Simvastatin induces heat shock factor 1 in vascular endothelial cells

Cytoprotective pathways in the vascular endothelium. Do they represent a viable therapeutic target?

The vascular endothelium is a critical interface, which separates the organs from the blood and its contents. The endothelium has a wide variety of functions and maintenance of endothelial homeostasis is a multi-dimensional active process, disruption of which has potentially deleterious consequences if not reversed. Vascular injury predisposes to endothelial apoptosis, dysfunction and development of atherosclerosis. Endothelial dysfunction is an end-point, a central feature of which is increased ROS generation, a reduction in endothelial nitric oxide synthase and increased nitric oxide consumption. A dysfunctional endothelium is a common feature of diseases including rheumatoid arthritis, systemic lupus erythematosus, diabetes mellitus and chronic renal impairment. The endothelium is endowed with a variety of constitutive and inducible mechanisms that act to minimise injury and facilitate repair. Endothelial cytoprotection can be enhanced by exogenous factors such as vascular endothelial growth factor, prostacyclin and laminar shear stress. Target genes include endothelial nitric oxide synthase, heme oxygenase-1, A20 and anti-apoptotic members of the B cell lymphoma protein-2 family. In light of the importance of endothelial function, and the link between its disruption and the risk of atherothrombosis, interest has focused on therapeutic conditioning and reversal of endothelial dysfunction. A detailed understanding of cytoprotective signalling pathways, their regulation and target genes is now required to identify novel therapeutic targets. The ultimate aim is to add vasculoprotection to current therapeutic strategies for systemic inflammatory diseases, in an attempt to reduce vascular injury and prevent or retard atherogenesis.

Pleiotropic effects of statins: new therapeutic targets in drug design

The HMG Co-enzyme inhibitors and new lipid-modifying agents expand their new therapeutic target options in the field of medical profession. Statins have been described as the most effective class of drugs to reduce serum cholesterol levels. Since the discovery of the first statin nearly 30 years ago, these drugs have become the main therapeutic approach to lower cholesterol levels. The present scientific research demonstrates numerous non-lipid modifiable effects of statins termed as pleiotropic effects of statins, which could be beneficial for the treatment of various devastating disorders. The most important positive effects of statins are anti-inflammatory, anti-proliferative, antioxidant, immunomodulatory, neuroprotective, anti-diabetes, and antithrombotic, improving endothelial dysfunction and attenuating vascular remodeling besides many others which are discussed under the scope of this review. In particular, inhibition of Rho and its downstream target, Rho-associated coiled-coil-containing protein kinase (ROCK), and their agonistic action on peroxisome proliferator-activated receptors (PPARs) can be viewed as the principle mechanisms underlying the pleiotropic effects of statins. With gradually increasing knowledge of new therapeutic targets of statins, their use has also been advocated in chronic inflammatory disorders for example rheumatoid arthritis (RA) and in systemic lupus erythematosus (SLE). In the scope of review, we highlight statins and their pleiotropic effects with reference to their harmful and beneficial effects as a novel approach for their use in the treatment of devastating disorders. Graphical abstract Pleiotropic effect of statins.

The antithrombotic effects of statins

Hypercholesterolemia is considered the primary risk factor for cardiovascular disease. An estimated 200 million prescriptions are issued per year for statins to treat hypercholesterolemia. Importantly, statins have additional beneficial effects independent of their effects on lipids. Recent studies have shown that statins reduce thrombosis via multiple pathways, including inhibiting platelet activation and reducing the pathologic expression of the procoagulant protein tissue factor. Many of the antithrombotic effects of statins are attributed to inhibiting prenylation of RhoA and effects on other intracellular signaling molecules such as NF-κB and KLF2. These antithrombotic activities of statins likely contribute to the ability of statins to reduce the incidence of cardiovascular death.

The multifunctional role and therapeutic potential of HO-1 in the vascular endothelium

SIGNIFICANCE

Heme oxygenases (HO-1 and HO-2) catalyze the degradation of the pro-oxidant heme into carbon monoxide (CO), iron, and biliverdin, which is subsequently converted to bilirubin. In the vasculature, particular interest has focused on antioxidant and anti-inflammatory properties of the inducible HO-1 isoform in the vascular endothelium. This review will present evidence that illustrates the potential therapeutic significance of HO-1 and its products, with special emphasis placed on their beneficial effects on the endothelium in vascular diseases.

RECENT ADVANCES

The understanding of the molecular basis for the regulation and functions of HO-1 has led to the identification of a variety of drugs that increase HO-1 activity in the vascular endothelium. Moreover, therapeutic delivery of HO-1 products CO, biliverdin, and bilirubin has been shown to have favorable effects, notably on endothelial cells and in animal models of vascular disease.

CRITICAL ISSUES

To date, mechanistic data identifying the downstream target genes utilized by HO-1 and its products to exert their actions remain relatively sparse. Likewise, studies in man to investigate the efficacy of therapeutics known to induce HO-1 or the consequences of the tissue-specific delivery of CO or biliverdin/bilirubin are rarely performed.

FUTURE DIRECTIONS

Based on the promising in vivo data from animal models, clinical trials to explore the safety and efficacy of the therapeutic induction of HO-1 and the delivery of its products should now be pursued further, targeting, for example, patients with severe atherosclerotic disease, ischemic limbs, restenosis injury, or at high risk of organ rejection.

New insights into intracellular locations and functions of heme oxygenase-1

SIGNIFICANCE

Heme oxygenase-1 (HMOX1) plays a critical role in the protection of cells, and the inducible enzyme is implicated in a spectrum of human diseases. The increasing prevalence of cardiovascular and metabolic morbidities, for which current treatment approaches are not optimal, emphasizes the necessity to better understand key players such as HMOX1 that may be therapeutic targets.

RECENT ADVANCES

HMOX1 is a dynamic protein that can undergo post-translational and structural modifications which modulate HMOX1 function. Moreover, trafficking from the endoplasmic reticulum to other cellular compartments, including the nucleus, highlights that HMOX1 may play roles other than the catabolism of heme.

CRITICAL ISSUES

The ability of HMOX1 to be induced by a variety of stressors, in an equally wide variety of tissues and cell types, represents an obstacle for the therapeutic exploitation of the enzyme. Any capacity to modulate HMOX1 in cardiovascular and metabolic diseases should be tempered with an appreciation that HMOX1 may have an impact on cancer. Moreover, the potential for heme catabolism end products, such as carbon monoxide, to amplify the HMOX1 stress response should be considered.

FUTURE DIRECTIONS

A more complete understanding of HMOX1 modifications and the properties that they impart is necessary. Delineating these parameters will provide a clearer picture of the opportunities to modulate HMOX1 in human disease.

Caveolin-1-eNOS/Hsp70 interactions mediate rosuvastatin antifibrotic effects in neonatal obstructive nephropathy

Evidence suggesting that statins may contribute to renoprotection has been provided in experimental and clinical studies. Statins restore endothelial nitric oxide (NO) levels by mechanisms including up-regulation of endothelial NO synthase (eNOS) expression. Caveolin-1/eNOS interaction is essential preventing inadequate NO levels. Here, we evaluated whether caveolin-1 associated with eNOS/Hsp70 expression may be involved in the mechanism by which rosuvastatin exerts tubulointerstitial fibrosis protection in neonatal unilateral ureteral obstruction (UUO). Neonatal rats subjected to UUO within 2 days of birth and controls were treated daily with vehicle or rosuvastatin (10 mg/kg/day) by oral gavage for 14 days. After UUO, morphometric evaluation of interstitial fibrosis showed increased interstitial volume (Vv) associated with reduced NO availability, increased mRNA and protein caveolin-1 expression as well as downregulation eNOS and heat shock protein 70 (Hsp70) expression. Conversely, rosuvastatin treatment attenuated the fibrotic response linked to high NO availability, decreased mRNA and protein caveolin-1 expression, and marked upregulation of eNOS and Hsp70 expression at transcriptional and posttranscriptional levels. Moreover, protein-protein interactions determined by immunoprecipitation and by immunofluorescence co-localization have shown decreased caveolin-1/eNOS as well as increased Hsp70/eNOS interaction, after rosuvastatin treatment. A dose dependent effect of rosuvastatin on decreased caveolin-1 expression was shown in control cortex. In conclusion, our data suggest that statins contribute to the protection against tubulointerstitial fibrosis injury in neonatal early kidney obstruction by increased NO availability, involving interaction of up-regulated eNOS/Hsp70 and down-regulated caveolin-1.

Aging does not reduce heat shock protein 70 in the absence of chronic insulin resistance

Heat shock protein (HSP)70 decreases with age. Often aging is associated with coincident insulin resistance and higher blood glucose levels, which also associate with lower HSP70. We aimed to understand how these factors interrelate through a series of experiments using vervet monkeys (Chlorocebus aethiops sabaeous). Monkeys (n = 284, 4-25 years) fed low-fat diets showed no association of muscle HSP70 with age (r = .04, p = .53), but levels were highly heritable. Insulin resistance was induced in vervet monkeys with high-fat diets, and muscle biopsies were taken after 0.3 or 6 years. HSP70 levels were significantly greater after 0.3 years (+72%, p < .05) but were significantly lower following 6 years of high-fat diet (-77%, p < .05). Associations with glucose also switched from being positive (r = .44, p = .03) to strikingly negative (r = -.84, p < .001) with increasing insulin resistance. In conclusion, a low-fat diet may preserve tissue HSP70 and health with aging, whereas high-fat diets, insulin resistance, and genetic factors may be more important than age for determining HSP70 levels.

Dual protective role of HO-1 in transplanted liver grafts: A review of experimental and clinical studies

Liver transplantation is considered as the most effective treatment for end-stage liver disease. However, serious complications still exist, particularly in two aspects: ischemia and subsequent reperfusion of the liver, causing postoperative hepatic dysfunction and even failure; and acute and chronic graft rejections, affecting the allograft survival. Heme oxygenase (HO), a stress-response protein, is believed to exert a protective function on both the development of ischemia-reperfusion injury (IRI) and graft rejection. In this review of current researches on allograft protection, we focused on the HO-1. We conjecture that HO-1 may link these two main factors affecting the prognosis of liver transplantations. In this review, the following aspects were emphasized: the basic biological functions of HO-1, its roles in IRI and allograft rejection, as well as methods to induce HO-1 and the prospects of a therapeutic application of HO-1 in liver transplantation.

Constitutively active heat shock factor 1 enhances glucose-driven insulin secretion

Weak pancreatic β-cell function is a cause of type 2 diabetes mellitus. Glucokinase regulates insulin secretion via phosphorylation of glucose. The present study focused on a system for the self-protection of pancreatic cell by expressing heat shock factor (HSF) and heat shock protein (HSP) to improve insulin secretion without inducing hypoglycemia. We previously generated a constitutively active form of human HSF1 (CA-hHSF1). An adenovirus expressing CA-hHSF1 using the cytomegalovirus promoter was generated to infect mouse insulinoma cells (MIN6 cells). An adenovirus expressing CA-hHSF1 using a human insulin promoter (Ins-CA-hHSF1) was also generated to infect rats. We investigated whether CA-hHSF1 induces insulin secretion in MIN6 cells and whether Ins-CA-hHSF1 can improve blood glucose and serum insulin levels in healthy Wister rats and type 2 diabetes mellitus model rats. CA-hHSF1 expression increased insulin secretion 1.27-fold compared with the overexpression of wild-type hHSF1 in MIN6 cells via induction of HSP90 expression and subsequent activation of glucokinase. This mechanism is associated with activation of both glucokinase and neuronal nitric oxide synthase. Ins-CA-hHSF1 improved blood glucose levels in neonatal streptozotocin-induced diabetic rats. Furthermore, Ins-CA-hHSF1 reduced oral glucose tolerance testing results in healthy Wister rats because of an insulin spike at 15 minutes; however, it did not induce hypoglycemia. CA-hHSF1 induced insulin secretion both in vitro and in vivo. These findings suggest that gene therapy with Ins-CA-hHSF1 will be able to be used to treat patients with type 2 diabetes mellitus and impaired glucose tolerance without causing hypoglycemia at fasting.

Heat-shock proteins in cardiovascular disease

Heat-shock proteins (HSPs) belong to a group of highly conserved families of proteins expressed by all cells and organisms and their expression may be constitutive or inducible. They are generally considered as protective molecules against different types of stress and have numerous intracellular functions. Secretion or release of HSPs has also been described, and potential roles for extracellular HSPs reported. HSP expression is modulated by different stimuli involved in all steps of atherogenesis including oxidative stress, proteolytic aggression, or inflammation. Also, antibodies to HSPs may be used to monitor the response to different types of stress able to induce changes in HSP levels. In the present review, we will focus on the potential implication of HSPs in atherogenesis and discuss the limitations to the use of HSPs and anti-HSPs as biomarkers of atherothrombosis. HSPs could also be considered as potential therapeutic targets to reinforce vascular defenses and delay or avoid clinical complications associated with atherothrombosis.

Extracellular heat shock protein 70 (HSPA1A) and classical vascular risk factors in a general population

Atherosclerosis is a chronic inflammatory and autoimmune disease. Candidate molecules/autoantigens include heat shock proteins (HSPs); Hsp70 (HSPA1A) is one of the best studied HSPs. Various studies have shown a correlation between extracellular Hsp70 (eHsp70) and anti-Hsp70/anti-Hsp60 antibody concentration and development of atherosclerosis. A random sample of 456 people aged 40-60 (218 males, 234 females) was studied to investigate the prevalence of traditional vascular risk factors and eHsp70 and anti-Hsp70/anti-Hsp60 antibodies levels, according to the risk of vascular disease. Task Force Chart was applied for classification. Subjects were divided into three groups: G0 (with no vascular risk factor or a risk lower than 5%), n = 239; G1 (moderated 10-20% risk, who do not have established disease) n = 161; and G2 (established atherosclerosis disease) n = 52. eHsp70 and anti-Hsp70 were significantly lower in the atherosclerosis group (group 2) with respect to the other groups. Disease-free people showed the highest anti-Hsp60 concentration compared with the other two groups. A correlation has not been demonstrated between the concentrations of circulating Hsp70 (HSPA1A), anti-Hsp70, and anti-Hsp60 and classical vascular risk factors and C-reactive protein. Low levels of eHsp70 and anti-Hsp70 antibodies should be considered as candidate FRV. Simultaneous decrease of eHsp70 and anti-Hsp70 antibodies would be explained by circulating immune complex formation, and both could be proposed as biomarkers for the progression of atherosclerotic disease. Levels of circulating anti-Hsp60 antibodies may constitute a marker of inflammation in atherosclerosis.

Highly active antiretroviral therapy drugs inhibit in vitro cholesterol efflux from human macrophage-derived foam cells

We previously reported that HIV protease inhibitor, ritonavir, could inhibit cholesterol efflux and induce endothelial dysfunction. In this study, we further determined the effects and molecular mechanisms of a clinically relevant combination of highly active antiretroviral therapy (HAART) drugs on in vitro cholesterol efflux from human macrophage-derived foam cells. Foam cells derived from human monocyte cell line (THP-1) and periphery blood mononuclear cells (PBMCs) treated with HAART drugs including stavudine, didanosine and indinavir individually or in combination of three drugs (3-plex), followed by the initiation of cholesterol efflux with apolipoprotein A-I (apoA-I). Clinically relevant concentrations of HAART 3-plex significantly reduced cholesterol efflux in foam cells derived from THP-1 and PBMCs. HAART 3-plex significantly reduced the intracellular cholesterol transport molecule caveolin-1, whereas it increased superoxide anion production in THP-1 foam cells as compared with controls. Furthermore, mitochondrial membrane potential was significantly reduced, whereas the expression of NADPH oxidase subunit p67(phox) was increased in HAART 3-plex-treated macrophages. Consequently, antioxidants including ginsenosides Rb1 and Rg1, S-allyl cysteine sulphoxide (SACS), simvastatin (SVT) and vitamin E significantly abolished HAART 3-plex-induced inhibition of cholesterol efflux. Therefore, HAART drugs significantly inhibit cholesterol efflux from human macrophage-derived foam cells through downregulation of caveolin-1 and increase of oxidative stress.

Atorvastatin modifies the protein profile of circulating human monocytes after an acute coronary syndrome

Aggressive treatment with high-dose atorvastatin reduces more effectively the incidence of cardiovascular events than moderate statin therapy. The mechanism of this benefit has not been fully elucidated. In order to know the potential effects of statin treatment on the protein expression of circulating monocytes in acute coronary syndrome (ACS) patients, a proteomic analysis of these cells was carried out by 2-DE and MS. Twenty-five patients with non-ST-elevation acute coronary syndrome (NSTEACS) were randomized, the fourth day after admission, to receive ATV 80 mg/dL (n = 14) or conventional treatment (CT) (n = 11), for two months. Blood was withdrawn at the end of the treatment, and monocytes were extracted for proteomic analysis and their protein expression patterns determined. Age, sex, total cholesterol, LDL, HDL, triglycerides, body mass index, presence of hypertension, diabetes, and smoking status were not significantly different between the two groups of patients. The expression of 20 proteins was modified by intensive ATV. Among the most relevant results stand out the normalization by intensive ATV treatment of the expression of proteins that modulate inflammation and thrombosis such as protein disulfide isomerase ER60 (PDI), Annexin I, and prohibitin, or that have other protective effects as HSP-70. Thus, this approach shed light at the molecular level of the beneficial mechanisms of anti-atherothrombotic drugs.

Induction of the cytoprotective enzyme heme oxygenase-1 by statins is enhanced in vascular endothelium exposed to laminar shear stress and impaired by disturbed flow

In addition to cholesterol-lowering properties, statins exhibit lipid-independent immunomodulatory, anti-inflammatory actions. However, high concentrations are typically required to induce these effects in vitro, raising questions concerning therapeutic relevance. We present evidence that endothelial cell sensitivity to statins depends upon shear stress. Using heme oxygenase-1 expression as a model, we demonstrate differential heme oxygenase-1 induction by atorvastatin in atheroresistant compared with atheroprone sites of the murine aorta. In vitro, exposure of human endothelial cells to laminar shear stress significantly reduced the statin concentration required to induce heme oxygenase-1 and protect against H(2)O(2)-mediated injury. Synergy was observed between laminar shear stress and atorvastatin, resulting in optimal expression of heme oxygenase-1 and resistance to oxidative stress, a response inhibited by heme oxygenase-1 small interfering RNA. Moreover, treatment of laminar shear stress-exposed endothelial cells resulted in a significant fall in intracellular cholesterol. Mechanistically, synergy required Akt phosphorylation, activation of Kruppel-like factor 2, NF-E2-related factor-2 (Nrf2), increased nitric-oxide synthase activity, and enhanced HO-1 mRNA stability. In contrast, heme oxygenase-1 induction by atorvastatin in endothelial cells exposed to oscillatory flow was markedly attenuated. We have identified a novel relationship between laminar shear stress and statins, demonstrating that atorvastatin-mediated heme oxygenase-1-dependent antioxidant effects are laminar shear stress-dependent, proving the principle that biomechanical signaling contributes significantly to endothelial responsiveness to pharmacological agents. Our findings suggest statin pleiotropy may be suboptimal at disturbed flow atherosusceptible sites, emphasizing the need for more specific therapeutic agents, such as those targeting Kruppel-like factor 2 or Nrf2.

HSP 70 and atherosclerosis--protector or activator?

BACKGROUND

Atherosclerosis and its complications represent the leading cause of morbidity and mortality. Heat shock protein 70 (HSP70) protects cellular elements from injury by reducing oxidation, inflammation and apoptosis and by refolding damaged proteins. HSP70 improves viability of stressed vascular smooth muscle cells, possibly via its chaperone functions. It has been proposed that the response mounted against bacterial HSPs results in an autoimmune reaction, which has the potential to cause complement-mediated endothelial injury, and hence accelerate atherogenesis.

OBJECTIVE

to examine the roles of HSPs in atherosclerosis.

METHODS

A literature review.

RESULTS/CONCLUSIONS

The role of HSPs in atherosclerosis is controversial. HSP60 probably acts as an autoantigen, and may trigger both cell- and antibody-mediated immune responses, while HSP70 is likely to be involved in cytoprotection. The significance of this inverse relation between HSP70 and atherosclerosis has not yet been elucidated. Whether HSPs will become therapeutic targets remains to be established.

Anti-atherogenic effect of statins: role of nitric oxide, peroxynitrite and haem oxygenase-1

BACKGROUND AND PURPOSE

The pleiotropic effects of HMG-CoA inhibitors (statins), which include anti-inflammation, antioxidation and immunomodulation, are not yet fully understood. The present study was designed to elucidate the role of nitric oxide (NO), peroxynitrite (ONOO(-)) and haem oxygenase-1 (HO-1) in the anti-atherogenic effect of statins.

EXPERIMENTAL APPROACH

Normal and atherosclerotic New Zealand rabbits were treated with atorvastatin or simvastatin in the presence or absence of inhibitors and promoters of endothelial nitric oxide synthase (eNOS) and HO-1. NO and ONOO(-) released from isolated aortae by calcium ionophore were measured with nanosensors placed 6 +/- 2 nm from aortic endothelium. Expression of eNOS and HO-1 protein, HO activity, plasma malondialdehyde (MDA) and vessel wall thickness were also measured.

KEY RESULTS

Hypercholesterolaemia decreased eNOS expression by 31 +/- 3%, decreased NO (230 +/- 16 vs. 433 +/- 17 nmol x L(-1) control) and increased cytotoxic ONOO(-) (299 +/- 15 vs. 187 +/- 11 nmol x L(-1) control). The concentration ratio of [NO]/[ONOO(-)] decreased from 2.3 +/- 0.1 (normal) to 0.7 +/- 0.1 indicating an increase of nitroxidative stress in atherosclerotic endothelium. Expression of HO-1 protein increased by 20 +/- 8% in atherosclerosis and further increased (about 30%) after treatment with statins. Statins partially restored the [NO]/[ONOO(-)] balance (1.5 +/- 0.1 for atorvastatin and 1.4 +/- 0.1 simvastatin), decreased MDA and wall thickening. Promoters of eNOS and HO-1 (L-arginine and haemin) ameliorated the [NO]/[ONOO(-)] ratio while their inhibitors (L-NAME or tin-protoporphyrin) showed no improvement in these ratio.

CONCLUSIONS AND IMPLICATIONS

Atherosclerosis induced an endothelial [NO]/[ONOO(-)] balance indicative of endothelial dysfunction. Statins showed anti-atherosclerotic effects mediated by HO-1/eNOS, restoring the [NO]/[ONOO(-)] imbalance and reducing lipid peroxidation.

Involvement of heat shock factor 1 in statin-induced transcriptional upregulation of endothelial thrombomodulin

Statins upregulate endothelial thrombomodulin (TM) by mechanisms that involve members of the Kruppel-like factor family. Although Kruppel-like factors are unequivocally implicated in this process, experimental evidence points to additional mechanisms. Deletion/mutation analysis of reporter constructs was used to demonstrate that mutation of the SP1/Kruppel-like factor element in the TM promoter only partially abolishes statin-induced TM upregulation, whereas simultaneous mutation of relevant heat shock elements and SP1/Kruppel-like factor element completely prevents statin-induced TM upregulation, thus demonstrating a role for heat shock factors (HSFs). We further identified the pathway by which statins increase binding of HSF1 to heat shock elements in the TM promoter. Specifically, statins caused NO-dependent dissociation of HSF1 from heat shock protein 90, nuclear translocation of HSF1, and binding to heat shock elements in the TM promoter. Statins also decreased nuclear content of the HSF1 chaperone 14-3-3beta. In addition to reducing TM upregulation, inhibition of HSF1 reduced statin-induced upregulation of tissue plasminogen activator, whereas downregulation of thrombomospondin, plasminogen activator inhibitor 1, or connective tissue growth factor was unaffected. Knockdown of 14-3-3beta or inhibition of HSF1 phosphorylation enhanced the effect of statins on TM and tissue plasminogen activator, but did not influence thrombomospondin, plasminogen activator inhibitor 1, or connective tissue growth factor. These data demonstrate that HSF1 is involved in statin-induced regulation of TM. They also suggest that analogous mechanisms may apply to genes that are upregulated by statins, but not to downregulated genes. These results may have broad implications and suggest the use of heat shock protein modulators to selectively regulate pleiotropic statin effects.

Pharmacological preconditioning with simvastatin protects liver from ischemia-reperfusion injury by heme oxygenase-1 induction

BACKGROUND

The protective role of heme oxygenase-1 (HO-1) against liver ischemia-reperfusion (I/R) injury in models of hypoxic and remote preconditioning has been proved. The feasible candidates who induce HO-1 and thorough which exert the protective effects are under investigation. The aim was to study the role of HO-1 in pharmacological preconditioning by simvastatin in a rat model.

METHODS

Pharmacological preconditioning by intraperitoneal injection of simvastatin (5 mg/kg) was tested on a partial liver I/R model on rats. The expression of HO-1 protein and enzyme activities in livers, serum alanine transaminase (ALT) levels, and TUNEL staining of liver after I/R injury were measured in rats with and without simvastatin preconditioning.

RESULTS

HO-1 was induced and persistently overexpressed in the hepatocytes 24 hr after simvastatin treatment. Simvastatin preconditioning diminished the elevation of serum ALT levels 4 hr after I/R injury (69.6+/-26.3 U/L) (P<0.05 vs. other groups) when compared with control (403.8+/-261.9 U/L) and zinc protoporphyrin (ZnPP)-pretreated (717.5+/-205.6 U/L) groups. Simvastatin preconditioning diminished the apoptosis after I/R injury as well (apoptosis index: 26.4+/-8 for Simvastatin, 78+/-7 for control, and 85.3+/-2 for ZnPP group; P<0.05). The addition of ZnPP negated the protective effects of simvastatin as evidenced in the ALT level (406.2+/-243.0 U/L) and apoptosis index (75.6+/-6). The heme oxygenase activity in treated rats correlated with these results.

CONCLUSIONS

The induction of HO-1 by simvastatin preconditioning played a protective role against hepatic I/R injury.

Statin-mediated cytoprotection of human vascular endothelial cells: a role for Kruppel-like factor 2-dependent induction of heme oxygenase-1

BACKGROUND

Heme oxygenase-1 (HO-1), by exerting anti-inflammatory, antiproliferative, antiapoptotic and antioxidant effects in the vasculature, protects against atherosclerosis and post-transplant vasculopathy. We noted the overlap between the effects of HO-1 and those attributed to 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins). This led to an investigation of the role of HO-1 in statin-mediated cytoprotection in primary human endothelial cells (ECs), and the ability of Kruppel-like factor 2 (KLF2) to regulate HO-1 function.

METHODS/RESULTS

Treatment of human umbilical vein and aortic ECs with atorvastatin significantly upregulated HO-1 promoter activity, mRNA expression and protein expression, increasing HO-1 enzymatic activity as shown by raised intracellular bilirubin IXalpha. This effect was indirect, dependent upon inhibition of HMG-CoA reductase and geranylgeranylation, and independent of nitric oxide or changes in mRNA stability. Atorvastatin protected ECs against the generation of reactive oxygen species and H(2)O(2)-induced injury. HO-1 inhibition, with small interfering RNA (siRNA) or zinc protoporphyrin IX, abrogated atorvastatin-mediated cytoprotection. Atorvastatin upregulated KLF2 expression, whereas KLF2 siRNA attenuated statin-induced HO-1 and its associated antioxidant cytoprotective effects. Iron chelation, adenoviral-mediated overexpression of ferritin or supplementation of culture media with biliverdin reversed the inhibitory effects of HO-1 and KLF2 siRNA, suggesting that bile pigments and ferritin mediate the antioxidant actions of statin-induced HO-1.

CONCLUSIONS

We have identified a novel link between KLF2 and HO-1 in human vascular ECs, demonstrating that atorvastatin-mediated HO-1 upregulation, and its associated antioxidant effect, is KLF2-dependent. The relationship between KLF2 and HO-1 is likely to represent an important component of the vasculoprotective profile of statins.

Atorvastatin prevents hypoxia-induced inhibition of endothelial nitric oxide synthase expression but does not affect heme oxygenase-1 in human microvascular endothelial cells

Beneficial cardiovascular effects of statins, the inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, are particularly assigned to the modulation of inflammation. Endothelial nitric oxide synthase (eNOS) and heme oxygenase-1 (HO-1) are listed among the crucial protective, anti-inflammatory genes in the vasculature. Here we show that atorvastatin at pharmacologically relevant concentration (0.1 microM) enhanced the expression of eNOS in human microvascular endothelial cells (HMEC-1). Moreover, atorvastatin prevented hypoxia-induced decrease in eNOS expression. However, in the same cells atorvastatin was ineffective in modulation of HO-1 protein level. Therefore, we suggest that the protective effect of statins at their pharmacological concentrations is not mediated by enhancement of HO-1 activity, but may involve eNOS.