論文宣讀

濾泡閉鎖(follicle atresia)主要起源於顆粒細胞(granulosa cells; GC)死亡，常伴隨卵巢功能退化，影響雞隻產蛋性能，給家禽業帶來顯著的經濟損失。熱緊迫(HS；heat stress) 是環境中最主要壓力來源，會導致顆粒細胞死亡與濾泡閉鎖，進而降低產蛋率。HS 能提高細胞內的神經醯胺 (Ceramide; Cer)濃度， Cer 是鞘脂質(sphingolipids)代謝的核心分子，具強烈生物活性，為激活protein kinase C zeta pathway的第二信使。Cer可以透過兩種途徑合成：由絲氨酸棕櫚酰轉移酶 (serine palmitoyl transferase; SPT) 催化的新生途徑，或由中性和酸性鞘磷脂酶 (neutral or acidic sphingomyelinase; nSMase/aSMase) 水解神經鞘磷脂 (sphingomyelin; SM)，而在 HS 壓力條件下，細胞會透過此兩途徑影響存活。SM是質膜中脂筏(lipid rafts)形成的關鍵結構脂質，其含量與Cer間的turnover關係到細胞功能與存活。脂毒性的特徵是一系列細胞內脂質的恆定異常，導致如游離脂肪酸(free fatty acids)、TAG (triacylglycerol)、或生物活性二醯甘油 (Diacylglycerol)和Cer神經醯胺的積累，誘發氧化壓力、發炎反應與死亡訊號，最終導致細胞死亡。先前研究顯示，雞的濾泡顆粒細胞、卵泡膜細胞和上皮細胞，表現功能性微粒體三酸甘油轉運蛋白 (microsomal triglyceride transfer protein, MTTP) 與載脂蛋白B (apoB)，能合成與分泌VLDL，而HS增強 MTTP 和 apoB 活性，導致 VLDL 分泌增加。儘管現有研究清楚證明Cer 在HS誘導細胞凋亡中的角色，但 Cer 和 SM 間turnover， HS誘發雞隻濾泡細胞VLDL 分泌的生理意涵，以及後續脂質毒性(lipotoxicity)與熱緊迫對濾泡細胞命運的關係尚未完全了解。本研究旨在了解鞘脂質路徑之間的複雜相互消長關係，特別關注神經醯胺和鞘磷脂週轉之間的動態及其與 VLDL 分泌在熱緊迫條件下GC脂質毒性的關係。目前結果顯示雞GC暴露於 HS（42℃）3 小時，然後恢復於37℃恢復0、2、5 和 13 小時，細胞存活率在熱緊迫3小時後恢復13小時顯著降低，，而細胞內SM 和 Cer 含量分別隨時間降低和升高。這些結果表明 HS 透過Cer 的累積和 SM 的減少，導致脂毒性，造成顆粒細胞死亡的主要原因。而在長時間熱緊迫下(8 hr)，抑制VLDL 分泌會提高細胞存活率，此顯示HS亦透過加速大宗脂肪(cargo lipids)分泌影響細胞存活。
 
關鍵字: 顆粒細胞、熱緊迫、細胞死亡、VLDL、脂質毒性

• Assersohn, K., P. Brekke, and N. Hemmings. 2021. Physiological factors influencing female fertility in birds. R. Soc. Open Sci. 8: 202274.
• Chung, H. S., S. R. Park, E. K. Choi, H.-J. Park, R. J. Griffin, C. W. Song, and H. Park. 2003. Role of sphingomyelin-MAPKs pathway in heat-induced apoptosis. Exp. Mol. Med. 35: 181–188.
• Chen, Y.H., P. Dettipponpong, M.Y. Sin, L.C. Chang, C.Y. Cheng, S.Y. Huang, R. L. Walzem, H.-C. Cheng, and S.-E. Chen. 2025. Ovarian expression of functional MTTP and apoB for VLDL assembly and secretion in chickens. Poult Sci 104(5): 104993.
• Jenkins, G. M., L. Ashley Cowart, P. Signorelli, B. J. Pettus, C. E. Chalfant, and Y. A. Hannun. 2002. Acute activation of de novo sphingolipid biosynthesis upon heat shock causes an accumulation of ceramide and subsequent dephosphorylation of SR proteins. J. Biol. Chem. 277: 42572–42578.
•  Kalo, D., and Z. Roth. 2011. Involvement of the sphingolipid ceramide in heat-shock-induced apoptosis of bovine oocytes. Reprod. Fertil. Dev. 23: 876.
• Kondo, T., T. Matsuda, T. Kitano, A. Takahashi, M. Tashima, H. Ishikura, H. Umehara, N. Domae, T. Uchiyama, and T. Okazaki. 2000. Role of c-jun expression increased by heat shock- and ceramide-activated caspase-3 in HL-60 cell apoptosis. The J. Biol. Chem. 275: 7668–7676.
• Kraveka, J. M., and Y. A. Hannun. 2009. Bioactive Sphingolipids: An overview on ceramide, ceramide-1-phosphate dihydroceramide, sphingosine, sphingosine-1-phosphate. Springer eBooks. 3: 373–383.
• Lee, S., H. G. Kang, P. S. Jeong, M. J. Kim, S. H. Park, B. S. Song, B. W. Sim, and S. U. Kim. 2021. Heat stress impairs oocyte maturation through ceramide-mediated apoptosis in pigs. Sci. Total Environ. 755: 144144.
• Luberto, C., D. F. Hassler, P. Signorelli, Y. Okamoto, H. Sawai, E. E. Boros, D. J. Hazen-Martin, L. M. Obeid, Y. A. Hannun, and G. A. Smith. 2002. Inhibition of tumor necrosis factor-induced cell death in MCF7 by a novel inhibitor of neutral sphingomyelinase. J. Biol. Chem. 277: 41128–41139.
• Milhas, D., N. Andrieu-Abadie, T. Levade, H. Benoist, and B. Ségui. 2012. The tricyclodecan-9-yl-xanthogenate D609 triggers ceramide increase and enhances FasL-induced caspase-dependent and -independent cell death in T lymphocytes. Int. J. Mol. Sci. 13: 8834–8852.
• Oancea-Castillo, L. R., C. Klein, A. Abdollahi, K. J. Weber, A. Régnier-Vigouroux, and I. Dokic. 2017. Comparative analysis of the effects of a sphingosine kinase inhibitor to temozolomide and radiation treatment on glioblastoma cell lines. Cancer Biol. Ther. 18: 400–406.
• Pfeilschifter, J., and A. Huwiler. 2000. Ceramides as Key Players in Cellular Stress Response. Physiology. 15: 11–15.
• Ru, M., H. Liang, J. Ruan, Ramlat Ali Haji, Y. Cui, C. Yin, Q. Wei, and J. Huang. 2024. Chicken ovarian follicular atresia: interaction network at organic, cellular, and molecular levels. Poult. Sci. 103: 103893–103893.
• Sah, D. K., Y. Rai, A. Chauhan, N. Kumari, M. M. Chaturvedi, and A. N. Bhatt. 2021. Sphingosine kinase inhibitor, SKI-II confers protection against the ionizing radiation by maintaining redox homeostasis most likely through Nrf2 signaling. Life Sci. 278: 119543–119543.
• Stephens, C. S., and P. A. Johnson. 2020. Reproductive physiology of poultry. Animal Agri. 331–347.
• Taniguchi, M., and T. Okazaki. 2020. Ceramide/Sphingomyelin rheostat regulated by sphingomyelin synthases and chronic diseases in murine models. J. Lipid Atheroscler. 9: 380–380.
• Yabu, T., S. Imamura, M. Yamashita, and T. Okazaki. 2008. Identification of Mg2+-dependent Neutral Sphingomyelinase 1 as a Mediator of Heat Stress-induced Ceramide Generation and Apoptosis. J. Biol. Chem. 283: 29971–29982.
• Yabu, T., H. Shiba, Y. Shibasaki, T. Nakanishi, S. Imamura, K. Touhata, and M. Yamashita. 2014. Stress-induced ceramide generation and apoptosis via the phosphorylation and activation of nSMase1 by JNK signaling. Cell Death Differ. 22: 258–273.