UNDERSTANDING THE EFFECTS OF CANCER RADIATION THERAPY ON ENDOTHELIAL CELL DYSFUNCTION – THE ROLE OF NFκB/JNK

Abstract

Cardiovascular disease is the principal cause of mortality in developed societies. Studies have identified a correlation between radiotherapy for cancer and atherosclerosis in later life1. Endothelial cell dysfunction is a defining feature of atherosclerosis initiation. This study aims to investigate the effect of radiation on endothelial cell intracellular signalling networks, including the Nuclear Factor-kappaB (NFκB) and c-Jun N-terminal kinase (JNK) pathways. Human umbilical vein endothelial cells (HUVECs) were exposed to 10 Gy X-rays using an X-RAD 225 biological irradiator. Western blotting was used to detect NFκB and JNK pathway activation in whole cell lysates using anti-phospho-p65, anti-IκBα, anti-tp100/p52 and anti-phospho-JNK antibodies and in nuclear extracts using anti-NFκB-p65 antibodies. An in vitro kinase assay utilising 32P enabled detection of JNK-mediated phosphorylation of c-Jun. X-irradiation induced p65 phosphorylation (fold increase at 2hrs; 2.5±0.42, p<0.05, n=3) and IκBα degradation (fold at 8hrs; 0.29±0.05, n=3) in HUVECs, markers of canonical NFκB pathway activation. Surprisingly, nuclear p65 levels were not increased suggesting absence of p65 nuclear translocation. Interestingly, tp100/p52 levels were unaltered after irradiation implying that the non-canonical pathway is not activated. X-irradiation also triggered JNK phosphorylation (fold increase at 4hrs; 2.73±0.66, n=3) and JNK kinase activity, observed as increased phosphorylated c-Jun expression 4 hours after irradiation. Thus stress-associated signalling pathways (canonical NFκB and JNK pathways) are activated in irradiated endothelial cells. Further investigations will confirm the cellular events that link radiotherapy and cardiovascular disease. Project supported by a British Heart Founation PhD studentship (no.Fs/13/25/30155).

Celecoxib Alleviates Radiation-Induced Brain Injury in Rats by Maintaining the Integrity of Blood-Brain Barrier

“…Radiation stimulates the formation of ceramide, thereby reducing the stability of the mitochondrial membrane and promoting apoptosis through the JNK pathway. 25,26 JNK can be activated by various stimuli, controls the intracellular and extracellular stress reactions of cells, which is called the stress-activated protein kinase (SAPK), and it plays a very important role in regulating cell apoptosis. 39,40 In the present study, irradiation increased the p-JNK and cleaved caspase-3 expression in HBMECs, while celecoxib partially reversed these increases.…”

“…On the other hand, radiation can stimulate the formation of ceramide, thereby reducing the stability of the mitochondrial membrane and promoting apoptosis through the c-Jun N-terminal kinase (JNK) pathway. 25,26 JNK can be activated by a variety of stimuli, such as oxidative damage, DNA and endoplasmic reticulum damage. 27 The activated form of JNK is phosphorylated JNK (p-JNK), which translocates to the cytoplasm, activating caspase-3 and the mitochondrial apoptotic pathway.…”

“…27 The activated form of JNK is phosphorylated JNK (p-JNK), which translocates to the cytoplasm, activating caspase-3 and the mitochondrial apoptotic pathway. 25,26 However, whether the radiation-induced brain injury involves JNK-mediated apoptosis signaling remains unclear.…”