Protein kinase C upregulates intercellular adhesion molecule-1 and leukocyte-endothelium interactions in hyperglycemia via activation of endothelial expressed calpain.
OBJECTIVE
We tested the hypothesis of a role for the calcium-dependent protease calpain in the endothelial dysfunction induced by hyperglycemic activation of protein kinase C (PKC).


RESULTS
Chronic hyperglycemia with insulin deficiency (type 1 diabetes) was induced in rats by streptozotocin. Total PKC and calpain activities, along with activity and expression level of the 2 endothelial-expressed calpains isoforms, μ- and m-calpain, were measured in vascular tissue homogenates by enzymatic assays and Western blot analysis, respectively. Intravital microscopy was used to measure and correlate leukocyte-endothelium interactions with calpain activity in the microcirculation. Expression levels and endothelial localization of the inflammatory adhesion molecule intercellular adhesion molecule-1 were studied by Western blot analysis and immunofluorescence, respectively. The mechanistic role of hyperglycemia alone in the process of PKC-induced calpain activation and actions was also investigated. We found that in the type 1 diabetic vasculature, PKC selectively upregulates the activity of the μ-calpain isoform. Mechanistic studies confirmed a role for hyperglycemia and PKCβ in this process. The functional implications of PKC-induced calpain activation were upregulation of endothelial expressed intercellular adhesion molecule-1 and leukocyte-endothelium interactions.


CONCLUSIONS
Our results uncover the role of μ-calpain in the endothelial dysfunction of PKC. Calpain may represent a novel molecular target for the treatment of PKC-associated diabetic vascular disease.
Department of Physiology and the Cardiovascular Research Center, School of Medicine, Temple University, 3500 N Broad St., Philadelphia, PA 19041, USA.
Amanda R
AR
Smolock
Gourav
G
Mishra
Kunie
K
Eguchi
Satoru
S
Eguchi
Rosario
R
Scalia
D000818:Animals; D002154:Calpain / Q000378:metabolism*; D002450:Cell Communication / Q000502:physiology*; D003921:Diabetes Mellitus, Experimental / Q000378:metabolism / Q000503:physiopathology; D003925:Diabetic Angiopathies / Q000378:metabolism / Q000503:physiopathology; D004195:Disease Models, Animal; D004730:Endothelium, Vascular / Q000166:cytology* / Q000378:metabolism; D006943:Hyperglycemia / Q000378:metabolism / Q000503:physiopathology*; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism*; D007962:Leukocytes / Q000166:cytology*; D008297:Male; D008638:Mesenteric Arteries / Q000378:metabolism; D008833:Microcirculation / Q000502:physiology; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015398:Signal Transduction / Q000502:physiology; D013311:Streptozocin; D015854:Up-Regulation / Q000502:physiology*
D018799:Intercellular Adhesion Molecule-1; D013311:Streptozocin; D011493:Protein Kinase C; D002154:Calpain