Estrogen Modulates the Differential Expression of Cardiac Myocyte Chymase Isoforms and Diastolic Function

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Background and objectiveCardiac angiotensin II (Ang II) is involved in the diastolic dysfunction in postmenopausal women. Chymases, a family of serine proteases with chymotryptic activity, play a significant role in cardiac Ang II formation from its substrate Ang‐(1–12) in both human and rodent models. While human tissue expresses only the α‐form of chymase, α‐ and β‐forms exist in rodents. Five of the ten rat mast cell proteases (rMCP‐1–5) display chymase activity, and rats express predominantly the β‐chymase isoforms. This study was designed to assess the differences in enzymatic activity among these rMCP isoforms in Ang II formation, particularly in the cardiomyocyte (CM), and the effects of estrogen status on MCP gene expression and activities in female rat models.Methods and resultsUsing conventional polymerase chain reaction (PCR) (Fig. 1A), real‐time PCR (Fig. 1B) and DNA sequencing (Fig. 1C), we demonstrated that MCP‐1, MCP‐2, MCP‐4, and MCP‐5 mRNAs are expressed in the CM of both spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto rats (WKY). While rMCP‐1 and rMCP‐5 gene transcripts were higher than other isoforms in both rat strains, WKY CM exhibits higher levels of rMCP‐1 and rMCP‐5 mRNAs compared to the SHR CM (Fig. 2). Ovariectomy (OVX) increased the expression of rMCP‐1 and rMCP‐5 mRNAs in WKY. In SHR, OVX was associated with a blunted increase in rMCP‐1 mRNA compared to OVX normotensive WKY. Chymase activity, measured by HPLC as Ang II formation from Ang‐(1–12), significantly correlated with rMCP‐1 and rMCP‐5 mRNA expression in both rat strains. Both rMCP‐1 and rMCP‐5 mRNA expressions were positively correlated with progressive diastolic dysfunction (increasing the ratio of early mitral inflow velocity‐to‐early mitral annular velocity, E/e′) and increases in left ventricular internal diameter end diastole.ConclusionThese data show rMCP‐1 and rMCP‐5 as the Ang II forming chymase isoforms participating in diastolic dysfunction due to ovariectomy in rodents.Support or Funding InformationThis work was funded by grants from the National Heart Lung and Blood Institute (CMF and LG) P01‐HL051952 and the National Institute on Aging (LG) AG033727 of the National Institute of Health.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.