Predictive Value of MR-proADM in the Risk Stratification and in the Adequate Care Setting of COVID-19 Patients Assessed at the Triage of the Emergency Department.

In the past two pandemic years, Emergency Departments (ED) have been overrun with COVID-19-suspicious patients. Some data on the role played by laboratory biomarkers in the early risk stratification of COVID-19 patients have been recently published. The aim of this study is to assess the potential role of the new biomarker mid-regional proadrenomedullin (MR-proADM) in stratifying the in-hospital mortality risk of COVID-19 patients at the triage. A further goal of the present study is to evaluate whether MR-proADM together with other biochemical markers could play a key role in assessing the correct care level of these patients. Data from 321 consecutive patients admitted to the triage of the ED with a COVID-19 infection were analyzed. Epidemiological; demographic; clinical; laboratory; and outcome data were assessed. All the biomarkers analyzed showed an important role in predicting mortality. In particular, an increase of MR-proADM level at ED admission was independently associated with a threefold higher risk of IMV. MR-proADM showed greater ROC curves and AUC when compared to other laboratory biomarkers for the primary endpoint such as in-hospital mortality, except for CRP. This study shows that MR-proADM seems to be particularly effective for early predicting mortality and the need of ventilation in COVID-19 patients admitted to the ED.

NLRP1 promotes tumor growth by enhancing inflammasome activation and suppressing apoptosis in metastatic melanoma.

Inflammasomes are mediators of inflammation, and constitutively activated NLRP3 inflammasomes have been linked to interleukin-1ß (IL-1ß)-mediated tumorigenesis in human melanoma. Whereas NLRP3 regulation of caspase-1 activation requires the adaptor protein ASC (apoptosis-associated speck-like protein containing a CARD (caspase recruitment domain)), caspase-1 activation by another danger-signaling sensor NLRP1 does not require ASC because NLRP1 contains a C-terminal CARD domain that facilitates direct caspase-1 activation via CARD-CARD interaction. We hypothesized that NLRP1 has additional biological activities besides IL-1ß maturation and investigated its role in melanoma tumorigenesis. NLRP1 expression in melanoma was confirmed by analysis of 216 melanoma tumors and 13 human melanoma cell lines. Unlike monocytic THP-1 cells with prominent nuclear localization of NLRP1, melanoma cells expressed NLRP1 mainly in the cytoplasm. Knocking down NLRP1 revealed a tumor-promoting property of NLRP1 both in vitro and in vivo. Mechanistic studies showed that caspase-1 activity, IL-1ß production, IL-1ß secretion and nuclear factor-kB activity were reduced by knocking down of NLRP1 in human metastatic melanoma cell lines 1205Lu and HS294T, indicating that NLRP1 inflammasomes are active in metastatic melanoma. However, unlike previous reports showing that NLRP1 enhances pyroptosis in macrophages, NLRP1 in melanoma behaved differently in the context of cell death. Knocking down NLRP1 increased caspase-2, -9 and -3/7 activities and promoted apoptosis in human melanoma cells. Immunoprecipitation revealed interaction of NLRP1 with CARD-containing caspase-2 and -9, whereas NLRP3 lacking a CARD motif did not interact with the caspases. Consistent with these findings, NLRP1 activation but not NLRP3 activation reduced caspase-2, -9 and -3/7 activities and provided protection against apoptosis in human melanoma cells, suggesting a suppressive role of NLRP1 in caspase-3/7 activation and apoptosis via interaction with caspase-2 and -9. In summary, we showed that NLRP1 promotes melanoma growth by enhancing inflammasome activation and suppressing apoptotic pathways. Our study demonstrates a tumor-promoting role of NLRP1 in cancer cells.

Antibody response in silver catfish (Rhamdia quelen) immunized with a model antigen associated with different adjuvants.

Adjuvants are essential to boost the immune response to inoculated antigen and play a central role in vaccine development. In this study, we investigated the efficacy of several adjuvants in the production of anti-bovine serum albumin (BSA) antibodies in silver catfish. Two hundred and seventy juvenile silver catfish (60-80 g) of both sexes were intraperitoneally vaccinated with BSA (200 µg/fish) alone or mixed to the following adjuvants: Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA), aluminum hydroxide (AlOH), Montanide, four types of cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) and three concentrations of ß-glucan, and the immune enhancing property was evaluated by measuring anti-BSA antibodies in blood samples at biweekly intervals. Our results demonstrated that CpGs ODNs and ß-glucan were as effective as classical adjuvants (FCA, FIA, AlOH and Montanide) in promoting anti-BSA antibodies and that the kinetics of antibody production induced by all adjuvants used in our study had a similar trend to that observed in other fish species, with a peak at 28 days post-vaccination. These results may be useful for the selection of adjuvants for vaccine formulation intended for silver catfish and for the development of vaccine and vaccination strategies to other fish species.

Combined blockade of the histamine H1 and H4 receptor suppresses peanut-induced intestinal anaphylaxis by regulating dendritic cell function.

BACKGROUND: Signaling through histamine receptors on dendritic cells (DCs) may be involved in the effector phase of peanut-induced intestinal anaphylaxis. OBJECTIVES: The objective of this study was to determine the role of histamine H1 (H1R) and H4 receptors (H4R) in intestinal allergic responses in a model of peanut allergy. METHODS: Balb/c mice were sensitized and challenged with peanut. During the challenge phase, mice were treated orally with the H1R antagonist, loratadine, and/or the H4R antagonist, JNJ7777120. Bone marrow-derived DCs (BMDCs) were adoptively transferred to nonsensitized WT mice. Symptoms, intestinal inflammation, and mesenteric lymph node and intestine mucosal DCs were assessed. Effects of the drugs on DC chemotaxis, calcium mobilization, and antigen-presenting cell function were measured. RESULTS: Treatment with loratadine or JNJ7777120 individually partially suppressed the development of diarrhea and intestinal inflammation and decreased the numbers of DCs in the mesenteric lymph nodes and lamina propria. Combined treatment with both drugs prevented the development of diarrhea and intestinal inflammation. In vitro, the combination suppressed DC antigen-presenting cell function to T helper cells and DC calcium mobilization and chemotaxis to histamine. CONCLUSION: Blockade of both H1R and H4R in the challenge phase had additive effects in preventing the intestinal consequences of peanut sensitization and challenge. These effects were mediated through the limitation of mesenteric lymph node and intestinal DC accumulation and function. Identification of this histamine H1R/H4R-DC-CD4+ T-cell axis provides new insights into the development of peanut-induced intestinal allergic responses and for prevention and treatment of peanut allergy.

Antibody response in silver catfish (Rhamdia quelen) immunized with a model antigen associated with different adjuvants

Adjuvants are essential to boost the immune response to inoculated antigen and play a central role in vaccine development. In this study, we investigated the efficacy of several adjuvants in the production of anti-bovine serum albumin (BSA) antibodies in silver catfish. Two hundred and seventy juvenile silver catfish (60–80 g) of both sexes were intraperitoneally vaccinated with BSA (200 µg/fish) alone or mixed to the following adjuvants: Freund’s complete adjuvant (FCA), Freund’s incomplete adjuvant (FIA), aluminum hydroxide (AlOH), Montanide, four types of cytosine-phosphate-guanine (CpG) oligodeoxynucleotides (ODNs) and three concentrations of β-glucan, and the immune enhancing property was evaluated by measuring anti-BSA antibodies in blood samples at biweekly intervals. Our results demonstrated that CpGs ODNs and β-glucan were as effective as classical adjuvants (FCA, FIA, AlOH and Montanide) in promoting anti-BSA antibodies and that the kinetics of antibody production induced by all adjuvants used in our study had a similar trend to that observed in other fish species, with a peak at 28 days post-vaccination. These results may be useful for the selection of adjuvants for vaccine formulation intended for silver catfish and for the development of vaccine and vaccination strategies to other fish species.

Role of prostaglandin D2 and CRTH2 blockade in early- and late-phase nasal responses.

BACKGROUND: Prostaglandin D2 (PGD2 ) plays an important role in allergic inflammation. The PGD2 receptor, CRTH2, is expressed on basophils, eosinophils, and Th2 lymphocytes and mediates chemotactic activity. OBJECTIVE: To define the role of CRTH2 in allergen-induced nasal responses in a mouse model of allergic rhinitis (AR), a potent, selective CRTH2 receptor antagonist, ARRY-063 was administered in a model of allergic rhinitis in mice. METHODS: ARRY-063 was administered orally to ovalbumin (OVA) sensitized and challenged mice. To assess nasal obstruction, respiratory frequency (RF) was monitored by whole-body plethysmography immediately after the 4th challenge (early-phase response, EPR) and 24 h after the 6th challenge (late-phase response, LPR). Nasal resistance (RNA ) was also measured in the LPR. PGD2 was administered with or without OVA to determine the effect of PGD2 on nasal responsiveness. Cytokine levels and histopathological changes in nasal tissue were analysed. RESULTS: Instillation of PGD2 in the nose of sensitized mice together with a low concentration of OVA induced both an EPR and LPR. Treatment with the CRTH2 receptor antagonist prevented the decreases in RF seen immediately following the 4th challenge of sensitized mice (EPR). In the LPR, decreases in RF and increases in RNA were also prevented by antagonist treatment associated with reduced cytokine levels and inflammation in nasal tissues. CONCLUSIONS: These data identify PGD2 as a mediator of both the EPR and LPR in this model of AR and suggest that antagonism of CRTH2 prevents the development of both the EPR and LPR as well as nasal inflammation.

Requirement for dual signals by anti-CD40 and IL-4 for the induction of nuclear factor-kappa B, IL-6, and IgE in human B lymphocytes.

Stimulation of human peripheral B cells via the CD40 receptor and IL-4R together lead to IgE synthesis and secretion, but the intracellular signaling mechanisms by which these signals lead to IgE production are unclear. Roles for the transcription factor NF-kappa B and IL-6 have been postulated in the induction of IgE synthesis by IL-4/CD40. We found that neither anti-CD40 Ab nor IL-4 alone was able to induce significant proliferation of human B cells. However, the combination of anti-CD40 and IL-4 was a potent inducer of B cell proliferation in addition to IgE production from purified human B cells. Furthermore, IL-4 and anti-CD40 synergized for the production of IL-6. While neither IL-4 alone nor anti-CD40 alone was able to induce significant NF-kappa B DNA binding activity, the combination of IL-4 and anti-CD40 induced a strong activation of NF-kappa B, a transcription factor that regulates IL-6 production. These data indicate that both IL-4 and anti-CD40 are required to induce NF-kappa B activation and IL-6 transcription and production, and implicate these events in a signaling pathway augmenting IgE production in human B lymphocytes.

Posttranscriptional regulation of T-cell IL-2 production by human pooled immunoglobin.

We evaluated the mechanism by which human pooled gamma-globulin for intravenous use (hIVIG) inhibits interleukin-2 (IL-2) production by human T cells. hIVIG reduced by 70-95% the amount of IL-2 in culture supernatants from mitogen-stimulated peripheral blood T cells or Jurkat cells. This reduction was not apparent at the transcriptional level: hIVIG had no effect on the levels of IL-2 mRNA or on the accumulation of firefly luciferase when its gene was linked to the IL-2 promoters. In contrast, hIVIG inhibited IL-2 protein synthesis, and the intracellular IL-2 was not restored by monensin. Our results indicate that the inhibition of IL-2 production by hIVIG occurred post-transcriptionally, and also suggest that secretion was unaffected, and that this effect of hIVIG was specific for IL-2 (and possibly other related cytokines). The data identify a previously uncharacterized regulatory mechanism of IL-2 production and predict that this immunomodulatory effect of hIVIG may be significant for its therapeutic actions in immune-mediated diseases.

Triggering through CD40 promotes interleukin-4-induced CD23 production and enhanced soluble CD23 release in atopic disease.

The pathogenesis of atopic disease is closely linked to the overproduction of IgE. CD23 and CD40 are two cellular receptors involved in the regulation of IgE production and both receptors are elevated in atopic disease. We have examined the role of CD40 in the regulation of CD23 and soluble CD23 production in healthy and atopic donors. Triggering of the B cell CD40 receptor directly enhances interleukin (IL)-4-mediated up-regulation of CD23 at both the protein and the mRNA level. When atopic donors were studied, the synergistic effect of CD40 triggering on the IL-4-induced up-regulation of CD23 and soluble CD23 (sCD23) was enhanced and there was a relative skewing toward production of sCD23. These studies implicate the CD40 receptor in the hyperproduction of CD23 and sCD23 in atopic disease and suggest that abnormalities may exist in the cellular pathways leading to sCD23 production.

Ouabain induces inhibition of the progression phase in human T-cell proliferation.

Ouabain, a specific inhibitor of the Na-K ATPase, has been shown to exert immunosuppressive effects. The goals of this study were to define the stage of the proliferative response which is sensitive to ouabain and to correlate the inhibitory action of ouabain on cell proliferation with its effect on Na-K ATPase activity. We found that ouabain inhibited T-cell proliferation in a dose-dependent manner and this inhibition was similar in CD4+ and CD8+ T cells. To define the role of the Na-K ATPase in early activation of T lymphocytes, we examined the effects of ouabain on the induction of competence (acquisition of responsiveness to interleukin (IL)-2 or IL-4) by phytohemagglutinin (PHA) or the combination of phorbol dibutyrate/ionomycin. Ouabain, at concentrations that completely inhibited the enzyme activity, did not interfere with the induction of competence, suggesting that although activated cells express increased activity of Na-K ATPase, this enzyme activity does not play a role in early activation pathways. In contrast, ouabain inhibited the progression phase to DNA synthesis in a dose-dependent manner even at concentrations that had little or no effect on Na-K ATPase activity. This inhibition was not due to a decrease in the production of IL-2 but rather to an inhibition of the expression of the p55 and p75 subunits of the IL-2 receptor (IL-2R). The inhibition of p55 appeared to occur at the mRNA level. These results indicate that the activity of the Na-K ATPase is not essential for the induction of competence or early activation. On the other hand, inhibition of cell proliferation and transcription of IL-2R subunits by low concentrations of ouabain may be related to changes in intracellular K+ concentrations or to inhibition of membranal phospholipid metabolism secondary to alteration in Na-K ATPase activity.

Differential regulation of the synthesis and activity of the major cyclin-dependent kinases, p34cdc2, p33cdk2, and p34cdk4, during cell cycle entry and progression in normal human T lymphocytes.

Three major cyclin-dependent kinases, p34cdc2, p33cdk2, and p34cdk4 were examined in normal human T cells stimulated to enter the cell cycle in vitro. None of the three genes was expressed in resting T cells. Transcripts form the cdk4 and cdk2 genes were detectable as early as 3 and 8 hr after stimulation, respectively, whereas cdc2 gene transcripts were not detectable until about 24 hr, shortly before S phase entry. Immunoblot analysis showed that resting T cells contained little p34cdk4, no p34cdc2, and a low level of p33cdk2 protein. Increased amounts of p34cdk4, p33cdk2, and p34cdc2 proteins were seen at about 7, 10, and 30 hr after stimulation, respectively. Immunoprecipitates of each of the kinases were assessed for histone H1 kinase activity. Activity due to p33cdk2 first became detectable in mid-G1 phase and increased dramatically after entry into S phase. Active p34cdc2 kinase was not detected until about 40 hr after stimulation, about 10 hr after the first appearance of the protein. Immunoprecipitates of p34cdk4 possessed almost no H1 histone kinase activity; however, activity was detected as early as 10 hr after cell activation when a protein (p60Rb) derived from the retinoblastoma susceptibility gene product was used as substrate. Cells were synchronized about the G1/S and G2/M borders by aphidicolin and nocodazole. Cells arrested prior to S-phase contained high levels of active p33cdk2 and essentially no active p34cdc2, despite the fact that large amounts of both proteins were present. Cells arrested by nocodazole had high levels of active p34cdc2 and greatly reduced levels of p33cdk2 kinase activity. The results suggest that the major role for the p34cdc2 kinase is at mitosis, whereas that for p33cdk2 is in late G1 and/or S phase. The p34cdk4 protein, present in aphidicolin-blocked cells, was nearly absent from cells arrested at the G2/M border; however, kinase activity was low in cells blocked at both points, suggesting that the major role for p34cdk4 may be in G1 phase.

Effects of iron-depletion on cell cycle progression in normal human T lymphocytes: selective inhibition of the appearance of the cyclin A-associated component of the p33cdk2 kinase.

Iron removal by the chelating-agent deferoxamine (DFO) arrests cell cycle progression of activated human T cells in late G1 phase, before the G1/S border. The effects of the drug on molecules that regulate progression through the cell cycle were defined. DFO (10 mumol/L) inhibited induction of transcription of the cdc2 gene, but had no effect on accumulation of cdk2, cdk4, or interleukin (IL)-2-transcripts. No detectable p34cdc2 protein accumulated, but synthesis of the p33cdk2 protein was begun. It accumulated to normal levels during the first 20 to 30 hours of incubation in the presence of DFO. Furthermore, p33cdk2 was activated as an H1 histone kinase. As active p33cdk2 primarily represents complexes of the p33 protein with cyclin E or cyclin A, the effects of DFO on these cyclins were examined. Although the induction of synthesis and early accumulation of cyclin E and cyclin E-associated kinase activity appeared normal, the appearance of cyclin A and cyclin A-associated kinase activity were inhibited by DFO. However, the production of cyclin A mRNA appeared to be normal in the presence of DFO. A major effect of DFO in blocking cell cycle progression may be mediated through inhibition of the appearance of cyclin A protein and, therefore, a major component of p33cdk2 activity. The results also indicate that the p33cdk2/cyclin E activity produced in the presence of DFO was not sufficient for completion of the G1 phase of the cell cycle.

Symmetry of the activation of cyclin-dependent kinases in mitogen and growth factor-stimulated T lymphocytes.

The entry of resting T cells into the G1 phase of the cell cycle after stimulation by mitogens is controlled by a series of biochemical events that are independent of growth factors. These events follow the initial signals stimulated through the engagement of the T-cell receptor and include activation of the cyclin-dependent kinases Cdk6, Cdk4, and Cdk2, as well as a transient phosphorylation of the retinoblastoma gene product (p110Rb) by one or several of these proteins. A progression signal such as that delivered by interleukin-2 then induces a second phase of Cdk6, Cdk4, and Cdk2 activation, along with sustained phosphorylation of p110Rb in the activated T cells. This second signal is required to carry the cells into the S phase and beyond. Quantitative and qualitative differences in the expression and activity of these proteins may be critical to maintain the delicate balance that is necessary to ensure the normal progression of T cells through the cell cycle.

Regulation of synthesis and activity of the PLSTIRE protein (cyclin-dependent kinase 6 (cdk6)), a major cyclin D-associated cdk4 homologue in normal human T lymphocytes.

The PLSTIRE protein (cyclin-dependent kinase 6 (cdk6)), which shares extensive sequence homology (approximately 70%) with cdk4, was identified as the earliest inducible member of the cdk family of proteins in human T lymphocytes induced to proliferate in vitro by stimulation either with phorbol 12,13-dibutyrate and ionomycin (PDB/I) or PHA. The p40cdk6 protein was present in resting cells and increased amounts were detected 6 h after stimulation. It increased in amount throughout the first cell cycle but was present in reduced amounts at later times. Activity of the kinase, determined by in vitro phosphorylation of recombinant truncated retinoblastoma tumor suppressor gene (Rb) protein (p60Rb), paralleled p40cdk6 protein amounts. Cyclins D2 and D3 were the major cyclins associated with p40cdk6, with D2 predominating in early G1 phase. Both PDB and ionomycin were required for maximal accumulation of p40cdk6, but either agent alone stimulated some increase in amount and activity of the protein. p40cdk6 also increased in amount in cells activated in the presence of cyclosporin A or FK506, drugs that inhibit production of IL-2 and cell proliferation, suggesting that initial induction occurred independently of IL-2-mediated cell cycle progression. Furthermore, increased accumulation of p40cdk6 protein and activity occurred in cells rendered "competent" (responsive to IL-2) by a brief treatment with PDB/I. Thus, increased accumulation of the protein and its activity begin before IL-2/IL-2 receptor interaction, suggesting that the cdk6-cyclin D2 complex might be involved in acquisition of the competent state in human T lymphocytes.

Differential requirements for interleukin-2 distinguish the expression and activity of the cyclin-dependent kinases Cdk4 and Cdk2 in human T cells.

We examined the expression and activity of Cdk4 and Cdk2 in resting, competent, and proliferating normal human T cells. Expression of Cdk4 but not of Cdk2 was induced in competent T cells independent of an IL-2 signal. This up-regulation of Cdk4 mRNA and protein was resistant to the immunosuppressant drugs cyclosporin A (CsA) and FK506. A further increase in Cdk4 expression was seen upon stimulation of competent T cells by IL-2, as was de novo expression of Cdk2. Cyclin D2, a Cdk4 partner, showed similar patterns of regulation as Cdk4. The increases in Cdk4 and cyclin D2 expression seen in competent T cells were functionally significant since Cdk4 immunoprecipitates from these cells phosphorylated recombinant RB protein in vitro. Despite the lack of an increase in the expression of Cdk2, a small pool of pre-existing Cdk2 protein detected in resting T cells could be activated upon induction of competence. These data demonstrate that 1) the signals that lead to induction of competence in T cells stimulate an IL-2-independent and CsA-resistant phase of Cdk4 and cyclin D2 expression, Cdk4 kinase activity, and Cdk2 kinase activity, and 2) IL-2 stimulates a second phase of Cdk4 and cyclin D2 expression and de novo expression of Cdk2 in these cells. The data show that the expression and activity of these major cell cycle regulatory proteins are controlled differentially by growth factors and indicate a role for Cdk4 and cyclin D2 in T-cell cycle entry and/or early G1 progression and for Cdk2 in later G1 progression and G1/S transition.

Role for Ca2+ in expression of cell cycle regulated genes in PAF-stimulated cells.

Platelet-activating factor (PAF) is a powerful stimulator of a wide variety of cells. In transformed human B-lymphoblastoid cell lines, PAF increases intracellular Ca2+ concentrations ([Ca2+]i) and induces the expression of the proto-oncogenes c-fos and early growth response gene-2 (EGR2). Here, we present data that evaluates the role of Ca2+ in the PAF-dependent induction of these cell-cycle activated genes. PAF (10(-7) M) increased c-fos and EGR2 mRNA levels in cells suspended in Ca(2+)-containing medium by 6-10-fold. In PAF-stimulated cells suspended in medium depleted of Ca2+, eliminating Ca2+ influx but not intracellular store release of Ca2+, the induction of gene expression was reduced by approx. 50%. In contrast, buffering of Ca2+ released from intracellular stores but maintaining transmembrane Ca2+ uptake had little effect on gene expression. When both sources of Ca2+ were eliminated, PAF-stimulated expression of these genes was completely prevented. This was not due to any toxicity to the cells since the response to phorbol ester under identical conditions was unaffected. The regulation of c-fos mRNA expression was paralleled by changes in levels of FOS protein. These data indicate that changes in [Ca2+]i, primarily from stimulated entry across the plasma membrane and to a lesser extent release of Ca2+ from sequestered intracellular stores, play an essential role in PAF-dependent triggering of c-fos and EGR2 mRNA expression.

Regulation of CD23 expression by IL-4 and corticosteroid in human B lymphocytes. Altered response after EBV infection.

Cellular CD23 has been implicated in various biologic and pathologic processes. Here, we have studied the regulation of B cell CD23 expression and function by the synthetic corticosteroid, dexamethasone (DEX). We report that DEX acts directly on B lymphocytes to down-regulate IL-4-induced CD23 expression, whereas in parallel the IL-4R is up-regulated. Down-regulation of CD23 occurred at the cell surface and for shed material in culture medium. EBV infection of B cells is linked to development of lymphoproliferative diseases, including lymphoma, and there is evidence that EBV-stimulated CD23 expression may be instrumental in the inappropriate survival of infected cells. We have determined that treatment of EBV-infected cells with IL-4 leads to a synergistic up-regulation of B cell CD23. Furthermore, infection of B cells by EBV introduced a relative resistance to the down-regulatory effects of DEX on IL-4-induced CD23 expression.

Ethanol inhibits early events in T-lymphocyte activation.

Ethanol has been reported to be immunosuppressive. We have studied the effects of ethanol on early activation events related to the proliferative response of human T lymphocytes. Ethanol inhibited T-cell proliferation in a dose-dependent manner. To define the target of this ethanol-mediated inhibition of T-cell function we examined its effect on the activation of T lymphocytes or induction of competence (acquisition of responsiveness to interleukin (IL)-2 or IL-4) by phytohemagglutinin (PHA) or the combination of phorbol dibutyrate (PDB)/ionomycin. Ethanol inhibited induction of competence with PHA by up to 50% when compared to control cells. In contrast to the effects on PHA-mediated activation of the cells, ethanol exerted no inhibitory action on the induction of competence by PDB/ionomycin. Ethanol also inhibited the induction of c-fos by PHA but not by PDB/ionomycin. To investigate the basis for these differences, the effects of ethanol on Ca2+ mobilization were examined. Ethanol inhibited PHA-induced Ca2+ mobilization in a dose-dependent manner. This inhibition was exerted mainly on transmembrane Ca2+ influx rather than on release of Ca2+ from intracellular stores. Ethanol did not affect Ca2+ mobilization induced by ionomycin. Co-incubation of ionomycin with PHA, during the induction of competence, abolished the inhibition exerted by ethanol when compared to cells treated with PHA alone. The inability of ethanol to exert complete inhibition on cell proliferation may be due to the activation of Ca(2+)-independent pathways by PHA, since combined treatment with ethanol and the intracellular Ca2+ chelator, BAPTA, did not completely inhibit the proliferative response. The inhibitory effects of ethanol on PHA-induced Ca2+ mobilization and subsequent induction of c-fos indicate that ethanol interferes with Ca(2+)-dependent pathways activated by PHA and this may provide the basis for its immunosuppressive action.

Effects of agents that inhibit cellular iron incorporation on bladder cancer cell proliferation.

Agents that interfere with cellular iron (Fe) incorporation inhibit tumor cell proliferation, including metals that bind to transferrin (Tf) such as gallium (Ga) or indium (In) and Fe chelators such as desferrioxamine (DFO). Ga nitrate is effective in the treatment of metastatic bladder cancer and these patients exhibit evidence for interference with Fe metabolism. We show here that bladder cancer cell proliferation in vitro is dependent on Tf-Fe. Concentrations of DFO that can be readily achieved in vivo inhibit cellular proliferation even in the presence of physiologic concentrations of Tf-Fe. Inhibition of proliferation by Tf-Ga is associated with decreased cellular Fe incorporation. However, when a physiologic concentration of Tf-Fe is added to an equimolar concentration of Tf-Ga, significant Fe incorporation is evident despite inhibition of proliferation. Thus, besides interference with Fe incorporation, Ga may also interfere with intracellular Fe distribution and/or directly inhibit an Fe- (or non-Fe-) requiring process necessary for cellular proliferation. DFO followed sequentially by Tf-Ga results in marked potentiation of inhibition of proliferation. The effects of this combination appear to be related to both interference with Fe metabolism and increased Ga uptake. This sequential combination may be useful in the treatment of bladder cancer.

Rapamycin blocks cell cycle progression of activated T cells prior to events characteristic of the middle to late G1 phase of the cycle.

The effects of rapamycin (RAP) on cell cycle progression of human T cells stimulated with PHA were examined. Cell cycle analysis showed that the RNA content of cells stimulated with PHA in the presence of RAP was similar to that of control T cells stimulated with PHA for 12-24 hr in the absence of the drug. This level was substantially higher than that seen in cells stimulated in the presence of cyclosporin A (CsA), an immunosuppressant known to block cell cycle progression at an early point in the cycle. However, the point in the cell cycle at which RAP acted appeared to be well before the G1/S transition, which occurs about 30-36 hr after stimulation with PHA. In an attempt to further localize the point in the cell cycle where arrest occurred, a set of key regulatory events leading to the G1/S boundary were examined, including p110Rb phosphorylation, which occurred at least 6 hr prior to DNA synthesis, p34cdc2 synthesis, and cyclin A synthesis. In control cultures, p110Rb phosphorylation was detected within 24 hr of PHA stimulation; p34cdc2 and cyclin A synthesis were detected within 30 hr. Addition of RAP to the cultures inhibited each of these events. In contrast, early events, including c-fos, IL-2, and IL-4 mRNAs expression, and IL-2 receptor (p55) expression, were only marginally affected, if at all, in PHA-stimulated T cells. Furthermore, the inhibition of cell proliferation by RAP could not be overcome by addition of exogenous IL-2. These results indicate that RAP blocks cell cycle progression of activated T cells after IL-2/IL-2 receptor interaction but prior to p110Rb phosphorylation and other key regulatory events signaling G1/S transition.