Hepatoprotective effects of S-adenosylmethionine and silybin on canine hepatocytes in vitro

Use of Milk Thistle in Farm and Companion Animals: A Review

Milk thistle, Silybum marianum, is a medicinal plant grown for its bioactive compounds with well-documented antioxidant and hepatoprotective properties. Milk thistle has a well-established pharmacological reputation for treatments of human liver disease, but it is also used in animals. This review summarizes the experimental evidence of milk thistle's effects on animals when administered as silymarin extract (feed additive) or a feed ingredient, if administered as seed or expeller/cake with the seed residue still containing the bioactive components. The use as a feed additive or feed ingredient is motivated by the complexity of silymarin registration as a veterinary drug. In farm animals, the drug improves the animals' performance and product quality and oxidative stability, supports liver function during the productive life-cycle, improves gut-health and morphology, and can reduce intestinal pathogens. In dogs and cats, the treatment is focused on acute and chronic liver diseases including the detoxification processes and support of drug treatments including chemotherapy. In equine athletes, milk seed cake showed positive effects and a faster return of cortisol to the resting values before exercise occurred. In aquaculture, it confirms its usefulness in supporting animal health and performance. In certain studies it is not clear what has been administered, and the composition and doses are not always clearly reported. A few studies reported no effects, but none reported problems connected to milk thistle administration. However, the overall picture shows that the use of milk thistle results in improved or restored health parameters or better animal performance.

Increases in serum carbonylated protein levels of dogs with hypercortisolism

Protein carbonylation is an irreversible and degenerative modification that can be used to evaluate oxidative stress caused by glucocorticoids. In this study, we focused on protein carbonylation in dogs with hypercortisolism (HC). Sera samples were collected from 14 dogs diagnosed with HC and treated with trilostane, 12 dogs with inflammatory diseases (disease control group), and eight clinically healthy dogs. When the carbonylated protein levels were detected by the immunoblot analysis, one band of approximately 40 kDa was predominantly increased in the dogs with HC. The band was identified as haptoglobin using the liquid chromatography tandem mass spectrometry method. Furthermore, haptoglobin immune reactivity was higher in the dogs with HC. Although the average protein carbonylation level of the HC group was not significantly different from that of the other groups, the carbonylation level was significantly higher for the poorly controlled HC cases than for the well-controlled HC group. Additionally, the primary culture of canine hepatocytes was used to clarify the direct effect of glucocorticoids on protein carbonylation in dog livers. Both the carbonylated protein and haptoglobin clearly increased after 72 h. These findings suggest that haptoglobin and its carbonylated form are increased with canine HC, and that the protein carbonylation ratio and/or haptoglobin level could be related to disease management. These factors could be useful as biomarkers for an oxidative stress reaction, at least in the liver, and for treatment monitoring of HC.

Combined hepatoprotective pharmacotherapy for liver disease

Fixed-dose drug products as well as non-fixed hepatoprotective drug combinations are commonly used in modern clinical practice. Combined and concurrent drug use makes it possible to augment the pharmacological effects of individual agents, or extend the range of their potential indications. The drugs most commonly considered for combination therapy include essential phospholipids, glycyrrhizinic acid, ursodeoxycholic acid, silibinin, and S-adenosylmethionine. This paper discusses the rationale for combined use of liver-targeting drugs from a pathogenetic viewpoint, and provides a review of the evidence from clinical trials on combined pharmacotherapy for liver disease.

Thiobarbituric acid reactive substances in dogs with spontaneous hypercortisolism

Thiobarbituric acid reactive substances (TBARS) are laboratory markers of oxidative stress, which can be used to evaluate the lipid peroxidation that characterizes cell membrane damage caused by excess free radicals. This prospective study aimed to assess TBARS as a parameter of lipid peroxidation in dogs with spontaneous hypercortisolism (HC) at the time of diagnosis, and after trilostane treatment. Furthermore, it aimed to investigate the correlations between TBARS levels, and laboratory and cardiovascular parameters. Sixteen dogs with HC were evaluated at 3 different time points: At diagnosis (T0), 6 mo after treatment (T1), and 12 mo after trilostane treatment (T2). A control group (n = 20) of dogs with a demographic profile similar to the HC group, but considered healthy was selected and evaluated. There was a significant difference (P < 0.001) in TBARS levels between the HC group at diagnosis (4.38 ± 1.16 nmoles MDA/mg protein) and the control group (2.15 ± 0.45 nmoles MDA/mg protein). Dogs in the HC group exhibited a significant reduction (P < 0.001) in TBARS levels after treatment. There was no significant difference in TBARS levels between the control group and the HC group at T1 and T2 evaluation. TBARS positively correlated with left atrial dimensions and hematocrit. The study demonstrates that lipid peroxidation is increased in canine HC and suggests that control of the disease is beneficial to normalize the state of oxidative stress.

Silybin Alleviates Experimental Autoimmune Encephalomyelitis by Suppressing Dendritic Cell Activation and Th17 Cell Differentiation

Silybin, a peculiar flavonoid compound derived from the fruit and seeds of Silybum marianum, exhibits strong anti-inflammatory activities. In the present study, we found that silybin effectively alleviated experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), via inhibition of dendritic cell (DC) activation and Th17 cell differentiation. Silybin treatment greatly ameliorated the disease severity and significantly declined inflammation and demyelination of the central nervous system (CNS) of EAE mice. Consistent with the disease development, silybin-treated bone marrow-derived DCs (BM-DCs) exhibited reduced costimulatory molecules (e.g., CD80 and CD86) and MHC II expression. These results demonstrated the distinguished bioactivity of silybin for suppressing DC activation, inhibiting pathogenic Th17 inflammatory cell responses, and, eventually, alleviating EAE severity. Taken together, our results show that silybin has high potential for the development of a novel therapeutic agent for the treatment of autoimmune diseases such as MS.

Cytotoxicity of Cultured Canine Primary Hepatocytes Exposed to Itraconazole Is Decreased by Pre-treatment With Glutathione

Objective: To identify the effect of glutathione (GSH) on cell survival in a novel in vitro model of itraconazole (ITZ)-associated hepatotoxicity using canine primary hepatocytes.

Sample: Commercially sourced, cryopreserved male dog (Beagle) primary hepatocytes from a single donor.

Procedures: Using a sandwich culture technique, canine primary hepatocytes were exposed to serial dilutions of ITZ. Calcein AM, 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT), and neutral red were investigated as potential cell viability assays. Hepatocytes were then pre-incubated with GSH, exposed to serial dilutions of ITZ, and cell viability determined at 4 and 24 h post-ITZ exposure. Each condition was performed in technical triplicate and the effect of time, GSH concentration, and ITZ concentration on % cytotoxicity assessed using a multivariate linear regression model. Tukey's post-hoc test was used to detect individual differences.

Results: The neutral red cell cytotoxicity assay was chosen based on its superior ability to detect dose-dependent changes in viability. Hepatocyte cytotoxicity significantly increased with ITZ concentration (P < 0.001) and time (P = 0.004) and significantly decreased with GSH treatment (P < 0.001).

Conclusions and Clinical Relevance: This in vitro model demonstrates dose- and time-dependent ITZ-induced cytotoxicity, which is similar to clinical changes observed in canine patients and in in vivo rodent studies. Pre-treating with GSH is protective against in vitro cell death. These results suggest that GSH precursors may have a role in the management or prevention of ITZ-associated hepatotoxicity in dogs. Clinical trials are needed to evaluate their utility for this adverse drug reaction.

S-adenosylmethionine: A metabolite critical to the regulation of autophagy

Autophagy is a mechanism that enables cells to maintain cellular homeostasis by removing damaged materials and mobilizing energy reserves in conditions of starvation. Although nutrient availability strongly impacts the process of autophagy, the specific metabolites that regulate autophagic responses have not yet been determined. Recent results indicate that S-adenosylmethionine (SAM) represents a critical inhibitor of methionine starvation-induced autophagy. SAM is primarily involved in four key metabolic pathways: transmethylation, transsulphuration, polyamine synthesis and 5'-deoxyadenosyl 5'-radical-mediated biochemical transformations. SAM is the sole methyl group donor involved in the methylation of DNA, RNA and histones, modulating the autophagic process by mediating epigenetic effects. Moreover, the metabolites of SAM, such as homocysteine, glutathione, decarboxylated SAM and spermidine, also exert important influences on the regulation of autophagy. From our perspective, nuclear-cytosolic SAM is a conserved metabolic inhibitor that connects cellular metabolic status and the regulation of autophagy. In the future, SAM might be a new target of autophagy regulators and be widely used in the treatment of various diseases.

Pre-treatment With PLGA/Silibinin Nanoparticles Mitigates Dacarbazine-Induced Hepatotoxicity

Drug-induced hepatotoxicity is one of the major barriers limiting application of current pharmaceuticals as well as clinical translation of novel and perspective drugs. In this context, numerous hepatoprotective molecules have been proposed to prevent or mitigate drug-induced hepatotoxicity. To date, silibinin (SBN) is a one the most studied hepatoprotective plant-derived agents for prevention/alleviation of drug-induced liver injury. Hepatoprotective mechanisms of SBN include scavenging of free radicals, upregulation of detoxifying enzymes via Nrf2 activation and inhibition of inflammatory activation of resident macrophages. However, low solubility of this phytochemical in water prevents its intravenous administration and constrains its bioavailability and efficacy. Here, we developed SBN-loaded poly(lactic-co-glycolic) acid (PLGA)-based nanoparticles for intravenous administration aiming at mitigation of drug-induced hepatotoxicity. Obtained nanoparticles demonstrated a slow drug release profile in vitro and caused upregulation of antioxidant and phase II enzymes in AML12 hepatocytes including superoxide dismutase 2, glutathione-S-transferase P1, and glutathione-reductase. Intravenous administration of PLGA nanoparticles to mice led to their fast liver accumulation. In vivo analysis of hepatoprotective effects of PLGA/SBN nanoparticles was carried out on melanoma tumor-bearing syngeneic mouse model treated with the antineoplastic drug dacarbazine (DTIC), which often causes severe hepatotoxicity including development of veno-occlusive disease. It was found that PLGA/SBN caused effective induction of detoxifying liver enzymes. Moreover, pre-treatment with PLGA/SBN nanoparticles reduced elevated transaminase and bilirubin levels in blood, caspase 3 activation, and morphological histology changes in liver tissue upon DTIC treatment. Treatment with PLGA/SBN nanoparticles did not interfere with therapeutic efficacy of DTIC.

Flavolignans from Silymarin as Nrf2 Bioactivators and Their Therapeutic Applications

Silymarin (SM) is a mixture of flavolignans extracted from the seeds of species derived from Silybum marianum, commonly known as milk thistle or St. Mary'sthistle. These species have been widely used in the treatment of liver disorders in traditional medicine since ancient times. Several properties had been attributed to the major SM flavolignans components, identified as silybin, isosilybin, silychristin, isosilychristin, and silydianin. Previous research reported antioxidant and protective activities, which are probably related to the activation of the nuclear factor erythroid 2 (NFE2)-related factor 2 (Nrf2), known as a master regulator of the cytoprotector response. Nrf2 is a redox-sensitive nuclear transcription factor able to induce the downstream-associated genes. The disruption of Nrf2 signaling has been associated with different pathological conditions. Some identified phytochemicals from SM had shown to participate in the Nrf2 signaling pathway; in particular, they have been suggested as activators that disrupt interactions in the Keap1-Nrf2 system, but also as antioxidants or with additional actions regarding Nrf2 regulation. Thus, the study of these molecules makes them appear attractive as novel targets for the treatment or prevention of several diseases.

Evidences on Molecules Most Frequently Included in Canine and Feline Complementary Feed to Support Liver Function

Numerous complementary feeds to support liver function are commercially available for small animals. Aiming to furnish a scientific support for clinicians/nutritionists that necessitate a complementary feed to support liver function in dogs and cats, with the present paper, we analyzed scientific evidences supporting the use, for this purpose, of ingredients/additives such as artichoke (Cynara scolymus), curcumin, dandelion (Taraxacum officinale), milk thistle (Silybum marianum), phosphatidylcholine, and S-adenosylmethionine. Although sustained by significant results, our review found only few scientific papers, and albeit we believe that they represent a significant aid in handling hepatopathies, in the authors' opinion, this topic probably deserves, and would benefit of, further studies.

Gallbladder Agenesis in a Dog: Clinicopathological, Histopathology, and Computed Tomography Findings

Three cases of gallbladder agenesis (GA) have been previously reported in the English-speaking veterinary literature. Affected dogs can be either asymptomatic or symptomatic with vomiting, retching, and anorexia previously reported. The previously reported cases and the dog in this report had marked elevations in alanine aminotransferase concentrations, and liver histopathology consistently showed bridging fibrosis and biliary hyperplasia. The condition is most often diagnosed in humans during exploratory surgery, which was also the case in the previous three dogs reported with GA. Computed tomography (CT) or MRI is now recommended for diagnosis of the condition in humans, and this is the first report of CT findings in an affected dog diagnosed without surgery. Bile stasis and cholangiohepatits have been proposed as secondary pathologies in both humans and dogs with GA, and histopathology and CT findings in this case support those theories.

Prophylactic Therapy of Silymarin (Milk Thistle) on Antituberculosis Drug-Induced Liver Injury: A Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Prophylactic therapy with silymarin to prevent the development of antituberculosis drug-induced liver injury (anti-TB DILI) has been under debate. We aimed to evaluate the effect of silymarin in the prevention of anti-TB DILI.

METHODS

We searched MEDLINE, PubMed, Embase, and Cochrane Central Register of Controlled Trials (CENTRAL) up to 30th November 2018. Randomized controlled trials (RCTs) that compared silymarin and placebo to prevent anti-TB DILI were included. All statistical analyses were conducted using STATA 12.0 software. Standardized mean difference (SMD) and risk ratio (RR) with 95% confidence intervals (CIs) were used to evaluate the effect of silymarin. The quality of included studies was assessed according to Cochrane handbook. Funnel plots and Egger's tests were carried out to evaluate publication bias. Sensitivity analysis was conducted to assess the influence of each study.

RESULTS

A total of 1198 patients from five RCTs (585 with silymarin and 613 with placebo groups) were included. Overall, silymarin significantly reduced the occurrence of anti-TB DILI at week 4 [RR: 0.33, 95% CI (0.15, 0.75)]. In addition, silymarin exerted protective effect on liver function in patients undergoing anti-TB drugs [SMD = - 0.15, 95% CI (-0.24, -0.07), P < 0.001 (ALT); SMD =-0.14, 95% CI (-0.23, -0.06), P = 0.001(AST); SMD =-0.12, 95% CI (-0.20, -0.03), P = 0.008 (ALP)]. Silymarin led to similar AEs in placebo groups [OR: 1.09, 95% CI (0.86, 1.39), P = 0.47].

CONCLUSION

Prophylactic therapy of silymarin is contributed to a noticeably reduced risk of development of anti-TB DILI four weeks after the initiation. In addition, silymarin significantly improved the liver function in patients who are receiving anti-TB drugs.

Zinc toxicosis in a dog secondary to prolonged zinc oxide ingestion

Zinc toxicosis is commonly associated with ingestion of metallic zinc objects. This report documents an uncommon presentation of zinc toxicosis, secondary to prolonged ingestion of a zinc oxide cream. A 5.6 kg 6-year-old ovariohysterectomised female Poodle cross presented as a transfer to an emergency practice for severe anaemia, pigmenturia, weakness, and inappetence. She had a history of vomiting and nine days of diarrhoea. Amongst other supportive treatments, a zinc oxide cream had been applied to her hind end due to severe diarrhoea scalding, and in hindsight, the owners realised she had ingested large quantities of this cream. She developed a severe Heinz body haemolytic anaemia, along with spherocytosis, left-shift neutrophilia, prolonged activated partial thromboplastin time, and mildly elevated blood urea nitrogen. The serum zinc concentration was markedly elevated. She was treated supportively and made a full recovery. This case illustrates the importance of a thorough medical history. Zinc toxicosis can have a good prognosis when diagnosed and treated promptly.

Inducers of Senescence, Toxic Compounds, and Senolytics: The Multiple Faces of Nrf2-Activating Phytochemicals in Cancer Adjuvant Therapy

The reactivation of senescence in cancer and the subsequent clearance of senescent cells are suggested as therapeutic intervention in the eradication of cancer. Several natural compounds that activate Nrf2 (nuclear factor erythroid-derived 2-related factor 2) pathway, which is involved in complex cytoprotective responses, have been paradoxically shown to induce cell death or senescence in cancer. Promoting the cytoprotective Nrf2 pathway may be desirable for chemoprevention, but it might be detrimental in later stages and advanced cancers. However, senolytic activity shown by some Nrf2-activating compounds could be used to target senescent cancer cells (particularly in aged immune-depressed organisms) that escape immunosurveillance. We herein describe in vitro and in vivo effects of fifteen Nrf2-interacting natural compounds (tocotrienols, curcumin, epigallocatechin gallate, quercetin, genistein, resveratrol, silybin, phenethyl isothiocyanate, sulforaphane, triptolide, allicin, berberine, piperlongumine, fisetin, and phloretin) on cellular senescence and discuss their use in adjuvant cancer therapy. In light of available literature, it can be concluded that the meaning and the potential of adjuvant therapy with natural compounds in humans remain unclear, also taking into account the existence of few clinical trials mostly characterized by uncertain results. Further studies are needed to investigate the therapeutic potential of those compounds that display senolytic activity.

S-adenosylmethionine reduces airway inflammation and fibrosis in a murine model of chronic severe asthma via suppression of oxidative stress

Increased oxidative stress has an important role in asthmatic airway inflammation and remodeling. A potent methyl donor, S-adenosylmethionine (SAMe), is known to protect against tissue injury and fibrosis through modulation of oxidative stress. The aim of this study was to evaluate the effect of SAMe on airway inflammation and remodeling in a murine model of chronic asthma. A mouse model was generated by repeated intranasal challenge with ovalbumin and Aspergillus fungal protease twice a week for 8 weeks. SAMe was orally administered every 24 h for 8 weeks. We performed bronchoalveolar lavage (BAL) fluid analysis and histopathological examination. The levels of various cytokines and 4-hydroxy-2-nonenal (HNE) were measured in the lung tissue. Cultured macrophages and fibroblasts were employed to evaluate the underlying anti-inflammatory and antifibrotic mechanisms of SAMe. The magnitude of airway inflammation and fibrosis, as well as the total BAL cell counts, were significantly suppressed in the SAMe-treated groups. A reduction in T helper type 2 pro-inflammatory cytokines and HNE levels was observed in mouse lung tissue after SAMe administration. Macrophages cultured with SAMe also showed reduced cellular oxidative stress and pro-inflammatory cytokine production. Moreover, SAMe treatment attenuated transforming growth factor-β (TGF-β)-induced fibronectin expression in cultured fibroblasts. SAMe had a suppressive effect on airway inflammation and fibrosis in a mouse model of chronic asthma, at least partially through the attenuation of oxidative stress and TGF-β-induced fibronectin expression. The results of this study suggest a potential role for SAMe as a novel therapeutic agent in chronic asthma.

Protective Effect of Tyrosol and S-Adenosylmethionine against Ethanol-Induced Oxidative Stress of Hepg2 Cells Involves Sirtuin 1, P53 and Erk1/2 Signaling

Oxidative stress plays a major role in ethanol-induced liver damage, and agents with antioxidant properties are promising as therapeutic opportunities in alcoholic liver disease. In the present work, we investigated the effect of S-adenosylmethionine (AdoMet), Tyrosol (Tyr), and their combination on HepG2 cells exposed to ethanol exploring the potential molecular mechanisms. We exposed HepG2 cells to 1 M ethanol for 4 and 48 h; thereafter, we recorded a decreased cell viability, increase of intracellular reactive oxygen species (ROS) and lipid accumulation, and the release into culture medium of markers of liver disease such as triacylglycerol, cholesterol, transaminases, albumin, ferritin, and homocysteine. On the other hand, AdoMet and Tyrosol were able to attenuate or antagonize these adverse changes induced by acute exposure to ethanol. The protective effects were paralleled by increased Sirtuin 1 protein expression and nuclear translocation and increased ERK1/2 phosphorylation that were both responsible for the protection of cells from apoptosis. Moreover, AdoMet increased p53 and p21 expression, while Tyrosol reduced p21 expression and enhanced the expression of uncleaved caspase 3 and 9, suggesting that its protective effect may be related to the inhibition of the apoptotic machinery. Altogether, our data show that AdoMet and Tyrosol exert beneficial effects in ethanol-induced oxidative stress in HepG2 cells and provide a rationale for their potential use in combination in the prevention of ethanol-induced liver damage.

A double-blinded randomized controlled trial of silymarin for the prevention of antituberculosis drug-induced liver injury

Background

Hepatitis is a common adverse effect of antituberculosis drugs. Silymarin prevented drug-induced hepatoxicity in animals with anti-oxidative mechanisms but its effect in human has been unknown. We aimed to evaluate the efficacy of silymarin for preventing antituberculosis-drug induced liver injury (antiTB-DILI) in patients with tuberculosis.

Methods

A double-blind randomized placebo-controlled trial was performed. Tuberculosis patients were randomly allocated to receive placebo or silymarin. The outcomes of interests were antiTB-DILI and the maximum liver enzymes at week 4. Antioxidative enzymes (i.e., superoxide dismutase (SOD), glutathione and malondialdehyde assays) were assessed. The risks of antiTB-DILI between the two groups were compared. A number need to treat was estimated.

Results

A total of 55 out of 70 expected numbers of patients were enrolled. There were 1/27 (3.7 %) and 9/28 (32.1 %) patients who developed antiTB-DILI in the silymarin and the placebo groups. Risk reduction was 0.28 (0.10, 0.47), i.e., receiving silymarin was 28 % at lower risk for antiTB-DILI than placebo. This led to prevention of 28 patients from being antiTB-DILI among 100 treated patients. Median (IQR) of ALT levels at week 4 in the placebo and the silymarin group were 35.0 (15, 415) IU/L and 31.5 (20, 184) IU/L (p = 0.455). The decline of SOD level at week 4 in the silymarin group was less than the placebo group (p < 0.027).

Conclusions

Silymarin reduced the incidence of antiTB-DILI. The benefit of silymarin may be explained from superoxide dismutase restoration. Larger clinical trials are required to confirm the result of our small study [Clinicaltrials.Gov Identifier Nct01800487].