Occupational class differences in ankle-brachial index and pulse wave velocity measurements to detect subclinical vascular disease

Background:

High pulse wave velocity (PWV) and low ankle brachial index (ABI) have been proposed as surrogate end-points for cardiovascular disease (CVD).

Objectives:

In a cross-sectional setting, we aimed at assessing the distributions of PWV and ABI among occupational classes (OC) in a population-based ever-employed salaried sample.

Methods:

We enrolled 1388 salaried CVD-free workers attending a CVD population-based survey, the RoCAV study, and classified them into four OC, based on current or last job title: manager/director (MD), non-manual (NMW), skilled-manual (SMW) and (UMW) unskilled-manual workers. We derived brachial-ankle PWV and ABI from four-limb blood pressures measurements, then carotid-femoral PWV (cfPWV) was estimated. We estimated the OC gradients in cfPWV and ABI using linear and logistic regression models.

Results:

Compared to MD (reference category), UMW had higher age- and BMI-adjusted cfPWV mean values both in men (0.63 m/s; 95%CI:0.11-1.16) and women (1.60 m/s; 0.43-2.77), only marginally reduced when adjusting for CVD risk factors. Decreased ABI mean values were also detected in lower OC. The overall detection rate of abnormal cfPWV (≥12 m/s) or ABI (≤0.9) values was 28%. Compared to MD, the prevalence of abnormal cfPWV or ABI was higher in NMW (OR=1.77; 95%CI:1.12-2.79), SMW (1.71; 1.05-2.78) and UMW (2.72; 1.65-4.50). Adjustment for CVD risk factors used in risk score equations did not change the results.

Discussion:

We found a higher prevalence of abnormal values of arterial stiffness measures in lower OC, and these differences were not explained by traditional CVD risk factors. These may be presumably determined by additional work- and environmental-related risk factors.

Hepatitis C virus structural proteins reside in the endoplasmic reticulum as well as in the intermediate compartment/cis-Golgi complex region of stably transfected cells

The intracellular localization of hepatitis C virus structural proteins was analyzed by confocal immunofluorescence microscopy, cell fractionation, and immunoelectron microscopy in stably transfected cells that do not overexpress the viral proteins. The results strongly suggest that at steady state the structural proteins reside not only in the endoplasmic reticulum but also in the intermediate compartment and cis-Golgi complex region. By analogy with other viral systems, this finding raises the possibility that the intermediate compartment and cis-Golgi complex play a role in the assembly and budding of hepatitis C virus.

Analysis of metal-regulated metallothionein and heat shock gene expression in HeLa-derived cadmium-resistant cells

The expression of metallothionein (MT) and heat shock protein gene families was investigated in normal and in HeLa-derived cadmium-resistant cells, named H454. In the absence of amplification of MT genes H454 cells accumulated elevated concentrations of cadmium ions and synthesized higher levels of MT proteins than unselected HeLa cells. Northern blot analyses revealed higher levels of MT mRNAs in the resistant cells than in wild-type cells after Cd2+ and Zn2+ exposure. Evaluation of the cytotoxic potential of the different metals confirmed the high resistance to cadmium of the H454 cells. Two proteins of the heat shock family, hsp70 and GRP78, were synthesized in Cd(2+)-exposed H454 cells at levels comparable to the ones present in Cd(2+)-treated normal cells. Northern blot analyses of the mRNA levels corresponding to these proteins revealed elevated expression of both hsp70 and GRP78 mRNAs in H454 cells upon exposure to cadmium ions and no response to zinc induction. These data suggest the existence in the H454 cells of a cadmium-specific pathway of regulation of MT and heat shock genes.

Different fate of a single reporter protein containing KDEL or KKXX targeting signals stably expressed in mammalian cells

In mammalian cells, resident luminal and type I transmembrane proteins of the endoplasmic reticulum usually contain KDEL and KKXX at the carboxyl terminus. These sequences induce retrieval from compartments located downstream in the secretory pathway. It has been suggested that the retrieval may occur from multiple sites, ranging from the intermediate compartment to the trans-Golgi network. To compare the retrieval of luminal and type I membrane proteins, we have used different forms of a single reporter, the human CD8 glycoprotein, stably expressed in FRT cells. Metabolic labeling and oligosaccharide analysis show that the mechanism based on the KDEL signal is leaky. With time, the KDEL-containing CD8 form reaches the trans/trans-Golgi network compartments, where the protein is terminally glycosylated. At this stage, the retrieval mechanism stops being effective and the protein is consequently secreted. Conversely, the mechanism based on the KKXX signal guarantees that most of the KKXX-containing CD8 form resides in the endoplasmic reticulum, little in the Golgi complex and undetectable levels at the plasma membrane. The O-glycosylation of this protein comprises for the vast majority the sole addition of peptide-bound GalNAc that occurs in an early Golgi compartment.

Effect of ATP depletion and DTT on the transport of membrane proteins from the endoplasmic reticulum and the intermediate compartment to the Golgi complex

Newly synthesized membrane proteins are exported from the endoplasmic reticulum to the Golgi complex through an intermediate compartment. Incubation at low temperature (15 degrees C) arrests the proteins in the intermediate compartment and prevents the entry into the Golgi complex. We have studied, in living cells, the effect of dithiothreitol (DTT) and ATP depletion on the transport to the Golgi complex of proteins accumulated either in the endoplasmic reticulum or in the intermediate compartment after a temperature block. The morphological results obtained with vesicular stomatitis virus ts-O45 G glycoprotein and the biochemical analysis performed with human CD8 protein, an O-glycosylated protein, showed that: 1) ATP depletion blocks the export to the Golgi complex of proteins located either in the endoplasmic reticulum or in the intermediate compartment and ii) DTT interferes with the folding and export of proteins located in the endoplasmic reticulum, but it does not prevent the transfer from the intermediate compartment to the Golgi complex.

Effect of rat liver cytosolic enzymes and cofactors on mutagenicity of 1-amino-8-nitropyrene

1-Amino-8-nitropyrene (1,8-ANP), a product of 1,8-dinitropyrene metabolism by either bacterial or mammalian enzymes, is weakly mutagenic to the 'classical nitroreductase'-deficient Salmonella tester strain TA98NR. The addition to the test system of rat liver cytosol without cofactors did not produce any effect on the 1,8-ANP mutagenic response toward TA98NR strain. Conversely, when both rat hepatic cytosol and NADPH (1 mM) were added to the mutagenicity assay, a 10-fold increase in 1,8-ANP mutagenic activity was observed. This suggests the involvement of rat hepatic cytosolic NADPH-dependent nitroreductase(s) in 1,8-ANP mutagenic activation. The addition to the mutagenesis assay of pentachlorophenol, an inhibitor of O-acetyltransferase and sulfotransferase, produced a dose-dependent decrease of 1,8-ANP mutagenic activation, whereas 2,6-dichloro-4-nitrophenol, a more specific inhibitor of sulfotransferase than O-acetyltransferase, did not affect the activation of 1,8-ANP to a mutagen at concentrations that selectively inhibit only bacterial sulfotransferase. This indicates that bacterial O-acetyltransferase but not sulfotransferase plays a role in the mutagenic activation of 1,8-ANP. Addition of acetyl co-enzyme A (AcCoA) and adenosine 3'-phosphate 5'-phosphosulfate (PAPS), cofactors for O-acetyl-transferase and sulfotransferase respectively, to the test system caused a dose-dependent inhibition of 1,8-ANP mutagenic activation by rat liver cytosol and NADPH, probably due to the formation of highly reactive O-acetoxy and N-sulfate ester derivatives of 1,8-ANP, which react with nucleophilic sites before reaching bacterial DNA. This hypothesis was confirmed by DNA covalent binding in in vitro experiments showing that both the cofactors AcCoA and PAPS enhanced the NADPH/rat liver cytosol-mediated covalent binding of 1,8-ANP to DNA from calf thymus 10- and 3-fold respectively. It seems likely that rat hepatic cytosolic nitroreductases activate 1,8-ANP to an N-hydroxyarylamine derivative which can be further metabolized to mutagenic species by either bacterial or mammalian O-acetyltransferase.

[In vivo studies on the transformation of cyclophosphamide to mutagenic metabolites]

Cyclophosphamide (CP), a widely used antineoplastic drug, requires hepatic mixed-function-oxidase-mediated activation to show alkylating activity as well as cytotoxicity, oncogenic transformation and chromosomal aberrations. Evidences are here reported that in vivo activation of CP to urinary mutagenic metabolites is catalyzed primarily by a phenobarbital-inducible cytochrome P-450 system. 24 hours urines from male Sprague-Dawley rats treated i.p. by a single CP administration were filtered through XAD-2 columns and mutagenicity of the acetonic extract was assayed by the Ames test in absence of enzymatic microsomal activation. a highly positive response with a linear dose-dependence was obtained in the range 0.500 mg/kg of CP. Treating rats with Phenobarbital, before CP (500 mg/kg) administration, induced a 250% increase in urine mutagenic activity, whereas. -Naphthoflavone pretreatment reduced the CP activation to urine mutagenic metabolites to 51% as compared with control CP-treated rats.

Mutagenic epoxide impurities discovered in two new beta-adrenergic blocking agents

Preparations of two new beta-adrenergic blocking drugs, Zami 1305 [1-(2-nitro-3-methyl-phenoxy)-3-tert-butylaminopropan-2-ol] and Zami 1327 [1-(6-nitro-3-methyl-phenoxy)-3-tert-butylaminopropan-2-ol], were found to be contaminated by expoxides which are direct acting mutagens on TA 100 and TA 1535 in the Salmonella/microsome mutagenicity test. Because of the suggested correlation between mutagenicity and carcinogenicity of a chemical [10,11], beta-adrenergic blocking agents contaminated by mutagenic expoxide impurities may be a health hazard.

Free and membrane-bound polyribosomes in BHK cells infected with Sindbis virus

The data presented in the paper demonstrate that in BHK cells infected with Sindbis virus virtually all the 42S mRNA not in nucleocapsid is associated with free polyribosomes, whereas the 26S mRNA is distributed between free and membrane-bound polyribosomes. We suggest that the 26S RNA polyribosomes are bound to the membranes through the nascent chains of the B1 protein and that a large percentage of 26S RNA polyribosomes free in the cytoplasm may be due to the small amount of rough endoplasmic reticulum in BHK cells. In addition, we found that intracellular nucleocapsid is in the nonmembrane fraction of the cytoplasm of infected cells.