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

Antioxidant Effects of Statins by Modulating Nrf2 and Nrf2/HO-1 Signaling in Different Diseases

Statins are competitive inhibitors of hydroxymethylglutaryl-CoA (HMG-CoA) reductase and have been used to treat elevated low-density lipoprotein cholesterol (LDL-C) for almost four decades. Antioxidant and anti-inflammatory properties which are independent of the lipid-lowering effects of statins, i.e., their pleiotropic effects, might be beneficial in the prevention or treatment of many diseases. This review discusses the antioxidant effects of statins achieved by modulating the nuclear factor erythroid 2 related factor 2/ heme oxygenase-1 (Nrf2/HO-1) pathway in different organs and diseases. Nrf2 and other proteins involved in the Nrf2/HO-1 signaling pathway have a crucial role in cellular responses to oxidative stress, which is a risk factor for ASCVD. Statins can significantly increase the DNA-binding activity of Nrf2 and induce the expression of its target genes, such as HO-1 and glutathione peroxidase) GPx, (thus protecting the cells against oxidative stress. Antioxidant and anti-inflammatory properties of statins, which are independent of their lipid-lowering effects, could be partly explained by the modulation of the Nrf2/HO-1 pathway.

Simvastatin does not alleviate muscle pathology in a mouse model of Duchenne muscular dystrophy

Background

Duchenne muscular dystrophy (DMD) is an incurable disease, caused by the mutations in the DMD gene, encoding dystrophin, an actin-binding cytoskeletal protein. Lack of functional dystrophin results in muscle weakness, degeneration, and as an outcome cardiac and respiratory failure. As there is still no cure for affected individuals, the pharmacological compounds with the potential to treat or at least attenuate the symptoms of the disease are under constant evaluation. The pleiotropic agents, 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, known as statins, have been suggested to exert beneficial effects in the mouse model of DMD. On the other hand, they were also reported to induce skeletal-muscle myopathy. Therefore, we decided to verify the hypothesis that simvastatin may be considered a potential therapeutic agent in DMD.

Methods

Several methods including functional assessment of muscle function via grip strength measurement, treadmill test, and single-muscle force estimation, enzymatic assays, histological analysis of muscle damage, gene expression evaluation, and immunofluorescence staining were conducted to study simvastatin-related alterations in the mdx mouse model of DMD.

Results

In our study, simvastatin treatment of mdx mice did not result in improved running performance, grip strength, or specific force of the single muscle. Creatine kinase and lactate dehydrogenase activity, markers of muscle injury, were also unaffected by simvastatin delivery in mdx mice. Furthermore, no significant changes in inflammation, fibrosis, and angiogenesis were noted. Despite the decreased percentage of centrally nucleated myofibers in gastrocnemius muscle after simvastatin delivery, no changes were noticed in other regeneration-related parameters. Of note, even an increased rate of necrosis was found in simvastatin-treated mdx mice.

Conclusion

In conclusion, our study revealed that simvastatin does not ameliorate DMD pathology.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13395-021-00276-3.

Nanocurcumin and arginine entrapped injectable chitosan hydrogel for restoration of hypoxia induced endothelial dysfunction

Hypoxia is a condition that gradually leads to ischemic damages in organs which is marked by poor tissue perfusion. Depending on the severity of the condition, revascularisation therapies are needed for reducing the risk of organ dysfunction. This study was aimed at developing an injectable nanocurcumin and arginine incorporated chitosan hydrogel (nC/R) that can prevent hypoxia induced endothelial damage. The prepared hydrogel has shear thinning, stable and injectable nature. The (nC and nC/R) hydrogels showed significant antioxidant activity and biodegradation in vitro. The release of curucmin and arginine from the nC/R was found to be higher at acidic pH, which predominates in an ischemic site. To mimic low oxygen environment, an in vitro hypoxic endothelial dysfunction model was developed which showed decreased expressions of phosphorylated eNOS (serine 1177) when compared to the cells cultured in normoxic condition. In vitro tube formation assay demonstrated the protective effect of nC/R towards hypoxia induced reduction of tube width. The nC/R hydrogel was found to enhance phosphorylation of eNOS at serine 1177 site in cultured endothelial cells subjected to hypoxia. Therefore, nC/R hydrogel could effectively deliver both curcumin and arginine and therapeutically reduce the effect of hypoxia induced endothelial dysfunction.

Atorvastatin and Conditioned Media from Atorvastatin-Treated Human Hematopoietic Stem/Progenitor-Derived Cells Show Proangiogenic Activity In Vitro but Not In Vivo

Myeloid angiogenic cells (MAC) derive from hematopoietic stem/progenitor cells (HSPCs) that are mobilized from the bone marrow. They home to sites of neovascularization and contribute to angiogenesis by production of paracrine factors. The number and function of proangiogenic cells are impaired in patients with diabetes or cardiovascular diseases. Both conditions can be accompanied by decreased levels of heme oxygenase-1 (HMOX1), cytoprotective, heme-degrading enzyme. Our study is aimed at investigating whether precursors of myeloid angiogenic cells (PACs) treated with known pharmaceuticals would produce media with better proangiogenic activity in vitro and if such media can be used to stimulate blood vessel growth in vivo. We used G-CSF-mobilized CD34⁺ HSPCs, FACS-sorted from healthy donor peripheral blood mononuclear cells (PBMCs). Sorted cells were predominantly CD133⁺. CD34⁺ cells after six days in culture were stimulated with atorvastatin (AT), acetylsalicylic acid (ASA), sulforaphane (SR), resveratrol (RV), or metformin (Met) for 48 h. Conditioned media from such cells were then used to stimulate human aortic endothelial cells (HAoECs) to enhance tube-like structure formation in a Matrigel assay. The only stimulant that enhanced PAC paracrine angiogenic activity was atorvastatin, which also had ability to stabilize endothelial tubes in vitro. On the other hand, the only one that induced heme oxygenase-1 expression was sulforaphane, a known activator of a HMOX1 inducer—NRF2. None of the stimulants changed significantly the levels of 30 cytokines and growth factors tested with the multiplex test. Then, we used atorvastatin-stimulated cells or conditioned media from them in the Matrigel plug in vivo angiogenic assay. Neither AT alone in control media nor conditioned media nor AT-stimulated cells affected numbers of endothelial cells in the plug or plug's vascularization. Concluding, high concentrations of atorvastatin stabilize tubes and enhance the paracrine angiogenic activity of human PAC cells in vitro. However, the effect was not observed in vivo. Therefore, the use of conditioned media from atorvastatin-treated PAC is not a promising therapeutic strategy to enhance angiogenesis.

Targeting angiogenesis in Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) represents one of the most devastating types of muscular dystrophies which affect boys already at early childhood. Despite the fact that the primary cause of the disease, namely the lack of functional dystrophin is known already for more than 30 years, DMD still remains an incurable disease. Thus, an enormous effort has been made during recent years to reveal novel mechanisms that could provide therapeutic targets for DMD, especially because glucocorticoids treatment acts mostly symptomatic and exerts many side effects, whereas the effectiveness of genetic approaches aiming at the restoration of functional dystrophin is under the constant debate. Taking into account that dystrophin expression is not restricted to muscle cells, but is present also in, e.g., endothelial cells, alterations in angiogenesis process have been proposed to have a significant impact on DMD progression. Indeed, already before the discovery of dystrophin, several abnormalities in blood vessels structure and function have been revealed, suggesting that targeting angiogenesis could be beneficial in DMD. In this review, we will summarize current knowledge about the angiogenesis status both in animal models of DMD as well as in DMD patients, focusing on different organs as well as age- and sex-dependent effects. Moreover, we will critically discuss some approaches such as modulation of vascular endothelial growth factor or nitric oxide related pathways, to enhance angiogenesis and attenuate the dystrophic phenotype. Additionally, we will suggest the potential role of other mediators, such as heme oxygenase-1 or statins in those processes.

Simvastatin Treatment Upregulates HO-1 in Patients with Abdominal Aortic Aneurysm but Independently of Nrf2

Heme oxygenase-1 (HO-1), encoded by HMOX1 gene and regulated by Nrf2 transcription factor, is a cytoprotective enzyme. Its deficiency may exacerbate abdominal aortic aneurysm (AAA) development, which is also often associated with hyperlipidemia. Beneficial effects of statins, the broadly used antilipidemic drugs, were attributed to modulation of Nrf2/HO-1 axis. However, the effect of statins on Nrf2/HO-1 pathway in patients with AAA has not been studied yet. We analyzed AAA tissue from patients treated with simvastatin (N = 28) or without statins (N = 14). Simvastatin treatment increased HO-1 protein level in AAA, both in endothelial cells (ECs) and in smooth muscle cells (SMCs), but increased Nrf2 localization was restricted only to vasa vasorum. Nrf2 target genes HMOX1, NQO1, and GCLM expression remained unchanged in AAA. In vitro studies showed that simvastatin raises HO-1 protein level slightly in ECs and to much higher extent in SMCs, which is not related to Nrf2/ARE activation, although HMOX1 expression is upregulated by simvastatin in both cell types. In conclusion, simvastatin-induced modulation of HO-1 level in ECs and SMCs in vitro is not related to Nrf2/ARE activity. Likewise, divergent HO-1 and Nrf2 localization together with stable expression of Nrf2 target genes, including HMOX1, in AAA tissue denotes Nrf2 independency.

Effect of simvastatin on mitochondrial enzyme activities, ghrelin, hypoxia-inducible factor 1α in hepatic tissue during early phase of sepsis

We aimed to investigate the effects of prior treatment of simvastatin on mitochondrial enzyme, ghrelin, and hypoxia-inducible factor 1 α (HIF-1 α) on hepatic tissue in rats treated with Lipopolysaccharides (LPS) during the early phase of sepsis. Rats were divided into four groups: control, LPS (20 mg/kg, i.p.), Simvastatin (20 mg/kg, p.o.), and LPS + Simvastatin group. We measured citrate synthase, complex I, II, I-III, II-III enzymes activities, serum and tissue levels of TNF-α, IL-10 using ELISA. Liver sections underwent histopathologic examination and TNF-α, IL-10, HIF-1α and ghrelin immunoreactivity were examined using immunohistochemistry methods. There were no differences in all groups for mitochondrial enzyme activities. In terms of both ELISA and immunohistochemistry findings; the levels of serum and tissue TNF-α and IL-10 were higher in the experimental groups than controls (P < 0.05). In the LPS group, the hepatocyte cell membrane and sinusoid structure were damaged. In the Simvastatin +LPS group, hepatocytes and sinusoidal cord structure were partially improved. For HIF-1α, in all experimental groups immunoreactivity was increased (P < 0.05). In the Simvastatin group, Ghrelin levels were increased in comparison with the other groups (P < 0.01). Ghrelin levels were greatly decreased in LPS (P < 0.05). We observed that the degree of hepatocellular degeneration was partially reduced depending on the dosage and duration of prior simvastatin treatment with LPS, probably due to alterations of Ghrelin and HIF-1α levels.

Drugs and acute porphyrias: reasons for a hazardous relationship

The porphyrias are a group of metabolic diseases caused by inherited or acquired enzymatic deficiency in the metabolic pathway of heme biosynthesis. Simplistically, they can be considered as storage diseases, because the partial enzymatic defect gives rise to a metabolic "bottleneck" in the biosynthetic pathway and hence to an accumulation of different metabolic intermediates, potentially toxic and responsible for the various (cutaneous or neurovisceral) clinical manifestations observed in these diseases. In the acute porphyrias (acute intermittent porphyria, hereditary coproporphyria, variegate porphyria, and the very rare delta-aminolevulinic acid dehydratase ALAD-d porphyria), the characteristic severe neurovisceral involvement is mainly ascribed to a tissue accumulation of delta-aminolevulinic acid, a neurotoxic nonporphyrin precursor. Many different factors, both endogenous and exogenous, may favor the accumulation of this precursor in patients who are carriers of an enzymatic defect consistent with an acute porphyria, thus contributing to trigger the serious (and potentially fatal) clinical manifestations of the disease (acute porphyric attacks). To date, many different drugs are known to be able to precipitate an acute porphyric attack, so that the acute porphyrias are also considered as pharmacogenetic or toxygenetic diseases. This article reviews the different biochemical mechanisms underlying the capacity of many drugs to precipitate a porphyric acute attack (drug porphyrogenicity) in carriers of genetic mutations responsible for acute porphyrias, and addresses the issue of prescribing drugs for patients affected by these rare, but extremely complex, diseases.

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.

Treatment With Low-dose Atorvastatin, Losartan, and Their Combination Increases Expression of Vasoactive-Related Genes in Rat Aortas

Recently it has been shown that statins and angiotensin receptor blockers (ARBs) at low doses express beneficial pleiotropic vascular effects. We aimed to explore whether these drugs at low doses induce the expression of vasoactive-related genes. Sixty adult Wistar rats were treated with low-dose atorvastatin (2 mg/kg), low-dose losartan (5 mg/kg), their combination or saline daily for 4, 6, or 8 weeks. Expression of the vasoactive-related genes endothelin receptor type A ( EDNRA), endothelial nitric oxide synthase 3 ( NOS3), inducible nitric oxide synthase 2 ( NOS2), and angiotensin II receptor type 1 ( AGTRL1a) was measured in isolated thoracic aortas. Expression of EDNRA gradually decreased, the lowest values being obtained after 8 weeks (low-dose atorvastatin, losartan [1.6- and 1-7-fold vs controls, respectively; both P < .05], and the combination [2.3-fold vs control, P < .001]). The highest values of NOS3 were obtained after 6 weeks (low-dose atorvastatin, losartan, and their combination, 3.1-fold, P < .01; 3.4-fold, P < .001; and 3.6-fold, P < .001 vs controls, respectively) and then declined after 8 weeks. The combination was more effective in inducing total NOS3 expression when compared to the separate drugs (1.4-fold; P < .05). Importantly, expression of NOS3 was associated with increased plasma NO levels and positively correlated with thoracic aorta relaxation. No changes in expression of NOS2 and AGTRL1a were observed. We showed that low-dose atorvastatin or losartan and especially their combination increases the expression of NOS3 and decreases the expression of EDNRA. These findings are valuable in explaining the effectiveness of the “low-dose pharmacological approach” for improvement in arterial function.

The index of microcirculatory resistance predicts myocardial infarction related to percutaneous coronary intervention

BACKGROUND

Periprocedural myocardial infarction (MI) occurs in a significant proportion of patients undergoing percutaneous coronary intervention (PCI) and portends poor outcomes. Currently, no clinically applicable method predicts periprocedural MI in the cardiac catheterization laboratory before it occurs. We hypothesized that impaired baseline coronary microcirculatory reserve, which reduces the ability to tolerate ischemic insults, is a risk for periprocedural MI and that the index of microcirculatory resistance (IMR) measured during PCI can predict occurrence of periprocedural MI.

METHODS AND RESULTS

Consecutive patients undergoing elective PCI of a single lesion in the left anterior descending coronary artery were recruited. A pressure-temperature sensor wire was used to measure IMR before PCI. Of the 50 patients studied, 10 had periprocedural MI. From binary logistic regression analyses of all clinical, procedural, and physiological parameters, univariable predictors of periprocedural MI were pre-PCI IMR (P=0.003) and the number of stents used (P=0.039). Pre-PCI IMR was the only independent predictor in bivariable regression analyses performed by adjusting for each available covariate one at a time (all P≤0.02). Pre-PCI IMR ≥27 U had 80.0% sensitivity and 85.0% specificity for predicting periprocedural MI (C statistic, 0.80; P=0.003). Pre-PCI IMR ≥27 U was independently associated with a 23-fold risk of developing periprocedural MI (odds ratio, 22.7; 95% CI, 3.8-133.9).

CONCLUSIONS

These data suggest that the status of the coronary microcirculation plays a role in determining susceptibility toward periprocedural MI at the time of elective PCI. The IMR can predict subsequent risk of developing myocardial necrosis and may guide adjunctive prevention strategies.

Hypoxia induces angiogenic factors in brain microvascular endothelial cells

Hypoxia is increasingly recognized as an important contributing factor to the development of brain diseases such as Alzheimer's disease (AD). In the periphery, hypoxia is a powerful regulator of angiogenesis. However, vascular endothelial cells are remarkably heterogeneous and little is known about how brain endothelial cells respond to hypoxic challenge. The objective of this study is to characterize the effect of hypoxic challenge on the angiogenic response of cultured brain-derived microvascular endothelial cells. Brain endothelial cell cultures were initiated from isolated rat brain microvessels and subjected to hypoxia (1% O(2)) for various time periods. The results showed that hypoxia induced rapid (≤ 0.5h) expression of hypoxia-inducible factor 1α (HIF-1α) and that cell viability, assessed by MTT assay, was unaffected within the first 8h. Examination of brain endothelial cell cultures for pro- and anti-angiogenic proteins by western blot, RT-PCR and ELISA revealed that within 0.5 to 2h of hypoxia levels of vascular endothelial growth factor and endothelin-1 mRNA and protein were elevated. The expression of heme oxygenase-1 also increased but only after 8h of hypoxia. In contrast, similar hypoxia exposure evoked a decrease in endothelial nitric oxide synthase and thrombospondin-2 levels. Exposure of brain endothelial cell cultures to hypoxia resulted in a significant (p<0.001) decrease (94%) in tube length, an in vitro index of angiogenesis, compared to control cultures. The data indicate that, despite a shift toward a pro-angiogenic phenotype, hypoxia inhibited vessel formation in brain endothelial cells. These results suggest that in brain endothelial cells expression of angiogenic factors is not sufficient for the development of new vessels. Further work is needed to determine what factors/conditions prevent hypoxia-induced angiogenic changes from culminating in the formation of new brain blood vessels and what role this may play in the pathologic changes observed in AD and other diseases characterized by cerebral hypoxia.

Protective role of heme oxygenase-1 against inflammation in atherosclerosis

Heme oxygenase-1 (HO-1) catalyzes the first and rate-limiting step in the metabolism of free heme into equimolar amounts of ferrous iron, carbon monoxide (CO), and biliverdin. Biliverdin is subsequently converted to bilirubin by biliverdin reductase. HO-1 has recently been identified as a promising therapeutic target in the treatment of vascular inflammatory disease, including atherosclerosis. HO-1 represses inflammation by removing the pro-inflammatory molecule heme and by generating CO and the bile pigments, biliverdin and bilirubin. These HO-1 reaction products are capable of blocking innate and adaptive immune responses by modifying the activation, differentiation, maturation, and/or polarization of numerous immune cells, including endothelial cells, monocytes/macrophages, dendritic cells, T lymphocytes, mast cells, and platelets. These cellular actions by CO and bile pigments result in diminished leukocyte recruitment and infiltration, and pro-inflammatory mediator production within atherosclerotic lesions. This review highlights the mechanisms by which HO-1 suppresses vascular inflammation in atherosclerosis, and explores possible therapeutic modalities by which HO-1 and its reaction products can be employed to ameliorate vascular inflammatory disease.

Targeting heme oxygenase-1 in vascular disease

Heme oxygenase-1 (HO-1) metabolizes heme to generate carbon monoxide (CO), biliverdin, and iron. Biliverdin is subsequently metabolized to bilirubin by biliverdin reductase. HO-1 has recently emerged as a promising therapeutic target in the treatment of vascular disease. Pharmacological induction or gene transfer of HO-1 ameliorates vascular dysfunction in animal models of atherosclerosis, post-angioplasty restenosis, vein graft stenosis, thrombosis, myocardial infarction, and hypertension, while inhibition of HO-1 activity or gene deletion exacerbates these disorders. The vasoprotection afforded by HO-1 is largely attributable to its end products: CO and the bile pigments, biliverdin and bilirubin. These end products exert potent anti-inflammatory, antioxidant, anti-apoptotic, and anti-thrombotic actions. In addition, CO and bile pigments act to preserve vascular homeostasis at sites of arterial injury by influencing the proliferation, migration, and adhesion of vascular smooth muscle cells, endothelial cells, endothelial progenitor cells, or leukocytes. Several strategies are currently being developed to target HO-1 in vascular disease. Pharmacological induction of HO-1 by heme derivatives, dietary antioxidants, or currently available drugs, is a promising near-term approach, while HO-1 gene delivery is a long-term therapeutic goal. Direct administration of CO via inhalation or through the use of CO-releasing molecules and/or CO-sensitizing agents provides an attractive alternative approach in targeting HO-1. Furthermore, delivery of bile pigments, either alone or in combination with CO, presents another avenue for protecting against vascular disease. Since HO-1 and its products are potentially toxic, a major challenge will be to devise clinically effective therapeutic modalities that target HO-1 without causing any adverse effects.

Heme oxygenase in the regulation of vascular biology: from molecular mechanisms to therapeutic opportunities

Heme oxygenases (HOs) are the rate-limiting enzymes in the catabolism of heme into biliverdin, free iron, and carbon monoxide. Two genetically distinct isoforms of HO have been characterized: an inducible form, HO-1, and a constitutively expressed form, HO-2. HO-1 is a kind of stress protein, and thus regarded as a sensitive and reliable indicator of cellular oxidative stress. The HO system acts as potent antioxidants, protects endothelial cells from apoptosis, is involved in regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in angiogenesis and vasculogenesis. Endothelial integrity and activity are thought to occupy the central position in the pathogenesis of cardiovascular diseases. Cardiovascular disease risk conditions converge in the contribution to oxidative stress. The oxidative stress leads to endothelial and vascular smooth muscle cell dysfunction with increases in vessel tone, cell growth, and gene expression that create a pro-thrombotic/pro-inflammatory environment. Subsequent formation, progression, and obstruction of atherosclerotic plaque may result in myocardial infarction, stroke, and cardiovascular death. This background provides the rationale for exploring the potential therapeutic role for HO system in the amelioration of vascular inflammation and prevention of adverse cardiovascular outcomes.

Hypoxia preconditioning by cobalt chloride enhances endurance performance and protects skeletal muscles from exercise-induced oxidative damage in rats

AIM

Training under hypoxia has several advantages over normoxic training in terms of enhancing the physical performance. Therefore, we tested the protective effect of hypoxia preconditioning by hypoxia mimetic cobalt chloride against exercise-induced oxidative damage in the skeletal muscles and improvement of physical performance.

METHOD

Male Sprague-Dawley rats were randomly divided into four groups (n=8), namely control, cobalt-supplemented, training and cobalt with training. The red gastrocnemius muscle was examined for all measurements, viz. free radical generation, lipid peroxidation, muscle damage and antioxidative capacity.

RESULTS

Hypoxic preconditioning with cobalt along with training significantly increased physical performance (33%, P<0.01) in rats compared with training-only rats. Cobalt supplementation activated cellular oxygen sensing system in rat skeletal muscle. It also protected against training-induced oxidative damage as observed by an increase in the GSH/GSSG ratio (36%, P<0.001; 28%, P<0.01 respectively) and reduced lipid peroxidation (15%, P<0.01; 31%, P<0.01 respectively) in both trained and untrained rats compared with their respective controls. Cobalt supplementation along with training enhanced the expression of antioxidant proteins haem oxygenase-1 (HO-1; 1.2-fold, P<0.05) and metallothionein (MT; 4.8-fold, P<0.001) compared with training only. A marked reduction was observed in exercise-induced muscle fibre damage as indicated by decreased necrotic muscle fibre, decreased lipofuscin content of muscle and plasma creatine kinase level (16%, P<0.01) in rats preconditioned with cobalt.

CONCLUSION

Our study provides strong evidence that hypoxic preconditioning with cobalt chloride enhances physical performance and protects muscle from exercise-induced oxidative damage via GSH, HO-1 and MT-mediated antioxidative capacity.

Heme oxygenase in the regulation of vascular biology: from molecular mechanisms to therapeutic opportunities

Heme oxygenases (HOs) are the rate-limiting enzymes in the catabolism of heme into biliverdin, free iron, and carbon monoxide. Two genetically distinct isoforms of HO have been characterized: an inducible form, HO-1, and a constitutively expressed form, HO-2. HO-1 is a kind of stress protein, and thus regarded as a sensitive and reliable indicator of cellular oxidative stress. The HO system acts as potent antioxidants, protects endothelial cells from apoptosis, is involved in regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in angiogenesis and vasculogenesis. Endothelial integrity and activity are thought to occupy the central position in the pathogenesis of cardiovascular diseases. Cardiovascular disease risk conditions converge in the contribution to oxidative stress. The oxidative stress leads to endothelial and vascular smooth muscle cell dysfunction with increases in vessel tone, cell growth, and gene expression that create a pro-thrombotic/pro-inflammatory environment. Subsequent formation, progression, and obstruction of atherosclerotic plaque may result in myocardial infarction, stroke, and cardiovascular death. This background provides the rationale for exploring the potential therapeutic role for HO system in the amelioration of vascular inflammation and prevention of adverse cardiovascular outcomes.

Simvastatin induces heme oxygenase-1 expression but fails to reduce inflammation in the capsule surrounding a silicone shell implant in rats

BACKGROUND

Statins are lipid-lowering agents that are widely used in medical practice. Some studies have demonstrated that statins reduce proinflammatory signaling and have antioxidant and anti-inflammatory effects. The inducible heme oxygenase-1 (HO-1) catalyzes the stepwise degradation of heme to produce equimolar quantities of biliverdin, iron, and carbon monoxide; it has also been suggested to promote the important cholesterol-independent cytoprotective action of statins against oxidative insults. However, overexpression of HO-1 may have dual effects under oxidative stress, and the overaccumulation of ferric iron from heme may result in detrimental rather than cytoprotective effects. This study was designed to investigate the effect of a specific statin, simvastatin, and the role of HO-1 on the inflammatory status of the capsule surrounding a silicone shell implant in rats.

METHODS

Sprague-Dawley rats were randomly assigned to different groups according to the indicated implantation time (1 , 2 wk, 1 , 2 , and 3 mo postimplant) and the presence or absence of additional treatment (2 mg/kg oral simvastatin daily and/or 2 mg/kg HO inhibitor zinc protoporphyrin (ZnPP) by intraperitoneal injection daily). The formed de novo capsular tissue around the silicone implant was dissected away at the indicated time of sacrifice for experiments regarding the HO-1 expression and the inflammatory status.

RESULTS

We found a biphasic pattern of inflammation of the capsule with increased production of TNF-α, IL-1β, and COX-2, and activation of NF-κB at 1 wk and again at 1 mo postimplantation. Numerous CD68+monocytes or macrophages were diffusely distributed in the capsule in the early stage but not in the late stage postimplantation. In addition, the implantation procedure induced HO-1 expression, which was significantly up-regulated in the first 2 wk but decreased after 1 mo. Although daily feeding of the rats with simvastatin at 2 mg/kg induced HO-1 expression in the capsule throughout the experimental period, simvastatin treatment failed to reduce the production of TNF-α, IL-1β, and COX-2, or limit NF-κB activation in the early or late stages after implantation. Additionally, simvastatin treatment did not decrease the amount of CD68+cells distributed in the capsule at 1 wk postimplantation. HO-1 up-regulation by simvastatin treatment or down-regulation by additional injection of ZnPP did not demonstrate significant correlation with the inflammatory status of the capsule.

CONCLUSION

Simvastatin failed to reduce inflammation of the capsule surrounding a silicone shell implant. Although simvastatin induced HO-1 expression throughout the experimental time, up-regulated HO-1 expression could not be attributed to the inflammatory status of the capsule.

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.

HIF-1 induction attenuates Nrf2-dependent IL-8 expression in human endothelial cells

Through hypoxia-inducible factor 1 (HIF-1), hypoxia regulates the expression of numerous genes and is a potent inducer of angiogenesis. However, interleukin-8 (IL-8), an important angiogenic mediator, has been reported to be downregulated by HIF-1, although the mechanisms have not been elucidated. HIF-1 was induced in human endothelial cells by hypoxia and dimethyloxaloylglycine (DMOG). Interestingly, both hypoxia and DMOG attenuated IL-8 expression, and a similar effect has been obtained by adenoviral overexpression of the stable form of HIF-1alpha. Heme oxygenase-1 (HO-1) expression was also downregulated by HIF-1 induction. This suggests similar mechanisms of regulation of IL-8 and HO-1, indicating the involvement of Nrf2, a transcription factor previously linked to hypoxia-mediated inhibition of HO-1. Indeed, HIF-1-mediated downregulation of both IL-8 and HO-1 was associated with both lowered Nrf2 expression and induction of Bach1, a repressor of Nrf2 transcriptional activity. Accordingly, overexpression of Nrf2 reversed the inhibitory effect of HIF-1 on IL-8 and HO-1 expression. However, neither overexpression of HO-1 nor HO-1 inhibition affected IL-8 synthesis. The data indicate that HIF-1-dependent inhibition of IL-8 expression is caused by downregulation of Nrf2. However, expression of IL-8 is independent of HO-1. Cross-talk between HIF-1 and Nrf2 may influence the outcome of anti-angiogenic therapies aimed at targeting HIF-1. Antioxid.

HIF-1 attenuates Ref-1 expression in endothelial cells: reversal by siRNA and inhibition of geranylgeranylation

Redox factor-1 (Ref-1), a multifunctional protein with DNA repairing activities, plays a cytoprotective function by post-translational redox modification of numerous transcription factors, including hypoxia inducible factor-1 (HIF-1). In the present study, activation of HIF-1 by hypoxia and dimethyloxaloylglycine (DMOG), a hypoxia mimic, diminished Ref-1 mRNA and protein expression in human microvascular endothelial cells (HMEC-1). Similarly, adenoviral delivery of the stabilized form of HIF-1alpha decreased Ref-1 mRNA and protein levels. Accordingly, HIF-1alpha siRNA abolished the hypoxia-induced inhibition of Ref-1 expression, indicating the role of HIF-1 in down-regulation of Ref-1. Also, translocation of Ref-1 from nucleus to cytoplasm after HIF-1 activation was noted. Interestingly, we observed the restoration of Ref-1 expression in hypoxia by pharmacologically relevant doses of atorvastatin. This effect was dependent on the inhibition of protein geranylgeranylation, but not farnesylation, as only the inhibitor of the former but not the latter prenylation step restored the Ref-1 expression. The regulation of Ref-1 by statins may be considered as a novel mechanism of their beneficial effects on endothelium.

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.

Effect of heme oxygenase-1 on vascular function and disease

PURPOSE OF REVIEW

Heme oxygenase-1 apart from converting heme to carbon monoxide, iron and biliverdin has been shown to exert anti-inflammatory, antiapoptotic and antioxidant actions. The present review summarizes the most recent studies about heme oxygenase-1 involvement in atherosclerosis, neovascularization and endothelial progenitor cells biology.

RECENT FINDINGS

Heme oxygenase-1 has been shown to be protective against atherosclerosis via decreasing ROS generation and proinflammatory cytokine production resulting in diminished lipid uptake and foam cell formation. Moreover, heme oxygenase-1 role in neovascularization and its involvement in response of endothelial progenitor cells to stromal cell derived factor-1 as well as endothelial cells to vascular endothelial growth factor has been stressed, recently. The detailed mechanisms of heme oxygenase-1 action in the processes of vasculogenesis and angiogenesis as well as the involvement of Nrf2 and KLF2 transcription factors in heme oxygenase-1-dependent vascular protection are among the subjects most intensively studied, currently.

SUMMARY

Recent studies underscore the critical role of heme oxygenase-1 in neovascularization, implicating heme oxygenase-1 as an attractive therapeutic target for treatment of cardiovascular disease.

Heme oxygenase-1 and the vascular bed: from molecular mechanisms to therapeutic opportunities

Heme oxygenase-1, an enzyme degrading heme to carbon monoxide, iron, and biliverdin, has been recognized as playing a crucial role in cellular defense against stressful conditions, not only related to heme release. HO-1 protects endothelial cells from apoptosis, is involved in blood-vessel relaxation regulating vascular tone, attenuates inflammatory response in the vessel wall, and participates in blood-vessel formation by means of angiogenesis and vasculogenesis. The latter functions link HO-1 not only to cardiovascular ischemia but also to many other conditions that, like development, wound healing, or cancer, are dependent on neovascularization. The aim of this comprehensive review is to address the mechanisms of HO-1 regulation and function in cardiovascular physiology and pathology and to demonstrate some possible applications of the vast knowledge generated so far. Recent data provide powerful evidence for the involvement of HO-1 in the therapeutic effect of drugs used in cardiovascular diseases. Novel studies open the possibilities of application of HO-1 for gene and cell therapy. Therefore, research in forthcoming years should help to elucidate both the real role of HO-1 in the effect of drugs and the clinical feasibility of HO-1-based cell and gene therapy, creating the effective therapeutic avenues for this refined antioxidant system.

Heme oxygenase-1 and carbon monoxide in vascular pathobiology: focus on angiogenesis

Angiogenesis involves the formation of new blood vessels and is critical for fundamental events such as development and repair after injury. Perturbances in angiogenesis contribute to the pathogenesis of diverse clinical conditions including cancer, complications of diabetes mellitus, ischemia/reperfusion injury of the heart and other organs, and preeclampsia, as well as a number of inflammatory disorders. Recent work has identified heme oxygenase-1 and its gaseous product, carbon monoxide, to possess potent proangiogenic properties in addition to well-recognized antiinflammatory, antioxidant, and antiapoptotic effects. Angiogenic factors, such as vascular endothelial growth factor and stromal cell-derived factor-1, mediate their proangiogenic effects through induction of heme oxygenase-1, making it an attractive target for therapeutic intervention. This review will provide an overview of the role of heme oxygenase-1 and carbon monoxide in angiogenesis.

Statin-induced heme oxygenase-1 increases NF-kappaB activation and oxygen radical production in cultured neuronal cells exposed to lipopolysaccharide

With potentially neuroprotective properties, heme oxygenase-1 (HO-1) has been suggested to be the main mediator of cholesterol-independent anti-inflammatory and antioxidant actions of statins. However, we had demonstrated that simvastatin-induced HO-1 increased apoptosis of Neuro 2A cells in glucose deprivation, and iron production from HO-1 activity may be responsible for the toxicity. This study was designed to explore the effect of simvastatin-induced HO-1 on cultured Neuro 2A and C6 cells exposed to lipopolysaccharide (LPS). We found that the HO-1 upregulation was significantly associated with increased nuclear factor kappa B (NF-kappaB) activation, manifested as IkappaBalpha phosphorylation and p65 nuclear translocation, as well as increased production of superoxides. Inhibition of the induced HO-1 by zinc protoporphyrin reduced the increased NF-kappaB activation and superoxides production. RNA interference with HO-1 siRNA reduced the expression of HO-1 transcripts and protein as well as oxygen radical production. Addition of the iron chelator desferrioxamine to reduce the accumulation of ferric iron from heme by HO-1 resulted in blockade of the aggravated oxygen radical production. There was no significant effect on production of oxygen radicals under these conditions in the presence of a CO donor (RuCO) or a CO scavenger (hemoglobin). In addition, the viable cells were significantly decreased in 48 h in those cells receiving simvastatin pretreatment plus LPS compared to those in control or exposed to simvastatin or LPS alone. This study revealed that simvastatin-induced HO-1 led to increased NF-kappaB activation and superoxides production in the neuronal cells when exposed to LPS, and iron production may play a role in such a response.

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.

Hypoxia and heme oxygenases: oxygen sensing and regulation of expression

Heme is an essential molecule for life, as it is involved in sensing and using oxygen. Heme must be synthesized and degraded within an individual nucleated cell. Physiologic heme degradation is catalyzed by two functional isozymes of heme oxygenase, heme oxygenase-1 (HO-1) and HO-2, yielding carbon monoxide, iron, and biliverdin, an immediate precursor to bilirubin. HO-1 is an inducible enzyme, but the expression level of HO-2 is maintained in a narrow range. Characteristically, human HO-1 contains no Cys residue, whereas human HO-2 contains three Cys residues, each of which might be involved in heme binding. These features suggest separate physiologic roles of HO-1 and HO-2. Recent studies have shown that the expression levels of HO-1 and HO-2 are reduced under hypoxia, depending on the cell types. Moreover, we have proposed HO-2 as a potential O(2) sensor, because HO-2-deficient mice show hypoxemia and a blunted hypoxic ventilatory response with normal hypercapnic ventilatory response. HO-2-deficient mice also show hypertrophy of the pulmonary venous myocardium and enlargement of the carotid body. These morphometric changes are attributable to chronic hypoxemia. Here, we update the understanding of the regulation of HO-1 and HO-2 expression and summarize the regulatory role of HO-2 in the intercellular communication.

Pharmacologic induction of heme oxygenase-1

Heme oxygenase-1 (HO-1) is a cytoprotective protein whose expression is consistently associated with therapeutic benefits in a number of pathologic conditions such as atherosclerotic vascular disease and inflammation. Although the expression of HO-1 in most tissues is low, a large number of clinical and experimental pharmacologic compounds have been demonstrated to induce HO-1. This induction is suggested to be at least partially responsible for the perceived therapeutic efficacy of these compounds. The increase in HO-1 expression in response to these compounds is the result of a complex regulatory network involving many signaling pathways and transcription factors. Understanding both the pathways by which HO-1 is induced and the mechanism through which the enzyme exerts its beneficial effects may facilitate the development of novel drugs.

Treatment with atorvastatin reduces serum adipocyte-fatty acid binding protein value in patients with hyperlipidaemia

BACKGROUND

Adipocyte-fatty acid binding protein (A-FABP) is a circulating protein expressed in adipocytes and macrophages. Several recent studies demonstrated that A-FABP might be involved in the pathogenesis of metabolic syndrome, particularly in dyslipidaemia, insulin resistance and atherosclerosis. The aim of this study was to investigate the influence of atorvastatin treatment (20 mg day(-1) for 3 months) on serum A-FABP value in subjects with hyperlipidaemia.

MATERIALS AND METHODS

Anthropometric and serum analyses were performed for body mass index, A-FABP, triglycerides, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, uric acid, alanine aminotransferase (ALT), aspartate aminotransferase (AST), high sensitive C-reactive protein (hs-CRP), creatine kinase (CK) and glucose on 26 subjects (BMI 30.3 +/- 6.0, mean age 62 +/- 10 years) with hyperlipidaemia who met the criteria: total cholesterol > 5.2 mmol L(-1), LDL cholesterol > 3.3 mmol L(-1) and triglycerides < 3 mmol L(-1).

RESULTS

After the 3-month therapy, a significant reduction in total cholesterol (P < 0.001), LDL cholesterol (P < 0.001), glucose (P < 0.001), A-FABP (from 44.6 +/- 26.2 to 38.6 +/- 19.3 g L(-1), P < 0.01), uric acid (P < 0.05), AST (P < 0.05) and triglycerides (P < 0.05) values was observed. No difference was found in BMI, CK, ALT, hs-CRP, or HDL cholesterol values. A significant difference in the serum A-FABP value before and after the therapy remains after the correction for total cholesterol value (P < 0.001). A positive correlation between serum A-FABP and glucose was found (P < 0.05).

CONCLUSIONS

In conclusion, our study confirmed in vivo that atorvastatin reduces serum A-FABP by a pleiotropic mechanism and supports the hypothesis that A-FABP is involved in atherosclerotic actions.

Statin treatment increases formation of carbon monoxide and bilirubin in mice: a novel mechanism of in vivo antioxidant protection

Heme oxygenase (HO) has a central role in cellular antioxidant defences and vascular protection, and it may mediate pleiotropic actions of drugs used in cardiovascular therapy. We investigated whether long-term use of statins upregulates HO activity and increases carbon monoxide (CO) and bilirubin levels in vivo. Adult FvB mice were given atorvastatin or rosuvastatin (5 mg/kg) daily by i.p. injections for 1, 2, or 3 weeks. HO activity, tissue CO, bilirubin, and antioxidant levels, total plasma bilirubin, and carboxyhemoglobin (COHb) were measured. Fold changes in heart HO activity significantly increased after 1, 2, and 3 weeks of atorvastatin (1.24 ± 0.06 (p ≤ 0.05); 1.29 ± 0.26 (p ≤ 0.03); 1.33 ± 0.08 (p < 0.01), respectively) and 2 and 3 weeks of rosuvastatin (1.23 ± 0.20 (p ≤ 0.03); 1.63 ± 0.42 (p < 0.01), respectively). Heart tissue CO and COHb levels also increased after 3 weeks with atorvastatin (1.30 ± 0.24 (p ≤ 0.05); 1.92 ± 0.17 (p ≤ 0.001), respectively) and rosuvastatin (1.47 ± 0.13 (p ≤ 0.004); 1.63 ± 0.12 (p ≤ 0.001), respectively). Significant increases in heart antioxidant levels were observed after statin treatment and corroborated by heart bilirubin content elevations. Antioxidant level increases were abolished by treatment with an HO inhibitor. These findings suggest that the induction of HO and the production of its products, CO and bilirubin, may be a mechanism by which statins exert antioxidant actions and confer cardioprotection in vivo.