The available evidence suggests that intrauterine and/or maternal bacterial infection is a major cause of early and late pregnancy complications. Current antibacterial and anti-inflammatory drugs used to treat bacterial infection during pregnancy are considered harmful to maternal and fetal health. Thus, continued research to look for better treatment options to avoid bacterial infection-induced pregnancy complications is alluring. The decidua and placenta are uniquely positioned at the maternal-embryonic interface to serve as a first line of defense against bacterial toxins, but their defensive mechanisms against bacterial toxins are poorly understood. Lipopolysaccharide (LPS) is an endotoxin of Gram-negative E. coli that is associated with infection-induced pregnancy defects. LPS recognition by cell surface proteins is an important step required for the initiation of its inflammatory signaling or inactivation by cell surface molecules. Our preliminary results establish that: 1) the uterine luminal epithelium, decidua and placenta express the LPS sensing and signaling TLR4/CD14/MD2 complex; 2) LPS injection on day 5 of pregnancy terminates pregnancy by day 8 via selective-activation of the MyD88-dependent TLR4 signaling pathway at the embryo implantation site (EIS); 3) LPS induces expression of proinflammatory cytokine genes such as Tnf-? & Il-1?, chemokine genes such as Cxcl1&2, and neutrophil recruitment to the EIS; 4) cell surfaces of the decidua and placenta express tissue- nonspecific alkaline phosphatase (TNAP) isozyme that is capable of dephosphorylating LPS; 5) dephosphorylated LPS is non-inflammatory and non-toxic to murine pregnancy; and 6) AP isozyme treatment alleviates LPS-induced early pregnancy loss in mice. These preliminary findings have led to the hypothesis that LPS-induced microenvironment disruption at the early EIS is a result of concerted action of resident decidual cells and recruited neutrophils, and LPS detoxification by supplementation and/or induction of TNAP production/activity may abrogate LPS-mediated early pregnancy defects/loss. To test our hypothesis, we have proposed three mechanistic aims.
In Aim 1, we will use Cre-lox and antibody- mediated neutralization technologies to establish that an important step in the development of LPS-induced unwanted inflammation at the early EIS is decidual cell-type-dependent recruitment of inflammatory neutrophils.
In Aim 2, we will generate novel female mice with uterine deletion of TNAP gene Alpl to determine whether endogenous TNAP deficiency in the uterus augments the response to LPS.
In Aim 3, we will examine the potential of TNAP and its activator or inducer in mitigating LPS- or E. coli-induced early pregnancy defects/loss. Upon completion of these aims, we hope to gain: 1) insights into the mechanisms of infection-induced inflammation at the early EIS; and 2) develop a novel LPS-detoxification therapeutic strategy to avoid bacteria- induced early pregnancy complications.
The uterine luminal epithelium, decidua and placenta are situated at the embryo-uterine interface to protect the integrity of the uterus and pregnancy against infection-induced inflammation. In the proposed study, we will focus on how uterine non-hematopoietic cell populations recognize endotoxin lipopolysaccharide (LPS) produced by Escherichia coli (E. coli), and utilize their tissue-nonspecific alkaline phosphatase for the maintenance of pregnancy against casual presence of LPS. Moreover, our pre-clinical study will assess the medical use of a therapeutic LPS detoxification strategy in mitigating E. coli-induced inflammation responsible for early pregnancy complications.
