The IGF2 methylation score for adrenocortical cancer: an ENSAT validation study

Adrenocortical carcinoma (ACC) is diagnosed using the histopathological Weiss score (WS), but remains clinically elusive unless it has metastasized or grows locally invasive. Previously, we proposed the objective IGF2 methylation score as diagnostic tool for ACC. This multicenter European cohort study validates these findings. Patient and tumor characteristics were obtained from adrenocortical tumor patients. DNA was isolated from frozen specimens, where after DMR2, CTCF3, and H19 were pyrosequenced. The predictive value of the methylation score for malignancy, defined by the WS or metastasis development, was assessed using receiver operating characteristic curves and logistic and Cox regression analyses. Seventy-six ACC patients and 118 patients with adrenocortical adenomas were included from seven centers. The methylation score and tumor size were independently associated with the pathological ACC diagnosis (OR 3.756 95% CI 2.224-6.343; OR 1.467 95% CI 1.202-1.792, respectively; Hosmer-Lemeshow test P = 0.903), with an area under the curve (AUC) of 0.957 (95% CI 0.930-0.984). The methylation score alone resulted in an AUC of 0.910 (95% CI 0.866-0.952). Cox regression analysis revealed that the methylation score, WS and tumor size predicted development of metastases in univariate analysis. In multivariate analysis, only the WS predicted development of metastasis (OR 1.682 95% CI 1.285-2.202; P < 0.001). In conclusion, we validated the high diagnostic accuracy of the IGF2 methylation score for diagnosing ACC in a multicenter European cohort study. Considering the known limitations of the WS, the objective IGF2 methylation score could potentially provide extra guidance on decisions on postoperative strategies in adrenocortical tumor patients.

Pilot study on circulating miRNA signature in children with obesity born small for gestational age and appropriate for gestational age

BACKGROUND

Children born small for gestational age (SGA) are at increased risk of metabolic dysfunction. Dysregulation of specific microRNAs (miRNAs) contributes to aberrant gene expression patterns underlying metabolic dysfunction.

OBJECTIVE

We aimed to determine and compare circulating miRNA (c-miRNA) profile of SGA and appropriate for gestational age (AGA) children with obesity and with normal weight, in order to identify biomarkers for early detection of increased risk of developing metabolic dysfunction in SGA and AGA children with obesity.

METHODS

Small non-coding RNAs from serum of 15 SGA children with obesity (OB-SGA), 10 SGA children with normal weight (NW-SGA), 17 AGA children with obesity (OB-AGA) and 12 AGA children with normal weight (NW-AGA) (mean age 11.2 ± 2.6) have been extracted and sequenced in order to detect and quantify miRNA expression profiles.

RESULTS

RNA-seq analyses showed 28 miRNAs dysregulated in OB-SGA vs. NW-SGA and 19 miRNAs dysregulated in OB-AGA vs. NW-AGA. Among these, miR-92a-3p, miR-122-5p, miR-423-5p, miR-484, miR-486-3p and miR-532-5p were up regulated, and miR-181b-5p was down regulated in both OB-SGA and OB-AGA compared with normal weight counterparts. Pathway analysis and miRNA target prediction suggested that these miRNAs were particularly involved in insulin signalling, glucose transport, insulin resistance, cholesterol and lipid metabolism.

CONCLUSION

We identified a specific profile of c-miRNAs in SGA and AGA children with obesity compared with SGA and AGA children with normal weight. These c-miRNAs could represent specific biomarkers for early detection of increased risk of developing metabolic dysfunction in SGA and AGA children with obesity.

Transcriptomic analysis of nickel exposure in Sphingobium sp. ba1 cells using RNA-seq

Nickel acts as cofactor for a number of enzymes of many bacteria species. Its homeostasis is ensured by proteins working as ion efflux or accumulation systems. These mechanisms are also generally adopted to counteract life-threatening high extra-cellular Ni²⁺ concentrations. Little is known regarding nickel tolerance in the genus Sphingobium. We studied the response of the novel Sphingobium sp. ba1 strain, able to adapt to high Ni²⁺ concentrations. Differential gene expression in cells cultured in 10 mM Ni²⁺, investigated by RNA-seq analysis, identified 118 differentially expressed genes. Among the 90 up-regulated genes, a cluster including genes coding for nickel and other metal ion efflux systems (similar to either cnrCBA, nccCBA or cznABC) and for a NreB-like permease was found. Comparative analyses among thirty genomes of Sphingobium species show that this cluster is conserved only in two cases, while in the other genomes it is partially present or even absent. The differential expression of genes encoding proteins which could also work as Ni²⁺-accumulators (HupE/UreJ-like protein, NreA and components of TonB-associated transport and copper-homeostasis systems) was also detected. The identification of Sphingobium sp. ba1 strain adaptive mechanisms to nickel ions, can foster its possible use for biodegradation of poly-aromatic compounds in metal-rich environments.

A novel group of IncQ1 plasmids conferring multidrug resistance

The IncQ is a group of non-conjugative but mobilisable plasmids that are found and stably maintained in a wide range of bacteria contributing to the spread of antimicrobial resistance genes and to the insurgence of multidrug resistant bacteria. Here we report the identification, in clinical Salmonella Typhimurium strains, of an IncQ1 plasmid (pNUC) which confers resistance to sulfamethoxazole, streptomycin and tetracycline through the presence of sul2, strAB and tetA genes, respectively. pNUC was detected in five multidrug resistant S. Typhimurium strains collected in Southern Italy from various hospitals and years of isolation. Bioinformatics analyses highlighted the presence of pNUC-like plasmids in pathogenic bacteria of various Enterobacteriaceae genera or species. Taken as a whole, these plasmids constitute a novel group of IncQ1 plasmids that might have originated through recombination events between a tetR-tetA gene cluster (possibly derived from a Tn1721) and a recipient IncQ1 plasmid related to RSF1010. Our findings raise concerns regarding the possible contribution of the newly identified group of IncQ1 plasmids to the spread of tetracycline resistance.

[Orthotopic murine model of head and neck squamous cell carcinoma]

PURPOSE

To develop a reliable animal model able to reproduce the behavior of head and neck squamous cell carcinomas (HNSCC). This model should facilitate our understanding of the molecular mechanisms of tumorigenicity and progression of these tumors, as well as the evaluation of novel therapies.

MATERIAL AND METHODS

20 nude mice nu/nu were injected intraorally and submucosally with a cell line derived from a human squamous cell carcinoma of the glottis.

RESULTS

90% of the mice developed locally agressive squamous cell carcinomas, invading the surrounding muscle fibers and into loose connective tissue structures. All the tumors showed perineural growth. Four (22%) of the 18 mice showed bone destruction, and 22% vascular invasion. Tumor cells invaded lymphatic vessels in all the specimens, and 100% of the mice developed regional lymph node metastases. None of the animals developed haematogenous metastases.

CONCLUSIONS

We present a metastasing model of HNSCC that resembles its human counterpart in many aspects.

Mycophenolate mofetil and roscovitine decrease cyclin expression and increase p27(kip1) expression in anti Thy1 mesangial proliferative nephritis

The response of mesangial cells to a phlogistic challenge includes cell proliferation and mesangial matrix expansion. Cell proliferation is a highly regulated process which includes enhancing factors such as cyclins, cyclin dependent kinases, and inhibitory proteins, such as p27(kip1). The aim of the study was to evaluate the effects of Mycophenolate mofetil (MMF), and roscovitine (R), on the cell cycle regulatory system when administered in the florid phase of the experimental model of mesangial proliferative nephritis induced by the anti Thy-1 antigen monoclonal antibody. Three days after nephritis induction, different groups were given MMF and R. Rats treated with MMF or R showed a slight decrease in mesangial proliferation and matrix expansion. Samples of cortical tissue were tested by 'real time' RT-PCR in order to study gene expression of cyclins B, D1, D2, D3, E, and the cyclin inhibitor p27(kip1). Localization of mRNA was evaluated by in situ hybridization. Real time RT-PCR analysis showed a significant decrease in cyclins B, D1, D2, and D3 in rats treated with either MMF or R as compared to controls. Both MMF and R treatment induced a significant increase in p27(kip1) mRNA expression. In situ hybridization showed a mesangial-endothelial expression pattern in glomeruli. The number of labelled cells per glomerulus, the number of positive glomeruli in each examined slide as well as cyclin D2 and D3 signal intensity was significantly lower in rats treated with MMF or R as compared to controls, whereas MMF or R treatment up-regulated p27(kip1) mRNA expression. Immunohistochemical evaluation of p27(kip1) aimed to examine the influence of MMF or R on protein expression confirmed up-regulation.

A small domain in the N terminus of the regulatory alpha-subunit Kv2. 3 modulates Kv2.1 potassium channel gating

Recent work has demonstrated the existence of regulatory K(+) channel alpha-subunits that are electrically silent but capable of forming heterotetramers with other pore-forming subunits to modify their function. We have investigated the molecular determinant of the modulatory effects of Kv2.3, a silent K(+) channel alpha-subunit specific of brain. This subunit induces on Kv2.1 channels a marked deceleration of activation, inactivation, and closing kinetics. We constructed chimeras of the Kv2.1 and Kv2.3 proteins and analyzed the K(+) currents resulting from the coexpression of the chimeras with Kv2.1. The data indicate that a region of 59 amino acids in the N terminus, adjacent to the first transmembrane segment, is the major structural element responsible for the regulatory function of Kv2.3. The sequence of this domain of Kv2.3 is highly divergent compared with the same region in the other channels of the Kv2 family. Replacement of the regulatory fragment of Kv2.3 by the equivalent of Kv2.1 leads to loss of modulatory function, whereas gain of modulatory function is observed when the Kv2.3 fragment is transferred to Kv2.1. Thus, this study identifies a N-terminus domain involved in Kv2.1 channel gating and in the modulation of this channel by a regulatory alpha-subunit.

Identification of RNA-protein contacts within functional ribonucleoprotein complexes by RNA site-specific labeling and UV crosslinking

A variety of cellular processes are carried out by highly complex ribonucleoprotein (RNP) particles in which multiple RNA-RNA, RNA-protein, and protein-protein interactions occur. The spliceosome, which executes the nuclear pre-mRNA splicing reaction, is a particularly striking example of a complex RNP, containing a minimum of 50 distinct protein components as well as five small nuclear RNAs. In order to identify which among the numerous proteins may play critical roles in the splicing reaction, we have assembled spliceosomal complexes on pre-mRNA containing a single 32P-labeled nucleotide, isolated the complexes by gel filtration, and then carried out UV crosslinking. The combination of these three methods has allowed the identification of proteins that crosslink to critical sequence elements during each stage in spliceosome assembly. These methods should be generally applicable to the analysis of RNP complexes assembled in vitro.

Fasting during promotion, but not during initiation, enhances the growth of methylnitrosourea-induced mammary tumours

The purpose of this work was to investigate the effect of fasting on the induction and growth of chemically-induced mammary carcinogenesis. Female Sprague-Dawley rats were given methylnitrosourea (MNU) i.p. (50 mg/kg) at 50 days of age; a group of rats were exposed to 4 day fasting followed by 1 day of refeeding before the administration of the carcinogen, while another group was exposed to three cycles of 3 days fasting in 10 days, beginning 1 week after MNU injection. Fasting enhanced the development of mammary tumours only in rats fasted after carcinogen damage, while it did not affect the induction of tumours in rats fasted before MNU, if compared with full-fed controls. The enhanced growth of mammary tumours sustained by fasting during promotion was observed in the cervical-thoracic region. In addition, exposure to fasting made rats susceptible to the development of MNU-induced extra-mammary cancers. Different from the preventive effect of caloric restriction on tumor development, these data demonstrate that fasting affects the promotion phase of carcinogenesis by enhancing the growth of MNU-induced mammary tumours.

Evidence that U5 snRNP recognizes the 3' splice site for catalytic step II in mammals

The first AG dinucleotide downstream from the branchpoint sequence (BPS) is chosen as the 3' splice site during catalytic step II of the splicing reaction. The mechanism and factors involved in selection of this AG are not known. Early in mammalian spliceosome assembly, U2AF65 binds to the pyrimidine tract between the BPS and AG. Here we show that U2AF65 crosslinking is replaced by crosslinking of three proteins of 110, 116 and 220 kDa prior to catalytic step II, and we provide evidence that all three proteins are components of U5 snRNP. These proteins interact with pre-mRNA in the region spanning from immediately downstream of U2 snRNP's binding site at the BPS to just beyond the 3' splice site. We also demonstrate that there are strict constraints on both the sequence and the distance between the BPS and AG for catalytic step II. Together, these observations suggest that U5 snRNP is positioned on the 3' splice site by an interaction (direct or indirect) with U2 snRNP bound at the BPS and by a direct interaction with the pyrimidine tract. The functional AG for catalytic step II may be specified, in turn, by its location with respect to the U5 snRNP binding site.

Identification and functional characterization of a K+ channel alpha-subunit with regulatory properties specific to brain

The physiological diversity of K+ channels mainly depends on the expression of several genes encoding different alpha-subunits. We have cloned a new K+ channel alpha-subunit (Kv2.3r) that is unable to form functional channels on its own but that has a major regulatory function. Kv2.3r can coassemble selectively with other alpha-subunits to form functional heteromultimeric K+ channels with kinetic properties that differ from those of the parent channels. Kv2.3r is expressed exclusively in the brain, being concentrated particularly in neocortical neurons. The functional expression of this regulatory alpha-subunit represents a novel mechanism without precedents in voltage-gated channels, which might contribute to further increase the functional diversity of K+ channels necessary to specify the intrinsic electrical properties of individual neurons.

Inhibitory effect of albumin-derived advanced glycosylation products on PMA-induced superoxide anion production by rat macrophages

Advanced glycosylation end products (AGE) are implicated in many of the complications of diabetes. In the same way, infectious diseases are frequently associated with this disease. An impaired respiratory burst in macrophages may be a cause of infectious complications in diabetic patients. To establish a possible mechanism of this altered cell function, we have analyzed the effect of AGE-modified proteins on PMA-dependent superoxide anion production (O2.-) from normal rat peritoneal macrophages. We have used AGE-modified bovine serum albumin (AGE-BSA) prepared by incubation with glucose. AGE-BSA partially inhibits the phorbol ester-dependent superoxide production by macrophages in vitro. The specificity of this inhibitory effect is demonstrated by the fact that aminoguanidine, an inhibitor of the formation of AGE products, fully prevents the effect of AGE-BSA in vitro. Macrophages from diabetic rats shown an inhibition on PMA dependent-O2.- production. However, the treatment in vivo with aminoguanidine produced a cancelation of the inhibitory effect observed in the diabetic state. These data suggest that AGE-modified proteins could be implicated in the impairment of macrophage respiratory burst in diabetes.

Phosphatidylethanolamine N-methyltransferase 2 and CTP-phosphocholine cytidylyltransferase expressions are related with protein kinase C isozymes in developmental liver growth

PEMT and CT activities were reciprocally regulated during the perinatal period. Consistently, PEMT2 expression was undetectable before birth when CT was highly expressed. Surprisingly, PEMT2 was relatively highly expressed at birth when the cell division and CT expression were still high. During development liver cell growth was associated with enhanced levels in the activity of beta, zeta and, particularly, alpha PKC. The activity of delta PKC was lower in foetal, higher in the newborn and again slightly lower than adult liver 10 days after birth. These data show that CT expression and alpha, beta and zeta PKC activities are positively, whereas PEMT2 expression and delta PKC activity are negatively associated with the liver cell division during development.

Choline feeding depresses the phospholipase C activity in the regenerating liver of female rats

The administration of an excess of choline for 3 weeks is able to delay the proliferative response to partial hepatectomy (PH) in female rats. Choline feeding can affect the phospholipid composition of cell membranes and, as a consequence, the transduction of the mitogenic signals. On these bases, we studied the turnover of phosphatidylinositol-4,5-biphosphate (PIP2) in the regenerating liver of female rats. The hydrolysis of PIP2 is catalysed by a specific phospholipase C (PL-C) and it generates the second messenger molecules, namely diacylglycerol and inositol-1,4,5-triphosphate (IP3). Our results showed that the administration of an excess of choline to females was able to reduce the PL-C activity and the membrane IP3 content in the quiescent liver. Both parameters remained lower than controls during liver regeneration, even if they were higher 1 and 2 h after PH in comparison with the quiescent liver, in choline-fed females. These data suggest that the delay in the liver regeneration by choline is due, at least in part, to the alteration in the pathway of PIP2 turnover for the transduction of mitogenic signals.

Fasting/refeeding enhances the crypt multiplicity in rat colon carcinogenesis induced by azoxymethane

Aberrant crypt foci (ACF) are putative preneoplastic lesions of colon cancer which are being utilized currently as a biological end point to evaluate the induction and modulation of colon carcinogenesis. In rodents, caloric restriction reduces carcinogen-induced colon cancer incidence. The present study was designed to investigate the effect of fasting followed by refeeding on the development of ACF. Male Fisher 344 rats were fasted for 4 days and they were given a single injection of azoxymethane (AOM) at the dose of 20 mg/kg body weight on the first day of refeeding, and killed 3 months later. Controls were fed ad libitum and received the same dose of AOM. The number and crypt multiplicity (number of crypts/focus) of ACF were measured on the medial colon. No effect of fasting/refeeding was observed in the total number of foci/medial colon. On the contrary, rats fasted for 4 days and refed developed foci with higher number of crypts than fed controls. Our results are of particular interest because the crypt multiplicity, rather than the number of foci, is a consistent predictor of tumor incidence. As a consequence these data suggest a possible role of fasting/refeeding in enhancing the colon tumor outcome.

Identification of proteins that interact with exon sequences, splice sites, and the branchpoint sequence during each stage of spliceosome assembly

We have carried out a systematic analysis of the proteins that interact with specific intron and exon sequences during each stage of mammalian spliceosome assembly. This was achieved by site-specifically labeling individual nucleotides within the 5' and 3' splice sites, the branchpoint sequence (BPS), or the exons with 32P and identifying UV-cross-linked proteins in the E, A, B, or C spliceosomal complex. Significantly, two members of the SR family of splicing factors, which are known to promote E-complex assembly, cross-link within exon sequences to a region approximately 25 nucleotides upstream from the 5' splice site. At the 5' splice site, cross-linking of the U5 small nuclear ribonucleoprotein particle protein, U5(200), was detected in both the B and C complexes. As observed in yeast cells, U5(200), also cross-links to intron/exon sequences at the 3' splice site in the C complex and may play a role in aligning the 5' and 3' exons for ligation. With label at the branch site, we detected three distinct proteins, designated BPS72,BpS70, and BPS56, which replace one another in the E, A, and C complexes. Another dynamic exchange was detected with pre-mRNA labeled at the AG dinucleotide of the 3' splice site. In this case, a protein, AG100,cross-links in the A complex and is replaced by another protein, AG75, in the C complex. The observation that these proteins are specifically associated with critical pre-mRNA sequence elements in functional complexes at different stages of spliceosome assembly implicates roles for these factors in key recognition events during the splicing pathway.

The delay in rat liver regeneration by choline is associated to alteration in c-myc expression

Previous data of our laboratory showed that female rats regenerated earlier than males and choline shifted the female growth pattern toward that of males. We investigated if the effect of choline on the liver compensatory growth was associated to a modulation of the expression and methylation pattern of an early cell cycle dependent proto-oncogene, c-myc. The peak of DNA synthesis was 22 h after 2/3 partial hepatectomy in female regenerating liver, while it was delayed to 30 h when female rats received choline for 3 weeks before liver surgery. Partial hepatectomy induced the expression of c-myc that was already maximal at 1 h. Choline reduced the c-myc expression and it shifted the maximum increase at 2 h. The methylation pattern of c-myc was studied with the Hpa II restriction enzyme. The delay in c-myc expression was not due to hypermethylation of the gene.

Fasting/refeeding enhances the development of mammary tumors induced by methylnitrosourea in the rat

The effect of fasting/refeeding on MNU-induced mammary carcinogenesis was investigated. Female Sprague-Dawley rats were given i.p. a single dose of MNU (50 mg/Kg body weight) and beginning 1 week after MNU administration were exposed to 3 cycles of 3 days fasting followed by refeeding (10 days). Rats were palpated twice a week and killed when tumor diameter was about 2 cm. Tumors palpated were registered by location. The exposure to fasting/refeeding after initiation increased the total number of mammary tumors about 2-fold compared to full-fed control group. In addition, fasted rats developed about 3-fold mammary tumors in the cervical-thoracic gland chains versus the abdominal-inguinal gland chains, while no difference in tumor distribution was observed in controls. The present study reports that fasting/refeeding enhances the development of MNU-induced mammary tumors.

Respiratory burst is decreased by human hyperlipemic serum in rat peritoneal macrophages

The effect of hyperlipemic human serum on superoxide anion (O2-) production by rat peritoneal macrophages was investigated. Phorbol myristate acetate (PMA)-stimulated O2- production was inhibited when cells were preincubated with hyperlipemic human serum. This inhibition was specifically carried out by a lipid fraction and was dependent on both cholesterol and triglyceride serum levels. This inhibitory effect was not exerted by a direct effect on NADPH-oxidase activity, nor by a putative superoxide dismutase activity present in the serum. With human neutrophils, we observed a decreased mobility of the cytosolic factor p47-phox to the membrane during the activation process, caused by hyperlipemic serum. We did not find any effect of hyperlipemic serum on NO2- production by cultured rat macrophages. These results suggest that a pathological increase of circulating plasma lipids may be associated with an impaired inflamatory capacity of macrophages.

A two-step mechanism for 5' and 3' splice-site pairing

A fundamental question in the splicing of precursor messenger RNA is how the 5' and 3' splice sites are recognized and paired during the splicing reaction. It has been proposed that spliceosome assembly in metazoan pre-mRNAs can be initiated through interaction between the 3' splice site and specific sequence elements on the downstream exon (an exonic enhancer or a 5' splice site). Pairing of the intronic 5' and 3' splice sites occurs subsequently. We report here that 5' and 3' splice sites located on separate synthetic pre-mRNA substrates can be efficiently trans-spliced if the 3' trans-splicing substrate contains these downstream sequence elements. Moreover, selection of the trans 5' splice site can occur after the second pre-spliceosomal complex A has assembled on the 3' trans-splicing substrate. Thus our data demonstrate that 5' and 3' splice-site pairing in metazoans can occur in two distinct steps.

Modulation of phorbol ester-induced respiratory burst by vanadate, genistein, and phenylarsine oxide in mouse macrophages

The effect of the inhibitors of tyrosine phosphatase (vanadate and phenylarsine oxide) and of an inhibitor of tyrosine kinase (genistein) on O2.- production in mouse peritoneal macrophages was examined. Vanadate and phenylarsine oxide produced a dose-dependent inhibition of phorbol myristate acetate (PMA)-induced O2.- production, whereas genistein potentiated O2.- production triggered by phorbol ester. Vanadate had no effect on the respiratory burst in human neutrophils challenged with fMLP, in agreement with previously published data on human intact neutrophils. It did not alter reduced nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase activity in membrane preparations of mouse peritoneal macrophages. These data suggest that the phosphorylation of protein(s) in tyrosine residues blocked the PMA-dependent respiratory burst in mouse macrophages.

Specific protein-protein interactions between the essential mammalian spliceosome-associated proteins SAP 61 and SAP 114

Spliceosome-associated proteins (SAPs) 61, 62, and 114 can be UV-crosslinked to pre-mRNA in purified spliceosomal complexes and are associated with U2 small nuclear ribonucleoproteins (snRNP). These proteins also compose the essential heterotrimeric splicing factor SF3a, and products of yeast pre-mRNA processing genes PRP9, PRP11, and PRP21 are their likely yeast counterparts. We report the isolation of a cDNA encoding SAP 61 and find that it is 30% identical in amino acid sequence to PRP9. A C-terminal Cys2His2 zinc-finger-like motif, which could be involved in the pre-mRNA binding, is the most highly conserved region of the protein. We also demonstrate specific protein-protein interactions between SAPs 61 and 114 and show that the N terminus of SAP 61 is required for this interaction. Significantly, the corresponding proteins are also known to interact in yeast: PRP9 interacts with PRP21, and the N-terminal portion of PRP9 is required. Previous work showed that direct interactions also occur between SAPs 62 and 114 and between the corresponding PRPs 11 and 21. These observations indicate that the specific protein-protein interactions that occur between the three prespliceosomal factors have been conserved between yeast and mammals.

A new bipartite DNA-binding domain: cooperative interaction between the cut repeat and homeo domain of the cut homeo proteins

The recently cloned Clox (Cut-like homeo box) and CDP (CCAAT displacement protein), two mammalian counterparts of the Drosophila Cut homeo protein, correspond to alternatively spliced products of the same gene (mClox, for mammalian Cut-like homeo box). Although these proteins reportedly bind to apparently unrelated DNA sequences, we show by in vitro selection of optimal binding sites that both Clox and CDP have the same preferred DNA-binding specificity. The palindromic consensus target sequence, 5'-(t/a)(a/t)tATCGATTAt(t/c)(t/g)(t/a)-3', contains a bona fide homeo domain binding motif (ATTA). In addition, 37% of the in vitro-selected sequences have a CCAAT box, the canonical target for members of the family of CCAAT-binding factors. A characteristic feature of the cut homeo proteins is the presence of three evolutionarily conserved 73-amino-acid repeats of unknown function, the so-called cut repeats. We present evidence that the cut repeat II binds to mClox consensus targets independently of the DNA-binding activity of the homeo domain. In vitro selection of binding sites shows that the optimal targets for the cut repeat II contain one or more CCAAT boxes and, like the homeo domain, an ATTA core. These results indicate that the DNA-binding activity of the second cut repeat can account for the suggested role of CDP mClox as CCAAT displacement protein, a putative repressor of gene expression. We also report that the mClox homeo domain and cut repeat II interact in vitro in the absence of DNA. This interaction, which greatly enhances the DNA-binding activity of the binary complex, is specific to the cut homeo proteins. No cooperativity was observed between the cut repeat II and the homeo domains of Oct-1 and Gtx. Furthermore, the Drosophila cut repeat II, which does not appear to bind to DNA, also enhances the DNA-binding activity of the mClox homeo domain. Thus, the bifunctional cut repeat II, which defines a new family of bipartite DNA-binding proteins, is likely to play an important role in the function of the cut homeo proteins.

Beta-naphthylamine induces anion superoxide production in rat peritoneal macrophages

Rat peritoneal macrophages were incubated in the presence of beta-naphthylamine (beta-NA), a well known carcinogenic agent, and some parameters of respiratory burst were studied. beta-NA induced a time- and dose-dependent stimulation of superoxide anion (O-2) production, and this enhancement was suppressed by the addition of superoxide dismutase enzyme. Also, no cooperative effect between beta-NA and phorbol 12-myristate 13-acetate was observed. Other observations were as follows: (i) the simultaneous presence of polymyxin B, and staurosporine inhibitors of protein kinase C, inhibited beta-NA-dependent O-2 production; (ii) NADPH-oxidase contained in postnuclear fraction from beta-NA-incubated macrophages showed a greater activity than control fractions; (iii) the stimulation of O-2 production elicited by beta-NA was several-fold enhanced in activated macrophages compared to resident cells. These data suggest that beta-NA produces the activation of NADPH-oxidase through protein kinase C.

Modulation of the inhibition of respiratory burst in mouse macrophages by cyclosporin A: effect of in vivo treatment, glucocorticoids and the state of activation of cells

Cyclosporin A (CsA) is an immunosuppressor without myelotoxicity. It is thought that its effect is mediated by inhibition of Interleukin-2 (IL-2) receptor expression in lymphocytes. We have recently described that CsA reduces phorbol 12-myristate 13-acetate (PMA)-dependent superoxide anion and H2O2 production by resident mice macrophages in vitro. The present work provides evidence that the capacity of CsA to produce this inhibition is abolished when macrophages are in the activated state. We also show that peritoneal macrophages from CsA-treated mice retain the capacity to inhibit O2- production. The interaction between CsA and glucocorticoids in vitro shows a co-operative effect between both agents. These studies demonstrate a novel action of CsA related to its modulation of the inhibition of the respiratory burst. The physiological role of these CsA effects and modulation need further exploration.

Cyclosporin A inhibits phorbol ester-induced activation of superoxide production in resident mouse peritoneal macrophages

Peritoneal resident macrophages from mice are sensitive to inhibition by cyclosporin A (CsA) of phorbol 12-myristate 13-acetate (PMA)-stimulated oxidative burst. Inhibition was assessed in terms of superoxide anion (O2.-) and H2O2 production. Key findings were as follows. (a) CsA inhibited in a dose-dependent manner the production of O2.- when cells were stimulated with PMA. CsA did not alter the respiratory burst induced by other stimuli (zymosan, concanavalin A and fMet-Leu-Phe). It was verified that CsA itself had no scavenger effect. (b) A concomitant decrease in H2O2 liberation following CsA exposure was found. This inhibition was observed both in the initial rate of synthesis and in the accumulation after 15 min of incubation. (c) NADPH oxidase activity in the crude supernatant was unaffected by the previous incubation of macrophages with CsA. CsA does not inhibit glucose transport measured as 14CO2 production. (d) The production of O2.- was strongly dependent on the glucose concentration. Sodium oleate also stimulated O2.- production in resident macrophages. These data might be correlated with the inhibitory effect of CsA upon other functions of macrophages.