Targeting PDE4B (Phosphodiesterase-4 Subtype B) for Cardioprotection in Acute Myocardial Infarction via Neutrophils and Microcirculation.

BACKGROUND: Timely and complete restoration of blood flow is the most effective intervention for patients with acute myocardial infarction. However, the efficacy is limited by myocardial ischemia-reperfusion (MI/R) injury. PDE4 (phosphodiesterase-4) hydrolyzes intracellular cyclic adenosine monophosphate and it has 4 subtypes A-D. This study aimed to delineate the role of PDE4B (phosphodiesterase-4 subtype B) in MI/R injury. METHODS: Mice were subjected to 30-minute coronary artery ligation, followed by 24-hour reperfusion. Cardiac perfusion was assessed by laser Doppler flow. Vasomotor reactivities were determined in mouse and human coronary (micro-)arteries. RESULTS: Cardiac expression of PDE4B, but not other PDE4 subtypes, was increased in mice following reperfusion. PDE4B was detected primarily in endothelial and myeloid cells of mouse and human hearts. PDE4B deletion strikingly reduced infarct size and improved cardiac function 24-hour or 28-day after MI/R. PDE4B in bone marrow-derived cells promoted MI/R injury and vascular PDE4B further exaggerated this injury. Mechanistically, PDE4B mediated neutrophil-endothelial cell interaction and PKA (protein kinase A)-dependent expression of cell adhesion molecules, neutrophil cardiac infiltration, and release of proinflammatory cytokines. Meanwhile, PDE4B promoted coronary microcirculatory obstruction and vascular permeability in MI/R, without affecting flow restriction-induced thrombosis. PDE4B blockade increased flow-mediated vasodilatation and promoted endothelium-dependent dilatation of coronary arteries in a PKA- and nitric oxide-dependent manner. Furthermore, postischemia administration with piclamilast, a PDE4 pan-inhibitor, improved cardiac microcirculation, suppressed inflammation, and attenuated MI/R injury in mice. Incubation with sera from patients with acute myocardial infarction impaired acetylcholine-induced relaxations in human coronary microarteries, which was abolished by PDE4 inhibition. Similar protection against MI/R-related coronary injury was recapitulated in mice with PDE4B deletion or inhibition, but not with the pure vasodilator, sodium nitroprusside. CONCLUSIONS: PDE4B is critically involved in neutrophil inflammation and microvascular obstruction, leading to MI/R injury. Selective inhibition of PDE4B might protect cardiac function in patients with acute myocardial infarction designated for reperfusion therapy.

Factor XII and prekallikrein promote microvascular inflammation and psoriasis in mice.

BACKGROUND AND PURPOSE: Psoriasis is an autoimmune inflammatory skin disease, featuring microvascular abnormalities and elevated levels of bradykinin. Contact activation of Factor XII can initiate the plasma kallikrein-kinin cascade, producing inflammation and angioedema. The role of Factor XII in psoriasis is unknown. EXPERIMENTAL APPROACH: The effects of deficiency of Factor XII or its enzymatic substrate, prekallikrein, were examined in the imiquimod-induced mouse model of psoriasis. Skin microcirculation was assessed using intravital confocal microscopy and laser Doppler flowmeter. A novel antibody blocking Factor XII activation was evaluated for psoriasis prevention. KEY RESULTS: Expression of Factor XII was markedly up-regulated in human and mouse psoriatic skin. Genetic deletion of Factor XII or prekallikrein, attenuated imiquimod-induced psoriatic lesions in mice. Psoriatic induction increased skin microvascular blood perfusion, causing vasodilation, hyperpermeability and angiogenesis. It also promoted neutrophil-vascular interaction, inflammatory cytokine release and enhanced Factor XII / prekallikrein enzymatic activity with elevated bradykinin. Factor XII or prekallikrein deficiency ameliorated these microvascular abnormalities and abolished bradykinin increase. Antagonism of bradykinin B2 receptors reproduced the microvascular protection of Factor XII / prekallikrein deficiency, attenuated psoriatic lesions, and prevented protection by Factor XII / prekallikrein deficiency against psoriasis. Furthermore, treatment of mice with Factor XII antibody alleviated experimentally induced psoriasis and suppressed microvascular inflammation. CONCLUSION AND IMPLICATIONS: Activation of Factor XII promoted psoriasis via prekallikrein-dependent formation of bradykinin, which critically mediated psoriatic microvascular inflammation. Inhibition of contact activation represents a novel therapeutic strategy for psoriasis.

A single-domain antibody targeting factor XII inhibits both thrombosis and inflammation.

Factor XII (FXII) is the zymogen of the plasma protease FXIIa that activates the intrinsic coagulation pathway and the kallikrein kinin-system. The role of FXII in inflammation has been obscure. Here, we report a single-domain antibody (nanobody, Nb) fused to the Fc region of a human immunoglobulin (Nb-Fc) that recognizes FXII in a conformation-dependent manner and interferes with FXIIa formation. Nb-Fc treatment inhibited arterial thrombosis in male mice without affecting hemostasis. In a mouse model of extracorporeal membrane oxygenation (ECMO), FXII inhibition or knockout reduced thrombus deposition on oxygenator membranes and systemic microvascular thrombi. ECMO increased circulating levels of D-dimer, alkaline phosphatase, creatinine and TNF-α and triggered microvascular neutrophil adherence, platelet aggregation and their interaction, which were substantially attenuated by FXII blockade. Both Nb-Fc treatment and FXII knockout markedly ameliorated immune complex-induced local vasculitis and anti-neutrophil cytoplasmic antibody-induced systemic vasculitis, consistent with selectively suppressed neutrophil migration. In human blood microfluidic analysis, Nb-Fc treatment prevented collagen-induced fibrin deposition and neutrophil adhesion/activation. Thus, FXII is an important mediator of inflammatory responses in vasculitis and ECMO, and Nb-Fc provides a promising approach to alleviate thrombo-inflammatory disorders.

Microsomal prostaglandin E synthase-1 inhibition prevents adverse cardiac remodelling after myocardial infarction in mice.

BACKGROUND AND PURPOSE: Heart failure with reduced ejection fraction (HFrEF) is a major consequence of myocardial infarction (MI). The microsomal prostaglandin E synthase-1 (mPGES-1)/PGE2 pathway has been shown to constrain reperfusion injury after acute myocardial ischaemia. However, it is unknown whether pharmacological inhibition of mPGES-1, a target with lower risk of thrombosis compared with selective inhibition of cyclooxygenase-2, affects chronic cardiac remodelling after MI. EXPERIMENTAL APPROACH: Mice were subjected to left anterior descending coronary artery ligation, followed by intraperitoneal treatment with the mPGES-1 inhibitor compound III (CIII) or 118, celecoxib (cyclooxygenase-2 inhibitor) or vehicle, once daily for 28 days. Urinary prostanoid metabolites were measured by liquid chromatography-tandem mass spectrometry. KEY RESULTS: Chronic administration of CIII improved cardiac function in mice after MI compared with vehicle or celecoxib. CIII did not affect thrombogenesis or blood pressure. In addition, CIII reduced infarct area, augmented scar thickness, decreased collagen I/III ratio, decreased the expression of fibrosis-related genes and increased capillary density in the ischaemic area. Shunting to urinary metabolites of PGI2 , not thromboxane B2 or PGD2 , after inhibition of mPGES-1 was positively correlated with cardiac function after MI. CIII administration significantly increased urinary PGI2 /PGE2 metabolite ratio compared to vehicle or celecoxib. The PGI2 /PGE2 metabolite ratio correlated positively with ejection fraction, fractional shortening and scar thickness. Treatment with 118 also improved cardiac function. CONCLUSION AND IMPLICATIONS: Inhibition of mPGES-1 prevented chronic adverse cardiac remodelling via an augmented PGI2 /PGE2 metabolite ratio and therefore represents a potential therapeutic strategy for development of HFrEF after MI.

Stage-Dependent Impact of RIPK1 Inhibition on Atherogenesis: Dual Effects on Inflammation and Foam Cell Dynamics.

Objective: Atherosclerosis is an arterial occlusive disease with hypercholesterolemia and hypertension as common risk factors. Advanced-stage stenotic plaque, which features inflammation and necrotic core formation, is the major reason for clinical intervention. Receptor interacting serine/threonine-protein kinase 1 (RIPK1) mediates inflammation and cell death and is expressed in atherosclerotic lesions. The role of RIPK1 in advanced-stage atherosclerosis is unknown. Approach and Results: To investigate the effect of RIPK1 inhibition in advanced atherosclerotic plaque formation, we used ApoE SA/SA mice, which exhibit hypercholesterolemia, and develop angiotensin-II mediated hypertension upon administration of doxycycline in drinking water. These mice readily develop severe atherosclerosis, including that in coronary arteries. Eight-week-old ApoE SA/SA mice were randomized to orally receive a highly selective RIPK1 inhibitor (RIPK1i, GSK547) mixed with a western diet, or control diet. RIPK1i administration reduced atherosclerotic plaque lesion area at 2 weeks of treatment, consistent with suppressed inflammation (MCP-1, IL-1ß, TNF-α) and reduced monocyte infiltration. However, administration of RIPK1i unexpectedly exacerbated atherosclerosis at 4 weeks of treatment, concomitant with increased macrophages and lipid deposition in the plaques. Incubation of isolated macrophages with oxidized LDL resulted in foam cell formation in vitro. RIPK1i treatment promoted such foam cell formation while suppressing the death of these cells. Accordingly, RIPK1i upregulated the expression of lipid metabolism-related genes (Cd36, Ppara, Lxrα, Lxrb, Srebp1c) in macrophage foam cells with ABCA1/ABCG1 unaltered. Furthermore, RIPK1i treatment inhibited ApoA1 synthesis in the liver and reduced plasma HDL levels. Conclusion: RIPK1 modulates the development of atherosclerosis in a stage-dependent manner, implicating both pro-atherosclerotic (monocyte infiltration and inflammation) and anti-atherosclerotic effects (suppressing foam cell accumulation and promoting ApoA1 synthesis). It is critical to identify an optimal therapeutic duration for potential clinical use of RIPK1 inhibitor in atherosclerosis or other related disease indications.