Prevention of inflammation-associated preterm birth by knockdown of the endothelin-1-matrix metalloproteinase-1 pathway

Preterm Birth Therapies to Target Inflammation

Preterm birth (PTB; defined as delivery before 37 weeks of pregnancy) is the leading cause of morbidity and mortality in infants and children aged <5 years, conferring potentially devastating short- and long-term complications. Despite extensive research in the field, there is currently a paucity of medications available for PTB prevention and treatment. Over the past few decades, inflammation in gestational tissues has emerged at the forefront of PTB pathophysiology. Even in the absence of infection, inflammation alone can prematurely activate the main components of parturition resulting in uterine contractions, cervical ripening and dilatation, membrane rupture, and subsequent PTB. Mechanistic studies have identified critical elements of the complex inflammatory molecular pathways involved in PTB. Here, we discuss therapeutic options that target such key mediators with an aim to prevent, postpone, or treat PTB. We provide an overview of more traditional therapies that are currently used or being tested in humans, and we highlight recent advances in preclinical studies introducing novel approaches with therapeutic potential. We conclude that urgent collaborative action is required to address the unmet need of developing effective strategies to tackle the challenge of PTB and its complications.

Low CLOCK and CRY2 in 2nd trimester human maternal blood and risk of preterm birth: A nested case-control study

Previous studies have observed an association between maternal circadian rhythm disruption and preterm birth (PTB). However, the underlying molecular mechanisms and the potential of circadian clock genes to serve as predictors of PTB remain unexplored. We examined the association of 10 core circadian transcripts in maternal blood with spontaneous PTB (sPTB) vs term births using a nested case-control study design. We used a public gene expression dataset (GSE59491), which was nested within the All Our Babies (AOB) study cohort in Canada. Maternal blood was sampled in trimesters 2-3 from women with sPTB (n = 51) and term births (n = 106), matched for 5 demographic variables. In 2nd trimester maternal blood, only CLOCK and CRY2 transcripts were significantly lower in sPTB vs term (p = 0.02 ~ 0.03, FDR < 0.20). A change of PER3 mRNA from trimesters 2 to 3 was significantly associated with sPTB (decline in sPTB, p = 0.02, FDR < 0.20). When CLOCK and CRY2 were modeled together in 2nd trimester blood, the odds ratio of being in the low level of both circadian gene transcripts was greater in sPTB vs term (OR = 4.86, 95%CI = (1.75,13.51), p < 0.01). Using GSVA and Pearson correlation, we identified 98 common pathways that were negatively or positively correlated with CLOCK and CRY2 expression (all p < 0.05, FDR < 0.10). The top three identified pathways were amyotrophic lateral sclerosis, degradation of extracellular matrix, and inwardly rectifying potassium channels. These three processes have previously been shown to be involved in neuron death, parturition, and uterine excitability during pregnancy, respectively.

Impact of Pregnancy History and 17-Hydroxyprogesterone Caproate on Cervical Cytokines and Matrix Metalloproteinases

OBJECTIVE

 The objective of this study was to evaluate the impact of pregnancy history and 17-hydroxyprogesterone caproate (17-OHPC) treatment on cervical fluid cytokines and matrix metalloproteinases (MMPs).

STUDY DESIGN

 Cervical fluid was obtained between 160/7 and 246/7 weeks from women with only prior term births (controls, n = 26), women with one or more prior spontaneous preterm births (SPTBs) choosing to receive 17-OHPC (17-OHPC, n = 24), or to not receive 17-OHPC (refusers, n = 12). Cervical fluid collections were repeated 2, 4, and 8 weeks after the first sample and concentrations of MMPs and cytokines were measured by multiplex immune assay.

RESULTS

 Among women whose earliest prior delivery occurred between 16 and 23 weeks, cervical fluid concentration of interleukin (IL)-6, IL-10, and tumor necrosis factor (TNF)-α at baseline were significantly elevated when compared with cervical cytokines of women whose earliest delivery occurred between 32 and 36 weeks (relative risk ratio was 3.37 for IL-6 [95% confidence interval, CI, 1.08-10.53, p < 0.05], 2.81 for IL-10 [95% CI, 1.39-5.70, p < 0.05], and 6.34 for TNF-α [95% CI, 2.19-18.68, p < 0.001]). Treatment with 17-OHPC had no significant impact on these cytokines.

CONCLUSION

 The cervical fluid of women with a history of an early prior SPTB is characterized by inflammation that is unaffected by 17-OHPC.

The bacterial etiology of preterm birth

Preterm birth is the leading cause of infant morbidity and mortality. Very preterm births, those occurring before 32 completed weeks of gestation, are associated with the greatest risks. The leading cause of very preterm birth is intrauterine infection, which can lead to an inflammatory response that triggers labor or preterm premature rupture of membranes. How bacteria invade the uterine cavity, which is normally a sterile environment, and the reasons why different species vary in their capacity to induce inflammation and preterm birth are still incompletely understood. However, advanced techniques that circumvent the need for cultivating bacteria, deep sequence analysis that allows for the comprehensive characterization of the microbiome of a given body site and detection of low-prevalence species, and transcriptomics and metabolomics approaches that shed light on the host response to bacterial invasion are all providing a more complete picture of the progression from vaginal colonization to uterine invasion to preterm labor and preterm birth.

Roles and regulation of the matrix metalloproteinase system in parturition

Significant tissue destruction, repair, and remodeling are involved in parturition, which involves fetal membrane rupture, cervical ripening, and uterine contraction and its subsequent involution. Extracellular matrix degradation and remodeling by proteolytic enzymes, such as matrix metalloproteinases (MMPs), are required for the final steps of parturition. MMPs participate in physiological degradation and remodeling through their proteolytic activities on specific substrates, and are balanced by the action of their inhibitors. Disruption to this balance can result in pathological stress that ends with preterm or post-term birth or pre-eclampsia. In this review, we examine the roles and regulation of the MMP system in physiological and pathological labor, and propose a model that illustrates the mechanisms by which the MMP system contributes to these processes.

Inhibition of sphingosine kinase prevents lipopolysaccharide-induced preterm birth and suppresses proinflammatory responses in a murine model

Premature delivery occurs in 12% of all births, and accounts for nearly half of long-term neurological morbidity, and 60% to 80% of perinatal mortality. Despite advances in obstetrics and neonatology, the rate of premature delivery has increased approximately 12% since 1990. The single most common cause of spontaneous preterm birth is infection. Several lines of evidence have demonstrated the role of endothelin-1 as both a constrictor of uterine myometrial smooth muscle and a proinflammatory mediator. Endothelin-1 activates the phospholipase C pathway, leading to activation of protein kinase C and, in turn, sphingosine kinase (SphK). The inhibition of SphK has been recently shown to control the proinflammatory response associated with sepsis. We show herein, for the first time, that SphK inhibition prevents inflammation-associated preterm birth in a murine model. Rescue of pups from premature abortion with an SphK inhibitor occurs by suppression of the proinflammatory cytokines tumor necrosis factor α, Il-1β, and Il-6 and attenuation of polymorphonuclear inflammatory cells into the placental labyrinth. Moreover, we postulate that inhibition of SphK leads to suppression of endothelin-converting enzyme-1 expression, indicating the presence of an endothelin-converting enzyme 1/endothelin 1-SphK positive feedback loop. This work introduces a novel approach for the control of infection-triggered preterm labor, a condition for which there is no effective treatment.

The CRTH2 agonist Pyl A prevents lipopolysaccharide-induced fetal death but induces preterm labour

We have previously demonstrated that the anti-inflammatory prostaglandin 15-deoxy-Δ 12,14-prostaglandin J(2) (15dPGJ(2)) delays inflammation-induced preterm labour in the mouse and improves pup survival through the inhibition of nuclear factor-κB (NF-κB) by a mechanism yet to be elucidated. 15dPGJ(2) is an agonist of the second prostaglandin D(2) receptor, chemoattractant receptor homologous to the T helper 2 cell (CRTH2). In human T helper cells CRTH2 agonists induce the production of the anti-inflammatory interleukins IL-10 and IL-4. We hypothesized that CRTH2 is involved in the protective effect of 15dPGJ(2) in inflammation-induced preterm labour in the murine model. We therefore studied the effects of a specific small molecule CRTH2 agonist on preterm labour and pup survival. An intrauterine injection of lipopolysaccharide (LPS) was administered to CD1 mice at embryonic day 16, ± CRTH2 agonist/vehicle controls. Mice were killed at 4.5 hr to assess fetal wellbeing and to harvest myometrium and pup brain for analysis of NF-κB, and T helper type 1/2 interleukins. To examine the effects of the CRTH2 agonist on LPS-induced preterm labour, mice were allowed to labour spontaneously. Direct effects of the CRTH2 agonist on uterine contractility were examined ex vivo on contracting myometrial strips. The CRTH2 agonist increased fetal survival from 20 to 100% in LPS-treated mice, and inhibited circular muscle contractility ex vivo. However, it augmented LPS-induced labour and significantly increased myometrial NF-κB, IL-1β, KC-GRO, interferon-γ and tumour necrosis factor-α. This suggests that the action of 15dPGJ(2) is not via CRTH2 and therefore small molecule CRTH2 agonists are not likely to be beneficial for the prevention of inflammation-induced preterm labour.

N,N-dimethylacetamide regulates the proinflammatory response associated with endotoxin and prevents preterm birth

The proinflammatory response leads to various types of pathologic pathways, including the development of preterm birth. Preterm birth occurs in 12% of deliveries in the United States and causes more than 70% of perinatal morbidity and mortality. The most common cause of spontaneous preterm birth is intrauterine infection in the mother. There is accumulating evidence indicating that the release of proinflammatory cytokines plays a critical role in the pathogenesis of inflammation-associated premature delivery. We found that the common organic solvent, N,N-dimethylacetamide (DMA), prevents endotoxin-induced preterm birth in timed pregnant C57BL/6 embryonic day (E)15.5 mice and rescues their pups from spontaneous abortion at doses many-fold lower than those currently used clinically and in a dose-dependent fashion. We also provide histologic evidence that DMA suppresses the endotoxin-triggered proinflammatory response by significantly attenuating inflammatory cell infiltration of placental tissue. Furthermore, immunoblotting analysis of placental tissue harvested from our murine models revealed DMA-mediated regulation of expression of the proinflammatory cytokines IL-1β, tumor necrosis factor α, and IL-6, and increased expression of the regulatory inflammatory cytokine IL-10. By using in vitro studies, we provide evidence that DMA suppresses macrophage function and that this small molecule prevents nuclear translocation of nuclear factor-kB. These results suggest that DMA represents a newly discovered, nontoxic therapy for a broad range of inflammatory disorders.

The endothelin axis in uterine leiomyomas: new insights

The endothelin axis, comprising endothelin-1 (ET-1) and its receptors (ETA and ETB), is involved in the pathophysiology of different human tumors. Here we review conventional approaches and gene expression profiling indicating the association of ET-1 and its cognate receptors with human and rat leiomyomas, the most common benign tumors of myometrium. Specifically, ET-1/ETA interactions affect human and rat leiomyoma cell proliferation through protein kinase C and mitogen-activated protein kinase-dependent signaling pathways. Recent experiments demonstrate that the ET-1 axis exerts a potent antiapoptotic effect involving sphingolipid metabolism and prostaglandin-endoperoxide synthase 2/prostaglandin system in the rat Eker leiomyoma tumor-derived ELT3 cell line. Evidence supports that steroid hormones, growth factors, and extracellular matrix are key regulators of the leiomyoma growth. Interestingly, the ET-1 axis is under steroid hormones and can cooperate with these growth factors. Therefore, ET-1 alone or in association with these factors could contribute to the complex regulation of uterine tumor growth, such as proliferation, survival, and extracellular matrix production. This review summarizes current knowledge and emerging data on ET-1 in uterine leiomyoma pathology.

Lobe-specific heterogeneity and matrix metalloproteinase activation after ischemia/reperfusion injury in rat livers

Studies assessing the effects of partial-hepatic ischemia/reperfusion (I/R) injury focused on the damage to the ischemic-lobe, whereas few data are available on non-ischemic lobe. This study investigated whether acute liver I/R does affect non-ischemic lobe function via modulation of extracellular matrix remodeling. Male Sprague-Dawley rats underwent left lateral- and median-lobe ischemia for 30 min and reperfusion for 60 min or sham operation. After reperfusion, blood samples and hepatic biopsies from both the ischemic (left-lobe, LL) and the non-ischemic lobe (right-lobe, RL) were collected. Serum hepatic enzymes and TNF-alpha, tissue matrix metalloproteinases (MMP-2, MMP-9), liver morphology, malondialdehyde (MDA), and myeloperoxidase (MPO) were evaluated. Liver I/R injury was confirmed by altered increased hepatic enzymes and TNF-alpha. I/R induced an altered morphology and an increase in MMP-2 and MMP-9 activity not only in left-ischemic lobe (LL) but also in the right-non-ischemic (RL) lobe. A lobar difference was detected for MDA formation and MPO activity in both sham and I/R submitted rats, with higher levels in the left lobe for both groups. This study indicates that an increase in MMPs, which may be TNF-alpha-mediated, occurs in both the ischemic- and the non-ischemic lobes; the heterogeneous lobe concentrations of MDA and MPO suggest that the random sampling of liver tissue should be avoided.

Endocervical immune mediator production following successful rescue or ultrasound indicated cerclage placement

OBJECTIVE

Placement of a cervical cerclage at mid-trimester in women at risk for preterm labor is a common procedure with apparent benefits for some women. However, the changes that occur in the cervix following this procedure remain incompletely identified.

METHODS

We evaluated the endocervical concentrations of mediators involved in extracellular matrix (ECM) stabilization or degradation prior to, and up to 120 days following, cerclage placement in 53 women who underwent an ultrasound-indicated or a rescue cerclage at 15-25 weeks of gestation due to a cervical length <1.5 cm. All delivered a healthy neonate at term. Samples were tested by enzyme-linked immunosorbent assay for concentrations of hyaluronan (HA), 27 kDa heat shock protein (hsp27), transforming growth factor-β (TGF-β), extracellular matrix metalloproteinase inducer (CD147/EMMPRIN), and matrix metalloproteinase (MMP)-1 and -8.

RESULTS

Concentrations of both HA and hsp27 were highest at the time of cerclage placement and then decreased while TGF-β and EMMPRIN increased in concentration following the procedure. The highest mean EMMPRIN level was measured at >90 days following the procedure while TGF-β levels peaked at 61-90 days post-cerclage. MMP-1 and MMP-8 were not detected over the study time period.

CONCLUSION

In women with a successful cerclage placement the selective regulation of mediators inhibits progression of ECM degradation and cervical ripening.