The hydrocortisone-responsive urinary metabolome of premature infants

BACKGROUND

Extremely premature infants are at risk for circulatory collapse or respiratory failure that are often treated with hydrocortisone (HC); however, there is no information on the metabolic consequences of this therapy.

METHODS

Longitudinal urine samples from infants <28 weeks gestation in the Trial of Late Surfactant were analyzed by untargeted UHPLC:MS/MS. Fourteen infants who received a tapering course of HC beginning at 3 mg/kg/day for ≥9 days were compared to 14 matched control infants. A secondary cross-sectional analysis by logistic regression used urines from 314 infants.

RESULTS

Of 1145 urinary metabolites detected, abundance of 219, representing all the major biochemical pathways, changed at p < 0.05 in the HC-treated group with 90% decreasing; 3 cortisol derivatives increased ~2-fold with HC therapy. Only 11% of regulated metabolites remained responsive at the lowest HC dose. Regulated metabolites included two steroids and thiamin that are associated with lung inflammation in infants. HC responsiveness was confirmed in 57% of metabolites by cross-sectional analysis.

CONCLUSIONS

HC treatment of premature infants influenced in a dose-dependent manner abundance of 19% of identified urinary metabolites of diverse biochemical systems, primarily reducing concentrations. These findings indicate that exposure to HC reversibly impacts the nutritional status of premature infants.

IMPACT

Hydrocortisone treatment of premature infants with respiratory failure or circulatory collapse alters levels of a subset of urinary metabolites representing all major biochemical pathways. This is the first description of the scope, magnitude, timing and reversibility of metabolomic changes in infants in response to hydrocortisone, and it confirms corticosteroid regulation of three biochemicals that are associated with lung inflammatory status. The findings indicate a dose-dependency of hydrocortisone for metabolomic and anti-inflammatory effects, that prolonged therapy may lower the supply of many nutrients, and that monitoring concentrations of cortisol and inflammation markers may be a useful clinical approach during corticosteroid therapy.

The Urinary Metabolomic Fingerprint in Extremely Preterm Infants on Total Parenteral Nutrition vs. Enteral Feeds

Total Parenteral Nutrition (TPN), which uses intravenous administration of nutrients, minerals and vitamins, is essential for sustaining premature infants until they transition to enteral feeds, but there is limited information on metabolomic differences between infants on TPN and enteral feeds. We performed untargeted global metabolomics on urine samples collected between 23-30 days of life from 314 infants born <29 weeks gestational age from the TOLSURF and PROP cohorts. Principal component analysis across all metabolites showed a separation of infants solely on TPN compared to infants who had transitioned to enteral feeds, indicating global metabolomic differences between infants based on feeding status. Among 913 metabolites that passed quality control filters, 609 varied in abundance between infants on TPN vs. enteral feeds at p < 0.05. Of these, 88% were in the direction of higher abundance in the urine of infants on enteral feeds. In a subset of infants in a longitudinal analysis, both concurrent and delayed changes in metabolite levels were observed with the initiation of enteral feeds. These infants had higher concentrations of essential amino acids, lipids, and vitamins, which are necessary for growth and development, suggesting the nutritional benefit of an enteral feeding regimen.

Composition and origin of lung fluid proteome in premature infants and relationship to respiratory outcome

Background

Infants born at extremely low gestational age are at high risk for bronchopulmonary dysplasia and continuing lung disease. There are no early clinical biomarkers for pulmonary outcome and limited therapeutic interventions.

Objectives

We performed global proteomics of premature infant tracheal aspirate (TA) and plasma to determine the composition and source of lung fluid proteins and to identify potential biomarkers of respiratory outcome.

Methods

TA samples were collected from intubated infants in the TOLSURF cohort before and after nitric oxide treatment, and plasma was collected from NO CLD infants. Protein abundance was assayed by HPLC/tandem mass spectrometry and Protein Prospector software. mRNA abundance in mid-gestation fetal lung was assessed by RNA sequencing. Pulmonary morbidity was defined as a need for ventilatory support at term and during the first year.

Results

Abundant TA proteins included albumin, hemoglobin, and actin-related proteins. 96 of 137 detected plasma proteins were present in TA (r = 0.69, p<0.00001). Based on lung RNAseq data, ~88% of detected TA proteins in injured infant lung are derived at least in part from lung epithelium with overrepresentation in categories of cell membrane/secretion and stress/inflammation. Comparing 37 infants at study enrollment (7–14 days) who did or did not develop persistent pulmonary morbidity, candidate biomarkers of both lung (eg., annexin A5) and plasma (eg., vitamin D-binding protein) origin were identified. Notably, levels of free hemoglobin were 2.9-fold (p = 0.03) higher in infants with pulmonary morbidity. In time course studies, hemoglobin decreased markedly in most infants after enrollment coincident with initiation of inhaled nitric oxide treatment.

Conclusions

We conclude that both lung epithelium and plasma contribute to the lung fluid proteome in premature infants with lung injury. Early postnatal elevation of free hemoglobin and heme, which are both pro-oxidants, may contribute to persistent lung disease by depleting nitric oxide and increasing oxidative/nitrative stress.

Dose-escalation trial of budesonide in surfactant for prevention of bronchopulmonary dysplasia in extremely low gestational age high-risk newborns (SASSIE)

BACKGROUND

Initial trials of lung-targeted budesonide (0.25 mg/kg) in surfactant to prevent bronchopulmonary dysplasia (BPD) in premature infants have shown benefit; however, the optimal safe dose is unknown.

METHODS

Dose-escalation study of budesonide (0.025, 0.05, 0.10 mg/kg) in calfactatant in extremely low gestational age neonates (ELGANs) requiring intubation at 3-14 days. Tracheal aspirate (TA) cytokines, blood budesonide concentrations, and untargeted blood metabolomics were measured. Outcomes were compared with matched infants receiving surfactant in the Trial Of Late SURFactant (TOLSURF).

RESULTS

Twenty-four infants with mean gestational age 25.0 weeks and 743 g birth weight requiring mechanical ventilation were enrolled at mean age 6 days. Budesonide was detected in the blood of all infants with a half-life of 3.4 h. Of 11 infants with elevated TA cytokine levels at baseline, treatment was associated with sustained decrease (mean 65%) at all three dosing levels. There were time- and dose-dependent decreases in blood cortisol concentrations and changes in total blood metabolites. Respiratory outcomes did not differ from the historic controls.

CONCLUSIONS

Budesonide/surfactant had no clinical respiratory benefit at any dosing levels for intubated ELGANs. One-tenth the dose used in previous trials had minimal systemic metabolic effects and appeared effective for lung-targeted anti-inflammatory action.

Cell fate analysis in fetal mouse lung reveals distinct pathways for TI and TII cell development

Alveolar type I (TI) cells are large squamous cells that cover >95% of the internal surface area of the lung; type II (TII) cells are small cuboidal cells with distinctive intracellular surfactant storage organelles. Based on autoradiographic studies in the 1970s, the long-held paradigm of alveolar epithelial development has been a linear progression from undifferentiated progenitor cells through TII cells to TI cells. Subsequent data support the existence of more complex pathways. Recently, a bipotent TI/TII progenitor cell at embryonic day E18 has been inferred both from marker expression in developing airways and from statistical analyses of gene expression data obtained from single-lung embryonic cells. To study cell lineage directly by fate mapping, we developed new transgenic mouse models in which rtTA is driven either by the rat podoplanin or the mouse Sftpc gene to mark cells irreversibly in development. Using these models, we found two distinct lineage pathways. One pathway, evident as early as E12-15, is devoted almost exclusively to TI cell development; a second pathway gives rise predominantly to TII cells but also a subpopulation of TI cells. We have defined the molecular phenotypes of these distinct progenitor populations and have identified potential regulatory factors in TI and TII cell differentiation. By analyzing gene pathways in mature TI and TII cells, we identified potential novel functions of each cell type. These results provide novel insights into lung development and suggest a basis for testing strategies to promote alveolar differentiation and repair, including potential transplantation of lineage-specific progenitor cells.

Surfactant status and respiratory outcome in premature infants receiving late surfactant treatment

BACKGROUND

Many premature infants with respiratory failure are deficient in surfactant, but the relationship to occurrence of bronchopulmonary dysplasia (BPD) is uncertain.

METHODS

Tracheal aspirates were collected from 209 treated and control infants enrolled at 7-14 days in the Trial of Late Surfactant. The content of phospholipid, surfactant protein B, and total protein were determined in large aggregate (active) surfactant.

RESULTS

At 24 h, surfactant treatment transiently increased surfactant protein B content (70%, p < 0.01), but did not affect recovered airway surfactant or total protein/phospholipid. The level of recovered surfactant during dosing was directly associated with content of surfactant protein B (r = 0.50, p < 0.00001) and inversely related to total protein (r = 0.39, p < 0.0001). For all infants, occurrence of BPD was associated with lower levels of recovered large aggregate surfactant, higher protein content, and lower SP-B levels. Tracheal aspirates with lower amounts of recovered surfactant had an increased proportion of small vesicle (inactive) surfactant.

CONCLUSIONS

We conclude that many intubated premature infants are deficient in active surfactant, in part due to increased intra-alveolar metabolism, low SP-B content, and protein inhibition, and that the severity of this deficit is predictive of BPD. Late surfactant treatment at the frequency used did not provide a sustained increase in airway surfactant.

Antiinflammatory Effects of Budesonide in Human Fetal Lung

Lung inflammation in premature infants contributes to the development of bronchopulmonary dysplasia (BPD), a chronic lung disease with long-term sequelae. Pilot studies administering budesonide suspended in surfactant have found reduced BPD without the apparent adverse effects that occur with systemic dexamethasone therapy. Our objective was to determine budesonide potency, stability, and antiinflammatory effects in human fetal lung. We cultured explants of second-trimester fetal lung with budesonide or dexamethasone and used microscopy, immunoassays, RNA sequencing, liquid chromatography/tandem mass spectrometry, and pulsating bubble surfactometry. Budesonide suppressed secreted chemokines IL-8 and CCL2 (MCP-1) within 4 hours, reaching a 90% decrease at 12 hours, which was fully reversed 72 hours after removal of the steroid. Half-maximal effects occurred at 0.04-0.05 nM, representing a fivefold greater potency than for dexamethasone. Budesonide significantly induced 3.6% and repressed 2.8% of 14,500 sequenced mRNAs by 1.6- to 95-fold, including 119 genes that contribute to the glucocorticoid inflammatory transcriptome; some are known targets of nuclear factor-κB. By global proteomics, 22 secreted inflammatory proteins were hormonally regulated. Two glucocorticoid-regulated genes of interest because of their association with lung disease are CHI3L1 and IL1RL1. Budesonide retained activity in the presence of surfactant and did not alter its surface properties. There was some formation of palmitate-budesonide in lung tissue but no detectable metabolism to inactive 16α-hydroxy prednisolone. We concluded that budesonide is a potent and stable antiinflammatory glucocorticoid in human fetal lung in vitro, supporting a beneficial antiinflammatory response to lung-targeted budesonide:surfactant treatment of infants for the prevention of BPD.

Expression of human carcinoembryonic antigen-related cell adhesion molecule 6 and alveolar progenitor cells in normal and injured lungs of transgenic mice

Carcinoembryonic antigen-related cell adhesion molecule 6 (CEACAM6) is expressed in the epithelium of various primate tissues, including lung airway and alveoli. In human lung, CEACAM6 is developmentally and hormonally regulated, protects surfactant function, has anti-apoptotic activity and is dysregulated in cancers. We hypothesized that alveolar CEACAM6 expression increases in lung injury and promotes cell proliferation during repair. Studies were performed in CEABAC transgenic mice-containing human CEACAM genes. The level of CEACAM6 in adult CEABAC lung was comparable to that in human infants; expression occurred in epithelium of airways and of some alveoli but rarely co-localized with markers of type I or type II cells. Ten days after bleomycin instillation, both the number of CEACAM6(+) cells and immunostaining intensity were elevated in injured lung areas, and there was increased co-localization with type I and II cell markers. To specifically address type II cells, we crossed CEABAC mice with animals expressing EGFP driven by the SP-C promoter. After bleomycin injury, partially flattened, elongated epithelial cells were observed that expressed type I cell markers and were primarily either EGFP(+) or CEACAM6(+). In cell cycle studies, mitosis was greater in CEACAM6(+) non-type II cells versus CEACAM6(+)/EGFP(+) cells. CEACAM6 epithelial expression was also increased after hyperoxic exposure and LPS instillation, suggesting a generalized response to acute lung injuries. We conclude that CEACAM6 expression is comparable in human lung and the CEABAC mouse. CEACAM6 in this model appears to be a marker of a progenitor cell population that contributes to alveolar epithelial cell replenishment after lung injury.

High-efficiency type II cell-enhanced green fluorescent protein expression facilitates cellular identification, tracking, and isolation

We have developed a transgenic mouse expressing enhanced green fluorescent protein (EGFP) in virtually all type II (TII) alveolar epithelial cells. The CBG mouse (SPC-BAC-EGFP) contains a bacterial artificial chromosome modified to express EGFP within the mouse surfactant protein (SP)-C gene 3' untranslated region. EGFP mRNA expression is limited to the lung. EGFP fluorescence is both limited to and exhibited by all cells expressing pro-SP-C; fluorescence is uniform throughout all lobes of the lung and does not change as mice age. EGFP(+) cells also express SP-B but do not express podoplanin, a type I (TI) cell marker. CBG mice show no evidence of lung disease with aging. In 3 hours, TII cells can be isolated in >99% purity from CBG mice by FACS; the yield of 3.7 ± 0.6 × 10(6) cells represents approximately 25 to 60% of the TII cells in the lung. By FACS analysis, approximately 0.9% of TII cells are in mitosis in uninjured lungs; after bleomycin injury, 4.1% are in mitosis. Because EGFP fluorescence can be detected for >14 days in culture, at a time that SP-C mRNA expression is essentially nil, this line may be useful for tracking TII cells in culture and in vivo. When CBG mice are crossed to transgenic mice expressing rat podoplanin, TI and TII cells can be easily simultaneously identified and isolated. When bred to other strains of mice, EGFP expression can be used to identify TII cells without the need for immunostaining for SP-C. These mice should be useful in models of mouse pulmonary disease and in studies of TII cell biology, biochemistry, and genetics.

Surface film formation in vitro by infant and therapeutic surfactants: role of surfactant protein B

BACKGROUND

Pulmonary surfactant provides an alveolar surface-active film that is critical for normal lung function. Our objective was to determine in vitro film formation properties of therapeutic and infant surfactants and the influence of surfactant protein (SP)-B content.

METHODS

We used a multiwell fluorescent assay measuring maximum phospholipid surface accumulation (Max), phospholipid concentration required for half-maximal film formation (½Max), and time for maximal accumulation (tMax).

RESULTS

Among five therapeutic surfactants, calfactant (highest SP-B content) had film formation values similar to natural surfactant, and addition of SP-B to beractant (lowest SP-B) normalized its Max value. Addition of budesonide to calfactant did not adversely affect film formation. In tracheal aspirates of preterm infants with evolving chronic lung disease, SP-B content correlated with ½Max and tMax values, and SP-B supplementation of SP-B-deficient infant surfactant restored normal film formation. Reconstitution of normal surfactant indicated a role for both SP-B and SP-C in film formation.

CONCLUSION

Film formation in vitro differs among therapeutic surfactants and is highly dependent on SP-B content in infant surfactant. The results support a critical role of SP-B for promoting surface film formation.

A small-molecule smoothened agonist prevents glucocorticoid-induced neonatal cerebellar injury

Glucocorticoids are used for treating preterm neonatal infants suffering from life-threatening lung, airway, and cardiovascular conditions. However, several studies have raised concerns about detrimental effects of postnatal glucocorticoid administration on the developing brain leading to cognitive impairment, cerebral palsy, and hypoplasia of the cerebellum, a brain region critical for coordination of movement and higher-order neurological functions. Previously, we showed that glucocorticoids inhibit Sonic hedgehog-Smoothened (Shh-Smo) signaling, the major mitogenic pathway for cerebellar granule neuron precursors. Conversely, activation of Shh-Smo in transgenic mice protects against glucocorticoid-induced neurotoxic effects through induction of the 11β-hydroxysteroid dehydrogenase type 2 (11β-HSD2) pathway. Here, we show that systemic administration of a small-molecule agonist of the Shh-Smo pathway (SAG) prevented the neurotoxic effects of glucocorticoids. SAG did not interfere with the beneficial effects of glucocorticoids on lung maturation, and despite the known associations of the Shh pathway with neoplasia, we found that transient (1-week-long) SAG treatment of neonatal animals was well tolerated and did not promote tumor formation. These findings suggest that a small-molecule agonist of Smo has potential as a neuroprotective agent in neonates at risk for glucocorticoid-induced neonatal cerebellar injury.

Distribution and surfactant association of carcinoembryonic cell adhesion molecule 6 in human lung

Carcinoembryonic cell adhesion molecule 6 (CEACAM6) is a glycosylated, glycophosphatidylinositol-anchored protein expressed in epithelial cells of various primate tissues. It binds gram-negative bacteria and is overexpressed in human cancers. CEACAM6 is associated with lamellar bodies of cultured type II cells of human fetal lung and protects surfactant function in vitro. In this study, we characterized CEACAM6 expression in vivo in human lung. CEACAM6 was present in lung lavage of premature infants at birth and increased progressively in intubated infants with lung disease. Of surfactant-associated CEACAM6, ∼80% was the fully glycosylated, 90-kDa form that contains the glycophosphatidylinositol anchor, and the concentration (3.9% of phospholipid for adult lung) was comparable to that for surfactant proteins (SP)-A/B/C. We examined the affinity of CEACAM6 by purification of surfactant on density gradient centrifugation; concentrations of CEACAM6 and SP-B per phospholipid were unchanged, whereas levels of total protein and SP-A decreased by 60%. CEACAM6 mRNA content decreased progressively from upper trachea to peripheral fetal lung, whereas protein levels were similar in all regions of adult lung, suggesting proximal-to-distal developmental expression in lung epithelium. In adult lung, most type I cells and ∼50% of type II cells were immunopositive. We conclude that CEACAM6 is expressed by alveolar and airway epithelial cells of human lung and is secreted into lung-lining fluid, where fully glycosylated protein binds to surfactant. Production appears to be upregulated during neonatal lung disease, perhaps related to roles of CEACAM6 in surfactant function, cell proliferation, and innate immune defense.

Regulated gene expression in cultured type II cells of adult human lung

Alveolar type II cells have multiple functions, including surfactant production and fluid clearance, which are critical for lung function. Differentiation of type II cells occurs in cultured fetal lung epithelial cells treated with dexamethasone plus cAMP and isobutylmethylxanthine (DCI) and involves increased expression of 388 genes. In this study, type II cells of human adult lung were isolated at approximately 95% purity, and gene expression was determined (Affymetrix) before and after culturing 5 days on collagen-coated dishes with or without DCI for the final 3 days. In freshly isolated cells, highly expressed genes included SFTPA/B/C, SCGB1A, IL8, CXCL2, and SFN in addition to ubiquitously expressed genes. Transcript abundance was correlated between fetal and adult cells (r = 0.88), with a subset of 187 genes primarily related to inflammation and immunity that were expressed >10-fold higher in adult cells. During control culture, expression increased for 8.1% of expressed genes and decreased for approximately 4% including 118 immune response and 10 surfactant-related genes. DCI treatment promoted lamellar body production and increased expression of approximately 3% of probed genes by > or =1.5-fold; 40% of these were also induced in fetal cells. Highly induced genes (> or =10-fold) included PGC, ZBTB16, DUOX1, PLUNC, CIT, and CRTAC1. Twenty-five induced genes, including six genes related to surfactant (SFTPA/B/C, PGC, CEBPD, and ADFP), also had decreased expression during control culture and thus are candidates for hormonal regulation in vivo. Our results further define the adult human type II cell molecular phenotype and demonstrate that a subset of genes remains hormone responsive in cultured adult cells.

Improving outpatient diabetes management through a collaboration of six competing, capitated Medicare managed care plans

This report addresses diabetes care in the managed care setting and improvement in care brought about by collaboration between 6 Medicare managed care plans (MCPs) and a Peer Review Organization (PRO). The objective was to improve the quality of care of outpatient diabetes patients provided by primary care physicians through the mutual collaboration of 6 Medicare managed care plans and a Medicare Peer Review Organization. The design involved pre-post intervention trial based on 2 random samples, a baseline sample drawn in 1995 and a remeasurement sample drawn in 1996. Medical records of patients in both samples were reviewed by the PRO to determine provision of 14 quality indicator services over a 1-year period. The setting was 6 Arizona Medicare managed care plans comprising approximately 40% of the Arizona Medicare population. Two random samples were drawn from type 2 diabetes patients continuously enrolled in the same managed care plan for at least 1 year. The intervention was comparative feedback of baseline data by the PRO, enabling each plan to compare itself to any other plan on any or all indicators. Each plan developed and implemented its own intervention in response to the 1995 baseline results. The main outcome measures were mean HbA1c, the proportion of HbA1c values below 8%, and positive change in provision of 14 quality indicator services. At postintervention remeasurement, mean HbA1c values fell from 8.9 +/- 2.2 to 7.9% +/- 2.1, and the proportion of patients with HbA1c values below 8.0% rose from 40% to 61.6%. The proportion of the 14 indicator services provided to patients rose from 35% to 55%. The mean number of physician office visits fell 13% and the number of services provided per visit doubled. We conclude that improving the process of care improves glycemic control. Better outpatient diabetes management in competing, capitated managed care plans is an attainable goal when mediated through a neutral third party such as a PRO.

Outpatient management of diabetes mellitus in five Arizona Medicare managed care plans

We report findings on the outpatient management of diabetes mellitus in Medicare beneficiaries enrolled in five Arizona Medicare-managed care plans. These findings are the baseline of an ongoing collaboration between the Health Services Advisory Group, Inc., Arizona's Peer Review Organization (PRO), and the five plans whose object is improved care of diabetes patients. The purpose of the study was to determine congruity between quality indicators identified by the five plans and the care actually received by diabetes patients enrolled in the five plans. The five plans agreed on a common set of quality indicators, including 10 services and 10 measures of patient status. Each plan has identified its diabetic population, 75 of whom are randomly selected each quarter by the PRO for chart review and inclusion in the study. The findings in this report cover two quarters of data. Data from chart review were examined to determine the extent to which actual practice reflected the indicators. The mean patient age was 71.8, and for most patients onset occurred between 55 and 69 years of age. About 25% had a positive family history, and we estimate the annual incidence of diabetes in this population to be about 1.1%. Mean hemoglobin A1c (HbA1c) was 8.9 +/- 2.1%; 46% were hypertensive; 42% continued to smoke cigarettes; 36% had retinopathy; 20% had proteinuria; and only 22% were on some kind of exercise program. Thirty-two percent were hospitalized during the 1-year baseline period, and the average number of outpatient visits per patient was 11.1 +/- 7.4. When care provided to diabetes patients enrolled in the plans was compared with the 10 quality standards identified by the plans themselves, only two of these standards was attained in more than 60% of patients: blood pressure, 98.7%; and foot examination, 62.7%. Two standards were achieved less than one-third of the time: urine dipstick, 10.4%, and appropriate use of angiotensin-converting enzyme (ACE) inhibitors, 31.25%. The others were all between 40 and 55%. Of the 10 service standards, about one-third received 1-4, one-third received 5-6, and one-third received 7-10. Only 5% of patients received 9 or 10 services. Outpatient management of diabetes patients in managed-care plans is similar to that in fee-for-service. When compared with fee-for-service or another HMO, a higher proportion of Arizona-managed care patients had HbA1c, and a much lower proportion had a dipstick test for urine protein. Values for other variables were usually within 10 percentage points of each other. Regardless of payment scheme, diabetes care is characterized by inconsistencies, omissions, and a lower than desirable level of services. Although few patients received most of the indicator services, diabetes patients are nevertheless high utilizers of medical care, both in and out of the hospital. The hospitalization rate is twice that of Arizona Medicare beneficiaries as a whole, and the number of office visits is three or four times that reported in other studies. Further, it seems that many visits are required to achieve even these modest service levels. Had the average number of visits been six or less, HbA1c rates, for example, would have fallen to less than one-third in three of the five plans. We believe that these data are conservative because it is likely that some and perhaps most of these indicators are underreported. It should be emphasized that these are baseline data whose purpose is to provide a basis against which subsequent improvements many be measured.

Effect of antitumor diarylsulfonylureas on in vivo and in vitro mitochondrial structure and functions

Diarylsulfonylureas are novel oncolytic agents shown to have therapeutic activity against both rodent solid tumors and xenografts of human tumors in mice. Previous studies have shown that diarylsulfonylureas localize in mitochondria and cause morphological changes in these organelles. We have investigated the mechanism of action of diarylsulfonylureas, namely, N-(5-indanylsulfonyl)-N'-(4-chlorophenyl)urea (ISCU) and the N-4-methyl analogue (MPCU), by studying their effect on mitochondrial morphology and uptake of rhodamine 123 in GC3/c1 cells in culture and the oxidative phosphorylation in isolated mitochondria from mouse liver, using pyruvate-malate and succinate as substrates. Morphometric analysis of mitochondria in GC3/c1 cells exposed to ISCU showed that ISCU (165 microM) doubled the mitochondrial size after 24-h exposure in culture. Also, ISCU (100 microM), like 40 microM carbonylcyanide p-trifluoromethoxyphenylhydrazone, significantly reduced the rhodamine 123 uptake by GC3/c1 cells studied by flow cytometry. In isolated mitochondria both ISCU and MPCU uncoupled oxidative phosphorylation at 50 microM, with pyruvate-malate as substrate, as was indicated by a significant increase in the State 4 oxygen consumption. This resulted in the loss of ADP phosphorylation and, therefore, the ADP/oxygen ratio was reduced to zero and the respiratory control ratio to one. The succinate oxidation was also significantly impaired by ISCU, causing some decrease in ADP phosphorylation. On the other hand, MPCU did not exhibit any significant effect on the oxidation of succinate. At concentrations of lower than 50 microM, both of these compounds exhibited a deleterious effect, causing damage to mitochondrial functions in the presence of pyruvate-malate as substrates. These data confirm, through morphometric analysis, our previous qualitative observations of abnormal mitochondrial morphology observed in GC3/c1 cells grown in the presence of high concentrations of ISCU and MPCU and further suggest that diarylsulfonylureas, by uncoupling mitochondrial oxidative phosphorylation, may lower cellular ATP. It is probable that this mechanism contributes, at least partially, to cytotoxicity in GC3/c1 cells exposed to high concentrations of ISCU for relatively brief periods (2 to 4 h) and possibly contributes to cytotoxicity at drug concentrations that can be achieved in rodents.

Influence of Extracellular pH on the Accumulation and Cytotoxicity of N-(4-Methylphenylsulfonyl)-N′-(4-chlorophenyl)urea in Human Cell Lines

The effect of extracellular pH (pH(e)) on the accumulation and cytotoxicity of the diarylsulfonylurea antitumor agent N-(4-methylphenylsulfonyl)-N'-(4-chlorophenyl)urea (MPCU) has been examined. In a human colon adenocarcinoma cell line, GC3/C1, the initial rate of uptake of [3H]MPCU (2.4 microM) was increased by 4.5-fold as pH(e) was reduced from 7.4 to 6.5. Steady state levels of MPCU were inversely proportional to pH(e) and were 5-fold greater at pH 6.0 compared to 7.4. Similar results were obtained using Rh30 cells derived from an alveolar rhabdomyosarcoma. MPCU rapidly re-equilibrated after achieving steady state when pH(e) was altered, indicating that MPCU was not tightly bound within cells. In both cell lines, the uncoupling agent, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), significantly reduced (GC3/C1) or completely inhibited (Rh30) accumulation of MPCU at each pH(e) examined. Sodium azide had the same effect on the accumulation of MPCU as FCCP. The effects of FCCP and azide appeared to be due to collapse of the pH differential across the mitochondrial inner membrane rather than the gradient across the plasma membrane. As extracellular pH (pH(e)) decreased, intracellular pH(pH(i)) also decreased in GC3/C1 cells, such that the greatest pH differential (pH(i) - pH(e)) was 0.2 units at pH(e) 6.0. Neither FCCP nor azide significantly altered this pH gradient, indicating a minor role, if any, for the plasma membrane pH gradient in accumulation of MPCU in GC3/C1 cells. The effect of pH(e) (7.4 to 6.0) on cytotoxicity of MPCU was determined after exposure of cells for 4 hr to various concentrations of MPCU in the presence of 10% fetal bovine serum. Decreasing the pH(e) from 7.4 to 6.0 increased the potency of MPCU by 4.7- and 4.5-fold in Rh30 and GC3/C1 cells, respectively. In cells exposed to drug/pH(e) combinations that resulted in 50% reduction in colony forming potential, the steady state levels of [3H]MPCU were similar (range 8.8 +/- 0.9 to 10.56 +/- 0.6 nmol/10(6) cells). These results demonstrate that decrease of pH(e) significantly enhanced the uptake of MPCU accumulation into an FCCP/azide-sensitive compartment, and cytotoxicity of this agent. These data further support the hypothesis that sequestration of diarylsulfonylureas into the FCCP/azide-sensitive compartment (probably mitochondria) was associated with its cytotoxicity. The role of pH(e) in determining therapeutic selectivity of diarylsulfonylureas is discussed.

Short-term release cues to stop-consonant place of articulation in child speech

In recent work Blumstein and Stevens (J. Acoust. Soc. Am. 66, 1001-1017 (19179); 67, 648-662 (1980) have proposed that the short-term onset spectra at stop-consonant releases provide invariant cues for the perception of place of articulation, and that the salient acoustic characteristics of these cues can be characterized by a set of templates. The present study investigated the suitability of these templates for characterizing place of articulation in utterance-initial voiced stop consonants produced by two children 71-75 weeks old in spontaneous discourse. The overall correct categorization rate for the templates was 65%, with 70% correct categorizations for the bilabial template, 85% for the alveolar template, and 40% for the velar template. The results of a perceptual study in which listeners were asked to identify place of articulation for computer-edited 15-, 25-, 40-, and 135-ms samples of the initial parts of these utterances were compared with the results of the template matching study. Although listeners' identification of place of articulation was at well above chance level on even the 15-ms tokens, there was no correlation between the results of the template-matching study and the perceptual data. The perceptual data thus indicate that short-term onset cues exist in the spontaneous speech of children at an early stage of language development, however, these cues do not appear to be adequately characterized by the Blumstein-Stevens templates.