Angiotensin II induces secretion of plasminogen activator inhibitor 1 and a tissue metalloprotease inhibitor-related protein from rat brain astrocytes.

Abstract

The present study investigates angiotensin (Ang) II effects on secretory protein synthesis in brain astrocytes cultured from neonatal and 21-day-old rats. Ang IIinduced changes in the de novo synthesis of [35S]methioninelabeled secretory proteins were visualized using two-dimensional NaDodSO4/PAGE. Astrocytes from 21-day-old rat brain possess specific high-affinity receptors for Ang II. These cells express two Ang 11-induced secretory proteins with M, 55,000 (AISP-55K) and Mr 30,000 (AISP-30K), which were time-and dose-dependent (EC50, 1 nM). [Sar', 11e8]Ang II (where Sar is sarcosine) inhibited Ang II-induced secretion of AISP-55K but not AISP-30K. N-terminal amino acid sequencing indicates that AISP-55K is identical to rat plasmiogen activator inhibitor 1, whereas AISP-30K exhibits 72-81% identity to three closely related proteins: human tissue inhibitor of metalloproteases, a rat phorbol ester-induced protein, and the murine growth-responsive protein 16C8. Immunofluorescent staining with rat plasminogen activator inhibitor 1 antibody was induced in the majority of cells in culture after Ang II treatment of astrocytes from 21-day-old rat brains. Absence of this response to Ang II in astrocytes from neonatal rat brain provides evidence that this action of Ang II on astrocytes is developmentally regulated.The octapeptide angiotensin (Ang) II has in recent years been implicated in the central control of blood pressure. Evidence in support of this view includes observations that centrally injected Ang II causes profound increases in blood pressure, that all components of the renin-Ang system are found in the brain (1-3), and that increased levels of Ang II and Ang II receptors are seen in brains of spontaneously hypertensive rats (4, 5). Cardiovascular effects of Ang II have been attributed to the modulation of sympathetic activity of neurons in relevant cardioregulatory centers of the brain (1, 2). In vitro studies with neurons in primary culture have further shown that occupation of neuronal Ang II receptors modulates both catecholamine synthesis and reuptake (6, 7). Increased levels of Ang II receptors have been found in neurons cultured from spontaneously hypertensive rats (8).In addition to a neuromodulatory role of Ang II, evidence exists for a distinct Ang II system in central nervous system (CNS) astrocytes. Receptors for Ang II (9), angiotensinogen mRNA (10,11), and Ang I and Ang 11 (12,13) have been demonstrated in cultures of astrocytes, and immunoreactive Ang I, Ang II, and angiotensinogen mRNA have been observed in astrocytes in vivo (14-16). Although the presence of an Ang II system in astrocytes is well documented, little is currently understood of its role in normal brain physiology.Recent studies have indicated that intercellular communication between astrocytes and other cells of the brain may be mediated by proteins secreted from astrocytes (17). Cells of astrocytic origin are thought to secrete several neurotrophic factors (18) and the neurotrophic properties of epidermal growth factor ...

Bradykinin B2 receptor knockout mice are protected from thrombosis by increased nitric oxide and prostacyclin

“…Usually, elevations of AngII are associated with vasoconstriction and increased thrombosis risk due to elevated PAI-1 and tissue factor. [40][41][42] However, the degree of elevation of plasma PAI-1 is not to the extent that one sees with endothelial-cell injury, suggesting that the slight increase is not clinically significant. [40][41][42] If AngII interacts with an overexpressed AT 2 R, then it could result in delay in thrombosis since it could elevate prostacyclin and nitrate levels.…”

Angiotensin II as a cardiovascular risk factor

“…49 Angiotensin II was reported to induce secretion of PAI-1 from cultured cells in vitro. 50 In vivo infusions of A II in both hypertensive patients and normotensive control subjects were found to induce a rapid dose-dependent increase in circulating levels of PAI-1. 51 The finding that A II enhances endothelial synthesis and secretion of PAI-1 suggests an additional mechanism by which activation of the renin-angiotensin system may increase the risk of coronary events.…”

A mutant, noninhibitory plasminogen activator inhibitor type 1 decreases matrix accumulation in experimental glomerulonephritis

“…31). Angiotensin II upregulates PAI-1 expression by mechanisms both independent of and dependent on TGF-β (32)(33)(34)(35)(36). Therapeutic strategies aimed at reduction of angiotensin II or TGF-β also reduce PAI-1 overexpression (3,23,30,(37)(38)(39).…”