Biomedical subjects
Publications and source records attributed to D E Macfarlane.
On the basis of a systematic SAR analysis of substituted quinolines, a derivative 32 was synthesized that shows half-maximal inhibition of the immunostimulatory effect of CpG-oligodeoxynucleotides in vitro at the concentration of 0.24 nM.
Bacterial DNA and synthetic single-stranded oligonucleotides having unmethylated CpG motifs (CpG-ODN) powerfully stimulate cellular immune responses by an unknown mechanism. There is evidence that internalization of the nucleotide is required for activity. Both CpG-ODN and engagement of CD40 protects WEHI-231 murine B lymphoma cells from apoptosis induced by antibody to surface IgM, and both agents induce interleukin-6 (IL-6) production by these cells. We now report the isolation of CpG-ODN-resistant subclones (designated CR) from WEHI 231 cells, as well as subclones that are sensitive to CpG-ODN (designated CS). CR clones completely fail to respond to CpG-ODN but they retain the capacity to respond normally to engagement of CD40. CR cells incorporate CpG-ODN into small, acidified perinuclear vesicles in the same way as do the parent WEHI 231 cells. The CR, CS, and WEHI 231 cells all had identical cytogenetics. The described CR clones have a stable and specific defect in the mechanism responsible for the intracellular recognition and response to CpG-ODN, suggesting that they harbor a mutation that disables the CpG-ODN detection mechanism. These clones may be useful to determine at a molecular level which proteins and cell components are required for immune cells to detect and respond to CpG-ODN.
Selected phosphorothioate oligodeoxynucleotides containing CpG (CpG-ODN) activate immune responses, including immunoglobulin synthesis, B cell proliferation, and cytokine production by monocytes. We examined the effect of a CpG-ODN (#1760) on the adhesion of macrophages derived from human blood monocytes in vitro. CpG-ODN (6 microg/mL) completely inhibited the adherence of macrophages to plastic or glass during 7 or more days of culture. A non-CpG control ODN (#1814) was without effect. Two other CpG-ODNs (#1826 and #1842) also completely inhibited macrophage adherence. The specific inhibitor of CpG-ODN, quinacrine (0.1 micromol/L), blocked this action. CpG-ODN reduced the rate of senescence and cell death of monocytes in culture but did not influence their phagocytosis, procoagulant activity, or support of the mixed lymphocyte response. Four days of exposure of monocytes to CpG-ODN up-regulated the expression of the endotoxin receptor CD14 and down-regulated the mannose (scavenger) receptor, a result that is consistent with blocking the maturation of monocytes to macrophages. Incubation of peripheral blood monocytes (PBMCs) with CpG-ODN resulted in the generation of a heat labile factor that inhibited macrophage differentiation and accounts for the efficacy of the CpG-ODN. T cells selected from PBMCs by magnetic beads generated the majority of this factor. Cytokines (interleukin-3 (IL-3), IL-4, IL-6, IL-10, interferon-gamma, tumor necrosis factor-alpha, transforming growth factor-beta, granulocyte-macrophage colony-stimulating factor, monocyte chemotactic protein-1) did not inhibit macrophage adherence like CpG-ODN did. Antibodies to IL-6 or IL-10 did not block the activity of CpG-ODN. Dexamethasone inhibited macrophage adherence, and lipopolysaccharide had a minor effect. We conclude that immunostimulatory CpG-ODNs inhibit macrophage adherence by provoking the production of an unidentified heat-labile factor.
Selected phosphorothioate oligodeoxynucleotides containing CpG (CpG-ODN) activate immune responses, including B-cell proliferation and cytokine production. The mechanism by which cells detect CpG-motifs is not known. There are conflicting reports in the literature concerning the ability of CpG-ODN linked to solid supports to stimulate immunity. We prepared a fluorescent, biotinylated CpG-ODN, a reagent that will support the growth of 7TD1 cells, a murine B-cell hybridoma line that requires CpG-ODN or interleukin-6 (IL-6) for survival. Stimulation of 7TD1 cell growth was not reduced by complexing biotinylated CpG-ODN to streptavidin, but cell growth was not supported by CpG-ODN coupled to streptavidin-coated latex, magnetic, gold, or agarose beads. A fluorescent CpG-ODN was also covalently attached to cyanogen bromide-activated Sepharose beads via a 5'-amine group. These derivatized Sepharose beads did support 7TD1 cell growth, but incubation of the beads with 7TD1 cells resulted in the appearance of fluorescence within the cells, suggesting that growth stimulation may be due to CpG-ODN leached from the beads. Our results are consistent with the need for CpG-ODN to be internalized into cells to be immunostimulatory.
Oligodeoxynucleotides with unmethylated CpG motifs are immunostimulatory. Chloroquine and a number of structural analogs specifically and powerfully inhibit this effect at nanomolar concentrations. We explored the mechanism of this inhibition, with 4-aminoquinolines, quinacrine, 9-aminoacridines, and novel dibasic analogs, many of which are fluorescent. WEHI 231 murine B-lymphoma cells accumulated analogs up to a concentration several hundredfold higher than the medium. Uptake was rapid, nonsaturable, reversible, and partially inhibited by monensin, an agent that collapses pH gradients within cells. Uptake did not correlate highly with efficacy as inhibitors of CpG-oligodeoxynucleotide (ODN)-induced effects, suggesting that analogs act by a specific action. Confocal microscopy revealed analogs concentrating in large peripheral organelles. CpG-ODN is taken up by cells into acidified, small, perinuclear vesicles. This uptake is thought to be necessary for immunostimulatory activity. Cellular uptake of fluorescent CpG-ODN was not inhibited by the analogs. The pH of intracellular CpG-ODN (6. 4) was not affected by analogs at the concentration required for inhibition, but pH was increased by higher concentrations. UV spectroscopy revealed no binding of analogs to CpG-ODN. Nuclear Overhauser effect spectroscopy revealed that an analog bound to phosphatidylcholine vesicles, with the ring structure of the analog buried within the lipid and the side chain facing the aqueous environment. We conclude that the analogs do not inhibit the action of CpG-ODN by preventing the uptake or acidification of CpG-ODN. It seems more likely that the analogs inhibit the efficacy of CpG-ODN by a specific action within acidified vesicles, possibly at the interface of a phospholipid membrane.
Phosphorothioate oligodeoxynucleotides containing CpG (CpG-ODN) activate immune responses. We report that quinacrine, chloroquine, and structurally related compounds completely inhibit the antiapoptotic effect of CpG-ODN on WEHI 231 murine B lymphoma cells and inhibit CpG-ODN-induced secretion of IL-6 by WEHI 231. They also inhibit IL-6 synthesis and thymidine uptake by human unfractionated PBMC induced by CpG-ODN. The compounds did not inhibit LPS-induced responses. Half-maximal inhibition required 10 nM quinacrine or 100 nM chloroquine. Inhibition was noncompetitive with respect to CpG-ODN. Quinine, quinidine, and primaquine were much less powerful. Quinacrine was effective even when added after the CpG-ODN. Near-toxic concentrations of ammonia plus bafilomycin A1 (used to inhibit vesicular acidification) did not reduce the efficacy of the quinacrine, but the effects of both quinacrine and chloroquine were enhanced by inhibition of the multidrug resistance efflux pump by verapamil. Agents that bind to DNA, including propidium iodide, Hoechst dye 33258, and coralyne chloride did not inhibit CpG-ODN effect, nor did 4-bromophenacyl bromide, an inhibitor of phospholipase A2. Examination of the structure-activity relationship of seventy 4-aminoquinoline and 9-aminoacridine analogues reveals that increased activity was conferred by bulky hydrophobic substituents on positions 2 and 6 of the quinoline nucleus. No correlation was found between published antimalarial activity and ability to block CpG-ODN-induced effects. These results are discussed in the light of the ability of quinacrine and chloroquine to induce remission of rheumatoid arthritis and lupus erythematosus.
The mouse-mouse hybridoma plasma cell line 7TD1 requires exogenous IL-6 for growth, and has been used to characterize and assay IL-6. Oligodeoxynucleotides containing CpG (CpG-ODN) and bacterial DNA are immunostimulatory, preventing B-cell apoptosis and inducing cytokine synthesis. We report that the phosphorothioate CpG-ODN 5'-ATAATCGACGTTCAAGCAAG-3' (half maximal effect at 0.3 microg/ml) supports the growth of 7TD1 cells in the absence of added IL-6. A non-CpG control ODN was without effect. No IL-6 production by 7TD1 cells incubated with CpG-ODN was detected by sensitive immunoassay. CpG-ODN-supported growth was not influenced by IL-6-neutralizing antibody, but was completely abolished by chloroquine and quinacrine, agents which inhibit CpG-ODN responses in other cells. Our results show that CpG-ODN can substitute for IL-6 in this cell line. This cell line may be useful for assaying CpG-ODN activity and for screening congeners of chloroquine and quinacrine for their ability to inhibit CpG effects.
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RNA is a highly informative molecule that has great potential as a target for diagnostic studies. This potential can be reached only when reliable methods for isolating RNA are available in the clinical environment. Cationic surfactants lyse cells and precipitate nucleic acids. We have described a novel cationic surfactant (tetradecyltrimethylammonium oxalate, Catrimox-14), which is particularly effective in precipitating RNA from cells and which can be applied to clinical specimens. We examine the utility of a method of recovering RNA from the surfactant-nucleic acid precipitate, in which 2 M lithium chloride is used to extract the DNA and surfactant from the precipitate; RNA (being insoluble in lithium chloride solution) remains in the pellet. The yield of RNA from peripheral blood mononuclear cells by the Catrimox-LiCl method we describe was the same yield by a conventional method using guanidine thiocyanate, phenol, and chloroform (GPC). The quality of the RNA, judged by agarose gel electrophoresis, A260/280 ratio and its ability to serve as a target for reverse transcription and PCR, was the same. RNA was isolated and amplified from blood stored for at least 2 weeks in Catrimox solution at room temperature. RNA was also easily isolated with the Catrimox-LiCl method in good yield from frozen sections of mouse liver, spleen, kidney and brain, and from core biopsies of liver and kidney. RNA isolated from needle aspirates of liver, spleen, kidney, pancreas, and brain was easily amplified by RT-PCR. The Catrimox-LiCl method is simple and does not call for the use of corrosive reagents. The Catrimox-LiCl method removes 98% of the DNA. We conclude that the Catrimox-LiCl method is suitable for use in clinical applications of RNA-based diagnosis.
Growth and differentiation of blood cell precursors are regulated by cytokines and hormones by mechanisms which are incompletely understood. Protein kinase C (PKC) isozymes are widely regarded as being important in signal transduction pathways. We have shown that one isozyme, PKC beta, is uniquely important in mediating phorbol ester-induced growth-arrest in the HL-60 myeloid cell line. 1,25-dihydroxyvitamin D3 induces differentiation and growth-arrest in many cells. It upregulates the expression of PKC beta, potentiating the action of phorbol ester. We tested the hypotheses that cytokines, which arrest the growth of hematopoietic cells, do so by activating PKC beta, and that differentiation and growth-arrest induced by 1,25-dihydroxyvitamin D3 is caused by upregulation of PKC beta isozyme gene expression. The influence on growth of combinations of five cytokines (TNF alpha, TGF beta 1, gamma-IFN, IL-1, and G-CSF) and 1,25-dihydroxyvitamin D3 on ten human leukemia cell lines (THP-1, HL-60 S, HL-60 PET, U937, K562, Jurkat, MOLT-4, RPM1 8402, KG-1, and KG-1a) was determined. Four cell lines (THP-1, HL-60 S and PET, and U937) exhibited total growth-arrest when incubated with 1,25-dihydroxyvitamin D3 followed by TGF beta 1. The expression by each cell line of mRNA encoding PKC alpha, beta, and delta, both before and after 24 or 48 h of incubation with 1,25-dihydroxyvitamin D3, was determined. Cell lines sensitive to TGF beta 1 each expressed PKC delta endogenously, or expression was up-regulated with 1,25-dihydroxyvitamin D3. U937 cells underexpressed PKC alpha, and HL-60 PET cells underexpressed PKC beta. These data suggested that PKC delta could be responsible for mediating growth-arrest by TGF beta 1. To test this hypothesis directly, we incubated the cells with two bisindolylmaleimide PKC inhibitors during the addition of 1,25-dihydroxyvitamin D3 and TGF beta 1. Surprisingly, the PKC inhibitors did not block the growth-arrest induced by 1,25-dihydroxyvitamin D3 and TGF beta 1. This experiment strongly suggests that neither growth-arrest induced by TGF beta 1 nor the potentiation of this growth-arrest by 1,25-dihydroxyvitamin D3 is mediated by a PKC isozyme which is inhibitable by the bisindolymaleimides.
Phorbol-12-myristate-13-acetate (PMA) induces p21WAF-1 expression in human myeloid leukaemic HL-60 cells. We show that this induction is specifically mediated by protein kinase C (PKC). In addition, the PKC inhibitor Ro 31-8220 with predominant PKC-alpha isoform specificity almost completely inhibited PMA-induced up-regulation of p21WAF1 in HL-60 cells as well as in the myelomonocytic leukaemic U937 cells. Pretreatment of HL-60 cells with Ro 31-8220 also inhibited PMA-induced activation of c-raf-1, a known PKC alpha target. In the phorbol ester-tolerant HL-60 subline (PET) with PKC-beta isoform deficiency PMA or bryostatin-1 induced p21WAF1 expression, but to a lesser extent than in wild-type HL-60 cells. In PET cells, Ro 31-8220 also inhibited PMA and bryostatin-1-induced up-regulation of p21WAF1 expression. Our findings indicate that at least in HL-60 cells up-regulation of p21WAF-1 is specifically activated by PKC. We suggest that PKC isoforms other than beta, presumably the PKC-alpha isoform, are involved in this process.
Certain oligodeoxynucleotides (ODN) containing cytosine followed by guanosine (CpG) protect B cells from apoptosis, and induce B-cell proliferation and cytokine production. We investigated the effect of phosphorothioate CpG-containing ODNs (5'-ATAATCGACGTTCAAGCAAG-3' or 5'-TCCATGACGTTCCTGACGTT-3') and control ODNs (which did not contain CpG) on apoptosis and cell growth in WEHI 231 murine B lymphoma cells. Anti-surface (alpha-s)IgM antibody induces 40-60% DNA degradation and growth arrest of WEHI 231 cells in 24 h. Both of these effects were substantially reversed by 30 ng/ml CpG-ODN added up to 8 hr after alpha-sIgM. Control ODNs not containing the CpG motif were without effect. We explored various hypotheses to account for these effects. The phorbol ester, 12-O-tetradecanoyl phorbol-13-acetate, inhibits apoptosis induced by alpha-sIgM, but the anti-apoptotic effect of CpG-ODN was not affected by inhibitors of protein kinase C, indicating that CpG-ODN does not act via protein kinase C. CpG-ODN inhibited apoptosis and growth arrest induced by C2- and C8-ceramide, sphingomyelinase and an intracellular Ca2+ pump inhibitor thapsigargin, indicating that inhibition is not mediated via suppression of the ceramide cycle or suppression of Ca2+ mobilization. CpG-ODN partially inhibited apoptosis induced by okadaic acid, a protein phosphatase inhibitor, and by menadione, a free radical generator. CpG-ODN also inhibited apoptosis and growth arrest induced by ultraviolet-irradiation, glucocorticoid, vinca alkaloids, and doxorubicin. CpG-ODN significantly protected cells from DNA fragmentation induced by alpha-sIgM in the presence of cycloheximide, but cycloheximide itself induces apoptosis which was unaffected by CpG-ODN. These results suggest that CpG-ODNs powerfully modulate the process by which immune cells are committed to death or proliferation by a mechanism acting on distal cell signalling events. CpG-ODNs may be able to decrease immunosuppression in patients undergoing cancer chemotherapy.
Hepatitis C virus (HCV) requires reverse transcriptase-polymerase chain reaction (RT-PCR) or branched DNA signal amplification assays to be detected in patient samples. Although conventional methods of RNA isolation are employed for samples of serum, plasma, and peripheral blood mononuclear cells (PBMCs), whole blood is generally considered an unsuitable source of RNA because of abundant RNases and polymerase inhibitors. Using a cationic surfactant, Catrimox-14, we adapted a procedure for RNA isolation from whole blood, plasma, and PBMCs that yields RNA template suitable for HCV RT-PCR. RNA isolation required less than 2 hr, and HCV sequences were easily detected in sample volumes of 50 microliters whole blood or plasma, and in less than 1 x 10(4) PBMC. Following the addition of blood to Catrimox, HCV RNA was stable in the mixture when incubated for at least 7 days at room temperature prior to RNA extraction. Comparison of whole blood HCV RNA and plasma HCV RNA from individuals with chronic hepatitis suggests that HDV RNA can be more reliably detected in whole blood. Three of 15 HCV antibody positive patients (20%) had HCV RNA present in whole blood but simultaneously obtained plasma samples were negative. Two of the HCV antibody negative individuals with chronic hepatitis contained HCV RNA in whole blood, yet one of these patient's plasma was negative for viral RNA. The Catrimox-14 method of RNA purification is useful for detecting HCV RNA in whole blood and blood subfractions, and provides a practical method of measuring plasma and PBMC HCV RNA from clinical specimens.
12-O-Tetradecanoylphorbol-13-acetate (TPA) induces growth arrest and differentiation of a number of leukemia cell lines including HL-60 human promyelocytic leukemia. We investigated the involvement of protein kinase C (PKC) isotypes in phorbol ester-induced differentiation using the phorbol ester-tolerant PET mutant of HL-60 cells, which (in contrast to the parent phorbol ester-sensitive (wild-type) S variant of HL-60 cells) does not growth-arrest, become adherent, or undergo apoptosis when exposed to TPA (Macfarlane, D. E., Gailani, D., and Vann, K. (1988) Br. J. Haematol. 68, 291-302). In comparison to S cells, we found that proliferating PET cells markedly underexpress mRNA for PKC beta, but do express PKC alpha and PKC delta. The PKC beta-selective activator 12-deoxyphorbol 13-phenylacetate 20-acetate induces growth arrest, adherence, surface expression of CD11a, and apoptosis in S cells, but not in PET cells. Expression of PKC beta in PET cells can be restored by exposing them to dihydroxyvitamin D3, and this treatment restores the ability of subsequently added 12-deoxyphorbol 13-phenylacetate 20-acetate or TPA to induce immediate cell adherence and growth arrest of PET cells. These data led us to conclude that activation of PKC beta is both necessary and sufficient for phorbol ester-induced growth arrest and adherence in these myeloid cells.
A novel cationic surfactant solution is used to lyse blood cells and precipitate RNA and DNA. The RNA is recovered by extracting the pellet with a small volume of guanidinium isothiocyanate or formamide.
One of the factors regulating the population size of a clone of proliferating cells is the induction of a physiological suicide mechanism known as apoptosis. We studied apoptosis in the HL-60 human promyelocytic leukemia cell line which differentiates when exposed to phorbol ester (S-cell), and in the PET-cell mutant of HL-60 which is defective in its response to phorbol ester. Exposing S-cells to 12-O-tetradecanoylphorbol 13-acetate (TPA) (3 nM and above) induced morphological changes characteristic of apoptosis (visualized by light microscopy), and induced fragmentation of chromatin DNA to oligonucleosomal lengths. These changes were obvious in 48 h. In contrast, 1000 nM TPA for five days did not induce apoptosis in the PET-cell. DNA fragmentation was induced in both cell lines by A23187 (0.25 microM) and etoposide (7 microM). Novobiocin (600 and 900 microM) induced DNA fragmentation in S-cells, but higher concentrations inhibited fragmentation. Novobiocin is believed to induce DNA fragmentation by a direct action on DNA. In the case of PET-cells, novobiocin did not induce DNA fragmentation at any concentration, and prior treatment of PET-cells with novobiocin (300-1200 microM for 30 min) inhibited DNA fragmentation induced by A23187. Novobiocin inhibited cell growth equally in S-cell and PET-cells. It is concluded that the promyelocytes have the capacity to undergo apoptosis in response to agents which activate protein kinase C, and that the PET-cell has a mutation which disables both protein-kinase C-induced and novobiocin-induced DNA fragmentation, leaving intact the ability of novobiocin to protect DNA from calcium-entry-initiated fragmentation. The elucidation of the lesion responsible for the PET phenotype is likely to increase our understanding of this important pathway for regulating cellular proliferation and how it bears on leukemogenesis and chemotherapy.
Traditional RNA isolation methods use chaotropic agents and anionic detergents to lyse cells and solubilize nucleic acids. In contrast, the cationic surfactant, Catrimox-14, lyses cells and simultaneously precipitates RNA, thereby protecting it from RNases. We describe and compare four methods for extracting RNA from cultured cells that differ in the technique used to extract the RNA from the precipitate. The first uses a high-salt solution (guanidinium isothiocyanate). In the second, the RNA is extracted with a polar solvent (formamide). The third involves conversion of the RNA to the sodium salt by treatment of the precipitate in situ with sodium acetate in ethanol. The fourth uses 2 M lithium chloride to convert the RNA in the pellet to the lithium salt in situ. We applied these methods to human leukemia cells growing in culture and each method resulted in excellent yields of RNA (typically 23 micrograms/million K562 cells, 13 micrograms/million HL-60 cells) over a wide range of cell concentrations (1 x 10(5) - 3 x 10(7)/ml) and of good to excellent quality as judged by agarose electrophoresis and UV absorbance data (OD260/280 1.90-2.05). The advantages and limitations of each method are discussed.