Up-Regulation of the Interleukin-1 Beta (IL-1b)—Tumor Necrosis Factor Alpha (TNF-a) Pathway in a Mouse Model of Infection-Associated Preterm Labor
Swapna Munnangi, Student, Chih-Hung Chen, Graduate, Haoting Yen, Graduate, Wei Wang, Graduate, College of Pharmacy and Health Sciences, Rajeevi Madankumar, and Susan J. Gross, Albert Einstein College of Medicine, Sandra E. Reznik, Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences
Background: Preterm labor, defined as labor before 37 weeks’ gestation, occurs in 12% of pregnancies, but is the cause of over 85% of perinatal morbidity and mortality. As the single most common cause of preterm labor is infection, we have used genomics technology to identify the genes and molecular pathways that are differentially expressed in infection-associated preterm labor in a tightly controlled validated animal model. This approach may help to identify novel potential therapeutic targets in the control of preterm labor.
Timed pregnant C57Bl/6 mice from Taconic Laboratories were used for all experiments. Twelve mice received an intraperitoneal (IP) injection of lipopolysaccharide at E15.5. Mice that delivered within 24 hours of the LPS injection (n=5) were placed in Group 1 and mice that did not deliver prematurely (n=7) were placed in Group 2. All mice were euthanized 24 hours after LPS injection at E16.5 and placentas were collected and stored in RNAlater. Messenger RNA was extracted from samples of total RNA, amplified and labeled by using an Amino Allyl Message AmpTM II aRNA Amplification Kit (Ambion). Microarray chips spotted with 32,000 oligonucleotides were hybridized with mRNA from each of the placentas from the delivering mice and reference mRNA pooled from all of the control placentas. The microarrys were then scanned at the Albert Einstein College of Medicine Microarray Facility and quantified with GenePix Pro 6.0 software. SAM and Pathway Architect Software (Stratagene) were used for analysis.
Several inflammatory mediators were up-regulated in the LPS-induced mice as compared to the mice that did not develop preterm labor, including macro inflammatory factor 2 (MIP2), interleukin-1 beta (IL-1 b) and growth regulated protein precursor (CXCL1). Molecular pathway analysis showed up-regulation of the IL-1 b--tumor necrosis factor alpha (TNF?) pathway. Furthermore, pathway analysis revealed that IL-1 b, which was up-regulated more than any other placental gene with 6.6-fold increased expression, lies at a central node at the intersection of several cytokine pathways. Microarray results were confirmed with real time rt pcr.
Up-regulation of the IL-1 b-- TNFa pathway is associated with endotoxin-triggered premature delivery in a mouse model.