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Phillip Factor

Publications and source records attributed to Phillip Factor.

At least 19 recordsLinked to original sources
PubMed2006

Alveolar fluid reabsorption is increased in rats with compensated heart failure.

Alveolar fluid reabsorption (AFR) is important in keeping the air spaces free of edema. This process is accomplished via active transport of Na(+) across the alveolo-capillary barrier mostly by apical Na(+) channels and basolateral Na(+)-K(+)-ATPases. Recently, we have reported that acute elevation of left atrial pressures is associated with decreased AFR in isolated rat lungs. However, the effect of chronic elevation of pulmonary capillary pressure, such as seen in patients with congestive heart failure (CHF), on AFR is unknown. CHF was induced by creating an aorto-caval fistula (ACF) in Sprague-Dawley male rats. Seven days after the placement of the fistula, AFR was studied in the isolated perfused rat lung model. AFR in control rats was 0.49 +/- 0.02 ml/h (all values are means +/- SE) and increased by approximately 40% (0.69 +/- 0.03 ml/h) in rats with chronic CHF (P < 0.001). The albumin flux from the pulmonary circulation into the air spaces did not increase in the experimental groups, indicating that lung permeability for large solutes was not increased. Na(+)-K(+)-ATPase activity and protein abundance at the plasma membrane of distal alveolar epithelial tissue were significantly increased in CHF rats compared with controls. These changes were associated with increased plasma norepinephrine levels in CHF rats compared with controls. We provide evidence that in a rat model of chronic compensated CHF, AFR is increased, possibly due to increased endogenous norepinephrine upregulating active sodium transport and protecting against alveolar flooding.

Adrenalectomy↗
PubMed2005

Interdependency of beta-adrenergic receptors and CFTR in regulation of alveolar active Na+ transport.

Beta-adrenergic receptors (betaAR) regulate active Na+ transport in the alveolar epithelium and accelerate clearance of excess airspace fluid. Accumulating data indicates that the cystic fibrosis transmembrane conductance regulator (CFTR) is important for upregulation of the active ion transport that is needed to maintain alveolar fluid homeostasis during pulmonary edema. We hypothesized that betaAR regulation of alveolar active transport may be mediated via a CFTR dependent pathway. To test this hypothesis we used a recombinant adenovirus that expresses a human CFTR cDNA (adCFTR) to increase CFTR function in the alveolar epithelium of normal rats and mice. Alveolar fluid clearance (AFC), an index of alveolar active Na+ transport, was 92% greater in CFTR overexpressing lungs than controls. Addition of the Cl- channel blockers NPPB, glibenclamide, or bumetanide and experiments using Cl- free alveolar instillate solutions indicate that the accelerated AFC in this model is due to increased Cl- channel function. Conversely, CFTR overexpression in mice with no beta1- or beta2-adrenergic receptors had no effect on AFC. Overexpression of a human beta2AR in the alveolar epithelium significantly increased AFC in normal mice but had no effect in mice with a non-functional human CFTR gene (Deltaphi508 mutation). These studies indicate that upregulation of alveolar CFTR function speeds clearance of excess fluid from the airspace and that CFTRs effect on active Na+ transport requires the betaAR. These studies reveal a previously undetected interdependency between CFTR and betaAR that is essential for upregulation of active Na+ transport and fluid clearance in the alveolus.

Animals↗
PubMed2005

In vivo molecular imaging characterizes pulmonary gene expression during experimental lung transplantation.

Experimental gene therapy is a promising strategy to prevent ischemia-reperfusion (I/R) injury and allograft rejection after lung transplantation, and methods will eventually be needed to characterize pulmonary transgene expression in vivo in humans. Therefore, we studied positron emission tomography (PET) as a means of performing in vivo molecular imaging in rodent models of lung transplantation. Rats were transfected endotracheally with adenovirus encoding a fusion gene of a mutant Herpes simplex virus-1 thymidine kinase and the green fluorescent protein gene (the former serving as an imaging reporter gene). Twenty-four hours after transfection, lungs were transplanted in groups representing normal transplantation, I/R injury and acute allograft rejection. Imaging was obtained either 24 h after transplantation to study reperfusion injury or 4 days after transplantation to study graft rejection. After imaging, lungs were excised and analyzed for thymidine kinase activity. Imaging detected transgene expression in transplanted lungs even in the presence of acute rejection or I/R injury. The PET imaging signal correlated with in vitro lung tissue assays of thymidine kinase activity (r(2) = 0.534). Thus, noninvasive molecular imaging with PET is a feasible, sensitive and quantitative method for characterizing pulmonary transgene expression in experimental lung transplantation.

Animals↗
PubMed2004

Apical trypsin increases ion transport and resistance by a phospholipase C-dependent rise of Ca2+.

We investigated the mechanisms by which serine proteases alter lung fluid clearance in rat lungs and vectorial ion transport in airway and alveolar epithelial cells. Inhibition of endogenous protease activity by intratracheal instillation of soybean trypsin inhibitor (SBTI) or alpha(1)-antitrypsin decreased amiloride-sensitive lung fluid clearance across rat fluid-filled lungs; instillation of trypsin partially restored this effect. Gelatin zymography demonstrated SBTI-inhibitable trypsin-like activity in rat lung lavage fluid. Apical trypsin and human neutrophil elastase, but not agonists of protease activated receptors, increased Na(+) and Cl(-) short-circuit currents (I(sc)) and transepithelial resistance (R(TE)) across human bronchial and nasal epithelial cells and rat alveolar type II cells, mounted in Ussing chambers, for at least 2 h. The increase in I(sc) was fully reversed by amiloride and glibenclamide. The increase in R(TE) was not prevented by ouabain, suggesting that trypsin decreased paracellular conductance. Apical trypsin also induced a transient increase in intracellular Ca(2+) in human airway cells; treatment of these cells with BAPTA-AM mitigated the trypsin-induced increases of intracellular Ca(2+) and of I(sc) and R(TE). Increasing intracellular Ca(2+) in airway cells with either ionomycin or thapsigargin reproduced the increase in I(sc), whereas inhibitors of phospholipase C (PLC) prevented the increases in both Ca(2+) and I(sc). These data indicate trypsin-like proteases and elastase, either present in lung cells or released by inflammatory cells into the alveolar space, play an important role in the clearance of alveolar fluid by increasing ion transport and paracellular resistance via a PLC-initiated rise of intracellular Ca(2+).

Animals↗
PubMed2004

Role of vasopressin in the management of septic shock.

Vasopressin is a potent vasopressor for improving organ perfusion during septic shock. The rationale for the use of vasopressin is its relative deficiency of plasma levels and hypersensitivity to its vasopressor effects during septic shock. Growing evidence suggests that low-dose (<0.04 U/min) vasopressin is safe and effective for the treatment of vasodilatory shock. Although it is being used more frequently, there are no randomized clinical trials comparing vasopressin as a first-line agent to commonly used vasopressors. However, vasopressin causes arterial smooth muscle cell contraction through a non-catecholamine receptor pathway, thus it represents an attractive adjunct to the management of septic shock, especially when catecholamines are ineffective.

Amino Acid Sequence↗
PubMed2004

Upregulation of alveolar epithelial active Na+ transport is dependent on beta2-adrenergic receptor signaling.

Alveolar epithelial beta-adrenergic receptor (betaAR) activation accelerates active Na+ transport in lung epithelial cells in vitro and speeds alveolar edema resolution in human lung tissue and normal and injured animal lungs. Whether these receptors are essential for alveolar fluid clearance (AFC) or if other mechanisms are sufficient to regulate active transport is unknown. In this study, we report that mice with no beta1- or beta2-adrenergic receptors (beta1AR-/-/beta2AR-/-) have reduced distal lung Na,K-ATPase function and diminished basal and amiloride-sensitive AFC. Total lung water content in these animals was not different from wild-type controls, suggesting that betaAR signaling may not be required for alveolar fluid homeostasis in uninjured lungs. Comparison of isoproterenol-sensitive AFC in mice with beta1- but not beta2-adrenergic receptors to beta1AR-/-/beta2AR-/- mice indicates that the beta2AR mediates the bulk of beta-adrenergic-sensitive alveolar active Na+ transport. To test the necessity of betaAR signaling in acute lung injury, beta1AR-/-/beta2AR-/-, beta1AR+/+/beta2AR-/-, and beta1AR+/+/beta2AR+/+ mice were exposed to 100% oxygen for up to 204 hours. beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice had more lung water and worse survival from this form of acute lung injury than wild-type controls. Adenoviral-mediated rescue of beta2-adrenergic receptor (beta2AR) function into the alveolar epithelium of beta1AR-/-/beta2AR-/- and beta1AR+/+/beta2AR-/- mice normalized distal lung beta2AR function, alveolar epithelial active Na+ transport, and survival from hyperoxia. These findings indicate that betaAR signaling may not be necessary for basal AFC, and that beta2AR is essential for the adaptive physiological response needed to clear excess fluid from the alveolar airspace of normal and injured lungs.

Amiloride↗
PubMed2004

Potential genetic therapies for acute lung injury.

Acute lung injury (ALI) is a common, highly lethal acquired disorder that affects over one hundred thousand people each year and for which there are no specific therapies. Extensive investigations in experimental models and humans with ALI have identified several maladaptive host responses and dysregulated protein systems that offer therapeutic opportunities for genetic intervention. Several lines of evidence suggest that gene transfer can be used to deliver protective proteins that improve alveolar epithelial and/or endothelial cell function or immunomodulators that augment lung defense mechanisms and speed clearance of infection. In many instances, gene transfer is the only avenue for producing localized expression of these pharmaceuticals. This article reviews recent translational, animal-based studies that tested the use of gene and cell based therapies to ameliorate or prevent ALI. The lack of effective therapies for ALI and the approachability of the lung for local gene transfer suggest that ALI is a unique example of an acute disease process that is suitable for gene therapy.

Animals↗
PubMed2004

Quantitation of pulmonary transgene expression with PET imaging.

UNLABELLED: PET imaging represents a promising approach for noninvasive monitoring of reporter gene expression in living subjects. We evaluated the relationship between various methods of quantifying the imaging signal and in vitro assays of the expression of a PET reporter gene (a mutant Herpes simplex virus-1 thymidine kinase (mHSV1-tk); 9-(4-(18)F-fluoro-3-hydroxymethylbutyl)guanine ((18)F-FHBG) was used as the PET reporter probe. METHODS: In 14 rats, pulmonary gene transfer was performed by intratracheal administration of various amounts of an adenovector containing a fusion gene encoding for mHSV1-tk and an enhanced green fluorescent protein. Three days later, the animals were divided into 2 groups. One group (n = 7) did not receive any other interventions. The other group was treated with alpha-naphthylthiourea (ANTU) to increase pulmonary vascular permeability. All rats were injected intravenously with (18)F-FHBG. Two additional rats in both groups received a null adenovector and served as controls. In the normal rats, repetitive blood samples were obtained and PET imaging was performed simultaneously using a dynamic imaging protocol. Rate constants estimating (18)F-FHBG transport (K(1)) or trapping (k(3)) within target cells were generated by compartmental modeling. After euthanasia, pulmonary uptake of (18)F-FHBG was determined using a gamma-counter in all rats, and in vitro assays of transgene expression were performed on lung tissue. RESULTS: In normal rats, pulmonary uptake of (18)F-FHBG increased as thymidine kinase (TK) activity increased only at low levels of mHSV1-tk expression and then plateaued as TK activity continued to increase. Compartmental modeling failed to improve the correlation with in vitro assays of transgene expression. However, a linear relationship was obtained between the pulmonary uptake of (18)F-FHBG and in vitro assays of TK activity in rats treated with ANTU. CONCLUSION: In rodent lungs, (18)F-FHBG uptake appears to be a function of both transport into tissues expressing the transgene as well as the level of transgene expression itself.

Animals↗
PubMed2003

Augmentation of endogenous dopamine production increases lung liquid clearance.

We have previously reported that dopamine increased active Na+ transport in rat lungs by upregulating the alveolar epithelial Na,K-ATPase. Here we tested whether alveolar epithelial cells produce dopamine and whether increasing endogenous dopamine production by feeding rats a 4% tyrosine diet (TSD) would increase lung liquid clearance. Alveolar Type II cells express the enzyme aromatic-L-amino acid decarboxylase (AADC) and, when incubated with the dopamine precursor, 3-hydroxy-L-tyrosine (L-dopa), produce dopamine. Rats fed TSD, a precursor of L-dopa and dopamine, had increased urinary dopamine levels, which were inhibited by benserazide, an inhibitor of AADC. Rats fed TSD for 15, 24, and 48 hours had a 26, 46, and 45% increase in lung liquid clearance, respectively, as compared with controls. Also, dopaminergic D1 receptor antagonist--but not dopaminergic D2 receptor antagonist--inhibited the TSD-mediated increase in lung liquid clearance. Alveolar Type II cells isolated from the lungs of rats after they had been fed TSD for 24 hours demonstrated increased protein abundance of Na,K-ATPase alpha1 and beta1 subunits. Basolateral membranes isolated from peripheral lung tissue of tyrosine-fed rats had increased Na,K-ATPase activity and Na,K-ATPase alpha1 subunit. These data provide the first evidence that alveolar epithelial cells produce dopamine and that increasing endogenous dopamine increases lung liquid clearance.

Animals↗
PubMed2003

Na,K-ATPase gene transfer increases liquid clearance during ventilation-induced lung injury.

Mechanical ventilation with high tidal volumes (HVT) downregulates alveolar Na,K-ATPase function and impairs lung liquid clearance. We hypothesized that overexpression of Na,K-ATPase in the alveolar epithelium could counterbalance these changes and increase clearance in a rat model of mild ventilation-induced lung injury. We used a surfactant-based system to deliver 4 x 10(9) plaque-forming units of E1a-/E3- recombinant adenovirus containing either a rat beta1 Na,K-ATPase subunit cDNA (adbeta1) or no cDNA (adnull) to rat lungs 7 days before ventilation with a VT of approximately 40 ml/kg (peak airway pressure of less than 35 cm H2O) for 40 minutes. Lung liquid clearance and Na, K-ATPase activity and protein abundance were increased in HVT adbeta1-infected lungs as compared with sham and adnull-infected HVT lungs. These results suggest that Na,K-ATPase subunit gene overexpression in the alveolar epithelium increases Na,K-ATPase function and lung liquid clearance in a model of HVT. We provide here the first evidence that using a genetic approach improves active Na+ transport and thus liquid clearance in the setting of mild ventilation-induced lung injury.

Animals↗
PubMed2003

In vivo timing of onset of transgene expression following adenoviral-mediated gene transfer.

Recombinant adenoviruses are efficient gene transfer vehicles that could be used for treatment of acute diseases. However, the time required for adenoviruses to produce physiologically relevant levels of transgene in vivo is unknown. To address this question rat lungs were infected with an E1a(-)/E3a(-) adenovirus that contains an hCMV-driven human beta(2)-adrenergic receptor (beta(2)AR) cDNA. Human beta(2)AR message and protein expression were noted 2-4 h postinfection without evidence of pseudotransduction. beta(2)AR function (cAMP production) was increased at 6 h postinfection. To determine when beta(2)AR gene transfer affects downstream catecholamine-sensitive pathways, we measured lung Na,K-ATPase expression and alveolar fluid clearance (AFC). beta(2)AR gene transfer increased Na,K-ATPase number by 80% at 6 h, and AFC by 20% at 8 h postinfection. These data indicate that recombinant adenoviruses can produce physiologically significant levels of transgene within hours of infection and that they may be suitable for gene therapies for acute, rapidly progressive diseases.

Adenoviridae↗
PubMed2003

Prevention and treatment of gastrointestinal complications in patients on mechanical ventilation.

There exists a complex, dynamic interaction between mechanical ventilation and the splanchnic vasculature that contributes to a myriad of gastrointestinal tract complications that arise during critical illness. Positive pressure-induced splanchnic hypoperfusion appears to play a pivotal role in the pathogenesis of these complications, the most prevalent of which are stress-related mucosal damage, gastrointestinal hypomotility and diarrhea. Furthermore, characteristics of the splanchnic vasculature make the gastrointestinal tract vulnerable to adverse effects related to positive pressure ventilation. While most of these complications seen in mechanically ventilated patients are reflections of altered gastrointestinal physiology, some may be attributed to medical interventions instituted to treat critical illness. Since maintenance of normal hemodynamics cannot always be achieved, pharmacologic prophylactic therapy has become a mainstay in the prevention of gastrointestinal complications in the intensive care unit. Improved understanding of the systemic effects of mechanical ventilation and greater application of lung-protective ventilatory strategies may potentially minimize positive pressure-induced reductions in splanchnic perfusion, systemic cytokine release and, consequently, reduce the incidence of gastrointestinal complications associated with mechanical ventilation. Herein, we discuss the pathophysiology of gastrointestinal complications associated with mechanical ventilation, summarize the most prevalent complications and focus on preventive strategies and available treatment options for these complications. The most common causes of gastrointestinal hemorrhage in mechanically ventilated patients are bleeding from stress-related mucosal damage and erosive esophagitis. In general, histamine H(2) receptor antagonists and proton pump inhibitors prevent stress-related mucosal disease by raising the gastric fluid pH. Proton pump inhibitors tend to provide more consistent pH control than histamine H(2) receptor antagonists. There is no consensus on the drug of choice for stress ulcer prophylaxis with several meta-analyses providing conflicting results on the superiority of any medication. Prevention of erosive esophagitis include careful use of nasogastric tubes and institution of strategies that improve gastric emptying. Many mechanically ventilated patients have gastrointestinal hypomotility and diarrhea. Treatment options for gastrointestinal motility are limited, thus, preventive measures such as correction of electrolyte abnormalities and avoidance of medications that impair gastrointestinal motility are crucial. Treatment of diarrhea depends on the underlying cause. When associated with Clostridium difficile infection antibacterial therapy should be discontinued, if possible, and treatment with oral metronidazole should be initiated.More studies are warranted to better understand the systemic effects of mechanical ventilation on the gastrointestinal tract and to investigate the impact of lung protective ventilatory strategies on gastrointestinal complications.

Gastrointestinal Diseases↗
PubMed2003

Gene therapy for asthma.

The accessibility of the airway epithelium and the limitations of current treatments for asthma make the disease a logical target for gene therapy. Study of the immunopathology of chronic airway inflammation has recently identified several pathways that lead to the maladaptive, antigen-induced polarization of CD4+ T cells to a type-2 phenotype. This polarization is thought to lead to IgE production and eosinophil recruitment and activation that is associated with epithelial cell injury and airway hyper-reactivity. Gene transfer to the bronchial epithelium has been used in experimental models to redirect these pathways toward a less injurious, type-1 phenotype. This mini-review highlights recent mechanism-based immunomodulatory and supportive gene transfer approaches to treat animal models of asthma. Although substantial hurdles to airway gene transfer remain, gene transfer offers the possibility of interrupting the pathophysiology of airway inflammation. Doing so can be expected to yield long-lasting protection from bronchospastic challenge and reduced dependence on inhaled and oral medications.

Animals↗
PubMed2002

Acute hyperoxic lung injury does not impede adenoviral-mediated alveolar gene transfer.

The transfer of protective genes to the alveolar epithelium can attenuate lung injury if accomplished before its onset. The pathobiology of acute lung injury (ALI) includes formidable hurdles to gene transfer, including alveoli filled with fluid, inflammatory cells, and cytokines, all of which may impair gene transfer after the onset of injury. We tested the hypothesis that adenovectors could efficiently transduce injured alveoli by exposing adult, male Sprague-Dawley rats to 100% oxygen for 48 or 60 h before endotracheal instillation of either 1 x 10(9) or 4 x 10(9) plaque-forming units of an adenovirus that expresses an Escherichia coli lac Z gene (adbeta-gal) in a surfactant-based vehicle (Survanta). X-gal staining 72 h postinfection revealed transgene expression in all segments of room air control and hyperoxic lungs infected with either dose of adbeta-gal. Net transgene expression in hyperoxic lungs was not different from room air controls despite the presence of pulmonary edema and severe histologic injury. These findings show that adenovectors can efficiently transduce the alveoli of acutely injured, edematous lungs. The data indicate that the pathophysiologic processes of ALI do not impair adenoviral-mediated alveolar gene transfer and provide support for the development of gene therapies for ALI.

Adenoviridae↗
PubMed2002

Na,K-ATPase overexpression improves alveolar fluid clearance in a rat model of elevated left atrial pressure.

BACKGROUND: Acute elevation of left atrial pressure (LAP) increases extravascular water and impairs active Na(+) transport in rat lungs. We have reported that overexpression of Na,K-ATPase subunit genes in the alveolar epithelium increases alveolar fluid clearance (AFC) in normal and injured rat lungs with normal LAP. We reasoned that adenovirus-mediated transfer of an Na,K-ATPase beta-subunit gene to the alveolar epithelium could improve AFC in rat lungs in the presence of acutely elevated LAP. METHODS AND RESULTS: Normal rats were infected with 4x10(9) plaque-forming units of E1a(-)/E3(-) recombinant adenoviruses that contained a cytomegalovirus promoter coupled to a rat Na,K-ATPase beta(1)-subunit cDNA (adbeta(1)) or no cDNA (adNull) 7 days before study. Na,K-ATPase alpha(1)- and beta(1)-subunit abundance in basolateral cell membranes isolated from the peripheral lung was significantly increased in adbeta(1)-infected lungs compared with sham and adNull-infected controls. In all groups, elevation of LAP reduced membrane-bound Na,K-ATPase abundance; however, abundance in adbeta(1)-infected lungs remained greater than in controls. AFC, measured with a fluid-filled isolated lung preparation in the presence of elevated LAP (15 cmH(2)O), in Na,K-ATPase beta(1)-subunit-overexpressing lungs was up to 100% greater than in controls and was not different from rats studied at normal LAP (0 cmH(2)O). CONCLUSIONS: These data suggest that alveolar overexpression of an Na,K-ATPase beta(1)-subunit can counteract downregulation of membrane-bound solute transporters owing to elevated pulmonary vascular pressures and can restore active Na(+) transport and AFC in this rat model of acute hydrostatic pulmonary edema.

Adenoviridae↗