Pulmonary Milieu Research Articles

Liposomes in Pulmonary Applications: Physicochemical Considerations, Pulmonary Distribution and Antioxidant Delivery

The application of liposomes for improved drug delivery to the lung is promising. Liposome-mediated pulmonary drug delivery promotes an increase in drug retention-time in the lung and more importantly, a reduction in extrapulmonary side-effects, invariably resulting in enhanced therapeutic efficacies. The engineering of an effective liposomal drug formulation for inhalation therapy must take into consideration the leakage problem associated with the nebulization process; vesicle stability and release kinetics within the pulmonary milieu; and, the altered pharmacokinetics of the entrapped drug. The delivery of liposome-entrapped antioxidants via the tracheobronchial route has been found to be very useful in increasing the half-times of the administered agents, thus providing a sustained release effect for prolonged drug action. The entrapment in liposomes of alpha-tocopherol, an extremely insoluble but highly effective antioxidant, has been shown to be very effective in ameliorating oxidant-induced injuries in the lung. The use of bifunctional liposomes containing two antioxidants have been determined to provide excellent resistance to an oxidative challenge and appears to hold promise for improved clinical applications in antioxidant therapy.

Enhanced expression of CD2 antigen on lung T cells.

CD2 molecules not only function in the adhesion of T cells to other cell types but also in the activation of T cells via an alternative pathway. To investigate the possible roles of CD2 molecules in the activation and accumulation of lung T cells, using monoclonal antibodies and a flow cytometer we evaluated CD2 antigen expression on lung and blood lymphocytes in 10 normal subjects, 30 patients with pulmonary sarcoidosis, 7 patients with interstitial pneumonia associated with collagen vascular disease, 5 patients with farmer's lung disease, and 8 patients with Crohn's disease. The mean fluorescence intensity (MFI) of CD2 on lung T cells obtained by bronchoalveolar lavage (BAL) was significantly higher than that on blood T cells in all study groups except the control group. In patients with pulmonary sarcoidosis this enhancement of the expression of CD2 antigen was observed only on CD4+ T cells. Since ligands for CD2 are present on immunocompetent cells of other types in the local pulmonary milieu, these results suggest that increased expression of CD2 molecules could facilitate the communication and interaction of lung T cells with their environment in the lung and thereby possibly contribute to the local accumulation of T cells.

Modulation of Accessory Molecules on Lung T Cells

Stimulation of T cells via the CD3/TCR complex is associated with the reduced expression of accessory molecules, a phenomenon called modulation. To investigate whether the modulation is implicated in the pathogenic mechanism of pulmonary disease, we determined the MFI of CD3, CD4 and CD8 on lung and blood lymphocytes in ten normal subjects and 54 patients with various pulmonary and extrapulmonary diseases. Although there were no significant differences in MFI of these accessory molecules on lung lymphocytes among the groups, MFI of CD3 on lung lymphocytes was significantly decreased compared with that on blood lymphocytes in all groups, demonstrating the modulation of CD3 on lung lymphocytes. Since it has been shown that T cells whose CD3/TCR is modulated are hyporesponsive to various mitogenic signals, our observation seems to represent another aspect of the mechanism whereby the local pulmonary milieu maintains the autoregulation of immune response.

815 CONCOMITANT LOSS OF MUCOID TRAIT AND ANTIBIOTIC RESISTANCE IN PSEUDOMONAS AERUGINOSA STRAINS FROM CYSTIC FIBROSIS PATIENTS

The unusual frequency of pulmonary colonization of cystic fibrosis patients by mucoid (mu+) strains of P. aeruginosa suggests a special relationship between these strains and the pulmonary milieu of CF patients. To better characterize the control of slime production, we isolated P. aeruginosa from sputum cultures of CF patients collected during respiratory therapy. 16 of 19 patients yielded P. aeruginosa which was identified by the API method with growth at 41° and on Pseudomonas isolation agar. Mu+ strains were isolated from 13 of 16 pattents; 11 of 16 had both mu+ and nonmucoid (mu−) strains. All 13 mu+ strains were unstable in nutrient broth, producing mu− variants at characterisic frequencies ranging from 1-97% of c.f.u. in 24 hours. Mu− segregation frequency is medium-and temperature-dependent. The low frequency (<1×10-5) of reversion of mu− to mu+ suggests inherited loss of the capacity to produce slime. 2 of 13 mu+ strains showed concomitant loss of slime production and selected anti-biotic resistance on Mueller-Hinton agar. Each of 10 independently derived mu−clones from VLO-1 became bactrim sensitive; MIC by the agar dilution method for trimethoprim and sulfamethoxazole were respectively 64 and 160μg/ml for VLO-lmu+ vs 8 and 40μg/ml for VLO-1mu−. Strain TWH-1mu− showed a similar increase in sensitivity to chloramphenicol. This suggests that slime production is encoded by a plasmid which also specifies resistance to certain antibiotics.