Mary Lou Eskew

Large porous particles for sustained protection from carbachol-induced bronchoconstriction in guinea pigs.

AbstractPurpose. To determine whether a new formulated albuterol aerosol could sustain inhibition to bronchoconstriction for approximately one day in guinea pigs challenged with carbachol. Methods. Large and porous particles, comprising a combination of endogenous or PDA-approved excipients and albuterol sulfate, were prepared by spray drying using a NIRO portable spray drier. The anesthetized animals inhaled 5 mg of large porous or small nonporous particles by forced ventilation via cannulae inserted in the lumen of their exposed tracheae. At regular intervals over a period of 36 hours after drug delivery, airway resistance was determined in response to carbachol challenge dose. Results. Whereas inhalation of small nonporous albuterol particles protected from the carbachol-induced bronchoconstriction for up to 5 hours, inhalation of large porous albuterol particles produced a significant inhibition of carbachol-induced bronchoconstriction for at least 16 hours. Conclusions. The absence of substantial side effects, verified over a period of 24 hours by evaluating cardio-respiratory parameters as well as pulmonary inflammation, supports the utility of large porous albuterol particles for sustained therapies in asthma and other types of lung disease.

Antioxidant effects on cell-mediated immunity.

Experiments were performed to determine the effects of dietary selenium and/or vitamin E deficiency on cell‐mediated cytotoxicity in the mouse. Natural killer cell‐mediated cytotoxicity (NKCC) was depressed after 8 wk on diets deficient in selenium and/or vitamin E. In contrast, antibody‐dependent cell‐mediated cytotoxicity (ADCC) was not affected by 8 wk of dietary deficiency of selenium and/or vitamin E. T‐lymphocyte‐mediated cytotoxicity (TCMC) was found to be depressed by combined selenium‐vitamin E deficiency after 7 weeks on diets.

The effects of ozone inhalation on the immunological response of selenium- and vitamin E-deprived rats

Deficiencies in vitamin E (E) or Se result in immune alterations, possibly due to reduction of antioxidant activity. Such reductions might greatly compromise the ability of the immune system to deal with additional oxidant stress, as encountered during exposure to air pollutants such as ozone (O3). To study possible interactions of these oxidative stresses on immune function, male Long-Evans hooded rats were maintained 5 weeks on torula yeast-based diets, with or without the addition of E or Se. Each dietary group was subdivided into O3-exposed and nonexposed groups. Two different regimens of O3 exposure were used: continuous (1.0 ppm, 8 hr/day for 7 days) or intermittent (2.0 ppm, 8 hr/day for 4 days, 2-4 days in ambient air followed by 1 day of exposure prior to sacrifice). Exposure to O3 in either regimen resulted in increased numbers of cells recovered by pulmonary lavage. With continuous exposure this increase was due to macrophage influx and, with intermittent exposure, due to influx of both macrophages and neutrophils. Combined deficiency of E and Se led to an enhanced ability of spleen and lung cells to mediate antibody-dependent cell-mediated cytotoxicity (ADCMC). In animals deficient in E, but not Se, O3 exposure depressed spleen cell ADCMC. Deficiencies of either E or Se also depressed lymphocyte response to mitogens. Although intermittent exposure to O3 caused no changes in mitogen response, in animals exposed continuously to O3 there was a significant enhancement of this response.

SELENIUM AND VITAMIN E DEFICIENCY IMPAIR TRANSFERRIN RECEPTOR INTERNALIZATION BUT NOT IL-2, IL-2 RECEPTOR, OR TRANSFERRIN RECEPTOR EXPRESSION

Vitamin E and Se deficiency increase the risk of disease by impairing the immune response. To aid in the understanding of how vitamin E and Se deficiency reduce immune competence, this study examined several mechanisms necessary for lymphocyte proliferation. Weanling rats were fed a vitamin E‐deficient, selenium‐deficient, or control diet for 8 weeks. At this time splenic mononuclear cells were isolated and stimulated with concanavalin A for 48 h. Although the percentage of lymphocytes and monocytes capable of proliferating were consistent among the dietary groups, lymphocyte proliferation was decreased significantly in vitamin E‐ and selenium‐deficient rats. This decrease in proliferation was not associated with alterations in interleukin‐2, interleukin‐2 receptor, or transferrin receptor expression. However, stimulated cells from vitamin E‐ and Sedeficient rats internalized few if any transferrin receptors. Reduced transferrin receptor internalization may limit lymphocyte expansion by depleting the intracellular iron stores needed for cellular function and proliferation. J. Leukoc. Biol. 63: 131–137; 1998.

Inhalation System for Pulmonary Aerosol Drug Delivery in Rodents Using Large Porous Particles

The pulmonary system is an attractive noninvasive route for effective delivery of drugs for both local and systemic therapies. In this study, an inhalation system was developed to effectively aerosolize and deliver small amounts (typically 1-5 mg) of dry powder polymeric and nonpolymeric particles to the lungs of anesthetized rodents over a very short period of time using a ventilator while the animals breathed spontaneously. The new aerosols were designed for size, porosity, and lightness and were characterized by particles of low mass density (rho less than or equal to 0.1 g/cm3) and large size (d approximately 10 mum). The inhalation system was tested in vivo to determine 1) whether the relatively efficient in vitro aerosolization of these large porous particles translated into a substantial respirable fraction in vivo; 2) whether the bioavailability of an encapsulated drug for systemic therapy could be increased and the drug release in the systemic circulation could be sustained; and 3) whether an encapsulated drug for local asthma therapy could sustain bronchodilation over a prolonged time period. Unlike the conventional (small non-porous) particles which deposit primarily in the tubing and trachea (80% of all particle mass delivered), 55% of the large porous particle mass deposited in the deep lung. The total systemic bioavailabilities of inhaled porous estradiol, insulin, and testosterone relative to subcutaneous injections were 86%, 88%, and 177%, respectively. The inhaled dry powder albuterol sulfate aerosol was capable of preventing sustained bronchoconstriction (in response to carbachol challenge) for approximately one day. Our data indicate that the experimental inhalation system we developed will be an excellent device for further testing of new therapeutics available in particulate form.

Effects of inadequate vitamin E and/or selenium nutrition on the release of arachidonic acid metabolites in rat alveolar macrophages

Effects of vitamin E and/or selenium (Se) deficiency on the secretion of arachidonic acid metabolites by zymosan-stimulated pulmonary alveolar macrophages (AM) were examined using cells from male Long-Evans hooded rats fed torula-yeast based diets with or without the supplementation of vitamin E (150 IU/kg) or Se (0.5 mg/kg). Alveolar macrophages obtained by lavage were purified by adherence and cultured for 4 h in Hanks balanced salt solution containing bovine serum albumin (0.1%) and zymosan (300 micrograms/ml). The arachidonic acid metabolites present in the culture supernatant were measured by radioimmunoassay. Altered vitamin E and Se nutrition had no effect on the number of cells or cell types recovered from the pulmonary airways. Alveolar macrophages derived from animals fed on diets deficient in vitamin E or Se or both nutrients secreted higher levels of prostaglandin E2 and thromboxane B2. Levels of both 5-hydroxyeicosatetraenoic acid and leukotriene B4 were significantly increased only in the group fed the diet adequate in Se but deficient in vitamin E. Our data suggest that vitamin E and Se might play an important role to control the levels of several physiologically and pathologically important arachidonic acid metabolites.

Comparative pathological aspects of chronic olivine and silica inhalation in mice

A comparative study was done in mice on the effects of silica and olivine inhalation. The exposure periods in the dust chambers were for periods of 150, 300, and 570 days, with the longest time period covering a large portion of the predicted life span of the Balb/c mouse. Detailed necropsies including histology were done at the end of the exposures and at 30 and 150 days following removal of animals from the 150- and 300-day dust exposures. The results indicate that silica causes considerably more tissue damage in lungs and mediastinal lymph nodes, leading to granulomas.

Effects of prolonged inhalation of silica and olivine dusts on immune functions in the mouse

Immunologic responses were determined in Balb/c mice following intermittent silica or olivine inhalations for 150, 300, or 570 days. Animals dust-exposed for 570 days were tested immediately postexposure, while those exposed for 150 or 300 days were tested immediately or were rested for 30 or 150 days as a measure of possible recovery from effects of the dust inhalations. Silica inhalation suppressed the number of specific plaque-forming cells (PFC) in the spleen produced in response to aerosolized Escherichia coli bacteria. When tested after 570 days, silica inhalation also reduced the ability of alveolar macrophages to phagocytize Staphylococcus aureus in vitro. Olivine inhalation also suppressed splenic PFCs and alveolar macrophage phagocytosis, but to a lesser degree than silica. In animals tested after 570 days of dust exposure, it was determined that the ability to lyse allogeneic tumor cells in vitro was impaired by olivine slightly more than by silica, while antibody-dependent cell-mediated cytotoxic and mitogenic responses by splenic lymphocytes were unchanged by inhalation of either dust. The effects of increased exposure periods, and of recovery periods after exposure, were confounded by age-related immunologic changes which were present after the longer exposures.

Immunological alterations in the mouse following injection or inhalation of silica and olivine dusts

Immunologic responses were determined in mice following silica or olivine inhalations of up to 300 days, or following intravenous (iv) and intraperitoneal (ip) injections of the dusts. The comparative toxicity of iv injected silica or olivine was also studied. Silica inhalation suppressed the splenic plaque-forming cell (PFC) responses to Escherichia coli given as an aerosol, while olivine inhalation caused less severe suppression. Similar decreases in specific serum antibody levels and alveolar macrophage phagocytic indices were also seen. Few changes were found in spleen lymphocyte responses to mitogens. Injections of silica (iv or ip) caused either enhancement, or in some cases suppression, of the response to antigenic stimulation, with lower doses generally stimulating and very high doses suppressing the response. Olivine injections, in general, produced similar but less severe alterations of the responses to antigenic stimulations. Comparison of lethal dose levels by iv injection indicated a greater toxicity for silica than olivine in this respect.

Effects of fly ash inhalation on murine immune function: Changes in macrophage-mediated activities

Mice were exposed to fly ash particles (<2.1 μm diameter) by inhalation for variable amounts of time at concentrations ranging from 535 to 2221 μg/m3. This fine fraction was approximately 32% by weight of the total dust generated. The effects of these exposures were assessed on macrophage-mediated functions. Phagocytosis of bacterial cells by the alveolar macrophages was depressed in the fly ash-exposed animals as was the ability to enhance T-cell mitogenesis. Fly ash exposure failed to produce a significant change in the cellular immune response (delayed-type hypersensitivity reaction) to antigenic challenge in the lungs of sensitized animals.