Lipocalin 2, a Regulator of Retinoid Homeostasis and Retinoid-mediated Thermogenic Activation in Adipose Tissue.

We have recently characterized the role of lipocalin 2 (Lcn2) as a new adipose-derived cytokine in the regulation of adaptive thermogenesis via a non-adrenergic pathway. Herein, we explored a potential non-adrenergic mechanism by which Lcn2 regulates thermogenesis and lipid metabolism. We found that Lcn2 is a retinoic acid target gene, and retinoic acid concurrently stimulated UCP1 and Lcn2 expression in adipocytes. Lcn2 KO mice exhibited a blunted effect of all-trans-retinoic acid (ATRA) on body weight and fat mass, lipid metabolism, and retinoic acid signaling pathway activation in adipose tissue under the high fat diet-induced obese condition. We further demonstrated that Lcn2 is required for the full action of ATRA on the induction of UCP1 and PGC-1α expression in brown adipocytes and the restoration of cold intolerance in Lcn2 KO mice. Interestingly, we discovered that Lcn2 KO mice have decreased levels of retinoic acid and retinol in adipose tissue. The protein levels of STRA6 responsible for retinol uptake were significantly decreased in adipose tissue. The retinol transporter RBP4 was increased in adipose tissue but decreased in the circulation, suggesting the impairment of RBP4 secretion in Lcn2 KO adipose tissue. Moreover, Lcn2 deficiency abolished the ATRA effect on RBP4 expression in adipocytes. All the data suggest that the decreased retinoid level and action are associated with impaired retinol transport and storage in adipose tissue in Lcn2 KO mice. We conclude that Lcn2 plays a critical role in regulating metabolic homeostasis of retinoids and retinoid-mediated thermogenesis in adipose tissue.

Fatty acids induce leukotriene C4 synthesis in macrophages in a fatty acid binding protein-dependent manner.

Obesity results in increased macrophage recruitment to adipose tissue that promotes a chronic low-grade inflammatory state linked to increased fatty acid efflux from adipocytes. Activated macrophages produce a variety of pro-inflammatory lipids such as leukotriene C4 (LTC4) and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE) suggesting the hypothesis that fatty acids may stimulate eicosanoid synthesis. To assess if eicosanoid production increases with obesity, adipose tissue of leptin deficient ob/ob mice was analyzed. In ob/ob mice, LTC4 and 12-HETE levels increased in the visceral (but not subcutaneous) adipose depot while the 5-HETE levels decreased and 15-HETE abundance was unchanged. Since macrophages produce the majority of inflammatory molecules in adipose tissue, treatment of RAW264.7 or primary peritoneal macrophages with free fatty acids led to increased secretion of LTC4 and 5-HETE, but not 12- or 15-HETE. Fatty acid binding proteins (FABPs) facilitate the intracellular trafficking of fatty acids and other hydrophobic ligands and in vitro stabilize the LTC4 precursor leukotriene A4 (LTA4) from non-enzymatic hydrolysis. Consistent with a role for FABPs in LTC4 synthesis, treatment of macrophages with HTS01037, a specific FABP inhibitor, resulted in a marked decrease in both basal and fatty acid-stimulated LTC4 secretion but no change in 5-HETE production or 5-lipoxygenase expression. These results indicate that the products of adipocyte lipolysis may stimulate the 5-lipoxygenase pathway leading to FABP-dependent production of LTC4 and contribute to the insulin resistant state.

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics.

Proinflammatory cytokines differentially regulate adipocyte mitochondrial metabolism, oxidative stress, and dynamics. Macrophage infiltration of adipose tissue and the chronic low-grade production of inflammatory cytokines have been mechanistically linked to the development of insulin resistance, the forerunner of type 2 diabetes mellitus. In this study, we evaluated the chronic effects of TNFα, IL-6, and IL-1ß on adipocyte mitochondrial metabolism and morphology using the 3T3-L1 model cell system. TNFα treatment of cultured adipocytes led to significant changes in mitochondrial bioenergetics, including increased proton leak, decreased ΔΨm, increased basal respiration, and decreased ATP turnover. In contrast, although IL-6 and IL-1ß decreased maximal respiratory capacity, they had no effect on ΔΨm and varied effects on ATP turnover, proton leak, or basal respiration. Only TNFα treatment of 3T3-L1 cells led to an increase in oxidative stress (as measured by superoxide anion production and protein carbonylation) and C16 ceramide synthesis. Treatment of 3T3-L1 adipocytes with cytokines led to decreased mRNA expression of key transcription factors and control proteins implicated in mitochondrial biogenesis, including PGC-1α and eNOS as well as deceased expression of COX IV and Cyt C. Whereas each cytokine led to effects on expression of mitochondrial markers, TNFα exclusively led to mitochondrial fragmentation and decreased the total level of OPA1 while increasing OPA1 cleavage, without expression of levels of mitofusin 2, DRP-1, or mitofilin being affected. In summary, these results indicate that inflammatory cytokines have unique and specialized effects on adipocyte metabolism, but each leads to decreased mitochondrial function and a reprogramming of fat cell biology.

Fatty acids induce leukotriene C4 synthesis in macrophages in a fatty acid binding protein-dependent manner.

Obesity results in increased macrophage recruitment to adipose tissue that promotes a chronic low-grade inflammatory state linked to increased fatty acid efflux from adipocytes. Activated macrophages produce a variety of pro-inflammatory lipids such as leukotriene C4 (LTC4) and 5-, 12-, and 15-hydroxyeicosatetraenoic acid (HETE) suggesting the hypothesis that fatty acids may stimulate eicosanoid synthesis. To assess if eicosanoid production increases with obesity, adipose tissue of leptin deficient ob/ob mice was analyzed. In ob/ob mice, LTC4 and 12-HETE levels increased in the visceral (but not subcutaneous) adipose depot while the 5-HETE levels decreased and 15-HETE abundance was unchanged. Since macrophages produce the majority of inflammatory molecules in adipose tissue, treatment of RAW264.7 or primary peritoneal macrophages with free fatty acids led to increased secretion of LTC4 and 5-HETE, but not 12- or 15-HETE. Fatty acid binding proteins (FABPs) facilitate the intracellular trafficking of fatty acids and other hydrophobic ligands and in vitro stabilize the LTC4 precursor leukotriene A4 (LTA4) from non-enzymatic hydrolysis. Consistent with a role for FABPs in LTC4 synthesis, treatment of macrophages with HTS01037, a specific FABP inhibitor, resulted in a marked decrease in both basal and fatty acid-stimulated LTC4 secretion but no change in 5-HETE production or 5-lipoxygenase expression. These results indicate that the products of adipocyte lipolysis may stimulate the 5-lipoxygenase pathway leading to FABP-dependent production of LTC4 and contribute to the insulin resistant state.

Serum FABP4 concentrations decrease after Roux-en-Y gastric bypass but not after intensive medical management.

BACKGROUND: Serum concentrations of fatty acid binding protein 4, an adipose tissue fatty acid chaperone, have been correlated with insulin resistance and cardiovascular risk factors. The objective of this study were to assess relationships among Roux-en-Y gastric bypass, intensive lifestyle modification and medical management protocol, fatty acid binding protein 4, and metabolic parameters in obese patients with severe type 2 diabetes mellitus; and to evaluate the relative contribution of abdominal subcutaneous adipose and visceral adipose to the secretion of fatty acid binding protein 4. METHODS: Participants were randomly assigned to intensive lifestyle modification and medical management protocol (n = 29) or to intensive lifestyle modification and medical management protocol augmented with Roux-en-Y gastric bypass (n = 34). Relationships among fatty acid binding protein 4 and demographic characteristics, metabolic parameters, and 12-month changes in these values were examined. Visceral and subcutaneous adipose tissue explants from obese nondiabetic patients (n = 5) were obtained and treated with forskolin to evaluate relative secretion of fatty acid binding protein 4 in the different adipose tissue depots. RESULTS: The intensive lifestyle modification and medical management protocol and Roux-en-Y gastric bypass cohorts had similar fasting serum fatty acid binding protein 4 concentrations at baseline. At 1 year, mean serum fatty acid binding protein 4 decreased by 42% in Roux-en-Y gastric bypass participants (P = .002) but did not change significantly in the intensive lifestyle modification and medical management protocol cohort. Percentage of weight change was not a significant predictor of 12-month fatty acid binding protein 4 within treatment arm or in multivariate models adjusted for treatment arm. In adipose tissue explants, fatty acid binding protein 4 was secreted similarly between visceral and subcutaneous adipose tissue. CONCLUSION: After Roux-en-Y gastric bypass, fatty acid binding protein 4 is reduced 12 months after surgery but not after intensive lifestyle modification and medical management protocol in patients with type 2 diabetes mellitus. Fatty acid binding protein 4 was secreted similarly between subcutaneous and visceral adipose tissue explants.

Biological evaluation of novel 6-Arylbenzimidazo[1,2-c]quinazoline derivatives as inhibitors of LPS-induced TNF-alpha secretion.

This study describes the effect of novel 6-Arylbenzimidazo[1,2-c]quinazoline derivatives as tumor necrosis factor alpha (TNF-alpha) production inhibitors. The newly synthesized compounds were tested for their in vitro ability to inhibit the lipolysaccharide (LPS) induced TNF-alpha secretion in the human promyelocytic cell line HL-60. The compound 6-Phenyl-benzimidazo[1,2-c]quinazoline, coded as Gl, resulted as the most potent inhibitor and with no significant cytotoxic activity. Thus, 6-Arylbenzimidazo[1,2-c]quinazoline derivatives may have a potential as anti-inflammatory agents.

Nox1-based NADPH oxidase-derived superoxide is required for VSMC activation by advanced glycation end-products.

Vascular diseases are important clinical complications of diabetes. Advanced glycation end-products (AGE) are mediators of vascular dysfunction, but their effects on vascular smooth muscle cell (VSMC) ROS production are unclear. We studied the source and downstream targets of AGE-mediated ROS and reactive nitrogen species production in these cells. Significant increases in superoxide production in AGE-treated VSMC were measured using lucigenin (7650+/-433 vs 4485+/-424 LU/10(6) cells, p<0.001) or coelenterazine (277,907+/-71,295 vs 120,456+/-4140 LU/10(6) cells, p<0.05) and confirmed by ESR spectroscopy. These signals were blocked by the flavin-containing oxidase inhibitor diphenylene iodonium (DPI). AGE-stimulated NF-kappaB activity was abolished by DPI and the superoxide scavenger MnTBAP. AGE differentially regulated VSMC NADPH oxidase catalytic subunits, stimulating the transcription of Nox1 (201+/-12.7%, p<0.0001), while having no effect on Nox4. AGE also increased 3-nitrotyrosine formation, which was inhibited by MnTBAP, DPI, or the NOS inhibitor L-NAME. Regarding the source of NO, AGE stimulated inducible nitric oxide synthase mRNA (1 vs 9.7+/-3.0, p=0.046), which was abolished by a NF-kappaB inhibitor, SOD, catalase, or siRNA against Nox1. This study establishes that AGE activate iNOS in VSMC through a ROS-sensitive, NF-kappaB-dependent mechanism involving ROS generation by a Nox1-based oxidase.

Hyperosmotic stress-dependent NFkappaB activation is regulated by reactive oxygen species and IGF-1 in cultured cardiomyocytes.

We have recently shown that hyperosmotic stress activates p65/RelB NFkappaB in cultured cardiomyocytes with dichotomic actions on caspase activation and cell death. It remains unexplored how NFkappaB is regulated in cultured rat cardiomyocytes exposed to hyperosmotic stress. We study here: (a) if hyperosmotic stress triggers reactive oxygen species (ROS) generation and in turn whether they regulate NFkappaB and (b) if insulin-like growth factor-1 (IGF-1) modulates ROS production and NFkappaB activation in hyperosmotically-stressed cardiomyocytes. The results showed that hyperosmotic stress generated ROS in cultured cardiac myocytes, in particular the hydroxyl and superoxide species, which were inhibited by N-acetylcysteine (NAC). Hyperosmotic stress-induced NFkappaB activation as determined by IkappaBalpha degradation and NFkappaB DNA binding. NFkappaB activation and procaspase-3 and -9 fragmentation were prevented by NAC and IGF-1. However, this growth factor did not decrease ROS generation induced by hyperosmotic stress, suggesting that its actions over NFkappaB and caspase activation may be due to modulation of events downstream of ROS generation. We conclude that hyperosmotic stress induces ROS, which in turn activates NFkappaB and caspases. IGF-1 prevents NFkappaB activation by a ROS-independent mechanism.

Nicotinamide protected first-phase insulin response (FPIR) and prevented clinical disease in first-degree relatives of type-1 diabetics.

BACKGROUND: After a study of ICA prevalence among relatives of Type-1 diabetics (DM1) in Santiago, Chile, parents of those who tested positive asked us to go on forward with an intervention study. METHODS: We had screened 1021 relatives, of which 30 had shown ICA > or = 20 JDF units (2.9%). Among the 26/30 who participated in the intervention study, the baseline screening showed normal glucose tolerance in all, and the first-phase insulin response (FPIR) was normal in 24/26 individuals, which were randomized into Nicotinamide (n = 12; oral Nicotinamide, 1200 mg m(-2) day(-1)) and Placebo (n = 12) groups. The FPIRs and ICAs were monitored yearly. Compliance was monitored by urine Nicotinamide. RESULTS: The 1.5, 3.0 and 5-year life-table estimates of keeping the FPIR > or = 10th centile were, for Nicotinamide group 100% in all time points, and for Placebo these were 90.0% (c.i. = 100-71.4), 72.0% (c.i. = 100-37.1) and 0.0% (c.i. = 0.0-0.0) (p = 0.0091). The 5-year life-table estimates of remaining diabetes-free were 100% for Nicotinamide and 62.5% for Placebo (p = 0.0483). No adverse effects were observed. CONCLUSIONS: Oral Nicotinamide protected beta-cell function and prevented clinical disease in ICA-positive first-degree relatives of type-1 diabetes.

Programmed death ligand-1 expression on donor T cells drives graft-versus-host disease lethality.

Programmed death ligand-1 (PD-L1) interaction with PD-1 induces T cell exhaustion and is a therapeutic target to enhance immune responses against cancer and chronic infections. In murine bone marrow transplant models, PD-L1 expression on host target tissues reduces the incidence of graft-versus-host disease (GVHD). PD-L1 is also expressed on T cells; however, it is unclear whether PD-L1 on this population influences immune function. Here, we examined the effects of PD-L1 modulation of T cell function in GVHD. In patients with severe GVHD, PD-L1 expression was increased on donor T cells. Compared with mice that received WT T cells, GVHD was reduced in animals that received T cells from Pdl1-/- donors. PD-L1-deficient T cells had reduced expression of gut homing receptors, diminished production of inflammatory cytokines, and enhanced rates of apoptosis. Moreover, multiple bioenergetic pathways, including aerobic glycolysis, oxidative phosphorylation, and fatty acid metabolism, were also reduced in T cells lacking PD-L1. Finally, the reduction of acute GVHD lethality in mice that received Pdl1-/- donor cells did not affect graft-versus-leukemia responses. These data demonstrate that PD-L1 selectively enhances T cell-mediated immune responses, suggesting a context-dependent function of the PD-1/PD-L1 axis, and suggest selective inhibition of PD-L1 on donor T cells as a potential strategy to prevent or ameliorate GVHD.

Red wine reduces oxidative stress in patients with acute coronary syndrome.

BACKGROUND: Moderate red wine consumption improved endothelial function in normal volunteers. Herein we explored the effects of moderate red wine consumption in endothelial function and in oxidative stress in patients with an acute coronary syndrome. METHODS: 20 patients treated with percutaneous coronary interventions after an acute coronary syndrome were randomized to a red-wine group (n=9, 250 ml daily, Cabernet Sauvignon) or to a control group (n=11, abstinence from alcoholic beverages). Studies were performed at baseline and after 2 months. Endothelial function was estimated by flow-mediated vasodilatation of the brachial artery. Plasma antioxidant capacity was measured by total antioxidant reactivity and ferric reducing antioxidant power. Oxidative damage was evaluated by measurements of 8-OH deoxyguanosine content in leukocyte deoxyribonucleic acid. RESULTS: The endothelium dependent/independent dilatation ratio significantly improved compared to baseline in both groups. The 8-OH deoxyguanosine content decreased significantly in both groups; this effect was more pronounced with wine (p<0.002 vs. control). Oxidative deoxyribonucleic acid damage in controls decreased from 13.1+/-1.1 to 10.0+/-1.0 (p<0.003); with wine from 13+/-0.8 to 5.6+/-0.7 per 10(5) guanosines (p<0.001; p<0.002 vs. control). Total antioxidant reactivity increased from 240+/-18 to 268+/-18 microM in the control group and from 273+/-20 to 330+/-15 microM in the wine group (p<0.03 vs. control). Ferric reducing antioxidant power increased from 1106+/-60 to 1235+/-42 microM in the control group and from 1219+/-82 to 1450+/-63 microM in the wine group (p<0.001 vs. control). CONCLUSIONS: The addition of moderate amounts of red wine did not improve endothelial function beyond conventional therapy, whereas it showed benefits in parameters of oxidative stress in these patients.

Roux-en-Y Gastric Bypass Acutely Decreases Protein Carbonylation and Increases Expression of Mitochondrial Biogenesis Genes in Subcutaneous Adipose Tissue.

BACKGROUND: Mitochondrial dysfunction in adipose tissue has been implicated as a pathogenic step in the development of type 2 diabetes mellitus (T2DM). In adipose tissue, chronic nutrient overload results in mitochondria driven increased reactive oxygen species (ROS) leading to carbonylation of proteins that impair mitochondrial function and downregulation of key genes linked to mitochondrial biogenesis. In patients with T2DM, Roux-en-Y gastric bypass (RYGB) surgery leads to improvements in glycemic profile prior to significant weight loss. Consequently, we hypothesized that improved glycemia early after RYGB would be paralleled by decreased protein carbonylation and increased expression of genes related to mitochondrial biogenesis in adipose tissue. METHODS: To evaluate this hypothesis, 16 obese individuals were studied before and 7-8 days following RYGB and adjustable gastric banding (AGB). Subcutaneous adipose tissue was obtained pre- and post-bariatric surgery as well as from eight healthy, non-obese individual controls. RESULTS: Prior to surgery, adipose tissue expression of PGC1α, NRF1, Cyt C, and eNOS (but not Tfam) showed significantly lower expression in the obese bariatric surgery group when compared to lean controls (p < 0.05). Following RYGB, but not after AGB, patients showed significant decrease in HOMA-IR, reduction in adipose protein carbonylation, and increased expression of genes linked to mitochondrial biogenesis. CONCLUSIONS: These results suggest that rapid reduction in protein carbonylation and increased mitochondrial biogenesis may explain postoperative metabolic improvements following RYGB.

Wine, diet, antioxidant defenses, and oxidative damage.

Oxidative stress is a central mechanism for the pathogenesis of ischemic heart disease and atherogenesis, for cancer and other chronic diseases in general, and it also plays a major role in the aging process. Dietary antioxidants constitute a large group of compounds that differ in mechanism of action, bioavailability and side effects. A systematic analysis of the role of the various antioxidants in chronic diseases is hampered by the difficulty of employing death or clinical events as end points in intervention studies. Therefore, valid markers for oxidative stress, which show dose response and are sensitive to changes in dietary supply of antioxidants, are potentially of great value when trying to establish healthy dietary patterns, or when one component, like red wine, is evaluated specifically. To evaluate potential oxidative stress markers we have studied the effect of different diets plus wine supplementation on antioxidant defenses and oxidative damage. In three experimental series, four groups of young male university students, one of older men and other of older women, 20-24 volunteers each, received Mediterranean or occidental (high-fat) diets alone or supplemented with red wine, white wine, or fruits and vegetables. Measurements included, leukocyte DNA 8-OH-deoxyguanosine (8OHdG), plasma 7 beta-hydroxycholesterol, TBARS and well-characterized antioxidants, and plasma and urine polyphenol antioxidants. In all experimental groups that received red wine, consumption resulted in marked decrease in 8OHdG. The changes observed in 8OHdG correlate positively with the other markers of oxidative damage, and shows a clear inverse correlation with the plasma level of well established antioxidants and with measurements of total antioxidant capacity. Urinary total polyphenol content as well as the sum of some specific plasma species also correlate inversely with 8OHdG. In conclusion, the results identify 8OHdG as a very promising general marker of oxidative stress in nutrition intervention studies in humans, and red wine shows a remarkable protective effect.

Lipocalin 2 expression and secretion is highly regulated by metabolic stress, cytokines, and nutrients in adipocytes.

Lipocalin 2 (Lcn2) has been recently characterized as a new adipokine having a role in innate immunity and energy metabolism. Nonetheless, the metabolic regulation of Lcn2 production in adipocytes has not been comprehensively studied. To better understand the Lcn2 biology, we investigated the regulation of Lcn2 expression in adipose tissue in response to metabolic stress in mice as well as the control of Lcn2 expression and secretion by cytokines and nutrients in 3T3-L1 adipocytes. Our results showed that the mRNA expression of Lcn2 was upregulated in white and brown adipose tissues as well as liver during fasting and cold stress in mice. Among pro-inflammatory cytokines TNFα, IL-1ß, and IL-6, IL-1ß showed most profound effect on Lcn2 expression and secretion in 3T3-L1 adipocytes. Insulin stimulated Lcn2 expression and secretion in a dose-dependent manner; this insulin effect was significantly abolished in the presence of low concentration of glucose. Moreover, insulin-stimulated Lcn2 expression and secretion was also attenuated when glucose was replaced by 3-O-methyl-d-glucose or by blocking NFκB pathway activation. Additionally, we showed that palmitate and oleate induced Lcn2 expression and secretion more significantly than EPA, while phytanic acid reduced Lcn2 production. Our results demonstrated that Lcn2 production in adipocytes is highly responsive to metabolic stress, cytokines, and nutrient signals, suggesting an important role of Lcn2 in adipocyte metabolism and inflammation.

Increased adipose protein carbonylation in human obesity.

Insulin resistance is associated with obesity but mechanisms controlling this relationship in humans are not fully understood. Studies in animal models suggest a linkage between adipose reactive oxygen species (ROS) and insulin resistance. ROS oxidize cellular lipids to produce a variety of lipid hydroperoxides that in turn generate reactive lipid aldehydes that covalently modify cellular proteins in a process termed carbonylation. Mammalian cells defend against reactive lipid aldehydes and protein carbonylation by glutathionylation using glutathione-S-transferase A4 (GSTA4) or carbonyl reduction/oxidation via reductases and/or dehydrogenases. Insulin resistance in mice is linked to ROS production and increased level of protein carbonylation, mitochondrial dysfunction, decreased insulin-stimulated glucose transport, and altered adipokine secretion. To assess protein carbonylation and insulin resistance in humans, eight healthy participants underwent subcutaneous fat biopsy from the periumbilical region for protein analysis and frequently sampled intravenous glucose tolerance testing to measure insulin sensitivity. Soluble proteins from adipose tissue were analyzed using two-dimensional gel electrophoresis and the major carbonylated proteins identified as the adipocyte and epithelial fatty acid-binding proteins. The level of protein carbonylation was directly correlated with adiposity and serum free fatty acids (FFAs). These results suggest that in human obesity oxidative stress is linked to protein carbonylation and such events may contribute to the development of insulin resistance.

Downregulation of adipose glutathione S-transferase A4 leads to increased protein carbonylation, oxidative stress, and mitochondrial dysfunction.

OBJECTIVE: Peripheral insulin resistance is linked to an increase in reactive oxygen species (ROS), leading in part to the production of reactive lipid aldehydes that modify the side chains of protein amino acids in a reaction termed protein carbonylation. The primary enzymatic method for lipid aldehyde detoxification is via glutathione S-transferase A4 (GSTA4) dependent glutathionylation. The objective of this study was to evaluate the expression of GSTA4 and the role(s) of protein carbonylation in adipocyte function. RESEARCH DESIGN AND METHODS: GSTA4-silenced 3T3-L1 adipocytes and GSTA4-null mice were evaluated for metabolic processes, mitochondrial function, and reactive oxygen species production. GSTA4 expression in human obesity was evaluated using microarray analysis. RESULTS: GSTA4 expression is selectively downregulated in adipose tissue of obese insulin-resistant C57BL/6J mice and in human obesity-linked insulin resistance. Tumor necrosis factor-alpha treatment of 3T3-L1 adipocytes decreased GSTA4 expression, and silencing GSTA4 mRNA in cultured adipocytes resulted in increased protein carbonylation, increased mitochondrial ROS, dysfunctional state 3 respiration, and altered glucose transport and lipolysis. Mitochondrial function in adipocytes of lean or obese GSTA4-null mice was significantly compromised compared with wild-type controls and was accompanied by an increase in superoxide anion. CONCLUSIONS: These results indicate that downregulation of GSTA4 in adipose tissue leads to increased protein carbonylation, ROS production, and mitochondrial dysfunction and may contribute to the development of insulin resistance and type 2 diabetes.

Reactive oxygen species mediates homocysteine-induced mitochondrial biogenesis in human endothelial cells: modulation by antioxidants.

It has been proposed that homocysteine (Hcy)-induces endothelial dysfunction and atherosclerosis by generation of reactive oxygen species (ROS). A previous report has shown that Hcy promotes mitochondrial damage. Considering that oxidative stress can affect mitochondrial biogenesis, we hypothesized that Hcy-induced ROS in endothelial cells may lead to increased mitochondrial biogenesis. We found that Hcy-induced ROS (1.85-fold), leading to a NF-kappaB activation and increase the formation of 3-nitrotyrosine. Furthermore, expression of the mitochondrial biogenesis factors, nuclear respiratory factor-1 and mitochondrial transcription factor A, was significantly elevated in Hcy-treated cells. These changes were accompanied by increase in mitochondrial mass and higher mRNA and protein expression of the subunit III of cytochrome c oxidase. These effects were significantly prevented by pretreatment with the antioxidants, catechin and trolox. Taken together, our results suggest that ROS is an important mediator of mitochondrial biogenesis induced by Hcy, and that modulation of oxidative stress by antioxidants may protect against the adverse vascular effects of Hcy.

Biological evaluation of novel 6-Arylbenzimidazo [1.2-c] quinazoline derivatives as inhibitors of LPS-induced TNF- alpha secretion

This study describes the effect of novel 6-Arylbenzimidazo [1,2-c] quinazoline derivatives as tumor necrosis factor alpha (TNF-á) production inhibitors. The newly synthesized compounds were tested for their in vitro ability to inhibit the lipolysaccharide (LPS) induced TNF-á secretion in the human promyelocytic cell line HL-60. The compound 6-Phenyl-benzimidazo [1,2-c] quinazoline, coded as Gl, resulted as the most potent inhibitor and with no significant cytotoxic activity. Thus, 6-Arylbenzimidazo [1,2-c] quinazoline derivatives may have a potential as anti-inflammatory agents.

Mecanismos moleculares en la remodelación cardíaca patológica por estrés mecánico experimental / Molecular mechanisms on the pathological cardiac remodeling induced by mechanical stress

Recientes estudios han establecido que las fuerzas mecánicas producen efectos importantes en la estructura y función de los distintos tipos celulares del sistema cardiovascular. El estrés mecánico no sólo afecta las propiedades mecánicas de los cardiomiocitos sino que también a la homeostasis de otras células cardíacas y a la composición y estructura de la matriz extracelular. La estimulación mecánica crónica, clínicamente representada por la hípertensión arterial, produce el desarrollo de hipertrofia y fibrosis, procesos celulares centrales de la remodelación cardíaca patológica, ya sea en forma directa o a través de la liberación y/o producción de diversas substancias neuroendocrinas y factores de crecimiento locales. Aunque no se han identificado y caracterizado del todo aquellos elementos que sensan y transducen molecularmente dichos cambios mecánicos, en esta revisión se recopilan los últimos avances en la mecanotransducción cardíaca y su relación con el proceso de remodelación cardíaca patológica, los cuales abren nuevas expectivas farmacoterapéuticas