Interactions of airway smooth muscle cells with their tissue matrix: implications for contraction

The ability of airway smooth muscle to alter its stiffness and contractility in response to mechanical oscillation and stretch is critically important for the regulation of normal airway responsiveness during breathing. The properties of mechanical adaptation in airway smooth muscle are proposed to result from dynamic cytoskeletal processes outside of the actomyosin interaction. The actomyosin interaction and crossbridge cycling are viewed as components of a complex and integrated array of cytoskeletal events that occur during cell contraction. These events are orchestrated by macromolecular protein complexes that associate with the cytoplasmic domains of integrin proteins at the adhesion junctions between muscle cells and the extracellular matrix. According to this paradigm, these concerted cytoskeletal events are essential components of the process of active tension generation in airway smooth muscle, and also serve to adapt the shape and stiffness of the smooth muscle cell to its environment. Contractile stimuli initiate actin polymerization within the submembranous cortex of the airway smooth muscle cell that may serve to determine the cells shape and strengthen the membrane. The recruitment of structural proteins such as alpha-actinin to adhesion junctions fortifies the strength of the connections between membrane adhesion junctions and actin filaments. These processes create a strong and rigid cytoskeletal framework for the transmission of force generated by the interaction of myosin and actin filaments. This model for the regulation of airway smooth muscle function can provide novel perspectives to explain the normal physiologic behavior of the airways and pathophysiologic properties of the airways in asthma.     

Paucity of antigen-specific IgA responses in sera and external secretions of HIV-type 1-infected individuals

This study was undertaken to resolve existing controversies with respect to the detection of IgA HIV-1-specific mucosal antibodies in infected individuals. External secretions, including tears, nasal, rectal, and vaginal washes, saliva, semen, urine, and sera were obtained from 50 HIV-1-infected individuals and 20 controls using collection procedures that minimize the irritation of mucosal surfaces. Levels of total and antigen (gp120 and gp160)-specific antibodies of the IgG and IgA isotypes were measured by assays that proved reliable in a large multicenter study: quantitative ELISA and chemiluminescence-enhanced Western blot analyses. Although the levels of total IgG and IgA were increased or remained unchanged in body fluids of HIV-1-infected individuals as compared to the controls, HIV-1-specific IgA antibodies were either absent or present at low levels even in secretions with characteristically high relative contents of total IgA vs. IgG (saliva, tears, and rectal and nasal washes). In these secretions, HIV-1-specific IgG antibodies dominated. In assessing levels and frequency of detection of IgG antibodies, both female and male genital tract secretions, urine, and nasal wash were preferable to parotid saliva and especially to rectal wash. External secretions contained IgG antibodies to gp160> gp120> gp41 and p24; when present, IgA antibodies were predominantly directed at gp160. Analyses of peripheral blood antibody-secreting cells (ASC) isolated from the same individuals paralleled these serological findings: gp160-specific IgG-secreting ASC were dominant. Therefore, in striking contrast to other mucosally encountered microbial infections, HIV-1 does not induce vigorous specific IgA responses in any body fluid examined or in ASC in peripheral blood.     

Macromolecular interactions and ion transport in cystic fibrosis

Cystic fibrosis (CF) is a genetic disease caused by autosomal recessive mutations of the CF transmembrane regulator, CFTR. CFTR functions in the plasma membrane of epithelial cells lining the lung, pancreas, liver, intestines, sweat duct, and the epididymis. The primary problem in CF is that mutations in CFTR affect its ability to be made, processed, and trafficked to the plasma membrane and/or its function as a Cl(-) channel and conductance regulator. Many proteins and processes normally interact with normal CFTR throughout its life cycle and mutant CFTR during the disease process. Understanding the function of these proteins and processes is expected to provide a clearer understanding of how normal CFTR is involved in salt movement and how mutant CFTR is handled by the cell and leads to the pathophysiology of CF. Recently, efforts to find therapies that correct defective CFTR have been intensifying. To facilitate our understanding of normal and mutant CFTR and the identification of new drug targets for developing novel therapies, a panel of experts was convened by the National Heart, Lung, and Blood Institute to explore the critical questions, challenges, and current opportunities to highlight new areas of research that would facilitate a integrated understanding of the processes and proteins that impact CFTR. The meeting highlighted the multiple pathways and interacting proteins involved in CFTR folding and biosynthesis, processing, and trafficking. A number of critical areas for future study were identified. Although these therapies are promising, a big question remains as to whether simply correcting defective CFTR will lead to significant improvement in patient health or whether the symptoms manifested in CF will require therapies in addition to those that target defective CFTR specifically.     

T-cell characterization in chronic allergic eye disease

Chronic allergic eye disease encompasses several disorders, but it is vernal keratoconjunctivitis (VKC) and atopic keratoconjunctivitis (AKC) that have sight-threatening sequelae. T cells, eosinophils, and mast cells are all found in the conjunctiva, and are thought to play a role in disease pathogenesis. Recently, the conjunctival epithelium has also been considered to play a key role. New and effective therapeutic strategies for the future for these patients depend on achieving a greater understanding of the roles and interactions of the cell populations in these sight-threatening disorders.     

Discovery and characterization of a selective, nonpeptidyl thrombopoietin receptor agonist

OBJECTIVE: Peptide and other small molecule agonists have been described for several cytokines and growth factors. Hydrazone compounds described here as thrombopoietin receptor agonists were identified as activating STAT proteins in a Tpo responsive cell line. METHODS: STAT activation and analysis of signal transduction pathways in cell lines and normal human platelets was elucidated by Western blot and electrophoretic mobility shift assays. Proliferation assays in cell types responsive to other cytokines determined specificity for Tpo receptor. Flow cytometry quantified differentiation of CD34(+) cells into CD41(+) megakaryocytes and platelet production in vitro. RESULTS: Activation of STAT5, mitogen-activated protein kinase, p38, and early response genes by SB 394725 was similar to that induced by Tpo. SB 394725 induced a reporter gene response under a STAT activation promoter as well as the megakaryocyte-specific gpIIb promoter. The compound induced proliferation of Tpo responsive lines but demonstrated no activity in cell lines responding to other cytokines, i.e., erythropoietin, granulocyte-colony stimulating factor, interleukin-3, interferon-gamma. The response of normal human Tpo receptors was elucidated by measuring growth and differentiation of human bone marrow in vitro. Activation of endogenous Tpo receptors by SB 394725 was demonstrated in human and chimp platelets, but not in platelets of other species including mouse, dog, rabbit, or cynomolgus monkey. CONCLUSIONS: SB 394725, a small molecule with a molecular weight of 452 Da, is capable of activating Tpo-specific signal transduction, proliferation, and differentiation responses similar to the responses and functions of the protein growth factor, Tpo.     

Diesel exhaust exposure enhances the expression of IL-13 in the bronchial epithelium of healthy subjects

Epidemiological studies have demonstrated adverse health effects of environmental pollution. Diesel exhaust (DE) is an important contributor to ambient particulate matter pollution. DE exposure has been shown to induce a pronounced inflammatory response in the airways, with an enhanced epithelial expression of IL-8, and Gro-alpha in healthy subjects. The present investigation was aimed to further characterise the epithelial response to DE in vivo, with particular reference to possible TH2 response, in non-atopic healthy subjects. To determine this response, 15 healthy, non-atopic non-smoking subjects with normal lung function were exposed to DE (PM10 300 microg/m3) and filtered air during 1 h on two separate randomised occasions. Bronchoscopy sampling of bronchial mucosal biopsies was performed 6 h after exposure. Immunohistochemical staining were performed using mAb for IL-10, IL-13 and IL-18 expression. DE exposure induced a significant increase in the expression of IL-13 in the bronchial epithelium cells, 2.1 (1.35-4.88) Md (Q1-Q3) vs. air 0.94 (0.53-1.23); P = 0.009. No significant changes were seen in IL-10 and IL-18 expression. This finding suggests an TH2-inflammatory response in the airways of non-atopic healthy individuals.     

Effects of nabumetone,celecoxib, and ibuprofen on blood pressure control in hypertensive patients on angiotensin converting enzyme inhibitors

Nonsteroidal anti-inflammatory drugs interfere with certain antihypertensive therapies. In a double-blind study, 385 hypertensive patients stabilized on an angiotensin converting enzyme inhibitor were treated with nabumetone, celecoxib, ibuprofen, or placebo for 4 weeks. Ibuprofen caused significantly greater increases in systolic (P < .001) and diastolic (P < .01) blood pressures (BPs) compared to placebo, but not nabumetone or celecoxib. The proportion of patients with systolic BP increases of clinical concern at end point was significantly higher (P < .001) for the ibuprofen group (16.7%; 15 of 90), but not for the nabumetone group (5.5%; 5 of 91) or the celecoxib group (4.6%; 4 of 87) compared to the placebo group (1.1%; 1 of 91).     

Clinical implications of changes in the modern diet: iron intake,absorption and status

The modern British diet contains less red meat and is lower in iron than that consumed 30 years ago. This is in spite of the fact that fortification of foods, particularly breakfast cereals, with iron has become more widespread. Although there is no clear relationship between dietary iron intake and iron status, isotope studies have identified multiple dietary factors that influence iron absorption, such as ascorbic acid, animal tissue, phytates and polyphenols. There is no evidence to suggest that current dietary changes will have a major impact on iron status in the general population; however, effects on the incidence of iron overload in individuals with HFE mutations and iron deficiency in children and premenopausal women remain to be determined.     

Traumatic cloaca

Deep laceration of the perineum after an obstetric injury may result in a cloacal deformity of the anus and vagina, causing complete fecal incontinence. A surgical technique consisting of reconstruction of the perineal body (perineoplasty) with puborectalis interposition and overlapping external sphincteroplasty is described to correct the defect and restore continence. This procedure has been used on 43 patients in a 10-year period with excellent anatomic and physiologic results.