NCBI Summary:
This gene encodes a member of the NOX-family of enzymes that functions as the catalytic subunit the NADPH oxidase complex. The encoded protein is localized to non-phagocytic cells where it acts as an oxygen sensor and catalyzes the reduction of molecular oxygen to various reactive oxygen species (ROS). The ROS generated by this protein have been implicated in numerous biological functions including signal transduction, cell differentiation and tumor cell growth. A pseudogene has been identified on the other arm of chromosome 11. Alternative splicing results in multiple transcript variants.[provided by RefSeq, Jan 2009]
General function
Enzyme
Comment
Cellular localization
Comment
Ovarian function
Comment
The NADPH oxidase 4 is a major source of hydrogen peroxide in human granulosa-lutein and granulosa tumor cells. Buck T et al. (2019) H2O2 is a reactive oxygen species (ROS), which can diffuse away from its site of generation and may act as a cell-to-cell signaling factor. The mechanisms responsible for the generation of H2O2 in human ovarian follicles and possible signaling role(s) of H2O2 are not well known. We identified a source of H2O2, the enzyme NADPH oxidase (NOX) 4, in isolated differentiated, in-vitro fertilisation-derived human granulosa-lutein cells (GCs), in proliferating human granulosa tumour cells (KGN), as well as in situ in cells of growing ovarian follicles. H2O2 was readily detected in the supernatant of cultured GCs and KGN cells. H2O2 levels were significantly lowered by the NOX4 blocker GKT137831, indicating a pronounced contribution of NOX4 to overall H2O2 generation by these cells. We provide evidence that extracellular H2O2 is taken up by GCs, which is facilitated by aquaporins (peroxiporins). We thus conclude that GC-derived H2O2 might act as autocrine/paracrine factor. Addition of H2O2 increased MAPK-phosphorylation in GCs. Moreover, reducing H2O2 production with GKT137831 slowed proliferation of KGN cells. Our results pinpoint NOX4 and H2O2 as physiological players in the regulation of GC functions.//////////////////
Expression regulated by
Growth Factors/ cytokines, PDGF
Comment
Pigment-Epithelium derived Factor (PEDF) and the human ovary: A role in the generation of ROS in granulosa cells. Kampfer C 2013 et al.
AIMS
Pigment Epithelium Derived Factor (PEDF) is a multifunctional factor, which was found in mouse ovary and in human ovarian follicular fluid (FF). Its ovarian functions include anti-angiogenic actions. This study aimed to explore other PEDF-actions and the sites of PEDF expression in the human ovary.
MATERIALS AND METHODS
We used paraffin-embedded human ovarian sections for PEDF-immunohistochemistry and IVF-derived human granulosa cells (GCs) for RT-PCR, Western blotting and functional studies, including measurement of cell viability (ATP-assay), apoptosis (caspase-assay) and reactive oxygen species (ROS).
KEY FINDINGS
Immunohistochemistry revealed PEDF in the cytoplasm of GCs of avascular follicles from the preantral to the antral stage and in FF. PEDF was also found in luteinized GCs of the highly vascularized corpus luteum, a result not in line with a sole anti-angiogenic action. Like GCs in vivo, cultured human luteinizing GCs express PEDF. They also responded to exogenous recombinant PEDF. In low concentrations PEDF did not affect cell viability but caused generation ROS. ROS-induction by PEDF was a concentration-dependent process and may be due to the activity of NADPH oxidase (NOX) type 4 and/or 5, which as we found are expressed by GCs. An antioxidant and apocynin, which inhibits NOX, blocked ROS generation. High levels of exogenous recombinant PEDF induced apoptosis of GCs, which was prevented by antioxidants, implying involvement of ROS.
SIGNIFICANCE
PEDF is emerging as an ovarian factor, which has unexpected ROS-augmenting activities in the human ovary. It may be involved in ovarian ROS homeostasis and may contribute to oxidative stress.
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