Activator protein-1 (AP-1) transcription factor plays a central role in hypoxia to modulate the expression of genes that decides the fate of the cell. The aim of the present study was to explore the role of AP-1 subunits in lung epithelial (A549) cells under hypoxia. Cell cycle studies by flow cytometry indicated that cell viability was unaffected by the initial hypoxia exposure (0.5% O2 at 37 °C) for 6 and 12 h. However, both transient cell cycle arrest and cell death was detected at 24 and 48 h. Flow cytometry and spectrofluorometry data confirmed the increase in ROS levels. Elevated ROS and calcium levels activated the stress-related MAPK signaling cascade. ERK and JNK were activated in early hypoxic exposure (within 6 h), whereas p38 were activated in 48 h of hypoxia. These subtypes further stimulated the subunits of AP-1 at different times of hypoxia exposure to orchestrate different genes responsible for cell proliferation (6 and 12 h) and apoptosis (24 and 48 h). Our results clearly depict the role of AP-1 heterodimer, i.e., p-c-jun/c-fos, p-c-jun/fosB, junD/c-fos, and junD/fosB in cell proliferation/survival by regulating the expression of Bcl-2 and cyclins (D1 and B1) at 6 h and 12 h of hypoxia, whereas junB/Fra-1 heterodimer have important role in apoptosis by regulating the expression of p53, Bax, and cyclin-dependent kinase inhibitors (p16, p21, p27) at 24 h and 48 h of hypoxia. Also, the cell survival signaling pathway NO-AKT interrupted at 24 h and 48 h of hypoxia indicating cell death. In conclusion, hypoxia for different time points activated different subunits of AP-1 that combined to form different heterodimers. These dimers regulated the expression of genes responsible for cell proliferation and apoptosis. Since, AP-1 plays a role in the decisive phenomenon of the cell to choose between proliferation and apoptosis; thus, its subunits or dimers could be a good therapeutic target for many diseases.
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The authors acknowledge the Defence Research and Development Organization (DRDO), Director, Defence Institute of Physiology and Allied Sciences (DIPAS) and Council of Scientific and Industrial Research, India for providing necessary facilities and funding for this study.
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Conflict of interest
The author(s) declare that they have no conflict of interest.
Dean OM, van den Buuse M, Berk M, Copolov DL, Mavros C, Bush AI (2011) N-acetyl cysteine restores brain glutathione loss in combined 2-cyclohexene-1-one and D-amphetamine-treated rats: relevance to schizophrenia and bipolar disorder. Neurosci Lett 499:149–153. doi:10.1016/j.neulet.2011.05.027CrossRefPubMedGoogle Scholar
Son Yong, Cheong Yong-Kwan, Kim Nam-Ho, Chung Hun-Taeg, Kang Dae Gill, Pae Hyun-Ock (2011) Mitogen-activated protein kinases and reactive oxygen species: how can ROS activate MAPK pathways? J Sign Transduct. doi:10.1155/2011/7926395Google Scholar
Bonomini F, Tengattini S, Fabiano A, Bianchi R, Rezzani R (2008) Atherosclerosis and oxidative stress. Histol Histopathol 23:381–390PubMedGoogle Scholar
Amer J, Ghoti H, Rachmilewitz E, Koren A, Levin C, Fibach E (2006) Red blood cells, platelets and polymorphonuclear neutrophils of patients with sickle cell disease exhibit oxidative stress that can be ameliorated by antioxidants. Br J Hematol 132:108–113. doi:10.1111/j.1365-2141.2005.05834CrossRefGoogle Scholar
Sheng Morgan, Greenberg Michael E (1990) The regulation and function of c-fos and other immediate early genes in the nervous system 4:477–485Google Scholar
Hoffman GE, Smith MS, Verbalis JG (1993) c-Fos and related immediate early gene products as markers of activity in neuroendocrine systems. Front Neuroendocrinol 14:173–213CrossRefPubMedGoogle Scholar
Bunn HF, Poyton RO (1996) Oxygen sensing and molecular adaptation to hypoxia. Physiol Rev 76:839–885PubMedGoogle Scholar
Semenza GL (2000) HIF-1: mediator of physiological and pathophysiological responses to hypoxia. J Appl Physiol 88:1474–1480PubMedGoogle Scholar
Kaminska Bozena, Pyrzynska Beata, Ciechomska Iwona, Wisniewska Marta (2000) Modulation of the composition of AP-1 complex and its impact on transcriptional activity. Acta Neurobiol 60:395–402Google Scholar
Ryseck Rolf-Peter, Bravo Rodrigo (1991) c-JUN, JUN B, and JUN D differ in their binding affinities to AP-1 and CRE consensus sequences: effect of FOS proteins. Oncogene 6:533–542PubMedGoogle Scholar
Angel P, Karin M (1991) The role of Jun, Fos and the AP-1 complex in cell-proliferation and transformation. Biochim Biophys Acta 1072:129–157PubMedGoogle Scholar
Van Dam H, Castellazzi M (2001) Distinct roles of Jun: Fos and Jun: ATF dimers in oncogenesis. Oncogene 20:2453–2464CrossRefPubMedGoogle Scholar
LeBel CP, Ali SF, McKee M, Bondy SC (1990) Organometal-induced increases in oxygen reactive species: the potential of 2′,7′-dichlorofluorescin diacetate as an index of neurotoxic damage. Toxicol Appl Pharmacol 104:17–24CrossRefPubMedGoogle Scholar
Bradford MM (1976) A rapid and sensitive for the quantitation of microgram quantities of protein utilizing the principle of protein-dye binding. Anal Biochem 72:248–254CrossRefPubMedGoogle Scholar
Sen CK, Packer L (1996) Antioxidant and redox regulation of gene transcription. FASEB J 10:709–720PubMedGoogle Scholar
Thiel G, Lesch A, Keim A (2012) Transcriptional response to calcium-sensing receptor stimulation. Endocrinology 153:4716–4728CrossRefPubMedGoogle Scholar
Yu Z, Sato Seiichi, Trackman Philip C, Kirsch Kathrin H, Sonenshein Gail E (2012) Blimp1 activation by AP-1 in human lung cancer cells promotes a migratory phenotype and is inhibited by the lysyl oxidase propeptide. PLoS ONE. doi:10.1371/journal.pone.0033287Google Scholar
Zhao Chunyan, Qiao Yichun, Jonsson Philip, Wang Jian, Li Xu, Rouhi Pegah, Sinha Indranil, Cao Yihai, Williams Cecilia, Dahlman-Wright Karin (2014) Genome-wide profiling of AP-1 regulated transcription provides insights into the invasiveness of triple-negative breast cancer. Am Assoc Cancer Res. doi:10.1158/0008-5472.CAN-13-3396Google Scholar
Eckert RL, Adhikary G, Young CA, Jans R, Crish JF, Xu W, Rorke EA (2013) AP1 transcription factors in epidermal differentiation and skin cancer. J Skin Cancer, Article ID 537028. doi:10.1155/2013/537028