Franco Dallegri

HUMAN MESENCHYMAL STEM CELLS INHIBIT NEUTROPHIL APOPTOSIS: A MODEL FOR NEUTROPHIL PRESERVATION IN THE BONE MARROW NICHE

Mesenchymal stem cells (MSC) establish close interactions with bone marrow sinusoids in a putative perivascular niche. These vessels contain a large storage pool of mature nonproliferating neutrophils. Here, we have investigated the effects of human bone marrow MSC on neutrophil survival and effector functions. MSC from healthy donors, at very low MSC:neutrophil ratios (up to 1:500), significantly inhibited apoptosis of resting and interleukin (IL)‐8‐activated neutrophils and dampened N‐formyl‐l‐methionin‐l‐leucyl‐l‐phenylalanine (f‐MLP)‐induced respiratory burst. The antiapoptotic activity of MSC did not require cell‐to‐cell contact, as shown by transwell experiments. Antibody neutralization experiments demonstrated that the key MSC‐derived soluble factor responsible for neutrophil protection from apoptosis was IL‐6, which signaled by activating STAT‐3 transcription factor. Furthermore, IL‐6 expression was detected in MSC by real‐time reverse transcription‐polymerase chain reaction and enzyme‐linked immunosorbent assay. Finally, recombinant IL‐6 was found to protect neutrophils from apoptosis in a dose‐dependent manner. MSC had no effect on neutrophil phagocytosis, expression of adhesion molecules, and chemotaxis in response to IL‐8, f‐MLP, or C5a. These results support the following conclusions: (a) in the bone marrow niche, MSC likely protect neutrophils of the storage pool from apoptosis, preserving their effector functions and preventing the excessive or inappropriate activation of the oxidative metabolism, and (b) a novel mechanism whereby the inflammatory potential of activated neutrophils is harnessed by inhibition of apoptosis and reactive oxygen species production without impairing phagocytosis and chemotaxis has been identified.

Taurine prevents apoptosis induced by high ambient glucose in human tubule renal cells

Background Hyperglycemia selectively triggers apoptosis in tubule and endothelial cells. Taurine, a conditionally essential amino acid, is abundant in several tubule segments, but its role has not been defined fully. It can serve as an osmolyte or as an endogenous antioxidant. Taurine metabolism is altered in diabetes mellitus, with extracellular and intracellular pools reduced. It is still unknown whether taurine can play a role as a protective agent in apoptosis induced by high glucose in tubular cells. Methods Apoptosis (by annexin V binding and the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end-labeling method), cellular reactive oxygen species (ROS) formation (by fluorescent probe 2′-7′ dichlorofluorescin diacetate and FACScan flow cytometry), and Bcl-2 and Bax proteins (by immunostaining) were studied in a human proximal tubular cell line (HK-2) grown in a medium with physiologic (5.5 mM) or high (30 mM) glucose concentrations for 48 hours. In separate experiments, taurine (3-24 mM) was added to the media. Results The exposure of human tubule cells to 30 mM glucose for 48 hours resulted in a significant increase in apoptosis compared with 5.5 mM glucose (35±8% vs. 6±3%, p<0.001). Thirty mM mannitol failed to induce the effects of high glucose. High glucose-mediated apoptosis was associated with a decrease in the expression of Bcl-2 (-87%) and a twofold increase in the expression of Bax protein. Taurine had a dose-dependent effect in preventing high-glucose-induced apoptosis (-78%, p<0.001 at 24 mM). Moreover, with taurine, intracellular ROS decreased by 34% (p<0.05), and changes in intracellular ROS formation induced by taurine at 24 hours predicted the variations in the apoptotic index at 48 hours (r=0.87, p<0.02). Other antioxidants, such as glutathione and N-acetylcysteine, also attenuated the high glucose-induced apoptosis. Conclusion These results demonstrate that taurine attenuates hyperglycemia-induced apoptosis in human tubular cells via an inhibition of oxidative stress. Taurine might act as an endogenous antioxidant in tubule cells and could exert a beneficial effect in preventing tubulointerstitial injury in diabetic nephropathy.

Anti-Apolipoprotein A-1 auto-antibodies are active mediators of atherosclerotic plaque vulnerability

AIMS Anti-Apolipoprotein A-1 auto-antibodies (anti-ApoA-1 IgG) represent an emerging prognostic cardiovascular marker in patients with myocardial infarction or autoimmune diseases associated with high cardiovascular risk. The potential relationship between anti-ApoA-1 IgG and plaque vulnerability remains elusive. Thus, we aimed to investigate the role of anti-ApoA-1 IgG in plaque vulnerability. METHODS AND RESULTS Potential relationship between anti-ApoA-1 IgG and features of cardiovascular vulnerability was explored both in vivo and in vitro. In vivo, we investigated anti-ApoA-1 IgG in patients with severe carotid stenosis (n = 102) and in ApoE-/- mice infused with polyclonal anti-ApoA-1 IgG. In vitro, anti-ApoA-1 IgG effects were assessed on human primary macrophages, monocytes, and neutrophils. Intraplaque collagen was decreased, while neutrophil and matrix metalloprotease (MMP)-9 content were increased in anti-ApoA-1 IgG-positive patients and anti-ApoA-1 IgG-treated mice when compared with corresponding controls. In mouse aortic roots (but not in abdominal aortas), treatment with anti-ApoA-1 IgG was associated with increased lesion size when compared with controls. In humans, serum anti-ApoA-1 IgG levels positively correlated with intraplaque macrophage, neutrophil, and MMP-9 content, and inversely with collagen. In vitro, anti-ApoA-1 IgG increased macrophage release of CCL2, CXCL8, and MMP-9, as well as neutrophil migration towards TNF-α or CXCL8. CONCLUSION These results suggest that anti-ApoA-1 IgG might be associated with increased atherosclerotic plaque vulnerability in humans and mice.

Tumor necrosis factor-alpha (TNF-α) induces integrin CD11b/CD18 (Mac-1) up-regulation and migration to the CC chemokine CCL3 (MIP-1α) on human neutrophils through defined signalling pathways

Strong evidence suggests that neutrophils may play an active role in acute and chronic inflammatory disorders, such as rheumatoid arthritis and atherosclerosis. Given the role of pro-inflammatory cytokine TNF-alpha in these inflammatory processes, we planned the present study to investigate the effect of short term incubation with TNF-alpha on neutrophil migration to CCL3, a chemokine produced in inflammatory sites and normally devoid of neutrophil chemotactic properties. We found that TNF-alpha primed neutrophils for migration to CCL3 via CCR5. TNF-alpha-induced migration was a consequence of the TNF-alpha-induced up-regulation of integrin CD11b/CD18 (Mac-1) on neutrophil surface. Furthermore, TNF-alpha activity was found to be strictly dependent on the activation of ERK 1/2 p44, cooperating with the intracellular pathways involving Src kinases, PI3K/Akt, p38 MAPK, well known as activated in response to classical chemoattractants (CXCL8) or priming agents (GM-CSF). On the contrary, the effect of TNF-alpha on neutrophil migration to CCL3 was not dependent on JNK 1/2. In conclusion, the present report shows that TNF-alpha unveils a previously unknown capacity of neutrophils to migrate to CCL3 through the intervention of Mac-1. TNF-alpha regulates Mac-1 up-regulation through signalling pathways, involving various kinases, but not JNK 1/2. Although highly speculative, ERK 1/2 p44 may represent a selective target for the pharmacologic manipulation of neutrophil-mediated adverse activities in TNF-alpha-mediated inflammatory states.

Oxidative Stress Mediates Apoptotic Changes Induced by Hyperglycemia in Human Tubular Kidney Cells

Reactive oxygen species (ROS) are important mediators for several biologic responses, including apoptosis. The present study evaluated the time course of changes in intracellular ROS production and apoptosis-related proteins, as well as apoptotic changes in human tubular proximal cells (HK-2 cells) exposed to hyperglycemia. Apoptosis (annexin V binding), ROS formation (fluorescence probe dichlorofluorescin diacetate and FACScan flow cytometry), and X chromosome-linked protein (XIAP; Western blot) were studied in HK-2 cells grown in a medium containing normal (NG) or high glucose (HG) concentrations (5.5 or 30 mM, respectively) for 18 to 48 h. HG promoted an increase (65% at 18 h and 73% at 24 h; P < 0.05 versus NG) in intracellular ROS generation. At 18 h, the NF-kB binding activity (evaluated by electrophoretic mobility-shift assay) was suppressed by HG. At the same time, the expression of NF-kB-induced antiapoptotic XIAP was reduced in HG-treated cells. Apoptotic changes were observed at 48 h (34 +/- 7% in HG versus 10 +/- 3% in NG; P < 0.001). Changes in ROS production at 24 h predicted changes in the apoptotic index at 48 h (r = 0.96, P < 0.0001). These results suggest that hyperglycemia induces apoptotic changes in human tubular cells via an increase in oxidative stress and that a downregulation of antiapoptotic protein XIAP is a component of this response.

Systemic and Intraplaque Mediators of Inflammation Are Increased in Patients Symptomatic for Ischemic Stroke

Background and Purpose— The concept of “vulnerable plaque” has been extended to the more recent definition of the “cardiovascular vulnerable patient,” in which “intraplaque” and “systemic” factors contribute to the cumulative risk of acute cardiovascular events. Thus, we investigated the possible role of systemic and intraplaque inflammation in patients asymptomatic versus symptomatic for ischemic stroke. Methods— Regions upstream and downstream the blood flow were isolated from internal carotid plaques of patients asymptomatic (n=63) or symptomatic (n=18) for ischemic stroke. Specimens were analyzed for lipid, collagen, macrophage, lymphocyte, neutrophil, mast cell and smooth muscle cell content, and chemokine and cytokine mRNA expression. Chemokine receptors and adhesion molecules were assessed on circulating leukocytes by flow cytometry. Systemic inflammatory markers and biochemical parameters were measured on total blood, plasma, and serum. Results— Tumor necrosis factor-&agr; and CCL5 serum levels as well as intercellular adhesion molecule-1 expression on circulating neutrophils were increased in symptomatic as compared with asymptomatic patients. Collagen content and smooth muscle cell infiltration were decreased in symptomatic plaques. In upstream regions of symptomatic plaques, lipid content and lymphocyte infiltration were increased. In downstream regions of symptomatic plaques, macrophage, neutrophil, and mast cell infiltration were increased. Intraplaque collagen content was positively correlated with smooth muscle cell infiltration and inversely correlated with macrophages, neutrophils, or serum tumor necrosis factor-&agr;. Collagen reduction in downstream regions and serum tumor necrosis factor-&agr; were independently associated with the likelihood of being symptomatic. Conclusions— Inflammatory mediators are increased in ischemic stroke. Despite statistically significant, the correlation between tumor necrosis factor-&agr; serum level and intraplaque vulnerability was weak and probably of limited biological importance.

Cytoprotection against neutrophil derived hypochlorous acid: a potential mechanism for the therapeutic action of 5-aminosalicylic acid in ulcerative colitis.

The aim of the present study was to investigate the effects of 5-aminosalicyclic acid (5-ASA) on the cell injury mediated by activated neutrophils. We used a system constituted of neutrophils, triggered with phorbol myristate acetate, and 51Cr-labelled Daudi cells as targets. The results show that 5-ASA is capable of efficiently preventing neutrophil-mediated lysis. 5-ASA was up to 10-fold more effective than taurine, which acts as an hypochlorous acid scavenger. Moreover, 5-ASA was found to compete with taurine for the neutrophil derived hypochlorous acid. The results are consistent with the conclusion that 5-ASA is capable of limiting the neutrophil mediated cell damage by scavenging the generated hypochlorous acid. This may represent a potential mechanism for the therapeutic action of 5-ASA in ulcerative colitis.

Induction of neutrophil chemotaxis by leptin: crucial role for p38 and Src kinases.

Abstract:  Leptin is involved in energy homeostasis, hematopoiesis, inflammation, and immunity. Although hypoleptinemia characterizing malnutrition has been strictly related to increased susceptibility to infection, other hyperleptinemic conditions, such as end‐stage renal disease (ESRD), are highly susceptible to bacterial infections. On the other hand, ESRD is characterized by neutrophil functional defects crucial for infectious morbidity, and several uremic toxins capable of depressing neutrophil functions have been identified. In the present study, we investigated leptins effects on neutrophil function. Our results show that leptin inhibits neutrophil migration in response to classical chemoattractants. Otherwise, leptin is endowed with chemotactic activity toward neutrophils. The two activities, inhibition of the cell response to chemokines and stimulation of neutrophil migration, could be detected at similar concentrations. On the contrary, neutrophils exposed to leptin did not display detectable [Ca2+]i mobilization, oxidant production, orβ2‐integrin upregulation. The results demonstrate that leptin is a pure chemoattractant devoid of secretagogue properties but capable of inhibiting neutrophil chemotaxis to classical neutrophilic chemoattractants. This effect is dependent on the activation of intracellular kinases involved in F‐actin polymerization and neutrophil locomotion. Indeed, p38 mitogen‐activated protein kinase (MAPK) and Src kinase, but not extracellular‐regulated kinase (ERK), were activated by short‐term incubation with leptin. Moreover, p38 MAPK inhibitor SB203580 and Src kinase inhibitor PP1, but not MEK inhibitor PD98059, blocked neutrophil chemotaxis toward leptin. Serum from patients with ESRD inhibits migration of normal neutrophils in response to N‐formyl‐methionine‐leucyl‐phenylalanine (FMLP) with a strict correlation between serum leptin levels and serum ability to suppress neutrophil locomotion. The serum inhibitory activity can be effectively prevented by immune‐depletion of leptin. Taking into account the crucial role of neutrophils in host defense, we show that leptin‐mediated ability of ERSD serum to inhibit neutrophil chemotaxis appears to be a mechanism contributing to neutrophil dysfunction in ESRD.

Leptin as a Uremic Toxin Interferes with Neutrophil Chemotaxis

Leptin is a pleiotropic molecule involved in energy homeostasis, hematopoiesis, inflammation, and immunity. Hypoleptinemia characterizing starvation has been strictly related to increased susceptibility to infection secondary to malnutrition. Nevertheless, ESRD is characterized by high susceptibility to bacterial infection despite hyperleptinemia. Defects in neutrophils play a crucial role in the infectious morbidity, and several uremic toxins that are capable of depressing neutrophil functions have been identified. Only a few and contrasting reports about leptin and neutrophils are available. This study provides evidence that leptin inhibits neutrophil migration in response to classical chemoattractants. Moreover, serum from patients with ESRD inhibits migration of normal neutrophils in response to N-formyl-methionyl-leucyl-phenylalanine with a strict correlation between serum leptin levels and serum ability to suppress neutrophil locomotion. Finally, the serum inhibitory activity can be effectively prevented by immune depletion of leptin. The results also show, however, that leptin by itself is endowed with chemotactic activity toward neutrophils. The two activities-inhibition of the cell response to chemokines and stimulation of neutrophil migration-could be detected at similar concentrations. On the contrary, neutrophils exposed to leptin did not display detectable [Ca(2+)](i) mobilization, oxidant production, or beta(2)-integrin upregulation. The results demonstrate that leptin is a pure chemoattractant devoid of secretagogue properties that are capable of inhibiting neutrophil chemotaxis to classical neutrophilic chemoattractants. Taking into account the crucial role of neutrophils in host defense, the leptin-mediated ability of ERSD serum to inhibit neutrophil chemotaxis appears as a potential mechanism that contributes to the establishment of infections in ERSD.

Nimesulide decreases superoxide production by inhibiting phosphodiesterase type IV

Nimesulide, the prototype of a new class of anti-inflammatory drugs, dose-dependently decreases the production of the superoxide anion (O2-.) in N-formyl-methionyl-leucyl-phenylalanine (fMLP)- and in phorbol myristate acetate (PMA)-stimulated polymorphonuclear leukocytes. The inhibition of O2-. is possibly related to its inhibitory effect on polymorphonuclear leukocyte cytosolic phosphodiesterase type IV (IC50 = 39 +/- 2 microM), to the related increase in cAMP (P < 0.01 at 1 microM) and the subsequent increase in protein kinase A activity. In fact H-89, a specific protein kinase A inhibitor, counteracts the inhibitory effect of nimesulide on O2-. production by fMLP and PMA. The activation of protein kinase A may prompt the phosphorylation of a number of substrates, thus inhibiting the assembly of NADPH-oxidase in the plasma membrane. Accordingly, nimesulide decreases PMA-induced assembly of NADPH-oxidase in polymorphonuclear leukocytes plasma membranes by about 35%. Protein kinase A activation may also interfere with chemotaxis. Nimesulide inhibits stimulated chemotaxis and the effect is decreased by H-89. Inhibition of phosphodiesterase type IV may explain many of nimesulides effects.