Prophylaxis is the new standard of care in patients with haemophilia

Randomised controlled clinical trial evidence on prophylaxis as optimal care for patients with haemophilia was generated more than a decade ago. However, this knowledge has not translated into clinical practice in South Africa (SA) owing to many barriers to prophylaxis. These include the high treatment burden imposed by prophylaxis (frequent injections two to four times a week), the need for intravenous access to administer replacement clotting factor therapies, and the higher volume of clotting factor required compared with episodic treatment. The recently introduced non-factor therapies in haemophilia care have addressed many of these barriers. For example, emicizumab, which is currently the only globally approved non-factor therapy, can be administered subcutaneously less frequently (weekly, fortnightly or every 4 weeks) and has led to global adoption of prophylaxis as the standard of care in haemophilia by the bleeding disorders community. Haemophilia A is the most prevalent clotting factor deficiency in SA, with >2 000 people diagnosed to date. However, only a few of these patients are currently on prophylaxis. In this 'In Practice' article, we review the rationale for prophylaxis, outline its goals and benefits, and provide evidence-based guidance on which haemophilia patients should be prioritised for emicizumab prophylaxis. This consensus guidance facilitates the adoption of prophylaxis as a national policy and the new standard of care in haemophilia in SA.

Hypertension in the South African public healthcare system: a cost-of-illness and burden of disease study

OBJECTIVES

To quantify the health and economic burden of hypertension in the South African public healthcare system.

SETTING

All inpatient, outpatient and rehabilitative care received in the national public healthcare system.

PARTICIPANTS

Adults, aged ≥20 years, who receive care in the public healthcare system.

OUTCOMES

Worksheet-based models synthesised data from multiple sources to estimate the burden of disease, direct healthcare costs, and societal costs associated with hypertension. Results were disaggregated by sex.

RESULTS

Approximately 8.22 million (30.8%, 95% CI 29.5% to 32.1%) South African adults with no private health insurance have hypertension. Hypertension was estimated to cause 14 000 (95% CI 11 100 to 17 200) ischaemic heart disease events, 13 300 (95% CI 10 600 to 16 300) strokes and 6100 (95% CI 4970 to 7460) cases of chronic kidney disease annually. Rates of hypertension, hypertension-related stroke and hypertension-related chronic kidney disease were greater for women compared with men.The direct healthcare costs associated with hypertension were estimated to be ZAR 10.1 billion (95% CI 8.98 to 11.3 billion) or US$0.711 billion (95% CI 0.633 to 0.793 billion). Societal costs were estimated to be ZAR 29.4 billion (95% CI 26.0 to 33.2 billion) or US$2.08 billion (95% CI 1.83 to 2.34 billion). Direct healthcare costs were greater for women (ZAR 6.11 billion or US$0.431 billion) compared with men (ZAR 3.97 billion or US$0.280 billion). Conversely, societal costs were lower for women (ZAR 10.5 billion or US$0.743 billion) compared with men (ZAR 18.9 billion or US$1.33 billion).

CONCLUSION

Hypertension exerts a heavy health and economic burden on South Africa. Establishing cost-effective best practice guidelines for hypertension treatment requires further research. Such research will be essential if South Africa is to make progress in its efforts to implement universal healthcare.

High prevalence of non-dipping patterns among black Africans with uncontrolled hypertension: a secondary analysis of the CREOLE trial

Background

Dipping of blood pressure (BP) at night is a normal physiological phenomenon. However, a non-dipping pattern is associated with hypertension mediated organ damage, secondary forms of hypertension and poorer long-term outcome. Identifying a non-dipping pattern may be useful in assessing risk, aiding the decision to investigate for secondary causes, initiating treatment, assisting decisions on choice and timing of anti-hypertensive therapy, and intensifying salt restriction.

Objectives

To estimate the prevalence and factors associated with non-dipping pattern and determine the effect of three 6-months anti-hypertensive regimens on the dipping pattern among Black African hypertensive patients.

Methods

This was a secondary analysis of the CREOLE Study which was a randomized, single blind, three-group trial conducted in 10 sites in 6 Sub-Saharan African countries. The participants were 721 Black African patients, aged between 30 and 79 years, with uncontrolled hypertension and a baseline 24-hour ambulatory blood pressure monitoring (ABPM). Dipping was calculated from the average day and average night systolic blood pressure measures.

Results

The prevalence of non-dipping pattern was 78% (564 of 721). Factors that were independently associated with non-dipping were: serum sodium >140mmol/l (OR=1.72, 95% CI: 1.17–2.51, p-value 0.005), a higher office systolic BP (OR=1.03, 95% CI: 1.01–1.05, p-value 0.003) and a lower office diastolic BP (OR=0.97, 95% CI: 0.95–0.99, p-value 0.03). Treatment allocation did not change dipping status at 6 months (McNemar's χ2 0.71, p-value 0.40).

Conclusion

There was a high prevalence of non-dipping among Black Africans with uncontrolled hypertension. ABPM should be considered more routinely in Black Africans with uncontrolled hypertension, if resources permit, to help personalise therapy. Further research is needed to understand the mechanisms and causes of non-dipping pattern and if targeting night-time BP improves clinical outcomes.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Fogarty International Center and the National Institutes of Health of the United States of America Figure 1

Remote ischemic preconditioning attenuates EGR-1 expression following myocardial ischemia reperfusion injury through activation of the JAK-STAT pathway

BACKGROUND/OBJECTIVES

Remote ischemic preconditioning (RIPC) protects the myocardium from ischemia/reperfusion (I/R) injury however the molecular pathways involved in cardioprotection are yet to be fully delineated. Transcription factor Early growth response-1 (Egr-1) is a key upstream activator in a variety of cardiovascular diseases. In this study, we elucidated the role of RIPC in modulating the regulation of Egr-1.

METHODS

This study subjected rats to transient blockade of the left anterior descending (LAD) coronary artery with or without prior RIPC of the hind-limb muscle and thereafter excised the heart 24h following surgical intervention. In vitro, rat cardiac myoblast H9c2 cells were exposed to ischemic preconditioning by subjecting them to 3cycles of alternating nitrogen-flushed hypoxia and normoxia. These preconditioned media were added to recipient H9c2 cells which were then subjected to 30min of hypoxia followed by 30min of normoxia to simulate myocardial I/R injury. Thereafter, the effects of RIPC on cell viability, apoptosis and inflammatory markers were assessed.

RESULTS

We showed reduced infarct size and suppressed Egr-1 in the heart of rats when RIPC was administered to the hind leg. In vitro, we showed that RIPC improved cell viability, reduced apoptosis and attenuated Egr-1 in recipient cells.

CONCLUSIONS

Selective inhibition of intracellular signaling pathways confirmed that RIPC increased production of intracellular nitric oxide (NO) and reactive oxygen species (ROS) via activation of the JAK-STAT pathway which then inactivated I/R-induced ERK 1/2 signaling pathways, ultimately leading to the suppression of Egr-1.

Primary aldosteronism and aldosterone-associated hypertension

The field of primary aldosteronism (PA) and aldosterone-related hypertension has undergone rapid evolution. From a relatively rare curiosity PA has become a common problem particularly in selected hypertensive populations. Patients with PA and aldosterone-related hypertension appear to be at higher cardiovascular and renal risk than comparable patients with essential hypertension probably due to the pleiotropic effects of aldosterone. Aldosterone is also linked to metabolic syndrome and diabetes. The aldosterone-to-renin ratio (ARR) has allowed the widespread screening for PA, but the exact cut-off values may vary in different population groups. All patients with hypertension and hypokalaemia, and young patients with hypertension, hypertension with an incidental adrenal mass, and severe or resistant hypertension should be screened. The use of the ARR to screen all hypertensives for PA is controversial as the test lacks specificity and many patients with false-positive tests will undergo complex and expensive testing to confirm the diagnosis. The fludrocortisone suppression test, the saline infusion test or 24-hour aldosterone excretion may be used to confirm PA in patients with a positive ARR. Adrenal venous sampling is the most reliable test to detect the presence of an aldosterone-producing adenoma, but spiral CT scan or adrenocortical scintigraphy may be useful in centres without facilities for adrenal venous sampling. Spironolactone is emerging as an important antihypertensive agent in patients with resistant hypertension and aldosterone-related hypertension. The ARR may be a useful guide to drug selection in hypertensives patients, but further research is needed to make more definitive recommendations.

The impact of ACE genotype on serum ACE activity in a black South African male population

The strong association between the angiotensin I-converting enzyme (ACE) gene I/D polymorphism with serum ACE activity appears lacking in Nigerians and Kenyans, but has not previously been well assessed in others of African origin. This study addressed this issue in an ethnically well defined black South African population. A putative association for the A22982G ACE gene variant, a QTL likely to impact on serum ACE activity, was also sought. Subjects were 200 healthy male black South African volunteers from the Xhosa ethnic group. Venous blood was obtained from all subjects for DNA extraction. ACE I/D and A22982G genotypes were determined and serum ACE activity measured. Age and blood pressure were recorded. For the group as a whole (mean +/- SD age 38.5 +/- 9.8 years, SBP 119.6 +/- 14.1 mmHg, DBP 78.2 +/- 10.1 mmHg) serum ACE activity was 38.2 +/- 11.2 nmol ml(-1)min(-1). ACE I/D genotype was not significantly associated with serum ACE activity. In contrast, the A22982G variant was significantly associated with serum ACE activity, being 35.9 +/- 9.6, 38.1 +/- 10.6 and 42.4 +/- 15.3 nmol ml(-1)min(-1) for AA, AG and GG genotypes respectively; p = 0.03 by ANOVA and p = 0.01 by linear trend. In keeping with the findings in some other African populations, the ACE I/D polymorphism is not strongly associated with serum ACE activity in Xhosa South Africans. As such, it cannot be used as a marker of ACE activity in these subjects. In this regard the use of the A22982G gene variant may be more appropriate.

The prevalence of microalbuminuria and ECG left ventricular hypertrophy in hypertensive patients in private practices in South Africa

INTRODUCTION

In South Africa a cluster of cardiovascular diseases accounts for 17% of all deaths. It is also predicted that South Africa will face an epidemic of chronic kidney disease due to obesity, type 2 diabetes and hypertension. It is important to estimate the burden of underlying cardiovascular and renal disease in South Africa.

OBJECTIVES

The primary objective of the study was to establish the prevalence of left ventricular hypertrophy by ECG criteria, and micro- and macroalbuminuria in mild, moderate and severe hypertensive groups. The secondary objective was to establish the prevalence of left ventricular hypertrophy and micro- and macroalbuminuria in hypertensive patients with underlying type 2 diabetes.

METHODS

Patients > or = 35 years with essential hypertension with or without type 2 diabetes were recruited from 100 general practices throughout South Africa. BP, weight, height, waist circumference and urinary albumin/creatinine ratio were measured, and an ECG was performed. The Sokolow-Lyon and Cornell criteria were used for estimation of left ventricular hypertrophy. An overall prevalence rate was determined using weights from the severity category distribution inside the study population.

RESULTS

One thousand and ninety-one patients were available for analysis. There were 530 (48.5%) males and 561 (51.5%) females, 691 (63.3%) whites, 162 (14.8%) blacks, 150 (13.7%) Asians and 88 (8.1%) Coloureds. Of the patients, 10.9% had newly diagnosed hypertension, 20% had type 2 diabetes, and 38.1% mild, 32.1% moderate and 30.6% severe hypertension. The prevalence of left ventricular hypertrophy in the sample weighted to the hypertensive population over the age of 35 years with access to medical aids was 18.9%. Relative to white ethnicity, black ethnicity (OR 2, p = 0.03), and relative to mild hypertension, moderate (OR 2.2, p = 0.05) and severe hypertension (OR 4.9, p < 0.0001) were independent predictors of left ventricular hypertrophy. The overall prevalence of micro- and macroalbuminuria in the weighted sample was 21.3 and 4.1%, respectively. In the diabetics the prevalence of microalbuminuria was 32.3% and macroalbuminuria 10.4%, respectively. The independent predictors of microalbuminuria or worse were severe hypertension (OR 2.9, p < 0.0001), type 2 diabetes (OR 2.5, p < 0.002), and Asian ethnic group (OR 2, p = 0.02).

CONCLUSIONS

The study, based on a convenience sample of hypertensives from private practices in South Africa showed that the prevalence of left ventricular hypertrophy and microalbuminuria or worse was 18.9 and 25.4%, respectively.

Potential renoprotective effects of the angiotensin receptor blocker eprosartan: a review of preliminary renal studies

The importance of the renin-angiotensin-aldosterone system (RAAS) in the pathogenesis of hypertension and in renal disease, particularly in patients with diabetes, has become increasingly evident. Pharmacological blockade of the RAAS offers potential for the therapeutic management of these pathologies. Angiotensin converting enzyme (ACE) inhibitors and angiotensin II (AII) receptor blockers have been shown to exhibit effectiveness in the treatment of hypertension. AII receptor blockers have a renal protective effect owing to their ability to reduce systemic blood and intraglomerular pressures. Eprosartan is a chemically distinct AII blocker, which displays a dual mode of action whereby it blocks both pre- and postsynaptic AT(1) receptors, potentially benefiting patients with hypertension and renal disease. In addition, evidence suggests that eprosartan is well tolerated by both healthy subjects and patients with varying degree of renal impairment, such that the dose does not need to be modified in patients with mild to moderate renal impairment. Results from preliminary studies demonstrates that eprosartan doses will below those required for blood pressure control have a pronounced effect on the kidney and do not compromise renal autoregulatory mechanisms. Therefore, eprosartan may have a benefit in the prevention or delay of renal damage in hypertensive patients with renal impairment, although this remains to be determined in a clinical setting.

Direct MALDI-TOF MS analysis of oligonucleotides on solid support through a photolabile linker

MALDI-TOF mass spectrometry was used to analyze oligonucleotides still anchored to long-chain alkylamine controlled-pore glass (LCAA-CPG) through a photolabile linker. This technique is useful to follow supported chemical reactions in real time and monitor by-products formation.

A two B-Z junction containing DNA resolves into an all right-handed double-helix

Natural and artificial oligonucleotides are capable of assuming many different conformations and functions. Here we present results of an NMR restrained molecular modelling study on the conformational preferences of the modified decanucleotide d((m)C1G2(m)C3G4C5(L)G6(L)(m)C7G8(m)C9G10) .d((m)C11G12(m)C13G14C15(L)G (L)16(m)C17-G18(m)C19G20 ) which contains L deoxynucleotides in its centre. This chimeric DNA was expected to form a right-left-right-handed B-type double-helix (BB*B) at low salt concentration. Actually, it matured into a fully right-handed double helix with its central C(L)pG(L) core forming a right-handed Z-DNA helix embedded in a B-DNA matrix (BZ*B). The interplay between base-base and base-sugar stackings within the core and its immediately adjacent residues was found to be critical in ensuring the stabilisation of the right-handed helix. The structure could serve as a model for the design of antisense oligonucleotides resistant to nucleases and capable of hybridising to natural DNAs and RNAs.

Prooligonucleotides exhibit less serum-protein binding than phosphodiester and phosphorothioate oligonucleotides

The protein-binding properties of dodecathymidine derivatives (prooligos) bearing either methyl- or tert-butyl-S-acylthioethyl (Me- or tBuSATE) protecting groups were evaluated. The dissociation constants (Kd) were estimated for complexes of prooligos with serum blood proteins and lactoferrin using prooligos to compete the binding of the radiolabeled, alkylating probe oligonucleotide CIRp(T)12 with the proteins. tBuSATE and MeSATE prooligos have decreased affinity of binding with serum proteins and lactoferrin compared with their parent oligos. These data suggest that prooligos should cause less side effects which combined with their stability to nucleases and enhanced permeability into cells make them potentially useful for design of therapeutics.

Stereochemical control of DNA biosynthesis

Stereochemical control of DNA biosynthesis was studied using several DNA-synthesizing complexes containing, in each case, a single substitution of a 2'-deoxy-D-nucleotide residue by an enantiomeric L-nucleotide residue in a DNA chain (either in the primer or in the template) as well as 2'-deoxy-L-ribonucleoside 5'-triphosphates (L-dNTPs) as substrates. Three template-dependent DNA polymerases were tested, Escherichia coli DNA polymerase I Klenow fragment, Thermus aquaticus DNA polymerase and avian myeloblastosis virus reverse transcriptase, as well as template-independent calf-thymus terminal deoxynucleotidyl transferase. Very stringent control of stereoselectivity was demonstrated for template-dependent DNA polymerases, whereas terminal deoxynucleotidyl transferase was less selective. DNA polymerase I and reverse transcriptase catalyzed formation of dinucleoside 5',5'-tetraphosphates when L-dTTP was used as substrate. Comparison between models of template-primer complexes, modified or not by a single L-nucleotide residue, revealed striking differences in their geometry.

Sediment provenance and flux in the Tees Estuary: the record from the Late Devensian to the present

The influences of sea-level, climate, human activity and coastal morphology on post-glacial sediment flux and deposition in the Tees Estuary were considered in a multidisciplinary investigation of the Late Pleistocene and Holocene sedimentary record. The following tripartite division was identified using a combination of lithostratigraphic and geochemical data: a Late Glacial laminated clay providing evidence of a former proglacial lake and a proxy record of climate change; an early-mid-Holocene intercalated sequence of tidal silts and clays and peats; and a late Holocene succession characterized by increasing evidence of human activity and metal contamination. Sea-level change has been identified as the main control on sedimentationviadecelerating sea-level rise and changing tidal dynamics betweenc.8 and 3 kabp. Climate controlled the sequence of rhythmite thickness in the Late Glacial clays, whilst increased wetness afterc.3 kabpmay have encouraged terrestrial sediment influx. Enhanced sediment supply to the coastal zone can also be attributed to increasing human activity in the catchment from the Bronze Age onward, first as a consequence of clearance, and subsequently as a result of mining and industrial expansion. Fine-grained sediment flux has almost exclusively been from the Tees catchment to the coast, extending offshore during rebound-induced collapse and erosion of the Late Glacial lake basin. The only notable onshore sediment flux has been the deposition of marine sands in the outer estuary betweenc.6.5 and 3.5 kabp.

Chiral and steric effects in the efficient binding of alpha-anomeric deoxyoligonucleoside N-alkylphosphoramidates to ssDNA and RNA

We report hybridization properties of new phosphate-modified alpha-oligonucleoside analogs with non-ionic or cationic internucleotide linkages such as methoxy-ethylphosphoramidate (PNHME), phosphoromorpholi-date (PMOR) and dimethylaminopropylphosphor-amidate (PNHDMAP). First we evaluated the chirality effect of the phosphorus atom on the affinity of alpha- or beta-dodecanucleoside phosphodiesters containing one chirally enriched N -alkylphosphoramidate linkage located in the middle of the sequence d(TCTT-AA*CCCACA). As for P-substituted beta-oligonucleo-tides, a difference in binding behavior between the two diastereoisomers (difference in Delta T (m)) exists in the hybridization properties of alpha-analogs when DNA was the target but this effect was not detrimental to duplex stability. This effect was considerably reduced when RNA was the target. Secondly we studied the effect of steric hindrance around phosphorus on the affinity of fully modified beta- and alpha-oligonucleoside N -alkylphosphoramidates for their DNA and RNA targets. This effect was very weak with alpha-analogs whereas it was more pronounced with beta-oligos. PNHME-modified alpha-oligonucleosides formed more stable duplexes with DNA (Delta T (m)+9.6 degrees C) and RNA (Delta T (m)+1.4 degrees C) targets than the 'parent' phosphodiester. Finally, base pairing specificity of these alpha-oligonucleo-side N -alkylphosphoramidates for their targets was found to be as high as for natural oligonucleoside phosphodiesters.

Lipophilic pro-oligonucleotides are rapidly and efficiently internalized in HeLa cells

Model t-Bu-SATE pro-dodecathymidines labeled with fluorescein and exhibiting various lipophilicities were evaluated for their uptake by cells in culture. Pro-oligonucleotides with appropriate lipophilicity were found to permeate across the HeLa cell membrane much more extensively than the control phosphorothioate oligo or than the hydrophilic pro-oligos. Fluorescence patterns of internalization were consistent with a diffusion mechanism resulting in the appearance of a uniform cytoplasmic distribution and nuclear accumulation, as confirmed by confocal microscopy.

First synthesis of alternating SATE-phosphotriester/phosphodiester prooligonucleotides on solid support

Prooligonucleotides with alternating S-Acyl-ThioEthyl (SATE) phosphotriester and phosphodiester linkages or a gap were synthesized by elimination of cyanoethyl group with non-nucleophilic base DBU. Their half-lives in the presence of Pig Liver Esterases (PLE) and in total cell extract were determined.

Anomeric inversion (from beta to alpha) in methylphosphonate oligonucleosides enhances their affinity for DNA and RNA

Here we report that the poor binding of methylphosphonate oligodeoxynucleosides (MP-ODNs) to their nucleic acid targets can be improved by additional inversion of the anomeric configuration (from beta to alpha) in the sugar moieties to give a new class of analogs, MP alpha-oligonucleosides. MP alpha-dT12and MP 5' alpha-d(TCTTAACCCACA) 3' were synthesized and their ability to form hybrids with complementary single stranded (ss)DNA and ssRNA, as well as with double stranded (ds)DNA, was evaluated. The thermal stability of hybrids formed with MP alpha-analogs was compared with the affinity of phosphodiester (PO) and phosphorothioate (PS) beta- and alpha-oligomers for their targets. Non-ionic MP alpha-oligonucleosides bound to their complementary DNA and RNA strands more tightly than their homologues with natural beta-anomeric configuration did. With DNA target, MP alpha-oligomers formed duplexes more stable than the corresponding natural PO beta-oligomer did. MP alpha-heteropolymer hybridized to RNA target better than PS beta-oligonucleotide did but the hybrid was less stable (DeltaTm-0.5 degrees C per mod.) than the hybrid formed with the natural PO beta-oligomer. Only MP alpha-dT12 bound to dsDNA target at low salt concentration (0.1 M NaCl).

Selective mRNA degradation by antisense oligonucleotide-2,5A chimeras: involvement of RNase H and RNase L

Antisense oligonucleotides (ON) allow the specific control of gene expression and phosphorothioate derivatives are currently being evaluated for possible clinical applications. Numerous second generation ON analogues with improved pharmacological properties have been described. Most of them, however, do not recruit RNase H, which is known to increase ON potency by eliciting the specific degradation of the target RNA. Silverman, Torrence and colleagues have conjugated 2,5A to natural antisense ON and demonstrated the preferential cleavage of a target RNA in cell-free and intact cell experiments. We have established for the first time that RNase H-incompetent ON, viz. alpha-anomeric ON analogues, can be converted into sequence-specific nucleases upon conjugation to 2,5A. The use of alpha-ON- and beta-ON-2,5A chimeras has allowed us to delineate the part played by RNase H and RNase L in target RNA degradation and translation arrest. Finally, the present studies have revealed limitations which are encountered in the choice of a suitable target for such ON-2,5A chimeras.

The pro-oligonucleotide approach: solid phase synthesis and preliminary evaluation of model pro-dodecathymidylates

A modified phosphoramidite method has been designed for the solid-phase synthesis of two dodecathymidine phosphotriesters and two dodecathymidine thionophosphotriesters. In these analogs, each internucleoside link bears an S -acyl-2-thioethyl (Me-SATE or tBu-SATE) group removable upon esterase activation. Efficient synthesis of these lipophilic analogs was achieved thanks to the use of a photolabile linker anchored to the solid support in combination with thymidine-3'- O -phosphoramidites having a SATE group in place of the regular 2-cyanoethyl one. Both dodecathymidine phosphotriester and thionophosphotriester having S -acetyl-2-thioethyl groups were found to be stable in the presence of snake venom and calf spleen phosphodiesterases whereas, upon incubation in CEM cell extracts, they were selectively hydrolyzed to the anionic parent dodecathymidylate and dodecathymidine phosphorothioate, respectively. In addition, Me-SATE-protected dodecathymidine thionophosphotriester was stable in mouse and human sera as well as in human gastric juice. These results depict the potential of SATE-protected oligonucleotides as prodrugs of antisense oligonucleotides.

Esterase-triggered fluorescence of fluorogenic oligonucleotides

In the prooligonucleotide approach, a step of activation by cellular esterases is necessary for the removal of internucleoside phosphate masking groups and subsequent intracellular delivery of active antisense oligonucleotides. The efficacy of this approach implies that prooligonucleotides, once they are taken up by cells, are demasked by esterases during their course to their nucleic acid targets. In this regard, a method for labeling oligomers with esterase-activable fluorogenic tag was designed. The two phenolic functions of carboxyfluorescein were protected by pivaloyl groups, yielding a nonfluorescent lactone which was further activated as a N-hydroxysuccinimide ester. Two nuclease-resistant phosphorothioate 18-mer and methylphosphonate 19-mer oligodeoxynucleosides were attached to this biprotected fluorescein derivative via an amino linker at the 5'-end of the oligomers. The two conjugates were assayed for their carboxyesterase substrate ability in different biological media. In the presence of purified esterases or when incubated in serum or cell extracts, both oligonucleotide conjugates became fluorescent. In addition, the phosphorothioate oligoconjugate was microinjected into the cytoplasm of human fibroblasts, and a fast cytoplasmic release of fluorescence was observed with a rapid translocation of the fluorescent oligomer into the nucleus.

Comparative stability of eight different triple helices formed by differently modified DNA or RNA pyrimidine strands and a DNA hairpin

The comparative stability of eight different triplexes constituted with 16-mer pyrimidine-modified oligodeoxynucleotides (wild-type ODN, PS-ODN, alpha-ODN, or alpha-PS-ODN) or oligoribonucleotides (wild-type ORN, alpha-ORN, 4'-thio-ORN, or 2'-O-MeORN) and a DNA hairpin, termed H36, was studied in five different buffers by UV melting curve analysis. The composition of buffers varied in pH (5.5 and 6.5), in salt concentration (100 mM and 1 M Na+), and in the presence or absence of divalent cation (0 or 3 mM Mg2+) or spermine (0 or 1 mM). At pH 5.5, the eight triplexes are formed with Tm values ranging from 24.7 degrees C to 50.9 degrees C (delta G298K between -8.1 and -16.8 kcal/mol). At pH 6.5, the triplexes are less stable, and thus 4'-thio-ORN and PS-ODN showed broad transitions that did not allow us to conclude triplex formation. An increase of salt concentration or the presence of spermine stabilizes the triplexes, whereas Mg2+ has a destabilizing effect (excepted for alpha-ORN). In general ORN:H36 and 2'-O-MeORN:H36 triplexes were the most stable. Finally, introduction of alpha-anomeric nucleosides led to an alpha-ORN analog that showed low binding with H36 and to alpha-ODN and alpha-PS-ODN analogs. Triplexes formed with alpha-ODN were slightly less stable than those formed with unmodified ODN. Surprisingly, introduction of phosphorothioate in an alpha analog led only to a low destabilization.

Stereoisomers of deoxynucleoside 5'-triphosphates as substrates for template-dependent and -independent DNA polymerases

All four possible stereoisomers of dNTP with regard to deoxyribofuranose C-1' and C-4' carbon atoms were studied as substrates for several template-dependent DNA polymerases and template-independent terminal deoxynucleotidyl transferase. It was shown that DNA polymerases alpha, beta, and epsilon from human placenta and reverse transcriptases of human immunodeficiency virus and avian myeloblastosis virus incorporate into the DNA chain only natural beta-D-dNTPs, whereas calf thymus terminal deoxynucleotidyl transferase incorporates two nucleotide residues of alpha-D-dNTP and extends the resulting oligonucleotide in the presence of beta-D-dNTPs. The latter enzyme also extended alpha-anomeric D-oligodeoxynucleotide primers in the presence of beta-D-dNTPs. None of the studied enzymes utilized L-dNTPs. These data indicate that template-dependent DNA polymerases are highly stereospecific with regard to dNTPs, whereas template-independent terminal deoxynucleotidyl transferase shows less stereodifferentiation. It is likely that the active center of the latter enzyme forms no specific contacts with the nucleic bases of both nucleotide substrate and oligonucleotide primer.

In vitro inhibition of hepatitis C virus gene expression by chemically modified antisense oligodeoxynucleotides

We have explored different domains within the hepatitis C virus (HCV) 5' noncoding region as potential targets for inhibition of HCV translation by antisense oligodeoxynucleotides (ODNs). Inhibition assays were performed with two different cell-free systems, rabbit reticulocyte lysate and wheat germ extract, and three types of chemical structures for the ODNs were evaluated: natural phosphodiesters (beta-PO), alpha-anomer phosphodiesters (alpha-PO), and phosphorothioates (PS). A total of six original ODNs, displaying sequence-specific inhibition ranging from 62 to 96%, that mapped in the pyrimidine-rich tract (nucleotides [nt] 104 to 127) and in the initiator AUG codon (nt 338 to 357) were identified. Two ODNs, which were targeted at the initiatory AUG (nt 341 to 367 and 351 to 377) and which had been previously described as active against genotype 1b and 2a sequences, were shown to exhibit inhibition of expression (> 95%) of a type 1a sequence. Control experiments with the irrelevant chloramphenicol acetyltransferase sequence as a marker and randomized ODNs demonstrated that levels of inhibition associated with the use of PS compounds (of as much as 94%) were mainly due to nonspecific effects. Both alpha- and beta-PO ODNs were found equally active, and no difference could be seen in the activity of beta-PO when it was tested in either rabbit reticulocyte lysate or wheat germ extract, suggesting that RNase H-independent mechanisms may be involved in the inhibitions observed. However, specific RNA cleavage products generated from beta-PO inhibition experiments could be identified, indicating that, with these compounds, control of translation also involves RNase H-dependent mechanisms. This study further delimits the existence of favorable target sequences for the action of ODNs within the HCV 5' noncoding region and indicates the possibility of using nuclease-resistant alpha-PO compounds in cellular studies.

The effect of recombinant human erythropoietin on haematopoiesis in patients undergoing haemodialysis

OBJECTIVE

To define the effect of intravenous recombinant human erythropoietin (rHuEPO) in patients with anaemia caused by chronic renal failure. Data collection included bone marrow response, ferrokinetics, red cell survival as well as the influence on red cell mass and plasma volume.

DESIGN

A convenience sample of stable individuals on haemodialysis, with haemoglobin (Hb) levels of less than 80 g/l, was surveyed over a 12-week period while they were receiving the hormone. Blood counts and iron studies were monitored serially, while 51Cr-labelled red cells and 59Fe (III) citrate were used in the radionuclide investigations carried out before and after the course of replacement therapy was completed (pre and post injection). Bone marrow aspiration and trephine biopsy were performed at each of these times.

RESULTS

The actual mean trial period was 14 weeks. Eight patients were enrolled but 1 was withdrawn after developing tuberculosis at the start of the study. Haemoglobin levels rose from 59 g/l (SD 8.8) to 96 g/l (SD 13.9) (P < 0.0001); mean red cell mass rose from 675 ml to 954 ml (P < 0.01). Concurrently, the serial studies in 6 patients showed prominent erythroid hyperplasia. Plasma iron turnover increased insignificantly from 42.5 to 118.9 mumol/l/day; erythron turnover increased from 42.5 to 87.3 mumol/l/day (P < 0.01). There was a marked shortening of the marrow transit time from 4.4 to 3.3 days (P < 0.03). Efficacy of erythropoiesis decreased from 1.17 to 0.65 (P < 0.05). Red cell survival was not altered.

CONCLUSIONS

The patient with end-stage renal failure remains fully responsive to erythropoietin therapy. This is reflected in improved ferrokinetics, red cell hyperplasia in the marrow and rise in haemoglobin level without alteration in mean erythrocyte lifespan. Simple hormonal replacement is therefore a rational approach to management.

Oligodeoxynucleoside phosphoramidates (P-NH2): synthesis and thermal stability of duplexes with DNA and RNA targets

Syntheses of non ionic oligodeoxynucleoside phosphoramidates (P-NH2) and mixed phosphoramidate- phosphodiester oligomers were accomplished on automated solid supported DNA synthesizer using both H-phosphonate and phosphoramidite chemistries, in combination with t-butylphenoxyacetyl for N-protection of nucleoside bases, an oxalyl anchored solid support and a final treatment with methanolic ammonia. Thermal stabilities of the hybrids formed between these new analogues and their DNA and RNA complementary strands were determined and compared with those of the corresponding unmodified oligonucleotides, as well as of the phosphorothioate and methylphosphonate derivatives. Dodecathymidines containing P-NH2 links form less stable duplexes with DNA targets, d(C2A12C2) (deltaTm/modification -1.4 degrees C) and poly dA (deltaTm/modification -1.1 degrees C) than the corresponding phosphodiester and methylphosphonate analogues, but the hybrids are slightly more stable than the one obtained with phosphorothioate derivative. The destabilization is more pronounced with poly rA as the target (deltaTm/modification -3 degrees C) and could be compared with that found with the dodecathymidine methylphosphonate. The modification is less destabilizing in an heteropolymer-RNA duplex (deltaTm/modification -2 degrees C). As expected, the P-NH2 modifications are highly resistant towards the action of various nucleases. It is also demonstrated that an all P-NH2 oligothymidine does not elicit Escherichia coli RNase H hydrolysis of the poly rA target but that the modification may be exploited in chimeric oligonucleotides combining P-NH2 sections with a central phosphodiester section.