Bioactive peptides,networks and systems biology

Bioactive peptides are a group of diverse intercellular signalling molecules. Almost half a century of research on this topic has resulted in an enormous amount of data. In this essay, a general perspective to interpret all these data will be given. In classical endocrinology, neuropeptides were thought of as simple signalling molecules that each elicit one response. However, the fact that the total bioactive peptide signal is far from simple puts this view under pressure. Cells and tissues express many different bioactive peptides and they are also able to respond to many different bioactive peptides, indicating that multiple receptors and signal transduction pathways are present in a single cell. Therefore, the authors suggest that the bioactive peptide signalling system should be regarded in the context of network and systems biology. Bioactive peptides can best be viewed as an extension of the protein interaction network that allows regulating and fine‐tuning the metabolism of the different cells and tissues in the body. The cell thus responds to the ‘peptidome’ instead of to a single peptide. The intracellular part of this signalling network consists of the various signalling transduction cascades. Recently, new systems biology approaches have emerged for the modelling of cell signalling. The network and systems biology approach is also able to shed new light on the evolution of intercellular signalling.     

Clinical Profiles and Factors Associated with Death in Adults with Dengue Admitted to Intensive Care Units,Minas Gerais,Brazil

The purpose of our study was to describe the clinical profile of dengue-infected patients admitted to Brazilian intensive care units (ICU) and evaluate factors associated with death. A longitudinal, multicenter case series study was conducted with laboratory-confirmed dengue patients admitted to nine Brazilian ICUs situated in Minas Gerais state, southeastern Brazil from January 1, 2008, to December 31, 2013. Demographic, clinical and laboratory data; disease severity scores; and mortality were evaluated. A total of 97 patients were studied. The in-ICU and in-hospital mortality rates were 18.6% and 19.6%, respectively. Patients classified as having severe dengue according to current World Health Organization classifications showed an increased risk of death in a univariate analysis. Nonsurvivors were older, exhibited lower serum albumin concentrations and higher total leukocyte counts and serum creatinine levels. Other risk factors (vomiting, lethargy/restlessness, dyspnea/respiratory distress) were also associated with death in a univariate analysis. Multivariate analysis indicated that in-hospital mortality was significantly associated with Acute Physiology and Chronic Health Evaluation II and the Sequential Organ Failure Assessment score. The ICU and in-hospital mortality observed in this study were higher than values reported in similar studies. An increased frequency of ICU admission due to severe organ dysfunction, higher severity indices and scarcity of ICU beds may partially explain the higher mortality.     

Antagonistic factors control the unproductive splicing of SC35 terminal intron

Alternative splicing is regulated in part by variations in the relative concentrations of a variety of factors, including serine/arginine-rich (SR) proteins. The SR protein SC35 self-regulates its expression by stimulating unproductive splicing events in the 3′ untranslated region of its own pre-mRNA. Using various minigene constructs containing the terminal retained intron and flanking exons, we identified in the highly conserved last exon a number of exonic splicing enhancer elements responding specifically to SC35, and showed an inverse correlation between affinity of SC35 and enhancer strength. The enhancer region, which is included in a long stem loop, also contains repressor elements, and is recognized by other RNA-binding proteins, notably hnRNP H protein and TAR DNA binding protein (TDP-43). Finally, in vitro and in cellulo experiments indicated that hnRNP H and TDP-43 antagonize the binding of SC35 to the terminal exon and specifically repress the use of SC35 terminal 3′ splice site. Our study provides new information about the molecular mechanisms of SC35-mediated splicing activation. It also highlights the existence of a complex network of self- and cross-regulatory mechanisms between splicing regulators, which controls their homeostasis and offers many ways of modulating their concentration in response to the cellular environment.     

<Emphasis Type="Italic">In vitro</Emphasis> organogenesis of <Emphasis Type="Italic">Passiflora alata</Emphasis>

Passiflora alata in vitro organogenesis was studied based on explant type, culture medium composition, and incubation conditions. The results indicated that the morphogenic process occurred more efficiently when hypocotyl segment-derived explants were cultured in media supplemented with cytokinin and AgNO₃ incubated under a 16-h photoperiod. The shoot bud elongation and plant development were obtained by transferring the material to MSM culture medium supplemented with GA₃ and incubated in flasks with vented lids. Histological analyses of the process revealed that the difficulties in obtaining plants could be related to the development of protuberances and leaf primordia structures, which did not contain shoot apical meristem. Roots developed easily by transferring elongated shoots to 1/2 MSM culture medium. Plant acclimatization occurred successfully, and somaclonal variation was not visually detected. The efficiency of this organogenesis protocol will be evaluated for genetic transformation of this species to obtain transgenic plants expressing genes that can influence the resistance to Cowpea aphid borne mosaic virus.     

Urinary Excretion of Zinc and Metabolic Control of Patients with Diabetes Type 2

The objective of this study was to assess urinary excretion of zinc and evaluation parameters of metabolic control in type 2 diabetic patients. Thirty-one type 2 diabetic patients, of both genders, with 5.8 ± 5.6 years average time of the disease, age range 20–60 years, were selected. Evaluation of the nutritional status was performed using anthropometric measurements. To evaluate food consumption, the 3-day alimentary log method was used, and its analysis was performed using a software. Determination of urinary zinc was by atomic absorption spectrophotometry. From the obtained results, it was concluded that 51.6% of the patients were overweight. The mean of found waist circumference was 100.4 and 92.2 cm for men and women, respectively. Blood glucose and glycated hemoglobin values were higher than reference values, and plasma albumin concentration was adequate. The median of found urinary zinc excretion was 474.9 μg/24 h, within normal standards (300–600 μg/day). Regarding diet composition, calorie and protein concentration were above recommendation, while mean zinc concentration was adequate. This data allow the conclusion that the evaluated patients presented adequate urinary zinc excretion in comparison with reference values.     

Alpha6beta1 integrin expressed by sperm is determinant in mouse fertilization

Background  

Based on inhibition tests, the alpha6beta1 integrin was suggested to be a sperm receptor, but further experiments using gene deletion techniques have shown that neither oocyte alpha6, nor beta1 integrin subunits were essential for mouse fertilization.     

Porphyromonas gingivalis participates in pathogenesis of human abdominal aortic aneurysm by neutrophil activation. Proof of concept in rats

Background

Abdominal Aortic Aneurysms (AAAs) represent a particular form of atherothrombosis where neutrophil proteolytic activity plays a major role. We postulated that neutrophil recruitment and activation participating in AAA growth may originate in part from repeated episodes of periodontal bacteremia.

Methods and Findings

Our results show that neutrophil activation in human AAA was associated with Neutrophil Extracellular Trap (NET) formation in the IntraLuminal Thrombus, leading to the release of cell-free DNA. Human AAA samples were shown to contain bacterial DNA with high frequency (11/16), and in particular that of Porphyromonas gingivalis (Pg), the most prevalent pathogen involved in chronic periodontitis, a common form of periodontal disease. Both DNA reflecting the presence of NETs and antibodies to Pg were found to be increased in plasma of patients with AAA. Using a rat model of AAA, we demonstrated that repeated injection of Pg fostered aneurysm development, associated with pathological characteristics similar to those observed in humans, such as the persistence of a neutrophil-rich luminal thrombus, not observed in saline-injected rats in which a healing process was observed.

Conclusions

Thus, the control of periodontal disease may represent a therapeutic target to limit human AAA progression.     

Portable light transmission measuring system for preserved corneas

Background  

The authors have developed a small portable device for the objective measurement of the transparency of corneas stored in preservative medium, for use by eye banks in evaluation prior to transplantation.     

Syndecan-4 is a signaling molecule for stromal cell-derived factor-1 (SDF-1)/ CXCL12

Stromal cell-derived factor-1 (SDF-1)/CXCL12, the ligand for CXCR4, induces signal transduction. We previously showed that CXCL12 binds to high- and low-affinity sites expressed by primary cells and cell lines, and forms complexes with CXCR4 as expected and also with a proteoglycan, syndecan-4, but does not form complexes with syndecan-1, syndecan-2, CD44 or beta-glycan. We also demonstrated the occurrence of a CXCL12-independent heteromeric complex between CXCR4 and syndecan-4. However, our data ruled out the glycosaminoglycan-dependent binding of CXCL12 to HeLa cells facilitating the binding of this chemokine to CXCR4. Here, we demonstrate that CXCL12 directly binds to syndecan-4 in a glycosaminoglycan-dependent manner. We show that upon stimulation of HeLa cells by CXCL12, CXCR4 becomes tyrosine phosphorylated as expected, while syndecan-4 (but not syndecan-1, syndecan-2 or beta-glycan) also undergoes such tyrosine phosphorylation. Moreover, tyrosine-phosphorylated syndecan-4 from CXCL12-stimulated HeLa cells physically coassociates with tyrosine phosphorylated CXCR4. Pretreatment of the cells with heparitinases I and III prevented the tyrosine phosphorylation of syndecan-4, which suggests that the heparan sulfate-dependent binding of SDF-1 to this proteoglycan is involved. Finally, by reducing syndecan-4 expression using RNA interference or by pretreating the cells with heparitinase I and III mixture, we suggest the involvement of syndecan-4 and heparan sulfate in p44/p42 mitogen-activated protein kinase and Jun N-terminal/stress-activated protein kinase activation by action of CXCL12 on HeLa cells. However, these treatments did not modify the calcium mobilization induced by CXCL12 in these cells. Therefore, syndecan-4 behaves as a CXCL12 receptor, selectively involved in some transduction pathways induced by SDF-1, and heparan sulfate plays a role in these events.