Lovastatin does not accentuate but is rather additive to palmitate-induced apoptosis in cardiomyocytes

The Effect of Oleic and Palmitic Acid on Induction of Steatosis and Cytotoxicity on Rat Hepatocytes in Primary Culture

In vitro models serve as a tool for studies of steatosis. Palmitic and oleic acids can induce steatosis in cultured hepatocytes. The aim of our study was to verify steatogenic and cytotoxic effects of palmitic acid (PA), oleic acid (OA) and their combinations as well as their impact on functional capacity of rat primary hepatocytes. Hepatocytes were exposed to OA or PA (0.125-2 mmol/l) or their combination at ratios of 3:1, 2:1 or 1:1 at the final concentrations of 0.5-1 mmol/l. Both OA and PA caused a dose-dependent increase in triacylglycerol content in hepatocytes. PA was more steatogenic at 0.25 and 0.5 mmol/l while OA at 0.75 and 1 mmol/l. PA exhibited a dose-dependent cytotoxic effect associated with ROS production, present markers of apoptosis and necrosis and a decrease in albumin production. OA induced a damage of the cytoplasmic membrane from 1 mM concentration. Mixture of OA and PA induced lower cytotoxicity with less weakened functional capacity than did PA alone. Extent of steatosis was comparable to that after exposure to OA alone. In conclusion, OA or combination of OA with PA is more suitable for simulation of simple steatosis than PA alone.

Anticancer activities of the extract from Longkong (Lansium domesticum) young fruits

"Longkong"(Lansium domesticum Corr., Family: Meliaceae) is a fruit found in the south of Thailand. This plant has been used in traditional medicines.

OBJECTIVES

To investigate the antiproliferative activities and the phytoconstituents of Longkong extracts.

MATERIALS AND METHODS

Cytotoxicity and apoptotic activity of 48 extracts were tested using the SRB assay and acridine orange (AO)/ethidium bromide (EB) staining, respectively. The extracts which gave the highest anticancer activity were selected to prepare the semipurified extracts and analysis for the constituents by gas chromatography-mass spectrometry (GC/MS).

RESULTS

The highest percentage yield (59.38%) was from the cold water extract of Longkong ripe fruits (RFWC). The highest total phenolic and flavonoid contents were observed in cold and hot methanol extract of Longkong stalks (STMC and STMH). The hot and cold chloroform young Longkong fruit extracts (YFCH and YFCC) exhibited a cytotoxic effect (IC(50) < 1 mg/mL) against cancer cells. For apoptotic induction, YFCH demonstrated the highest activity against KB of 13.84 ± 4.21% at 0.5 mg/mL which was 0.88 and 1.35 times of cisplatin and 5-FU, respectively, while apoptotic cells in HT-29 were 8.68 ± 1.85% at 5 mg/mL, which was 0.61 and 1.43 times of cisplatin and 5-FU, respectively. YFCC showed the highest apoptotic effect against KB cells at 10.70 ± 2.15% at 0.5 mg/mL, which was 0.68 and 1.07 times of cisplatin and 5-FU, respectively. The major phytoconstituents in YFCH were hexadecanoic acid (11.53%) and ethyl oleate (10.58%).

DISCUSSION AND CONCLUSION

The crude extracts of Longkong showed anticancer activities and may provide new lead compounds for the development of anticancer products.

Dual pathways of p53 mediated glucolipotoxicity-induced apoptosis of rat cardiomyoblast cell: activation of p53 proapoptosis and inhibition of Nrf2-NQO1 antiapoptosis

Reactive oxygen species (ROS), driven by excessive levels of glucose and free fatty acids, appears to induce cell apoptosis. However, the underlying molecular mechanism of this process remains unclear in cardiac myocytes. We investigated the glucolipotoxicity effects of high glucose and palmitic acid (C16:0) on the rat cardiomyoblast cell line (H9c2) focusing on tumor suppressor p53. Cultured H9c2 rat cardiomyoblasts were exposed to palmitate and /or to an elevated glucose concentration for 18 hours. Only the glucolipotoxic condition of 30 mM glucose in combination with 250 μM palmitate resulted in significant generation of ROS and upregulation of p53 which caused to an increased cleavage of caspase-3. On the other hand, the expression of NF-E2-related factor 2 (Nrf2) showed increased tendency while the expression of NAD(P)H: quinone oxidoreductase-1 (NQO1) was decreased. N-acetyl L cysteins and pifithrin-α, an inhibitor of p53 abrogated glucolipotoxicity-induced ROS generation and p53 expression. Chromatin immunoprecipitation analysis revealed that p53 interacted antioxidant responsive elements (ARE)-containing promoter of NQO1. Upregulated p53 counteracted the Nrf2-induced transcription of ARE-containing promoter of NQO1 gene and leaded to decrease in NQO1 expression. We demonstrated that the elevated p53 mediated glucolipotoxicity-induced apoptosis of rat cardiomyoblast cell through dual pathways: stimulating pro-apoptosis signaling as well as suppressing anti-apoptosis pathway of Nrf2-NQO1 signaling.

Stearic acid-induced cardiac lipotoxicity is independent of cellular lipid and is mitigated by the fatty acids oleic and capric acid but not by the PPAR agonist troglitazone

The objective of this study was to examine the potential of stearic acid to induce cardiomyocyte cell death and the hypothesis that the amount of cellular lipid is a determinant of cell death. In cardiomyocytes from embryonic chick heart, stearic acid (SA) produced a significant (P < 0.001) concentration-dependent increase in cell death with an ED(50) of 71 microM. In contrast, capric (C10:0) or oleic acid (OA; C18:1), at < 200 microM, did not alter cell viability. Stearic acid-induced cell death was significantly reduced by OA and to a lesser extent by capric acid. Neither OA nor capric acid altered cell death produced by potassium cyanide and deoxyglucose. Stearic acid (100 microM) induced a significant (P < 0.05) twofold increase in cellular lipid as assessed by Nile blue and Sudan Black staining. A role for cellular lipid in cardiomyocyte death was excluded because OA increased cellular lipid, at concentrations that did not induce cell death; OA did not alter SA-induced cellular fat stores but reduced cell death; and the PPARgamma; agonist troglitazone at concentrations that reduced cellular lipid content did not alter cell death. High concentrations of troglitazone, however, induced cell death. In summary, SA is a potent inducer of cardiac cell death and intracellular lipid accumulation. The amount of intracellular lipid, however, is not a determinant of cardiomyocyte cell death. Troglitazone has potential cardiotoxicity at high doses but, at lower concentrations, does not prevent cardiac lipotoxicity, which can be completely prevented by low concentrations of oleic acid.

Isolation of fatty acids with anticancer activity from Protaetia brevitarsis larva

In this study, biologically active compounds were isolated from Protaetia brevitarsis larva (PBL) by dichloromethane extraction. The dichloromethane extract from PBL was highly cytotoxic to various cancer cells. From a silica gel column chromatograpy of this extract, we obtained four fractions (F-2, F-4, F-5 and F-7) having apoptosis-inducing activity. These fractions induced DNA ladder and caspase-3 activation during apoptosis in colon 26 tumor cells. In 1H and 13C NMR and mass spectral analysis of the fraction F-2 showing the highest apoptosis-inducing activity, we found that the fraction was composed of three free fatty acids such as palmitic acid, (Z)-9-octadecenoic acid and octadecenoic acid. These results indicate that the dichloromethane extract of PBL includes anticancer components composed of at least three fatty acids, and apoptosis-inducing activity of the extract was mediated by caspase-3 activation in tumor cells.

Reduction of protein synthesis and statin-induced cardiomyocyte cell death

The objective of this study was to determine whether an HMG Co A reductase inhibitor (statin) reduces protein synthesis in cardiomyocytes and whether this action maybe an underlying mechanism for statin-induced cell death. Cardiomyocytes from embryonic chick heart were maintained in culture. Cells exposed to lovastatin for 4 h showed a concentration dependent reduction in protein synthesis as assessed by [3H] leucine incorporation and [35S] methionine incorporation. Compared to control, lovastatin 100 microM, which produced a 25% increase in cell death, induced a three-fold reduction in methionine incorporation. [35S] methionine autoradiography showed little (new) protein synthesis at concentrations of lovastatin of 70 microM or higher; an effect that was not limited to specific proteins. Cardiomyocytes treated with lovastatin showed morphologic changes in the nucleoli consistent with insufficient protein synthesis. These cardiomyocytes manifested cell death under conditions of reduced protein synthesis. Interruption of protein synthesis with cycloheximide, a ribosomal RNA transcription inhibitor or reduction in protein substrate availability by lowering the media concentration of fetal calf serum was associated with a concentration-dependent reductions in cell viability. Importantly, stimulation of protein synthesis by higher concentrations of fetal calf serum limited lovastatin-induced cell death. These data suggest that statin-induced inhibition of protein synthesis is an underlying mechanism for statin-induced cell death.

Ceramide activates a mitochondrial p38 mitogen-activated protein kinase: a potential mechanism for loss of mitochondrial transmembrane potential and apoptosis

This study examined the impact of ceramide, an intracellular mediator of apoptosis, on the mitochondria to test the hypothesis that ceramide utilized p38 MAPK in the mitochondria to alter mitochondrial potential and induce apoptosis. The capacity of ceramide to adversely affect mitochondria was demonstrated by the significant loss of mitochondrial potential (DeltaPsim), indicated by a J-aggregate fluorescent probe, after embryonic chick cardiomyocytes were treated with the cell permeable ceramide analogue C2-ceramide. p38 MAPK was identified in the mitochondrial fraction of the cell and p38 MAPK phosphorylation in this mitochondrial fraction of the cell occurred with ceramide treatment. In addition, SAPK phosphorylation and a decrease in ERK phosphorylation occurred in whole cell lysates after ceramide treatment. The p38 MAPK inhibitor SB 202190 but not the MEK inhibitor PD 98059 significantly inhibited ceramide-induced apoptosis and loss of DeltaPsim. These data suggest that p38 MAPK is present in the mitochondria and its activation by ceramide indicates local signaling more directly coupled to the mitochondrial pathway in apoptosis.

The association between RhoB and caspase-2: changes with lovastatin-induced apoptosis

Because cytoskeletal actin is regulated, in part, by Rho, and because Rho and caspases are involved in apoptosis, we sought to determine whether there was an association between RhoB and caspase-2. A RhoB–caspase-2 association was consistently demonstrated in neonatal mouse cardiomyocytes with Western Blotting, either after im mun o precipitation with RhoB followed by immunoblotting with caspase-2, or in reciprocal experiments after immuno precipitation with caspase-2 and immunoblotting with RhoB (n = 14). Although the RhoB–caspase-2 complex was constitutively present, the link between RhoB and caspase-2 may be operative in apoptosis because the HMG-CoA reductase inhibitor lovastatin increased the RhoB–caspase complex, especially in the nuclear fraction of the cell, with a peak occurrence 2 h after treatment. This association was unaffected by the caspase-2 inhibitor zVDVAD. Lovastatin produced apoptosis that was accompanied by an activation of caspase-2, as demonstrated by its immunohistochemistry and by the fact that the caspase-2 inhibitor zVDVAD reduced lovastatin-induced apoptosis. Lovastatin induced dramatic changes in cell morphology and a reduction in F-actin. Immunoblotting for actin suggests that lovastatin does not induce a degradation of the actin molecule, but rather affects filamentous F-actin. Caspase-2 inhibition with zVDVAD reduced lovastatin-induced alteration in cytoskeletal F-actin. The Rho inhibitor, Clostridium difficile toxin B, blunted the ability of lovastatin to induce apoptosis. In summary, these data show a previously unrecognized association between RhoB and caspase-2 in the cytosolic and nuclear fractions, which has ramifications for processes regulated by RhoB and caspase-2, including apoptosis.Key words: actin, apoptosis, caspase-2, cardiomyocyte, heart, lovastatin.

Reduction of palmitate-induced cardiac apoptosis by fenofibrate

The objective of this study was to test the hypothesis that a strategy based on alteration of lipid metabolism would moderate the cellular toxicity of the C16:0 saturated fatty acid-palmitate. Cardiomyocytes from neonatal mice and embryonic chicks were treated with palmitate and both oncotic and apoptotic death were observed. Fenofibrate pretreatment, 1 microM, 24 h prior to palmitate, significantly (p < 0.05) reduced palmitate-induced apoptosis. In contrast, fenofibrate had no significant effect on palmitate-induced apoptosis when fenofibrate treatment was concomitant with palmitate. The protective effect of fenofibrate was restricted to the apoptotic population. The more potent and specific PPARalpha agonist WY 14643, 1 microM, also reduced palmitate-induced apoptosis but to a smaller extent than fenofibrate. The long pretreatment time, 24 h, was necessary to show fenofibrate's effect on apoptosis, suggesting an increase in gene transcription and protein expression. Indeed, fenofibrate increased PPARalpha expression that was mainly demonstrated in the nucleus. These data suggest a novel approach to the reduction of cardiac apoptosis by the chronic treatment with the PPARalpha agonist fenofibrate.

The possible role of cytochrome c oxidase in stress-induced apoptosis and degenerative diseases

Apoptotic cell death can occur by two different pathways. Type 1 is initiated by the activation of death receptors (Fas, TNF-receptor-family) on the plasma membrane followed by activation of caspase 8. Type 2 involves changes in mitochondrial integrity initiated by various effectors like Ca(2+), reactive oxygen species (ROS), Bax, or ceramide, leading to the release of cytochrome c and activation of caspase 9. The release of cytochrome c is followed by a decrease of the mitochondrial membrane potential DeltaPsi(m). Recent publications have demonstrated, however, that induction of apoptosis by various effectors involves primarily a transient increase of DeltaPsi(m) for unknown reason. Here we propose a new mechanism for the increased DeltaPsi(m) based on experiments on the allosteric ATP-inhibition of cytochrome c oxidase at high matrix ATP/ADP ratios, which was concluded to maintain low levels of DeltaPsi(m) in vivo under relaxed conditions. This regulatory mechanism is based on the potential-dependency of the ATP synthase, which has maximal activity at DeltaPsi(m)=100-120 mV. The mechanism is turned off either through calcium-activated dephosphorylation of cytochrome c oxidase or by 3,5-diiodo-L-thyronine, palmitate, and probably other so far unknown effectors. Consequently, energy metabolism changes to an excited state. We propose that this change causes an increase in DeltaPsi(m), a condition for the formation of ROS and induction of apoptosis.

Lovastatin-induced cardiac toxicity involves both oncotic and apoptotic cell death with the apoptotic component blunted by both caspase-2 and caspase-3 inhibitors

The objective of this study was to evaluate the cardiac toxicity of the HMG-CoA reductase inhibitors by testing the hypothesis that lovastatin induces apoptotic and/or oncotic cell death in the myocyte element of the heart and further that cell death is mediated through interruption of the mevalonate pathway and that apoptosis is induced through activation of caspase-2 and caspase-3. Cardiomyocytes were cultured from embryonic chick heart. Lovastatin-induced apoptosis in these cells was demonstrated by three independent techniques, namely (1) FACS analysis of low DNA content by propidium iodide (PI); (2) microscopic assessment for cellular changes of apoptosis; and (3) FACS analysis of cells stained with PI and fluorescein diacetate. Lovastatin produced a concentration-dependent increase in apoptotic cell death and 100 microM lovastatin showed over a 4-fold increase in apoptosis compared to control. Lovastatin also induced oncotic cell death, as there was a 2.5-fold increase in the amount of oncotic cell death compared to control. Lovastatin-induced apoptosis operated, in part, through the mevalonate pathway. The caspase-2 inhibitor z-VDVAD-fmk and the caspase-3 inhibitor Ac-DEVD-CHO reduced the extent of lovastatin-induced cardiac apoptosis. In contrast, lovastatin-induced oncosis was not only insensitive to these caspase-2 or -3 inhibitors but occurred through a mevalonate-independent mechanism of action. In summary, lovastatin-induced cardiotoxicity is complex and represents the sum of two distinct modes of cell death operating in part through the mevalonate pathway with the apoptotic component subject to modification by inhibitors of the initiator caspase, caspase-2, as well as the effector caspase, caspase-3.