Toxicological assessment of kretek cigarettes: Part 2: kretek and American-blended cigarettes, smoke chemistry and in vitro toxicity

Two commercial kretek cigarettes typical for the Indonesian market and a reference kretek cigarette were compared to the American-blended reference cigarette 2R4F by smoke chemistry characterization and in vitro cytotoxicity and mutagenicity assessments. Despite the widely diverse designs and deliveries of the selected kretek cigarettes, their smoke composition and in vitro toxicity data present a consistent pattern when data were normalized to total particulate matter (TPM) deliveries. This confirms the applicability of the studies' conclusions to a wide range of kretek cigarette products. After normalization to TPM delivery, nicotine smoke yields of kretek cigarettes were 29-46% lower than that of the 2R4F. The yields of other nitrogenous compounds were also much lower, less than would be expected from the mere substitution of one third of the tobacco filler by clove material. Yields of light molecular weight pyrolytic compounds, notably aldehydes and hydrocarbons, were reduced, while yields of polycyclic aromatic hydrocarbons were unchanged and phenol yield was increased. The normalized in vitro toxicity was lowered accordingly, reflecting the yield reductions in gas-phase cytotoxic compounds and some particulate-phase mutagenic compounds. These results do not support a higher toxicity of the smoke of kretek cigarettes compared to American-blended cigarettes.

Reduced reactivation rate in mutant CuZnSOD and progression rate of amyotrophic lateral sclerosis

Mutations in the SOD1 gene are associated with familial amyotrophic lateral sclerosis (fALS). The mechanisms by which these mutations lead to anterior horn cell loss are unknown, however, increased binding of Hsps on the demetallated mutant SOD1 has been described which would make the HSPs unavailable for other purposes, and reduce the SOD1 concentration in mitochondria, thereby creating a proapoptotic situation finally leading to motor neuron death. Here we report the recombinant expression of four human copper/zinc superoxide dismutase (CuZnSOD) variants, including the wild-type enzyme and mutant proteins associated with familial ALS. The bacterial expression level of soluble mutated proteins was influenced by the mutations leading to drastically reduced levels of soluble CuZnSOD. Simultaneously, increasing levels of insoluble and probably aggregated mutated CuZnSOD were identified in bacterial cell pellets. In addition, altered reactivation kinetics of the purified mutant apoproteins after expression in bacterial culture was shown. Biophysical and biochemical analysis showed that zinc incorporation is severely reduced in the CuZnSOD proteins associated with the most severely forms of fALS (A4V, G93A). These data indicate that a reduced holoenzyme formation rate of mutant enzymes may be a critical factor in the etiopathology of fALS.

A novel calcineurin splice variant that modifies calcineurin activity

Calcineurin is a Ca(2+)/calmodulin dependent phosphoprotein phosphatase implicated in a wide range of disorders. Here, we report the cloning of a novel calcineurin A alpha splice variant that lacks both the catalytic and calcineurin B binding domains. Biochemical analysis revealed a stimulating effect on calcineurin activity at low calcium concentrations as well as protein-protein interaction with the catalytic calcineurin holoenzyme. By Western blot analysis, expression of similar short splice variants could be seen in the spinal cord of an animal model of familial amyotrophic lateral sclerosis, suggesting a role of these new variants in motor neuron disease.

Adenylyl cyclase type 7 is the predominant isoform in the bovine retinal pigment epithelium

The retinal pigment epithelium (RPE) fulfills important supporting tasks to maintain the visual functions of the sensorineural retina. One major signalling mechanism by which adjacent tissues impinge on the RPE is the adenylyl cyclase (AC)/cAMP pathway. In the RPE, cAMP seems to modulate unique functions such as the phagocytosis of discs shed from the rod outer segments, transport of vitamin A or the ion and fluid control in the subretinal space. We analyzed the AC expression pattern in the retina and the RPE and found AC type 7 to be almost the only isoform expressed in the RPE. We cloned AC type 7 from a cDNA library established with fresh bovine RPE, expressed this isoform in eukaryotic cells and characterized some of its properties.

Recessively inherited amyotrophic lateral sclerosis: a Germany family with the D90A CuZn-SOD mutation

Mutations of the SOD1 gene encoding the free radical scavenging enzyme copper-zinc superoxide dismutase (CuZn-SOD) occur in patients with familial amyotrophic lateral sclerosis (ALS). Recent reports have shown homozygosity for a CuZn-SOD mutation in exon 4, the D90A (Asp90A1a) mutation. Other mutations described to date show an autosomal dominant pattern of inheritance. This is the first description of autosomal recessively inherited ALS in an out-bred population in central Europe. This study confirms the earlier described characteristic phenotype reported in D90A homozygous ALS patients in Scandinavia and supports the theory of the existence of a strong modifying factor in some cases of ALS associated with mutations in the CuZn-SOD gene.

Impaired tolerance to repetitive hypoxia in hippocampal slices of Cu,Zn superoxide dismutase transgenic mice

Energy metabolism is impaired in the Cu,Zn superoxide dismutase transgenic mouse model of amyotrophic lateral sclerosis. The goal was to investigate tolerance against single and repetitive hypoxia in C57B6SJL-TgN(SOD1-G93A)1GUR mice (G93A mice). Posthypoxic recovery (15 min hypoxia, 45 min recovery) of population spike amplitude in hippocampal region CA1 was 38 +/- 29% (mean +/- SD) in controls and 67 +/- 41% (ns) in G93A mice at day 40. Upon in vivo pretreatment with 20 mg/kg 3-nitropropionate posthypoxic recovery increased to 82 +/- 32% (P < 0.01) in controls and decreased to 35 +/- 33% in G93A mice (P < 0.05 to pretreated controls). Results at day 80 and 110 were similar. We conclude that G93A mice show a long-lasting impairment to sustain repetitive hypoxic episodes whereas tolerance to a single hypoxic episode is comparable to controls.

The EAAT2 (GLT-1) gene in motor neuron disease: absence of mutations in amyotrophic lateral sclerosis and a point mutation in patients with hereditary spastic paraplegia

OBJECTIVES

To investigate if sequence alterations of the excitatory amino acid transporter gene EAAT2 (GLT-1) may be a contributory factor to the pathogenesis of motor system degeneration. EAAT2 serves as a candidate gene as its reduced expression was reported in patients with amyotrophic lateral sclerosis (ALS). Furthermore, neurolathyrism, a motor neuron disease clinically related to hereditary spastic paraplegia (HSP), has been associated with an exogenous excitotoxin.

METHODS

Sequence alterations were screened for in the coding region of EAAT2 in 55 patients with ALS and one family with autosomal dominant HSP (AD-HSP).

RESULTS

In ALS, no sequence alteration in the EAAT2 gene have been found. Interestingly, a heterozygous A79G mutation of the EAAT2 gene was detected in two of seven affected patients with AD-HSP in the same kindred. The absence of cosegregation with the familial disease showed that the detected variant was not the cause of disease. The A79G sequence variant was not found in 55 patients with ALS or in 50 non-neurological controls.

CONCLUSION

The allelic variant of the EAAT2 gene in conjunction with the primary gene defect may be a modifying factor for the highly variable AD-HSP phenotype.

5'-heterogeneity of the human excitatory amino acid transporter cDNA EAAT2 (GLT-1)

TWO novel transcripts of the human excitatory amino acid transporter EAAT2 (GLT-1) were cloned using PCR cloning techniques. Comparative sequence analysis of the 5'-untranslated region (UTR) of five EAAT2 transcripts led to the definition of five putative 5'-untranslated exons that are combined in a variable manner. Alternative splicing is a likely mechanism for the 5' complexity of the EAAT2 cDNA. The potential functional meaning of this finding such as differential expression of the EAAT2 transcripts in the central nervous system remains to be demonstrated.

Alternative splicing of the glutamate transporter EAAT2 (GLT-1)

The human glutamate transporter EAAT2 (GLT-1) is of major importance for synaptic glutamate reuptake, and reportedly, a candidate gene for neurodegenerative diseases such as amyotrophic lateral sclerosis, Alzheimer's disease and epilepsy. Here we report the polymerase chain reaction (PCR) cloning of two novel EAAT2 transcripts, named EAAT2-C1 and EAAT2-C2, which originate from alternative splicing of the human EAAT2 gene. EAAT2-C1 results from skipping of the protein coding exon eight. In contrast, EAAT2-C2 is characterized by usage of internal splice sites in the exons five and six. The splicing events lead to a deletion of 45 and 107 amino acids, respectively, located in the C-terminal and central part of the putative protein.

Hyperpolarization- and depolarization-activated Ca2+ currents in Paramecium trigger behavioral changes and cGMP formation independently

Using 5% ethanol as a deciliating agent, 20 mm colchicine to prevent reciliation and 1 mm amiloride to affect ion fluxes in Paramecium we examined the compartmentation and function of Ca2+ fluxes employing the biosynthesis of cGMP and the stereotypic swimming behavior as indicators for Ca2+ entry. As a function of extracellular Ca2+ Paramecia responded to colchicine and amiloride with a short-lived ciliary augmentation (fast swimming) which indicated hyperpolarization, and formation of cGMP, i.e., the reported hyperpolarization-activated Ca2+ inward current in the somatic membrane is coupled to intracellular generation of cGMP. This is comparable to the coupling of the depolarization-activated, ciliary Ca2+ inward current and ciliary cGMP formation.Ethanol-deciliated cells and ethanol-treated, yet ciliated control cells did not respond to a depolarization with backward swimming or formation of cGMP. Both responses recovered with similar kinetics. A persistent effect of an ethanol exposure on the axonemal apparatus or on guanylyl cyclase activity of ciliated control cells was excluded using permeabilized cells and cell-free enzyme, respectively. Further, in the presence of 20 mm colchicine ethanol-treated cells only recovered the depolarization-dependent avoiding reaction whereas the formation of cGMP remained depressed, i.e., the drug dissected both responses. Similarly, ethanol exposure of Paramecia did not affect the fast swimming response towards the hyperpolarizing agent amiloride whereas the cGMP formation was abrogated and recovered over a period of 7 hr, i.e., amiloride dissected the hyperpolarization-elicited behavioral response from the intracellular cGMP formation. The data demonstrate that in Paramecium depolarization- and hyperpolarization-stimulated behavioral responses and cGMP formation are not coupled. The behavioral changes are triggered by smaller Ca2+ inward currents than the formation of intracellular cGMP.

Cathepsin L is an intracellular and extracellular protease in Paramecium tetraurelia. Purification, cloning, sequencing and specific inhibition by its expressed propeptide

The ciliate Paramecium tetraurelia secretes large amounts of a cysteine protease into the growth medium, presumably for extracellular food digestion. Two endoprotease isozymes (30 and 33 kDa on SDS/PAGE, respectively), both present in cell homogenates and in spent growth medium, were purified to homogeneity. Peptide sequence analysis revealed that these isozymes share identities at the amino acid level but are probably differently processed. Enzymatic characterization of the isolated proteases and sequencing of the cloned cDNA demonstrated that the enzymes belong to the cathepsin-L protease subfamily. Although the identity with mammalian and other protozoan L cathepsins was only around 30%, all important signature sequences for cathepsin L in the preproregion as well as in the catalyst of the enzyme were fully retained. The cDNA of this cysteine protease codes for a preproregion of 108 amino acids. The putative proregion of 86 amino acids which contained the characteristic conserved ERFNIN motif, was fused with a His6 tag, expressed in Escherichia coli, and purified. Both cathepsin L isozymes of Paramecium tetraurelia were inhibited by their cognate propeptide in the nanomolar concentration range. All other cysteine proteases tested (papain and mammalian cathepsin B, G and H) were unaffected by the propeptide up to 10 microM.

Cloning and expression of a bovine adenylyl cyclase type VII specific to the retinal pigment epithelium

A cDNA of a type 7 adenylyl cyclase isoform was cloned from a bovine retinal pigment epithelium cDNA library using oligonucleotides developed to conserved regions common to mammalian adenylyl cyclases. A 6.7 kb mRNA of very high abundance was uniquely present on Northern blots containing mRNA or total RNA from the pigment epithelium. This transcript was undetectable in all other tissues examined. The cDNA encoded a protein of 1,097 amino acids and exhibited the known doublet of 6 transmembrane-spanning regions in a hydrophobicity plot. The novel member of the type 7 adenylyl cyclase isoform was expressed in COS-1 cells. It was stimulated 10- and 20-fold by 10 microM GTP gamma S and 100 microM forskolin, respectively. The high expression rate exclusively in the retinal pigment epithelium suggests that this adenylyl cyclase isoform is involved in processes specific to this functionally exceedingly important subretinal cell layer.

Nicotine and cotinine accumulation in pigmented and unpigmented rat hair

This study was performed to assess the contribution of systemic and external uptake to nicotine accumulation in hair. The systemic nicotine uptake in hair was determined in pigmented rats (Brown Norway) and albino rats (Sprague-Dawley) after subcutaneous administration of 3 doses of nicotine with osmotic minipumps [5, 10, and 20 mg/(kg x day) for 3 weeks], the highest dose also following metabolic enzyme induction. The external nicotine uptake was determined in cut hair of both strains after exposure to room-aged cigarette sidestream smoke, a surrogate for environmental tobacco smoke (nicotine concentration: 5 micrograms/liter for 1, 2, and 3 weeks). Nicotine and its metabolite cotinine were determined using capillary GC after complete alkaline digestion of the hair sample and solvent extraction. Systemic uptake: Nicotine and cotinine concentrations in hair were dose-dependent and correlated with plasma concentrations. The nicotine concentration was approximately 20 times higher in pigmented than in unpigmented hair. The cotinine concentration was approximately 10 times lower than the nicotine concentration in pigmented hair. After enzyme induction before administration, nicotine and cotinine concentrations in hair were significantly reduced in parallel to the reduced plasma concentrations, showing the influence of metabolism. External uptake: Nicotine was found in the hair of both strains, the concentration in pigmented hair being a factor of 1.5 higher than in unpigmented hair. Thus, hair pigmentation had a major influence on systemic uptake in hair and a minor influence on external uptake in hair.(ABSTRACT TRUNCATED AT 250 WORDS)