Expression of glutaredoxin (thioltransferase) in the rat ovary during the oestrous cycle and postnatal development

Abstract

Glutaredoxins (Grxs) are low-molecular-weight proteins which participate in redox events in association with glutathione (GSH) and are involved in a variety of cellular processes. It is known that oxidative stress plays important physiological roles within the ovary. In the present study, we have prepared specific antibodies against rat Grx and have used them to localize the protein in the ovaries of rats during postnatal development and during the oestrous cycle, by immunohistochemical methods. We have also performed a quantitative analysis of Grx by ELISA and Western blotting in homogenates of whole ovaries of cycling and pseudopregnant rats. We have found a prominent presence of Grx in the oocytes and in corpora lutea (CL) during developmental and oestrous cycle changes. Grx was absent from the oocytes in the first days of postnatal life when marked oocyte degeneration takes place, but its presence was very conspicuous in the cytoplasm of oocytes in healthy and attretic follicles in rats from 10 days of age onward, independently of the day of oestrous cycle. Follicular cells were negative. Grx immunostaining in the CL was strong in infiltrating macrophages and in a population of steroidogenic cells that survived the apoptotic burst in regressing CL and in CL remnants, but was faint or absent in young CL of the current cycle and in CL during pseudopregnancy. Grx content and oxidoreductase activity in whole ovaries increased significantly during the phase transition from proestrous to oestrous along the cycle. These results support a role of Grx in the maintenance of functional oocytes and in luteal cells surviving the regression process, probably as a consequence of the demonstrated deglutathionylating function of this protein in an antioxidant and antiapoptotic context.

Reactive oxygen and nitrogen species in normal physiological processes

“…The ROS (O 2 − ˙, H 2 O 2 and lipid peroxides) are present in the female reproductive system. They are periodically formed within the follicle as physiological by‐products of steroid synthesis in each menstrual cycle during ovulation, and in the luteal phase (Gonzalez‐Fernandez et al. 2005).…”

“…Some studies indicate the prominent role of the GSH‐Grx in this protection (Sawai et al. 1997, Gonzalez‐Fernandez et al. 2005).…”

“…The ROS (O 2 ) ·, H 2 O 2 and lipid peroxides) are present in the female reproductive system. They are periodically formed within the follicle as physiological by-products of steroid synthesis in each menstrual cycle during ovulation, and in the luteal phase (Gonzalez-Fernandez et al 2005). They can also originate from macrophages and neutrophils as these cells are present in high numbers in the ovaries during ovulation (this event is, in certain aspects, similar to inflammation).…”

“…The redox homeostasis is secured by a complex system of antioxidants the production of which changes cyclically in the endometrium (Agarwal et al 2006). Some studies indicate the prominent role of the GSH-Grx in this protection (Sawai et al 1997, Gonzalez-Fernandez et al 2005. Glutathione peroxidase seems to regulate the levels of hydroperoxides inside the follicle (Paszkowski et al 1995).…”

Postnatal exposure to chromium through mother’s milk accelerates follicular atresia in F1 offspring through increased oxidative stress and depletion of antioxidant enzymes

“…GLRX binds to apoptosis signal-regulating kinase and prevents the onset of apoptosis [69]. Degenerating oocytes showed a significant decrease or absence of GLRX expression [70]. Moreover, cells overexpressing GLRX are more resistant to cadmium-induced apoptosis [71].…”