Ribonucleases and host defense: identification, localization and gene expression in adherent monocytes in vitro

Role of Atypical Chemokines and Chemokine Receptors Pathways in the Pathogenesis of COPD

Chronic obstructive pulmonary disease (COPD) represents a heightened inflammatory response in the lung generally resulting from tobacco smoking-induced recruitment and activation of inflammatory cells and/or activation of lower airway structural cells. Several mediators can modulate activation and recruitment of these cells, particularly those belonging to the chemokines (conventional and atypical) family. There is emerging evidence for complex roles of atypical chemokines and their receptors (such as high mobility group box 1 (HMGB1), antimicrobial peptides, receptor for advanced glycosylation end products (RAGE) or toll-like receptors (TLRs)) in the pathogenesis of COPD, both in the stable disease and during exacerbations. Modulators of these pathways represent potential novel therapies for COPD and many are now in preclinical development. Inhibition of only a single atypical chemokine or receptor may not block inflammatory processes because there is redundancy in this network. However, there are many animal studies that encourage studies for modulating the atypical chemokine network in COPD. Thus, few pharmaceutical companies maintain a significant interest in developing agents that target these molecules as potential antiinflammatory drugs. Antibody-based (biological) and small molecule drug (SMD)-based therapies targeting atypical chemokines and/or their receptors are mostly at the preclinical stage and their progression to clinical trials is eagerly awaited. These agents will most likely enhance our knowledge about the role of atypical chemokines in COPD pathophysiology and thereby improve COPD management.

The Responses of the Ribonuclease A Superfamily to Urinary Tract Infection

The lower urinary tract is routinely exposed to microbes residing in the gastrointestinal tract, yet the urothelium resists invasive infections by gut microorganisms. This infection resistance is attributed to innate defenses in the bladder urothelium, kidney epithelium, and resident or circulating immune cells. In recent years, surmounting evidence suggests that these cell types produce and secrete soluble host defense peptides, including members of the Ribonuclease (RNase) A Superfamily, to combat invasive bacterial challenge. While some of these peptides, including RNase 4 and RNase 7, are abundantly produced by epithelial cells, the expression of others, like RNase 3 and RNase 6, increase at infection sites with immune cell recruitment. The objective of this mini-review is to highlight recent evidence showing the biological importance and responses of RNase A Superfamily members to infection in the kidney and bladder.

Immune Modulation by Human Secreted RNases at the Extracellular Space

The ribonuclease A superfamily is a vertebrate-specific family of proteins that encompasses eight functional members in humans. The proteins are secreted by diverse innate immune cells, from blood cells to epithelial cells and their levels in our body fluids correlate with infection and inflammation processes. Recent studies ascribe a prominent role to secretory RNases in the extracellular space. Extracellular RNases endowed with immuno-modulatory and antimicrobial properties can participate in a wide variety of host defense tasks, from performing cellular housekeeping to maintaining body fluid sterility. Their expression and secretion are induced in response to a variety of injury stimuli. The secreted proteins can target damaged cells and facilitate their removal from the focus of infection or inflammation. Following tissue damage, RNases can participate in clearing RNA from cellular debris or work as signaling molecules to regulate the host response and contribute to tissue remodeling and repair. We provide here an overall perspective on the current knowledge of human RNases’ biological properties and their role in health and disease. The review also includes a brief description of other vertebrate family members and unrelated extracellular RNases that share common mechanisms of action. A better knowledge of RNase mechanism of actions and an understanding of their physiological roles should facilitate the development of novel therapeutics.

Abundance of RNase4 and RNase5 mRNA and protein in host defence related tissues and secretions in cattle

Members of the RNaseA family are present in various tissues and secretions but their function is not well understood. Some of the RNases are proposed to participate in host defence. RNase4 and RNase5 are present in cows' milk and have antimicrobial activity. However, their presence in many tissues and secretions has not been characterised. We hypothesised that these two RNases are present in a range of tissues and secretions where they could contribute to host defence. We therefore, determined the relative abundance of RNase4 and RNase5 mRNA as well as protein levels in a range of host defence related and other tissues as well as a range of secretions in cattle, using real time PCR and western blotting. The two RNases were found to be expressed in liver, lung, pancreas, mammary gland, placenta, endometrium, small intestine, seminal vesicle, salivary gland, kidney, spleen, lymph node, skin as well as testes. Corresponding proteins were also detected in many of the above tissues, as well as in seminal fluid, mammary secretions and saliva. This study provides evidence for the presence of RNase4 and RNase5 in a range of tissues and secretions, as well as some major organs in cattle. The data are consistent with the idea that these proteins could contribute to host defence in these locations. This work contributes to growing body of data suggesting that these proteins contribute to the physiology of the organism in a more complex way than acting merely as digestive enzymes.

•

RNase4 and RNase5 are present in several tissues and secretions in cattle.

•

mRNA and protein levels of the RNases correlate in various tissues analysed.

•

The RNases could contribute to host defence in these tissues and secretions.

The Ribonuclease A Superfamily in Humans: Canonical RNases as the Buttress of Innate Immunity

In humans, the ribonuclease A (RNase A) superfamily contains eight different members that have RNase activities, and all of these members are encoded on chromosome 14. The proteins are secreted by a large variety of different tissues and cells; however, a comprehensive understanding of these proteins’ physiological roles is lacking. Different biological effects can be attributed to each protein, including antiviral, antibacterial and antifungal activities as well as cytotoxic effects against host cells and parasites. Different immunomodulatory effects have also been demonstrated. This review summarizes the available data on the human RNase A superfamily and illustrates the significant role of the eight canonical RNases in inflammation and the host defence system against infections.

Three decades of research on angiogenin: a review and perspective

As a member of the vertebrate-specific secreted ribonucleases, angiogenin (ANG) was first isolated and identified solely by its ability to induce new blood vessel formation, and now, it has been recognized to play important roles in various physiological and pathological processes through regulating cell proliferation, survival, migration, invasion, and/or differentiation. ANG exhibits very weak ribonucleolytic activity that is critical for its biological functions, and exerts its functions through activating different signaling transduction pathways in different target cells. A series of recent studies have indicated that ANG contributes to cellular nucleic acid metabolism. Here, we comprehensively review the results of studies regarding the structure, mechanism, and function of ANG over the past three decades. Moreover, current problems and future research directions of ANG are discussed. The understanding of the function and mechanism of ANG in a wide context will help to better delineate its roles in diseases, especially in cancer and neurodegenerative diseases.

The Human Host Defense Ribonucleases 1, 3 and 7 Are Elevated in Patients with Sepsis after Major Surgery--A Pilot Study

Sepsis is the most common cause of death in intensive care units and associated with widespread activation of host innate immunity responses. Ribonucleases (RNases) are important components of the innate immune system, however the role of RNases in sepsis has not been investigated. We evaluated serum levels of RNase 1, 3 and 7 in 20 surgical sepsis patients (Sepsis), nine surgical patients (Surgery) and 10 healthy controls (Healthy). RNase 1 and 3 were elevated in Sepsis compared to Surgery (2.2- and 3.1-fold, respectively; both p < 0.0001) or compared to Healthy (3.0- and 15.5-fold, respectively; both p < 0.0001). RNase 1 showed a high predictive value for the development of more than two organ failures (AUC 0.82, p = 0.01). Patients with renal dysfunction revealed higher RNase 1 levels than without renal dysfunction (p = 0.03). RNase 1 and 3 were higher in respiratory failure than without respiratory failure (p < 0.0001 and p = 0.02, respectively). RNase 7 was not detected in Healthy patients and only in two patients of Surgery, however RNase 7 was detected in 10 of 20 Sepsis patients. RNase 7 was higher in renal or metabolic failure than without failure (p = 0.04 and p = 0.02, respectively). In conclusion, RNase 1, 3 and 7 are secreted into serum under conditions with tissue injury, such as major surgery or sepsis. Thus, RNases might serve as laboratory parameters to diagnose and monitor organ failure in sepsis.

Structural basis of substrate specificity in porcine RNase 4

RNase 4, a member of the RNase A superfamily with substrate preference for uridine, has roles in host defence, angiogenesis and neurodegenerative diseases. It also exhibits the highest interspecies amino acid sequence similarity amongst RNase A family members. However, compared to other members of the RNase A family, including eosinophil-derived neurotoxin, eosinophil cationic protein and angiogenin, little is known about the molecular basis of substrate specificity in RNase 4. Here we report high to medium resolution structures of native porcine RNase 4 (PL3), a 'substrate-specificity' determining mutant D80A and their respective complexes with deoxyuridine 5'-monophosphate (dUMP) and deoxycytidine 5'-monophosphate (dCMP). These structures provide insight into the structural basis of the uridine versus cytosine substrate specificity in RNase 4: in the D80A mutant (D80A•dCMP), the side chain of Arg101 is positioned further away from the substrate-binding pocket due to the loss of the Asp80 side chain, reducing the repulsion force on the less favoured dCMP from Arg101 and allowing the ligand to occupy the binding pocket. This can also explain the observation that the ligand in the D80A•dCMP complex is stabilized only by a small number of hydrogen bonds. Compared to the previously reported structure of the human RNase 4•2'-deoxyuridine 3'-phosphate complex, the structure of PL3•dUMP complex shows additional hydrogen bonds between the ligand and the protein. In addition, the interaction between Arg101 and the dUMP ligand is absent. These observed differences are probably the result of the flexibility and different 'positioning' of the phosphate group among the mononucleotide ligands.

DATABASE

The atomic coordinates and structure factors for PL3 (5AR6), D80A (5ARJ), PL3∙dUMP (5ARK) and D80A∙dCMP (5ARL) complexes have been deposited with the Protein Data Bank, Research Collaboratory for Structural Bioinformatics, Rutgers University, New Brunswick, NJ, USA (http://www.rcsb.org/).

Mechanism and Function of Angiogenin in Prostate Cancer

Angiogenin (ANG), the fifth member of the vertebrate-specific ribonuclease (RNase) A superfamily, is a secreted angiogenic ribonuclease strongly up-regulated in human prostate cancers. ANG is translocated to the nucleus in both prostate cancer epithelial cells and endothelial cells to exert its role in prostate cancer progression by mediating tumor angiogenesis, cancer cell survival and proliferation through rRNA biogenesis. ANG-stimulated rRNA is required not only for prostate intraepithelial neoplasia (PIN) formation, but also for androgen-independent growth of prostate cancer cells. Targeting ANG by various antagonists that inhibit its nuclear translocation, function and/or activity has proven to inhibit prostate cancer growth in animal models. Furthermore, the role of ANG in androgen independence has been firmly established, suggesting a strong rationale for therapeutically targeting ANG in the treatment of castration resistant prostate cancer.

Eosinophil-associated ribonuclease 11 is a macrophage chemoattractant

RNase A is the prototype of an extensive family of divergent proteins whose members share a unique disulfide-bonded tertiary structure, conserved catalytic motifs, and the ability to hydrolyze polymeric RNA. Several members of this family maintain independent roles as ribonucleases and modulators of innate immunity. Here we characterize mouse eosinophil-associated RNase (Ear) 11, a divergent member of the eosinophil ribonuclease cluster, and the only known RNase A ribonuclease expressed specifically in response to Th2 cytokine stimulation. Mouse Ear 11 is differentially expressed in somatic tissues at baseline (brain ≪ liver < lung < spleen); systemic stimulation with IL-33 results in 10-5000-fold increased expression in lung and spleen, respectively. Ear 11 is also expressed in response to protective priming of the respiratory mucosa with Lactobacillus plantarum; transcripts are detected both locally in lung as well as systemically in bone marrow and spleen. Mouse Ear 11 is enzymatically active, although substantially less so than mEar 1 and mEar 2; the relative catalytic efficiency (kcat/Km) of mEar 11 is diminished ∼1000-1500-fold. However, in contrast to RNase 2/EDN and mEar 2, which have been characterized as selective chemoattractants for CD11c(+) dendritic cells, mEar 11 has prominent chemoattractant activity for F4/80(+)CD11c(-) tissue macrophages. Chemoattractant activity is not dependent on full enzymatic activity, and requires no interaction with the pattern recognition receptor, Toll-like receptor 2 (TLR2). Taken together, this work characterizes a divergent RNase A ribonuclease with a unique expression pattern and function, and highlights the versatility of this family in promoting innate immunity.

Comparative transcriptome profiling of a resistant vs. susceptible tomato (Solanum lycopersicum) cultivar in response to infection by tomato yellow leaf curl virus

Tomato yellow leaf curl virus (TYLCV) threatens tomato production worldwide by causing leaf yellowing, leaf curling, plant stunting and flower abscission. The current understanding of the host plant defense response to this virus is very limited. Using whole transcriptome sequencing, we analyzed the differential gene expression in response to TYLCV infection in the TYLCV-resistant tomato breeding line CLN2777A (R) and TYLCV-susceptible tomato breeding line TMXA48-4-0 (S). The mixed inoculated samples from 3, 5 and 7 day post inoculation (dpi) were compared to non-inoculated samples at 0 dpi. Of the total of 34831 mapped transcripts, 209 and 809 genes were differentially expressed in the R and S tomato line, respectively. The proportion of up-regulated differentially expressed genes (DEGs) in the R tomato line (58.37%) was higher than that in the S line (9.17%). Gene ontology (GO) analyses revealed that similar GO terms existed in both DEGs of R and S lines; however, some sets of defense related genes and their expression levels were not similar between the two tomato lines. Genes encoding for WRKY transcriptional factors, R genes, protein kinases and receptor (-like) kinases which were identified as down-regulated DEGs in the S line were up-regulated or not differentially expressed in the R line. The up-regulated DEGs in the R tomato line revealed the defense response of tomato to TYLCV infection was characterized by the induction and regulation of a series of genes involved in cell wall reorganization, transcriptional regulation, defense response, ubiquitination, metabolite synthesis and so on. The present study provides insights into various reactions underlining the successful establishment of resistance to TYLCV in the R tomato line, and helps in the identification of important defense-related genes in tomato for TYLCV disease management.

Sperm nuclear DNA fragmentation rate is associated with differential protein expression and enriched functions in human seminal plasma

OBJECTIVE

To analyse the proteomic profile of seminal plasma with the aim of identifying the proteins and post-genomic pathways associated with sperm DNA fragmentation.

MATERIALS AND METHODS

A cross-sectional study including 89 subjects from a human reproduction service was carried out. All semen samples were assessed for sperm DNA fragmentation using a comet assay. Results from 60 sperm were analysed using Komet 6.0.1 software and the 'Olive tail moment' variable was used to stratify these into low and high sperm DNA fragmentation groups. Seminal plasma proteins from the two groups were pooled and used for proteomic analysis. Quantitative data were used for functional enrichment studies.

RESULTS

Seventy-two proteins were identified or quantified in seminal plasma. Of these, nine were differentially expressed in the low group and 21 in the high group. Forty-two proteins were conserved between these groups. Functional enrichment analysis indicated that sperm DNA fragmentation was related to functions such as lipoprotein particle remodelling and regulation, fatty acid binding and immune response. Proteins found exclusively in the low group may be involved in correcting spermatogenesis and/or improving sperm function. Proteins in the high group were associated with increased innate immune response, sperm motility and/or maturation and inhibition of mitochondrial apoptosis.

CONCLUSION

Protein expression and post-genomic pathways of seminal plasma differ according to the rate of sperm DNA integrity.

Mapping, phylogenetic and expression analysis of the RNase (RNase A) locus in cattle

The mammalian secreted ribonucleases (RNases) comprise a large family of structurally related proteins displaying considerable sequence variation, and have been used in evolutionary studies. RNase 1 (RNase A) has been assumed to play a role in digestion, while other members have been suggested to contribute to host defence. Using the recently assembled bovine genome sequence, we characterised the complete repertoire of genes present in the RNaseA family locus in cattle, and compared this with the equivalent locus in the human and mouse genomes. Several additions and corrections to the earlier analysis of the RNase locus in the mouse genome are presented. The bovine locus encodes 19 RNases, of which only six have unambiguous equivalent genes in the other two species. Chromosomal mapping and phylogenetic analysis indicate that a number of distinct gene duplication events have occurred in the cattle lineage since divergence from the human and mouse lineages. Substitution analysis suggests that some of these duplicated genes are under evolutionary pressure for purifying selection and may therefore be important to the physiology of cattle. Expression analysis revealed that individual RNases have a wide pattern of expression, including diverse mucosal epithelia and immune-related cells and tissues. These data clarify the full repertoire of bovine RNases and their relationships to those in humans and mice. They also suggest that RNase gene duplication within the bovine lineage accompanied by altered tissue-specific expression has contributed a survival advantage.

Plasmacytoid dendritic cells and C1q differentially regulate inflammatory gene induction by lupus immune complexes

Immune complexes (ICs) play a pivotal role in causing inflammation in systemic lupus erythematosus (SLE). Yet, it remains unclear what the dominant blood cell type(s) and inflammation-related gene programs stimulated by lupus ICs are. To address these questions, we exposed normal human PBMCs or CD14(+) isolated monocytes to SLE ICs in the presence or absence of C1q and performed microarray analysis and other tests for cell activation. By microarray analysis, we identified genes and pathways regulated by SLE ICs that are both type I IFN dependent and independent. We also found that C1q-containing ICs markedly reduced expression of the majority of IFN-response genes and also influenced the expression of multiple other genes induced by SLE ICs. Surprisingly, IC activation of isolated CD14(+) monocytes did not upregulate CD40 and CD86 and only modestly stimulated inflammatory gene expression. However, when monocyte subsets were purified and analyzed separately, the low-abundance CD14(dim) ("patrolling") subpopulation was more responsive to ICs. These observations demonstrate the importance of plasmacytoid dendritic cells, CD14(dim) monocytes, and C1q as key regulators of inflammatory properties of ICs and identify many pathways through which they act.

Alarmins and antimicrobial immunity

Alarmins are endogenous mediators capable of enhancing innate and adaptive immune response through induction of concomitant recruitment and activation of antigen-presenting cells. Here we provide a brief overview of various alarmins, highlight their critical roles in innate and adaptive antimicrobial immunity, and speculate on potential usage of alarmins in combating aspergillosis.

Immune components of colostrum and milk--a historical perspective

Key developments in the understanding of the immune functions of milk and colostrum are reviewed, focusing on their proteinaceous components. The topics covered include the immunoglobulins, immune cells, immunomodulatory substances, and antimicrobial proteins. The contributions of new technologies and the introduction of fresh approaches from other fields are highlighted, as are the contributions that mammary biology research has made to the development of other fields. Finally, a summary of some current outstanding questions and likely future directions of the field are given.

Mammalian antimicrobial proteins and peptides: overview on the RNase A superfamily members involved in innate host defence

The review starts with a general outlook of the main mechanisms of action of antimicrobial proteins and peptides, with the final aim of understanding the biological function of antimicrobial RNases, and identifying the key events that account for their selective properties. Although most antibacterial proteins and peptides do display a wide-range spectrum of action, with a cytotoxic activity against bacteria, fungi, eukaryotic parasites and viruses, we have only focused on their bactericidal activity. We start with a detailed description of the main distinctive structural features of the bacteria target and on the polypeptides, which act as selective host defence weapons.Following, we include an overview of all the current available information on the mammalian RNases which display an antimicrobial activity. There is a wealth of information on the structural, catalytic mechanism and evolutionary relationships of the RNase A superfamily. The bovine pancreatic RNase A (RNase A), the reference member of the mammalian RNase family, has been the main research object of several Nobel laureates in the 60s, 70s and 80s. A potential antimicrobial function was only recently suggested for several members of this family. In fact, the recent evolutionary studies indicate that this protein family may have started off with a host defence function. Antimicrobial RNases constitute an interesting example of proteins involved in the mammalian innate immune defence system. Besides, there is wealth of available information on the mechanism of action of short antimicrobial peptides, but little is known on larger polypeptides, that is, on proteins. Therefore, the identification of the mechanisms of action of antimicrobial RNases would contribute to the understanding of the proteins involved in the innate immunity.

Effects of increased cellular zinc levels on gene and protein expression in HT-29 cells

High cellular zinc concentrations lead to impairments in ATP synthesis and cell cycle control particularly in neurons and epithelial cells. The molecular basis for these dysfunctions is still not fully elucidated. Here we analyzed the effects of a high zinc exposure (10 ppm) on gene and protein expression in the human epithelial cell line HT-29. Of the 1176 genes analyzed with cDNA arrays, nine differentially expressed genes were identified. Proteome analysis based on 1310 detected proteins identified 11 molecular targets. Most of the identified genes/proteins have not been linked to cellular zinc status before (e.g. PEC-60, R-ras3). More than half of the targets participate in ATP production or stress response. Therefore, it appears that higher zinc concentrations mediate their effects mainly via impairments in cellular energy metabolism and stress response.

Human ribonuclease A superfamily members, eosinophil-derived neurotoxin and pancreatic ribonuclease, induce dendritic cell maturation and activation

A number of mammalian antimicrobial proteins produced by neutrophils and cells of epithelial origin have chemotactic and activating effects on host cells, including cells of the immune system. Eosinophil granules contain an antimicrobial protein known as eosinophil-derived neurotoxin (EDN), which belongs to the RNase A superfamily. EDN has antiviral and chemotactic activities in vitro. In this study, we show that EDN, and to a lesser extent human pancreatic RNase (hPR), another RNase A superfamily member, activates human dendritic cells (DCs), leading to the production of a variety of inflammatory cytokines, chemokines, growth factors, and soluble receptors. Human angiogenin, a RNase evolutionarily more distant to EDN and hPR, did not display such activating effects. Additionally, EDN and hPR also induced phenotypic and functional maturation DCs. These RNases were as efficacious as TNF-alpha, but induced a different set of cytokine mediators. Furthermore, EDN production by human macrophages could be induced by proinflammatory stimuli. The results reveal the DC-activating activity of EDN and hPR and suggest that they are likely participants of inflammatory and immune responses. A number of endogenous mediators in addition to EDN have been reported to have both chemotactic and activating effects on APCs, and can thus amplify innate and Ag-specific immune responses to danger signals. We therefore propose these mediators be considered as endogenous multifunctional immune alarmins.

Multiple roles of antimicrobial defensins, cathelicidins, and eosinophil-derived neurotoxin in host defense

Mammals generate a diverse array of antimicrobial proteins, largely represented by defensins or cathelicidins. The direct in vitro microbicidal activity of antimicrobial proteins has long been considered an important innate immune defense, although the in vivo relevance has only very recently been established for certain defensins and cathelicidins. Mammalian defensins and cathelicidins have also been shown to have multiple receptor-mediated effects on immune cells. Beta-defensins interact with CCR6; murine beta-defensin-2 in addition activates TLR4. Cathelicidins act on FPRL1-expressing cells. Furthermore, several defensins have considerable immunoenhancing activity. Thus, it appears that mammalian antimicrobial proteins contribute to both innate and adaptive antimicrobial immunity.

Elevated angiogenin levels in synovial fluid from patients with inflammatory arthritis and secretion of angiogenin by cultured synovial fibroblasts

Angiogenesis is a key process in the pathogenesis of inflammatory arthritis. Angiogenin is one of the most potent inducers of neovascularization in experimental models in vivo. To look for evidence that angiogenin is involved in inflammatory joint disease, we examined plasma and synovial fluid (SF) samples from rheumatology patients and synovial fibroblast cell culture supernatants. Angiogenin levels were determined by radioimmunoassay and ELISA. Plasma angiogenin concentrations ranged from 96 to 478 ng/ml, with no significant difference between patients and normal controls. In SF, angiogenin concentrations were significantly higher in patients with acute or chronic synovitis (rheumatoid arthritis (RA): median, 104 ng/ml; range 13-748, n = 14; crystal-induced arthritis (CIA): median, 149 ng/ml; range, 37-616, n = 14, and other chronic inflammatory arthritis: median, 42 ng/ml; range, 15-205; n = 9) than in the 18 patients with osteoarthritis (OA) (median, 20 ng/ml; range 8-116) (P < 0.0001, anova). Angiogenin levels in SF from RA patients in remission with secondary OA were similar to those achieved in primary OA, and decreased in parallel with the resolution of acute gout. Angiogenin protein was released by cultured synovial fibroblasts from OA and RA patients, and reached 1.18 ng/106 cells/day. These data suggest that angiogenin may mediate local inflammation in arthritis via effects on angiogenesis and leucocyte regulation.

Human endothelial cells selectively express large amounts of pancreatic-type ribonuclease (RNase 1)

Pyrimidine-specific ribonucleases are a superfamily of structurally related enzymes with distinct catalytic and biological properties. We used a combination of enzymatic and non-enzymatic assays to investigate the release of such enzymes by isolated cells in serum-free and serum-containing media. We found that human endothelial cells typically expressed large amounts of a pancreatic-type RNase that is related to, if not identical to, human pancreatic RNase. This enzyme exhibits pyrimidine-specific catalytic activity, with a marked preference for poly(C) substrate over poly(U) substrate. It was potently inhibited by placental RNase inhibitor, the selective pancreatic-type RNase inhibitor Inhibit-Ace, and a polyclonal antibody against human pancreatic RNase. The enzyme isolated from medium conditioned by immortalized umbilical vein endothelial cells (EA.hy926) possesses an amino-terminal sequence identical to that of pancreatic RNase, and shows molecular heterogeneity (molecular weights 18,000-26,000) due to different degrees of N-glycosylation. Endothelial cells from arteries, veins, and capillaries secreted up to 100 ng of this RNase daily per million cells, whereas levels were low or undetectable in media conditioned by other cell types examined. The corresponding messenger RNA was detected by RT-PCR in most cell types tested so far, and level of its expression was in keeping with the amounts of protein. The selective strong release of pancreatic-type RNase by endothelial cells suggests that it is endowed with non-digestive functions and involved in vascular homeostasis.

T(H)2-mediated pulmonary inflammation leads to the differential expression of ribonuclease genes by alveolar macrophages

The eosinophil-associated ribonuclease (Ear) family in the mouse consists of thirteen genes, eleven of which encode RNases that have physical/functional properties similar to the human Ears, eosinophil-derived neurotoxin and eosinophil cationic protein. The expression of Ear genes in the mouse is confined to sites of known eosinophilopoiesis, with the exception of the lung. Two Ear genes, Ear1 and Ear2, are predominantly expressed in the lungs of naive mice. Total Ear gene expression and RNase activity in bronchoalveolar lavage fluid increases significantly upon the induction of pulmonary inflammation using an ovalbumin (OVA) model of allergic sensitization and challenge. Interestingly, pulmonary Ear11 transcripts, which are absent in naive mice, accumulate as a consequence of OVA-mediated T(H)2 inflammation in the lung. The induction of Ear11 expression is dependent on the presence of T cells, in particular, CD4(+) T lymphocytes. This effect is likely the result of the elaboration of T(H)2 cytokine levels, because pulmonary instillation of interleukin-4 or interleukin-13 induces the accumulation of Ear11 transcripts in naive animals. This study demonstrates that despite an allergen-mediated pulmonary eosinophilia and earlier studies showing that Ears are constituents of eosinophil secondary granules, alveolar macrophages are a significant source of these RNases in lungs of OVA-treated mice.

Polymerization of nontemplate bases before transcription initiation at the 3' ends of templates by an RNA-dependent RNA polymerase: an activity involved in 3' end repair of viral RNAs

The 3' ends of RNAs associated with turnip crinkle virus (TCV), including subviral satellite (sat)C, terminate with the motif CCUGCCC-3'. Transcripts of satC with a deletion of the motif are repaired to wild type (wt) in vivo by RNA-dependent RNA polymerase (RdRp)-mediated extension of abortively synthesized oligoribonucleotide primers complementary to the 3' end of the TCV genomic RNA. Repair of shorter deletions, however, are repaired by other mechanisms. SatC transcripts with the 3' terminal CCC replaced by eight nonviral bases were repaired in plants by homologous recombination between the similar 3' ends of satC and TCV. Transcripts with deletions of four or five 3' terminal bases, in the presence or absence of nonviral bases, generated progeny with a mixture of wt and non-wt 3' ends in vivo. In vitro, RdRp-containing extracts were able to polymerize nucleotides in a template-independent fashion before using these primers to initiate transcription at or near the 3' end of truncated satC templates. The nontemplate additions at the 5' ends of the nascent complementary strands were not random, with a preference for consecutive identical nucleotides. The RdRp was also able to initiate transcription opposite cytidylate, uridylate, guanylate, and possibly adenylate residues without exhibiting an obvious preference, flexibility previously unreported for viral RdRp. The unexpected existence of three different repair mechanisms for TCV suggests that 3' end reconstruction is critical to virus survival.

RT-PCR from eosinophil-depleted leukocytes without RNA extraction: cell selection using streptavidin PCR tubes

OBJECTIVES

The major RNase activity of leukocytes has been attributed to eosinophil-derived neurotoxin EDN. Depletion of eosinophils enables RT-PCR from 10(5) leukocytes without RNA extraction. In this study we introduced streptavidin-coated PCR tube strips for the selection of eosinophil-free leukocytes for RT-PCR analysis.

DESIGN AND METHODS

Polypropylene 0.2 ml PCR tube strips were coated with streptavidin and biotinylated antibodies against cell surface antigens were attached to the tubes. CD7-positive T-lymphocytes, CD19-positive B-lymphocytes and CD16-positive cells (mainly neutrophils and monocytes) were positively selected by incubating of 1-2 x 10(5) leukocytes in the antibody-coated PCR tubes for 30 min at 23 degrees C.

RESULTS

The mean amount of cells bound into a tube was 31,500 (CV25%) T-cells and 8,600 (CV61%) B-cells from 12 blood samples, and 23,600 (CV22%) CD16+ cells from 17 samples. The influence of selected cell lysate on the RT-PCR analysis of Philadelphia chromosome (bcr/abl translocation) from 100 K562 cells was small: 78% (CV28%) of the leukocyte-free signal was obtained in the presence of CD16+ cells or 89% (CV15%) and 99% (CV11%) and in the presence of T-cells and B-cells, respectively.

CONCLUSIONS

These results suggest that through the introduction of eosinophil-free cell population into RT-PCR a reproducible method with reasonable leukocyte yield and avoiding RNA extraction was developed.

Major Interference from Leukocytes in Reverse Transcription-PCR Identified as Neurotoxin Ribonuclease from Eosinophils: Detection of Residual Chronic Myelogenous Leukemia from Cell Lysates by Use of an Eosinophil-depleted Cell Preparation

Background: The extraction of RNA from leukocytes for reverse transcription-PCR (RT-PCR) is time-consuming and contributes to variation in analysis of the Philadelphia (Ph1) chromosome of chronic myelogenous leukemia (CML) by RT-PCR. To detect residual CML after bone marrow transplantation, mRNA from at least 105 leukocytes should be analyzed, but the RNase activity of the cells precludes simple leukocytes lysis as an alternative to RNA extraction. We sought to identify the main source of RNase activity of leukocytes.

Methods: We used a three-step chromatographic process and amino acid sequence analysis. We selected eosinophil-free granulocytes by using a biotinylated CD16 antibody and selected mononuclear cells by fractionating the leukocytes with a Ficoll-Paque® density gradient.

Results: Chromatography and amino acid sequencing identified eosinophil-derived neurotoxin (EDN) as the main source of leukocyte RNase. Depletion of eosinophils reduced the EDN content of cell lysates by ∼90%, allowing a signal from a lysate of 50 K562 Ph1-positive cells mixed with 105 CD16+ granulocytes that was equivalent to 77% of the signal in the absence of leukocytes. A similar lysate with mononuclear cells gave a signal equivalent to 53% of that without mononuclear cells. RNA extraction gave a signal equivalent to only 24% of the leukocyte-free control.

Conclusion: The depletion of eosinophils during the preparation of leukocyte samples for RT-PCR efficiently reduces the risk of mRNA degradation by ribonucleases, enabling RT-PCR analysis directly from cell lysates with a better signal than can be obtained by RNA extraction.

Structure-function relationships of acid ribonucleases: lysosomal, vacuolar, and periplasmic enzymes

It is surprising that only relatively recently has attention been directed to the characterization of the properties of acid ribonucleases (RNases), leading to some understanding of their biochemistry and their functional roles. The present review summarizes current progress in this field under the following general topics: (1) the wide distribution of acid RNases in organisms from viruses to animals; (2) recent findings concerning their primary and three-dimensional structure; (3) the structure-function relationship of acid RNases, with a fungal RNase from Rhizopus niveus as a model enzyme; (4) the unique localization of acid RNases in the periplasm of bacteria, vacuoles in plants, and lysosomes of animals and protozoa; and (5) the diversity of physiological roles, depending on the organism, such as self-incompatibility factors and defense proteins in some plants, the surface protein of an animal virus related to pathogenicity, and possible relationship to human cancer.