Impaired activation of mast cells upon IgE-mediated antigen stimulation in a stroke-prone spontaneously hypertensive rat strain, SHRSP.Z

We investigated IgE-mediated allergic responses in a metabolic syndrome model rat strain, SHRSP.Z, which develops obesity and hypertension to cast light on the relationship between metabolic disturbances and allergic responses. IgE-mediated cutaneous anaphylactic responses were severely attenuated in this strain regardless of the presence of fa/fa mutation, compared with the parental WKY/Izm strain. Furthermore, in the peritoneal mast cells of both the SHRSP.Z and SHRSP/Izm strains, IgE-mediated activation, such as degranulation and protein tyrosine phosphorylation, was severely impaired whereas no significant differences were found in morphology and number of peritoneal mast cells. Immunoblot analyses revealed that phosphorylation levels of Syk upon IgE-mediated antigen stimulation were significantly decreased and basal expression of linker for activation of T cells (LAT) was down-regulated in peritoneal mast cells of the SHRSP strains. These results suggest that attenuated cutaneous allergic responses in the SHRSP.Z strain might be attributed to impaired FcɛRI-mediated signal transduction in mast cells.