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Biomedical subjects

C Riccardi

Publications and source records attributed to C Riccardi.

At least 73 records · Page 4Linked to original sources
PubMed1994

Dexamethasone and interleukins modulate apoptosis of murine thymocytes and peripheral T-lymphocytes.

Glucocorticoid hormones (GCH) induce apoptotic cell death in immature thymocytes through an active process, characterized by extensive DNA fragmentation into oligonucleosomal subunits. This requires macromolecular synthesis and is inhibited by interleukins (ILs). We performed experiments to analyse the possible effect of GCH on more differentiated lymphocytes, i.e. peripheral (from lymph nodes and spleen) T-lymphocytes. The results show that in vitro dexamethasone (DEX) induces DNA fragmentation and cell death not only in thymocytes but also in mature T cells. We also tested the possible role of interleukins (ILs) in the modulation of apoptotic cell death. We show that DEX-induced apoptosis is inhibited by IL-2 and IL-4 and that the IL-4 induced inhibition correlates with induction of c-jun (a component of AP-1 transcription factor). Furthermore high doses of IL-2 are able to induce apoptosis in both thymocytes and peripheral T cells. These data indicate that both thymocytes and peripheral T cells undergo apoptosis in response to appropriate stimuli and suggest that GCH and ILs interact in regulating T-lymphocytes apoptotic death.

Animals↗
PubMed1994

Immunomodulating activity of pidotimod.

Experiments were performed to analyze the effect of the immunomodulating agent pidotimod ((R)-3-[(S)-(5-oxo-2-pyrrolidinyl) carbonyl]-thiazolidine-4-carboxylic acid, PGT/1A, CAS 121808-62-6) on the mouse splenic proliferative response to Con-A and IL-2, natural killer (NK) cell activity and thymocyte apoptosis. The results indicate that in vivo treatment with pidotimod (200 mg/kg i.p. for 5 days) causes a significant increase in the proliferative response to mitogens (including Con-A and IL-2) and the cytotoxic activity mediated by NK cells. Pidotimod inhibits in vitro thymocyte apoptosis caused by other inducing agents such as protein kinase C activator 12-O-tetradecanoyl-phorbol-13-acetate, Ca(++)-ionophore A23187, genistein and interleukin-2 (IL-2).

Adjuvants, Immunologic↗
PubMed1994

Dexamethasone induces apoptosis in mouse natural killer cells and cytotoxic T lymphocytes.

Glucocorticoid hormones (GCH) induce apoptotic cell death in immature thymocytes through an active mechanism, characterized by extensive DNA fragmentation into oligonucleosomal subunits. This requires macromolecular synthesis and is inhibited by protein kinase C (PKC) inhibitors, interleukin-4 (IL-4) and heat shock (hs). We performed experiments to analyse the possible effect of GCH on more differentiated lymphocytes, i.e. mouse natural killer (NK) cells and CD8+ alloreactive cytotoxic T lymphocytes (CTL). The results show that dexamethasone (DEX) induces DNA fragmentation and cell death in NK cells and CTL in vitro. In both NK cells and CTL, DEX-induced apoptosis is inhibited by IL-2 and IL-4 but, unlike that induced in thymocytes, is augmented by mRNA and protein synthesis inhibitors, PKC inhibitors and HS.

Animals↗
PubMed1993

Interleukin-4 protects double-negative and CD4 single-positive thymocytes from dexamethasone-induced apoptosis.

Glucocorticoid hormones (GCH) and anti-CD3 monoclonal antibodies (MoAbs) induce in mouse thymocytes and T-cell tumor lines an active process of cell death called apoptosis. Interleukins (IL), including IL-1 and IL-2, have been reported to inhibit such apoptosis. In this study we show that IL-4 also reduced the DNA fragmentation characteristic of dexamethasone (DEX)-induced apoptosis in thymocytes. This effect, studied in both time-course and dose-response experiments, was also detected at low IL-4 concentrations (1 U/mL) and against high DEX levels (10(-7) mol/L). The effect of IL-4 was blocked by an anti-IL-4 but not by an anti-IL-1 alpha MoAb, and was thus both specific and direct. Phenotypic analysis showed that IL-4 protects predominantly CD4-CD8- and CD4+CD8- cells. Our findings suggest that intrathymic T-cell development may be influenced by IL-4.

Animals↗
PubMed1993

Interleukin-2 induces apoptosis in mouse thymocytes.

Interleukins play a role in the process of T-cell development and, like other cytokines, seem able to modulate apoptosis. Interleukin-2 has been reported to inhibit apoptotic cell death of thymocytes induced in vitro by either activation of CD3/TCR complex or treatment with glucocorticoid hormone. We demonstrate here that IL-2 can provoke DNA fragmentation and cell death of CD4+ CD8+ mouse thymocytes by activating an endogenous apoptotic pathway. Thymocytes, incubated with high IL-2 concentrations in vitro, showed the morphological characteristics of apoptotic cells, including reduction in nuclear size, derangement in chromatin structure, and DNA fragmentation in oligonucleosomal subunits. Inhibition of mRNA and protein synthesis and addition of the PKC-inhibitor H-7, Zn2+ ions, and IL-4 counteracted the IL-2 effect. These data suggest that high IL-2 concentrations may induce an active process of cell death on mouse thymocytes in vitro.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Cellular stress and glucocorticoid hormones protect L929 mouse fibroblasts from tumor necrosis factor alpha cytotoxicity.

Adaptive responses to the environment depend on the induction of the "stress response" in less differentiated organisms and cultured cells and the activation of the hypothalamic-pituitary-adrenal axis in animals and humans. This indicates that adrenal steroids and stress proteins play an important role in regulating cell survival in response to noxious stimuli. In an in vitro model, we analyzed the effects of either dexamethasone (DEX) treatment or environmental changes which can elicit a stress response, on the survival of cultured L-929 mouse fibroblasts exposed to the cytotoxic cytokine tumor necrosis factor alpha (TNF-alpha). DEX treatment produced a significant reduction in the apoptotic death of L-929 cells produced by TNF-alpha. Abrogation of the protective effect of DEX by actinomycin D and cycloheximide demonstrated that protection against TNF-alpha requires de novo synthesis of mRNA and proteins. The results were similar when L-929 cells were exposed to metabolic (serum starvation) or thermal (heat shock) stresses before TNF-alpha treatment. In both cases the stress process afforded significant protection against TNF-alpha cytotoxicity. Inhibition of mRNA and protein synthesis abrogated the protection exerted by stress (serum starvation) or produced massive death during the stress event (heat shock). The similarities in the protective activities of DEX and stress response and the reported interactions between heat shock proteins and glucocorticoid hormones suggest that stress proteins and glucocorticoids both belong to an ancient evolutionary pathway which controls cell survival.

Animals↗
PubMed1993

PMA inhibits NK cell generation, cytotoxic activity and NK-1.1 expression.

We investigated the role of protein kinase C activator phorbol 12-myristate 13-acetate (PMA) on IL-2-driven NK cell differentiation, by using an in vitro model previously set up by our laboratory. Bone marrow precursor cells, from mice treated with 5-fluorouracil (FUBM), when cultured with IL-2, generated mature NK cells. The biochemical system involved in this process has not yet been defined. We investigated the possible mechanism by analyzing the effect of PCK activator PMA on NK cell differentiation and lytic activity of mature NK cells. We now report that: (1) PMA inhibited the IL-2-induced NK cell differentiation and induced development of cells which lyse the NK-resistant target P815. (2) PMA inhibited the lytic ability of mature NK cells against NK-sensitive target YAC-1. We evaluated the effects of PMA using the expression of NK-associated antigen NK-1.1 and the ability to lyse YAC target as parameters of NK cell differentiation. PMA down-regulated both these parameters, reducing their expression during the differentiation process of NK cells and inducing down-modulation of these in mature NK cells. The results suggest that PKC regulatory control could be under the process of differentiation and activation of NK cells.

Animals↗
PubMed1993

Genistein inhibits tumour cell growth in vitro but enhances mitochondrial reduction of tetrazolium salts: a further pitfall in the use of the MTT assay for evaluating cell growth and survival.

The natural isoflavone genistein inhibits the growth of a number of tumour cell lines in vitro. During investigations on the antiproliferative effects of genistein we observed that, with respect to direct cell counting, a tetrazolium (MTT) colorimetric assay consistently underestimated the growth inhibitory activity of the substance. Cell proliferation was markedly inhibited by genistein in three tumour cell lines (MCF-7, human breast tumour; Jurkat cells, human T-cell leukaemia; L-929, mouse transformed fibroblasts) when cell number was evaluated by direct counting, whereas a 72-h MTT assay failed to reveal any growth-inhibitory effect. Cell cycle analysis by propidium iodide staining and flow-cytometry revealed a G2/M cell cycle arrest after genistein treatment. Genistein-treated cells displayed an increase in cell volume and in mitochondrial number and/or activity, as revealed by enhanced formazan generation and increased uptake of the vital mitochondrial dye rhodamine 123. These results suggest that alterations in cell cycle phase redistribution of tumour cells by genistein may significantly influence mitochondrial number and/or function and, consequently, MTT reduction to formazan. This may constitute an important bias in analysing the effects of genistein, and possibly other drugs that block the G2/M transition, on growth and viability of cancer cells in vitro by MTT assay.

Animals↗
PubMed1993

Cytostatic and cytotoxic effects of tumor necrosis factor alpha on MCF-7 human breast tumor cells are differently inhibited by glucocorticoid hormones.

To investigate the mechanisms of growth inhibition exerted by TNF-alpha on tumor cells in vitro, we analyzed the cytokine effects on growth and cell-cycle parameters of cultured MCF-7 human breast cancer cells. TNF-alpha exerted a dose-dependent inhibition of MCF-7 cell growth, which reached its maximum at 1000 U/ml TNF-alpha concentrations. Flow-cytometric analysis of cell nuclei revealed two main components in TNF-alpha activity: an earlier cytostatic effect (G1/S block), was followed by nuclear shrinkage and cytolysis. The 55-60-kDa TNF-alpha receptor is involved in the growth inhibitory activity of the cytokine, since the H398 anti-55-kDa receptor antibody significantly counteracted the cytostatic and cytotoxic effects of TNF-alpha while an antibody (htr-9) with agonistic activity on the same receptor produced both cytostasis and cytolysis. Culture conditions strongly influenced the MCF-7 cell response to TNF-alpha. Serum deprivation of log-growing (i.e., high S phase percentage) cultures potentiated the cytotoxic effect, while reduction in S phase cell percentage by preculture in serum-free medium resulted in a significant inhibition of TNF-alpha action. Mitogenic hormones, such as insulin and 17 beta-estradiol+insulin, restored the sensitivity of MCF-7 cells precultured in serum-free medium to both the cytostatic and cytolytic effects of TNF-alpha. The synthetic glucocorticoid hormone dexamethasone, at micromolar concentrations, counteracted the TNF-alpha effect on MCF-7 cell growth. Flow-cytometric analysis showed that dexamethasone did not antagonize the cytostatic activity of either TNF-alpha or htr-9 agonistic antibody, but only the subsequent cytolysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Antibodies↗
PubMed1992

Growth and spread of human malignant T lymphoblasts in immunosuppressed nude mice: a model for meningeal leukemia.

Previous work has shown that nude (nu/nu) mice additionally immunosuppressed by splenectomy, sublethal irradiation, and treatment with antiasialo GM1 antiserum (SIA-nu/nu mice) have no detectable natural killer activity and allow the growth of human malignant lymphoblasts. We show here that all SIA-nu/nu mice engrafted intravenously with 5 x 10(6) malignant lymphoblasts originally derived from a child with a T-cell acute lymphoblastic leukemia (PF382) and from a boy with a T-cell lymphoma (ST-4) develop lethal meningeal leukemia and die within 35 days. Histologic examination of moribund SIA-nu/nu mice showed that vertebral and skull bone marrow was always replaced by proliferating human T lymphoblasts. From the spinal canal, lymphoblasts spread to the meninges, causing hind leg paralysis. Leaving the skull, they permeated the meninges and then invaded the nervous parenchyma. This efficient and reproducible experimental model may be suitable for experimental studies on the pathogenesis of meningeal leukemia.

Animals↗
PubMed1992

Interleukins modulate glucocorticoid-induced thymocyte apoptosis.

Glucocorticoid hormones, calcium ionophores and anti-CD3 monoclonal antibodies induce apoptosis in mouse thymocytes. This type of cell death, which is characterized by an extensive DNA fragmentation into oligonucleosomal subunits, occurs in the intrathymic process of negative selection, and is involved in the deletion of autoreactive T-cells during thymic maturation. A number of cytokines are able to modulate apoptosis, and interleukins, including interleukin-1, interleukin-2, and interleukin-4, play a crucial role in thymic maturation and T-cell development. We tested the effects of several cytokines on the glucocorticoid hormone-induced apoptosis of mouse thymocytes in vitro, and demonstrated that interleukin-1 alpha, interleukin-2, and interleukin-4 inhibit the apoptosis induced by dexamethasone, but that interleukin-3 and interleukin-6 exert no noteworthy effect. Dose-response experiments indicated that interleukin-4 is more potent than interleukin-1 alpha and interleukin-2 in inhibiting dexamethasone-induced apoptosis. Furthermore, interleukin-4 fully inhibited the DNA fragmentation induced by the protein kinase-C activator 12-O-tetradecanoylphorbol-13-acetate, but was ineffective against apoptosis induced by the calcium ionophore A23187. These results suggest that interleukins regulate the thymic selection process by acting as modulators of the negative selection process.

Animals↗
PubMed1992

Heat shock induces apoptosis in mouse thymocytes and protects them from glucocorticoid-induced cell death.

Thymocyte death is a complex phenomenon under the control of different signals and stimuli. We evaluated the effect of elevated temperature (heat shock, HS) on mouse thymocyte apoptosis. Incubation of thymocytes at 43 degrees C for 20 min induced DNA fragmentation and cell death, but it was also able to decrease the apoptosis induced by dexamethasone (DEX), TPA or Ca2+ ionophore. The anti-apoptotic effect was correlated with induction of heat shock proteins (HSPs) and abolished by protein synthesis inhibition. On the other hand, HS-induced unlike DEX-induced apoptosis was not inhibited by protein synthesis and mRNA transcription inhibitors, the PKC inhibitors H-7 and staurosporine, or interleukin-4 (IL-4), but only by Zn2+. These results suggest that HS interferes in thymocyte death by either inducing or inhibiting thymocyte apoptosis and that the induction process mechanisms are different from those of GCH.

Animals↗
PubMed1992

IL-2-dependent generation of natural killer cells from bone marrow: role of MAC-1-, NK1-1- precursors.

We have previously shown that interleukin-2 (IL-2) is able to induce the generation of natural killer (NK) activity in bone marrow (BM) cell cultures from mice pretreated with 5-fluorouracil (5-FU). Cell fractionation experiments to analyze the nature of BM precursors indicate that MAC-1-, NK1-1- noncytotoxic precursors are induced by IL-2 to proliferate and generate cytolytic NK cells. These data demonstrate that the phenotype and functional characteristics of the IL-2-responsive cells in the FUBM are different from those of mature NK cells in that they are MAC-1+, NK1.1+, CD3- and susceptible to boosting by IFN-alpha.

Animals↗
PubMed1992

Glucocorticoid-induced DNA fragmentation: role of protein-kinase-C activity.

Glucocorticoid hormones (GCH) and IL-2 induce apoptotic cell death by a PKC-dependent mechanism. IL-4 counteracts apoptosis by inhibiting PKC activity. GCH and IL-2 show antagonistic effects on apoptosis when administered together. These data indicate that PKC activation in response to different stimuli can both enhance or reduce thymocyte survival.

Animals↗