Sarah Ullevig

Redox regulation of MAPK phosphatase 1 controls monocyte migration and macrophage recruitment

Monocytic adhesion and chemotaxis are regulated by MAPK pathways, which in turn are controlled by redox-sensitive MAPK phosphatases (MKPs). We recently reported that metabolic disorders prime monocytes for enhanced recruitment into vascular lesions by increasing monocytes’ responsiveness to chemoattractants. However, the molecular details of this proatherogenic mechanism were not known. Here we show that monocyte priming results in the S-glutathionylation and subsequent inactivation and degradation of MKP-1. Chronic exposure of human THP-1 monocytes to diabetic conditions resulted in the loss of MKP-1 protein levels, the hyperactivation of ERK and p38 in response to monocyte chemoattractant protein-1 (MCP-1), and increased monocyte adhesion and chemotaxis. Knockdown of MKP-1 mimicked the priming effects of metabolic stress, whereas MKP-1 overexpression blunted both MAPK activation and monocyte adhesion and migration induced by MCP-1. Metabolic stress promoted the S-glutathionylation of MKP-1, targeting MKP-1 for proteasomal degradation. Preventing MKP-1 S-glutathionylation in metabolically stressed monocytes by overexpressing glutaredoxin 1 protected MKP-1 from degradation and normalized monocyte adhesion and chemotaxis in response to MCP-1. Blood monocytes isolated from diabetic mice showed a 55% reduction in MKP-1 activity compared with nondiabetic mice. Hematopoietic MKP-1 deficiency in atherosclerosis-prone mice mimicked monocyte priming and dysfunction associated with metabolic disorders, increased monocyte chemotaxis in vivo, and accelerated atherosclerotic lesion formation. In conclusion, we identified MKP-1 as a central redox-sensitive regulator of monocyte adhesion and migration and showed that the loss of MKP-1 activity is a critical step in monocyte priming and the metabolic stress-induced conversion of blood monocytes into a proatherogenic phenotype.

Bioenergetic Profiles Diverge During Macrophage Polarization: Implications for the Interpretation of 18F-FDG PET Imaging of Atherosclerosis

Conventional cardiovascular imaging is invaluable for the assessment of late sequelae of atherosclerosis, such as diminished perfusion reserve and luminal stenosis. Molecular imaging provides complementary information about plaque composition and ongoing biologic processes in the vessel wall, allowing the early diagnosis and risk stratification of patients. Detection of enhanced glucose uptake, using 18F-FDG PET, has been proposed as a noninvasive approach to track macrophage activation as a critical event in the development and progression of atherosclerosis. In this study, we determined the impact of macrophage polarization on glucose metabolism and oxidative phosphorylation. Methods: Murine peritoneal macrophages were incubated in the presence of interferon-γ (IFN-γ) plus tumor necrosis factor-α (TNF-α), lipopolysaccharide (LPS), or interleukin-4 (IL-4) to induce classic (M1 and MLPS) or alternative (M2) polarization, respectively. Glucose uptake was measured using 3H-deoxyglucose. Oxidative phosphorylation was evaluated using an extracellular flux analyzer. Mitochondrial DNA copy numbers were quantified by polymerase chain reaction. The expression of glucose transporter-1 (Glut-1), hexokinase-1 and -2 (Hk-1 and Hk-2, respectively), mitochondrial transcription factor-1 (Tfam), and cytochrome c oxidase subunit I (Cox-1) was determined by quantitative reverse transcription polymerase chain reaction. Results: Stimulation of macrophages by LPS, but not polarization with either IFN-γ plus TNF-α (M1) or IL-4 (M2), resulted in a 2.5-fold increase in 3H-deoxyglucose uptake. Enhanced glucose uptake by MLPS macrophages paralleled the overexpression of rate-limiting proteins involved in transmembrane transport and intracellular trapping of glucose—that is, Glut-1, Hk-1, and Hk-2. Alternatively polarized M2 macrophages developed a markedly higher spare respiratory capacity than both nonpolarized and classically polarized M1 macrophages. M2 polarization was associated with a 4.6-fold increase in mitochondrial content of the cells, compared with nonpolarized macrophages. The expression of Tfam, a major regulator of mitochondrial biogenesis, and Cox-1, a critical component of respiratory chain, was significantly increased in M2 polarized macrophages. Conclusion: Polarization of macrophages induces distinct metabolic profiles with respect to glycolysis versus oxidative phosphorylation, with alternatively polarized macrophages shifting to mitochondria as their main source of adenosine triphosphate. Only MLPS, but not M1 or M2 polarized macrophages, showed increased glucose uptake, suggesting that glucose metabolism is regulated independent of the polarization state and macrophage polarization may not be detectable by 18F-FDG PET.

Ursolic acid protects diabetic mice against monocyte dysfunction and accelerated atherosclerosis

AIMS Accelerated atherosclerosis is a major diabetic complication initiated by the enhanced recruitment of monocytes into the vasculature. In this study, we examined the therapeutic potential of the phytonutrients ursolic acid (UA) and resveratrol (RES) in preventing monocyte recruitment and accelerated atherosclerosis. METHODS AND RESULTS Dietary supplementation with either RES or UA (0.2%) protected against accelerated atherosclerosis induced by streptozotocin in high-fat diet-fed LDL receptor-deficient mice. However, mice that received dietary UA for 11 weeks were significantly better protected and showed a 53% reduction in lesion formation while mice fed a RES-supplemented diet showed only a 31% reduction in lesion size. Importantly, UA was also significantly more effective in preventing the appearance of proinflammatory GR-1(high) monocytes induced by these diabetic conditions and reducing monocyte recruitment into MCP-1-loaded Matrigel plugs implanted into these diabetic mice. Oxidatively stressed THP-1 monocytes mimicked the behavior of blood monocytes in diabetic mice and showed enhanced responsiveness to monocyte chemoattractant protein-1 (MCP-1) without changing MCP-1 receptor (CCR2) surface expression. Pretreatment of THP-1 monocytes with RES or UA (0.3-10μM) for 15h resulted in the dose-dependent inhibition of H(2)O(2)-accelerated chemotaxis in response to MCP-1, but with an IC(50) of 0.4μM, UA was 2.7-fold more potent than RES. CONCLUSION Dietary UA is a potent inhibitor of monocyte dysfunction and accelerated atherosclerosis induced by diabetes. These studies identify ursolic acid as a potential therapeutic agent for the treatment of diabetic complications, including accelerated atherosclerosis, and provide a novel mechanism for the anti-atherogenic properties of ursolic acid.

NADPH Oxidase 4 Mediates Monocyte Priming and Accelerated Chemotaxis Induced by Metabolic Stress

Objective—Metabolic disorders increase monocyte chemoattractant protein-1 (MCP-1)-induced monocyte chemotaxis in mice. The goal of this study was to determine the molecular mechanisms responsible for the enhanced responsiveness of monocytes to chemoattractants induced by metabolic stress. Methods and Results—Chronic exposure of monocytes to diabetic conditions induced by human LDL plus high D-glucose concentrations (LDL+HG) promoted NADPH Oxidase 4 (Nox4) expression, increased intracellular H2O2 formation, stimulated protein S-glutathionylation, and increased chemotaxis in response to MCP-1, platelet-derived growth factor B, and RANTES. Both H2O2 added exogenously and overexpression of Nox4 mimicked LDL+HG-induced monocyte priming, whereas Nox4 knockdown protected monocytes against metabolic stress-induced priming and accelerated chemotaxis. Exposure of monocytes to LDL+HG promoted the S-glutathionylation of actin, decreased the F-actin/G-actin ratio, and increased actin remodeling in response to MCP-1. Preventing LDL+HG-induced protein S-glutathionylation by overexpressing glutaredoxin 1 prevented monocyte priming and normalized monocyte chemotaxis in response to MCP-1. Induction of hypercholesterolemia and hyperglycemia in C57BL/6 mice promoted Nox4 expression and protein S-glutathionylation in macrophages, and increased macrophage recruitment into MCP-1–loaded Matrigel plugs implanted subcutaneous in these mice. Conclusion—By increasing actin-S-glutathionylation and remodeling, metabolic stress primes monocytes for chemoattractant-induced transmigration and recruitment to sites of vascular injury. This Nox4-dependent process provides a novel mechanism through which metabolic disorders promote atherogenesis.

Regulation of Monocyte Adhesion and Migration by Nox4.

We showed that metabolic disorders promote thiol oxidative stress in monocytes, priming monocytes for accelerated chemokine-induced recruitment, and accumulation at sites of vascular injury and the progression of atherosclerosis. The aim of this study was to identify both the source of reactive oxygen species (ROS) responsible for thiol oxidation in primed and dysfunctional monocytes and the molecular mechanisms through which ROS accelerate the migration and recruitment of monocyte-derived macrophages. We found that Nox4, a recently identified NADPH oxidase in monocytes and macrophages, localized to focal adhesions and the actin cytoskeleton, and associated with phospho-FAK, paxillin, and actin, implicating Nox4 in the regulation of monocyte adhesion and migration. We also identified Nox4 as a new, metabolic stress-inducible source of ROS that controls actin S-glutathionylation and turnover in monocytes and macrophages, providing a novel mechanistic link between Nox4-derived H2O2 and monocyte adhesion and migration. Actin associated with Nox4 was S-glutathionylated, and Nox4 association with actin was enhanced in metabolically-stressed monocytes. Metabolic stress induced Nox4 and accelerated monocyte adhesion and chemotaxis in a Nox4-dependent mechanism. In conclusion, our data suggest that monocytic Nox4 is a central regulator of actin dynamics, and induction of Nox4 is the rate-limiting step in metabolic stress-induced monocyte priming and dysfunction associated with accelerated atherosclerosis and the progression of atherosclerotic plaques.

Resveratrol and Quercetin Interact to Inhibit Neointimal Hyperplasia in Mice with a Carotid Injury

Restenosis is a critical complication of angioplasty and stenting. Restenosis is multifactorial, involving endothelial injury, inflammation, platelet activation, and vascular smooth muscle cell (VSMC) proliferation. Thus, dietary strategies to prevent restenosis likely require the use of more than one agent. Resveratrol (R) and quercetin (Q) are polyphenols that are known to exhibit vascular protective effects. We tested whether R and Q administered in the diet interact to inhibit vessel stenosis in mice with a carotid injury. B6.129 mice were administered a high-fat diet containing 21% fat and 0.2% cholesterol along with R (25 mg/kg), Q (10 mg/kg), or R + Q for 2 wk. A carotid injury was induced and the mice were again administered the enriched diet for 2 wk. Compared with the controls, R significantly decreased stenosis, assessed as an intima:media ratio, by 76%. Although Q treatment alone exhibited no effect, it potentiated the effect of R in that treatment with R + Q significantly decreased the intima:media ratio by 94%. Moreover, this effect was greater than that of R treatment alone (P < 0.05). Although treatments with R, Q, and R + Q significantly affected platelet activation and endothelial function, the responses observed for R + Q were less than additive. Specifically, the effects of R + Q were less than the sum of effects for treatments with R and Q alone. In contrast, treatment with R + Q exhibited more-than-additive effects on inflammatory markers and significant interactions between R and Q were observed. The presence of synergy between R and Q was thus tested in cultures of VSMC and macrophages. Isobolographic analysis revealed that 2:1 molar ratios of R:Q exhibited synergistic inhibition of VSMC proliferation and macrophage chemotaxis. In conclusion, in combination, R and Q can interact to reduce the extent of restenosis, perhaps due to their synergistic inhibition of VSMC proliferation and inflammation.

S-Glutathionylation in Monocyte and Macrophage (Dys)Function

Atherosclerosis is a chronic inflammatory disease involving the accumulation of monocytes and macrophages in the vascular wall. Monocytes and macrophages play a central role in the initiation and progression of atherosclerotic lesion development. Oxidative stress, which occurs when reactive oxygen species (ROS) overwhelm cellular antioxidant systems, contributes to the pathophysiology of many chronic inflammatory diseases, including atherosclerosis. Major targets of ROS are reactive thiols on cysteine residues in proteins, which when oxidized can alter cellular processes, including signaling pathways, metabolic pathways, transcription, and translation. Protein-S-glutathionylation is the process of mixed disulfide formation between glutathione (GSH) and protein thiols. Until recently, protein-S-glutathionylation was associated with increased cellular oxidative stress, but S-glutathionylation of key protein targets has now emerged as a physiologically important redox signaling mechanism, which when dysregulated contributes to a variety of disease processes. In this review, we will explore the role of thiol oxidative stress and protein-S-glutathionylation in monocyte and macrophage dysfunction as a mechanistic link between oxidative stress associated with metabolic disorders and chronic inflammatory diseases, including atherosclerosis.

Redox Regulation of 14-3-3ζ Controls Monocyte Migration

Objective—Metabolic stress primes monocytes for accelerated chemokine-mediated adhesion, migration, and recruitment into vascular lesions by increasing actin remodeling. The mechanism linking metabolic stress to accelerated actin turnover and enhanced monocyte migration was not known. We tested the hypothesis that in metabolically primed monocytes, the acceleration of monocyte chemoattractant protein-1–induced chemotaxis is mediated by the hyperactivation of cofilin. Approach and Results—Metabolic priming was induced by exposing human THP-1 monocytes to diabetic conditions, that is, human native low-density lipoprotein plus high glucose concentrations. In healthy monocytes, monocyte chemoattractant protein-1 induced the phosphorylation and inactivation of cofilin. This response was completely blocked in metabolically primed monocytes but restored by overexpression of the thiol transferase, glutaredoxin 1. Cofilin kinase, LIM kinase 1, and cofilin phosphatase, Slingshot-1L, were not affected by metabolic stress. However, metabolic priming increased 3.8-fold the S-glutathionylation of the Slingshot-1L-binding protein 14-3-3&zgr; (zeta), resulting in its caspase-dependent degradation. Glutaredoxin 1 overexpression inhibited low-density lipoprotein plus high glucose–induced S-glutathionylation and degradation of 14-3-3&zgr;. The C25S mutant of 14-3-3&zgr; was resistant to both S-glutathionylation and degradation induced by low-density lipoprotein plus high glucose. Overexpression of the C25S mutant restored monocyte chemoattractant protein-1–induced cofilin phosphorylation and prevented accelerated migration of metabolically stressed monocytes, suggesting that loss of 14-3-3&zgr; increases the pool of free Slingshot-1L phosphatase, thereby preventing the phosphorylation and deactivation of cofilin in response to chemokine activation. Conclusions—By preventing the inactivation of cofilin, metabolic stress–induced degradation of 14-3-3&zgr; promotes the conversion of blood monocytes into a hypermigratory, proatherogenic phenotype.

Redox Regulation of 14-3-3zeta Controls Monocyte Migration

Objective—Metabolic stress primes monocytes for accelerated chemokine-mediated adhesion, migration, and recruitment into vascular lesions by increasing actin remodeling. The mechanism linking metabolic stress to accelerated actin turnover and enhanced monocyte migration was not known. We tested the hypothesis that in metabolically primed monocytes, the acceleration of monocyte chemoattractant protein-1–induced chemotaxis is mediated by the hyperactivation of cofilin. Approach and Results—Metabolic priming was induced by exposing human THP-1 monocytes to diabetic conditions, that is, human native low-density lipoprotein plus high glucose concentrations. In healthy monocytes, monocyte chemoattractant protein-1 induced the phosphorylation and inactivation of cofilin. This response was completely blocked in metabolically primed monocytes but restored by overexpression of the thiol transferase, glutaredoxin 1. Cofilin kinase, LIM kinase 1, and cofilin phosphatase, Slingshot-1L, were not affected by metabolic stress. However, metabolic priming increased 3.8-fold the S-glutathionylation of the Slingshot-1L-binding protein 14-3-3&zgr; (zeta), resulting in its caspase-dependent degradation. Glutaredoxin 1 overexpression inhibited low-density lipoprotein plus high glucose–induced S-glutathionylation and degradation of 14-3-3&zgr;. The C25S mutant of 14-3-3&zgr; was resistant to both S-glutathionylation and degradation induced by low-density lipoprotein plus high glucose. Overexpression of the C25S mutant restored monocyte chemoattractant protein-1–induced cofilin phosphorylation and prevented accelerated migration of metabolically stressed monocytes, suggesting that loss of 14-3-3&zgr; increases the pool of free Slingshot-1L phosphatase, thereby preventing the phosphorylation and deactivation of cofilin in response to chemokine activation. Conclusions—By preventing the inactivation of cofilin, metabolic stress–induced degradation of 14-3-3&zgr; promotes the conversion of blood monocytes into a hypermigratory, proatherogenic phenotype.

Impact of Home-Delivered Meals on Nutrition Status and Nutrient Intake among Older Adults in Central Texas

ObjectiveThis study aimed to measure changes in nutrition risk and nutrient intake after older adults received home-delivered meals (HDM) for 3 months.DesignThis study used a pre-posttest study design, with data collected before and after 3 months of HDM services.SettingTwo HDM programs that serve the metropolitan areas of Austin and San Antonio, Texas.ParticipantsStudy participants were aged 60 years or older, without dementia or terminal illness, and receiving HDM in Austin, Texas and San Antonio, Texas for 3 months.MeasurementsThe Nutrition Screening Initiative (NSI) and Mini Nutrition Assessment-Short Form (MNA-SF) were used to assess nutritional risk. The National Cancer Institute Diet History Questionnaire II (DHQ II) was used to assess nutrient intake over the past month.ResultsAfter receiving 3 months of HDM, nutrition status significantly improved as measured by the NSI and MNA-SF. More participants met or exceeded the recommended dietary allowances (RDA) for magnesium and zinc after receiving HDM compared to before receiving HDM. Dietary supplement intake was associated with a higher nutritional risk.ConclusionImprovements in nutrition status were found after 3 months of receiving HDM, whereas intake of most nutrients did not change significantly. Results of this study provide further evidence that HDM can reduce nutritional risk of older adults, and may inform HDM programs on the differences of NSI and/or MNA-SF to assess nutritional risk of clients.