Pioglitazone, an antihyperglycemic drug, increases plasma high-density lipoprotein (HDL)-cholesterol in patients with type 2 diabetes. The mechanisms by which pioglitazone regulate HDL levels are not clear. This study examined the effect of pioglitazone on hepatocyte apolipoprotein AI (apoA-I) and apoA-II production and HDL-protein/cholesterol ester uptake.In human hepatoblastoma (HepG2) cells, pioglitazone, dose-dependently (0.5 to 10 micromol/L), increased the de novo synthesis (up to 45%), secretion (up to 44%), and mRNA expression (up to 59%) of apoA-I. Pioglitazone also increased apoA-II de novo synthesis (up to 73%) and mRNA expression (up to 129%). Pioglitazone did not affect the uptake of HDL3-protein or HDL3-cholesterol ester in HepG2 cells. The pioglitazone-induced apoA-I lipoprotein particles increased cholesterol efflux from THP-1 macrophages. The pioglitazone-induced apoA-I secretion or mRNA expression by the HepG2 cells was abrogated with the suppression of PPAR-alpha by small interfering RNA or a specific inhibitor of PPAR-alpha, MK886.The data indicate that pioglitazone increases HDL by stimulating the de novo hepatic synthesis of apoA-I without affecting hepatic HDL-protein or HDL-cholesterol removal. We suggest that pioglitazone-mediated hepatic activation of PPAR-alpha may be one of the mechanisms of action of pioglitazone to raise hepatic apoA-I and HDL.
Objective: Synthetic class A amphipathic helical peptide analogs of apolipoprotein-AI (apoAI; with varied phenylalanine residues) are emerging therapeutic approaches under investigation for atherosclerosis. Utilizing retroinverso sequencing, we designed reverse-D4F (Rev-D4F) peptide with 18 d-amino acids containing 4 phenylalanine residues and reverse order that allows the side chain residues to be of exact alignment and superimposable to those of the parent l-amino acid peptide. This study examined the effect of Rev-D4F on atherosclerosis in apolipoprotein E (apoE)-null mice and the underlying mechanisms. Materials/Methods: ApoE-null mice were fed a chow diet and administered water (control), Rev-D4F, or L4F mimetic peptides (0.4 mg/mL, equivalent to 1.6 mg/d) orally in drinking water for 6 weeks. Aortic root atherosclerotic lesion area, lesion macrophage content, and the ability of plasma high-density lipoprotein (HDL) to influence monocyte chemotaxis were measured. Results: Rev-D4F significantly decreased aortic sinus atherosclerotic lesion area and lesion macrophage content without affecting plasma total and HDL-cholesterol levels in apoE-null mice. The HDL from Rev-D4F-treated mice showed enhanced anti-inflammatory monocyte chemotactic activity, while low-density lipoprotein (LDL) exhibited reduced proinflammatory activity. In in vitro studies, Rev-D4F inhibited LDL oxidation, endothelial cell vascular cell adhesion molecule 1 (VCAM-1), and monocyte chemotactic factor 1 (MCP-1) expression, and monocyte adhesion to aortic endothelial cells. Conclusions: The Rev-D4F inhibits atherosclerosis by inhibiting endothelial inflammatory/oxidative events and improving HDL function. The data suggest that Rev-D4F may be an effective apoAI mimetic peptide for further development in preventing atherosclerosis.
Hypothesis: Phospholipid transfer protein (PLTP) has a direct effect on platelet aggregation, since PLTP knockout mice have longer bleeding time. Methods and Results: Platelets from humans or mice were prepared as were mouse platelet-rich plasma and human recombinant PLTP (rPLTP). In mice, we assessed ADP- and collagen-induced platelet aggregation, phosphatidylserine (PS) externalization, and photothrombosis-induced cerebral infarction. We found that human platelets produce PLTP. Platelet aggregation increased upon PLTP overexpression whereas it decreased with PLTP deficiency in a gene dose-dependent manner. Human rPLTP increased mouse or human platelet aggregation in a dose-dependent manner. PS externalization provides a water/lipid surface for the interaction of coagulation factors, which accelerates thrombosis. Compared with wild type controls, platelets from PLTP transgenic mice had significantly greater amounts of PS on the exterior surface of the plasma membrane, whereas platelets from PLTP-deficient mice had significantly less on the surface, thus influencing fibrinogen binding. Moreover, rPLTP together with ADP significantly increased PS exposure on the plasma membrane of PLTP-deficient platelets, thereby increasing fibrinogen binding. Importantly, PLTP overexpression significantly accelerated the incidence of photothrombosis-induced infarction, whereas PLTP deficiency reduced the incidence. Conclusions: PLTP promotes PS externalization at the plasma membrane of platelets and accelerates ADP- or collagen-induced platelet aggregation. Thus, PLTP is involved in hypercoagulation. Therefore, PLTP inhibition could be a novel approach for countering thrombosis.
The present study aimed to investigate the role of D4F, an apolipoprotein A-I mimetic peptide, in macrophage apoptosis induced by the glycated high-density lipoprotein (gly-HDL)-induced endoplasmic reticulum (ER) stress C/EBP homologous protein (CHOP) pathway, and unravel the regulatory role of autophagy in this process. Our results revealed that except for suppressing the accumulation of lipids within RAW264.7 macrophages caused by gly-HDL, D4F inhibited gly-HDL-induced decrease in the cell viability and increase in lactate dehydrogenase leakage and cell apoptosis, which were similar to 4-phenylbutyric acid (PBA, an ER stress inhibitor). Besides, similar to PBA, D4F inhibited gly-HDL-induced ER stress response activation evaluated through the decreased PERK and eIF2α phosphorylation, together with reduced ATF6 nuclear translocation as well as the downregulation of GRP78 and CHOP. Interestingly, D4F facilitated gly-HDL-triggered activation of autophagy, measured as elevated levels of beclin-1, LC3-II, and ATG5 expressions in macrophages. Furthermore, the inhibition effect of D4F on gly-HDL-induced ER stress-CHOP-induced apoptosis of macrophages was restrained after beclin-1 siRNA and 3-methyladenine (3-MA, an inhibitor of autophagy) treatments, while this effect was further reinforced after rapamycin (Rapa, an inducer of autophagy) treatment. Furthermore, administering D4F or Rapa to T2DM mice upregulated LC3-II and attenuated CHOP expression, cell apoptosis, and atherosclerotic lesions. However, the opposite results were obtained when 3-MA was administered to these mice. These results support that D4F effectively protects macrophages against gly-HDL-induced ER stress-CHOP-mediated apoptosis by promoting autophagy.
Objective . Molecular hydrogen (H 2 ) has been considered a potential therapeutic target in many cancers. Therefore, we sought to assess the potential effect of H 2 on colorectal cancer (CRC) in this study. Methods . The effect of H 2 on the proliferation and apoptosis of RKO, SW480, and HCT116 CRC cell lines was assayed by CCK‐8, colony formation, and flow cytometry assays. The effect of H 2 on tumor growth was observed in xenograft implantation models (inhalation of 67% hydrogen two hours per day). Western blot and immunohistochemistry analyses were performed to examine the expression of p‐PI3K, PI3K, AKT, pAKT, and SCD1 in CRC cell lines and xenograft mouse models. The expression of SCD1 in 491 formalin‐fixed, paraffin‐embedded CRC specimens was investigated with immunochemistry. The relationship between SCD1 status and clinicopathological characteristics and outcomes was determined. Results . Hydrogen treatment suppressed the proliferation of CRC cell lines independent of apoptosis, and the cell lines showed different responses to different doses of H 2 . Hydrogen also elicited a potent antitumor effect to reduce CRC tumor volume and weight in vivo . Western blot and IHC staining demonstrated that H 2 inhibits CRC cell proliferation by decreasing pAKT/SCD1 levels, and the inhibition of cell proliferation induced by H 2 was reversed by the AKT activator SC79. IHC showed that SCD1 expression was significantly higher in CRC tissues than in normal epithelial tissues (70.3% vs. 29.7%, p = 0.02) and was correlated with a more advanced TNM stage (III vs. I + II; 75.9% vs. 66.3%, p = 0.02), lymph node metastasis (with vs. without; 75.9% vs. 66.3%, p = 0.02), and patients without a family history of CRC (78.7% vs. 62.1%, p = 0.047). Conclusion . This study demonstrates that high concentrations of H 2 exert an inhibitory effect on CRC by inhibiting the pAKT/SCD1 pathway. Further studies are warranted for clinical evaluation of H 2 as SCD1 inhibitor to target CRC.
Metabolic syndrome (MetS) is a constellation of cardiovascular risk factors, including central obesity, dysglycemia, hypertension, and dyslipidemia. The anti-inflammatory properties of high density lipoprotein (HDL) can be compromised in MetS. Exercise is recognized as an important factor in the prevention and treatment of MetS.This study was designed to investigate whether walk/run training without any specific diet could enhance anti-inflammation capacity of HDL from MetS patients.This was a case control study.The study was conducted in a Zhoudian community, Taian.Thirty nine patients with MetS were recruited and divided into a control group (n = 12) remaining in an untrained state and exercise group (n = 27) performing a 10-week walk/run training program.The anti-inflammation capacities of HDL3 (HDL subfractions) from MetS patients with or without exercise were investigated by co-incubating with TNF- α-injured endothelial cells in vitro.The training did not influence serum lipoprotein level in MetS patients and cholesterol efflux capacity of circulating HDL. However, walk/run training increased paraoxonase-1 (PON1) activity and decreased the levels of malondialdehyde in either serum or isolated HDL from MetS patients prominently. More importantly, HDL3 isolated from MetS patients with 10 weeks training protected endothelial cells against tumor necrosis factor-a (TNF-a) -induced injury, decreased monocyte chemotactic protein-1 levels in media and vascular cell adhesion molecule-1 expression markedly. Furthermore, HDL3 isolated from MetS patients with walk/run training inhibited the TNF-á-induced monocyte adhesion to endothelial cells and obviously increased nitric oxide production by activating endothelial nitric oxide synthase.Walk/run training leads to a significant improvement in HDL anti-inflammation capacity in subjects with MetS without restricted diet, the mechanism underlying which at least partially is due to increased PON1 activity in HDL, NO production, and eNOS expression in endothelial cells.
Molecular hydrogen (H2) has been shown to have diverse biomedical effects. As a small molecular gas, hydrogen can be diffused to the target without hindrance. A variety of related hydrogen products used in medical research and public health have been developed. There are various methods of administration of H2, mainly including inhaling hydrogen gas, drinking hydrogen water, injecting hydrogen-saline, orally taking solid-state H2 sustained-release agents, and stimulating intestinal microbiomes to produce hydrogen. Pharmacokinetics of H2 in vivo vary with methods of administration and thus influence its biomedical effects. This review summarizes the types of H2 donors and their pharmacokinetics in vivo.
Plasma low-density lipoprotein (LDL) is primarily cleared by LDL receptor (LDLR). LDLR can be proteolytically cleaved to release its soluble ectodomain (sLDLR) into extracellular milieu. However, the proteinase responsible for LDLR cleavage is unknown. Here we report that membrane type 1-matrix metalloproteinase (MT1-MMP) co-immunoprecipitates and co-localizes with LDLR and promotes LDLR cleavage. Plasma sLDLR and cholesterol levels are reduced while hepatic LDLR is increased in mice lacking hepatic MT1-MMP. Opposite effects are observed when MT1-MMP is overexpressed. MT1-MMP overexpression significantly increases atherosclerotic lesions, while MT1-MMP knockdown significantly reduces cholesteryl ester accumulation in the aortas of apolipoprotein E (apoE) knockout mice. Furthermore, sLDLR is associated with apoB and apoE-containing lipoproteins in mouse and human plasma. Plasma levels of sLDLR are significantly increased in subjects with high plasma LDL cholesterol levels. Thus, we demonstrate that MT1-MMP promotes ectodomain shedding of hepatic LDLR, thereby regulating plasma cholesterol levels and the development of atherosclerosis.
The inhibition of tumor cell growth without toxicity to normal cells is an important target in cancer therapy. One possible way to increase the efficacy of anticancer drugs and to decrease toxicity or side effects is to develop traditional natural products, especially from medicinal plants. Paris polyphylla Smith has shown anti-tumour effects by inhibition of tumor promotion and inducement of tumor cell apoptosis, but mechanisms are still not well understood. The present study was to explore the effect of Paris polyphylla Smith extract (PPSE) on connexin26 and growth control in human esophageal cancer ECA109 cells.The effects of PPSE on Connexin26 were examined by RT-PCR, western blot and immunofluorescence; cell growth and proliferation were examined by the 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyl-tetrazolium bromide (MTT) assay.PPSE inhibited the growth and proliferation on esophageal cancer ECA109 cells, while increasing the expression of connexin26 mRNA and protein; conversely, PPSE decreased Bcl-2 and increased Bad.This study firstly shows that PPSE can increase connexin26 expression at mRNA and protein level, exerting anti-tumour effects on esophageal cacner ECA109 cells via inhibiting cell proliferation and inducing cell apoptosis.
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