Rationale:: PhosPhatidic Acid Phosphatase type 2B (PPAP2B), an integral membrane protein known as lipid phosphate phosphatase (LPP3) that inactivates lysophosphatidic acid, was implicated in coronary artery disease (CAD) by genome-wide association studies. However, it is unclear whether genome-wide association studies–identified coronary artery disease genes, including PPAP2B , participate in mechanotransduction mechanisms by which vascular endothelia respond to local atherorelevant hemodynamics that contribute to the regional nature of atherosclerosis. Objective:: To establish the critical role of PPAP2B in endothelial responses to hemodynamics. Methods and Results:: Reduced PPAP2B was detected in vivo in mouse and swine aortic arch (AA) endothelia exposed to chronic disturbed flow, and in mouse carotid artery endothelia subjected to surgically induced acute disturbed flow. In humans, PPAP2B was reduced in the downstream part of carotid plaques where low shear stress prevails. In culture, reduced PPAP2B was measured in human aortic endothelial cells under atherosusceptible waveform mimicking flow in human carotid sinus. Flow-sensitive microRNA-92a and transcription factor KLF2 were identified as upstream inhibitor and activator of endothelial PPAP2B , respectively. PPAP2B suppression abrogated atheroprotection of unidirectional flow; inhibition of lysophosphatidic acid receptor 1 restored the flow-dependent, anti-inflammatory phenotype in PPAP2B-deficient cells. PPAP2B inhibition resulted in myosin light-chain phosphorylation and intercellular gaps, which were abolished by lysophosphatidic acid receptor 1/2 inhibition. Expression quantitative trait locus mapping demonstrated PPAP2B coronary artery disease risk allele is not linked to PPAP2B expression in various human tissues but significantly associated with reduced PPAP2B in human aortic endothelial cells. Conclusions:: Atherorelevant flows dynamically modulate endothelial PPAP2B expression through miR-92a and KLF2. Mechanosensitive PPAP2B plays a critical role in promoting anti-inflammatory phenotype and maintaining vascular integrity of endothelial monolayer under atheroprotective flow.

The renin-angiotensin system is an essential regulatory system for blood pressure and fluid homeostasis. Angiotensinogen is the only known precursor of all the peptides generated in this system. While many of the basic understandings of angiotensinogen have come from research efforts to define its role in blood pressure regulation, novel pathophysiological functions of angiotensinogen have been discovered in the last two decades including kidney developmental abnormalities, atherosclerosis, and obesity. Despite the impressive advance in the understanding of angiotensinogen gene structure and protein functions, some fundamental questions remain unanswered. In this short review, we provide contemporary insights into the molecular characteristics of angiotensinogen and its pathophysiological features. In light of the recent progress, we emphasize some newly recognized functional features of angiotensinogen other than its regulation on blood pressure.

Objective—: This study determined whether angiotensinogen (AGT) has angiotensin II–independent effects using multiple genetic and pharmacological manipulations. Approach and Results—: All study mice were in low-density lipoprotein receptor −/− background and fed a saturated fat–enriched diet. In mice with floxed alleles and a neomycin cassette in intron 2 of the AGT gene (hypoAGT mice), plasma AGT concentrations were >90% lower compared with their wild-type littermates. HypoAGT mice had lower systolic blood pressure, less atherosclerosis, and diminished body weight gain and liver steatosis. Low plasma AGT concentrations and all phenotypes were recapitulated in mice with hepatocyte-specific deficiency of AGT or pharmacological inhibition of AGT by antisense oligonucleotide administration. In contrast, inhibition of AGT cleavage by a renin inhibitor, aliskiren, failed to alter body weight gain and liver steatosis in low-density lipoprotein receptor −/− mice. In mice with established adiposity, administration of AGT antisense oligonucleotide versus aliskiren led to equivalent reductions of systolic blood pressure and atherosclerosis. AGT antisense oligonucleotide administration ceased body weight gain and further reduced body weight, whereas aliskiren did not affect body weight gain during continuous saturated fat–enriched diet feeding. Structural comparisons of AGT proteins in zebrafish, mouse, rat, and human revealed 4 highly conserved sequences within the des(angiotensin I)AGT domain. des(angiotensin I)AGT, through adeno-associated viral infection in hepatocyte-specific AGT-deficient mice, increased body weight gain and liver steatosis, but did not affect atherosclerosis. Conclusions—: AGT contributes to body weight gain and liver steatosis through functions of the des(angiotensin I)AGT domain, which are independent of angiotensin II production.

Multiple types of renin-angiotensin system (RAS) blockers exist, allowing interference with the system at the level of renin, angiotensin-converting enzyme, or the angiotensin II receptor. Yet, in particular, for the treatment of hypertension, the number of patients with uncontrolled hypertension continues to rise, either due to patient noncompliance or because of the significant renin rises that may, at least partially, overcome the effect of RAS blockade (RAS escape). New approaches to target the RAS are either direct antisense oligonucleotides that inhibit angiotensinogen RNA translation, or small interfering RNA (siRNA) that function via the RNA interference pathway. Since all angiotensins stem from angiotensinogen, lowering angiotensinogen has the potential to circumvent the RAS escape phenomenon. Moreover, antisense oligonucleotides and small interfering RNA require injections only every few weeks to months, which might reduce noncompliance. Of course, angiotensinogen suppression also poses a threat in situations where the RAS is acutely needed, for instance in women becoming pregnant during treatment, or in cases of emergency, when severe hypotension occurs. This review discusses all preclinical data on angiotensinogen suppression, as well as the limited clinical data that are currently available. It concludes that it is an exciting new tool to target the RAS with high specificity and a low side effect profile. Its long-term action might revolutionize pharmacotherapy, as it could overcome compliance problems. Preclinical and clinical programs are now carefully investigating its efficacy and safety profile, allowing an optimal introduction as a novel drug to treat cardiovascular and renal diseases in due time.

Crosstalk between coagulation and innate immunity contributes to the progression of many diseases, including infection and cardiovascular disease. Venous thromboembolism (VTE), including pulmonary embolism and deep vein thrombosis (DVT), is among the most common causes of cardiovascular death. Here, we show that inflammasome activation and subsequent pyroptosis play an important role in the development of venous thrombosis. Using a flow restriction–induced mouse venous thrombosis model in the inferior vena cava (IVC), we show that deficiency of caspase-1, but not caspase-11, protected against flow restriction–induced thrombosis. Interleukin-1β expression increased in the IVC following ligation, indicating that inflammasome is activated during injury. Deficiency of gasdermin D (GSDMD), an essential mediator of pyroptosis, protected against restriction-induced venous thrombosis. After induction of venous thrombosis, fibrin was deposited in the veins of wild-type mice, as detected using immunoblotting with a monoclonal antibody that specifically recognizes mouse fibrin, but not in the caspase-1–deficient or GSDMD-deficient mice. Depletion of macrophages by gadolinium chloride or deficiency of tissue factor also protected against venous thrombosis. Our data reveal that tissue factor released from pyroptotic monocytes and macrophages following inflammasome activation triggers thrombosis.