Divergent functions for airway epithelial matrix metalloproteinase 7 and retinoic acid in experimental asthma.

The innate immune response of airway epithelial cells to airborne allergens initiates the development of T cell responses that are central to allergic inflammation. Although proteinase allergens induce the expression of interleukin 25, we show here that epithelial matrix metalloproteinase 7 (MMP7) was expressed during asthma and was required for the maximum activity of interleukin 25 in promoting the differentiation of T helper type 2 cells. Allergen-challenged Mmp7(-/-) mice had less airway hyper-reactivity and production of allergic inflammatory cytokines and higher expression of retinal dehydrogenase 1. Inhibition of retinal dehydrogenase 1 restored the asthma phenotype of Mmp7(-/-) mice and inhibited the responses of lung regulatory T cells, whereas exogenous administration of retinoic acid attenuated the asthma phenotype. Thus, MMP7 coordinates allergic lung inflammation by activating interleukin 25 while simultaneously inhibiting retinoid-dependent development of regulatory T cells.

A reproductive and developmental toxicity screening study of 1,3-butadiene in Sprague-Dawley rats.

1,3 Butadiene (BD) is an industrial intermediate used primarily in product manufacturing with the greatest exposure potential via inhalation. BD was evaluated for reproductive and developmental effects in a Good Laboratory Practice (GLP)-compliant, extended OECD 421 guideline study (completed 2003). Twelve-week old rats (12/sex/dose) were exposed via whole-body inhalation to BD vapor (0, 300, 1500, 6000 ppm) for 6 h/day, 7 days/week, starting 14 days prior to mating through the day prior to euthanasia (total exposures: 83-84 days for F0 males 60-70 days for F0 females). Select F1 offspring (1/sex/litter) were dosed 7 days (postnatal days 21-27 or 28-34), then necropsied. At 1500 and 6000 ppm, treatment-related facial soiling was seen in F0 males and females with decreased body weights/gains in F0 males. F1 males and females exhibited similar effects at 1500 and 6000 ppm. Importantly, the F0 generation had no evidence of altered sperm production, testicular effects, or ovarian atrophy, which were sensitive responses in mice. The no-observed-adverse-effect-level (NOAEL) is 300 ppm due to decreased body weight/gain and facial soiling at 1500 ppm, whereas 6000 ppm serves as a NOAEL for reproductive and developmental endpoints. This study contributes to the weight-of-evidence of differential BD reproductive toxicity in rats and mice.

Boric acid inhibits stored Ca2+ release in DU-145 prostate cancer cells.

Boron (B) is a developmental and reproductive toxin. It is also essential for some organisms. Plants use uptake and efflux transport proteins to maintain homeostasis, and in humans, boron has been reported to reduce prostate cancer. Ca2+ signaling is one of the primary mechanisms used by cells to respond to their environment. In this paper, we report that boric acid (BA) inhibits NAD+ and NADP+ as well as mechanically induced release of stored Ca2+ in growing DU-145 prostate cancer cells. Cell proliferation was inhibited by 30% at 100 microM, 60% at 250 microM, and 97% at 1,000 microM BA. NAD+-induced Ca2+ transients were partly inhibited at 250 microM BA and completely at 1,000 microM BA, whereas both NADP+ and mechanically induced transients were inhibited by 1,000 microM BA. Expression of CD38 protein increased in proportion to BA exposure (0-1,000 microM). In vitro mass spectrometry analysis showed that BA formed adducts with the CD38 products and Ca2+ channel agonists cyclic adenosine diphosphate ribose (cADPR) and nicotinic acid adenine dinucleotide phosphate (NAADP). Vesicles positive for the Ca2+ fluorophore fluo-3 acetoxymethyl ester accumulated in cells exposed to 250 and 1,000 microM BA. The BA analog, methylboronic acid (MBA; 250 and 1,000 microM), did not inhibit cell proliferation or NAD+, NADP+, or mechanically stimulated Ca2+ store release. Nor did MBA increase CD38 expression or cause the formation of intracellular vesicles. Thus, mammalian cells can distinguish between BA and its synthetic analog MBA and exhibit graded concentration-dependent responses. Based on these observations, we hypothesize that toxicity of BA stems from the ability of high concentrations to impair Ca2+ signaling.

Boric acid inhibits human prostate cancer cell proliferation.

The role of boron in biology includes coordinated regulation of gene expression in mixed bacterial populations and the growth and proliferation of higher plants and lower animals. Here we report that boric acid, the dominant form of boron in plasma, inhibits the proliferation of prostate cancer cell lines, DU-145 and LNCaP, in a dose-dependent manner. Non-tumorigenic prostate cell lines, PWR-1E and RWPE-1, and the cancer line PC-3 were also inhibited, but required concentrations higher than observed human blood levels. Studies using DU-145 cells showed that boric acid induced a cell death-independent proliferative inhibition, with little effect on cell cycle stage distribution and mitochondrial function.

A reversible, non-invasive method for airway resistance measurements and bronchoalveolar lavage fluid sampling in mice.

Airway hyperreactivity (AHR) measurements and bronchoalveolar lavage (BAL) fluid sampling are essential to experimental asthma models, but repeated procedures to obtain such measurements in the same animal are generally not feasible. Here, we demonstrate protocols for obtaining from mice repeated measurements of AHR and bronchoalveolar lavage fluid samples. Mice were challenged intranasally seven times over 14 days with a potent allergen or sham treated. Prior to the initial challenge, and within 24 hours following each intranasal challenge, the same animals were anesthetized, orally intubated and mechanically ventilated. AHR, assessed by comparing dose response curves of respiratory system resistance (RRS) induced by increasing intravenous doses of acetylcholine (Ach) chloride between sham and allergen-challenged animals, were determined. Afterwards, and via the same intubation, the left lung was lavaged so that differential enumeration of airway cells could be performed. These studies reveal that repeated measurements of AHR and BAL fluid collection are possible from the same animals and that maximal airway hyperresponsiveness and airway eosinophilia are achieved within 7-10 days of initiating allergen challenge. This novel technique significantly reduces the number of mice required for longitudinal experimentation and is applicable to diverse rodent species, disease models and airway physiology instruments.

Evaluation of ecological and in vitro effects of boron on prostate cancer risk (United States).

OBJECTIVE: To determine: (1) the correlation of prostate cancer incidence and mortality with groundwater boron and selenium concentrations; and (2) the impact of boron on prostate cancer cell proliferation during co-treatment with alternative chemo-preventative agents, along with boron pre-treatment effects on cell sensitivity to ionizing radiation. METHODS: For regression analysis, data on prostate cancer incidence and mortality were obtained from the Texas Cancer Registry, while groundwater boron and selenium concentrations were derived from the Texas Water Development Board. Cultured DU-145 prostate cancer cells were used to assess the impact of boric acid on cell proliferation when applied in combination with selenomethionine and genistein, or preceding radiation exposure. RESULTS: Groundwater boron levels correlated with a decrease in prostate cancer incidence (R = 0.6) and mortality (R = 0.6) in state planning regions, whereas selenium did not (R = 0.1; R = 0.2). Growth inhibition was greater during combined treatments of boric acid and selenomethionine, or boric acid and genistein, versus singular treatments. 8-day boric acid pre-exposure enhanced the toxicity of ionizing radiation treatment, while dose-dependently decreasing the expression of anti-apoptotic protein Bcl-2. CONCLUSIONS: Increased groundwater boron concentrations, across the state of Texas, correlate with reduced risk of prostate cancer incidence and mortality. Also, boric acid improves the anti-proliferative effectiveness of chemo-preventative agents, selenomethionine and genistein, while enhancing ionizing radiation cell kill.