Inhibitory Effect Of Hg Research Articles

Higenamine attenuates cardiac fibroblast abstract and fibrosis via inhibition of TGF-β1/Smad signaling

RationaleHigenamine (HG), is one of the main active components in many widely used Chinese herbs, and a common ingredient of health products in Europe and North America. Several groups, including our own, have previously shown the beneficial effects of HG against cardiomyocyte death during acute ischemic damage. However, the effect of HG on chronic cardiac remodeling, such as cardiac fibrosis, remains unknown. ObjectiveHerein, we aim to investigate the role of HG in cardiac fibrosis in vivo as well as its cellular and molecular mechanisms. Methods and resultsChronic pressure overload with transverse aortic constriction (TAC) significantly increased cardiac hypertrophy, fibrosis, and cardiac dysfunction in mice, which were significantly attenuated by HG. Consistently, cardiac fibrosis induced by the chronic infusion of isoproterenol (ISO), was also significantly reduced by HG. Interestingly, our results showed that HG had no effect on adult mouse CM hypertrophy in vitro. However, HG suppressed the activation of cardiac fibroblasts (CFs) in vitro. Furthermore, TGF-β1-induced expression of ACTA2, a marker of fibroblast activation, was significantly suppressed by HG. Concomitantly, HG inhibited TGF-β1-induced phosphorylation of Smad2/3 in CFs. HG also reduced the expression of extracellular matrix molecules such as collagen I and collagen III. To our surprise, the inhibitory effect of HG on CFs activation was independent of the activation of the beta2 adrenergic receptor (β2-AR) that is known to mediate the effect of HG on antagonizing CMs apoptosis. ConclusionOur findings suggest that HG ameliorates pathological cardiac fibrosis and dysfunction at least partially by suppressing TGF-β1/Smad signaling and CFs activation.

Astilbin inhibits high glucose-induced autophagy and apoptosis through the PI3K/Akt pathway in human proximal tubular epithelial cells

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease. It has been found that astilbin, a flavonoid compound, exerts a protective effect on DN. However, the role of astilbin in autophagy during DN is unknown. The human proximal tubular epithelial cells (HK-2 cells) were treated with high glucose (HG, 30 mM) in the presence or absence of astilbin. Cell viability was measured by MTT assay. The autophagy was determined by detecting the expression of LC3-II and p62 using western blot. The cell apoptosis was evaluated by detecting the apoptosis rate, caspase-3 activity, and the expression of Bcl-2 and Bax. The expression levels of protein kinase B (Akt) and p-Akt were detected by western blot. To determine whether the phosphatidylinositol-3-kinase (PI3K)/Akt pathway was involved in the effect of astilbin, cells were treated with the inhibitor of Akt, LY294002. We found that astilbin (10 and 20 μM) did not affect the viability of HK-2 cells, but attenuated HG-induced cell viability. Astilbin attenuated HG-induced autophagy and apoptosis in HK-2 cells. The expression of p-Akt was inhibited by HG treatment, while the inhibitory effect of HG was attenuated by astilbin. Inhibition of the PI3K/Akt signaling resisted the effect of astilbin on HG-induced apoptosis and autophagy. In conclusion, astilbin attenuated HG-induced autophagy and apoptosis in HK-2 cells through the PI3K/Akt pathway. The results indicated that astilbin might be a new therapeutic agent and be useful for improving clinical management of DN.

Mercury effects on Thalassiosira weissflogii: Applications of two-photon excitation chlorophyll fluorescence lifetime imaging and flow cytometry

The toxic effects of inorganic mercury [Hg(II)] and methylmercury (MeHg) on the photosynthesis and population growth in a marine diatom Thalassiosira weissflogii were investigated using two methods: two-photon excitation fluorescence lifetime imaging (FLIM) and flow cytometry (FCM). For photosynthesis, Hg(II) exposure increased the average chlorophyll fluorescence lifetime, whereas such increment was not found under MeHg stress. This may be caused by the inhibitory effect of Hg(II) instead of MeHg on the electron transport chain. For population growth, modeled specific growth rate data showed that the reduction in population growth by Hg(II) mainly resulted from an increased number of injured cells, while the live cells divided at the normal rates. However, MeHg inhibitory effects on population growth were contributed by the reduced division rates of all cells. Furthermore, the cell images and the FCM data reflected the morphological changes of diatom cells under Hg(II)/MeHg exposure vividly and quantitatively. Our results demonstrated that the toxigenicity mechanisms between Hg(II) and MeHg were different in the algal cells.

Effects of high glucose plus high insulin on proliferation and apoptosis of mouse endothelial progenitor cells

To study the effects of high glucose plus high insulin (GI) on proliferation, apoptosis, morphology and differentiation of endothelial progenitor cells (EPC). EPC were isolated and identified by magnetic cell sorting and flow cytometry. EPC proliferation and apoptosis were measured by MTT assay and Annexin-V/PI double labeling, respectively. Cell proliferation- and apoptosis-related factors were examined by Western blotting. Seven days after GI treatment, EPC were arrested at the G(0)/G(1) phase. Treatment with high glucose alone (HG) or GI but not HI (high insulin alone) decreased EPC proliferation and their expression of cyclin E, cdk2 and PCNA compared to control. The inhibitory effects of HG on EPC proliferation and growth-related proteins were more significant than those of GI. HG, GI and HI promoted EPC apoptosis along with caspase-3 overexpression. The result indicated that GI-induced apoptosis and growth inhibition might be one of mechanisms of EPC reduction and dysfunction in diabetes.

Hyperglycemia Accelerated Endothelial Progenitor Cell Senescence via the Activation of p38 Mitogen-Activated Protein Kinase

Both the number and function of bone marrow-derived endothelial progenitor cells (EPCs) have been shown to be impaired in patients with diabetes mellitus. Therefore, we investigated the effect of glucose on the senescence of EPCs. EPCs were isolated from human peripheral blood and characterized to evaluate the effect of glucose (in 5-12.5 mmol/L) on the rate of senescence by acidic beta-galactosidase staining. The phosphorylation of p38 mitogen-activated protein kinase (MAPK) level was analyzed by ELISA. The exposure of cultured EPC to high glucose (HG; 12.5 mmol/L) significantly accelerated the rate of senescence compared with that in osmolar control (L-glucose) during 10 days culture. An inhibitory effect of HG on EPC proliferation disclosed by an MTS assay. The phosphorylation of p38 MAPK in EPCs was also increased by glucose compared with control in a dose-dependent manner. HG-induced EPC senescence was significantly inhibited by the addition of an inhibitor of the p38 MAPK, SB203580. HG accelerates the onset of EPCs senescence leading to the impairment of proliferative activity, which might be related to the phosphorylation of p38 MAPK.

2,3-Dimercaptopropane-1-sulfonic acid and meso-2,3-dimercaptosuccinic acid increase mercury- and cadmium-induced inhibition of δ-aminolevulinate dehydratase

Compounds derived from Dimercaprol, such as meso-2,3-dimercaptosuccinic acid (DMSA) and 2,3-dimercaptopropane-1-sulfonic acid (DMPS), are becoming common agents for treating humans exposed to heavy metals. Heavy metals such as Pb 2+, Hg 2+ and Cd 2+ can inhibit δ-aminolevulinate dehydratase (δ-ALA-D) activity. δ-ALA-D catalyzes the condensation of two δ-aminolevulinic acid (δ-ALA) molecules with the formation of porphobilinogen, a heme precursor. The effects of DMSA and DMPS alone or in combination with Cd 2+, Hg 2+, or Pb 2+ on hepatic δ-ALA-D were examined. DMPS and DMSA caused a dose-dependent inhibition of hepatic δ-ALA-D. In the presence of Hg 2+ or Cd 2+ the inhibitory potency of DMPS increased. Similarly, the inhibitory effects of Hg 2+ and Cd 2+ were markedly increased in the presence of DMSA. In contrast, the inhibitory effect of DMPS was not changed by inclusion of Pb 2+. As observed with DMSA, Zn 2+ did not modified the inhibitory effect of DMPS. Data of the present report support the idea that the complexes formed (metals–DMSA or DMPS) were more inhibitory than the metal (Hg 2+ and Cd 2+) or the chelating agent alone to the hepatic δ-ALA-D activity, in vitro. The mechanism of hepatic δ-ALA-D inhibition by Hg 2+–DMPS/DMSA and Cd 2+–DMPS/DMSA complexes involve the essential thiol groups of the enzyme.

Effect of insulin on basal and cholecystokinin-stimulated gallbladder motility in humans

Background/Aims: Acute hyperglycemia inhibits gallbladder contraction. In non-diabetic subjects this inhibitory effect may result from endogenous hyperinsulinemia. Therefore we investigated the effects of acute hyperglycemia and euglycemic hyperinsulinemia on basal and cholecystokinin-stimulated gallbladder motility. Methods: Gallbladder volume (ultrasonography) and duodenal bilirubin output were studied simultaneously in nine healthy volunteers (age 20–52 years) on 3 separate occasions in random order during: (a) saline infusion (control), (b) hyperglycemic hyperinsulinemic clamping (HG; plasma glucose at 15 mmol/l), and (c) euglycemic hyperinsulinemic clamping (HI; plasma insulin at 150 mU/l, glucose at 4–5 mmol/l). After a 2-h basal clamp period, cholecystokinin was infused intravenously for 60 min at 0.25 IDU · kg −1 · h −1, followed by another 60 min at 0.5 IDU · kg −1 · h −1. Results: HI and HG significantly ( p<0.05) reduced basal duodenal bilirubin output compared to control, while basal gallbladder volume did not change. At the low dose cholecystokinin, gallbladder emptying during HG (25±3%) and HI (39±4%) was significantly ( p<0.01) reduced compared to control (61±4%). The inhibitory effect of HG was significantly ( p<0.05) stronger compared to HI. Duodenal bilirubin output during the low dose cholecystokinin was significantly ( p<0.05) reduced by HG, but not by HI. No inhibitory effect of HG and HI on gallbladder emptying and duodenal bilirubin output was observed with the high dose of cholecystokinin. Conclusions: In healthy subjects acute hyperglycemia and euglycemic hyperinsulinemia reduce basal duodenal bilirubin output and inhibit gallbladder emptying stimulated by low dose cholecystokinin. These results suggest that insulin is involved in the inhibitory effect of hyperglycemia on basal and cholecystokinin-stimulted gallbladder motility.

In Vitro Effect of Mercury on Aryl Hydrocarbon Hydroxylase, Quinone Reductase, Catecholamine‐O‐methyltransferase and Glucose‐6‐phosphate Dehydrogenase Activities in Term Human Placenta

The effect of HgCl2 on human term placental aryl hydrocarbon hydroxylase (AHH), quinone reductase (QR), catecholamine-O-methyltransferase (COMT), and glucose-6-phosphate dehydrogenase (G-6-PD) enzyme activities was studied after incubation of placental explants with the salt for either a 6 or 24 hr period. Mercury (Hg) increased the activities of AHH, QR and COMT, but decreased that of G-6-PD. The increases in enzyme activities, as well as the decrease in G-6-PD activity observed were in all cases time- and dose-dependent. The data suggest that Hg exerts an enhancing effect on the activity of placental phase I enzyme (AHH) and phase II enzymes (QR and COMT). This enhancement may be due to increased de novo synthesis, elimination of some suppressing agent(s), or the decreased breakdown of enzyme protein. Also, the inhibitory effect of Hg on G-6-PD activity appears to indicate that this enzyme is appreciably more sensitive to Hg than the other three enzymes. These findings may imply increased cellular resistance to Hg toxicity. The altered state of activity may also be used as a tool for monitoring exposure to this metal.

Spectrophotometric Determination of Mercury(II) by Flow Injection Analysis

Abstract A new spectrophotometric FIA method for total mercury determination in water is proposed for the 5-40ng ml range. The method is based on the inhibitory effect of Hg(II) in the catalytic action of iodides on the As(III)-Ce(IV) reaction. By means of preconcentration techniques using KMnO4 traps, ppt levels of mercury in water can be detected.

Ionophorous properties of the 13 000-Da fragment from sarcoplasmic reticulum (Ca 2+ + Mg 2+)-ATPase

The 25 000-Da tryptic fragment from rabbit muscle sarcoplasmic reticulum (Ca 2+ + Mg 2+)-ATPase was subjected to cyanogen bromide digestion, and the four fragments isolated. Only the 13 000-Da fragment induced ionophorous activity in planar thin lipid membranes made with 5:1 (w/w) phosphatidylcholine/cholesterol in decane. The membranes became cation selective, with a selectivity sequence among divalent of Mn 2+ > Ca 2+ > Ba 2+ > Sr 2+ > Mg 2+. This is different from that of the 25 000-Da fragment (A.E. Shamoo, 1978, J. Memb. Biol. 43, 227–242), it's ‘parent’ 55 000-Da fragment, and the intact enzyme, all of which have the same selectivity sequence. The inhibitory effects of Hg 2+, Cd 2+ and Zn 2+ were also examined. All were inhibitory, with Zn 2+ being the most effective of these. The heavy-metal-induced inhibition of Ca 2+ conductance could be reversed by selective chelation of the heavy metals by EDTA. From changes in the selectivity as well as changes in heavy-metal-induced inhibition behavior, we conclude that the ion transport site of the 13 000-Da fragment may not be the same site as that of the parent fragment. It is either a different site altogether or has been physically modified by peptide cleavage.