Atherogenic properties of human monocytes induced by the carboxyl terminal proteolytic fragment of alpha-1-antitrypsin

SERPINA1 long transcripts produce non-secretory alpha1-antitrypsin isoform: In vitro translation in living cells

SERPINA1 is a well-studied serpin gene due to its dramatic impact on human health. Translation initiation at the main SERPINA1 start codon produces the only known alpha1-antitrypsin (AAT) isoform intended for secretion. AAT performs essential functions by inhibiting proteases and modulating immunity. However, SERPINA1 expression at the level of translation is not sufficiently studied. Here we hypothesize that the main SERPINA1 ORF can be alternatively translated, producing a non-secretory AAT isoform by either masking or excluding a signal peptide. We defined SERPINA1 long mRNA isoforms specific for prostate (DU145) and liver (HepG2) cell lines and studied their individual expression by in vitro assay. We found that all long transcripts produce both glycosylated secretory AAT-eGFP fusion protein and non-glycosylated intracellular AAT-eGFP (initiated from an alternative AUG-2 start codon), with the proportion regulated by the SERPINA1 5'-UTR. Both fusion proteins localize to distinct cellular compartments: in contrast to a fusion with the secretory AAT accumulating in the ER, the intracellular one exhibits nuclear-cytoplasmic shuttling. We detected putative endogenous AAT isoform enriching the nuclear speckles. CONCLUSION: Alternative translation initiation might be a mechanism through which SERPINA1 expands the biological diversity of its protein products. Our findings open up new prospects for the study of SERPINA1 gene expression.

Plasma Mitochondrial DNA--a Novel DAMP in Pediatric Sepsis

Mitochondrial DNA (mtDNA) is a novel danger-associated molecular pattern that on its release into the extracellular milieu acts via toll-like receptor-9, a pattern recognition receptor of the immune system. We hypothesized that plasma mtDNA concentrations will be elevated in septic children, and these elevations are associated with an increase in the severity of illness. In a separate set of in vitro experiments, we test the hypothesis that exposing peripheral blood mononuclear cells (PBMC) to mtDNA activates the immune response and induces tumor necrosis factor (TNF) release. Children with sepsis/systemic inflammatory response syndrome or control groups were enrolled within 24  h of admission to the pediatric intensive care unit. Mitochondrial gene cytochrome c oxidase 1 (COX1) concentrations were measured by real-time quantitative PCR in the DNA extracted from plasma. PBMCs were treated with mtDNA (10  μg/mL) and supernatant TNF levels were measured. The median plasma mtDNA concentrations were significantly elevated in the septic patients as compared with the critically ill non-septic and healthy control patients [1.75E+05 (IQR 6.64E+04-3.67E+05) versus 5.73E+03 (IQR 3.90E+03-1.28E+04) and 6.64E+03 (IQR 5.22E+03-1.63E+04) copies/μL respectively]. The median concentrations of plasma mtDNA were significantly greater in patients with MOF as compared with patients without MOF (3.2E+05 (IQR 1.41E+05-1.08E+06) vs. 2.9E+04 (IQR 2.47E+04-5.43E+04) copies/μL). PBMCs treated with mtDNA demonstrated higher supernatant TNF levels as compared with control cells (6.5 ± 1.8 vs. 3.5 ± 0.5  pg/mL, P > 0.05). Our data suggest that plasma mtDNA is a novel danger-associated molecular pattern in pediatric sepsis and appears to be associated with MOF.

Serpin A1 C-Terminal Peptides as Collagen Turnover Modulators

The modulation of collagen turnover can be a relevant pharmacological target in the context of treating either pathological or pathophysiological conditions, such as collagen-related diseases and skin aging. Our recent work has focused on the search for short-chain peptides as lead compounds for further development of compounds that enhance the production of type I collagen. In this study we selected and synthesized overlapping peptides of the C-terminal portion of serpin A1 (residues 393-418), the impact of which on collagen production has been reported previously, in order to identify shorter and still active fragments and to provide insight on the mechanisms involved. The biological activity of each fragment was evaluated with cultured normal human dermal fibroblasts, and changes in the amounts of collagen were monitored in collected culture media by a sandwich ELISA technique developed in house. Interestingly, we identified a decapeptide, termed SA1-III (Ac-MGKVVNPTQK-NH2 ), as a promising candidate for our purposes; it is able to induce a significant increase in type I collagen levels in the culture medium of treated cells at micromolar concentrations.

Expanding the clinical indications for α(1)-antitrypsin therapy

α(1)-Antitrypsin (AAT) is a 52-kDa circulating serine protease inhibitor. Production of AAT by the liver maintains 0.9-1.75 mg/mL circulating levels. During acute-phase responses, circulating AAT levels increase more than fourfold. In individuals with one of several inherited mutations in AAT, low circulating levels increase the risk for lung, liver and pancreatic destructive diseases, particularly emphysema. These individuals are treated with lifelong weekly infusions of human plasma-derived AAT. An increasing amount of evidence appears to suggest that AAT possesses not only the ability to inhibit serine proteases, such as elastase and proteinase-3 (PR-3), but also to exert antiinflammatory and tissue-protective effects independent of protease inhibition. AAT modifies dendritic cell maturation and promotes T regulatory cell differentiation, induces interleukin (IL)-1 receptor antagonist and IL-10 release, protects various cell types from cell death, inhibits caspases-1 and -3 activity and inhibits IL-1 production and activity. Importantly, unlike classic immunosuppressants, AAT allows undeterred isolated T-lymphocyte responses. On the basis of preclinical and clinical studies, AAT therapy for nondeficient individuals may interfere with disease progression in type 1 and type 2 diabetes, acute myocardial infarction, rheumatoid arthritis, inflammatory bowel disease, cystic fibrosis, transplant rejection, graft versus host disease and multiple sclerosis. AAT also appears to be antibacterial and an inhibitor of viral infections, such as influenza and human immunodeficiency virus (HIV), and is currently evaluated in clinical trials for type 1 diabetes, cystic fibrosis and graft versus host disease. Thus, AAT therapy appears to have advanced from replacement therapy, to a safe and potential treatment for a broad spectrum of inflammatory and immune-mediated diseases.

Serpin A1 and CD91 as host instruments against HIV-1 infection: are extracellular antiviral peptides acting as intracellular messengers?

Serpin A1 (alpha1-antitrypsin, alpha1-proteinase inhibitor) has been shown to be a non-cytolytic antiviral factor present in blood and effective against HIV infection. The best known physiological role of serpin A1 is to inhibit neutrophil elastase, a proteinase which is secreted by neutrophils at sites of infection and inflammation. Decreased HIV-infectivity is associated with decreased density of membrane-associated elastase. The enzyme may facilitate binding of the HIV membrane protein gp120 to host cells, and it specifically cleaves SDF-1, the physiological ligand of the HIV-1 co-receptor CXCR4. It has been suggested that one of the actions of serpin A1 as antiviral agent is to reduce HIV infectivity, and this property could be due to elastase inhibition. However, the most dramatic effect of serpin A1 is inhibition of HIV production. In vitro experiments indicate that the C-terminal peptide of serpin A1, produced during the formation of the complex of serpin with serine proteinases, may be responsible for the inhibition of HIV-1 expression in infected cells. This peptide, an integral part of the serpin-enzyme complex, is internalized by several scavenger receptors. Peptides corresponding to the C-terminal section of serpin A1 inhibit HIV-1 long-terminal-repeat-driven transcription and interact with nuclear proteins, such as alpha1-fetoprotein transcription factor. LDL-receptor-related protein 1 (LRP1/CD91), the best known receptor for serpin-enzyme complexes, is up-regulated in monocytes of HIV-1-infected true non-progressors. CD91 could be one of the major players in host resistance against HIV-1. It has the capacity of internalizing antiviral peptides such as serpin C-terminal fragments and alpha-defensins, and is at the same time the receptor for heat-shock proteins in antigen-presenting cells, in which chaperoned viral peptides could lead to the induction of cytotoxic T-cell responses.

Extracellular heat shock protein-70 induces endotoxin tolerance in THP-1 cells

Recent data suggest that heat shock protein-70 (HSP-70), an intracellular protein, can exist in the extracellular compartment and signal through the CD14/TLR4 pathway. In this study, we tested the hypothesis that extracellular HSP-70 induces endotoxin (LPS) tolerance. Using human monocyte cell line (THP-1), initial dose-response experiments were conducted to determine a subthreshold concentration of HSP-70 that does not induce NF-kappaB activity. Differentiated THP-1 cells were preconditioned with subthreshold concentration (0.03 microg/ml HSP-70) for 18 h, followed by LPS stimulation (1 microg/ml) for 4 h. Preconditioning with HSP-70 decreased subsequent LPS-mediated NF-kappaB-dependent promoter activity and was accompanied by significant decreases of supernatant TNF levels. Furthermore, human monocytes isolated from human volunteers, subsequently preconditioned with HSP-70, demonstrated LPS tolerance as evidenced by abrogated supernatant TNF levels. Additional experiments were conducted to exclude the possibility of endotoxin contamination of HSP-70 by boiling HSP-70 at 100 degrees C for 1 h or preconditioning with equivalent concentrations of endotoxin as present in the HSP-70 preparation. These experiments indicated that induction of tolerance was not secondary to endotoxin contamination. Neutralization experiments with an anti-HSP-70 Ab confirmed the specificity of HSP-70 in tolerance induction. Preconditioning with HSP-70 attenuated cytosolic degradation of inhibitor kappaB-alpha and inhibited activation of inhibitor kappaB kinase following LPS stimulation. HSP-70 preconditioning decreased phosphorylation of the p65 subunit of NF-kappaB following LPS stimulation. These data suggest a novel role for extracellular HSP-70 in modifying mononuclear cell responses to subsequent LPS challenge.

Untangling the role of amyloid in atherosclerosis

PURPOSE OF REVIEW

Amyloid deposits are a defining feature of several age-related and debilitating diseases. Their widespread presence in atherosclerotic plaques suggests a potential role in lesion development. This review discusses the proteins known to accumulate in atheroma and examines the evidence that amyloid-like structures activate macrophage signaling pathways linked to inflammation and prothrombotic potential.

RECENT FINDINGS

Numerous proteins that accumulate in atherosclerotic plaques form amyloid fibrils in vivo, including apolipoproteins, beta-amyloid, and alpha1-antitrypsin. In addition, oxidation or enzymatic modification of low-density lipoproteins induces a structural reorganization of the particle, including the acquisition of amyloid-like properties. Similarly, glycation of serum albumin, as observed in diabetes, is accompanied by the formation of aggregates with all the hallmarks of amyloid. Several receptors implicated in atherogenesis modulate the fate of amyloid fibrils by mediating their clearance (scavenger receptors A and B-I), activating inflammatory signaling cascades (receptor for advanced glycation endproducts), or both (CD36). Finally, recent studies indicate that amyloid deposition accelerates diet-induced atherosclerosis in mice.

SUMMARY

Given the substantial evidence that amyloid fibrils or preamyloidogenic species are cytotoxic, the aberrant deposition of amyloid in the intima may be pathologically important in vascular inflammation and the promotion of atherosclerosis.

The C-terminal 26-residue peptide of serpin A1 is an inhibitor of HIV-1

Serpin A1 (alpha1-proteinase inhibitor) inhibits human immunodeficiency virus 1 (HIV-1) production by mechanisms which remain to be elucidated. The complex formation of serpin A1 with proteinases eliminates the proteolytic activity and generates a fragment corresponding to the serpin C-terminal 36-residue peptide. Here, we show that the C-terminal 26-residue peptide of serpin A1 (A1-C26) inhibits HIV-long terminal repeat (LTR)-driven transcription in epithelial cells transfected with HIV-1 LTR promoter-driven genes. A1-C26 increased STAT1 phosphorylation and strongly reduced viral expression in a monocytic cell line infected with HIV-1 NL4-3. This reduction of expression was also observed in HIV-1 infected, PHA-activated peripheral blood mononuclear cells. In HIV-1 infected cells, the inhibitory activity of HIV-1 caused by B9-C23 and C1-C26, the A1-C26 homologues corresponding to the C-terminal sections of serpin B9 and serpin C1, was much lower than that obtained with A1-C26. These serpin peptides represent a novel class of antiviral agents.

The C-terminal 26-residue peptide of serpin A1 stimulates proliferation of breast and liver cancer cells: role of protein kinase C and CD47

C26, the C-terminal 26 residue peptide of serpin A1, significantly increased cell proliferation in cultures of hepatoma cells, but not in porcine kidney epithelial cells, human skin fibroblasts or keratinocytes. The mitogenic activity of C26 was preferentially inhibited with a protein kinase C (PKC) inhibitor, an antibody against CD47 and CD47 short interfering RNA. The mutant C26-K19R,N22M, imitating a thrombospondin-like cell adhesion motif, increased the mitogenic activity in both Hep G2 cells and MCF-7 breast cancer cells. Phosphorylation of C26 at T24 (a putative PKC phosphorylation site) resulted in a 1.9-2.5 increase in mitogenic activity over C26 in MCF-7 cells.

Activation of protein kinase C by phorbol esters in human macrophages reduces the metabolism of modified LDL by down-regulation of scavenger receptor activity

Atherogenesis and inflammation are dependent on macrophage function. Signalling pathways are involved in the modulation of the classical low density lipopotein (LDL)-receptor and scavenger receptors activities, which are both expressed by macrophages. This study has evaluated the role of activation of the protein kinase A and C pathways in human macrophages on the metabolism of lipid carried by native, acetylated and oxidised LDL. We found that [3H]oleate incorporation into cholesteryl ester and triacylglycerol is increased by an analogue of cAMP, but strongly inhibited by treatment with phorbol ester (PMA) (100 nM, 6 h) in the presence of acLDL and oxLDL and, to a lesser extent, nLDL. The mechanisms underlying the effects of the phorbol ester were investigated further. The protein kinase C inhibitors, calphostin C and herbimycin A, prevented the PMA-mediated inhibition of cholesterol esterification. PMA also reduced [14C]acetate incorporation into newly synthesised lipids especially in the presence of nLDL, and reduced the uptake of cholesterol carried by modified LDL. Furthermore, the effects of PMA were not modified by inhibition of proteases activities, ruling out the hypothesis that CD163, a scavenger receptor which is shed by the cell surface in the presence of phorbol, is involved in the phorbol-induced reduction of cholesterol accumulation in macrophages in response to LDL. We conclude that binding of modified LDL to macrophages induces an appropriate pattern of scavenger receptor phosphorylation which, in turn, determines the optimal receptor internalisation process. PMA activates PKC pathways and prevents the optimal ligand-induced phosphorylation of the receptors, compromising the processes of degradation of modified LDL. The data also suggest that this mechanism may be related to the decreased uptake by activated macrophages of lipid carried by modified lipoproteins during the early phases of inflammation (284).

Progression of atherosclerosis is associated with variation in the alpha1-antitrypsin gene

OBJECTIVE

Alpha1-Antitrypsin (AAT) protects elastic tissue and may play a role in atherogenesis. The association of atherosclerosis progression with common AAT variants was considered in 2 clinical trials.

METHODS AND RESULTS

We examined the association of AAT V213A, S and Z deficiency alleles, and the functional 3' UTR 11478G>A with change in minimal luminal diameter, a measure of focal disease, in the Lopid Coronary Angiography Trial gemfibrozil study of post-bypass men. S or Z carriers (n=14) showed strong progression of disease on placebo (11.5%) but responded well to treatment (3% regression). 11478A carriers treated with placebo or gemfibrozil showed significantly more disease progression (n=8, -14.5% and n=16, -4.0%, respectively) than 11478GG men (n=107, -7.0% and n=108, -1.4%, respectively; overall, P=0.003). VV213 men treated with gemfibrozil (n=68) showed -4.8% progression, whereas A213 carriers (n=55) showed +1.4% regression of disease (P=0.001). No V213A effect was seen on placebo (P=0.11). In the Diabetes Atherosclerosis Intervention Study fenofibrate trial of angiographic progression in type 2 diabetes, the association of 11478A with increased disease progression was confirmed in the treatment group, but not the gemfibrozil-treated A213 association with regression, suggesting a pharmacogenetic difference.

CONCLUSIONS

Disease progression is associated with variation in AAT, and low AAT levels promote atherogenesis.

In vivo complex formation of oxidized alpha(1)-antitrypsin and LDL

An inactivated form of alpha(1)-antitrypsin (AT) and LDL coelutes in gel permeation chromatography. To characterize and to quantify the amount of this fraction of AT, a monoclonal antibody was established against chloramine T-oxidized AT and named OxAT-4. OxAT-4 recognized the oxidatively modified AT, including hexylaldehyde- or 4-hydroxy-2-nonenal-modified AT, but neither normal active AT nor trypsin/AT complex. Comigration of apoB and oxidized AT was demonstrated by Western blotting analysis of AT-LDL by means of anti-apoB monoclonal antibody and OxAT-4. A complex of oxidized AT and LDL (AT-LDL) was isolated from human plasma LDL by affinity column with an OxAT-4 antibody-coated carrier. AT-LDL was degraded 4 times more effectively by mouse peritoneal macrophages, but this was not mediated by scavenger receptor class A type I. Localization of AT-LDL was detected in human atherosclerotic lesions of the coronary artery, but distribution of it was not completely identical to that of macrophages. In situ hybridization revealed AT expression by macrophages, which were present in intimal layers of the coronary artery. From these findings, we concluded that AT is produced and oxidized by macrophages, then attached to LDL in the intimal layer of the arterial wall. Although AT-LDL that escapes into the blood stream can be cleared by hepatocytes, the remaining AT-LDL may be taken up by macrophages and contribute to the lipid accumulation in arterial wall cells as the early stage of atherogenesis.

C-terminal fragment of alpha1-antitrypsin activates human monocytes to a pro-inflammatory state through interactions with the CD36 scavenger receptor and LDL receptor

Monocyte scavenger receptor, CD36 has been implicated in the pathogenesis of atherosclerosis as a major oxidised LDL receptor mediating lipid accumulation and foam cell formation. Previously, we found that treatment of monocyte cultures with the carboxyl terminal fragment of alpha1-antitrypsin (C-36) increases lipid binding and uptake, induces LDL receptor mRNA and CD36 receptor protein expression, and also significantly increases production of pro-inflammatory molecules. To assess the role of the CD36 receptor in proatherogenic monocyte activation by the C-36 fragment, we tested whether specific anti-CD36 receptor antibodies would block the effects of C-36 on monocyte activation. We find that pre-incubation of cells with anti-LDL and anti-CD36 receptor antibodies (10 microg/ml) blocks binding of 125I-C-36 by about 50%. Similarly, cells pre-incubated with oxidised LDL or native LDL at concentrations from 2.5 to 10 microg/ml showed a loss of 125I-C-36 binding (up to 49 and 57%) and uptake (up to 47 and 59.8%), respectively. In parallel experiments, monocytes were first incubated for 1 or 6 h with anti-CD36 antibodies (10 microg/ml) prior to adding C-36 peptide. Anti-CD36 antibodies suppressed C-36-induced production of gelatinase B, monocyte chemoattractant protein-1, interleukin-6 and cellular oxygen consumption to control levels, whereas levels of TNFalpha were unaffected. In contrast, saturation of LDL receptors with excess of anti-LDL (20 microg/ml) significantly inhibited C-36 induced TNFalpha levels. Results indicate that the C-36 peptide binds to both LDL and CD36 scavenger receptors which involves selective upregulation of pro-inflammatory molecules and activation of the respiratory burst in human monocytes. This also supports important roles for CD36 and LDL receptors in atherogenesis and suggests that blockade of CD36 receptor can be protective in pro-inflammatory activation of human monocytes.

Conformational properties of serine proteinase inhibitors (serpins) confer multiple pathophysiological roles

Serine proteinase inhibitors (Serpins) are irreversible suicide inhibitors of proteases that regulate diverse physiological processes such as coagulation, fibrinolysis, complement activation, angiogenesis, apoptosis, inflammation, neoplasia and viral pathogenesis. The molecular structure and physical properties of serpins permit these proteins to adopt a number of variant conformations under physiological conditions including the native inhibitory form and several inactive, non-inhibitory forms, such as complexes with protease or other ligands, cleaved, polymerised and oxidised. Alterations of a serpin which affect its structure and/or secretion and thus reduce its functional levels may result in pathology. Serpin dysfunction has been implicated in thrombosis, emphysema, liver cirrhosis, immune hypersensitivity and mental disorders. The loss of inhibitory activity of serpins necessarily results in an imbalance between proteases and their inhibitors, but it may also have other physiological effects through the generation of abnormal concentrations of modified, non-inhibitory forms of serpins. Although these forms of inhibitory serpins are detected in tissues and fluids recovered from inflammatory sites, the important questions of which conditions result in generation of different molecular forms of serpins, what biological function these forms have, and which of them are directly linked to pathologies and/or may be useful markers for characterisation of disease states, remain to be answered. Elucidation of the biological activities of non-inhibitory forms of serpins may provide useful insights into the pathogenesis of diseases and suggest new therapeutic strategies.

Effects of Noninhibitory α-1-Antitrypsin on Primary Human Monocyte Activation in Vitro

A major function of alpha-1-antitrypsin (AAT) is the inhibition of overexpressed serine proteinases during inflammation. However, it is also known that the biological activity of AAT is affected by chemical modifications, including oxidation of the reactive-site methionine, polymerization, and cleavage by unspecific proteases, all of which will result in AAT inactivation and/or degradation. All inactive forms of AAT can be detected in tissues and fluids recovered from inflammatory sites. To test for a possible link between the inflammation-generated, noninhibitory, cleaved form of AAT and cellular processes associated with inflammation, we studied the effects of this form at varying concentrations on human monocytes in culture. We found that cleaved AAT at concentrations ranging between 1 and 10 microM in monocyte cultures over 24 h induces elevation in monocyte chemoattractant protein-1 (MCP-1) and pro-inflammatory cytokines such as TNFalpha and IL-6 and also increases production of interstitial collagenase (MMP-1) and gelatinase B (MMP-9), members of two different classes of matrix metalloproteinase. Moreover, monocytes stimulated with higher doses of cleaved AAT show an increase in cellular oxygen consumption by about 30%, while native AAT under the same experimental conditions inhibits oxygen consumption by about 50%. These results indicate that the cleaved form of AAT may play a role in monocyte recruitment and pro-inflammatory activation during inflammatory processes, and also suggest that changes in structure occurring upon AAT cleavage could alter its functional properties with potential pathological consequences.

The carboxyl-terminal fragment of alpha1-antitrypsin is present in atherosclerotic plaques and regulates inflammatory transcription factors in primary human monocytes

alpha1-Antitrypsin (AAT) serine proteinase inhibitor is found in most biological fluids, diffuses into most tissues, and is an important factor in controlling tissue damage by proteases in inflammatory diseases such as atherosclerosis. We have previously reported that the C-terminal fragment (C-36) generated during the cleavage of AAT by proteinases forms amyloid fibrils which have biological effects unrelated to precursor functions. Here we show that the C-36 fragment is present in atherosclerotic plaques, particularly within the fibrous cap at the base of the lipid core. We also found that human monocyte stimulation with C-36 fibrils led to a strong activation of both peroxisome proliferator-activated receptors alpha and gamma (PPARalpha and PPARgamma) at 1, 2, and 18 h of cell culture. A parallel increase in the intracellular lipid accumulation was also observed. Furthermore, stimulation of monocytes with C-36 for 18 h led to activator protein-1 (AP-1) and nuclear factor-kappaB (NF-kappaB) activation. These data for the first time demonstrate the peptide of AAT as a component of atherosclerotic plaques and as a novel activator of PPARalpha, PPARgamma, NF-kappaB, and AP-1 in cultured monocytes. Taken together, the effects of the peptide represent a new mechanism of monocyte activation that may be of importance not only in atherogenesis, but also in other inflammatory processes.

Activation of primary human monocytes by the oxidized form of alpha1-antitrypsin

The oxidation of methionine residues in many proteins, including the serine proteinase inhibitor alpha1-antitrypsin (AAT), can result in functional inactivation. In this study we investigated the pro-inflammatory properties of oxidized AAT (oxAAT), specifically its ability to activate human monocytes in culture. Monocytes stimulated with oxAAT at concentrations up to 0.2 mg/ml for 24 h showed significant elevation in monocyte chemoattractant protein-1, cytokine interleukin-6, and tumor necrosis factor-alpha expression and increased NADPH oxidase activity. Monocytes activated with oxAAT showed surprising effects on lipid metabolism. Expression of low density lipoprotein (LDL) receptors increased by up to 76% compared with controls but was not accompanied by any changes in (125)I-labeled LDL binding and, paradoxically, decreased LDL uptake, degradation, and intracellular cholesterol synthesis. oxAAT also down-regulated the scavenger receptor CD36, which takes up and is up-regulated by oxidized LDL and is down-regulated by cholesterol efflux. As a by-product of oxidative events accompanying inflammation, oxAAT has multiple effects on cytokine expression, generation of reactive oxygen species, and on intracellular lipid metabolism. The up-regulation of monocyte-derived reactive oxygen by oxAAT could potentially result in self-amplification of AAT oxidation and, thereby, the other effects deriving from it. This implies that there are as yet unidentified regulatory processes that control this cycle.