Cardiovascular subphenotypes in patients with COVID-19 pneumonitis whose lungs are mechanically ventilated: a single-centre retrospective observational study

Unsupervised clustering methods of transthoracic echocardiography variables have not been used to characterise circulatory failure mechanisms in patients with COVID‐19 pneumonitis. We conducted a retrospective, single‐centre cohort study in ICU patients with COVID‐19 pneumonitis whose lungs were mechanically ventilated and who underwent transthoracic echocardiography between March 2020 and May 2021. We performed latent class analysis of echocardiographic and haemodynamic variables. We characterised the identified subphenotypes by comparing their clinical parameters, treatment responses and 90‐day mortality rates. We included 305 patients with a median (IQR [range]) age 59 (49–66 [16–83]) y. Of these, 219 (72%) were male, 199 (65%) had moderate acute respiratory distress syndrome and 113 (37%) did not survive more than 90 days. Latent class analysis identified three cardiovascular subphenotypes: class 1 (52%; normal right ventricular function); class 2 (31%; right ventricular dilation with mostly preserved systolic function); and class 3 (17%; right ventricular dilation with systolic impairment). The three subphenotypes differed in their clinical characteristics and response to prone ventilation and outcomes, with 90‐day mortality rates of 22%, 42% and 73%, respectively (p < 0.001). We conclude that the identified subphenotypes aligned with right ventricular pathophysiology rather than the accepted definitions of right ventricular dysfunction, and these identified classifications were associated with clinical outcomes.

Association of clinical factors and recent anticancer therapy with COVID-19 severity among patients with cancer: a report from the COVID-19 and Cancer Consortium

BACKGROUND

Patients with cancer may be at high risk of adverse outcomes from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. We analyzed a cohort of patients with cancer and coronavirus 2019 (COVID-19) reported to the COVID-19 and Cancer Consortium (CCC19) to identify prognostic clinical factors, including laboratory measurements and anticancer therapies.

PATIENTS AND METHODS

Patients with active or historical cancer and a laboratory-confirmed SARS-CoV-2 diagnosis recorded between 17 March and 18 November 2020 were included. The primary outcome was COVID-19 severity measured on an ordinal scale (uncomplicated, hospitalized, admitted to intensive care unit, mechanically ventilated, died within 30 days). Multivariable regression models included demographics, cancer status, anticancer therapy and timing, COVID-19-directed therapies, and laboratory measurements (among hospitalized patients).

RESULTS

A total of 4966 patients were included (median age 66 years, 51% female, 50% non-Hispanic white); 2872 (58%) were hospitalized and 695 (14%) died; 61% had cancer that was present, diagnosed, or treated within the year prior to COVID-19 diagnosis. Older age, male sex, obesity, cardiovascular and pulmonary comorbidities, renal disease, diabetes mellitus, non-Hispanic black race, Hispanic ethnicity, worse Eastern Cooperative Oncology Group performance status, recent cytotoxic chemotherapy, and hematologic malignancy were associated with higher COVID-19 severity. Among hospitalized patients, low or high absolute lymphocyte count; high absolute neutrophil count; low platelet count; abnormal creatinine; troponin; lactate dehydrogenase; and C-reactive protein were associated with higher COVID-19 severity. Patients diagnosed early in the COVID-19 pandemic (January-April 2020) had worse outcomes than those diagnosed later. Specific anticancer therapies (e.g. R-CHOP, platinum combined with etoposide, and DNA methyltransferase inhibitors) were associated with high 30-day all-cause mortality.

CONCLUSIONS

Clinical factors (e.g. older age, hematological malignancy, recent chemotherapy) and laboratory measurements were associated with poor outcomes among patients with cancer and COVID-19. Although further studies are needed, caution may be required in utilizing particular anticancer therapies.

CLINICAL TRIAL IDENTIFIER

NCT04354701.

A time-sensitive analysis of the prognostic utility of vasopressor dose in septic shock

It is unclear whether the association between vasopressor dose and mortality is affected by duration of administration. We examined whether prognostication in septic shock is feasible through the use of daily median vasopressor doses. We undertook a single-centre retrospective cohort study. We included patients with a diagnosis of septic shock admitted to the intensive care unit at Queen Elizabeth Hospital, Birmingham, UK, between April 2016 and July 2019. The primary outcome measure was 90-day mortality. We defined vasopressor dose as the median norepinephrine equivalent dose (equivalent infusion rates of all vasopressors and inotropes) recorded for each day, for the first four days of septic shock. We divided patients into groups by vasopressor dose quintiles and calculated their 90-day mortality rate. We examined area under the receiver operator characteristic curves for prognostic ability. In total, 844 patients were admitted with septic shock and had a 90-day mortality of 43% (n = 358). Over the first four days, median vasopressor dose decreased in 93% of survivors and increased in 56% of non-survivors. The mortality rate associated with a given vasopressor dose quintile increased on sequential days of septic shock. The area under the receiver operator characteristic curves of daily median vasopressor dose against mortality increased from day 1 to day 4 (0.67 vs. 0.86, p < 0.0001). By day 4, a median daily vasopressor dose > 0.05 μg.kg^-1 .min^-1 had an 80% sensitivity and specificity for mortality. The prognostic utility of vasopressor dose improved considerably with shock duration. Prolonged administration of small vasopressor doses was associated with a high attributable mortality.

Renal impairment and its impact on clinical outcomes in patients who are critically ill with COVID-19: a multicentre observational study

Renal impairment is common in patients who are critically ill with coronavirus disease-19 (COVID-19). We examined the association between acute and chronic kidney disease with clinical outcomes in 372 patients with coronavirus disease-19 admitted to four regional intensive care units between 10 March 2020 and 31 July 2020. A total of 216 (58%) patients presented with COVID-19 and renal impairment. Acute kidney injury and/or chronic kidney disease was associated with greater in-hospital mortality compared with patients with preserved renal function (107/216 patients (50%) (95%CI 44-57) vs. 32/156 (21%) (95%CI 15-28), respectively; p < 0.001, relative risk 2.4 (95%CI 1.7-3.4)). Mortality was greatest in patients with renal transplants (6/7 patients (86%) (95%CI 47-100)). Mortality rates increased in patients with worsening renal injury according to the Kidney Disease: Improving Global Outcomes classification: stage 0 mortality 33/157 patients (21%) (95%CI 15-28) vs. stages 1-3 mortality 91/186 patients (49%) (95%CI 42-56); p < 0.001, relative risk 2.3 (95%CI 1.7-3.3). Survivors were less likely to require renal replacement therapy compared with non-survivors (57/233 patients (24%) vs. 64/139 patients (46%), respectively; p < 0.001, relative risk 1.9 (95%CI 1.4-2.5)). One-fifth of survivors who required renal replacement therapy acutely in intensive care continued to require renal support following discharge. Our data demonstrate that renal impairment in patients admitted to intensive care with COVID-19 is common and is associated with a high mortality and requirement for on-going renal support after discharge from critical care. Our findings have important implications for future pandemic planning in this patient cohort.

Fibrillar Collagen Quantification With Curvelet Transform Based Computational Methods

Quantification of fibrillar collagen organization has given new insight into the possible role of collagen topology in many diseases and has also identified candidate image-based bio-markers in breast cancer and pancreatic cancer. We have been developing collagen quantification tools based on the curvelet transform (CT) algorithm and have demonstrated this to be a powerful multiscale image representation method due to its unique features in collagen image denoising and fiber edge enhancement. In this paper, we present our CT-based collagen quantification software platform with a focus on new features and also giving a detailed description of curvelet-based fiber representation. These new features include C++-based code optimization for fast individual fiber tracking, Java-based synthetic fiber generator module for method validation, automatic tumor boundary generation for fiber relative quantification, parallel computing for large-scale batch mode processing, region-of-interest analysis for user-specified quantification, and pre- and post-processing modules for individual fiber visualization. We present a validation of the tracking of individual fibers and fiber orientations by using synthesized fibers generated by the synthetic fiber generator. In addition, we provide a comparison of the fiber orientation calculation on pancreatic tissue images between our tool and three other quantitative approaches. Lastly, we demonstrate the use of our software tool for the automatic tumor boundary creation and the relative alignment quantification of collagen fibers in human breast cancer pathology images, as well as the alignment quantification of in vivo mouse xenograft breast cancer images.

Chronic Pruritus: A Review of Neurophysiology and Associated Immune Neuromodulatory Treatments

Chronic pruritus remains a difficult condition to treat with many non-specific therapeutic options. Recent scientific discoveries have elucidated the physiology associated with pruritus. Combined with clinical and experimental trials with immune-modulatory agents, chronic pruritus now has novel treatment options with known mechanisms of action. This review goes over recent scientific progress in understanding the molecular mechanisms governing pruritus, the cross-talk between the immune and nervous systems that regulate itch, and central nervous pathways and projections affected by itch. In light of these recent discoveries, we briefly discuss a growing body of data from relevant clinical trials investigating immunomodulatory drugs targeting specific interleukin receptors (IL-4/13/31) and intracellular signaling (e.g., Janus kinase) pathways. We focus on the physiological processes that control this complex physical and emotional experience, as well as the role of newer drugs used to treat chronic itch.

A Natural Language Interface for Dissemination of Reproducible Biomedical Data Science

Computational tools in the form of software packages are burgeoning in the field of medical imaging and biomedical research. These tools enable biomedical researchers to analyze a variety of data using modern machine learning and statistical analysis techniques. While these publicly available software packages are a great step towards a multiplicative increase in the biomedical research productivity, there are still many open issues related to validation and reproducibility of the results. A key gap is that while scientists can validate domain insights that are implicit in the analysis, the analysis itself is coded in a programming language and that domain scientist may not be a programmer. Thus, there is no/limited direct validation of the program that carries out the desired analysis. We propose a novel solution, building upon recent successes in natural language understanding, to address this problem. Our platform allows researchers to perform, share, reproduce and interpret the analysis pipelines and results via natural language. While this approach still requires users to have a conceptual understanding of the techniques, it removes the burden of programming syntax and thus lowers the barriers to advanced and reproducible neuroimaging and biomedical research.

Caprine leptospirosis: Hematobiochemical and urinalyses studies

AIM

The present study was designed to evaluate clinicopathological alterations in naturally occurring leptospirosis in goats of South Gujarat region, Gujarat.

MATERIALS AND METHODS

A total 459 blood/serum and 292 urine samples were collected from different districts of South Gujarat region, India. Blood/serum and urine samples were subjected to hematobiochemical analyses and urinalyses. The serum samples were screened for anti-leptospiral antibodies using the microscopic agglutination test (MAT). On the bases of presence or absence of anti-leptospiral antibodies in serum, seropositive and seronegative groups were made. The results were analyzed using standard statistical methods to know pathological changes in the disease.

RESULTS

In MAT, out of 459, 116 goats were seropositive, and 343 were seronegative. In hematobiochemical analyses, statistically significant (p<0.01) decrease in values of packed cell volume, hemoglobin (Hb) concentration, mean corpuscular Hb concentration and total protein and increased activity/level of alanine aminotransferase, aspartate aminotransferase and total bilirubin between seropositive and seronegative goats were noted. Urinalyses did not reveal any specific changes. In the dark field microscopy, urine samples were found to be negative for leptospires.

CONCLUSION

Hematobiochemical changes noted in seropositive goats were indicative of hepatic damage, and this knowledge would aid in the therapeutic management of the disease.

Identification of cross-species shared transcriptional networks of diabetic nephropathy in human and mouse glomeruli

Murine models are valuable instruments in defining the pathogenesis of diabetic nephropathy (DN), but they only partially recapitulate disease manifestations of human DN, limiting their utility. To define the molecular similarities and differences between human and murine DN, we performed a cross-species comparison of glomerular transcriptional networks. Glomerular gene expression was profiled in patients with early type 2 DN and in three mouse models (streptozotocin DBA/2, C57BLKS db/db, and eNOS-deficient C57BLKS db/db mice). Species-specific transcriptional networks were generated and compared with a novel network-matching algorithm. Three shared human-mouse cross-species glomerular transcriptional networks containing 143 (Human-DBA STZ), 97 (Human-BKS db/db), and 162 (Human-BKS eNOS(-/-) db/db) gene nodes were generated. Shared nodes across all networks reflected established pathogenic mechanisms of diabetes complications, such as elements of Janus kinase (JAK)/signal transducer and activator of transcription (STAT) and vascular endothelial growth factor receptor (VEGFR) signaling pathways. In addition, novel pathways not previously associated with DN and cross-species gene nodes and pathways unique to each of the human-mouse networks were discovered. The human-mouse shared glomerular transcriptional networks will assist DN researchers in selecting mouse models most relevant to the human disease process of interest. Moreover, they will allow identification of new pathways shared between mice and humans.

Toxicopathological evaluation in Wistar rats (Rattus norvegicus) following repeated oral exposure to acephate

The present study was carried out to evaluate the effects of exposure at different doses of acephate on hematology, blood biochemistry, oxidative stress and immune system of Wistar rats. The experiment was carried out on 40 Wistar rats, which were divided in four groups. Animals of the three treatment groups were given with different sublethal doses (1/40th, 1/20th, 1/10th of lethal dose 50 value) of acephate by oral gavage. The hematology, blood biochemistry, oxidative stress marker, humoral immune response and cell-mediated immunity were evaluated following acephate exposure. Significant alteration in hematological parameters was not observed following different doses of acephate; however, significant alteration in alkaline phosphatase, gamma glutamyl transferase, acetyl cholinesterase, lipid peroxidase and superoxide dismutase was observed in medium- and high-dose group animals. Nonsignificant decrease in antibody titer in animals exposed to high dose has been observed compared with animals of control group. However, significant alteration in cell-mediated immunity was not observed in animals treated with acephate at different doses.

Exploratory data mining analysis identifying subgroups of patients with depression who are at high risk for suicide

OBJECTIVE

Although prior research has identified a number of separate risk factors for suicide among patients with depression, little is known about how these factors may interact to modify suicide risk. Using an empirically based decision tree analysis for a large national sample of Veterans Affairs (VA) health system patients treated for depression, we identified subgroups with particularly high or low rates of suicide.

METHOD

We identified 887,859 VA patients treated for depression between April 1, 1999, and September 30, 2004. Randomly splitting the data into 2 samples (primary and replication samples), we developed a decision tree for the primary sample using recursive partitioning. We then tested whether the groups developed within the primary sample were associated with increased suicide risk in the replication sample.

RESULTS

The exploratory data analysis produced a decision tree with subgroups of patients at differing levels of risk for suicide. These were identified by a combination of factors including a co-occurring substance use disorder diagnosis, male sex, African American race, and psychiatric hospitalization in the past year. The groups developed as part of the decision tree accurately discriminated between those with and without suicide in the replication sample. The patients at highest risk for suicide were those with a substance use disorder who were non-African American and had an inpatient psychiatric stay within the past 12 months.

CONCLUSIONS

Study findings suggest that the identification of depressed patients at increased risk for suicide is improved through the examination of higher order interactions between potential risk factors.

BatchGenAna: a batch platform for large-scale genomic analysis of mammalian small RNAs

An increasing number of small RNAs have been discovered in mammals. However, their primary transcripts and upstream regulatory networks remain largely to be determined. Genomic analysis of small RNAs facilitates identification of their primary transcripts, and hence contributes to researches of their upstream regulatory networks. We here report a batch platform, BatchGenAna, which is specifically designed for large-scale genomic analysis of mammalian small RNAs. It can map and annotate for as many as 1000 small RNAs or 10,000 genomic loci of small RNAs at a time. It provides genomic features including RefSeq genes, mRNAs, ESTs and repeat elements in tabular and graphical results. It also allows extracting flanking sequences of submitted queries, specified genomic regions and host transcripts, which facilitates subsequent analysis such as scanning transcription factor binding sites in upstream sequences and poly(A) signals in downstream sequences. Besides small RNA fields, BatchGenAna can also be applied to other research fields, e.g. in silico analysis of target genes of transcription factors.

ProbeMatch: rapid alignment of oligonucleotides to genome allowing both gaps and mismatches

SUMMARY

We have developed a tool, called ProbeMatch, for matching a large set of oligonucleotide sequences against a genome database using gapped alignments. Unlike most of the existing tools such as ELAND which only perform ungapped alignments allowing at most two mismatches, ProbeMatch generates both ungapped and gapped alignments allowing up to three errors including insertion, deletion and mismatch. To speedup sequence alignment, ProbeMatch uses gapped q-grams and q-grams of various patterns to identify target hits to a query sequence. This approach results in fewer initial sequences to examine with no loss in sensitivity. ProbeMatch has been used to align 169,095 Illumina GAII reads against the human genome, which could not be mapped by ELAND, and found alignments for 28,625 reads of the 169,095 reads in less than 3 h.

AVAILABILITY

Source code is freely available at (http://www.cs.wisc.edu/~jignesh/probematch/).

Efficient evaluation of radial queries using the target tree

We propose a novel indexing structure, called the target tree, which is designed to answer a new type of spatial query, called the radial query. A radial query finds all objects in the spatial data set that intersect with line segments emanating from a single target point. Many biomedical applications use radial queries, including neurosurgical planning. A target tree uses a regular hierarchical decomposition of space using wedge shapes that emanate from the target point. We compare the target tree with the R*-tree and quadtree, and show that the target tree is significantly faster than these methods.

Thiazide-induced subtle renal injury not observed in states of equivalent hypokalemia

Hydrochlorothiazide (HCTZ) is used to manage hypertension and heart failure; however, its side effects include mild hypokalemia, metabolic abnormalities, and volume depletion, which might have deleterious effects on renal and endothelial function. We studied whether HCTZ cause renal injury and/or altered vasoreactivity and if these changes are hypokalemia-dependent. Rats were given a normal diet or a diet moderately low in potassium K+ with or without HCTZ. Animals fed either a low K+ diet alone or HCTZ developed mild hypokalemia. There was no significant difference in systolic blood pressure in the different treatment groups. All three groups with hypokalemia had mild proteinuria; low K(+)-HCTZ rats had reduced creatinine clearance. HCTZ-treated rats displayed hypomagnesemia, hypertriglyceridemia, hyperglycemia, insulin resistance, and hyperaldosteronism. No renal injury was observed in the groups without HCTZ; however, increased kidney weight, glomerular ischemia, medullary injury, and cortical oxidative stress were seen with HCTZ treatment. Endothelium-dependent vasorelaxation was reduced in all hypokalemic groups and correlated with reduced serum K+, serum, and urine nitric oxide. Our results show that HCTZ is associated with greater renal injury for the same degree of hypokalemia as the low K+ diet, suggesting that factors such as chronic ischemia and hyperaldosteronism due to volume depletion may be responsible agents. We also found impaired endothelium-dependent vasorelaxation was linked to mild hypokalemia.

SAGA: a subgraph matching tool for biological graphs

MOTIVATION

With the rapid increase in the availability of biological graph datasets, there is a growing need for effective and efficient graph querying methods. Due to the noisy and incomplete characteristics of these datasets, exact graph matching methods have limited use and approximate graph matching methods are required. Unfortunately, existing graph matching methods are too restrictive as they only allow exact or near exact graph matching. This paper presents a novel approximate graph matching technique called SAGA. This technique employs a flexible model for computing graph similarity, which allows for node gaps, node mismatches and graph structural differences. SAGA employs an indexing technique that allows it to efficiently evaluate queries even against large graph datasets.

RESULTS

SAGA has been used to query biological pathways and literature datasets, which has revealed interesting similarities between distinct pathways that cannot be found by existing methods. These matches associate seemingly unrelated biological processes, connect studies in different sub-areas of biomedical research and thus pose hypotheses for new discoveries. SAGA is also orders of magnitude faster than existing methods.

AVAILABILITY

SAGA can be accessed freely via the web at http://www.eecs.umich.edu/saga. Binaries are also freely available at this website.

A framework for protein structure classification and identification of novel protein structures

Background

Protein structure classification plays a central role in understanding the function of a protein molecule with respect to all known proteins in a structure database. With the rapid increase in the number of new protein structures, the need for automated and accurate methods for protein classification is increasingly important.

Results

In this paper we present a unified framework for protein structure classification and identification of novel protein structures. The framework consists of a set of components for comparing, classifying, and clustering protein structures. These components allow us to accurately classify proteins into known folds, to detect new protein folds, and to provide a way of clustering the new folds. In our evaluation with SCOP 1.69, our method correctly classifies 86.0%, 87.7%, and 90.5% of new domains at family, superfamily, and fold levels. Furthermore, for protein domains that belong to new domain families, our method is able to produce clusters that closely correspond to the new families in SCOP 1.69. As a result, our method can also be used to suggest new classification groups that contain novel folds.

Conclusion

We have developed a method called proCC for automatically classifying and clustering domains. The method is effective in classifying new domains and suggesting new domain families, and it is also very efficient. A web site offering access to proCC is freely available at

miBLAST: scalable evaluation of a batch of nucleotide sequence queries with BLAST

A common task in many modern bioinformatics applications is to match a set of nucleotide query sequences against a large sequence dataset. Exis-ting tools, such as BLAST, are designed to evaluate a single query at a time and can be unacceptably slow when the number of sequences in the query set is large. In this paper, we present a new algorithm, called miBLAST, that evaluates such batch workloads efficiently. At the core, miBLAST employs a q-gram filtering and an index join for efficiently detecting similarity between the query sequences and database sequences. This set-oriented technique, which indexes both the query and the database sets, results in substantial performance improvements over existing methods. Our results show that miBLAST is significantly faster than BLAST in many cases. For example, miBLAST aligned 247 965 oligonucleotide sequences in the Affymetrix probe set against the Human UniGene in 1.26 days, compared with 27.27 days with BLAST (an improvement by a factor of 22). The relative performance of miBLAST increases for larger word sizes; however, it decreases for longer queries. miBLAST employs the familiar BLAST statistical model and output format, guaranteeing the same accuracy as BLAST and facilitating a seamless transition for existing BLAST users.

Effect of node size on the performance of cache-conscious B + -trees

In main-memory databases, the number of processor cache misses has a critical impact on the performance of the system. Cache-conscious indices are designed to improve performance by reducing the number of processor cache misses that are incurred during a search operation. Conventional wisdom suggests that the index's node size should be equal to the cache line size in order to minimize the number of cache misses and improve performance. As we show in this paper, this design choice ignores additional effects, such as the number of instructions executed and the number of TLB misses, which play a significant role in determining the overall performance. To capture the impact of node size on the performance of a cache-conscious B+ tree (CSB+-tree), we first develop an analytical model based on the fundamental components of the search process. This model is then validated with an actual implementation, demonstrating that the model is accurate. Both the analytical model and experiments confirm that using node sizes much larger than the cache line size can result in better search performance for the CSB+-tree.

Angiotensin IV-mediated pulmonary artery vasorelaxation is due to endothelial intracellular calcium release

Angiotensin (ANG) IV stimulation of pulmonary artery (PA) endothelial cells (PAECs) but not of PA smooth muscle cells (PASMCs) resulted in significant increased production of cGMP in PASMCs. ANG IV receptors are not present in PASMCs, and PASMC nitric oxide synthase activity was not altered by ANG IV. ANG IV caused a dose-dependent vasodilation of U-46619-precontracted endothelium-intact but not endothelium-denuded PAs, and this response was blocked by the ANG IV receptor antagonist divalinal ANG IV but not by ANG II type 1 and 2 receptor blockers. ANG IV receptor-mediated increased intracellular Ca(2+) concentration ([Ca(2+)](i)) release from intracellular stores in PAECs was blocked by divalinal ANG IV as well as by the G protein, phospholipase C, and phosphoinositide (PI) 3-kinase inhibitors guanosine 5'-O-(2-thiodiphosphate), U-73122, and LY-294002, respectively, and was regulated by both PI 3-kinase- and ryanodine-sensitive Ca(2+) stores. Basal and ANG IV-mediated vasorelaxation of endothelium-denuded PAs was restored by exogenous PAECs but not by exogenous PAECs pretreated with the intracellular Ca(2+) chelator 1,2-bis(o-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM. These results demonstrate that ANG IV-mediated vasodilation of PAs is endothelium dependent and regulated by [Ca(2+)](i) release through receptor-coupled G protein-phospholipase C-PI 3-kinase signaling mechanisms.

Nitric oxide-induced reduction of lung cell and whole lung thioredoxin expression is regulated by NF-kappaB

We examined whether nitric oxide (NO)-induced inhibition of thioredoxin (Thx) expression is regulated by a mechanism mediated by a transcription factor, i.e., nuclear factor-kappaB (NF-kappaB), in cultured porcine pulmonary artery endothelial cells (PAEC) and in mouse lungs. Western blot analysis revealed that IkappaB-alpha content was reduced by 20 and 60% in PAEC exposed to 8.5 ppm NO for 2 and 24 h, respectively. NO exposure also caused significant reductions of cytosol fraction p65 and p52 content in PAEC. The nuclear fraction p65 and p52 contents were significantly reduced only in PAEC exposed to NO for 24 h. Exposure to NO resulted in a 50% reduction of p52 mRNA but not of the IkappaB-alpha subunit. DNA binding activity of the oligonucleotide encoding the NF-kappaB sequence in the Thx gene was significantly reduced in PAEC exposed to NO for 24 h. Exposure of mice to 10 ppm NO for 24 h resulted in a significant reduction of lung Thx and IkappaB-alpha mRNA and protein expression and in the oligonucleotide encoding Thx and NF-kappaB/DNA binding. These results 1) demonstrate that the effects of NO exposure on Thx expression in PAEC are comparable to those observed in intact lung and 2) suggest that reduced expression of the NF-kappaB subunit, leading to reduced NF-kappaB/DNA binding, is associated with the loss of Thx expression in PAEC and in intact mouse lungs.

Increased expression of calreticulin is linked to ANG IV-mediated activation of lung endothelial NOS

This study demonstrates that ANG IV-induced activation of lung endothelial cell nitric oxide synthase (ecNOS) is mediated through mobilization of Ca(2+) concentration and by increased expression and release of the Ca(2+) binding protein calreticulin in pulmonary artery endothelial cells (PAEC). In Ca(2+)-free medium and in the presence of the ANG II AT(1) and AT(2) receptor antagonists losartan and PD-123319 (1 microM each), respectively, ANG IV (5, 50, and 500 nM) significantly increased intracellular Ca(2+) release in PAEC (P < 0.05 for all concentrations). In contrast, ANG IV-mediated activation of ecNOS was abolished by the intracellular Ca(2+) chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM. ANG IV stimulation resulted in significantly increased expression of calreticulin in cells as well as release of calreticulin into the medium of cells as early as 2 h after ANG IV stimulation (P < 0.05). Catalytic activity of purified ecNOS in the absence of calmodulin was increased in a concentration-dependent fashion by calreticulin. Immunocoprecipitation studies revealed that ecNOS and calreticulin were coprecipitated in ANG IV-stimulated PAEC. These results demonstrate that ANG IV-mediated activation of ecNOS is regulated by intracellular Ca(2+) mobilization and by increased expression of calreticulin, which appears to involve interaction of ecNOS and calreticulin proteins in PAEC.

Angiotensin II-stimulated nitric oxide release from porcine pulmonary endothelium is mediated by angiotensin IV

In this study, a nitric oxide (NO) sensor was used to examine the ability of angiotensin II (AngII), AngIV, and bradykinin (Bk) to stimulate NO release from porcine pulmonary artery (PPAE) and porcine aortic endothelial (PAE) cells and to explore the mechanism of the AngII-stimulated NO release. Physiologic concentrations of AngII, but not Bk, caused release of NO from PPAE cells. In contrast, Bk, but not AngII, stimulated NO release from PAE cells. AngIII-stimulated NO release from PPAE cells required extracellular L-arginine and was inhibited by L-nitro-arginine methyl ester. AT1 and AT2 receptor inhibition had no affect on AngII-mediated NO release or activation of NO synthase (NOS). AngIV, an AngII metabolite with binding sites that are pharmacologically distinct from the classic AngII receptors, stimulated considerably greater NO release and greater endothelial-type constitutive NOS activity than the same amount of AngII. The AngIV receptor antagonist, divalinal AngIV, blocked both AngII- and AngIV-mediated NO release as well as NOS activation. The results demonstrate that AngIV and the AngIV receptor are responsible, at least in part, for AngII-stimulated NO release and the associated endothelium-dependent vasorelaxation. Furthermore, these results suggest that differences exist in both AngII- and Bk-mediated NO release between PPAE and PAE cells, which may reflect important differences in response to these hormones between vascular beds.

CD4+ T cell enumeration in HIV infection with limited resources

The incidence of human immunodeficiency virus (HIV) infection continues to increase in South Africa. Limited resources are available for diagnosis and management of the disease and the development of affordable strategies is required. Absolute CD4 counts are used locally predominantly to monitor disease progression and institute prophylaxis against opportunistic infections. A dramatic increase in demand for CD4 counts prompted an investigation for a more cost-effective flow cytometry method than those currently recommended by the Centers for Disease Control (CDC). CD4 counts generated by two different single tube methods using CD3/CD4/CD8 [1(3)] and CD4 [1(1)] antibodies, respectively, were compared to the CDC recommended 6 tube 2 colour panel [6(2)]. Whole blood analysis using the Coulter Multi-Q-Prep system and an Epics XL Flow Cytometer (Coulter, Hialeah, FL) was performed for each of the three methods. Random samples from HIV positive adult patients were compared. A mean difference in the absolute CD4 counts of less than 10x10(6)/l was generated by both of the alternative panels when compared with the 6(2) panel. The precision of the three methods is comparable. In reagents alone, the 1(3) and 1(1) methods represent a cost saving of 76% and 93%, respectively, over the 6(2) method. The 1(3) and 1(1) panels would permit more affordable CD4 counts to be determined by the gold standard methodology of flow cytometry with no clinically significant sacrifices in accuracy or precision.

Angiotensin IV receptor-mediated activation of lung endothelial NOS is associated with vasorelaxation

The hexapeptide angiotensin (ANG) IV, a metabolic product of ANG II, has been reported to play a functional role in the regulation of blood flow in extrapulmonary tissues. Here, we demonstrate that ANG IV-specific (AT4) receptors are present in porcine pulmonary arterial endothelial cells (PAECs) and that the binding of ANG IV to AT4 receptors can be blocked by its antagonist divalinal ANG IV but not by the ANG II-, AT1-, and AT2-receptor blockers [Sar1,Ile8]ANG II, losartan, and PD-123177, respectively. ANG IV significantly increased endothelial cell constitutive nitric oxide synthase (ecNOS) activity (P < 0.05) as well as cellular cGMP content (P < 0. 001). Western blot analysis revealed that ecNOS protein expression was comparable in control and ANG IV-stimulated cells. Divalinal ANG IV but not [Sar1,Ile8]ANG II, losartan, or PD-123177 inhibited the ANG II- and ANG IV-stimulated increases in ecNOS activity and cGMP content in PAECs. Incubation in the presence of N-nitro-L-arginine methyl ester (L-NAME) or methylene blue but not of indomethacin significantly diminished ANG IV-stimulated as well as basal levels of cGMP (P < 0.001). Similarly, in situ studies with precontracted porcine pulmonary arterial rings showed that ANG IV caused an endothelium-dependent relaxation that was blocked by L-NAME or methylene blue. Collectively, these results demonstrate that ANG IV binds to AT4 receptors, activates ecNOS by posttranscriptional modulation, stimulates cGMP accumulation in PAECs, and causes pulmonary arterial vasodilation, suggesting that ANG IV plays a role in the regulation of blood flow in the pulmonary circulation.

Hypoxia-specific upregulation of calpain activity and gene expression in pulmonary artery endothelial cells

The effects of exposure to hypoxia on the catalytic activity and mRNA expression of calpain, a calcium-regulated neutral cysteine protease, were examined in porcine pulmonary artery endothelial cells (PAECs). Specificity of the response to hypoxia was determined by comparing the effects of hypoxic exposure with exposure to oxidants such as nitrogen dioxide (NO2) and nitric oxide (NO), as well as to the sulfhydryl reactive chemical acrolein. Exposure of cells to hypoxia (0% O2) for 1 and 12 h significantly increased catalytic activity (P < 0.01 for both 1 and 12 h vs. control cells), as well as mRNA expression (P < 0.01 for 1 h and P < 0.05 for 12 h vs. control cells) of calpain. With more prolonged exposure to 24 h of hypoxia, calpain activity remained significantly elevated, whereas calpain mRNA expression returned to the control level. Calpain activities in cells exposed to NO2 [5 parts/million (ppm)] or NO (7.5 ppm) for 1 h or to acrolein (5 microM) for 1 and 24 h were unchanged. However, calpain activities in cells exposed to NO2 or NO for 24 h were significantly (P < 0.05) reduced compared with control cells. The hypoxia-induced increases in calpain mRNA content were prevented by the transcriptional inhibitor actinomycin D and by calpain inhibitor I. In addition, hypoxia increased the degradation of nuclear factor-kappaB (NF-kappaB) inhibitor IkappaB and enhanced the translocation of the p50 subunit of NF-kappaB to the nuclear membrane. Pretreatment with the calpain-specific inhibitor E-64d prevented hypoxia-induced mRNA expression and degradation of IkappaBalpha, as well as translocation of p50 subunit to the nuclear membrane. These results demonstrate for the first time that hypoxia upregulates calpain activity and mRNA expression in PAECs and that the upregulation is specific to hypoxia. Upregulation appears to involve activation of the transcription factor NF-kappaB.

Thioredoxin overexpression prevents NO-induced reduction of NO synthase activity in lung endothelial cells

We recently reported that nitric oxide (NO) induces posttranscriptional modulation of lung endothelial cell NO synthase (ecNOS) that results in loss of activity. The loss of activity can be reversed by the redox regulatory proteins thioredoxin (Thx)/thioredoxin reductase (Thx-R). The present study was designed to examine whether diminished expression of endogenous Thx and Thx-R may account for regulation of ecNOS activity in NO-exposed cells and whether overexpression of Thx can prevent NO-induced reduction of ecNOS activity in cultured porcine pulmonary artery endothelial cells (PAEC). Exposure to 8.5 ppm NO gas for 24 h resulted in an 80% decrease of Thx and a 27% decrease of Thx-R mRNA expression. Similarly, NO exposure caused 30 and 50% reductions in Thx and Thx-R protein mass, respectively. This NO-induced decrease in the expression of Thx-R mRNA and protein was accompanied by a significant (P < 0.05) decrease in the catalytic activity of Thx-R but not of glutaredoxin or the cellular levels of reduced glutathione and oxidized glutathione. Overexpression of Thx gene in PAEC was achieved by transient transfection of these cells with pcDNA 3.1 vector inserted in sense or antisense (native) orientation in a human Thx cDNA. Thx mRNA and protein contents in transfected cells were four- and threefold higher, respectively, than those in native PAEC. Exposure of native cells to 10 microM NO solution for 30 min resulted in a significant (P < 0.01) loss of ecNOS activity, whereas ecNOS activity was comparable in Thx-overexpressed cells with or without NO exposure. These results demonstrate that NO exposure results in diminished expression of Thx and Thx-R in PAEC. Endogenous levels of Thx are critical to restoring the NO-induced loss of ecNOS activity because overexpression of Thx prevented the NO-induced loss of ecNOS catalytic activity. These results also demonstrate that NO modulation of ecNOS and Thx proteins is regulated by a physiologically relevant redox mechanism.

Proinflammatory cytokines downregulate gene expression and activity of constitutive nitric oxide synthase in porcine pulmonary artery endothelial cells

We evaluated the effects of cytokines on the catalytic activity and expression of porcine pulmonary artery endothelial cell (PAEC) constitutive (eNOS) and inducible (iNOS) isoforms of nitric oxide synthase (NOS). Exposure of PAEC to the combination of IFN-gamma, TNF-alpha, and IL-1 beta did not alter iNOS activity in cytosolic and membrane fractions but significantly (p < 0.01) reduced eNOS activity in the membrane fraction, but not in the cytosolic fraction, after a 24-h exposure. The cytokine-induced loss of membrane fraction eNOS activity was associated with significant reductions of eNOS mRNA and protein content (p < 0.01 for both). Treatment with the protein synthesis inhibitor, cycloheximide, but not the transcriptional inhibitor actinomycin D prevented cytokine-induced reduction of eNOS mRNA expression. These results suggest that cytokine-induced loss of catalytic activity of eNOS is associated with a reduction in eNOS mRNA and protein mass and that cytokines alter eNOS mRNA stability. Inhibition of protein synthesis prevented reduction of eNOS mRNA by cytokines, suggesting that the mechanism by which cytokines alter eNOS mRNA stability involves protein synthesis.

Molecular cloning, characterization and expression of a nitric oxide synthase from porcine pulmonary artery endothelial cells

The lack of sequence information and clones of porcine pulmonary artery endothelial cell (PAEC) constitutive nitric oxide synthase (ecNOS) cDNA limits comparative analysis between porcine and human PAEC. Therefore, we cloned, characterized and expressed the ecNOS cDNA from porcine PAEC. Two oligonucleotide primers were designed based on the published human ecNOS cDNA sequence and used to clone porcine PAEC ecNOS using 5' and 3' rapid amplification of cDNA ends reverse transcriptase polymerase chain reaction technique. A full-length ecNOS cDNA was cloned and sequenced, representing a protein of 1205 amino acids with a molecular mass of 134 kDa. A mammalian expression vector (pcDNA3) containing this cDNA was transfected into COS-7 cells, and ecNOS activity was detected by monitoring the formation of [3H]-citrulline from [3H]-L-arginine. Expression of ecNOS activity was predominantly associated (> 90%) with the total membrane fraction of these transfected cells. The deduced amino acid sequence of porcine ecNOS cDNA, containing binding sites for NADPH, flavin adenine dinucleotide and bound flavin mononucleotide, shows 94% identity to human ecNOS. The molecular weight of porcine ecNOS mRNA was estimated to be 4.7 kb by Northern blot analysis, similar to human ecNOS mRNA. This suggests that porcine ecNOS is similar to human ecNOS in deduced amino acid sequence and structure.

Overexpression of plasma membrane annexin II in NO2-exposed pulmonary artery endothelial cells

Because exposure to nitrogen dioxide (NO2) alters plasma membrane structure and function in pulmonary artery endothelial cells (PAEC), we examined whether NO2 exposure is associated with upregulation of plasma membrane-specific proteins in PAEC. Exposure to 5 ppm NO2 for 24 h had no significant effect on total protein synthesis. However, two-dimensional gel electrophoresis of isolated plasma membranes from [35S]-methionine pulse-labeled PAEC exposed to NO2 for 24 h demonstrated 3- to 9-fold increases in the synthesis of several proteins with molecular masses of 36, 39, and 40 kDa compared with controls. N-terminal amino acid sequencing and immunodetection analysis identified the 36kDa plasma membrane protein as annexin II (lipocortin II). Northern blotting analysis demonstrated that the mRNA expression for annexin II in NO2-exposed cells was also increased. These results suggest that exposure to NO2 results in induction of plasma membrane annexin II, an important multifunctional calcium- and phospholipid-binding protein in PAEC.

Reductase domain cysteines 1048 and 1114 are critical for catalytic activity of human endothelial cell nitric oxide synthase as probed by site-directed mutagenesis

We examined whether highly conserved cysteine residues in the reductase domain of the constitutive isoform of nitric oxide synthase in human endothelial cells (ecNOS) are crucial for catalytic activity of the enzyme. Substitution of alanine for cysteines 976 (Cys-976), 991 (Cys-991), 1048 (Cys-1048), or 1114 (Cys-1114), located in the reductase domain of human ecNOS, was achieved by oligonucleotide-directed mutagenesis and expression in COS-7 cells. The specific activity of ecNOS was > 7-fold increased in wild-type and in mutants Cys-976 and Cys-991, but not in mutants Cys-1048 and Cys-1114. However, Western blot analysis indicated that expression of ecNOS protein was comparable in wild-type and in all mutants. NADPH concentration-dependent L-citrulline formation and NADPH oxidation during L-arginine metabolism were reduced in mutants Cys-1048 and Cys-1114 compared to wild-type. Similarly, NADPH cytochrome c reductase activity was increased in a time-dependent fashion in wild-type but not in mutants Cys-1048 and Cys-1114. These results indicate that Cys-1048 and Cys-1114 residues in the NADPH binding site of the reductase domain are critical for human ecNOS activity. The lack of utilization of NADPH in L-arginine metabolism and in cytochrome c reduction suggests that these active site cysteine residues may be responsible for binding of NADPH and/or for electron transfer in human ecNOS.

Nitric oxide-induced inhibition of lung endothelial cell nitric oxide synthase via interaction with allosteric thiols: role of thioredoxin in regulation of catalytic activity

Nitric oxide (NO) synthase is a hemoprotein containing several cysteinyl residues including thiolate as its proximal heme ligand. Exposure to NO is known to induce S-nitrosylation of protein thiols and modulation of enzyme activities, including the catalytic activity of NO synthase. Because S-nitrosylation of vicinal thiols promotes disulfide formation, we determined whether exposure to NO results in modulation of the catalytic activity of NO synthase and whether disulfide reduction catalyzed by thioredoxin/thioredoxin reductase (T/TR) and/or by glutaredoxin restores the catalytic activity of NO synthase in pulmonary artery endothelial cells (PAEC). Exposure of intact PAEC, isolated total membranes, plasma membranes, or purified NO synthase to NO significantly reduced NO synthase catalytic activity. Similarly, exposure of isolated total membranes or purified NO synthase to potassium ferricyanide (FeCN) also reduced catalytic activity of NO synthase in a concentration-dependent fashion. Although the catalytic activity of NO synthase was significantly reduced following exposure of intact cells to NO, the expression of NO synthase mRNA was unchanged. NO synthase activity in intact cells or isolated membranes exposed to nitrate, nitrite, or 10 ppm nitrogen dioxide gas was comparable to controls. Incubation in the presence of oxyhemoglobin prevented but did not reverse NO-induced inhibition of NO synthase. Incubation in the presence of T/TR but not glutaredoxin reversed NO-induced reduction of NO synthase activity and a purified enzyme preparation exposed directly to NO. Similarly, FeCN-induced reduction of NO synthase activity was also reversed in the presence of T/TR but not by glutaredoxin. These results demonstrate that the interaction of NO with the regulatory domain of NO synthase protein is responsible for post-translational reduction of its catalytic activity. Thioredoxin-regulated reversal of NO-induced modulation of NO synthase protein suggests that an oxidative conformational change in vicinal thiols, resulting in the formation of intramolecular or intermolecular disulfides or both, is involved.

NO2-induced expression of specific protein kinase C isoforms and generation of phosphatidylcholine-derived diacylglycerol in cultured pulmonary artery endothelial cells

The present study examines whether nitrogen dioxide (NO2)-induced activation of protein kinase C (PKC) is associated with increased expression of specific PKC isoforms and/or with enhanced generation of phosphatidylcholine(PC)-derived diacylglycerol (DAG) in pulmonary artery endothelial cells (PAEC). Western blot analysis revealed that exposure to 5 ppm NO2 resulted in increased expression of PKC alpha and epsilon isoforms in both cytosol and membrane fractions in a time-dependent fashion compared with controls. A time-dependent elevated expression of PKC isoform beta was observed in the cytosol fraction only of N02-exposed cells. PKC isoform gamma was not detectable in either the cytosolic or membrane fractions from control or N02-exposed cells. Scatchard analysis of [3h]phorbol 12,13-dibutyrate (PDBu) binding showed that exposure to N02 for 24 h increased the maximal number of binding sites (Bmax) from 15.2 +/- 2.3 pmol/mg (control) to 42.3 +/- 5.3 pmol/mg (p < 0.01, n = 4) (NO2-exposed). Exposure to NO2 significantly increased PC specific-phospholipase C and phospholipase D activities in the plasma membrane of PAEC (p < 0.05 and p < 0.001, respectively). When [3H]-myristic acid-labeled cells were exposed to NO2, significantly increased radioactivity was associated with cellular DAG. These results show for the first time that exposure of PAEC to NO2 results in elevated expression of specific PKC isoforms and in enhanced generation of cellular DAG, and the latter appears to arise largely from the hydrolysis of plasma membrane PC.

Nitrogen dioxide-induced expression of a 78 kDa protein in pulmonary artery endothelial cells

Exposure to nitrogen dioxide (NO2) activates signal transduction in cultured pulmonary artery endothelial cells (PAEC). We examined whether NO2-induced activation of signal transduction results in increased expression of proteins in PAEC. Exposure to 5 ppm NO2 for 4, 12, and 24 h had no significant effect on total protein synthesis. However, two-dimensional gel electrophoresis of [35S]-methionine-labeled PAEC exposed to NO2 for 24 h, but not 4 and 12 h, demonstrated increased synthesis of several proteins including a two- to five-fold increase of some proteins with molecular masses of 47, 64, 78, and 105 kDa compared to controls. N-terminal amino acid sequencing and immunodetection analysis identified the 78 kDa protein as 78 kDa glucose-regulated protein (GRP-78). Induction of GRP-78 by NO2 exposure was regulated at the transcriptional level, and the induction required de novo protein synthesis. Exposure to NO2 for 24 h also significantly (p < .05) decreased glycosylation of proteins in PAEC. Exposure of cell monolayers to tunicamycin, an inhibitor of protein glycosylation, mimicked the effect of NO2 exposure on expression of GRP-78. Increased expression of GRP-78 was also detected when cell monolayers were exposed to the calcium ionophore A 23187, to 2-deoxyglucose, or to glucose-free medium, which are also known to cause perturbations in protein glycosylation. These results demonstrate that exposure to NO2 increases expression of a number of proteins including GRP-78 in PAEC. Increased expression of GRP-78 in NO2-exposed cells appears to be associated with inhibition of glycosylation or through coordinated alterations in metabolic events that lead to inhibition of protein glycosylation.

Nitric oxide exposure and sulfhydryl modulation alter L-arginine transport in cultured pulmonary artery endothelial cells

The effect of nitric oxide (NO) exposure and sulfhydryl-reactive chemicals on L-arginine transport in pulmonary artery endothelial cells was evaluated. Exposure of pulmonary artery endothelial cells to 7.5 ppm (0.4 microM) NO for 4 h resulted in a significant (p < 0.05) reduction of Na(+)-dependent but not Na(+)-independent L-arginine transport. More prolonged exposure for 12-24 h reduced both Na(+)-dependent and Na(+)-independent transport of L-arginine with maximal loss of transport after 18 h of exposure (p < 0.02 for both). Similarly, incubation of cells in the presence of 50-200 microM S-nitroso-acetyl-penicillamine (SNAP) (but not 500 microM each of nitrate or nitrite) for 2 h also reduced both the Na(+)-dependent and Na(+)-independent transport of L-arginine (p < 0.05 for all concentrations). The SNAP-induced reduction of L-arginine transport was blocked by the NO scavenger oxyhemoglobin. When cell monolayers were exposed to varying concentrations of the sulfhydryl reactive chemicals N-ethylmaleimide (NEM) and acrolein, a dose-dependent reduction of L-arginine transport by both Na(+)-dependent and Na(+)-independent processes was observed. Na(+)-dependent L-arginine transport was more susceptible to inhibition by exposure to NO and to sulfhydryl reactive chemicals. Incubation of cells with 0.5 mM of the thiol-containing agent N-acetyl-L-cysteine prior to and during NEM or acrolein exposure blocked NEM and acrolein-induced reduction of L-arginine transport by both Na(+)-dependent and Na(+)-independent processes. Similarly, NO-induced reductions of Na(+)-dependent and Na(+)-independent L-arginine transport were reversed to control levels 24 h after termination of NO exposure. Treatment with the disulfide reducing agent dithiothreitol after exposure to NO resulted in partial reversal of the decreases in L-arginine transport. These results demonstrate that exposure to exogenous NO is responsible for reversible reductions of plasma membrane-dependent L-arginine transport mediated by both the Na(+)-dependent (system Bo,+) and the Na(+)-independent (system y+) transport processes. Modulation of the sulfhydryl status of plasma membrane proteins involved in L-arginine transport, such as L-arginine transporters and/or Na+/K(+)-ATPase, may be responsible, at least in part, for reductions in overall L-arginine transport in pulmonary artery endothelial cells.

Sulfhydryl-disulfide modulation and the role of disulfide oxidoreductases in regulation of the catalytic activity of nitric oxide synthase in pulmonary artery endothelial cells

The role of sulfhydryl groups (SH) and disulfide bonds as well as disulfide oxidoreductases in regulation of the catalytic activity of the membrane-bound constitutive isoform of nitric oxide (NO) synthase from porcine pulmonary artery endothelial cells (PAEC) was examined. Treatment of intact PAEC or a total membrane preparation isolated from PAEC with the SH alkylating agent N-ethylmaleimide (NEM) (10 to 50 microM) or with the intramolecular disulfide-forming agent diamide (20 to 100 microM) resulted in the reduction of NO synthase activity in a dose-dependent fashion. Similar loss of enzyme activity was observed when purified NO synthase from the membrane fraction of PAEC was incubated in the presence of NEM. The loss of membrane protein SH content from NEM- and diamide-treated preparations was associated with loss of NO synthase activity. In contrast, when intact PAEC or isolated total membranes derived from PAEC were treated with increasing concentrations (1 to 5 mM) of the disulfide-reducing agent dithiothreitol (DTT), but not oxidized DTT, NO synthase activity was increased by 20 to 85%. DTT reduction of native disulfides from NEM-treated preparations or of disulfides formed after diamide treatment of membranes reversed the inhibition of NO synthase activity. Similarly, enzymatic reduction by thioredoxin/thioredoxin reductase, but not by glutaredoxin, reversed the inhibition of membrane fraction and purified NO synthase isolated from diamide-treated cells. This enzyme-catalyzed disulfide reduction was > 1,000-fold more efficient than the DTT-induced reduction.(ABSTRACT TRUNCATED AT 250 WORDS)

Nitrogen dioxide-induced phosphatidylserine biosynthesis and subcellular translocation in cultured pulmonary artery endothelial cells

Exposure to nitrogen dioxide (NO2) increases phosphatidylserine (PS) content in the plasma membranes of pulmonary artery endothelial cells (PAEC). We examined whether the increased PS content is associated with increased uptake of L-serine and/or biosynthesis of PS. Exposure to 5 ppm NO2 increased uptake and incorporation of exogenous L-[14C]serine into whole cells, total cellular lipids, phospholipids, and phospholipid subclasses compared to control. Incorporation of L-[14C]serine into the total lipid extracts from isolated plasma membranes, mitochondria, and microsomes from NO2-exposed cells was increased by 45, 32, and 31%, respectively (p < 0.05 for all membranes). Increased incorporation of L-[14C]serine into the total phospholipids of plasma membranes, mitochondria, and microsomes of NO2-exposed cells was increased by 31, 48, and 33%, respectively (p < 0.05 for all membranes). Incorporation of L-[14C]serine into the PS of plasma membranes and microsomes from NO2-exposed cells was increased by 63 and 89%, respectively (p < 0.05 for both membranes). The incorporation of radioactivity from L-[14C]serine into the phosphatidylethanolamine and phosphatidylcholine contents of plasma membranes, mitochondria, and microsomes from NO2-exposed cells was also observed. Exposure of PAEC to NO2 resulted in a significant (p < 0.01) increase in the activity of PS synthase, the serine base-exchange enzyme located in the microsomes of these cells. When L-[14C]serine-prelabeled microsomes were incubated with unlabeled mitochondria from control and NO2-exposed cells, transfer of PS-derived radioactivity from microsomes to mitochondrial phospholipids was observed. These results demonstrate that exposure to NO2 increases uptake and incorporation of exogenous serine as well as intracellular biosynthesis of PS, resulting in increases in the PS content of PAEC and their plasma membranes.

Acrolein-induced injury to cultured pulmonary artery endothelial cells

We evaluated the specific effects of acrolein on sulfhydryl status and plasma membrane-dependent functions of cultured pulmonary artery endothelial cells. Acrolein exposure caused a dose-dependent increase in lactate dehydrogenase (LDH) release and decreases in reduced glutathione (GSH) and protein sulfhydryl (P-SH) content, whereas oxidized glutathione (GSSG) content was not altered. Exposure to 4.5 microM, but not 1.5 or 3.0 microM, of acrolein caused significant (p < 0.05) LDH release. With increasing concentrations (25 microM) of acrolein, LDH release was increased to 66% (p < 0.001). Acrolein (3.0-25 microM) resulted in 36 to 100% reductions in GSH content, whereas reductions in P-SH content at these concentrations of acrolein ranged from 11 to 37%. Uptake of amino acids (cystine, glycine, and glutamic acid) and incorporation of valine into the protein fraction were significantly reduced in a dose-dependent fashion in acrolein (1.5-4.5 microM)-exposed cells. Reductions in cystine, glycine, and glutamic acid uptakes were maximal in cells exposed to 3 and 4.5 microM acrolein (p < 0.001). Similarly, maximum reductions (p < 0.001) in both uptake and incorporation of valine into the protein fraction were observed at 3.0 and 4.5 microM acrolein. Acrolein (1.5 microM) also resulted in significant loss of plasma membrane-specific Na+/K(+)-ATPase as well as plasma membrane P-SH content (p < 0.05 for both). When cells were treated with ouabain, reductions in amino acid uptake were observed, and this appeared to mimic the effect of acrolein exposure. When isolated plasma membranes were exposed to a known SH-alkylating agent, N-ethylmaleimide, losses of Na+/K(+)-ATPase and P-SH content were observed and were similar to the effects following exposure to acrolein. These results demonstrate that acrolein exposure results in alterations of plasma membrane-dependent transport in pulmonary artery endothelial cells, leading to reduced availability of precursor amino acids used in GSH and protein synthesis. This plasma membrane injury is accompanied by reductions in the GSH and P-SH contents of these cells. Loss of the plasma membrane P-SH appears to be associated with specific inactivation of Na+/K(+)-ATPase.