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M Castedo

Publications and source records attributed to M Castedo.

36 records · Page 2Linked to original sources
PubMed1996

Mitochondrial permeability transition is a central coordinating event of apoptosis.

In a number of experimental systems, the early stage of the apoptotic process, i.e., the stage that precedes nuclear disintegration, is characterized by the breakdown of the inner mitochondrial transmembrane potential (delta psi m). This delta psi m disruption is mediated by the opening of permeability transition (PT) pores and appears to be critical for the apoptotic cascade, since it is directly regulated by Bcl-2 and since mitochondria induced to undergo PT in vitro become capable of inducing nuclear chromatinolysis in a cell-free system of apoptosis. Here, we addressed the question of which apoptotic events are secondary to mitochondrial PT. We tested the effect of a specific inhibitor of PT, bongkrekic acid (BA), a ligand of the mitochondrial adenine nucleotide translocator, on a prototypic model of apoptosis glucocorticoid-induced thymocyte death. In addition to abolishing the apoptotic delta psi m disruption, BA prevents a number of phenomena linked to apoptosis: depletion of nonoxidized glutathione, generation of reactive oxygen species, translocation of NF kappa B, exposure of phosphatidylserine residues on the outer plasma membrane, cytoplasmic vacuolization, chromatin condensation, and oligonucleosomal DNA fragmentation. BA is also an efficient inhibitor of p53-dependent thymocyte apoptosis induced by DNA damage. These data suggest that a number of apoptotic phenomena are secondary to PT. In addition, we present data indicating that apoptotic delta psi m disruption is secondary to transcriptional events. These data connect the PT control point to the p53- and ICE/ Ced 3-regulated control points of apoptosis and place PT upstream of nuclear and plasma membrane features of PCD.

Animals↗
PubMed1996

Sequential acquisition of mitochondrial and plasma membrane alterations during early lymphocyte apoptosis.

When cells undergo nuclear apoptosis (chromatin condensation, DNA fragmentation), they already manifest at least three alterations that can be quantified cytofluorometrically at the single-cell level: 1) a loss of mitochondrial transmembrane potential (delta psi m), 2) an increased production of superoxide anions, and 3) the aberrant exposure of phosphatidylserine (PS) residues on the outer plasma membrane leaflet. This latter alteration allows for the phagocytic recognition/elimination of apoptotic cells. In this work, we show that cells first undergo the delta psi m disruption and that PS exposure only affects cells that already have a low delta psi m. Pharmacologic modulation of apoptosis with inhibitors of macromolecule synthesis or proteases, as well as with drugs stabilizing the delta psi m, indicates that delta psi m disruption and PS exposure are coregulated. Interventions on apoptosis-regulatory genes (p53, bcl-2) confirm the coregulation of delta-psi-m disruption, PS exposure, and nuclear signs of apoptosis. In all conditions in which apoptosis is prevented, the delta psi m remains stable and PS cannot be detected on the cell surface. Reactive oxygen species do not contribute to PS exposure, based on two lines of evidence. First, among thymocytes undergoing apoptosis in response to dexamethasone, delta psi mlow cells first expose PS and then hyperproduce superoxide anion. Second, exogenous sources of reactive oxygen species or the superoxide anion-generating drug menadione fail to cause rapid PS exposure. Instead, direct interventions on mitochondria using inhibitors of the respiratory chain or the F1 ATP synthase cause PS exposure in cells subsequent to delta psi m disruption. This effect is also obtained in anucleate cells, indicating that the nucleus does not intervene in the sequence of events coupling mitochondrial dysfunction to PS exposure. Altogether, these data underline the functional impact of mitochondrial alterations on the apoptotic process.

Animals↗
PubMed1996

Apoptosis-associated derangement of mitochondrial function in cells lacking mitochondrial DNA.

U937 cells lacking mitochondrial DNA (rho [symbol: see text] cells) are auxotrophic for uridine and pyruvate, hypersensitive to hypoglycemic conditions, and resistant to antimycin A-induced apoptosis. In spite of their obvious metabolic defects, rho [symbol: see text] cells possess a normal mitochondrial transmembrane potential, as well as near-normal capacity to generate superoxide anion after menadione treatment. Similarly to rho + controls, rho [symbol: see text] cells undergo apoptosis in response to tumor necrosis factor-alpha plus cycloheximide. Detailed comparison of the apoptotic process in rho + and rho [symbol: see text] cells reveals essentially the same sequence of events. In response to tumor necrosis factor/cycloheximide, cells first lose their mitochondrial transmembrane potential (delta psi m) and then manifest late apoptotic alterations, such as generation of reactive oxygen species and DNA fragmentation. Experiments involving isolated mitochondria from rho + and rho [symbol: see text] cells confirm that rho [symbol: see text] mitochondria can be induced to undergo permeability transition, a process thought to account for the pre-apoptotic delta psi m disruption in cells. Like rho + mitochondria, rho [symbol: see text] mitochondria contain a pre-formed soluble factor that is capable of inducing chromatin condensation in isolated nuclei in vitro. This factor is released from mitochondria upon induction of permeability transition by calcium or the specific ligand of the adenine nucleotide translocator atractyloside. In conclusion, it appears that all structures involved in the maintenance and pre-apoptotic disruption of the delta psi m, as well as a mitochondrial apoptotic factor(s), are present in rho [symbol: see text] cells and thus are controlled by the nuclear rather than by the mitochondrial genome. These findings underline the contribution of mitochondria to the apoptotic process.

Apoptosis↗
PubMed1996

Inhibitors of permeability transition interfere with the disruption of the mitochondrial transmembrane potential during apoptosis.

In a number of experimental systems, the early stage of the apoptotic process, i.e. the stage which precedes nuclear disintegration, is characterized by the breakdown of the inner mitochondrial transmembrane potential (delta psi m). Here we address the question as to whether mitochondrial permeability transition (PT) pores may account for the delta psi m dissipation in lymphocyte apoptosis. Drugs known for their PT-inhibitory potential (bongkrekic acid, cyclosporin A, and the non-immunosuppressive cyclosporin A analogue N-methyl-Val-4-cyclosporin A) are capable of preventing the apoptotic delta psi m disruption. Moreover, pharmacological modulation of PT-mediated delta psi m dissipation can prevent apoptosis. Thus, while suppressing the delta psi m disruption, bongkrekic acid also inhibits the apoptotic chromatinolysis. In conclusion, these data are compatible with the hypothesis that apoptotic delta psi m disruption is mediated by the formation of PT pores and that PT-mediated delta psi m disruption is a critical event of the apoptotic cascade.

Animals↗
PubMed1996

Mitochondrial control of nuclear apoptosis.

Anucleate cells can be induced to undergo programmed cell death (PCD), indicating the existence of a cytoplasmic PCD pathway that functions independently from the nucleus. Cytoplasmic structures including mitochondria have been shown to participate in the control of apoptotic nuclear disintegration. Before cells exhibit common signs of nuclear apoptosis (chromatin condensation and endonuclease-mediated DNA fragmentation), they undergo a reduction of the mitochondrial transmembrane potential (delta psi m) that may be due to the opening of mitochondrial permeability transition (PT) pores. Here, we present direct evidence indicating that mitochondrial PT constitutes a critical early event of the apoptotic process. In a cell-free system combining purified mitochondria and nuclei, mitochondria undergoing PT suffice to induce chromatin condensation and DNA fragmentation. Induction of PT by pharmacological agents augments the apoptosis-inducing potential of mitochondria. In contrast, prevention of PT by pharmacological agents impedes nuclear apoptosis, both in vitro and in vivo. Mitochondria from hepatocytes or lymphoid cells undergoing apoptosis, but not those from normal cells, induce disintegration of isolated Hela nuclei. A specific ligand of the mitochondrial adenine nucleotide translocator (ANT), bongkreik acid, inhibits PT and reduces apoptosis induction by mitochondria in a cell-free system. Moreover, it inhibits the induction of apoptosis in intact cells. Several pieces of evidence suggest that the proto-oncogene product Bcl-2 inhibits apoptosis by preventing mitochondrial PT. First, to inhibit nuclear apoptosis, Bcl-2 must be localized in mitochondrial but not nuclear membranes. Second, transfection-enforced hyperexpression of Bcl-2 directly abolishes the induction of mitochondrial PT in response to a protonophore, a pro-oxidant, as well as to the ANT ligand atractyloside, correlating with its apoptosis-inhibitory effect. In conclusion, mitochondrial PT appears to be a critical step of the apoptotic cascade.

Animals↗
PubMed1996

Effects of Mycoplasma fermentans on the myelomonocytic lineage. Different molecular entities with cytokine-inducing and cytocidal potential.

Mycoplasma fermentans is a mycoplasma species that has been accused of serving as a cofactor of AIDS development. Here, we show that M. fermentans affects the function of human monocytes and myelomonocytic cell lines on at least two different levels. Heat-inactivated mycoplasma particles induce inflammatory cytokines such as IL-1, IL-6, and TNF in monocytes, as well as in THP-1 cells. Moreover, M. fermentans induces IL-10 (but not IL-12) in freshly isolated human monocytes. The cytokine-inducing effect is mediated by lipid-associated molecules. In addition, we have detected a novel biologic activity that resides in the nonlipid-associated protein fraction of M. fermentans (approximate molecular mass: 15 to 30 kDa) and that has a cytocidal effect on nondifferentiated myelomonocytic cell lines (U937 cells, HL-60 cells), as well as on actinomycin-D-sensitized monocytes. Death is accompanied by oligonucleosomal DNA fragmentation and loss of chromosomal DNA. U937 and HL-60 cells fail to produce cytokines and rather undergo cell death in response to heat-inactivated M. fermentans, provided that they are kept in a relatively undifferentiated stage. Whereas the cytokine-inducing activity is a general feature of many mycoplasma species, it appears that only a restricted panel of mycoplasma species exert a cell death-inducing activity. In addition to M. fermentans strains, Mycoplasma penetrans, another hypothetical cofactor of AIDS, possess a cytocidal activity. This does not apply to other mycoplasma species, including pathogenic ones such as Mycoplasma pneumoniae and Ureaplasma urealyticum. The cell death-inducing effect of M. fermentans is not mediated by cytokines and obeys different principles than TNF-alpha-mediated apoptosis. Thus, in contrast to TNF-alpha-induced death, it is not accompanied by a decrease in the mitochondrial transmembrane potential and is not inhibited by preincubation with the antioxidant drug N-acetylcysteine. In synthesis, it appears that certain AIDS-associated mycoplasma species perturb the function and/or generation of cells from the myelomonocytic lineage via several distinct pathways.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Polyethylene glycol-modified IL-2 abrogates superantigen-induced anergy without affecting peripheral clonal deletion in vivo.

As compared with the native molecule, recombinant human interleukin-2 that is modified by covalently attached polyethylene glycol residues (IL-2-PEG) exhibits a markedly enhanced half-life in vivo, thus facilitating its biological evaluation. We have characterized the effect of IL-2-PEG on the Staphylococcus aureus enterotoxin B (SEB)-induced tolerance of peripheral SEB-reactive (V beta 8+) T cells. Treatment with sublethal doses of IL-2-PEG does not modulate (inhibit or enhance) the SEB-triggered apoptosis and deletion of V beta 8+ T cells. In contrast, in vivo treatment with IL-2-PEG partially abolishes the SEB-triggered anergy of V beta 8+ T cells, i.e., the failure to proliferate in response to SEB in vitro. To abolish SEB-triggered anergy, IL-2-PEG must act for an extended period in vivo; short term treatment in vivo (2 days) or exposure of anergic T cells to IL-2 in vitro fails to reconstitute proliferative responses. Moreover, the effect of in vivo treatment with IL-2-PEG on lymphokine production by anergic T cells is partial. IL-2-PEG restores IL-4-dependent autocrine proliferation in response to SEB but does not reestablish defective IL-2 production. These data are compatible with the notion that IL-2 is a regulator of postdeletional rather than deletional T cell tolerance.

Animals↗
PubMed1995

Mitochondrial dysfunctions in circulating T lymphocytes from human immunodeficiency virus-1 carriers.

In several models of lymphocyte apoptosis, two alterations of mitochondrial function precede advanced DNA fragmentation: (1) a reduction of mitochondrial transmembrane potential (delta psi m) and (2) an increase in mitochondrial generation of superoxide anion. Here we show that two fluorochromes allow for the identification of analogous mitochondrial perturbations in circulating T lymphocytes from human immunodeficiency virus (HIV)-1+ donors. The first among these fluorochromes, the cationic lipophilic dye DiOC6(3), measures delta psi m; the second marker, hydroethidine (HE), is nonfluorescent, unless it is oxidized by superoxide anions to the product ethidium (Eth). CD4+ or CD8+ cells from clinically asymptomatic HIV-1 carriers contain a significantly elevated percentage of cells endowed with enhanced HE --> Eth conversion and/or reduced DiOC6(3) uptake as compared with normal controls. Phenotypic characterization of (HE --> Eth)high cells from HIV+ donors shows that these cells possess a low delta psi m, thus demonstrating a functional alteration of mitochondria. In addition, (HE --> Eth)high cells display a reduced incorporation of the cardiolipin-specific dye nonyl-acridine orange (NAO), showing a structural defect of the cardiolipin-containing inner mitochondrial membrane. Control experiments involving rotenone, an inhibitor of the respiratory chain complex I, indicate that the reactive oxygen species responsible for HE --> Eth conversion is generated during mitochondrial electron transport. In synthesis, it appears that mitochondrial alterations occur in a significant percentage of circulating T lymphocytes from HIV-1 carriers. The extent of delta psi m reduction, as determined ex vivo, correlates with the frequency of cells undergoing DNA fragmentation after overnight in vitro culture. These observations may be important for the understanding and for the direct ex vivo quantitation of HIV-triggered lymphocyte destruction.

Acquired Immunodeficiency Syndrome↗
PubMed1995

Sequential reduction of mitochondrial transmembrane potential and generation of reactive oxygen species in early programmed cell death.

Programmed cell death (PCD) is a physiological process commonly defined by alterations in nuclear morphology (apoptosis) and/or characteristic stepwise degradation of chromosomal DNA occurring before cytolysis. However, determined characteristics of PCD such as loss in mitochondrial reductase activity or cytolysis can be induced in enucleated cells, indicating cytoplasmic PCD control. Here we report a sequential disregulation of mitochondrial function that precedes cell shrinkage and nuclear fragmentation. A first cyclosporin A-inhibitable step of ongoing PCD is characterized by a reduction of mitochondrial transmembrane potential, as determined by specific fluorochromes (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine++ + iodide; 3,3'dihexyloxacarbocyanine iodide). Cytofluorometrically purified cells with reduced mitochondrial transmembrane potential are initially incapable of oxidizing hydroethidine (HE) into ethidium. Upon short-term in vitro culture, such cells acquire the capacity of HE oxidation, thus revealing a second step of PCD marked by mitochondrial generation of reactive oxygen species (ROS). This step can be selectively inhibited by rotenone and ruthenium red yet is not affected by cyclosporin A. Finally, cells reduce their volume, a step that is delayed by radical scavengers, indicating the implication of ROS in the apoptotic process. This sequence of alterations accompanying early PCD is found in very different models of apoptosis induction: glucocorticoid-induced death of lymphocytes, activation-induced PCD of T cell hybridomas, and tumor necrosis factor-induced death of U937 cells. Transfection with the antiapoptotic protooncogene Bcl-2 simultaneously inhibits mitochondrial alterations and apoptotic cell death triggered by steroids or ceramide. In vivo injection of fluorochromes such as 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolcarbocyanine iodide; 3,3'dihexyloxacarbocyanine iodide; or HE allows for the detection of cells that are programmed for death but still lack nuclear DNA fragmentation. In particular, assessment of mitochondrial ROS generation provides an accurate picture of PCD-mediated lymphocyte depletion. In conclusion, alterations of mitochondrial function constitute an important feature of early PCD.

Animals↗
PubMed1995

Reduction in mitochondrial potential constitutes an early irreversible step of programmed lymphocyte death in vivo.

In a number of experimental systems in which lymphocyte depletion was induced by apoptosis-inducing manipulations, no apoptotic morphology and ladder-type DNA fragmentation were detected among freshly isolated peripheral lymphocytes ex vivo. Here we report that one alteration that can be detected among splenocytes stimulated with lymphocyte-depleting doses of dexamethasone (DEX) in vivo is a reduced uptake of 3,3'dihexyloxacarbocyanine iodide (DiOC6[3]), a fluorochrome which incorporates into cells dependent upon their mitochondrial transmembrane potential (delta psi m). In contrast, ex vivo isolated splenocytes still lacked established signs of programmed cell death (PCD):DNA degradation into high or low molecular weight fragments, ultrastructural changes of chromatin arrangement and endoplasmatic reticulum, loss in viability, or accumulation of intracellular peroxides. Moreover, no changes in cell membrane potential could be detected. A reduced delta psi m has been observed in response to different agents inducing lymphoid cell depletion in vivo (superantigen and glucocorticoids [GC]), in mature T and B lymphocytes, as well as their precursors. DEX treatment in vivo, followed by cytofluorometric purification of viable delta psi mlow splenic T cells ex vivo, revealed that this fraction of cells is irreversibly committed to undergoing DNA fragmentation. Immediately after purification neither delta psi mlow, nor delta psi mhigh cells, exhibit detectable DNA fragmentation. However, after short-term culture (37 degrees C, 1 h) delta psi mlow cells show endonucleolysis, followed by cytolysis several hours later. Incubation of delta psi mlow cells in the presence of excess amount of the GC receptor antagonist RU38486 (which displaces DEX from the GC receptor), cytokines that inhibit DEX-induced cell death, or cycloheximide fails to prevent cytolysis. The antioxidant, N-acetylcysteine, as well as linomide, an agent that effectively inhibits DEX or superantigen-induced lymphocyte depletion in vivo, also stabilize the DiOC6(3) uptake. In contrast, the endonuclease inhibitor, aurintricarboxylic acid acts at later stages of apoptosis and only retards the transition from the viable delta psi mlow to the nonviable fraction. Altogether, these data suggest a sequence of PCD-associated events in which a reduction in delta psi m constitutes an obligate irreversible step of ongoing lymphocyte death, preceding other alterations of cellular physiology, and thus allowing for the ex vivo assessment of PCD.

Animals↗
PubMed1995

Self-reactive anti-class II T helper type 2 cell lines derived from gold salt-injected rats trigger B cell polycolonal activation and transfer autoimmunity in CD8-depleted normal syngeneic recipients.

Brown Norway (BN) rats given gold salts develop an autoimmune syndrome with an immune complex-type glomerulonephritis in the context of a polyclonal B cell activation that was suspected to be due to the emergence of anti-self major histocompatibility complex (MHC) class II T cells. In the present study, six anti-self MHC class II T cell lines have been derived from six gold salt-treated rats by repeated stimulations with normal syngeneic MHC class II-bearing cells. The T cell lines proliferated in the presence of self MHC class II-positive B cell-enriched or B cell-depleted cells and the proliferation was inhibited by preincubating stimulator cells with an anti-IA monoclonal antibody. The T cell lines produced interleukin (IL)-4 only or IL-4 and some interferon (IFN)-gamma and could, therefore, be considered as T helper type 2 (Th2) and Th0 cells, respectively. They triggered normal syngeneic B cells to produce in vitro IgE, anti-DNA, anti-laminin and anti-2,4-6-trinitrophenol antibodies through, at least in part, cognate interactions. More interestingly, these lines when transferred into normal BN rats induced an autoimmune syndrome similar to or even more severe than the one observed in the active gold model, provided the recipients were CD8 depleted. These manifestations included a dramatic increase in serum IgE concentration and the production of anti-DNA and anti-laminin antibodies. In addition, all recipients displayed an autoimmune glomerulonephritis due to anti-laminin antibodies, granular IgG deposits in the interstitium, in the vessel walls and along the tubular basement membranes and a severe tubulointerstitial nephritis with marked mononuclear cell infiltration. An anti-ovalbumin T cell line that produced IL-4 and low amounts of IFN-gamma was used as a control and did not induce autoimmunity. These results demonstrate for the first time the ability of autoreactive Th2 as well as Th0 cell lines to induce antibody-mediated autoimmunity. They also show that CD8+ cells play a crucial role in the control of such autoreactive cells. Finally, this work suggests that Th2 cells could initiate cell-mediated reactions either directly or indirectly.

Animals↗
PubMed1995

Mitochondrial perturbations define lymphocytes undergoing apoptotic depletion in vivo.

We have recently shown that lymphocyte apoptosis induced by dexamethasone or superantigens is accompanied by reduction of mitochondrial transmembrane potential (delta psi m) which precedes nuclear DNA fragmentation. Here, we demonstrate that fluorochromes such as 3,3' dihexyloxacarbocyanine iodide [DiOC6(3)] which measure delta psi m, or fluorochromes such as hydroethidine (HE) which measure mitochondrial superoxide anion production allow the identification of thymocytes or peripheral T lymphocytes which are eliminated by apoptosis in vivo. In mice bearing transgenic alpha/beta T cell receptor (TCR) specific for a class I-restricted male-specific peptide, the superoxide-mediated oxidation of HE into ethidium (Eth) is enhanced among thymocytes which are being deleted due to negative selection (CD4+ CD8+ cells expressing the transgenic TCR in male mice) or lack of positive selection (CD4+ CD8- thymocytes from female mice). delta psi m reduction and/or enhanced HE oxidation are also found when apoptosis is induced by a series of pathogenic agents. Thus, lethal irradiation provokes mitochondrial and nuclear signs of apoptosis, and both these alterations are absent in mice bearing a p53 null mutation, underlying the correlation between mitochondrial perturbation and nuclear apoptosis. Similarly, superantigen-triggered deletion of peripheral T cells in vivo is accompanied by enhanced HE-->Eth conversion and reduced DiOC6(3) uptake. More importantly, as compared to normal controls, CD4+ or CD8+ cells from clinically asymptomatic human immunodeficiency virus-1 (HIV-1) carriers also contain a significantly elevated percentage of cells endowed with reduced DiOC6(3) uptake. In superantigen- and HIV-induced apoptosis, the percentage of T lymphocytes with a subnormal DiOC6(3) uptake is more important than that of cells marked by enhanced HE-->Eth conversion. In conclusion, mitochondrial alterations precede and/or accompany nuclear signs of apoptosis induced by physiological and a variety of different pathogenic agents in vivo.

Animals↗
PubMed1994

Pertussis toxin inhibits activation-induced cell death of human thymocytes, pre-B leukemia cells and monocytes.

Activation of human thymocytes and pre-B cells via the CD3/T cell receptor (TCR) complex or the IgM/B cell receptor complex, respectively, results in apoptotic cell death. Similarly, cross-linking of the activation marker CD69, which belongs to the natural killer complex, causes apoptosis of lipopolysaccharide-preactivated monocytes. Here we show that pertussis toxin (PTX) inhibits the activation-induced apoptosis of these three cell types, though it fails to prevent the programmed cell death that follows exposure of cells to the synthetic glucocorticoid dexamethasone (thymocytes, pre-B cells) or to interleukin 4 (monocytes). The capacity of pertussis toxin to suppress activation-induced death is not due to quenching of the activation signal, because thymocytes exposed to PTX are still capable of mobilizing Ca2+ after TCR-alpha/beta cross-linking and proliferate in response to costimulation with PTX and CD3/TCR ligation. The apoptosis-inhibitory effect of PTX depends on the presence of an intact adenosine diphosphate (ADP)-ribosylating moiety, since a mutant pertussis toxin molecule that lacks enzymatic activity, but still possesses the membrane translocating activity, fails to interfere with activation-induced cell death. A toxin that induces a different spectrum of ADP ribosylation than PTX, cholera toxin, fails to inhibit apoptosis. To suppress apoptosis, the intact PTX holotoxin must be added to cells before the lethal activation step; its addition 30 min after initial activation remains without effect on apoptosis. These data unravel a PTX sensitive signal transduction event that intervenes during an early step of activation-induced cell death of immune cells.

Apoptosis↗
PubMed1994

[Autoimmunity and toxic agents].

In certain subjects medicinal drugs or toxic agents may induce organ-specific or systemic diseases. The mechanisms of this induction vary according to the type of toxic agent involved. The modification of autoantigens by a toxic agent might be the cause of autoimmune disorders. Thus, certain drugs metabolized by enzymes are known to bind on these enzymes in a covalent manner, thereby making the enzyme immunogenic. The immune reaction thus induced could be responsible for hepatitis. If the modified autoantigen is a molecule, such as the class II molecules of the major histocompatibility complex, which plays an important role in communication between the immune system cells, the autoimmune reaction could result in polyclonal lymphocyte B activation and in a lupus-like autoimmune disease. It is also possible that a drug interferes with one of the element which control the advent of autoreactive T cells and in this way becomes responsible for autoimmune systemic manifestations.

Animals↗
PubMed1994

Improvement of TH1 functions during the regulation phase of mercury disease in brown Norway rats.

Brown Norway (BN) rats are poor responders to T-cell mitogens and alloantigens when compared to Lewis (LEW) rats. This is dependent partly upon a defect in IL-2 production. The TH2-mediated immune abnormalities observed in BN rats injected with mercuric chloride (HgCl2) are self-limited and it is probable that this regulation phase involves TH1-like cells. This paper reports on a study of the ability of lymph node cells (LNC) from normal BN and LEW rats and from HgCl2-injected BN rats to produce IL-2 and to proliferate when stimulated in vitro by Con A or alloantigens in mixed lymphocyte reaction (MLR), as well as to develop a cytotoxic T lymphocyte (CTL) response to alloantigens. This study will confirm that LNC from BN rats proliferate less than LNC from LEW rats, that the former produce less IL-2 than the latter, and that the proliferative response is restored partially after addition of IL-2. In addition, it is shown (1) that the CTL response is defective in normal BN rats when compared to that of normal LEW rats, and (2) that, after the second week of HgCl2 injections, the proliferative responses to Con A and alloantigens are improved as well as IL-2 production, and a complete restoration of CTL function is observed. These results show that normal BN rats are deficient in the induction of TH1-like cells and that, from the second week of HgCl2 injections, these TH1 functions improve.

Animals↗
PubMed1993

Mercury-induced autoreactive anti-class II T cell line protects from experimental autoimmune encephalomyelitis by the bias of CD8+ antiergotypic cells in Lewis rats.

Brown-Norway (BN) rats injected with HgCl2 develop a systemic autoimmune disease associated with a polyclonal B cell activation, due to autoreactive T cells specific for self-class II molecules, while Lewis (LEW) rats injected with HgCl2 do not exhibit autoimmunity and develop a non-antigen-specific, CD8-mediated immunosuppression assessed by a depression of T cell functions, and a protection against experimental autoimmune encephalomyelitis (EAE). Resistance to HgCl2-induced autoimmunity is not due to these suppressor cells since treatment with an anti-CD8 monoclonal antibody (mAb) did not allow autoimmunity to appear. The absence of autoimmunity in this strain could result from the absence of autoreactive T cells, or from quantitative or qualitative differences of these cells between susceptible and resistant strains. In the present study, we show that CD4+ anti-class II T cells are present in HgCl2-injected LEW rats and are as frequent as in BN rats when assessed by limiting dilution analysis. LEW CD4+ autoreactive T cell lines were derived. They proliferated in the presence of normal class II-bearing cells, secreted interleukin 2, and did not induce B cells to produce immunoglobulins. Transfer of one of these lines, LEW Hg A, into normal LEW rats led to the appearance of CD8+ cells responsible for a non-antigen-specific immunosuppression that induced complete protection from EAE. Immunosuppression was abrogated after treatment with an anti-CD8 mAb. In vitro, CD8+ cells from rats injected with the LEW Hg A T cell line proliferated in the presence of activated T cells whatever their origin. We conclude that HgCl2 induces CD4+ autoreactive T cells that proliferate in the presence of class II+ cells in susceptible BN as well as in resistant LEW rats. But while these cells collaborate with B cells to produce autoantibodies in BN rats, they initiate in LEW rats a suppressor circuit involving antiergotypic CD8+ suppressor cells.

Animals↗
PubMed1993

Anti-renin T cells trigger normal B cells to produce anti-renin antibodies and normalize blood pressure in spontaneously hypertensive rats.

Spontaneously hypertensive (SH) rats immunized with mouse renin produce anti-renin antibodies, responsible for down-modulation of blood pressure, associated with an infiltration of kidneys by mononuclear cells. In this work, anti-renin T cells from SH rats immunized with renin have been stimulated in vitro, and we have studied in vitro and in vivo their effect on anti-renin antibody production by normal syngeneic B cells. We show that, in vitro, renin-activated T cells induce a renin-specific antibody response without addition of exogenous renin. Anti-renin T cells injected into naive SH rats trigger normal B cells to secrete high amounts of monospecific anti-renin IgG antibodies as early as day 5. These antibodies interfere with the homeostasis of the renin-angiotensin system leading to the normalization of blood pressure without any nephritis. These results show that anti-renin B cells are either not tolerant per se or in a reversible state of anergy. Our results also suggest that anti-renin B cells constitutively express renin-derived peptides in such a way that they may be stimulated by activated anti-renin T cells; these cells express IL-4 mRNA indicating that IL-4 could play a role in the differentiation of B cells.

Animals↗