The lipid peroxidation product 4-hydroxynonenal contributes to oxidative stress-mediated deterioration of the ageing oocyte

Abstract

An increase in intraovarian reactive oxygen species (ROS) has long been implicated in the decline in oocyte quality associated with maternal ageing. Oxidative stress (OS)-induced lipid peroxidation and the consequent generation of highly electrophilic aldehydes, such as 4-hydroxynonenal (4-HNE), represents a potential mechanism by which ROS can inflict damage in the ageing oocyte. In this study, we have established that aged oocytes are vulnerable to damage by 4-HNE resulting from increased cytosolic ROS production within the oocyte itself. Further, we demonstrated that the age-related induction of OS can be recapitulated by exposure of germinal vesicle (GV) oocytes to exogenous H2O2. Such treatments stimulated an increase in 4-HNE generation, which remained elevated during in vitro oocyte maturation to metaphase II. Additionally, exposure of GV oocytes to either H2O2 or 4-HNE resulted in decreased meiotic completion, increased spindle abnormalities, chromosome misalignments and aneuploidy. In seeking to account for these data, we revealed that proteins essential for oocyte health and meiotic development, namely α-, β-, and γ-tubulin are vulnerable to adduction via 4-HNE. Importantly, 4-HNE-tubulin adduction, as well as increased aneuploidy rates, were resolved by co-treatment with the antioxidant penicillamine, demonstrating a possible therapeutic mechanism to improve oocyte quality in older females.

Oxidative damage in naturally aged mouse oocytes is exacerbated by dysregulation of proteasomal activity

“…Perhaps most intriguing was the observation that these phenotypic changes were positively correlated with 4-HNE modification of a subset of vulnerable oocyte proteins, including those of the tubulin family. Moreover, interventions designed to limit 4-HNE bioavailability, and thus reduce tubulin adduction, were able to ameliorate the deleterious effect of oxidative stress on oocyte quality (29). Such findings are in accord with the key role of the microtubule network in supporting faithful meiotic completion, with defects in these cytoskeletal elements associated with elevated rates of oocyte aneuploidy (44,45).…”

“…Despite the pervasive impact of oxidative stress on oocyte quality, the mechanisms by which this insult inflicts such damage are still being actively debated. In this context, recent studies have identified elevated production of lipid aldehydes accompanying the induction of oxidative stress in oocytes and have shown that these highly reactive entities contribute, in part, to the loss of oocyte quality (28,29). This situation mirrors the response of somatic cells in which the induction of oxidative stress precipitates the peroxidation and breakdown of membrane lipids (including glycolipids, phospholipids, and cholesterol) (30 -32), with -6 polyunsaturated fatty acids such as arachidonic and linoleic acids being particularly susceptible (33,34).…”

“…The contribution of reactive aldehydes to the deterioration of the aging oocyte has been alluded to on the basis of elevated 4-HNE levels detected in the ovarian tissue of naturally aged mice (11,43). Our own research has uncovered a similar increase in 4-HNE accumulation in pre-ovulatory germinal vesicle (GV) and post-ovulatory metaphase II (MII)-staged oocytes of aged mice, when compared with oocytes recovered from young mice (29). Additionally, we were able to establish a correlative link between elevated levels of 4-HNE and an increase in age-associated phenotypes, with in vitro 4-HNE challenge inducing pronounced spindle defects and aneuploidy in the oocytes of young mice.…”

Melatonin promotes human oocyte maturation and early embryo development by enhancing clathrin‐mediated endocytosis

“…To demonstrate if melatonin regulated CME by its antioxidative mechanism, H 2 O 2 was supplemented in the IVM culture solution at a final concentration of 35 μM, as referenced from murine oocytes . GV‐stage oocytes were divided into three IVM groups—the control group, 35 μM H 2 O 2 alone (the H group), or 35 μM H 2 O 2 along with 10 −11 M melatonin (the H + M group).…”

“…To demonstrate if melatonin regulated CME by its antioxidative mechanism, H 2 O 2 was supplemented in the IVM culture solution at a final concentration of 35 μM, as referenced from murine oocytes. 33…”