CRISPR-Based Epigenome Editing and Genome Wide Screening Define Mediators of Chemotherapy Response in Glioblastoma

PURPOSE/OBJECTIVE(S)

Alkylating chemotherapies exhibit survival benefit for patients with glioblastoma (GBM), the most common malignant primary brain tumor. CRISPRoff is a programmable epigenetic memory writer that stably and heritably silences any gene through DNA methylation. Epigenetic silencing of MGMT via promoter methylation is predictive of response to alkylating agents as well as prognostic for progression free and overall survival. Here we performed epigenome editing using CRISPRoff to stably silence MGMT through induced promoter methylation, as a therapeutically tractable approach for potentiating GBM to temozolomide (TMZ) or lomustine (CCNU). We then used genome-wide engineered CRISPR/Cas9 systems to broadly define sensitizers of GBM cells to alkylating agents, as a platform to discover novel sensitizing targets.

MATERIALS/METHODS

Targeted epigenome editing was performed through electroporation of modified mRNAs encoding CRISPRoff machinery comprising deactivated Cas9 fused to a DNA methyltransferase complex, combined with sgRNAs, into MGMT unmethylated GBM cell lines (LN18, T98G) and then treated with either vehicle, TMZ, or CCNU. Parallel experiments were performed through electroporation of sgRNA/Cas9 ribonucleoproteins. Gene silencing was assessed using bisulfite targeted sequencing, RT-qPCR, and western blot. Drug sensitization was determined using luminescent cell viability assays. Genome-wide CRISPR interference (CRISPRi) screens were performed in triplicate cultures.

RESULTS

Epigenomic silencing of the MGMT promoter through CRISPRoff-induced methylation reduced MGMT transcript levels by 96.7% and generated up to 88-fold sensitization to TMZ mediated cell death in GBM cells, with IC50 superior to GBM cells with baseline methylated MGMT. In addition, CRISPRoff of MGMT induced 20-fold sensitization to CCNU. CRISPRoff methylation of MGMT was equivalent to CRISPR/Cas9 homozygous deletion of the MGMT gene for drug sensitization and was superior to polyclonal Cas9 mediated deletion of MGMT by a factor of 10. To define additional mediators of chemotherapy response in GBM, CRISPRi screens revealed 185 and 266 genetic sensitizers to TMZ treatment in LN18 and T98G cells, respectively, in addition to validating MGMT. One hundred eighty and 238 sensitizers to CCNU were identified in LN18 and T98G cells, respectively. TMZ sensitizing genes conserved across cell lines were enriched for the ATR (i.e., BCRA2), DNA repair (i.e., REV1), and cell cycle pathways (i.e., PSMD13), while CCNU sensitizing genes were enriched for the Fanconi anemia pathway (i.e., FANCI, FANCD2). In contrast, gene hits that resulted in resistance to alkylating agents were enriched for the mismatch repair pathway (i.e., MSH2, PMS2).

CONCLUSION

We integrate targeted epigenome editing with unbiased genome-wide approaches to build a novel discovery and therapeutic platform in glioblastoma, a framework that is well suited for targeting diseases with known or suspected epigenetic vulnerabilities.

Malignant Peripheral Nerve Sheath Tumors Activate Distinct Immunosuppressive Pathways Following Radiotherapy and are Associated with Immune Depletion In Vivo

PURPOSE/OBJECTIVE(S)

Patients with neurofibromatosis type I, caused by NF1 loss, develop benign plexiform neurofibromas (pNF) in their peripheral nervous system (PNS). Malignant transformation of pNFs into malignant peripheral nerve sheath tumors (MPNSTs) occurs following CDKN2A/B and SUZ12 loss, a process associated with radiotherapy (RT). However, the molecular mechanisms underlying RT responses by different PNS cell types remain unclear. We hypothesized normal peripheral nerve cells, pNFs, and MPNSTs harbor distinct RT responses.

MATERIALS/METHODS

Patient derived NF1 WT immortalized peripheral nerve cells (iPNs), NF1 mutant pNF cells, and NF1/CDKN2AB/SUZ12 mutant MPNST cells were used to study RT responses in vitro. CRISPRi was used to assess the functional effects of candidate gene repression. In vitro viability was measured by cell counts. Transcriptomic signatures were measured by bulk RNA-sequencing and integrated with single-cell RNA sequencing (scRNA-seq) data from patient-derived pNF and MPNST resection specimens.

RESULTS

Radiation dose response curves revealed pNF cells (IC50 0.61 Gy) were more radiosensitive than MPNST cells (4.15 Gy). WT iPNs, NF1 deficient iPNs, and pNFs cells displayed no difference in cell viability (p = 0.67; t-test) following initiation of 2 Gy x 5 fractions, while MPNST cells were significantly more viable (p = 0.02; t-test). Principal component analysis of bulk RNA-sequencing data at 5 or 14 days following 2 Gy x 5 fractions revealed cell line of origin accounted for the greatest inter-sample variation (64.9% variance), with additional components separating samples based on radiation presence and timing. Using the most variable genes in PCA space to identify markers of RT response, iPNs and pNFs upregulated pro-apoptotic pathways (BAD, DAPK3) at 5 days post-radiation while MPNST cells alone upregulated pro-survival growth factor signaling). At 14 days post radiation, MPNST cells uniquely upregulated TGFβ signaling and interferon response circuits. Incorporation of scRNA-seq data revealed enrichment of growth factor signaling and TGFβ signatures in MPNSTs compared to pNF. Moreover, MPNST harbored significantly fewer immune cells than pNFs (p = 0.008, t-test), suggesting cell-autonomous signaling and crosstalk with the microenvironment are both critical to MPNST radioresistance.

CONCLUSION

Our data indicate additional genetic hits beyond NF1 loss may be required for RT-associated malignant transformation of pNFs and radioresistance in MPNSTs. Analysis of transcriptomic responses to RT suggests that upregulated growth factor signaling and TGFβ-associated immunosuppression are distinct features of MPNST. Future work will focus on CRISPRi screens to unbiasedly nominate functional modifiers of RT response in NF1/CDKN2AB deficient tumors, which may be broadly useful in cancer.

Identifying Gene-Treatment Interactions and Targetable Radiation Vulnerabilities in Glioblastoma through Coupling of In Vivo CRISPR Perturbation and Single Cell Transcriptomics

PURPOSE/OBJECTIVE(S)

Glioblastoma (GBM) is an incurable brain tumor comprised of dynamic malignant cell states and microenvironment components that underlie treatment resistance. Here we use genome-wide CRISPR/Cas9 functional genomics to define biological drivers and therapeutic vulnerabilities across human and mouse GBM models. To interrogate these mechanisms in the context of the tumor microenvironment and in vivo physiology, we established in vivo Perturb-seq intracranially, a technique coupling functional genomics with single cell transcriptomics, where each cell is an individual experiment.

MATERIALS/METHODS

Orthotopic intracranial tumor models were established using human (GBM6, GBM43) or mouse (GL261, SB28) GBM cells stably expressing CRISPR interference (CRISPRi) machinery. Perturb-seq target selection for phenotyping of gene-treatment interactions was performed using genome-wide CRISPRi screens ± radiotherapy in cell cultures. Dual sgRNA lentivirus libraries were transduced either ex vivo prior to intracranial GBM cell transplantation or in vivo using intratumor convection enhanced delivery (CED). Transcriptional phenotyping was performed using single-cell RNA-seq with CRISPR direct capture following focal brain radiotherapy (2 Gy x 5) or mock treatment. GBM cell states were validated using single-nucleus RNA-seq data from 86 primary-recurrent patient-matched GBMs. Mechanistic and functional validation was performed using small molecule inhibitors, immunohistochemistry, clonogenic assays, and in vivo survival experiments.

RESULTS

In vivo Perturb-seq ± radiotherapy of 48 genes underlying GBM radiotherapy responses, which were enriched for DNA damage response and metabolic pathways, was performed in > 425,000 single cells. Radiotherapy induced 16 distinct GBM cell states, and genetic perturbations reprogrammed these cell states in a treatment-dependent fashion. Quantitative modeling of gene/radiotherapy interactions using high dimensional manifolds revealed in vivo-specific genetic dependencies. We revealed a critical role for Prkdc, the catalytic subunit of DNA-dependent protein kinase (DNA-PK), as a radiotherapy sensitizer through regulation of cell intrinsic growth and oxidative stress pathways, and cell extrinsic interferon and signaling pathways that altered cell-cell interactions in vivo. These pathways were also disrupted in single-nucleus RNA-seq analysis of post-radiotherapy human GBM tumors. Inhibition of Prkdc using a Food and Drug Administration approved small molecule sensitized GBM cells to radiotherapy and extended survival in mice harboring human intracranial xenografts.

CONCLUSION

We establish in vivo Perturb-seq in orthotopic GBM models as a platform for simultaneous functional genomic discovery and characterization of therapeutic targets, revealing an underappreciated role for Prkdc in GBM tumors in vivo that is targetable using small molecules. These tools are adaptable for a wide range of disease models and treatment modalities.

Serelaxin as a potential treatment for renal dysfunction in cirrhosis: Preclinical evaluation and results of a randomized phase 2 trial

BACKGROUND

Chronic liver scarring from any cause leads to cirrhosis, portal hypertension, and a progressive decline in renal blood flow and renal function. Extreme renal vasoconstriction characterizes hepatorenal syndrome, a functional and potentially reversible form of acute kidney injury in patients with advanced cirrhosis, but current therapy with systemic vasoconstrictors is ineffective in a substantial proportion of patients and is limited by ischemic adverse events. Serelaxin (recombinant human relaxin-2) is a peptide molecule with anti-fibrotic and vasoprotective properties that binds to relaxin family peptide receptor-1 (RXFP1) and has been shown to increase renal perfusion in healthy human volunteers. We hypothesized that serelaxin could ameliorate renal vasoconstriction and renal dysfunction in patients with cirrhosis and portal hypertension.

METHODS AND FINDINGS

To establish preclinical proof of concept, we developed two independent rat models of cirrhosis that were characterized by progressive reduction in renal blood flow and glomerular filtration rate and showed evidence of renal endothelial dysfunction. We then set out to further explore and validate our hypothesis in a phase 2 randomized open-label parallel-group study in male and female patients with alcohol-related cirrhosis and portal hypertension. Forty patients were randomized 1:1 to treatment with serelaxin intravenous (i.v.) infusion (for 60 min at 80 μg/kg/d and then 60 min at 30 μg/kg/d) or terlipressin (single 2-mg i.v. bolus), and the regional hemodynamic effects were quantified by phase contrast magnetic resonance angiography at baseline and after 120 min. The primary endpoint was the change from baseline in total renal artery blood flow. Therapeutic targeting of renal vasoconstriction with serelaxin in the rat models increased kidney perfusion, oxygenation, and function through reduction in renal vascular resistance, reversal of endothelial dysfunction, and increased activation of the AKT/eNOS/NO signaling pathway in the kidney. In the randomized clinical study, infusion of serelaxin for 120 min increased total renal arterial blood flow by 65% (95% CI 40%, 95%; p < 0.001) from baseline. Administration of serelaxin was safe and well tolerated, with no detrimental effect on systemic blood pressure or hepatic perfusion. The clinical study's main limitations were the relatively small sample size and stable, well-compensated population.

CONCLUSIONS

Our mechanistic findings in rat models and exploratory study in human cirrhosis suggest the therapeutic potential of selective renal vasodilation using serelaxin as a new treatment for renal dysfunction in cirrhosis, although further validation in patients with more advanced cirrhosis and renal dysfunction is required.

TRIAL REGISTRATION

ClinicalTrials.gov NCT01640964.

Note: advancement in tip etching for preparation of tunable size scanning tunneling microscopy tips

The two aspects of a scanning tunneling microscopy tip, the macroscopic profile and the nanoscale apex, can be tailored by controlling the tension during electrochemical etching and the solution-electrode contact area via acetone vapor. The apex diameter is shown to be proportional to the square root of the tension, and is demonstrated over apex diameters of 150-500 nm. The apex was found to be created in four distinct shapes where a secondary etching can reshape the tip into a single geometry. Improvement in tip height and stability of the profile are demonstrated versus a non-acetone fabrication control.

Inhibition of mTOR affects protein stability of OGT

Autophagy regulates cellular homeostasis through degradation of aged or damaged subcellular organelles and components. Interestingly, autophagy-deficient beta cells, for example Atg7-mutant mice, exhibited hypoinsulinemia and hyperglycemia. Also, autophagy response is diminished in heart of diabetic mice. These results implied that autophagy and diabetes are closely connected and affect each other. Although protein O-GlcNAcylation is up-regulated in hyperglycemia and diabetes, and O-GlcNAcylated proteins play an important role in metabolism and nutrient sensing, little is known whether autophagy affects O-GlcNAc modification and vice versa. In this study, we suppressed the action of mTOR by treatment of mTOR catalytic inhibitors (PP242 and Torin1) to induce autophagic flux. Results showed a decrease in global O-GlcNAcylation, which is due to decreased OGT protein and increased OGA protein. Interestingly, knockdown of ATG genes or blocking of lysosomal degradation enhanced protein stability of OGT. In addition, when proteasomal inhibitor was treated together with mTOR inhibitor, protein level of OGT almost recovered to control level. These data suggest that mTOR inhibition is a more efficient way to reduce protein level of OGT rather than that of CHX treatment. We also showed that not only proteasomal degradation regulated OGT stability but autophagic degradation also affected OGT stability in part. We concluded that mTOR signaling regulates protein O-GlcNAc modification through adjustment of OGT stability.

Long-term control of bone turnover in Paget's disease with zoledronic acid and risedronate

A single 5-mg infusion of zoledronic acid restores biochemical markers of bone turnover into the reference range in the majority of patients with Paget's disease and maintains biochemical remission for at least 2 years. This effect is largely independent of pretreatment disease activity and prior bisphosphonate therapy.

INTRODUCTION

Zoledronic acid (ZOL) is a potent bisphosphonate that produces a rapid and complete control of the increased bone turnover of Paget's disease. Long-term control of disease activity is an important aim of treatment in the hope that this will reduce the risk of complications such as deformity, fracture, and degenerative joint disease.

MATERIALS AND METHODS

This study compares the ability of ZOL 5 mg given as a 15-minute intravenous infusion with risedronate (RIS) 30 mg daily by mouth for 60 days to maintain long-term control of bone turnover. No bisphosphonate was given during the extension study. All patients (n = 296) who achieved a therapeutic response, defined as normalization or a >75% reduction in the total alkaline phosphatase (total ALP) excess above the midpoint of the reference range, were eligible for inclusion.

RESULTS

ZOL maintained the mean level of total ALP at the middle of the reference range, whereas those treated with risedronate showed a linear increase in total ALP from the 6-month post-treatment time-point. Both treatments resulted in a linear relationship between the 6-month nadir and 24-month total ALP. The relationship for RIS was shifted upward, showing that for a given level of post-treatment biochemical activity, bone turnover increased with time. This was in contrast to the ZOL-treated patients where total ALP generally remained unchanged over this 18-month extension period. A similar pattern of response was seen with the other bone turnover markers.

CONCLUSIONS

ZOL maintains bone turnover within the reference range over 24 months from the initiation of treatment. A reduction in the incidence and severity of long-term complications may require persistent normalization of bone turnover over many years, and this now seems a realistic possibility with ZOL.

Comparison of a single infusion of zoledronic acid with risedronate for Paget's disease

BACKGROUND

The advent of bisphosphonates advanced therapy for Paget's disease, but more effective and convenient agents are needed to increase adherence. Zoledronic acid, a bisphosphonate administered as a single intravenous infusion, might meet these needs.

METHODS

In two identical, randomized, double-blind, actively controlled trials of 6 months' duration, we compared one 15-minute infusion of 5 mg of zoledronic acid with 60 days of oral risedronate (30 mg per day). The primary efficacy end point was the rate of therapeutic response at six months, defined as a normalization of alkaline phosphatase levels or a reduction of at least 75 percent in the total alkaline phosphatase excess. The results of the studies were pooled.

RESULTS

At six months, 96.0 percent of patients receiving zoledronic acid had a therapeutic response (169 of 176), as compared with 74.3 percent of patients receiving risedronate (127 of 171, P<0.001). Alkaline phosphatase levels normalized in 88.6 percent of patients in the zoledronic acid group and 57.9 percent of patients in the risedronate group (P<0.001). Zoledronic acid was associated with a shorter median time to a first therapeutic response (64 vs. 89 days, P<0.001). Higher response rates in the zoledronic acid group were consistent across all demographic, disease-severity, and treatment-history subgroups and with changes in other bone-turnover markers. The physical-component summary score of the Medical Outcomes Study 36-item Short-Form General Health Survey, a measure of the quality of life, increased significantly from baseline at both three and six months in the zoledronic acid group and differed significantly from those in the risedronate group at three months. Pain scores improved in both groups. During post-trial follow-up (median, 190 days), 21 of 82 patients in the risedronate group had a loss of therapeutic response, as compared with 1 of 113 patients in the zoledronic acid group (P<0.001).

CONCLUSIONS

A single infusion of zoledronic acid produces more rapid, more complete, and more sustained responses in Paget's disease than does daily treatment with risedronate.

Activity of phosphoforms and truncated versions of Ndt80, a checkpoint-regulated sporulation-specific transcription factor of Saccharomyces cerevisiae

Ndt80 contributes to the highly regulated cascade of sequential gene expression that directs spore formation in Saccharomyces cerevisiae. This DNA-binding transcriptional activator, which is responsible for the expression of a set of middle sporulation-specific genes, is a target of the meiotic recombination checkpoint. Triggering of this checkpoint prevents phosphorylation and accumulation of active Ndt80. In this study we have investigated the requirements for the activation function of Ndt80 by exploring the role of phosphorylation in the regulation of its activity and by examining the effect of C-terminal truncations. Of three phosphoforms of Ndt80 that we resolved, which we refer to as P approximately Ndt80", P approximately Ndt80', and P approximately Ndt80 in order of increasing electrophoretic mobility, the P approximately Ndt80" and P approximately Ndt80' isoforms correlated with active Ndt80. In particular, P approximately Ndt80" was present in lysates from wild-type sporulating cells and in cells that bypassed checkpoint-mediated arrest as a result of mutations in RAD17, SUM1, or SWE1, or overexpression of NDT80. P approximately Ndt80' was the slowest-migrating isoform that accumulated in Delta ime2/Delta ime2 Delta sum1/Delta sum1 cells in sporulation medium and in mitotic cells that ectopically expressed NDT80. Nonphosphorylated Ndt80 and P approximately Ndt80, which had a slightly lower mobility than nonphosphorylated Ndt80 and was the predominant phosphoform present in checkpoint-arrested cells, correlated with inactive Ndt80. These data are consistent with the notion that extensive phosphorylation, but not Ime2-dependent phosphorylation, of Ndt80 is required for its activity. Examination of the effect of increasingly extensive truncation of the C terminal region of Ndt80 revealed that some functions of Ndt80 were more sensitive to a reduction in its activity than others. In particular, we found that a truncated version of Ndt80 that lacked the last 110 residues was able to promote expression of some middle sporulation-specific genes, but could not direct spore formation. Full activity, however, could be restored to this version of Ndt80 by increasing its level of expression.

Safety of sputum induction in moderate-to-severe chronic obstructive pulmonary disease

This retrospective study was designed to evaluate the safety and efficacy of a bronchoprotective sputum induction protocol in moderate to severe chronic obstructive pulmonary disease (COPD). Forty-two adults with COPD (FEV1 = 51.7 +/- 3.2% predicted (mean +/- SEM)) under went sputum induction using a protocol designed to minimize hypertonic saline-induced bronchoconstriction. Hypertonic (3%) saline was used for subjects with FEV1 > or = 50%, and normal (0.9%) saline was used for subjects with FEV1 < 50%. Primary outcomes were change in peak flow, FEV1 and oxygen saturation. Mean decline in peak flow during sputum induction was 13.2 +/- 2.1%. FEV1 fell by 11.4 +/- 2.3%, an absolute fall of 0.14 +/- 0.031. Oxygen saturation did not change. A fall in peak flow of > or = 20% reliably predicted a fall in FEV1 of > or = 20%. Thirty-five of 42 subjects (83.3%) produced an acceptable sputum sample. Sputum eosinophil and neutrophil percentages were 2.8 +/- 0.9 and 73.0 +/- 3.0%, respectively, and were not correlated with changes in peak flow, FEV1 or oxygen saturation. A protocol for sputum induction which restricts the use of hypertonic saline based on lung function is both safe and effective in subjects with moderate to severe COPD.

Distal lung dysfunction at night in nocturnal asthma

We have previously shown that patients with nocturnal worsening of asthma (nocturnal asthma) exhibit increased parenchymal inflammation at night. To evaluate the functional significance of this parenchymal inflammation, 10 subjects with nocturnal asthma (NA), four subjects with non-nocturnal asthma (NNA), and four normal control subjects underwent bronchoscopy with measurement of peripheral airways resistance (Rp) at 4:00 P.M. and at 4:00 A.M. Employing a wedged bronchoscope technique, Rp was measured. Flow was stopped, and the pressure reached after 10 s of decay was termed the plateau pressure. The time constant of this decay (tau) was measured, and the peripheral compliance (Cp) was calculated as tau/Rp. The NA group exhibited the highest Rp values at 4:00 P.M. and at 4:00 A.M. as compared with the NNA and control groups, but all groups were significantly different from each other at 4:00 P.M.: NA, 0.113 +/- 0.02 cm H(2)O/ml/min; NNA, 0.033 +/- 0.005 cm H(2)O/ml/min; Control subjects, 0.010 +/- 0.001 cm H(2)O/ ml/min; p = 0.0001; and at 4:00 A.M.: NA, 0.129 +/- 0.023 cm H(2)O/ ml/min; NNA, 0.035 +/- 0.007 cm H(2)O/ml/min; Control subjects, 0.009 +/- 0.002 cm H(2)O/ml/min; p = 0.0003. None of the groups exhibited statistically significant differences in Rp between 4:00 P.M. and 4:00 A.M. The plateau pressure increased significantly from 4:00 P.M. to 4:00 A.M., but only in the NA group (7.7 +/- 0.9 cm H(2)O at 4:00 P.M. versus 16.9 +/- 4.6 cm H(2)O at 4:00 A.M.; p = 0.0004). Cp was decreased in the NA group as compared with the NNA and control groups at both 4:00 P.M. (p = 0.0003) and 4:00 A.M. (p = 0.003). The Rp positively correlated with the residual volume at both 4:00 P.M. (r = 0.71, p = 0.004) and 4:00 A.M. (r = 0.59, p = 0.03). We conclude that the distal lung units, specifically the collateral channels, and may be functionally altered at night in NA.

Exhaled nitric oxide correlated with induced sputum findings in COPD

STUDY OBJECTIVES

Neutrophilic airway inflammation may underlie the pathogenesis of COPD. We examined repeated measurements of the fractional concentration of exhaled nitric oxide (FENO) and the correlation with cells and mediators in induced sputum (IS) from patients with COPD.

PARTICIPANTS

Eleven COPD subjects (9 men and 2 women, aged 46 to 69 years) with predicted FEV(1) of 45 to 70%.

SETTING

A hospital research laboratory.

DESIGN

Single-cohort, prospective study with four visits at two weekly intervals.

INTERVENTIONS

FENO and spirometry were assessed at all visits, and IS for differential cell count, leukotriene-B(4) (LTB(4)) and interleukin (IL)-8, nitrite, and nitrate at visit 1, visit 3, and visit 4.

RESULTS

During the study, there were significant declines in mean percent predicted FEV(1), from 55.2 to 51.6% (p = 0.029), and mean FEV(1)/FVC ratio, from 50.4 to 45.4% (p = 0.001), accompanied by a significant increase in FENO geometric mean (95% confidence limits), from 15.2 (10.9 to 21.2) to 23.6 (17.1 to 32.4) parts per billion (p = 0.037), and sputum LTB(4), from 1.79 (1.03 to 3.11) to 3.57 (1.95 to 6.53) ng/mL (p = 0.033), but no significant change in other sputum parameters. From visits 1 to 4, the change in percent neutrophils correlated with the changes in FENO and IL-8 (r = 0.648, p = 0.028; r = 0.60, p = 0.05, respectively). Hypertonic saline solution induction of sputum caused a fall in FEV(1), from 1.83 +/- 0.44 to 1.46 +/- 0.44 L (p = 0.049).

CONCLUSIONS

The worsening spirometry results were accompanied by significant increases in FENO and sputum LTB(4). FENO may be related to neutrophilic inflammation driven by the chemoattractant IL-8. FENO and IS may be useful markers of airway inflammation in COPD patients. Sputum induction with hypertonic saline solution causes a significant fall in FEV(1) requiring appropriate caution.

Role of Ha-ras activation in superficial papillary pathway of urothelial tumor formation

Urothelial tumors develop along two distinctive phenotypic pathways (superficial papillary non-invasive tumors versus flat carcinoma in situ lesions), with markedly different biological behavior and prognosis. Although multiple genetic alterations have been identified in human bladder cancer, their cause-effect relationship with the two pathways has not been firmly established. Using a urothelium-specific promoter of the uroplakin II gene, we showed earlier in transgenic mice that the urothelial expression of SV40T antigen, which inactivates p53 and pRb, induced carcinoma in situ and invasive and metastatic bladder cancer. In striking contrast, we demonstrate here that the urothelial expression of an activated Ha-ras in transgenic mice caused urothelial hyperplasia and superficial papillary non-invasive bladder tumors. These results provide strong, direct experimental evidence that the two phenotypical pathways of bladder tumorigenesis are caused by distinctive genetic defects. Our results indicate that Ha-ras activation can induce urothelial proliferation in vivo; and that urothelial hyperplasia is a precursor of low-grade, superficial papillary bladder tumors. Our transgenic models provide unique opportunities to study the detailed molecular events underlying different types of bladder neoplasms, and can serve as useful preclinical models for evaluating the in vivo efficacy of preventive and therapeutic agents that act on various signaling pathways in bladder cancer.

Tamm-Horsfall protein binds to type 1 fimbriated Escherichia coli and prevents E. coli from binding to uroplakin Ia and Ib receptors

The adherence of uropathogenic Escherichia coli to the urothelial surface, a critical first step in the pathogenesis of urinary tract infection (UTI), is controlled by three key elements: E. coli adhesins, host receptors, and host defense mechanisms. Although much has been learned about E. coli adhesins and their urothelial receptors, little is known about the role of host defense in the adherence process. Here we show that Tamm-Horsfall protein (THP) is the principal urinary protein that binds specifically to type 1 fimbriated E. coli, the main cause of UTI. The binding was highly specific and saturable and could be inhibited by d-mannose and abolished by endoglycosidase H treatment of THP, suggesting that the binding is mediated by the high-mannose moieties of THP. It is species-conserved, occurring in both human and mouse THPs. In addition, the binding to THP was much greater with an E. coli strain bearing a phenotypic variant of the type 1 fimbrial FimH adhesin characteristic of those prevalent in UTI isolates compared with the one prevalent in isolates from the large intestine of healthy individuals. Finally, a physiological concentration of THP completely abolished the binding of type 1 fimbriated E. coli to uroplakins Ia and Ib, two putative urothelial receptors for type 1 fimbriae. These results establish, on a functional level, that THP contains conserved high-mannose moieties capable of specific interaction with type 1 fimbriae and strongly suggest that this major urinary glycoprotein is a key urinary anti-adherence factor serving to prevent type 1 fimbriated E. coli from binding to the urothelial receptors.

Serum lidocaine concentrations in asthmatics undergoing research bronchoscopy

STUDY OBJECTIVES

To determine how often serum lidocaine concentrations (SLC) fall into the potentially toxic range (> 5 mg/L) in asthmatics undergoing research bronchoscopy, and to determine whether subject or procedure characteristics are associated with higher SLC.

DESIGN

Prospective, observational study.

SETTING

Academic research center.

PARTICIPANTS

Fifty-one volunteers with mild to moderate asthma enrolled in three separate bronchoscopy protocols to study airway inflammation in asthma.

INTERVENTIONS

Lidocaine was administered topically to the upper airway and tracheobronchial tree to achieve local anesthesia for bronchoscopy. Venous blood was sampled during bronchoscopy, 30 min after upper airway anesthesia was completed (time 1), and 30 min after bronchoscopy was completed (time 2).

MEASUREMENTS AND RESULTS

The mean total amount of lidocaine administered was 600 +/- 122 mg (8.2 +/- 2.0 mg/kg). No signs or symptoms of lidocaine toxicity were observed in any of the subjects. SLC ranged between 0.10 and 2.90 mg/L at time 1 and 0.50 and 3.20 mg/L at time 2. SLC was significantly correlated with the total amount of lidocaine (milligrams/kilogram) administered at both points (time 1, r = 0.33, p = 0.021; time 2, r = 0.33, p = 0.023). No statistically significant relationship was observed between SLC and subject age, sex, weight, baseline FEV(1), procedure length, or study protocol. No statistically significant relationship was found between subject FEV(1) and either total lidocaine dose or procedure length.

CONCLUSIONS

An average total dose of 600 mg (8.2 mg/kg) of lidocaine appears to be safe in mild to moderate asthmatics undergoing research bronchoscopy.

Airway-parenchyma uncoupling in nocturnal asthma

Airway flow resistance is well known to be dependent upon lung volume. The rise in lung volume that occurs in asthma is therefore thought to be an important mechanism that defends airway patency. The purpose of the current study was to investigate the interdependence or mechanical coupling between airways and lung parenchyma during the inflammatory processes that occur in the patient with nocturnal asthma. Five patients with documented nocturnal asthma were studied in both a vertical and a horizontal body plethysmograph. Lung volume was altered with continuous negative pressure as applied to the chest wall with a poncho cuirass in different postures and during sleep. We found during the awake phase that an increase in lung volume decreased lower pulmonary resistance (Rlp); however, within 30 min of sleep onset, functional residual capacity (FRC) fell and Rlp rose more than would be expected for the fall in FRC. Restoring FRC to presleep values either at an early (half-hour) or a late (3-h) time point did not cause Rlp to significantly fall. A second phase of the study showed that the loss of Rlp dependence on lung volume was not due to the assumption of the supine posture. Indirect measurements of lung compliance were consistent with a stiffening of the lung. We conclude that with sleep there is an immediate uncoupling of the parenchyma to the airway, resulting in a loss of interdependence that persists throughout sleep and may contribute to the morbidity and mortality associated with nocturnal asthma.

A method for the standardized offline collection of exhaled nitric oxide

STUDY OBJECTIVES

Exhaled nitric oxide (ENO) is a noninvasive marker of airway inflammation. The purpose of this study was to compare a standardized offline ENO measurement apparatus with a validated on-line method.

DESIGN

Asthmatic volunteers (n = 21) had ENO measured by the two following methods: (1) inhalation to total lung capacity (TLC) followed by exhalation at a constant flow (45 mL/s) against a high resistance, while monitoring nitric oxide (NO) and pressure on-line; and (2) inhalation to TLC and exhalation into mylar balloons via an apparatus that included the same resistance and flow rate as used in the on-line method. We also examined NO stability in mylar balloons over 48 h.

MEASUREMENTS AND RESULTS

ENO values (given as geometric mean in parts per billion [ppb]; 95% confidence intervals) differed between the on-line method (69.6; 42.6 to 113.8) and the offline method (49.5; 30.9 to 79.3), indicating that the offline method gave lower ENO measures than the on-line method (p < 0.001). Furthermore, this difference between measures increased with increasing mean values. The intraclass correlation coefficient (0.931), however, showed excellent correlation between the on-line and offline methods. Within-subject repeatability, as assessed by the coefficient of repeatability (CR), was good for both the on-line and offline methods (CR, 1.09 and 1.17, respectively). Geometric mean NO concentrations (95% confidence limits) in mylar balloons containing exhalate increased from a baseline of 55.8 ppb (36.9, 84.4) to 64.5 ppb (45.6, 91.1) and 69.5 ppb (51.4, 94.0) at 24 h and 48 h, respectively.

CONCLUSIONS

The offline method gave reproducible ENO values that were consistently smaller than, but showed good correlation with, values obtained with on-line ENO collection. This method is suitable for offline collection, but the measured values are not interchangeable with those obtained by on-line measurement.

Urothelium-specific expression of an oncogene in transgenic mice induced the formation of carcinoma in situ and invasive transitional cell carcinoma

Although many genetic alterations are known to be associated with human transitional cell carcinoma (TCC) of the urinary bladder, relatively little is known about the roles of these molecular defects, singular or in combination, in bladder tumorigenesis. We have developed a transgenic mouse model of bladder tumorigenesis using a 3.6-kb promoter of uroplakin II gene to drive the urotheliums-specific expression of oncogenes. In this study, we demonstrate that transgenic mice bearing a low copy number of SV40T transgene developed bladder carcinoma in situ (CIS), whereas those bearing high copies developed CIS as well as invasive and metastatic TCCs. These results indicate that the SV40T inactivation of p53 and retinoblastoma gene products, defects frequently found in human bladder CIS and invasive TCCs, can cause the aggressive form of TCC. Our results also provide experimental proof that CIS is a precursor of invasive TCCs, thus supporting the concept of two distinct pathways of bladder tumorigenesis (papillary versus CIS/invasive TCC). This transgenic system can be used for the systematic dissection of the roles of individual or combinations of specific molecular events in bladder tumorigenesis.

Characterization of a mutant T-cell hybridoma line with defects in the TCR-mediated apoptotic pathway

A mutant T-cell hybridoma line named mutant 51 was developed that, unlike the parental line, did not die after T-cell receptor (TCR) engagement and demonstrated reduced death in response to dexamethasone. Intracellular calcium measurements showed that available calcium stores were markedly reduced in the mutant cell line. Unlike control cells, secretion of IL-2 from mutant cells was also greatly reduced, although addition of exogenous IL-2 did not facilitate increased apoptosis. Although levels of the cell death gene product Nur77 were equivalent, additional studies showed that mutant cells expressed Nur77 predominantly in the cytoplasm following TCR engagement, while parental cells displayed a nuclear translocalization of Nur77. In addition, Fas levels and Fas ligand dependant killing were both markedly reduced in the mutant clone. From these data we hypothesize a role for available calcium stores and Nur77 nuclear localization in TCR-mediated apoptosis in T-cell hybridomas.

Changes in temporal acuity with age and with hearing impairment in the mouse: a study of the acoustic startle reflex and its inhibition by brief decrements in noise level

Temporal acuity for brief gaps in noise was studied in mice of different ages (1-36 months) from strains with differing susceptibility to age-related hearing loss, using reflex modification audiometry. Prepulse inhibition of the acoustic startle reflex (ASR) increased with gap depth (GD: 10-40 dB in 70 dB SPL noise) and lead time (LT: 1-15 ms). The increase in inhibition with LT followed an exponential function in which the two parameters, asymptotic inhibition (AINH) and the time constant (tau), were both affected by GD. AINH rapidly declined from 1 to 6 and then to 18 months of age in C57BL/6J mice with progressively severe hearing loss, but first increased with maturation and then gradually declined beyond 6-12 months of age in CBA/CaJ and CBA x C57BL Fl-hybrid mice, which show no apparent change in sensory function at these ages. In contrast, tau was unaffected by hearing loss or by age, this suggesting that age-related changes in this form of temporal acuity occur because of a reduction in the efficiency with which gaps are centrally processed, not from any reduced ability to follow their rapid shift in noise level.

Serum cortisol in asthma: marker of nocturnal worsening of symptoms and lung function?

Changes in the hormone cortisol have been implicated in the pathogenesis of nocturnal worsening of asthma, or nocturnal asthma (NA). We studied 45 patients, 15 with NA, 15 subjects with non-nocturnal asthma (NNA), and 15 controls over a 24h period, measuring forced expiratory volume in 1 second (FEV1) and serum cortisol at 08:00, 12:00, 16:00, 20:00, 23:00, 04:00, and 08:00 the following day. Evaluation of the time response curves for cortisol revealed a significant difference in the shape of the curves (p = 0.04 by mixed-effects model). Evaluation of individual time points revealed that the cortisol levels in the NNA and control groups were significantly lower than in the NA group at 20:00 (NNA: 3.5 +/- 0.8 mg/mL;

CONTROLS

3.4 +/- 0.8 mg/mL; NA: 4.9 +/- 0.8 mg/mL; p = 0.007). The percentage (%) predicted FEV1 was significantly different among the three groups over the 24h period (p < 0.001). The percentage predicted FEV1 was significantly lower in the NA group compared to the control group at all time points and significantly lower than the NNA group at 16:00, 23:00, and 04:00. The difference among the groups was most pronounced at 04:00, when the percentage predicted FEV1 was 58.9 +/- 2.2% in the NA group, 76.8 +/- 2.9% in the NNA group, and 91.6 +/- 2.8% in the control group (p = 0.001, where each group is significantly different from the others). Although the time response curves for cortisol were significantly different among the three groups, the differences in serum levels of cortisol do not appear to be clinically significant. Therefore, serum levels of cortisol may not be the appropriate measurement to assess the role of cortisol in nocturnal asthma.

Cellular and axonal migrations are misguided along both body axes in the maternal-effect mau-2 mutants of Caenorhabditis elegans

We have characterized the mau-2 mutants of Caenorhabditis elegans and found that migrating cells and axons are mispositioned along both the antero-posterior and dorsoventral body axes. This is in contrast to previously characterized guidance mutations in Caenorhabditis and in Drosophila, which have been found to be axis-specific. Two observations suggest that mau-2 acts very early during development: most behavioral phenotypes of mau-2 can be rescued by a maternal effect, and variations in expressivity involve an entire body side at a time. The possibility that mau-2 is involved in the spatial organization of guidance cues encoded by other genes is discussed.

Methotrexate or total lymphoid radiation for treatment of persistent or recurrent allograft cellular rejection: a comparative study

BACKGROUND

Methotrexate and total lymphoid irradiation (TLI) have been used successfully for treatment of recurrent and persistent rejection in orthotopic heart transplant recipients; however, there has been no comparison of these two modalities.

METHODS

We retrospectively compared the efficacy of methotrexate (n = 29) versus TLI (n = 28) in heart transplant recipients with recurrent or persistent rejection. All patients received induction therapy (rabbit anti-thymocyte globulin or OKT3) and standard triple immunosuppressive therapy. Methotrexate (7.5 mg to 22.5 mg per wk) or TLI (80 cGy x 10 fractions) was used for the treatment of recurrent or persistent rejection on the basis of clinical indications. Average biopsy scores (International Society of Heart and Lung Transplantation biopsy score/total number of biopsies performed) calculated over 3-month periods, daily maintenance prednisone dose before and after methotrexate or TLI treatment, and actuarial survival and freedom from angiographic coronary artery disease and infection were compared. To control for the general decrease in prednisone with increased time from transplantation, a control group matched for time from transplantation was selected.

RESULTS

Recipient sex and age at transplant, donor age, and donor ischemic time were similar in both groups. Days after transplantation to start of therapy was longer in patients receiving methotrexate; however, this did not reach statistical significance. Patients receiving TLI had received more cumulative corticosteroids and OKT3 before the start of TLI therapy (p < 0.001). There were no differences in actuarial freedom from infection or coronary artery disease between the two groups and between the treatment groups and the control group. Actuarial survival was reduced in patients receiving TLI 3 years after transplantation (p < 0.05). Maintenance prednisone doses from 3 months before until 9 months after therapy (mg/kg) were not different between patients receiving TLI and methotrexate and were significantly greater than the prednisone doses in the control group. Four months after treatment initiation, the prednisone dose was significantly reduced in both treatment groups compared with the pretherapy dose (methotrexate 0.28 +/- 0.16 to 0.22 +/- 0.13, p = 0.05; TLI 0.36 +/- 0.16 to 0.22 +/- .07, p < 0.001). The average biopsy score was significantly reduced by both methotrexate and TLI therapy (methotrexate 1.8 +/- 0.7 to 0.83 +/- 0.9, p = 0.0001; TLI 2.1 +/- 0.8 to 1.0 +/- 0.9, p = 0.0001).

CONCLUSION

Methotrexate and TLI are both effective for the treatment of recurrent or persistent rejection after heart transplantation, reducing average biopsy scores and daily maintenance prednisone doses. There was a reduction in actuarial survival rates in patients treated with TLI, possibly reflecting the greater rejection therapy received before TLI initiation. Because both agents are effective, the choice of methotrexate or TLI may be based on clinical indications, as well as other issues, such as cost, compliance, and availability.

Theophylline's effect on neutrophil function and the late asthmatic response

BACKGROUND

The decrement in lung function associated with the late asthmatic response after allergen challenge is believed to be mediated by an inflammatory response in the airways. Theophylline has been shown to inhibit the late asthmatic response, but the mechanisms are not clear.

OBJECTIVE

The study was designed to determine whether theophylline would inhibit the late asthmatic response by reducing neutrophil activation and subsequent superoxide production.

METHODS

Twelve subjects with asthma underwent treatment in this double-blind, randomized, crossover study. Each subject received theophylline and placebo in random order in two treatment periods of 3 weeks each. Each treatment period was followed by an allergen challenge and blood neutrophil function analysis.

RESULTS

At therapeutic levels theophylline increased FEV1 at baseline and during the allergen challenge and increased the percentage suppression of neutrophil superoxide production by adenosine.

CONCLUSION

Theophylline improved pulmonary function at baseline and during an allergen challenge, in part perhaps, by increasing the neutrophil's response to feedback inhibition by adenosine. However, theophylline did not decrease the severity and duration of the late asthmatic response.

Fast inversion recovery for myelin suppression (FIRMS). A new MRI pulse sequence for highlighting cerebral gray matter

The purpose of this study is to test a new pulse sequence, fast inversion recovery for myelin suppression (FIRMS) for its ability to improve the conspicuity of gray matter. Twenty-six seizure patients were scanned with FIRMS as well as standard sequences. Gray matter conspicuity was evaluated objectively using region-of-interest calculations, including image contrast, contrast ratios, and contrast:noise (C/N). In evaluation of the hippocampus and cortex, all objective measurements of conspicuity were highest for FIRMS. In five clinical cases of suspected cortical dysplasia, FIRMS improved delineation of pathology in positive cases and ruled out the diagnosis in negative cases. In a case of hippocampal sclerosis, FIRMS was able to demonstrate atrophy of the alveus. Fast inversion recovery for myelin suppression holds promise for its ability to highlight the cerebral cortex and hippocampus.

Moloney murine leukemia virus activates NF-kappa B

Nonacutely transforming retroviruses, such as Moloney murine leukemia virus (M-MuLV), differ from transforming viruses in their mechanisms of tumor induction. While the transforming viruses cause tumors by transduction of oncogenes, the leukemia retroviruses, lacking oncogenes, employ other mechanisms, including promoter insertion and enhancer activation. Although these two mechanisms occur in many tumors induced by leukemia viruses, a substantial proportion of such tumors do not show site-specific proviral insertions. Thus, other, unidentified virus-driven mechanisms may participate in tumorigenesis. In these studies, we show that infection of cells by M-MuLV activates expression of Rel family transcription factors. In murine cells chronically infected with M-MuLV, gel shift analyses with kappaB DNA-binding motifs from the murine immunoglobulin kappa light chain enhancer demonstrated induction of at least two distinct kappaB enhancer-binding complexes. Supershifting and immunoblotting analyses defined p50, p52, RelB, and c-Rel subunits as constituents of these virus-induced protein complexes. Transient transfections performed with kappaB-dependent reporter plasmids showed transcriptional activation in M-MuLV-infected cells relative to uninfected cells. Induction of Rel/NF-kappaB transcription factor activity by M-MuLV infection may prove relevant to the mechanism of M-MuLV-induced leukemia.

Giant paraganglioma of the cauda equina in adolescence: magnetic resonance imaging demonstration

A case of giant paraganglioma of the cauda equina is presented. This is only the second reported case in a minor and the first with magnetic resonance imaging. At 13 cm long, this is the largest paraganglioma of the cauda equina ever recorded.

Genetic polymorphisms of the beta 2-adrenergic receptor in nocturnal and nonnocturnal asthma. Evidence that Gly16 correlates with the nocturnal phenotype

Nocturnal asthma represents a unique subset of patients with asthma who experience worsening symptoms and airflow obstruction at night. The basis for this phenotype of asthma is not known, but beta 2-adrenergic receptors (beta 2AR) are known to downregulate overnight in nocturnal asthmatics but not normal subjects or nonnocturnal asthmatics. We have recently delineated three polymorphic loci within the coding block of the beta 2AR which alter amino acids at positions 16, 27, and 164 and impart specific biochemical and pharmacologic phenotypes to the receptor. In site-directed mutagenesis/recombinant expression studies we have found that glycine at position 16 (Gly16) imparts an accelerated agonist-promoted downregulation of beta 2AR as compared to arginine at this position (Arg16). We hypothesized that Gly16 might be overrepresented in nocturnal asthmatics and thus determined the beta 2AR genotypes of two well-defined asthmatic cohorts: 23 nocturnal asthmatics with 34 +/- 2% nocturnal depression of peak expiratory flow rates, and 22 nonnocturnal asthmatics with virtually no such depression (2.3 +/- 0.8%). The frequency of the Gly16 allele was 80.4% in the nocturnal group as compared to 52.2% in the nonnocturnal group, while the Arg16 allele was present in 19.6 and 47.8%, respectively. This overrepresentation of the Gly16 allele in nocturnal asthma was significant at P = 0.007 with an odds ratio of having nocturnal asthma and the Gly16 polymorphism being 3.8. Comparisons of the two cohorts as to homozygosity for Gly16, homozygosity for Arg16, or heterozygosity were also consistent with segregation of Gly16 with nocturnal asthma. There was no difference in the frequency of polymorphisms at loci 27 (Gln27 or Glu27) and 164 (Thr164 or Ile164) between the two groups. Thus the Gly16 polymorphism of the beta 2AR, which imparts an enhanced downregulation of receptor number, is overrepresented in nocturnal asthma and appears to be an important genetic factor in the expression of this asthmatic phenotype.

The relationship between vessel wall tension and the magnitude and frequency of oscillation in rat aorta

Aortic rings from adult normotensive rats display spontaneous rhythmic activity that is enhanced by vasoconstricting agents. Graded doses of norepinephrine as well as combinations of norepinephrine and vasodilators produced levels of tension that were inversely related to the magnitude of oscillation and directly related to the frequency. A similar result occurred with KCl stimulation. Oscillations were only slightly affected by removal of the endothelium. These results, when combined with other reported studies, suggest that the oscillations in rat aorta are a manifestation of feedback control that may involve the cyclic release of one or more agents affecting calcium channels.

Monoclonal antibody to murine PECAM-1 (CD31) blocks acute inflammation in vivo

A murine model of peritonitis was used to test the role of platelet/endothelial cell adhesion molecule 1 (PECAM-1/CD31) in acute inflammation. A monoclonal antibody (mAb) specific for murine PECAM-1 injected intravenously 4 h before the intraperitoneal injection of thioglycollate broth blocked leukocyte emigration into the peritoneal cavity for up to 48 h. This block was particularly evident for neutrophils. Control mAb, including one that bound to murine CD18 without blocking its function, failed to block emigration when used at the same or higher concentrations. The decreased emigration seen with the anti-PECAM-1 antibody was not due to neutropenia or neutrophil sequestration in the lung, spleen, or other organs; peripheral blood leukocyte counts were not diminished in these mice. In the mesenteric venules of the mice treated with anti-PECAM-1 mAb, leukocytes were frequently seen in association with the luminal surface of the vessel, but did not appear to emigrate. Thus, the requirement for PECAM-1 in the transendothelial migration of leukocytes previously seen in an in vitro model holds true in this in vivo model of acute inflammation.

Effect of lung volume maintenance during sleep in nocturnal asthma

Previous studies have shown that lung volume decreases and airway resistance increases during sleep in patients with nocturnal asthma. To determine whether the fall in lung volume per se causes the overnight decrement in forced expiratory volume in 1 s (FEV1) and/or increase in bronchial responsiveness, we investigated the effect of preventing this nocturnal decrease in lung volume. The mean volume change on a baseline night was -16.3 +/- 1.6% from presleep values and on the volume maintenance night +7.1 +/- 3.0% (P = 0.0001). However, this maintenance of lung volume did not alter the overnight decrement in FEV1 (-29.6 +/- 5.2% baseline vs. -30.2 +/- 5.8% volume maintenance). Similarly, the increase in bronchial responsiveness was also unaltered from baseline to volume maintenance nights, with presleep provocative concentrations of methacholine producing a 20% decrement in FEV1 of 0.28 +/- 0.15 vs. 0.22 +/- 0.7 mg/ml, respectively, and postsleep values of 0.07 +/- 0.03 vs. 0.04 +/- 0.02 mg/ml, respectively. Thus the fall in lung volume during sleep in the nocturnal asthmatic patient is a result, not a cause, of the overnight worsening of lung function.

Overnight theophylline concentrations and effects on sleep and lung function in chronic obstructive pulmonary disease

Circadian alterations in lung function occur in respiratory disorders, with the nadir during the sleep-related hours. Higher therapeutic serum theophylline concentrations (STC) during the night have been shown to improve lung function in reversible airway disease. To determine what effect higher nocturnal STC would have in patients with chronic obstructive pulmonary disease (COPD) on overnight lung function, oxygen saturation, and sleep quality, two different theophylline products were used to give higher or lower STC during the night. We found that with a higher STC (15.0 +/- 1.0 versus 11.0 +/- 1.0 micrograms/ml, p = 0.005) at 7:00 A.M., the overnight changes in FEV1 (+7.4 +/- 5.7% versus -18.9 +/- 7.9%, respectively) and FVC (+1.8 +/- 7.5% versus -17.2 +/- 3.9%, respectively) were significantly better. However, there was no apparent effect on oxygen saturation (mean sleep values for higher STC were 85.3 +/- 1.2%, and for lower STC they were 86.5 +/- 0.8%). The higher STC did not adversely affect sleep latency, sleep efficiency, or sleep staging. We conclude that a higher therapeutic STC during sleep will improve lung function without altering oxygen saturation in patients with COPD. In this group of patients, the higher STC did not interfere with sleep characteristics.

Nasal CPAP in nonapneic nocturnal asthma

Nasal CPAP has been shown to improve nocturnal asthma in those patients with associated sleep apnea. We studied seven nonapneic, nonsnoring asthmatics to determine the effect of CPAP in this patient population. On the CPAP night vs the baseline night, there was a significant worsening of sleep architecture. This included increased awake time and decreased REM sleep. For the group, the overnight decrement in FEV1 was not improved. Of interest, two patients did have a marked improvement in FEV1 associated with improved oxygen saturation on the CPAP night. These individuals were restudied only on supplemental oxygen. This intervention also improved the overnight FEV1 and allowed the patients to have better sleep compared to the CPAP night. We concluded that CPAP is associated with disrupted sleep architecture in nonapneic asthmatics and nocturnal oxygen desaturation may play a role in the development of nocturnal asthma.

Influence of posture and sustained loss of lung volume on pulmonary function in awake asthmatic subjects

Nocturnal worsening occurs commonly in the asthmatic patient population and contributes substantially to the morbidity and even mortality of asthma. However, no physiologic process has yet been identified as the major contributor to this pattern. Sleep is typically associated with both the supine posture and substantial decrements in lung volume, and both have been proposed to have a role in the pattern of nocturnal worsening. To assess the effects of posture and sleep-associated reductions in functional residual capacity on pulmonary function, eight asthmatic patients were first monitored overnight in a horizontal volume-displacement body plethysmograph to determine mean FRC during sleep for each subject. We then compared, during wakefulness, the effects on FEV1 and methacholine responsiveness from chest wall and abdomen strapping (to maintain FRC at mean sleep levels) for 6 h in the supine and upright postures. FEV1 was significantly decreased after strapping in the supine posture (2.54 +/- 0.36 versus 3.38 +/- 0.29 L on control day, p = 0.0001) but was not affected by strapping in the upright posture (3.07 +/- 0.30 versus 3.34 +/- 0.31 L on control day, not significant, NS). Bronchial responsiveness to methacholine was not altered after strapping in either posture. These observations suggest that the supine posture, in conjunction with the reduction in lung volume associated with sleep, may contribute to the nocturnal worsening of asthma.

Assessment of bronchodilator response to a beta-adrenergic delivered from an ultrasonic nebulizer

We assessed the bronchodilator response to a recently available ultrasonic nebulizer (USN) in a population of 17 stable asthmatic patients. These patients were also evaluated for bronchodilator response to two other aerosol delivery systems routinely used in standard clinical practice, the metered-dose inhaler (MDI) and the jet nebulizer (JN). Albuterol was administered from each of the delivery systems in the following manner: MDI, two actuations (180 micrograms); JN, 0.5 ml of 0.5 percent solution (2.5 mg) in 1.0 ml saline solution diluent; and USN, 0.5 ml of 0.5 percent solution (2.5 mg) in 2.5 ml saline solution diluent. Patients demonstrated significant bronchodilator responses to all three delivery systems (p less than 0.0001). The USN produced a greater percentage of increase in FEV1 15 minutes after treatment with albuterol (35.8 +/- 2.3 percent) than either the MDI (18.2 +/- 3.4 percent) or JN (20.8 +/- 3.1 percent) (p less than 0.005). The mean percentage of increase in FE1 observed over a 4-h period after treatment was also greater for the USN (26.5 +/- 2.5 percent) than either the MDI (18.8 +/- 1.8 percent) or JN (15.0 +/- 1.6 percent) (p less than 0.001). We conclude that the USN yields effective bronchodilation in a population of stable asthmatics.

Effect of sleep and sleep deprivation on ventilatory response to bronchoconstriction

To characterize ventilatory responses to bronchoconstriction during sleep and to assess the effect of prior sleep deprivation on ventilatory and arousal responses to bronchoconstriction, bronchoconstriction was induced in eight asthmatic subjects while they were awake, during normal sleep, and during sleep after a 36-h period of sleep deprivation. Each subject was bronchoconstricted with increasing concentrations of aerosolized methacholine while ventilatory patterns and lower airway resistance (Rla) were continually monitored. The asthmatic patients maintained their minute ventilation as Rla increased under all conditions, demonstrating a stable tidal volume with a mild increase in respiratory frequency. Inspiratory drive, as measured by occlusion pressure (P0.1), increased progressively and significantly as Rla increased under all conditions (slopes of P0.1 vs. Rla = 0.249, 0.112, and 0.154 for awake, normal sleep, and sleep after sleep deprivation, respectively, P less than 0.0006). Chemostimuli did not appear to contribute significantly to the observed increases in P0.1. Prior sleep deprivation had no effect on ventilatory and P0.1 responses to bronchoconstriction but did significantly raise the arousal threshold to induced bronchoconstriction. We conclude that ventilatory responses to bronchoconstriction, unlike extrinsic loading, are not imparied by the presence of sleep, nor are they chemically mediated. However, prior sleep deprivation does increase the subsequent arousal threshold.

Influence of sleep on lung volume in asthmatic patients and normal subjects

To assess the effect of sleep on functional residual capacity (FRC) in normal subjects and asthmatic patients, 10 adult subjects (5 asthmatic patients with nocturnal worsening, 5 normal controls) were monitored overnight in a horizontal volume-displacement body plethysmograph. With the use of a single inspiratory occlusion technique, we determined that when supine and awake, asthmatic patients were hyperinflated relative to normal controls (FRC = 3.46 +/- 0.18 and 2.95 +/- 0.13 liters, respectively; P less than 0.05). During sleep FRC decreased in both groups, but the decrease was significantly greater in asthmatic patients such that during rapid-eye-movement (REM) sleep FRC was equivalent between the asthmatic and normal groups (FRC = 2.46 +/- 0.23 and 2.45 +/- 0.09 liters, respectively). Specific pulmonary conductance decreased progressively and significantly in the asthmatic patients during the night, falling from 0.047 +/- 0.007 to 0.018 +/- 0.002 cmH2O-1.s-1 (P less than 0.01). There was a significant linear relationship through the night between FRC and pulmonary conductance in only two of the five asthmatic patients (r = 0.55 and 0.65, respectively). We conclude that 1) FRC falls during sleep in both normal subjects and asthmatic patients, 2) the hyperinflation observed in awake asthmatic patients is diminished during non-REM sleep and eliminated during REM sleep, and 3) sleep-associated reductions in FRC may contribute to but do not account for all the nocturnal increase in airflow resistance observed in asthmatic patients with nocturnal worsening.