Effects of Eicosapentaenoic Acid on the Cytoprotection Through Nrf2-Mediated Heme Oxygenase-1 in Human Endothelial Cells.

Consumption of omega-3 polyunsaturated fatty acid, particularly eicosapentaenoic acid (EPA), is associated with a significant reduction in the risk of developing cardiovascular disease. The aim of this study was to investigate whether heme oxygenase-1 (HO-1) induction contributes to the cytoprotective effects of EPA in endothelial cells threatened with oxidative damage. In this study, we investigated the effect of EPA on the induction of HO-1 by NF-E2-related factor 2 (Nrf2) in human umbilical vein endothelial cells. In cells treated with low concentrations of EPA (10-25 µM), HO-1 expression increased in a time- and concentration-dependent manner. Additionally, EPA treatment increased Nrf2 nuclear translocation and antioxidant response element activity, leading to the upregulation of HO-1 expression. Furthermore, treatment with EPA reduced hydrogen peroxide (H(2)O(2))-induced cell death. The reduction in cell death was reversed by treatment with zinc protoporphyrin, an inhibitor of HO-1, indicating that HO-1 contributed to the protective effect of EPA. These data suggest that EPA protects against H(2)O(2)-induced oxidative stress in endothelial cells by activating Nrf2 and inducting HO-1 expression.

Eriodictyol Protects Endothelial Cells against Oxidative Stress-Induced Cell Death through Modulating ERK/Nrf2/ARE-Dependent Heme Oxygenase-1 Expression.

The pathophysiology of cardiovascular diseases is complex and may involve oxidative stress-related pathways. Eriodictyol is a flavonoid present in citrus fruits that demonstrates anti-inflammatory, anti-cancer, neurotrophic, and antioxidant effects in a range of pathophysiological conditions including vascular diseases. Because oxidative stress plays a key role in the pathogenesis of cardiovascular disease, the present study was designed to verify whether eriodictyol has therapeutic potential. Upregulation of heme oxygenase-1 (HO-1), a phase II detoxifying enzyme, in endothelial cells is considered to be helpful in cardiovascular disease. In this study, human umbilical vein endothelial cells (HUVECs) treated with eriodictyol showed the upregulation of HO-1 through extracellular-regulated kinase (ERK)/nuclear factor erythroid 2-related factor 2 (Nrf2)/antioxidant response element (ARE) signaling pathways. Further, eriodictyol treatment provided protection against hydrogen peroxide-provoked cell death. This protective effect was eliminated by treatment with a specific inhibitor of HO-1 and RNA interference-mediated knockdown of HO-1 expression. These data demonstrate that eriodictyol induces ERK/Nrf2/ARE-mediated HO-1 upregulation in human endothelial cells, which is directly associated with its vascular protection against oxidative stress-related endothelial injury, and propose that targeting the upregulation of HO-1 is a promising approach for therapeutic intervention in cardiovascular disease.

The VUS Challenge in Cystic Kidney Disease: A Case-Based Review.

Genetic testing in nephrology is becoming increasingly important to diagnose patients and to provide appropriate care. This is especially true for autosomal dominant polycystic kidney disease (ADPKD) because this is a common cause of kidney failure and genetically complex. In addition to the major genes, PKD1 and PKD2 , there are at least six minor loci, and phenotypic, and in some cases, genetic overlap with other cystic disorders. Targeted next-generation sequencing, a low-cost, high-throughput technique, has made routine genetic testing viable in nephrology clinics. Appropriate pre- and post-testing genetic counseling is essential to the testing process. Carefully assessing variants is also critical, with the genetic report classifying variants in accordance with American College of Medical Genetics and Genomics guidelines. However, variant of uncertain significance (VUSs) may pose a significant challenge for the ordering clinician. In ADPKD, and particularly within PKD1 , there is high allelic heterogeneity; no single variant is present in more than 2% of families. The Mayo/Polycystic Kidney Disease Foundation variant database, a research tool, is the best current database of PKD1 and PKD2 variants containing over 2300 variants identified in individuals with polycystic kidney disease, but novel variants are often identified. In patients with a high pretest probability of ADPKD on the basis of clinical criteria, but no finding of a pathogenic (P) or likely pathogenic (LP) variant in a cystic kidney gene, additional evaluation of cystic gene VUS can be helpful. In this case-based review, we propose an algorithm for the assessment of such variants in a clinical setting and show how some can be reassigned to a diagnostic grouping. When assessing the relevance of a VUS, we consider both patient/family-specific and allele-related factors using population and variant databases and available prediction tools, as well as genetic expertise. This analysis plus further family studies can aid in making a genetic diagnosis.

Genome-wide profiling in melatonin-exposed human breast cancer cell lines identifies differentially methylated genes involved in the anticancer effect of melatonin.

Epigenetic alterations have emerged as an important mechanism involved in tumorigenesis. The epigenetic impact of DNA methylation in various types of human cancer is not completely understood. Previously, we observed melatonin-induced differential expression of miRNA and miRNA-related genes in human breast cancer cell lines that indicated an anticancer effect of melatonin. In this report, we further characterized epigenetic changes in melatonin-exposed MCF-7 cells through the analysis of DNA methylation profiles in breast cancer cells to provide new insights into the potential mechanisms of the anticancer effect of melatonin. Microarray-based DNA methylation and gene expression profiling were carried out using human breast cancer cell lines. We further identified a number of mRNAs whose expression levels show an inverse correlation with DNA methylation levels. The mRNA expression levels and methylation status of candidate genes in melatonin-exposed cells were confirmed by real-time quantitative PCR and bisulfite PCR. This approach led to the detection of cancer-related genes, which were oncogenic genes, including EGR3 and POU4F2/Brn-3b were down-regulated, while the tumor suppressor gene, GPC3, was up-regulated by 1 nm melatonin-treated MCF-7 cells. Our results provide detailed insights into the DNA methylation patterns induced by melatonin and suggest a potential mechanism of the anticancer effect of aberrant DNA methylation in melatonin-treated breast cancer cells.

Genetic Spectrum of Polycystic Kidney and Liver Diseases and the Resulting Phenotypes.

Polycystic kidney diseases are a group of monogenically inherited disorders characterized by cyst development in the kidney with defects in primary cilia function central to pathogenesis. Autosomal dominant polycystic kidney disease (ADPKD) has progressive cystogenesis and accounts for 5-10% of kidney failure (KF) patients. There are two major ADPKD genes, PKD1 and PKD2, and seven minor loci. PKD1 accounts for ∼80% of patients and is associated with the most severe disease (KF is typically at 55-65 years); PKD2 accounts for ∼15% of families, with KF typically in the mid-70s. The minor genes are generally associated with milder kidney disease, but for DNAJB11 and ALG5, the age at KF is similar to PKD2. PKD1 and PKD2 have a high level of allelic heterogeneity, with no single pathogenic variant accounting for >2% of patients. Additional genetic complexity includes biallelic disease, sometimes causing very early-onset ADPKD, and mosaicism. Autosomal dominant polycystic liver disease is characterized by severe PLD but limited PKD. The two major genes are PRKCSH and SEC63, while GANAB, ALG8, and PKHD1 can present as ADPKD or autosomal dominant polycystic liver disease. Autosomal recessive polycystic kidney disease typically has an infantile onset, with PKHD1 being the major locus and DZIP1L and CYS1 being minor genes. In addition, there are a range of mainly recessive syndromic ciliopathies with PKD as part of the phenotype. Because of the phenotypic and genic overlap between the diseases, employing a next-generation sequencing panel containing all known PKD and ciliopathy genes is recommended for clinical testing.

Classification of BRCA2 Variants of Uncertain Significance (VUS) Using an ACMG/AMP Model Incorporating a Homology-Directed Repair (HDR) Functional Assay.

PURPOSE: The identification of variants of uncertain significance (VUS) in the BRCA1 and BRCA2 genes by hereditary cancer testing poses great challenges for the clinical management of variant carriers. The ACMG/AMP (American College of Medical Genetics and Genomics/Association for Molecular Pathology) variant classification framework, which incorporates multiple sources of evidence, has the potential to establish the clinical relevance of many VUS. We sought to classify the clinical relevance of 133 single-nucleotide substitution variants encoding missense variants in the DNA-binding domain (DBD) of BRCA2 by incorporating results from a validated functional assay into an ACMG/AMP-variant classification model from a hereditary cancer-testing laboratory. EXPERIMENTAL DESIGN: The 133 selected VUS were evaluated using a validated homology-directed double-strand DNA break repair (HDR) functional assay. Results were combined with clinical and genetic data from variant carriers in a rules-based variant classification model for BRCA2. RESULTS: Of 133 missense variants, 44 were designated as non-functional and 89 were designated as functional in the HDR assay. When combined with genetic and clinical information from a single diagnostic laboratory in an ACMG/AMP-variant classification framework, 66 variants previously classified by the diagnostic laboratory were correctly classified, and 62 of 67 VUS (92.5%) were reclassified as likely pathogenic (n = 22) or likely benign (n = 40). In total, 44 variants were classified as pathogenic/likely pathogenic, 84 as benign/likely benign, and 5 remained as VUS. CONCLUSIONS: Incorporation of HDR functional analysis into an ACMG/AMP framework model substantially improves BRCA2 VUS re-classification and provides an important tool for determining the clinical relevance of individual BRCA2 VUS.

Fisetin induces Nrf2-mediated HO-1 expression through PKC-δ and p38 in human umbilical vein endothelial cells.

Fisetin is a natural flavonoid from fruits and vegetables that exhibits antioxidant, neurotrophic, anti-inflammatory, and anti-cancer effects in various disease models. Up-regulation of heme oxygenase-1 (HO-1) expression protects against oxidative stress-induced cell death, and therefore, plays a crucial role in cytoprotection in a variety of pathological models. In the present study, we investigated the effect of fisetin on the up-regulation of HO-1 in human umbilical vein endothelial cells (HUVECs). Small interfering RNA and pharmacological inhibitors of PKC-δ and p38 MAPK attenuated HO-1 induction in fisetin-stimulated HUVECs. Fisetin treatment resulted in significantly increased NF-E2-related factor 2 (Nrf2) nuclear translocation, and antioxidant response element (ARE)-luciferase activity, leading to up-regulation of HO-1 expression. In addition, fisetin pretreatment reduced hydrogen peroxide (H(2)O(2))-induced cell death, and this effect was reversed by ZnPP, an inhibitor of HO-1. In summary, these findings suggest that induction of HO-1 expression via Nrf2 activation may contribute to the cytoprotection exerted by fisetin against H(2)O(2) -induced oxidative stress in HUVECs.

Microinflammation in hemodialysis patients is associated with increased CD14CD16(+) pro-inflammatory monocytes: possible modification by on-line hemodiafiltration.

BACKGROUND: An increased percentage of pro-inflammatory CD14(+)CD16(+) monocytes might contribute to inflammation in hemodialysis (HD) patients. The purpose of the study was to evaluate the possible contribution of pro-inflammatory monocytes to inflammation in HD patients and also to evaluate the effect of on-line hemodiafiltration (HDF). METHODS: Flow cytometric detection of monocytes in patients undergoing HD, on-line HDF and healthy controls as well as plasma cytokines and cytokine mRNA measurement were performed. RESULTS: Percent pro-inflammatory monocytes, plasma cytokines and cytokine mRNA significantly increased in HD patients. Intracellular cytokine staining showed pro-inflammatory monocytes were the predominant source of tumor necrosis factor-α. Percent pro-inflammatory monocytes positively correlated with plasma inflammatory cytokines. Percent pro-inflammatory monocytes, plasma cytokines and cytokine mRNA significantly decreased in on-line HDF patients. CONCLUSION: Increased pro-inflammatory monocytes are likely to contribute to inflammation in HD patients, and beneficial effect of on-line HDF might be partially mediated by modulating the inflammatory response.

BRAF inhibition in melanoma is associated with the dysregulation of histone methylation and histone methyltransferases.

The development of mutant BRAF inhibitors has improved the outcome for melanoma patients with BRAFV600E mutations. Although the initial response to these inhibitors can be dramatic, sometimes resulting in complete tumor regression, the majority of melanomas become resistant. To study resistance to BRAF inhibition, we developed a novel mouse model of melanoma using a tetracycline/doxycycline-regulated system that permits control of mutant BRAF expression. Treatment with doxycycline leads to loss of mutant BRAF expression and tumor regression, but tumors recur after a prolonged period of response to treatment. Vemurafenib, encorafenib and dabrafenib induce cell cycle arrest and apoptosis in BRAF melanoma cell lines; however, a residual population of tumor cells survive. Comparing gene expression in human cell lines and mouse tumors can assist with the identification of novel mechanisms of resistance. Accordingly, we conducted RNA sequencing analysis and immunoblotting on untreated and doxycycline-treated dormant mouse melanomas and human mutant BRAF melanoma cell lines treated with 2 µM vemurafenib for 20  days. We found conserved expression changes in histone methyltransferase genes ASH2, EZH2, PRMT5, SUV39H1, SUV39H2, and SYMD2 in P-ERK low, p-38 high melanoma cells following prolonged BRAF inhibition. Quantitative mass spectrometry, determined a corresponding reduction in histone Lys9 and Lys27 methylation and increase in Lys36 methylation in melanoma cell lines treated with 2 µM vemurafenib for 20  days. Thus, these changes as are part of the initiate response to BRAF inhibition and likely contribute to the survival of melanoma cells.

Effect of Korean Red Ginseng treatment on the gene expression profile of diabetic rat retina.

BACKGROUND: Korean Red Ginseng (KRG) is a herbal medicine used in Asian countries and is very popular for its beneficial biological properties. Diabetes mellitus (DM) and its complications are rapidly becoming a global public health concern. The literature on transcriptional changes induced by KRG in rat models of diabetic retinopathy is limited. Considering these facts, we designed this study to determine whether retinopathy-associated genes are altered in retinas of rats with DM and whether the induced changes are reversed by KRG. METHODS: Male Sprague-Dawley rats were intravenously injected with streptozotocin (50 mg/kg body weight) to induce DM, following which, KRG powder (200 mg/kg body weight) was orally administered to the KRG-treated DM rat group for 10 wks. The rats were then sacrificed, and their retinas were harvested for total RNA extraction. Microarray gene expression profiling was performed on the extracted RNA samples. RESULTS: From among > 31,000 genes investigated, the expression of 268 genes was observed to be upregulated and that of 58 genes was downregulated, with twofold altered expression levels in the DM group compared with those in the control group. Moreover, 39 genes were upregulated more than twofold and 84 genes were downregulated in the KRG-treated group compared to the DM group. The expression of the genes was significantly reversed by KRG treatment; some of these genes were analyzed further to verify the results of the microarray experiments. CONCLUSION: Taken together, our data suggest that reversed changes in the gene expression may mediate alleviating activities of KRG in rats with diabetic retinopathy.

ß2 integrins (CD11/18) are essential for the chemosensory adhesion and migration of polymorphonuclear leukocytes on bacterial cellulose.

Bacterial cellulose (BC) has been studied widely for applications in biomedical materials such as prosthetic artificial blood vessels owing to its unique characteristics, which include nontoxicity and nonimmunogenicity as compared with synthetic biopolymers such as expanded polytetrafluorethylene (ePTFE). However, to date, studies on the relative effect of leukocytes on BC as a prosthetic vascular graft are insufficient. Polymorphonuclear leukocytes (PMN) play a pivotal role in early-phase immune response to bacterial or periprosthetic infection. PMN recruitment at sites of infection or inflammation mediated by various integrins such as ß2 integrin family (CD11/CD18 family). Therefore, we discuss our investigations into the mechanisms by which ß2 integrins-mediated chemosensory adhesion and migration of PMN on the vascular graft surface, BC. Our results show that CD11b/CD18 components mainly mediate PMN adherence on BC. CD11b/CD18 displays weak coordination with the other two α subunits (CD11a and CD11c). Furthermore, it was found that the ß subunit (CD18) plays a critical role in both the adhesion and migration of N-formylmethionyl-leucyl-phenylalanine (fMLP)-stimulated PMN on BC. The activity of CD18 contrasts with that of the individual α subunits. Among these, only CD11b displayed inhibition of PMN migration on BC surfaces.

Induction of Thioredoxin Reductase 1 by Korean Red Ginseng Water Extract Regulates Cytoprotective Effects on Human Endothelial Cells.

Korean Red Ginseng is a popular herbal medicine and is widely used in many food products. KRG has biological benefits related to vascular diseases including diabetes, hypertension, atherosclerosis, and other cardiac diseases and KRG has antioxidant and anti-hyperlipidemic actions. KRG decreases the level of oxidative stress and suppresses proinflammatory cytokines and cell adhesion molecules, thus protecting endothelial dysfunction. Mammalian Thioredoxin reductase 1 is an NADPH-dependent selenoprotein, essential for antioxidant defense and DNA synthesis and repair, that regulates the redox system by modulating redox-sensitive transcription factors and thiol-containing proteins. Here, we show that KRG water extract increases the expression of TrxR1 in human umbilical vein endothelial cells via the p38 and PKC-δ signaling pathways. The induction of TrxR1 expression by KRG was confirmed by Western blot analysis and reverse transcription polymerase chain reaction. However, the increase in TrxR1 expression was abolished by specific silencing of the p38 and PKC-δ genes. In addition, we demonstrated that auranofin, a TrxR1 inhibitor, weakens the protective effect of KRG against H2O2-induced cell death as measured by the terminal transferase dUTP nick end labeling assay. These results suggest that KRG may have protective effects in vascular diseases by upregulating TrxR1 in endothelial cells, thereby inhibiting the generation of reactive oxygen species and cell death.

Hemeoxygenase-1 mediates an adaptive response to spermidine-induced cell death in human endothelial cells.

Spermidine (SPD) is a ubiquitous polycation that is commonly distributed in living organisms. Intracellular levels of SPD are tightly regulated, and SPD controls cell proliferation and death. However, SPD undergoes oxidation in the presence of serum, producing aldehydes, hydrogen peroxide, and ammonia, which exert cytotoxic effect on cells. Hemeoxygenase-1 (HO-1) is thought to have a protective effect against oxidative stress. Upregulation of HO-1 in endothelial cells is considered to be beneficial in the cardiovascular disease. In the present study, we demonstrate that the ubiquitous polyamine, SPD, induces HO-1 in human umbilical vein endothelial cells (HUVECs). SPD-induced HO-1 expression was examined by Western blot and reverse transcription-polymerase chain reaction (RT-PCR). Involvement of reactive oxygen species, serum amine oxidase, PI3K/Akt signaling pathway, and transcription factor Nrf2 in the induction of HO-1 by SPD was also investigated. Furthermore, small interfering RNA knockdown of Nrf2 or HO-1 and treatment with the specific HO-1 inhibitor ZnPP exhibited a noteworthy increase of death of SPD-stimulated HUVECs. In conclusion, these results suggest that SPD induces PI3K/Akt-Nrf2-mediated HO-1 expression in human endothelial cells, which may have a role in cytoprotection of the cells against oxidative stress-induced death.

Crotonaldehyde induces heat shock protein 72 expression that mediates anti-apoptotic effects in human endothelial cells.

Crotonaldehyde is a highly reactive aldehyde and a common environmental pollutant. It occurs in cigarette smoke and automobile exhaust, and is also endogenously generated by lipid peroxidation. Reactive aldehydes, such as crotonaldehyde, are considered to be important mediators of cell damage. Since endothelial apoptosis is considered to be the first step in the pathogenesis of cardiovascular disease, there have been many efforts to protect endothelial cell from oxidative stress. Heat shock protein 72 (HSP72) is a representative stress-inducible HSP70 family protein, and its synthesis is increased in response to multiple stressors. In the present study, we investigated the effect of crotonaldehyde on the up-regulation of HSP72 in human umbilical vein endothelial cells (HUVECs). Crotonaldehyde treatment caused nuclear accumulation of the heat shock transcription factor 1 (HSF1), leading to the induction of HSP72. Inhibition of the c-Jun N-terminal kinases (JNK) signaling pathways, reduction of intracellular calcium level and blocking of reactive oxygen species (ROS) generation resulted in significant blockage of crotonaldehyde-mediated HSP72 induction. In addition, HSP72 silencing by siRNA or calcium chelating by BAPTA/AM resulted in an obvious increase in the rate of apoptosis in crotonaldehyde-stimulated HUVECs. In summary, our data demonstrated that crotonaldehyde-induced HSP72 expression in HUVECs is mediated by the JNK-HSF1 pathway, and involves calcium ions and ROS, which is an adaptive response to oxidative stress caused by crotonaldehyde.

Extract of Salvia miltiorrhiza (Danshen) induces Nrf2-mediated heme oxygenase-1 expression as a cytoprotective action in RAW 264.7 macrophages.

ETHNOPHARMACOLOGICAL RELEVANCE: Danshen (Salvia miltiorrhiza) is widely used in traditional herbal medicines for relief of a variety of symptoms related to complications arising from vascular diseases such as hypertension, diabetes, and atherosclerosis. Induction of heme oxygenase-1 (HO-1) expression protects against oxidative stress-induced cell damage, which plays an important role in cytoprotection in a variety of pathological models. MATERIALS AND METHODS: In the present study, we investigated the effect of Danshen on the up-regulation of HO-1, an inducible and cytoprotective enzyme in RAW 264.7 macrophages. Molecular mechanisms underlying the effects, especially protective effects, was elucidated by analyzing the activation of transcription factors and their upstream signalling, and by evaluating the inhibitory effect of HO-1 on ROS production. RESULTS: Danshen induced HO-1 mRNA expression and protein production, and nuclear translocation of NF-E2-related factor 2 in RAW 264.7 macrophages. Pharmacological inhibitors of PI3K/Akt and MEK1 attenuated HO-1 induction in Danshen-stimulated RAW 264.7 macrophages. Furthermore, Danshen pretreatment reduced intracellular production of reactive oxygen species after stimulation with hydrogen peroxide; this effect was reversed by the HO-1 inhibitor ZnPP. CONCLUSION: Danshen induced HO-1 expression through PI3K/Akt-MEK1-Nrf2 pathway and reduced intracellular production of reactive oxygen species via induction of HO-1 expression. The results support a role of HO-1 in the cytoprotective effect of Danshen.

Induction of heme oxygenase-1 inhibits cell death in crotonaldehyde-stimulated HepG2 cells via the PKC-δ-p38-Nrf2 pathway.

BACKGROUND: Crotonaldehyde, an alpha, beta-unsaturated aldehyde present in cigarette smoke, is an environmental pollutant and a product of lipid peroxidation. It also produces adverse effects to humans and is considered as a risk factor for various diseases. Heme oxygenase-1 (HO-1) plays important roles in protecting cells against oxidative stress as a prime cellular defense mechanism. However, HO-1 may be associated with cell proliferation and resistance to apoptosis in cancer cells. The aim of this study was to examine the effects of HO-1 induction on cell survival in crotonaldehyde-stimulated human hepatocellular carcinoma (HepG2) cells. METHODS: To investigate the signaling pathway involved in crotonaldehyde-induced HO-1 expression, we compared levels of inhibition efficiency of specific inhibitors and specific small interfering RNAs (siRNAs) of several kinases. The cell-cycle and cell death was measured by FACS and terminal dUTP nick-end labeling (TUNEL) staining. RESULTS: Treatment with crotonaldehyde caused a significant increase in nuclear translocation of NF-E2 related factor (Nrf2). Treatment with inhibitors of the protein kinase C-δ (PKC-δ) and p38 pathways resulted in obvious blockage of crotonaldehyde-induced HO-1 expression. Furthermore, treatment with HO-1 siRNA and the specific HO-1 inhibitor zinc-protoporphyrin produced an increase in the G(0)/G(1) phase of the cell cycle in crotonaldehyde-stimulated HepG2 cells. CONCLUSIONS: Taken together, the results support an anti-apoptotic role for HO-1 in crotonaldehyde-stimulated human hepatocellular carcinoma cells and provide a mechanism by which induction of HO-1 expression via PKC-δ-p38 MAPK-Nrf2 pathway may promote tumor resistance to oxidative stress.

Up-regulation of Heme Oxygenase-1 by Korean Red Ginseng Water Extract as a Cytoprotective Effect in Human Endothelial Cells.

Korean red ginseng (KRG) is used worldwide as a popular traditional herbal medicine. KRG has shown beneficial effects on cardiovascular diseases, such as atherosclerosis, diabetes, and hypertension. Up-regulation of a cytoprotective protein, heme oxygenase (HO)-1, is considered to augment the cellular defense against various agents that may induce cytotoxic injury. In the present study, we demonstrate that KRG water extract induces HO-1 expression in human umbilical vein endothelial cells (HUVECs) and possible involvement of the anti-oxidant transcription factor nuclear factor-eythroid 2-related factor 2 (Nrf2). KRG-induced HO-1 expression was examined by western blots, reverse transcriptase polymerase chain reaction and immunofluorescence staining. Specific silencing of Nrf2 genes with Nrf2-siRNA in HUVECs abolished HO-1 expression. In addition, the HO inhibitor zinc protoporphyrin blunted the preventive effect of KRG on H2O2-induced cell death, as demonstrated by terminal transferase dUTP nick end labeling assay. Taken together, these results suggest that KRG may exert a vasculoprotective effect through Nrf2- mediated HO-1 induction in human endothelial cell by inhibition of cell death.

Upregulation of heme oxygenase-1 as an adaptive mechanism for protection against crotonaldehyde in human umbilical vein endothelial cells.

Crotonaldehyde, a highly reactive α, ß-unsaturated aldehyde, is a ubiquitous environmental pollutant and a product of endogenous lipid peroxidation. It is also a major component of cigarette smoke and is present in many foods and beverages, and has also been linked to development of various diseases. Activation of endothelial cells by stimuli such as cigarette smoke is an important risk factor for cardiovascular diseases, including atherosclerosis. Heme oxygenase-1 (HO-1) is a protective antioxidant enzyme with a critical role in resistance to oxidative stress and other cellular functions. In this study, we examined the effects of crotonaldehyde on HO-1 induction and determined the signaling pathways in human umbilical vein endothelial cells (HUVECs). Inhibition of the protein kinase C-δ (PKC-δ) and p38 pathways resulted in significant blockage of crotonaldehyde-mediated HO-1 induction. Crotonaldehyde treatment caused a dramatic increase in translocation of NF-E2 related factor (Nrf2), leading to induction of HO-1. In addition, small interfering RNA knockdown of Nrf2 and treatment with the specific HO-1 inhibitor ZnPP exhibited an obvious increase of apoptosis of crotonaldehyde-treated HUVECs. Taken together, our results demonstrated that crotonaldehyde-induced HO-1 expression is mediated by the PKC-δ-p38 MAPK-Nrf2-HO-1 pathway in HUVECs, which is an adaptive response to oxidative stress.