The Role of Bioactive Lipids in Stem Cell Mobilization and Homing: Novel Therapeutics for Myocardial Ischemia

Despite significant advances in medical therapy and interventional strategies, the prognosis of millions of patients with acute myocardial infarction (AMI) and ischemic heart disease (IHD) remains poor. Currently, short of heart transplantation with all of its inherit limitations, there are no available treatment strategies that replace the infarcted myocardium. It is now well established that cardiomyocytes undergo continuous renewal, with contribution from bone marrow (BM)-derived stem/progenitor cells (SPCs). This phenomenon is upregulated during AMI by initiating multiple innate reparatory mechanisms through which BMSPCs are mobilized towards the ischemic myocardium and contribute to myocardial regeneration. While a role for the SDF-1/CXCR4 axis in retention of BMSPCs in bone marrow is undisputed, its exclusive role in their mobilization and homing to a highly proteolytic microenvironment, such as the ischemic/infarcted myocardium, is currently being challenged. Recent evidence suggests a pivotal role for bioactive lipids in the mobilization of BMSPCs at the early stages following AMI and their homing towards ischemic myocardium. This review highlights the recent advances in our understanding of the mechanisms of stem cell mobilization, provides newer evidence implicating bioactive lipids in BMSPC mobilization and differentiation, and discusses their potential as therapeutic agents in the treatment of IHD

Sphingosine-1-Phosphate-Mediated Mobilization of Hematopoietic Stem/Progenitor Cells During Intravascular Hemolysis Requires Attenuation of SDF-1-CXCR4 Retention Signaling in Bone Marrow

Sphingosine-1-phosphate (S1P) is a crucial chemotactic factor in peripheral blood (PB) involved in the mobilization process and egress of hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM). Since S1P is present at high levels in erythrocytes, one might assume that, by increasing the plasma S1P level, the hemolysis of red blood cells would induce mobilization of HSPCs. To test this assumption, we induced hemolysis in mice by employing phenylhydrazine (PHZ). We observed that doubling the S1P level in PB from damaged erythrocytes induced only a marginally increased level of mobilization. However, if mice were exposed to PHZ together with the CXCR4 blocking agent, AMD3100, a robust synergistic increase in the number of mobilized HSPCs occurred. We conclude that hemolysis, even if it significantly elevates the S1P level in PB, also requires attenuation of the CXCR4-SDF-1 axis-mediated retention in BM niches for HSPC mobilization to occur. Our data also further confirm that S1P is a major chemottractant present in plasma and chemoattracts HSPCs into PB under steady-state conditions. However, to egress from BM, HSPCs first have to be released from BM niches by blocking the SDF-1-CXCR4 retention signal

33354 Efficacy of apremilast in patients with mild to moderate psoriasis assessed by the physician global assessment and body surface area composite tool: Post hoc analysis from ADVANCE

Background: In ADVANCE (NCT03721172), apremilast 30 mg BID (APR) demonstrated significantly greater sPGA response vs. PBO at Week 16 (22% vs. 4%; P \u3c.0001) in patients with mild-to-moderate psoriasis. The Physician Global Assessment and Body Surface Area Composite Tool (PGA × BSA) is a simple, sensitive measure of psoriasis severity for patients with BSA\u3c10%. We performed a post hoc analysis of the efficacy results from ADVANCE using the PGA×BSA. Methods: This current post hoc analysis included all randomized patients. Missing data were imputed by multiple imputation. PGAxBSA-50/75/90 was 50%, 75% and 90% improvement in PGAxBSA from baseline. Results: Of 595 randomized patients (APR: 297; PBO: 298), baseline characteristics were similar for mean BSA (APR: 6.4; PBO: 6.3), sPGA score 2 (APR 31%; PBO: 31%), sPGA score 3 (APR: 69%; PBO: 70%), and mean PGA×BSA (APR: 17.6; PBO: 17.5). At Week 16, significantly more patients achieved PGAxBSA-50/75/90 response with APR vs. PBO: PGA×BSA-50, 67% vs. 26% (P \u3c.0001), difference 41%, 95%CI (32.7,48.5) PGA×BSA-75, 46% vs. 13% (P \u3c.0001), difference 33%, 95%CI (25.8,40.2) PGA×BSA-90, 27% vs. 3% (P \u3c.0001), difference 24%, 95%CI (18.3,29.6) A significant improvement from baseline at Week 16 in PGA×BSA was observed with APR vs PBO: Mean % change (SE) in PGA×BSA, -51.8 (4.2) vs. 1.97 (4.3); difference (95%CI): -53.8 (-65.4, -42.2), P \u3c.0001. Conclusions: The PGA×BSA Composite Tool appeared to be a sensitive and a relevant measure for mild-to-moderate psoriasis that showed significantly greater treatment differences at 50%, 75%, and 90% response thresholds at Week 16 with APR compared with PBO in ADVANCE

Sphingosine-1-phosphate-Mediated Mobilization of Hematopoietic Stem/Progenitor Cells during Intravascular Hemolysis Requires Attenuation of SDF-1-CXCR4 Retention Signaling in Bone Marrow

Sphingosine-1-phosphate (S1P) is a crucial chemotactic factor in peripheral blood (PB) involved in the mobilization process and egress of hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM). Since S1P is present at high levels in erythrocytes, one might assume that, by increasing the plasma S1P level, the hemolysis of red blood cells would induce mobilization of HSPCs. To test this assumption, we induced hemolysis in mice by employing phenylhydrazine (PHZ). We observed that doubling the S1P level in PB from damaged erythrocytes induced only a marginally increased level of mobilization. However, if mice were exposed to PHZ together with the CXCR4 blocking agent, AMD3100, a robust synergistic increase in the number of mobilized HSPCs occurred. We conclude that hemolysis, even if it significantly elevates the S1P level in PB, also requires attenuation of the CXCR4-SDF-1 axis-mediated retention in BM niches for HSPC mobilization to occur. Our data also further confirm that S1P is a major chemottractant present in plasma and chemoattracts HSPCs into PB under steady-state conditions. However, to egress from BM, HSPCs first have to be released from BM niches by blocking the SDF-1-CXCR4 retention signal

33356 A multinational chart review to examine gastrointestinal symptoms and their management in patients treated with apremilast for plaque psoriasis

Background: Diarrhea and nausea are the most common adverse events observed in phase 3 clinical trials and real-world studies of apremilast, an oral phosphodiesterase-4 inhibitor indicated for moderate-to-severe plaque psoriasis. Methods: A retrospective chart review was conducted between June and November 2020 in the United States (US) and France among patients with moderate psoriasis experiencing gastrointestinal (GI) symptoms within 3 months of initiating apremilast. Results: Dermatologists in US (200) and in France (52) abstracted patient charts (US: 494, France: 128). The following GI symptoms were reported: ‒diarrhea (US: 67% [331/494]; France: 76% [97/128]) with median time from onset to resolution/improvement of 26 days (US) and 21 days (France) ‒nausea (US: 52% [255/494]; France: 34% [44/128]) with median time from onset to resolution/improvement of 21 days (US) and 24 days (France). Management strategies for diarrhea included pharmacologic (loperamide/bismuth subsalicylate/racecadotril) with or without nonpharmacologic (dietary modifications, taking with food)/fiber (US: 30% [99/331], France: 41% [40/97]) and nonpharmacologic only (US: 32% [105/331], France: 27% [26/97]). Management strategies for nausea included pharmacologic (diphenhydramine/metoclopramide/metopimazine) with or without nonpharmacologic (dietary modifications, taking with food, avoidance of vigorous activity) (US: 5% [14/255], France: 30% [13/44]) and nonpharmacologic only (US: 58% [147/255], France: 36% [16/44]). Resolution/improvement of GI symptoms was observed in patients who used pharmacologic strategies and nonpharmacologic strategies. Conclusions: Recommendations to manage diarrhea and nausea after apremilast initiation with pharmacologic or non-pharmacologic strategies were effective and symptoms usually resolved within 3-4 weeks of onset

Coronary Artery Remodeling in a Model of Left Ventricular Pressure Overload is Influenced by Platelets and Inflammatory Cells

Left ventricular hypertrophy (LVH) is usually accompanied by intensive interstitial and perivascular fibrosis, which may contribute to arrhythmogenic sudden cardiac death. The mechanisms underlying the development of cardiac fibrosis are incompletely understood. To investigate the role of perivascular inflammation in coronary artery remodeling and cardiac fibrosis during hypertrophic ventricular remodeling, we used a well-established mouse model of LVH (transverse aortic constriction [TAC]). Three days after pressure overload, macrophages and T lymphocytes accumulated around and along left coronary arteries in association with luminal platelet deposition. Consistent with these histological findings, cardiac expression of IL-10 was upregulated and in the systemic circulation, platelet white blood cell aggregates tended to be higher in TAC animals compared to sham controls. Since platelets can dynamically modulate perivascular inflammation, we investigated the impact of thrombocytopenia on the response to TAC. Immunodepletion of platelets decreased early perivascular T lymphocytes\u27 accumulation and altered subsequent coronary artery remodeling. The contribution of lymphocytes were examined in Rag1(-/-) mice, which displayed significantly more intimal hyperplasia and perivascular fibrosis compared to wild-type mice following TAC. Collectively, our studies support a role of early perivascular accumulation of platelets and T lymphocytes in pressure overload-induced inflammation

Bioactive Lipids and Circulating Progenitor Cells in Patients with Cardiovascular Disease

Bone marrow-derived progenitor cells are mobilized into the peripheral blood after acute myocardial injury and in chronic ischemic heart disease. However, the mechanisms responsible for this mobilization are poorly understood. We examined the relationship between plasma levels of bioactive lipids and number of circulating progenitor cells (CPCs) in patients (N = 437) undergoing elective or emergent cardiac catheterization. Plasma levels of sphingosine-1 phosphate (S1P) and ceramide-1 phosphate (C1P) were quantified using mass spectrometry. CPCs were assessed using flow cytometry. S1P levels correlated with the numbers of CD34+, CD34+/CD133+, and CD34+/CXCR4+ CPCs even after adjustment for potential confounding factors. However, no significant correlation was observed between C1P levels and CPC count. Plasma levels of S1P correlated with the number of CPCs in patients with coronary artery disease, suggesting an important mechanistic role for S1P in stem cell mobilization. The therapeutic effects of adjunctive S1P therapy to mobilize endogenous stem cells need to be investigated

Bioactive Lipids and Cationic Antimicrobial Peptides as New Potential Regulators for Trafficking of Bone Marrow-Derived Stem Cells in Patients with Acute Myocardial Infarction

Acute myocardial infarction (AMI) triggers mobilization of stem cells from bone marrow (BM) into peripheral blood (PB). Based on our observation that the bioactive sphingophospholipids, sphingosine-1 phosphate (S1P), and ceramide-1 phosphate (C1P) regulate trafficking of hematopoietic stem cells (HSCs), we explored whether they also direct trafficking of non-hematopoietic stem cells (non-HSCs). We detected a 3–6-fold increase in circulating CD34+, CD133+, and CXCR4+ lineage-negative (Lin−)/CD45− cells that are enriched in non-HSCs [including endothelial progenitors (EPCs) and very small embryonic-like stem cells (VSELs)] in PB from AMI patients (P\u3c0.05 vs. controls). Concurrently, we measured a 3-fold increase in S1P and C1P levels in plasma from AMI patients. At the same time, plasma obtained at hospital admission and 6 h after AMI strongly chemoattracted human BM-derived CD34+/Lin− and CXCR4+/Lin− cells in Transwell chemotaxis assays. This effect of plasma was blunted after depletion of S1P level by charcoal stripping and was further inhibited by the specific S1P1 receptor antagonist such as W146 and VPC23019. We also noted that the expression of S1P receptor 1 (S1P1), which is dominant in naïve BM, is reduced after the exposure to S1P at concentrations similar to the plasma S1P levels in patients with AMI, thus influencing the role of S1P in homing to the injured myocardium. Therefore, we examined mechanisms, other than bioactive lipids, that may contribute to the homing of BM non-HSCs to the infarcted myocardium. Hypoxic cardiac tissue increases the expression of cathelicidin and β-2 defensin, which could explain why PB cells isolated from patients with AMI migrated more efficiently to a low, yet physiological, gradient of stromal-derived factor-1 in Transwell migration assays. Together, these observations suggest that while elevated S1P and C1P levels early in the course of AMI may trigger mobilization of non-HSCs into PB, cathelicidin and β-2 defensin could play an important role in their homing to damaged myocardium

Sphingosine-1-phosphate-Mediated Mobilization of Hematopoietic Stem/Progenitor Cells during Intravascular Hemolysis Requires Attenuation of SDF-1-CXCR4 Retention Signaling in Bone Marrow

Sphingosine-1-phosphate (S1P) is a crucial chemotactic factor in peripheral blood (PB) involved in the mobilization process and egress of hematopoietic stem/progenitor cells (HSPCs) from bone marrow (BM). Since S1P is present at high levels in erythrocytes, one might assume that, by increasing the plasma S1P level, the hemolysis of red blood cells would induce mobilization of HSPCs. To test this assumption, we induced hemolysis in mice by employing phenylhydrazine (PHZ). We observed that doubling the S1P level in PB from damaged erythrocytes induced only a marginally increased level of mobilization. However, if mice were exposed to PHZ together with the CXCR4 blocking agent, AMD3100, a robust synergistic increase in the number of mobilized HSPCs occurred. We conclude that hemolysis, even if it significantly elevates the S1P level in PB, also requires attenuation of the CXCR4-SDF-1 axismediated retention in BM niches for HSPC mobilization to occur. Our data also further confirm that S1P is a major chemottractant present in plasma and chemoattracts HSPCs into PB under steady-state conditions. However, to egress from BM, HSPCs first have to be released from BM niches by blocking the SDF-1-CXCR4 retention signal