal, family, and economic life. Among these, Alzheimer's disease (AD) and Parkinson's disease (PD) are the major disorders that lead to mild to severe cognitive and physical impairment and dementia. Interestingly, those diseases may show onset of prodromal symptoms early after middle age. Commonly, the evaluation of these neurodegenerative diseases is based on the detection of biomarkers, where functional and structural magnetic resonance imaging (MRI) have shown a central role in revealing early or prodromal phases, although it can be expensive, time-consuming, and not always available. The aforementioned diseases have a common impact on the visual system due to the pathophysiological mechanisms shared between the eye and the brain. In Parkinson's disease, α-synuclein deposition in the retinal cells, as well as in dopaminergic neurons of the substantia nigra, alters the visual cortex and retinal function, resulting in modifications to the visual field. Similarly, the visual cortex is modified by the neurofibrillary tangles and neuritic amyloid β plaques typically seen in the Alzheimer's disease brain, and this may reflect the accumulation of these biomarkers in the retina during the early stages of the disease, as seen in postmortem retinas of AD patients. In this light, the ophthalmic evaluation of retinal neurodegeneration could become a cost-effective method for the early diagnosis of those diseases, overcoming the limitations of functional and structural imaging of the deep brain. This analysis is commonly used in ophthalmic practice, and interest in it has risen in recent years. This review will discuss the relationship between Alzheimer's disease and Parkinson's disease with retinal degeneration, highlighting how retinal analysis may represent a noninvasive and straightforward method for the early diagnosis of these neurodegenerative diseases.

Mitochondria-Targeted Antioxidants, an Innovative Class of Antioxidant Compounds for Neurodegenerative Diseases: Perspectives and Limitations

Neurodegenerative diseases comprise a wide spectrum of pathologies characterized by progressive loss of neuronal functions and structures. Despite having different genetic backgrounds and etiology, in recent years, many studies have highlighted a point of convergence in the mechanisms leading to neurodegeneration: mitochondrial dysfunction and oxidative stress have been observed in different pathologies, and their detrimental effects on neurons contribute to the exacerbation of the pathological phenotype at various degrees. In this context, increasing relevance has been acquired by antioxidant therapies, with the purpose of restoring mitochondrial functions in order to revert the neuronal damage. However, conventional antioxidants were not able to specifically accumulate in diseased mitochondria, often eliciting harmful effects on the whole body. In the last decades, novel, precise, mitochondria-targeted antioxidant (MTA) compounds have been developed and studied, both in vitro and in vivo, to address the need to counter the oxidative stress in mitochondria and restore the energy supply and membrane potentials in neurons. In this review, we focus on the activity and therapeutic perspectives of MitoQ, SkQ1, MitoVitE and MitoTEMPO, the most studied compounds belonging to the class of MTA conjugated to lipophilic cations, in order to reach the mitochondrial compartment.

Purinergic Signaling in Controlling Macrophage and T Cell Functions During Atherosclerosis Development

Atherosclerosis is a hardening and narrowing of arteries causing a reduction of blood flow. It is a leading cause of death in industrialized countries as it causes heart attacks, strokes, and peripheral vascular disease. Pathogenesis of the atherosclerotic lesion (atheroma) relies on the accumulation of cholesterol-containing low-density lipoproteins (LDL) and on changes of artery endothelium that becomes adhesive for monocytes and lymphocytes. Immunomediated inflammatory response stimulated by lipoprotein oxidation, cytokine secretion and release of pro-inflammatory mediators, worsens the pathological context by amplifying tissue damage to the arterial lining and increasing flow-limiting stenosis. Formation of thrombi upon rupture of the endothelium and the fibrous cup may also occur, triggering thrombosis often threatening the patient’s life. Purinergic signaling, i.e., cell responses induced by stimulation of P2 and P1 membrane receptors for the extracellular nucleotides (ATP, ADP, UTP, and UDP) and nucleosides (adenosine), has been implicated in modulating the immunological response in atherosclerotic cardiovascular disease. In this review we will describe advancements in the understanding of purinergic modulation of the two main immune cells involved in atherogenesis, i.e., monocytes/macrophages and T lymphocytes, highlighting modulation of pro- and anti-atherosclerotic mediated responses of purinergic signaling in these cells and providing new insights to point out their potential clinical significance.

Repositioning of Tak-475 In Mevalonate Kinase Disease: Translating Theory Into Practice

BACKGROUND

Mevalonate Kinase Deficiency (MKD, OMIM #610377) is a rare autosomal recessive metabolic and inflammatory disease. In MKD, defective function of the enzyme mevalonate kinase, due to a mutation in the MVK gene, leads to the shortage of mevalonate- derived intermediates, which results in unbalanced prenylation of proteins and altered metabolism of sterols. These defects lead to a complex multisystem inflammatory and metabolic syndrome.

OBJECTIVE

Although biologic therapies aimed at blocking the inflammatory cytokine interleukin- 1 can significantly reduce inflammation, they cannot completely control the clinical symptoms that affect the nervous system. For this reason, MKD can still be considered an orphan drug disease. The availability of MKD models reproducing the MKD-systematic inflammation, is crucial to improve the knowledge on its pathogenesis, which is still unknown. New therapies are also required in order to improve pateints' conditions and their quality of life.

METHODS

MKD-cellular models can be obtained by biochemical inhibition of mevalonatederived isoprenoids. Of note, these cells present an exaggerated response to inflammatory stimuli that can be reduced by treatment with zaragozic acid, an inhibitor of squalene synthase, thus increasing the availability of isoprenoids intermediates upstream the enzymatic block.

RESULTS

A similar action might be obtained by lapaquistat acetate (TAK-475, Takeda), a drug that underwent extensive clinical trials as a cholesterol lowering agent 10 years ago, with a good safety profile.

CONCLUSIONS

Here we describe the preclinical evidence supporting the possible repositioning of TAK-475 from its originally intended use to the treatment of MKD and discuss its potential to modulate the mevalonate pathway in inflammatory diseases.

Ibrutinib synergizes with MDM-2 inhibitors in promoting cytotoxicity in B chronic lymphocytic leukemia

OBJECTIVE

The aim of this study was to investigate the anti-leukemic activity of the Bruton tyrosine kinase inhibitor Ibrutinib in combination with the small molecule MDM-2 inhibitor Nutlin-3 in preclinical models.

METHODS

The potential efficacy of the Ibrutinib/Nutlin-3 combination was evaluated in vitro in a panel of B leukemic cell lines (EHEB, JVM-2, JVM-3, MEC-1, MEC-2) and in primary B-chronic lymphocytic leukemia (B-CLL) patient samples, by assessing cell viability, cell cycle profile, apoptosis and intracellular pathway modulations. Validation of the combination therapy was assessed in a B leukemic xenograft mouse model.

RESULTS

Ibrutinib exhibited variable anti-leukemic activity in vitro and the combination with Nutlin-3 synergistically enhanced the induction of apoptosis independently from the p53 status. Indeed, the Ibrutinib/Nutlin-3 combination was effective in promoting cytotoxicity also in primary B-CLL samples carrying 17p13 deletion and/or TP53 mutations, already in therapy with Ibrutinib. Molecular analyses performed on both B-leukemic cell lines as well as on primary B-CLL samples, while confirming the switch-off of the MAPK and PI3K pro-survival pathways by Ibrutinib, indicated that the synergism of action with Nutlin-3 was independent by p53 pathway and was accompanied by the activation of the DNA damage cascade signaling through the phosphorylation of the histone protein H2A.X. This observation was confirmed also in the JVM-2 B leukemic xenograft mouse model.

CONCLUSIONS

Taken together, our data emphasize that the Ibrutinib/Nutlin-3 combination merits to be further evaluated as a therapeutic option for B-CLL.

Pre-eclampsia affects procalcitonin production in placental tissue

PROBLEM

Procalcitonin (PCT) is the prohormone of calcitonin which is usually released from neuroendocrine cells of the thyroid gland (parafollicular) and the lungs (K cells). PCT is synthesized by almost all cell types and tissues, including monocytes and parenchymal tissue, upon LPS stimulation. To date, there is no evidence for PCT expression in the placenta both in physiological and pathological conditions.

METHOD

Circulating and placental PCT levels were analysed in pre-eclamptic (PE) and control patients. Placental cells and macrophages (PBDM), stimulated with PE sera, were analysed for PCT expression. The effect of anti-TNF-α antibody was analysed.

RESULTS

Higher PCT levels were detected in PE sera and in PE placentae compared to healthy women. PE trophoblasts showed increased PCT expression compared to those isolated from healthy placentae. PE sera induced an upregulation of PCT production in macrophages and placental cells. The treatment of PBDM with PE sera in the presence of anti-TNF-α completely abrogated the effect induced by pathologic sera.

CONCLUSION

Trophoblast cells are the main producer of PCT in PE placentae. TNF-α, in association with other circulating factors present in PE sera, upregulates PCT production in macrophages and normal placental cells, thus contributing to the observed increased in circulating PCT in PE sera.

PI3K isoform inhibition associated with anti Bcr-Abl drugs shows in vitro increased anti-leukemic activity in Philadelphia chromosome-positive B-acute lymphoblastic leukemia cell lines

B-acute lymphoblastic leukemia (B-ALL) is a malignant disorder characterized by the abnormal proliferation of B-cell progenitors. Philadelphia chromosome-positive (Ph+) B-ALL is a subtype that expresses the Bcr-Abl fusion protein which represents a negative prognostic factor. Constitutive activation of the phosphatidylinositol 3-kinase/Akt/mammalian target of rapamycin (PI3K/Akt/mTOR) network is a common feature of B-ALL, influencing cell growth and survival. In the present study, we aimed to investigate the efficacy of PI3K isoform inhibition in B-ALL cell lines harboring the Bcr-Abl fusion protein.We studied the effects of anti Bcr-Abl drugs Imatinib, Nilotinib and GZD824 associated with PI3K isoform inhibitors. We used a panel of six compounds which specifically target PI3K isoforms including the pan-PI3K inhibitor ZSTK474, p110α BYL719 inhibitor and the dual p110γ/p110δ inhibitor IPI145. The effects of single drugs and of several drug combinations were analyzed to assess cytotoxicity by MTS assays, apoptosis and autophagy by flow cytometry and Western blot, as well as the phosphorylation status of the pathway.ZSTK474, BYL719 and IPI145 administered in combination with imatinib, nilotinib and GZD824 for 48 h, decreased cell viability, induced apoptosis and autophagy in a marked synergistic manner.These findings suggest that selected PI3K isoform inhibitors used in combination with anti Bcr-Abl drugs may be an attractive novel therapeutic intervention in Ph+ B-ALL.

Complement component C1q as potential diagnostic but not predictive marker of preeclampsia

PROBLEM

We have previously found that C1q is constitutively expressed by invading trophoblast and endothelial cells of decidua and contributes to vascular and tissue remodeling. Based on these findings, we sought to determine whether there were changes in the circulating level of C1q that may be used as a diagnostic and predictive marker of preeclampsia.

METHOD OF STUDY

We measured the levels of C1q, C4, and complement activation products in serum or plasma of normal pregnant women and preeclamptic patients from different cohorts.

RESULTS

We observed a marked decrease in the concentration of C1q associated with a reduced level of C4 in preeclamptic patients as compared to matched healthy pregnant woman but no significant difference in the circulating level of the activating products C5a and the soluble terminal complement complex sC5b-9. Analysis of serum samples collected at early phase of pregnancy from women who later developed preeclampsia failed to show a decrease in C1q level.

CONCLUSION

The results of the present investigation demonstrate that low levels of C1q and C4 are associated with preeclampsia but cannot be used as predictive markers.

Sodium dichloroacetate exhibits anti-leukemic activity in B-chronic lymphocytic leukemia (B-CLL) and synergizes with the p53 activator Nutlin-3

The anti-leukemic activity of the mitochondria-targeting small molecule sodium dichloroacetate (DCA), used alone and in association with the small molecule inhibitor of the p53/MDM2 interaction Nutlin-3, was analyzed in primary B-chronic lymphocytic leukemia (B-CLL) samples (n=22), normal peripheral blood cells (n=10) and in p53wild-type EHEB, JVM-2, JVM-3 B lymphoblastoid cell lines. DCA exhibited a dose-dependent anti-leukemic activity in both primary B-CLL and B leukemic cell lines with a functional p53 status and showed a synergistic cytotoxic activity when used in combination with Nutlin-3. At the molecular level, DCA positively regulated p53 activity, as documented by post-transcriptional modifications of p53 protein and synergized with Nutlin-3 in increasing the expression of the p53-target genes MDM2, PUMA, TIGAR and in particular p21. The potential role of p21 in mediating the DCA+Nutlin-3 anti-leukemic activity was underscored in knocking-down experiments. Indeed, transfection of leukemic cells with p21 siRNAs significantly decreased the DCA+Nutlin-3-induced cytotoxicity. Taken together, our data emphasize that DCA is a molecule that merits to be further evaluated as a chemotherapeutic agent for B-CLL, likely in combination with other therapeutic compounds.

Potential role of circulating microRNAs as early markers of preeclampsia

OBJECTIVE

To identify microRNAs (miRNAs) differentially expressed at early stages of gestation (12-14 weeks) in the serum of pregnant women, who later developed severe preeclampsia (sPE) in the third trimester of pregnancy (n = 24) compared to women with normal pregnancy (n = 24).

MATERIALS AND METHODS

Sera from 12-14-week-gestation whole blood were subjected to microarray analysis with TaqMan Low Density Array chips (human microRNA panel V3.0), and to quantitative real-time polymerase chain reaction.

RESULTS

By using the TaqMan Low Density Array chip technology, 19 mature miRNAs appeared differentially expressed in the group of women who later developed sPE as compared to normal women. The expression of four miRNAs (miR-1233, miR-520, miR-210, miR-144) was validated by quantitative real-time polymerase chain reaction analysis. MiR-1233 was the most overexpressed in the serum of women who later developed sPE.

CONCLUSION

Circulating miRNAs deserve further investigation in order to explore their potential role in the pathogenesis of preeclampsia. In particular, miR-1233 might represent a potential marker of early sPE.

Levels of circulating TNF-related apoptosis-inducing ligand in celiac disease

It has previously been demonstrated that the circulating levels of TNF-related apoptosis-inducing ligand (TRAIL) are significantly lower in patients with type 1 diabetes (T1D) than in normal age- and gender-matched controls. Since celiac disease (CD) is often associated with T1D, a retrospective study was performed to analyze the sera of a cohort of pediatric subjects: i) patients with CD at onset (n=100); ii) patients with potential CD (n=45); iii) patients with CD associated with other auto-immune diseases (n=17); and iv) patients with eosinophilic esophagitis (n=15). Among the patients with CD, 49 were also analyzed after six months on a gluten-free diet, while data were also available for 13 patients after one year on a gluten-free diet. No significant differences were found in the circulating levels of TRAIL between the patients with CD and the patients with either eosinophilic esophagitis or potential CD. Patients with CD associated with other auto-immune diseases showed significantly lower levels of TRAIL when compared with patients with CD alone. The gluten-free diet did not significantly modify the levels of circulating TRAIL at 6 or 12 months. Thus, although T1D and CD share common immunological features, the circulating levels of TRAIL show a significant difference between the two pathologies, and do not appear to be modulated in CD.

Soluble TRAIL is present at high concentrations in seminal plasma and promotes spermatozoa survival

The expression of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL(TNFSF10)) and of its receptors (TRAILR1, TRAILR2, TRAILR3, and TRAILR4) have been documented in testis, but the presence of soluble TRAIL in seminal fluid, as well as the potential physiopathological role of the TRAIL/TRAILR system in spermatozoa, has not been previously investigated. Male donors (n=123) among couples presenting for infertility evaluation were consecutively enrolled in this study. The presence of soluble TRAIL was analyzed in seminal samples by ELISA, while the surface expression of TRAIL receptors was investigated by flow cytometry. High levels of soluble TRAIL were detected in seminal plasma (median, 11 621 pg/ml and mean±s.d., 13 371±8367 pg/ml) and flow cytometric analysis revealed a variable expression of TRAIL receptors in the sperm cellular fraction among different subjects. In addition, the effect of physiologically relevant concentrations of recombinant TRAIL was investigated on survival and motility of spermatozoa. Of interest, the in vitro exposure of capacitated spermatozoa to recombinant TRAIL (10 ng/ml) significantly preserved their overall survival. Therefore, the present study demonstrates for the first time the presence of elevated levels of the anti-inflammatory cytokine TRAIL in seminal fluids. Moreover, the demonstration that recombinant TRAIL promotes spermatozoa survival after capacitation suggests potential therapeutic implications.

NF-κB pathways in hematological malignancies

The nuclear factor κB or NF-κB transcription factor family plays a key role in several cellular functions, i.e. inflammation, apoptosis, cell survival, proliferation, angiogenesis, and innate and acquired immunity. The constitutive activation of NF-κB is typical of most malignancies and plays a major role in tumorigenesis. In this review, we describe NF-κB and its two pathways: the canonical pathway (RelA/p50) and the non-canonical pathway (RelB/p50 or RelB/p52). We then consider the role of the NF-κB subunits in the development and functional activity of B cells, T cells, macrophages and dendritic cells, which are the targets of hematological malignancies. The relevance of the two pathways is described in normal B and T cells and in hematological malignancies, acute and chronic leukemias (ALL, AML, CLL, CML), B lymphomas (DLBCLs, Hodgkin's lymphoma), T lymphomas (ATLL, ALCL) and multiple myeloma. We describe the interaction of NF-κB with the apoptotic pathways induced by TRAIL and the transcription factor p53. Finally, we discuss therapeutic anti-tumoral approaches as mono-therapies or combination therapies aimed to block NF-κB activity and to induce apoptosis (PARAs and Nutlin-3).

Upregulation of SOCS-1 by Nutlin-3 in acute myeloid leukemia cells but not in primary normal cells

OBJECTIVE

It has been shown that SOCS-1 plays an important role in the proper control of cytokine/growth factor responses and acts as a tumor suppressor in acute myeloid leukemias. Therefore, the objective of the present study was to evaluate the in vitro effect of treatment with Nutlin-3, a small molecule inhibitor of the MDM2/p53 interaction, on the expression of the suppressor of cytokine signaling 1 in primary acute myeloid leukemia cells and in myeloid cell lines with differential p53 status.

METHOD

The expression of the suppressor of cytokine signaling 1 was quantitatively analyzed by real-time PCR in myeloid p53wild-type (OCI and MOLM) and p53null HL-60, leukemic cell lines, in patient-derived acute myeloid leukemia blasts, and in primary normal cell types, such as macrophages, endothelial cells, and bone marrow mesenchymal stem cells. The p53-dependence of the suppressor of cytokine signaling 1 upregulation that is induced by Nutlin-3 was analyzed in experiments performed using siRNA for p53, while the functional upregulation of the suppressor of cytokine signaling 1 was analyzed by assessing the levels of phosphorylated STAT-3.

RESULTS

Nutlin-3 significantly upregulated the transcription of the suppressor of cytokine signaling 1 in p53wild-type OCI and MOLM but not in p53deleted p53null HL60, myeloid leukemic cell lines, as well as in primary acute myeloid leukemia blasts. Conversely, and somewhat unexpectedly, Nutlin-3 did not modulate the suppressor of cytokine signaling 1 expression in primary normal macrophages, endothelial cells, and bone marrow mesenchymal stem cells. The p53-dependent upregulation of the suppressor of cytokine signaling 1 by Nutlin-3 was associated with the downregulation of phosphorylated STAT-3, a major molecular target of the suppressor of cytokine signaling 1.

CONCLUSION

Overall, our data suggest a potential role for the suppressor of cytokine signaling 1 as a therapeutic target of Nutlin-3 in p53 wild-type acute myeloid leukemias.

MDM2 non-genotoxic inhibitors as innovative therapeutic approaches for the treatment of pediatric malignancies

Since the discovery of p53 as "guardian of the genome", a large number of efforts have been put in place in order to find molecular strategies aiming to restore p53 wild-type functions, particularly in the light of the fact that its pathway results ineffective in most tumors even though they have non-mutated p53. In this context, pediatric cancers, that are mostly p53 wild-type at the time of diagnosis, represent an ideal target for such therapeutic approach. Within the several mechanisms and proteins ruling p53 activity, the murine double minute 2 (MDM2) is its crucial negative regulator, frequently found overexpressed in p53-wild-type tumors. The development of new technologies such as nuclear magnetic resonance structure analyses, computational structure-based design studies, and library peptides screening have recently led to the discovery and characterization of a large number of compounds belonging to different chemical families that are able to target the interaction p53-MDM2, rescuing the p53 wild-type pathway with an overall pro-apoptotic and anticancer activity. Within the preclinical assessment of these molecules, the cis-imidazoline analogue Nutlin-3 has definitely attracted great interest for its in vitro and in vivo antitumor activity in several pediatric cancer models, either as single agent on in combination with standard chemotherapy. In this light, the aim of this review is to summarize the main preclinical evidences of the potential of MDM2 inhibitors for the treatment of childhood cancers and the key suggestions coming from their assessment in the treatment of adult cancers as proof of concept for future pediatric clinical studies.

Hiv-1 tat protein suppresses the nerve growth-factor (ngf)-mediated differentiation of PC12 rat pheochromocytoma cell-line

In order to evaluate the effect of the regulatory human immunodeficiency virus-type 1 (HIV-1) Tat protein on the process of neuronal differentiation, two tat-transfected and mock-transfected PC12 cell lines were cultured in the absence or presence of 100-1000 ng/ml of nerve growth factor (NGF). As expected, NGF was able to induce a clearcut morphological differentiation of mock-transfected PC12 into sympathetic-like neurons, also reducing the percentage of cells in S phase. On the other hand, NGF was unable to reduce the percentage of PC12-tat cells in S phase and/or to induce their neuronal differentiation. Only the addition in culture of 5 mu g/ml neutralizing anti-Tat antibody plus 1000 ng/ml NGF was effective in decreasing the percentage of PC12-tat in S phase and inducing partial signs of neuronal differentiation in serum-free cultures. The ability of Tat protein to suppress the neuronal differentiation pathway controlled by NGF further contribute to the definition of its role in tumor promotion during the course of HTV-1 disease.

The sorafenib plus nutlin-3 combination promotes synergistic cytotoxicity in acute myeloid leukemic cells irrespectively of FLT3 and p53 status

BACKGROUND

Both the multi-kinase inhibitor sorafenib and the small molecule inhibitor of the MDM2/p53 interaction, nutlin-3, used alone, have shown promising anti-leukemic activity in acute myeloid leukemia cells. Thus, in this study we investigated the effect of the combination of sorafenib plus nutlin-3 in acute myeloid leukemia.

DESIGN AND METHODS

Primary acute myeloid leukemia blasts (n=13) and FLT3(wild-type)/p53(wild-type) (OCI-AML3), FLT3(mutated)/p53(wild-type) (MOLM), FLT3(mutated)/p53(mutated) (MV4-11), FLT3(wild-type)/p53(deleted) (HL60) or FLT3(wild-type)/p53(mutated) (NB4) acute myeloid cell lines were exposed to sorafenib, used alone or in association with nutlin-3 at a 1:1 ratio, in a range of clinically achievable concentrations (1-10 μM). Induction of apoptosis and autophagy was evaluated by transmission electron microscopy and by specific flow cytometry analyses. The levels of Mcl-1, p53 and Bak proteins were analyzed by western blotting. Knock-down of Bax and Bak gene expression was performed in transfection experiments with specific short interfering RNA.

RESULTS

The sorafenib+nutlin-3 drug combination exhibits synergistic cytotoxicity in primary acute myeloid leukemia blasts and in acute myeloid leukemia cell lines with maximal cytotoxicity in FLT3(mutated) MV4-11 and MOLM, followed by the FLT3(wild-type) OCI-AML3, HL60 and NB4 cell lines. The cytotoxic activity of sorafenib+nutlin-3 was characterized by an increase of both apoptosis and autophagy. Moreover, Bax and Bak showed prominent roles in mediating the decrease of cell viability in response to the drug combination in p53(wild-type) OCI-AML3 and p53(deleted) HL-60 cells, respectively, as demonstrated in transfection experiments performed with specific short interfering RNA.

CONCLUSIONS

Our data demonstrate that acute myeloid leukemia cells show a variable but overall good susceptibility to the innovative therapeutic combination of sorafenib+nutlin-3, which differentially involves the pro-apoptotic Bcl-2 family members Bax and Bak in p53(wild-type) and p53(deleted) cells.

Fine tuning of protein kinase C (PKC) isoforms in cancer: shortening the distance from the laboratory to the bedside

The serine/threonine protein kinase C (PKC) family was first identified as intracellular receptor(s) for the tumor promoting agents phorbol esters. Thirty years after the discovery of PKC, the role of specific PKC isoforms has been described in relationship with an altered pattern of expression in different types of cancer and a good number of small molecule inhibitors (inhibitory peptides, antisense oligonucleotides or natural compounds) targeting PKC are now available. Despite all these achievements and a huge amount of basic research studies on the biochemical regulation of PKC, there has been a delay in clinical trials with drugs targeting PKC function. This delay is easily explained taking into account the extreme biological complexity of the PKC family of isoforms and the incomplete understanding of the specific role of each PKC isozyme in different types of cancers. Some of the difficulties in developing pharmacological compounds selectively tuning the different PKCs have started to be overcome. In this review, the growing evidences of the role of the PKC isoforms α, βII, δ, ε, ζ and ι is in promoting or counteracting tumor progression will be discussed in relationship with promising therapeutic perspectives.

Trail down-regulates the release of osteoprotegerin (OPG) by primary stromal cells

The soluble member of the TNF-R superfamily osteoprotegerin (OPG) is abundantly released under basal conditions by both mesenchymal stem cells (MSC) and fibroblasts and by endothelial cells upon stimulation with inflammatory cytokines. Since MSC, fibroblasts and endothelial cells represent key elements of the normal and tumor microenvironment and express detectable levels of surface TRAIL receptors, we investigated the effect of TRAIL on OPG release. Unexpectedly, recombinant TRAIL decreased the spontaneous OPG release in all cell types examined. Moreover, TRAIL decreased OPG release also in stromal cells co-cultured with lymphoma cells and counteracted the OPG induction by TN-alpha in HUVEC and MSC. Such down-regulation was not due to a masking effect in the ELISA quantification of the OPG released in the culture supernatants due to binding of OPG to its ligands (TRAIL and RANKL), as demonstrated by competition experiments with recombinant TRAIL and by the lack of RANKL release/induction. In addition, OPG down-regulation was not due to induction of cytotoxic effects by TRAIL, since the degree of apoptosis in response to TRAIL was negligible in all primary cell types. With regards to the possible molecular mechanism accounting for the down-regulation of OPG release by TRAIL, we found that treatment of MSC with TRAIL significantly decreased the phosphorylation levels of p38/MAPK. There is a suggestion that this pathway is involved in the stabilization of OPG mRNA. In this respect, the ability of TRAIL to decrease the release of OPG, in the absence of cell cytotoxicity, was mimicked by the p38/MAPK inhibitor SB203580.

Total extract of Beta vulgaris var. cicla seeds versus its purified phenolic components: antioxidant activities and antiproliferative effects against colon cancer cells

INTRODUCTION

Beta vulgaris var. cicla (BV) leaves contain chemopreventive compounds that have been investigated for new drug discovery. These compounds belong to the family of the apigenin-glycosides. Since the leaves are seasonal products containing high percentages of water, they are easily degradable during storage in fresh conditions. To be stored they require a drying process, consuming time and a large amount of energy. The extraction of apigenin-glycosides may also be conveniently performed from BV seeds, which represent a stable and year-long available biomass.

OBJECTIVES

The present report was undertaken to find a strategy of purification of bioactive flavonoids from BV seeds and test their ability to inhibit proliferation both on human colon cancer (RKO) cells and normal human fibroblasts (HF).

MATERIALS AND METHODS

The ethyl-acetate extract of BV seeds was fractionated on a Sephadex LH 20 column. A fraction of this extract, labeled as P4, exploited a marked antiproliferative activity on RKO cells. The components of P4 were purified on an RP₁₈ column chromatography and identified by HPLC-ESI-MS as 2,4,5-trihydroxybenzaldehyde, 2,5-dihydroxybenzaldehyde, vanillic acid, xylosylvitexin, glucopyranosyl-glucopyrasyl-rhamnetin and glucopyranosyl-xylosyl-rhamnetin. All of them were tested for cytostatic and cytotoxic activity on RKO and HF cells.

RESULTS

Xylosylvitexin exhibited the strongest antiproliferative activity on RKO cells, together with an enhancement of the apoptosis, an increase of cells in the G₁ phase and a reduction of cells in the S phase; on the contrary, the proliferation of HF was significantly stimulated.

CONCLUSION

Xylosylvitexin is the main and more efficient chemopreventive compound in BV seeds, but the natural cocktail of molecules, represented by P4 fraction, showed a better compromise between the antiproliferative activity on RKO cells and the enhancement of HF proliferation.

Treatment with recombinant tumor necrosis factor-related apoptosis-inducing ligand alleviates the severity of streptozotocin-induced diabetes

OBJECTIVE

To evaluate the potential therapeutic effect of recombinant human tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) treatment in a model of type 1 diabetes.

RESEARCH DESIGN AND METHODS

Recombinant TRAIL was added in vitro to primary human and mouse peripheral blood mononuclear cells (PBMCs) and isolated human islets to evaluate the expression of the immunoregulatory gene SOCS1. Diabetes was induced by five consecutive daily injections of low-concentration (50 mg/kg) streptozotocin (STZ) in C57 black mice (n = 24). A group of these mice (n = 12) was co-injected with recombinant TRAIL (20 microg/day) for 5 days, and the diabetic status (glycemia and body weight) was followed over time. After 6 weeks, circulating levels of insulin, TNF-alpha, and osteoprotegerin (OPG) were measured, and animals were killed to perform the histological analysis of the pancreas.

RESULTS

The in vitro exposure of both PBMCs and human islets to recombinant TRAIL significantly upregulated the expression of SOCS1. With respect to STZ-treated animals, mice co-injected with STZ+TRAIL were characterized by 1) lower levels of hyperglycemia, 2) higher levels of body weight and insulinemia, 3) a partial preservation of pancreatic islets with normal morphology, and 4) a lower expression of both systemic (TNF-alpha and OPG) and pancreatic (vascular cell adhesion molecule [VCAM]-1) inflammatory markers.

CONCLUSIONS

Overall, these data demonstrate that the administration of recombinant TRAIL ameliorates the severity of STZ-induced type 1 diabetes, and this effect was accompanied by the upregulation of SOCS1 expression.

Human full-length osteoprotegerin induces the proliferation of rodent vascular smooth muscle cells both in vitro and in vivo

BACKGROUND/AIMS

Since elevated plasma levels of osteoprotegerin (OPG) represent a risk factor for death and heart failure in patients affected by diabetes mellitus and coronary artery disease, this study aimed to elucidate potential roles of OPG in the pathogenesis of atherosclerosis.

METHODS AND RESULTS

Recombinant human full-length OPG, used at concentrations comparable to the elevated levels found in the serum of diabetic patients, significantly increased the proliferation rate of rodent vascular smooth muscle cells (VSMC). To mimic the moderate chronic elevation of OPG observed in diabetic patients, low doses (1 microg/mouse) of full-length human OPG were injected intraperitoneally every 3 weeks in diabetic apolipoprotein E (apoE)-null mice. The group of animals treated for 12 weeks with recombinant OPG showed a small increase in the total aortic plaque area at necropsy in comparison to vehicle-treated animals. Importantly, while no differences in the amount of interstitial collagen or the degree of macrophage infiltration were observed between OPG-treated and vehicle-treated apoE-null diabetic animals, a significant increase in the number of alpha-actin-positive smooth muscle cells was observed in the plaques of OPG-treated mice.

CONCLUSIONS

Our data suggest that OPG promotes VSMC proliferation and might be directly involved in pathogenetic aspects of atherosclerosis.

Activation of PKC-ε counteracts maturation and apoptosis of HL-60 myeloid leukemic cells in response to TNF family members

Protein kinase C (PKC)-ε, a component of the serine/threo-nine PKC family, has been shown to influence the survival and differentiation pathways of normal hematopoietic cells. Here, we have modulated the activity of PKC-ε with specific small molecule activator or inhibitor peptides. PKC-ε inhibitor and activator peptides showed modest effects on HL-60 maturation when added alone, but PKC-ε activator peptide significantly counteracted the pro-maturative activity of tumor necrosis factor (TNF)-α towards the monocytic/macrophagic lineage, as evaluated in terms of CD14 surface expression and morphological analyses. Moreover, while PKC-ε inhibitor peptide showed a reproducible increase of TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis, PKC-ε activator peptide potently counteracted the pro-apoptotic activity of TRAIL. Taken together, the anti-maturative and anti-apoptotic activities of PKC-ε envision a potentially important proleukemic role of this PKC family member.

Activation of PKC-epsilon counteracts maturation and apoptosis of HL-60 myeloid leukemic cells in response to TNF family members

Protein kinase C (PKC)-epsilon, a component of the serine/threonine PKC family, has been shown to influence the survival and differentiation pathways of normal hematopoietic cells. Here, we have modulated the activity of PKC-epsilon with specific small molecule activator or inhibitor peptides. PKC-epsilon inhibitor and activator peptides showed modest effects on HL-60 maturation when added alone, but PKC-epsilon activator peptide significantly counteracted the pro-maturative activity of tumor necrosis factor (TNF)-alpha towards the monocytic/macrophagic lineage, as evaluated in terms of CD14 surface expression and morphological analyses. Moreover, while PKC-epsilon inhibitor peptide showed a reproducible increase of TNF-related apoptosis inducing ligand (TRAIL)-induced apoptosis, PKC-epsilon activator peptide potently counteracted the pro-apoptotic activity of TRAIL. Taken together, the anti-maturative and anti-apoptotic activities of PKC-epsilon envision a potentially important proleukemic role of this PKC family member.

An update on the xenograft and mouse models suitable for investigating new therapeutic compounds for the treatment of B-cell malignancies

B-cell malignancies account for over the 90% of all lymphoid neoplasms. The clonal proliferations of B-cells show a high degree of variation in terms of clinical and presenting features, histopathology, immunophenotype, and genetics. Primary tumor samples are useful for examining the characteristics of a patient's own tumor, although both primary leukemic cells and cell lines provide an initial step for screening novel compounds for their activity in some hematological malignancies, they should be followed by models in intact animals. In this review, we try to summarize the animal models generated to study B-cell malignancies, in particular, B-cell lymphoma, B-cell CLL and MM that represent the major part of B-cell malignancies. Animals that spontaneously develop cancer are flawed to predict human disease. The development of human tumor xenograft models represented a big step towards more clinically relevant models. The major problems of these models are the requirement of immuno-compromised animals and the inability of these models to recapitulate the complex relationship between the tumor and the microenvironment. A number of strategies have been also applied to develop genetically engineered models of malignancies, in which the tumor arises "naturally" in the host. The disadvantages of these models include the differences between rodent and human stroma and that they can not be used to characterise anti-tumor activity of many immunotherapeutic drugs. These models can be used to study the molecular processes critical for the development, proliferation and survival of hematological malignancies and to characterise potential therapeutic targets.

Insulin down-regulates TRAIL expression in vascular smooth muscle cells both in vivo and in vitro

To dissect the effect of hyperinsulinemia versus hyperglycemia on TNF-related apoptosis inducing ligand (TRAIL) expression in the macrovascular district, we measured TRAIL mRNA and protein in four groups of animals: streptozotocin (SZT)-induced diabetic rats, vehicle-treated control animals, diabetic rats treated with insulin and non-diabetic rats treated with insulin. While the aortas of diabetic rats did not show significant differences in TRAIL expression with respect to vehicle-treated control animals, the aortas of both diabetic and non-diabetic rats treated in vivo for 16 days with insulin showed a significant decrease in TRAIL expression with respect to either diabetic and control rats. Moreover, in vitro treatment of both rat and human vascular smooth muscle cells (VSMC) with insulin induced the down-regulation of TRAIL protein. While the addition of recombinant TRAIL to rat VSMC promoted the dose-dependent release of bioactive nitric oxide (NO), this effect was significantly counteracted by pre-exposure of VSMC to insulin. These findings suggest that TRAIL might act as an endogenous regulator of the vascular tone and that chronic elevation of insulin might contribute to the vascular abnormalities characterizing type-2 diabetes mellitus by down-regulating TRAIL expression and activity.

Osteoprotegerin increases leukocyte adhesion to endothelial cells both in vitro and in vivo

Recombinant osteoprotegerin (OPG) promoted the adhesion of both primary polymorphonuclear neutrophils (PMNs) and leukemic HL60 cells to endothelial cells. Leukocyte/endothelial cell adhesion was promoted by short (peak at 1 hour) preincubation of either endothelial cells or PMNs with OPG, and the peak of proadhesive activity was observed in the same range of OPG concentrations detected in the sera of patients affected by cardiovascular diseases. Although the cognate high-affinity ligands for OPG, membrane receptor activator of nuclear factor-kappaB ligand (RANKL) and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), were detected at significant levels on both PMNs and HL60 cells, they were not expressed on the surface of endothelial cells. However, preincubation of OPG with heparin abrogated its proadhesive activity, whereas pretreatment of endothelial cells with chondroitinase plus heparinases significantly decreased the proadhesive activity of OPG. Taken together, these findings suggest the involvement of both the ligand binding and the N-terminal heparin-binding domains of OPG in mediating its pro-adhesive activity. The relevance of these in vitro findings was underscored by in vivo experiments, in which the topical administration of recombinant OPG increased leukocyte rolling and adhesion to rat mesenteric postcapillary venules. Our data suggest that a pathological increase of OPG serum levels might play an important role in promoting leukocyte/endothelial cell adhesion.

An increased osteoprotegerin serum release characterizes the early onset of diabetes mellitus and may contribute to endothelial cell dysfunction

Serum osteoprotegerin (OPG) is significantly increased in diabetic patients, prompting expanded investigation of the correlation between OPG production/release and glycemic levels. Serum levels of OPG, but not of its cognate ligand receptor activator of nuclear factor-kappaB ligand (RANKL), were significantly increased in type 2 diabetes mellitus patients compared with healthy blood donors. Serum OPG was also significantly elevated in a subgroup of recently diagnosed diabetic patients (within 2 years). The relationship between serum OPG and diabetes mellitus onset was next investigated in apoE-null and littermate mice. Serum OPG increased early after diabetes induction in both mouse strains and showed a positive correlation with blood glucose levels and an inverse correlation with the levels of free (OPG-unbound) RANKL. The in vitro addition of tumor necrosis factor-alpha to human vascular endothelial cells, but not human peripheral blood mononuclear cells, markedly enhanced OPG release in culture. In contrast, high glucose concentrations did not modulate OPG release when used alone or in association with tumor necrosis factor-alpha. Moreover, the ability of soluble RANKL to activate the extracellular signal-regulated kinase/mitogen-activated protein kinase and endothelial nitric-oxide synthase pathways in endothelial cells was neutralized by preincubation with recombinant OPG. Altogether, these findings suggest that increased OPG production represents an early event in the natural history of diabetes mellitus, possibly contributing to disease-associated endothelial cell dysfunction.

Aberrant expression of TRAIL in B chronic lymphocytic leukemia (B-CLL) cells

Analysis of peripheral blood (>85% CD19+/CD5+ B) lymphocytes, obtained from 44 patients affected by B chronic lymphoid leukemia (B-CLL), showed that surface TNF-related apoptosis inducing ligand (TRAIL) was expressed in all samples and at higher levels with respect to unfractionated lymphocytes and purified CD19+ B cells, obtained from 15 normal blood donors. Of note, in a subset of B-CLL samples, the addition to B-CLL cultures of a TRAIL-R1-Fc chimera, which binds at high affinity to surface TRAIL, significantly decreased the percentage of viable cells with respect to untreated control B-CLL cells, suggesting that surface TRAIL may play an unexpected role in promoting B-CLL cell survival. In spite of the majority of B-CLL lymphocytes expressed variable surface levels of "death receptors" TRAIL-R1 and TRAIL-R2, the addition in culture of recombinant TRAIL increased (>20% vs. controls) the degree of spontaneous apoptosis in only 11/44 of the B-CLL samples, had no effect in 19/44, while it significantly increased leukemic cell survival in 14/44. Taken together, these findings suggest that an aberrant expression of TRAIL might contribute to the pathogenesis of B-CLL by promoting the survival in a subset of B-CLL cells.

Potential pathogenetic implications of cyclooxygenase-2 overexpression in B chronic lymphoid leukemia cells

Evidence suggests that cyclooxygenase-2 (COX-2) increases tumorigenic potential by promoting resistance to apoptosis. Because B chronic lymphoid leukemia (B-CLL) cells exhibit a defective apoptotic response, we analyzed CD19(+) B lymphocytes purified from the peripheral blood of B-CLL patients. Microarray analysis showed a variable (up to 38-fold) increase in the steady-state mRNA levels of COX-2 in B-CLL lymphocytes compared with normal CD19(+) B lymphocytes. The up-regulation of COX-2 in B-CLL cells was confirmed by reverse transcriptase-polymerase chain reaction and Western blot analyses. Moreover, immunohistochemical analysis of B-CLL bone marrow infiltrates confirmed clear expression of COX-2 in leukemic cells. Ex vivo treatment with the COX-2 inhibitor NS-398 significantly decreased the survival of leukemic cells by increasing the rate of spontaneous apoptosis in 13 of 16 B-CLL samples examined, but it did not affect the survival of normal lymphocytes. Pretreatment with NS-398 significantly potentiated the cytotoxicity induced by chlorambucil in 8 of 16 B-CLL samples examined. Moreover, although recombinant tumor necrosis factor-related apoptosis inducing ligand (TRAIL)/Apo2L showed little cytotoxic effect in most B-CLL samples examined, pretreatment with NS-398 sensitized 8 of 16 B-CLL samples to TRAIL-induced apoptosis. Taken together, our data indicate that COX-2 overexpression likely represents an additional mechanism of resistance to apoptosis in B-CLL and that pharmacological suppression of COX-2 might enhance chemotherapy-mediated apoptosis.

Functional expression of TRAIL and TRAIL-R2 during human megakaryocytic development

The expression and function of surface TRAIL and TRAIL receptors were investigated in primary megakaryocytic cells, generated in serum-free liquid phase from peripheral human CD34(+) cells. The surface expression of both TRAIL and "death receptor" TRAIL-R2 became detectable starting from the early phase of megakaryocytic differentiation (day 6 of culture) and persisted at later (days10-14) culture times. On the other hand, "death receptor" TRAIL-R1, "decoy receptors" TRAIL-R3, and TRAIL-R4 were barely detectable or undetectable at any time point examined. Addition of recombinant TRAIL at day 6 of culture increased the rate of spontaneous apoptosis of CD34(+)/CD41(dim) megakaryoblasts and it significantly decreased the total output of mature megakaryocytic cells evaluated after additional 4-8 days of culture. Conversely, addition in culture of TRAIL-R2-Fc chimera, which blocked the interaction between endogenous TRAIL and TRAIL-R2 on the surface of cultured megakaryocytic cells, increased the total megakaryocytic cell count. In addition, recombinant TRAIL promoted a small but reproducible increase of maturation in the surviving megakaryocytic cell population, evaluated by both phenotypic analysis and morphology. A similar pro-maturation effect was observed when TRAIL was added to bone marrow-derived CD61(+) megakaryocytic cells. Thus, our data suggest a role of TRAIL as a regulator of megakaryocytopoiesis.

TNF-related apoptosis-inducing ligand (TRAIL) blocks osteoclastic differentiation induced by RANKL plus M-CSF

The role of the tumor necrosis factor (TNF) superfamily member receptor activator of nuclear factor kappa B ligand (RANKL) in promoting the differentiation of osteoclasts has been extensively characterized. In this study, we have investigated the effect of TNF-related apoptosis-inducing ligand (TRAIL), a member of the TNF superfamily of cytokines, in osteoclastogenesis, by using human peripheral blood mononuclear cells and the RAW264.7 murine monocytic cell line. Both cell models differentiate into osteoclast-like cells in presence of RANKL plus macrophage-colony-stimulating factor (M-CSF), as evaluated in terms of tartrate-resistant acid phosphatase (TRAP)-positive multinucleated cells and bone resorption activity. Unexpectedly, when added in culture in combination with RANKL plus M-CSF, TRAIL inhibited osteoclastic differentiation in both cell models. To investigate the molecular mechanism underlining such inhibitory activity, we analyzed the effect of TRAIL on the mitogen-activated protein kinases (MAPKs) pathways, which play a key role in osteoclastogenesis. Treatment with RANKL plus M-CSF activated both the ERK1/2 and p38/MAPK pathways, which are essential for proliferation and differentiation of preosteoclasts, respectively. Of note, the addition of TRAIL to RANKL plus M-CSF did not affect ERK1/2 but it profoundly inhibited p38/MAPK phosphorylation. Thus, our data demonstrate that TRAIL blocks osteoclastic differentiation and suggest that inhibition of the p38/MAPK pathway by TRAIL likely plays an important role in this process. (Blood. 2004;104:2044-2050)

Modulation of the expression and activity of cyclooxygenases in normal and accelerated erythropoiesis

OBJECTIVE

The present study was aimed at characterizing the expression and activity of cyclooxygenase (COX) isoenzymes in erythropoiesis.

METHODS

The expression and activity of cyclooxygenase (COX) and prostaglandin (PG) synthases were investigated in: 1) erythroblasts developed in culture from human CD34(+) hematopoietic progenitors, 2) erythroblasts in bone marrow specimens, and 3) peripheral erythrocytes isolated from healthy donors and from patients with a high regeneration rate of erythrocytes.

RESULTS

While COX-1 protein was observed at each stage of erythroblast development, COX-2 protein was induced at later stages through a p38/MAPK-dependent pathway. Both COX isoforms were also observed in mature erythroblasts of the bone marrow. Erythroblasts developed in culture synthesized significantly more PGE(2) than TXB(2) and indomethacin delayed erythroid maturation. COX-1 and COX-2 were also observed in erythrocytes by immunostainings, although COX expression was confined to a fraction of circulating erythrocytes. Peripheral erythrocytes synthesized low but detectable amounts of PGE(2) and TXB(2). Similarly to erythroblast progenitors, PGE(2) was the prevalent prostanoid released by erythrocytes. This biosynthetic capacity was significantly increased in erythrocytes from patients with accelerated erythropoiesis as compared to controls.

CONCLUSIONS

Both COX isoforms are present and enzymatically active during human erythropoiesis, although with different kinetics, and COX-derived prostanoids may play a role in erythroid maturation. Furthermore, peripheral erythrocytes retain in part the capacity of expressing COX and synthesizing prostanoids, which may contribute to the hemostatic/thrombotic response to vascular injury in different diseases, including congenital hemolytic disorders.

Association of PI 3-K with tyrosine phosphorylated Vav is essential for its activity in neutrophil-like maturation of myeloid cells

The importance of the Vav family of signal transduction molecules in hematopoietic cells has long been acknowledged, even though its role and its regulatory mechanism are not completely understood. We have previously demonstrated that tyrosine-phosphorylated Vav, also located inside the nucleus of myeloid cells, is up-regulated during maturation of promyelocytic precursors induced by all-trans-retinoic acid (ATRA). Here, we report that the tyrosine phosphorylation of Vav during granulocytic maturation is dependent on the tyrosine kinase Syk and is essential for the morphological changes of the cell nucleus. These ATRA-induced events are independent on the guanine nucleotide exchange activity of Vav. We also found that, in differentiating cells, and in both cytoplasmic and nuclear compartments, tyrosine phosphorylated Vav associates with the regulatory subunit of phosphoinositide 3-kinase (PI 3-K). The Vav/p85 interaction is essential for the ATRA-induced PI 3-K activity and for association of PI 3-K with actin, particularly in the nucleus. Our data indicate an unprecedented crucial function for Vav in modulating the morphological maturation process of myeloid cells in a GDP-GTP exchange factor (GEF)-independent manner and suggest a role of Vav as an adaptor protein responsible of targeting PI 3-K to its intranuclear substrates.

Tumour necrosis factor-related apoptosis-inducing ligand sequentially activates pro-survival and pro-apoptotic pathways in SK-N-MC neuronal cells

The SK-N-MC neuroblastoma cell line, which expresses surface tumour necrosis factor-related apoptosis-inducing ligand (TRAIL) receptors TRAIL-R2 and TRAIL-R4, was used as a model system to examine the effect of TRAIL on key intracellular pathways involved in the control of neuronal cell survival and apoptosis. TRAIL induced distinct short-term (1-60 min) and long-term (3-24 h) effects on the protein kinase B (PKB)/Akt (Akt), extracellular signal-regulated kinase (ERK), cAMP response element-binding protein (CREB), nuclear factor kappa B (NF-kappaB) and caspase pathways. TRAIL rapidly (from 20 min) induced the phosphorylation of Akt and ERK, but not of c-Jun NH2-terminal kinase (JNK). Moreover, TRAIL increased CREB phosphorylation and phospho-CREB DNA binding activity in a phosphatidylinositol 3-kinase (PI 3K)/Akt-dependent manner. At later time points (from 3 to 6 h onwards) TRAIL induced a progressive degradation of inhibitor of kappaB (IkappaB)beta and IkappaBepsilon, but not IkappaBalpha, coupled to the nuclear translocation of NF-kappaB and an increase in its DNA binding activity. In the same time frame, TRAIL started to activate caspase-8 and caspase-3, and to induce apoptosis. Remarkably, caspase-dependent cleavage of NF-kappaB family members as well as of Akt and CREB proteins, but not of ERK, became prominent at 24 h, a time point coincident with the peak of caspase-dependent apoptosis.

Tumor necrosis factor-related apoptosis-inducing ligand induces monocytic maturation of leukemic and normal myeloid precursors through a caspase-dependent pathway

Treatment of the human HL-60 cell line with tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL) resulted in rapid (6-24 hours) cytotoxicity associated with progressive maturation of the surviving cells along the monocytic lineage. The occurrence of monocytic maturation was demonstrated by a significant increase of both CD14 and CD11b surface expression, the acquisition of morphologic features typical of mature monocytes, and phagocytic capacity in TRAIL-treated cultures. By using selective pharmacologic inhibitors, it was possible to demonstrate that activation of the caspase cascade played a crucial role in mediating TRAIL cytotoxicity and monocytic maturation of HL-60 cells. Moreover, experiments performed using agonistic polyclonal antibodies, which mimic the interactions between TRAIL and each TRAIL receptor, indicated that TRAIL-R1 was responsible for mediating the TRAIL-induced maturation. Importantly, the maturational effects of TRAIL were observed also in primary normal CD34(+) cells, seeded in serum-free liquid cultures for 4 to 8 days in the presence of SCF + GM-CSF. After treatment with TRAIL for 3 additional days, a significant increase in CD14 and CD11b expression, coupled with an increased number of mature monocytes and macrophages, was noticed in the absence of cytotoxicity. These data disclose a novel role for TRAIL as a positive regulator of myeloid differentiation. Moreover, the dichotomous effect of TRAIL on malignant cells (early induction of apoptosis and monocytic maturation of the surviving cells) might have important therapeutic implications for the treatment of acute myeloid leukemia.

Erythropoietin-induced erythroid differentiation of K562 cells is accompanied by the nuclear translocation of phosphatidylinositol 3-kinase and intranuclear generation of phosphatidylinositol (3,4,5) trisphosphate

D-3 phosphorylated inositides are a peculiar class of lipids, synthesized by phosphatidylinositol 3-kinase (PtdIns 3-K), which are also present in the nucleus. In order to clarify a possible role for nuclear D-3 phosphorylated inositides during human erythroid differentiation, we have examined the issue of whether or not, in K562 human erythroleukemia cells, erythropoietin (EPO) may generate nuclear translocation of an active PtdIns 3-K. Immunoprecipitation with an anti-p85 regulatory subunit of PtdIns 3-K, revealed that both the intranuclear amount and the activity of the kinase increased rapidly and transiently in response to EPO. Enzyme translocation was blocked by the specific PtdIns 3-K pharmacological inhibitor, LY294002, which also inhibited erythroid differentiation. In vivo, intranuclear synthesis of phosphatidylinositol (3,4,5) trisphosphate (PtdIns (3,4,5)P(3)) was stimulated by EPO. Almost all PtdIns 3-K that translocated to the nucleus was highly phosphorylated on tyrosine residues of the p85 regulatory subunit. These findings strongly suggest that an important step in the signaling pathways that mediate EPO-induced erythroid differentiation may be represented by the intranuclear translocation of an active PtdIns 3-K.

Human herpesvirus 7 induces the functional up-regulation of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) coupled to TRAIL-R1 down-modulation in CD4(+) T cells

Human herpesvirus 7 (HHV-7) is endemic in the adult human population. Although HHV-7 preferentially infects activated CD4(+) T lymphocytes, the consequence of T-cell infection for viral pathogenesis and immunity are still largely unknown. HHV-7 infection induces apoptosis mostly in uninfected bystander cells but not in productively infected CD4(+) T cells. To dissect the underlying molecular events, the role of death-inducing ligands belonging to the tumor necrosis factor (TNF) cytokine superfamily was investigated. HHV-7 selectively up-regulated the expression of TNF-related apoptosis-inducing ligand (TRAIL), but not that of CD95 ligand or TNF-alpha in lymphoblastoid (SupT1) or primary activated CD4(+) T cells. Moreover, in a cell-to-cell-contact assay, HHV-7-infected CD4(+) T lymphocytes were cytotoxic for bystander uninfected CD4(+) T cells through the TRAIL pathway. By contrast, HHV-7 infection caused a marked decrease of surface TRAIL-R1, but not of TRAIL-R2, CD95, TNF-R1, or TNF-R2. Of note, the down-regulation of TRAIL-R1 selectively occurred in cells coexpressing HHV-7 antigens that became resistant to TRAIL-mediated cytotoxicity. These findings suggest that the TRAIL-mediated induction of T-cell death may represent an important immune evasion mechanism of HHV-7, helping the virus to persist in the host organism throughout its lifetime.