Akt Kinase Mediates the Prosurvival Effect of Smoking Compounds in Pancreatic Ductal Cells

Abstract

Objectives Cigarette smoking is a major risk factor for pancreatic cancer (PaCa). However, the mechanisms of smoking-induced PaCa remain unknown. Here we investigated the effect of smoking compounds on cell death pathways in pancreatic ductal cells, precursors of PaCa. Methods Human pancreatic ductal cells (HPDE6-c7) were cultured with cigarette smoking extract (CSE) or smoking compound 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK). Apoptosis and autophagy were assessed by DNA fragmentation and immunofluorescence, respectively. Results Exposure to CSE or NNK decreased DNA fragmentation and up-regulated BclxL. Akt kinase was activated by smoking compounds through ROS-dependent mechanism. Specifically, Akt activation was prevented by inhibition of NAD(P)H oxidase. Molecular or pharmacologic inhibitions of Akt prevented anti-apoptotic effect of smoking compounds. Smoking compounds stimulated rapid (1h) and transient activation of AMPK and formation of autophagic vacuoles indicating stimulation of autophagy. Repeated exposure to CSE/NNK (48h or longer) abolished the early activation of autophagic markers. Inhibition of Akt prevented the anti-autophagic effect of long exposure to smoking compounds indicating that smoking-induced late activation of Akt prevents autophagy. Conclusions long exposure of pancreatic ductal cells to smoking compounds inhibited apoptosis and autophagy. The results revealed a central role for Akt kinase in mediating key pro-carcinogenic effects of smoking compounds.

Alcohol and Cigarette Smoke Components Activate Human Pancreatic Stellate Cells: Implications for the Progression of Chronic Pancreatitis

“…The mechanisms mediating the effects of smoking compounds AE EtOH on PSC functions are not known, but could include the (i) induction of nAChR expression in the cells as observed in the present study; (ii) increased oxidant stressdue to increased production of ROS in PSCs upon exposure to EtOH, as has been reported previously (Apte et al, 2000) and the ROS known to be present in cigarette smoke (Pryor, 1997); and (iii) activation of signaling pathways such as MAPK, PI3 kinase, and protein kinase C (each of which have been reported to be activated in PSCs in response to EtOH) (Park et al, 2012;Russell et al, 1980).…”

“…EtOH at 10 mM corresponds to blood alcohol levels seen with social drinking such as that typically seen with 2 standard drinks (Apte et al, 2000). The concentrations chosen for CSE and nicotine fall within the range of nicotine levels found in the plasma of light to heavy smokers with a light smoker, consuming 5 cigarettes per day, and a heavy smoker, consuming 25 cigarettes or a pack a day (Park et al, 2012;Russell et al, 1980). The range of NNK concentrations reflect levels of NNK found in human pancreatic juice from light to heavy smokers (Alexandre et al, 2012).…”

Smoking and Pancreatic Disease

“…We showed that NNK and cigarette smoke extract stimulate proliferation and inhibit apoptosis of normal pancreatic ductal cells through a mechanism that involves Akt and AMP kinases [ 50 ]. In pancreatic cancer cells nicotine stimulates proliferation and invasion of the AsPC1 pancreatic cancer cell line.…”

The Neuro-Psychological Axis of Pancreatic Cancer as a Novel Target for Intervention

“…Moreover, it was shown that NNK caused dose-and time-dependent increases in the proliferation and migration of PDAC cells BXPC-3 and MIAPACA-2 accompanied by increases in FAK and ERK activation and inhibited by the beta-blocker propranolol or the cruciferous vegetable flavone Apigenin [62]. In addition, immortalized pancreatic duct epithelial cells exposed in vitro to cigarette smoke or NNK responded with AKT-dependent reduction in apoptosis while autophagy was stimulated [63]. The modulation of signaling proteins and transcription factors in response to nicotine in the cited publications were frequently interpreted as effects immediately downstream of nAChRs.…”