Iron in boreal river catchments: Biogeochemical, ecological and management implications.

Iron (Fe) is an important element in aquatic ecosystems worldwide because it is intimately tied with multiple abiotic and biotic phenomena. Here, we give a survey of manifold influences of Fe, and the key factors affecting it in the boreal catchments and their waters. It includes the perspectives of biogeochemistry, hydrology, ecology, and river basin management. We emphasize views on the dynamics and impacts of different forms of Fe in riverine environments, including organic colloids and particles, as well as inorganic fractions. We also provide perspectives for land use management in boreal catchments and suggest guidelines for decision making and water management. Based on our survey, the main emphases of water protection and management programs should be (i) prevention of Fe mobilization from soil layers by avoiding unnecessary land-use activities and minimizing soil disturbance in high-risk areas; (ii) disconnecting Fe-rich ground water discharge from directly reaching watercourses; and (iii) decreasing transport of Fe to watercourses by applying efficient water pollution control approaches. These approaches may require specific methods that should be given attention depending on catchment conditions in different areas. Finally, we highlight issues requiring additional research on boreal catchments. A key issue is to increase our understanding of the role of Fe in the utilization of DOM in riverine food webs, which are typically highly heterotrophic. More knowledge is needed on the metabolic and behavioral resistance mechanisms that aquatic organisms, such as algae, invertebrates, and fish, have developed to counter the harmful impacts of Fe in rivers with naturally high Fe and DOM concentrations. It is also emphasized that to fulfil the needs presented above, as well as to develop effective methods for decreasing the harmful impacts of Fe in water management, the biogeochemical processes contributing to Fe transport from catchments via rivers to estuaries should be better understood.

Catchment properties and the photosynthetic trait composition of freshwater plant communities.

Unlike in land plants, photosynthesis in many aquatic plants relies on bicarbonate in addition to carbon dioxide (CO2) to compensate for the low diffusivity and potential depletion of CO2 in water. Concentrations of bicarbonate and CO2 vary greatly with catchment geology. In this study, we investigate whether there is a link between these concentrations and the frequency of freshwater plants possessing the bicarbonate use trait. We show, globally, that the frequency of plant species with this trait increases with bicarbonate concentration. Regionally, however, the frequency of bicarbonate use is reduced at sites where the CO2 concentration is substantially above the air equilibrium, consistent with this trait being an adaptation to carbon limitation. Future anthropogenic changes of bicarbonate and CO2 concentrations may alter the species compositions of freshwater plant communities.

Prevalence of Drug Injection, Sexual Activity, Tattooing, and Piercing Among Prison Inmates.

Prisoners engage in a range of risk behaviors that can lead to the transmission of viral infections, such as HIV, hepatitis B and hepatitis C. In this review, we summarize the epidemiologic literature from 2007 to 2017 on 4 key risk behaviors for human immunodeficiency virus and hepatitis C virus among prisoners globally: drug injection, sexual activity, tattooing, and piercing. Of 9,303 peer-reviewed and 4,150 gray literature publications, 140 and 14, respectively, met inclusion criteria covering 53 countries (28%). Regions with high levels of injection drug use were Asia Pacific (20.2%), Eastern Europe and Central Asia (17.3%), and Latin America and the Caribbean (11.3%), although the confidence interval for Latin America was high. Low levels of injection drug use in prison were found in African regions. The highest levels of sexual activity in prison were in Europe and North America (12.1%) and West and Central Africa (13.6%); low levels were reported from the Middle East and North African regions (1.5%). High levels of tattooing were reported from Europe and North America (14.7%), Asia Pacific (21.4%), and Latin America (45.4%). Prisons are burdened with a high prevalence of infectious diseases and risk behaviors for transmission of these diseases, and, commonly, a striking lack of evidence-based infection control measures, even when such measures are available in the surrounding community. Given that most prisoners return to these communities, failure to implement effective responses has repercussions not only prisoner health but also for public health.

Epithelial Microvesicles Promote an Inflammatory Phenotype in Fibroblasts.

Microvesicles (MVs) are extracellular vesicles secreted by various cell types that are involved in intercellular communication. We hypothesized that in human periodontal disease, the pocket epithelium releases MVs, which then modulate gene expression in the underlying fibroblasts to control periodontal inflammation. MVs were isolated from culture medium of gingival epithelial cells (GECs) treated with oral bacterial biofilm extract or left untreated. Biofilm treatment significantly increased MV release from the GECs. Mass spectrometry of GEC-MVs identified a total of 2,173 proteins, of which about 80% were detected in MVs from both control and biofilm-treated GECs. Among 80 signature genes of human gingival fibroblasts, 20 were significantly regulated (P < 0.05) by MVs from control and biofilm-treated GECs in a similar manner. Matrix metalloproteinase 1 and 3 and interleukin 6 and 8 showed the strongest regulation at the mRNA and protein levels. Several cellular signaling pathways were activated by GEC-MVs in human gingival fibroblasts, including Smad and mitogen-activated protein kinase-associated pathways ERK1/2, JNK, and p38. However, ERK1/2 signaling dominated in the MV-induced gene expression changes. The results demonstrate that GEC-MVs have a strong regulatory effect on the expression of fibroblast genes associated with inflammation and matrix degradation and that bacterial biofilm stimulates the generation of GEC-MVs. This suggests that bacterial biofilms can contribute to the initiation and progression of periodontal disease by promoting a tissue-destructive phenotype in gingival fibroblasts via the enhanced secretion of epithelial MVs.

Cellular recognition and macropinocytosis-like internalization of nanoparticles targeted to integrin α2ß1.

Targeting nanoparticles to desired intracellular compartments is a major challenge. Integrin-type adhesion receptors are connected to different endocytosis routes in a receptor-specific manner. According to our previous observations, the internalization of an α2ß1-integrin-echovirus-1 complex takes place via a macropinocytosis-like mechanism, suggesting that the receptor could be used to target nanoparticles to this specific entry route. Here, silica-based nanoparticles, carrying monoclonal antibodies against the α2ß1 integrin as address labels, were synthesized. Studies with flow cytometry, atomic force microscopy and confocal microscopy showed the particles to attach to the cell surface via the α2ß1 integrin. Furthermore, quantitative analysis of nanoparticle trafficking inside the cell performed with the BioImageXD software indicated that the particles enter cells via a macropinocytosis-like process and end up in caveolin-1 positive structures. Thus, we suggest that different integrins can guide particles to distinct endocytosis routes and, subsequently, also to specific intracellular compartments. In addition, we show that with the BioImageXD software it is possible to conduct sensitive and complex analyses of the behavior of small fluorescent particles inside cells, using basic confocal microscopy images.

Luminosity-independent measurement of the proton-proton total cross section at √s=8 TeV.

The TOTEM collaboration has measured the proton-proton total cross section at √s=8 TeV using a luminosity-independent method. In LHC fills with dedicated beam optics, the Roman pots have been inserted very close to the beam allowing the detection of ~90% of the nuclear elastic scattering events. Simultaneously the inelastic scattering rate has been measured by the T1 and T2 telescopes. By applying the optical theorem, the total proton-proton cross section of (101.7±2.9) mb has been determined, well in agreement with the extrapolation from lower energies. This method also allows one to derive the luminosity-independent elastic and inelastic cross sections: σ(el)=(27.1±1.4) mb; σ(inel)=(74.7±1.7) mb.

Double diffractive cross-section measurement in the forward region at the LHC.

The first double diffractive cross-section measurement in the very forward region has been carried out by the TOTEM experiment at the LHC with a center-of-mass energy of sqrt[s]=7 TeV. By utilizing the very forward TOTEM tracking detectors T1 and T2, which extend up to |η|=6.5, a clean sample of double diffractive pp events was extracted. From these events, we determined the cross section σDD=(116±25) µb for events where both diffractive systems have 4.7<|η|min<6.5.

Epithelial integrins with special reference to oral epithelia.

Adhesion of epithelium to the extracellular matrix is crucial for the maintenance of systemic and oral health. In the oral cavity, teeth or artificial dental implants penetrate the soft tissue of the gingiva. In this interface, gingival soft tissue needs to be well attached via the epithelial seal to the tooth or implant surface to maintain health. After injury or wounding, epithelial tissue rapidly migrates to form the initial epithelial cover to restore the barrier against infection. These events are crucially dependent on deposition of extracellular matrix and proper activation and function of integrin receptors in the epithelial cells. Recent experimental evidence suggests that epithelial integrins also participate in the regulation of periodontal inflammation. In this review, we will discuss the structure and function of epithelial integrins and their extracellular ligands and elaborate on their potential role in disease and repair processes in the oral cavity.

A small-molecule inhibitor of integrin alpha2 beta1 introduces a new strategy for antithrombotic therapy.

Interaction of blood platelets with vascular collagen is an initiating event in haemostasis and thrombus formation. Based on molecular modelling of human integrin alpha2I domain and cell-based screening assays we have developed sulfonamide derivatives, a mechanistically novel class of molecules. These molecules show antiplatelet efficacy by selectively inhibiting alpha2beta1 integrin-mediated collagen binding. One sulfonamide derivative, named BTT-3016, showed inhibitory capacity in several assessments of human platelet interaction with collagen. It inhibited about 90% of the aggregation of gel-filtered magnesium-supplemented platelets and 70% of aggregation in PPACK-anticoagulated platelet-rich plasma when stimulated with collagen but not with ADP. The antiplatelet activity of BTT-3016 was dependent on alpha2beta1 integrin, since in collagen binding test BTT-3016 had no effect on the platelets derived from alpha2 integrin null mice. When tested in an in vivo model in mice, BTT-3016 clearly reduced thrombus formation on the vessel wall after vascular injury. Furthermore, BTT-3016 prolonged tail-bleeding time in a manner comparable to aspirin. We show that new alpha2beta1 inhibitors exert collagen-specific antiplatelet activity and regulate thrombus growth in vivo without compromising primary haemostasis more than aspirin. We suggest that the alpha2beta1 inhibiting strategy could be further developed for the prevention and treatment of arterial thrombosis.

Collagen XVII promotes integrin-mediated squamous cell carcinoma transmigration--a novel role for alphaIIb integrin and tirofiban.

The expression of collagen XVII (BP180), a transmembrane hemidesmosomal component, is upregulated in invasive areas of epithelial tumors. The collagenous ectodomain of collagen XVII is cleaved from the plasma membrane of keratinocytes and malignant epithelial cells. The released ectodomain is predicted to regulate cell detachment, differentiation, and motility. We report that the cell adhesion domain of collagen XVII, Col15, is able to chemotactically attract invasive HSC-3 SCC cells but not keratinocytes. Analysis of integrin expression revealed that HSC-3 cells, unlike keratinocytes, express alphaIIb integrin, a platelet-specific fibrinogen receptor. We show that this novel chemotactic function is mediated by the known Col15-binding integrins alpha5beta1 and alphav and the platelet integrin alphaIIb. Moreover, we report that tirofiban, a FDA-proved alphaIIb integrin-blocking drug widely used for the therapy of acute coronary ischaemic syndrome and the prevention of thrombotic complications, inhibits the Col15 chemotaxis of HSC-3 carcinoma cells. Together, these data demonstrate a novel interaction between collagen XVII and alphaIIb integrin and also suggest a possibility to use tirofiban to inhibit the invasion and progression of alphaIIb expressing SCC tumors.

Measles virus enhances the expression of cellular immediate-early genes and DNA-binding of transcription factor AP-1 in lung epithelial A549 cells.

In this work we investigated the effect of measles virus (MV) infection on the expression of immediate-early genes junB, c-jun and c-fos mRNA as well as AP-1 DNA-binding activity in the lung epithelial-like adenocarcinoma cell line A549. The transcription factor AP-1, which is a group of dimeric complexes of the Fos and Jun family proteins, is an important regulator in many cellular responses to different extracellular stimuli. Membrane cofactor protein CD46, which acts as a receptor for laboratory-adapted and vaccine strains of MV, has been reported to associate with beta1 integrin molecules, which are known to trigger signaling events and activate immediate-early genes. The expression of junB and c-jun mRNA was rapidly induced by MV. It was observed already at 1 h postinfection and detected again at the later phase of infection. Moreover, the expression of c-fos mRNA seemed to be weak and transient. The early induction was apparently associated with MV binding and CD46 clustering, whereas the later induction coincided with virus replication. MV infection also enhanced the activation of AP-1 DNA-binding. Our results suggest that changes in the expression of immediate-early genes and in the activation of AP-1 DNA-binding may have an important role in many cellular events detected in MV-infected cells.

Selective binding of collagen subtypes by integrin alpha 1I, alpha 2I, and alpha 10I domains.

Four integrins, namely alpha(1)beta(1), alpha(2)beta(1), alpha(10)beta(1), and alpha(11)beta(1), form a special subclass of cell adhesion receptors. They are all collagen receptors, and they recognize their ligands with an inserted domain (I domain) in their alpha subunit. We have produced the human integrin alpha(10)I domain as a recombinant protein to reveal its ligand binding specificity. In general, alpha(10)I did recognize collagen types I-VI and laminin-1 in a Mg(2+)-dependent manner, whereas its binding to tenascin was only slightly better than to albumin. When alpha(10)I was tested together with the alpha(1)I and alpha(2)I domains, all three I domains seemed to have their own collagen binding preferences. The integrin alpha(2)I domain bound much better to fibrillar collagens (I-III) than to basement membrane type IV collagen or to beaded filament-forming type VI collagen. Integrin alpha(1)I had the opposite binding pattern. The integrin alpha(10)I domain was similar to the alpha(1)I domain in that it bound very well to collagen types IV and VI. Based on the previously published atomic structures of the alpha(1)I and alpha(2)I domains, we modeled the structure of the alpha(10)I domain. The comparison of the three I domains revealed similarities and differences that could potentially explain their functional differences. Mutations were introduced into the alphaI domains, and their binding to types I, IV, and VI collagen was tested. In the alpha(2)I domain, Asp-219 is one of the amino acids previously suggested to interact directly with type I collagen. The corresponding amino acid in both the alpha(1)I and alpha(10)I domains is oppositely charged (Arg-218). The mutation D219R in the alpha(2)I domain changed the ligand binding pattern to resemble that of the alpha(1)I and alpha(10)I domains and, vice versa, the R218D mutation in the alpha(1)I and alpha(10)I domains created an alpha(2)I domain-like ligand binding pattern. Thus, all three collagen receptors appear to differ in their ability to recognize distinct collagen subtypes. The relatively small structural differences on their collagen binding surfaces may explain the functional specifics.

The cell adhesion domain of type XVII collagen promotes integrin-mediated cell spreading by a novel mechanism.

Type XVII collagen (BP180) is a keratinocyte transmembrane protein that exists as the full-length protein in hemidesmosomes and as a 120-kDa shed ectodomain in the extracellular matrix. The largest collagenous domain of type XVII collagen, COL15, has been described previously as a cell adhesion domain (Tasanen, K., Eble, J. A., Aumailley, M., Schumann, H., Baetge, J, Tu, H., Bruckner, P., and Bruckner-Tuderman, L. (2000) J. Biol. Chem. 275, 3093-3099). In the present work, the integrin binding of triple helical, human recombinant COL15 was tested. Solid phase binding assays using recombinant integrin alpha(1)I, alpha(2)I, and alpha(10)I domains and cell spreading assays with alpha(1)beta(1)- and alpha(2)beta(1)-expressing Chinese hamster ovary cells showed that, unlike other collagens, COL15 was not recognized by the collagen receptors. Denaturation of the COL15 domain increased the spreading of human HaCaT keratinocytes, which could migrate on the denatured COL15 domain as effectively as on fibronectin. Spreading of HaCaT cells on the COL15 domain was mediated by alpha(5)beta(1) and alpha(V)beta(1) integrins, and it could be blocked by RGD peptides. The collagen alpha-chains in the COL15 domain do not contain RGD motifs but, instead, contain 12 closely related KGD motifs, four in each of the three alpha-chains. Twenty-two overlapping, synthetic peptides corresponding to the entire COL15 domain were tested; three peptides, all containing the KGD motif, inhibited the spreading of HaCaT cells on denatured COL15 domain. Furthermore, this effect was lost by mutation from D to E (KGE instead of KGD). We suggest that the COL15 domain of type XVII collagen represents a specific collagenous structure, unable to interact with the cellular receptors for other collagens. After being shed from the cell surface, it may support keratinocyte spreading and migration.

Regulation of alpha7 integrin by mechanical stress during skeletal muscle regeneration.

The continuity of the tendon-myofibre-tendon units disrupted by shearing injury must be re-established during regeneration. We have previously demonstrated in freely moving rats that transected myofibres reinforce their lateral integrin-mediated adhesion, with the maximum around days 5-7. After day 14, most integrin molecules are redistributed to the newly formed myotendinous junctions, by which the ends of regenerating myofibres attach to the scar between the stumps. Here, we analyzed the effects of mechanical stress (free and forced mobilization vs. immobilization and denervation separately and in combination) on the expression of alpha7 integrin and merosin in regenerating myofibres using quantitative in situ hybridization and immunohistochemistry. In all groups, alpha7 integrin expression was upregulated at mRNA level, whereas increased protein accumulation in lateral sarcolemma occurred only in the mobilized groups. The accumulation of merosin was not affected by the stress level. The results demonstrate that active mechanical stress reinforces early lateral integrin-mediated adhesion; molecules may at the same time mediate signals from matrix to cells for adaptation to the altered biomechanical status.

Bacterial heat shock protein-60 increases epithelial cell proliferation through the ERK1/2 MAP kinases.

Heat shock proteins (hsp) have important roles in the regulation and protection of both prokaryotic and eukaryotic cells, especially during environmental stress. Hsps are also important bacterial virulence factors. We investigated whether bacterial hsp60 can alter epithelial cell mitogen-activated protein kinase (MAPK) signaling and cell proliferation. Human skin keratinocytes (HaCaT cell line) were cultured in the presence of hsp60 purified from Actinobacillus actinomycetemcomitans, an important oral pathogen. Protein kinases in the ERK1/2 and p38 MAPK signaling pathways were probed with kinase-specific and phosphorylation-site-specific antibodies on Western blots. In quiescent cultures, hsp60 increased ERK1/2 phosphorylation in a sustained manner and p38 phosphorylation transiently. Hsp60 also increased epithelial cell proliferation by about 30%. Inhibition of the ERK1/2 pathway by PD 98059 (a MEK1 inhibitor) reversed partially ERK1/2 phosphorylation and totally cell proliferation indicating that the ERK1/2 MAPK pathway is involved in the hsp60-induced cell growth. This was supported by findings that hsp60 stimulated phosphorylation of RSK1/2 and cyclic AMP response element-binding protein and increased expression of transcription factors c-Jun and c-Fos. Recombinant human hsp60 did not alter ERK1/2 or p38 phosphorylation and had no effect on epithelial cell proliferation. Inhibition of p38 MAPK pathway by SB 203580 increased both ERK1/2 phosphorylation and cell proliferation demonstrating that the inhibitor can either directly or indirectly activate the ERK1/2 MAPK pathway. The results show that exogenous bacterial hsp60 is able to activate ERK1/2 phosphorylation and thereby cause increased epithelial proliferation. In case of mucosal infection this effect may either lead to increased wound repair or participate in the pathological mechanism of some bacterial diseases that involve increased epithelial proliferation.

Identification of alpha6beta1 integrin positive cells in synovial lining layer as type B synoviocytes.

OBJECTIVE: In rheumatoid arthritis (RA) the synovial lining is responsible for cartilage destruction. Laminin is one of the major matrix molecules surrounding the lining cells. We investigated the laminin adhesion mechanism of synovial lining cells by analyzing the presence of its receptor, alpha6beta1 integrin, on type A and type B synoviocytes. METHODS: The alpha6 integrin subunit and a macrophage marker were simultaneously localized by immunohistochemistry in 29 RA derived, 6 osteoarthritis derived, and 2 healthy synovial samples by light and electron microscopy. We also used enzyme treatments to release cells from synovial tissue samples and localized the same antigens on adherent cells. RESULTS: The alpha6beta1 integrin positive cells were localized in basal areas of the lining layer and many of them were negative for the macrophage markers. By immunolabeling electron microscopy the alpha6 integrin positive cells were confirmed to represent the fibroblast-like type B cells. Further, in freshly isolated synoviocyte cultures the type B cells were positive for alpha6 integrin, whereas all other cell types were negative for this laminin receptor. CONCLUSION: Integrin alpha6beta1 is known to be a laminin receptor of endothelial cells, adipocytes, and macrophages, not usually expressed on fibroblasts. However, in synovial lining layer it is expressed on fibroblastic type B cells, but the macrophage population is negative. The unique characteristics of synovial lining cells distinguish them from other connective tissue cells and must be taken into account in all considerations of the pathogenic mechanisms of rheumatoid disease.

Entry of human parechovirus 1.

Human parechovirus 1 (HPEV-1) is a prototype member of parechoviruses, a recently established picornavirus genus. Although there is preliminary evidence that HPEV-1 recognizes alpha(V) integrins as cellular receptors, our understanding of early events during HPEV-1 infection is still very limited. The aim of this study was to clarify the entry mechanisms of HPEV-1, including the attachment of the virus onto the host cell surface and subsequent internalization. In blocking experiments with monoclonal antibodies against different receptor candidates, antibodies against alpha(V) and beta(3) integrin subunits, in particular in combination, appeared to be the most efficient ones in preventing the HPEV-1 infection. To find out whether HPEV-1 uses clathrin-coated vesicles or other routes for the entry into the host cell, we carried out double-labeling experiments of virus-infected cells with anti-HPEV-1 antibodies and antibodies against known markers of the clathrin and the caveolin routes. At the early phase of infection (5 min postinfection [p.i.]) HPEV-1 colocalized with EEA1 (early endosomes), and later, after 30 min p.i., it colocalized with mannose-6-phosphate receptor (late endosomes), whereas no colocalization with caveolin-1 was observed. The data indicate that HPEV-1 utilizes the clathrin-dependent endocytic pathway for entry into the host cells. Interestingly, endocytosed HPEV-1 capsid proteins were observed in the endoplasmic reticulum and cis-Golgi network 30 to 60 min p.i. Depolymerization of microtubules with nocodazole inhibited translocation of the virus to the late endosomes but did not block HPEV-1 replication, suggesting that the RNA genome may be released early during the entry process.

Three-dimensional collagen regulates collagen gene expression by a mechanism that requires serine/threonine kinases and is independent of mechanical contraction.

Integrin alpha1beta1, one of the cellular collagen receptors, can participate in the regulation of collagen accumulation by acting as a negative feedback regulator. The molecular mechanism behind this phenomenon has been unknown. We have plated cells inside three-dimensional collagen and analyzed a set of chemical inhibitors for various signal transduction pathways. Only two wide-spectrum serine/threonine kinase inhibitors, H-7 and iso-H-7 could prevent the down-regulation of alpha1(I) collagen mRNA levels in cells exposed to three-dimensional collagen. In monolayer iso-H-7 slightly down-regulated collagen gene expression, indicating that inside collagen it affected integrin signaling rather than having a direct stimulatory effect on collagen mRNA levels. The effect of iso-H-7 was not dependent on its ability to inhibit protein kinases A, C, or G. H-7 and iso-H-7 could also inhibit collagen gel contraction, but this mechanism was independent of collagen gene regulation. Three-dimensional collagen could also up-regulate the mRNA levels of several matrix metalloproteinases (MMPs) but H-7 and iso-H-7 had no effect on the regulation of MMP genes. Our data indicate that three-dimensional collagenous matrix regulates distinct cellular signaling pathways and that collagen gene regulation is independent of the other effects of the matrix.

Interferon-gamma-induced inhibition of wound healing in vivo and in vitro.

This work was undertaken to study the effects of various doses of interferon-gamma (IFN-gamma) on developing granulation tissue in rats and on granulation tissue-derived fibroblasts in culture. For in vivo studies cylindrical hollow sponge implants were used as an inductive matrix for the growth of granulation tissue. In the test groups the implants were injected daily for four days with a solution containing 160, 800, 4000, or 20000 units of IFN-gamma while the implants of the control group were treated correspondingly with the carrier solution only. Analyses of granulation tissue in the sponge cylinders, carried out 7 days after implantation, showed an IFN-gamma-related decrease in the formation of new granulation tissue. The largest, dose-dependent effect was seen in the accumulation of collagen. For in vitro studies, cultures of rat granulation tissue fibroblasts were treated with 100, 500, 1000, or 5000 units/ml of IFN-gamma. IFN-gamma decreased collagen synthesis to about 50 per cent of that in controls. IFN-gamma treatment also decreased type I procollagen mRNA levels maximally by 41 per cent from the control level. It is concluded that IFN-gamma inhibits the formation of new granulation tissue by decreasing collagen synthesis.