Showing papers in "Journal of Clinical Investigation in 2005"
TL;DR: The molecular and cellular underpinnings of obesity-induced inflammation and the signaling pathways at the intersection of metabolism and inflammation that contribute to diabetes are discussed.
Abstract: Over the last decade, an abundance of evidence has emerged demonstrating a close link between metabolism and immunity. It is now clear that obesity is associated with a state of chronic low-level inflammation. In this article, we discuss the molecular and cellular underpinnings of obesity-induced inflammation and the signaling pathways at the intersection of metabolism and inflammation that contribute to diabetes. We also consider mechanisms through which the inflammatory response may be initiated and discuss the reasons for the inflammatory response in obesity. We put forth for consideration some hypotheses regarding important unanswered questions in the field and suggest a model for the integration of inflammatory and metabolic pathways in metabolic disease.
3,913 citations
TL;DR: In this article, the authors quantified the biological sources of hepatic and plasma lipoprotein TAG in NAFLD patients, using stable isotopes for four days to label and track serum nonesterified fatty acids (NEFAs), dietary fatty acids, and those derived from the de novo lipogenesis (DNL) pathway, present in liver tissue and lipid TAG.
Abstract: Nonalcoholic fatty liver disease (NAFLD) is characterized by the accumulation of excess liver triacylglycerol (TAG), inflammation, and liver damage The goal of the present study was to directly quantify the biological sources of hepatic and plasma lipoprotein TAG in NAFLD Patients (5 male and 4 female; 44 ± 10 years of age) scheduled for a medically indicated liver biopsy were infused with and orally fed stable isotopes for 4 days to label and track serum nonesterified fatty acids (NEFAs), dietary fatty acids, and those derived from the de novo lipogenesis (DNL) pathway, present in liver tissue and lipoprotein TAG Hepatic and lipoprotein TAG fatty acids were analyzed by gas chromatography/mass spectrometry NAFLD patients were obese, with fasting hypertriglyceridemia and hyperinsulinemia Of the TAG accounted for in liver, 590% ± 99% of TAG arose from NEFAs; 261% ± 67%, from DNL; and 149% ± 70%, from the diet The pattern of labeling in VLDL was similar to that in liver, and throughout the 4 days of labeling, the liver demonstrated reciprocal use of adipose and dietary fatty acids DNL was elevated in the fasting state and demonstrated no diurnal variation These quantitative metabolic data document that both elevated peripheral fatty acids and DNL contribute to the accumulation of hepatic and lipoprotein fat in NAFLD
2,870 citations
TL;DR: Important roles for ER-initiated cell death pathways have been recognized for several diseases, including hypoxia, ischemia/reperfusion injury, neurodegeneration, heart disease, and diabetes.
Abstract: Disturbances in the normal functions of the ER lead to an evolutionarily conserved cell stress response, the unfolded protein response, which is aimed initially at compensating for damage but can eventually trigger cell death if ER dysfunction is severe or prolonged. The mechanisms by which ER stress leads to cell death remain enigmatic, with multiple potential participants described but little clarity about which specific death effectors dominate in particular cellular contexts. Important roles for ER-initiated cell death pathways have been recognized for several diseases, including hypoxia, ischemia/reperfusion injury, neurodegeneration, heart disease, and diabetes.
2,146 citations
TL;DR: Gestational diabetes mellitus (GDM) is defined as glucose intolerance of various degrees that is first detected during pregnancy and provides a unique opportunity to study the early pathogenesis of diabetes and to develop interventions to prevent the disease.
Abstract: Gestational diabetes mellitus (GDM) is defined as glucose intolerance of various degrees that is first detected during pregnancy. GDM is detected through the screening of pregnant women for clinical risk factors and, among at-risk women, testing for abnormal glucose tolerance that is usually, but not invariably, mild and asymptomatic. GDM appears to result from the same broad spectrum of physiological and genetic abnormalities that characterize diabetes outside of pregnancy. Indeed, women with GDM are at high risk for having or developing diabetes when they are not pregnant. Thus, GDM provides a unique opportunity to study the early pathogenesis of diabetes and to develop interventions to prevent the disease.
1,960 citations
TL;DR: It is concluded that FGF-21, which was discovered to be a potent regulator of glucose uptake in mouse 3T3-L1 and primary human adipocytes, exhibits the therapeutic characteristics necessary for an effective treatment of diabetes.
Abstract: Diabetes mellitus is a major health concern, affecting more than 5% of the population. Here we describe a potential novel therapeutic agent for this disease, FGF-21, which was discovered to be a potent regulator of glucose uptake in mouse 3T3-L1 and primary human adipocytes. FGF-21-transgenic mice were viable and resistant to diet-induced obesity. Therapeutic administration of FGF-21 reduced plasma glucose and triglycerides to near normal levels in both ob/ob and db/db mice. These effects persisted for at least 24 hours following the cessation of FGF-21 administration. Importantly, FGF-21 did not induce mitogenicity, hypoglycemia, or weight gain at any dose tested in diabetic or healthy animals or when overexpressed in transgenic mice. Thus, we conclude that FGF-21, which we have identified as a novel metabolic factor, exhibits the therapeutic characteristics necessary for an effective treatment of diabetes.
1,921 citations
TL;DR: The visualization of autophagosomes in dying cells has led to the belief that autophagy is a nonapoptotic form of programmed cell death, but this concept has now been evaluated using cells and organisms deficient in Autophagy genes to indicate that, at least in cells with intact apoptotic machinery, it is primarily a pro-survival rather than aPro-death mechanism.
Abstract: The visualization of autophagosomes in dying cells has led to the belief that autophagy is a nonapoptotic form of programmed cell death. This concept has now been evaluated using cells and organisms deficient in autophagy genes. Most evidence indicates that, at least in cells with intact apoptotic machinery, autophagy is primarily a pro-survival rather than a pro-death mechanism. This review summarizes the evidence linking autophagy to cell survival and cell death, the complex interplay between autophagy and apoptosis pathways, and the role of autophagy-dependent survival and death pathways in clinical diseases.
1,708 citations
TL;DR: This review examines the fundamental pathogenetic mechanisms underlying osteoporosis, which include: (a) failure to achieve a skeleton of optimal strength during growth and development; (b) excessive bone resorption resulting in loss of bone mass and disruption of architecture; and (c) Failure to replace lost bone due to defects in bone formation.
Abstract: Osteoporosis is a disorder in which loss of bone strength leads to fragility fractures. This review examines the fundamental pathogenetic mechanisms underlying this disorder, which include: (a) failure to achieve a skeleton of optimal strength during growth and development; (b) excessive bone resorption resulting in loss of bone mass and disruption of architecture; and (c) failure to replace lost bone due to defects in bone formation. Estrogen deficiency is known to play a critical role in the development of osteoporosis, while calcium and vitamin D deficiencies and secondary hyperparathyroidism also contribute. There are multiple mechanisms underlying the regulation of bone remodeling, and these involve not only the osteoblastic and osteoclastic cell lineages but also other marrow cells, in addition to the interaction of systemic hormones, local cytokines, growth factors, and transcription factors. Polymorphisms of a large number of genes have been associated with differences in bone mass and fragility. It is now possible to diagnose osteoporosis, assess fracture risk, and reduce that risk with antiresorptive or other available therapies. However, new and more effective approaches are likely to emerge from a better understanding of the regulators of bone cell function.
1,600 citations
1,554 citations
TL;DR: These data provide the first clear evidence that functionally distinct subpopulations of macrophages exist in the same tissue and that these macrophage play critical roles in both the injury and recovery phases of inflammatory scarring.
Abstract: Macrophages perform both injury-inducing and repair-promoting tasks in different models of inflammation, leading to a model of macrophage function in which distinct patterns of activation have been proposed. We investigated macrophage function mechanistically in a reversible model of liver injury in which the injury and recovery phases are distinct. Carbon tetrachloride--–induced liver fibrosis revealed scar-associated macrophages that persisted throughout recovery. A transgenic mouse (CD11b-DTR) was generated in which macrophages could be selectively depleted. Macrophage depletion when liver fibrosis was advanced resulted in reduced scarring and fewer myofibroblasts. Macrophage depletion during recovery, by contrast, led to a failure of matrix degradation. These data provide the first clear evidence that functionally distinct subpopulations of macrophages exist in the same tissue and that these macrophages play critical roles in both the injury and recovery phases of inflammatory scarring.
1,422 citations
TL;DR: A constant supply of oxygen is indispensable for cardiac viability and function, and oxygen is a major determinant of cardiac gene expression, and a critical participant in the formation of ROS and numerous other cellular processes.
Abstract: A constant supply of oxygen is indispensable for cardiac viability and function. However, the role of oxygen and oxygen-associated processes in the heart is complex, and they and can be either beneficial or contribute to cardiac dysfunction and death. As oxygen is a major determinant of cardiac gene expression, and a critical participant in the formation of ROS and numerous other cellular processes, consideration of its role in the heart is essential in understanding the pathogenesis of cardiac dysfunction.
1,378 citations
TL;DR: This Review highlights the molecular machinery and inflammatory pathways used by platelets to initiate and accelerate atherothrombosis.
Abstract: Platelets represent an important linkage between inflammation, thrombosis, and atherogenesis Inflammation is characterized by interactions among platelets, leukocytes, and ECs These interactions trigger autocrine and paracrine activation processes that lead to leukocyte recruitment into the vascular wall Platelet-induced chronic inflammatory processes at the vascular wall result in development of atherosclerotic lesions and atherothrombosis This Review highlights the molecular machinery and inflammatory pathways used by platelets to initiate and accelerate atherothrombosis
TL;DR: STI571 reverses vascular remodeling and cor pulmonale in severe experimental pulmonary hypertension regardless of the initiating stimulus, and offers a unique novel approach for antire-modeling therapy in progressed pulmonary hypertension.
Abstract: Progression of pulmonary hypertension is associated with increased proliferation and migration of pulmonary vascular smooth muscle cells. PDGF is a potent mitogen and involved in this process. We now report that the PDGF receptor antagonist STI571 (imatinib) reversed advanced pulmonary vascular disease in 2 animal models of pulmonary hypertension. In rats with monocrotaline-induced pulmonary hypertension, therapy with daily administration of STI571 was started 28 days after induction of the disease. A 2-week treatment resulted in 100% survival, compared with only 50% in sham-treated rats. The changes in RV pressure, measured continuously by telemetry, and right heart hypertrophy were reversed to near-normal levels. STI571 prevented phosphorylation of the PDGF receptor and suppressed activation of downstream signaling pathways. Similar results were obtained in chronically hypoxic mice, which were treated with STI571 after full establishment of pulmonary hypertension. Moreover, expression of the PDGF receptor was found to be significantly increased in lung tissue from pulmonary arterial hypertension patients compared with healthy donor lung tissue. We conclude that STI571 reverses vascular remodeling and cor pulmonale in severe experimental pulmonary hypertension regardless of the initiating stimulus. This regimen offers a unique novel approach for antire-modeling therapy in progressed pulmonary hypertension.
TL;DR: It is concluded that anandamide acting at hepatic CB(1) contributes to diet-induced obesity and that the FAS pathway may be a common molecular target for central appetitive and peripheral metabolic regulation.
Abstract: Endogenous cannabinoids acting at CB1 receptors stimulate appetite, and CB1 antagonists show promise in the treatment of obesity. CB1–/– mice are resistant to diet-induced obesity even though their caloric intake is similar to that of wild-type mice, suggesting that endocannabinoids also regulate fat metabolism. Here, we investigated the possible role of endocannabinoids in the regulation of hepatic lipogenesis. Activation of CB1 in mice increases the hepatic gene expression of the lipogenic transcription factor SREBP-1c and its targets acetyl-CoA carboxylase-1 and fatty acid synthase (FAS). Treatment with a CB1 agonist also increases de novo fatty acid synthesis in the liver or in isolated hepatocytes, which express CB1. High-fat diet increases hepatic levels of the endocannabinoid anandamide (arachidonoyl ethanolamide), CB1 density, and basal rates of fatty acid synthesis, and the latter is reduced by CB1 blockade. In the hypothalamus, where FAS inhibitors elicit anorexia, SREBP-1c and FAS expression are similarly affected by CB1 ligands. We conclude that anandamide acting at hepatic CB1 contributes to diet-induced obesity and that the FAS pathway may be a common molecular target for central appetitive and peripheral metabolic regulation.
TL;DR: It is shown that DAB(389)IL-2 is capable of selectively eliminating CD25-expressing Tregs from the PBMCs of cancer patients without inducing toxicity on other cellular subsets with intermediate or low expression of CD25.
Abstract: In this study, we investigated whether elimination of CD4+/CD25+ Tregs using the recombinant IL-2 diphtheria toxin conjugate DAB(389)IL-2 (also known as denileukin diftitox and ONTAK) is capable of enhancing the immunostimulatory efficacy of tumor RNA-transfected DC vaccines. We show that DAB(389)IL-2 is capable of selectively eliminating CD25-expressing Tregs from the PBMCs of cancer patients without inducing toxicity on other cellular subsets with intermediate or low expression of CD25. DAB(389)IL-2-mediated Treg depletion resulted in enhanced stimulation of proliferative and cytotoxic T cell responses in vitro but only when DAB(389)IL-2 was omitted during T cell priming. DAB(389)IL-2 significantly reduced the number of Tregs present in the peripheral blood of metastatic renal cell carcinoma (RCC) patients and abrogated Treg-mediated immunosuppressive activity in vivo. Moreover, DAB(389)IL-2-mediated elimination of Tregs followed by vaccination with RNA-transfected DCs significantly improved the stimulation of tumor-specific T cell responses in RCC patients when compared with vaccination alone. Our findings may have implications in the design of immune-based strategies that may incorporate the Treg depletion strategy to achieve potent antitumor immunity with therapeutic impact.
TL;DR: Questions that remain to be addressed are whether this hazard extends to all or some of the traditional NSAIDs; whether adjuvant therapies, such as low-dose aspirin, will mitigate the hazard and if so, at what cost; whether COX-2 inhibitors result in cardiovascular risk transformation during chronic dosing; and how to identify individuals most likely to benefit or suffer from such drugs in the future.
Abstract: Inhibitors selective for prostaglandin G/H synthase-2 (PGHS-2) (known colloquially as COX-2) were designed to minimize gastrointestinal complications of traditional NSAIDs--adverse effects attributed to suppression of COX-1-derived PGE2 and prostacyclin (PGI2). Evidence from 2 randomized controlled-outcome trials (RCTs) of 2 structurally distinct selective inhibitors of COX-2 supports this hypothesis. However, 5 RCTs of 3 structurally distinct inhibitors also indicate that such compounds elevate the risk of myocardial infarction and stroke. The clinical information is biologically plausible, as it is compatible with evidence that inhibition of COX-2-derived PGI2 removes a protective constraint on thrombogenesis, hypertension, and atherogenesis in vivo. However, the concept of simply tipping a "balance" between COX-2-derived PGI2 and COX-1-derived platelet thromboxane is misplaced. Among the questions that remain to be addressed are the following: (a) whether this hazard extends to all or some of the traditional NSAIDs; (b) whether adjuvant therapies, such as low-dose aspirin, will mitigate the hazard and if so, at what cost; (c) whether COX-2 inhibitors result in cardiovascular risk transformation during chronic dosing; and (d) how we might identify individuals most likely to benefit or suffer from such drugs in the future.
TL;DR: The presence of a conserved BMI-1-driven pathway, which is similarly engaged in both normal stem cells and a highly malignant subset of human cancers diagnosed in a wide range of organs and uniformly exhibiting a marked propensity toward metastatic dissemination as well as a high probability of unfavorable therapy outcome, is suggested.
Abstract: Activation in transformed cells of normal stem cells’ self-renewal pathways might contribute to the survival life cycle of cancer stem cells and promote tumor progression. The BMI-1 oncogene–driven gene expression pathway is essential for the self-renewal of hematopoietic and neural stem cells. We applied a mouse/human comparative translational genomics approach to identify an 11-gene signature that consistently displays a stem cell–resembling expression profile in distant metastatic lesions as revealed by the analysis of metastases and primary tumors from a transgenic mouse model of prostate cancer and cancer patients. To further validate these results, we examined the prognostic power of the 11-gene signature in several independent therapy-outcome sets of clinical samples obtained from 1,153 cancer patients diagnosed with 11 different types of cancer, including 5 epithelial malignancies (prostate, breast, lung, ovarian, and bladder cancers) and 5 nonepithelial malignancies (lymphoma, mesothelioma, medulloblastoma, glioma, and acute myeloid leukemia). Kaplan-Meier analysis demonstrated that a stem cell–like expression profile of the 11-gene signature in primary tumors is a consistent powerful predictor of a short interval to disease recurrence, distant metastasis, and death after therapy in cancer patients diagnosed with 11 distinct types of cancer. These data suggest the presence of a conserved BMI-1–driven pathway, which is similarly engaged in both normal stem cells and a highly malignant subset of human cancers diagnosed in a wide range of organs and uniformly exhibiting a marked propensity toward metastatic dissemination as well as a high probability of unfavorable therapy outcome.
TL;DR: Both heart size and cardiac function areAngiogenesis dependent, and disruption of coordinated tissue growth and angiogenesis in the heart contributes to the progression from adaptive cardiac hypertrophy to heart failure.
Abstract: Although increased external load initially induces cardiac hypertrophy with preserved contractility, sustained overload eventually leads to heart failure through poorly understood mechanisms. Here we describe a conditional transgenic system in mice characterized by the sequential development of adaptive cardiac hypertrophy with preserved contractility in the acute phase and dilated cardiomyopathy in the chronic phase following the induction of an activated Akt1 gene in the heart. Coronary angiogenesis was enhanced during the acute phase of adaptive cardiac growth but reduced as hearts underwent pathological remodeling. Enhanced angiogenesis in the acute phase was associated with mammalian target of rapamycin-dependent induction of myocardial VEGF and angiopoietin-2 expression. Inhibition of angiogenesis by a decoy VEGF receptor in the acute phase led to decreased capillary density, contractile dysfunction, and impaired cardiac growth. Thus, both heart size and cardiac function are angiogenesis dependent, and disruption of coordinated tissue growth and angiogenesis in the heart contributes to the progression from adaptive cardiac hypertrophy to heart failure.
TL;DR: The findings suggest that the current methodology for selecting T cells for transfer is inadequate and provide new criteria for the generation and the screening of optimal lymphocyte populations for adoptive immunotherapy.
Abstract: T cell differentiation is a progressive process characterized by phenotypic and functional changes. By transferring tumor-specific CD8+ T cells into tumor-bearing mice at various stages of differentiation, we evaluated their efficacy for adoptive immunotherapy. We found that administration of naive and early effector T cells, in combination with active immunization and IL-2, resulted in the eradication of large, established tumors. Despite enhanced in vitro antitumor properties, more-differentiated effector T cells were less effective for in vivo tumor treatment. Several events may underlie this paradoxical phenomenon: (a) downregulation of lymphoid-homing and costimulatory molecules; (b) inability to produce IL-2 and access homeostatic cytokines; and (c) entry into a proapoptotic and replicative senescent state. While the progressive acquisition of terminal effector properties is characterized by pronounced in vitro tumor killing, in vivo T cell activation, proliferation, and survival are progressively impaired. These findings suggest that the current methodology for selecting T cells for transfer is inadequate and provide new criteria for the generation and the screening of optimal lymphocyte populations for adoptive immunotherapy.
TL;DR: It is shown that a single dose of Ngal, introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia, and it provides a unique method for their treatment.
Abstract: Neutrophil gelatinase-associated lipocalin (Ngal), also known as siderocalin, forms a complex with iron-binding siderophores (Ngal:siderophore:Fe). This complex converts renal progenitors into epithelial tubules. In this study, we tested the hypothesis that Ngal:siderophore:Fe protects adult kidney epithelial cells or accelerates their recovery from damage. Using a mouse model of severe renal failure, ischemia-reperfusion injury, we show that a single dose of Ngal (10 microg), introduced during the initial phase of the disease, dramatically protects the kidney and mitigates azotemia. Ngal activity depends on delivery of the protein and its siderophore to the proximal tubule. Iron must also be delivered, since blockade of the siderophore with gallium inhibits the rescue from ischemia. The Ngal:siderophore:Fe complex upregulates heme oxygenase-1, a protective enzyme, preserves proximal tubule N-cadherin, and inhibits cell death. Because mouse urine contains an Ngal-dependent siderophore-like activity, endogenous Ngal might also play a protective role. Indeed, Ngal is highly accumulated in the human kidney cortical tubules and in the blood and urine after nephrotoxic and ischemic injury. We reveal what we believe to be a novel pathway of iron traffic that is activated in human and mouse renal diseases, and it provides a unique method for their treatment.
TL;DR: It is shown that intestinal stromal cell-derived products downregulate both monocyte receptor expression and, via TGF-beta, cytokine production but not phagocytic or bacteriocidal activity, eliciting the phenotype and functional profile of intestinal macrophages.
Abstract: Intestinal macrophages, which are thought to orchestrate mucosal inflammatory responses, have received little investigative attention compared with macrophages from other tissues. Here we show that human intestinal macrophages do not express innate response receptors, including the receptors for LPS (CD14), Fcα (CD89), Fcγ (CD64, CD32, CD16), CR3 (CD11b/CD18), and CR4 (CD11c/CD18); the growth factor receptors IL-2 (CD25) and IL-3 (CD123); and the integrin LFA-1 (CD11a/CD18). Moreover, resident intestinal macrophages also do not produce proinflammatory cytokines, including IL-1, IL-6, IL-10, IL-12, RANTES, TGF-β, and TNF-α, in response to an array of inflammatory stimuli but retain avid phagocytic and bacteriocidal activity. Thus, intestinal macrophages are markedly distinct in phenotype and function from blood monocytes, although intestinal macrophages are derived from blood monocytes. To explain this paradox, we show that intestinal stromal cell–derived products downregulate both monocyte receptor expression and, via TGF-β, cytokine production but not phagocytic or bacteriocidal activity, eliciting the phenotype and functional profile of intestinal macrophages. These findings indicate a mechanism in which blood monocytes recruited to the intestinal mucosa retain avid scavenger and host defense functions but acquire profound “inflammatory anergy,” thereby promoting the absence of inflammation characteristic of normal intestinal mucosa despite the close proximity of immunostimulatory bacteria.
TL;DR: Results indicate that NPD1 promotes brain cell survival via the induction of antiapoptotic and neuroprotective gene-expression programs that suppress Abeta42-induced neurotoxicity.
Abstract: Deficiency in docosahexaenoic acid (DHA), a brain-essential omega-3 fatty acid, is associated with cognitive decline. Here we report that, in cytokine-stressed human neural cells, DHA attenuates amyloid-β (Aβ) secretion, an effect accompanied by the formation of NPD1, a novel, DHA-derived 10,17S-docosatriene. DHA and NPD1 were reduced in Alzheimer disease (AD) hippocampal cornu ammonis region 1, but not in the thalamus or occipital lobes from the same brains. The expression of key enzymes in NPD1 biosynthesis, cytosolic phospholipase A2 and 15-lipoxygenase, was altered in AD hippocampus. NPD1 repressed Aβ42-triggered activation of proinflammatory genes while upregulating the antiapoptotic genes encoding Bcl-2, Bcl-xl, and Bfl-1(A1). Soluble amyloid precursor protein-α stimulated NPD1 biosynthesis from DHA. These results indicate that NPD1 promotes brain cell survival via the induction of antiapoptotic and neuroprotective gene-expression programs that suppress Aβ42-induced neurotoxicity.
TL;DR: It is shown that DNA-containing immune complexes within lupus serum, but not protein-containing ICs from other autoimmune rheumatic diseases, stimulates plasmacytoid DCs to produce cytokines and chemokines via a cooperative interaction between Toll-like receptor 9 (TLR9) and FcgammaRIIa (CD32).
Abstract: Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by pathogenic autoantibodies against nucleoproteins and DNA. Here we show that DNA-containing immune complexes (ICs) within lupus serum (SLE-ICs), but not protein-containing ICs from other autoimmune rheumatic diseases, stimulates plasmacytoid DCs (PDCs) to produce cytokines and chemokines via a cooperative interaction between Toll-like receptor 9 (TLR9) and FcgammaRIIa (CD32). SLE-ICs transiently colocalized to a subcellular compartment containing CD32 and TLR9, and CD32+, but not CD32-, PDCs internalized and responded to SLE-ICs. Our findings demonstrate a novel functional interaction between Fc receptors and TLRs, defining a pathway in which CD32 delivers SLE-ICs to intracellular lysosomes containing TLR9, inducing a signaling cascade leading to PDC activation. These data demonstrate that endogenous DNA-containing autoantibody complexes found in the serum of patients with SLE activate the innate immune system and suggest a novel mechanism whereby these ICs contribute to the pathogenesis of this autoimmune disease.
TL;DR: Biglycan acts in macrophages as an endogenous ligand of TLR4 and TLR2, which mediate innate immunity, leading to rapid activation of p38, ERK, and NF-kappaB and thereby stimulating the expression of TNF-alpha and macrophage inflammatory protein-2 (MIP-2).
Abstract: Biglycan, a small leucine-rich proteoglycan, is a ubiquitous ECM component; however, its biological role has not been elucidated in detail. Here we show that biglycan acts in macrophages as an endogenous ligand of TLR4 and TLR2, which mediate innate immunity, leading to rapid activation of p38, ERK, and NF-kappaB and thereby stimulating the expression of TNF-alpha and macrophage inflammatory protein-2 (MIP-2). In agreement, the stimulatory effects of biglycan are significantly reduced in TLR4-mutant (TLR4-M), TLR2-/-, and myeloid differentiation factor 88-/- (MyD88-/-) macrophages and completely abolished in TLR2-/-/TLR4-M macrophages. Biglycan-null mice have a considerable survival benefit in LPS- or zymosan-induced sepsis due to lower levels of circulating TNF-alpha and reduced infiltration of mononuclear cells in the lung, which cause less end-organ damage. Importantly, when stimulated by LPS-induced proinflammatory factors, macrophages themselves are able to synthesize biglycan. Thus, biglycan, upon release from the ECM or from macrophages, can boost inflammation by signaling through TLR4 and TLR2, thereby enhancing the synthesis of TNF-alpha and MIP-2. Our results provide evidence for what is, to our knowledge, a novel role of the matrix component biglycan as a signaling molecule and a crucial proinflammatory factor. These findings are potentially relevant for the development of new strategies in the treatment of sepsis.
TL;DR: In this paper, the authors explored the nature of the mitochondrial dysfunction and insulin resistance that occur in the muscle of young, lean, normoglycemic, insulin-resistant offspring of parents with type 2 diabetes (IR offspring), and measured mitochondrial content by electron microscopy and insulin signaling in muscle biopsy samples obtained from these individuals before and during a hyperinsulinemic-euglycemic clamp.
Abstract: To further explore the nature of the mitochondrial dysfunction and insulin resistance that occur in the muscle of young, lean, normoglycemic, insulin-resistant offspring of parents with type 2 diabetes (IR offspring), we measured mitochondrial content by electron microscopy and insulin signaling in muscle biopsy samples obtained from these individuals before and during a hyperinsulinemic-euglycemic clamp. The rate of insulin-stimulated muscle glucose uptake was approximately 60% lower in the IR offspring than the control subjects and was associated with an approximately 60% increase in the intramyocellular lipid content as assessed by 1H magnetic resonance spectroscopy. Muscle mitochondrial density was 38% lower in the IR offspring. These changes were associated with a 50% increase in IRS-1 Ser312 and IRS-1 Ser636 phosphorylation and an approximately 60% reduction in insulin-stimulated Akt activation in the IR offspring. These data provide new insights into the earliest defects that may be responsible for the development of type 2 diabetes and support the hypothesis that reductions in mitochondrial content result in decreased mitochondrial function, which predisposes IR offspring to intramyocellular lipid accumulation, which in turn activates a serine kinase cascade that leads to defects in insulin signaling and action in muscle.
TL;DR: Inhibition of IKK-driven NF-kappaB activation offers a strategy for treatment of different malignancies and can convert inflammation- induced tumor growth to inflammation-induced tumor regression.
Abstract: IkappaB kinase/NF-kappaB (IKK/NF-kappaB) signaling pathways play critical roles in a variety of physiological and pathological processes. One function of NF-kappaB is promotion of cell survival through induction of target genes, whose products inhibit components of the apoptotic machinery in normal and cancerous cells. NF-kappaB can also prevent programmed necrosis by inducing genes encoding antioxidant proteins. Regardless of mechanism, many cancer cells, of either epithelial or hematopoietic origin, use NF-kappaB to achieve resistance to anticancer drugs, radiation, and death cytokines. Hence, inhibition of IKK-driven NF-kappaB activation offers a strategy for treatment of different malignancies and can convert inflammation-induced tumor growth to inflammation-induced tumor regression.
TL;DR: This study provides a direct link between peptide marker profiles of disease and differential protease activity, and the patterns described may have clinical utility as surrogate markers for detection and classification of cancer.
Abstract: Recent studies have established distinctive serum polypeptide patterns through mass spectrometry (MS) that reportedly correlate with clinically relevant outcomes. Wider acceptance of these signatures as valid biomarkers for disease may follow sequence characterization of the components and elucidation of the mechanisms by which they are generated. Using a highly optimized peptide extraction and matrix-assisted laser desorption/ionization-time-of-flight (MALDI-TOF) MS-based approach, we now show that a limited subset of serum peptides (a signature) provides accurate class discrimination between patients with 3 types of solid tumors and controls without cancer. Targeted sequence identification of 61 signature peptides revealed that they fall into several tight clusters and that most are generated by exopeptidase activities that confer cancer type-specific differences superimposed on the proteolytic events of the ex vivo coagulation and complement degradation pathways. This small but robust set of marker peptides then enabled highly accurate class prediction for an external validation set of prostate cancer samples. In sum, this study provides a direct link between peptide marker profiles of disease and differential protease activity, and the patterns we describe may have clinical utility as surrogate markers for detection and classification of cancer. Our findings also have important implications for future peptide biomarker discovery efforts.
TL;DR: The hypothesis that organ-specific metastasis by breast cancer cells is controlled by metastasis-specific genes that are separate from a general poor-prognosis gene expression signature is supported.
Abstract: We used bioluminescence imaging to reveal patterns of metastasis formation by human breast cancer cells in immunodeficient mice. Individual cells from a population established in culture from the pleural effusion of a breast cancer patient showed distinct patterns of organ-specific metastasis. Single-cell progenies derived from this population exhibited markedly different abilities to metastasize to the bone, lung, or adrenal medulla, which suggests that metastases to different organs have different requirements. Transcriptomic profiling revealed that these different single-cell progenies similarly express a previously described “poor-prognosis” gene expression signature. Unsupervised classification using the transcriptomic data set supported the hypothesis that organ-specific metastasis by breast cancer cells is controlled by metastasis-specific genes that are separate from a general poor-prognosis gene expression signature. Furthermore, by using a gene expression signature associated with the ability of these cells to metastasize to bone, we were able to distinguish primary breast carcinomas that preferentially metastasized to bone from those that preferentially metastasized elsewhere. These results suggest that the bone-specific metastatic phenotypes and gene expression signature identified in a mouse model may be clinically relevant.
TL;DR: IL-1 mediates the osteoclastogenic effect of TNF by enhancing stromal cell expression of RANKL and directly stimulating differentiation of osteoclass precursors under the aegis of p38 MAPK.
Abstract: TNF-induced receptor activator NF-kappaB ligand (RANKL) synthesis by bone marrow stromal cells is a fundamental component of inflammatory osteolysis. We found that this process was abolished by IL-1 receptor antagonist (IL-1Ra) or in stromal cells derived from type I IL-1 receptor-deficient (IL-1RI-deficient) mice. Reflecting sequential signaling of the cytokines TNF and IL-1, TNF induces stromal cell expression of IL-1 and IL-1RI. These data suggest that TNF regulates RANKL expression via IL-1, and, therefore, IL-1 plays a role in TNF-induced periarticular osteolysis. Consistent with this posture, TNF-stimulated osteoclastogenesis in cultures consisting of WT marrow macrophages and stromal cells exposed to IL-1Ra or in cocultures established with IL-1RI-deficient stromal cells was reduced approximately 50%. The same magnitude of osteoclast inhibition occurred in IL-1RI-deficient mice following TNF administration in vivo. Like TNF, IL-1 directly targeted osteoclast precursors and promoted the osteoclast phenotype in a TNF-independent manner in the presence of permissive levels of RANKL. IL-1 is able to induce RANKL expression by stromal cells and directly stimulate osteoclast precursor differentiation under the aegis of p38 MAPK. Thus, IL-1 mediates the osteoclastogenic effect of TNF by enhancing stromal cell expression of RANKL and directly stimulating differentiation of osteoclast precursors.
TL;DR: In humans, the biological limitations to cardiac regenerative growth create a clinical imperative and a clinical opportunity for using cells, genes, and proteins to rescue cardiac muscle cell number or in other ways promote more efficacious cardiac repair.
Abstract: In humans, the biological limitations to cardiac regenerative growth create both a clinical imperative — to offset cell death in acute ischemic injury and chronic heart failure — and a clinical opportunity; that is, for using cells, genes, and proteins to rescue cardiac muscle cell number or in other ways promote more efficacious cardiac repair. Recent experimental studies and early-phase clinical trials lend credence to the visionary goal of enhancing cardiac repair as an achievable therapeutic target.
TL;DR: The results suggest that nitrite is a biological storage reserve of NO subserving a critical function in tissue protection from ischemic injury and an unexpected and novel therapy for diseases such as myocardial infarction, organ preservation and transplantation, and shock states.
Abstract: Nitrite represents a circulating and tissue storage form of NO whose bioactivation is mediated by the enzymatic action of xanthine oxidoreductase, nonenzymatic disproportionation, and reduction by deoxyhemoglobin, myoglobin, and tissue heme proteins. Because the rate of NO generation from nitrite is linearly dependent on reductions in oxygen and pH levels, we hypothesized that nitrite would be reduced to NO in ischemic tissue and exert NO-dependent protective effects. Solutions of sodium nitrite were administered in the setting of hepatic and cardiac ischemia-reperfusion (I/R) injury in mice. In hepatic I/R, nitrite exerted profound dose-dependent protective effects on cellular necrosis and apoptosis, with highly significant protective effects observed at near-physiological nitrite concentrations. In myocardial I/R injury, nitrite reduced cardiac infarct size by 67%. Consistent with hypoxia-dependent nitrite bioactivation, nitrite was reduced to NO, S-nitrosothiols, N-nitros-amines, and iron-nitrosylated heme proteins within 1-30 minutes of reperfusion. Nitrite-mediated protection of both the liver and the heart was dependent on NO generation and independent of eNOS and heme oxygenase-1 enzyme activities. These results suggest that nitrite is a biological storage reserve of NO subserving a critical function in tissue protection from ischemic injury. These studies reveal an unexpected and novel therapy for diseases such as myocardial infarction, organ preservation and transplantation, and shock states.