The role of lysophosphatidic acid receptors in phenotypic modulation of vascular smooth muscle cells

Metabolomics-based study of the effect of dietary N-carbamoylglutamic acid addition to heifers in late pregnancy on newborn calves

It has been demonstrated that supplementing late-gestation cow diets with NCG (N-carbamoylglutamic acid) increases the serum protein level, boosts immunological function, and increases the birth weight of the calves. However, the underlying mechanism remains unclear. In this experiment, 30 late-gestation Angus heifers almost at same conditions were chosen for this experiment. They were randomly divided into two groups of 15 cows each. A basal diet was provided to the control group, and 30 g/(d-head) of NCG was added to the basal diet of the test group (NCG group). Blood samples were collected from the jugular vein after birth and before the end (when the calves were 90 days old) of the experiment for plasma metabolomics analysis. The metabolomics analysis identified 53 metabolites between the NCG group and control group, with 40 significantly up-regulated and 13 significantly down-regulated. Among them, 33 lipids and lipid-like molecules made up 57.89% of all the metabolites that were found. Thirty-three metabolic pathways enriched by metabolites showed p.adjust <0.05, among which glycerophospholipid and sphingolipid metabolism pathways were the most abundant. In conclusion, the addition of NCG in late-gestation cows appears to primarily affect calf growth and development through the regulation of phospholipid metabolism, which plays a role in nerve conduction, brain activity, and cell metabolism and function. This study provides valuable insights into how nutritional supplementation by late-gestation cows might improve the growth and development of newborn calves.

Role of G-protein coupled receptors in cardiovascular diseases

Cardiovascular diseases (CVDs) are the leading cause of death globally, with CVDs accounting for nearly 30% of deaths worldwide each year. G-protein-coupled receptors (GPCRs) are the most prominent family of receptors on the cell surface, and play an essential regulating cellular physiology and pathology. Some GPCR antagonists, such as β-blockers, are standard therapy for the treatment of CVDs. In addition, nearly one-third of the drugs used to treat CVDs target GPCRs. All the evidence demonstrates the crucial role of GPCRs in CVDs. Over the past decades, studies on the structure and function of GPCRs have identified many targets for the treatment of CVDs. In this review, we summarize and discuss the role of GPCRs in the function of the cardiovascular system from both vascular and heart perspectives, then analyze the complex ways in which multiple GPCRs exert regulatory functions in vascular and heart diseases. We hope to provide new ideas for the treatment of CVDs and the development of novel drugs.

Hypoxia-Induced Phenotypic Transformation of Corpus Cavernosum Smooth Muscle Cells After Cavernous Nerve Crush Injury by Down-Regulating P38 Mitogen-Activated Protein Kinase Expression

INTRODUCTION

Cavernosal nerve (CN) injury is commonly caused by radical prostatectomy surgery, and it might directly lead to erectile dysfunction (ED). Currently, the role of mitogen-activated protein kinase (MAPK) family proteins in phenotypic transformation of corpus cavernosum smooth muscle cell (CCSMC) after CNs injury is poorly understood.

AIM

To investigate the role of p38 MAPK in hypoxia-induced phenotypic transformation of CCSMCs after CN injury.

METHODS

In total, 20 Sprague-Dawley rats (male and 8 weeks of age) were randomly divided into 2 groups, including a sham group and CNCI group. In the sham group, rats were sham-operated by identifying 2 CNs without causing direct damage to the CNs. In the CNCI group, rats were subjected to bilateral CN crush injury. CCSMCs were isolated from the normal corpus cavernosum tissues of the Sprague-Dawley rat and then cultured in 21% or 1% O₂ concentration context for 48 hours.

MAIN OUTCOME MEASURES

Intracavernous pressure/mean arterial pressure were analyzed to measure erectile response. The impact of hypoxia on penile pathology, as well as the expression of extracellular signal-regulated kinases, the c-Jun NH2-terminal kinase, and p38 MAPK, were analyzed.

RESULTS

Compared with the sham group, the intracavernous pressure/mean arterial pressure rate and α-smooth muscle actin expression of CNCI group were decreased significantly (P = .0001; P = .016, respectively), but vimentin expression was significantly increased (P = .023). Phosphorylated p38 level in CNCI group was decreased significantly (P = .017; sham: 0.17 ± 0.005; CNCI: 0.14 ± 0.02). The CCSMCs in the normoxia group were long fusiform, whereas the morphology of CCSMCs in the hypoxia group became hypertrophic. After hypoxia for 48 hours, the expression of α-smooth muscle actin and phosphorylated p38 MAPK was decreased significantly (P = .01; P = .024, normoxia: 0.66 ± 0.18, hypoxia: 0.26 ± 0.08, respectively), and the expression of hypoxia-inducible factor-1α and collagen I was increased significantly in hypoxia group (P = .04; P = .012, respectively).

CONCLUSIONS

Hypoxia induced the phenotypic transformation of CCSMCs after CNCI might be associated with the downregulation of phosphorylated p38 MAPK. Chen S, Huang X, Kong X, et al. Hypoxia-Induced Phenotypic Transformation of Corpus Cavernosum Smooth Muscle Cells After Cavernous Nerve Crush Injury by Down-Regulating p38 Mitogen-Activated Protein Kinase Expression. Sex Med 2019;7:433-440.

LPA receptor 4 deficiency attenuates experimental atherosclerosis

The widely expressed lysophosphatidic acid (LPA) selective receptor 4 (LPAR4) contributes to vascular development in mice and zebrafish. LPAR4 regulates endothelial permeability, lymphocyte migration, and hematopoiesis, which could contribute to atherosclerosis. We investigated the role of LPAR4 in experimental atherosclerosis elicited by adeno-associated virus expressing PCSK9 to lower LDL receptor levels. After 20 weeks on a Western diet, cholesterol levels and lipoprotein distribution were similar in WT male and Lpar4Y/- mice (P = 0.94). The atherosclerotic lesion area in the proximal aorta and arch was ∼25% smaller in Lpar4Y/- mice (P = 0.009), and less atherosclerosis was detected in Lpar4Y/- mice at any given plasma cholesterol. Neutral lipid accumulation in aortic root sections occupied ∼40% less area in Lpar4Y/- mice (P = 0.001), and CD68 expression was ∼25% lower (P = 0.045). No difference in α-smooth muscle actin staining was observed. Bone marrow-derived macrophages isolated from Lpar4Y/- mice displayed significantly increased upregulation of the M2 marker Arg1 in response to LPA compared with WT cells. In aortic root sections from Lpar4Y/- mice, heightened M2 "repair" macrophage marker expression was detected by CD206 staining (P = 0.03). These results suggest that LPAR4 may regulate the recruitment of specific sets of macrophages or their phenotypic switching in a manner that could influence the development of atherosclerosis.

Lysophosphatidic acid induces integrin activation in vascular smooth muscle and alters arteriolar myogenic vasoconstriction

In vascular smooth muscle cells (VSMC) increased integrin adhesion to extracellular matrix (ECM) proteins, as well as the production of reactive oxygen species (ROS) are strongly stimulated by lysophosphatidic acid (LPA). We hypothesized that LPA-induced generation of ROS increases integrin adhesion to the ECM. Using atomic force microscopy (AFM) we determined the effects of LPA on integrin adhesion to fibronectin (FN) in VSMC isolated from rat (Sprague-Dawley) skeletal muscle arterioles. In VSMC, exposure to LPA (2 μM) doubled integrin-FN adhesion compared to control cells (P < 0.05). LPA-induced integrin-FN adhesion was reduced by pre-incubation with antibodies against β1 and β3 integrins (50 μg/ml) by 66% (P < 0.05). Inhibition of LPA signaling via blockade of the LPA G-protein coupled receptors LPAR1 and LPAR3 with 10 μM Ki16425 reduced the LPA-enhanced adhesion of VSCM to FN by 40% (P < 0.05). Suppression of ROS with tempol (250 μM) or apocynin (300 μM) also reduced the LPA-induced FN adhesion by 47% (P < 0.05) and 59% (P < 0.05), respectively. Using confocal microscopy, we observed that blockade of LPA signaling, with Ki16425, reduced ROS by 45% (P < 0.05), to levels similar to control VSMC unexposed to LPA. In intact isolated arterioles, LPA (2 μM) exposure augmented the myogenic constriction response to step increases in intraluminal pressure (between 40 and 100 mm Hg) by 71% (P < 0.05). The blockade of LPA signaling, with Ki16425, decreased the LPA-enhanced myogenic constriction by 58% (P < 0.05). Similarly, blockade of LPA-induced ROS release with tempol or gp91 ds-tat decreased the LPA-enhanced myogenic constriction by 56% (P < 0.05) and 55% (P < 0.05), respectively. These results indicate that, in VSMC, LPA-induced integrin activation involves the G-protein coupled receptors LPAR1 and LPAR3, and the production of ROS, and that LPA may play an important role in the control of myogenic behavior in resistance vessels through ROS modulation of integrin activity.

Lysophosphatidic acid in atherosclerotic diseases

Lysophosphatidic acid (LPA) is a potent bioactive phospholipid. As many other biological active lipids, LPA is an autacoid: it is formed locally on demand, and it acts locally near its site of synthesis. LPA has a plethora of biological activities on blood cells (platelets, monocytes) and cells of the vessel wall (endothelial cells, smooth muscle cells, macrophages) that are all key players in atherosclerotic and atherothrombotic processes. The specific cellular actions of LPA are determined by its multifaceted molecular structures, the expression of multiple G-protein coupled LPA receptors at the cell surface and their diverse coupling to intracellular signalling pathways. Numerous studies have now shown that LPA has thrombogenic and atherogenic actions. Here, we aim to provide a comprehensive, yet concise, thoughtful and critical review of this exciting research area and to pinpoint potential pharmacological targets for inhibiting thrombogenic and atherogenic activities of LPA. We hope that the review will serve to accelerate knowledge of basic and clinical science, and to foster drug development in the field of LPA and atherosclerotic/atherothrombotic diseases.

Current progress in non-Edg family LPA receptor research

Lysophosphatidic acid (LPA) is the simplest phospholipid yet possesses myriad biological functions. Until 2003, the functions of LPA were thought to be elicited exclusively by three subtypes of the endothelial differentiation gene (Edg) family of G protein-coupled receptors - LPA(1), LPA(2), and LPA(3). However, several biological functions of LPA could not be assigned to any of these receptors indicating the existence of one or more additional LPA receptor(s). More recently, the discovery of a second cluster of LPA receptors which includes LPA(4), LPA(5), and LPA(6) has paved the way for new avenues of LPA research. Analyses of these non-Edg family LPA receptors have begun to fill in gaps to understand biological functions of LPA such as platelet aggregation and vascular development that could not be ascribed to classical Edg family LPA receptors and are also unveiling new biological functions. Here we review recent progress in the non-Edg family LPA receptor research, with special emphasis on the pharmacology, signaling, and physiological roles of this family of receptors. This article is part of a Special Issue entitled Advances in Lysophospholipid Research.