Isoprenoids and protein prenylation: implications in the pathogenesis and therapeutic intervention of Alzheimer's disease.

The mevalonate-isoprenoid-cholesterol biosynthesis pathway plays a key role in human health and disease. The importance of this pathway is underscored by the discovery that two major isoprenoids, farnesyl and geranylgeranyl pyrophosphate, are required to modify an array of proteins through a process known as protein prenylation, catalyzed by prenyltransferases. The lipophilic prenyl group facilitates the anchoring of proteins in cell membranes, mediating protein-protein interactions and signal transduction. Numerous essential intracellular proteins undergo prenylation, including most members of the small GTPase superfamily as well as heterotrimeric G proteins and nuclear lamins, and are involved in regulating a plethora of cellular processes and functions. Dysregulation of isoprenoids and protein prenylation is implicated in various disorders, including cardiovascular and cerebrovascular diseases, cancers, bone diseases, infectious diseases, progeria, and neurodegenerative diseases including Alzheimer's disease (AD). Therefore, isoprenoids and/or prenyltransferases have emerged as attractive targets for developing therapeutic agents. Here, we provide a general overview of isoprenoid synthesis, the process of protein prenylation and the complexity of prenylated proteins, and pharmacological agents that regulate isoprenoids and protein prenylation. Recent findings that connect isoprenoids/protein prenylation with AD are summarized and potential applications of new prenylomic technologies for uncovering the role of prenylated proteins in the pathogenesis of AD are discussed.

Trans-Cinnamaldehyde, An Essential Oil in Cinnamon Powder, Ameliorates Cerebral Ischemia-Induced Brain Injury via Inhibition of Neuroinflammation Through Attenuation of iNOS, COX-2 Expression and NFκ-B Signaling Pathway.

Trans-cinnamaldehyde (TCA), an essential oil in cinnamon powder, may have beneficial effects as a treatment for stroke which is the second leading cause of death worldwide. Post-ischemic inflammation induces neuronal cell damage after stroke, and activation of microglia, in particular, has been thought as the main contributor of proinflammatory and neurotoxic factors. The purpose of this study was to investigate the neuroprotective effects of TCA in an animal model of ischemia/reperfusion (I/R)-induced brain injury and the neuroprotective mechanism was verified in LPS-induced inflammation of BV-2 microglial cells. Our results showed that TCA (10-30 mg/kg, p.o.) significantly reduced the infarction area, neurological deficit score and decreased iNOS and COX-2 protein expression level in I/R-induced injury brain tissue. It inhibited 0.5 µg/ml LPS-induced NO production in BV-2 microglial cells without affecting cell viability, reduced protein expression of iNOS and COX-2, and attenuated inhibition of p53 protein. TCA also suppressed the effects of LPS-induced nuclear translocation of NF-κB p65 and p50 and increased cytosolic IκBα. It also reduced LPS-induced mRNA expression of iNOS, COX-2, and TNFα. We concluded that TCA has a potential neuroprotective effect to against the ischemic stroke, which may be via the inhibition of neuroinflammation through attenuating iNOS, COX-2 expression and NF-κB signaling pathway.

Crude extract of Euphorbia formosana induces apoptosis of DU145 human prostate cancer cells acts through the caspase-dependent and independent signaling pathway.

Prostate cancer is the most frequently diagnosed malignancy in men and the second highest contributor of male cancer mortality. The crude extract of Euphorbia formosana (CEEF) has been used for treatment of different diseases but the cytotoxic effects of CEEF on human cancer cells have not been reported. The purpose of the present experiments was to determine effects of CEEF on cell cycle distribution and induction of apoptosis in DU145 human prostate cancer cells in vitro. Contrast-phase microscope was used for examining cell morphological changes. Flow cytometric assays were used for cell viability, cell cycle, apoptosis, reactive oxygen species, and Ca2+ production and mitochondria membrane potential (ΔΨm ). Western blotting was used for examining protein expression of cell cycle and apoptosis associated proteins. Real-time PCR was used for examining mRNA levels of caspase-3, -8, and -9, AIF, and Endo G. Confocal laser microscope was used to examine the translocation of AIF, Endo G, and cytochrome in DU145 cells after CEEF exposure. CEEF-induced cell morphological changes, decreased the percentage of viable cells, and induced S phase arrest and apoptosis in DU145 cells. Furthermore, CEEF promoted RAS and Ca2+ production and reduced ΔΨm levels. Real-time QPCR confirmed that CEEF promoted the mRNA expression of caspase-3 and -9, AIF and Endo G and we found that AIF and Endo G and cytochrome c were released from mitochondria. Taken together, CEEF-induced cytotoxic effects via ROS production, induced S phase arrest and induction of apoptosis through caspase-dependent and independent and mitochondria-dependent pathways in DU245 cancer cells. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1600-1611, 2016.

Latex of Euphorbia antiquorum-induced S-phase arrest via active ATM kinase and MAPK pathways in human cervical cancer HeLa cells.

Latex of Euphorbia antiquorum (EA) has demonstrated great chemotherapeutic potential for cancer. However, the mechanisms of anti-proliferation of EA on cancer cell remain to be further investigated. The purpose of this study was to explore the influence of EA in human cervical cancer cells. Here, the cell cycle distribution by flow cytometry was examined and the protein expression by the western blotting methods was analyzed. From the cytometric results it was shown that EA-induced S-phase arrest in a concentration manner both in human cervical cancer HeLa and CaSki cells. According the western blot results it was illustrated that EA could downregulate early cyclin E1-Cdk2; and cyclin A-Cdc2 provides a significant additional quantity of S-phase promotion, that in turn promoted the expression of p21(waf1/cip1) and p27(kip1) which were the inhibitors in the complex of cyclin A and Cdc2 that led to cell cycle arrest. Moreover, EA promoted the activation of ataxia telangiectasia mutated (ATM) and check-point kinase-2 (Chk2); however, it negatively regulated the expression of Topoisomerases I and II, Cdc25A, and Cdc25C signaling. Caffeine, an ATM/ATR inhibitor significantly reversed EA downregulation in the levels of Cdc25A. Furthermore, JNK inhibitor SP600125 and p38 MAPK inhibitor SB203580 both could reverse the EA upregulation of the protein of Chk2 level, significantly. This study, therefore, revealed that EA could downregulate topoisomerase, and activate ATM kinase, which then induce parallel Chk 1/2 and MAPK signaling pathways to promote the degradation of Cdc25A to induced S-phase arrest in human cervical cancer HeLa cells.

Beneficial effects of dietary EGCG and voluntary exercise on behavior in an Alzheimer's disease mouse model.

Alzheimer's disease (AD) is a progressive, age-dependent neurodegenerative disorder affecting specific brain regions that control memory and cognitive functions. Epidemiological studies suggest that exercise and dietary antioxidants are beneficial in reducing AD risk. To date, botanical flavonoids are consistently associated with the prevention of age-related diseases. The present study investigated the effects of 4 months of wheel-running exercise, initiated at 2-months of age, in conjunction with the effects of the green tea catechin (-)-epigallocatechin-3-gallate (EGCG) administered orally in the drinking water (50 mg/kg daily) on: (1) behavioral measures: learning and memory performance in the Barnes maze, nest building, open-field, anxiety in the light-dark box; and (2) soluble amyloid-ß (Aß) levels in the cortex and hippocampus in TgCRND8 (Tg) mice. Untreated Tg mice showed hyperactivity, relatively poor nest building behaviors, and deficits in spatial learning in the Barnes maze. Both EGCG and voluntary exercise, separately and in combination, were able to attenuate nest building and Barnes maze performance deficits. Additionally, these interventions lowered soluble Aß1-42 levels in the cortex and hippocampus. These results, together with epidemiological and clinical studies in humans, suggest that dietary polyphenols and exercise may have beneficial effects on brain health and slow the progression of AD.

Statins and neuroprotection: basic pharmacology needed.

Statins are attracting great interest albeit with some controversy in treating certain neurodegenerative diseases such as Alzheimer disease, Parkinson disease, multiple sclerosis, ischemic stroke, and traumatic brain injury. Support for the use of statins has come from human studies and animal and cell models. Despite the intense level of interest, there is a deficiency in information on the basic pharmacokinetics and pharmacodynamics of statins in the brain. The purpose of this focused review is to examine what is known and the gaps in our knowledge on detectability of statin lactones and acids in the brain, membrane partitioning and active transport of statins across the blood-brain barrier, and statin effects on brain isoprenoid levels. Statins may be efficacious in treating certain neurodegenerative diseases. Having basic information on statin pharmacokinetics and pharmacodynamics in the brain would provide insight into specific drug targets and also provide the rationale for optimizing statins in terms of enhancing brain influx and inhibiting efflux.

Cholesterol as a causative factor in Alzheimer's disease: a debatable hypothesis.

High serum/plasma cholesterol levels have been suggested as a risk factor for Alzheimer's disease (AD). Some reports, mostly retrospective epidemiological studies, have observed a decreased prevalence of AD in patients taking the cholesterol lowering drugs, statins. The strongest evidence causally linking cholesterol to AD is provided by experimental studies showing that adding/reducing cholesterol alters amyloid precursor protein (APP) and amyloid beta-protein (Ab) levels. However, there are problems with the cholesterol-AD hypothesis. Cholesterol levels in serum/plasma and brain of AD patients do not support cholesterol as a causative factor in AD.Prospective studies on statins and AD have largely failed to show efficacy. Even the experimental data are open to interpretation given that it is well-established that modification of cholesterol levels has effects on multiple proteins, not only amyloid precursor protein and Ab. The purpose of this review, therefore, was to examine the above-mentioned issues, discuss the pros and cons of the cholesterol-AD hypothesis, involvement of other lipids in the mevalonate pathway, and consider that AD may impact cholesterol homeostasis.

Evaluation of prenylated peptides for use in cellular imaging and biochemical analysis.

Protein prenylation involves the addition of a farnesyl (C15) or geranylgeranyl (C20) isoprenoid moiety onto the C-terminus of approximately 2 % of all mammalian proteins. This hydrophobic modification serves to direct membrane association of the protein. Due to the finding that the oncogenic protein Ras is naturally prenylated, several researchers have developed inhibitors of the prenyltransferase enzymes as cancer therapeutics. Despite numerous studies on the enzymology of prenylation in vitro, many questions remain about the process of prenylation in living cells. Using a combination of flow cytometry and confocal microscopy, we have shown that synthetic fluorescently labeled prenylated peptides enter a variety of different cell types. Additionally, using capillary electrophoresis we have shown that these peptides can be detected in minute quantities from lysates of cells treated with these peptides. This method will allow for further study of the enzymology of protein prenylation in living cells.

Effects of chitosan on xenograft models of melanoma in C57BL/6 mice and hepatoma formation in SCID mice.

According to the World Health Organization, Complementary and alternative medicine (CAM) is a comprehensive term referring to traditional medical treatments and various forms of indigenous medicines, also known as indigenous or folk medicine. Cancer patients often use CAM in the form of nutritional supplements, psychological techniques and natural medical approaches in the place of or in parallel to conventional medicine. The present study aimed to determine if Chitosan can inhibit lung metastasis and hepatoma formation, by studying xenograft of B16F10 melanoma cells in C57BL/6 mice and of Smmu 7721 cells in SCID mice, respectively. For the lung metastasis model, after a five-week treatment, the survival rates of B6 mice were 15% for the control group and 35%, 20%, 45% and 40% for the 320,000 kDa, 173,000 kDa, 86,000 kDa and 8,000 kDa molecular-weight treatment groups, respectively. Chitosan treatment dramatically increased lifespan and inhibited tumor metastasis especially in treatment groups of the low-molecular weight compound. For the hepatoma growth model, the size of the liver tumor mass was approximately >14 mm in the control group. In comparison to the control group, the tumor mass grew slowly with Chitosan treatment, especially at the low-molecular weight treatment group. Chitosan slowed-down the rate of tumor growth but did not inhibit tumor formation. Data presented herein demonstrate that Chitosan has anticancer effects and thus further study of the substance is warranted to examine for mechanisms of action and optimal dosage.

Pipoxolan ameliorates cerebral ischemia via inhibition of neuronal apoptosis and intimal hyperplasia through attenuation of VSMC migration and modulation of matrix metalloproteinase-2/9 and Ras/MEK/ERK signaling pathways.

Pipoxolan (PIPO) has anti-spasmodic effects, and it is used clinically to relieve smooth muscle spasms. Cerebrovascular disease is one of the leading causes of disability and death worldwide. The main aim of this study was to investigate the effects of PIPO on cerebral ischemia and vascular smooth muscle cell (VSMC) migration in vivo and in vitro. Cerebral infarction area, ratio of intima to media area (I/M ratio) and PCNA antibody staining of the carotid artery in vivo were measured. Cell viability of A7r5 cells, PDGF-BB-stimulated cell migration, and potential mechanisms of PIPO were evaluated by wound healing, transwell and Western blotting. PIPO (10 and 30 mg/kg p.o.) reduced: the cerebral infarction area; neurological deficit; TUNEL-positive cells; cleaved caspase 3-positive cells; intimal hyperplasia; and inhibited proliferating cell nuclear antigen (PCNA)-positive cells in rodents. PIPO (5, 10 and 15 µM) significantly inhibited PDGF-BB-stimulated VSMC migration and reduced Ras, MEK, and p-ERK levels. Moreover, PIPO decreased levels of matrix metalloproteinases -2 and -9 in PDGF-BB-stimulated A7r5 cells. In summary, PIPO is protective in models of ischemia/reperfusion-induced cerebral infarction, carotid artery ligation-induced intimal hyperplasia and VSMC migration both in vivo and in vitro. PIPO could be potentially efficacious in preventing cerebrovascular and vascular diseases.

Statins, Bcl-2, and apoptosis: cell death or cell protection?

Statins have proven their effectiveness in the treatment of cardiovascular disease. This class of drugs has also attracted attention as a potential treatment for dissimilar diseases such as certain types of cancers and neurodegenerative diseases. What appears to be a contradiction is that, in the case of cancer, it has been suggested that statins increase apoptosis and alter levels of Bcl-2 family members (e.g., reduce Bcl-2 and increase Bax), whereas studies mainly using noncancerous cells report opposite effects. This review examined studies reporting on the effects of statins on Bcl-2 family members, apoptosis, cell death, and cell protection. Much, but not all, of the evidence supporting the pro-apoptotic effects of statins is based on data in cancer cell lines and the use of relatively high drug concentrations. Studies indicating an anti-apoptotic effect of statins are fewer in number and generally used much lower drug concentrations and normal cells. Those conclusions are not definitive, and certainly, there is a need for additional research to determine if statin repositioning is justified for noncardiovascular diseases.

Paeonia lactiflora Extract Attenuating Cerebral Ischemia and Arterial Intimal Hyperplasia Is Mediated by Paeoniflorin via Modulation of VSMC Migration and Ras/MEK/ERK Signaling Pathway.

Paeonia lactiflora is a well-known traditional Chinese medicine. Paeoniflorin is an active component found in Paeonia lactiflora, which is used to treat smooth muscle spasms and pain and to protect the cardiovascular system. The objective of this study was to determine if Paeonia lactiflora would be protective in rodent models of cerebral ischemia and arterial intimal hyperplasia. Paeonia lactiflora extract (PLex) and paeoniflorin (PF) significantly attenuated cerebral infarction in ischemia/reperfusion injury rats and the severity of intimal hyperplasia in mice where the carotid artery was ligated. PLex and PF reduced PDGF-stimulated VSMC proliferation and migration in a dose-dependent manner by MTT, wound healing, and transwell assays. PF significantly reduced protein levels of Ras, MEK, p-MEK and p-ERK, but not MMP-2 and MMP-9. In summary, Paeonia lactiflora reduced cerebral ischemia and arterial intimal hyperplasia which were mainly made via the intermediary of PF. The protective effect of PF was related to the modulation of the Ras/MEK/ERK signaling pathway.

Up-regulation and activation of the P2Y(2) nucleotide receptor mediate neurite extension in IL-1ß-treated mouse primary cortical neurons.

The pro-inflammatory cytokine interleukin-1ß (IL-1ß), whose levels are elevated in the brain in Alzheimer's and other neurodegenerative diseases, has been shown to have both detrimental and beneficial effects on disease progression. In this article, we demonstrate that incubation of mouse primary cortical neurons (mPCNs) with IL-1ß increases the expression of the P2Y2 nucleotide receptor (P2Y2R) and that activation of the up-regulated receptor with UTP, a relatively selective agonist of the P2Y2R, increases neurite outgrowth. Consistent with the accepted role of cofilin in the regulation of neurite extension, results indicate that incubation of IL-1ß-treated mPCNs with UTP increases the phosphorylation of cofilin, a response absent in PCNs isolated from P2Y2R(-/-) mice. Other findings indicate that function-blocking anti-αv ß3/5 integrin antibodies prevent UTP-induced cofilin activation in IL-1ß-treated mPCNs, suggesting that established P2Y2R/αv ß3/5 interactions that promote G12 -dependent Rho activation lead to cofilin phosphorylation involved in neurite extension. Cofilin phosphorylation induced by UTP in IL-1ß-treated mPCNs is also decreased by inhibitors of Ca(2+)/calmodulin-dependent protein kinase II (CaMKII), suggesting a role for P2Y2R-mediated and Gq-dependent calcium mobilization in neurite outgrowth. Taken together, these studies indicate that up-regulation of P2Y2Rs in mPCNs under pro-inflammatory conditions can promote cofilin-dependent neurite outgrowth, a neuroprotective response that may be a novel pharmacological target in the treatment of neurodegenerative diseases.

Crude extract of Euphorbia formosana inhibits the migration and invasion of DU145 human prostate cancer cells: The role of matrix metalloproteinase-2/9 inhibition via the MAPK signaling pathway.

Prostate cancer is a common worldwide health problem in males with a poor prognosis due in part to tumor invasion and migration. The crude extract of Euphorbia formosana (CEEF) has been used for the treatment of numerous diseases, however, its effects on the migration and invasion of prostate cancer cells have yet to be examined. In the present study, we investigated the effects of CEEF on the migration and invasion of DU145 human prostate cancer cells in vitro. The wound healing assay and the Matrigel-uncoated migration assay were used to examine the migration of cancer cells. Western blotting was used to examine the levels of proteins associated with migration and invasion, and gelatin zymography was used to examine the secretion levels of matrix metalloproteinases-2 and -9 (MMP­2/9) from DU145 cells following exposure to CEEF. The results indicated that CEEF suppressed the migration and invasion of DU145 prostate cancer cells and that these effects are exerted in a concentration- and time-dependent manner. CEEF inhibited the ERK1/2, p38, JNK, SOS1, PKC, PI3K and MMP-2/9 protein expression in DU145 cells. The results demonstrated that CEEF suppressed the migration and invasion of DU145 cells through inhibition of the mitogen-activated protein kinase (MAPK) signaling pathway resulting in the inhibition of MMP-2/9 in DU145 human prostate cancer cells.

Green Tea Extract Ameliorates Learning and Memory Deficits in Ischemic Rats via Its Active Component Polyphenol Epigallocatechin-3-gallate by Modulation of Oxidative Stress and Neuroinflammation.

Ischemic stroke results in brain damage and behavioral deficits including memory impairment. Protective effects of green tea extract (GTex) and its major functional polyphenol (-)-epigallocatechin gallate (EGCG) on memory were examined in cerebral ischemic rats. GTex and EGCG were administered 1 hr before middle cerebral artery ligation in rats. GTex, EGCG, and pentoxifylline (PTX) significantly improved ishemic-induced memory impairment in a Morris water maze test. Malondialdehyde (MDA) levels, glutathione (GSH), and superoxide dismutase (SOD) activity in the cerebral cortex and hippocampus were increased by long-term treatment with GTex and EGCG. Both compounds were also associated with reduced cerebral infraction breakdown of MDA and GSH in the hippocampus. In in vitro experiments, EGCG had anti-inflammatory effects in BV-2 microglia cells. EGCG inhibited lipopolysaccharide- (LPS-) induced nitric oxide production and reduced cyclooxygenase-2 and inducible nitric oxide synthase expression in BV-2 cells. GTex and its active polyphenol EGCG improved learning and memory deficits in a cerebral ischemia animal model and such protection may be due to the reduction of oxidative stress and neuroinflammation.

Brain isoprenoids farnesyl pyrophosphate and geranylgeranyl pyrophosphate are increased in aged mice.

The mevalonate/isoprenoids/cholesterol pathway has a fundamental role in the brain. Increasing age could be associated with specific changes in mevalonate downstream products. Other than age differences in brain cholesterol and dolichol levels, there has been little if any evidence on the short-chain isoprenoids farnesylpyrophosphate (FPP) and geranylgeranylpyrophosphate (GGPP), as well as downstream lipid products. The purpose of the present study was to determine whether brain levels of FPP, GGPP and sterol precursors and metabolites would be altered in aged mice (23 months) as compared to middle-aged mice (12 months) and young mice (3 months). FPP and GGPP levels were found to be significantly higher in brain homogenates of 23-months-old mice. The ratio of FPP to GGPP did not differ among the three age groups suggesting that increasing age does not alter the relative distribution of the two isoprenoids. Gene expression of FPP synthase and GGPP synthase did not differ among the three age groups. Gene expression of HMG-CoA reductase was significantly increased with age but in contrast gene expression of squalene synthase was reduced with increasing age. Levels of squalene, lanosterol and lathosterol did not differ among the three age groups. Desmosterol and 7-dehydroxycholesterol, which are direct precursors in the final step of cholesterol biosynthesis were significantly lower in brains of aged mice. Levels of cholesterol and its metabolites 24S- and 25S-hydroxycholesterol were similar in all three age groups. Our novel find ings on increased FPP and GGPP levels in brains of aged mice may impact on protein prenylation and contribute to neuronal dysfunction observed in aging and certain neurodegenerative diseases.

Chrysophanol-induced necrotic-like cell death through an impaired mitochondrial ATP synthesis in Hep3B human liver cancer cells.

Liver cancer is the most common form of cancer in Taiwan and it usually responds to chemotherapy. However, patients often have side effects to the chemotherapeutic drugs. Thus new agents are urgently required to treat liver cancer. Chrysophanol, one of the anthraquinone derivatives, was reported to inhibit some human cancer cell growth which may be due to the induction of apoptosis similar to other anthraquinone derivatives though such actions have not been reported. In the present study, we reported that chrysophanol inhibits cell growth in Hep3B liver cancer cells based on the following observations: 1) induc cell morphological changes; 2) decreased percentage of viable cells; 3) induced S phase arrest of cell cycle progression; 4) induced DNA damage as measured by comet assay and DAPI staining. Chrysophanol-induced cell death however, seems to be related to necrotic processes rather than typical apoptosis. Chrysophanol induced reactive oxygen species and Ca(2+) production and decreased mitochondrial membrane potential (ΔΨm) and ATP levels in Hep3B cells. No effects were observed on known protein regulators of apoptosis such as Bax and Bcl-2. Chrysophanol-induced cell death took place independently of caspase-8 and -9. Based on our findings, we propose that chrysophanol reduces cellular ATP levels causing a drop in energy resulting in necrotic-like cell death.