Polarization-dependent apical membrane CFTR targeting underlies cAMP-stimulated Cl- secretion in epithelial cells

Dual-specificity phosphatase (DUSP) genetic variants predict pulmonary hypertension in patients with bronchopulmonary dysplasia

BACKGROUND

Pulmonary hypertension (PH) in patients with bronchopulmonary dysplasia (BPD) results from vasoconstriction and/or vascular remodeling, which can be regulated by mitogen-activated protein kinases (MAPKs). MAPKs are deactivated by dual-specificity phosphatases (DUSPs). We hypothesized that single-nucleotide polymorphisms (SNPs) in DUSP genes could be used to predict PH in BPD.

METHODS

Preterm infants diagnosed with BPD (n = 188) were studied. PH was defined by echocardiographic criteria. Genomic DNA isolated from patient blood samples was analyzed for 31 SNPs in DUSP genes. Clinical characteristics and minor allele frequencies were compared between BPD-PH (cases) and BPD-without PH (control) groups. Biomarker models to predict PH in BPD using clinical and SNP data were tested by calculations of area under the ROC curve.

RESULTS

In our BPD cohort, 32% (n = 61) had PH. Of the DUSP SNPs evaluated, DUSP1 SNP rs322351 was less common, and DUSP5 SNPs rs1042606 and rs3793892 were more common in cases than in controls. The best fit biomarker model combines clinical and DUSP genetic data with an area under the ROC curve of 0.76.

CONCLUSION

We identified three DUSP SNPs as potential BPD-PH biomarkers. Combining clinical and DUSP genetic data yields the most robust predictor for PH in BPD.

Three Cases of Primary Ciliary Dyskinesia Combined With Reduced Exhaled Nitric Oxide

OBJECTIVES

The diagnosis of primary ciliary dyskinesia (PCD) is often delayed in part related to the limitations of the available diagnostic tests. We present 3 cases of PCD diagnosed using an exhaled nitric oxide (eNO) measurement.

METHODS

Three cases with a clinical phenotype consistent with PCD were evaluated using an eNO assay with additional transmission electron microscopy (TEM) and/or genetic panel testing.

RESULTS

One male and 2 female patients presented with common symptoms included recurrent respiratory infection from early childhood and a history of neonatal respiratory distress as term newborn. Two of them had situs inversus totalis. Fractional eNO measurement revealed extremely low NO levels, and subsequently, TEM analysis confirmed ciliary ultrastructural defects in all patients. One patient had compound heterozygous mutation of the PCD-causative gene (DNAH5) identified using next generation sequencing.

CONCLUSION

Our report stresses the reliability of eNO measurement in the diagnosis of PCD, accompanied by clinical phenotypes and additional diagnostic tools, such as TEM analysis and genetic testing.

Biological activity of Echinops spinosus on inhibition of paracetamol-induced renal inflammation

This study was designed to evaluate the possible mechanisms through which Echinops spinosus (ES) extract demonstrates nephroprotective effect on the paracetamol acetominophen (N-acetyl-p-aminophenol (APAP)) induced nephrotoxicity in rats. Twenty-four Swiss albino rats were divided into four groups (six rats each). The placebo group was orally administered sterile saline, the APAP group received APAP (200 mg·kg–1·day–1 i.p.) daily, the ES group was given ES extract orally (250 mg/kg), and the APAP + ES group received APAP as for the APAP group and administrated the ES extract as for the ES group. Pretreatment of methyl alcohol extract of ES reduced the protein expression of inflammatory parameters including cyclooxygenase-2 and nuclear factor κB in the kidney. It also reduced the mRNA gene expression of tumor necrosis factor-α and interleukin-1β. The ES extract compensated for deficits in the total antioxidant activity, suppressed lipid peroxidation, and amended the APAP-induced histopathological kidney alterations. Moreover, ES treatment restored the elevated levels of urea nitrogen in the blood and creatinine in the serum by APAP. The ES extract attenuated the APAP-induced elevations in renal nitric oxide levels. We clarified that the ES extract has the potential to defend the kidney from APAP-induced inflammation, and the protection mechanism might be through decreasing oxidative stress and regulating the inflammatory signaling pathway through modulating key signaling inflammatory biomarkers.

Role of Exchange Protein Activated by cAMP 1 in Regulating Rates of Microtubule Formation in Cystic Fibrosis Epithelial Cells

The regulation of microtubule dynamics in cystic fibrosis (CF) epithelial cells and the consequences of reduced rates of microtubule polymerization on downstream CF cellular events, such as cholesterol accumulation, a marker of impaired intracellular transport, are explored here. It is identified that microtubules in both CF cell models and in primary CF nasal epithelial cells repolymerize at a slower rate compared with respective controls. Previous studies suggest a role for cAMP in modulating organelle transport in CF cells, implicating a role for exchange protein activated by cAMP (EPAC) 1, a regulator of microtubule elongation, as a potential mechanism. EPAC1 activity is reduced in CF cell models and in Cftr(-/-) mouse lung compared with respective non-CF controls. Stimulation of EPAC1 activity with the selective EPAC1 agonist, 8-cpt-2-O-Me-cAMP, stimulates microtubule repolymerization to wild-type rates in CF cells. EPAC1 activation also alleviates cholesterol accumulation in CF cells, suggesting a direct link between microtubule regulation and intracellular transport. To verify the relationship between transport and microtubule regulation, expression of the protein, tubulin polymerization-promoting protein, was knocked down in non-CF human tracheal (9/HTEo(-)) cells to mimic the microtubule dysregulation in CF cells. Transduced cells with short hairpin RNA targeting tubulin polymerization-promoting protein exhibit CF-like perinuclear cholesterol accumulation and other cellular manifestations of CF cells, thus supporting a role for microtubule regulation as a mechanism linking CFTR function to downstream cellular manifestation.

Exhaled nitric oxide from the central airway and alveoli in OSAHS patients: the potential correlations and clinical implications

BACKGROUND

The aim of the study was to evaluate exhaled nitric oxide (eNO) derived from different areas of airway in obstructive sleep apnea hypopnea syndrome (OSAHS) patients with NO exchange model and investigate the potential application and interpretation of eNO in clinical setting.

METHODS

This study was divided into two parts. Firstly, we performed a case control study in 32 OSAHS patients and 27 non-OSAHS participants. Fractional eNO (FeNO) and eNO from the central airway (J'awNO) and from alveoli (CANO) were compared in OSAHS and control groups. Also, correlation of eNO to severity of OSAHS was analyzed. Secondly, a prospective study was conducted in 30 severe OSAHS patients who received a short-term nasal continuous positive airway pressure (nCPAP) treatment. We evaluated eNO, plasma ET-1 concentration, and echocardiography during the treatment process and explored the potential relationship among them.

RESULTS

FeNO and J'awNO were higher in OSAHS and associated with disease severity, while CANO was relatively lower. After nCPAP treatment in severe OSAHS patients, FeNO and J'awNO decreased and CANO increased significantly. Substantial agreement was shown between the elevation of CANO and the decrease of plasma ET-1 concentration after nCPAP by Kappa analysis for consistency. Tei index, which is considered indicative of global right ventricular function, might be predicted by plasma ET-1 levels in severe OSAHS patients.

CONCLUSIONS

NO exchange model provides us with more information of eNO derived from different areas. eNO is not only confirmed to be an effective method for airway inflammation evaluation in the follow-up of OSAHS, CANO may also serve as a useful marker in monitoring endothelial function, resistance of pulmonary circulation, and right ventricular function for clinical implication.

Traditional Chinese medicine's intervention in endothelial nitric oxide synthase activation and nitric oxide synthesis in cardiovascular system

Cardiovascular disease (CVD) is one of the most dangerous diseases which has become a major cause of human death. Many researches evidenced that nitric oxide (NO)/endothelial nitric oxide synthase (eNOS) system plays a significant role in the occurrence and development of CVD. NO, an important signaling molecule, closely associated with the regulation of vasodilatation, blood rheology, blood clotting and other physiological and pathological processes. The synthesis of NO in the endothelial cells primarily depends on the eNOS activity, thus the exploration of the mechanisms and effects of the eNOS activation on NO production is of great significance. Recently, studies on the effects of traditional Chinese medicine (TCM) and its extracts on eNOS activation and NO synthesis have gradually attracted more and more attentions. In this paper, we reviewed the mechanisms of NO synthesis and eNOS activation in the vascular endothelial cells (VECs) and intervention of TCM, so as to provide reference and train of thought to the intensive study of NO/eNOS system and the research and development of new drug for the treatment of CVD.

Mimicking the host and its microenvironment in vitro for studying mucosal infections by Pseudomonas aeruginosa

Why is a healthy person protected from Pseudomonas aeruginosa infections, while individuals with cystic fibrosis or damaged epithelium are particularly susceptible to this opportunistic pathogen? To address this question, it is essential to thoroughly understand the dynamic interplay between the host microenvironment and P. aeruginosa. Therefore, using model systems that represent key aspects of human mucosal tissues in health and disease allows recreating in vivo host-pathogen interactions in a physiologically relevant manner. In this review, we discuss how factors of mucosal tissues, such as apical-basolateral polarity, junctional complexes, extracellular matrix proteins, mucus, multicellular complexity (including indigenous microbiota), and other physicochemical factors affect P. aeruginosa pathogenesis and are thus important to mimic in vitro. We highlight in vitro cell and tissue culture model systems of increasing complexity that have been used over the past 35 years to study the infectious disease process of P. aeruginosa, mainly focusing on lung models, and their respective advantages and limitations. Continued improvements of in vitro models based on our expanding knowledge of host microenvironmental factors that participate in P. aeruginosa pathogenesis will help advance fundamental understanding of pathogenic mechanisms and increase the translational potential of research findings from bench to the patient's bedside.

Disrupted interaction between CFTR and AF-6/afadin aggravates malignant phenotypes of colon cancer

How mutations or dysfunction of CFTR may increase the risk of malignancies in various tissues remains an open question. Here we report the interaction between CFTR and an adherens junction molecule, AF-6/afadin, and its involvement in the development of colon cancer. We have found that CFTR and AF-6/afadin are co-localized at the cell-cell contacts and physically interact with each other in colon cancer cell lines. Knockdown of CFTR results in reduced epithelial tightness and enhanced malignancies, with increased degradation and reduced stability of AF-6/afadin protein. The enhanced invasive phenotype of CFTR-knockdown cells can be completely reversed by either AF-6/afadin over-expression or ERK inhibitor, indicating the involvement of AF-6/MAPK pathway. More interestingly, the expression levels of CFTR and AF-6/afadin are significantly downregulated in human colon cancer tissues and lower expression of CFTR and/or AF-6/afadin is correlated with poor prognosis of colon cancer patients. The present study has revealed a previously unrecognized interaction between CFTR and AF-6/afadin that is involved in the pathogenesis of colon cancer and indicated the potential of the two as novel markers of metastasis and prognostic predictors for human colon cancer.

Molecular motors and apical CFTR traffic in epithelia

Intracellular protein traffic plays an important role in the regulation of Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) chloride channels. Microtubule and actin-based motor proteins direct CFTR movement along trafficking pathways. As shown for other regulatory proteins such as adaptors, the involvement of protein motors in CFTR traffic is cell-type specific. Understanding motor specificity provides insight into the biology of the channel and opens opportunity for discovery of organ-specific drug targets for treating CFTR-mediated diseases.

Mucosal intestinal alteration in experimental colitis correlates with nitric oxide production by peritoneal macrophages: effect of probiotics and prebiotics

Inflammatory bowel disease (IBD) consists mainly of Ulcerative colitis (UC) and Crohn disease (CD). Although its aetiology is still not clearly established, it is thought to be due to overly aggressive immune response to enteric bacteria in genetically predisposed individuals. Manipulating the microbiota using probiotics or prebiotics is considered as a promising field of new therapeutic strategies used to attenuate immune disorders observed during IBD. The production of nitric oxide (NO) seems to be implicated in IBD pathogenesis. In our study, an acute UC was induced in Swiss mice using 3% Dextran Sulfate Sodium (DSS). The preventive effects of "Ultrabiotique®" (a probiotic) and inulin (a prebiotic) on the colitis were investigated. The production of NO was evaluated in the supernatants of peritoneal macrophages (pMφ) cultures. Colonic mucosa histology was subsequently examined. Results showed severe acute UC after administration of DSS. High levels of NO in pMφ cultures were also observed compared to control samples. These findings correlated with a significant destruction of the colonic mucosa. Oral administration of Ultrabiotique® or inulin decreased the severity of DSS-induced colitis. These treatments lead to a decrease in NO levels in pMφ cultures. A considerable reduction of colonic lesions was also noticed. Our findings suggest the involvement of NO in experimental UC pathogenesis. Pre- and pro-biotics, as discussed herein, seem to have an anti-inflammatory effect.

Influence of nitric oxide on in vitro growth, survival, steroidogenesis, and apoptosis of follicle stimulating hormone stimulated buffalo (Bubalus bubalis) preantral follicles

Effect of sodium nitroprusside (SNP), a nitric oxide (NO) donor, on in vitro survival, growth, steroidogenesis, and apoptosis of buffalo preantral follicles (PFs) was investigated. PFs (200~250 µm) were isolated by micro-dissection and cultured in 0 (control), 10^-3, 10^-5, 10^-7, and 10^-9 M SNP. To examine the reversible effect of SNP, PFs were cultured with 10^-5 M SNP + 1 mM N^ω-nitro-L-arginine methyl ester (L-NAME) or 1.0 µg hemoglobin (Hb). The results showed that greater concentrations of SNP (10^-3, 10^-5, 10^-7 M) inhibited (p < 0.05) FSH-induced survival, growth, antrum formation, estradiol production, and oocyte apoptosis in a dose-dependent manner. However, a lower dose of SNP (10^-9 M) significantly stimulated (p < 0.05) the survival, growth, antrum formation, follicular oocyte maturation, and stimulated progesterone secretion compared to the control. A combination of SNP + L-NAME promoted the inhibitor effect of SNP while a SNP + Hb combination reversed this effect. Nitrate and nitrite concentrations in the culture medium increased (p < 0.05) in a dose-dependent manner according to SNP concentration in the culture medium. At higher concentrations, SNP had a cytotoxic effect leading to follicular oocyte apoptosis whereas lower concentrations have stimulatory effects. In conclusion, NO exerts a dual effect on its development of buffalo PFs depending on the concentration in the culture medium.

Smoking and atherosclerotic cardiovascular disease: Part I: atherosclerotic disease process

The normal endothelium inhibits platelet and leukocyte adhesion to the vascular surface maintaining a balance of profibrinolytic and prothrombotic activity. Endothelial function is assessed largely as endothelium-dependent vasomotion, partly based on the assumption that impaired endothelium-dependent vasodilation reflects the alteration of important endothelial functions. Atherosclerotic risk factors, such as hypercholesterolemia, hypertension, diabetes and smoking, are associated with endothelial dysfunction. In the diseased endothelium, the balance between pro- and antithrombotic, pro- and anti-inflammatory, pro- and antiadhesive or pro- and antioxidant effects shifts towards a proinflammatory, prothrombotic, pro-oxidative and proadhesive phenotype of the endothelium. A common mechanism underlying endothelial dysfunction is related to the increased vascular production of reactive oxygen species. Recent studies suggest that inflammation per se, and C-reactive protein in particular, may contribute directly to endothelial dysfunction. The loss of endothelial integrity is a hallmark of atherosclerosis and the causal possible link between each individual risk factor, the development of atherosclerosis and the subsequent clinical events, such as myocardial infarction or stroke.

A keratinocytes-melanocytes coculture system for the evaluation of active ingredients' effects on UV-induced melanogenesis

A new experimental design, more reliable for in vitro testing of active ingredients' effect on ultraviolet (UV)-induced melanogenesis has been carried out. It uses a bicompartmental coculture system where cell communication between keratinocytes and melanocytes can take place. Thus, this experimental situation enables to monitor the effect of biological agents released by both cell types on melanogenesis and the interference of tested compounds with this 'paracrine linkage'. Experiments with UVB-irradiated cocultures show the importance of cell communication in the melanogenic response. In this model, the endogenous mediator, nitric oxide (NO), increased melanin production. Different compounds were tested in the coculture system, and comparison with data obtained from irradiated monocultures of melanocytes enables to distinguish a specific effect on cell communication. In addition, this more close-to-reality experimental model proved to provide a valuable first approach for the assessment of the 'bioavailability' of the tested substances. Finally, the effect of an innovative photoprotective agent capable of 'boosting' UV-induced melanogenic cell communication is presented.

Toll-like receptor 2-mediated peptidoglycan uptake by immature intestinal epithelial cells from apical side and exosome-associated transcellular transcytosis

Peptidoglycan (PGN) is a potent immune adjuvant derived from bacterial cell walls. Previous investigations suggest that intestinal epithelium may absorb PGN from the lumen. Nonetheless, how PGN is taken up and crosses intestinal epithelium remains largely unclear. Here, we first characterized PGN transport in vitro using IEC-18 and HT29-CL19A cells, which represent less mature epithelial cells in intestinal crypts. With fluorescent microscopy, we visualized internalization of dual-labeled PGN by enterocytes. Engulfed PGN was found to form a complex with PGN recognition protein-3, which may facilitate delivering PGN in vivo. Utilizing electronic microscopy, we revealed that uptake of apical PGN across intestinal epithelial monolayers was involved in phagocytosis, multivesicular body formation, and exosome secretion. We also studied transport of PGN using the transwell system. Our data indicated that apically loaded PGN was exocytosed to the basolateral compartment with exosomes by HT29-CL19A cells. The PGN-contained basolateral exosome extracts induced macrophage activation. Through gavaging mice with labeled PGN, we found that luminal PGN was taken up by columnar epithelial cells in crypts of the small intestine. Furthermore, we showed that pre-confluent immature but not post-confluent mature C2BBe1 cells engulfed PGN via a toll-like receptor 2-dependent manner. Together, our findings suggest that (1) crypt-based immature intestinal epithelial cells play an important role in transport of luminal PGN over the intestinal epithelium; and (2) luminal PGN is transcytosed across intestinal epithelia via a toll-like receptor 2-mediated phagocytosis-multivesicular body-exosome pathway. The absorbed PGN and its derivatives may facilitate maintenance of intestinal immune homeostasis.

Genetic modification of adeno-associated viral vector type 2 capsid enhances gene transfer efficiency in polarized human airway epithelial cells

Cystic fibrosis (CF) is a common genetic disease characterized by defects in the expression of the CF transmembrane conductance regulator (CFTR) gene. Gene therapy offers better hope for the treatment of CF. Adeno-associated viral (AAV) vectors are capable of stable expression with low immunogenicity. Despite their potential in CF gene therapy, gene transfer efficiency by AAV is limited because of pathophysiological barriers in these patients. Although a few AAV serotypes have shown better transduction compared with the AAV2-based vectors, gene transfer efficiency in human airway epithelium has still not reached therapeutic levels. To engineer better AAV vectors for enhanced gene delivery in human airway epithelium, we developed and characterized mutant AAV vectors by genetic capsid modification, modeling the well-characterized AAV2 serotype. We genetically incorporated putative high-affinity peptide ligands to human airway epithelium on the GH loop region of AAV2 capsid protein. Six independent mutant AAV were constructed, containing peptide ligands previously reported to bind with high affinity for known and unknown receptors on human airway epithelial cells. The vectors were tested on nonairway cells and nonpolarized and polarized human airway epithelial cells for enhanced infectivity. One of the mutant vectors, with the peptide sequence THALWHT, not only showed the highest transduction in undifferentiated human airway epithelial cells but also indicated significant transduction in polarized cells. Interestingly, this modified vector was also able to infect cells independently of the heparan sulfate proteoglycan receptor. Incorporation of this ligand on other AAV serotypes, which have shown improved gene transfer efficiency in the human airway epithelium, may enhance the application of AAV vectors in CF gene therapy.

Nitric oxide: what a vascular surgeon needs to know

Atherosclerosis in the form of peripheral arterial disease results in significant morbidity and mortality. Surgical treatment options for peripheral arterial disease include angioplasty with and without stenting, endarterectomy, and bypass grafting. Unfortunately, all of these procedures injure the vascular endothelium, which impairs its ability to produce nitric oxide (NO) and ultimately leads to neointimal hyperplasia and restenosis. To improve on current patency rates after vascular procedures, investigators are engaged in research to improve the bioavailability of NO at the site of vascular injury in an attempt to reduce the risk of thrombosis and restenosis after successful revascularization. This article reviews some of the previous research that has aimed to improve NO bioavailability after vascular procedures whether through systemic or local delivery, as well as to describe some of the NO-releasing products that are currently undergoing study for use in clinical practice.

Purinergic receptors in gastrointestinal inflammation

Purinergic receptors comprise a family of transmembrane receptors that are activated by extracellular nucleosides and nucleotides. The two major classes of purinergic receptors, P1 and P2, are expressed widely in the gastrointestinal tract as well as immune cells. The purinergic receptors serve a variety of functions from acting as neurotransmitters, to autocoid and paracrine signaling, to cell activation and immune response. Nucleosides and nucleotide agonist of purinergic receptors are released by many cell types in response to specific physiological signals, and their levels are increased during inflammation. In the past decade, the advent of genetic knockout mice and the development of highly potent and selective agonists and antagonists for the purinergic receptors have significantly advanced the understanding of purinergic receptor signaling in health and inflammation. In fact, agonist/antagonists of purinergic receptors are emerging as therapeutic modalities to treat intestinal inflammation. In this article, the distribution of the purinergic receptors in the gastrointestinal tract and their physiological and pathophysiological role in intestinal inflammation will be reviewed.

Exogenous arginine in sepsis

Sepsis is a severe condition in critically ill patients and is considered an arginine deficiency state. The rationale for arginine deficiency in sepsis is mainly based on the reduced arginine levels in sepsis that are associated with the specific changes in arginine metabolism related to endothelial dysfunction, severe catabolism, and worse outcome. Exogenous arginine supplementation in sepsis shows controversial results with only limited data in humans and variable results in animal models of sepsis. Since in these studies the severity of sepsis varies but also the route, timing, and dose of arginine, it is difficult to draw a definitive conclusion for sepsis in general without considering the influence of these factors. Enhanced nitric oxide production in sepsis is related to suggested detrimental effects on hemodynamic instability and enhanced oxidative stress. Potential mechanisms for beneficial effects of exogenous arginine in sepsis include enhanced (protein) metabolism, improved microcirculation and organ function, effects on immune function and antibacterial effects, improved gut function, and an antioxidant role of arginine. We recently performed a study indicating that arginine can be given to septic patients without major effects on hemodynamics, suggesting that more studies can be conducted on the effects of arginine supplementation in septic patients.

Effect of homocysteine on nitric oxide production in coronary microvascular endothelial cells

Hyperhomocysteinemia is widely recognized as an independent risk factor for coronary artery vascular disease, although the underlying mechanisms are not well understood. This study aims to investigate the effect of homocysteine on nitric oxide (NO) production in coronary microvascular endothelial cells (CMECs) and putative mechanisms mediating this effect. CMECs were isolated on Langendorff system by collagenase perfusion of hearts from male rats and cultured. The effect of homocysteine (0.01 to 1 mM) on basal and stimulated NO production was evaluated by measuring nitrite in the culture media after incubation with or without N(G)-nitro-L-arginine methyl ester (L-NAME) (1 mM), superoxide dismutase (100 U/mL), or catalase (1000 U/mL) for 24 h. Total nitrite was measured using Griess reaction after reduction of nitrate to nitrite with nitrate reductase. Homocysteine did not affect basal nitrite accumulation; however, it significantly increased the nitrite accumulation induced by the calcium ionophore A23187 or interleukin-1beta only at 1 mM. This effect of homocysteine was significantly inhibited by L-NAME, superoxide dismutase, and catalase. In conclusion, homocysteine increases NO release from stimulated CMECs without affecting basal NO production, which is probably accompanied by increased production of reactive oxygen species. It can be postulated that endothelial cells generate NO in order to minimize the damage caused by homocysteine.

Methods using stable isotopes to measure nitric oxide (NO) synthesis in the l-arginine/NO pathway in health and disease

Nitric oxide (NO) is an important gaseous radical involved in many physiological processes. It is produced from the amino acid L-arginine by the action of nitric oxide synthases (NOS) in what is called the L-arginine/NO pathway. Tracking its metabolic fate in biological fluids is of particular interest as it may indicate how the human body responds in health and disease. However, due to its short life span (a few seconds) it is very difficult to accurately monitor any up- or down-regulation in body fluids in vivo. As a consequence, methods have been developed based on the measurement of the NO-derived products nitrite and nitrate or on the substrate of NO, L-arginine and its simultaneously generated product, L-citrulline. Considering only a fraction of the endogenous L-arginine pool is used for the synthesis of NO, NO-production cannot be estimated by measuring changes in the concentrations of L-arginine and/or L-citrulline alone. Instead, to estimate NO-related changes in the L-arginine and/or L-citrulline pools a form of tagging these metabolites for the NOS-mediated reaction is required. The application of stable isotopes is an elegant way to track NOS-mediated changes. The present paper is focussed on the application of various combinations of chromatography and mass spectrometry to measure isotopic enrichments resulting from the conversion of L-arginine to NO and L-citrulline in a one-to-one stoichiometry. In addition, the various aspects and principles involved in the application of stable isotopes in metabolic studies in general and the study of the activity of NOS in particular are discussed.

Comparison of nitrite/nitrate concentration in human plasma and serum samples measured by the enzymatic batch Griess assay, ion-pairing HPLC and ion-trap GC-MS: the importance of a correct removal of proteins in the Griess assay

Mass spectrometry-based approaches are the reference techniques for the determination of nitrite and nitrate in plasma and serum. However, due to their simplicity and rapidity, assays based on the Griess reaction or HPLC are generally used in clinical studies, but they generate diverging values for nitrite/nitrate concentration. In this study, particular attention is paid to the optimization of the deproteinization procedure for plasma and serum samples prior to nitrite/nitrate analysis by an enzymatic batch Griess assay, HPLC and GC-MS. A method is reported to verify completeness of deproteinization and to correct for nonspecific contribution to the absorbance of the diazo dye at 540 nm. With the application of such optimized procedures, we were able to significantly improve the correlation between Griess and HPLC method or the GC-MS technique for nitrite+nitrate concentrations in human serum and plasma. Despite remaining potentially interfering pre-analytical and analytical factors, the procedures reported in the present study may be helpful in a critical evaluation of limits and possibilities of the enzymatic batch Griess assay as a large-scale method for nitrite/nitrate determination in human serum in clinical studies.

Compensatory renal growth protects mice against Shiga toxin 2-induced toxicity

Uninephrectomy (Unx) is followed by the compensatory renal growth (CRG) of the remaining kidney. Previous evidence has shown that during CRG, renal tissue is resistant to a variety of pathologies. We tested the hypothesis that the functional changes that take place during CRG could attenuate Shiga toxin (Stx) toxicity in a mouse model of Stx2-induced hemolytic uremic syndrome (HUS). The participation of nitric oxide (NO) was analyzed. After CRG induction with Unx, mice were exposed to a lethal dose of Stx2, and the degree of renal damage and mortality was measured. Stx2 effects on the growth, renal blood flow (RBF) and NO synthase (NOS) intrarenal expression in the remaining kidney were then studied. The induction of CRG strongly prevented Stx2-mediated mortality and renal damage. Administration of the NOS inhibitor NG-nitro-L-arginine methyl ester (L-NAME) during CRG partially impaired the protection. Both Stx2 and L-NAME interfered with the hypertrophic and hyperplastic responses to Unx, as well as with the increase in RBF. In intact mice, Stx2 decreased renal perfusion, inhibited endothelial NOS basal expression and enhanced inducible NOS expression; all of these effects were attenuated by prior Unx. It is concluded that during CRG mice are highly protected against Stx2 toxicity and lethality. The protective capacity of CRG could be related to the enhancement of renal perfusion and preservation of eNOS renal expression, counterbalancing two major pathogenic mechanisms of Stx2.

Chronic PKC-beta activation in HT-29 Cl.19a colonocytes prevents cAMP-mediated ion secretion by inhibiting apical membrane current generation

We investigated the effects of PKC-stimulating 12-deoxyphorbol 13-phenylacetate 20-acetate (DOPPA) and phorbol 12-myristate 13-acetate (PMA) phorbol esters on cAMP-dependent, forskolin (FSK)-stimulated, short-circuit Cl- current (ISC-cAMP) generation by colonocyte monolayers. These agonists elicited different actions depending on their dose and incubation time; PMA effects at the onset (<5 min) were independent of cAMP agonist and were characterized by transient anion-dependent transcellular and apical membrane ISC generation. DOPPA failed to elicit similar responses. Whereas chronic (24 h) exposure to both agents inhibited FSK-stimulated transcellular and apical membrane ISC-cAMP, the effects of DOPPA were more complex: this conventional PKC-beta-specific agonist also stimulated Ba2+-sensitive basolateral membrane-dependent facilitation of transcellular ISC-cAMP. PMA did not elicit a similar phenomenon. Prolonged exposure to high-dose PMA but not DOPPA led to apical membrane ISC-cAMP recovery. Changes in PKC alpha-, beta1-, gamma-, and epsilon-isoform membrane partitioning and expression correlated with these findings. PMA-induced transcellular ISC correlated with PKC-alpha membrane association, whereas low doses of both agents inhibited transcellular and apical membrane ISC-cAMP, increased PKC-beta1, decreased PKC-beta2 membrane association, and caused reciprocal changes in isoform mass. During the apical membrane ISC-cAMP recovery after prolonged high-dose PMA exposure, an almost-complete depletion of cellular PKC-beta1 and a significant reduction in PKC-epsilon mass occurred. Thus activated PKC-beta1 and/or PKC-epsilon prevented, whereas activated PKC-alpha facilitated, apical membrane ISC-cAMP. PKC-beta-dependent augmentation of transcellular ISC-cAMP at the level of the basolateral membrane demonstrated that transport events with geographically distinct subcellular membranes can be independently regulated by the PKC beta-isoform.

Chronic PKC-beta2 activation in HT-29 Cl.19a colonocytes prevents cAMP-mediated ion secretion by inhibiting apical membrane CFTR targeting

We investigated the effects of chronically applied PKC-stimulating phorbol esters on subcellular CFTR expression and localization in polarized HT-29 Cl.19A monolayers. Modulation of PKC activity with the PKC-beta-specific agonist 12-deoxyphorbol 13-phenylacetate 20-acetate (DOPPA) or nonisoform-selective PMA altered monolayer CFTR immunofluorescence. A decrease in the CFTR signal within the luminal cellular pole was noted with both phorbol esters. Volumetric analysis of the intracellular CFTR signal revealed that both compounds promoted CFTR accumulation into punctate vesicle-like structures found adjacent to the cellular tight junction [labeled with zona occludens (ZO)-1 antibody], extending basally (DOPPA) into the cell. Puncta were more frequent with DOPPA and larger in size with PMA. DOPPA also promoted ZO-1 accumulation at tricellular corners associated with enhanced CFTR puncta number. The observed loss of CFTR immunofluorescence signal induced by low-dose PMA was related to CFTR sequestration into fewer cytoplasmic puncta and correlated with larger increases in PKC substrate phosphorylation. Both phorbol esters downregulated steady-state cellular CFTR mRNA levels by 70%. However, the effects of DOPPA and PMA were largely independent of CFTR biosynthesis: expression levels were 80-85% of control, and the glycosylation status of immunoprecipitated protein remained largely unchanged. Thus changes in cellular CFTR localization correlated with our companion study showing that PMA-induced inhibition of transcellular cAMP-dependent short-circuit current (ISC) was accompanied by cytoplasmic PKC-beta2 accumulation and modest activation of PKC-beta1 and PKC-epsilon. The inhibitory effect of DOPPA on ISC was related solely to increased cytoplasmic PKC-beta2 levels. Thus PKC-beta2 is hypothesized to participate in the regulation of CFTR apical plasma membrane targeting within the constitutive cellular biosynthetic pathway.

The Basic Science of Wound Healing

Understanding wound healing today involves much more than simply stating that there are three phases: "inflammation, proliferation, and maturation." Wound healing is a complex series of reactions and interactions among cells and "mediators." Each year, new mediators are discovered and our understanding of inflammatory mediators and cellular interactions grows. This article will attempt to provide a concise report of the current literature on wound healing by first reviewing the phases of wound healing followed by "the players" of wound healing: inflammatory mediators (cytokines, growth factors, proteases, eicosanoids, kinins, and more), nitric oxide, and the cellular elements. The discussion will end with a pictorial essay summarizing the wound-healing process.

Neonatal programming of body weight regulation and energetic metabolism

Programming is an epigenetic phenomena by which nutritional, hormonal, physical psychological and other stressful events acting in a critical period of life, such as gestation and lactation, modifies in a prolonged way certain physiological functions. This process was preserved by natural selection as an important adaptive tool for survival of organisms living in nutritional impaired areas. So, malnutrition during gestation and lactation turns on different genes that provide the organism with a thrifty phenotype. In the case of an abundant supply of nutrients after this period, those organisms that were adapted to a low metabolic waste and higher energy utilization will be in a higher risk of developing metabolic diseases, such as obesity, hyperlipidemia, diabetes mellitus and hypertension. The kind of malnutrition, duration and intensity are important for the type of programming obtained. We discuss some of the hormonal and metabolic changes that occur in gestation or lactation, when malnutrition is applied to the mothers and their offspring. Some of these changes, such as an increase of maternal triiodothyronine (T(3)), leptin and glucocorticoids (GC) and decrease in prolactin are by itself potential programming factors. Most of these hormones can be transfer through the milk that has other important macronutrients composition changes in malnourished dams. We discuss the programming effects of some of these hormones upon body weight and composition, leptin, thyroid and adrenal functions, and their effects on liver, muscle and adipose tissue metabolism and the consequences on thermogenesis.

Lipopolysaccharide-induced alterations in oxygen consumption and radical generation in endothelial cells

Oxygen consumption rate (OCR) and generation of superoxide and nitric oxide (NO) in mouse aortic endothelial cells (MAECs) treated with lipopolysaccharide (LPS) were studied. The OCR was determined in cell suspensions at 37 degrees C by electron paramagnetic resonance (EPR) spectroscopy. LPS significantly altered the OCR in a dose and time-dependent fashion. The OCR was significantly elevated immediately following the treatment of MAECs with LPS (5 and 10 microg/ml) and NADPH (100 microM) whereas the same was depressed 1 h after exposure to similar conditions of incubation. Under similar experimental conditions, superoxide generation was also determined by EPR spectroscopy and cytochrome c reduction assays. A marginal increase in the superoxide production was observed when the cells were treated with LPS and NADPH alone whereas the same was further enhanced significantly when the cells were treated with LPS and NADPH together. The increase in oxygen consumption and superoxide production caused by LPS was inhibited by diphenyleneiodonium (DPI), suggesting the involvement of NAD(P)H oxidase. A significant increase in the NO production by MAECs was noticed 1 h after treatment with LPS and was inhibited by L-NAME, further suggesting the involvement of nitric oxide synthase (NOS). Thus, on a temporal scale, LPS-induced alterations in oxygen consumption by MAECs may be under the control of dual regulation by NAD(P)H oxidase and NOS.

Exhaled nitric oxide in paediatric asthma

Assessment of airway function is difficult in young children with asthma, and in addition, only reflects the status of the disease at the time of the measurement. Thus, there is increasing interest in monitoring airway inflammation in asthma, which may provide a longer term assessment of disease activity. Most methods of assessing asthmatic inflammation are invasive, and are not feasible in the paediatric population. This review discusses exhaled nitric oxide as a marker of asthmatic inflammation, and compares it with other recognized markers. Exhaled nitric oxide has the potential to become a noninvasive method of assessing asthma control in the paediatric population.

Roles of nitric oxide and nitric oxide synthases in tissue damage of obstructed ureters in rats

OBJECTIVE

To investigate the roles of nitric oxide (NO) and NO synthases [endothelial constitutive NO synthase (eNOS) and inducible NO synthase (iNOS)] in the pathogenesis of ureteric damage during the course of obstructive uropathy.

MATERIAL AND METHODS

The expression of nitrotyrosine, eNOS and iNOS was studied in 54 Sprague-Dawley rats using immunohistochemistry with concurrent immunohistochemical staining.

RESULTS

Hypertrophy and fibrotic changes of the smooth muscle of the obstructed ureters were noticed after ureteric ligation. The expression of iNOS, eNOS and nitrotyrosine in the smooth muscle layer was noticed from Days 7, 10 and 14 after ligation, respectively, increased until Day 21 post-ligation and then decreased. The expression of nitrotyrosine in the smooth muscle layer was significantly correlated with the expression of iNOS and eNOS (r=0.9698 and 0.9683, respectively; p<0.0001 for both).

CONCLUSION

NO and NO synthases may play important roles in tissue damage of the smooth muscle layer in obstructed ureters.

Activators of viral gene expression in polarized epithelial monolayers identified by rapid-throughput drug screening

Epithelial polarity and tight junction formation limit the ability of adenovirus, retrovirus and adeno-associated virus (AAV) to deliver and express virally encoded genes. Using an extended half-life luciferase assay and high-throughput luminometry, we screened 23 000 compounds and natural product extracts as potentiators to overcome this barrier. Seven strong activators were discovered (up to several hundred fold above control) and two of these exhibited spectrum of activity in multiple cell types (HeLa (human cervical carcinoma), cystic fibrosis bronchial epithelial (human bronchial), HT29 (human colonic carcinoma), Calu3 (airway serous glandular)). Enhanced transduction by unrelated gene transfer vectors (adenovirus, lentivirus, AAV, liposomal) was also observed. These results establish a strategy for identifying compounds that improve viral gene transfer to resistant cell types, and provide new tools for examining epithelial defense against viral infection. The compounds should have broad usefulness in experimental therapies for cancer and genetic diseases.

Review: hypoxia-inducible factor-1 (HIF-1): a novel transcription factor in immune reactions

Hypoxia-inducible factor-1 (HIF-1) is a dimeric transcriptional complex that has been recognized primarily for its role in the maintenance of oxygen and energy homoeostasis. The HIF-1alpha subunit is O(2) labile and is degraded by the proteasome following prolyl-hydroxylation and ubiquitination in normoxic cells. The present review summarizes evidence that HIF-1 is also involved in immune reactions. Immunomodulatory peptides, including interleukin-1 (IL-1) and tumor necrosis factor-alpha (TNF-alpha), stimulate HIF-1 dependent gene expression even in normoxic cells. Both the hypoxic and the cytokine-induced activation of HIF-1 involve the phosphatidylinositol- 3-kinase (PI3K) and the mitogen-activated protein kinase (MAPK) signaling pathways. In addition, heat shock proteins (HSP) and other cofactors interact with HIF-1 subunits. HIF-1 increases the transcription of several genes for proteins that promote blood flow and inflammation, including vascular endothelial growth factor (VEGF), heme oxygenase-1, endothelial and inducible nitric oxide synthase (NOS) and cyclooxygenase-2 (COX-2). The pharmacologic activation of the HIF-1 complex can be desirable in ischemic and inflammatory disorders. In contrast, HIF-1 blockade may be beneficial to prevent tumor angiogenesis and tumor growth.

Effect of chronic cold stress on intestinal epithelial cell proliferation and inflammation in rats

The present study evaluated the effect of chronic cold stress on intestinal epithelial cell proliferation and inflammation. Male Wistar rats were subjected to cold exposure for three weeks. At the end of the cold exposure, intestinal cell proliferation, luminal nitrite and protein levels, intestinal myeloperoxidase activity and mast cell numbers were evaluated. Severely compromised proliferation rate of the crypt-base cells was observed under chronic stress conditions. Cells isolated from stressed rats showed a decreased DNA content in villus and lower villus cell fractions and an increased DNA content in the crypt cells, as compared to controls. Chronic cold stress resulted in increased luminal nitrite, luminal protein levels, and intestinal myeloperoxidase activity. The number of mast cells was significantly elevated under chronic stress conditions. Chronic cold stress resulted in a compromised intestinal epithelial cell proliferation rate and induced inflammation in the rat small intestine, through the combined action of nitric oxide, neutrophils and mast cells.

Cell-mediated effector molecules and complicated malaria

In this review I attempt to advance hypotheses that might help contribute toward understanding the molecular pathogenesis of cerebral malaria (CM) and other complications based on a now widely accepted argument that the illness and pathology occasioned by Plasmodiumfalciparum infection might not necessarily be due to the direct effects of the parasite's 'toxins' and/or exoantigens or even its sequestration and consequent attendant effects in vital organs but rather to the parasite's mediated production of microbicidal molecules by the host. Tumor necrosis factor (TNF)-alpha is implicated in the pathogenesis of complicated malaria. There is a positive correlation between high levels of TNF-alpha and severity of malaria. The role of nitric oxide in the pathophysiology of complicated malaria is not clearly understood. Mononuclear phagocytes by virtue of their capacity to secrete toxic intermediates like reactive oxygen intermediates can inhibit the growth of both murine and human plasmodia. The role of interleukin-10 (IL-10) in malaria is also not well characterized to date. IL-10 is a powerful immunosuppressor factor. It acts as a natural dampener of immunoproliferative and inflammatory responses. Although transforming growth factor-beta has a crucial role in inflammation and repair, its role in complicated malaria is not too clearly understood. Furthermore, the anatomical source of these microbicidal molecules is not precisely known. The role of immune complexes (IC) in the pathophysiology of complicated malaria has hitherto not been tested. I argue here that IC play a critical role in influencing the outcome of malarial disease; IC-mediated stimulation of leukocytes to produce high levels of both TNF-alpha and NO and the fact that leukocytes are probably the principal anatomical source of these microbicidal and other pro-inflammatory mediators in complicated malaria provide a much more plausible explanation for the pathogenesis of CM and other complications. I also review the arguments that help contribute to rationalize hypoglycemia and hyperlactatemia in malarial disease and to some extent severe anemia. I am therefore tempted to conclude that CM and other complications are probably immune-mediated diseases or, at least, they present an inflammatory pathogenesis.

A comparison of 14 antibodies for the biochemical detection of the cystic fibrosis transmembrane conductance regulator protein

Interest in the biochemical detection of the cystic fibrosis (CF) transmembrane conductance regulator (CFTR) protein followed soon after cloning of the gene and prediction of the protein structure. Ever since, antibodies (Abs) have been produced and used to detect CFTR in both heterologously and endogenously expressing cells and tissues. Although designed to be sensitive and specific, these Abs produce, in most cases, unsatisfactory results when used for the biochemical detection of CFTR either by Western blot or by immunoprecipitation. The lack of Abs that can reliably detect the CFTR protein is a major constraint to studies of CF. We compared 14 different Abs for their ability to detect CFTR in both stably transfected and endogenously expressing cell lines.

T cell-mediated vascular dysfunction of human allografts results from IFN-gamma dysregulation of NO synthase

Allograft vascular dysfunction predisposes to arteriosclerosis and graft loss. We examined how dysfunction develops in transplanted human arteries in response to circulating allogeneic T cells in vivo using immunodeficient murine hosts. Within 7-9 days, transplanted arteries developed endothelial cell (EC) dysfunction but remained sensitive to exogenous NO. By 2 weeks, the grafts developed impaired contractility and desensitization to NO, both signs of VSMC dysfunction. These T cell-dependent changes correlated with loss of eNOS and expression of iNOS--the latter predominantly within infiltrating T cells. Neutralizing IFN-gamma completely prevented both vascular dysfunction and changes in NOS expression; neutralizing TNF reduced IFN-gamma production and partially prevented dysfunction. Inhibiting iNOS partially preserved responses to NO at 2 weeks and reduced graft intimal expansion after 4 weeks in vivo. In vitro, memory CD4+ T cells acted on allogeneic cultured ECs to reduce eNOS activity and expression of protein and mRNA. These effects required T cell activation by class II MHC antigens and costimulators (principally lymphocyte function-associated antigen-3, or LFA-3) on the ECs and were mediated by production of soluble mediators including IFN-gamma and TNF. We conclude that IFN-gamma is a central mediator of vascular dysfunction and, through dysregulation of NOS expression, links early dysfunction with late arteriosclerosis.

Is nitric oxide a key target in the pathogenesis of brain lesions during the development of Alzheimer's disease?

Nitric oxide (NO) is a short-life key bioregulatory active molecule in the cardiovascular, immune and nervous systems. NO is synthesized by converting L-arginine to L-citrulline by enzymes called NO synthase (NOS). The growing body of evidence strongly supports the theory that this molecule appears to be one of the key targets for the disruption of normal brain homeostasis, which causes the development of brain lesions and pathology such as in Alzheimer's disease (AD) or other related dementia. The vascular content of NO activity appears especially to be a main contributor to this pathology before the over-expression of other NOS isoforms activity in a different brain cellular compartment. We speculate that pharmacological intervention using NO donors and/or NO suppressors will be able to delay or minimize the development of brain pathology and further progression of mental retardation.

Sepsis: an arginine deficiency state?

OBJECTIVE

Sepsis is a major health problem considering its significant morbidity and mortality rate. The amino acid L-arginine has recently received substantial attention in relation to human sepsis. However, knowledge of arginine metabolism during sepsis is limited. Therefore, we reviewed the current knowledge about arginine metabolism in sepsis.

DATA SOURCE

This review summarizes the literature on arginine metabolism both in general and in relation to sepsis. Moreover, arginine-related therapies are reviewed and discussed, which includes therapies of both nitric oxide (NO) and arginine administration and therapies directed toward inhibition of NO.

DATA

In sepsis, protein breakdown is increased, which is a key process to maintain arginine delivery, because both endogenous de novo production from citrulline and food intake are reduced. Arginine catabolism, on the other hand, is markedly increased by enhanced use of arginine in the arginase and NO pathways. As a result, lowered plasma arginine levels are usually found. Clinical symptoms of sepsis that are related to changes in arginine metabolism are mainly related to hemodynamic alterations and diminished microcirculation. NO administration and arginine supplementation as a monotherapy demonstrated beneficial effects, whereas nonselective NO synthase inhibition seemed not to be beneficial, and selective NO synthase 2 inhibition was not beneficial overall.

CONCLUSIONS

Because sepsis has all the characteristics of an arginine-deficiency state, we hypothesise that arginine supplementation is a logical option in the treatment of sepsis. This is supported by substantial experimental and clinical data on NO donors and NO inhibitors. However, further evidence is required to prove our hypothesis.

Zymosan induces nitric oxide production by peritoneal mesothelial cells

INTRODUCTION

The production of nitric oxide is an important peritoneal defense mechanism. We have evaluated the effect of various putative stimulants on nitric oxide production by peritoneal mesothelial cells.

METHODS

Wistar rats were randomized to either a control group or a peritonitis group (5 mg zymosan intraperitoneally). Groups of five animals were sacrificed at 4, 18, 24, 48 and 96 h after the induction of peritonitis and their peritoneal fluid was harvested for assay. Cultures of peritoneal mesothelial cells were stimulated with lipopolysaccharide, myeloperoxidase, TNFalpha, zymosan, peritoneal fluid from a control animal and peritoneal fluid from a peritonitis animal. Supernatants were collected after incubation for 4, 24 and 48 h for assay. The assay for nitric oxide was based upon the nitrite content of the samples.

RESULTS

The intraperitoneal administration of zymosan was associated with an increased production of nitric oxide (NO) when compared with control animals (P < 0.01). In cultures of peritoneal mesothelial cells, zymosan, but not the other putative stimulants, was associated with a marked output of nitric oxide (P < 0.001).

CONCLUSION

Zymosan has a direct effect on peritoneal mesothelial cells, which are able to generate nitric oxide in the absence of co-stimulatory molecules. This suggests that it may be possible to use some form of external stimulation to up-regulate the NO response by peritoneal mesothelial cells.

The cardiovascular effects of nitric oxide and carbon monoxide in the nucleus tractus solitarii of rats

OBJECTIVE

Nitric oxide (NO) and carbon monoxide (CO) are endogenously synthesized gaseous molecules that act as neurotransmitters in both central and peripheral nervous systems. Previously, we have shown the involvement of NO and CO in central cardiovascular regulation and baroreflex modulation. In this study we investigated the possible interaction of NO and CO in the nucleus tractus solitarii (NTS) on cardiovascular effects in rats.

DESIGN AND METHODS

Male Sprague-Dawley rats were anesthetized with urethane, and mean blood pressure (MBP) and heart rate (HR) were monitored intra-arterially. l-Arginine (3.3 nmol), the precursor of NO, or hematin (1 nmol), a heme molecule cleaved by heme oxygenase (HO) to yield CO, were microinjected unilaterally into the NTS. Cardiovascular effects were evaluated before and after microinjection of the HO inhibitor zinc deuteroporphyrin 2,4-bis glycol (ZnDPBG: 1 nmol) or the NO synthase (NOS) inhibitors N -monomethyl-l-arginine (l-NMMA: 10, 33 and 100 nmol) and N-nitro-l-arginine methyl ester (l-NAME: 10, 33 and 100 nmol).

RESULTS

Unilateral microinjection of l-arginine or hematin into the NTS produced decreases in blood pressure and heart rate. These cardiovascular effects of both l-arginine and hematin were attenuated by prior administration of the NOS inhibitors l-NMMA or l-NAME in a dose-dependent manner. However, prior administration of ZnDPBG attenuated only the cardiovascular effects of hematin but not l-arginine.

CONCLUSIONS

These results demonstrated that the HO/CO pathway might couple to the activation of NOS via the liberation of NO, to participate in central regulation of cardiovascular function. They also suggested a possible interaction between the NO/NOS and CO/HO systems in the NTS of rats.

Efficient intracellular processing of the endogenous cystic fibrosis transmembrane conductance regulator in epithelial cell lines

The cystic fibrosis transmembrane conductance regulator (CFTR) is a cAMP-dependent protein kinase A-activated chloride channel that resides on the apical surface of epithelial cells. One unusual feature of this protein is that during biogenesis, approximately 75% of wild type CFTR is degraded by the endoplasmic reticulum (ER)-associated degradative (ERAD) pathway. Examining the biogenesis and structural instability of the molecule has been technically challenging due to the limited amount of CFTR expressed in epithelia. Consequently, investigators have employed heterologous overexpression systems. Based on recent results that epithelial specific factors regulate both CFTR biogenesis and function, we hypothesized that CFTR biogenesis in endogenous CFTR expressing epithelial cells may be more efficient. To test this, we compared CFTR biogenesis in two epithelial cell lines endogenously expressing CFTR (Calu-3 and T84) with two heterologous expression systems (COS-7 and HeLa). Consistent with previous reports, 20 and 35% of the newly synthesized CFTR were converted to maturely glycosylated CFTR in COS-7 and HeLa cells, respectively. In contrast, CFTR maturation was virtually 100% efficient in Calu-3 and T84 cells. Furthermore, inhibition of the proteasome had no effect on CFTR biogenesis in Calu-3 cells, whereas it stabilized the immature form of CFTR in HeLa cells. Quantitative reverse transcriptase-PCR indicated that CFTR message levels are approximately 4-fold lower in Calu-3 than HeLa cells, yet steady-state protein levels are comparable. Our results question the structural instability model of wild type CFTR and indicate that epithelial cells endogenously expressing CFTR efficiently process this protein to post-Golgi compartments.

Measurement of oxygen consumption in mouse aortic endothelial cells using a microparticulate oximetry probe

The purpose of this study was to determine the rate of oxygen consumption in mouse aortic endothelial cells (MAECs) and to determine the effect of a variety of inhibitors and stimulators of oxygen consumption measured by electron paramagnetic resonance (EPR) spectroscopy utilizing a new particulate oximetry probe. We have previously demonstrated that the octa-n-butoxy derivative of naphthalocyanine neutral radical (LiNc-BuO) enables accurate, precise, and reproducible measurements of pO(2) in cellular suspensions. In the current study, we carried out measurements to provide an accurate determination of pO(2) in small volume with less number of cells (20,000 cells) that has not been possible with other techniques. To establish the reliability of this method, agents such as menadione, lipopolysaccharide (LPS), potassium cyanide, rotenone, and diphenyleneiodonium chloride (DPI) were used to modulate the oxygen consumption rate in the cells. We observed an increase in oxygen consumption by the cells upon treatment with menadione and LPS, whereas treatment with cyanide, rotenone, and DPI inhibited oxygen consumption. This study clearly demonstrated the utilization of EPR spectrometry with LiNc-BuO probe for determination of oxygen concentration in cultured cells.

Exhaled Nitric Oxide and Acute Lung Injury in a Rat Model of Extracorporeal Circulation

Exhaled nitric oxide (NO) concentration, a marker of pulmonary inflammation, has been shown to be elevated in various models of acute lung injury (ALI). This study was undertaken to evaluate the pulmonary NO production in a rat model of postextracorporeal circulation (ECC) ALI. Wistar rats underwent either a partial femorofemoral ECC in normothermia for 3 h (n = 10) or a sham procedure (n = 10). The extracorporeal circuit consisted of a roller pump and a membrane oxygenator. Exhaled NO concentration was monitored with a chemiluminescence analyzer. After sacrifice, lungs were harvested for microscopic studies and to analyze the inducible nitric oxide synthase (iNOS) activity and expression (Western blot). ECC was responsible for an ALI characterized by a decreased arterial blood oxygen saturation (88.9% [51.7-94.2] vs. 93.7% [91.4-98.6] P = 0.005) and pulmonary histological changes (marked alveolar neutrophil infiltration; interstitial edema; intraalveolar hemorrhage). The lung injury score was significantly higher in the ECC group (n = 5; 3.0 [2-4]) in comparison to the sham group (n = 5; 1.0 [0-2]). Exhaled NO concentration remained stable throughout the experiment in all sham rats whereas it significantly increased in the ECC group from baseline (2 ppb [1-5]) until the end of experiment (33.5 ppb [1-47]). Lung iNOS activity and expression were also significantly increased in the ECC group. An increase in exhaled NO, however, did not correlate with the decrease in arterial oxygen pressure. ECC was responsible for an ALI in rats and for an elevated pulmonary NO production. Determination of the relationship between exhaled NO and the severity of the inflammatory process in ALI will require further studies.

The role of regulated CFTR trafficking in epithelial secretion

The focus of this review is the regulated trafficking of the cystic fibrosis transmembrane conductance regulator (CFTR) in distal compartments of the protein secretory pathway and the question of how changes in CFTR cellular distribution may impact on the functions of polarized epithelial cells. We summarize data concerning the cellular localization and activity of CFTR and attempt to synthesize often conflicting results from functional studies of regulated endocytosis and exocytosis in CFTR-expressing cells. In some instances, findings that are inconsistent with regulated CFTR trafficking may result from the use of overexpression systems or nonphysiological experimental conditions. Nevertheless, judging from data on other transporters, an appropriate cellular context is necessary to support regulated CFTR trafficking, even in epithelial cells. The discovery that disease mutations can influence CFTR trafficking in distal secretory and recycling compartments provides support for the concept that regulated CFTR recycling contributes to normal epithelial function, including the control of apical CFTR channel density and epithelial protein secretion. Finally, we propose molecular mechanisms for regulated CFTR endocytosis and exocytosis that are based on CFTR interactions with other proteins, particularly those whose primary function is membrane trafficking. These models provide testable hypotheses that may lead to elucidation of CFTR trafficking mechanisms and permit their experimental manipulation in polarized epithelial cells.

The role of the C terminus and Na+/H+ exchanger regulatory factor in the functional expression of cystic fibrosis transmembrane conductance regulator in nonpolarized cells and epithelia

The conserved C-terminal peptide motif (1476DTRL) of the cystic fibrosis transmembrane conductance regulator (CFTR) ensures high affinity binding to different PSD-95/Disc-large/zonula occludens-1 (PDZ) domain-containing molecules, including the Na+/H+ exchanger regulatory factor (NHERF)/ezrin-radixin-moesin-binding phosphoprotein of 50 kDa. The physiological relevance of NHERF binding to CFTR is not fully understood. Individuals with mutations resulting in premature termination of CFTR (S1455X or Delta26 CFTR) have moderately elevated sweat Cl- concentration, without an obvious lung and pancreatic phenotype, implying that the CFTR function is largely preserved. Surprisingly, when expressed heterologously, the Delta26 mutation was reported to abrogate channel activity by destabilizing the protein at the apical domain and inducing its accumulation at the basolateral membrane (Moyer, B., Denton, J., Karlson, K., Reynolds, D., Wang, S., Mickle, J., Milewski, M., Cutting, G., Guggino, W., Li, M., and Stanton, B. (1999) J. Clin. Invest. 104, 1353-1361). The goals of this study were to resolve the contrasting clinical and cellular phenotype of the Delta26 CFTR mutation and evaluate the role of NHERF in the functional expression of CFTR at the plasma membrane. Complex formation between CFTR and NHERF was disrupted by C-terminal deletions, C-terminal epitope tag attachments, or overexpression of a dominant negative NHERF mutant. These perturbations did not alter CFTR expression, metabolic stability, or function in nonpolarized cells. Likewise, inhibition of NHERF binding had no discernible effect on the apical localization of CFTR in polarized tracheal, pancreatic, intestinal, and kidney epithelia and did not influence the metabolic stability or the cAMP-dependent protein kinase-activated chloride channel conductance in polarized pancreatic epithelia. On the other hand, electrophysiological studies demonstrated that NHERF is able to stimulate the cAMP-dependent protein kinase-phosphorylated CFTR channel activity in intact cells. These results help to reconcile the discordant genotype-phenotype relationship in individuals with C-terminal truncations and indicate that apical localization of CFTR involves sorting signals other than the C-terminal 26 amino acid residues and the PDZ-binding motif in differentiated epithelia.

Nicotinamide increases systemic vascular resistance in ovine endotoxemia

OBJECTIVE

The nuclear enzyme Poly(ADP-Ribose)-Polymerase (PARP) has been hypothesized as playing a major role in various forms of inflammation. PARP activation is induced by DNA strand breakage and can result in intracellular energy depletion and, ultimately, cell death. Further, it is thought to influence cardiovascular function and organ failure in endotoxemia. Here, we investigated the effect of the PARP inhibitor nicotinamide on cardiovascular and liver function in healthy and chronically endotoxemic sheep.

DESIGN

Prospective controlled trial.

SETTING

University research laboratory.

SUBJECTS

12 female adult sheep.

INTERVENTIONS

Six healthy sheep, instrumented for chronic study, received nicotinamide intravenously as a bolus of 40 mg/kg followed by a continuous infusion of 10 mg.kg(-1).h(-1); six animals received the vehicle. One hour after bolus application, a continuous infusion of endotoxin ( Salmonella typhosa, 10 ng.kg(-1).min(-1)) was started. Hemodynamic parameters were determined before and during endotoxemia.

MEASUREMENTS AND RESULTS

Treatment with nicotinamide resulted in a significantly higher systemic vascular resistance index and lower cardiac index in endotoxemic animals, but not in controls. It also attenuated endotoxin-induced increase in gamma-glutamyl transferase.

CONCLUSIONS

The PARP inhibitor nicotinamide attenuates impairment of cardiovascular function during endotoxemia. In addition, PARP activation may be involved in endotoxin-induced liver injury.