Date of Award

1-1-2008

Embargo Period

11-20-2024

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Molecular and Cellular Biology and Pathobiology

College

College of Graduate Studies

First Advisor

Ayad Jaffa

Second Advisor

Louis Lutrell

Third Advisor

Monika Gooz

Fourth Advisor

Maria Trojanowska

Fifth Advisor

Craig Beeson

Abstract

Despite the clear association between diabetes and atherosclerotic vascular disease, the factors and mechanisms underlying the association between the two diseases are not well understood. Our preliminary studies, based on data obtained from the national Diabetes Control and Complication Trial/Epidemiology of Diabetes and Complications (DCCT/EDIC) cohort of type 1 diabetes subjects, suggest that diabetic atherosclerosis is linked to defects in the Kallikrein-Kinin System (KKS). Our research also found that apoliporotein E (ApoE) knockout mice, which have marked increase in total plasma cholesterol levels and a higher number of atherosclerotic lesions compared to wild type mice, have markedly higher plasma prekallikrein (PK) levels compared to wild type mice. Furthermore, we showed that the levels of plasma PK rise upon the induction of diabetes in both wild type and ApoE knockout mice. Since vascular smooth muscle cell dysfunction, namely hyperplasia and apoptosis, in the tunica media of major arteries is a hallmark of atherosclerosis, we investigated the hypothesis that plasma Prekallikrein and Kallikrein induced a cascade of molecular events in rat and human primary aortic smooth muscle cells (R- and H-AoSMC). We found that PK activates members of the mitogen-activated protein kinase (MAPK) family, specifically extracellular signal-regulated kinase (ERK) and c-Jun N-terminal kinases (JNK). The phosphorylation of ERK and JNK was markedly increased with increasing concentrations of PK in R-AoSMCs. Moreover, we showed that PK-induced phosphorylation of MAPK family elements occurs through the transactivation of Epithelial Growth Factor Receptor (EGFR). We therefore explored the possibility of ADAM (A Disintegrin And Metalloprotease) involvement in plasma PK-induced MAPK activation and found that ADAM-17 was specifically activated by plasma Kallikrein. In fact, we found that the activation of ADAM-17 by plasma Kallikrein induces the shedding of the ADAM substrates TNF-�� and Amphiregulin. Moreover the phosphorylation of both ERK and EGFR was significantly blunted by the inhibition of the MMP inhibitor GM6001. When investigating the identity of the receptor(s) initiating this cascade, we found that two members of the protease activated receptor (PAR) family, PAR-1 and PAR-2, were activated and internalized by plasma Kallikrein in HEK-293 cells over-expressing these receptors. Furthermore, we found that specific PAR-1 and PAR-2 inhibitor peptides blunted the activation of ADAM-17 by plasma Kallikrein. These novel findings bring us closer to elucidating a novel pathway that contributes to the pathophysiology of vascular disease in Type 1 Diabetes.

Rights

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