The effect of peroxisome proliferator-activated receptor gamma (PPARγ) as a mediator of dietary fatty acids and thiazolidinedione in pulmonary arterial hypertension induced by cold stress of broilers

The objective of this experiment was to evaluate the effects of dietary fish oil and pioglitazone as peroxisome proliferators-activated receptor gamma (PPARγ) activating ligands on the reduction of cold-induced ascites in broiler chickens. A total of 480 one-day-old (Ross 308) male chicks were randomly allocated to four treatment groups with eight replicates of 15 birds each. The following treatments were used: 1) ambient temperature (negative control), with basal diet; 2) cold-induced ascites (positive control), with basal diet; 3) cold-induced ascites, with basal diet +10 mg/kg/day pioglitazone and 4) cold-induced ascites, with basal diet +1% of fish oil. When compared with the positive control, body weight gain was higher (P ≤ 0.05) for broilers fed diets containing fish oil and pioglitazone at 28, 42, and 0-42 d. Broilers under cold-induced ascites had the highest blood pressure at 21 and 42 d, while fish oil and pioglitazone treatment reduced the blood pressure (P ≤ 0.05). Red blood cells, white blood cells, hematocrit, erythrocyte osmotic fragility, bursa of Fabricius and spleen weights were improved (P ≤ 0.05) for chickens fed fish oil diets and pioglitazone compared to the cold-induced ascites (positive control). Exposure to cold temperature resulted in an increase in plasma T3 and T3/T4 ratio and decline in plasma T4 (P ≤ 0.05). In conclusion, PPARγ agonist pioglitazone and fish oil as source of omega-3 polyunsaturated fatty acid could be used as a strategy to reduce the negative effects of pulmonary arterial hypertension and ascites in broiler chickens.

Peroxisome proliferator-activated receptor gamma (PPARγ) activation: a potential treatment for ascites syndrome in broiler chickens

Ascites (serous fluid accumulation in the abdominal cavity) has been observed worldwide in fast growing broilers. Pulmonary vascular remodeling is an important pathological feature of broiler ascites syndrome. Peroxisome proliferators-activated receptor gamma (PPARγ) and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α) are expressed in pulmonary vascular endothelial cells and vascular smooth muscle cells (VSMC) where they participate in the regulation of normal pulmonary vascular function. The objective of the present study was to investigate the effects of omega-3 fatty acids (found in fish oil) and pioglitazone (PIO) as natural and synthetic PPARγ ligands supplementation on PPARγ and PGC-1α expression in the prevention of pulmonary arterial hypertension (PAH) syndrome in broiler chickens. The experiment was conducted with 4 treatment groups: 1) negative control, normal temperature conditions with basal diet; 2) positive control, low-temperature conditions with basal diet; 3) positive control + 10 mg PIO/kg of weight/d and 4) positive control + 1% FO. Each treatment had 5 replicates. Ascites heart index (RV/TV) was significantly (P < 0.05) reduced in chickens receiving FO (0.20) and PIO (0.21) compared to the positive control group (0.26). The addition of PIO in broilers under cold-induced ascites significantly increased the expression of PPARγ (9.44) and PGC-1α (5.81) genes in lung tissue compared to the negative control group (1.03, P < 0.05). Proliferative indexes of VSMC in pulmonary arteries such as PMT, PIT, and percentage wall thickness were significantly elevated in positive control group, indicating that pulmonary vascular remodeling occurred following VSMC proliferation in ascites. The vessel internal diameter was increased in FO and PIO groups. Based on these results, activation and expression of PPARγ and PGC-1α genes as a critical regulator of pulmonary artery smooth muscle cell using ligands, especially PIO, can be effective in reducing the incidence of PAH in broiler chickens.

Underlying mechanism of Qiling Jiaogulan Powder in the treatment of broiler ascites syndrome

Broiler ascites syndrome (AS), is a nutritional and metabolic disease that occurs in fast-growing commercial broiler chickens. AS can cause poor growth and a significant increase in the rate of broiler deaths, which has resulted in serious economic losses to the poultry industry. The classic traditional Chinese medicine Qiling Jiaogulan Powder (QLJP) has been demonstrated to have a certain therapeutic effect on broiler AS. However, its pharmacological mechanism remains to be elucidated. This study was performed to investigate the multitarget action mechanism of QLJP in the treatment of broiler AS based on network pharmacology analysis using a broiler AS model. First, all chemical components and targets of QLJP were obtained from the Traditional Chinese Medicine System Pharmacology Analysis Platform (TCMSP). Targets related to broiler AS were further obtained through the GeneCards database and the NCBI Gene sub-database. A protein-protein interaction (PPI) network was constructed. Then, enrichment analyses were performed to predict the potential mechanisms of QLJP in the treatment of broiler AS. Finally, the treatment effect of QLJP on AS was verified in a broiler AS model. Network pharmacology analysis generated 49 active ingredients and 167 core targets of QLJP, and a QLJP-single drug-target-disease network was successfully constructed. Gene enrichment analysis indicated that the core targets have played major roles in the Cell cycle, FOXO signaling pathways, etc. We demonstrated that QLJP improved clinical and organ damage symptoms and significantly reduced the ascites heart index in broilers with AS induced by administration of high-energy, high-protein diets and high-sodium drinking water in a low-temperature environment. QLJP may regulate lung oxidative stress, the cell cycle and apoptosis by activating the FOXO3a signaling pathway to interfere with the occurrence and development of AS in broilers. QLJP administration may be a good clinical strategy for the prevention and treatment of broiler AS.

Dysregulated expression of mRNA and SNP in pulmonary artery remodeling in ascites syndrome in broilers

Broiler ascites syndrome (AS), also called pulmonary artery hypertension, is a metabolic disorder that has been observed worldwide in fast-growing broilers. Pulmonary arterial remodeling is a key step in the development of AS. The precise relationship between mRNA and SNP of the pulmonary artery in regulating AS progression remains unclear. In this study, we obtained pulmonary artery tissues from broilers with AS to perform pathologic section and pathologic anatomic observation. SNP, InDel, and mRNA data analysis were carried out using GATK and ANNOVAR software to study the SNP loci of 985 previously reported genes (437 upregulated and 458 downregulated). The pathology results showed that there was a lot of yellow fluid in the abdominal cavity and pericardium, that the ascites cardiac index and hematocrit changed significantly, and that the pulmonary artery had remodeled and become thicker in the disease group. Myocardial sections showed vacuolar degeneration of myocytes and rupture of muscle fibers. In addition, ALDH7A1, IRG1, GGT5, IGSF1, DHX58, USP36, TREML2, SPAG1, CD34, and PLEKHA7 were found to be closely associated with the pathogenesis of pulmonary artery remodeling in AS progression. Taken together, our present study further illuminates the molecular mechanism of pulmonary artery remodeling underlying AS progression.

Selenium Deficiency-Induced Apoptosis of Chick Embryonic Vascular Smooth Muscle Cells and Correlations with 25 Selenoproteins

Selenium deficiency is the major cause of exudative diathesis in chicks. Subcutaneous hemorrhage is one of the typical symptoms of the disease. However, the reason for the occurrence of blood exudation remains unknown. In the present study, the vascular smooth muscle cells (VSMCs) were isolated from 17-day-old broiler chick embryos. Cell viability, cell apoptosis, and intracellular reactive oxygen species level under different concentrations of selenium (0-0.9 μM) were investigated. The mRNA expression levels of 25 selenoproteins and apoptosis-related genes (p53, CytC, Caspase-3, Caspase-8, Bcl-2, and Bax) were also measured. Selenium deficiency significantly decreased cell viability and increased cell apoptosis (p < 0.05). Supplementation with selenium could alleviate these changes. In general, at all levels of selenium addition, Gpx1, Gpx3, Gpx4, SepW1, and Sep15 mRNAs were all highly expressed in VSMCs, whereas Gpx2, Dio1, SepN1, SelO, and SelPb were at lower levels. There was a high correlation between Gpx2, Gpx3, Gpx4, Dio1, Txnrd1, Txnrd2, and Txnrd3 gene expression. Additionally, Gpx3, Gpx4, Dio1, Txnrd1, Txnrd2, Txnrd3, SelS, and SelPb showed a strong negative correlation with pro-apoptotic gene Caspase-3 as well as a strong positive correlation with anti-apoptotic gene Bcl-2, especially SelI (r = 0.913 and r = 0.929, p < 0.01). These results suggest that selenium deficiency could induce VSMC apoptosis, and several selenoproteins may be involved in the development of apoptosis. Our findings provide information on the molecular mechanism of vascular injury by selenium deficiency.

The influence of oral copper-methionine on matrix metalloproteinase-2 gene expression and activation in right-sided heart failure induced by cold temperature: A broiler chicken perspective

This study was designed to investigate the expression, activation and activity of matrix metalloproteinase-2 (MMP-2) in the heart of broiler chickens reared in cold conditions and fed with copper-methionine supplement at different levels. The chickens (n=480) were randomly allotted to six treatments and four replicates. Treatments included two rearing temperatures (i.e. normal and cold temperatures) each combined with three levels of supplemental copper-methionine (i.e. 0, 100 and 200mg/kg). On d 38 and 45 of age, four broilers from each treatment were sacrificed and their hearts were stored at -80°C. Right-sided heart failure, as evident from abdominal and pericardial fluid accumulation, was observed in broilers under cold stress and not receiving supplemental copper. This clinical observation was confirmed at molecular level through increased MMP-2 expression, activation and activity in this group. Birds reared under normal temperature, however, were not involved in right-sided heart failure nor benefitted from copper-methionine supplementation. In contrast, gelatin zymography and real-time PCR demonstrated that dietary supplementation with copper-methionine decreased pro-MMP-2 and MMP-2 in the heart of chickens reared in cold conditions. However, gelatin reverse zymography did not show any difference between treatments in tissue inhibitor of metalloproteinase-2. Level of supplementation showed similar effects on parameters determined. It is concluded that dietary supplementation with copper-methionine reduced right-sided heart failure at clinical and molecular levels in cold-stressed chickens.

Effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid supplementation on growth performance, indices of ascites syndrome, and antioxidant capacity of broilers reared at low ambient temperature

This study examined the effects of dietary DL-2-hydroxy-4(methylthio)butanoic acid (DL-HMTBA) supplementation on growth performance, antioxidant capacity, and ascites syndrome (AS) in broilers reared at low ambient temperature (LAT) from 7 to 28 days of age. Eight hundred 7-day-old broilers were randomly assigned to two ambient temperatures (LAT and normal ambient temperature [NAT]), four supplemental DL-HMTBA levels (0.17, 0.34, 0.51, and 0.68 %) of the basal diet in a 2 × 4 factorial arrangement (ten replicate pens; ten birds/pen). LAT and NAT indicate temperatures of 12-14 and 24-26 °C in two chambers, respectively, and broilers were reared at these temperatures from 7 to 28 days of age. LAT significantly decreased body weight gain (P < 0.001), serum glutathione (GSH) content (day 14, P = 0.02; day 28, P = 0.045), glutathione peroxidase (GSH-Px) activity, and total antioxidant capacity (T-AOC) at 21 days (P = 0.001, 0.015) and 28 days (P = 0.017, 0.010) and increased feed conversion ratio (FCR) (P < 0.001), serum malondialdehyde (day 21, P = 0.000) and protein carbonyl Level (day 14, P = 0.003; day 21, P = 0.035). As for incidence of AS, there were significant effects of LAT on red blood cell (RBC) count (P < 0.05), hematocrit (HCT) (P < 0.05), and the right to total ventricular weight ratio (RV/TV) at 21 days (P = 0.012) and 28 days (P = 0.046). Supplementation of DL-HMTBA markedly decreased RV/TV at day 28 (P = 0.021), RBC (day 21, P = 0.008), HCT (day 21, P < 0.001), mean cell hemoglobin (day 14, P = 0.035; day 21, P = 0.003), and serum protein carbonyl level (day 21, P = 0.009), while significantly increased serum GSH content (day 14, P = 0.022; day 28, P = 0.001), SOD and GSH-Px activities at 21 days of age (P < 0.001 and P = 0.037). The optimal supplemental DL-HMTBA levels in basal diet of broilers aged from 7 to 28 days under low or normal temperatures were similar, so the authors recommended supplemental of DL-HMTBA level was 0.46 %.

Effects of Dietary Copper-Methionine on Matrix Metalloproteinase-2 in the Lungs of Cold-Stressed Broilers as an Animal Model for Pulmonary Hypertension

The objective of the present study was to investigate the effects of different levels of copper (as supplemental copper-methionine) on ascites incidence and matrix metalloproteinase-2 (MMP-2) changes in the lungs of cold-stressed broilers. For this purpose, 480 1-day-old Ross 308 broiler chickens were randomly assigned to six treatments. Treatments consisted of two ambient temperatures (thermoneutral and cold stress) each combined with 0, 100, and 200 mg supplemental copper/kg as copper-methionine in a 2 × 3 factorial arrangement in a completely randomized design with four replicates. Ascites was diagnosed based on abdominal and pericardial fluid accumulation at 45 days of age. Fourty-eight broilers were killed at 38 and 45 days of age, and their lungs were collected for biological analysis. Results showed that MMP-2 increased in the lungs of ascitic broilers and that copper-methionine supplementation significantly reduced MMP-2 in cold-stressed broiler chickens. Treatments did not affect tissue inhibitor of metalloproteinase-2 (TIMP-2) at 38 and 45 days of age, and no difference was observed between 100 and 200 mg/kg copper-methionine treatments. In conclusion, copper-methionine at higher than conventional levels of supplementation decreased ascites incidence in low temperature through reduced MMP-2 concentration. Further research is warranted to investigate the effect of copper on MMP-2 concentrations in other tissues with high oxygen demand.

Transcriptome Analysis and Gene Identification in the Pulmonary Artery of Broilers with Ascites Syndrome

BACKGROUND

Pulmonary arterial hypertension, also known as Ascites syndrome (AS), remains a clinically challenging disease with a large impact on both humans and broiler chickens. Pulmonary arterial remodeling presents a key step in the development of AS. The precise molecular mechanism of pulmonary artery remodeling regulating AS progression remains unclear.

METHODOLOGY/PRINCIPAL FINDINGS

We obtained pulmonary arteries from two positive AS and two normal broilers for RNA sequencing (RNA-seq) analysis and pathological observation. RNA-seq analysis revealed a total of 895 significantly differentially expressed genes (DEGs) with 437 up-regulated and 458 down-regulated genes, which were significantly enriched to 12 GO (Gene Ontology) terms and 4 KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways (Padj<0.05) regulating pulmonary artery remodeling and consequently occurrence of AS. These GO terms and pathways include ribosome, Jak-STAT and NOD-like receptor signaling pathways which regulate pulmonary artery remodeling through vascular smooth cell proliferation, inflammation and vascular smooth cell proliferation together. Some notable DEGs within these pathways included downregulation of genes like RPL 5, 7, 8, 9, 14; upregulation of genes such as IL-6, K60, STAT3, STAT5 Pim1 and SOCS3; IKKα, IkB, P38, five cytokines IL-6, IL8, IL-1β, IL-18, and MIP-1β. Six important regulators of pulmonary artery vascular remodeling and construction like CYP1B1, ALDH7A1, MYLK, CAMK4, BMP7 and INOS were upregulated in the pulmonary artery of AS broilers. The pathology results showed that the pulmonary artery had remodeled and become thicker in the disease group.

CONCLUSIONS/SIGNIFICANCE

Our present data suggested some specific components of the complex molecular circuitry regulating pulmonary arterial remodeling underlying AS progression in broilers. We revealed some valuable candidate genes and pathways that involved in pulmonary artery remodeling further contributing to the AS progression.

Involvement of matrix metalloproteinase-2 in medial hypertrophy of pulmonary arterioles in broiler chickens with pulmonary arterial hypertension

Medial hypertrophy of pulmonary arterioles during pulmonary arterial hypertension (PAH) in humans is associated with enhanced proliferation of smooth muscle cells (SMCs). Elevated matrix metalloproteinase (MMP)-2 has been found in pulmonary artery SMCs (PA-SMCs) in humans with idiopathic PAH, leading to the hypothesis that MMP-2 contributes to the proliferation and migration of vascular SMCs in the pathogenesis of PAH. Rapidly growing meat-type (broiler) chickens provide a model of spontaneous PAH. The present study was conducted to determine whether MMP-2 is involved in the medial hypertrophy of pulmonary arterioles in this model. Cultured PA-SMCs from normal birds were used to evaluate the effect of MMPs on cell proliferation. Gelatin zymography showed that endothelin (ET)-1-induced proliferation of PA-SMCs was concomitant with increased pro- and active MMP-2 production. Reverse transcription PCR demonstrated upregulation of MMP-2 mRNA. However, PA-SMC proliferation was inhibited by the MMP inhibitors doxycycline and cis-9-octadecenoyl-N-hydroxylamide. In vivo experiments revealed a significant increase of MMP-2 expression in hypertrophied pulmonary arterioles of PAH broiler chickens, which was positively correlated with wall thickness and medial hypertrophy. MMP-2 may contribute to medial hypertrophy in pulmonary arterioles during PAH in broiler chickens by enhancing the proliferation of vascular SMCs.