Pancreatic stellate cells exhibit adaptation to oxidative stress evoked by hypoxia

Abstract

Background information. Pancreatic stellate cells play a key role in the fibrosis that develops in diseases such as pancreatic cancer. In the growing tumour, a hypoxia condition develops under which cancer cells are able to proliferate. The growth of fibrotic tissue contributes to hypoxia. In this study, the effect of hypoxia (1% O 2) on pancreatic stellate cells physiology was investigated. Changes in intracellular free-Ca 2+ concentration, mitochondrial free-Ca 2+ concentration and mitochondrial membrane potential were studied by fluorescence techniques. The status of enzymes responsible for the cellular oxidative state was analyzed by quantitative reverse transcriptionpolymerase chain reaction, high-performance liquid chromatography, spectrophotometric and fluorimetric methods and by Western blotting analysis. Cell viability and proliferation were studied by crystal violet test, 5-bromo-2deoxyuridine cell proliferation test and Western blotting analysis. Finally, cell migration was studied employing the wound healing assay. Results. Hypoxia induced an increase in intracellular and mitochondrial free-Ca 2+ concentration, whereas mitochondrial membrane potential was decreased. An increase in mitochondrial reactive oxygen species production was observed. Additionally, an increase in the oxidation of proteins and lipids was detected. Moreover, cellular total antioxidant capacity was decreased. Increases in the expression of superoxide dismutase 1 and 2 were observed and superoxide dismutase activity was augmented. Hypoxia evoked a decrease in the oxidized/reduced glutathione ratio. An increase in the phosphorylation of nuclear factor erythroid 2-related factor and in expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1 and heme oxygenase-1 were detected. The expression of cyclin A was decreased, whereas expression of cyclin D and the content of 5-bromo-2-deoxyuridine were increased. This was accompanied by an increase in cell viability. The phosphorylation state of c-Jun NH 2-terminal kinase was increased, whereas that of p44/42 and p38 was decreased. Finally, cells subjected to hypoxia maintained migration ability. Conclusions and Significance. Hypoxia creates pro-oxidant conditions in pancreatic stellate cells to which cells adapt and leads to increased viability and proliferation.

Targeting hypoxic tumor microenvironment in pancreatic cancer

“…However, mitochondrial ROS increase slightly, and no increase in cytosolic ROS is detected. Consistent with these observations, PSCs exhibit activation of major antioxidant mechanisms to counteract the hypoxia-triggered pro-oxidative status, including augmented SOD1/2 activity, increased phosphorylation of transcription factor Nrf2, and overexpressed Nrf2-regulated antioxidant enzymes, such as the catalytic subunit of glutamate-cysteine ligase (GClc), catalase, NAD(P)H quinone oxidoreductase 1 (NQO1), and heme oxygenase-1 (HO-1) [92]. In PDAC cells, hypoxia also upregulates the expression of HO-1, which reduces intracellular ROS levels and provides a survival advantage to cancer cells [93].…”

Melatonin Induces Apoptosis and Modulates Cyclin Expression and MAPK Phosphorylation in Pancreatic Stellate Cells Subjected to Hypoxia

“…We have previously shown that PSCs proliferate under hypoxia [ 6 ]. Moreover, we have shown that melatonin decreases the viability of pancreatic cancer cells [ 22 ] and also of PSCs incubated under normoxia [ 19 , 20 , 21 ].…”

“…In relation to these observations, we have recently shown that PSCs proliferate under hypoxia. Similar to tumor cells, PSCs undergo certain changes that allow them to survive under a low oxygen supply [ 6 ]. Interestingly, the maneuvers developed by PSCs under low oxygen availability could contribute to fibrosis in the tumor and aid the growth of malignant cells [ 7 ].…”

The Role of Stellate Cells in Pancreatic Ductal Adenocarcinoma: Targeting Perspectives

“…Moreover, the high secretion of ECM also led to the increased interstitial pressure in PDAC ( 83 ), which contributed to vascular atrophy, hypoxia, insufficient blood flow, and depletion of nutrients ( 84 ). Two recent studies indicated that under hypoxic condition, PSCs exhibited adaptation to oxidative stress and kept continuously activated, increased migration ability, and released elevated molecules like MMP-2, MMP-3 that influenced the ECM remodeling ( 85 , 86 ). The role of PSCs in remodeling TME mechanically can be further evidenced by the studies using all-trans retinoic acid (ATRA) and tamoxifen.…”