Reciprocal antagonism of PIN1-APC/CCDH1 governs mitotic protein stability and cell cycle entry

Induced oncoproteins degradation provides an attractive anti-cancer modality. Activation of anaphase-promoting complex (APC/CCDH1) prevents cell-cycle entry by targeting crucial mitotic proteins for degradation. Phosphorylation of its co-activator CDH1 modulates the E3 ligase activity, but little is known about its regulation after phosphorylation and how to effectively harness APC/CCDH1 activity to treat cancer. Peptidyl-prolyl cis-trans isomerase NIMA-interacting 1 (PIN1)-catalyzed phosphorylation-dependent cis-trans prolyl isomerization drives tumor malignancy. However, the mechanisms controlling its protein turnover remain elusive. Through proteomic screens and structural characterizations, we identify a reciprocal antagonism of PIN1-APC/CCDH1 mediated by domain-oriented phosphorylation-dependent dual interactions as a fundamental mechanism governing mitotic protein stability and cell-cycle entry. Remarkably, combined PIN1 and cyclin-dependent protein kinases (CDKs) inhibition creates a positive feedback loop of PIN1 inhibition and APC/CCDH1 activation to irreversibly degrade PIN1 and other crucial mitotic proteins, which force permanent cell-cycle exit and trigger anti-tumor immunity, translating into synergistic efficacy against triple-negative breast cancer.

Clinical characteristics, racial inequities, and outcomes in patients with breast cancer and COVID-19: A COVID-19 and cancer consortium (CCC19) cohort study

Background

Limited information is available for patients with breast cancer (BC) and coronavirus disease 2019 (COVID-19), especially among underrepresented racial/ethnic populations.

Methods

This is a COVID-19 and Cancer Consortium (CCC19) registry-based retrospective cohort study of females with active or history of BC and laboratory-confirmed severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection diagnosed between March 2020 and June 2021 in the US. Primary outcome was COVID-19 severity measured on a five-level ordinal scale, including none of the following complications, hospitalization, intensive care unit admission, mechanical ventilation, and all-cause mortality. Multivariable ordinal logistic regression model identified characteristics associated with COVID-19 severity.

Results

1383 female patient records with BC and COVID-19 were included in the analysis, the median age was 61 years, and median follow-up was 90 days. Multivariable analysis revealed higher odds of COVID-19 severity for older age (aOR per decade, 1.48 [95% CI, 1.32-1.67]); Black patients (aOR 1.74; 95 CI 1.24-2.45), Asian Americans and Pacific Islander patients (aOR 3.40; 95 CI 1.70-6.79) and Other (aOR 2.97; 95 CI 1.71-5.17) racial/ethnic groups; worse ECOG performance status (ECOG PS ≥2: aOR, 7.78 [95% CI, 4.83-12.5]); pre-existing cardiovascular (aOR, 2.26 [95% CI, 1.63-3.15])/pulmonary comorbidities (aOR, 1.65 [95% CI, 1.20-2.29]); diabetes mellitus (aOR, 2.25 [95% CI, 1.66-3.04]); and active and progressing cancer (aOR, 12.5 [95% CI, 6.89-22.6]). Hispanic ethnicity, timing, and type of anti-cancer therapy modalities were not significantly associated with worse COVID-19 outcomes. The total all-cause mortality and hospitalization rate for the entire cohort was 9% and 37%, respectively however, it varied according to the BC disease status.

Conclusions

Using one of the largest registries on cancer and COVID-19, we identified patient and BC-related factors associated with worse COVID-19 outcomes. After adjusting for baseline characteristics, underrepresented racial/ethnic patients experienced worse outcomes compared to non-Hispanic White patients.

Funding

This study was partly supported by National Cancer Institute grant number P30 CA068485 to Tianyi Sun, Sanjay Mishra, Benjamin French, Jeremy L Warner; P30-CA046592 to Christopher R Friese; P30 CA023100 for Rana R McKay; P30-CA054174 for Pankil K Shah and Dimpy P Shah; KL2 TR002646 for Pankil Shah and the American Cancer Society and Hope Foundation for Cancer Research (MRSG-16-152-01-CCE) and P30-CA054174 for Dimpy P Shah. REDCap is developed and supported by Vanderbilt Institute for Clinical and Translational Research grant support (UL1 TR000445 from NCATS/NIH). The funding sources had no role in the writing of the manuscript or the decision to submit it for publication.

Clinical trial number

CCC19 registry is registered on ClinicalTrials.gov, NCT04354701.

Simultaneous isolation of hormone receptor-positive breast cancer organoids and fibroblasts reveals stroma-mediated resistance mechanisms

Recurrent hormone receptor-positive (HR+) breast cancer kills more than 600,000 women annually. Although HR+ breast cancers typically respond well to therapies, approximately 30% of patients relapse. At this stage, the tumors are usually metastatic and incurable. Resistance to therapy, particularly endocrine therapy is typically thought to be tumor intrinsic (e.g., estrogen receptor mutations). However, tumor-extrinsic factors also contribute to resistance. For example, stromal cells, such as cancer-associated fibroblasts (CAFs), residing in the tumor microenvironment, are known to stimulate resistance and disease recurrence. Recurrence in HR+ disease has been difficult to study due to the prolonged clinical course, complex nature of resistance, and lack of appropriate model systems. Existing HR+ models are limited to HR+ cell lines, a few HR+ organoid models, and xenograft models that all lack components of the human stroma. Therefore, there is an urgent need for more clinically relevant models to study the complex nature of recurrent HR+ breast cancer, and the factors contributing to treatment relapse. Here, we present an optimized protocol that allows a high take-rate, and simultaneous propagation of patient-derived organoids (PDOs) and matching CAFs, from primary and metastatic HR+ breast cancers. Our protocol allows for long-term culturing of HR+ PDOs that retain estrogen receptor expression and show responsiveness to hormone therapy. We further show the functional utility of this system by identifying CAF-secreted cytokines, such as growth-regulated oncogene α , as stroma-derived resistance drivers to endocrine therapy in HR+ PDOs.

Clinical Characteristics, Racial Inequities, and Outcomes in Patients with Breast Cancer and COVID-19: A COVID-19 and Cancer Consortium (CCC19) Cohort Study

Background

Limited information is available for patients with breast cancer (BC) and coronavirus disease 2019 (COVID-19), especially among underrepresented racial/ethnic populations.

Methods

This is a COVID-19 and Cancer Consortium (CCC19) registry-based retrospective cohort study of females with active or history of BC and laboratory-confirmed severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection diagnosed between March 2020 and June 2021 in the US. Primary outcome was COVID-19 severity measured on a five-level ordinal scale, including none of the following complications, hospitalization, intensive care unit admission, mechanical ventilation, and all-cause mortality. Multivariable ordinal logistic regression model identified characteristics associated with COVID-19 severity.

Results

1,383 female patient records with BC and COVID-19 were included in the analysis, the median age was 61 years, and median follow-up was 90 days. Multivariable analysis revealed higher odds of COVID-19 severity for older age (aOR per decade, 1.48 [95% CI, 1.32 - 1.67]); Black patients (aOR 1.74; 95 CI 1.24-2.45), Asian Americans and Pacific Islander patients (aOR 3.40; 95 CI 1.70 - 6.79) and Other (aOR 2.97; 95 CI 1.71-5.17) racial/ethnic groups; worse ECOG performance status (ECOG PS ≥2: aOR, 7.78 [95% CI, 4.83 - 12.5]); pre-existing cardiovascular (aOR, 2.26 [95% CI, 1.63 - 3.15])/pulmonary comorbidities (aOR, 1.65 [95% CI, 1.20 - 2.29]); diabetes mellitus (aOR, 2.25 [95% CI, 1.66 - 3.04]); and active and progressing cancer (aOR, 12.5 [95% CI, 6.89 - 22.6]). Hispanic ethnicity, timing and type of anti-cancer therapy modalities were not significantly associated with worse COVID-19 outcomes. The total all-cause mortality and hospitalization rate for the entire cohort was 9% and 37%, respectively however, it varied according to the BC disease status.

Conclusions

Using one of the largest registries on cancer and COVID-19, we identified patient and BC related factors associated with worse COVID-19 outcomes. After adjusting for baseline characteristics, underrepresented racial/ethnic patients experienced worse outcomes compared to Non-Hispanic White patients.

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.

Abstract P1-14-02: Phase II study of adjuvant endocrine therapy with CDK 4/6 inhibitor, ribociclib, for localized ER+/HER2- breast cancer (LEADER, part 1)

Background: CDK 4/6 inhibitors have demonstrated substantial efficacy in treating ER+/HER2- metastatic breast cancer. Therefore, there is great interest in exploring their ability to reduce recurrence risk in early breast cancer. However, conflicting results were observed in the large adjuvant phase 3 clinical trials investigating combination of endocrine therapy and CDK 4/6 inhibitor (PALLAS, MONARCH-E). While these adjuvant clinical trials evaluated upfront use of CDK 4/6 inhibitor, the optimal timing of adding CDK 4/6 inhibitor for HR+/HER2- breast cancer remains unknown. We conducted a prospective phase II clinical trial to evaluate the addition of a CDK 4/6 inhibitor, ribociclib, in patients who were already on adjuvant endocrine therapy. Methods: In part 1 of the clinical trial, eligibility included patients with localized stage I-III ER+ (≥ 10%), HER2- breast cancer; completed surgery; and were on adjuvant endocrine therapy (any number of years) with at least one year or more of treatment remaining. Patients were randomized to two different ribociclib schedules: continuous (400 mg daily of 28-day cycle; arm 1) or intermittent (600 mg daily on days 1-21 of 28-day cycle; arm 2) for one year. Patients were concurrently treated with an aromatase inhibitor (plus GnRH agonist if premenopausal). Tolerance was evaluated via CTCAE version 4.03 and proportion of subjects who discontinued CDK 4/6 treatment early. Stratification factors for statistical analysis included: disease stage (III vs lower), duration of prior endocrine therapy (within 2 years; 2-5 years vs &gt; 5 years), and whether the patient received prior chemotherapy or not. Baseline characteristics and risk factors for recurrence and for early discontinuation were compared between the arms of the study using Pearson's chi-squared test. Actuarial analysis of time to recurrence was done using the Kaplan-Meier estimator. The primary objective of part 1 was to estimate adherence to ribociclib treatment in the adjuvant setting. Results: In total, 81 patients were enrolled between February 2018 and September 2019, and 25 (31%) discontinued ribociclib treatment early, with no significant difference between study arms. The most common grade 3 or greater adverse events (AEs) leading to study discontinuation were neutropenia (44%), alanine aminotransferase increase (28%), and aspartate aminotransferase increase (16%). Among patients who discontinued early, neutropenia was more frequent in the 600 mg arm, 9 of 12 patients (75%), versus 2 of 13 patients (15%) in the 400 mg arm. No patients discontinued early due to prolonged QTc. Ribociclib was dose reduced for 22 patients (27%), with no significant difference between study arms (p = 0.12). After a median follow-up of 20 months, two patients have experienced disease recurrence with recurrence-free survival of 100% at 1 year and 97% (95% CI 88-99%) at 2 years. Biomarker (ctDNA) results will be reported at the meeting. Conclusions: Results demonstrate that while serious AEs with one year of adjuvant ribociclib are low, a substantial number of patients discontinued adjuvant CDK 4/6 inhibitor within 1 year. Overall, with limited follow-up, only two patients had recurrent disease since completion of ribociclib treatment. Tolerability and identifying patient subsets who will most benefit need to be carefully considered with CDK 4/6 inhibitors in the adjuvant setting.

Citation Format: Laura M Spring, Lauren Scarpetti, Andrzej Niemierko, Steven J Isakoff, Beverly Moy, Seth A Wander, Elisabeth Smith, Elizabeth Abraham, Jennifer Shin, Jaymin M Patel, Amy Comander, Therese Mulvey, Aditya Bardia. Phase II study of adjuvant endocrine therapy with CDK 4/6 inhibitor, ribociclib, for localized ER+/HER2- breast cancer (LEADER, part 1) [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P1-14-02.

The CoVID-TE risk assessment model for venous thromboembolism in hospitalized patients with cancer and COVID-19

BACKGROUND

Hospitalized patients with COVID-19 have increased risks of venous (VTE) and arterial thromboembolism (ATE). Active cancer diagnosis and treatment are well-known risk factors; however, a risk assessment model (RAM) for VTE in patients with both cancer and COVID-19 is lacking.

OBJECTIVES

To assess the incidence of and risk factors for thrombosis in hospitalized patients with cancer and COVID-19.

METHODS

Among patients with cancer in the COVID-19 and Cancer Consortium registry (CCC19) cohort study, we assessed the incidence of VTE and ATE within 90 days of COVID-19-associated hospitalization. A multivariable logistic regression model specifically for VTE was built using a priori determined clinical risk factors. A simplified RAM was derived and internally validated using bootstrap.

RESULTS

From March 17, 2020 to November 30, 2020, 2804 hospitalized patients were analyzed. The incidence of VTE and ATE was 7.6% and 3.9%, respectively. The incidence of VTE, but not ATE, was higher in patients receiving recent anti-cancer therapy. A simplified RAM for VTE was derived and named CoVID-TE (Cancer subtype high to very-high risk by original Khorana score +1, VTE history +2, ICU admission +2, D-dimer elevation +1, recent systemic anti-cancer Therapy +1, and non-Hispanic Ethnicity +1). The RAM stratified patients into two cohorts (low-risk, 0-2 points, n = 1423 vs. high-risk, 3+ points, n = 1034) where VTE occurred in 4.1% low-risk and 11.3% high-risk patients (c statistic 0.67, 95% confidence interval 0.63-0.71). The RAM performed similarly well in subgroups of patients not on anticoagulant prior to admission and moderately ill patients not requiring direct ICU admission.

CONCLUSIONS

Hospitalized patients with cancer and COVID-19 have elevated thrombotic risks. The CoVID-TE RAM for VTE prediction may help real-time data-driven decisions in this vulnerable population.

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.

Safety and activity of single-agent giredestrant (GDC-9545) from a phase Ia/b study in patients (pts) with estrogen receptor-positive (ER+), HER2-negative locally advanced/metastatic breast cancer (LA/mBC)

1017

Background: Targeting ER activity and/or E synthesis is a mainstay of ER+ BC treatment, but many pts relapse during/after adjuvant endocrine therapy (ET) or develop resistance via ESR1 mutations that drive E-independent transcription and proliferation. Most tumors remain ER signaling-dependent and pts may respond to second-/third-line ET after disease progression (PD) on prior therapies (Di Leo 2010; Baselga 2012). Giredestrant, a highly potent, nonsteroidal oral selective ER degrader, achieves robust ER occupancy, is active despite ESR1 mutations, and was well tolerated ± palbociclib with encouraging antitumor activity in the nonrandomized, open-label, dose-escalation and -expansion, phase Ia/b GO39932 study (NCT03332797; Jhaveri 2019; Lim 2020). We present updated interim data from the dose-escalation and -expansion single-agent giredestrant cohorts. Methods: Pts had ≤2 prior therapies in the LA/mBC setting with disease recurrence/PD while being treated with adjuvant ET for ≥24 mo and/or ET in the LA/mBC setting, and derived a clinical benefit (CB) from therapy (tumor response/stable disease [SD] ≥6 mo). Pts received 10, 30, 90/100, or 250 mg PO giredestrant QD on D1–28 of each 28-day cycle. Pts were postmenopausal (medical menopause on LHRH agonists was allowed with ≥100 mg giredestrant). Results: Clinical cutoff: Jul 31, 2020; median prior therapy lines in the LA/mBC setting: 1; mean dose intensity: 98%. Safety/activity: see the table below. No adverse events (AEs) led to study drug withdrawal. No dose-limiting toxicities (DLTs) occurred; maximum tolerated dose was not reached. Most common AEs in 107 pts: fatigue (22; 21%), arthralgia (18; 17%), and nausea (17; 16%); largely grade 1/2. Related grade 3 AEs were infrequent (5; 5%); none were grade 4/5 per investigator assessment (grade 5 duodenal perforation occurred with 90/100 mg after stopping giredestrant due to PD). 8 (7%) had bradycardia (none with 10 mg or the 30 mg phase 3 dose; all grade 1 except one grade 2 at 250 mg; no treatment interruptions/dose reductions were required). Objective responses and CB were observed at all doses. Conclusions: Single-agent giredestrant was well tolerated at all doses, with no DLTs. AEs were generally low grade and in keeping with expected AEs for ETs. Clinical activity was observed at all doses. Updated data, including biomarker and correlative data, will be presented. Clinical trial information: NCT03332797 .[Table: see text]

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.

Time to SARS-CoV-2 clearance among patients with cancer and COVID-19

Background

For cancer patients, coronavirus disease 19 (COVID‐19) infection can lead to delays in cancer therapy both due to the infection itself and due to the need to minimize exposure to other patients and to staff. Clearance guidelines have been proposed, but expected time to clearance has not been established.

Methods

We identified all patients at a tertiary care hospital cancer center between 25 March 2020 and 6 June 2020 with a positive nasopharyngeal reverse transcriptase polymerase chain reaction (RT‐PCR) test for the severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2), a cancer‐related visit within 3 years, and at least one follow‐up assay. We determined the time to clearance using American Society of Clinical Oncology (ASCO), the UK National Institute for Health and Care Excellence (UK‐NICE), and Centers for Disease Control and Prevention (CDC) criteria. A matched non‐cancer comparison cohort was also identified.

Results

Thirty‐two cancer patients were identified. Nineteen were cleared by ASCO criteria, with estimated median time to clearance of 50 days. Fourteen patients resumed chemotherapy prior to clearance. Using UK‐NICE criteria, median time to clearance would have been 31 days, and using CDC criteria, it would have been 13 days. The matched non‐cancer cohort had similar clearance time, but with less frequent testing.

Conclusion

SARS‐CoV‐2 clearance times differ substantially depending on the criteria used and may be prolonged in cancer patients. This could lead to a delay in cancer care, increased use of clearance testing, and extension of infection control precautions.

Outcomes of COVID-19 in Patients With a History of Cancer and Comorbid Cardiovascular Disease

BACKGROUND

Cancer and cardiovascular disease (CVD) are independently associated with adverse outcomes in patients with COVID-19. However, outcomes in patients with COVID-19 with both cancer and comorbid CVD are unknown.

METHODS

This retrospective study included 2,476 patients who tested positive for SARS-CoV-2 at 4 Massachusetts hospitals between March 11 and May 21, 2020. Patients were stratified by a history of either cancer (n=195) or CVD (n=414) and subsequently by the presence of both cancer and CVD (n=82). We compared outcomes between patients with and without cancer and patients with both cancer and CVD compared with patients with either condition alone. The primary endpoint was COVID-19-associated severe disease, defined as a composite of the need for mechanical ventilation, shock, or death. Secondary endpoints included death, shock, need for mechanical ventilation, need for supplemental oxygen, arrhythmia, venous thromboembolism, encephalopathy, abnormal troponin level, and length of stay.

RESULTS

Multivariable analysis identified cancer as an independent predictor of COVID-19-associated severe disease among all infected patients. Patients with cancer were more likely to develop COVID-19-associated severe disease than were those without cancer (hazard ratio [HR], 2.02; 95% CI, 1.53-2.68; P<.001). Furthermore, patients with both cancer and CVD had a higher likelihood of COVID-19-associated severe disease compared with those with either cancer (HR, 1.86; 95% CI, 1.11-3.10; P=.02) or CVD (HR, 1.79; 95% CI, 1.21-2.66; P=.004) alone. Patients died more frequently if they had both cancer and CVD compared with either cancer (35% vs 17%; P=.004) or CVD (35% vs 21%; P=.009) alone. Arrhythmias and encephalopathy were also more frequent in patients with both cancer and CVD compared with those with cancer alone.

CONCLUSIONS

Patients with a history of both cancer and CVD are at significantly higher risk of experiencing COVID-19-associated adverse outcomes. Aggressive public health measures are needed to mitigate the risks of COVID-19 infection in this vulnerable patient population.

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.

Time to COVID-19 RT-PCR clearance among patients with cancer

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Background: COVID-19 in oncologic patients presents a clinical dilemma. To reduce the risk of adverse events as well as the risk of exposing others, many institutions have established protocols to define COVID-19 clearance. However, the optimal criteria for discontinuing infection precautions and/or resuming anticancer therapy in COVID-19 patients is unknown. Methods: We identified patients with a positive COVID-19 PCR at a tertiary care hospital between 3/25/2020 and 6/6/2020, and who also had seen an oncologist for a cancer-related diagnosis within the last 3 years. COVID-19 PCR testing was performed using the Abbott Laboratories m2000 platform in conjunction with either the Aldatu Biosciences PANDAA qDxTM SARS-CoV-2 or Abbott RealTime SARS-CoV-2 assays. At our institution, and per current ASCO guidelines, discontinuation of COVID-19 precautions requires two consecutive negative viral PCR tests > 24 hours apart. Results: During the follow-up period, we identified 32 patients with a positive COVID-19 PCR who were receiving active oncology care. Half of this cohort (16/32) had metastatic disease at the time of COVID-19 diagnosis. 17 patients were on active treatment at time of COVID-19 diagnosis (8 receiving cytotoxic chemotherapy). Among patients who met criteria for COVID-19 PCR clearance, median time to clearance was 37 days (range, 10-58 days). When accounting for censoring at the time of last COVID-19 assay, median time to clearance for all patients was estimated at 50 days. 14 patients resumed anti-cancer treatment prior to COVID-19 clearance (5 received cytotoxic chemotherapy), requiring substantial allocation of staff and resources for safe treatment isolated from other oncology patients. Among the 13 patients who met clearance criteria, 2 subsequently had a positive COVID-19 PCR after resumption of treatment. We explored COVID-19 clearance time under an alternative symptom/time based strategy based on CDC criteria (at least 10 days after first positive PCR and 3 days after last day of symptoms). Under this strategy, median time to COVID-19 clearance would be 14 days. Conclusions: In patients with cancer who develop COVID-19 infection, viral shedding can persist for many weeks after disease onset, but the implications of this shedding on likelihood of infection is unknown. Treatment of COVID-19 positive oncology patients requires substantial planning and resources. Test-based versus symptom/time-based strategies for determining discontinuation of precautions and resumption of treatment should be further investigated to provide safe and effective care.

Time to SARS-CoV-2 Clearance Among Patients with Cancer and COVID-19

QUESTION

What is the median time to clearance of SARS-CoV-2 among cancer patients according to currently used criteria?

FINDINGS

In this single-institution retrospective cohort study, the median time to SARS-CoV-2 clearance was 50 days using the ASCO/CDC criteria of 2 negative RT-PCR assays >24 hours apart. Using alternative criteria of 1 negative RT-PCR assay (UK-NICE) or CDC clinical criteria (10 days after first positive RT-PCR and 3 days after last symptoms), median clearance times were 31 days and 13 days, respectively. Meaning: SARS-CoV-2 clearance times differ substantially depending on criteria used and may be prolonged in cancer patients.

Retinoblastoma protein expression and its predictors in triple-negative breast cancer

Retinoblastoma protein (Rb) is a product of the RB tumor suppressor gene. Its expression is highly prevalent in luminal breast cancers and is critical to the success of cyclin-dependent kinase (CDK) 4/6 inhibitor therapy. Expression of Rb in triple-negative breast cancer (TNBC), tumors generally associated with basal biology, is not well known. However, heterogeneity among TNBC and presence of subtypes with luminal features are well described. The purpose of this study was to determine prevalence and predictors of Rb protein expression in BRCA1-associated and sporadic TNBCs. We studied 180 TNBC patients (70 BRCA1-associated and 110 sporadic). The clinical and pathologic features of these cases were previously assessed and reported. For this study, immunohistochemical stains for Rb were performed on tissue microarray sections. Details of treatment and outcome were abstracted from medical records. Fifty-one percent of TNBC were Rb positive (≥10% nuclei staining), and 85% of these cases had ≥50% nuclei staining. Rb expression was significantly associated with sporadic TNBC (71.4% vs 49.4%; p < 0.001), androgen receptor (AR) expression (16.5% vs 3.4%; p = 0.007), histologic grade 1 or 2 (9.9% vs 2.2%; p = 0.04), and first recurrence in bone (8.8% vs 1.1%; p = 0.03). Expression of p53 was not associated with Rb expression. Expression of Rb in TNBC was significantly associated with sporadic TNBC, AR expression, lower histologic grade, and metastasis to bone. These observations characterize a TNBC subtype with features suggestive of luminal-like biology and the potential to benefit from CDK 4/6 inhibition.

Phase II study of adjuvant endocrine therapy with CDK 4/6 inhibitor, ribociclib, for localized ER+/HER2- breast cancer (LEADER)

531

Background: Given the success of CDK 4/6 inhibitors for ER+/HER2- metastatic breast cancer, there is much interest in exploring these agents in early breast cancer to potentially reduce recurrence risk. However, tolerability and adherence are important considerations in the adjuvant setting. We evaluated the tolerability and adherence of adjuvant endocrine therapy with the CDK 4/6 inhibitor, ribociclib, in two different schedules, in a prospective phase II clinical trial. Methods: Eligible patients were those with localized stage I-III ER+ (≥ 10%), HER2- breast cancer who had completed surgery and were on adjuvant endocrine therapy with at least one year or more of treatment remaining. Patients were randomized to receive continuous ribociclib (400 mg daily of 28-day cycle; arm 1) or intermittent ribociclib (600 mg daily on days 1-21 of 28-day cycle; arm 2) for one year, in addition to an aromatase inhibitor (plus GnRH agonist if premenopausal). Toxicities were evaluated using CTCAE version 4.03. Adherence was monitored by review of patient diaries and pill count. Results: Of the 81 patients enrolled, 24 discontinued early. The table shows the current status of the patients based on treatment arm (data cut-off as of 1/31/20; updated results will be presented at meeting). A total of 8 serious adverse events (AEs) have occurred thus far: grade 3 transaminitis (1), grade 4 transaminitis (3), grade 3 colitis (1), grade 3 infection (2), and grade 4 lymphopenia (1). The most common grade 3 or greater AEs leading to study discontinuation thus far were transaminitis (8.6%), neutropenia (2.5%), and fatigue (2.5%). No patients discontinued early due to prolonged QTc. Adherence results will be reported at the meeting. Conclusions: Interim results demonstrate that while serious AEs with one year of adjuvant ribociclib are low, a number of patients discontinued adjuvant CDK 4/6 inhibitor. Tolerability and adherence patterns will need to be carefully considered with CDK 4/6 inhibitors in the adjuvant setting. Clinical trial information: NCT03285412 . [Table: see text]

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.

Abstract 2773: A DNA-damaging lupus autoantibody synergizes with PARP inhibitors against DNA repair-deficient tumor cells

The lupus anti-DNA autoantibody 3E10 is a compelling candidate for development as a targeted therapy for DNA repair-deficient malignancies. 3E10 has previously been shown to localize to tumors due to its attraction to DNA released by dying cancer cells, penetrate into cell nuclei, inhibit DNA repair, and kill cancer cells with defects in homology-directed repair (HDR) of DNA double-strand breaks. A more potent derivative of 3E10 with increased affinity for DNA has been developed (referred to here as 3E10EN), and identification of optimal combination therapies with 3E10EN is needed to facilitate planning for upcoming clinical trials. In the present study, we found that 3E10EN increases the activity of the DNA repair enzyme poly (ADP-ribose) polymerase (PARP) in HDR-deficient cells and hypothesized that combination treatment with 3E10EN and PARP inhibitors (PARPi) would yield synergistic effects on HDR-deficient cancer cell survival.

PARP content and activity in HDR-deficient and proficient cells prior to and following treatment with 3E10EN was evaluated. 3E10EN did not impact PARP protein content but yielded a significant increase in pADPr signal in HDR-deficient cells, which suggests a compensatory increase in PARP activity in response to DNA damage accumulation in HDR-deficient cells. Combinations of 3E10EN and the PARPi olaparib were tested on a panel of HDR-deficient cells, and a matched pair of BRCA2-deficient and proficient DLD1 cells. Olaparib inhibited the increase in pADPr caused by 3E10EN, and colony formation assays analyzed by the Chou-Talalay method confirmed that 3E10EN and olaparib synergized against HDR-deficient cancer cells. Conversely, HDR-proficient cells were resistant to 3E10EN and olaparib combination treatment.

The original 3E10 is a murine antibody isolated from a lupus mouse model, and in preparation for its further development as a new drug we have recently designed Deoxymab 1 (DX1), a humanized version of 3E10EN. DX1 exhibits improved activity relative to the 3E10EN prototype, and when tested on a panel of HDR-deficient and proficient cells, DX1 and olaparib exhibited synergistic effects similar to that observed with the 3E10EN prototype.

In conclusion, we have found that both the prototype 3E10EN and humanized DX1 synergize with PARPi against HDR-deficient tumor cells. These findings provide the rationale for further studies to determine the potential for this approach to be translated into a clinically relevant therapeutic strategy.

Citation Format: Zahra Rattray, Jaymin M. Patel, Philip W. Noble, Valentina Dubljevic, Deanne L. Greenwood, James A. Campbell, James E. Hansen. A DNA-damaging lupus autoantibody synergizes with PARP inhibitors against DNA repair-deficient tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2773.

Retinoblastoma (Rb) protein expression in triple-negative breast cancer

1097

Background: Expression of Rb, the protein product of the RB tumor suppressor gene, is required for cyclin D kinase (CDK) 4/6 inhibition in luminal breast cancers. Triple negative breast cancers (TNBC) frequently exhibit Rb loss and are thus believed to be poor candidates for CDK4/6 inhibition. However, the features associated with Rb loss in TNBC are poorly-defined. We aimed to assess whether TNBC that express the androgen receptor (AR) and resemble a more luminal subtype retain Rb more often than other TNBC. Methods: To assess the frequency and correlates of Rb expression in TNBC, we stained tissue microarrays (TMAs) containing 180 Stage I-III TNBC, 71 with germline BRCA1 mutations ( BRCA1+) and 109 without BRCA1 mutation (sporadic), using a mouse monoclonal antibody to human Rb (clone G3-245, BD Biosciences). Assessment of tumor size, histologic type, grade, lymphovascular invasion and lymph node status were assessed on histologic review. The TMAs, containing three 0.6mm cores/tumor, had been previously stained for AR, CK5/6, CK14 and EGFR. Log-binomial regression was used to calculate risk ratios (RR). Results: Fifty percent of TNBC were Rb-positive (Rb+; ≥10% nuclei staining) of which 84.4% had > 50% nuclei staining. Among TNBC that were Rb-negative, 76.6% had < 1% nuclei staining for Rb. AR expression (≥10% nuclei staining) was more common in Rb+ than Rb-negative TNBC (16.7% vs 4.5%; p = 0.01). In addition, Rb expression was significantly more common among sporadic than BRCA1+ TNBC (59.6% vs 35.2%, p = 0.001). Compared with Rb-negative TNBC, Rb+ tumors were associated with older age (mean 48.7 vs 45.7 years; p = 0.06) and lower histologic grade (grade 1 or 2: 9.2% vs 2.2%; p = 0.05). No other clinical or pathologic features were significantly associated with Rb status. In a multivariable model, both AR expression (RR, 1.65; 95% CI, 1.31-2.08) and lack of BRCA1 mutation (RR, 1.63; 95% CI, 1.17-2.29) significantly predicted for Rb expression among TNBC. Conclusions: Sporadic TNBC is significantly more likely to be Rb+ than BRCA1+ TNBC. Among TNBC, AR expression significantly predicts for Rb expression. These results suggest clinically relevant biomarkers that may predict for Rb expression and potential targeted therapies in TNBC.

Abstract 4276: Engineering a trivalent lupus anti-DNA autoantibody fragment for cancer therapy

Discovery and design of agents that selectively kill malignant cells but spare normal tissue is critical to the development of effective cancer therapies. 3E10 is a lupus anti-DNA autoantibody that penetrates cell nuclei, binds DNA and inhibits DNA repair in a manner that does not kill normal cells but is synthetically lethal to cancer cells with defective homology-directed repair of DNA double-strand breaks due to BRCA2-deficiency. To develop a more potent version of 3E10 for further testing in cancer therapy, we have engineered a trivalent fragment of 3E10 with mutations that enhance nuclear penetration and DNA binding. cDNA encoding a tandem trivalent single chain variable fragment of 3E10 (3E10 tri-scFv) with the D31N enhancing mutation in CDR1 of the heavy chain variable regions was designed and cloned into the pPICZαA yeast expression vector. 3E10 tri-scFv was expressed in and purified from Pichia pastoris. Biochemical characterization of 3E10 tri-scFv by SDS-PAGE and Western blotting confirmed purification of the expected protein product, and cell-penetration assays demonstrated increased efficacy of nuclear uptake by 3E10 tri-scFv. Clonogenic survival assays with BRCA2-deficient cancer cells similarly indicated enhanced synthetic lethality mediated by 3E10 tri-scFv. These findings indicate 3E10 tri-scFv is a promising candidate for further development as a targeted therapy for DNA repair-deficient malignancies and demonstrate the potential utility in engineering multivalent derivatives of other promising lupus autoantibodies intended for development as targeted cancer therapies.

Citation Format: Jaymin M. Patel, Phil W. Noble, Grace Chan, Richard H. Weisbart, James E. Hansen. Engineering a trivalent lupus anti-DNA autoantibody fragment for cancer therapy. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 4276. doi:10.1158/1538-7445.AM2015-4276

Melphalan, lenalidomide and dexamethasone for the treatment of immunoglobulin light chain amyloidosis: results of a phase II trial

We report results of a phase II trial of combination of melphalan, lenalidomide, and dexamethasone for the treatment of immunoglobulin light chain (AL) amyloidosis. The primary objectives were tolerability and hematologic response rate; secondary objectives were organ responses and survival. Treatment protocol consisted of melphalan 5 mg/m(2)/day for four days, lenalidomide 10 mg/day for 21 days and dexamethasone 20-40 mg once a week every 28 days for a total of 12 cycles. Sixteen subjects were enrolled of whom 14 completed at least 3 cycles and were evaluable for response. Grade 3/4 toxicities were experienced by 88% (n=14), the most common being myelosuppression (n=7). Dose reductions occurred in 85% (n=12 of 14) of subjects. Hematologic partial and complete responses were achieved by 43% (n=6 of 14) and 7% (n=1 of 14), respectively. The median overall survival has not been reached and median progression-free survival is 24 months. In conclusion, this combination is associated with significant myelosuppression leading to dose modifications and producing minor hematologic responses in AL amyloidosis. http://clinicaltrials.gov/ct2/show/NCT00679367.

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.

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.