Mast cell chymase limits the cardiac efficacy of Ang I-converting enzyme inhibitor therapy in rodents

Department of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
The Journal of clinical investigation (Impact Factor: 13.22). 03/2010; 120(4):1229-39. DOI: 10.1172/JCI39345
Source: PubMed

ABSTRACT Ang I-converting enzyme (ACE) inhibitors are widely believed to suppress the deleterious cardiac effects of Ang II by inhibiting locally generated Ang II. However, the recent demonstration that chymase, an Ang II-forming enzyme stored in mast cell granules, is present in the heart has added uncertainty to this view. As discussed here, using microdialysis probes tethered to the heart of conscious mice, we have shown that chronic ACE inhibitor treatment did not suppress Ang II levels in the LV interstitial fluid (ISF) despite marked inhibition of ACE. However, chronic ACE inhibition caused a marked bradykinin/B2 receptor-mediated increase in LV ISF chymase activity that was not observed in mast cell-deficient KitW/KitW-v mice. In chronic ACE inhibitor-treated mast cell-sufficient littermates, chymase inhibition decreased LV ISF Ang II levels substantially, indicating the importance of mast cell chymase in regulating cardiac Ang II levels. Chymase-dependent processing of other regulatory peptides also promotes inflammation and tissue remodeling. We found that combined chymase and ACE inhibition, relative to ACE inhibition alone, improved LV function, decreased adverse cardiac remodeling, and improved survival after myocardial infarction in hamsters. These results suggest that chymase inhibitors could be a useful addition to ACE inhibitor therapy in the treatment of heart failure.

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Available from: Ahsan Husain, Sep 27, 2015
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    • "Microdialysis probes were positioned in the LV (Figure 1a and b): three probes in I/R and two in non I/R zones (arrowheads) for ISF infusion of chymase-selective substrate [Pro11, DAla12] Ang I (2.5 µM) and angiotensin-converting enzyme (ACE)-selective substrate [Pro10] Ang I (0.5 µM) as previously described [3]. The probe effluents were collected for chymase and ACE activity analysis at 5 time points: 50 min and 100 minutes after probe insertion and before the left anterior descending artery (LAD) ligation, during the 60 min of the LAD ligation (160 min time point), and 50 and 100 min during reperfusion (210 and 260 time points, Figure 1c–f). "
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    ABSTRACT: Cardiac ischemia and reperfusion (I/R) injury occurs because the acute increase in oxidative/inflammatory stress during reperfusion culminates in the death of cardiomyocytes. Currently, there is no drug utilized clinically that attenuates I/R injury in patients. Previous studies have demonstrated degranulation of mast cell contents into the interstitium after I/R. Using a dog model of I/R, we tested the role of chymase, a mast cell protease, in cardiomyocyte injury using a specific oral chymase inhibitor (CI). 15 adult mongrel dogs had left anterior descending artery occlusion for 60 min and reperfusion for 100 minutes. 9 dogs received vehicle and 6 were pretreated with a specific CI. In vivo cardiac microdialysis demonstrated a 3-fold increase in interstitial fluid chymase activity in I/R region that was significantly decreased by CI. CI pretreatment significantly attenuated loss of laminin, focal adhesion complex disruption, and release of troponin I into the circulation. Microarray analysis identified an I/R induced 17-fold increase in nuclear receptor subfamily 4A1 (NR4A1) and significantly decreased by CI. NR4A1 normally resides in the nucleus but can induce cell death on migration to the cytoplasm. I/R caused significant increase in NR4A1 protein expression and cytoplasmic translocation, and mitochondrial degradation, which were decreased by CI. Immunohistochemistry also revealed a high concentration of chymase within cardiomyocytes after I/R. In vitro, chymase added to culture HL-1 cardiomyocytes entered the cytoplasm and nucleus in a dynamin-dependent fashion, and promoted cytoplasmic translocation of NR4A1 protein. shRNA knockdown of NR4A1 on pre-treatment of HL-1 cells with CI significantly decreased chymase-induced cell death and mitochondrial damage. These results suggest that the beneficial effects of an orally active CI during I/R are mediated in the cardiac interstitium as well as within the cardiomyocyte due to a heretofore-unrecognized chymase entry into cardiomyocytes.
    PLoS ONE 04/2014; 9(4):e94732. DOI:10.1371/journal.pone.0094732 · 3.23 Impact Factor
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    • "Chymase activity in the heart and skin was measured as described previously 9. In the heart, mRNA levels of human chymase, mouse chymase (MMCP-4), angiotensin converting enzyme (ACE) and AT1a receptor were also measured as described previously 10. "
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    ABSTRACT: We examined the effects of overexpressed human chymase on survival and activity in lipopolysaccharide (LPS)-treated mice. Human chymase transgenic (Tg) and wild-type C57BL/6 (WT) mice were treated with LPS (0.03, 0.1 and 0.3 mg/day; intraperitoneal) for 2 weeks. Treatment with 0.03 mg LPS did not affect survival in either WT or Tg mice. WT mice were not affected by 0.1 mg/day of LPS, whereas 25% of Tg mice died. Survival of mice treated with 0.3 mg/day of LPS was 87.5% and 0% in WT and Tg, respectively. LPS-induced increases in chymase activity in the heart and skin were significantly greater in Tg than WT mice. These data suggest a possible contribution of human chymase activation to LPS-induced mortality.
    International journal of medical sciences 01/2014; 11(3):222-5. DOI:10.7150/ijms.7382 · 2.00 Impact Factor
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    • "Bradykinin is a well known chemotactic stimulus for many types of inflammatory cells [29]. We have demonstrated BK2 receptors on mast cells and that BK2 receptor blockade prevents ACE inhibitor-mediated increases in LV ISF chymase activity in the normal mouse [17] and mast cell accumulation in the 5 day ACF rat [5]. To connect ISF bradykinin with mast cell and collagen loss, the current study demonstrates that cardiac interstitial bradykinin infusion increases mast cell numbers and causes collagen loss, both of which are prevented by BK2 receptor blockade. "
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    ABSTRACT: The clinical problem of a "pure volume overload" as in isolated mitral or aortic regurgitation currently has no documented medical therapy that attenuates collagen loss and the resultant left ventricular (LV) dilatation and failure. Here, we identify a potential mechanism related to upregulation of the kallikrein-kinin system in the volume overload of aortocaval fistula (ACF) in the rat. LV interstitial fluid (ISF) collection, hemodynamics, and echocardiography were performed in age-matched shams and 4 and 15 wk ACF rats. ACF rats had LV dilatation and a 2-fold increase in LV end-diastolic pressure, along with increases in LV ISF bradykinin, myocardial kallikrein and bradykinin type-2 receptor (BK(2)R) mRNA expression. Mast cell numbers were increased and interstitial collagen was decreased at 4 and 15 wk ACF, despite increases in LV ACE and chymase activities. Treatment with the kallikrein inhibitor aprotinin preserved interstitial collagen, prevented the increase in mast cells, and improved LV systolic function at 4 wk ACF. To establish a cause and effect between ISF bradykinin and mast cell-mediated collagen loss, direct LV interstitial bradykinin infusion in vivo for 24 hrs produced a 2-fold increase in mast cell numbers and a 30% decrease in interstitial collagen, which were prevented by BK(2)R antagonist. To further connect myocardial stretch with cellular kallikrein-kinin system upregulation, 24 hrs cyclic stretch of adult cardiomyocytes and fibroblasts produced increased kallikrein, BK(2)R mRNA expressions, bradykinin protein and gelatinase activity, which were all decreased by the kallikrein inhibitor-aprotinin. A pure volume overload is associated with upregulation of the kallikrein-kinin system and ISF bradykinin, which mediates mast cell infiltration, extracellular matrix loss, and LV dysfunction-all of which are improved by kallikrein inhibition. The current investigation provides important new insights into future potential medical therapies for the volume overload of aortic and mitral regurgitation.
    PLoS ONE 06/2012; 7(6):e40110. DOI:10.1371/journal.pone.0040110 · 3.23 Impact Factor
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