Jin-Wen Xu

Quercetin Induces Rapid eNOS Phosphorylation and Vasodilation by an Akt-Independent and PKA-Dependent Mechanism

Consumption of the flavonoid quercetin exerts beneficial effects on many chronic diseases. The mechanisms involved in the vasorelaxant effect of quercetin remain uncertain. In the present study, we examined the role of quercetin in vasodilation and rapid endothelial nitric oxide synthase (eNOS) activity in endothelial cells. Quercetin induced a rapid, dose-dependent phosphorylation of eNOS at serine 1179. PKA, Akt and ERK1/2 were all quickly phosphorylated in the process too, but not AMPK and CaMK II. The specific kinase inhibitors for Akt or ERK1/2 could not abolish the quercetin-induced eNOS phosphorylation at Ser1179, which, however, was significantly abolished by H89, an inhibitor of PKA. Concomitantly, intracellular cAMP production was quickly increased by quercetin stimulation and an adenylate cyclase activator, forskolin, also induced eNOS phosphorylation at Ser1179. Quercetin enhanced nitric oxide (NO) production, which was abolished by an eNOS inhibitor, L-NAME or H89. Quercetin exerted a vasodilatory effect on rings with an intact endothelium but not on endothelium-deprived rings, and also inhibited vascular contractility induced by angiotensin II or phenylephrine in rat aortic rings. We conclude that quercetin quickly phosphorylates eNOS at Ser1179 via an Akt-independent, cAMP/PKA-mediated pathway to enhance the production of NO and to promote vasodilation.

Scropolioside B Inhibits IL-1β and Cytokines Expression through NF-κB and Inflammasome NLRP3 Pathways

Chronic inflammation is associated with various chronic illnesses including immunity disorders, cancer, neurodegeneration, and vascular diseases. Iridoids are compounds with anti-inflammatory properties. However their anti-inflammatory mechanism remains unclear. Here, we report that scropolioside B, isolated from a Tibetan medicine (Scrophularia dentata Royle ex Benth.), blocked expressions of TNF, IL-1, and IL-32 through NF-κB pathway. Scropolioside B inhibited NF-κB activity in a dose-dependent manner with IC50 values of 1.02 μmol/L. However, catalpol, similar to scropolioside B, was not effective in inhibiting NF-κB activity. Interestingly, scropolioside B and catalpol decreased the expression of NLRP3 and cardiolipin synthetase at both the mRNA and protein level. Our results showed that scropolioside B is superior in inhibiting the expression, maturation, and secretion of IL-1β compared to catalpol. These observations provide further understanding of the anti-inflammatory effects of iridoids and highlight scropolioside B as a potential drug for the treatment of rheumatoid arthritis and atherosclerosis.

Bavachalcone-induced manganese superoxide dismutase expression through the AMP-activated protein kinase pathway in human endothelial cells.

Mitochondrial oxidative stress has been suggested as a major etiological factor in cardiovascular diseases. Manganese superoxide dismutase (MnSOD) is an essential antioxidant mitochondrial enzyme. Although polyphenols can induce MnSOD expression, their mechanism of action remains unclear. We examined the effect of bavachalcone, a bioactive compound isolated from Psoralea corylifolia, on MnSOD protein expression and explored whether this effect is mediated through the AMP-activated protein kinase (AMPK) signaling pathway. Our data showed that bavachalcone enhanced the luciferase activity of the MnSOD promoter and increased MnSOD mRNA and protein expressions. Moreover, bavachalcone suppressed the mitochondrial superoxide production in endothelial cells. Conversely, bavachalcone stimulated liver kinase B1 and AMPKα phosphorylation. mRNA interference by using short hairpin RNA (shRNA) of AMPK inhibited bavachalcone-induced MnSOD expression. A-769662, an AMPK activator, also stimulated AMPK activity and increased MnSOD expression. Furthermore, AMPK knockdown by shRNA-AMPK reversed the inhibitory effects of bavachalcone on mitochondrial superoxide production in endothelial cells. These findings indicate that bavachalcone can protect the endothelial function by increasing AMPK activity and MnSOD expression and reducing mitochondrial oxidative stress.

Aortic Remodelling Is Improved by 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside Involving the Smad3 Pathway in Spontaneously Hypertensive Rats

Hypertension is a common health problem that substantially increases the risk of cardiovascular disease. The condition increases blood pressure, which causes alterations in vascular structure and leads to the development of vascular pathologies. 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside (THSG), a resveratrol analogue extracted from a Chinese medicinal plant, has been proven to have numerous vascular protection functions. This study investigated whether THSG can improve vascular remodeling, which has thus far remained unclear. Orally administering THSG to spontaneously hypertensive rats (SHRs) aged 12 weeks for 14 weeks significantly inhibited intima-media thickness in the lower parts of the aortic arch, increased the vascular diastolic rate in response to acetylcholine, and reduced remodelling-related mRNA expression, such as that of ACTA2, CCL3, COL1A2, COL3A1, TIMP1 WISP2, IGFBP1, ECE1, KLF5, MYL1 BMP4, FN1, and PAI-1. Immunofluorescence staining also showed an inhibitory effect similar to that of THSG on PAI-1 protein expression in rat aortas. Results from immunoprecipitation and a Western blot assay showed that THSG inhibited the acetylation of Smad3. A chromatin immunoprecipitation assay showed that THSG prevented Smad3 binding to the PAI-1 proximal promoter in SHR aortas. In conclusion, our results demonstrated that the inhibitory effect of THSG on aortic remodelling involved the deacetylating role of Smad3 with increasing blood flow and with constant blood pressure.

2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside Promotes Expression of the Longevity Gene Klotho

The longevity gene klotho has numerous physiological functions, such as regulating calcium and phosphorus levels, delaying senescence, improving cognition, reducing oxidative stress, and protecting vascular endothelial cells. This study tested whether 2,3,5,4′-Tetrahydroxystilbene-2-O-β-D-glucoside (THSG), a small molecule with antiaging effects, regulates the expression and physiological effects of klotho. Our results showed that THSG dose-dependently increased the luciferase reporter activity of the klotho gene, reversed the decrease in mRNA and protein expression of klotho which was induced by angiotensin II in NRK-52E renal tubular epithelial cells, and increased klotho mRNA expression in the cerebral cortex, hippocampus, testis, and kidney medulla of spontaneously hypertensive rats. THSG also reduced the number of senescent cells induced by angiotensin II and improved the antioxidant capacity and enhanced the bone strength in vivo. Based on klothos role in promoting cognition, regulating bone metabolism, and improving renal function, the effect of THSG on klotho expression will be beneficial to the functional improvement or enhancement of the expressed organs or tissues.

Anti-Inflammatory Activity Comparison among Scropoliosides—Catalpol Derivatives with 6-O-Substituted Cinnamyl Moieties

We have previously shown that scropolioside B has higher anti-inflammatory activity than catalpol does after the inhibition of nuclear factor (NF)-κB activity and IL-1β expression, maturation, and secretion. Various scropoliosides were extracted, isolated, and purified from Scrophularia dentata Royle ex Benth. We then compared their anti-inflammatory activities against LPS-induced NF-κB activity, cytokines mRNA expression, IL-1β secretion, and cyclooxygenase-2 activity. The inhibitory effects of the scropoliosides varied depending on whether the 6-O-substituted cinnamyl moiety was linked to C′′ 2-OH, C′′3-OH, or C′′4-OH, and on the number of moieties linked, which is closely related to the enhancement of antiinflammatory activity. Among these compounds, scropolioside B had the strongest antiinflammatory effects.

ERK5/HDAC5‐mediated, resveratrol‐, and pterostilbene‐induced expression of MnSOD in human endothelial cells

SCOPE Mitochondrial oxidative stress is closely correlated with numerous cardiovascular diseases. Manganese superoxide dismutase (MnSOD) is an important antioxidant enzyme in mitochondria. Although polyphenols can induce the expression of MnSOD, their corresponding mechanisms remains unclear. In this study, we tested the hypothesis that resveratrol and pterostilbene can activate the expression of MnSOD through an AMPK-ERK5/HDAC5-KLF2 pathway. METHODS AND RESULTS Our results revealed that two stilbenes reduced mitochondrial superoxide-free radicals, and endothelial cell senescence, and increased the mRNA expression of several genes related to mitochondrial function, including MnSOD. Moreover, two stilbenes upregulated the activation of human MnSOD promoter luciferase reporter gene and protein level in human umbilical vein endothelial cells. Similarly, two stilbenes also stimulated LKB1, AMPKα, extracellular-signal related kinase 5 (ERK5) phosphorylation, and histone acetylase 5 (HDAC5) and Kruppel-like factor 2 (KLF2) expression. The knockdown of AMP-activated protein kinase (AMPK), ERK5, and HDAC5 by using short-hairpin RNA blocked pterostilbene-induced phosphorylation of their downstream signaling proteins and the expression of KLF2. Furthermore, using a chromatin immunoprecipitation-PCR detection method, we found that resveratrol and pterostilbene promoted KLF2 binding to CACCC sites of the human MnSOD promoter. CONCLUSION Resveratrol and pterostilbene can activate MnSOD expression through ERK5/HDAC5 pathway, thus alleviating mitochondrial oxidative stress in endothelial cells that relates to cardiovascular disease.

Bavachalcone Enhances RORα Expression, Controls Bmal1 Circadian Transcription, and Depresses Cellular Senescence in Human Endothelial Cells.

The circadian clock regulates many aspects of (patho)physiology in the central nervous system and in the peripheral tissues. RAR-related orphan receptor α (RORα), an orphan nuclear receptor, is involved in circadian rhythm regulation, including regulation of cardiovascular function. Bavachalcone, a prenylchalcone, is a major bioactive chalcone isolated from Psoralea corylifolia. This natural ingredient activated RORα1 luciferase reporter activity on drug screening. In addition, bavachalcone induced RORα1 expression in mRNA and protein levels in a dose-dependent manner and enhanced the circadian amplitude of Bmal1 mRNA expression after serum shock. Moreover, bavachalcone suppressed senescence in human endothelial cells and mRNA expression of p16ink4a (a marker of replicative senescence) and IL-1α (a proinflammatory cytokine of the senescence-associated secretory phenotype). These inhibitory effects were partially reversed by the RORα inhibitor VPR-66. Our results demonstrate that bavachalcone, as a natural medicine ingredient, has a pharmacological function in regulating RORα1.

Higher-Order Chromatin Regulation of Inflammatory Gene Expression

Whether it is caused by viruses and bacteria infection, or low-grade chronic inflammation of atherosclerosis and cellular senescence, the transcription factor (TF) NF-κB plays a central role in the inducible expression of inflammatory genes. Accumulated evidence has indicated that the chromatin environment is the main determinant of TF binding in gene expression regulation, including the stimulus-responsive NF-κB. Dynamic changes in intra- and interchromosomes are the key regulatory mechanisms promoting the binding of TFs. When an inflammatory process is triggered, NF-κB binds to enhancers or superenhancers, triggering the transcription of enhancer RNA (eRNA), driving the chromatin of the NF-κB-binding gene locus to construct transcriptional factories, and forming intra- or interchromosomal contacts. These processes reveal a mechanism in which intrachromosomal contacts appear to be cis-control enhancer-promoter communications, whereas interchromosomal regulatory elements construct trans-form relationships with genes on other chromosomes. This article will review emerging evidence on the genome organization hierarchy underlying the inflammatory response.

Dunye Guanxinning Improves Acute Myocardial Ischemia-Reperfusion Injury by Inhibiting Neutrophil Infiltration and Caspase-1 Activity

Acute myocardial infarction is the most serious manifestation of cardiovascular disease, and it is a life-threatening condition. Dunye Guanxinning (DG) is a protective traditional Chinese patent herbal medicine with high clinical efficacy and suitable for the treatment of myocardial infarction. However, the mechanism through which it is beneficial is unclear. In this study, we hypothesized that DG improves acute myocardial ischemia-reperfusion injury by inhibiting neutrophil infiltration and caspase-1 activity. We found that DG administration decreased infarct size and cardiomyocyte apoptosis and improved left ventricular ejection fraction, fractional shortening, end-systolic volume index, end-systolic diameter, and carotid arterial blood flow output in rats. DG administration also improved hemorheological parameters, myocardial damage biomarkers, and oxidative stress indexes. The findings showed that DG administration inhibited neutrophil infiltration and reduced the serum interleukin-1 beta (IL-1β) level and myocardial IL-1β maturation. Moreover, DG administration inhibited caspase-1 activity and activated adenosine monophosphate-activated protein kinase (AMPK) phosphorylation in rat hearts. These results suggested that DG administration inhibits inflammasome activity and IL-1β release through the AMPK pathway. Our findings support the clinical efficacy of DG and partially reveal its mechanism, which is beneficial for understanding the therapeutic effects of this protective traditional Chinese patent drug.