73: Activation of p38MAPK and senescence in fetal membranes induced by telomere overhang sequence: a novel mechanism for preterm birth

Oxidative stress (OS)-induced telomere reduction in fetal tissues has been associated with preterm birth. Telomere sequences are vulnerable to OS and short fragments can be released into tissue environment. We tested if telomere mimetic overhang sequence (T-oligo) activates mitogen-activated protein kinase (MAPK) in fetal tissues, leading to cellular senescence and inflammation. Primary human epithelial amniotic cells were exposed to 40μM of T-oligo, [TTAGGG]2) or control oligonucleotides (cont-oligo, [AATCCC]2) for 48h. We evaluated p38MAPK activation by Western blot, DNA damage foci by gamma-histone2A (γH2AX) immunofluorescence staining, senescence by staining of senescence associated β-Galactosidase (β-Gal) and IL-8 as senescence associated secretory phenotype by ELISA and PCR. Further experiments were done with p38MAPK inhibitor (SB203580). In addition, T-oligo or cont-oligo were injected into the uterus of pregnant CD1 mice (n=5/group) on day 14. Amniotic sacs were collected on day 18, subjected to oxidative stress marker staining (3-nitrotyrosine modified proteins, 3-NT) and to p38MAPK Western blot. Data were analyzed by Anova, p<0.05 was used for significance. T-oligo treated cells exhibited p38MAPK phosphorylation, γH2AX staining increase, higher β-Gal positivity and IL-8 levels (gene and protein) compared to control. SB203580 decreased p38 activation, β-Gal positivity and IL-8 protein levels (Figure 1-left). Murine amniotic sac showed higher 3-NT staining and p38MAPK phosphorylation after T-oligo treatment compared to control. SB203580 reduced p38 activation (Figure 1-right). This study provides firsthand evidences that telomere fragments can promote OS in fetal membrane cells in an autocrine fashion. This in turn leads to further DNA damage resulting in senescence and senescence associated inflammation. Our findings point to a novel OS-induced and non-infectious inflammatory pathway activation that can result in preterm birth.