Charles C Oh1, Michael Q Nguy2, Dawn C Schwenke2, Raymond Q Migrino2, Kent Thornburg3, Peter Reaven2. 1. Phoenix VA HealthCare System, Phoenix, AZ, United States. Electronic address: charles.oh@va.gov. 2. Phoenix VA HealthCare System, Phoenix, AZ, United States. 3. Oregon Health and Science University, 3181 Sam Jackson Park Rd, Portland, OR 97239, United States.
Abstract
RATIONALE: The mechanisms underlying lipotoxic/diabetic cardiomyopathy remain poorly understood. Saturated fatty acid (SFA) levels, elevated in obesity and type 2 diabetes, induce apoptosis in many cell types including cardiomyocytes. Signaling pathways, including the p38α mitogen-activated kinase (MAPK)-dependent pathway, have been implicated in apoptosis due to a diverse range of insults. OBJECTIVE: We tested the hypothesis that SFA-induced cardiomyocyte apoptosis is dependent on p38α activation. METHODS AND RESULTS: Human adult ventricular cardiomyocytes (AC16 cells) were exposed to high physiological levels of palmitate (PA), a SFA. The apoptotic response was measured using annexin-V by flow cytometry, and the p38α-dependent pathway was evaluated using a p38 inhibitor PD169316, and by p38α small interfering RNA (siRNA) knockdown. PA exposure for 16 h dose-dependently increased apoptosis in AC16 cardiomyocytes (control: 2.6±0.6%, 150 μM PA: 3.5±0.9%, 300 μM PA: 11.5±1.6%, n=4, p<0.01). PA did not change total p38α protein levels, but increased p38α phosphorylation dose-dependently (n=5, p<0.01). PD169316 tended to reduce PA-induced apoptosis (n=4, p=0.05). Specific p38α siRNA markedly reduced the expression of p38α but not p38β (n=3, p<0.0001), and dose-dependently attenuated PA-induced apoptosis (control siRNA: 7.7±1.0%, 300 μM PA: 34.4±5.0%, 300 μM PA+30 pmol siRNA: 23.7±4.4%, 300 μM PA+60 pmol siRNA: 19.7±2.6%, 300 μM PA+120 pmol siRNA: 17.3±2.8%, n=4, p<0.0001). CONCLUSIONS: These results demonstrate that PA induces p38α activation, and reducing p38α expression attenuates PA-induced cardiomyocyte apoptosis. Our results support a potential mechanism by which high plasma SFA levels through p38α activation may lead to the development of lipotoxic/diabetic cardiomyopathy. Published by Elsevier Inc.
RATIONALE: The mechanisms underlying lipotoxic/diabetic cardiomyopathy remain poorly understood. Saturated fatty acid (SFA) levels, elevated in obesity and type 2 diabetes, induce apoptosis in many cell types including cardiomyocytes. Signaling pathways, including the p38α mitogen-activated kinase (MAPK)-dependent pathway, have been implicated in apoptosis due to a diverse range of insults. OBJECTIVE: We tested the hypothesis that SFA-induced cardiomyocyte apoptosis is dependent on p38α activation. METHODS AND RESULTS:Human adult ventricular cardiomyocytes (AC16 cells) were exposed to high physiological levels of palmitate (PA), a SFA. The apoptotic response was measured using annexin-V by flow cytometry, and the p38α-dependent pathway was evaluated using a p38 inhibitor PD169316, and by p38α small interfering RNA (siRNA) knockdown. PA exposure for 16 h dose-dependently increased apoptosis in AC16 cardiomyocytes (control: 2.6±0.6%, 150 μM PA: 3.5±0.9%, 300 μM PA: 11.5±1.6%, n=4, p<0.01). PA did not change total p38α protein levels, but increased p38α phosphorylation dose-dependently (n=5, p<0.01). PD169316 tended to reduce PA-induced apoptosis (n=4, p=0.05). Specific p38α siRNA markedly reduced the expression of p38α but not p38β (n=3, p<0.0001), and dose-dependently attenuated PA-induced apoptosis (control siRNA: 7.7±1.0%, 300 μM PA: 34.4±5.0%, 300 μM PA+30 pmol siRNA: 23.7±4.4%, 300 μM PA+60 pmol siRNA: 19.7±2.6%, 300 μM PA+120 pmol siRNA: 17.3±2.8%, n=4, p<0.0001). CONCLUSIONS: These results demonstrate that PA induces p38α activation, and reducing p38α expression attenuates PA-induced cardiomyocyte apoptosis. Our results support a potential mechanism by which high plasma SFA levels through p38α activation may lead to the development of lipotoxic/diabetic cardiomyopathy. Published by Elsevier Inc.
Authors: Colleen A Lopez; Heba Hussain A A Al-Siddiqi; Ujang Purnama; Sonia Iftekhar; Arne A N Bruyneel; Matthew Kerr; Rabia Nazir; Maria da Luz Sousa Fialho; Sophia Malandraki-Miller; Rita Alonaizan; Fatemeh Kermani; Lisa C Heather; Jan Czernuszka; Carolyn A Carr Journal: Sci Rep Date: 2021-04-08 Impact factor: 4.379