Gestational diabetes, inflammation, and late vascular disease

Physiological changes of pregnancy include insulin resistance and activation of the innate immunity with an inflammatory response. The working hypothesis is that the sub-clinical inflammation associated with excessive adiposity may favor the development of gestational diabetes (GDM) and Type 2 diabetes and other metabolic abnormalities related to cardiovascular disease later in life. In this paper we review the complex interrelationship among inflammatory markers, metabolic syndrome, and endothelium dysfunction in women with GDM and discuss if women with previous GDM (pGDM) could be considered at risk for cardiovascular diseases. MEDLINE was searched for articles relating GDM and the adipokines (tumor necrosis factor-alpha and adiponectin) as well as the acute-phase inflammatory biomarker C-reactive protein that contribute to the development of diabetic pregnancy and vascular complications. However, to date, in pGDM women no prospective study is available, to corroborate the hypothesis that inflammatory pattern could be taken as predictor of cardiovascular disease later in life. Therefore, our paper should provide arguments to perform follow-up programs to prevent cardiovascular events in women with pGDM. Control of body weight, regular physical exercise are indeed powerful intervention tools able at improving insulin sensitivity and reduce sub-clinical inflammation, both involved in the pathogenesis of cardiovascular disease.     

Innate immunity in triggering and resolution of acute gouty inflammation

Gout has long been recognized as a disease of recurrent bouts of acute inflammation that undergo self-resolution. This inflammation is triggered by the body’s response to monosodium urate (MSU) crystals. In this paper, we focus on recent studies that describe how interactions of MSU crystals with the components of the innate immune system trigger acute gouty inflammation as well as mechanisms that are involved in the resolution of this inflammation. Specifically, we describe how toll-like receptors mediate the uptake of MSU crystals involved in the initiation and resolution of gouty inflammation. We also describe recent findings on the role of apoptotic clearance in the resolution of gouty inflammation. In addition, how therapies used to treat gout act on the innate immune system to inhibit MSU crystal-induced inflammation and promote the resolution of inflammation is discussed.     

Innate immunity in triggering and resolution of acute gouty inflammation

Gout has long been recognized as a disease of recurrent bouts of acute inflammation that undergo self-resolution. This inflammation is triggered by the body's response to monosodium urate (MSU) crystals. In this paper, we focus on recent studies that describe how interactions of MSU crystals with the components of the innate immune system trigger acute gouty inflammation as well as mechanisms that are involved in the resolution of this inflammation. Specifically, we describe how toll-like receptors mediate the uptake of MSU crystals involved in the initiation and resolution of gouty inflammation. We also describe recent findings on the role of apoptotic clearance in the resolution of gouty inflammation. In addition, how therapies used to treat gout act on the innate immune system to inhibit MSU crystal-induced inflammation and promote the resolution of inflammation is discussed.     

Protein kinase C activation contributes to microvascular barrier dysfunction in the heart at early stages of diabetes

The functional disturbance of microvasculature is recognized as an initiating mechanism that underlies the development of various diabetic complications. Although a causal relationship between microvascular leakage and tissue damage has been well documented in diabetic kidneys and eyes, there is a lack of information regarding the barrier function of coronary exchange vessels in the disease state. The aim of the present study was to evaluate the permeability property of coronary microvessels during the early development of experimental diabetes with a focus on the protein kinase C (PKC)-dependent signaling mechanism. The apparent permeability coefficient of albumin (Pa) was measured in isolated and perfused porcine coronary venules. The administration of high concentrations of D-glucose induced a dose-dependent increase in the Pa value, which was prevented by blockage of PKC with its selective inhibitors bisindolylmaleimide and Goe 6976. More importantly, an elevated basal permeability to albumin was observed in coronary venules at the early onset of streptozotocin-induced diabetes. The hyperpermeability was corrected with bisindolylmaleimide and the selective PKCbeta inhibitor hispidin. Concomitantly, protein kinase assay showed a high PKC activity in isolated diabetic venules. Immunoblot analysis of the diabetic heart revealed a significant subcellular translocation of PKCbetaII and PKCepsilon from the cytosol to the membrane, indicating that the specific activity of these isoforms was preferentially elevated. The results suggest that endothelial barrier dysfunction attributed to the activation of PKC occurs at the coronary exchange vessels in early diabetes.     

ADAMTS13 reduces vascular inflammation and the development of early atherosclerosis in mice

ADAMTS13, a metalloprotease, plays a pivotal role in preventing spontaneous microvascular thrombosis by cleaving hyperactive ultra large von Willebrand factor multimers into smaller, less active multimers. Reduced ADAMTS13 activity in plasma has been described in many diseases associated with systemic inflammation. It remains uncertain, however, whether ADAMTS13 contributes to disease pathogenesis or rather simply serves as an inflammation-associated marker. We hypothesized that, by decreasing vascular inflammation, ADAMTS13 reduces the development of early atherosclerotic plaques. Using intravital fluorescence microscopy, we observed excessive leukocyte adhesion and accelerated atherosclerotic plaque formation at the carotid sinus of Adamts13(-/-)/ApoE(-/-) mice compared with ApoE(-/-) mice fed a high-fat Western diet. At 4 months of age, there was a significant increase in atherosclerosis in the aorta and aortic sinus of Adamts13(-/-)/ApoE(-/-) mice compared with ApoE(-/-) mice. Interestingly, we detected a 2-fold increase in macrophage recruitment to the atherosclerotic plaque of the Adamts13(-/-)/ApoE(-/-) mice compared with ApoE(-/-) mice, suggesting that the atherosclerotic lesions in these mice were not only larger but also more inflammatory. These findings reveal a new functional role for the antithrombotic enzyme ADAMTS13 in reducing excessive vascular inflammation and plaque formation during early atherosclerosis.     

The roles of cytokines, inflammation and immunity in vascular diseases

Recent findings regarding the roles of cytokines, inflammation and immunity during the development of atherosclerosis were reviewed. Especially, the relationships among pro-inflammatory cytokines such as interleukin (IL)-1, IL-18 and osteopontin, and anti-inflammatory cytokines such as IL-1 receptor antagonist, IL-10 and IL-18 binding protein to inflammation and atherosclerosis were investigated and are described in detail. In addition, helicobacter pylori and C pneumoniae infections to inflammations regarding the persistence of inflammation have been pointed out. A pro-inflammatory genotype or haplotype and toll-like receptors have been shown to be involved in human atherosclerosis. Atherosclerosis might therefore be a specific form of the chronic inflammatory process. In addition to hyperlipidemia, infections, cytokines and immunity might also be involved in the development of atherosclerosis. Certain treatments that reduce coronary risk also limit inflammation. Statins possess multiple pleiotropic effects such as an anti-inflammatory effect in addition to a lipid-lowering effect.     

Levels of various components of the classical and alternative pathways of complement activation in diabetes mellitus patients

The state of the complement system was studied in 91 patients with insulin dependent and in 47 patients with non-insulin dependent diabetes. A study was made of the quantity of hemolytically effective molecules of some components C2, C4, C3, C5 of classic and factors B and D of alternative pathway of activation. Complement components were studied for control in 51 healthy blood donors. Antigens B8 and B18 of the HLA-histocompatibility system were studied in parallel in 24 patients and 21 donors. A significantly raised level of components C3 and C4, factors B and D was revealed in the patients with insulin dependent diabetes as compared to the controls (p less than 0.05). In non-insulin dependent diabetes C4, factors B and D were significantly raised and the level of C5 was lowered (p less than 0.05). In the patients with insulin dependent diabetes having antigens B18 the level of C3 was raised and the level of C4 was lowered as compared to the controls. The level of factors B and D was also lower than that in the diabetic patients. An analysis of the content of the complement components in 31 diabetic patients with diabetic nephropathy indicated a decrease in the levels of components C3 and C5 and an increase in the content of C4 (p less than 0.001) as compared to the normal. Diabetes was accompanied by considerable variations as compared to normal values characterizing the state of the complement system and reflecting, to a certain extent, the main features of the pathogenesis of disease.     

Autoantibody-mediated complement c3a receptor activation contributes to the pathogenesis of preeclampsia

Preeclampsia (PE) is a prevalent life-threatening hypertensive disorder of pregnancy associated with increased complement activation. However, the causative factors and pathogenic role of increased complement activation in PE are largely unidentified. Here we report that a circulating maternal autoantibody, the angiotensin II type 1 receptor agonistic autoantibody, which emerged recently as a potential pathogenic contributor to PE, stimulates deposition of complement C3 in placentas and kidneys of pregnant mice via angiotensin II type 1 receptor activation. Next, we provide in vivo evidence that selectively interfering with C3a signaling by a complement C3a receptor-specific antagonist significantly reduces hypertension from 167±7 to 143±5 mm Hg and proteinuria from 223.5±7.5 to 78.8±14.0 μg of albumin per milligram creatinine (both P<0.05) in angiotensin II type 1 receptor agonistic autoantibody-injected pregnant mice. In addition, we demonstrated that complement C3a receptor antagonist significantly inhibited autoantibody-induced circulating soluble fms-like tyrosine kinase 1, a known antiangiogenic protein associated with PE, and reduced small placental size with impaired angiogenesis and intrauterine growth restriction. Similarly, in humans, we demonstrate that C3 deposition is significantly elevated in the placentas of preeclamptic patients compared with normotensive controls. Lastly, we show that complement C3a receptor activation is a key mechanism underlying autoantibody-induced soluble fms-like tyrosine kinase 1 secretion and decreased angiogenesis in cultured human villous explants. Overall, we provide mouse and human evidence that angiotensin II type 1 receptor agonistic autoantibody-mediated activation contributes to elevated C3 and that complement C3a receptor signaling is a key mechanism underlying the pathogenesis of the disease. These studies are the first to link angiotensin II type 1 receptor agonistic autoantibody with complement activation and to provide important new opportunities for therapeutic intervention in PE.     

Local complement activation, thromboxane-mediated vasoconstriction, and vascular leakage in isolated lungs. Role of the terminal complement sequence

In situ complement activation was induced in isolated, ventilated, and blood-free perfused rabbit lungs. Six to 11% human serum (vol/vol) was repeatedly admixed to the recirculating Krebs Henseleit buffer during 10-min periods, interrupted by rinsing phases with serum-free medium. This caused dose-dependent, reversible, and reproducible pulmonary artery pressor responses with pressure peaks or plateaus of 8 to 22 mm Hg. Pressor responses were paralleled by a marked release of thromboxane (TxA2) and prostaglandin I2 into the medium. Heat-inactivated serum, purified fluid-phase SC5b-9, and serum that had been activated with inulin in the absence or presence of a carboxypeptidase inhibitor all failed to elicit pressor responses. Both pressor response and prostanoid release were strictly dependent on complement factor C8, and evidence for C8 binding was obtained with the use of 125I-C8. Inhibitor studies collectively indicated that TxA2 was the predominant vasoconstrictive agent. Although repetitive short-term application of human serum induced no major lung weight gain, prolonged exposure to serum (40 to 80 min) without intermittent rinsing phases caused a delayed increase in the capillary filtration coefficient to maximally 3- to 4-fold values, with marked lung edema formation. We conclude that in situ activation of complement in the rabbit lung vasculature causes immediate intrapulmonary prostanoid generation and thromboxane-mediated vasoconstriction, independent of circulating leukocytes, but dependent on the formation of terminal membrane-complement complexes. Continuous complement activation results in a delayed increase in lung vascular permeability.     

NADPH oxidase contributes to vascular inflammation, insulin resistance, and remodeling in the transgenic (mRen2) rat

Reduced insulin sensitivity is characteristic of various pathological conditions such as type 2 diabetes mellitus and hypertension. Angiotensin II, acting through its angiotensin type 1 receptor, inhibits the actions of insulin in the vasculature which may lead to deleterious effects such as vascular inflammation, remodeling, endothelial dysfunction, and insulin resistance. In contrast, insulin normally exerts vasodilatory, antiinflammatory, and prosurvival actions. To explore the impact of angiotensin II on insulin signaling, NADPH oxidase-derived reactive oxygen species formation, vascular inflammation, apoptosis, and remodeling, we used transgenic TG(mRen2)27 (Ren2) rats, which harbor the mouse renin transgene and exhibits elevated tissue angiotensin II levels. Compared with Sprague-Dawley controls, Ren2 aortas exhibited greater NADPH oxidase activity, reactive oxygen species levels, C-reactive protein, tumor necrosis factor-alpha expression, apoptosis, and wall thickness, which were significantly attenuated by in vivo treatment with angiotensin type 1 receptor blockade (valsartan) or the superoxide dismutase/catalase mimetic (tempol). There was substantially diminished Akt and endothelial NO synthase activation in Ren2 aortas in response to in vivo insulin stimulation, and this was significantly improved by in vivo treatment with valsartan or tempol. In vivo treatment with valsartan, but not tempol, significantly reduced blood pressure in Ren2 rats. Further, there was reduced insulin induced Akt activation and increased tumor necrosis factor-alpha levels in vascular smooth muscle cells from Ren2 and Sprague-Dawley rats treated with angiotensin II, abnormalities that were abrogated by angiotensin type 1 receptor blockade with valsartan or antioxidant N-acetylcysteine. Collectively, these data suggest that increased angiotensin type 1 receptor/NADPH oxidase activation/reactive oxygen species contribute to vascular insulin resistance, endothelial dysfunction, apoptosis, and inflammation.     

Effects of complement activation in the isolated heart. Role of the terminal complement components.

The mechanisms of the complement-mediated myocardial injury associated with ischemia and reperfusion have not been elucidated fully. Complement activation may directly mediate injury through actions of the anaphylatoxins C3a and C5a or generation of the membrane attack complex C5b-9. A model was developed to examine the direct effects of complement activation on heart function, assess myocardial tissue damage, and determine which complement components mediate tissue injury. Isolated rabbit hearts were perfused with Krebs-Henseleit buffer by using a modified Langendorff apparatus. Human plasma was added to the perfusate as a source of complement. Rabbit tissue activates human complement. Treatment with 6% normal plasma resulted in complement activation as assessed by the generation of Bb, C3a, C5a, and SC5b-9. Functional changes in cardiac performance became apparent 7-15 minutes after plasma addition and developed fully over the next 20-30 minutes. The effects were dependent on the complement titer and included 1) an increase in the end-diastolic pressure, 2) a decrease in the developed pressure, 3) an increase in the coronary perfusion pressure, and 4) an increase in lymphatic fluid formation. These effects were not elicited when an inhibitor of complement activation (FUT-175) was present or when heat-inactivated plasma was used. The effects of complement activation on myocardial function could not be reproduced by treatment with recombinant human C5a, zymosan-activated plasma, or plasma selectively depleted of C8. Myocardial tissue accumulated sodium and calcium and lost potassium as a result of complement activation. Activation caused the release of creatine kinase from myocytes and an increase in the radiolabeled albumin space of the hearts. The data demonstrate that complement activation caused decrements in myocardial function and increased the coronary perfusion pressure and lymphatic fluid flow rate. The effects were not mediated by the anaphylatoxins but were dependent on the distal complement component C8, suggesting that C5b-9 was responsible for the physiological changes. Complement activation directly mediated tissue injury in a manner consistent with plasmalemmal disruption as a result of C5b-9 formation. The data suggest that the C5b-9 complex, which is known to form under conditions of ischemia, may contribute directly to myocardial cell injury.     

Platelet activation and binding of complement components to platelets induced by immune complexes

Clinical disorders such as malignant diseases, infectious diseases or autoimmune diseases are associated with circulating immune complexes. These immune complexes can activate the complement system in the blood or interact with complement or Fc receptors on the surface of cells. Complement activation may cause cytolysis and the immune complex interaction with receptors may cause activation of cells. We have used flow cytometry and labelled chicken antibodies to study the in vitro effects of model immune complexes on platelets and show that such immune complexes activate platelets and deposit Clq, C4 and C5 on them. Either low levels or no C3 could be detected on the platelets by flow cytometry. The immune complexes also induced formation of microparticles from purified platelets. Flow cytometry might become a useful tool in estimation of risk of thrombosis or thrombocytopenia in patients with autoimmune disease. Chicken antibodies are superior to mammalian antibodies for the measurement of platelet bound plasma proteins as they do not induce complement activation or platelet activation.     

Role of miR-181 family in regulating vascular inflammation and immunity

The microRNA family, miR-181, plays diverse roles in regulating key aspects of cellular growth, development, and activation. Accumulating evidence supports a central role for the miR-181 family in vascular inflammation by controlling critical signaling pathways, such as downstream NF-κB signaling, and targets relevant to endothelial cell activation and immune cell homeostasis. This review examines the current knowledge of the miR-181 family's role in key cell types that critically control cardiovascular inflammation under pathological and physiological stimuli.     

Cannabinoid 1 receptor activation contributes to vascular inflammation and cell death in a mouse model of diabetic retinopathy and a human retinal cell line

Aims/hypothesis  

Recent studies have demonstrated that cannabinoid-1 (CB₁) receptor blockade ameliorated inflammation, endothelial and/or cardiac dysfunction, and cell death in models of nephropathy, atherosclerosis and cardiomyopathy. However the role of CB₁ receptor signalling in diabetic retinopathy remains unexplored. Using genetic deletion or pharmacological inhibition of the CB₁ receptor with SR141716 (rimonabant) in a rodent model of diabetic retinopathy or in human primary retinal endothelial cells (HREC) exposed to high glucose, we explored the role of CB₁ receptors in the pathogenesis of diabetic retinopathy.     

Non-HDL cholesterol level is reliable to be an early predictor for vascular inflammation in type 2 diabetes mellitus

Although LDL is the primary target for lipid-lowering therapy and non-HDL cholesterol is a secondary target in patients with elevated triglyceride (TG) levels, non-HDL cholesterol is still an early, reliable, and practical predictor for vascular inflammation. However, in comparison with LDL, further evidence for superiority in non-HDL cholesterol as the primary therapeutic target is required. A total of 189 type 2 diabetic patients (88 men and 101 women; mean age 58.4 +/- 14.0 years; duration of diabetes 9.8 +/- 4.2 years) who had not used anti-inflammatory agents in the past two years were enrolled in this study. Levels of various lipid fractions and C-reactive protein (CRP) and the cholesterol retention fraction (CRF) were measured. Lipid levels and CRF in samples with CRP levels below or above different cutoffs were compared. Statistically significant differences were seen at all CRP cutoffs in the levels of TG, HDL, and non-HDL cholesterol and the CRF, but no differences were seen in total cholesterol and LDL cholesterol levels. CRP levels correlated with non-HDL cholesterol levels (r = 0.16, P = 0.0236) and the CRF (r = 0.18, P = 0.14), but not with levels of HDL or TG. Besides, non-HDL levels showed a marked correlation with CRF (r = 0.68, P < 0.0001). On the basis of CRP levels, non-HDL levels are reliable in predicting vascular inflammation, and CRF could be another important predictor for cardiovascular events. Our results suggest that the emphasis placed on non-HDL cholesterol should be reevaluated in comparison with that placed on LDL cholesterol.     

Endothelin contributes differently to peripheral vascular tone and blood pressure in human obesity and diabetes

Endothelin contributes to abnormalities in peripheral blood vessel function of subjects with obesity, with or without concurrent type 2 diabetes mellitus, but it is unknown if endothelin contributes specifically to obesity and diabetes-associated changes in blood pressure. We evaluated the effect of systemic endothelin antagonism on peripheral and central hemodynamics and peripheral vascular tone in lean, obese, and type 2 diabetic subjects without overt hypertension by cuff plethysmography. We measured the effects of acute systemic infusions of BQ123 (an antagonist of type A endothelin receptors) in seven lean (body mass index [BMI] 22.7 ± 3.2 kg/m²), seven obese (BMI 35.8 ± 4.6), and six diabetic subjects (BMI 38.2 ± 5.0, glycosylated hemoglobin 8.1 ± 2.2%). BQ123 was infused via antecubital vein sequentially at infusion rates from 0.1 to 1.0 μmol/min. Diastolic blood pressure was significantly lower than baseline across this dose range, but without a clear dose dependence and without differences in the dose response across groups. Obese and diabetic subjects exhibited progressive dilation of peripheral blood vessels (P ≤ .01), with 0.03 and 1.0 μmol/min BQ123 (P = .03 comparing integrated response across groups). No significant changes were observed in systolic blood pressure, cardiac index, or stroke index. These observations confirm the relevance of endothelin in the abnormal regulation of peripheral vascular tone in obesity and diabetes, but they argue against a specific effect of endothelin in diabetes- and obesity-associated blood pressure elevations.     

Toll-like receptor activation in basophils contributes to the development of IgG4-related disease

Background

IgG4-related disease (IRD) is characterized by systemic IgG4 antibody responses and by infiltration of IgG4-expressing plasma cells into the affected organs. Although T helper type 2 (Th2) cytokines are implicated in enhanced IgG4 responses, molecular mechanisms accounting for the development of IgG4 antibody responses are poorly defined. Since basophils function as antigen-presenting cells for Th2 responses, we tried to clarify the role of basophils in the development of IgG4 responses in this study.

Methods

IgG4 and cytokine responses to various nucleotide-binding oligomerization domain-like receptor and Toll-like receptor (TLR) ligands were examined by using basophils isolated from healthy controls and from patients with IgG4-related disease.

Results

Activation of TLRs in basophils from healthy controls induced IgG4 production by B cells, which effect was associated with enhanced production of B cell activating factor (BAFF) and IL-13. In addition, activation of TLRs in basophils from patients with IRD induced a large amount of IgG4 by B cells from healthy controls. This enhancement of IgG4 production was again associated with BAFF and IL-13.

Conclusions

These data suggest that innate immune responses mediated through TLRs may play a role in the development of IgG4-related disease, in part by production of BAFF from basophils.