ROS介导的氧化应激与自噬

自噬是真核细胞所特有的细胞内物质成分被溶酶体降解过程的统称。生命体借此清除细胞内的废物,重建结构从而维持蛋白质代谢平衡及细胞内环境稳定。氧化应激是指体内氧化与抗氧化作用失衡,倾向于氧化,导致中性粒细胞炎性浸润,蛋白酶分泌增加,产生大量活性氧中介物(ROS),而ROS直接参与细胞存活和死亡调节。大量研究表明,氧化应激中产生的ROS在多种条件下都是自噬的重要调节因子,它能诱导自噬发生,而自噬能通过不同的信号通路来缓解氧化应激造成的损伤,从而保护细胞存活。ROS在多种条件下都是自噬的重要调节因子。作者主要对自噬的形成过程、氧化应激诱导自噬产生机制(包括调控mTOR信号通路、丝裂原活化蛋白激酶(MAPK)信号通路机制)及自噬缓解氧化应激的途径(mTOR信号通路、PI3K介导的信号通路和调控p53等)进行综述,以期为畜牧生产中通过调控自噬缓解动物氧化应激的措施提供理论依据。     

ROS介导的氧化应激与自噬

自噬是真核细胞所特有的细胞内物质成分被溶酶体降解过程的统称。生命体借此清除细胞内的废物，重建结构从而维持蛋白质代谢平衡及细胞内环境稳定。氧化应激是指体内氧化与抗氧化作用失衡，倾向于氧化，导致中性粒细胞炎性浸润，蛋白酶分泌增加，产生大量活性氧中介物（ROS），而ROS直接参与细胞存活和死亡调节。大量研究表明，氧化应激中产生的ROS在多种条件下都是自噬的重要调节因子，它能诱导自噬发生，而自噬能通过不同的信号通路来缓解氧化应激造成的损伤，从而保护细胞存活。ROS在多种条件下都是自噬的重要调节因子。作者主要对自噬的形成过程、氧化应激诱导自噬产生机制（包括调控mTOR信号通路、丝裂原活化蛋白激酶（MAPK）信号通路机制）及自噬缓解氧化应激的途径（mTOR信号通路、PI3K介导的信号通路和调控p53等）进行综述，以期为畜牧生产中通过调控自噬缓解动物氧化应激的措施提供理论依据。     

猪卵巢颗粒细胞和黄体细胞凋亡的调控机制研究进展

母猪卵巢皮质上存在大量卵泡，卵泡由原始卵泡向初级卵泡、次级卵泡逐步发育为排卵前的成熟卵泡时，伴随着卵泡闭锁的发生。目前认为颗粒细胞凋亡是导致卵泡闭锁的主要因素，并且已经证实。卵泡成熟后会破裂排卵，如果卵子未受精，则黄体会发生萎缩并退化，形成称作白体的结缔组织，最终被组织吸收。细胞凋亡受到多基因严格控制，随着分子生物学技术的发展，已经证明存在多个信号通路。本文以猪卵巢为模型，综述了卵泡闭锁期间颗粒细胞凋亡和黄体退化过程中黄体细胞凋亡的调控机制，以期为深入研究卵巢细胞凋亡提供理论基础。     

绵羊卵泡发育过程中关键信号通路研究进展

卵泡从原始卵泡发育为成熟卵泡，直至排卵、黄体发育等过程都受到精密的调控，产生大量的优势卵泡是绵羊产多羔及实现快速扩繁的关键因素。研究发现，相关信号通路和转录因子通过影响绵羊卵泡中卵母细胞、颗粒细胞的生长，进而调控卵泡的发育成熟，对这些信号通路进行深入了解，有助于探索卵泡发育的调控机制，早日实现绵羊高效繁育。Notch是卵泡发育过程中发挥重要作用的高度保守信号通路，PI3K/AKT/mTOR信号通路各成员都是广泛存在于细胞内的信号转导分子，在卵泡发育早期发挥了主要作用，还有间隙连接（gap junction，GJ）和跨带突触（transzonal projections，TZPs）等物理连接方式，在细胞间的交流通讯起到重要作用。作者详细介绍了Notch信号通路、PI3K/AKT/mTOR信号通路、间隙连接及跨带突触的结构功能在绵羊卵泡发育中的调控作用，为进一步探明绵羊卵泡发育的调控机制提供参考。     

热休克蛋白在细胞凋亡级联中的调控作用

机体在高温刺激下可诱导合成热应激相关蛋白,这些蛋白主要是热休克蛋白家族成员。热休克蛋白在信息传递、细胞代谢、生长及分化等过程中发挥着关键的调控作用,并在细胞凋亡过程中发挥着重要的调控作用,以最大限度地保护机体。热休克蛋白在线粒体信号通路和死亡受体信号通路的级联反应中通过削弱、阻断凋亡信号,或激活存活信号对凋亡进行负调控,从而减少细胞损伤,促进细胞存活。     

一氧化氮与哺乳动物卵泡发育

一氧化氮作为一种分子物质参与哺乳动物生殖活动,参与卵泡发育周期的各个阶段,如原始卵泡、腔前卵泡、有腔卵泡,排卵和黄体阶段。文章主要围绕卵泡发育的各个阶段,一氧化氮合成酶在卵泡中不同细胞中的定位,一氧化氮与卵母细胞的成熟、排卵及卵泡闭锁方面进行综述。     

自噬对奶牛乳腺发育和功能影响的研究进展

自噬是细胞降解自身受损细胞器和长寿命蛋白的过程,有助于在饥饿、应激等情况下保护细胞存活。奶牛乳腺组织在青春期和妊娠期经历生长发育,在泌乳后期和干奶期进行退化再生,自噬在这2个过程中均发挥重要作用,既可以保护乳腺上皮细胞存活,又可以促使细胞发生程序性死亡。自噬也与机体中许多生理、病理过程相互作用,并受体内外多种因素的影响。本文就自噬的过程、自噬在奶牛乳腺组织生长发育和退化再生过程中发挥的作用及其影响因素进行综述,以期为通过调控自噬改善奶牛生产性能提供理论依据。     

颗粒细胞对卵泡发育的影响

卵泡发育是一个复杂的生理过程,通过间隙连接,颗粒细胞在卵母细胞的生长发育过程中起营养作用,并促进卵母细胞的成熟;颗粒细胞和膜细胞的相互作用是卵泡发育和维持正常功能的重要条件。作为卵泡发育的标志,颗粒细胞的生长分化是原始卵泡启动和生长的关键,并通过受体介导途径调控生长期卵泡的发育及卵泡闭锁,从而在卵泡发育过程中起重要的调控作用。     

MAPK信号通路介导的自噬调控破骨细胞分化的研究进展

破骨细胞具有骨吸收活性,与骨组织稳态密切相关。丝裂原活化蛋白激酶(MAPK)通路是细胞介导胞内外刺激传导的信号通路,参与细胞的增殖、分化、自噬等多种生理过程。MAPK介导的自噬在调控破骨细胞分化中具有重要作用。探究MAPK的三条经典通路(ERK1/2、JNK及p38 MAPK信号通路)介导的自噬与破骨细胞分化之间的关系,对于寻找与破骨细胞相关的骨代谢疾病的新疗法具有重要意义。     

雌激素受体在卵泡发育中作用的研究进展

雌激素受体(ERs)影响动物繁殖性能依赖于雌激素信号通路调控卵泡发育与排卵。文章通过分析ERs的组成和结构的基础、ERs核转录和膜转录体系进行信号传递的机制,比较ERs引起的基因与非基因效应之间的关系,概括了ERs配体在机体生长与发育中的调控作用,重点阐述了ERs在卵泡发育与排卵中的表达与调控机制。     

颗粒细胞凋亡影响家禽卵泡闭锁的研究进展

卵巢是家禽的重要繁殖器官,会产生大量卵泡,而卵泡在生长发育的各个阶段中都可能因为不同因素的调控而发生闭锁,最终导致繁殖性能衰退。颗粒细胞对卵泡的生长发育有重要调控作用,其凋亡会诱导卵泡发生闭锁。诱导颗粒细胞发生凋亡的因素较多,包括激素、细胞因子、氧化应激、线粒体及其他体外因素。颗粒细胞凋亡主要由线粒体途径导致,其涉及到半胱天冬酶（Caspase）家族参与,当线粒体裂解时会释放细胞色素C （Cyt-C）,随后形成凋亡小体激活Caspase-3和Caspase-8,最终激活Caspase-9导致颗粒细胞凋亡;当颗粒细胞发生凋亡,家禽体内卵泡丧失生物功能并且卵泡细胞之间的调控失衡,促使卵泡内卵母细胞和膜细胞凋亡,最终导致卵泡发生闭锁;颗粒细胞在存活状态下所分泌的生长因子、性腺类固醇、细胞因子能减少卵母细胞氧化损伤,防止细胞内活性氧（ROS）水平过高导致的线粒体DNA损伤,从而避免线粒体功能障碍而造成的颗粒细胞凋亡。作者从颗粒细胞凋亡及其影响因素、颗粒细胞凋亡和卵泡闭锁的关系、颗粒细胞凋亡对卵泡闭锁的影响3个方面进行阐述,以期为减少卵泡闭锁、提高家禽繁殖性能提供理论依据。     

The regulation of ovarian granulosa cell death by pro- and anti-apoptotic molecules

In the mammalian ovary, follicular development and atresia are closely regulated by cell death and survival-promoting factors, including hormones (gonadotropins) and intraovarian regulators (gonadal steroids, cytokines, and intracellular proteins). Several hundred thousand primordial follicles are present in the mammalian ovary; however, only a limited number of primordial follicles develop to the preovulatory stage and ovulate. The others, more than 99% of follicles, will be eliminated via a degenerative process known as "atresia". The endocrinological regulatory mechanisms involved in follicular development and atresia have been characterized to a large extent, but the precise temporal and molecular mechanisms involved in the regulation of these events have remained largely unknown. Recent studies suggest that the apoptosis of ovarian granulosa cells plays a major role in follicular atresia. In this review, we provide an overview of development and atresia of follicles, and apoptosis of granulosa cells in mammals.     

Nutritional influences on folliculogenesis

Folliculogenesis is an intricate process that involves the proliferation and differentiation of both somatic and germ cells. This process depends on complex interactions between systemic factors such as both pituitary gonadotrophins and metabolic hormones and/or local factors produced by the ovarian somatic and germ cells, such as the IGF system and TGF-β superfamily members. In domestic ruminants, follicular development begins during foetal life with formation of primordial follicles from the association of germ cells and pre-granulosa cells. After follicular formation, folliculogenesis begins with a primordial follicle progressing into more developed stages (i.e. primary, secondary, pre-antral and antral) in a continuous, progressive process to either ovulation or, as in most cases, to atresia. Even early stages of follicular formation and subsequent development are influenced by both internal (e.g. genotype) and/or external environmental (e.g. nutrition and season) factors. Among these external factors, nutrition is one of the most important affecting reproductive function, and this is the focus of this review, because other reviews in this issue discuss other environmental factors. A number of studies have now shown that nutrition can have both positive and negative effects on follicular growth, oestrous activity, oocyte quality, blastocyst development and pregnancy outcome. Therefore, understanding the intricate processes involved during folliculogenesis and the ways in which factors, such as nutrition, affect them is leading to new opportunities to improve pregnancy rates by influencing follicle development and oocyte quality. This review will focus on follicular development from foetal to adult stages and the influences that nutrition has during some of these developmental stages.     

Expression of Mitochondria‐Associated Genes (PPARGC1A,NRF‐1, BCL‐2 and BAX) in Follicular Development and Atresia of Goat Ovaries

Most follicles undergo atresia during the developmental process. Follicular atresia is predominantly regulated by apoptosis of granulosa cells, but the mechanism underlying apoptosis via the mitochondria‐dependent apoptotic pathway is unclear. We aimed to investigate whether the mitochondria‐associated genes peroxisome proliferator‐activated receptor‐gamma, coactivator1‐alpha (PPARGC1A), nuclear respiratory factor‐1 (NRF‐1), B‐cell CLL/lymphoma 2 (BCL‐2) and BCL2‐associated X protein (BAX) played a role in follicular atresia through this pathway. The four mitochondria‐associated proteins (PGC‐1α, which are encoded by the PPARGC1A gene, NRF‐1, BCL‐2 and BAX) mainly expressed in granulosa cells. The mRNA and protein levels of PPARGC1A/PGC‐1α and NRF‐1 in granulosa cells increased with the follicular development. These results showed that these genes may play a role in the regulation of the follicular development. In addition, compared with healthy follicles, the granulosa cell in atretic follicles had a reduced expression of NRF‐1, increased BAX expression and increased ratio of BAX to BCL‐2 expression. These results suggested that changes of the mitochondria‐associated gene expression patterns in granulosa cells may lead to follicular atresia during goat follicle development.     

家禽卵泡颗粒细胞体外培养方法研究进展

家禽卵巢中颗粒细胞在卵泡发育和闭锁中起着重要作用,包括信号传递、营养供给以及离子平衡等。卵泡颗粒细胞的增殖与分化自身也受到生殖激素和细胞因子的综合调节,其作用机制是当前研究热点。家禽卵泡颗粒细胞的体外培养可作为研究繁殖生理调节的理想细胞模型。本文对家禽卵泡颗粒细胞的体外培养研究现状及颗粒细胞在卵泡生长发育和闭锁中的作用进行简要概述,并总结了原代颗粒细胞体外培养模型的建立方法。     

Follicular growth and atresia in mammalian ovaries: regulation by survival and death of granulosa cells

The mammalian ovary is an extremely dynamic organ in which a large majority of follicles are effectively eliminated throughout their reproductive life. Due to the numerous efforts of researchers, mechanisms regulating follicular growth and atresia in mammalian ovaries have been clarified, not only their systemic regulation by hormones (gonadotropins) but also their intraovarian regulation by gonadal steroids, growth factors, cytokines and intracellular proteins. Granulosa cells in particular have been demonstrated to play a major role in deciding the fate of follicles, serving molecules that are essential for follicular growth and maintenance as well as killing themselves by an apoptotic process that results in follicular atresia. In this review, we discuss the factors that govern follicular growth and atresia, with a special focus on their regulation by granulosa cells. First, ovarian folliculogenesis in adult life is outlined. Then, we explain about the regulation of follicular growth and atresia by granulosa cells, in which hormones, growth factors and cytokines, death ligand-receptor system and B cell lymphoma/leukemia 2 (BCL2) family members (mitochondria-mediated apoptosis) are further discussed.     

Control of ovarian follicles activity in the ewe.

During the ovine estrous cycles, three waves of follicular growth, closely associated with the FSH secretion pattern, were observed. The parameters of these follicular waves and the ability of follicles to produce steroids in vitro were studied in various conditions. In vivo, the follicular events were similar between the breeding season and the anestrus, except for the lack of ovulation; but at the end of the breeding season and in anestrus, the follicles lose a big part of their aromatization ability. In ewes carrying the Booroola fecundity gene or Cambridge fecundity gene, the reduction in follicular atresia seems to be one of the main follicular features implicated in the control of high ovulation rate. In vitro, the most relevant difference is an early acquisition of estrogen production ability of small follicles in Booroola fecundity gene barring ewes. Fluoro-gestone-acetate (FGA) pessaries reduced the number of growing follicles; despite this effect disappearing after the sponge withdrawal, the ovulation rate is significantly reduced. But an equine chorionic gonadotrophin (eCG) treatment restores the ovulation rate (OR) by reducing the atresia rate of pre-ovulatory follicles. In similar conditions, a pretreatment of the ewes with melatonin again reduced the atresia rate of large follicles and resulted in an increased ovulation rate. In vitro, FGA blocked aromatization ability, and melatonin inhibited both androstenedione and estradiol production, but a further treatment with eCG partly restores the steroid secretion. Immunization against androstenedione leads to a higher OR, owning to a reduced atresia of large follicles. Daily growth hormone injections for a hole cycle resulted in an increased follicular population and ovulation rate, while FSH plasma levels decreased and the follicle sensitivity to gonadotrophins was reduced.     

Comparative morphometry and steroidogenic function of antral ovine follicles destined for ovulation or atresia.

An experimental model was established in the ewe allowing one to predict with accuracy an antral follicle that coincidentally would either undergo ovulation (6-8 mm diameter) or atresia (3-4 mm diameter) following synchronization of luteal regression and the onset of the gonadotropin surge. Quantitative morphometric and hormonal criteria were used to make direct comparisons of such follicles collected throughout the preovulatory period. There were progressive alterations in percentages of granulosa cells exhibiting pyknotic nuclei, dispersion of granulosa cells, oocyte maturation, thecal vascular dynamics and extravasation of leukocytes. Nevertheless, no significant variations in temporal patterns were observed between follicular classification. The most notable anatomical distinction between preovulatory and atretogenic follicles was that the former had come into closer contact with the ovarian surface epithelium. The dominant follicle had a higher capacity than the subordinate follicle to produce estradiol before the gonadotropin surge; however, ensuing profiles of steroidogenic function (i.e., shift from the delta 5 to delta 4 pathway) occurred in parallel. Thus, in many respects the follicular mechanics of ovulation and atresia in the sheep appear analogous.     

Characteristics of Ovarian Follicle Development in Domestic Animals

In most domestic animals the later stages of follicle development occurs in a wave‐like pattern during oestrous cycles (cattle, sheep, goats, horses and buffalo) or periods of reproductive activity (llamas and camels). A follicle wave is the organized development of a cohort of gonadotrophin‐dependent follicles all of which initially increase in size, but most of which subsequently regress and die by atresia (subordinate follicles). The number of remaining (dominant) follicles is specific to the species and is indicative of litter size. Follicle waves develop during both luteal and follicular phases and it is the dominant follicle(s) of the last follicular wave that ovulates. However, there are cases where dominant follicles from the last two follicle waves can ovulate (sheep and goats). There are exceptions to the organized wave‐like pattern of follicle growth where follicle development is apparently continuous (pigs and chickens). In these animals many follicles develop to intermediate diameters and at specific times follicles that are destined to ovulate are selected from this pool and continue growing to ovulation. Understanding the pattern of follicle development in different species is increasingly important for designing improved methods to manipulate reproduction in domestic animals.