C. Anacker

Interplay between the pro-oxidant and antioxidant systems and proinflammatory cytokine levels, in relation to iron metabolism and the erythron in depression

As there is strong evidence for inflammation and oxidative stress in depression, the aim of this study was to elucidate the relationship between oxidative imbalance and cellular immune response and to ask whether these processes are linked with iron metabolism in depressed patients. Blood was collected from patients diagnosed with recurrent depressive disorder (n=15) and from healthy controls (n=19). Whole-blood reduced glutathione (GSH), erythrocyte superoxide dismutase (SOD-1), glutathione peroxidase (GPx-1), glutathione reductase, malondialdehyde (MDA), and methemoglobin (MetHb) and plasma H₂O₂ were assayed spectrophotometrically. The serum heme oxygenase 1 (HO-1), cytokine, neopterin, and iron statuses were measured by ELISA. DNA damage was analyzed by comet assay. Serum concentrations of ferritin and soluble transferrin receptor were assayed by ELISA. MetHb saturation was analyzed spectrophotometrically in red blood cell hemolysate. The erythron variables were measured using a hematological analyzer. We observed a significant decrease in GPx-1 and SOD-1 activities and decreased levels of HO-1 and GSH in depressed patients compared to controls. Conversely, compared with controls, we found increased concentrations of MDA and H₂O₂ and more DNA damage in depressed patients. Furthermore, the levels of the proinflammatory cytokine interleukin-6 and of neopterin were increased in depressed patients along with decreased hemoglobin and hematocrit. A strong association between antioxidant defense, cytokine levels, and iron homeostasis was also revealed. These findings show that depression is associated with increased oxidative stress, inflammation, and restrictions on the available iron supply for red blood cell production. Furthermore, decreased antioxidant defense correlates with an increased cellular inflammatory response, whereas both concur with erythron and iron status, the latter explained by significant canonical correlations with the set of free radical scavenging enzymes and proinflammatory enzymes. The strong links between immune function, oxidative stress, and iron homeostasis suggest the presence of a self-sustaining multipathway mechanism that may progressively worsen, i.e., throughout accumulation of oxidative damage, producing the functional and structural consequences associated with depression. Hence, identifying viable therapeutic strategies to tackle oxidative stress and accompanying physiological disturbances, including inflammation and anemia, of chronic disease provides more opportunities for the treatment and, ultimately, prevention of depression.

P.4.017 Cortisol decreases hippocampal neurogenesis by regulating the enzyme serum- and glucocorticoid-regulated kinase 1

Chronic stress increases circulating glucocorticoid hormones, which impair hippocampal neurogenesis by activating the glucocorticoid receptor (GR) [1], and thereby potentially contribute to the development of depressive symptoms [2]. However, the molecular mechanisms underlying this effect are unknown. The enzyme, serum-and glucocorticoid-regulated kinase 1 (SGK1) has been shown to mediate some glucocorticoid effects on the brain [3]. We therefore hypothesized that SGK1 may also mediate the effects of glucocorticoids on hippocampal neurogenesis in humans. We treated human hippocampal progenitor cells (HPC03A/07, ReNeuron, UK) with high concentrations of the glucocorticoid, cortisol (100mM), and with the SGK1-inhibitor, GSK650394 (100nM) (Tocris Biosciences). We analysed cell proliferation by 5′-bromodeoxyuridine (BrdU, 10mM) incorporation, and neuronal differentiation by immunocytochemistry for the neuronal marker, microtubule-associated protein-2 (MAP2). GR activation was examined by Western blot using specific antibodies for the GR phosphorylation-sites, S203, S211 and S226. Cortisol decreased BrdU-positive, proliferating cells (by −13±2%; p = 0.03, n = 3), and neuronal differentiation into MAP2positive neurons (by −16±2%; p = 0.04, n = 3). The SGK1inhibitor, GSK650394 (100nM), counteracted the effects of cortisol on proliferation (p = 0.0027, n = 4) and on neuronal differentiation (p = 0.03, n = 3). Moreover, cortisol induced GR phosphorylation at S203 (1.5±0.1 fold; p = 0.01, n = 3), S211 (3.0±0.5 fold; p = 0.004, n = 3) and S226 (1.6±0.2 fold; p = 0.04, n = 3). Cotreatment with GSK650394 (100nM) counteracted the cortisolinduced GR phosphorylation at S203 (p = 0.01, n = 3) and S211 (p = 0.03, n = 3), but not at the S226 phospho-site (p = 0.8, n = 3). In summary, our data identify the kinase, SGK1, as a novel mechanism mediating the effects of cortisol on human hippocampal neurogenesis and GR function.