Inhibition of protein kinase R protects against palmitic acid–induced inflammation, oxidative stress, and apoptosis through the JNK/NF‐kB/NLRP3 pathway in cultured H9C2 cardiomyocytes

Abstract

Background and Purpose: Double-stranded RNA-dependent protein kinase (PKR) is a critical regulator of apoptosis, oxidative stress, and inflammation under hyperlipidemic and insulin resistance conditions. Saturated free fatty acids, such as palmitic acid (PA), are known inducers of apoptosis in numerous cell types. However, the underlying molecular mechanism is not fully understood. The aim of the present study was to examine the effect of PA on cultured rat H9C2 cardiac myocytes cells and to investigate the PKR mediated harmful effects of PA in vitro in cultured cardiomyocytes.Experimental Approach: PKR expression was determined by immunofluorescence and immunoblotting. Oxidative stress and apoptosis were determined by flow cytometry and assay kits. The expression of different gene markers of apoptosis, oxidative stress, and inflammation were measured by Western blot analysis and reverse transcription polymerase chain reaction.Key Results: PKR expression, reactive oxygen species levels as well as apoptosis were increased in PA-treated cultured H9C2 cardiomyocytes. The harmful effects of PA were attenuated by a selective PKR inhibitor, C16.Moreover, we observed that upregulation of c-Jun N-terminal kinase (JNK), nuclear factor-kB (NF-kB) and NACHT, LRR and PYD domains-containing protein 3 (NLRP3) pathways is associated with increased expression of interleukin 6 and tumor necrosis factor-α in PA-treated cardiomyocytes and attenuation by a selective PKR inhibitor.Conclusion and Implications: Our study reports, for the first time, that PKRmediated harmful effects of PA in cultured cardiomyocytes via activation of

Synergistic activation of p53 by actinomycin D and nutlin-3a is associated with the upregulation of crucial regulators and effectors of innate immunity

“…We do not know if C16 blocks the activity of kinases that directly phosphorylate p53 on Ser46 and Ser392 or if it blocks the activity of a kinase, which phosphorylates p53 on other amino acid forming a signal for other kinases to modify Ser46 and Ser392. Some studies demonstrated that C16 protects against tissue damage and inflammation, especially in the central nervous system [36,50,51]. In light of our observation that C16 inhibits p53 activation and the fact that p53 is strong inducer of cell death, it must be considered that some cytoprotective activities of this compound are mediated through the inhibition of p53-induced apoptosis or inflammation.…”

Increased Dynamin‐Related Protein 1–Dependent Mitochondrial Fission Contributes to High‐Fat‐Diet‐Induced Cardiac Dysfunction and Insulin Resistance by Elevating Tafazzin in Mouse Hearts

“…For example, exposure of myotubes to palmitic acid leads to attenuated insulin signaling, but exposure to oleic acid does not cause these changes; in addition, co‐incubation of palmitic acid–exposed cells with a lower concentration of oleic acid reverses the effects of the latter . In our in vitro study, we used palmitate to induce insulin resistance, which is a classic insulin resistance model that has been used in many studies . Although we did not determine whether stearate and oleate have the same effects on mitochondria in our experiment, it would be interesting and worth further investigation.…”

<p>The Role of JNk Signaling Pathway in Obesity-Driven Insulin Resistance</p>

“…Inflammation induced by obesity activates JNK and NF-κB signaling pathways in insulin target cells, which plays a key role in insulin resistance. 41,42 At the cellular level, Inflammation induced by obesity may be involved in phosphorylation of the transcription factor NF-κB leading to an increase of the expression of TNFα and IL-6 genes associated with insulin resistance. 43 Inflammatory cytokines may inhibit IRS-1 Tyr phosphorylation in the insulin signaling pathway, also lead to increase in JNK phosphorylation, and decrease Akt phosphorylation.…”