Esther J. Pavón

Melatonin reduces endothelin-1 expression and secretion in colon cancer cells through the inactivation of FoxO-1 and NF-κβ

Melatonin is an indoleamine that is synthesised from tryptophan under the control of the enzymes arylalkylamine N‐acetyltransferase (AA‐NAT) and acetylserotonin methyltransferase (ASMT). Melatonin inhibits colon cancer growth in both in vivo and in vitro models; however, a precise mechanism responsible for inhibiting tumour growth has not been clearly described. Endothelin‐1 (ET‐1) is a peptide that acts as a survival factor in colon cancer, inducing cell proliferation, protecting carcinoma cells from apoptosis and promoting angiogenesis. The data presented show that melatonin inhibits edn‐1 mRNA expression (the first step in ET‐1 synthesis), ECE‐1 protein expression and the release of ET‐1 from colorectal cancer cells in vitro. ET‐1 levels in cultured media present a similar inhibition pattern to that of edn‐1 mRNA expression despite the inhibition of ECE‐1 protein after melatonin treatment, which suggests that an endopeptidase other than ECE‐1 could be mainly responsible for ET‐1 synthesis. The inhibition of edn‐1 expression is due to an inactivation of FoxO1 and NF‐κβ transcription factors. FoxO1 inactivation is associated with an increased Src phosphorylation, due to elevated cAMP content and PKA activity, whereas NF‐κβ inactivation is associated with the blockade of Akt and ERK phosphorylation due to the inhibition of PKC activity after melatonin treatment. Melatonin also inhibits edn‐1 promoter activity regulated by FoxO1 and NF‐κβ. Finally, a significant correlation was observed between AA‐NAT and edn‐1 expression downregulation in human colorectal cancer tissues. In conclusion, melatonin may be useful in treating colon carcinoma in which the activation of ET‐1 plays a role in tumour growth and progression.

Exosomes from human lymphoblastoid B cells express enzymatically active CD38 that is associated with signaling complexes containing CD81, Hsc-70 and Lyn.

Exosome vesicles of endocytic origin are involved in communication between tumor and immune cells. In addition, membrane rafts (MR) may support the sorting of proteins associated with exosomes. CD38 is found at the plasma membrane and in recycling endosomes, which are both redistributed toward the immunological synapse (IS) upon T cell antigen receptor (TCR) engagement. The data of this study provide evidence that CD38 is expressed on the surface of secreted exosomes derived from lymphoblastoid B cells. Exosomic CD38 is associated with the signaling molecules CD81, Hsc-70 and Lyn. Likewise, in MR, CD38 is associated with CD81, CD19, Lyn, Galphai-2, Hsc-70 and actin. Therefore, a high degree of overlap in the pattern of signaling proteins associated with CD38 in exosomes and MR exists. Exosomic and MR CD38, by virtue of these interactions, have signaling potential. Indeed, CD38 is enzymatically active in both exosomes and MR, and CD38 ligation induces Akt/PKB and Erk activation, which is accompanied by increased translocation of CD38 into MR. In conclusion, the present study indicates that CD38 localizes to MR, where it promotes cell signaling, and it is exported out of the cells through the exosome-mediated exocytic pathway, where it may act as an intercellular messenger.

Increased expression and phosphorylation of the two S100A9 isoforms in mononuclear cells from patients with systemic lupus erythematosus: a proteomic signature for circulating low-density granulocytes.

Proteins differentially expressed in peripheral blood mononuclear cells (PBMCs) from systemic lupus erythematosus (SLE) patients versus Normal controls were identified by 2-DE and MALDI-MS. Thus, S100A9 expression was significantly increased in SLE PBMCs relative to Normal PBMCs at both mRNA and protein levels. Increased S100A9 levels in SLE PBMCs correlated positively with the abnormal presence of low-density granulocytes (LDGs) detected by flow-cytometry in the mononuclear cell fractions. Another set of proteins that were differentially expressed in SLE PBMCs formed S100A9-independent clusters, suggesting that these differences in protein expression are in fact reflecting changes in the abundance of specific cell types. In SLE PBMCs spots of the two S100A9 isoforms, S100A9-l and S100A9-s, and their phosphorylated counterparts were identified and confirmed to be phosphorylated at Thr(113) by MS/MS analyses. In addition, the phorbol ester PMA alone or in combination with ionomycin induced a stronger increase in threonine phosphorylation of S100A9 in SLE than in Normal PBMCs, while the same stimuli caused the opposite effect on phosphorylation and activation of Erk1/2, suggesting the existence of an abnormal S100A9 signaling in SLE PBMCs. Therefore, the expansion and activation of LDGs in SLE seems to underlie this prominent S100A9 signature.

Increased CD38 expression in T cells and circulating anti-CD38 IgG autoantibodies differentially correlate with distinct cytokine profiles and disease activity in systemic lupus erythematosus patients

CD38 is a multifunctional protein possessing ADP-ribosyl cyclase activity responsible for both the synthesis and the degradation of several Ca(2+)-mobilizing second messengers. In mammals, CD38 also functions as a receptor. In this study CD38 expression in CD4(+), CD8(+), or CD25(+) T cells was significantly higher in systemic lupus erythematosus (SLE) patients than in Normal controls. Increased CD38 expression in SLE T cells correlated with plasma levels of Th2 (IL-4, IL-10, IL-13) and Th1 (IL-1β, IL-12, IFN-γ, TNF-α) cytokines, and was more prevalent in clinically active SLE patients than in Normal controls. In contrast, elevated anti-CD38 IgG autoantibodies were more frequent in clinically quiescent SLE patients (SLEDAI=0) than in Normal controls, and correlated with moderate increased plasma levels of IL-10 and IFN-γ. However, clinically active SLE patients were mainly discriminated from quiescent SLE patients by increased levels of IL-10 and anti-dsDNA antibodies, with odds ratios (ORs) of 3.7 and 4.8, respectively. Increased frequency of anti-CD38 autoantibodies showed an inverse relationship with clinical activity (OR=0.43), and in particular with the frequency of anti-dsDNA autoantibodies (OR=0.21). Increased cell death occurred in CD38(+) Jurkat T cells treated with anti-CD38(+) SLE plasmas, and not in these cells treated with anti-CD38(-) SLE plasmas, or Normal plasmas. This effect did not occur in CD38-negative Jurkat T cells, suggesting that it could be attributed to anti-CD38 autoantibodies. These results support the hypothesis that anti-CD38 IgG autoantibodies or their associated plasma factors may dampen immune activation by affecting the viability of CD38(+) effector T cells and may provide protection from certain clinical SLE features.

Factors associated with hepatic steatosis in obese children and adolescents.

Objectives: Obesity is associated with high prevalence of hepatic steatosis. We speculate that determinant factors of susceptibility to hepatic steatosis in obesity could differ between children and adolescents. Patients and Methods: Blood biochemical parameters, systemic oxidative stress markers, proinflammatory cytokines, and adipokine levels were determined in 157 obese children and adolescents. The subjects were divided into 2 groups: children and adolescents, identified as such in accordance with Tanner stage and the measured level of dehydroepiandrosterone sulphate. Steatosis was evaluated by ultrasonography in 127 subjects. Results: Steatosis prevalence was 44.8%. In the “children” group, those with hepatic steatosis presented higher levels of erythrocyte oxidised glutathione (GSSG) and resistin, lower levels of high-density lipoprotein (HDL) cholesterol, and lower enzymatic activities of erythrocyte glutathione reductase (GRd) and glutathione oxidase (GPx). In the “adolescents” group, those with hepatic steatosis presented higher values for body mass index z score (BMIz), insulin, peptide C, homeostatic model assessment index (HOMA-IR), alanine aminotransferase (ALT), aspartate aminotransferase (AST), triglycerides, GSSG, and leptin. These subjects also presented lower values for soluble leptin receptor, GRd, and GPx. In the “children” group, the only independent factor of steatosis was a decrease in GRd activity (odds ratio [OR] 0.165, 95% CI 0.03–0.84, P = 0.030). Moreover, in the “adolescent” group, the independent factors were higher for GSSG (OR 6.8, 95% CI 1.6–28.7, P = 0.010) and HOMA-IR (OR 1.9, 95% CI 1.17–3.1, P = 0.009). Conclusions: Factors associated with hepatic steatosis differ between obese children and adolescents. Oxidative stress is seen to be the main process in children, whereas in adolescents oxidative stress and insulin resistance are significant factors for steatosis.

Cytometric analysis of adipose tissue reveals increments of adipocyte progenitor cells after weight loss induced by bariatric surgery

Obesity-related comorbidities are, in large part, originated from the dysfunction of adipose tissue. Most of them revert after the normalization of body mass. Adipose tissue is essentially occupied by adipocytes. However, different populations of immunological cells and adipocyte precursor cells (AdPCs) are the main cellular components of tissue. During obesity, body fat depots acquire a low-level chronic inflammation and adipocytes increase in number and volume. Conversely, weight loss improves the inflammatory phenotype of adipose tissue immune cells and reduces the volume of adipocytes. Nevertheless, very little is known about the evolution of the human AdPCs reservoir. We have developed a flow cytometry-based methodology to simultaneously quantify the main cell populations of adipose tissue. Starting from this technical approach, we have studied human adipose tissue samples (visceral and subcutaneous) obtained at two different physiological situations: at morbid obesity and after bariatric surgery-induced weight loss. We report a considerable increase of the AdPCs reservoir after losing weight and several changes in the immune cells populations of adipose tissue (mast cells increase, neutrophils decrease and macrophages switch phenotype). No changes were observed for T-lymphocytes, which are discussed in the context of recent findings.