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A recent study showed that silymarin, a standardized extract of S. marianum might be used in the prevention of equine laminitis. We investigated the effects of quercetin and some compounds found in silymarin (silybin, taxifolin and dehydrosilybin) on reactive oxygen species (ROS) production and myeloperoxidase (MPO) release by stimulated equine neutrophils (PMNs) and on MPO activity. All compounds (tested between 100 n m and 100 μ m) inhibited superoxide anion production by stimulated PMNs in a dose-dependent manner. Dehydrosilybin and quercetin inhibited superoxide production and MPO release from 10 μ m. Classical MPO assay showed quercetin as the most potent inhibitor, followed by taxifolin, dehydrosilybin and silybin. SIEFED MPO assay highlighting the binding of tested compounds to MPO showed that only quercetin and taxifolin maintained an efficient inhibition above 90% at 10 μ m. Altogether, our results showed a strong inhibition of PMN activation by planar compounds such as quercetin and dehydrosilybin and a strong inhibition of MPO activity by the smallest molecules, quercetin and taxifolin. In conclusion, the compounds from silymarin may be useful for modulating the oxidative response of PMNs, involved in the pathogenesis of laminitis, but further in vivo studies are needed. [ABSTRACT FROM AUTHOR]

Silymarin, a standardised extract of Silybum marianum (milk thistle), comprises mainly of silybin, with dehydrosilybin (DHSB), quercetin, taxifolin, silychristin and a number of other compounds which are known to possess a range of salutary effects. Indeed, there is evidence for their role in reducing tumour growth, preventing liver toxicity, and protecting a number of organs against ischemic damage. The hepatoprotective effects of silymarin, especially in preventing Amanita and alcohol intoxication induced damage to the liver, are a well established fact. Likewise, there is weighty evidence that silymarin possesses antimicrobial and anticancer activities. Additionally, it has emerged that in animal models, silymarin can protect the heart, brain, liver and kidneys against ischemia reperfusion injury, probably by preconditioning. The mechanisms of preconditioning are, in general, well studied, especially in the heart. On the other hand, the mechanism by which silymarin protects the heart from ischemia remains largely unexplored. This review, therefore, focuses on evaluating existing studies on silymarin induced cardioprotection in the context of the established mechanisms of preconditioning. [ABSTRACT FROM AUTHOR]

This study examined the biotransformation of phytocannabinoids in human hepatocytes. The susceptibility of the tested compounds to transformations in hepatocytes exhibited the following hierarchy: cannabinol (CBN) > cannabigerol (CBG) > cannabichromene (CBC) > cannabidiol (CBD). Biotransformation included hydroxylation, oxidation to a carboxylic acid, dehydrogenation, hydrogenation, dehydration, loss/shortening of alkyl, glucuronidation and sulfation. CBN was primarily metabolized by oxidation of a methyl to a carboxylic acid group, while CBD, CBG and CBC were preferentially metabolized by direct glucuronidation. The study also screened for the activity of recombinant human cytochromes P450 (CYPs) and UDP-glucuronosyltransferases (UGTs), which could catalyze the hydroxylation and glucuronidation of the tested compounds, respectively. We found that CBD was hydroxylated mainly by CYPs 2C8, 2C19, 2D6; CBN by 1A2, 2C9, 2C19 and 2D6; and CBG by 2B6, 2C9, 2C19 and 2D6. CBC exhibited higher susceptibility to CYP-mediated transformation than the other tested compounds, mainly with CYPs 1A2, 2B6, 2C8, 2C19, 2D6 and 3A4 being involved. Further, CBD was primarily glucuronidated by UGTs 1A3, 1A7, 1A8, 1A9 and 2B7; CBN by 1A7, 1A8, 1A9 and 2B7; CBG by 1A3, 1A7, 1A8, 1A9, 2B4, 2B7 and 2B17; and the glucuronidation of CBC was catalyzed by UGTs 1A1, 1A8, 1A9 and 2B7., Competing Interests: Declaration of Competing Interest J.S. is CEO and has financial interests in CB21 Pharma Ltd. (Brno, Czech Republic), CBDepot Ltd. (Teplice, Czech Republic), PharmaCan Ltd. (Prague, Czech Republic) and CB21 R&D Ltd. (Prague, Czech Republic). J.Va. is involved in the scientific board of CB21 Pharma Ltd. The authors have scientific collaborations with and financial support from CB21 Pharma Ltd. and CBDepot Ltd. The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Jan Vacek reports financial support was provided by Palacky University in Olomouc and OP EIC Operational Programme., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Polyphenols, secondary metabolites of plants, exhibit different anti-cancer and cytoprotective properties such as anti-radical, anti-angiogenic, anti-inflammation, or cardioprotective. Some of these activities could be linked to modulation of miRNAs expression. MiRNAs play an important role in posttranscriptional regulation of their target genes that could be important within cell signalling or preservation of cell homeostasis, e.g., cell survival/apoptosis. We evaluated the influence of a non-toxic concentration of taxifolin and quercetin on the expression of majority human miRNAs via Affymetrix GeneChip™ miRNA 3.0 Array. For the evaluation we used two cell models corresponding to liver tissue, Hep G2 and primary human hepatocytes. The array analysis identified four miRNAs, miR-153, miR-204, miR-211, and miR-377-3p, with reduced expression after taxifolin treatment. All of these miRNAs are linked to modulation of ZEB2 expression in various models. Indeed, ZEB2 protein displayed upregulation after taxifolin treatment in a dose dependent manner. However, the modulation did not lead to epithelial mesenchymal transition. Our data show that taxifolin inhibits Akt phosphorylation, thereby diminishing ZEB2 signalling that could trigger carcinogenesis. We conclude that biological activity of taxifolin may have ambiguous or even contradictory outcomes because of non-specific effect on the cell.

Photodynamic therapy (PDT) is gradually becoming an alternative method in the treatment of several diseases. Here, we investigated the role of oxygen in photodynamically treated cervical cancer cells (HeLa). The effect of PDT on HeLa cells was assessed by exposing cultured cells to disulphonated zinc phthalocyanine (ZnPcS 2 ) and tetrasulphonated zinc tetraphenylporphyrin (ZnTPPS 4 ). Fluorescence microscopy revealed their different localizations within the cells. ZnTPPS 4 seems to be mostly limited to the cytosol and lysosomes, whereas ZnPcS 2 is most likely predominantly attached to membrane structures, including plasmalemma and the mitochondrial membrane. Phototoxicity assays of PDT-treated cells carried out under different partial pressures of oxygen showed dose-dependent responses. Interestingly, ZnPcS 2 was also photodynamically effective at a minimal level of oxygen, under a nitrogen atmosphere. On the other hand, hyperbaric oxygenation did not lead to a higher PDT efficiency of either photosensitizer. Although both photosensitizers can induce a significant drop in mitochondrial membrane potential, ZnPcS 2 has a markedly higher effect on mitochondrial respiration that was completely blocked after two short light cycles. In conclusion, our observations suggest that PDT can be effective even in hypoxic conditions if a suitable sensitizer is chosen, such as ZnPcS 2 , which can inhibit mitochondrial respiration.

Quercetin, a flavonoid with multiple proven health benefits to both man and animals, displays a plethora of biological activities, collectively referred to as pleiotropic. The most studied of these are antioxidant and anti-inflammatory but modulation of signalling pathways is important as well. One of the lesser-known and recently discovered roles of quercetin, is modulation of microRNA (miRNA) expression. miRNAs are important posttranscriptional modulators that play a critical role in health and disease and many of these non-coding oligonucleotides are recognized as oncogenic or tumor suppressor miRNAs. This review is an evaluation of the recent relevant literature on the subject, with focus on the ability of quercetin to modulate miRNA expression. It includes a summary of recent knowledge on miRNAs deregulated by quercetin, an overview of quercetin pharmacokinetics and miRNA biogenesis, for the interested reader.

Quercetin and dehydrosilybin are polyphenols which are known to behave like uncouplers of respiration in isolated mitochondria. Here we investigated whether the effect is conserved in whole cells. Following short term incubation, neither compound uncouples mitochondrial respiration in whole H9c2 cells below 50μM. However, following hypoxia, or long term incubation, leak (state IV with oligomycin) oxygen consumption is increased by quercetin. Both compounds partially protected complex I respiration, but not complex II in H9c2 cells following hypoxia. In a permeabilised H9c2 cell model, the increase in leak respiration caused by quercetin is lowered by increased [ADP] and is increased by adenine nucleotide transporter inhibitor, atractyloside, but not bongkrekic acid. Both quercetin and dehydrosilybin dissipate mitochondrial membrane potential in whole cells. In the case of quercetin, the effect is potentiated post hypoxia. Genetically encoded Ca++ sensors, targeted to the mitochondria, enabled the use of fluorescence microscopy to show that quercetin decreased mitochondrial [Ca++] while dehydrosilybin did not. Likewise, quercetin decreases accumulation of [Ca++] in mitochondria following hypoxia. Fluorescent probes were used to show that both compounds decrease plasma membrane potential and increase cytosolic [Ca++]. We conclude that the uncoupler-like effects of these polyphenols are attenuated in whole cells compared to isolated mitochondria, but downstream effects are nevertheless apparent. Results suggest that the effect of quercetin observed in whole and permeabilised cells may originate in the mitochondria, while the mechanism of action of cardioprotection by dehydrosilybin may be less dependent on mitochondrial uncoupling than originally thought. Rather, protective effects may originate due to interactions at the plasma membrane.

The development of new methods and strategies for the investigation of membrane proteins is limited by poor solubility of these proteins in an aqueous environment and hindered by a number of other problems linked to the instability of the proteins outside lipid bilayers. Therefore, current research focuses on an analysis of membrane proteins incorporated into model lipid membrane, most frequently liposomes. In this work, we introduce a new electrochemical methodology for the analysis of transmembrane proteins reconstituted into a liposomal system. The proposed analytical approach is based on proteoliposomal sample adsorption on the surface of working electrodes followed by analysis of the anodic and cathodic signals of the reconstituted proteins. It works based on the fact that proteins are electroactive species, in contrast to the lipid components of the membranes under the given experimental conditions. Electroanalytical experiments were performed with two transmembrane proteins; the Na(+)/K(+)ATPase that contains transmembrane as well as large extramembraneous segments and the mitochondrial uncoupling protein 1, which is a transmembrane protein essentially lacking extramembraneous segments. Electrochemical analyses of proteoliposomes were compared with analyses of both proteins solubilized with detergents (C12E8 and octyl-PoE) and supported by the following complementary methods: microscopy techniques, protein activity testing, molecular model visualizations, and immunochemical identification of both proteins. The label-free electrochemical platform presented here enables studies of reconstituted transmembrane proteins at the nanomolar level. Our results may contribute to the development of new electrochemical sensors and microarray systems applicable within the field of poorly water-soluble proteins.

2,3-dehydrosilybin (DHS) is a minor flavonolignan component of Silybum marianum seed extract known for its hepatoprotective activity. Recently we identified DHS as a potentially cardioprotective substance during hypoxia/reoxygenation in isolated neonatal rat cardiomyocytes. This is the first report of positive inotropic effect of DHS on perfused adult rat heart. When applied to perfused adult rat heart, DHS caused a dose-dependent inotropic effect resembling that of catecholamines. The effect was apparent with DHS concentration as low as 10 nM. Suspecting direct interaction with β-adrenergic receptors, we tested whether DHS can trigger β agonist-dependent gene transcription in a model cell line. While DHS alone was unable to trigger β agonist-dependent gene transcription, it enhanced the effect of isoproterenol, a known unspecific β agonist. Further tests confirmed that DHS could not induce cAMP accumulation in isolated neonatal rat cardiomyocytes even though high concentrations (≥ 10 μM) of DHS were capable of decreasing phosphodiesterase activity. Pre-treatment of rats with reserpine, an indole alkaloid which depletes catecholamines from peripheral sympathetic nerve endings, abolished the DHS inotropic effect in perfused hearts. Our data suggest that DHS causes the inotropic effect without acting as a β agonist. Hence we identify DHS as a novel inotropic agent.

Aims: MicroRNAs of the miR-29 family members were one of the first microRNAs identified as possible therapeutic agents in malignant hematopoiesis. The aim of our review is to summarize the current state of knowledge on miR-29 family members., Methods: We performed literature searches involving miR-29 family members and their relationship to individual hematological malignancies, namely acute myeloid leukemia (AML), chronic lymphoblastic leukemia (CLL) and chronic myeloid leukemia (CML). We also searched for subgroups of hematological malignancies, e.g. multiple myeloma, that are regarded as members of the acute or chronic types of leukemias., Results: A number of genes appear to be regulated by miR-29 family members in various physiological and pathological situations. In our view regulation of Tcl-1, Mcl-1 and DNA methyltransferases is relevant in case of hematological malignancies, hence these are the focus of this review. miR-29 family members also function during normal T-cell and B-cell development., Conclusion: MiR-29 family members appear to govern some general features in commonly heterogenous hematological malignancies and therefore form a potential target for treatment.

Introduction: MicroRNAs (miRNAs) are small non-coding single-stranded RNA molecules that regulate gene expression at the post-transcriptional level. In the pathogenesis of chronic lymphocytic leukemia (CLL), miR-15a and miR-16-1 play an important role. These miRNAs are located on chromosome 13 in the 13q14.3 region, which is deleted in more than 55% of CLL patients. This aberration affects expression of miRNAs., Objectives: The study aimed at performing a molecular genetic analysis of miR-15a and miR-16-1 expression in a group of 39 patients diagnosed with CLL and determining the association between the expression of the two miRNAs and types of deletions in the 13q14 region., Methods: We used fluorescence in situ hybridiziation (FISH) for determination of mono- or biallelic deletion 13q and quantitative polymerase chain reaction (Q-RT-PCR) to revealed expression miR-15a and miR-16-1 in 39 patients suffering from CLL., Results: The analysis comprised 19 patients with monoallelic 13q14 deletion, 3 patients with biallelic deletion, 9 patients with both monoallelic and biallelic deletions, and 8 patients without 13q14 deletion serving as controls. The results showed different levels of miRNA expression in individual patients. Significantly higher normalized levels of miR-15a expression were found in the control group and patients with monoallelic 13q14 expression compared with patients with biallelic deletion. There was a significantly decreased expression of both miRNAs in patients with biallelic deletion of the 13q14 region but only when deletions were present in 77% or more of cells, as detected by fluorescent in situ hybridization (FISH).

The isoquinoline alkaloids protopine and allocryptopine are present in phytopreparations from medicinal plants, such as Fumaria officinalis. Since nothing is known about effects of the alkaloids on the expression of xenobiotic-metabolizing enzymes, we examined whether protopine or allocryptopine affect the expression of cytochromes P450 (CYPs) 1A1 and 1A2 in primary cultures of human hepatocytes and human hepatoma HepG2 cells. In HepG2 cells, protopine and allocryptopine significantly increased CYP1A1 mRNA levels after 24h exposure at concentrations from 25 and 10 μM, respectively, as shown by real-time PCR. Both protopine and allocryptopine also dose-dependently increased CYP1A1 and CYP1A2 mRNA levels in human hepatocytes. However, the effects of the tested alkaloids on both cell models were much lower than the effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a prototypical CYP1A inducer. Using gene reporter assays performed in transiently transfected HepG2 cells, we demonstrated that the induction of CYP1A1 expression by either protopine or allocryptopine was associated with mild or negligible activation of the aryl hydrocarbon receptor. In contrast to TCDD, CYP1A mRNA levels induced by protopine or allocryptopine in both HepG2 cells and human hepatocytes did not result in elevated CYP1A protein or activity levels as shown by western blotting and EROD assays, respectively. We conclude that the use of products containing protopine and/or allocryptopine may be considered safe in terms of possible induction of CYP1A enzymes., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Background: Discovery of uncoupling protein 2 (UCP2) in 1997 and demonstration of its wide tissue expression has triggered an important question about controlled oxidative phosphorylation uncoupling and the physiological function of this process. Uncoupling protein 2 (UcP2) is a mitochondrial protein that can influence the mitochondrial membrane potential and hence the production of reactive oxygen species by mitochondria. It is also thought to be involved in apoptotic signaling pathways and it has been suggested to be important in cardio- and neuroprotection., Methods and Results: We examined the recent literature (2003-2007) in the MedLine database for evidence linking p38, one of the stress-related protein kinases, with modulation of UCP2 expression in the heart. While two reports clearly demonstrate p38 as down-regulating UcP2 expression, only circumstantial evidence exists for cardiomyocytes. Conflicting results on p38-regulated cardiomyocyte survival after ischemia leave an open venue for hypotheses on the differential regulation of protein expression, including UCP2., Conclusions: Reviewing the evidence connecting UCP2 and its cytoprotective activities, we propose a tissue specific link that may explain the variable influence of p38 via modulation of UCP2 expression.

Cytochrome P450 (CYP) 1A1 attracts attention mainly because of its role in production of carcinogenic reactive metabolites from polycyclic aromatic hydrocarbons such as benzo[a]pyrene, but recent developments indicate its apparent role in cell cycle progression. Expression of the enzyme is subject to regulation by aryl hydrocarbon receptor (AhR). It has been shown that induction of CYP 1A1 in HepG2 cells and primary rat hepatocytes by tetrachloro-p-dibenzodioxin (TCDD) is diminished by colchicine and nocodazole. Both compounds decrease CYP1A1 mRNA, protein, and activity levels in HepG2 cells and mRNA level in primary rat hepatocytes. Neither compound significantly affected [(3)H]-TCDD binding to AhR, thus their effect on AhR transcriptional activity proceeds via indirect means. For colchicine and nocodazole are well-known microtubule interfering agents, we also assessed their effect on microtubule integrity in both cell types under investigation. Both compounds disrupt cytoskeleton integrity with differential potency depending on cell type. The observed suppression of AhR transcriptional activity by colchicine and nocodazole can be associated with G2/M cell cycle arrest in HepG2 cells, as demonstrated by Myt1 protein hyperphosphorylation and FACS analysis. However, in primary rat hepatocytes, cytoskeleton disruption is independent of cell cycle while displaying the same influence on AhR-dependent gene transcription. In our view, this is evidence in favor of modulatory role of cytoskeleton in AhR-dependent expression.

Superfamily of cytochrome P450 enzymes (CYPs), a distinctive enzyme system by which human body defends itself against toxic compounds, is the subject of a complex regulation process involving various mechanisms, on the levels of expression and activity. Apart from physiological factors, several patho-physiological ones such as inflammation, infection, and stress affect CYP expression. The aim of this review is to summarize the current knowledge on the role of microtubules network in the regulation of drug metabolizing CYPs. Experiments on human and animal cell models revealed that microtubules disruption severely impaired basal and inducible expression of human CYP 1A1, 2B6, 2C8, 2C9, 2C19, and 3A4, and rat CYP 1A2, 2B1, 2B2, and 3A23. Inhibition of aryl hydrocarbon receptor (AhR) and glucocorticoid receptor (GR) transcriptional activity by microtubules disarray was found to be responsible for the suppressed CYP enzymes expression. However, the mechanism by which microtubules interfering agents (MIAs) inhibit GR and AhR transcriptional activities is not fully understood yet. Several lines of evidence indicate that: i) the cell cycle, G2/M phase in particular, has an influence on AhR and GR transcriptional activity, and ii) MIAs negatively modulate GR transcriptional activity via the activation of c-Jun-N-terminal kinase. In conclusion, down-regulation of major CYP enzymes by microtubules disarray is intriguing from the mechanistic point of view and in relation to the cell differentiation.

The xenobiotic-mediated induction of three major human liver cytochrome P450 genes, CYP2B6, CYP2C9, and CYP3A4, is known to be regulated by the constitutive androstane receptor (CAR) and the pregnane X receptor (PXR). CAR and PXR are regulated, at least in part, by the glucocorticoid receptor (GR) and the hypothesis of a signal transduction cascade GR-[CAR/PXR]-P450 has been proposed. This study was aimed at testing this hypothesis in primary human hepatocytes by using the tubulin network disrupting agent colchicine. Colchicine (COL) decreased both basal and rifampicin- and phenobarbital-inducible expression of CYP2B6, CYP2C8/9, and CYP3A4. A parallel down-regulation of mRNA expression of CAR, PXR, and tyrosine aminotransferase, a prototypic gene directly regulated by GR, was observed. COL affected neither the level of GR mRNA nor ligand binding to GR. To evaluate the effect of colchicine on GR-mediated gene transactivation, HeLa cells stably or transiently transfected with a GR-responsive element-dependent luciferase reporter gene were used. COL decreased the dexamethasone-induced luciferase expression in stably transfected cell line by 50%, whereas GR transactivation in transiently transfected cells was not affected by COL. In contrast, ligand-dependent GR translocation in the human embryonic kidney 293 cell line transiently transfected with GFP-GR was inhibited by COL. We conclude that alteration of the signal transduction mediated through the GR-[CAR/PXR]-P450 cascade by colchicine is responsible for the down-regulation of CYP2C9 and CYP3A4, implicating cytoskeleton as necessary for correct functioning of this cascade under physiological conditions.

Effective scavenging of reactive radicals and low reactivity of generated secondary antioxidant radicals towards vital intracellular components are two critical requirements for a chain-breaking antioxidant. Tubulin-binding properties aside, colchicine metabolites remain largely untested for other possible biological activities, including antioxidant activity. Mourelle et al. [Life Sci. 45 (1989) 891] proposed that colchiceine (EIN) acts as an antioxidant and protective agent against lipid peroxidation in a rat model of liver injury. Since EIN as well as two other colchicine metabolites, 2-demethylcolchicine (2DM) and 3-demethylcolchicine (3DM), possess a hydroxy-group on their carbon ring that could participate in radical scavenging, we tested whether they can act as chain-breaking antioxidants. Using our fluorescence-HPLC assay with metabolically incorporated oxidation-sensitive cis-parinaric acid (PnA) we studied the effects of colchicine metabolites on peroxidation of different classes of membrane phospholipids in HL-60 cells. None of the colchicine metabolites in concentrations ranging from 10(-6) to 10(-4) M was able to protect phospholipids against peroxidation induced by either azo-initiators of peroxyl radicals or via myeloperoxidase (MPO)-catalyzed reactions in the presence of hydrogen peroxide. However, the metabolites did exhibit dose-dependent depletion of glutathione, resembling the behavior of etoposide, a hindered phenol with antioxidant properties against lipid peroxidation. Electron spin resonance (ESR) experiments demonstrated that in a catalytic system containing horseradish peroxidase (HRP)/H(2)O(2), colchicine metabolites undergo one-electron oxidation to form phenoxyl radicals that, in turn, cause ESR-detectable ascorbate radicals by oxidation of ascorbate. Phenoxyl radicals of colchicine metabolites formed through MPO-catalyzed H(2)O(2)-dependent reactions in HL-60 cells and via HRP/H(2)O(2) in model systems can also oxidize GSH. Thus, colchicine metabolites possess the prerequisites of many antioxidants, i.e. a nucleophilic hydroxy-group on a carbon ring and the ability to scavenge reactive radicals and form a secondary radical. However, the latter retain high reactivity towards critical biomolecules in cells such as lipids, thiols, ascorbate, thereby, rendering colchicine metabolites effective radical scavengers but not effective chain-breaking antioxidants.