Raised concentration of serum bile acids following occupational exposure to halogenated solvents, 1,1,2-trichloro-1,2,2-trifluoroethane and trichloroethylene

Use of bile acids as potential markers of liver dysfunction in humans: A systematic review

OBJECTIVE

This study aimed to determine the effectiveness of using total, individual serum, or urinary bile acids (BA) as potential markers of liver dysfunction.

METHODS

We searched the PubMed and Web of Science databases using the following keywords- "serum bile acids," "liver dysfunction," "liver injury," "liver disease," "traditional liver function tests," "Chronic liver disease," "acute liver injury". The search was complemented by manual screening of the list of references for relevant articles. We selected only English-language manuscripts for adult patients based on predetermined inclusion and exclusion criteria. Animal studies and studies on neonates and children were not included.

OUTCOME MEASURES

Changes in BA concentrations or ratios at or prior to changes in liver function tests.

RESULTS

A total of 547 studies were identified, of which 28 were included after reading the entire manuscript. These studies included 1630 patients and 836 controls published between 1990 and 2017. The methods used in BA assays varied significantly, and the studies did not agree. on specific individual BA or BA ratios as biomarkers of specific liver injury or dysfunction. Except for the prognostic value of BA in intrahepatic cholestasis of pregnancy (ICP), studies have failed to provide evidence for BA as a liver biomarker.

CONCLUSIONS

Despite the research conducted on BA for over 27 years, there are inconsistencies in the reported results and a lack of solid evidence to support the use of individual BA or BA ratios as biomarkers of liver injury. Adequately conducted studies needed to resolve this limitation in the literature.

Target Organ Metabolism, Toxicity, and Mechanisms of Trichloroethylene and Perchloroethylene: Key Similarities, Differences, and Data Gaps

Trichloroethylene (TCE) and perchloroethylene or tetrachloroethylene (PCE) are high-production volume chemicals with numerous industrial applications. As a consequence of their widespread use, these chemicals are ubiquitous environmental contaminants to which the general population is commonly exposed. It is widely assumed that TCE and PCE are toxicologically similar; both are simple olefins with three (TCE) or four (PCE) chlorines. Nonetheless, despite decades of research on the adverse health effects of TCE or PCE, few studies have directly compared these two toxicants. Although the metabolic pathways are qualitatively similar, quantitative differences in the flux and yield of metabolites exist. Recent human health assessments have uncovered some overlap in target organs that are affected by exposure to TCE or PCE, and divergent species- and sex-specificity with regard to cancer and noncancer hazards. The objective of this minireview is to highlight key similarities, differences, and data gaps in target organ metabolism and mechanism of toxicity. The main anticipated outcome of this review is to encourage research to 1) directly compare the responses to TCE and PCE using more sensitive biochemical techniques and robust statistical comparisons; 2) more closely examine interindividual variability in the relationship between toxicokinetics and toxicodynamics for TCE and PCE; 3) elucidate the effect of coexposure to these two toxicants; and 4) explore new mechanisms for target organ toxicity associated with TCE and/or PCE exposure.

Serum bile acids as a sensitive biological marker for evaluating hepatic effects of organic solvents

Serum bile acids (SBAs) are suggested as a potentially sensitive and specific indicator of liver function which, accordingly, could provide an early indication of hepatobiliary dysfunction. This offers advantages over more traditional parameters of liver integrity/function. Recent studies have shown that occupational exposure to low levels of halogenated aliphatic or non-halogenated aromatic solvents is associated with significant increases in SBA levels. As this has often been evident in the absence of any effect on conventional parameters of hepatobiliary integrity/function, elevated SBA levels may well be regarded as a sensitive biological marker of exposure/effect of these compounds. In addition, it may be considered that they provide an early indicator of solvent-induced changes in hepatobiliary function. Extensive studies with experimental animals have also provided supporting evidence for these observations in solvent-exposed individuals. Investigations of the mechanisms at cellular and subcellular levels by which these increases occur have suggested that these effects are likely to be the result of selective, dose-related and reversible inhibition of bile acid uptake at the sinusoidal domain of the hepatocyte plasma membrane. Increased concentrations of SBA under low levels of exposure to different solvents have been demonstrated to be a short-lived and reversible effect which is not accompanied by any other evidence of liver damage. Therefore, it could be assumed that it is unlikely that there would be pathological sequelae to these effects, although the longer term ramifications of such effects have not been thoroughly investigated. Nevertheless, the available evidence indicates that investigation of SBA in solvent-exposed workers could provide useful indications of exposure and effect.

Plasma bile acid concentrations in patients with human immunodeficiency virus infection receiving protease inhibitor therapy: possible implications for hepatotoxicity

STUDY OBJECTIVES

To evaluate whether patients with human immunodeficiency virus (HIV) infection who were receiving protease inhibitor therapy had altered bile acid concentrations compared with noninfected control subjects, and whether bile acid concentrations could predict the onset of hepatotoxicity caused by protease inhibitors.

DESIGN

Retrospective sample analysis from a prospectively conducted clinical trial.

SETTING

Academic research center.

PATIENTS

Eleven adults with advanced HIV disease who were taking protease inhibitor-based antiretroviral therapy, one of whom had developed protease inhibitor-induced hepatotoxicity.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of cholic acid (CA), chenodeoxycholic acid (CDCA), deoxycholic acid (DCA), lithocholic acid (LCA), ursodeoxycholic acid (UDCA), and taurocholic acid (TC) were analyzed by using a novel high-performance liquid chromatography with tandem mass spectrometry detection method. Comparisons of the relative contribution of each bile acid to the total bile acid pool were made with previously published values and with bile acid concentrations contained in two pooled plasma samples from healthy, non-HIV-infected volunteers analyzed in our laboratory. Each pooled plasma sample used for this analysis contained contributions from three non-HIV-infected volunteers. The LCA and TC concentrations in HIV-infected patients were 3-4-fold higher than those previously reported for non-HIV-infected subjects; concentrations of other bile acids were similar to those of previous reports. The relative contribution of CDCA to the total bile acid pool was 9% in HIV-infected patients compared with 30-50% in noninfected subjects. Total and individual bile acid concentrations in the HIV-infected patient who developed hepatotoxicity were similar to the bile acid concentrations from the other study patients who did not develop hepatotoxicity.

CONCLUSION

These data suggest that bile acid concentrations may be altered by HIV infection and/or protease inhibitor therapy. However, further investigations should be performed to assess whether antiretroviral-associated hepatotoxicity can be predicted by alterations in individual bile acid concentrations.

Increased serum bile acids as a possible biomarker of hepatotoxicity in Brazilian workers exposed to solvents in car repainting shops

The objective was to evaluate total serum bile acids (SBA) as a biological marker of hepatotoxicity in car painters exposed to organic solvents and to compare their performance with classic biochemical parameters of liver function. SBA were analysed in a selected group of workers (n=57) occupationally exposed to a mixture of organic solvents and in a control group (n=51). In addition, aspartate aminotransferase (AST), alanine aminotransferase (ALT), total bilirubin (TB), gamma-glutamyltransferase (GGT) and alkaline phosphatase (ALP) were determined in the two groups. Urinary hippuric acid was measured in all samples. Statistical analysis of the data revealed a significant increase in the concentration of SBA, AST, ALP and TB in exposed workers compared with controls (Mann-Whitney, p</=0.05). However, SBA was the parameter most frequently altered in exposed workers and showed higher significance between the two groups (chi-square test) compared with the upper limit of the reference range (8 micromol l(-1)). In conclusion, SBA can be considered to be a sensitive parameter of hepatotoxicity induced by organic solvents than the traditional tests and it can be used as an biological marker of subclinical liver injury.

Reduction of occupational exposure to perchloroethylene and trichloroethylene in metal degreasing over the last 30 years: influences of technology innovation and legislation

Occupational exposure to trichloroethylene (TRIC) and perchloroethylene (PERC) in metal degreasing is analyzed by calculating airborne concentrations for a large set of possible exposure scenarios (Scenario-Based Risk Assessment, SceBRA). Different types of degreasing machines ranging from open-top machines used until the 1980s to closed-loop nonvented machines used since the 1990s are investigated; the scope of the study is Germany. Concentrations are calculated for different kinds of releases (emissions from open baths, leakage, release of contaminated air during loading and unloading) with a dynamic two-box model for the near-field and the far-field. The concentration estimates are in good agreement with measured data. The airborne concentrations are compared to maximum workplace concentrations (MAK values). The full set of scenarios shows for which situations MAK values were exceeded and how the transition to newer degreasing machines reduced the occupational exposure by more than one order of magnitude. In addition, numbers of exposed workers are estimated for different years. While more than 25,000 workers in the near-field were exposed to TRIC and PERC in 1985, the number is below 3000 since 1996, which is mainly due to technology changes, rationalization, automatization, and replacement of TRIC and PERC by nonchlorinated solvents.

Exposure of Danish workers to trichloroethylene, 1947-1989

The aim of this study was to investigate the exposure of Danish workers to trichloroethylene (TCE) and the factors that affected such exposure. Data from Danish health authorities were evaluated for use in an epidemiological study of possible adverse health effects of TCE. The paper files relating to 1,075 air measurements taken between 1947 and 1989 at 150 companies were examined to extract information about calendar year, company, industry, type of measurement, and worker. Multiple regression models were used to analyze the effects of various factors on the concentration of TCE. TCE concentrations decreased over the four decades studied. The geometric mean was 329 mg/m3 for measurements taken 1947-1959, and 260 mg/m3, 53 mg/m3, and 23 mg/m3, respectively, for the three subsequent decades. Regression analyses showed that 1) TCE concentrations decreased on average 4 percent per year before 1964 and 15 percent per year afterward; 2) area and personal measurements gave similar concentrations (for the same calendar period, industry, and duration of measurement); 3) longer-duration measurements were associated with lower TCE concentrations; 4) high TCE concentrations occurred in the iron and metal industry; and, 5) in this industry men were exposed to concentrations two times those of women. Moreover, this study indicated that both the exposure level and the proportion of exposed workers in Danish companies increased with decreasing number of employees. Epidemiological studies of health effects of TCE may benefit from evaluating potential risk within different strata of calendar time, number of company employees, sex, and type of industry.

Effects of long-term solvent exposure on blood cytokine levels and antioxidant enzyme activities in house painters

The aim of this study was to examine solvent-associated effects on blood cytokine levels, antioxidant enzyme activities, and malondialdehyde (MDA) concentration in house painters. Trace element (Cu and Zn) and nitrite and nitrate levels as well as protein concentrations in erythrocytes and serum were determined. Thirty male house painters and 30 male clerical workers were included in the study. There were 13 smokers and 17 nonsmokers in each group. Hemoglobin concentrations were significantly lower in house-painter blood compared to controls. House painters had significantly higher concentrations of erythrocyte protein (excluding hemoglobin), whereas no significant difference was observed between serum protein levels. Proinflammatory cytokine levels, such as tumor necrosis factor-alpha and interleukin-8, were significantly increased in house painters' sera. Interleukin-6 was below the detection limit of the assay in both groups. Interleukin-1beta and cytokine receptor interleukin 2R concentrations were not significantly affected. Furthermore, a three- to fourfold increase in nitrite and nitrate concentrations was found in house painters' sera. Serum superoxide dismutase (SOD) and glutathione peroxidase (GSHPx) activities were significantly lower in house painters compared to controls. Malondialdehyde (MDA) concentration, a measure of lipid peroxidation, was found to be significantly elevated. In house painters, erythrocyte carbonic anhydrase and catalase activities were elevated approximately 11- fold and 2-fold, respectively. Zinc levels were significantly decreased in house painters' sera. Smoking was not found to be a major confounder for the association between solvent exposure and blood parameters.