Lysophosphatidylcholine increases C-type natriuretic peptide expression in human vascular smooth muscle cells via membrane distortion

Comparison of Adiposomal Lipids between Obese and Non-Obese Individuals

Our recent findings revealed that human adipose tissues (AT)-derived extracellular vesicles (adiposomes) vary in cargo among obese and lean individuals. The main objective of this study was to investigate the adiposomal lipid profiles and their correlation with cardiometabolic risk factors. AT samples were collected from obese subjects and lean controls and analyzed for their characteristics and lipid content. In addition, we measured the correlation between adiposomal lipid profiles and body composition, glucose and lipid metabolic profiles, brachial artery vasoreactivity, AT arteriolar flow-induced dilation, and circulating markers such as IL-6, C-reactive protein, and nitric oxide (NO). Compared to lean controls, adiposomes isolated from obese subjects were higher in number after normalization to AT volume. The two major lipid classes differentially expressed were lysophosphatidylcholine/phosphatidylcholine (LPC/PC) and ceramides (Cer). All lipids in the LPC/PC class were several-fold lower in adiposomes from obese subjects compared to lean controls, on top of which were PC 18:2, PC 18:1, and PC 36:3. Most ceramides were markedly upregulated in the obese group, especially Cer d37:0, Cer d18:0, and Cer d39:0. Regression analyses revealed associations between adiposomal lipid profiles and several cardiometabolic risk factors such as body mass index (BMI), fat percentage, insulin resistance, arteriolar and brachial artery vasoreactivity, NO bioavailability, and high-density lipoproteins (HDL-C). We conclude that the ability of adiposomes from obese subjects to disrupt cardiometabolic function could be partly attributed to the dysregulated lipid cargo.

Decreased level of serum NT-proCNP associates with disease severity in COVID-19

BACKGROUND

C-type natriuretic peptide (CNP) is an endothelium-derived paracrine molecule with an important role in vascular homeostasis. In septic patients, the serum level of the amino-terminal propeptide of CNP (NT-proCNP) shows a strong positive correlation with inflammatory biomarkers and, if elevated, correlates with disease severity and indicates a poor outcome. It is not yet known whether NT-proCNP also correlates with the clinical outcome of patients suffering from severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. In the current study, we aimed to determine possible changes in the NT-proCNP levels of patients with coronavirus disease 2019 (COVID-19), with special regard to disease severity and outcome.

METHODS

In this retrospective analysis, we determined the serum level of NT-proCNP in hospitalized patients with symptoms of upper respiratory tract infection, using their blood samples taken on admission, stored in a biobank. The NT-proCNP levels of 32 SARS-CoV-2 positive and 35 SARS-CoV-2 negative patients were measured to investigate possible correlation with disease outcome. SARS-CoV-2 positive patients were then divided into two groups based on their need for intensive care unit treatment (severe and mild COVID-19).

RESULTS

The NT-proCNP was significantly different in the study groups (e.g. severe and mild COVID-19 and non-COVID-19 patients), but showed inverse changes compared to previous observations in septic patients: lowest levels were detected in critically ill COVID-19 patients, while highest levels in the non-COVID-19 group. A low level of NT-proCNP on admission was significantly associated with severe disease outcome.

CONCLUSIONS

Low-level NT-proCNP on hospital admission is associated with a severe COVID-19 disease course. The pathomechanism underlying this observation remains to be elucidated, while future studies in larger patient cohorts are necessary to confirm these observations and reveal therapeutic importance. Trial registration DRKS00026655 Registered 26. November 2021.

An Updated Review of Pro- and Anti-Inflammatory Properties of Plasma Lysophosphatidylcholines in the Vascular System

Lysophosphatidylcholines are a group of bioactive lipids heavily investigated in the context of inflammation and atherosclerosis development. While present in plasma during physiological conditions, their concentration can drastically increase in certain inflammatory states. Lysophosphatidylcholines are widely regarded as potent pro-inflammatory and deleterious mediators, but an increasing number of more recent studies show multiple beneficial properties under various pathological conditions. Many of the discrepancies in the published studies are due to the investigation of different species or mixtures of lysophatidylcholines and the use of supra-physiological concentrations in the absence of serum or other carrier proteins. Furthermore, interpretation of the results is complicated by the rapid metabolism of lysophosphatidylcholine (LPC) in cells and tissues to pro-inflammatory lysophosphatidic acid. Interestingly, most of the recent studies, in contrast to older studies, found lower LPC plasma levels associated with unfavorable disease outcomes. Being the most abundant lysophospholipid in plasma, it is of utmost importance to understand its physiological functions and shed light on the discordant literature connected to its research. LPCs should be recognized as important homeostatic mediators involved in all stages of vascular inflammation. In this review, we want to point out potential pro- and anti-inflammatory activities of lysophospholipids in the vascular system and highlight recent discoveries about the effect of lysophosphatidylcholines on immune cells at the endothelial vascular interface. We will also look at their potential clinical application as biomarkers.

Epidermal growth factor-network signaling mediates luteinizing hormone regulation of BNP and CNP and their receptor NPR2 during porcine oocyte meiotic resumption

The epidermal growth factor (EGF) network, induced by luteinizing hormone (LH), plays an essential role during the regulation of oocyte maturation, cumulus expansion, and ovulation. Binding of brain natriuretic peptide (BNP) and C-type natriuretic peptide (CNP) to natriuretic receptor 2 (NPR2) generates cyclic guanosine monophosphate (cGMP), a key inhibitor that sustains porcine oocyte meiotic arrest. This correlation suggests that LH interacts with natriuretic-peptide signaling, possibly via the EGF network, to promote porcine meiotic resumption. In testing this hypothesis, we found that the majority of porcine oocytes remain arrested in the germinal-vesicle stage after 44 hr of co-culturing cumulus-oocyte complexes with 10(7) granulosa cells, which secreted active BNP and CNP; these natriuretic peptides associate with NPR2 on cumulus cells, thereby inhibiting porcine oocyte maturation. This inhibitory effect of BNP and CNP was relieved by EGF-like growth factors, whose expression naturally increases in granulosa cells 18 hr after human chorionic gonadotropin injection. LH and the EGF-like peptide amphiregulin (AREG) decreased BNP and CNP production in granulosa cells and down-regulated NPR2 expression in cumulus cells, which together decreased oocyte cGMP to levels that permit meiotic resumption. The effects of AREG on the gene expression of natriuretic-peptide signaling components and on oocyte maturation were completely blocked by the EGF receptor kinase inhibitor AG1478; the effect of LH, however, was only partially reversed by AG1478. Based on these results, LH regulates natriuretic-peptide signaling, although other pathways also cooperate with the EGF network to induce porcine oocyte maturation.

Regulation of C-type natriuretic peptide expression

C-type natriuretic peptide (CNP) is a member of the small family of natriuretic peptides that also includes atrial natriuretic peptide (ANP) and brain, or B-type natriuretic peptide (BNP). Unlike them, it performs its major functions in an autocrine or paracrine manner. Those functions, mediated through binding to the membrane guanylyl cyclase natriuretic peptide receptor B (NPR-B), or by signaling through the non-enzyme natriuretic peptide receptor C (NPR-C), include the regulation of endochondral ossification, reproduction, nervous system development, and the maintenance of cardiovascular health. To date, the regulation of CNP gene expression has not received the attention that has been paid to regulation of the ANP and BNP genes. CNP expression in vitro is regulated by TGF-β and receptor tyrosine kinase growth factors in a cell/tissue-specific and sometimes species-specific manner. Expression of CNP in vivo is altered in diseased organs and tissues, including atherosclerotic vessels, and the myocardium of failing hearts. Analysis of the human CNP gene has led to the identification of a number of regulatory sites in the proximal promoter, including a GC-rich region approximately 50 base pairs downstream of the Tata box, and shown to be a binding site for several putative regulatory proteins, including transforming growth factor clone 22 domain 1 (TSC22D1) and a serine threonine kinase (STK16). The purpose of this review is to summarize the current literature on the regulation of CNP expression, emphasizing in particular the putative regulatory elements in the CNP gene and the potential DNA-binding proteins that associate with them.

Transforming growth factor-β1 regulation of C-type natriuretic peptide expression in human vascular smooth muscle cells: dependence on TSC22D1

C-type natriuretic peptide (CNP) possesses nitric oxide-like signaling mechanisms and actions in the vasculature, including the inhibition of fibrosis and vascular remodeling through counterregulation of transforming growth factor-β (TGF-β) signaling. The leucine zipper protein transforming growth factor stimulated clone 22 domain 1 (TSC22D1), cloned via its presumed binding to a GC-rich element in the CNP promoter, was the first protein to be described as a CNP transcription factor, but the lack of supporting evidence since its discovery and its lack of a classical DNA-binding site have left in question its role in the regulation of CNP by TGF-β and other factors. To define a specific role for TSC22D1 in CNP transcription, we have examined the effects of the profibrotic growth factors TGF-β1 and PDGF-BB on CNP mRNA expression in cultured human vascular smooth muscle cells (SMC) in which TSC22D1 expression was suppressed with small interfering RNA. Results showed that TGF-β and PDGF-BB significantly increased CNP expression in all three SMC types. Twenty-four-hour TGF-β-induced elevations in CNP were strongly correlated with changes in TSC22D1 mRNA levels, and both genes exhibited their greatest response to TGF-β1 in coronary artery SMC. Furthermore, siRNA suppression of TSC22D1 expression in coronary artery and aortic SMC by ∼90% resulted in 45–65% reductions of both PDGF- and TGF-β-stimulated CNP expression, respectively. These results support a postulated role of TSC22D1 as an enhancer of CNP transcription and suggest that TGF-β-induced upregulation of CNP expression in SMC may be mediated in part by increased transcription of TSC22D1.