Proteoglycan changes in the extracellular matrix of lung tissue from patients with pulmonary emphysema.

To characterize the changes in the extracellular matrix in smoking-related pulmonary emphysema, we undertook immunohistochemical studies in lung tissues from controls (n = 7), from patients with mild (n = 11) and severe (n = 8) emphysema, and from patients with lung fibrosis (n = 6). We studied collagens, laminin, fibronectin, proteoglycans (PGs), and beta1-integrins. The majority of the patients with severe emphysema showed diminished staining for the interstitial PGs, decorin and biglycan, in the peribronchiolar area, compared with patients in the control and fibrosis groups. Only a minority of patients with mild emphysema showed this diminished staining. In contrast, decorin and biglycan were well preserved in the perivascular area of all of the specimens from the emphysema group. Heparan sulfate PG staining was diminished in the respiratory airspace walls of patients with emphysema and fibrosis. Staining for Types I, III, and IV collagen, as well as for laminin, fibronectin, and the integrins, showed no differences between the four groups. The specific loss of interstitial PGs may be crucial for elastic recoil loss and subsequent bronchiolar obstruction, as seen in patients with smoking-related emphysema.

Why do microencapsulated islet grafts fail in the absence of fibrotic overgrowth?

The survival of microencapsulated islet grafts is limited, even if capsular overgrowth is restricted to a small percentage of the capsules. In search of processes other than overgrowth contributing to graft failure, we have studied the islets in non-overgrown capsules at several time points after allotransplantation in the rat. All recipients of islet allografts became normoglycemic. Grafts were retrieved at 4 and 8 weeks after implantation and at 15.3 +/- 2.3 weeks postimplant, 2 weeks after the mean time period at which graft failure occurred. Overgrowth of capsules was complete within 4 weeks postimplant, and it was usually restricted to <10% of the capsules. During the first 4 weeks of implantation, 40% of the initial number of islets was lost. Thereafter, we observed a decrease in function rather than in numbers of islets, as illustrated by a decline in the ex vivo glucose-induced insulin response. At 4 and 8 weeks postimplant, beta-cell replication was 10-fold higher in encapsulated islets than in islets in the normal pancreas, but these high replication rates were insufficient to prevent a progressive increase in the percentage of nonviable tissue in the islets. Necrosis and not apoptosis proved to be the major cause of cell death in the islets. The necrosis mainly occurred in the center of the islets, which indicates insufficient nutrition as a major causative factor. Our study demonstrates that not only capsular overgrowth but also an imbalance between beta-cell birth and beta-cell death contributes to the failure of encapsulated islet grafts. Our observations indicate that we should focus on finding or creating a transplantation site that, more than the unmodified peritoneal cavity, permits for close contact between the blood and the encapsulated islet tissue.

Macrophages in lung tissue from patients with pulmonary emphysema express both inducible and endothelial nitric oxide synthase.

To provide information concerning a possible biologic role of nitric oxide (NO) in smoking-related emphysema, we performed immunohistochemical studies in lung tissue from control subjects and patients with mild and severe emphysema. We studied the presence of inducible and endothelial NO synthases (iNOS and eNOS, respectively) and determined nicotinamide diphosphate (NADPH) diaphorase activity. Patients with severe emphysema showed lower percentages of iNOS- and eNOS-positive alveolar macrophages in situ than did patients with mild emphysema. In patients with both iNOS and eNOS immunoreactivity in macrophages, the majority of the macrophages expressed either iNOS or eNOS, whereas only a minority of the macrophages showed iNOS and eNOS immunoreactivity simultaneously. Immunoreactivity for eNOS in endothelial and/or bronchiolar epithelial cells and NADPH diaphorase activity in macrophages and in endothelial, epithelial, and smooth muscle cells were similar in the three studied groups. The expression of eNOS in macrophages suggests that eNOS plays an additional role, besides iNOS, in the NO housekeeping in inflammatory processes in pulmonary tissue. We suggest that NO might have a protective role in maintenance of structural integrity of pulmonary tissue after smoke-induced damage.

The regulation of interleukin 5 and interleukin 3 gene expression in human T cells.

Interleukin 5 (IL-5) and Interleukin 3 (IL-3) mRNA levels in human peripheral blood T cells were compared by semi-quantitative polymerase chain reaction (PCR) analysis. Unstimulated T Cells did not express IL-5 and IL-3 mRNA. IL-5 and IL-3 mRNA expression were similarly induced by the lectin concanavalin A (Con A). The protein kinase C (PKC) activator phorbol myristate acetate (PMA) triggered both IL-3 and IL-5 mRNA expression, whereby IL-5 and IL-3 mRNA expression was observed after 9 and 3 h treatment, respectively. Stimulation with calcium ionophore A23187 induced IL-3 mRNA expression, whereas it failed to induce IL-5 mRNA. In contrast to IL-3 mRNA, the expression of IL-5 mRNA was dependent on de novo protein synthesis, since cycloheximide (CHX) blocked the Con A plus PMA induced IL-5 mRNA expression. In contrast, cyclosporin A (CsA) inhibited but failed to completely block the expression of IL-3 and IL-5 mRNA. mRNA studies in T cell subsets revealed that the expression of IL-5 mRNA was restricted to the CD4 positive T cell subset in response to Con A plus PMA stimulation. On the other hand, IL-3 mRNA expression was noticed in both the CD4 and the CD8 positive T cell subset. These data indicate that the selective expression of IL-5 by human T cells can either be explained by activation of a selective intracellular signalling pathway or by selective activation of a T cell subset. Alternatively, both processes could be involved.

The efficacy of intraperitoneal pancreatic islet isografts in the reversal of diabetes in rats.

The peritoneal cavity is of renewed interest for pancreatic islet transplantation, since it is the preferable site for transplantation of immunoisolated islets. In this study we investigated the minimum islet graft volume needed to restore normoglycemia after free intraperitoneal isogenic transplantation in streptozotocin diabetic rats. Furthermore, graft function was tested by measuring glucose and insulin response to an intravenous glucose load and spontaneously ingested carbohydrate-rich meal. Three graft volumes were used: 8.0-10.0 (group A); 4.0-5.0 (group B); and 2.0-2.3 microliters (group C); 1 microliter contained about 300 islets. All 10 rats in group A and 7 out of 9 rats in group B became normoglycemic for at least 6 months posttransplant, with blood glucose levels not significantly different from normal control animals. Only 3 out of 9 animals in group C became normoglycemic and never for longer than 3 months. The insulin responses to IVGTT in group A and group B were proportional to the grafted islet volume and always significantly lower than those of normal control rats. The insulin response to the test meal showed a similar tendency, which was found to be associated with the absence of preabsorptive insulin secretion. Maximum postprandial blood glucose levels in group A and group B were 0.8 and 1.5 mM higher than in normal control rats. We conclude that intraperitoneal transplantation of at least 4.0-5.0-microliters islet tissue is needed to reverse blood glucose in streptozotocin diabetic rats, and that glucose and insulin levels on IVGTT and test meal in rats with islet grafts of 8.0-10.0 microliters are not completely normalized. It is suggested that the impaired glucose tolerance is due to an insufficient beta-cell mass and a lack of parasympathetic innervation of the transplanted islet tissue.