Reactive oxygen species alter autocrine and paracrine signaling

Abstract

Cytochrome P450 (P450) 3A4 (CYP3A4) is the most abundant P450 protein in human liver and intestine, and is highly inducible by a variety of drugs and other compounds. The P450 catalytic cycle is known to uncouple and release reactive oxygen species (ROS), but the effects of ROS from P450 and other enzymes in the endoplasmic reticulum has been poorly studied from the perspective of effects on cell biology. In this study, we express low levels of CYP3A4 in HepG2 cells, a human hepatocarcinoma cell line, and examine effects on intracellular levels of ROS and on the secretion of a variety of growth factors that are important in extracellular communication. Using the redox sensitive dye, RedoxSensor Red, we demonstrate that CYP3A4 expression increases levels of ROS in viable cells. A custom ELISA microarray platform was employed to demonstrate that expression of CYP3A4 increased secretion of amphiregulin, intracellular adhesion molecule 1, matrix metalloprotease 2, platelet-derived growth factor (PDGF) and vascular endothelial growth factor but suppressed secretion of CD14. The antioxidant, N-acetylcysteine, suppressed all P450-dependent changes in protein secretion except for CD14. Quantitative RT-PCR demonstrated that changes in protein secretion were consistently associated with corresponding changes in gene expression. Inhibition of the NF-κB pathway blocked P450 effects on PDGF secretion. CYP3A4 expression also altered protein secretion in human mammary epithelial cells and C10 mouse lung cells. Overall, these results suggest that increased ROS production in the endoplasmic reticulum alters the secretion of proteins that have key roles in paracrine and autocrine signaling.

Casein hydrolysate diet controls intestinal T cell activation, free radical production and microbial colonisation in NOD mice

“…RONS production is associated with proinflammatory cytokine, antibacterial lectin and Th17 responses RONS production can exert autocrine and paracrine effects [31] on homeostasis and signalling of many cell types, thus promoting local inflammatory reactions and immune reactivity. Accordingly, Il1, Il6, Il18, Il23 and Il17 levels were all high in the ileum of NOD mice fed normal chow (Fig.…”

Reactive Oxygen Species Induce Procalcitonin Expression in Trigeminal Ganglia Glia

“…We next considered signaling mechanisms that could act only on cells intimately close to their origin. Reactive oxygen species (ROS) are unstable signaling molecules, and generally act in an autocrine or paracrine manner 37 . We tested whether ROS in cultured ganglia were responsible for the increase in CT mRNA by adding the antioxidant tempol to the culture media.…”

Oxidatively modified proteins as plasma biomarkers in breast cancer

“…We also analyzed a number of secreted proteins reported by others to be produced by normal or cancerous breast tissue. Finally, we evaluated a selection of proteins that we identified as being secreted at higher levels in human mammary cells in response to modest changes in intracellular ROS or to epidermal-growth-factor signaling [8, 9, 22, 23]. …”

“…Reactive oxygen species (ROS), which are responsible for oxidative protein modifications, regulate important processes in epithelial cancers such as activation of MAPK/Erk and PI3K/Akt pathways [7]. In cultured human mammary epithelial cells, we found that both of these signaling pathways and intracellular ROS regulate the secretion of a variety of autocrine factors, paracrine factors and matrix metalloproteases [8, 9]. Based on these studies, we hypothesized that alterations in cell signaling and oxidative stress associated with breast cancer would not only results in increased levels of certain proteins that are secreted into blood but that these proteins would have unusually high oxidation rates.…”