Publications

Localized absence of epithelial Langerhans cells (LC) has been shown to affect systemic immune responses, allow microbial colonization and play a possible role in carcinogenesis. Because use of smokeless tobacco is associated with abnormal oral mucosal changes and development of carcinoma, we examined lesion and control specimens from 17 current users of smokeless tobacco to determine whether lesions showed changes in LC number or antigen expression. We identified LC by immunohistochemistry with antibodies to the antigens T6, HLA-DR, HLA-DQ, and HLA-DP. Lesion specimens contained fewer LC (means of 6 LC/mm and 10 LC/mm2) than did the corresponding control specimens (means of 14 LC/mm and 30 LC/mm2), and in each pair of lesion and autologous control specimens the reduction in LC was on average 58% (range, 3% to 95%). There were no apparent differences between lesion and control specimens in the number of LC expressing each of the four marker antigens. Reductions in LC occurred in all types of smokeless tobacco-associated lesions, regardless of increased epithelial thickness or changes in keratinization. Our data indicate that smokeless tobacco reduces the number of Langerhans cells at its site of contact with the oral mucosa.

The mesangial cell MMPs and their inhibitor may represent proteins through which biological modifiers such as cytokines and growth factors can control and influence the organization of the glomerulus. At the present we can only speculate on their exact function in glomerular disease. They could conceivably play a role in glomerular conditions where mesangial hypercellularity and cytoplasmic interposition between the endothelium and the basement membrane are frequent occurrences, and in which cytokine-enhanced synthesis of matrix-degrading enzymes could result in severe structural damage. A number of glomerular diseases such as diabetic nephropathy are characterized by the accumulation of glomerular matrix proteins. This could be explained by the inappropriate expression of intrinsic mesangial cell MMPs or TIMP. Further investigation of these proteins in experimental models of glomerular disease or in situ hybridization studies using the available probes promises to be a rewarding area of research during the next few years. For these studies the availability of rTIMP and recent developments in the design of synthetic inhibitors of MMPs may allow more searching investigations into the role of MMP in the pathophysiology of glomerular disease.

Cultured rat glomerular epithelial cells (GEC) were examined for their ability to release extracellular matrix-degrading proteinases with [3H]gelatin as substrate. GEC-conditioned media, under serum-free conditions, contained modest amounts of gelatinase activity (1 to 10 U/mg of protein); the activity was maximal at neutral pH, was inhibited by zinc chelators, was not inhibited by tissue inhibitor of metalloproteinase-2, and could not be further activated by trypsin or organomercurials. Gelatin substrate sodium dodecyl sulfate-polyacrylamide gels of GEC-conditioned medium revealed several zones of lysis, with molecular sizes of 150 kd (major band), and 220, 86 to 93, and 52 to 54 kd (minor bands). Northern blot analysis demonstrated that the GEC metalloproteinase(s) were distinct from the 68- to 72-kd type IV collagenase/gelatinase present in mesangial cells or the 92-kd type IV collagenase present in neutrophils. The GEC gelatinolytic activity also degraded insoluble type IV collagen in glomerular basement membrane in a dose-dependent manner. The major metalloproteinase activity responsible for the type IV collagen degradation has a molecular size of 150 kd with a type IV collagen substrate gel. Thus, GEC produce several neutral metalloproteinases, which, by virtue of their substrate specificity, may play an important role in glomerular basement membrane remodeling and in glomerular diseases characterized by alterations in basement membrane permeability.