International Commission for Protection against Environmental Mutagens and Carcinogens. An evaluation of the genetic toxicity of paracetamol

Involvement of TNFα, IL-1β, COX-2 and NO in the anti-inflammatory activity of Tamarix aphylla in Wistar albino rats: an in-vivo and in-vitro study

BACKGROUND

With the emergence of many side effects from synthetic drugs, there is an urgent need to find a natural alternative to these products. Therefore, our primary aim was to evaluate the anti-inflammatory activity of Tamarix aphylla (TA) and investigate the potential mechanism underlying this action.

METHODS

Initially, to ensure the safety of the extract and for dose selection, we performed an acute oral toxicity Assay through the oral administration of graded doses up to 4 g\kg in Wistar rats. then, we used the carrageenan-induced edema model to elucidate the anti-inflammatory activity. Using specific ELISA kits, we measured the levels of TNF-α, IL-1β, COX-2 and NO inside the inflamed paw tissue. Finally, for the in-vitro anti-inflammatory experiment, we used the erythrocyte membrane stability test.

RESULTS

Based on the acute oral toxicity assay, T. aphylla was considered generally safe and three different doses of 100, 200, and 400 mg/kg were chosen for further experiments. Additionally, TA expressed a significant (P < 0.05) anti-inflammatory activity, showing the maximum inhibition percentage at the fifth hour of measurement at 53.47% and 70.06%, at doses of 200 and 400 mg/kg respectively, compared to 63.81% for the standard drug. Similarly, we found that TA effectively reduced the levels of TNF-α and IL-1β at all tested doses (100-200-400 mg/kg) to a greater extent than the standard drug. Moreover, at 400 mg/kg, TA was able to significantly lower the levels of COX-2 and NO inside the inflamed tissue to a level comparable (P < 0.05) with that measured inside the paw tissue of normal rats. Finally, Tamarix aphylla at 100, 200 and 400 mg/kg doses significantly (P < 0.05) inhibited the heat-induced hemolysis of RBCs membrane by 67.78, 74.82 and 82.08%, respectively, compared to 83.89% produced by Aspirin.

CONCLUSION

T. aphylla produced a significant (P < 0.05) anti-inflammatory activity compared to the standard drugs either through the reduction of pro-inflammatory mediators or the protection of the lysosomal membrane.

Analgesic Activity of 5-Acetamido-2-Hydroxy Benzoic Acid Derivatives and an In-Vivo and In-Silico Analysis of Their Target Interactions

The design, synthesis, and evaluation of novel non-steroidal anti-inflammatory drugs (NSAIDs) with better activity and lower side effects are big challenges today. In this work, two 5-acetamido-2-hydroxy benzoic acid derivatives were proposed, increasing the alkyl position (methyl) in an acetamide moiety, and synthesized, and their structural elucidation was performed using 1H NMR and 13C NMR. The changes in methyl in larger groups such as phenyl and benzyl aim to increase their selectivity over cyclooxygenase 2 (COX-2). These 5-acetamido-2-hydroxy benzoic acid derivatives were prepared using classic methods of acylation reactions with anhydride or acyl chloride. Pharmacokinetics and toxicological properties were predicted using computational tools, and their binding affinity (kcal/mol) with COX-2 receptors (Mus musculus and Homo sapiens) was analyzed using docking studies (PDB ID 4PH9, 5KIR, 1PXX and 5F1A). An in-silico study showed that 5-acetamido-2-hydroxy benzoic acid derivates have a better bioavailability and binding affinity with the COX-2 receptor, and in-vivo anti-nociceptive activity was investigated by means of a writhing test induced by acetic acid and a hot plate. PS3, at doses of 20 and 50 mg/kg, reduced painful activity by 74% and 75%, respectively, when compared to the control group (20 mg/kg). Regarding the anti-nociceptive activity, the benzyl showed reductions in painful activity when compared to acetaminophen and 5-acetamido-2-hydroxy benzoic acid. However, the proposed derivatives are potentially more active than 5-acetamido-2-hydroxy benzoic acid and they support the design of novel and safer derivative candidates. Consequently, more studies need to be conducted to evaluate the different pharmacological actions, the toxicity of possible metabolites that can be generated, and their potential use in inflammation and pain therapy.

Lung cancer associated with combustion particles and fine particulate matter (PM2.5) - The roles of polycyclic aromatic hydrocarbons (PAHs) and the aryl hydrocarbon receptor (AhR)

Air pollution is the leading cause of lung cancer after tobacco smoking, contributing to 20% of all lung cancer deaths. Increased risk associated with living near trafficked roads, occupational exposure to diesel exhaust, indoor coal combustion and cigarette smoking, suggest that combustion components in ambient fine particulate matter (PM2.5), such as polycyclic aromatic hydrocarbons (PAHs), may be central drivers of lung cancer. Activation of the aryl hydrocarbon receptor (AhR) induces expression of xenobiotic-metabolizing enzymes (XMEs) and increase PAH metabolism, formation of reactive metabolites, oxidative stress, DNA damage and mutagenesis. Lung cancer tissues from smokers and workers exposed to high combustion PM levels contain mutagenic signatures derived from PAHs. However, recent findings suggest that ambient air PM2.5 exposure primarily induces lung cancer development through tumor promotion of cells harboring naturally acquired oncogenic mutations, thus lacking typical PAH-induced mutations. On this background, we discuss the role of AhR and PAHs in lung cancer development caused by air pollution focusing on the tumor promoting properties including metabolism, immune system, cell proliferation and survival, tumor microenvironment, cell-to-cell communication, tumor growth and metastasis. We suggest that the dichotomy in lung cancer patterns observed between smoking and outdoor air PM2.5 represent the two ends of a dose-response continuum of combustion PM exposure, where tumor promotion in the peripheral lung appears to be the driving factor at the relatively low-dose exposures from ambient air PM2.5, whereas genotoxicity in the central airways becomes increasingly more important at the higher combustion PM levels encountered through smoking and occupational exposure.

In vitro and in vivo assessment of the anti-inflammatory activity of olive leaf extract in rats

Inflammation is a complex and crucial process that protects the body against pathogens. Here in our study, we propose to scientifically justify the anti-inflammatory activity of olive leaf (OL). Initially, we ensured the safety of olive leaf extract (OLE) through acute oral administration of graded doses up to 4 g\kg in Wistar rats. Thus, the extract was considered generally safe. We also evaluated the ability of the extract to reduce carrageenan-induced rat paw edema. Compared to diclofenac sodium (10 mg/kg PO), OLE showed significant (P < 0.05) anti-inflammatory activity, showing the maximum inhibition percentage at the fifth hour of measurement at 42.31% and 46.99%, at doses of 200 and 400 m/kg, respectively, compared to 63.81% for the standard drug. To elucidate the potential mechanism, we measured TNF, IL-1, COX-2 and NO inside the paw tissue. Interestingly, OLE at all tested doses reduced the concentration of TNF and IL-1 to a level that was lower than that obtained by the standard drug. Additionally, OLE at the dose of 400 mg/kg reduced the levels of COX-2 and NO inside the paw tissue to a level that was statistically equivalent to the level observed in the normal control group. Finally, olive leaf extract at doses of 100, 200 and 400 mg/kg doses significantly (P < 0.05) inhibited the heat-induced hemolysis of RBCs membrane by 25.62, 57.40 and 73.88%, respectively, compared to 83.89% produced by aspirin. Consequently, we concluded that olive leaf extract has a significant anti-inflammatory activity through the reduction of TNF, IL-1, COX-2 and NO.

Intracellular Quantum Sensing of Free-Radical Generation Induced by Acetaminophen (APAP) in the Cytosol, in Mitochondria and the Nucleus of Macrophages

Acetaminophen overdoses cause cell injury in the liver. It is widely accepted that liver toxicity is initiated by the reactive N-acetyl-para-aminophenol (APAP) metabolite N-acetyl-p-benzoquinone imine (NAPQI), which first depletes glutathione and then irreversibly binds to mitochondrial proteins and nuclear DNA. As a consequence, mitochondrial respiration is inhibited, and DNA strands break. NAPQI also promotes the oxidative stress since glutathione is one of the main free-radical scavengers in the cell. However, so far it is unknown where exactly free radicals are generated. In this study, we used relaxometry, a novel technique that allows nanoscale magnetic resonance imaging detection of free radicals. The method is based on fluorescent nanodiamonds, which change their optical properties based on their magnetic surrounding. To achieve subcellular resolution, these nanodiamonds were targeted to cellular locations, that is, the cytoplasm, mitochondria, and the nucleus. Since relaxometry is sensitive to spin noise from radicals, we were able to measure the radical load in these different organelles. For the first time, we measured APAP-induced free-radical production in an organelle-specific manner, which helps predict and better understand cellular toxicity.

Paracetamol Intake and Hematologic Malignancies: A Meta-Analysis of Observational Studies

Hematologic malignancies cause more than half a million deaths every year worldwide. Analgesics were suggested as chemopreventive agents for several cancers but so far, results from individual studies about the relationship between paracetamol (acetaminophen) use and hematologic malignancies are conflicting. Therefore, we decided to perform a systematic review and meta-analysis. We retrieved studies published in any language by systematically searching Medline, Embase, Conference Proceedings Citation Index, Open Access Theses and Dissertations, and the five regional bibliographic databases of the World Health Organization until December 2020. Pooled odds ratios (OR) and their 95% confidence intervals (CI) were calculated according to the inverse of their variances. We performed separate analyses by histologic type. We also evaluated publication bias and assessed quality. A total of 17 study units met our inclusion criteria. The results show an association of hematologic malignancies with any paracetamol intake (OR 1.49, 95% CI 1.23-1.80) and with high paracetamol intake (OR 1.77, 95% CI 1.45-2.16). By subtype, risk was higher for multiple myeloma (OR 2.13, 95% CI 1.54-2.94) for any use and OR 3.16, 95% CI 1.96-5.10 for high intake, while risk was lower and non-significant for non-Hodgkin lymphoma. This meta-analysis provides evidence that paracetamol intake may be associated with hematologic malignancies and suggests that a dose-response effect is plausible. These results are unlikely to be due to publication bias or low quality of studies. Future research should focus on assessing the dose-response relationship.

Inhibitory activity of black mulberry (Morus nigra) extract against testicular, liver and kidney toxicity induced by paracetamol in mice

Black mulberry (Morus nigra) leaves is broadly used in traditional medicine worldwide. However, there are no scientific reports regarding testicular protection, hepato-and nephroprotective activities of M. nigra leaves. The present investigation was assessed the protective mechanism by which methanol extract from M. nigra leaves suppressed the damaging effects induced by paracetamol (APAP) in different mouse tissues. Male mice were orally given APAP (500 mg/kg) with or without M. nigra extract (150, 300, and 500 mg/kg) for four consecutive days. The results showed that crude extract possessed potent antioxidant activity (EC₅₀ = 42.97 µg extract/mL) due to the presence of a high amount of polyphenol and flavonoid compounds. Gallic acid, chlorogenic acid, catechin, and rutin were isolated from the n-butanol fraction of M. nigra extract. Unexpectedly, oral administration of APAP did not induce chromosomal aberrations in mouse bone marrow; however, it produced damaging effects on testis, liver, and kidney tissues. Interestingly, M. nigra extract suppressed APAP-induced genotoxicity by lowering meiotic chromosomal aberrations in spermatocytes, morphological sperm abnormalities, and % DNA damage in comet tail in the liver and kidney tissues. The altered levels of glutathione S transferase activity, lipid peroxidation, liver, and kidney functions were significantly reversed when M. nigra was given to APAP group. The restoring of the histo-architectural distortions and decreasing over-expression of p53 protein as determined by immunohistochemistry in the liver, kidney, and testis sections were strengthened the protective activity of M. nigra extract. Conclusion, the bioactive components in the leaves of black mulberry appear to be a good candidate for genetic protection, treatment of oxidative stress-induced organotoxicity.

What are the Potential Sites of DNA Attack by N-Acetyl-p-benzoquinone Imine (NAPQI)?

Metabolic bioactivation of small molecules can produce electrophilic metabolites that can covalently modify proteins and DNA. Paracetamol (APAP) is a commonly used over-the-counter analgesic, and its hepatotoxic side effects have been postulated to be due to the formation of the electrophilic metabolite N-acetylbenzoquinone imine (NAPQI). It has been established that NAPQI reacts to form covalent bonds to the side-chain functional groups of cysteine, methionine, tyrosine, and tryptophan residues. While there have been scattered reports that APAP can form adducts with DNA the nature of these adducts have not yet been fully characterised. Here the four deoxynucleosides, deoxyguanosine (dG), deoxyadenosine (dA), deoxycytidine (dC), and deoxythymidine (dT) were reacted with NAPQI and the formation of adducts was profiled using liquid chromatography–mass spectrometry with positive-ion mode electrospray ionisation and collision-induced dissociation. Covalent adducts were detected for dG, dA, and dC and tandem mass spectrometry (MS/MS) spectra revealed common neutral losses of deoxyribose (116 amu) arising from cleavage of the glyosidic bond with formation of the modified nucleobase. Of the four deoxynucleosides, dC proved to be the most reactive, followed by dG and dA. A pH dependence was found, with greater reactivity being observed at pH 5.5. The results of density functional theory calculations aimed at understanding the relative reactivities of the four deoxynucleosides towards NAPQI are described.

Paracetamol - toxicity and microbial utilization. Pseudomonas moorei KB4 as a case study for exploring degradation pathway

Paracetamol, a widely used analgesic and antipyretic drug, is currently one of the most emerging pollutants worldwide. Besides its wide prevalence in the literature only several bacterial strains able to degrade this compound have been described. In this study, we isolated six new bacterial strains able to remove paracetamol. The isolated strains were identified as the members of Pseudomonas, Bacillus, Acinetobacter and Sphingomonas genera and characterized phenotypically and biochemically using standard methods. From the isolated strains, Pseudomonas moorei KB4 was able to utilize 50 mg L^-1 of paracetamol. As the main degradation products, p-aminophenol and hydroquinone were identified. Based on the measurements of specific activity of acyl amidohydrolase, deaminase and hydroquinone 1,2-dioxygenase and the results of liquid chromatography analyses, we proposed a mechanism of paracetamol degradation by KB4 strain under co-metabolic conditions with glucose. Additionally, toxicity bioassays and the influence of various environmental factors, including pH, temperature, heavy metals at no-observed-effective-concentrations, and the presence of aromatic compounds on the efficiency and mechanism of paracetamol degradation by KB4 strain were determined. This comprehensive study about paracetamol biodegradation will be helpful in designing a treatment systems of wastewaters contaminated with paracetamol.

Interindividual variation in gene expression responses and metabolite formation in acetaminophen-exposed primary human hepatocytes

Acetaminophen (APAP) is a readily available over-the-counter drug and is one of the most commonly used analgesics/antipyretics worldwide. Large interindividual variation in susceptibility toward APAP-induced liver failure has been reported. However, the exact underlying factors causing this variability in susceptibility are still largely unknown. The aim of this study was to better understand this variability in response to APAP by evaluating interindividual differences in gene expression changes and APAP metabolite formation in primary human hepatocytes (PHH) from several donors (n = 5) exposed in vitro to a non-toxic to toxic APAP dose range. To evaluate interindividual variation, gene expression data/levels of metabolites were plotted against APAP dose/donor. The correlation in APAP dose response between donors was calculated by comparing data points from one donor to the data points of all other donors using a Pearson-based correlation analysis. From that, a correlation score/donor for each gene/metabolite was defined, representing the similarity of the omics response to APAP in PHH of a particular donor to all other donors. The top 1 % highest variable genes were selected for further evaluation using gene set overrepresentation analysis. The biological processes in which the genes with high interindividual variation in expression were involved include liver regeneration, inflammatory responses, mitochondrial stress responses, hepatocarcinogenesis, cell cycle, and drug efficacy. Additionally, the interindividual variation in the expression of these genes could be associated with the variability in expression levels of hydroxyl/methoxy-APAP and C8H13O5N-APAP-glucuronide. The before-mentioned metabolites or their derivatives have also been reported in blood of humans exposed to therapeutic APAP doses. Possibly these findings can contribute to elucidating the causative factors of interindividual susceptibility toward APAP.

Mechanisms linked to differences in the mutagenic potential of 1,3-dinitropyrene and 1,8-dinitropyrene

This study explores and characterizes the toxicity of two closely related carcinogenic dinitro-pyrenes (DNPs), 1,3-DNP and 1,8-DNP, in human bronchial epithelial BEAS-2B cells and mouse hepatoma Hepa1c1c7 cells. Neither 1,3-DNP nor 1,8-DNP (3–30 μM) induced cell death in BEAS-2B cells. In Hepa1c1c7 cells only 1,3-DNP (10–30 μM) induced a mixture of apoptotic and necrotic cell death after 24 h. Both compounds increased the level of reactive oxygen species (ROS) in BEAS-2B as measured by CM-H₂DCFDA-fluorescence. A corresponding increase in oxidative damage to DNA was revealed by the formamidopyrimidine-DNA glycosylase (fpg)-modified comet assay. Without fpg, DNP-induced DNA damage detected by the comet assay was only found in Hepa1c1c7 cells. Only 1,8-DNP formed DNA adduct measured by ³²P-postlabelling. In Hepa1c1c cells, 1,8-DNP induced phosphorylation of H2AX (γH2AX) and p53 at a lower concentration than 1,3-DNP and there was no direct correlation between DNA damage/DNA damage response (DR) and induced cytotoxicity. On the other hand, 1,3-DNP-induced apoptosis was inhibited by pifithrin-α, an inhibitor of p53 transcriptional activity. Furthermore, 1,3-DNP triggered an unfolded protein response (UPR), as measured by an increased expression of CHOP, ATF4 and XBP1. Thus, other types of damage possibly linked to endoplasmic reticulum (ER)-stress and/or UPR could be involved in the induced apoptosis. Our results suggest that the stronger carcinogenic potency of 1,8-DNP compared to 1,3-DNP is linked to its higher genotoxic effects. This in combination with its lower potency to induce cell death may increase the probability of causing mutations.

Recent advances in particulate matter and nanoparticle toxicology: a review of the in vivo and in vitro studies

Epidemiological and clinical studies have linked exposure to particulate matter (PM) to adverse health effects, which may be registered as increased mortality and morbidity from various cardiopulmonary diseases. Despite the evidence relating PM to health effects, the physiological, cellular, and molecular mechanisms causing such effects are still not fully characterized. Two main approaches are used to elucidate the mechanisms of toxicity. One is the use of in vivo experimental models, where various effects of PM on respiratory, cardiovascular, and nervous systems can be evaluated. To more closely examine the molecular and cellular mechanisms behind the different physiological effects, the use of various in vitro models has proven to be valuable. In the present review, we discuss the current advances on the toxicology of particulate matter and nanoparticles based on these techniques.

The role of non-steroidal anti-inflammatory drugs in the risk of development and treatment of hematologic malignancies

Non-steroidal anti-inflammatory drugs (NSAIDs) comprise the group of structurally diverse but similarly acting compounds that are used for relieving signs and symptoms of inflammation, especially in treatment of rheumatic diseases. Recent reports suggested potential association between regular use of NSAIDs and the risk of development of hematological malignancies. However, the data distinctly differ depending on type of NSAID used, period of its administration and type of malignancy. Regular use of aspirin and other NSAIDs was shown to correlate with reduced risk of lymphoid malignancies. Frequent use of aspirin was found to be associated with decreased risk of acute leukemia (AL) development. In contrast, correlation between long-term acetaminophen usage and increased incidence of AL and multiple myeloma (MM) was indicated. On the other hand, NSAIDs were found to exert anti-cancer effects, inhibiting proliferation and invasive growth or inducing cell apoptosis in several tumors, including hematologic malignancies. One of those agents, non-cyclooxygenase 2-inhibiting R-enantiomer of etodolac (SDX-101), exerts cytotoxic effects against chronic lymphocytic leukemia (CLL) and MM cells, and is currently investigated in phase II clinical trial in CLL. The indole-pyran analogue of SDX-101, SDX-308 (CEP-18082), showed more potent cytotoxicity than SDX-101 against MM cells and inhibited osteoclast formation and activity of mature osteoclasts. Thus, SDX-308 may be an ideal agent for bone disease in MM and related diseases. Another analogue of SDX-101, SDX-309, showed also significant anti-tumor activity in first preclinical studies. The potential role of NSAIDs in prevention and treatment of hematologic malignancies is the subject of this review.

Genotoxic Activities of Aniline and its Metabolites and Their Relationship to the Carcinogenicity of Aniline in the Spleen of Rats

Aniline (in the form of its hydrochloride) has been shown to induce a rather rare spectrum of tumors in the spleen of Fischer 344 rats. The dose levels necessary for this carcinogenic activity were in a range where also massive effects on the blood and non-neoplastic splenotoxicity as a consequence of methemoglobinemia were to be observed. This review aimed at clarifying if aniline itself or one of its metabolites has a genotoxic potential which would explain the occurrence of the spleen tumors in rats as a result of a primary genetic activity. The database for aniline and its metabolites is extremely heterogeneous. With validated assays it ranges from a few limited Ames tests (o- and m-hydroxyacetanilide, phenylhydroxylamine, nitrosobenzene) to a broad range of studies covering all genetic endpoints partly with several studies of the same or different test systems (aniline, p-aminophenol, p-hydroxyacetanilide). This makes a direct comparison rather difficult. In addition, a varying number of results with as yet not validated systems are available for aniline and its metabolites. Most results, especially those with validated and well performed/documented studies, did not indicate a potential of aniline to induce gene mutations. In five different mouse lymphoma tests, where colony sizing was performed only in one test, aniline was positive. If this indicates a peculiar feature of a point mutagenic potential or does represent a part of the clastogenic activity for which there is evidence in vitro as well as in vivo remains to be investigated. There is little evidence for a DNA damaging potential of aniline. The clastogenic activity in vivo is confined to dose levels, which are close to lethality essentially due to hematotoxic effects. The quantitatively most important metabolites for experimental animals as well as for humans (p-aminophenol, p-hydroxyacetanilide) seem to have a potential for inducing chromosomal damage in vitro and, at relatively high dose levels, also in vivo. This could be the explanation for the clastogenic effects that have been observed after high doses/concentrations with aniline. They do not induce gene mutations and there is little evidence for a DNA damaging potential. None of these metabolites revealed a splenotoxic potential comparable to that of aniline in studies with repeated or long-term administration to rats. The genotoxicity database on those metabolites with a demonstrated and marked splenotoxic potential, i.e. phenylhydroxylamine, nitrosobenzene, is unfortunately very limited and does not allow to exclude with certainty primary genotoxic events in the development of spleen tumors. But quite a number of considerations by analogy from other investigations support the conclusion that the effects in the spleen do not develop on a primary genotoxic basis. The weight of evidences suggests that the carcinogenic effects in the spleen of rats are the endstage of a chronic high-dose damage of the blood leading to a massive overload of the spleen with iron, which causes chronic oxidative stress. This conclusion, based essentially on pathomorphological observations, and analogy considerations thereof by previous authors, is herewith reconfirmed under consideration of the more recently reported studies on the genotoxicity of aniline and its metabolites, on biochemical measurements indicating oxidative stress, and on the metabolism of aniline. It is concluded that there is no relationship between the damage to the chromosomes at high, toxic doses of aniline and its major metabolites p-aminophenol/p-hydroxyacetanilide and the aniline-induced spleen tumors in the rat.

Regular analgesic use and risk of multiple myeloma

Analgesic use has been implicated in the chemoprevention of a number of solid tumors, but to date no previous research has focused on the role of analgesics in the etiology of multiple myeloma (MM). We conducted a hospital-based case-control study of 117 patients with primary, incident MM and 483 age and residence matched controls without benign or malignant neoplasms. All participants received medical services at Roswell Park Cancer Institute in Buffalo, NY, and completed a comprehensive epidemiological questionnaire. Participants who reported analgesic use at least once a week for at least 6 months were classified as regular users; individuals who did not use analgesics regularly served as the reference group throughout the analyses. We used unconditional logistic regression analyses to compute crude and adjusted odds ratios (ORs) with corresponding 95% confidence intervals (CIs). Compared to non-users, regular aspirin users were not at reduced risk of MM (adjusted OR=0.99; 95% CI 0.65-1.49), nor were participants with the highest frequency or duration of aspirin use. A significant risk elevation was found for participants who were regular acetaminophen users (adjusted OR=2.95; 95% CI 1.72-5.08). Further, marked increases in risk of MM were noted with both greater frequency (>7 tablets weekly; adjusted OR=4.36; 95% CI 1.70-11.2) and greater duration (>10 years; adjusted OR=3.26; 95% CI 1.52-7.02) of acetaminophen use. We observed no evidence of a chemoprotective effect of aspirin on MM risk, but observed significant risk elevations with various measures of acetaminophen use. Our results warrant further investigation in population-based case-control and cohort studies and should be interpreted with caution in light of the limited sample size and biases inherent in hospital-based studies.

Opposing effects of aspirin and acetaminophen use on risk of adult acute leukemia

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of hematologic cancer, although previous results have been inconsistent. The current study investigated the effects of aspirin or acetaminophen use on adult acute leukemia risk among 169 individuals with leukemia and 676 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with a modest decrease in leukemia risk [adjusted odds ratio (aOR), 0.84; 95% confidence interval (CI), 0.59-1.21]. In contrast, ever using acetaminophen was associated with elevated leukemia risk (aOR, 1.53; 95% CI, 1.03-2.26). Results did not differ between men and women. Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated acute leukemia risk observed among acetaminophen users.

Regular use of aspirin or acetaminophen and risk of non-Hodgkin lymphoma

Regular use of aspirin and other non-steroidal anti-inflammatory drugs (NSAIDs) has been hypothesized to be associated with reduced risk of non-Hodgkin lymphoma (NHL), although previous results have been inconsistent. The current study investigated the effects of regular aspirin or acetaminophen use on non-Hodgkin lymphoma risk among 625 individuals with primary, incident NHL and 2512 age and sex matched hospital controls with non-neoplastic conditions who completed a comprehensive epidemiologic questionnaire. Results indicate that regular aspirin use may be associated with decreased NHL risk among men [adjusted odds ratio (aOR) 0.82, 95% confidence interval (CI), 0.65--1.04], but not among women (aOR 0.93, 95% CI, 0.71--1.23). In contrast, regular acetaminophen use was associated with elevated NHL risk among women (aOR 1.71, 95% CI, 1.18--2.50) but not among men (aOR 0.75, 95% CI, 0.48--1.17). Other studies have demonstrated that acetaminophen is associated with transient decreases in DNA repair, and lymphocytes may be particularly susceptible to DNA damage, suggesting a mechanism for the elevated NHL risk observed.

Rat testicular structure and ultrastructure after paracetamol treatment

The morphological modifications of Wistar rat testicles were investigated for animals treated with paracetamol. The rats (n = 6) received a single dose of 4.4 mmol/kg paracetamol, while controls (n = 6) received the same volume of physiological solution. After 5, 10 and 50 days, the rats were perfused with Karnovsky's fixative and processed by routine methods for light and electron microscopy. Some altered seminiferous tubules were found, as well as a few degenerating tubules. Within the tubules, Sertoli cells appeared fragmented while the spermatids showed unusually well-developed rough endoplasmic reticulum and Golgi complexes and had irregularly compacted chromatin. Morphologically altered late spermatids were found retaining a larger volume of residual cytoplasm than spermatids of controls. An indirect cause of alterations was also suggested based on the occurrence of dilated blood vessels and edema.

Paracetamol (acetaminophen)-induced toxicity: molecular and biochemical mechanisms, analogues and protective approaches

An overview is presented on the molecular aspects of toxicity due to paracetamol (acetaminophen) and structural analogues. The emphasis is on four main topics, that is, bioactivation, detoxication, chemoprevention, and chemoprotection. In addition, some pharmacological and clinical aspects are discussed briefly. A general introduction is presented on the biokinetics, biotransformation, and structural modification of paracetamol. Phase II biotransformation in relation to marked species differences and interorgan transport of metabolites are described in detail, as are bioactivation by cytochrome P450 and peroxidases, two important phase I enzyme families. Hepatotoxicity is described in depth, as it is the most frequent clinical observation after paracetamol-intoxication. In this context, covalent protein binding and oxidative stress are two important initial (Stage I) events highlighted. In addition, the more recently reported nuclear effects are discussed as well as secondary events (Stage II) that spread over the whole liver and may be relevant targets for clinical treatment. The second most frequent clinical observation, renal toxicity, is described with respect to the involvement of prostaglandin synthase, N-deacetylase, cytochrome P450 and glutathione S-transferase. Lastly, mechanism-based developments of chemoprotective agents and progress in the development of structural analogues with an improved therapeutic index are outlined.

Non-opioid postoperative analgesia

Although significant improvement has been made in the treatment of pain in the postoperative period, many patients still experience unnecessary discomfort resulting in distress, higher morbidity and prolonged stay in hospital. The standard pillar of postoperative treatment of severe pain is the use of opioids. However, adverse reactions to opioids make their use unfavourable. A better understanding of the pathophysiology of pain has helped clinicians to a more balanced approach to postoperative pain treatment. The development of the multimodal approach to postoperative analgesia, with the use of different drugs acting via different routes to give good analgesia, with minimal side-effects, represents a major development in the treatment of postoperative pain. Early, aggressive mobilisation and feeding must follow in order to restore normal conditions quickly. Alternatives to opioids should be used as extensively as possible. Local anaesthesia, used as regional blocks or as wound infiltration, is most beneficial. Paracetamol has good basic analgesic properties, and should probably be used in dosages higher than recommended today. The combination with a NSAID results in better and longer-lasting analgesia. The intravenous form propacetamol will increase the possibilities of its use. The new concept of selective COX-2 inhibiting NSAIDs will result in analgesic and anti-inflammatory drugs with fewer side-effects. The well-known inexpensive group of corticosteroids have good analgesic and anti-emetic properties, and are especially interesting to use in patients who do not tolerate NSAIDs. The alpha2-receptor agonists like clonidine, when administered epidurally or intrathecally, are useful adjuncts, but their adverse effects on sedation and hypotension limit their use. NMDA-receptor antagonists are of limited value in the postoperative period. Adenosine and neostigimine are still on a research level but may lead to new, clinically useful analgesic drugs. In the future, cannabinoids, cholecystokinin-receptor antagonists and neurokinin-1 antagonists may become important analgesic drugs.

Analgesic agents for the postoperative period. Nonopioids

For many reasons, nonopioid analgesics have proven to be of immense benefit in postoperative pain relief. Consideration of the limitations and side effects of opioids confirms the need for alternative, complementary analgesics. The current understanding of pain pathophysiology recognizes that many tissue and neuronal factors and changes are invoked by tissue damage, producing peripheral and central sensitization, and some of these may be modulated by the use of NSAIDs, NMDA antagonists, and local anesthetic agents. If successful preemptive analgesic techniques are developed, they will likely include the use of NSAIDs and perhaps NMDA antagonists. Nonopioids are of benefit in multimodal analgesia and allow acute rehabilitation of surgical patients. Acetaminophen, NSAIDs, alpha 2-antagonists, and NMDA antagonists are in routine use as components of multimodal analgesia, in combination with opioids or local anesthetic techniques. Tramadol is interesting because it has nonopioid and opioid actions that can be attributed to the two isomers found in the racemic mixture. Spinal neostigmine and the use of adenosine represent completely different mechanisms of nonopioid analgesia being investigated. Nonopioids, including lidocaine, ketamine, the anticonvulsants, and the antidepressants, are necessary for the treatment of patients with the difficult clinical problem of neuropathic pain that can present in the postoperative period.

Zonal location of compensatory hepatocyte proliferation following chemically induced hepatotoxicity in rats and humans

Hepatocyte proliferation stimulated by partial hepatectomy occurs first in periportal cells, with midlobular and then perivenous cell division occurring later. We have previously shown that this pattern of compensatory cell proliferation also occurs following the hepatotoxicity of N-nitrosodimethylamine. We examined the generality of this pattern in livers of rats given a minimally toxic dose of an hepatotoxin and in liver biopsy samples from patients who had taken overdoses of acetaminophen. Proliferating hepatocytes were detected immunohistochemically (5'-bromodeoxyuridine or Ki-67 antigens). The perivenous necrogens N-nitrosodiethylamine, carbon tetrachloride (CCl4), bromobenzene, and acetaminophen all induced periportal hepatocyte proliferation. With CCl4, bromobenzene, and acetaminophen, the initial appearance of proliferating periportal hepatocytes was followed 12-24 hr later by division in the midlobular region, with a few cells dividing adjacent to the perivenous region of necrosis. The periportal necrogen allyl alcohol also induced periportal cell division. In the human studies, perivenous necrosis was accompanied by periportal and midlobular hepatocyte proliferation. These results suggest that regardless of its lobular location chemically induced hepatotoxicity stimulates cell proliferation that begins in the periportal zone and then moves in an orchestrated response into the midlobular and perivenous zones.

Cytotoxic Effects of Paracetamol in Vitro: The Effects of an S9 Fraction

The cytotoxic effects of short-term and long-term exposure of HeLa cells to paracetamol (acetaminophen) were assayed by total protein content reduction (microprotein assay) and by [14C]-L-leucine incorporation into macromolecular acid-insoluble cell fraction. The level of total protein content was followed over 72 hours and the level of [14C]-L-leucine incorporation over 24 hours, after paracetamol treatment. Statistical evaluation did not show a significant difference between results obtained by these two methods. In addition, the influence of S9 fraction on [14C]-L-leucine incorporation and the growth activity of paracetamol-treated HeLa cells were assayed. In these experiments, short-term paracetamol treatments (2 hours in phosphate buffered saline), were used. Statistical analysis of the data did not show an increase in paracetamol-induced cytotoxicity in the presence of the S9 fraction; on the contrary, a protective effect of S9 fraction on paracetamol-treated cells was found.

Evaluation of the ability of paracetamol to produce chromosome aberrations in man

The ability of paracetamol to induce structural chromosome aberrations in human peripheral blood lymphocytes in vivo was evaluated in volunteers who had been administered a single oral dose of 3 g paracetamol, in patients who had received 2 g of propacetamol by intravenous infusion every 6 h for at least 7 days, and in self-poisoned patients who, for suicidal reasons, had ingested more than 15 g paracetamol. In addition to the in vivo observations, the effectiveness of paracetamol to interfere with fusorial microtubule polymerisation was assayed in vitro in order to detect a possible effect of paracetamol on the distribution of chromosomes during cell division. The negative results obtained in all those assays strongly suggest that paracetamol has no mutagenic properties in human. There was, indeed, no significant difference in the percentage of abnormal cells before and after application of paracetamol in volunteers (0.2% before ingestion of 3 g paracetamol, 0.12% after 24 h, 0.04% after 72 h and 0.04% after 168 h) and in patients (0.5% of abnormal cells before treatment versus 0.44% after intravenous infusion of a total of 28 g paracetamol). Moreover, the yield of abnormal cells was not modified in self-poisoned persons (0.24%), in spite of an important decrease in the mitotic index of the PHA stimulated lymphocytes. In the in vitro assay, no inhibition of microtubule polymerisation was detected with concentrations of 2.5, 5 and 10 mM paracetamol.

Series: current issues in mutagenesis and carcinogenesis, No. 65. The genotoxicity and carcinogenicity of paracetamol: a regulatory (re)view

The publication of several studies reporting genotoxic effects of paracetamol, one of the world's most popular over-the-counter drugs, has raised the question of regulatory action. Paracetamol does not cause gene mutations, either in bacteria or in mammalian cells. There are, however, published data giving clear evidence that paracetamol causes chromosomal damage in vitro in mammalian cells at high concentrations and indicating that similar effects occur in vivo at high dosages. Available data point to three possible mechanisms of paracetamol-induced genotoxicity: (1) inhibition of ribonucleotide reductase; (2) increase in cytosolic and intranuclear Ca2+ levels; (3) DNA damage caused by NAPQI after glutathione depletion. All mechanisms involve dose thresholds. Studies of the relationship between genotoxicity and toxic effects in the rat (induction of micronuclei in rat bone marrow including dose-response relationship, biotransformation of paracetamol at different dosages, concomitant toxicity and biochemical markers) have recently been completed. These studies, which employed doses ranging from the dose resulting in human therapeutic peak plasma levels to highly toxic doses, give convincing evidence that genotoxic effects of paracetamol appear only at dosages inducing pronounced liver and bone marrow toxicity and that the threshold level for genotoxicity is not reached at therapeutic dosage. Reliable studies on the ability of paracetamol to affect germ cell DNA are not available. However, based on the amount of drug likely to reach germ cells and the evidence of thresholds, paracetamol is not expected to cause heritable damage in man. Various old and poorly designed long-term studies of paracetamol in the mouse and rat have given equivocal results. A few of these studies showed increased incidence of liver and bladder tumours at hepatotoxic doses. National Toxicology Program (U.S.A.) feeding studies have shown that paracetamol is non-carcinogenic when given at non-hepatotoxic doses up to 300 mg/kg/d to the rat and up to 1000 mg/kg/d to the mouse. Taking into account the knowledge of the hepatotoxicity and metabolism of paracetamol and the existence of thresholds for its genotoxicity, the animal studies do not indicate a carcinogenic potential at non-hepatotoxic dose levels. Based on this updated assessment of the genotoxicity and carcinogenicity of paracetamol, it is concluded that there is no need for regulatory action.

Inhibitory effects of paracetamol on DNA repair in mammalian cells

Paracetamol blocks DNA replication by inhibiting deoxyribonucleotide (dNTP) synthesis and may therefore also interfere with DNA repair. In the present work various mammalian cell types were treated with genotoxic agents and allowed to repair in the presence or absence of paracetamol. Alkaline elution was used to assay DNA single-strand breaks plus alkali-labile sites (= SSBs). Resting human mononuclear blood cells (MNC) exposed to 4-nitroquinoline N-oxide (NQO, 3 microM) plus 0.3 mM paracetamol contained twice as many DNA SSBs compared to MNC exposed to NQO alone, and the level of SSBs decreased more slowly during repair in the presence of paracetamol. Deoxyribonucleosides reversed the effects of paracetamol. SSBs induced by MMS or X-rays (2.6 Gy) were not increased by paracetamol. Resting and growth-stimulated MNC, HL-60 cells, rat hepatocytes and human fibroblasts exposed to UV-C (3-12 J/m2) showed varying levels of transient SSBs formed during repair but these were consistently higher in the presence of paracetamol (0.3-1 mM). In rat testicular cells SSBs were induced by NQO and the levels were further increased in the presence of paracetamol, whereas after UV almost no SSBs were detected during repair. The cell-type specific levels of transient SSBs after UV did not correlate with the rate of incision of DNA lesions, measured as the rate of SSB accumulation in the presence of repair inhibitors Ara C plus hydroxyurea. Transient SSBs were present in resting MNC for at least 24 h after UV and paracetamol increased these breaks 4-fold however the overall rate of removal of excisable photodamage during repair did not appear to be reduced by the presence of paracetamol. The present data indicate that paracetamol interferes with nucleotide excision repair in several mammalian cell types. This constitutes a mechanism by which paracetamol may contribute to genotoxicity in humans.