Suppression of allergic inflammatory response in the skin of alloxan-diabetic rats: relationship with reduced local mast cell numbers.
BACKGROUND
Diabetic patients are refractory to allergic inflammatory diseases. In this study, the influence of alloxan-induced diabetes on allergic skin inflammation was investigated.


METHODS
Diabetes was induced by intravenous injection of alloxan into male Wistar rats, and the analyses were performed 21 days later. Animals were actively sensitized with a mixture of aluminium hydroxide plus ovalbumin and challenged intradermally with ovalbumin on day 14.


RESULTS
Diabetic sensitized rats exhibited a less pronounced antigen-induced protein extravasation in the dorsal skin when compared with normal animals. Also, fragments of the dorsal subcutaneous tissue from diabetic sensitized rats showed a reduction in histamine release after stimulation with antigen in vitrowhen compared with fragments obtained from nondiabetic sensitized rats. Optical microscopy analysis revealed that the dorsal skin of diabetic rats showed a marked reduction in dermis thickness, as compared with that seen in normal animals. A significant decrease in the number of skin mast cells was also noted, a phenomenon that paralleled with the reduction in the expression of extracellular matrix components laminin, fibronectin and collagen. Administration of insulin into diabetic rats restored basal mast cell numbers as well as the levels of laminin, fibronectin and collagen.


CONCLUSIONS
Our findings show that alloxan diabetes induces downregulation of the skin allergic inflammatory response in rats, and this was correlated with reduction in local mast cell numbers and expression of extracellular matrix components. Lastly, these alterations were reversed with insulin treatment.
de F Carvalho
Vinicius
V
Laboratório de Inflamação, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz, Rio de Janeiro, Brazil.
Campos
Leandro V
LV
Farias-Filho
Francisco A
FA
Florim
Luisa T
LT
Barreto
Emiliano O
EO
Pirmez
Claude
C
Savino
Wilson
W
Martins
Marco A
MA
e Silva
Patrícia M R
PM
D000485:Allergens / Q000276:immunology; D000496:Alloxan / Q000008:administration & dosage*; D000536:Aluminum Hydroxide / Q000276:immunology; D000818:Animals; D003921:Diabetes Mellitus, Experimental / Q000139:chemically induced / Q000276:immunology*; D015536:Down-Regulation; D005109:Extracellular Matrix / Q000378:metabolism; D006636:Histamine Release; D006967:Hypersensitivity / Q000276:immunology*; D007249:Inflammation / Q000276:immunology*; D008297:Male; D008407:Mast Cells / Q000166:cytology / Q000276:immunology*; D010047:Ovalbumin / Q000276:immunology; D051381:Rats; D017208:Rats, Wistar; D012867:Skin / Q000276:immunology*
D000485:Allergens; D000536:Aluminum Hydroxide; D000496:Alloxan; D010047:Ovalbumin