Augmented expression of inducible NO synthase in vascular smooth muscle cells during aging is associated with enhanced NF-kappaB activation

MFG-E8 mediates arterial aging by promoting the proinflammatory phenotype of vascular smooth muscle cells

BACKGROUND

Among older adults, arterial aging is the major factor contributing to increased risk for cardiovascular disease-related morbidity and mortality. The chronic vascular inflammation that accompanies aging causes diffuse intimal-medial thickening of the arterial wall, thus increasing the vulnerability of aged vessels to vascular insults. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a biomarker for aging arteries. This integrin-binding glycoprotein, induced by angiotensin II, facilitates vascular smooth muscle cell (VSMC) proliferation and invasion in aging vasculatures. This study investigated whether MFG-E8 directly mediates the initial inflammatory responses in aged arteries or VSMCs.

METHODS

A model of neointimal hyperplasia was induced in the common carotid artery (CCA) of aged mice to exacerbate age-associated vascular remodeling. Recombinant MFG-E8 (rMFG-E8) was administered to the injured artery using Pluronic gel to accentuate the effect on age-related vascular pathophysiology. The MFG-E8 level, leukocyte infiltration, and proinflammatory cell adhesion molecule (CAM) expression in the arterial wall were evaluated through immunohistochemistry. By using immunofluorescence and immunoblotting, the activation of the critical proinflammatory transcription factor nuclear factor (NF)-κB in the injured CCAs was analyzed. Immunofluorescence, immunoblotting, and quantitative real-time polymerase chain reaction were conducted using VSMCs isolated from the aortas of young and aged mice to assess NF-κB nuclear translocation, NF-κB-dependent gene expression, and cell proliferation. The extent of intimal-medial thickening in the injured vessels was analyzed morphometrically. Finally, Transwell migration assay was used to examine VSMC migration.

RESULTS

Endogenous MFG-E8 expression in aged CCAs was significantly induced by ligation injury. Aged CCAs treated with rMFG-E8 exhibited increased leukocyte extravasation, CAM expression, and considerably increased NF-κB activation induced by rMFG-E8 in the ligated vessels. Exposure of early passage VSMCs from aged aortas to rMFG-E8 substantially increased NF-κB activation, proinflammatory gene expression, and cell proliferation. However, rMFG-E8 attenuated VSMC migration.

CONCLUSIONS

MFG-E8 promoted the proinflammatory phenotypic shift of aged VSMCs and arteries, rendering the vasculature prone to vascular diseases. MFG-E8 may constitute a novel therapeutic target for retarding the aging processes in such vessels.

Oxidative stress and vascular inflammation in aging

Vascular aging, a determinant factor for cardiovascular disease and health status in the elderly, is now viewed as a modifiable risk factor. Impaired endothelial vasodilation is a early hallmark of arterial aging that precedes the clinical manifestations of vascular dysfunction, the first step to cardiovascular disease and influencing vascular outcomes in the elderly. Accordingly, the preservation of endothelial function is thought to be an essential determinant of healthy aging. With special attention on the effects of aging on the endothelial function, this review is focused on the two main mechanisms of aging-related endothelial dysfunction: oxidative stress and inflammation. Aging vasculature generates an excess of the reactive oxygen species (ROS), superoxide and hydrogen peroxide, that compromise the vasodilatory activity of nitric oxide (NO) and facilitate the formation of the deleterious radical, peroxynitrite. Main sources of ROS are mitochondrial respiratory chain and NADPH oxidases, although NOS uncoupling could also account for ROS generation. In addition, reduced antioxidant response mediated by erythroid-2-related factor-2 (Nrf2) and downregulation of mitochondrial manganese superoxide dismutase (SOD2) contributes to the establishment of chronic oxidative stress in aged vessels. This is accompanied by a chronic low-grade inflammatory phenotype that participates in defective endothelial vasodilation. The redox-sensitive transcription factor, nuclear factor-κB (NF-κB), is upregulated in vascular cells from old subjects and drives a proinflammatory shift that feedbacks oxidative stress. This chronic NF-κB activation is contributed by increased angiotensin-II signaling and downregulated sirtuins and precludes adequate cellular response to acute ROS generation. Interventions targeted to recover endogenous antioxidant capacity and cellular stress response rather than exogenous antioxidants could reverse oxidative stress-inflammation vicious cycle in vascular aging. Lifestyle attitudes such as caloric restriction and exercise training appear as effective ways to overcome defective antioxidant response and inflammation, favoring successful vascular aging and decreasing the risk for cardiovascular disease.

Attenuated expression of gelsolin in association with induction of aquaporin-1 and nitric oxide synthase in dysfunctional hearts of aging mice exposed to endotoxin

Sepsis triggered by endotoxinemia may impair cardiac function. A decline in tolerance to septic shock occurs with aging. This study addressed the hypothesis that aging negatively impairs expression of gelsolin, and axerts the regulatory effects on the water channel protein aquaporin-1 (AQP-1) and endotoxin-inducible nitric oxide synthase (iNOS). We explored whether the age-related gene changes are associated with the cardiac dysfunction induced by endotoxic stress exposure. Male mice at young (3-month) and old (12-month) ages received intraperitoneal injections of saline or lipopolysaccharide (LPS, 30mg/Kg). Cardiac performance and morphology were analyzed by echocardiography at baseline and 2 and 24 h after injection. At the end of treatment, the animals were sacrificed, and cardiac tissues were collected for assessing expression of gelsolin, AQP-1, iNOS, and transcription-3 (STAT3). LPS administration led to a decreased contractility while increasing cardiac dimensions in both young and old mice. LPS also markedly induced expression of gelsolin in both animal groups. However, compared to young mice, old mice showed compromised induction of gelsolin and cardiac performance in response to endotoxin. Meanwhile, the LPS-exposed old animals exhibited higher levels of AQP-1, iNOS, and phosphorylated STAT3. Gelsolin-null mice had increased expression of glycosylated AQP-1 and STAT3 phosphorylation as well as cardiac dysfunction. Thus, endotoxin administration induces expression of gelsolin, AQP-1 and pro-inflammatory genes, such as iNOS. Our data suggest that changed expression of gelsolin, AQP-1 and iNOS may contribute to dysfunction of hearts in aged subjects with septic endotoxinemia.

Age-related changes in redox signaling and VSMC function

Epidemiological studies have shown that advancing age is associated with an increased prevalence of cardiovascular disease (CVD). Vascular smooth muscle cells (VSMC) comprise the major arterial cell population, and changes in VSMC behavior, function, and redox status with age contribute to alterations in vascular remodeling and cell signaling. Over two decades of work on aged animal models provide support for age-related changes in VSMC and/or arterial tissues. Enhanced production of reactive oxygen species (ROS) and insufficient removal by scavenging systems are hallmarks of vascular aging. VSMC proliferation and migration are core processes in vascular remodeling and influenced by growth factors and signaling networks. The intrinsic link between gene regulation and aging often relates directly to transcription factors and their regulatory actions. Modulation of growth factor signaling leads to up- or downregulation of transcription factors that control expression of genes associated with VSMC proliferation, inflammation, and ROS production. Four major signaling pathways related to the transcription factors, AP-1, NF-kappaB, FoxO, and Nrf2, will be reviewed. Knowledge of age-related changes in signaling pathways in VSMC that lead to alterations in cell behavior and function consistent with disease progression may help in efforts to attenuate age-related CVD, such as atherosclerosis.

Effects of exercise on cyclooxygenase-2 expression and nuclear factor-kappaB DNA binding in human peripheral blood mononuclear cells

There are multiple lines of compelling evidence supporting the beneficial effect of exercise on the prevention and/or improvement of certain chronic diseases. However, exhaustive or intense exercise causes oxygen free radical generation and oxidative stress, which can lead to injuries and chronic fatigue as well as inflammation. Abnormal upregulation of cyclooxygenase-2 (COX-2), a rate-limiting enzyme in prostaglandin biosynthesis, has been implicated in many inflammation-associated chronic disorders. Nuclear factor-kappaB (NF-kappaB) is a major transcription factor involved in regulation of COX-2 gene expression. To determine whether inflammation induction is dependent on intensity of exercise, COX-2 expression and NF-kappaB activation were adopted as the main targets. Thirteen volunteers who participated in the exercise program were subject to four exercise intensities [40, 60, 80, and 100% of heart rate reserve (HRR)] on a treadmill and to resting conditions. Isolated human peripheral blood mononuclear cells (PBMCs) were collected during the resting state and immediately after exercise and subjected to the electrophoretic mobility gel shift assay and Western blot analysis. As exercise intensity increased, both COX-2 expression and NF-kappaB DNA-binding activity were enhanced. The expression of IkappaB kinase alpha (IKKalpha) and IkappaBalpha were not significantly altered. However, exhaustive/vigorous exercise (100% HRR) could induce the phosphorylation of both IKKalpha and IkappaBalpha. In conclusion, a single bout of exercise induced COX-2 expression and DNA-binding activity of NF-kappaB in human PBMCs, and both COX-2 expression and DNA-binding activity of NF-kappaB were dependent on exercise intensity.

Age-associated inflammation and toll-like receptor dysfunction prime the lungs for pneumococcal pneumonia

BACKGROUND

Aging is associated with increased inflammation and risk of community-acquired pneumonia. Streptococcus pneumoniae co-opts the nuclear factor kappa B (NFkB)-regulated proteins polymeric immunoglobulin receptor (pIgR) and platelet-activating factor receptor (PAFr) to attach and invade cells. We sought to determine whether aging and chronic inflammation were associated with increased pIgR and PAFr levels in the lungs and increased susceptibility to S. pneumoniae infection.

METHODS

Lung protein and messenger RNA levels were quantitated using Western blot and quantitative polymerase chain reaction. NFkB activation was measured by electrophoretic mobility shift assay. Cytokine levels were measured by cytometric bead analysis. To model chronic inflammation, mice were implanted with osmotic pumps that delivered tumor necrosis factor-alpha.

RESULTS

Aged mice and those infused with tumor necrosis factor-alpha had increased levels of pIgR and PAFr in their lungs and were more susceptible to S. pneumoniae infection. During pneumonia, aged mice had reduced levels of pIgR and PAFr and less NFkB activation, despite greater bacterial burden. We determined that aged mice had decreased amounts of lung Toll-like receptors 1, 2, and 4 and reduced capacity to respond to S. pneumoniae with proinflammatory cytokine production.

CONCLUSIONS

Aged mice and, potentially, elderly humans are more susceptible to pneumonia because of a priming effect of chronic inflammation and Toll-like receptor dysfunction.

Alterations in transcriptional responses associated with vascular aging

Vascular aging is an independent risk factor for cardiovascular disease that can occur in the absence of other traditional risk factors. Inflammation is a hallmark of vascular aging that ultimately leads to structural changes in the vessel wall including an increase in medial thickness and perivascular fibrosis. Several classes of transcription factors have been identified that participate in the regulation of cellular responses associated with vascular aging. Nuclear factor (NF)-κB is the prototypic example of a transcriptional activator in the setting of inflammation, being activated in response to multiple inflammatory mediators including pro-inflammatory cytokines and bacterial endotoxin. In contrast, the activation of the nuclear hormone receptor and transcription factor peroxisome proliferator-activated receptor-alpha (PPAR-α) results in its translocation from the cell surface to the nucleus where it exerts anti-inflammatory effects. Vascular aging is also associated with endothelial dysfunction. One important repair mechanism for improving endothelial function is the recruitment of endothelial progenitor cells (EPCs). In the setting of aging the number of EPCs diminishes which has been linked to a decrease in the activity and/or expression of the transcription factor hypoxia inducible factor (HIF)-1 alpha. A change in the balance of the activity of pro-inflammatory transcription factors versus those that inhibit inflammation likely contributes to the process of vascular aging. The purpose of this review is to summarize our current knowledge of these age-related changes in transcriptional responses, and to discuss the therapeutic potential of targeting some of these factors.

Endothelial glutathione-S-transferase A4-4 protects against oxidative stress and modulates iNOS expression through NF-kappaB translocation

Our recent work in endothelial cells and human atherosclerotic plaque showed that overexpression of glutathione-S-tranferases (GSTs) in endothelium protects against oxidative damage from aldehydes such as 4-HNE. Nuclear factor (NF)-kappaB plays a crucial role during inflammation and immune responses by regulating the expression of inducible genes such as inducible nitric oxide synthase (iNOS). 4-HNE induces apoptosis and affects NF-kappaB mediated gene expression, but conflicting results on 4-HNE's effect on NF-kappaB have been reported. We compared the effect of 4-HNE on iNOS and the NF-kappaB pathway in control mouse pancreatic islet endothelial (MS1) cells and those transfected with mGSTA4, a alpha-class GST with highest activity toward 4-HNE. When treated with 4-HNE, mGSTA4-transfected cells showed significant upregulation of iNOS and nitric oxide (NO) through (NF)-kappaB (p65) translocation in comparison with wild-type or vector-transfected cells. Immunohistochemical studies of early human plaques showed lower 4-HNE content and upregulation of iNOS, which we take to indicate that GSTA4-4 induction acts as an enzymatic defense against high levels of 4-HNE, since 4-HNE accumulated in more advanced plaques, when detoxification and exocytotic mechanisms are likely to be overwhelmed. These studies suggest that GSTA4-4 may play an important defensive role against atherogenesis through detoxification of 4-HNE and upregulation of iNOS.

Skeletal muscle changes after hemiparetic stroke and potential beneficial effects of exercise intervention strategies

Stroke is the leading cause of disability in the United States. New evidence reveals significant structural and metabolic changes in skeletal muscle after stroke. Muscle alterations include gross atrophy and shift to fast myosin heavy chain in the hemiparetic (contralateral) leg muscle; both are related to gait deficit severity. The underlying molecular mechanisms of this atrophy and muscle phenotype shift are not known. Inflammatory markers are also present in contralateral leg muscle after stroke. Individuals with stroke have a high prevalence of insulin resistance and diabetes. Skeletal muscle is a major site for insulin-glucose metabolism. Increasing evidence suggests that inflammatory pathway activation and oxidative injury could lead to wasting, altered function, and impaired insulin action in skeletal muscle. The health benefits of exercise in disabled populations have now been recognized. Aerobic exercise improves fitness, strength, and ambulatory performance in subjects with chronic stroke. Therapeutic exercise may modify or reverse skeletal muscle abnormalities.

Induction of neutrophil gelatinase-associated lipocalin in vascular injury via activation of nuclear factor-kappaB

Neutrophil gelatinase-associated lipocalin (NGAL) has recently emerged as an important modulator of cell homeostasis. Elevated plasma NGAL levels, possibly because of activation of blood leukocytes, are associated with atherosclerosis. However, little is known about induction of NGAL expression in blood vessels. Using a rat carotid artery injury model, we found that NGAL was highly induced in the intima after angioplasty but was attenuated by adenovirus-mediated expression of a dominant-negative mutant of inhibitor of nuclear factor (NF)-kappaB kinase beta (dnIKKbeta). Expression of NGAL mRNA and protein was also up-regulated in an NF-kappaB-dependent manner in rat and human vascular smooth muscle cells (SMCs) in response to interleukin-1beta stimulation. Rat SMC-produced NGAL was present as mono- and homomeric forms in the cytosol and in a complex containing matrix metalloproteinase-9 (MMP-9) after secretion. In agreement with levels of NGAL, proteolytic activity of MMP-9 was markedly high in the intima of injured vessels and in the culture supernatant of activated intimal SMCs but was reduced in the vessels transduced with dnIKKbeta. The present study reveals a previously unrecognized vascular response to an-gioplastic injury, characterized by NF-kappaB-dependent expression of NGAL in vascular SMCs. Further-more, SMC-produced NGAL interacts with MMP-9, a mechanism by which NGAL may modulate MMP-9 proteolytic activity in the vascular repair process.

Age-dependent lipopolysaccharide-induced iNOS expression and multiorgan failure in rats: effects of melatonin treatment

Senescence amplifies the sensitivity to endotoxemia, which correlates with increased nitric oxide (NO) levels and mortality. Melatonin displays antioxidant and anti-inflammatory effects, but its levels decrease with age. Lipopolysaccharide (LPS) (10 mg/kg) was injected to 3- and 18-month-old rats 6 h before they were killed, and melatonin (60 mg/kg) was injected before and/or after LPS. Inducible nitric oxide synthase (iNOS) expression and activity, nitrite content, lipoperoxidation (LPO) levels, and serum markers of liver, renal, and metabolic dysfunction, were measured in liver and lung of these animals. An age-dependent increase in iNOS activity, NO content, and LPO levels was observed, and these changes were augmented further by LPS. Melatonin decreased the expression and activity of iNOS, reducing NO and LPO levels to basal values in both septic LPS-treated groups. Liver, kidney, and metabolic dysfunctions were also significantly higher in aged that in young rats and further increased by LPS. Melatonin treatment counteracted these alterations in young and aged septic rats. Melatonin reduced LPS-dependent iNOS expression and multiorgan failure in a similar extent in young and aged rats. Because aged rats showed higher organ and metabolic impairment than young animals in response to LPS, the results also suggest an increased efficacy of the anti-septic properties of melatonin in the aged animals.

Neopterin induces pro-atherothrombotic phenotype in human coronary endothelial cells

BACKGROUND

Inflammation plays a pivotal role in atherothrombosis. Recent data indicate that serum levels of neopterin, a marker of inflammation and immune modulator secreted by monocytes/macrophages, are elevated in patients with acute coronary syndromes and seem to be a prognostic marker for major cardiovascular events. The aim of the present study was to determine whether neopterin might affect the thrombotic and atherosclerotic characteristics of human coronary artery endothelial cells (HCAECs).

METHODS AND RESULTS

In HCAECs, neopterin induced TF-mRNA transcription as demonstrated by real time polymerase chain reaction and expression of functionally active tissue factor (TF) as demonstrated by procoagulant activity assay, and of cellular adhesion molecules (CAMs) as demonstrated by FACS analysis, in a dose-dependent fashion. These neopterin effects were prevented by lovastatin, a HMG-CoA reductase inhibitor. Neopterin-induced TF and CAMs expression was mediated by oxygen free radicals through the activation of the transcription factor, nuclear factor-kappa B (NF-kappaB), as demonstrated by electrophoretic mobility shift assay and by suppression of CAMs and TF expression by superoxide dismutase and by NF-kappaB inhibitor, pyrrolidine-dithio-carbamate ammonium.

CONCLUSIONS

These data indicate that neopterin exerts direct effects on HCAECs by promoting CAMs and TF expression and support the hypothesis that neopterin, besides representing a marker of inflammation, might be an effector molecule able to induce a pro-atherothrombotic phenotype in cells of the coronary circulation.

Aging, smooth muscle cells and vascular pathobiology: Implications for atherosclerosis

Epidemiological and autopsy studies suggest a close link between aging and the clinical manifestation of atherosclerosis. Several experiments show increased arterial susceptibility to atherogenetic stimuli in aged subjects. All together, these findings support the concept that aging represents an independent atherogenetic risk factor, intimately associated to other parietal, microenvironmental and systemic noxae. Smooth muscle cells (SMCs) represent the major arterial cell population. As aging occurs, SMCs progressively migrate from the tunica media and accumulate into the tunica intima. Myointimal thickening may represent the site where low-grade atherogenic stimuli cause early development and more severe lesion progression. Intimal SMC accumulation is characterized from a switch, from a differentiated to a synthetic phenotype, with reduced myocytic cytoskeletal markers and the expression of new proteins. Aging also associates to changes of SMC proliferative and apoptotic behavior and response to growth factors, such as transforming growth factor-beta1. The alteration of SMC properties represents a crucial event in the pathobiology of arterial wall, since it contributes to the vascular remodeling and decline of function with aging and favors the progression of atherosclerosis. Increased knowledge of biomolecular mechanisms regulating these events helps to develop new strategies aimed at contrasting the adverse effect of vascular aging.

Molecular mechanisms of aging-associated inflammation

A direct relationship exists between aging and increasing incidences of chronic diseases. In fact, with most age-associated diseases individuals manifest an underlying chronic inflammatory state as evidenced by local infiltration of inflammatory cells, such as macrophages, and higher circulatory levels of pro-inflammatory cytokines, complement components and adhesion molecules. Consequently, treatment with anti-inflammatory agents provide symptomatic relief to several aging-associated diseases, even as remote as Alzheimer's or Parkinson's disease, indicating that chronic inflammation may play a substantial role in the pathogenesis of these disease states. The molecular mechanisms underlying this chronic inflammatory condition during cellular senescence is presently unclear. Cellular damage by oxygen free radicals is a primary driving force for aging and increased activation of redox-regulated transcription factors, such as NF-kappaB that regulate the expression of pro-inflammatory molecules, has been documented in aged animals/individuals versus their young counterparts. Human polynucleotide phosphorylase (hPNPase(old-35)), a RNA degradation enzyme shown to be upregulated during differentiation and cellular senescence, may represent a molecular link between aging and its associated inflammation. hPNPase(old-35) promotes reactive oxygen species (ROS) production, activates the NF-kappaB pathway and initiates the production of pro-inflammatory cytokines, such as IL-6 and IL-8. In these contexts, inhibition of hPNPase(old-35) may represent a novel molecular target for intervening in aging-associated chronic diseases.

High glucose enhances inducible nitric oxide synthase expression. Role of protein kinase C-betaII

The aim was to determine whether high glucose levels interfere with nitric oxide (NO) production and inducible NO synthase (iNOS) protein expression in interleukin-1beta-stimulated vascular smooth muscle cells from normotensive Wistar Kyoto and spontaneously hypertensive rats. Cells were incubated with either normal (5.5 mM) or high (22 mM) d-glucose for 72 h and with interleukin-1beta (10 ng/ml) for the last 24 h. High glucose increased nitrite levels, iNOS expression and protein kinase C activity in cells from normotensive rats and had no effect in cells from hypertensive rats. High glucose effects on nitrite production and iNOS expression was abolished by the selective inhibitor for the protein kinase C-betaII, 5,21:12,17-dimetheno-18H-dibenzo[i,o]pyrrolo[3,4-1] [1,8]diacyclohexadecine-18,20 (19H)-dione, 8-[(dimethylamino) methyl]-6,7,8,9,10,11-hexahydro-monomethanesulfonate (LY379196, 30 nM). Calphostin C (1 microM) and LY379196 (10 microM) reduced nitrite levels and iNOS expression only in cells from normotensive rats treated with both media. These results suggest that high glucose increases inducible nitric oxide synthase induction and subsequent NO production by activating the protein kinase C-betaII; this mechanism seems to be altered in hypertension.

Angiotensin II activates matrix metalloproteinase type II and mimics age-associated carotid arterial remodeling in young rats

Increased angiotensin II (Ang II), matrix metalloproteinase type II (MMP2), and sympathetic activity accompany age-associated arterial remodeling. To analyze this relationship, we infused a low subpressor dose of Ang II into young (8 months old) rats. This increased carotid arterial MMP2 transcription, translation, and activation, as well as transforming growth factor-beta1 activity and collagen deposition. A higher Ang II concentration, which increased arterial pressure to that of old (30 months old) untreated rats, produced carotid media thickening and intima infiltration by vascular smooth muscle cells (VSMCs). Ex vivo, Ang II increased MMP2 activity in carotid rings from young rats to that of untreated old rats. Ang II also increased the ability of early passage VSMCs from young rats to invade a synthetic basement membrane, similar to that of untreated VSMCs from old rats. The MMP inhibitor GM6001 and the AT1 receptor antagonist Losartan inhibited these effects. The alpha-adrenoreceptor agonist phenylephrine increased arterial Ang II protein, causing MMP2 activation and intima and media thickening. Exposure of young VSMCs to phenylephrine in vitro increased Ang II protein and MMP2 activity to the levels of old VSMCs; Losartan abolished these effects. Thus, Ang II-induced effects on MMP2, transforming growth factor-beta1, collagen, and VSMCs are central to the arterial remodeling that accompanies advancing age.

Changes in the human peritoneal mesothelial cells during aging

The number of older patients admitted to peritoneal dialysis (PD) programmes is growing. At the same time, there is increasing data about the role of mesothelial cells in determining the functional alteration of the peritoneum during PD. However, little is known about the functional changes accompanying the ageing process in mesothelial cells. We aimed to evaluate whether the aging process is accompanied by changes in some functional characteristic of the human peritoneal mesothelial cells (HPMC), which could account for the poor prognosis observed in old patients with PD. HPMCs were isolated from patients undergoing a nonurgent, nonseptic abdominal surgical procedure, without renal, vascular or inflammatory disease. Cytokine levels (by enzyme-linked immunosorbent assay (ELISA)), nitrates+nitrites, and cyclooxygenase (COX) activity (by a chemiluminescence assay), cytokines, COX, nitric oxide synthase (NOS), and nuclear factor (NF)-kappaB1, two messenger ribonucleic acid (mRNA) gene expressions (by reverse transcriptase (RT)-Multiplex PCR), COX, and NOS promoter gene activities, and NF-kappaB-dependent transcription (by transient transfection assays) were determined. Our data show a significant increase in cytokines, COX, and NOS activities, and mRNA expression of cytokines, COX-2, inducible nitric oxide synthase (iNOS) and precursors of NF-kappaB in HPMCs from old people. This was also the case for COX-2 and iNOS promoter gene activities and NF-kappaB-dependent transcription. There was a positive correlation between the age of the donor's cell and the proinflammatory profile of the HPMCs. Such age-dependent increase (around two-three times) is partially abolished by different antioxidant or free-radical scavengers. Thus, aging is accompanied by the presence of an inflammatory state in HPMCs, which involves the participation of different reactive oxygen species.

IKKbeta-dependent NF-kappaB pathway controls vascular inflammation and intimal hyperplasia

Nuclear factor-kappaB (NF-kappaB)-mediated vascular inflammation is a prominent characteristic of atherogenesis and restenosis. We noted that angioplastic injury to carotid artery elicited two phases of NF-kappaB activation characterized by an early activation in the arterial media and a late activation coupled with high levels of inhibitor of IkappaB kinase (IKK) activity in intima. These findings prompted us to elucidate the role for the different phases of NF-kappaB activation and IKK in the progress of vascular repair. Our results show that blockade of the early NF-kappaB activation by perivascular administration of pyrrolidine dithiocarbamate transiently attenuates the expression of proinflammatory genes in the injured vessels but does not affect intimal formation. Interruption of IKKbeta by overexpressing a dominant-negative IKKbeta in the injured artery effectively inhibited the late phase of NF-kappaB activation, resulting in down-regulation of inducible nitric oxide synthase, tumor necrosis factor alpha, and monocyte chemoattractant protein-1 expression in conjunction with a 36% reduction in intima size, albeit with a lack of inhibitory effect on the early NF-kappaB activation. Collectively, these findings show that the IKKbeta-mediated late-phase NF-kappaB activation contributes to intimal hyperplasia and the accompanied vascular inflammatory responses.

Development of age-dependent glomerular lesions in galectin-3/AGE-receptor-3 knockout mice

Aging is characterized by renal functional and structural abnormalities resembling those observed in diabetes. These changes have been related to the progressive accumulation of advanced glycation end-products (AGEs) and cumulative oxidative stress occurring in both conditions. We previously reported that galectin-3 ablation is associated with increased susceptibility to diabetes- and AGE-induced glomerulopathy, thus indicating a protective role of galectin-3 as an AGE receptor. To investigate the role of the AGE/AGE receptor pathway in the pathogenesis of age-related renal disease, we evaluated the development of glomerular lesions in aging galectin-3 knockout (KO) vs. wild-type (WT) mice and their relation to the increased AGE levels and oxidative stress characterizing the aging process. KO mice showed significantly more pronounced age-dependent increases in proteinuria, albuminuria, glomerular sclerosis, and glomerular and mesangial areas, starting at 18 mo, as well as renal extracellular matrix mRNA and protein expression, starting at 12 mo vs. age-matched WT mice. Circulating and renal AGEs, plasma isoprostane 8-epi-PGF2alpha levels, glomerular content of the glycoxidation and lipoxidation products N(epsilon)-carboxymethyllysine and 4-hydroxy-2-nonenal, and renal nuclear factor-kappaB activity also increased more markedly with age in KO than WT mice. AGE levels correlated significantly with renal functional and structural parameters. These data indicate that aging galectin-3 KO mice develop more pronounced changes in renal function and structure than coeval WT mice, in parallel with a more marked degree of AGE accumulation, oxidative stress, and associated low-grade inflammation, thus supporting the concept that the AGE/AGE receptor pathway is implicated in age-related renal disease.

Modulation of smooth muscle cell proliferation and migration: role of smooth muscle cell heterogeneity

Proliferation and migration of smooth muscle cells (SMCs) from the media towards the intima are key events in atherosclerosis and restenosis. During these processes, SMC undergo phenotypic modulations leading to SMC dedifferentiation. The identification and characterization of factors controlling these phenotypic changes are crucial in order to prevent the formation of intimal thickening. One of the questions which presently remains open, is to know whether any SMCs of the media are capable of accumulating into the intima or whether only a predisposed medial SMC subpopulation is involved in this process. The latter hypothesis implies that arterial SMCs are phenotypically heterogenous. In this chapter, we will describe the distinct SMC phenotypes identified in arteries of various species, including humans. Their role in the formation of intimal thickening will be discussed.

Human polynucleotide phosphorylase (hPNPaseold-35): a potential link between aging and inflammation

Chronic inflammation is a characteristic feature of aging, and the relationship between cellular senescence and inflammation, although extensively studied, is not well understood. An overlapping pathway screen identified human polynucleotide phosphorylase (hPNPase(old-35)), an evolutionary conserved 3',5'-exoribonuclease, as a gene up-regulated during both terminal differentiation and cellular senescence. Enhanced expression of hPNPase(old-35) via a replication-incompetent adenovirus (Ad.hPNPase(old-35)) in human melanoma cells and normal human melanocytes results in a characteristic senescence-like phenotype. Reactive oxygen species (ROS) play a key role in the induction of both in vitro and in vivo senescence. We now document that overexpression of hPNPase(old-35) results in increased production of ROS, leading to activation of the nuclear factor (NF)-kappaB pathway. Ad.hPNPase(old-35) infection promotes degradation of IkappaBalpha and nuclear translocation of NF-kappaB and markedly increases binding of the transcriptional activator p50/p65. The generation of ROS and activation of NF-kappaB by hPNPase(old-35) are prevented by treatment with a cell-permeable antioxidant, N-acetyl-l-cysteine. Infection with Ad.hPNPase(old-35) enhances the production of interleukin (IL)-6 and IL-8, two classical NF-kappaB-responsive cytokines, and this induction is inhibited by N-acetyl-l-cysteine. A cytokine array reveals that Ad.hPNPase(old-35) infection specifically induces the expression of proinflammatory cytokines, such as IL-6, IL-8, RANTES, and matrix metalloproteinase (MMP)-3. We hypothesize that hPNPase(old-35) might play a significant role in producing pathological changes associated with aging by generating proinflammatory cytokines via ROS and NF-kappaB. Understanding the relationship between hPNPase(old-35) and inflammation and aging provides a unique opportunity to mechanistically comprehend and potentially intervene in these physiologically important processes.

Endogenous prostacyclin increases neuronal nitric oxide release in mesenteric artery from spontaneously hypertensive rats

The aim of this study was to analyse the possible influence of endogenous prostacyclin on neuronal nitric oxide (NO) release induced by electrical field stimulation in mesenteric arteries from spontaneously hypertensive rats (SHR). Preincubation with the prostacyclin synthesis inhibitor tranylcypromine decreased NO release induced by electrical field stimulation, which was reversed by exogenous prostacyclin. Preincubation with tranylcypromine increased basal and electrical field stimulation-induced [3H]noradrenaline release. The nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl esther (L-NAME) increased the vasoconstrictor response induced by electrical field stimulation. In the presence of tranylcypromine, L-NAME did not modify the vasoconstrictor response induced by electrical field stimulation. In the presence of tranylcypromine and prostacyclin, LNAME increased the vasoconstrictor response to electrical field stimulation. These results indicate that endogenous prostacyclin positively modulates the neuronal NO release induced by electrical field stimulation and that this neuronal NO participates in the regulation of the vasomotor response.

Functional and molecular evidence of MaxiK channel beta1 subunit decrease with coronary artery ageing in the rat

Large-conductance, voltage- and Ca2+ -activated K+ channels (MaxiK, BK) are key regulators of vascular tone. Vascular MaxiK are formed by the pore-forming alpha subunit and the modulatory beta1 subunit, which imprints unique kinetics, Ca2+/voltage sensitivities and pharmacology to the channel. As age progresses, alpha subunit functional expression and protein levels diminish in coronary myocytes. However, whether ageing modifies beta1 subunit expression or the mechanism of alpha subunit reduction is unknown. Thus, we examined functional and pharmacological characteristics of MaxiK, as well as alpha and beta1 transcript levels in coronary myocytes from young and old F344 rats. The mechanism of age-dependent alpha subunit protein reduction involves its transcript downregulation. A corresponding loss of beta1 transcripts was also detected in old myocytes, suggesting a proportional age-dependent decrease of beta1 to alpha subunit protein. Indeed, MaxiK channel properties, defined by coassembly of beta1 and alpha subunits, were equivalent in young versus old, for example in terms of (i) activation kinetics, (ii) sensitivity to Ca2+ levels > 1 microm (iii) dehydrosoyasaponin-I-induced activation, and (iv) iberiotoxin blockade. Consistent with less MaxiK expression/function in older myocytes, the ability of iberiotoxin to contract coronary rings was reduced approximately 50% with ageing confirming our previous findings. 5-Hydroxytryptamine (5-HT) contractile efficacy was reduced by iberiotoxin pretreatment in young > old coronary arteries (explained by larger iberiotoxin-induced contraction and decreased dynamic range for 5-HT contraction in young versus old) with no apparent differences in nitroglycerine-induced relaxation. We propose that the age-related MaxiK reduction involves a parallel decrease of alpha and beta1 functional expression via a transcript downregulatory mechanism; a major impact on basal and possibly stimulated coronary contraction may contribute to altered coronary flow regulation and coronary morbidity in the elderly.

Involvement of Rel/NF-kappa B transcription factors in senescence

Senescence is now established as a genetically controlled phenomenon that alters different cell functions, including proliferation, apoptosis, resistance to stress, and energetic metabolism. Underlying changes in gene expression are governed by some transcription factors, whose expression or activity must change with senescence as well. Transcription factors of the Rel/NF-kappa B family are good candidates to participate in the establishment of senescence. Arguments range from correlation between cell functions controlled by these factors and cell functions altered during senescence, to phenotypes resulting from in vitro manipulations of Rel/NF-kappa B activity.

Overexpressed nuclear factor kappaB correlates with enhanced expression of interleukin-1beta and inducible nitric oxide synthase in aged murine lungs to endotoxic stress

BACKGROUND

Transcriptional regulation is a major determinant of interleukin-1beta (IL-1beta) protein synthesis. Nuclear factor kappaB (NF-kappaB) plays a central role in the regulation of IL-1beta and subsequent IL-1beta-dependent inflammatory processes. Previously, we observed in a murine endotoxic stress model a progressive increase with age in the amount of IL-1beta mRNA. We test the aging pulmonary response of NF-kappaB and NF-kappaB-dependent genes, IL-1beta, and inducible nitric oxide synthase (iNOS) in the same model.

METHODS

Young (2-month-old) and senescent (25-month-old) mice were given 0.5 mg/kg lipopolysaccharide (LPS) intraperitoneally. Lung and blood samples were harvested after 4 hours. IL-1beta production in blood samples and the expression levels of protein and mRNA of IL-1beta and iNOS in lung tissues were measured. NF-kappaB binding activity in lung tissues was also determined.

RESULTS

LPS induced higher levels of IL-1beta in the sera and lungs of senescent mice over young mice. Northern and Western blot analyses showed that mRNA and protein signals of IL-1beta and iNOS were significantly higher in old lungs than in young lungs. Electrophoretic mobility shift assay also showed that NF-kappaB activation was significantly higher in the older animals.

CONCLUSIONS

Our results suggest that elevated activation of NF-kappaB, at least in part, contributes to the dysregulated expression of IL-1beta and iNOS in the lungs of senescent animals. Thus increased expression of proinflammatory cytokines and inflammatory responsive genes in the lung may play a role in the increased susceptibility in aging animals to endotoxic stress.

Involvement of Rel/nuclear factor-kappaB transcription factors in keratinocyte senescence

After a finite doubling number, normal cells become senescent, i.e., nonproliferating and apoptosis resistant. Because Rel/nuclear factor (NF)-kappaB transcription factors regulate both proliferation and apoptosis, we have investigated their involvement in senescence. cRel overexpression in young normal keratinocytes results in premature senescence, as defined by proliferation blockage, apoptosis resistance, enlargement, and appearance of senescence-associated beta-galactosidase (SA-beta-Gal) activity. Normal senescent keratinocytes display a greater endogenous Rel/NF-kappaB DNA binding activity than young cells; inhibiting this activity in presenescent cells decreases the number of cells expressing the SA-beta-Gal marker. Normal senescent keratinocytes and cRel-induced premature senescent keratinocytes overexpressed manganese superoxide dismutase (MnSOD), a redox enzyme encoded by a Rel/NF-kappaB target gene. MnSOD transforms the toxic O()(2) into H(2)O(2), whereas catalase and glutathione peroxidase convert H(2)O(2) into H(2)O. Neither catalase nor glutathione peroxidase is up-regulated during cRel-induced premature senescence or during normal senescence, suggesting that H(2)O(2) accumulates. Quenching H(2)O(2) by catalase delays the occurrence of both normal and premature cRel-induced senescence. Conversely, adding a nontoxic dose of H(2)O(2) to the culture medium of young normal keratinocytes induces a premature senescence-like state. All these results indicate that Rel/NF-kappaB factors could take part in the occurrence of senescence by generating an oxidative stress via the induction of MnSOD.

Age- and endothelium-dependent changes in coronary artery reactivity to serotonin and calcium

The influence of ageing and endothelium removal on the sensitivity and contractile response of rat coronary arteries to intracellular Ca2+ ([Ca2+]i) during activation with serotonin (5-HT) and membrane depolarisation with 125 mM K+ was investigated. The sensitivity and contractile response of coronary arteries to 5-HT were significantly higher in 2-year-old than in 3-month-old rats. The receptor responsible for the 5-HT-induced contractions in coronary arteries belongs to a population of 5-HT2 receptors in both young and old rats based on the Schild plot. The resting levels of [Ca2+]i and active tension were both increased by age and endothelium removal. During depolarisation with 125 mM K+, the sensitivity to [Ca2+]i and maximal tension induced by [Ca2+]i were not affected by age or endothelium. During activation with 10 microM 5-HT, the maximal tension induced by [Ca2+]i was increased by age but not affected by endothelium, whereas the sensitivity to [Ca2+]i was increased by endothelium removal. In conclusion, ageing is associated with an increased sensitivity to 5-HT in rat coronary small arteries. The increased sensitivity to 5-HT seems to involve an augmented contractile response to [Ca 2+]i in 5-HT-activated coronary arteries and a diminished endothelial basal vasodilator function.

Age-associated increase in oxidative stress and nuclear factor kappaB activation are attenuated in rat liver by regular exercise

The combined effects of aging and regular physical exercise was investigated on the production of reactive oxygen species (ROS), lipid peroxidation, glutathione status, and the activity of nuclear factor-kappaB (NF-kappaB) in rat liver. A group of 24 male F344 rats was divided into the following categories: adult control (18 months), adult exercised (18 months), and aged control (28 months) and aged exercised (28 months). The ROS formation increased as a function of age and exercise training decreased the rate of ROS formation in the two age groups. Significant positive correlation was found between ROS production and lipid peroxidation (LIPOX). The reduced glutathione (GSH) level was higher and the oxidized glutathione (GSSG) level lower in exercised groups compared with the sedentary controls (P<0.05). An age-associated increase in NF-kappaB activity was attenuated by the regular exercise. The content of p50 and p65 subunits of NF-kappaB increased with age and decreased with exercise training. The content of inhibitory factor-kappaB was inversely related to NF-kappaB activation. Regular exercise-induced adaptive responses, including attenuation of an increase in ROS production, LIPOX level, NF-kappaB activation, and reduced GSH/GSSG ratio, appear to be capable, even in old age, of reducing increases in inflammatory and other detrimental consequences that are often associated with advancing age.

Role of redox imbalance in the molecular mechanisms responsible for immunosenescence

The elderly suffer impairments to their immune system, evidenced by higher susceptibility to infections, cancer, and many diseases believed to be autoimmune in nature. A dysregulated overexpression of many proinflammatory cytokines also occurs with aging, as does the synthesis of enzymes that control expression of inflammatory lipid mediators and reactive oxygen species. An inappropriate activation of redox-controlled transcription factors, like nuclear factor-kappaB, occurs in many tissues from aged donors, and has been linked to excesses in cellular oxidative stress. Recently, the peroxisome proliferator-activated receptor-alpha (PPARalpha) has been evaluated for its effects on inflammatory and adaptive immune processes. PPARalpha provides redox-balancing influences on various lymphoid cell types and their inducible responses. We recently discovered that PPARalpha transiently suppresses the transcription of gamma-interferon (IFNgamma) by inhibiting the induction of T-bet. We now report that PPARalpha expression in CD4+ T cells is affected by the aging process. Lower PPARalpha levels are present in aged CD4+ T cells, and appear responsible for the suppressed interleukin-2 and exaggerated IFNgamma responses by these cells. Restoration of PPARalpha, T-bet, interleukin-2, and IFNgamma responses was found in T cells from aged animals supplemented with vitamin E, suggesting that interventions that focus on restoring redox balance might benefit the ailing aged immune system.

Age-related increases in LPS-stimulated nitric oxide production from cultured rat bone marrow cells

OBJECTIVE

To understand bone metabolism during senescence, we examined age-related change in nitric oxide (NO) production from bone marrow cells stimulated by lipopolysaccharide (LPS).

METHODS

We evaluated the age-related change in the NO production and expression of iNOS protein and mRNA of LPS-stimulated bone marrow cells collected from the tibiae of young and retired female and young and retired male rats. In addition, we used flow cytometry to assess changes in the distribution of CD14, a cell surface receptor of LPS.

RESULTS

The results revealed that NO production from bone marrow cells stimulated with LPS changed with aging. The NO levels in old rats were significantly higher (P<0.05) than those in young rats. Polymerase chain reaction (PCR) analysis indicated that the LPS-induced expression of iNOS mRNA was augmented in retired rats. Although the distribution pattern of the bone marrow cells was similar between young and retired rats, the percentage of CD14-positive cells in specific populations differed between the age groups. Specifically, in the granule-containing bone marrow cells, the percentage of CD14-positive cells was increased in retired rats.

CONCLUSION

Our results indicate that LPS-stimulated NO production from rat bone marrow cells increased with age and that the difference in responsiveness might be due to changes in the percentage of CD14-positive cells in the bone marrow.

Inducible nitric oxide synthase is present in human abdominal aortic aneurysm and promotes oxidative vascular injury

OBJECTIVE

Nitric oxide (NO), catalyzed by inducible NO synthase (iNOS), may be important in the pathophysiologic characteristics of many vascular diseases. Although there is indirect evidence to support the presence of iNOS in abdominal aortic aneurysm (AAA) in human beings, no definitive study has confirm this finding. The present study was designed to assess expression of iNOS in AAA in human beings. Furthermore, the activity of iNOS and the oxidative vascular injury initiated by iNOS were assessed with detection of nitrotyrosine, which is a marker indicative of formation and activity of the NO-derived oxidant peroxynitrite.

METHODS

We studied 25 patients with AAA and 10 patients with normal abdominal aortas. In situ hybridization and immunohistochemistry were used in tissue sections to localize iNOS messenger RNA (mRNA) and protein. Double staining with a combination of in situ hybridization and immunohistochemistry was used to simultaneously demonstrate iNOS mRNA expression and its cellular localization. The presence of peroxynitrite was indirectly assessed with immunostaining with anti-nitrotyrosine antibodies.

RESULTS

In situ hybridization and immunohistochemistry confirmed the presence of iNOS in media and adventitia of AAA in all 25 patients. Specific cell markers identified iNOS mRNA-positive cells mainly as T and B lymphocytes, macrophages, and smooth muscle cells. Positive immunostaining for nitrotyrosine was present in macrophages and smooth muscle cells. Normal abdominal aorta demonstrated virtually no iNOS or nitrotyrosine expression.

CONCLUSION

Stimulated expression of iNOS is associated with degeneration of AAA in human beings, and the activity of this enzyme under such conditions preferentially promotes formation and activity of peroxynitrite and further contributes to oxidative tissue and cellular injury in AAA. This may be important in the pathogenesis of AAA.

Aging-induced proinflammatory shift in cytokine expression profile in coronary arteries

The phenotypic and functional changes of coronary arteries with aging promote ischemic heart disease. We hypothesized that these alterations reflect an aging-induced proinflammatory shift in vascular regulatory mechanisms. Thus, in isolated coronary arteries of young (3-month-old) and aged (25-month-old) male Fischer 344 rats the expression of 96 cytokines, chemokines, and their receptors were screened by a cDNA-based microarray technique. In aged vessels expressions of tumor necrosis factor (TNF)-alpha (3.3x), interleukin (IL)-1beta (3.0x), IL-6 (2.9x), IL-6Ralpha (2.8x) and IL-17 (6.1x) genes were significantly increased over young vessels. Quantitative reverse transcriptase-polymerase chain reaction confirmed these results. Western blotting demonstrated that protein expressions of TNF-alpha, IL-1beta, IL-6, and IL-17 were also significantly increased in vessels of aged rats compared with those of young rats. Immunofluorescent double labeling showed that in aged vessels IL-1beta and IL-6 are predominantly localized in the endothelium, whereas TNF-alpha and IL-17 are localized in smooth muscle. Thus, a proinflammatory shift in the profile of vascular cytokine expression may contribute to the aging-induced phenotypic changes in coronary arteries, promoting the development of ischemic heart disease in the elderly.

Ceramide-induced and age-associated increase in macrophage COX-2 expression is mediated through up-regulation of NF-kappa B activity

We have shown that the age-associated increase in lipopolysaccharide (LPS)-stimulated macrophages (M phi) prostaglandin E(2) (PGE(2)) production is because of ceramide-induced up-regulation of cyclooxygenase (COX)-2 transcription that leads to increased COX-2 expression and enzyme activity. To determine the mechanism of the age-related and ceramide-dependent increase in COX-2 transcription, we investigated the role of various transcription factors involved in COX-2 gene expression. The results showed that LPS-initiated activations of both consensus and COX-2-specific NF-kappa B, but not AP-1 and CREB, were significantly higher in M phi from old mice than those from young mice. We further showed that the higher NF-kappa B activation in old M phi was because of greater I kappa B degradation in the cytoplasm and p65 translocation to the nucleus. An I kappa B phosphorylation inhibitor, Bay 11-7082, inhibited NF-kappa B activation, as well as PGE(2) production, COX activity, COX-2 protein, and mRNA expression in both young and old M phi. Similar results were obtained by blocking NF-kappa B binding activity using a NF-kappa B decoy. Furthermore, NF-kappa B inhibition resulted in significantly greater reduction in PGE(2) production and COX activity in old compared with young M phi. Addition of ceramide to the young M phi, in the presence or absence of LPS, increased NF-kappa B activation in parallel with PGE(2) production. Bay 11-7082 or NF-kappa B decoy prevented this ceramide-induced increase in NF-kappa B binding activity and PGE(2) production. These findings strongly suggest that the age-associated and ceramide-induced increase in COX-2 transcription is mediated through higher NF-kappa B activation, which is, in turn, because of a greater I kappa B degradation in old M phi.

Neuronal and inducible nitric oxide synthase expressions and activities in the hippocampi and cortices of young adult, aged cognitively unimpaired, and impaired Long-Evans rats

Nitric oxide (NO) is a neurosignaling molecule that appears to play a significant role in learning and memory. This molecule has also been implicated in neurotoxicity due to its oxidative properties. Previous experiments from our laboratories have demonstrated elevated hippocampal and cortical neuronal nitric oxide synthase (NOS) mRNA levels in aged cognitively unimpaired and impaired Long-Evans rats, which could represent either increased neuronal NOS activity thereby leading to NO-mediated neurotoxicity, or a compensatory response by aged neurones to maintain physiological nitric oxide output. The current study measured the protein expression and activity levels of neuronal and inducible NOS in young adult (6 months) and aged (24-26 months) Long-Evans rats by means of western blotting and NOS activity assay. Aged animals were assigned as either cognitively unimpaired or aged with moderate cognitive impairments based on their performances in the Morris water maze behavioural task. Our results showed that hippocampal and cortical neuronal NOS expressions were significantly decreased in aged animals. These aged animals also exhibited increased hippocampal and cortical inducible NOS expressions. Between the two aged animal groups, cognitively impaired rats showed significantly lower hippocampal and cortical neuronal but higher hippocampal inducible NOS expressions. Young adult rats exhibited significantly higher hippocampal and cortical NOS activities than the aged animals. Aged animals with cognitive deficits showed significantly lower hippocampal NOS activity than cognitively unimpaired aged rats. Our data indicate that aging is associated with a decline in neuronal but elevated inducible NOS functioning in brain areas involved in learning and memory. These phenomena could contribute to the cognitive deficits observed in a sub-population of aged animals.

Hyperglycemia enhances VSMC proliferation with NF-kappaB activation by angiotensin II and E2F-1 augmentation by growth factors

To clarify the mechanisms of hyperglycemia-induced proliferation of vascular smooth muscle cells (VSMC), we examined the effects of high glucose (HG) on nuclear factor (NF)-kappaB and E2F-1. Angiotensin II (Ang II) significantly enhanced DNA binding activity of NF-kappaB under HG (25.6 mM) conditions with an increase in p65 subunit of NF-kappaB, and did it slightly under normal glucose (NG; 5.6 mM) conditions. Ang II failed to induce E2F-1 expression, or its binding to the cdc2 promoter, even under HG conditions. HG greatly augmented the cdc2 inducibility of fetal calf serum (FCS), through the increase in E2F-1 activity. These data indicate that hyperglycemia contributes to abnormal proliferation of VSMC by two mechanisms; the induction of NF-kappaB activation by Ang II, which facilitates transcription of certain growth factors, and the augmentation of E2F-1 in response to growth factors.

Alpha-lipoic acid modulates NF-kappaB activity in human monocytic cells by direct interaction with DNA

The constitutive activity of the redox-sensitive transcription factor, NF-kappaB, which regulates the production of many inflammatory cytokines and adhesion molecules, appears to be up-regulated in an age-associated manner and it is thought this might contribute to the increased incidence of chronic inflammatory conditions observed with increasing age. As some antioxidants have demonstrated protective effects against rheumatoid arthritis, we are investigating the effects of vitamin E, vitamin C and alpha-lipoic acid (ALA) on NF-kappaB activity and on the expression of intracellular adhesion molecule (ICAM)-1. MonoMac6 cells (a human monocytic cell line) stimulated with tumour necrosis factor-alpha (TNF-alpha) were treated with antioxidants at physiological achievable levels and ICAM-1 mRNA levels investigated. Both vitamin E and vitamin C had no effect on ICAM-1 expression at the doses used, but ALA reduced the TNF-alpha-stimulated ICAM-1 expression in a dose-dependent manner, to levels observed in unstimulated cells. Alpha-lipoic acid also reduced NF-kappaB activity in these cells in a dose-dependent manner. Addition of ALA to the binding reaction of nuclear extract with DNA prior to gel-shift analysis showed that it caused inhibition at this level. These initial results suggest that antioxidant modulation of monocyte activity might have potential benefits in inhibiting the dysregulated activity of redox-sensitive transcription factors that occurs with increasing age.

Activation of macrophage nuclear factor-kappa B and induction of inducible nitric oxide synthase by LPS

BACKGROUND

Chronic lung disease (CLD) of prematurity is a major problem of neonatal care. Bacterial infection and inflammatory response have been thought to play an important role in the development of CLD and steroids have been given, with some benefit, to neonates with this disease. In the present study, we assessed the ability of lipopolysaccharide (LPS) to stimulate rat alveolar macrophages to produce nitric oxide (NO), express inducible nitric oxide synthase (iNOS) and activate nuclear factor-kappaB (NF-kappaB) in vitro. In addition, we investigated the impact of dexamethasone and budesonide on these processes.

METHODS

Griess reaction was used to measure the nitrite level. Western blot and a semi-quantitative RT-PCR were performed to detect iNOS expression. Electrophoretic mobility shift assay (EMSA) was performed to analyze the activation of NF-kappaB.

RESULTS

We found that LPS stimulated the rat alveolar macrophages to produce NO in a dose (>or=10 ng/ml) and time dependent manner (p < 0.05). This effect was further enhanced by IFN-gamma (>or=10 IU/ml, p < 0.05), but was attenuated by budesonide (10(-4)-10(-10) M) and dexamethasone (10(-4)-10(-6) M) (p < 0.05). The mRNA and protein levels of iNOS were also induced in response to LPS and attenuated by steroids. LPS triggered NF-kappaB activation, a mechanism responsible for the iNOS expression.

CONCLUSION

Our findings imply that Gram-negative bacterial infection and the inflammatory responses are important factors in the development of CLD. The down-regulatory effect of steroids on iNOS expression and NO production might explain the beneficial effect of steroids in neonates with CLD.

Lipopolysaccharide can activate BK channels of arterial smooth muscle in the absence of iNOS expression

The role of inducible nitric oxide synthase (iNOS) in the acute activation of large-conductance, Ca(2+)-dependent K(+) channels (BK channels) by Escherichia coli endotoxin (lipopolysaccharide, LPS) was studied in murine vascular smooth muscle cells. Confocal laser scanning microscopy and patch clamp recordings were utilised. Within 2 h of donor rat sacrifice, iNOS-like immunoreactivity could be detected in cerebrovascular smooth muscle cells (CVSMCs) enzymatically dispersed from rat cerebral arteries. This staining was absent in cells fixed immediately after donor rat sacrifice. LPS was then applied to the cytoplasmic face of inside-out membrane patches excised from rat CVSMCs within 2-4 h of donor rat sacrifice. It was found that LPS (10-100 microg/ml) rapidly and reversibly increased the open probability of BK channels in these patches. This LPS response was not altered in the presence of the non-isoform specific NOS inhibitor N(omega)-nitro-L-arginine. LPS responses were then compared in aortic smooth muscle (ASMC) BK channels derived from wild-type and iNOS-knockout (iNOS-KO) mice. LPS activated BK channels in inside-out patches of ASMC membrane derived from both wild-type and iNOS-knockout mice. These studies establish that LPS can activate BK channels by a mechanism quite independent of the well-established pathway mediated by iNOS in vascular smooth muscle cells.

Meconium induces expression of inducible NO synthase and activation of NF-kappaB in rat alveolar macrophages

Meconium aspiration causes intensive inflammatory reactions in the lungs, and may lead to neonatal respiratory disorder. Infiltrated inflammatory cells, particularly macrophages, play an important role in such an inflammation. A rat alveolar macrophage cell line (ATCC8383) was exposed to meconium alone or in combination with dexamethasone, budesonide, or interferon-gamma. Nitric oxide (NO) accumulation in the supernatant of the cell culture was detected by Griess reaction, and mRNA of inducible NO synthase (iNOS) expression was detected by reverse transcriptase-PCR. Nuclear factor-kappa B was analyzed by electrophoretic mobility shift assay, and iNOS location and nuclear factor-kappa B transactivation were determined by immunostaining. Our results showed that meconium was capable of inducing production of NO and expression of iNOS in alveolar macrophages in a dose- (1-25 mg/mL, p < 0.05) and time- (4-48 h, p < 0.05) dependent manner. This capability of meconium could be further enhanced in the presence of interferon-gamma (100 IU/mL, p < 0.05). Budesonide (10(-4)-10(-10) M) or dexamethasone (10(-4)-10(-6) M) effectively inhibited the meconium-induced NO production (p < 0.05). Using the protein synthesis inhibitor cycloheximide, we demonstrated that meconium directly induced iNOS in macrophages. Furthermore, meconium also triggered nuclear factor-kappa B activation, a mechanism possibly responsible for the iNOS expression. Our findings suggest that meconium is a potent inflammatory stimulus, resulting in iNOS expression, leading to overproduction of NO from the macrophages, which may be of pathogenic importance in meconium aspiration syndrome. In vitro steroids down-regulated the iNOS expression, thus suggesting a potential to down-regulate NO-mediated inflammation in neonates with meconium aspiration syndrome.

Salicylates, nitric oxide, malaria, and Reye's syndrome

Reye's syndrome virtually disappeared from much of the world after the use of salicylate in febrile children was successfully discouraged. This severe sepsis-like disease was thought to be caused by a hypersensitivity to salicylates in children with mild viral infections, although no mechanism consistent with this proposal was ever established. Salicylate toxicity in African children has been noted to have many clinical features in common with severe falciparum malaria, including acidosis, altered consciousness, convulsions, and hypoglycaemia. Salicylates are widely available in various formulations in many African countries, and are commonly used for initial treatment of the symptoms that malaria shares with other diseases. There is now experimental evidence that salicylate increases and prolongs the activity of key elements along the signalling pathway through which interferon gamma generates inducible nitric oxide synthase (iNOS), and we have shown that iNOS is strongly expressed in fatal malaria and other acute fevers in African children. We further propose that, in areas where salicyaltes are still used to treat the symptoms of febrile illnesses in children, this mechanism could exacerbate potentially serious infectious diseases, including falciparum malaria. In contrast, the absence of salicylate use in children in some Pacific islands could contribute to the milder outcome of falciparum malaria than is observed in Africa. Widespread expression of iNOS has also been seen in the tissues of a patient with fatal clinically defined Reye's syndrome. This finding suggests that Reye's syndrome can be mediated through salicylate enhancement of iNOS expression, the initial trigger in this instance usually being a viral infection.

Activation of nuclear factor kappaB and induction of inducible nitric oxide synthase by Ureaplasma urealyticum in macrophages

Chronic lung disease (CLD) of prematurity is an inflammatory disease with a multifactorial etiology. The importance of Ureaplasma urealyticum in the development of CLD is debated, and steroids produce some improvement in neonates with this disease. In the present study, the capability of U. urealyticum to stimulate rat alveolar macrophages to produce nitric oxide (NO), express inducible nitric oxide synthase (iNOS), and activate nuclear factor kappaB (NF-kappaB) in vitro was characterized. The effect of NO on the growth of U. urealyticum was also investigated. In addition, the impact of dexamethasone and budesonide on these processes was examined. We found that U. urealyticum antigen (> or =4 x 10(7) color-changing units/ml) stimulated alveolar macrophages to produce NO in a dose- and time-dependent manner (P<0.05). This effect was further enhanced by gamma interferon (100 IU/ml; P<0.05) but was attenuated by budesonide and dexamethasone (10(-4) to 10(-6) M) (P<0.05). The mRNA and protein levels of iNOS were also induced in response to U. urealyticum and inhibited by steroids. U. urealyticum antigen triggered NF-kappaB activation, a possible mechanism for the induced iNOS expression, which also was inhibited by steroids. NO induced by U. urealyticum caused a sixfold reduction of its own growth after infection for 10 h. Our findings imply that U. urealyticum may be an important factor in the development of CLD. The host defense response against U. urealyticum infection may also be influenced by NO. The down-regulatory effect of steroids on NF-kappaB activation, iNOS expression, and NO production might partly explain the beneficial effect of steroids in neonates with CLD.

New concepts in vascular nitric oxide signaling

Low levels of nitric oxide (NO) control the activities of guanylate cyclase and mitochondrial respiration. Increasing NO levels interact with multiple signaling systems through the formation of peroxynitrite and other oxidation products. Signaling mechanisms linked to NO participate in the prevention of acute responses such as vasoconstriction, thrombosis and the recruitment of inflammatory cells. In contrast, processes related to vascular remodeling, and responses to injury that are associated with the progression and adaptation to disease processes, are not as well understood. Many of the opposing processes involved in these adaptations may originate from the diverse signaling mechanisms that NO and its oxidized products can regulate in a cell-specific manner in the vessel wall.