Expression of LONP1 Is High in Visceral Adipose Tissue in Obesity, and Is Associated with Glucose and Lipid Metabolism

BACKGROUND

The nature and role of the mitochondrial stress response in adipose tissue in relation to obesity are not yet known. To determine whether the mitochondrial unfolded protein response (UPRmt) in adipose tissue is associated with obesity in humans and rodents.

METHODS

Visceral adipose tissue (VAT) was obtained from 48 normoglycemic women who underwent surgery. Expression levels of mRNA and proteins were measured for mitochondrial chaperones, intrinsic proteases, and components of electron-transport chains. Furthermore, we systematically analyzed metabolic phenotypes with a large panel of isogenic BXD inbred mouse strains and Genotype-Tissue Expression (GTEx) data.

RESULTS

In VAT, expression of mitochondrial chaperones and intrinsic proteases localized in inner and outer mitochondrial membranes was not associated with body mass index (BMI), except for the Lon protease homolog, mitochondrial, and the corresponding gene LONP1, which showed high-level expression in the VAT of overweight or obese individuals. Expression of LONP1 in VAT positively correlated with BMI. Analysis of the GTEx database revealed that elevation of LONP1 expression is associated with enhancement of genes involved in glucose and lipid metabolism in VAT. Mice with higher Lonp1 expression in adipose tissue had better systemic glucose metabolism than mice with lower Lonp1 expression.

CONCLUSION

Expression of mitochondrial LONP1, which is involved in the mitochondrial quality control stress response, was elevated in the VAT of obese individuals. In a bioinformatics analysis, high LONP1 expression in VAT was associated with enhanced glucose and lipid metabolism.

Differential roles of GDF15 and FGF21 in systemic metabolic adaptation to the mitochondrial integrated stress response

Perturbation of mitochondrial proteostasis provokes cell autonomous and cell non-autonomous responses that contribute to homeostatic adaptation. Here, we demonstrate distinct metabolic effects of hepatic metabokines as cell non-autonomous factors in mice with mitochondrial OxPhos dysfunction. Liver-specific mitochondrial stress induced by a loss-of-function mutation in Crif1 (LKO) leads to aberrant oxidative phosphorylation and promotes the mitochondrial unfolded protein response. LKO mice are highly insulin sensitive and resistant to diet-induced obesity. The hepatocytes of LKO mice secrete large quantities of metabokines, including GDF15 and FGF21, which confer metabolic benefits. We evaluated the metabolic phenotypes of LKO mice with global deficiency of GDF15 or FGF21 and show that GDF15 regulates body and fat mass and prevents diet-induced hepatic steatosis, whereas FGF21 upregulates insulin sensitivity, energy expenditure, and thermogenesis in white adipose tissue. This study reveals that the mitochondrial integrated stress response (ISR^mt) in liver mediates metabolic adaptation through hepatic metabokines.

Mitohormesis in Hypothalamic POMC Neurons Mediates Regular Exercise-Induced High-Turnover Metabolism

Low-grade mitochondrial stress can promote health and longevity, a phenomenon termed mitohormesis. Here, we demonstrate the opposing metabolic effects of low-level and high-level mitochondrial ribosomal (mitoribosomal) stress in hypothalamic proopiomelanocortin (POMC) neurons. POMC neuron-specific severe mitoribosomal stress due to Crif1 homodeficiency causes obesity in mice. By contrast, mild mitoribosomal stress caused by Crif1 heterodeficiency in POMC neurons leads to high-turnover metabolism and resistance to obesity. These metabolic benefits are mediated by enhanced thermogenesis and mitochondrial unfolded protein responses (UPR^mt) in distal adipose tissues. In POMC neurons, partial Crif1 deficiency increases the expression of β-endorphin (β-END) and mitochondrial DNA-encoded peptide MOTS-c. Central administration of MOTS-c or β-END recapitulates the adipose phenotype of Crif1 heterodeficient mice, suggesting these factors as potential mediators. Consistently, regular running exercise at moderate intensity stimulates hypothalamic MOTS-c/β-END expression and induces adipose tissue UPR^mt and thermogenesis. Our findings indicate that POMC neuronal mitohormesis may underlie exercise-induced high-turnover metabolism.

Cellular and Intercellular Homeostasis in Adipose Tissue with Mitochondria-Specific Stress

Paracrine interactions are imperative for the maintenance of adipose tissue intercellular homeostasis, and intracellular organelle dysfunction results in local and systemic alterations in metabolic homeostasis. It is currently accepted that mitochondrial proteotoxic stress activates the mitochondrial unfolded protein response (UPRmt) in vitro and in vivo. The induction of mitochondrial chaperones and proteases during the UPRmt is a key cell-autonomous mechanism of mitochondrial quality control. The UPRmt also affects systemic metabolism through the secretion of cell non-autonomous peptides and cytokines (hereafter, metabokines). Mitochondrial function in adipose tissue plays a pivotal role in whole-body metabolism and human diseases. Despite continuing interest in the role of the UPRmt and quality control pathways of mitochondria in energy metabolism, studies on the roles of the UPRmt and metabokines in white adipose tissue are relatively sparse. Here, we describe the role of the UPRmt in adipose tissue, including adipocytes and resident macrophages, and the interactive roles of cell non-autonomous metabokines, particularly growth differentiation factor 15, in local adipose cellular homeostasis and systemic energy metabolism.

An adipocyte-specific defect in oxidative phosphorylation increases systemic energy expenditure and protects against diet-induced obesity in mouse models

AIMS/HYPOTHESIS

Mitochondrial oxidative phosphorylation (OxPhos) is essential for energy production and survival. However, the tissue-specific and systemic metabolic effects of OxPhos function in adipocytes remain incompletely understood.

METHODS

We used adipocyte-specific Crif1 (also known as Gadd45gip1) knockout (AdKO) mice with decreased adipocyte OxPhos function. AdKO mice fed a normal chow or high-fat diet were evaluated for glucose homeostasis, weight gain and energy expenditure (EE). RNA sequencing of adipose tissues was used to identify the key mitokines affected in AdKO mice, which included fibroblast growth factor 21 (FGF21) and growth differentiation factor 15 (GDF15). For in vitro analysis, doxycycline was used to pharmacologically decrease OxPhos in 3T3L1 adipocytes. To identify the effects of GDF15 and FGF21 on the metabolic phenotype of AdKO mice, we generated AdKO mice with global Gdf15 knockout (AdGKO) or global Fgf21 knockout (AdFKO).

RESULTS

Under high-fat diet conditions, AdKO mice were resistant to weight gain and exhibited higher EE and improved glucose tolerance. In vitro pharmacological and in vivo genetic inhibition of OxPhos in adipocytes significantly upregulated mitochondrial unfolded protein response-related genes and secretion of mitokines such as GDF15 and FGF21. We evaluated the metabolic phenotypes of AdGKO and AdFKO mice, revealing that GDF15 and FGF21 differentially regulated energy homeostasis in AdKO mice. Both mitokines had beneficial effects on obesity and insulin resistance in the context of decreased adipocyte OxPhos, but only GDF15 regulated EE in AdKO mice.

CONCLUSIONS/INTERPRETATION

The present study demonstrated that the adipose tissue adaptive mitochondrial stress response affected systemic energy homeostasis via cell-autonomous and non-cell-autonomous pathways. We identified novel roles for adipose OxPhos and adipo-mitokines in the regulation of systemic glucose homeostasis and EE, which facilitated adaptation of an organism to local mitochondrial stress.

Isocitrate dehydrogenase 2 deficiency induces endothelial inflammation via p66sh-mediated mitochondrial oxidative stress

Isocitrate dehydrogenase 2 (IDH2) is an essential enzyme in the mitochondrial antioxidant system, which produces nicotinamide adenine dinucleotide phosphate, and thereby defends against oxidative stress. We have shown that IDH2 downregulation results in mitochondrial dysfunction and reactive oxygen species (ROS) generation in mouse endothelial cells. The redox enzyme p66shc is a key factor in regulating the level of ROS in endothelial cells. In this study, we hypothesized that IDH2 knockdown-induced mitochondrial dysfunction stimulates endothelial inflammation, which might be regulated by p66shc-mediated oxidative stress. Our results showed that IDH2 downregulation led to mitochondrial dysfunction by decreasing the expression of mitochondrial oxidative phosphorylation complexes I, II, and IV, reducing oxygen consumption, and depolarizing mitochondrial membrane potential in human umbilical vein endothelial cells (HUVECs). The dysfunction not only increased mitochondrial ROS levels but also activated p66shc expression in HUVECs and IDH2 knockout mice. IDH2 deficiency increased intercellular adhesion molecule (ICAM)-1 expression and mRNA levels of pro-inflammatory cytokines (tumor necrosis factor [TNF]-α, and interleukin [IL]-1β) in HUVECs. The mRNA expression of ICAM-1 in endothelial cells and plasma levels of TNF-α and IL-1β were also markedly elevated in IDH2 knockout mice. However, p66shc knockdown rescued IDH2 deficiency-induced mitochondrial ROS levels, monocyte adhesion, ICAM-1, TNF-α, and IL-1β expression in HUVECs. These findings suggest that IDH2 deficiency induced endothelial inflammation via p66shc-mediated mitochondrial oxidative stress.

Reduced oxidative capacity in macrophages results in systemic insulin resistance

Oxidative functions of adipose tissue macrophages control the polarization of M1-like and M2-like phenotypes, but whether reduced macrophage oxidative function causes systemic insulin resistance in vivo is not clear. Here, we show that mice with reduced mitochondrial oxidative phosphorylation (OxPhos) due to myeloid-specific deletion of CR6-interacting factor 1 (Crif1), an essential mitoribosomal factor involved in biogenesis of OxPhos subunits, have M1-like polarization of macrophages and systemic insulin resistance with adipose inflammation. Macrophage GDF15 expression is reduced in mice with impaired oxidative function, but induced upon stimulation with rosiglitazone and IL-4. GDF15 upregulates the oxidative function of macrophages, leading to M2-like polarization, and reverses insulin resistance in ob/ob mice and HFD-fed mice with myeloid-specific deletion of Crif1. Thus, reduced macrophage oxidative function controls systemic insulin resistance and adipose inflammation, which can be reversed with GDF15 and leads to improved oxidative function of macrophages.

M1-like polarization of macrophages is thought to control adipose inflammation and associated insulin resistance and metabolic syndrome. Here the authors show that macrophage-specific deletion of the OxPhos-related gene Crif1 results in an M1-like phenotype in mice, and that the effects can be reversed by recombinant GDF15.

Growth Differentiation Factor 15 Mediates Systemic Glucose Regulatory Action of T-Helper Type 2 Cytokines

T-helper type 2 (Th2) cytokines, including interleukin (IL)-13 and IL-4, produced in adipose tissue, are critical regulators of intra-adipose and systemic lipid and glucose metabolism. Furthermore, IL-13 is a potential therapy for insulin resistance in obese mouse models. Here, we examined mediators produced by adipocytes that are responsible for regulating systemic glucose homeostasis in response to Th2 cytokines. We used RNA sequencing data analysis of cultured adipocytes to screen factors secreted in response to recombinant IL-13. Recombinant IL-13 induced expression of growth differentiation factor 15 (GDF15) via the Janus kinase-activated STAT6 pathway. In vivo administration of α-galactosylceramide or IL-33 increased IL-4 and IL-13 production, thereby increasing GDF15 levels in adipose tissue and in plasma of mice; however, these responses were abrogated in STAT6 knockout mice. Moreover, administration of recombinant IL-13 to wild-type mice fed a high-fat diet (HFD) improved glucose intolerance; this was not the case for GDF15 knockout mice fed the HFD. Taken together, these data suggest that GDF15 is required for IL-13-induced improvement of glucose intolerance in mice fed an HFD. Thus, beneficial effects of Th2 cytokines on systemic glucose metabolism and insulin sensitivity are mediated by GDF15. These findings open up a potential pharmacological route for reversing insulin resistance associated with obesity.

CR6-Interacting Factor 1 Deficiency Impairs Vascular Function by Inhibiting the Sirt1-Endothelial Nitric Oxide Synthase Pathway

AIMS

Mitochondrial dysfunction has emerged as a major contributing factor to endothelial dysfunction and vascular disease, but the key mechanisms underlying mitochondrial dysfunction-induced endothelial dysfunction remain to be elucidated. In this study, we aim at determining whether mitochondrial dysfunction in endothelial cells plays a key role in vascular disease, by examining the phenotype of endothelial-specific CR6-interacting factor 1 (CRIF1) knockout mice. We also used siRNA-mediated downregulation of CRIF1 gene in the endothelial cells to study about the in vitro pathophysiological underlying mechanisms.

RESULTS

Downregulation of CRIF1 in endothelial cells caused disturbances of mitochondrial oxidative phosphorylation complexes and membrane potential, leading to enhanced mitochondrial reactive oxygen species production. Gene silencing of CRIF1 results in decreased SIRT1 expression along with increased endothelial nitric oxide synthase (eNOS) acetylation, leading to reduced nitric oxide production both in vitro and in vivo. Endothelium-dependent vasorelaxation of aortic rings from CRIF1 knockout (KO) mice was considerably less than in wild-type mice, and it was partially recovered by Sirt1 overexpression in CRIF1 KO mice.

INNOVATION

Our results show for the first time a relationship between mitochondrial dysfunction and impaired vascular function induced in CRIF1 deficiency conditions and also the possible underlying pathway involved.

CONCLUSION

These findings indicate that CRIF1 plays an important role in maintaining mitochondrial and endothelial function through its effects on the SIRT1-eNOS pathway. Antioxid. Redox Signal. 27, 234-249.

Compensatory structural and functional adaptation after radical nephrectomy for renal cell carcinoma according to preoperative stage of chronic kidney disease. Choi DK, Jung SB, Park BH, Jeong BC, Seo SI, Jeon SS, Lee HM, Choi HY, Jeon HG.J Urol. 2015 Oct;194(4):910-5. [Epub 2015 Apr 28]. doi: 10.1016/j.juro.2015.04.093

PURPOSE

We investigated structural hypertrophy and functional hyperfiltration as compensatory adaptations after radical nephrectomy in patients with renal cell carcinoma according to the preoperative chronic kidney disease stage.

MATERIALS AND METHODS

We retrospectively identified 543 patients who underwent radical nephrectomy for renal cell carcinoma between 1997 and 2012. Patients were classified according to preoperative glomerular filtration rate as no chronic kidney disease-glomerular filtration rate 90ml/min/1.73m² or greater (230, 42.4%), chronic kidney disease stage II-glomerular filtration rate 60 to less than 90ml/min/1.73m² (227, 41.8%), and chronic kidney disease stage III-glomerular filtration rate 30 to less than 60ml/min/1.73m² (86, 15.8%). Computerized tomography performed within 2 months before surgery and 1 year after surgery was used to assess functional renal volume for measuring the degree of hypertrophy of the remnant kidney, and the preoperative and postoperative glomerular filtration rate per unit volume of functional renal volume was used to calculate the degree of hyperfiltration.

RESULTS

Among all patients (mean age = 56.0y) mean preoperative glomerular filtration rate, functional renal volume, and glomerular filtration rate/functional renal volume were 83.2ml/min/1.73m², 340.6cm³, and 0.25ml/min/1.73m²/cm³, respectively. The percent reduction in glomerular filtration rate was statistically significant according to chronic kidney disease stage (no chronic kidney disease 31.2% vs. stage II 26.5% vs. stage III 12.8%, P<0.001). However, the degree of hypertrophic functional renal volume in the remnant kidney was not statistically significant (no chronic kidney disease 18.5% vs. stage II 17.3% vs. stage III 16.5%, P = 0.250). The change in glomerular filtration rate/functional renal volume was statistically significant (no chronic kidney disease 18.5% vs. stage II 20.1% vs. stage III 45.9%, P<0.001). Factors that increased glomerular filtration rate/functional renal volume above the mean value were body mass index (P = 0.012), diabetes mellitus (P = 0.023), hypertension (P = 0.015), and chronic kidney disease stage (P<0.001).

CONCLUSIONS

Patients with a lower preoperative glomerular filtration rate had a smaller reduction in postoperative renal function than those with a higher preoperative glomerular filtration rate due to greater degrees of functional hyperfiltration.

Growth differentiation factor 15 is a myomitokine governing systemic energy homeostasis

Chung et al. show that the myomitokine GDF15 can act to modulate oxidative and lipolytic function in a non–cell-autonomous manner, thereby regulating systemic energy homeostasis in skeletal muscle-specific Crif1-deficient mice. This pathway may be a potential therapeutic target for preventing the onset of obesity and insulin resistance.

Reduced mitochondrial electron transport chain activity promotes longevity and improves energy homeostasis via cell-autonomous and –non-autonomous factors in multiple model systems. This mitohormetic effect is thought to involve the mitochondrial unfolded protein response (UPR^mt), an adaptive stress-response pathway activated by mitochondrial proteotoxic stress. Using mice with skeletal muscle–specific deficiency of Crif1 (muscle-specific knockout [MKO]), an integral protein of the large mitoribosomal subunit (39S), we identified growth differentiation factor 15 (GDF15) as a UPR^mt-associated cell–non-autonomous myomitokine that regulates systemic energy homeostasis. MKO mice were protected against obesity and sensitized to insulin, an effect associated with elevated GDF15 secretion after UPR^mt activation. In ob/ob mice, administration of recombinant GDF15 decreased body weight and improved insulin sensitivity, which was attributed to elevated oxidative metabolism and lipid mobilization in the liver, muscle, and adipose tissue. Thus, GDF15 is a potent mitohormetic signal that safeguards against the onset of obesity and insulin resistance.

Nafamostat mesilate promotes endothelium-dependent vasorelaxation via the Akt-eNOS dependent pathway

Nafamostat mesilate (NM), a synthetic serine protease inhibitor, has anticoagulant and anti-inflammatory properties. The intracellular mediator and external anti-inflammatory external signal in the vascular wall have been reported to protect endothelial cells, in part due to nitric oxide (NO) production. This study was designed to examine whether NM exhibit endothelium dependent vascular relaxation through Akt/endothelial nitric oxide synthase (eNOS) activation and generation of NO. NM enhanced Akt/eNOS phosphorylation and NO production in a dose- and time-dependent manner in human umbilical vein endothelial cells (HUVECs) and aorta tissues obtained from rats treated with various concentrations of NM. NM concomitantly decreased arginase activity, which could increase the available arginine substrate for NO production. Moreover, we investigated whether NM increased NO bioavailability and decreased aortic relaxation response to an eNOS inhibitor in the aorta. These results suggest that NM increases NO generation via the Akt/eNOS signaling pathway, leading to endothelium-dependent vascular relaxation. Therefore, the vasorelaxing action of NM may contribute to the regulation of cardiovascular function.

Rg3-enriched Korean Red Ginseng enhances blood pressure stability in spontaneously hypertensive rats

Background

Korean Red Ginseng (Panax ginseng) has been shown to exert antihypertensive effects. In particular, ginsenoside Rg3 is thought to be a potent modulator of vascular function. The present study was performed to examine the antihypertensive efficacy of Korean Red Ginseng (KRG) extract and Rg3-enriched KRG (REKRG) extract.

Methods

Spontaneously hypertensive rats (SHRs) and Wistar–Kyoto rats (WKYs) were divided into six groups (WKY control, WKY-KRG, WKY-REKRG, SHR control, SHR-KRG, and SHR-REKRG), and systolic blood pressure (SBP) and diastolic blood pressure (DBP) were measured at the carotid artery, followed by injection of 3 mg/kg KRG or 3 mg/kg REKRG.

Results

REKRG treatment significantly decreased SBP and DBP 3 hours post-treatment in the SHR group compared with SHR control group. However, SBP and DBP were not significantly different in KRG-treated SHRs compared with control SHRs. REKRG treatment did not significantly alter SBP or DBP 3 hours post-treatment in the WKY group compared with WKY control group. Similarly, there were no differences in SBP or DBP with KRG treatment in the WKY group and WKY control group. Both KRG and REKRG increased endothelial nitric oxide synthase phosphorylation levels in the aorta, and the increases in endothelial nitric oxide synthase phosphorylation levels by REKRG treatment were higher than those with KRG treatment. Similarly, nitric oxide production in plasma from WKYs and SHRs was also increased by both KRG and REKRG.

Conclusion

These results suggest that REKRG has a more beneficial effect on blood pressure control than KRG in SHRs.

IDH2 deficiency impairs mitochondrial function in endothelial cells and endothelium-dependent vasomotor function

Mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDH2) plays an essential role protecting cells against oxidative stress-induced damage. A deficiency in IDH2 leads to mitochondrial dysfunction and the production of reactive oxygen species (ROS) in cardiomyocytes and cancer cells. However, the function of IDH2 in vascular endothelial cells is mostly unknown. In this study the effects of IDH2 deficiency on mitochondrial and vascular function were investigated in endothelial cells. IDH2 knockdown decreased the expression of mitochondrial oxidative phosphorylation (OXPHOS) complexes I, II and III, which lead to increased mitochondrial superoxide. In addition, the levels of fission and fusion proteins (Mfn-1, OPA-1, and Drp-1) were significantly altered and MnSOD expression also was decreased by IDH2 knockdown. Furthermore, knockdown of IDH2 decreased eNOS phosphorylation and nitric oxide (NO) concentration in endothelial cells. Interestingly, treatment with Mito-TEMPO, a mitochondrial-specific superoxide scavenger, recovered mitochondrial fission-fusion imbalance and blunted mitochondrial superoxide production, and reduced the IDH2 knockdown-induced decrease in MnSOD expression, eNOS phosphorylation and NO production in endothelial cells. Endothelium-dependent vasorelaxation was impaired, and the concentration of bioavailable NO decreased in the aortic ring in IDH2 knockout mice. These findings suggest that IDH2 deficiency induces endothelial dysfunction through the induction of dynamic mitochondrial changes and impairment in vascular function.

Nafamostat mesilate attenuates transient focal ischemia/reperfusion-induced brain injury via the inhibition of endoplasmic reticulum stress

Nafamostat mesilate (NM), a serine protease inhibitor, has a broad range of clinical applications that include use as an anticoagulant during hemodialysis in cerebral hemorrhage patients, as a hemoperfusion anticoagulant for patients with intravascular coagulation, hemorrhagic lesions, and hemorrhagic tendencies, and for the improvement of acute pancreatitis. However, the effects of NM on acute cerebral ischemia have yet to be investigated. Thus, the present study utilized a rat model in which transient middle cerebral artery occlusion (MCAO) was used to induce ischemic injury to investigate the effects of NM on infarct volume and histological and biological changes. NM (1mg/kg) was intravenously administered prior to and after the MCAO procedure. Compared to control rats, the administration of NM significantly decreased infarct size and the extent of brain edema after the induction of focal ischemia via MCAO. Additionally, NM treatment attenuated MCAO-induced neuronal degeneration and activation of microglia and astrocytes. NM treatment also inhibited the MCAO-induced expression levels of glucose-regulated protein 78 (GRP78), CATT/EBP homologous protein (CHOP), and p-eukaryotic initiation factor 2α (eIF2α), which are endoplasmic reticulum (ER) stress markers, in the cerebral cortex. The present findings demonstrate that NM exerts neuroprotective effects in the brain following focal ischemia via, at least in part, the inhibition of ER stress.

Nafamostat Mesilate Inhibits TNF-α-Induced Vascular Endothelial Cell Dysfunction by Inhibiting Reactive Oxygen Species Production

Nafamostat mesilate (NM) is a serine protease inhibitor with anticoagulant and anti-inflammatory effects. NM has been used in Asia for anticoagulation during extracorporeal circulation in patients undergoing continuous renal replacement therapy and extra corporeal membrane oxygenation. Oxidative stress is an independent risk factor for atherosclerotic vascular disease and is associated with vascular endothelial function. We investigated whether NM could inhibit endothelial dysfunction induced by tumor necrosis factor-α (TNF-α). Human umbilical vein endothelial cells (HUVECs) were treated with TNF-α for 24 h. The effects of NM on monocyte adhesion, vascular cell adhesion molecule-1 (VCAM-1) and intracellular adhesion molecule-1 (ICAM-1) protein expression, p38 mitogen-activated protein kinase (MAPK) activation, and intracellular superoxide production were then examined. NM (0.01~100 µg/mL) did not affect HUVEC viability; however, it inhibited the increases in reactive oxygen species (ROS) production and p66shc expression elicited by TNF-α (3 ng/mL), and it dose dependently prevented the TNF-α-induced upregulation of endothelial VCAM-1 and ICAM-1. In addition, it mitigated TNF-α-induced p38 MAPK phosphorylation and the adhesion of U937 monocytes. These data suggest that NM mitigates TNF-α-induced monocyte adhesion and the expression of endothelial cell adhesion molecules, and that the anti-adhesive effect of NM is mediated through the inhibition of p66shc, ROS production, and p38 MAPK activation.

Redox factor-1 activates endothelial SIRTUIN1 through reduction of conserved cysteine sulfhydryls in its deacetylase domain

Apurinic/Apyrmidinic Endonuclease 1/Redox Factor-1 (APE1/Ref-1) is a reductant which is important for vascular homeostasis. SIRTUIN1 (SIRT1) is a lysine deacetylase that also promotes endothelium-dependent vasorelaxation. We asked if APE1/Ref-1 governs the redox state and activity of SIRT1, and whether SIRT1 mediates the effect of APE1/Ref-1 on endothelium-dependent vascular function. APE1/Ref-1 maintains sulfhydryl (thiol) groups of cysteine residues in SIRT1 in the reduced form and promotes endothelial SIRT1 activity. APE1/Ref-1 stimulates SIRT1 activity by targeting highly conserved vicinal thiols 371 and 374 which form a zinc tetra-thiolate motif in the deacetylase domain of SIRT1. Cysteine residues in the N-terminal redox domain of APE1/Ref-1 are essential for reducing SIRT1 and stimulating its activity. APE1/Ref-1 protects endothelial SIRT1 from hydrogen peroxide-induced oxidation of sulfhydryls and from inactivation. APE1/Ref-1 also promotes lysine deacetylation of the SIRT1 target endothelial nitric oxide synthase (eNOS). SIRT1 mutated at cysteines 371 and 374, which renders it non-reducible by APE1/Ref-1, prevents lysine deacetylation of eNOS by APE1/Ref-1. SIRT1 free thiol (reduced sulfhydryl) content and deacetylase activity are diminished in all examined tissues of APE1/Ref-1^+/− mice, including the vasculature. Overexpression of SIRT1 in aortas of APE1/Ref-1^+/− mice restores endothelium-dependent vasorelaxation and bioavailable nitric oxide (NO) to levels similar to those observed in wild-type mice. Thus, APE1/Ref-1, by maintaining functionally important cysteine sulfhydryls in SIRT1 in the reduced form, promotes endothelial SIRT1 activity. This reductive activation of endothelial SIRT1 by APE1/Ref-1 mediates the effect of APE1/Ref-1 on eNOS acetylation, promoting endothelium-derived NO and endothelium-dependent vasorelaxation.

Abstract 470: Redox Rgulation of SIRTUIN1 in Endothelium-Dependent Vascular Function

Objective: The DNA repair enzyme/reducing protein Apurinic/Apyrmidinic Endonuclease 1/Redox Factor-1 (APE/Ref-1) maintains normal endothelial function, as mice heterozygous for APE1/Ref-1 (+/-) have impaired endothelium-dependent vasorelaxation and are hypertensive. APE1/Ref-1 maintains many redox sensitive transcription factors in their reduced active form. The SIRTUIN1 (SIRT1) protein deacetylase also promotes endothelial nitric oxide (NO) production and endothelium-dependent vasorelaxation. Although SIRT1 activity is subject to redox regulation, whether it is governed by APE1/Ref-1 is not known. The purpose of this study is to determine if APE1/Ref-1 governs the redox state and activity of SIRT1, and whether SIRT1 mediates the effect of APE1/Ref-1 on endothelium-dependent vascular function.

Methods and results: In endothelial cells APE1/Ref-1 maintains cysteine (thiol) residues in SIRT1 in the reduced (free) form and is obligatory for endothelial SIRT1 activity. In vitro APE1/Ref-1 increases the free thiol content of SIRT1, targeting functionally critical cysteine residues in the catalytic domain of SIRT1 for reduction, and activates SIRT1. Cysteine residues in the N-terminal redox domain of APE1/Ref-1 are essential for activating SIRT1 and for increasing free thiol content of SIRT1. APE1/Ref-1 protects endothelial SIRT1 from hydrogen peroxide-induced oxidation and inactivation. Moreover, APE1/Ref-1 stimulates lysine deacetylation of nitric oxide synthase, a target of SIRT1 in endothelial cells. When compared to wild-type mice, APE1/Ref-1(+/-) mice have lower free thiol content of SIRT1, and diminished SIRT1 activity in tissues. Overexpression of SIRT1 in aortas of APE1/Ref-1 (+/-) mice restores endothelium-dependent vasorelaxation and vascular bioavailable NO to levels similar to those observed in wild-type mice.

Conclusions: APE1/Ref-1 maintains endothelial SIRT1 in the reduced form, and is required for maintaining SIRT1 activity. This relationship between SIRT1 and APE1/Ref-1 is an important mechanism responsible for APE1/Ref-1-stimulated endothelium-dependent vasorelaxation.

Homocysteine promotes human endothelial cell dysfunction via site-specific epigenetic regulation of p66shc

AIMS

Hyperhomocysteinaemia is an independent risk factor for atherosclerotic vascular disease and is associated with vascular endothelial dysfunction. Homocysteine modulates cellular methylation reactions. P66shc is a protein that promotes oxidative stress whose expression is governed by promoter methylation. We asked if homocysteine induces endothelial p66shc expression via hypomethylation of CpG dinucleotides in the p66shc promoter, and whether p66shc mediates homocysteine-stimulated endothelial cell dysfunction.

METHODS AND RESULTS

Homocysteine stimulates p66shc transcription in human endothelial cells and hypomethylates specific CpG dinucleotides in the human p66shc promoter. Knockdown of p66shc inhibits the increase in reactive oxygen species, and decrease in nitric oxide, elicited by homocysteine in endothelial cells and prevents homocysteine-induced up-regulation of endothelial intercellular adhesion molecule-1. In addition, knockdown of p66shc mitigates homocysteine-induced adhesion of monocytes to endothelial cells. Inhibition of DNA methyltransferase activity or knockdown of DNA methyltransferase 3b abrogates homocysteine-induced up-regulation of p66shc. Comparison of plasma homocysteine in humans with coronary artery disease shows a significant difference between those with highest and lowest p66shc promoter CpG methylation in peripheral blood leucocytes.

CONCLUSION

Homocysteine up-regulates human p66shc expression via hypomethylation of specific CpG dinucleotides in the p66shc promoter, and this mechanism is important in homocysteine-induced endothelial cell dysfunction.

A single-nucleotide variation in a p53-binding site affects nutrient-sensitive human SIRT1 expression

The SIRTUIN1 (SIRT1) deacetylase responds to changes in nutrient availability and regulates mammalian physiology and metabolism. Human and mouse SIRT1 are transcriptionally repressed by p53 via p53 response elements in their proximal promoters. Here, we identify a novel p53-binding sequence in the distal human SIRT1 promoter that is required for nutrient-sensitive SIRT1 transcription. In addition, we show that a common single-nucleotide (C/T) variation in this sequence affects nutrient deprivation-induced SIRT1 transcription, and calorie restriction-induced SIRT1 expression. The p53-binding sequence lies in a region of the SIRT1 promoter that also binds the transcriptional repressor Hypermethylated-In-Cancer-1 (HIC1). Nutrient deprivation increases occupancy by p53, while decreasing occupancy by HIC1, of this region of the promoter. HIC1 and p53 compete with each other for promoter occupancy. In comparison with the T variation, the C variation disrupts the mirror image symmetry of the p53-binding sequence, resulting in decreased binding to p53, decreased nutrient sensitivity of the promoter and impaired calorie restriction-stimulated tissue expression of SIRT1 and SIRT1 target genes AMPKα2 and PGC-1β. Thus, a common SNP in a novel p53-binding sequence in the human SIRT1 promoter affects nutrient-sensitive SIRT1 expression, and could have a significant impact on calorie restriction-induced, SIRT1-mediated, changes in human metabolism and physiology.

p53 impairs endothelial function by transcriptionally repressing Kruppel-Like Factor 2

OBJECTIVE

To evaluate if p53 decreases Kruppel-Like Factor 2 (KLF2) expression and determine whether p53-mediated suppression of KLF2 plays a role in p53-induced endothelial dysfunction.

METHODS AND RESULTS

Endothelial KLF2 mediates endothelium-dependent vascular homeostasis by differentially regulating endothelial genes, leading to an anti-inflammatory and antithrombotic endothelial surface with normal vasodilatory function. In contrast, the tumor suppressor p53 leads to inflammatory gene expression and impairs endothelium-dependent vasodilatation, thus promoting endothelial dysfunction. The effect of p53 on KLF2 expression was determined. p53 inhibited KLF2 transcription in a histone deacetylase-dependent and a histone acetyltransferase-independent fashion. KLF2 expression was suppressed by p53 via a conserved p53-binding repressor sequence in its promoter. p53 bound to, and stimulated, deacetylation of Histone H3 at the KLF2 promoter. The effect of p53 on endothelial KLF2 target genes was examined. Downregulation of p53 increased expression of endothelial NO synthase and thrombomodulin and inhibited expression of plasminogen activator inhibitor 1. Conversely, overexpression of p53 suppressed endothelial NO synthase and thrombomodulin expression and stimulated plasminogen activator inhibitor 1 and endothelin-1 expression. Knockdown of KLF2 abolished the p53-induced decrease in thrombomodulin and increase in endothelin-1. Both, overexpression of p53 and knockdown of KLF2 in endothelial cells increased blood coagulation on an endothelial cell monolayer. The p53-induced increase in coagulation was rescued by forced expression of KLF2. p53 also impaired endothelium-dependent vasodilatation and decreased bioavailable vascular NO, both of which were rescued by forced KLF2 expression.

CONCLUSIONS

These findings illustrate a novel p53-dependent mechanism for the regulation of endothelial KLF2 expression. In addition, they show that downregulation of KLF2, in part, mediates a p53-stimulated dysfunctional endothelium.

Histone deacetylase 3 antagonizes aspirin-stimulated endothelial nitric oxide production by reversing aspirin-induced lysine acetylation of endothelial nitric oxide synthase

RATIONALE

Low-dose acetylsalicylic acid (aspirin) is widely used in the treatment and prevention of vascular atherothrombosis. Cardiovascular doses of aspirin also reduce systemic blood pressure and improve endothelium-dependent vasorelaxation in patients with atherosclerosis or risk factors for atherosclerosis. Aspirin can acetylate proteins, other than its pharmacological target cyclooxygenase, at lysine residues. The role of lysine acetylation in mediating the effects of low-dose aspirin on the endothelium is not known.

OBJECTIVE

To determine the role of lysine acetylation of endothelial nitric oxide synthase (eNOS) in the regulation of endothelial NO production by low-dose aspirin and to examine whether the lysine deacetylase histone deacetylase (HDAC)3 antagonizes the effect of low-dose aspirin on endothelial NO production by reversing acetylation of functionally critical eNOS lysine residues.

METHODS AND RESULTS

Low concentrations of aspirin induce lysine acetylation of eNOS, stimulating eNOS enzymatic activity and endothelial NO production in a cyclooxygenase-1-independent fashion. Low-dose aspirin in vivo also increases bioavailable vascular NO in an eNOS-dependent and cyclooxygenase-1-independent manner. Low-dose aspirin promotes the binding of eNOS to calmodulin. Lysine 609 in the calmodulin autoinhibitory domain of bovine eNOS mediates aspirin-stimulated binding of eNOS to calmodulin and eNOS-derived NO production. HDAC3 inhibits aspirin-stimulated (1) lysine acetylation of eNOS, (2) eNOS enzymatic activity, (3) eNOS-derived NO, and (4) binding of eNOS to calmodulin. Conversely, downregulation of HDAC3 promotes lysine acetylation of eNOS and endothelial NO generation.

CONCLUSIONS

Lysine acetylation of eNOS is a posttranslational protein modification supporting low-dose aspirin-induced vasoprotection. HDAC3, by deacetylating aspirin-acetylated eNOS, antagonizes aspirin-stimulated endothelial production of NO.

SIRT1 deacetylates APE1 and regulates cellular base excision repair

Apurinic/apyrimidinic endonuclease-1 (APE1) is an essential enzyme in the base excision repair (BER) pathway. Here, we show that APE1 is a target of the SIRTUIN1 (SIRT1) protein deacetylase. SIRT1 associates with APE1, and this association is increased with genotoxic stress. SIRT1 deacetylates APE1 in vitro and in vivo targeting lysines 6 and 7. Genotoxic insults stimulate lysine acetylation of APE1 which is antagonized by transcriptional upregulation of SIRT1. Knockdown of SIRT1 increases cellular abasic DNA content, sensitizing cells to death induced by genotoxic stress, and this vulnerability is rescued by overexpression of APE1. Activation of SIRT1 with resveratrol promotes binding of APE1 to the BER protein X-ray cross-complementing-1 (XRCC1), while inhibition of SIRT1 with nicotinamide (NAM) decreases this interaction. Genotoxic insult also increases binding of APE1 to XRCC1, and this increase is suppressed by NAM or knockdown of SIRT1. Finally, resveratrol increases APE activity in XRCC1-associated protein complexes, while NAM or knockdown of SIRT1 suppresses this DNA repair activity. These findings identify APE1 as a novel protein target of SIRT1, and suggest that SIRT1 plays a vital role in maintaining genomic integrity through regulation of the BER pathway.

P53 Impairs Endothelium-Dependent Vasomotor Function Through Transcriptional Upregulation of P66shc

The transcription factor, p53, and the adaptor protein, p66shc, both play essential roles in promoting oxidative stress in the vascular system. However, the relationship between the two in the context of endothelium-dependent vascular tone is unknown. Here, we report a novel, evolutionarily conserved, p53-mediated transcriptional mechanism that regulates p66shc expression and identify p53 as an important determinant of endothelium-dependent vasomotor function. We provide evidence of a p53 response element in the promoter of p66shc and show that angiotensin II-induced upregulation of p66shc in endothelial cells is dependent on p53. In addition, we demonstrate that downregulation of p66shc expression, as well as inhibition of p53 function in mice, mitigates angiotensin II-induced impairment of endothelium-dependent vasorelaxation, decrease in bioavailable nitric oxide, and hypertension. These findings reveal a novel p53-dependent transcriptional mechanism for the regulation of p66shc expression that is operative in the vascular endothelium and suggest that this mechanism is important in impairing endothelium-dependent vascular relaxation.

SIRT1 promotes endothelium-dependent vascular relaxation by activating endothelial nitric oxide synthase

Reduced caloric intake decreases arterial blood pressure in healthy individuals and improves endothelium-dependent vasodilation in obese and overweight individuals. The SIRT1 protein deacetylase mediates many of the effects of calorie restriction (CR) on organismal lifespan and metabolic pathways. However, the role of SIRT1 in regulating endothelium-dependent vasomotor tone is not known. Here we show that SIRT1 promotes endothelium-dependent vasodilation by targeting endothelial nitric oxide synthase (eNOS) for deacetylation. SIRT1 and eNOS colocalize and coprecipitate in endothelial cells, and SIRT1 deacetylates eNOS, stimulating eNOS activity and increasing endothelial nitric oxide (NO). SIRT1-induced increase in endothelial NO is mediated through lysines 496 and 506 in the calmodulin-binding domain of eNOS. Inhibition of SIRT1 in the endothelium of arteries inhibits endothelium-dependent vasodilation and decreases bioavailable NO. Finally, CR of mice leads to deacetylation of eNOS. Our results demonstrate that SIRT1 plays a fundamental role in regulating endothelial NO and endothelium-dependent vascular tone by deacetylating eNOS. Furthermore, our results provide a possible molecular mechanism connecting the effects of CR on the endothelium and vascular tone to SIRT1-mediated deacetylation of eNOS.

Diacyltrehalose ofMycobacterium tuberculosisinhibits lipopolysaccharide- and mycobacteria-induced proinflammatory cytokine production in human monocytic cells

The lipids located in the outer layer of Mycobacterium tuberculosis, which include sulfolipid, phthiocerol dimycocerosate (PDIM), diacyltrehalose, and polyacyltrehalose, may play a role in host-pathogen interactions. These lipids were purified using thin-layer chromatography, and their ability to induce proinflammatory cytokines in human monocytes and in a human acute monocytic leukemia cell line (THP-1) was examined. None of the lipids tested induced significant interleukin (IL)-12p40 or tumor necrosis factor (TNF)-alpha production in monocytic cells. Diacyltrehalose significantly inhibited lipopolysaccharide- and M. tuberculosis-induced IL-12p40, TNF-alpha, and IL-6 productions in human monocytes, whereas other lipids had no effect. However, diacyltrehalose was unable to inhibit peptidoglycan-induced IL-12p40 production. These results suggest that diacyltrehalose is a mycobacterial factor capable of modulating host immune responses.

Mycobacterium tuberculosis HBHA protein reacts strongly with the serum immunoglobulin M of tuberculosis patients

Identification and characterization of serologically active mycobacterial antigens are prerequisites for the development of diagnostic reagents. We examined the humoral immune responses of active tuberculosis (TB) patients against Triton-soluble proteins extracted from Mycobacterium tuberculosis by immunoblotting. A 29-kDa protein reacted with immunoglobulin M (IgM) in the pooled sera of the patients, and its N-terminal amino acid sequence matched that of the heparin-binding hemagglutinin (HBHA). Recombinant full-length HBHA was expressed in Escherichia coli (rEC-HBHA) and M. smegmatis (rMS-HBHA). In immunoblot analysis, the IgM antibodies of the TB patients reacted strongly with rMS-HBHA but not with rEC-HBHA, whereas the IgG antibodies of these patients reacted weakly with both recombinant HBHA proteins. In enzyme-linked immunosorbent assay analysis using rMS-HBHA and 85B as antigens, the mean levels and sensitivities of the anti-HBHA IgM antibodies of the TB patients were significantly higher than those of the anti-antigen 85B IgM antibodies, while the IgG antibodies showed the opposite results. Of interest in this respect, the pooled sera from the TB patients that contained anti-HBHA IgM antibodies neutralized the entry of M. tuberculosis into epithelial cells. These findings suggest that IgM antibody to HBHA may play a role in protection against extrapulmonary dissemination.

Role of the phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathways in the secretion of tumor necrosis factor-alpha and interleukin-10 by the PPD antigen of Mycobacterium tuberculosis

Here we investigated the role of the phosphatidylinositol 3-kinase (PI 3-K) and mitogen-activated protein kinase (MAPK) pathways in the secretion of tumor necrosis factor (TNF)-alpha and interleukin (IL)-10 in human primary monocytes after stimulation with the PPD antigen of Mycobacterium tuberculosis. MAPK [extracellular signal-regulated kinase (ERK) 1/2 and p38] and Akt are rapidly phosphorylated in human monocytes stimulated with PPD. We found that the PI 3-K-Akt pathway stimulated by PPD is essential for both IL-10 and TNF-alpha production, although the inhibition of IL-10 production was more pronounced. The analysis of cytokine production using specific inhibitors of the MAPK pathway revealed that both p38 and ERK activation are essential for PPD-induced TNF-alpha production, whereas p38, but not ERK, activation is essential for IL-10 secretion. The inhibition of PI 3-K did not significantly activate p38 MAPK or ERK 1/2 in PPD-stimulated human monocytes. Further, the Src inhibitor PP2 inhibited the release of TNF-alpha but enhanced IL-10 release, suggesting the differential regulation of Src kinase in upstream signaling. Collectively, these data suggest that the PI 3-K and MAPK pathways play a central role in the regulation of both pro- and anti-inflammatory cytokines by the PPD antigen of M. tuberculosis.

Intracellular network of phosphatidylinositol 3-kinase, mammalian target of the rapamycin/70 kDa ribosomal S6 kinase 1, and mitogen-activated protein kinases pathways for regulating mycobacteria-induced IL-23 expression in human macrophages

We previously demonstrated that Mycobacterium tuberculosis (M. tbc)-induced interleukin (IL)-12 expression is negatively regulated by the phosphatidylinositol 3-kinase (PI3K) and extracellular signal-regulated kinase (ERK) 1/2 pathways in human monocyte-derived macrophages (MDMs). To extend these studies, we examined the nature of the involvement of toll-like receptors (TLRs) and intracellular signalling pathways downstream from PI3K in M. tbc-induced IL-23 expression in human MDMs. M. tbc-induced Akt activation and IL-23 expression were essentially dependent on TLR2. Blockade of the mammalian targets of rapamycin (mTOR)/70 kDa ribosomal S6 kinase 1 (S6K1) pathway by the specific inhibitor rapamycin greatly enhanced M. tbc-induced IL-12/IL-23 p40 (p40) and IL-23 p19 (p19) mRNA and IL-23 protein expression. In sharp contrast, p38 mitogen-activated protein kinase (MAPK) inhibition abrogated the p40 and p19 mRNA and IL-23 protein expression induced by M. tbc. Furthermore, the inhibition of PI3K-Akt, but not ERK 1/2 pathway, attenuated M. tbc-induced S6K1 phosphorylation, whereas PI3K inhibition enhanced p38 phosphorylation and apoptosis signal-regulating kinase 1 activity during exposure to M. tbc. Although the negative or positive regulation of IL-23 was not reversed by neutralization of IL-10, it was significantly modulated by blocking TLR2. Collectively, these findings provide new insight into the homeostatic mechanism controlling type 1 immune responses during mycobacterial infection involving the intracellular network of PI3K, S6K1, ERK 1/2 and p38 MAPK pathways in a TLR2-dependent manner.

The mycobacterial 38-kilodalton glycolipoprotein antigen activates the mitogen-activated protein kinase pathway and release of proinflammatory cytokines through Toll-like receptors 2 and 4 in human monocytes

Although the 38-kDa glycolipoprotein of Mycobacterium tuberculosis H37Rv is known to evoke prominent cellular and humoral immune responses in human tuberculosis (TB), little information is known about intracellular regulatory mechanisms involved in 38-kDa antigen (Ag)-induced host responses. In this study, we found that purified 38-kDa glycolipoprotein activates mitogen-activated protein kinases (MAPKs; extracellular signal-regulated kinase 1/2 [ERK1/2] and p38) and induces tumor necrosis factor alpha (TNF-alpha) and interleukin 6 (IL-6) in human monocytes. When the 38-kDa Ag was applied to monocytes from TB patients and healthy controls, the activation of ERK1/2 and p38 MAPK and the subsequent cytokine secretion were greater in the monocytes from the active pulmonary TB patients than in monocytes from the healthy controls. Additionally, neutralizing antibodies for Toll-like receptor 2 (TLR2) or TLR4 significantly reduced the ERK1/2 and p38 activation induced by the 38-kDa protein when the antibodies were applied to HEK293 cells overexpressing TLR2 or TLR4 as well as human primary monocytes. Furthermore, the inhibition of TLR2 significantly, and that of TLR4 partially, decreased the 38-kDa Ag-induced secretion of TNF-alpha and IL-6 in human monocytes. The intact protein moieties of the 38-kDa protein were responsible for biologic activities by this Ag. These data collectively demonstrate that the 38-kDa glycolipoprotein, acting through both TLR2 and TLR4, induces the activation of the ERK1/2 and p38 MAPK pathways, which in turn play an essential role in TNF-alpha and IL-6 expression during mycobacterial infection.

Identification of the new T-cell-stimulating antigens from Mycobacterium tuberculosis culture filtrate

The proteins secreted by Mycobacterium tuberculosis are an important target for vaccine development. To identify the antigens from M. tuberculosis culture filtrate (CF) that strongly stimulate T-cells, the CF was fractionated by ion-exchange chromatography and then non-reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis with mini-whole gel elution. Each fraction was screened for its ability to induce interferon-gamma (IFN-gamma) production in peripheral blood mononuclear cells isolated from healthy tuberculin reactors. The protein bands that strongly induced IFN-gamma production were subjected to N-terminal sequencing. Two new proteins, a 17-kDa protein (Rv0164, MTSP17) and an 11-kDa (Rv3204, MTSP11) protein, were identified. The recombinant MTSP17 (rMTSP17) and rMTSP11 induced significant production of IFN-gamma and interleukin (IL)-12p40 in peripheral blood mononuclear cells from healthy tuberculin reactors. Interestingly, IL-12p40 production in response to rMTSP11 was significantly higher than that in response to rMTSP17 or the three components of the antigen 85 complex. These results suggest that MTSP11 antigen should be further evaluated as a component of a subunit vaccine.

Biosynthesis of polyhydroxyalkanoate copolyester containing cyclohexyl groups by Pseudomonas oleovorans

Production of polyhydroxyalkanoates (PHAs) substituted with cyclohexyl groups by Pseudomonas oleovorans grown with 4-cyclohexylbutyric acid (4-CHB) and its mixtures with nonanoic acid (NA) was investigated. Addition of NA to medium gave rise to an increase in the total concentration of 3-hydroxy-4-cyclohexylbutyrate repeating unit in the PHAs, indicating that the bioconversion rate of 4-CHB to polyester was significantly improved by the cometabolic effect. Increasing the proportion of NA from 1.0 to 7.5 mM at a concentration of 10 mM total carbon substrate also accelerated the uptake speed of 4-CHB by the organism and resulted in an increase of the ratio of 3-hydroxynonanoate to 3-hydroxyheptanoate from 1.28 to 2.05. Differential scanning calorimetric analysis of the PHAs bearing the corresponding functional groups showed one melting transition and one glass transition temperature varying according to the composition. These results indicated that random copolyesters were obtained from the carbon substrates used in this study.

Comparison of two immunization schedules for a Pseudomonas aeruginosa outer membrane proteins vaccine in burn patients

The aim of the present study was to compare two immunization schedules for a Pseudomonas aeruginosa outer membrane proteins (OMPs) vaccine in burn patients. In a double-blind, randomized and placebo-controlled clinical trial, 95 adult patients with burn injuries in 10% or greater of total body surface area were randomly allocated to either placebo or immunization groups. Three doses of the vaccine (0.5 or 1.0 mg) were administered intramuscularly at either 3- or 7-day intervals. The vaccine was well tolerated, and no severe adverse reactions were observed in any of the vaccinees. After three immunizations, 88 patients were available for evaluation of serum antibody titers. Elevation of OMPs-specific antibody titers in the immunization groups was significantly higher as compared with the placebo group, and the highest antibody response was obtained by immunization with 1.0-mg doses at 3-day intervals. Conventional blood culture, tissue culture of wound biopsy specimens and a nested polymerase chain reaction (PCR) assay of blood specimens were performed to determine the protective efficacy. The results of the nested PCR indicated that the overall detection rate of P. aeruginosa in blood was significantly lower among immunized patients than placebo patients (6.1 vs. 40.0%, P<0.001). Based on these results, we concluded that the P. aeruginosa OMPs vaccine is safe and highly immunogenic in burn patients, especially with 1.0-mg doses at 3-day intervals, and may be effective in conferring protection against P. aeruginosa bacteremia in burn patients.

Immunization of burn-patients with a Pseudomonas aeruginosa outer membrane protein vaccine elicits antibodies with protective efficacy

The aim of this study was to determine whether the antibodies raised in burn patients by active immunization with a Pseudomonas aeruginosa OMPs vaccine have a protective efficacy against infection with P. aeruginosa. The binding patterns with P. aeruginosa OMPs of immunized burn patient sera were similar to the sera of immunized healthy humans as determined by immunoblot and immunoprecipitation analyses. The sera pooled from immunized burn patients after three immunizations showed a significantly higher opsonophagocytic-killing activity than the corresponding pre-immune sera, while the sera from unimmunized patients collected at the same day did not. Passive immunization of mice with post-immune sera of burn patients significantly enhanced the survival rate upon a lethal challenge with P. aeruginosa compared to the pre-immune sera, indicating the protective ability of the antibodies induced in burn patients by immunization. These results suggest that anti-P. aeruginosa OMPs antibodies elicited in burn patients by active immunization are protective against infection with P. aeruginosa, and provide a rational for further development of the vaccine for prevention against P. aeruginosa infection in burn patients.

Conformation-dependent antibody response to Pseudomonas aeruginosa outer membrane proteins induced by immunization in humans

Outer membrane proteins (OMPs) of pathogenic bacteria have been used as protective antigens in developing bacterial vaccines. In the present study, we compared the antibody responses to a Pseudomonas aeruginosa OMP vaccine elicited in humans and rabbits by immunization. Immunization with the vaccine induced high titers of serum IgG antibody both in rabbits and humans but reactivities of the induced antibodies with the OMPs were different. The rabbit immune sera recognized most of the OMPs in the vaccine both in immunoblot and immunoprecipitation analyses. In contrast, a great variation in band pattern and intensity was observed among the human immune sera in immunoblot analysis, but not in immunoprecipitation analysis. Denaturation of the OMPs did not affect the binding activity of the rabbit immune sera as determined by ELISA, but substantially reduced those of the human immune sera and anti-OMP IgG purified from a pooled normal human plasma. These data suggest that antibody response to P. aeruginosa OMPs elicited by immunization in humans is mainly directed against discontinuous or conformation-dependent epitopes, which should be taken into account in developing vaccines, especially for OMP-derived synthetic peptides.

Protection of mice against P. aeruginosa infections by large-scale affinity-purified human IgG specific to P. aeruginosa outer membrane proteins

In order to develop an effective means to treat Pseudomonas aeruginosa infections, we designed a large-scale process for purification of human IgG specific to P. aeruginosa outer membrane proteins (Oprs) from normal human sera. The process we developed includes affinity column chromatography using P. aeruginosa Oprs as ligands, protein A column chromatography and ultrafiltration, which enriched P. aeruginosa Oprs-specific IgG antibody by 500-fold. The purified anti-Oprs IgG was specific to the Oprs as confirmed by an ELISA competition assay and retained opsonophagocytic-killing capacity. In vivo protective efficacy of anti-Oprs IgG was evaluated by passive protection assays in mice where the 50% protective dose of anti-Oprs IgG against P. aeruginosa infections was 41 microg/kg, which was 20 times lower than that of normal serum IgG. When administered to mice 3 h after bacterial challenge, only anti-Oprs IgG afforded protection. These data demonstrate the feasibility of use of the purification process in producing functionally active target-specific human antibodies for clinical use and provide a rationale for use of anti-Oprs IgG as a valuable adjunct to treat P. aeruginosa infections.

Human anti-Pseudomonas aeruginosa outer membrane proteins IgG cross-protective against infection with heterologous immunotype strains of P. aeruginosa

In order to develop an effective means to treat and prevent Pseudomonas aeruginosa infections, we have purified P. aeruginosa outer membrane protein (Oprs)-specific human IgG antibody using a large-scale affinity column. In this study, we investigated the cross-protective activity of the purified anti-Oprs IgG against various immunotype strains of P. aeruginosa. The anti-Oprs IgG reacted with Oprs isolated from seven Fisher-Devlin immunotype strains of P. aeruginosa and was able to promote opsonophagocytic killing of all seven immunotype strains by human phagocytic cells. Administration of 500 microg anti-Oprs IgG to mice raised the LD50 of the P. aeruginosa strains by 8-250-fold, indicating the protective capacity against heterologous P. aeruginosa strains as well as homologous strains. In contrast, despite high titers against P. (aeruginosa Oprs, total serum IgG isolated from burn patient sera was no better than normal serum IgG in protecting mice from infection with P. aeruginosa. These data demonstrate that the affinity-purified human anti-Oprs IgG could afford protection against heterologous immunotype P. aeruginosa strains and provide a rationale to use anti-Oprs IgG as an adjunct for treatment of P. aeruginosa infections in humans.

Human immune response to a Pseudomonas aeruginosa outer membrane protein vaccine

In order to evaluate in humans the safety and immunogenicity of a Pseudomonas aeruginosa vaccine composed of outer membrane proteins (OMPs), CFC-101, we carried out a phase I/IIa clinical trial in healthy male volunteers. Groups of six volunteers were immunized either subcutaneously (s.c.) or intramuscularly (i.m.) with three dosages of the vaccine three times at 7-day intervals. The vaccine was well tolerated by volunteers. Local reactions in the injection sites were generally mild and transient. Significant increases in OMP-specific antibody were observed in both route groups after vaccinations but was higher in the i.m.-immunized group, where vaccination with 0.5 or 1.0 mg doses yielded 100% seroconversion. The specificity of the induced antibodies to P. aeruginosa OMP was demonstrated by western blot analysis and immunoprecipitation assay. An increase in Clq-binding capacity and ability to confer mice protection from lethal challenges with P. aeruginosa indicated the protective efficacy of the elicited antibodies. Based on these data, we concluded that the P. aeruginosa OMP vaccine is safe and effective in humans with an optimal dose of 0.5 and 1.0 mg and that i.m. is the better route than s.c. for this vaccine.

Cloning and sequencing of genes encoding malonate decarboxylase in Acinetobacter calcoaceticus

Malonate decarboxylase from Acinetobacter calcoaceticus was isolated and characterized (Kim, Y.S., Byun, H.S., J. Biol. Chem. 269 (1994) 29636-29641), and its subunits were reanalyzed recently to be alpha, beta, gamma, and delta. The genes for the subunits, MdcA (548 a.a.), B (295 a.a.), C (238 a.a.), and D (102 a.a.), of the enzyme have been cloned by using oligonucleotide primers deduced from amino acid sequences of peptides isolated from the purified enzyme, and sequenced to be clustered in an operon in the order of A-D-B-C. The operon was found to encode more genes than mdcABCD. The Escherichia coli, transformed with the vector containing the insert mdcADBC and about 1.7 kb of an upstream region, expressed the four subunits of the enzyme but the proteins did not show enzyme activity. It indicates that, like the enzymes from Malonomonas rubra and Klebsiella pneumoniae, more genes are needed for the formation of the functional malonate decarboxylase.