Metoprolol does not attenuate atherosclerosis in lipid-fed rabbits exposed to environmental tobacco smoke

BACKGROUND

We previously demonstrated that exposure to environmental tobacco smoke (ETS) increases the development of atherosclerosis in lipid-fed rabbits. Clinical studies have suggested a protective effect of beta-blockers in smokers. Accordingly, we evaluated the effects of metoprolol in this animal model to see whether this beta-blocker would block the atherogenic effects of ETS.

METHODS AND RESULTS

Thirty-two New Zealand White male rabbits on a 0.3% cholesterol diet were randomly divided into four groups: ETS-metoprolol (ETS-M), ETS-control (ETS-C), and non-ETS with metoprolol (NETS-M) and without metoprolol (NETS-C). The two metoprolol-treated groups received metoprolol at a dose of 0.4 mg.kg-1.h-1 administered subcutaneously by an osmotic pump. Rabbits in the ETS groups were exposed to sidestream smoke from four Marlboro cigarettes per 15 minutes, 6 hours a day, for 10 weeks. Average air carbon monoxide (CO), nicotine, and total particulates (TP) in the exposure chambers were 67.2 +/- 3.1 (SEM) ppm, 1133.7 +/- 78.4 micrograms/m3, and 37.7 +/- 3.0 mg/m3, respectively. Plasma nicotine was significantly higher in ETS-exposed rabbits than in nonexposed rabbits (7.1 +/- 1.9 versus 0.5 +/- 0.1 ng/mL, P < .01). Blood carbon monoxide hemoglobin (COHb) in the ETS-M group was significantly higher than that in the NETS-M group (4.0 +/- 0.2% versus 1.3 +/- 0.1%, P < .0001). The lipid lesions in the aorta and pulmonary artery were 57.2 +/- 7.6% and 33.1 +/- 6.4% (ETS-M), 62.8 +/- 8.4% and 58.4 +/- 6.1% (ETS-C), 38.7 +/- 9.4% and 24.8 +/- 7.7% (NETS-M), and 49.8 +/- 8.7% and 32.7 +/- 7.1% (NETS-C). There were significant differences in lipid deposits of the arteries between the controls and the ETS-exposed rabbits (37 +/- 1% versus 53 +/- 1%, P = .004) and between the controls and metoprolol-treated rabbits (51 +/- 1% versus 38 +/- 1%, P = .027). The benefit of metoprolol was independent of ETS exposure (ETS x metoprolol interaction, P = .595).

CONCLUSIONS

Exposure to ETS significantly accelerated and metoprolol decreased the development of atherosclerosis in lipid-fed rabbits, but there was no interaction between the effects of ETS exposure and metoprolol. Metoprolol did not protect against the effects of ETS on atherosclerosis, suggesting that the beta-adrenergic system is not the mechanism of ETS-induced atherosclerosis.

Is the reduction of myocardial infarct size by dietary fish oil the result of altered platelet function?

Sprague-Dawley rats fed a diet containing 12% fish oil (18% eicosapentaenoic acid [EPA] and 12% docosahexaenoic acid [DHA]), for 1 week (group I, n = 9) or 8 weeks (group III, n = 42) and controls (group II, n = 8; group IV, n = 36, respectively) were subjected to 35 minutes of left coronary artery occlusion followed by 120 minutes of reperfusion. Compared to the controls, infarct size was significantly reduced in group III (15% +/- 2%, n = 42 vs 34% +/- 4%, n = 36; p < 0.001; infarct mass/risk area x 100%), but no change in group I (39% +/- 5%, n = 9 vs 35% +/- 5%, n = 8; p = not significant). Bleeding time was prolonged in group III (290 +/- 73 sec) compared to group IV (99 +/- 10 sec, p = 0.015). Omega-3 fatty acid (EPA and DHA) levels in platelets were significantly higher in the rats fed 8 weeks of fish oil (group III) compared to the controls (group IV) and the rats fed 8 weeks of fish oil and then a regular diet until bleeding time normalized (group V) (7.2% +/- 0.6% vs 1.2% +/- 0.2% and 4.9% +/- 0.5%; 3.8% +/- 0.7% vs 1.8% +/- 0.3% and 2.8% +/- 0.6%, p < 0.001 and 0.05, respectively). These data indicate that long-term (8 weeks) dietary fish oil supplementation significantly reduces infarct size; short-term (1 week) does not. This reduction of infarct size appears to correlate with altered platelet function and EPA and DHA levels in platelets.

The utero-placental circulation, eugenics and the prevention and treatment of high risk pregnancies

Through systematic experimental and clinical studies, the physiological regulation of utero-placental circulation and the relation of the disturbance in this acirculation to pathogenic mechanisms of high risk pregnancies-Intrauterine Growth Retardation (IUGR) and Pregnancy-induced hypertension (PIH) were explored. The pharmacological effects and mechanism of a Chinese herbal medicine-Qingxintong in improving, the utero-placental circulation and the therapeutic efficacy in treatment of IUGR and PIH, both accompanied by disturbance of utero-placental circulation, were investigated as well.

Exposure to environmental tobacco smoke increases myocardial infarct size in rats

BACKGROUND

Exposure to environmental tobacco smoke (ETS) has been epidemiologically linked to death from ischemic heart disease in nonsmokers. In this study, we evaluated the influence of 3 days, 3 weeks, and 6 weeks of ETS exposure on myocardial infarct size in a rat ischemia/reperfusion model.

METHODS AND RESULTS

Sprague-Dawley rats exposed to ETS (four Marlboro cigarettes per 15 minutes, 6 hours per day, 5 days per week) for 3 days (n = 24), 3 weeks (n = 21), or 6 weeks (n = 12) and control rats (n = 24, n = 21, and n = 12, respectively) were subjected to 35 minutes of left coronary artery occlusion and 2 hours of reperfusion. Infarct size and risk area were determined by triphenyltetrazolium chloride and phthalocyanine blue staining, respectively. Air nicotine, carbon monoxide, and total particulates were measured during ETS exposure. Serum lipids, plasma carbon monoxide hemoglobin (COHb), nicotine, and cotinine concentrations were measured in additional groups (6 to 13 rats each) exposed to 3 days, 3 weeks, or 6 weeks of ETS and controls. Average air nicotine, carbon monoxide, and total particulate concentrations were 1103 micrograms/m3, 92 ppm, and 60 mg/m3 for the ETS-exposed rats. Infarct size (infarct mass/risk area x 100%) increased significantly in the ETS groups compared with the control groups in a dose-dependent manner (P = .023), with longer exposure associated with larger infarct size. Infarct size nearly doubled with 6 weeks of ETS exposure (61 +/- 5% versus 34 +/- 3% for control, mean +/- SEM). Plasma COHb, nicotine, and cotinine levels increased significantly in the ETS groups in a dose-dependent manner (all P < .001).

CONCLUSIONS

Exposure to passive smoking increases myocardial infarct size in a rat model of ischemia and reperfusion. This increase of infarct size exhibited a dose-response relation. These results are consistent with epidemiological studies demonstrating that ETS increases the risk of heart death.

[Familial essential hypertension and HLA]

Ten families living in Shenyang city with multiple cases of essential hypertension were studied by HLA haplotype analysis. They were selected strictly in accordance with the methods of sibling pair analysis and lods analysis. The obtained ratio of HLA haplotype sharing among affected siblings were 28.6%(2): 52.4%(1): 19.0%(0), P > 0.9. It is indicated that the haplotype shared randomly among affected siblings. The results of Lods analysis were Q = 0.40, Lods = 0.046, Pr = 1.112. These results showed that there is no evidence of patients with essential hypertension susceptible to gene linked with HLA.

Effects of etidronate and lovastatin on the regression of atherosclerosis in cholesterol-fed rabbits

Eighty New Zealand rabbits in eight groups (10 each) were fed a 0.5% cholesterol diet for 12 weeks. One group served as a control and was sacrificed at the end of 12 weeks. Seven other groups were shifted to a normal diet and received a drug(s) or placebo for the second 12 weeks. The high dose of etidronate (3 mg/kg/day) with lovastatin (6 mg/kg/day) significantly reduced the percent of aortic atherosclerotic lesions [56 +/- 21 vs. 77 +/- 17% (mean +/- SD), p < 0.05] in the regression study. Compared to the control groups for etidronate and lovastatin, the high or low dose (0.15 mg/kg/day) of etidronate significantly reduced aortic standardized plaque volume per unit (18.7 +/- 7.9 or 18.8 +/- 9.1 vs. 28.4 +/- 11.8 mm.%, p < 0.05). Lovastatin reduced pulmonary artery maximum plaque thickness (0.13 +/- 0.10 vs. 0.23 +/- 0.11 mm, p < 0.05). There were no differences in serum lipid and calcium levels in the control and treated groups. The high dose of etidronate inhibited bone mineralization as expected, whereas the low dose of etidronate did not. These data suggest that etidronate with lovastatin can regress aortic atherosclerosis in the cholesterol-fed rabbit placed on a normal diet.

Aspirin inhibits platelet activity but does not attenuate experimental atherosclerosis

We evaluated the antiatherosclerotic potential of aspirin, a platelet inhibitor, in lipid-fed rabbits (0.3% cholesterol diet). Seventy-five male New Zealand white rabbits were divided into treated or control groups. The treated groups were given aspirin by daily gavage for 12 weeks (1 mg/kg, 10 mg/kg, 30 mg/kg, and 60 mg/kg) and 10 rabbits served as controls. Increased bleeding time was observed in the aspirin-treated groups (average, 58 +/- 10 seconds to 75 +/- 17 seconds; p < 0.001). Only high-dose aspirin (60 mg/kg/day) significantly inhibited platelet aggregation (1.04 +/- 0.15 vs 0.67 +/- 0.14; p < 0.05). Seventeen additional rabbits had aortic endothelial injury produced by a balloon catheter. Eight of them were given aspirin (40 mg/kg/day), and the other nine served as controls. The average percent of surface lesions and lesion thickness of the aorta and pulmonary artery were not significantly reduced by aspirin. These results show that at doses that cause antiplatelet effects, aspirin does not attenuate atherosclerosis.

Passive smoking increases experimental atherosclerosis in cholesterol-fed rabbits

OBJECTIVES

We evaluated the influence of passive smoking on experimental atherosclerosis in cholesterol-fed rabbits.

BACKGROUND

Exposure to environmental tobacco smoke (ETS) has been epidemiologically linked to death from ischemic heart disease in nonsmokers.

METHODS

New Zealand male rabbits were randomly divided into three groups after 2 weeks of a 0.3% cholesterol diet. Sixteen rabbits were exposed to a high and 16 rabbits to a low dose of ETS; 32 rabbits located in another room served as an unexposed control group. After 10 weeks of ETS exposure, all rabbits were killed, and the percent of aortic and pulmonary artery endothelial surfaces covered by lipid lesions was measured by staining and planimetry.

RESULTS

Average air nicotine, carbon monoxide and total particulate concentrations were 1,040 micrograms/m3, 60.2 ppm and 32.8 mg/m3 for the high dose ETS group, 30 micrograms/m3, 18.8 ppm and 4.0 mg/m3 for the low dose ETS group and < 1 microgram/m3, 3.1 ppm and 0.13 mg/m3 for the control group. The percent atherosclerotic involvement of the aorta and pulmonary artery increased significantly with ETS exposure (for the aorta, 30 +/- 19% [mean +/- SD] for the control group, 36 +/- 14% for the low dose ETS group and 52 +/- 21% for the high dose ETS group, p < 0.001; for the pulmonary artery, 22 +/- 15% for the control group, 29 +/- 25% for the low dose ETS group, and 45 +/- 12% for the high dose ETS group, p < 0.001). Bleeding time was significantly shorter in the two ETS groups than in the control group (86 +/- 17 vs. 68 +/- 15, 68 +/- 18 s, p < 0.001). There were no significant differences in serum triglycerides, cholesterol and high density lipoprotein cholesterol at the end of the study.

CONCLUSIONS

Environmental tobacco smoke affects platelet function and increases aortic and pulmonary artery atherosclerosis. This increase of atherosclerosis was independent of changes in serum lipids and exhibited a dose-response relation. These results are consistent with data from epidemiologic studies demonstrating that ETS increases the risk of death due to heart disease.

Effect of lovastatin on suppression and regression of atherosclerosis in lipid-fed rabbits

The present study was designed to evaluate the effects of lovastatin on suppression and regression of atherosclerosis in the lipid-fed rabbit. Fifty-seven New Zealand rabbits in six groups were fed a 0.3% cholesterol diet for 10 weeks. In the progression phase of the study, group C10 served as a control and received 1 ml of DMSO daily by gavage. Two other groups, L10 and H10, received low (L)-dose (10 mg/day) or high (H)-dose (20 mg/day) lovastatin dissolved in 1 ml of DMSO for 10 weeks. In the regression phase of the study, three groups of rabbits received the high lipid diet for 10 weeks and were then shifted to a normal diet for the second 10 weeks. During the second 10 weeks, the control group C20 received 1 ml of DMSO daily, and groups L20 and H20 received 10 and 20 mg/day of lovastatin by gavage, respectively. In the progression phase of the study, lovastatin significantly attenuated the percent of aortic lesions in groups L10 (8 +/- 7%) and H10 (9 +/- 14%) vs. the control group C10 (31 +/- 17%; p less than 0.01). There was a similar reduction in pulmonary lesions in groups L10 (10 +/- 6%) and H10 (4 +/- 5%) compared to the control group C10 (30 +/- 16%; p less than 0.01). There was also a reduction in plaque thickness in both the aorta and pulmonary artery, and hence an even greater reduction in estimated plaque volume. In the regression phase of the study, lovastatin also significantly reduced the percent of aortic lesions (groups L20 and H20 vs. C20: 27 +/- 18 and 22 +/- 7% vs. 40 +/- 17%; p less than 0.05) and pulmonary lesions (21 +/- 10 and 17 +/- 6% vs. 26 +/- 9%; p greater than 0.05 and p less than 0.05, respectively); the average maximum plaque thickness of aorta (0.24 and 0.26 mm vs. 0.49 mm; p less than 0.01); and the standardized plaque volume per unit area of aorta (4.5 and 3.4 vs. 12.1 mm-%; p less than 0.05 and p less than 0.01, respectively). However, there was no significant difference in the percent of aortic lesions between groups L20 and H20 and group C10 (27 +/- 18 and 22 +/- 7 vs. 31 +/- 17%; p greater than 0.05).(ABSTRACT TRUNCATED AT 400 WORDS)

[Effect of 3,4-dihydroxyacetophenone on platelet aggregation in normal pregnancy and pregnancy induced hypertension]

The effect of 3,4-Dihydroxyacetophenone (DHAP) on platelet aggregation in normal pregnancy and pregnancy induced hypertension (PIH) in the third-trimester was studied by optical method. The IC50 values of DHAP in inhibiting ADP-induced platelet aggregation in normal pregnancy and PIH were 1.0 x 10(-3) mol/L and 2.4 x 10(-3) mol/L respectively. A dose-effect relationship of DHAP was also demonstrated (r greater than 0.92). At various time-phases of ADP-induced platelet aggregation, the addition of DHAP to the platelet-rich plasma could rapidly decrease the two-phase aggregation. DHAP of 200-240 mg/d x 3-5 days by i.v. drips given to patients with PIH also inhibited ADP-induced platelet aggregation. The authors conclude that DHAP is a potent antithrombogenic agent both in vitro and in vivo and is therefore a promising drug to improve utero-placenta-fetal circulation.

Alleles at four HLA class II loci determined by oligonucleotide hybridization and their associations in five ethnic groups

The use of polymerase chain reaction (PCR) and oligonucleotide hybridization offers a new approach for the definition of HLA class II alleles. It has been possible to determine 43 alleles of DRB1, four of DRB3, two of DRB4, four of DRB5, eight of DQA1, and 14 of DQB1. These alleles are inherited together in members of families and form closely associated groups which are found repeatedly and in characteristic patterns in different populations. We have determined the HLA class II alleles and analyzed their association in 431 healthy unrelated subjects including 161 North American Caucasians, 53 Latin Americans, 61 Blacks, 88 Chinese, and 68 Israeli Jews. For-locus haplotypes (DRB1; DRB3/4/5; DQA1; DQB1) were derived from 79 B cell lines and the analysis of segregation in 34 nuclear families. The B-cell lines yielded 37 and the families showed the same, and 20 other, haplotypic combinations. In addition to these 57 haplotypes, associated alleles were assigned in the unrelated panels following certain rules. The resulting haplotypes were assigned to groups known to share associated alleles. The groups were: 1) DR1, DR2, and DRw10 (13 haplotypes); 2) DR3 and DRw6 (26 haplotypes); 3) DR5 and DRw8 (24 haplotypes); 4) DR4, DR7, and DR9 (24 haplotypes). Their distribution in populations with different ethnic backgrounds was analyzed. The expressed DRB4 allele and its null mutant were determined by PCR and oligonucleotide hybridization. The different DR7 haplotypes resulting from these determinations were analyzed in a panel of 130 North American Caucasoids. This comprehensive analysis of class II HLA haplotypes in human populations should be useful in understanding the role of these genes and in various applications including anthropology, disease susceptibility, and transplantation of allogeneic organs and tissues.

Simultaneous detection of thiol- and disulfide-containing peptides by electrochemical high-performance liquid chromatography with identification by mass spectrometry

A new HPLC electrochemical detector that can be used to detect selectively and simultaneously both thiol- and disulfide-containing peptides is described. One electrode responds only to thiol-containing peptides, while a second electrode located downstream from a third electrode responds to thiol- as well as disulfide-containing peptides. All three electrodes are located in a single block and sample the HPLC effluent simultaneously. Since the electrochemical detector responds only to peptides that contain thiol or disulfide functionalities, it is ideal for detecting these types of peptides when they are present in complex mixtures. Peptides can be identified by their retention times if reference peptides are available, or by their molecular weights if the appropriate chromatographic fractions are collected and analyzed by mass spectrometry. The utility of the three-electrode electrochemical detector for detecting thiol- and disulfide-containing peptides in a single chromatographic analysis is illustrated with proteolytic digests of bovine alpha A-crystallin and partially reduced bovine insulin.

DNA typing for HLA-DR, and -DP alleles in a Chinese population using the polymerase chain reaction (PCR) and oligonucleotide probes

We have determined alleles of HLA-DRB1, DRB3, DRB5, DQA1, DQB1, and DPB1 loci in 91 unrelated healthy individuals from North China. Group-specific PCR primers were employed for the analysis of subsets of DR1, DR2, DR4, DRw52, and DPB. With allele-specific probes, 22 DRB1, 8 DQA1, 13 DQB1, and 12 DPB1 alleles were found in this panel. Allele frequencies showed that 25.3% of the subjects had DR7 and 26.4% had DR9, only 5.5% had DRB1*0301 (DRw17). In the DR4 group, DRB1*0405 (Dw15, 8.8%) and 0406 (KT2, 9.9%) were the most prevalent alleles. DRB1*0404 (Dw14.1), 0407 (Dw13.2) and 0408 (Dw14.2) were absent and the other alleles of the DR4 group were rare. The most common DRw6 subset was DRB1*1401 (8.8%). DRB1*0802 and 0803 were present (2.2%, 6.6%), and DRB1*0801 was not found. Associations with DQA1 and DQB1 were generally similar to those found in other populations. DPB1*0501 was the most frequent (60.2%) allele at the DPB1 locus. Overall our study shows that the distribution of class II alleles in a population from Mainland China is quite different from other ethnic groups. The high frequency of the KT2 subset of DR4. (DRB1*0406) and of DPB1*0501 are the most striking features found. A new type of DR4 was determined in one subject. It was like DR4-Dw15 (DRB1*0405) but, according to our hybridization patterns, it encoded valine instead of glycine in position 86. It is now called DRB1*0410.

Aspartic acid at position 57 of the HLA-DQ beta chain in insulin-dependent diabetes mellitus: an association with one DRw9-DQw9 subtype in the Chinese population

Eighteen unrelated Chinese patients with insulin-dependent diabetes mellitus (IDDM) were analyzed for HLA Class II genes using a variety of molecular biological techniques including restriction fragment length polymorphism (RFLP), polymerase chain reaction with allele-specific oligonucleotides (PCR-ASO) and direct DNA sequencing. The high frequency of DR3/DR4 heterozygotes found in the Chinese with IDDM strengthens the importance of this combination of haplotypes in IDDM susceptibility since it is present in two genetically distant populations--Chinese and Caucasians. The frequency of DRw9, a rare allele in the Caucasian population, is much higher in the Chinese. Moreover, the DQ beta chain linkage of DRw9 was different in IDDM patients compared with control subjects. In contrast with previous results, codon 57 of the DQ beta chain was aspartic acid in DRw9 Chinese IDDM patients. Furthermore, one particular DRw9-DQw9 haplotype may be associated with IDDM susceptibility in the Chinese population.

The protective effect of sulfite on menadione- and diquat-induced cytotoxicity in isolated rat hepatocytes

Menadione and diquat cause toxicity in isolated hepatocytes. The toxicities of both menadione and diquat are primarily due to redox cycling and consequent oxidative stress. Menadione toxicity, however, has another component as the compound also possesses alkylating and oxidating properties allowing it to interact directly with cellular nucleophiles. Sulfite afforded considerable protection of isolated rat hepatocytes against the toxicity of menadione. This protective effect of sulfite may have several components. Sulfite effectively competed with glutathione (GSH) for conjugation with menadione, sparing intracellular GSH which may continue to detoxify reactive oxygen species formed through menadione redox cycling. The menadione sulfite conjugate undergoes much slower redox cycling than both menadione and the menadione glutathione conjugate. Sulfite also showed some degree of protection of hepatocytes from the toxicity of diquat. Diquat is a "pure" redox cycling agent and the protective effect of sulfite may involve the liberation of GSH from GSSG by sulfitolysis. This would again bolster intracellular GSH levels allowing further GSH-dependent detoxification of reactive oxygen species through cellular GSH peroxidases. In conclusion, our data illustrate the potential of inorganic sulfite to support the intracellular detoxification function of GSH, both against reactive electrophilic metabolites and against agents undergoing redox cycling.

Identification of disulfide-containing peptides in endocrine tissue extracts by HPLC-electrochemical detection and mass spectrometry

A new procedure to selectively identify disulfide-containing peptides in extracts of biological tissues is described. Disulfide-containing peptides are detected by their UV absorbance and electrochemical (EC) activity after chromatographic separation, and subsequently identified by fast atom bombardment mass spectrometry (FABMS). This combination of fractionation by HPLC and selective detection is attractive because it is rapid, highly specific for disulfide-containing peptides, and applicable to all disulfide-containing peptides that may be present in complex biological mixtures. Useful procedures for applying the method are demonstrated with tissue extracts from bovine pituitary and catfish pancreas. In addition to finding the expected disulfide-containing peptides, evidence for two forms of catfish insulin are presented. The merits of this and other methods used to detect peptides in similar tissue extracts are discussed.

The metabolism of sulfite in liver. Stimulation of sulfate conjugation and effects on paracetamol and allyl alcohol toxicity

Sulfite is rapidly oxidized to sulfate in the liver. This was shown both in isolated rat hepatocytes and isolated perfused liver. In addition sulfite treatment resulted in release of GSH originating probably from low molecular disulfides such as GSSG and/or mixed disulfides between GSH and protein sulfhydryl groups. Sulfite was demonstrated to be an efficient precursor for sulfate conjugation. This was demonstrated using paracetamol as a substrate. Sulfite was even more efficient in supplying sulfate for sulfate conjugation than inorganic sulfate. Sulfite was furthermore shown to be protective against the toxicity of both N-acetyl-p-benzoquinone imine (NAPQI), the reactive paracetamol metabolite, and acrolein, a reactive aldehyde which is a metabolite of allyl alcohol. This protection is most likely due to direct reaction between sulfite and these reactive metabolites in a manner similar to that occurring with GSH and other thiols. When NAPQI and acrolein were generated intracellularly in isolated hepatocytes from paracetamol and allyl alcohol, respectively, toxicity was also expressed. In this case sulfite only protected against allyl alcohol induced toxicity and not against paracetamol induced toxicity. The reason for this discrepancy is not clear but may depend on factors such as site of generation of the reactive metabolite or the reactivity of the reactive metabolite.

The polymorphism of HLA antigens in the Chinese

Remarkable differences were observed in antigen frequencies (AF), gene frequencies (GF) and haplotype frequencies (HF) when 2441 healthy Chinese individuals representing nine different ethnic groups and living in 14 different geographic locations were examined for the genetic distribution of the various HLA Class I and II markers. A sizable number of individuals of each ethnic group within each of the three major categories of the Chinese population, namely, Hans, Mongols, and Southern minorities, have been studied here, providing useful population statistics for applications such as determination of probabilities of paternity, comparisons for HLA and disease associations, and anthropologic studies.