Effects of volatile aromatics, aldehydes, and phenols in tobacco smoke on viability and proliferation of mouse lymphocytes

Using three statistical methods to analyze the association between aldehyde exposure and markers of inflammation and oxidative stress

BACKGROUND

Exposure to aldehydes has been linked to adverse health outcomes such as inflammation and oxidative stress, but research on the effects of these compounds is limited. This study is aimed at assessing the association between aldehyde exposure and markers of inflammation and oxidative stress.

METHODS

The study used data from the NHANES 2013-2014 survey (n = 766) and employed multivariate linear models to investigate the relationship between aldehyde compounds and various markers of inflammation (alkaline phosphatase (ALP) level, absolute neutrophil count (ANC), and lymphocyte count) and oxidative stress (bilirubin, albumin, and iron levels) while controlling for other relevant factors. In addition to generalized linear regression, weighted quantile sum (WQS) and Bayesian kernel machine regression (BKMR) analyses were applied to examine the single or overall effect of aldehyde compounds on the outcomes.

RESULTS

In the multivariate linear regression model, each 1 standard deviation (SD) change in propanaldehyde and butyraldehyde was significantly associated with increases in serum iron levels (beta and 95% confidence interval, 3.25 (0.24, 6.27) and 8.40 (0.97, 15.83), respectively) and the lymphocyte count (0.10 (0.04, 0.16) and 0.18 (0.03, 0.34), respectively). In the WQS regression model, a significant association was discovered between the WQS index and both the albumin and iron levels. Furthermore, the results of the BKMR analysis showed that the overall impact of aldehyde compounds was significantly and positively correlated with the lymphocyte count, as well as the levels of albumin and iron, suggesting that these compounds may contribute to increased oxidative stress.

CONCLUSIONS

This study reveals the close association between single or overall aldehyde compounds and markers of chronic inflammation and oxidative stress, which has essential guiding value for exploring the impact of environmental pollutants on population health.

Acrylonitrile induction of rodent neoplasia: Potential mechanism of action and relevance to humans

Acrylonitrile, an industrial chemical, is a multisite carcinogen in rats and mice, producing tumors in four tissues with barrier function, that is, brain, forestomach, Zymbal’s gland, and Harderian gland. To assess mechanism(s) of action (MoA) for induction of neoplasia and to evaluate whether the findings in rodents are indicative of human hazard, data on the potential key effects produced by acrylonitrile in the four rodent target tissues of carcinogenicity were evaluated. A notable finding was depletion of glutathione in various organs, including two target tissues, the brain, and forestomach, suggesting that this effect could be a critical initiating event. An additional combination of oxidative DNA damage and cytotoxic effects of acrylonitrile and its metabolites, cyanide, and 2-cyanoethylene oxide, could initiate pro-inflammatory signaling and sustained cell and tissue injury, leading to compensatory cell proliferation and neoplastic development. The in vivo DNA-binding and genotoxicity of acrylonitrile has been studied in several target tissues with no compelling positive results. Thus, while some mutagenic effects were reported in acrylonitrile-exposed rodents, data to determine whether this mutagenicity stems from direct DNA reactivity of acrylonitrile are insufficient. Accordingly, the induction of tumors in rodents is consistent primarily with a non-genotoxic MoA, although a contribution from weak mutagenicity cannot be ruled out. Mechanistic data to support conclusions regarding human hazard from acrylonitrile exposure is weak. Comparison of metabolism of acrylonitrile between rodents and humans provide little support for human hazard. Three of the tissues affected in bioassays (forestomach, Zymbal’s gland, and Harderian gland) are present only in rodents, while the brain is anatomically different between rodents and humans, diminishing relevance of tumor induction in these tissues to human hazard. Extensive epidemiological data has not revealed causation of human cancer by acrylonitrile.

Use of In Vivo and In Vitro Data to Derive a Chronic Reference Value for Crotonaldehyde Based on Relative Potency to Acrolein

The Texas Commission on Environmental Quality (TCEQ) conducted a chronic inhalation noncancer toxicity assessment for crotonaldehyde (CRO). Since there were limited toxicity data for CRO, a reference value (ReV) was derived using a relative potency factor (RPF) approach with acrolein as the index chemical. Both CRO and acrolein are α,β-unsaturated carbonyls and share common steps in their mode of action (MOA). Only studies that investigated the effects of CRO and acrolein in the same study were used to calculate a CRO:acrolein RPF. In vivo findings measuring both 50% respiratory depression in rats and two species of mice and subcutaneous 50% lethality in rats and mice were used to calculate an RPF of 3 (rounded to one significant figure). In vitro data were useful to compare the MOA of CRO and acrolein and to support the RPF determined using in vivo data. In vitro cell culture studies investigating cytotoxicity in normal human lung fibroblast cultures using the propidium iodide cytotoxicity assay and in mouse lymphocyte cultures using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) cytotoxicity assay were used to calculate an in vitro RPF of 3, which supports the in vivo RPF. The chronic ReV for acrolein of 1.2 ppb derived by TCEQ was multiplied by the RPF of 3 to calculate the ReV for CRO of 3.6 ppb (10 μg/m(3)). The ReV for CRO was developed to protect the general public from adverse health effects from chronic exposure to CRO in ambient air.

Purification and characterization of NAD+ -dependent salicylaldehyde dehydrogenase from carbaryl-degrading Pseudomonas sp. strain C6

NAD+-dependent salicylaldehyde dehydrogenase (SALDH) which catalyzes the oxidation of salicylaldehyde to salicylate was purified form carbaryl-degrading Pseudomonas sp. strain C6. The enzyme was found to be a functional homotrimer (150 kDa) with subunit molecular mass of 50 kDa and contained calcium (1.8 mol/mol of enzyme). These properties were found to be unique. External addition of metal ions showed no effect on the activity and addition of chelators showed moderate inhibition of the activity. Potassium ions were found to enhance the activity significantly. SALDH showed higher affinity for salicylaldehyde (Km = 4.5 μM) and accepts mono- as well as di-aromatic aldehydes; however it showed poor activity on aliphatic aldehydes. Chloro-/nitro-substituted benzaldehydes were potent substrate inhibitors as compared to benzaldehyde and 3-hydroxybenzaldehyde, while 2-naphthaldehyde and salicylaldehyde were moderate. The kinetic data revealed that SALDH, though having broad specificity, is more efficient for the oxidation of salicylaldehyde as compared to other aromatic aldehyde dehydrogenases which gives an advantage for Pseudomonas sp. strain C6 to bioremediate carbaryl and other aromatic aldehydes efficiently.

Small molecule metabolite biomarker candidates in urine from mice exposed to formaldehyde

Formaldehyde (FA) is a ubiquitous compound used in a wide variety of industries, and is also a major indoor pollutant emitted from building materials, furniture, etc. Because FA is rapidly metabolized and endogenous to many materials, specific biomarkers for exposure have not been identified. In this study, we identified small metabolite biomarkers in urine that might be related FA exposure. Mice were allowed to inhale FA (0, 4, 8 mg/m³) 6 h per day for 7 consecutive days, and urine samples were collected on the 7th day of exposure. Liquid chromatography coupled with time of flight-mass spectrometry and principal component analysis (PCA) was applied to determine alterations of endogenous metabolites in urine. Additionally, immune toxicity studies were conducted to ensure that any resultant toxic effects could be attributed to inhalation of FA. The results showed a significant decrease in the relative rates of T lymphocyte production in the spleen and thymus of mice exposed to FA. Additionally, decreased superoxide dismutase activity and increased reactive oxygen species levels were found in the isolated spleen cells of exposed mice. A total of 12 small molecules were found to be altered in the urine, and PCA analysis showed that urine from the control and FA exposed groups could be distinguished from each other based on the altered molecules. Hippuric acid and cinnamoylglycine were identified in urine using exact mass and fragment ions. Our results suggest that the pattern of metabolites found in urine is significantly changed following FA inhalation, and hippuric acid and cinnamoylglycine might represent potential biomarker candidates for FA exposure.

Sequential fractionation with concurrent chemical and toxicological characterization of the combustion products of chlorogenic acid

Chlorogenic acid is the most abundant polyphenol found in the tobacco plant. The biological effects of its combustion products remain largely unknown. In this study, chlorogenic acid was burned at 640 degrees C for 2 min and the particulate matter of the smoke was collected onto Cambridge filter pads followed by selective extraction in five different solvents. Various fractions of the chlorogenic acid combustion products were tested for induction of micronuclei in V79 Chinese hamster fibroblast cells. Over 40 compounds were identified in the dimethyl sulfoxide (DMSO) extract by high-performance liquid chromatography coupled to electrospray time-of-flight mass spectrometry (HPLC/TOF-MS). The DMSO extract was then fractionated into three major fractions by preparative LC. The fraction inducing the highest degree of toxicity was further separated into four sub-fractions. The sub-fraction responsible for the most toxic response was determined to contain catechol as its major component. The overall reproducibility of the combustion, the extraction procedure and the chemical characterization of the compounds responsible for the toxicity in the chlorogenic acid smoke were evaluated by LC/TOF-MS.

The effects of prenatal exposure of mice to cigarette smoke on offspring immune parameters

While direct exposure to cigarette smoke (CS) was shown in numerous human and animal studies to impair host immune responses, effects on the offspring following in utero CS exposure are relatively unknown. Thus, a toxicological study was performed that extended our previous investigations examining the effects of relatively low-dose CS exposure on immune tumor surveillance parameters of the prenatally exposed offspring. In the current study, pregnant B6C3F1 mice were exposed by inhalation to mainstream CS (at a concentration equivalent to smoking approximately 1 pack of cigarettes/d) for 5 d/wk, 4 h/d from gestational day 4 to parturition. Smoke-induced effects on a number of immune parameters were examined in 3- (and/or 5-), 10-, and 20-wk-old male and female offspring, including lymphoid organ weight/cellularity; blood and bronchopulmonary lavage cell numbers/profiles; splenic lymphocyte proliferation; mixed lymphocyte reactions; and, host resistance against transplanted melanoma cells. Exposure in utero to CS significantly increased circulating white blood cell and lymphocyte numbers in both sexes for up to 2.5 mo after birth (compared to their age-/sex-matched, air-exposed counterparts). In addition, 3-wk-old male and female offspring from smoke-exposed mothers had decreased mitogen-stimulated T-lymphocyte proliferation, while 5-wk-old male pups had increased mixed lymphocyte response compared to their sex-matched, air-exposed counterparts. Although effects of prenatal smoke exposure on overall offspring immunity were relatively modest, these findings could suggest that early toxic insult by CS may alter subsequent immune homeostasis in the offspring, leading, possibly, to changes in disease vulnerability.

In vivo hydroquinone exposure impairs allergic lung inflammation in rats

Hydroquinone (HQ) is naturally found in the diet, drugs, as an environmental contaminant and endogenously generated after benzene exposure. Considering that HQ alters the immune system and its several source of exposures in the environment, we hypothesized that prolonged exposure of HQ could affect the course of an immune-mediated inflammatory response. For this purpose, male Wistar rats were intraperitoneally exposed to vehicle or HQ once a day, for 22 days with a 2-day interval every 5 days. On day 10 after exposure with vehicle or HQ, animals were ovalbumin (OA)-sensitized and OA-aerosolized challenged on day 23. HQ exposure did not alter the number of circulating leukocytes but impaired allergic inflammation, evidenced by lower number of leukocytes in the bronchoalveolar lavage fluid 24h after OA-challenge. Reduced force contraction of ex vivo tracheal segments upon OA-challenge and impaired mesentery mast cell degranulation after in situ OA-challenge were also detected in tissues from HQ exposed animals. The OA-specificity on the decreased responses was corroborated by normal trachea contraction and mast cell degranulation in response to compound 48/80. In fact, lower levels of circulating OA-anaphylactic antibodies were found in HQ exposed rats, as assessed by passive cutaneous anaphylaxis assay. The reduced level of OA-anaphylactic antibody was not dependent on lower number or proliferation of lymphocytes. Nevertheless, lower expression of the co-stimulatory molecules CD6 and CD45R on OA-activated lymphocytes from HQ exposed rats indicate the interference of HQ exposure with signaling of the humoral response during allergic inflammation. Together, these data indicate specific effects of HQ exposure manifested during an immune host defense.

Effect of in vivo phenol or hydroquinone exposure on events related to neutrophil delivery during an inflammatory response

Phenol (PHE) and hydroquinone (HQ) are metabolites of benzene that affect leukocytes after solvent intoxication. Hence, we investigated the effects of PHE or HQ exposure on neutrophil mobilization during an inflammatory response. Male Wistar rats received intraperitoneal injections of PHE, HQ or vehicle only and assays were performed 24 h after the last dose. Quantifications of bone marrow or circulating leukocytes showed that only HQ exposure induced neutrophilia, probably due to the accelerated mobilization from the bone marrow compartment, since reduced numbers of segmented cells in the last phase of maturation were detected there. Intravital microscopy showed that circulating leukocytes of HQ-exposed rats increased their rolling behavior and adherence to the mesenteric postcapillary venule wall in vivo. The enhanced leukocyte-endothelium interaction was not dependent on microvascular reactivity or perivascular mast cell degranulation. Instead, it was the result of neutrophil activation, demonstrated by a decrease in L-selectin and an increase in beta2 integrin expression on neutrophil membranes. This pattern of neutrophil activation may have contributed to the higher number of neutrophils in the subcutaneous inflammatory response of HQ-exposed rats after oyster glycogen injection. Taken together, our results indicate that HQ exposure alters neutrophil mobilization, which results in an exacerbated response after an injury. Although PHE is endogenously metabolized to HQ, PHE exposure only induced an increment in rolling behavior, which was not sufficient to alter the inflammatory response.

Cytotoxicity of pivoxil esters of antiviral acyclic nucleoside phosphonates: adefovir dipivoxil versus adefovir

Biological effectiveness of antiviral acyclic nucleoside phosphonate adefo vir, 9-[2-(phosphonomethoxy)ethy]ade nine (PMEA) and its more lipophilic (bis)pivaloyloxymethyl ester prodrug adefovir dipivoxil (bis-POM-PMEA) were compared under in vitro conditions in mammalian cell systems. Proliferation of murine splenocytes was inhibited in a concentration-dependent manner, the bis-POM-PMEA being more effective than PMEA. In contrast to PMEA, bis-POM-PMEA inhibited production of nitric oxide (NO) in macrophages activated with interferon-gamma (IFN-gamma) and lipopolysaccharide (LPS). Viability of both splenocytes and macrophages remained uninfluenced by PMEA, whereas pronounced cytocidal effects were exhibited by bis-POM-PMEA. The IC(50)s reached the values of 15 microM and 30 microM in cultures of macrophages and splenocytes, respectively (assayed at the interval of 24 hrs). The effects could partly be mimicked by formaldehyde, a decomposition product of the pivoxil moiety of bis-POM-PMEA. The other possible product, pivalic acid, was ineffective in this respect. The present data are consistent with the view that pivoxil prodrug of PMEA, bis-POM-PMEA possesses enhanced but also broader spectrum of biological effects than the parent compound.