Preterm birth is the leading cause of neonatal morbidity and mortality. Management of preterm labor relies on the use of tocolytics, like nifedipine, which fail to prevent preterm birth and related morbidities. Interleukin-1β plays significant roles in the pathophysiology of preterm birth including inflammation and uterine activation. The interleukin-1 allosteric receptor antagonist rytvela effectively suppresses inflammation and prevents preterm birth. We compared side-by-side rytvela and nifedipine in affecting preterm birth and offspring outcomes in a treatment modality approach. In a model of lipopolysaccharide-induced preterm birth, as of 2 hours post-lipopolysaccharide administration (peak inflammatory surge), pregnant CD-1 mice were treated with rytvela, nifedipine, or vehicle (water). Gestational tissues were collected to quantify inflammatory mediators. Neonatal integrity was evaluated through histological analysis of major organs. All datasets were analyzed by a one-way ANOVA or the Kruskal-Wallis test where appropriate and compared to the vehicle group. Preterm birth rates were assessed by a χ2 test. Unlike nifedipine, rytvela significantly decreased prematurity and mortality. Rytvela inhibited proinflammatory and uterine activation mediators in gestational tissues and improved neonatal outcomes, resulting in higher weight and length by day 7, and preserving lung, intestine, retinal, and brain microvascular integrity. Nifedipine failed to confer similar benefits. Administration of rytvela in a treatment mode after the onset of preterm labor curbed the inflammatory surge and mitigated adverse outcomes, surpassing the effects of nifedipine. Rytvela represents a promising treatment approach for preventing preterm birth complications and addressing this unmet medical need unfulfilled by current tocolytics.

Preterm birth (PTB) is a major cause of neonatal mortality and morbidity. Evidence supports a determinant role for interleukin-6 (IL-6) in the pathophysiology of PTB. Our group developed a small peptide, HSJ633, that antagonizes the interleukin-6 receptor (IL-6R). Binding assays performed on HEK-Blue IL-6 cells reveal that HSJ633 appears to bind to IL-6R on a site remote from the IL-6 binding domain. Concordantly, HSJ633 selectively inhibits STAT3 phosphorylation while preserving the activation of cytoprotective AKT, p38, and ERK 1/2. In vivo, in a murine model of LPS-induced PTB, HSJ633 reduces inflammation in gestational and fetal tissues, preserves the integrity of fetal organs, and improves the survival of neonatal progeny when administered before and after the induction of labor by an inflammatory stimulus. Relevantly, the pharmacological inhibition of STAT3 in mice is sufficient to prevent PTB. Findings reveal first-in-class efficacy of a small peptide inhibitor of IL-6R, namely HSJ633, in impeding the inflammatory cascade associated with PTB and mitigating adverse neonatal outcomes.

The subretina, composed of the choroid and the retinal pigment epithelium (RPE), plays a critical role in proper vision. In addition to phagocytosis of photoreceptor debris, the RPE shuttles oxygen and nutrients to the neuroretina. For their own energy production, RPE cells mainly rely on lactate, a major by-product of glycolysis. Lactate, in turn, conveys most of its biological effects via the hydroxycarboxylic acid receptor 1 (HCAR1). Herein, the lactate-specific receptor, HCAR1, was found to be exclusively expressed in the RPE cells within the subretina, and Hcar1-/- mice exhibited a substantially thinner choroidal vasculature during development. Notably, the angiogenic properties of lactate on the choroid were impacted by the absence of Hcar1. HCAR1-deficient mice exhibited elevated endoplasmic reticulum stress along with eukaryotic translation initiation factor 2α phosphorylation, a significant decrease in the global protein translation rate, and a lower proliferation rate of choroidal vasculature. Strikingly, inhibition of the integrated stress response using an inhibitor that reverses the effect of eukaryotic translation initiation factor 2α phosphorylation restored protein translation and rescued choroidal thinning. These results provide evidence that lactate signalling via HCAR1 is important for choroidal development/angiogenesis and highlight the importance of this receptor in establishing mature vision.

The GPCR SUCNR1/GPR91 exerts proangiogenesis upon stimulation with the Krebs cycle metabolite succinate. GPCR signaling depends on the surrounding environment and intracellular localization through location bias. Here, we show by microscopy and by cell fractionation that in neurons, SUCNR1 resides at the endoplasmic reticulum (ER), while being fully functional, as shown by calcium release and the induction of the expression of the proangiogenic gene for VEGFA. ER localization was found to depend upon N-glycosylation, particularly at position N8; the nonglycosylated mutant receptor localizes at the plasma membrane shuttled by RAB11. This SUCNR1 glycosylation is physiologically regulated, so that during hypoxic conditions, SUCNR1 is deglycosylated and relocates to the plasma membrane. Downstream signal transduction of SUCNR1 was found to activate the prostaglandin synthesis pathway through direct interaction with COX-2 at the ER; pharmacologic antagonism of the PGE2 EP4 receptor (localized at the nucleus) was found to prevent VEGFA expression. Concordantly, restoring the expression of SUCNR1 in the retina of SUCNR1-null mice renormalized vascularization; this effect is markedly diminished after transfection of the plasma membrane-localized SUCNR1 N8A mutant, emphasizing that ER localization of the succinate receptor is necessary for proper vascularization. These findings uncover an unprecedented physiologic process where GPCR resides at the ER for signaling function.

In pursuit of more effective-labor delaying tocolytic agents, the prostaglandin F2α (PGF2α) receptor (FP) modulator PDC113.824 [(6S)-2] represents a potent lead for developing therapy to treat preterm birth. Derivatives of FP modulator (6S)-2 were synthesized, possessing respectively 5- and 7-hydroxyl groups on the indolizidin-2-one amino acid (I2 aa) residue. The effects of the alcohol substituents were examined in a PGF2α-induced myometrial contraction assay. Based on knowledge of dihedral angle values of model I2 aa peptides from X-ray analyses, the results of the study indicate respectively encouraging and limited potential for creating improved tocolytic agents by modifications at the 5- and 7-positions.

BACKGROUND: Preterm birth is the leading cause of neonatal morbidity and mortality. Studies have shown that interleukin 1 plays a major role in the pathophysiology of preterm birth by inducing the pro-duction of proinflammatory mediators and uterine activation proteins leading to labor. More importantly, uteroplacental inflammation, associ-ated with preterm birth parturition pathways, is detrimental to fetal tissues and leads to long-term sequelae. Our group has developed an allosteric antagonist of the interleukin 1 receptor, rytvela, found to be potent and safe in preventing preterm birth by suppressing inflammation via the in-hibition of the mitogen-activated protein kinase pathway while preserving the Nuclear factor kappa B pathway (important in immune vigilance). Rytvela has been shown to inhibit inflammatory up-regulation and uterine activation while preserving fetal development.OBJECTIVE: This study aimed to further the preclinical development of rytvela by evaluating its optimal dose and minimal duration of treatment to inhibit the inflammatory cascade, prolong gestation, and promote neonatal outcomes.STUDY DESIGN: Pregnant CD-1 mice were administered with lipopolysaccharide (10mg, intraperitoneal administration) or interleukin 1 (1 mg/kg, intrauterine administration) on gestational day 16 to induce preterm labor. Rytvela was administered at different doses (0.1, 0.5, 1.0, 2.0, 4.0 mg/kg/d subcutaneously) from gestational days 16 to 18.5. To evaluate the minimal duration of treatment, the mice were administered with rytvela (2 mg/kg/d subcutaneously) for 24, 36, or 48 hours. The rate of prematurity (gestational day <18.5) and neonate survival and weight were evaluated. Gestational tissues were collected at gestational day 17.5 to quantify cytokines, proinflammatory mediators, and uterine activating proteins by real-time quantitative polymerase chain reaction and enzyme-linked immunosorbent assay. The neonatal lungs and intestines were collected from postnatal days 5 to 7 and analyzed by histology.RESULTS: Rytvela exhibited a dose-response profile and achieved maximum efficacy at a dose of 2 mg/kg/d by reducing 70% of lipopolysaccharide-induced preterm births and 60% of interleukin 1b- induced preterm births. In addition, rytvela attained maximum efficacy at a dose of 1 mg/kg/d by increasing neonate survival by up to 65% in both models of preterm birth. Rytvela protected fetuses from inflammatory insult as of 24 hours, preserving lung and intestinal integrity, and pre-vented preterm birth and fetal mortality by 60% and 50%, respectively, as of 36 hours of treatment. CONCLUSION: The maximum efficacy of rytvela was achieved at 2 mg/kg/d with improved birth outcomes and prevented inflammatory up-regulation upon 36 hours (only) of treatment. Rytvela exhibited desirable properties for the safe prevention of preterm birth and fetal protection.

Perinatal hypoxic/ischemic (HI) brain injury is a major clinical problem with devastating neurodevelopmental outcomes in neonates. During HI brain injury, dysregulated factor production contributes to microvascular impairment. Glycolysis-derived lactate accumulated during ischemia has been proposed to protect against ischemic injury, but its mechanism of action is poorly understood. Herein, we hypothesize that lactate via its G-protein coupled receptor (GPR81) controls postnatal brain angiogenesis and plays a protective role after HI injury. We show that GPR81 is predominantly expressed in neurons of the cerebral cortex and hippocampus. GPR81-null mice displayed a delay in cerebral microvascular development linked to reduced levels of various major angiogenic factors and augmented expression of anti-angiogenic Thrombospondin-1 (TSP-1) in comparison to their WT littermates. Coherently, lactate stimulation induced an increase in growth factors (VEGF, Ang1 and 2, PDGF) and reduced TSP-1 expression in neurons, which contributed to accelerating angiogenesis. HI injury in GPR81-null animals curtailed vascular density and consequently increased infarct size compared to changes seen in WT mice; conversely intracerebroventricular lactate injection increased vascular density and diminished infarct size in WT but not in GPR81-null mice. Collectively, we show that lactate acting via GPR81 participates in developmental brain angiogenesis, and attenuates HI injury by restoring compromised microvasculature.