Probucol suppresses human glioma cell proliferation in vitro via ROS production and LKB1-AMPK activation

PGC-1α promotes colorectal carcinoma metastasis through regulating ABCA1 transcription

Colorectal cancer (CRC) is a highly aggressive cancer in which metastasis plays a key role. However, the mechanisms underlying metastasis have not been fully elucidated. Peroxisome proliferator-activated receptor gamma coactivator 1α (PGC-1α), a regulator of mitochondrial function, has been reported as a complicated factor in cancer. In this study, we found that PGC-1α was highly expressed in CRC tissues and was positively correlated with lymph node and liver metastasis. Subsequently, PGC-1α knockdown was shown to inhibit CRC growth and metastasis in both in vitro and in vivo studies. Transcriptomic analysis revealed that PGC-1α regulated ATP-binding cassette transporter 1 (ABCA1) mediated cholesterol efflux. Mechanistically, PGC-1α interacted with YY1 to promote ABCA1 transcription, resulting in cholesterol efflux, which subsequently promoted CRC metastasis through epithelial-to-mesenchymal transition (EMT). In addition, the study identified the natural compound isoliquiritigenin (ISL) as an inhibitor that targeted ABCA1 and significantly reduced CRC metastasis induced by PGC-1α. Overall, this study sheds light on how PGC-1α promotes CRC metastasis by regulating ABCA1-mediated cholesterol efflux, providing a basis for further research to inhibit CRC metastasis.

Probucol Self-Emulsified Drug Delivery System: Stability Testing and Bioavailability Assessment in Human Volunteers

BACKGROUND

Self-Emulsifying Drug Delivery System (SEDDS), if taken orally, is expected to self-emulsify in GIT and improve the absorption and bioavailability. Probucol (PB) is a highly lipophilic compound with very low and variable bioavailability.

OBJECTIVE

The objectives of this study were to examine the stability and conduct bioavailability of the prepared Probucol Self-Emulsified Drug Delivery System (PBSEDDS) in human volunteers.

METHODS

The methods included preparation of different PBSEDDS using soybean oil (solvent), Labrafil M1944CS (surfactant) and Capmul MCM-C8 (co-surfactant). The formulations were characterized in vitro for spontaneity of emulsification, droplet size, turbidity and dissolution in water after packing in HPMC capsules. The optimized formulations were evaluated for stability at different storage temperatures and human bioavailability compared with the drug dissolved in soybean oil (reference).

RESULTS

The results showed that formulations (F1-F4) were stable if stored at 20 °C. The mean (n=3) pharmacokinetic parameters for stable formulations were: The Cmax, 1070.76, 883.16, 2876.43, 3513.46 and 1047.37 ng/ml; the Tmax, 7.93, 7.33, 3.96, 3.67 and 4.67 hr.; the AUC (0-t), 41043.41, 37763.23, 75006.26, 46731.36 and 26966.43 ng.hr/ml for F1, F2, F3, F4 and reference, respectively. The percentage relative bioavailability was in this order: F3> F4> F1> F2>.

CONCLUSION

In conclusion, the PBSEDDS formulations were stable at room temperature. F4 showed the highest Cmax and the shortest Tmax. All the formulations showed significant enhancement of bioavailability compared with the reference. The results illustrated the potential use of SEDDS for the delivery of probucol hydrophobic compound.

Cordyceps sinensis prevents contrast-induced nephropathy in diabetic rats: its underlying mechanism

Apoptosis is recognized as an important mechanism in contrast-induced nephropathy (CIN). This study investigated the renal protective effect of cordyceps sinensis (CS) in a diabetic rat model of CIN and the mechanism of its effect. Sixty SD rats were randomly divided into 4 groups, the control group, model group, probucol group, and CS group. We used a diabetic rat model of Iodixanol-induced CIN. Serum creatinine (Scr), blood urea nitrogen (BUN), urinary kidney injury molecule-1 (KIM-1), neutrophil gelatinase associated lipocalin (NGAL) levels were measured to evaluate renal function. Total antioxidative ability (T-AOC), superoxide dismutase (SOD), and malonaldehyde (MDA) levels were assessed to discuss the effect of probucol and CS on oxidative stress. The pathologic changes in the kidney were observed by hematoxylin and eosin (HE) staining and periodic acid-Schiff (PAS) staining. Apoptosis was assessed by transmission electron microscopy and TUNEL staining. Caspase-3, Bax, Bcl2 and phospho-p38 mitogen-activated protein kinase (MAPK) protein expressions were assessed by Western blotting. The model group of rats showed significantly elevated levels of BUN, Scr, urinary KIM-1, NGAL, and parameters of oxidative stress (P<0.05). Both the probucol and CS groups demonstrated significantly lower Scr, BUN, and urinary KIM-1, NGAL levels compared to the model group (P<0.05), with no significant difference between these two groups. The probucol group and the CS group had significantly lower MDA and higher T-AOC, SOD than the model group after modeling (P<0.05). Caspase-3, Bax activation were effectively repressed while Bcl-2 expression was increased by probucol and CS pretreatment. Mechanistically, probucol and CS decreased the expression of JNK protein and increased the expression of ERK protein. CS can effectively reduce kidney damage caused by contrast medium. The underlying mechanism may be that CS accelerates the recovery of renal function and renal pathology by reducing local renal oxidative stress and influencing MAPK signal pathways.

Reactive oxygen species dependent phosphorylation of the liver kinase B1/AMP activated protein kinase/ acetyl-CoA carboxylase signaling is critically involved in apoptotic effect of lambertianic acid in hepatocellular carcinoma cells

Though lambertianic acid (LA) is reported to have hypolipidemic activity in liver, its underlying anticancer mechanism is poorly understood so far. Thus, in the present study, apoptotic mechanism of LA was elucidated in HepG2 and SK-Hep1 hepatocellular carcinoma (HCC) cells. Here LA increased cytotoxicity, sub-G1 population and Annexin V/PI positive cells in two HCC cells. Also, LA cleaved caspase-3 and poly(ADP-ribose) polymerase (PARP), activated phosphorylation of liver kinase B1 (LKB1)/AMP activated protein kinase (AMPK)/ acetyl-CoA carboxylase (ACC) pathway and also suppressed antiapoptotic proteins such as phosphorylation of Akt/ mammalian target of rapamycin (mTOR) and the expression of B cell lymphoma-2 (Bcl-2)/ B-cell lymphoma-extra large (Bcl-xL) and cyclooxygenase-2 (COX-2) in two HCC cells. Furthermore, LA generated reactive oxygen species (ROS) in HepG2 cells and AMPK inhibitor compound C or ROS inhibitor N-acetyl-L-cysteine (NAC) blocked the apoptotic ability of LA to cleave PARP or increase sub G1 population in HepG2 cells. Consistently, cleavages of PARP and caspase-3 were induced by LA only in AMPK^+/+ MEF cells, but not in AMPK^-/- MEF cells. Also, immunoprecipitation (IP) revealed that phosphorylation of LKB1/AMPK through their binding was enhanced in LA treated HepG2 cells. Overall, these findings suggest that ROS dependent phosphorylation of LKB1/AMPK/ACC signaling is critically involved in LA induced apoptosis in HCCs.

Probucol ameliorates renal injury in diabetic nephropathy by inhibiting the expression of the redox enzyme p66Shc

AIMS

Probucol is an anti-hyperlipidemic agent and a potent antioxidant drug that can delay progression of diabetic nephropathy (DN) and reverses renal oxidative stress in diabetic animal models; however, the mechanisms underlying these effects remain unclear. p66Shc is a newly recognized mediator of mitochondrial ROS production in renal cells under high-glucose (HG) ambience. We previously showed that p66Shc can serve as a biomarker for renal oxidative injury in DN patients and that p66Shc up-regulation is correlated with renal damage in vivo and in vitro. Here, we determined whether probucol ameliorates renal injury in DN by inhibiting p66Shc expression.

RESULTS

We found that the expression of SIRT1, Ac-H3 and p66Shc in kidneys of DN patients was altered. Also, probucol reduced the levels of serum creatinine, urine protein and LDL-c and attenuated renal oxidative injury and fibrosis in STZ induced diabetic mice. In addition, probucol reversed p-AMPK, SIRT1, Ac-H3 and p66Shc expression. Correlation analyses showed that p66Shc expression was correlated with p-AMPK and Sirt1 expression and severity of renal injury. In vitro pretreatment of HK-2 cells with p-AMPK and SIRT1 siRNA negated the beneficial effects of probucol. Furthermore, we noted that probucol activates p-AMPK and Sirt1 and inhibits p66shc mRNA transcription by facilitating the binding of Sirt1 to the p66Shc promoter and modulation of Ac-H3 expression in HK-2 cells under HG ambience.

INNOVATION AND CONCLUSION

Our results suggest for the first time that probucol ameliorates renal damage in DN by epigenetically suppressing p66Shc expression via the AMPK-SIRT1-AcH3 pathway.

CREB1 regulates glucose transport of glioma cell line U87 by targeting GLUT1

Glioma is stemmed from the glial cells in the brain, which is accounted for about 45% of all intracranial tumors. The characteristic of glioma is invasive growth, as well as there is no obvious boundary between normal brain tissue and glioma tissue, so it is difficult to resect completely with worst prognosis. The metabolism of glioma is following the Warburg effect. Previous researches have shown that GLUT1, as a glucose transporter carrier, affected the Warburg effect, but the molecular mechanism is not very clear. CREB1 (cAMP responsive element-binding protein1) is involved in various biological processes, and relevant studies confirmed that CREB1 protein regulated the expression of GLUT1, thus mediating glucose transport in cells. Our experiments mainly reveal that the CREB1 could affect glucose transport in glioma cells by regulating the expression of GLUT1, which controlled the metabolism of glioma and affected the progression of glioma.

Metabolic Reprogramming in Glioma

Many cancers have long been thought to primarily metabolize glucose for energy production—a phenomenon known as the Warburg Effect, after the classic studies of Otto Warburg in the early twentieth century. Yet cancer cells also utilize other substrates, such as amino acids and fatty acids, to produce raw materials for cellular maintenance and energetic currency to accomplish cellular tasks. The contribution of these substrates is increasingly appreciated in the context of glioma, the most common form of malignant brain tumor. Multiple catabolic pathways are used for energy production within glioma cells, and are linked in many ways to anabolic pathways supporting cellular function. For example: glycolysis both supports energy production and provides carbon skeletons for the synthesis of nucleic acids; meanwhile fatty acids are used both as energetic substrates and as raw materials for lipid membranes. Furthermore, bio-energetic pathways are connected to pro-oncogenic signaling within glioma cells. For example: AMPK signaling links catabolism with cell cycle progression; mTOR signaling contributes to metabolic flexibility and cancer cell survival; the electron transport chain produces ATP and reactive oxygen species (ROS) which act as signaling molecules; Hypoxia Inducible Factors (HIFs) mediate interactions with cells and vasculature within the tumor environment. Mutations in the tumor suppressor p53, and the tricarboxylic acid cycle enzymes Isocitrate Dehydrogenase 1 and 2 have been implicated in oncogenic signaling as well as establishing metabolic phenotypes in genetically-defined subsets of malignant glioma. These pathways critically contribute to tumor biology. The aim of this review is two-fold. Firstly, we present the current state of knowledge regarding the metabolic strategies employed by malignant glioma cells, including aerobic glycolysis; the pentose phosphate pathway; one-carbon metabolism; the tricarboxylic acid cycle, which is central to amino acid metabolism; oxidative phosphorylation; and fatty acid metabolism, which significantly contributes to energy production in glioma cells. Secondly, we highlight processes (including the Randle Effect, AMPK signaling, mTOR activation, etc.) which are understood to link bio-energetic pathways with oncogenic signals, thereby allowing the glioma cell to achieve a pro-malignant state.

Downregulation of LKB1 promotes tumor progression and predicts unfavorable prognosis in patients with glioma

The liver kinase B1 (LKB1)/5′-adenosine monophosphate-activated protein kinase pathway has been reported to facilitate glioma cell growth by improving growth conditions. To investigate the clinical significance of LKB1 in human gliomas western blot analysis and quantitative polymerase chain reaction experiments were performed. The present study demonstrated that LKB1 expression was markedly decreased at the messenger RNA and protein levels in 30 freshly prepared glioma tissues, compared with non-neoplastic brain tissues (P<0.001). Subsequently, immunohistochemical analysis demonstrated that LKB1 immunostaining in 180 glioma tissues was significantly decreased compared with that in the corresponding non-neoplastic brain tissues (P<0.001). Notably, this downregulation frequently occurred in high-grade gliomas, and statistical analysis revealed that low LKB1 expression was significantly associated with large tumor size (P=0.02), advanced World Health Organization grade (P=0.006) and low Karnofsky performance scale (P=0.01). The prognostic value of LKB1 expression in patients with glioma was additionally evaluated using Kaplan-Meier survival curves and Cox proportional hazards regression models. As a result, the overall survival time of patients with glioma with low LKB1 expression was shorter compared with that of patients with high LKB1 expression (P<0.001), and low LKB1 expression also indicated decreased survival time in patients with high-grade glioma (P<0.001). Collectively, the present data indicated that the downregulation of LKB1 was closely associated with the malignant degree of human gliomas, exhibiting lower expression at a higher grade. Notably, LKB1 may serve as a potential prognostic biomarker for patients with glioma following surgery.

Renal Protective Effect of Probucol in Rats with Contrast-Induced Nephropathy and its Underlying Mechanism

Background

Contrast-induced nephropathy (CIN) refers to acute renal damage that occurs after the use of contrast agents. This study investigated the renal protective effect of probucol in a rat model of contrast-induced nephropathy and the mechanism of its effect.

Material/Methods

Twenty-eight Wistar rats were randomly divided into the control group, model group, N-acetylcysteine(NAC) group, and probucol group. We used a rat model of iopromide-induced CIN. One day prior to modeling, the rats received gavage. At 24 h after the modeling, blood biochemistry and urine protein were assessed. Malondialdehyde (MDA) and superoxide dismutase (SOD) were measured in renal tissue. Kidney sections were created for histopathological examination.

Results

The model group of rats showed significantly elevated levels of blood creatinine, urea nitrogen, 24-h urine protein, histopathological scores, and parameters of oxidative stress (P<0.05). Both the NAC and probucol groups demonstrated significantly lower Scr, BUN, and urine protein levels compared to the model group (P<0.05), with no significant difference between these 2 groups. The NAC group and the probucol group had significantly lower MDA and higher SOD than the model group at 24 h after modeling (P<0.05). The 8-OHdG-positive tubule of the probucol group and NAC group were significantly lower than those of the model group (p=0.046, P=0.0008), with significant difference between these 2 groups (P=0.024).

Conclusions

Probucol can effectively reduce kidney damage caused by contrast agent. The underlying mechanism may be that probucol accelerates the recovery of renal function and renal pathology by reducing local renal oxidative stress.