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Response and acclimatisation of symptomless smokers on changing to a low tar, low nicotine cigarette.

Ten symptomless smokers were switched from their usual cigarette to a low tar, low nicotine test cigarette for two weeks to investigate their immediate response and subsequent acclimatisation to the test cigarette. The tar (T) and nicotine (N) yields of the test cigarettes were T = 3.8 mg, N = 0.6 mg; the median yields of the usual cigarettes were T = 16.4 mg, N = 1.4 mg. The subjects were monitored over a six week period comprising a control period (usual cigarette), a test period (test cigarette), and a return period (usual cigarette), each lasting two weeks. The inhaled smoke volume (smoke from the burning tip of the cigarette which is subsequently inhaled) was measured with a non-invasive radiotracer technique. Puffing indices were recorded using an electronic smoking analyser and flowhead cigarette holder. Measurements were made at the beginning of the control period, at the beginning and end of the test period, and at the end of the return period. Subjects kept records of their cigarette consumption during each of the three periods. Apart from a small change in puff duration, cigarettes were smoked in the same way during the control and return periods. Mean and total puff volumes increased with the low tar, low nicotine cigarette but did not change from the beginning to the end of the test period. There was no significant change between the control, test, and return periods for mean inhaled smoke volume, total inhaled smoke volume, or cigarette consumption. It is concluded that when smokers are switched to a low tar, low nicotine cigarette the puff volume increases but there is no change in the inhaled smoke volume or daily consumption.

Adult↗

Lentiviral transduction of Tar Decoy and CCR5 ribozyme into CD34+ progenitor cells and derivation of HIV-1 resistant T cells and macrophages.

BACKGROUND: RNA based antiviral approaches against HIV-1 are among the most promising for long-term gene therapy. These include ribozymes, aptamers (decoys), and small interfering RNAs (siRNAs). Lentiviral vectors are ideal for transduction of such inhibitory RNAs into hematopoietic stem cells due to their ability to transduce non-dividing cells and their relative refractiveness to gene silencing. The objective of this study is to introduce an HIV-1 Tar aptamer either alone or in combination with an anti-CCR5 ribozyme into CD34+ hematopoietic progenitor cells via an HIV-based lentiviral vector to derive viral resistant progeny T cells and macrophages. RESULTS: High efficiency and sustained gene transfer into CD34+ cells were achieved with lentiviral vector constructs harboring either Tar decoy or Tar decoy in combination with CCR5 ribozyme. Cells transduced with these constructs differentiated normally into T-lymphocytes in vivo in thy/liv grafts of SCID-hu mice, and into macrophages in vitro in the presence of appropriate growth factors. When challenged in vitro, the differentiated T lymphocytes and macrophages showed marked resistance against HIV-1 infection. CONCLUSIONS: Viral resistant transgenic T cells and macrophages that express HIV-1 Tar aptamer either alone or in combination with an anti-CCR5 ribozyme could be obtained by lentiviral gene transduction of CD34+ progenitor cells. These results showed for the first time that expression of these anti-HIV-1 transgenes in combination do not interfere with normal thymopoiesis and thus have set the stage for their application in stem cell based gene therapy for HIV/AIDS.

Journal Article↗

RNA as a target for drug design, the example of Tat-TAR interaction.

One of the new targets in the battle against HIV-1 infection is the interaction between the viral transactivator and the transactivation response (TAR) element, which is necessary for HIV-1 replication. After an overview of the most recent structural studies of the Tat-TAR system, new TAR-targeted inhibitors are presented in several classes: antisense oligonucleotides, cationic peptides, intercalators and a large class of small RNA binding molecules. The method of library screening of RNA binding ligands in the search for new inhibitors is explained in detail. Inhibition of Tat-TAR interaction is considered as a realistic approach to develop new anti-HIV compounds. The RNA binding molecules in this review also demonstrate that the development of drugs that target RNA will become a feasible goal and that such compounds will be added in the future to the therapeutic arsenal to combat several diseases.

Anti-HIV Agents↗

Interaction of 68-kDa TAR RNA-binding protein and other cellular proteins with prion protein-RNA stem-loop.

The RNA stem-loop structure of the trans-activating region TAR sequence of human immunodeficiency virus-1 mRNA is the binding site for a number of host cell proteins. A virtually identical set of proteins from HeLa nuclear extracts was found to bind to the predicted RNA hairpin element of prion protein (PrP) mRNA, as demonstrated in UV cross-linking/RNase protection and Northwestern assays. We show that the cellular TAR loop-binding protein, p68, is among those proteins which associate with PrP RNA. Competition experiments with various TAR RNA mutants revealed that binding of partially purified p68 to PrP RNA stem-loop occurs sequence-specifically. The 100-kDa 2-5A synthetase which is involved in the cellular antiviral defense was able to bind to PrP mRNA stem-loop in Northwestern blots with cytosolic proteins from HeLa cells treated with interferon. However, the PrP RNA failed to activate this enzyme in vitro, in contrast to TAR RNA.

2',5'-Oligoadenylate Synthetase↗

Selection by phage display of peptides targeting the HIV-1 TAR element.

As transcription regulatory element, the HIV-1 TAR RNA element is a promising target to inhibit viral replication; indeed, ligands of TAR RNA could prevent the transcription trans-activation process. Phage display in vitro selection was undertaken to select peptidic ligands of TAR RNA. In preliminary experiments, the selection was performed in a magnesium rich buffer (3 mM), but only phages targeted to plastic wells or streptavidin emerged; in addition, a "super-infectious" phage present in the New England Biolabs library (SVSVGMKPSPRP) selected by others with different targets was cloned, due to a high amplification potential. In contrast, the absence of magnesium or an increasing magnesium concentration (0 to 0.5 mM) led to phage selection with 57 amino acid peptides. K(D)s of 420-550 nM were measured by filter binding assays; a significant specificity was obtained when TAR target was compared with unrelated RNA targets. Surprisingly, the binding of selected peptides does not depend on the magnesium concentration.

Buffers↗

Existence of a differentiation blockage at the stage of a megakaryocyte precursor in the thrombocytopenia and absent radii (TAR) syndrome.

The thrombocytopenia and absent radii (TAR) syndrome is a rare disease associating bilateral radial agenesis and congenital thrombocytopenia. Here, we investigated in vitro megakaryocyte (MK) differentiation and expression of c-mpl in 6 patients. Using blood or marrow CD34(+) cells, the colony-forming unit (CFU)-MK number was markedly reduced. CD34(+) cells were also cultured in liquid medium in the presence of a combination of 3 cytokines (stem cell factor, interleukin-3, and interleukin-6) or megakaryocyte growth and development factor (PEG-rHuMGDF) with or without SCF. In the presence of PEG-rHuMGDF, the majority of mature megakaryocytes (CD41 high, CD42 high) underwent apoptosis. This phenomenon was also observed in cultures stimulated by three cytokines. However, this last combination of cytokines allowed a more complete terminal MK differentiation. Surprisingly, a homogeneous population of CD34(-)CD41(+)CD42(-) cells accumulated during the cultures. This population was unable to differentiate along the myeloid pathways. This result suggests that a fraction of MK cells is unable to differentiate in the TAR syndrome. We subsequently investigated whether this could be related to an abnormality in c-mpl. No mutation or rearrangement in the c-mpl gene was found by Southern blots or by sequencing of the c-mpl coding region and its promoter in any of the patients. Using Western blot analysis, a decreased level of Mpl was found in patient platelets. A decreased level of c-mpl messenger RNA in TAR platelets was also detected with a lower c-mpl-P to c-mpl-K ratio in comparison to adult platelets. Altogether, these results demonstrate that the thrombocytopenia of the TAR syndrome is associated with a dysmegakaryocytopoiesis characterized by cells blocked at an early stage of differentiation. (Blood. 2000;95:1633-1641)

Adolescent↗

The compensating behavior of smokers: taxes, tar, and nicotine.

Using data from the 1979 and 1987 National Health Interview Survey (NHIS), we test whether smokers alter their smoking habits in the face of higher taxes. Smokers in high-tax states are more likely to smoke cigarettes higher in tar and nicotine. Although taxes reduce the number of cigarettes consumed per day among remaining smokers, total daily tar and nicotine intake is unaffected. Young smokers, aged 18-24, are much more responsive to changes in taxes than are older smokers, and their total daily tar and nicotine intake actually increases after a tax hike. We illustrate that tax-induced compensating behavior may eliminate some health benefits generated by reduced smoking participation. A more appropriate tax might be based on the tar and nicotine content of cigarettes.

Health Behavior↗

Mutagenicity of the fractionated organic emissions from diesel, cigarette smoke condensate, coke oven, and roofing tar in the Ames assay.

Mobile and stationary combustion sources emit particle-bound organics that, after extraction, are mutagenic to Salmonella typhimurium. In this study, the organic emissions from diesel, cigarette smoke condensate (CSC), coke oven, and roofing tar were fractionated and compared for mutagenicity in the Ames assay. This study demonstrated major differences in the distribution of mutagenicity among the four emission sources. Within each source, the relative mutagenicity of each fraction was significantly different in the presence and absence of an exogenous metabolic activation. In the diesel sample, over 90% of the mutagenic activity is located in the aromatic and polar neutral (PN) fractions; nitrated polynuclear aromatic hydrocarbons (NO2-PNAs) can account for a significant portion of this activity. Most of the mutagenicity of the coke oven main sample was found in the organic base (BASE) and PN fractions, which contained aromatic amines and nitrogen heterocycles. The CSC sample also had a high percentage of the mutagenic activity in the BASE fraction. Chemical analysis, however, indicates that the components in the CSC differed from those of the coke oven main sample. The roofing tar sample, which was not mutagenic in the absence of metabolic activation, contained several components that were very mutagenic after fractionation. This may be due to the separation of toxic components from the mutagenic components. The roofing tar emissions contained aromatic and polar mutagenic constituents. Although the specific mutagens in these different sources are not identical, they all cause frameshift mutations and appear to be compounds that could be classified as polycyclic organic matter.

Animals↗

Lung cancer incidence in Australia: impact of filter-tip cigarettes with unchanged tar yields.

Filter-tip cigarettes became popular in Australia in the late 1950s, but "tar" yields remained high for another decade. Because of this, the effect of filters independently of tar reductions can be estimated by comparing the age-adjusted incidence of lung cancer for relevant birth cohorts of Australians. Separate analyses by histologic type may throw some light on the specific effects of filters. Age-adjusted incidence of squamous cell carcinoma (SCC), small cell lung carcinoma (SCLC) and adenocarcinoma (AC) was estimated by Poisson regression for 5-year birth cohorts of Australians using lung cancer registration data for 1982-95. To take account of changes in smoking prevalence, ever-smoker less never-smoker differences in age-adjusted incidence were estimated. Comparisons were made for smokers born during 1930-34 and 1940-44. Smokers born in 1940-44 commenced smoking at the time of introduction of filter-tips. Age-adjusted incidence of SCC (-23%) and SCLC (-21%) but not AC (+7%) was lower for female smokers born during 1940-44. For male smokers, rates of SCC (-42%), SCLC (-43%) and AC (-24%) were each lower. The high rates overall of 1940s-born women were due to disproportionately higher incidence of AC, the type that comprised 42% of diagnoses with histologic confirmation. In Australia, the switch to filter-tip cigarettes prior to any reduction in tar yields was associated with reduced incidence of SCC and SCLC, and of AC for men only. Rates of AC were not reduced for women, indicating that other factors were important for this type of lung cancer.

Adenocarcinoma↗

A prospective study of cigarette tar yield and lung cancer.

We examined the relationship of cigarette tar yield and other cigarette-usage characteristics in current smokers to the incidence of lung cancer in a study population of 79,946 Kaiser Permanente Medical Care Program members, aged 30-89 years, who completed a detailed, self-administered, smoking-habit questionnaire during the years 1979 through 1985. Mean length of follow-up was 5.6 years. There were 302 incident lung cancers, of which 89 percent occurred in current or former smokers. The tar yield of the current cigarette brand was unassociated with lung cancer incidence (relative risk [RR] = 1.02 per 1 mg tar-yield in men, 95 percent confidence interval [CI] = 0.98-1.05; RR = 0.99, CI = 0.96-1.03 in women). However, in long-term (> 20 years) smokers, the risk of lung cancer was decreased in women who had smoked filtered cigarettes for 20 or more years relative to lifelong smokers of unfiltered cigarettes (RR = 0.36, CI = 0.18-0.75), but not in men who had smoked filtered cigarettes for 20 or more years (RR = 1.04, CI = 0.58-1.87).

Adult↗

Effect of crude coal tar in the mouse-tail model of psoriasis.

A histological comparison was made between normal mouse tails and those treated with crude coal tar, and the effect of crude coal tar on the keratin profile of the living cells of treated animals was examined. The prophylactic effect of crude coal tar on the neonatal mouse tail is described. The variation in the anatomical site of prekeratin of the dorsal and tail epidermis of the mouse is reported. These results are discussed with reference to the use of the mouse tail as a model for screening drugs for the treatment of psoriasis.

Animals↗

Pyridine and other coal tar constituents as free radical-generating environmental neurotoxicants.

We have tested the hypothesis that chronic exposure to the principal constituents of the aqueous fraction of coal tar extracts can lead to the in vivo formation of substances which may produce neurological damage as the result of free radical generation and lipid peroxidation, these may be involved in the etiology of some neurological disorders. Artificial mixtures of the aqueous fraction of coal tar extracts were given in low concentrations to pigmented mice in their drinking water over a 3-month period. This resulted in significant increases in lipid peroxidation in the striatum, cerebellum and liver of the mice under test, the rank order being striatum greater than cerebellum greater than liver. These results are compatible with the possibility that coal tar emissions (as would be recovered or liberated in the burning, refining or beneficiation of coal) constitute a potential source of neurotoxicants with a predilection for damaging the nigrostriatal neuronal pathway. Our observations may thus have identified an important and hitherto unsuspected environmental source of neurotoxic chemicals, a possibility consistent with the proposed involvement of an environmental chemical factor in Parkinson's disease and perhaps in other neurological disorders.

Animals↗

Ultraviolet phototherapy in psoriasis with hydrophilic ointment alone or with crude coal tar.

Plaques of 12 psoriatic patients treated with crude coal tar and ultraviolet irradiation were compared with symmetric areas treated with the same ultraviolet light (UVL) source and a hydrophilic ointment vehicle. Of the 12 patients, 10 received 75-100% clearing at both sites regardless whether the tar or the vehicle was applied. Treatment three times weekly was as effective as five times weekly. It was uncertain if the addition of UV-A irradiation to the UVL system in a small group using tar had a more beneficial effect.

Coal Tar↗

Mortality in a group of tar distillery workers and roofers.

OBJECTIVE: A retrospective cohort mortality study was conducted to assess long-term health risk in a group of tar distillery workers and roofers in order to investigate the existence of carcinogenic effects related to the occupational exposures. METHODS: The study population consisted of 907 tar distillery workers and 866 roofers, employed at least one half-year between January 1947 and January 1980. This group was followed for mortality until January 1988. For the deceased workers the cause of death was provided by the Central Bureau of Statistics. The observed cause-specific mortality was compared with the expected cause-specific mortality calculated by means of the national mortality rates of The Netherlands. RESULTS: Mortality from cancer of the lungs and trachea was higher than expected in both groups, but not statistically significant. In addition the roofers had experienced an excess mortality rate from external causes. CONCLUSIONS: The study provides some additional support for the carcinogenicity of coal tar exposures, but the findings were not statistically significant.

Cause of Death↗

The effects of coal tar based pavement sealer on amphibian development and metamorphosis.

Coal tar based pavement sealers are applied regularly to parking lots and contain significant levels of polycyclic aromatic hydrocarbons (PAHs). Recently a connection between elevated levels of PAHs in streams and storm water runoff from parking lots has been identified. We tested the hypothesis that coal tar based pavement sealers could alter the survival, growth, and development of amphibians using a model species, Xenopus laevis. Ten fertilized individuals were placed singly into containers containing one of four treatment groups: control, low, medium, and high (respective nominal concentrations 0, 3, 30, and 300 ppm TPAH). All of the individuals in the high exposure group died by the sixth day of exposure. By day 14 there were significant patterns of stunted growth (p<0.0001) and slower development (p=0.006) in the medium and high exposure groups relative to the control and low treatment groups. When the experiment ended on day 52 the control and low-dose individuals had achieved more advanced developmental stages than the medium group (p=0.0007). These data indicate that these commonly used coal tar based pavement sealers may potentially affect the amphibian taxa living in areas that receive storm water runoff.

Animals↗

Effect of tar condensate from smoking tobacco and water-extract of snuff on the oral mucosa of mice with latent herpes simplex virus.

Upper lips were inoculated with virus to establish a latent infection in the trigeminal ganglia. During the latent period, tobacco smoke tar condensate or water-extract of snuff were topically applied to the primary inoculation site for two or three consecutive months. Tar condensate induced re-activation of latent HSV in the ganglia of 10 to 20 per cent of animals but snuff extract did not. Infectious virus was also detected in lips after the chronic application of tar condensate in 10 per cent of animals. Three months' exposure to tobacco produced epithelial dysplasia and other changes in a significant number of latent HSV-infected mice, whereas tobacco alone did not induce dysplasia in the labial epithelium of uninfected mice.

Animals↗

Fractionation, chemical analysis, and mutagenicity testing of low-Btu coal gasifier tar.

A tar from a low-Btu coal gasifier was subjected to parallel fractionation, chemical analysis, and bacterial mutagenicity (Salmonella) assay. Like other coal-derived tars, it was a complex mixture containing some high-molecular-weight material and several classes of organic compounds as major constituents. The results of bacterial mutagenicity testing of fractions and subfractions of the tar suggest that neutral nitrogen-containing compounds, phenols, organic bases, polycyclic aromatic hydrocarbons, and some uncharacterized high-molecular-weight materials are mutagenic to Salmonella and therefore are potentially mutagenic in higher systems.

Chemical Phenomena↗

In vitro cytotoxicity to alveolar macrophages of tar from a low-Btu coal gasifier.

The cytotoxicity of fractions, subfractions, and some individual components present in tar from a low-Btu coal gasifier was determined in vitro with cultured dog alveolar macrophages. A subfraction of the tar which contained phenols and neutral nitrogen heterocycles was found to be a major contributor to the cytotoxic activity of the tar. Four compounds present in this subfraction were tested individually. Ranked from the most to the least toxic they were: 9-phenanthrol, 2-fluorenol, phenanthridone, and carbazole.

Animals↗