Resurrection of endogenous retroviruses during aging reinforces senescence.

Whether and how certain transposable elements with viral origins, such as endogenous retroviruses (ERVs) dormant in our genomes, can become awakened and contribute to the aging process is largely unknown. In human senescent cells, we found that HERVK (HML-2), the most recently integrated human ERVs, are unlocked to transcribe viral genes and produce retrovirus-like particles (RVLPs). These HERVK RVLPs constitute a transmissible message to elicit senescence phenotypes in young cells, which can be blocked by neutralizing antibodies. The activation of ERVs was also observed in organs of aged primates and mice as well as in human tissues and serum from the elderly. Their repression alleviates cellular senescence and tissue degeneration and, to some extent, organismal aging. These findings indicate that the resurrection of ERVs is a hallmark and driving force of cellular senescence and tissue aging.

Omics and Transgenic Analyses Reveal that Salvianolic Acid B Exhibits its Anti-Inflammatory Effects through Inhibiting the Mincle-Syk-Related Pathway in Macrophages.

Salvianolic acid B (Sal B), the main water-soluble compound in Salvia miltiorrhiza, is known to exhibit anti-inflammatory activity, however, the underlying mechanism(s) is not completely uncovered. In this study, Sal B inhibited lipopolysaccharide (LPS)-induced M1 activation and promoted the transformation of macrophages from M1- to M2-type polarization. The altered lipid profiles of LPS-induced RAW 264.7 macrophages were partly restored by Sal B treatment. At the proteomic level, a total of 5612 proteins were identified and 432 were significantly changed in macrophages under LPS treatment. The differential proteins were classified into four clusters according to their expression level in blank, LPS, and Sal B groups. LPS-induced proteins in Cluster IV including Kif14, Mincle, and Sec62 were significantly recovered to almost normal levels by Sal B treatment. Use of knockdown Mincle or picetannol (inhibitor of Syk) led to significant reductions in the gene expressions of IL-1ß, iNOS, and IL-12 and the release of NO. The converse was, however, observed for overexpressed Mincle. In addition, LPS- or trehalose-6,6-dibehenate-induced phosphorylation of Syk and PKCδ was decreased by Sal B treatment. These results suggest that Sal B inhibition of LPS-induced inflammation might be through inhibition of the Mincle-Syk-PKCδ signaling pathway.

Integrative omic and transgenic analyses reveal the positive effect of ultraviolet-B irradiation on salvianolic acid biosynthesis through upregulation of SmNAC1.

Salvianolic acids (SalAs), a group of secondary metabolites in Salvia miltiorrhiza, are widely used for treating cerebrovascular diseases. Their biosynthesis is modulated by a variety of abiotic factors, including ultraviolet-B (UV-B) irradiation; however, the underlying mechanisms remain largely unknown. Here, an integrated metabolomic, proteomic, and transcriptomic approach coupled with transgenic analyses was employed to dissect the mechanisms underlying UV-B irradiation-induced SalA biosynthesis. Results of metabolomics showed that 28 metabolites, including 12 SalAs, were elevated in leaves of UV-B-treated S. miltiorrhiza. Meanwhile, the contents of several phytohormones, including jasmonic acid and salicylic acid, which positively modulate the biosynthesis of SalAs, also increased in UV-B-treated S. miltiorrhiza. Consistently, 20 core biosynthetic enzymes and numerous transcription factors that are involved in SalA biosynthesis were elevated in treated samples as indicated by a comprehensive proteomic analysis. Correlation and gene expression analyses demonstrated that the NAC1 gene, encoding a NAC transcriptional factor, was positively involved in UV-B-induced SalA biosynthesis. Accordingly, overexpression and RNA interference of NAC1 increased and decreased SalA contents, respectively, through regulation of key biosynthetic enzymes. Furthermore, ChIP-qPCR and Dual-LUC assays showed that NAC1 could directly bind to the CATGTG and CATGTC motifs present in the promoters of the SalA biosynthesis-related genes PAL3 and TAT3, respectively, and activate their expression. Our results collectively demonstrate that NAC1 plays a crucial role in UV-B irradiation-induced SalA biosynthesis. Taken together, our findings provide mechanistic insights into the UV-B-induced SalA biosynthesis in S. miltiorrhiza, and shed light on a great potential for the development of SalA-abundant varieties through genetic engineering.

Mangiferin activates Nrf2 to attenuate cardiac fibrosis via redistributing glutaminolysis-derived glutamate.

Cardiac injury is followed by fibrosis, characterized by myofibroblast activation. Excessive deposition of extracellular matrix (ECM) impairs the plasticity of myocardium and results in myocardial systolic and diastolic dysfunction. Mangiferin is a xanthonoid derivative rich in plants mangoes and iris unguicularis, exhibiting the ability to ameliorate metabolic disorders. This study aims to investigate whether mangiferin attenuates cardiac fibrosis via redox regulation. The transverse aortic constriction (TAC) in mice induced cardiac fibrosis with impaired heart function. Oral administration of mangiferin (50 mg/kg, 4 weeks) inhibited myofibroblast activation with reduced formation of ECM. The impaired left ventricular contractive function was also improved by mangiferin. TGF-ß1 stimulation increased glutaminolysis to fuel intracellular glutamate pool for the increased demands of nutrients to support cardiac myofibroblast activation. Mangiferin degraded Keap1 to promote Nrf2 protein accumulation by improving its stability, leading to Nrf2 activation. Nrf2 transcriptionally promotes the synthesis of antioxidant proteins. By activating Nrf2, mangiferin promoted the synthesis of glutathione (GSH) in cardiac fibroblasts, likely due to the consumption of glutaminolysis-derived glutamate as a source. Meanwhile, mangiferin promoted the exchange of intracellular glutamate for the import of extracellular cystine to support GSH generation. As a result of redistribution, the reduced glutamate availability failed to support myofibroblast activation. In support of this, the addition of extracellular glutamate or α-ketoglutarate diminished the inhibitory effects of mangiferin on cardiac myofibroblast proliferation and activation. Moreover, cardiac knockdown of Nrf2 attenuated the cardioprotective effects of mangiferin in mice subjected to TAC. In conclusion, we demonstrated that activated myofibroblasts were sensitive to glutamate availability. Mangiferin activated Nrf2 and redistributed intracellular glutamate for the synthesis of GSH, consequently impairing cardiac myofibroblast activation due to decreased glutamate availability. These results address that pharmacological activation of Nrf2 could restrain cardiac fibrosis via metabolic regulation.

Succinate accumulation impairs cardiac pyruvate dehydrogenase activity through GRP91-dependent and independent signaling pathways: Therapeutic effects of ginsenoside Rb1.

Altered mitochondrial oxidation increases vulnerability to cardiac ischemia/reperfusion (I/R) injury in metabolic disorders. However, the metabolic signaling responsible for the dysfunction remains partly unknown. We sought to test whether or not hypoxic succinate accumulation could inhibit pyruvate dehydrogenase (PDH) activity and subsequently aggravate I/R injury. Results showed that saturated fatty acid palmitate stimulation increased fatty acid oxidation and induced hypoxia in cardiomyocytes, leading to succinate accumulation. Intracellular succinate induced hypoxia inducible factor-1α (HIF-1α) expression and impaired PDH activity via upregulation of pyruvate dehydrogenase kinase 4 (PDK4) expression. Luciferase reporter assay showed that succinate increased PDK4 expression through gene promoter induction in a HIF-1α-dependent manner. Palmitate also induced the release of succinate into extracellular space. By activating GRP91, extracellular succinate induced the translocation of PKCδ to mitochondria and further exacerbated PDH impairment. These results demonstrated that succinate impaired PDH activity via GPR91-dependent and independent pathways. Ginsenoside Rb1 (a major compound isolated from ginseng) and trimetazidine (fatty acid ß-oxidation inhibitor) prevented hypoxic succinate accumulation in cardiomyocytes and improved PDH activity by blocking succinate-associated HIF-1α activation and GPR91 signaling. Through improving PDH activity, Rb1 and trimetazidine prevented cardiac acidification, ameliorated mitochondrial dysfunction and thereby reduced apoptosis during hypoxia/reoxygenation insult. In isolated working rat hearts perfused with palmitate and in high-fat diet-fed mice, early intervention of Rb1 and trimetazidine reduced succinate production and resultantly increased heart resistance to ischemia/reperfusion injury. Taken together, our findings demonstrated that early intervention by targeting inhibition of succinate accumulation-induced PDH impairment is an effective strategy to alleviate I/R injury.

Decitabine Downregulates TIGAR to Induce Apoptosis and Autophagy in Myeloid Leukemia Cells.

Decitabine (DAC) is a well-known DNA methyltransferase inhibitor, which has been widely used for the treatment of acute myeloid leukemia (AML). However, in addition to hypomethylation, DAC in AML is also involved in cell metabolism, apoptosis, and immunity. The TP53-induced glycolysis and apoptosis regulator (TIGAR) functions to inhabit glycolysis and protect cancer cells from reactive oxygen species- (ROS-) associated apoptosis. Our previous study revealed that TIGAR is highly expressed in myeloid leukemia cell lines and AML primary cells and associated with poor prognosis in adult patients with cytogenetically normal AML. In the present study, it was found that in a time- and concentration-dependent manner, DAC downregulates the TIGAR expression, induces ROS production, and promotes apoptosis in HL-60 and K562 cells. However, blocking the glycolytic pathway partially reversed the combined effects of DAC and TIGAR knockdown on apoptosis, ROS production, and cell cycle arrest, indicating that DAC induced apoptosis through the glycolytic pathway. Furthermore, TIGAR also has a negative impact on autophagy, while DAC treatment upregulates autophagy-related proteins LC3, Beclin-1, ATG3, and ATG-5, downregulates p62, and promotes the formation of autophagosomes, indicating that DAC may activate autophagy by downregulating TIGAR. Taken together, DAC plays an unmethylated role in inducing apoptosis and activating autophagy in myeloid leukemia by downregulating TIGAR.

Melatonin as an inducer of arecoline and their coordinated roles in anti-oxidative activity and immune responses.

Arecoline is one of the main medicinal constituents in areca. Melatonin is an amine molecule with multiple functions in plants and animals. However, the interaction between arecoline and melatonin remains unknown. Herein, metabolomics analysis showed that multiple metabolites including arecoline were induced in areca by exogenous melatonin. In vitro assay demonstrated that the induced arecoline had strong antioxidant capacities, being similar to the traditional function of melatonin. Both arecoline and melatonin could significantly improve plant disease resistance against Colletotrichum kahawae and delay post-harvest physiological deterioration (PPD) of areca fruits, through modulation of the levels of jasmonic acid (JA), salicylic acid (SA), ethylene (ETH) and abscisic acid (ABA), reactive oxygen species (ROS) level as well as glycolytic activity. In addition, animal and cell assays indicated that arecoline and melatonin could commonly enhance anti-inflammatory effects through regulating ROS and hypoxia inducible factor-1α (HIF-1α). Taken together, melatonin could serve as an inducer of arecoline and they show coordinated roles in antioxidative activity and immune responses in areca and animals. This study greatly extends the knowledge of the action of melatonin in areca and animals.

Compounds containing trace element copper or zinc exhibit as potent hyperuricemia inhibitors via xanthine oxidase inactivation.

Compounds containing trace elements copper or zinc are potential gout and hyperuricemia suppressant by virtue of their inhibiting effect on xanthine oxidase/xanthine dehydrogenase (XOD/XDH) and anti-inflammatory and anti-oxidative function. In this study, compounds Cu(hmy-paa)·SO4·H2O (simplified as CuHP) and Zn(hmy-paa)·SO4·H2O (simplified as ZnHP) are synthesized, where hmy-paa stands for 3-(4-hydroxy-3-methoxyphenyl)-N-(1H-pyrazol-3-yl)acrylamide). The ligand hmy-paa is composed of functional ferulic acid and 3-aminopyrazole. The XOD and XDH activity of the mouse liver homogenate could efficiently be inhibited by CuHP and ZnHP. XOD has been recognized as one of the promising targets for the treatment of hyperuricemia. Fluorescence spectrometry study indicates that the interaction between the compound and XOD could be strengthened by the introduction of metals. In vitro drug efficacy study illustrates that metals copper and zinc distinctly improves the uric acid reducing efficacy by suppressing XOD activation. Hyperuricemia mouse model is induced by co-treatment of hypoxanthine and oteracil potassium. Intraperitoneal injection of CuHP and ZnHP to hyperuricemia mice exhibits a significant effect on reducing serum uric acid. The serum creatinine value detection indicates that the side effect of CuHP and ZnHP on renal function is weak. The computational docking simulation exhibits the tightly binding mode between the compound and XOD. Consequently, compounds CuHP and ZnHP are new type candidates for the treatment of gout and hyperuricemia.

Succinate induces aberrant mitochondrial fission in cardiomyocytes through GPR91 signaling.

Altered mitochondrial metabolism acts as an initial cause for cardiovascular diseases and metabolic intermediate succinate emerges as a mediator of mitochondrial dysfunction. This work aims to investigate whether or not extracellular succinate accumulation and its targeted G protein-coupled receptor-91 (GPR91) activation induce cardiac injury through mitochondrial impairment. The results showed that extracellular succinate promoted the translocation of dynamin-related protein 1 (Drp1) to mitochondria via protein kinase Cδ (PKCδ) activation, and induced mitochondrial fission factor (MFF) phosphorylation via extracellular signal-regulated kinases-1/2 (ERK1/2) activation in a GPR91-dependent manner. As a result, enhanced localization of MFF and Drp1 in mitochondria promoted mitochondrial fission, leading to mitochondrial dysfunction and cardiomyocyte apoptosis. We further showed that inhibition of succinate release and GPR91 signaling ameliorated oxygen-glucose deprivation-induced injury in cardiomyocytes and isoproterenol-induced myocardial ischemia injury in mice. Taken together, these results showed that in response to cardiac ischemia, succinate release activated GPR91 and induced mitochondrial fission via regulation of PKCδ and ERK1/2 signaling branches. These findings suggest that inhibition of extracellular succinate-mediated GPR91 activation might be a potential therapeutic strategy for protecting cardiomyocytes from ischemic injury.

Inhibition of lipolysis by ilexgenin A via AMPK activation contributes to the prevention of hepatic insulin resistance.

Adipose dysfunction links tightly to hepatic insulin resistance and gluconeogenesis. Ilexgenin A is reported with the ability to regulate lipid profile and protect the liver against high fat diet (HFD) -induced impairment. Here, we propose that ilexgenin A ameliorates hepatic insulin signaling and gluconeogenesis by regulating lipolysis in white adipose tissue (WAT). Pyruvate tolerance test and biochemical analysis coupled with the ex vivo siRNA knockdown and co-culture studies demonstrate that ilexgenin A suppresses inflammation-associated lipolysis in epididymal fat pad via 5'-AMP-activated protein kinase (AMPK) activation, thus inhibits diacylglycerol (DAG) accumulation and protein kinase C ε (PKCε) translocation in liver, leading to the improvement of insulin sensitivity and hepatic glucose production. These findings suggest that the relationship between adipose function and hepatic insulin action may be targeted by natural bioactive components for the potential treatment of hepatic insulin resistance related disorders.