The role of the complement factor B-arginase-polyamine molecular axis in uremia-induced cardiac remodeling in mice

Cardiac biogenic amine profile and its relationship with parameters of cardiovascular disease in obesity

AIMS

To identify the cardiac biogenic amine profile of obese rats and associate these compounds with parameters of cardiovascular disease.

MAIN METHODS

Wistar rats (n = 20) were randomly distributed into two groups: control and obese. Obesity was induced by a high-sugar fat diet. Biochemical parameters were evaluated. Doppler Echocardiography and systolic blood pressure; interleukin-10 (IL-10), tumor necrosis factor-alpha (TNF-α), protein carbonylation, ferric reducing antioxidant power (FRAP), and catalase activity were measured in cardiac tissue. HPLC evaluated the cardiac biogenic profile. Data were compared using the Student's T or Mann-Whitney tests and Spearman's correlation at 5% significance. The principal component analysis (PCA) was performed.

KEY FINDINGS

Obesity generated hypertension, cardiac remodeling and dysfunction, and imbalanced all biochemical, inflammatory, and oxidative markers (p < 0.001). Eight biogenic amines were found in cardiac tissue. Obesity increased serotonin and decreased agmatine, putrescine, cadaverine, and spermidine. Serotonin (r = 0.534 to 0.808) was strong and positively correlated with obesity, biochemical parameters, cardiac inflammation, oxidative stress, hypertension, cardiac remodeling, and dysfunction (p < 0.001). Spermidine (r = -0.560 to -0.680), putrescine (r = -0.532 to -0.805), cadaverine (r = -0.534 to -0.860), and agmatine (r = -0.579 to -0.884) were inversely correlated with the same parameters (p < 0.001). PCA allowed for distinguishing the control and obese groups.

SIGNIFICANCE

There are strong correlations between cardiac biogenic amine levels, cardiac remodeling, and dysfunction resulting from obesity.

CONCLUSION

There is an association between cardiac biogenic amines and cardiovascular disease in obesity. In addition, agmatine, putrescine, cadaverine, and, mainly, serotonin may be new biomarkers for cardiovascular health in obesity and help to improve the diagnosis and treatment of CVD resulting or not from obesity. However, more research is needed to support this conclusion.

Dehydration Accelerates Cytogenesis and Cyst Growth in Pkd1-/- Mice by Regulating Macrophage M2 Polarization

Adult autosomal dominant polycystic kidney disease (ADPKD) has been shown to be related as a "third hit" to the occurrence of acute or chronic kidney injury. Here, we examined whether dehydration, as a common kidney risk factor, could cause cystogenesis in chronic-onset Pkd1-/- mice by regulating macrophage activation. First, we confirmed that dehydration accelerated cytogenesis in Pkd1-/- mice and that macrophages infiltrated the kidney tissues even earlier than macroscopic cyst formation. Then, microarray analysis suggested that glycolysis pathway may be involved in macrophage activation in Pkd1-/- kidneys under conditions of dehydration. Further, we confirmed glycolysis pathway was activated and lactic acid (L-LA) was overproduced in the Pkd1-/- kidney under conditions of dehydration. We have already proved that L-LA strongly stimulated M2 macrophage polarization and overproduction of polyamine in macrophage in vitro, and in the present study, we further discovered that M2 polarization-induced polyamine production shortened the primary cilia length by disrupting the PC1/PC2 complex. Finally, the activation of L-LA-arginase 1-polyamine pathway contributed to cystogenesis and progressive cyst growth in Pkd1-/- mice recurrently exposed to dehydration.

Arginine Dysregulation and Myocardial Dysfunction in a Mouse Model and Children with Chronic Kidney Disease

Cardiovascular disease is the leading cause of death in chronic kidney disease (CKD). Arginine, the endogenous precursor for nitric oxide synthesis, is produced in the kidneys. Arginine bioavailability contributes to endothelial and myocardial dysfunction in CKD. Plasma from 129X1/SvJ mice with and without CKD (5/6th nephrectomy), and banked plasma from children with and without CKD were analyzed for amino acids involved in arginine metabolism, ADMA, and arginase activity. Echocardiographic measures of myocardial function were compared with plasma analytes. In a separate experiment, a non-specific arginase inhibitor was administered to mice with and without CKD. Plasma citrulline and glutamine concentrations correlated with multiple measures of myocardial dysfunction. Plasma arginase activity was significantly increased in CKD mice at 16 weeks vs. 8 weeks (p = 0.002) and ventricular strain improved after arginase inhibition in mice with CKD (p = 0.03). In children on dialysis, arginase activity was significantly increased vs. healthy controls (p = 0.04). Increasing ADMA correlated with increasing RWT in children with CKD (r = 0.54; p = 0.003). In a mouse model, and children, with CKD, arginine dysregulation correlates with myocardial dysfunction.

Macrophages promote heat stress nephropathy in mice via the C3a-C3aR-TNF pathway

Heat-stress nephropathy (HSN) is associated with recurrent dehydration. However, the mechanisms underlying HSN remain largely unknown. In this study, we evaluated the role of dehydration in HSN and kidney injury in mice. Firstly, we found that complement was strongly activated in the mice that were exposed to dehydration; and among complement components, the interaction between C3a and its receptor, C3aR, was more closely associated with kidney injury. Then two-month-old mice were intraperitoneally injected with 2% dimethyl sulfoxide (DMSO) or the C3aR inhibitor SB290157 during dehydration. DMSO-treated mice exhibited excessive macrophage infiltration, renal cell apoptosis, and kidney fibrosis. In contrast, SB290157-treated mice had no apparent kidney injury. By fluorescence-activated cell sorting (FACS), we found that SB290157 treatment in mice remarkably inhibited macrophage infiltration and suppressed CCR2 expression in macrophages. In addition, C3a binding to C3aR promoted macrophage polarization toward the M1 phenotype and increased the production of TNF-α, which induced renal tubular epithelial cell (RTEC) apoptosis in vivo and in vitro. Interestingly, C3a treatment failed to directly induce TNF-α production and apoptosis in RTECs. However, TNF-α production in response to C3a treatment was significantly elevated when RTECs were cocultured with macrophages, suggesting that macrophages rather than RTECs are the target of C3a-C3aR interaction. At last, we proved that infusion of macrophages which highly expressed TNF-α would significantly deteriorate HSN in TNF-KO mice when they were exposed to recurrent dehydration. This study uncovers a novel mechanism underlying the pathogenesis of HSN, and a potential pathway to prevent kidney injury during dehydration.

Arginase: shedding light on the mechanisms and opportunities in cardiovascular diseases

Arginase, a binuclear manganese metalloenzyme in the urea, catalyzes the hydrolysis of L-arginine to urea and L-ornithine. Both isoforms, arginase 1 and arginase 2 perform significant roles in the regulation of cellular functions in cardiovascular system, such as senescence, apoptosis, proliferation, inflammation, and autophagy, via a variety of mechanisms, including regulating L-arginine metabolism and activating multiple signal pathways. Furthermore, abnormal arginase activity contributes to the initiation and progression of a variety of CVDs. Therefore, targeting arginase may be a novel and promising approach for CVDs treatment. In this review, we give a comprehensive overview of the physiological and biological roles of arginase in a variety of CVDs, revealing the underlying mechanisms of arginase mediating vascular and cardiac function, as well as shedding light on the novel and promising therapeutic approaches for CVDs therapy in individuals.

Involvement of Polyamines From Cardiac Mast Cells in Myocardial Remodeling Induced by Pressure Overload Through Mitochondrial Permeability Transition Pore Opening

Objective

Polyamines mainly contain spermine (SPM), spermidine (SPD), and putrescine (PUT). Many research results suggest that polyamines participate in cell proliferation, differentiation, and the regulation of gene expression, and have a close relationship with the occurrence and development of many diseases. However, the role and possible mechanisms of action of polyamines from cardiac mast cells in myocardial remodeling induced by pressure overload remain to be elucidated.

Methods

Pressure overload was induced by abdominal aortic constriction (AAC). Toluidine blue staining was used to visualize mast cells in cardiac tissue. The polyamine content of cardiac tissue was analyzed using high-performance liquid chromatography. Opening of the mitochondrial permeability transition pore (MPTP) was determined by the Ca²⁺-induced swelling of isolated cardiac mitochondria, measured as a reduction in A₅₂₀.

Results

Compared with sham rats, the cardiac mast cell density, the polyamine content (PUT, SPB, and SPM), and myocardial MPTP opening in rats with AAC were significantly increased (P < 0.05), and were accompanied by increased myocardial fibrosis and heart weight/body weight ratio. Intraperitoneal injection of polyamines mimicked these results, and these effects were reversed by cromolyn sodium, a mast cell stabilizer (P < 0.05). Myocardial MPTP opening increased in rats with AAC (P < 0.05), and the three polyamines also increased myocardial MPTP opening (P < 0.05).

Conclusion

Mast cell-derived polyamines are involved in pressure overload-induced myocardial remodeling by increasing opening of the MPTP.

Common variants in AGR1 genes contributed to the risk and traits of cirrhotic cardiomyopathy in Han Chinese population

Aim: This study aimed to determine the association between polymorphisms of the ARG1 gene and the risk and traits of cirrhotic cardiomyopathy (CCM). Methods: A total of 468 CCM and 1012 cirrhosis patients were enrolled, and 12 single-nucleotide polymorphisms (SNPs) in the ARG1 gene were genotyped. Differences in genotype, allele and haplotype frequencies of the SNPs between the CCM and cirrhosis groups were analyzed by chi-square test. Correlations of the genotypes of SNPs and representative traits of liver and heart function were performed using linear regression analysis. Results: SNPs rs2781666 and rs2781667 were associated with the risk of CCM in both dominant and additive inheritance models. The GG genotype frequency of rs2781666 and CC genotype frequency of rs2781667 were lower in the CCM group than in the cirrhosis group. The G-C haplotype frequency of the block consisting of rs2781666 and rs2781667 was higher and the T-T haplotype frequency was lower in CCM patients than in cirrhosis patients. SNP rs2781666 was associated with the alanine transaminase level, and rs2781667 was associated with the ARG1 level and left atrial diameter. Conclusion: SNPs rs2781666 and rs2781667 in the ARG1 gene were associated with susceptibility to and traits of CCM in the Han Chinese population.