Oxidative potential of mineral dust particles: A focus on chemical components and cell-free assay

<p>Oxidative potential (OP) assays are feasible methods to comprehensively understand how exposure to atmospheric chemical components can influence the formation of reactive oxygen species (ROS) in the human body. The increase of ROS concentration can enhance the oxidation of numerous components, such as of the DNA, proteins, and lipids, which cause mutations and cell damage, leading to respiratory illness. According to available studies, the mechanisms of PM-related health effects are not totally understood. The aim of the present study is to assess which available assays are suitable for evaluating the OP of different Mineral dust (MD) samples and what limitations may apply to either method. Cell-free assays are assessed including methods based on the interaction of ascorbic acid (AA) and dithiothreitol (DTT) with soluble aerosol chemical components.</p> <p>Oxidative potential experiments were carried out on both commercially available standard solutions, ultrapure water (DTT) and buffer solution (AA), as well as on soluble extracts of one-quarter filter samples obtained using both shaking and ultrasound procedures. Most limitations were related to high concentrations of transition metals in the buffer solution composition, which was treated using Chelex 100 sodium resin. Transition metals were strongly correlated to both methods, such as Ti, Cr, V, and Mn for DTT assays, and Fe, and Sr for AA assay. The mineral dust OP values were lower than the OP of particulate matter samples from urban metropolitan centers. Such results could be related to the fewer metal and quinone concentrations in the MD samples in comparison to the urban sample. DTT assay has shown more sensibility to the MD content compared with AA chemical procedure. These assays contribute to building an impact-evaluation model for assessing the variation of MD OP based on its different chemical composition.</p>

Evaluation of the Anti-Oxidative Effects of Monocyte Cells Treated with Bone Marrow Mesenchymal Stem Cells Supernatant on Experimental Colitis in BALB/c Mice

Background: Alternate activation of monocytes could induce anti-inflammatory impacts. This study aimed to investigate whether monocyte cells treated with bone marrow mesenchymal stem cells supernatant (MSC-Sp) could improve anti-inflammatory responses as a cell transfer therapy for colitis. Materials and Methods: The induction of experimental colitis was done by acetic acid in four groups of male BALB/c mice, including the control colitis, treated-monocytes, non-treated-monocytes, and mesalazine groups. Following MSCs culture, the supernatant was harvested, and then 50% conditioned media, or negative control media was added to the monocytes for 24 h. After ten days, peritoneal injection of treated or non-treated-monocytes (105 cells/100µL) was performed in animals' relevant groups of colitis. Ten days later, the oxidative stress profile and histopathological evaluation of colon tissue were assessed. Results: Treated monocytes showed a significant improvement in the oxidative stress profile, namely myeloperoxidase (0.126±0.008), nitric oxide (0.153±0.01), and malondialdehyde (0.148±0.014) compared to the control colitis group (P<0.05). Also, histopathological results revealed that the rate of damage in the treated-monocytes group was less than in normal mice. Conclusion: Our study indicated that the treated monocytes had anti-oxidative potential in colitis mice and were usable as a complementary therapy. [GMJ.2021;10:e2131]

Optical properties and oxidative potential of aqueous-phase products from OH and ³C^*-initiated photolysis of eugenol

In ambient air, aqueous-phase oxidation may turn precursors into more light-absorbing and toxic products, leading to air quality deterioration and adverse health effects. In this study, we investigated eugenol degradation in aqueous phase under direct photolysis, and triplet excited organic (3C*) and hydroxyl radical (OH) as oxidants. Results showed degradation rates of eugenol followed the order of 3C* > OH > direct photolysis. Relative contributions of reactive oxygen species (ROS) and 3C* were evaluated via quenching and O2-free experiments. 3C* played a dominant role in eugenol degradation for 3C*-initiated oxidation, while both O2 and O2•-generated were important for eugenol degradation for OH-initiated oxidation. Rate constants under O2, air and N2 followed the order of ko2＞kAir＞kN2 under both direct photolysis and OH oxidation, and it changed to kAir＞kN2＞ko2 in 3C*-initiated oxidation. Light absorption spectra showed absorbance at 300–400 nm increased as photolysis progressed, and there were new broad fluorescent spectra at excitation/emission (Ex/Em) = 250/(400–500) nm, suggesting the formation of new chromophores and fluorophores, such as humic-like substances (HULIS). Additionally, distinct fluorescence peaks appeared at Ex/Em=(300–350)/300 nm at different stages. Concentration of generated HULIS increased gradually over time, then leveled off. Dithiothreitol (DTT) assay was applied to assess the oxidation potential of products, which was greater than pure eugenol, suggesting more harmful species were produced during oxidation. Detailed reaction pathways were elucidated via analyses of chemical characteristics of the products.

A semi-automated instrument for cellular oxidative potential evaluation (SCOPE) of water-soluble extracts of ambient particulate matter

Several automated instruments exist to measure the acellular oxidative potential (OP) of ambient particulate matter (PM). However, cellular OP of the ambient PM is still measured manually, which severely limits the comparison between two types of assays. Cellular assays could provide a more comprehensive assessment of the PM-induced oxidative stress, as they incorporate more biological processes involved in the PM-catalyzed reactive oxygen species (ROS) generation. Considering this need, we developed a semi-automated instrument, the first of its kind, for measuring the cellular OP based on a macrophage ROS assay using rat alveolar macrophages. The instrument named SCOPE – semi-automated instrument for cellular oxidative potential evaluation – uses dichlorofluorescein diacetate (DCFH-DA) as a probe to detect the OP of PM samples extracted in water. SCOPE is capable of analyzing a batch of six samples (including one negative and one positive control) in 5 h and is equipped to operate continuously for 24 h with minimal manual intervention after every batch of analysis, i.e., after every 5 h. SCOPE has a high analytical precision as assessed from both positive controls and ambient PM samples (coefficient of variation (CoV)<17 %). The results obtained from the instrument were in good agreement with manual measurements using tert-butyl hydroperoxide (t-BOOH) as the positive control (slope =0.83 for automated vs. manual, R2=0.99) and ambient samples (slope =0.83, R2=0.71). We further demonstrated the ability of SCOPE to analyze a large number of both ambient and laboratory samples and developed a dataset on the intrinsic cellular OP of several compounds, such as metals, quinones, polycyclic aromatic hydrocarbons (PAHs) and inorganic salts, commonly known to be present in ambient PM. This dataset is potentially useful in future studies to apportion the contribution of key chemical species in the overall cellular OP of ambient PM.

Oral administration of tartrazine (E102) accelerates the incidence and the development of 7,12-dimethylbenz(a) anthracene (DMBA)-induced breast cancer in rats

Background Despite the considerable advances made in the treatment of cancer, it remains a global threat. Tartrazine (E102) is a synthetic dye widely used in food industries; it has recently been shown to induce oxidative stress (a well known risk factor of cancer) in rat tissues. The present work therefore aimed to assess the impact of a regular consumption of tartrazine on the incidence of breast cancer in rats. Methods Forty (40) Wistar rats aged 55 to 60 days were randomly assigned into 5 groups (n = 8) including two groups serving as normal controls and receiving distilled water (NOR) or tartrazine (NOR + TARZ). The three remaining groups were exposed to the carcinogen DMBA (50 mg/kg) and treated for 20 weeks with either distilled water (DMBA), tartrazine 50 mg/kg (DMBA + TARZ) or a natural dye (DMBA + COL). The parameters evaluated were the incidence, morphology and some biomarkers (CA 15–3, estradiol and α-fetoprotein) of breast cancer. The oxidative status and histomorphology of the tumors were also assessed. Results A regular intake of tartrazine led to an early incidence of tumors (100% in rats that received TARZ only vs 80% in rats that received DMBA only), with significantly larger tumors (p < 0.001) (mass = 3500 mg/kg and volume = 4 cm3). The invasive breast carcinoma observed on the histological sections of the animals of the DMBA + TARZ group was more developed than those of the DMBA group. The increase in serum α-fetoprotein (p < 0.05) and CA 15–3 (p < 0.01) levels corroborate the changes observed in tumors. The presence of oxidative activity in animals of the DMBA + TARZ group was confirmed by a significant decrease (p < 0.001) in the activity of antioxidant enzymes (SOD and catalase) as well as the level of GSH and increase in the level of MDA compared to the rats of the DMBA and NOR groups. Conclusion Tartrazine therefore appears to be a promoter of DMBA-induced breast tumorigenesis in rats through its oxidative potential. This work encourages further studies on the mechanisms of action of tartrazine (E102) and its limits of use.