Catherine Pasquier Memorial Award Lecture (shared): Critical role of oxidative and nitrosative stress in pathophysiology: Inflammation, cell injury and cancer

Abstract

The presence of chronic inflammation associated with sustained cell death and proliferation turnover is a potential tissue environment for cancer development. In this situation, oxidative and nitrosative stress are the major driving force playing a key role either as a preventing or inducer/promoter of tumorigenesis. During inflammatory response, activated macrophages release a great variety of protease that degraded extracellular matrix, inflammatory mediators that plays a relevant role in chemotaxis and cell signaling, as well as oxygen and nitrogen reactive species (ROS and RNS, respectively) actively involved in cell defense through oxidation of essential biological molecules such as DNA, carbohydrates, proteins and lipids. Iron-loosely bound plays a relevant role in promoting oxidative-dependent reactions leading to cell damage. In this sense, we have shown that locally iron overload induced an accumulation of neutrophils with increased NADPH-derived superoxide anion generation in exudates from rats submitted to carrageenan-induced granuloma model. The increase of lipid peroxidation products was associated with the presence of iron-loosely bound, reduction of antioxidant status in inflammatory exudates and blood, as well as induction of hepatic acute phase response. A similar pro-inflammatory and oxidant reaction was observed by intraperitoneal iron-dextran administration in animals with Mycobacterium butyricum-induced adjuvant arthritis. The administration of a diet devoid of polyunsaturated fatty acids reduced the substrate for lipid peroxidation, and consequently a decrease of conjugated diennes and thiobarbituric acid-reactive substances in plasma and hepatic microsomal fraction were observed in animals with adjuvant arthritis. The acute phase response induced by different inflammatory mediators in hepatocytes has been studied in detail. The induction of carrageenan-induced granuloma drastically reduced the expression of drug metabolizing enzymes (DME) (CYP3A1, CYP4A, CYP2B1, CYP2D and CYP2E1) and their related-activities in rat livers. Cytokines (IL-1α, IL-6 and TNF-α) exerted a specific timely-dependent regulation of DME expression (CYP1A1, CYP1A2 and CYP3A4) and secretion of acute phase reactants (albumin, ferritin, fibrinogen and ceruloplasmin) in cultured primary human hepatocytes. Although TNF-α induces acute phase response and liver injury in different experimental settings such as sepsis, we have also shown that TNF-α-dependent induction of nitric oxide synthase type II (NOS-2) hepatic expression during PGE1 pre-administration drastically reduces D-galactosamine (D-GalN)-induced liver injury in rats. The pre-administration of PGE1 also reduced cell death induced by D-GalN in primary culture of human and rat hepatocytes. However, the cytoprotective properties of PGE1 do not involve a reduction of D-GalN-induced ROS production. Nitric oxide (NO) has demonstrated to exert pro- and anti-apoptotic properties according to local concentration, target cell, as well as the presence of other ROS such as superoxide anion generating high reactive peroxynitrite. We have observed that moderate increase of PGE1-dependent NO prevented further potent NF-kB-dependent NOS-2 expression and apoptosis induced by D-GalN in cultured rat hepatocytes. However, the administration of PGE1 at advanced stages of cell injury or high doses of NO donor increased cell death in D-GalN-treated human and rat hepatocytes. The induction of apoptosis by D-GalN was associated with ROS production, mitochondrial dysfunction and post-translation (S-nitrosylation and Tyrosine nitration) modifications of proteins involved in unfolded protein response, enzymatic antioxidants, cell metabolism and death in cultured human hepatocytes. In consequences, the administration of antioxidants such as N-acetylcysteine, Q10 and MnTBAB reduced ROS generation, mitochondrial dysfunction and apoptosis induced by D-GalN and glycochenodeoxycholate (GCDCA) in cultured human hepatocytes. The cytoprotective properties of α-tocopherol appears to mostly related to gene regulation (NOS-2, PPAR-α and carnitine palmitoyl transferase) rather than to its antioxidant activity in D-GalN-induced cell death in hepatocytes. The reduction of cell death by α-tocopherol was also associated with reduction of CYP7A1, Na+-taurocholate co-transporting polypeptide (NTCP), and heme oxygenase-1 expression, as well as increased NOS-2 expression and NO production in GCDCA-treated hepatocytes. α-Tocopherol and NO donors increased NTCP cysteine S-nitrosylation and Tyrosine nitration, and reduced Taurocholic acid uptake in hepatocytes. The pro-apoptotic properties of high NO donor concentration have been successfully applied to exert antitumoral activity in liver cancer cells. In this sense, the administration of NO donor or NOS-3 overexpression induces p53-dependent cell death receptor expression and apoptosis in hepatoma cell lines. The first generation adenovirus specifically designed to induce NOS-3 overexpression in liver cancer cells induced oxidative and nitrosative stress, DNA damage, p53, cell death receptors expression and their S-nitrosylation, and apoptosis that was correlated to a reduction of cell proliferation and growth of tumors orthotopically implanted in fibrotic livers. The S-nitrosylation of cell death receptors (TNF-α, CD95 and TRAIL-R1) plays a critical role on the shift from extrinsic to intrinsic cell death pathways during antitumoral molecular therapy (Sorafenib Tosylate) in liver cancer cells. In conclusion, new data are emerging that elucidate the extraordinary role that plays ROS- and RNS-dependent posttranslational target modifications in regulating intracellular cell signaling.