High risk of adrenal toxicity of N1-desoxy quinoxaline 1,4-dioxide derivatives and the protection of oligomeric proanthocyanidins (OPC) in the inhibition of the expression of aldosterone synthetase in H295R cells

Nanocellulose-based porous lightweight materials with flame retardant properties: A review

This review discusses the development and application of nanocellulose (NC)-aerogels, a sustainable and biodegradable biomaterial, with enhanced flame retardant (FR) properties. NC-aerogels combine the excellent physical and mechanical properties of NC with the low density and thermal conductivity of aerogels, making them promising for thermal insulation and other fields. However, the flammability of NC-aerogels limits their use in some applications, such as electromagnetic interference shielding, oil/water separation, and flame-resistant textiles. The review covers the design, fabrication, modification, and working mechanism of NC porous materials, focusing on how advanced technologies can impart FR properties into them. The review also evaluates the FR performance of NC-aerogels by employing widely recognized tests, such as the limited oxygen index, cone calorimeter, and UL-94. The review also explores the integration of innovative and eco-friendly materials, such as MXene, metal-organic frameworks, dopamine, lignin, and alginate, into NC-aerogels, to improve their FR performance and functionality. The review concludes by outlining the potential, challenges, and limitations of future research on FR NC-aerogels, identifying the obstacles and potential solutions, and understanding the current progress and gaps in the field.

Advances in Metabolism and Metabolic Toxicology of Quinoxaline 1,4-Di-N-oxides

Quinoxaline 1,4-di-N-Oxides (QdNOs) have been used as synthetic antimicrobial agents in animal husbandry and aquaculture. The metabolism and potential toxicity have been also concerns in recently years. The metabolism investigations showed that there were 8 metabolites of Carbadox (CBX), 34 metabolites of Cyadox (CYA), 33 metabolites of Mequindox (MEQ), 35 metabolites of Olaquindox (OLA), and 56 metabolites of Quinocetone (QCT) in different animals. Among them, Cb3 and Cb8, M6, and O9 are metabolic residual markers of CBX, MEQ and OLA, which are associated with N → O reduction. Toxicity studies revealed that QdNOs exhibited severe tumorigenicity, cytotoxicity, and adrenal toxicity. Metabolic toxicology showed that toxicity of QdNOs metabolites might be related to the N → O group reduction, and some metabolites exhibited higher toxic effects than the precursor, which could provide guidance for further research on the metabolic toxicology of QdNOs and provide a wealth of information for food safety evaluation.

The Reproductive Toxicity of Mequindox in a Two-Generation Study in Wistar Rats

Mequindox (MEQ), belonging to quinoxaline-di-N-oxides (QdNOs), has been extensively used as a synthetic antibacterial agent. To evaluate the reproductive toxicity of MEQ, different concentrations of MEQ were administered to Wistar rats by feeding diets containing 0, 25, 55, 110, and 275 mg/kg, respectively. Each group consisting of 25 males and 25 females (F₀) was treated with different concentrations of MEQ for 12-week period time, prior to mating and during mating, gestation, parturition and lactation. At weaning, 25 males and 25 females of F₁ generation weanlings per group were randomly selected as parents for the F₂ generation. Selected F₁ weanlings were exposed to the same diet and treatment as their parents. The number of live litter and indexes of mating and fertility were significantly decreased in the F1 and F2 generation at 110 and 275 mg/kg groups. Significant decrease in pup vitality during lactation was observed in F1 litter at 275 mg/kg group, in F2 litter at 55, 110, and 275 mg/kg groups. A downward trend in the body weights was observed in F₁ pups at 55, 110, and 275 mg/kg MEQ groups, and in F₂ pups at 110 and 275 mg/kg MEQ groups. The changed levels of ALT, AST, CREA, BUN, UA, Na, and K were noted in the serum of rats. The histopathologic examination showed that MEQ induced toxicity in the liver, kidney, adrenal, uterus and testis. The no-observed-adverse-effect level (NOAEL) for reproduction toxicity of MEQ was 25 mg/kg diet. The malformations and severe maternal toxicity of MEQ caused adverse effects on the conceptus and embryo, which result in fetal malformations and fetal deaths. In summary, the present study showed that MEQ induced maternal, embryo and reproductive toxicities as well as teratogenicity in rats.

DNA damage response induced by Etoposide promotes steroidogenesis via GADD45A in cultured adrenal cells

Glucocorticoid production is regulated by adrenocorticotropic hormone (ACTH) via the cyclic adenosine monophosphate (cAMP)/protein kinase A (PKA) pathway in the adrenal cortex, but the changes in steroidogenesis associated with aging are unknown. In this study, we show that cell-autonomous steroidogenesis is induced by non-ACTH- mediated genotoxic stress in human adrenocortical H295R cells. Low-dose etoposide (EP) was used to induce DNA damage as a genotoxic stress, leading to cellular senescence. We found that steroidogenesis was promoted in cells stained with γH2AX, a marker of DNA damaged cells. Among stress-associated and p53-inducible genes, the expression of GADD45A and steroidogenesis-related genes was significantly upregulated. Immunofluorescence analysis revealed that GADD45A accumulated in the nuclei. Metabolite assay using cultured media showed that EP-treated cells were induced to produce and secrete considerable amounts of glucocorticoid. Knockdown of GADD45A using small interfering RNA markedly inhibited the EP-induced upregulation of steroidogenesis-related gene expression, and glucocorticoid production. A p38MAPK inhibitor, but not a PKA inhibitor, suppressed EP-stimulated steroidogenesis. These results suggest that DNA damage itself promotes steroidogenesis via one or more unprecedented non-ACTH-mediated pathway. Specifically, GADD45A plays a crucial role in the steroidogenic processes triggered by EP-stimulated genotoxic stress. Our study sheds new light on an alternate mechanism of steroidogenesis in the adrenal cortex.

Mequindox-Induced Kidney Toxicity Is Associated With Oxidative Stress and Apoptosis in the Mouse

Mequindox (MEQ), belonging to quinoxaline-di-N-oxides (QdNOs), is a synthetic antimicrobial agent widely used in China. Previous studies found that the kidney was one of the main toxic target organs of the QdNOs. However, the mechanisms underlying the kidney toxicity caused by QdNOs in vivo still remains unclear. The present study aimed to explore the molecular mechanism of kidney toxicity in mice after chronic exposure to MEQ. MEQ led to the oxidative stress, apoptosis, and mitochondrial damage in the kidney of mice. Meanwhile, MEQ upregulated Bax/Bcl-2 ratio, disrupted mitochondrial permeability transition pores, caused cytochrome c release, and a cascade activation of caspase, eventually induced apoptosis. The oxidative stress mediated by MEQ might led to mitochondria damage and apoptosis in a mitochondrial-dependent apoptotic pathway. Furthermore, upregulation of the Nrf2-Keap1 signaling pathway was also observed. Our findings revealed that the oxidative stress, mitochondrial dysfunction, and the Nrf2-Keap1 signaling pathway were associated with the kidney apoptosis induced by MEQ in vivo.

Mechanisms of the Testis Toxicity Induced by Chronic Exposure to Mequindox

Mequindox (MEQ) is a synthetic antimicrobial agent widely used in China since the 1980s. Although the toxicity of MEQ is well recognized, its testis toxicity has not been adequately investigated. In the present study, we provide evidence that MEQ triggers oxidative stress, mitochondrion dysfunction and spermatogenesis deficiency in mice after exposure to MEQ (0, 25, 55, and 110 mg/kg in the diet) for up to 18 months. The genotoxicity and adrenal toxicity may contribute to sperm abnormalities caused by MEQ. Moreover, using LC/MS-IT-TOF analysis, two metabolites, 3-methyl-2-(1-hydroxyethyl) quinoxaline-N4-monoxide (M4) and 3-methyl-2-(1-hydroxyethyl) quinoxaline-N1-monoxide (M8), were detected in the serum of mice, which directly confirms the relationship between the N→O group reduction metabolism of MEQ and oxidative stress. Interestingly, only M4 was detected in the testes, suggesting that the higher reproductive toxicity of M4 than M8 might be due to the increased stability of M4-radical (M4-R) compared to M8-radical (M8-R). Furthermore, the expression of the blood-testis barrier (BTB)-associated junctions such as tight junctions, gap junctions and basal ectoplasmic specializations were also examined. The present study demonstrated for the first time the role of the M4 in testis toxicity, and illustrated that the oxidative stress, mitochondrion dysfunction and interference in spermatogenesis, as well as the altered expression of BTB related junctions, were involved in the reproductive toxicity mediated by MEQ in vivo.

Toxic metabolites, Sertoli cells and Y chromosome related genes are potentially linked to the reproductive toxicity induced by mequindox

Mequindox (MEQ) is a relatively new synthetic antibacterial agent widely applied in China since the 1980s. However, its reproductive toxicity has not been adequately performed. In the present study, four groups of male Kunming mice (10 mice/group) were fed diets containing MEQ (0, 25, 55 and 110 mg/kg in the diet) for up to 18 months. The results show that M4 could pass through the blood-testis barrier (BTB), and demonstrate that Sertoli cells (SCs) are the main toxic target for MEQ to induce spermatogenesis deficiency. Furthermore, adrenal toxicity, adverse effects on the hypothalamic-pituitary-testicular axis (HPTA) and Leydig cells, as well as the expression of genes related to steroid biosynthesis and cholesterol transport, were responsible for the alterations in sex hormones in the serum of male mice after exposure to MEQ. Additionally, the changed levels of Y chromosome microdeletion related genes, such as DDX3Y, HSF2, Sly and Ssty2 in the testis might be a mechanism for the inhibition of spermatogenesis induced by MEQ. The present study illustrates for the first time the toxic metabolites of MEQ in testis of mice, and suggests that SCs, sex hormones and Y chromosome microdeletion genes are involved in reproductive toxicity mediated by MEQ in vivo.

Toxic metabolites, MAPK and Nrf2/Keap1 signaling pathways involved in oxidative toxicity in mice liver after chronic exposure to Mequindox

Mequindox (MEQ) is a synthetic antimicrobial agent of quinoxaline-1,4-dioxide group (QdNOs). The liver is regarded as the toxicity target of QdNOs, and the role of N → O group-associated various toxicities mediated by QdNOs is well recognized. However, the mechanism underlying the in vivo effects of MEQ on the liver, and whether the metabolic pathway of MEQ is altered in response to the pathophysiological conditions still remain unclear. We now provide evidence that MEQ triggers oxidative damage in the liver. Moreover, using LC/MS-ITTOF analysis, two metabolites of MEQ were detected in the liver, which directly confirms the potential connection between N → O group reduction metabolism of MEQ and liver toxicity. The gender difference in MEQ-induced oxidative stress might be due to adrenal toxicity and the generation of M4 (2-isoethanol 1-desoxymequindox). Furthermore, up-regulation of the MAPK and Nrf2-Keap1 family and phase II detoxifying enzymes (HO-1, GCLC and NQO1) were also observed. The present study demonstrated for the first time the protein peroxidation and a proposal metabolic pathway after chronic exposure of MEQ, and illustrated that the MAPK, Nrf2-Keap1 and NF-кB signaling pathways, as well as the altered metabolism of MEQ, were involved in oxidative toxicity mediated by MEQ in vivo.