Institute of Animal Molecular Biotechnology, Department of Biotechnology, College of Life Sciences and Biotechnology, Korea University, Seoul, 02841, Republic of Korea.
Department of Biomedical Sciences, Catholic Kwandong University, Gangneung, 25601, Republic of Korea.
J Dairy Sci. 2018 May;101(5):4527-4541. doi: 10.3168/jds.2017-13966. Epub 2018 Feb 14.
C-C motif chemokine ligand 2 (CCL2) is a small chemokine which belongs to the CC-type chemokine family, and has chemoattractant activity for recruitment of monocytes to sites of inflammation. Overexpressed CCL2 binding to its receptor C-C chemokine receptor 2 increases the risk of breast cancer in humans, but its effects on proliferation of bovine mammary epithelial cells is not known. Maintaining a high level of proliferative activity in bovine mammary epithelial cells during lactation is important for improving milk yield and can benefit the dairy industry economically. In the present study, we demonstrated that CCL2 induces proliferation of MAC-T cells, a bovine mammary epithelial cell line, and stimulates progression of the cell cycle through stimulation of expression of cyclin D1. Moreover, CCL2 activates phosphoinositide 3-kinase (PI3K)/AKT [AKT, P70-S6 kinase 1 (P70S6K), ribosomal protein S6 (S6)] and mitogen activated protein kinase (MAPK) [extracellular signal-regulated kinase-1/2 (ERK1/2), c-Jun N-terminal kinase (JNK), and P38] pathways, which are involved in proliferation of MAC-T cells, as evidenced by co-treatment of MAC-T cells with pharmacological inhibitors of cell signaling transcription factors including Wortmannin, U0126, and SP600125. The CCL2 in MAC-T cells attenuates endoplasmic reticulum stress induced by tunicamycin, suggesting that CCL2 regulates intracellular synthesis of proteins and lipids and prevents activation of apoptotic pathways initiated in response to endoplasmic reticulum stress. Furthermore, CCL2 is involved in alleviating lipopolysaccharide (LPS)-induced inflammatory responses in MAC-T cells by reducing LPS-induced expression of IL8, IL6, and nuclear factor kappa B subunit 1 (NFKB1). Collectively, CCL2 is a novel target for improving the quantity and quality of milk from cows through stimulation of proliferation on mammary epithelial cells and attenuation of LPS-induced inflammatory responses.
C-C 基序趋化因子配体 2（CCL2）是一种小分子趋化因子，属于 CC 型趋化因子家族，具有招募单核细胞到炎症部位的趋化活性。在人类中，过表达的 CCL2 与其受体 C-C 趋化因子受体 2 结合会增加乳腺癌的风险，但它对牛乳腺上皮细胞增殖的影响尚不清楚。在哺乳期维持牛乳腺上皮细胞的高增殖活性对于提高产奶量很重要，并且可以从经济上使乳制品行业受益。在本研究中，我们证明 CCL2 诱导牛乳腺上皮细胞系 MAC-T 细胞增殖，并通过刺激细胞周期蛋白 D1 的表达来刺激细胞周期的进展。此外，CCL2 通过激活磷酸肌醇 3-激酶（PI3K）/AKT [AKT、P70-S6 激酶 1（P70S6K）、核糖体蛋白 S6（S6）]和丝裂原激活的蛋白激酶（MAPK）[细胞外信号调节激酶 1/2（ERK1/2）、c-Jun N-末端激酶（JNK）和 P38]途径激活 MAC-T 细胞，这一点通过用包括 Wortmannin、U0126 和 SP600125 在内的细胞信号转导转录因子的药理学抑制剂共同处理 MAC-T 细胞得到证实。MAC-T 细胞中的 CCL2 减轻了衣霉素诱导的内质网应激，表明 CCL2 调节细胞内蛋白质和脂质的合成，并防止响应内质网应激而引发的凋亡途径的激活。此外，CCL2 通过降低 LPS 诱导的 IL8、IL6 和核因子 kappa B 亚单位 1（NFKB1）的表达，参与减轻 LPS 诱导的 MAC-T 细胞炎症反应。总之，CCL2 通过刺激乳腺上皮细胞增殖和减轻 LPS 诱导的炎症反应，成为提高奶牛产奶量和质量的新靶点。
