Quantification of mRNA in human tissue using fluorescent nested reverse-transcriptase polymerase chain reaction

Angioimmunoblastic T cell lymphoma is derived from mature T-helper cells with varying expression and loss of detectable CD4

Angioimmunoblastic T cell lymphoma (AILT) is a rare lymphoma that is regarded as a clinicopathologic entity but shows considerable histomorphologic diversity, variable immunophenotypes and inconsistent T cell receptor (TCR) gene rearrangement. One hundred four paraffin blocks of AILT were investigated defining tumor cell lineage by triple immunostains with a confocal laser scanning microscope and correlating morphology, immunophenotype and TCRgamma gene rearrangement to clinical outcome. Ninety-nine cases were CD4(+), some of them showing a mixture of CD4(+) and CD4(-) tumor cells. The remaining 5 specimens were CD3(+)/CD4(-)/CD8(-). A considerable number of T cells of different subtypes could always be found, but even in 13 cases predominated by CD8(+) cells, proliferation could be attributed to atypical CD4(+) cells. TCRgamma gene rearrangement was monoclonal in 48 cases (69%) among 70 tested. In 29 of these semi-quantitative gene scan analysis resulted in a median proportion of monoclonal peak of 35% of PCR-products. Clinical outcome was identical grouping patients by clonality of TCRgamma, absence or presence of clear cell clusters and international prognostic index. We conclude that AILT is mainly derived from CD2(+)CD3(+)CD4(+)CD5(+)CD7(-) mature T-helper cells with varying expression and partial loss of detectable CD4. A significant number of non-neoplastic T cells (resting CD4(+) T cells and activated small or medium-sized CD8(+) lymphocytes) may coexist with a minor neoplastic T cell population. Clinicopathologic correlation suggests AILT to be a well defined homogeneous entity with poor prognosis. Currently no prognostic factors can be derived.

Function of the endothelinB receptor in cardiovascular physiology and pathophysiology

One of the two receptors by which the potent vasoactive effects of endothelin (ET)-1 are mediated is the ET(B) receptor (ET(BR)), which is found in several tissues, but, more importantly from a cardiovascular point of view, on the endothelial cell. The endothelial cell also has the unique capability of releasing ET-1, as well as other factors, such as the endothelial-derived relaxing factors and prostacyclin, which counteract the myotropic effects of the peptide. The secretory and contractile responses to ET-1 rely on G-protein-coupled ET(BR)s, as well as ET(A)-G-protein-coupled receptor-like proteins. The mitogenic properties of ET-1 via ET(A) receptors (ET(AR)s) coupled to mitogen-activated protein kinases and tyrosine kinases on the vascular smooth muscle may occur in conjunction with the anti-apoptotic characteristics of the endothelial ET(BR)s. Interestingly, most of the relevant antagonists and agonists for both ET(AR)s and ET(BR)s have been developed by the pharmaceutical industry. This highlights the therapeutical potential of compounds that act on ET receptors. In normal as well as in physiopathological conditions, the ET(BR) plays an important role in the control of vascular tone, and must be taken into account when using ET receptor antagonists for the treatment of cardiovascular diseases. For the management of congestive heart failure, renal failure and primary pulmonary hypertension, the most recent literature supports the use of selective ET(AR) antagonists rather than mixed antagonists of ET(AR)s and ET(BR)s. Nonetheless, validation of this view will have to await the first clinical trials comparing the actions of ET(A) to mixed ET(A)/ET(B) receptor antagonists.

Oxidative stress in a rat model of obesity-induced hypertension

The mechanisms underlying the development of hypertension in obesity are not yet fully understood. We recently reported the development of hypertension in a rat model of diet-induced obesity. When Sprague-Dawley rats (n=60) are fed a moderately high fat diet (32 kcal% fat) for 10 to 16 weeks, approximately half of them develop obesity (obesity-prone [OP] group) and mild hypertension (158+/-3.4 mm Hg systolic pressure), whereas the other half (obesity-resistant [OR] group) maintains a body weight equivalent to that of a low fat control group and is normotensive (135.8+/-3.8 mm Hg). We examined the potential role of oxidative stress in the development of hypertension in this model. Lipid peroxides measured as thiobarbituric acid-reactive substances showed a significant increase in the LDL fraction of OP rats (2.8+/-0.32 nmol malondialdehyde/mg protein) compared with OR and control rats (0.9+/-0.3 nmol malondialdehyde/mg protein). Also, aortic and kidney thiobarbituric acid-reactive substances showed a significant (3- and 5- fold) increase in OP rats after 16 weeks of diet. In addition, superoxide generation by aortic rings, measured by lucigenin luminescence, showed a 2-fold increase in the OP group compared with both the OR and control groups. In addition, free isoprostane excretion and nitrotyrosine in the kidney showed an increase in OP rats only. The urine and plasma nitrate/nitrite measured by the LDH method showed a 1.8-fold decrease in OP rats compared with OR rats. However, endothelial NO synthase expression in the kidney cortex and medulla assessed by reverse transcriptase-polymerase chain reaction showed a strong increase in the OP rats versus OR and control rats (endothelial NO synthase/beta-actin ratio 1.3+/-0.04 in OP rats versus 0.44+/-0.02 in OR rats), suggesting a possible shift toward superoxide production by the enzyme. Collectively, the data show a decreased NO bioavailability in OP animals that is due in part to the increased oxidative stress.

Interleukin-13 protects endothelial cells from apoptosis and activation: association with the protective genes A20 and A1

BACKGROUND

Chronic rejection is the major obstacle to long-term survival of allografts and is associated with graft endothelial cell activation and apoptosis. Recent reports have found an association between graft survival, presence of Th2 cytokines, and expression by endothelial cells of cytoplasmic "protective" molecules that prevent apoptosis and down-regulate the inflammatory process.

METHODS

Cultured human umbilical vein endothelial cells (HUVEC) were used. Apoptotic cells were detected by staining with FITC-annexinV followed by flow cytometry. Expression of vascular cell adhesion molecule-1, E-selectin, and intercellular adhesion molecule-1 were also measured by flow cytometry. Transcripts were detected by reverse transcription-PCR and quantitation was achieved by co-amplification of competing, internal standard RNA.

RESULTS

We demonstrate that exposure of HUVEC to interleukin (IL)-13 for 72 hr afforded partial protection from apoptosis induced by tumor necrosis factor-alpha/cycloheximide or serum starvation. Pretreatment with IL-13 also modulated induction of E-selectin after acute exposure to tumor necrosis factor-alpha or IL-1alpha. Protection was associated with transcription of the genes A1 and A20. Prolonged treatment with IL-13 had minimal proinflammatory effects and did not induce expression of E-selectin or vascular cell adhesion molecule-1 or increase intercellular adhesion molecule-1 above basal levels.

CONCLUSIONS

Our data provide a possible explanation for the observed association between Th2 cytokines and expression of protective genes in the endothelium of long-surviving allografts and xenografts.

Qualitative and semiquantitative polymerase chain reaction testing for cytomegalovirus DNA in serum allows prediction of CMV related disease in liver transplant recipients

AIM

To identify cytomegalovirus (CMV) infection in liver transplant recipients by polymerase chain reaction (PCR) techniques and to separate the cases in which CMV related disease will occur, for whom treatment is indicated, from those in whom infection will remain innocuous.

METHODS

The combination of qualitative and semiquantitative PCR of serum and urine was assessed to determine whether these assays can identify those at risk of CMV related disease and compared their performance with conventional approaches to diagnosis.

RESULTS

Qualitative PCR of serum had superior specificity, sensitivity, and positive and negative predictive values compared with urine DEAFF (detection of early antigen fluorescent foci) and PCR of urine. All episodes of CMV related disease were associated with the presence of CMV DNA by PCR in serum or urine; CMV was detected before clinical onset in 70% and 60% of cases, respectively. The period over which CMV DNA could be detected was not correlated with CMV related disease. Both peak viral load and cumulative viral load estimated using a semiquantitative PCR method on serum samples positive by the qualitative method could be used to distinguish asymptomatic infection from CMV related disease with 100% specificity and sensitivity. In contrast semiquantitative PCR of urine was of little value.

CONCLUSIONS

An approach based on PCR testing with a combination of qualitative and subsequently semiquantitative serum samples would improve the diagnosis of CMV infection and aid identification of those patients at risk of CMV related disease, allowing treatment to be targeted specifically.

Quantification of mRNA levels of endothelin receptor subtypes and preproEndothelin-1 in renal needle biopsies by competitive reverse transcriptase polymerase chain reaction

The vasoconstrictive peptide endothelin-1 (ET-1) is an autocrine/paracrine peptide of putative pathophysiological importance in renal transplant medicine. The aim of the present study was to develop a method for analysis of gene expression of the renal endothelin system in humans. Only small amounts of tissue are available from renal cortical needle biopsies. Thus, in the present study we developed a quantitative assay based on the competitive reverse transcriptase polymerase chain reaction (RT-PCR) technology. We quantified endothelin A (ET(A)) and B (ET(B)) receptor subtype mRNAs and preproET-1 mRNA levels in renal cortex biopsies obtained before nephrectomy of healthy kidney donors. Mean (+/- SEM) mRNA levels of the ET(A) and ET(B) receptor subtypes in 26 living donors were 212 +/- 23 and 368 +/- 56 amol/microg total RNA, respectively. The preproET-1 mRNA level in 19 living donors was 213 +/- 28 amol/microg total RNA. The inter-assay coefficient of variation (CV) for the assay was 10%; the intra-assay CV was 6-13%. The competitive RT-PCR assay described provides an accurate tool for gene expression investigation of the human endothelin system in renal cortical needle biopsies.

A simple nested RT-PCR method for quantitation of the relative amounts of multiple cytokine mRNAs in small tissue samples

It is difficult to quantitate cytokine mRNA profiles in small human tissue specimens obtained by a needle biopsy, even using standard RT-PCR methods, because the amount of mRNA in the specimens is very small. To address this problem, we developed highly sensitive, quantitative, nested RT-PCR techniques to evaluate the expression of multiple cytokine mRNAs in synovial specimens obtained by needle biopsy. To reduce effects of variation of initial RNA concentrations, cDNA from each target RNA sample was normalized, using a simplified competitive PCR method, to the levels of beta-actin cDNA. The first and the second (nested) PCR were performed in the same tube to prevent contamination. The number of PCR-product bands, evident on polyacrylamide gel electrophoresis, was used to quantitate the relative amounts of target cDNA. Using our methods, it was possible to evaluate, in a single synovial tissue specimen obtained by needle biopsy, the relative amounts of mRNAs for 10 cytokines (TNF-alpha, IL-1 beta, IL-2, IL-4, IL-6, IL-10, IL-12 p40, IL-13, IL-15, IFN-gamma) and CD3 delta chain. Our methods are particularly valuable if there are multiple target mRNAs, numerous samples, or if the amounts of mRNAs are limited. The methods are applicable to a wide variety of tissues and target mRNAs.

Differential distribution of endothelin peptides and receptors in human adrenal gland

Sub-type selective ligands revealed a differential distribution of endothelin (ET) receptors within human adrenal glands. High densities of ETA receptors were localized, using [125I]-PD151242, to the smooth muscle layer of the arteries, smaller vessels within the capsular plexus and to the secretory cells of zona glomerulosa (KD = 139.8 +/- 39.7, Bmax = 69.7 +/- 9.1 fmol mg-1 protein, mean of 3 individuals+/-sem). ETB receptors were present in the medulla (KD = 145.2 +/- 16.4, Bmax = 75.5 +/- 12.3), zona glomerulosa (KD = 100.6 +/- 35.1, Bmax = 63.1 +/- 10.0), fasiculata (KD 145.1 +/- 16.2, Bmax = 67.9 +/- 6.9) and reticularis (KD = 118.2 +/- 18.6, Bmax = 71.9 +/- 6.5). ETB receptors were not detected within the smooth muscle of the vasculature. Messenger RNA encoding both sub-types was present in adrenals. ET-like immunoreactivity was localized to the cytoplasm of the endothelial cells from arteries supplying the gland and resistance vessels within the capsular plexus. Staining was also detected in these cells using anti-big ET-1 and less intensely with anti-big ET-2 antisera but not within cells within the cortex or medulla. Big ET-3-like immunoreactivity was localized to secretory cells of the medulla. Staining was not found using antiserum that could detect ET-3, suggesting further processing of big ET-3 may occur within the plasma, and that the adrenals could be a source of ET-3. The presence of ET-1 was confirmed by high performance liquid chromatography and radioimmunoassay although ET-3 was not detected. The results suggest that ET-1 is the predominant mature isoform, which is localized mainly to adrenal vasculature, particularly the capsular plexus, and may contribute to blood flow regulation in the gland.

A competitive quantitative polymerase chain reaction assay for bovine transforming growth factor-B1 mRNA

We have developed a flexible reverse transcription (RT) coupled quantitative polymerase chain reaction (PCR) assay for transforming growth factor beta-1 (TGF-b) mRNA. A deletion mutant cDNA internal standard was prepared from the wild type cDNA and used to normalize intersample PCR efficiency differences. The assay is compatible with samples from cow and other species. Using RT-PCR, we determined that TGF-b mRNA in bovine pulmonary artery endothelial cells is increased by TGF-b 7.5-fold within 6h and remains 4-fold above baseline after 12h. In addition, unlike TGF-b bioactivity, mRNA levels in endothelial cells are not decreased upon exposure of the cells to either glutathione (reduced or oxidized), cysteine, or N-acetylcysteine for 24h.

A short CIC-2 mRNA transcript is produced by exon skipping

CIC-2 is a voltage- and volume-regulated chloride channel expressed in many tissues. We have shown that CIC-2 in rat lung airways is significantly down-regulated after birth [Murray,C.B. et al. (1995) Am. J. Respir. Cell Mol. Biol., 12, 597-604]. During PCR amplification from rat lung cDNA, a second transcript was identified which is 60 bp shorter than the full length sequence. The peptide translated from this 60 bp sequence contains many positively charged amino acid residues. Rat genomic DNA sequencing showed that the 60 bp sequence is an intact exon. A 71% pyrimidine content and an AAG 3'-end splice site in the intron immediately upstream from the 60 bp sequence were identified which may account for the alternative splicing of the following exon. Human genomic sequence analyses demonstrated similar intron-exon arrangement. A high CT content and an AAG 3' acceptor site were conserved in the intron corresponding to the rat upstream intron. The presence of the full length short form transcript was confirmed in rat kidney by RT-PCR, and the ratio of the long and the short form transcripts varied significantly according to the tissues examined, with the lowest long/short form ratio found in the lung among the tissues studied. Our data demonstrated that the alternatively spliced short form (CIC-2S) is transcribed in many rat tissues, the ratio of the long/short form transcripts is lower in the lung compared with the brain, and the genomic organization in this area is conserved in rat and human.

RT-PCR analysis of MMP-9 expression in human articular cartilage chondrocytes and synovial fluid cells

This report presents a method for analyzing matrix metalloproteinase-9 (92 kD gelatinase) MMP-9 mRNA expression using reverse transcription polymerase chain reaction (RT-PCR). With this method, chondrocytes isolated from small samples of osteoarthritic cartilage showed significantly elevated signal for MMP-9 mRNA compared to normal cartilage. In addition, cells of synovial fluid samples aspirated from osteoarthritic joints also exhibited MMP-9 expression using this technique. RT-PCR proved to be a sensitive method for assessing MMP-9 regulation in osteoarthritic and normal cartilage, and may provide a useful index of arthritic cartilage and synovial fluid cell metabolism when limited tissue is available.

Endothelin ETA and ETB mRNA and receptors expressed by smooth muscle in the human vasculature: majority of the ETA sub-type

1. We measured the ratio of ETA and ETB sub-types in the media (containing mainly smooth muscle) of human cardiac arteries (aorta, pulmonary and coronary), internal mammary arteries and saphenous veins. 2. In saturation experiments, [125I]-endothelin-1 ([125I]-ET-1) bound with high affinity to the media of each vessel (n = 3 individuals or homogenate preparations +/- s.e. mean): coronary artery, KD = 0.14 +/- 0.02 nM, Bmax = 71.0 +/- 21.0 fmol mg-1 protein; pulmonary artery, KD = 0.85 +/- 0.25 nM, Bmax = 15.2 +/- 10.3 fmol mg-1 protein; aorta, KD = 0.51 +/- 0.02 nM, Bmax = 9.4 +/- 4.4 fmol mg-1 protein; internal mammary artery. KD = 0.34 +/- 0.31 nM, Bmax = 2.0 +/- 0.5 fmol mg-1 protein and saphenous vein, KD = 0.28 +/- 0.05 nM, Bmax = 52.8 +/- 1.0 fmol mg-1 protein. In each vessel, over the concentration-range tested, Hill slopes were close to unity and a one site fit was preferred to a two site model. 3. In competition binding assays, the ETA selective ligand, BQ123 inhibited the binding of 0.1 nM [125I]-ET-1 to the media in a biphasic manner. In each case, a two site fit was preferred to a one or three site model: coronary artery, KDETA = 0.85 +/- 0.03 nM, KDETB = 7.58 +/- 2.27 microM, ratio = 89:11%; pulmonary artery, KDETA = 0.27 +/- 0.05 nM, KDETB = 24.60 +/- 5.34 microM, ratio = 92:8%; aorta, KDETA = 0.80 +/- 0.40 nM, KDETB = 2.67 +/- 2.60 microM ratio = 89:11%; saphenous vein, KDETA = 0.55 +/- 0.17 nM, KDETB = 14.4 +/- 0.26 microM, 85:15% (n = 3 individuals or homogenate preparations +/- s.e. mean). BQ123 showed up to 18000 fold selectivity for the ETA over the ETB sub-type. The ETA-selective ligand, [125I]-PD151242 labelled 85% of the receptors detected by a fixed concentration of [125I]-ET-1 in media of internal mammary artery, measured by quantitative autoradiography. In contrast, the density of ETB receptors detected with [125I]-BQ3020 was 7.0 +/- 1.5 amol mm-2, representing about 8% of [125I]-ET-1. 4. A single band corresponding to the expected position for mRNA encoding the ETA receptor (299 base pairs) was found in the media in each of the five vessels (n = 3 individuals) using reverse transcript as epolymerase chain reaction assays. A single band corresponding to the ETB sub-type (428 base pairs) was also always detected.5. 35S-labelled antisense probes to ETA and ETB hybridised to the media of epicardial coronary arteries as well as intramyocardial vessels, confirming the presence of mRNA encoding both sub-types in the vascular smooth muscle of the vessel wall.6 Although mRNA for both receptors was detected, competition binding using BQ123 demonstrated that the majority (at least 85%) of ET receptors present in smooth muscle are the ETA sub-type. These results provide further support for the hypothesis that the ETA sub-type is the receptor that must be blocked in humans to produce a beneficial vasodilatation in pathophysiological conditions where there is an increase in peptide concentration or receptor density.

[125I]-PD151242: a selective ligand for endothelin ETA receptors in human kidney which localizes to renal vasculature

1. The linear tetrapeptide radioligand, [125I]-PD151242 was used to characterize ETA receptors in human kidney which is an ETB-rich tissue. Saturation binding assays with [125I]-PD151242 revealed a single population of high affinity endothelin receptors: KD = 0.75 +/- 0.07 nM and Bmax = 48.4 +/- 1.6 fmol mg-1 protein (n = 3 individuals +/- s.e.mean). Hill slopes were close to unity and a one site fit was preferred to a two site model. 2. ETA-receptor-selective ligands competed for [125I]-PD151242 binding with sub-nanomolar affinity: BQ123 KD = 0.43 +/- 0.10 nM, Bmax = 46.6 +/- 7.9 fmol mg-1 protein; FR139317, KD = 0.37 +/- 0.06 nM, Bmax = 39.5 +/- 6.5 fmol mg-1 protein (n = 3 individuals +/- s.e.mean). In each case, monophasic inhibition curves were obtained and a one site fit was preferred to a two site model. The ETB-selective agonist, BQ3020 at the highest concentration tested (10 microM) inhibited binding by only 50%. The non-selective RO462005 competed for the binding of [125I]-PD151242: KD = 1.31 +/- 1.38 microM, Bmax = 33.0 +/- 9.7 fmol mg-1 protein. Endothelin-2 and sarafotoxin S6B inhibited [125I]-PD151242 binding to renal tissue whereas ET-3 and sarafotoxin S6C were less effective. Non-endothelin and non-sarafotoxin peptides did not compete. 3. No degradation of [125I]-PD151242 was detected following incubation of the ligand with renal tissue under the conditions of the binding assay. 4. Polymerase chain reaction products corresponding to the expected size for mRNA encoding ETA and ETB receptor sub-types were detected in cortex and medulla in each of the five individuals examined.5. Autoradiographical studies showed that ETA receptors visualised with ['25I]-PD151242 were mainly localized to blood vessels including interlobular and arcuate arteries, arterioles and adjacent arcuate veins. ETB receptors localized with ['251]-BQ3020 were concentrated in the medulla and the density of binding to vessels was low.6. These data suggest [251I]-PDl51242 is selective for ETA receptors in human kidney and this sub-type is mainly localized to the renal vasculature. The results provide further evidence that the human vasculature mainly expresses the ETA receptor.