The role of shared receptor motifs and common Stat proteins in the generation of cytokine pleiotropy and redundancy by IL-2, IL-4, IL-7, IL-13, and IL-15

To understand the molecular bases for cytokine redundancy and pleiotropy, we have compared the Stat proteins activated in peripheral blood lymphocytes (PBLs) by cytokines with shared and distinct actions. Interleukin-2 (IL-2) rapidly activated Stat5 in fresh PBL, and Stat3 and Stat5 in preactivated PBL. IL-7 and IL-15 induced the same complexes as IL-2, a feature explained by the existence of similar tyrosine-phosphorylated motifs in the cytoplasmic domains of IL-2R beta and IL-7R that can serve as docking sites for Stat proteins. IL-13 Induced the same complexes as IL-4, a finding explained by our studies implicating IL-4R as a shared component of the receptors. These studies demonstrate that a single cytokine can activate different combinations of Stat proteins under different physiological conditions, and also indicate two mechanisms by which distinct cytokines can activate the same Stat protein.

Transcriptional activators direct histone acetyltransferase complexes to nucleosomes

Transcriptional co-activators were originally identified as proteins that act as intermediaries between upstream activators and the basal transcription machinery. The discovery that co-activators such as Tetrahymena and yeast Gcn5, as well as human p300/CBP, pCAF, Src-1, ACTR and TAFII250, can acetylate histones suggests that activators may be involved in targeting acetylation activity to promoters. Several histone deacetylases have been linked to transcriptional co-repressor proteins, suggesting that the action of both acetylases and deacetylases is important in the regulation of many genes. Here we demonstrate the binding of two native yeast histone acetyltransferase (HAT) complexes to the herpesvirus VP16 activation domain and the yeast transcriptional activator Gcn4, and show that it is their interaction with the VP16 activation domain that targets Gal4-VP16-bound nucleosomes for acetylation. We find that Gal4-VP16-driven transcription from chromatin templates is stimulated by both HAT complexes in an acetyl CoA-dependent reaction. Our results demonstrate the targeting of native HAT complexes by a transcription-activation domain to nucleosomes in order to activate transcription.

Functional analysis of a growth factor-responsive transcription factor complex

Serum response factor (SRF) forms a ternary complex at the c-fos serum response element (SRE) with an accessory factor, Elk-1. We constructed altered-binding specificity derivatives of SRF and Elk-1 that form a ternary complex at a mutated, inactive SRE; like Elk-1, the Elk-1 variant only binds its target as part of a ternary complex with SRF. Simultaneous expression of these SRF and Elk-1 derivatives restores serum-regulated activity to the mutated SRE in transfected cells. Efficient transcriptional activation is dependent on the regulated phosphorylation of Elk-1 C-terminal MAP kinase sites and requires the C-terminal sequences of SRF as well as SRF sequences that mediate ternary complex formation. These experiments provide direct evidence that SRF and Elk-1 functionally cooperate in the ternary complex at the SRE to regulate transcription.

Expanded lysine acetylation specificity of Gcn5 in native complexes

The coactivator/adaptor protein Gcn5 is a conserved histone acetyltransferase, which functions as the catalytic subunit in multiple yeast transcriptional regulatory complexes. The ability of Gcn5 to acetylate nucleosomal histones is significantly reduced relative to its activity on free histones, where it predominantly modifies histone H3 at lysine 14. However, the association of Gcn5 in multisubunit complexes potentiates its nucleosomal histone acetyltransferase activity. Here, we show that the association of Gcn5 with other proteins in two native yeast complexes, Ada and SAGA (Spt-Ada-Gcn5-acetyltransferase), directly confers upon Gcn5 the ability to acetylate an expanded set of lysines on H3. Furthermore Ada and SAGA have overlapping, yet distinct, patterns of acetylation, suggesting that the association of specific subunits determines site specificity.

Lipid peroxidative damage on pyrethroid exposure and alterations in antioxidant status in rat erythrocytes: a possible involvement of reactive oxygen species

Pyrethroid pesticides are used preferably over organochlorines and organophosphates due to their high effectiveness, low toxicity to non-target organisms and easy biodegradibility. However, it is possible that during the pyrethroid metabolism, there is generation of reactive oxygen species (ROS) and pyrethroids may produce oxidative stress in intoxicated rats. The present study was therefore, undertaken to determine pyrethroid-induced lipid peroxidation (LPO) and to show whether pyrethroid intoxication alters the antioxidant system in erythrocytes. A single dose of cypermethrin and/or fenvalerate (0.001% LD50) was administered orally to rats and the animals were sacrificed at 0, 1, 3, 7 and 14 days of treatment. The results showed that lipid peroxidation (LPO) in erythrocytes increased within 3 days of pyrethroid treatment. The increased oxidative stress resulted in an increase in the activity of antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). The increase in reduced glutathione (GSH) content in erythrocytes may probably be an initial adaptive response to increased oxidative stress in pyrethroid intoxicated rats. Erythrocytes and serum acetylcholinesterase (AChE) activity was measured in pyrethroid-induced oxidative stress as it may mimic inhibition in target tissues such as muscle and brain. The inhibition in erythrocytes and serum AChE activity was partially relieved over a period of time indicating recovery from pyrethroid intoxication. The increase in erythrocyte LPO correlated with the inhibition in erythrocyte AChE activity and so erythrocyte AChE can be a marker enzyme in pyrethroid toxicity. The results show oxidative stress and alteration in antioxidant enzymes in erythrocytes of pyrethroid intoxicated rats.

Functional association of Nmi with Stat5 and Stat1 in IL-2- and IFNgamma-mediated signaling

Using the coiled-coil region of Stat5b as the bait in a yeast two-hybrid screen, we identified the association of Nmi, a protein of unknown function previously reported as an N-Myc interactor. We further show that Nmi interacts with all STATs except Stat2. We evaluated two cytokine systems, IL-2 and IFNgamma, and demonstrate that Nmi augments STAT-mediated transcription in response to these cytokines. Interestingly, Nmi lacks an intrinsic transcriptional activation domain; instead, Nmi enhances the association of CBP/p300 coactivator proteins with Stat1 and Stat5, and together with CBP/p300 can augment IL-2- and IFNgamma-dependent transcription. Therefore, our data not only reveal that Nmi can potentiate STAT-dependent transcription, but also suggest that it can augment coactivator protein recruitment to at least some members of a group of sequence-specific transcription factors.

Protective effect of vitamin E in dimethoate and malathion induced oxidative stress in rat erythrocytes

Organophosphate (OP) pesticides such as dimethoate and malathion intoxication has been shown to produce oxidative stress due to the generation of free radicals and alter the antioxidant defense system in erythrocytes. It is possible that vitamin E being present at the cell membrane site may prevent OP-induced oxidative damage. In the present study, rats were pretreated orally with vitamin E (250 mg/kg body wt, twice a week for 6 weeks) prior to oral administration of a single low dose of dimethoate and/or malathion (0.01% LD(50)). The result showed that treatment with OP increased lipid peroxidation (LPO) in erythrocytes, however, vitamin E pretreated rats administered OP's showed decreased LPO in erythrocytes. The increase in the activities of superoxide dismutase (SOD) and catalase (CAT) and total-SH content in erythrocytes from dimethoate and/or malathion treated rats as compared to control appears to be a response towards increased oxidative stress. Vitamin E pretreated animals administered OP's showed a lowering in these parameters as compared to OP treated rats which indicates that vitamin E provide protection against OP-induced oxidative stress. The glutathione-S-transferase (GST) activity in erythrocytes was inhibited in OP intoxicated rats which partially recovered in vitamin E pretreated animals administered OP's. Inhibition in erythrocyte and serum acetylcholinesterase (AChE) activity was not relieved in vitamin E pretreated rats administered OP's probably due to the competitive nature of enzyme inhibition by OP's. The results show that vitamin E may amelierate OP-induced oxidative stress by decreasing LPO and altering antioxidant defense system in erthrocytes.

A frameshift mutation in prominin (mouse)-like 1 causes human retinal degeneration

The disks of vertebrate photoreceptors are produced by outgrowths of the plasma membrane. Hence genes that encode retinal proteins targeted to plasma membrane protrusions represent candidates for inherited retinal degenerations. One such candidate is the gene encoding human prominin (mouse)-like 1 (PROML1, previously known as AC133 antigen) which belongs to the prominin family of 5-transmembrane domain proteins. Murine prominin (prom) shows a strong preference for plasma membrane protrusions in a variety of epithelial cells whereas PROML1 is expressed in retinoblastoma cell lines and adult retina. In the present study, molecular genetic analyses of a pedigree segregating for autosomal recessive retinal degeneration indicated that the affected individuals were homozygous for a nucleotide 1878 deletion in PROML1. This alteration is predicted to result in a frameshift at codon 614 with premature termination of translation. Expression of a similar prom deletion mutant in CHO cells indicated that the truncated protein does not reach the cell surface. Immunocytochemistry revealed that prom is concentrated in the plasma membrane evaginations at the base of the outer segments of rod photoreceptors. These findings suggest that loss of prominin causes retinal degeneration, possibly because of impaired generation of the evaginations and/or impaired conversion of the evaginations to disks.

Regulation of cell-type-specific interleukin-2 receptor alpha-chain gene expression: potential role of physical interactions between Elf-1, HMG-I(Y), and NF-kappa B family proteins

The interleukin 2 receptor alpha-chain (IL-2R alpha) gene is rapidly and potently induced in T cells in response to mitogenic stimuli. Previously, an inducible enhancer between nucleotides -299 and -228 that contains NF-kappa B and CArG motifs was identified. We now report the characterization of a second essential positive regulatory element located between nucleotides -137 and -64 that binds Elf-1 and HMG-I(Y). This element had maximal activity in lymphoid cells, paralleling the cell type specificity of Elf-1 expression. Transcription from the IL-2R alpha promoter was inhibited when either the Elf-1 or the HMG-I(Y) binding site was mutated. Coexpression of both proteins activated transcription of the -137 to -64 element in COS-7 cells. Elf-1 physically associated with HMG-I and with NF-kappa B p50 and c-Rel in vitro, suggesting that protein-protein interactions might functionally coordinate the actions of the upstream and downstream positive regulatory elements. This is the first report of a physical interaction between an Ets family member and NF-kappa B family proteins. These findings provide significant new insights into the protein-protein and protein-DNA interactions that regulate cell-type-specific and inducible IL-2R alpha gene expression and also have implications for other genes regulated by Elf-1 and NF-kappa B family proteins.

Histone H3 specific acetyltransferases are essential for cell cycle progression

Longstanding observations suggest that acetylation and/or amino-terminal tail structure of histones H3 and H4 are critical for eukaryotic cells. For Saccharomyces cerevisiae, loss of a single H4-specific histone acetyltransferase (HAT), Esa1p, results in cell cycle defects and death. In contrast, although several yeast HAT complexes preferentially acetylate histone H3, the catalytic subunits of these complexes are not essential for viability. To resolve the apparent paradox between the significance of H3 versus H4 acetylation, we tested the hypothesis that H3 modification is essential, but is accomplished through combined activities of two enzymes. We observed that Sas3p and Gcn5p HAT complexes have overlapping patterns of acetylation. Simultaneous disruption of SAS3, the homolog of the MOZ leukemia gene, and GCN5, the hGCN5/PCAF homolog, is synthetically lethal due to loss of acetyltransferase activity. This key combination of activities is specific for these two HATs because neither is synthetically lethal with mutations of other MYST family or H3-specific acetyltransferases. Further, the combined loss of GCN5 and SAS3 functions results in an extensive, global loss of H3 acetylation and arrest in the G(2)/M phase of the cell cycle. The strikingly similar effect of loss of combined essential H3 HAT activities and the loss of a single essential H4 HAT underscores the fundamental biological significance of each of these chromatin-modifying activities.

Increased bioavailability of nitric oxide after lipid-lowering therapy in hypercholesterolemic patients: a randomized, placebo-controlled, double-blind study

BACKGROUND

Impaired endothelium-dependent vasodilation is an early sign of atherosclerosis in hypercholesterolemic patients. We hypothesized that lipid-lowering therapy can improve endothelial function and that this effect is mainly mediated by increased bioavailability of nitric oxide (NO).

METHODS AND RESULTS

In a randomized, double-blind, placebo-controlled trial, we studied 29 patients (age, 50+/-12 years) with hypercholesterolemia (LDL cholesterol > or = 160 mg/dL) randomly assigned to receive either fluvastatin (40 mg twice daily; 17 patients) or placebo (12 patients). Forearm blood flow was measured by plethysmography before and after 24 weeks of treatment. Endothelium-dependent vasodilation was assessed by intra-arterial infusion of acetylcholine (ACh; 3, 12, 24, and 48 microg/min) and basal NO synthesis rate by intra-arterial infusion of NG-monomethyl-L-arginine (L-NMMA; 1, 2, and 4 micromol/min). Simultaneous intra-arterial infusion of L-NMMA (4 micromol/min) and ACh (12, 24, and 48 microg/min) was used to test whether any increase in endothelium-dependent vasodilation after lipid-lowering therapy could be blocked by this NO synthase inhibitor. Endothelium-dependent vasodilation improved significantly after 24 weeks of lipid-lowering therapy compared with before therapy (ACh 24 microg/min: 240+/-34% before versus 347+/-50% after therapy; P< or =0.01) and placebo (changes between after and before therapy with ACh 24 microg/min: 108+/-39% for fluvastatin versus -26+/-32% for placebo; P< or =0.05). This improvement in endothelium-dependent vasodilation could be blocked by simultaneous administration of L-NMMA (ACh 24 microg/min plus L-NMMA 4 micromol/min: 170+/-69% before versus 219+/-47% after treatment; P=NS).

CONCLUSIONS

Lipid-lowering therapy with fluvastatin can improve disturbed endothelial function in hypercholesterolemic patients compared with placebo. This improvement is mediated by increased bioavailability of NO.

The significance of tetramerization in promoter recruitment by Stat5

Stat5a and Stat5b are rapidly activated by a wide range of cytokines and growth factors, including interleukin-2 (IL-2). We have previously shown that these signal transducers and activators of transcription (STAT proteins) are key regulatory proteins that bind to two tandem gamma interferon-activated site (GAS) motifs within an IL-2 response element (positive regulatory region III [PRRIII]) in the human IL-2Ralpha promoter. In this study, we demonstrate cooperative binding of Stat5 to PRRIII and explore the molecular basis underlying this cooperativity. We demonstrate that formation of a tetrameric Stat5 complex is essential for the IL-2-inducible activation of PRRIII. Stable tetramer formation of Stat5 is mediated through protein-protein interactions involving a tryptophan residue conserved in all STATs and a lysine residue in the Stat5 N-terminal domain (N domain). The functional importance of tetramer formation is shown by the decreased levels of transcriptional activation associated with mutations in these residues. Moreover, the requirement for STAT protein-protein interactions for gene activation from a promoter with tandemly linked GAS motifs can be relieved by strengthening the avidity of protein-DNA interactions for the individual binding sites. Taken together, these studies demonstrate that a dimeric but tetramerization-deficient Stat5 protein can activate only a subset of target sites. For functional activity on a wider range of potential recognition sites, N-domain-mediated oligomerization is essential.

Lipid peroxidation and antioxidant enzymes in isoproterenol induced oxidative stress in rat tissues

The oxidative metabolism of catecholamines produce quinones which react with oxygen to produce superoxide anions (O2-.) and H2O2. The catecholamines, however, are important under stress conditions but may have damaging effects due to the generation of reactive oxygen species (ROS) and formation of oxidation products. ROS are involved as causative factors in many diseases, therefore, the generation of ROS by catecholamines may also contribute to this process. Isoproterenol (ISO) was administered to rats in two doses so as to evaluate their beta-adrenergic and toxicological actions in terms of lipid peroxidation (LPO) and the changes in the antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST) and glutathione (GSH) content in heart, liver and kidney. ISO treatment caused LPO in tissues, however, the heart initially showed decreased LPO. This is attributed to the condition of hypertrophy by which the heart can protect itself to a limited extent against oxidative stress. The second dose of ISO, administered 24 h after the first treatment, showed toxic effects resulting in a higher increase in LPO. The increased SOD activity in tissues 3 days after a dose of ISO suggests that the ROS may induce SOD activity to dismutate O2-. However, increased amounts of O2-., inhibited SOD activity at 3 and 6 h with recovery towards control values at 12 h of a second dose of ISO treatment. CAT activity in tissues increased at 6 h of a second dose of ISO treatment. The elevated SOD and CAT enzymes in tissues indicate a response due to increased ROS. The increase in GSH content in the heart, liver and kidney at day 2 of ISO treatment and 12 h after the second dose of ISO may also neutralise oxidative stress. The inhibition in GST activity in tissues was observed probably due to increased ROS generation, however, GST activity partially recovered by 12 h after the second dose of ISO, in an attempt to counteract oxidative stress. The result shows that ISO induced oxidative stress and the increase of the antioxidant system in tissues may attenuate oxidative stress. It is suggested that ROS generation in the oxidation of catecholamines may be partially counteracted by the antioxidant system in tissues.

Nucleosome positioning on the MMTV LTR results from the frequency-biased occupancy of multiple frames

The translational positions of nucleosomes in the promoter region of the mouse mammary tumor virus (MMTV) were defined at high resolution. Nucleosome boundaries were determined in primer extension assays using full-length single-stranded mononucleosomal DNA prepared from cells treated with formaldehyde, a reversible protein-DNA cross-linking agent. Multiple boundaries were observed in both the nucleosome A (Nuc-A) and Nuc-B region of the promoter, indicating multiple nucleosome translational frames. The different nucleosome frames in both the Nuc-A and Nuc-B regions were occupied unequally. The most frequently occupied frames were found clustered within 50-60 bases of each other, resulting in a distribution centered in the positions defined previously at low resolution for Nuc-A and Nuc-B. The most abundant 5' ends of the frames in the B region were found between -235 and -187, and the 3' ends between -86 and -36, whereas in the A region the most abundant 5' ends were between -22 and +42, and the 3' ends between +121 and +186. Although frames in the Nuc-B region of the LTR extend at a low frequency in the 5' direction toward the Nuc-C region, there is a sharp discontinuity in the 3' direction toward Nuc-A, suggesting the presence of a boundary constraint in the A-B linker. The positions and relative occupancies of nucleosome frames, in either the B or the A region, did not change when the promoter was activated with dexamethasone.

DNA binding site selection of dimeric and tetrameric Stat5 proteins reveals a large repertoire of divergent tetrameric Stat5a binding sites

We have defined the optimal binding sites for Stat5a and Stat5b homodimers and found that they share similar core TTC(T/C)N(G/A)GAA interferon gamma-activated sequence (GAS) motifs. Stat5a tetramers can bind to tandemly linked GAS motifs, but the binding site selection revealed that tetrameric binding also can be seen with a wide range of nonconsensus motifs, which in many cases did not allow Stat5a binding as a dimer. This indicates a greater degree of flexibility in the DNA sequences that allow binding of Stat5a tetramers than dimers. Indeed, in an oligonucleotide that could bind both dimers and tetramers, it was possible to design mutants that affected dimer binding without affecting tetramer binding. A spacing of 6 bp between the GAS sites was most frequently selected, demonstrating that this distance is favorable for Stat5a tetramer binding. These data provide insights into tetramer formation by Stat5a and indicate that the repertoire of potential binding sites for this transcription factor is broader than expected.

Closed mitral valvotomy: early results and long-term follow-up of 3724 consecutive patients

Between 1956 and 1980 closed mitral valvotomies were performed in 3724 consecutive patients (male:female ratio 1.1:1) with mitral stenoses. Their ages ranged from 6 to 69 years, with a mean (SD) of 27.3 (9.3). Mitral stenosis in the younger age group is a unique condition and a great majority of these patients rapidly develop significant pulmonary hypertension and congestive cardiac failure. In this study a large number of subjects belonged to functional class IV (41.5%). Hospital mortality was 1.5% over the last 5 years. After valvotomy, 11 patients (0.3%) developed severe mitral regurgitation that made valve replacement necessary in the immediate postoperative period. Early postoperative embolism occurred in 0.4% of those who were in atrial fibrillation and had preoperative anticoagulation whereas it occurred in 0.95% of those in sinus rhythm who had no anticoagulation. Late postoperative embolism occurred at a rate of 0.3 to 1.6 per 1000 patients per year over a 20 year period. Rheumatic reactivity occurred at a rate of 1.3 to 2.2 per 1000 patients per year during the same period. Rate of occurrence of restenosis varied from 4.2 to 11.4 per 1000 patients per year between the fifth and fifteenth year of follow-up. Closed transventricular revalvotomy for restenosis was accomplished in 130 subjects with a 6.7% mortality. Excellent symptomatic improvement was evident in 86% of long-term survivors at the end of 15 years. Actuarial survival was 95%, 93.1%, 89.5%, and 84.2% at 6, 12, 18, and 24 years, respectively, after closed mitral valvotomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Psychosocial challenges and protective influences for socio-emotional coping of HIV+ adolescents in South Africa: a qualitative investigation

INTRODUCTION

While the roll-out of antiretroviral therapy in South Africa should lead to a reduction in mother to child transmission, mortality and orphaning, it will also be accompanied by a large number of children entering adolescence and adulthood with a chronic infectious disease. Adolescence is a particularly vulnerable period for HIV-infected people in relation to mental health problems and engagement in high-risk behaviours, including non-compliance with medical treatment. The goal of this qualitative study was to develop an understanding of the psychosocial challenges as well as protective influences promoting socio-emotional coping in HIV+ adolescents in order to inform mental health promotion and HIV prevention programming for this population in South Africa.

METHOD

In-depth qualitative interviews were conducted with HIV+ adolescents (25) and caregivers of HIV+ children (15) at a large HIV/AIDS Clinic in South Africa. Data were analysed thematically using NVivo8 software.

RESULTS

Psycho-social challenges for adolescents included dealing with loss of biological parents in the case of orphans; coming to terms with their HIV+ status including identity difficulties; external stigma and discrimination; and disclosure difficulties. For caregivers, disclosure and lack of financial, family and social support emerged as key challenges. Medication, HIV information, a future orientation and social support was identified as important for coping and general well-being of adolescents, with financial and social support emerging as key for promoting supportive caregiving contexts.

CONCLUSION

While HIV+ adolescents in South Africa experience similar concerns to those in high-income countries, socio-emotional coping may be compromised by increased levels of loss due to the late roll-out of ARVS and challenges to caregiving contexts including poverty, stigma and minimally supported foster care arrangements. There is a need for mental health promotion programmes for adolescents to adopt an ecological approach, strengthening protective influences at the individual, interpersonal, community and policy levels.

Upregulation of CD40 and CD40 ligand (CD154) in patients with moderate hypercholesterolemia

BACKGROUND

Hypercholesterolemia, a risk factor for cardiovascular disease, is associated with inflammation and hypercoagulability. Both can be mediated by the CD40 system. This study investigated whether the CD40 system is upregulated in patients with moderate hypercholesterolemia and whether it is influenced by therapy with a hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitor.

METHODS AND RESULTS

Fifteen patients with moderate hypercholesterolemia and 15 healthy control subjects were investigated. CD154 and P-selectin were analyzed on platelets and CD40 was analyzed on monocytes before and under therapy with the statin cerivastatin by double-label flow cytometry. Blood concentrations of soluble CD154 and monocyte chemoattractant protein-1 (MCP-1) were evaluated. Our main findings were as follows. Patients with moderate hypercholesterolemia showed a significant increase of CD154 and P-selectin on platelets and CD40 on monocytes compared with healthy subjects. Soluble CD154 showed a nonsignificant trend for higher plasma levels in patients. A positive correlation was found for total or LDL cholesterol and CD154, but not for CD40 on monocytes. The latter was upregulated in vitro by C-reactive protein, which was found to be significantly elevated in patients with moderate hypercholesterolemia. CD154 on platelets proved to be biologically active because it enhanced the release of MCP-1, which was markedly elevated in an in vitro platelet-endothelial cell coculture model and in the serum of patients. Short-term therapy with a HMG-CoA reductase inhibitor significantly downregulated CD40 on monocytes and serum levels of MCP-1.

CONCLUSION

Patients with moderate hypercholesterolemia show upregulation of the CD40 system, which may contribute to the known proinflammatory, proatherogenic, and prothrombotic milieu found in these patients.

Impaired endothelial function in arterial hypertension and hypercholesterolemia: potential mechanisms and differences

This review focuses on the role of impaired endothelial function for the development of atherosclerosis in human arterial hypertension and hypercholesterolemia in vivo. Potential mechanisms underlying impaired endothelial function and decreased bioavailability of nitric oxide under these clinical conditions are discussed and potential differences in these mechanisms between arterial hypertension and hypercholesterolemia are outlined. It further addresses therapeutic strategies aiming to improve the bioavailability of nitric oxide in these patients. The overall conclusion is that the bioavailability of nitric oxide is probably impaired not by a single defect, but by various mechanisms affecting nitric oxide synthesis as well as nitric oxide breakdown. In both diseases, increased superoxide anion production and oxidative stress represents a major mechanism. However, potential differences in the underlying mechanisms of superoxide production or nitric oxide synthesis are evident between arterial hypertension and hypercholesterolemia. Decreased bioavailability of nitric oxide does not only impair endothelium-dependent vasodilation, but also activates other mechanisms that play an important role in the pathogenesis of atherosclerosis. Thus, therapeutic strategies should aim to restore bioavailability of nitric oxide, which has been demonstrated for lipid-lowering therapy in hypercholesterolemia. The mechanisms by which nitric oxide bioavailability can be improved by any drug therapy remain to be elucidated and may provide further insights into the mechanisms that are involved in impaired endothelial function and atherogenesis.

Effects of continuous haemofiltration vs intermittent haemodialysis on systemic haemodynamics and splanchnic regional perfusion in septic shock patients: a prospective, randomized clinical trial

BACKGROUND

Parameters of splanchnic regional perfusion, like intramucosal pH (pHi) and pCO(2) (pCO(2)i), may predict outcome in septic shock patients. Continuous venovenous haemofiltration (CVVH) has been considered beneficial in haemodynamically unstable septic shock patients. In a prospective, randomized, clinical study, we investigated whether CVVH, in comparison to intermittent haemodialysis (IHD), is able to improve splanchnic regional perfusion in critically ill patients.

METHODS

Thirty septic shock patients with acute renal failure were randomized to either CVVH (n=20) or IHD (n=10) groups for renal replacement therapy. Patient characteristics at baseline were not different in terms of severity of illness (APACHE II scores), haemodynamics, and pHi/pCO(2)i values. Systemic haemodynamics, oxygen transport variables, and splanchnic regional perfusion parameters were measured at 0.5, 2, 4 and 24 h after initiation of renal replacement therapy. There were no major changes in vasopressor support throughout the 24-h study period.

RESULTS

In contrast to IHD, CVVH caused a decrease in heart rate (-3+/-11 vs +9+/-8/min, P<0.01) and an increase in systolic blood pressure (+12+/-1 vs -5+/-17 mmHg, P<0.05) after 2 h. After 24 h, increased systemic vascular resistance was found in the CVVH group in comparison with the IHD group (+312+/-755 vs -29+/-89 dyne/cm(5), P<0.05) and was accompanied by a decrease in cardiac output (-1.54+/-1.4 vs -0.25+/-0.9 l/min, P<0.01). However pHi values remained constant throughout the 24-h study period in both groups and were not different between the groups (CVVH 7.19+/-0.1 vs IHD 7.19+/-0.1, n.s.) as did the pCO(2)i values (CVVH +7+/-17 vs IHD 0+/-15 mmHg, n.s.) and pCO(2) gap values (CVVH +6+/-15 vs IHD +5+/-12 mmHg, n.s.).

CONCLUSIONS

Despite different changes of systemic haemodynamics between CVVH and IHD, CVVH did not improve parameters of splanchnic regional perfusion like pHi, pCO(2)i or pCO(2) gap in septic shock patients.