Honors Theses
Date of Award
2014
Document Type
Undergraduate Thesis
Department
Pharmaceutics and Drug Delivery
First Advisor
Ziaeddin Shariat-Madar
Relational Format
Dissertation/Thesis
Abstract
Cellular senescence is a slow, biological process of aging that involves the accumulation of various changes to the internal environment of a cell, most notably the buildup of acidic B-galactosidase. These changes, both structural and molecular in nature, disable metabolism of many cellular processes and eventually induce apoptosis. As cells divide, the ends of chromosomes, telomeres, slowly shorten. Once telomere shortening reaches critical levels, those chromosomes may no longer replicate properly, leading to cellular process complication and apoptosis. Telomerase is a reverse transcriptase that adds nucleotides to telomeres, elongating them and successfully delaying endothelial cell senescence. Endothelial cells serve an irreplaceably important part in our body as the thin layer of cells that line the furthest interior surface of our blood vessels. They are the site of reception between molecules circulating in the blood. These endothelial cells are the sites of many physiological processes; especially blood clotting, vasoconstriction, vasodilation, and inflammation. The biochemical processes of the proteins in the kinin-kallikrein system drive the responses of inflammation, blood pressure regulation, and blood coagulation via many mediators. One of the most important products, bradykinin, is generated from human plasma when prolylcarboxypeptidase (PRCP) converts prekallikrein (PK), bound to high molecular weight kininogen (HK) on the negatively charged surface of human endothelial cells. This bradykinin drives vasodilation as it produces nitric oxide and prostacyclin. These vasodilative properties increase oxygen delivery and promote further angiogenesis and delay cellular death. Keeping this in mind, PRCP, as an indirect vasodilator, and basic fibroblast growth factor (FGF-2), as a promoter for angiogenesis, should both promote cell survival and delay endothelial cell senescence. As a control, B-actin and glyceraldehyde-3-phosphate dehyedrogenase (GAPDH) were used; B-actin is prevalent in all cells throughout their life as an integral cytoskeletal actin, and GAPDH is an important step in the process of glycolysis, the breakdown of glucose for energy and carbon molecules. In our results, we found that the activity of HK-PK peaked at Passage 18, and to support that, we found that the converting enzyme, PRCP, shared the same peak in activity. Our results were supported when we found that nitric oxide (NO), a downstream product of the PRCP-catalyzed HK-PK system, and endothelial nitric oxide synthase (eNOS), responsible for another method of NO production shared the same peak in activity as PRCP. Human telomerase reverse transcriptase (hTERT) mRNA concentration was examined alongside B-galactosidase (B-gal) cell staining, a universal marker for cellular senescence. Our results show that the decline in hTERT precedes the onset of endothelial cell senescence, and that the buildup of B-gal is a sufficient indicator for the arrival of endothelial senescence. This study has emphasized the role that HK and PK play in cellular health and the delay of endothelial cellular senescence. We propose that nitric oxide and FGF-2 delay endothelial cell senescence by slowing the age-related degradation of telomerase.
Recommended Citation
Boullard, Nicholas, "Cardiovascular Protective Agents and their Biochemical Role in Endothelial Cell Senescence" (2014). Honors Theses. 735.
https://egrove.olemiss.edu/hon_thesis/735
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