The influence of melatonin and N-acetylcysteine in delta-aminolevulinic acid and lead induced genotoxicity in lymphocytes in vitro

Derivation of a biological limit value (BLV) for inorganic lead based on lead-induced genotoxicity in workers using the benchmark dose approach (BMD)

BACKGROUND

Safe exposure levels for industrial chemicals are a prerequisite to the safety of workers in occupational settings.

METHODS

The application areas of the benchmark dose (BMD) approach have tremendously increased in recent years. Quantitative analyzes of dose-response relationships of genotoxic chemicals are among these application areas too. This study investigates the applicability of sister chromatid exchange (SCE) frequencies in lymphocytes of lead-exposed workers to derive a biological limit value (BLV) for inorganic lead. To this end, our previously published occupational lead exposure data were pooled and re-examined by using the BMD approach. Subsequently, we determined the point of departure (POD) value for lead-induced SCE frequencies in lymphocytes. Accordingly, the blood lead concentrations and SCE frequencies in lymphocytes of 26 control and 108 lead-exposed male voluntary workers employed in a battery manufacturing plant were subjected to BMD modeling to determine the BMD confidence interval (BMD-CI).

RESULTS

According to our data set, benchmark dose lower bound (BMDL) of 6.55 μg Pb/dL blood for the SCE frequencies in lymphocytes of lead-exposed workers has been obtained.

CONCLUSION

The blood lead concentration of 6.55 μg/dL might be proposed as the BLV for lead and its inorganic lead compounds based on our dataset.

Antigenotoxic effect of melatonin against mercuric chloride in human peripheral blood lymphocytes

Melatonin (MLT) is an extraordinary antioxidant, which plays an important role in reducing reactive oxygen species (ROS) by scavenging them directly or indirectly. Mercury (Hg) is a heavy metal, which induces cytogenetic alterations via various mechanisms, leading to genotoxicity. It induces genotoxicity by enhancing the ROS chiefly. In the present study, the antigenotoxic effect of MLT was evaluated against mercuric chloride (HgCl₂). All experiments were conducted in vitro in peripheral blood lymphocytes. Blood cultures were exposed to various concentrations of HgCl₂ (2.63, 6.57, and 10.52 microM) for 24 h to study a range of genotoxic parameters. MLT (0.2 mM) supplementation, alone and in combination with the high concentration of Hg, was administered to blood cultures for 24 h. Genotoxic parameters, such as chromosomal aberrations (CAs; structural aberrations (chromatid gaps and breaks, chromosomal gaps and breaks) and numerical aberrations), micronuclei (MNs), and comet assay, were evaluated and analyzed using suitable statistical analysis. Hg treatment revealed a significant increase in CAs, MNs, and comet length. Co-supplementation of MLT along with Hg showed marked protection of these genotoxic end points in treated cultures. In conclusion, our findings suggest that MLT protects against Hg-induced augmentation in genotoxic indices because of its antioxidant property.

Melatonin and oral cavity

While initially the oral cavity was considered to be mainly a source of various bacteria, their toxins and antigens, recent studies showed that it may also be a location of oxidative stress and periodontal inflammation. Accordingly, this paper focuses on the involvement of melatonin in oxidative stress diseases of oral cavity as well as on potential therapeutic implications of melatonin in dental disorders. Melatonin has immunomodulatory and antioxidant activities, stimulates the proliferation of collagen and osseous tissue, and acts as a protector against cellular degeneration associated with aging and toxin exposure. Arising out of its antioxidant actions, melatonin protects against inflammatory processes and cellular damage caused by the toxic derivates of oxygen. As a result of these actions, melatonin may be useful as a coadjuvant in the treatment of certain conditions of the oral cavity. However, the most important effect of melatonin seems to result from its potent antioxidant, immunomodulatory, protective, and anticancer properties. Thus, melatonin could be used therapeutically for instance, locally, in the oral cavity damage of mechanical, bacterial, fungal, or viral origin, in postsurgical wounds caused by tooth extractions and other oral surgeries. Additionally, it can help bone formation in various autoimmunological disorders such as Sjorgen syndrome, in periodontal diseases, in toxic effects of dental materials, in dental implants, and in oral cancers.

Perspectives on the use of melatonin to reduce cytotoxic and genotoxic effects of methacrylate-based dental materials

Melatonin (5-methoxy-N-acetyltryptamine), an indoleamine produced in the pineal gland and many other organs, displays a wide spectrum of protective effects against cell injury of various origins. Contemporary dental restorative materials mainly consist of methacrylate polymers with some additives. However, because of the incompleteness of polymerization process in situ as well as mechanical shearing and enzymatic degradation, methacrylate monomers are released from the restoration into the oral cavity and the pulp, from where they gain access to other tissues and organs. Such monomers have displayed toxic properties in many in vivo and in vitro studies, including cytotoxicity and genotoxicity and a considerable portion of these effects is underlined by the oxidative action of these compounds. As melatonin shows biocompatibility with the oral cavity and displays antioxidative properties, it may be considered as a protective agent against harmful effects of methacrylate monomers derived from dental restorations. Melatonin decreases cytotoxic and genotoxic effects of methacrylate monomers used in dentistry, and it does not influence the bond strength of dental composites. This opens a new possible application of melatonin to improve properties of biomaterials used in dentistry.

Evaluation of in vitro anti-genotoxic potential of melatonin against arsenic and fluoride in human blood cultures

Melatonin has been known for its anti-oxidant potential but not much studied for the anti-genotoxic potential. The current study elucidate the role of melatonin against in vitro genotoxicity by arsenic (As) and fluoride (F). Human peripheral blood cultures were exposed to As (1.4 microM) and F (34 microM), alone and in combination, with and without melatonin (0.2 mM). Ethyl methane sulphonate (EMS; 1.9 mM) was selected as the positive control to analyze the genotoxic parameters like sister chromatid exchanges (SCEs), cell cycle proliferative index (CCPI) and primary DNA damage. The frequency of SCE/cell, SCE/chromosome and primary DNA damage reduced significantly (p<0.001) accompanied with a marked increase in CCPI upon addition of melatonin. Similarly marked recovery was attained by melatonin from As and F induced primary DNA damage as studied using comet assay. The results clearly indicate towards the protection of lymphocytes from toxic effects af As and F by melatonin in vitro.

Induction of excision repairable DNA lesions in lymphocytes exposed to lead and ALA in vitro

Numbers of studies have been carried out on the potential of lead genotoxicity. The mechanisms of lead genotoxicity are not fully known but partly attributed to the formation of highly reactive oxygen metabolites (ROM). However, lead ions have no ability to generate ROM. In this study, we have investigated the ability of lead and ALA to induce excision repairable DNA lesions by using cytosine arabinoside or cytokinesis block micronucleus (ARA-C/CBMN) assay. N-methyl-N-nitrosourea was used as a positive control which is a mutagen and known to induce excision repair. The results of the ARA-C/CBMN assay show that ALA exposures have significantly (p < 0.01) increased the ratio of excision repairable DNA lesions in peripheral blood lymphocytes; however, lead have not. Accordingly, accumulation of ALA should be considered as an effective partner of lead induced DNA damage in lead exposure.