TISSUE MAST CELLS AND ACUTE INFLAMMATION IN EXPERIMENTAL CUTANEOUS MUCORMYCOSIS OF NORMAL, 48/80-TREATED, AND DIABETIC RATS

The role of the tissue mast cells in relation to the acute inflammatory reaction to experimental cutaneous mucormycosis was studied histologically in normal rats, in animals whose tissue mast cells had been depleted of their cytoplasmic granules prior to infection by the administration of compound 48/80 and in others in whom acute alloxan diabetes with acidosis had been produced before injection of the fungus. The discharge of the tissue mast cell granules in normal rats occurred within minutes at the site of infection and appeared to initiate the rapid onset of acute inflammation. The degranulation of the tissue mast cells subsided in a short time and the cells reassumed a normal histologic appearance while inflammation progressed with the formation of circumscribed lesions. In animals pretreated with compound 48/80 in which the tissue mast cells contained no granules, the onset of inflammation was briefly delayed, the intensity of the process was somewhat decreased, fibroblastic proliferation was retarded, and the fungus growth in the early lesions was increased. However, the infection did not spread and the lesions were well localized. The tissue mast cells in the diabetic and acidotic rats completely failed to discharge their cytoplasmic granules, the onset and intensity of the acute inflammatory response were markedly delayed and decreased and the infection progressed rapidly with massive fungus growth invading adjacent tissues. A relationship between the discharged tissue mast cell granules and eosinophilic granulocytes was noted since the latter were numerous among the inflammatory cell exudate in normal rats and scarce in the lesions of the diabetic animals. It is concluded that a function of the tissue mast cells in the normal rat is the rapid initiation of acute inflammation at the site of injury and that degranulation of these cells prior to infection somewhat delays the inflammatory response and therefore slightly diminishes host resistance. Furthermore, a severe metabolic disorder such as acute alloxan diabetes with acidosis, inhibits the normal function of the tissue mast cells, delays and decreases inflammation, and in this manner contributes to the greatly increased susceptibility of the host to infection.

[Rheumatic diseases in pregnancy]

Rheumatic diseases can influence the reproduction, the course of pregnancy and the development of the fetus. The inflammatory rheumatic disease itself can be modulated in its activity in terms of amelioration or exacerbation of the rheumatic symptoms. The associations between rheumatic diseases and pregnancy will be illustrated with rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and systemic lupus erythematosus as examples. Antirheumatic drug therapy during pregnancy and the breast feeding period has to be adapted critically.

Hyperosmotic stress induces Axl activation and cleavage in cerebral endothelial cells

Because of the relative impermeability of the blood-brain barrier (BBB), many drugs are unable to reach the CNS in therapeutically relevant concentration. One method to deliver drugs to the CNS is the osmotic opening of the BBB using mannitol. Hyperosmotic mannitol induces a strong phosphorylation on tyrosine residues in a broad spectrum of proteins in cerebral endothelial cells, the principal components of the BBB. Previously, we have shown that among targets of tyrosine phosphorylation are beta-catenin, extracellular signal-regulated kinase 1/2 and the non-receptor tyrosine kinase Src. The aim of this study was to identify new signalling pathways activated by hypertonicity in cerebral endothelial cells. Using an antibody array and immunoprecipitation we identified the receptor tyrosine kinase Axl to become tyrosine phosphorylated in response to hyperosmotic mannitol. Besides activation, Axl was also cleaved in response to osmotic stress. Degradation of Axl proved to be metalloproteinase- and proteasome-dependent and resulted in 50-55 kDa C-terminal products which remained phosphorylated even after degradation. Specific knockdown of Axl increased the rate of apoptosis in hyperosmotic mannitol-treated cells; therefore, we assume that activation of Axl may be a protective mechanism against hypertonicity-induced apoptosis. Our results identify Axl as an important element of osmotic stress-induced signalling.