Heat stress (HS) occurs when temperatures exceed a physiological range, overwhelming compensatory mechanisms. Most mammalian testes are ∼4-5 °C cooler than core body temperature. Systemic HS or localized warming of the testes affects all types of testicular cells, although germ cells are more sensitive than either Sertoli or Leydig cells. Increased testicular temperature has deleterious effects on sperm motility, morphology and fertility, with effects related to extent and duration of the increase. The major consequence of HS on testis is destruction of germ cells by apoptosis, with pachytene spermatocytes, spermatids and epididymal sperm being the most susceptible. In addition to the involvement of various transcription factors, HS triggers production of reactive oxygen species (ROS), which cause apoptosis of germ cells and DNA damage. Effects of HS on testes can be placed in three categories: testicular cells, sperm quality, and ability of sperm to fertilize oocytes and support development. Various substances have been given to animals, or added to semen, in attempts to ameliorate heat stress-induced damage to testes and sperm. They have been divided into various groups according to their composition or activity, as follows: amino acids, antibiotics, antioxidant cocktails, enzyme inhibitors, hormones, minerals, naturally produced substances, phenolic compounds, traditional herbal medicines, and vitamins. Herein, we summarized those substances according to their actions to mitigate HS' three main mechanisms: oxidative stress, germ cell apoptosis, and sperm quality deterioration and testicular damage. The most promising approaches are to use substances that overcome these mechanisms, namely reducing testicular oxidative stress, reducing or preventing apoptosis and promoting recovery of testicular tissue and restoring sperm quality. Although some of these products have considerable promise, further studies are needed to clarify their ability to preserve or restore fertility following HS; these may include more advanced sperm analysis techniques, e.g. sperm epigenome or proteome, or direct assessment of fertilization and development, including in vitro fertilization or breeding data (either natural service or artificial insemination).

中文翻译：

---

改善热应激引起的睾丸损伤和精子质量

当温度超过生理范围时会发生热应激 (HS)，压倒性的补偿机制。大多数哺乳动物的睾丸比核心体温低 4-5°C。全身性 HS 或睾丸局部升温会影响所有类型的睾丸细胞，尽管生殖细胞比 Sertoli 或 Leydig 细胞更敏感。睾丸温度升高会对精子活力、形态和生育能力产生有害影响，其影响与升高的程度和持续时间有关。HS对睾丸的主要后果是通过细胞凋亡破坏生殖细胞，粗线期精母细胞、精子细胞和附睾精子最容易受到影响。除了各种转录因子的参与外，HS 还会引发活性氧 (ROS) 的产生，从而导致生殖细胞凋亡和 DNA 损伤。HS对睾丸的影响可分为三类：睾丸细胞、精子质量和精子使卵母细胞受精和支持发育的能力。已将各种物质给予动物或添加到精液中，以试图改善热应激引起的睾丸和精子损伤。它们根据其组成或活性分为以下几类：氨基酸、抗生素、抗氧化混合物、酶抑制剂、激素、矿物质、天然产生的物质、酚类化合物、传统草药和维生素。在此，我们根据这些物质减轻 HS 的三个主要机制的作用总结了这些物质：氧化应激、生殖细胞凋亡、精子质量下降和睾丸损伤。最有前景的方法是使用克服这些机制的物质，即减少睾丸氧化应激，减少或防止细胞凋亡，促进睾丸组织的恢复和恢复精子质量。尽管其中一些产品具有相当大的前景，但需要进一步研究以阐明它们在 HS 后保持或恢复生育能力的能力；这些可能包括更先进的精子分析技术，例如精子表观基因组或蛋白质组，或受精和发育的直接评估，包括体外受精或育种数据（自然授精或人工授精）。尽管其中一些产品具有相当大的前景，但需要进一步研究以阐明它们在 HS 后保持或恢复生育能力的能力；这些可能包括更先进的精子分析技术，例如精子表观基因组或蛋白质组，或受精和发育的直接评估，包括体外受精或育种数据（自然授精或人工授精）。尽管其中一些产品具有相当大的前景，但需要进一步研究以阐明它们在 HS 后保持或恢复生育能力的能力；这些可能包括更先进的精子分析技术，例如精子表观基因组或蛋白质组，或受精和发育的直接评估，包括体外受精或育种数据（自然授精或人工授精）。