The Protective Effect of Silibinin Against Mitomycin C–Induced Intrinsic Apoptosis in Human Melanoma A375-S2 Cells

Protective effect of Anneslea fragrans ethanolic extract against CCl4-induced liver injury by inhibiting inflammatory response, oxidative stress and apoptosis

Anneslea Fragrans Wall. (AF) is a medicinal and edible plant distributed in China. Its leaves and bark generally used for the treatments of diarrhea, fever, and liver diseases. While its ethnopharmacological application against liver diseases has not been fully studied. This study was aimed to evaluate the hepatoprotective effect of ethanolic extract from A. fragrans (AFE) on CCl₄ induced liver injury in mice. The results showed that AFE could effectively reduce plasma activities of ALT and AST, increase antioxidant enzymes activities (SOD and CAT) and GSH level, and decrease MDA content in CCl₄ induced mice. AFE effectively decreased the expressions of inflammatory cytokines (IL-1β, IL-6, TNF-α, COX-2 and iNOS), cell apoptosis-related proteins (Bax, caspase-3 and caspase-9) and increased Bcl-2 protein expression via inhibiting MAPK/ERK pathway. Additionally, TUNEL staining, Masson and Sirius red staining, immunohistochemical analyses revealed that AFE could inhibit the CCl₄-induced hepatic fibrosis formation via reducing depositions of α-SMA, collagen I and collagen III. Conclusively, the present study demonstrated that AFE had an hepatoprotective effect by MAPK/ERK pathway to inhibit oxidative stress, inflammatory response and apoptosis in CCl₄-induced liver injury mice, suggesting that AFE might be served as a hepatoprotective ingredient in the prevention and treatment of liver injury.

Silymarin prevents apoptosis through inhibiting the Bax/caspase-3 expression and suppresses toll like receptor-4 pathway in the SNc of 6-OHDA intoxicated rats

BACKGROUND AND PURPOSE

Several lines of evidence show that apoptosis, oxidative stress and neuroinflammation are associated with the development of Parkinson's disease (PD). In the present study, we investigated the effect of pre-treatment with silymarin (SM) on oxidative stress, apoptosis and toll-like receptor 4 (TLR4) expression in substantia nigra pars copmacta (SNc) of 6-hydroxydopamine (6-OHDA)-lesioned rats.

METHODS

Animals were pretreated with 100, 200 or 300 mg/kg of SM daily for 5 days and at 6th day 6-OHDA (8 μg/2 μl) was infused unilaterally into the central region of the SNc.

RESULTS

6-OHDA decreased the total glutathione and antioxidant enzymes activity in the SNc. Interestingly, we found that 6-OHDA caused to TLR4 up regulation. The SNc levels of glutathione, superoxide dismutase, glutathione peroxidase, glutathione reductase and catalase were significantly higher in the SM pretreated rats. SM strongly decreased 6-OHDA-induced elevation of SNc apoptosis, caspase-3 and Bax/Bcl-2 ratio. Furthermore, SM markedly (p < 0.001) prevented from SNc over expression of TLR4 caused by 6-OHDA. A significantly high positive correlation was seen between TLR4 activity with caspase-3 protein levels (r = 0.896, P < 0.01), Bax protein levels (r = 0.96, P < 0.01).

CONCLUSION

Pre-treatment of 6-OHDA-lesioned rats with SM reduces SNc neuronal apoptosis possibly through inhibition of TLR4 over expression. Further clinical study should be carried out to prove potential application of SM for protection against PD in susceptible individuals.

Silibinin Induced Human Glioblastoma Cell Apoptosis Concomitant with Autophagy through Simultaneous Inhibition of mTOR and YAP

Silibinin, also known as silybin, is the major flavonolignan isolated from Silybum marianum. Although previous reports demonstrated that silibinin exhibits significant tumor suppressor activities in various cancers by promoting cell apoptosis, it was also shown to trigger autophagy to counteract apoptosis induced by exogenous stresses in several types of cells. However, there is no report to address the role of silibinin induced autophagy in human A172 and SR glioblastoma cells. Our study showed that silibinin treatment not only inhibited the metabolic activities of glioblastoma cells but also promoted their apoptosis through the regulation of caspase 3 and PARP-1 in concentration- and time-dependent manners. Meanwhile, silibinin induced autophagy through upregulation of microtubule-associated protein a light chain 3- (LC3-) II. And autophagy inhibition with chloroquine, a lysosomotropic agent, significantly enhanced silibinin induced glioblastoma cell apoptosis. Moreover, silibinin dose-dependently downregulated the phosphorylation levels of mTOR at Ser-2448, p70S6K at Thr-389, and 4E-BP1 at Thr-37/46. Furthermore, the expression of YAP, the downstream effector of Hippo signal pathway, was also suppressed by silibinin. These results suggested that silibinin induced glioblastoma cell apoptosis concomitant with autophagy which might be due to simultaneous inhibition of mTOR and YAP and silibinin induced autophagy exerted a protective role against cell apoptosis in both A172 and SR cells.

Immunosuppressive properties of mitomycin C-incubated human myeloid blood cells (MIC) in vitro

Previous animal studies showed that donor-derived blood cells treated with mitomycin C (MMC) prolong allograft survival when injected into recipients. This model was effective with whole blood, peripheral blood mononuclear cells (PBMC) (monocytes being the active cell subpopulation) or dendritic cells. In view of a potential clinical application, we study now the immunosuppressive properties of human myeloid cells in vitro. Mature dendritic cells (generated from naïve monocytes) or monocytes treated with mitomycin C do not or only weakly inhibit allogeneic T cells in vitro, whereas cells in an early differentiation state between monocytes and DC exert suppressive activity when treated with MMC. In contrast, DC generated from MMC-treated monocytes show the morphology and phenotype of early immature DC (iDC) and suppress T-cell responses. It is known that untreated monocytes injected into a recipient encounter a cytokine milieu which differentiates them to stimulatory DC. In our in vitro experiment MMC-treated monocytes cultured in a DC-maturing milieu transform themselves into suppressive early iDC. This reproduces a process which takes place when administering MMC-monocytes to a recipient. In conclusion, human MMC-DC or MMC-monocytes are not or only weakly suppressive in vitro. When MMC-monocytes are differentiated to DC the resulting cells become suppressive.

Silymarin as a Natural Antioxidant: An Overview of the Current Evidence and Perspectives

Silymarin (SM), an extract from the Silybum marianum (milk thistle) plant containing various flavonolignans (with silybin being the major one), has received a tremendous amount of attention over the last decade as a herbal remedy for liver treatment. In many cases, the antioxidant properties of SM are considered to be responsible for its protective actions. Possible antioxidant mechanisms of SM are evaluated in this review. (1) Direct scavenging free radicals and chelating free Fe and Cu are mainly effective in the gut. (2) Preventing free radical formation by inhibiting specific ROS-producing enzymes, or improving an integrity of mitochondria in stress conditions, are of great importance. (3) Maintaining an optimal redox balance in the cell by activating a range of antioxidant enzymes and non-enzymatic antioxidants, mainly via Nrf2 activation is probably the main driving force of antioxidant (AO)  action of SM. (4) Decreasing inflammatory responses by inhibiting NF-κB pathways is an emerging mechanism of SM protective effects in liver toxicity and various liver diseases. (5) Activating vitagenes, responsible for synthesis of protective molecules, including heat shock proteins (HSPs), thioredoxin and sirtuins and providing additional protection in stress conditions deserves more attention. (6) Affecting the microenvironment of the gut, including SM-bacteria interactions, awaits future investigations. (7) In animal nutrition and disease prevention strategy, SM alone, or in combination with other hepatho-active compounds (carnitine, betaine, vitamin B₁₂, etc.), might have similar hepatoprotective effects as described in human nutrition.

The Fanconi anemia pathway sensitizes to DNA alkylating agents by inducing JNK-p53-dependent mitochondrial apoptosis in breast cancer cells

The Fanconi anemia/BRCA (FA/BRCA) DNA damage repair pathway plays a pivotal role in the cellular response to DNA alkylating agents and greatly influences drug response in cancer treatment. However, the molecular mechanisms underlying the FA/BRCA pathway reversed resistance have received limited attention. In the present study, we investigated the effect of Fanconi anemia complementation group F protein (FANCF), a critical factor of the FA/BRCA pathway, on cancer cell apoptosis induced by DNA alkylating agents such as mitomycin c (MMC). We found that FANCF shRNA potentiated MMC-induced cytotoxicity and apoptosis in MCF-7 and MDA-MB-231 breast cancer cells. At a mechanistic level, FANCF shRNA downregulated the anti-apoptotic protein Bcl-2 and upregulated the pro-apoptotic protein Bax, accompanied by release of cyt-c and smac into the cytosol in MMC-treated cells. Furthermore, activation of caspase-3 and -9, other than caspase-8, cleavage of poly(ADP ribose) polymerase (PARP), and a decrease of mitochondrial membrane potential (MMP) indicated that involvement of the mitochondrial apoptotic pathway in FANCF silencing of MMC-treated breast cancer cells. A decrease in IAP family proteins XIAP and survivin were also observed following FANCF silencing in MMC-treated breast cancer cells. Notably, FANCF shRNA was able to increase p53 levels through activation of the JNK pathway in MMC-treated breast cancer cells. Furthermore, p53 inhibition using pifithrin-α abolished the induction of caspase-3 and PARP by FANCF shRNA and MMC, indicating that MMC-induced apoptosis is substantially enhanced by FANCF shRNA via p53-dependent mechanisms. To our knowledge, we provide new evidence for the potential application of FANCF as a chemosensitizer in breast cancer therapy.

Silencing of fanconi anemia complementation group f exhibits potent chemosensitization of mitomycin C activity in breast cancer cells

PURPOSE

Fanconi anemia complementation group F (FANCF) is a key factor to maintaining the function of Fanconi anaemia/BRCA (FA/BRCA) pathway, a DNA-damage response pathway. However, the functional role of FANCF in breast cancer has not been elucidated. In the present study, we evaluated the chemosensitization effect of FANCF in breast cancer cells.

METHODS

We performed specific knockdown of the endogenous FANCF in breast cancer cells by transfecting the cells with an FANCF short hairpin RNA (shRNA) vector. Cell viability was measured with a Cell Counting Kit-8, and DNA damage was assessed with the alkaline comet assay. The apoptosis, cell cycle, and drug accumulation were measured by flow cytometric analysis. Protein expression levels were determined by Western blot analysis, using specific antibodies.

RESULTS

The analyses of two breast cancer cell lines (MCF-7 and MDA-MB-435S) demonstrated that the FANCF shRNA could effectively block the FA/BRCA pathway through the inhibition of Fanconi anemia complementation group D2 ubiquitination. Moreover, FANCF silencing potentiated the sensitivity of cells to mitomycin C (MMC), where combined FANCF shRNA/MMC treatment inhibited cell proliferation, induced S-phase arrest, apoptosis, and DNA fragmentation, and reduced the mitochondrial membrane potential, compared with MMC treatment alone.

CONCLUSION

Taken together, this study demonstrates that the inhibition of FANCF by its shRNA leads to a synergistic enhancement of MMC cytotoxicity in breast cancer cells. These results suggest that the inhibition of the FA/BRCA pathway is a useful adjunct to cytotoxic chemotherapy for the treatment of breast cancer.

Inhibition of c-Met promoted apoptosis, autophagy and loss of the mitochondrial transmembrane potential in oridonin-induced A549 lung cancer cells

OBJECTIVE

Herein, inhibition of hepatocyte growth factor receptor, c-Met, significantly increased cytochrome c release and Bax/Bcl-2 ratio, indicating that c-Met played an anti-apoptotic role. The following experiments are to elucidate this anti-apoptotic mechanism, then the effect of c-Met on autophagy has also been discussed.

METHODS

Investigated was the influence of c-Met on apoptosis, autophagy and loss of mitochondrial transmembrane potential (Δψm), and the relevant proteins were examined.

KEY FINDINGS

First, we found that activation of extracellular signal-regulated kinase (ERK), p53 was promoted by c-Met interference. Subsequent studies indicated that ERK was the upstream effector of p53, and this ERK-p53 pathway mediated release of cytochrome c and up-regulation of Bax/Bcl-2 ratio. Secondly, the inhibition of c-Met augmented oridonin-induced loss of mitochondrial transmembrane potential (Δψm), resulting apoptosis. Finally, the inhibition of c-Met increased oridonin-induced A549 cell autophagy accompanied by Beclin-1 activation and conversion from microtubule-associated protein light chain 3 (LC3)-I to LC3-II. Activation of ERK-p53 was also detected in autophagy process and could be augmented by inhibition of c-Met. Moreover, suppression of autophagy by 3-methyladenine (3-MA) or small interfering RNA against Beclin-1 or Atg5 decreased oridonin-induced apoptosis. Inhibition of apoptosis by pan-caspase inhibitor (z-VAD-fmk) decreased oridonin-induced autophagy as well and Loss of Δψm also occurred during autophagic process.

CONCLUSION

Thus, inhibiting c-Met enhanced oridonin-induced apoptosis, autophagy and loss of Δψm in A549 cells.

Apoptosis induction by OTA and TNF-α in cultured primary rat hepatocytes and prevention by silibinin

In cultures of primary rat hepatocytes, apoptosis occurred after application of 20 ng/mL tumor necrosis factor alpha (TNF-α). However, this was only in the presence of 200 ng/mL of the transcriptional inhibitor actinomycin D (ActD). This toxic effect was completely prevented in the presence of 25 µg/mL soluble TNF-α receptor I (sTNFR I) in the supernatant of hepatocyte cell cultures. Apoptosis also occurred after application of 12.5 µmol/L ochratoxin A (OTA). However, that was not prevented by up to 500 µg/mL sTNFR I, indicating that TNF-α/TNFR I is not involved in OTA mediated apoptosis in hepatocytes. The antioxidative flavanolignan silibinin in doses from 130 to 260 µmol/L prevented chromatin condensation, caspase-3 activation, and apoptotic DNA fragmentation that were induced by OTA, by 10 mmol/L hydrogen peroxide (H₂O₂) and by ultraviolet (UV-C) light (50 mJ/cm²), respectively. To achieve protection by silibinin, the drug was applied to the cell cultures for 2 h in advance. OTA stimulated lipid peroxidation on cultured immortalized rat liver HPCT cells, as was revealed by malondialdehyde (MDA) production. Lipid peroxidation occurred further by H₂O₂ and ActD/TNF-α incubation. These reactions were also suppressed by silibinin pretreatment. We conclude that the anti-apoptotic activity of silibinin against OTA, H₂O₂ and ActD/ TNF-α is caused in vitro by the antioxidative effects of the flavanolignan. Furthermore, cytotoxicity of the pro-apoptotic toxins was revealed by MTT-test. When applied separately, ActD and TNF-α showed no cytotoxic effects after 24 h, but were cytotoxic if applied in combination. The used concentrations of OTA, H₂O₂ and the dose of UV-C caused a substantial decrease in viability within 36 h that was prevented mostly by silibinin. We conclude that silibinin is a potent protective compound against apoptosis and cytotoxicity caused by OTA and the investigated compounds.

Interruption of mitochondrial complex IV activity and cytochrome c expression activated O₂·⁻-mediated cell survival in silibinin-treated human melanoma A375-S2 cells via IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC pathways

Silibinin was reported to have high cyto-toxicity in many malignant cell lines, however, it showed low cyto-toxicity in treatment of human melanoma A375-S2 cells and even protected these cells against certain stress insults. Reactive oxygen species was reported to have controversial effects on cancer chemotherapy. In this study we investigated the mechanism of reactive oxygen species generation and the role of reactive oxygen species in protecting cells against silibinin induced cyto-toxicity in A375-S2 cells. We found that silibinin induced the generation of large amount of superoxide anion (O(2)(∙-)) and small amount of hydrogen peroxide (H(2)O(2)) through down-regulating the activity of mitochondrial complex IV and the protein level of cytochrome c. We also discovered that O(2)(∙-) generation activated insulin like growth factor-1 receptor (IGF-1R) and its down-stream phosphatidylinositol 3-kinases-Akt (PI3K-Akt) and phospholipase C γ-protein kinase C (PLC γ-PKC) signaling pathways, which were augmented by H(2)O(2) scavenger catalase. Scavenging O(2)(∙-) by superoxide dismutase (SOD) or inhibition of IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC signaling pathways increased cell apoptosis. Therefore, O(2)(∙-) mediated cell resistance to silibinin via activating IGF-1R-PI3K-Akt and IGF-1R-PLC γ-PKC pathways in silibinin treated A375-S2 cells.

Silibinin pretreatment protects against ochratoxin A-mediated apoptosis in primary rat hepatocytes

The inhibitory effect of silibinin on ochratoxin A (OTA)-mediated apoptosis on primary rat hepatocytes was investigated. Rat hepatocytes were prepared by two different methods: the classical enzymatic digestion method by collagenase perfusion and a new EDTA-perfusion method. The EDTA-perfusion method yielded hepatocytes, which were stably cultivated without DNA fragmentation for up to 96 h, whereas the collagenase-prepared hepatocytes showed apoptosis events as early as from the start of preparation even in the absence of OTA. Treatment with 12.5 μmol/l OTA of cultured hepatocytes prepared under ETDA perfusion developed DNA-laddering after 24-36 h. Lipopolysaccharide (LPS) of 0.1 up to 12.5 μg/ml showed no apoptotic DNA-effects under these conditions. A low concentration of 26 μmol/l silibinin given prior to OTA slightly prevented OTA-mediated DNA-laddering, whereas a five times higher concentration of silibinin (130 μmol/l) completely inhibited OTA-mediated apoptosis. Under the same conditions, caspase-3 activity in hepatocytes increased in a time-dependent manner under OTA exposure within 12-24 h but was blocked by 130 μmol/l silibinin. In contrast, LPS incubation for 12 and 24 h did not alter caspase-3 activity. To measure viability of OTA-/LPS-treated hepatocytes, the MTT-test and Live/Dead kit were applied. The results demonstrated that the used OTA concentration of 12.5 μmol/l only moderately decreased viability for up to 24 h but showed cytotoxic effects depending on longer incubation times (≥36 h). In contrast, LPS up to 12.5 μg/ml exhibited no cytotoxic effects up to 48 h. In summary, our results showed contrasting effects on apoptosis in primary rat hepatocytes by OTA (produces apoptosis) versus LPS (produces no apoptosis), also depending on the method of hepatocyte preparation. Silibinin at 130 μmol/l showed significant hepatoprotective and antiapoptotic effects against OTA-mediated cell damage on cultured rat hepatocytes.

Botanicals for the prevention and treatment of cutaneous melanoma

Cutaneous melanoma, a cancer of melanocytes, when detected at later stages is arguably one of the most lethal cancers and the cause of more years of lost life than any other cancer among young adults. There is no standard therapy for advanced-stage melanoma and the median survival time for patients with metastatic melanoma is <1 yr. An urgent need for novel strategies against melanoma has directed research towards the development of new chemotherapeutic and biologic agents that can target the tumor by several different mechanisms. Recently, several dietary agents are being investigated for their role in the prevention and treatment of various forms of cancer and may represent the future modality of the treatment. Here, we have reviewed emerging data on botanicals that are showing promise for their potential inhibitory effect against cutaneous melanoma.