If blocking potency of ivabradine is preserved under elevated endotoxin levels in human atrial myocytes

Mechanical interaction between cells – specifically distortion of tensional homeostasis-emerged as an important aspect of breast cancer genesis and progression. We investigated the biophysical characteristics of mechanosensitive ion channels (MSCs) in the malignant MCF-7 breast cancer cell line. MSCs turned out to be the most abundant ion channel species and could be activated by negative pressure at the outer side of the cell membrane in a saturable manner. Assessing single channel conductance (GΛ) for different monovalent cations revealed an increase in the succession: Li+ < Na+ < K+ ≈Rb+ ≈ Cs+. Divalent cations permeated also with the order: Ca2+ < Ba2+. Comparison of biophysical properties enabled us to identify MSCs in MCF-7 as ion channels formed by the Piezo1 protein. Using patch clamp technique no functional MSCs were observed in the benign MCF-10A mammary epithelial cell line. Blocking of MSCs by GsMTx-4 resulted in decreased motility of MCF-7, but not of MCF-10A cells, underscoring a possible role of Piezo1 in invasion and metastatic propagation. The role of Piezo1 in biology and progression of breast cancer is further substantiated by markedly reduced overall survival in patients with increased Piezo1 mRNA levels in the primary tumor.

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“…MCF-7, MCF-10A and HEK-293 cells were cultured as described 17 18 . Medium was changed every 2–3 days.…”

Section: Methodsmentioning

confidence: 99%

Piezo1 forms mechanosensitive ion channels in the human MCF-7 breast cancer cell line

Rezania

Kammerer

et al. 2015

Sci Rep

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“…In addition to these well‐known inflammatory reactions, we and other laboratories have shown previously that LPS can directly interfere with the electrophysiological properties of HCN‐channels . This may explain (at least in part) the disturbance of HR regulation found in severe sepsis mentioned above.…”

Section: Introductionmentioning

confidence: 83%

Direct inhibition, but indirect sensitization of pacemaker activity to sympathetic tone by the interaction of endotoxin with HCN‐channels

Ebelt

Geißler

Ruccius

et al. 2015

Clin Exp Pharma Physio

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In critically ill patients regulation of heart-rate is often severely disturbed. Interaction of bacterial endotoxin (lipopolysaccharide, LPS) with hyperpolarization-activated cyclic nucleotide-gated cation-(HCN)-channels may interfere with heart-rate regulation. This study analyzes the effect of LPS, the HCN-channel blocker ivabradine or Ca(2+) -channel blockers (nifedipine, verapamil) on pacemaking in spontaneously beating neonatal rat cardiomyocytes (CM) in vitro. In vivo, the effect of LPS on the heart-rate of adult CD1-mice with and without autonomic blockade is analyzed telemetrically. LPS (100 ng/mL) and ivabradine (5 μg/mL) reduced the beating-rate of CM by 20.1% and 24.6%, respectively. Coincubation of CM with both, LPS and ivabradine, did not further reduce the beating-rate, indicating interaction of both compounds with HCN-channels, while coincubation with Ca(2+) -channel blockers and LPS caused additive beating-rate reduction. In CD1-mice (containing an active autonomic-nervous-system), injection of LPS (0.4 mg/kg) expectedly resulted in increased heart-rate. However, if the autonomic nervous system was blocked by propranolol and atropine, in line with the in vitro data, LPS induced a significant reduction of heart-rate, which was not additive to ivabradine. The in vivo and in vitro results indicate that LPS interacts with HCN-channels of cardiomyocytes. Thus, LPS indirectly sensitizes HCN-channels for sympathetic activation (tachycardic-effect), and in parallel directly inhibits channel activity (bradycardic-effect). Both effects may contribute to the detrimental effects of septic cardiomyopathy and septic autonomic dysfunction.

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“…HL-1 cells (a murine cardiomyocyte cell line, Sigma-Aldrich, Vienna, Austria) were cultured in fibronectin (0.5% [w/v])/gelatin (0.02% [w/v]) coated flasks and maintained in Claycomb medium (Sigma-Aldrich) ( Claycomb et al, 1998 ) containing 10% (v/v) fetal bovine serum (FBS, Thermo Fisher Scientific, IL, United States), 0.1 mM norepinephrine, 2 mM L-glutamine, 100 IU/ml penicillin and 100 μg/ml streptomycin (Sigma-Aldrich), and kept at 37°C under 5% CO 2 , as previously described ( Scheruebel et al, 2014 ).…”

Section: Methodsmentioning

confidence: 99%

Saxagliptin but Not Sitagliptin Inhibits CaMKII and PKC via DPP9 Inhibition in Cardiomyocytes

et al. 2018

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Some oral anti-hyperglycemic drugs, including gliptins that inhibit dipeptidyl peptidase 4 (DPP4), have been linked to the increased risk of heart failure (HF) in type-2 diabetic patients. While the cardiovascular safety trial, TECOS, revealed no link between sitagliptin and the risk of HF, a substantial 27% increase in the hospitalization for HF was observed in type-2 diabetic patients treated with saxagliptin within the SAVOR-TIMI 53 trial. A previous in vitro study revealed that saxagliptin impairs the Ca2+/calmodulin-dependent protein kinase II (CaMKII)-phospholamban (PLB)-sarcoplasmic reticulum Ca2+-ATPase 2a axis and protein kinase C (PKC) activity in cardiomyocytes leading to impaired cardiac contractility and electrophysiological function. However, the link between saxagliptin and its target proteins (CaMKII and PKC) remains to be explored. Since DPP8 and DPP9 (but not DPP4) are expressed by cardiomyocytes and saxagliptin is internalized by cardiomyocytes, we investigated whether DPP8/9 contribute to saxagliptin-mediated inhibition of CaMKII and PKC activity. Structural analysis revealed that the DPP4-saxagliptin interaction motif (S630, Y547) for the cyanopyrrolidine group is conserved in DPP8 (S755, Y669) and DPP9 (S730, Y644). Conversely, F357 that facilitates binding of the anchor lock domain of sitagliptin in the S2 extensive subsite of DPP4 is not conserved in DPP8/9. In parallel, unlike saxagliptin, sitagliptin did not affect phosphorylation of CaMKII/PLB or activity of PKC in HL-1 cardiomyocytes. These findings were recapitulated by pharmacological inhibition (TC-E-5007, a DPP8/9 antagonist) and knock-down of DPP9 (but not DPP8). In primary mouse ventricular cardiomyocytes, saxagliptin (but not sitagliptin) impaired Ca2+ transient relaxation and prolonged action potential duration (APD). These results suggest that saxagliptin-DPP9 interaction impairs the CaMKII-PLB and PKC signaling in cardiomyocytes. We reveal a novel and potential role of DPP9 in cardiac signaling. The interaction of saxagliptin with DPP9 may represent an underlying mechanism for the link between saxagliptin and HF. Elucidation of saxagliptin-DPP9 interaction and downstream events may foster a better understanding of the role of gliptins as modulators of cardiac signaling.

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If blocking potency of ivabradine is preserved under elevated endotoxin levels in human atrial myocytes

Cited by 22 publications

References 58 publications

Piezo1 forms mechanosensitive ion channels in the human MCF-7 breast cancer cell line

Piezo1 forms mechanosensitive ion channels in the human MCF-7 breast cancer cell line

Direct inhibition, but indirect sensitization of pacemaker activity to sympathetic tone by the interaction of endotoxin with HCN‐channels

Saxagliptin but Not Sitagliptin Inhibits CaMKII and PKC via DPP9 Inhibition in Cardiomyocytes

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