Effects of Chrysin and Chrysin-7-sulfate on Ochratoxin A-Albumin Interactions and on the Plasma and Kidney Levels of the Mycotoxin in Rats

The nephrotoxic mycotoxin ochratoxin A (OTA) is a common food contaminant. OTA binds to the Sudlow's Site I region of serum albumin with very high affinity, resulting in its slow elimination. The displacement of OTA from albumin may be beneficial due to the faster excretion of the mycotoxin, while it may also lead to the increased tissue uptake of OTA. Furthermore, it is challenging to displace the mycotoxin from albumin even with high-affinity Site I ligands. In this study, we tested the impacts of Site I and Heme site ligands on OTA-albumin interactions by applying fluorescence spectroscopic, ultracentrifugation, and modeling studies. Chrysin-7-sulfate (C7S) strongly displaced OTA from both human and rat albumins; therefore, the impacts of C7S (single intravenous administration) and the parent flavonoid chrysin (repeated peroral treatment) were examined on the plasma and kidney levels of OTA in rats. Chrysin barely influenced the concentrations of mycotoxin in plasma and kidneys. In the first few hours, C7S significantly decreased the plasma levels of OTA compared to the control animals; while after 24 h, only minor differences were noticed. Our study highlights the superior displacing ability of C7S vs OTA regarding human and rat albumins.

Interaction of mycotoxins zearalenone, α-zearalenol, and β-zearalenol with cytochrome P450 (CYP1A2, 2C9, 2C19, 2D6, and 3A4) enzymes and organic anion transporting polypeptides (OATP1A2, OATP1B1, OATP1B3, and OATP2B1)

Zearalenone (ZEN) is a mycoestrogen produced by Fusarium fungi. ZEN is a frequent contaminant in cereal-based products, representing significant health threat. The major reduced metabolites of ZEN are α-zearalenol (α-ZEL) and β-zearalenol (β-ZEL). Since the toxicokinetic interactions of ZEN/ZELs with cytochrome P450 enzymes (CYPs) and organic anion transporting polypeptides (OATPs) have been barely characterized, we examined these interactions applying in vitro models. ZEN and ZELs were relatively strong inhibitors of CYP3A4 and moderate inhibitors of CYP1A2 and CYP2C9. Both CYP1A2 and CYP3A4 decreased ZEN and β-ZEL concentrations in depletion assays, while only CYP1A2 reduced α-ZEL levels. OATPs tested were strongly or moderately inhibited by ZEN and ZELs; however, these mycotoxins did not show higher cytotoxicity in OATP-overexpressing cells. Our results help the deeper understanding of the toxicokinetic/pharmacokinetic interactions of ZEN, α-ZEL, and β-ZEL.

Inhibition of xanthine oxidase-catalyzed xanthine and 6-mercaptopurine oxidation by luteolin, naringenin, myricetin, ampelopsin and their conjugated metabolites

Luteolin, naringenin, myricetin, and ampelopsin are abundant flavonoids in nature, and several dietary supplements also contain them at very high doses. After the peroral intake, flavonoids go through extensive presystemic biotransformation; therefore, typically their sulfate/glucuronic acid conjugates reach high concentrations in the circulation. Xanthine oxidase (XO) enzyme is involved in uric acid production, and it also takes part in the elimination of certain drugs (e.g., 6-mercaptopurine). The inhibitory effects of flavonoid aglycones on XO have been widely studied; however, only limited data are available regarding their sulfate and glucuronic acid conjugates. In this study, we examined the impacts of luteolin, naringenin, myricetin, ampelopsin, and their sulfate/glucuronide derivatives on XO-catalyzed xanthine and 6-mercaptopurine oxidations employing in vitro enzyme incubation assays and molecular modeling studies. Our major results/conclusions are the following: (1) Sulfate metabolites were stronger while glucuronic acid derivatives were weaker inhibitors of XO compared to the parent flavonoids. (2) Naringenin, ampelopsin, and their metabolites were weak inhibitors of the enzyme. (3) Luteolin, myricetin, and their sulfates were highly potent inhibitors of XO, and the glucuronides of luteolin showed moderate inhibitory impacts. (4) Conjugated metabolites of luteolin and myricetin can be involved in the inhibitory effects of these flavonoids on XO enzyme.

The anti-inflammatory effect of dimethyl trisulfide in experimental acute pancreatitis

Various organosulfur compounds, such as dimethyl trisulfide (DMTS), display anti-inflammatory properties. We aimed to examine the effects of DMTS on acute pancreatitis (AP) and its mechanism of action in both in vivo and in vitro studies. AP was induced in FVB/n mice or Wistar rats by caerulein, ethanol-palmitoleic acid, or L-ornithine-HCl. DMTS treatments were administered subcutaneously. AP severity was assessed by pancreatic histological scoring, pancreatic water content, and myeloperoxidase activity measurements. The behaviour of animals was followed. Pancreatic heat shock protein 72 (HSP72) expression, sulfide, and protein persulfidation were measured. In vitro acinar viability, intracellular Ca2+ concentration, and reactive oxygen species production were determined. DMTS dose-dependently decreased the severity of AP. It declined the pancreatic infiltration of leukocytes and cellular damage in mice. DMTS upregulated the HSP72 expression during AP and elevated serum sulfide and low molecular weight persulfide levels. DMTS exhibited cytoprotection against hydrogen peroxide and AP-inducing agents. It has antioxidant properties and modulates physiological but not pathophysiological Ca2+ signalling. Generally, DMTS ameliorated AP severity and protected pancreatic acinar cells. Our findings indicate that DMTS is a sulfur donor with anti-inflammatory and antioxidant effects, and organosulfur compounds require further investigation into this potentially lethal disease.

Probing the Interactions of 31 Mycotoxins with Xanthine Oxidase: Alternariol, Alternariol-3-Sulfate, and α-Zearalenol Are Allosteric Inhibitors of the Enzyme

Mycotoxins are frequent toxic contaminants in foods and beverages, causing a significant health threat. Interactions of mycotoxins with biotransformation enzymes (e.g., cytochrome P450 enzymes, sulfotransferases, and uridine 5'-diphospho-glucuronosyltransferases) may be important due to their possible detoxification or toxic activation during enzymatic processes. Furthermore, mycotoxin-induced enzyme inhibition may affect the biotransformation of other molecules. A recent study described the strong inhibitory effects of alternariol and alternariol-9-methylether on the xanthine oxidase (XO) enzyme. Therefore, we aimed to test the impacts of 31 mycotoxins (including the masked/modified derivatives of alternariol and alternariol-9-methylether) on XO-catalyzed uric acid formation. Besides the in vitro enzyme incubation assays, mycotoxin depletion experiments and modeling studies were performed. Among the mycotoxins tested, alternariol, alternariol-3-sulfate, and α-zearalenol showed moderate inhibitory actions on the enzyme, representing more than tenfold weaker impacts compared with the positive control inhibitor allopurinol. In mycotoxin depletion assays, XO did not affect the concentrations of alternariol, alternariol-3-sulfate, and α-zearalenol in the incubates; thus, these compounds are inhibitors but not substrates of the enzyme. Experimental data and modeling studies suggest the reversible, allosteric inhibition of XO by these three mycotoxins. Our results help the better understanding of the toxicokinetic interactions of mycotoxins.

Interactions of Mycotoxin Alternariol with Cytochrome P450 Enzymes and OATP Transporters

Alternariol (AOH) is an emerging mycotoxin produced by Alternaria strains. The acute toxicity of the mycotoxin is low; however, chronic exposure to AOH may result in the development of endocrine disruptor and/or carcinogenic effects. The toxicokinetic properties of AOH have barely been characterized. Therefore, in this study, we aimed to investigate its interactions with CYP (1A2, 2C9, 2C19, 2D6, and 3A4) enzymes and OATP (1A2, 1B1, 1B3, and 2B1) transporters employing in vitro enzyme assays and OATP overexpressing cells, respectively. Our results demonstrated that AOH is a strong inhibitor of CYP1A2 (IC₅₀ = 0.15 μM) and CYP2C9 (IC₅₀ = 7.4 μM). Based on the AOH depletion assays in the presence of CYP enzymes, CYP1A2 is mainly involved, while CYP2C19 is moderately involved in the CYP-catalyzed biotransformation of the mycotoxin. AOH proved to be a strong inhibitor of each OATP transporter examined (IC₅₀ = 1.9 to 5.4 μM). In addition, both direct and indirect assays suggest the involvement of OATP1B1 in the cellular uptake of the mycotoxin. These findings promote the deeper understanding of certain toxicokinetic interactions of AOH.

Development of Capsaicin-Containing Analgesic Silicone-Based Transdermal Patches

Transdermal therapeutic systems (TTSs) enable convenient dosing in drug therapy. Modified silicone-polymer-based patches are well-controlled and cost-effective matrix diffusion systems. In the present study, we investigated the substance release properties, skin penetration, and analgesic effect of this type of TTS loaded with low-dose capsaicin. Release properties were measured in Franz diffusion cell and continuous flow-through cell approaches. Capsaicin was detected with HPLC-UV and UV spectrophotometry. Raman spectroscopy was conducted on human skin samples exposed to the TTS. A surgical incision or carrageenan injection was performed on one hind paw of male Wistar rats. TTSs were applied to the epilated dorsal skin. Patches were kept on the animals for 6 h. The thermal hyperalgesia and mechanical pain threshold of the hind paws were detected. Patches exhibited controlled, zero-order kinetic capsaicin release. According to the Raman mapping, capsaicin penetrated into the epidermis and dermis of human skin, where the target receptors are expressed. The thermal pain threshold drop of the operated rat paws was reversed by capsaicin treatment compared to that of animals treated with control patches. It was concluded that our modified silicone-polymer-based capsaicin-containing TTS is suitable for the relief of traumatic and inflammatory pain.