Early Predictive Biomarkers for Hypertension Using Human Fetal Astrocytes

Abstract

Hypertension is a major risk factor for cardiovascular and cerebrovascular diseases, causing high numbers of deaths and /or disabilities worldwide. Previous studies have reported numerous biomolecules, such as, triglycerides and fibrinogen as biomarkers of hypertension (HTN), but none of these biomolecules could be considered as ‘true’ predictive biomarkers as they were produced after the establishment of HTN. Therefore, there is an urgent need for identifying and monitoring molecules that are linked to early pre-HTN stages, that is, prior to the onset of HTN. Astrocytes are the most abundant cells in the nervous system and through their long processes, astrocytes can communicate with both neuronal and non-neuronal cells such as endothelial cells lining blood vessels. Thus, any biochemical changes in astrocytes will affect both blood vessels and neurons. We are using human fetal astrocytes (HFAs) to investigate the molecules which may possibly act as early predictive biomarkers for hypertension. Astrocytic processes are mostly supported by the intermediate filaments, an example is the glial fibrillary acidic protein (GFAP) which is a type III intermediate filament. Elevated GFAP levels are being considered as a marker of astroglial injury, indicating the conversion of non-reactive (A2) into reactive (A1) astrocytes. Our initial immunohistochemistry studies using anti-GFAP antibodies on astrocytes from spontaneous hypertensive rats (SHRs) and their normal counter parts (WKY) rats showed a similar profile to that of reactive (A1) and non-reactive (A2) HFAs, respectively. Numerous studies point to a significant role of calcium ion channel proteins in hypertension, and calcium channel blockers such as Amlodipine (Norvasc) Diltiazem (Cardizem) are commonly used as antihypertensive drugs. By using liquid chromatography–tandem mass spectrometry (LC–MS/MS) we observed that reactive (A1) astrocytes, contain more calcium-activated proteins such as calpain, calpastatin, cathepsin and mitogen activated protein kinase (MAPK) as compare to normal (A2) HFAs, suggesting their possible link to the future onset of HTN. Hence these proteins could be considered as potential early predictive biomarkers of HTN.