Prostaglandin I2 Analogue Research Articles

Integrated-omics analysis with explainable deep networks on pathobiology of infant bronchiolitis

Bronchiolitis is the leading cause of infant hospitalization. However, the molecular networks driving bronchiolitis pathobiology remain unknown. Integrative molecular networks, including the transcriptome and metabolome, can identify functional and regulatory pathways contributing to disease severity. Here, we integrated nasopharyngeal transcriptome and metabolome data of 397 infants hospitalized with bronchiolitis in a 17-center prospective cohort study. Using an explainable deep network model, we identified an omics-cluster comprising 401 transcripts and 38 metabolites that distinguishes bronchiolitis severity (test-set AUC, 0.828). This omics-cluster derived a molecular network, where innate immunity-related metabolites (e.g., ceramides) centralized and were characterized by toll-like receptor (TLR) and NF-κB signaling pathways (both FDR < 0.001). The network analyses identified eight modules and 50 existing drug candidates for repurposing, including prostaglandin I2 analogs (e.g., iloprost), which promote anti-inflammatory effects through TLR signaling. Our approach facilitates not only the identification of molecular networks underlying infant bronchiolitis but the development of pioneering treatment strategies.

Long peripheral catheters for intravenous infusions of iloprost or alprostadil therapy in rheumatologic outpatients.

Long peripheral catheters (LPCs) role in Difficult IntraVenous Access (DIVA) patients admitted to the emergency department has already been studied, resulting in a rapid, safe, and cost-effective procedure. Although their use in outpatient settings is established, there is a lack of studies assessing their benefits. In particular, rheumatologic outpatients affected by scleroderma, especially those affected by digital ulcers, are often treated with intravenous infusions of prostaglandin I2 (PGI2) analog (IV-PGI2A). From 1 October 2021 to 31 March 2024, we conducted a prospective study enrolling DIVA outpatients affected by systemic sclerosis or undifferentiated connective tissue disease who needed IV-PGI2A therapy at L. Sacco Hospital in Milan (Italy). Each treatment cycle consisted of four consecutive days of infusion of iloprost or alprostadil. The primary aim was to assess the efficacy and potential complications associated with LPCs for IV-PGI2A. Twenty-six patients were enrolled 23 were females (88.5%), and the median age was 72 years (IQR 56-78.7). In total, 97 LPCs were inserted, with a mean number of insertions per patient/year of 2.3. An increase in LPCs insertion during the 30 months of the enrollment period was observed. Eighteen patients required more than one LPC placement, and in 61% of them, the second venipuncture was executed at a different site. No procedural complications were registered (accidental puncture of the brachial artery, accidental median nerve puncture, bleeding) nor late complications (Catheter-Related Thrombosis, Catheter-Related Bloodstream Infections, Accidental Removal). Our experience shows that LPCs could be valuable and safe for rheumatologic outpatients. The increased number of insertions and new and total patients enrolled each year defines the satisfaction of patients and health care professionals.

Hepatic ischemia-reperfusion syndrome and its effect on the cardiovascular system: The role of treprostinil, a synthetic prostacyclin analog.

Hepatic ischemia-reperfusion syndrome has been the subject of intensive study and experimentation in recent decades since it is responsible for the outcome of several clinical entities, such as major hepatic resections and liver transplantation. In addition to the organ's post reperfusion injury, this syndrome appears to play a central role in the dysfunction of distant tissues and systems. Thus, continuous research should be directed toward finding effective therapeutic options to improve the outcome and reduce the postoperative morbidity and mortality rates. Treprostinil is a synthetic analog of prostaglandin I2, and its experimental administration has shown encouraging results. It has already been approved by the Food and Drug Administration in the United States for pulmonary arterial hypertension and has been used in liver transplantation, where preliminary encouraging results showed its safety and feasibility by using continuous intravenous administration at a dose of 5 ng/kg/min. Treprostinil improves renal and hepatic function, diminishes hepatic oxidative stress and lipid peroxidation, reduces hepatictoll-like receptor 9 and inflammation, inhibits hepatic apoptosis and restores hepatic adenosine triphosphate (ATP) levels and ATP synthases, which is necessary for functional maintenance of mitochondria. Treprostinil exhibits vasodilatory properties and antiplatelet activity and regulates proinflammatory cytokines; therefore, it can potentially minimize ischemia-reperfusion injury. Additionally, it may have beneficial effects on cardiovascular parameters, and much current research interest is concentrated on this compound.

Inhaled therapies targeting prostacyclin pathway in pulmonary hypertension due to COPD: systematic review.

Pulmonary hypertension due to chronic obstructive pulmonary disease (COPD) and interstitial lung disease (ILD) is classified as group 3 pulmonary hypertension. Inhaled treprostinil, a prostaglandin I2 analogue also known as prostacyclin, has recently been approved as a first drug for patients with pulmonary hypertension secondary to ILD. However, due to a lack of evidence, no therapies are currently approved for those with COPD-associated pulmonary hypertension. Thus, this systematic review aims to summarise the current evidence to assess the impact of inhaled prostaglandin I2 analogue use on the pulmonary hemodynamics, exercise function, lung function, and gas exchange in patients with pulmonary hypertension due to COPD. We systematically searched the electronic databases of Medline, Embase, Scopus and Cochrane from inception to 1 February 2023. Studies of adult patients with a confirmed diagnosis of COPD-associated pulmonary hypertension who received inhaled drugs targeting the prostacyclin pathway were included in the systematic review. Case reports, systematic reviews, conference abstracts with no full text, non-full-text articles, non-English manuscripts and book chapters were excluded from this systematic review. A risk-of-bias assessment was carried out for the studies included in this review, using two different Cochrane risk-of-bias tools for randomised and non-randomised clinical trials. A total of four studies met our inclusion criteria and were included in this systematic review. The results of one prospective clinical trial showed an improvement in the pulmonary hemodynamics (e.g., cardiac index, cardiac output and mean pulmonary artery pressure) in response to inhaled prostacyclin use in patients with pulmonary hypertension secondary to COPD. However, the severity of dyspnoea, lung function, exercise capacity and gas exchange were not affected when inhaled prostacyclin was used for patients with COPD-related pulmonary hypertension. This systematic review demonstrated that although inhaled prostacyclin does not seem to improve COPD-related outcomes (e.g., lung function and exercise capacity), short-term use of inhaled prostacyclin has the potential to reduce mean pulmonary artery pressure and pulmonary vascular resistance without impairing ventilation-perfusion mismatch. Further studies with larger sample sizes are warranted. CRD42022372803, https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=372803.

Iloprost for the treatment of frostbite: a scoping review

ABSTRACT We performed a scoping review to identify the extent of the literature describing the use of iloprost in the treatment of frostbite. Iloprost is a stable synthetic analog of prostaglandin I2. As a potent inhibitor of platelet aggregation and vasodilator, it has been used to address the post-rewarming reperfusion injury in frostbite. The search using iloprost and frostbite as key words and MeSH terms yielded 200 articles. We included in our review the literature examining iloprost for the treatment of frostbite in humans in the form of primary research, conference proceedings and abstracts. Twenty studies published from 1994 to 2022 were selected for analysis. The majority were retrospective case series consisting of a homogeneous population of mountain sport enthusiasts. A total of 254 patients and over 1000 frostbitten digits were included among the 20 studies. The larger case series demonstrated a decrease in amputation rates relative to untreated patients. Primary gaps in the literature include a paucity of randomised trials and relatively limited study populations to date. While the case evidence is promising, a multi-centre collaboration would be crucial to adequately power prospective randomised studies to definitively determine if iloprost has a role in the treatment of frostbite.

ODP484 Hyperthyroidism During Prostaglandin I2 Treatment in Pulmonary Hypertension and Its Molecular Mechanism

Abstract Continuous intravenous infusion of prostaglandin I2 (PGI2) analog, epoprostenol, has improved the survival rate for severe pulmonary hypertension, but longer treatment with PGI2 sometimes occurs hyperthyroidism. For the hyperthyroidism during PGI2 treatment, two molecular mechanisms are speculated; the direct effect of PGI2 on thyroid follicular cells via PGI2 receptor which is coupled with G-protein alpha subunit like TSH receptor, and the indirect effect of PGI2 on activated T helper 17 cells which are associated with autoimmune disease (1). Here, we experienced three different cases of hyperthyroidism during PGI2 treatment in pulmonary hypertension. In case 1, epoprostenol had been administered intravenously for about ten months before the onset of hyperthyroidism. TSAb became positive (591%) and technetium uptake was elevated (4.7%), which were similar to the typical observations in Grave's disease. Total thyroidectomy was needed to control the thyroid function in case 1. In case 2, no thyroid antibody was detected and technetium uptake was almost vanished, as in the destructive thyroiditis. The thyroid function eventually normalized without any intervention. In case 3, hyperthyroidism occurred during oral PGI2 analog selexipag administration, but no evidence of Grave's disease or destructive thyroiditis was observed. Hyperthyroidism was declined when the dose of selexipag was reduced. To investigate the molecular mechanism underlying each case, we added the drugs which were used in each case on a thyroid follicular cell line, FRTL5. The thyroid tissue which was resected in case 1 and FRTL5 cells expressed PGI2 receptors in immunohistochemistry and immunofluorescence study. Human thyrotropin alpha (TSH) and epoprostenol elevated the intracellular cyclic AMP (cAMP) in FRTL5 (1.33 fold and 1.20 fold each, P&amp;lt;0. 05, n=3), but the other PGI2 analogs and the other drugs for pulmonary hypertension didn't change the cAMP in FRTL5. The gene expression level of Na/I symporter was up-regulated only by TSH (2.39 fold, P=0. 02, n=3), but not by PGI2 analogs in qPCR study. It is suggested that PGI2 increases the intracellular cAMP in thyroid follicular cells, but does not cause the same genetic changes as TSH. In conclusion, PGI2 analog may not directly affect the thyroid hormone synthesis in follicular cells, but further analysis is needed to elucidate the molecular mechanism underlying hyperthyroidism during PGI2 analog treatment. Reference: (1) Satoh et al.,Endocrine Journal 2017,64(12),1173-1180 Presentation: No date and time listed

Prostaglandin I2 signaling licenses Treg suppressive function and prevents pathogenic reprogramming.

Tregs restrain both the innate and adaptive immune systems to maintain homeostasis. Allergic airway inflammation, characterized by a Th2 response that results from a breakdown of tolerance to innocuous environmental antigens, is negatively regulated by Tregs. We previously reported that prostaglandin I2 (PGI2) promoted immune tolerance in models of allergic inflammation; however, the effect of PGI2 on Treg function was not investigated. Tregs from mice deficient in the PGI2 receptor IP (IP KO) had impaired suppressive capabilities during allergic airway inflammatory responses compared with mice in which PGI2 signaling was intact. IP KO Tregs had significantly enhanced expression of immunoglobulin-like transcript 3 (ILT3) compared with WT Tregs, which may contribute to the impairment of the IP KO Treg's ability to suppress Th2 responses. Using fate-mapping mice, we reported that PGI2 signaling prevents Treg reprogramming toward a pathogenic phenotype. PGI2 analogs promoted the differentiation of naive T cells to Tregs in both mice and humans via repression of β-catenin signaling. Finally, a missense variant in IP in humans was strongly associated with chronic obstructive asthma. Together, these data support that PGI2 signaling licenses Treg suppressive function and that PGI2 is a therapeutic target for enhancing Treg function.

PGI2 Inhibits Intestinal Epithelial Permeability and Apoptosis to Alleviate Colitis.

Background & AimsInflammatory bowel diseases (IBDs) that encompass both ulcerative colitis and Crohn’s disease are a major public health problem with an etiology that has not been fully elucidated. There is a need to improve disease outcomes and preventive measures by developing new effective and lasting treatments. Although polyunsaturated fatty acid metabolites play an important role in the pathogenesis of several disorders, their contribution to IBD is yet to be understood.MethodsPolyunsaturated fatty acids metabolite profiles were established from biopsy samples obtained from Crohn’s disease, ulcerative colitis, or control patients. The impact of a prostaglandin I2 (PGI2) analog on intestinal epithelial permeability was tested in vitro using Caco-2 cells and ex vivo using human or mouse explants. In addition, mice were treated with PGI2 to observe dextran sulfate sodium (DSS)-induced colitis. Tight junction protein expression, subcellular location, and apoptosis were measured in the different models by immunohistochemistry and Western blotting.ResultsA significant reduction of PGI2 in IBD patient biopsies was identified. PGI2 treatment reduced colonic inflammation, increased occludin expression, decreased caspase-3 cleavage and intestinal permeability, and prevented colitis development in DSS-induced mice. Using colonic explants from mouse and human control subjects, the staurosporine-induced increase in paracellular permeability was prevented by PGI2. PGI2 also induced the membrane location of occludin and reduced the permeability observed in colonic biopsies from IBD patients.ConclusionsThe present study identified a PGI2 defect in the intestinal mucosa of IBD patients and demonstrated its protective role during colitis.

Prostaglandin I2 (PGI2) inhibits Brucella abortus internalization in macrophages via PGI2 receptor signaling, and its analogue affects immune response and disease outcome in mice

To date, the implications of prostaglandin I2 (PGI2), a prominent lipid mediator for modulation of immune responses, has not been clearly understood in Brucella infection. In this study, we found that cyclooxygenase-2 (COX-2) was significantly expressed in both infected bone marrow-derived macrophages (BMMs) and RAW 264.7 cells. Prostaglandin I2 synthase (PTGIS) expression was not significantly changed, and PGI2receptor (PTGIR) expression was downregulated in BMMs but upregulated in RAW 264.7 macrophages at late infection. Here, we presented that PGI2, a COX-derived metabolite, was produced by macrophages during Brucella infection and its production was regulated by COX-2 and IL-10. We suggested that PGI2 and selexipag, a potent PGI2 analogue, inhibited Brucella internalization through IP signaling which led to down-regulation of F-actin polymerization and p38α MAPK activity. Administration with selexipag suppressed immune responses and resulted in a notable reduction in bacterial burden in spleen of Brucella-challenged mice. Taken together, our study is the first to characterize PGI2 synthesis and its effect in evasion strategy of macrophages against Brucella infection.

PGI2 Analog Attenuates Salt-Induced Renal Injury through the Inhibition of Inflammation and Rac1-MR Activation.

Renal inflammation is known to be involved in salt-induced renal damage, leading to end-stage renal disease. This study aims to evaluate the role of inflammation in anti-inflammatory and renoprotective effects of beraprost sodium (BPS), a prostaglandin I2 (PGI2) analog, in Dahl salt-sensitive (DS) rats. Five-week-old male DS rats were fed a normal-salt diet (0.5% NaCl), a high-salt diet (8% NaCl), or a high-salt diet plus BPS treatment for 3 weeks. BPS treatment could inhibit marked proteinuria and renal injury in salt-loaded DS rats with elevated blood pressure, accompanied by renal inflammation suppression. Notably, high salt increased renal expression of active Rac1, followed by increased Sgk1 expressions, a downstream molecule of mineralocorticoid receptor (MR) signal, indicating salt-induced activation of Rac1-MR pathway. However, BPS administration inhibited salt-induced Rac1-MR activation as well as renal inflammation and damage, suggesting that Rac1-MR pathway is involved in anti-inflammatory and renoprotective effects of PGI2. Based upon Rac1 activated by inflammation, moreover, BPS inhibited salt-induced activation of Rac1-MR pathway by renal inflammation suppression, resulting in the attenuation of renal damage in salt-loaded DS rats. Thus, BPS is efficacious for the treatment of salt-induced renal injury.

Loss of DP1 Aggravates Vascular Remodeling in Pulmonary Arterial Hypertension via mTORC1 Signaling.

Rationale: Vascular remodeling, including smooth muscle cell hypertrophy and proliferation, is the key pathological feature of pulmonary arterial hypertension (PAH). Prostaglandin I2 analogs (beraprost, iloprost, and treprostinil) are effective in the treatment of PAH. Of note, the clinically favorable effects of treprostinil in severe PAH may be attributable to concomitant activation of DP1 (D prostanoid receptor subtype 1).Objectives: To study the role of DP1 in the progression of PAH and its underlying mechanism.Methods: DP1 levels were examined in pulmonary arteries of patients and animals with PAH. Multiple genetic and pharmacologic approaches were used to investigate DP1-mediated signaling in PAH.Measurements and Main Results: DP1 expression was downregulated in hypoxia-treated pulmonary artery smooth muscle cells and in pulmonary arteries from rodent PAH models and patients with idiopathic PAH. DP1 deletion exacerbated pulmonary artery remodeling in hypoxia-induced PAH, whereas pharmacological activation or forced expression of the DP1 receptor had the opposite effect in different rodent models. DP1 deficiency promoted pulmonary artery smooth muscle cell hypertrophy and proliferation in response to hypoxia via induction of mTORC1 (mammalian target of rapamycin complex 1) activity. Rapamycin, an inhibitor of mTORC1, alleviated the hypoxia-induced exacerbation of PAH in DP1-knockout mice. DP1 activation facilitated raptor dissociation from mTORC1 and suppressed mTORC1 activity through PKA (protein kinase A)-dependent phosphorylation of raptor at Ser791. Moreover, treprostinil treatment blocked the progression of hypoxia-induced PAH in mice in part by targeting the DP1 receptor.Conclusions: DP1 activation attenuates hypoxia-induced pulmonary artery remodeling and PAH through PKA-mediated dissociation of raptor from mTORC1. These results suggest that the DP1 receptor may serve as a therapeutic target for the management of PAH.

Iloprost-treated dendritic cells promote antigen-specific regulatory T cell differentiation in mice

Abstract Iloprost, a stable prostaglandin I2 (PGI2) analog, can inhibit allergic inflammation in an OVA-induced asthma model via inhibition of airway dendritic cell (DC) function. However, the underlying mechanism of PGI2 signaling-mediated immunosuppression remains unclear. This study explored whether iloprost-treated DCs can suppress inflammation by promoting antigen-specific regulatory T cell (Treg) differentiation. We established an allergic lung inflammation model using a hydrogel biomaterial delivery system and observed that iloprost significantly suppressed OVA-induced Th2 lung inflammation and increased the frequency of OVA-specific Tregs in vivo. We further observed that iloprost-treated DCs displayed tolerogenic characteristics, including low inflammatory cytokine (IL-12p70, TNF-α, IL-6, IL-23) expression levels, high anti-inflammatory cytokine (IL-10) production, and a semimature phenotype. In addition, iloprost-treated DCs increased OVA-specific CD4+Foxp3+ T cell differentiation from naïve T cells in vitro and in vivo. Blocking experiments showed that iloprost-treated DCs promoted Treg differentiation, at least in part, through PD-L1. Furthermore, iloprost treatment suppressed DC-mediated airway inflammation and increased the frequency of OVA-specific Tregs through PD-L1 in vivo. Taken together, these results show that PGI2 signaling in DCs may lead to immune tolerance, suggesting that the PGI2 analog has the potential to be applied therapeutically for tolerogenic DC immunotherapy in autoimmune diseases or allergic asthma.

Iloprost inhibits acute allergic nasal inflammation by GATA3 -ILC2 pathway in mice

BackgroundAcute allergic nasal inflammation is very common in the clinical allergic diseases, Prostaglandin I2 (PGI2) has been found to effective in combating inflammation. Iloprost, as an analog of PGI2, whose role and mechanisms in the acute allergic nasal inflammation remains unclear. It’s necessary to elucidate the efficacy and potential mechanism of Iloprost in acute allergic nasal inflammation. Methods36 female mice were randomly divided into DMSO group, IL 33 group, Iloprost group and IL 33+Iloprost intervention group. Mice were stimulated with IL 33 to construct an acute allergic nasal inflammation model. Hematoxylin and eosin (HE) and periodic acid Schiff reagent (PAS) staining, flow cytometry, Real time PCR and Enzyme linked immunosorbent assay (ELISA) was used to identify the role of Iloprost in acute allergic nasal inflammation. The comparison between multiplied groups was analyzed by ANOVA, and the Bonferroni method was used for further comparison of two groups. ResultsCompared with IL 33 group, the inflammatory cell infiltration around the trachea and blood vessels of the lung tissue in the IL 33+ Iloprost group were reduced; goblet cell hyperplasia was observed in airway mucosa of IL 33 group, and the mucus secretion increased; the percentage of EOS and ILC2s in the BALF and lung single cell suspensions in IL 33+ Iloprost group were statistically lower than that of IL 33 group (p < 0.05); The mRNA expression levels of IL 5, IL 13, ST2 and GATA3 in the lung tissue of IL 33 group were higher than those in DMSO group (p < 0.05). After intervention with Iloprost, the mRNA expression levels of IL 5, IL 13, GATA3 and ST2 were lower than those in IL 33 group (p < 0.05) ConclusionIloprost may potentially inhibit the proliferation and activation of innate lymphoid cells 2 in mice with acute allergic inflammation, which maybe an effective option for the treatment of acute allergic inflammation related diseases.

Dendritic cells treated with a prostaglandin I2 analog, iloprost, promote antigen-specific regulatory T cell differentiation in mice

Iloprost, a stable prostaglandin I2 (PGI2) analog, can inhibit allergic inflammation in an ovalbumin (OVA)-induced asthma model via inhibition of airway dendritic cell (DC) function. However, the underlying mechanism of PGI2 signaling-mediated immunosuppression remains unclear. This study explored whether iloprost-treated DCs can suppress inflammation by promoting antigen-specific regulatory T cell (Treg) differentiation through PGI2-G-protein-coupled receptor (IP). We established an allergic lung inflammation model using a hydrogel biomaterial delivery system and observed that iloprost significantly suppressed OVA-induced Th2 lung inflammation and increased the frequency of OVA-specific Tregs in vivo. We further observed that iloprost-treated DCs displayed tolerogenic characteristics, including low inflammatory cytokine (IL-12, TNF-α, IL-6, IL-23) expression levels, high anti-inflammatory cytokine (IL-10) production, and a semimature phenotype. In addition, iloprost-treated DCs increased OVA-specific CD4+Foxp3+ T cell differentiation from naïve T cells in an IP-dependent pathway in vitro and in vivo. Blocking experiments showed that iloprost-treated DCs promoted Treg differentiation, at least in part, through programmed death ligand 1 (PD-L1), whereas iloprost-induced PD-L1 expression in DCs was through the IP receptor. Furthermore, iloprost treatment suppressed DC-mediated airway inflammation and increased the frequency of OVA-specific Tregs through PD-L1 in vivo. Taken together, these results show that PGI2-IP signaling mediated by iloprost in DCs may lead to immune tolerance, suggesting that the PGI2 analog has the potential to be applied therapeutically for tolerogenic DC immunotherapy in autoimmune diseases or allergic asthma.

Thyroid Dysfunction in Patients with Pulmonary Artery Hypertension (PAH): The Effect of Therapies Affecting the Prostanoid Pathway.

Epoprostenol, a synthetic prostaglandin I2 (PGI2) analog, has been the mainstay of treatment for severe pulmonary arterial hypertension (PAH) for the last two decades. Treprostinil, another synthetic prostaglandin analog, and selexipag, an oral selective Inositol Phosphate (IP) prostacyclin receptor agonist, have also been approved for treatment of PAH. Prostacyclin and its analogs cause a variety of side effects in patients with PAH; however, thyroid dysfunction is rarely reported. After treating an index case of thyroid dysfunction occurring after initiation of epoprostenol, we reviewed our databases of PAH patients treated with epoprostenol, treprostinil or selexipag to identify the occurrence of this association. We identified six cases of thyroid dysfunction in our cohort: five after initiation of an intravenous prostacyclin (epoprostenol) and one after initiation of an oral prostacyclin receptor agonist (selexipag). Four of the patients presented with hyperthyroidism and two with a large autoimmune goiter. Graves' disease was seen in three patients, Hashimoto's disease in two patients and thyrotoxicosis in one patient. Therapy with medications targeting the prostacyclin pathway is a potential risk factor for the development of symptomatic thyroid disease.

Prostaglandin I2 in the Endosteal Bone Marrow Niche As a Novel Regulator of Hematopoietic Stem Cells

Haematopoietic stem cells (HSCs) are regulated by their immediate microenvironment or niche. The most potent functional HSCs are enriched at the endosteum near the bone, which comprises ~10% of total bone marrow (BM). To identify novel niche factors that regulate HSCs, we performed a gene expression microarray seeking genes that were >2-fold overexpressed in the endosteal BM relative to the central BM. In this screen, we uncovered known essential HSC niche factors overexpressed in the endosteal BM such as Scf, Cxcl12, and Angpt1, which validated our approach.Among the genes overexpressed in the endosteal BM, prostaglandin I2 (PGI2) synthase (Ptgis) was one of the highest enriched genes in the endosteum (>10-fold by qRT-PCR, p<0.001). Within the endosteal BM, Ptgis was most abundantly expressed by osteoblasts, followed by mesenchymal stem/progenitor cells and endothelial cells. Ptgis is the sole enzyme responsible for biosynthesis of PGI2, originally discovered as a potent anti-thrombotic and vasodilating agent. PGI2 has no reported roles in HSC regulation in the BM and was chosen as candidate niche factor for further investigation. Due to the extreme lability of PGI2, we employed a clinically approved PGI2 analogue iloprost for all subsequent experiments.In initial experiments where we cultured fluorescence activated cell sorted (FACS) BM lineage- Kit+ Sca-1- (LKS+) haematopoietic stem and progenitor cells (HSPCs) for 7 days in serum free conditions, we found iloprost treatment potently reduced proliferation and differentiation compared to vehicle controls, assessed by flow cytometry phenotyping (p<0.0001). To determine whether iloprost treatment alters HSC function, we pulse treated whole BM cells with iloprost for 1 hour before competitive transplant and found iloprost pulse-treatment resulted in 14-fold increased multilineage reconstitution potential (p<0.05). This suggests that PGI2 enhances HSC function by dampening differentiation.We next sought to determine whether iloprost affects HSC function in vivo. In steady state, low dose 0.1mg/kg iloprost administration to mice for 15 days did not alter BM HSPC phenotypes by flow cytometry nor HSC reconstitution potential in competitive transplants compared to vehicle controls suggesting PGI2 does not alter HSC function in homeostasis. To further test the effect of PGI2 following stress, mice were sub-lethally (6.5 Gy) irradiated or administered pro-inflammatory granulocyte colony stimulating factor (G-CSF) for 3 days. We found low dose iloprost administration partially rescued BM HSC reconstitution potential 21 days following irradiation (p<0.05) or 3 days following G-CSF administration (p<0.01). These data suggest that PGI2 protects HSC from stress.To understand the extrinsic mechanisms through which PGI2 regulates HSC in the BM following stress, we performed a HSC homing assay using naïve donors transplanted into 2-day G-CSF administered recipients. Analysis of HSPC homing to the BM at 4 hours post-transplantation revealed ~4-fold greater proportion of LKS+ HSPC homing to the BM of iloprost co-administered recipients compared to vehicle controls (p<0.01). We assessed mRNA expression of essential HSC niche factors in the BM of 2-day G-CSF-administered mice and found that G-CSF administration decreased Scf and Cxcl12 expression, which were both partially rescued with iloprost co-administration (p<0.05). Together the data suggest that preservation of the BM niche function is one of the mechanisms through which PGI2 protects HSC during stress.In summary, we have identified PGI2 as a novel HSC niche factor abundant in the endosteal BM. PGI2 analogues like Iloprost are well-tolerated and used clinically to treat vascular diseases such as pulmonary arterial hypertension and Raynaud's phenomenon. Our research suggests that PGI2 analogues can be rapidly repurposed in the clinic to improve HSC transplant outcomes and protect against BM failure following acute stressors such as accidental irradiation or inflammation. DisclosuresLevesque:GlycoMimetics: Equity Ownership, Patents & Royalties.

Endogenous PGI2 signaling through IP inhibits neutrophilic lung inflammation in LPS-induced acute lung injury mice model

Endogenous prostaglandin I2 (PGI2) has inhibitory effects on immune responses against pathogens or allergens; however, the immunomodulatory activity of endogenous PGI2 signaling in endotoxin-induced inflammation is unknown. To test the hypothesis that endogenous PGI2 down-regulates endotoxin-induced lung inflammation, C57BL/6 wild type (WT) and PGI2 receptor (IP) KO mice were challenged intranasally with LPS. Urine 6-keto-PGF1α, a stable metabolite of PGI2, was significantly increased following the LPS-challenge, suggesting that endogenous PGI2 signaling modulates the host response to LPS-challenge. IPKO mice had a significant increase in neutrophils in the BAL fluid as well as increased proteins of KC, LIX, and TNF-α in lung homogenates compared with WT mice. In contrast, IL-10 was decreased in LPS-challenged IPKO mice compared with WT mice. The PGI2 analog cicaprost significantly decreased LPS-induced KC, and TNF-α, but increased IL-10 and AREG in bone marrow-derived dendritic cells (BMDCs) and bone marrow-derived macrophages (BMMs) compared with vehicle-treatment. These results indicated that endogenous PGI2 signaling attenuated neutrophilic lung inflammation through the reduced inflammatory cytokine and chemokine and enhanced IL-10.

Effectiveness of beraprost sodium in maintaining vascular access patency in patients on hemodialysis.

Hemodialysis vascular access dysfunction, mostly attributed to neointimal hyperplasia, is a major cause of morbidity and hospitalization in patients on hemodialysis. It has been reported that prostaglandin I2 has pleiotropic effects including anti-platelet, vasodilating, anti-inflammatory, and anti-atherogenic properties. In addition, several studies have shown that prostaglandin I2 can inhibit neointimal formation after vascular injury. This study aimed to investigate the effects of beraprost sodium, an oral synthetic analog of prostaglandin I2, on vascular access patency in patients on hemodialysis who experienced primary hemodialysis vascular access failure. Fifty-five patients with end-stage renal disease who were on hemodialysis were prospectively selected for this study. Twenty-three patients were assigned to be treated with 120µg/day of beraprost sodium, while remaining patients (n=32) were assigned to a control group. The primary outcome was primary unassisted vascular access patency at 2years. The incidence of primary unassisted patency at 2years was 83% in the beraprost sodium group and 38% in the control group (p=0.001). Analysis of covariables indicated that this effect occurred mainly as a result of beraprost sodium administration. No life-threatening adverse event or severe bleeding was recorded in any of the groups. Our data indicated that an oral prostaglandin I2 analog, beraprost sodium, is effective and safe for the maintenance of vascular access patency in patients on hemodialysis with primary vascular access failure.

Asthma causes inflammation of human pulmonary arteries and decreases vasodilatation induced by prostaglandin I2 analogs

ABSTRACTObjective: Asthma is a chronic inflammatory disease associated with increased cardiovascular events. This study assesses the presence of inflammation and the vascular reactivity of pulmonary arteries in patients with acute asthma. Methods: Rings of human pulmonary arteries obtained from non-asthmatic and asthmatic patients were set up in organ bath for vascular tone monitoring. Reactivity was induced by vasoconstrictor and vasodilator agents. Protein expression of inflammatory markers was detected by western blot. Prostanoid releases and cyclic adenosine monophosphate (cAMP) levels were quantified using specific enzymatic kits. Results: Protein expression of cluster of differentiation 68, intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and cyclooxygenase-2 was significantly increased in arteries obtained from asthmatic patients. These effects were accompanied by an alteration of vasodilatation induced by iloprost and treprostinil, a decrease in cAMP levels and an increase in prostaglandin (PG) E2 and PGI2 synthesis. The use of forskolin (50 µmol/L) has restored the vasodilatation and cAMP release. No difference was observed between the two groups in reactivity induced by norepinephrine, angiotensin II, PGE2, KCl, sodium nitroprusside, and acetylcholine. Conclusion: Acute asthma causes inflammation of pulmonary arteries and decreases vasodilation induced by PGI2 analogs through the impairment of cAMP pathway.

Distal vessel stiffening is an early and pivotal mechanobiological regulator of vascular remodeling and pulmonary hypertension.

Pulmonary arterial (PA) stiffness is associated with increased mortality in patients with pulmonary hypertension (PH); however, the role of PA stiffening in the pathogenesis of PH remains elusive. Here, we show that distal vascular matrix stiffening is an early mechanobiological regulator of experimental PH. We identify cyclooxygenase-2 (COX-2) suppression and corresponding reduction in prostaglandin production as pivotal regulators of stiffness-dependent vascular cell activation. Atomic force microscopy microindentation demonstrated early PA stiffening in experimental PH and human lung tissue. Pulmonary artery smooth muscle cells (PASMC) grown on substrates with the stiffness of remodeled PAs showed increased proliferation, decreased apoptosis, exaggerated contraction, enhanced matrix deposition, and reduced COX-2-derived prostanoid production compared with cells grown on substrates approximating normal PA stiffness. Treatment with a prostaglandin I2 analog abrogated monocrotaline-induced PA stiffening and attenuated stiffness-dependent increases in proliferation, matrix deposition, and contraction in PASMC. Our results suggest a pivotal role for early PA stiffening in PH and demonstrate the therapeutic potential of interrupting mechanobiological feedback amplification of vascular remodeling in experimental PH.