Kelvin D. MacDonald

Lubiprostone Activates CFTR, but not ClC-2, via the Prostaglandin Receptor (EP4)

The goal of this study was to determine the mechanism of lubiprostone activation of epithelial chloride transport. Lubiprostone is a bicyclic fatty acid approved for the treatment of constipation [1]. There is uncertainty, however, as to how lubiprostone increases epithelial chloride transport. Direct stimulation of ClC-2 and CFTR chloride channels as well as stimulation of these channels via the EP(4) receptor has been described [2-5]. To better define this mechanism, two-electrode voltage clamp was used to assay Xenopus oocytes expressing ClC-2, with or without co-expression of the EP(4) receptor or β adrenergic receptor (βAR), for changes in conductance elicited by lubiprostone. Oocytes co-expressing CFTR and either βAR or the EP(4) receptor were also studied. In oocytes co-expressing ClC-2 and βAR conductance was stimulated by hyperpolarization and acidic pH (pH = 6), but there was no response to the β adrenergic agonist, isoproterenol. Oocytes expressing ClC-2 only or co-expressing ClC-2 and EP(4) did not respond to the presence of 0.1, 1, or 10 μM lubiprostone in the superperfusate. Oocytes co-expressing CFTR and βAR did not respond to hyperpolarization, acidic pH, or 1 μM lubiprostone. However, conductance was elevated by isoproterenol and inhibited by CFTR(inh)172. Co-expression of CFTR and EP(4) resulted in lubiprostone-stimulated conductance, which was also sensitive to CFTR(inh)172. The EC(50) for lubiprostone mediated CFTR activation was ~10 nM. These results demonstrate no direct action of lubiprostone on either ClC-2 or CFTR channels expressed in oocytes. However, the results confirm that CFTR can be activated by lubiprostone via the EP(4) receptor in oocytes.

Oral antimicrobial use in outpatient cystic fibrosis pulmonary exacerbation management: a single-center experience.

Introduction:  Cystic fibrosis (CF) pulmonary disease is characterized by intermittent episodes of acute lung symptoms known as ‘pulmonary exacerbations’. While exacerbations are classically treated with parenteral antimicrobials, oral antibiotics are often used in ‘mild’ cases.

Aqueous cigarette smoke extract induces a voltage-dependent inhibition of CFTR expressed in Xenopus oocytes

The cystic fibrosis transmembrane conductance regulator (CFTR) chloride channel inhabits the apical membrane of airway epithelia, where its function is essential for mucus hydration, mucociliary clearance, and airway defense. Chronic obstructive pulmonary disease (COPD), most often a consequence of cigarette smoke (CS) exposure, affects 15 million persons in the US. Clinically, COPD is characterized by many of the salient features of cystic fibrosis lung disease, where CFTR is either absent or reduced in function. CS is an acidic aerosol (pH 5.3 to 6.3) reported to contain over 4,000 constituents. Acute CS exposure has been reported to decrease airway transepithelial voltage in vivo and short-circuit current in vitro; however, the mechanistic basis of these effects is uncertain. The goal of the studies described here was to develop a bioassay to characterize the effects of aqueous CS preparations on the channel function of CFTR. We studied aqueous CS extract (CSE) prepared in our laboratory, as well as commercial cigarette smoke condensate (CSC) in Xenopus oocytes expressing human CFTR. Application of CSE at pH 5.3 produced a reversible, voltage-dependent inhibition of CFTR conductance. CSE neutralized to pH 7.3 produced less inhibition of CFTR conductance. Serial dilution of CSE revealed a dose-dependent effect at acidic and neutral pH. In contrast, CSC did not inhibit CFTR conductance in oocytes. We conclude that one or more components of CSE inhibits CFTR in a manner similar to diphenylamine-2-carboxylate, a negatively charged, open-channel blocker.

Maternal high‐fat diet in mice leads to innate airway hyperresponsiveness in the adult offspring

Maternal obesity prior to and during pregnancy has been associated with an increased incidence of childhood asthma. As diets rich in saturated fat are linked to obesity and inflammation, we created a murine model to investigate the effect of maternal high‐fat diet (HFD) on adult offspring airway hyperreactivity (AHR), a cardinal feature of asthma. Balb/cByJ dams were fed a HFD (60% fat Calories) or normal‐fat diet (NFD) (10% fat Calories) from 8 weeks prior to first breeding through their pregnancies. Pups were weaned to either a HFD or NFD (at 4 weeks of age). AHR was measured in the 10‐week‐old offspring following inhaled methacholine challenge by end‐inflation technique. Bronchial alveolar lavage fluid (BALF) was analyzed for cell count, total protein, and IL‐6. Offspring of HFD dams weaned to NFD had increased AHR compared to offspring of NFD dams weaned to NFD. Offspring of HFD dams that remained on HFDs had increased AHR compared to offspring of NFD dams weaned to HFDs. Offspring of HFD dams had higher BALF cell counts, higher neutrophil percentage, greater total protein, and IL‐6 in the BALF. These results demonstrate that a maternal diet high in saturated fat through pregnancy and lactation plays a key role in programming adult offspring AHR.

Maternal body mass index before pregnancy is associated with increased bronchodilator dispensing in early childhood: A cross-sectional study.

Maternal prepregnancy obesity has been associated with early wheeze and childhood asthma in their offspring. Some of these studies have been in minority, urban, and disadvantaged populations using parental recall and questionnaires. The association of maternal prepregnancy obesity with bronchodilator dispensing to their offspring, in a primarily insured, non‐urban, White population in the United States is unknown.

Maternal body mass index before pregnancy is associated with increased bronchodilator dispensing in early childhood

Maternal prepregnancy obesity has been associated with early wheeze and childhood asthma in their offspring. Some of these studies have been in minority, urban, and disadvantaged populations using parental recall and questionnaires. The association of maternal prepregnancy obesity with bronchodilator dispensing to their offspring, in a primarily insured, non‐urban, White population in the United States is unknown.

Cost effectiveness of vitamin c supplementation for pregnant smokers to improve offspring lung function at birth and reduce childhood wheeze/asthma

Objective:To determine the implications of supplemental vitamin C for pregnant tobacco smokers and its effects on the prevalence of pediatric asthma, asthma-related mortality, and associated costs.Study design:A decision-analytic model built via TreeAge compared the outcome of asthma in a theoretical annual cohort of 480,000 children born to pregnant smokers through 18 years of life. Vitamin C supplementation (500 mg/day) with a standard prenatal vitamin was compared to a prenatal vitamin (60 mg/day). Model inputs were derived from the literature. Deterministic and probabilistic sensitivity analyses assessed the impact of assumptions.Result:Additional vitamin C during pregnancy would prevent 1637 cases of asthma at the age of 18 per birth cohort of pregnant smokers. Vitamin C would reduce asthma-related childhood deaths and save

One Center’s Guide to Outpatient Management of Pediatric Cystic Fibrosis Acute Pulmonary Exacerbation

31,420,800 in societal costs over 18 years per birth cohort.Conclusion:Vitamin C supplementation in pregnant smokers is a safe and inexpensive intervention that may reduce the economic burden of pediatric asthma.

Evaluation of the Risk for Acute Kidney Injury in Adult Cystic Fibrosis Patients Receiving Concomitant Vancomycin and Tobramycin

Cystic fibrosis (CF) is a chronic disorder characterized by acute pulmonary exacerbations that comprise increased cough, chest congestion, increased mucus production, shortness of breath, weight loss, and fatigue. Typically, severe episodes are treated in the inpatient setting and include intravenous antimicrobials, airway clearance therapy, and nutritional support. Children with less-severe findings can often be managed as outpatients with oral antimicrobials and increased airway clearance therapy at home without visiting the specialty CF center to begin treatment. Selection of specific antimicrobial agents is dependent on pathogens found in surveillance culture, activity of an agent in patients with CF, and the unique physiology of these patients. In this pediatric review, we present our practice for defining acute pulmonary exacerbation, deciding treatment location, initiating treatment either in-person or remotely, determining the frequency of airway clearance, selecting antimicrobial therapy, recommending timing for follow-up visit, and recognizing and managing treatment failures.

Aerosol Delivery Of Methacholine During Oral Intubated Measurement Of Murine Lung Mechanics

Background The risk for acute kidney injury (AKI) has been associated with both tobramycin and vancomycin. Objective To determine whether the rate of drug therapy-related nephrotoxicity is greater in Cystic Fibrosis (CF) patients receiving concomitant vancomycin and tobramycin than patients receiving either agent alone. Methods Adult CF patients admitted for acute pulmonary exacerbation (APE) over a seven-year period (2008-2014), who received at least 72 hours of intravenous vancomycin, tobramycin or a combination of the two agents were evaluated for AKI. AKI was defined as a 1.5-fold increase in serum creatinine per RIFLE criteria. One hundred seventy-four hospital encounters from 72 unique patients were assessed in this single-center, cross-sectional study. Results AKI outcomes were not statistically different. AKI rates were 19% for vancomycin, 8.7% for tobramycin, and 19.7% for combination cohorts (p = 0.16). Conclusion Our data suggest there is no significant difference in AKI risk when vancomycin and tobramycin combination therapy is used.