Arterial inflammation in patients with HIV

CONTEXT

Cardiovascular disease is increased in patients with human immunodeficiency virus (HIV), but the specific mechanisms are unknown.

OBJECTIVE

To assess arterial wall inflammation in HIV, using 18fluorine-2-deoxy-D-glucose positron emission tomography (18F-FDG-PET), in relationship to traditional and nontraditional risk markers, including soluble CD163 (sCD163), a marker of monocyte and macrophage activation.

DESIGN, SETTING, AND PARTICIPANTS

A cross-sectional study of 81 participants investigated between November 2009 and July 2011 at the Massachusetts General Hospital. Twenty-seven participants with HIV without known cardiac disease underwent cardiac 18F-FDG-PET for assessment of arterial wall inflammation and coronary computed tomography scanning for coronary artery calcium. The HIV group was compared with 2 separate non-HIV control groups. One control group (n = 27) was matched to the HIV group for age, sex, and Framingham risk score (FRS) and had no known atherosclerotic disease (non-HIV FRS-matched controls). The second control group (n = 27) was matched on sex and selected based on the presence of known atherosclerotic disease (non-HIV atherosclerotic controls).

MAIN OUTCOME MEASURE

Arterial inflammation was prospectively determined as the ratio of FDG uptake in the arterial wall of the ascending aorta to venous background as the target-to-background ratio (TBR).

RESULTS

Participants with HIV demonstrated well-controlled HIV disease (mean [SD] CD4 cell count, 641 [288] cells/μL; median [interquartile range] HIV-RNA level, <48 [<48 to <48] copies/mL). All were receiving antiretroviral therapy (mean [SD] duration, 12.3 [4.3] years). The mean FRS was low in both HIV and non-HIV FRS-matched control participants (6.4; 95% CI, 4.8-8.0 vs 6.6; 95% CI, 4.9-8.2; P = .87). Arterial inflammation in the aorta (aortic TBR) was higher in the HIV group vs the non-HIV FRS-matched control group (2.23; 95% CI, 2.07-2.40 vs 1.89; 95% CI, 1.80-1.97; P < .001), but was similar compared with the non-HIV atherosclerotic control group (2.23; 95% CI, 2.07-2.40 vs 2.13; 95% CI, 2.03-2.23; P = .29). Aortic TBR remained significantly higher in the HIV group vs the non-HIV FRS-matched control group after adjusting for traditional cardiovascular risk factors (P = .002) and in stratified analyses among participants with undetectable viral load, zero calcium, FRS of less than 10, a low-density lipoprotein cholesterol level of less than 100 mg/dL (<2.59 mmol/L), no statin use, and no smoking (all P ≤ .01). Aortic TBR was associated with sCD163 level (P = .04) but not with C-reactive protein (P = .65) or D-dimer (P = .08) among patients with HIV.

CONCLUSION

Participants infected with HIV vs noninfected control participants with similar cardiac risk factors had signs of increased arterial inflammation, which was associated with a circulating marker of monocyte and macrophage activation.

Risk assessment in immunotoxicology. II. Relationships between immune and host resistance tests

We have reported on the design and content of a screening battery using a "tier" approach for detecting potential immunotoxic compounds in mice (Luster et al., Fundam. Appl. Toxicol., 10, 2-19, 1988). The data base generated from these studies, which consists of over 50 selected compounds, has been collected and analyzed in an attempt to improve future testing strategies and provide information to aid in developing future quantitative risk assessment for immunotoxicity. In a recent study it was shown that as few as two or three immune parameters were needed to predict immunotoxicants in mice (Luster et al., Fundam. Appl. Toxicol., 18, 200-210, 1992). In particular, enumeration of lymphocyte populations and quantitation of the T-dependent antibody response were particularly beneficial. Furthermore, commonly employed apical measures (e.g., leukocyte counts, lymphoid organ weights) were fairly insensitive. The present analyses focus on the use of this data base to develop statistical models that examine the qualitative and quantitative relationship(s) between the immune function and host resistance tests. The conclusion derived from these analyses are: (1) A good correlation exists between changes in the immune tests and altered host resistance in that there were no instances where host resistance was altered without affecting an immune test(s). However, in some instances immune changes occurred without corresponding changes in host resistance. (2) No single immune test could be identified which was fully predictive for altered host resistance, although most assays were relatively good indicators (i.e., > 70%). Several others, such as proliferative response to lipopolysaccharide and leukocyte counts, were found to be relatively poor indicators for host resistance changes. (3) The ability to resist infectious agent challenge is dependent upon the degrees of immunosuppression and the quantity of infectious agent administered. (4) Logistic and standard regression modeling using one extensive chemical data set from the immunosuppressive agent, cyclophosphamide, indicated that most immune function-host resistance relationships followed linear rather than linear-quadratic (threshold-like) models. For most of the relationships this could not be confirmed using a large chemical data set and, thus, a more mechanistically based approach for modeling will need to be developed. (5) Using this limited data set, methods were developed for modeling the precise quantitative relationships between changes in selected immune tests and host resistance tests.

The C5a receptor (C5aR) C5L2 is a modulator of C5aR-mediated signal transduction

The complement anaphylatoxin C5a is a proinflammatory component of host defense that functions through two identified receptors, C5a receptor (C5aR) and C5L2. C5aR is a classical G protein-coupled receptor, whereas C5L2 is structurally homologous but deficient in G protein coupling. In human neutrophils, we show C5L2 is predominantly intracellular, whereas C5aR is expressed on the plasma membrane. Confocal analysis shows internalized C5aR following ligand binding is co-localized with both C5L2 and beta-arrestin. Antibody blockade of C5L2 results in a dramatic increase in C5a-mediated chemotaxis and ERK1/2 phosphorylation but does not alter C5a-mediated calcium mobilization, supporting its role in modulation of the beta-arrestin pathway. Association of C5L2 with beta-arrestin is confirmed by cellular co-immunoprecipitation assays. C5L2 blockade also has no effect on ligand uptake or C5aR endocytosis in human polymorphonuclear leukocytes, distinguishing its role from that of a rapid recycling or scavenging receptor in this cell type. This is thus the first example of a naturally occurring seven-transmembrane segment receptor that is both obligately uncoupled from G proteins and a negative modulator of signal transduction through the beta-arrestin pathway. Physiologically, these properties provide the possibility for additional fine-tuning of host defense.

Pesticide induced immunotoxicity in humans: a comprehensive review of the existing evidence

The immune system can be the target of many chemicals, with potentially severe adverse effects on the host's health. In Western countries pesticides, together with new and modified patterns of exposure to chemicals, have been implicated in the increasing prevalence of diseases associated with alterations of the immune response, such as hypersensitivity reactions, certain autoimmune diseases and cancers. Xenobiotics may initiate, facilitate or exacerbate pathological immune processes, resulting in immunotoxicity by induction of mutations in genes coding for immunoregulatory factors, modifying immune tolerance and activation pathways. The purpose of this article is to update the evidence of pesticide immunotoxicity. Even if experimental data as well as sporadic human studies indicate that some pesticides can affect the immune system, overall, existing epidemiological studies are inadequate to raise conclusions on the immunotoxic risk associated to pesticide exposure. The available studies on the effects of pesticides on human immune system have several limitations including poor indication on exposure levels, multiple chemical exposures, heterogeneity of the approach, and difficulty in giving a prognostic significance to the slight changes often observed. Further studies are necessary, and they should be preferably carried out through comparison of pre and post-exposure findings in the same group of subjects with a matched control group. Attempt should be made to define the prognostic significance of slight changes often observed. Animal and in vitro studies are also important and necessary to scientifically support epidemiological evidences on pesticide-induced immunotoxicity.

Focal arterial inflammation precedes subsequent calcification in the same location: a longitudinal FDG-PET/CT study

BACKGROUND

Arterial calcium (Ca) deposition has been identified as an active inflammatory process. We sought to test the hypothesis that local vascular inflammation predisposes to subsequent arterial calcium deposition in humans.

METHODS AND RESULTS

From a hospital database, we identified 137 patients (age, 61 ± 13 years; 48.1% men) who underwent serial positron-emission tomography/computed tomography (1-5 years apart). Focal arterial inflammation was prospectively determined by measuring 18F-flourodeoxyglucose uptake (using baseline positron-emission tomography) within predetermined locations of the thoracic aortic wall and was reported as a standardized uptake value. A separate, blinded investigator evaluated calcium deposition (on the baseline and follow-up computed tomographic scans) along the same standardized sections of the aorta. New calcification was prospectively defined using square root-transformed difference of calcium volume score, with a cutoff value of 2.5. Accordingly, vascular segment was classified as either with or without subsequent calcification. Overall, 67 (9%) of aortic segments demonstrated subsequent calcification. Baseline median (interquartile range) standardized uptake value was higher in segments with versus without subsequent calcification (2.09 [1.84-2.44] versus 1.92 [1.72-2.20], P=0.002). This was also true in the subset of segments with Ca present at baseline (2.08 [1.81-2.40] versus 1.86 [1.66-2.09], P=0.02), as well as those without (2.17 [1.87-2.51] versus 1.93 [1.73-2.20], P=0.04). Furthermore, across all patients, subsequent Ca deposition was associated with the underlying 18F-flourodeoxyglucose uptake (inflammatory signal), measured as standardized uptake value (odds ratio [95% confidence interval]=2.94 [1.27-6.89], P=0.01) or target-to-background ratio (2.59 [1.18-5.70], =0.02), after adjusting for traditional cardiovascular risk factors.

CONCLUSIONS

Here, we provide first-in-man evidence that arterial inflammation precedes subsequent Ca deposition, a marker of plaque progression, within the underlying location in the artery wall.

Glia increase degeneration of hippocampal neurons through release of tumor necrosis factor-alpha

This study characterizes the role of glial cells in chemically induced neurodegeneration. We evaluated the effect of trimethyltin, a trisubstituted organotin compound that elicits distinct lesions in the central nervous system in vivo, on a sandwich co-culture of neurons and glia. Exposure of a 98% pure culture of rat hippocampal neurons to 0.1-1 microM trimethyltin for 24 h caused neural cell death and nuclear changes typical of apoptosis; at these doses glial cells viability was not affected but the cells released significant amounts of tumor necrosis factor-alpha (TNF-alpha). Neuronal apoptosis and TNF-alpha release from glial cells both increased when the two cell types were exposed together to trimethyltin, which indicates synergy. Treatment of a neuron-glia co-culture with TNF-alpha antibody prevented the increase in neuronal apoptosis, and TNF-alpha administration induced apoptosis in hippocampal cells. We conclude that glial cells and TNF-alpha both modulate trimethyltin-induced neurodegeneration.

Organotins induce apoptosis by disturbance of [Ca(2+)](i) and mitochondrial activity, causing oxidative stress and activation of caspases in rat thymocytes

Di-n-butyltin dichloride (DBTC) and tri-n-butyltin chloride (TBTC) cause thymus atrophy in rodents. At low doses, antiproliferative modes of action have been shown to be involved, whereas at higher doses apoptosis seems to be the mechanism of thymotoxicity by these chemicals. In vitro, a similar concentration-dependency has been observed. The purpose of the present research was to investigate the mechanisms underlying DNA fragmentation induced by these organotin compounds in freshly isolated rat thymocytes. As previously shown for TBTC, DBTC is also able to significantly increase intracellular Ca(2+) level ([Ca(2+)](i)). The rise in [Ca(2+)](i), already evident 5 min after treatment, was followed by a dose- and time-dependent generation of reactive oxygen species (ROS) at the mitochondrial level. Simultaneously, organotins induced the release of cytochrome c from the mitochondrial membrane into the cytosol. ROS production and the release of cytochrome c were reduced by BAPTA, an intracellular Ca(2+) chelator, or rotenone, an inhibitor of the electron entry from complex I to ubiquinone, indicating the important role of Ca(2+) and mitochondria during these early intracellular events. Furthermore, we demonstrated that rotenone prevents apoptosis induced by 3 microM DBTC or TBTC and, in addition, that both BAPTA and Z-DEVD FMK (mainly a caspase-3 inhibitor) decreased apoptosis by DBTC (already shown for TBTC). Taken together these data show the apoptotic pathway followed by organotin compounds starts with an increase of [Ca(2+)](i), then continues with release of ROS and cytochrome c from mitochondria, activation of caspases, and finally results in DNA fragmentation.

Epidermal cytokines in experimental contact dermatitis

Topical exposure to a variety of xenobiotics may result in irritant as well as allergic contact dermatitis both in rodents and in humans. Despite their induction by different mechanisms, they cannot be differentiated by macroscopic appearance and, by histological examination they are both generally characterized by a perivascular mononuclear cell infiltrate and capillary hyperpermeability. Recently, cytokines, a family of inducible glycoproteins that play a pivotal role in immune and inflammatory reactions, have been identified as useful tools for differentiation of irritant and allergic contact dermatitis. In this article the role of cytokines in the development and differentiation of irritant and allergic contact dermatitis is discussed.

Cytokines and irritant contact dermatitis

Skin irritation is a complex phenomenon that involves resident epidermal cells, fibroblasts of dermis, and endothelial cells as well as invading leukocytes interacting with each other under the control of a network of cytokines and lipid mediators. Keratinocytes play an important role in the initiation and perpetuation of skin inflammatory reactions through the release of, and responses to cytokines. While resting keratinocytes produce some cytokines constitutively, a variety of environmental stimuli, such as tumor promoters, ultraviolet light and chemical agents, can induce epidermal keratinocytes to release inflammatory cytokines (IL-1, TNF-alpha), chemotactic cytokines (IL-8, IP-10), growth promoting cytokines (IL-6, IL-7, IL-15, GM-CSF, TGF-alpha) and cytokines regulating humoral vs. cellular immunity (IL-10, IL-12, IL-18). The role of cytokines in xenobiotics-induced skin irritation and the early molecular events that follow the treatment with irritant compounds will be discussed.

Endothelium and the brain in CNS lupus

Central nervous system (CNS) involvement in systemic lupus erythematosus (SLE) is common and results in different clinical manifestations. Several pathogenic mechanisms have been suggested to play a rolein determiningsuch a varietyof clinicalsymptoms.The thrombophilicstateassociatedto the presence of antiphospholipidantibodies has been suggested to be responsible for a noninflammatory vasculopathywhichcauses clear ischaemiceventsas well as alterationsof the cerebralmicrocirculation that are likely associated to seizures, cognitive dysfunction or psychosis. Although less frequent, a true vasculitic process affecting cerebral circulation has also been reported. In both cases, brain endothelium does represent the target of the pathogenic mechanisms. Brain endothelial cells display peculiar functional and phenotypical characteristics in comparison with endothelial cells from other anatomical districts, raising the possibility that this might be the reason for its susceptibility in lupus disease. We review and present data suggesting that a higher and firmer expression of beta 2 glycoprotein I on endothelialcell membranes can be responsiblefor a selective damage/activation by circulating anti-beta 2 glycoprotein I, and that antiendothelial cell antibodies crossreact with brain endothelium and in some cases, specifically bind brain endothelial cells only in lupus patients with central nervous involvement.

Effects of pesticide exposure on the human immune system

Epidemiological evidence from Western countries indicates that the prevalence of diseases associated with alterations in the immune response, such as asthma, certain autoimmune diseases and cancer, are increasing to such an extent that it cannot be attributed to improved diagnostics alone. There is some concern that this trend could be, at least, partially attributable to new or modified patterns of exposures to chemicals, including pesticides. The purpose of this article is to review the evidence on pesticide immunotoxicity in humans. Overall, the available data are inadequate to draw firm conclusions on the immunotoxic risk associated with pesticide exposure. The available studies on the effects of pesticides on the human immune system have several limitations, including limited data on exposure levels, heterogeneity of the applied methods, and difficulties in assessing the prognostic significance of observed slight changes and in the interpretation of the reported findings. Further studies are needed and preferably as prospective studies, comparing pre- and post-exposure data in the same group of subjects and including an appropriate non-exposed control group. More knowledge is required regarding the prognostic significance of the small changes observed.

Sodium arsenate induces overproduction of interleukin-1alpha in murine keratinocytes: role of mitochondria

It has recently been demonstrated that arsenic induces overexpression of keratinocyte-derived growth factors, which are likely to have a significant role in arsenic-induced skin hyperkeratoses and cancer. The mechanism(s) involved in this induction are, however, still elusive. The purpose of this study was to investigate the early intracellular events that follow in vitro treatment with sodium arsenate in a murine keratinocyte cell line (HEL30), which leads to cytokine overproduction. First, we observed that sodium arsenate induced a concentration-dependent production of interleukin-1alpha and a significant increase in cell proliferation, that could be suppressed by the addition of a neutralizing antibody against murine interleukin-1alpha, confirming the ability of arsenic to induce keratinocyte growth-promoting cytokines. Electron microscopic analysis revealed that arsenate induced a dramatic alteration in keratinocyte mitochondria. This effect could be prevented by rotenone pretreatment, which suggests the possible involvement of mitochondria-derived reactive oxygen species. Arsenic induced a concentration- and time-dependent increase in cellular oxidative activity, which was followed by activation of redox-sensitive transcription factors such as nuclear factor-kappaB and activator protein-1, that are essential for interleukin-1alpha synthesis. Prior treatment with rotenone or prolonged treatment with ethidium bromide, an inhibitor of mitochondrial DNA and RNA synthesis, to deplete cells of functional mitochondria, completely prevented sodium arsenate-induced interleukin-1alpha production, this indicates the pivotal role of these organelles in sodium arsenate-induced keratinocyte growth factors.

Periaortic adipose tissue and aortic dimensions in the Framingham Heart Study

Background

Periaortic fat, because of its contiguity with the aorta, may promote vascular remodeling and aortic dilatation. However, the relations between perioartic fat depots and aortic dimensions have not been previously described.

Methods and Results

A total of 3001 individuals (mean age 50±10 years, 49% women) from the Framingham Offspring and Third Generation cohorts underwent computed tomography for quantification of periaortic fat and aortic dimensions. We estimated the association between quantitative periaortic and visceral adipose tissue volumes (per standard deviation [SD] increment of volume) with aortic dimensions in both the thorax and abdomen. Thoracic periaortic fat was associated with higher thoracic aortic dimensions (β coefficient per SD of fat volume 0.67 mm, 95% confidence interval 0.58 to 0.76 mm; P<0.001). The association persisted after adjustment for age, sex, and cardiovascular risk factors including body mass index and visceral adipose tissue volume. Results for the association of periaortic fat and abdominal aortic dimensions were similar. Further adjustment for adipokines (resistin and adiponectin) had no significant impact on these associations.

Conclusions

Periaortic fat volume was associated with aortic dimensions in both the thorax and abdomen, supporting the notion that local fat depots may contribute to aortic remodeling. Further work to understand the mechanisms underlying this association is warranted.

Low level exposure to chemicals and immune system

Industrialized countries are facing an increase of diseases attributable to an alteration of the immune system function, and concern is growing that this trend could be at least partially attributable to new and modified patterns of exposure to chemicals. Among chemicals matter of concern, pesticides can be included. The Authors have reviewed the existing evidence of pesticide immunotoxicity in humans, showing that existing data are inadequate to raise conclusions on the immunotoxic risk related to these compounds. The limits of existing studies are: poor knowledge on exposure levels, heterogeneity of the approach, and difficulty in giving a prognostic significance to the slight changes often observed. To overcome these limits, the Authors have proposed a tier approach, based on three steps: the first, addressed at pointing out a possible immunomodulation; the second, at refining the results and the third one, when needed, to finalize the study and to point out concordance with previous results. Studies should preferably be carried out through comparison of pre- and post-exposure findings in the same groups of subjects to be examined immediately after the end of the exposure. A simplification of the first step approach can be used by the occupational health physician and the occupational toxicologist. Conclusions on the prognostic significance of the slight changes often observed will be reached only by validating the hypothesis generated by field studies with an epidemiological approach. In this field, the most useful option is represented by longitudinal perspective studies.

In vitro tests to evaluate immunotoxicity: A preliminary study

The implementation of Registration, Evaluation and Authorisation of new and existing Chemicals (REACH) will increase the number of laboratory animals used, if alternative methods will not be available. In the meantime, REACH promotes the use of in vitro tests and, therefore, a set of appropriated alternative testing methods and assessment strategies are needed. The immune system can be a target for many chemicals including environmental contaminants and drugs with potential adverse effects on human health. The aim of this study was to evaluate the predictivity of a set of in vitro assays to detect immunosuppression. The tests have been performed on human, rat and murine cells. Different endpoints have been assessed: cytotoxicity, cytokine release, myelotoxicity and mitogen responsiveness. For each of these endpoints IC50s values have been calculated. Six chemical substances, representative of the full range of in vivo responses and for which good human and/or animal data are available either from databases or literature, have been selected: two chemicals classified as not immunotoxic (Urethane and Furosemide), and four (tributyltin chloride (TBTC), Verapamil, Cyclosporin A, Benzo(a)pyrene) with different effect on immune system. All the tests confirmed the strong immunotoxic effect of TBTC as well as they confirmed the negative controls. For one chemical (Verapamil) the IC50 is similar through the different tests. The IC50s obtained with the other chemicals depend on the endpoints and on the animal species. The clonogenic test (CFU-GM) and the mitogen responsiveness showed similar IC50s between human and rodent cells except for Cyclosporin A and TBTC. All different tests classified the compounds analyzed in the same way.

Reactive oxygen species generated by glia are responsible for neuron death induced by human immunodeficiency virus-glycoprotein 120 in vitro

Human immunodeficiency virus infection is often followed by neurodegeneration, the cause of motor and cognitive impairment in some patients affected by acquired immunodeficiency. Several in vitro data indicate glycoprotein (gp) 120 as one of the substances responsible for the neurodegenerative event that takes place only if non-neuronal cells (glial cells) are present. Our purpose was to investigate the molecular mechanisms through which glial cells could affect neuron viability after exposure to gp120 protein. We used a sandwich co-culture of primary hippocampal neurons and primary glial cells, where the two cell populations face each other but are separable. Exposure of 1-week-old rat hippocampal neurons in co-culture with glia to 600 pM gp120 protein resulted in the death of 30% of neurons after 6 days of treatment. A significant increase of intracellular calcium ([Ca2+]i), evident 72 h after gp120 exposure (control 45.8+/-7.6 nM, gp120 176.5+/-43.6 nM), preceded neuron death. The gp120 protein affected neither the viability nor the morphology or [Ca2+]i of glial cells. However, a significant amount of reactive oxygen species as well as of interleukin-1beta was produced. Treatment of the co-culture with an antibody against interleukin-1beta prevented neuron increase of [Ca2+]i and cell death but not glial production of reactive oxygen species, whereas prior incubation of glial cells with Trolox, an antioxidant analog of vitamin E, down-regulated interleukin-1beta expression and completely prevented neuron cell death. Our results indicate that reactive oxygen species produced in glial cells by gp120 exposure cause neurodegeneration by inducing the synthesis of interleukin-1beta.

Endogenous interleukin-1 alpha associated with skin irritation induced by tributyltin

Tributyltin (TBT) salts are well-known skin irritants in both human and rodents. This study investigated the role of interleukin-1alpha (IL-1alpha) in the process in mice and in murine keratinocytes. The ears of Balb/c mice were painted with different amounts of TBT (67-536 nmol in acetone) or with acetone alone. Two hours later there was dose-related production of IL-1alpha along with ear swelling and accumulation of skin water, all of which were partially prevented by intraperitoneal injection of antibody against murine IL-1alpha. By reverse transcription-polymerase chain reaction we were able to show that the neutralizing antibody also partially prevented TBT-induced in vivo IL-6 expression but no TBT-induced TNF-alpha expression, suggesting a paracrine effect of IL-1alpha on IL-6 production but not TNF-alpha expression and indicating that other inflammatory mediators are involved. TBT induced both intracellular production of IL-1alpha and its release into culture medium in a murine keratinocyte cell line (HEL30). IL-1alpha production was inhibited by addition of a neutralizing antibody against IL-1alpha, which suggests an autocrine effect of IL-1alpha on its own production. The intracellular production of IL-1alpha could he significantly inhibited by prior treatment with antioxidants, which strongly suggests a role for oxidative species in the mechanism of action of TBT in IL-1alpha induction. The complex-1 inhibitor rotenone also significantly inhibits IL-1alpha production. Since TBT causes disturbances in the respiratory chain in mitochondria, the mechanism of its action may be the production of reactive oxygen intermediates at the ubiquinone site, which activate transcription factors and promote IL-1alpha synthesis.

Use of IL-8 release and p38 MAPK activation in THP-1 cells to identify allergens and to assess their potency in vitro

The local lymph node assay (LLNA) has been developed to assess skin sensitization, and based on the EC3 value, it can also be used to evaluate allergen potency. Therefore, in the development of in vitro alternatives to the LLNA assay, one should not only consider the hazard identification but also the possibility to classify allergens relatively to their potency. We have recently described a selective release of interleukin-8 (IL-8) by chemical allergens in THP-1 cell line, and identified the activation of p38 mitogen-activated protein kinase (p38 MAPK) as a common pathway. Therefore, the purpose of this study was to expand the number of chemicals tested and to investigate whether IL-8 production and p38 MAPK activation can be used to classify allergens according to their potency. THP-1 cells were exposed to the contact allergens (p-benzoquinone, 2-aminophenol, isoeugenol, diethyl maleate, citral and imidazolidinyl urea), selected according to their potency in the LLNA, and to lactic acid and propylene glycol as non-sensitizers. p38 MAPK activation was evaluated 5-15 min after treatment by FACS analysis, while IL-8 release was assed by ELISA following 24h of incubation. p38 MAPK was activated by all contact allergens, including the pro-apten isoeugenol, whereas IL-8 release was significantly increased after stimulation with all allergens tested, except for isoeugenol. The failure of isoeugenol may be due to decrease in the stability of IL-8 mRNA. Irritants exposure, as expected, failed to induce both p38 MAPK activation and IL-8 release. A significant correlation between IL-8 release and the LLNA EC(3) was found (Pearson correlation r=0.743, p=0.0036, n=12). On the contrary, the activation of p38 MAPK showed no significant correlation between LLNA data and vigor of p38 MAPK activation. Overall, data presented confirm our previous observations and reveal IL-8 as potential tool not only to identify sensitizers, with the exception of pro-haptens, but also to classify them according to their potency, while p38 MAPK activation allows the identification of all sensitizers, including pro-haptens, but was not useful for potency classification.

Immune parameters in biological monitoring of pesticide exposure: current knowledge and perspectives

Exposure to pesticides can cause a number of effects on the immune system, varying from a slight modulation of immune functions to the development of clinical immune diseases. The aim of this study has been reviewing published data on immune effects of pesticides in humans, with particular attention for effects observed in absence of any other change, and to the possibility of identifying a dose effect relationship. Some evidence of immunotoxic effects in man involve organophosphorus compounds, some organochlorine insecticides (OC), some carbamates, some phenoxy herbicides, dithiocarbamates, and pentachlorophenol (PCP). The alterations are usually observed in absence of any other change; in some cases, data suggest the presence of a dose effect relationship. The prognostic significance of the observed changes is still unclear. The Authors propose a tier approach to assess immune effects in humans.

Evaluation of eye and skin irritation of arginine-derivative surfactants using different in vitro endpoints as alternatives to the in vivo assays

Arginine-derivative surfactants constitute a novel class of surfactants, which can be regarded as an alternative to conventional surfactants. Prior to human exposure, it is necessary to assess their irritation potential. The classical in vivo evaluation of the irritancy potential via the Draize test has been extensively criticized. In that regard, a great number of in vitro alternatives have been developed. Erythrocytes were chosen as the target cells for eye irritation assessment and hemolysis and hemoglobin denaturation were selected as appropriate endpoints. For skin irritancy assessment, the keratinocyte cell line NCTC 2544 was used and different in vitro endpoints were measured: two cytotoxicity assays (NRU and MTT) and the synthesis of the proinflammatory cytokine IL-1alpha. The eye and skin Draize tests were also performed for comparative purposes. The results point out that, according to in vivo and in vitro assays, the new arginine-derivative surfactants have lower eye and skin irritation potential than the synthetic surfactant SDS. Furthermore, in vitro methods were also able to detect differences in irritancy among the new surfactants not noticeable by the Draize tests, indicating that in vitro methods can be more sensitive than the in vivo test, offering the opportunity to detect subtle differences in irritancy.

Further development of the NCTC 2544 IL-18 assay to identify in vitro contact allergens

Several European Union legislations request the use of in vitro methods for toxicological evaluations, including sensitization, in order to increase consumer safety but also to reduce the use of animals. The EU project SENS-IT-IV addresses the need of developing predictive in vitro tests to assess contact and respiratory hypersensitivity reactions. In this context, we have recently reported the possibility to use IL-18 production in the human keratinocyte cell line NCTC 2544 to discriminate contact sensitizer from irritants and low molecular weight respiratory allergens. The aims of the present study were to further develop this assay in order to optimize experimental conditions; to develop a 96-well plate format to establish a high throughput assay; to test the performance of other available keratinocyte cell lines, and to understand the signal transduction pathway involved in p-phenylenediamine (PPD)-induced IL-18 production. If cells reach confluence at the moment of treatment, the ability to identify contact allergens is lost; therefore a careful check for the optimal cell density using PPD as reference contact allergen is critical. In our hands, a cell density of 1-2.5 × 10(5)cells/ml gave optimal stimulation. In order to develop a high throughput test, cells seeded in 96-well plate were exposed to contact allergens (2,4-dinitrochlorobenzene, p-phenylenediamine, isoeugenol, cinnamaldehyde, tetramethylthiuram disulfite, resorcinol, cinnamic alcohol and eugenol), irritants (phenol, sodium laurel sulphate, lactic acid and salicylic acid) and respiratory allergens (hexachloroplatinate, diphenylmethane diisocyanate, trimellitic anhydride). A selective increase in total (intracellular plus released) IL-18 was observed 24h later in cells treated with contact allergens, whereas no changes were observed following treatment with respiratory allergens and irritants, confirming previous results obtained in a 24-well format assay. A selective induction of IL-18 was also obtained testing with PPD other keratinocyte cell lines, namely HPKII and HaCaT, with the HPKII showing the highest stimulation index. Regarding the signal transduction pathway, we could demonstrate using selective inhibitors a role for oxidative stress, NF-κB and p38 MAPK activation in PPD-induced IL-18 production. In conclusion, results obtained suggest that the production of IL-18 represents a promising endpoint for the screening of potential contact allergens. The assay can be performed in a 96-well plate format, different keratinocyte cell lines can be used, and a role for oxidative stress in contact allergen-induced IL-18 was demonstrated.

Epidermal stratification reduces the effects of UVB (but not UVA) on keratinocyte cytokine production and cytotoxicity

Ultraviolet (UV) radiation induces cytokine release from cultured keratinocytes as well as from epidermis in vivo. The purpose of this study was to determine whether differentiation of cultured keratinocytes into stratified epithelium decreases the effects of UVA and UVB radiation on cytokine release. Interleukin-1 (IL-1) alpha, IL-1 beta and tumor necrosis factor (TNF)-alpha release from human keratinocytes and reconstituted human epidermis was measured after exposure to UVA or UVB radiation. Release of IL-1 alpha, IL-1 beta, and TNF-alpha was induced by both UVA and UVB radiation from both keratinocytes and reconstituted epidermis. Release of these cytokines was correlated with cytotoxicity. Keratinocyte cultures were far more sensitive to UVB radiation than reconstituted epidermis, in terms of both cytotoxicity and cytokine release. In contrast, epidermal stratification/differentiation had much less effect on the sensitivity to UVA radiation. We conclude that epidermal stratification and the formation of a stratum corneum provide protection against UVB radiation but have limited barrier effect against UVA radiation.

Cycloheximide blocks the fall of plasma and tissue tryptophan levels after tryptophan-free amino acid mixtures

The hypothesis that incorporation of tryptophan (TRY) into proteins is the mechanism underlying the decrease in plasma and tissue TRY levels after a TRY-free amino acid mixture was investigated. Rats fasted 15 hours were pretreated with saline or with the protein synthesis inhibitor cycloheximide (CHEX) and treated with saline or a TRY-free amino acid mixture. In a first experiment, in saline pretreated rats the TRY-free mixture caused a decrease of 49% in total plasma TRY, of 64% in free plasma TRY, of 66% in brain TRY and of 42% in liver TRY. After 5 mg/kg of CHEX the same TRY-free diet caused a decrease of 5% in total plasma TRY, 14% in free plasma TRY, 18% in brain TRY and 9% in liver TRY. In a second experiment, the TRY-free diet caused a 43% decrease of total plasma TRY in saline pretreated animals and a decrease of 15%, 6% and 2% respectively after the pretreatment with 0.3, 1.0 and 5.0 mg/kg of CHEX. In brain TRY, the TRY-free diet caused a 62% decrease in saline pretreated rats and a decrease of 38%, 20% and 19% respectively after the pretreatment with 0.3, 1.0 and 5.0 mg/kg of CHEX. Since 5.0 mg/kg of CHEX almost completely block protein synthesis and since doses of CHEX from 0.3 to 5.0 mg/kg cause a dose-dependent inhibition of protein synthesis, our data support the hypothesis that protein synthesis is the mechanism through which TRY-free mixtures decrease TRY levels.

NF-kappaB activation by triphenyltin triggers apoptosis in HL-60 cells

Trisubstituted organotin pesticides are lethal for different cell types. In this study we investigated whether triphenyltin chloride (TPT) causes apoptosis in HL-60 promyelocytic cells and, if so, by what mechanisms. We report that 5 microM TPT increased intracellular Ca2+ in HL-60 cells within seconds; concomitantly actin depolymerization was detected 30 s and 1 min after the treatment. This was followed 15 min later by NF-kappaB activation, and apoptotic bodies and DNA fragmentation were evident after 3 and 6 h, respectively. At these times TPT also induced the release of tumor necrosis factor-alpha (TNF-alpha). Prior treatment of the cells with a polyclonal antibody to human TNF-alpha abolished TPT-induced DNA fragmentation, which suggests that the ultimate effect of TPT may be mediated by TNF-alpha. Prior treatment of the cells with 100 microM pyrrolidine dithiocarbamate, an antioxidant and potent inhibitor of NF-kappaB activation, prevented actin depolymerization, NF-kappaB activation, and DNA fragmentation, although it did not affect TPT-induced Ca2+ mobilization. These findings suggest that TPT increases intracellular Ca2+, alters actin polymerization and the cytoskeleton, and induces NF-kappaB activation, TNF-alpha synthesis, DNA degradation, and apoptosis. Reactive oxygen species seem to be essential to NF-kappaB activation, TNF-alpha synthesis, and the subsequent steps.

Early aortic valve inflammation precedes calcification: a longitudinal FDG-PET/CT study

OBJECTIVES

Recent data shows a relationship between aortic valve (AV) inflammation and calcification. However, direct evidence linking early valve inflammation (prior to hemodynamic compromise) to subsequent calcium (Ca) deposition is lacking in humans. We sought to test the hypothesis whether local AV inflammation predisposes to subsequent AV Ca deposition.

METHODS

We identified 111 individuals (age 60[49, 68], 50.5% male) without active cancer or aortic stenosis who underwent 2 PET/CT studies 1-5 years apart for cancer surveillance. AV inflammation was determined by measuring FDG uptake (maximum standardized uptake value, SUVmax) within the AV on baseline PET/CT. Subsequent deposition of AV Ca was determined by comparing baseline and follow-up CT scans, determined as an increase in AV Ca volume score (CaVS). Patients were classified as "non-progressors" or "progressors" based on Square Root difference in CaVS (using a pre-determined cut-off value of 2.5). CT and PET measurements were conducted by 2 mutually blinded laboratories.

RESULTS

During follow-up, AV Ca increased in 23 patients (20.2%) classified as "progressors", of whom 9 (9.2%) demonstrated subsequent 'incident' AV Ca. The AV SUVmax (mean ± SD) was higher in progressors vs. non-progressors (2.03 ± 0.52 vs.1.74 ± 0.36, p = 0.02) and especially in patients with-vs. without-incident AV Ca (2.28 ± 0.42 vs. 1.73 ± 0.36, p < 0.001). Moreover, AV inflammation (AV SUVmax) independently predicted subsequent calcification after adjusting for cardiovascular risk factors [OR (95%CI): 4.99 (1.30-19.15), p = 0.02].

CONCLUSION

The findings suggest that early AV inflammation may predispose to AV sclerosis. The evaluation of valvular metabolic activity may prove useful for developing a better understanding of calcific valve disease.