Follicular Fluid Concentrations of Metabolic Stressors in Normal, Obese, Metabolic Stressed and Emaciated Ewes

N-acetylcysteine modulates non-esterified fatty acid-induced pyroptosis and inflammation in granulosa cells

In the perinatal period of dairy cows, negative energy balance (NEB) is likely to occur, which increases the level of non-esterified fatty acids (NEFA) in the follicular fluid, hinders the proliferation of granulosa cells (GCs), and thus endangers the development of oocytes and the fecundity of dairy cows. We found that there were oxidative stress and inflammatory response in the serum of cows with perinatal ketosis. Whether the oxidative stress induced by NEFA is involved in the pyroptosis and inflammation of GCs remains unclear. After NEFA treatment, the expression of NLRP3 and caspase-1 and the release of inflammatory cytokines IL-1β were increased in a dose-dependent manner, indicating that NEFA may contribute to pyroptosis. Besides, NEFA stimulation induced oxidative stress, resulting in the phosphorylation of NF-κB, and increased the production of interleukin (IL)-6 and nitric oxide (NO), indicating that NEFA may induce inflammation in GCs. However, the NEFA-mediated effects were observably reversed when the GCs were pre-treated with antioxidant and radical scavenger, N-acetylcysteine (NAC). Taken together, our results reveal that NEFA can induce pyroptosis and inflammation through NLRP3 inflammasome and TLR4/NF-κB pathway, respectively, and NAC can alleviate these conditions.

Non-Esterified Fatty Acid-Induced Reactive Oxygen Species Mediated Granulosa Cells Apoptosis Is Regulated by Nrf2/p53 Signaling Pathway

Negative energy balance (NEB) during the perinatal period can affect dairy cow follicular development and reduce the fecundity. Non-esterified fatty acid (NEFA) concentration is elevated during NEB, and is known to be toxic for multiple cell types. In the ovary, NEB increased NEFA, and may influences follicular growth and development. However, the effect and mechanism of NEFA on granulosa cells (GCs) in vitro remains unknown. In this study, we found that NEFA dose-dependently induced apoptosis in primary cultured granulosa cells. Mechanistically, our data showed that NEFA significantly increased reactive oxygen species (ROS) levels, resulting in the activation of endoplasmic reticulum stress (ERS) and eventually cell apoptosis in GCs. Moreover, NEFA also increased the phosphorylation levels of ERK1/2 and p38MAPK pathways, upregulated the expression of p53 and potentially promoted its translocation to the nuclear, thus transcriptionally activated Bax, a downstream gene of this pathway. NEFA also promoted nuclear factor E2 (Nrf2) expression and its level in the nuclear. To elucidate the mechanism of NEFA action, N-acetyl-l-cysteine (NAC), a ROS scavenger was used to verify the role of ROS in NEFA induced apoptosis of GCs. NAC pretreatment reversed the NEFA-induced ERS-related protein and apoptosis-related protein levels. Meanwhile, NAC pretreatment also blocked the phosphorylation of ERK1/2 and p38 induced by NEFA, and the nucleation of Nrf2 and p53, suggesting that ROS plays a crucial role in regulating the NEFA-induced apoptosis of GCs. Together, these findings provide an improved understanding of the mechanisms underlying GCs apoptosis, which could potentially be useful for improving ovarian function.

Nutritional and metabolic stressors on ovine oocyte development and granulosa cell functions in vitro

The present study was undertaken to study the effect of ammonia, urea, non-esterified fatty acid (NEFA), and β-hydroxybutyric acid (β-OHB) on oocyte development and granulosa cell (GC) growth parameter of ovine (Ovis aries). Ovine oocytes were matured in vitro in the presence of different concentration of ammonia, urea, NEFA, and β-OHB for 24 h, in vitro inseminated and evaluated for cleavage and blastocyst yield. Same concentrations of ammonia, urea, NEFA, and β-OHB were examined on growth parameters and hormone secretion activity of granulosa cells in vitro. Real-time reverse transcription polymerase chain reaction was used to evaluate the expression of steroidogenic genes (steroidogenic cytochrome P-450 (CYP11A1, CYP19A1)), cell proliferation-related genes (GDF9, FSHr), and apoptosis-related genes (BCL-2 and BAX). The maturation, cleavage, and blastocyst production rates were significantly lowered in media containing either 200 μM ammonia or 5 mM urea or high combo NEFA or 1 μM β-OHB. Exposure of granulosa cell to 400 μM ammonia or 1 μM β-OHB or very high combo or 6 mM urea significantly decreased all the parameters examined compared to lower levels of all nutritional and metabolic stressors. Elevated concentration of metabolic stressors induced GC apoptosis through the BAX/BCL-2 pathway and reduced the steroidogenic gene messenger RNA (mRNA) expression and cell proliferation gene mRNA expression. These results suggested that the decreased function of GCs may cause ovarian dysfunction and offered an improved understanding of the molecular mechanism responsible for the low fertility in metabolic stressed condition.