Occurrence and risk characterization of aflatoxin M1 in milk samples from southeastern Iran using the margin of exposure approach.

This study aimed to investigate Aflatoxin-M1 (AFM1) contamination in pasteurized and raw milk samples consumed in Kerman and Rafsanjan in southeastern Iran. In this cross-sectional study, a total of 100 samples of raw (n = 67) and pasteurized (n = 33) milk were randomly collected from retail stores, supermarkets, and milk transport tankers in the winter of 2020 and the summer of 2021. The level of AFM1 contamination in the collected samples was evaluated by high-performance liquid chromatography with fluorescence detection (HPLC-FD). AFM1 was detected in 95% of samples and its median concentration was 17.38 ng/L. The median concentration of AFM1 in the pasteurized milk samples (24.89 ng/L) was significantly higher than in the raw milk samples (13.54 ng/L). The AFM1 contamination level in 20% (raw = 13% and pasteurized = 7%) of the samples was higher than the maximum permitted level (MPL) recommended by the European Union (i.e., 50 ng/L), whilst 4% (raw = 3% and pasteurized = 1%) of the samples was higher than the Iranian maximum standard limit (i.e., 100 ng/L). The hazard index (HI) was higher than 1 in 16%, 18%, and 35% of total milk samples for men, women, and children, respectively. The AFM1 contamination level in the milk samples collected in southeastern Iran was worrying. The margin of exposure (MoE) values were lower than 10,000 for children. Because aflatoxins are among the most potent carcinogens known, prevention of milk contamination in all stages from the farm to the table can considerably reduce the community's exposure to AFM1 and its consequent health risks.

Involvement of Nrf2 signaling in lead-induced toxicity.

Nuclear factor erythroid 2-related factor 2 (Nrf2) is used as one of the main protective factors against various pathological processes, as it regulates cells resistant to oxidation. Several studies have extensively explored the relationship between environmental exposure to heavy metals, particularly lead (Pb), and the development of various human diseases. These metals have been reported to be able to, directly and indirectly, induce the production of reactive oxygen species (ROS) and cause oxidative stress in various organs. Since Nrf2 signaling is important in maintaining redox status, it has a dual role depending on the specific biological context. On the one hand, Nrf2 provides a protective mechanism against metal-induced toxicity; on the other hand, it can induce metal-induced carcinogenesis upon prolonged exposure and activation. Therefore, the aim of this review was to summarize the latest knowledge on the functional interrelation between toxic metals, such as Pb and Nrf2 signaling.

Contamination of breast milk with lead, mercury, arsenic, and cadmium in Iran: a systematic review and meta-analysis.

Breast milk is a complete food for the development of the newborn, but it can also be an important route for environmental pollutants transmission to the infants. This study was aimed to evaluate the status of heavy metals including lead (Pb), mercury (Hg), cadmium (Cd) and arsenic (As) in the breast milk of Iranian mothers. The international databases including Scopus, PubMed, Web of Science and the Persian electronic databases including Scientific Information Database, IranMedex and Magiran were examined to find relevant articles published until July 2021. A total of 23 studies examined the levels of toxic metals in Iranian breast milk samples. According to the findings, the pooled average concentrations (µg/L) of Pb, Cd, Hg and As were 25.61, 2.40, 1.29 and 1.16, respectively. The concentration of Hg and Pb in colostrum milk was more than twice of mature milk. The Hg mean concentration in the breast milk of mothers with at least one amalgam-filled tooth was approximately three times that of mothers without amalgam-filled teeth. Risk assessment analysis indicated that the intake of Pb and Hg by infants through breastfeeding can be considered a health concern in Iran. It seems necessary to reduce the Pb exposure of pregnant and lactating women in Iran. However, more extensive studies are needed to clarify the toxic metals' exposure status of infants through breast milk in other parts of the country.

Influence of cellular redox environment on aryl hydrocarbon receptor ligands induced melanogenesis.

Many environmental pollutants, natural compounds, as well as endogenous chemicals exert their biological/toxicological effects by reacting with the aryl hydrocarbon receptor (AhR). Previous evidence shed new light on the role of AhR in skin physiology by regulating melanin production. In this study, we investigated the effect of oxidative imbalance induced by AhR ligands on the melanogenesis process in B16 murine melanoma cells. Exposure to 6-formylindolo[3,2-b] carbazole (FICZ) or benzo-α-pyrene (BαP) led to enhanced expression of CTNNB1, MITF, and TYR genes following increased tyrosinase enzyme activity and melanin content in an AhR-dependent manner. Analysis of the presence of reactive oxygen species (ROS) as well as reduced glutathione (GSH) / oxidized glutathione (GSSG) ratio revealed that treatment with AhR ligands is associated with oxidative stress which can be ameliorated with NAC (N-acetyl cysteine) or diphenyleneiodonium chloride (DPI). On the other hand, NAC and DPI enhanced melanogenesis induced by AhR ligands by reducing the level of ROS. We have shown for the first time that a cellular redox status is a critical event during AhR ligand-induced melanogenesis.

Aryl hydrocarbon receptor engagement during redox alteration determines the fate of CD4+ T cells in C57BL/6 mice.

The preservation of the redox homeostasis is critical for cell survival and functionality. Redox imbalance is an essential inducer of several pathological states. CD4+ /helper T cells are highly dependent on the redox state of their surrounding milieu. The potential of the aryl hydrocarbon receptor (AhR) engagement in controlling CD4+ T-cell fate during redox alteration is still challenging. C57BL/6 mice were treated with AhR agonist 6-formylindolo[3,2-b]carbazole (FICZ), AhR antagonist CH223191, an inhibitor of glutathione biosynthesis buthionine sulfoximine (BSO), and the antioxidant N-acetylcysteine (NAC) alone or in combination. Six days later, splenocytes were evaluated for the expression of the redox-related genes and the possible changes in T-cell subsets. FICZ like BSO significantly elevated the expression of HMOX1, GCLC, and GCLM genes but it failed to increase the expression of the Nrf2 gene. Moreover, FICZ + BSO increased while FICZ + CH223191 or NAC decreased the expression of these genes. FICZ also significantly increased Th1 cell numbers but decreased Tregs in a dose-dependent manner. Furthermore, a high dose of FICZ + CH223191 + NAC significantly enhanced Th1, Th17, and Treg cells but its low dose in such a situation increased Th2 and Th17 while decreased Treg cells. AhR engagement during redox alteration can determine the fate of CD4 + T cells, so, AhR agonists or antagonists might be useful in assessing immune responses. However, these results need further verifications in vitro and in animal models of various diseases.

Introducing a delivery system for melanogenesis inhibition in melanoma B16F10 cells mediated by the conjugation of tyrosine ammonia-lyase and a TAT-penetrating peptide.

Hyperpigmentation disorders negatively influence an individual's quality of life and may cause emotional distress. Over the years, various melanogenesis inhibitors (mainly tyrosinase inhibitors) have been developed, most of which with low efficacy or high toxicity. Although metabolic engineering by deviation in the flux of substrate is of considerable interest, trials to develop a melanogenesis inhibitor based on L-tyrosine (L-Tyr) restriction are missing. We propose a novel proteinaceous melanogenesis inhibitor called tyrosine ammonia-lyase (TAL), an enzyme that catalyzes the conversion of L-Tyr to p-coumaric acid and ammonia. Since the cell membrane can act as a barrier for intracellular protein delivery, we have covalently conjugated a recombinant TAL enzyme from Rhodobacter sphaeroides (RsTAL) to a trans-activator of transcription (TAT) cell-penetrating peptide (CPP) to afford the intracellular delivery. The heterologously expressed TAT-RsTAL fusion protein was delivered successfully into B16F10 melanocytes as confirmed by the direct fluorescence microscopy with increased intensity from 30 to 180 min. TAT-RsTAL showed sufficient intracellular activity of about 0.83 ± 0.04 and 0.34 ± 0.03 nmol•mg-1 •s-1 for the native and inclusion body-extracted conjugates, respectively. The conjugate inhibited melanin biosynthesis in B16F10 cells in a time-dependent manner. Melanin accumulation was inhibited by 12.7 ± 6.2%, 28.2 ± 5.7%, and 33.9 ± 2.9% compared to the nontreated control groups after 24, 48, and 72 hr of incubation, respectively. L-Tyr restriction had no significant effect on the cell viability up to a concentration of 100 µgml-1 even after 72 hr. According to the observed hypopigmentary effect of the conjugate in this study, TAT-RsTAL can be suggested as a melanogenesis inhibitor for further investigations.

Protective effect of magnesium and selenium on cadmium toxicity in the isolated perfused rat liver system.

The isolated perfused rat liver (IPRL) model has been used into toxicology study of rat liver. This model provides an opportunity at evaluation of liver function in an isolated setting. Studies showed that Cd, in a dose-dependent manner, induced toxic effects in IPRL models, and these effects were associated with aminotransferase activity and lipid peroxidation. The aim of this study was to investigate whether Mg  and/or Se could have protective effects against the Cd toxicity in the IPRL model. Male Wistar rats (9-10 weeks) weighing 260-300 gr were used in this study. They were randomly divided into 8 groups of 4-6 rats per cage. In group 1, liver was perfused by Krebs-Henseleit buffer without MgSO4 (Control). Groups 2-8 were exposed to Mg, Se, Cd, Mg +Se, Cd + Mg, Cd + Se, Cd + Mg + Se respectively in Krebs-Henseleit buffer with no added MgSo4. Biochemical changes in the liver were examined within 90 minutes, and the result showed that the exposure to Cd, lowered glutathione level, while it increased malondialdehyde level and aminotransferase activities in IPRL model. Mg administration during exposure to Cd reduces the toxicity of Cd in the liver isolated while Se administration during exposure to Cd did not decrease Cd hepatotoxicity. Nevertheless, simultaneous treatment with Se and Mg on Cd toxicity have strengthened protective effects than the supplementation of Se alone in the liver.