Where Does Inflammation Fit?

PURPOSE OF REVIEW

This review focuses on the complex relationship between inflammation and the onset of acute coronary syndrome and heart failure.

RECENT FINDINGS

In the last few years, two important lines of research brought new and essential information to light in the pathogenesis of acute coronary syndrome: a) the understanding of the immune mediate mechanisms of inflammation in Ischemic Heart Disease (IHD) and b) evidence that the inflammatory mechanisms associated with atherosclerosis and its complications can be modulated by anti-inflammatory molecules. A large amount of data also suggests that inflammation is a major component in the development and exacerbation of heart failure (HF), in a symbiotic relationship. In particular, recent evidence underlies peculiar aspects of the phenomenon: oxidative stress and autophagy; DAMPS and TLR-4 signaling activation; different macrophages lineage and the contribution of NLRP-3 inflammasome; adaptive immune system. A possible explanation that could unify the pathogenic mechanism of these different conditions is the rising evidence that increased bowel permeability may allow translation of gut microbioma product into the circulation. These findings clearly establish the role of inflammation as the great trigger for two of the major cardiovascular causes of death and morbidity. Further studies are needed, to better clarify the issue and to define more targeted approaches to reduce pathological inflammation while preserving the physiological one.

Transcriptome Analysis of K-877 (a Novel Selective PPARα Modulator (SPPARMα))-Regulated Genes in Primary Human Hepatocytes and the Mouse Liver

AIM

Selective PPARα modulators (SPPARMα) are under development for use as next-generation lipid lowering drugs. In the current study, to predict the pharmacological and toxicological effects of a novel SPPARMα K-877, comprehensive transcriptome analyses of K-877-treated primary human hepatocytes and mouse liver tissue were carried out.

METHODS

Total RNA was extracted from the K-877 treated primary human hepatocytes and mouse liver and adopted to the transcriptome analysis. Using a cluster analysis, commonly and species specifically regulated genes were identified. Also, the profile of genes regulated by K-877 and fenofibrate were compared to examine the influence of different SPPARMα on the liver gene expression.

RESULTS

Consequently, a cell-based transactivation assay showed that K-877 activates PPARα with much greater potency and selectivity than fenofibric acid, the active metabolite of clinically used fenofibrate. K-877 upregulates the expression of several fatty acid β-oxidative genes in human hepatocytes and the mouse liver. Almost all genes up- or downregulated by K-877 treatment in the mouse liver were also regulated by fenofibrate treatment. In contrast, the K-877-regulated genes in the mouse liver were not affected by K-877 treatment in the Ppara-null mouse liver. Depending on the species, the peroxisomal biogenesis-related gene expression was robustly induced in the K-877-treated mouse liver, but not human hepatocytes, thus suggesting that the clinical dose of K-877 may not induce peroxisome proliferation or liver toxicity in humans. Notably, K-877 significantly induces the expression of clinically beneficial target genes (VLDLR, FGF21, ABCA1, MBL2, ENPEP) in human hepatocytes.

CONCLUSION

These results indicate that changes in the gene expression induced by K-877 treatment are mainly mediated through PPARα activation. K-877 regulates the hepatic gene expression as a SPPARMα and thus may improve dyslipidemia as well as metabolic disorders, such as metabolic syndrome and type 2 diabetes, without untoward side effects.

Molecular mechanisms responsible for the reduced expression of cholesterol transporters from macrophages by low-dose endotoxin

OBJECTIVE

Atherosclerosis is characterized as a chronic inflammatory condition that involves cholesterol deposition in arteries. Together with scavenger receptor B1 (SR-B1), the ATP-binding cassette transporters ABCA1 and ABCG1 are the major components of macrophage cholesterol efflux. Recent studies have shown that low-grade inflammation plays a distinct regulatory role in the expression of SR-B1 and ABCA1/ABCG1. However, the mechanisms linking low-grade inflammation and cholesterol accumulation are poorly understood.

METHODS AND RESULTS

Using primary bone-marrow-derived macrophages, we demonstrate that subclinical low-dose lipopolysaccharide potently reduces the expression of SR-B1 and ABCA1/ABCG1, as well as cholesterol efflux from macrophages through interleukin-1 receptor-associated kinase 1 and Toll-interacting-protein. Low-dose lipopolysaccharide downregulates the nuclear levels of retinoic acid receptor-α, leading to their reduced binding to the promoters of SR-B1 and ABCA1/ABCG1. We observe that glycogen synthase kinase 3β activation by low-dose lipopolysaccharide through interleukin-1 receptor-associated kinase 1 and Toll-interacting-protein is responsible for reduced levels of retinoic acid receptor-α, and reduced expression of SR-B1 and ABCA1/ABCG1. Interleukin-1 receptor-associated kinase M, however, counteracts the function of interleukin-1 receptor associated kinase 1.

CONCLUSIONS

Collectively, our data reveal a novel intracellular network regulated by low-dose endotoxemia that disrupts cholesterol efflux from macrophages and leads to the pathogenesis of atherosclerosis.

Pomegranate: a fruit that ameliorates metabolic syndrome

Pomegranate is an ancient fruit that is still part of the diet in the Mediterranean area, the Middle East, and India. Health-promoting effects have long been attributed to this fruit. Modern research corroborates the use of pomegranate as a folk remedy for diabetes and metabolic syndrome, and is responsible for a new evaluation of nutritional and pharmaceutical aspects of pomegranate in the general public. In the last decade, industry and agricultural production have been adapted to meet higher market demands for pomegranate. In vivo and in vitro studies have demonstrated that pomegranate exerts hypoglycaemic effects, including increased insulin sensitivity, inhibition of α-glucosidase, and impact on glucose transporter type 4 function, but is also responsible for a reduction of total cholesterol, and the improvement of blood lipid profiles, as well as anti-inflammatory effects through the modulation of peroxisome proliferator-activated receptor pathways. These effects may also explain how pomegranate-derived compounds function in the amelioration of adverse health effects caused by metabolic syndrome. Pomegranate contains polyphenols such as ellagitannins and anthocyanins, as well as phenolic acids, fatty acids and a variety of volatile compounds. Ellagitannins are some of the most prevalent compounds present in pomegranate, and may be responsible for certain benevolent characteristics associated with pomegranate. A brief overview of rising health problems due to obesity will be provided, followed by characterisation of the biological activity, bioavailability, and safety of pomegranate and pomegranate-derived compounds. Although the fruit is consumed in many countries, epidemiological and clinical studies are unavailable. Additional research is necessary to corroborate the promise of current in vivo and in vitro findings.