Index Of Epithelial Permeability Research Articles

Dermatophagoides pteronyssinus and bioelectric properties of airway epithelium: role of cysteine proteases.

Several epidemiological studies suggest that exposure to house dust mite allergens plays a role in the pathogenesis of asthma. Since many of these allergens exhibit enzymatic properties, they may damage the airway epithelium. To characterize the effects of low doses of Dermatophagoides pteronyssinus on the airway epithelium, the effect of D. pteronyssinus on the epithelial bioelectric properties of tracheal fragments of non-sensitized Lewis rats was studied, using Ussing-type chamber technique. The addition of a crude D. pteronyssinus extract containing 20 microg mL(-1) of Der pI allergen in the presence of 1.5 mM dithiothreitol (DTT, an activator of cysteine proteases), induced a progressive increase in bioelectrical conductance (+12.0+/-1.5%, n=12, p<0.005), an index of epithelial permeability, without affecting the short circuit current (which reflects active ion transports). The D. pteronyssinus-induced increase in epithelial conductance was related to the cysteine-protease activity of the allergen since it was not observed in the absence of DTT (n=12), and was completely suppressed in the presence of 10 nM E-64, a specific inhibitor of cysteine proteases (n=12). D. pteronyssinus-induced increase in epithelial conductance could be entirely attributed to an increase in the paracellular conductance (+11.2+/-1.2%, n=8, p<0.01). There was no electrophysiological evidence of rupture in epithelial continuity, and no cell detachment was observed on microscopic examination. In conclusion, the cysteine protease activity of crude Dermatophagoides pteronyssinus extract is able to increase the epithelial paracellular conductance of rat tracheal tissues, even at relatively low doses that do not induce cell detachment or cell death.

Exaggerated Intestinal Histamine Release by Casein and Casein Hydrolysate but Not Whey Hydrolysate

Loops of rabbit distal small intestine received luminal acetic acid (pH 4.0) alone or in combination with bovine casein, casein hydrolysate, or whey hydrolysate. Blood-to-lumen movement of 51Cr-labeled ethylenediaminetetraacetic acid (EDTA) (an index of epithelial permeability) and loop fluid histamine levels were quantified after 45 min. Luminal acetic acid caused a marked increase in 51Cr-EDTA accumulation which was not modified by the addition of bovine casein or hydrolysates by of casein or whey. However, acetic acid-induced histamine release was potentiated by casein and casein hydrolysate (six- and four-fold respectively) but was not altered by whey hydrolysate. Casein hydrolysate-dependent histamine release was evident in naloxone-pretreated rabbits, suggesting that beta-casomorphins were not solely responsible. We conclude that luminal casein or casein hydrolysate, but not whey hydrolysate. can activate intestinal mast cells under conditions of enhanced epithelial permeability. This effect appears to involve components other than beta-casomorphins.

The effect of a rumen microbial fermentation on urea and nitrogen metabolism of sheep nourished by intragastric infusion

Four sheep were maintained by infusion of volatile fatty acid (VFA), mineral and buffer solutions to the rumen and casein to the abomasum. After a 3 week period in which control measurements were made, glucose was introduced gradually to the rumen infusion mixture until glucose replaced about 65% of VFA energy. Further measurements were made in the fourth week of glucose additions after which the control VFA infusions were re-established and measurements repeated. Urea kinetics were measured with [14C]urea. Rumen ATP concentrations were used as an index of microbial growth and increased from 1.5 nmol ml-1 on control treatments to 46 nmol ml-1 when glucose was given. The presence of a rumen fermentation resulted in a 40% decrease in plasma urea concentration but was without effect on rumen ammonia concentration. Urea irreversible loss rate decreased from 18.0 to 12.8 g urea day-1 when glucose was given. This, however, was matched by a decrease in urinary urea excretion, with the result that urea degradation, obtained by difference, remained constant throughout the three treatment periods. Daily nitrogen (N) retention increased from 1.0 to 2.7 g when a rumen microbial population was present. A model of urea and NH3 transactions for the two dietary situations is presented. Calculations indicated that 0.40 of the casein N supply was reutilized as urea by the rumen micro-organisms. It is suggested, however, that the improvement in N retention resulted from a change in protein:energy ratio of the infused nutrients rather than from an enhanced supply of protein to the intestine. The use of endogenous urea clearance as an index of epithelial permeability to urea is questioned.

Antigen-induced Lung Solute Clearance in Rats Is Dependent on Capsaicin-sensitive Nerves

Chemosensitive sensory nerves have an important effector role in the control of vascular permeability in rat airways after neurogenic inflammation. To investigate whether they also have a role in antigen-induced lung inflammation, we have studied the changes in lung solute clearance (LSC) in sensitized rats after aerosol challenge with allergen and the effect of prior capsaicin-induced denervation on these changes. Sprague-Dawley rats were immunized with egg albumin (EA), using aluminum hydroxide and Bordetella pertussis as adjuvants. After 11 days, the animals were challenged for 5 min with aerosolized EA, and the clearance from the lungs of aerosolized 99mTc diethylenetriamine pentaacetic acid (99mTc-DTPA) over 7.5 min (LSC 7.5) was subsequently measured at various times after challenge as an index of epithelial permeability or integrity. Sensitized animals responded to the challenge with immediate respiratory symptoms and with an increased 99mTc-DTPA clearance rate that was detectable at 20 min (mean +/- SE LSC 7.5: baseline, 6 +/- 1%; 20 min, 17 +/- 3%; p less than 0.05), persisted at 4 h (14 +/- 1%; p less than 0.05), and returned to normal values after 24 h. Unsensitized rats exposed to EA and sensitized rats exposed to PBS or to bovine serum albumin did not show any change. Bronchoalveolar lavage failed to show significant changes of cell populations until 24 h, when an increased presence of lymphocytes, PMN, and eosinophils was observed.(ABSTRACT TRUNCATED AT 250 WORDS)