Heme-binding to the nuclear receptor retinoid X receptor α (RXRα) leads to the inhibition of the transcriptional activity

The therapeutic effect of wine-processed Corni Fructus on chronic renal failure in rats through the interference with the LPS/IL-1-mediated inhibition of RXR function

ETHNOPHARMACOLOGICAL RELEVANCE

Corni Fructus, derived from the fruit of Cornus officinalis Sieb. et Zucc, is a widely utilized traditional Chinese medicine (TCM) with established efficacy in the treatment of diverse chronic kidney diseases. Crude Corni Fructus (CCF) and wine-processed Corni Fructus (WCF) are the main processed forms of Corni Fructus. Generally, TCM is often used after processing (paozhi). Despite the extensive use of processed TCM, the underlying mechanisms of processing for most TCMs have been unclear so far.

AIM OF THE STUDY

In this study, an integrated strategy combined renal metabolomics with proteomics was established and investigated the potential processing mechanisms of CCF or WCF on chronic renal failure (CRF) models.

MATERIALS AND METHODS

Firstly, the differences in biochemical parameters and pathological histology were compared to evaluate the effects of CCF and WCF on CRF model rats. Then, the tissue differential metabolites and proteins between CCF and WCF on CRF model rats were screened based on metabolomics and proteomics technology. Concurrently, a combined approach of metabolomics and proteomics was employed to investigate the underlying mechanisms associated with these marker metabolic products and proteins.

RESULTS

Compared to the MG group, there were 27 distinct metabolites and 143 different proteins observed in the CCF-treatment group, while the WCF-treatment group exhibited 24 distinct metabolites and 379 different proteins. Further, the integration interactions analysis of the protein and lipid metabolite revealed that both WCF and CCF improved tryptophan degradation and LPS/IL-1-mediated inhibition of RXR function. WCF inhibited RXR function more than CCF via the modulation of LPS/IL-1 in the CRF model. Experimental results were validated by qRT-PCR and western blotting. Notably, the gene expression amount and protein levels of FMO3 and CYP2E1 among 8 genes influenced by WCF were higher compared to CCF.

CONCLUSION

The results of this study provide a theoretical basis for further study of Corni Fructus with different processing techniques in CRF. The findings also offer guidance for investigating the mechanism of action of herbal medicines in diseases employing diverse processing techniques.

Hemin Improves Insulin Sensitivity and Lipid Metabolism in Cultured Hepatocytes and Mice Fed a High-Fat Diet

Hemin is a breakdown product of hemoglobin. It has been reported that the injection of hemin improves lipid metabolism and insulin sensitivity in various genetic models. However, the effect of hemin supplementation in food on lipid metabolism and insulin sensitivity is still unclear, and whether hemin directly affects cellular insulin sensitivity is yet to be elucidated. Here we show that hemin enhances insulin-induced phosphorylation of insulin receptors, Akt, Gsk3β, FoxO1 and cytoplasmic translocation of FoxO1 in cultured primary hepatocytes under insulin-resistant conditions. Furthermore, hemin diminishes the accumulation of triglyceride and increases in free fatty acid content in primary hepatocytes induced by palmitate. Oral administration of hemin decreases body weight, energy intake, blood glucose and triglyceride levels, and improves insulin and glucose tolerance as well as hepatic insulin signaling and hepatic steatosis in male mice fed a high-fat diet. In addition, hemin treatment decreases the mRNA and protein levels of some hepatic genes involved in lipogenic regulation, fatty acid synthesis and storage, and increases the mRNA level and enzyme activity of CPT1 involved in fatty acid oxidation. These data demonstrate that hemin can improve lipid metabolism and insulin sensitivity in both cultured hepatocytes and mice fed a high-fat diet, and show the potential beneficial effects of hemin from food on lipid and glucose metabolism.

Evolution of the SOUL Heme-Binding Protein Superfamily Across Eukarya

SOUL homologs constitute a heme-binding protein superfamily putatively involved in heme and tetrapyrrole metabolisms associated with a number of physiological processes. Despite their omnipresence across the tree of life and the biochemical characterization of many SOUL members, their functional role and the evolutionary events leading to such remarkable protein repertoire still remain cryptic. To explore SOUL evolution, we apply a computational phylogenetic approach, including a relevant number of SOUL homologs, to identify paralog forms and reconstruct their genealogy across the tree of life and within species. In animal lineages, multiple gene duplication or loss events and paralog functional specializations underlie SOUL evolution from the dawn of ancestral echinoderm and mollusc SOUL forms. In photosynthetic organisms, SOUL evolution is linked to the endosymbiosis events leading to plastid acquisition in eukaryotes. Derivative features, such as the F2L peptide and BH3 domain, evolved in vertebrates and provided innovative functionality to support immune response and apoptosis. The evolution of elements such as the N-terminal protein domain DUF2358, the His42 residue, or the tetrapyrrole heme-binding site is modern, and their functional implications still unresolved. This study represents the first in-depth analysis of SOUL protein evolution and provides novel insights in the understanding of their obscure physiological role.

Complicity of haem in some adverse drug-reactions

Genetic variants in haem metabolism enzymes can be predisposition factors for adverse reactions in some individuals. New areas of haem biology may also be associated with idiosyncratic effects which are yet to be identified.

Imaging of heme/hemeproteins in nucleus of the living cells expressing heme-binding nuclear receptors

Several factors involved in the core circadian rhythm are PAS domain proteins, one of which, neuronal PAS2 (NPAS2), contains a heme-binding motif. It is thought that heme controls the transcriptional activity of core circadian factors BMAL1-NPAS2, and that the heme-binding nuclear receptor REV-erbα negatively regulates the expression of BMAL1. To examine the role of heme in the nucleus, we expressed nuclear hemeproteins including the nuclear localization signal-added cytoglobin, NPAS2 and REV-erbα. Then, the living cells expressing these proteins were treated with 2',7'-dichlorodihydrofluorescin diacetate (DCFH-DA). The fluorescent signal derived from DCFH-DA was observed in the nucleus. When the cells were cultured with hemin, the signal of heme in the nucleus increased. Considering that DCFH-DA reacted with heme, we propose that the use of DCFH-DA could be useful in detection of the heme moiety of hemeprotein in vivo.

The p53-dependent expression of frataxin controls 5-aminolevulinic acid-induced accumulation of protoporphyrin IX and photo-damage in cancerous cells

Mitochondrial frataxin is involved in various functions such as iron homeostasis, iron-sulfur cluster biogenesis, the protection from oxidative stress and apoptosis and acts as a tumor suppressor protein. We now show that the expression of frataxin is stimulated in a p53-dependent manner and prove that frataxin is a direct p53 target gene by showing that the p53-responsive element in the promoter of the mouse frataxin gene is bound by p53. The bacterial expression of human frataxin stimulated maturation of human ferrochelatase, which catalyzes the insertion of iron into protoporphyrin at the last step of heme biosynthesis. Overexpression of frataxin in human cancer A431 and HeLa cells lowered 5-aminolevulinic acid(ALA)-induced accumulation of protoporphyrin and induced resistance to ALA-induced photo-damage, whereas p53 silencing with siRNA in non tumor HEK293T cells down-regulated the expression of frataxin and increased the accumulation of protoporphyrin. Thus, the decrease of the expression of frataxin unregulated by p53 in tumor cells enhances ALA-induced photo-damage, by down-regulation of mitochondrial functions.