Melatonin Modulates the Antioxidant Defenses and the Expression of Proinflammatory Mediators in Pancreatic Stellate Cells Subjected to Hypoxia

Abstract

Pancreatic stellate cells (PSC) play a major role in the formation of fibrotic tissue in pancreatic tumors. On its side, melatonin is a putative therapeutic agent for pancreatic cancer and inflammation. In this work, the actions of melatonin on PSC subjected to hypoxia were evaluated. Reactive oxygen species (ROS) generation reduced (GSH) and oxidized (GSSG) levels of glutathione, and protein and lipid oxidation were analyzed. The phosphorylation of nuclear factor erythroid 2-related factor (Nrf2), nuclear factor kappa-light-chain-enhancer of activated B cells (NF-kB), and the regulatory protein nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor-alpha (IκBα) was studied. The expression of Nrf2-regulated antioxidant enzymes, superoxide dismutase (SOD) enzymes, cyclooxygenase 2 (COX-2), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were also studied. Total antioxidant capacity (TAC) was assayed. Finally, cell viability was studied. Under hypoxia and in the presence of melatonin generation of ROS was observed. No increases in the oxidation of proteins or lipids were detected. The phosphorylation of Nrf2 and the expression of the antioxidant enzymes catalytic subunit of glutamate-cysteine ligase, catalase, NAD(P)H-quinone oxidoreductase 1, heme oxygenase-1, SOD1, and of SOD2 were augmented. The TAC was increased. Protein kinase C was involved in the effects of melatonin. Melatonin decreased the GSH/GSSG ratio at the highest concentration tested. Cell viability dropped in the presence of melatonin. Finally, melatonin diminished the phosphorylation of NF-kB and the expression of COX-2, IL-6, and TNF-α. Our results indicate that melatonin, at pharmacological concentrations, modulates the red-ox state, viability, and the expression of proinflammatory mediators in PSC subjected to hypoxia.

Melatonin and Related Compounds: Antioxidant and Anti-Inflammatory Actions

“…Curiously, PSCs do not express membrane melatonin receptors, making the mechanism of the action of melatonin on these cells perplexing. Estaras et al examined this mechanism using PSCs prepared in hypoxic conditions and treated with a range of melatonin concentrations [14]. It was demonstrated that melatonin inhibited inflammatory proteins and promoted ROS generation from PSCs in a concentration-dependent manner, decreasing the ratio of reduced-to-oxidized levels of glutathione (GSH/GSSG ratio).…”

Membrane Lipid Derivatives: Roles of Arachidonic Acid and Its Metabolites in Pancreatic Physiology and Pathophysiology

“…Melatonin, the main product of the pineal gland, exhibits several pharmacological properties, including anti-inflammatory effects. In this context, this indolamine reduced the expression of COX-2 though the inhibition of NFκB signaling in pancreatic stellate cells subjected to hypoxia [144]. Melatonin has shown a significant antifibrotic role in the pancreas and some of its effects may be mediated by its anti-inflammatory actions exerted by modulating COX-2 expression.…”

Pancreatic stellate cells: Key players in pancreatic health and diseases (Review)

“…The transcription factor HIF-1α, which is widely present in hypoxic environments, is also closely related to the malignant phenotype of tumors (35,36). Previous studies have revealed that in pancreatic diseases, particularly pancreatitis and pancreatic tumors, hypoxia drives malignant progression, and an important factor is that hypoxia promotes the activation of PSCs and pancreatic fibrosis, which causes the aforementioned results (37,38). When Masamune et al (39) explored the role of hypoxia in PSCs, it was revealed that PSCs were activated by HIF-1α under hypoxic conditions, which promoted their proliferation and migration.…”