TY - JOUR
T1 - Activation of PKG and Akt is required for cardioprotection by ramelteon-induced preconditioning and is located upstream of mKCa-channels
AU - Torregroza, Carolin
AU - Jalajel, Osameh
AU - Raupach, Annika
AU - Feige, Katharina
AU - Bunte, Sebastian
AU - Heinen, André
AU - Mathes, Alexander
AU - Hollmann, Markus W.
AU - Huhn, Ragnar
AU - Stroethoff, Martin
PY - 2020/4/1
Y1 - 2020/4/1
N2 - Ramelteon is a Melatonin 1 (MT1)-and Melatonin 2 (MT2)-receptor agonist conferring cardioprotection by pharmacologic preconditioning. While activation ofmitochondrial calcium-sensitive potassium (mKCa)-channels is involved in this protective mechanism, the specific upstream signaling pathway of Ramelteon-induced cardioprotection is unknown. In the present study, we (1) investigated whether Ramelteon-induced cardioprotection involves activation of protein kinase G (PKG) and/or protein kinase B (Akt) and (2) determined the precise sequence of PKGandAkt in the signal transduction pathway ofRamelteon-inducedpreconditioning. Hearts ofmalewistar ratswere randomizedandplaced on a Langendorff system, perfused with Krebs-Henseleit buffer at a constant pressure of 80 mmHg. All heartswere subjected to 33min of global ischemia and 60min of reperfusion. Before ischemia, hearts were perfused with Ramelteon (Ram) with or without the PKG or Akt inhibitor KT5823 and MK2206, respectively (KT5823 + Ram, KT5823,MK2206 + Ram,MK2206). To determine the precise signaling sequence, subsequent experiments were conducted with the guanylate cyclase activator BAY60-2770 and the mKCa-channel activator NS1619. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Ramelteon-induced infarct size reduction was completely blocked by KT5823 (p = 0.0012) andMK2206 (p = 0.0005). MK2206 with Ramelteon combined with BAY60-2770 reduced infarct size significantly (p = 0.0014) indicating that PKG activation takes place after Akt. Ramelteon and KT5823 (p = 0.0063) or MK2206 (p = 0.006) respectively combined with NS1619 also significantly reduced infarct size, indicating that PKG and Akt are located upstream of mKCa-channels. This study shows for the first time that Ramelteon-induced preconditioning (1) involves activation of PKG and Akt; (2) PKG is located downstream of Akt and (3) both enzymes are located upstream of mKCa-channels in the signal transduction pathway.
AB - Ramelteon is a Melatonin 1 (MT1)-and Melatonin 2 (MT2)-receptor agonist conferring cardioprotection by pharmacologic preconditioning. While activation ofmitochondrial calcium-sensitive potassium (mKCa)-channels is involved in this protective mechanism, the specific upstream signaling pathway of Ramelteon-induced cardioprotection is unknown. In the present study, we (1) investigated whether Ramelteon-induced cardioprotection involves activation of protein kinase G (PKG) and/or protein kinase B (Akt) and (2) determined the precise sequence of PKGandAkt in the signal transduction pathway ofRamelteon-inducedpreconditioning. Hearts ofmalewistar ratswere randomizedandplaced on a Langendorff system, perfused with Krebs-Henseleit buffer at a constant pressure of 80 mmHg. All heartswere subjected to 33min of global ischemia and 60min of reperfusion. Before ischemia, hearts were perfused with Ramelteon (Ram) with or without the PKG or Akt inhibitor KT5823 and MK2206, respectively (KT5823 + Ram, KT5823,MK2206 + Ram,MK2206). To determine the precise signaling sequence, subsequent experiments were conducted with the guanylate cyclase activator BAY60-2770 and the mKCa-channel activator NS1619. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Ramelteon-induced infarct size reduction was completely blocked by KT5823 (p = 0.0012) andMK2206 (p = 0.0005). MK2206 with Ramelteon combined with BAY60-2770 reduced infarct size significantly (p = 0.0014) indicating that PKG activation takes place after Akt. Ramelteon and KT5823 (p = 0.0063) or MK2206 (p = 0.006) respectively combined with NS1619 also significantly reduced infarct size, indicating that PKG and Akt are located upstream of mKCa-channels. This study shows for the first time that Ramelteon-induced preconditioning (1) involves activation of PKG and Akt; (2) PKG is located downstream of Akt and (3) both enzymes are located upstream of mKCa-channels in the signal transduction pathway.
KW - Akt
KW - Myocardial infarction
KW - PKG
KW - Preconditioning
KW - Ramelteon
UR - http://www.scopus.com/inward/record.url?scp=85083262226&partnerID=8YFLogxK
U2 - https://doi.org/10.3390/ijms21072585
DO - https://doi.org/10.3390/ijms21072585
M3 - Article
C2 - 32276406
SN - 1661-6596
VL - 21
JO - International journal of molecular sciences
JF - International journal of molecular sciences
IS - 7
M1 - 2585
ER -